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Pironet A, Vandewiele F, Vennekens R. Exploring the role of TRPM4 in calcium-dependent triggered activity and cardiac arrhythmias. J Physiol 2024; 602:1605-1621. [PMID: 37128952 DOI: 10.1113/jp283831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 04/28/2023] [Indexed: 05/03/2023] Open
Abstract
Cardiac arrhythmias pose a major threat to a patient's health, yet prove to be often difficult to predict, prevent and treat. A key mechanism in the occurrence of arrhythmias is disturbed Ca2+ homeostasis in cardiac muscle cells. As a Ca2+-activated non-selective cation channel, TRPM4 has been linked to Ca2+-induced arrhythmias, potentially contributing to translating an increase in intracellular Ca2+ concentration into membrane depolarisation and an increase in cellular excitability. Indeed, evidence from genetically modified mice, analysis of mutations in human patients and the identification of a TRPM4 blocking compound that can be applied in vivo further underscore this hypothesis. Here, we provide an overview of these data in the context of our current understanding of Ca2+-dependent arrhythmias.
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Affiliation(s)
- Andy Pironet
- Laboratory of Ion Channel Research, VIB Centre for Brain and Disease Research, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Frone Vandewiele
- Laboratory of Ion Channel Research, VIB Centre for Brain and Disease Research, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Rudi Vennekens
- Laboratory of Ion Channel Research, VIB Centre for Brain and Disease Research, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
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Christa M, Dithmar F, Weinaus T, Kohlhaas M, Arias-Loza AP, Hofmann M, Elabyad IA, Gutjahr FT, Maack C, Bauer WR. A new approach to characterize cardiac sodium storage by combining fluorescence photometry and magnetic resonance imaging in small animal research. Sci Rep 2024; 14:2426. [PMID: 38287086 PMCID: PMC10825176 DOI: 10.1038/s41598-024-52377-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 01/18/2024] [Indexed: 01/31/2024] Open
Abstract
Cardiac myocyte sodium (Na+) homoeostasis is pivotal in cardiac diseases and heart failure. Intracellular Na+ ([Na+]i) is an important regulator of excitation-contraction coupling and mitochondrial energetics. In addition, extracellular Na+ ([Na+]e) and its water-free storage trigger collagen cross-linking, myocardial stiffening and impaired cardiac function. Therefore, understanding the allocation of tissue Na+ to intra- and extracellular compartments is crucial in comprehending the pathophysiological processes in cardiac diseases. We extrapolated [Na+]e using a three-compartment model, with tissue Na+ concentration (TSC) measured by in vivo 23Na-MRI, extracellular volume (ECV) data calculated from T1 maps, and [Na+]i measured by in vitro fluorescence microscopy using Na+ binding benzofuran isophthalate (SBFI). To investigate dynamic changes in Na+ compartments, we induced pressure overload (TAC) or myocardial infarction (MI) via LAD ligation in mice. Compared to SHAM mice, TSC was similar after TAC but increased after MI. Both TAC and MI showed significantly higher [Na+]i compared to SHAM (around 130% compared to SHAM). Calculated [Na+]e increased after MI, but not after TAC. Increased TSC after TAC was primarily driven by increased [Na+]i, but the increase after MI by elevations in both [Na+]i and [Na+]e.
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Affiliation(s)
- Martin Christa
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany.
- Department of Internal Medicine I, University Hospital Würzburg, Oberdürrbacher Straße 6, Haus A3, 97080, Würzburg, Germany.
