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Neeman-Egozi S, Livneh I, Dolgopyat I, Nussinovitch U, Milman H, Cohen N, Eisen B, Ciechanover A, Binah O. Stress-Induced Proteasome Sub-Cellular Translocation in Cardiomyocytes Causes Altered Intracellular Calcium Handling and Arrhythmias. Int J Mol Sci 2024; 25:4932. [PMID: 38732146 PMCID: PMC11084437 DOI: 10.3390/ijms25094932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Revised: 04/18/2024] [Accepted: 04/24/2024] [Indexed: 05/13/2024] Open
Abstract
The ubiquitin-proteasome system (UPS) is an essential mechanism responsible for the selective degradation of substrate proteins via their conjugation with ubiquitin. Since cardiomyocytes have very limited self-renewal capacity, as they are prone to protein damage due to constant mechanical and metabolic stress, the UPS has a key role in cardiac physiology and pathophysiology. While altered proteasomal activity contributes to a variety of cardiac pathologies, such as heart failure and ischemia/reperfusion injury (IRI), the environmental cues affecting its activity are still unknown, and they are the focus of this work. Following a recent study by Ciechanover's group showing that amino acid (AA) starvation in cultured cancer cell lines modulates proteasome intracellular localization and activity, we tested two hypotheses in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs, CMs): (i) AA starvation causes proteasome translocation in CMs, similarly to the observation in cultured cancer cell lines; (ii) manipulation of subcellular proteasomal compartmentalization is associated with electrophysiological abnormalities in the form of arrhythmias, mediated via altered intracellular Ca2+ handling. The major findings are: (i) starving CMs to AAs results in proteasome translocation from the nucleus to the cytoplasm, while supplementation with the aromatic amino acids tyrosine (Y), tryptophan (W) and phenylalanine (F) (YWF) inhibits the proteasome recruitment; (ii) AA-deficient treatments cause arrhythmias; (iii) the arrhythmias observed upon nuclear proteasome sequestration(-AA+YWF) are blocked by KB-R7943, an inhibitor of the reverse mode of the sodium-calcium exchanger NCX; (iv) the retrograde perfusion of isolated rat hearts with AA starvation media is associated with arrhythmias. Collectively, our novel findings describe a newly identified mechanism linking the UPS to arrhythmia generation in CMs and whole hearts.
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Affiliation(s)
- Shunit Neeman-Egozi
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Ido Livneh
- The Rappaport-Technion Integrated Cancer Center (R-TICC) and The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 319060, Israel; (I.L.); (N.C.)
| | - Irit Dolgopyat
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Udi Nussinovitch
- Department of Cardiology, Edith Wolfson Medical Center, Holon 5822012, Israel
- The Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Helena Milman
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Nadav Cohen
- The Rappaport-Technion Integrated Cancer Center (R-TICC) and The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 319060, Israel; (I.L.); (N.C.)
| | - Binyamin Eisen
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
| | - Aaron Ciechanover
- The Rappaport-Technion Integrated Cancer Center (R-TICC) and The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 319060, Israel; (I.L.); (N.C.)
| | - Ofer Binah
- Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa 3190601, Israel; (S.N.-E.); (B.E.)
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Bai J, Lo A, Kennelly J, Sharma R, Zhao N, Trew ML, Zhao J. Mechanisms of pulmonary arterial hypertension-induced atrial fibrillation: insights from multi-scale models of the human atria. Interface Focus 2023; 13:20230039. [PMID: 38106916 PMCID: PMC10722211 DOI: 10.1098/rsfs.2023.0039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 10/25/2023] [Indexed: 12/19/2023] Open
Abstract
This study aimed to use multi-scale atrial models to investigate pulmonary arterial hypertension (PAH)-induced atrial fibrillation mechanisms. The results of our computer simulations revealed that, at the single-cell level, PAH-induced remodelling led to a prolonged action potential (AP) (ΔAPD: 49.6 ms in the right atria (RA) versus 41.6 ms in the left atria (LA)) and an increased calcium transient (CaT) (ΔCaT: 7.5 × 10-2 µM in the RA versus 0.9 × 10-3 µM in the LA). Moreover, heterogeneous remodelling increased susceptibility to afterdepolarizations, particularly in the RA. At the tissue level, we observed a significant reduction in conduction velocity (CV) (ΔCV: -0.5 m s-1 in the RA versus -0.05 m s-1 in the LA), leading to a shortened wavelength in the RA, but not in the LA. Additionally, afterdepolarizations in the RA contributed to enhanced repolarization dispersion and facilitated unidirectional conduction block. Furthermore, the increased fibrosis in the RA amplified the likelihood of excitation wave breakdown and the occurrence of sustained re-entries. Our results indicated that the RA is characterized by increased susceptibility to afterdepolarizations, slow conduction, reduced wavelength and upregulated fibrosis. These findings shed light on the underlying factors that may promote atrial fibrillation in patients with PAH.
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Affiliation(s)
- Jieyun Bai
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou, People's Republic of China
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Andy Lo
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - James Kennelly
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Roshan Sharma
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Na Zhao
- School of Instrument Science and Engineering, Southeast University, Nanjing, People's Republic of China
| | - Mark L. Trew
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Jichao Zhao
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
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3
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Jin Q, Greenstein JL, Winslow RL. Estimating the probability of early afterdepolarizations and predicting arrhythmic risk associated with long QT syndrome type 1 mutations. Biophys J 2023; 122:4042-4056. [PMID: 37705243 PMCID: PMC10598291 DOI: 10.1016/j.bpj.2023.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 08/29/2023] [Accepted: 09/08/2023] [Indexed: 09/15/2023] Open
Abstract
Early afterdepolarizations (EADs) are action potential (AP) repolarization abnormalities that can trigger lethal arrhythmias. Simulations using biophysically detailed cardiac myocyte models can reveal how model parameters influence the probability of these cellular arrhythmias; however, such analyses can pose a huge computational burden. We have previously developed a highly simplified approach in which logistic regression models (LRMs) map parameters of complex cell models to the probability of ectopic beats. Here, we extend this approach to predict the probability of EADs (P(EAD)) as a mechanistic metric of arrhythmic risk. We use the LRM to investigate how changes in parameters of the slow-activating delayed rectifier current (IKs) affect P(EAD) for 17 different long QT syndrome type 1 (LQTS1) mutations. In this LQTS1 clinical arrhythmic risk prediction task, we compared P(EAD) for these 17 mutations with two other recently published model-based arrhythmia risk metrics (AP morphology metric across populations of myocyte models and transmural repolarization prolongation based on a one-dimensional [1D] tissue-level model). These model-based risk metrics yield similar prediction performance; however, each fails to stratify clinical risk for a significant number of the 17 studied LQTS1 mutations. Nevertheless, an interpretable ensemble model using multivariate linear regression built by combining all of these model-based risk metrics successfully predicts the clinical risk of 17 mutations. These results illustrate the potential of computational approaches in arrhythmia risk prediction.
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Affiliation(s)
- Qingchu Jin
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Joseph L Greenstein
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Raimond L Winslow
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland.
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4
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Ferreira G, Cardozo R, Sastre S, Costa C, Santander A, Chavarría L, Guizzo V, Puglisi J, Nicolson GL. Bacterial toxins and heart function: heat-labile Escherichia coli enterotoxin B promotes changes in cardiac function with possible relevance for sudden cardiac death. Biophys Rev 2023; 15:447-473. [PMID: 37681088 PMCID: PMC10480140 DOI: 10.1007/s12551-023-01100-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 07/11/2023] [Indexed: 09/09/2023] Open
Abstract
Bacterial toxins can cause cardiomyopathy, though it is not its most common cause. Some bacterial toxins can form pores in the membrane of cardiomyocytes, while others can bind to membrane receptors. Enterotoxigenic E. coli can secrete enterotoxins, including heat-resistant (ST) or labile (LT) enterotoxins. LT is an AB5-type toxin that can bind to specific cell receptors and disrupt essential host functions, causing several common conditions, such as certain diarrhea. The pentameric B subunit of LT, without A subunit (LTB), binds specifically to certain plasma membrane ganglioside receptors, found in lipid rafts of cardiomyocytes. Isolated guinea pig hearts and cardiomyocytes were exposed to different concentrations of purified LTB. In isolated hearts, mechanical and electrical alternans and an increment of heart rate variability, with an IC50 of ~0.2 μg/ml LTB, were observed. In isolated cardiomyocytes, LTB promoted significant decreases in the amplitude and the duration of action potentials. Na+ currents were inhibited whereas L-type Ca2+ currents were augmented at their peak and their fast inactivation was promoted. Delayed rectifier K+ currents decreased. Measurements of basal Ca2+ or Ca2+ release events in cells exposed to LTB suggest that LTB impairs Ca2+ homeostasis. Impaired calcium homeostasis is linked to sudden cardiac death. The results are consistent with the recent view that the B subunit is not merely a carrier of the A subunit, having a role explaining sudden cardiac death in children (SIDS) infected with enterotoxigenic E. coli, explaining several epidemiological findings that establish a strong relationship between SIDS and ETEC E. coli. Supplementary Information The online version contains supplementary material available at 10.1007/s12551-023-01100-6.
