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Woltz RL, Zheng Y, Choi W, Ngo K, Trinh P, Ren L, Thai PN, Harris BJ, Han Y, Rouen KC, Mateos DL, Jian Z, Chen-Izu Y, Dickson EJ, Yamoah EN, Yarov-Yarovoy V, Vorobyov I, Zhang XD, Chiamvimonvat N. Atomistic mechanisms of the regulation of small-conductance Ca 2+-activated K + channel (SK2) by PIP2. Proc Natl Acad Sci U S A 2024; 121:e2318900121. [PMID: 39288178 DOI: 10.1073/pnas.2318900121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 06/24/2024] [Indexed: 09/19/2024] Open
Abstract
Small-conductance Ca2+-activated K+ channels (SK, KCa2) are gated solely by intracellular microdomain Ca2+. The channel has emerged as a therapeutic target for cardiac arrhythmias. Calmodulin (CaM) interacts with the CaM binding domain (CaMBD) of the SK channels, serving as the obligatory Ca2+ sensor to gate the channels. In heterologous expression systems, phosphatidylinositol 4,5-bisphosphate (PIP2) coordinates with CaM in regulating SK channels. However, the roles and mechanisms of PIP2 in regulating SK channels in cardiomyocytes remain unknown. Here, optogenetics, magnetic nanoparticles, combined with Rosetta structural modeling, and molecular dynamics (MD) simulations revealed the atomistic mechanisms of how PIP2 works in concert with Ca2+-CaM in the SK channel activation. Our computational study affords evidence for the critical role of the amino acid residue R395 in the S6 transmembrane segment, which is localized in propinquity to the intracellular hydrophobic gate. This residue forms a salt bridge with residue E398 in the S6 transmembrane segment from the adjacent subunit. Both R395 and E398 are conserved in all known isoforms of SK channels. Our findings suggest that the binding of PIP2 to R395 residue disrupts the R395:E398 salt bridge, increasing the flexibility of the transmembrane segment S6 and the activation of the channel. Importantly, our findings serve as a platform for testing of structural-based drug designs for therapeutic inhibitors and activators of the SK channel family. The study is timely since inhibitors of SK channels are currently in clinical trials to treat atrial arrhythmias.
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Grants
- NIH R01 HL085727 NIH R01 HL085844 NIH R01 HL137228 HHS | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- NIH R01 HL158961 HHS | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- NIH F32 HL151130 HHS | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- NIH T32 HL86350 HHS | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- NIH R01 HL128537 HHS | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- NIH R01 HL152681 HHS | NIH | National Heart, Lung, and Blood Institute (NHLBI)
- NIH R01 AG060504 and NIH 2P01 AG051443 HHS | NIH | National Institute on Aging (NIA)
- NIH R01 DC016099 HHS | NIH | National Institute on Deafness and Other Communication Disorders (NIDCD)
- NIH R35 GM149211 HHS | NIH | National Institute of General Medical Sciences (NIGMS)
- Anton 2 allocation MCB210014P Pittsburgh Supercomputing Center
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Affiliation(s)
- Ryan L Woltz
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA 95616
| | - Yang Zheng
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA 95616
| | - Woori Choi
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA 95616
| | - Khoa Ngo
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Pauline Trinh
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA 95616
| | - Lu Ren
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA 94305
| | - Phung N Thai
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA 95616
| | - Brandon J Harris
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Yanxiao Han
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Kyle C Rouen
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Diego Lopez Mateos
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Zhong Jian
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Ebenezer N Yamoah
- Department of Translational Neuroscience, University of Arizona College of Medicine, Phoenix, AZ 85004
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
- Department of Anesthesiology and Pain Medicine, University of California, Davis, CA 95616
| | - Igor Vorobyov
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Xiao-Dong Zhang
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA 95616
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, CA 95616
- Department of Pharmacology, University of California, Davis, CA 95616
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004
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Xu J, Zhang D, Ma Y, Du H, Wang Y, Luo W, Wang R, Yi F. ROS in diabetic atria regulate SK2 degradation by Atrogin-1 through the NF-κB signaling pathway. J Biol Chem 2024; 300:105735. [PMID: 38336298 PMCID: PMC10938124 DOI: 10.1016/j.jbc.2024.105735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 01/13/2024] [Accepted: 01/19/2024] [Indexed: 02/12/2024] Open
Abstract
One of the independent risk factors for atrial fibrillation is diabetes mellitus (DM); however, the underlying mechanisms causing atrial fibrillation in DM are unknown. The underlying mechanism of Atrogin-1-mediated SK2 degradation and associated signaling pathways are unclear. The aim of this study was to elucidate the relationship among reactive oxygen species (ROS), the NF-κB signaling pathway, and Atrogin-1 protein expression in the atrial myocardia of DM mice. We found that SK2 expression was downregulated comitant with increased ROS generation and enhanced NF-κB signaling activation in the atrial cardiomyocytes of DM mice. These observations were mimicked by exogenously applicating H2O2 and by high glucose culture conditions in HL-1 cells. Inhibition of ROS production by diphenyleneiodonium chloride or silencing of NF-κB by siRNA decreased the protein expression of NF-κB and Atrogin-1 and increased that of SK2 in HL-1 cells with high glucose culture. Moreover, chromatin immunoprecipitation assay demonstrated that NF-κB/p65 directly binds to the promoter of the FBXO32 gene (encoding Atrogin-1), regulating the FBXO32 transcription. Finally, we evaluated the therapeutic effects of curcumin, known as a NF-κB inhibitor, on Atrogin-1 and SK2 expression in DM mice and confirmed that oral administration of curcumin for 4 weeks significantly suppressed Atrogin-1 expression and protected SK2 expression against hyperglycemia. In summary, the results from this study indicated that the ROS/NF-κB signaling pathway participates in Atrogin-1-mediated SK2 regulation in the atria of streptozotocin-induced DM mice.
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Affiliation(s)
- Jian Xu
- Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China; Senior Department of Cardiology, The Sixth Medical Center of PLA General Hospital, Beijing, China
| | - Dong Zhang
- Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Yibo Ma
- Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Hui Du
- Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Yi Wang
- Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Wenping Luo
- Institute of Cardiovascular and Vascular Disease, Shaanxi University of Traditional Chinese Medicine, Xianyang, China
| | - Ruxing Wang
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Fu Yi
- Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
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3
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Babini H, Jiménez-Sábado V, Stogova E, Arslanova A, Butt M, Dababneh S, Asghari P, Moore EDW, Claydon TW, Chiamvimonvat N, Hove-Madsen L, Tibbits GF. hiPSC-derived cardiomyocytes as a model to study the role of small-conductance Ca 2+-activated K + (SK) ion channel variants associated with atrial fibrillation. Front Cell Dev Biol 2024; 12:1298007. [PMID: 38304423 PMCID: PMC10830749 DOI: 10.3389/fcell.2024.1298007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 01/05/2024] [Indexed: 02/03/2024] Open
Abstract
Atrial fibrillation (AF), the most common arrhythmia, has been associated with different electrophysiological, molecular, and structural alterations in atrial cardiomyocytes. Therefore, more studies are required to elucidate the genetic and molecular basis of AF. Various genome-wide association studies (GWAS) have strongly associated different single nucleotide polymorphisms (SNPs) with AF. One of these GWAS identified the rs13376333 risk SNP as the most significant one from the 1q21 chromosomal region. The rs13376333 risk SNP is intronic to the KCNN3 gene that encodes for small conductance calcium-activated potassium channels type 3 (SK3). However, the functional electrophysiological effects of this variant are not known. SK channels represent a unique family of K+ channels, primarily regulated by cytosolic Ca2+ concentration, and different studies support their critical role in the regulation of atrial excitability and consequently in the development of arrhythmias like AF. Since different studies have shown that both upregulation and downregulation of SK3 channels can lead to arrhythmias by different mechanisms, an important goal is to elucidate whether the rs13376333 risk SNP is a gain-of-function (GoF) or a loss-of-function (LoF) variant. A better understanding of the functional consequences associated with these SNPs could influence clinical practice guidelines by improving genotype-based risk stratification and personalized treatment. Although research using native human atrial cardiomyocytes and animal models has provided useful insights, each model has its limitations. Therefore, there is a critical need to develop a human-derived model that represents human physiology more accurately than existing animal models. In this context, research with human induced pluripotent stem cells (hiPSC) and subsequent generation of cardiomyocytes derived from hiPSC (hiPSC-CMs) has revealed the underlying causes of various cardiovascular diseases and identified treatment opportunities that were not possible using in vitro or in vivo studies with animal models. Thus, the ability to generate atrial cardiomyocytes and atrial tissue derived from hiPSCs from human/patients with specific genetic diseases, incorporating novel genetic editing tools to generate isogenic controls and organelle-specific reporters, and 3D bioprinting of atrial tissue could be essential to study AF pathophysiological mechanisms. In this review, we will first give an overview of SK-channel function, its role in atrial fibrillation and outline pathophysiological mechanisms of KCNN3 risk SNPs. We will then highlight the advantages of using the hiPSC-CM model to investigate SNPs associated with AF, while addressing limitations and best practices for rigorous hiPSC studies.
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Affiliation(s)
- Hosna Babini
- Cellular and Regenerative Medicine Centre, BC Children’s Hospital Research Institute, Vancouver, BC, Canada
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Verónica Jiménez-Sábado
- Cellular and Regenerative Medicine Centre, BC Children’s Hospital Research Institute, Vancouver, BC, Canada
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
- IIB SANT PAU, and CIBERCV, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Ekaterina Stogova
- Cellular and Regenerative Medicine Centre, BC Children’s Hospital Research Institute, Vancouver, BC, Canada
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Alia Arslanova
- Cellular and Regenerative Medicine Centre, BC Children’s Hospital Research Institute, Vancouver, BC, Canada
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Mariam Butt
- Cellular and Regenerative Medicine Centre, BC Children’s Hospital Research Institute, Vancouver, BC, Canada
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Saif Dababneh
- Cellular and Regenerative Medicine Centre, BC Children’s Hospital Research Institute, Vancouver, BC, Canada
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Parisa Asghari
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Edwin D. W. Moore
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Thomas W. Claydon
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | | | - Leif Hove-Madsen
- IIB SANT PAU, and CIBERCV, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
- Instituto de Investigaciones Biomédicas de Barcelona (IIBB-CSIC), Barcelona, Spain
| | - Glen F. Tibbits
- Cellular and Regenerative Medicine Centre, BC Children’s Hospital Research Institute, Vancouver, BC, Canada
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
- Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
- School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
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4
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Liu T, Li T, Xu D, Wang Y, Zhou Y, Wan J, Huang CLH, Tan X. Small-conductance calcium-activated potassium channels in the heart: expression, regulation and pathological implications. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220171. [PMID: 37122223 PMCID: PMC10150224 DOI: 10.1098/rstb.2022.0171] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 12/25/2022] [Indexed: 05/02/2023] Open
Abstract
Ca2+-activated K+ channels are critical to cellular Ca2+ homeostasis and excitability; they couple intracellular Ca2+ and membrane voltage change. Of these, the small, 4-14 pS, conductance SK channels include three, KCNN1-3 encoded, SK1/KCa2.1, SK2/KCa2.2 and SK3/KCa2.3, channel subtypes with characteristic, EC50 ∼ 10 nM, 40 pM, 1 nM, apamin sensitivities. All SK channels, particularly SK2 channels, are expressed in atrial, ventricular and conducting system cardiomyocytes. Pharmacological and genetic modification results have suggested that SK channel block or knockout prolonged action potential durations (APDs) and effective refractory periods (ERPs) particularly in atrial, but also in ventricular, and sinoatrial, atrioventricular node and Purkinje myocytes, correspondingly affect arrhythmic tendency. Additionally, mitochondrial SK channels may decrease mitochondrial Ca2+ overload and reactive oxygen species generation. SK channels show low voltage but marked Ca2+ dependences (EC50 ∼ 300-500 nM) reflecting their α-subunit calmodulin (CaM) binding domains, through which they may be activated by voltage-gated or ryanodine-receptor Ca2+ channel activity. SK function also depends upon complex trafficking and expression processes and associations with other ion channels or subunits from different SK subtypes. Atrial and ventricular clinical arrhythmogenesis may follow both increased or decreased SK expression through decreased or increased APD correspondingly accelerating and stabilizing re-entrant rotors or increasing incidences of triggered activity. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Ting Liu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Tao Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Dandi Xu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yan Wang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yafei Zhou
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Juyi Wan
- Department of Cardiovascular Surgery, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Christopher L.-H. Huang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Physiological Laboratory and Department of Biochemistry, University of Cambridge, Cambridge CB2 3EG, UK
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Physiology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
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5
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Zhang XD, Chiamvimonvat N. Targeting Small-Conductance Calcium-Activated Potassium Channels in Atrial Fibrillation: Therapeutic Opportunities. Circ Res 2023; 132:1104-1106. [PMID: 37104564 PMCID: PMC10155264 DOI: 10.1161/circresaha.123.322777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine (X.-D.Z., N.C.), School of Medicine, University of California, Davis
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine (X.-D.Z., N.C.), School of Medicine, University of California, Davis
- Department of Pharmacology (N.C.), School of Medicine, University of California, Davis
- Department of Veterans Affairs, Northern California Health Care System, Mather (N.C.)
