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Li E, van der Heyden MAG. The network of cardiac K IR2.1: its function, cellular regulation, electrical signaling, diseases and new drug avenues. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2024:10.1007/s00210-024-03116-5. [PMID: 38683369 DOI: 10.1007/s00210-024-03116-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 04/19/2024] [Indexed: 05/01/2024]
Abstract
The functioning of the human heart relies on complex electrical and communication systems that coordinate cardiac contractions and sustain rhythmicity. One of the key players contributing to this intricate system is the KIR2.1 potassium ion channel, which is encoded by the KCNJ2 gene. KIR2.1 channels exhibit abundant expression in both ventricular myocytes and Purkinje fibers, exerting an important role in maintaining the balance of intracellular potassium ion levels within the heart. And by stabilizing the resting membrane potential and contributing to action potential repolarization, these channels have an important role in cardiac excitability also. Either gain- or loss-of-function mutations, but also acquired impairments of their function, are implicated in the pathogenesis of diverse types of cardiac arrhythmias. In this review, we aim to elucidate the system functions of KIR2.1 channels related to cellular electrical signaling, communication, and their contributions to cardiovascular disease. Based on this knowledge, we will discuss existing and new pharmacological avenues to modulate their function.
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Affiliation(s)
- Encan Li
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM, Utrecht, Netherlands
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM, Utrecht, Netherlands.
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2
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Zhou J, Cui B, Wang X, Wang H, Zheng J, Guo F, Sun Y, Fan H, Shen J, Su J, Wang J, Zhao H, Tang Y, Gong T, Sun N, Liang P. Overexpression of KCNJ2 enhances maturation of human-induced pluripotent stem cell-derived cardiomyocytes. Stem Cell Res Ther 2023; 14:92. [PMID: 37061738 PMCID: PMC10105952 DOI: 10.1186/s13287-023-03312-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 03/07/2023] [Indexed: 04/17/2023] Open
Abstract
BACKGROUND Although human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are a promising cell resource for cardiovascular research, these cells exhibit an immature phenotype that hampers their potential applications. The inwardly rectifying potassium channel Kir2.1, encoded by the KCNJ2 gene, has been thought as an important target for promoting electrical maturation of iPSC-CMs. However, a comprehensive characterization of morphological and functional changes in iPSC-CMs overexpressing KCNJ2 (KCNJ2 OE) is still lacking. METHODS iPSC-CMs were generated using a 2D in vitro monolayer differentiation protocol. Human KCNJ2 construct with green fluorescent protein (GFP) tag was created and overexpressed in iPSC-CMs via lentiviral transduction. The mixture of iPSC-CMs and mesenchymal cells was cocultured with decellularized natural heart matrix for generation of 3D human engineered heart tissues (EHTs). RESULTS We showed that mRNA expression level of KCNJ2 in iPSC-CMs was dramatically lower than that in human left ventricular tissues. KCNJ2 OE iPSC-CMs yielded significantly increased protein expression of Kir2.1 and current density of Kir2.1-encoded IK1. The larger IK1 linked to a quiescent phenotype that required pacing to elicit action potentials in KCNJ2 OE iPSC-CMs, which can be reversed by IK1 blocker BaCl2. KCNJ2 OE also led to significantly hyperpolarized maximal diastolic potential (MDP), shortened action potential duration (APD) and increased maximal upstroke velocity. The enhanced electrophysiological maturation in KCNJ2 OE iPSC-CMs was accompanied by improvements in Ca2+ signaling, mitochondrial energy metabolism and transcriptomic profile. Notably, KCNJ2 OE iPSC-CMs exhibited enlarged cell size and more elongated and stretched shape, indicating a morphological phenotype toward structural maturation. Drug testing using hERG blocker E-4031 revealed that a more stable MDP in KCNJ2 OE iPSC-CMs allowed for obtaining significant drug response of APD prolongation in a concentration-dependent manner. Moreover, KCNJ2 OE iPSC-CMs formed more mature human EHTs with better tissue structure and cell junction. CONCLUSIONS Overexpression of KCNJ2 can robustly enhance maturation of iPSC-CMs in electrophysiology, Ca2+ signaling, metabolism, transcriptomic profile, cardiomyocyte structure and tissue engineering, thus providing more accurate cellular model for elucidating cellular and molecular mechanisms of cardiovascular diseases, screening drug-induced cardiotoxicity, and developing personalized and precision cardiovascular medicine.
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Affiliation(s)
- Jingjun Zhou
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Baiping Cui
- Institute of Geriatrics (Shanghai University), Affiliated Nantong Hospital of Shanghai University (The Sixth People's Hospital of Nantong), School of Medicine, Shanghai University, Nantong, 226011, China
- Shanghai Engineering Research Center of Organ Repair, School of Medicine, Shanghai University, Shanghai, 200444, China
| | - Xiaochen Wang
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Hongkun Wang
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Junnan Zheng
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310003, Zhejiang, China
| | - Fengfeng Guo
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Yaxun Sun
- Department of Cardiology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, 310016, Zhejiang, China
| | - Hangping Fan
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Jiaxi Shen
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Jun Su
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Jue Wang
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China
| | - Haige Zhao
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310003, Zhejiang, China
| | - Yiquan Tang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200032, China
| | - Tingyu Gong
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China.
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China.
| | - Ning Sun
- Wuxi School of Medicine, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214028, Jiangsu, China.
| | - Ping Liang
- Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, The First Affiliated Hospital, Zhejiang University School of Medicine, 79 Qingchun Road, Hangzhou, 310003, Zhejiang, China.
- Institute of Translational Medicine, Zhejiang University, Hangzhou, 310029, Zhejiang, China.
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3
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Mitochondrial Dysfunction in Cardiac Arrhythmias. Cells 2023; 12:cells12050679. [PMID: 36899814 PMCID: PMC10001005 DOI: 10.3390/cells12050679] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 02/14/2023] [Accepted: 02/17/2023] [Indexed: 02/24/2023] Open
Abstract
Electrophysiological and structural disruptions in cardiac arrhythmias are closely related to mitochondrial dysfunction. Mitochondria are an organelle generating ATP, thereby satisfying the energy demand of the incessant electrical activity in the heart. In arrhythmias, the homeostatic supply-demand relationship is impaired, which is often accompanied by progressive mitochondrial dysfunction leading to reduced ATP production and elevated reactive oxidative species generation. Furthermore, ion homeostasis, membrane excitability, and cardiac structure can be disrupted through pathological changes in gap junctions and inflammatory signaling, which results in impaired cardiac electrical homeostasis. Herein, we review the electrical and molecular mechanisms of cardiac arrhythmias, with a particular focus on mitochondrial dysfunction in ionic regulation and gap junction action. We provide an update on inherited and acquired mitochondrial dysfunction to explore the pathophysiology of different types of arrhythmias. In addition, we highlight the role of mitochondria in bradyarrhythmia, including sinus node dysfunction and atrioventricular node dysfunction. Finally, we discuss how confounding factors, such as aging, gut microbiome, cardiac reperfusion injury, and electrical stimulation, modulate mitochondrial function and cause tachyarrhythmia.
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4
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Adenosine and Adenosine Receptors: Advances in Atrial Fibrillation. Biomedicines 2022; 10:biomedicines10112963. [PMID: 36428533 PMCID: PMC9687155 DOI: 10.3390/biomedicines10112963] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 11/07/2022] [Accepted: 11/14/2022] [Indexed: 11/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common arrhythmia in the world. Because the key to developing innovative therapies that limit the onset and the progression of AF is to fully understand the underlying molecular mechanisms of AF, the aim of the present narrative review is to report the most recent advances in the potential role of the adenosinergic system in the pathophysiology of AF. After a comprehensive approach describing adenosinergic system signaling and the mechanisms of the initiation and maintenance of AF, we address the interactions of the adenosinergic system's signaling with AF. Indeed, adenosine release can activate four G-coupled membrane receptors, named A1, A2A, A2B and A3. Activation of the A2A receptors can promote the occurrence of delayed depolarization, while activation of the A1 receptors can shorten the action potential's duration and induce the resting membrane's potential hyperpolarization, which promote pulmonary vein firing, stabilize the AF rotors and allow for functional reentry. Moreover, the A2B receptors have been associated with atrial fibrosis homeostasis. Finally, the adenosinergic system can modulate the autonomous nervous system and is associated with AF risk factors. A question remains regarding adenosine release and the adenosine receptors' activation and whether this would be a cause or consequence of AF.
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5
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Manuel AIM, Gutiérrez LK, Pedrosa MLV, Uréndez FMC, Jiménez FJB, Carrascoso IM, Pérez PS, Macías Á, Jalife J. Molecular stratification of arrhythmogenic mechanisms in the Andersen Tawil Syndrome. Cardiovasc Res 2022; 119:919-932. [PMID: 35892314 PMCID: PMC10153646 DOI: 10.1093/cvr/cvac118] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 06/20/2022] [Accepted: 07/01/2022] [Indexed: 11/12/2022] Open
Abstract
Andersen Tawil Syndrome (ATS) is a rare inheritable disease associated with loss-of-function mutations in KCNJ2, the gene coding the strong inward rectifier potassium channel Kir2.1, which forms an essential membrane protein controlling cardiac excitability. ATS is usually marked by a triad of periodic paralysis, life-threatening cardiac arrhythmias and dysmorphic features, but its expression is variable and not all patients with a phenotype linked to ATS have a known genetic alteration. The mechanisms underlying this arrhythmogenic syndrome are poorly understood. Knowing such mechanisms would be essential to distinguish ATS from other channelopathies with overlapping phenotypes and to develop individualized therapies. For example, the recently suggested role of Kir2.1 as a countercurrent to sarcoplasmic calcium reuptake might explain the arrhythmogenic mechanisms of ATS and its overlap with catecholaminergic polymorphic ventricular tachycardia (CPVT). Here we summarize current knowledge on the mechanisms of arrhythmias leading to sudden cardiac death in ATS. We first provide an overview of the syndrome and its pathophysiology, from the patient´s bedside to the protein, and discuss the role of essential regulators and interactors that could play a role in cases of ATS. The review highlights novel ideas related to some post-translational channel interactions with partner proteins that might help define the molecular bases of the arrhythmia phenotype. We then propose a new all-embracing classification of the currently known ATS loss-of-function mutations according to their position in the Kir2.1 channel structure and their functional implications. We also discuss specific ATS pathogenic variants, their clinical manifestations and treatment stratification. The goal is to provide a deeper mechanistic understanding of the syndrome toward the development of novel targets and personalized treatment strategies.
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Affiliation(s)
| | - Lilian K Gutiérrez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC) Carlos III, 28029 Madrid, Spain
| | | | | | - Francisco José Bermúdez Jiménez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC) Carlos III, 28029 Madrid, Spain.,Departamento de Cardiología, Hospital Virgen de las Nieves, GranadaSpain
| | | | - Patricia Sánchez Pérez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC) Carlos III, 28029 Madrid, Spain
| | - Álvaro Macías
- Centro Nacional de Investigaciones Cardiovasculares (CNIC) Carlos III, 28029 Madrid, Spain
| | - José Jalife
- Centro Nacional de Investigaciones Cardiovasculares (CNIC) Carlos III, 28029 Madrid, Spain.,CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain.,Departments of Medicine and Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
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6
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Chen K, Man Q, Miao J, Xu W, Zheng Y, Zhou X, Gao Z. Kir2.1 channel regulates macrophage polarization via Ca2+/CaMK II/ERK/NF-κB signaling pathway. J Cell Sci 2022; 135:275689. [PMID: 35694964 DOI: 10.1242/jcs.259544] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 06/06/2022] [Indexed: 11/20/2022] Open
Abstract
Macrophage polarization plays a key role in inflammatory response. Various ion channels expressed in macrophages has been documented, but very little is known about their roles in macrophage polarization. We find that knockdown or blockade of Kir2.1 channel significantly inhibits M1 polarization, but promotes M2 polarization. LPS induced M1 polarization is also remarkably suppressed in high extracellular K+ solutions (70 mM K+), and this inhibition is partially abolished by adding Ca2+ in the culture medium. Calcium imaging shows that Ca2+ influx is dependent on the hyperpolarized membrane potential generated by Kir2.1 channel. The upregulation of p-CaMK II, p-ERK1/2, and p-NF-κB proteins in RAW264.7 macrophages stimulated with LPS are significantly reversed by blocking Kir2.1 channel or culturing the cells with 70 mM K+ medium. Furthermore, in vivo study shows that mice treated with Kir2.1 channel blocker are protected from LPS-induced peritonitis. In summary, our data reveal the essential role of Kir2.1 channel in regulating macrophage polarization via Ca2+ / CaMK II / ERK1/2 / NF-κB pathway.
