title: Activation of p38 mitogen-activated protein kinase/cytosolic phospholipase A2 cascade in hydroperoxide-stressed platelets.
abstract: 12-Hydroperoxy-eicosatetraenoic acid (12-HpETE), the main hydroperoxide formed in platelets from arachidonic acid (AA) by 12-lipoxygenase, has been shown to increase the sensitivity of platelets to agonists resulting in increased aggregation. The aim of the present study was to determine the direct effect of low concentrations of 12-HpETE on the signaling pathways leading to AA release from membrane phospholipids and thromboxane A2 (TxA2) formation. Exogenous 12-HpETE activated platelet p38 mitogen-activated protein kinase (p38 MAPK), as assessed by its phosphorylation, at a concentration as low as 100 nM and was much more potent than hydrogen peroxide. Moreover, the incubation of platelets with 100 nM 12-HpETE for 2 min led to the phosphorylation of cytosolic phospholipase A2 (cPLA2). It was associated with a significant decrease in the concentration of AA esterified in phospholipids and an increased concentration of thromboxane B2, the stable catabolite of TxA2. Additionally, decreasing glutathione peroxidase activity pharmacologically favored endogenous 12-HpETE formation and led to an increase in phosphorylated p38 MAPK, while a thiol-reducing agent such as N-acetyl-cysteine fully prevented it. Finally, significant activation of p38 MAPK was also observed in platelets from type 2 diabetic patients with mild hyperglycemia. In conclusion, our data provide a new insight into the mechanism of 12-HpETE-induced platelet priming, suggesting that hydroperoxide-induced p38 MAPK activation could play a relevant role in the exacerbated platelet activation associated with oxidative stress as found in diabetes.
authors.affiliation: UMR 585 INSERM/INSA-Lyon, Villeurbanne, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Coulon
authors.forename: Catherine
authors.initials: C
authors.lastname: Calzada
authors.forename: Philippe
authors.initials: P
authors.lastname: Moulin
authors.forename: Evelyne
authors.initials: E
authors.lastname: Véricel
authors.forename: Michel
authors.initials: M
authors.lastname: Lagarde
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D016718:Arachidonic Acid / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D004789:Enzyme Activation / Q000187:drug effects; D005979:Glutathione Peroxidase / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D015289:Leukotrienes / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects*; D010100:Oxygen / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D015289:Leukotrienes; D010743:Phospholipids; D016718:Arachidonic Acid; C021201:12-HPETE; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D010100:Oxygen; D000111:Acetylcysteine