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H2O2-induced dilation in human coronary arterioles: role of protein kinase G dimerization and large-conductance Ca2+-activated K+ channel activation.

Abstract：

RATIONALE:Hydrogen peroxide (H(2)O(2)) serves as a key endothelium-derived hyperpolarizing factor mediating flow-induced dilation in human coronary arterioles (HCAs). The precise mechanisms by which H(2)O(2) elicits smooth muscle hyperpolarization are not well understood. An important mode of action of H(2)O(2) involves the oxidation of cysteine residues in its target proteins, including protein kinase G (PKG)-Iα, thereby modulating their activities. OBJECTIVE:Here we hypothesize that H(2)O(2) dilates HCAs through direct oxidation and activation of PKG-Iα leading to the opening of the large-conductance Ca(2+)-activated K(+) (BK(Ca)) channel and subsequent smooth muscle hyperpolarization. METHODS AND RESULTS:Flow and H(2)O(2) induced pressure gradient/concentration-dependent vasodilation in isolated endothelium-intact and -denuded HCAs, respectively. The dilation was largely abolished by iberiotoxin, a BK(Ca) channel blocker. The PKG inhibitor Rp-8-Br-PET-cGMP also markedly inhibited flow- and H(2)O(2)-induced dilation, whereas the soluble guanylate cyclase inhibitor ODQ had no effect. Treatment of coronary smooth muscle cells (SMCs) with H(2)O(2) elicited dose-dependent, reversible dimerization of PKG-Iα, and induced its translocation to the plasma membrane. Patch-clamp analysis identified a paxilline-sensitive single-channel K(+) current with a unitary conductance of 246-pS in freshly isolated coronary SMCs. Addition of H(2)O(2) into the bath solution significantly increased the probability of BK(Ca) single-channel openings recorded from cell-attached patches, an effect that was blocked by the PKG-Iα inhibitor DT-2. H(2)O(2) exhibited an attenuated stimulatory effect on BK(Ca) channel open probability in inside-out membrane patches. CONCLUSIONS:H(2)O(2) dilates HCAs through a novel mechanism involving protein dimerization and activation of PKG-Iα and subsequent opening of smooth muscle BK(Ca) channels.

journal_name

Circ Res

journal_title

Circulation research

authors

Zhang DX,Borbouse L,Gebremedhin D,Mendoza SA,Zinkevich NS,Li R,Gutterman DD

doi

10.1161/CIRCRESAHA.111.258871

subject

Has Abstract

pub_date

2012-02-03 00:00:00

pages

471-80

issue

eissn

0009-7330

issn

1524-4571

pii

CIRCRESAHA.111.258871

journal_volume

110

pub_type

杂志文章

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H2O2-induced dilation in human coronary arterioles: role of protein kinase G dimerization and large-conductance Ca2+-activated K+ channel activation.