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Baldwin SN, Jepps TA, Greenwood IA. Cycling matters: Sex hormone regulation of vascular potassium channels. Channels (Austin) 2023; 17:2217637. [PMID: 37243715 PMCID: PMC10228406 DOI: 10.1080/19336950.2023.2217637] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/07/2023] [Accepted: 05/19/2023] [Indexed: 05/29/2023] Open
Abstract
Sex hormones and the reproductive cycle (estrus in rodents and menstrual in humans) have a known impact on arterial function. In spite of this, sex hormones and the estrus/menstrual cycle are often neglected experimental factors in vascular basic preclinical scientific research. Recent research by our own laboratory indicates that cyclical changes in serum concentrations of sex -hormones across the rat estrus cycle, primary estradiol, have significant consequences for the subcellular trafficking and function of KV. Vascular potassium channels, including KV, are essential components of vascular reactivity. Our study represents a small part of a growing field of literature aimed at determining the role of sex hormones in regulating arterial ion channel function. This review covers key findings describing the current understanding of sex hormone regulation of vascular potassium channels, with a focus on KV channels. Further, we highlight areas of research where the estrus cycle should be considered in future studies to determine the consequences of physiological oscillations in concentrations of sex hormones on vascular potassium channel function.
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Affiliation(s)
- Samuel N Baldwin
- Vascular Biology Group, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas A Jepps
- Vascular Biology Group, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Iain A Greenwood
- Vascular Biology Research Centre, Institute of Molecular and Clinical Sciences, St George’s University of London, London, UK
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Jiménez-Altayó F, Cabrera A, Bagán A, Giménez-Llort L, D’Ocon P, Pérez B, Pallàs M, Escolano C. An Imidazoline 2 Receptor Ligand Relaxes Mouse Aorta via Off-Target Mechanisms Resistant to Aging. Front Pharmacol 2022; 13:826837. [PMID: 35645795 PMCID: PMC9133327 DOI: 10.3389/fphar.2022.826837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 04/26/2022] [Indexed: 11/13/2022] Open
Abstract
Imidazoline receptors (IR) are classified into three receptor subtypes (I1R, I2R, and I3R) and previous studies showed that regulation of I2R signaling has neuroprotective potential. In order to know if I2R has a role in modulating vascular tone in health and disease, we evaluated the putative vasoactive effects of two recently synthesized I2R ligands, diethyl (1RS,3aSR,6aSR)-5-(3-chloro-4-fluorophenyl)-4,6-dioxo-1-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole -1-phosphonate (B06) and diethyl [(1-(3-chloro-4-fluorobenzyl)-5,5-dimethyl-4-phenyl-4,5-dihydro-1H-imidazol-4-yl]phosphonate] (MCR5). Thoracic aortas from Oncins France 1 (3- to 4-months-old) and C57BL/6 (3- to 4- and 16- to 17-months-old mice) were mounted in tissue baths to measure isometric tension. In young mice of both strains, MCR5 induced greater relaxations than either B06 or the high-affinity I2R selective ligand 2-(2-benzofuranyl)-2-imidazoline (2-BFI), which evoked marginal responses. MCR5 relaxations were independent of I2R, as IR ligands did not significantly affect them, involved activation of smooth muscle KATP channels and inhibition of L-type voltage-gated Ca2+ channels, and were only slightly modulated by endothelium-derived nitric oxide (negatively) and prostacyclin (positively). Notably, despite the presence of endothelial dysfunction in old mice, MCR5 relaxations were preserved. In conclusion, the present study provides evidence against a functional contribution of I2R in the modulation of vascular tone in the mouse aorta. Moreover, the I2R ligand MCR5 is an endothelium-independent vasodilator that acts largely via I2R-independent pathways and is resistant to aging. We propose MCR5 as a candidate drug for the management of vascular disease in the elderly.
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Affiliation(s)
- Francesc Jiménez-Altayó
- Department of Pharmacology, Therapeutics and Toxicology, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
- *Correspondence: Francesc Jiménez-Altayó,
| | - Anna Cabrera
- Department of Pharmacology, Therapeutics and Toxicology, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Andrea Bagán
- Laboratory of Medicinal Chemistry (Associated Unit to CSIC), Department of Pharmacology, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
| | - Lydia Giménez-Llort
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
- Department of Psychiatry and Forensic Medicine, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Pilar D’Ocon
- Department of Pharmacology, School of Medicine, Universidad de Valencia, Burjassot, Spain
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universidad de Valencia, Valencia, Spain
| | - Belén Pérez
- Department of Pharmacology, Therapeutics and Toxicology, School of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Mercè Pallàs
- Pharmacology Section, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, Institut de Neurociències, University of Barcelona, Barcelona, Spain
| | - Carmen Escolano
- Laboratory of Medicinal Chemistry (Associated Unit to CSIC), Department of Pharmacology, Toxicology and Medicinal Chemistry, Faculty of Pharmacy and Food Sciences, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
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Li P, Halabi CM, Stewart R, Butler A, Brown B, Xia X, Santi C, England S, Ferreira J, Mecham RP, Salkoff L. Sodium-activated potassium channels moderate excitability in vascular smooth muscle. J Physiol 2019; 597:5093-5108. [PMID: 31444905 PMCID: PMC6800802 DOI: 10.1113/jp278279] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 08/19/2019] [Indexed: 12/12/2022] Open
Abstract
KEY POINTS We report that a sodium-activated potassium current, IKNa , has been inadvertently overlooked in both conduit and resistance arterial smooth muscle cells. IKNa is a major K+ resting conductance and is absent in cells of IKNa knockout (KO) mice. The phenotype of the IKNa KO is mild hypertension, although KO mice react more strongly than wild-type with raised blood pressure when challenged with vasoconstrictive agents. IKNa is negatively regulated by angiotensin II acting through Gαq protein-coupled receptors. In current clamp, KO arterial smooth muscle cells have easily evoked Ca2+ -dependent action potentials. ABSTRACT Although several potassium currents have been reported to play a role in arterial smooth muscle (ASM), we find that one of the largest contributors to membrane conductance in both conduit and resistance ASMs has been inadvertently overlooked. In the present study, we show that IKNa , a sodium-activated potassium current, contributes a major portion of macroscopic outward current in a critical physiological voltage range that determines intrinsic cell excitability; IKNa is the largest contributor to ASM cell resting conductance. A genetic knockout (KO) mouse strain lacking KNa channels (KCNT1 and KCNT2) shows only a modest hypertensive phenotype. However, acute administration of vasoconstrictive agents such as angiotensin II (Ang II) and phenylephrine results in an abnormally large increase in blood pressure in the KO animals. In wild-type animals Ang II acting through Gαq protein-coupled receptors down-regulates IKNa , which increases the excitability of the ASMs. The complete genetic removal of IKNa in KO mice makes the mutant animal more vulnerable to vasoconstrictive agents, thus producing a paroxysmal-hypertensive phenotype. This may result from the lowering of cell resting K+ conductance allowing the cells to depolarize more readily to a variety of excitable stimuli. Thus, the sodium-activated potassium current may serve to moderate blood pressure in instances of heightened stress. IKNa may represent a new therapeutic target for hypertension and stroke.
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Affiliation(s)
- Ping Li
- Dept. of Neuroscience, Washington University School of Medicine, Saint Louis. MO 63110
- Equal contributors
| | - Carmen M. Halabi
- Dept. of Pediatrics, Washington University School of Medicine, Saint Louis. MO 63110
- Equal contributors
| | - Richard Stewart
- Dept. of Neuroscience, Washington University School of Medicine, Saint Louis. MO 63110
| | - Alice Butler
- Dept. of Neuroscience, Washington University School of Medicine, Saint Louis. MO 63110
| | - Bobbie Brown
- Dept. of Neuroscience, Washington University School of Medicine, Saint Louis. MO 63110
| | - Xiaoming Xia
- Dept. of Anesthesiology, Washington University School of Medicine, Saint Louis. MO 63110
| | - Celia Santi
- Dept. of Neuroscience, Washington University School of Medicine, Saint Louis. MO 63110
- Dept. of OBGYN, Washington University School of Medicine, Saint Louis. MO 63110
| | - Sarah England
- Dept. of OBGYN, Washington University School of Medicine, Saint Louis. MO 63110
| | - Juan Ferreira
- Dept. of Neuroscience, Washington University School of Medicine, Saint Louis. MO 63110
- Dept. of OBGYN, Washington University School of Medicine, Saint Louis. MO 63110
| | - Robert P. Mecham
- Dept. of Cell Biology, Washington University School of Medicine, Saint Louis. MO 63110
| | - Lawrence Salkoff
- Dept. of Neuroscience, Washington University School of Medicine, Saint Louis. MO 63110
- Dept. of Genetics, Washington University School of Medicine, Saint Louis. MO 63110
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Pabbidi MR, Kuppusamy M, Didion SP, Sanapureddy P, Reed JT, Sontakke SP. Sex differences in the vascular function and related mechanisms: role of 17β-estradiol. Am J Physiol Heart Circ Physiol 2018; 315:H1499-H1518. [DOI: 10.1152/ajpheart.00194.2018] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The incidence of cardiovascular disease (CVD) is lower in premenopausal women but increases with age and menopause compared with similarly aged men. Based on the prevalence of CVD in postmenopausal women, sex hormone-dependent mechanisms have been postulated to be the primary factors responsible for the protection from CVD in premenopausal women. Recent Women’s Health Initiative studies, Cochrane Review studies, the Early Versus Late Intervention Trial with Estradiol Study, and the Kronos Early Estrogen Prevention Study have suggested that beneficial effects of hormone replacement therapy (HRT) are seen in women of <60 yr of age and if initiated within <10 yr of menopause. In contrast, the beneficial effects of HRT are not seen in women of >60 yr of age and if commenced after 10 yr of menopause. The higher incidence of CVD and the failure of HRT in postmenopausal aged women could be partly associated with fundamental differences in the vascular structure and function between men and women and in between pre- and postmenopausal women, respectively. In this regard, previous studies from human and animal studies have identified several sex differences in vascular function and associated mechanisms. The female sex hormone 17β-estradiol regulates the majority of these mechanisms. In this review, we summarize the sex differences in vascular structure, myogenic properties, endothelium-dependent and -independent mechanisms, and the role of 17β-estradiol in the regulation of vascular function.