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Affiliation(s)
- Kuihao Chen
- Department of Cardiology, The Affiliated Hospital of Medical School of Ningbo University, 247 Renmin Rd, Ningbo, China.,Department of Pharmacology, Ningbo University School of Medicine, 818 Fenghua Rd, Ningbo, China
| | - Qiaoyan Man
- Department of Pharmacology, Ningbo University School of Medicine, 818 Fenghua Rd, Ningbo, China
| | - Jiaen Miao
- Department of Pharmacology, Ningbo University School of Medicine, 818 Fenghua Rd, Ningbo, China
| | - Wenjing Xu
- Department of Pharmacology, Ningbo University School of Medicine, 818 Fenghua Rd, Ningbo, China
| | - Yangchen Zheng
- Department of Pharmacology, Ningbo University School of Medicine, 818 Fenghua Rd, Ningbo, China
| | - Xiuli Zhou
- Department of Pharmacology, Ningbo University School of Medicine, 818 Fenghua Rd, Ningbo, China
| | - Zhe Gao
- Department of Cardiology, The Affiliated Hospital of Medical School of Ningbo University, 247 Renmin Rd, Ningbo, China.,Ningbo Institute of Medical Sciences, 42 Yangshan Rd, Ningbo, China
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7
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Klein MG, Krantz MJ, Fatima N, Watters A, Colon-Sanchez D, Geiger RM, Goldstein RE, Solhjoo S, Mehler PS, Flagg TP, Haigney MC. Methadone Blockade of Cardiac Inward Rectifier K + Current Augments Membrane Instability and Amplifies U Waves on Surface ECGs: A Translational Study. J Am Heart Assoc 2022; 11:e023482. [PMID: 35658478 PMCID: PMC9238736 DOI: 10.1161/jaha.121.023482] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Background Methadone is associated with a disproportionate risk of sudden death and ventricular tachyarrhythmia despite only modest inhibition of delayed rectifier K+ current (IKr), the principal mechanism of drug-associated arrhythmia. Congenital defects of inward rectifier K+ current (IK1) have been linked to increased U-wave amplitude on ECG and fatal arrhythmia. We hypothesized that methadone may also be a potent inhibitor of IK1, contributing to delayed repolarization and manifesting on surface ECGs as augmented U-wave integrals. Methods and Results Using a whole-cell voltage clamp, methadone inhibited both recombinant and native IK1 with a half-maximal inhibitory concentration IC50) of 1.5 μmol/L, similar to that observed for IKr block (half-maximal inhibitory concentration of 2.9 μmol/L). Methadone modestly increased the action potential duration at 90% repolarization and slowed terminal repolarization at low concentrations. At higher concentrations, action potential duration at 90% repolarization lengthening was abolished, but its effect on terminal repolarization rose steadily and correlated with increased fluctuations of diastolic membrane potential. In parallel, patient ECGs were analyzed before and after methadone initiation, with 68% of patients having a markedly increased U-wave integral compared with premethadone (lead V3; mean +38%±15%, P=0.016), along with increased QT and TPeak to TEnd intervals, likely reflective of IKr block. Conclusions Methadone is a potent IK1 inhibitor that causes augmentation of U waves on surface ECG. We propose that increased membrane instability resulting from IK1 block may better explain methadone's arrhythmia risk beyond IKr inhibition alone. Drug-induced augmentation of U waves may represent evidence of blockade of multiple repolarizing ion channels, and evaluation of the effect of that agent on IK1 may be warranted.
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Affiliation(s)
- Michael G Klein
- Cardiology Division Department of Medicine Uniformed Services University Bethesda MD
| | - Mori J Krantz
- Denver Health Medical Center Cardiology Division Denver CO.,Department of Medicine University of Colorado School of Medicine Aurora CO.,Chief Science Advisor Cardiac Safety and Cardiovascular Imaging, Clario Inc. Philadelphia PA
| | - Naheed Fatima
- Department of Anatomy, Physiology & Genetics Uniformed Services University Bethesda MD
| | - Ashlie Watters
- ACUTE at Denver Health Denver CO.,Department of Medicine University of Colorado School of Medicine Aurora CO
| | - Dayan Colon-Sanchez
- Psychiatry Division Outpatient Behavioral Health Services, Denver Health, & University of Colorado School of Medicine Denver CO
| | - Robert M Geiger
- Department of Anatomy, Physiology & Genetics Uniformed Services University Bethesda MD
| | - Robert E Goldstein
- Cardiology Division Department of Medicine Uniformed Services University Bethesda MD
| | - Soroosh Solhjoo
- Cardiology Division Department of Medicine Uniformed Services University Bethesda MD.,Military Cardiovascular Outcomes Research (MiCOR) Bethesda MD
| | - Philip S Mehler
- ACUTE at Denver Health Denver CO.,Department of Medicine University of Colorado School of Medicine Aurora CO
| | - Thomas P Flagg
- Department of Anatomy, Physiology & Genetics Uniformed Services University Bethesda MD
| | - Mark C Haigney
- Cardiology Division Department of Medicine Uniformed Services University Bethesda MD.,Military Cardiovascular Outcomes Research (MiCOR) Bethesda MD
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8
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Abramochkin DV, Filatova TS, Pustovit KB, Voronina YA, Kuzmin VS, Vornanen M. Ionic currents underlying different patterns of electrical activity in working cardiac myocytes of mammals and non-mammalian vertebrates. Comp Biochem Physiol A Mol Integr Physiol 2022; 268:111204. [PMID: 35346823 DOI: 10.1016/j.cbpa.2022.111204] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 03/21/2022] [Accepted: 03/22/2022] [Indexed: 12/19/2022]
Abstract
The orderly contraction of the vertebrate heart is determined by generation and propagation of cardiac action potentials (APs). APs are generated by the integrated activity of time- and voltage-dependent ionic channels which carry inward Na+ and Ca2+ currents, and outward K+ currents. This review compares atrial and ventricular APs and underlying ion currents between different taxa of vertebrates. We have collected literature data and attempted to find common electrophysiological features for two or more vertebrate groups, show differences between taxa and cardiac chambers, and indicate gaps in the existing data. Although electrical excitability of the heart in all vertebrates is based on the same superfamily of channels, there is a vast variability of AP waveforms between atrial and ventricular myocytes, between different species of the same vertebrate class and between endothermic and ectothermic animals. The wide variability of AP shapes is related to species-specific differences in animal size, heart rate, stage of ontogenetic development, excitation-contraction coupling, temperature and oxygen availability. Some of the differences between taxa are related to evolutionary development of genomes, which appear e.g. in the expression of different Na+ and K+ channel orthologues in cardiomyocytes of vertebrates. There is a wonderful variability of AP shapes and underlying ion currents with which electrical excitability of vertebrate heart can be generated depending on the intrinsic and extrinsic conditions of animal body. This multitude of ionic mechanisms provides excellent material for studying how the function of the vertebrate heart can adapt or acclimate to prevailing physiological and environmental conditions.
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Affiliation(s)
- Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia.
| | - Tatiana S Filatova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia
| | - Ksenia B Pustovit
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia
| | - Yana A Voronina
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia; Laboratory of Cardiac Electrophysiology, National Medical Research Center for Cardiology, 3(rd) Cherepkovskaya str., 15A, Moscow, Russia
| | - Vladislav S Kuzmin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia; Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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9
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Brown KA, Anderson C, Reilly L, Sondhi K, Ge Y, Eckhardt LL. Proteomic Analysis of the Functional Inward Rectifier Potassium Channel (Kir) 2.1 Reveals Several Novel Phosphorylation Sites. Biochemistry 2021; 60:3292-3301. [PMID: 34676745 DOI: 10.1021/acs.biochem.1c00555] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Membrane proteins represent a large family of proteins that perform vital physiological roles and represent key drug targets. Despite their importance, bioanalytical methods aiming to comprehensively characterize the post-translational modification (PTM) of membrane proteins remain challenging compared to other classes of proteins in part because of their inherent low expression and hydrophobicity. The inward rectifier potassium channel (Kir) 2.1, an integral membrane protein, is critical for the maintenance of the resting membrane potential and phase-3 repolarization of the cardiac action potential in the heart. The importance of this channel to cardiac physiology is highlighted by the recognition of several sudden arrhythmic death syndromes, Andersen-Tawil and short QT syndromes, which are associated with loss or gain of function mutations in Kir2.1, often triggered by changes in the β-adrenergic tone. Therefore, understanding the PTMs of this channel (particularly β-adrenergic tone-driven phosphorylation) is important for arrhythmia prevention. Here, we developed a proteomic method, integrating both top-down (intact protein) and bottom-up (after enzymatic digestion) proteomic analyses, to characterize the PTMs of recombinant wild-type and mutant Kir2.1, successfully mapping five novel sites of phosphorylation and confirming a sixth site. Our study provides a framework for future work to assess the role of PTMs in regulating Kir2.1 functions.
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Affiliation(s)
- Kyle A Brown
- Department of Surgery, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.,Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Corey Anderson
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Kunal Sondhi
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Ying Ge
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States.,Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
| | - Lee L Eckhardt
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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10
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Kibler NA, Nuzhny VP, Kharin SN, Shmakov DN. Effect of atrial artificial electrical stimulation on depolarization and repolarization and hemodynamics of the heart ventricle in rainbow trout Oncorhynchus mykiss. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1329-1339. [PMID: 34241764 DOI: 10.1007/s10695-021-00983-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 06/25/2021] [Indexed: 06/13/2023]
Abstract
The spatial-temporal organization of the activation, repolarization and hemodynamics of the heart ventricle in rainbow trout, Oncorhynchus mykiss, adapted to a temperature of 5-7 °C, were studied from the normal sinus rhythm (21.6 ± 4.9 bpm) to the highest possible heart rhythm (HR) (60 bpm), during which deterioration of the contractile activity of the myocardium occurred. Regardless of the HR, the main pattern of excitation of the heart ventricle was the movement of the depolarization wave from the dorsal areas of the base in the base-apical and ventral directions with the capture of the entire thickness of the walls, with a slight difference in the time of activation of the subendocardium compared to the subepicardium. The increase in HR above the sinus rhythm caused significant shortening of local repolarization durations in all areas and layers (endocardial, intramural and subepicardial) of the heart ventricle. Changes in local durations of repolarization led to an increase in the heterogeneity of repolarization of the ventricular myocardium; as a result, a deterioration of its contractility was observed. In relation to the sinus rhythm, the maximal systolic pressure in the heart ventricle decreased, the diastolic and end-diastolic pressure increased, and the maximum rates of pressure rise and fall decreased. In rainbow trout adapted to a temperature of 5-7 °C at sinus rhythm, the pumping function of the heart was probably within the upper limit of the physiological norm, and a further increase in the heart rate led to a decline in myocardial contractility.
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Affiliation(s)
- Natalya A Kibler
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia.
| | - Vladimir P Nuzhny
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
| | - Sergey N Kharin
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
| | - Dmitry N Shmakov
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
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11
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Ozturk N, Uslu S, Ozdemir S. Diabetes-induced changes in cardiac voltage-gated ion channels. World J Diabetes 2021; 12:1-18. [PMID: 33520105 PMCID: PMC7807254 DOI: 10.4239/wjd.v12.i1.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 11/05/2020] [Accepted: 11/13/2020] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus affects the heart through various mechanisms such as microvascular defects, metabolic abnormalities, autonomic dysfunction and incompatible immune response. Furthermore, it can also cause functional and structural changes in the myocardium by a disease known as diabetic cardiomyopathy (DCM) in the absence of coronary artery disease. As DCM progresses it causes electrical remodeling of the heart, left ventricular dysfunction and heart failure. Electrophysiological changes in the diabetic heart contribute significantly to the incidence of arrhythmias and sudden cardiac death in diabetes mellitus patients. In recent studies, significant changes in repolarizing K+ currents, Na+ currents and L-type Ca2+ currents along with impaired Ca2+ homeostasis and defective contractile function have been identified in the diabetic heart. In addition, insulin levels and other trophic factors change significantly to maintain the ionic channel expression in diabetic patients. There are many diagnostic tools and management options for DCM, but it is difficult to detect its development and to effectively prevent its progress. In this review, diabetes-associated alterations in voltage-sensitive cardiac ion channels are comprehensively assessed to understand their potential role in the pathophysiology and pathogenesis of DCM.
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Affiliation(s)
- Nihal Ozturk
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
| | - Serkan Uslu
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
| | - Semir Ozdemir
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
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12
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Liu Q, Sun J, Zhang L, Xu Y, Wu B, Cao J. The Agonist of Inward Rectifier Potassium Channel (I K1) Attenuates Rat Reperfusion Arrhythmias Linked to CaMKII Signaling. Int Heart J 2021; 62:1348-1357. [PMID: 34853227 DOI: 10.1536/ihj.21-379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Inward rectifier potassium channels (IK1, Kir) are known to play critical roles in arrhythmogenesis. Thus, how IK1 agonist affects reperfusion arrhythmias needs to be clarified, and its underlying mechanisms should be determined. Reperfusion arrhythmias were modeled by coronary ligation (ischemia, 15 minutes) and release (reperfusion, 15 minutes). Zacopride (1.5-50 μg/kg in vivo, or 0.1-10 μmol/Lex vivo) was applied in the settings of pretreatment (3 minutes before coronary ligation) and posttreatment (5 minutes after coronary ligation). Hypoxia (45 minutes) /reoxygenation (30 minutes) model was established in cultured H9c2 (2-1) cardiomyocytes. Zacopride or KN93 was applied before hypoxia (pretreatment). In the setting of pre- or posttreatment, zacopride at 15 μg/kg in vivo or 1 μmol/Lin vitro exhibited superlative protections on reperfusion arrhythmias or intracellular calcium overload. Western blot data from ex vivo hearts or H9c2 (2-1) cardiomyocytes showed that I/R (H/R) induced the inhibition of Kir2.1 (the dominant subunit of IK1 channel in ventricle), phosphorylation and oxidation of CaMKII, downregulation of SERCA2, phosphorylation of phospholamban (at Thr17), and activation of caspase-3. Zacopride treatment (1 μmol/L) was noted to strikingly restore the expression of Kir2.1 and SERCA2 and decrease the activity of CaMKII, phospholamban, and caspase-3. These effects were largely eliminated by co-application of IK1 blocker BaCl2. CaMKII inhibitor KN93 attenuated calcium overload and p-PLB (Thr17) in an IK1-independent manner. IK1-depedent inhibition of CaMKII activity is found to be a key cardiac salvage signaling under Ca2+ dyshomeostasis and reactive oxygen species (ROS) stress. IK1 might be a novel target for pharmacological conditioning of reperfusion arrhythmia, especially for the application after unpredictable ischemia.
