Cre-estrogen receptor-mediated hepatitis C virus structural protein expression in mice.

Hepatocyte apoptosis is an important feature of liver injury in hepatitis C virus (HCV) infection. However, the mechanism of apoptosis and consequences on disease progression in vivo have not been investigated fully in part due to the lack of adequate small animal models. In this study, transgenic (tg) mice were produced that express conditionally HCV structural proteins (core, E1, E2 and p7) in the liver following Cre-mediated DNA recombination. Using a novel Cre-estrogen receptor fusion protein (Cre-ER) induction strategy, tamoxifen was injected intraperitoneally (i.p.), which induced Cre nuclear translocation, transgene recombination and HCV protein expression in the liver. Hepatic expression of HCV core and envelope proteins resulted in increased hepatocyte apoptosis, detected by the TUNEL assay, between 7 and 33 days after induction. These results were confirmed by the presence of increased levels of apoptosis-associated cytokeratin 18 (CK-18) in the sera of the same animals. The presence of cleaved caspase-3 and elevated levels of CHOP/GADD153 in the liver suggests an endoplasmic reticulum (ER) stress-associated apoptosis mechanism. This study suggests an in vivo correlation between HCV structural protein expression, ER stress and hepatocyte apoptosis, implicating a potentially important mechanism of HCV pathogenesis.