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Rodríguez-Carlos A, Jacobo-Delgado Y, Santos-Mena AO, García-Hernández MH, De Jesus-Gonzalez LA, Lara-Ramirez EE, Rivas-Santiago B. Histone deacetylase (HDAC) inhibitors- based drugs are effective to control Mycobacterium tuberculosis infection and promote the sensibility for rifampicin in MDR strain. Mem Inst Oswaldo Cruz 2023; 118:e230143. [PMID: 38126492 PMCID: PMC10740574 DOI: 10.1590/0074-02760230143] [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: 08/15/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023] Open
Abstract
BACKGROUND Tuberculosis (TB) is a major public health problem, which has been aggravated by the alarming growth of drug-resistant tuberculosis. Therefore, the development of a safer and more effective treatment is needed. OBJECTIVES The aim of this work was repositioning and evaluate histone deacetylases (HDAC) inhibitors- based drugs with potential antimycobacterial activity. METHODS Using an in silico pharmacological repositioning strategy, three molecules that bind to the catalytic site of histone deacetylase were selected. Pneumocytes type II and macrophages were infected with Mycobacterium tuberculosis and treated with pre-selected HDAC inhibitors (HDACi). Subsequently, the ability of each of these molecules to directly promote the elimination of M. tuberculosis was evaluated by colony-forming unit (CFU)/mL. We assessed the expression of antimicrobial peptides and respiratory burst using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). FINDINGS Aminoacetanilide (ACE), N-Boc-1,2-phenylenediamine (N-BOC), 1,3-Diphenylurea (DFU), reduce bacillary loads in macrophages and increase the production of β-defensin-2, LL-37, superoxide dismutase (SOD) 3 and inducible nitric oxide synthase (iNOS). While only the use of ACE in type II pneumocytes decreases the bacterial load through increasing LL-37 expression. Furthermore, the use of ACE and rifampicin inhibited the survival of intracellular multi-drug resistance M. tuberculosis. MAIN CONCLUSIONS Our data support the usefulness of in silico approaches for drug repositioning to provide a potential adjunctive therapy for TB.
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Affiliation(s)
- Adrián Rodríguez-Carlos
- Medical Research Unit-Zacatecas, Mexican Institute for Social Security-IMSS, Zacatecas, Mexico
| | - Yolanda Jacobo-Delgado
- Medical Research Unit-Zacatecas, Mexican Institute for Social Security-IMSS, Zacatecas, Mexico
| | | | | | | | - Edgar E Lara-Ramirez
- Instituto Politécnico Nacional, Centro de Biotecnología Genómica, Laboratorio de Biotecnología Farmacéutica, Reynosa, Mexico
| | - Bruno Rivas-Santiago
- Medical Research Unit-Zacatecas, Mexican Institute for Social Security-IMSS, Zacatecas, Mexico
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2
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Zangerl-Plessl EM, Wu W, Sanguinetti MC, Stary-Weinzinger A. Binding of RPR260243 at the intracellular side of the hERG1 channel pore domain slows closure of the helix bundle crossing gate. Front Mol Biosci 2023; 10:1137368. [PMID: 36911523 PMCID: PMC9996038 DOI: 10.3389/fmolb.2023.1137368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 02/07/2023] [Indexed: 02/25/2023] Open
Abstract
The opening and closing of voltage-dependent potassium channels is dependent on a tight coupling between movement of the voltage sensing S4 segments and the activation gate. A specific interaction between intracellular amino- and carboxyl-termini is required for the characteristically slow rate of channel closure (deactivation) of hERG1 channels. Compounds that increase hERG1 channel currents represent a novel approach for prevention of arrhythmia associated with prolonged ventricular repolarization. RPR260243 (RPR), a quinoline oxo-propyl piperidine derivative, inhibits inactivation and dramatically slows the rate of hERG1 channel deactivation. Here we report that similar to its effect on wild-type channels, RPR greatly slows the deactivation rate of hERG1 channels missing their amino-termini, or of split channels lacking a covalent link between the voltage sensor domain and the pore domain. By contrast, RPR did not slow deactivation of C-terminal truncated hERG1 channels or D540K hERG1 mutant channels activated by hyperpolarization. Together, these findings indicate that ability of RPR to slow deactivation requires an intact C-terminus, does not slow deactivation by stabilizing an interaction involving the amino-terminus or require a covalent link between the voltage sensor and pore domains. All-atom molecular dynamics simulations using the cryo-EM structure of the hERG1 channel revealed that RPR binds to a pocket located at the intracellular ends of helices S5 and S6 of a single subunit. The slowing of channel deactivation by RPR may be mediated by disruption of normal S5-S6 interactions.
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Affiliation(s)
| | - Wei Wu
- Department of Internal Medicine, Nora Eccles Harrison Cardiovascular Research & Training Institute, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT, United States
| | - Michael C Sanguinetti
- 3 Department of Internal Medicine, Division of Cardiovascular Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt LakeCity, UT, United States
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3
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El Harchi A, Brincourt O. Pharmacological activation of the
hERG
K
+
channel for the management of the long
QT
syndrome: A review. J Arrhythm 2022; 38:554-569. [PMID: 35936037 PMCID: PMC9347208 DOI: 10.1002/joa3.12741] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/28/2022] [Accepted: 05/16/2022] [Indexed: 11/10/2022] Open
Abstract
In the human heart, the rapid delayed rectifier K+ current (IKr) contributes significantly to ventricular action potential (AP) repolarization and to set the duration of the QT interval of the surface electrocardiogram (ECG). The pore‐forming (α) subunit of the IKr channel is encoded by KCNH2 or human ether‐à‐go‐go‐related gene 1 (hERG1). Impairment of hERG function through either gene mutation (congenital) or pharmacological blockade by diverse drugs in clinical use (acquired) can cause a prolongation of the AP duration (APD) reflected onto the surface ECG as a prolonged QT interval or Long QT Syndrome (LQTS). LQTS can increase the risk of triggered activity of ventricular cardiomyocytes and associated life‐threatening arrhythmia. Current treatments all focus on reducing the incidence of arrhythmia or terminating it after its onset but there is to date no prophylactic treatment for the pharmacological management of LQTS. A new class of hERG modulators (agonists) have been suggested through direct interaction with the hERG channel to shorten the action potential duration (APD) and/or increase the postrepolarisation refractoriness period (PRRP) of ventricular cardiomyocytes protecting thereby against triggered activity and associated arrhythmia. Although promising drug candidates, there remain major obstacles to their clinical development. The aim of this review is to summarize the latest advances as well as the limitations of this proposed pharmacotherapy.
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Affiliation(s)
- Aziza El Harchi
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences Building University of Bristol, University Walk Bristol UK
| | - Oriane Brincourt
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences Building University of Bristol, University Walk Bristol UK
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4
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Husti Z, Varró A, Baczkó I. Arrhythmogenic Remodeling in the Failing Heart. Cells 2021; 10:cells10113203. [PMID: 34831426 PMCID: PMC8623396 DOI: 10.3390/cells10113203] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/05/2021] [Accepted: 11/11/2021] [Indexed: 12/12/2022] Open
Abstract
Chronic heart failure is a clinical syndrome with multiple etiologies, associated with significant morbidity and mortality. Cardiac arrhythmias, including ventricular tachyarrhythmias and atrial fibrillation, are common in heart failure. A number of cardiac diseases including heart failure alter the expression and regulation of ion channels and transporters leading to arrhythmogenic electrical remodeling. Myocardial hypertrophy, fibrosis and scar formation are key elements of arrhythmogenic structural remodeling in heart failure. In this article, the mechanisms responsible for increased arrhythmia susceptibility as well as the underlying changes in ion channel, transporter expression and function as well as alterations in calcium handling in heart failure are discussed. Understanding the mechanisms of arrhythmogenic remodeling is key to improving arrhythmia management and the prevention of sudden cardiac death in patients with heart failure.
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Affiliation(s)
- Zoltán Husti
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research Network, 6720 Szeged, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
- Correspondence:
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5
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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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6
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Kemp JM, Whittaker DG, Venkateshappa R, Pang Z, Johal R, Sergeev V, Tibbits GF, Mirams GR, Claydon TW. Electrophysiological characterization of the hERG R56Q LQTS variant and targeted rescue by the activator RPR260243. J Gen Physiol 2021; 153:212555. [PMID: 34398210 PMCID: PMC8493834 DOI: 10.1085/jgp.202112923] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 06/11/2021] [Accepted: 07/21/2021] [Indexed: 11/20/2022] Open
Abstract
Human Ether-à-go-go (hERG) channels contribute to cardiac repolarization, and inherited variants or drug block are associated with long QT syndrome type 2 (LQTS2) and arrhythmia. Therefore, hERG activator compounds present a therapeutic opportunity for targeted treatment of LQTS. However, a limiting concern is over-activation of hERG resurgent current during the action potential and abbreviated repolarization. Activators that slow deactivation gating (type I), such as RPR260243, may enhance repolarizing hERG current during the refractory period, thus ameliorating arrhythmogenicity with reduced early repolarization risk. Here, we show that, at physiological temperature, RPR260243 enhances hERG channel repolarizing currents conducted in the refractory period in response to premature depolarizations. This occurs with little effect on the resurgent hERG current during the action potential. The effects of RPR260243 were particularly evident in LQTS2-associated R56Q mutant channels, whereby RPR260243 restored WT-like repolarizing drive in the early refractory period and diastolic interval, combating attenuated protective currents. In silico kinetic modeling of channel gating predicted little effect of the R56Q mutation on hERG current conducted during the action potential and a reduced repolarizing protection against afterdepolarizations in the refractory period and diastolic interval, particularly at higher pacing rates. These simulations predicted partial rescue from the arrhythmic effects of R56Q by RPR260243 without risk of early repolarization. Our findings demonstrate that the pathogenicity of some hERG variants may result from reduced repolarizing protection during the refractory period and diastolic interval with limited effect on action potential duration, and that the hERG channel activator RPR260243 may provide targeted antiarrhythmic potential in these cases.
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Affiliation(s)
- Jacob M Kemp
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Dominic G Whittaker
- Centre for Mathematical Medicine & Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, UK
| | | | - ZhaoKai Pang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Raj Johal
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Valentine Sergeev
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Glen F Tibbits
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Gary R Mirams
- Centre for Mathematical Medicine & Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, UK
| | - Thomas W Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
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7
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Borgini M, Mondal P, Liu R, Wipf P. Chemical modulation of Kv7 potassium channels. RSC Med Chem 2021; 12:483-537. [PMID: 34046626 PMCID: PMC8128042 DOI: 10.1039/d0md00328j] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/01/2020] [Indexed: 01/10/2023] Open
Abstract
The rising interest in Kv7 modulators originates from their ability to evoke fundamental electrophysiological perturbations in a tissue-specific manner. A large number of therapeutic applications are, in part, based on the clinical experience with two broad-spectrum Kv7 agonists, flupirtine and retigabine. Since precise molecular structures of human Kv7 channel subtypes in closed and open states have only very recently started to emerge, computational studies have traditionally been used to analyze binding modes and direct the development of more potent and selective Kv7 modulators with improved safety profiles. Herein, the synthetic and medicinal chemistry of small molecule modulators and the representative biological properties are summarized. Furthermore, new therapeutic applications supported by in vitro and in vivo assay data are suggested.