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Affiliation(s)
- Qinghua Liu
- Department of Pathophysiology, Shanxi Medical University
| | - Jiaxing Sun
- Department of Pathophysiology, Shanxi Medical University
| | - Lijun Zhang
- Department of Pathophysiology, Shanxi Medical University
| | - Yanwu Xu
- Department of Biochemistry, Shanghai University of Traditional Chinese Medicine
| | - Bowei Wu
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University
| | - Jimin Cao
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University
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13
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Folkerts EJ, Heuer RM, Flynn S, Stieglitz JD, Benetti DD, Alessi DS, Goss GG, Grosell M. Exposure to Hydraulic Fracturing Flowback Water Impairs Mahi-Mahi ( Coryphaena hippurus) Cardiomyocyte Contractile Function and Swimming Performance. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:13579-13589. [PMID: 33138383 DOI: 10.1021/acs.est.0c02719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Publicly available toxicological studies on wastewaters associated with unconventional oil and gas (UOG) activities in offshore regions are nonexistent. The current study investigated the impact of hydraulic fracturing-generated flowback water (HF-FW) on whole organism swimming performance/respiration and cardiomyocyte contractility dynamics in mahi-mahi (Coryphaena hippurus-hereafter referred to as "mahi"), an organism which inhabits marine ecosystems where offshore hydraulic fracturing activity is intensifying. Following exposure to 2.75% HF-FW for 24 h, mahi displayed significantly reduced critical swimming speeds (Ucrit) and aerobic scopes (reductions of ∼40 and 61%, respectively) compared to control fish. Additionally, cardiomyocyte exposures to the same HF-FW sample at 2% dilutions reduced a multitude of mahi sarcomere contraction properties at various stimulation frequencies compared to all other treatment groups, including an approximate 40% decrease in sarcomere contraction size and a nearly 50% reduction in sarcomere relaxation velocity compared to controls. An approximate 8-fold change in expression of the cardiac contractile regulatory gene cmlc2 was also seen in ventricles from 2.75% HF-FW-exposed mahi. These results collectively identify cardiac function as a target for HF-FW toxicity and provide some of the first published data on UOG toxicity in a marine species.
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Affiliation(s)
- Erik J Folkerts
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Rachael M Heuer
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, United States
| | - Shannon Flynn
- School of Natural and Environmental Science, Newcastle University, Newcastle Upon Tyne NE1 7RU, U.K
| | - John D Stieglitz
- Department of Marine Ecosystems and Society, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, United States
| | - Daniel D Benetti
- Department of Marine Ecosystems and Society, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, United States
| | - Daniel S Alessi
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
| | - Greg G Goss
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
- National Research Council Nanotechnology Initiative, Edmonton, Alberta T6G 2M9, Canada
| | - Martin Grosell
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, United States
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14
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Reilly L, Alvarado FJ, Lang D, Abozeid S, Van Ert H, Spellman C, Warden J, Makielski JC, Glukhov AV, Eckhardt LL. Genetic Loss of IK1 Causes Adrenergic-Induced Phase 3 Early Afterdepolariz ations and Polymorphic and Bidirectional Ventricular Tachycardia. Circ Arrhythm Electrophysiol 2020; 13:e008638. [PMID: 32931337 PMCID: PMC7574954 DOI: 10.1161/circep.120.008638] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/23/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND Arrhythmia syndromes associated with KCNJ2 mutations have been described clinically; however, little is known of the underlying arrhythmia mechanism. We create the first patient inspired KCNJ2 transgenic mouse and study effects of this mutation on cardiac function, IK1, and Ca2+ handling, to determine the underlying cellular arrhythmic pathogenesis. METHODS A cardiac-specific KCNJ2-R67Q mouse was generated and bred for heterozygosity (R67Q+/-). Echocardiography was performed at rest, under anesthesia. In vivo ECG recording and whole heart optical mapping of intact hearts was performed before and after adrenergic stimulation in wild-type (WT) littermate controls and R67Q+/- mice. IK1 measurements, action potential characterization, and intracellular Ca2+ imaging from isolated ventricular myocytes at baseline and after adrenergic stimulation were performed in WT and R67Q+/- mice. RESULTS R67Q+/- mice (n=17) showed normal cardiac function, structure, and baseline electrical activity compared with WT (n=10). Following epinephrine and caffeine, only the R67Q+/- mice had bidirectional ventricular tachycardia, ventricular tachycardia, frequent ventricular ectopy, and/or bigeminy and optical mapping demonstrated high prevalence of spontaneous and sustained ventricular arrhythmia. Both R67Q+/- (n=8) and WT myocytes (n=9) demonstrated typical n-shaped IK1IV relationship; however, following isoproterenol, max outward IK1 increased by ≈20% in WT but decreased by ≈24% in R67Q+/- (P<0.01). R67Q+/- myocytes (n=5) demonstrated prolonged action potential duration at 90% repolarization and after 10 nmol/L isoproterenol compared with WT (n=7; P<0.05). Ca2+ transient amplitude, 50% decay rate, and sarcoplasmic reticulum Ca2+ content were not different between WT (n=18) and R67Q+/- (n=16) myocytes. R67Q+/- myocytes (n=10) under adrenergic stimulation showed frequent spontaneous development of early afterdepolarizations that occurred at phase 3 of action potential repolarization. CONCLUSIONS KCNJ2 mutation R67Q+/- causes adrenergic-dependent loss of IK1 during terminal repolarization and vulnerability to phase 3 early afterdepolarizations. This model clarifies a heretofore unknown arrhythmia mechanism and extends our understanding of treatment implications for patients with KCNJ2 mutation.
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Affiliation(s)
- Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Francisco J Alvarado
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Di Lang
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Sara Abozeid
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Hannah Van Ert
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Cordell Spellman
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Jarrett Warden
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Jonathan C Makielski
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Alexey V Glukhov
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Lee L Eckhardt
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
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15
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Salvage SC, Huang CLH, Jackson AP. Cell-Adhesion Properties of β-Subunits in the Regulation of Cardiomyocyte Sodium Channels. Biomolecules 2020; 10:biom10070989. [PMID: 32630316 PMCID: PMC7407995 DOI: 10.3390/biom10070989] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 06/25/2020] [Accepted: 06/27/2020] [Indexed: 12/17/2022] Open
Abstract
Voltage-gated sodium (Nav) channels drive the rising phase of the action potential, essential for electrical signalling in nerves and muscles. The Nav channel α-subunit contains the ion-selective pore. In the cardiomyocyte, Nav1.5 is the main Nav channel α-subunit isoform, with a smaller expression of neuronal Nav channels. Four distinct regulatory β-subunits (β1–4) bind to the Nav channel α-subunits. Previous work has emphasised the β-subunits as direct Nav channel gating modulators. However, there is now increasing appreciation of additional roles played by these subunits. In this review, we focus on β-subunits as homophilic and heterophilic cell-adhesion molecules and the implications for cardiomyocyte function. Based on recent cryogenic electron microscopy (cryo-EM) data, we suggest that the β-subunits interact with Nav1.5 in a different way from their binding to other Nav channel isoforms. We believe this feature may facilitate trans-cell-adhesion between β1-associated Nav1.5 subunits on the intercalated disc and promote ephaptic conduction between cardiomyocytes.
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Affiliation(s)
- Samantha C. Salvage
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK;
- Correspondence: (S.C.S.); (A.P.J.); Tel.: +44-1223-765950 (S.C.S.); +44-1223-765951 (A.P.J.)
| | - Christopher L.-H. Huang
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK;
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Antony P. Jackson
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK;
- Correspondence: (S.C.S.); (A.P.J.); Tel.: +44-1223-765950 (S.C.S.); +44-1223-765951 (A.P.J.)
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16
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Akyuz E, Villa C. A novel role of cardiac inwardly rectifying potassium channels explaining autonomic cardiovascular dysfunctions in a cuprizone-induced mouse model of multiple sclerosis. Auton Neurosci 2020; 225:102647. [PMID: 32087534 DOI: 10.1016/j.autneu.2020.102647] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 01/16/2020] [Accepted: 02/12/2020] [Indexed: 12/16/2022]
Abstract
Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS), believed to have an autoimmune etiology. MS patients showed an increased cardiovascular (CV) risk probably related to an impairment in the autonomic control of CV functions, but the underlying molecular mechanisms are not completely elucidated. Inwardly-rectifying potassium (Kir) channels play a key role in cardiac excitability by contributing to the repolarization phase of action potential and were recently identified as target of the autoantibody response in MS patients. Therefore, we investigated the role of cardiac Kir channels in the CV dysfunctions occurring in MS. Cardiac functions were evaluated by electrocardiographic recordings (ECG) in cuprizone-fed C57BL/6 mice, a classic demyelination animal model. Gene expression profiling of cardiac Kir2.2, Kir4.1 and Kir6.2 channels was performed using real-time PCR in mice. Cuprizone-induced mouse model was confirmed by immunohistochemistry analysis showing demyelination in the corpus callosum. ECG recordings from mice showed a significant decreased duration of the P wave and RR interval as well as an increase of the heart rate in cuprizone-treated mice as compared with the controls. Significant increased relative expression levels of Kcnj11 and Kcnj12, encoding for Kir6.2 and Kir2.2 channels respectively, were observed in mouse heart tissue, whereas no differences were found in mRNA levels of Kir4.1 channel as compared with controls. For the first time, these findings provided valuable insights into the potential role of Kir channels in cardiac problems associated with MS.
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Affiliation(s)
- Enes Akyuz
- Department of Biophysics, Faculty of Medicine, Yozgat Bozok University, Yozgat, Turkey.
| | - Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca, Italy
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17
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Marris CR, Kompella SN, Miller MR, Incardona JP, Brette F, Hancox JC, Sørhus E, Shiels HA. Polyaromatic hydrocarbons in pollution: a heart-breaking matter. J Physiol 2020; 598:227-247. [PMID: 31840250 PMCID: PMC7003748 DOI: 10.1113/jp278885] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 11/19/2019] [Indexed: 01/17/2023] Open
Abstract
Air pollution is associated with detrimental effects on human health, including decreased cardiovascular function. However, the causative mechanisms behind these effects have yet to be fully elucidated. Here we review the current epidemiological, clinical and experimental evidence linking pollution with cardiovascular dysfunction. Our focus is on particulate matter (PM) and the associated low molecular weight polycyclic aromatic hydrocarbons (PAHs) as key mediators of cardiotoxicity. We begin by reviewing the growing epidemiological evidence linking air pollution to cardiovascular dysfunction in humans. We next address the pollution-based cardiotoxic mechanisms first identified in fish following the release of large quantities of PAHs into the marine environment from point oil spills (e.g. Deepwater Horizon). We finish by discussing the current state of mechanistic knowledge linking PM and PAH exposure to mammalian cardiovascular patho-physiologies such as atherosclerosis, cardiac hypertrophy, arrhythmias, contractile dysfunction and the underlying alterations in gene regulation. Our aim is to show conservation of toxicant pathways and cellular targets across vertebrate hearts to allow a broad framework of the global problem of cardiotoxic pollution to be established. AhR; Aryl hydrocarbon receptor. Dark lines indicate topics discussed in this review. Grey lines indicate topics reviewed elsewhere.
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Affiliation(s)
- C. R. Marris
- Division of Cardiovascular SciencesFaculty of Biology Medicine and HealthUniversity of ManchesterManchesterUK
| | - S. N. Kompella
- Division of Cardiovascular SciencesFaculty of Biology Medicine and HealthUniversity of ManchesterManchesterUK
| | - M. R. Miller
- BHF Centre for Cardiovascular ScienceQueens Medical Research InstituteThe University of EdinburghEdinburghUK
| | - J. P. Incardona
- Environmental and Fisheries Sciences DivisionNorthwest Fisheries Science CenterNational Oceanic and Atmospheric AdministrationSeattleWA98112USA
| | - F. Brette
- INSERMCentre de Recherche Cardio‐Thoracique de BordeauxU1045BordeauxFrance
- Université de BordeauxCentre de Recherche Cardio‐ThoraciqueU1045BordeauxFrance
- IHU LirycElectrophysiology and Heart Modeling InstituteFondation Bordeaux UniversitéPessac‐BordeauxFrance
| | - J. C. Hancox
- School of PhysiologyPharmacology and NeuroscienceBristol Heart InstituteUniversity of BristolBristolBS2 8HWUK
| | - E. Sørhus
- Institute of Marine ResearchPO Box 1870 Nordes NO‐5871BergenNorway
| | - H. A. Shiels
- Division of Cardiovascular SciencesFaculty of Biology Medicine and HealthUniversity of ManchesterManchesterUK
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18
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Horigome H, Ishikawa Y, Kokubun N, Yoshinaga M, Sumitomo N, Lin L, Kato Y, Tanabe-Kameda Y, Ohno S, Nagashima M, Horie M. Multivariate analysis of TU wave complex on electrocardiogram in Andersen-Tawil syndrome with KCNJ2 mutations. Ann Noninvasive Electrocardiol 2019; 25:e12721. [PMID: 31724784 PMCID: PMC7358888 DOI: 10.1111/anec.12721] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 09/26/2019] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND The exact differences between the TU wave complex of ATS1 and that of healthy individuals remain to be investigated. We sought to characterize the TU wave complex of Andersen-Tawil syndrome type 1 (ATS1) using high frequency electrocardiogram (ECG) data. METHODS Electrocardiograms were recorded as time series data with a 2 kHz frequency ECG amplifier in 13 patients with ATS1 (positive for KCNJ2 mutation, ATS1 group) and age-matched healthy individuals (control group). Conventional ECG parameters were measured, and principal component analysis (PCA) and independent component analysis (ICA) were applied to the TU wave complex. RESULTS Time from T peak (Tp) to U peak (Up), time from bottom (B) to Up, and time from B to U end (BUe, U duration) (0.232 ± 0.018 vs. 0.165 ± 0.017, p < .0001), where B is the lowest point between T and U waves, were all longer in the ATS1 group than the control group. Multivariate logistic regression analysis revealed that BUe could completely differentiate the two groups. PCA ratios in the ATS1 group were significantly larger than the control group (26.5 ± 12.3 vs. 10.4 ± 6.2, p = .0005). ICA revealed 1 or 2 U-wave-specific independent components (ICs) that exclusively comprise the U wave in ATS1, whereas U waves in the control group were composed of some ICs that also comprised T waves. CONCLUSIONS U-wave-related temporal parameters, particularly BUe, and the existence of U-wave-specific ICs, extracted in the ICA, are useful for differentiation of U waves in ATS1 from those in healthy individuals.
