The Ca2+/calmodulin/calmodulin-dependent protein kinase II (Ca2+/CaM/CaMKII) pathway is involved in oxidative stress-induced mitochondrial permeability transition pore (MPTP) and apoptosis in isolated rat hepatocytes

TOLEDO FD; BASIGLIO CL; BOAGLIO AC; MISCZUK G; OCHOA JE; SANCHEZ POZZI EJ; ROMA MG

Buenos Aires

Congreso; VIII International Congress of the SFRBM - South American Group; 2013

Society for Free Radical Biology and Medicine (SFRBM)

Oxidative stress (OS) is a common event in most hepatopathies, leading to formation of MPTP, and further exacerbation of both radical oxygen species (ROS) generation from mitochondrial origin and cell death. OS-associated intracellular Ca2+ elevations play a permissive role in these events, but the underlying mechanisms are virtually unknown. We examined whether the Ca2+/CaM/CaMKII signaling pathway is involved in MPTP-mediated ROS generation, and in the apoptotic hepatocyte death induced by the pro-oxidizing, model compound tert-butyl hydroperoxide (tBOOH). Intracellular Ca2+ sequestration with BAPTA/AM, blockage of CaM with W7 or trifluoperazine, and inhibition of CaMKII with KN-62 all fully prevented tBOOH (500 µM)-induced MPTP formation, and abrogated lipid peroxidation to a similar extent to the MPTP blocker clyclosporin A. tBOOH also increased the apoptotic index, which was associated with the triggering of number of pro-apoptotic events, namely increase in the Bax-to-Bcl-xL ratio, release of cytochrome c into cytosol, caspase-3 activation, and activation of p38 and JNK MAPKs; again, the Ca2+-CaM-CaMKII signaling antagonists fully prevented these effects. We concluded that elevations of intracellular Ca2+ elevations under oxidative stress conditions induce MPTP formation, and that activation of Ca2+/CaM/CaMKII pathway participates in the generation of ROS from mitochondrial origin and the further apoptotic hepatocellular death.