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Souza DSD, Menezes-Filho JERD, Santos-Miranda A, Jesus ICGD, Silva Neto JA, Guatimosim S, Cruz JS, Vasconcelos CMLD. Calcium overload-induced arrhythmia is suppressed by farnesol in rat heart. Eur J Pharmacol 2019; 859:172488. [DOI: 10.1016/j.ejphar.2019.172488] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 06/20/2019] [Accepted: 06/20/2019] [Indexed: 01/01/2023]
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Hou P, Shi J, White KM, Gao Y, Cui J. ML277 specifically enhances the fully activated open state of KCNQ1 by modulating VSD-pore coupling. eLife 2019; 8:e48576. [PMID: 31329101 PMCID: PMC6684268 DOI: 10.7554/elife.48576] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/22/2019] [Indexed: 12/16/2022] Open
Abstract
Upon membrane depolarization, the KCNQ1 potassium channel opens at the intermediate (IO) and activated (AO) states of the stepwise voltage-sensing domain (VSD) activation. In the heart, KCNQ1 associates with KCNE1 subunits to form IKs channels that regulate heart rhythm. KCNE1 suppresses the IO state so that the IKs channel opens only to the AO state. Here, we tested modulations of human KCNQ1 channels by an activator ML277 in Xenopus oocytes. It exclusively changes the pore opening properties of the AO state without altering the IO state, but does not affect VSD activation. These observations support a distinctive mechanism responsible for the VSD-pore coupling at the AO state that is sensitive to ML277 modulation. ML277 provides insights and a tool to investigate the gating mechanism of KCNQ1 channels, and our study reveals a new strategy for treating long QT syndrome by specifically enhancing the AO state of native IKs currents.
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Affiliation(s)
- Panpan Hou
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
| | - Jingyi Shi
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
| | - Kelli McFarland White
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
| | | | - Jianmin Cui
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
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Johnson EK, Springer SJ, Wang W, Dranoff EJ, Zhang Y, Kanter EM, Yamada KA, Nerbonne JM. Differential Expression and Remodeling of Transient Outward Potassium Currents in Human Left Ventricles. Circ Arrhythm Electrophysiol 2019; 11:e005914. [PMID: 29311162 DOI: 10.1161/circep.117.005914] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 11/30/2017] [Indexed: 11/16/2022]
Abstract
BACKGROUND Myocardial, transient, outward currents, Ito, have been shown to play pivotal roles in action potential (AP) repolarization and remodeling in animal models. The properties and contribution of Ito to left ventricular (LV) repolarization in the human heart, however, are poorly defined. METHODS AND RESULTS Whole-cell, voltage-clamp recordings, acquired at physiological (35°C to 37°C) temperatures, from myocytes isolated from the LV of nonfailing human hearts identified 2 distinct transient currents, Ito,fast (Ito,f) and Ito,slow (Ito,s), with significantly (P<0.0001) different rates of recovery from inactivation and pharmacological sensitives: Ito,f recovers in ≈10 ms, 100× faster than Ito,s, and is selectively blocked by the Kv4 channel toxin, SNX-482. Current-clamp experiments revealed regional differences in AP waveforms, notably a phase 1 notch in LV subepicardial myocytes. Dynamic clamp-mediated addition/removal of modeled human ventricular Ito,f, resulted in hyperpolarization or depolarization, respectively, of the notch potential, whereas slowing the rate of Ito,f inactivation resulted in AP collapse. AP-clamp experiments demonstrated that changes in notch potentials modified the time course and amplitudes of voltage-gated Ca2+ currents, ICa. In failing LV subepicardial myocytes, Ito,f was reduced and Ito,s was increased, notch and plateau potentials were depolarized (P<0.0001) and AP durations were prolonged (P<0.001). CONCLUSIONS Ito,f and Ito,s are differentially expressed in nonfailing human LV, contributing to regional heterogeneities in AP waveforms. Ito,f regulates notch and plateau potentials and modulates the time course and amplitude of ICa. Slowing Ito,f inactivation results in dramatic AP shortening. Remodeling of Ito,f in failing human LV subepicardial myocytes attenuates transmural differences in AP waveforms.
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Affiliation(s)
- Eric K Johnson
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO
| | - Steven J Springer
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO
| | - Wei Wang
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO
| | - Edward J Dranoff
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO
| | - Yan Zhang
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO
| | - Evelyn M Kanter
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO
| | - Kathryn A Yamada
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO
| | - Jeanne M Nerbonne
- From the Cardiovascular Division, Department of Medicine (E.K.J., S.J.S., W.W., E.J.D., Y.Z., E.M.K., K.A.Y., J.M.N.) and Department of Developmental Biology (J.M.N.), Washington University School of Medicine, St. Louis, MO.
