Submitted on January 16, 2008
Revised on April 7, 2008
Accepted on April 7, 2008
Decreased iPLA2
expression induces lipid peroxidation, cell death, and sensitizes cells to oxidant-induced apoptosis
Gilbert R. Kinsey, Jason L. Blum, Marisa D. Covington, Brian S. Cummings, Jane McHowat, and Rick G. Schnellmann
Pharmaceutical and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425
Corresponding Author: schnell{at}musc.edu
Our previous studies showed that renal proximal tubular cells (RPTC) express Ca2+-independent phospholipase A2
(iPLA2) in endoplasmic reticulum (ER) and mitochondria and iPLA2 prevents and/or repairs lipid peroxidation induced by oxidative stress. Our present studies determined the importance of iPLA2 in mitochondrial and cell function using an iPLA2-specific shRNA adenovirus. iPLA2 expression and activity decreased in the ER by 24 hr and in the mitochondria by 48 hr compared to scrambled shRNA adenovirus-treated cells. Lipid peroxidation was elevated 2 fold at 24 hr and remained elevated through 72 hr in cells with decreased iPLA2. Using electrospray ionization-mass spectrometry, primarily phosphatidylcholines and phosphatidylethanolamines were increased in iPLA2-shRNA-treated cells. At 48 hr post-exposure to the iPLA2 shRNA, uncoupled oxygen consumption was inhibited 25% and apoptosis was observed at 72 and 96 hr. RPTC with decreased iPLA2 expression underwent apoptosis when exposed to a non-lethal concentration of the oxidant tert-butylhydroperoxide (TBHP). Exposure of control cells to a non-lethal concentration of TBHP induced iPLA2 expression in RPTC. These results suggest that iPLA2 is required for the prevention and repair of basal lipid peroxidation and maintenance of mitochondrial function and viability providing further evidence for a cytoprotective role for iPLA2 from oxidative stress.
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