Type I IFN induced IL1-Ra expression in hepatocytes is mediated by activating STAT6 through the formation of STAT2: STAT6 heterodimer

The biological activities of type I interferons (IFNs) are mediated by their binding to a heterodimer receptor complex (IFNAR1 and IFNAR2), resulting in the activation of the JAK (JAK1 and TYK2)-STAT (1, 2, 3, 5 isotypes) signalling pathway. Although several studies have indicated that IFN-α and IFN-β can activate complexes containing STAT6, the biological role of this activation is still unknown. We found that exposure of hepatoma cells (HuH7 and Hep3B) to IFN-α or IFN-β led to the activation of STAT6. Activated STAT6 in turn induced the formation of STAT2: STAT6 complexes, which led to the secretion of IL-1Ra. The activation of STAT6 by type I IFN in hepatocytes was mediated by JAK1 and Tyk2. In addition, IFN-α or IFN-β significantly enhanced the stimulatory effect of IL-1β on production of IL-1Ra. The present study suggests a novel function of IFN-α and IFN-β signalling in human hepatocytes. Our results provide evidence for the mechanism how IFN-α and IFN-β modulate inflammatory responses through activation of STAT6 and production of secreted IL-1Ra.