Aspirin / acetylsalicylic acid

1. Cos-1 cells transfected with native or Ser-530-to-alanine mutant sheep prostaglandin endoperoxide synthase expressed comparable cyclooxygenase and hydroperoxidase activities, with the same Km for arachidonate of 8 micromolar and the same ID50 values for reversible inhibition by flurbiprofen at 5 micromolar, flufenamate at 20 micromolar and aspirin at 20 millimolar; however only the native enzyme was irreversibly inactivated by aspirin, so the active site Ser-530 is not essential for catalysis or substrate binding.

   Cyclooxygenase-1 with alanine substituted at position 530 → The cyclooxygenase activity of prostaglandin endoperoxide synthase source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/2108169.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50", "start_char": 0, "end_char": 2076, "text_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50"}

   experimental_model

   Site-directed mutagenesis of sheep prostaglandin endoperoxide synthase expressed in Cos-1 cells

   exposure

   Serine 530 replaced with alanine, compared with the native enzyme against aspirin and reversible inhibitors

   limitations

   The decisive experiment for the mechanism: it separates what the serine does for catalysis from what acetylating it does. Recombinant sheep enzyme, not human enzyme in a tissue.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Sheep and mouse enzyme

   plain_language

   Remove the serine and the enzyme still works; it is there to be acetylated, not to do the chemistry.

   primary_references

   [asa-p2108169] The aspirin and heme-binding sites of ovine and murine prostaglandin endoperoxide synthases. (1990). https://pubmed.ncbi.nlm.nih.gov/2108169/ DOI: 10.1016/s0021-9258(19)34105-5

   tissue_or_cell_type

   Recombinant enzyme in Cos-1 cells

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 78–89

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Site-directed mutagenesis of sheep prostaglandin endoperoxide synthase expressed in Cos-1 cells · source_derived_draft · unverified_draft

   ### asa-serine-is-not-catalytic Cos-1 cells transfected with native or Ser-530-to-alanine mutant sheep prostaglandin endoperoxide synthase expressed comparable cyclooxygenase and hydroperoxidase activities, with the same Km for arachidonate of 8 micromolar and the same ID50 values for reversible inhibition by flurbiprofen at 5 micromolar, flufenamate at 20 micromolar and aspirin at 20 millimolar; however only the native enzyme was irreversibly inactivated by aspirin, so the active site Ser-530 is not essential for catalysis or substrate binding. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Remove the serine and the enzyme still works; it is there to be acetylated, not to do the chemistry. organism: Sheep and mouse enzyme tissue_or_cell_type: Recombinant enzyme in Cos-1 cells experimental_model: Site-directed mutagenesis of sheep prostaglandin endoperoxide synthase expressed in Cos-1 cells limitations: The decisive experiment for the mechanism: it separates what the serine does for catalysis from what acetylating it does. Recombinant sheep enzyme, not human enzyme in a tissue. exposure: Serine 530 replaced with alanine, compared with the native enzyme against aspirin and reversible inhibitors evidence_span: {"source_cache": "artifacts/aspirin-research/2108169.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50", "start_char": 0, "end_char": 2076, "text_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50"} [asa-p2108169] The aspirin and heme-binding sites of ovine and murine prostaglandin endoperoxide synthases. (1990). https://pubmed.ncbi.nlm.nih.gov/2108169/ DOI: 10.1016/s0021-9258(19)34105-5

   Complete structured claim and evidence

2. Acetylation of Ser-530 of sheep prostaglandin endoperoxide synthase by aspirin causes irreversible inactivation of the cyclooxygenase activity of the enzyme, and since the serine hydroxyl is not required for catalysis the acetylation apparently introduces a bulky side chain at position 530 which interferes with arachidonate binding; a sequence of 35 residues with Ser-530 at the midpoint was identical in the sheep and mouse enzymes.

   Aspirin / acetylsalicylic acid → Serine 530 of cyclooxygenase-1 source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/2108169.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50", "start_char": 0, "end_char": 2076, "text_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50"}

   experimental_model

   Site-directed mutagenesis of sheep prostaglandin endoperoxide synthase expressed in Cos-1 cells

   exposure

   Serine 530 replaced with alanine, compared with the native enzyme against aspirin and reversible inhibitors

   limitations

   The decisive experiment for the mechanism: it separates what the serine does for catalysis from what acetylating it does. Recombinant sheep enzyme, not human enzyme in a tissue.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Sheep and mouse enzyme

   plain_language

   The acetyl group works by being in the way, not by removing something the enzyme needed.

   primary_references

   [asa-p2108169] The aspirin and heme-binding sites of ovine and murine prostaglandin endoperoxide synthases. (1990). https://pubmed.ncbi.nlm.nih.gov/2108169/ DOI: 10.1016/s0021-9258(19)34105-5

   tissue_or_cell_type

   Recombinant enzyme in Cos-1 cells

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 91–102

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Site-directed mutagenesis of sheep prostaglandin endoperoxide synthase expressed in Cos-1 cells · source_derived_draft · unverified_draft

   ### asa-acetylation-is-steric Acetylation of Ser-530 of sheep prostaglandin endoperoxide synthase by aspirin causes irreversible inactivation of the cyclooxygenase activity of the enzyme, and since the serine hydroxyl is not required for catalysis the acetylation apparently introduces a bulky side chain at position 530 which interferes with arachidonate binding; a sequence of 35 residues with Ser-530 at the midpoint was identical in the sheep and mouse enzymes. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The acetyl group works by being in the way, not by removing something the enzyme needed. organism: Sheep and mouse enzyme tissue_or_cell_type: Recombinant enzyme in Cos-1 cells experimental_model: Site-directed mutagenesis of sheep prostaglandin endoperoxide synthase expressed in Cos-1 cells limitations: The decisive experiment for the mechanism: it separates what the serine does for catalysis from what acetylating it does. Recombinant sheep enzyme, not human enzyme in a tissue. exposure: Serine 530 replaced with alanine, compared with the native enzyme against aspirin and reversible inhibitors evidence_span: {"source_cache": "artifacts/aspirin-research/2108169.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50", "start_char": 0, "end_char": 2076, "text_sha256": "c7b11508521a3854b432f3836de6e92ba9863c8edb244d747bb1c37634c0bb50"} [asa-p2108169] The aspirin and heme-binding sites of ovine and murine prostaglandin endoperoxide synthases. (1990). https://pubmed.ncbi.nlm.nih.gov/2108169/ DOI: 10.1016/s0021-9258(19)34105-5

   Complete structured claim and evidence

3. The Ala530 mutant of prostaglandin endoperoxide synthase had both cyclooxygenase and hydroperoxidase activity while the Asn530 mutant lacked cyclooxygenase activity but retained hydroperoxidase activity, establishing that the hydroxyl group of Ser530 is not essential for catalysis or substrate binding and suggesting that a bulky group at position 530, such as that introduced by aspirin acetylation, prevents arachidonate binding to the cyclooxygenase active site.

   Cyclooxygenase-1 with asparagine substituted at position 530 → The cyclooxygenase activity of prostaglandin endoperoxide synthase source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/2144687.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0a66f17b41129423ecb73bf520dad47b666792a6477552db04272474fc79be24", "start_char": 0, "end_char": 1595, "text_sha256": "0a66f17b41129423ecb73bf520dad47b666792a6477552db04272474fc79be24"}

   experimental_model

   Sequence comparison and site-directed mutagenesis across sheep, mouse and human prostaglandin endoperoxide synthase

   exposure

   Ser530 replaced with alanine and with asparagine, and tetranitromethane modification with ibuprofen protection

   limitations

   Extends the single mutant to a pair that differ in bulk. Sequence-based assignment of the heme ligands is inference from similarity, not structure.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Sheep, mouse and human enzyme

   plain_language

   Swap in a small residue and the enzyme is fine; swap in a bigger one and the cyclooxygenase half stops.

   primary_references

   [asa-p2144687] Structure-function relationships in sheep, mouse, and human prostaglandin endoperoxide G/H synthases. (1990). https://pubmed.ncbi.nlm.nih.gov/2144687/

   tissue_or_cell_type

   Recombinant enzyme

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 104–115

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Sequence comparison and site-directed mutagenesis across sheep, mouse and human prostaglandin endoperoxide synthase · source_derived_draft · unverified_draft

   ### asa-bulk-not-identity The Ala530 mutant of prostaglandin endoperoxide synthase had both cyclooxygenase and hydroperoxidase activity while the Asn530 mutant lacked cyclooxygenase activity but retained hydroperoxidase activity, establishing that the hydroxyl group of Ser530 is not essential for catalysis or substrate binding and suggesting that a bulky group at position 530, such as that introduced by aspirin acetylation, prevents arachidonate binding to the cyclooxygenase active site. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Swap in a small residue and the enzyme is fine; swap in a bigger one and the cyclooxygenase half stops. organism: Sheep, mouse and human enzyme tissue_or_cell_type: Recombinant enzyme experimental_model: Sequence comparison and site-directed mutagenesis across sheep, mouse and human prostaglandin endoperoxide synthase limitations: Extends the single mutant to a pair that differ in bulk. Sequence-based assignment of the heme ligands is inference from similarity, not structure. exposure: Ser530 replaced with alanine and with asparagine, and tetranitromethane modification with ibuprofen protection evidence_span: {"source_cache": "artifacts/aspirin-research/2144687.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0a66f17b41129423ecb73bf520dad47b666792a6477552db04272474fc79be24", "start_char": 0, "end_char": 1595, "text_sha256": "0a66f17b41129423ecb73bf520dad47b666792a6477552db04272474fc79be24"} [asa-p2144687] Structure-function relationships in sheep, mouse, and human prostaglandin endoperoxide G/H synthases. (1990). https://pubmed.ncbi.nlm.nih.gov/2144687/

   Complete structured claim and evidence

4. Using site-directed mutagenesis to prepare five further substitutions of Ser-530, the presence of amino acids with bulky side chains at position 530 inhibited cyclooxygenase activity and decreased the apparent affinity of the enzyme for arachidonate, consistent with the proposal that aspirin inhibits by placing a larger than normal side chain at position 530; residues 529 to 533 all proved important for the peroxidase as well as the cyclooxygenase activity, and Phe-529 in particular was critical for structure and catalysis.

   Serine 530 of cyclooxygenase-1 → Binding of arachidonate in the cyclooxygenase active site source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/1601897.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "616cbc367eb38194b858872cbf91108baa3b1dec7aa039a40f69a29fa7157c2d", "start_char": 0, "end_char": 1744, "text_sha256": "616cbc367eb38194b858872cbf91108baa3b1dec7aa039a40f69a29fa7157c2d"}

   experimental_model

   Five further substitutions at Ser-530 and substitutions at adjoining residues, expressed transiently in cos-1 cells

   exposure

   A graded series of side chains at position 530, plus substitutions at Phe-529, Leu-531, Lys-532 and Gly-533

   limitations

   Tests the steric hypothesis by varying the bulk systematically rather than with one mutant. Transient expression in a heterologous cell line.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Enzyme

   plain_language

   The bigger the group put at that position, the worse the enzyme binds its substrate.

   primary_references

   [asa-p1601897] Prostaglandin endoperoxide synthase. The aspirin acetylation region. (1992). https://pubmed.ncbi.nlm.nih.gov/1601897/ DOI: 10.1016/s0021-9258(19)49852-9

   tissue_or_cell_type

   Recombinant prostaglandin endoperoxide H synthase-1

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 117–128

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Five further substitutions at Ser-530 and substitutions at adjoining residues, expressed transiently in cos-1 cells · source_derived_draft · unverified_draft

   ### asa-graded-bulk-series Using site-directed mutagenesis to prepare five further substitutions of Ser-530, the presence of amino acids with bulky side chains at position 530 inhibited cyclooxygenase activity and decreased the apparent affinity of the enzyme for arachidonate, consistent with the proposal that aspirin inhibits by placing a larger than normal side chain at position 530; residues 529 to 533 all proved important for the peroxidase as well as the cyclooxygenase activity, and Phe-529 in particular was critical for structure and catalysis. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The bigger the group put at that position, the worse the enzyme binds its substrate. organism: Enzyme tissue_or_cell_type: Recombinant prostaglandin endoperoxide H synthase-1 experimental_model: Five further substitutions at Ser-530 and substitutions at adjoining residues, expressed transiently in cos-1 cells limitations: Tests the steric hypothesis by varying the bulk systematically rather than with one mutant. Transient expression in a heterologous cell line. exposure: A graded series of side chains at position 530, plus substitutions at Phe-529, Leu-531, Lys-532 and Gly-533 evidence_span: {"source_cache": "artifacts/aspirin-research/1601897.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "616cbc367eb38194b858872cbf91108baa3b1dec7aa039a40f69a29fa7157c2d", "start_char": 0, "end_char": 1744, "text_sha256": "616cbc367eb38194b858872cbf91108baa3b1dec7aa039a40f69a29fa7157c2d"} [asa-p1601897] Prostaglandin endoperoxide synthase. The aspirin acetylation region. (1992). https://pubmed.ncbi.nlm.nih.gov/1601897/ DOI: 10.1016/s0021-9258(19)49852-9

   Complete structured claim and evidence

5. The 3.4 angstrom X-ray crystal structure of prostaglandin H2 synthase isoform-1 inactivated by the potent aspirin analogue 2-bromoacetoxy-benzoic acid shows that acetylation abolishes cyclooxygenase activity by steric blockage of the active-site channel and not through a large conformational change, with two rotameric states of the acetyl-serine side chain blocking the channel to different extents, a result which may explain the dissimilar effects of aspirin on the two isoforms.

   Aspirin-acetylated cyclooxygenase-1 → The hydrophobic substrate channel of the cyclooxygenase active site source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/7552725.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1", "start_char": 0, "end_char": 751, "text_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1"}

   experimental_model

   X-ray crystal structure at 3.4 angstrom of prostaglandin H2 synthase-1 inactivated by a potent aspirin analogue

   exposure

   2-bromoacetoxy-benzoic acid acetylation, with salicylic acid soaked into the structure

   limitations

   Direct structural evidence rather than inference from mutants, though at modest resolution and using an analogue rather than aspirin itself.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Enzyme

   plain_language

   The picture confirms it: the acetyl group simply plugs the tunnel the fatty acid has to travel down.

   primary_references

   [asa-p7552725] The structural basis of aspirin activity inferred from the crystal structure of inactivated prostaglandin H2 synthase. (1995). https://pubmed.ncbi.nlm.nih.gov/7552725/ DOI: 10.1038/nsb0895-637

   tissue_or_cell_type

   Crystallised prostaglandin H2 synthase-1

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 130–141

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · X-ray crystal structure at 3.4 angstrom of prostaglandin H2 synthase-1 inactivated by a potent aspirin analogue · source_derived_draft · unverified_draft

   ### asa-structure-shows-blockage The 3.4 angstrom X-ray crystal structure of prostaglandin H2 synthase isoform-1 inactivated by the potent aspirin analogue 2-bromoacetoxy-benzoic acid shows that acetylation abolishes cyclooxygenase activity by steric blockage of the active-site channel and not through a large conformational change, with two rotameric states of the acetyl-serine side chain blocking the channel to different extents, a result which may explain the dissimilar effects of aspirin on the two isoforms. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The picture confirms it: the acetyl group simply plugs the tunnel the fatty acid has to travel down. organism: Enzyme tissue_or_cell_type: Crystallised prostaglandin H2 synthase-1 experimental_model: X-ray crystal structure at 3.4 angstrom of prostaglandin H2 synthase-1 inactivated by a potent aspirin analogue limitations: Direct structural evidence rather than inference from mutants, though at modest resolution and using an analogue rather than aspirin itself. exposure: 2-bromoacetoxy-benzoic acid acetylation, with salicylic acid soaked into the structure evidence_span: {"source_cache": "artifacts/aspirin-research/7552725.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1", "start_char": 0, "end_char": 751, "text_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1"} [asa-p7552725] The structural basis of aspirin activity inferred from the crystal structure of inactivated prostaglandin H2 synthase. (1995). https://pubmed.ncbi.nlm.nih.gov/7552725/ DOI: 10.1038/nsb0895-637

   Complete structured claim and evidence

6. In the crystal structure of the inactivated enzyme the product salicylic acid was observed binding at a site consistent with its antagonistic effect on aspirin activity.

   Salicylate / salicylic acid → Aspirin / acetylsalicylic acid source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/7552725.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1", "start_char": 0, "end_char": 751, "text_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1"}

   experimental_model

   X-ray crystal structure at 3.4 angstrom of prostaglandin H2 synthase-1 inactivated by a potent aspirin analogue

   exposure

   2-bromoacetoxy-benzoic acid acetylation, with salicylic acid soaked into the structure

   limitations

   Direct structural evidence rather than inference from mutants, though at modest resolution and using an analogue rather than aspirin itself.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Enzyme

   plain_language

   The breakdown product sits in the same place the drug needs to reach, and gets in its way.

   primary_references

   [asa-p7552725] The structural basis of aspirin activity inferred from the crystal structure of inactivated prostaglandin H2 synthase. (1995). https://pubmed.ncbi.nlm.nih.gov/7552725/ DOI: 10.1038/nsb0895-637

   tissue_or_cell_type

   Crystallised prostaglandin H2 synthase-1

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 143–154

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · X-ray crystal structure at 3.4 angstrom of prostaglandin H2 synthase-1 inactivated by a potent aspirin analogue · source_derived_draft · unverified_draft

   ### asa-salicylate-antagonises-at-the-site In the crystal structure of the inactivated enzyme the product salicylic acid was observed binding at a site consistent with its antagonistic effect on aspirin activity. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The breakdown product sits in the same place the drug needs to reach, and gets in its way. organism: Enzyme tissue_or_cell_type: Crystallised prostaglandin H2 synthase-1 experimental_model: X-ray crystal structure at 3.4 angstrom of prostaglandin H2 synthase-1 inactivated by a potent aspirin analogue limitations: Direct structural evidence rather than inference from mutants, though at modest resolution and using an analogue rather than aspirin itself. exposure: 2-bromoacetoxy-benzoic acid acetylation, with salicylic acid soaked into the structure evidence_span: {"source_cache": "artifacts/aspirin-research/7552725.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1", "start_char": 0, "end_char": 751, "text_sha256": "dd61431f20eb312313942bc8a89f970d5d2e33600b32abe692f20d9d5c57d7b1"} [asa-p7552725] The structural basis of aspirin activity inferred from the crystal structure of inactivated prostaglandin H2 synthase. (1995). https://pubmed.ncbi.nlm.nih.gov/7552725/ DOI: 10.1038/nsb0895-637

   Complete structured claim and evidence

7. The crystal structures reveal that the acetylated Ser-530 completely blocks access to the hydrophobic groove, that the observed binding pose of salicylate is reflective of the enzyme-inhibitor complex prior to acetylation, and that the observed Thr-530 rotamer in the S530T mutant does not impede access to the groove; differential acetylation of COX-2 purified in various detergent systems and nanodiscs indicates that detergent and lipid binding within the membrane-binding domain alters the rate of the acetylation reaction in vitro.

