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Meijering RAM, Zhang D, Hoogstra-Berends F, Henning RH, Brundel BJJM. Loss of proteostatic control as a substrate for atrial fibrillation: a novel target for upstream therapy by heat shock proteins. Front Physiol 2012; 3:36. [PMID: 22375124 PMCID: PMC3284689 DOI: 10.3389/fphys.2012.00036] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2011] [Accepted: 02/09/2012] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common, sustained clinical tachyarrhythmia associated with significant morbidity and mortality. AF is a persistent condition with progressive structural remodeling of the atrial cardiomyocytes due to the AF itself, resulting in cellular changes commonly observed in aging and in other heart diseases. While rhythm control by electrocardioversion or drug treatment is the treatment of choice in symptomatic AF patients, its efficacy is still limited. Current research is directed at preventing first-onset AF by limiting the development of substrates underlying AF progression and resembles mechanism-based therapy. Upstream therapy refers to the use of non-ion channel anti-arrhythmic drugs that modify the atrial substrate- or target-specific mechanisms of AF, with the ultimate aim to prevent the occurrence (primary prevention) or recurrence of the arrhythmia following (spontaneous) conversion (secondary prevention). Heat shock proteins (HSPs) are molecular chaperones and comprise a large family of proteins involved in the protection against various forms of cellular stress. Their classical function is the conservation of proteostasis via prevention of toxic protein aggregation by binding to (partially) unfolded proteins. Our recent data reveal that HSPs prevent electrical, contractile, and structural remodeling of cardiomyocytes, thus attenuating the AF substrate in cellular, Drosophila melanogaster, and animal experimental models. Furthermore, studies in humans suggest a protective role for HSPs against the progression from paroxysmal AF to persistent AF and in recurrence of AF. In this review, we discuss upregulation of the heat shock response system as a novel target for upstream therapy to prevent derailment of proteostasis and consequently progression and recurrence of AF.
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Affiliation(s)
- Roelien A M Meijering
- Department of Clinical Pharmacology, Groningen University Institute for Drug Exploration, University Medical Center Groningen, University of Groningen Groningen, Netherlands
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52
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Collins TP, Terrar DA. Ca(2+)-stimulated adenylyl cyclases regulate the L-type Ca(2+) current in guinea-pig atrial myocytes. J Physiol 2012; 590:1881-93. [PMID: 22351635 DOI: 10.1113/jphysiol.2011.227066] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Ca(2+)-stimulated adenylyl cyclases (ACs) have recently been shown to play important roles in pacemaking in the sino-atrial node. Here we present evidence that Ca(2+)-stimulated ACs are functionally active in guinea-pig atrial myocytes. Basal activity of an AC in isolated atrial myocytes was demonstrated by the observations that MDL 12,330A (10 μm), an AC inhibitor, reduced L-type Ca(2+) current (I(CaL)) amplitude, while inhibition of phosphodiesterases with IBMX (100 μm) increased I(CaL) amplitude. Buffering of cytosolic Ca(2+) by exposure of myocytes to BAPTA-AM (5 μm) reduced I(CaL) amplitude, as did inhibition of Ca(2+) release from the sarcoplasmic reticulum with ryanodine (2 μm) and thapsigargin (1 μm). [Ca(2+)]i-activated calmodulin kinase II (CaMKII) inhibition with KN-93 (1 μm) reduced I(CaL), but subsequent application of BAPTA-AM further reduced I(CaL). This effect of BAPTA-AM, in the presence of CaMKII inhibition, demonstrates that there is an additional Ca(2+)-modulated pathway (not dependent on CaMKII) that regulates I(CaL) in atrial myocytes. The effects of BAPTA could be reversed by forskolin (10 μm), a direct stimulator of all AC isoforms, which would restore cAMP levels. In the presence of BAPTA-AM, the actions of IBMX were reduced. In addition, inclusion of cAMP in the patch electrode in the whole-cell configuration prevented the effects of BAPTA. These effects are all consistent with a role for Ca(2+)-stimulated AC in the regulation of atrial myocyte I(CaL).
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Affiliation(s)
- Thomas P Collins
- National Heart and Lung Institute, Imperial College, Guy Scadding Building, Dovehouse Street, London SW3 6LY, UK.
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Voigt N, Nattel S, Dobrev D. Proarrhythmic atrial calcium cycling in the diseased heart. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:1175-91. [PMID: 22453988 DOI: 10.1007/978-94-007-2888-2_53] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
During the last decades Ca(2+) has been found to play a crucial role in cardiac arrhythmias associated with heart failure and a number of congenital arrhythmia syndromes. Recent studies demonstrated that altered atrial Ca(2+) cycling may promote the initiation and maintenance of atrial fibrillation, the most common clinical arrhythmia that contributes significantly to population morbidity and mortality. This article describes physiological Ca(2+) cycling mechanisms in atrial cardiomyocytes and relates them to fundamental cellular proarrhythmic mechanisms involving Ca(2+) signaling abnormalities in the atrium during atrial fibrillation.
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Affiliation(s)
- Niels Voigt
- Division of Experimental Cardiology, Medical Faculty Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany.