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Affiliation(s)
- Hitoshi Horigome
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | | | - Norito Kokubun
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - Masao Yoshinaga
- Department of Pediatrics, National Hospital Organization Kagoshima Medical Center, Kagoshima, Japan
| | - Naokata Sumitomo
- Department of Pediatric Cardiology, Saitama Medical University International Medical Center, Hidaka, Japan
| | - Lisheng Lin
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Yoshiaki Kato
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Yuri Tanabe-Kameda
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Seiko Ohno
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Suita, Japan
| | | | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
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19
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Li Z, He Q, Wu C, Chen L, Bi F, Zhou Y, Shan H. Apelin shorten QT interval by inhibiting Kir2.1/I K1 via a PI3K way in acute myocardial infarction. Biochem Biophys Res Commun 2019; 517:272-277. [PMID: 31349969 DOI: 10.1016/j.bbrc.2019.07.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 07/15/2019] [Indexed: 12/24/2022]
Abstract
QT interval prolongation and depolarization of resting membrane potential (RMP) were found in acute myocardial infarction (MI) which is involved in the arrhythmogenic mechanism and raising the risk to initiate torsade de pointes. However, clinical anti-arrhythmic agents that primarily act on QT interval and RMP are not currently available. Our objective was to determine whether Apelin, an endogenous peptide ligand of receptor APJ, affects QT interval and RMP and underlying mechanisms. To test this viewpoint, mice were subjected to MI by ligating the left main coronary artery and Apelin was applied through tail vein at 5 min prior coronary occlusion in tested group. Compared to MI group, pretreatment of Apelin (15 μg/kg) shortened QTc and QT interval induced by MI, significantly elevated RMP and shortened action potential duration (APD) by increased IK1 currents recorded using whole-cell patch technique from cardiomyocytes underwent MI. In cultured neonatal mouse cardiomyocytes, Apelin (1 μmol/L) restored hypoxia-induced Kir2.1 down-regulation, which was abolished by IP3K inhibitor LY-294002. Additionally, Apelin elicited a time-dependent increase in phosphorylation of Akt leading to increase in PI3-kinase activity. These results showed that Apelin enhanced IK1/Kir2.1 currents via IP3K pathway as by rescue ischemia- and hypoxia-induced RMP depolarization and prolongation of QT interval, which may prevent or cure acute ischemic-mediated arrhythmias. This study brings new information to anti-arrhythmic theories and provides a potential target for the clinical management of acute ischemia-related arrhythmias.
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Affiliation(s)
- Zhongrui Li
- Department of Pharmacology (the State-Province Key Laboratories of Biomedicine Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), College of Pharmacy, Harbin Medical University, Harbin, 150081, China; Department of Ophthalmology, The First Affiliated Hospital of Harbin Medical University, Harbin Medical University, Harbin, 150081, China
| | - Qiufu He
- Department of General Practice, The Forth Affiliated Hospital of Harbin Medical University, Harbin Medical University, Harbin, 150081, China
| | - Chengyu Wu
- Department of Pharmacology (the State-Province Key Laboratories of Biomedicine Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), College of Pharmacy, Harbin Medical University, Harbin, 150081, China
| | | | - Fangfang Bi
- Department of Pharmacology (the State-Province Key Laboratories of Biomedicine Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), College of Pharmacy, Harbin Medical University, Harbin, 150081, China
| | - Yuhong Zhou
- Department of Pharmacology (the State-Province Key Laboratories of Biomedicine Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), College of Pharmacy, Harbin Medical University, Harbin, 150081, China.
| | - Hongli Shan
- Department of Pharmacology (the State-Province Key Laboratories of Biomedicine Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), College of Pharmacy, Harbin Medical University, Harbin, 150081, China.
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Sapelnikov OV, Kulikov AA, Favorova OO, Matveeva NA, Cherkashin DI, Nikolaeva OA, Akchurin RS. Genetic, Epigenetic and Transcription Factors in Atrial Fibrillation. RATIONAL PHARMACOTHERAPY IN CARDIOLOGY 2019. [DOI: 10.20996/1819-6446-2019-15-3-407-415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Atrial fibrillation (AF) is one of the most common arrhythmia that occurs in patients with cardiovascular diseases. Congenital forms of AF are quite rare. Many studies have shown that genetic, epigenetic and transcription factors may play an important role in the development and the progression of AF. In our review, studies have been conducted on the identification of mutations in ionic and non-ionic channels, possibly associated with AF. These mutations were found only in isolated groups of patients with AF, and in general, monogenic forms of AF are a rare subtype of the disease. Genomic association studies have helped to identify potential links between single nucleotide polymorphisms and AF. The risk of AF in the general population is likely to be determined by the interaction between environmental factors and many alleles. In recent years, the emergence of a genome-wide associative studies has significantly expanded the understanding of the genetic basis for the inheritance of AF and has led to the emergence of new evidence of the important role of genetic factors in the development of AF, in the risk stratification of AF and the recurrence of AF. Epigenetic factors are also important in AF. Epigenetic therapy aimed at treating a disease through exposure to epigenome is currently under development. A newly emerged area of ablatogenomics includes the use of genetic profiles that allow assessing the likelihood of recurrence of AF after catheter ablation. The results of genetic studies in AF show that, in addition to their role in the appearance of congenital heart pathologies, transcription factors play an important role in the pathogenesis of AF.
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Affiliation(s)
| | | | - O. O. Favorova
- National Medical Research Center of Cardiology
Pirogov Russian National Research Medical University
| | - N. A. Matveeva
- National Medical Research Center of Cardiology
Pirogov Russian National Research Medical University
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Vaidyanathan R, Van Ert H, Haq KT, Morotti S, Esch S, McCune EC, Grandi E, Eckhardt LL. Inward Rectifier Potassium Channels (Kir2.x) and Caveolin-3 Domain-Specific Interaction: Implications for Purkinje Cell-Dependent Ventricular Arrhythmias. Circ Arrhythm Electrophysiol 2019; 11:e005800. [PMID: 29326130 DOI: 10.1161/circep.117.005800] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/30/2017] [Indexed: 01/05/2023]
Abstract
BACKGROUND In human cardiac ventricle, IK1 is mainly comprised Kir2.1, but Kir2.2 and Kir2.3 heterotetramers occur and modulate IK1. Long-QT syndrome-9-associated CAV3 mutations cause decreased Kir2.1 current density, but Kir2.x heterotetramers have not been studied. Here, we determine the effect of long-QT syndrome-9-CAV3 mutation F97C on Kir2.x homo- and heterotetramers and model-associated arrhythmia mechanisms. METHODS AND RESULTS Super-resolution microscopy, co-immunoprecipitation, cellular electrophysiology, on-cell Western blotting, and simulation of Purkinje and ventricular myocyte mathematical models were used. Kir2.x isoforms have unique subcellular colocalization in human cardiomyocytes and coimmunoprecipitate with Cav3. F97C-Cav3 decreased peak inward Kir2.2 current density by 50% (-120 mV; P=0.019) and peak outward by 75% (-40 mV; P<0.05) but did not affect Kir2.3 current density. FRET (Förster resonance energy transfer) efficiency for Kir2.2 with Cav3 is high, and on-cell Western blotting demonstrates decreased Kir2.2 membrane expression with F97C-Cav3. Cav3-F97C reduced peak inward and outward current density of Kir2.2/Kir2.1 or Kir2.2/Kir2.3 heterotetramers (P<0.05). Only Cav3 scaffolding and membrane domains co-immunoprecipitation with Kir2.1 and Kir2.2 and Kir2.x-N-terminal Cav3 binding motifs are required for interaction. Mathematical Purkinje, but not ventricular, myocyte model incorporating simulated current reductions, predicts spontaneous delayed after-depolarization-mediated triggered activity. CONCLUSIONS Kir2.x isoforms have a unique intracellular pattern of distribution in association with specific Cav3 domains and that critically depends on interaction with N-terminal Kir2.x Cav3-binding motifs. Long-QT syndrome-9-CAV3 mutation differentially regulates current density and cell surface expression of Kir2.x homomeric and heteromeric channels. Mathematical Purkinje cell model incorporating experimental findings suggests delayed after-depolarization-type triggered activity as a possible arrhythmia mechanism.
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Affiliation(s)
- Ravi Vaidyanathan
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Hanora Van Ert
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Kazi T Haq
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Stefano Morotti
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Samuel Esch
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Elise C McCune
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Eleonora Grandi
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Lee L Eckhardt
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.).
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22
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Kuzmin VS, Egorov YV, Rozenshtraukh LV. [Electrhopysiological Effect of the Polyamine Spermine in Normoxic and Ischemic Ventricular Myocardium]. ACTA ACUST UNITED AC 2019; 59:43-51. [PMID: 30990140 DOI: 10.18087/cardio.2019.3.10240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Accepted: 04/13/2019] [Indexed: 11/18/2022]
Abstract
Cytoplasmic polyamines (PA) are involved in control of many cellular functions and are well known as regulators of so called inward-rectifier potassium ion channels. Nevertheless, functional significance of extracellular PA in the heart is poorly elucidated. Aim of this study was to study effects of endogenous PA spermine in the ventricular myocardium. Effects of the extracellular spermine were investigated in isolated multicellular preparations of rabbit and rat ventricular myocardium. Langendorff-perfused isolated rat and rabbit hearts were also used. Action potential (APs) duration and pattern of excitation in ventricular myocardium were estimated using standard microelectrode technique and optical mapping. Functional refractory periods were assessed in Langendorff perfused hearts with the help of programmedelectrical stimulation of the ventricle. In this study extracellular PA spermine (0.1-5 mM) induced shortening of the APs in multicellular preparations of rat ventricular myocardium registered using sharp microelectrode technique. However, spermine caused only weak effect in preparations of ventricular myocardium from rabbit heart: highest tested concentration of spermine (5 mM) induced 4.7 % APs shortening. Similarly, 0.1-1 mM of spermine was unable to alter substantially ventricular effective refractory periods in isolated perfused rabbit hearts. In two animal species tested (rat and rabbit) 0.1-1 mM of spermine failed to affect conduction velocity and activation pattern in ventricles of isolated Langendorff-perfused hearts under normoxia. However, in the rat no-flow model of ischemia-reperfusion extracellular spermine improved conduction of excitation in ventricles. Our results allow suggesting that extracellular spermine can prevent ischemia-induced proarrhythmic changes in ventricular myocardium probably due to reduction of calcium accumulation, but this effect is significant only when PA is applied in millimolar concentrations. Also, potential anti-ischemic effect of the PA may be species specific.
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Affiliation(s)
| | - Yu V Egorov
- Institute of Experimental Cardiology of National Medical Research Center for Cardiology
| | - L V Rozenshtraukh
- Institute of Experimental Cardiology of National Medical Research Center for Cardiology
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23
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Sanson C, Schombert B, Filoche-Rommé B, Partiseti M, Bohme GA. Electrophysiological and Pharmacological Characterization of Human Inwardly Rectifying K ir2.1 Channels on an Automated Patch-Clamp Platform. Assay Drug Dev Technol 2019; 17:89-99. [PMID: 30835490 PMCID: PMC6479253 DOI: 10.1089/adt.2018.882] [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] [Indexed: 01/08/2023] Open
Abstract
Inwardly rectifying IK1 potassium currents of the heart control the resting membrane potential of ventricular cardiomyocytes during diastole and contribute to their repolarization after each action potential. Mutations in the gene encoding Kir2.1 channels, which primarily conduct ventricular IK1, are associated with inheritable forms of arrhythmias and sudden cardiac death. Therefore, potential iatrogenic inhibition of Kir2.1-mediated IK1 currents is a cardiosafety concern during new drug discovery and development. Kir2.1 channels are part of the panel of cardiac ion channels currently considered for refined early compound risk assessment within the Comprehensive in vitro Proarrhythmia Assay initiative. In this study, we have validated a cell-based assay allowing functional quantification of Kir2.1 inhibitors using whole-cell recordings of Chinese hamster ovary cells stably expressing human Kir2.1 channels. We reproduced key electrophysiological and pharmacological features known for native IK1, including current enhancement by external potassium and voltage- and concentration-dependent blockade by external barium. Furthermore, the Kir inhibitors ML133, PA-6, and chloroquine, as well as the multichannel inhibitors chloroethylclonidine, chlorpromazine, SKF-96365, and the class III antiarrhythmic agent terikalant demonstrated slowly developing inhibitory activity in the low micromolar range. The robustness of this assay authorizes medium throughput screening for cardiosafety purposes and could help to enrich the currently limited Kir2.1 pharmacology.
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Affiliation(s)
- Camille Sanson
- 1 Integrated Drug Discovery, High-Content Biology, Sanofi Research and Development, Vitry-sur-Seine, France
| | - Brigitte Schombert
- 1 Integrated Drug Discovery, High-Content Biology, Sanofi Research and Development, Vitry-sur-Seine, France
| | - Bruno Filoche-Rommé
- 2 Integrated Drug Discovery, Medicinal Chemistry, Sanofi Research and Development, Vitry-sur-Seine, France
| | - Michel Partiseti
- 1 Integrated Drug Discovery, High-Content Biology, Sanofi Research and Development, Vitry-sur-Seine, France
| | - G Andrees Bohme
- 1 Integrated Drug Discovery, High-Content Biology, Sanofi Research and Development, Vitry-sur-Seine, France
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24
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Yuan D, Zheng P, Tan C, Huang SH, Li D, Huang J. Influence of Continuous Training on Atrial Myocytes I K1 and I KAch and on Induction of Atrial Fibrillation in a Rabbit Model. Cardiol Res Pract 2018; 2018:3795608. [PMID: 30662768 PMCID: PMC6313976 DOI: 10.1155/2018/3795608] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/01/2018] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Elucidation of mechanisms underlying continuous training-related atrial fibrillation (AF) may inform formulation of novel therapeutic approaches and training method selection. This study was aimed at assessing mechanisms underlying continuous training-induced AF in an animal model. METHODS Healthy New Zealand rabbits were divided into three groups (n=8 each), namely, control (C), and moderate intensity (M), and high intensity (H) continuous training according to treadmill speed. Atrial size andintrinsic and resting heart rates were measured by transthoracic echocardiography before, and 8 and 12 weeks after training. Using a Langendorff perfusion system, AF was induced by S1S2 stimulation and the induction rate was recorded. Atrial IK1 and IKAch ion current densities were recorded using whole-cell patch-clamp technique in isolated atrial myocytes. Changes in atrial Kir2.1, Kir2.2, Kir3.1, and Kir3.4 mRNA expression were assessed by reverse transcriptase-coupled polymerase chain reaction. RESULTS After 8 and 12 weeks, Groups M and H vs. Group C had greater (all P < 0.05) atrial anteroposterior diameter; greater incidence of AF (60% and 90% vs. 45%, respectively; P < 0.05, also between Groups H and M); and greater atrial IKAch current density. In Group H, Kir2.1 and Kir2.2 mRNA expression in the left and right atria was increased (P < 0.05, vs. Groups C and M) as was left atrial Kir3.1 and Kir3.4 mRNA expression (P < 0.05, vs. Group C). CONCLUSION In a rabbit model, continuous training enlarges atrial diameter leading to atrial structural and electrical remodeling and increased AF incidence.
