Oxidative stress and regulation of anti-oxidant enzymes in cytochrome P4502E1 transgenic mouse model of non-alcoholic fatty liver

Background and Aim: Reactive oxygen species produced by cytochrome P4502E1 (CYP2E1) are believed to play a role in pathophysiology of non-alcoholic fatty liver disease (NAFLD). However, little is known about the expression, protein content and activity of anti-oxidant enzymes and the role of inducible nitric oxide synthase (iNOS), a source of reactive nitrogen species, in NAFLD. In the present study, we evaluate gene expression, protein content and activity of anti-oxidant enzymes, and iNOS, in a CYP2E1 overexpressing model of non-alcoholic fatty liver (NAFL). Methods: Non-transgenic (nTg) and CYP2E1 transgenic (Tg) mice were fed rodent chow for 8 months. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), liver triglycerides, malondialdehyde and protein carbonyls were measured. Gene expression of NF-E2-related factor (Nrf2), superoxide dismutase-1, -2 (SOD-1,2), catalase (CAT), glutathione peroxidase (GPx), heme oxygenase-1 (HO-1) and iNOS were determined. Protein content, activity and nitrosylation of the enzymes were also measured. Results: Tg mice had greater CYP2E1 activity and histological liver injury. MDA and protein carbonyls were increased, indicating insufficient anti-oxidant response. Gene expression of Nrf2, CAT, GPx, HO-1 and iNOS were significantly increased. Protein content and enzyme activities of most anti-oxidant enzymes were not correspondingly increased. iNOS activity and nitrosylation of CAT and SOD was greater in Tg mice liver. Conclusion: Hepatocyte-specific CYP2E1 overexpression results in increased oxidative stress and nitrosative stress. Several anti-oxidant enzymes are upregulated. Failure of corresponding increase in total protein and activity of anti-oxidant enzymes suggests modification/degradation, possibly by nitrosylation, due to increased iNOS activity in a CYP2E1 overexpressing NAFL mouse model.