HCV dynamics and cellular gene expression in uPA-SCID chimeric mice with humanized livers during intravenous silibinin monotherapy

Background/Aim: Legalon SIL (SIL) is a chemically hydrophilized version of silibinin that has exhibited hepatoprotective and antiviral effectiveness against hepatitis C virus (HCV) in patients leading to viral clearance in combination with ribavirin. To elucidate the incompletely understood mode of action of SIL against HCV, we studied viral response kinetics and cellular gene expression during SIL treatment in the absence of an adaptive immune response in uPA-SCID chimeric mice with humanized livers. Methods: Chronically HCV-infected mice were treated with daily intravenous SIL at 469 mg/kg (n=5), 265 mg/kg (n=5) or 61.5 mg/kg (n=5). Serum HCV and human albumin (hAlb) were measured frequently and liver HCV RNA was analyzed at days 3 and 14. Microarray analysis of human hepatocyte gene expression was performed at days 0, 3, and 14 of treatment. Mathematical modeling was used to estimate viral kinetic parameters and SIL effectiveness. Results: While hAlb remained constant, a biphasic viral decline in serum was observed consisting of a rapid 1st phase followed by a 2nd slower (or plateau with the two lower SIL dosing) phase. SIL effectiveness in blocking viral production was similar among dosing groups (median =77%). However, the rate of HCV-infected hepatocyte decline, δ, was dose-dependent. Intracellular HCV RNA levels correlated (r=0.66, P=.01) with serum HCV RNA. Pathway analysis revealed increased anti-inflammatory and anti-proliferative gene expression in human hepatocytes in SIL-treated mice. Conclusions: The results suggest that SIL could lead to a continuous 2nd phase viral decline, i.e., potentially viral clearance, in the absence of adaptive immune response along with increased anti-inflammatory and anti-proliferative gene expression in human hepatocytes. In this study, 6 human hepatocyte chimeric mice were treated with SIL and sacrificed at either 3 or 14 days after treatment. An additional 3 mice were used as controls. Human hepatocytes were finely dissected, and total RNA was extracted for microarray analysis to examine the effect of SIL on gene expression over time.