1
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Sato D, Uchinoumi H, Bers DM. Increasing SERCA function promotes initiation of calcium sparks and breakup of calcium waves. J Physiol 2021; 599:3267-3278. [PMID: 33963531 PMCID: PMC8249358 DOI: 10.1113/jp281579] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/04/2021] [Indexed: 01/16/2023] Open
Abstract
KEY POINTS Increasing sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) pump activity enhances sarcoplasmic reticulum calcium (Ca) load, which increases both ryanodine receptor opening and driving force of Ca release flux. Both of these effects promote Ca spark formation and wave propagation. However, increasing SERCA activity also accelerates local cytosolic Ca decay as the wave front travels to the next cluster, which limits wave propagation. As a result, increasing SERCA pump activity has a biphasic effect on the propensity of arrhythmogenic Ca waves, but a monotonic effect to increase Ca spark frequency and amplitude. ABSTRACT Waves of sarcoplasmic reticulum (SR) calcium (Ca) release can cause arrhythmogenic afterdepolarizations in cardiac myocytes. Ca waves propagate when Ca sparks at one Ca release unit (CRU) recruit new Ca sparks in neighbouring CRUs. Under normal conditions, Ca sparks are too small to recruit neighbouring Ca sparks where Ca sensitivity is also low. However, under pathological conditions such as a Ca overload or ryanodine receptor (RyR) sensitization, Ca sparks can be larger and propagate more readily as macro-sparks or full Ca waves. Increasing SERCA pump activity promotes SR Ca load, which promotes RyR opening and increases driving force of the Ca release flux from SR to cytosol, promoting Ca waves. However, high sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) activity can also decrease local cytosolic [Ca] as it approaches the next CRU, thereby reducing wave appearance and propagation. In this study, we use a physiologically detailed model of subcellular Ca cycling and experiments in phospholamban-knockout mice, to show how Ca waves are initiated and propagate and how different conditions contribute to the generation and propagation of Ca waves. We show that reducing diffusive coupling between Ca sparks by increasing SERCA activity prevents Ca waves by reducing [Ca] at the next CRU, as do Ca buffers, low intra-SR Ca diffusion and distance between CRUs. Increasing SR Ca uptake rate has a biphasic effect on Ca wave propagation; initially it enhances Ca spark probability and amplitude and CRU coupling, thereby promoting arrhythmogenic Ca wave propagation, but at higher levels SR Ca uptake can abort those arrhythmogenic Ca waves.
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Affiliation(s)
- Daisuke Sato
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA
| | - Hitoshi Uchinoumi
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA.,Department of Cardiology, Yamaguchi University School of Medicine, Yamaguchi, Japan
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA
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2
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Bond RC, Choisy SC, Bryant SM, Hancox JC, James AF. Ion currents, action potentials, and noradrenergic responses in rat pulmonary vein and left atrial cardiomyocytes. Physiol Rep 2020; 8:e14432. [PMID: 32401431 PMCID: PMC7219272 DOI: 10.14814/phy2.14432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 04/06/2020] [Accepted: 04/10/2020] [Indexed: 11/30/2022] Open
Abstract
The electrophysiological properties of pulmonary vein (PV)‐cardiomyocytes, and their responses to the sympathetic neurotransmitter, noradrenaline (NA), are thought to differ from those of the left atrium (LA) and contribute to atrial ectopy. The aim of this study was to examine rat PV cardiomyocyte electrophysiology and responses to NA in comparison with LA cells. LA and PV cardiomyocytes were isolated from adult male Wistar rat hearts, and membrane potentials and ion currents recorded at 36°C using whole‐cell patch‐clamp techniques. PV and LA cardiomyocytes did not differ in size. In control, there were no differences between the two cell‐types in zero‐current potential or action potential duration (APD) at 1 Hz, although the incidence of early afterdepolarizations (EADs) was greater in PV than LA cardiomyocytes. The L‐type Ca2+ current (ICaL) was ~×1.5 smaller (p = .0029, Student's t test) and the steady‐state K+ current (IKss) was ~×1.4 larger (p = .0028, Student's t test) in PV than in LA cardiomyocytes. PV cardiomyocyte inward‐rectifier current (IK1) was slightly smaller than LA cardiomyocyte IK1. In LA cardiomyocytes, NA significantly prolonged APD30. In PV cells, APD30 responses to 1 μM NA were heterogeneous: while the mean percentage change in APD30 was not different from 0 (16.5 ± 9.7%, n cells/N animals = 12/10, p = .1177, one‐sample t test), three cells showed shortening (‐18.8 ± 6.0%) whereas nine showed prolongation (28.3 ± 10.1%, p = .008, Student's t test). NA had no effect on IK1 in either cell‐type but inhibited PV IKss by 41.9 ± 4.1% (n/N = 23/11 p < .0001), similar to LA cells. NA increased ICaL in most PV cardiomyocytes (median × 2.2‐increase, p < .0001, n/N = 32/14, Wilcoxon‐signed‐rank test), although in 7/32 PV cells ICaL was decreased following NA. PV cardiomyocytes differ from LA cells and respond heterogeneously to NA.