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Dhein S. Remodeling bei Vorhofflimmern. ZEITSCHRIFT FUR HERZ THORAX UND GEFASSCHIRURGIE 2011. [DOI: 10.1007/s00398-011-0879-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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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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Yu T, Deng C, Wu R, Guo H, Zheng S, Yu X, Shan Z, Kuang S, Lin Q. Decreased expression of small-conductance Ca2+-activated K+ channels SK1 and SK2 in human chronic atrial fibrillation. Life Sci 2011; 90:219-27. [PMID: 22154908 DOI: 10.1016/j.lfs.2011.11.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Revised: 10/19/2011] [Accepted: 11/12/2011] [Indexed: 01/13/2023]
Abstract
AIMS Small-conductance Ca2+-activated K+ (SK) channels are recognized as new ion channel candidates in atrial fibrillation (AF), with pivotal implications as novel drug targets due to their atrial-selective distribution in humans. The purpose of this study was to investigate whether SK channels and the Ca2+-activated K+ current (IK,Ca) are involved in electrical remodeling of human chronic AF (cAF) and whether they display the differential distribution between the right (RA) and left atria (LA). MAIN METHODS The right (RAA) and left atrial appendage (LAA) myocytes were obtained from 29 sinus rhythm (SR) and 22 cAF patients. The IK,Ca and action potential (AP) were recorded using the patch-clamp technique. Three SK channel subtypes (SK1-3) expressions were assayed by western blot and real-time quantitative PCR analysis. KEY FINDINGS The IK,Ca was decreased and its role in AP repolarization was attenuated in cAF, concomitant with a significant decrease in protein and mRNA levels of SK1 and SK2. In either SR or cAF, there was no difference in the IK,Ca density and protein and mRNA expression levels of SK1-3 between RAA and LAA myocytes. SIGNIFICANCE Our results demonstrated that SK1 and SK2 are involved in electrical remodeling of cAF. SK1-3 and IK,Ca do not display the inter-atrial differential distribution in SR or cAF. These findings provide a new insight into mechanisms of electrical remodeling of human cAF.
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Affiliation(s)
- Tao Yu
- Department of Cardiac surgery, Guangdong Cardiovascular Institute, 96 Dongchuan Road, Guangzhou 510080, China
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57
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Friedrichs K, Klinke A, Baldus S. Inflammatory pathways underlying atrial fibrillation. Trends Mol Med 2011; 17:556-63. [DOI: 10.1016/j.molmed.2011.05.007] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 05/09/2011] [Accepted: 05/20/2011] [Indexed: 01/29/2023]
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Grandi E, Pandit SV, Voigt N, Workman AJ, Dobrev D, Jalife J, Bers DM. Human atrial action potential and Ca2+ model: sinus rhythm and chronic atrial fibrillation. Circ Res 2011; 109:1055-66. [PMID: 21921263 DOI: 10.1161/circresaha.111.253955] [Citation(s) in RCA: 257] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
RATIONALE Understanding atrial fibrillation (AF) requires integrated understanding of ionic currents and Ca2+ transport in remodeled human atrium, but appropriate models are limited. OBJECTIVE To study AF, we developed a new human atrial action potential (AP) model, derived from atrial experimental results and our human ventricular myocyte model. METHODS AND RESULTS Atria versus ventricles have lower I(K1), resulting in more depolarized resting membrane potential (≈7 mV). We used higher I(to,fast) density in atrium, removed I(to,slow), and included an atrial-specific I(Kur). I(NCX) and I(NaK) densities were reduced in atrial versus ventricular myocytes according to experimental results. SERCA function was altered to reproduce human atrial myocyte Ca2+ transients. To simulate chronic AF, we reduced I(CaL), I(to), I(Kur) and SERCA, and increased I(K1),I(Ks) and I(NCX). We also investigated the link between Kv1.5 channelopathy, [Ca2+]i, and AF. The sinus rhythm model showed a typical human atrial AP morphology. Consistent with experiments, the model showed shorter APs and reduced AP duration shortening at increasing pacing frequencies in AF or when I(CaL) was partially blocked, suggesting a crucial role of Ca2+ and Na+ in this effect. This also explained blunted Ca2+ transient and rate-adaptation of [Ca2+]i and [Na+]i in chronic AF. Moreover, increasing [Na+]i and altered I(NaK) and I(NCX) causes rate-dependent atrial AP shortening. Blocking I(Kur) to mimic Kv1.5 loss-of-function increased [Ca2+]i and caused early afterdepolarizations under adrenergic stress, as observed experimentally. CONCLUSIONS Our study provides a novel tool and insights into ionic bases of atrioventricular AP differences, and shows how Na+ and Ca2+ homeostases critically mediate abnormal repolarization in AF.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California, Davis, 451 Health Sciences Dr, GBSF Room 3513, Davis, CA 95616-8636, USA
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Dobrev D. Prevention of atrial fibrillation complications with antiarrhythmic drugs: still an unmet need in clinical practice. Expert Opin Pharmacother 2011; 12:1195-1199. [PMID: 21548721 DOI: 10.1517/14656566.2011.568476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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60
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Richards MA, Clarke JD, Saravanan P, Voigt N, Dobrev D, Eisner DA, Trafford AW, Dibb KM. Transverse tubules are a common feature in large mammalian atrial myocytes including human. Am J Physiol Heart Circ Physiol 2011; 301:H1996-2005. [PMID: 21841013 DOI: 10.1152/ajpheart.00284.2011] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Transverse (t) tubules are surface membrane invaginations that are present in all mammalian cardiac ventricular cells. The apposition of L-type Ca(2+) channels on t tubules with the sarcoplasmic reticulum (SR) constitutes a "calcium release unit" and allows close coupling of excitation to the rise in systolic Ca(2+). T tubules are virtually absent in the atria of small mammals, and therefore Ca(2+) release from the SR occurs initially at the periphery of the cell and then propagates into the interior. Recent work has, however, shown the occurrence of t tubules in atrial myocytes from sheep. As in the ventricle, Ca(2+) release in these cells occurs simultaneously in central and peripheral regions. T tubules in both the atria and the ventricle are lost in disease, contributing to cellular dysfunction. The aim of this study was to determine if the occurrence of t tubules in the atrium is restricted to sheep or is a more general property of larger mammals including humans. In atrial tissue sections from human, horse, cow, and sheep, membranes were labeled using wheat germ agglutinin. As previously shown in sheep, extensive t-tubule networks were present in horse, cow, and human atrial myocytes. Analysis shows half the volume of the cell lies within 0.64 ± 0.03, 0.77 ± 0.03, 0.84 ± 0.03, and 1.56 ± 0.19 μm of t-tubule membrane in horse, cow, sheep, and human atrial myocytes, respectively. The presence of t tubules in the human atria may play an important role in determining the spatio-temporal properties of the systolic Ca(2+) transient and how this is perturbed in disease.