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6
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Abstract
Cardiac alternans arises from dynamical instabilities in the electrical and calcium cycling systems of the heart, and often precedes ventricular arrhythmias and sudden cardiac death. In this review, we integrate clinical observations with theory and experiment to paint a holistic portrait of cardiac alternans: the underlying mechanisms, arrhythmic manifestations and electrocardiographic signatures. We first summarize the cellular and tissue mechanisms of alternans that have been demonstrated both theoretically and experimentally, including 3 voltage-driven and 2 calcium-driven alternans mechanisms. Based on experimental and simulation results, we describe their relevance to mechanisms of arrhythmogenesis under different disease conditions, and their link to electrocardiographic characteristics of alternans observed in patients. Our major conclusion is that alternans is not only a predictor, but also a causal mechanism of potentially lethal ventricular and atrial arrhythmias across the full spectrum of arrhythmia mechanisms that culminate in functional reentry, although less important for anatomic reentry and focal arrhythmias.
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Affiliation(s)
- Zhilin Qu
- Departments of Medicine (Cardiology), Physiology, and Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - James N. Weiss
- Departments of Medicine (Cardiology), Physiology, and Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
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7
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Huang C, Song Z, Qu Z. Synchronization of spatially discordant voltage and calcium alternans in cardiac tissue. Phys Rev E 2022; 106:024406. [PMID: 36109882 PMCID: PMC11316446 DOI: 10.1103/physreve.106.024406] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Accepted: 07/18/2022] [Indexed: 06/01/2023]
Abstract
The heart is an excitable medium which is excited by membrane potential depolarization and propagation. Membrane potential depolarization brings in calcium (Ca) through the Ca channels to trigger intracellular Ca release for contraction of the heart. Ca also affects voltage via Ca-dependent ionic currents, and thus, voltage and Ca are bidirectionally coupled. It has been shown that the voltage subsystem or the Ca subsystem can generate its own dynamical instabilities which are affected by their bidirectional couplings, leading to complex dynamics of action potential and Ca cycling. Moreover, the dynamics become spatiotemporal in tissue in which cells are diffusively coupled through voltage. A widely investigated spatiotemporal dynamics is spatially discordant alternans (SDA) in which action potential duration (APD) or Ca amplitude exhibits temporally period-2 and spatially out-of-phase patterns, i.e., APD-SDA and Ca-SDA patterns, respectively. However, the mechanisms of formation, stability, and synchronization of APD-SDA and Ca-SDA patterns remain incompletely understood. In this paper, we use cardiac tissue models described by an amplitude equation, coupled iterated maps, and reaction-diffusion equations with detailed physiology (the ionic model) to perform analytical and computational investigations. We show that, when the Ca subsystem is stable, the Ca-SDA pattern always follows the APD-SDA pattern, and thus, they are always synchronized. When the Ca subsystem is unstable, synchronization of APD-SDA and Ca-SDA patterns depends on the stabilities of both subsystems, their coupling strengths, and the spatial scales of the initial Ca-SDA patterns. Spontaneous (initial condition-independent) synchronization is promoted by enhancing APD instability and reducing Ca instability as well as stronger Ca-to-APD and APD-to-Ca coupling, a pattern formation caused by dynamical instabilities. When Ca is more unstable and APD is less unstable or APD-to-Ca coupling is weak, synchronization of APD-SDA and Ca-SDA patterns is promoted by larger initially synchronized Ca-SDA clusters, i.e., initial condition-dependent synchronization. The synchronized APD-SDA and Ca-SDA patterns can be locked in-phase, antiphase, or quasiperiodic depending on the coupling relationship between APD and Ca. These theoretical and simulation results provide mechanistic insights into the APD-SDA and Ca-SDA dynamics observed in experimental studies.
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Affiliation(s)
- Chunli Huang
- School of Mathematics and Statistics, Guangdong University of Foreign Studies, Guangzhou 510420, China
- Department of Medicine, University of California, Los Angeles, California 90095, USA
| | - Zhen Song
- Peng Cheng Laboratory, Shenzhen, Guangdong, China
| | - Zhilin Qu
- Department of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Computational Medicine, University of California, Los Angeles, California 90095, USA
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8
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PKC regulation of ion channels: The involvement of PIP 2. J Biol Chem 2022; 298:102035. [PMID: 35588786 PMCID: PMC9198471 DOI: 10.1016/j.jbc.2022.102035] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/24/2022] Open
Abstract
Ion channels are integral membrane proteins whose gating has been increasingly shown to depend on the presence of the low-abundance membrane phospholipid, phosphatidylinositol (4,5) bisphosphate. The expression and function of ion channels is tightly regulated via protein phosphorylation by specific kinases, including various PKC isoforms. Several channels have further been shown to be regulated by PKC through altered surface expression, probability of channel opening, shifts in voltage dependence of their activation, or changes in inactivation or desensitization. In this review, we survey the impact of phosphorylation of various ion channels by PKC isoforms and examine the dependence of phosphorylated ion channels on phosphatidylinositol (4,5) bisphosphate as a mechanistic endpoint to control channel gating.
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9
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Yang B, Jiang Q, He S, Li T, Ou X, Chen T, Fan X, Jiang F, Zeng X, Huang CLH, Lei M, Tan X. Ventricular SK2 upregulation following angiotensin II challenge: Modulation by p21-activated kinase-1. J Mol Cell Cardiol 2022; 164:110-125. [PMID: 34774547 DOI: 10.1016/j.yjmcc.2021.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 10/15/2021] [Accepted: 11/03/2021] [Indexed: 12/11/2022]
Abstract
Effects of hypertrophic challenge on small-conductance, Ca2+-activated K+(SK2) channel expression were explored in intact murine hearts, isolated ventricular myocytes and neonatal rat cardiomyocytes (NRCMs). An established experimental platform applied angiotensin II (Ang II) challenge in the presence and absence of reduced p21-activated kinase (PAK1) (PAK1cko vs. PAK1f/f, or shRNA-PAK1 interference) expression. SK2 current contributions were detected through their sensitivity to apamin block. Ang II treatment increased such SK2 contributions to optically mapped action potential durations (APD80) and their heterogeneity, and to patch-clamp currents. Such changes were accentuated in PAK1cko compared to PAK1f/f, intact hearts and isolated cardiomyocytes. They paralleled increased histological and echocardiographic hypertrophic indices, reduced cardiac contractility, and increased SK2 protein expression, changes similarly greater with PAK1cko than PAK1f/f. In NRCMs, Ang II challenge replicated such increases in apamin-sensitive SK patch clamp currents as well as in real-time PCR and western blot measures of SK2 mRNA and protein expression and cell hypertrophy. Furthermore, the latter were enhanced by shRNA-PAK1 interference and mitigated by the PAK1 agonist FTY720. Increased CaMKII and CREB phosphorylation accompanied these effects. These were rescued by both FTY720 as well as the CaMKII inhibitor KN93, but not its inactive analogue KN92. Such CREB then specifically bound to the KCNN2 promoter sequence in luciferase assays. These findings associate Ang II induced hypertrophy with increased SK2 expression brought about by a CaMKII/CREB signaling convergent with the PAK1 pathway thence upregulating the KCNN2 promoter activity. SK2 may then influence cardiac electrophysiology under conditions of cardiac hypertrophy and failure.
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Affiliation(s)
- Binbin Yang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Oral & Maxillofacial Reconstruction and Regeneration Laboratory, The Affiliated Stomatology Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Qin Jiang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Shicheng He
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Tao Li
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xianhong Ou
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Tangting Chen
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xuehui Fan
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Feng Jiang
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xiaorong Zeng
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Christopher L-H Huang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Physiological Laboratory and Department of Biochemistry, University of Cambridge, Cambridge CB2 3EG, UK
| | - Ming Lei
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China.
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10
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Ledford HA, Park S, Muir D, Woltz RL, Ren L, Nguyen PT, Sirish P, Wang W, Sihn CR, George AL, Knollmann BC, Yamoah EN, Yarov-Yarovoy V, Zhang XD, Chiamvimonvat N. Different arrhythmia-associated calmodulin mutations have distinct effects on cardiac SK channel regulation. J Gen Physiol 2021; 152:211546. [PMID: 33211795 PMCID: PMC7681919 DOI: 10.1085/jgp.202012667] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 08/25/2020] [Accepted: 10/19/2020] [Indexed: 12/21/2022] Open
Abstract
Calmodulin (CaM) plays a critical role in intracellular signaling and regulation of Ca2+-dependent proteins and ion channels. Mutations in CaM cause life-threatening cardiac arrhythmias. Among the known CaM targets, small-conductance Ca2+-activated K+ (SK) channels are unique, since they are gated solely by beat-to-beat changes in intracellular Ca2+. However, the molecular mechanisms of how CaM mutations may affect the function of SK channels remain incompletely understood. To address the structural and functional effects of these mutations, we introduced prototypical human CaM mutations in human induced pluripotent stem cell–derived cardiomyocyte-like cells (hiPSC-CMs). Using structural modeling and molecular dynamics simulation, we demonstrate that human calmodulinopathy-associated CaM mutations disrupt cardiac SK channel function via distinct mechanisms. CaMD96V and CaMD130G mutants reduce SK currents through a dominant-negative fashion. By contrast, specific mutations replacing phenylalanine with leucine result in conformational changes that affect helix packing in the C-lobe, which disengage the interactions between apo-CaM and the CaM-binding domain of SK channels. Distinct mutant CaMs may result in a significant reduction in the activation of the SK channels, leading to a decrease in the key Ca2+-dependent repolarization currents these channels mediate. The findings in this study may be generalizable to other interactions of mutant CaMs with Ca2+-dependent proteins within cardiac myocytes.
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Affiliation(s)
- Hannah A Ledford
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Seojin Park
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Duncan Muir
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Ryan L Woltz
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Lu Ren
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Phuong T Nguyen
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA
| | - Padmini Sirish
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Wenying Wang
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Choong-Ryoul Sihn
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Björn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Department of Medicine, School of Medicine, Vanderbilt University, Nashville, TN
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA
| | - Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA
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11
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Crotti L, Odening KE, Sanguinetti MC. Heritable arrhythmias associated with abnormal function of cardiac potassium channels. Cardiovasc Res 2021; 116:1542-1556. [PMID: 32227190 DOI: 10.1093/cvr/cvaa068] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/24/2020] [Accepted: 03/26/2020] [Indexed: 12/16/2022] Open
Abstract
Cardiomyocytes express a surprisingly large number of potassium channel types. The primary physiological functions of the currents conducted by these channels are to maintain the resting membrane potential and mediate action potential repolarization under basal conditions and in response to changes in the concentrations of intracellular sodium, calcium, and ATP/ADP. Here, we review the diversity and functional roles of cardiac potassium channels under normal conditions and how heritable mutations in the genes encoding these channels can lead to distinct arrhythmias. We briefly review atrial fibrillation and J-wave syndromes. For long and short QT syndromes, we describe their genetic basis, clinical manifestation, risk stratification, traditional and novel therapeutic approaches, as well as insights into disease mechanisms provided by animal and cellular models.
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Affiliation(s)
- Lia Crotti
- Center for Cardiac Arrhythmias of Genetic Origin, Istituto Auxologico Italiano, IRCCS, Milan, Italy.,Laboratory of Cardiovascular Genetics, Istituto Auxologico Italiano, IRCCS, Milan, Italy.,Department of Cardiovascular, Neural and Metabolic Sciences, Istituto Auxologico Italiano, IRCCS, San Luca Hospital, Milan, Italy.,Department of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy
| | - Katja E Odening
- Department of Cardiology and Angiology I, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Institute of Experimental Cardiovascular Medicine, Heart Center University of Freiburg, Medical Faculty, Freiburg, Germany.,Department of Cardiology, Translational Cardiology, Inselspital, Bern University Hospital, and Institute of Physiology, University of Bern, Bern, Switzerland
| | - Michael C Sanguinetti
- Department of Internal Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
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12
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Rahm AK, Wieder T, Gramlich D, Müller ME, Wunsch MN, El Tahry FA, Heimberger T, Sandke S, Weis T, Most P, Katus HA, Thomas D, Lugenbiel P. Differential regulation of K Ca 2.1 (KCNN1) K + channel expression by histone deacetylases in atrial fibrillation with concomitant heart failure. Physiol Rep 2021; 9:e14835. [PMID: 34111326 PMCID: PMC8191401 DOI: 10.14814/phy2.14835] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 01/12/2023] Open
Abstract
Atrial fibrillation (AF) with concomitant heart failure (HF) poses a significant therapeutic challenge. Mechanism‐based approaches may optimize AF therapy. Small‐conductance, calcium‐activated K+ (KCa, KCNN) channels contribute to cardiac action potential repolarization. KCNN1 exhibits predominant atrial expression and is downregulated in chronic AF patients with preserved cardiac function. Epigenetic regulation is suggested by AF suppression following histone deacetylase (HDAC) inhibition. We hypothesized that HDAC‐dependent KCNN1 remodeling contributes to arrhythmogenesis in AF complicated by HF. The aim of this study was to assess KCNN1 and HDAC1–7 and 9 transcript levels in AF/HF patients and in a pig model of atrial tachypacing‐induced AF with reduced left ventricular function. In HL‐1 atrial myocytes, tachypacing and anti‐Hdac siRNAs were employed to investigate effects on Kcnn1 mRNA levels. KCNN1 expression displayed side‐specific remodeling in AF/HF patients with upregulation in left and suppression in right atrium. In pigs, KCNN1 remodeling showed intermediate phenotypes. HDAC levels were differentially altered in humans and pigs, reflecting highly variable epigenetic regulation. Tachypacing recapitulated downregulation of Hdacs1, 3, 4, 6, and 7 with a tendency towards reduced Kcnn1 levels in vitro, indicating that atrial high rates induce remodeling. Finally, Kcnn1 expression was decreased by knockdown of Hdacs2, 3, 6, and 7 and enhanced by genetic Hdac9 inactivation, while anti‐Hdac1, 4, and 5 siRNAs did not affect Kcnn1 transcript levels. In conclusion, KCNN1 and HDAC expression is differentially remodeled in AF complicated by HF. Direct regulation of KCNN1 by HDACs in atrial myocytes provides a basis for mechanism‐based antiarrhythmic therapy.
