Nobiletin ameliorates monosodium urate-induced gouty arthritis in mice by enhancing AMPK/mTOR-mediated autophagy to inhibit NF-κB/NLRP3 inflammasome activation

Background: Gouty arthritis (GA) is a common rheumatic disease caused by the release of monosodium urate crystal (MSU) deposits into joint space. Nobiletin is a polymethoxylated flavonoid isolated from citrus fruits and has many beneficial activities. This study aimed to elucidate the therapeutic efficacy of nobiletin in GA and to reveal its potential mechanisms. Methods: Phorbol-12-myristate-13-acetate (PMA)-differentiated THP-1 macrophages were primed with lipopolysaccharide (LPS) and then stimulated with MSU crystals in the presence or absence of nobiletin. Cell viability as well as the levels of proinflammatory cytokines, pathway-related proteins, NLRP3 inflammasomes, and autophagy-related proteins were evaluated. MSU was used to induce GA in mice. Hematoxylin-eosin staining was conducted to assess histological morphology changes. Immunofluorescence staining was performed to measure LC3 expression in THP-1 cells and ankle joint tissues. Results: For in vitro analysis, nobiletin reduced LPS and MSU-induced cell viability inhibition. Additionally, nobiletin inhibited inflammation and NF-kappa B/NLRP3 pathway in THP-1 cells. Moreover, nobiletin inhibited the activation of NLRP3 inflammasome by promoting AMPK/mTOR-mediated autophagy. For in vivo analysis, nobiletin attenuated MSU-induced GA in mice. Additionally, nobiletin suppressed inflammation and NF-kappa B/ NLRP3 pathway and promoted tissue autophagy in GA mice. Conclusion: Nobiletin prevents MSU-induced GA in mice by inhibiting NF-kappa B/NLRP3 inflammasome activation through AMPK/mTOR-mediated autophagy.