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Affiliation(s)
- Richard C Bond
- Cardiovascular Research Laboratories, School of Physiology, Biomedical Sciences Building, University of Bristol, Bristol, UK
| | - Stéphanie C Choisy
- Cardiovascular Research Laboratories, School of Physiology, Biomedical Sciences Building, University of Bristol, Bristol, UK
| | - Simon M Bryant
- Cardiovascular Research Laboratories, School of Physiology, Biomedical Sciences Building, University of Bristol, Bristol, UK
| | - Jules C Hancox
- Cardiovascular Research Laboratories, School of Physiology, Biomedical Sciences Building, University of Bristol, Bristol, UK
| | - Andrew F James
- Cardiovascular Research Laboratories, School of Physiology, Biomedical Sciences Building, University of Bristol, Bristol, UK
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3
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Takagi D, Okamoto Y, Ohba T, Yamamoto H, Ono K. Comparative study of hyperpolarization-activated currents in pulmonary vein cardiomyocytes isolated from rat, guinea pig, and rabbit. J Physiol Sci 2020; 70:6. [PMID: 32046630 PMCID: PMC7012960 DOI: 10.1186/s12576-020-00736-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 10/03/2019] [Indexed: 02/05/2023]
Abstract
Pulmonary vein (PV) cardiomyocytes have the potential to generate spontaneous activity, in contrast to working myocytes of atria. Different electrophysiological properties underlie the potential automaticity of PV cardiomyocytes, one being the hyperpolarization-activated inward current (Ih), which facilitates the slow diastolic depolarization. In the present study, we examined pharmacological characteristics of the Ih of PV cardiomyocytes in rat, guinea pig and rabbit. The results showed that guinea pig and rat PV cardiomyocytes possessed sizeable amplitudes of the Ih, and the Ih of guinea pig was suppressed by Cs+, a blocker of the hyperpolarization-activated cation current. However, the Ih of rat was not suppressed by Cs+, but by Cd2+, a blocker of the Cl− current. The current density of the Ih of rabbit PV cardiomyocytes was significantly smaller than those of other species. This suggests that the ion channels that carry the Ih of PV cardiomyocytes differ among the animal species.
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Affiliation(s)
- Daichi Takagi
- Department of Cardiovascular Surgery, Akita University Graduate School of Medicine, Hondo 1-1-1, Akita, 010-8543, Japan
| | - Yosuke Okamoto
- Department of Cell Physiology, Akita University Graduate School of Medicine, Hondo 1-1-1, Akita, 010-8543, Japan
| | - Takayoshi Ohba
- Department of Cell Physiology, Akita University Graduate School of Medicine, Hondo 1-1-1, Akita, 010-8543, Japan
| | - Hiroshi Yamamoto
- Department of Cardiovascular Surgery, Akita University Graduate School of Medicine, Hondo 1-1-1, Akita, 010-8543, Japan
| | - Kyoichi Ono
- Department of Cell Physiology, Akita University Graduate School of Medicine, Hondo 1-1-1, Akita, 010-8543, Japan.
