Calcium-dependent protein kinases in oxidative stress-induced mitochondrial permeability transition

PEREZ, LEONARDO MARTÍN; OCHOA, J ELENA; SANCHEZ POZZI, EJ; ROMA, MARCELO G

Estambul, Turquía

Congreso; 31st FEBS Congress; 2006

Federation of European Biochemical Societies

Mitochondrial permeability transition (MPT) is a key event in oxidative stress-induced hepatocellular death. Although Ca2+ plays a crucial role, its mechanisms are largely unknown. We examined here whether activation of Ca2+-dependent protein kinases (PK) are involved in lipid peroxidation and MPT induced by tert-butylhydroperoxide (tBOOH) in isolated hepatocytes. tBOOH (500 lM) increased cytosolic Ca2+ and lipid peroxidation by 2623% and 723%, respectively. Ca2+ chelation with BAPTA, calmodulin (CM) inhibition with W7 or trifluoperazine, and CM-dependent-PKII inhibition with KN-62 reduced lipid peroxidation to a similar extent to CsA, without additive effect; this suggests PKII-dependency of MPT. In line with this, tBOOH-induced mitochondrial membrane depolarisation, a surrogate MPT marker, was counteracted by all these compounds to a similar extent to CsA (ca. ?30%, P < 0.025). Neither PKC inhibition with staurosporine nor PKC activation with phorbol myristate acetate had any effect, despite tBOOH increased thrice Ca2+-dependent PKCa in membrane. Involvement of calcineurin, a CsA-sensitive, CM-dependent protein with MPT-pore-openingproperties, was also discarded, as its specific inhibitor, FK506, had no effect. We concluded that Ca2+ facilitates tBOOH oxidative damage via MPT, by a mechanism involving CM formation and further PKII activation.