Puerarin, isolated from Pueraria lobata (Willd.), protects against hepatotoxicity via specific inhibition of the TGF-β1/Smad signaling pathway, thereby leading to anti-fibrotic effect

Abstract

Recently, the TGF-β1/Smad signaling pathway has been investigated in the pathogenesis of hepatofibrosis, and pharmacological treatment of liver fibrosis targeted this pathway to determine its contribution to the inhibition of fibrotic development. Importantly, ethnopharmacology-derived Pueraria lobata has been reported to effectively reverse the fibrotic process in the liver. In the present study, we performed dimethylnitrosamine (DMN)-induced liver fibrosis in rats to assess the benefits of puerarin (PR), which was isolated from Pueraria lobata (Willd.), on ECM-derived hepatocytes associated with the TGF-β1/Smad pathway. Our results showed that the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), laminin (LN), type III precollagen (PCIII) and type IV collagen (CIV) were significantly reduced by PR treatment, while hepatic homogenates showed decreased levels of hydroxyproline (Hyp) and collagen I (Col I). Masson's trichrome staining indicated that the DMN-induced liver fibrosis was alleviated. In addition, the protein expression levels of transforming growth factor-β l (TGF-β l), smad2, smad3, α-SMA and TIMP-1 were downregulated specifically by PR treatment, whereas the protein expression levels of smad7 and MMP-1 were upregulated. Furthermore, we evaluated the PR-mediated inhibitory effect on TGF-β1-treated proliferation and activation in a rat liver stellate cell line (HSC-T6). These data resulted in inhibition of the cell growth of HSC-T6 in a dose-dependent manner and a reduction in TβRI, smad2 and smad3 expressed proteins in the presence of PR on TGF-β1-treated HSC-T6 cells, while smad7 levels were downregulated. Taken together, these findings identify a unique effect for PR-regulation of the TGF-β1/Smad pathway in blocking fibrotic development and provide a promising strategy for hepatofibrosis treatment.

Keywords: Hepatic stellate cell; Liver fibrosis; Pueraria lobata; Puerarin; TGF-β1/Smad pathway.