Polyprenols from Taxus chinensis var. mairei prevent the development of CCl₄-induced liver fibrosis in rats

ETHNOPHARMACOLOGICAL RELEVANCE: The aim of this study was to investigate the anti-fibrotic effects and the possible underlying mechanisms of taxus polyprenols (TPs) isolated from the needles of Taxus chinensis var. mairei. MATERIALS AND METHODS: The animals were randomly divided into normal control with vehicles only (olive oil), rat model given CCl₄ only, CCl₄+low TPs (48mg/kg), CCl₄+medium TPs (120mg/kg), CCl₄+high TPs (300mg/kg), and CCl₄+Polyene phosphatidylcholine (PP, 120mg/kg). The rat model of liver fibrosis was induced by subcutaneous injection of 40% (v/v) of CCl₄ diluted in olive oil (3mL/kg body weight) twice per week for 8 weeks. Liver histopathological study was performed. Aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and albumin (ALB) of the serum were determined for evaluating the liver function. In order to reveal the possible mechanisms of the anti-fibrotic effects, oxidative stress level, hepatic collagen metabolism, and hepatic stellate cells (HSCs) activation were investigated. Furthermore, the mRNA expression of the fibrotic-related factors was measured by the quantitative real-time RT-PCR. RESULTS: TPs successfully attenuated liver injury induced by CCl₄ shown by histopathological sections of livers and improved liver function as indicated by decreased ALT, AST and ALP levels and increased ALB levels in serum of the rats. TPs significantly increased the hepatic Cu/Zn SOD and GSH-Px activities along with GSH content while a remarkable decrease in MDA content. Both immunohistochemical staining and mRNA expression levels of α-SMA indicated a profound suppression of HSCs activation. Furthermore, it significantly inhibited the mRNA expression of the pro-fibrotic cytokines Col α1(I), Col α1(Ш), MMP-2, TIMP-1, TIMP-2, PDGF-β, TGF-β1, CTGF and TNF-α and restored the hepatoprotective factor HGF. CONCLUSION: These results suggest that the protective effects of TPs in chronic CCl₄-induced liver fibrosis might be related with the reduction of oxidative damage, the inhibition of HSCs activation, the down-regulation of pro-fibrogenic stimuli and the protection of hepatocytes.