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Affiliation(s)
- Dou Yuan
- Department of Thoracic and Cardiovascular Surgery, Cheng Du Shang Jin Nan Fu Hospital, West China Hospital of Sichuan University, Chengdu, China
| | - Ping Zheng
- Clinical Department of Strategic Support Force Aerospace Systems in Beijing Space City, Beijing, China
| | - Chen Tan
- Department of Cardiology, HeBei Yan Da Hospital, Langfang, China
| | - Si Hui Huang
- Department of Cardiology, Peking University First Hospital, Beijing, China
| | - Dan Li
- Department of Ultrasound, PLA Army General Hopsital, Beijing, China
| | - Jian Huang
- Fuwai Heart Disease Hospital, CAMS and PUMC, Beijing, China
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Voltage-Dependent Sarcolemmal Ion Channel Abnormalities in the Dystrophin-Deficient Heart. Int J Mol Sci 2018; 19:ijms19113296. [PMID: 30360568 PMCID: PMC6274787 DOI: 10.3390/ijms19113296] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 10/18/2018] [Accepted: 10/19/2018] [Indexed: 12/28/2022] Open
Abstract
Mutations in the gene encoding for the intracellular protein dystrophin cause severe forms of muscular dystrophy. These so-called dystrophinopathies are characterized by skeletal muscle weakness and degeneration. Dystrophin deficiency also gives rise to considerable complications in the heart, including cardiomyopathy development and arrhythmias. The current understanding of the pathomechanisms in the dystrophic heart is limited, but there is growing evidence that dysfunctional voltage-dependent ion channels in dystrophin-deficient cardiomyocytes play a significant role. Herein, we summarize the current knowledge about abnormalities in voltage-dependent sarcolemmal ion channel properties in the dystrophic heart, and discuss the potentially underlying mechanisms, as well as their pathophysiological relevance.
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Gong X, Han X, Lu X, Chen J, Huang J, Kelly TN, Chen CS, He J, Gu D, Chen S. Association of Kir genes with blood pressure responses to dietary sodium intervention: the GenSalt study. Hypertens Res 2018; 41:1045-1053. [PMID: 30323262 DOI: 10.1038/s41440-018-0113-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 04/19/2018] [Accepted: 05/12/2018] [Indexed: 12/19/2022]
Abstract
Blood pressure (BP) responses to dietary sodium intervention vary among individuals. The inwardly rectifying potassium channel (Kir) is a potassium-selective ion channel that allows potassium ions to move more easily into rather than out of the cell. We aimed to investigate the associations of Kir genes with BP responses to dietary sodium intervention. A 7-day low-sodium intervention followed by a 7-day high-sodium intervention was conducted among 1906 participants. BP measurements were obtained at baseline and during each dietary intervention. Both single-marker and gene-based analyses were performed to explore the associations between Kir gene variants and BP responses to dietary sodium interventions. The genetic risk score (GRS) was used to assess the cumulative effect of the variants on the BP response to the sodium interventions. During the low-sodium intervention, markers rs858009, rs2835904, and rs860795 in KCNJ6 were significantly associated with the systolic BP (SBP) response (P = 8.82 × 10-6, 3.32 × 10-6, and 2.39 × 10-4, respectively), whereas rs858009 and rs2835904 were significantly correlated with the mean arterial pressure (MAP) response (P = 1.64 × 10-4 and 2.72 × 10-4, respectively). Marker rs2836023 showed a significant association with the SBP response (P = 5.72 × 10-5) to the high-sodium intervention. The GRS stratified by quartile grouping or as a continuous variable was associated with the BP response to the sodium interventions. Gene-based analyses consistently revealed that KCNJ6 was significantly associated with the BP response to the sodium interventions. These findings suggest that KCNJ6 may contribute to variation of BP responses to dietary sodium interventions. Future studies are warranted to confirm these findings and to identify functional variants for salt sensitivity.
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Affiliation(s)
- Xinyuan Gong
- Department of Epidemiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xikun Han
- Department of Epidemiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xiangfeng Lu
- Department of Epidemiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jing Chen
- Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Jianfeng Huang
- Department of Epidemiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Tanika N Kelly
- Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Chung-Shiuan Chen
- Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Jiang He
- Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Dongfeng Gu
- Department of Epidemiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Shufeng Chen
- Department of Epidemiology, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
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27
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Gélinas R, El Khoury N, Chaix MA, Beauchamp C, Alikashani A, Ethier N, Boucher G, Villeneuve L, Robb L, Latour F, Mondesert B, Rivard L, Goyette P, Talajic M, Fiset C, Rioux JD. Characterization of a Human Induced Pluripotent Stem Cell-Derived Cardiomyocyte Model for the Study of Variant Pathogenicity: Validation of a KCNJ2 Mutation. ACTA ACUST UNITED AC 2018; 10:CIRCGENETICS.117.001755. [PMID: 29021306 DOI: 10.1161/circgenetics.117.001755] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/10/2017] [Indexed: 01/11/2023]
Abstract
BACKGROUND Long-QT syndrome is a potentially fatal condition for which 30% of patients are without a genetically confirmed diagnosis. Rapid identification of causal mutations is thus a priority to avoid at-risk situations that can lead to fatal cardiac events. Massively parallel sequencing technologies are useful for the identification of sequence variants; however, electrophysiological testing of newly identified variants is crucial to demonstrate causality. Long-QT syndrome could, therefore, benefit from having a standardized platform for functional characterization of candidate variants in the physiological context of human cardiomyocytes. METHODS AND RESULTS Using a variant in Kir2.1 (Gly52Val) revealed by whole-exome sequencing in a patient presenting with symptoms of long-QT syndrome as a proof of principle, we demonstrated that commercially available human induced pluripotent stem cell-derived cardiomyocytes are a powerful model for screening variants involved in genetic cardiac diseases. Immunohistochemistry experiments and whole-cell current recordings in human embryonic kidney cells expressing the wild-type or the mutant Kir2.1 demonstrated that Kir2.1-52V alters channel cellular trafficking and fails to form a functional channel. Using human induced pluripotent stem cell-derived cardiomyocytes, we not only confirmed these results but also further demonstrated that Kir2.1-52V is associated with a dramatic prolongation of action potential duration with evidence of arrhythmic activity, parameters which could not have been studied using human embryonic kidney cells. CONCLUSIONS Our study confirms the pathogenicity of Kir2.1-52V in 1 patient with long-QT syndrome and also supports the use of isogenic human induced pluripotent stem cell-derived cardiomyocytes as a physiologically relevant model for the screening of variants of unknown function.
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Affiliation(s)
- Roselle Gélinas
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Nabil El Khoury
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Marie-A Chaix
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Claudine Beauchamp
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Azadeh Alikashani
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Nathalie Ethier
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Gabrielle Boucher
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Louis Villeneuve
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Laura Robb
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Frédéric Latour
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Blandine Mondesert
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Lena Rivard
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Philippe Goyette
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Mario Talajic
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada
| | - Céline Fiset
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada.
| | - John David Rioux
- From the Research Center (R.G., N.E.K., M.-A.C., C.B., A.A., N.E., G.B., L.V., L.R., F.L., B.M., L.R., P.G., M.T., C.F., J.D.R.) and Cardiovascular Genetics Center (L. Robb, L. Rivard, M.T.), Montreal Heart Institute, Quebec, Canada; and Department of Medicine (R.G., M.-A.C., B.M., L.R., M.T., J.D.R.) and Faculty of Pharmacy (N.E.K., C.F.), Université de Montréal, Quebec, Canada.
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Possible association of CAG repeat polymorphism in KCNN3 encoding the potassium channel SK3 with oxaliplatin-induced neurotoxicity. Cancer Chemother Pharmacol 2018; 82:149-157. [PMID: 29774408 DOI: 10.1007/s00280-018-3600-1] [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: 12/01/2017] [Accepted: 05/09/2018] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Data suggest a role of the potassium channel SK3 (KCNN3 gene) in oxaliplatin-induced neurotoxicity (OIN). Length variations in the polymorphic CAG repeat of the KCNN3 gene may be associated with the risk of OIN. MATERIALS AND METHODS We performed patch-clamp experiments on HEK293 cell lines, expressing SK3 channel isoforms with short (11) or long (24) CAG repetitions, to measure intracellular calcium concentrations to test the effects of oxaliplatin on current density. A retrospective study was carried out on patients with colorectal cancer who had received oxaliplatin-based chemotherapy. DNA for KCNN3 genotyping was extracted from leukocytes. The region containing the CAG repeats was amplified by PCR and the products separated by capillary electrophoresis for length analysis. The patients were divided into three groups depending on whether they carried two short alleles, one short allele and one long allele, or two long alleles. The primary endpoint was the onset of grade 2 or 3 neuropathy to oxaliplatin. RESULTS There was no difference in current density, but oxaliplatin induced a differential effect on apamin-sensitive current density between the two isoforms expressed in the HEK cell lines. There was a significant reduction of store-operated calcium entry into cells expressing the short and more active isoform only after high concentration of oxaliplatin exposition. Eighty-six patients were included in the clinical study. There was no significant association between OIN and KCNN3 polymorphism for the three groups. CONCLUSION We observed a slight association between OIN and CAG repeat polymorphisms of the KCNN3 gene in a preclinical model, but not a clinical study.
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Abstract
Although the mechanism of sudden cardiac death (SCD) in heart failure is not completely known, genetic variations are known to play key roles in this process. Increasing numbers of mutations and variants are being discovered through genome-wide association studies. The genetic variations involved in the mechanisms of SCD have aroused widespread concern. Comprehensive understanding of the genetic variations involved in SCD may help prevent it. To this end, we briefly reviewed the genetic variations involved in SCD and their associations and interactions, and observed that cardiac ion channels are the core molecules involved in this process. Genetic variations involved in cardiac structure, cardiogenesis and development, cell division and differentiation, and DNA replication and transcription are all speculated to be loci involved in SCD. Additionally, the systems involved in neurohumoral regulation as well as substance and energy metabolism are also potentially responsible for susceptibility to SCD. They form an elaborate network and mutually interact with each other to govern the fate of SCD-susceptible individuals.
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Huang X, Lee SH, Lu H, Sanders KM, Koh SD. Molecular and functional characterization of inwardly rectifying K + currents in murine proximal colon. J Physiol 2018; 596:379-391. [PMID: 29205356 PMCID: PMC5792581 DOI: 10.1113/jp275234] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 11/20/2017] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS Interstitial cells of Cajal (ICC) from murine colonic muscles express genes encoding inwardly rectifying K+ channels. Transcripts of Kcnj2 (Kir2.1), Kcnj4 (Kir2.3), Kcnj14 (Kir2.4), Kcnj5 (Kir3.4), Kcnj8 (Kir 6.1) and Kcnj11 (Kir6.2) were found in colonic ICC. A conductance with properties consistent with Kir2 channels was observed in ICC but not in smooth muscle cells (SMC). Despite expression of gene transcripts, G-protein gated K+ channel (Kir3) and KATP (Kir6) currents were not resolved in ICC. KATP is a conductance prominent in SMC. Kir2 antagonist caused depolarization of freshly dispersed ICC and colonic smooth muscles, suggesting that this conductance is active under resting conditions in colonic muscles. The conclusion of the present study is that ICC express the Ba2+ -sensitive, inwardly rectifying K+ conductance in colonic muscles. This conductance is most probably a result of heterotetramers of Kir2 gene products, with this regulating resting potentials and the excitability of colonic muscles. ABSTRACT Membrane potentials of gastrointestinal muscles are important because voltage-dependent Ca2+ channels in smooth muscle cells (SMC) provide the Ca2+ that triggers contraction. Regulation of membrane potential is complicated because SMC are electrically coupled to interstitial cells of Cajal (ICC) and PDGFRα+ cells. Activation of conductances in any of these cells affects the excitability of the syncytium. We explored the role of inward rectifier K+ conductances in colonic ICC that might contribute to regulation of membrane potential. ICC expressed Kcnj2 (Kir2.1), Kcnj4 (Kir2.3), Kcnj14 (Kir2.4), Kcnj5 (Kir3.4), Kcnj8 (Kir 6.1) and Kcnj11 (Kir6.2). Voltage clamp experiments showed activation of inward current when extracellular K+ ([K+ ]o ) was increased. The current was inwardly rectifying and inhibited by Ba2+ (10 μm) and ML-133 (10 μm). A similar current was not available in SMC. The current activated in ICC by elevated [K+ ]o was not affected by Tertiapin-Q. Gβγ, when dialysed into cells, failed to activate a unique, Tertiapin-Q-sensitive conductance. Freshly dispersed ICC showed no evidence of functional KATP . Pinacidil failed to activate current and the inward current activated by elevated [K+ ]o was insensitive to glibenclamide. Under current clamp, ML-133 caused the depolarization of isolated ICC and also that of cells impaled with microelectrodes in intact muscle strips. These findings show that ICC, when isolated freshly from colonic muscles, expressed a Ba2+ -sensitive, inwardly rectifying K+ conductance. This conductance is most probably a result of the expression of multiple Kir2 family paralogues, and the inwardly rectifying conductance contributes to the regulation of resting potentials and excitability of colonic muscles.
