Isorhapontigenin suppresses inflammation, proliferation and aggressiveness of rheumatoid arthritis fibroblast-like synoviocytes by targeting farnesyl diphosphate synthase.

BACKGROUND

Isorhapontigenin (ISO) has been reported to exhibit various therapeutic effects including anti-inflammation and anti-cancer. However, it is still unclear whether ISO has therapeutic efficacy on rheumatoid arthritis (RA). This study aimed to determine the effects of ISO on regulating functions of RA fibroblast-like synoviocytes (FLS) and further to explore the underlying mechanisms.

METHODS

Cell viability was assessed by CCK8 kit, cell apoptosis was measured using Annexin V-APC/PI assay and cell proliferation was evaluated with EdU assay. The cell scratch assay, Transwell assay, and pseudopodia formation assay were applied to detect the migration and invasion of RA FLS. Proinflammatory cytokines and MMPs mRNA expression was analyzed using RT-qPCR, while protein expression was examined by western blotting assay. Furthermore, RNA sequencing was employed to identify the potential downstream targets of ISO. Collagen-induced arthritis (CIA) mice were constructed to investigate the vivo efficacy of ISO.

RESULTS

ISO (12.5, 25, and 50 μΜ) showed inhibition of TNF-α-induced IL-6, IL-8, and MMP-3 expression, as well as proliferation, migration and invasion of RA FLS. However, it did not affect viability or apoptosis. Moreover, there were no significant difference in the efficacy on the proliferation, migration and invasion among ISO, methotrexate and dexamethasone. Mechanistically, farnesyl diphosphate synthase (FDPS) was identified as the novel target of ISO in RA FLS through RNA sequencing and Reactome enrichment analysis. FDPS expression was upregulated in FLS and synovial tissues from RA patients compared to healthy controls. Furthermore, both ISO treatment and FDPS knockdown were found to reduce TNF-α-induced activation of the AKT and ERK1/2 pathways. Interestingly, ISO treatment ameliorated synovial inflammation and joint destruction, and decreased synovial FDPS expression in CIA mice.

CONCLUSION

ISO treatment may attenuate the pathological behaviours of RA FLS by targeting FDPS-mediated phosphorylation of AKT and ERK1/2 pathways. Our data suggest that ISO might be a novel potential agent for RA treatment.