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Albrakati A. Caveolar disruption with methyl-β-cyclodextrin causes endothelium-dependent contractions in Wistar rat carotid arteries. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:63071-63080. [PMID: 35445923 DOI: 10.1007/s11356-022-20226-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 04/09/2022] [Indexed: 06/14/2023]
Abstract
Caveolae are organizing centers for cellular signal transduction in endothelial cells (ED) and smooth muscle cells (SMCs) in the blood vessels. Myography was used to investigate the effects of a caveolar disruption using methyl-β-cyclodextrin (MBCD) on maxi-K channels in rat carotid arteries. Incubation of carotid segments with MBCD augmented contractions in response to BaK (chemical channel agonist) but not those induced by depolarizing high potassium physiological saline (KPSS). In contrast, incubation with cholesterol-saturated MBCD (Ch-MBCD) abolished the effects of MBCD. Mechanical removal of endothelial cells by MBCD triggered a small contraction in response to BaK. Incubation with nitroarginine methyl ester (L-NAME) inhibited nitric oxide (NO) release, causing increased contractions in response to BaK, and this effect was reversed by pretreatment with MBCD. These results suggest that MBCD inhibits endothelial NO release. Contrastingly, inhibition of maxi-K channels with iberiotoxin enhanced contractions in response to BaK. Likewise, L-NAME decreased the contractile effect of iberiotoxin, as in the ED-denuded arteries. Transmission electron microscopy (TEM) showed the presence and absence of caveolae in intact blood vessels before and after MBCD treatment, respectively, whereas histology confirmed ED removal after the treatment. Caveolar disruption using MBCD impairs ED-dependent relaxation by inhibiting the release of NO from the ED and altered the contractility of SMCs independent of the ED due to reduced contribution of maxi-K channels to the SMC membrane potential, causing depolarization and increasing carotid artery contraction. These findings might help to understand the physiological role of the maxi-K channels in rat carotid arteries.
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Affiliation(s)
- Ashraf Albrakati
- Department of Human Anatomy, College of Medicine, Taif University, P.O. Box 11099, Taif, 21944, Saudi Arabia.
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2
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Tyan L, Turner D, Komp KR, Medvedev RY, Lim E, Glukhov AV. Caveolin-3 is required for regulation of transient outward potassium current by angiotensin II in mouse atrial myocytes. Am J Physiol Heart Circ Physiol 2021; 320:H787-H797. [PMID: 33416459 PMCID: PMC8082791 DOI: 10.1152/ajpheart.00569.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 11/10/2020] [Accepted: 12/04/2020] [Indexed: 01/21/2023]
Abstract
Angiotensin II (AngII) is a key mediator of the renin-angiotensin system and plays an important role in the regulation of cardiac electrophysiology by affecting various cardiac ion currents, including transient outward potassium current, Ito. AngII receptors and molecular components of Ito, Kv4.2 and Kv4.3 channels, have been linked to caveolae structures. However, their functional interaction and the importance of such proximity within 50- to 100-nm caveolar nanodomains remain unknown. To address this, we studied the mechanisms of Ito regulation by AngII in atrial myocytes of wild-type (WT) and cardiac-specific caveolin-3 (Cav3) conditional knockout (Cav3KO) mice. We showed that in WT atrial myocytes, a short-term (2 h) treatment with AngII (5 µM) significantly reduced Ito density. This effect was prevented 1) by a 30-min pretreatment with a selective antagonist of AngII receptor 1 (Ang1R) losartan (2 µM) or 2) by a selective inhibition of protein kinase C (PKC) by BIM1 (10 µM). The effect of AngII on Ito was completely abolished in Cav3-KO mice, with no change in a baseline Ito current density. In WT atria, Ang1Rs co-localized with Cav3, and the expression of Ang1Rs was significantly decreased in Cav3KO in comparison with WT mice, whereas no change in Kv4.2 and Kv4.3 protein expression was observed. Overall, our findings demonstrate that Cav3 is involved in the regulation of Ang1R expression and is required for the modulation of Ito by AngII in mouse atrial myocytes.NEW & NOTEWORTHY Angiotensin II receptor 1 is associated with caveolae and caveolar scaffolding protein caveolin-3 in mouse atrial myocytes that is required for the regulation of Ito by angiotensin II. Downregulation of caveolae/caveolin-3 disrupts this regulation and may be implicated in pathophysiological atrial remodeling.
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Affiliation(s)
- Leonid Tyan
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Daniel Turner
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Karlie R Komp
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Roman Y Medvedev
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Evi Lim
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Alexey V Glukhov
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
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Structural Complexity and Plasticity of Signaling Regulation at the Melanocortin-4 Receptor. Int J Mol Sci 2020; 21:ijms21165728. [PMID: 32785054 PMCID: PMC7460885 DOI: 10.3390/ijms21165728] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 08/03/2020] [Accepted: 08/06/2020] [Indexed: 02/06/2023] Open
Abstract
The melanocortin-4 receptor (MC4R) is a class A G protein-coupled receptor (GPCR), essential for regulation of appetite and metabolism. Pathogenic inactivating MC4R mutations are the most frequent cause of monogenic obesity, a growing medical and socioeconomic problem worldwide. The MC4R mediates either ligand-independent or ligand-dependent signaling. Agonists such as α-melanocyte-stimulating hormone (α-MSH) induce anorexigenic effects, in contrast to the endogenous inverse agonist agouti-related peptide (AgRP), which causes orexigenic effects by suppressing high basal signaling activity. Agonist action triggers the binding of different subtypes of G proteins and arrestins, leading to concomitant induction of diverse intracellular signaling cascades. An increasing number of experimental studies have unraveled molecular properties and mechanisms of MC4R signal transduction related to physiological and pathophysiological aspects. In addition, the MC4R crystal structure was recently determined at 2.75 Å resolution in an inactive state bound with a peptide antagonist. Underpinned by structural homology models of MC4R complexes simulating a presumably active-state conformation compared to the structure of the inactive state, we here briefly summarize the current understanding and key players involved in the MC4R switching process between different activity states. Finally, these perspectives highlight the complexity and plasticity in MC4R signaling regulation and identify gaps in our current knowledge.
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Williams EA, Russo V, Ceraso S, Gupta D, Barrett-Jolley R. Anti-arrhythmic properties of non-antiarrhythmic medications. Pharmacol Res 2020; 156:104762. [PMID: 32217149 PMCID: PMC7248574 DOI: 10.1016/j.phrs.2020.104762] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 03/10/2020] [Accepted: 03/17/2020] [Indexed: 02/06/2023]
Abstract
Traditional anti-arrhythmic drugs are classified by the Vaughan-Williams classification scheme based on their mechanisms of action, which includes effects on receptors and/or ion channels. Some known anti-arrhythmic drugs do not perfectly fit into this classification scheme. Other medications/molecules with established non-anti-arrhythmic indications have shown anti-arrhythmic properties worth exploring. In this narrative review, we discuss the molecular mechanisms and evidence base for the anti-arrhythmic properties of traditional non-antiarrhythmic drugs such as inhibitors of the renin angiotensin system (RAS), statins and polyunsaturated fatty acids (PUFAs). In summary, RAS antagonists, statins and PUFAs are 'upstream target modulators' that appear to have anti-arrhythmic roles. RAS blockers prevent the downstream arrhythmogenic effects of angiotensin II - the main effector peptide of RAS - and the angiotensin type 1 receptor. Statins have pleiotropic effects including anti-inflammatory, immunomodulatory, modulation of autonomic nervous system, anti-proliferative and anti-oxidant actions which appear to underlie their anti-arrhythmic properties. PUFAs have the ability to alter ion channel function and prevent excessive accumulation of calcium ions in cardiac myocytes, which might explain their benefits in certain arrhythmic conditions. Clearly, whilst a number of anti-arrhythmic drugs exist, there is still a need for randomised trials to establish whether additional agents, including those already in clinical use, have significant anti-arrhythmic effects.
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Affiliation(s)
- Emmanuel Ato Williams
- Department of Cardiology, Liverpool Heart and Chest Hospital, Thomas Drive, Liverpool, L14 3PE, United Kingdom; Institute of Aging and Chronic Disease, University of Liverpool, United Kingdom
| | - Vincenzo Russo
- Chair of Cardiology, Department of Medical Translational Sciences, University of Campania "Luigi Vanvitelli", Monaldi Hospital, Naples, Italy
| | - Sergio Ceraso
- Specialization Fellow in Cardiology, Department of Medical Translational Sciences, University of Campania "Luigi Vanvitelli" - Monaldi Hospital, Naples, Italy
| | - Dhiraj Gupta
- Department of Cardiology, Liverpool Heart and Chest Hospital, Thomas Drive, Liverpool, L14 3PE, United Kingdom
| | - Richard Barrett-Jolley
- Chair Neuropharmacology, Institute of Aging and Chronic Disease, University of Liverpool, United Kingdom.
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Kurakami K, Norota I, Nasu F, Ohshima S, Nagasawa Y, Konno Y, Obara Y, Ishii K. KCNQ1 is internalized by activation of α1 adrenergic receptors. Biochem Pharmacol 2019; 169:113628. [DOI: 10.1016/j.bcp.2019.113628] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 08/30/2019] [Indexed: 01/25/2023]
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Tafoya C, Singh A. Cardiac Memory: A Case Report and Review of the Literature. J Emerg Med 2019; 57:85-93. [PMID: 31047746 DOI: 10.1016/j.jemermed.2019.02.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 02/16/2019] [Accepted: 02/18/2019] [Indexed: 11/24/2022]
Abstract
BACKGROUND A variety of clinical syndromes can cause T-wave inversion (TWI), ranging from life-threatening events to benign conditions. One benign cause of TWI is cardiac memory, which is characterized by the transient inversion of T-waves following abnormal activation of the ventricles, commonly due to intermittent left bundle branch block (LBBB), tachydysrhythmias, electrical pacing, or ventricular pre-excitation. CASE REPORT A 72-year-old man presented to the emergency department with chest pain, nausea, vomiting, and headache. Upon arrival, his electrocardiogram (ECG) showed new-onset LBBB with appropriate secondary ST-T wave changes. A subsequent ECG showed disappearance of LBBB and newly inverted T-waves in precordial leads V1-V5, followed by a repeat ECG that again showed LBBB. Serial troponin testing was unremarkable. During hospitalization, echocardiogram and nuclear perfusion stress test were normal. The transient TWIs in this patient were believed to be due to cardiac memory. We performed a literature review and identified 39 published cases of cardiac memory. The most common etiology for cardiac memory was after cardiac pacemaker placement, followed by intermittent LBBB (as was seen in our patient), and post-tachydysrhythmia. Patient ages ranged from 21 to 88 years, with an equal number of cases reported in men and women. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Cardiac memory is a poorly understood, rarely observed phenomenon that can occur in the setting of intermittent LBBB. Testing for acute cardiac ischemia and underlying coronary artery disease is still recommended, as the diagnosis of cardiac memory can only be made after negative workup.
