Estrogens and Glucocorticoids Inhibit Endothelial Vascular Cell Adhesion Molecule-1 Expression by Different Transcriptional Mechanisms

Abstract

The antiatherogenic effect of estrogen is mediated, in part, by inhibitory effects on endothelial vascular cell adhesion molecule-1 (VCAM-1) expression. To determine the mechanism by which estrogen regulates VCAM-1 expression, we compared the effect of 17beta-estradiol (E(2)) and of the glucocorticoid dexamethasone (Dex) on lipopolysaccharide (LPS)-induced VCAM-1 expression in human endothelial cells. E(2) decreased LPS-induced VCAM-1 mRNA and protein expression to a greater extent than Dex. Dex, but not E(2), stabilized VCAM-1 mRNA. This correlated with inhibition of monocytoid U937 cell adhesion to endothelial cells. Transfection of endothelial cells with a functional VCAM-1 promoter construct showed that E(2) inhibited LPS-induced VCAM-1 gene transcription more potently than did Dex. However, using a truncated construct containing only the nuclear factor-kappaB (NF-kappaB)-responsive elements but lacking the consensus sequences for activator protein-1 (AP-1) and GATA, E(2) and Dex had similar inhibitory effects. Consistently, gel-shift assays showed that E(2) and Dex comparably inhibit LPS-induced activation of NF-kappaB, whereas E(2) inhibited LPS-induced activation of AP-1 and GATA to a greater extent than Dex. E(2) inhibition of NF-kappaB after LPS treatment was associated with decreased inhibitor kappaB (IkappaB) kinase activity and with a stabilization of the NF-kappaB inhibitor IkappaBalpha. These results indicate that E(2) decreases VCAM-1 gene expression through the inhibition of NF-kappaB, AP-1, and GATA and suggest novel mechanisms for the antiatherogenic effect of estrogen on the vascular wall.