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Perissinotti L, Guo J, Kudaibergenova M, Lees-Miller J, Ol'khovich M, Sharapova A, Perlovich GL, Muruve DA, Gerull B, Noskov SY, Duff HJ. The Pore-Lipid Interface: Role of Amino-Acid Determinants of Lipophilic Access by Ivabradine to the hERG1 Pore Domain. Mol Pharmacol 2019; 96:259-271. [PMID: 31182542 DOI: 10.1124/mol.118.115642] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 05/28/2019] [Indexed: 12/14/2022] Open
Abstract
Abnormal cardiac electrical activity is a common side effect caused by unintended block of the promiscuous drug target human ether-à-go-go-related gene (hERG1), the pore-forming domain of the delayed rectifier K+ channel in the heart. hERG1 block leads to a prolongation of the QT interval, a phase of the cardiac cycle that underlies myocyte repolarization detectable on the electrocardiogram. Even newly released drugs such as heart-rate lowering agent ivabradine block the rapid delayed rectifier current IKr, prolong action potential duration, and induce potentially lethal arrhythmia known as torsades de pointes. In this study, we describe a critical drug-binding pocket located at the lateral pore surface facing the cellular membrane. Mutations of the conserved M651 residue alter ivabradine-induced block but not by the common hERG1 blocker dofetilide. As revealed by molecular dynamics simulations, binding of ivabradine to a lipophilic pore access site is coupled to a state-dependent reorientation of aromatic residues F557 and F656 in the S5 and S6 helices. We show that the M651 mutation impedes state-dependent dynamics of F557 and F656 aromatic cassettes at the protein-lipid interface, which has a potential to disrupt drug-induced block of the channel. This fundamentally new mechanism coupling the channel dynamics and small-molecule access from the membrane into the hERG1 intracavitary site provides a simple rationale for the well established state-dependence of drug blockade. SIGNIFICANCE STATEMENT: The drug interference with the function of the cardiac hERG channels represents one of the major sources of drug-induced heart disturbances. We found a novel and a critical drug-binding pocket adjacent to a lipid-facing surface of the hERG1 channel, which furthers our molecular understanding of drug-induced QT syndrome.
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Affiliation(s)
- Laura Perissinotti
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Jiqing Guo
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Meruyert Kudaibergenova
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - James Lees-Miller
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Marina Ol'khovich
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Angelica Sharapova
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - German L Perlovich
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Daniel A Muruve
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Brenda Gerull
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Sergei Yu Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
| | - Henry J Duff
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada (L.P., M.K., S.Y.N.); Libin Cardiovascular Institute of Alberta (J.G., J.-L.M., H.J.D.) and Snyder Institute for Chronic Diseases (D.A.M.), Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russian Federation (M.O., A.S., G.L.P.); Department of Cardiac Sciences and Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (B.G.); and Comprehensive Heart Failure Center and Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany (B.G.)
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55
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Osman J, Tan SC, Lee PY, Low TY, Jamal R. Sudden Cardiac Death (SCD) - risk stratification and prediction with molecular biomarkers. J Biomed Sci 2019; 26:39. [PMID: 31118017 PMCID: PMC6530025 DOI: 10.1186/s12929-019-0535-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 05/16/2019] [Indexed: 12/15/2022] Open
Abstract
Sudden cardiac death (SCD) is a sudden, unexpected death that is caused by the loss of heart function. While SCD affects many patients suffering from coronary artery diseases (CAD) and heart failure (HF), a considerable number of SCD events occur in asymptomatic individuals. Certain risk factors for SCD have been identified and incorporated in different clinical scores, however, risk stratification using such algorithms is only useful for health management rather than for early detection and prediction of future SCD events in high-risk individuals. In this review, we discuss different molecular biomarkers that are used for early detection of SCD. This includes genetic biomarkers, where the majority of them are genomic variants for genes that encode for ion channels. Meanwhile, protein biomarkers often denote proteins that play roles in pathophysiological processes that lead to CAD and HF, notably (i) atherosclerosis that involves oxidative stress and inflammation, as well as (ii) cardiac tissue damage that involves neurohormonal and hemodynamic regulation and myocardial stress. Finally, we outline existing challenges and future directions including the use of OMICS strategy for biomarker discovery and the multimarker panels.
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Affiliation(s)
- Junaida Osman
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
| | - Shing Cheng Tan
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
| | - Pey Yee Lee
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
| | - Teck Yew Low
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia.