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Affiliation(s)
- Xu Huang
- Department of Physiology and Cell BiologyUniversity of Nevada School of MedicineRenoNVUSA
| | - Si Hyung Lee
- Present address: Division of Gastroenterology and Hepatology, Department of Internal MedicineYeungnam University College of MedicineNam‐GuDaeguSouth Korea
| | - Hongli Lu
- Department of Physiology and Cell BiologyUniversity of Nevada School of MedicineRenoNVUSA
| | - Kenton M. Sanders
- Department of Physiology and Cell BiologyUniversity of Nevada School of MedicineRenoNVUSA
| | - Sang Don Koh
- Department of Physiology and Cell BiologyUniversity of Nevada School of MedicineRenoNVUSA
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Chen K, Zuo D, Wang SY, Chen H. Kir2 inward rectification-controlled precise and dynamic balances between Kir2 and HCN currents initiate pacemaking activity. FASEB J 2018; 32:3047-3057. [PMID: 29401592 DOI: 10.1096/fj.201701260r] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Spontaneous rhythmic action potential or pacemaking activity of pacemaker cells controls rhythmic signaling such as heartbeat. The mechanism underlying the origin of pacemaking activity is not well understood. In this study, we created human embryonic kidney (HEK) 293 cells that show pacemaking activity through heterologous expression of strong inward rectifier K+ subfamily 2 isoform 1 (Kir2.1) channels, hyperpolarization-activated cyclic nucleotide-gated isoform 2 (HCN2) nonselective cation channels, and voltage-gated Na+ subfamily 1 isoform 5 or Ca2+ subfamily 3 isoform 1 (Nav1.5 or Cav3.1) channels. A range of relative levels of Kir2.1 and HCN2 currents dynamically counterbalance, generating spontaneous rhythmic oscillation of resting membrane potential between -64 and -34 mV and determining oscillation rates. Each oscillation cycle begins with an autodepolarization phase, which slowly proceeds to the threshold potential that activates Nav1.5 or Cav3.1 channels and triggers action potential, causing engineered HEK293 cells to exhibit pacemaking activity at a rate of ≤67 beats/min. Engineered HEK293 cells with Kir2.1 and either HCN3 or HCN4 also show the oscillation. Engineered HEK293 cells expressing HCN2 and other Kir2 channels, which lack Kir2.1-like complete inward rectification, do not show the oscillation. Therefore, Kir2.1-like inward rectification-controlled precise and dynamic balances between Kir2 and HCN currents initiate spontaneous rhythmic action potential and form an origin of pacemaking activity; Kir2 and HCN channels play essential roles in pacemaking activity.-Chen, K., Zuo, D., Wang, S.-Y. Chen, H. Kir2 inward rectification-controlled precise and dynamic balances between Kir2 and HCN currents initiate pacemaking activity.
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Affiliation(s)
- Kuihao Chen
- Department of Biological Sciences, University at Albany, State University of New York, Albany, New York, USA
| | - Dongchuan Zuo
- Department of Biological Sciences, University at Albany, State University of New York, Albany, New York, USA
| | - Sho-Ya Wang
- Department of Biological Sciences, University at Albany, State University of New York, Albany, New York, USA
| | - Haijun Chen
- Department of Biological Sciences, University at Albany, State University of New York, Albany, New York, USA
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Chen K, Zuo D, Liu Z, Chen H. Kir2.1 channels set two levels of resting membrane potential with inward rectification. Pflugers Arch 2017; 470:599-611. [PMID: 29282531 DOI: 10.1007/s00424-017-2099-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 12/08/2017] [Accepted: 12/17/2017] [Indexed: 01/27/2023]
Abstract
Strong inward rectifier K+ channels (Kir2.1) mediate background K+ currents primarily responsible for maintenance of resting membrane potential. Multiple types of cells exhibit two levels of resting membrane potential. Kir2.1 and K2P1 currents counterbalance, partially accounting for the phenomenon of human cardiomyocytes in subphysiological extracellular K+ concentrations or pathological hypokalemic conditions. The mechanism of how Kir2.1 channels contribute to the two levels of resting membrane potential in different types of cells is not well understood. Here we test the hypothesis that Kir2.1 channels set two levels of resting membrane potential with inward rectification. Under hypokalemic conditions, Kir2.1 currents counterbalance HCN2 or HCN4 cation currents in CHO cells that heterologously express both channels, generating N-shaped current-voltage relationships that cross the voltage axis three times and reconstituting two levels of resting membrane potential. Blockade of HCN channels eliminated the phenomenon in K2P1-deficient Kir2.1-expressing human cardiomyocytes derived from induced pluripotent stem cells or CHO cells expressing both Kir2.1 and HCN2 channels. Weakly inward rectifier Kir4.1 or inward rectification-deficient Kir2.1•E224G mutant channels do not set such two levels of resting membrane potential when co-expressed with HCN2 channels in CHO cells or when overexpressed in human cardiomyocytes derived from induced pluripotent stem cells. These findings demonstrate a common mechanism that Kir2.1 channels set two levels of resting membrane potential with inward rectification by balancing inward currents through different cation channels such as hyperpolarization-activated HCN channels or hypokalemia-induced K2P1 leak channels.
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Affiliation(s)
- Kuihao Chen
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, 12222, USA
| | - Dongchuan Zuo
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, 12222, USA
| | - Zheng Liu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Haijun Chen
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, 12222, USA.
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Simkin D, Robin G, Giuliano S, Vukolic A, Moceri P, Guy N, Wagner KD, Lacampagne A, Allard B, Bendahhou S. Andersen's syndrome mutants produce a knockdown of inwardly rectifying K + channel in mouse skeletal muscle in vivo. Cell Tissue Res 2017; 371:309-323. [PMID: 29018970 DOI: 10.1007/s00441-017-2696-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 09/05/2017] [Indexed: 11/30/2022]
Abstract
Andersen's syndrome (AS) is a rare autosomal disorder that has been defined by the triad of periodic paralysis, cardiac arrhythmia, and developmental anomalies. AS has been directly linked to over 40 different autosomal dominant negative loss-of-function mutations in the KCNJ2 gene, encoding for the tetrameric strong inward rectifying K+ channel KIR2.1. While KIR2.1 channels have been suggested to contribute to setting the resting membrane potential (RMP) and to control the duration of the action potential (AP) in skeletal and cardiac muscle, the mechanism by which AS mutations produce such complex pathophysiological symptoms is poorly understood. Thus, we use an adenoviral transduction strategy to study in vivo subcellular distribution of wild-type (WT) and AS-associated mutant KIR2.1 channels in mouse skeletal muscle. We determined that WT and D71V AS mutant KIR2.1 channels are localized to the sarcolemma and the transverse tubules (T-tubules) of skeletal muscle fibers, while the ∆314-315 AS KIR2.1 mutation prevents proper trafficking of the homo- or hetero-meric channel complexes. Whole-cell voltage-clamp recordings in individual skeletal muscle fibers confirmed the reduction of inwardly rectifying K+ current (IK1) after transduction with ∆314-315 KIR2.1 as compared to WT channels. Analysis of skeletal muscle function revealed reduced force generation during isometric contraction as well as reduced resistance to muscle fatigue in extensor digitorum longus muscles transduced with AS mutant KIR2.1. Together, these results suggest that KIR2.1 channels may be involved in the excitation-contraction coupling process required for proper skeletal muscle function. Our findings provide clues to mechanisms associated with periodic paralysis in AS.
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Affiliation(s)
- Dina Simkin
- UMR 7370 CNRS, LP2M, Laboratoire d'Excellence - ICST, Université Côte d'Azur, Faculté de Médecine, 06107, Nice, France.,Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Gaëlle Robin
- UMR CNRS 5534, Université Claude Bernard Lyon 1, 69622, Lyon, France
| | - Serena Giuliano
- UMR 7370 CNRS, LP2M, Laboratoire d'Excellence - ICST, Université Côte d'Azur, Faculté de Médecine, 06107, Nice, France
| | - Ana Vukolic
- Institute for Molecular Health Science, ETH Zurich, 8093, Zurich, Switzerland
| | - Pamela Moceri
- UMR 7370 CNRS, LP2M, Laboratoire d'Excellence - ICST, Université Côte d'Azur, Faculté de Médecine, 06107, Nice, France.,Service de Cardiologie, Pasteur Hospital, CHU de Nice, 06107, Nice, France
| | - Nicolas Guy
- UMR 7275 CNRS, IPMC, Université Côte d'Azur, 06560, Valbonne, France
| | - Kay-Dietrich Wagner
- UMR 7284 CNRS, INSERM, IBV, Université Côte d'Azur, Faculté de Médecine, 06107, Nice, France
| | - Alain Lacampagne
- INSERM U1046, UMR CNRS 9214, Université de Montpellier, CHRU de Montpellier, 34295, Montpellier, France
| | - Bruno Allard
- UMR CNRS 5534, Université Claude Bernard Lyon 1, 69622, Lyon, France
| | - Saïd Bendahhou
- UMR 7370 CNRS, LP2M, Laboratoire d'Excellence - ICST, Université Côte d'Azur, Faculté de Médecine, 06107, Nice, France.
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Jeevaratnam K, Chadda KR, Huang CLH, Camm AJ. Cardiac Potassium Channels: Physiological Insights for Targeted Therapy. J Cardiovasc Pharmacol Ther 2017; 23:119-129. [PMID: 28946759 PMCID: PMC5808825 DOI: 10.1177/1074248417729880] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The development of novel drugs specifically directed at the ion channels underlying particular features of cardiac action potential (AP) initiation, recovery, and refractoriness would contribute to an optimized approach to antiarrhythmic therapy that minimizes potential cardiac and extracardiac toxicity. Of these, K+ channels contribute numerous and diverse currents with specific actions on different phases in the time course of AP repolarization. These features and their site-specific distribution make particular K+ channel types attractive therapeutic targets for the development of pharmacological agents attempting antiarrhythmic therapy in conditions such as atrial fibrillation. However, progress in the development of such temporally and spatially selective antiarrhythmic drugs against particular ion channels has been relatively limited, particularly in view of our incomplete understanding of the complex physiological roles and interactions of the various ionic currents. This review summarizes the physiological properties of the main cardiac potassium channels and the way in which they modulate cardiac electrical activity and then critiques a number of available potential antiarrhythmic drugs directed at them.
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Affiliation(s)
- Kamalan Jeevaratnam
- 1 Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,2 School of Medicine, Perdana University-Royal College of Surgeons Ireland, Serdang, Selangor Darul Ehsan, Malaysia
| | - Karan R Chadda
- 1 Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,3 Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L-H Huang
- 3 Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,4 Division of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - A John Camm
- 5 Cardiac Clinical Academic Group, St George's Hospital Medical School, University of London, Cranmer Terrace, London, United Kingdom
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Zuo D, Chen K, Zhou M, Liu Z, Chen H. Kir2.1 and K2P1 channels reconstitute two levels of resting membrane potential in cardiomyocytes. J Physiol 2017; 595:5129-5142. [PMID: 28543529 DOI: 10.1113/jp274268] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 05/22/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Outward and inward background currents across the cell membrane balance, determining resting membrane potential. Inward rectifier K+ channel subfamily 2 (Kir2) channels primarily maintain the resting membrane potential of cardiomyocytes. Human cardiomyocytes exhibit two levels of resting membrane potential at subphysiological extracellular K+ concentrations or pathological hypokalaemia, however, the underlying mechanism is unclear. In the present study, we show that human cardiomyocytes derived from induced pluripotent stem cells with enhanced expression of isoform 1 of Kir2 (Kir2.1) channels and mouse HL-1 cardiomyocytes with ectopic expression of two pore-domain K+ channel isoform 1 (K2P1) recapitulate two levels of resting membrane potential, indicating the contributions of Kir2.1 and K2P1 channels to the phenomenon. In Chinese hamster ovary cells that express the channels, Kir2.1 currents non-linearly counterbalance hypokalaemia-induced K2P1 leak cation currents, reconstituting two levels of resting membrane potential. These findings support the hypothesis that Kir2 currents non-linearly counterbalance inward background cation currents, such as K2P1 currents, accounting for two levels of resting membrane potential in human cardiomyocytes and demonstrating a novel mechanism that regulates excitability. ABSTRACT Inward rectifier K+ channel subfamily 2 (Kir2) channels primarily maintain the normal resting membrane potential of cardiomyocytes. At subphysiological extracellular K+ concentrations or pathological hypokalaemia, human cardiomyocytes show both hyperpolarized and depolarized resting membrane potentials; these depolarized potentials cause cardiac arrhythmia; however, the underlying mechanism is unknown. In the present study, we show that inward rectifier K+ channel subfamily 2 isoform 1 (Kir2.1) currents non-linearly counterbalance hypokalaemia-induced two pore-domain K+ channel isoform 1 (K2P1) leak cation currents, reconstituting two levels of resting membrane potential in cardiomyocytes. Under hypokalaemic conditions, both human cardiomyocytes derived from induced pluripotent stem cells with enhanced Kir2.1 expression and mouse HL-1 cardiomyocytes with ectopic expression of K2P1 channels recapitulate two levels of resting membrane potential. These cardiomyocytes display N-shaped current-voltage relationships that cross the voltage axis three times and the first and third zero-current potentials match the two levels of resting membrane potential. Inhibition of K2P1 expression eliminates the phenomenon, indicating contributions of Kir2.1 and K2P1 channels to two levels of resting membrane potential. Second, in Chinese hamster ovary cells that heterologously express the channels, Kir2.1 currents non-linearly counterbalance hypokalaemia-induced K2P1 leak cation currents, yielding the N-shaped current-voltage relationships, causing the resting membrane potential to spontaneously jump from hyperpolarization at the first zero-current potential to depolarization at the third zero-current potential, again recapitulating two levels of resting membrane potential. These findings reveal ionic mechanisms of the two levels of resting membrane potential, demonstrating a previously unknown mechanism for the regulation of excitability, and support the hypothesis that Kir2 currents non-linearly balance inward background cation currents, accounting for two levels of resting membrane potential of human cardiomyocytes.