   Aspirin-acetylated cyclooxygenase-2 → The hydrophobic substrate channel of the cyclooxygenase active site source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/26859324.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2d5dab1d6b7576a909c9cef6b5c247e6a399946afbf7ef6d428d67475a363c34", "start_char": 0, "end_char": 1553, "text_sha256": "2d5dab1d6b7576a909c9cef6b5c247e6a399946afbf7ef6d428d67475a363c34"}

   experimental_model

   Crystal structures of an S530T murine COX-2 mutant, aspirin-acetylated human COX-2 and human COX-2 with salicylate, at 1.9 to 2.4 angstrom

   exposure

   Aspirin acetylation and salicylate binding, with an S530T/G533V double mutant and purification in several detergent systems

   limitations

   Much higher resolution than the 1995 structure and it captures salicylate separately. The authors note that detergent and lipid in the membrane-binding domain change the acetylation rate in vitro, which is a caution about all such measurements.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Mouse and human enzyme

   plain_language

   At high resolution the acetyl group seals the groove completely, and salicylate is caught sitting where aspirin sits before it reacts.

   primary_references

   [asa-p26859324] Crystal Structure of Aspirin-Acetylated Human Cyclooxygenase-2: Insight into the Formation of Products with Reversed Stereochemistry. (2016). https://pubmed.ncbi.nlm.nih.gov/26859324/ DOI: 10.1021/acs.biochem.5b01378

   tissue_or_cell_type

   Crystallised cyclooxygenase-2

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 156–167

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Crystal structures of an S530T murine COX-2 mutant, aspirin-acetylated human COX-2 and human COX-2 with salicylate, at 1.9 to 2.4 angstrom · source_derived_draft · unverified_draft

   ### asa-acetyl-blocks-the-groove The crystal structures reveal that the acetylated Ser-530 completely blocks access to the hydrophobic groove, that the observed binding pose of salicylate is reflective of the enzyme-inhibitor complex prior to acetylation, and that the observed Thr-530 rotamer in the S530T mutant does not impede access to the groove; differential acetylation of COX-2 purified in various detergent systems and nanodiscs indicates that detergent and lipid binding within the membrane-binding domain alters the rate of the acetylation reaction in vitro. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: At high resolution the acetyl group seals the groove completely, and salicylate is caught sitting where aspirin sits before it reacts. organism: Mouse and human enzyme tissue_or_cell_type: Crystallised cyclooxygenase-2 experimental_model: Crystal structures of an S530T murine COX-2 mutant, aspirin-acetylated human COX-2 and human COX-2 with salicylate, at 1.9 to 2.4 angstrom limitations: Much higher resolution than the 1995 structure and it captures salicylate separately. The authors note that detergent and lipid in the membrane-binding domain change the acetylation rate in vitro, which is a caution about all such measurements. exposure: Aspirin acetylation and salicylate binding, with an S530T/G533V double mutant and purification in several detergent systems evidence_span: {"source_cache": "artifacts/aspirin-research/26859324.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2d5dab1d6b7576a909c9cef6b5c247e6a399946afbf7ef6d428d67475a363c34", "start_char": 0, "end_char": 1553, "text_sha256": "2d5dab1d6b7576a909c9cef6b5c247e6a399946afbf7ef6d428d67475a363c34"} [asa-p26859324] Crystal Structure of Aspirin-Acetylated Human Cyclooxygenase-2: Insight into the Formation of Products with Reversed Stereochemistry. (2016). https://pubmed.ncbi.nlm.nih.gov/26859324/ DOI: 10.1021/acs.biochem.5b01378

   Complete structured claim and evidence

8. Diclofenac inhibition was unaffected by mutation of Arg-120 to alanine but was dramatically attenuated by the S530A mutation, and the crystal structure of diclofenac with murine COX-2 shows it bound in an inverted conformation with its carboxylate hydrogen-bonded to Tyr-385 and Ser-530, the first experimental demonstration that an acidic non-steroidal anti-inflammatory drug can bind in an orientation that precludes a salt bridge with Arg-120; Ser-530 is also important in time-dependent inhibition by nimesulide and piroxicam.

   Serine 530 of cyclooxygenase-1 → Diclofenac source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/12925531.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "732e941e7f912ae2495715634eabdef176dae39e32359609f15b05a230d5f6e0", "start_char": 0, "end_char": 1473, "text_sha256": "732e941e7f912ae2495715634eabdef176dae39e32359609f15b05a230d5f6e0"}

   experimental_model

   Site-directed mutants of COX-2 at Arg-120, Tyr-355, Tyr-348 and Ser-530 tested against a series of inhibitors, with a diclofenac co-crystal structure

   exposure

   Diclofenac, nimesulide and piroxicam against the mutant panel

   limitations

   Shows the acetylation serine is also a general binding determinant for other drugs. The structural work is on murine rather than human enzyme.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Mouse enzyme

   plain_language

   The same serine aspirin attacks is where several other anti-inflammatories anchor themselves.

   primary_references

   [asa-p12925531] A novel mechanism of cyclooxygenase-2 inhibition involving interactions with Ser-530 and Tyr-385. (2003). https://pubmed.ncbi.nlm.nih.gov/12925531/ DOI: 10.1074/jbc.m305481200

   tissue_or_cell_type

   Cyclooxygenase-2

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 169–180

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Site-directed mutants of COX-2 at Arg-120, Tyr-355, Tyr-348 and Ser-530 tested against a series of inhibitors, with a diclofenac co-crystal structure · source_derived_draft · unverified_draft

   ### asa-ser530-binds-other-drugs Diclofenac inhibition was unaffected by mutation of Arg-120 to alanine but was dramatically attenuated by the S530A mutation, and the crystal structure of diclofenac with murine COX-2 shows it bound in an inverted conformation with its carboxylate hydrogen-bonded to Tyr-385 and Ser-530, the first experimental demonstration that an acidic non-steroidal anti-inflammatory drug can bind in an orientation that precludes a salt bridge with Arg-120; Ser-530 is also important in time-dependent inhibition by nimesulide and piroxicam. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The same serine aspirin attacks is where several other anti-inflammatories anchor themselves. organism: Mouse enzyme tissue_or_cell_type: Cyclooxygenase-2 experimental_model: Site-directed mutants of COX-2 at Arg-120, Tyr-355, Tyr-348 and Ser-530 tested against a series of inhibitors, with a diclofenac co-crystal structure limitations: Shows the acetylation serine is also a general binding determinant for other drugs. The structural work is on murine rather than human enzyme. exposure: Diclofenac, nimesulide and piroxicam against the mutant panel evidence_span: {"source_cache": "artifacts/aspirin-research/12925531.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "732e941e7f912ae2495715634eabdef176dae39e32359609f15b05a230d5f6e0", "start_char": 0, "end_char": 1473, "text_sha256": "732e941e7f912ae2495715634eabdef176dae39e32359609f15b05a230d5f6e0"} [asa-p12925531] A novel mechanism of cyclooxygenase-2 inhibition involving interactions with Ser-530 and Tyr-385. (2003). https://pubmed.ncbi.nlm.nih.gov/12925531/ DOI: 10.1074/jbc.m305481200

   Complete structured claim and evidence

9. Valeryl (pentanoyl) salicylate was the only compound of eight acyl salicylates to show isozyme selectivity and inhibited human cyclooxygenase-1 much more effectively than cyclooxygenase-2 in a time-dependent manner, inhibited ovine cyclooxygenase-1 but did not inhibit the S530A mutant of ovine cyclooxygenase-1 which is also refractory to acetylsalicylate, so valeryl salicylate acylates the active site serine.

   Valeryl (pentanoyl) salicylate → Cyclooxygenase-1 (PTGS1) source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/aspirin-research/7872783.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "f7e8a07a2704cb600938505ec51355671355769c01868ed0966731382901425b", "start_char": 0, "end_char": 1756, "text_sha256": "f7e8a07a2704cb600938505ec51355671355769c01868ed0966731382901425b"}

   experimental_model

   Eight acyl salicylates tested against human cyclooxygenase-1 and -2 expressed transiently in cos-1 cells, with the S530A mutant as a control

   exposure

   Valeryl salicylate and related esters compared with acetylsalicylate

   limitations

   Uses the acetylation chemistry as a design principle and confirms the serine requirement with a mutant. Recombinant enzyme and a murine fibroblast line, not human tissue.

   nutrient_topic

   Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

   organism

   Human and sheep enzyme

   plain_language

   Swap aspirin’s acetyl group for a bigger one and you get a drug that hits only the first enzyme.

   primary_references

   [asa-p7872783] Selective inhibition of prostaglandin endoperoxide synthase-1 (cyclooxygenase-1) by valerylsalicylic acid. (1995). https://pubmed.ncbi.nlm.nih.gov/7872783/ DOI: 10.1006/abbi.1995.1130

   tissue_or_cell_type

   Recombinant cyclooxygenase

   Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 182–193

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Eight acyl salicylates tested against human cyclooxygenase-1 and -2 expressed transiently in cos-1 cells, with the S530A mutant as a control · source_derived_draft · unverified_draft

   ### asa-bigger-acyl-group-selective Valeryl (pentanoyl) salicylate was the only compound of eight acyl salicylates to show isozyme selectivity and inhibited human cyclooxygenase-1 much more effectively than cyclooxygenase-2 in a time-dependent manner, inhibited ovine cyclooxygenase-1 but did not inhibit the S530A mutant of ovine cyclooxygenase-1 which is also refractory to acetylsalicylate, so valeryl salicylate acylates the active site serine. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Swap aspirin’s acetyl group for a bigger one and you get a drug that hits only the first enzyme. organism: Human and sheep enzyme tissue_or_cell_type: Recombinant cyclooxygenase experimental_model: Eight acyl salicylates tested against human cyclooxygenase-1 and -2 expressed transiently in cos-1 cells, with the S530A mutant as a control limitations: Uses the acetylation chemistry as a design principle and confirms the serine requirement with a mutant. Recombinant enzyme and a murine fibroblast line, not human tissue. exposure: Valeryl salicylate and related esters compared with acetylsalicylate evidence_span: {"source_cache": "artifacts/aspirin-research/7872783.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "f7e8a07a2704cb600938505ec51355671355769c01868ed0966731382901425b", "start_char": 0, "end_char": 1756, "text_sha256": "f7e8a07a2704cb600938505ec51355671355769c01868ed0966731382901425b"} [asa-p7872783] Selective inhibition of prostaglandin endoperoxide synthase-1 (cyclooxygenase-1) by valerylsalicylic acid. (1995). https://pubmed.ncbi.nlm.nih.gov/7872783/ DOI: 10.1006/abbi.1995.1130

   Complete structured claim and evidence

10. Aspirin causes time-dependent inhibition and acetylation of plant allene oxide synthase leading to irreversible inactivation of this cytochrome P450, acetylating three serine residues near the C-terminal region that are highly conserved among allene oxide synthases but not among classical P450s; unlike animal cyclooxygenase, where acetylation of a single serine within the substrate channel causes inactivation, these three serines are not thought to line the putative substrate channel, so inhibition may be by a different mechanism, and aspirin could inhibit other P450s with similar motifs.

    Aspirin / acetylsalicylic acid → Plant allene oxide synthase, a cytochrome P450 source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/9660772.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "49e5d050a7b1505f537ae535df4e7a51563a72d528973779baf53c963b50c259", "start_char": 0, "end_char": 1662, "text_sha256": "49e5d050a7b1505f537ae535df4e7a51563a72d528973779baf53c963b50c259"}

    experimental_model

    Inhibition and acetylation of plant allene oxide synthase, a cytochrome P450

    exposure

    Aspirin and salicylic acid applied to the plant oxylipin pathway

    limitations

    Recorded because it shows the acetyl group is not specific to cyclooxygenase. The three acetylated serines here are not thought to line the substrate channel, so the mechanism may differ from the one at cyclooxygenase.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Plant

    plain_language

    Aspirin hands its acetyl group to other enzymes too, including one in plants, and not always at the substrate channel.

    primary_references

    [asa-p9660772] Aspirin inhibition and acetylation of the plant cytochrome P450, allene oxide synthase, resembles that of animal prostaglandin endoperoxide H synthase. (1998). https://pubmed.ncbi.nlm.nih.gov/9660772/ DOI: 10.1074/jbc.273.29.18139

    tissue_or_cell_type

    Allene oxide synthase

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 195–206

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Inhibition and acetylation of plant allene oxide synthase, a cytochrome P450 · source_derived_draft · unverified_draft

    ### asa-acetylates-other-enzymes Aspirin causes time-dependent inhibition and acetylation of plant allene oxide synthase leading to irreversible inactivation of this cytochrome P450, acetylating three serine residues near the C-terminal region that are highly conserved among allene oxide synthases but not among classical P450s; unlike animal cyclooxygenase, where acetylation of a single serine within the substrate channel causes inactivation, these three serines are not thought to line the putative substrate channel, so inhibition may be by a different mechanism, and aspirin could inhibit other P450s with similar motifs. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Aspirin hands its acetyl group to other enzymes too, including one in plants, and not always at the substrate channel. organism: Plant tissue_or_cell_type: Allene oxide synthase experimental_model: Inhibition and acetylation of plant allene oxide synthase, a cytochrome P450 limitations: Recorded because it shows the acetyl group is not specific to cyclooxygenase. The three acetylated serines here are not thought to line the substrate channel, so the mechanism may differ from the one at cyclooxygenase. exposure: Aspirin and salicylic acid applied to the plant oxylipin pathway evidence_span: {"source_cache": "artifacts/aspirin-research/9660772.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "49e5d050a7b1505f537ae535df4e7a51563a72d528973779baf53c963b50c259", "start_char": 0, "end_char": 1662, "text_sha256": "49e5d050a7b1505f537ae535df4e7a51563a72d528973779baf53c963b50c259"} [asa-p9660772] Aspirin inhibition and acetylation of the plant cytochrome P450, allene oxide synthase, resembles that of animal prostaglandin endoperoxide H synthase. (1998). https://pubmed.ncbi.nlm.nih.gov/9660772/ DOI: 10.1074/jbc.273.29.18139

    Complete structured claim and evidence

11. Aspirin treatment of human cyclooxygenase-1 caused time-dependent inactivation of oxygenase activity, whereas aspirin treatment of cyclooxygenase-2 produced an enzyme which retained oxygenase activity but formed exclusively 15-hydroxyeicosatetraenoic acid instead of prostaglandin H2, exclusively of the 15R configuration, with Km values for arachidonate of native and aspirin-treated cyclooxygenase-2 about the same, suggesting arachidonate binds to both in a similar manner.

    Aspirin-acetylated cyclooxygenase-2 → 15(R)-hydroxyeicosatetraenoic acid source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/8175750.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9", "start_char": 0, "end_char": 1786, "text_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9"}

    experimental_model

    Human cyclooxygenase-1 and -2 expressed in cos-1 cells treated with aspirin and with carbon-14 labelled aspirin, with a mutant series at Ser-516

    exposure

    Aspirin acetylation, with S516A, S516N, S516Q and S516M substitutions

    limitations

    Identifies the site by direct labelling and explains the isoform difference by active site volume. Recombinant enzyme in a heterologous cell line.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human enzyme

    plain_language

    Acetylating the second enzyme does not switch it off; it turns it into a machine that makes something else.

    primary_references

    [asa-p8175750] Acetylation of human prostaglandin endoperoxide synthase-2 (cyclooxygenase-2) by aspirin. (1994). https://pubmed.ncbi.nlm.nih.gov/8175750/ DOI: 10.1016/s0021-9258(17)36820-5

    tissue_or_cell_type

    Recombinant cyclooxygenase

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 208–219

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human cyclooxygenase-1 and -2 expressed in cos-1 cells treated with aspirin and with carbon-14 labelled aspirin, with a mutant series at Ser-516 · source_derived_draft · unverified_draft

    ### asa-cox2-becomes-a-lipoxygenase Aspirin treatment of human cyclooxygenase-1 caused time-dependent inactivation of oxygenase activity, whereas aspirin treatment of cyclooxygenase-2 produced an enzyme which retained oxygenase activity but formed exclusively 15-hydroxyeicosatetraenoic acid instead of prostaglandin H2, exclusively of the 15R configuration, with Km values for arachidonate of native and aspirin-treated cyclooxygenase-2 about the same, suggesting arachidonate binds to both in a similar manner. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Acetylating the second enzyme does not switch it off; it turns it into a machine that makes something else. organism: Human enzyme tissue_or_cell_type: Recombinant cyclooxygenase experimental_model: Human cyclooxygenase-1 and -2 expressed in cos-1 cells treated with aspirin and with carbon-14 labelled aspirin, with a mutant series at Ser-516 limitations: Identifies the site by direct labelling and explains the isoform difference by active site volume. Recombinant enzyme in a heterologous cell line. exposure: Aspirin acetylation, with S516A, S516N, S516Q and S516M substitutions evidence_span: {"source_cache": "artifacts/aspirin-research/8175750.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9", "start_char": 0, "end_char": 1786, "text_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9"} [asa-p8175750] Acetylation of human prostaglandin endoperoxide synthase-2 (cyclooxygenase-2) by aspirin. (1994). https://pubmed.ncbi.nlm.nih.gov/8175750/ DOI: 10.1016/s0021-9258(17)36820-5

    Complete structured claim and evidence

12. When microsomal human cyclooxygenase-2 was incubated with acetyl-carbon-14 labelled aspirin the enzyme was acetylated, while an S516A mutant which retains enzyme activity was not acetylated, indicating that Ser-516 is the site of aspirin acetylation and is homologous to the active site serine of cyclooxygenase-1; an S516N mutant was catalytically active whereas an S516Q mutant lacked cyclooxygenase but retained peroxidase activity, and because in cyclooxygenase-1 the smaller asparagine substitution suffices to eliminate cyclooxygenase activity the active site of cyclooxygenase-2 is slightly larger.

