Estrogen‐mediated nitric oxide (NO) production in cultured human vascular endothelial cells

Abstract

Estrogen (E2) is reported to induce the rapid activation of endothelial nitric oxide synthase (eNOS) and NO release, resulting in vasodilation, decreased platelet adhesion and angiogenesis in the vessel wall. In this study, we have used a cell line (EA.hy926) derived from human umbilical vein endothelial cells (HUVECs) to investigate the cellular mechanism underlying E2-induced NO synthesis. Experimentally, NO production and cytosolic free [Ca2+] were monitored using the NO-sensitive dye DAF-FM and Fluo-3, respectively, and agonist-induced changes in membrane potential were recorded using patch clamp techniques. E2 dose-dependently induced rapid increases in NO synthesis, and only modest changes in cytosolic [Ca2+]. The PI3 kinase inhibitor LY294002, the E2 receptor antagonist ICI 182,780, and the eNOS inhibitor L-NAME all blocked E2-mediated NO synthesis. Interestingly, removal of extracellular Ca2+, buffering of cytosolic Ca2+ by BAPTA or inhibition of SK and IK Ca-activated K+ channels by apamin and charybdotoxin did not affect NO production in response to E2, but attenuated ATP-mediated NO synthesis. Unlike ATP or histamine, E2 did not induce hyperpolarization of endothelial cell membrane potential. These observations indicate that in human vascular endothelial cells, E2 induces rapid NO production via a cellular pathway distinct from that utilized by Ca-mobilizing stimuli. (Funded by CIHR)