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Affiliation(s)
- Ann-Kathrin Rahm
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Teresa Wieder
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany
| | - Dominik Gramlich
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Mara Elena Müller
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Maximilian N Wunsch
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Fadwa A El Tahry
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Tanja Heimberger
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Steffi Sandke
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Tanja Weis
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Patrick Most
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Patrick Lugenbiel
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
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13
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Rahm AK, Gramlich D, Wieder T, Müller ME, Schoeffel A, El Tahry FA, Most P, Heimberger T, Sandke S, Weis T, Ullrich ND, Korff T, Lugenbiel P, Katus HA, Thomas D. Trigger-Specific Remodeling of K Ca2 Potassium Channels in Models of Atrial Fibrillation. Pharmgenomics Pers Med 2021; 14:579-590. [PMID: 34045886 PMCID: PMC8144362 DOI: 10.2147/pgpm.s290291] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 04/06/2021] [Indexed: 11/23/2022] Open
Abstract
AIM Effective antiarrhythmic treatment of atrial fibrillation (AF) constitutes a major challenge, in particular, when concomitant heart failure (HF) is present. HF-associated atrial arrhythmogenesis is distinctly characterized by prolonged atrial refractoriness. Small-conductance, calcium-activated K+ (KCa, SK, KCNN) channels contribute to cardiac action potential repolarization and are implicated in AF susceptibility and therapy. The mechanistic impact of AF/HF-related triggers on atrial KCa channels is not known. We hypothesized that tachycardia, stretch, β-adrenergic stimulation, and hypoxia differentially determine KCa2.1-2.3 channel remodeling in atrial cells. METHODS KCNN1-3 transcript levels were assessed in AF/HF patients and in a pig model of atrial tachypacing-induced AF with reduced left ventricular function. HL-1 atrial myocytes were subjected to proarrhythmic triggers to investigate the effects on Kcnn mRNA and KCa channel protein. RESULTS Atrial KCNN1-3 expression was reduced in AF/HF patients. KCNN2 and KCNN3 suppression was recapitulated in the corresponding pig model. In contrast to human AF, KCNN1 remained unchanged in pigs. Channel- and stressor-specific remodeling was revealed in vitro. Lower expression levels of KCNN1/KCa2.1 were linked to stretch and β-adrenergic stimulation. Furthermore, KCNN3/KCa2.3 expression was suppressed upon tachypacing and hypoxia. Finally, KCNN2/KCa2.2 abundance was specifically enhanced by hypoxia. CONCLUSION Reduction of KCa2.1-2.3 channel expression might contribute to the action potential prolongation in AF complicated by HF. Subtype-specific KCa2 channel remodeling induced by tachypacing, stretch, β-adrenergic stimulation, or hypoxia is expected to differentially determine atrial remodeling, depending on patient-specific activation of each triggering factor. Stressor-dependent KCa2 regulation in atrial myocytes provides a starting point for mechanism-based antiarrhythmic therapy.
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Affiliation(s)
- Ann-Kathrin Rahm
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Dominik Gramlich
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Teresa Wieder
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Mara Elena Müller
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Axel Schoeffel
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Fadwa A El Tahry
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Patrick Most
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Tanja Heimberger
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Steffi Sandke
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Tanja Weis
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Nina D Ullrich
- Institute of Physiology and Pathophysiology, Department of Cardiovascular Physiology, Heidelberg University, Heidelberg, 69120, Germany
| | - Thomas Korff
- Institute of Physiology and Pathophysiology, Department of Cardiovascular Physiology, Heidelberg University, Heidelberg, 69120, Germany
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Mannheim, 68167, Germany
| | - Patrick Lugenbiel
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
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14
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Targeting of Potassium Channels in Cardiac Arrhythmias. Trends Pharmacol Sci 2021; 42:491-506. [PMID: 33858691 DOI: 10.1016/j.tips.2021.03.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 03/14/2021] [Accepted: 03/17/2021] [Indexed: 02/07/2023]
Abstract
Cardiomyocytes are endowed with a complex repertoire of ion channels, responsible for the generation of action potentials (APs), travelling waves of electrical excitation, propagating throughout the heart and leading to cardiac contractions. Cardiac AP waveforms are shaped by a striking diversity of K+ channels. The pivotal role of K+ channels in cardiac health and disease is underscored by the dramatic impact that K+ channel dysfunction has on cardiac arrhythmias. The development of drugs targeted to specific K+ channels is expected to provide an optimized approach to antiarrhythmic therapy. Here, we review the functional roles of cardiac potassium channels under normal and diseased states. We survey current antiarrhythmic drugs (AADs) targeted to voltage-gated and Ca2+-activated K+ channels and highlight future research opportunities.
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15
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Qi MM, Qian LL, Wang RX. Modulation of SK Channels: Insight Into Therapeutics of Atrial Fibrillation. Heart Lung Circ 2021; 30:1130-1139. [PMID: 33642173 DOI: 10.1016/j.hlc.2021.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 01/12/2021] [Accepted: 01/31/2021] [Indexed: 11/19/2022]
Abstract
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the world. Although much technological progress in the treatment of AF has been made, there is an urgent need for better treatment of AF due to its high rates of morbidity and mortality. The anti-arrhythmic drugs currently approved for marketing have significant limitations and side effects such as life-threatening ventricular arrhythmias and hypotension. The small conductance Ca2+-activated K+ channels (SK channels) are dependent on intracellular Ca2+ concentrations, which tightly integrate with membrane potential. Given the predominant expression in the atria of many species, including humans, they are now emerging as a therapeutic target for treating AF. This review aimed to illustrate the characteristics and function of SK channels. Moreover, it discussed the regulation of SK channels and their potential as a therapeutic target of AF.
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Affiliation(s)
- Miao-Miao Qi
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ling-Ling Qian
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ru-Xing Wang
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China.
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16
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Zhang XD, Thai PN, Lieu DK, Chiamvimonvat N. Cardiac small-conductance calcium-activated potassium channels in health and disease. Pflugers Arch 2021; 473:477-489. [PMID: 33624131 PMCID: PMC7940285 DOI: 10.1007/s00424-021-02535-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/22/2022]
Abstract
Small-conductance Ca2+-activated K+ (SK, KCa2) channels are encoded by KCNN genes, including KCNN1, 2, and 3. The channels play critical roles in the regulation of cardiac excitability and are gated solely by beat-to-beat changes in intracellular Ca2+. The family of SK channels consists of three members with differential sensitivity to apamin. All three isoforms are expressed in human hearts. Studies over the past two decades have provided evidence to substantiate the pivotal roles of SK channels, not only in healthy heart but also with diseases including atrial fibrillation (AF), ventricular arrhythmia, and heart failure (HF). SK channels are prominently expressed in atrial myocytes and pacemaking cells, compared to ventricular cells. However, the channels are significantly upregulated in ventricular myocytes in HF and pulmonary veins in AF models. Interests in cardiac SK channels are further fueled by recent studies suggesting the possible roles of SK channels in human AF. Therefore, SK channel may represent a novel therapeutic target for atrial arrhythmias. Furthermore, SK channel function is significantly altered by human calmodulin (CaM) mutations, linked to life-threatening arrhythmia syndromes. The current review will summarize recent progress in our understanding of cardiac SK channels and the roles of SK channels in the heart in health and disease.
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Affiliation(s)
- Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
| | - Phung N Thai
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA
| | - Deborah K Lieu
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, 95616, USA.
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17
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Wu AZ, Chen M, Yin D, Everett TH, Chen Z, Rubart M, Weiss JN, Qu Z, Chen PS. Sex-specific I KAS activation in rabbit ventricles with drug-induced QT prolongation. Heart Rhythm 2021; 18:88-97. [PMID: 32707174 PMCID: PMC7796981 DOI: 10.1016/j.hrthm.2020.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 06/30/2020] [Accepted: 07/13/2020] [Indexed: 01/23/2023]
Abstract
BACKGROUND Female sex is a known risk factor for drug-induced long QT syndrome (diLQTS). We recently demonstrated a sex difference in apamin-sensitive small-conductance Ca2+-activated K+ current (IKAS) activation during β-adrenergic stimulation. OBJECTIVE The purpose of this study was to test the hypothesis that there is a sex difference in IKAS in the rabbit models of diLQTS. METHODS We evaluated the sex difference in ventricular repolarization in 15 male and 22 female Langendorff-perfused rabbit hearts with optical mapping techniques during atrial pacing. HMR1556 (slowly activating delayed rectifier K+ current [IKs] blocker), E4031 (rapidly activating delayed rectifier K+ current [IKr] blocker) and sea anemone toxin (ATX-II, late Na+ current [INaL] activator) were used to simulate types 1-3 long QT syndrome, respectively. Apamin, an IKAS blocker, was then added to determine the magnitude of further QT prolongation. RESULTS HMR1556, E4031, and ATX-II led to the prolongation of action potential duration at 80% repolarization (APD80) in both male and female ventricles at pacing cycle lengths of 300-400 ms. Apamin further prolonged APD80 (pacing cycle length 350 ms) from 187.8±4.3 to 206.9±7.1 (P=.014) in HMR1556-treated, from 209.9±7.8 to 224.9±7.8 (P=.003) in E4031-treated, and from 174.3±3.3 to 188.1±3.0 (P=.0002) in ATX-II-treated female hearts. Apamin did not further prolong the APD80 in male hearts. The Cai transient duration (CaiTD) was significantly longer in diLQTS than baseline but without sex differences. Apamin did not change CaiTD. CONCLUSION We conclude that IKAS is abundantly increased in female but not in male ventricles with diLQTS. Increased IKAS helps preserve the repolarization reserve in female ventricles treated with IKs and IKr blockers or INaL activators.
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Affiliation(s)
- Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Michael Rubart
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - James N Weiss
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Zhilin Qu
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Cedars-Sinai Medical Center, Los Angeles, California.
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18
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Rahm AK, Wieder T, Gramlich D, Müller ME, Wunsch MN, El Tahry FA, Heimberger T, Weis T, Most P, Katus HA, Thomas D, Lugenbiel P. HDAC2-dependent remodeling of K Ca2.2 (KCNN2) and K Ca2.3 (KCNN3) K + channels in atrial fibrillation with concomitant heart failure. Life Sci 2020; 266:118892. [PMID: 33310041 DOI: 10.1016/j.lfs.2020.118892] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 11/30/2020] [Accepted: 12/07/2020] [Indexed: 12/16/2022]
Abstract
AIMS Atrial fibrillation (AF) with concomitant heart failure (HF) is associated with prolonged atrial refractoriness. Small-conductance, calcium-activated K+ (KCa, KCNN) channels promote action potential (AP) repolarization. KCNN2 and KCNN3 variants are associated with AF risk. In addition, histone deacetylase (HDAC)-related epigenetic mechanisms have been implicated in AP regulation. We hypothesized that HDAC2-dependent remodeling of KCNN2 and KCNN3 expression contributes to atrial arrhythmogenesis in AF complicated by HF. The objectives were to assess HDAC2 and KCNN2/3 transcript levels in AF/HF patients and in a pig model, and to investigate cellular epigenetic effects of HDAC2 inactivation on KCNN expression. MATERIALS AND METHODS HDAC2 and KCNN2/3 transcript levels were quantified in patients with AF and HF, and in a porcine model of atrial tachypacing-induced AF and reduced left ventricular function. Tachypacing and anti-Hdac2 siRNA treatment were employed in HL-1 atrial myocytes to study effects on KCNN2/3 mRNA and KCa protein abundance. KEY FINDINGS Atrial KCNN2 and KCNN3 expression was reduced in AF/HF patients and in a corresponding pig model. HDAC2 displayed significant downregulation in humans and a tendency towards reduced expression in right atrial tissue of pigs. Tachypacing recapitulated downregulation of Kcnn2/KCa2.2, Kcnn3/KCa2.3 and Hdac2/HDAC2, indicating that high atrial rates trigger epigenetic remodeling mechanisms. Finally, knock-down of Hdac2 in vitro reduced Kcnn3/KCa2.3 expression. SIGNIFICANCE KCNN2/3 and HDAC2 expression is suppressed in AF complicated by HF. Hdac2 directly regulates Kcnn3 mRNA levels in atrial cells. The mechanistic and therapeutic significance of epigenetic electrophysiological effects in AF requires further validation.
