Estrogens Increase Transcription of the Human Endothelial NO Synthase Gene

Abstract

Abstract-Estrogens have been found to reduce the incidence of cardiovascular disease that has been ascribed in part to an increased expression and/or activity of the vasoprotective endothelial NO synthase (NOS III). Some reports have shown that the level of expression of this constitutive enzyme can be upregulated by estrogens. The current study investigates the molecular mechanism of the NOS III upregulation in human endothelial EA.hy 926 cells. Incubation of EA.hy 926 cells with 17␤-estradiol or the more stable 17␣-ethinyl estradiol enhanced NOS III mRNA and protein expression up to 1.8-fold, without changing the stability of the NOS III mRNA. There was no enhancement of NOS III mRNA after incubation of EA.hy 926 cells with testosterone, progesterone, or dihydrocortisol or when 17␣-ethinyl estradiol was added together with the estrogen antagonist RU58668, indicating a specific estrogenic response. Nuclear run-on assays indicated that the increase in NOS III mRNA is the result of an estrogen-induced enhancement of NOS III gene transcription. In transient transfection experiments using a 1.6 kb human NOS III promoter fragment (which contains no bona fide estrogen-responsive element, ERE), basal promoter activity was enhanced 1.7-fold by 17␣-ethinyl estradiol. In electrophoretic mobility shift assays, nuclear extracts from estrogen-incubated EA.hy 926 cells showed no enhanced binding activity either for the ERE-like motif in the human NOS III promoter or for transcription factor GATA. However, binding of transcription factor Sp1 (which is essential for the activity of the human NOS III promoter) was significantly enhanced by estrogens. These data suggest that the estrogen stimulation of the NOS III promoter could be mediated in part by an increased activity of transcription factor Sp1. (Hypertension. 1998;31:582-588.)Key Words: 17␣-ethinyl estradiol Ⅲ 17␤-estradiol Ⅲ nitric oxide synthase Ⅲ transcription factor Sp1 S ex differences in the incidence of coronary heart disease are well established. The incidence of coronary heart disease is relatively low among premenopausal women and increases sharply with the occurrence of menopause.

Elevated mean arterial pressure in the ovariectomized rat was normalized by ETA receptor antagonist therapy: absence of cardiac hypertrophy and fibrosis

“…Several studies have demonstrated that oestrogen stimulated the synthesis and release of the vasodilator/antiproliferative factor nitric oxide via both a genomic and non-genomic mechanism acting at the level of nitric oxide synthase (Kim et al, 1999;Kleinert et al, 1998). Secondly, oestrogen increased the synthesis of the potent vasodilator prostacylin via a non-genomic action in endothelial cells (Jun et al, 1998).…”

“…Acting via genomic and non-genomic pathways, oestrogen treatment of endothelial cells stimulated nitric oxide synthase mRNA transcription and enzyme activity, respectively (Kim et al, 1999;Kleinert et al, 1998). Nitric oxide is a potent vasodilator of the underlying vasculature, and an important antiproliferative factor (Lloyd-Jones & Bloch, 1996;Garg & Hassid, 1989).…”

Nitric oxide and coronary vascular endothelium adaptations in hypertension

“…endothelium-dependent genomic action of estrogen in the coronary vasculature Activation of estrogen receptors (ER) mediates the upregulation of eNOS 128,132 via a specific estrogen response element in the eNOS gene promoter region (Figure 2). 133 Muller-Delp and colleagues demonstrated that estrogen treatment increased eNOS protein in coronary arteries of ovariectomized ER α -deficient mice.…”

Progesterone enhances cytokine-stimulated nitric oxide synthase II expression and cell death in human breast cancer cells

“…Inhibition by L-NAME, a specific inhibitor of NOSIII, and the fact that NOSII is not expressed under these circumstances, indicate that the most likely candidate for this effect is NOSIII. Indeed it has previously been shown that E2 induces NOSIII expression 21 and activity. 34 Several studies have shown a positive correlation of NOSIII and oestrogen receptors in breast tumours 35,36 and that the low level of NO produced by NOSIII is associated with endothelial proliferation.…”