ICAM-2 is a cell surface adhesion molecule constitutively expressed on the endothelium, involved in leukocyte recruitment into tissues. We recently showed that pro-inflammatory cytokines tumour necrosis factor (TNF)-α and interleukin (IL)-1β down-regulate ICAM-2 expression at the transcriptional level. Here we investigate the elements in the ICAM-2 promoter required for the TNF-α-mediated down-regulation. Site directed mutagenesis of the ICAM-2 promoter implicated three consensus sites for Ets transcription factors in basal activity; two of these sites were also involved in the TNF-α-induced down-regulation. Electrophoretic mobility shift assays (EMSA) performed in human umbilical vein endothelial cells (HUVEC) showed that all three Ets binding sites (EBS) bind nuclear proteins.

TNF-α treatment (10 ng/ml for 24 hours) decreased binding to the double −135/−127EBS, but not to the −44EBS. The Ets family member Erg was found to be constitutively expressed in HUVEC, and TNF-α down-regulated Erg protein levels. Furthermore, an Erg cDNA transactivated the ICAM-2 promoter when transiently transfected into both HeLa cells and HUVEC. Protein expression of ICAM-2 and Erg was found to be similarly regulated by TNF-α in an ex vivo artery model. These data suggest that constitutive endothelial genes ICAM-2 and Erg are on the same pathway of cytokine-dependent regulation of gene expression.