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Affiliation(s)
- Ann-Kathrin Rahm
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Teresa Wieder
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Dominik Gramlich
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Mara Elena Müller
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Maximilian N Wunsch
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Fadwa A El Tahry
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Tanja Heimberger
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Tanja Weis
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Patrick Most
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
| | - Patrick Lugenbiel
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
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Nantsupawat T, Wongcharoen W, Chattipakorn SC, Chattipakorn N. Effects of metformin on atrial and ventricular arrhythmias: evidence from cell to patient. Cardiovasc Diabetol 2020; 19:198. [PMID: 33234131 PMCID: PMC7687769 DOI: 10.1186/s12933-020-01176-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 11/15/2020] [Indexed: 12/23/2022] Open
Abstract
Metformin has been shown to have various cardiovascular benefits beyond its antihyperglycemic effects, including a reduction in stroke, heart failure, myocardial infarction, cardiovascular death, and all-cause mortality. However, the roles of metformin in cardiac arrhythmias are still unclear. It has been shown that metformin was associated with decreased incidence of atrial fibrillation in diabetic patients with and without myocardial infarction. This could be due to the effects of metformin on preventing the structural and electrical remodeling of left atrium via attenuating intracellular reactive oxygen species, activating 5′ adenosine monophosphate-activated protein kinase, improving calcium homeostasis, attenuating inflammation, increasing connexin-43 gap junction expression, and restoring small conductance calcium-activated potassium channels current. For ventricular arrhythmias, in vivo reports demonstrated that activation of 5′ adenosine monophosphate-activated protein kinase and phosphorylated connexin-43 by metformin played a key role in ischemic ventricular arrhythmias reduction. However, metformin failed to show anti-ventricular arrhythmia benefits in clinical trials. In this review, in vitro and in vivo reports regarding the effects of metformin on both atrial arrhythmias and ventricular arrhythmias are comprehensively summarized and presented. Consistent and controversial findings from clinical trials are also summarized and discussed. Due to limited numbers of reports, further studies are needed to elucidate the mechanisms and effects of metformin on cardiac arrhythmias. Furthermore, randomized controlled trials are needed to clarify effects of metformin on cardiac arrhythmias in human.
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Affiliation(s)
- Teerapat Nantsupawat
- Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.,Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Chiang Mai, 50200, Thailand.,Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
| | - Wanwarang Wongcharoen
- Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.,Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Chiang Mai, 50200, Thailand.,Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
| | - Siriporn C Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Chiang Mai, 50200, Thailand.,Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
| | - Nipon Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Chiang Mai, 50200, Thailand. .,Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand. .,Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
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20
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Sung YL, Lin TT, Syu JY, Hsu HJ, Lin KY, Liu YB, Lin SF. Reverse electromechanical modelling of diastolic dysfunction in spontaneous hypertensive rat after sacubitril/valsartan therapy. ESC Heart Fail 2020; 7:4040-4050. [PMID: 32969191 PMCID: PMC7755015 DOI: 10.1002/ehf2.13013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 09/02/2020] [Accepted: 09/02/2020] [Indexed: 11/25/2022] Open
Abstract
Aims Hypertension is a significant risk for the development of left ventricular hypertrophy, diastolic dysfunction, followed by heart failure and sudden cardiac death. While therapy with sacubitril/valsartan (SV) reduces the risk of sudden cardiac death in patients with heart failure and systolic dysfunction, the effect on those with diastolic dysfunction remains unclear. We hypothesized that, in the animal model of hypertensive heart disease, treatment with SV reduces the susceptibility to ventricular arrhythmia. Methods and results Young adult female spontaneous hypertensive rats (SHRs) were randomly separated into three groups, which were SHRs, SHRs treated with valsartan, and SHRs treated with SV. In addition, the age‐matched and weight‐matched Wistar Kyoto rats were considered as controls, and there were 12 rats in each group. In vivo ventricular tachyarrhythmia induction and in vitro optical mapping were used to measure the inducibility of ventricular arrhythmias and to characterize the dynamic properties of electrical propagation. The level of small‐conductance Ca2+‐activated potassium channel type 2 (KCNN2) was analysed in cardiac tissue. Compared with SHR with left ventricular hypertrophy, treatment with SV significantly improved cardiac geometry (relative wall thickness, 0.68 ± 0.11 vs. 0.76 ± 0.13, P < 0.05) and diastolic dysfunction (isovolumetric relaxation time, 59.4 ± 3.2 vs. 70.5 ± 4.2 ms, P < 0.05; deceleration time of mitral E wave, 46 ± 4.8 vs. 42 ± 3.8, P < 0.05). The incidence of induced ventricular arrhythmia was significantly reduced in SHR treated with SV compared with SHR (ventricular tachycardia, 1.14 ± 0.32 vs. 2.91 ± 0.5 episodes per 10 stimuli, P < 0.001; ventricular fibrillation, 1.72 ± 0.31 vs. 5.81 ± 0.42 episodes per 10 stimuli, P < 0.001). The prolonged action potential duration (APD) and increase of the maximum slope of APD restitution were observed in SHR, while the treatment of SV improved the arrhythmogeneity (APD, 37.12 ± 6.18 vs. 92.41 ± 10.71 ms at 250 ms pacing cycle length, P < 0.001; max slope 0.29 ± 0.01 vs. 1.48 ± 0.04, P < 0.001). These effects were strongly associated with down‐regulation of KCNN2 (0.38 ± 0.07 vs. 0.74 ± 0.12 ng/ml, P < 0.001). The treatment of SV also decreased the level of N‐terminal pro‐B‐type natriuretic peptide, cardiac bridging integrator‐1, and intramyocardial fibrosis of SHR. Conclusions In conclusion, synergistic blockade of the neprilysin and the renin–angiotensin system by SV in SHRs results in KCNN2‐associated electrical remodelling in ventricle, which stabilizes electrical dynamics and attenuates arrhythmogenesis.
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Affiliation(s)
- Yen-Ling Sung
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan.,Department of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, Taiwan
| | - Ting-Tse Lin
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan.,Department of Internal Medicine, National Taiwan University Hospital Hsin-Chu Biomedical Park Branch, Hsinchu, Taiwan.,Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Jhen-Yang Syu
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Hung-Jui Hsu
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Kai-Yuan Lin
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Yen-Bin Liu
- Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.,Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Shien-Fong Lin
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
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21
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Impact of I SK Voltage and Ca 2+/Mg 2+-Dependent Rectification on Cardiac Repolarization. Biophys J 2020; 119:690-704. [PMID: 32668235 DOI: 10.1016/j.bpj.2020.06.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 06/02/2020] [Accepted: 06/10/2020] [Indexed: 10/24/2022] Open
Abstract
Cardiac small conductance Ca2+-activated K+ (SK) channels are activated solely by Ca2+, but the SK current (ISK) is inwardly rectified. However, the impact of inward rectification in shaping action potentials (APs) in ventricular cardiomyocytes under β-adrenergic stimulation or in disease states remains undefined. Two processes underlie this inward rectification: an intrinsic rectification caused by an electrostatic energy barrier from positively charged amino acids at the inner pore and a voltage-dependent Ca2+/Mg2+ block. Thus, Ca2+ has a biphasic effect on ISK, activating at low [Ca2+] yet inhibiting ISK at high [Ca2+]. We examined the effect of ISK rectification on APs in rat cardiomyocytes by simultaneously recording whole-cell apamin-sensitive currents and Ca2+ transients during an AP waveform and developed a computer model of SK channels with rectification features. The typical profile of ISK during AP clamp included an initial peak (mean 1.6 pA/pF) followed by decay to the point that submembrane [Ca2+] reached ∼10 μM. During the rest of the AP stimulus, ISK either plateaued or gradually increased as the cell repolarized and submembrane [Ca2+] decreased further. We used a six-state gating model combined with intrinsic and Ca2+/Mg2+-dependent rectification to simulate ISK and investigated the relative contributions of each type of rectification to AP shape. This SK channel model replicates key features of ISK recording during AP clamp showing that intrinsic rectification limits ISK at high Vm during the early and plateau phase of APs. Furthermore, the initial rise of Ca2+ transients activates, but higher [Ca2+] blocks SK channels, yielding a transient outward-like ISK trajectory. During the decay phase of Ca2+, the Ca2+-dependent block is released, causing ISK to rise again and contribute to repolarization. Therefore, ISK is an important repolarizing current, and the rectification characteristics of an SK channel determine its impact on early, plateau, and repolarization phases of APs.
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22
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Landaw J, Zhang Z, Song Z, Liu MB, Olcese R, Chen PS, Weiss JN, Qu Z. Small-conductance Ca 2+-activated K + channels promote J-wave syndrome and phase 2 reentry. Heart Rhythm 2020; 17:1582-1590. [PMID: 32333974 DOI: 10.1016/j.hrthm.2020.04.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/30/2020] [Accepted: 04/10/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Small-conductance Ca2+-activated potassium (SK) channels play complex roles in cardiac arrhythmogenesis. SK channels colocalize with L-type Ca2+ channels, yet how this colocalization affects cardiac arrhythmogenesis is unknown. OBJECTIVE The purpose of this study was to investigate the role of colocalization of SK channels with L-type Ca2+ channels in promoting J-wave syndrome and ventricular arrhythmias. METHODS We carried out computer simulations of single-cell and tissue models. SK channels in the model were assigned to preferentially sense Ca2+ in the bulk cytosol, subsarcolemmal space, or junctional cleft. RESULTS When SK channels sense Ca2+ in the bulk cytosol, the SK current (ISK) rises and decays slowly during an action potential, the action potential duration (APD) decreases as the maximum conductance increases, no complex APD dynamics and phase 2 reentry can be induced by ISK. When SK channels sense Ca2+ in the subsarcolemmal space or junctional cleft, ISK can rise and decay rapidly during an action potential in a spike-like pattern because of spiky Ca2+ transients in these compartments, which can cause spike-and-dome action potential morphology, APD alternans, J-wave elevation, and phase 2 reentry. Our results can account for the experimental finding that activation of ISK induced J-wave syndrome and phase 2 reentry in rabbit hearts. CONCLUSION Colocalization of SK channels with L-type Ca2+ channels so that they preferentially sense Ca2+ in the subsarcolemmal or junctional space may result in a spiky ISK, which can functionally play a similar role of the transient outward K+ current in promoting J-wave syndrome and ventricular arrhythmias.
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Affiliation(s)
- Julian Landaw
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhaoyang Zhang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Michael B Liu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
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Role of intermediate-conductance calcium-activated potassium channels in atrial fibrillation in canines with rapid atrial pacing. J Interv Card Electrophysiol 2020; 60:247-253. [PMID: 32248426 DOI: 10.1007/s10840-020-00736-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 03/24/2020] [Indexed: 10/24/2022]
Abstract
PURPOSE The aim of the present study was to explore the role of intermediate-conductance Ca2+-activated K+ (SK4) in atrial fibrillation (AF) inducibility in canines with rapid atrial pacing. METHODS Eighteen dogs were divided into the control group, the pacing group and the stellate ganglion ablation (SGA) + pacing group. In the pacing group, dogs were subjected to rapid atrial pacing, and the atrial effective refractory period (AERP) and AF inducibility were measured. After cessation of 7-h pacing, SK4 inhibitor (TRAM-34) was administered. After SGA, the SGA + pacing group received the same procedure of pacing and electrophysiological measurement as the pacing group. The expression of SK4 was measured in the left atrium (LA) and the right atrium (RA) in the three groups. RESULTS The duration of the AERP decreased, while the number of AF episodes, the duration of induced AF, and the amplitude of stellate ganglion neural activity all increased after rapid atrial pacing. TRAM-34 completely inhibited AF induction in the pacing group. There was no significant difference in AERP shortening or AF vulnerability between the SGA + pacing group and the control group. The expression of SK4 in the LA and RA was higher in the pacing group than in the control and SGA + pacing groups. However, there was no significant difference in the expression of SK4 in the LA or the RA between the SGA + pacing group and the control group. CONCLUSION The higher expression of SK4 plays an important role in AF induction and the increased expression of SK4 in the atrium is related to SG activity during rapid atrial pacing.
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Cardiomyocyte calcium handling in health and disease: Insights from in vitro and in silico studies. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 157:54-75. [PMID: 32188566 DOI: 10.1016/j.pbiomolbio.2020.02.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/31/2019] [Accepted: 02/29/2020] [Indexed: 02/07/2023]
Abstract
Calcium (Ca2+) plays a central role in cardiomyocyte excitation-contraction coupling. To ensure an optimal electrical impulse propagation and cardiac contraction, Ca2+ levels are regulated by a variety of Ca2+-handling proteins. In turn, Ca2+ modulates numerous electrophysiological processes. Accordingly, Ca2+-handling abnormalities can promote cardiac arrhythmias via various mechanisms, including the promotion of afterdepolarizations, ion-channel modulation and structural remodeling. In the last 30 years, significant improvements have been made in the computational modeling of cardiomyocyte Ca2+ handling under physiological and pathological conditions. However, numerous questions involving the Ca2+-dependent regulation of different macromolecular complexes, cross-talk between Ca2+-dependent regulatory pathways operating over a wide range of time scales, and bidirectional interactions between electrophysiology and mechanics remain to be addressed by in vitro and in silico studies. A better understanding of disease-specific Ca2+-dependent proarrhythmic mechanisms may facilitate the development of improved therapeutic strategies. In this review, we describe the fundamental mechanisms of cardiomyocyte Ca2+ handling in health and disease, and provide an overview of currently available computational models for cardiomyocyte Ca2+ handling. Finally, we discuss important uncertainties and open questions about cardiomyocyte Ca2+ handling and highlight how synergy between in vitro and in silico studies may help to answer several of these issues.
