Antiarthritic Effects of Celastrol Associated with Hsp90-mediated Inhibition of the NLRP3 Inflammasome

Objective: Rheumatoid arthritis (RA) is a chronic, progressive autoimmune disease characterized by aggressive and symmetric polyarthritis. Our previous study showed that celastrol (Cel) protected against RA by inhibiting the NLRP3 inflammasome pathway, but the molecular mechanism has not been clarified. Methods: A type II collagen-induced arthritis (CIA) DBA/1 mouse model was used to study the antiarthritic effects of Cel, and paw swelling, arthritis scores, serum cytokine levels, and pathological examinations were carried out. The effects of Cel on the fibroblast-like synoviocytes (FLSs) viability, proliferation and migration of tumour necrosis factor-α (TNF-α)-induced FLSs were tested by MMT assays, EdU staining and scratch wound healing assays. The proinflammatory factors were evaluated by ELISA. The expression of NLRP3, ASC, cleaved caspase-1, p-p65, p65 and p-IκB-α was examined in vitro and in vivo by western blotting and immunofluorescence analysis, respectively. The putative binding sites between Cel and Hsp90 were predicted through molecular docking analysis, the Octet RED96 system and coimmunoprecipitation. Results: The results showed that Cel decreased arthritis severity and reduced TNF-α-induced FLS migration and proliferation. Additionally, Cel decreased the protein expression of NLRP3, ASC, and cleaved caspase-1 and the secretion of proinflammatory cytokines. Furthermore, Cel directly interacted with Hsp90, which interacts with NLRP3, and Cel blocked the interaction between Hsp90 and NLRP3 in FLSs. Conclusion: In summary, our findings demonstrate that Cel regulates NLRP3 inflammasome pathway in vivo and in vitro. Cel inhibits the proliferation and migration of FLSs by blocking the interaction between Hsp90 and NLRP3, thus inhibiting NLRP3 inflammasome pathway.