Effect of microRNA-155 on the interferon-gamma signaling pathway in biliary atresia.

MicroRNAs (miRNAs) are ~22-nucleotide long RNAs that negatively regulate gene expression and inflammatory responses in eukaryotes. The aim of this work was to evaluate the roles of miRNA (miR)-155 on the interferon-γ (IFN-γ)-induced response in biliary atresia (BA), which is the most common form of pediatric chronic liver disease and a leading indication for pediatric liver transplantation. The expression of miR-155 and the suppressor of cytokine signaling 1 (SOCS1) gene in human and mice liver tissues of BA and healthy controls was evaluated. IFN-γ-induced expression of miR-155, inflammatory cytokines and chemokines was determined in bile duct cells. A miR-155 inhibitor was used to determine the influence in the IFN-γ-induced signaling pathway by western blot analysis. A strong up-regulation of miR-155 expression was observed in BA histologic sections and mouse bile duct cells treated with IFN-γ. miR-155 down-regulated SOCS1 protein expression by targeting its mRNA. Up-regulation of miR-155 expression by IFN-γ in bile duct cells led to the activation of signal transducers and activators of transcription 1 (Stat1) and inflammatory cytokines through the Janus kinase (Jak)/Stat pathway, whereas targeted inhibition of miR-155 expression by anti-miRNA oligonucleotides significantly decreased the mRNA or protein expression levels of these inflammatory cytokines and Stat1. Overall, our results suggest that miR-155 regulates the IFN-γ signaling pathway by targeting SOCS1 expression and may be a potential target in BA therapy.