No abstract

Objective. The aim of this study was to evaluate the ability of glucocorticoids to inhibit lymphocyte adhesion to human synovial fibroblasts. Methods. Adhesion of lymphocytes to cultured synovial fibroblasts was measured by counting the number of cells bound to fibroblasts. Surface expression of intercellular adhesion molecule 1 (ICAM‐1) was measured by enzyme‐linked immunosorbent assay, while vascular cell adhesion molecule 1 (VCAM‐1) surface expression was measured by flow cytometry. ICAM‐1 and VCAM‐1 messenger RNA (mRNA) levels were assessed by Northern blot analysis. Results. Stimulation of synovial fibroblasts by the proinflammatory cytokines tumor necrosis factor α, interleukin‐1β, and interferon‐γ resulted in a dose‐dependent increase in lymphocyte adhesion to synovial fibroblasts. This response was inhibited by preincubation of the cells with the synthetic glucocorticoid dexa‐methasone. Since lymphocyte adhesion to synovial fibroblasts is known to be mediated by VCAM‐1 and ICAM‐1, we examined the modulation of VCAM‐1 and ICAM‐1 expression in these cells. All 3 cytokines stimulated VCAM‐1 and ICAM‐1 surface and mRNA expression. Dexamethasone inhibited both VCAM‐1 and ICAM‐1 surface and mRNA expression in a dose‐dependent manner, which correlated with the inhibition of lymphocyte adhesion. Conclusion. Taken together, these results suggest that glucocorticoids may reduce inflammatory responses at extravascular sites by inhibiting the expression of these adhesion molecules, thereby reducing the adhesion of lymphocytes to connective tissue cells.

An in vitro angiogenesis system was designed for screening angiogenic agonists and antagonists. In order to obtain large quantities of cells and reproducibility, human endothelial cells with extended life spans were developed by retroviral transfection. The resulting cells grown in a serum-free medium containing endothelial cell growth supplement (ECGS) have a telomerase activity, extended life spans of at least 21 passages, and an endothelial cell phenotype (diI-acetylated-LDL upake, factor VIII-related antigen, VEGFR-1 and R-2, and tissue-type plasminogen activator (tPA)) that resembled that of unaltered primary endothelial cells. Exceptions were (i) a higher expression of tPA, and (ii) a non-significant growth response to FGF-2 or VEGF stimulation. Within three-dimensional fibrin gels, specific cell clones rapidly formed tubular structures in a more reproducible manner than those observed with low-passage primary cells. Tube formation by primary endothelial cells and those with extended life spans was dependent upon FGF-2 and ECGS, respectively. Both cell types produced FGF-2 and VEGF cytokines. Increasing doses of suramin significantly decreased the size of microvessels formed by both cell lines. These functional results indicate that a vascular matrix system containing human cells with extended life spans can be successfully utilized as an in vitro assay for antiangiogenic compounds.

These combined results provide further evidence of an important role of ICAM-1 in inflammatory synovitis, as well as a potentially novel site of antiinflammatory action of glucocorticoids.