In Vivo And In Vitro Action Of Dexamethasone On Adhesion Between Pbmncs And Endothelial Cells

Dexamethasone (Dx) is a synthetic steroid commonly used in the acute phases of multiple sclerosis (MS). It has a wide spectrum of activity on immune cells; it may also act on endothelial cells preventing mononuclear cell/endothelium adhesion. The authors studied the in vitro adhesion of PBMNCs (CD4(+), CD8(+)) from eight healthy controls to endothelial monolayers pre-stimulated with Dx, gamma-IFN, or both. The effects of Dx in vitro on endothelial cells did not counteract gamma-IFN-induced enhanced adhesion of control PBMNCs. Adhesion phenomena were also studied between cultured human umbilical vein endothelial cells (HUVECs) and PBMNCs (CD45(+), CD14(+)) from six MS patients treated in vivo with Dx (8 mg, intravenously). After the in vivo Dx treatment, PBMNC adhesion to endothelium decreased at 3 h, particularly for CD14(+) cells, while after 24 h the adhesion was higher, but not significantly different from the baseline level in stimulated or unstimulated HUVECs. The lack of efficacy of in vitro Dx treatment of HUVECs in modulation of PBMNCs, as opposed to in vitro-Dx-induced changes in PBMNCs adhesion, suggests that under our experimental conditions Dx exerts its modulating activity on adhesive processes mainly via direct or indirect action on circulating immunocytes.