Actions of Estrogen on Uterine Artery Endothelium

Project Summary
Our work funded by this RO1 during this last funding cycle has established that endogenous hydrogen
sulfide (H2S) produced by selective upregulated H2S synthesizing enzyme cystathionine β-synthase (CBS) is
a new uterine artery (UA) dilator system contributing to estrogen-induced and pregnancy-associated rises in
uterine blood flow. This novel pathway has reshaped the view how uterine hemodynamics is regulated during
normal pregnancy. More recently, we reported that H2S stimulates human UA relaxation via activating smooth
muscle (SM) large conductance Ca2+-activated voltage-gated potassium (BKCa) channels; yet, how H2S
mediates estrogen-induced UA dilation in normal and complicated pregnancies remains largely unknown.
Formation of -SSH groups on reactive cysteine(s) in proteins, referred to as sulfhydration or persulfidation,
has emerged as the main signaling route for H2S to exert its biological function. Sulfhydration converts free
thiols (-SH) to persulfide (-SSH) resulting in increased reactivity of modified cysteines due to increased
nucleophilicity of SSH compared with SH. In this competitive renewal RO1 application, we present new data
showing that estrogen and pregnancy can significantly stimulate protein sulfhydration in human UA; and more
interestingly, the elevated levels of total sulfhydrated proteins and sulfhydrated β1 and γ1 subunits of BKCa
channels in human UA in normal pregnancy is significantly reduced in preeclampsia. Thus, we propose to
test a novel hypothesis herein that augmented CBS/H2S sulfhydrates the increased β1 and γ1 BKCa (via
estrogen receptor-dependent transcription) resulting in activation of SM BKCa to mediate estrogen-induced
UA dilation in normal pregnancy and this mechanism is impaired in preeclampsia. This conjecture will be
tested by two specific aims targeting on determining the estrogen-responsive BKCa channels and how
sulfhydration results in activation of these BKCa channels pertaining to UA dilation in pregnancy and
preeclampsia, with comprehensive biochemical, cellular, molecular, pharmacological, and physiological and
electrophysiology approaches using in vitro primary cell culture models of UA smooth muscle cells, ex vivo
studies of human main UA samples associated with different estrogens status from hysterectomy and
myometrial UA samples from normal and preeclamptic pregnancies, and in vivo rat models to study the role
of exogenous and endogenous estrogens in vivo. The proposed studies will establish a novel mechanism for
BKCa channel activation via sulfhydrating its regulatory β1 and γ1 subunits to broadly impact on ion channel
biology. These studies will comprehend specific mechanisms for activation of the estrogen-responsive SM
BKCa channels pertaining to estrogen-induced UA dilation in pregnancy and preeclampsia. Data obtained will
advance our understanding of estrogens and uterine blood flow biology, informing new pathways to assist the
development of alternative strategies for combating preeclampsia. New data obtained will also shed lights
on the understanding of the cardiovascular protective effects of estrogens.
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Grant Number: 3R01HL070562-16S1
NIH Institute/Center: NIH
Principal Investigator: DONGBAO CHEN