Anti–interleukin-6 receptor antibody therapy reduces vascular endothelial growth factor production in rheumatoid arthritis.

To investigate whether interleukin-6 (IL-6) is a regulator of vascular endothelial growth factor (VEGF) in rheumatoid arthritis (RA). Serum VEGF levels in RA patients were assayed before and after 8 weeks or 24 weeks of maintenance therapy with humanized anti–IL-6 receptor monoclonal antibody (anti–IL-6R mAb). VEGF secreted by RA synovial fibroblasts cultured in the presence of IL-6, IL-1β, and/or tumor necrosis factor α (TNFα) was measured. The inhibitory effect of anti–IL-6R mAb, recombinant IL-1 receptor antagonist (IL-1Ra), and anti-TNFα mAb on VEGF production was also examined. Serum VEGF levels in RA patients before anti–IL-6R mAb therapy were significantly higher than those in healthy controls (P < 0.0005). Treatment of RA patients with anti–IL-6R mAb normalized serum VEGF levels. In the in vitro study, IL-6 and IL-1β each induced a slight amount of VEGF production in synovial cells, but TNFα did not. Although VEGF-inducing activity of these cytokines was not remarkable when they were added alone, IL-6 acted synergistically with IL-1β or TNFα to induce VEGF production. There was no synergistic effect between IL-1β and TNFα. In the presence of all of these cytokines, anti–IL-6R mAb eliminated the synergistic effect of IL-6, IL-1β, and TNFα, while IL-1Ra or anti-TNFα mAb did not. Anti–IL-6R mAb therapy reduced VEGF production in RA. IL-6 is the pivotal cytokine that induces VEGF production in synergy with IL-1β or TNFα, and this may be the mechanism by which IL-6 blockade effectively suppresses VEGF production in synovial fibroblasts. [ABSTRACT FROM AUTHOR]