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Affiliation(s)
- M A Richards
- Unit of Cardiac Physiology, University of Manchester, Core Technology Facility, Manchester, United Kingdom
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61
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Decreased sarcolipin protein expression and enhanced sarco(endo)plasmic reticulum Ca2+ uptake in human atrial fibrillation. Biochem Biophys Res Commun 2011; 410:97-101. [PMID: 21640081 DOI: 10.1016/j.bbrc.2011.05.113] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 05/19/2011] [Indexed: 11/24/2022]
Abstract
Sarcolipin (SLN), a key regulator of cardiac sarco(endo)plasmic reticulum (SR) Ca(2+) ATPase, is predominantly expressed in atria and mediates β-adrenergic responses. Studies have shown that SLN mRNA expression is decreased in human chronic atrial fibrillation (AF) and in aortic banded mouse atria; however, SLN protein expression in human atrial pathology and its role in atrial SR Ca(2+) uptake are not yet elucidated. In the present study, we determined the expression of major SR Ca(2+) handling proteins in atria of human AF patients and in human and in a mouse model of heart failure (HF). We found that the expression of SR Ca(2+) uptake and Ca(2+) release channel proteins are significantly decreased in atria but not in the ventricles of pressure-overload induced HF in mice. In human AF and HF, the expression of SLN protein was significantly decreased; whereas the expressions of other major SR Ca(2+) handling proteins were not altered. Further, we found that the SR Ca(2+) uptake was significantly increased in human AF. The selective downregulation of SLN and enhanced SR Ca(2+) uptake in human AF suggest that SLN downregulation could play an important role in abnormal intracellular Ca(2+) cycling in atrial pathology.
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62
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Bootman MD, Smyrnias I, Thul R, Coombes S, Roderick HL. Atrial cardiomyocyte calcium signalling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:922-34. [DOI: 10.1016/j.bbamcr.2011.01.030] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 01/21/2011] [Accepted: 01/25/2011] [Indexed: 11/25/2022]
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Hashimoto K. Emerging antiarrhythmic agents: a personal view from the Far East. Expert Opin Emerg Drugs 2011; 16:23-9. [PMID: 21352067 DOI: 10.1517/14728214.2011.521151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Arrhythmia treatments today take three different approaches. One uses electronic devices, such as electronic pacemakers or defibrillators, and this is regarded as life-saving in cases of bradyarrhythmias and ventricular fibrillation. Another is the ablation technique which eliminates abnormal pacemakers and/or conductive pathways by applying thermal or cryo-injury to pathological portions of the heart. The most classical one is the antiarrhythmic drugs, but are they effective and safe? AREAS COVERED Recent development of the understanding of arrhythmias, cardiac ionic channels and antiarrhythmic drugs covered by papers mostly published after 2000 are discussed. EXPERT OPINION The market size of the antiarrhythmic drugs is small, but various multichannel acting drugs may become candidates as antiarrhythmic drugs. As the cardiac ionic channels have become recognized as proteins, the molecular target for antiarrhythmic drugs has become apparent, but at the same time accurate data on clinical effectiveness and safety are required for drug approval; thus, few atrium selective drugs, such as IKur, IKACh and IKAde blocking drugs and amiodarone-like multichannel acting drugs are being developed.
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Affiliation(s)
- Keitaro Hashimoto
- Yokohama College of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan.