| | - Franziska Dithmar
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
- Department of Internal Medicine I, University Hospital Würzburg, Oberdürrbacher Straße 6, Haus A3, 97080, Würzburg, Germany
| | - Tobias Weinaus
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
- Department of Internal Medicine I, University Hospital Würzburg, Oberdürrbacher Straße 6, Haus A3, 97080, Würzburg, Germany
| | - Michael Kohlhaas
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
| | - Anahi-Paula Arias-Loza
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
| | - Michelle Hofmann
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
| | - Ibrahim A Elabyad
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
| | | | - Christoph Maack
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
| | - Wolfgang R Bauer
- Comprehensive Heart Failure Center, University and University Hospital Würzburg, Würzburg, Germany
- Department of Internal Medicine I, University Hospital Würzburg, Oberdürrbacher Straße 6, Haus A3, 97080, Würzburg, Germany
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MacLeod KT. Changes in cellular Ca 2+ and Na + regulation during the progression towards heart failure. J Physiol 2023; 601:905-921. [PMID: 35946572 PMCID: PMC10952717 DOI: 10.1113/jp283082] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 08/02/2022] [Indexed: 11/08/2022] Open
Abstract
In adapting to disease and loss of tissue, the heart shows great phenotypic plasticity that involves changes to its structure, composition and electrophysiology. Together with parallel whole body cardiovascular adaptations, the initial decline in cardiac function resulting from the insult is compensated. However, in the long term, the heart muscle begins to fail and patients with this condition have a very poor prognosis, with many dying from disturbances of rhythm. The surviving myocytes of these hearts gain Na+ , which is positively inotropic because of alterations to Ca2+ fluxes mediated by the Na+ /Ca2+ exchange, but compromises Ca2+ -dependent energy metabolism in mitochondria. Uptake of Ca2+ into the sarcoplasmic reticulum (SR) is reduced because of diminished function of SR Ca2+ ATPases. The result of increased Ca2+ influx and reduced SR Ca2+ uptake is an increase in the diastolic cytosolic Ca2+ concentration, which promotes spontaneous SR Ca2+ release and induces delayed afterdepolarisations. Action potential duration prolongs because of increased late Na+ current and changes in expression and function of other ion channels and transporters increasing the probability of the formation of early afterdepolarisations. There is a reduction in T-tubule density and so the normal spatial arrangements required for efficient excitation-contraction coupling are compromised and lead to temporal delays in Ca2+ release from the SR. Therefore, the structural and electrophysiological responses that occur to provide compensation do so at the expense of (1) increasing the likelihood of arrhythmogenesis; (2) activating hypertrophic, apoptotic and Ca2+ signalling pathways; and (3) decreasing the efficiency of SR Ca2+ release.
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Affiliation(s)
- Kenneth T. MacLeod
- National Heart & Lung InstituteImperial Centre for Translational and Experimental MedicineImperial CollegeHammersmith HospitalLondonUK
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Trum M, Riechel J, Wagner S. Cardioprotection by SGLT2 Inhibitors-Does It All Come Down to Na +? Int J Mol Sci 2021; 22:ijms22157976. [PMID: 34360742 PMCID: PMC8347698 DOI: 10.3390/ijms22157976] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/22/2021] [Accepted: 07/22/2021] [Indexed: 12/15/2022] Open
Abstract
Sodium-glucose co-transporter 2 inhibitors (SGLT2i) are emerging as a new treatment strategy for heart failure with reduced ejection fraction (HFrEF) and—depending on the wistfully awaited results of two clinical trials (DELIVER and EMPEROR-Preserved)—may be the first drug class to improve cardiovascular outcomes in patients suffering from heart failure with preserved ejection fraction (HFpEF). Proposed mechanisms of action of this class of drugs are diverse and include metabolic and hemodynamic effects as well as effects on inflammation, neurohumoral activation, and intracellular ion homeostasis. In this review we focus on the growing body of evidence for SGLT2i-mediated effects on cardiac intracellular Na+ as an upstream mechanism. Therefore, we will first give a short overview of physiological cardiomyocyte Na+ handling and its deterioration in heart failure. On this basis we discuss the salutary effects of SGLT2i on Na+ homeostasis by influencing NHE1 activity, late INa as well as CaMKII activity. Finally, we highlight the potential relevance of these effects for systolic and diastolic dysfunction as well as arrhythmogenesis.
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Firth JM, Yang HY, Francis AJ, Islam N, MacLeod KT. The Effect of Estrogen on Intracellular Ca 2+ and Na + Regulation in Heart Failure. ACTA ACUST UNITED AC 2020; 5:901-912. [PMID: 33015413 PMCID: PMC7524784 DOI: 10.1016/j.jacbts.2020.06.013] [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: 03/26/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 12/31/2022]
Abstract
During the progression toward heart failure, indicators of in vivo whole-heart function suggest greater impairment in the absence of estrogen. At the single cardiac myocyte level, the absence of estrogen results in further reduction of Ca2+ transient amplitudes, further slowing of transient decay kinetics, less SR Ca2+ content, and a further increase in Ca2+ spark frequencies and spark-mediated SR leak compared with animals with normal estrus cycles. Cardiac myocyte Na+ regulation is also more disrupted in the absence of estrogen.
