NLRP3 inflammasome mediates oxidative stress-induced pancreatic islet dysfunction

Inflammasomes are multi-protein inflammatory platforms that induce caspase-1 activation and subsequently interleukin (IL)-1 beta and IL-18 processing. The NLRP3 inflammasome is activated by different forms of oxidative stress, and based on the central role of IL-1 beta in the destruction of pancreatic islets, it could be related to the development of diabetes. We therefore investigated responses in wild-type C57B1/6 (WT), NLRP3(-/-) and ASC(-/-) mice after exposing islets to short-term hypoxia or alloxan induced islet damage. NLRP3 deficient islets compared to WT islets had preserved function ex vivo and were protected against hypoxia-induced cell death. Further, NLRP3 and ASC deficient mice were protected against oxidative stress-induced diabetes caused by repetitive low dose alloxan administration, and this was associated with reduced beta-cell death and reduced macrophage infiltration. This suggests that the beneficial effect of NLRP3 inflammasome deficiency on oxidative stress-mediated beta-cell damage could involve reduced macrophage infiltration and activation. To support the role of macrophage activation in alloxan-induced diabetes, we injected WT mice with liposomal clodronate which causes macrophage depletion prior to induction of a diabetic phenotype by alloxan treatment resulting in improved glucose homeostasis in WT mice. We show here that the NLRP3 inflammasome acts as a mediator of hypoxia and oxidative stress in insulin producing cells, suggesting that inhibition of the NLRP3 inflammasome could have beneficial effects on beta-cell preservation.