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Affiliation(s)
- Gonzalo Ferreira
- Ion Channels, Biological Membranes and Cell Signaling Laboratory, Dept. Of Biophysics, Facultad de Medicina, Universidad de la Republica, Gral Flores 2125, 11800 Montevideo, CP Uruguay
| | - Romina Cardozo
- Ion Channels, Biological Membranes and Cell Signaling Laboratory, Dept. Of Biophysics, Facultad de Medicina, Universidad de la Republica, Gral Flores 2125, 11800 Montevideo, CP Uruguay
| | - Santiago Sastre
- Ion Channels, Biological Membranes and Cell Signaling Laboratory, Dept. Of Biophysics and Centro de Investigaciones Biomédicas (CeInBio), Facultad de Medicina, Universidad de la Republica, Gral Flores 2125, 11800 Montevideo, CP Uruguay
| | - Carlos Costa
- Ion Channels, Biological Membranes and Cell Signaling Laboratory, Dept. Of Biophysics, Facultad de Medicina, Universidad de la Republica, Gral Flores 2125, 11800 Montevideo, CP Uruguay
| | - Axel Santander
- Ion Channels, Biological Membranes and Cell Signaling Laboratory, Dept. Of Biophysics, Facultad de Medicina, Universidad de la Republica, Gral Flores 2125, 11800 Montevideo, CP Uruguay
| | - Luisina Chavarría
- Ion Channels, Biological Membranes and Cell Signaling Laboratory, Dept. Of Biophysics, Facultad de Medicina, Universidad de la Republica, Gral Flores 2125, 11800 Montevideo, CP Uruguay
| | - Valentina Guizzo
- Ion Channels, Biological Membranes and Cell Signaling Laboratory, Dept. Of Biophysics, Facultad de Medicina, Universidad de la Republica, Gral Flores 2125, 11800 Montevideo, CP Uruguay
| | - José Puglisi
- College of Medicine, California North State University, 9700 West Taron Drive, Elk Grove, CA 95757 USA
| | - G. L. Nicolson
- Institute for Molecular Medicine, Beach, Huntington, CA USA
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5
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Arslanova A, Shafaattalab S, Ye K, Asghari P, Lin L, Kim B, Roston TM, Hove-Madsen L, Van Petegem F, Sanatani S, Moore E, Lynn F, Søndergaard M, Luo Y, Chen SRW, Tibbits GF. Using hiPSC-CMs to Examine Mechanisms of Catecholaminergic Polymorphic Ventricular Tachycardia. Curr Protoc 2021; 1:e320. [PMID: 34958715 DOI: 10.1002/cpz1.320] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal inherited cardiac arrhythmia condition, triggered by physical or acute emotional stress, that predominantly expresses early in life. Gain-of-function mutations in the cardiac ryanodine receptor gene (RYR2) account for the majority of CPVT cases, causing substantial disruption of intracellular calcium (Ca2+ ) homeostasis particularly during the periods of β-adrenergic receptor stimulation. However, the highly variable penetrance, patient outcomes, and drug responses observed in clinical practice remain unexplained, even for patients with well-established founder RyR2 mutations. Therefore, investigation of the electrophysiological consequences of CPVT-causing RyR2 mutations is crucial to better understand the pathophysiology of the disease. The development of strategies for reprogramming human somatic cells to human induced pluripotent stem cells (hiPSCs) has provided a unique opportunity to study inherited arrhythmias, due to the ability of hiPSCs to differentiate down a cardiac lineage. Employment of genome editing enables generation of disease-specific cell lines from healthy and diseased patient-derived hiPSCs, which subsequently can be differentiated into cardiomyocytes. This paper describes the means for establishing an hiPSC-based model of CPVT in order to recapitulate the disease phenotype in vitro and investigate underlying pathophysiological mechanisms. The framework of this approach has the potential to contribute to disease modeling and personalized medicine using hiPSC-derived cardiomyocytes. © 2021 Wiley Periodicals LLC.
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Affiliation(s)
- Alia Arslanova
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sanam Shafaattalab
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Kevin Ye
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Parisa Asghari
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Lisa Lin
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - BaRun Kim
- Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Thomas M Roston
- British Columbia Children's Hospital Heart Center, Vancouver, British Columbia, Canada
| | - Leif Hove-Madsen
- Cardiac Rhythm and Contraction Group, IIBB-CSIC, CIBERCV, IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shubhayan Sanatani
- British Columbia Children's Hospital Heart Center, Vancouver, British Columbia, Canada
| | - Edwin Moore
- Cardiac Rhythm and Contraction Group, IIBB-CSIC, CIBERCV, IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Francis Lynn
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | | | - Yonglun Luo
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - S R Wayne Chen
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - Glen F Tibbits
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.,School of Biomedical Engineering, University of British Columbia, Vancouver, British Columbia, Canada
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6
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Estimating ectopic beat probability with simplified statistical models that account for experimental uncertainty. PLoS Comput Biol 2021; 17:e1009536. [PMID: 34665814 PMCID: PMC8577785 DOI: 10.1371/journal.pcbi.1009536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 11/09/2021] [Accepted: 10/06/2021] [Indexed: 11/21/2022] Open
Abstract
Ectopic beats (EBs) are cellular arrhythmias that can trigger lethal arrhythmias. Simulations using biophysically-detailed cardiac myocyte models can reveal how model parameters influence the probability of these cellular arrhythmias, however such analyses can pose a huge computational burden. Here, we develop a simplified approach in which logistic regression models (LRMs) are used to define a mapping between the parameters of complex cell models and the probability of EBs (P(EB)). As an example, in this study, we build an LRM for P(EB) as a function of the initial value of diastolic cytosolic Ca2+ concentration ([Ca2+]iini), the initial state of sarcoplasmic reticulum (SR) Ca2+ load ([Ca2+]SRini), and kinetic parameters of the inward rectifier K+ current (IK1) and ryanodine receptor (RyR). This approach, which we refer to as arrhythmia sensitivity analysis, allows for evaluation of the relationship between these arrhythmic event probabilities and their associated parameters. This LRM is also used to demonstrate how uncertainties in experimentally measured values determine the uncertainty in P(EB). In a study of the role of [Ca2+]SRini uncertainty, we show a special property of the uncertainty in P(EB), where with increasing [Ca2+]SRini uncertainty, P(EB) uncertainty first increases and then decreases. Lastly, we demonstrate that IK1 suppression, at the level that occurs in heart failure myocytes, increases P(EB). An ectopic beat is an abnormal cellular electrical event which can trigger dangerous arrhythmias in the heart. Complex biophysical models of the cardiac myocyte can be used to reveal how cell properties affect the probability of ectopic beats. However, such analyses can pose a huge computational burden. We develop a simplified approach that enables a highly complex biophysical model to be reduced to a rather simple statistical model from which the functional relationship between myocyte model parameters and the probability of an ectopic beat is determined. We refer to this approach as arrhythmia sensitivity analysis. Given the efficiency of our approach, we also use it to demonstrate how uncertainties in experimentally measured myocyte model parameters determine the uncertainty in ectopic beat probability. We find that, with increasing model parameter uncertainty, the uncertainty in probability of ectopic beat first increases and then decreases. In general, our approach can efficiently analyze the relationship between cardiac myocyte parameters and the probability of ectopic beats and can be used to study how uncertainty of these cardiac myocyte parameters influences the ectopic beat probability.