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64
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Wittköpper K, Dobrev D, Eschenhagen T, El-Armouche A. Phosphatase-1 inhibitor-1 in physiological and pathological β-adrenoceptor signalling. Cardiovasc Res 2011; 91:392-401. [PMID: 21354993 DOI: 10.1093/cvr/cvr058] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Control of protein phosphorylation-dephosphorylation events occurs through regulation of protein kinases and phosphatases. Phosphatase type 1 (PP-1) provides the main activity of serine/threonine protein phosphatases in the heart. Inhibitor-1 (I-1) was the first endogenous molecule found to inhibit PP-1 specifically. Notably, I-1 is activated by cAMP-dependent protein kinase A (PKA), and the subsequent prevention of target dephosphorylation by PP-1 provides distal amplification of β-adrenoceptor (β-AR) signalling. I-1 was found to be down-regulated and hypo-phosphorylated in human and experimental heart failure but hyperactive in human atrial fibrillation, implicating I-1 in the pathogenesis of heart failure and arrhythmias. Consequently, the therapeutic potential of I-1 in heart failure and arrhythmias has recently been addressed by the generation and analysis of several I-1 genetic mouse models. This review summarizes and discusses these data, highlights partially controversial issues on whether I-1 should be therapeutically reinforced or inhibited and suggests future directions to better understand the functional role of I-1 in physiological and pathological β-AR signalling.
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Affiliation(s)
- Katrin Wittköpper
- Department of Pharmacology, University Medical Center Göttingen, Georg August University Göttingen, Göttingen, Germany
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65
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Koivumäki JT, Korhonen T, Tavi P. Impact of sarcoplasmic reticulum calcium release on calcium dynamics and action potential morphology in human atrial myocytes: a computational study. PLoS Comput Biol 2011; 7:e1001067. [PMID: 21298076 PMCID: PMC3029229 DOI: 10.1371/journal.pcbi.1001067] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 12/21/2010] [Indexed: 02/02/2023] Open
Abstract
Electrophysiological studies of the human heart face the fundamental challenge that experimental data can be acquired only from patients with underlying heart disease. Regarding human atria, there exist sizable gaps in the understanding of the functional role of cellular Ca²+ dynamics, which differ crucially from that of ventricular cells, in the modulation of excitation-contraction coupling. Accordingly, the objective of this study was to develop a mathematical model of the human atrial myocyte that, in addition to the sarcolemmal (SL) ion currents, accounts for the heterogeneity of intracellular Ca²+ dynamics emerging from a structurally detailed sarcoplasmic reticulum (SR). Based on the simulation results, our model convincingly reproduces the principal characteristics of Ca²+ dynamics: 1) the biphasic increment during the upstroke of the Ca²+ transient resulting from the delay between the peripheral and central SR Ca²+ release, and 2) the relative contribution of SL Ca²+ current and SR Ca²+ release to the Ca²+ transient. In line with experimental findings, the model also replicates the strong impact of intracellular Ca²+ dynamics on the shape of the action potential. The simulation results suggest that the peripheral SR Ca²+ release sites define the interface between Ca²+ and AP, whereas the central release sites are important for the fire-diffuse-fire propagation of Ca²+ diffusion. Furthermore, our analysis predicts that the modulation of the action potential duration due to increasing heart rate is largely mediated by changes in the intracellular Na+ concentration. Finally, the results indicate that the SR Ca²+ release is a strong modulator of AP duration and, consequently, myocyte refractoriness/excitability. We conclude that the developed model is robust and reproduces many fundamental aspects of the tight coupling between SL ion currents and intracellular Ca²+ signaling. Thus, the model provides a useful framework for future studies of excitation-contraction coupling in human atrial myocytes.
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Affiliation(s)
- Jussi T. Koivumäki
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Topi Korhonen
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Pasi Tavi
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
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66
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Dobrev D, Wehrens XHT. Calmodulin kinase II, sarcoplasmic reticulum Ca2+ leak, and atrial fibrillation. Trends Cardiovasc Med 2010; 20:30-4. [PMID: 20685575 DOI: 10.1016/j.tcm.2010.03.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Although it is generally accepted that excitation-contraction coupling is defective in patients with atrial fibrillation, the underlying cellular mechanisms remain incompletely understood. Recent studies suggest that abnormal sarcoplasmic reticulum calcium "leak" via ryanodine receptors contributes to atrial arrhythmogenesis. Increased activity of the enzyme calmodulin kinase II (CaMKII) and, specifically, enhanced CaMKII phosphorylation of ryanodine receptors appear to play a critical role in the induction and perhaps maintenance of atrial fibrillation. In this review, we will summarize new insights into the role of enhanced CaMKII in sarcoplasmic reticulum calcium leak and atrial arrhythmogenesis during atrial fibrillation.
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Affiliation(s)
- Dobromir Dobrev
- Department of Pharmacology and Toxicology, Dresden University of Technology, Germany.
