The effect of idebenone, a coenzyme Q analogue, on hydrophobic bile acid toxicity to isolated rat hepatocytes and hepatic mitochondria

Oxidant stress induced by hydrophobic bile acids has been implicated in the pathogenesis of liver injury in cholestatic liver disorders. We evaluated the effect of idebenone, a coenzyme Q analogue, on taurochenodeoxycholic acid (TCDC)-induced cell injury and oxidant stress in isolated rat hepatocytes and on glycochenodeoxycholic acid (GCDC)-induced generation of hydroperoxides in fresh hepatic mitochondria. Isolated rat hepatocytes in suspension under 9% oxygen atmosphere were preincubated with 0, 50, and 100 mu mol/l idebenone for 30 min and then exposed to 1000 mu mol/l TCDC for 4 h. LDH release (cell injury) and thiobarbituric acid reactive substances (measure of lipid peroxidation) increased after TCDC exposure but were markedly suppressed by idebenone pretreatment. In a second set of experiments, the addition of 100 mu mol/l idebenone up to 3 h after hepatocytes were exposed to 1000 mu mol/l TCDC resulted in abrogation of subsequent cell injury and markedly reduced oxidant damage to hepatocytes. Chenodeoxycholic acid concentrations increased to 5.15 nmol/10(6) cells after 2 h and to 7.05 after 4 h of incubation of hepatocytes with 1000 mu mol/l TCDC, and did not differ in the presence of idebenone. In freshly isolated rat hepatic mitochondria, when respiration was stimulated by succinate, 10 mu mol/l idebenone abrogated the generation of hydroperoxides during a 90-minute exposure to 400 mu mol/l GCDC. These data demonstrate that idebenone functions as a potent protective hepatocyte antioxidant during hydrophobic bile acid toxicity, perhaps by reducing generation of oxygen free radicals in mitochondria.