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Affiliation(s)
- Mallikarjuna R. Pabbidi
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi
| | - Maniselvan Kuppusamy
- Division of Endocrinology, University of Mississippi Medical Center, Jackson, Mississippi
| | - Sean P. Didion
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi
| | - Padmaja Sanapureddy
- Department of Primary Care and Medicine, G. V. (Sonny) Montgomery Veterans Affairs Medical Center, Jackson, Mississippi
| | - Joey T. Reed
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi
| | - Sumit P. Sontakke
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi
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Ribeiro Junior RF, Fiorim J, Marques VB, de Sousa Ronconi K, Botelho T, Grando MD, Bendhack LM, Vassallo DV, Stefanon I. Vascular activation of K+ channels and Na+-K+ ATPase activity of estrogen-deficient female rats. Vascul Pharmacol 2017; 99:23-33. [DOI: 10.1016/j.vph.2017.09.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 09/09/2017] [Accepted: 09/09/2017] [Indexed: 11/27/2022]
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Arsyad A, Dobson GP. Adenosine relaxation in isolated rat aortic rings and possible roles of smooth muscle Kv channels, KATP channels and A2a receptors. BMC Pharmacol Toxicol 2016; 17:23. [PMID: 27211886 PMCID: PMC4876563 DOI: 10.1186/s40360-016-0067-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 04/29/2016] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND An area of ongoing controversy is the role adenosine to regulate vascular tone in conduit vessels that regulate compliance, and the role of nitric oxide (NO), potassium channels and receptor subtypes involved. The aim of our study was to investigate adenosine relaxation in rat thoracic aortic rings, and the effect of inhibitors of NO, prostanoids, Kv, KATP channels, and A2a and A2b receptors. METHODS Aortic rings were freshly harvested from adult male Sprague Dawley rats and equilibrated in an organ bath containing oxygenated, modified Krebs-Henseleit solution, 11 mM glucose, pH 7.4, 37 °C. Isolated rings were pre-contracted sub-maximally with 0.3 μM norepinephrine (NE), and the effect of increasing concentrations of adenosine (1 to 1000 μM) were examined. The drugs L-NAME, indomethacin, 4-aminopyridine (4-AP), glibenclamide, 5-hydroxydecanoate, ouabain, 8-(3-chlorostyryl) caffeine and PSB-0788 were examined in intact and denuded rings. Rings were tested for viability after each experiment. RESULTS Adenosine induced a dose-dependent, triphasic relaxation response, and the mechanical removal of the endothelium significantly deceased adenosine relaxation above 10 μM. Interestingly, endothelial removal significantly decreased the responsiveness (defined as % relaxation per μM adenosine) by two-thirds between 10 and 100 μM, but not in the lower (1-10 μM) or higher (>100 μM) ranges. In intact rings, L-NAME significantly reduced relaxation, but not indomethacin. Antagonists of voltage-dependent Kv (4-AP), sarcolemma KATP (glibenclamide) and mitochondrial KATP channels (5-HD) led to significant reductions in relaxation in both intact and denuded rings, with ouabain having little or no effect. Adenosine-induced relaxation appeared to involve the A2a receptor, but not the A2b subtype. CONCLUSIONS It was concluded that adenosine relaxation in NE-precontracted rat aortic rings was triphasic and endothelium-dependent above 10 μM, and relaxation involved endothelial nitric oxide (not prostanoids) and a complex interplay between smooth muscle A2a subtype and voltage-dependent Kv, SarcKATP and MitoKATP channels. The possible in vivo significance of the regulation of arterial compliance to left ventricular function coupling is discussed.
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Affiliation(s)
- Aryadi Arsyad
- Physiology Department, Medical Faculty, Hasanuddin University, Jl. Perintis Kemerdekaan, Km. 10, Tamalanrea, Makassar, 90213, Indonesia
| | - Geoffrey P Dobson
- Heart, Trauma and Sepsis Research Laboratory, Australian Institute of Tropical Health and Medicine, College of Medicine and Dentistry, James Cook University, 1 James Cook Drive, Queensland, 4811, Australia.
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Zhou Y, Lingle CJ. Paxilline inhibits BK channels by an almost exclusively closed-channel block mechanism. ACTA ACUST UNITED AC 2015; 144:415-40. [PMID: 25348413 PMCID: PMC4210426 DOI: 10.1085/jgp.201411259] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Paxilline, a tremorogenic fungal alkaloid, potently inhibits large conductance Ca(2+)- and voltage-activated K(+) (BK)-type channels, but little is known about the mechanism underlying this inhibition. Here we show that inhibition is inversely dependent on BK channel open probability (Po), and is fully relieved by conditions that increase Po, even in the constant presence of paxilline. Manipulations that shift BK gating to more negative potentials reduce inhibition by paxilline in accordance with the increase in channel Po. Measurements of Po times the number of channels at negative potentials support the idea that paxilline increases occupancy of closed states, effectively reducing the closed-open equilibrium constant, L(0). Gating current measurements exclude an effect of paxilline on voltage sensors. Steady-state inhibition by multiple paxilline concentrations was determined for four distinct equilibration conditions, each with a distinct Po. The IC50 for paxilline shifted from around 10 nM when channels were largely closed to near 10 µM as maximal Po was approached. Model-dependent analysis suggests a mechanism of inhibition in which binding of a single paxilline molecule allosterically alters the intrinsic L(0) favoring occupancy of closed states, with affinity for the closed conformation being >500-fold greater than affinity for the open conformation. The rate of inhibition of closed channels was linear up through 2 µM paxilline, with a slope of 2 × 10(6) M(-1)s(-1). Paxilline inhibition was hindered by either the bulky cytosolic blocker, bbTBA, or by concentrations of cytosolic sucrose that hinder ion permeation. However, paxilline does not hinder MTSET modification of the inner cavity residue, A313C. We conclude that paxilline binds more tightly to the closed conformation, favoring occupancy of closed-channel conformations, and propose that it binds to a superficial position near the entrance to the central cavity, but does not hinder access of smaller molecules to this cavity.
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Affiliation(s)
- Yu Zhou
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Christopher J Lingle
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110
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Chien CCC, Su MJ. 5-hydroxytryptamine has an endothelium-derived hyperpolarizing factor-like effect on coronary flow in isolated rat hearts. J Biomed Sci 2015; 22:42. [PMID: 26076928 PMCID: PMC4467052 DOI: 10.1186/s12929-015-0149-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/19/2015] [Indexed: 01/07/2023] Open
Abstract
Background 5-hydroxytryptamine (5-HT)-induced coronary artery responses have both vasoconstriction and vasorelaxation components. The vasoconstrictive effects of 5-HT have been well studied while the mechanism(s) of how 5-HT causes relaxation of coronary arteries has been less investigated. In isolated rat hearts, 5-HT-induced coronary flow increases are partially resistant to the nitric oxide synthase inhibitor Nω-Nitro-L-arginine methyl ester (L-NAME) and are blocked by 5-HT7 receptor antagonists. In the present study, we investigated the role of 5-HT7 receptor in 5-HT-induced coronary flow increases in isolated rat hearts in the absence of L-NAME, and we also evaluated the involvement of endothelium-derived hyperpolarizing factor (EDHF) in 5-HT-induced coronary flow increases in L-NAME-treated hearts with the inhibitors of arachidonic acid metabolism and the blockers of Ca2+-activated K+ channels. Results In isolated rat hearts, 5-HT and the 5-HT7 receptor agonist 5-carboxamidotryptamine induced coronary flow increases, and both of these effects were blocked by the selective 5-HT7 receptor antagonist SB269970; in SB269970-treated hearts, 5-HT induced coronary flow decreases, which effect was blocked by the 5-HT2A receptor blocker R96544. In L-NAME-treated hearts, 5-HT-induced coronary flow increases were blocked by the phospholipase A2 inhibitor quinacrine and the cytochrome P450 inhibitor SKF525A, but were not inhibited by the cyclooxygenase inhibitor indomethacin. As to the effects of the Ca2+-activated K+ channel blockers, 5-HT-induced coronary flow increases in L-NAME-treated hearts were inhibited by TRAM-34 (intermediate-conductance Ca2+-activated K+ channel blocker) and UCL1684 (small-conductance Ca2+-activated K+ channel blocker), but effects of the large-conductance Ca2+-activated K+ channel blockers on 5-HT-induced coronary flow increases were various: penitrem A and paxilline did not significantly affect 5-HT-induced coronary flow responses while tetraethylammonium suppressed the coronary flow increases elicited by 5-HT. Conclusion In the present study, we found that 5-HT-induced coronary flow increases are mediated by the activation of 5-HT7 receptor in rat hearts in the absence of L-NAME. Metabolites of cytochrome P450s, small-conductance Ca2+-activated K+ channel, and intermediate-conductance Ca2+-activated K+ channel are involved in 5-HT-induced coronary flow increases in L-NAME-treated hearts, which resemble the mechanisms of EDHF-induced vasorelaxation. The role of large-conductance Ca2+-activated K+ channel in 5-HT-induced coronary flow increases in L-NAME-treated hearts needs further investigation.
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Affiliation(s)
- Ching-Chia Chang Chien
- Institute of Pharmacology, College of Medicine, National Taiwan University, 11F No.1 Sec.1, Ren-ai Rd, Taipei, 10051, Taiwan.
| | - Ming-Jai Su
- Institute of Pharmacology, College of Medicine, National Taiwan University, 11F No.1 Sec.1, Ren-ai Rd, Taipei, 10051, Taiwan.