Contradictory findings of estrogen supplementation in cardiac disease highlight the need to investigate the involvement of estrogen in the progression of heart failure in an animal model that lacks traditional comorbidities. Heart failure was induced by aortic constriction (AC) in female guinea pigs. Selected AC animals were ovariectomized (ACOV), and a group of these received 17β-estradiol supplementation (ACOV+E). One hundred-fifty days post-AC surgery, left-ventricular myocytes were isolated, and their electrophysiology and Ca2+ and Na+ regulation were examined. Long-term absence of ovarian hormones exacerbates the decline in cardiac function during the progression to heart failure. Estrogen supplementation reverses these aggravating effects.
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Key Words
- AC, aortic constriction
- ACOV+E, aortic constriction with ovariectomy, supplemented with 17β-estradiol
- ACOV, aortic constriction with ovariectomy
- FS, fractional shortening
- ICa, l-type Ca2+ channel current (cadmium-sensitive)
- INa,L, late Na+ current (ranolazine-sensitive)
- NCX, Na+/Ca2+ exchange
- OV, ovariectomy
- SERCA, Sarco/endoplasmic reticulum Ca2+-ATPase
- SR, sarcoplasmic reticulum
- calcium regulation
- cardiomyocytes
- estrogen
- excitation-contraction coupling
- female
- heart failure
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Affiliation(s)
- Jahn M Firth
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, London, United Kingdom
| | - Hsiang-Yu Yang
- Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (R.O.C.)
| | - Alice J Francis
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, London, United Kingdom
| | - Najah Islam
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, London, United Kingdom
| | - Kenneth T MacLeod
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, London, United Kingdom
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Horváth B, Hézső T, Kiss D, Kistamás K, Magyar J, Nánási PP, Bányász T. Late Sodium Current Inhibitors as Potential Antiarrhythmic Agents. Front Pharmacol 2020; 11:413. [PMID: 32372952 PMCID: PMC7184885 DOI: 10.3389/fphar.2020.00413] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 03/18/2020] [Indexed: 12/19/2022] Open
Abstract
Based on recent findings, an increased late sodium current (INa,late) plays an important pathophysiological role in cardiac diseases, including rhythm disorders. The article first describes what is INa,late and how it functions under physiological circumstances. Next, it shows the wide range of cellular mechanisms that can contribute to an increased INa,late in heart diseases, and also discusses how the upregulated INa,late can play a role in the generation of cardiac arrhythmias. The last part of the article is about INa,late inhibiting drugs as potential antiarrhythmic agents, based on experimental and preclinical data as well as in the light of clinical trials.
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Affiliation(s)
- Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Dénes Kiss
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Division of Sport Physiology, University of Debrecen, Debrecen, Hungary
| | - Péter P. Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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Sossalla S, Vollmann D. Arrhythmia-Induced Cardiomyopathy. DEUTSCHES ARZTEBLATT INTERNATIONAL 2019; 115:335-341. [PMID: 29875055 DOI: 10.3238/arztebl.2018.0335] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 10/01/2017] [Accepted: 02/22/2018] [Indexed: 12/28/2022]
Abstract
BACKGROUND Heart failure affects 1–2% of the population and is associated with elevated morbidity and mortality. Cardiac arrhythmias are often a result of heart failure, but they can cause left-ventricular systolic dysfunction (LVSD) as an arrhythmia-induced cardiomyopathy (AIC). This causal relationship should be borne in mind by the physician treating a patient with systolic heart failure in association with cardiac arrhythmia. METHODS This review is based on pertinent publications retrieved by a selective search in PubMed (1987–2017) and on the recommendations in current guidelines. RESULTS The key criterion for the diagnosis of an AIC is the demonstration of a persistent arrhythmia (including pathological tachycardia) together with an LVSD whose origin cannot be explained on any other basis. Nearly any type of tachyarrhythmia or frequent ventricular extrasystoles can lead, if persistent, to a progressively severe LVSD. The underlying pathophysiologic mechanisms are incompletely understood; the increased ventricular rate, asynchronous cardiac contractions, and neurohumoral activation all seem to play a role. The most common precipitating factors are supraventricular tachycardias in children and atrial fibrillation in adults. Recent studies have shown that the causal significance of atrial fibrillation in otherwise unexplained LVSD is underappreciated. The treatment of AIC consists primarily of the treatment of the underlying arrhythmia, generally with drugs such as beta-blockers and amiodarone. Depending on the type of arrhythmia, catheter ablation for long-term treatment should also be considered where appropriate. The diagnosis of AIC is considered to be well established when the LVSD normalizes or improves within a few weeks or months of the start of targeted treatment of the arrhythmia. CONCLUSION An AIC is potentially reversible. The timely recognition of this condition and the appropriate treatment of the underlying arrhythmia can substantially improve patient outcomes.
