Glutamine limits NLRP3 inflammasome activation and pyroptosis in macrophages by sustaining the IRG1/itaconate axis.

Abstract

Aberrant activation of NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome increases the release of mature pro-inflammatory cytokines interleukin (IL)-1β and IL-18, and enhances pyroptosis; thereby necessitating tight regulation of the NLRP3 inflammasome. Dysfunctional glutamine metabolism contributes to the pathogenesis of multiple inflammatory disorders, and the precise mechanism remains to be elucidated. Here, we provide evidence that glutamine deprivation enhances NLRP3 inflammasome activation in macrophages. Indeed, the absence of exogenous glutamine specifically enhanced NLRP3 inflammasome assembly, thereby accelerating pyroptosis and promoting the maturation of IL-1β and IL-18. Inhibition of glutaminolysis exhibited a similar effect to glutamine deprivation, whereas this effect was reversed by α-ketoglutarate (α-KG), a tricarboxylic acid (TCA)-cycle intermediate that can be replenished by glutamine supply. We further observed reduced generation of endogenous itaconate by glutamine deprivation and verified that both exogenous supplementation of itaconate derivative and increased endogenous itaconate production by overexpressing immune-responsive gene 1 [IRG1; also known as aconitate decarboxylase 1 (ACOD1)] could replace glutamine to inhibit the NLRP3 inflammasome. Mechanistically, glutamine deprivation decreased the source of substrate and inhibited transcription factor EB (TFEB)-dependent transcriptional upregulation of IRG1, thereby impairing the IRG1/itaconate axis that suppresses the NLRP3 inflammasome. Furthermore, glutamine deficiency was detected in a murine sepsis model, whereas extrinsic glutamine supplementation conferred protection against intestinal inflammation and tissue damage in septic mice. Taken together, our findings provide a novel insight into the link between glutamine metabolism and NLRP3 inflammasome activation, highlighting the target of glutamine metabolism, which holds as a potential therapeutic strategy for inflammatory diseases.