    Aspirin / acetylsalicylic acid → Serine 516 of cyclooxygenase-2 source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/8175750.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9", "start_char": 0, "end_char": 1786, "text_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9"}

    experimental_model

    Human cyclooxygenase-1 and -2 expressed in cos-1 cells treated with aspirin and with carbon-14 labelled aspirin, with a mutant series at Ser-516

    exposure

    Aspirin acetylation, with S516A, S516N, S516Q and S516M substitutions

    limitations

    Identifies the site by direct labelling and explains the isoform difference by active site volume. Recombinant enzyme in a heterologous cell line.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human enzyme

    plain_language

    The labelled acetyl group lands on one serine, and the second enzyme’s pocket is roomier, which is why the two behave differently.

    primary_references

    [asa-p8175750] Acetylation of human prostaglandin endoperoxide synthase-2 (cyclooxygenase-2) by aspirin. (1994). https://pubmed.ncbi.nlm.nih.gov/8175750/ DOI: 10.1016/s0021-9258(17)36820-5

    tissue_or_cell_type

    Recombinant cyclooxygenase

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 221–232

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human cyclooxygenase-1 and -2 expressed in cos-1 cells treated with aspirin and with carbon-14 labelled aspirin, with a mutant series at Ser-516 · source_derived_draft · unverified_draft

    ### asa-ser516-is-the-site When microsomal human cyclooxygenase-2 was incubated with acetyl-carbon-14 labelled aspirin the enzyme was acetylated, while an S516A mutant which retains enzyme activity was not acetylated, indicating that Ser-516 is the site of aspirin acetylation and is homologous to the active site serine of cyclooxygenase-1; an S516N mutant was catalytically active whereas an S516Q mutant lacked cyclooxygenase but retained peroxidase activity, and because in cyclooxygenase-1 the smaller asparagine substitution suffices to eliminate cyclooxygenase activity the active site of cyclooxygenase-2 is slightly larger. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The labelled acetyl group lands on one serine, and the second enzyme’s pocket is roomier, which is why the two behave differently. organism: Human enzyme tissue_or_cell_type: Recombinant cyclooxygenase experimental_model: Human cyclooxygenase-1 and -2 expressed in cos-1 cells treated with aspirin and with carbon-14 labelled aspirin, with a mutant series at Ser-516 limitations: Identifies the site by direct labelling and explains the isoform difference by active site volume. Recombinant enzyme in a heterologous cell line. exposure: Aspirin acetylation, with S516A, S516N, S516Q and S516M substitutions evidence_span: {"source_cache": "artifacts/aspirin-research/8175750.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9", "start_char": 0, "end_char": 1786, "text_sha256": "9ba85af90c62b157cf53032375ca703e8b78eff6ddd22ad627bbd7e65965d8e9"} [asa-p8175750] Acetylation of human prostaglandin endoperoxide synthase-2 (cyclooxygenase-2) by aspirin. (1994). https://pubmed.ncbi.nlm.nih.gov/8175750/ DOI: 10.1016/s0021-9258(17)36820-5

    Complete structured claim and evidence

13. While prostaglandin synthesis by both isoforms is inhibited by aspirin, 15-R-hydroxyeicosatetraenoic acid synthesis by cyclooxygenase-2 but not cyclooxygenase-1 is stimulated by preincubation with aspirin, and enzyme activity and inhibitor sensitivity studies of mutants provide evidence that Ser516 is the aspirin acetylation site of human cyclooxygenase-2 and that substitution of a methionine at this position can mimic the effects of aspirin acetylation on enzyme activity.

    Cyclooxygenase-2 with methionine substituted at position 516 → 15(R)-hydroxyeicosatetraenoic acid source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/8143845.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "ddf63e3296e1f35a88de948bc23fda6654c2eaf247b1d6d3987e95989c966f93", "start_char": 0, "end_char": 903, "text_sha256": "ddf63e3296e1f35a88de948bc23fda6654c2eaf247b1d6d3987e95989c966f93"}

    experimental_model

    Mutants of the putative acetylation site of human cyclooxygenase-2 expressed in COS-7 cells by recombinant vaccinia virus

    exposure

    Substitution at Ser516, including methionine, compared with aspirin preincubation

    limitations

    A second, independent identification of the same residue with a substitution that mimics the acetylated state. Vaccinia-driven expression in a heterologous line.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human enzyme

    plain_language

    Putting a methionine where the acetyl group would go reproduces the switch without any drug.

    primary_references

    [asa-p8143845] Mutation of serine-516 in human prostaglandin G/H synthase-2 to methionine or aspirin acetylation of this residue stimulates 15-R-HETE synthesis. (1994). https://pubmed.ncbi.nlm.nih.gov/8143845/ DOI: 10.1016/0014-5793(94)80579-2

    tissue_or_cell_type

    Recombinant cyclooxygenase-2

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 234–245

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Mutants of the putative acetylation site of human cyclooxygenase-2 expressed in COS-7 cells by recombinant vaccinia virus · source_derived_draft · unverified_draft

    ### asa-methionine-mimics-acetyl While prostaglandin synthesis by both isoforms is inhibited by aspirin, 15-R-hydroxyeicosatetraenoic acid synthesis by cyclooxygenase-2 but not cyclooxygenase-1 is stimulated by preincubation with aspirin, and enzyme activity and inhibitor sensitivity studies of mutants provide evidence that Ser516 is the aspirin acetylation site of human cyclooxygenase-2 and that substitution of a methionine at this position can mimic the effects of aspirin acetylation on enzyme activity. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Putting a methionine where the acetyl group would go reproduces the switch without any drug. organism: Human enzyme tissue_or_cell_type: Recombinant cyclooxygenase-2 experimental_model: Mutants of the putative acetylation site of human cyclooxygenase-2 expressed in COS-7 cells by recombinant vaccinia virus limitations: A second, independent identification of the same residue with a substitution that mimics the acetylated state. Vaccinia-driven expression in a heterologous line. exposure: Substitution at Ser516, including methionine, compared with aspirin preincubation evidence_span: {"source_cache": "artifacts/aspirin-research/8143845.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "ddf63e3296e1f35a88de948bc23fda6654c2eaf247b1d6d3987e95989c966f93", "start_char": 0, "end_char": 903, "text_sha256": "ddf63e3296e1f35a88de948bc23fda6654c2eaf247b1d6d3987e95989c966f93"} [asa-p8143845] Mutation of serine-516 in human prostaglandin G/H synthase-2 to methionine or aspirin acetylation of this residue stimulates 15-R-HETE synthesis. (1994). https://pubmed.ncbi.nlm.nih.gov/8143845/ DOI: 10.1016/0014-5793(94)80579-2

    Complete structured claim and evidence

14. Acetylated cyclooxygenase-2 is essentially a lipoxygenase making 15(R)- and 11(R)-hydroxyeicosatetraenoic acid whereas acetylated cyclooxygenase-1 is unable to oxidise arachidonic acid to any products, and site-directed mutagenesis of Val-434, Arg-513 and Val-523 in mouse cyclooxygenase-2 to their cyclooxygenase-1 equivalents abrogated 11- and 15-HETE production after aspirin treatment, confirming these residues as the major isoform selectivity determinants; V228F and G533A produced wild-type-like profiles but on acetylation neither could make HETE products, suggesting arachidonic acid orientates in an L-shaped binding configuration.

    Residues Val-434, Arg-513 and Val-523 that distinguish the two cyclooxygenase active sites → 15(R)-hydroxyeicosatetraenoic acid source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/10692466.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9da1ede1fbf95d6f42d4bb15dc08b5d1869549a7cd94cbfa9da9f9865fd780ff", "start_char": 0, "end_char": 2055, "text_sha256": "9da1ede1fbf95d6f42d4bb15dc08b5d1869549a7cd94cbfa9da9f9865fd780ff"}

    experimental_model

    Site-directed mutagenesis of mouse COX-2 residues predicted from comparison of the two isoform crystal structures

    exposure

    Val-434, Arg-513, Val-523, Val-228 and Gly-533 mutated towards their cyclooxygenase-1 equivalents, then acetylated

    limitations

    Explains the isoform difference residue by residue. Murine enzyme, and the L-shaped substrate configuration is an inference from the mutant product profiles.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Mouse enzyme

    plain_language

    Three amino acids are the whole difference between an enzyme aspirin kills and one aspirin repurposes.

    primary_references

    [asa-p10692466] Spatial requirements for 15-(R)-hydroxy-5Z,8Z,11Z, 13E-eicosatetraenoic acid synthesis within the cyclooxygenase active site of murine COX-2. Why acetylated COX-1 does not synthesize 15-(R)-hete. (2000). https://pubmed.ncbi.nlm.nih.gov/10692466/ DOI: 10.1074/jbc.275.9.6586

    tissue_or_cell_type

    Cyclooxygenase-2

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 247–258

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Site-directed mutagenesis of mouse COX-2 residues predicted from comparison of the two isoform crystal structures · source_derived_draft · unverified_draft

    ### asa-three-residues-decide Acetylated cyclooxygenase-2 is essentially a lipoxygenase making 15(R)- and 11(R)-hydroxyeicosatetraenoic acid whereas acetylated cyclooxygenase-1 is unable to oxidise arachidonic acid to any products, and site-directed mutagenesis of Val-434, Arg-513 and Val-523 in mouse cyclooxygenase-2 to their cyclooxygenase-1 equivalents abrogated 11- and 15-HETE production after aspirin treatment, confirming these residues as the major isoform selectivity determinants; V228F and G533A produced wild-type-like profiles but on acetylation neither could make HETE products, suggesting arachidonic acid orientates in an L-shaped binding configuration. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Three amino acids are the whole difference between an enzyme aspirin kills and one aspirin repurposes. organism: Mouse enzyme tissue_or_cell_type: Cyclooxygenase-2 experimental_model: Site-directed mutagenesis of mouse COX-2 residues predicted from comparison of the two isoform crystal structures limitations: Explains the isoform difference residue by residue. Murine enzyme, and the L-shaped substrate configuration is an inference from the mutant product profiles. exposure: Val-434, Arg-513, Val-523, Val-228 and Gly-533 mutated towards their cyclooxygenase-1 equivalents, then acetylated evidence_span: {"source_cache": "artifacts/aspirin-research/10692466.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9da1ede1fbf95d6f42d4bb15dc08b5d1869549a7cd94cbfa9da9f9865fd780ff", "start_char": 0, "end_char": 2055, "text_sha256": "9da1ede1fbf95d6f42d4bb15dc08b5d1869549a7cd94cbfa9da9f9865fd780ff"} [asa-p10692466] Spatial requirements for 15-(R)-hydroxy-5Z,8Z,11Z, 13E-eicosatetraenoic acid synthesis within the cyclooxygenase active site of murine COX-2. Why acetylated COX-1 does not synthesize 15-(R)-hete. (2000). https://pubmed.ncbi.nlm.nih.gov/10692466/ DOI: 10.1074/jbc.275.9.6586

    Complete structured claim and evidence

15. Both the S516M mutant and the aspirin-acetylated form of cyclooxygenase-2 synthesise 15(R)-HETE with apparent Km values for arachidonic acid within tenfold of untreated enzyme and with similar time courses of turnover-dependent inactivation, and the conversion of arachidonic acid to 15-HETE by acetylated cyclooxygenase-2 is an efficient process providing a unique mechanism among non-steroidal anti-inflammatory drugs that will not lead to arachidonic acid accumulation or shunting to other biosynthetic pathways.

    Aspirin-acetylated cyclooxygenase-2 → 15(R)-hydroxyeicosatetraenoic acid source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/9016346.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b", "start_char": 0, "end_char": 1899, "text_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b"}

    experimental_model

    Kinetic characterisation of aspirin-acetylated cyclooxygenase-2 and the S516M mutant against a panel of non-steroidal anti-inflammatory drugs

    exposure

    Aspirin acetylation and the methionine mutant, tested with indomethacin, diclofenac, meclofenamic acid and selective inhibitors

    limitations

    Quantifies how efficient the new activity is, which most descriptions of the switch do not. Purified and recombinant enzyme rather than intact cells.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Enzyme

    plain_language

    The rerouted enzyme works well enough that arachidonate does not pile up and spill into other pathways.

    primary_references

    [asa-p9016346] Altered sensitivity of aspirin-acetylated prostaglandin G/H synthase-2 to inhibition by nonsteroidal anti-inflammatory drugs. (1997). https://pubmed.ncbi.nlm.nih.gov/9016346/ DOI: 10.1124/mol.51.1.52

    tissue_or_cell_type

    Cyclooxygenase-2

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 260–271

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Kinetic characterisation of aspirin-acetylated cyclooxygenase-2 and the S516M mutant against a panel of non-steroidal anti-inflammatory drugs · source_derived_draft · unverified_draft

    ### asa-the-new-activity-is-efficient Both the S516M mutant and the aspirin-acetylated form of cyclooxygenase-2 synthesise 15(R)-HETE with apparent Km values for arachidonic acid within tenfold of untreated enzyme and with similar time courses of turnover-dependent inactivation, and the conversion of arachidonic acid to 15-HETE by acetylated cyclooxygenase-2 is an efficient process providing a unique mechanism among non-steroidal anti-inflammatory drugs that will not lead to arachidonic acid accumulation or shunting to other biosynthetic pathways. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The rerouted enzyme works well enough that arachidonate does not pile up and spill into other pathways. organism: Enzyme tissue_or_cell_type: Cyclooxygenase-2 experimental_model: Kinetic characterisation of aspirin-acetylated cyclooxygenase-2 and the S516M mutant against a panel of non-steroidal anti-inflammatory drugs limitations: Quantifies how efficient the new activity is, which most descriptions of the switch do not. Purified and recombinant enzyme rather than intact cells. exposure: Aspirin acetylation and the methionine mutant, tested with indomethacin, diclofenac, meclofenamic acid and selective inhibitors evidence_span: {"source_cache": "artifacts/aspirin-research/9016346.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b", "start_char": 0, "end_char": 1899, "text_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b"} [asa-p9016346] Altered sensitivity of aspirin-acetylated prostaglandin G/H synthase-2 to inhibition by nonsteroidal anti-inflammatory drugs. (1997). https://pubmed.ncbi.nlm.nih.gov/9016346/ DOI: 10.1124/mol.51.1.52

    Complete structured claim and evidence

16. The production of 15-HETE by aspirin-modified cyclooxygenase-2 was sensitive to inhibition by most non-steroidal anti-inflammatory drugs including selective cyclooxygenase-2 inhibitors and the inhibition by indomethacin was time-dependent, but two potent structurally related drugs, diclofenac and meclofenamic acid, did not inhibit either the acetylated enzyme or the S516M mutant, so Ser516 plays an important role in the interaction with fenamate inhibitors.

    Diclofenac → 15(R)-hydroxyeicosatetraenoic acid source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/9016346.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b", "start_char": 0, "end_char": 1899, "text_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b"}

    experimental_model

    Kinetic characterisation of aspirin-acetylated cyclooxygenase-2 and the S516M mutant against a panel of non-steroidal anti-inflammatory drugs

    exposure

    Aspirin acetylation and the methionine mutant, tested with indomethacin, diclofenac, meclofenamic acid and selective inhibitors

    limitations

    Quantifies how efficient the new activity is, which most descriptions of the switch do not. Purified and recombinant enzyme rather than intact cells.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Enzyme

    plain_language

    Two common anti-inflammatories cannot touch the rerouted enzyme, because they needed the serine aspirin has taken.

    primary_references

    [asa-p9016346] Altered sensitivity of aspirin-acetylated prostaglandin G/H synthase-2 to inhibition by nonsteroidal anti-inflammatory drugs. (1997). https://pubmed.ncbi.nlm.nih.gov/9016346/ DOI: 10.1124/mol.51.1.52

    tissue_or_cell_type

    Cyclooxygenase-2

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 273–284

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Kinetic characterisation of aspirin-acetylated cyclooxygenase-2 and the S516M mutant against a panel of non-steroidal anti-inflammatory drugs · source_derived_draft · unverified_draft

    ### asa-fenamates-do-not-block-it The production of 15-HETE by aspirin-modified cyclooxygenase-2 was sensitive to inhibition by most non-steroidal anti-inflammatory drugs including selective cyclooxygenase-2 inhibitors and the inhibition by indomethacin was time-dependent, but two potent structurally related drugs, diclofenac and meclofenamic acid, did not inhibit either the acetylated enzyme or the S516M mutant, so Ser516 plays an important role in the interaction with fenamate inhibitors. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Two common anti-inflammatories cannot touch the rerouted enzyme, because they needed the serine aspirin has taken. organism: Enzyme tissue_or_cell_type: Cyclooxygenase-2 experimental_model: Kinetic characterisation of aspirin-acetylated cyclooxygenase-2 and the S516M mutant against a panel of non-steroidal anti-inflammatory drugs limitations: Quantifies how efficient the new activity is, which most descriptions of the switch do not. Purified and recombinant enzyme rather than intact cells. exposure: Aspirin acetylation and the methionine mutant, tested with indomethacin, diclofenac, meclofenamic acid and selective inhibitors evidence_span: {"source_cache": "artifacts/aspirin-research/9016346.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b", "start_char": 0, "end_char": 1899, "text_sha256": "2cc2efefceabbee7bb4f1052db8fc86ee218409fe56981cf92b707c7b0ef531b"} [asa-p9016346] Altered sensitivity of aspirin-acetylated prostaglandin G/H synthase-2 to inhibition by nonsteroidal anti-inflammatory drugs. (1997). https://pubmed.ncbi.nlm.nih.gov/9016346/ DOI: 10.1124/mol.51.1.52

    Complete structured claim and evidence

17. Acetylated cyclooxygenase-2 also retains cyclooxygenase activity forming predominantly 15R-configuration prostaglandins, 70% or 62% 15R by radiolabelled substrate or LC-MS respectively, and although the Km of arachidonic acid for the acetylated enzyme was about threefold lower than for uninhibited enzyme the catalytic efficiency for prostaglandin formation was reduced tenfold through a decrease in Vmax.

