Hepatitis B virus X protein promotes proliferation and upregulates TGF-β1 and CTGF in human hepatic stellate cell line, LX-2

BACKGROUND: Chronic hepatitis B virus (HBV) infection is a major cause of liver fibrosis, but the mechanisms underlying HBV-related fibrogenesis are still unknown. Although the roles of HBV X protein (HBx) remain poorly understood, it is thought to play an important role in the regulation of cellular growth and hepatocarcinogenesis. The aim of this study was to determine the role of HBx in liver fibrogenesis by studying the effect of HBx on the proliferation and expression of fibrosis-related molecules in the human hepatic stellate cell line, LX-2. METHODS: We established an in vitro co-culture system with LX-2 cells and a stable QSG7701-HBx cell line which had been transfected with the HBx gene. H-3-TdR incorporation and flow cytometry were used to determine the effects of HBx on the proliferation of LX-2 cells. a-smooth muscle actin (alpha-SMA), transforming growth factor-beta 1 (TGF-beta 1), transforming growth factor-beta receptor II (TGF-beta R II), and connective tissue growth factor (CTGF) in LX-2 cells were analyzed by Western blotting. In addition, the expression levels of collagen type I (Col I) from the co-cultured media were measured by ELISA. RESULTS: H-3-TdR incorporation increased significantly in LX-2 cells co-cultured with QSG7701-HBx cells compared to those cultured with QSG7701-pcDNA3 and QSG7701 (non-tumorigenic human liver cell line). Cell cycle results revealed that HBx accelerated the progression of G1 to S in LX-2 cells. The expressions of a-SMA, TGF-beta 1, TGF-beta R 11, CTGF and Col I were significantly increased in the cocultures of LX-2 cells with stable QSG7701-HBx cells. CONCLUSION: These results suggest that HBx may facilitate liver fibrosis by promoting hepatic stellate cell proliferation and upregulating the expression of fibrosis-related molecules.