| | - Rahman Jamal
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
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56
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Policarová M, Novotný T, Bébarová M. Impaired Adrenergic/Protein Kinase A Response of Slow Delayed Rectifier Potassium Channels as a Long QT Syndrome Motif: Importance and Unknowns. Can J Cardiol 2019; 35:511-522. [DOI: 10.1016/j.cjca.2018.11.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 11/20/2018] [Accepted: 11/20/2018] [Indexed: 12/29/2022] Open
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57
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Hamilton S, Polina I, Terentyeva R, Bronk P, Kim TY, Roder K, Clements RT, Koren G, Choi BR, Terentyev D. PKA phosphorylation underlies functional recruitment of sarcolemmal SK2 channels in ventricular myocytes from hypertrophic hearts. J Physiol 2019; 598:2847-2873. [PMID: 30771223 PMCID: PMC7496687 DOI: 10.1113/jp277618] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 02/08/2019] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Small-conductance Ca2+ -activated K+ (SK) channels expressed in ventricular myocytes are dormant in health, yet become functional in cardiac disease. SK channels are voltage independent and their gating is controlled by intracellular [Ca2+ ] in a biphasic manner. Submicromolar [Ca2+ ] activates the channel via constitutively-bound calmodulin, whereas higher [Ca2+ ] exerts inhibitory effect during depolarization. Using a rat model of cardiac hypertrophy induced by thoracic aortic banding, we found that functional upregulation of SK2 channels in hypertrophic rat ventricular cardiomyocytes is driven by protein kinase A (PKA) phosphorylation. Using site-directed mutagenesis, we identified serine-465 as the site conferring PKA-dependent effects on SK2 channel function. PKA phosphorylation attenuates ISK rectification by reducing the Ca2+ /voltage-dependent inhibition of SK channels without changing their sensitivity to activating submicromolar [Ca2+ ]i . This mechanism underlies the functional recruitment of SK channels not only in cardiac disease, but also in normal physiology, contributing to repolarization under conditions of enhanced adrenergic drive. ABSTRACT Small-conductance Ca2+ -activated K+ (SK) channels expressed in ventricular myocytes (VMs) are dormant in health, yet become functional in cardiac disease. We aimed to test the hypothesis that post-translational modification of SK channels under conditions accompanied by enhanced adrenergic drive plays a central role in disease-related activation of the channels. We investigated this phenomenon using a rat model of hypertrophy induced by thoracic aortic banding (TAB). Western blot analysis using anti-pan-serine/threonine antibodies demonstrated enhanced phosphorylation of immunoprecipitated SK2 channels in VMs from TAB rats vs. Shams, which was reversible by incubation of the VMs with PKA inhibitor H89 (1 μmol L-1 ). Patch clamped VMs under basal conditions from TABs but not Shams exhibited outward current sensitive to the specific SK inhibitor apamin (100 nmol L-1 ), which was eliminated by inhibition of PKA (1 μmol L-1 ). Beta-adrenergic stimulation (isoproterenol, 100 nmol L-1 ) evoked ISK in VMs from Shams, resulting in shortening of action potentials in VMs and ex vivo optically mapped Sham hearts. Using adenoviral gene transfer, wild-type and mutant SK2 channels were overexpressed in adult rat VMs, revealing serine-465 as the site that elicits PKA-dependent phosphorylation effects on SK2 channel function. Concurrent confocal Ca2+ imaging experiments established that PKA phosphorylation lessens rectification of ISK via reduction Ca2+ /voltage-dependent inhibition of the channels at high [Ca2+ ] without affecting their sensitivity to activation by Ca2+ in the submicromolar range. In conclusion, upregulation of SK channels in diseased VMs is mediated by hyperadrenergic drive in cardiac hypertrophy, with functional effects on the channel conferred by PKA-dependent phosphorylation at serine-465.
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Affiliation(s)
- Shanna Hamilton
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Iuliia Polina
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Medical University of South Carolina, Department of Medicine, Division of Nephrology, Charleston, SC, USA
| | - Radmila Terentyeva
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Peter Bronk
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Tae Yun Kim
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Karim Roder
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Richard T Clements
- Department of Surgery, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, RI, USA
| | - Gideon Koren
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Bum-Rak Choi
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Dmitry Terentyev
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
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58
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Kyo M, Hosokawa K, Ohshimo S, Kida Y, Tanabe Y, Ota K, Shime N. High serum potassium level is associated with successful electrical cardioversion for new-onset atrial fibrillation in the intensive care unit: A retrospective observational study. Anaesth Intensive Care 2019; 47:52-59. [PMID: 30864476 DOI: 10.1177/0310057x18811815] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Electrical cardioversion (ECV) is a potentially life-saving treatment for haemodynamically unstable new-onset atrial fibrillation (AF); however, its efficacy is unsatisfactory. We aimed to elucidate the factors associated with successful ECV and prognosis in patients with AF. This retrospective observational study was conducted in two mixed intensive care units (ICUs) in a university hospital. Patients with new-onset AF who received ECV in the ICU were enrolled. We defined an ECV session as consecutive shocks within 15 minutes. The success of ECV was evaluated five minutes after the session. We analysed the factors associated with successful ECV and ICU mortality. Eighty-five AF patients who received ECV were included. ECV was successful in 41 (48%) patients, and 11 patients (13%) maintained sinus rhythm until ICU discharge. A serum potassium level ≥3.8 mol/L was independently associated with successful ECV in multivariate analysis (odds ratio (OR), 3.13; 95% confidence interval (CI), 1.07-9.11; p = 0.04). Maintenance of sinus rhythm until ICU discharge was significantly associated with ICU survival (OR 9.35; 95% CI 1.02-85.78, p = 0.048). ECV was successful in 48% of patients with new-onset AF developed in the ICU. A serum potassium level ≥3.8 mol/L was independently associated with successful ECV, and sinus rhythm maintained until ICU discharge was independently associated with ICU survival. These results suggested that maintaining a high serum potassium level may be important when considering the effectiveness of ECV for AF in the ICU.
