Role of activating protein-1 in the regulation of the vascular cell adhesion molecule-1 gene expression by tumor necrosis factor-α

Endothelial cell surface expression of VCAM-1 is one of the initial steps in the pathogenesis of atherosclerosis, The inflammatory response transcription factor nuclear factor (NF)-kappa B plays an important role in the regulation of VCAM-1 expression by various stimuli including tumor necrosis factor (TNF)-alpha. Other transcription factors may modulate this response through interaction with NF-kappa B factors. Since c-Fos/c-Jun (activating protein-1 (AP-1)) are expressed in vascular endothelium during proinflammatory conditions, pie investigated the role of AP-1 proteins in the expression of VCAM-1 by TNF-alpha in SV40 immortalized human microvascular endothelial cells (HMEC), TNF-alpha induced expression of both early protooncogenes, c-fos and c-jun. The ability of TNF-alpha to activate the kappa B-motif (kappa L-kappa R)-dependent VCAM-1 promoter-chloramphenicol acetyltransferase (CAT) reporter gene lacking a consensus AP-I element was markedly inhibited by co-transfection of the expression vector encoding c-fos ribozyme, which decreases the level of c-fos by degrading c-fos mRNA, or c-fos or c-jun oligonucleotides. Conversely, co-transfection of c-Fos and c-Jun encoding expression vectors potentiated the p65/NF-kappa B-mediated transactivation of the VCAM-1 promoter-CAT reporter gene, Furthermore the c-Fos encoding expression vector potentiated by a-fold the transactivation activity of a chimeric transcriptional factor Gal/P65 (containing the transactivation domain of p65 and the DNA binding domain of the yeast transcriptional factor Gal-4). Consistent with the promoter studies, curcumin and. NDGA, inhibitors of AP-I activation, markedly inhibited the ability of TNF-alpha to activate the expression of VCAM-1 mRNA levels at concentration that; did not inhibit the activation of NF-kappa B, In gel mobility supershift assays, the antibodies to c-Fos or c-Jun inhibited the binding of TNF-alpha-activated nuclear NF-kappa B to the kappa L-kappa R, suggesting that both e-Fos and c-Jun interacted with NF-kappa B. These results suggest that AP-I proteins may mediate the effect of TNF-alpha in the regulation of VCAM-1 expression through interaction with NF-kappa B factors in endothelial cells.