title: Human platelets generate phospholipid-esterified prostaglandins via cyclooxygenase-1 that are inhibited by low dose aspirin supplementation.
abstract: Oxidized phospholipids (oxPLs) generated nonenzymatically display pleiotropic biological actions in inflammation. Their generation by cellular cyclooxygenases (COXs) is currently unknown. To determine whether platelets generate prostaglandin (PG)-containing oxPLs, then characterize their structures and mechanisms of formation, we applied precursor scanning-tandem mass spectrometry to lipid extracts of agonist-activated human platelets. Thrombin, collagen, or ionophore activation stimulated generation of families of PGs comprising PGE₂ and D₂ attached to four phosphatidylethanolamine (PE) phospholipids (16:0p/, 18:1p/, 18:0p/, and 18:0a/). They formed within 2 to 5 min of activation in a calcium, phospholipase C, p38 MAP kinases, MEK1, cPLA₂, and src tyrosine kinase-dependent manner (28.1 ± 2.3 pg/2 × 10⁸ platelets). Unlike free PGs, they remained cell associated, suggesting an autocrine mode of action. Their generation was inhibited by in vivo aspirin supplementation (75 mg/day) or in vitro COX-1 blockade. Inhibitors of fatty acyl reesterification blocked generation significantly, while purified COX-1 was unable to directly oxidize PE in vitro. This indicates that they form in platelets via rapid esterification of COX-1 derived PGE₂/D₂ into PE. In summary, COX-1 in human platelets acutely mediates membrane phospholipid oxidation via formation of PG-esterified PLs in response to pathophysiological agonists.
authors.affiliation: Institute of Infection and Immunity, School of Medicine, Cardiff University.
authors.forename: Maceler
authors.initials: M
authors.lastname: Aldrovandi
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Hammond
authors.forename: Helen
authors.initials: H
authors.lastname: Podmore
authors.forename: Martin
authors.initials: M
authors.lastname: Hornshaw
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Clark
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Marnett
authors.forename: David A
authors.initials: DA
authors.lastname: Slatter
authors.forename: Robert C
authors.initials: RC
authors.lastname: Murphy
authors.forename: Peter W
authors.initials: PW
authors.lastname: Collins
authors.forename: Valerie B
authors.initials: VB
authors.lastname: O'Donnell
mesh_terms: D001241:Aspirin / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D051545:Cyclooxygenase 1 / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004951:Esterification / Q000187:drug effects; D025461:Feedback, Physiological / Q000187:drug effects; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D015539:Platelet Activation / Q000187:drug effects; D015230:Prostaglandin D2 / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D016861:Cyclooxygenase Inhibitors; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D011453:Prostaglandins; D044463:Receptor, PAR-1; C483858:phosphatidylethanolamine; D051545:Cyclooxygenase 1; D019061:src-Family Kinases; D011493:Protein Kinase C; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D013917:Thrombin; D015232:Dinoprostone; D001241:Aspirin; D015230:Prostaglandin D2; D002118:Calcium
keywords: Oxidized phospholipids; PGE2/D2-PEs; atherosclerosis