HCV proteins increase expression of heme oxygenase-1 (HO-1) and decrease expression of Bach1 in human hepatoma cells

Hepatitis C infection induces hepatic oxidative stress. Heme oxygenase (HO), the rate-controlling enzyme of heme catabolism, plays a key role as a protector against oxidative, and other stresses. Other recent work has implicated Bach1, a heme binding protein that represses gene expression, in the regulation of HO-1 gene expression.

We investigated the effects of HCV polyprotein expression on expression of HO-1 and Bach1 genes in human hepatoma cells (Huh-7 cells).

HO-1 was up-regulated in the cell line expressing HCV proteins from core up to the aminoterminal domain of NS3. Addition of increasing concentrations of N-acetylcysteine (NAC) led to down-regulation of HO-1 in cells expressing HCV proteins. In contrast, Bach1 was significantly down-regulated in these cells. Sodium arsenite, a strong inducer of oxidative stress and HO-1, reduced Bach1 expression in wild type Huh-7 cells, and NAC partially abrogated this decrease.

Huh-7 cells expressing HCV proteins show significant up-regulation of the HO-1 gene, and reciprocal down-regulation of the Bach1 gene. Exogenous oxidative stressors and anti-oxidants can modulate expression of these genes. These and other results suggest a key role of down-regulation of Bach1 and up-regulation of HO-1 in diminishing cytotoxic effects of HCV proteins in human hepatocytes.