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Ip JE, Xu L, Dai J, Steegborn C, Jaffré F, Evans T, Cheung JW, Basson CT, Panaghie G, Krogh-Madsen T, Abbott GW, Lerman BB. Constitutively Activating GNAS Somatic Mutation in Right Ventricular Outflow Tract Tachycardia. Circ Arrhythm Electrophysiol 2021; 14:e010082. [PMID: 34587755 PMCID: PMC8569928 DOI: 10.1161/circep.121.010082] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- James E. Ip
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Linna Xu
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Jie Dai
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Clemens Steegborn
- Department of Biochemistry, Weill-Cornell Medical College, New York, NY
- Present Address: Department of Biochemistry, University of Bayreuth, Germany
| | - Fabrice Jaffré
- Department of Surgery, Weill-Cornell Medical College, New York, NY
| | - Todd Evans
- Department of Surgery, Weill-Cornell Medical College, New York, NY
| | - Jim W. Cheung
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Craig T. Basson
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
- Present Address: Boston Pharmaceuticals, Cambridge, MA
| | - Gianina Panaghie
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Trine Krogh-Madsen
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
| | - Geoffrey W. Abbott
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
- Present Address: Department of Physiology & Biophysics, University of California, Irvine, CA
| | - Bruce B. Lerman
- Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY
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8
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Wright PT, Gorelik J, Harding SE. Electrophysiological Remodeling: Cardiac T-Tubules and ß-Adrenoceptors. Cells 2021; 10:cells10092456. [PMID: 34572106 PMCID: PMC8468945 DOI: 10.3390/cells10092456] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 09/13/2021] [Accepted: 09/16/2021] [Indexed: 01/09/2023] Open
Abstract
Beta-adrenoceptors (βAR) are often viewed as archetypal G-protein coupled receptors. Over the past fifteen years, investigations in cardiovascular biology have provided remarkable insights into this receptor family. These studies have shifted pharmacological dogma, from one which centralized the receptor to a new focus on structural micro-domains such as caveolae and t-tubules. Important studies have examined, separately, the structural compartmentation of ion channels and βAR. Despite links being assumed, relatively few studies have specifically examined the direct link between structural remodeling and electrical remodeling with a focus on βAR. In this review, we will examine the nature of receptor and ion channel dysfunction on a substrate of cardiomyocyte microdomain remodeling, as well as the likely ramifications for cardiac electrophysiology. We will then discuss the advances in methodologies in this area with a specific focus on super-resolution microscopy, fluorescent imaging, and new approaches involving microdomain specific, polymer-based agonists. The advent of powerful computational modelling approaches has allowed the science to shift from purely empirical work, and may allow future investigations based on prediction. Issues such as the cross-reactivity of receptors and cellular heterogeneity will also be discussed. Finally, we will speculate as to the potential developments within this field over the next ten years.
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Affiliation(s)
- Peter T. Wright
- School of Life & Health Sciences, University of Roehampton, Holybourne Avenue, London SW15 4JD, UK;
- Cardiac Section, National Heart and Lung Institute (NHLI), Faculty of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK;
| | - Julia Gorelik
- Cardiac Section, National Heart and Lung Institute (NHLI), Faculty of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK;
| | - Sian E. Harding
- Cardiac Section, National Heart and Lung Institute (NHLI), Faculty of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK;
- Correspondence:
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Implications of SGLT Inhibition on Redox Signalling in Atrial Fibrillation. Int J Mol Sci 2021; 22:ijms22115937. [PMID: 34073033 PMCID: PMC8198069 DOI: 10.3390/ijms22115937] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/25/2021] [Accepted: 05/26/2021] [Indexed: 12/20/2022] Open
Abstract
Atrial fibrillation (AF) is the most common sustained (atrial) arrhythmia, a considerable global health burden and often associated with heart failure. Perturbations of redox signalling in cardiomyocytes provide a cellular substrate for the manifestation and maintenance of atrial arrhythmias. Several clinical trials have shown that treatment with sodium-glucose linked transporter inhibitors (SGLTi) improves mortality and hospitalisation in heart failure patients independent of the presence of diabetes. Post hoc analysis of the DECLARE-TIMI 58 trial showed a 19% reduction in AF in patients with diabetes mellitus (hazard ratio, 0.81 (95% confidence interval: 0.68-0.95), n = 17.160) upon treatment with SGLTi, regardless of pre-existing AF or heart failure and independent from blood pressure or renal function. Accordingly, ongoing experimental work suggests that SGLTi not only positively impact heart failure but also counteract cellular ROS production in cardiomyocytes, thereby potentially altering atrial remodelling and reducing AF burden. In this article, we review recent studies investigating the effect of SGLTi on cellular processes closely interlinked with redox balance and their potential effects on the onset and progression of AF. Despite promising insight into SGLTi effect on Ca2+ cycling, Na+ balance, inflammatory and fibrotic signalling, mitochondrial function and energy balance and their potential effect on AF, the data are not yet conclusive and the importance of individual pathways for human AF remains to be established. Lastly, an overview of clinical studies investigating SGLTi in the context of AF is provided.
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MD1 Depletion Predisposes to Ventricular Arrhythmias in the Setting of Myocardial Infarction. Heart Lung Circ 2020; 30:869-881. [PMID: 33257269 DOI: 10.1016/j.hlc.2020.09.938] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 09/21/2020] [Accepted: 09/23/2020] [Indexed: 11/23/2022]
Abstract
BACKGROUND Myeloid differentiation protein 1 (MD1) is expressed in the human heart and is a negative regulator of Toll-like receptor 4 (TLR4) signalling. MD1 exerts anti-arrhythmic effects. AIM The aim of this study was to determine the role of MD1 in myocardial infarction (MI)-related ventricular arrhythmias (VAs). METHOD Myocardial infarction was induced by surgical ligation of the left anterior coronary artery in MD1 knockout (KO) mice and their wild-type littermates. Myocardial infarction-induced vulnerability to VAs and its underlying mechanisms were evaluated. RESULTS Myeloid differentiation protein 1 was downregulated in the MI mice. Myeloid differentiation protein 1 deficiency decreased post-MI left ventricular (LV) function and increased the infarct size. The MI mice exhibited prolonged action potential duration (APD), enhanced APD alternans thresholds, and a higher incidence of VAs. Myocardial infarction-induced LV fibrosis and inflammation decreased the expression levels of Kv4.2, Kv4.3, Kv1.5, and Kv2.1, increased Cav1.2 expression, and disturbed Ca2+ handling protein expression. These MI-induced adverse effects were further exacerbated in KO mice. Mechanistically, MD1 deletion markedly enhanced the activation of the TLR4/calmodulin-dependent protein kinase II (CaMKII) signalling pathway in post-MI mice. CONCLUSIONS Myeloid differentiation protein 1 deletion increases the vulnerability to VAs in post-MI mice. This is mainly caused by the aggravated maladaptive LV fibrosis and inflammation and interference with the expressions of ion channels and Ca2+ handling proteins, which is related to enhanced activation of the TLR4/CaMKII signalling pathway.
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11
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Njegic A, Wilson C, Cartwright EJ. Targeting Ca 2 + Handling Proteins for the Treatment of Heart Failure and Arrhythmias. Front Physiol 2020; 11:1068. [PMID: 33013458 PMCID: PMC7498719 DOI: 10.3389/fphys.2020.01068] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 08/04/2020] [Indexed: 12/18/2022] Open
Abstract
Diseases of the heart, such as heart failure and cardiac arrhythmias, are a growing socio-economic burden. Calcium (Ca2+) dysregulation is key hallmark of the failing myocardium and has long been touted as a potential therapeutic target in the treatment of a variety of cardiovascular diseases (CVD). In the heart, Ca2+ is essential for maintaining normal cardiac function through the generation of the cardiac action potential and its involvement in excitation contraction coupling. As such, the proteins which regulate Ca2+ cycling and signaling play a vital role in maintaining Ca2+ homeostasis. Changes to the expression levels and function of Ca2+-channels, pumps and associated intracellular handling proteins contribute to altered Ca2+ homeostasis in CVD. The remodeling of Ca2+-handling proteins therefore results in impaired Ca2+ cycling, Ca2+ leak from the sarcoplasmic reticulum and reduced Ca2+ clearance, all of which contributes to increased intracellular Ca2+. Currently, approved treatments for targeting Ca2+ handling dysfunction in CVD are focused on Ca2+ channel blockers. However, whilst Ca2+ channel blockers have been successful in the treatment of some arrhythmic disorders, they are not universally prescribed to heart failure patients owing to their ability to depress cardiac function. Despite the progress in CVD treatments, there remains a clear need for novel therapeutic approaches which are able to reverse pathophysiology associated with heart failure and arrhythmias. Given that heart failure and cardiac arrhythmias are closely associated with altered Ca2+ homeostasis, this review will address the molecular changes to proteins associated with both Ca2+-handling and -signaling; their potential as novel therapeutic targets will be discussed in the context of pre-clinical and, where available, clinical data.