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Affiliation(s)
- Matteo Borgini
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Pravat Mondal
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Ruiting Liu
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
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8
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Optimized Tuning of Auditory Inner Hair Cells to Encode Complex Sound through Synergistic Activity of Six Independent K + Current Entities. Cell Rep 2021; 32:107869. [PMID: 32640234 DOI: 10.1016/j.celrep.2020.107869] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 04/08/2020] [Accepted: 06/16/2020] [Indexed: 02/06/2023] Open
Abstract
Auditory inner hair cells (IHCs) convert sound vibrations into receptor potentials that drive synaptic transmission. For the precise encoding of sound qualities, receptor potentials are shaped by K+ conductances tuning the properties of the IHC membrane. Using patch-clamp and computational modeling, we unravel this membrane specialization showing that IHCs express an exclusive repertoire of six voltage-dependent K+ conductances mediated by Kv1.8, Kv7.4, Kv11.1, Kv12.1, and BKCa channels. All channels are active at rest but are triggered differentially during sound stimulation. This enables non-saturating tuning over a far larger potential range than in IHCs expressing fewer current entities. Each conductance contributes to optimizing responses, but the combined activity of all channels synergistically improves phase locking and the dynamic range of intensities that IHCs can encode. Conversely, hypothetical simpler IHCs appear limited to encode only certain aspects (frequency or intensity). The exclusive channel repertoire of IHCs thus constitutes an evolutionary adaptation to encode complex sound through multifaceted receptor potentials.
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9
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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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10
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Su S, Sun J, Wang Y, Xu Y. Cardiac hERG K + Channel as Safety and Pharmacological Target. Handb Exp Pharmacol 2021; 267:139-166. [PMID: 33829343 DOI: 10.1007/164_2021_455] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The human ether-á-go-go related gene (hERG, KCNH2) encodes the pore-forming subunit of the potassium channel responsible for a fast component of the cardiac delayed rectifier potassium current (IKr). Outward IKr is an important determinant of cardiac action potential (AP) repolarization and effectively controls the duration of the QT interval in humans. Dysfunction of hERG channel can cause severe ventricular arrhythmias and thus modulators of the channel, including hERG inhibitors and activators, continue to attract intense pharmacological interest. Certain inhibitors of hERG channel prolong the action potential duration (APD) and effective refractory period (ERP) to suppress premature ventricular contraction and are used as class III antiarrhythmic agents. However, a reduction of the hERG/IKr current has been recognized as a predominant mechanism responsible for the drug-induced delayed repolarization known as acquired long QT syndromes (LQTS), which is linked to an increased risk for "torsades de pointes" (TdP) ventricular arrhythmias and sudden cardiac death. Many drugs of different classes and structures have been identified to carry TdP risk. Hence, assessing hERG/IKr blockade of new drug candidates is mandatory in the drug development process according to the regulatory agencies. In contrast, several hERG channel activators have been shown to enhance IKr and shorten the APD and thus might have potential antiarrhythmic effects against pathological LQTS. However, these activators may also be proarrhythmic due to excessive shortening of APD and the ERP.
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Affiliation(s)
- Shi Su
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Jinglei Sun
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yi Wang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yanfang Xu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China.
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11
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Shi YP, Pang Z, Venkateshappa R, Gunawan M, Kemp J, Truong E, Chang C, Lin E, Shafaattalab S, Faizi S, Rayani K, Tibbits GF, Claydon VE, Claydon TW. The hERG channel activator, RPR260243, enhances protective IKr current early in the refractory period reducing arrhythmogenicity in zebrafish hearts. Am J Physiol Heart Circ Physiol 2020; 319:H251-H261. [PMID: 32559136 DOI: 10.1152/ajpheart.00038.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Human ether-à-go-go related gene (hERG) K+ channels are important in cardiac repolarization, and their dysfunction causes prolongation of the ventricular action potential, long QT syndrome, and arrhythmia. As such, approaches to augment hERG channel function, such as activator compounds, have been of significant interest due to their marked therapeutic potential. Activator compounds that hinder channel inactivation abbreviate action potential duration (APD) but carry risk of overcorrection leading to short QT syndrome. Enhanced risk by overcorrection of the APD may be tempered by activator-induced increased refractoriness; however, investigation of the cumulative effect of hERG activator compounds on the balance of these effects in whole organ systems is lacking. Here, we have investigated the antiarrhythmic capability of a hERG activator, RPR260243, which primarily augments channel function by slowing deactivation kinetics in ex vivo zebrafish whole hearts. We show that RPR260243 abbreviates the ventricular APD, reduces triangulation, and steepens the slope of the electrical restitution curve. In addition, RPR260243 increases the post-repolarization refractory period. We provide evidence that this latter effect arises from RPR260243-induced enhancement of hERG channel-protective currents flowing early in the refractory period. Finally, the cumulative effect of RPR260243 on arrhythmogenicity in whole organ zebrafish hearts is demonstrated by the restoration of normal rhythm in hearts presenting dofetilide-induced arrhythmia. These findings in a whole organ model demonstrate the antiarrhythmic benefit of hERG activator compounds that modify both APD and refractoriness. Furthermore, our results demonstrate that targeted slowing of hERG channel deactivation and enhancement of protective currents may provide an effective antiarrhythmic approach.NEW & NOTEWORTHY hERG channel dysfunction causes long QT syndrome and arrhythmia. Activator compounds have been of significant interest due to their therapeutic potential. We used the whole organ zebrafish heart model to demonstrate the antiarrhythmic benefit of the hERG activator, RPR260243. The activator abbreviated APD and increased refractoriness, the combined effect of which rescued induced ventricular arrhythmia. Our findings show that the targeted slowing of hERG channel deactivation and enhancement of protective currents caused by the RPR260243 activator may provide an effective antiarrhythmic approach.
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Affiliation(s)
- Yu Patrick Shi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - ZhaoKai Pang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Ravichandra Venkateshappa
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Marvin Gunawan
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Jacob Kemp
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Elson Truong
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Cherlene Chang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Eric Lin
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Sanam Shafaattalab
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Shoaib Faizi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Kaveh Rayani
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Glen F Tibbits
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Victoria E Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Thomas W Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
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12
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Hull CM, Genge CE, Hobbs Y, Rayani K, Lin E, Gunawan M, Shafaattalab S, Tibbits GF, Claydon TW. Investigating the utility of adult zebrafish ex vivo whole hearts to pharmacologically screen hERG channel activator compounds. Am J Physiol Regul Integr Comp Physiol 2019; 317:R921-R931. [PMID: 31664867 DOI: 10.1152/ajpregu.00190.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is significant interest in the potential utility of small-molecule activator compounds to mitigate cardiac arrhythmia caused by loss of function of hERG1a voltage-gated potassium channels. Zebrafish (Danio rerio) have been proposed as a cost-effective, high-throughput drug-screening model to identify compounds that cause hERG1a dysfunction. However, there are no reports on the effects of hERG1a activator compounds in zebrafish and consequently on the utility of the model to screen for potential gain-of-function therapeutics. Here, we examined the effects of hERG1a blocker and types 1 and 2 activator compounds on isolated zkcnh6a (zERG3) channels in the Xenopus oocyte expression system as well as action potentials recorded from ex vivo adult zebrafish whole hearts using optical mapping. Our functional data from isolated zkcnh6a channels show that under the conditions tested, these channels are blocked by hERG1a channel blockers (dofetilide and terfenadine), and activated by type 1 (RPR260243) and type 2 (NS1643, PD-118057) hERG1a activators with higher affinity than hKCNH2a channels (except NS1643), with differences accounted for by different biophysical properties in the two channels. In ex vivo zebrafish whole hearts, two of the three hERG1a activators examined caused abbreviation of the action potential duration (APD), whereas hERG1a blockers caused APD prolongation. These data represent, to our knowledge, the first pharmacological characterization of isolated zkcnh6a channels and the first assessment of hERG enhancing therapeutics in zebrafish. Our findings lead us to suggest that the zebrafish ex vivo whole heart model serves as a valuable tool in the screening of hKCNH2a blocker and activator compounds.
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Affiliation(s)
- Christina M Hull
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Christine E Genge
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Yuki Hobbs
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Kaveh Rayani
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Eric Lin
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Marvin Gunawan
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sanam Shafaattalab
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Glen F Tibbits
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Tom W Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
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13
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Qile M, Beekman HDM, Sprenkeler DJ, Houtman MJC, van Ham WB, Stary-Weinzinger A, Beyl S, Hering S, van den Berg DJ, de Lange ECM, Heitman LH, IJzerman AP, Vos MA, van der Heyden MAG. LUF7244, an allosteric modulator/activator of K v 11.1 channels, counteracts dofetilide-induced torsades de pointes arrhythmia in the chronic atrioventricular block dog model. Br J Pharmacol 2019; 176:3871-3885. [PMID: 31339551 PMCID: PMC6780032 DOI: 10.1111/bph.14798] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 07/08/2019] [Accepted: 07/11/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND PURPOSE Kv 11.1 (hERG) channel blockade is an adverse effect of many drugs and lead compounds, associated with lethal cardiac arrhythmias. LUF7244 is a negative allosteric modulator/activator of Kv 11.1 channels that inhibits early afterdepolarizations in vitro. We tested LUF7244 for antiarrhythmic efficacy and potential proarrhythmia in a dog model. EXPERIMENTAL APPROACH LUF7244 was tested in vitro for (a) increasing human IKv11.1 and canine IKr and (b) decreasing dofetilide-induced action potential lengthening and early afterdepolarizations in cardiomyocytes derived from human induced pluripotent stem cells and canine isolated ventricular cardiomyocytes. In vivo, LUF7244 was given intravenously to anaesthetized dogs in sinus rhythm or with chronic atrioventricular block. KEY RESULTS LUF7244 (0.5-10 μM) concentration dependently increased IKv11.1 by inhibiting inactivation. In vitro, LUF7244 (10 μM) had no effects on IKIR2.1 , INav1.5 , ICa-L , and IKs , doubled IKr , shortened human and canine action potential duration by approximately 50%, and inhibited dofetilide-induced early afterdepolarizations. LUF7244 (2.5 mg·kg-1 ·15 min-1 ) in dogs with sinus rhythm was not proarrhythmic and shortened, non-significantly, repolarization parameters (QTc: -6.8%). In dogs with chronic atrioventricular block, LUF7244 prevented dofetilide-induced torsades de pointes arrhythmias in 5/7 animals without normalization of the QTc. Peak LUF7244 plasma levels were 1.75 ± 0.80 during sinus rhythm and 2.34 ± 1.57 μM after chronic atrioventricular block. CONCLUSIONS AND IMPLICATIONS LUF7244 counteracted dofetilide-induced early afterdepolarizations in vitro and torsades de pointes in vivo. Allosteric modulators/activators of Kv 11.1 channels might neutralize adverse cardiac effects of existing drugs and newly developed compounds that display QTc lengthening.