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Affiliation(s)
- Dongchuan Zuo
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, USA
| | - Kuihao Chen
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, USA
| | - Min Zhou
- Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Zheng Liu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Haijun Chen
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, USA
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The IK1/Kir2.1 channel agonist zacopride prevents and cures acute ischemic arrhythmias in the rat. PLoS One 2017; 12:e0177600. [PMID: 28542320 PMCID: PMC5436763 DOI: 10.1371/journal.pone.0177600] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 04/20/2017] [Indexed: 12/13/2022] Open
Abstract
Arrhythmogenesis in acute myocardial infarction (MI) is associated with depolarization of resting membraine potential (RMP) and decrease of inward rectifier potassium current (IK1) in cardiomyocytes. However, clinical anti-arrhythmic agents that primarily act on RMP by enhancing the IK1 channel are not currently available. We hypothesized that zacopride, a selective and moderate agonist of the IK1/Kir2.1 channels, prevents and cures acute ischemic arrhythmias. To test this viewpoint, adult Sprague-Dawley (SD) rats were subjected to MI by ligating the left main coronary artery. The antiarrhythmic effects of zacopride (i.v. infusion) were observed in the settings of pre-treatment (zacopride given 3 min prior to coronary occlusion), post-treatment (zacopride given 3 min after coronary occlusion) and therapeutic treatment (zacopride given 30 s after the onset of the first sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) post MI). In all the three treatment modes, zacopride (15 μg/kg) inhibited MI-induced ventricular tachyarrhythmias, as shown by significant decreases in the premature ventricular contraction (PVC) and the duration and incidence of VT or VF. In Langendorff perfused rat hearts, the antiarrhythmic effect of 1 μmol/L zacopride were reversed by 1 μmol/L BaCl2, a blocker of IK1 channel. Patch clamp results in freshly isolated rat ventricular myocytes indicated that zacopride activated the IK1 channel and thereby reversed hypoxia-induced RMP depolarization and action potential duration (APD) prolongation. In addition, zacopride (1 μmol/L) suppressed hypoxia- or isoproterenol- induced delayed afterdepolarizations (DADs). In Kir2.x transfected Chinese hamster ovary (CHO) cells, zacopride activated the Kir2.1 homomeric channel but not the Kir2.2 or Kir2.3 channels. These results support our hypothesis that moderately enhancing IK1/Kir2.1 currents as by zacopride rescues ischemia- and hypoxia- induced RMP depolarization, and thereby prevents and cures acute ischemic arrhythmias. This study brings a new viewpoint to antiarrhythmic theories and provides a promising target for the treatment of acute ischemic arrhythmias.
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Huang H, Pugsley MK, Fermini B, Curtis MJ, Koerner J, Accardi M, Authier S. Cardiac voltage-gated ion channels in safety pharmacology: Review of the landscape leading to the CiPA initiative. J Pharmacol Toxicol Methods 2017; 87:11-23. [PMID: 28408211 DOI: 10.1016/j.vascn.2017.04.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 03/27/2017] [Accepted: 04/06/2017] [Indexed: 12/15/2022]
Abstract
Voltage gated ion channels are central in defining the fundamental properties of the ventricular cardiac action potential (AP), and are also involved in the development of drug-induced arrhythmias. Many drugs can inhibit cardiac ion currents, including the Na+ current (INa), L-type Ca2+ current (Ica-L), and K+ currents (Ito, IK1, IKs, and IKr), and thereby affect AP properties in a manner that can trigger or sustain cardiac arrhythmias. Since publication of ICH E14 and S7B over a decade ago, there has been a focus on drug effects on QT prolongation clinically, and on the rapidly activating delayed rectifier current (IKr), nonclinically, for evaluation of proarrhythmic risk. This focus on QT interval prolongation and a single ionic current likely impacted negatively some drugs that lack proarrhythmic liability in humans. To rectify this issue, the Comprehensive in vitro proarrhythmia assay (CiPA) initiative has been proposed to integrate drug effects on multiple cardiac ionic currents with in silico modelling of human ventricular action potentials, and in vitro data obtained from human stem cell-derived ventricular cardiomyocytes to estimate proarrhythmic risk of new drugs with improved accuracy. In this review, we present the physiological functions and the molecular basis of major cardiac ion channels that contribute to the ventricle AP, and discuss the CiPA paradigm in drug development.
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Affiliation(s)
- Hai Huang
- CiToxLAB North America, 445, Armand-Frappier Boul, Laval H7V 4B3, QC, Canada
| | - Michael K Pugsley
- Department of Toxicology, Purdue Pharma L.P., Cranbury, NJ 08512, USA
| | | | - Michael J Curtis
- Cardiovascular Division, Faculty of Life Sciences & Medicine, King's College London, Rayne Institute, St Thomas' Hospital, London SE17EH, UK
| | - John Koerner
- Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, MD 20993, USA
| | - Michael Accardi
- CiToxLAB North America, 445, Armand-Frappier Boul, Laval H7V 4B3, QC, Canada
| | - Simon Authier
- CiToxLAB North America, 445, Armand-Frappier Boul, Laval H7V 4B3, QC, Canada.
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Klein MG, Shou M, Stohlman J, Solhjoo S, Haigney M, Tidwell RR, Goldstein RE, Flagg TP, Haigney MC. Role of suppression of the inward rectifier current in terminal action potential repolarization in the failing heart. Heart Rhythm 2017; 14:1217-1223. [PMID: 28396172 DOI: 10.1016/j.hrthm.2017.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Indexed: 11/19/2022]
Abstract
BACKGROUND The failing heart exhibits an increased arrhythmia susceptibility that is often attributed to action potential (AP) prolongation due to significant ion channel remodeling. The inwardly rectifying K+ current (IK1) has been reported to be reduced, but its contribution to shaping the AP waveform and cell excitability in the failing heart remains unclear. OBJECTIVE The purpose of this study was to define the effect of IK1 suppression on the cardiac AP and excitability in the normal and failing hearts. METHODS We used electrophysiological and pharmacological approaches to investigate IK1 function in a swine tachy-pacing model of heart failure (HF). RESULTS Terminal repolarization of the AP (TRAP; the time constant of the exponential fit to terminal repolarization) was markedly prolonged in both myocytes and arterially perfused wedges from animals with HF. TRAP was increased by 54.1% in HF myocytes (P < .001) and 26.2% in HF wedges (P = .014). The increase in TRAP was recapitulated by the potent and specific IK1 inhibitor, PA-6 (pentamidine analog 6), indicating that IK1 is the primary determinant of the final phase of repolarization. Moreover, we find that IK1 suppression reduced the ratio of effective refractory period to AP duration at 90% of repolarization, permitting re-excitation before full repolarization, reduction of AP upstroke velocity, and likely promotion of slow conduction. CONCLUSION Using an objective measure of terminal repolarization, we conclude that IK1 is the major determinant of the terminal repolarization time course. Moreover, suppression of IK1 prolongs repolarization and reduces postrepolarization refractoriness without marked effects on the overall AP duration. Collectively, these findings demonstrate how IK1 suppression may contribute to arrhythmogenesis in the failing heart.
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Affiliation(s)
- Michael G Klein
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
| | - Matie Shou
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Jayna Stohlman
- Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland
| | - Soroosh Solhjoo
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Myles Haigney
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Richard R Tidwell
- Department of Pathology and Laboratory Medicine, School of Medicine, The University of North Carolina, Chapel Hill, North Carolina
| | - Robert E Goldstein
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Thomas P Flagg
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Mark C Haigney
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
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Scherer D, Schworm B, Seyler C, Xynogalos P, Scholz EP, Thomas D, Katus HA, Zitron E. Inhibition of inwardly rectifying Kir2.x channels by the novel anti-cancer agent gambogic acid depends on both pore block and PIP 2 interference. Naunyn Schmiedebergs Arch Pharmacol 2017; 390:701-710. [PMID: 28365825 DOI: 10.1007/s00210-017-1372-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 03/23/2017] [Indexed: 12/21/2022]
Abstract
The caged xanthone gambogic acid (GA) is a novel anti-cancer agent which exhibits anti-proliferative, anti-inflammatory and cytotoxic effects in many types of cancer tissues. In a recent phase IIa study, GA exhibits a favourable safety profile. However, limited data are available concerning its interaction with cardiac ion channels. Heteromeric assembly of Kir2.x channels underlies the cardiac inwardly rectifying IK1 current which is responsible for the stabilization of the diastolic resting membrane potential. Inhibition of the cardiac IK1 current may lead to ventricular arrhythmia due to delayed afterdepolarizations. Compared to Kv2.1, hERG and Kir1.1, a slow, delayed inhibition of Kir2.1 channels by GA in a mammalian cell line was reported before but no data exist in literature concerning action of GA on homomeric Kir2.2 and Kir2.3 and heteromeric Kir2.x channels. Therefore, the aim of this study was to provide comparative data on the effect of GA on homomeric and heteromeric Kir2.x channels. Homomeric and heteromeric Kir2.x channels were heterologously expressed in Xenopus oocytes, and the two-microelectrode voltage-clamp technique was used to record Kir2.x currents. To investigate the mechanism of the channel inhibition by GA, alanine-mutated Kir2.x channels with modifications in the channels pore region or at phosphatidylinositol 4,5-bisphosphate (PIP2)-binding sites were employed. GA caused a slow inhibition of homomeric and heteromeric Kir2.x channels at low micromolar concentrations (with IC50 Kir2.1/2.2 < Kir2.2 < Kir2.2/2.3 < Kir2.3 < Kir2.1 < Kir2.1/2.3). The effect did not reach saturation within 60 min and was not reversible upon washout for 30 min. The inhibition showed no strong voltage dependence. We provide evidence for a combination of direct channel pore blockade and a PIP2-dependent mechanism as a molecular basis for the observed effect. We conclude that Kir2.x channel inhibition by GA may be relevant in patients with pre-existing cardiac disorders such as chronic heart failure or certain rhythm disorders and recommend a close cardiac monitoring for those patients when treated with GA.
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Affiliation(s)
- Daniel Scherer
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.
| | - Benedikt Schworm
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany
| | - Claudia Seyler
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Panagiotis Xynogalos
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany
| | - Eberhard P Scholz
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Edgar Zitron
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, D-69120, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, Heidelberg, Germany
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40
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Role of plasma membrane-associated AKAPs for the regulation of cardiac IK1 current by protein kinase A. Naunyn Schmiedebergs Arch Pharmacol 2017; 390:493-503. [DOI: 10.1007/s00210-017-1344-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 01/12/2017] [Indexed: 12/20/2022]
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41
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Takeuchi Y, Omeki Y, Horio K, Nishio M, Nagata R, Oikawa S, Mizutani Y, Nagatani A, Funamoto Y, Uchida H, Fujino M, Eryu Y, Boda H, Miyata M, Hata T. Relationship between QT and JT peak interval variability in prepubertal children. Ann Noninvasive Electrocardiol 2017; 22. [PMID: 28211121 DOI: 10.1111/anec.12444] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 12/28/2016] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND The QT variability index (QTVI) is a noninvasive index of repolarization lability that has been applied to subjects with cardiovascular disease. QTVI provides a ratio of normalized QT variability to normalized heart rate variability, and therefore includes an assessment of autonomic nervous activity. However, measurement of QT time is particularly difficult in children, who exhibit physiologically high heart rates compared with adults. In this study, we developed a set of standard values of J-point to Tpeak interval (JTp) for infants by age, and assessed the correlation of QTVI with the JTp variability index (JTpVI). METHODS Subjects included 623 infants and children (0-7 years of age) without heart disease and 57 healthy university students. All subjects were divided into three groups by age. QTVI and JTpVI were calculated based on an electrocardiogram, and age-specific standard values, a gender-specific classification, and a standard growth curve were constructed. RESULTS JTpVI markedly decreased in infancy and slowly decreased thereafter, reaching adult values by school age. There was also a strong correlation of JTpVI with QTVI (r = .856). CONCLUSIONS JTp can be used to evaluate the variability of the repolarization time in healthy infants, and may be useful for detection of early repolarization abnormalities.
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Affiliation(s)
- Yuka Takeuchi
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Yumi Omeki
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Kayo Horio
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Miki Nishio
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Rina Nagata
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Shota Oikawa
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Yuri Mizutani
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Arisa Nagatani
- Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Yuri Funamoto
- Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Hidetoshi Uchida
- Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Masayuki Fujino
- Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Yoshihiko Eryu
- Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Hiroko Boda
- Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Masafumi Miyata
- Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Tadayoshi Hata
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.,Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan
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Koepple C, Scherer D, Seyler C, Scholz E, Thomas D, Katus HA, Zitron E. Dual Mechanism for Inhibition of Inwardly Rectifying Kir2.x Channels by Quinidine Involving Direct Pore Block and PIP 2-interference. J Pharmacol Exp Ther 2017; 361:209-218. [PMID: 28188270 DOI: 10.1124/jpet.116.238287] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 02/08/2017] [Indexed: 11/22/2022] Open
Abstract
Class IA antiarrhythmic drug quinidine was one of the first clinically used compounds to terminate atrial fibrillation and acts as multichannel inhibitor with well-documented inhibitory effects on several cardiac potassium channels. In the mammalian heart, heteromeric assembly of Kir2.1-2.3 channels underlies IK1 current. Although a low-affinity block of quinidine on Kir2.1 has already been described, a comparative analysis of effects on other Kir2.x channels has not been performed to date. Therefore, we analyzed the effects of quinidine on wild-type and mutant Kir2.x channels in the Xenopus oocyte expression system. Quinidine exerted differential inhibitory effects on Kir2.x channels with the highest affinity toward Kir2.3 subunits. Onset of block was slow and solely reversible in Kir2.2 subunits. Quinidine inhibited Kir2.x currents in a voltage-independent manner. By means of comparative Ala-scanning mutagenesis, we further found that residues E224, F254, D259, and E299 are essential for quinidine block in Kir2.1 subunits. Analogously, quinidine mediated Kir2.3 inhibition by binding corresponding residues E216, D247, D251, and E291. In contrast, Kir2.2 current block merely involved corresponding residue D260. Using channel mutants with altered (phosphatidylinositol 4,5-bisphosphate PIP2) affinities, we were able to demonstrate that high PIP2 affinities (i.e., Kir2.3 I214L) correlate with low quinidine sensitivity. Inversely, mutant channels interacting only weakly with PIP2 (i.e., Kir2.1 K182Q, and L221I) are prone to a higher inhibitory effect. Thus, we conclude that inhibition of Kir2.x channels by quinidine is mediated by joint modes of action involving direct cytoplasmic pore block and an impaired channel stabilization via interference with PIP2.