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4
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Cheniti G, Vlachos K, Pambrun T, Hooks D, Frontera A, Takigawa M, Bourier F, Kitamura T, Lam A, Martin C, Dumas-Pommier C, Puyo S, Pillois X, Duchateau J, Klotz N, Denis A, Derval N, Jais P, Cochet H, Hocini M, Haissaguerre M, Sacher F. Atrial Fibrillation Mechanisms and Implications for Catheter Ablation. Front Physiol 2018; 9:1458. [PMID: 30459630 PMCID: PMC6232922 DOI: 10.3389/fphys.2018.01458] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 09/26/2018] [Indexed: 01/14/2023] Open
Abstract
AF is a heterogeneous rhythm disorder that is related to a wide spectrum of etiologies and has broad clinical presentations. Mechanisms underlying AF are complex and remain incompletely understood despite extensive research. They associate interactions between triggers, substrate and modulators including ionic and anatomic remodeling, genetic predisposition and neuro-humoral contributors. The pulmonary veins play a key role in the pathogenesis of AF and their isolation is associated to high rates of AF freedom in patients with paroxysmal AF. However, ablation of persistent AF remains less effective, mainly limited by the difficulty to identify the sources sustaining AF. Many theories were advanced to explain the perpetuation of this form of AF, ranging from a single localized focal and reentrant source to diffuse bi-atrial multiple wavelets. Translating these mechanisms to the clinical practice remains challenging and limited by the spatio-temporal resolution of the mapping techniques. AF is driven by focal or reentrant activities that are initially clustered in a relatively limited atrial surface then disseminate everywhere in both atria. Evidence for structural remodeling, mainly represented by atrial fibrosis suggests that reentrant activities using anatomical substrate are the key mechanism sustaining AF. These reentries can be endocardial, epicardial, and intramural which makes them less accessible for mapping and for ablation. Subsequently, early interventions before irreversible remodeling are of major importance. Circumferential pulmonary vein isolation remains the cornerstone of the treatment of AF, regardless of the AF form and of the AF duration. No ablation strategy consistently demonstrated superiority to pulmonary vein isolation in preventing long term recurrences of atrial arrhythmias. Further research that allows accurate identification of the mechanisms underlying AF and efficient ablation should improve the results of PsAF ablation.
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Affiliation(s)
- Ghassen Cheniti
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France.,Cardiology Department, Hopital Sahloul, Universite de Sousse, Sousse, Tunisia
| | - Konstantinos Vlachos
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Thomas Pambrun
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Darren Hooks
- Cardiology Department, Wellington Hospital, Wellington, New Zealand
| | - Antonio Frontera
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Masateru Takigawa
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Felix Bourier
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Takeshi Kitamura
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Anna Lam
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Claire Martin
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | | | - Stephane Puyo
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Xavier Pillois
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France
| | - Josselin Duchateau
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Nicolas Klotz
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Arnaud Denis
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Nicolas Derval
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Pierre Jais
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Hubert Cochet
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France.,Department of Cardiovascular Imaging, Hopital Haut Leveque, Bordeaux, France
| | - Meleze Hocini
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Michel Haissaguerre
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
| | - Frederic Sacher
- Cardiac Electrophysiology Department, Hopital Haut Leveque, Bordeaux, France.,Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, Pessac, France
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5
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Wang Y, Wilson C, Cartwright EJ, Lei M. Plasma membrane Ca 2+ -ATPase 1 is required for maintaining atrial Ca 2+ homeostasis and electrophysiological stability in the mouse. J Physiol 2017; 595:7383-7398. [PMID: 29023784 PMCID: PMC5730856 DOI: 10.1113/jp274110] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 10/06/2017] [Indexed: 11/22/2022] Open
Abstract
Key points The role of plasma membrane Ca2+‐ATPase 1 (PMCA1) in Ca2+ homeostasis and electrical stability in atrial tissue has been investigated at both organ and cellular levels in mice with cardiomyocyte‐specific deletion of PMCA1 (PMCA1cko) The PMCA1cko hearts became more susceptible to atrial arrhythmic stress conditions than PMCA1loxP/loxP hearts. PMCA1 deficiency alters cellular Ca2+ homeostasis under both baseline and stress conditions. PMCA1 is required for maintaining cellular Ca2+ homeostasis and electrical stability in murine atria under stress conditions.
