Increased expression of ICAM-1, E-selectin, and VCAM-1 by cultured human endothelial cells upon exposure to haptens

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Abstract
Contact allergens induce several accessory signals which promote the activation of antigen-specific T cells. One of these signals is the increased expression of adhesion molecules on antigen-presenting cells and endothelial cells. Epicutaneous application of non-toxic doses of 2,4-dinitrofluorobenzene (DNFB) onto the skin of non-sensitized individuals elicited progressive staining for ICAM-1 on dermal microvascular endothelial cells. To elucidate the question of whether contact allergens can act directly on endothelial cells to elevate their expression of surface structures that bind leukocytes, confluent monolayers of human umbilical vein endothelial cells were incubated with the contact allergens NiSO4, CoSO4 or DNFB. The ICAM-1, E-selectin and HLA-DR expression were quantified by immunofluorescence flow cytometric analysis. Furthermore VCAM-1, E-selectin and ICAM-1 transcription were demonstrated by Northern blot hybridization. Constitutive ICAM-1 expression on HUVEC increased similarly to that obtained after LPS (20 micrograms/ml) stimulation after 4 and 24 hours of incubation with 1 or 2 mM NiSO4 or CoSO4, respectively. Pulse-stimulation with 100 or 500 nM DNFB resulted in a modest but significant increase of ICAM-1-positive cells. E-selectin and VCAM-1 were not expressed on untreated HUVEC; 4 to 6 hours exposure to nickel sulfate and LPS resulted in a potent induction of E-selectin and VCAM-1 expression. DNFB and PMA had no significant influence on VCAM-1 expression. None of the tested contact allergens was capable of inducing HLA-DR expression on EC at 48 to 72 hours. Enhanced expression of adhesion molecules may be an important early unspecific mechanism for induction and elicitation of a contact dermatitis.