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Affiliation(s)
- Alexandra Njegic
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom.,Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Claire Wilson
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom.,Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Elizabeth J Cartwright
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom
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12
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Whittaker DG, Clerx M, Lei CL, Christini DJ, Mirams GR. Calibration of ionic and cellular cardiac electrophysiology models. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2020; 12:e1482. [PMID: 32084308 PMCID: PMC8614115 DOI: 10.1002/wsbm.1482] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/17/2020] [Accepted: 01/18/2020] [Indexed: 12/30/2022]
Abstract
Cardiac electrophysiology models are among the most mature and well-studied mathematical models of biological systems. This maturity is bringing new challenges as models are being used increasingly to make quantitative rather than qualitative predictions. As such, calibrating the parameters within ion current and action potential (AP) models to experimental data sets is a crucial step in constructing a predictive model. This review highlights some of the fundamental concepts in cardiac model calibration and is intended to be readily understood by computational and mathematical modelers working in other fields of biology. We discuss the classic and latest approaches to calibration in the electrophysiology field, at both the ion channel and cellular AP scales. We end with a discussion of the many challenges that work to date has raised and the need for reproducible descriptions of the calibration process to enable models to be recalibrated to new data sets and built upon for new studies. This article is categorized under: Analytical and Computational Methods > Computational Methods Physiology > Mammalian Physiology in Health and Disease Models of Systems Properties and Processes > Cellular Models.
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Affiliation(s)
- Dominic G. Whittaker
- Centre for Mathematical Medicine & Biology, School of Mathematical SciencesUniversity of NottinghamNottinghamUK
| | - Michael Clerx
- Computational Biology & Health Informatics, Department of Computer ScienceUniversity of OxfordOxfordUK
| | - Chon Lok Lei
- Computational Biology & Health Informatics, Department of Computer ScienceUniversity of OxfordOxfordUK
| | | | - Gary R. Mirams
- Centre for Mathematical Medicine & Biology, School of Mathematical SciencesUniversity of NottinghamNottinghamUK
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13
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Lo ACY, Bai J, Gladding PA, Fedorov VV, Zhao J. Afterdepolarizations and abnormal calcium handling in atrial myocytes with modulated SERCA uptake: a sensitivity analysis of calcium handling channels. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190557. [PMID: 32448059 PMCID: PMC7287332 DOI: 10.1098/rsta.2019.0557] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/23/2020] [Indexed: 05/21/2023]
Abstract
Delayed afterdepolarizations (DADs) and spontaneous depolarizations (SDs) are typically triggered by spontaneous diastolic Ca2+ release from the sarcoplasmic reticulum (SR) which is caused by an elevated SR Ca2+-ATPase (SERCA) uptake and dysfunctional ryanodine receptors. However, recent studies on the T-box transcription factor gene (TBX5) demonstrated that abnormal depolarizations could occur despite a reduced SERCA uptake. Similar findings have also been reported in experimental or clinical studies of diabetes and heart failure. To investigate the sensitivity of SERCA in the genesis of DADs/SDs as well as its dependence on other Ca2+ handling channels, we performed systematic analyses using the Maleckar et al. model. Results showed that the modulation of SERCA alone cannot trigger abnormal depolarizations, but can instead affect the interdependency of other Ca2+ handling channels in triggering DADs/SDs. Furthermore, we discovered the existence of a threshold value for the intracellular concentration of Ca2+ ([Ca2+]i) for abnormal depolarizations, which is modulated by the maximum SERCA uptake and the concentration of Ca2+ in the uptake and release compartments in the SR ([Ca2+]up and [Ca2+]rel). For the first time, our modelling study reconciles different mechanisms of abnormal depolarizations in the setting of 'lone' AF, reduced TBX5, diabetes and heart failure, and may lead to more targeted treatment for these patients. This article is part of the theme issue 'Uncertainty quantification in cardiac and cardiovascular modelling and simulation'.
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Affiliation(s)
- Andy C. Y. Lo
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Jieyun Bai
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou, People's Republic of China
| | - Patrick A. Gladding
- Department of Cardiology, Waitemata District Health Board, Auckland, New Zealand
| | - Vadim V. Fedorov
- Department of Physiology and Cell Biology and Bob and Corrine Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Jichao Zhao
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
- e-mail:
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14
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Trovato C, Passini E, Nagy N, Varró A, Abi-Gerges N, Severi S, Rodriguez B. Human Purkinje in silico model enables mechanistic investigations into automaticity and pro-arrhythmic abnormalities. J Mol Cell Cardiol 2020; 142:24-38. [PMID: 32251669 PMCID: PMC7294239 DOI: 10.1016/j.yjmcc.2020.04.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 03/30/2020] [Accepted: 04/01/2020] [Indexed: 02/06/2023]
Abstract
Cardiac Purkinje cells (PCs) are implicated in lethal arrhythmias caused by cardiac diseases, mutations, and drug action. However, the pro-arrhythmic mechanisms in PCs are not entirely understood, particularly in humans, as most investigations are conducted in animals. The aims of this study are to present a novel human PCs electrophysiology biophysically-detailed computational model, and to disentangle ionic mechanisms of human Purkinje-related electrophysiology, pacemaker activity and arrhythmogenicity. The new Trovato2020 model incorporates detailed Purkinje-specific ionic currents and Ca2+ handling, and was developed, calibrated and validated using human experimental data acquired at multiple frequencies, both in control conditions and following drug application. Multiscale investigations were performed in a Purkinje cell, in fibre and using an experimentally-calibrated population of PCs to evaluate biological variability. Simulations demonstrate the human Purkinje Trovato2020 model is the first one to yield: (i) all key AP features consistent with human Purkinje recordings; (ii) Automaticity with funny current up-regulation (iii) EADs at slow pacing and with 85% hERG block; (iv) DADs following fast pacing; (v) conduction velocity of 160 cm/s in a Purkinje fibre, as reported in human. The human in silico PCs population highlights that: (1) EADs are caused by ICaL reactivation in PCs with large inward currents; (2) DADs and triggered APs occur in PCs experiencing Ca2+ accumulation, at fast pacing, caused by large L-type calcium current and small Na+/Ca2+ exchanger. The novel human Purkinje model unlocks further investigations into the role of cardiac Purkinje in ventricular arrhythmias through computer modeling and multiscale simulations.
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Affiliation(s)
- Cristian Trovato
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford OX13QD, United Kingdom.
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford OX13QD, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged H-6720, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged H-6720, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Najah Abi-Gerges
- AnaBios Corporation, San Diego Science Center, San Diego, CA 92109, USA
| | - Stefano Severi
- Department of Electrical, Electronic and Information Engineering, University of Bologna, Cesena 47521, Italy
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford OX13QD, United Kingdom.
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15
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Bartolucci C, Passini E, Hyttinen J, Paci M, Severi S. Simulation of the Effects of Extracellular Calcium Changes Leads to a Novel Computational Model of Human Ventricular Action Potential With a Revised Calcium Handling. Front Physiol 2020; 11:314. [PMID: 32351400 PMCID: PMC7174690 DOI: 10.3389/fphys.2020.00314] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 03/19/2020] [Indexed: 01/13/2023] Open
Abstract
The importance of electrolyte concentrations for cardiac function is well established. Electrolyte variations can lead to arrhythmias onset, due to their important role in the action potential (AP) genesis and in maintaining cell homeostasis. However, most of the human AP computer models available in literature were developed with constant electrolyte concentrations, and fail to simulate physiological changes induced by electrolyte variations. This is especially true for Ca2+, even in the O'Hara-Rudy model (ORd), one of the most widely used models in cardiac electrophysiology. Therefore, the present work develops a new human ventricular model (BPS2020), based on ORd, able to simulate the inverse dependence of AP duration (APD) on extracellular Ca2+ concentration ([Ca2+]o), and APD rate dependence at 4 mM extracellular K+. The main changes needed with respect to ORd are: (i) an increased sensitivity of L-type Ca2+ current inactivation to [Ca2+]o; (ii) a single compartment description of the sarcoplasmic reticulum; iii) the replacement of Ca2+ release. BPS2020 is able to simulate the physiological APD-[Ca2+]o relationship, while also retaining the well-reproduced properties of ORd (APD rate dependence, restitution, accommodation and current block effects). We also used BPS2020 to generate an experimentally-calibrated population of models to investigate: (i) the occurrence of repolarization abnormalities in response to hERG current block; (ii) the rate adaptation variability; (iii) the occurrence of alternans and delayed after-depolarizations at fast pacing. Our results indicate that we successfully developed an improved version of ORd, which can be used to investigate electrophysiological changes and pro-arrhythmic abnormalities induced by electrolyte variations and current block at multiple rates and at the population level.
