Abstract
Estradiol (E(2)) causes endothelium-dependent vasodilation, mediated, in part, by enhanced nitric oxide (NO) release. We have previously shown that E(2)-induced activation of endothelial nitric oxide synthase (eNOS) reduces its calcium dependence. This pathway of eNOS activation is unique to a limited number of stimuli, including shear stress, the response to which is herbimycin-inhibitable. Consistent with this, herbimycin and geldanamycin pretreatment of human umbilical vein endothelial cells (HUVEC) abrogated E(2)-stimulated NO release and cGMP production, respectively. These benzoquinone ansamycins are potent inhibitors of Hsp90 function, which has recently been shown to play a role in stimulus-dependent eNOS activation. As in response to shear, E(2) induced an Hsp90-eNOS association, peaking at 30 min and completely inhibited by the conventional estrogen receptor antagonist ICI 182,780. These findings suggest that Hsp90 plays an important role in the rapid, estrogen receptor-mediated modulation of eNOS activation by estrogen.
Highlights
Estradiol (E2) causes endothelium-dependent vasodilation, mediated, in part, by enhanced nitric oxide (NO) release
E2 does not affect the total amount of calmodulin bound to endothelial nitric oxide synthase (eNOS) in human umbilical vein endothelial cells (HUVEC). This suggests that the mechanism by which E2 activates eNOS does not involve significant changes in calmodulin binding to the enzyme complex in the absence of increased cytosolic calcium
Because herbimycin has a potent effect on E2-stimulated NO release and heat shock protein 90 (Hsp90) appears to have a regulatory effect on eNOS function [23], we evaluated whether E2 stimulation of human endothelial cells (EC) promotes an Hsp90eNOS association, one that could be critical in modulating eNOS activity
Summary
(Received for publication, August 3, 1999, and in revised form, December 2, 1999). Kerry Strong Russell‡, M. Shown that the increase in NO release is due to activation of the endothelial form of NO synthase (eNOS or NOS 3) This activation appears to significantly reduce the calcium-calmodulin dependence of the enzyme, and we have further demonstrated that treatment of human umbilical vein EC (HUVEC) with estrogen, under conditions which result in NO release, does not result in a measurable increase in free intracellular calcium [6]. This pathway of eNOS activation is unique to a limited number of stimuli, which include the sustained phase of shear stress-induced vasodilation (9 –11). These findings demonstrate that Hsp plays an important role in the regulation of eNOS function by estrogen
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call