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Affiliation(s)
- Muge Qile
- Department of Medical Physiology, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Henriette D M Beekman
- Department of Medical Physiology, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - David J Sprenkeler
- Department of Medical Physiology, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Marien J C Houtman
- Department of Medical Physiology, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Willem B van Ham
- Department of Medical Physiology, University Medical Centre Utrecht, Utrecht, The Netherlands.,Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | | | - Stanislav Beyl
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Steffen Hering
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Dirk-Jan van den Berg
- Division of Systems Biomedicine and Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Elizabeth C M de Lange
- Division of Systems Biomedicine and Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Laura H Heitman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Ad P IJzerman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Marc A Vos
- Department of Medical Physiology, University Medical Centre Utrecht, Utrecht, The Netherlands
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14
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De Zio R, Gerbino A, Forleo C, Pepe M, Milano S, Favale S, Procino G, Svelto M, Carmosino M. Functional study of a KCNH2 mutant: Novel insights on the pathogenesis of the LQT2 syndrome. J Cell Mol Med 2019; 23:6331-6342. [PMID: 31361068 PMCID: PMC6714209 DOI: 10.1111/jcmm.14521] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/02/2019] [Accepted: 06/08/2019] [Indexed: 12/29/2022] Open
Abstract
The K+ voltage-gated channel subfamily H member 2 (KCNH2) transports the rapid component of the cardiac delayed rectifying K+ current. The aim of this study was to characterize the biophysical properties of a C-terminus-truncated KCNH2 channel, G1006fs/49 causing long QT syndrome type II in heterozygous members of an Italian family. Mutant carriers underwent clinical workup, including 12-lead electrocardiogram, transthoracic echocardiography and 24-hour ECG recording. Electrophysiological experiments compared the biophysical properties of G1006fs/49 with those of KCNH2 both expressed either as homotetramers or as heterotetramers in HEK293 cells. Major findings of this work are as follows: (a) G1006fs/49 is functional at the plasma membrane even when co-expressed with KCNH2, (b) G1006fs/49 exerts a dominant-negative effect on KCNH2 conferring specific biophysical properties to the heterotetrameric channel such as a significant delay in the voltage-sensitive transition to the open state, faster kinetics of both inactivation and recovery from the inactivation and (c) the activation kinetics of the G1006fs/49 heterotetrameric channels is partially restored by a specific KCNH2 activator. The functional characterization of G1006fs/49 homo/heterotetramers provided crucial findings about the pathogenesis of LQTS type II in the mutant carriers, thus providing a new and potential pharmacological strategy.
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Affiliation(s)
- Roberta De Zio
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Andrea Gerbino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Cinzia Forleo
- Cardiology Unit, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy
| | - Martino Pepe
- Cardiology Unit, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy
| | - Serena Milano
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Stefano Favale
- Cardiology Unit, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy
| | - Giuseppe Procino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Monica Carmosino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy.,Department of Sciences, University of Basilicata, Potenza, Italy
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15
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Dong X, Liu Y, Niu H, Wang G, Dong L, Zou A, Wang K. Electrophysiological characterization of a small molecule activator on human ether-a-go-go-related gene (hERG) potassium channel. J Pharmacol Sci 2019; 140:284-290. [DOI: 10.1016/j.jphs.2019.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 07/30/2019] [Accepted: 08/01/2019] [Indexed: 02/02/2023] Open
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16
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Jackson WF. K V channels and the regulation of vascular smooth muscle tone. Microcirculation 2018; 25. [PMID: 28985443 DOI: 10.1111/micc.12421] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 10/01/2017] [Indexed: 12/31/2022]
Abstract
VSMCs in resistance arteries and arterioles express a diverse array of KV channels with members of the KV 1, KV 2 and KV 7 families being particularly important. Members of the KV channel family: (i) are highly expressed in VSMCs; (ii) are active at the resting membrane potential of VSMCs in vivo (-45 to -30 mV); (iii) contribute to the negative feedback regulation of VSMC membrane potential and myogenic tone; (iv) are activated by cAMP-related vasodilators, hydrogen sulfide and hydrogen peroxide; (v) are inhibited by increases in intracellular Ca2+ and vasoconstrictors that signal through Gq -coupled receptors; (vi) are involved in the proliferative phenotype of VSMCs; and (vii) are modulated by diseases such as hypertension, obesity, the metabolic syndrome and diabetes. Thus, KV channels participate in every aspect of the regulation of VSMC function in both health and disease.
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Affiliation(s)
- William F Jackson
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, USA
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17
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Manipulation-free cultures of human iPSC-derived cardiomyocytes offer a novel screening method for cardiotoxicity. Acta Pharmacol Sin 2018; 39:1590-1603. [PMID: 29620051 DOI: 10.1038/aps.2017.183] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 12/31/2017] [Indexed: 12/27/2022] Open
Abstract
Induced pluripotent stem cell (iPSC)-based cardiac regenerative medicine requires the efficient generation, structural soundness and proper functioning of mature cardiomyocytes, derived from the patient's somatic cells. The most important functional property of cardiomyocytes is the ability to contract. Currently available methods routinely used to test and quantify cardiomyocyte function involve techniques that are labor-intensive, invasive, require sophisticated instruments or can adversely affect cell vitality. We recently developed optical flow imaging method analyses and quantified cardiomyocyte contractile kinetics from video microscopic recordings without compromising cell quality. Specifically, our automated particle image velocimetry (PIV) analysis of phase-contrast video images captured at a high frame rate yields statistical measures characterizing the beating frequency, amplitude, average waveform and beat-to-beat variations. Thus, it can be a powerful assessment tool to monitor cardiomyocyte quality and maturity. Here we demonstrate the ability of our analysis to characterize the chronotropic responses of human iPSC-derived cardiomyocytes to a panel of ion channel modulators and also to doxorubicin, a chemotherapy agent with known cardiotoxic side effects. We conclude that the PIV-derived beat patterns can identify the elongation or shortening of specific phases in the contractility cycle, and the obtained chronotropic responses are in accord with known clinical outcomes. Hence, this system can serve as a powerful tool to screen the new and currently available pharmacological compounds for cardiotoxic effects.
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18
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Qiu B, Wang Y, Li C, Guo H, Xu Y. Utility of the JT Peak Interval and the JT Area in Determining the Proarrhythmic Potential of QT-Shortening Agents. J Cardiovasc Pharmacol Ther 2018; 24:160-171. [PMID: 30092655 DOI: 10.1177/1074248418791999] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Drug-induced long QT increases the risk of ventricular tachyarrhythmia known as torsades de pointes (TdP). Many biomarkers have been used to predict TdP. At present, however, there are few biomarkers for arrhythmias induced by QT-shortening drugs. The objective of the present study was to identify the best biomarkers for predicting arrhythmias caused by the 4 potassium channel openers ICA-105574, NS-1643, R-L3, and pinacidil. Our results showed that, at higher concentrations, all 4 potassium channel openers induced ventricular tachycardia (VT) and ventricular fibrillation (VF) in Langendorff-perfused guinea pig hearts, but not in rabbit hearts. The electrocardiography parameters were measured including QT/QTc, JT peak, Tp-e interval, JT area, short-term beat-to-beat QT interval variability (STV), and index of cardiac electrophysiological balance (iCEB). We found that the potassium channel openers at test concentrations shortened the QT/QTc and the JT peak interval and increased the JT area. Nevertheless, even at proarrhythmic concentrations, they did not always change STV, Tp-e, or iCEB. Receiver operating characteristic curve analysis showed that the JT peak interval representing the early repolarization phase and the JT area reflecting the dispersion of ventricular repolarization were the best predictors of VT/VF. Action potential recordings in guinea pig papillary muscle revealed that except for pinacidil, the potassium channel openers shortened APD30 in a concentration-dependent manner. They also evoked early or delayed afterdepolarizations at fast pacing rates. Patch-clamp recordings in guinea pig ventricular cardiomyocytes showed that the potassium channel openers enhanced the total outward currents during the early phase of action potential repolarization, especially at proarrhythmic concentrations. We concluded that the JT peak interval and the JT area are surrogate biomarkers identifying the risk of proarrhythmia associated with the administration of QT-shortening agents. The acceleration of early-phase repolarization and the increased dispersion of ventricular repolarization may contribute to the occurrence of arrhythmias.
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Affiliation(s)
- Bo Qiu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China.,Hebei General Hospital, Shijiazhuang, China
| | - Yuhong Wang
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Beijing Union Medical College, Beijing, China
| | - Congxin Li
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China
| | - Huicai Guo
- Department of Toxicology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yanfang Xu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China
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19
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Dierich M, Evers S, Wilke BU, Leitner MG. Inverse Modulation of Neuronal K v12.1 and K v11.1 Channels by 4-Aminopyridine and NS1643. Front Mol Neurosci 2018; 11:11. [PMID: 29440988 PMCID: PMC5797642 DOI: 10.3389/fnmol.2018.00011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 01/09/2018] [Indexed: 01/24/2023] Open
Abstract
The three members of the ether-à-go-go-gene-like (Elk; Kv12.1-Kv12.3) family of voltage-gated K+ channels are predominantly expressed in neurons, but only little information is available on their physiological relevance. It was shown that Kv12.2 channels modulate excitability of hippocampal neurons, but no native current could be attributed to Kv12.1 and Kv12.3 subunits yet. This may appear somewhat surprising, given high expression of their mRNA transcripts in several brain areas. Native Kv12 currents may have been overlooked so far due to limited knowledge on their biophysical properties and lack of specific pharmacology. Except for Kv12.2, appropriate genetically modified mouse models have not been described; therefore, identification of Kv12-mediated currents in native cell types must rely on characterization of unique properties of the channels. We focused on recombinant human Kv12.1 to identify distinct properties of these channels. We found that Kv12.1 channels exhibited significant mode shift of activation, i.e., stabilization of the voltage sensor domain in a “relaxed” open state after prolonged channel activation. This mode shift manifested by a slowing of deactivation and, most prominently, a significant shift of voltage dependence to hyperpolarized potentials. In contrast to related Kv11.1, mode shift was not sensitive to extracellular Na+, which allowed for discrimination between these isoforms. Sensitivity of Kv12.1 and Kv11.1 to the broad-spectrum K+ antagonist 4-aminopyridine was similar. However, 4-AP strongly activated Kv12.1 channels, but it was an inhibitor of Kv11 channels. Interestingly, the agonist of Kv11 channels NS1643 also differentially modulated the activity of these channels, i.e., NS1643 activated Kv11.1, but strongly inhibited Kv12.1 channels. Thus, these closely related channels are distinguished by inverse pharmacological profiles. In summary, we identified unique biophysical and pharmacological properties of Kv12.1 channels and established straightforward experimental protocols to characterize Kv12.1-mediated currents. Identification of currents in native cell types with mode shift that are activated through 4-AP and inhibited by NS1643 can provide strong evidence for contribution of Kv12.1 to whole cell currents.
