Identification of calcium-independent phospholipase A2 in mitochondria and its role in mitochondrial oxidative stress

Kinsey GR, McHowat J, Beckett CS, Schnellmann RG. Identification of calcium-independent phospholipase A2 in mitochondria and its role in mitochondrial oxidative stress. Am J Physiol Renal Physiol 292: F853–F860, 2007. First published October 17, 2006; doi:10.1152/ajprenal.00318.2006.—Oxidant-induced lipid peroxidation and cell death mediate pathologies associated with ischemiareperfusion and inflammation. Our previous work in rabbit renal proximal tubular cells (RPTC) demonstrated that inhibition of Ca independent phospholipase A2 (iPLA2) potentiates oxidant-induced lipid peroxidation and necrosis, implicating iPLA2 in phospholipid repair. This study was conducted to identify a RPTC mitochondrial PLA2 and determine the role of PLA2 in oxidant-induced mitochondrial dysfunction. iPLA2 activity was detected in Percoll-purified rabbit renal cortex mitochondria (RCM) and in isolated mitochondrial inner membrane fractions from rabbit and human RCM. Immunoblot analysis and inhibitor sensitivity profiles revealed that iPLA2 is the RCM iPLA2 activity. RCM iPLA2 activity was enhanced in the presence of ATP and was blocked by the PKC V1–2 inhibitor. Oxidant-induced mitochondrial lipid peroxidation and swelling were accelerated by pretreatment with R-BEL, but not S-BEL. Furthermore, oxidant treatment of isolated RCM resulted in decreased iPLA2 activity. These results reveal that RCM iPLA2 is iPLA2 , RCM iPLA2 is regulated by phosphorylation by PKC , iPLA2 protects RCM from oxidant-induced lipid peroxidation and dysfunction, and that a strategy to preserve or enhance iPLA2 activity may be of therapeutic benefit.