Genetic Ablation of Calcium-independent Phospholipase A2γ (iPLA2γ) Attenuates Calcium-induced Opening of the Mitochondrial Permeability Transition Pore and Resultant Cytochrome c Release

Serine Hydrolase Inhibitors Block Necrotic Cell Death by Preventing Calcium Overload of the Mitochondria and Permeability Transition Pore Formation

“…Several studies have strongly implicated iPLA 2 ␥ (PNPLA8) in regulating calcium-induced MPTP formation based on genetic ablation and use of the iPLA 2 ␥ enantioselective inhibitor R-bromoenolactone (28,29,31). However, we found that racemic bromoenolactone, which inhibits iPLA 2 ␥ (PNPLA8) and iPLA 2 ␤, did not inhibit A23187-induced MPTP formation or fatty acid release.…”

“…However, the serine hydrolase inhibitors did not have a direct effect on blocking calcium uptake in isolated mitochondria in contrast to the results using intact or permeabilized cells. Pyrrophenone has also been shown not to inhibit calcium-induced swelling of isolated mitochondria from mouse liver (31).…”

Regulation of the Ca -independent phospholipase A2 in liver mitochondria by changes in the energetic state

“…While it is clear that regulation of the mitochondrial iPLA 2 is not completely understood at the protein level, it can also be said that the same is true regarding the physiological and pathophysiological functions of the enzymes. We originally demonstrated that activity of the mitochondrial iPLA 2 promotes the permeability transition ( 26,27 ), and this has been verifi ed and extended by other reports ( 31,48 ). That consequence of activity was expected, given the well-established effects of FFAs on the phenomenon (see Introduction).…”

Heart failure–induced activation of phospholipase iPLA2γ generates hydroxyeicosatetraenoic acids opening the mitochondrial permeability transition pore

“…Desthiobiotin-fluorophosphonate was purchased from Thermo Fisher Scientific. Lipid internal standards, including 17:0-LPC and d 4 -16:0-fatty acid, were purchased from Avanti Polar Lipids, Inc., and Cambridge Isotope Laboratories, Inc. A rabbit polyclonal antibody directed against human iPLA 2 ␥ was generated in our laboratory as described previously (12). Antibodies against biotin, VDAC, ANT, and CypD were obtained from Santa Cruz Biotechnology.…”

“…Recently, we demonstrated that genetic knock-out of the active site of iPLA 2 ␥ (PNPLA8) results in the attenuation of mPTP opening and that iPLA 2 ␥ is largely responsible for the calcium-dependent production of oxidized fatty acid metabolites (e.g. eicosanoids, docosanoids, and oxidized linoleic acid metabolites) emanating from the mitochondrial compartment in murine hepatic and myocardial tissues (12)(13)(14). Moreover, loss of mitochondrial transmembrane potential evoked by either inhibition of mitochondrial electron transport chain complexes or prolonged calcium transients results in the further activation of iPLA 2 ␥ (6).…”