Abstract To determine the role of plasma membrane Ca2+‐ATPase 1 (PMCA1) in maintaining Ca2+ homeostasis and electrical stability in the atrium under physiological and stress conditions, mice with a cardiomyocyte‐specific deletion of PMCA1 (PMCA1cko) and their control littermates (PMCA1loxP/loxP) were studied at the organ and cellular levels. At the organ level, the PMCA1cko hearts became more susceptible to atrial arrhythmias under rapid programmed electrical stimulation compared with the PMCA1loxP/loxP hearts, and such arrhythmic events became more severe under Ca2+ overload conditions. At the cellular level, the occurrence of irregular‐type action potentials of PMCA1cko atrial myocytes increased significantly under Ca2+ overload conditions and/or at higher frequency of stimulation. The decay of Na+/Ca2+ exchanger current that followed a stimulation protocol was significantly prolonged in PMCA1cko atrial myocytes under basal conditions, with Ca2+ overload leading to even greater prolongation. In conclusion, PMCA1 is required for maintaining Ca2+ homeostasis and electrical stability in the atrium. This is particularly critical during fast removal of Ca2+ from the cytosol, which is required under stress conditions. The role of plasma membrane Ca2+‐ATPase 1 (PMCA1) in Ca2+ homeostasis and electrical stability in atrial tissue has been investigated at both organ and cellular levels in mice with cardiomyocyte‐specific deletion of PMCA1 (PMCA1cko) The PMCA1cko hearts became more susceptible to atrial arrhythmic stress conditions than PMCA1loxP/loxP hearts. PMCA1 deficiency alters cellular Ca2+ homeostasis under both baseline and stress conditions. PMCA1 is required for maintaining cellular Ca2+ homeostasis and electrical stability in murine atria under stress conditions.
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Affiliation(s)
- Yanwen Wang
- Department of Pharmacology, University of Oxford, Oxford, UK.,Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Claire Wilson
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Elizabeth J Cartwright
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Ming Lei
- Department of Pharmacology, University of Oxford, Oxford, UK
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6
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Rietdorf K, Bootman MD, Sanderson MJ. Spontaneous, pro-arrhythmic calcium signals disrupt electrical pacing in mouse pulmonary vein sleeve cells. PLoS One 2014; 9:e88649. [PMID: 24586364 PMCID: PMC3930634 DOI: 10.1371/journal.pone.0088649] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 01/08/2014] [Indexed: 11/18/2022] Open
Abstract
The pulmonary vein, which returns oxygenated blood to the left atrium, is ensheathed by a population of unique, myocyte-like cells called pulmonary vein sleeve cells (PVCs). These cells autonomously generate action potentials that propagate into the left atrial chamber and cause arrhythmias resulting in atrial fibrillation; the most common, often sustained, form of cardiac arrhythmia. In mice, PVCs extend along the pulmonary vein into the lungs, and are accessible in a lung slice preparation. We exploited this model to study how aberrant Ca(2+) signaling alters the ability of PVC networks to follow electrical pacing. Cellular responses were investigated using real-time 2-photon imaging of lung slices loaded with a Ca(2+)-sensitive fluorescent indicator (Ca(2+) measurements) and phase contrast microscopy (contraction measurements). PVCs displayed global Ca(2+) signals and coordinated contraction in response to electrical field stimulation (EFS). The effects of EFS relied on both Ca(2+) influx and Ca(2+) release, and could be inhibited by nifedipine, ryanodine or caffeine. Moreover, PVCs had a high propensity to show spontaneous Ca(2+) signals that arose via stochastic activation of ryanodine receptors (RyRs). The ability of electrical pacing to entrain Ca(2+) signals and contractile responses was dramatically influenced by inherent spontaneous Ca(2+) activity. In PVCs with relatively low spontaneous Ca(2+) activity (<1 Hz), entrainment with electrical pacing was good. However, in PVCs with higher frequencies of spontaneous Ca(2+) activity (>1.5 Hz), electrical pacing was less effective; PVCs became unpaced, only partially-paced or displayed alternans. Because spontaneous Ca(2+) activity varied between cells, neighboring PVCs often had different responses to electrical pacing. Our data indicate that the ability of PVCs to respond to electrical stimulation depends on their intrinsic Ca(2+) cycling properties. Heterogeneous spontaneous Ca(2+) activity arising from stochastic RyR opening can disengage them from sinus rhythm and lead to autonomous, pro-arrhythmic activity.