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Affiliation(s)
- Marlen Dierich
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany
| | - Saskia Evers
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany
| | - Bettina U Wilke
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany
| | - Michael G Leitner
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany.,Division of Physiology, Department of Physiology and Medical Physics, Innsbruck Medical University, Innsbruck, Austria
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20
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Discovery and electrophysiological characterization of SKF-32802: A novel hERG agonist found through a large-scale structural similarity search. Eur J Pharmacol 2018; 818:306-327. [DOI: 10.1016/j.ejphar.2017.10.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 10/06/2017] [Accepted: 10/10/2017] [Indexed: 01/10/2023]
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21
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Colman MA, Perez Alday EA, Holden AV, Benson AP. Trigger vs. Substrate: Multi-Dimensional Modulation of QT-Prolongation Associated Arrhythmic Dynamics by a hERG Channel Activator. Front Physiol 2017; 8:757. [PMID: 29046643 PMCID: PMC5632683 DOI: 10.3389/fphys.2017.00757] [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: 08/02/2017] [Accepted: 09/19/2017] [Indexed: 11/13/2022] Open
Abstract
Background: Prolongation of the QT interval of the electrocardiogram (ECG), underlain by prolongation of the action potential duration (APD) at the cellular level, is linked to increased vulnerability to cardiac arrhythmia. Pharmacological management of arrhythmia associated with QT prolongation is typically achieved through attempting to restore APD to control ranges, reversing the enhanced vulnerability to Ca2+-dependent afterdepolarisations (arrhythmia triggers) and increased transmural dispersion of repolarisation (arrhythmia substrate) associated with APD prolongation. However, such pharmacological modulation has been demonstrated to have limited effectiveness. Understanding the integrative functional impact of pharmacological modulation requires simultaneous investigation of both the trigger and substrate. Methods: We implemented a multi-scale (cell and tissue) in silico approach using a model of the human ventricular action potential, integrated with a model of stochastic 3D spatiotemporal Ca2+ dynamics, and parameter modification to mimic prolonged QT conditions. We used these models to examine the efficacy of the hERG activator MC-II-157c in restoring APD to control ranges, examined its effects on arrhythmia triggers and substrates, and the interaction of these arrhythmia triggers and substrates. Results: QT prolongation conditions promoted the development of spontaneous release events underlying afterdepolarisations during rapid pacing. MC-II-157c applied to prolonged QT conditions shortened the APD, inhibited the development of afterdepolarisations and reduced the probability of afterdepolarisations manifesting as triggered activity in single cells. In tissue, QT prolongation resulted in an increased transmural dispersion of repolarisation, which manifested as an increased vulnerable window for uni-directional conduction block. In some cases, MC-II-157c further increased the vulnerable window through its effects on INa. The combination of stochastic release event modulation and transmural dispersion of repolarisation modulation by MC-II-157c resulted in an integrative behavior wherein the arrhythmia trigger is reduced but the arrhythmia substrate is increased, leading to variable and non-linear overall vulnerability to arrhythmia. Conclusion: The relative balance of reduced trigger and increased substrate underlies a multi-dimensional role of MC-II-157c in modulation of cardiac arrhythmia vulnerability associated with prolonged QT interval.
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Affiliation(s)
- Michael A Colman
- School of Biomedical Sciences and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom
| | - Erick A Perez Alday
- Division of Cardiovascular Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Arun V Holden
- School of Biomedical Sciences and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom
| | - Alan P Benson
- School of Biomedical Sciences and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom
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22
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Jeevaratnam K, Chadda KR, Huang CLH, Camm AJ. Cardiac Potassium Channels: Physiological Insights for Targeted Therapy. J Cardiovasc Pharmacol Ther 2017; 23:119-129. [PMID: 28946759 PMCID: PMC5808825 DOI: 10.1177/1074248417729880] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The development of novel drugs specifically directed at the ion channels underlying particular features of cardiac action potential (AP) initiation, recovery, and refractoriness would contribute to an optimized approach to antiarrhythmic therapy that minimizes potential cardiac and extracardiac toxicity. Of these, K+ channels contribute numerous and diverse currents with specific actions on different phases in the time course of AP repolarization. These features and their site-specific distribution make particular K+ channel types attractive therapeutic targets for the development of pharmacological agents attempting antiarrhythmic therapy in conditions such as atrial fibrillation. However, progress in the development of such temporally and spatially selective antiarrhythmic drugs against particular ion channels has been relatively limited, particularly in view of our incomplete understanding of the complex physiological roles and interactions of the various ionic currents. This review summarizes the physiological properties of the main cardiac potassium channels and the way in which they modulate cardiac electrical activity and then critiques a number of available potential antiarrhythmic drugs directed at them.
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Affiliation(s)
- Kamalan Jeevaratnam
- 1 Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,2 School of Medicine, Perdana University-Royal College of Surgeons Ireland, Serdang, Selangor Darul Ehsan, Malaysia
| | - Karan R Chadda
- 1 Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,3 Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L-H Huang
- 3 Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,4 Division of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - A John Camm
- 5 Cardiac Clinical Academic Group, St George's Hospital Medical School, University of London, Cranmer Terrace, London, United Kingdom
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23
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Huo J, Guo X, Lu Q, Qiang H, Liu P, Bai L, Huang CLH, Zhang Y, Ma A. NS1643 enhances ionic currents in a G604S-WT hERG co-expression system associated with long QT syndrome 2. Clin Exp Pharmacol Physiol 2017; 44:1125-1133. [PMID: 28741726 DOI: 10.1111/1440-1681.12820] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 06/27/2017] [Accepted: 07/17/2017] [Indexed: 12/19/2022]
Affiliation(s)
- JianHua Huo
- Department of Cardiovascular Medicine; First Affiliated Hospital of Xi'an Jiaotong University; Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University); Ministry of Education; Xi'an Shaanxi China
| | - Xueyan Guo
- Shaanxi Provincial People's Hospital; Xi'an Shaanxi China
| | - Qun Lu
- Department of Cardiovascular Medicine; First Affiliated Hospital of Xi'an Jiaotong University; Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University); Ministry of Education; Xi'an Shaanxi China
| | - Hua Qiang
- Department of Cardiovascular Medicine; First Affiliated Hospital of Xi'an Jiaotong University; Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University); Ministry of Education; Xi'an Shaanxi China
| | - Ping Liu
- Department of Cardiovascular Medicine; First Affiliated Hospital of Xi'an Jiaotong University; Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University); Ministry of Education; Xi'an Shaanxi China
| | - Ling Bai
- Department of Cardiovascular Medicine; First Affiliated Hospital of Xi'an Jiaotong University; Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University); Ministry of Education; Xi'an Shaanxi China
| | | | - Yanmin Zhang
- Department of Pediatric Cardiology; Childrens Research Institute; affiliate children's hospital of Xi'an Jiaotong University; Xi'an Shaanxi China
| | - Aiqun Ma
- Department of Cardiovascular Medicine; First Affiliated Hospital of Xi'an Jiaotong University; Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University); Ministry of Education; Xi'an Shaanxi China
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24
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Barrese V, Cidad P, Yeung SY, López-López JR, McNeish AJ, Ohya S, Pérez-García MT, Greenwood IA. Proliferative Role of Kv11 Channels in Murine Arteries. Front Physiol 2017; 8:500. [PMID: 28747891 PMCID: PMC5506201 DOI: 10.3389/fphys.2017.00500] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 06/29/2017] [Indexed: 12/22/2022] Open
Abstract
K+ channels encoded by the ether-a-go-go related gene (ERG1 or KCNH2) are important determinants of the cardiac action potential. Expression of both cardiac isoforms (ERG1a and ERG1b) were identified in murine portal vein and distinctive voltage-gated K+ currents were recorded from single myocytes. The aim of the present study was to ascertain the expression and functional impact of ERG channels in murine arteries. Methods: Quantitative RT-PCR was undertaken on RNA extracted from a number of murine arteries. Immunofluorescence was performed on single vascular smooth muscle cells using antibodies against the ERG1 expression product (Kv11.1). Single cell electrophysiology was performed on myocytes from portal vein and several different arteries, complimented by isometric tension recordings. Proliferation assays were undertaken on smooth muscle cells isolated from femoral arteries. Results: ERG1 transcripts were detected in all murine blood vessels, and Kv11.1 immunofluorescence was observed in all smooth muscle cells. However, K+ currents with properties consistent with ERG channels were only recorded in portal vein myocytes. Moreover, ERG channel blockers (E4031 or dofetilide, 1 μM) failed to depolarize carotid arteries or produce contraction. Proliferation of arterial smooth muscle cells was associated with a marked increase in ERG1 expression and ERG blockers suppressed proliferation significantly. Conclusions: These data reveal that arterial blood vessels express ERG channels that appear to be functional silent in contractile smooth muscle but contribute to proliferative response.