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Dias FMV, Ribeiro Júnior RF, Fernandes AA, Fiorim J, Travaglia TCF, Vassallo DV, Stefanon I. Na+K+-ATPase activity and K+ channels differently contribute to vascular relaxation in male and female rats. PLoS One 2014; 9:e106345. [PMID: 25187951 PMCID: PMC4154682 DOI: 10.1371/journal.pone.0106345] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 08/07/2014] [Indexed: 11/19/2022] Open
Abstract
Gender associated differences in vascular reactivity regulation might contribute to the low incidence of cardiovascular disease in women. Cardiovascular protection is suggested to depend on female sex hormones' effects on endothelial function and vascular tone regulation. We tested the hypothesis that potassium (K+) channels and Na+K+-ATPase may be involved in the gender-based vascular reactivity differences. Aortic rings from female and male rats were used to examine the involvement of K+ channels and Na+K+-ATPase in vascular reactivity. Acetylcholine (ACh)-induced relaxation was analyzed in the presence of L-NAME (100 µM) and the following K+ channels blockers: tetraethylammonium (TEA, 2 mM), 4-aminopyridine (4-AP, 5 mM), iberiotoxin (IbTX, 30 nM), apamin (0.5 µM) and charybdotoxin (ChTX, 0.1 µM). The ACh-induced relaxation sensitivity was greater in the female group. After incubation with 4-AP the ACh-dependent relaxation was reduced in both groups. However, the dAUC was greater in males, suggesting that the voltage-dependent K+ channel (Kv) participates more in males. Inhibition of the three types of Ca2+-activated K+ channels induced a greater reduction in Rmax in females than in males. The functional activity of the Na+K+-ATPase was evaluated by KCl-induced relaxation after L-NAME and OUA incubation. OUA reduced K+-induced relaxation in female and male groups, however, it was greater in males, suggesting a greater Na+K+-ATPase functional activity. L-NAME reduced K+-induced relaxation only in the female group, suggesting that nitric oxide (NO) participates more in their functional Na+K+-ATPase activity. These results suggest that the K+ channels involved in the gender-based vascular relaxation differences are the large conductance Ca2+-activated K+ channels (BKCa) in females and Kv in males and in the K+-induced relaxation and the Na+K+-ATPase vascular functional activity is greater in males.
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Affiliation(s)
- Fernanda Moura Vargas Dias
- Universidade Federal do Espírito Santo, Departamento de Ciências Fisiológicas, Vitória, Espírito Santo, Brasil
| | | | - Aurélia Araújo Fernandes
- Universidade Federal do Espírito Santo, Departamento de Ciências Fisiológicas, Vitória, Espírito Santo, Brasil
| | - Jonaina Fiorim
- Universidade Federal do Espírito Santo, Departamento de Ciências Fisiológicas, Vitória, Espírito Santo, Brasil
| | | | - Dalton Valentim Vassallo
- Universidade Federal do Espírito Santo, Departamento de Ciências Fisiológicas, Vitória, Espírito Santo, Brasil
| | - Ivanita Stefanon
- Universidade Federal do Espírito Santo, Departamento de Ciências Fisiológicas, Vitória, Espírito Santo, Brasil
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Joseph BK, Thakali KM, Moore CL, Rhee SW. Ion channel remodeling in vascular smooth muscle during hypertension: Implications for novel therapeutic approaches. Pharmacol Res 2013; 70:126-38. [PMID: 23376354 PMCID: PMC3607210 DOI: 10.1016/j.phrs.2013.01.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 01/10/2013] [Accepted: 01/17/2013] [Indexed: 02/07/2023]
Abstract
Ion channels are multimeric, transmembrane proteins that selectively mediate ion flux across the plasma membrane in a variety of cells including vascular smooth muscle cells (VSMCs). The dynamic interplay of Ca(2+) and K(+) channels on the plasma membrane of VSMCs plays a pivotal role in modulating the vascular tone of small arteries and arterioles. The abnormally-elevated arterial tone observed in hypertension thus points to an aberrant expression and function of Ca(2+) and K(+) channels in the VSMCs. In this short review, we focus on the three well-studied ion channels in VSMCs, namely the L-type Ca(2+) (CaV1.2) channels, the voltage-gated K(+) (KV) channels, and the large-conductance Ca(2+)-activated K(+) (BK) channels. First, we provide a brief overview on the physiological role of vascular CaV1.2, KV and BK channels in regulating arterial tone. Second, we discuss the current understanding of the expression changes and regulation of CaV1.2, KV and BK channels in the vasculature during hypertension. Third, based on available proof-of-concept studies, we describe the potential therapeutic approaches targeting these vascular ion channels in order to restore blood pressure to normotensive levels.
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Affiliation(s)
- Biny K Joseph
- Venenum Biodesign, 8 Black Forest Road, Hamilton, NJ 08691, USA
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Fiorim J, Ribeiro Júnior RF, Azevedo BF, Simões MR, Padilha AS, Stefanon I, Alonso MJ, Salaices M, Vassallo DV. Activation of K+ channels and Na+/K+ ATPase prevents aortic endothelial dysfunction in 7-day lead-treated rats. Toxicol Appl Pharmacol 2012; 262:22-31. [DOI: 10.1016/j.taap.2012.04.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/10/2012] [Accepted: 04/12/2012] [Indexed: 11/15/2022]
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12
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Senejoux F, Girard C, Aisa HA, Bakri M, Kerram P, Berthelot A, Bévalot F, Demougeot C. Vasorelaxant and hypotensive effects of a hydroalcoholic extract from the fruits of Nitraria sibirica Pall. (Nitrariaceae). JOURNAL OF ETHNOPHARMACOLOGY 2012; 141:629-634. [PMID: 21864668 DOI: 10.1016/j.jep.2011.08.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 07/13/2011] [Accepted: 08/03/2011] [Indexed: 05/31/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Fruits of Nitraria sibirica Pall. are traditionally used in Uighur medicine to treat hypertension. This study aimed to support that folk use by defining their vasoactive and hypotensive properties. MATERIALS AND METHODS The vasorelaxant activity and the underlying mechanisms of a hydroalcoholic extract from the fruits of Nitraria sibirica Pall. (NSHE) were evaluated on thoracic aortic rings isolated from Wistar rats. In addition, the acute hypotensive effect of NSHE was assessed in anesthetized spontaneously hypertensive rats (SHR) and in their normotensive control Wistar Kyoto (WKY) rats. RESULTS NSHE (0.1-10 g/l) was clearly more effective to induce vasodilation of phenylephrine- (PE, 1 μM) than high KCl- (60mM) pre-contracted aortic rings with respective E(max) values of 82.9±2.2% and 34.8±3.6%. The removal of endothelium almost abolished the relaxant effect of the extract. In addition, pre-treatment with N(w)-nitro-L-arginine-methyl ester (L-NAME, 100 μM), atropine (1 μM) or charybdotoxin (30 nM) plus apamin (30 nM), respective blockers of nitric oxide (NO) synthase, muscarinic receptors and endothelium-derived hyperpolarizing factor (EDHF), significantly reduced the observed effect of NSHE. By contrast, the cyclooxygenase (COX) inhibitor indomethacin (10 μM) or the K(+) channels blockers glibenclamide (10 μM), iberiotoxin (30 nM) and 4-amino-pyridine (4-AP, 1 mM) failed to modify the vasodilation. Finally, the acute intravenous injection of NSHE (1, 5, 10, 20 mg/kg) induced an immediate and transient hypotensive effect in anesthetized SHR and in WKY rats. CONCLUSIONS This experimental animal study suggests that hydroalcoholic extract from the fruits of Nitraria sibirica Pall. induces vasorelaxation through an endothelium-dependent pathway involving NO synthase (NOS) activation, EDHF production and muscarinic receptor stimulation. Additionally, our results determine that this vasorelaxant effect is translated by a significant hypotensive effect.
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MESH Headings
- Animals
- Antihypertensive Agents/chemistry
- Antihypertensive Agents/isolation & purification
- Antihypertensive Agents/pharmacology
- Biological Factors/metabolism
- Blood Pressure/drug effects
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiopathology
- Enzyme Activation
- Ethanol/chemistry
- Fruit
- Hypertension/drug therapy
- Hypertension/metabolism
- Hypertension/physiopathology
- Magnoliopsida/chemistry
- Male
- Nitric Oxide/metabolism
- Nitric Oxide Synthase/metabolism
- Phenols/isolation & purification
- Phenols/pharmacology
- Plant Extracts/chemistry
- Plant Extracts/isolation & purification
- Plant Extracts/pharmacology
- Plants, Medicinal
- Potassium Channels/drug effects
- Potassium Channels/metabolism
- Rats
- Rats, Inbred SHR
- Rats, Inbred WKY
- Rats, Wistar
- Receptors, Muscarinic/drug effects
- Receptors, Muscarinic/metabolism
- Solvents/chemistry
- Vasodilation/drug effects
- Vasodilator Agents/chemistry
- Vasodilator Agents/isolation & purification
- Vasodilator Agents/pharmacology
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Affiliation(s)
- François Senejoux
- EA 4267 Sciences Séparatives, Biologiques et Pharmaceutiques, UFR des Sciences Médicales et Pharmaceutiques, 25030 Besançon, France
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13
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Senejoux F, Girard-Thernier C, Berthelot A, Bévalot F, Demougeot C. New insights into the mechanisms of the vasorelaxant effects of apocynin in rat thoracic aorta. Fundam Clin Pharmacol 2012; 27:262-70. [PMID: 22233502 DOI: 10.1111/j.1472-8206.2011.01025.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Apocynin is a naturally occurring acetophenone widely used as an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Recent data suggested that apocynin might exert NADPH oxidase-independent pharmacological properties. Among them, vasorelaxant properties have been described, but the mechanisms still give rise to debates. The present study investigated the mechanisms involved in the vasorelaxant effect of apocynin on the in vitro model of rat isolated thoracic aortic rings. Apocynin (30 μM to 10 mM) induced a dose-dependent relaxation in both endothelium-intact and endothelium-denuded aortic rings with respective EC50 values of 0.78 ± 0.08 and 1.91 ± 0.21 mM. Endothelium removal or inhibition of nitric oxide (NO) synthase with N(ω)-nitro-L-arginine-methyl ester (L-NAME) significantly decreased but did not abolish the effect of apocynin. By contrast, apocynin-induced relaxation was unchanged after incubation with indomethacin or charybdotoxin plus apamin. In endothelium-denuded aortas, the vasorelaxant effect of apocynin was significantly reduced by glibenclamide but not by 4-aminopyridine nor by iberiotoxin. Apocynin significantly decreased Ca(2+)-induced contraction and inhibited intracellular Ca(2+) mobilization after contraction with phenylephrine. Finally, the acute intravenous injection of apocynin led to an immediate and transient hypotensive effect in spontaneously hypertensive rats (SHR). In conclusion, our data demonstrated that apocynin induces both endothelium-independent relaxant effects involving inhibition of Ca(2+) mobilization and activation of KATP channels in vascular smooth muscle cells and endothelium-dependent effects mediated by NO. These results should provide a basis for caution when interpreting results on the vascular effects of apocynin.