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Affiliation(s)
- Samuel Sossalla
- Department of Internal Medicine II, Cardiology, Pneumology, Intensive Care, University Hospital Regensburg
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Ke HY, Yang HY, Francis AJ, Collins TP, Surendran H, Alvarez-Laviada A, Firth JM, MacLeod KT. Changes in cellular Ca 2+ and Na + regulation during the progression towards heart failure in the guinea pig. J Physiol 2019; 598:1339-1359. [PMID: 30811606 PMCID: PMC7187457 DOI: 10.1113/jp277038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 02/26/2019] [Indexed: 12/19/2022] Open
Abstract
Key points During compensated hypertrophy in vivo fractional shortening (FS) remains constant until heart failure (HF) develops, when FS decreases from 70% to 39%. Compensated hypertrophy is accompanied by an increase in INa,late and a decrease in Na+,K+‐ATPase current. These changes persist as HF develops. SR Ca2+ content increases during compensated hypertrophy then decreases in HF. In healthy cells, increases in SR Ca2+ content and Ca2+ transients can be achieved by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant during compensated hypertrophy then decreases in HF, when there is also an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment.
Abstract We followed changes in cardiac myocyte Ca2+ and Na+ regulation from the formation of compensated hypertrophy (CH) until signs of heart failure (HF) are apparent using a trans‐aortic pressure overload (TAC) model. In this model, in vivo fractional shortening (FS) remained constant despite HW:BW ratio increasing by 39% (CH) until HF developed 150 days post‐TAC when FS decreased from 70% to 39%. Using live and fixed fluorescence imaging and electrophysiological techniques, we found an increase in INa,late from –0.34 to –0.59 A F−1 and a decrease in Na+,K+‐ATPase current from 1.09 A F−1 to 0.54 A F−1 during CH. These changes persisted as HF developed (INa,late increased to –0.82 A F−1 and Na+,K+‐ATPase current decreased to 0.51 A F−1). Sarcoplasmic reticulum (SR) Ca2+ content increased during CH then decreased in HF (from 32 to 15 μm l−1) potentially supporting the maintenance of FS in the whole heart and Ca2+ transients in single myocytes during the former stage. We showed using glycoside blockade in healthy myocytes that increases in SR Ca2+ content and Ca2+ transients can be driven by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant in CH but decreases (τ for SERCA‐mediated Ca2+ removal changed from 6.3 to 3.0 s−1) in HF. In HF there was an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment. During compensated hypertrophy in vivo fractional shortening (FS) remains constant until heart failure (HF) develops, when FS decreases from 70% to 39%. Compensated hypertrophy is accompanied by an increase in INa,late and a decrease in Na+,K+‐ATPase current. These changes persist as HF develops. SR Ca2+ content increases during compensated hypertrophy then decreases in HF. In healthy cells, increases in SR Ca2+ content and Ca2+ transients can be achieved by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant during compensated hypertrophy then decreases in HF, when there is also an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment.
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Affiliation(s)
- H-Y Ke
- Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (ROC)
| | - H-Y Yang
- Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (ROC)
| | - A J Francis
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - T P Collins
- The Wellcome Trust, Gibbs Building, 215 Euston Road, London, NW1 2BE, UK
| | - H Surendran
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - A Alvarez-Laviada
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - J M Firth
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - K T MacLeod
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
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Despa S. Myocyte [Na +] i Dysregulation in Heart Failure and Diabetic Cardiomyopathy. Front Physiol 2018; 9:1303. [PMID: 30258369 PMCID: PMC6144935 DOI: 10.3389/fphys.2018.01303] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 08/29/2018] [Indexed: 12/19/2022] Open
Abstract
By controlling the function of various sarcolemmal and mitochondrial ion transporters, intracellular Na+ concentration ([Na+]i) regulates Ca2+ cycling, electrical activity, the matching of energy supply and demand, and oxidative stress in cardiac myocytes. Thus, maintenance of myocyte Na+ homeostasis is vital for preserving the electrical and contractile activity of the heart. [Na+]i is set by the balance between the passive Na+ entry through numerous pathways and the pumping of Na+ out of the cell by the Na+/K+-ATPase. This equilibrium is perturbed in heart failure, resulting in higher [Na+]i. More recent studies have revealed that [Na+]i is also increased in myocytes from diabetic hearts. Elevated [Na+]i causes oxidative stress and augments the sarcoplasmic reticulum Ca2+ leak, thus amplifying the risk for arrhythmias and promoting heart dysfunction. This mini-review compares and contrasts the alterations in Na+ extrusion and/or Na+ uptake that underlie the [Na+]i increase in heart failure and diabetes, with a particular emphasis on the emerging role of Na+ - glucose cotransporters in the diabetic heart.