    Aspirin-acetylated cyclooxygenase-2 → 15R-configuration prostaglandins source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/30096040.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8", "start_char": 0, "end_char": 1666, "text_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8"}

    experimental_model

    Radiolabelled substrate and LC-MS analysis of aspirin-acetylated COX-2 products, with human leukocytes and platelet aggregation assays

    exposure

    Aspirin acetylation, with lipopolysaccharide-induced cyclooxygenase-2 in leukocytes and a thromboxane receptor agonist on platelets

    limitations

    Shows the acetylated enzyme keeps more of its original chemistry than the HETE story implies, and links the product to a measured platelet effect. Isolated cells rather than treated people.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    The rerouted enzyme has not stopped making prostaglandins; it makes mirror-image ones, more slowly.

    primary_references

    [asa-p30096040] Residual cyclooxygenase activity of aspirin-acetylated COX-2 forms 15 R-prostaglandins that inhibit platelet aggregation. (2019). https://pubmed.ncbi.nlm.nih.gov/30096040/ DOI: 10.1096/fj.201801018r

    tissue_or_cell_type

    Recombinant enzyme and isolated leukocytes and platelets

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 286–297

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Radiolabelled substrate and LC-MS analysis of aspirin-acetylated COX-2 products, with human leukocytes and platelet aggregation assays · source_derived_draft · unverified_draft

    ### asa-it-still-makes-prostaglandins Acetylated cyclooxygenase-2 also retains cyclooxygenase activity forming predominantly 15R-configuration prostaglandins, 70% or 62% 15R by radiolabelled substrate or LC-MS respectively, and although the Km of arachidonic acid for the acetylated enzyme was about threefold lower than for uninhibited enzyme the catalytic efficiency for prostaglandin formation was reduced tenfold through a decrease in Vmax. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The rerouted enzyme has not stopped making prostaglandins; it makes mirror-image ones, more slowly. organism: Human tissue_or_cell_type: Recombinant enzyme and isolated leukocytes and platelets experimental_model: Radiolabelled substrate and LC-MS analysis of aspirin-acetylated COX-2 products, with human leukocytes and platelet aggregation assays limitations: Shows the acetylated enzyme keeps more of its original chemistry than the HETE story implies, and links the product to a measured platelet effect. Isolated cells rather than treated people. exposure: Aspirin acetylation, with lipopolysaccharide-induced cyclooxygenase-2 in leukocytes and a thromboxane receptor agonist on platelets evidence_span: {"source_cache": "artifacts/aspirin-research/30096040.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8", "start_char": 0, "end_char": 1666, "text_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8"} [asa-p30096040] Residual cyclooxygenase activity of aspirin-acetylated COX-2 forms 15 R-prostaglandins that inhibit platelet aggregation. (2019). https://pubmed.ncbi.nlm.nih.gov/30096040/ DOI: 10.1096/fj.201801018r

    Complete structured claim and evidence

18. Aspirin increased 15R-prostaglandin D2 but not 15R-prostaglandin E2 in isolated human leukocytes activated with lipopolysaccharide to induce cyclooxygenase-2, and 15R-prostaglandin D2 inhibited human platelet aggregation induced by the thromboxane receptor agonist U46,619, an effect abrogated by an antagonist of the DP1 prostanoid receptor, so 15R-prostaglandins are novel products of aspirin therapy that may contribute to its antiplatelet and other effects.

    15R-prostaglandin D2 → Cyclooxygenase-dependent platelet aggregation source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/30096040.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8", "start_char": 0, "end_char": 1666, "text_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8"}

    experimental_model

    Radiolabelled substrate and LC-MS analysis of aspirin-acetylated COX-2 products, with human leukocytes and platelet aggregation assays

    exposure

    Aspirin acetylation, with lipopolysaccharide-induced cyclooxygenase-2 in leukocytes and a thromboxane receptor agonist on platelets

    limitations

    Shows the acetylated enzyme keeps more of its original chemistry than the HETE story implies, and links the product to a measured platelet effect. Isolated cells rather than treated people.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    One of those mirror-image products is itself an antiplatelet agent, working through a different receptor.

    primary_references

    [asa-p30096040] Residual cyclooxygenase activity of aspirin-acetylated COX-2 forms 15 R-prostaglandins that inhibit platelet aggregation. (2019). https://pubmed.ncbi.nlm.nih.gov/30096040/ DOI: 10.1096/fj.201801018r

    tissue_or_cell_type

    Recombinant enzyme and isolated leukocytes and platelets

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 299–310

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Radiolabelled substrate and LC-MS analysis of aspirin-acetylated COX-2 products, with human leukocytes and platelet aggregation assays · source_derived_draft · unverified_draft

    ### asa-15r-pgd2-blocks-platelets Aspirin increased 15R-prostaglandin D2 but not 15R-prostaglandin E2 in isolated human leukocytes activated with lipopolysaccharide to induce cyclooxygenase-2, and 15R-prostaglandin D2 inhibited human platelet aggregation induced by the thromboxane receptor agonist U46,619, an effect abrogated by an antagonist of the DP1 prostanoid receptor, so 15R-prostaglandins are novel products of aspirin therapy that may contribute to its antiplatelet and other effects. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: One of those mirror-image products is itself an antiplatelet agent, working through a different receptor. organism: Human tissue_or_cell_type: Recombinant enzyme and isolated leukocytes and platelets experimental_model: Radiolabelled substrate and LC-MS analysis of aspirin-acetylated COX-2 products, with human leukocytes and platelet aggregation assays limitations: Shows the acetylated enzyme keeps more of its original chemistry than the HETE story implies, and links the product to a measured platelet effect. Isolated cells rather than treated people. exposure: Aspirin acetylation, with lipopolysaccharide-induced cyclooxygenase-2 in leukocytes and a thromboxane receptor agonist on platelets evidence_span: {"source_cache": "artifacts/aspirin-research/30096040.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8", "start_char": 0, "end_char": 1666, "text_sha256": "2bd9c817ec4fe31752028634955f604eb00829efc93a72d5fc7e22be7f5739b8"} [asa-p30096040] Residual cyclooxygenase activity of aspirin-acetylated COX-2 forms 15 R-prostaglandins that inhibit platelet aggregation. (2019). https://pubmed.ncbi.nlm.nih.gov/30096040/ DOI: 10.1096/fj.201801018r

    Complete structured claim and evidence

19. Aspirin triggered transcellular biosynthesis of a previously unrecognised class of eicosanoids during coincubations of human umbilical vein endothelial cells and neutrophils, generated with aspirin but not by indomethacin, salicylate or dexamethasone, enhanced by interleukin-1-beta which induced cyclooxygenase-2 but not 15-lipoxygenase; four products proved to be 15R-epimers of lipoxins, two were potent inhibitors of leukotriene B4-mediated neutrophil adhesion to endothelium, with 15-epi-lipoxin A4 active in the nanomolar range, an example of a drug pirating endogenous biosynthetic mechanisms to trigger new mediators.

    Aspirin / acetylsalicylic acid → Aspirin-triggered 15R-epimeric lipoxins source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/7568157.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d9e7b80265068fb60f67e97c9d46de7a25e0099151b6d7fbc688f70a29ee9b9b", "start_char": 0, "end_char": 2036, "text_sha256": "d9e7b80265068fb60f67e97c9d46de7a25e0099151b6d7fbc688f70a29ee9b9b"}

    experimental_model

    Coincubations of human umbilical vein endothelial cells and neutrophils with physical characterisation of the products

    exposure

    Aspirin compared against indomethacin, salicylate and dexamethasone, with interleukin-1-beta induction and several costimuli

    limitations

    The comparator set is what makes this strong: three other anti-inflammatory drugs including salicylate failed to produce the same products. It is a cell coincubation, and the nanomolar activity is measured on adhesion in vitro.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human cells

    plain_language

    Aspirin, and not the other anti-inflammatories tested, makes the body build a mediator it otherwise never makes.

    primary_references

    [asa-p7568157] Aspirin triggers previously undescribed bioactive eicosanoids by human endothelial cell-leukocyte interactions. (1995). https://pubmed.ncbi.nlm.nih.gov/7568157/ DOI: 10.1073/pnas.92.21.9475

    tissue_or_cell_type

    Endothelium and neutrophils

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 312–323

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Coincubations of human umbilical vein endothelial cells and neutrophils with physical characterisation of the products · source_derived_draft · unverified_draft

    ### asa-aspirin-triggers-lipoxins Aspirin triggered transcellular biosynthesis of a previously unrecognised class of eicosanoids during coincubations of human umbilical vein endothelial cells and neutrophils, generated with aspirin but not by indomethacin, salicylate or dexamethasone, enhanced by interleukin-1-beta which induced cyclooxygenase-2 but not 15-lipoxygenase; four products proved to be 15R-epimers of lipoxins, two were potent inhibitors of leukotriene B4-mediated neutrophil adhesion to endothelium, with 15-epi-lipoxin A4 active in the nanomolar range, an example of a drug pirating endogenous biosynthetic mechanisms to trigger new mediators. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Aspirin, and not the other anti-inflammatories tested, makes the body build a mediator it otherwise never makes. organism: Human cells tissue_or_cell_type: Endothelium and neutrophils experimental_model: Coincubations of human umbilical vein endothelial cells and neutrophils with physical characterisation of the products limitations: The comparator set is what makes this strong: three other anti-inflammatory drugs including salicylate failed to produce the same products. It is a cell coincubation, and the nanomolar activity is measured on adhesion in vitro. exposure: Aspirin compared against indomethacin, salicylate and dexamethasone, with interleukin-1-beta induction and several costimuli evidence_span: {"source_cache": "artifacts/aspirin-research/7568157.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d9e7b80265068fb60f67e97c9d46de7a25e0099151b6d7fbc688f70a29ee9b9b", "start_char": 0, "end_char": 2036, "text_sha256": "d9e7b80265068fb60f67e97c9d46de7a25e0099151b6d7fbc688f70a29ee9b9b"} [asa-p7568157] Aspirin triggers previously undescribed bioactive eicosanoids by human endothelial cell-leukocyte interactions. (1995). https://pubmed.ncbi.nlm.nih.gov/7568157/ DOI: 10.1073/pnas.92.21.9475

    Complete structured claim and evidence

20. Aspirin maximally acetylates one monomer of human cyclooxygenase-2, the acetylated monomer forming 15-hydroperoxyeicosatetraenoic acid from arachidonic acid while the nonacetylated partner monomer forms mainly prostaglandin H2 but at only 15 to 20% of the rate of native enzyme, conclusions based on diclofenac binding a single monomer of native enzyme having an unmodified Ser530 and on diclofenac inhibiting prostaglandin H2 but not 15-hydroperoxyeicosatetraenoic acid formation by the acetylated enzyme.

    Aspirin / acetylsalicylic acid → The cyclooxygenase-2 homodimer source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/20194532.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf", "start_char": 0, "end_char": 1441, "text_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf"}

    experimental_model

    Quantitative characterisation of aspirin-acetylated human cyclooxygenase-2 monomers using diclofenac to distinguish them

    exposure

    Aspirin acetylation with arachidonic, eicosapentaenoic and docosahexaenoic acid as substrates

    limitations

    Measures rates rather than presence, and reaches a much less generous estimate of resolvin formation than the reports it tests. It is an in vitro enzyme study, so it does not exclude accumulation or amplification in a living tissue.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human enzyme

    plain_language

    Aspirin only ever modifies half of the paired enzyme, and the untouched half carries on at a fifth speed.

    primary_references

    [asa-p20194532] Asymmetric acetylation of the cyclooxygenase-2 homodimer by aspirin and its effects on the oxygenation of arachidonic, eicosapentaenoic, and docosahexaenoic acids. (2010). https://pubmed.ncbi.nlm.nih.gov/20194532/ DOI: 10.1124/mol.109.063115

    tissue_or_cell_type

    Cyclooxygenase-2 homodimer

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 325–336

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Quantitative characterisation of aspirin-acetylated human cyclooxygenase-2 monomers using diclofenac to distinguish them · source_derived_draft · unverified_draft

    ### asa-only-one-monomer-is-acetylated Aspirin maximally acetylates one monomer of human cyclooxygenase-2, the acetylated monomer forming 15-hydroperoxyeicosatetraenoic acid from arachidonic acid while the nonacetylated partner monomer forms mainly prostaglandin H2 but at only 15 to 20% of the rate of native enzyme, conclusions based on diclofenac binding a single monomer of native enzyme having an unmodified Ser530 and on diclofenac inhibiting prostaglandin H2 but not 15-hydroperoxyeicosatetraenoic acid formation by the acetylated enzyme. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Aspirin only ever modifies half of the paired enzyme, and the untouched half carries on at a fifth speed. organism: Human enzyme tissue_or_cell_type: Cyclooxygenase-2 homodimer experimental_model: Quantitative characterisation of aspirin-acetylated human cyclooxygenase-2 monomers using diclofenac to distinguish them limitations: Measures rates rather than presence, and reaches a much less generous estimate of resolvin formation than the reports it tests. It is an in vitro enzyme study, so it does not exclude accumulation or amplification in a living tissue. exposure: Aspirin acetylation with arachidonic, eicosapentaenoic and docosahexaenoic acid as substrates evidence_span: {"source_cache": "artifacts/aspirin-research/20194532.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf", "start_char": 0, "end_char": 1441, "text_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf"} [asa-p20194532] Asymmetric acetylation of the cyclooxygenase-2 homodimer by aspirin and its effects on the oxygenation of arachidonic, eicosapentaenoic, and docosahexaenoic acids. (2010). https://pubmed.ncbi.nlm.nih.gov/20194532/ DOI: 10.1124/mol.109.063115

    Complete structured claim and evidence

21. Characterising the oxygenation of omega-3 fatty acids by aspirin-treated human cyclooxygenase-2 in vitro suggested that the 18R- and 17R-resolvins putatively involved in resolution of inflammation, reportedly formed via aspirin-acetylated cyclooxygenase-2 from eicosapentaenoic and docosahexaenoic acid, could be formed only at low rates corresponding to less than 1 and 5% respectively of the rates of formation of prostaglandin H2 by the native enzyme.

    Aspirin-acetylated cyclooxygenase-2 → 17R and 18R resolvins source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/20194532.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf", "start_char": 0, "end_char": 1441, "text_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf"}

    experimental_model

    Quantitative characterisation of aspirin-acetylated human cyclooxygenase-2 monomers using diclofenac to distinguish them

    exposure

    Aspirin acetylation with arachidonic, eicosapentaenoic and docosahexaenoic acid as substrates

    limitations

    Measures rates rather than presence, and reaches a much less generous estimate of resolvin formation than the reports it tests. It is an in vitro enzyme study, so it does not exclude accumulation or amplification in a living tissue.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human enzyme

    plain_language

    Measured as rates rather than as presence, the celebrated resolution mediators come out at a fraction of a percent.

    primary_references

    [asa-p20194532] Asymmetric acetylation of the cyclooxygenase-2 homodimer by aspirin and its effects on the oxygenation of arachidonic, eicosapentaenoic, and docosahexaenoic acids. (2010). https://pubmed.ncbi.nlm.nih.gov/20194532/ DOI: 10.1124/mol.109.063115

    tissue_or_cell_type

    Cyclooxygenase-2 homodimer

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 338–349

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Quantitative characterisation of aspirin-acetylated human cyclooxygenase-2 monomers using diclofenac to distinguish them · source_derived_draft · unverified_draft

    ### asa-resolvin-rates-are-low Characterising the oxygenation of omega-3 fatty acids by aspirin-treated human cyclooxygenase-2 in vitro suggested that the 18R- and 17R-resolvins putatively involved in resolution of inflammation, reportedly formed via aspirin-acetylated cyclooxygenase-2 from eicosapentaenoic and docosahexaenoic acid, could be formed only at low rates corresponding to less than 1 and 5% respectively of the rates of formation of prostaglandin H2 by the native enzyme. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Measured as rates rather than as presence, the celebrated resolution mediators come out at a fraction of a percent. organism: Human enzyme tissue_or_cell_type: Cyclooxygenase-2 homodimer experimental_model: Quantitative characterisation of aspirin-acetylated human cyclooxygenase-2 monomers using diclofenac to distinguish them limitations: Measures rates rather than presence, and reaches a much less generous estimate of resolvin formation than the reports it tests. It is an in vitro enzyme study, so it does not exclude accumulation or amplification in a living tissue. exposure: Aspirin acetylation with arachidonic, eicosapentaenoic and docosahexaenoic acid as substrates evidence_span: {"source_cache": "artifacts/aspirin-research/20194532.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf", "start_char": 0, "end_char": 1441, "text_sha256": "09427e18078449741ea9ea42dc91a16f50ca9f604ec05c4decbb255731104eaf"} [asa-p20194532] Asymmetric acetylation of the cyclooxygenase-2 homodimer by aspirin and its effects on the oxygenation of arachidonic, eicosapentaenoic, and docosahexaenoic acids. (2010). https://pubmed.ncbi.nlm.nih.gov/20194532/ DOI: 10.1124/mol.109.063115

    Complete structured claim and evidence

22. A mechanistic hypothesis identifying steric shielding as the main determinant of oxygenation stereospecificity in cyclooxygenase-2 is supported by a computational model which accurately reproduces experimental oxygenation patterns on both native and aspirin-inhibited enzyme, addressing why Ser530 acetylation shifts the stereochemistry and relative abundance of generated products.

    Steric blockade of a substrate channel by an introduced side chain → 15(R)-hydroxyeicosatetraenoic acid source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/23786234.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "bdf3d33c4cc14fc4b2190180d78b68971144966047e654abb59b9ca7a83ab824", "start_char": 0, "end_char": 834, "text_sha256": "bdf3d33c4cc14fc4b2190180d78b68971144966047e654abb59b9ca7a83ab824"}

    experimental_model

    Computational modelling of oxygenation stereospecificity in native and aspirin-acetylated cyclooxygenase-2

    exposure

    A mechanistic hypothesis tested against experimental oxygenation patterns

    limitations

    A computational model reproducing known patterns, not a new measurement. It offers an explanation for the switch rather than evidence that it occurs.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Enzyme

    plain_language

    The same bulk that blocks the first enzyme explains why the second one makes mirror-image products.

    primary_references

    [asa-p23786234] A mechanistic hypothesis for the aspirin-induced switch in lipid mediator production by cyclooxygenase-2. (2013). https://pubmed.ncbi.nlm.nih.gov/23786234/ DOI: 10.1021/ja402870k

    tissue_or_cell_type

    Cyclooxygenase-2

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 351–362

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Computational modelling of oxygenation stereospecificity in native and aspirin-acetylated cyclooxygenase-2 · source_derived_draft · unverified_draft

    ### asa-steric-shielding-explains-stereochemistry A mechanistic hypothesis identifying steric shielding as the main determinant of oxygenation stereospecificity in cyclooxygenase-2 is supported by a computational model which accurately reproduces experimental oxygenation patterns on both native and aspirin-inhibited enzyme, addressing why Ser530 acetylation shifts the stereochemistry and relative abundance of generated products. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The same bulk that blocks the first enzyme explains why the second one makes mirror-image products. organism: Enzyme tissue_or_cell_type: Cyclooxygenase-2 experimental_model: Computational modelling of oxygenation stereospecificity in native and aspirin-acetylated cyclooxygenase-2 limitations: A computational model reproducing known patterns, not a new measurement. It offers an explanation for the switch rather than evidence that it occurs. exposure: A mechanistic hypothesis tested against experimental oxygenation patterns evidence_span: {"source_cache": "artifacts/aspirin-research/23786234.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "bdf3d33c4cc14fc4b2190180d78b68971144966047e654abb59b9ca7a83ab824", "start_char": 0, "end_char": 834, "text_sha256": "bdf3d33c4cc14fc4b2190180d78b68971144966047e654abb59b9ca7a83ab824"} [asa-p23786234] A mechanistic hypothesis for the aspirin-induced switch in lipid mediator production by cyclooxygenase-2. (2013). https://pubmed.ncbi.nlm.nih.gov/23786234/ DOI: 10.1021/ja402870k

    Complete structured claim and evidence

23. Single doses of 6 to 100 milligrams of aspirin produced a linear inhibition of platelet thromboxane B2 production ranging from 12 to 95% after 24 hours, and a daily dose of 0.45 milligrams per kilogram for 7 days produced cumulative and virtually complete inhibition without significantly reducing urinary excretion of prostaglandin E2, prostaglandin F2-alpha or 6-keto-prostaglandin F1-alpha in both men and women, an effect maintained unaltered through one month of therapy with no cumulative inhibition of renal prostaglandin synthesis, while furosemide-induced renal prostacyclin synthesis and renin release were unaffected.