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Affiliation(s)
- François Senejoux
- EA 3185 Fonctions et Dysfonctions Epithéliales, UFR des Sciences Médicales et Pharmaceutiques, 25030 Besançon, France
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14
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Jepps TA, Chadha PS, Davis AJ, Harhun MI, Cockerill GW, Olesen SP, Hansen RS, Greenwood IA. Downregulation of Kv7.4 channel activity in primary and secondary hypertension. Circulation 2011; 124:602-11. [PMID: 21747056 DOI: 10.1161/circulationaha.111.032136] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Voltage-gated potassium (K(+)) channels encoded by KCNQ genes (Kv7 channels) have been identified in various rodent and human blood vessels as key regulators of vascular tone; however, nothing is known about the functional impact of these channels in vascular disease. We ascertained the effect of 3 structurally different activators of Kv7.2 through Kv7.5 channels (BMS-204352, S-1, and retigabine) on blood vessels from normotensive and hypertensive animals. METHODS AND RESULTS Precontracted thoracic aorta and mesenteric artery segments from normotensive rats were relaxed by all 3 Kv7 activators, with potencies of BMS-204352=S-1>retigabine. We also tested these agents in the coronary circulation using the Langendorff heart preparation. BMS-204352 and S-1 dose dependently increased coronary perfusion at concentrations between 0.1 and 10 μmol/L, whereas retigabine was effective at 1 to 10 μmol/L. In addition, S-1 increased K(+) currents in isolated mesenteric artery myocytes. The ability of these agents to relax precontracted vessels, increase coronary flow, or augment K(+) currents was impaired considerably in tissues isolated from spontaneously hypertensive rats (SHRs). Of the 5 KCNQ genes, only the expression of KCNQ4 was reduced (≈3.7 fold) in SHRs aorta. Kv7.4 protein levels were ≈50% lower in aortas and mesenteric arteries from spontaneously hypertensive rats compared with normotensive vessels. A similar attenuated response to S-1 and decreased Kv7.4 were observed in mesenteric arteries from mice made hypertensive by angiotensin II infusion compared with normotensive controls. CONCLUSIONS In 2 different rat and mouse models of hypertension, the functional impact of Kv7 channels was dramatically downregulated.
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Affiliation(s)
- Thomas A Jepps
- Division of Biomedical Sciences, St. George's, University of London, United Kingdom
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15
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Baek EB, Kim SJ. Mechanisms of myogenic response: Ca2+-dependent and -independent signaling. J Smooth Muscle Res 2011; 47:55-65. [DOI: 10.1540/jsmr.47.55] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Eun Bok Baek
- Department of in vitro toxicology, LG life science, Daejeon, Republic of Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
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16
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Contributory role of endothelium and voltage-gated potassium channels in apocynin-induced vasorelaxations. J Hypertens 2010; 28:2102-10. [DOI: 10.1097/hjh.0b013e32833d0197] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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17
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Ko EA, Park WS, Firth AL, Kim N, Yuan JXJ, Han J. Pathophysiology of voltage-gated K+ channels in vascular smooth muscle cells: Modulation by protein kinases. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 103:95-101. [DOI: 10.1016/j.pbiomolbio.2009.10.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
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18
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Zhou Y, Tang QY, Xia XM, Lingle CJ. Glycine311, a determinant of paxilline block in BK channels: a novel bend in the BK S6 helix. ACTA ACUST UNITED AC 2010; 135:481-94. [PMID: 20421373 PMCID: PMC2860595 DOI: 10.1085/jgp.201010403] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The tremorogenic fungal metabolite, paxilline, is widely used as a potent and relatively specific blocker of Ca2+- and voltage-activated Slo1 (or BK) K+ channels. The pH-regulated Slo3 K+ channel, a Slo1 homologue, is resistant to blockade by paxilline. Taking advantage of the marked differences in paxilline sensitivity and the homology between subunits, we have examined the paxilline sensitivity of a set of chimeric Slo1/Slo3 subunits. Paxilline sensitivity is associated with elements of the S5–P loop–S6 module of the Slo1 channel. Replacement of the Slo1 S5 segment or the second half of the P loop results in modest changes in paxilline sensitivity. Replacing the Slo1 S6 segment with the Slo3 sequence abolishes paxilline sensitivity. An increase in paxilline affinity and changes in block kinetics also result from replacing the first part of the Slo1 P loop, the so-called turret, with Slo3 sequence. The Slo1 and Slo3 S6 segments differ at 10 residues. Slo1-G311S was found to markedly reduce paxilline block. In constructs with a Slo3 S6 segment, S300G restored paxilline block, but most effectively when paired with a Slo1 P loop. Other S6 residues differing between Slo1 and Slo3 had little influence on paxilline block. The involvement of Slo1 G311 in paxilline sensitivity suggests that paxilline may occupy a position within the central cavity or access its blocking position through the central cavity. To explain the differences in paxilline sensitivity between Slo1 and Slo3, we propose that the G311/S300 position in Slo1 and Slo3 underlies a structural difference between subunits in the bend of S6, which influences the occupancy by paxilline.
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Affiliation(s)
- Yu Zhou
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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19
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Haba M, Hatakeyama N, Kinoshita H, Teramae H, Azma T, Hatano Y, Matsuda N. The Modulation of Vascular ATP-Sensitive K+ Channel Function via the Phosphatidylinositol 3-Kinase–Akt Pathway Activated by Phenylephrine. J Pharmacol Exp Ther 2010; 334:673-8. [DOI: 10.1124/jpet.110.167775] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
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20
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Moskalenko AV, Yarova PL, Gordeev SN, Smirnov SV. Single protein molecule mapping with magnetic atomic force microscopy. Biophys J 2010; 98:478-87. [PMID: 20141762 PMCID: PMC2814202 DOI: 10.1016/j.bpj.2009.10.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 10/06/2009] [Accepted: 10/15/2009] [Indexed: 02/04/2023] Open
Abstract
Understanding the structural organization and distribution of proteins in biological cells is of fundamental importance in biomedical research. The use of conventional fluorescent microscopy for this purpose is limited due to its relatively low spatial resolution compared to the size of a single protein molecule. Atomic force microscopy (AFM), on the other hand, allows one to achieve single-protein resolution by scanning the cell surface using a specialized ligand-coated AFM tip. However, because this method relies on short-range interactions, it is limited to the detection of binding sites that are directly accessible to the AFM tip. We developed a method based on magnetic (long-range) interactions and applied it to investigate the structural organization and distribution of endothelin receptors on the surface of smooth muscle cells. Endothelin receptors were labeled with 50-nm superparamagnetic microbeads and then imaged with magnetic AFM. Considering its high spatial resolution and ability to "see" magnetically labeled proteins at a distance of up to 150 nm, this approach may become an important tool for investigating the dynamics of individual proteins both on the cell membrane and in the submembrane space.
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Affiliation(s)
| | - Polina L. Yarova
- Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom
| | | | - Sergey V. Smirnov
- Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom
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21
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Halichlorine is a novel L-type Ca2+ channel inhibitor isolated from the marine sponge Halichondria okadai Kadota. Eur J Pharmacol 2010; 628:128-31. [DOI: 10.1016/j.ejphar.2009.11.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 11/10/2009] [Indexed: 11/20/2022]
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22
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Exercise training changes the gating properties of large-conductance Ca2+-activated K+ channels in rat thoracic aorta smooth muscle cells. J Biomech 2010; 43:263-7. [DOI: 10.1016/j.jbiomech.2009.08.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2009] [Revised: 08/26/2009] [Accepted: 08/27/2009] [Indexed: 12/25/2022]
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23
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Beard JD, Burbridge DJ, Moskalenko AV, Dudko O, Yarova PL, Smirnov SV, Gordeev SN. An atomic force microscope nanoscalpel for nanolithography and biological applications. NANOTECHNOLOGY 2009; 20:445302. [PMID: 19801772 DOI: 10.1088/0957-4484/20/44/445302] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present the fabrication of specialized nanotools, termed nanoscalpels, and their application for nanolithography and nanomechanical manipulation of biological objects. Fabricated nanoscalpels have the shape of a thin blade with the controlled thickness of 20-30 nm and width of 100-200 nm. They were fabricated using electron beam induced deposition at the apex of atomic force microscope probes and are hard enough for a single cut to penetrate a approximately 45 nm thick gold layer; and thus can be used for making narrow electrode gaps required for fabrication of nanoelectronic devices. As an atomic force microscope-based technique the nanoscalpel provides simultaneous control of the applied cutting force and the depth of the cut. Using mammalian cells as an example, we demonstrated their ability to make narrow incisions and measurements of local elastic and inelastic characteristics of a cell, making nanoscalpels also useful as a nanosurgical tool in cell biology. Therefore, we believe that the nanoscalpel could serve as an important tool for nanofabrication and nanosurgery on biological objects.
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Affiliation(s)
- J D Beard
- Department of Physics, University of Bath, Bath BA2 7AY, UK.