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Affiliation(s)
- Chiara Bartolucci
- Computational Physiopathology Unit, Department of Electrical, Electronic and Information Engineering “Guglielmo Marconi”, University of Bologna, Cesena, Italy
| | - Elisa Passini
- Computational Physiopathology Unit, Department of Electrical, Electronic and Information Engineering “Guglielmo Marconi”, University of Bologna, Cesena, Italy
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Jari Hyttinen
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Michelangelo Paci
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Stefano Severi
- Computational Physiopathology Unit, Department of Electrical, Electronic and Information Engineering “Guglielmo Marconi”, University of Bologna, Cesena, Italy
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16
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Bai J, Lo A, Gladding PA, Stiles MK, Fedorov VV, Zhao J. In silico investigation of the mechanisms underlying atrial fibrillation due to impaired Pitx2. PLoS Comput Biol 2020; 16:e1007678. [PMID: 32097431 PMCID: PMC7059955 DOI: 10.1371/journal.pcbi.1007678] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 03/06/2020] [Accepted: 01/22/2020] [Indexed: 01/04/2023] Open
Abstract
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is a major cause of stroke and morbidity. Recent genome-wide association studies have shown that paired-like homeodomain transcription factor 2 (Pitx2) to be strongly associated with AF. However, the mechanisms underlying Pitx2 modulated arrhythmogenesis and variable effectiveness of antiarrhythmic drugs (AADs) in patients in the presence or absence of impaired Pitx2 expression remain unclear. We have developed multi-scale computer models, ranging from a single cell to tissue level, to mimic control and Pitx2-knockout atria by incorporating recent experimental data on Pitx2-induced electrical and structural remodeling in humans, as well as the effects of AADs. The key findings of this study are twofold. We have demonstrated that shortened action potential duration, slow conduction and triggered activity occur due to electrical and structural remodelling under Pitx2 deficiency conditions. Notably, the elevated function of calcium transport ATPase increases sarcoplasmic reticulum Ca2+ concentration, thereby enhancing susceptibility to triggered activity. Furthermore, heterogeneity is further elevated due to Pitx2 deficiency: 1) Electrical heterogeneity between left and right atria increases; and 2) Increased fibrosis and decreased cell-cell coupling due to structural remodelling slow electrical propagation and provide obstacles to attract re-entry, facilitating the initiation of re-entrant circuits. Secondly, our study suggests that flecainide has antiarrhythmic effects on AF due to impaired Pitx2 by preventing spontaneous calcium release and increasing wavelength. Furthermore, our study suggests that Na+ channel effects alone are insufficient to explain the efficacy of flecainide. Our study may provide the mechanisms underlying Pitx2-induced AF and possible explanation behind the AAD effects of flecainide in patients with Pitx2 deficiency.
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Affiliation(s)
- Jieyun Bai
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou, China
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Andy Lo
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Patrick A. Gladding
- Department of Cardiology, Waitemata District Health Board, Auckland, New Zealand
| | - Martin K. Stiles
- Waikato Clinical School, Faculty of Medical and Health Sciences, University of Auckland, New Zealand
| | - Vadim V. Fedorov
- Department of Physiology & Cell Biology and Bob and Corrine Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States of America
| | - Jichao Zhao
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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17
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Zhabyeyev P, McLean B, Chen X, Vanhaesebroeck B, Oudit GY. Inhibition of PI3Kinase-α is pro-arrhythmic and associated with enhanced late Na + current, contractility, and Ca 2+ release in murine hearts. J Mol Cell Cardiol 2019; 132:98-109. [PMID: 31095940 DOI: 10.1016/j.yjmcc.2019.05.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 04/11/2019] [Accepted: 05/09/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Phosphoinositide 3-kinase α (PI3Kα) is a proto-oncogene with high activity in the heart. BYL719 (BYL) is a PI3Kα-selective small molecule inhibitor and a prospective drug for advanced solid tumors. We investigated whether acute pharmacological inhibition of PI3Kα has pro-arrhythmic effects. METHODS & RESULTS In isolated wild-type (WT) cardiomyocytes, pharmacological inhibition of PI3Kα (BYL719) increased contractility by 28%, Ca2+ release by 20%, and prolonged action potential (AP) repolarization by 10-15%. These effects of BYL719 were abolished by inhibition of reverse-mode Na+/Ca2+ exchanger (NCX) (KB-R7943) or by inhibition of late Na+ current (INa-L) (ranolazine). BYL719 had no effect on PI3Kα-deficient cardiomyocytes, suggesting BYL719 effects were PI3Kα-dependent and mediated via NCX and INa-L. INa-L was suppressed by activation of PI3Kα, application of exogenous intracellular PIP3, or ranolazine. Investigation of AP and Ca2+ release in whole heart preparations using epicardial optical mapping showed that inhibition of PI3Kα similarly led to prolongation of AP and enhancement of Ca2+ release. In hearts of PI3Kα-deficient mice, β-adrenergic stimulation in the presence of high Ca2+ concentrations and 12-Hz burst pacing led to delayed afterdepolarizations and ventricular fibrillation. In vivo, administration of BYL719 prolonged QT interval [QTcF (Fridericia) increased by 15%] in WT, but not in PI3Kα-deficient mice. CONCLUSIONS Pharmacological inhibition of PI3Kα is arrhythmogenic due to activation of INa-L leading to increased sarcoplasmic reticulum Ca2+ load and prolonged QT interval. Therefore, monitoring of cardiac electrical activity in patients receiving PI3K inhibitors may provide further insights into the arrhythmogenic potential of PI3Ka inhibition.
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Affiliation(s)
- Pavel Zhabyeyev
- Department of Medicine, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
| | - Brent McLean
- Department of Medicine, University of Alberta, Edmonton, Canada; Department of Physiology, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
| | - Xueyi Chen
- Department of Medicine, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
| | | | - Gavin Y Oudit
- Department of Medicine, University of Alberta, Edmonton, Canada; Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada.
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18
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Vaidyanathan R, Reilly L, Eckhardt LL. Caveolin-3 Microdomain: Arrhythmia Implications for Potassium Inward Rectifier and Cardiac Sodium Channel. Front Physiol 2018; 9:1548. [PMID: 30473666 PMCID: PMC6238080 DOI: 10.3389/fphys.2018.01548] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 10/16/2018] [Indexed: 11/13/2022] Open
Abstract
In human cardiac ventricular myocytes, caveolin-3 functions as a scaffolding and regulatory protein for signaling molecules and compartmentalizes ion channels. Our lab has recently explored this sub-cellular microdomain and found that potassium inward rectifier Kir2.x is found in association with caveolin-3. The three cardiac Kir2.x isoforms (Kir2.1, Kir2.2, and Kir2.3) are the molecular correlates of IK1 in the heart, of which Kir2.1 is the dominant isoform in the ventricle. Kir2.1 channels assemble with Kir2.2 and Kir2.3 forming hetero-tetramers that modulate IK1. IK1 sets the resting membrane potential and assists with terminal phase 3 ventricular repolarization. In our studies using native human ventricular tissue, Kir2.x co-localizes with caveolin-3 and significance of the association between Kir2.x and caveolin-3 is emphasized in relation to mutations in the gene which encodes caveolin-3, CAV3, associated with Long QT Syndrome 9 (LQT9). LQT9-associated CAV3 mutations cause decreased current density in Kir2.1 and Kir2.2 as homomeric and heteromeric channels, which affects repolarization and membrane potential stability. A portion of Kir2.1 cardiac localization parallels that of the cardiac sodium channel (Nav1.5). This may have implications for Long QT9 in which CAV3 mutations cause an increase in the late current of Nav1.5 (INa-L) via nNOS mediated nitrosylation of Nav1.5. In iPS-CMs, expression of LQT9 CAV3 mutations resulted in action potential duration (APD) prolongation and early-after depolarizations (EADs), supporting the arrhythmogenicity of LQT9. To evaluate the combined effect of the CAV3 mutants on INa-L and IK1, we studied both ventricular and Purkinje myocyte mathematical modeling. Interestingly, mathematical ventricular myocytes, similar to iPS-CMs, demonstrated EADs but no sustained arrhythmia. In contrast, Purkinje modeling demonstrated delayed-after depolarizations (DADs) driven mechanism for sustained arrhythmia, dependent on the combined loss of IK1 and gain of INa-L. This finding changes the overall assumed arrhythmia phenotype for LQT9. In future studies, we are exploring caveolar micro-domain disruption in heart failure and how this effects Kir2.x and Nav1.5. Here we review the caveolae cardiac microdomain of Kir2.x and Nav1.5 and explore some of the downstream effects of caveolin-3 and caveolae disruption in specific clinical scenarios.