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67
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Transforming growth factor beta 1 (TGF-beta 1) in atrial fibrillation and acute congestive heart failure. Clin Res Cardiol 2010; 100:335-42. [PMID: 21069358 DOI: 10.1007/s00392-010-0248-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Accepted: 10/20/2010] [Indexed: 10/18/2022]
Abstract
PURPOSE Atrial fibrillation (AF) and acute congestive heart failure (aCHF) are characterized by an adverse cardiac remodeling. Arrhythmogenic or structural remodeling can be caused by interstitial fibrosis. Transforming growth factor beta 1 (TGF-beta 1) represents a central regulator of cardiac fibrosis. This study investigates serum levels of TGF-beta 1 in patients with AF and aCHF. METHODS 401 patients presenting with symptoms of dyspnea or peripheral edema were prospectively enrolled. Blood samples for measurement of TGF-beta 1 (R&D Systems, Inc.) and amino-terminal pro-brain natriuretic peptide (NT-proBNP) (DadeBehring ltd.) were collected after the initial clinical evaluation. RESULTS Median TGF-beta 1 levels were lower in patients with AF (21.0 ng/ml, interquartile range (IR) 15.4-27.6 ng/ml, n = 107) compared to those without (25.0 ng/ml, IR 18.5-31.6 ng/ml, n = 294) (p = 0.009). Patients with aCHF had lower TGF-beta 1 levels (median 22.0 ng/ml, IR 15.6-27.1 ng/ml, n = 122) than those without (median 24.9 ng/ml, IR 18.1-31.9 ng/ml, n = 279) (p = 0.0005). In logistic regression models TGF-beta 1 was still associated with AF (odds ratio (OR) 3.00, 95% CI 1.37-6.61, p = 0.0001) and aCHF (OR 3.98, 95% CI 1.55-10.19, p = 0.004). TGF-beta 1 inversely correlated with left atrial diameter (r = -0.30, p = 0.007) and NT-proBNP (r = -0.14, p = 0.007). CONCLUSIONS Low serum levels of TGF-beta 1 are associated with AF and aCHF. This decrease may result from a higher consumption of TGF-beta 1 within the impaired myocardium or antifibrotic functions of natriuretic peptides.
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De Jong AM, Maass AH, Oberdorf-Maass SU, Van Veldhuisen DJ, Van Gilst WH, Van Gelder IC. Mechanisms of atrial structural changes caused by stretch occurring before and during early atrial fibrillation. Cardiovasc Res 2010; 89:754-65. [PMID: 21075756 DOI: 10.1093/cvr/cvq357] [Citation(s) in RCA: 192] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Structural remodelling occurring before, due to the underlying heart disease, and during atrial fibrillation (AF) sets the stage for permanent AF. Current therapy in AF aims to maintain sinus rhythm in symptomatic patients, but outcome is unfortunately poor. Stretch of the atria is a main contributor to atrial remodelling. In this review, we describe different aspects of structural remodelling as seen in animal models and in patients with AF, including atrial enlargement, cellular hypertrophy, dedifferentiation, fibrosis, apoptosis, and loss of contractile elements. In the second part, we describe downstream signals of mechanical stretch and their contribution to AF and structural remodelling. Ultimately, knowledge of mechanisms underlying structural remodelling may help to identify new pharmacological targets for AF prevention.
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Affiliation(s)
- Anne Margreet De Jong
- Department of Experimental Cardiology, University Medical Center Groningen, University of Groningen, The Netherlands
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69
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Abstract
Atrial fibrillation (AF) is the most commonly encountered clinical arrhythmia associated with pronounced morbidity, mortality, and socio-economic burden. This pathological entity is associated with an altered expression profile of genes that are important for atrial function. MicroRNAs (miRNAs), a new class of non-coding mRNAs of around 22 nucleotides in length, have rapidly emerged as one of the key players in the gene expression regulatory network. The potential roles of miRNAs in controlling AF have recently been investigated. The studies have provided some promising results for our better understanding of the molecular mechanisms of AF. In this review article, we provide a synopsis of the studies linking miRNAs to cardiac excitability and other processes pertinent to AF. To introduce the main topic, we discuss basic knowledge about miRNA biology and our current understanding of mechanisms for AF. The most up-to-date research data on the possible roles of miRNAs in AF initiation and maintenance are presented, and the available experimental results on miRNA and AF are discussed. Some speculations pertinent to the subject are made. Finally, perspectives on future directions of research on miRNAs in AF are provided.
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Affiliation(s)
- Zhiguo Wang
- Research Center, Montreal Heart Institute, 5000 Belanger East, Montreal, Canada PQ H1T 1C8.
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Dobrev D, Voigt N, Wehrens XHT. The ryanodine receptor channel as a molecular motif in atrial fibrillation: pathophysiological and therapeutic implications. Cardiovasc Res 2010; 89:734-43. [PMID: 20943673 DOI: 10.1093/cvr/cvq324] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with substantial morbidity and mortality. It causes profound changes in sarcoplasmic reticulum (SR) Ca(2+) homeostasis, including ryanodine receptor channel dysfunction and diastolic SR Ca(2+) leak, which might contribute to both decreased contractile function and increased propensity to atrial arrhythmias. In this review, we will focus on the molecular basis of ryanodine receptor channel dysfunction and enhanced diastolic SR Ca(2+) leak in AF. The potential relevance of increased incidence of spontaneous SR Ca(2+) release for both AF induction and/or maintenance and the development of novel mechanism-based therapeutic approaches will be discussed.