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24
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Zheng J, Zheng P, Zhou X, Yan L, Zhou R, Fu XY, Dai GD. Relaxant effects of matrine on aortic smooth muscles of guinea pigs. BIOMEDICAL AND ENVIRONMENTAL SCIENCES : BES 2009; 22:327-332. [PMID: 19950528 DOI: 10.1016/s0895-3988(09)60063-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
OBJECTIVE To determine whether matrine, a kind of traditional Chinese medicinal alkaloid, can relax the aortic smooth muscles isolated from guinea pigs and to investigate the mechanism of its relaxant effects. METHODS Phenylephrine or potassium chloride concentration-dependent relaxation response of aortic smooth muscles to matrine was studied in the precontracted guinea pigs. RESULTS Matrine (1 x 10(-4) mol/L -3.3 x 10(3) mol/L) relaxed the endothelium-denuded aortic rings pre-contracted sub-maximally with phenylephrine, in a concentration-dependent manner, and its pre-incubation (3.3 x 10(-3) mol/L) produced a significant rightward shift in the phenylephrine dose-response curve, but had no effects on the potassium chloride-induced contraction. The anti-contractile effect of matrine was not reduced by the highly selective ATP-dependent K+ channel blocker glibenclamide (10(-5) mol/L), either by the non-selective K+ channel blocker tetraethylammonium (10(-3) mol/L), or by the beta-antagonist propranolol (10(-5) mol/L). In either "normal" or "Ca(2+)-free" bathing medium, the phenylephrine-induced contraction was attenuated by matrine (3.3 x 10(-3) mol/L), indicating that the vasorelaxation was due to inhibition of intracellular and extracellular Ca2+ mobilization. CONCLUSION Matrine inhibits phenylephrine-induced contractions by inhibiting activation of alpha-adrenoceptor and interfering with the release of intracellular Ca2+ and the influx of extracellular Ca2+.
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Affiliation(s)
- Jie Zheng
- Department of Pharmacology, School of Basic Medical Science, Ningxia Medical University, Yinchuan 750004, Ningxia, China.
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25
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Han WQ, Zhu DL, Wu LY, Chen QZ, Guo SJ, Gao PJ. N-acetylcysteine-induced vasodilation involves voltage-gated potassium channels in rat aorta. Life Sci 2009; 84:732-7. [PMID: 19268479 DOI: 10.1016/j.lfs.2009.02.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 01/12/2009] [Accepted: 02/19/2009] [Indexed: 02/05/2023]
Abstract
AIMS N-acetylcysteine (NAC) has a protective effect against vascular dysfunction by decreasing the level of reactive oxygen species (ROS) in experimental and human hypertension. This study was designed to examine whether NAC would relax vascular rings in vitro via nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, extracellular Ca2+ and/or K+ channels. MAIN METHODS Rat aortic arteries were mounted in an organ bath, contracted with 0.1, 0.5 or 1 micromol/L phenylephrine to plateau, and the vasodilatory effect of NAC was examined in the absence or presence of ROS scavengers, inhibitors of NO-cGMP pathway or K+ channels. Vascular smooth muscle cells (VSMCs) were loaded with a calcium sensitive fluorescent dye fluo-3 AM, and [Ca2+](i) was determined with laser-scanning confocal microscopy. KEY FINDINGS NAC (0.1-4 mmol/L) dose-dependently relaxed rat aorta pre-contracted with phenylephrine. Endothelium removal, endothelial nitric oxide synthase inhibitor N(omega)-Nitro-l-arginine (L-NNA) (100 micromol/L) or soluble guanylyl cyclase (sGC) inhibitor (ODQ) (10 micromol/L) did not affect NAC-induced vasodilation. In contrast, NAC-induced vasodilation was blunted after extracellular calcium was removed and calcium imaging showed that 4 mmol/L NAC quickly decreased [Ca2+](i) in fluo-3 AM loaded VSMCs. NAC-induced vasodilation was significantly reduced in the presence of voltage-gated K+ channels (Kv) inhibitor 4-aminopyridine (4-AP). SIGNIFICANCE The vasodilatory effect of NAC may be explained at least partly by activation of voltage-gated K+ channels.
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Affiliation(s)
- Wei-Qing Han
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
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26
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Three Types of Single Voltage-Dependent Potassium Channels in the Sarcolemma of Frog Skeletal Muscle. J Membr Biol 2009; 228:51-62. [DOI: 10.1007/s00232-009-9158-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Accepted: 01/31/2009] [Indexed: 10/21/2022]
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27
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Functional and molecular consequences of ionizing irradiation on large conductance Ca2+-activated K+ channels in rat aortic smooth muscle cells. Life Sci 2009; 84:164-71. [DOI: 10.1016/j.lfs.2008.11.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 10/27/2008] [Accepted: 11/10/2008] [Indexed: 11/23/2022]
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28
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Zeng H, Gordon E, Lin Z, Lozinskaya IM, Willette RN, Xu X. 1-[1-Hexyl-6-(methyloxy)-1H-indazol-3-yl]-2-methyl-1-propanone, a Potent and Highly Selective Small Molecule Blocker of the Large-Conductance Voltage-Gated and Calcium-Dependent K+Channel. J Pharmacol Exp Ther 2008; 327:168-77. [DOI: 10.1124/jpet.108.139733] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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29
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Firth AL, Yuill KH, Smirnov SV. Mitochondria-dependent regulation of Kv currents in rat pulmonary artery smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2008; 295:L61-70. [PMID: 18469114 PMCID: PMC2494784 DOI: 10.1152/ajplung.90243.2008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Voltage-gated K+ (Kv) channels are important in the regulation of pulmonary vascular function having both physiological and pathophysiological implications. The pulmonary vasculature is essential for reoxygenation of the blood, supplying oxygen for cellular respiration. Mitochondria have been proposed as the major oxygen-sensing organelles in the pulmonary vasculature. Using electrophysiological techniques and immunofluorescence, an interaction of the mitochondria with Kv channels was investigated. Inhibitors, blocking the mitochondrial electron transport chain at different complexes, were shown to have a dual effect on Kv currents in freshly isolated rat pulmonary arterial smooth muscle cells (PASMCs). These dual effects comprised an enhancement of Kv current in a negative potential range (manifested as a 5- to 14-mV shift in the Kv activation to more negative membrane voltages) with a decrease in current amplitude at positive potentials. Such effects were most prominent as a result of inhibition of Complex III by antimycin A. Investigation of the mechanism of antimycin A-mediated effects on Kv channel currents (IKv) revealed the presence of a mitochondria-mediated Mg2+ and ATP-dependent regulation of Kv channels in PASMCs, which exists in addition to that currently proposed to be caused by changes in intracellular reactive oxygen species.
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Affiliation(s)
- Amy L Firth
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
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Hou S, Xu R, Heinemann SH, Hoshi T. Reciprocal regulation of the Ca2+ and H+ sensitivity in the SLO1 BK channel conferred by the RCK1 domain. Nat Struct Mol Biol 2008; 15:403-10. [PMID: 18345016 PMCID: PMC2905141 DOI: 10.1038/nsmb.1398] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 02/01/2008] [Indexed: 01/08/2023]
Abstract
Increasing evidence suggests that intracellular H+ directly stimulates large-conductance Ca2+- and voltage-activated K+ (SLO1 BK) channels, thus providing a crucial link between membrane excitability and cell metabolism. Here we report that two histidine residues, His365 and His394, located in the intracellular regulator of conductance for K+ (RCK) 1 domain, serve as the H+ sensors of the SLO1 BK channel. Activation of the channel by H+ requires electrostatic interactions between the histidine residues and a nearby negatively charged residue involved in the channel's high-affinity Ca2+ sensitivity. Reciprocally, His365 and His394 also participate in the Ca2+-dependent activation of the channel, functioning as Ca2+ mimetics once they are protonated. Therefore, a common motif in the RCK1 domain mediates the stimulatory effects of both H+ and Ca2+, and provides a basis for the bidirectional coupling of cell metabolism and membrane electrical excitability.
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Affiliation(s)
- Shangwei Hou
- Department of Physiology, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia, Pennsylvania 19104, USA
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31
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Palani D, Ghildyal P, Manchanda R. Effects of heptanol and carbenoxolone on noradrenaline induced contractions in guinea pig vas deferens. Auton Neurosci 2007; 137:56-62. [PMID: 17716954 DOI: 10.1016/j.autneu.2007.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 07/13/2007] [Accepted: 07/18/2007] [Indexed: 10/22/2022]
Abstract
We examined the effects of two putative gap junction blockers, heptanol and carbenoxolone, on noradrenaline-induced contractions in guinea pig vas deferens. The force generated due to the exogenously added noradrenaline (20 microM) consisted of two components: the tonic and the oscillatory. 2 mM heptanol abolished the oscillatory contractions and drastically suppressed both the maximum force (by 85.4 +/- 18.2%) as well as the tonic component (by 28.8 +/- 5.1%) (P<0.01, n=7). However, the effects of carbenoxolone (50 microM) were strikingly different, with the spikes of the oscillatory component being merged into a steady, "fused" contraction, without affecting the maximum force developed. The L-type Ca(2+) channel blocker nifedipine (2 microM) abolished the oscillatory component of the contractions and significantly reduced the maximum force and tonic component (by 82.4 +/- 6.8% and 19.7 +/- 6.4% respectively; P<0.01, n=4), in a manner similar to that elicited by heptanol. Our results indicate that (i) while carbenoxolone specifically blocks gap junctions, heptanol appears to exert its actions through non-gap junctional mechanisms, possibly by blocking VGCCs in smooth muscle; (ii) gap junctions play a significant modulatory role in the generation of noradrenaline-induced contractions in guinea pig vas deferens, particularly in the emergence of oscillatory contractions, while the maximum force developed may be independent of gap junctional contribution.
