Objective: Vascular endothelial growth factor (VEGF) has been suggested to play a critical role in the pathogenesis of rheumatoid arthritis (RA). It has been demonstrated that synthetic arginine-rich hexapeptide, RRKRRR, shows significant inhibition of VEGF-induced angiogenesis, and also retarded the growth and metastasis of colon carcinoma cell by blocking the interaction between VEGF and its receptor. In this study, we investigated whether anti-VEGF RRKRRR peptide (dRK6) could regulate the activation of mononuclear cells of RA patients and suppress collagen-induced arthritis (CIA) in mice. Methods: Synovial fluid mononuclear cells (SFMC) or synoviocytes from RA patients were cultured in the presence of VEGF, and the levels of TNF-Ձ and IL-6 were determined in the culture supernatants by ELISA. Blocking experiments were performed by adding dRK6 to thecells stimulated with VEGF. Additionally, the in vivo effect of dRK6 on the development of arthritis was tested in collagen induced arthritis (CIA) in DBA/1 mice. T cell responses to type II collagen (CII) and IgG antibodies to CII were examined in draining lymph node cells and sera of the mice, respectively. Results: dRK6 showed concentration-dependent inhibitory activity for the VEGF binding to its receptor on human vascular endothelial cells. The treatment of dRK6 completely abrogated the VEGF-induced productions of TNF-Ձ and IL-6 by RA SFMC or synoviocytes. Moreover, a subcutaneous injection of dRK6 resulted in a dose-dependent decrease in the severity and incidence of CIA in mice. In these mice, the T cell responses to type II collagen (CII) in lymph node cells and circulating IgG antibodies to CII were also dose-dependently inhibited by the peptides. Conclusion: We observed firstly that anti-VEGF dRK6 blocked the VEGF-induced production of pro-inflammatory cytokine from RA SFMC and synoviocytes, and suppressed the ongoing paw inflammation in mice. These data suggest that dRK6 may be an effective strategy in the treatment of RA, and could be applied to modulate various chronic VEGF-dependent inflammatory diseases.

Keywords: Rheumatoid arthritis, Vascular endothelial growth factor, RRKRRR, Collagen induced arthritis