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 p hases of multiple sclerosis (MS). It has a wide spectrum of activity o n immune cells; it may also act on endothelial cells preventing mononu clear cell/endothelium adhesion. The authors studied the in vitro adhe sion of PBMNCs (CD4(+), CD8(+)) from eight healthy controls to endothe lial monolayers pre-stimulated with Dx, gamma-IFN, or both. The effect s of Dx in vitro on endothelial cells did not counteract gamma-IFN-ind uced enhanced adhesion of control PBMNCs. Adhesion phenomena were also studied between cultured human umbilical vein endothelial cells (HUVE Cs) 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(+) cel ls, while after 24 h the adhesion was higher, but not significantly di fferent 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 adhesio n, suggests that under our experimental conditions Dx exerts its modul ating activity on adhesive processes mainly via direct or indirect act ion on circulating immunocytes.