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Affiliation(s)
- Katja Rietdorf
- Department of Microbiology and Physiological Systems, University of Massachusetts, Medical School, Worcester, Massachusetts, United States of America
- Department of Life, Health and Chemical Science, The Open University, Milton Keynes, United Kingdom
- * E-mail:
| | - Martin D. Bootman
- Department of Life, Health and Chemical Science, The Open University, Milton Keynes, United Kingdom
- Signalling Programme, The Babraham Institute, Cambridge, United Kingdom
| | - Michael J. Sanderson
- Department of Microbiology and Physiological Systems, University of Massachusetts, Medical School, Worcester, Massachusetts, United States of America
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7
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Greiser M, Schotten U. Dynamic remodeling of intracellular Ca2+ signaling during atrial fibrillation. J Mol Cell Cardiol 2013; 58:134-42. [DOI: 10.1016/j.yjmcc.2012.12.020] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 12/14/2012] [Accepted: 12/17/2012] [Indexed: 12/23/2022]
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8
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Burashnikov A, Antzelevitch C. Novel pharmacological targets for the rhythm control management of atrial fibrillation. Pharmacol Ther 2011; 132:300-13. [PMID: 21867730 PMCID: PMC3205214 DOI: 10.1016/j.pharmthera.2011.08.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 08/05/2011] [Indexed: 12/19/2022]
Abstract
Atrial fibrillation (AF) is a growing clinical problem associated with increased morbidity and mortality. Development of safe and effective pharmacological treatments for AF is one of the greatest unmet medical needs facing our society. In spite of significant progress in non-pharmacological AF treatments (largely due to the use of catheter ablation techniques), anti-arrhythmic agents (AADs) remain first line therapy for rhythm control management of AF for most AF patients. When considering efficacy, safety and tolerability, currently available AADs for rhythm control of AF are less than optimal. Ion channel inhibition remains the principal strategy for termination of AF and prevention of its recurrence. Practical clinical experience indicates that multi-ion channel blockers are generally more optimal for rhythm control of AF compared to ion channel-selective blockers. Recent studies suggest that atrial-selective sodium channel block can lead to safe and effective suppression of AF and that concurrent inhibition of potassium ion channels may potentiate this effect. An important limitation of the ion channel block approach for AF treatment is that non-electrical factors (largely structural remodeling) may importantly determine the generation of AF, so that "upstream therapy", aimed at preventing or reversing structural remodeling, may be required for effective rhythm control management. This review focuses on novel pharmacological targets for the rhythm control management of AF.
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9
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Schotten U, Verheule S, Kirchhof P, Goette A. Pathophysiological mechanisms of atrial fibrillation: a translational appraisal. Physiol Rev 2011; 91:265-325. [PMID: 21248168 DOI: 10.1152/physrev.00031.2009] [Citation(s) in RCA: 852] [Impact Index Per Article: 65.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Atrial fibrillation (AF) is an arrhythmia that can occur as the result of numerous different pathophysiological processes in the atria. Some aspects of the morphological and electrophysiological alterations promoting AF have been studied extensively in animal models. Atrial tachycardia or AF itself shortens atrial refractoriness and causes loss of atrial contractility. Aging, neurohumoral activation, and chronic atrial stretch due to structural heart disease activate a variety of signaling pathways leading to histological changes in the atria including myocyte hypertrophy, fibroblast proliferation, and complex alterations of the extracellular matrix including tissue fibrosis. These changes in electrical, contractile, and structural properties of the atria have been called "atrial remodeling." The resulting electrophysiological substrate is characterized by shortening of atrial refractoriness and reentrant wavelength or by local conduction heterogeneities caused by disruption of electrical interconnections between muscle bundles. Under these conditions, ectopic activity originating from the pulmonary veins or other sites is more likely to occur and to trigger longer episodes of AF. Many of these alterations also occur in patients with or at risk for AF, although the direct demonstration of these mechanisms is sometimes challenging. The diversity of etiological factors and electrophysiological mechanisms promoting AF in humans hampers the development of more effective therapy of AF. This review aims to give a translational overview on the biological basis of atrial remodeling and the proarrhythmic mechanisms involved in the fibrillation process. We pay attention to translation of pathophysiological insights gained from in vitro experiments and animal models to patients. Also, suggestions for future research objectives and therapeutical implications are discussed.
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Affiliation(s)
- Ulrich Schotten
- Department of Physiology, University Maastricht, Maastricht, The Netherlands.
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10
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Abstract
Atrial fibrillation is the most common clinical cardiac arrhythmia. It is often initiated by ectopic beats arising from the pulmonary veins and atria. While pulmonary vein myocytes most likely contribute to atrial ectopic beats initiating atrial fibrillation, emerging evidence suggests the existence of other cell populations that may also contribute to atrial arrhythmias. In addition to sinus node-like and intestinal Cajal-like cells, we recently characterized a novel, melanocyte-like cell population in murine and human hearts that may contribute to atrial arrhythmogenic triggers in mice. Murine cardiac melanocyte-like cells are electrically excitable, and express adrenergic and muscarinic receptors. Adult mice lacking the gene encoding dopachrome tautomerase (Dct) are susceptible to atrial arrhythmias, and Dct is expressed by both murine and human cardiac melanocytes. While Dct-expressing cells are present in human hearts in regions from which atrial arrhythmias often arise, the contribution of these cells to clinical atrial arrhythmias remains to be determined.