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Affiliation(s)
- Chelsea Tafoya
- Department of Emergency Medicine, Alameda Health System, Highland Hospital, Oakland, California
| | - Amandeep Singh
- Department of Emergency Medicine, Alameda Health System, Highland Hospital, Oakland, California
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Jansen HJ, Mackasey M, Moghtadaei M, Belke DD, Egom EE, Tuomi JM, Rafferty SA, Kirkby AW, Rose RA. Distinct patterns of atrial electrical and structural remodeling in angiotensin II mediated atrial fibrillation. J Mol Cell Cardiol 2018; 124:12-25. [PMID: 30273558 DOI: 10.1016/j.yjmcc.2018.09.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 09/25/2018] [Accepted: 09/26/2018] [Indexed: 01/14/2023]
Abstract
Atrial fibrillation (AF) is prevalent in hypertension and elevated angiotensin II (Ang II); however, the mechanisms by which Ang II leads to AF are poorly understood. Here, we investigated the basis for this in mice treated with Ang II or saline for 3 weeks. Ang II treatment increased susceptibility to AF compared to saline controls in association with increases in P wave duration and atrial effective refractory period, as well as reductions in right and left atrial conduction velocity. Patch-clamp studies demonstrate that action potential (AP) duration was prolonged in right atrial myocytes from Ang II treated mice in association with a reduction in repolarizing K+ currents. In contrast, APs in left atrial myocytes from Ang II treated mice showed reductions in upstroke velocity and overshoot, as well as greater prolongations in AP duration. Ang II reduced Na+ current (INa) in the left, but not the right atrium. This reduction in INa was reversible following inhibition of protein kinase C (PKC) and PKCα expression was increased selectively in the left atrium in Ang II treated mice. The transient outward K+ current (Ito) showed larger reductions in the left atrium in association with a shift in the voltage dependence of activation. Finally, Ang II caused fibrosis throughout the atria in association with changes in collagen expression and regulators of the extracellular matrix. This study demonstrates that hypertension and elevated Ang II cause distinct patterns of electrical and structural remodeling in the right and left atria that collectively create a substrate for AF.
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Affiliation(s)
- Hailey J Jansen
- Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Martin Mackasey
- Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Motahareh Moghtadaei
- Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Darrell D Belke
- Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Emmanuel E Egom
- Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jari M Tuomi
- Department of Medicine, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada
| | - Sara A Rafferty
- Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Adam W Kirkby
- Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Robert A Rose
- Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
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8
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He J, Xu Y, Yang L, Xia G, Deng N, Yang Y, Tian Y, Fu Z, Huang Y. Regulation of inward rectifier potassium current ionic channel remodeling by AT1
-Calcineurin-NFAT signaling pathway in stretch-induced hypertrophic atrial myocytes. Cell Biol Int 2018; 42:1149-1159. [PMID: 29719087 DOI: 10.1002/cbin.10983] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/28/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Jionghong He
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
| | - Yanan Xu
- Department of Rehabilitation Medicine; Xiaotangshan Hospital; Beijing 102211 China
| | - Long Yang
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
| | - Guiling Xia
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
| | - Na Deng
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
| | - Yongyao Yang
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
| | - Ye Tian
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
| | - Zenan Fu
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
| | - Yongqi Huang
- Department of Cardiology; Guizhou Provincial People's Hospital; Guiyang 550002 China
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Prolonged AT 1R activation induces Ca V1.2 channel internalization in rat cardiomyocytes. Sci Rep 2017; 7:10131. [PMID: 28860469 PMCID: PMC5578992 DOI: 10.1038/s41598-017-10474-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 08/10/2017] [Indexed: 12/18/2022] Open
Abstract
The cardiac L-type calcium channel is a multi-subunit complex that requires co-assembling of the pore-forming subunit CaV1.2 with auxiliary subunits CaVα2δ and CaVβ. Its traffic has been shown to be controlled by these subunits and by the activation of various G-protein coupled receptors (GPCR). Here, we explore the consequences of the prolonged activation of angiotensin receptor type 1 (AT1R) over CaV1.2 channel trafficking. Bioluminescence Resonance Energy Transfer (BRET) assay between β-arrestin and L-type channels in angiotensin II-stimulated cells was used to assess the functional consequence of AT1R activation, while immunofluorescence of adult rat cardiomyocytes revealed the effects of GPCR activation on CaV1.2 trafficking. Angiotensin II exposure results in β-arrestin1 recruitment to the channel complex and an apparent loss of CaV1.2 immunostaining at the T-tubules. Accordingly, angiotensin II stimulation causes a decrease in L-type current, Ca2+ transients and myocyte contractility, together with a faster repolarization phase of action potentials. Our results demonstrate that prolonged AT1R activation induces β-arrestin1 recruitment and the subsequent internalization of CaV1.2 channels with a half-dose of AngII on the order of 100 nM, suggesting that this effect depends on local renin-angiotensin system. This novel AT1R-dependent CaV1.2-trafficking modulation likely contributes to angiotensin II-mediated cardiac remodeling.
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Pressure-overload-induced angiotensin-mediated early remodeling in mouse heart. PLoS One 2017; 12:e0176713. [PMID: 28464037 PMCID: PMC5413013 DOI: 10.1371/journal.pone.0176713] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 04/15/2017] [Indexed: 11/19/2022] Open
Abstract
Our previous work on angiotensin II-mediated electrical-remodeling in canine left ventricle, in connection with a long history of other studies, suggested the hypothesis: increases in mechanical load induce autocrine secretion of angiotensin II (A2), which coherently regulates a coterie of membrane ion transporters in a manner that increases contractility. However, the relation between load and A2 secretion was correlative. We subsequently showed a similar or identical system was present in murine heart. To investigate whether the relation between mechanical load and A2-mediated electrical remodeling was causal, we employed transverse aortic constriction in mice to subject the left ventricle to pressure overload for short-term (1 to 2 days) or long-term (1 to 2 weeks) periods. Heart-to-body weight ratios and cell capacitance measurements were used to determine hypertrophy. Whole-cell patch clamp recordings of the predominant repolarization currents Ito,fast and IK,slow were used to assess electrical remodeling. Hearts or myocytes subjected to long-term load displayed significant hypertrophy, which was not evident in short-term load. However, short-term load induced significant reductions in Ito,fast and IK,slow. Incubation of these myocytes with the angiotensin II type 1 receptor inhibitor saralasin for 2 hours restored Ito,fast and IK,slow to control levels. The number of Ito.fast or IK,slow channels did not change with A2 or long-term load, however the hypertrophic increase in membrane area reduced the current densities for both channels. For Ito,fast but not IK,slow there was an additional reduction that was reversed by inhibition of angiotensin receptors. These results suggest increased load activates an endogenous renin angiotensin system that initially reduces Ito,fast and IK,slow prior to the onset of hypertrophic growth. However, there are functional interactions between electrical and anatomical remodeling. First, hypertrophy tends to reduce all current densities. Second, the hypertrophic program can modify signaling between the angiotensin receptor and target current.
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Rodrigues Junior LF, de Azevedo Carvalho AC, Pimentel EB, Mill JG, Nascimento JHM. Chronic enalapril treatment increases transient outward potassium current in cardiomyocytes isolated from right ventricle of spontaneously hypertensive rats. Naunyn Schmiedebergs Arch Pharmacol 2016; 390:225-234. [PMID: 27915452 DOI: 10.1007/s00210-016-1322-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 11/21/2016] [Indexed: 01/19/2023]
Abstract
It has been well established that chronic pressure overload resulting from hypertension leads to ventricular hypertrophy and electrophysiological remodeling. The transient outward potassium current (I to) reduction described in hypertensive animals delays ventricular repolarization, leading to complex ventricular arrhythmias and sudden death. Antihypertensive drugs, as angiotensin-converting enzyme inhibitors (ACEi), can restore I to and reduce the incidence of arrhythmic events. The purpose of this study was to evaluate the differential effects of long-term treatment with ACEi or direct-acting smooth muscle relaxant on the I to of left and right ventricle myocytes of spontaneously hypertensive rats (SHR). Animals were divided into four groups: normotensive Wistar-Kyoto rats (WKY), hypertensive (SHR), SHR treated for 6 weeks with enalapril 10 mg/kg/day (SHRE), or hydralazine 20 mg/kg/day (SHRH). Systolic blood pressure (SBP) and hypertrophy index (heart weight/body weight (HW/BW)) were determined at the end of treatment period. Cell membrane capacitance (C m) and I to were assessed in cardiomyocytes isolated from left and right ventricles. The SHR exhibited significantly increased SBP and HW/BW when compared to the WKY. The treated groups, SHRE and SHRH, restored normal SBP but not HW/BW. The SHR group exhibited a diminished I to in the left but not the right ventricle. Both the treated groups restored I to in the left ventricle. However, in the right ventricle, only enalapril treatment modified I to. The SHRE group exhibited a significant increase in I to compared to all the other groups. These findings suggest that enalapril may increase I to by a pressure overload independent mechanism.
