Nimbolide ameliorates ARDS and ulcerative colitis by disrupting NLRP3 inflammasome activation.

Excessive activation of the NLRP3 inflammasome drives the pathogenesis of diverse inflammatory diseases. However, the clinical application of NLRP3 inflammasome inhibitors remains a significant challenge. Here, we screen a natural product library of 126 compounds and identify Nimbolide (NIM), a triterpenoid from Azadirachta indica, as a potent suppressor of IL-1β secretion. Cellular studies reveal that NIM dose-dependently suppresses NLRP3 inflammasome activation, thereby the blocking Caspase-1 cleavage, IL-1β release, and pyroptosis in macrophages. Importantly, NIM exhibits high selectivity for NLRP3 inflammasome, showing no significant inhibition of non-NLRP3 inflammasomes. Mechanistically, NIM exerts dual effects by suppressing both NF-κB-dependent priming and NLRP3 inflammasome assembly. Molecular investigations reveal that NIM directly targets the Lys565 within the NLRP3 NACHT domain, thereby hindering inflammasome assembly. Using male C57BL/6 and Nlrp3-knockout mice, we demonstrate that NIM administration effectively alleviates inflammation and pathological damage in models of LPS-induced acute respiratory distress syndrome (ARDS) and DSS-induced ulcerative colitis. Collectively, our findings highlight NIM as a natural inhibitor that targets both the priming and assembly phases of NLRP3 inflammasome activation, offering a dual-modulatory strategy for treating NLRP3-driven inflammatory disorder.