H2O2 AND TUMOR-NECROSIS-FACTOR-ALPHA ACTIVATE INTERCELLULAR-ADHESION MOLECULE-1 (ICAM-1) GENE-TRANSCRIPTION THROUGH DISTINCT CIS-REGULATORYELEMENTS WITHIN THE ICAM-1 PROMOTER

We investigated the mechanisms by which H2O2 increases intercellular a dhesion molecule 1 (ICAM-1; CD54) expression in endothelial cells. The H2O2-induced increase in ICAM-1 mRNA was inhibited by actinomycin D, by the antioxidant N-acetylcysteine, and by 3-aminobenzamide (which bl ocks oxidant-induced AP-1 activity), but not by pyrrolidine dithiocarb amate (which blocks oxidant-induced NF-kappa B activity). Nuclear run- on and transient transfections of ICAM-1 promoter constructs indicated that H2O2 stimulated ICAM-1 gene transcription by activation of a dis tinct region of the ICAM-1 promoter. The H2O2-responsive element was l ocalized to sequences between -981 and -769 (relative to the start cod on). Located within this region are two 16-base pair repeats, each con taining binding sites for the transcription factors AP-1 and Ets. A si milar composite AP-1/Ets element isolated from the macrophage scavenge r receptor gene conferred H2O2 responsiveness to a minimal promoter. M utation of the 16-base pair repeats within the ICAM-1 promoter prevent ed H2O2-induced DNA binding activity, and their deletion abrogated the H2O2-induced transcriptional activity. In contrast, TNF alpha induced ICAM-1 transcription via activation of promoter sequences between -39 3 and -176, a region with C/EBP and NF-kappa B binding sites. The resu lts indicate that H2O2 activates ICAM-1 transcription through AP-1/Ets elements within the ICAM-1 promoter, which are distinct from NF-kappa B-mediated ICAM-1 expression induced by TNF alpha.