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Affiliation(s)
- Sanda Despa
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, United States
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Reher TA, Wang Z, Hsueh CH, Chang PC, Pan Z, Kumar M, Patel J, Tan J, Shen C, Chen Z, Fishbein MC, Rubart M, Boyden P, Chen PS. Small-Conductance Calcium-Activated Potassium Current in Normal Rabbit Cardiac Purkinje Cells. J Am Heart Assoc 2017; 6:JAHA.117.005471. [PMID: 28550095 PMCID: PMC5669169 DOI: 10.1161/jaha.117.005471] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Background Purkinje cells (PCs) are important in cardiac arrhythmogenesis. Whether small‐conductance calcium‐activated potassium (SK) channels are present in PCs remains unclear. We tested the hypotheses that subtype 2 SK (SK2) channel proteins and apamin‐sensitive SK currents are abundantly present in PCs. Methods and Results We studied 25 normal rabbit ventricles, including 13 patch‐clamp studies, 4 for Western blotting, and 8 for immunohistochemical staining. Transmembrane action potentials were recorded in current‐clamp mode using the perforated‐patch technique. For PCs, the apamin (100 nmol/L) significantly prolonged action potential duration measured to 80% repolarization by an average of 10.4 ms (95% CI, 0.11–20.72) (n=9, P=0.047). Voltage‐clamp study showed that apamin‐sensitive SK current density was significantly larger in PCs compared with ventricular myocytes at potentials ≥0 mV. Western blotting of SK2 expression showed that the SK2 protein expression in the midmyocardium was 58% (P=0.028) and the epicardium was 50% (P=0.018) of that in the pseudotendons. Immunostaining of SK2 protein showed that PCs stained stronger than ventricular myocytes. Confocal microscope study showed SK2 protein was distributed to the periphery of the PCs. Conclusions SK2 proteins are more abundantly present in the PCs than in the ventricular myocytes of normal rabbit ventricles. Apamin‐sensitive SK current is important in ventricular repolarization of normal PCs.
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Affiliation(s)
- Thomas A Reher
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Zhuo Wang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN.,Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Chia-Hsiang Hsueh
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Po-Cheng Chang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Zhenwei Pan
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Mohineesh Kumar
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Jheel Patel
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Jian Tan
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Changyu Shen
- Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Zhenhui Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Michael C Fishbein
- Department of Pathology and Laboratory Medicine, UCLA Medical Center, Los Angeles, CA
| | - Michael Rubart
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
| | - Penelope Boyden
- Department of Pharmacology, Columbia University, New York, NY
| | - Peng-Sheng Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
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Clancy CE, Chen-Izu Y, Bers DM, Belardinelli L, Boyden PA, Csernoch L, Despa S, Fermini B, Hool LC, Izu L, Kass RS, Lederer WJ, Louch WE, Maack C, Matiazzi A, Qu Z, Rajamani S, Rippinger CM, Sejersted OM, O'Rourke B, Weiss JN, Varró A, Zaza A. Deranged sodium to sudden death. J Physiol 2015; 593:1331-45. [PMID: 25772289 DOI: 10.1113/jphysiol.2014.281204] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/14/2014] [Indexed: 12/19/2022] Open
Abstract
In February 2014, a group of scientists convened as part of the University of California Davis Cardiovascular Symposium to bring together experimental and mathematical modelling perspectives and discuss points of consensus and controversy on the topic of sodium in the heart. This paper summarizes the topics of presentation and discussion from the symposium, with a focus on the role of aberrant sodium channels and abnormal sodium homeostasis in cardiac arrhythmias and pharmacotherapy from the subcellular scale to the whole heart. Two following papers focus on Na(+) channel structure, function and regulation, and Na(+)/Ca(2+) exchange and Na(+)/K(+) ATPase. The UC Davis Cardiovascular Symposium is a biannual event that aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The focus on Na(+) in the 2014 symposium stemmed from the multitude of recent studies that point to the importance of maintaining Na(+) homeostasis in the heart, as disruption of homeostatic processes are increasingly identified in cardiac disease states. Understanding how disruption in cardiac Na(+)-based processes leads to derangement in multiple cardiac components at the level of the cell and to then connect these perturbations to emergent behaviour in the heart to cause disease is a critical area of research. The ubiquity of disruption of Na(+) channels and Na(+) homeostasis in cardiac disorders of excitability and mechanics emphasizes the importance of a fundamental understanding of the associated mechanisms and disease processes to ultimately reveal new targets for human therapy.