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Affiliation(s)
- Luiz Fernando Rodrigues Junior
- Institute of Biophysics Carlos Chagas Filho, Laboratory of Cardiac Electrophysiology Antonio Paes de Carvalho, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373 - CCS Bloco G - Ilha do Fundao, 21, Rio de Janeiro, RJ, 941-902, Brazil.,Department of Physiological Sciences, Laboratory of Cardiovascular Biophysics, Federal University of State of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Ana Carolina de Azevedo Carvalho
- Institute of Biophysics Carlos Chagas Filho, Laboratory of Cardiac Electrophysiology Antonio Paes de Carvalho, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373 - CCS Bloco G - Ilha do Fundao, 21, Rio de Janeiro, RJ, 941-902, Brazil
| | | | - José Geraldo Mill
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, Brazil
| | - José Hamilton Matheus Nascimento
- Institute of Biophysics Carlos Chagas Filho, Laboratory of Cardiac Electrophysiology Antonio Paes de Carvalho, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373 - CCS Bloco G - Ilha do Fundao, 21, Rio de Janeiro, RJ, 941-902, Brazil.
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12
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Cohen IS, Mathias RT. The renin-angiotensin system regulates transmural electrical remodeling in response to mechanical load. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 122:187-201. [PMID: 27645328 PMCID: PMC5161618 DOI: 10.1016/j.pbiomolbio.2016.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 09/13/2016] [Indexed: 06/06/2023]
Affiliation(s)
- Ira S Cohen
- Department of Physiology & Biophysics, Institute for Molecular Cardiology, Stony Brook University, United States.
| | - Richard T Mathias
- Department of Physiology & Biophysics, Institute for Molecular Cardiology, Stony Brook University, United States
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Chaugai S, Sherpa LY, Sepehry AA, Arima H, Wang DW. Effect of RAAS blockers on adverse clinical outcomes in high CVD risk subjects with atrial fibrillation: A meta-analysis and systematic review of randomized controlled trials. Medicine (Baltimore) 2016; 95:e4059. [PMID: 27368043 PMCID: PMC4937957 DOI: 10.1097/md.0000000000004059] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Recent studies have demonstrated that atrial fibrillation significantly increases the risk of adverse clinical outcomes in high cardiovascular disease risk subjects. Application of renin-angiotensin-aldosterone system blockers for prevention of recurrence of atrial fibrillation and adverse clinical outcomes in subjects with atrial fibrillation is a theoretically appealing concept. However, results of clinical trials evaluating the effect of renin-angiotensin-aldosterone blockers on adverse clinical outcomes in high cardiovascular disease risk subjects with atrial fibrillation remain inconclusive.A pooled study of 6 randomized controlled trials assessing the efficacy of renin-angiotensin-aldosterone blockers on subjects with atrial fibrillation was performed.A total of 6 randomized controlled trials enrolled a total of 53,510 patients followed for 1 to 5 years. RAAS blockade therapy was associated with 14% reduction in the incidence of heart failure (OR: 0.86, [95%CI: 0.76- 0.97], P=0.018) and 17% reduction in the incidence of CVE (OR: 0.83, [95%CI: 0.70-0.99], P = 0.038). The corresponding decline in absolute risk against heart failure (ARR: 1.4%, [95%CI: 0.2-2.6%], P = 0.018) and CVE (ARR: 3.5%, [95%CI: 0.0-6.9%], P = 0.045) in the AF group was much higher than the non-AF group for heart failure (ARR: 0.4%, [95%CI: 0.0-0.7%], P = 0.057) and CVE (ARR: 1.6%, [95%CI: -0.1% to 3.3%], P = 0.071). No significant effect was noted on all-cause or cardiovascular mortality, stroke, or myocardial infarction.This study suggests that RAAS blockade offers protection against heart failure and cardiovascular events in high cardiovascular disease risk subjects with atrial fibrillation.
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Affiliation(s)
- Sandip Chaugai
- Department of Internal Medicine and Institute of Hypertension, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN
| | - Lhamo Yanchang Sherpa
- Department of Community Medicine, Section of Preventive Medicine and Epidemiology, University of Oslo, Oslo, Norway
| | - Amir A. Sepehry
- University of British Columbia, Division of Neurology, Vancouver, Canada
| | - Hisatomi Arima
- The George Institute for Global Health, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - Dao Wen Wang
- Department of Internal Medicine and Institute of Hypertension, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- Correspondence: Dao Wen Wang, Department of Internal Medicine and Institute of Hypertension, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, P. R. China (e-mail: )
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14
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Chaugai S, Meng WY, Ali Sepehry A. Effects of RAAS Blockers on Atrial Fibrillation Prophylaxis. J Cardiovasc Pharmacol Ther 2016; 21:388-404. [DOI: 10.1177/1074248415619490] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 10/19/2015] [Indexed: 01/23/2023]
Abstract
Background: Impact of atrial fibrillation on clinical outcomes is well recognized, and application of renin–angiotensin–aldosterone system (RAAS) blockers for the prevention of atrial fibrillation (AF) is a theoretically appealing concept. However, clinical trials have yielded inconsistent results. Methods: A pooled study of 26 randomized controlled trials (RCTs) assessing the efficacy of RAAS blockers on AF prophylaxis was performed. Results: A total of 28 reports from 26 randomized controlled trials enrolled 165 387 patients, with an overall 24% reduction in the incidence of AF (odds ratio [OR]: 0.76, 95% confidence interval [CI]: 0.68-0.85], P = .000). Forty-nine percent reduction in the incidence of AF (OR: 0.51, 95% CI: 0.30-0.85, P = .010) in systolic heart failure was observed, whereas no significant effect was observed in patients with diastolic heart failure, postmyocardial infarction, and high cardiovascular disease risk. There was a 19% (OR: 0.81, 95% CI: 0.67-1.00, P = .037) reduction in new-onset and 54% (OR: 0.46, 95% CI: 0.33-0.62, P = .000) reduction in recurrent AF in hypertensive patients with 39% (OR: 0.61, 95% CI: 0.44-0.84, P = .003) risk reduction against calcium blockers and 41% (OR: 0.59, 95% CI: 0.44-0.80, P = .001) risk reduction against β blockers. Angiotensin-receptor blocker appeared marginally superior to angiotensin-converting enzyme inhibitor in primary and secondary prevention. Conclusion: This study suggests that RAAS blockade effectively suppresses AF in systolic heart failure, and hypertensives derive greater benefit against new-onset and recurrent AF compared to β blockers, calcium channel blockers, and diuretics.
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Affiliation(s)
- Sandip Chaugai
- Department of Internal Medicine, Institute of Hypertension, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wen Yeng Meng
- Department of Internal Medicine, Institute of Hypertension, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Amir Ali Sepehry
- Graduate Program in Neuroscience, College for Interdisciplinary Studies, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Medicine, Division of Neurology, University of British Columbia, Vancouver, Canada
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15
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Cardiac memory: The slippery slope twixt normalcy and pathology. Trends Cardiovasc Med 2015; 25:687-96. [DOI: 10.1016/j.tcm.2015.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/17/2015] [Accepted: 02/18/2015] [Indexed: 12/19/2022]
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Kim J, Gao J, Cohen IS, Mathias RT. Angiotensin II Type 1 Receptor-Mediated Electrical Remodeling in Mouse Cardiac Myocytes. PLoS One 2015; 10:e0138711. [PMID: 26430746 PMCID: PMC4591968 DOI: 10.1371/journal.pone.0138711] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 09/02/2015] [Indexed: 01/14/2023] Open
Abstract
We recently characterized an autocrine renin angiotensin system (RAS) in canine heart. Activation of Angiotensin II Type 1 Receptors (AT1Rs) induced electrical remodeling, including inhibition of the transient outward potassium current Ito, prolongation of the action potential (AP), increased calcium entry and increased contractility. Electrical properties of the mouse heart are very different from those of dog heart, but if a similar system existed in mouse, it could be uniquely studied through genetic manipulations. To investigate the presence of a RAS in mouse, we measured APs and Ito in isolated myocytes. Application of angiotensin II (A2) for 2 or more hours reduced Ito magnitude, without affecting voltage dependence, and prolonged APs in a dose-dependent manner. Based on dose-inhibition curves, the fast and slow components of Ito (Ito,fast and IK,slow) appeared to be coherently regulated by [A2], with 50% inhibition at an A2 concentration of about 400 nM. This very high K0.5 is inconsistent with systemic A2 effects, but is consistent with an autocrine RAS in mouse heart. Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking. Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes. These data demonstrate AT1R mediated regulation of Ito in mouse heart. Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.
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Affiliation(s)
- Jeremy Kim
- Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America
| | - Junyuan Gao
- Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America
| | - Ira S. Cohen
- Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America
| | - Richard T. Mathias
- Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America
- * E-mail:
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17
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Chan YH, Tsai WC, Ko JS, Yin D, Chang PC, Rubart M, Weiss JN, Everett TH, Lin SF, Chen PS. Small-Conductance Calcium-Activated Potassium Current Is Activated During Hypokalemia and Masks Short-Term Cardiac Memory Induced by Ventricular Pacing. Circulation 2015; 132:1377-86. [PMID: 26362634 DOI: 10.1161/circulationaha.114.015125] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Accepted: 06/11/2015] [Indexed: 01/26/2023]
Abstract
BACKGROUND Hypokalemia increases the vulnerability to ventricular fibrillation. We hypothesize that the apamin-sensitive small-conductance calcium-activated potassium current (IKAS) is activated during hypokalemia and that IKAS blockade is proarrhythmic. METHODS AND RESULTS Optical mapping was performed in 23 Langendorff-perfused rabbit ventricles with atrioventricular block and either right or left ventricular pacing during normokalemia or hypokalemia. Apamin prolonged the action potential duration (APD) measured to 80% repolarization (APD80) by 26 milliseconds (95% confidence interval [CI], 14-37) during normokalemia and by 54 milliseconds (95% CI, 40-68) during hypokalemia (P=0.01) at a 1000-millisecond pacing cycle length. In hypokalemic ventricles, apamin increased the maximal slope of APD restitution, the pacing cycle length threshold of APD alternans, the pacing cycle length for wave-break induction, and the area of spatially discordant APD alternans. Apamin significantly facilitated the induction of sustained ventricular fibrillation (from 3 of 9 hearts to 9 of 9 hearts; P=0.009). Short-term cardiac memory was assessed by the slope of APD80 versus activation time. The slope increased from 0.01 (95% CI, -0.09 to 0.12) at baseline to 0.34 (95% CI, 0.23-0.44) after apamin (P<0.001) during right ventricular pacing and from 0.07 (95% CI, -0.05 to 0.20) to 0.54 (95% CI, 0.06-1.03) after apamin infusion (P=0.045) during left ventricular pacing. Patch-clamp studies confirmed increased IKAS in isolated rabbit ventricular myocytes during hypokalemia (P=0.038). CONCLUSIONS Hypokalemia activates IKAS to shorten APD and maintain repolarization reserve at late activation sites during ventricular pacing. IKAS blockade prominently lengthens the APD at late activation sites and facilitates ventricular fibrillation induction.
