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Neeman-Egozi S, Livneh I, Dolgopyat I, Nussinovitch U, Milman H, Cohen N, Eisen B, Ciechanover A, Binah O. Stress-Induced Proteasome Sub-Cellular Translocation in Cardiomyocytes Causes Altered Intracellular Calcium Handling and Arrhythmias. Int J Mol Sci 2024; 25:4932. [PMID: 38732146 PMCID: PMC11084437 DOI: 10.3390/ijms25094932] [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: 03/10/2024] [Revised: 04/18/2024] [Accepted: 04/24/2024] [Indexed: 05/13/2024] Open
Abstract
The ubiquitin-proteasome system (UPS) is an essential mechanism responsible for the selective degradation of substrate proteins via their conjugation with ubiquitin. Since cardiomyocytes have very limited self-renewal capacity, as they are prone to protein damage due to constant mechanical and metabolic stress, the UPS has a key role in cardiac physiology and pathophysiology. While altered proteasomal activity contributes to a variety of cardiac pathologies, such as heart failure and ischemia/reperfusion injury (IRI), the environmental cues affecting its activity are still unknown, and they are the focus of this work. Following a recent study by Ciechanover's group showing that amino acid (AA) starvation in cultured cancer cell lines modulates proteasome intracellular localization and activity, we tested two hypotheses in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs, CMs): (i) AA starvation causes proteasome translocation in CMs, similarly to the observation in cultured cancer cell lines; (ii) manipulation of subcellular proteasomal compartmentalization is associated with electrophysiological abnormalities in the form of arrhythmias, mediated via altered intracellular Ca2+ handling. The major findings are: (i) starving CMs to AAs results in proteasome translocation from the nucleus to the cytoplasm, while supplementation with the aromatic amino acids tyrosine (Y), tryptophan (W) and phenylalanine (F) (YWF) inhibits the proteasome recruitment; (ii) AA-deficient treatments cause arrhythmias; (iii) the arrhythmias observed upon nuclear proteasome sequestration(-AA+YWF) are blocked by KB-R7943, an inhibitor of the reverse mode of the sodium-calcium exchanger NCX; (iv) the retrograde perfusion of isolated rat hearts with AA starvation media is associated with arrhythmias. Collectively, our novel findings describe a newly identified mechanism linking the UPS to arrhythmia generation in CMs and whole hearts.
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Affiliation(s)
- Shunit Neeman-Egozi
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Ido Livneh
- The Rappaport-Technion Integrated Cancer Center (R-TICC) and The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 319060, Israel; (I.L.); (N.C.)
| | - Irit Dolgopyat
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Udi Nussinovitch
- Department of Cardiology, Edith Wolfson Medical Center, Holon 5822012, Israel
- The Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Helena Milman
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Nadav Cohen
- The Rappaport-Technion Integrated Cancer Center (R-TICC) and The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 319060, Israel; (I.L.); (N.C.)
| | - Binyamin Eisen
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Aaron Ciechanover
- The Rappaport-Technion Integrated Cancer Center (R-TICC) and The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 319060, Israel; (I.L.); (N.C.)
| | - Ofer Binah
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
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Hu CH, Wu SN, So EC. Tyrosine kinase inhibitors, ionic currents, and cardiac arrhythmia. Front Oncol 2023; 13:1218821. [PMID: 37554165 PMCID: PMC10405512 DOI: 10.3389/fonc.2023.1218821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 06/19/2023] [Indexed: 08/10/2023] Open
Affiliation(s)
- Chi-Hao Hu
- Department of Physiology, National Cheng Kung University Medical College, Tainan, Taiwan
| | - Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan, Taiwan
- School of Medicine, National Sun Yat-sen University College of Medicine, Kaohsiung, Taiwan
- Department of Education and Research, An Nan Hospital, China Medical University, Tainan, Taiwan
| | - Edmund Cheung So
- Department of Anesthesia, An Nan Hospital, China Medical University, Tainan, Taiwan
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Lerma C, Manzano-Cabada J, Valencia P, Márquez-Murillo MF. Ventricular bigeminy characterization in 24-h Holter monitoring from Andersen-Tawil patients: An initial proof of concept versus patients with ischemic heart disease. J Electrocardiol 2023; 77:37-40. [PMID: 36584547 DOI: 10.1016/j.jelectrocard.2022.12.005] [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: 09/09/2022] [Revised: 12/05/2022] [Accepted: 12/19/2022] [Indexed: 12/27/2022]
Abstract
AIM To characterize ventricular bigeminy from 24-h Holter recordings of Andersen-Tawil syndrome (ATS) patients, a first comparison with a large database of post-myocardial infarction (post-MI) patients with frequent premature ventricular complexes (PVC) was performed. METHODS Baseline Holter recordings from 6 ATS1 patients and 618 post-MI patients were analyzed to assess total number of PVC, quantification of coupling intervals (CI), total number of bigeminy episodes, and percentage of PVC in bigeminy. RESULTS A non-significant difference in total number of PVCs, mean CI and CI standard deviation was found. The median number of episodes of bigeminy (1038 vs 1; p = 0.004) and of PVC in bigeminy (51.1 vs 0.1%; p = 0.002) was significantly higher in ATS1 patients. Having ≥42 episodes of bigeminy or ≥ 36.1% of PVC in bigeminy distinguish PVC from ATS from post-MI patients with a sensitivity and specificity >80%. CONCLUSION In this first approach, patients with ATS had a characteristic burden of episodes of ventricular bigeminy, compared with post-MI patients.
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Affiliation(s)
- Claudia Lerma
- Department of Electromechanical Instrumentation, National Institute of Cardiology Ignacio Chavez, Mexico City 14080, Mexico
| | - Janneth Manzano-Cabada
- Department of Electrocardiology, National Institute of Cardiology Ignacio Chavez, Mexico City 14080, Mexico
| | - Paola Valencia
- Department of Electromechanical Instrumentation, National Institute of Cardiology Ignacio Chavez, Mexico City 14080, Mexico
| | - Manlio F Márquez-Murillo
- Department of Electrocardiology, National Institute of Cardiology Ignacio Chavez, Mexico City 14080, Mexico.
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Cubeddu LX, de la Rosa D, Ameruoso M. Antiviral and anti-inflammatory drugs to combat COVID-19: Effects on cardiac ion channels and risk of ventricular arrhythmias. BIOIMPACTS : BI 2022; 12:9-20. [PMID: 35087712 PMCID: PMC8783084 DOI: 10.34172/bi.2021.23630] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 10/11/2021] [Accepted: 10/14/2021] [Indexed: 12/27/2022]
Abstract
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Introduction: Drugs with no indication for the treatment of cardiovascular diseases (e.g., drugs employed to treat COVID-19) can increase the risk of arrhythmias. Of interest, a six-fold increase in the number of arrhythmic events was reported in patients with severe COVID-19. In this study, we reviewed (i) the pro-arrhythmic action of drugs given to patients with COVID-19 infection, and (ii) the effects of inflammatory cytokines on cardiac ion channels and possible generation of arrhythmias.
Methods: We conducted a literature search on the drugs with purported or demonstrated efficacy against COVID-19 disease, emphasizing the mechanisms by which anti-COVID-19 drugs and inflammatory cytokines interfere with cardiac ion channels.
Results:Antibiotics (azithromycin), antimalarials (hydroxychloroquine, chloroquine), antivirals (ritonavir/lopinavir, atazanavir), and some of the tyrosine kinase inhibitors (vandetanib) could induce long QT and increase risk for ventricular arrhythmias. The pro-arrhythmic action results from drug-induced inhibition of Kv11.1 (hERG) channels interfering with the repolarizing potassium IKr currents, leading to long QT and increased risk of triggered arrhythmias. At higher concentrations, these drugs may interfere with IKs, IK1, and/or Ito potassium currents, and even inhibit sodium (INa) and calcium (ICa) currents, inducing additional cardiac toxicity. Ibrutinib, an inhibitor of Bruton’s TK, increased the incidence of atrial fibrillation and ventricular tachycardia associated with a short QT interval. Inflammatory cytokines IL-6 and TNF-α inhibit IKr and Ito repolarizing potassium currents. High levels of inflammatory cytokines could contribute to the arrhythmic events. For remdesivir, favipiravir, dexamethasone, tocilizumab, anakinra, baricitinib, and monoclonal antibodies (bamlanivimab, etesevimab, and casirivimab), no evidence supports significant effects on cardiac ion channels, changes in the QT interval, and increased risk for ventricular arrhythmias.