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Affiliation(s)
- D Palani
- Biomedical Engineering Group, School of Biosciences and Bioengineering, Indian Institute of Technology-Bombay, Mumbai-400076, India
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Cairrão E, Álvarez E, Santos-Silva AJ, Verde I. Potassium channels are involved in testosterone-induced vasorelaxation of human umbilical artery. Naunyn Schmiedebergs Arch Pharmacol 2007; 376:375-83. [DOI: 10.1007/s00210-007-0213-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Accepted: 10/28/2007] [Indexed: 10/22/2022]
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Soares PMG, Lima RF, de Freitas Pires A, Souza EP, Assreuy AMS, Criddle DN. Effects of anethole and structural analogues on the contractility of rat isolated aorta: Involvement of voltage-dependent Ca2+-channels. Life Sci 2007; 81:1085-93. [PMID: 17869309 DOI: 10.1016/j.lfs.2007.08.027] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Revised: 08/22/2007] [Accepted: 08/26/2007] [Indexed: 10/22/2022]
Abstract
Anethole is a naturally occurring aromatic oxidant, present in a variety of medicinal plant extracts, which is commonly used by the food and beverage industry. Despite its widespread occurrence and commercial use, there is currently little information regarding effects of this compound on the vasculature. Therefore the actions of anethole on the contractility of rat isolated aorta were compared with those of eugenol, and their respective isomeric forms, estragole and isoeugenol. In aortic rings precontracted with phenylephrine (PE; 1 microM), anethole (10(-6) M-10(-4) M) induced contraction in preparations possessing an intact endothelium, but not in endothelium-denuded tissues. At higher concentrations (10(-3) M-10(-2) M), anethole-induced concentration-dependent and complete relaxation of all precontracted preparations, irrespective of whether the endothelium was intact or not, an action shared by eugenol, estragole and isoeugenol. The contractile and relaxant effects of anethole in PE-precontracted preparations were not altered by L-NAME (10 microM) or indomethacin (10 microM), indicating that neither nitric oxide nor prostaglandins were involved in these actions. The mixed profile of effects was not confined to PE-mediated contraction, since similar responses were obtained to anethole when tissues were precontracted with 25 mM KCl. Anethole and estragole (10(-6)-10(-4) M), but not eugenol or isoeugenol, increased the basal tonus of endothelium-denuded aortic rings, an action that was abolished by VDCC blockers nifedipine (1 microM) and diltiazem (1 microM), or by withdrawal of extracellular Ca(2+). Our data suggest complex effects of anethole on isolated blood vessels, inducing contraction at lower doses, mediated via opening of voltage-dependent Ca(2+)-channels, and relaxant effects at higher concentrations that are shared by structural analogues.
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Affiliation(s)
- Pedro Marcos G Soares
- Instituto Superior de Ciências Biomédicas, ISCB-CCS, Universidade Estadual do Ceará, Av. Paranjana 1700, 60740-000, Fortaleza-CE, Brazil
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Seto SW, Au ALS, Lam TY, Chim SSC, Lee SMY, Wan S, Tjiu DCS, Shigemura N, Yim APC, Chan SW, Tsui SKW, Leung GPH, Kwan YW. Modulation by simvastatin of iberiotoxin-sensitive, Ca2+-activated K+ channels of porcine coronary artery smooth muscle cells. Br J Pharmacol 2007; 151:987-97. [PMID: 17558433 PMCID: PMC2042927 DOI: 10.1038/sj.bjp.0707327] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Statins (3-hydroxy-3-methyl-glutaryl coenzyme A (HMG CoA) reductase inhibitors) have been demonstrated to reduce cardiovascular mortality. It is unclear how the expression level of HMG CoA reductase in cardiovascular tissues compares with that in cells derived from the liver. We hypothesized that this enzyme exists in different cardiovascular tissues, and simvastatin modulates the vascular iberiotoxin-sensitive Ca2+-activated K(+) (BK(Ca)) channels. EXPERIMENTAL APPROACHES Expression of HMG CoA reductase in different cardiovascular preparations was measured. Effects of simvastatin on BK(Ca) channel gatings of porcine coronary artery smooth muscle cells were evaluated. KEY RESULTS Western immunoblots revealed the biochemical existence of HMG CoA reductase in human cardiovascular tissues and porcine coronary artery. In porcine coronary artery smooth muscle cells, extracellular simvastatin (1, 3 and 10 microM) (hydrophobic), but not simvastatin Na+ (hydrophilic), inhibited the BK(Ca) channels with a minimal recovery upon washout. Isopimaric acid (10 microM)-mediated enhancement of the BK(Ca) amplitude was reversed by external simvastatin. Simvastatin Na+ (10 microM, applied internally), markedly attenuated isopimaric acid (10 microM)-induced enhancement of the BK(Ca) amplitude. Reduced glutathione (5 mM; in the pipette solution) abolished simvastatin -elicited inhibition. Mevalonolactone (500 microM) and geranylgeranyl pyrophosphate (20 microM) only prevented simvastatin (1 and 3 microM)-induced responses. simvastatin (10 microM ) caused a rottlerin (1 microM)-sensitive (cycloheximide (10 microM)-insensitive) increase of PKC-delta protein expression. CONCLUSIONS AND IMPLICATIONS Our results demonstrated the biochemical presence of HMG CoA reductase in different cardiovascular tissues, and that simvastatin inhibited the BK(Ca) channels of the arterial smooth muscle cells through multiple intracellular pathways.
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MESH Headings
- Adult
- Aged
- Animals
- Blotting, Western
- Caveolin 1/biosynthesis
- Cell Line
- Cell Line, Tumor
- Coronary Vessels/cytology
- Coronary Vessels/drug effects
- Coronary Vessels/physiology
- Dose-Response Relationship, Drug
- Enzyme Activation/drug effects
- Female
- Humans
- Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology
- Imidazoles/pharmacology
- In Vitro Techniques
- Male
- Membrane Potentials/drug effects
- Middle Aged
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/physiology
- Peptides/pharmacology
- Phorbol Esters/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/metabolism
- Potassium Channels, Calcium-Activated/physiology
- Protein Kinase C-delta/metabolism
- Pyridines/pharmacology
- Simvastatin/chemistry
- Simvastatin/pharmacology
- Swine
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Affiliation(s)
- S W Seto
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - A L S Au
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - T Y Lam
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - S S C Chim
- Department of Obstetrics and Gynaecology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - S M Y Lee
- Institute of Chinese Medical Sciences, University of Macau Macau, PR China
| | - S Wan
- Department of Surgery, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - D C S Tjiu
- Department of Surgery, United Christian Hospital, The Hong Kong Polytechnic University Hong Kong SAR, PR China
| | - N Shigemura
- Department of Surgery, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - A P C Yim
- Department of Surgery, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
| | - S W Chan
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University Hong Kong SAR, PR China
| | - S K W Tsui
- Department of Biochemistry, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong SAR, PR China
| | - G P H Leung
- Department of Pharmacology, University of Hong Kong Hong Kong SAR, PR China
| | - Y W Kwan
- Department of Pharmacology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong Hong Kong, PR China
- Author for correspondence:
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Kim SH, Bae YM, Sung DJ, Park SW, Woo NS, Kim B, Cho SI. Ketamine blocks voltage-gated K(+) channels and causes membrane depolarization in rat mesenteric artery myocytes. Pflugers Arch 2007; 454:891-902. [PMID: 17342532 DOI: 10.1007/s00424-007-0240-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2006] [Accepted: 02/17/2007] [Indexed: 10/23/2022]
Abstract
Clinical doses of ketamine typically increase blood pressure, heart rate, and cardiac output. However, the precise mechanism by which ketamine produces these cardiovascular effects remains unclear. The voltage-gated K(+) (K(V)) channel is the major regulator of resting membrane potential (E (m)) and vascular tone in many arteries. Therefore, we sought to evaluate the effects of ketamine on K(V) currents using the standard whole-cell patch clamp recordings in single myocytes, enzymatically dispersed from rat mesenteric arteries. Ketamine [(+/-)-racemic mixture] inhibited K(V) currents reversibly and concentration dependently with a K ( d ) of 566.7 +/- 32.3 microM and Hill coefficient of 0.75 +/- 0.03. The inhibition of K(V) currents by ketamine was voltage independent, and the time courses of channel activation and inactivation were little affected. The effects of ketamine on steady-state activation and inactivation curves were also minimal. Use-dependent inhibition was not observed either. S(+)-ketamine inhibited K(V) currents with similar potency and efficacy as the racemic mixture. The average resting E (m) in rat mesenteric artery myocytes was -44.1 +/- 4.2 mV, and both racemic and S(+)-ketamine induced depolarization of E (m) (15.8 +/- 3.6 and 24.3 +/- 5.0 mV at 100 microM, respectively). We conclude that ketamine induces E (m) depolarization in vascular myocytes by blocking K(V) channels in a state-independent manner, which may contribute to the increased vascular tone and blood pressure produced by this drug under a clinical setting.
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Affiliation(s)
- Seong Hyop Kim
- Department of Anesthesiology, College of Medicine, Konkuk University, Seoul, South Korea
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36
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Mubagwa K, Gwanyanya A, Zakharov S, Macianskiene R. Regulation of cation channels in cardiac and smooth muscle cells by intracellular magnesium. Arch Biochem Biophys 2007; 458:73-89. [PMID: 17123458 DOI: 10.1016/j.abb.2006.10.014] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 10/16/2006] [Accepted: 10/16/2006] [Indexed: 01/06/2023]
Abstract
Magnesium regulates various ion channels in many tissues, including those of the cardiovascular system. General mechanisms by which intracellular Mg(2+) (Mg(i)(2+)) regulates channels are presented. These involve either a direct interaction with the channel, or an indirect modification of channel function via other proteins, such as enzymes or G proteins, or via membrane surface charges and phospholipids. To provide an insight into the role of Mg(i)(2+) in the cardiovascular system, effects of Mg(i)(2+) on major channels in cardiac and smooth muscle cells and the underlying mechanisms are then reviewed. Although Mg(i)(2+) concentrations are known to be stable, conditions under which they may change exist, such as following stimulation of beta-adrenergic receptors and of insulin receptors, or during pathophysiological conditions such as ischemia, heart failure or hypertension. Modifications of cardiovascular electrical or mechanical function, possibly resulting in arrhythmias or hypertension, may result from such changes of Mg(i)(2+) and their effects on cation channels.