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Affiliation(s)
- Ravi Vaidyanathan
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI, United States
| | - Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI, United States
| | - Lee L Eckhardt
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI, United States
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19
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Johnson DM, Antoons G. Arrhythmogenic Mechanisms in Heart Failure: Linking β-Adrenergic Stimulation, Stretch, and Calcium. Front Physiol 2018; 9:1453. [PMID: 30374311 PMCID: PMC6196916 DOI: 10.3389/fphys.2018.01453] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 09/25/2018] [Indexed: 12/22/2022] Open
Abstract
Heart failure (HF) is associated with elevated sympathetic tone and mechanical load. Both systems activate signaling transduction pathways that increase cardiac output, but eventually become part of the disease process itself leading to further worsening of cardiac function. These alterations can adversely contribute to electrical instability, at least in part due to the modulation of Ca2+ handling at the level of the single cardiac myocyte. The major aim of this review is to provide a definitive overview of the links and cross talk between β-adrenergic stimulation, mechanical load, and arrhythmogenesis in the setting of HF. We will initially review the role of Ca2+ in the induction of both early and delayed afterdepolarizations, the role that β-adrenergic stimulation plays in the initiation of these and how the propensity for these may be altered in HF. We will then go onto reviewing the current data with regards to the link between mechanical load and afterdepolarizations, the associated mechano-sensitivity of the ryanodine receptor and other stretch activated channels that may be associated with HF-associated arrhythmias. Furthermore, we will discuss how alterations in local Ca2+ microdomains during the remodeling process associated the HF may contribute to the increased disposition for β-adrenergic or stretch induced arrhythmogenic triggers. Finally, the potential mechanisms linking β-adrenergic stimulation and mechanical stretch will be clarified, with the aim of finding common modalities of arrhythmogenesis that could be targeted by novel therapeutic agents in the setting of HF.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiothoracic Surgery, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
| | - Gudrun Antoons
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
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20
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Paci M, Pölönen RP, Cori D, Penttinen K, Aalto-Setälä K, Severi S, Hyttinen J. Automatic Optimization of an in Silico Model of Human iPSC Derived Cardiomyocytes Recapitulating Calcium Handling Abnormalities. Front Physiol 2018; 9:709. [PMID: 29997516 PMCID: PMC6028769 DOI: 10.3389/fphys.2018.00709] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/22/2018] [Indexed: 12/20/2022] Open
Abstract
The growing importance of human induced pluripotent stem cell-derived cardiomyoyctes (hiPSC-CMs), as patient-specific and disease-specific models for studying cellular cardiac electrophysiology or for preliminary cardiotoxicity tests, generated better understanding of hiPSC-CM biophysical mechanisms and great amount of action potential and calcium transient data. In this paper, we propose a new hiPSC-CM in silico model, with particular attention to Ca2+ handling. We used (i) the hiPSC-CM Paci2013 model as starting point, (ii) a new dataset of Ca2+ transient measurements to tune the parameters of the inward and outward Ca2+ fluxes of sarcoplasmic reticulum, and (iii) an automatic parameter optimization to fit action potentials and Ca2+ transients. The Paci2018 model simulates, together with the typical hiPSC-CM spontaneous action potentials, more refined Ca2+ transients and delayed afterdepolarizations-like abnormalities, which the old Paci2013 was not able to predict due to its mathematical formulation. The Paci2018 model was validated against (i) the same current blocking experiments used to validate the Paci2013 model, and (ii) recently published data about effects of different extracellular ionic concentrations. In conclusion, we present a new and more versatile in silico model, which will provide a platform for modeling the effects of drugs or mutations that affect Ca2+ handling in hiPSC-CMs.
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Affiliation(s)
- Michelangelo Paci
- Faculty of Biomedical Sciences and Engineering, BioMediTech Institute, Tampere University of Technology, Tampere, Finland
| | - Risto-Pekka Pölönen
- Faculty of Medicine and Life Sciences, BioMediTech Institute, University of Tampere, Tampere, Finland
| | - Dario Cori
- Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Cesena, Italy
| | - Kirsi Penttinen
- Faculty of Medicine and Life Sciences, BioMediTech Institute, University of Tampere, Tampere, Finland
| | - Katriina Aalto-Setälä
- Faculty of Medicine and Life Sciences, BioMediTech Institute, University of Tampere, Tampere, Finland.,Heart Hospital, Tampere University Hospital, Tampere, Finland
| | - Stefano Severi
- Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Cesena, Italy
| | - Jari Hyttinen
- Faculty of Biomedical Sciences and Engineering, BioMediTech Institute, Tampere University of Technology, Tampere, Finland
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21
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Walker MA, Gurev V, Rice JJ, Greenstein JL, Winslow RL. Estimating the probabilities of rare arrhythmic events in multiscale computational models of cardiac cells and tissue. PLoS Comput Biol 2017; 13:e1005783. [PMID: 29145393 PMCID: PMC5689829 DOI: 10.1371/journal.pcbi.1005783] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 09/18/2017] [Indexed: 11/24/2022] Open
Abstract
Ectopic heartbeats can trigger reentrant arrhythmias, leading to ventricular fibrillation and sudden cardiac death. Such events have been attributed to perturbed Ca2+ handling in cardiac myocytes leading to spontaneous Ca2+ release and delayed afterdepolarizations (DADs). However, the ways in which perturbation of specific molecular mechanisms alters the probability of ectopic beats is not understood. We present a multiscale model of cardiac tissue incorporating a biophysically detailed three-dimensional model of the ventricular myocyte. This model reproduces realistic Ca2+ waves and DADs driven by stochastic Ca2+ release channel (RyR) gating and is used to study mechanisms of DAD variability. In agreement with previous experimental and modeling studies, key factors influencing the distribution of DAD amplitude and timing include cytosolic and sarcoplasmic reticulum Ca2+ concentrations, inwardly rectifying potassium current (IK1) density, and gap junction conductance. The cardiac tissue model is used to investigate how random RyR gating gives rise to probabilistic triggered activity in a one-dimensional myocyte tissue model. A novel spatial-average filtering method for estimating the probability of extreme (i.e. rare, high-amplitude) stochastic events from a limited set of spontaneous Ca2+ release profiles is presented. These events occur when randomly organized clusters of cells exhibit synchronized, high amplitude Ca2+ release flux. It is shown how reduced IK1 density and gap junction coupling, as observed in heart failure, increase the probability of extreme DADs by multiple orders of magnitude. This method enables prediction of arrhythmia likelihood and its modulation by alterations of other cellular mechanisms.
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Affiliation(s)
- Mark A. Walker
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, United States of America
| | - Viatcheslav Gurev
- TJ Watson Research Center, IBM, Yorktown Heights, NY, United States of America
| | - John J. Rice
- TJ Watson Research Center, IBM, Yorktown Heights, NY, United States of America
| | - Joseph L. Greenstein
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, United States of America
| | - Raimond L. Winslow
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, United States of America
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Gray RA, Pathmanathan P. A Parsimonious Model of the Rabbit Action Potential Elucidates the Minimal Physiological Requirements for Alternans and Spiral Wave Breakup. PLoS Comput Biol 2016; 12:e1005087. [PMID: 27749895 PMCID: PMC5066986 DOI: 10.1371/journal.pcbi.1005087] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/21/2016] [Indexed: 11/19/2022] Open
Abstract
Elucidating the underlying mechanisms of fatal cardiac arrhythmias requires a tight integration of electrophysiological experiments, models, and theory. Existing models of transmembrane action potential (AP) are complex (resulting in over parameterization) and varied (leading to dissimilar predictions). Thus, simpler models are needed to elucidate the "minimal physiological requirements" to reproduce significant observable phenomena using as few parameters as possible. Moreover, models have been derived from experimental studies from a variety of species under a range of environmental conditions (for example, all existing rabbit AP models incorporate a formulation of the rapid sodium current, INa, based on 30 year old data from chick embryo cell aggregates). Here we develop a simple "parsimonious" rabbit AP model that is mathematically identifiable (i.e., not over parameterized) by combining a novel Hodgkin-Huxley formulation of INa with a phenomenological model of repolarization similar to the voltage dependent, time-independent rectifying outward potassium current (IK). The model was calibrated using the following experimental data sets measured from the same species (rabbit) under physiological conditions: dynamic current-voltage (I-V) relationships during the AP upstroke; rapid recovery of AP excitability during the relative refractory period; and steady-state INa inactivation via voltage clamp. Simulations reproduced several important "emergent" phenomena including cellular alternans at rates > 250 bpm as observed in rabbit myocytes, reentrant spiral waves as observed on the surface of the rabbit heart, and spiral wave breakup. Model variants were studied which elucidated the minimal requirements for alternans and spiral wave break up, namely the kinetics of INa inactivation and the non-linear rectification of IK.The simplicity of the model, and the fact that its parameters have physiological meaning, make it ideal for engendering generalizable mechanistic insight and should provide a solid "building-block" to generate more detailed ionic models to represent complex rabbit electrophysiology.