Conclusion: This study supports the concept of hERG channel promiscuity. Different drug classes given to COVID-19 patients might delay repolarization, and increase the risk of ventricular arrhythmias. The presence of comorbid pro-arrhythmic disease states, and elevated levels of pro-arrhythmic cytokines, could increase the risk of ventricular arrhythmias. Discontinuation of nonessential drugs and correction of electrolyte abnormalities could prevent severe ventricular arrhythmias. Altogether, the most effective therapies against COVID-19 (remdesivir, dexamethasone, monoclonal antibodies) lack pro-arrhythmic activity.
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Affiliation(s)
- Luigi X Cubeddu
- Nova SE University, Health Professions Division, 3200 S, University Drive, Davie, FL 33328, USA
| | - Daisy de la Rosa
- Nova SE University, Health Professions Division, 3200 S, University Drive, Davie, FL 33328, USA
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Effective Perturbations on the Amplitude and Hysteresis of Erg-Mediated Potassium Current Caused by 1-Octylnonyl 8-[(2-hydroxyethyl)[6-oxo-6(undecyloxy)hexyl]amino]-octanoate (SM-102), a Cationic Lipid. Biomedicines 2021; 9:biomedicines9101367. [PMID: 34680484 PMCID: PMC8533363 DOI: 10.3390/biomedicines9101367] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/24/2021] [Accepted: 09/28/2021] [Indexed: 01/31/2023] Open
Abstract
SM-102 (1-octylnonyl 8-[(2-hydroxyethyl)[6-oxo-6-(undecyloxy)hexyl]amino]-octanoate) is an amino cationic lipid that has been tailored for the formation of lipid nanoparticles and it is one of the essential ingredients present in the ModernaTM COVID-19 vaccine. However, to what extent it may modify varying types of plasmalemmal ionic currents remains largely uncertain. In this study, we investigate the effects of SM-102 on ionic currents either in two types of endocrine cells (e.g., rat pituitary tumor (GH3) cells and mouse Leydig tumor (MA-10) cells) or in microglial (BV2) cells. Hyperpolarization-activated K+ currents in these cells bathed in high-K+, Ca2+-free extracellular solution were examined to assess the effects of SM-102 on the amplitude and hysteresis of the erg-mediated K+ current (IK(erg)). The SM-102 addition was effective at blocking IK(erg) in a concentration-dependent fashion with a half-maximal concentration (IC50) of 108 μM, a value which is similar to the KD value (i.e., 134 μM) required for its accentuation of deactivation time constant of the current. The hysteretic strength of IK(erg) in response to the long-lasting isosceles-triangular ramp pulse was effectively decreased in the presence of SM-102. Cell exposure to TurboFectinTM 8.0 (0.1%, v/v), a transfection reagent, was able to inhibit hyperpolarization-activated IK(erg) effectively with an increase in the deactivation time course of the current. Additionally, in GH3 cells dialyzed with spermine (30 μM), the IK(erg) amplitude progressively decreased; moreover, a further bath application of SM-102 (100 μM) or TurboFectin (0.1%) diminished the current magnitude further. In MA-10 Leydig cells, the IK(erg) was also blocked by the presence of SM-102 or TurboFectin. The IC50 value for SM-102-induced inhibition of IK(erg) in MA-10 cells was 98 μM. In BV2 microglial cells, the amplitude of the inwardly rectifying K+ current was inhibited by SM-102. Taken together, the presence of SM-102 concentration-dependently inhibited IK(erg) in endocrine cells (e.g., GH3 or MA-10 cells), and such action may contribute to their functional activities, assuming that similar in vivo findings exist.
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Gaur N, Qi XY, Benoist D, Bernus O, Coronel R, Nattel S, Vigmond EJ. A computational model of pig ventricular cardiomyocyte electrophysiology and calcium handling: Translation from pig to human electrophysiology. PLoS Comput Biol 2021; 17:e1009137. [PMID: 34191797 PMCID: PMC8277015 DOI: 10.1371/journal.pcbi.1009137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 07/13/2021] [Accepted: 06/01/2021] [Indexed: 12/01/2022] Open
Abstract
The pig is commonly used as an experimental model of human heart disease, including for the study of mechanisms of arrhythmia. However, there exist differences between human and porcine cellular electrophysiology: The pig action potential (AP) has a deeper phase-1 notch, a longer duration at 50% repolarization, and higher plateau potentials than human. Ionic differences underlying the AP include larger rapid delayed-rectifier and smaller inward-rectifier K+-currents (IKr and IK1 respectively) in humans. AP steady-state rate-dependence and restitution is steeper in pigs. Porcine Ca2+ transients can have two components, unlike human. Although a reliable computational model for human ventricular myocytes exists, one for pigs is lacking. This hampers translation from results obtained in pigs to human myocardium. Here, we developed a computational model of the pig ventricular cardiomyocyte AP using experimental datasets of the relevant ionic currents, Ca2+-handling, AP shape, AP duration restitution, and inducibility of triggered activity and alternans. To properly capture porcine Ca2+ transients, we introduced a two-step process with a faster release in the t-tubular region, followed by a slower diffusion-induced release from a non t-tubular subcellular region. The pig model behavior was compared with that of a human ventricular cardiomyocyte (O’Hara-Rudy) model. The pig, but not the human model, developed early afterdepolarizations (EADs) under block of IK1, while IKr block led to EADs in the human but not in the pig model. At fast rates (pacing cycle length = 400 ms), the human cell model was more susceptible to spontaneous Ca2+ release-mediated delayed afterdepolarizations (DADs) and triggered activity than pig. Fast pacing led to alternans in human but not pig. Developing species-specific models incorporating electrophysiology and Ca2+-handling provides a tool to aid translating antiarrhythmic and arrhythmogenic assessment from the bench to the clinic. The pig is an animal commonly used experimentally to study diseases of the heart, as well as investigate therapies to treat them, such as drugs. However, although similar, pigs differ from humans in certain aspects which may mean experimental results do not always directly translate between species. We propose a mathematical model of porcine electrophysiology which can serve as a tool to understand differences between the species and translate responses. Using new measurements along with values from literature, we built a computer model of porcine cardiac myocyte which replicated voltage and calcium behaviour over a range of pacing frequencies. The pig cell had a two-stage calcium release, unlike humans with a single stage. We predict that pigs and humans differ in the type of potassium current block that makes them most susceptible to cardiac arrhythmia. The model we developed can elucidate important differences between human and pig arrhythmia response.
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Affiliation(s)
- Namit Gaur
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac- Bordeaux, France
- Univ. Bordeaux, IMB, UMR 5251, Talence, France
| | - Xiao-Yan Qi
- Montreal Heart Institute and Université de Montréal, Montreal, Canada
| | - David Benoist
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac- Bordeaux, France
- Univ. Bordeaux, Inserm, CRCTB, U1045, Pessac, France
| | - Olivier Bernus
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac- Bordeaux, France
- Univ. Bordeaux, Inserm, CRCTB, U1045, Pessac, France
| | - Ruben Coronel
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac- Bordeaux, France
- Department of Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Stanley Nattel
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac- Bordeaux, France
- Montreal Heart Institute and Université de Montréal, Montreal, Canada
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Edward J. Vigmond
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac- Bordeaux, France
- Univ. Bordeaux, IMB, UMR 5251, Talence, France
- * E-mail:
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"Electrifying dysmorphology": Potassium channelopathies causing dysmorphic syndromes. ADVANCES IN GENETICS 2020; 105:137-174. [PMID: 32560786 DOI: 10.1016/bs.adgen.2020.03.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Potassium channels are a heterogeneous group of membrane-bound proteins, whose functions support a diverse range of biological processes. Genetic disorders arising from mutations in potassium channels are classically recognized by symptoms arising from acute channel dysfunction, such as periodic paralysis, ataxia, seizures, or cardiac conduction abnormalities, often in a patient with otherwise normal examination findings. In this chapter, we review a distinct subgroup of rare potassium channelopathies whose presentations are instead suggestive of a developmental disorder, with features including intellectual disability, craniofacial dysmorphism or other physical anomalies. Known conditions within this subgroup are: Andersen-Tawil syndrome, Birk-Barel syndrome, Cantú syndrome, Keppen-Lubinsky syndrome, Temple-Baraitser syndrome, Zimmerman-Laband syndrome and a very similar disorder called Bauer-Tartaglia or FHEIG syndrome. Ion channelopathies are unlikely to be routinely considered in the differential diagnosis of children presenting with developmental concerns, and so detailed description and photographs of the clinical phenotype are provided to aid recognition. For several of these disorders, functional characterization of the genetic mutations responsible has led to identification of candidate therapies, including drugs already commonly used for other indications, which adds further impetus to their prompt recognition. Together, these cases illustrate the potential for mechanistic insights gained from genetic diagnosis to drive translational work toward targeted, disease-modifying therapies for rare disorders.