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Affiliation(s)
- Dobromir Dobrev
- Division of Experimental Cardiology, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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71
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Ravens U. Antiarrhythmic therapy in atrial fibrillation. Pharmacol Ther 2010; 128:129-45. [DOI: 10.1016/j.pharmthera.2010.06.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Accepted: 06/11/2010] [Indexed: 12/19/2022]
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72
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Zhang Y, Fraser JA, Jeevaratnam K, Hao X, Hothi SS, Grace AA, Lei M, Huang CLH. Acute atrial arrhythmogenicity and altered Ca(2+) homeostasis in murine RyR2-P2328S hearts. Cardiovasc Res 2010; 89:794-804. [PMID: 20621925 PMCID: PMC3039245 DOI: 10.1093/cvr/cvq229] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Aims The experiments explored for atrial arrhythmogenesis and its possible physiological background in recently developed hetero-(RyR2+/S) and homozygotic (RyR2S/S) RyR2-P2328S murine models for catecholaminergic polymorphic ventricular tachycardia (VT) for the first time. They complement previous clinical and experimental reports describing increased ventricular arrhythmic tendencies associated with physical activity, stress, or catecholamine infusion, potentially leading to VT and ventricular fibrillation. Methods and results Atrial arrhythmogenic properties were compared at the whole animal, Langendorff-perfused heart, and single, isolated atrial myocyte levels using electrophysiological and confocal fluorescence microscopy methods. This demonstrated that: (i) electrocardiographic parameters in intact anaesthetized wild-type (WT), RyR2+/S and RyR2S/S mice were statistically indistinguishable both before and after addition of isoproterenol apart from increases in heart rates. (ii) Bipolar electrogram and monophasic action potential recordings showed significantly higher incidences of arrhythmogenesis in isolated perfused RyR2S/S, but not RyR2+/S, relative to WT hearts during either regular pacing or programmed electrical stimulation. The addition of isoproterenol increased such incidences in all three groups. (iii) However, there were no accompanying differences in cardiac anatomy or action potential durations at 90% repolarization and refractory periods. (iv) In contrast, episodes of diastolic Ca2+ release were observed under confocal microscopy in isolated fluo-3-loaded RyR2S/S, but not RyR2+/S or WT, atrial myocytes. The introduction of isoproterenol resulted in significant diastolic Ca2+ release in all three groups. Conclusions These findings establish acute atrial arrhythmogenic properties in RyR2-P2328S hearts and correlate these with altered Ca2+ homeostasis in an absence of repolarization abnormalities for the first time.
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Affiliation(s)
- Yanmin Zhang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
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73
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Orabi AI, Shah AU, Ahmad MU, Choo-Wing R, Parness J, Jain D, Bhandari V, Husain SZ. Dantrolene mitigates caerulein-induced pancreatitis in vivo in mice. Am J Physiol Gastrointest Liver Physiol 2010; 299:G196-204. [PMID: 20448143 PMCID: PMC2904115 DOI: 10.1152/ajpgi.00498.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Acute pancreatitis is a painful, inflammatory disorder for which adequate treatments are lacking. An early, critical step in its development is the aberrant signaling of Ca(2+) within the pancreatic acinar cell. This Ca(2+) release is modulated by the intracellular Ca(2+) channel the ryanodine receptor (RYR). We have previously shown that RYR inhibition reduces pathological intra-acinar protease activation, an early marker of pancreatitis. In this study, we examined whether pretreatment with the RYR inhibitor dantrolene attenuates the severity of caerulein-induced pancreatitis in mice. Immunofluorescent labeling for RYR from mouse pancreatic sections showed localization to the basolateral region of the acinar cell. After 1 h of caerulein hyperstimulation in vivo, dantrolene 1) reduced pancreatic trypsin activity by 59% (P < 0.05) and 2) mitigated early ultrastructural derangements within the acinar cell. Eight hours after pancreatitis induction, dantrolene reduced pancreatic trypsin activity and serum amylase by 61 and 32%, respectively (P < 0.05). At this later time point, overall histological severity of pancreatitis was reduced by 63% with dantrolene pretreatment (P < 0.05). TUNEL-positive cells were reduced by 58% (P < 0.05). These data suggest that the RYR plays an important role in mediating early acinar cell events during in vivo pancreatitis and contributes to disease severity. Blockade of Ca(2+) signals and particularly RYR-Ca(2+) may be useful as prophylactic treatment for this disease in high-risk settings for pancreatitis.
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Affiliation(s)
| | | | | | | | - Jerome Parness
- 2Department of Anesthesiology, Children's Hospital of Pittsburgh/University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Dhanpat Jain
- 3Pathology, Yale University School of Medicine, New Haven, Connecticut; and
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74
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Abstract
Atrial fibrillation (AF) is a growing clinical problem associated with increased morbidity and mortality. Currently available antiarrhythmic drugs (AADs), although highly effective in acute cardioversion of paroxysmal AF, are generally only moderately successful in long-term maintenance of sinus rhythm. The use of AADs is often associated with an increased risk of ventricular proarrhythmia, extracardiac toxicity, and exacerbation of concomitant diseases such as heart failure. AF is commonly associated with intracardiac and extracardiac disease, which can modulate the efficacy and safety of AAD therapy. In light of the multifactorial intracardiac and extracardiac causes of AF generation, current development of anti-AF agents is focused on modulation of ion channel activity as well as on upstream therapies that reduce structural substrates. The available data indicate that multiple ion channel blockers exhibiting potent inhibition of peak I(Na) with relatively rapid unbinding kinetics, as well as inhibition of late I(Na) and I(Kr), may be preferable for the management of AF when considering both safety and efficacy.
