NLRP3 is an innate immune sensor contributing to the development of different diseases including monogenic autoinflammatory syndromes, gout, atherosclerosis, and Alzheimer’s disease. The molecule sulfonylurea MCC950 is a NLRP3 inflammasome inhibitor with potential clinical utility. However, the mechanism of action of MCC950 remains unknown. Here, we characterize the mechanism of action of MCC950 in both wild-type and autoinflammatory-related NLRP3 mutants, demonstrating that MCC950 closes the ‘open’ conformation of active NLRP3.

Sepsis is characterized by a systemic inflammatory response followed by immunosuppression of the host. Metabolic defects and mitochondrial failure are common in immunocompromised patients with sepsis. The NLRP3 inflammasome is important for establishing an inflammatory response after activation by the purinergic P2X7 receptor. Here, we study a cohort of individuals with intra-abdominal origin sepsis and show that patient monocytes have impaired NLRP3 activation by the P2X7 receptor. Furthermore, most sepsis-related deaths are among patients whose NLRP3 activation is profoundly altered. In monocytes from sepsis patients, the P2X7 receptor is associated with mitochondrial dysfunction. Furthermore, activation of the P2X7 receptor results in mitochondrial damage, which in turn inhibits NLRP3 activation by HIF-1α. We show that mortality increases in a mouse model of sepsis when the P2X7 receptor is activated in vivo. These data reveal a molecular mechanism initiated by the P2X7 receptor that contributes to NLRP3 impairment during infection.

Pharmacological inhibition of NLRP3 inflammasome activation may offer a new option in the treatment of inflammatory bowel disease. In this work, we report the design, synthesis, and biological screening of a series of acrylate derivatives as NLRP3 inhibitors. The in vitro determination of reactivity, cytotoxicity, NLRP3 ATPase inhibition, and antipyroptotic properties allowed the selection of 11 (INF39), a nontoxic, irreversible NLRP3 inhibitor able to decrease interleukin-1β release from macrophages. Bioluminescence resonance energy transfer experiments proved that this compound was able to directly interfere with NLRP3 activation in cells. In vivo studies confirmed the ability of the selected lead to alleviate the effects of colitis induced by 2,4-dinitrobenzenesulfonic acid in rats after oral administration.

In PAAND, disruption of the +2 position of a 14-3-3 binding motif in pyrin results in its constitutive activation, with spontaneous production of IL-1β and IL-18, associated with inflammatory cell death. The altered serum cytokine profile may explain the different clinical features exhibited by PAAND patients compared with those with FMF.