COMPARISON OF CHANGES IN ENDOTHELIAL ADHESION MOLECULE EXPRESSION FOLLOWING UVB IRRADIATION OF SKIN AND A HUMAN DERMAL MICROVASCULAR CELL-LINE (HMEC-1)

We have assessed the pattern of dermal endothelial adhesion molecule e xpression following broadband UVB irradiation in vivo and in vitro. Sk in biopsies were taken from 4 human volunteers at baseline and at 4, 8 and 24 h post-irradiation with 2.5 minimal erythema doses of UVB. Sec tions were stained immunohistochemically for E-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM -1), CD31 and neutrophil elastase. The effect of direct UVB irradiatio n on E-selectin, ICAM-1 and VCAM-1 was examined in a human dermal micr ovascular endothelial cell line, HMEC-1. Cultured HMEC-1 were irradiat ed with 2.5-40 mJ/cm(2) of UVB, and assessed for adhesion molecule exp ression by immunofluorescence microscopy and fluorescence-activated ce ll sorter analysis. In vivo, E-selectin was minimally expressed on EC at baseline and was induced by 4 h following irradiation, P<0.01. ICAM -1 was moderately expressed at baseline and appeared mildly induced at 24 h, although this did not reach statistical significance. VCAM-1 na s weakly expressed in unirradiated skin while CD31 was moderately expr essed, but neither was induced by UVB irradiation. A significant neutr ophilic infiltrate appeared by 8 h and was maximal at 24 h, P<0.05. Ne utrophil infiltration correlated with E-selectin expression, r=0.96. I n HMEC-1, ICAM-1 was upregulated at 24 h post-irradiation, with an inc rease in mean channel fluorescence from 100% at baseline to 145 (SD12) % at 24 h, P<0.05. No change was seen in expression of E-selectin, VCA M-1 or CD31. These studies support the involvement of endothelial adhe sion molecules E-selectin and ICAM-1 in UVB-induced inflammation. Wher eas ICAM-1 is upregulated by direct irradiation of endothelial cells, E-selectin stimulation appears to be an indirect effect.