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Affiliation(s)
- Michihito Kyo
- Department of Emergency and Critical Care Medicine, Graduate School of Biomedical & Health Sciences, Hiroshima University, Japan
| | - Koji Hosokawa
- Department of Emergency and Critical Care Medicine, Graduate School of Biomedical & Health Sciences, Hiroshima University, Japan
| | - Shinichiro Ohshimo
- Department of Emergency and Critical Care Medicine, Graduate School of Biomedical & Health Sciences, Hiroshima University, Japan
| | - Yoshiko Kida
- Department of Emergency and Critical Care Medicine, Graduate School of Biomedical & Health Sciences, Hiroshima University, Japan
| | - Yuko Tanabe
- Department of Emergency and Critical Care Medicine, Graduate School of Biomedical & Health Sciences, Hiroshima University, Japan
| | - Kohei Ota
- Department of Emergency and Critical Care Medicine, Graduate School of Biomedical & Health Sciences, Hiroshima University, Japan
| | - Nobuaki Shime
- Department of Emergency and Critical Care Medicine, Graduate School of Biomedical & Health Sciences, Hiroshima University, Japan
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59
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Calloe K. Doctoral Dissertation: The transient outward potassium current in healthy and diseased hearts. Acta Physiol (Oxf) 2019; 225 Suppl 717:e13225. [PMID: 30628199 DOI: 10.1111/apha.13225] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 11/20/2018] [Accepted: 11/21/2018] [Indexed: 12/13/2022]
Affiliation(s)
- Kirstine Calloe
- Section for Anatomy; Biochemistry and Physiology; Department for Veterinary and Animal Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Frederiksberg C Denmark
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Mutations in KCNK4 that Affect Gating Cause a Recognizable Neurodevelopmental Syndrome. Am J Hum Genet 2018; 103:621-630. [PMID: 30290154 DOI: 10.1016/j.ajhg.2018.09.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 08/31/2018] [Indexed: 12/15/2022] Open
Abstract
Aberrant activation or inhibition of potassium (K+) currents across the plasma membrane of cells has been causally linked to altered neurotransmission, cardiac arrhythmias, endocrine dysfunction, and (more rarely) perturbed developmental processes. The K+ channel subfamily K member 4 (KCNK4), also known as TRAAK (TWIK-related arachidonic acid-stimulated K+ channel), belongs to the mechano-gated ion channels of the TRAAK/TREK subfamily of two-pore-domain (K2P) K+ channels. While K2P channels are well known to contribute to the resting membrane potential and cellular excitability, their involvement in pathophysiological processes remains largely uncharacterized. We report that de novo missense mutations in KCNK4 cause a recognizable syndrome with a distinctive facial gestalt, for which we propose the acronym FHEIG (facial dysmorphism, hypertrichosis, epilepsy, intellectual disability/developmental delay, and gingival overgrowth). Patch-clamp analyses documented a significant gain of function of the identified KCNK4 channel mutants basally and impaired sensitivity to mechanical stimulation and arachidonic acid. Co-expression experiments indicated a dominant behavior of the disease-causing mutations. Molecular dynamics simulations consistently indicated that mutations favor sealing of the lateral intramembrane fenestration that has been proposed to negatively control K+ flow by allowing lipid access to the central cavity of the channel. Overall, our findings illustrate the pleiotropic effect of dysregulated KCNK4 function and provide support to the hypothesis of a gating mechanism based on the lateral fenestrations of K2P channels.
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61
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Hu Z, Du D, Du Y. Generalized polynomial chaos-based uncertainty quantification and propagation in multi-scale modeling of cardiac electrophysiology. Comput Biol Med 2018; 102:57-74. [PMID: 30248513 DOI: 10.1016/j.compbiomed.2018.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 09/11/2018] [Accepted: 09/11/2018] [Indexed: 11/19/2022]
Abstract
Uncertainty and physiological variability are ubiquitous in cardiac electrical signaling. It is important to address the uncertainty and variability in cardiac modeling to provide reliable and realistic predictions of heart function, thus ensuring trustworthy computer-aided medical decision-making and treatment planning. Statistical techniques such as Monte Carlo (MC) simulations have been applied to uncertainty quantification and propagation in cardiac modeling. However, MC simulation-based methods are computationally prohibitive for complex cardiac models with a great number of parameters and governing equations. In this paper, we propose to use the Generalized Polynomial Chaos (gPC) expansion in combination with Galerkin projection to analytically quantify parametric uncertainty in ion channel models of mouse ventricular cell, and further propagate the uncertainty across different organizational levels of cell and tissue. To identify the most significant parametric uncertainty in cardiac ion channel and cell models, variance decomposition-based sensitivity analysis was first performed. Following this, gPC was integrated with deterministic cardiac models to propagate uncertainty through ion current, ventricular cell, 1D cable, and 2D tissue to account for the stochasticity and cell-to-cell variability. As compared to MC, the gPC in this work shows the superior performance in terms of computational efficiency. In addition, the gPC models can provide a measure of confidence in model predictions, which can improve the reliability of computer simulations of cardiac electrophysiology for clinical applications.
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Affiliation(s)
- Zhiyong Hu
- Department of Industrial, Manufacturing and Systems Engineering, Texas Tech University, Lubbock, TX, 79409, USA
| | - Dongping Du
- Department of Industrial, Manufacturing and Systems Engineering, Texas Tech University, Lubbock, TX, 79409, USA.
| | - Yuncheng Du
- Department of Chemical and Biomolecular Engineering, Clarkson University, Potsdam, NY, 33613, USA.