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Affiliation(s)
- Yi-Hsin Chan
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Wei-Chung Tsai
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Jum-Suk Ko
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Dechun Yin
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Po-Cheng Chang
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Michael Rubart
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - James N Weiss
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Thomas H Everett
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Shien-Fong Lin
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Peng-Sheng Chen
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.).
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Ghamari-Langroudi M, Digby GJ, Sebag JA, Millhauser GL, Palomino R, Matthews R, Gillyard T, Panaro BL, Tough IR, Cox HM, Denton JS, Cone RD. G-protein-independent coupling of MC4R to Kir7.1 in hypothalamic neurons. Nature 2015; 520:94-8. [PMID: 25600267 PMCID: PMC4383680 DOI: 10.1038/nature14051] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 11/10/2014] [Indexed: 02/04/2023]
Abstract
The regulated release of anorexigenic α-melanocyte stimulating hormone (α-MSH) and orexigenic Agouti-related protein (AgRP) from discrete hypothalamic arcuate neurons onto common target sites in the central nervous system has a fundamental role in the regulation of energy homeostasis. Both peptides bind with high affinity to the melanocortin-4 receptor (MC4R); existing data show that α-MSH is an agonist that couples the receptor to the Gαs signalling pathway, while AgRP binds competitively to block α-MSH binding and blocks the constitutive activity mediated by the ligand-mimetic amino-terminal domain of the receptor. Here we show that, in mice, regulation of firing activity of neurons from the paraventricular nucleus of the hypothalamus (PVN) by α-MSH and AgRP can be mediated independently of Gαs signalling by ligand-induced coupling of MC4R to closure of inwardly rectifying potassium channel, Kir7.1. Furthermore, AgRP is a biased agonist that hyperpolarizes neurons by binding to MC4R and opening Kir7.1, independently of its inhibition of α-MSH binding. Consequently, Kir7.1 signalling appears to be central to melanocortin-mediated regulation of energy homeostasis within the PVN. Coupling of MC4R to Kir7.1 may explain unusual aspects of the control of energy homeostasis by melanocortin signalling, including the gene dosage effect of MC4R and the sustained effects of AgRP on food intake.
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Affiliation(s)
- Masoud Ghamari-Langroudi
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Gregory J Digby
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Julien A Sebag
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Glenn L Millhauser
- Department of Chemistry &Biochemistry, University of California, Santa Cruz, California 95064, USA
| | - Rafael Palomino
- Department of Chemistry &Biochemistry, University of California, Santa Cruz, California 95064, USA
| | - Robert Matthews
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Taneisha Gillyard
- 1] Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA [2] Department of Pharmacology, Meharry Medical College, Nashville, Tennessee 37208, USA
| | - Brandon L Panaro
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Iain R Tough
- King's College London, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK
| | - Helen M Cox
- King's College London, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK
| | - Jerod S Denton
- 1] Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA [2] Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Roger D Cone
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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Lian H, Wang X, Wang J, Liu N, Zhang L, Lu Y, Yang Y, Zhang L. Heart-specific overexpression of (pro)renin receptor induces atrial fibrillation in mice. Int J Cardiol 2015; 184:28-35. [DOI: 10.1016/j.ijcard.2015.01.088] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 12/23/2014] [Accepted: 01/28/2015] [Indexed: 11/30/2022]
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20
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Autocrine A2 in the T-system of ventricular myocytes creates transmural gradients in ion transport: a mechanism to match contraction with load? Biophys J 2015; 106:2364-74. [PMID: 24896115 DOI: 10.1016/j.bpj.2014.04.042] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 04/14/2014] [Accepted: 04/17/2014] [Indexed: 11/20/2022] Open
Abstract
Transmural heterogeneities in Na/K pump current (IP), transient outward K(+)-current (Ito), and Ca(2+)-current (ICaL) play an important role in regulating electrical and contractile activities in the ventricular myocardium. Prior studies indicated angiotensin II (A2) may determine the transmural gradient in Ito, but the effects of A2 on IP and ICaL were unknown. In this study, myocytes were isolated from five muscle layers between epicardium and endocardium. We found a monotonic gradient in both Ip and Ito, with the lowest currents in ENDO. When AT1Rs were inhibited, EPI currents were unaffected, but ENDO currents increased, suggesting endogenous extracellular A2 inhibits both currents in ENDO. IP- and Ito-inhibition by A2 yielded essentially the same K0.5 values, so they may both be regulated by the same mechanism. A2/AT1R-mediated inhibition of IP or Ito or stimulation of ICaL persisted for hours in isolated myocytes, suggesting continuous autocrine secretion of A2 into a restricted diffusion compartment, like the T-system. Detubulation brought EPI IP to its low ENDO value and eliminated A2 sensitivity, so the T-system lumen may indeed be the restricted diffusion compartment. These studies showed that 33-50% of IP, 57-65% of Ito, and a significant fraction of ICaL reside in T-tubule membranes where they are transmurally regulated by autocrine secretion of A2 into the T-system lumen and activation of AT1Rs. Increased AT1R activation regulates each of these currents in a direction expected to increase contractility. Endogenous A2 activation of AT1Rs increases monotonically from EPI to ENDO in a manner similar to reported increases in passive tension when the ventricular chamber fills with blood. We therefore hypothesize load is the signal that regulates A2-activation of AT1Rs, which create a contractile gradient that matches the gradient in load.
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Tan XQ, Cheng XL, Yang Y, Yan L, Gu JL, Li H, Zeng XR, Cao JM. Tanshinone II-A sodium sulfonate (DS-201) enhances human BKCa channel activity by selectively targeting the pore-forming α subunit. Acta Pharmacol Sin 2014; 35:1351-63. [PMID: 25345746 PMCID: PMC4220078 DOI: 10.1038/aps.2014.85] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 07/18/2014] [Indexed: 11/15/2022] Open
Abstract
Aim: Tanshinone II-A sodium sulfonate (DS-201), a water-soluble derivative of Tanshinone II-A, has been found to induce vascular relaxation and activate BKCa channels. The aim of this study was to explore the mechanisms underlying the action of DS-201 on BKCa channels. Methods: Human BKCa channels containing α subunit alone or α plus β1 subunits were expressed in HEK293 cells. BKCa currents were recorded from the cells using patch-clamp technique. The expression and trafficking of BKCa subunits in HEK293 cells or vascular smooth muscle cells (VSMCs) were detected by Western blotting, flow cytometry and confocal microscopy. Results: DS-201 (40–160 μmol/L) concentration-dependently increased the total open probability of BKCa channels in HEK293 cells, associated with enhancements of Ca2+ and voltage dependence as well as a delay in deactivation. Coexpression of β1 subunit did not affect the action of DS-201: the values of EC50 for BKCa channels containing α subunit alone and α plus β1 subunit were 66.6±1.5 and 62.0±1.1 μmol/L, respectively. In both HEK293 cells and VSMCs, DS-201 (80 μmol/L) markedly increased the expression of α subunit without affecting β1 subunit. In HEK293 cells, DS-201 enriched the membranous level of α subunit, likely by accelerating the trafficking and suppressing the internalization of α subunit. In both HEK293 cells and VSMCs, DS-201 (≥320 μmol/L) induced significant cytotoxicity. Conclusion: DS-201 selectively targets the pore-forming α subunit of human BKCa channels, thus enhancing the channel activities and increasing the subunit expression and trafficking, whereas the β1 subunit does not contribute to the action of DS-201.
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Nair GM, Nery PB, Redpath CJ, Birnie DH. The Role Of Renin Angiotensin System In Atrial Fibrillation. J Atr Fibrillation 2014; 6:972. [PMID: 27957054 DOI: 10.4022/jafib.972] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2013] [Revised: 02/26/2014] [Accepted: 02/28/2014] [Indexed: 01/23/2023]
Abstract
Atrial fibrillation (AF) is the most prevalent arrhythmia and its incidence is on the rise. AF causes significant morbidity and mortality leading to rising AF-related health care costs. There is experimental and clinical evidence from animal and human studies that suggests a role for the renin angiotensin system (RAS) in the etiopathogenesis of AF. This review appraises the current understanding of RAS antagonism, using angiotensin converting enzyme inhibitors (ACE-I), angiotensin receptor blockers (ARB) and aldosterone antagonists (AA), for prevention of AF. RAS antagonism has proven to be effective for primary and secondary prevention of AF in subjects with heart failure and left ventricular (LV) dysfunction.However, most of the evidence for the protective effect of RAS antagonism is from clinical trials that had AF as a secondary outcome or from unspecified post-hoc analyses. The evidence for prevention in subjects without heart failure and with normal LV function is not as clear. RAS antagonism, in the absence of concomitant antiarrhythmic therapy, was not shown to reduce post cardioversion AF recurrences. RAS antagonism in subjects undergoing catheter ablation has also been ineffective in preventing AF recurrences.