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Affiliation(s)
- Vickas V Patel
- Penn Cardiovascular Institute and Division of Cardiovascular Medicine, 905 BRB II/III, 421 Curie Boulevard, University of Pennsylvania, Philadelphia, PA 19104-6160, USA.
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11
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Neef S, Dybkova N, Sossalla S, Ort KR, Fluschnik N, Neumann K, Seipelt R, Schöndube FA, Hasenfuss G, Maier LS. CaMKII-Dependent Diastolic SR Ca
2+
Leak and Elevated Diastolic Ca
2+
Levels in Right Atrial Myocardium of Patients With Atrial Fibrillation. Circ Res 2010; 106:1134-44. [DOI: 10.1161/circresaha.109.203836] [Citation(s) in RCA: 290] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale
:
Although research suggests that diastolic Ca
2+
levels might be increased in atrial fibrillation (AF), this hypothesis has never been tested. Diastolic Ca
2+
leak from the sarcoplasmic reticulum (SR) might increase diastolic Ca
2+
levels and play a role in triggering or maintaining AF by transient inward currents through Na
+
/Ca
2+
exchange. In ventricular myocardium, ryanodine receptor type 2 (RyR2) phosphorylation by Ca
2+
/calmodulin-dependent protein kinase (CaMK)II is emerging as an important mechanism for SR Ca
2+
leak.
Objective
:
We tested the hypothesis that CaMKII-dependent diastolic SR Ca
2+
leak and elevated diastolic Ca
2+
levels occurs in atrial myocardium of patients with AF.
Methods and Results
:
We used isolated human right atrial myocytes from patients with AF versus sinus rhythm and found CaMKII expression to be increased by 40±14% (
P
<0.05), as well as CaMKII phosphorylation by 33±12% (
P
<0.05). This was accompanied by a significantly increased RyR2 phosphorylation at the CaMKII site (Ser2814) by 110±53%. Furthermore, cytosolic Ca
2+
levels were elevated during diastole (229±20 versus 164±8 nmol/L,
P
<0.05). Most likely, this resulted from an increased SR Ca
2+
leak in AF (
P
<0.05), which was not attributable to higher SR Ca
2+
load. Tetracaine experiments confirmed that SR Ca
2+
leak through RyR2 leads to the elevated diastolic Ca
2+
level. CaMKII inhibition normalized SR Ca
2+
leak and cytosolic Ca
2+
levels without changes in L-type Ca
2+
current.
Conclusion
:
Increased CaMKII-dependent phosphorylation of RyR2 leads to increased SR Ca
2+
leak in human AF, causing elevated cytosolic Ca
2+
levels, thereby providing a potential arrhythmogenic substrate that could trigger or maintain AF.
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Affiliation(s)
- Stefan Neef
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Nataliya Dybkova
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Samuel Sossalla
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Katharina R. Ort
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Nina Fluschnik
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Kay Neumann
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Ralf Seipelt
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Friedrich A. Schöndube
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Gerd Hasenfuss
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
| | - Lars S. Maier
- From the Departments of Cardiology and Pneumology (S.N., N.D., S.S., K.R.O., N.F., K.N., G.H., L.S.M.) and Thoracic and Cardiovascular Surgery (R.S., F.A.S.), Georg-August-University, Göttingen, Germany
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Kushiyama Y, Osaka T, Yokoyama E, Hasebe H, Kuroda Y, Kamiya K, Kodama I. Verapamil eliminates the hierarchical nature of activation frequencies from the pulmonary veins to the atria during paroxysmal atrial fibrillation. Heart Rhythm 2010; 7:577-83. [PMID: 20206318 DOI: 10.1016/j.hrthm.2010.01.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Accepted: 01/05/2010] [Indexed: 10/20/2022]
Abstract
BACKGROUND There is evidence that verapamil promotes the persistence of paroxysmal atrial fibrillation (AF). Little is known about the underlying mechanisms. OBJECTIVE The purpose of this study was to determine the effect of verapamil on dominant frequencies (DFs) in the pulmonary veins (PVs) and atria during paroxysmal AF with reference to its potential arrhythmogenicity. METHODS Forty-three patients with paroxysmal AF were studied. Bipolar electrograms were recorded simultaneously during AF from the right atrial free wall (RAFW), coronary sinus (CS) and three PVs, or two PVs and the left atrial appendage (LAA). The DFs were obtained by fast Fourier transform analysis before and after infusion of verapamil (0.1 mg/kg, intravenously). RESULTS At baseline, the maximum DF among the PVs (6.9 +/- 0.9 Hz) was significantly higher than the DF in the RAFW (6.2 +/- 0.7 Hz), CS (5.7 +/- 0.5 Hz), or LAA (5.9 +/- 0.7 Hz) (P<.01); there was a substantial PV-to-atrial DF gradient (RAFW 0.7 +/- 0.9, CS 1.1 +/- 0.7, LAA 0.7 +/- 0.9 Hz). Verapamil increased the atrial DF to 6.9 +/- 0.8, 6.6 +/- 0.7, and 7.2 +/- 1.0 Hz in the RAFW, CS, and LAA, respectively (P<.0001) but did not affect the maximum PV DF (7.1 +/- 0.7 Hz). The PV-to-atrial DF gradient was eliminated after verapamil (RAFW 0.2 +/- 0.8, CS 0.5 +/- 0.6, LAA -0.4 +/- 0.8 Hz; P<.01 vs. baseline). CONCLUSION Verapamil increases the activation frequency in the atria but not in the PVs, eliminating the PV-to-atrial DF gradient during paroxysmal AF.