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Affiliation(s)
- Vincenzo Barrese
- Vascular Research Centre, Institute of Molecular & Clinical Sciences, St George's University of LondonLondon, United Kingdom
| | - Pilar Cidad
- Departmento de Fisiología, Universidad de ValladolidValladolid, Spain
| | - Shuk Y Yeung
- Vascular Research Centre, Institute of Molecular & Clinical Sciences, St George's University of LondonLondon, United Kingdom
| | | | - Alister J McNeish
- Reading School of Pharmacy, University of ReadingReading, United Kingdom
| | - Susumu Ohya
- Department of Pharmacology, Kyoto Pharmaceutical UniversityKyoto, Japan
| | | | - Iain A Greenwood
- Vascular Research Centre, Institute of Molecular & Clinical Sciences, St George's University of LondonLondon, United Kingdom
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25
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Sale H, Roy S, Warrier J, Thangathirupathy S, Vadari Y, Gopal SK, Krishnamurthy P, Ramarao M. Modulation of K v 11.1 (hERG) channels by 5-(((1H-indazol-5-yl)oxy)methyl)-N-(4-(trifluoromethoxy)phenyl)pyrimidin-2-amine (ITP-2), a novel small molecule activator. Br J Pharmacol 2017; 174:2484-2500. [PMID: 28500657 DOI: 10.1111/bph.13859] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 05/04/2017] [Accepted: 05/05/2017] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND AND PURPOSE Activators of Kv 11.1 (hERG) channels have potential utility in the treatment of acquired and congenital long QT (LQT) syndrome. Here, we describe a new hERG channel activator, 5-(((1H-indazol-5-yl)oxy)methyl)-N-(4-(trifluoromethoxy)phenyl)pyrimidin-2-amine (ITP-2), with a chemical structure distinct from previously reported compounds. EXPERIMENTAL APPROACH Conventional electrophysiological methods were used to assess the effects of ITP-2 on hERG1a and hERG1a/1b channels expressed heterologously in HEK-293 cells. KEY RESULTS ITP-2 selectively increased test pulse currents (EC50 1.0 μM) and decreased tail currents. ITP-2 activated hERG1a homomeric channels primarily by causing large depolarizing shifts in the midpoint of voltage-dependent inactivation and hyperpolarizing shifts in the voltage-dependence of activation. In addition, ITP-2 slowed rates of inactivation and made recovery from inactivation faster. hERG1a/1b heteromeric channels showed reduced sensitivity to ITP-2 and their inactivation properties were differentially modulated. Effects on midpoint of voltage-dependent inactivation and rates of inactivation were less pronounced for hERG1a/1b channels. Effects on voltage-dependent activation and activation kinetics were not different from hERG1a channels. Interestingly, hERG1b channels were inhibited by ITP-2. Inactivation-impairing mutations abolished activation by ITP-2 and led to inhibition of hERG channels. ITP-2 exerted agonistic effect from extracellular side of the membrane and could activate one of the arrhythmia-associated trafficking-deficient LQT2 mutants. CONCLUSIONS AND IMPLICATIONS ITP-2 may serve as another novel lead molecule for designing robust activators of hERG channels. hERG1a/1b gating kinetics were differentially modulated by ITP-2 leading to altered sensitivity. ITP-2 is capable of activating an LQT2 mutant and may be potentially useful in the development of LQT2 therapeutics.
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Affiliation(s)
- Harinath Sale
- Disease Sciences and Technology, Biocon Bristol-Myers Squibb Research and Development Center, Syngene International Limited, Bangalore, India
| | - Samrat Roy
- Disease Sciences and Technology, Biocon Bristol-Myers Squibb Research and Development Center, Syngene International Limited, Bangalore, India
| | - Jayakumar Warrier
- Medicinal Chemistry, Biocon Bristol Myers-Squibb Research and Development Center, Syngene International Limited, Bangalore, India
| | - Srinivasan Thangathirupathy
- Medicinal Chemistry, Biocon Bristol Myers-Squibb Research and Development Center, Syngene International Limited, Bangalore, India
| | - Yoganand Vadari
- Disease Sciences and Technology, Biocon Bristol-Myers Squibb Research and Development Center, Syngene International Limited, Bangalore, India
| | - Shruthi K Gopal
- Disease Sciences and Technology, Biocon Bristol-Myers Squibb Research and Development Center, Syngene International Limited, Bangalore, India
| | - Prasad Krishnamurthy
- Disease Sciences and Technology, Biocon Bristol-Myers Squibb Research and Development Center, Syngene International Limited, Bangalore, India
| | - Manjunath Ramarao
- Disease Sciences and Technology, Biocon Bristol-Myers Squibb Research and Development Center, Syngene International Limited, Bangalore, India
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Nozaki Y, Honda Y, Watanabe H, Saiki S, Koyabu K, Itoh T, Nagasawa C, Nakamori C, Nakayama C, Iwasaki H, Suzuki S, Tanaka K, Takahashi E, Miyamoto K, Morimura K, Yamanishi A, Endo H, Shinozaki J, Nogawa H, Shinozawa T, Saito F, Kunimatsu T. CSAHi study-2: Validation of multi-electrode array systems (MEA60/2100) for prediction of drug-induced proarrhythmia using human iPS cell-derived cardiomyocytes: Assessment of reference compounds and comparison with non-clinical studies and clinical information. Regul Toxicol Pharmacol 2017. [PMID: 28634147 DOI: 10.1016/j.yrtph.2017.06.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
With the aim of reconsidering ICH S7B and E14 guidelines, a new in vitro assay system has been subjected to worldwide validation to establish a better prediction platform for potential drug-induced QT prolongation and the consequent TdP in clinical practice. In Japan, CSAHi HEART team has been working on hiPS-CMs in the MEA (hiPS-CMs/MEA) under a standardized protocol and found no inter-facility or lot-to-lot variability for proarrhythmic risk assessment of 7 reference compounds. In this study, we evaluated the responses of hiPS-CMs/MEA to another 31 reference compounds associated with cardiac toxicities, and gene expression to further clarify the electrophysiological characteristics over the course of culture period. The hiPS-CMs/MEA assay accurately predicted reference compounds potential for arrhythmogenesis, and yielded results that showed better correlation with target concentrations of QTc prolongation or TdP in clinical setting than other current in vitro and in vivo assays. Gene expression analyses revealed consistent profiles in all samples within and among the testing facilities. This report would provide CiPA with informative guidance on the use of the hiPS-CMs/MEA assay, and promote the establishment of a new paradigm, beyond conventional in vitro and in vivo assays for cardiac safety assessment of new drugs.
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Affiliation(s)
- Yumiko Nozaki
- Preclinical Research Laboratories, Sumitomo Dainippon Pharma Co., Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-0022, Japan.
| | - Yayoi Honda
- Preclinical Research Laboratories, Sumitomo Dainippon Pharma Co., Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-0022, Japan
| | - Hitoshi Watanabe
- Preclinical Research Laboratories, Sumitomo Dainippon Pharma Co., Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-0022, Japan
| | - Shota Saiki
- Research Laboratory for Development, Shionogi & Co., Ltd., 3-1-1, Futaba-cho, Toyonaka, Osaka 561-0825, Japan; Consortium for Safety Assessment using Human iPS Cells (CSAHi), Japan
| | - Kiyotaka Koyabu
- Research Laboratory for Development, Shionogi & Co., Ltd., 3-1-1, Futaba-cho, Toyonaka, Osaka 561-0825, Japan
| | - Tetsuji Itoh
- Research Laboratory for Development, Shionogi & Co., Ltd., 3-1-1, Futaba-cho, Toyonaka, Osaka 561-0825, Japan
| | - Chiho Nagasawa
- Drug Safety, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan; Consortium for Safety Assessment using Human iPS Cells (CSAHi), Japan
| | - Chiaki Nakamori
- Drug Safety, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan
| | - Chiaki Nakayama
- Drug Safety, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan
| | - Hiroshi Iwasaki
- Drug Safety, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan
| | - Shinobu Suzuki
- Nippon Boehringer Ingelheim Co., Ltd., 6-7-5, Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Kohji Tanaka
- Nippon Boehringer Ingelheim Co., Ltd., 6-7-5, Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Etsushi Takahashi
- Research Laboratories, Toyama Chemical Co., Ltd., 4-1, Shimookui 2-chome, Toyama 930-8508, Japan; Consortium for Safety Assessment using Human iPS Cells (CSAHi), Japan
| | - Kaori Miyamoto
- Research Laboratories, Toyama Chemical Co., Ltd., 4-1, Shimookui 2-chome, Toyama 930-8508, Japan
| | - Kaoru Morimura
- Research Laboratories, Toyama Chemical Co., Ltd., 4-1, Shimookui 2-chome, Toyama 930-8508, Japan
| | - Atsuhiro Yamanishi
- Toxicology Research Laboratory, Kyorin Pharmaceutical Co., Ltd., 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi 329-0114, Japan; Consortium for Safety Assessment using Human iPS Cells (CSAHi), Japan
| | - Hiroko Endo
- Toxicology Research Laboratory, Kyorin Pharmaceutical Co., Ltd., 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi 329-0114, Japan
| | - Junko Shinozaki
- Toxicology Research Laboratory, Kyorin Pharmaceutical Co., Ltd., 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi 329-0114, Japan
| | - Hisashi Nogawa
- Toxicology Research Laboratory, Kyorin Pharmaceutical Co., Ltd., 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi 329-0114, Japan
| | - Tadahiro Shinozawa
- Drug Safety Research Laboratories, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome Fujisawa, Kanagawa 251-8555, Japan; Consortium for Safety Assessment using Human iPS Cells (CSAHi), Japan; Japan Pharmaceutical Manufacturers Association, Drug Evaluation Committee, Non-Clinical Evaluation Expert Committee, Japan
| | - Fumiyo Saito
- Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Japan (CERI), 1600, Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama 345-0043, Japan; Consortium for Safety Assessment using Human iPS Cells (CSAHi), Japan
| | - Takeshi Kunimatsu
- Preclinical Research Laboratories, Sumitomo Dainippon Pharma Co., Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-0022, Japan; Consortium for Safety Assessment using Human iPS Cells (CSAHi), Japan; Japan Pharmaceutical Manufacturers Association, Drug Evaluation Committee, Non-Clinical Evaluation Expert Committee, Japan.
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Application of optical action potentials in human induced pluripotent stem cells-derived cardiomyocytes to predict drug-induced cardiac arrhythmias. J Pharmacol Toxicol Methods 2017; 87:53-67. [PMID: 28501647 DOI: 10.1016/j.vascn.2017.05.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 04/25/2017] [Accepted: 05/08/2017] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) are emerging as new and human-relevant source in vitro model for cardiac safety assessment that allow us to investigate a set of 20 reference drugs for predicting cardiac arrhythmogenic liability using optical action potential (oAP) assay. METHODS Here, we describe our examination of the oAP measurement using a voltage sensitive dye (Di-4-ANEPPS) to predict adverse compound effects using hiPS-CMs and 20 cardioactive reference compounds. Fluorescence signals were digitized at 10kHz and the records subsequently analyzed off-line. Cells were exposed to 30min incubation to vehicle or compound (n=5/dose, 4 doses/compound) that were blinded to the investigating laboratory. Action potential parameters were measured, including rise time (Trise) of the optical action potential duration (oAPD). RESULTS Significant effects on oAPD were sensitively detected with 11 QT-prolonging drugs, while oAPD shortening was observed with ICa-antagonists, IKr-activator or ATP-sensitive K+ channel (KATP)-opener. Additionally, the assay detected varied effects induced by 6 different sodium channel blockers. The detection threshold for these drug effects was at or below the published values of free effective therapeutic plasma levels or effective concentrations by other studies. DISCUSSION The results of this blinded study indicate that OAP is a sensitive method to accurately detect drug-induced effects (i.e., duration/QT-prolongation, shortening, beat rate, and incidence of early after depolarizations) in hiPS-CMs; therefore, this technique will potentially be useful in predicting drug-induced arrhythmogenic liabilities in early de-risking within the drug discovery phase.
