Convallatoxin ameliorates fibroblast-like synoviocytes-mediated synovial inflammation and joint destruction in rheumatoid arthritis by targeting IDH1

Convallatoxin (CNT), a cardiac glycoside purified from a traditional Chinese herb Adonis amurensis Regel et Radde, has been reported to exert anti-inflammatory and antitumor effects. However, its therapeutic effect on rheumatoid arthritis (RA), a chronic inflammatory disorder, remains unexplored. Thus, this study aimed to investigate the impact of CNT on regulating key functions of fibroblast-like synoviocytes (FLS) from patients with RA, evaluate its therapeutic efficacy on Collagen induced arthritis (CIA) mouse model and further elucidate the underlying molecular mechanisms. Cell viability, proliferation and Apoptosis were assessed using CCK8, EdU and Annexin V-AF647/ PI assays, respectively. RA FLS migration and invasion were evaluated using wound healing assay, Transwell and Matrigel assays. mRNA and protein levels of proinflammatory cytokines and Matrix Metalloproteinases (MMPs) were analyzed by RT-qPCR and ELISA, respectively. Protein expression in RA FLS and synovial tissues was examined via Western blotting and immunohistochemistry. Furthermore, RNA Sequencing was employed to identify the potential downstream targets of CNT. The in vivo therapeutic efficacy of CNT was investigated using a CIA mouse model. In vitro experiments demonstrated that CNT (7.5, 15 and 30 nM) dose dependently inhibited migration, invasion and expression of IL-6, CCL2, MMP-2 and MMP-13 of RA FLS, without affecting proliferation and Apoptosis. In vivo study showed that CNT treatment (50ug/kg/d and 150ug/kg/d) attenuated synovial inflammation and joint destruction in mice with CIA. Mechanistically, IDH1 was identified as the potential downstream target of CNT in RA FLS. IDH1 expression was significantly elevated in RA FLS and RA synovial tissues. Moreover, both CNT treatment and IDH1 knockdown suppressed Akt and NF-κB p65 phosphorylation. CNT inhibits aggressive behavior and inflammatory response of RA FLS by inhibiting IDH1-mediated activation of the Akt and NF-κB signaling pathways. Our findings suggest that CNT may be a potential novel therapeutic agent for RA.

Convallatoxin; Fibroblast-like synoviocytes; IDH1; Joint destruction; Rheumatoid arthritis; Synovial inflammation.