Formation of 4-hydroxynonenal adducts with cytochrome c oxidase in rats following short-term ethanol intake

This study addresses the role of the lipid peroxidation product, 4-hydroxyn onenal (HNE), in ethanol-related damage of cytochrome c oxidase (COX) in vi vo. It utilizes an animal model with acute ethanol exposure in which HNE le vels in liver mitochondria are strikingly increased. Pregnant female Spragu e-Dawley rats were administered 5 doses of ethanol (4 gm/kg, po at 12-hour intervals) beginning on day 17 of gestation and were sacrificed on day 19. Controls were pair-fed and received dextrose isocaloric to ethanol. Mitocho ndria were isolated from maternal and fetal livers and COX activities were measured spectrophoto-metrically. Compared with the pair-fed controls, COX activity was decreased with exposure to ethanol by 25% in maternal rats and 43% in fetal rats (P<.05). Western Blot with an HNE-Histidine antibody sho wed enhanced formation of HNE adducts with COX from ethanol-exposed rats, w hich was more pronounced in fetal than in adult livers. The HNE adducts wer e mainly with subunit IV of COX. The cause and effect relationship between HNE adduct formation and COX inhibition was examined in vitro by incubating purified COX with HNE. COX inhibition was accompanied by concentration-dep endent HNE adduct formation that was consistent with those found in in vivo ethanol-exposed samples. These results suggest that the ethanol-related de creases in COX activity found in liver mitochondria could be attributable t o HNE adduct formation with the enzyme complex. This could be an important mechanism by which modification of proteins occur in in vivo oxidative stre ss.