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62
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Tian G, Sun Y, Liu S, Li C, Chen S, Qiu R, Zhang X, Li Y, Li M, Shang H. Therapeutic Effects of Wenxin Keli in Cardiovascular Diseases: An Experimental and Mechanism Overview. Front Pharmacol 2018; 9:1005. [PMID: 30233380 PMCID: PMC6134428 DOI: 10.3389/fphar.2018.01005] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 08/16/2018] [Indexed: 02/05/2023] Open
Abstract
Cardiovascular diseases (CVDs) are the major public health problem and a leading cause of morbidity and mortality on a global basis. Wenxin Keli (WXKL), a formally classical Chinese patent medicine with obvious efficacy and favorable safety, plays a great role in the management of patients with CVDs. Accumulating evidence from various animal and cell studies has showed that WXKL could protect myocardium and anti-arrhythmia against CVDs. WXKL exhibited its cardioprotective roles by inhibiting inflammatory reaction, decreasing oxidative stress, regulating vasomotor disorders, lowering cell apoptosis, and protection against endothelial injure, myocardial ischemia, cardiac fibrosis, and cardiac hypertrophy. Besides, WXKL could effectively shorten the QRS and Q-T intervals, decrease the incidence of atrial/ventricular fibrillation and the number of ventricular tachycardia episodes, improve the severity of arrhythmias by regulating various ion channels with different potencies, mainly comprising peak sodium current (INa), late sodium current (INaL), transient outward potassium current (Ito), L-type calcium current (ICaL), and pacemaker current (If).
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Affiliation(s)
- Guihua Tian
- Chinese Cochrane Center, West China Hospital, Sichuan University, Chengdu, China
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Yang Sun
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Shuo Liu
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Chengyu Li
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Shiqi Chen
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Ruijin Qiu
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Xiaoyu Zhang
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Youping Li
- Chinese Cochrane Center, West China Hospital, Sichuan University, Chengdu, China
| | - Min Li
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Hongcai Shang
- Key Laboratory of Chinese Internal Medicine of Ministry of Education and Beijing, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
- Institute of Integration of Traditional Chinese and Western Medicine, Guangzhou Medical University, Guangzhou, China
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63
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Qiu B, Wang Y, Li C, Guo H, Xu Y. Utility of the JT Peak Interval and the JT Area in Determining the Proarrhythmic Potential of QT-Shortening Agents. J Cardiovasc Pharmacol Ther 2018; 24:160-171. [PMID: 30092655 DOI: 10.1177/1074248418791999] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Drug-induced long QT increases the risk of ventricular tachyarrhythmia known as torsades de pointes (TdP). Many biomarkers have been used to predict TdP. At present, however, there are few biomarkers for arrhythmias induced by QT-shortening drugs. The objective of the present study was to identify the best biomarkers for predicting arrhythmias caused by the 4 potassium channel openers ICA-105574, NS-1643, R-L3, and pinacidil. Our results showed that, at higher concentrations, all 4 potassium channel openers induced ventricular tachycardia (VT) and ventricular fibrillation (VF) in Langendorff-perfused guinea pig hearts, but not in rabbit hearts. The electrocardiography parameters were measured including QT/QTc, JT peak, Tp-e interval, JT area, short-term beat-to-beat QT interval variability (STV), and index of cardiac electrophysiological balance (iCEB). We found that the potassium channel openers at test concentrations shortened the QT/QTc and the JT peak interval and increased the JT area. Nevertheless, even at proarrhythmic concentrations, they did not always change STV, Tp-e, or iCEB. Receiver operating characteristic curve analysis showed that the JT peak interval representing the early repolarization phase and the JT area reflecting the dispersion of ventricular repolarization were the best predictors of VT/VF. Action potential recordings in guinea pig papillary muscle revealed that except for pinacidil, the potassium channel openers shortened APD30 in a concentration-dependent manner. They also evoked early or delayed afterdepolarizations at fast pacing rates. Patch-clamp recordings in guinea pig ventricular cardiomyocytes showed that the potassium channel openers enhanced the total outward currents during the early phase of action potential repolarization, especially at proarrhythmic concentrations. We concluded that the JT peak interval and the JT area are surrogate biomarkers identifying the risk of proarrhythmia associated with the administration of QT-shortening agents. The acceleration of early-phase repolarization and the increased dispersion of ventricular repolarization may contribute to the occurrence of arrhythmias.
