Mitochondrial involvement in cocaine-treated rat hepatocytes: effect of N-acetylcysteine and deferoxamine

1 The cytotoxicity of cocaine (0 - 1000 muM), was studied on parameters rel ated to the mitochondrial role and the cascade of events that lead to apopt osis in hepatocyte cultures from phenobarbitone (PB) pretreated rats. 2 Cytotoxicity was dose-dependent and LDH leakage was significantly enhance d above 100 muM cocaine. Apoptosis was visualized by DNA fragmentation on a garose gel, and appeared at 50 and 100 muM cocaine. Cocaine induced biphasi c changes in mitochondrial transmembrane potential and significantly increa sed the mitochondrial release of cytochrome c, the caspase-3 like DEVDase a ctivity and the level of 20 kDa subunit, a product of pro-caspase-3 cleavag e. 3 The protective effect of N-acetylcysteine (NAC) and deferoxamine (DFO) on all these parameters confirmed the involvement of oxygen radicals in cocai ne-induced necrosis/apoptosis. 4 We conclude: first, that the biphasic changes recorded in mitochondrial i nner membrane potential by the effect of cocaine, were parallel to apoptosi s; second, that caspase-3 activity and cleavage to it p20 subunit increased sharply in parallel to the translocation of cytochrome c from mitochondria to cytosol; and third, that the antioxidants, NAC or DFO exerted a noticea ble protective role in counteracting the cytotoxicity of cocaine, these eff ects being more pronounced in the case of DFO than NAG. 5 These findings demonstrate that cocaine cytotoxicity involves mitochondri al damage.