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Affiliation(s)
- Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome Building Rm 3503, Davis, CA, 95616-8636, USA
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Lambert R, Srodulski S, Peng X, Margulies KB, Despa F, Despa S. Intracellular Na+ Concentration ([Na+]i) Is Elevated in Diabetic Hearts Due to Enhanced Na+-Glucose Cotransport. J Am Heart Assoc 2015; 4:e002183. [PMID: 26316524 PMCID: PMC4599504 DOI: 10.1161/jaha.115.002183] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Background Intracellular Na+ concentration ([Na+]i) regulates Ca2+ cycling, contractility, metabolism, and electrical stability of the heart. [Na+]i is elevated in heart failure, leading to arrhythmias and oxidative stress. We hypothesized that myocyte [Na+]i is also increased in type 2 diabetes (T2D) due to enhanced activity of the Na+–glucose cotransporter. Methods and Results To test this hypothesis, we used myocardial tissue from humans with T2D and a rat model of late-onset T2D (HIP rat). Western blot analysis showed increased Na+–glucose cotransporter expression in failing hearts from T2D patients compared with nondiabetic persons (by 73±13%) and in HIP rat hearts versus wild-type (WT) littermates (by 61±8%). [Na+]i was elevated in HIP rat myocytes both at rest (14.7±0.9 versus 11.4±0.7 mmol/L in WT) and during electrical stimulation (17.3±0.8 versus 15.0±0.7 mmol/L); however, the Na+/K+-pump function was similar in HIP and WT cells, suggesting that higher [Na+]i is due to enhanced Na+ entry in diabetic hearts. Indeed, Na+ influx was significantly larger in myocytes from HIP versus WT rats (1.77±0.11 versus 1.29±0.06 mmol/L per minute). Na+–glucose cotransporter inhibition with phlorizin or glucose-free solution greatly reduced Na+ influx in HIP myocytes (to 1.20±0.16 mmol/L per minute), whereas it had no effect in WT cells. Phlorizin also significantly decreased glucose uptake in HIP myocytes (by 33±9%) but not in WT, indicating an increased reliance on the Na+–glucose cotransporter for glucose uptake in T2D hearts. Conclusions Myocyte Na+–glucose cotransport is enhanced in T2D, which increases Na+ influx and causes Na+ overload. Higher [Na+]i may contribute to arrhythmogenesis and oxidative stress in diabetic hearts.
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Affiliation(s)
- Rebekah Lambert
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY (R.L., S.S., X.P., F.D., S.D.)
| | - Sarah Srodulski
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY (R.L., S.S., X.P., F.D., S.D.)
| | - Xiaoli Peng
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY (R.L., S.S., X.P., F.D., S.D.)
| | - Kenneth B Margulies
- Cardiovascular Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA (K.B.M.)
| | - Florin Despa
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY (R.L., S.S., X.P., F.D., S.D.)
| | - Sanda Despa
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY (R.L., S.S., X.P., F.D., S.D.)
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Horvath B, Bers DM. The late sodium current in heart failure: pathophysiology and clinical relevance. ESC Heart Fail 2014; 1:26-40. [PMID: 28834665 DOI: 10.1002/ehf2.12003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 07/13/2014] [Accepted: 07/14/2014] [Indexed: 12/19/2022] Open
Abstract
Large and growing body of data suggest that an increased late sodium current (INa,late ) can have a significant pathophysiological role in heart failure and other heart diseases. The first goal of this article is to describe how INa,late functions under physiological circumstances. The second goal is to show the wide range of cellular mechanisms that can increase INa,late in cardiac disease, and also to describe how the up-regulated INa,late contributes to the pathophysiology of heart failure. The final section of the article discusses the possible use of INa,late -modifying drugs in heart failure, on the basis of experimental and preclinical data.
