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

ObjectiveTo investigate the effect of interleukin-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).MethodsWe established a CIA mouse model and injected IL-35 intraperitoneally. The articular index (AI) 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-α, and INF-γ were detected by reverse transcription PCR (RT-PCR) and western blots, respectively.ResultsThe IL-35 treatment decreased the AI and the synovial histological scores of CIA mice. Immunohistochemistry results revealed that the IL-35 treatment downregulated VEGF, Flt-1, Flk-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-α mRNA expression than those of the PBS-treated mice. While there was no significant difference in the level of INF-γ 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-α in CIA mice, but the level of INF-γ was not significantly affected.ConclusionThese 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 Flk-1.