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Affiliation(s)
- Girish M Nair
- Arrhythmia Service, Division of Cardiology University of Ottawa Heart Institute 40 Ruskin Ave, Ottawa Canada - K1Y 4W7
| | - Pablo B Nery
- Arrhythmia Service, Division of Cardiology University of Ottawa Heart Institute 40 Ruskin Ave, Ottawa Canada - K1Y 4W7
| | - Calum J Redpath
- Arrhythmia Service, Division of Cardiology University of Ottawa Heart Institute 40 Ruskin Ave, Ottawa Canada - K1Y 4W7
| | - David H Birnie
- Arrhythmia Service, Division of Cardiology University of Ottawa Heart Institute 40 Ruskin Ave, Ottawa Canada - K1Y 4W7
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Tseng GN. Short-term memory in the heart: a road map for channel trafficking required. Heart Rhythm 2012; 9:1873-4. [PMID: 22885920 DOI: 10.1016/j.hrthm.2012.08.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Indexed: 10/28/2022]
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Özgen N, Lu Z, Boink GJJ, Lau DH, Shlapakova IN, Bobkov Y, Danilo P, Cohen IS, Rosen MR. Microtubules and angiotensin II receptors contribute to modulation of repolarization induced by ventricular pacing. Heart Rhythm 2012; 9:1865-72. [PMID: 22820054 DOI: 10.1016/j.hrthm.2012.07.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Indexed: 01/09/2023]
Abstract
BACKGROUND Left ventricular pacing (LVP) in canine heart alters ventricular activation, leading to reduced transient outward potassium current (I(to)), loss of the epicardial action potential notch, and T-wave vector displacement. These repolarization changes, referred to as cardiac memory, are initiated by locally increased angiotensin II (AngII) levels. In HEK293 cells in which Kv4.3 and KChIP2, the channel subunits contributing to I(to), are overexpressed with the AngII receptor 1 (AT1R), AngII induces a decrease in I(to) as the result of internalization of a Kv4.3/KChIP2/AT1R macromolecular complex. OBJECTIVE To test the hypothesis that in canine heart in situ, 2h LVP-induced decreases in membrane KChIP2, AT1R, and I(to) are prevented by blocking subunit trafficking. METHODS We used standard electrophysiological, biophysical, and biochemical methods to study 4 groups of dogs: (1) Sham, (2) 2h LVP, (3) LVP + colchicine (microtubule-disrupting agent), and (4) LVP + losartan (AT1R blocker). RESULTS The T-wave vector displacement was significantly greater in LVP than in Sham and was inhibited by colchicine or losartan. Epicardial biopsies showed significant decreases in KChIP2 and AT1R proteins in the membrane fraction after LVP but not after sham treatment, and these decreases were prevented by colchicine or losartan. Colchicine but not losartan significantly reduced microtubular polymerization. In isolated ventricular myocytes, AngII-induced I(to) reduction and loss of action potential notch were blocked by colchicine. CONCLUSIONS LVP-induced reduction of KChIP2 in plasma light membranes depends on an AngII-mediated pathway and intact microtubular status. Loss of I(to) and the action potential notch appear to derive from AngII-initiated trafficking of channel subunits.
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Affiliation(s)
- Nazira Özgen
- Department of Pharmacology, Columbia University, New York, New York 10032, USA
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Grubb S, Calloe K, Thomsen MB. Impact of KChIP2 on Cardiac Electrophysiology and the Progression of Heart Failure. Front Physiol 2012; 3:118. [PMID: 22586403 PMCID: PMC3343377 DOI: 10.3389/fphys.2012.00118] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/11/2012] [Indexed: 01/16/2023] Open
Abstract
Electrophysiological remodeling of cardiac potassium ion channels is important in the progression of heart failure. A reduction of the transient outward potassium current (Ito) in mammalian heart failure is consistent with a reduced expression of potassium channel interacting protein 2 (KChIP2, a KV4 subunit). Approaches have been made to investigate the role of KChIP2 in shaping cardiac Ito, including the use of transgenic KChIP2 deficient mice and viral overexpression of KChIP2. The interplay between Ito and myocardial calcium handling is pivotal in the development of heart failure, and is further strengthened by the dual role of KChIP2 as a functional subunit on both KV4 and CaV1.2. Moreover, the potential arrhythmogenic consequence of reduced Ito may contribute to the high relative incidence of sudden death in the early phases of human heart failure. With this review, we offer an overview of the insights into the physiological and pathological roles of KChIP2 and we discuss the limitations of translating the molecular basis of electrophysiological remodeling from animal models of heart failure to the clinical setting.
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Affiliation(s)
- Søren Grubb
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, University of Copenhagen Copenhagen, Denmark
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Cliff B, Younis N, Hama S, Soran H. The role of the renin-angiotensin system blocking in the management of atrial fibrillation. J Drug Assess 2012; 1:55-64. [PMID: 27536429 PMCID: PMC4980732 DOI: 10.3109/21556660.2012.672353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/29/2012] [Indexed: 12/02/2022] Open
Abstract
OBJECTIVE To review current available evidence for the role of renin-angiotensin system blockade in the management of atrial fibrillation. METHOD We conducted a PubMed and Medline literature search (January 1980 through July 2011) to identify all clinical trials published in English concerning the use of angiotensin converting enzyme inhibitors or angiotensin II receptor blockers for primary and secondary prevention of atrial fibrillation. We also discussed renin-angiotensin system and its effects on cellular electrophysiology. CONCLUSION The evidence from the current studies discussed does not provide a firm definitive indication for the use of angiotensin converting enzyme inhibitors or angiotensin II receptor blockers in the primary or secondary prevention of atrial fibrillation. Nevertheless, modest benefits were observed in patients with left ventricular dysfunction. In view of the possible benefits and the low incidence of side-effects with angiotensin converting enzyme inhibitors and angiotensin II receptor blockers, they can be given to patients with recurrent AF, specifically those with hypertension, heart failure and diabetes mellitus.
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Affiliation(s)
- Brett Cliff
- University Department of Medicine, Central Manchester University Hospitals NHS Foundation Trust, ManchesterUK
| | - Naveed Younis
- Department of Diabetes and Endocrinology, South Manchester University Hospitals NHS Foundation Trust, ManchesterUK
| | - Salam Hama
- Cardiovascular Research Group, School of Biomedicine, Core Technology Facility (3rd Floor), University of Manchester, ManchesterUK
| | - Handrean Soran
- University Department of Medicine, Central Manchester University Hospitals, ManchesterUK
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Cravedi P, Remuzzi G, Ruggenenti P. Targeting the Renin Angiotensin System in Dialysis Patients. Semin Dial 2011; 24:290-7. [DOI: 10.1111/j.1525-139x.2011.00939.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Zografos T, Katritsis DG. Inhibition of the renin-angiotensin system for prevention of atrial fibrillation. Pacing Clin Electrophysiol 2011; 33:1270-85. [PMID: 20636314 DOI: 10.1111/j.1540-8159.2010.02832.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Atrial fibrillation (AF) is a source of considerable morbidity and mortality. There has been compelling evidence supporting the role of renin-angiotensin system (RAS) in the genesis and perpetuation of AF through atrial remodeling, and experimental studies have validated the utilization of RAS inhibition for AF prevention. This article reviews clinical trials on the use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) for the prevention of AF. Results have been variable, depending on the clinical background of treated patients. ACEIs and ARBs appear beneficial for primary prevention of AF in patients with heart failure, whereas they are not equally effective in hypertensive patients with normal left ventricular function. Furthermore, the use of ACEIs or ARBs for secondary prevention of AF has been found beneficial only after electrical cardioversion. Additional data are needed to establish the potential clinical role of renin-angiotensin inhibition for prevention of AF.
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Affiliation(s)
- Theodoros Zografos
- Department of Cardiology, Athens Euroclinic, 9 Athanassiadou Street, Athens, Greece
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Schneider MP, Hua TA, Böhm M, Wachtell K, Kjeldsen SE, Schmieder RE. Prevention of atrial fibrillation by Renin-Angiotensin system inhibition a meta-analysis. J Am Coll Cardiol 2010; 55:2299-307. [PMID: 20488299 DOI: 10.1016/j.jacc.2010.01.043] [Citation(s) in RCA: 271] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 12/21/2009] [Accepted: 01/02/2010] [Indexed: 10/19/2022]
Abstract
OBJECTIVES The authors reviewed published clinical trial data on the effects of renin-angiotensin system (RAS) inhibition for the prevention of atrial fibrillation (AF), aiming to define when RAS inhibition is most effective. BACKGROUND Individual studies examining the effects of RAS inhibition on AF prevention have reported controversial results. METHODS All published randomized controlled trials reporting the effects of treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers in the primary or secondary prevention of AF were included. RESULTS A total of 23 randomized controlled trials with 87,048 patients were analyzed. In primary prevention, 6 trials in hypertension, 2 trials in myocardial infarction, and 3 trials in heart failure were included (some being post-hoc analyses of randomized controlled trials). In secondary prevention, 8 trials after cardioversion and 4 trials assessing the medical prevention of recurrence were included. Overall, RAS inhibition reduced the odds ratio for AF by 33% (p < 0.00001), but there was substantial heterogeneity among trials. In primary prevention, RAS inhibition was effective in patients with heart failure and those with hypertension and left ventricular hypertrophy but not in post-myocardial infarction patients overall. In secondary prevention, RAS inhibition was often administered in addition to antiarrhythmic drugs, including amiodarone, further reducing the odds for AF recurrence after cardioversion by 45% (p = 0.01) and in patients on medical therapy by 63% (p < 0.00001). CONCLUSIONS This analysis supports the concept of RAS inhibition as an emerging treatment for the primary and secondary prevention of AF but acknowledges the fact that some of the primary prevention trials were post-hoc analyses. Further areas of uncertainty include potential differences among specific RAS inhibitors and possible interactions or synergistic effects with antiarrhythmic drugs.