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Yin D, Yang N, Tian Z, Wu AZ, Xu D, Chen M, Kamp NJ, Wang Z, Shen C, Chen Z, Lin SF, Rubart-von der Lohe M, Chen PS, Everett TH. Effects of ondansetron on apamin-sensitive small conductance calcium-activated potassium currents in pacing-induced failing rabbit hearts. Heart Rhythm 2019; 17:332-340. [PMID: 31513946 DOI: 10.1016/j.hrthm.2019.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Indexed: 12/16/2022]
Abstract
BACKGROUND Ondansetron, a widely prescribed antiemetic, has been implicated in drug-induced long QT syndrome. Recent patch clamp experiments have shown that ondansetron inhibits the apamin-sensitive small conductance calcium-activated potassium current (IKAS). OBJECTIVE The purpose of this study was to determine whether ondansetron causes action potential duration (APD) prolongation by IKAS inhibition. METHODS Optical mapping was performed in rabbit hearts with pacing-induced heart failure (HF) and in normal hearts before and after ondansetron (100 nM) infusion. APD at 80% repolarization (APD80) and arrhythmia inducibility were determined. Additional studies with ondansetron were performed in normal hearts perfused with hypokalemic Tyrode's (2.4 mM) solution before or after apamin administration. RESULTS The corrected QT interval in HF was 326 ms (95% confidence interval [CI] 306-347 ms) at baseline and 364 ms (95% CI 351-378 ms) after ondansetron infusion (P < .001). Ondansetron significantly prolonged APD80 in the HF group and promoted early afterdepolarizations, steepened the APD restitution curve, and increased ventricular vulnerability. Ventricular fibrillation was not inducible in HF ventricles at baseline, but after ondansetron infusion, ventricular fibrillation was induced in 5 of the 7 ventricles (P = .021). In hypokalemia, apamin prolonged APD80 from 163 ms (95% CI 146-180 ms) to 180 ms (95% CI 156-204 ms) (P = .018). Subsequent administration of ondansetron failed to further prolong APD80 (180 ms [95% CI 156-204 ms] vs 179 ms [95% CI 165-194 ms]; P = .789). The results were similar when ondansetron was administered first, followed by apamin. CONCLUSION Ondansetron is a specific IKAS blocker at therapeutic concentrations. Ondansetron may prolong the QT interval in HF by inhibiting small conductance calcium-activated potassium channels, which increases the vulnerability to ventricular arrhythmias.
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Affiliation(s)
- Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, the First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Na Yang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Gynecological and Obstetric Ultrasound, the First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Zhipeng Tian
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Central Hospital Affiliated to Shenyang Medical College, Shenyang, China
| | - Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Institute of Biomedical Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Dongzhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Nicholas J Kamp
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Changyu Shen
- Richard and Susan Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Institute of Biomedical Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | | | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
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Peyronnet R, Ravens U. Atria-selective antiarrhythmic drugs in need of alliance partners. Pharmacol Res 2019; 145:104262. [PMID: 31059791 DOI: 10.1016/j.phrs.2019.104262] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 04/30/2019] [Accepted: 05/03/2019] [Indexed: 12/15/2022]
Abstract
Atria-selective antiarrhythmic drugs in need of alliance partners. Guideline-based treatment of atrial fibrillation (AF) comprises prevention of thromboembolism and stroke, as well as antiarrhythmic therapy by drugs, electrical rhythm conversion, ablation and surgical procedures. Conventional antiarrhythmic drugs are burdened with unwanted side effects including a propensity of triggering life-threatening ventricular fibrillation. In order to solve this therapeutic dilemma, 'atria-selective' antiarrhythmic drugs have been developed for the treatment of supraventricular arrhythmias. These drugs are designed to aim at atrial targets, taking advantage of differences in atrial and ventricular ion channel expression and function. However it is not clear, whether such drugs are sufficiently antiarrhythmic or whether they are in need of an alliance partner for clinical efficacy. Atria-selective Na+ channel blockers display fast dissociation kinetics and high binding affinity to inactivated channels. Compounds targeting atria-selective K+ channels include blockers of ultra rapid delayed rectifier (Kv1.5) or acetylcholine-activated inward rectifier K+ channels (Kir3.x), inward rectifying K+ channels (Kir2.x), Ca2+-activated K+ channels of small conductance (SK), weakly rectifying two-pore domain K+ channels (K2P), and transient receptor potential channels (TRP). Despite good antiarrhythmic data from in-vitro and animal model experiments, clinical efficacy of atria-selective antiarrhythmic drugs remains to be demonstrated. In the present review we will briefly summarize the novel compounds and their proposed antiarrhythmic action. In addition, we will discuss the evidence for putative improvement of antiarrhythmic efficacy and potency by addressing multiple pathophysiologically relevant targets as possible alliance partners.
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Affiliation(s)
- Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen, Medical Center, University of Freiburg, Freiburg, Germany; Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ursula Ravens
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen, Medical Center, University of Freiburg, Freiburg, Germany; Institute of Physiology, Medical Faculty TU Dresden, Dresden, Germany.
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27
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Verkerk AO, Lodder EM, Wilders R. Aquaporin Channels in the Heart-Physiology and Pathophysiology. Int J Mol Sci 2019; 20:ijms20082039. [PMID: 31027200 PMCID: PMC6514906 DOI: 10.3390/ijms20082039] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 04/19/2019] [Accepted: 04/23/2019] [Indexed: 12/11/2022] Open
Abstract
Mammalian aquaporins (AQPs) are transmembrane channels expressed in a large variety of cells and tissues throughout the body. They are known as water channels, but they also facilitate the transport of small solutes, gasses, and monovalent cations. To date, 13 different AQPs, encoded by the genes AQP0–AQP12, have been identified in mammals, which regulate various important biological functions in kidney, brain, lung, digestive system, eye, and skin. Consequently, dysfunction of AQPs is involved in a wide variety of disorders. AQPs are also present in the heart, even with a specific distribution pattern in cardiomyocytes, but whether their presence is essential for proper (electro)physiological cardiac function has not intensively been studied. This review summarizes recent findings and highlights the involvement of AQPs in normal and pathological cardiac function. We conclude that AQPs are at least implicated in proper cardiac water homeostasis and energy balance as well as heart failure and arsenic cardiotoxicity. However, this review also demonstrates that many effects of cardiac AQPs, especially on excitation-contraction coupling processes, are virtually unexplored.
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Affiliation(s)
- Arie O Verkerk
- Department of Medical Biology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
- Department of Experimental Cardiology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Elisabeth M Lodder
- Department of Experimental Cardiology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
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28
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Ling TY, Yi F, Lu T, Wang XL, Sun X, Willis MS, Wu LQ, Shen WK, Adelman JP, Lee HC. F-box protein-32 down-regulates small-conductance calcium-activated potassium channel 2 in diabetic mouse atria. J Biol Chem 2019; 294:4160-4168. [PMID: 30635400 DOI: 10.1074/jbc.ra118.003837] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 12/28/2018] [Indexed: 11/06/2022] Open
Abstract
Diabetes mellitus (DM) is an independent risk factor for atrial fibrillation, but the underlying ionic mechanism for this association remains unclear. We recently reported that expression of the small-conductance calcium-activated potassium channel 2 (SK2, encoded by KCCN2) in atria from diabetic mice is significantly down-regulated, resulting in reduced SK currents in atrial myocytes from these mice. We also reported that the level of SK2 mRNA expression is not reduced in DM atria but that the ubiquitin-proteasome system (UPS), a major mechanism of intracellular protein degradation, is activated in vascular smooth muscle cells in DM. This suggests a possible role of the UPS in reduced SK currents. To test this possibility, we examined the role of the UPS in atrial SK2 down-regulation in DM. We found that a muscle-specific E3 ligase, F-box protein 32 (FBXO-32, also called atrogin-1), was significantly up-regulated in diabetic mouse atria. Enhanced FBXO-32 expression in atrial cells significantly reduced SK2 protein expression, and siRNA-mediated FBXO-32 knockdown increased SK2 protein expression. Furthermore, co-transfection of SK2 with FBXO-32 complementary DNA in HEK293 cells significantly reduced SK2 expression, whereas co-transfection with atrogin-1ΔF complementary DNA (a nonfunctional FBXO-32 variant in which the F-box domain is deleted) did not have any effects on SK2. These results indicate that FBXO-32 contributes to SK2 down-regulation and that the F-box domain is essential for FBXO-32 function. In conclusion, DM-induced SK2 channel down-regulation appears to be due to an FBXO-32-dependent increase in UPS-mediated SK2 protein degradation.
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Affiliation(s)
- Tian-You Ling
- From the Department of Cardiology, Ruijin Hospital, Shanghai JiaoTong University School of Medicine, Shanghai 200025, China.,the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Fu Yi
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905, .,the Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Tong Lu
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Xiao-Li Wang
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Xiaojing Sun
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Monte S Willis
- the Department of Pathology and Laboratory Medicine, Indiana Center for Musculoskeletal Health, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Li-Qun Wu
- From the Department of Cardiology, Ruijin Hospital, Shanghai JiaoTong University School of Medicine, Shanghai 200025, China
| | - Win-Kuang Shen
- the Department of Cardiovascular Diseases, Mayo Clinic, Phoenix, Arizona 85259, and
| | - John P Adelman
- the Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239
| | - Hon-Chi Lee
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905,
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29
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Chen M, Xu DZ, Wu AZ, Guo S, Wan J, Yin D, Lin SF, Chen Z, Rubart-von der Lohe M, Everett TH, Qu Z, Weiss JN, Chen PS. Concomitant SK current activation and sodium current inhibition cause J wave syndrome. JCI Insight 2018; 3:122329. [PMID: 30429367 PMCID: PMC6302939 DOI: 10.1172/jci.insight.122329] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/17/2018] [Indexed: 12/18/2022] Open
Abstract
The mechanisms of J wave syndrome (JWS) are incompletely understood. Here, we showed that the concomitant activation of small-conductance calcium-activated potassium (SK) current (IKAS) and inhibition of sodium current by cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) recapitulate the phenotypes of JWS in Langendorff-perfused rabbit hearts. CyPPA induced significant J wave elevation and frequent spontaneous ventricular fibrillation (SVF), as well as sinus bradycardia, atrioventricular block, and intraventricular conduction delay. IKAS activation by CyPPA resulted in heterogeneous shortening of action potential (AP) duration (APD) and repolarization alternans. CyPPA inhibited cardiac sodium current (INa) and decelerated AP upstroke and intracellular calcium transient. SVFs were typically triggered by short-coupled premature ventricular contractions, initiated with phase 2 reentry and originated more frequently from the right than the left ventricles. Subsequent IKAS blockade by apamin reduced J wave elevation and eliminated SVF. β-Adrenergic stimulation was antiarrhythmic in CyPPA-induced electrical storm. Like CyPPA, hypothermia (32.0°C) also induced J wave elevation and SVF. It facilitated negative calcium-voltage coupling and phase 2 repolarization alternans with spatial and electromechanical discordance, which were ameliorated by apamin. These findings suggest that IKAS activation contributes to the development of JWS in rabbit ventricles.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Adonis Z. Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiothoracic Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Michael Rubart-von der Lohe
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Thomas H. Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - James N. Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
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30
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Niu J, Dick IE, Yang W, Bamgboye MA, Yue DT, Tomaselli G, Inoue T, Ben-Johny M. Allosteric regulators selectively prevent Ca 2+-feedback of Ca V and Na V channels. eLife 2018; 7:35222. [PMID: 30198845 PMCID: PMC6156082 DOI: 10.7554/elife.35222] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 09/09/2018] [Indexed: 12/31/2022] Open
Abstract
Calmodulin (CaM) serves as a pervasive regulatory subunit of CaV1, CaV2, and NaV1 channels, exploiting a functionally conserved carboxy-tail element to afford dynamic Ca2+-feedback of cellular excitability in neurons and cardiomyocytes. Yet this modularity counters functional adaptability, as global changes in ambient CaM indiscriminately alter its targets. Here, we demonstrate that two structurally unrelated proteins, SH3 and cysteine-rich domain (stac) and fibroblast growth factor homologous factors (fhf) selectively diminish Ca2+/CaM-regulation of CaV1 and NaV1 families, respectively. The two proteins operate on allosteric sites within upstream portions of respective channel carboxy-tails, distinct from the CaM-binding interface. Generalizing this mechanism, insertion of a short RxxK binding motif into CaV1.3 carboxy-tail confers synthetic switching of CaM regulation by Mona SH3 domain. Overall, our findings identify a general class of auxiliary proteins that modify Ca2+/CaM signaling to individual targets allowing spatial and temporal orchestration of feedback, and outline strategies for engineering Ca2+/CaM signaling to individual targets.