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Affiliation(s)
- Balazs Horvath
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Donald M Bers
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, USA
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Despa S, Bers DM. Na⁺ transport in the normal and failing heart - remember the balance. J Mol Cell Cardiol 2013; 61:2-10. [PMID: 23608603 DOI: 10.1016/j.yjmcc.2013.04.011] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 03/22/2013] [Accepted: 04/11/2013] [Indexed: 12/12/2022]
Abstract
In the heart, intracellular Na(+) concentration ([Na(+)]i) is a key modulator of Ca(2+) cycling, contractility and cardiac myocyte metabolism. Several Na(+) transporters are electrogenic, thus they both contribute to shaping the cardiac action potential and at the same time are affected by it. [Na(+)]i is controlled by the balance between Na(+) influx through various pathways, including the Na(+)/Ca(2+) exchanger and Na(+) channels, and Na(+) extrusion via the Na(+)/K(+)-ATPase. [Na(+)]i is elevated in HF due to a combination of increased entry through Na(+) channels and/or Na(+)/H(+) exchanger and reduced activity of the Na(+)/K(+)-ATPase. Here we review the major Na(+) transport pathways in cardiac myocytes and how they participate in regulating [Na(+)]i in normal and failing hearts. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes."
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Affiliation(s)
- Sanda Despa
- Department of Pharmacology, University of California, Davis, CA, USA.
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Hsieh YC, Chang PC, Hsueh CH, Lee YS, Shen C, Weiss JN, Chen Z, Ai T, Lin SF, Chen PS. Apamin-sensitive potassium current modulates action potential duration restitution and arrhythmogenesis of failing rabbit ventricles. Circ Arrhythm Electrophysiol 2013; 6:410-8. [PMID: 23420832 DOI: 10.1161/circep.111.000152] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
BACKGROUND Apamin-sensitive K currents (I(KAS)) are upregulated in heart failure. We hypothesize that apamin can flatten action potential duration restitution (APDR) curve and can reduce ventricular fibrillation duration in failing ventricles. METHODS AND RESULTS We simultaneously mapped membrane potential and intracellular Ca (Ca(i)) in 7 rabbit hearts with pacing-induced heart failure and in 7 normal hearts. A dynamic pacing protocol was used to determine APDR at baseline and after apamin (100 nmol/L) infusion. Apamin did not change APD(80) in normal ventricles, but prolonged APD(80) in failing ventricles at either long (≥300 ms) or short (≤170 ms) pacing cycle length, but not at intermediate pacing cycle length. The maximal slope of APDR curve was 2.03 (95% confidence interval, 1.73-2.32) in failing ventricles and 1.26 (95% confidence interval, 1.13-1.40) in normal ventricles at baseline (P=0.002). After apamin administration, the maximal slope of APDR in failing ventricles decreased to 1.43 (95% confidence interval, 1.01-1.84; P=0.018), whereas no significant changes were observed in normal ventricles. During ventricular fibrillation in failing ventricles, the number of phase singularities (baseline versus apamin, 4.0 versus 2.5), dominant frequency (13.0 versus 10.0 Hz), and ventricular fibrillation duration (160 versus 80 s) were all significantly (P<0.05) decreased by apamin. CONCLUSIONS Apamin prolongs APD at long and short, but not at intermediate pacing cycle length in failing ventricles. I(KAS) upregulation may be antiarrhythmic by preserving the repolarization reserve at slow heart rate, but is proarrhythmic by steepening the slope of APDR curve, which promotes the generation and maintenance of ventricular fibrillation.
