CD40 engagement on synovial fibroblast up-regulates production of vascular endothelial growth factor

We tested the impact of CD40 engagement on the production of vascular endothelial growth factor (VEGF) from rheumatoid synovial fibroblasts, Fibroblast-like synovial cells (FLS) were prepared from the synovial tissues of rheumatoid arthritis patients and cultured in the presence of CD40 ligand-transfected (CD40L(+)) L cells. VEGF levels were determined in the culture supernatants by ELISA. Stimulation of FLS by CD40L(+) L cells increased the production of VEGF by 4.1-fold over the constitutive levels of unstimulated FLS, The CD40L on activated T cells from rheumatoid synovial fluid also up-regulated VEGF production from FLS. Neither indomethacin nor Abs to IL-1 beta, TNF-alpha, and TGF-beta did affect CD40L-induced VEGF production. Stimulation of FLS with TNF-alpha, IL-1 beta, and TGF-beta increased VEGF production by 1.6-, 2.0-, and 5.2-fold, respectively, and displayed an additive effect on the production of VEGF by CD40L. VEGF mRNA expression was also up-regulated by the stimulation of FLS with membranes from the CD40L(+) L cells. Dexamethasone completely abrogated CD40L-induced VEGF production. In addition, pyrrolidine dithiocarbamate partially down-regulated CD40L-induced VEGF production, showing that the NF-kappa B pathway was partly involved in the signaling of CD40L leading to VEGF production. Collectively, these results suggest that the interaction between CD40 on synovial fibroblasts and CD40L expressed on activated T lymphocytes may be directly involved in the neovascularization in rheumatoid synovitis by enhancing the production of VEGF.