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Affiliation(s)
- Kanigula Mubagwa
- Division of Experimental Cardiac Surgery, Department of Heart and Vessel Diseases, Katholieke Universiteit Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
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Magnusson L, Sorensen CM, Braunstein TH, Holstein-Rathlou NH, Salomonsson M. Renovascular BKCachannels are not activated in vivo under resting conditions and during agonist stimulation. Am J Physiol Regul Integr Comp Physiol 2007; 292:R345-53. [PMID: 16973937 DOI: 10.1152/ajpregu.00337.2006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the role of large-conductance Ca2+-activated K+(BKCa) channels for the basal renal vascular tone in vivo. Furthermore, the possible buffering by BKCaof the vasoconstriction elicited by angiotensin II (ANG II) or norepinephrine (NE) was investigated. The possible activation of renal vascular BKCachannels by cAMP was investigated by infusing forskolin. Renal blood flow (RBF) was measured in vivo using electromagnetic flowmetry or ultrasonic Doppler. Renal preinfusion of tetraethylammonium (TEA; 3.0 μmol/min) caused a small reduction of baseline RBF, but iberiotoxin (IBT; 0.3 nmol/min) did not have any effect. Renal injection of ANG II (1–4 ng) or NE (10–40 ng) produced a transient decrease in RBF. These responses were not affected by preinfusion of TEA or IBT. Renal infusion of the BKCaopener NS-1619 (90.0 nmol/min) did not affect basal RBF or the response to NE, but it attenuated the response to ANG II. Coadministration of NS-1619 with TEA or IBT abolished this effect. Forskolin caused renal vasodilation that was not inhibited by IBT. The presence of BKCachannels in the preglomerular vessels was confirmed by immunohistochemistry. Despite their presence, there is no indication for a major role for BKCachannels in the control of basal renal tone in vivo. Furthermore, BKCachannels do not have a buffering effect on the rat renal vascular responses to ANG II and NE. The fact that NS-1619 attenuates the ANG II response indicates that the renal vascular BKCachannels can be activated under certain conditions.
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Affiliation(s)
- Linda Magnusson
- Division of Renal and Cardiovascular Research, Department of Medical Physiology, The Panum Institute, University of Copenhagen, Copenhagen, Denmark
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38
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Brueggemann LI, Moran CJ, Barakat JA, Yeh JZ, Cribbs LL, Byron KL. Vasopressin stimulates action potential firing by protein kinase C-dependent inhibition of KCNQ5 in A7r5 rat aortic smooth muscle cells. Am J Physiol Heart Circ Physiol 2006; 292:H1352-63. [PMID: 17071736 PMCID: PMC2577603 DOI: 10.1152/ajpheart.00065.2006] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
[Arg(8)]-vasopressin (AVP), at low concentrations (10-500 pM), stimulates oscillations in intracellular Ca(2+) concentration (Ca(2+) spikes) in A7r5 rat aortic smooth muscle cells. Our previous studies provided biochemical evidence that protein kinase C (PKC) activation and phosphorylation of voltage-sensitive K(+) (K(v)) channels are crucial steps in this process. In the present study, K(v) currents (I(Kv)) and membrane potential were measured using patch clamp techniques. Treatment of A7r5 cells with 100 pM AVP resulted in significant inhibition of I(Kv). This effect was associated with gradual membrane depolarization, increased membrane resistance, and action potential (AP) generation in the same cells. The AVP-sensitive I(Kv) was resistant to 4-aminopyridine, iberiotoxin, and glibenclamide but was fully inhibited by the selective KCNQ channel blockers linopirdine (10 microM) and XE-991 (10 microM) and enhanced by the KCNQ channel activator flupirtine (10 microM). BaCl(2) (100 microM) or linopirdine (5 microM) mimicked the effects of AVP on K(+) currents, AP generation, and Ca(2+) spiking. Expression of KCNQ5 was detected by RT-PCR in A7r5 cells and freshly isolated rat aortic smooth muscle. RNA interference directed toward KCNQ5 reduced KCNQ5 protein expression and resulted in a significant decrease in I(Kv) in A7r5 cells. I(Kv) was also inhibited in response to the PKC activator 4beta-phorbol 12-myristate 13-acetate (10 nM), and the inhibition of I(Kv) by AVP was prevented by the PKC inhibitor calphostin C (250 nM). These results suggest that the stimulation of Ca(2+) spiking by physiological concentrations of AVP involves PKC-dependent inhibition of KCNQ5 channels and increased AP firing in A7r5 cells.
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Amberg GC, Santana LF. Kv2 channels oppose myogenic constriction of rat cerebral arteries. Am J Physiol Cell Physiol 2006; 291:C348-56. [PMID: 16571867 DOI: 10.1152/ajpcell.00086.2006] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
By hyperpolarizing arterial smooth muscle, voltage-gated, Ca2+-independent K+ (Kv) channels decrease calcium influx and thus oppose constriction. However, the molecular nature of the Kv channels function in arterial smooth muscle remains controversial. Recent investigations have emphasized a predominant role of Kv1 channels in regulating arterial tone. In this study, we tested the hypothesis Kv2 channels may also significantly regulate tone of rat cerebral arteries. We found that Kv2.1 transcript and protein are present in cerebral arterial smooth muscle. In addition, our analysis indicates that a substantial component (≈50%) of the voltage dependencies and kinetics of Kv currents in voltage-clamped cerebral arterial myocytes is consistent with Kv2 channels. Accordingly, we found that stromatoxin, a specific inhibitor of Kv2 channels, significantly decreased Kv currents in these cells. Furthermore, stromatoxin enhanced myogenic constriction of pressurized arterial segments. We also found that during angiotensin II-induced hypertension, Kv2 channel function was reduced in isolated myocytes and in intact arteries. This suggests that impaired Kv2 channel activity may contribute to arterial dysfunction during hypertension. On the basis of these novel observations, we propose a new model of Kv channel function in arterial smooth muscle in which Kv2 channels (in combination with Kv1 channels) contribute to membrane hyperpolarization and thus oppose constriction.
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Affiliation(s)
- Gregory C Amberg
- Dept. of Physics and Biophysics, Univ. of Washington, PO Box 357290, Seattle, WA 98195, USA
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40
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Lam FFY, Seto SW, Kwan YW, Yeung JHK, Chan P. Activation of the iberiotoxin-sensitive BKCa channels by salvianolic acid B of the porcine coronary artery smooth muscle cells. Eur J Pharmacol 2006; 546:28-35. [PMID: 16928370 DOI: 10.1016/j.ejphar.2006.07.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 07/20/2006] [Accepted: 07/20/2006] [Indexed: 11/20/2022]
Abstract
In this study, we examined the effects of Salvia miltiorrhiza (Danshen) crude extract, some of its lipid-soluble components (tanshinone I, tanshinone II(A), cryptotanshinone, dihydroisotanshinone I) and the water-soluble compounds (danshensu and salvianolic acid B) on the K(+) channels such as the iberiotoxin-sensitive Ca(2+)-activated K(+) (BK(Ca)) channels and the glibenclamide-sensitive ATP-dependent K(+) (IK(ATP)) channels of the porcine left anterior descending coronary artery smooth muscle cells. Cumulative application of salvianolic acid B (30-300 microM) caused a l-NNA (100 microM)-insensitive, potentiation of the outward BK(Ca) current amplitude with no apparent effect on the IK(ATP) channels opening. Salvianolic acid B (300 microM) caused an ODQ (10 microM, a guanylate cyclase inhibitor)-sensitive enhancement of the outward BK(Ca) current amplitude. In contrast, none of the other isolated chemical constituents of S. miltiorrhiza modified the openings of the two types of K(+) channels studied. In conclusion, our results suggest that salvianolic acid B, a major hydrophilic constituent found in Radix S. miltiorrhiza, activated the opening of the BK(Ca) channels of the porcine coronary artery smooth muscle cells through the activation of guanylate cyclase without the involvement of the nitric oxide synthase activation.
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MESH Headings
- Animals
- Benzofurans/pharmacology
- Coronary Vessels/drug effects
- Coronary Vessels/metabolism
- Cromakalim/pharmacology
- Dose-Response Relationship, Drug
- Drugs, Chinese Herbal/pharmacology
- Enzyme Activation/drug effects
- Enzyme Inhibitors/pharmacology
- Glyburide/pharmacology
- Guanylate Cyclase/antagonists & inhibitors
- Guanylate Cyclase/metabolism
- In Vitro Techniques
- Ion Channel Gating/drug effects
- Membrane Potentials/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Nitric Oxide Synthase/antagonists & inhibitors
- Nitroarginine/pharmacology
- Oxadiazoles/pharmacology
- Patch-Clamp Techniques
- Peptides/pharmacology
- Potassium Channel Blockers/pharmacology
- Potassium Channels/drug effects
- Potassium Channels/metabolism
- Potassium Channels, Calcium-Activated/drug effects
- Potassium Channels, Calcium-Activated/metabolism
- Quinoxalines/pharmacology
- Receptors, Drug/drug effects
- Receptors, Drug/metabolism
- Salvia miltiorrhiza
- Swine
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Affiliation(s)
- Francis Fu Yuen Lam
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, PR China
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41
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Au ALS, Seto SW, Chan SW, Chan MS, Kwan YW. Modulation by homocysteine of the iberiotoxin-sensitive, Ca2+ -activated K+ channels of porcine coronary artery smooth muscle cells. Eur J Pharmacol 2006; 546:109-19. [PMID: 16908017 DOI: 10.1016/j.ejphar.2006.06.073] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2006] [Revised: 06/28/2006] [Accepted: 06/28/2006] [Indexed: 11/21/2022]
Abstract
We evaluated the acute effect of homocysteine on the iberiotoxin-sensitive, Ca(2+)-activated K(+) (BK(Ca)) channels of the porcine coronary artery smooth muscle cells. NS 1619 (1 to 30 microM) caused a concentration-dependent enhancement of the BK(Ca) amplitude (recorded using the whole-cell, membrane-rupture configuration) only with an elevated [Ca(2+)](i) of approximately 444 nM, but not with [Ca(2+)](i) of approximately 100 nM. Homocysteine (30 microM) caused a small inhibition ( approximately 16%) of the BK(Ca) amplitude ([Ca(2+)](i)= approximately 444 nM), and a greater inhibition ( approximately 77%) was observed with 100 microM NADH present in the pipette solution. The inhibition persisted after washing. With NADPH (100 microM), a smaller magnitude of inhibition ( approximately 34%) of the BK(Ca) amplitude was recorded. The NS 1619-mediated enhancement of the BK(Ca) amplitude (with elevated [Ca(2+)](i) plus NADH in the pipette) was attenuated by homocysteine. The homocysteine-mediated inhibition of the BK(Ca) amplitude was suppressed by Tiron (10 mM) or diphenylene iodonium (30 nM), applied alone, but not by superoxide dismutase (500 U/ml) and catalase (500 U/ml). Generation of superoxide (O(2)(-)) of the smooth muscle cells (with NADH presence), measured using the lucigenin-enhanced chemiluminescence, was markedly increased by angiotensin II (100 nM) and homocysteine (30 microM). The chemiluminescence signal was sensitive to apocynin (300 microM) or Tiron, applied alone, but not to superoxide dismutase and catalase. In conclusion, our results demonstrate that acute homocysteine application inhibits the iberiotoxin-sensitive BK(Ca) channels (with elevated [Ca(2+)](i) and NADH present) which is probably caused by the NADH oxidase activation and the concomitant generation of intracellular superoxide.