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Affiliation(s)
- Yasunori Kushiyama
- Division of Arrhythmia and Electrophysiology, Shizuoka Saiseikai General Hospital, Shizuoka, Japan
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Abstract
Bisphosphonates are the most commonly used treatment for osteoporosis and have proven efficacy in the reduction of vertebral and nonvertebral fractures. Recently, concerns have been raised about a possible association between bisphosphonate therapy and atrial fibrillation (AF) following the report of a significant increase in risk of serious AF in women treated with zoledronic acid in the HORIZON study. Subsequent studies have produced conflicting results but have not excluded the possibility of such an association. Currently there is no direct evidence that bisphosphonates exert either acute or chronic effects on cardiac electrophysiology. Nevertheless, altered intracellular electrolyte homeostasis and proinflammatory, profibrotic, and antiangiogenic effects provide potential mechanisms by which atrial conduction could be affected in patients treated with bisphosphonates. In studies in which an increase in risk of AF has been identified, there is no evidence that this translates into increased mortality or increased risk of stroke, and the risk-benefit balance of bisphosphonate therapy in patients with osteoporosis and other forms of metabolic bone disease remains strongly positive.
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Stambler BS, Laurita KR. Atrial fibrillation in heart failure: steady progress but still a long way to go. Circ Arrhythm Electrophysiol 2009; 1:77-9. [PMID: 19808396 DOI: 10.1161/circep.108.785071] [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] [Indexed: 11/16/2022]
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Vaudry D, Falluel-Morel A, Bourgault S, Basille M, Burel D, Wurtz O, Fournier A, Chow BKC, Hashimoto H, Galas L, Vaudry H. Pituitary Adenylate Cyclase-Activating Polypeptide and Its Receptors: 20 Years after the Discovery. Pharmacol Rev 2009; 61:283-357. [DOI: 10.1124/pr.109.001370] [Citation(s) in RCA: 829] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Zhang Y, Schwiening C, Killeen MJ, Zhang Y, Ma A, Lei M, Grace AA, Huang CLH. Pharmacological changes in cellular Ca2+ homeostasis parallel initiation of atrial arrhythmogenesis in murine Langendorff-perfused hearts. Clin Exp Pharmacol Physiol 2009; 36:969-80. [PMID: 19298534 PMCID: PMC2841827 DOI: 10.1111/j.1440-1681.2009.05170.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
1. Intracellular Ca(2+) overload has been associated with established atrial arrhythmogenesis. The present experiments went on to correlate acute initiation of atrial arrhythmogenesis in Langendorff-perfused mouse hearts with changes in Ca(2+) homeostasis in isolated atrial myocytes following pharmacological procedures that modified the storage or release of sarcoplasmic reticular (SR) Ca(2+) or inhibited entry of extracellular Ca(2+). 2. Caffeine (1 mmol/L) elicited diastolic Ca(2+) waves in regularly stimulated atrial myocytes immediately following addition. This was followed by a decline in the amplitude of the evoked transients and the disappearance of such diastolic events, suggesting partial SR Ca(2+) depletion. 3. Cyclopiazonic acid (CPA; 0.15 micromol/L) produced more gradual reductions in evoked Ca(2+) transients and abolished diastolic Ca(2+) events produced by the further addition of caffeine. 4. Nifedipine (0.5 micromol/L) produced immediate reductions in evoked Ca(2+) transients. Further addition of caffeine produced an immediate increase followed by a decline in the amplitude of the evoked Ca(2+) transients, without eliciting diastolic Ca(2+) events. 5. These findings correlated with changes in spontaneous and provoked atrial arrhythmogenecity in mouse isolated Langendorf-perfused hearts. Thus, caffeine was pro-arrhythmogenic immediately following but not > 5 min after application and both CPA and nifedipine pretreatment inhibited such arrhythmogenesis. 6. Together, these findings relate acute atrial arrhythmogenesis in intact hearts to diastolic Ca(2+) events in atrial myocytes that, in turn, depend upon a finite SR Ca(2+) store and diastolic Ca(2+) release following Ca(2+)-induced Ca(2+) release initiated by the entry of extracellular Ca(2+).