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Affiliation(s)
- Markus P Schneider
- Department of Nephrology and Hypertension, University of Erlangen-Nuremberg, Erlangen, Germany
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Bierhuizen MFA, Vos MA. The molecular labyrinth of electrical remodeling: making sense of cardiac memory. Heart Rhythm 2010; 7:971-2. [PMID: 20382268 DOI: 10.1016/j.hrthm.2010.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Indexed: 12/28/2022]
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Ozgen N, Lau DH, Shlapakova IN, Sherman W, Feinmark SJ, Danilo P, Rosen MR. Determinants of CREB degradation and KChIP2 gene transcription in cardiac memory. Heart Rhythm 2010; 7:964-70. [PMID: 20346417 DOI: 10.1016/j.hrthm.2010.03.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Accepted: 03/19/2010] [Indexed: 01/12/2023]
Abstract
BACKGROUND Left ventricular pacing (LVP) to induce cardiac memory (CM) in dogs results in a decreased transient outward K current (I(to)) and reduced mRNA and protein of the I(to) channel accessory subunit, KChIP2. The KChIP2 decrease is attributed to a decrease in its transcription factor, cyclic adenosine monophosphate response element binding protein (CREB). OBJECTIVE This study sought to determine the mechanisms responsible for the CREB decrease that is initiated by LVP. METHODS CM was quantified as T-wave vector displacement in 18 LVP dogs. In 5 dogs, angiotensin II receptor blocker, saralasin, was infused before and during pacing. In 3 dogs, proteasomal inhibitor, lactacystin, was injected into the left anterior descending artery before LVP. Epicardial biopsy samples were taken before and after LVP. Neonatal rat cardiomyocytes (NRCM) were incubated with H(2)O(2) (50 micromol/l) for 1 hour with or without lactacystin. RESULTS LVP significantly displaced the T-wave vector and was associated with increased lipid peroxidation and increased tissue angiotensin II levels. Saralasin prevented T-vector displacement and lipid peroxidation. CREB was significantly decreased after 2 hours of LVP and was comparably decreased in H(2)O(2)-treated NRCM. Lactacystin inhibited the CREB decrease in LVP dogs and H(2)O(2)-treated NRCM. LVP and H(2)O(2) both induced CREB ubiquitination, and the H(2)O(2)-induced CREB decrease was prevented by knocking down ubiquitin. CONCLUSION LVP initiates myocardial angiotensin II production and reactive oxygen species synthesis, leading to CREB ubiquitination and its proteasomal degradation. This sequence of events would explain the pacing-induced reduction in KChIP2, and contribute to altered repolarization and the T-wave changes of cardiac memory.
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Affiliation(s)
- Nazira Ozgen
- Department of Pharmacology, Columbia University, New York, New York 10032, USA.
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Barra S, Silvestri N, Vitagliano G, Madrid A, Gaeta G. Angiotensin II receptor blockers in the prevention of atrial fibrillation. Expert Opin Pharmacother 2010; 10:1395-411. [PMID: 19466911 DOI: 10.1517/14656560902973736] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Atrial fibrillation (AF) is the most common sustained arrhythmia. While antiarrhythmic agents and electrical cardioversion are highly effective in restoring sinus rhythm, the results obtained in prevention of recurrences are disappointing. Recently, angiotensin II has been recognized as a key factor in atrial structural and electrical remodeling associated with AF. So there are several potential mechanisms by which inhibition of the renin-angiotensin-aldosterone system may reduce AF. In this review, we report the results of studies evaluating the effect of angiotensin II receptor blockers (ARBs) in various clinical settings (i.e., lone AF, hypertension, high-risk patients, congestive heart failure, secondary prevention). However, many of these studies are small and retrospective and have a limited follow-up; moreover, since AF is related to several causes, chiefly heart diseases, patients with different characteristics have often been enrolled. Thus, it is not surprising that the results obtained are frequently conflicting. With these limitations and considering only the results of larger studies with longer follow-up, ARBs are effective in preventing AF in patients with congestive heart failure or hypertension with left ventricular hypertrophy or coronary artery/cerebrovascular disease. In any case, the use of ARBs is not recommended at present in clinical practice to prevent AF.
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Affiliation(s)
- Silvia Barra
- Antonio Cardarelli Hospital, Cardiology Unit, Via Antonio Cardarelli 9, 80128 Naples, Italy
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Abstract
The following article is a personal reflection on my study of a subject which has long interested me. The subject is the T wave, and especially the T wave changes occurring as a marker of cardiac memory. My interest evolved over coffees that Mauricio Rosenbaum and I used to share at the Hotel Algonquin during his frequent trips from Buenos Aires to New York. There is something about the Algonquin, whose scarred wooden tabletops carry the imprints of Robert Benchley, Dorothy Parker, and the 1920's New York literati, and there was something about Mauricio-clinician-scientist, friend, and raconteur extraordinaire-that made his repeated challenges to me to "look at cardiac memory before you begin losing your own" irresistible. So began my personal voyage into trying to understand the T wave. My guideposts were the experiments of Wilson and Finch,(1) the astute observations of a host of investigators who followed, and Mauricio's iconoclastic insights. The story is far from over...I doubt I'll see the end of it in my lifetime. But if the beauty of discovery is in the voyage, then it has been - for me - a memorable trip.
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Affiliation(s)
- Michael R Rosen
- Department of Pharmacology, Center for Molecular Therapeutics, and Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
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Li GR, Dong MQ. Pharmacology of Cardiac Potassium Channels. CARDIOVASCULAR PHARMACOLOGY - HEART AND CIRCULATION 2010; 59:93-134. [DOI: 10.1016/s1054-3589(10)59004-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Niwa N, Nerbonne JM. Molecular determinants of cardiac transient outward potassium current (I(to)) expression and regulation. J Mol Cell Cardiol 2009; 48:12-25. [PMID: 19619557 DOI: 10.1016/j.yjmcc.2009.07.013] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 06/25/2009] [Accepted: 07/10/2009] [Indexed: 12/21/2022]
Abstract
Rapidly activating and inactivating cardiac transient outward K(+) currents, I(to), are expressed in most mammalian cardiomyocytes, and contribute importantly to the early phase of action potential repolarization and to plateau potentials. The rapidly recovering (I(t)(o,f)) and slowly recovering (I(t)(o,s)) components are differentially expressed in the myocardium, contributing to regional heterogeneities in action potential waveforms. Consistent with the marked differences in biophysical properties, distinct pore-forming (alpha) subunits underlie the two I(t)(o) components: Kv4.3/Kv4.2 subunits encode I(t)(o,f), whereas Kv1.4 encodes I(t)(o,s), channels. It has also become increasingly clear that cardiac I(t)(o) channels function as components of macromolecular protein complexes, comprising (four) Kvalpha subunits and a variety of accessory subunits and regulatory proteins that influence channel expression, biophysical properties and interactions with the actin cytoskeleton, and contribute to the generation of normal cardiac rhythms. Derangements in the expression or the regulation of I(t)(o) channels in inherited or acquired cardiac diseases would be expected to increase the risk of potentially life-threatening cardiac arrhythmias. Indeed, a recently identified Brugada syndrome mutation in KCNE3 (MiRP2) has been suggested to result in increased I(t)(o,f) densities. Continued focus in this area seems certain to provide new and fundamentally important insights into the molecular determinants of functional I(t)(o) channels and into the molecular mechanisms involved in the dynamic regulation of I(t)(o) channel functioning in the normal and diseased myocardium.
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Affiliation(s)
- Noriko Niwa
- Department of Developmental Biology, Washington University School of Medicine, 660 South Euclid Avenue, Box 8103, St. Louis, MO 63110-1093, USA
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Abstract
Cardiac memory is a form of electrophysiological remodeling generally considered benign, although it shares transduction pathways with factors that may be pathological, such as angiotensin II and reactive oxygen species. When induced by electrical pacing, memory provides a window into the mechanisms engaged during cardiac device therapy. Emphasis is placed on the complexity of signaling processes occurring downstream to the simple intervention of cardiac pacing and the relationship of resultant ion channel changes to their expression in action potentials and body surface recordings.
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Rottensteiner J, Kaneppele A, Stockner I, Ladurner C, Panizza G, Wiedermann CJ. Precordial T-wave inversion of "cardiac memory" pattern after high-dose methylprednisolone pulse therapy. Intern Emerg Med 2008; 3:375-8. [PMID: 18274710 DOI: 10.1007/s11739-008-0121-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Accepted: 11/12/2007] [Indexed: 01/09/2023]
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Inhibition of the renin-angiotensin system: effects on tachycardia-induced early electrical remodelling in rabbit atrium. J Renin Angiotensin Aldosterone Syst 2008; 9:125-32. [DOI: 10.1177/1470320308095262] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Introduction. Tachycardia-induced atrial remodelling (as an equivalent to atrial fibrillation) can be influenced by the renin-angiotensin system. Effects of a seven-day enalapril pre-treatment (EPT, 0.16 mg/kg body weight subcutaneously every 24 h) on ionic currents underlying tachycardia-induced early electrical remodelling after 24 h rapid atrial pacing (RAP, 600 beats/min) in rabbit atrium were studied. Materials and methods. Animals were divided into four groups (n=4 each): control; paced only; enalapril only; and enalapril and paced, respectively. Using patch-clamp technique in whole-cell mode, current densities were measured in isolated atrial myocytes. Results. EPT nearly doubled L-type calcium current (ICa,L, −7.7±0.6 pA/pF [control] vs. f −12.3±1.2 pA/pF [enalapril only]). RAP reduced ICa,L to −3.6±0.7 pA/pF (paced only). Also after EPT, RAP led to a significant downregulation of ICa,L by 39% (−7.5±1.3 pA/pF [paced and enalapril]). RAP decreased transient outward potassium current (Ito, −45%, 51.5±3.9 pA/pF [control] vs. 28.5±4.5 pA/pF [paced only]). EPT did not alter Ito (44.2±8.1 pA/pF [enalapril only]). However, RAP did not affect Ito in enalapril-treated animals and averaged 50.4±9.8 pA/pF (paced and enalapril). Conclusions. In summary, EPT has several effects on ion channels in rabbit atrium: 1) EPT increases ICa,L current density, but cannot prevent its downregulation due to RAP; 2) EPT has no influence on Ito current density, but can prevent its downregulation due to RAP. Although changes of single ion channels must be interpreted in context of the complex atrial electrophysiology as a whole, our results provide a possible explanation of the in vivo observation that angiotensin-converting enzyme inhibition is mainly beneficial on the early electrical remodelling due to the atrial fibrillation-equivalent RAP.