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8
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So EC, Liu PY, Wu SN. Effectiveness in the inhibition of dapagliflozin and canagliflozin on M-type K + current and α-methylglucoside-induced current in pituitary tumor (GH 3) and pheochromocytoma PC12 cells. Eur J Pharmacol 2020; 879:173141. [PMID: 32353360 DOI: 10.1016/j.ejphar.2020.173141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 04/21/2020] [Accepted: 04/21/2020] [Indexed: 12/22/2022]
Abstract
Dapagliflozin (DAPA) or canagliflozin (CANA), Na+-dependent glucose co-transporter type 2 (SGLT2) inhibitors, were used for treatment of type II diabetes mellitus. Addition of DAPA or CANA suppressed M-type K+ current (IK(M)) in pituitary tumor (GH3) and pheochromocytoma PC12 cells. The IC50 value for DAPA- or CANA-mediated inhibition of IK(M) in GH3 cells was 0.11 or 0.42 μM, respectively. The presence of DAPA (0.1 μM) shifted the steady-state activation of IK(M) to less depolarized potential without changing the gating charge of the current. During high-frequency depolarizing pulses, IK(M) magnitude was reduced by DAPA; however, DAPA-induced block of IK(M) remained effective. The amplitude of neither erg-mediated K+ current nor hyperpolarization-activated cation current in GH3 cells was modified in the presence of 1 μM DAPA. Alternatively, addition of DAPA, CANA, phlorizin or chlorotoxin effectively suppressed α-methylglucoside-(αMG-) induced current (IαMG) in GH3 cells, albeit inability of tefluthrin (activator of INa) to suppress this current. DAPA shifted the charge-voltage relation of presteady-state IαMG in a rightward and downward direction with no change in the gating charge of the IαMG. Under current-clamp recordings, subsequent additions of DAPA, but still in the continued presence of αMG, increased the firing rate of spontaneous action potentials stimulated by αMG. Our results suggested that activity of SGLT was expressed functionally in GH3 and PC12 cells. Therefore, inhibitory actions of DAPA or CANA on the amplitude and gating of IK(M) might provide a yet unidentified mechanism through which the SGLT1 or SGLT2 activity were attenuated in unclamped cells occurring in vivo.
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Affiliation(s)
- Edmund Cheung So
- Department of Anesthesia and Medical Research, An Nan Hospital, China Medical University, Tainan City, Taiwan; Graduate Institute of Medical Sciences, Chang Jung Christian University, Tainan City, Taiwan
| | - Ping-Yen Liu
- Division of Cardiovascular Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Sheng-Nan Wu
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City, Taiwan; Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan.
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Differential Inhibitory Actions of Multitargeted Tyrosine Kinase Inhibitors on Different Ionic Current Types in Cardiomyocytes. Int J Mol Sci 2020; 21:ijms21051672. [PMID: 32121388 PMCID: PMC7084345 DOI: 10.3390/ijms21051672] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 02/25/2020] [Accepted: 02/27/2020] [Indexed: 12/31/2022] Open
Abstract
Lapatinib (LAP) and sorafenib (SOR) are multitargeted tyrosine kinase inhibitors (TKIs) with antineoplastic properties. In clinical observations, LAP and SOR may contribute to QTc prolongation, but the detailed mechanism for this has been largely unexplored. In this study, we investigated whether LAP and SOR affect the activities of membrane ion channels. Using a small animal model and primary cardiomyocytes, we studied the impact of LAP and SOR on Na+ and K+ currents. We found that LAP-induced QTc prolongation in mice was reversed by isoproterenol. LAP or SOR suppressed the amplitude of the slowly activating delayed-rectifier K+ current (IK(S)) in H9c2 cells in a time- and concentration-dependent fashion. The LAP-mediated inhibition of IK(S) was reversed by adding isoproterenol or meclofenamic acid, but not by adding diazoxide. The steady-state activation curve of IK(S) during exposure to LAP or SOR was shifted toward a less negative potential, with no change in the gating charge required to activate the current. LAP shortened the recovery from IK(S) deactivation. As rapid repetitive stimuli, the IK(S) amplitude decreased; however; the LAP-induced inhibition of IK(S) remained effective. LAP or SOR alone also suppressed inwardly rectifying K+ and voltage-gated Na+ current in neonatal rat ventricular myocytes. The inhibition of ionic currents during exposure to TKIs could be an important mechanism underlying changes in QTc intervals.
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10
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Kistamás K, Veress R, Horváth B, Bányász T, Nánási PP, Eisner DA. Calcium Handling Defects and Cardiac Arrhythmia Syndromes. Front Pharmacol 2020; 11:72. [PMID: 32161540 PMCID: PMC7052815 DOI: 10.3389/fphar.2020.00072] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 01/24/2020] [Indexed: 12/13/2022] Open
Abstract
Calcium ions (Ca2+) play a major role in the cardiac excitation-contraction coupling. Intracellular Ca2+ concentration increases during systole and falls in diastole thereby determining cardiac contraction and relaxation. Normal cardiac function also requires perfect organization of the ion currents at the cellular level to drive action potentials and to maintain action potential propagation and electrical homogeneity at the tissue level. Any imbalance in Ca2+ homeostasis of a cardiac myocyte can lead to electrical disturbances. This review aims to discuss cardiac physiology and pathophysiology from the elementary membrane processes that can cause the electrical instability of the ventricular myocytes through intracellular Ca2+ handling maladies to inherited and acquired arrhythmias. Finally, the paper will discuss the current therapeutic approaches targeting cardiac arrhythmias.
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Affiliation(s)
- Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Division of Cardiovascular Sciences, School of Medical Sciences, University of Manchester, Manchester, United Kingdom
| | - Roland Veress
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Department of Dental Physiology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - David A Eisner
- Division of Cardiovascular Sciences, School of Medical Sciences, University of Manchester, Manchester, United Kingdom
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11
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Hsiao HT, Lee YC, Liu YC, Kuo PC, Wu SN. Differential suppression of delayed-rectifier and inwardly rectifier K + currents by a group of ent-kaurane-type diterpenoids from Croton tonkinensis, in microglial cells. Eur J Pharmacol 2019; 856:172414. [PMID: 31129155 DOI: 10.1016/j.ejphar.2019.172414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 05/14/2019] [Accepted: 05/22/2019] [Indexed: 12/11/2022]
Abstract
Croton is an extensive flowering plant genus in the spurge family, Euphorbiaceae. Three croton compounds with the common ent-kaurane skeleton were purified from Croton tonkinensis. By using patch-clamp recording technique, we thoroughly examined the effect of a group of croton compounds, croton-01 (ent-18-acetoxy-7α-hydroxykaur-16-en-15-one), croton-02 (ent-7α,14β-dihydroxykaur-16-en-15-one), and croton-03 (ent-1β-acetoxy-7α,14β-dihydroxykaur-16-en-15-one), on the membrane current in SM826 and BV2 microglial cells. Although neither voltage-gated Na+ nor Ca2+ currents were present in these cells, both delayed-rectifier K+ outward (IK(DR)) and inwardly rectifying K+ currents (IK(IR)) were readily detected. Croton-03 differentially caused inhibition of IK(DR) or IK(IR) in a concentration-dependent manner. According to a minimal scheme, the shortening of the time constant in either the IK(DR)-related block or IK(IR) caused by different concentrations of croton-03 was quantitatively estimated with a dissociation constant of 6.45 and 29.5 μM, respectively. In SM826 cells differentiated with β-amyloid, inhibitory action on these K+ currents remained unaltered. In ultraviolet C-irradiated cells, the magnitude of IK(IR) was still decreased by addition of croton-03. Therefore, our study suggests that these ent-kaurane diterpenoids ought to somehow act on the cellular mechanisms by which they influence the functional activities of microglial cells.
