title: Identification of the phospholipase A(2) isoforms that contribute to arachidonic acid release in hypoxic endothelial cells: limits of phospholipase A(2) inhibitors.
abstract: Changes in endothelium functions during ischemia are thought to be of importance in numerous pathological conditions, with, for instance, an increase in the release of inflammatory mediators like prostaglandins. Here, we showed that hypoxia increases phospholipase A(2) (PLA(2)) activity in human umbilical vein endothelial cells. Both basal PLA(2) activity and PG synthesis are sensitive to BEL and AACOCF3, respectively, inhibitors of calcium-independent PLA(2) (iPLA(2)) and cytosolic PLA(2) (cPLA(2)), while OPC, an inhibitor of soluble PLA(2) (sPLA(2)) only inhibited the hypoxia-induced AA release and PGF(2alpha) synthesis. Hypoxia does not alter expression of iPLA(2), sPLA(2) and cPLA(2) and cycloheximide did not inhibit PLA(2) activation, indicating that hypoxia-induced increase in PLA(2) activity is due to activation rather than induction. However, mRNA levels for sPLA(2) displayed a 2-fold increase after 2 hr incubation under hypoxia. BAPTA, an intracellular calcium chelator, partially inhibited the AA release in normoxia and in hypoxia. Direct assays of specific PLA(2) activity showed an increase in sPLA(2) activity but not in cPLA(2) activity after 2hr hypoxia. Taken together, these results indicate that the hypoxia-induced increase in PLA(2) activity is mostly due to the activation of sPLA(2).
authors.affiliation: Laboratoire de Biochimie et Biologie Cellulaire, Facultes Universitaires Notre Dame de la Paix, 61 rue de Bruxelles, 5000, Namur, Belgium. carine.michiels@fundp.ac.be
authors.forename: Carine
authors.initials: C
authors.lastname: Michiels
authors.forename: Patricia
authors.initials: P
authors.lastname: Renard
authors.forename: Najat
authors.initials: N
authors.lastname: Bouaziz
authors.forename: Nathalie
authors.initials: N
authors.lastname: Heck
authors.forename: Francois
authors.initials: F
authors.lastname: Eliaers
authors.forename: Noelle
authors.initials: N
authors.lastname: Ninane
authors.forename: Rozenn
authors.initials: R
authors.lastname: Quarck
authors.forename: Paul
authors.initials: P
authors.lastname: Holvoet
authors.forename: Martine
authors.initials: M
authors.lastname: Raes
mesh_terms: D016718:Arachidonic Acid / Q000378:metabolism*; D001095:Arachidonic Acids / Q000494:pharmacology; D015687:Cell Hypoxia; D002478:Cells, Cultured; D015237:Dinoprost / Q000096:biosynthesis; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification* / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology; D010741:Phospholipases A / Q000302:isolation & purification* / Q000378:metabolism; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011753:Pyrones / Q000494:pharmacology
chemical_list: D001095:Arachidonic Acids; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009281:Naphthalenes; D011753:Pyrones; C081565:arachidonyltrifluoromethane; D010767:Phosphorylcholine; D016718:Arachidonic Acid; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; C068170:oleyloxyethylphosphorylcholine; D015237:Dinoprost; D010741:Phospholipases A