    Aspirin / acetylsalicylic acid → Serum thromboxane B2 after whole blood clotting source_derived_draftungraded
    Experimental context and source evidence

    availability_state

    biomarker_context Imported condition classification; unverified.

    evidence_span

    {"source_cache": "artifacts/aspirin-research/7045161.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "58bb82650f675f1ba3dd21b6dcf3d83b71a56c437a687f72d2af9dcdc07abadb", "start_char": 0, "end_char": 1963, "text_sha256": "58bb82650f675f1ba3dd21b6dcf3d83b71a56c437a687f72d2af9dcdc07abadb"}

    experimental_model

    Radioimmunoassay of serum thromboxane B2 and urinary prostaglandin excretion in 46 healthy subjects given single or repeated oral aspirin

    exposure

    Single doses of 6 to 100 milligrams, and 0.45 milligrams per kilogram daily for 7 days and up to one month

    limitations

    The dose-ranging design across 46 subjects is what makes the selectivity claim testable. Urinary prostaglandin excretion is an indirect measure of renal synthesis.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    A very small daily dose wipes out platelet thromboxane and leaves the kidney untouched.

    primary_references

    [asa-p7045161] Selective cumulative inhibition of platelet thromboxane production by low-dose aspirin in healthy subjects. (1982). https://pubmed.ncbi.nlm.nih.gov/7045161/ DOI: 10.1172/jci110576

    tissue_or_cell_type

    Platelets and kidney

    trigger_kind

    biomarker_context Imported condition classification; unverified.

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 364–375

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Radioimmunoassay of serum thromboxane B2 and urinary prostaglandin excretion in 46 healthy subjects given single or repeated oral aspirin · source_derived_draft · unverified_draft

    ### asa-cumulative-and-selective Single doses of 6 to 100 milligrams of aspirin produced a linear inhibition of platelet thromboxane B2 production ranging from 12 to 95% after 24 hours, and a daily dose of 0.45 milligrams per kilogram for 7 days produced cumulative and virtually complete inhibition without significantly reducing urinary excretion of prostaglandin E2, prostaglandin F2-alpha or 6-keto-prostaglandin F1-alpha in both men and women, an effect maintained unaltered through one month of therapy with no cumulative inhibition of renal prostaglandin synthesis, while furosemide-induced renal prostacyclin synthesis and renin release were unaffected. Condition category: biomarker_context nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: A very small daily dose wipes out platelet thromboxane and leaves the kidney untouched. organism: Human tissue_or_cell_type: Platelets and kidney experimental_model: Radioimmunoassay of serum thromboxane B2 and urinary prostaglandin excretion in 46 healthy subjects given single or repeated oral aspirin limitations: The dose-ranging design across 46 subjects is what makes the selectivity claim testable. Urinary prostaglandin excretion is an indirect measure of renal synthesis. exposure: Single doses of 6 to 100 milligrams, and 0.45 milligrams per kilogram daily for 7 days and up to one month evidence_span: {"source_cache": "artifacts/aspirin-research/7045161.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "58bb82650f675f1ba3dd21b6dcf3d83b71a56c437a687f72d2af9dcdc07abadb", "start_char": 0, "end_char": 1963, "text_sha256": "58bb82650f675f1ba3dd21b6dcf3d83b71a56c437a687f72d2af9dcdc07abadb"} [asa-p7045161] Selective cumulative inhibition of platelet thromboxane production by low-dose aspirin in healthy subjects. (1982). https://pubmed.ncbi.nlm.nih.gov/7045161/ DOI: 10.1172/jci110576

    Complete structured claim and evidence

24. Two hours after 150 or 300 milligrams of aspirin, 81 to 100% inhibition of vein-wall prostacyclin synthesis was demonstrated with 86% inhibition still evident in one subject at eight hours, while platelet thromboxane B2 production was completely inhibited for more than 24 hours, leading to the conclusion that there is little difference between the initial inhibitory response of platelet cyclooxygenase and that of vessel-wall cyclooxygenase to these doses, and that the prolonged bleeding time after aspirin is not a consequence of selective inhibition of platelet thromboxane production.

    Aspirin / acetylsalicylic acid → Prostacyclin synthesis by the vessel wall source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/7003384.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b54b61e084b6ec232b9c86ef5de713b0d5a57def2525eb6d3d50e5d7768e5c38", "start_char": 0, "end_char": 1148, "text_sha256": "b54b61e084b6ec232b9c86ef5de713b0d5a57def2525eb6d3d50e5d7768e5c38"}

    experimental_model

    Vein segments and platelets sampled from five subjects before and after aspirin, with radioimmunoassay of stable metabolites

    exposure

    150 or 300 milligrams of oral aspirin

    limitations

    Five subjects, and the vein segments are surgically obtained rather than sampled in situ. Its conclusion is the opposite of the low-dose study in this collection and the doses differ tenfold.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    At ordinary tablet doses the vessel wall is hit about as hard as the platelet.

    primary_references

    [asa-p7003384] Inhibition of prostacyclin and platelet thromboxane A2 after low-dose aspirin. (1981). https://pubmed.ncbi.nlm.nih.gov/7003384/ DOI: 10.1056/nejm198101083040203

    tissue_or_cell_type

    Vein wall and platelets

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 377–388

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Vein segments and platelets sampled from five subjects before and after aspirin, with radioimmunoassay of stable metabolites · source_derived_draft · unverified_draft

    ### asa-no-selectivity-at-higher-dose Two hours after 150 or 300 milligrams of aspirin, 81 to 100% inhibition of vein-wall prostacyclin synthesis was demonstrated with 86% inhibition still evident in one subject at eight hours, while platelet thromboxane B2 production was completely inhibited for more than 24 hours, leading to the conclusion that there is little difference between the initial inhibitory response of platelet cyclooxygenase and that of vessel-wall cyclooxygenase to these doses, and that the prolonged bleeding time after aspirin is not a consequence of selective inhibition of platelet thromboxane production. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: At ordinary tablet doses the vessel wall is hit about as hard as the platelet. organism: Human tissue_or_cell_type: Vein wall and platelets experimental_model: Vein segments and platelets sampled from five subjects before and after aspirin, with radioimmunoassay of stable metabolites limitations: Five subjects, and the vein segments are surgically obtained rather than sampled in situ. Its conclusion is the opposite of the low-dose study in this collection and the doses differ tenfold. exposure: 150 or 300 milligrams of oral aspirin evidence_span: {"source_cache": "artifacts/aspirin-research/7003384.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b54b61e084b6ec232b9c86ef5de713b0d5a57def2525eb6d3d50e5d7768e5c38", "start_char": 0, "end_char": 1148, "text_sha256": "b54b61e084b6ec232b9c86ef5de713b0d5a57def2525eb6d3d50e5d7768e5c38"} [asa-p7003384] Inhibition of prostacyclin and platelet thromboxane A2 after low-dose aspirin. (1981). https://pubmed.ncbi.nlm.nih.gov/7003384/ DOI: 10.1056/nejm198101083040203

    Complete structured claim and evidence

25. In rabbits lower doses of aspirin produced major inhibition of platelet aggregation and minor inhibition of prostacyclin synthesis while higher doses inhibited both, in humans a dose equivalent to approximately one quarter of one 300 milligram tablet consistently produced major inhibition of cyclooxygenase-dependent platelet aggregation in a pattern similar to that in rabbits where most prostacyclin synthetic capacity was not inhibited, and it took rabbit vasculature over 24 hours to return to control prostacyclin synthetic capacity after a single high dose.

    Aspirin / acetylsalicylic acid → Cyclooxygenase-dependent platelet aggregation source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/6156337.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e0d904fae5d8c006bd180213b6b2cbc88c87bb103b9c8b8872705330c349b074", "start_char": 0, "end_char": 1502, "text_sha256": "e0d904fae5d8c006bd180213b6b2cbc88c87bb103b9c8b8872705330c349b074"}

    experimental_model

    Human and rabbit platelet aggregation with rabbit aortic prostacyclin synthesis measured across aspirin doses

    exposure

    Graded oral aspirin doses, sampled three hours after dosing, with recovery followed over 24 hours in rabbits

    limitations

    Sets the dose at which the two tissues start to separate, but the vascular arm is rabbit aorta and the human arm measures aggregation rather than prostacyclin.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human and rabbit

    plain_language

    About a quarter of a tablet stops the platelets while mostly leaving the vessel wall alone.

    primary_references

    [asa-p6156337] Effect of oral aspirin dose on platelet aggregation and vascular prostacyclin (PGI2) synthesis in humans and rabbits. (1980). https://pubmed.ncbi.nlm.nih.gov/6156337/ DOI: 10.1097/00005344-198007000-00006

    tissue_or_cell_type

    Platelets and aorta

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 390–401

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human and rabbit platelet aggregation with rabbit aortic prostacyclin synthesis measured across aspirin doses · source_derived_draft · unverified_draft

    ### asa-a-quarter-tablet In rabbits lower doses of aspirin produced major inhibition of platelet aggregation and minor inhibition of prostacyclin synthesis while higher doses inhibited both, in humans a dose equivalent to approximately one quarter of one 300 milligram tablet consistently produced major inhibition of cyclooxygenase-dependent platelet aggregation in a pattern similar to that in rabbits where most prostacyclin synthetic capacity was not inhibited, and it took rabbit vasculature over 24 hours to return to control prostacyclin synthetic capacity after a single high dose. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: About a quarter of a tablet stops the platelets while mostly leaving the vessel wall alone. organism: Human and rabbit tissue_or_cell_type: Platelets and aorta experimental_model: Human and rabbit platelet aggregation with rabbit aortic prostacyclin synthesis measured across aspirin doses limitations: Sets the dose at which the two tissues start to separate, but the vascular arm is rabbit aorta and the human arm measures aggregation rather than prostacyclin. exposure: Graded oral aspirin doses, sampled three hours after dosing, with recovery followed over 24 hours in rabbits evidence_span: {"source_cache": "artifacts/aspirin-research/6156337.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e0d904fae5d8c006bd180213b6b2cbc88c87bb103b9c8b8872705330c349b074", "start_char": 0, "end_char": 1502, "text_sha256": "e0d904fae5d8c006bd180213b6b2cbc88c87bb103b9c8b8872705330c349b074"} [asa-p6156337] Effect of oral aspirin dose on platelet aggregation and vascular prostacyclin (PGI2) synthesis in humans and rabbits. (1980). https://pubmed.ncbi.nlm.nih.gov/6156337/ DOI: 10.1097/00005344-198007000-00006

    Complete structured claim and evidence

26. Following ingestion of 650 milligrams of acetylsalicylate as compressed tablets, platelet cyclooxygenase activity was inhibited 95% within 45 minutes, enzyme activity was observed to increase within 8 hours and reached 10% of control level by 24 hours, a pattern suggesting that only circulating platelets are affected by ingestion; enteric-coated tablets gave comparable inhibition with a delayed onset reflecting delayed appearance of acetylsalicylate in plasma, and returned to control along a similar pattern.

    Aspirin / acetylsalicylic acid → The cyclooxygenase activity of prostaglandin endoperoxide synthase source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/7355437.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "01e0a159576fdabca8185271b0d6acd2e790cff32c06ba1e68906afb3a63544a", "start_char": 0, "end_char": 909, "text_sha256": "01e0a159576fdabca8185271b0d6acd2e790cff32c06ba1e68906afb3a63544a"}

    experimental_model

    High pressure liquid chromatography of plasma acetylsalicylate and salicylate with radiometric platelet cyclooxygenase assay

    exposure

    650 milligrams of aspirin as compressed or enteric-coated tablets

    limitations

    Measures the parent drug and the metabolite separately alongside the enzyme effect, which is exactly the distinction this chapter turns on. Healthy subjects and a single dose.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    The drug catches the platelets that are in the blood at the time, and nothing else.

    primary_references

    [asa-p7355437] Plasma acetylsalicylate and salicylate and platelet cyclooxygenase activity following plain and enteric-coated aspirin. (1980). https://pubmed.ncbi.nlm.nih.gov/7355437/ DOI: 10.1161/01.str.11.1.9

    tissue_or_cell_type

    Plasma and platelets

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 403–414

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · High pressure liquid chromatography of plasma acetylsalicylate and salicylate with radiometric platelet cyclooxygenase assay · source_derived_draft · unverified_draft

    ### asa-only-circulating-platelets Following ingestion of 650 milligrams of acetylsalicylate as compressed tablets, platelet cyclooxygenase activity was inhibited 95% within 45 minutes, enzyme activity was observed to increase within 8 hours and reached 10% of control level by 24 hours, a pattern suggesting that only circulating platelets are affected by ingestion; enteric-coated tablets gave comparable inhibition with a delayed onset reflecting delayed appearance of acetylsalicylate in plasma, and returned to control along a similar pattern. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The drug catches the platelets that are in the blood at the time, and nothing else. organism: Human tissue_or_cell_type: Plasma and platelets experimental_model: High pressure liquid chromatography of plasma acetylsalicylate and salicylate with radiometric platelet cyclooxygenase assay limitations: Measures the parent drug and the metabolite separately alongside the enzyme effect, which is exactly the distinction this chapter turns on. Healthy subjects and a single dose. exposure: 650 milligrams of aspirin as compressed or enteric-coated tablets evidence_span: {"source_cache": "artifacts/aspirin-research/7355437.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "01e0a159576fdabca8185271b0d6acd2e790cff32c06ba1e68906afb3a63544a", "start_char": 0, "end_char": 909, "text_sha256": "01e0a159576fdabca8185271b0d6acd2e790cff32c06ba1e68906afb3a63544a"} [asa-p7355437] Plasma acetylsalicylate and salicylate and platelet cyclooxygenase activity following plain and enteric-coated aspirin. (1980). https://pubmed.ncbi.nlm.nih.gov/7355437/ DOI: 10.1161/01.str.11.1.9

    Complete structured claim and evidence

27. Megakaryocyte thromboxane production was depressed by 70% and that of platelets by 85% at two hours after 20 milligrams per kilogram oral aspirin, full megakaryocyte thromboxane recovery occurred by 72 hours and preceded complete platelet recovery by 24 hours, megakaryocyte synthesis showed substantial recovery by 36 hours while platelet recovery did not begin for 24 hours, and the authors conclude that thromboxane synthesis develops in rat megakaryocytes after approximately 48 hours of cytoplasmic differentiation toward platelet shedding.

    Megakaryocyte → Recovery of platelet cyclooxygenase activity after aspirin source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/6812167.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "fd3cbdc85225aabdb23690613d2ba4bd49151f144c362d6121721eb45e969389", "start_char": 0, "end_char": 1366, "text_sha256": "fd3cbdc85225aabdb23690613d2ba4bd49151f144c362d6121721eb45e969389"}

    experimental_model

    Radioimmunoassay of megakaryocyte and platelet thromboxane B2 recovery in rats after a single oral aspirin dose

    exposure

    20 milligrams per kilogram oral aspirin dissolved in dimethyl sulphoxide

    limitations

    Follows the precursor cell rather than the platelet, which is where the recovery kinetics are actually set. A rat study and the maturation timing is inferred from transit times.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Rat

    plain_language

    The marrow recovers first and the blood follows, because new platelets have to be built and released.

    primary_references

    [asa-p6812167] Aspirin inhibits rat megakaryocyte thromboxane synthesis. (1982). https://pubmed.ncbi.nlm.nih.gov/6812167/ DOI: 10.1016/0090-6980(82)90128-9

    tissue_or_cell_type

    Bone marrow megakaryocytes and platelets

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 416–427

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Radioimmunoassay of megakaryocyte and platelet thromboxane B2 recovery in rats after a single oral aspirin dose · source_derived_draft · unverified_draft

    ### asa-recovery-starts-in-the-marrow Megakaryocyte thromboxane production was depressed by 70% and that of platelets by 85% at two hours after 20 milligrams per kilogram oral aspirin, full megakaryocyte thromboxane recovery occurred by 72 hours and preceded complete platelet recovery by 24 hours, megakaryocyte synthesis showed substantial recovery by 36 hours while platelet recovery did not begin for 24 hours, and the authors conclude that thromboxane synthesis develops in rat megakaryocytes after approximately 48 hours of cytoplasmic differentiation toward platelet shedding. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The marrow recovers first and the blood follows, because new platelets have to be built and released. organism: Rat tissue_or_cell_type: Bone marrow megakaryocytes and platelets experimental_model: Radioimmunoassay of megakaryocyte and platelet thromboxane B2 recovery in rats after a single oral aspirin dose limitations: Follows the precursor cell rather than the platelet, which is where the recovery kinetics are actually set. A rat study and the maturation timing is inferred from transit times. exposure: 20 milligrams per kilogram oral aspirin dissolved in dimethyl sulphoxide evidence_span: {"source_cache": "artifacts/aspirin-research/6812167.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "fd3cbdc85225aabdb23690613d2ba4bd49151f144c362d6121721eb45e969389", "start_char": 0, "end_char": 1366, "text_sha256": "fd3cbdc85225aabdb23690613d2ba4bd49151f144c362d6121721eb45e969389"} [asa-p6812167] Aspirin inhibits rat megakaryocyte thromboxane synthesis. (1982). https://pubmed.ncbi.nlm.nih.gov/6812167/ DOI: 10.1016/0090-6980(82)90128-9

    Complete structured claim and evidence

28. In human megakaryocytic cell lines a single 10 micromolar aspirin exposure suppressed thromboxane B2 by 90% and 85% respectively with full recovery within 48 to 72 hours, selective cyclooxygenase-1 inhibition by SC-560 reduced thromboxane B2 by more than 75% whereas cyclooxygenase-2 inhibition by NS-398 had minimal effect, and repeated exposure every 24 hours produced concentration- and time-dependent suppression reaching 89% by day 2 at 1 micromolar and 73% by day 4 at 0.1 micromolar, with delayed recovery likely reflecting de novo synthesis of cyclooxygenase-1 protein.