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Affiliation(s)
- Yu-Cheng Hsieh
- Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Milberg P, Pott C, Frommeyer G, Fink M, Ruhe M, Matsuda T, Baba A, Klocke R, Quang TH, Nikol S, Stypmann J, Osada N, Müller FU, Breithardt G, Noble D, Eckardt L. Acute inhibition of the Na(+)/Ca(2+) exchanger reduces proarrhythmia in an experimental model of chronic heart failure. Heart Rhythm 2011; 9:570-8. [PMID: 22075452 DOI: 10.1016/j.hrthm.2011.11.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Indexed: 11/19/2022]
Abstract
BACKGROUND Molecular remodeling in heart failure includes slowing of repolarization, leading to proarrhythmia. OBJECTIVE To evaluate the effects of Na(+)/Ca(2+) exchanger (NCX) inhibition on repolarization as a novel antiarrhythmic concept in chronic heart failure (CHF). METHODS AND RESULTS CHF was induced by rapid ventricular pacing in rabbits. Left ventricular function was assessed by echocardiography. Monophasic action potentials (MAPs) showed a prolongation of repolarization in CHF after atrioventricular block and stimulation at different cycle lengths. Sotalol (100 μM, n = 13) or veratridine (0.5 μM; n = 15) resulted in a further significant increase in the MAP duration. CHF was associated with an increased dispersion of repolarization, as compared with sotalol-treated (+22 ± 7 ms; P < .05) and veratridine-treated (+20 ± 6 ms; P < .05) sham hearts. In the presence of a low potassium concentration, sotalol and veratridine reproducibly induced early afterdepolarizations (EADs) and polymorphic ventricular tachyarrhythmias (VTs). SEA0400 (1 μM), a pharmacological inhibitor of NCX, significantly shortened the MAP duration (P < .01) and reduced dispersion (P < .05). It suppressed EAD in 6 of 13 sotalol-treated failing hearts and in 9 of 10 veratridine-treated failing hearts, leading to a reduction in VT (60% in sotalol-treated failing hearts and 83% in veratridine-treated failing hearts). Simulations using a mathematical model showed a reduction in the action potential duration and the number of EADs by the NCX block in all subgroups. CONCLUSIONS In an experimental model of CHF, the acute inhibition of NCX (1) reduces the MAP duration, (2) decreases dispersion of repolarization, and (3) suppresses EAD and VT. Our observations indicate for the first time that pharmacological NCX inhibition increases repolarization reserve and protects against VTs in heart failure.
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Affiliation(s)
- Peter Milberg
- Division of Clinical and Experimental Electrophysiology, Department of Cardiology and Angiology, Westfälische Wilhelms-University, University Hospital Münster, Münster, Germany.
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Slow contractions characterize failing rat hearts. Basic Res Cardiol 2008; 103:328-44. [DOI: 10.1007/s00395-008-0719-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Accepted: 02/08/2008] [Indexed: 10/22/2022]
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Schillinger W, Christians C, Sossalla S, Teucher N, Nguyen Van P, Kögler H, Zeitz O, Hasenfuss G. α1-adrenergic stress induces downregulation of Na+/Ca2+exchanger in myocardial preparations from rabbits at physiological preload. Eur J Heart Fail 2007; 9:329-35. [PMID: 17257893 DOI: 10.1016/j.ejheart.2006.10.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2006] [Revised: 07/27/2006] [Accepted: 10/12/2006] [Indexed: 11/25/2022] Open
Abstract
Alpha1-adrenergic stimulation and mechanical load are considered crucial for the expression of sarcolemmal Na+/Ca2+ exchanger (NCX1). However, the interaction between these processes is unknown. We investigated electrically stimulated (1 Hz, 1.75 mmol/L Ca2+) rabbit ventricular trabeculae at physiological preload under stimulation by the selective alpha1-agonist phenylephrine (PE, 10 micromol/L). Using quantitative real-time PCR, downregulation of mRNA to 76.5% (p<0.05) was found, while B-type natriuretic peptide (BNP) was increased to 569.5% (p<0.05) compared to control. These changes were abolished in the presence of both the alpha1-blocker prazosin (13 micromol/L) and the PKC inhibitor GF109203X (1 micromol/L). Furthermore, no changes in NCX mRNA levels under the influence of PE were found in unstretched trabeculae or in unstretched isolated rabbit myocytes (24 h), while BNP was increased in both preparations. In addition, since the alpha1-adrenergic effect could be Ca2+-dependent we tested increased extracellular Ca2+ (3.0 mmol/L) in stretched trabeculae and found downregulation of NCX1 to 75.2% (p<0.05). alpha1-stimulation decreases NCX1 mRNA in rabbit myocardium via PKC. This is critically load-dependent and may be mediated by changes in [Ca2+]. In hypertrophy and heart failure, distinct phenotypes with respect to NCX1 expression may result from the interaction between mechanical load and alpha1-adrenergic stimulation.
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Affiliation(s)
- Wolfgang Schillinger
- Universitaet Goettingen, Herzzentrum, Kardiologie und Pneumologie, Goettingen, Germany.
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