Regulation of the β-cell inflammasome and contribution to stress-induced cellular dysfunction and apoptosis

beta-Cells may be a source of IL-1 beta that is produced as inactive pro-IL-1 beta and processed into biologically-active IL-1 beta by enzymatic cleavage mediated by the NLRP1-, NLRP3- and NLRC4-inflammasomes. Little is known about the beta-cell inflammasomes. NLRP1-expression was upregulated in islet-cells from T2D-patients and by IL-1 beta + IFN gamma in INS-1 cells in a histone-deacetylase dependent manner. NLRP3 was downregulated by cytokines in INS-1 cells. NLRC4 was barely expressed and not regulated by cytokines. High extracellular K+ reduced cytokine-induced apoptosis and NO production and restored cytokine-inhibited accumulated insulin-secretion. Basal inflammasome expression was JNK1-3 dependent. Knock-down of the ASC interaction domain common for NLRP1 and 3 improved insulin secretion and ameliorated IL-1 beta and/or glucolipotoxicity-induced cell death and reduced cytokine-induced NO-production. Broad inflammasome-inhibition, but not NLRP3-selective inhibition, protected against IL-1 beta-induced INS-1 cell-toxicity. We suggest that IL-1 beta causes beta-cell toxicity in part by NLRP1 mediated caspase-l-activation and maturation of IL-1 beta leading to an autocrine potentiation loop.