Interleukin-35 attenuates collagen-induced arthritis through suppression of vascular endothelial growth factor and its receptors

Objective: To investigate the effect of interleuldn-35 (IL-35) on vascular endothelial growth factor (VEGF) and its receptors, Flt-1 and Flk-1, in a collagen-induced arthritis (CIA) mouse model of rheumatoid arthritis (RA). Methods: We established a CIA mouse model and injected IL-35 intraperitoneally. The articular index (Al) was measured based on the amount of erythema, swelling, or joint rigidity and synovial histology was measured by hematoxylin and eosin staining (HE staining). The levels of VEGF, Flt-1, Flk-1, and von Willebrand factor (vWF) expression in CIA synovial tissue were determined by immunohistochemistry. The mRNA and protein expression levels of VEGF, Flt-1, Flk-1, TNF-alpha, and INF-gamma were detected by reverse transcription PCR (RT-PCR) and western blots, respectively. Results: The IL-35 treatment decreased the Al and the synovial histological scores of CIA mice. Immunohistochemistry results revealed that the IL-35 treatment downregulated VEGF, Flt-1, Elk-1, and vWF expression in the CIA mice. RT-PCR results showed that the IL-35-treated mice had lower levels of VEGF, Flt-1, Flk-1, and TNF-alpha mRNA expression than those of the PBS-treated mice. While there was no significant difference in the level of INF-gamma mRNA expression between IL-35-treated and PBS-treated mice. Western blot results showed that the IL-35 treatment downregulated the levels of VEGF, Flt-1, Flk-1, and TNF-alpha in CIA mice, but the level of INF-gamma was not significantly affected. Conclusion: These findings show that IL-35 may represent a novel therapeutic agent for RA, and the probable mechanisms may rely on inhibiting VEGF and its receptors Flt-1 and Elk-1. (C) 2016 Elsevier B.V. All rights reserved.