Effects of triterpenoid and iridoid of Eucommiae Cortex on collagen-induced arthritis in rats

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The ethyl acetate fraction of ethanol extract of Eucommiae Cortex can effectively inhibit joint inflammation and bone destruction in rats with collagen-induced arthritis(CIA) and has a potential therapeutic effect on rheumatoid arthritis. The triterpenoid(EU-Tid) and iridoid(EU-Idd) of Eucommiae Cortex are derivatives isolated from the ethyl acetate fraction of the ethanol extract of Eucommiae Cortex, and it is not clear whether they have inhibitory effects on joint inflammation and bone erosion in CIA rats. Therefore, based on the CIA model, the effects of EU-Tid, EU-Idd, and their combination(EU-TP) on arthritis in rats were observed, and the material basis of Eucommiae Cortex against arthritis was further clarified. The samples were collected two and four weeks after administration to observe the pathological changes in different stages of arthritis in CIA rats. For the rats in the model control group, with the prolongation of the disease course, the paw volume and arthritis score increased and histopathological lesions aggravated. Compared with the model control group, the drug administration groups showed reduced paw volumes and arthritis scores, and improved joint lesions and cartilage destruction. Additionally, the mRNA expression levels of tumor necrosis factor-α(TNF-α), interleukin-17(IL-17), and interleukin-23(IL-23) in the spleen were down-regulated in the drug administration groups. EU-TP and EU-Tid at concentrations of 160 and 320 μg·mL~(-1) could significantly inhibit the proliferation of human fibroblast-like synoviocytes-RA(HFLS-RA) and nitric oxide(NO) release in the supernatant of RAW264.7 cells induced by lipopolysaccharide(LPS) at the concentration range of 10-80 μg·mL~(-1) in vitro. EU-Idd had no effect on the proliferation of HFLS-RA but could reduce the NO release at concentrations of 40 and 80 μg·mL~(-1). The results indicated that the terpenoids of Eucommiae Cortex had great potential in the treatment of rheumatoid arthritis.