Hydrogen Sulfide Relaxes Human Uterine Artery via Activating Smooth Muscle BKCa Channels.

Yan Li,Jin Bai,Yi-Hua Yang,Naoto Hoshi,Dong-Bao Chen

doi:10.3390/antiox9111127

Abstract

Opening of large conductance calcium-activated and voltage-dependent potassium (BKCa) channels hyperpolarizes plasma membranes of smooth muscle (SM) to cause vasodilation, underling a key mechanism for mediating uterine artery (UA) dilation in pregnancy. Hydrogen sulfide (H2S) has been recently identified as a new UA vasodilator, yet the mechanism underlying H2S-induced UA dilation is unknown. Here, we tested whether H2S activated BKCa channels in human UA smooth muscle cells (hUASMC) to mediate UA relaxation. Multiple BKCa subunits were found in human UA in vitro and hUASMC in vitro, and high β1 and γ1 proteins were localized in SM cells in human UA. Baseline outward currents, recorded by whole-cell and single-channel patch clamps, were significantly inhibited by specific BKCa blockers iberiotoxin (IBTX) or tetraethylammonium, showing specific BKCa activity in hUASMC. H2S dose (NaHS, 1–1000 µM)-dependently potentiated BKCa currents and open probability. Co-incubation with a Ca2+ blocker nifedipine (5 µM) or a chelator (ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), 5 mM) did not alter H2S-potentiated BKCa currents and open probability. NaHS also dose-dependently relaxed phenylephrine pre-constricted freshly prepared human UA rings, which was inhibited by IBTX. Thus, H2S stimulated human UA relaxation at least partially via activating SM BKCa channels independent of extracellular Ca2+.

Highlights

Normal pregnancy is associated with dramatically increased uterine perfusion, reflected by as high as 20–80-fold rises in uterine blood flow in the third trimester in a singleton pregnant woman [1]
Since β1, γ1, and γ3 subunits are the most important ones for mediating uterine artery (UA) adaptation to pregnancy [27,31,37], we further examined their proteins in human uterine arteries and cultured human UA smooth muscle cells (hUASMC)
The γ1 subunit was only detectable by Western blot with one antibody (PA5-38058) but not by immunofluorescence microscopy, whereas γ3 subunit was detectable by immunofluorescence microscopy with the Abcam antibody but not by Western blot with all other commercial antibodies

Summary

Introduction

Normal pregnancy is associated with dramatically increased uterine perfusion, reflected by as high as 20–80-fold rises in uterine blood flow in the third trimester in a singleton pregnant woman [1]. Pregnancy-associated uterine vasodilation is rate-limiting for pregnancy health since rise in uterine blood flow delivers nutrients and O2 from the mother to fetus and exhausting CO2 and metabolic wastes from the fetus to mother, mandatory to support fetal development and survival. The mechanisms underlying pregnancy-associated uterine vasodilation are complex and incompletely understood; compelling evidence has pinpointed down a key role of locally produced vasodilators in relaxing the uterine artery (UA) smooth muscle (SM). Local UA NO inhibition only modestly (≈26%) inhibits baseline pregnancy-associated uterine vasodilation [10]. These studies clearly suggest that additional mechanisms are involved to mediate pregnancy-associated uterine vasodilation

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