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Affiliation(s)
- Richard A. Gray
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland, United States of America
- * E-mail:
| | - Pras Pathmanathan
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland, United States of America
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Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) has emerged as key enzyme in many cardiac pathologies, especially heart failure (HF), myocardial infarction and cardiomyopathies, thus leading to contractile dysfunction and malignant arrhythmias. While many pathways leading to CaMKII activation have been elucidated in recent years, hardly any clinically viable compounds affecting CaMKII activity have progressed from basic in vitro science to in vivo studies. This review focuses on recent advances in anti-arrhythmic strategies involving CaMKII. Specifically, both inhibition of CaMKII itself to prevent arrhythmias, as well as anti-arrhythmic approaches affecting CaMKII activity via alterations in signaling cascades upstream and downstream of CaMKII will be discussed.
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Affiliation(s)
- Julian Mustroph
- Universitäres Herzzentrum Regensburg, Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany
| | - Stefan Neef
- Universitäres Herzzentrum Regensburg, Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany
| | - Lars S Maier
- Universitäres Herzzentrum Regensburg, Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany.
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24
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Pueyo E, Orini M, Rodríguez JF, Taggart P. Interactive effect of beta-adrenergic stimulation and mechanical stretch on low-frequency oscillations of ventricular action potential duration in humans. J Mol Cell Cardiol 2016; 97:93-105. [DOI: 10.1016/j.yjmcc.2016.05.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 03/21/2016] [Accepted: 05/03/2016] [Indexed: 01/27/2023]
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Horváth B, Váczi K, Hegyi B, Gönczi M, Dienes B, Kistamás K, Bányász T, Magyar J, Baczkó I, Varró A, Seprényi G, Csernoch L, Nánási PP, Szentandrássy N. Sarcolemmal Ca(2+)-entry through L-type Ca(2+) channels controls the profile of Ca(2+)-activated Cl(-) current in canine ventricular myocytes. J Mol Cell Cardiol 2016; 97:125-39. [PMID: 27189885 DOI: 10.1016/j.yjmcc.2016.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 04/20/2016] [Accepted: 05/10/2016] [Indexed: 12/15/2022]
Abstract
Ca(2+)-activated Cl(-) current (ICl(Ca)) mediated by TMEM16A and/or Bestrophin-3 may contribute to cardiac arrhythmias. The true profile of ICl(Ca) during an actual ventricular action potential (AP), however, is poorly understood. We aimed to study the profile of ICl(Ca) systematically under physiological conditions (normal Ca(2+) cycling and AP voltage-clamp) as well as in conditions designed to change [Ca(2+)]i. The expression of TMEM16A and/or Bestrophin-3 in canine and human left ventricular myocytes was examined. The possible spatial distribution of these proteins and their co-localization with Cav1.2 was also studied. The profile of ICl(Ca), identified as a 9-anthracene carboxylic acid-sensitive current under AP voltage-clamp conditions, contained an early fast outward and a late inward component, overlapping early and terminal repolarizations, respectively. Both components were moderately reduced by ryanodine, while fully abolished by BAPTA, but not EGTA. [Ca(2+)]i was monitored using Fura-2-AM. Setting [Ca(2+)]i to the systolic level measured in the bulk cytoplasm (1.1μM) decreased ICl(Ca), while application of Bay K8644, isoproterenol, and faster stimulation rates increased the amplitude of ICl(Ca). Ca(2+)-entry through L-type Ca(2+) channels was essential for activation of ICl(Ca). TMEM16A and Bestrophin-3 showed strong co-localization with one another and also with Cav1.2 channels, when assessed using immunolabeling and confocal microscopy in both canine myocytes and human ventricular myocardium. Activation of ICl(Ca) in canine ventricular cells requires Ca(2+)-entry through neighboring L-type Ca(2+) channels and is only augmented by SR Ca(2+)-release. Substantial activation of ICl(Ca) requires high Ca(2+) concentration in the dyadic clefts which can be effectively buffered by BAPTA, but not EGTA.
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Affiliation(s)
- Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Faculty of Pharmacy, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Krisztina Váczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Bence Hegyi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Mónika Gönczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; MTA-DE Momentum, Laboratory of Protein Dynamics, Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Beatrix Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary
| | - György Seprényi
- Department of Medical Biology, Faculty of Medicine, University of Szeged, H-6720 Szeged, Somogyi Béla utca 4, P.O. Box 427, Hungary
| | - László Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Norbert Szentandrássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary.
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26
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Foteinou PT, Greenstein JL, Winslow RL. Mechanistic Investigation of the Arrhythmogenic Role of Oxidized CaMKII in the Heart. Biophys J 2016; 109:838-49. [PMID: 26287635 DOI: 10.1016/j.bpj.2015.06.064] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 05/16/2015] [Accepted: 06/30/2015] [Indexed: 10/23/2022] Open
Abstract
Oxidative stress and calcium (Ca(2+))/calmodulin (CaM)-dependent protein kinase II (CaMKII) both play important roles in the pathogenesis of cardiac disease. Although the pathophysiological relevance of reactive oxygen species (ROS) and CaMKII has been appreciated for some time, recent work has shown that ROS can directly oxidize CaMKII, leading to its persistent activity and an increase of the likelihood of cellular arrhythmias such as early afterdepolarizations (EADs). Because CaMKII modulates the function of many proteins involved in excitation-contraction coupling, elucidation of its role in cardiac function, in both healthy and oxidative stress conditions, is challenging. To investigate this role, we have developed a model of CaMKII activation that includes both the phosphorylation-dependent and the newly identified oxidation-dependent activation pathways. This model is incorporated into our previous local-control model of the cardiac myocyte that describes excitation-contraction coupling via stochastic simulation of individual Ca(2+) release units and CaMKII-mediated phosphorylation of L-type Ca(2+) channels (LCCs), ryanodine receptors and sodium (Na(+)) channels. The model predicts the experimentally measured slow-rate dependence of H2O2-induced EADs. Upon increased H2O2, simulations suggest that selective activation of late Na(+) current (INaL), although it prolongs action potential duration, is not by itself sufficient to produce EADs. Similar results are obtained if CaMKII effects on LCCs and ryanodine receptors are considered separately. However, EADs emerge upon simultaneous activation of both LCCs and Na(+) channels. Further modeling results implicate activation of the Na(+)-Ca(2+) exchanger (NCX) as an important player in the generation of EADs. During bradycardia, the emergence of H2O2-induced EADs was correlated with a shift in the timing of NCX current reversal toward the plateau phase earlier in the action potential. Using the timing of NCX current reversal as an indicator event for EADs, the model identified counterintuitive ionic changes-difficult to experimentally dissect-that have the greatest influence on ROS-related arrhythmia propensity.
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Affiliation(s)
- Panagiota T Foteinou
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Joseph L Greenstein
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Raimond L Winslow
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland.
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27
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Filament Dynamics during Simulated Ventricular Fibrillation in a High-Resolution Rabbit Heart. BIOMED RESEARCH INTERNATIONAL 2015; 2015:720575. [PMID: 26587544 PMCID: PMC4637469 DOI: 10.1155/2015/720575] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 02/06/2015] [Indexed: 11/30/2022]
Abstract
The mechanisms underlying ventricular fibrillation (VF) are not well understood. The electrical activity on the heart surface during VF has been recorded extensively in the experimental setting and in some cases clinically; however, corresponding transmural activation patterns are prohibitively difficult to measure. In this paper, we use a high-resolution biventricular heart model to study three-dimensional electrical activity during fibrillation, focusing on the driving sources of VF: “filaments,” the organising centres of unstable reentrant scroll waves. We show, for the first time, specific 3D filament dynamics during simulated VF in a whole heart geometry that includes fine-scale anatomical structures. Our results suggest that transmural activity is much more complex than what would be expected from surface observations alone. We present examples of complex intramural activity, including filament breakup and reattachment, anchoring to the thin right ventricular apex; rapid transitions among various filament shapes; and filament lengths much greater than wall thickness. We also present evidence for anatomy playing a major role in VF development and coronary vessels and trabeculae influencing filament dynamics. Overall, our results indicate that intramural activity during simulated VF is extraordinarily complex and suggest that further investigation of 3D filaments is necessary to fully comprehend recorded surface patterns.