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Affiliation(s)
- Bo Qiu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China.,Hebei General Hospital, Shijiazhuang, China
| | - Yuhong Wang
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Beijing Union Medical College, Beijing, China
| | - Congxin Li
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China
| | - Huicai Guo
- Department of Toxicology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yanfang Xu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China
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64
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Zankov DP, Salloum FN, Jiang M, Tseng GN. Chronic in vivo angiotensin II administration differentially modulates the slow delayed rectifier channels in atrial and ventricular myocytes. Heart Rhythm 2018; 16:108-116. [PMID: 30075281 DOI: 10.1016/j.hrthm.2018.07.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Indexed: 11/30/2022]
Abstract
BACKGROUND In the heart, slow delayed rectifier channels provide outward currents (IKs) for action potential (AP) repolarization in a region- and context-dependent manner. In diseased hearts, chronic elevation of angiotensin II (Ang II) may remodel IKs in a region-dependent manner, contributing to atrial and ventricular arrhythmias of different mechanisms. OBJECTIVE The purpose of this study was to study whether/how chronic in vivo Ang II administration remodels IKs in atrial and ventricular myocytes. METHODS We used the guinea pig (GP) model whose myocytes express robust IKs. GPs were implanted with minipumps containing Ang II or vehicle. Treatment continued for 4-6 weeks. We used patch clamp, immunofluorescence/confocal microscopy, and immunoblots to evaluate changes in IKs function and to explore the underlying mechanisms. RESULTS We confirmed the pathologic state of the heart after chronic Ang II treatment. IKs density was increased in atrial myocytes but decreased in ventricular myocytes in Ang II- vs vehicle-treated animals. The former was correlated with an increase in KCNQ1/KCNE1 colocalization in myocyte periphery, whereas the latter was correlated with a decrease in KCNQ1 protein level. Interestingly, these changes in IKs were not translated into expected alterations in AP duration or plateau voltage, indicating that other currents were involved. In atrial myocytes from Ang II-treated animals, the L-type Ca channel current was increased, contributing to AP plateau elevation and AP duration prolongation. CONCLUSION IKs is differentially modulated by chronic in vivo Ang II administration between atrial and ventricular myocytes. Other currents remodeled by Ang II treatment also contribute to changes in action potentials.
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Affiliation(s)
- Dimitar P Zankov
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Fadi N Salloum
- Department of Internal Medicine, Division of Cardiology, Virginia Commonwealth University, Richmond, Virginia
| | - Min Jiang
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Gea-Ny Tseng
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia; Department of Internal Medicine, Division of Cardiology, Virginia Commonwealth University, Richmond, Virginia.
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65
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Abstract
OBJECTIVES In normal conditions, sudden heart rate acceleration provokes a rapid reduction in ventricular action potential duration (APD). The protracted APD rate adaptation favors early afterdepolarizations and precipitates arrhythmia. Nevertheless, it is uncertain as to whether the rate-dependent changes of ventricular repolarization can be adversely modified by arrhythmogenic drugs (quinidine and procainamide) and hypokalemia, in comparison to the agents with safe therapeutic profile, such as lidocaine. DESIGN The rate adaptation of QT interval and monophasic APD obtained from the left ventricular (LV) and the right ventricular (RV) epicardium was examined during rapid cardiac pacing applied in isolated, perfused guinea-pig heart preparations. RESULTS At baseline, an abrupt increase in cardiac activation rate was associated with a substantial reduction of the QT interval and ventricular APD in the first two cardiac cycles, which was followed by a gradual shortening of repolarization over subsequent pacing intervals. The time constants of the fast (τfast) and slow (τslow) components of the APD dynamics determined from a double exponential fit were longer in RV compared to LV chamber. Quinidine, procainamide, and hypokalemia prolonged ventricular repolarization and delayed the rate adaptation of the QT interval and APD in LV and RV, as evidenced by increased τfast and τslow values. In contrast, lidocaine had no effect on the dynamic changes of ventricular repolarization upon heart rate acceleration. CONCLUSIONS The rate adaptation of ventricular repolarization is delayed by arrhythmogenic interventions, such as quinidine, procainamide, and hypokalemia, but not changed by lidocaine, a clinically safe antiarrhythmic agent.
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Affiliation(s)
- Oleg E Osadchii
- a Department of Biomedical Sciences , University of Copenhagen , Copenhagen , Denmark.,b Department of Health Science and Technology , University of Aalborg , Aalborg , Denmark
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66
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Jones DK, Johnson AC, Roti Roti EC, Liu F, Uelmen R, Ayers RA, Baczko I, Tester DJ, Ackerman MJ, Trudeau MC, Robertson GA. Localization and functional consequences of a direct interaction between TRIOBP-1 and hERG proteins in the heart. J Cell Sci 2018; 131:jcs.206730. [PMID: 29507111 DOI: 10.1242/jcs.206730] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 02/12/2018] [Indexed: 12/22/2022] Open
Abstract
Reduced levels of the cardiac human (h)ERG ion channel protein and the corresponding repolarizing current IKr can cause arrhythmia and sudden cardiac death, but the underlying cellular mechanisms controlling hERG surface expression are not well understood. Here, we identified TRIOBP-1, an F-actin-binding protein previously associated with actin polymerization, as a putative hERG-interacting protein in a yeast-two hybrid screen of a cardiac library. We corroborated this interaction by performing Förster resonance energy transfer (FRET) in HEK293 cells and co-immunoprecipitation in HEK293 cells and native cardiac tissue. TRIOBP-1 overexpression reduced hERG surface expression and current density, whereas reducing TRIOBP-1 expression via shRNA knockdown resulted in increased hERG protein levels. Immunolabeling in rat cardiomyocytes showed that native TRIOBP-1 colocalized predominantly with myosin-binding protein C and secondarily with rat ERG. In human stem cell-derived cardiomyocytes, TRIOBP-1 overexpression caused intracellular co-sequestration of hERG signal, reduced native IKr and disrupted action potential repolarization. Ca2+ currents were also somewhat reduced and cell capacitance was increased. These findings establish that TRIOBP-1 interacts directly with hERG and can affect protein levels, IKr magnitude and cardiac membrane excitability.
