Matrix conditions and KLF2-dependent induction of heme oxygenase-1 modulate inhibition of HCV replication by fluvastatin.

BACKGROUND & AIMS: HMG-CoA-reductase-inhibitors (statins) have been shown to interfere with HCV replication in vitro. We investigated the mechanism, requirements and contribution of heme oxygenase-1(HO-1)-induction by statins to interference with HCV replication. METHODS: HO-1-induction by fluva-, simva-, rosuva-, atorva- or pravastatin was correlated to HCV replication, using non-infectious replicon systems as well as the infectious cell culture system. The mechanism of HO-1-induction by statins as well as its relevance for interference with HCV replication was investigated using transient or permanent knockdown cell lines. Polyacrylamide(PAA) gels of different density degrees or the Rho-kinase-inhibitor Hydroxyfasudil were used in order to mimic matrix conditions corresponding to normal versus fibrotic liver tissue. RESULTS: All statins used, except pravastatin, decreased HCV replication and induced HO-1 expression, as well as interferon response in vitro. HO-1-induction was mediated by reduction of Bach1 expression and induction of the Nuclear factor (erythroid-derived 2)-like 2 (NRF2) cofactor Krueppel-like factor 2 (KLF2). Knockdown of KLF2 or HO-1 abrogated effects of statins on HCV replication. HO-1-induction and anti-viral effects of statins were more pronounced under cell culture conditions mimicking advanced stages of liver disease. CONCLUSIONS: Statin-mediated effects on HCV replication seem to require HO-1-induction, which is more pronounced in a microenvironment resembling fibrotic liver tissue. This implicates that certain statins might be especially useful to support HCV therapy of patients at advanced stages of liver disease.

Selective induction of apoptosis by HMG-CoA reductase inhibitors in hepatoma cells and dependence on p53 expression.

HMG-CoA-reductase inhibitors (statins) are widely used drugs to interfere with cholesterol biosynthesis. Besides this usage, evidence is increasing that statins might also be useful in therapy of viral infections or cancer. We investigated the effects of fluva-, simva-, atorva-, rosuva- and lovastatin on the viability of primary mouse and human hepatocytes as well as mouse (Hepa1-6) and human (Huh7, HepG2) hepatoma cell lines. Our results show selective cytotoxic effects of fluva-, simva- and lovastatin on hepatoma cells in comparison to primary hepatocytes. Using human hepatoma cells we found significant reduction of cell viability and induction of apoptosis in HepG2 cells, while statins did not affect Huh7 cells at concentrations not toxic for primary hepatocytes. Stable knockdown of endogenous p53, which is overexpressed in Huh7 cells, was able to restore susceptibility of Huh7 cells towards statin-induced toxicity. The anti-tumor effect of statins did not depend on a lack of cholesterol production, but was restored by supplementation of mevalonate or geranyl-geranyl pyrophosphate, prerequisites for prenylation of small G proteins. In conclusion, statins display a selective apoptotic effect on human hepatoma cells, with fluva-, simva- and lovastatin being both, most selective for tumor cells and most effective in inducing tumor cell apoptosis. Additionally, our results implicate that anti-tumor activity of statins requires cell proliferation and is reduced by p53 overexpression.