Regulation of epithelial injury and bile duct obstruction by NLRP3, IL-1R1 in experimental biliary atresia

摘要

Background & AimsBiliary atresia (BA) results from a neonatal inflammatory and fibrosing obstruction of bile ducts of unknown etiology. Although the innate immune system has been linked to the virally induced mechanism of disease, the role of inflammasome-mediated epithelial injury remains largely undefined. Here, we hypothesized that disruption of the inflammasome suppresses the neonatal proinflammatory response and prevents experimental BA. MethodsWe determined the expression of key inflammasome-related genes in livers from infants at diagnosis of BA and in extrahepatic bile ducts (EHBDs) of neonatal mice after infection with rotavirus (RRV) immediately after birth. Then, we determined the impact of the wholesale inactivation of the genes encoding IL-1R1 (Il1r1?/?), NLRP3 (Nlrp3?/?) or caspase-1 (Casp1?/?) on epithelial injury and bile duct obstruction. ResultsIL1R1, NLRP3andCASP1mRNA increased significantly in human livers at the time of diagnosis, and in EHBDs of RRV-infected mice. InIl1r1?/?mice, the epithelial injury of EHBDs induced by RRV was suppressed, with dendritic cells unable to activate natural killer cells. A similar protection was observed inNlrp3?/?mice, with decreased injury and inflammation of livers and EHBDs. Long-term survival was also improved. In contrast, the inactivation of theCasp1gene had no impact on tissue injury, and all mice died. Tissue analyses inIl1r1?/?andNlrp3?/?mice showed decreased populations of dendritic cells and natural killer cells and suppressed expression of type-1 cytokines and chemokines. ConclusionsGenes of the inflammasome are overexpressed at diagnosis of BA in humans and in the BA mouse model. In the experimental model, the targeted loss of IL-1R1 or NLRP3, but not of caspase-1, protected neonatal mice against RRV-induced bile duct obstruction. Lay summaryBiliary atresia is a severe inflammatory and obstructive disease of bile ducts occurring in infancy. Although the cause is unknown, activation of the innate and adaptive immune systems injures the bile duct epithelium. In this study we found that patients’ livers had increased expression of inflammasome genes. Using mice engineered to inactivate individual inflammasome genes, the epithelial injury and bile duct obstruction were prevented by the loss of Il1r1 or Nlrp3,with a decreased activation of natural killer cells and expression of cytokines and chemokines. In contrast, the loss of Casp1 did not change the disease phenotype. Combined, the findings point to a differential role of inflammasome gene products in the pathogenic mechanisms of biliary atresia.