    Cyclooxygenase-1 (PTGS1) → Thromboxane A2 source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/41265381.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "88710110438cddd108a51822aeb63c5f0a8125192eecc85eeeaf1edf3c3d85cc", "start_char": 0, "end_char": 2110, "text_sha256": "88710110438cddd108a51822aeb63c5f0a8125192eecc85eeeaf1edf3c3d85cc"}

    experimental_model

    Aspirin pharmacodynamics in MEG-01 and CHRF-288-11 human megakaryocytic cell lines with selective isoform inhibitors

    exposure

    Single and repeated aspirin exposures from 0.1 to 10 micromolar, with SC-560 and NS-398 as isoform probes

    limitations

    A surrogate for a tissue that cannot ethically be sampled repeatedly. Cell lines rather than primary megakaryocytes, which the authors state.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human cells

    plain_language

    The precursor cell makes its thromboxane with the first enzyme, and has to build new enzyme to recover.

    primary_references

    [asa-p41265381] Aspirin inhibition and recovery of cyclooxygenase activity and thromboxane biosynthesis in human megakaryocytes: a translational surrogate model. (2025). https://pubmed.ncbi.nlm.nih.gov/41265381/ DOI: 10.1016/j.jpet.2025.103762

    tissue_or_cell_type

    Megakaryocytic cell lines

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 429–440

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Aspirin pharmacodynamics in MEG-01 and CHRF-288-11 human megakaryocytic cell lines with selective isoform inhibitors · source_derived_draft · unverified_draft

    ### asa-megakaryocyte-cox1 In human megakaryocytic cell lines a single 10 micromolar aspirin exposure suppressed thromboxane B2 by 90% and 85% respectively with full recovery within 48 to 72 hours, selective cyclooxygenase-1 inhibition by SC-560 reduced thromboxane B2 by more than 75% whereas cyclooxygenase-2 inhibition by NS-398 had minimal effect, and repeated exposure every 24 hours produced concentration- and time-dependent suppression reaching 89% by day 2 at 1 micromolar and 73% by day 4 at 0.1 micromolar, with delayed recovery likely reflecting de novo synthesis of cyclooxygenase-1 protein. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The precursor cell makes its thromboxane with the first enzyme, and has to build new enzyme to recover. organism: Human cells tissue_or_cell_type: Megakaryocytic cell lines experimental_model: Aspirin pharmacodynamics in MEG-01 and CHRF-288-11 human megakaryocytic cell lines with selective isoform inhibitors limitations: A surrogate for a tissue that cannot ethically be sampled repeatedly. Cell lines rather than primary megakaryocytes, which the authors state. exposure: Single and repeated aspirin exposures from 0.1 to 10 micromolar, with SC-560 and NS-398 as isoform probes evidence_span: {"source_cache": "artifacts/aspirin-research/41265381.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "88710110438cddd108a51822aeb63c5f0a8125192eecc85eeeaf1edf3c3d85cc", "start_char": 0, "end_char": 2110, "text_sha256": "88710110438cddd108a51822aeb63c5f0a8125192eecc85eeeaf1edf3c3d85cc"} [asa-p41265381] Aspirin inhibition and recovery of cyclooxygenase activity and thromboxane biosynthesis in human megakaryocytes: a translational surrogate model. (2025). https://pubmed.ncbi.nlm.nih.gov/41265381/ DOI: 10.1016/j.jpet.2025.103762

    Complete structured claim and evidence

29. Platelet function and prostaglandin synthesis recovered completely 26 hours after ingestion of ibuprofen but remained compromised 26 hours after taking aspirin, and when 650 milligrams of aspirin was administered after ibuprofen, platelet function and cyclooxygenase activity recovered as completely at 26 hours as in platelets exposed to ibuprofen alone, so prior exposure to ibuprofen in vivo completely protected cyclooxygenase from the irreversible effects of aspirin.

    Ibuprofen → Aspirin / acetylsalicylic acid source_derived_draftungraded
    Experimental context and source evidence

    availability_state

    biomarker_context Imported condition classification; unverified.

    evidence_span

    {"source_cache": "artifacts/aspirin-research/6411052.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a685344a88574182dbad6f8d70308dce88384a63ed0c561ccaec4d522000b132", "start_char": 0, "end_char": 1551, "text_sha256": "a685344a88574182dbad6f8d70308dce88384a63ed0c561ccaec4d522000b132"}

    experimental_model

    Platelet aggregation and cyclooxygenase activity in subjects given ibuprofen before aspirin, in vitro and in vivo

    exposure

    Ibuprofen ingestion followed by 650 milligrams of aspirin, with recovery followed to 26 hours

    limitations

    The observation is clean and has been confirmed since. The authors’ inference from it, that aspirin must act on the heme group rather than by acetylating the protein, is contradicted by the mutant and crystallographic records in this collection and is not adopted here.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    Take ibuprofen first and aspirin never gets its chance; the protection wears off in a day like ibuprofen, not like aspirin.

    primary_references

    [asa-p6411052] Ibuprofen protects platelet cyclooxygenase from irreversible inhibition by aspirin. (1983). https://pubmed.ncbi.nlm.nih.gov/6411052/ DOI: 10.1161/01.atv.3.4.383

    tissue_or_cell_type

    Platelets

    trigger_kind

    biomarker_context Imported condition classification; unverified.

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 442–453

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Platelet aggregation and cyclooxygenase activity in subjects given ibuprofen before aspirin, in vitro and in vivo · source_derived_draft · unverified_draft

    ### asa-ibuprofen-blocks-aspirin Platelet function and prostaglandin synthesis recovered completely 26 hours after ingestion of ibuprofen but remained compromised 26 hours after taking aspirin, and when 650 milligrams of aspirin was administered after ibuprofen, platelet function and cyclooxygenase activity recovered as completely at 26 hours as in platelets exposed to ibuprofen alone, so prior exposure to ibuprofen in vivo completely protected cyclooxygenase from the irreversible effects of aspirin. Condition category: biomarker_context nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Take ibuprofen first and aspirin never gets its chance; the protection wears off in a day like ibuprofen, not like aspirin. organism: Human tissue_or_cell_type: Platelets experimental_model: Platelet aggregation and cyclooxygenase activity in subjects given ibuprofen before aspirin, in vitro and in vivo limitations: The observation is clean and has been confirmed since. The authors’ inference from it, that aspirin must act on the heme group rather than by acetylating the protein, is contradicted by the mutant and crystallographic records in this collection and is not adopted here. exposure: Ibuprofen ingestion followed by 650 milligrams of aspirin, with recovery followed to 26 hours evidence_span: {"source_cache": "artifacts/aspirin-research/6411052.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a685344a88574182dbad6f8d70308dce88384a63ed0c561ccaec4d522000b132", "start_char": 0, "end_char": 1551, "text_sha256": "a685344a88574182dbad6f8d70308dce88384a63ed0c561ccaec4d522000b132"} [asa-p6411052] Ibuprofen protects platelet cyclooxygenase from irreversible inhibition by aspirin. (1983). https://pubmed.ncbi.nlm.nih.gov/6411052/ DOI: 10.1161/01.atv.3.4.383

    Complete structured claim and evidence

30. Although ibuprofen, naproxen and celecoxib all had the potential to compete with aspirin for access to the substrate binding channel of cyclooxygenase-1 in vitro, measuring aspirin target engagement directly by mass spectrometry after a single therapeutic dose of each followed by 325 milligrams of aspirin revealed a potent drug-drug interaction between ibuprofen and aspirin and between naproxen and aspirin but not between celecoxib and aspirin.

    Naproxen → Aspirin / acetylsalicylic acid source_derived_draftungraded
    Experimental context and source evidence

    availability_state

    biomarker_context Imported condition classification; unverified.

    evidence_span

    {"source_cache": "artifacts/aspirin-research/25385584.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b2de8f18887f336c8c735f7ffbd1b72b92e5da43aa6388c229590dea120439f2", "start_char": 0, "end_char": 1242, "text_sha256": "b2de8f18887f336c8c735f7ffbd1b72b92e5da43aa6388c229590dea120439f2"}

    experimental_model

    Mass-spectrometric assay of cyclooxygenase-1 acetylation in platelets from volunteers given an NSAID followed by aspirin

    exposure

    A single therapeutic dose of ibuprofen, naproxen or celecoxib followed by 325 milligrams of aspirin

    limitations

    Measures target engagement directly rather than inferring it from platelet function, and separates the drugs. A single dose of each, in volunteers rather than patients.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    Ibuprofen and naproxen block aspirin in people; celecoxib does not.

    primary_references

    [asa-p25385584] Differential impairment of aspirin-dependent platelet cyclooxygenase acetylation by nonsteroidal antiinflammatory drugs. (2014). https://pubmed.ncbi.nlm.nih.gov/25385584/ DOI: 10.1073/pnas.1406997111

    tissue_or_cell_type

    Platelets

    trigger_kind

    biomarker_context Imported condition classification; unverified.

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 455–466

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Mass-spectrometric assay of cyclooxygenase-1 acetylation in platelets from volunteers given an NSAID followed by aspirin · source_derived_draft · unverified_draft

    ### asa-which-nsaids-interact Although ibuprofen, naproxen and celecoxib all had the potential to compete with aspirin for access to the substrate binding channel of cyclooxygenase-1 in vitro, measuring aspirin target engagement directly by mass spectrometry after a single therapeutic dose of each followed by 325 milligrams of aspirin revealed a potent drug-drug interaction between ibuprofen and aspirin and between naproxen and aspirin but not between celecoxib and aspirin. Condition category: biomarker_context nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Ibuprofen and naproxen block aspirin in people; celecoxib does not. organism: Human tissue_or_cell_type: Platelets experimental_model: Mass-spectrometric assay of cyclooxygenase-1 acetylation in platelets from volunteers given an NSAID followed by aspirin limitations: Measures target engagement directly rather than inferring it from platelet function, and separates the drugs. A single dose of each, in volunteers rather than patients. exposure: A single therapeutic dose of ibuprofen, naproxen or celecoxib followed by 325 milligrams of aspirin evidence_span: {"source_cache": "artifacts/aspirin-research/25385584.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b2de8f18887f336c8c735f7ffbd1b72b92e5da43aa6388c229590dea120439f2", "start_char": 0, "end_char": 1242, "text_sha256": "b2de8f18887f336c8c735f7ffbd1b72b92e5da43aa6388c229590dea120439f2"} [asa-p25385584] Differential impairment of aspirin-dependent platelet cyclooxygenase acetylation by nonsteroidal antiinflammatory drugs. (2014). https://pubmed.ncbi.nlm.nih.gov/25385584/ DOI: 10.1073/pnas.1406997111

    Complete structured claim and evidence

31. The anti-inflammatory drugs sodium salicylate and aspirin inhibited activation of nuclear factor kappa B, an inhibition which prevented degradation of the inhibitor I-kappa-B so that nuclear factor kappa B was retained in the cytosol, and both also inhibited nuclear factor kappa B-dependent transcription from the immunoglobulin kappa enhancer and the human immunodeficiency virus long terminal repeat in transfected T cells.

    Salicylate / salicylic acid → Activation of nuclear factor kappa B source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/8052854.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d1d488e1bc53706da4f733f3fecc2bb981c09c0aa2dccae2bac9fac1bb04cec1", "start_char": 0, "end_char": 737, "text_sha256": "d1d488e1bc53706da4f733f3fecc2bb981c09c0aa2dccae2bac9fac1bb04cec1"}

    experimental_model

    Electrophoretic mobility shift and reporter transcription assays in transfected T cells

    exposure

    Sodium salicylate and aspirin applied to nuclear factor kappa B activation

    limitations

    A cell-based mechanism recorded at the concentrations used in the assay, which are far above those reached by antiplatelet dosing. It does not distinguish the two compounds from one another.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human cells

    plain_language

    Both compounds keep an inflammatory master switch locked out of the nucleus.

    primary_references

    [asa-p8052854] Inhibition of NF-kappa B by sodium salicylate and aspirin. (1994). https://pubmed.ncbi.nlm.nih.gov/8052854/ DOI: 10.1126/science.8052854

    tissue_or_cell_type

    T lymphocytes

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 468–479

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Electrophoretic mobility shift and reporter transcription assays in transfected T cells · source_derived_draft · unverified_draft

    ### asa-salicylate-blocks-nfkb The anti-inflammatory drugs sodium salicylate and aspirin inhibited activation of nuclear factor kappa B, an inhibition which prevented degradation of the inhibitor I-kappa-B so that nuclear factor kappa B was retained in the cytosol, and both also inhibited nuclear factor kappa B-dependent transcription from the immunoglobulin kappa enhancer and the human immunodeficiency virus long terminal repeat in transfected T cells. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Both compounds keep an inflammatory master switch locked out of the nucleus. organism: Human cells tissue_or_cell_type: T lymphocytes experimental_model: Electrophoretic mobility shift and reporter transcription assays in transfected T cells limitations: A cell-based mechanism recorded at the concentrations used in the assay, which are far above those reached by antiplatelet dosing. It does not distinguish the two compounds from one another. exposure: Sodium salicylate and aspirin applied to nuclear factor kappa B activation evidence_span: {"source_cache": "artifacts/aspirin-research/8052854.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d1d488e1bc53706da4f733f3fecc2bb981c09c0aa2dccae2bac9fac1bb04cec1", "start_char": 0, "end_char": 737, "text_sha256": "d1d488e1bc53706da4f733f3fecc2bb981c09c0aa2dccae2bac9fac1bb04cec1"} [asa-p8052854] Inhibition of NF-kappa B by sodium salicylate and aspirin. (1994). https://pubmed.ncbi.nlm.nih.gov/8052854/ DOI: 10.1126/science.8052854

    Complete structured claim and evidence

32. Sodium salicylate inhibited activation of nuclear factor kappa B by preventing phosphorylation and subsequent degradation of I-kappa-B-alpha without affecting tumour necrosis factor alpha-induced phosphorylation of ATF-2, blocked the increase in adhesion molecule messenger RNA and gave dose-dependent inhibition of surface vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 with higher doses required for endothelial-leukocyte adhesion molecule 1, and inhibited transendothelial migration of neutrophils; indomethacin, a nonsalicylate cyclooxygenase inhibitor, had no effect on surface expression, suggesting the effects were not due to inhibition of cyclooxygenase.

    Salicylate / salicylic acid → Surface expression of endothelial leukocyte adhesion molecules source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/8621937.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9b5aff676845bd0a47f25a0f63564880f70af7667b5ab9d667cece58d05356f1", "start_char": 0, "end_char": 1767, "text_sha256": "9b5aff676845bd0a47f25a0f63564880f70af7667b5ab9d667cece58d05356f1"}

    experimental_model

    Adhesion molecule expression, neutrophil adhesion and transendothelial migration in human umbilical vein endothelial cells

    exposure

    Sodium salicylate against tumour necrosis factor alpha stimulation, with indomethacin as a cyclooxygenase control

    limitations

    The indomethacin control is the important part: it shows the effect is not a cyclooxygenase effect. High salicylate concentrations, which the authors relate to high-dose therapy rather than to antiplatelet dosing.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human cells

    plain_language

    A cyclooxygenase blocker does nothing here, so this arm of salicylate is not about prostaglandins at all.

    primary_references

    [asa-p8621937] Salicylates inhibit I kappa B-alpha phosphorylation, endothelial-leukocyte adhesion molecule expression, and neutrophil transmigration. (1996). https://pubmed.ncbi.nlm.nih.gov/8621937/ DOI: 10.4049/jimmunol.156.10.3961

    tissue_or_cell_type

    Endothelium

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 481–492

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Adhesion molecule expression, neutrophil adhesion and transendothelial migration in human umbilical vein endothelial cells · source_derived_draft · unverified_draft

    ### asa-not-a-cyclooxygenase-effect Sodium salicylate inhibited activation of nuclear factor kappa B by preventing phosphorylation and subsequent degradation of I-kappa-B-alpha without affecting tumour necrosis factor alpha-induced phosphorylation of ATF-2, blocked the increase in adhesion molecule messenger RNA and gave dose-dependent inhibition of surface vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 with higher doses required for endothelial-leukocyte adhesion molecule 1, and inhibited transendothelial migration of neutrophils; indomethacin, a nonsalicylate cyclooxygenase inhibitor, had no effect on surface expression, suggesting the effects were not due to inhibition of cyclooxygenase. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: A cyclooxygenase blocker does nothing here, so this arm of salicylate is not about prostaglandins at all. organism: Human cells tissue_or_cell_type: Endothelium experimental_model: Adhesion molecule expression, neutrophil adhesion and transendothelial migration in human umbilical vein endothelial cells limitations: The indomethacin control is the important part: it shows the effect is not a cyclooxygenase effect. High salicylate concentrations, which the authors relate to high-dose therapy rather than to antiplatelet dosing. exposure: Sodium salicylate against tumour necrosis factor alpha stimulation, with indomethacin as a cyclooxygenase control evidence_span: {"source_cache": "artifacts/aspirin-research/8621937.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "9b5aff676845bd0a47f25a0f63564880f70af7667b5ab9d667cece58d05356f1", "start_char": 0, "end_char": 1767, "text_sha256": "9b5aff676845bd0a47f25a0f63564880f70af7667b5ab9d667cece58d05356f1"} [asa-p8621937] Salicylates inhibit I kappa B-alpha phosphorylation, endothelial-leukocyte adhesion molecule expression, and neutrophil transmigration. (1996). https://pubmed.ncbi.nlm.nih.gov/8621937/ DOI: 10.4049/jimmunol.156.10.3961

    Complete structured claim and evidence

33. At concentrations reached in plasma after administration of salsalate or of aspirin at high doses, salicylate activates AMP-activated protein kinase by binding at the same site as the synthetic activator A-769662 to cause allosteric activation and inhibition of dephosphorylation of the activating phosphorylation site threonine-172, and in knockout mice the effects of salicylate to increase fat utilisation and to lower plasma fatty acids in vivo were lost.

