Article

Hypercholesterolemia abolishes voltage-dependent K+ channel contribution to adenosine-mediated relaxation in porcine coronary arterioles.

Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri 65211, USA.
AJP Heart and Circulatory Physiology (Impact Factor: 4.01). 03/2005; 288(2):H568-76. DOI: 10.1152/ajpheart.00157.2004
Source: PubMed

ABSTRACT Hypercholesterolemic patients display reduced coronary flow reserve in response to adenosine infusion. We previously reported that voltage-dependent K+ (Kv) channels contribute to adenosine-mediated relaxation of coronary arterioles isolated from male miniature swine. For this study, we hypothesized that hypercholesterolemia attenuates Kv channel contribution to adenosine-induced vasodilatation. Pigs were randomly assigned to a control or high fat/high cholesterol diet for 20-24 wk, and then killed. After completion of the experimental treatment, arterioles (approximately 150 microm luminal diameter) were isolated from the left-ventricular free wall near the apical region of the heart, cannulated, and pressurized at 40 mmHg. Adenosine-mediated relaxation was significantly attenuated in both endothelium-intact and -denuded arterioles from hypercholesterolemic compared with control animals. The classic Kv channel blocker, 4-aminopyridine (1 mM), significantly attenuated adenosine-mediated relaxation in arterioles isolated from control but not hypercholesterolemic animals. Furthermore, the nonselective K+ channel blocker, tetraethylammonium (TEA; 1 mM) significantly attenuated adenosine-mediated relaxation in arterioles from control but not hypercholesterolemic animals. In additional experiments, coronary arteriolar smooth muscle cells were isolated, and whole cell Kv currents were measured. Kv currents were significantly reduced (approximately 15%) in smooth muscle cells from hypercholesterolemic compared with control animals. Furthermore, Kv current sensitive to low concentrations of TEA was reduced (approximately 45%) in smooth muscle cells from hypercholesterolemic compared with control animals. Our data indicate that hypercholesterolemia abolishes Kv channel contribution to adenosine-mediated relaxation in coronary arterioles, which may be attributable to a reduced contribution of TEA-sensitive Kv channels in smooth muscle of hypercholesterolemic animals.

0 Bookmarks
 · 
50 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective Test the hypothesis that exercise training increases the contribution of BKCa channels to endothelium‐mediated dilation in coronary arterioles from collateral‐dependent myocardial regions of chronically occluded pig hearts and may function downstream of H2O2. Methods An ameroid constrictor was placed around the proximal left circumflex coronary artery to induce gradual occlusion in Yucatan miniature swine. Eight weeks postoperatively, pigs were randomly assigned to sedentary or exercise training (treadmill; 14 week) regimens. ResultsExercise training significantly enhanced bradykinin‐mediated dilation in collateral‐dependent arterioles (~125 μm diameter) compared with sedentary pigs. The BKCa‐channel blocker, iberiotoxin alone or in combination with the H2O2 scavenger, polyethylene glycol catalase, reversed exercise training‐enhanced dilation in collateral‐dependent arterioles. Iberiotoxin‐sensitive whole‐cell K+ currents (i.e., BKCa‐channel currents) were not different between smooth muscle cells of nonoccluded and collateral‐dependent arterioles of sedentary and exercise trained groups. Conclusions These data provide evidence that BKCa‐channel activity contributes to exercise training‐enhanced endothelium‐dependent dilation in collateral‐dependent coronary arterioles despite no change in smooth muscle BKCa‐channel current. Taken together, our findings suggest that a component of the bradykinin signaling pathway, which stimulates BKCa channels, is enhanced by exercise training in collateral‐dependent arterioles and suggest a potential role for H2O2 as the mediator.
    Microcirculation 02/2013; 20(2). · 2.26 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: NADPH oxidase (NOX) is the primary source of reactive oxygen species (ROS) in vascular smooth muscle cells (SMC) and is proposed to play a key role in redox signaling involved in the pathogenesis of cardiovascular disease. Growth factors and cytokines stimulate coronary SMC (CSMC) phenotypic modulation, proliferation, and migration during atherosclerotic plaque development and restenosis. We previously demonstrated that increased expression and activity of intermediate-conductance Ca2+-activated K+ channels (KCNN4) is necessary for CSMC phenotypic modulation and progression of stenotic lesions. Therefore, the purpose of this study was to determine whether NOX is required for KCNN4 upregulation induced by mitogenic growth factors.
    PLoS ONE 08/2014; 9(8):e105337. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cholesterol is the major sterol component of all mammalian plasma membranes. Recent studies have shown that cholesterol inhibits both bacterial (KirBac1.1 and KirBac3.1) and eukaryotic (Kir2.1) inward rectifier K(+) (Kir) channels. Lipid-sterol interactions are not enantioselective, and the enantiomer of cholesterol (ent-cholesterol) does not inhibit Kir channel activity, suggesting that inhibition results from direct enantiospecific binding to the channel, and not indirect effects of changes to the bilayer. Furthermore, conservation of the effect of cholesterol among prokaryotic and eukaryotic Kir channels suggests an evolutionary conserved cholesterol-binding pocket, which we aimed to identify. Computational experiments were performed by docking cholesterol to the atomic structures of Kir2.2 (PDB: 3SPI) and KirBac1.1 (PDB: 2WLL) using Autodock 4.2. Poses were assessed to ensure biologically relevant orientation and then clustered according to location and orientation. The stability of cholesterol in each of these poses was then confirmed by molecular dynamics simulations. Finally, mutation of key residues (S95H and I171L) in this putative binding pocket found within the transmembrane domain of Kir2.1 channels were shown to lead to a loss of inhibition by cholesterol. Together, these data provide support for this location as a biologically relevant pocket. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.
    Biophysical journal. 12/2014; 107(12):2786-96.

Preview

Download
0 Downloads