Role of oxidant stress in the permeability transition induced in rat hepatic mitochondria by hydrophobic bile acids

Hydrophobic bile acids may cause hepatocellular necrosis and apoptosis duri ng cholestatic liver diseases. The mechanism for this injury may involve mi tochondrial dysfunction and the generation of oxidant stress. The purpose o f this study was to determine the relationship of oxidant stress and the mi tochondrial membrane permeability transition (MMPT) in hepatocyte necrosis induced by bile acids. The MMPT was measured spectrophotometrically and mor phologically in rat liver mitochondria exposed to glycochenodeoxycholic aci d (GCDC). Freshly isolated rat hepatocytes were exposed to GCDC and hepatoc ellular necrosis was assessed by lactate dehydrogenase release, hy droperox ide generation by dichlorofluorescein fluorescence, and the MMPT in cells b y JC1 and tetramethylrhodamine methylester fluorescence on how cytometry. G CDC induced the MMPT in a dose- and Ca2+-dependent manner. Antioxidants sig nificantly inhibited the GCDC-induced MMPT and the generation of hydroperox ides in isolated mitochondria. Other detergents failed to induce the MMPT a nd a calpain-like protease inhibitor had no effect on the GCDC-induced MMPT . In isolated rat hepatocytes, GCDC induced the MMPT. which was inhibited b y antioxidants. Blocking the MMPT in hepatocytes reduced hepatocyte necrosi s and oxidant stress caused by GCDC. Oxidant stress, and not detergent effe cts or the stimulation of calpain-like proteases. mediates the GCDC-induced MMPT in hepatocytes. We propose that reducing mitochondrial generation of reactive oxygen species or preventing increases in mitochondrial Ca2+ may p rotect the hepatocyte against bile acid-induced necrosis.