NLRP3 inflammasome is expressed and regulated in human islets

NRLP3 inflammasome is a protein complex involved in the maturation of IL1 beta. In the onset of type 1 diabetes as well as in islet transplantation, IL-1 beta is one of the cytokines involved in the recruitment of immune cells in islets and eventually in islet destruction. Whether IL-1 beta is produced by islet cells is still under debate and NLRP3 inflammasome-dependent IL-1 beta production has not been yet determined in human islets. The aim of this study was to determine the expression and the regulation of the NRLP3 inflammasome in human islets. Human islets were stimulated with LPS and successively with ATP (LPS + ATP) in the presence or absence of the inflammasome inhibitor glyburide. Islets were also incubated in hypoxic or normoxic conditions for 24 h in the presence or absence of glyburide. Then, IL1B and NLRP3 expression was studied by real time PCR, protein expression by western blot, protein localization by immunofluorescence and protein secretion by ELISA. LPS + ATP increased gene expression of NRLP3 and IL1B. Glyburide partially prevented this effect. IL-1 beta protein was localized in beta and non-beta cells. Moreover, LPS + ATP increased IL-1 beta protein expression and production, which were prevented by glyburide. Hypoxia increased gene expression of NRLP3 and IL1B and induced IL-1 beta and caspase-1 production. Finally, hypoxia-induced cell death which was not prevented by inhibition of NLRP3 inflammasome. NRLP3 inflammasome is expressed and plays a role in IL-1 beta production by human islets. By contrast, NRLP3 inflammasome activation is not involved in islet cell death induced by hypoxia.