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Affiliation(s)
- Jacqueline Niu
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, United States
| | - Ivy E Dick
- Department of Physiology, University of Maryland, Baltimore, United States
| | - Wanjun Yang
- Department of Cardiology, Johns Hopkins University, Baltimore, United States
| | | | - David T Yue
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, United States
| | - Gordon Tomaselli
- Department of Cardiology, Johns Hopkins University, Baltimore, United States
| | - Takanari Inoue
- Department of Cell Biology, Johns Hopkins University, Baltimore, United States.,Center for Cell Dynamics, Institute for Basic Biomedical Sciences, Johns Hopkins University, Baltimore, United States
| | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, College of Physicians and Surgeons, Columbia University, New York, United States
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31
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Ko JS, Guo S, Hassel J, Celestino-Soper P, Lynnes TC, Tisdale JE, Zheng JJ, Taylor SE, Foroud T, Murray MD, Kovacs RJ, Li X, Lin SF, Chen Z, Vatta M, Chen PS, Rubart M. Ondansetron blocks wild-type and p.F503L variant small-conductance Ca 2+-activated K + channels. Am J Physiol Heart Circ Physiol 2018; 315:H375-H388. [PMID: 29677462 PMCID: PMC6139629 DOI: 10.1152/ajpheart.00479.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 04/11/2018] [Accepted: 04/11/2018] [Indexed: 01/24/2023]
Abstract
Apamin-sensitive small-conductance Ca2+-activated K+ (SK) current ( IKAS) is encoded by Ca2+-activated K+ channel subfamily N ( KCNN) genes. IKAS importantly contributes to cardiac repolarization in conditions associated with reduced repolarization reserve. To test the hypothesis that IKAS inhibition contributes to drug-induced long QT syndrome (diLQTS), we screened for KCNN variants among patients with diLQTS, determined the properties of heterologously expressed wild-type (WT) and variant KCNN channels, and determined if the 5-HT3 receptor antagonist ondansetron blocks IKAS. We searched 2,306,335 records in the Indiana Network for Patient Care and found 11 patients with diLQTS who had DNA available in the Indiana Biobank. DNA sequencing discovered a heterozygous KCNN2 variant (p.F503L) in a 52-yr-old woman presenting with corrected QT interval prolongation at baseline (473 ms) and further corrected QT interval lengthening (601 ms) after oral administration of ondansetron. That patient was also heterozygous for the p.S38G and p.P2835S variants of the QT-controlling genes KCNE1 and ankyrin 2, respectively. Patch-clamp experiments revealed that the p.F503L KCNN2 variant heterologously expressed in human embryonic kidney (HEK)-293 cells augmented Ca2+ sensitivity, increasing IKAS density. The fraction of total F503L-KCNN2 protein retained in the membrane was higher than that of WT KCNN2 protein. Ondansetron at nanomolar concentrations inhibited WT and p.F503L SK2 channels expressed in HEK-293 cells as well as native SK channels in ventricular cardiomyocytes. Ondansetron-induced IKAS inhibition was also demonstrated in Langendorff-perfused murine hearts. In conclusion, the heterozygous p.F503L KCNN2 variant increases Ca2+ sensitivity and IKAS density in transfected HEK-293 cells. Ondansetron at therapeutic (i.e., nanomolar) concentrations is a potent IKAS blocker. NEW & NOTEWORTHY We showed that ondansetron, a 5-HT3 receptor antagonist, blocks small-conductance Ca2+-activated K+ (SK) current. Ondansetron may be useful in controlling arrhythmias in which increased SK current is a likely contributor. However, its SK-blocking effects may also facilitate the development of drug-induced long QT syndrome.
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Affiliation(s)
- Jum-Suk Ko
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Wonkwang University School of Medicine and Hospital, Iksan, South Korea
| | - Shuai Guo
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Jonathan Hassel
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Patricia Celestino-Soper
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - Ty C Lynnes
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - James E Tisdale
- Department of Pharmacy Practice, College of Pharmacy, Purdue University , West Lafayette, Indiana
- Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | | | - Stanley E Taylor
- Department of Biostatistics, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Tatiana Foroud
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - Michael D Murray
- Department of Pharmacy Practice, College of Pharmacy, Purdue University , West Lafayette, Indiana
- Regenstrief Institute , Indianapolis, Indiana
| | - Richard J Kovacs
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Xiaochun Li
- Department of Biostatistics, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Shien-Fong Lin
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Matteo Vatta
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine , Indianapolis, Indiana
| | - Peng-Sheng Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Michael Rubart
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine , Indianapolis, Indiana
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Tsutsui K, Monfredi OJ, Sirenko-Tagirova SG, Maltseva LA, Bychkov R, Kim MS, Ziman BD, Tarasov KV, Tarasova YS, Zhang J, Wang M, Maltsev AV, Brennan JA, Efimov IR, Stern MD, Maltsev VA, Lakatta EG. A coupled-clock system drives the automaticity of human sinoatrial nodal pacemaker cells. Sci Signal 2018; 11:eaap7608. [PMID: 29895616 PMCID: PMC6138244 DOI: 10.1126/scisignal.aap7608] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The spontaneous rhythmic action potentials generated by the sinoatrial node (SAN), the primary pacemaker in the heart, dictate the regular and optimal cardiac contractions that pump blood around the body. Although the heart rate of humans is substantially slower than that of smaller experimental animals, current perspectives on the biophysical mechanisms underlying the automaticity of sinoatrial nodal pacemaker cells (SANCs) have been gleaned largely from studies of animal hearts. Using human SANCs, we demonstrated that spontaneous rhythmic local Ca2+ releases generated by a Ca2+ clock were coupled to electrogenic surface membrane molecules (the M clock) to trigger rhythmic action potentials, and that Ca2+-cAMP-protein kinase A (PKA) signaling regulated clock coupling. When these clocks became uncoupled, SANCs failed to generate spontaneous action potentials, showing a depolarized membrane potential and disorganized local Ca2+ releases that failed to activate the M clock. β-Adrenergic receptor (β-AR) stimulation, which increases cAMP concentrations and clock coupling in other species, restored spontaneous, rhythmic action potentials in some nonbeating "arrested" human SANCs by increasing intracellular Ca2+ concentrations and synchronizing diastolic local Ca2+ releases. When β-AR stimulation was withdrawn, the clocks again became uncoupled, and SANCs reverted to a nonbeating arrested state. Thus, automaticity of human pacemaker cells is driven by a coupled-clock system driven by Ca2+-cAMP-PKA signaling. Extreme clock uncoupling led to failure of spontaneous action potential generation, which was restored by recoupling of the clocks. Clock coupling and action potential firing in some of these arrested cells can be restored by β-AR stimulation-induced augmentation of Ca2+-cAMP-PKA signaling.
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Affiliation(s)
- Kenta Tsutsui
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Oliver J Monfredi
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
- Institute of Cardiovascular Sciences, University of Manchester, Manchester M13 9NT, UK
- Department of Cardiovascular Electrophysiology, Johns Hopkins Hospital, 1800 Orleans Street, Baltimore, MD 21287, USA
| | | | - Larissa A Maltseva
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Rostislav Bychkov
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Mary S Kim
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Bruce D Ziman
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Kirill V Tarasov
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Yelena S Tarasova
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Jing Zhang
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Mingyi Wang
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Alexander V Maltsev
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Jaclyn A Brennan
- Department of Biomedical Engineering, George Washington University, Washington, DC 20052, USA
| | - Igor R Efimov
- Department of Biomedical Engineering, George Washington University, Washington, DC 20052, USA
| | - Michael D Stern
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Victor A Maltsev
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD 21224, USA.
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Gu M, Zhu Y, Yin X, Zhang DM. Small-conductance Ca 2+-activated K + channels: insights into their roles in cardiovascular disease. Exp Mol Med 2018; 50:1-7. [PMID: 29651007 PMCID: PMC5938042 DOI: 10.1038/s12276-018-0043-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 12/11/2017] [Accepted: 12/12/2017] [Indexed: 12/13/2022] Open
Abstract
Life-threatening malignant arrhythmias in pathophysiological conditions can increase the mortality and morbidity of patients with cardiovascular diseases. Cardiac electrical activity depends on the coordinated propagation of excitatory stimuli and the generation of action potentials in cardiomyocytes. Action potential formation results from the opening and closing of ion channels. Recent studies have indicated that small-conductance calcium-activated potassium (SK) channels play a critical role in cardiac repolarization in pathophysiological but not normal physiological conditions. The aim of this review is to describe the role of SK channels in healthy and diseased hearts, to suggest cardiovascular pathophysiologic targets for intervention, and to discuss studies of agents that target SK channels for the treatment of cardiovascular diseases.
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Affiliation(s)
- Mingxia Gu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Jiangsu, 210006, Nanjing, China
- Department of Cardiology, Nanjing Central Hospital, Jiangsu, 210018, Nanjing, China
| | - Yanrong Zhu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Jiangsu, 210006, Nanjing, China
| | - Xiaorong Yin
- Department of Cardiology, Nanjing Central Hospital, Jiangsu, 210018, Nanjing, China
| | - Dai-Min Zhang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Jiangsu, 210006, Nanjing, China.
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34
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Coupling of SK channels, L-type Ca 2+ channels, and ryanodine receptors in cardiomyocytes. Sci Rep 2018; 8:4670. [PMID: 29549309 PMCID: PMC5856806 DOI: 10.1038/s41598-018-22843-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/01/2018] [Indexed: 01/01/2023] Open
Abstract
Small-conductance Ca2+-activated K+ (SK) channels regulate the excitability of cardiomyocytes by integrating intracellular Ca2+ and membrane potentials on a beat-to-beat basis. The inextricable interplay between activation of SK channels and Ca2+ dynamics suggests the pathology of one begets another. Yet, the exact mechanistic underpinning for the activation of cardiac SK channels remains unaddressed. Here, we investigated the intracellular Ca2+ microdomains necessary for SK channel activation. SK currents coupled with Ca2+ influx via L-type Ca2+ channels (LTCCs) continued to be elicited after application of caffeine, ryanodine or thapsigargin to deplete SR Ca2+ store, suggesting that LTCCs provide the immediate Ca2+ microdomain for the activation of SK channels in cardiomyocytes. Super-resolution imaging of SK2, Cav1.2 Ca2+ channel, and ryanodine receptor 2 (RyR2) was performed to quantify the nearest neighbor distances (NND) and localized the three molecules within hundreds of nanometers. The distribution of NND between SK2 and RyR2 as well as SK2 and Cav1.2 was bimodal, suggesting a spatial relationship between the channels. The activation mechanism revealed by our study paved the way for the understanding of the roles of SK channels on the feedback mechanism to regulate the activities of LTCCs and RyR2 to influence local and global Ca2+ signaling.
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35
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Fan HK, Luo TX, Zhao WD, Mu YH, Yang Y, Guo WJ, Tu HY, Zhang Q. Functional interaction of Junctophilin 2 with small- conductance Ca 2+ -activated potassium channel subtype 2(SK2) in mouse cardiac myocytes. Acta Physiol (Oxf) 2018; 222. [PMID: 29055091 PMCID: PMC6084295 DOI: 10.1111/apha.12986] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 10/15/2017] [Accepted: 10/15/2017] [Indexed: 12/17/2022]
Abstract
Aim Junctophilins (JPs), a protein family of the junctional membrane complex, maintain the close conjunction between cell surface and intracellular membranes in striate muscle cells mediating the crosstalk between extracellular Ca2+ entry and intracellular Ca2+ release. The small‐conductance Ca2+‐activated K+ channels are activated by the intracellular calcium and play an essential role in the cardiac action potential profile. Molecular mechanisms of regulation of the SK channels are still uncertain. Here, we sought to determine whether there is a functional interaction of junctophilin type 2 (JP2) with the SK channels and whether JP2 gene silencing might modulate the function of SK channels in cardiac myocytes. Methods Association of JP2 with SK2 channel in mouse heart tissue as well as HEK293 cells was studied using in vivo and in vitro approaches. siRNA knockdown of JP2 gene was assessed by real‐time PCR. The expression of proteins was analysed by Western blotting. Ca2+‐activated K+ current (IK,Ca) in infected adult mouse cardiac myocytes was recorded using whole‐cell voltage‐clamp technique. The intracellular Ca2+ transient was measured using an IonOptix photometry system. Results We showed for the first time that JP2 associates with the SK2 channel in native cardiac tissue. JP2, via the membrane occupation and recognition nexus (MORN motifs) in its N‐terminus, directly interacted with SK2 channels. A colocalization of the SK2 channel with its interaction protein of JP2 was found in the cardiac myocytes. Moreover, we demonstrated that JP2 is necessary for the proper cell surface expression of the SK2 channel in HEK293. Functional experiments indicated that knockdown of JP2 caused a significant decrease in the density of IK,Ca and reduced the amplitude of the Ca2+ transient in infected cardiomyocytes. Conclusion The present data provide evidence that the functional interaction between JP2 and SK2 channels is present in the native mouse heart tissue. Junctophilin 2, as junctional membrane complex (JMC) protein, is an important regulator of the cardiac SK channels.
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Affiliation(s)
- H. K. Fan
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - T. X. Luo
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - W. D. Zhao
- Faculty of Medicine; KU Leuven; Leuven Belgium
| | - Y. H. Mu
- Department of Pathophysiology; School of Medicine; Xinxiang Medical College; Xinxiang China
| | - Y. Yang
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - W. J. Guo
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - H. Y. Tu
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - Q. Zhang
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
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36
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Mathew John C, Khaddaj Mallat R, George G, Kim T, Mishra RC, Braun AP. Pharmacologic targeting of endothelial Ca 2+-activated K + channels: A strategy to improve cardiovascular function. Channels (Austin) 2018; 12:126-136. [PMID: 29577810 PMCID: PMC5972810 DOI: 10.1080/19336950.2018.1454814] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 03/15/2018] [Indexed: 12/17/2022] Open
Abstract
Endothelial small and intermediate-conductance, Ca2+-activated K+ channels (KCa2.3 and KCa3.1, respectively) play an important role in the regulation of vascular function and systemic blood pressure. Growing evidence indicates that they are intimately involved in agonist-evoked vasodilation of small resistance arteries throughout the circulation. Small molecule activators of KCa2.x and 3.1 channels, such as SKA-31, can acutely inhibit myogenic tone in isolated resistance arteries, induce effective vasodilation in intact vascular beds, such as the coronary circulation, and acutely decrease systemic blood pressure in vivo. The blood pressure-lowering effect of SKA-31, and early indications of improvement in endothelial dysfunction suggest that endothelial KCa channel activators could eventually be developed into a new class of endothelial targeted agents to combat hypertension or atherosclerosis. This review summarises recent insights into the activation of endothelial Ca2+ activated K+ channels in various vascular beds, and how tools, such as SKA-31, may be beneficial in disease-related conditions.