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Affiliation(s)
- Hung-Tsung Hsiao
- Department of Anesthesiology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Yu-Chi Lee
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan
| | - Yen-Chin Liu
- Department of Anesthesiology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Ping-Chung Kuo
- School of Pharmacy, National Cheng Kung University, Tainan City, Taiwan
| | - Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan; Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City, Taiwan.
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12
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Rai MK, Pai R, Prabhu MA, Pasha SW, Kedambadi RC, Kamath P, Augustine AJ, Bhavani GS, Girisha KM. Short-term response to phenytoin sodium in Andersen-Tawil syndrome-1 with a cardiac-dominant phenotype. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2018; 42:201-207. [DOI: 10.1111/pace.13569] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 11/11/2018] [Accepted: 11/28/2018] [Indexed: 01/10/2023]
Affiliation(s)
- Maneesh K. Rai
- Department of Cardiology; Kasturba Medical College, Manipal Academy of Higher Education; Mangalore Karnataka India
| | - Rohith Pai
- Department of Neurology; Kasturba Medical College, Manipal Academy of Higher Education; Mangalore Karnataka India
| | - Mukund A. Prabhu
- Department of Cardiology; Kasturba Medical College, Manipal Academy of Higher Education; Mangalore Karnataka India
| | - Syed Waleem Pasha
- Department of Cardiology; Kasturba Medical College, Manipal Academy of Higher Education; Mangalore Karnataka India
| | - Rakshith C. Kedambadi
- Department of Neurology; Kasturba Medical College, Manipal Academy of Higher Education; Mangalore Karnataka India
| | - Padmanabh Kamath
- Department of Cardiology; Kasturba Medical College, Manipal Academy of Higher Education; Mangalore Karnataka India
| | - Alfred J. Augustine
- Department of Surgery; Kasturba Medical College, Manipal Academy of Higher Education; Mangalore Karnataka India
| | - Gangham SriLakshmi Bhavani
- Department of Medical Genetics; Kasturba Medical College, Manipal Academy of Higher Education; Manipal Karnataka India
| | - Katta M. Girisha
- Department of Medical Genetics; Kasturba Medical College, Manipal Academy of Higher Education; Manipal Karnataka India
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13
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Abstract
There has been a significant progress in our understanding of the molecular mechanisms by which calcium (Ca2+) ions mediate various types of cardiac arrhythmias. A growing list of inherited gene defects can cause potentially lethal cardiac arrhythmia syndromes, including catecholaminergic polymorphic ventricular tachycardia, congenital long QT syndrome, and hypertrophic cardiomyopathy. In addition, acquired deficits of multiple Ca2+-handling proteins can contribute to the pathogenesis of arrhythmias in patients with various types of heart disease. In this review article, we will first review the key role of Ca2+ in normal cardiac function-in particular, excitation-contraction coupling and normal electric rhythms. The functional involvement of Ca2+ in distinct arrhythmia mechanisms will be discussed, followed by various inherited arrhythmia syndromes caused by mutations in Ca2+-handling proteins. Finally, we will discuss how changes in the expression of regulation of Ca2+ channels and transporters can cause acquired arrhythmias, and how these mechanisms might be targeted for therapeutic purposes.
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Affiliation(s)
- Andrew P Landstrom
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.)
| | - Dobromir Dobrev
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.)
| | - Xander H T Wehrens
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.).
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14
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Kuroda Y, Yuasa S, Watanabe Y, Ito S, Egashira T, Seki T, Hattori T, Ohno S, Kodaira M, Suzuki T, Hashimoto H, Okata S, Tanaka A, Aizawa Y, Murata M, Aiba T, Makita N, Furukawa T, Shimizu W, Kodama I, Ogawa S, Kokubun N, Horigome H, Horie M, Kamiya K, Fukuda K. Flecainide ameliorates arrhythmogenicity through NCX flux in Andersen-Tawil syndrome-iPS cell-derived cardiomyocytes. Biochem Biophys Rep 2017; 9:245-256. [PMID: 28956012 PMCID: PMC5614591 DOI: 10.1016/j.bbrep.2017.01.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 12/09/2016] [Accepted: 01/10/2017] [Indexed: 12/15/2022] Open
Abstract
Andersen-Tawil syndrome (ATS) is a rare inherited channelopathy. The cardiac phenotype in ATS is typified by a prominent U wave and ventricular arrhythmia. An effective treatment for this disease remains to be established. We reprogrammed somatic cells from three ATS patients to generate induced pluripotent stem cells (iPSCs). Multi-electrode arrays (MEAs) were used to record extracellular electrograms of iPSC-derived cardiomyocytes, revealing strong arrhythmic events in the ATS-iPSC-derived cardiomyocytes. Ca2+ imaging of cells loaded with the Ca2+ indicator Fluo-4 enabled us to examine intracellular Ca2+ handling properties, and we found a significantly higher incidence of irregular Ca2+ release in the ATS-iPSC-derived cardiomyocytes than in control-iPSC-derived cardiomyocytes. Drug testing using ATS-iPSC-derived cardiomyocytes further revealed that antiarrhythmic agent, flecainide, but not the sodium channel blocker, pilsicainide, significantly suppressed these irregular Ca2+ release and arrhythmic events, suggesting that flecainide's effect in these cardiac cells was not via sodium channels blocking. A reverse-mode Na+/Ca2+exchanger (NCX) inhibitor, KB-R7943, was also found to suppress the irregular Ca2+ release, and whole-cell voltage clamping of isolated guinea-pig cardiac ventricular myocytes confirmed that flecainide could directly affect the NCX current (INCX). ATS-iPSC-derived cardiomyocytes recapitulate abnormal electrophysiological phenotypes and flecainide suppresses the arrhythmic events through the modulation of INCX. iPS cells are generated from three patients with ATS. ATS-iPS cell-derived cardiomyocytes show abnormal electrophysiological phenotypes. Flecainide suppresses abnormal electrophysiological phenotypes in ATS-iPS cell-derived cardiomyocytes.
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Affiliation(s)
- Yusuke Kuroda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan.,Department of Cardiology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Shinsuke Yuasa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yasuhide Watanabe
- Division of Pharmacological Science, Department of Health Science, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Shogo Ito
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Toru Egashira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tomohisa Seki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tetsuhisa Hattori
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Seiko Ohno
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan.,Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Shiga, Japan
| | - Masaki Kodaira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tomoyuki Suzuki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan.,Department of Cardiology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Hisayuki Hashimoto
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Shinichiro Okata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Atsushi Tanaka
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yoshiyasu Aizawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Mitsushige Murata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Laboratory Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Takeshi Aiba
- Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Naomasa Makita
- Department of Molecular Pathophysiology-1, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Tetsushi Furukawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
| | - Itsuo Kodama
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan
| | - Satoshi Ogawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Norito Kokubun
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - Hitoshi Horigome
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Kaichiro Kamiya
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
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15
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Cubeddu LX. Drug-induced Inhibition and Trafficking Disruption of ion Channels: Pathogenesis of QT Abnormalities and Drug-induced Fatal Arrhythmias. Curr Cardiol Rev 2016; 12:141-54. [PMID: 26926294 PMCID: PMC4861943 DOI: 10.2174/1573403x12666160301120217] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 02/29/2016] [Indexed: 01/11/2023] Open
Abstract
Risk of severe and fatal ventricular arrhythmias, presenting as Torsade de Pointes (TdP), is increased in congenital and acquired forms of long QT syndromes (LQTS). Drug-induced inhibition of K+ currents, IKs, IKr, IK1, and/or Ito, delay repolarization, prolong QT, and increase the risk of TdP. Drug-induced interference with IKr is the most common cause of acquired LQTS/TdP. Multiple drugs bind to KNCH2-hERG-K+ channels affecting IKr, including antiarrythmics, antibiotics, antivirals, azole-antifungals, antimalarials, anticancer, antiemetics, prokinetics, antipsychotics, and antidepressants. Azithromycin has been recently added to this list. In addition to direct channel inhibition, some drugs interfere with the traffic of channels from the endoplasmic reticulum to the cell membrane, decreasing mature channel membrane density; e.g., pentamidine, geldalamicin, arsenic trioxide, digoxin, and probucol. Other drugs, such as ketoconazole, fluoxetine, norfluoxetine, citalopram, escitalopram, donepezil, tamoxifen, endoxifen, atazanavir, and roxitromycin, induce both direct channel inhibition and impaired channel trafficking. Although many drugs prolong the QT interval, TdP is a rare event. The following conditions increase the risk of drug-induced TdP: a) Disease states/electrolyte levels (heart failure, structural cardiac disease, bradycardia, hypokalemia); b) Pharmacogenomic variables (presence of congenital LQTS, subclinical ion-channel mutations, history of or having a relative with history of drug-induced long QT/TdP); c) Pharmacodynamic and kinetic factors (high doses, women, elderly, metabolism inhibitors, combining two or more QT prolonging drugs, drugs that prolong the QT and increase QT dispersion, and drugs with multiple actions on ion channels). Because most of these conditions are preventable, careful evaluation of risk factors and increased knowledge of drug use associated with repolarization abnormalities are strongly recommended.
