Inhibitory effects of interferons on pancreatic stellate cell activation

AIM: To analyze and to compare the effects of interferon (IFN)-alpha, IFN-beta, and IFN-gamma on pancreatic stellate cell (PSC) activation in vitro and to elucidate the molecular basis of IFN action. METHODS: PSCs were isolated from rat's pancreatic tissue, cultured and stimulated with recombinant rat IFNs. Cell proliferation and collagen synthesis were assessed by measuring the incorporation of 5-bromo-2' -deoxyuridine (BrdU) into DNA and [H-3]-proline into acetic acid-soluble proteins, respectively. Apoptotic cells were determined by FACS analysis (sub-G(1) peak method). Exhibition of the myofibroblastic PSC phenotype was monitored by immunoblot analysis of alpha-smooth muscle actin (alpha-SMA) expression. To assess the activation of signal transducer and activator of transcription (STAT), Western blots using phosphoSTAT-specific antibodies were performed. In studies on STAT1 function, expression of the protein was inhibited by siRNA. RESULTS: IFN-beta and IFN-gamma, but not IFN-alpha significantly diminished PSC proliferation and collagen synthesis. IFN-gamma was the only IFN that clearly inhibited cc-SMA expression. Under the experimental conditions used I no enhanced rate of apoptotic cell death was observed in response to any IFN treatment. IFN-beta and IFN-gamma induced a strong increase of STAT1 and STAT3 tyrosine phosphorylation, while the effect of IFN-alpha was much weaker. Inhibition of STAT1 expression with siRNA was associated with a significantly reduced growth-inhibitory effect of IFN-gamma. CONCLUSION: IFN-beta and particularly IFN-gamma display inhibitory effects on PSC activation in vitro and should