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75
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Paraoxon attenuates vascular smooth muscle contraction through inhibiting Ca2+ influx in the rabbit thoracic aorta. J Biomed Biotechnol 2010; 2010:829190. [PMID: 20445738 PMCID: PMC2859412 DOI: 10.1155/2010/829190] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Revised: 01/31/2010] [Accepted: 02/03/2010] [Indexed: 12/04/2022] Open
Abstract
We investigated the effect of paraoxon on vascular contractility using organ baths in thoracic aortic rings of rabbits and examined the effect of paraoxon on calcium homeostasis using a whole-cell patch-clamp technique in isolated aortic smooth muscle cells of rabbits. The findings show that administration of paraoxon (30 μM) attenuated thoracic aorta contraction induced by phenylephrine (1 μM) and/or a high K+
environment (80 mM) in both the presence and absence of thoracic aortic endothelium. This inhibitory effect of paraoxon on vasoconstrictor-induced contraction was abolished in the absence of extracellular Ca2+, or in the presence of the Ca2+ channel inhibitor, verapamil. But atropine had little effect on the inhibitory effect of paraoxon on phenylephrine-induced contraction. Paraoxon also attenuated vascular smooth muscle contraction induced by the cumulative addition of CaCl2
and attenuated an increase of intracellular Ca2+ concentration induced by K+
in vascular smooth muscle cells. Moreover, paraoxon (30 μM) inhibited significantly L-type calcium current in isolated aortic smooth muscle cells of rabbits. In conclusion, our results demonstrate that paraoxon attenuates vasoconstrictor-induced contraction through inhibiting Ca2+ influx in the rabbits thoracic aorta.
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76
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Abstract
Inadequacies in current therapies for atrial fibrillation have made new drug development crucial. Conventional antiarrhythmic drugs increase the risk of ventricular proarrhythmia. In drug development, the focus has been on favourable multichannel-blocking profiles, atrial-specific ion-channels, and novel non-channel targets (upstream therapy). Molecular modification of the highly effective multichannel blocker, amiodarone, to improve safety and tolerability has produced promising analogues such as dronedarone, although this drug seems less effective than does amiodarone. Vernakalant, an atrial-selective drug with reduced proarrhythmic risk, might be useful for cardioversion in atrial fibrillation. Ranolazine, another atrial-selective agent initially developed as an antianginal, has efficacy for atrial fibrillation and is being tested in prospective clinical trials. So-called upstream therapy with angiotensin-converting enzyme and angiotensin-receptor inhibitors, statins, or omega-3 fatty acids and fish oil that target atrial remodelling could be effective, but need further clinical validation. We focus on the basic and clinical pharmacology of newly emerging antiarrhythmic drugs and non-traditional approaches such as upstream therapy for atrial fibrillation.
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Affiliation(s)
- Dobromir Dobrev
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany.
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77
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Korantzopoulos P, Goudevenos JA. Aldosterone signaling in atrial fibrillation another piece in the puzzle of atrial remodeling. J Am Coll Cardiol 2010; 55:771-3. [PMID: 20170815 DOI: 10.1016/j.jacc.2009.10.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 10/06/2009] [Indexed: 11/29/2022]
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78
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Workman AJ. Cardiac adrenergic control and atrial fibrillation. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2010; 381:235-49. [PMID: 19960186 PMCID: PMC2855383 DOI: 10.1007/s00210-009-0474-0] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 11/08/2009] [Indexed: 10/20/2022]
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia, and it causes substantial mortality. The autonomic nervous system, and particularly the adrenergic/cholinergic balance, has a profound influence on the occurrence of AF. Adrenergic stimulation from catecholamines can cause AF in patients. In human atrium, catecholamines can affect each of the electrophysiological mechanisms of AF initiation and/or maintenance. Catecholamines may produce membrane potential oscillations characteristic of afterdepolarisations, by increasing Ca(2+) current, [Ca(2+)](i) and consequent Na(+)-Ca(2+) exchange, and may also enhance automaticity. Catecholamines might affect reentry, by altering excitability or conduction, rather than action potential terminal repolarisation or refractory period. However, which arrhythmia mechanisms predominate is unclear, and likely depends on cardiac pathology and adrenergic tone. Heart failure (HF), a major cause of AF, causes adrenergic activation and adaptational changes, remodelling, of atrial electrophysiology, Ca(2+) homeostasis, and adrenergic responses. Chronic AF also remodels these, but differently to HF. Myocardial infarction and AF cause neural remodelling that also may promote AF. beta-Adrenoceptor antagonists (beta-blockers) are used in the treatment of AF, mainly to control the ventricular rate, by slowing atrioventricular conduction. beta-Blockers also reduce the incidence of AF, particularly in HF or after cardiac surgery, when adrenergic tone is high. Furthermore, the chronic treatment of patients with beta-blockers remodels the atria, with a potentially antiarrhythmic increase in the refractory period. Therefore, the suppression of AF by beta-blocker treatment may involve an attenuation of arrhythmic activity that is caused by increased [Ca(2+)](i), coupled with effects of adaptation to the treatment. An improved understanding of the involvement of the adrenergic system and its control in basic mechanisms of AF under differing cardiac pathologies might lead to better treatments.
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Affiliation(s)
- Antony J Workman
- British Heart Foundation Glasgow Cardiovascular Research Centre, Division of Cardiovascular and Medical Sciences, Faculty of Medicine, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK.
