Protective effects of IRG1/itaconate on acute colitis through the inhibition of gasdermins-mediated pyroptosis and inflammation response

Inflammatory bowel disease (IBD) is a chronic relapsing gastrointestinal disorder, while the treatment effect is not satisfactory. Immune responsive gene 1 (IRG1) is a highly expressed gene in macrophage in response to inflammatory response and catalyzes the production of itaconate. Studies have reported that IRG1/itaconate has a significant antioxidant effect. This study aimed to investigate the effect and mechanism of IRG1/itaconate on dextran sulfate sodium (DSS)-induced colitis in vivo and in vitro. In vivo experiments, we found IRG1/itaconate exerted protective effects against acute colitis by increasing mice weight, the length of colon, reducing disease activity index and colonic inflammation. Meanwhile, IRG1 deletion aggravated the macrophages/CD4⁺/CD8⁺ T-cell accumulation, and increased the release of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-6, the activation of nuclear factor-κB (NF-κB)/mitogen-activated protein kinase (MAPK) signaling pathway, and gasdermin D (GSDMD) mediated Pyroptosis. Four-octyl itaconate (4-OI), a derivative of itaconate, attenuated these changes, therefore relieved DSS-induced colitis. In vitro experiment, we found 4-OI inhibited the Reactive Oxygen Species production, thereby inhibiting the activation of MAPK/NF-κB signaling pathway in RAW264.7 and murine bone-marrow-derived macrophages. Simultaneously, we found 4-OI inhibited caspase1/GSDMD-mediated Pyroptosis to reduce the release of cytokines. Finally, we found anti-TNF-α agent reduced the severity of DSS-induced colitis and inhibited gasdermin E (GSDME)-mediated Pyroptosis in vivo. Meanwhile, our study revealed that 4-OI inhibited caspase3/GSDME-mediated Pyroptosis induced by TNF-α in vitro. Taken together, IRG1/itaconate exerted a protective role in DSS-induced colitis by inhibiting inflammatory response and GSDMD/GSDME-mediated Pyroptosis, which could be a promising candidate for IBD therapy.