Activation of endothelial-leukocyte adhesion molecule 1 (ELAM-1) gene transcription

Leukocyte adherence to endothelium is in part mediated by the transient expression of endothelial-leukocyte adhesion molecule 1 (ELAM-1) on endothelial surfaces stimulated by tumor necrosis factor α (TNF), interleukin (IL) 1, or bacterial lipopolysaccharide (LPS). The intracellular factors controlling induction of ELAM-1 mRNA and protein are unknown. In nuclear runoff experiments with cultured human umbilical vein endothelial cells (HUVEC), we demonstrate that transcriptional activation of the ELAM-1 gene occurs following stimulation with TNF. Sequence analysis of the 5′ flanking region of the ELAM-1 gene reveals consensus DNA-binding sequences for two known transcription factors, NF-κB and AP-1. Gel mobility shift assays demonstrate that TNF, IL-1, or LPS (but not IL-2, IL-4, IL-6, interferon γ, histamine, or transforming growth factor β) induces activation of NF-κB-like DNA binding activity in HUVEC. In contrast, neither TNF, IL-1, nor LPS activates proteins that bind to an AP-1 consensus sequence under these experimental conditions. Phorbol 12-myristate 13-acetate, a known activator of protein kinase C (PKC), weakly induces NF-κB-like activity, ELAM-1 mRNA, and ELAM-1 surface expression in HUVEC. However, TNF, IL-1, and LPS do not activate PKC in HUVEC at doses that strongly induce NF-κB-like protein activation and ELAM-1 gene expression. PKC blockade with H7 does not inhibit activation of these NF-κB-like proteins but does inhibit ELAM-1 gene transcription. We conclude that PKC-independent activation of NF-κB in HUVEC with TNF, IL-1, or LPS is associated with, but not sufficient for, activation of ELAM-1 gene transcription.