Antifibrotic effects of tetrandrine on hepatic stellate cells and dimethylnitrosamine-intoxicated rats

Tetrandrine (C38H42O8N2, molecular weight: 622, Tet), an alkaloid isolated from the Chinese medicinal herb Stephania tetrandra, has been shown to elicit anti-inflammatory activity in pulmonary diseases and anti-fibrotic effects in various cell types. In this study, we investigated the in vitro and in vivo effects of Tet on hepatic fibrosis. A cell line of rat hepatic stellate cells (HSC-T6) was stimulated with transforming growth factor-β1 (TGF-β1) or tumor necrosis factor α (TNF-α). The inhibitory effects of Tet (0.5 – 5.0 μM) on IKKα expression, IκBα phosphorylation, NFκB transcriptional activity, the mRNA expression of intercellular adhension molecule (ICAM-1), and α-smooth muscle actin (α-SMA) secretion, were assessed. Fibrosis was induced by dimethylnitrosamine (DMN) administration in rats for 4 weeks. Fibrotic rats were randomly assigned to one of the four groups: vehicle (0.7% Carboxyl Methyl Cellulose, CMC), Tet (1 mg/kg), Tet (5 mg/kg), or silymarin (50 mg/kg), each given by gavage twice daily for 3 weeks starting after 1 week DMN pre-treatment. Tet (0.5 – 5.0 μM) concentration-dependently inhibited NFκB transcriptional activity induced by TNF-α. Tet reduced IKKα expression, TNF-α-induced IκBα phosphorylation, and attenuated TNF-α-stimulated the mRNA expression level of ICAM-1 in HSC-T6 cells. In addition, Tet also inhibited TGF-β1-induced α-SMA secretion and collagen deposition in HSC-T6 cells. Fibrosis scores of livers from DMN-treated rats with high dose of Tet (1.3 ± 0.3) were significantly reduced in comparison with DMN-treated rats receiving saline (2.0 ± 0.2). Hepatic collagen contents of DMN rats were significantly reduced by either Tet or silymarin treatment. Double staining results showed that α-SMA positive cells with NFκB activation were decreased in the fibrotic livers by Tet and silymarin treatments. The mRNA expression level of ICAM-1 was attenuated by Tet and silymarin treatment. In addition, the mRNA expression levels of α-SMA, TGF-β1 were only attenuated by high dose of Tet, but not silymarin treatment. Moreover, levels of plasma AST and ALT activities were reduced by Tet and silymarin treatment. In conclusion, our results showed that Tet exerted anti-fibrotic effects in both HSC-T6 cells and in rats with DMN-induced fibrosis.