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Affiliation(s)
- Luigi X Cubeddu
- Division of Cardio-Metabolic Research, Department of Pharmaceutical Sciences, Health professions Division, Nova Southeastern University, 3200 S. University Dr., Davie, FL, 333218, USA.
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16
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Adams DS, Uzel SGM, Akagi J, Wlodkowic D, Andreeva V, Yelick PC, Devitt-Lee A, Pare JF, Levin M. Bioelectric signalling via potassium channels: a mechanism for craniofacial dysmorphogenesis in KCNJ2-associated Andersen-Tawil Syndrome. J Physiol 2016; 594:3245-70. [PMID: 26864374 PMCID: PMC4908029 DOI: 10.1113/jp271930] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 02/01/2016] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Xenopus laevis craniofacial development is a good system for the study of Andersen-Tawil Syndrome (ATS)-associated craniofacial anomalies (CFAs) because (1) Kcnj2 is expressed in the nascent face; (2) molecular-genetic and biophysical techniques are available for the study of ion-dependent signalling during craniofacial morphogenesis; (3) as in humans, expression of variant Kcnj2 forms in embryos causes a muscle phenotype; and (4) variant forms of Kcnj2 found in human patients, when injected into frog embryos, cause CFAs in the same cell lineages. Forced expression of WT or variant Kcnj2 changes the normal pattern of Vmem (resting potential) regionalization found in the ectoderm of neurulating embryos, and changes the normal pattern of expression of ten different genetic regulators of craniofacial development, including markers of cranial neural crest and of placodes. Expression of other potassium channels and two different light-activated channels, all of which have an effect on Vmem , causes CFAs like those induced by injection of Kcnj2 variants. In contrast, expression of Slc9A (NHE3), an electroneutral ion channel, and of GlyR, an inactive Cl(-) channel, do not cause CFAs, demonstrating that correct craniofacial development depends on a pattern of bioelectric states, not on ion- or channel-specific signalling. Using optogenetics to control both the location and the timing of ion flux in developing embryos, we show that affecting Vmem of the ectoderm and no other cell layers is sufficient to cause CFAs, but only during early neurula stages. Changes in Vmem induced late in neurulation do not affect craniofacial development. We interpret these data as strong evidence, consistent with our hypothesis, that ATS-associated CFAs are caused by the effect of variant Kcnj2 on the Vmem of ectodermal cells of the developing face. We predict that the critical time is early during neurulation, and the critical cells are the ectodermal cranial neural crest and placode lineages. This points to the potential utility of extant, ion flux-modifying drugs as treatments to prevent CFAs associated with channelopathies such as ATS. ABSTRACT Variants in potassium channel KCNJ2 cause Andersen-Tawil Syndrome (ATS); the induced craniofacial anomalies (CFAs) are entirely unexplained. We show that KCNJ2 is expressed in Xenopus and mouse during the earliest stages of craniofacial development. Misexpression in Xenopus of KCNJ2 carrying ATS-associated mutations causes CFAs in the same structures affected in humans, changes the normal pattern of membrane voltage potential regionalization in the developing face and disrupts expression of important craniofacial patterning genes, revealing the endogenous control of craniofacial patterning by bioelectric cell states. By altering cells' resting potentials using other ion translocators, we show that a change in ectodermal voltage, not tied to a specific protein or ion, is sufficient to cause CFAs. By adapting optogenetics for use in non-neural cells in embryos, we show that developmentally patterned K(+) flux is required for correct regionalization of the resting potentials and for establishment of endogenous early gene expression domains in the anterior ectoderm, and that variants in KCNJ2 disrupt this regionalization, leading to the CFAs seen in ATS patients.
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Affiliation(s)
- Dany Spencer Adams
- Department of Biology and Tufts Centre for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA, 02155, USA
| | - Sebastien G M Uzel
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Jin Akagi
- School of Applied Sciences, RMIT University, Melbourne, Australia
| | - Donald Wlodkowic
- School of Applied Sciences, RMIT University, Melbourne, Australia
| | - Viktoria Andreeva
- Department of Orthodontics, Division of Craniofacial and Molecular Genetics, Tufts University School of Dental Medicine, Boston, MA 02111, USA
| | - Pamela Crotty Yelick
- Department of Orthodontics, Division of Craniofacial and Molecular Genetics, Tufts University School of Dental Medicine, Boston, MA 02111, USA
| | - Adrian Devitt-Lee
- Department of Biology and Tufts Centre for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA, 02155, USA
| | - Jean-Francois Pare
- Department of Biology and Tufts Centre for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA, 02155, USA
| | - Michael Levin
- Department of Biology and Tufts Centre for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA, 02155, USA
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17
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Finsterer J, Stöllberger C, Maeztu C. Sudden cardiac death in neuromuscular disorders. Int J Cardiol 2016; 203:508-15. [DOI: 10.1016/j.ijcard.2015.10.176] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 09/25/2015] [Accepted: 10/24/2015] [Indexed: 12/31/2022]
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18
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Wu SN, Huang YM, Kao CA, Chen BS, Lo YC. Investigations on contribution of glial inwardly-rectifying K(+) current to membrane potential and ion flux: an experimental and theoretical study. Kaohsiung J Med Sci 2014; 31:9-17. [PMID: 25600915 DOI: 10.1016/j.kjms.2014.10.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 07/01/2014] [Accepted: 08/20/2014] [Indexed: 01/29/2023] Open
Abstract
The inwardly rectifying K(+) current [IK(IR)] allows large inward K(+) currents at potentials negative to K(+) equilibrium potential (EK) and it becomes small outward K(+) currents at those positive to EK. How changes of such currents enriched in glial cells can influence the functions of glial cell, neurons, or both is not clearly defined, although mutations of Kir4.1 channels have been demonstrated to cause serious neurological disorders. In this study, we identified the presence of IK(IR) in human glioma cells (U373 and U87 cells). The amplitude of IK(IR) in U373 cells was subject to inhibition by amitriptyline, arecoline, or BaCl2. The activity of inwardly rectifying K(+) channels was also clearly detected, and single-channel conductance of these channels was calculated to be around 23 pS. Moreover, based on a simulation model derived from neuron-glial interaction mediated by ion flux, we further found out that incorporation of glial IK(IR) conductance into the model can significantly contribute to regulation of extracellular K(+) concentrations and glial resting potential, particularly during high-frequency stimulation. Glial cells and neurons can mutually modulate their expression of ion channels through K(+) ions released into the extracellular space. It is thus anticipated that glial IK(IR) may be a potential target utilized to influence the activity of neuronal and glial cells as well as their interaction.