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Affiliation(s)
- Cini Mathew John
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Rayan Khaddaj Mallat
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Grace George
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Taeyeob Kim
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Ramesh C. Mishra
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Andrew P. Braun
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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37
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Nam YW, Orfali R, Liu T, Yu K, Cui M, Wulff H, Zhang M. Structural insights into the potency of SK channel positive modulators. Sci Rep 2017; 7:17178. [PMID: 29214998 PMCID: PMC5719431 DOI: 10.1038/s41598-017-16607-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 11/15/2017] [Indexed: 12/26/2022] Open
Abstract
Small-conductance Ca2+-activated K+ (SK) channels play essential roles in the regulation of cellular excitability and have been implicated in neurological and cardiovascular diseases through both animal model studies and human genetic association studies. Over the past two decades, positive modulators of SK channels such as NS309 and 1-EBIO have been developed. Our previous structural studies have identified the binding pocket of 1-EBIO and NS309 that is located at the interface between the channel and calmodulin. In this study, we took advantage of four compounds with potencies varying over three orders of magnitude, including 1-EBIO, NS309, SKS-11 (6-bromo-5-methyl-1H-indole-2,3-dione-3-oxime) and SKS-14 (7-fluoro-3-(hydroxyimino)indolin-2-one). A combination of x-ray crystallographic, computational and electrophysiological approaches was utilized to investigate the interactions between the positive modulators and their binding pocket. A strong trend exists between the interaction energy of the compounds within their binding site calculated from the crystal structures, and the potency of these compounds in potentiating the SK2 channel current determined by electrophysiological recordings. Our results further reveal that the difference in potency of the positive modulators in potentiating SK2 channel activity may be attributed primarily to specific electrostatic interactions between the modulators and their binding pocket.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences & Structural Biology Research Center, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences & Structural Biology Research Center, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Tingting Liu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Kunqian Yu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, MA, 02115, USA
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, 95616, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences & Structural Biology Research Center, Chapman University School of Pharmacy, Irvine, CA, 92618, USA.
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38
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Lee K, Isogai A, Antoh M, Kajioka S, Eto M, Hashitani H. Role of K + channels in regulating spontaneous activity in the muscularis mucosae of guinea pig bladder. Eur J Pharmacol 2017; 818:30-37. [PMID: 29050967 DOI: 10.1016/j.ejphar.2017.10.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 10/11/2017] [Accepted: 10/13/2017] [Indexed: 12/30/2022]
Abstract
To explore the roles of various K+ channels in regulating the spontaneous activity of bladder muscularis mucosae (MM) that is considered to play an important role in maintaining mucosal function. Effects of K+ channel modulators on electrical and contractile activity in the guinea-pig bladder MM were examined using intracellular microelectrode and isometric tension recording. The MM predominately generated bursting spontaneous action potentials (SAPs) and phasic contractions (SPCs) that were blocked by nifedipine (1µM). NS309 (10µM), a small-conductance Ca2+-activated K+ (SK) channel opener, dramatically prolonged after-hyperpolarisation (AHP) and converted bursting SAPs into individually action potentials in an apamin (100nM)-sensitive manner. Apamin alone increased the number of SAPs during bursts. NS1619 (10µM), a large-conductance Ca2+-activated K+ (BK) channel opener, abolished SAPs in a manner reversed by iberiotoxin (IbTX, 100nM), a BK channel blocker. IbTX alone enlarged SAPs and abolished their AHPs. Flupirtine (10µM), a voltage-dependent K+ channel (Kv7) opener, diminished SAPs in a manner reversed by XE991 (10µM), a Kv7 channel blocker. XE991 alone exerted modest excitatory effects on SAPs. These K+ channel modulators had corresponding effects on SPCs. Bursting SAP firing appears to result from a lower level activation of SK channels in MM than that DSM. BK channels play a predominant role in regulating SAP configuration, while Kv7 channels have only a marginal role. The prevention of bursting SAPs and associated reduction in SPCs upon the pharmacological activation of a reserved population of SK channels may well have a considerable therapeutic potential.
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Affiliation(s)
- Ken Lee
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan; Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
| | - Ayu Isogai
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Minori Antoh
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Shunichi Kajioka
- Department of Applied Urology and Molecular Medicine, Kyushu University, Fukuoka, Japan
| | - Masatoshi Eto
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hikaru Hashitani
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
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39
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Chen KH, Liu H, Sun HY, Jin MW, Xiao GS, Wang Y, Li GR. The Natural Flavone Acacetin Blocks Small Conductance Ca 2+-Activated K + Channels Stably Expressed in HEK 293 Cells. Front Pharmacol 2017; 8:716. [PMID: 29081746 PMCID: PMC5646423 DOI: 10.3389/fphar.2017.00716] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Accepted: 09/25/2017] [Indexed: 01/06/2023] Open
Abstract
The natural flavone acacetin inhibits several voltage-gated potassium currents in atrial myocytes, and has anti-atrial fibrillation (AF) effect in experimental AF models. The present study investigates whether acacetin inhibits the Ca2+-activated potassium (KCa) currents, including small conductance (SKCa1, SKCa2, and SKCa3), intermediate conductance (IKCa), and large-conductance (BKCa) channels stably expressed in HEK 293 cells. The effects of acacetin on these KCa channels were determined with a whole-cell patch voltage-clamp technique. The results showed that acacetin inhibited the three subtype SKCa channel currents in concentration-dependent manner with IC50 of 12.4 μM for SKCa1, 10.8 μM for SKCa2, and 11.6 μM for SKCa3. Site-directed mutagenesis of SKCa3 channels generated the mutants H490N, S512T, H521N, and A537V. Acacetin inhibited the mutants with IC50 of 118.5 μM for H490N, 275.2 μM for S512T, 15.3 μM for H521N, and 10.6 μM for A537V, suggesting that acacetin interacts with the P-loop helix of SKCa3 channel. However, acacetin at 3–10 μM did not decrease, but induced a slight increase of BKCa (+70 mV) by 8% at 30 μM. These results demonstrate the novel information that acacetin remarkably inhibits SKCa channels, but not IKCa or BKCa channels, which suggests that blockade of SKCa by acacetin likely contributes to its anti-AF property previously observed in experimental AF.
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Affiliation(s)
- Kui-Hao Chen
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong.,Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hui Liu
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong.,Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hai-Ying Sun
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong
| | - Man-Wen Jin
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Guo-Sheng Xiao
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Yan Wang
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Gui-Rong Li
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong.,Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
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40
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Heijman J, Ghezelbash S, Dobrev D. Investigational antiarrhythmic agents: promising drugs in early clinical development. Expert Opin Investig Drugs 2017; 26:897-907. [PMID: 28691539 PMCID: PMC6324729 DOI: 10.1080/13543784.2017.1353601] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
INTRODUCTION Although there have been important technological advances for the treatment of cardiac arrhythmias (e.g., catheter ablation technology), antiarrhythmic drugs (AADs) remain the cornerstone therapy for the majority of patients with arrhythmias. Most of the currently available AADs were coincidental findings and did not result from a systematic development process based on known arrhythmogenic mechanisms and specific targets. During the last 20 years, our understanding of cardiac electrophysiology and fundamental arrhythmia mechanisms has increased significantly, resulting in the identification of new potential targets for mechanism-based antiarrhythmic therapy. Areas covered: Here, we review the state-of-the-art in arrhythmogenic mechanisms and AAD therapy. Thereafter, we focus on a number of antiarrhythmic targets that have received significant attention recently: atrial-specific K+-channels, the late Na+-current, the cardiac ryanodine-receptor channel type-2, and the small-conductance Ca2+-activated K+-channel. We highlight for each of these targets available antiarrhythmic agents and the evidence for their antiarrhythmic effect in animal models and early clinical development. Expert opinion: Targeting AADs to specific subgroups of well-phenotyped patients is likely necessary to detect improved outcomes that may be obscured in the population at large. In addition, specific combinations of selective AADs may have synergistic effects and may enable a mechanism-based tailored antiarrhythmic therapy.
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Affiliation(s)
- Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Shokoufeh Ghezelbash
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
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41
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Reher TA, Wang Z, Hsueh CH, Chang PC, Pan Z, Kumar M, Patel J, Tan J, Shen C, Chen Z, Fishbein MC, Rubart M, Boyden P, Chen PS. Small-Conductance Calcium-Activated Potassium Current in Normal Rabbit Cardiac Purkinje Cells. J Am Heart Assoc 2017; 6:JAHA.117.005471. [PMID: 28550095 PMCID: PMC5669169 DOI: 10.1161/jaha.117.005471] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Background Purkinje cells (PCs) are important in cardiac arrhythmogenesis. Whether small‐conductance calcium‐activated potassium (SK) channels are present in PCs remains unclear. We tested the hypotheses that subtype 2 SK (SK2) channel proteins and apamin‐sensitive SK currents are abundantly present in PCs. Methods and Results We studied 25 normal rabbit ventricles, including 13 patch‐clamp studies, 4 for Western blotting, and 8 for immunohistochemical staining. Transmembrane action potentials were recorded in current‐clamp mode using the perforated‐patch technique. For PCs, the apamin (100 nmol/L) significantly prolonged action potential duration measured to 80% repolarization by an average of 10.4 ms (95% CI, 0.11–20.72) (n=9, P=0.047). Voltage‐clamp study showed that apamin‐sensitive SK current density was significantly larger in PCs compared with ventricular myocytes at potentials ≥0 mV. Western blotting of SK2 expression showed that the SK2 protein expression in the midmyocardium was 58% (P=0.028) and the epicardium was 50% (P=0.018) of that in the pseudotendons. Immunostaining of SK2 protein showed that PCs stained stronger than ventricular myocytes. Confocal microscope study showed SK2 protein was distributed to the periphery of the PCs. Conclusions SK2 proteins are more abundantly present in the PCs than in the ventricular myocytes of normal rabbit ventricles. Apamin‐sensitive SK current is important in ventricular repolarization of normal PCs.
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Affiliation(s)
- Thomas A Reher
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Zhuo Wang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN.,Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Chia-Hsiang Hsueh
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Po-Cheng Chang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Zhenwei Pan
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Mohineesh Kumar
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Jheel Patel
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Jian Tan
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Changyu Shen
- Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Zhenhui Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Michael C Fishbein
- Department of Pathology and Laboratory Medicine, UCLA Medical Center, Los Angeles, CA
| | - Michael Rubart
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
| | - Penelope Boyden
- Department of Pharmacology, Columbia University, New York, NY
| | - Peng-Sheng Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
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Pharmacological blockade of small conductance Ca 2+-activated K + channels by ICA reduces arrhythmic load in rats with acute myocardial infarction. Pflugers Arch 2017; 469:739-750. [PMID: 28285409 DOI: 10.1007/s00424-017-1962-6] [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: 12/15/2016] [Revised: 02/07/2017] [Accepted: 02/20/2017] [Indexed: 01/02/2023]
Abstract
Acute myocardial infarction (AMI) with development of ventricular fibrillation (VF) is a common cause of sudden cardiac death (SCD). At present, no pharmacological treatment has successfully been able to prevent VF in the acute stage of AMI. This study investigates the antiarrhythmic effect of inhibiting small conductance Ca2+-activated K+ (SK) channels using the pore blocker N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) in AMI rats. Acute coronary ligation was performed in 26 anesthetized rats, and ECG, monophasic action potentials (MAPs), and ventricular effective refractory period (vERP) were recorded. Rats were randomized into four groups: (i) 3 mg/kg i.v. ICA with AMI (AMI-ICA-group, n = 9), (ii) vehicle with AMI (AMI-vehicle-group, n = 9), (iii) vehicle with sham operation (sham-vehicle-group, n = 8), and (iv) 3 mg/kg i.v. ICA with sham operation (sham-ICA-group, n = 6). At the end of experiments, hearts were stained for the non-perfused area at risk (AAR). AMI resulted in the development of ventricular tachycardia (VT) in all AMI-vehicle and AMI-ICA rats; however, ICA significantly decreased VT duration. VF occurred in 44% of AMI-vehicle rats but not in AMI-ICA rats. Monophasic action potential duration at 80% repolarization (MAPD80) in the ischemic area decreased rapidly in both AMI-vehicle and AMI-ICA rats. However, 5 min after occlusion, MAPD80 returned to baseline in AMI-ICA rats but not in AMI-vehicle rats. The vERP was prolonged in the AMI-ICA group compared to AMI-vehicle after ligation. AAR was similar between the AMI-vehicle group and the AMI-ICA group. In rats with AMI, ICA reduces the burden of arrhythmia.
