Shugan Huoxue Huayu Fang attenuates carbon tetrachloride-induced hepatic fibrosis in rats by inhibiting transforming growth factor-β1/Smad signaling.

OBJECTIVE

To investigate the potential mechanism by which Shugan Huoxue Huayu Fang (SGHXHYF) ameliorates liver fibrosis.

METHODS

Liver fibrosis was induced in rats by intraperitoneal injection of carbon tetrachloride (CCl4) in peanut oil solution (40%, 3 mL/kg body weight) twice a week for 8 weeks. A normal control group received the same volume of peanut oil alone. During weeks 5-8, the CCl4-injected rat groups were administered saline (vehicle control), colchicine (0.1 mg/mL, 1 mg/kg, positive control), or SGHXHYF (0.1 mg/mL; 0.3, 0.6 and 1.2 mg/kg) once daily by oral gavage. Rats were sacrificed 24 h after the last treatment. Blood samples were collected for measurement of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), albumin (ALB), collagen Ⅰ and collagen Ⅲ levels. Liver samples were analyzed by histopathological staining, Masson's staining of extracellular matrix proteins, and immune-ohistochemical staining of αsmooth muscle actin (α-SMA). TGF-β1/Smad protein and mRNA levels were analyzed by Western blot and quantitative reverse transcription-polymerase chain reaction analysis, respectively. In vitro experiments were also performed using rat hepatic stellate cells (HSCs).

RESULTS

Compared with the control animals, CCl4-exposed rats exhibited elevated serum levels of ALT, AST, ALP, collagen I, and collagen III; reduced serum levels of ALB; and increased collagen deposition and αSMA expression in liver sections, reflecting liver fibrosis. CCl4 also increased expression of TGF-β1 and the activated (phosphorylated) forms of Smad2 and Smad3 but reduced expression of the negative regulator Smad7 in the liver. Notably, concomitant administration of SGHXHYF to CCl4-exposed rats was found to significantly reverse or abolish the pro-fibrotic effects of CCl4 in the liver and reduced serum transferase levels. Analysis of HSCs in vitro confirmed that, mechanistically, SGHXHYF inhibited activation of the TGF-β1/Smad signaling pathway by downregulating phosphorylated Smad2 and Smad3 and upregulating Smad7 levels.

CONCLUSION

SGHXHYF ameliorated CCl4-induced liver fibrosis by inhibiting the TGF-β1/Smad signaling pathway. These findings suggest that SGHXHYF may have clinical utility for the treatment or prevention of liver fibrosis.