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Affiliation(s)
- Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan; Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City, Taiwan.
| | - Yan-Ming Huang
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan
| | - Ching-An Kao
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan
| | - Bing-Shuo Chen
- Department of Anaesthesiology, Chi-Mei Medical Center, Tainan City, Taiwan
| | - Yi-Ching Lo
- Department of Pharmacology, Kaohsiung Medical University, Kaohsiung City, Taiwan
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19
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Márquez MF, Totomoch-Serra A, Vargas-Alarcón G, Cruz-Robles D, Pellizzon OA, Cárdenas M. [Andersen-Tawil syndrome: a review of its clinical and genetic diagnosis with emphasis on cardiac manifestations]. ARCHIVOS DE CARDIOLOGIA DE MEXICO 2014; 84:278-85. [PMID: 25270337 DOI: 10.1016/j.acmx.2013.12.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 12/12/2013] [Accepted: 12/12/2013] [Indexed: 10/24/2022] Open
Abstract
The Andersen-Tawil syndrome is a cardiac ion channel disease that is inherited in an autosomal dominant way and is classified as type 7 of the congenital long QT syndromes. Affected gene is KCNJ2, which forms the inward rectifier potassium channel designated Kir2.1. This protein is involved in stabilizing the resting membrane potential and controls the duration of the action potential in skeletal muscle and heart. It also participates in the terminal repolarization phase of the action potential in ventricular myocytes and is a major component responsible for the correction in the potassium current during phase 3 of the action potential repolarization. Kir 2.1 channel has a predominant role in skeletal muscle, heart and brain. Alterations in this channel produce flaccid paralysis, arrhythmias, impaired skeletal development primarily in extremities and facial area. In this review we address the disease from the point of view of clinical and molecular diagnosis with emphasis on cardiac manifestations.
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Affiliation(s)
- Manlio F Márquez
- Departamento de Electrofisiología, Instituto Nacional de Cardiología Ignacio Chávez, México D.F., México.
| | - Armando Totomoch-Serra
- Departamento de Biología Molecular, Instituto Nacional de Cardiología Ignacio Chávez, México D.F., México; Maestría en Investigación Clínica Experimental en Salud, Universidad Nacional Autónoma de México, México D.F., México
| | - Gilberto Vargas-Alarcón
- Departamento de Biología Molecular, Instituto Nacional de Cardiología Ignacio Chávez, México D.F., México
| | - David Cruz-Robles
- Departamento de Biología Molecular, Instituto Nacional de Cardiología Ignacio Chávez, México D.F., México
| | - Oscar A Pellizzon
- Centro de Arritmias Cardíacas, Hospital Universitario del Centenario, Rosario (Santa Fe), Argentina
| | - Manuel Cárdenas
- Departamento de Electrofisiología, Instituto Nacional de Cardiología Ignacio Chávez, México D.F., México
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20
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Iyer V, Sampson KJ, Kass RS. Modeling tissue- and mutation- specific electrophysiological effects in the long QT syndrome: role of the Purkinje fiber. PLoS One 2014; 9:e97720. [PMID: 24892747 PMCID: PMC4043730 DOI: 10.1371/journal.pone.0097720] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 03/28/2014] [Indexed: 12/05/2022] Open
Abstract
Congenital long QT syndrome is a heritable family of arrhythmias caused by mutations in 13 genes encoding ion channel complex proteins. Mounting evidence has implicated the Purkinje fiber network in the genesis of ventricular arrhythmias. In this study, we explore the hypothesis that long QT mutations can demonstrate different phenotypes depending on the tissue type of expression. Using computational models of the human ventricular myocyte and the Purkinje fiber cell, the biophysical alteration in channel function in LQT1, LQT2, LQT3, and LQT7 are modeled. We identified that the plateau potential was important in LQT1 and LQT2, in which mutation led to minimal action potential prolongation in Purkinje fiber cells. The phenotype of LQT3 mutation was dependent on the biophysical alteration induced as well as tissue type. The canonical ΔKPQ mutation causes severe action potential prolongation in both tissue types. For LQT3 mutation F1473C, characterized by shifted channel availability, a more severe phenotype was seen in Purkinje fiber cells with action potential prolongation and early afterdepolarizations. The LQT3 mutation S1904L demonstrated striking effects on action potential duration restitution and more severe action potential prolongation in Purkinje fiber cells at higher heart rates. Voltage clamp simulations highlight the mechanism of effect of these mutations in different tissue types, and impact of drug therapy is explored. We conclude that arrhythmia formation in long QT syndrome may depend not only on the basis of mutation and biophysical alteration, but also upon tissue of expression. The Purkinje fiber network may represent an important therapeutic target in the management of patients with heritable channelopathies.
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Affiliation(s)
- Vivek Iyer
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York, New York, United States of America
- * E-mail:
| | - Kevin J. Sampson
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York, New York, United States of America
| | - Robert S. Kass
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York, New York, United States of America
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21
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Combined inhibition of Na+ and Ca2+ channels: A novel paradigm for the treatment of incessant ventricular arrhythmias in Andersen-Tawil syndrome. Heart Rhythm 2014; 11:318-20. [DOI: 10.1016/j.hrthm.2013.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Indexed: 12/23/2022]
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23
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Bonilla IM, Belevych AE, Sridhar A, Nishijima Y, Ho HT, He Q, Kukielka M, Terentyev D, Terentyeva R, Liu B, Long VP, Györke S, Carnes CA, Billman GE. Endurance exercise training normalizes repolarization and calcium-handling abnormalities, preventing ventricular fibrillation in a model of sudden cardiac death. J Appl Physiol (1985) 2012; 113:1772-83. [PMID: 23042911 DOI: 10.1152/japplphysiol.00175.2012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The risk of sudden cardiac death is increased following myocardial infarction. Exercise training reduces arrhythmia susceptibility, but the mechanism is unknown. We used a canine model of sudden cardiac death (healed infarction, with ventricular tachyarrhythmias induced by an exercise plus ischemia test, VF+); we previously reported that endurance exercise training was antiarrhythmic in this model (Billman GE. Am J Physiol Heart Circ Physiol 297: H1171-H1193, 2009). A total of 41 VF+ animals were studied, after random assignment to 10 wk of endurance exercise training (EET; n = 21) or a matched sedentary period (n = 20). Following (>1 wk) the final attempted arrhythmia induction, isolated myocytes were used to test the hypotheses that the endurance exercise-induced antiarrhythmic effects resulted from normalization of cellular electrophysiology and/or normalization of calcium handling. EET prevented VF and shortened in vivo repolarization (P < 0.05). EET normalized action potential duration and variability compared with the sedentary group. EET resulted in a further decrement in transient outward current compared with the sedentary VF+ group (P < 0.05). Sedentary VF+ dogs had a significant reduction in repolarizing K(+) current, which was restored by exercise training (P < 0.05). Compared with controls, myocytes from the sedentary VF+ group displayed calcium alternans, increased calcium spark frequency, and increased phosphorylation of S2814 on ryanodine receptor 2. These abnormalities in intracellular calcium handling were attenuated by exercise training (P < 0.05). Exercise training prevented ischemically induced VF, in association with a combination of beneficial effects on cellular electrophysiology and calcium handling.
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Affiliation(s)
- Ingrid M Bonilla
- College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, USA
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Lin YK, Chen YC, Chen JH, Chen SA, Chen YJ. Adipocytes modulate the electrophysiology of atrial myocytes: implications in obesity-induced atrial fibrillation. Basic Res Cardiol 2012; 107:293. [DOI: 10.1007/s00395-012-0293-1] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 07/17/2012] [Accepted: 07/31/2012] [Indexed: 01/19/2023]
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Wang CL, Tsai ML, Wu SN. Evidence for mitoxantrone-induced block of inwardly rectifying K(+) channels expressed in the osteoclast precursor RAW 264.7 cells differentiated with lipopolysaccharide. Cell Physiol Biochem 2012; 30:687-701. [PMID: 22854649 DOI: 10.1159/000341449] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Mitoxanthrone (MX) is an anthracenedione antineoplastic agent. Whether this drug and other related compounds have any effects on ion currents in osteoclasts remains largely unclear. METHODS In this study, the effects of MX and other related compounds on inwardly rectifying K(+) current (I(K(IR))) were investigated in RAW 264.7 osteoclast precursor cells treated with lipopolysaccharide. RESULTS The I(K(IR))in these cells are blocked by BaCl(2) (1 mM). MX (1-100 µM) decreased the amplitude of I(K(IR)) in a concentration-dependent manner with an IC(50) value of 6.4 µM. MX also slowed the time course of I(K(IR)) inactivation elicited by large hyperpolarization. Doxorubicin (10 µM), 17β-estradiol (10 µM) and tertiapin (1 µM) decreased the I(K(IR)) amplitude in these cells. In bafilomycin A(1)-treated cells, MX-mediated block of I(K(IR)) still existed. In cell-attached configuration, when the electrode was filled with MX (10 µM), the activity of inwardly rectifying K(+) (Kir) channels was decreased with no change in single-channel conductance. MX-mediated reduction of channel activity is accompanied by a shortening of mean open time. Under current-clamp conditions, addition of MX resulted in membrane depolarization. Therefore, MX can interact with the Kir channels to decrease the I(K(IR)) amplitude and to depolarize the membrane in these cells. CONCLUSION The block by this drug of Kir2.1 channels appears to be one of the important mechanisms underlying its actions on the resorptive activity of osteoclasts, if similar results occur in vivo. Targeting at Kir channels may be clinically useful as an adjunctive regimen to anti-cancer drugs (e.g., MX or doxorubicin) in influencing the resorptive activity of osteoclasts.
