Phytoestrogens increase the capacity of serum to stimulate prostacyclin release in human endothelial cells

Background. Both the estrogen receptor (ER) alpha and beta isoforms are expressed in the endothelium. The ER beta has been assigned a crucial role in normal vascular wall function. Prostacyclin has been ascribed a beneficial effect on vessel wall physiology. Isoflavones bind with higher affinity to ER beta. We investigated the hypothesis that their administration to postmenopausal women can promote endothelial prostacyclin production. Methods. Twenty-five healthy postmenopausal women with mild climacteric symptoms received capsules containing 55 mg/day isoflavones derived from soy and red clover for 6 months. Cultured human umbilical vein endothelial cells (HUVECs) were exposed for 24 h to serum collected before the initiation of therapy and then after 3 and 6 months of continuous therapy. Prostaglandin production was measured in culture medium. Results. In the presence of serum obtained after isoflavone treatment, the prostacyclin production increased significantly from 2.7 +/- 0.5 ng/mg protein at baseline to 3.4 +/- 0.7 ng/mg protein at 3 months (p less than or equal to 0.05), and to 3.8 +/- 0.7 ng/mg protein at 6 months (p less than or equal to 0.05 vs. baseline and 3 months' treatment). Conclusions. Serum obtained from postmenopausal women treated with isoflavones stimulates the capacity to produce prostacyclin by HUVECs in culture, an effect that could contribute to a beneficial cardiovascular effect of phytoestrogens.