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Affiliation(s)
- Yanmin Zhang
- Physiological Laboratory, University of Cambridge, Cambridge, UK
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Luk HN, Lo CP, Tien HC, Lee D, Chen ZL, Wang F, Hsin ST, Day YJ. Mechanical characterization of rabbit pulmonary vein sleeves in in vitro intact ring preparation. J Chin Med Assoc 2008; 71:610-8. [PMID: 19114325 DOI: 10.1016/s1726-4901(09)70003-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Pulmonary vein (PV) sleeves, composed of cardiomyocytes, play certain roles in arrhythmogenesis. In the literature, it has been frequently reported that PV sleeves possess intrinsic spontaneous pacemaking activity and triggered activity in normal dogs and rabbits. In contrast, other research groups presented totally opposite findings which showed absence of such pacemakers in dogs, rabbits and rats. The present study was designed to clarify this puzzle and contradiction. METHODS A novel methodology using in vitro experimentation was used to examine the electromechanical activity of whole segments of PV sleeves. The ring preparation was composed of a small piece of left atrial (LA) free wall, PV ostium and sleeve from rabbits. A circumferential contraction of the PV sleeve was measured when the preparation was electrically driven from the LA free wall. Mechanical force of the ring preparation was measured using a force transducer. The action potentials were recorded using conventional intracellular recording technique in strip preparation. RESULTS In 15 rabbits, no spontaneous pacemaking activity or triggered activity was found in the in vitro ring preparation of PV sleeve. The circumferential contraction of PV sleeves was external calcium-dependent. Frequency-force relation displayed a negative staircase at 0.1-0.5 Hz and a positive staircase at 1-5 Hz. Post-rest potentiation was prominent between 15 s and 120 s. Intracellular action potential recording did not display any automaticity or triggered activity in PV sleeves. CONCLUSION In an intact ring preparation of rabbit PV sleeves, intrinsic spontaneous pacemaking activity or triggered activity was not found.
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Affiliation(s)
- Hsiang-Ning Luk
- Department of Anesthesiology, Taichung Veterans General Hospital, Providence University, Taichung, Taiwan, ROC.
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Eckstein J, Verheule S, de Groot N, Allessie M, Schotten U. Mechanisms of perpetuation of atrial fibrillation in chronically dilated atria. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:435-51. [DOI: 10.1016/j.pbiomolbio.2008.02.019] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
The thoracic veins are important foci for the genesis of ectopic atrial tachycardia and play a critical role in the pathophysiology of paroxysmal and permanent atrial fibrillation. The pulmonary veins have the highest arrhythmogenic activity and other venous structures (eg, superior vena cava, coronary sinus and ligament of Marshall) have also been shown arrhythmogenic potential. Thoracic veins contain cardiomyocytes with distinct electrical activities and complex anatomical structures. This review summaries the current understanding of the basic and clinical electrophysiology of thoracic vein arrhythmias.
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Affiliation(s)
- Yi-Jen Chen
- Division of Cardiovascular Medicine, Taipei Medical University-Wan-Fang Hospital and School of Medicine, Taipei Medical University, Taipei, Taiwan
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