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

Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, United States
AJP Heart and Circulatory Physiology (Impact Factor: 3.84). 03/2005; 288(2):H568-76. DOI: 10.1152/ajpheart.00157.2004
Source: PubMed


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.

9 Reads
  • Source
    • "Whole cell K+ current (IK) was measured as previously described [7], [62], [63]. Cultured CSMCs were trypsinized then suspended in a low-Ca2+ PSS containing 20 mM HEPES and stored at 4°C until use (0–1 days). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Aims 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. Methods and Results Dihydroethidium micro-fluorography in porcine CSMCs demonstrated that basic fibroblast growth factor (bFGF) increased superoxide production, which was blocked by the NOX inhibitor apocynin (Apo). Apo also blocked bFGF-induced increases in KCNN4 mRNA levels in both right coronary artery sections and CSMCs. Similarly, immunohistochemistry and whole cell voltage clamp showed bFGF-induced increases in CSMC KCNN4 protein expression and channel activity were abolished by Apo. Treatment with Apo also inhibited bFGF-induced increases in activator protein-1 promoter activity, as measured by luciferase activity assay. qRT-PCR demonstrated porcine coronary smooth muscle expression of NOX1, NOX2, NOX4, and NOX5 isoforms. Knockdown of NOX5 alone prevented both bFGF-induced upregulation of KCNN4 mRNA and CSMC migration. Conclusions Our findings provide novel evidence that NOX5-derived ROS increase functional expression of KCNN4 through activator protein-1, providing another potential link between NOX, CSMC phenotypic modulation, and atherosclerosis.
    PLoS ONE 08/2014; 9(8):e105337. DOI:10.1371/journal.pone.0105337 · 3.23 Impact Factor
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: We believe that the filtering problem for a digital local exchange is best studied by division into two parts. The quantisation noise filter design entails a trade-off between this filter and the type of coder. The complexity of the bandlimiting filter to achieve the CCITT specification is divided between the analogue prefilter and the second part of the digital filter. Several designs of digital filter are described which may be suitable for large scale integration.
    Acoustics, Speech, and Signal Processing, IEEE International Conference on ICASSP '76.; 05/1976
Show more


9 Reads