Iridoid from Eucommia ulmoides Oliv. Exerts Antiarthritis Effects by Inhibiting the JAK2/STAT3 Signaling Pathway In Vivo and In Vitro

The purpose of this study was to investigate the anti-inflammatory effects of EU-Idd both in vivo and in vitro. In vivo, we used the collagen-induced arthritis (CIA) rat model to investigate the efficacy of EU-Idd on rheumatoid arthritis. Hematoxylin-eosin staining and Safranin O-fast green staining were used to evaluate the pathological status of the ankle joints in CIA rats. Micro-CT scanning was used to investigate bone erosion of the ankle joints. In vitro, the effect of EU-Idd on Th17 cell differentiation was identified by flow cytometry. TRAP staining was used to detect osteoclast cells. HFLS-RA model cells, induced by tumor necrosis factor-α(TNF-α), were used to evaluate the anti-inflammatory effects of EU-Idd while the levels of related inflammatory cytokines and JAK2/STAT3 proteins were detected by RT-qPCR and western blotting. EU-Idd alleviated joint inflammation in CIA rats and exerted protective effects on the ankle joints. EU-Idd also prevented the differentiation of CD4(+) T cells into Th17 cells, reduced the number of osteoclasts, and improved the expression levels of bone metabolism-related proteins including OPG and RANKL. Moreover, EU-Idd inhibited the invasion and migration of HFLS-RA cells and downregulated the expression of related inflammatory cytokine genes and the protein expression levels of p-JAK2 and p-STAT3, both in vivo and in vitro. EU-Idd exerts anti-inflammatory and osteoprotective effects by regulating the JAK2/STAT3 pathway in rheumatoid arthritis. These results are beneficial to excavate new pharmaceutical ingredients for rheumatoid arthritis from iridoid.