    Salicylate / salicylic acid → AMP-activated protein kinase complexes source_derived_draftungraded
    Experimental context and source evidence

    availability_state

    biomarker_context Imported condition classification; unverified.

    evidence_span

    {"source_cache": "artifacts/aspirin-research/22517326.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1a48863bf252421416f67d62acb18c9f44f170075c5aff6f775eba14bba2b1b4", "start_char": 0, "end_char": 887, "text_sha256": "1a48863bf252421416f67d62acb18c9f44f170075c5aff6f775eba14bba2b1b4"}

    experimental_model

    Allosteric activation and dephosphorylation assays with AMP-activated protein kinase knockout mice

    exposure

    Salicylate at concentrations reached in plasma after salsalate or high-dose aspirin, against the synthetic activator A-769662

    limitations

    The knockout arm ties the whole-animal effect to the kinase. The concentrations are those of high-dose salicylate therapy, not of antiplatelet aspirin, which the authors state explicitly.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human enzyme and mouse

    plain_language

    The old plant compound switches on the cell’s energy sensor directly, at doses far above a daily aspirin.

    primary_references

    [asa-p22517326] The ancient drug salicylate directly activates AMP-activated protein kinase. (2012). https://pubmed.ncbi.nlm.nih.gov/22517326/ DOI: 10.1126/science.1215327

    tissue_or_cell_type

    AMP-activated protein kinase

    trigger_kind

    biomarker_context Imported condition classification; unverified.

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 494–505

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Allosteric activation and dephosphorylation assays with AMP-activated protein kinase knockout mice · source_derived_draft · unverified_draft

    ### asa-salicylate-activates-ampk At concentrations reached in plasma after administration of salsalate or of aspirin at high doses, salicylate activates AMP-activated protein kinase by binding at the same site as the synthetic activator A-769662 to cause allosteric activation and inhibition of dephosphorylation of the activating phosphorylation site threonine-172, and in knockout mice the effects of salicylate to increase fat utilisation and to lower plasma fatty acids in vivo were lost. Condition category: biomarker_context nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The old plant compound switches on the cell’s energy sensor directly, at doses far above a daily aspirin. organism: Human enzyme and mouse tissue_or_cell_type: AMP-activated protein kinase experimental_model: Allosteric activation and dephosphorylation assays with AMP-activated protein kinase knockout mice limitations: The knockout arm ties the whole-animal effect to the kinase. The concentrations are those of high-dose salicylate therapy, not of antiplatelet aspirin, which the authors state explicitly. exposure: Salicylate at concentrations reached in plasma after salsalate or high-dose aspirin, against the synthetic activator A-769662 evidence_span: {"source_cache": "artifacts/aspirin-research/22517326.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1a48863bf252421416f67d62acb18c9f44f170075c5aff6f775eba14bba2b1b4", "start_char": 0, "end_char": 887, "text_sha256": "1a48863bf252421416f67d62acb18c9f44f170075c5aff6f775eba14bba2b1b4"} [asa-p22517326] The ancient drug salicylate directly activates AMP-activated protein kinase. (2012). https://pubmed.ncbi.nlm.nih.gov/22517326/ DOI: 10.1126/science.1215327

    Complete structured claim and evidence

34. Intracellular salicylate concentrations increased within five minutes in both rat fast-twitch and slow-twitch muscle, threonine-172 phosphorylation of the AMP-activated protein kinase alpha subunit increased dose- and time-dependently with increases in both alpha-1 and alpha-2 activity, and these were accompanied by increased 3-O-methyl-D-glucose transport and decreases in ATP, phosphocreatine and glycogen, while phosphorylation of insulin receptor substrate 1, Akt and p70 S6 kinase was unchanged.

    Salicylate / salicylic acid → Insulin-independent glucose transport in skeletal muscle source_derived_draftungraded
    Experimental context and source evidence

    availability_state

    biomarker_context Imported condition classification; unverified.

    evidence_span

    {"source_cache": "artifacts/aspirin-research/25256746.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e8cd347665e1de7dc2cadee06da087e2526d4fc11aefef6f7ce15cb33f6234c2", "start_char": 0, "end_char": 1171, "text_sha256": "e8cd347665e1de7dc2cadee06da087e2526d4fc11aefef6f7ce15cb33f6234c2"}

    experimental_model

    Incubation of rat fast-twitch epitrochlearis and slow-twitch soleus muscle with salicylate

    exposure

    Salicylate applied to isolated muscle with glucose transport and nucleotide measurements

    limitations

    Adds the tissue and the energy measurements. Isolated muscle at concentrations set by the incubation buffer, which is not a plasma concentration.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Rat

    plain_language

    Muscle takes up more glucose without any help from insulin, and its energy stores fall while it happens.

    primary_references

    [asa-p25256746] Salicylate acutely stimulates 5'-AMP-activated protein kinase and insulin-independent glucose transport in rat skeletal muscles. (2014). https://pubmed.ncbi.nlm.nih.gov/25256746/ DOI: 10.1016/j.bbrc.2014.09.066

    tissue_or_cell_type

    Skeletal muscle

    trigger_kind

    biomarker_context Imported condition classification; unverified.

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 507–518

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Incubation of rat fast-twitch epitrochlearis and slow-twitch soleus muscle with salicylate · source_derived_draft · unverified_draft

    ### asa-muscle-glucose-uptake Intracellular salicylate concentrations increased within five minutes in both rat fast-twitch and slow-twitch muscle, threonine-172 phosphorylation of the AMP-activated protein kinase alpha subunit increased dose- and time-dependently with increases in both alpha-1 and alpha-2 activity, and these were accompanied by increased 3-O-methyl-D-glucose transport and decreases in ATP, phosphocreatine and glycogen, while phosphorylation of insulin receptor substrate 1, Akt and p70 S6 kinase was unchanged. Condition category: biomarker_context nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Muscle takes up more glucose without any help from insulin, and its energy stores fall while it happens. organism: Rat tissue_or_cell_type: Skeletal muscle experimental_model: Incubation of rat fast-twitch epitrochlearis and slow-twitch soleus muscle with salicylate limitations: Adds the tissue and the energy measurements. Isolated muscle at concentrations set by the incubation buffer, which is not a plasma concentration. exposure: Salicylate applied to isolated muscle with glucose transport and nucleotide measurements evidence_span: {"source_cache": "artifacts/aspirin-research/25256746.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e8cd347665e1de7dc2cadee06da087e2526d4fc11aefef6f7ce15cb33f6234c2", "start_char": 0, "end_char": 1171, "text_sha256": "e8cd347665e1de7dc2cadee06da087e2526d4fc11aefef6f7ce15cb33f6234c2"} [asa-p25256746] Salicylate acutely stimulates 5'-AMP-activated protein kinase and insulin-independent glucose transport in rat skeletal muscles. (2014). https://pubmed.ncbi.nlm.nih.gov/25256746/ DOI: 10.1016/j.bbrc.2014.09.066

    Complete structured claim and evidence

35. Several authors have reported that salicylate blocks and reverses aspirin inhibition of prostaglandin synthesis by platelets and arterial wall, but when rats were given sodium salicylate at 15 or 100 milligrams per kilogram two minutes before aspirin at 10 milligrams per kilogram, a significant antithrombotic effect of aspirin was observed in all cases regardless of prior salicylate administration with results similar to aspirin alone, so competition between salicylate and aspirin as reported in vitro does not appear to significantly affect the in vivo antithrombotic action in this model.

    Salicylate / salicylic acid → Arterial thrombosis source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/6792646.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "55b09486e54c42e6ecdac3476a0ae8b9d9819f06b5b01a9fc33087fd621a9c82", "start_char": 0, "end_char": 767, "text_sha256": "55b09486e54c42e6ecdac3476a0ae8b9d9819f06b5b01a9fc33087fd621a9c82"}

    experimental_model

    Electrically induced carotid artery thrombosis in male rats with salicylate pretreatment

    exposure

    Sodium salicylate 15 or 100 milligrams per kilogram intravenously two minutes before aspirin 10 milligrams per kilogram

    limitations

    A direct in vivo test of an in vitro observation. One model, one species, and thrombus generation measured indirectly by downstream temperature.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Rat

    plain_language

    The metabolite gets in the drug’s way in a test tube, but giving it first did not stop aspirin working in a rat.

    primary_references

    [asa-p6792646] Non-interference by salicylate with aspirin inhibition of arterial thrombosis in rats. (1981). https://pubmed.ncbi.nlm.nih.gov/6792646/ DOI: 10.1016/0161-4630(81)90052-5

    tissue_or_cell_type

    Carotid artery

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 520–531

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Electrically induced carotid artery thrombosis in male rats with salicylate pretreatment · source_derived_draft · unverified_draft

    ### asa-antagonism-not-seen-in-vivo Several authors have reported that salicylate blocks and reverses aspirin inhibition of prostaglandin synthesis by platelets and arterial wall, but when rats were given sodium salicylate at 15 or 100 milligrams per kilogram two minutes before aspirin at 10 milligrams per kilogram, a significant antithrombotic effect of aspirin was observed in all cases regardless of prior salicylate administration with results similar to aspirin alone, so competition between salicylate and aspirin as reported in vitro does not appear to significantly affect the in vivo antithrombotic action in this model. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The metabolite gets in the drug’s way in a test tube, but giving it first did not stop aspirin working in a rat. organism: Rat tissue_or_cell_type: Carotid artery experimental_model: Electrically induced carotid artery thrombosis in male rats with salicylate pretreatment limitations: A direct in vivo test of an in vitro observation. One model, one species, and thrombus generation measured indirectly by downstream temperature. exposure: Sodium salicylate 15 or 100 milligrams per kilogram intravenously two minutes before aspirin 10 milligrams per kilogram evidence_span: {"source_cache": "artifacts/aspirin-research/6792646.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "55b09486e54c42e6ecdac3476a0ae8b9d9819f06b5b01a9fc33087fd621a9c82", "start_char": 0, "end_char": 767, "text_sha256": "55b09486e54c42e6ecdac3476a0ae8b9d9819f06b5b01a9fc33087fd621a9c82"} [asa-p6792646] Non-interference by salicylate with aspirin inhibition of arterial thrombosis in rats. (1981). https://pubmed.ncbi.nlm.nih.gov/6792646/ DOI: 10.1016/0161-4630(81)90052-5

    Complete structured claim and evidence

36. Neither sodium salicylate nor acetylsalicylic acid given intravenously affected intramural pH or caused ulceration at luminal pH 7 or 3.5, but at luminal pH 1 both compounds caused ulceration and subtle changes in net ion fluxes without altering intramural pH, and since intravenous sodium salicylate and acetylsalicylic acid both cause ulceration but only acetylsalicylic acid alters prostaglandin synthesis, interference with prostaglandin metabolism does not appear to be a prerequisite for the occurrence of ulceration.

    Salicylate / salicylic acid → Gastric antral mucosal ulceration source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/7064099.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b1e175ec209c9a177b7514b5931c3b02d3ca7c09a0d3629d55fcbd2b2f9088b4", "start_char": 0, "end_char": 1514, "text_sha256": "b1e175ec209c9a177b7514b5931c3b02d3ca7c09a0d3629d55fcbd2b2f9088b4"}

    experimental_model

    Measurement of intramural pH in the antral mucosa with ulceration scoring across luminal pH and routes of administration

    exposure

    Luminal and intravenous sodium salicylate and acetylsalicylic acid at luminal pH 7, 3.5 and 1

    limitations

    Separates the two compounds and the two routes against a controlled luminal acidity. The comparison of prostaglandin effects is stated rather than measured in this study.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Animal

    plain_language

    The metabolite, which does not touch prostaglandins, ulcerates the stomach just as the drug does, so prostaglandins are not the whole story.

    primary_references

    [asa-p7064099] Effects of sodium salicylate and acetylsalicylic acid on intramural pH and ulceration of rabbit antral mucosa. (1982). https://pubmed.ncbi.nlm.nih.gov/7064099/

    tissue_or_cell_type

    Gastric antral mucosa

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 533–544

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Measurement of intramural pH in the antral mucosa with ulceration scoring across luminal pH and routes of administration · source_derived_draft · unverified_draft

    ### asa-ulceration-without-prostaglandins Neither sodium salicylate nor acetylsalicylic acid given intravenously affected intramural pH or caused ulceration at luminal pH 7 or 3.5, but at luminal pH 1 both compounds caused ulceration and subtle changes in net ion fluxes without altering intramural pH, and since intravenous sodium salicylate and acetylsalicylic acid both cause ulceration but only acetylsalicylic acid alters prostaglandin synthesis, interference with prostaglandin metabolism does not appear to be a prerequisite for the occurrence of ulceration. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The metabolite, which does not touch prostaglandins, ulcerates the stomach just as the drug does, so prostaglandins are not the whole story. organism: Animal tissue_or_cell_type: Gastric antral mucosa experimental_model: Measurement of intramural pH in the antral mucosa with ulceration scoring across luminal pH and routes of administration limitations: Separates the two compounds and the two routes against a controlled luminal acidity. The comparison of prostaglandin effects is stated rather than measured in this study. exposure: Luminal and intravenous sodium salicylate and acetylsalicylic acid at luminal pH 7, 3.5 and 1 evidence_span: {"source_cache": "artifacts/aspirin-research/7064099.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b1e175ec209c9a177b7514b5931c3b02d3ca7c09a0d3629d55fcbd2b2f9088b4", "start_char": 0, "end_char": 1514, "text_sha256": "b1e175ec209c9a177b7514b5931c3b02d3ca7c09a0d3629d55fcbd2b2f9088b4"} [asa-p7064099] Effects of sodium salicylate and acetylsalicylic acid on intramural pH and ulceration of rabbit antral mucosa. (1982). https://pubmed.ncbi.nlm.nih.gov/7064099/

    Complete structured claim and evidence

37. The adverse effect of aspirin in asthmatics is often attributed to inhibition of the synthesis and release of defensive modulatory endogenous prostaglandins in the lungs, removing their negative feedback on allergic mediator release, and in addition work suggests diversion of arachidonic acid metabolism via the lipoxygenase pathway after cyclooxygenase inhibition, leading to formation of hydroperoxy acids and leukotrienes whose accumulation in sensitive individuals could explain the mechanism of aspirin-induced asthma.

    Aspirin / acetylsalicylic acid → Diversion of unmetabolised arachidonate into the 5-lipoxygenase pathway source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/6113615.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "184fc232146a3837f396109d951c9755155f181c524a3ffaa330645138d8a616", "start_char": 0, "end_char": 2083, "text_sha256": "184fc232146a3837f396109d951c9755155f181c524a3ffaa330645138d8a616"}

    experimental_model

    Review of arachidonate metabolism in airway hyperreactivity and aspirin-induced asthma

    exposure

    Cyclooxygenase inhibition and the proposed diversion of arachidonate into the lipoxygenase pathway

    limitations

    A review from 1981 setting out the shunting hypothesis. It is recorded as the proposal that later work tested, not as evidence that the proposal is right.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    The standard explanation: block one pathway and the raw material spills into another that makes bronchoconstrictors.

    primary_references

    [asa-p6113615] Lipoxygenase pathway and hydroperoxy acids: possible relevance to aspirin-induced asthma and hyperirritability of airways in asthmatics. (1981). https://pubmed.ncbi.nlm.nih.gov/6113615/ DOI: 10.1016/0161-4630(81)90097-5

    tissue_or_cell_type

    Airway

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 546–557

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Review of arachidonate metabolism in airway hyperreactivity and aspirin-induced asthma · source_derived_draft · unverified_draft

    ### asa-shunting-proposed The adverse effect of aspirin in asthmatics is often attributed to inhibition of the synthesis and release of defensive modulatory endogenous prostaglandins in the lungs, removing their negative feedback on allergic mediator release, and in addition work suggests diversion of arachidonic acid metabolism via the lipoxygenase pathway after cyclooxygenase inhibition, leading to formation of hydroperoxy acids and leukotrienes whose accumulation in sensitive individuals could explain the mechanism of aspirin-induced asthma. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The standard explanation: block one pathway and the raw material spills into another that makes bronchoconstrictors. organism: Human tissue_or_cell_type: Airway experimental_model: Review of arachidonate metabolism in airway hyperreactivity and aspirin-induced asthma limitations: A review from 1981 setting out the shunting hypothesis. It is recorded as the proposal that later work tested, not as evidence that the proposal is right. exposure: Cyclooxygenase inhibition and the proposed diversion of arachidonate into the lipoxygenase pathway evidence_span: {"source_cache": "artifacts/aspirin-research/6113615.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "184fc232146a3837f396109d951c9755155f181c524a3ffaa330645138d8a616", "start_char": 0, "end_char": 2083, "text_sha256": "184fc232146a3837f396109d951c9755155f181c524a3ffaa330645138d8a616"} [asa-p6113615] Lipoxygenase pathway and hydroperoxy acids: possible relevance to aspirin-induced asthma and hyperirritability of airways in asthmatics. (1981). https://pubmed.ncbi.nlm.nih.gov/6113615/ DOI: 10.1016/0161-4630(81)90097-5

    Complete structured claim and evidence

38. Excretion of leukotriene E4 was increased by a mean of 361% during aspirin-induced asthma episodes, but the degree of increase for individual patients did not correlate with the degree of bronchospasm or with inhibition of platelet thromboxane B2 formation, so although endogenous synthesis of potent bronchoconstrictor leukotrienes increases during aspirin-induced bronchospasm it appears unlikely that direct shunting of unmetabolised arachidonate into leukotriene synthesis represents the mechanism of aspirin-induced asthma.

    Urinary leukotriene E4 excretion → Aspirin-induced bronchospasm source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/1309376.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "115a13f9e08205c2b6ea376e5a1fcb90cc6887b277041acc114908c7d85f6e05", "start_char": 0, "end_char": 1427, "text_sha256": "115a13f9e08205c2b6ea376e5a1fcb90cc6887b277041acc114908c7d85f6e05"}

    experimental_model

    Urinary leukotriene E4 measured during aspirin-induced asthma episodes across a range of provoking doses

    exposure

    Aspirin doses from 30 to 365 milligrams in individual aspirin-sensitive patients

    limitations

    Tests the shunting hypothesis by asking whether the leukotriene rise tracks the bronchospasm, which it does not. Urinary leukotriene E4 is a whole-body measure rather than an airway one.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    The leukotrienes do rise, but how much they rise says nothing about how badly the patient wheezes.

    primary_references

    [asa-p1309376] Increased excretion of leukotriene E4 during aspirin-induced asthma. (1992). https://pubmed.ncbi.nlm.nih.gov/1309376/

    tissue_or_cell_type

    Airway and urine

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 559–570

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Urinary leukotriene E4 measured during aspirin-induced asthma episodes across a range of provoking doses · source_derived_draft · unverified_draft

    ### asa-shunting-does-not-track Excretion of leukotriene E4 was increased by a mean of 361% during aspirin-induced asthma episodes, but the degree of increase for individual patients did not correlate with the degree of bronchospasm or with inhibition of platelet thromboxane B2 formation, so although endogenous synthesis of potent bronchoconstrictor leukotrienes increases during aspirin-induced bronchospasm it appears unlikely that direct shunting of unmetabolised arachidonate into leukotriene synthesis represents the mechanism of aspirin-induced asthma. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The leukotrienes do rise, but how much they rise says nothing about how badly the patient wheezes. organism: Human tissue_or_cell_type: Airway and urine experimental_model: Urinary leukotriene E4 measured during aspirin-induced asthma episodes across a range of provoking doses limitations: Tests the shunting hypothesis by asking whether the leukotriene rise tracks the bronchospasm, which it does not. Urinary leukotriene E4 is a whole-body measure rather than an airway one. exposure: Aspirin doses from 30 to 365 milligrams in individual aspirin-sensitive patients evidence_span: {"source_cache": "artifacts/aspirin-research/1309376.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "115a13f9e08205c2b6ea376e5a1fcb90cc6887b277041acc114908c7d85f6e05", "start_char": 0, "end_char": 1427, "text_sha256": "115a13f9e08205c2b6ea376e5a1fcb90cc6887b277041acc114908c7d85f6e05"} [asa-p1309376] Increased excretion of leukotriene E4 during aspirin-induced asthma. (1992). https://pubmed.ncbi.nlm.nih.gov/1309376/

    Complete structured claim and evidence

39. After nasal instillation of 12 milligrams of acetylsalicylic acid, significant levels of peptide leukotrienes were detected in sensitive asthmatic patients at 60 minutes in association with a significant increase in symptoms, with no increase in either insensitive patients or healthy subjects, while inhibition of prostaglandin E2 and F2-alpha release was detected in all three groups; aspirin also inhibited prostaglandin D2 release in insensitive asthmatic patients but not in sensitive patients or healthy subjects.

