NLRP3 inflammasome activation results in liver inflammation and fibrosis in mice infected with Schistosoma japonicum in a Syk-dependent manner.

Granulomatous and fibrosing inflammation in response to soluble egg antigen (SEA) from Schistosoma japonicum (S. japonicum) is the main pathological process of S. japonicum infection. Inflammasome activation has recently been implicated in the pathogenesis of liver disease. However, the role of inflammasome activation in schistosomiasis-associated liver fibrosis (SSLF) has not been extensively studied. In this study, it is demonstrated that the NLRP3 inflammasome is markedly activated in mouse HSCs both in vivo and in vitro during S. japonicum infection. Furthermore, it is demonstrated that inhibition of NLRP3 inflammasome significantly alleviates the liver inflammation and collagen deposition that are induced by infection with S. japonicum. The mechanism of SEA-induced NLRP3 inflammasome activation is studied in isolated, cultured mouse HSCs and it is shown that SEA-induced NLRP3 inflammasome activation in HSCs is dependent upon the activities of spleen tyrosine kinase (Syk), an enzyme usually associated with a pathogen recognition receptor for fungal pathogens. Moreover, it is demonstrated that Dectin-1 and JNK signaling are also involved in SEA-induced NLRP3 inflammasome activation in HSCs. These data shed new light on the mechanisms of NLRP3 inflammasome activation during an infection with S. japonicum, and further characterize its role in schistosomiasis-associated liver fibrosis (SSLF).