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Doupnik CA. GPCR-Kir channel signaling complexes: defining rules of engagement. J Recept Signal Transduct Res 2008; 28:83-91. [PMID: 18437632 DOI: 10.1080/10799890801941970] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Ion channels and G protein-coupled receptors (GPCRs) are integral transmembrane proteins vital to a multitude of cell signaling and physiological functions. Members of these large protein families are known to interact directly with various intracellular protein partners in a dynamic and isoform-dependent manner, ultimately shaping their life cycle and signal output. The family of G protein-gated inwardly rectifying potassium channels (Kir3 or GIRK) expressed in brain, heart, and endocrine tissues were recently shown to stably associate with several different GPCRs, forming the basis of a macromolecular ion channel-GPCR signaling complex. The molecular determinants that mediate and maintain GPCR-Kir3 channel complexes are currently not well understood. Recent findings and emerging hypotheses on the assembly and stability of multiprotein GPCR-Kir channel signaling complexes are discussed, highlighting distinct mechanisms used by different Kir channel families. These protein-protein interaction processes are crucial in determining both the synaptic response times and the extent of GPCR "cross-talk" in Kir3-mediated inhibitory synaptic transmission.
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Affiliation(s)
- Craig A Doupnik
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida 33612, USA.
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Enyeart JA, Liu H, Enyeart JJ. Curcumin inhibits bTREK-1 K+ channels and stimulates cortisol secretion from adrenocortical cells. Biochem Biophys Res Commun 2008; 370:623-8. [PMID: 18406348 DOI: 10.1016/j.bbrc.2008.04.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Accepted: 04/02/2008] [Indexed: 11/18/2022]
Abstract
Bovine adrenal zona fasciculata (AZF) cells express bTREK-1 K(+) channels that set the resting membrane potential. Inhibition of these channels by adrenocorticotropic hormone (ACTH) is coupled to membrane depolarization and cortisol secretion. Curcumin, a phytochemical with medicinal properties extracted from the spice turmeric, was found to modulate both bTREK-1 K(+) currents and cortisol secretion from AZF cells. In whole-cell patch clamp experiments, curcumin inhibited bTREK-1 with an IC(50) of 0.93muM by a mechanism that was voltage-independent. bTREK-1 inhibition by curcumin occurred through interaction with an external binding site and was independent of ATP hydrolysis. Curcumin produced a concentration-dependent increase in cortisol secretion that persisted for up to 24h. At a maximally effective concentration of 50muM, curcumin increased secretion as much as 10-fold. These results demonstrate that curcumin potently inhibits bTREK-1 K(+) channels and stimulates cortisol secretion from bovine AZF cells. The inhibition of bTREK-1 by curcumin may be linked to cortisol secretion through membrane depolarization. Since TREK-1 is widely expressed in a variety of cells, it is likely that some of the biological actions of curcumin, including its therapeutic effects, may be mediated through inhibition of these K(+) channels.
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Affiliation(s)
- Judith A Enyeart
- Department of Neuroscience, The Ohio State University, College of Medicine and Public Health, 5196 Graves Hall, 333 W.10th Avenue, Columbus, OH 43210-1239, USA.
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Comparative Evaluation of Effect of Valsartan/Amlodipine and Atenolol/Amlodipine Combinations on Atrial Fibrillation Recurrence in Hypertensive Patients With Type 2 Diabetes Mellitus. J Cardiovasc Pharmacol 2008; 51:217-22. [DOI: 10.1097/fjc.0b013e318160b42a] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Potapova IA, Cohen IS, Doronin SV. Voltage-gated ion channel Kv4.3 is associated with Rap guanine nucleotide exchange factors and regulates angiotensin receptor type 1 signaling to small G-protein Rap. FEBS J 2007; 274:4375-84. [PMID: 17725712 DOI: 10.1111/j.1742-4658.2007.05966.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The voltage-gated potassium channel Kv4.3 was coexpressed with its beta-subunit Kv channel-interacting protein 2 and the angiotensin type 1 receptor in HEK-293 cells. Proteomic analysis of proteins coimmunoprecipitated with Kv4.3 revealed that Kv4.3 is associated with Rap guanine nucleotide exchange factors MR-GEF and EPAC-1. Previously, we demonstrated that Kv4.3 interacts with the angiotensin type 1 receptor in HE293 cells and cardiac myocytes. On the basis of this, we investigated the angiotensin type 1 receptor signaling to small G-proteins Ras and Rap-1 in the presence and absence of the Kv4.3-Kv channel-interacting protein 2 macromolecular complex. Ras activation was not significantly affected by coexpression of Kv4.3 and Kv channel-interacting protein 2. Ras exhibited a rapid activation-inactivation pattern with maximum activity at 2.5 min after addition of angiotensin II. In contrast, activation of Rap-1 was affected dramatically by coexpression of Kv4.3 and Kv channel-interacting protein 2 with the angiotensin type 1 receptor. In the absence of Kv4.3 and Kv channel-interacting protein 2, stimulation of the angiotensin type 1 receptor resulted in steady activation of Rap-1 that reached a plateau 25 min after addition of angiotensin II. In the presence of Kv4.3 and Kv channel-interacting protein 2, Rap-1 reaches a maximum activity 2.5 min after addition of angiotensin II and then deactivates rapidly, demonstrating a pattern of activation similar to that of Ras. Our findings show that Kv4.3 regulates angiotensin type 1 receptor signaling to the small G-protein Rap-1.
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Affiliation(s)
- Irina A Potapova
- Department of Physiology and Biophysics, Institute of Molecular Cardiology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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Horie M. [Atrial fibrillation up to date. 4) Are prevention and modification of atrial remodeling possible?]. NIHON NAIKA GAKKAI ZASSHI. THE JOURNAL OF THE JAPANESE SOCIETY OF INTERNAL MEDICINE 2007; 96:1909-1911. [PMID: 17929431 DOI: 10.2169/naika.96.1909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
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Ji H, Zheng W, Falconetti C, Roesch DM, Mulroney SE, Sandberg K. 17β-Estradiol deficiency reduces potassium excretion in an angiotensin type 1 receptor-dependent manner. Am J Physiol Heart Circ Physiol 2007; 293:H17-22. [PMID: 17449550 DOI: 10.1152/ajpheart.00950.2006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the effects of ovariectomy (OVX) and 17β-estradiol (E2) replacement (OVX + E2) on renal function in Sprague-Dawley rats. OVX caused a 40% decrease in the fractional excretion of potassium (FEK+) that was prevented by E2 replacement [Sham, 24.2 ± 2.9%; OVX, 14.5 ± 2.1% ( P < 0.05 vs. OVX + E2); and OVX + E2, 26.2 ± 2.7%; n = 7–11] and that corresponded to significant increases in plasma potassium [(in mmol/l): Sham, 3.15 ± 0.087; OVX, 3.42 ± 0.048 ( P < 0.05 vs. OVX + E2); and OVX + E2, 3.19 ± 0.11; n = 7–11]. No effects of OVX were detected on plasma levels of sodium and aldosterone. Angiotensin II type 1 receptor (AT1R) densities in ovariectomized rats were 1.4-fold and 1.3-fold higher in glomerular [maximum binding capacity (Bmax; in fmol/mg protein): Sham, 482 ± 21; OVX, 666 ± 20 ( P < 0.05 vs. OVX + E2); and OVX + E2, 504 ± 26; n = 7–11] and proximal tubular [Bmax (in fmol/mg protein): Sham, 721 ± 16; OVX, 741 ± 24 ( P < 0.05 vs. OVX + E2); and OVX + E2, 569 ± 23; n = 7–11] membranes compared with E2 replete animals, respectively. Both the angiotensin-converting enzyme inhibitor captopril and the AT1R antagonist losartan prevented the OVX-induced decrease in the FEK+ and the increase in renal AT1R densities, suggesting that E2 deficiency reduces potassium excretion in an ANG II/AT1R-dependent manner. These findings may have implications for renal function in postmenopausal women as well as contribute to the reasons underlying the age-induced increase in susceptibility to hypertension-associated disease in women.
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Affiliation(s)
- Hong Ji
- Center for the Study of Sex Differences, Georgetown University, 4000 Reservoir Road NW, Washington, DC 20057, USA.
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Shen C, Lin MJ, Yaradanakul A, Lariccia V, Hill JA, Hilgemann DW. Dual control of cardiac Na+ Ca2+ exchange by PIP(2): analysis of the surface membrane fraction by extracellular cysteine PEGylation. J Physiol 2007; 582:1011-26. [PMID: 17540704 PMCID: PMC2075243 DOI: 10.1113/jphysiol.2007.132720] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We describe a new assay to determine the fraction of cardiac Na(+)-Ca(2+) exchangers (NCX1) in the surface membrane of cells (F(surf)). An extracellular NCX1 disulphide bond is rapidly reduced by tris(2-carboxyethyl)phosphine hydrochloride (TCEP), cysteines are 'PEGylated' by alkylation with an impermeable conjugate of maleimide and a 5000 MW polyethylene glycol (MPEG), and F(surf) is quantified from Western blots as the fraction of NCX1 that migrates at a higher molecular weight. F(surf) remains less than 0.1 when NCX1 is expressed via transient transfections. Values of 0.15-0.4 are obtained for cell lines with stable NCX1 expression, 0.3 for neonatal myocytes and 0.6-0.8 for adult hearts. To validate the assay, we analysed an intervention that promotes clathrin-independent endocytosis in fibroblasts. Using BHK cells, removal of extracellular potassium (K(+)) caused yellow fluorescent protein (YFP)-tagged NCX1 to redistribute diffusely into the cytoplasm within 30 min, F(surf) decreased by 35%, and whole-cell exchange currents decreased by > 50%. In both HEK 293 and BHK cell lines, expression of human hPIP5Ibeta kinase significantly decreases F(surf). In BHK cells expressing M1 receptors, a muscarinic agonist (carbachol) causes a 40% decrease of F(surf) in normal media. This decrease is blocked by a high wortmannin concentration (3 mum), suggesting that type III phosphatidylinositol-4-kinase (PI4K) activity is required. As predicted from functional studies, carbachol increases F(surf) when cytoplasmic Ca(2) is increased by removing extracellular Na(+). Phorbol esters are without effect in BHK cells. In intact hearts, interventions that change contractility have no effect within 15 min, but we have identified two long-term changes. First, we analysed the diurnal dependence of F(surf) because messages for cardiac phosphatidylinositol-4-phosphate (PIP) 5-kinases increase during the light phase in entrained mice (i.e. during sleep). Cardiac phosphatidylinositol-(4,5)-bis-phosphate (PIP(2)) levels increase during the light phase and F(surf) decreases in parallel. Second, we analysed effects of aortic banding because NCX1 currents do not mirror the increases of NCX1 message and protein that occur in this model. F(surf) decreases significantly within 10 days, and cardiac PIP and PIP(2) levels are significantly increased. In summary, multiple experimental approaches suggest that PIP(2) synthesis favours NCX1 internalization, that NCX1 internalization is probably clathrin-independent, and that significant changes of NCX1 surface expression occur physiologically and pathologically in intact myocardium.