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28
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Garny A, Hunter PJ. OpenCOR: a modular and interoperable approach to computational biology. Front Physiol 2015; 6:26. [PMID: 25705192 PMCID: PMC4319394 DOI: 10.3389/fphys.2015.00026] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 01/16/2015] [Indexed: 11/26/2022] Open
Abstract
Computational biologists have been developing standards and formats for nearly two decades, with the aim of easing the description and exchange of experimental data, mathematical models, simulation experiments, etc. One of those efforts is CellML (cellml.org), an XML-based markup language for the encoding of mathematical models. Early CellML-based environments include COR and OpenCell. However, both of those tools have limitations and were eventually replaced with OpenCOR (opencor.ws). OpenCOR is an open source modeling environment that is supported on Windows, Linux and OS X. It relies on a modular approach, which means that all of its features come in the form of plugins. Those plugins can be used to organize, edit, simulate and analyze models encoded in the CellML format. We start with an introduction to CellML and two of its early adopters, which limitations eventually led to the development of OpenCOR. We then go onto describing the general philosophy behind OpenCOR, as well as describing its openness and its development process. Next, we illustrate various aspects of OpenCOR, such as its user interface and some of the plugins that come bundled with it (e.g., its editing and simulation plugins). Finally, we discuss some of the advantages and limitations of OpenCOR before drawing some concluding remarks.
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Affiliation(s)
- Alan Garny
- Auckland Bioengineering Institute, The University of AucklandAuckland, New Zealand
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29
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Driessen HE, Bourgonje VJA, van Veen TAB, Vos MA. New antiarrhythmic targets to control intracellular calcium handling. Neth Heart J 2014; 22:198-213. [PMID: 24733689 PMCID: PMC4016334 DOI: 10.1007/s12471-014-0549-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Sudden cardiac death due to ventricular arrhythmias is a major problem. Drug therapies to prevent SCD do not provide satisfying results, leading to the demand for new antiarrhythmic strategies. New targets include Ca2+/Calmodulin-dependent protein kinase II (CaMKII), the Na/Ca exchanger (NCX), the Ryanodine receptor (RyR, and its associated protein FKBP12.6 (Calstabin)) and the late component of the sodium current (INa-Late), all related to intracellular calcium (Ca2+) handling. In this review, drugs interfering with these targets (SEA-0400, K201, KN-93, W7, ranolazine, sophocarpine, and GS-967) are evaluated and their future as clinical compounds is considered. These new targets prove to be interesting; however more insight into long-term drug effects is necessary before clinical applicability becomes reality.
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Affiliation(s)
- H E Driessen
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM, Utrecht, the Netherlands,
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30
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Lascano EC, Said M, Vittone L, Mattiazzi A, Mundiña-Weilenmann C, Negroni JA. Role of CaMKII in post acidosis arrhythmias: a simulation study using a human myocyte model. J Mol Cell Cardiol 2013; 60:172-83. [PMID: 23624090 DOI: 10.1016/j.yjmcc.2013.04.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 03/15/2013] [Accepted: 04/15/2013] [Indexed: 02/08/2023]
Abstract
Postacidotic arrhythmias have been associated to increased sarcoplasmic reticulum (SR) Ca(2+) load and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) activation. However, the molecular mechanisms underlying these arrhythmias are still unclear. To better understand this process, acidosis produced by CO2 increase from 5% to 30%, resulting in intracellular pH (pHi) change from 7.15 to 6.7, was incorporated into a myocyte model of excitation-contraction coupling and contractility, including acidotic inhibition of L-type Ca(2+) channel (I(CaL)), Na(+)-Ca(2+) exchanger, Ca(2+) release through the SR ryanodine receptor (RyR2) (I(rel)), Ca(2+) reuptake by the SR Ca(2+) ATPase2a (I(up)), Na(+)-K(+) pump, K(+) efflux through the inward rectifier K(+) channel and the transient outward K(+) flow (I(to)) together with increased activity of the Na(+)-H(+) exchanger (I(NHE)). Simulated CaMKII regulation affecting I(rel), I(up), I(CaL), I(NHE) and I(to) was introduced in the model to partially compensate the acidosis outcome. Late Na(+) current increase by CaMKII was also incorporated. Using this scheme and assuming that diastolic Ca(2+) leak through the RyR2 was modulated by the resting state of this channel and the difference between SR and dyadic cleft [Ca(2+)], postacidotic delayed after depolarizations (DADs) were triggered upon returning to normal pHi after 6 min acidosis. The model showed that DADs depend on SR Ca(2+) load and on increased Ca(2+) leak through RyR2. This postacidotic arrhythmogenic pattern relies mainly on CaMKII effect on I(CaL) and I(up), since its individual elimination produced the highest DAD reduction. The model further revealed that during the return to normal pHi, DADs are fully determined by SR Ca(2+) load at the end of acidosis. Thereafter, DADs are maintained by SR Ca(2+) reloading by Ca(2+) influx through the reverse NCX mode during the time period in which [Na(+)]i is elevated.
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Affiliation(s)
- Elena C Lascano
- Department of Biology, Universidad Favaloro, Buenos Aires, Argentina.
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31
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Atrial fibrillation in the elderly: the potential contribution of reactive oxygen species. J Geriatr Cardiol 2013; 9:379-88. [PMID: 23341843 PMCID: PMC3545256 DOI: 10.3724/sp.j.1263.2012.08141] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 10/16/2012] [Accepted: 10/18/2012] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most commonly encountered cardiac arrhythmia, and is a significant source of healthcare expenditures throughout the world. It is an arrhythmia with a very clearly defined predisposition for individuals of advanced age, and this fact has led to intense study of the mechanistic links between aging and AF. By promoting oxidative damage to multiple subcellular and cellular structures, reactive oxygen species (ROS) have been shown to induce the intra- and extra-cellular changes necessary to promote the pathogenesis of AF. In addition, the generation and accumulation of ROS have been intimately linked to the cellular processes which underlie aging. This review begins with an overview of AF pathophysiology, and introduces the critical structures which, when damaged, predispose an otherwise healthy atrium to AF. The available evidence that ROS can lead to damage of these critical structures is then reviewed. Finally, the evidence linking the process of aging to the pathogenesis of AF is discussed.
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32
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Roberts BN, Yang PC, Behrens SB, Moreno JD, Clancy CE. Computational approaches to understand cardiac electrophysiology and arrhythmias. Am J Physiol Heart Circ Physiol 2012; 303:H766-83. [PMID: 22886409 DOI: 10.1152/ajpheart.01081.2011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Cardiac rhythms arise from electrical activity generated by precisely timed opening and closing of ion channels in individual cardiac myocytes. These impulses spread throughout the cardiac muscle to manifest as electrical waves in the whole heart. Regularity of electrical waves is critically important since they signal the heart muscle to contract, driving the primary function of the heart to act as a pump and deliver blood to the brain and vital organs. When electrical activity goes awry during a cardiac arrhythmia, the pump does not function, the brain does not receive oxygenated blood, and death ensues. For more than 50 years, mathematically based models of cardiac electrical activity have been used to improve understanding of basic mechanisms of normal and abnormal cardiac electrical function. Computer-based modeling approaches to understand cardiac activity are uniquely helpful because they allow for distillation of complex emergent behaviors into the key contributing components underlying them. Here we review the latest advances and novel concepts in the field as they relate to understanding the complex interplay between electrical, mechanical, structural, and genetic mechanisms during arrhythmia development at the level of ion channels, cells, and tissues. We also discuss the latest computational approaches to guiding arrhythmia therapy.
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Affiliation(s)
- Byron N Roberts
- Tri-Institutional MD-PhD Program, Physiology, Biophysics and Systems Biology Graduate Program, Weill Cornell Medical College/The Rockefeller University/Sloan-Kettering Cancer Institute, Weill Medical College of Cornell University, New York, New York, USA
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33
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Noble D, Garny A, Noble PJ. How the Hodgkin-Huxley equations inspired the Cardiac Physiome Project. J Physiol 2012; 590:2613-28. [PMID: 22473779 DOI: 10.1113/jphysiol.2011.224238] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Early modelling of cardiac cells (1960-1980) was based on extensions of the Hodgkin-Huxley nerve axon equations with additional channels incorporated, but after 1980 it became clear that processes other than ion channel gating were also critical in generating electrical activity. This article reviews the development of models representing almost all cell types in the heart, many different species, and the software tools that have been created to facilitate the cardiac Physiome Project.
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Affiliation(s)
- Denis Noble
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford OX1 3PT, UK.
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