Background & aims: Ethanol causes oxidative stress in the hepatic mitochondria of experimental animals and mitochondrial DNA deletions in alcoholics. We postulated that ethanol intoxication may cause mitochondrial DNA strand breaks.
Methods: Effects of an intragastric dose of ethanol (5 g/kg) on hepatic mitochondrial DNA levels, structure, and synthesis were determined by slot blot hybridization, Southern blot hybridization, and in vivo [3H]thymidine incorporation, respectively.
Results: Two hours after ethanol administration, ethane exhalation (an index of lipid peroxidation) increased by 133%, although hepatic lipids were unchanged. Mitochondrial DNA was depleted by 51%. Its supercoiled form disappeared, whereas linearized forms increased. Long polymerase chain reaction evidenced lesions blocking polymerase progress on the mitochondrial genome. Mitochondrial transcripts decreased. Subsequently, [3H]thymidine incorporation into mitochondrial DNA increased, and mitochondrial DNA levels were restored. In contrast, nuclear DNA was not fragmented and its [3H]thymidine incorporation was unchanged. Liver ultrastructure only showed inconstant mitochondrial lesions. Ethanol-induced mitochondrial DNA depletion was prevented by 4-methylpyrazole, an inhibitor of ethanol metabolism, and attenuated by melatonin, an antioxidant.
Conclusions: After an alcoholic binge, ethanol metabolism causes oxidative stress and hepatic mitochondrial DNA degradation in mice. DNA strand breaks may be involved in the development of mitochondrial DNA deletions in alcoholics.