Inhibition of ALOX5-dependent ferroptosis by 6-C-methylquercetin: a potential therapeutic approach for alleviating rheumatoid arthritis.

Rheumatoid arthritis (RA), a chronic autoimmune disease, requires novel therapeutic targets. Ferroptosis, an iron-dependent form of regulated cell death, is closely linked to RA pathogenesis through its mediation of inflammation, oxidative stress, and lipid peroxidation. ALOX5, a member of the lipoxygenase family, is an important regulator of ferroptosis. Inhibiting ALOX5-dependent ferroptosis in joint synovial tissue may thus offer a potential therapeutic strategy for RA. Natural compound 6-C-Methylquercetin possesses robust anti-inflammatory and antioxidant properties, and network pharmacology identifies ALOX5 as its key target against RA. This study aimed to elucidate the pathogenic roles of ALOX5-mediated ferroptosis in RA and evaluate the therapeutic potential of 6-C-methylquercetin. Through in vivo and in vitro experiments, ALOX5 overexpression in RA fibroblast-like synoviocytes (FLSs) was shown to activate ferroptosis, characterized by elevated levels of MDA, lipid ROS, ROS, Fe, ACSL3, NOX1, and COX2, alongside reduced GSH/GSSG ratio and GPX4 expression. Conversely, 6-C-methylquercetin ameliorated RA progression by targeting ALOX5 to disrupt the ALOX5-COTL1 interaction, inhibit aberrant PI3K/AKT pathway activation, and consequently suppress ferroptosis and pro-inflammatory cytokine secretion in FLSs. Further molecular computational simulations, surface plasmon resonance (SPR) and cellular thermal shift assay (CETSA) validated ALOX5 as a direct target of 6-C-methylquercetin, and high-affinity binding was achieved through the B-ring C4'-hydroxyl group of 6-C-methylquercetin, forming a hydrogen-bond network with amino acid residue (ARG411) in the ALOX5 active site. In the collagen-induced arthritis (CIA) mouse model, 6-C-methylquercetin effectively alleviated synovial inflammation and ankle joint damage, reconfirmed its inhibitory effect on ferroptosis, and demonstrated favorable in vivo biosafety. These findings establish ALOX5-driven ferroptosis as a novel therapeutic target for RA, while 6-C-methylquercetin demonstrates dual anti-ferroptotic and anti-inflammatory efficacy through specific ALOX5 inhibition, highlighting its translational promise.