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79
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Novel pharmacological approaches for antiarrhythmic therapy. Naunyn Schmiedebergs Arch Pharmacol 2010; 381:187-93. [DOI: 10.1007/s00210-009-0487-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 12/17/2009] [Indexed: 01/14/2023]
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80
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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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81
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Affiliation(s)
- Pamela K Mason
- Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, VA 22908, USA
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82
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Involvement of Src in L-type Ca2+ channel depression induced by macrophage migration inhibitory factor in atrial myocytes. J Mol Cell Cardiol 2009; 47:586-94. [DOI: 10.1016/j.yjmcc.2009.08.030] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 08/24/2009] [Accepted: 08/29/2009] [Indexed: 11/22/2022]
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83
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Dobrev D. Atrial Ca2+ signaling in atrial fibrillation as an antiarrhythmic drug target. Naunyn Schmiedebergs Arch Pharmacol 2009; 381:195-206. [PMID: 19784635 DOI: 10.1007/s00210-009-0457-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 09/11/2009] [Indexed: 12/19/2022]
Abstract
Atrial fibrillation (AF) is the most frequent arrhythmia and is associated with increased morbidity and mortality. Current drugs for AF treatment have moderate efficacy and increase the risk of life-threatening antiarrhythmias, making novel drug development crucial. Newer antiarrhythmic drugs like dronedarone and possibly vernakalant are efficient and may have less proarrhythmic potential. Emerging evidence suggests that abnormal intracellular Ca(2+) signaling is the key contributor to focal firing, substrate evolution, and atrial remodeling during AF. Accordingly, identification of the underlying atrial Ca(2+)-handling abnormalities is expected to discover novel mechanistically based therapeutic targets. This article reviews the molecular mechanisms of altered Ca(2+) signaling in AF and discusses the potential value of novel approaches targeting atrial Ca(2+)-handling abnormalities.
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Affiliation(s)
- Dobromir Dobrev
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany.
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84
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Kirchhof P, Bax J, Blomstrom-Lundquist C, Calkins H, Camm AJ, Cappato R, Cosio F, Crijns H, Diener HC, Goette A, Israel CW, Kuck KH, Lip GY, Nattel S, Page RL, Ravens U, Schotten U, Steinbeck G, Vardas P, Waldo A, Wegscheider K, Willems S, Breithardt G. Early and comprehensive management of atrial fibrillation: executive summary of the proceedings from the 2nd AFNET-EHRA consensus conference ‘research perspectives in AF’. Eur Heart J 2009; 30:2969-77c. [DOI: 10.1093/eurheartj/ehp235] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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85
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Kirchhof P, Bax J, Blomstrom-Lundquist C, Calkins H, Camm AJ, Cappato R, Cosio F, Crijns H, Diener HC, Goette A, Israel CW, Kuck KH, Lip GY, Nattel S, Page RL, Ravens U, Schotten U, Steinbeck G, Vardas P, Waldo A, Wegscheider K, Willems S, Breithardt G. Early and comprehensive management of atrial fibrillation: Proceedings from the 2nd AFNET/EHRA consensus conference on atrial fibrillation entitled 'research perspectives in atrial fibrillation'. Europace 2009; 11:860-85. [DOI: 10.1093/europace/eup124] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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86
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Dobrev D, Teos LY, Lederer WJ. Unique atrial myocyte Ca2+ signaling. J Mol Cell Cardiol 2008; 46:448-51. [PMID: 19150353 DOI: 10.1016/j.yjmcc.2008.12.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 12/11/2008] [Accepted: 12/12/2008] [Indexed: 12/19/2022]
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87
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Differences in intracellular calcium homeostasis between atrial and ventricular myocytes. J Mol Cell Cardiol 2008; 46:463-73. [PMID: 19059414 DOI: 10.1016/j.yjmcc.2008.11.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 10/13/2008] [Accepted: 11/02/2008] [Indexed: 11/22/2022]
Abstract
The role that Ca(2+) plays in ventricular excitation contraction coupling is well defined and much is known about the marked differences in the spatiotemporal properties of the systolic Ca(2+) transient between atrial and ventricular myocytes. However, to date there has been no systematic appraisal of the Ca(2+) homeostatic mechanisms employed by atrial cells and how these compare to the ventricle. In the present study we sought to determine the fractional contributions made to the systolic Ca(2+) transient and the decay of [Ca(2+)](i) by the sarcoplasmic reticulum and sarcolemmal mechanisms. Experiments were performed on single myocytes isolated from the atria and ventricles of the rat. Intracellular Ca(2+) concentration, membrane currents, SR Ca(2+) content and cellular Ca(2+) buffering capacity were measured at 23 degrees C. Atrial cells had smaller systolic Ca(2+) transients (251+/-39 vs. 376+/-41 nmol x L(-1)) that decayed more rapidly (7.4+/-0.6 vs. 5.45+/-0.3 s(-1)). This was due primarily to an increased rate of SR mediated Ca(2+) uptake (k(SR), 6.88+/-0.6 vs. 4.57+/-0.3 s(-1)). SR Ca(2+) content was 289% greater and Ca(2+) buffering capacity was increased approximately 3-fold in atrial cells (B(max) 371.9+/-32.4 vs. 121.8+/-8 micromol x L(-1), all differences P<0.05). The fractional release of Ca(2+) from the SR was greater in atrial cells, although the gain of excitation contraction coupling was the same in both cell types. In summary our data demonstrate fundamental differences in Ca(2+) homeostasis between atrial and ventricular cells and we speculate that the increased SR Ca(2+) content may be significant in determining the increased prevalence of arrhythmias in the atria.
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