Ethanol Affects Liver Oxidative Stress and Methylation Status in HCV-infection: study on NS5ATransgenic Mice

Background: Alcohol consumption accelerates the progression and worsens the outcomes of
hepatitis C viral (HCV) infection in heavy and moderate drinkers. Non-structural NS5A protein is a
known inducer of oxidative stress and carcinogenesis. Although alcohol consumption exacerbates the
course of HCV-infection, the combined effects of NS5A protein and alcohol have not been studied and
experimental animal HCV models as well as ways of ethanol administration to animals are not
optimized. Our aim was to investigate the effects of two modes of oral ethanol feeding on induction
of oxidative stress, methylation status and changes in proteasome activity in livers of NS5Atransgenic
(Tg) mice.
Methods: Ethanol was administered either in drinking water (chow- fed mice given 20% ethanol in
water; designated chow-EtOH) or in Lieber DeCarli liquid diet (LCD-EtOH). Appropriate controls were
used. The mechanisms of alcohol and NS5A-induced changes in oxidative stress, liver methylation
status and 20S proteasome activity were determined after 5 weeks of the feeding regimen.
Results: Ethanol administration using both feeding regimens induced oxidative stress and
suppressed cytosolic proteasome activity. However, only LCD-EtOH diet induced fatty changes in the
liver, which correlated with higher levels of oxidative stress, impaired methylation potential and
reduced cytosolic and nuclear proteasome activity. Importantly, LCD diet administration by itself
promoted lipid peroxidation in NS5A-expressing mice.
Conclusion: We conclude that both modes of oral ethanol feeding (chow and LCD-based) induce
oxidative stress in NS5A-Tg mice that suppresses proteasome activity. Nonetheless, impaired
methylation potential, higher level of oxidative stress and suppression of nuclear proteasome was
observed only in LCD-EtOH mice. However, the effects of LCD-control liquid diet in inducing lipid
peroxidation in NS5A-Tg mice, in certain cases, tended to mask the effects of ethanol, indicating that
fatty diet serves as a second hit for NS5A-protein-induced stress response of liver cells.