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43
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Kennedy M, Bers DM, Chiamvimonvat N, Sato D. Dynamical effects of calcium-sensitive potassium currents on voltage and calcium alternans. J Physiol 2017; 595:2285-2297. [PMID: 27902841 DOI: 10.1113/jp273626] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 11/22/2016] [Indexed: 01/12/2023] Open
Abstract
KEY POINTS A mathematical model of a small conductance Ca2+ -activated potassium (SK) channel was developed and incorporated into a physiologically detailed ventricular myocyte model. Ca2+ -sensitive K+ currents promote negative intracellular Ca2+ to membrane voltage (CAi2+ → Vm ) coupling. Increase of Ca2+ -sensitive K+ currents can be responsible for electromechanically discordant alternans and quasiperiodic oscillations at the cellular level. At the tissue level, Turing-type instability can occur when Ca2+ -sensitive K+ currents are increased. ABSTRACT Cardiac alternans is a precursor to life-threatening arrhythmias. Alternans can be caused by instability of the membrane voltage (Vm ), instability of the intracellular Ca2+ ( Ca i2+) cycling, or both. Vm dynamics and Ca i2+ dynamics are coupled via Ca2+ -sensitive currents. In cardiac myocytes, there are several Ca2+ -sensitive potassium (K+ ) currents such as the slowly activating delayed rectifier current (IKs ) and the small conductance Ca2+ -activated potassium (SK) current (ISK ). However, the role of these currents in the development of arrhythmias is not well understood. In this study, we investigated how these currents affect voltage and Ca2+ alternans using a physiologically detailed computational model of the ventricular myocyte and mathematical analysis. We define the coupling between Vm and Ca i2+ cycling dynamics ( Ca i2+→Vm coupling) as positive (negative) when a larger Ca2+ transient at a given beat prolongs (shortens) the action potential duration (APD) of that beat. While positive coupling predominates at baseline, increasing IKs and ISK promote negative Ca i2+→Vm coupling at the cellular level. Specifically, when alternans is Ca2+ -driven, electromechanically (APD-Ca2+ ) concordant alternans becomes electromechanically discordant alternans as IKs or ISK increase. These cellular level dynamics lead to different types of spatially discordant alternans in tissue. These findings help to shed light on the underlying mechanisms of cardiac alternans especially when the relative strength of these currents becomes larger under pathological conditions or drug administrations.
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Affiliation(s)
- Matthew Kennedy
- Department of Biomedical Engineering, University of California, Davis, CA, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, USA
| | - Daisuke Sato
- Department of Pharmacology, University of California, Davis, CA, USA
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44
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Chiamvimonvat N, Chen-Izu Y, Clancy CE, Deschenes I, Dobrev D, Heijman J, Izu L, Qu Z, Ripplinger CM, Vandenberg JI, Weiss JN, Koren G, Banyasz T, Grandi E, Sanguinetti MC, Bers DM, Nerbonne JM. Potassium currents in the heart: functional roles in repolarization, arrhythmia and therapeutics. J Physiol 2017; 595:2229-2252. [PMID: 27808412 DOI: 10.1113/jp272883] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/11/2016] [Indexed: 12/19/2022] Open
Abstract
This is the second of the two White Papers from the fourth UC Davis Cardiovascular Symposium Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias (3-4 March 2016), a biennial event that brings together leading experts in different fields of cardiovascular research. The theme of the 2016 symposium was 'K+ channels and regulation', and the objectives of the conference were severalfold: (1) to identify current knowledge gaps; (2) to understand what may go wrong in the diseased heart and why; (3) to identify possible novel therapeutic targets; and (4) to further the development of systems biology approaches to decipher the molecular mechanisms and treatment of cardiac arrhythmias. The sessions of the Symposium focusing on the functional roles of the cardiac K+ channel in health and disease, as well as K+ channels as therapeutic targets, were contributed by Ye Chen-Izu, Gideon Koren, James Weiss, David Paterson, David Christini, Dobromir Dobrev, Jordi Heijman, Thomas O'Hara, Crystal Ripplinger, Zhilin Qu, Jamie Vandenberg, Colleen Clancy, Isabelle Deschenes, Leighton Izu, Tamas Banyasz, Andras Varro, Heike Wulff, Eleonora Grandi, Michael Sanguinetti, Donald Bers, Jeanne Nerbonne and Nipavan Chiamvimonvat as speakers and panel discussants. This article summarizes state-of-the-art knowledge and controversies on the functional roles of cardiac K+ channels in normal and diseased heart. We endeavour to integrate current knowledge at multiple scales, from the single cell to the whole organ levels, and from both experimental and computational studies.
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Affiliation(s)
- Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, 95655, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA.,Department of Biomedical Engineering, University of California, Davis, Genome and Biomedical Science Facility, Rm 2303, Davis, CA, 95616, USA
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Isabelle Deschenes
- Department of Physiology and Biophysics, and Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44109, USA.,Heart and Vascular Research Center, MetroHealth Medical Center, Cleveland, OH, 44109, USA
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Leighton Izu
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Zhilin Qu
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia
| | - James N Weiss
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Gideon Koren
- Cardiovascular Research Center, Rhode Island Hospital and the Cardiovascular Institute, The Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Tamas Banyasz
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research & Training Institute, Salt Lake City, UT, 84112, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jeanne M Nerbonne
- Departments of Developmental Biology and Internal Medicine, Cardiovascular Division, Washington University Medical School, St Louis, MO, 63110, USA
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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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46
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Zhang Z, Ledford HA, Park S, Wang W, Rafizadeh S, Kim HJ, Xu W, Lu L, Lau VC, Knowlton AA, Zhang XD, Yamoah EN, Chiamvimonvat N. Distinct subcellular mechanisms for the enhancement of the surface membrane expression of SK2 channel by its interacting proteins, α-actinin2 and filamin A. J Physiol 2016; 595:2271-2284. [PMID: 27779751 PMCID: PMC5374114 DOI: 10.1113/jp272942] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/19/2016] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS Ion channels are transmembrane proteins that are synthesized within the cells but need to be trafficked to the cell membrane for the channels to function. Small-conductance, Ca2+ -activated K+ channels (SK, KCa 2) are unique subclasses of K+ channels that are regulated by Ca2+ inside the cells; they are expressed in human atrial myocytes and responsible for shaping atrial action potentials. We have previously shown that interacting proteins of SK2 channels are important for channel trafficking to the membrane. Using total internal reflection fluorescence (TIRF) and confocal microscopy, we studied the mechanisms by which the surface membrane localization of SK2 (KCa 2.2) channels is regulated by their interacting proteins. Understanding the mechanisms of SK channel trafficking may provide new insights into the regulation controlling the repolarization of atrial myocytes. ABSTRACT The normal function of ion channels depends critically on the precise subcellular localization and the number of channel proteins on the cell surface membrane. Small-conductance, Ca2+ -activated K+ channels (SK, KCa 2) are expressed in human atrial myocytes and are responsible for shaping atrial action potentials. Understanding the mechanisms of SK channel trafficking may provide new insights into the regulation controlling the repolarization of atrial myocytes. We have previously demonstrated that the C- and N-termini of SK2 channels interact with the actin-binding proteins α-actinin2 and filamin A, respectively. However, the roles of the interacting proteins on SK2 channel trafficking remain incompletely understood. Using total internal reflection fluorescence (TIRF) microscopy, we studied the mechanisms of surface membrane localization of SK2 (KCa 2.2) channels. When SK2 channels were co-expressed with filamin A or α-actinin2, the membrane fluorescence intensity of SK2 channels increased significantly. We next tested the effects of primaquine and dynasore on SK2 channels expression. Treatment with primaquine significantly reduced the membrane expression of SK2 channels. In contrast, treatment with dynasore failed to alter the surface membrane expression of SK2 channels. Further investigations using constitutively active or dominant-negative forms of Rab GTPases provided additional insights into the distinct roles of the two cytoskeletal proteins on the recycling processes of SK2 channels from endosomes. α-Actinin2 facilitated recycling of SK2 channels from both early and recycling endosomes while filamin A probably aids the recycling of SK2 channels from recycling endosomes.
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Affiliation(s)
- Zheng Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Hannah A Ledford
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Seojin Park
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Wenying Wang
- Department of Physiology and Cell Biology, University of Nevada, Reno, NV, 89557, USA
| | - Sassan Rafizadeh
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Hyo Jeong Kim
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Wilson Xu
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Ling Lu
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA.,Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing, 210046, China
| | - Victor C Lau
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Anne A Knowlton
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, 95655, USA
| | - Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, NV, 89557, USA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, 95655, USA
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47
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Grandi E, Sanguinetti MC, Bartos DC, Bers DM, Chen-Izu Y, Chiamvimonvat N, Colecraft HM, Delisle BP, Heijman J, Navedo MF, Noskov S, Proenza C, Vandenberg JI, Yarov-Yarovoy V. Potassium channels in the heart: structure, function and regulation. J Physiol 2016; 595:2209-2228. [PMID: 27861921 DOI: 10.1113/jp272864] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 07/18/2016] [Indexed: 12/22/2022] Open
Abstract
This paper is the outcome of the fourth UC Davis Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias Symposium, a biannual event that aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2016 symposium was 'K+ Channels and Regulation'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies and challenges on the topic of cardiac K+ channels. This paper summarizes the topics of formal presentations and informal discussions from the symposium on the structural basis of voltage-gated K+ channel function, as well as the mechanisms involved in regulation of K+ channel gating, expression and membrane localization. Given the critical role for K+ channels in determining the rate of cardiac repolarization, it is hardly surprising that essentially every aspect of K+ channel function is exquisitely regulated in cardiac myocytes. This regulation is complex and highly interrelated to other aspects of myocardial function. K+ channel regulatory mechanisms alter, and are altered by, physiological challenges, pathophysiological conditions, and pharmacological agents. An accompanying paper focuses on the integrative role of K+ channels in cardiac electrophysiology, i.e. how K+ currents shape the cardiac action potential, and how their dysfunction can lead to arrhythmias, and discusses K+ channel-based therapeutics. A fundamental understanding of K+ channel regulatory mechanisms and disease processes is fundamental to reveal new targets for human therapy.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, 84112, USA
| | - Daniel C Bartos
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA.,Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Brian P Delisle
- Department of Physiology, University of Kentucky, Lexington, KY, 40536, USA
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Sergei Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado - Anschutz Medical Campus, Denver, CO, 80045, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California, Davis, CA, 95616, USA
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48
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Mechanisms of arrhythmogenesis related to calcium-driven alternans in a model of human atrial fibrillation. Sci Rep 2016; 6:36395. [PMID: 27812021 PMCID: PMC5095679 DOI: 10.1038/srep36395] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 10/11/2016] [Indexed: 11/08/2022] Open
Abstract
The occurrence of atrial fibrillation (AF) is associated with progressive changes in the calcium handling system of atrial myocytes. Calcium cycling instability has been implicated as an underlying mechanism of electrical alternans observed in patients who experience AF. However, the extent to which calcium-induced alternation of electrical activity in the atria contributes to arrhythmogenesis is unknown. In this study, we investigated the effects of calcium-driven alternans (CDA) on arrhythmia susceptibility in a biophysically detailed, 3D computer model of the human atria representing electrical and structural remodeling secondary to chronic AF. We found that elevated propensity to CDA rendered the atria vulnerable to ectopy-induced arrhythmia. It also increased the complexity and persistence of arrhythmias induced by fast pacing, with unstable scroll waves meandering and frequently breaking up to produce multiple wavelets. Our results suggest that calcium-induced electrical instability may increase arrhythmia vulnerability and promote increasing disorganization of arrhythmias in the chronic AF-remodeled atria, thus playing an important role in the progression of the disease.
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49
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Abstract
Multiple types of voltage-gated K(+) and non-voltage-gated K(+) currents have been distinguished in mammalian cardiac myocytes based on differences in time-dependent and voltage-dependent properties and pharmacologic sensitivities. Many of the genes encoding voltage-gated K(+) (Kv) and non-voltage-gated K(+) (Kir and K2P) channel pore-forming and accessory subunits are expressed in the heart, and a variety of approaches have been, and continue to be, used to define the molecular determinants of native cardiac K(+) channels and to explore the molecular mechanisms controlling the diversity, regulation, and remodeling of these channels in the normal and diseased myocardium.
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Affiliation(s)
- Jeanne M Nerbonne
- Department of Internal Medicine, Washington University Medical School, 660 South Euclid Avenue, Box 8086, St Louis, MO 63110, USA; Department of Developmental Biology, Washington University Medical School, St Louis, MO 63110, USA.
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50
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Abstract
Any disturbance of electrical impulse formation in the heart and of impulse conduction or action potential (AP) repolarization can lead to rhythm disorders. Potassium (K(+)) channels play a prominent role in the AP repolarization process. In this review we describe the causes and mechanisms of proarrhythmic effects that arise as a response to blockers of cardiac K(+) channels. The largest and chemically most diverse groups of compound targets are Kv11.1 (hERG) and Kv7.1 (KvLQT1) channels. Finally, the proarrhythmic propensity of atrial-selective K(+) blockers inhibiting Kv1.5, Kir3.1/3.4, SK, and K2P channels is discussed.
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Affiliation(s)
- Lasse Skibsbye
- Danish Arrhythmia Research Centre, Faculty of Health and Medical Sciences, University of Copenhagen, 3 Blegdamsvej, 3 Copenhagen N DK-2200, Denmark
| | - Ursula Ravens
- Department of Pharmacology and Toxicology, Medical Faculty Carl Gustav Carus, Institut für Pharmakologie und Toxikologie, TU Dresden, Fetscherstrasse 74, Dresden D-01307, Germany.
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