RSV upregulates CYP7A1 expression in HepG2 cells. (A) Time-dependent induction of CYP7A1 mRNA expression. Cultured HepG2 cells were incubated with RSV (50 μM) for the indicated times. CYP7A1 expression was then evaluated by quantitative RT-PCR. The figure shown is representative of 3 independent experiments. The abundance of CYP7A1 mRNA in untreated control cells was defined as 1 and the amounts of CYP7A1 mRNA from RSV-treated cells were then expressed as fold-changes in this control value. Asterisks, significantly different from 0 h ( P < 0.05). (B) Dose-dependent induction of CYP7A1 mRNA expression. HepG2 cells were treated with RSV for 24 h at the indicated concentrations and total RNA was isolated for the analysis of CYP7A1 and GAPDH mRNA expression by quantitative PCR. Asterisks, significantly different from control ( P < 0.05). (C) CYP7A1 protein expression was measured by Western blot.