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Affiliation(s)
- Chung-Lin Wang
- Department of Nursing, Chung Jen College of Nursing, Health Sciences and Management, Chiayi city, Taiwan
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Adeniran I, El Harchi A, Hancox JC, Zhang H. Proarrhythmia in KCNJ2-linked short QT syndrome: insights from modelling. Cardiovasc Res 2012; 94:66-76. [DOI: 10.1093/cvr/cvs082] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Sung RJ, Lo CP, Hsiao PY, Tien HC. Targeting intracellular calcium cycling in catecholaminergic polymorphic ventricular tachycardia: a theoretical investigation. Am J Physiol Heart Circ Physiol 2011; 301:H1625-38. [DOI: 10.1152/ajpheart.00696.2010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a malignant arrhythmogenic disorder linked to mutations in the cardiac ryanodine receptor (RyR2) and calsequestrin, predisposing the young to syncope and cardiac arrest. To define the role of β-adrenergic stimulation (BAS) and to identify potential therapeutic targeted sites relating to intracellular calcium cycling, we used a Luo-Rudy dynamic ventricular myocyte model incorporated with interacting Markov models of the L-type Ca2+ channel ( ICa,L) and RyR2 to simulate the heterozygous state of mouse RyR2 R4496C mutation (RyR2R4496C+/−) comparable with CPVT patients with RyR2 R4497C mutation. Characteristically, in simulated cells, pacing at 4 Hz or faster or pacing at 2 Hz under BAS with effects equivalent to those of isoproterenol at ≥0.1 μM could readily induce delayed afterdepolarizations (DADs) and DAD-mediated triggered activity (TA) in RyR2R4496C+/− but not in the wild-type via enhancing both ICa,L and sarcoplasmic reticulum (SR) Ca2+ ATPase ( IUP). Moreover, with the use of steady state values of isolated endocardial (Endo), mid-myocardial (M), and epicardial (Epi) cells as initial data for conducting single cell and one-dimensional strand studies, the M cell was more vulnerable for developing DADs and DAD-mediated TA than Endo and Epi cells, and the gap junction coupling represented by diffusion coefficient ( D) of ≤0.000766*98 cm2/ms was required for generating DAD-mediated TA in RyR2R4496C+/−. Whereas individual reduction of Ca2+ release channel of SR and Na-Ca exchanger up to 50% was ineffective, 30% or more reduction of either ICa,L or IUP could totally suppress the inducibility of arrhythmia under BAS. Of note, 15% reduction of both ICa,L and IUP exerted a synergistic antiarrhythmic efficacy. Findings of this model study confirm that BAS facilitates induction of ventricular tachyarrhythmias via its action on intracellular Ca2+ cycling and a pharmacological regimen capable of reducing ICa,L could be an effective adjunctive to β-adrenergic blockers for suppressing ventricular tachyarrhythmias during CPVT.
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Affiliation(s)
- Ruey J. Sung
- Institute of Life Sciences, National Central University, Taoyuan
- Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California
| | - Chu-Pin Lo
- Department of Financial and Computational Mathematics, Providence University, Taichung, Taiwan; and
| | - Pi Yin Hsiao
- Institute of Life Sciences, National Central University, Taoyuan
| | - Hui-Chun Tien
- Department of Financial and Computational Mathematics, Providence University, Taichung, Taiwan; and
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Radwański PB, Veeraraghavan R, Poelzing S. Cytosolic calcium accumulation and delayed repolarization associated with ventricular arrhythmias in a guinea pig model of Andersen-Tawil syndrome. Heart Rhythm 2010; 7:1428-1435.e1. [PMID: 20380896 DOI: 10.1016/j.hrthm.2010.03.044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 03/31/2010] [Indexed: 11/25/2022]
Abstract
BACKGROUND Andersen-Tawil syndrome (ATS1)-associated ventricular arrhythmias are initiated by frequent, hypokalemia-exacerbated, triggered activity. Previous ex vivo studies in drug-induced Andersen-Tawil syndrome (DI-ATS1) models have proposed that arrhythmia propensity in DI-ATS1 derives from cytosolic Ca(2+) ([Ca(2+)](i)) accumulation leading to increased triggered activity. OBJECTIVE The purpose of this study was to test the hypothesis that elevated [Ca(2+)](i) with concomitant APD prolongation, rather than APD dispersion, underlies arrhythmia propensity during DI-ATS1. METHODS DI-ATS1 was induced in isolated guinea pig ventricles by perfusion of 2 mM KCl Tyrode solution containing 10 μM BaCl(2). APD and [Ca(2+)](i) from the anterior epicardium were quantified by ratiometric optical voltage (di-4-ANEPPS) or Ca(2+) (Indo-1) mapping during right ventricular pacing with or without the ATP-sensitive potassium channel opener pinacidil (15 μM). RESULTS APD gradients under all conditions were insufficient for arrhythmia induction by programmed stimulation. However, 38% of DI-ATS1 preparations experienced ventricular tachycardias (VTs), and all preparations experienced a high incidence of premature ventricular complexes (PVCs). Pinacidil decreased APD and APD dispersion and reduced VTs (to 6%), and PVC frequency (by 79.5%). However, PVC frequency remained significantly greater relative to control (0.5% ± 0.3% of DI-ATS1). Importantly, increased arrhythmia propensity during DI-ATS1 was associated with diastolic [Ca(2+)](i) accumulation and increased [Ca(2+)](i) transient amplitudes. Pinacidil partially attenuated the former but did not alter the latter. CONCLUSION The study data suggest that arrhythmias during DI-ATS1 may be a result of triggered activity secondary to prolonged APD and altered [Ca(2+)](i) cycling and less likely dependent on large epicardial APD gradients forming the substrate for reentry. Therefore, therapies aimed at reducing [Ca(2+)](i) rather than APD gradients may prove effective in treatment of ATS1.
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Affiliation(s)
- Przemysław B Radwański
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah 84112-5000, USA
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Sung RJ, Wu YH, Lai NHJ, Teng CH, Luo CH, Tien HC, Lo CP, Wu SN. β-Adrenergic modulation of arrhythmogenesis and identification of targeted sites of antiarrhythmic therapy in Timothy (LQT8) syndrome: a theoretical study. Am J Physiol Heart Circ Physiol 2010; 298:H33-44. [DOI: 10.1152/ajpheart.00232.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Timothy syndrome (TS) is a malignant form of congenital long QT syndrome with a mode of arrhythmia onset often triggered by enhanced sympathetic tone. We sought to explore mechanisms by which β-adrenergic stimulation (BAS) modulates arrhythmogenesis and to identify potential targeted sites of antiarrhythmic therapy in TS. Using a dynamic Luo-Rudy ventricular myocyte model incorporated with detailed intracellular Ca2+ cycling, along with its one-dimensional multicellular strand, we simulated various clinical scenarios of TS, with stepwise increase in the percentage of G406R Cav1.2 channels from 0 to 11.5 and 23%, and to 38.5 and 77%, respectively, for heterozygous and homozygous states of TS1 and TS2. Progressive prolongation of action potential duration (APD) and QT interval, accompanied by amplification of transmural dispersion of repolarization, steepening of APD restitution, induction of delayed afterdepolariztions (DADs), and both DAD and phase 3 early afterdepolariztion-mediated triggered activities, correlated well with the extent of G406R Cav1.2 channel mutation. BAS amplified transmural dispersion of repolarization, steepened APD restitution, and facilitated inducibility of DAD-mediated triggered activity. Systematic analysis of intracellular Ca2+ cycling revealed that sarcoplasmic reticulum Ca2+ ATPase (uptake current) played an essential role in BAS-induced facilitation of DAD-mediated triggered activity and, in addition to L-type calcium current, it could be an effective site of antiarrhythmic therapy under the influence of BAS. Thus G406R Cav1.2 channel mutation confers not only a trigger, but also a substrate for lethal ventricular arrhythmias, which can be exaggerated by BAS. It is suggested that, besides β-adrenergic blockers and L-type calcium current channel blockers, an agent aimed at reduction of sarcoplasmic reticulum Ca2+ ATPase uptake current may provide additional antiarrhythmic effect in patients with TS.
