title: Dual role of the p38 MAPK/cPLA2 pathway in the regulation of platelet apoptosis induced by ABT-737 and strong platelet agonists.
abstract: p38 Mitogen-activated protein (MAP) kinase is involved in the apoptosis of nucleated cells. Although platelets are anucleated cells, apoptotic proteins have been shown to regulate platelet lifespan. However, the involvement of p38 MAP kinase in platelet apoptosis is not yet clearly defined. Therefore, we investigated the role of p38 MAP kinase in apoptosis induced by a mimetic of BH3-only proteins, ABT-737, and in apoptosis-like events induced by such strong platelet agonists as thrombin in combination with convulxin (Thr/Cvx), both of which result in p38 MAP kinase phosphorylation and activation. A p38 inhibitor (SB202190) inhibited the apoptotic events induced by ABT-737 but did not influence those induced by Thr/Cvx. The inhibitor also reduced the phosphorylation of cytosolic phospholipase A2 (cPLA2), an established p38 substrate, induced by ABT-737 or Thr/Cvx. ABT-737, but not Thr/Cvx, induced the caspase 3-dependent cleavage and inactivation of cPLA2. Thus, p38 MAPK promotes ABT-737-induced apoptosis by inhibiting the cPLA2/arachidonate pathway. We also show that arachidonic acid (AA) itself and in combination with Thr/Cvx or ABT-737 at low concentrations prevented apoptotic events, whereas at high concentrations it enhanced such events. Our data support the hypothesis that the p38 MAPK-triggered arachidonate pathway serves as a defense mechanism against apoptosis under physiological conditions.
authors.affiliation: 1] Institute of Clinical Biochemistry and Pathobiochemistry, University of Würzburg, Würzburg D-97080, Germany [2] Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St Petersburg 194223, Russia.
authors.forename: N
authors.initials: N
authors.lastname: Rukoyatkina
authors.forename: I
authors.initials: I
authors.lastname: Mindukshev
authors.forename: U
authors.initials: U
authors.lastname: Walter
authors.forename: S
authors.initials: S
authors.lastname: Gambaryan
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001713:Biphenyl Compounds / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D003435:Crotalid Venoms / Q000494:pharmacology; D005434:Flow Cytometry; D054513:Group IV Phospholipases A2 / Q000378:metabolism*; D006801:Humans; D037181:Lectins, C-Type; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D009596:Nitrophenols / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: C501332:ABT-737; D001713:Biphenyl Compounds; D003435:Crotalid Venoms; D037181:Lectins, C-Type; D009596:Nitrophenols; D010879:Piperazines; D017382:Reactive Oxygen Species; D013449:Sulfonamides; C028890:convulxin; D048051:p38 Mitogen-Activated Protein Kinases; D054513:Group IV Phospholipases A2