Estrogens in vascular biology and disease: where do we stand today?

Whereas hormone therapy may increase the risk of coronary heart disease and stroke in menopausal women, epidemiological studies (protection in premenopausal women) suggest and experimental studies (prevention of fatty streak development in animals) demonstrate a major atheroprotective action of estradiol. There is also evidence for a thrombogenic effect of oral estrogens. An understanding of the deleterious and beneficial effects of estrogens is thus required.

The immuno-inflammatory system plays a key role in the development of fatty streak deposit as well as in the rupture of the atherosclerotic plaque. Whereas estradiol favors an anti-inflammatory effect in vitro (cultured cells), it rather elicits a pro-inflammatory response in vivo involving several subpopulations of the immuno-inflammatory system, which could contribute to plaque destabilization. Endothelium is another important target for estrogens, since estradiol potentiates endothelial nitric oxide and prostacyclin production. The respective actions of estrogens on these cell populations may be influenced by the timing of hormonal therapy initiation, hormone regimens, status of the vessel wall and expression of isoforms of estrogen receptors alpha and beta.

A better understanding of the balance between the deleterious and beneficial effects of estrogens is required and should help to improve hormonal therapy safety and to optimize the prevention of cardiovascular disease after menopause.