Role of an endoplasmic reticulum Ca(2+)-independent phospholipase A(2) in oxidant-induced renal cell death.
Phospholipase A(2) (PLA(2)) hydrolyzes the sn-2 ester bond in phospholipids, releasing a fatty acid and a lysophospholipid. Recently, a novel 85-kDa membrane-bound-Ca(2+)-independent PLA(2) (iPLA(2)) was identified in insect and bacterial cells transfected with candidate PLA(2) sequences. However, few data exist demonstrating a membrane-bound-iPLA(2) in mammalian cells, its subcellular localization, or its physiological role. Herein, we demonstrate the expression of an 85-kDa endoplasmic reticulum (ER)-Ca(2+)-iPLA(2) (ER-iPLA(2)) in rabbit renal proximal tubule cells (RPTC) that is plasmalogen selective and is inhibited by the specific Ca(2+)-iPLA(2) inhibitor bromoenol lactone (BEL). RPTC exposed to tert-butylhydroperoxide for 24 h exhibited 20% oncosis compared with 2% in controls. Inhibition of ER-iPLA(2) with BEL before tert-butylhydroperoxide exposure resulted in 50% oncosis. To determine whether this effect was common to oxidants, we tested the ability of BEL to potentiate oncosis induced by cumene hydroperoxide, menadione, duraquinone, cisplatin, and the nonoxidant antimycin A. All oxidants tested produced oncosis after 24 h, and prior inhibition of ER-iPLA(2) potentiated oncosis at least twofold. In contrast, inhibition of ER-iPLA(2) did not alter antimycin A-induced oncosis. Lipid peroxidation increased from 1.4- to 5.2-fold in RPTC treated with BEL before oxidant exposure, whereas no change was seen in antimycin A-treated RPTC. These results are the first to demonstrate the expression and subcellular localization of an ER-iPLA(2). These results also suggest that ER-iPLA(2) functions to protect against oxidant-induced lipid peroxidation and oncosis.
Cummings
Brian S
BS
Department of Pharmaceutical Sciences, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
McHowat
Jane
J
Schnellmann
Rick G
RG
D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D001555:Benzene Derivatives / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects*; D002945:Cisplatin / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015151:Immunoblotting; D007668:Kidney / Q000166:cytology*; D007687:Kidney Tubules, Proximal / Q000201:enzymology; D015227:Lipid Peroxidation / Q000187:drug effects; D008861:Microsomes / Q000201:enzymology; D009281:Naphthalenes / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000502:physiology*; D010955:Plasmalogens / Q000378:metabolism; D011753:Pyrones / Q000494:pharmacology; D011817:Rabbits; D013379:Substrate Specificity; D024483:Vitamin K 3 / Q000494:pharmacology
D001555:Benzene Derivatives; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D016877:Oxidants; D010955:Plasmalogens; D011753:Pyrones; D000968:Antimycin A; D024483:Vitamin K 3; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D010741:Phospholipases A; C007164:cumene hydroperoxide; D002945:Cisplatin; D002118:Calcium