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Affiliation(s)
- David K Jones
- Department of Neuroscience, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison SMPH, 1111 Highland Ave. #5505, Madison, WI 53705, USA
| | - Ashley C Johnson
- Department of Physiology, University of Maryland School of Medicine, 660 W. Redwood St., Baltimore, MD 21201, USA
| | - Elon C Roti Roti
- Department of Neuroscience, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison SMPH, 1111 Highland Ave. #5505, Madison, WI 53705, USA
| | - Fang Liu
- Department of Neuroscience, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison SMPH, 1111 Highland Ave. #5505, Madison, WI 53705, USA
| | - Rebecca Uelmen
- Department of Neuroscience, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison SMPH, 1111 Highland Ave. #5505, Madison, WI 53705, USA
| | - Rebecca A Ayers
- Department of Neuroscience, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison SMPH, 1111 Highland Ave. #5505, Madison, WI 53705, USA
| | - Istvan Baczko
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged 6720, Hungary
| | - David J Tester
- Department of Cardiovascular Diseases, Division of Heart Rhythm Service, Mayo Clinic, Rochester, NY 55905, USA
| | - Michael J Ackerman
- Department of Cardiovascular Diseases, Division of Heart Rhythm Service, Mayo Clinic, Rochester, NY 55905, USA
| | - Matthew C Trudeau
- Department of Physiology, University of Maryland School of Medicine, 660 W. Redwood St., Baltimore, MD 21201, USA
| | - Gail A Robertson
- Department of Neuroscience, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison SMPH, 1111 Highland Ave. #5505, Madison, WI 53705, USA
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Arrhythmogenic drugs can amplify spatial heterogeneities in the electrical restitution in perfused guinea-pig heart: An evidence from assessments of monophasic action potential durations and JT intervals. PLoS One 2018; 13:e0191514. [PMID: 29352276 PMCID: PMC5774816 DOI: 10.1371/journal.pone.0191514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/06/2018] [Indexed: 01/01/2023] Open
Abstract
Non-uniform shortening of the action potential duration (APD90) in different myocardial regions upon heart rate acceleration can set abnormal repolarization gradients and promote arrhythmia. This study examined whether spatial heterogeneities in APD90 restitution can be amplified by drugs with clinically proved proarrhythmic potential (dofetilide, quinidine, procainamide, and flecainide) and, if so, whether these effects can translate to the appropriate changes of the ECG metrics of ventricular repolarization, such as JT intervals. In isolated, perfused guinea-pig heart preparations, monophasic action potentials and volume-conducted ECG were recorded at progressively increased pacing rates. The APD90 measured at distinct ventricular sites, as well as the JTpeak and JTend values were plotted as a function of preceding diastolic interval, and the maximum slopes of the restitution curves were determined at baseline and upon drug administration. Dofetilide, quinidine, and procainamide reverse rate-dependently prolonged APD90 and steepened the restitution curve, with effects being greater at the endocardium than epicardium, and in the right ventricular (RV) vs. the left ventricular (LV) chamber. The restitution slope was increased to a greater extent for the JTend vs. the JTpeak interval. In contrast, flecainide reduced the APD90 restitution slope at LV epicardium without producing effect at LV endocardium and RV epicardium, and reduced the JTpeak restitution slope without changing the JTend restitution. Nevertheless, with all agents, these effects translated to the amplified epicardial-to-endocardial and the LV-to-RV non-uniformities in APD90 restitution, paralleled by the increased JTend vs. JTpeak difference in the restitution slope. In summary, these findings suggest that arrhythmic drug profiles are partly attributable to the accentuated regional heterogeneities in APD90 restitution, which can be indirectly determined through ECG assessments of the JTend vs. JTpeak dynamics at variable pacing rates.
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Pro-arrhythmic effects of low plasma [K +] in human ventricle: An illustrated review. Trends Cardiovasc Med 2017; 28:233-242. [PMID: 29203397 DOI: 10.1016/j.tcm.2017.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 10/18/2017] [Accepted: 11/05/2017] [Indexed: 12/25/2022]
Abstract
Potassium levels in the plasma, [K+]o, are regulated precisely under physiological conditions. However, increases (from approx. 4.5 to 8.0mM) can occur as a consequence of, e.g., endurance exercise, ischemic insult or kidney failure. This hyperkalemic modulation of ventricular electrophysiology has been studied extensively. Hypokalemia is also common. It can occur in response to diuretic therapy, following renal dialysis, or during recovery from endurance exercise. In the human ventricle, clinical hypokalemia (e.g., [K+]o levels of approx. 3.0mM) can cause marked changes in both the resting potential and the action potential waveform, and these may promote arrhythmias. Here, we provide essential background information concerning the main K+-sensitive ion channel mechanisms that act in concert to produce prominent short-term ventricular electrophysiological changes, and illustrate these by implementing recent mathematical models of the human ventricular action potential. Even small changes (~1mM) in [K+]o result in significant alterations in two different K+ currents, IK1 and HERG. These changes can markedly alter in resting membrane potential and/or action potential waveform in human ventricle. Specifically, a reduction in net outward transmembrane K+ currents (repolarization reserve) and an increased substrate input resistance contribute to electrophysiological instability during the plateau of the action potential and may promote pro-arrhythmic early after-depolarizations (EADs). Translational settings where these insights apply include: optimal diuretic therapy, and the interpretation of data from Phase II and III trials for anti-arrhythmic drug candidates.