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Durdagi S, Erol I, Salmas RE, Patterson M, Noskov SY. First universal pharmacophore model for hERG1 K + channel activators: acthER. J Mol Graph Model 2017; 74:153-170. [PMID: 28499268 DOI: 10.1016/j.jmgm.2017.03.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 03/28/2017] [Accepted: 03/29/2017] [Indexed: 01/31/2023]
Abstract
The intra-cavitary drug blockade of hERG1 channel has been extensively studied, both experimentally and theoretically. Structurally diverse ligands inadvertently block the hERG1 K+ channel currents lead to drug induced Long QT Syndrome (LQTS). Accordingly, designing either hERG1 channel openers or current activators, with the potential to target other binding pockets of the channel, has been introduced as a viable approach in modern anti-arrhythmia drug development. However, reports and investigations on the molecular mechanisms underlying activators binding to the hERG1 channel remain sparse and the overall molecular design principles are largely unknown. Most of the hERG1 activators were discovered during mandatory screening for hERG1 blockade. To fill this apparent deficit, the first universal pharmacophore model for hERG1 K+ channel activators was developed using PHASE. 3D structures of 18 hERG1 K+ channel activators and their corresponding measured binding affinity values were used in the development of pharmacophore models. These compounds spanned a range of structurally different chemotypes with moderate variation in binding affinity. A five sites AAHRR (A, hydrogen-bond accepting, H, hydrophobic, R, aromatic) pharmacophore model has shown reasonable high statistical results compared to the other developed more than 1000 hypotheses. This model was used to construct steric and electrostatic contour maps. The predictive power of the model was tested with 3 external test set compounds as true unknowns. Finally, the pharmacophore model was combined with the previously developed receptor-based model of hERG1 K+ channel to develop and screen novel activators. The results are quite striking and it suggests a greater future role for pharmacophore modeling and virtual drug screening simulations in deciphering complex patterns of molecular mechanisms of hERG1 channel openers at the target sites. The developed model is available upon request and it may serve as basis for the synthesis of novel therapeutic hERG1 activators.
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Affiliation(s)
- Serdar Durdagi
- Computational Biology and Molecular Simulations Laboratory, Department of Biophysics, School of Medicine, Bahcesehir University, Istanbul, Turkey.
| | - Ismail Erol
- Computational Biology and Molecular Simulations Laboratory, Department of Biophysics, School of Medicine, Bahcesehir University, Istanbul, Turkey; Department of Chemistry, Gebze Technical University, Kocaeli, Turkey
| | - Ramin Ekhteiari Salmas
- Computational Biology and Molecular Simulations Laboratory, Department of Biophysics, School of Medicine, Bahcesehir University, Istanbul, Turkey
| | - Matthew Patterson
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Sergei Y Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
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Bohnen MS, Peng G, Robey SH, Terrenoire C, Iyer V, Sampson KJ, Kass RS. Molecular Pathophysiology of Congenital Long QT Syndrome. Physiol Rev 2017; 97:89-134. [PMID: 27807201 PMCID: PMC5539372 DOI: 10.1152/physrev.00008.2016] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ion channels represent the molecular entities that give rise to the cardiac action potential, the fundamental cellular electrical event in the heart. The concerted function of these channels leads to normal cyclical excitation and resultant contraction of cardiac muscle. Research into cardiac ion channel regulation and mutations that underlie disease pathogenesis has greatly enhanced our knowledge of the causes and clinical management of cardiac arrhythmia. Here we review the molecular determinants, pathogenesis, and pharmacology of congenital Long QT Syndrome. We examine mechanisms of dysfunction associated with three critical cardiac currents that comprise the majority of congenital Long QT Syndrome cases: 1) IKs, the slow delayed rectifier current; 2) IKr, the rapid delayed rectifier current; and 3) INa, the voltage-dependent sodium current. Less common subtypes of congenital Long QT Syndrome affect other cardiac ionic currents that contribute to the dynamic nature of cardiac electrophysiology. Through the study of mutations that cause congenital Long QT Syndrome, the scientific community has advanced understanding of ion channel structure-function relationships, physiology, and pharmacological response to clinically employed and experimental pharmacological agents. Our understanding of congenital Long QT Syndrome continues to evolve rapidly and with great benefits: genotype-driven clinical management of the disease has improved patient care as precision medicine becomes even more a reality.
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Affiliation(s)
- M S Bohnen
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - G Peng
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - S H Robey
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - C Terrenoire
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - V Iyer
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - K J Sampson
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - R S Kass
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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31
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Lu HR, Gallacher DJ, Yan GX. Assessment of drug-induced proarrhythmia: The importance of study design in the rabbit left ventricular wedge model. J Pharmacol Toxicol Methods 2016; 81:151-60. [PMID: 27374776 DOI: 10.1016/j.vascn.2016.06.006] [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: 01/27/2016] [Revised: 06/22/2016] [Accepted: 06/26/2016] [Indexed: 01/09/2023]
Abstract
In the present study, we investigated an impact of the stimulation rate on the detection of the proarrhythmic potential of 10 reference compounds with effects on different cardiac ion channels in the isolated arterially-perfused rabbit left ventricular wedge preparation. The compounds were tested in the wedge model using two distinct protocols; including baseline stimulation at 1-Hz followed by a brief period at 0.5-Hz, either without an additional brief period of 2-Hz stimulation (i.e. Protocol 1) or with 2-Hz stimulation (i.e. Protocol 2). As expected, QT-prolonging drugs (ibutilide and quinidine) prolonged the QT interval, similarly increased the Torsades de Pointes (TdP) score, and elicited early afterdepolarizations (EADs) in both protocols. HMR1556 and JNJ-303 (IKs blockers) also prolonged the QT interval up to 1μM similarly in both protocols. Nifedipine (Ca(2+) antagonist) shortened the QT interval, and reduced force of contraction similarly in both protocols. However, Na(+) channel blockers (Ia, Ib, Ic) widened the QRS duration more in Protocol 2 than in Protocol 1. Furthermore, it was only possible to detect non-TdP-like ventricular tachycardia/fibrillation (VT/VF) induced by Na(+) blockers and by QT-shortening drugs (levcromakalim and mallotoxin) using the 2-Hz stimulation (Protocol 2). Our data suggest that the inclusion of a brief period of fast stimulation at 2Hz is critical for detecting drug-induced slowing of conduction (QRS widening), QT shortening and associated (non-TdP-like) VT/VF, which are distinct from the QT prolongation/TdP proarrhythmia in isolated, arterially-perfused rabbit left ventricular wedges.
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Affiliation(s)
- Hua Rong Lu
- Global Safety Pharmacology, Discovery Sciences, Janssen Research & Development, Janssen Pharmaceutica NV, Belgium.
| | - David J Gallacher
- Global Safety Pharmacology, Discovery Sciences, Janssen Research & Development, Janssen Pharmaceutica NV, Belgium
| | - Gan-Xin Yan
- Lankenau Institute for Medical Research, Wynnewood, PA, USA
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Rezazadeh S, Duff H. Dissociative States: hERG Channel (Kv11.1) Modulators That Enhance Dissociation of Drugs From Their Blocking Receptor. Circ Arrhythm Electrophysiol 2016; 9:e004003. [DOI: 10.1161/circep.116.004003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Saman Rezazadeh
- From the Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Henry Duff
- From the Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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A dual potassium channel activator improves repolarization reserve and normalizes ventricular action potentials. Biochem Pharmacol 2016; 108:36-46. [PMID: 27002181 DOI: 10.1016/j.bcp.2016.03.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/17/2016] [Indexed: 11/22/2022]
Abstract
BACKGROUND A loss of repolarization reserve due to downregulation of K(+) currents has been observed in cultured ventricular myocytes. A similar reduction of K(+) currents is well documented under numerous pathophysiological conditions. We examined the extent of K(+) current downregulation in cultured canine cardiac myocytes and determined whether a dual K(+) current activator can normalize K(+) currents and restore action potential (AP) configuration. METHODS AND RESULTS Ventricular myocytes were isolated and cultured for up to 48 h. Current and voltage clamp recordings were made using patch electrodes. Application of NS3623 to coronary-perfused left ventricular wedges resulted in increased phase 1 magnitude, epicardial AP notch and J wave amplitude. Patch clamp measurements of IKr and Ito revealed an increase in the magnitude of both currents. Culturing of Mid ventricular cells resulted in a significant decrease in Ito and IKr density. NS3623 increased Ito from 16.4 ± 2.23 to 31.8 ± 4.5 pA/pF, and IKr from 0.28 ± 0.06 to 0.47 ± 0.09 pA/pF after 2 days in culture. AP recordings from 2 day cultured cells exhibited a reduced phase 1 repolarization, AP prolongation, and early afterdepolarizations (EADs). NS3623 restored the AP notch and was able to suppress EADs. CONCLUSIONS NS3623 is a dual Ito and IKr activator. Application of this compound to cells with a reduced repolarization reserve resulted in an increase in these currents and a shortening of AP duration, increase in phase 1 repolarization and suppression of EADs. Our results suggest a potential benefit of K(+) current activators under conditions of reduced repolarization reserve including heart failure.
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Wu W, Sanguinetti MC. Molecular Basis of Cardiac Delayed Rectifier Potassium Channel Function and Pharmacology. Card Electrophysiol Clin 2016; 8:275-84. [PMID: 27261821 DOI: 10.1016/j.ccep.2016.01.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Human cardiomyocytes express 3 distinct types of delayed rectifier potassium channels. Human ether-a-go-go-related gene (hERG) channels conduct the rapidly activating current IKr; KCNQ1/KCNE1 channels conduct the slowly activating current IKs; and Kv1.5 channels conduct an ultrarapid activating current IKur. Here the authors provide a general overview of the mechanistic and structural basis of ion selectivity, gating, and pharmacology of the 3 types of cardiac delayed rectifier potassium ion channels. Most blockers bind to S6 residues that line the central cavity of the channel, whereas activators interact with the channel at 4 symmetric binding sites outside the cavity.
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Affiliation(s)
- Wei Wu
- Department of Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, 95 South 2000 East, Salt Lake City, UT 84112, USA
| | - Michael C Sanguinetti
- Department of Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, 95 South 2000 East, Salt Lake City, UT 84112, USA.
