Role of Ca2+-independent phospholipase A2gamma in Ca2+-induced mitochondrial permeability transition.
Our laboratory previously demonstrated Ca2+-independent phospholipase A2gamma (iPLA2gamma) is localized to mitochondria and that iPLA2 inhibition blocks cisplatin-induced caspase-mediated apoptosis. Whereas the mitochondrial permeability transition (MPT) is a key control point for apoptosis, the role of mitochondrial iPLA2gamma in MPT has not been established. In the present study, we addressed this issue. Ca2+-induced renal cortex mitochondrial (RCM) swelling was blocked by the MPT inhibitor cyclosporine A. The R-isomer of bromoenol lactone (R-BEL), which enantiospecifically inhibits iPLA2gamma, inhibited Ca2+-induced RCM MPT, whereas S-BEL (negative control) had no effect. Ca2+ treatment resulted in a significant increase in free arachidonic acid (AA) (>50 microM) in the RCM suspension that was blocked by pretreatment with BEL. No increases in free myristic, palmitic, stearic, oleic, linoleic, or docosahexaenoic acid were detected after Ca2+ treatment. The addition of AA (18 microM) to Ca2+-treated RCM with inhibited iPLA2gamma activity restored MPT. We also determined that RCM iPLA2gamma displays higher activity against plasmenylcholine with AA in the sn-2 position than oleic acid. Ca2+ exposure significantly increased RCM iPLA2gamma activity; however, the Ca2+-induced activation of iPLA2gamma was not the result of mitochondrial membrane potential dissipation, opening of the MPT pore, or mitochondrial swelling. Taken together these findings provide strong evidence that Ca2+-induced RCM MPT is mediated by iPLA2gamma-catalyzed AA liberation.
Kinsey
Gilbert R
GR
Medical University of South Carolina, Department of Pharmaceutical Sciences, 280 Calhoun St., Charleston, SC 29425, USA.
McHowat
Jane
J
Patrick
Kennerly S
KS
Schnellmann
Rick G
RG
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D005260:Female; D054522:Group VI Phospholipases A2; D007672:Kidney Cortex / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D009281:Naphthalenes / Q000494:pharmacology; D010741:Phospholipases A / Q000502:physiology*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011753:Pyrones / Q000494:pharmacology; D011817:Rabbits
D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D009281:Naphthalenes; D011753:Pyrones; D016718:Arachidonic Acid; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D011092:Polyethylene Glycols; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; D002118:Calcium