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Affiliation(s)
- Christoph Koepple
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Daniel Scherer
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Claudia Seyler
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Eberhard Scholz
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Edgar Zitron
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
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Edwards AG, Louch WE. Species-Dependent Mechanisms of Cardiac Arrhythmia: A Cellular Focus. CLINICAL MEDICINE INSIGHTS-CARDIOLOGY 2017; 11:1179546816686061. [PMID: 28469490 PMCID: PMC5392019 DOI: 10.1177/1179546816686061] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 11/20/2016] [Indexed: 12/17/2022]
Abstract
Although ventricular arrhythmia remains a leading cause of morbidity and mortality, available antiarrhythmic drugs have limited efficacy. Disappointing progress in the development of novel, clinically relevant antiarrhythmic agents may partly be attributed to discrepancies between humans and animal models used in preclinical testing. However, such differences are at present difficult to predict, requiring improved understanding of arrhythmia mechanisms across species. To this end, we presently review interspecies similarities and differences in fundamental cardiomyocyte electrophysiology and current understanding of the mechanisms underlying the generation of afterdepolarizations and reentry. We specifically highlight patent shortcomings in small rodents to reproduce cellular and tissue-level arrhythmia substrate believed to be critical in human ventricle. Despite greater ease of translation from larger animal models, discrepancies remain and interpretation can be complicated by incomplete knowledge of human ventricular physiology due to low availability of explanted tissue. We therefore point to the benefits of mathematical modeling as a translational bridge to understanding and treating human arrhythmia.
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Affiliation(s)
- Andrew G Edwards
- Center for Biomedical Computing, Simula Research Laboratory, Lysaker, Norway.,Center for Cardiological Innovation, Simula Research Laboratory, Lysaker, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K.G. Jebsen Cardiac Research Centre and Center for Heart Failure Research, University of Oslo, Oslo, Norway
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Kuroda Y, Yuasa S, Watanabe Y, Ito S, Egashira T, Seki T, Hattori T, Ohno S, Kodaira M, Suzuki T, Hashimoto H, Okata S, Tanaka A, Aizawa Y, Murata M, Aiba T, Makita N, Furukawa T, Shimizu W, Kodama I, Ogawa S, Kokubun N, Horigome H, Horie M, Kamiya K, Fukuda K. Flecainide ameliorates arrhythmogenicity through NCX flux in Andersen-Tawil syndrome-iPS cell-derived cardiomyocytes. Biochem Biophys Rep 2017; 9:245-256. [PMID: 28956012 PMCID: PMC5614591 DOI: 10.1016/j.bbrep.2017.01.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 12/09/2016] [Accepted: 01/10/2017] [Indexed: 12/15/2022] Open
Abstract
Andersen-Tawil syndrome (ATS) is a rare inherited channelopathy. The cardiac phenotype in ATS is typified by a prominent U wave and ventricular arrhythmia. An effective treatment for this disease remains to be established. We reprogrammed somatic cells from three ATS patients to generate induced pluripotent stem cells (iPSCs). Multi-electrode arrays (MEAs) were used to record extracellular electrograms of iPSC-derived cardiomyocytes, revealing strong arrhythmic events in the ATS-iPSC-derived cardiomyocytes. Ca2+ imaging of cells loaded with the Ca2+ indicator Fluo-4 enabled us to examine intracellular Ca2+ handling properties, and we found a significantly higher incidence of irregular Ca2+ release in the ATS-iPSC-derived cardiomyocytes than in control-iPSC-derived cardiomyocytes. Drug testing using ATS-iPSC-derived cardiomyocytes further revealed that antiarrhythmic agent, flecainide, but not the sodium channel blocker, pilsicainide, significantly suppressed these irregular Ca2+ release and arrhythmic events, suggesting that flecainide's effect in these cardiac cells was not via sodium channels blocking. A reverse-mode Na+/Ca2+exchanger (NCX) inhibitor, KB-R7943, was also found to suppress the irregular Ca2+ release, and whole-cell voltage clamping of isolated guinea-pig cardiac ventricular myocytes confirmed that flecainide could directly affect the NCX current (INCX). ATS-iPSC-derived cardiomyocytes recapitulate abnormal electrophysiological phenotypes and flecainide suppresses the arrhythmic events through the modulation of INCX. iPS cells are generated from three patients with ATS. ATS-iPS cell-derived cardiomyocytes show abnormal electrophysiological phenotypes. Flecainide suppresses abnormal electrophysiological phenotypes in ATS-iPS cell-derived cardiomyocytes.
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Affiliation(s)
- Yusuke Kuroda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan.,Department of Cardiology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Shinsuke Yuasa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yasuhide Watanabe
- Division of Pharmacological Science, Department of Health Science, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Shogo Ito
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Toru Egashira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tomohisa Seki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tetsuhisa Hattori
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Seiko Ohno
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan.,Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Shiga, Japan
| | - Masaki Kodaira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tomoyuki Suzuki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan.,Department of Cardiology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Hisayuki Hashimoto
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Shinichiro Okata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Atsushi Tanaka
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yoshiyasu Aizawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Mitsushige Murata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Laboratory Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Takeshi Aiba
- Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Naomasa Makita
- Department of Molecular Pathophysiology-1, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Tetsushi Furukawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
| | - Itsuo Kodama
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan
| | - Satoshi Ogawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Norito Kokubun
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - Hitoshi Horigome
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Kaichiro Kamiya
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
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Bohnen MS, Peng G, Robey SH, Terrenoire C, Iyer V, Sampson KJ, Kass RS. Molecular Pathophysiology of Congenital Long QT Syndrome. Physiol Rev 2017; 97:89-134. [PMID: 27807201 PMCID: PMC5539372 DOI: 10.1152/physrev.00008.2016] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ion channels represent the molecular entities that give rise to the cardiac action potential, the fundamental cellular electrical event in the heart. The concerted function of these channels leads to normal cyclical excitation and resultant contraction of cardiac muscle. Research into cardiac ion channel regulation and mutations that underlie disease pathogenesis has greatly enhanced our knowledge of the causes and clinical management of cardiac arrhythmia. Here we review the molecular determinants, pathogenesis, and pharmacology of congenital Long QT Syndrome. We examine mechanisms of dysfunction associated with three critical cardiac currents that comprise the majority of congenital Long QT Syndrome cases: 1) IKs, the slow delayed rectifier current; 2) IKr, the rapid delayed rectifier current; and 3) INa, the voltage-dependent sodium current. Less common subtypes of congenital Long QT Syndrome affect other cardiac ionic currents that contribute to the dynamic nature of cardiac electrophysiology. Through the study of mutations that cause congenital Long QT Syndrome, the scientific community has advanced understanding of ion channel structure-function relationships, physiology, and pharmacological response to clinically employed and experimental pharmacological agents. Our understanding of congenital Long QT Syndrome continues to evolve rapidly and with great benefits: genotype-driven clinical management of the disease has improved patient care as precision medicine becomes even more a reality.
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Affiliation(s)
- M S Bohnen
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - G Peng
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - S H Robey
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - C Terrenoire
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - V Iyer
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - K J Sampson
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - R S Kass
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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Effects of zacopride, a moderate I K1 channel agonist, on triggered arrhythmia and contractility in human ventricular myocardium. Pharmacol Res 2016; 115:309-318. [PMID: 27914945 DOI: 10.1016/j.phrs.2016.11.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 10/13/2016] [Accepted: 11/20/2016] [Indexed: 11/23/2022]
Abstract
Ventricular tachycardia is the leading cause of sudden arrhythmic death in the U.S. Recently, the moderate IK1 channel activator, zacopride, was shown to suppress triggered ventricular tachycardia in rats. Nonetheless, concerns were raised about the possibility of pro-arrhythmic activity after IK1 channel stimulation based on the promising anti-arrhythmic strategy of IK1 blockade in other animal models. Therefore, the goal of the current study was to investigate the ex-vivo effects of zacopride on triggered arrhythmia and contractility in ventricular human myocardium in order to validate data that was solely obtained from animal models. Application of 100nmol/L isoproterenol and 0.5mmol/L caffeine led to triggered arrhythmia in isolated cardiac muscles from non-failing and end-stage failing hearts. However, the occurrence of arrhythmia in muscles of non-failing hearts was markedly higher than those of end-stage failing hearts. Interestingly, zacopride eliminated the ex-vivo triggered arrhythmia in these muscles of non-failing and failing hearts in a concentration-dependent manner, with an effective IC50 in the range of 28-40μmol/L. Conversely, in the absence of isoproterenol/caffeine, zacopride led to a negative inotropic effect in a concentration-dependent manner. Reduced cardiac contraction was clearly observed at high zacopride concentration of 200μmol/L, along with the occurrence of contractile alternans in muscles of non-failing and failing hearts. Zacopride shows promising antiarrhythmic effects against triggered arrhythmia in human ventricular myocardium. However, in the absence of Ca2+ overload/arrhythmia, zacopride, albeit at high concentrations, decreases the force of contraction and increases the likelihood of occurrence of contractile alternans, which may predispose the heart to contractile dysfunction and/or arrhythmia. Overall, our results represent a key step in translating this drug from the benchtop to the bedside in the research area.
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48
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Activation of the Ca 2+-sensing receptors increases currents through inward rectifier K + channels via activation of phosphatidylinositol 4-kinase. Pflugers Arch 2016; 468:1931-1943. [PMID: 27838849 PMCID: PMC5138266 DOI: 10.1007/s00424-016-1901-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Revised: 10/26/2016] [Accepted: 11/06/2016] [Indexed: 10/25/2022]
Abstract
Inward rectifier K+ channels are important for maintaining normal electrical function in many cell types. The proper function of these channels requires the presence of membrane phosphoinositide 4,5-bisphosphate (PIP2). Stimulation of the Ca2+-sensing receptor CaR, a pleiotropic G protein-coupled receptor, activates both Gq/11, which decreases PIP2, and phosphatidylinositol 4-kinase (PI-4-K), which, conversely, increases PIP2. How membrane PIP2 levels are regulated by CaR activation and whether these changes modulate inward rectifier K+ are unknown. In this study, we found that activation of CaR by the allosteric agonist, NPSR568, increased inward rectifier K+ current (I K1) in guinea pig ventricular myocytes and currents mediated by Kir2.1 channels exogenously expressed in HEK293T cells with a similar sensitivity. Moreover, using the fluorescent PIP2 reporter tubby-R332H-cYFP to monitor PIP2 levels, we found that CaR activation in HEK293T cells increased membrane PIP2 concentrations. Pharmacological studies showed that both phospholipase C (PLC) and PI-4-K are activated by CaR stimulation with the latter played a dominant role in regulating membrane PIP2 and, thus, Kir currents. These results provide the first direct evidence that CaR activation upregulates currents through inward rectifier K+ channels by accelerating PIP2 synthesis. The regulation of I K1 plays a critical role in the stability of the electrical properties of many excitable cells, including cardiac myocytes and neurons. Further, synthetic allosteric modulators that increase CaR activity have been used to treat hyperparathyroidism, and negative CaR modulators are of potential importance in the treatment of osteoporosis. Thus, our results provide further insight into the roles played by CaR in the cardiovascular system and are potentially valuable for heart disease treatment and drug safety.
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49
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Jalife J. Dynamics and Molecular Mechanisms of Ventricular Fibrillation in Structurally Normal Hearts. Card Electrophysiol Clin 2016; 8:601-612. [PMID: 27521093 DOI: 10.1016/j.ccep.2016.04.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Ventricular fibrillation (VF) is the most severe cardiac rhythm disturbance and one of the most important immediate causes of sudden cardiac death. In the structurally normal heart, a small number of stable reentrant sources, perhaps 1 or 2, underlie the mechanism of VF, and the stabilization of the sources, their frequency, and the complexity of the turbulent waves they generate depend on the expression, spatial distribution, and intermolecular interactions of the 2 most important ion channels that control cardiac excitability: the inward rectifier potassium channel, Kir2.1, and the alpha subunit of the main cardiac sodium channel, NaV1.5.
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Affiliation(s)
- José Jalife
- Center for Arrhythmia Research, North Campus Research Complex, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI 48109, USA.
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50
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Rubi L, Koenig X, Kubista H, Todt H, Hilber K. Decreased inward rectifier potassium current I K1 in dystrophin-deficient ventricular cardiomyocytes. Channels (Austin) 2016; 11:101-108. [PMID: 27560040 PMCID: PMC5398571 DOI: 10.1080/19336950.2016.1228498] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Kir2.x channels in ventricular cardiomyocytes (most prominently Kir2.1) account for the inward rectifier potassium current IK1, which controls the resting membrane potential and the final phase of action potential repolarization. Recently it was hypothesized that the dystrophin-associated protein complex (DAPC) is important in the regulation of Kir2.x channels. To test this hypothesis, we investigated potential IK1 abnormalities in dystrophin-deficient ventricular cardiomyocytes derived from the hearts of Duchenne muscular dystrophy mouse models. We found that IK1 was substantially diminished in dystrophin-deficient cardiomyocytes when compared to wild type myocytes. This finding represents the first functional evidence for a significant role of the DAPC in the regulation of Kir2.x channels.
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Affiliation(s)
- Lena Rubi
- a Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology , Medical University of Vienna , Vienna , Austria
| | - Xaver Koenig
- a Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology , Medical University of Vienna , Vienna , Austria
| | - Helmut Kubista
- a Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology , Medical University of Vienna , Vienna , Austria
| | - Hannes Todt
- a Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology , Medical University of Vienna , Vienna , Austria
| | - Karlheinz Hilber
- a Department of Neurophysiology and Pharmacology, Center for Physiology and Pharmacology , Medical University of Vienna , Vienna , Austria
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