Identification of Authentic Estrogen Receptor in Cultured Endothelial Cells

Abstract

Background Estrogen plays a major role in the delayed expression of coronary heart disease (CHD) in women, and recent data indicate that postmenopausal estrogen therapy reduces the incidence of CHD by >40%. The mechanism or mechanisms through which estrogen exerts this benefit are unknown, although effects on blood pressure, carbohydrate and lipid metabolism, and coagulation have been suggested. We hypothesized that at least part of the effect of estrogen in reducing the incidence of CHD is due to an effect on endothelial cell function. Methods and Results In the present study, we examined human aortic and umbilical vein endothelial cells and bovine aortic endothelial cells for the presence of estrogen receptors (ERs) through immunoblot and mRNA analyses. Electrophoretic mobility shift assays were also performed to determine the DNA-binding properties of the putative ERs. Nuclear extracts from all three endothelial cell types were found to contain a 67-kD protein that reacted with anti-ER monoclonal antibodies specific to different domains of the ERs. Each of these types of cells expresses proteins that bind specifically to consensus estrogen-responsive elements. Finally, Northern blots verified that endothelial cells express abundant amount of mRNA for the ER. Conclusions These data indicate that endothelial cells constitutively possess the potential for transcriptional regulation of target genes by estrogen. The evolutionary conservation of this receptor in bovine and human endothelial cells suggests a common mechanism for estrogen regulation of endothelial function.