    Aspirin / acetylsalicylic acid → Peptide (cysteinyl) leukotrienes source_derived_draftungraded
    Experimental context and source evidence

    evidence_span

    {"source_cache": "artifacts/aspirin-research/1309968.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a81a9ed941df59e6b8aa8c7c730d9a14766e2b8bd358b712ee464ae96c67e4e2", "start_char": 0, "end_char": 1685, "text_sha256": "a81a9ed941df59e6b8aa8c7c730d9a14766e2b8bd358b712ee464ae96c67e4e2"}

    experimental_model

    Double-blind nasal lavage challenge in ten aspirin-sensitive asthmatics, ten insensitive asthmatics and seven healthy subjects

    exposure

    12 milligrams of acetylsalicylic acid instilled nasally against saline

    limitations

    Three groups including two control groups, with mediators measured directly in the target tissue. Radioimmunoassay of nasal lavage fluid, and a small number per group.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    The drug blocks prostaglandins in everyone, but only in the sensitive patients does a flood of leukotrienes follow.

    primary_references

    [asa-p1309968] Release of peptide leukotriene into nasal secretions after local instillation of aspirin in aspirin-sensitive asthmatic patients. (1992). https://pubmed.ncbi.nlm.nih.gov/1309968/ DOI: 10.1164/ajrccm/145.1.65

    tissue_or_cell_type

    Nasal mucosa

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 572–583

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Double-blind nasal lavage challenge in ten aspirin-sensitive asthmatics, ten insensitive asthmatics and seven healthy subjects · source_derived_draft · unverified_draft

    ### asa-only-sensitive-patients-release After nasal instillation of 12 milligrams of acetylsalicylic acid, significant levels of peptide leukotrienes were detected in sensitive asthmatic patients at 60 minutes in association with a significant increase in symptoms, with no increase in either insensitive patients or healthy subjects, while inhibition of prostaglandin E2 and F2-alpha release was detected in all three groups; aspirin also inhibited prostaglandin D2 release in insensitive asthmatic patients but not in sensitive patients or healthy subjects. Condition category: normal nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: The drug blocks prostaglandins in everyone, but only in the sensitive patients does a flood of leukotrienes follow. organism: Human tissue_or_cell_type: Nasal mucosa experimental_model: Double-blind nasal lavage challenge in ten aspirin-sensitive asthmatics, ten insensitive asthmatics and seven healthy subjects limitations: Three groups including two control groups, with mediators measured directly in the target tissue. Radioimmunoassay of nasal lavage fluid, and a small number per group. exposure: 12 milligrams of acetylsalicylic acid instilled nasally against saline evidence_span: {"source_cache": "artifacts/aspirin-research/1309968.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a81a9ed941df59e6b8aa8c7c730d9a14766e2b8bd358b712ee464ae96c67e4e2", "start_char": 0, "end_char": 1685, "text_sha256": "a81a9ed941df59e6b8aa8c7c730d9a14766e2b8bd358b712ee464ae96c67e4e2"} [asa-p1309968] Release of peptide leukotriene into nasal secretions after local instillation of aspirin in aspirin-sensitive asthmatic patients. (1992). https://pubmed.ncbi.nlm.nih.gov/1309968/ DOI: 10.1164/ajrccm/145.1.65

    Complete structured claim and evidence

40. In young male ferrets made hyperammonaemic and comatose by brief feeding of an arginine-deficient diet, synergism of the three factors hyperammonaemia, influenza infection and aspirin treatment was observed in causing Reye-syndrome-like alterations in serum ammonia, transaminase, ornithine carbamoyltransferase, bilirubin and salicylate levels and in liver lipids, proteins and urea-cycle enzymes; the relationship of aspirin treatment to influenza and ammonia toxicity cannot be examined directly in patients because aspirin is usually started by family members in the prodrome before the syndrome is diagnosed.

    Aspirin / acetylsalicylic acid → Reye syndrome source_derived_draftungraded
    Experimental context and source evidence

    availability_state

    biomarker_context Imported condition classification; unverified.

    evidence_span

    {"source_cache": "artifacts/aspirin-research/6961432.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "53631b4bef8684ad8023f1dcc822f8191323e61fd073a93ce4c4872916cb5beb", "start_char": 0, "end_char": 1430, "text_sha256": "53631b4bef8684ad8023f1dcc822f8191323e61fd073a93ce4c4872916cb5beb"}

    experimental_model

    Factorial study in young male ferrets made hyperammonaemic by brief arginine-deficient feeding

    exposure

    Influenza infection and aspirin treatment, alone and together, in control and hyperammonaemic animals

    limitations

    An animal model of a syndrome whose human definition is clinical, testing three factors that cannot be separated in patients because dosing precedes diagnosis. Synergism is reported across biochemical parameters rather than as a disease endpoint.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Ferret

    plain_language

    In this model aspirin only does damage alongside a viral infection and a failing urea cycle; no one factor is enough.

    primary_references

    [asa-p6961432] Interactions of aspirin and other potential etiologic factors in an animal model of Reye syndrome. (1982). https://pubmed.ncbi.nlm.nih.gov/6961432/ DOI: 10.1073/pnas.79.23.7557

    tissue_or_cell_type

    Liver and blood

    trigger_kind

    biomarker_context Imported condition classification; unverified.

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 585–596

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Factorial study in young male ferrets made hyperammonaemic by brief arginine-deficient feeding · source_derived_draft · unverified_draft

    ### asa-reye-needs-three-factors In young male ferrets made hyperammonaemic and comatose by brief feeding of an arginine-deficient diet, synergism of the three factors hyperammonaemia, influenza infection and aspirin treatment was observed in causing Reye-syndrome-like alterations in serum ammonia, transaminase, ornithine carbamoyltransferase, bilirubin and salicylate levels and in liver lipids, proteins and urea-cycle enzymes; the relationship of aspirin treatment to influenza and ammonia toxicity cannot be examined directly in patients because aspirin is usually started by family members in the prodrome before the syndrome is diagnosed. Condition category: biomarker_context nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: In this model aspirin only does damage alongside a viral infection and a failing urea cycle; no one factor is enough. organism: Ferret tissue_or_cell_type: Liver and blood experimental_model: Factorial study in young male ferrets made hyperammonaemic by brief arginine-deficient feeding limitations: An animal model of a syndrome whose human definition is clinical, testing three factors that cannot be separated in patients because dosing precedes diagnosis. Synergism is reported across biochemical parameters rather than as a disease endpoint. exposure: Influenza infection and aspirin treatment, alone and together, in control and hyperammonaemic animals evidence_span: {"source_cache": "artifacts/aspirin-research/6961432.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "53631b4bef8684ad8023f1dcc822f8191323e61fd073a93ce4c4872916cb5beb", "start_char": 0, "end_char": 1430, "text_sha256": "53631b4bef8684ad8023f1dcc822f8191323e61fd073a93ce4c4872916cb5beb"} [asa-p6961432] Interactions of aspirin and other potential etiologic factors in an animal model of Reye syndrome. (1982). https://pubmed.ncbi.nlm.nih.gov/6961432/ DOI: 10.1073/pnas.79.23.7557

    Complete structured claim and evidence

41. Among 964 colorectal cancer patients, regular aspirin use after diagnosis was associated with superior colorectal-cancer-specific survival in those with mutated-PIK3CA cancers, multivariate hazard ratio for cancer-related death 0.18 with 95% confidence interval 0.06 to 0.61, and superior overall survival at hazard ratio 0.54, whereas among patients with wild-type PIK3CA there was no association with cancer-specific survival at hazard ratio 0.96 or overall survival at 0.94, with the interaction between aspirin and PIK3CA yielding a p value of 0.009.

    Aspirin / acetylsalicylic acid → Colorectal-cancer-specific survival source_derived_draftungraded
    Experimental context and source evidence

    availability_state

    biomarker_context Imported condition classification; unverified.

    evidence_span

    {"source_cache": "artifacts/aspirin-research/23094721.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0fab66fe6fa87b7288d31cfbda54b13b3a1d81fd32302054aa4c791b9d6ede43", "start_char": 0, "end_char": 2456, "text_sha256": "0fab66fe6fa87b7288d31cfbda54b13b3a1d81fd32302054aa4c791b9d6ede43"}

    experimental_model

    Molecular pathological epidemiology in 964 colorectal cancer patients from the Nurses’ Health Study and the Health Professionals Follow-up Study

    exposure

    Regular aspirin use after diagnosis, stratified by tumour PIK3CA mutation status

    limitations

    Observational cohorts with tumour genotyping, not a randomised trial, so aspirin use after diagnosis is chosen rather than assigned and may travel with other differences between patients.

    nutrient_topic

    Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. · Aspirin / acetylsalicylic acid

    organism

    Human

    plain_language

    Aspirin after diagnosis tracked with much better survival, but only in tumours carrying one particular mutation.

    primary_references

    [asa-p23094721] Aspirin use, tumor PIK3CA mutation, and colorectal-cancer survival. (2012). https://pubmed.ncbi.nlm.nih.gov/23094721/ DOI: 10.1056/nejmoa1207756

    tissue_or_cell_type

    Colorectal tumour

    trigger_kind

    biomarker_context Imported condition classification; unverified.

    Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22) · lines 598–609

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Molecular pathological epidemiology in 964 colorectal cancer patients from the Nurses’ Health Study and the Health Professionals Follow-up Study · source_derived_draft · unverified_draft

    ### asa-benefit-tracks-pik3ca Among 964 colorectal cancer patients, regular aspirin use after diagnosis was associated with superior colorectal-cancer-specific survival in those with mutated-PIK3CA cancers, multivariate hazard ratio for cancer-related death 0.18 with 95% confidence interval 0.06 to 0.61, and superior overall survival at hazard ratio 0.54, whereas among patients with wild-type PIK3CA there was no association with cancer-specific survival at hazard ratio 0.96 or overall survival at 0.94, with the interaction between aspirin and PIK3CA yielding a p value of 0.009. Condition category: biomarker_context nutrient_topic: Aspirin research collection; topical membership is not evidence of a direct clinical effect, and aspirin is recorded separately from salicylate, the metabolite it becomes. plain_language: Aspirin after diagnosis tracked with much better survival, but only in tumours carrying one particular mutation. organism: Human tissue_or_cell_type: Colorectal tumour experimental_model: Molecular pathological epidemiology in 964 colorectal cancer patients from the Nurses’ Health Study and the Health Professionals Follow-up Study limitations: Observational cohorts with tumour genotyping, not a randomised trial, so aspirin use after diagnosis is chosen rather than assigned and may travel with other differences between patients. exposure: Regular aspirin use after diagnosis, stratified by tumour PIK3CA mutation status evidence_span: {"source_cache": "artifacts/aspirin-research/23094721.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0fab66fe6fa87b7288d31cfbda54b13b3a1d81fd32302054aa4c791b9d6ede43", "start_char": 0, "end_char": 2456, "text_sha256": "0fab66fe6fa87b7288d31cfbda54b13b3a1d81fd32302054aa4c791b9d6ede43"} [asa-p23094721] Aspirin use, tumor PIK3CA mutation, and colorectal-cancer survival. (2012). https://pubmed.ncbi.nlm.nih.gov/23094721/ DOI: 10.1056/nejmoa1207756

    Complete structured claim and evidence

• Aspirin: the serine it acetylates, the enzyme that acetylation creates, the dose that separates platelet from vessel wall, and the metabolite that is a different drug (2026-09-22)AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · unverified_draftRead preserved source

• Do aspirin-triggered pro-resolving mediators form in amounts that matter?Coincubating human endothelial cells with neutrophils, aspirin and not indomethacin, salicylate or dexamethasone triggered a class of 15R-epimeric lipoxins, two of which inhibited leukotriene B4-mediated neutrophil adhesion with 15-epi-lipoxin A4 active in the nanomolar range. A later quantitative study of the same enzyme measured rates rather than presence and found that the analogous 18R- and 17R-resolvins could be formed only at less than 1% and 5% of the rate at which native enzyme makes prostaglandin H2, and that aspirin acetylates only one monomer of the homodimer, the untouched partner continuing at 15 to 20% of native rate. The two are not measuring the same thing: one asks whether a potent mediator is produced and acts, the other asks how fast. A mediator active at nanomolar concentrations does not need a high rate of formation, and an isolated enzyme preparation does not capture transcellular amplification. The disagreement about whether this route is quantitatively important is recorded, not resolved.Read the recorded disagreement
• Does aspirin spare the vessel wall and kidney while suppressing the platelet?A study in 46 healthy subjects found that 0.45 milligrams per kilogram daily, roughly thirty milligrams, suppressed platelet thromboxane production virtually completely and cumulatively while leaving urinary prostaglandin excretion unchanged and renal prostacyclin still inducible by furosemide. A study in five subjects given 150 or 300 milligrams found 81 to 100% inhibition of vein-wall prostacyclin synthesis alongside complete platelet inhibition, and concluded there is little difference between the two tissues. The doses differ by about tenfold and the tissues sampled differ, vein wall against kidney, so the records are better read as a dose-response than as a flat contradiction: selectivity is a property of the dose rather than of the drug, and it is lost as the dose rises. A third record in this collection, in rabbits and humans, places the transition around a quarter of a 300 milligram tablet. What dose achieves selectivity in a given person is not settled here, and the second study also shows that the prolonged bleeding time is not explained by platelet thromboxane suppression alone.Read the recorded disagreement
• Does the metabolite get in the way of the parent drug?Crystallography places salicylic acid in the cyclooxygenase channel at a site consistent with an antagonistic effect on aspirin, a later and higher-resolution structure finds its binding pose reflects the enzyme-inhibitor complex immediately before acetylation, and the 1981 report notes that several authors had found salicylate blocks and reverses aspirin inhibition of prostaglandin synthesis in vitro. Against that, giving rats salicylate at up to ten times the aspirin dose two minutes beforehand did not reduce aspirin’s antithrombotic effect at all. The structural and in vitro evidence that the two compete for one site is strong; whether the competition matters depends on the concentrations each reaches at the enzyme and on timing, and the in vivo test is a single rat thrombosis model with intravenous dosing. The mechanism is recorded as real and its clinical consequence as unestablished.Read the recorded disagreement
• Is aspirin-induced asthma caused by arachidonate spilling into the leukotriene pathway?The long-standing proposal is that inhibiting cyclooxygenase removes a protective prostaglandin brake and diverts unmetabolised arachidonate into the 5-lipoxygenase pathway, producing bronchoconstrictor leukotrienes. Measuring urinary leukotriene E4 during provoked episodes across doses from 30 to 365 milligrams confirmed a mean 361% rise but found that the size of the rise in an individual predicted neither the severity of bronchospasm nor the degree of cyclooxygenase inhibition, and those authors concluded direct shunting is unlikely to be the mechanism. A nasal challenge study found peptide leukotrienes released only in sensitive patients and not in insensitive patients or healthy subjects, which locates the abnormality in the patient rather than in the amount of substrate diverted. Separately, an enzyme study in this collection notes that aspirin-acetylated cyclooxygenase-2 keeps metabolising arachidonate efficiently and so does not cause it to accumulate. The leukotrienes are real and the dose-dependence on cyclooxygenase potency is real; the simple shunting account of why is not supported.Read the recorded disagreement

• Whether aspirin-triggered lipoxins and resolvins are made in humans in quantities that change anything.They are potent at nanomolar concentrations and were produced by aspirin and not by indomethacin, salicylate or dexamethasone in cell coincubation, but a quantitative study of the same enzyme put resolvin formation at under 1 and 5% of the rate of native prostaglandin synthesis and showed aspirin acetylates only one monomer of the pair.
• What dose separates the platelet from the vessel wall in a given person.Roughly thirty milligrams daily spared renal prostaglandin synthesis across 46 subjects, a quarter of a 300 milligram tablet mostly spared rabbit vascular prostacyclin, and 150 to 300 milligrams inhibited vein-wall prostacyclin by 81 to 100%. No record here identifies the threshold for an individual.
• Why aspirin-sensitive patients release leukotrienes when others given the same drug do not.Prostaglandin E2 and F2-alpha release was inhibited in sensitive patients, insensitive patients and healthy subjects alike, yet peptide leukotrienes rose only in the sensitive group, and the size of the leukotriene rise did not predict the severity of bronchospasm. The abnormality is in the patient and no record here identifies it.
• How much of aspirin’s gastric injury is cyclooxygenase inhibition at all.Intravenous sodium salicylate, which does not alter prostaglandin synthesis, caused antral ulceration at luminal pH 1 just as acetylsalicylic acid did, leading its authors to conclude that interference with prostaglandin metabolism is not a prerequisite for ulceration.
• Which proteins other than cyclooxygenase aspirin acetylates at therapeutic doses, and whether it matters.Aspirin irreversibly acetylates a plant cytochrome P450 at three serines that do not line its substrate channel, and those authors raise the possibility that other P450s carrying similar motifs are targets. No record here surveys human proteins.
• Whether the AMP-activated protein kinase route contributes at antiplatelet doses.Salicylate activates the kinase at concentrations reached after salsalate or high-dose aspirin and the whole-animal effects are lost in knockout mice, but the authors are explicit that these are high-dose concentrations, and no record here measures the kinase after a daily low-dose tablet.

Chapters are assembled from supplied drafts and curated literature summaries. Statements remain unverified against the primary studies, and the ledger is not medical advice.