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Affiliation(s)
- Chengcheng Shen
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA
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Nattel S, Maguy A, Le Bouter S, Yeh YH. Arrhythmogenic Ion-Channel Remodeling in the Heart: Heart Failure, Myocardial Infarction, and Atrial Fibrillation. Physiol Rev 2007; 87:425-56. [PMID: 17429037 DOI: 10.1152/physrev.00014.2006] [Citation(s) in RCA: 597] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Rhythmic and effective cardiac contraction depends on appropriately timed generation and spread of cardiac electrical activity. The basic cellular unit of such activity is the action potential, which is shaped by specialized proteins (channels and transporters) that control the movement of ions across cardiac cell membranes in a highly regulated fashion. Cardiac disease modifies the operation of ion channels and transporters in a way that promotes the occurrence of cardiac rhythm disturbances, a process called “arrhythmogenic remodeling.” Arrhythmogenic remodeling involves alterations in ion channel and transporter expression, regulation and association with important protein partners, and has important pathophysiological implications that contribute in major ways to cardiac morbidity and mortality. We review the changes in ion channel and transporter properties associated with three important clinical and experimental paradigms: congestive heart failure, myocardial infarction, and atrial fibrillation. We pay particular attention to K+, Na+, and Ca2+channels; Ca2+transporters; connexins; and hyperpolarization-activated nonselective cation channels and discuss the mechanisms through which changes in ion handling processes lead to cardiac arrhythmias. We highlight areas of future investigation, as well as important opportunities for improved therapeutic approaches that are being opened by an improved understanding of the mechanisms of arrhythmogenic remodeling.
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Affiliation(s)
- Stanley Nattel
- Department of Medicine and Research Center, Montreal Heart Institute and Université de Montréal, Quebec, Canada.
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Yeung SYM, Ohya S, Sergeant GP, Pucovský V, Greenwood IA. Pharmacological and molecular evidence for the involvement of Kv4.3 in ultra-fast activating K+ currents in murine portal vein myocytes. Br J Pharmacol 2006; 149:676-86. [PMID: 17016508 PMCID: PMC2014655 DOI: 10.1038/sj.bjp.0706903] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of this study was to determine the molecular identity of a transient K+ current (termed IUF) in mouse portal vein myocytes using pharmacological and molecular tools. EXPERIMENTAL APPROACH Whole cell currents were recorded using the ruptured patch con from either acutely dispersed single smooth muscle cells from the murine portal vein or human embryonic kidney cells. Reverse transcriptase polymerase reaction (RT-PCR) experiments were undertaken on RNA isolated from mouse portal vein using primers specific for various voltage-dependent K+ channels, auxillary subunits and calcium-binding proteins. Immunocytochemistry was undertaken using an antibody specific for Kv4.3. KEY RESULTS IUF had a mean amplitude at +40 mV of 558 +/- 50 pA (n = 32) with a mean time to peak at +40 mV of approximately 4 ms. IUF activated and inactivated with a half maximal voltage of -12 +/- 2 mV and -85 +/- 2 mV, respectively. IUF was relatively resistant to 4-aminopyridine (5 mM produced 30 +/- 6 % block at +20 mV) but was inhibited effectively by flecainide (IC50 value was 100 nM) and phrixotoxin II. This pharmacological profile is consistent with IUF being comprised of Kv4.x proteins and this is supported by the results from the quantitative PCR and immunocytochemical experiments. CONCLUSIONS AND IMPLICATIONS These data represent a rigorous investigation of the molecular basis of vascular transient K+ currents and implicates Kv4.3 as a major component of the channel complex.
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Affiliation(s)
- S Y M Yeung
- Division of Basic Medical Sciences, Ion Channels and Cell Signalling Research Centre, St George's, University of London London, UK
| | - S Ohya
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City UniversityJapan
| | - G P Sergeant
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk Co Louth, Ireland
| | - V Pucovský
- Division of Basic Medical Sciences, Ion Channels and Cell Signalling Research Centre, St George's, University of London London, UK
| | - I A Greenwood
- Division of Basic Medical Sciences, Ion Channels and Cell Signalling Research Centre, St George's, University of London London, UK
- Author for correspondence:
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Patlolla V, Alsheikh-Ali AA, Al-Ahmad AM. The Renin-Angiotensin System: A Therapeutic Target in Atrial Fibrillation. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2006; 29:1006-12. [PMID: 16981926 DOI: 10.1111/j.1540-8159.2006.00477.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
There is growing evidence to suggest a role for the renin-angiotensin system (RAS) in the pathogenesis of atrial fibrillation (AF). Experimental animal data suggest RAS-dependent mechanisms for the development of a structural and electrophysiologic substrate for AF. This is consistent with clinical data demonstrating the effectiveness of RAS blockade in preventing new-onset or recurrent AF in a variety of patient populations including patients with hypertension and left ventricular hypertrophy, congestive heart failure, and those undergoing electrical cardioversion for AF. This review summarizes experimental and clinical evidence to date relating to the role of RAS in the pathogenesis of AF, and the efficacy of its inhibition in managing this common arrhythmia.
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Affiliation(s)
- Vishnu Patlolla
- Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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Li YL, Schultz HD. Enhanced sensitivity of Kv channels to hypoxia in the rabbit carotid body in heart failure: role of angiotensin II. J Physiol 2006; 575:215-27. [PMID: 16777942 PMCID: PMC1819433 DOI: 10.1113/jphysiol.2006.110700] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Angiotensin II (Ang II) plays an important role in the enhanced chemoreflex function that occurs in congestive heart failure (CHF), but the mechanism of this effect within the carotid body (CB) is not known. We investigated the sensitivity of Ca2+-independent, voltage-gated K+ (Kv) channels to hypoxia in CB glomus cells from CHF rabbits, and whether endogenous angiotensin II (Ang II) modulates this action. Using the conventional whole-cell patch clamp technique, we found that Kv currents (IK) under normoxic conditions were blunted in the CB glomus cells from CHF rabbits compared with sham rabbits. In addition, the inhibition of IK and the decrease of resting membrane potential (RMP) induced by hypoxia were greater in CHF versus sham glomus cells. Ang II, at 100 pM, had no direct effect on IK at constant normoxic PO2, but increased the sensitivity of IK and RMP to hypoxia in sham glomus cells. In CHF glomus cells, an AT1 receptor (AT1R) antagonist, L-158 809 (1 microM), alone did not affect IK at normoxia, but it decreased the sensitivity of IK and RMP to hypoxia. At higher concentrations, Ang II dose dependently (0.1-100 nM) reduced IK under constant normoxic conditions in sham and CHF glomus cells, with threshold concentrations of about 900 and 600 pM, respectively. Immunocytochemical and Western blot assessments demonstrated the down-expression of Kv3.4 but not Kv4.3 channels in CHF glomus cells. These results indicate that: (1) Ang II/AT1R signalling increases the sensitivity of Kv channels to hypoxia in CB glomus cells from CHF rabbits; (2) high concentrations of Ang II (> 1 nM) directly inhibit IK in CB glomus cells from sham and CHF rabbits; (3) changes in Kv channel protein expression (Kv3.4 versus Kv4.3) in the CB glomus cell may contribute to the suppression of IK and enhanced sensitivity of IK to hypoxia in CHF.
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Affiliation(s)
- Yu-Long Li
- Department of Cellular and Integrative Physiology, University of, Nebraska Medical Center, Omaha, NE 68198-5850, USA
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Gassanov N, Brandt MC, Michels G, Lindner M, Er F, Hoppe UC. Angiotensin II-induced changes of calcium sparks and ionic currents in human atrial myocytes: potential role for early remodeling in atrial fibrillation. Cell Calcium 2006; 39:175-86. [PMID: 16303176 DOI: 10.1016/j.ceca.2005.10.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2005] [Revised: 10/11/2005] [Accepted: 10/17/2005] [Indexed: 10/25/2022]
Abstract
AIMS Atrial angiotensin II (ANG II) levels have been shown to be increased in atrial fibrillation (AF). The purpose of the study was to evaluate a potential role of ANG II in the early remodeling and susceptibility to chronicization of AF. METHODS AND RESULTS Isolated human atrial myocytes were incubated in ANG II and/or angiotensin type 1 receptor blocker candesartan. ANG II markedly increased the frequency of spontaneous Ca(2+) sparks, spark full duration, time to peak Ca(2+) fluorescence and decay time measured by confocal imaging. Sarcoplasmic reticulum calcium content estimated by caffeine-evoked calcium release did not differ between ANG II-treated cells and controls. Patch-clamp recordings revealed that ANG II significantly decreased I(to) and increased I(Ca,L) current densities. Candesartan blocked these ANG II-mediated alterations. ANG II exhibited no effect on I(K1), I(Kur) and I(f) current size. Expression of connexin 40 and connexin 43 was not significantly changed by ANG II as assessed by immunohistochemistry and Western blot analysis. CONCLUSION ANG II-induced alterations of calcium handling and electrophysiological changes in human atrial cells similar to those previously observed in the onset of AF. Prevention of these alterations by candesartan might constitute a useful pharmacological strategy for the treatment of AF.
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Affiliation(s)
- Natig Gassanov
- Department of Internal Medicine III, University of Cologne, Kerpener Str. 62, Cologne 50937, Germany
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