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Affiliation(s)
- Ruey J. Sung
- Institute of Life Sciences, College of Sciences, National Central University, Taoyuan
- Division of Cardiovascular Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, California
| | - Yung-Han Wu
- Institute of Basic Medical Research, College of Medicine,
| | | | | | - Ching-Hsing Luo
- Institute of Electrical Engineering, College of Engineering and Computer Science, National Cheng Kung University, Tainan; and
| | - Hui-Chun Tien
- Department of Applied Mathematics, Providence University, Taichung, Taiwan; and
| | - Chu-Pin Lo
- Department of Applied Mathematics, Providence University, Taichung, Taiwan; and
| | - Sheng-Nan Wu
- Institute of Basic Medical Research, College of Medicine,
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Vassalle M, Catanzaro JN, Nett MP, Rota M. Essential role of diastolic oscillatory potentials in adrenergic control of guinea pig sino-atrial node discharge. J Biomed Sci 2009; 16:101. [PMID: 19922640 PMCID: PMC2789063 DOI: 10.1186/1423-0127-16-101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Accepted: 11/18/2009] [Indexed: 11/23/2022] Open
Abstract
Background The diastolic oscillatory after-potential Vos and pre-potential ThVos play an essential role in the pacemaker mechanism of sino-atrial node (SAN). The aim of this study was to investigate whether these oscillatory potentials are also involved in adrenergic control of SAN discharge. Methods Vos and ThVos were visualized by superfusing guinea pig SAN in high [K+]o. The actions of adrenergic agonists on oscillatory potentials were studied by means of a microelectrode technique. Statistical significance was determined by means of Student's paired t-test. Results In non-spontaneous SAN, norepinephrine (NE) decreased the resting potential into a voltage range ("oscillatory zone") where increasingly larger ThVos appeared and initiated spontaneous discharge. In slowly discharging SAN, NE gradually increased the rate by increasing the amplitude and slope of earlier-occurring ThVos and of Vos until these oscillations fused with initial diastolic depolarization (DD1). In the presence of NE, sudden fast rhythms were initiated by large Vos that entered a more negative oscillatory zone and initiated a large ThVos. Recovery from NE exposure involved the converse changes. The β-adrenergic agonist isoproterenol had similar actions. Increasing calcium load by decreasing high [K+]o, by fast drive or by recovery in Tyrode solution led to growth of Vos and ThVos which abruptly fused when a fast sudden rhythm was induced. Low [Ca2+]o antagonized the adrenergic actions. Cesium (a blocker of If) induced spontaneous discharge in quiescent SAN through ThVos. In spontaneous SAN, Cs+increased Vos and ThVos, thereby increasing the rate. Cs+ did not hinder the positive chronotropic action of NE. Barium increased the rate, as Cs+ did. Conclusion Adrenergic agonists: (i) initiate SAN discharge by decreasing the resting potential and inducing ThVos; (ii) gradually accelerate SAN rate by predominantly increasing size and slope of earlier and more negative ThVos; (iii) can induce sudden fast rhythms through the abrupt fusion of large Vos with large ThVos; (iv) increase Vos and ThVosby increasing cellular calcium; and (v) do not modify the oscillatory potentials by means of the hyperpolarization-activated current If. The results provide evidence for novel mechanisms by which the SAN dominant pacemaker activity is initiated and enhanced by adrenergic agonists.
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Affiliation(s)
- Mario Vassalle
- Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA.
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Vega AL, Tester DJ, Ackerman MJ, Makielski JC. Protein kinase A-dependent biophysical phenotype for V227F-KCNJ2 mutation in catecholaminergic polymorphic ventricular tachycardia. Circ Arrhythm Electrophysiol 2009; 2:540-7. [PMID: 19843922 DOI: 10.1161/circep.109.872309] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND KCNJ2 encodes Kir2.1, a pore-forming subunit of the cardiac inward rectifier current, I(K1). KCNJ2 mutations are associated with Andersen-Tawil syndrome and catecholaminergic polymorphic ventricular tachycardia. The aim of this study was to characterize the biophysical and cellular phenotype of a KCNJ2 missense mutation, V227F, found in a patient with catecholaminergic polymorphic ventricular tachycardia. METHODS AND RESULTS Kir2.1-wild-type (WT) and V227F channels were expressed individually and together in Cos-1 cells to measure I(K1) by voltage clamp. Unlike typical Andersen-Tawil syndrome-associated KCNJ2 mutations, which show dominant negative loss of function, Kir2.1WT+V227F coexpression yielded I(K1) indistinguishable from Kir2.1-WT under basal conditions. To simulate catecholamine activity, a protein kinase A (PKA)-stimulating cocktail composed of forskolin and 3-isobutyl-1-methylxanthine was used to increase PKA activity. This PKA-simulated catecholaminergic stimulation caused marked reduction of outward I(K1) compared with Kir2.1-WT. PKA-induced reduction in I(K1) was eliminated by mutating the phosphorylation site at serine 425 (S425N). CONCLUSIONS Heteromeric Kir2.1-V227F and WT channels showed an unusual latent loss of function biophysical phenotype that depended on PKA-dependent Kir2.1 phosphorylation. This biophysical phenotype, distinct from typical Andersen-Tawil syndrome mutations, suggests a specific mechanism for PKA-dependent I(K1) dysfunction for this KCNJ2 mutation, which correlates with adrenergic conditions underlying the clinical arrhythmia.
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Affiliation(s)
- Amanda L Vega
- Department of Medicine, University of Wisconsin, Madison, Wisconsin 53792, USA
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Ryan AM, Matthews E, Hanna MG. Skeletal-muscle channelopathies: periodic paralysis and nondystrophic myotonias. Curr Opin Neurol 2007; 20:558-63. [PMID: 17885445 DOI: 10.1097/wco.0b013e3282efc16c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
PURPOSE OF REVIEW To provide a current review of clinical phenotypes, genetics, molecular pathophysiology, and electro-diagnostic testing strategies of periodic paralysis and nondystrophic myotonias. RECENT FINDINGS The number of pathogenic mutations causing periodic paralysis and nondystrophic myotonias continues to increase. Important insight into the molecular pathogenesis of muscle sodium channelopathies has been revealed by the finding of 'leaky' closed sodium channels. Previously, alterations in sodium-channel activation or inactivation have been identified as important disease mechanisms. The recent discovery that substitutions of key arginine residues in the voltage-sensing segment of the channel may lead to a 'pore leak' when the channel is closed suggests a new mechanism. Since similar mutations exist in corresponding positions of other channels, this mechanism may apply to other channel diseases. The recognition of different electrophysiological patterns that are specific to muscle ion-channel genotypes will be useful in diagnosis and in guiding genetic testing. Recent studies demonstrate that magnetic resonance imaging may be used to detect intramuscular accumulation of sodium during episodes of weakness. SUMMARY Recent advances have refined our ability to make a precise molecular diagnosis in muscle channelopathies. The description of a pore leak with voltage-sensor mutations may represent a new disease mechanism.
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Affiliation(s)
- Aisling M Ryan
- MRC Centre for Neuromuscular Disease, Department of Molecular Neuroscience, Institute of Neurology, University College London, London, UK
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Xu Y, Zhang Q, Chiamvimonvat N. IK1 and cardiac hypoxia: after the long and short QT syndromes, what else can go wrong with the inward rectifier K+ currents? J Mol Cell Cardiol 2007; 43:15-7. [PMID: 17561108 PMCID: PMC3745007 DOI: 10.1016/j.yjmcc.2007.04.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Indexed: 10/23/2022]
Affiliation(s)
- Yanfang Xu
- Division of Cardiovascular Medicine, University of California, Davis, Davis, CA
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China 050017
| | - Qian Zhang
- Division of Cardiovascular Medicine, University of California, Davis, Davis, CA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, University of California, Davis, Davis, CA
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA
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