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MESH Headings
- 1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt/pharmacology
- Acetophenones/pharmacology
- Angiotensin II/pharmacology
- Animals
- Benzimidazoles/pharmacology
- Calcium/metabolism
- Coronary Vessels/cytology
- Coronary Vessels/drug effects
- Coronary Vessels/metabolism
- Dose-Response Relationship, Drug
- Enzyme Activation/drug effects
- Enzyme Inhibitors/pharmacology
- Homocysteine/analogs & derivatives
- Homocysteine/pharmacology
- In Vitro Techniques
- Ion Channel Gating/drug effects
- Membrane Potentials/drug effects
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- NAD/metabolism
- NADPH Oxidases/antagonists & inhibitors
- NADPH Oxidases/metabolism
- Patch-Clamp Techniques
- Peptides/pharmacology
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/drug effects
- Potassium Channels, Calcium-Activated/metabolism
- Superoxides/metabolism
- Swine
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Alice L S Au
- Department of Pharmacology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, PR China
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42
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Erdei N, Papp Z, Pollesello P, Édes I, Bagi Z. The levosimendan metabolite OR-1896 elicits vasodilation by activating the K(ATP) and BK(Ca) channels in rat isolated arterioles. Br J Pharmacol 2006; 148:696-702. [PMID: 16715115 PMCID: PMC1751872 DOI: 10.1038/sj.bjp.0706781] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. We characterized the vasoactive effects of OR-1896, the long-lived metabolite of the inodilator levosimendan, in coronary and skeletal muscle microvessels. 2. The effect of OR-1896 on isolated, pressurized (80 mmHg) rat coronary and gracilis muscle arteriole (approximately 150 microm) diameters was investigated by videomicroscopy. 3. OR-1896 elicited concentration-dependent (1 nM-10 microM) dilations in coronary (maximal dilation: 66+/-6%, relative to that in Ca2+-free solutions; pD2: 7.16+/-0.42) and gracilis muscle arterioles (maximal dilation: 73+/-4%; pD2: 6.71+/-0.42), these dilations proving comparable to those induced by levosimendan (1 nM-10 microM) in coronary (maximal dilation: 83+/-6%; pD2: 7.06+/-0.14) and gracilis muscle arterioles (maximal dilation: 73+/-12%; pD2: 7.05+/-0.1). 4. The maximal dilations in response to OR-1896 were significantly (P<0.05) attenuated by the nonselective K+ channel inhibitor tetraethylammonium (1 mM) in coronary (to 34+/-9%) and gracilis muscle arterioles (to 28+/-6%). 5. Glibenclamide (5 or 10 microM), a selective ATP-sensitive K+ channel (KATP) blocker, elicited a greater reduction of OR-1896-induced dilations in skeletal muscle arterioles than in coronary microvessels. 6. Conversely, the selective inhibition of the large conductance Ca2+-activated K+ channels (BK(Ca)) with iberiotoxin (100 nM) significantly reduced the OR-1896-induced maximal dilation in coronary arterioles (to 21+/-6%), but was ineffective in skeletal muscle arterioles (72+/-8%). 7. Accordingly, OR-1896 elicits a substantial vasodilation in coronary and skeletal muscle arterioles, by activating primarily BK(Ca) and K(ATP) channels, respectively, and it is suggested that OR-1896 contributes to the long-term hemodynamic effects of levosimendan.
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Affiliation(s)
- Nóra Erdei
- Division of Clinical Physiology, Institute of Cardiology, University of Debrecen, Debrecen H-4004, Hungary
| | - Zoltán Papp
- Division of Clinical Physiology, Institute of Cardiology, University of Debrecen, Debrecen H-4004, Hungary
| | | | - István Édes
- Division of Clinical Physiology, Institute of Cardiology, University of Debrecen, Debrecen H-4004, Hungary
| | - Zsolt Bagi
- Division of Clinical Physiology, Institute of Cardiology, University of Debrecen, Debrecen H-4004, Hungary
- Author for correspondence:
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Ghatta S, Nimmagadda D, Xu X, O'Rourke ST. Large-conductance, calcium-activated potassium channels: structural and functional implications. Pharmacol Ther 2005; 110:103-16. [PMID: 16356551 DOI: 10.1016/j.pharmthera.2005.10.007] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Accepted: 10/13/2005] [Indexed: 12/16/2022]
Abstract
The large-conductance, calcium-activated potassium channels (BK, also termed BK(Ca), Slo, or MaxiK) distributed in both excitable and non-excitable cells are involved in many cellular functions such as action potential repolarization; neuronal excitability; neurotransmitter release; hormone secretion; tuning of cochlear hair cells; innate immunity; and modulation of the tone of vascular, airway, uterine, gastrointestinal, and urinary bladder smooth muscle tissues. Because of their high conductance, activation of BK channels has a strong effect on membrane potential. BK channels differ from all other potassium (K(+)) channels due to their high sensitivity to both intracellular calcium (Ca(2+)) concentrations and voltage. These features make BK channels ideal negative feedback regulators in many cell types by decreasing voltage-dependent Ca(2+) entry through membrane potential hyperpolarization. The current review aims to give a comprehensive understanding of the structure and molecular biology of BK channels and their relevance to various pathophysiological conditions. The review will also focus on the therapeutic potential and pharmacology of the various BK channel activators and blockers.
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Affiliation(s)
- Srinivas Ghatta
- Department of Pharmaceutical Sciences, College of Pharmacy, North Dakota State University, Fargo, 58105, USA.
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Miguel-Velado E, Moreno-Domínguez A, Colinas O, Cidad P, Heras M, Pérez-García MT, López-López JR. Contribution of Kv channels to phenotypic remodeling of human uterine artery smooth muscle cells. Circ Res 2005; 97:1280-7. [PMID: 16269658 DOI: 10.1161/01.res.0000194322.91255.13] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Vascular smooth muscle cells (VSMCs) perform diverse functions that can be classified into contractile and synthetic (or proliferating). All of these functions can be fulfilled by the same cell because of its capacity of phenotypic modulation in response to environmental changes. The resting membrane potential is a key determinant for both contractile and proliferating functions. Here, we have explored the expression of voltage-dependent K+ (Kv) channels in contractile (freshly dissociated) and proliferating (cultured) VSMCs obtained from human uterine arteries to establish their contribution to the functional properties of the cells and their possible participation in the phenotypic switch. We have studied the expression pattern (both at the mRNA and at the protein level) of Kvalpha subunits in both preparations as well as their functional contribution to the K+ currents of VSMCs. Our results indicate that phenotypic remodeling associates with a change in the expression and distribution of Kv channels. Whereas Kv currents in contractile VSMCs are mainly performed by Kv1 channels, Kv3.4 is the principal contributor to K+ currents in cultured VSMCs. Furthermore, selective blockade of Kv3.4 channels resulted in a reduced proliferation rate, suggesting a link between Kv channels expression and phenotypic remodeling.
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Affiliation(s)
- Eduardo Miguel-Velado
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética, Universidad de Valladolid, Facultad de Medicina, Consejo Superior de Investigaciones Científicas, Valladolid, Spain
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Cole WC, Chen TT, Clément-Chomienne O. Myogenic regulation of arterial diameter: role of potassium channels with a focus on delayed rectifier potassium current. Can J Physiol Pharmacol 2005; 83:755-65. [PMID: 16333377 DOI: 10.1139/y05-082] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The phenomenon of myogenic constriction of arterial resistance vessels in response to increased intraluminal pressure has been known for over 100 years, yet our understanding of the molecular mechanisms involved remains incomplete. The focus of this paper concerns the potassium (K+) channels that provide a negative feedback control of the myogenic depolarization of vascular smooth muscle cells that is provoked by elevations in intraluminal pressure, and specifically, the contribution of delayed rectifier (KDR) channels. Our knowledge of the important role played by KDR channels, as well as their molecular identity and acute modulation via changes in gating, has increased dramatically in recent years. Several lines of evidence point to a crucial contribution by heteromultimeric KV1 subunit-containing KDR channels in the control of arterial diameter and myogenic reactivity, but other members of the KV superfamily are also expressed by vascular myocytes, and less is known concerning their specific functions. The effect of pharmacological modulation of KDR channels is discussed, with particular reference to the actions of anorexinogens on KV1- and KV2-containing KDR channels. Finally, the need for a greater understanding of the mechanisms that control KDR channel gene expression is stressed in light of evidence indicating that there is a reduced expression of KDR channels in diseases associated with abnormal myogenic reactivity and vascular remodelling.Key words: resistance arteries, myogenic response, potassium channels, delayed rectifier K+ current, KV channels, KV1, KV2.
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Affiliation(s)
- William C Cole
- The Smooth Muscle Research Group, Department of Pharmacology & Therapeutics, Universityk of Calgary, Calgary, Canada.
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