A FACTOR IN HUMAN PLASMA PERMITS PERSISTENT EXPRESSION OF E-SELECTIN BY HUMAN ENDOTHELIAL-CELLS

E-selectin is an inducible endothelial cell adhesion protein that is a critical element in the binding of leukocytes to activated endothelia l cells. It is induced by a variety of proinflammatory soluble substan ces including interleukin-1 (IL-1), tumor necrosis factor (TNF), or ba cterial lipopolysaccharide (LPS). In vitro studies of large vessel end othelial cells demonstrate that stimulation with TNF or IL-1 leads to a rapid, but transient, induction of E-selectin expression that disapp ears within 24 hours. However, in vivo studies have shown that microva scular endothelial cells persistently express E-selectin in chronic in flammatory states, particularly in the skin where it serves as a homin g receptor for memory T cells. Stimulation of dermal-derived microvasc ular endothelial cells (HDMECs) with single doses of IL-1 alpha, TNF a lpha, or LPS resulted in transient but slightly more persistent expres sion of E-selectin than seen after stimulation of large vessel derived umbilical vein endothelial cells (HUVECs). However, stimulation of ei ther HDMECs or HUVECs with repetitive doses of IL-1 alpha, TNF alpha, or LPS in the presence of human serum or plasma resulted in persistent E-selectin expression in vitro. The persistent E-selectin cell surfac e expression was associated with persistent E-selectin mRNA expression and correlated with E-selectin-mediated HL-60 binding to endothelial cell monolayers. The effect of human plasma or serum was dose dependen t, and fractionation of human plasma by gel filtration demonstrated th at the E-selectin persistence activity resolved into high and low mole cular peaks. These data demonstrate that human endothelial cells are c apable of persistent E-selectin expression in vitro and that factors i n human serum or plasma are critical in preventing cytokine refractori ness and loss of E-selectin expression. This study provides a basis to resolve the apparent discrepancies between previous in vivo and in vi tro dynamics of E-selectin expression.