Abstract
BACKGROUND & AIMS: Connective tissue growth factor (CTGF) expression is intimately associated with hepatic fibrotic pathophysiology. In this study, CTGF production and action was investigated in ethanol-treated mouse primary hepatic stellate cells (HSC) or human LX-2 cells. METHODS: CTGF, transforming growth factor-beta1 (TGF-β1), alpha-smooth muscle actin (α-SMA) or collagen α1(I) mRNA were quantified by real-time PCR after treatment of HSC with ethanol or acetaldehyde. CTGF protein production was assessed by immunoprecipitation or ELISA. Ethanol-stimulated CTGF transcription was investigated using CTGF promoter reporter constructs. The TGF-β1- or CTGF-dependency of ethanol-induced CTGF, α-SMA, or collagen α1(I) was determined using small interfering RNA (siRNA) to TGF-β1 or CTGF. RESULTS: In human steatohepatitis, CTGF was produced by presumptive activated HSC. In cultured human or mouse HSC, production of CTGF, α-SMA and/or collagen was increased by ethanol treatment, an effect mimicked by acetaldehyde and blocked by 4-methylpyrazole (4-MP) or N-acetylcysteine (NAC). CTGF promoter activity was stimulated in a sustained fashion by ethanol or TGF-β1. Mutation of the Smad site or basal control element (BCE-1) in the CTGF promoter caused a 5-fold reduction in ethanol-stimulated CTGF promoter activity. Administration of TGF-β1 siRNA or CTGF siRNA significantly decreased ethanol- or acetaldehyde-stimulated mRNA or protein levels of CTGF, α-SMA or collagen I in LX-2 cells. In mouse HSC, TGF-β1- or ethanol-stimulated CTGF, α-SMA or collagen I were significantly attenuated by CTGF siRNA. CONCLUSIONS: Ethanol-induced α-SMA or collagen α1(I) in HSC are mediated via TGF-β-dependent CTGF production, highlighting potential therapeutic benefits of targeting CTGF in alcoholic liver disease.