| Summary: | 碩士 === 國防醫學院 === 病理及寄生蟲學研究所 === 105 === Shigellosis is a foodborne illness caused by Shigella species. More than 165 million pepeple have bloody diarrhea and million people died due to Shigella species infection worldwide. In Taiwan, there are 186 reported cases of Shigella species in 2015 and Shigella sonnei is endemic in HIV infected men who have sex with men. Symptoms of shigella infection usually developed diarrhea, abdominal pain, nausea, vomiting, fever and blood in stool due to inflammation in intestinal mucosa. NLRP3 inflammasome controlled the IL-1β secretion and plays important role in the pathogenesis of many diseases. However, the effect of S. sonnei on NLRP3 inflammasome activation is unclear. The goal of this study is to investigate whether S. sonnei would activate NLRP3 inflammasome in macrophage and dissect the mode of action. We found that S. sonnei alone could not significantly activate NLRP3 inflammasome. Notably, S. sonnei activates NLRP3 inflammasome in the presence of lipopolysaccharide, suggesting that S. sonnei provided the activation signal of NLRP3 inflammasome. In addition, we found that S. sonnei induced reactive oxygen species (ROS) production and antioxidant NAC reduced S. sonnei-mediated caspase-1 activation and IL-1β secretion. Extracellular KCl and glybenclamide (ATP-sensitive K+ channels blocker) significantly reduced S. sonnei-mediated IL-1β secretion, indicating that potassium efflux regulated IL-1β secretion, and this effect was associated with P2X7 receptor. In addition, S. sonnei induced mitochondrial ROS production and mitochondrial membrane permeability transition. MitoSOX, an inhibitor of mitochondrial ROS and cyclosporine, an inhibitor of the mitochondrial membrane permeability transition, reduced S. sonnei-mediated IL-1β secretion, suggesting a role for mitochondria in NLRP3 inflammasome activation in response to S. sonnei infection. Furthermore, lysosomal acidification inhibitors NH4Cl and chloroquine diphosphate reduced S. sonnei-mediated IL-1β secretion, indicating that lysosomal acidification was important for S. sonnei-mediated NLRP3 inflammasome activation. Taken together, we demonstrated that S. sonnei induced NLRP3 inflammsome activation through ROS production, potassium efflux, mitochondrial damage and lysosomal acidification.
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