Sweroside ameliorates rheumatoid arthritis-associated bone destruction by targeting Stat2-Drp1-dependent mitochondrial remodeling and reducing ROS production in osteoclastogenesis.

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by persistent synovial inflammation and progressive bone erosion. Excessive osteoclastogenesis is a central pathological event driving RA-associated bone destruction. Sweroside, a bioactive iridoid glycoside, has been reported to exert anti-inflammatory and cytoprotective effects, but its therapeutic potential against inflammatory osteolysis and its direct molecular target remain unclear.

PURPOSE: This study aimed to investigate whether sweroside protects against RA-associated bone destruction and to identify its direct molecular target and the underlying mechanism, with a particular focus on osteoclastogenesis, mitochondrial remodeling, metabolic reprogramming, and redox homeostasis.

METHODS

Therapeutic efficacy was evaluated in collagen-induced arthritis (CIA) rats by arthritis scoring, histopathological assessment, micro-computed tomography, TRAP staining, immunohistochemistry, and Western blotting. In vitro, RANKL-stimulated BMMs were used to assess osteoclast differentiation, F-actin ring formation, bone resorption, ROS production, mitochondrial biogenesis, mitochondrial membrane potential, ATP generation, and metabolic reprogramming. The molecular mechanism was explored using network pharmacology, DARTS-LC-MS/MS, CETSA, SPR, molecular docking, co-immunoprecipitation, immunofluorescence, and gain- and loss-of-function experiments.

RESULTS

Sweroside markedly ameliorated arthritis severity, synovial inflammation, cartilage destruction, and bone erosion in CIA rats, accompanied by reduced osteoclast accumulation and suppression of Stat2-Drp1 signaling in vivo. In RANKL-stimulated BMMs, sweroside dose-dependently inhibited osteoclast formation, F-actin ring assembly, and bone-resorptive activity, with the most pronounced effect observed during the early stage of osteoclast differentiation. Sweroside also reduced intracellular and mitochondrial ROS levels through activation of the Nrf2-Keap1 antioxidant pathway. In parallel, sweroside suppressed mitochondrial biogenesis and metabolic reprogramming, as reflected by decreases in mitochondrial mass, mitochondrial membrane potential, mtDNA copy number, ATP production, oxidative phosphorylation, and glycolytic activity. Target identification and validation demonstrated that Stat2 is a direct binding target of sweroside. Mechanistically, sweroside disrupted the interaction between Stat2 and Drp1, reduced Stat2 expression and phosphorylation, inhibited Drp1 phosphorylation at Ser616, and attenuated downstream NF-κB activation. Furthermore, Stat2 silencing enhanced, whereas overexpression of Stat2 or phosphomimetic Drp1 partially reversed, the anti-osteoclastogenic effects of sweroside.

CONCLUSION

Sweroside ameliorates RA-associated bone destruction by directly targeting Stat2, thereby suppressing Stat2-Drp1-dependent mitochondrial remodeling, metabolic reprogramming, and oxidative stress. These findings support sweroside as a promising phytotherapeutic candidate for RA and other inflammatory bone-destructive diseases.