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Mannikko R, Bridgland-Taylor MH, Pye H, Swallow S, Abi-Gerges N, Morton MJ, Pollard CE. Pharmacological and electrophysiological characterization of AZSMO-23, an activator of the hERG K(+) channel. Br J Pharmacol 2015; 172:3112-25. [PMID: 25684549 DOI: 10.1111/bph.13115] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 01/31/2015] [Accepted: 02/09/2015] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE We aimed to characterize the pharmacology and electrophysiology of N-[3-(1H-benzimidazol-2-yl)-4-chloro-phenyl]pyridine-3-carboxamide (AZSMO-23), an activator of the human ether-a-go-go-related gene (hERG)-encoded K(+) channel (Kv 11.1). EXPERIMENTAL APPROACH Automated electrophysiology was used to study the pharmacology of AZSMO-23 on wild-type (WT), Y652A, F656T or G628C/S631C hERG, and on other cardiac ion channels. Its mechanism of action was characterized with conventional electrophysiology. KEY RESULTS AZSMO-23 activated WT hERG pre-pulse and tail current with EC50 values of 28.6 and 11.2 μM respectively. At 100 μM, pre-pulse current at +40 mV was increased by 952 ± 41% and tail current at -30 mV by 238 ± 13% compared with vehicle values. The primary mechanism for this effect was a 74.5 mV depolarizing shift in the voltage dependence of inactivation, without any shift in the voltage dependence of activation. Structure-activity relationships for this effect were remarkably subtle, with close analogues of AZSMO-23 acting as hERG inhibitors. AZSMO-23 blocked the mutant channel, hERG Y652A, but against another mutant channel, hERG F656T, its activator activity was enhanced. It inhibited activity of the G628C/S631C non-inactivating hERG mutant channel. AZSMO-23 was not hERG selective, as it blocked hKv 4.3-hKChIP2.2, hCav 3.2 and hKv 1.5 and activated hCav 1.2/β2/α2δ channels. CONCLUSION AND IMPLICATIONS The activity of AZSMO-23 and those of its close analogues suggest these compounds may be of value to elucidate the mechanism of type 2 hERG activators to better understand the pharmacology of this area from both a safety perspective and in relation to treatment of congenital long QT syndrome.
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Affiliation(s)
- R Mannikko
- Institute of Neurology, Faculty of Brain Sciences, University College London, London, Middlesex, UK
| | | | - H Pye
- AstraZeneca, Macclesfield, Cheshire, UK
| | - S Swallow
- AstraZeneca, Macclesfield, Cheshire, UK
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Perissinotti LL, Guo J, De Biase PM, Clancy CE, Duff HJ, Noskov SY. Kinetic model for NS1643 drug activation of WT and L529I variants of Kv11.1 (hERG1) potassium channel. Biophys J 2015; 108:1414-1424. [PMID: 25809254 PMCID: PMC4375712 DOI: 10.1016/j.bpj.2014.12.056] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 11/24/2014] [Accepted: 12/08/2014] [Indexed: 11/28/2022] Open
Abstract
Congenital and acquired (drug-induced) forms of the human long-QT syndrome are associated with alterations in Kv11.1 (hERG) channel-controlled repolarizing IKr currents of cardiac action potentials. A mandatory drug screen implemented by many countries led to a discovery of a large group of small molecules that can activate hERG currents and thus may act as potent antiarrhythmic agents. Despite significant progress in identification of channel activators, little is known about their mechanism of action. A combination of electrophysiological studies with molecular and kinetic modeling was used to examine the mechanism of a model activator (NS1643) action on the hERG channel and its L529I mutant. The L529I mutant has gating dynamics similar to that of wild-type while its response to application of NS1643 is markedly different. We propose a mechanism compatible with experiments in which the model activator binds to the closed (C3) and open states (O). We suggest that NS1643 is affecting early gating transitions, probably during movements of the voltage sensor that precede the opening of the activation gate.
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Affiliation(s)
- Laura L Perissinotti
- Centre for Molecular Modeling, Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, Alberta, Canada
| | - Jiqing Guo
- Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Pablo M De Biase
- Centre for Molecular Modeling, Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, Alberta, Canada
| | - Colleen E Clancy
- Department of Pharmacology, University of California at Davis, Davis, California.
| | - Henry J Duff
- Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
| | - Sergei Y Noskov
- Centre for Molecular Modeling, Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, Alberta, Canada.
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Rasmusson RL, Anumonwo JM. Activation of HERG channels: opening new applications for the biophysics of antiarrhythmic therapy. Biophys J 2015; 108:1309-1311. [PMID: 25809242 DOI: 10.1016/j.bpj.2015.01.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 01/14/2015] [Accepted: 01/16/2015] [Indexed: 11/26/2022] Open
Affiliation(s)
- Randall L Rasmusson
- Department of Physiology and Biophysics, State University of New York, University at Buffalo, Buffalo, New York
| | - Justus M Anumonwo
- Department of Internal Medicine-Cardiovascular Medicine, University of Michigan Medical School, Ann Arbor, Michigan; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan.
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38
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Bellin M, Greber B. Human iPS cell models of Jervell and Lange-Nielsen syndrome. Rare Dis 2015; 3:e1012978. [PMID: 26481773 PMCID: PMC4588220 DOI: 10.1080/21675511.2015.1012978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 01/25/2015] [Indexed: 02/02/2023] Open
Abstract
Recessive mutations in the ion channel-encoding KCNQ1 gene may cause Jervell and Lange-Nielsen syndrome (JLNS), a fatal cardiac disease leading to arrhythmia and sudden cardiac death in young patients. Mutations in KCNQ1 may also cause a milder and dominantly inherited form of the disease, long QT syndrome 1 (LQT1). However, why some mutations cause LQT1 and others cause JLNS can often not be understood a priori. In a recent study,1 we have generated human induced pluripotent stem cell (hiPSC) models of JLNS. Our work mechanistically revealed how distinct classes of JLNS-causing genetic lesions, namely, missense and splice-site mutations, may promote the typical severe features of the disease at the cellular level. Interestingly, the JLNS models also displayed highly sensitive responses to pro-arrhythmic stresses. We hence propose JLNS hiPSCs as a powerful system for evaluating both phenotype-correcting as well as cardiotoxicity-causing drug effects.
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Affiliation(s)
- Milena Bellin
- Department of Anatomy and Embryology; Leiden University Medical Center ; Leiden, The Netherlands
| | - Boris Greber
- Human Stem Cell Pluripotency Group; Max Planck Institute for Molecular Biomedicine ; Münster, Germany ; Chemical Genomics Center of the Max Planck Society ; Dortmund, Germany
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Recessive cardiac phenotypes in induced pluripotent stem cell models of Jervell and Lange-Nielsen syndrome: disease mechanisms and pharmacological rescue. Proc Natl Acad Sci U S A 2014; 111:E5383-92. [PMID: 25453094 DOI: 10.1073/pnas.1419553111] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Jervell and Lange-Nielsen syndrome (JLNS) is one of the most severe life-threatening cardiac arrhythmias. Patients display delayed cardiac repolarization, associated high risk of sudden death due to ventricular tachycardia, and congenital bilateral deafness. In contrast to the autosomal dominant forms of long QT syndrome, JLNS is a recessive trait, resulting from homozygous (or compound heterozygous) mutations in KCNQ1 or KCNE1. These genes encode the α and β subunits, respectively, of the ion channel conducting the slow component of the delayed rectifier K(+) current, IKs. We used complementary approaches, reprogramming patient cells and genetic engineering, to generate human induced pluripotent stem cell (hiPSC) models of JLNS, covering splice site (c.478-2A>T) and missense (c.1781G>A) mutations, the two major classes of JLNS-causing defects in KCNQ1. Electrophysiological comparison of hiPSC-derived cardiomyocytes (CMs) from homozygous JLNS, heterozygous, and wild-type lines recapitulated the typical and severe features of JLNS, including pronounced action and field potential prolongation and severe reduction or absence of IKs. We show that this phenotype had distinct underlying molecular mechanisms in the two sets of cell lines: the previously unidentified c.478-2A>T mutation was amorphic and gave rise to a strictly recessive phenotype in JLNS-CMs, whereas the missense c.1781G>A lesion caused a gene dosage-dependent channel reduction at the cell membrane. Moreover, adrenergic stimulation caused action potential prolongation specifically in JLNS-CMs. Furthermore, sensitivity to proarrhythmic drugs was strongly enhanced in JLNS-CMs but could be pharmacologically corrected. Our data provide mechanistic insight into distinct classes of JLNS-causing mutations and demonstrate the potential of hiPSC-CMs in drug evaluation.
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40
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Li P, Chen X, Zhang Q, Zheng Y, Jiang H, Yang H, Gao Z. The human ether-a-go-go-related gene activator NS1643 enhances epilepsy-associated KCNQ channels. J Pharmacol Exp Ther 2014; 351:596-604. [PMID: 25232191 DOI: 10.1124/jpet.114.217703] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Human ether-a-go-go-related gene (hERG) and KCNQ channels are two classes of voltage-gated potassium channels. Specific mutations have been identified that are causal for type II long QT (LQT2) syndrome, neonatal epilepsy, and benign familial neonatal convulsions. Increasing evidence from clinical studies suggests that LQT2 and epilepsy coexist in some patients. Therefore, an integral approach to investigating and treating the two diseases is likely more effective. In the current study, we found that NS1643 [1,3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea], a previously reported hERG activator, is also an activator of KCNQ channels. It potentiates the neuronal KCNQ2, KCNQ4, and KCNQ2/Q3 channels, but not the cardiac KCNQ1. The effects of NS1643 on the KCNQ2 channel include left shifting of voltage for reaching 50% of the maximum conductance and slowing of deactivation. Analysis of the dose-response curve of NS1643 revealed an EC50 value of 2.44 ± 0.25 μM. A hydrophobic phenylalanine (F137) located at the middle region of the voltage-sensing domain was identified as critical for NS1643 activity on KCNQ2. When testing NS1643 effects in rescuing LQT2 hERG mutants and the KCNQ2 BFNC mutants, we found it is particularly efficacious in some cases. Considering the substantial relationship between LQT2 and epilepsy, these findings reveal that NS1643 is a useful compound to elucidate the causal connection of LQT2 and epilepsy. More generally, this may provide a strategy in the development of therapeutics for LQT2 and epilepsy.
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Affiliation(s)
- Ping Li
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xueqin Chen
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Qiansen Zhang
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Yueming Zheng
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hualiang Jiang
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Huaiyu Yang
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Zhaobing Gao
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
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41
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Schmitt N, Grunnet M, Olesen SP. Cardiac potassium channel subtypes: new roles in repolarization and arrhythmia. Physiol Rev 2014; 94:609-53. [PMID: 24692356 DOI: 10.1152/physrev.00022.2013] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K+ channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K+ channels drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K+ channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure. The underlying posttranscriptional and posttranslational remodeling of the individual K+ channels changes their activity and significance relative to each other, and they must be viewed together to understand their role in keeping a stable heart rhythm, also under menacing conditions like attacks of reentry arrhythmia.
