Celastrol attenuates synovial inflammation and experimental arthritis by modulating PTGS2-associated ferroptosis...

Rheumatoid arthritis (RA) is characterized by persistent synovial inflammation and aggressive activation of fibroblast-like synoviocytes (FLS). Celastrol has recognized anti-inflammatory activity, but its mechanism in RA remains incompletely defined. This study investigated whether the anti-arthritic effect of celastrol is associated, at least in part, with a PTGS2-associated ferroptosis-resistance pathway in FLS. Potential targets of celastrol in RA were identified through integrated bioinformatic analyses. Collagen-induced arthritis (CIA) rats and primary FLS were used to evaluate the effects of celastrol in vivo and in vitro. Joint pathology, inflammatory mediator expression, oxidative stress, iron accumulation, lipid peroxidation, and ferroptosis-related proteins were assessed. Loss- and gain-of-function experiments were performed to examine the functional role of PTGS2. Bioinformatic screening identified PTGS2 as a candidate functional mediator linking celastrol to RA. In CIA rats, celastrol reduced paw swelling, arthritis severity, synovial hyperplasia, inflammatory cell infiltration, and cartilage and bone destruction. In FLS, celastrol suppressed cell proliferation and migration and decreased the expression of pro-inflammatory cytokines. Mechanistically, the combined changes in intracellular iron, lipid peroxidation, mitochondrial function, and ferroptosis-related proteins supported attenuation of a ferroptosis-resistant phenotype after celastrol treatment. PTGS2 expression was markedly elevated in RA models and was downregulated by celastrol. PTGS2 overexpression attenuated the anti-inflammatory effects of celastrol and reversed several ferroptosis-associated changes, supporting a functional role for PTGS2 in this process. Celastrol alleviates synovial inflammation and experimental arthritis, at least in part, in association with PTGS2 modulation and attenuation of a ferroptosis-resistant phenotype in FLS. To our knowledge, these findings provide experimental evidence linking celastrol, PTGS2-associated regulation, and ferroptosis resistance in RA models.