SIN supressed angiogenesis in RA via HIF-1α–VEGF–ANG-1 axis. To treat with SIN could depress the arthritis index, histopathologic scores and microvessel density, downregulated the level of HIF-1α, VEGF and ANG-1 in peripheral serum and CIA synovium. CFA, complete Freund’s adjuvant; CII, type II collagen; HIF-1α, hypoxia-inducible factor-1α; VEGF, vascular endothelial growth factor; ANG-1 angiopoietin 1.

The objective of the present study is to investigate the inhibitory effects of sinomenine (SIN) on angiogenesis in a collagen-induced arthritis (CIA) mouse model.

Arthritis assessments for all mice were recorded. The histopathological assessments were performed following haematoxylin and eosin (HE) staining. Immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) analyses were used to detect the expression of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and angiopoietin 1 (ANG-1) in the serum and in the membrane. Immunohistochemistry was employed to detect the synovium microvessel density (MVD).

Compared with the CIA model group, SIN significantly ameliorated swelling and erythema extension, decreased the arthritis index, reduced inflammation, cartilage damage and bone erosion, and lessened the number of CD31 positive cells on the synovium. Moreover, the levels of HIF-1α, VEGF and ANG-1 in the synovium and in the peripheral serum were increased in the untreated CIA model group but were significantly reduced in the 30 mg/kg, 100 mg/kg and 300 mg/kg SIN treatment groups.

SIN could mitigate CIA by inhibiting angiogenesis, and the mechanism may associate with the HIF-1α–VEGF–ANG-1 axis. Additionally, our study provides a referable experimental basis for the use of SIN for the treatment of rheumatoid arthritis.