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42
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Wu W, Sachse FB, Gardner A, Sanguinetti MC. Stoichiometry of altered hERG1 channel gating by small molecule activators. ACTA ACUST UNITED AC 2014; 143:499-512. [PMID: 24638994 PMCID: PMC3971662 DOI: 10.1085/jgp.201311038] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Agonists bind to sites on all four subunits to activate human ether-a-go-go–related gene 1 (hERG1) K+ channels. Voltage-gated K+ channels are tetramers formed by coassembly of four identical or highly related subunits. All four subunits contribute to formation of the selectivity filter, the narrowest region of the channel pore which determines K+ selective conductance. In some K+ channels, the selectivity filter can undergo a conformational change to reduce K+ flux by a mechanism called C-type inactivation. In human ether-a-go-go–related gene 1 (hERG1) K+ channels, C-type inactivation is allosterically inhibited by ICA-105574, a substituted benzamide. PD-118057, a 2-(phenylamino) benzoic acid, alters selectivity filter gating to enhance open probability of channels. Both compounds bind to a hydrophobic pocket located between adjacent hERG1 subunits. Accordingly, a homotetrameric channel contains four identical activator binding sites. Here we determine the number of binding sites required for maximal drug effect and determine the role of subunit interactions in the modulation of hERG1 gating by these compounds. Concatenated tetramers were constructed to contain a variable number (zero to four) of wild-type and mutant hERG1 subunits, either L646E to inhibit PD-118057 binding or F557L to inhibit ICA-105574 binding. Enhancement of hERG1 channel current magnitude by PD-118057 and attenuated inactivation by ICA-105574 were mediated by cooperative subunit interactions. Maximal effects of the both compounds required the presence of all four binding sites. Understanding how hERG1 agonists allosterically modify channel gating may facilitate mechanism-based drug design of novel agents for treatment of long QT syndrome.
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Affiliation(s)
- Wei Wu
- Division of Cardiovascular Medicine, Department of Internal Medicine, 2 Nora Eccles Harrison Cardiovascular Research and Training Institute, and 3 Department of Bioengineering, University of Utah, Salt Lake City, UT 84112
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43
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González C, Baez-Nieto D, Valencia I, Oyarzún I, Rojas P, Naranjo D, Latorre R. K(+) channels: function-structural overview. Compr Physiol 2013; 2:2087-149. [PMID: 23723034 DOI: 10.1002/cphy.c110047] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Potassium channels are particularly important in determining the shape and duration of the action potential, controlling the membrane potential, modulating hormone secretion, epithelial function and, in the case of those K(+) channels activated by Ca(2+), damping excitatory signals. The multiplicity of roles played by K(+) channels is only possible to their mammoth diversity that includes at present 70 K(+) channels encoding genes in mammals. Today, thanks to the use of cloning, mutagenesis, and the more recent structural studies using x-ray crystallography, we are in a unique position to understand the origins of the enormous diversity of this superfamily of ion channels, the roles they play in different cell types, and the relations that exist between structure and function. With the exception of two-pore K(+) channels that are dimers, voltage-dependent K(+) channels are tetrameric assemblies and share an extremely well conserved pore region, in which the ion-selectivity filter resides. In the present overview, we discuss in the function, localization, and the relations between function and structure of the five different subfamilies of K(+) channels: (a) inward rectifiers, Kir; (b) four transmembrane segments-2 pores, K2P; (c) voltage-gated, Kv; (d) the Slo family; and (e) Ca(2+)-activated SK family, SKCa.
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Affiliation(s)
- Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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44
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Zeng H, Balasubramanian B, Penniman JR, Kinose F, Salata JJ, Lagrutta A. Halide ion effects on human Ether-à-go-go related gene potassium channel properties. Assay Drug Dev Technol 2013; 11:544-50. [PMID: 24147984 DOI: 10.1089/adt.2013.531] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The human Ether-à-go-go related gene (hERG) potassium channel has been widely used to counter screen potential pharmaceuticals as a biomarker to predict clinical QT prolongation. Thus, higher throughput assays of hERG are valuable for early in vitro screening of drug candidates to minimize failure in later-stage drug development due to this potentially adverse cardiac risk. We have developed a novel method utilizing potassium fluoride to improve throughput of hERG counter screening with an automated patch clamp system, PatchXpress 7000A. In that method, ∼50% substitution of internal Cl(-) with F(-) greatly increases success rate without substantially altering the biophysical properties of the hERG channel or compromising data quality. However, effect of F(-) or other halide ions on hERG channel properties has not been studied in detail. In this study, we examined effects of complete replacement of Cl(-) in internal solution with halide ions, F(-), or Br(-). We found that (1) F(-) slightly shifts the voltage dependence of hERG channel activation to more positive voltages, while Br(-) shifts it to more negative voltages; (2) Br(-) shifts to more positive voltages both the inactivation-voltage relationship and the peak position of channel full activation of hERG; (3) F(-) slows hERG activation, while both F(-) and Br(-) make the channel close faster; (4) neither F(-) nor Br(-) have any effect on hERG inactivation kinetics. In conclusion, compared to Cl(-), F(-) has subtle effect on hERG activation, while Br(-) has distinct effects on certain, but not all biophysical properties of hERG channel.
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Affiliation(s)
- Haoyu Zeng
- Safety Assessment and Laboratory Animal Resources, Merck Research Laboratories , West Point, Pennsylvania
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45
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Meng J, Shi C, Li L, Du Y, Xu Y. Compound ICA-105574 prevents arrhythmias induced by cardiac delayed repolarization. Eur J Pharmacol 2013; 718:87-97. [PMID: 24041920 DOI: 10.1016/j.ejphar.2013.09.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 08/27/2013] [Accepted: 09/04/2013] [Indexed: 01/14/2023]
Abstract
Impaired ventricular repolarization can lead to long QT syndrome (LQT), a proarrhythmic disease with high risk of developing lethal ventricular tachyarrhythmias. The compound ICA-105574 is a recently developed hERG activator and it enhances IKr current with very high potency by removing the channel inactivation. The present study was designed to investigate antiarrhythmic properties of ICA-105574. For comparison, the effects of another compound NS1643 was in-parallel assessed, which also acts primarily to attenuate channel inactivation with moderate potency. We found that both ICA-105574 and NS1643 concentration-dependently shortened action potential duration (APD) in ventricular myocytes, and QT/QTc intervals in isolated guinea-pig hearts. ICA-105574, but not NS1643, completely prevented ventricular arrhythmias in intact guinea-pig hearts caused by IKr and IKs inhibitors, although both ICA-105574 and NS1643 could reverse the drug-induced prolongation of APD in ventricular myocytes. Reversing prolongation of QT/QTc intervals and antagonizing the increases in transmural dispersion of repolarization and instability of the QT interval induced by IKr and IKs inhibitors contributed to antiarrhythmic effect of ICA-105574. Meanwhile, ICA-105574 at higher concentrations showed a potential proarrhythmic risk in normal hearts. Our results suggest that ICA-105574 has more efficient antiarrhythmic activity than NS1643. However, its potential proarrhythmic risk implies that benefits and risks should be seriously taken into consideration for further developing this type of hERG activators.
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Affiliation(s)
- Jing Meng
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education; The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Hebei Province, Shijiazhuang 050017, China; Department of Pharmaceutical Chemistry, Hebei Medical University, Shijiazhuang, China
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46
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Rampe D, Brown AM. A history of the role of the hERG channel in cardiac risk assessment. J Pharmacol Toxicol Methods 2013; 68:13-22. [DOI: 10.1016/j.vascn.2013.03.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 03/14/2013] [Accepted: 03/14/2013] [Indexed: 01/25/2023]
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47
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Lansu K, Gentile S. Potassium channel activation inhibits proliferation of breast cancer cells by activating a senescence program. Cell Death Dis 2013; 4:e652. [PMID: 23744352 PMCID: PMC3698542 DOI: 10.1038/cddis.2013.174] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Traditionally the hERG1 potassium channel has been known to have a fundamental role in membrane excitability of several mammalian cells including cardiac myocytes. hERG1 has recently been found to be expressed in non-excitable cancer cells of different histogenesis, but the role of this channel in cancer biology is unknown. Results form recent studies on the effect hERG1 inhibition in some breast cancer cells are controversial as it can lead to apoptosis or protect against cell death. Nevertheless, these data suggest that the hERG1 channel could have an important role in cancer biology. Here we report the effects of hyperstimulation of hERG1 channel in human mammary gland adenocarcinoma-derived cells. Application of the hERG1 activator, the diphenylurea derivative NS1643, inhibits cell proliferation irreversibly. This event is accompanied by a preferential arrest of the cell cycle in G0/G1 phase without the occurrence of apoptotic events. Consequently, cells responded to NS1643 by developing a senescence-like phenotype associated with increased protein levels of the tumor suppressors p21 and p16(INK4a) and by a positive β-galactosidase assay. These data suggest that prolonged stimulation of the hERG1 potassium channel may activate a senescence program and offers a compelling opportunity to develop a potential antiproliferative cancer therapy.
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Affiliation(s)
- K Lansu
- Molecular Pharmacology and Therapeutics, Loyola University, Chicago, IL, USA
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48
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49
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Garg V, Stary-Weinzinger A, Sanguinetti MC. ICA-105574 interacts with a common binding site to elicit opposite effects on inactivation gating of EAG and ERG potassium channels. Mol Pharmacol 2013; 83:805-13. [PMID: 23319419 DOI: 10.1124/mol.112.084384] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Rapid and voltage-dependent inactivation greatly attenuates outward currents in ether-a-go-go-related gene (ERG) K(+) channels. In contrast, inactivation of related ether-a-go-go (EAG) K(+) channels is very slow and minimally reduces outward currents. ICA-105574 (ICA, or 3-nitro-N-[4-phenoxyphenyl]-benzamide) has opposite effects on inactivation of these two channel types. Although ICA greatly attenuates ERG inactivation by shifting its voltage dependence to more positive potentials, it enhances the rate and extent of EAG inactivation without altering its voltage dependence. Here, we investigate whether the inverse functional response to ICA in EAG and ERG channels is related to differences in ICA binding site or to intrinsic mechanisms of inactivation. Molecular modeling coupled with site-directed mutagenesis suggests that ICA binds in a channel-specific orientation to a hydrophobic pocket bounded by the S5/pore helix/S6 of one subunit and S6 of an adjacent subunit. ICA is a mixed agonist of mutant EAG and EAG/ERG chimera channels that inactivate by a combination of slow and fast mechanisms. With the exception of three residues, the specific amino acids that form the putative binding pocket for ICA in ERG are conserved in EAG. Mutations introduced into EAG to replicate the ICA binding site in ERG did not alter the functional response to ICA. Together these findings suggest that ICA binds to the same site in EAG and ERG channels to elicit opposite functional effects. The resultant agonist or antagonist activity is determined solely by channel-specific differences in the mechanisms of inactivation gating.
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Affiliation(s)
- Vivek Garg
- Nora Eccles Harrison Cardiovascular Research & Training Institute, Department of Physiology, University of Utah, Salt Lake City, Utah 84112, USA
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50
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Asayama M, Kurokawa J, Shirakawa K, Okuyama H, Kagawa T, Okada JI, Sugiura S, Hisada T, Furukawa T. Effects of an hERG Activator, ICA-105574, on Electrophysiological Properties of Canine Hearts. J Pharmacol Sci 2013; 121:1-8. [DOI: 10.1254/jphs.12220fp] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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