Direct binding to NLRP3 pyrin domain is a novel strategy to prevent NLRP3‐driven inflammation and gouty arthritis

OBJECTIVE: The NLR family pyrin domain-containing 3 (NLRP3) inflammasome is closely linked to the pathophysiology of a wide range of inflammatory diseases. We aimed to identify small molecules that directly bind to NLRP3 to develop pharmacological interventions for NLRP3-related diseases. METHODS: A structure-based virtual screening analysis was performed with approximately 62,800 compounds to select efficient NLRP3 inhibitors. The production of caspase-1(p10) and IL-1beta was measured by immunoblotting and ELISA to examine NLRP3 inflammasome activation. Two gouty arthritis models and an air pouch inflammation model induced by MSU crystal injection were used for in vivo experiments. Primary synovial fluid cells from gout patients were used to determine human relevance. RESULTS: beta-Carotene (provitamin A) suppressed the NLRP3 inflammasome activation induced by various activators including MSU crystals, in mouse bone marrow-derived primary macrophages (p<0.05). Surface plasmon resonance analysis demonstrated the direct binding of beta-carotene to the pyrin domain (PYD) of NLRP3 (KD =3.41E-06). Molecular modeling and mutation assays revealed the interaction mode between beta-carotene and the NLRP3 PYD. Inflammatory symptoms induced by MSU crystals were attenuated by oral administration of beta-carotene in gouty arthritis mouse models (p<0.05), correlating with its suppressive effects on the NLRP3 inflammasome in inflamed tissues. Furthermore, beta-carotene reduced IL-1beta secretion from human synovial fluid cells isolated from gout patients (p<0.05), showing its inhibitory efficacy in human patient cells. CONCLUSION: Our results present beta-carotene as a selective and direct inhibitor of NLRP3 and the binding to NLRP3 PYD as a novel pharmacological strategy to combat NLRP3 inflammasome-driven diseases, including gouty arthritis.