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69
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Verkerk AO, Veerman CC, Zegers JG, Mengarelli I, Bezzina CR, Wilders R. Patch-Clamp Recording from Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes: Improving Action Potential Characteristics through Dynamic Clamp. Int J Mol Sci 2017; 18:ijms18091873. [PMID: 28867785 PMCID: PMC5618522 DOI: 10.3390/ijms18091873] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 08/22/2017] [Accepted: 08/22/2017] [Indexed: 01/10/2023] Open
Abstract
Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) hold great promise for studying inherited cardiac arrhythmias and developing drug therapies to treat such arrhythmias. Unfortunately, until now, action potential (AP) measurements in hiPSC-CMs have been hampered by the virtual absence of the inward rectifier potassium current (IK1) in hiPSC-CMs, resulting in spontaneous activity and altered function of various depolarising and repolarising membrane currents. We assessed whether AP measurements in "ventricular-like" and "atrial-like" hiPSC-CMs could be improved through a simple, highly reproducible dynamic clamp approach to provide these cells with a substantial IK1 (computed in real time according to the actual membrane potential and injected through the patch-clamp pipette). APs were measured at 1 Hz using perforated patch-clamp methodology, both in control cells and in cells treated with all-trans retinoic acid (RA) during the differentiation process to increase the number of cells with atrial-like APs. RA-treated hiPSC-CMs displayed shorter APs than control hiPSC-CMs and this phenotype became more prominent upon addition of synthetic IK1 through dynamic clamp. Furthermore, the variability of several AP parameters decreased upon IK1 injection. Computer simulations with models of ventricular-like and atrial-like hiPSC-CMs demonstrated the importance of selecting an appropriate synthetic IK1. In conclusion, the dynamic clamp-based approach of IK1 injection has broad applicability for detailed AP measurements in hiPSC-CMs.
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Affiliation(s)
- Arie O Verkerk
- Department of Medical Biology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
- Department of Experimental Cardiology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Christiaan C Veerman
- Department of Experimental Cardiology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Jan G Zegers
- Department of Medical Biology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Isabella Mengarelli
- Department of Experimental Cardiology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Connie R Bezzina
- Department of Experimental Cardiology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Ronald Wilders
- Department of Medical Biology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
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Heijman J, Ghezelbash S, Dobrev D. Investigational antiarrhythmic agents: promising drugs in early clinical development. Expert Opin Investig Drugs 2017; 26:897-907. [PMID: 28691539 PMCID: PMC6324729 DOI: 10.1080/13543784.2017.1353601] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
INTRODUCTION Although there have been important technological advances for the treatment of cardiac arrhythmias (e.g., catheter ablation technology), antiarrhythmic drugs (AADs) remain the cornerstone therapy for the majority of patients with arrhythmias. Most of the currently available AADs were coincidental findings and did not result from a systematic development process based on known arrhythmogenic mechanisms and specific targets. During the last 20 years, our understanding of cardiac electrophysiology and fundamental arrhythmia mechanisms has increased significantly, resulting in the identification of new potential targets for mechanism-based antiarrhythmic therapy. Areas covered: Here, we review the state-of-the-art in arrhythmogenic mechanisms and AAD therapy. Thereafter, we focus on a number of antiarrhythmic targets that have received significant attention recently: atrial-specific K+-channels, the late Na+-current, the cardiac ryanodine-receptor channel type-2, and the small-conductance Ca2+-activated K+-channel. We highlight for each of these targets available antiarrhythmic agents and the evidence for their antiarrhythmic effect in animal models and early clinical development. Expert opinion: Targeting AADs to specific subgroups of well-phenotyped patients is likely necessary to detect improved outcomes that may be obscured in the population at large. In addition, specific combinations of selective AADs may have synergistic effects and may enable a mechanism-based tailored antiarrhythmic therapy.
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Affiliation(s)
- Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Shokoufeh Ghezelbash
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
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Abstract
There has been a significant progress in our understanding of the molecular mechanisms by which calcium (Ca2+) ions mediate various types of cardiac arrhythmias. A growing list of inherited gene defects can cause potentially lethal cardiac arrhythmia syndromes, including catecholaminergic polymorphic ventricular tachycardia, congenital long QT syndrome, and hypertrophic cardiomyopathy. In addition, acquired deficits of multiple Ca2+-handling proteins can contribute to the pathogenesis of arrhythmias in patients with various types of heart disease. In this review article, we will first review the key role of Ca2+ in normal cardiac function-in particular, excitation-contraction coupling and normal electric rhythms. The functional involvement of Ca2+ in distinct arrhythmia mechanisms will be discussed, followed by various inherited arrhythmia syndromes caused by mutations in Ca2+-handling proteins. Finally, we will discuss how changes in the expression of regulation of Ca2+ channels and transporters can cause acquired arrhythmias, and how these mechanisms might be targeted for therapeutic purposes.
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Affiliation(s)
- Andrew P Landstrom
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.)
| | - Dobromir Dobrev
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.)
| | - Xander H T Wehrens
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.).
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Affiliation(s)
- Donald M Bers
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, CA, USA
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