title: The transfer of VLDL-associated phospholipids to activated platelets depends upon cytosolic phospholipase A2 activity.
abstract: We previously reported that VLDL could transfer phospholipids (PLs) to activated platelets. To identify the metabolic pathway involved in this process, the transfer of radiolabeled PLs from VLDL (200 microM PL) to platelets (2 x 10(8)/ml) was measured after incubations of 1 h at 37 degrees C, with or without thrombin (0.1 U/ml) or LPL (500 ng/ml), in the presence of various inhibitors, including aspirin, a cyclooxygenase inhibitor (300 microM); esculetin, a 12-lipoxygenase inhibitor (20 microM); methyl-arachidonyl-fluorophosphonate (MAFP), a phospholipase A(2) (PLA(2)) inhibitor (100 microM); 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl) ester (BAPTA-AM), a Ca(2+) chelator (20 microM); bromoenol lactone (BEL), a Ca(2+)- independent phospholipase A(2) (iPLA(2)) inhibitor (100 nM); and 1-[6-[[17beta-3-methoxyestra-1,3,5(10)-trien-17-yl-]amino]hexyl]1H-pyrrole-2,5-dione (U73122), a phospholipase C (PLC) inhibitor (20 microM). Aspirin and esculetin had no effect, showing that PL transfer was not dependent upon cyclooxygenase or lipoxygenase pathways. The transfer of PL was inhibited by MAFP, U73122, and BAPTA-AM. Although MAFP inhibited both cytosolic phospholipase A(2) (cPLA(2)) and iPLA(2), only cPLA(2) is a calcium-dependent enzyme. Because calcium mobilization is favored by PLC and inhibited by BAPTA-AM, the transfer of PL from VLDL to platelets appeared to result from a cPLA(2)-dependent process. The inhibition of iPLA(2) by BEL had no effect on PL transfers.
authors: Université de Lyon, Lyon, F-69003 France.
authors: Salam
authors: S
authors: Ibrahim
authors: Catherine
authors: C
authors: Calzada
authors: Valérie
authors: V
authors: Pruneta-Deloche
authors: Michel
authors: M
authors: Lagarde
authors: Gabriel
authors: G
authors: Ponsin
mesh_terms: D001095:Arachidonic Acids / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D008071:Lipoprotein Lipase / Q000502:physiology; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D009281:Naphthalenes / Q000494:pharmacology; D063065:Organophosphonates / Q000494:pharmacology; D010741:Phospholipases A / Q000502:physiology*; D054467:Phospholipases A2; D049294:Phospholipid Transfer Proteins / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D015539:Platelet Activation; D011753:Pyrones / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D014468:Umbelliferones / Q000494:pharmacology
chemical_list: D001095:Arachidonic Acids; D004963:Estrenes; D008079:Lipoproteins, VLDL; D009281:Naphthalenes; D063065:Organophosphonates; C493430:PLTP protein, human; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D011753:Pyrones; D011760:Pyrrolidinones; D014468:Umbelliferones; C104810:methyl arachidonylfluorophosphonate; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D010741:Phospholipases A; D008071:Lipoprotein Lipase; D054467:Phospholipases A2; D013917:Thrombin; D001241:Aspirin; C007628:esculetin