REGULATION OF THE EXPRESSION OF INTERCELLULAR-ADHESION MOLECULE-1 IN CULTURED HUMAN ENDOTHELIAL-CELLS DERIVED FROM RHEUMATOID SYNOVIUM

Objective. To examine the regulation of intercellular adhesion molecul e 1 (ICAM-1) in human synovial microvascular endothelial cells (HSE) a nd human umbilical vein endothelial cells (HUVE) upon exposure to a va riety of agents. Methods. Cultured endothelial cells were treated with various cytokines alone and in combination. The expression of ICAM-1 was evaluated at several levels, including an investigation of messeng er RNA (mRNA) and surface protein expression. Results. Treatment of HS E with interleukin-1alpha (IL-1alpha) or tumor necrosis factor alpha ( TNFalpha) resulted in minimal increases in ICAM-1 expression, in contr ast to findings with HUVE. Incubation of HUVE or HSE with IL-1 or TNF in combination with interferon-gamma (IFNgamma) greatly potentiated th e increase in ICAM-1 surface expression. The synergistic effect of IFN gamma and TNF was confirmed by several methods, including a cell-based enzyme-linked immunosorbent assay, fluorescence-activated cell sortin g, immunofluorescence staining, and determination of mRNA levels. IFNg amma also augmented the actions of several other agonists on HSE, i.e. , IL-4, lipopolysaccharide, and TNFbeta/lymphotoxin. Immunoprecipitati on of TNFalpha + IFNgamma-stimulated, I-125-labeled HSE cells with ant i-ICAM-1 revealed a single 90-kd band, similar in size to ICAM-1 from HUVE treated in an identical manner. Unexpectedly, IFNgamma alone was a potent stimulus for HSE ICAM-1 mRNA synthesis, but was relatively in effective in HUVE. Conclusion. These studies indicate that IFNgamma pl ays a critical synergistic role in the regulation of ICAM-1 expression in human synovial endothelial cells.