1
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Luo Y, Safabakhsh S, Palumbo A, Fiset C, Shen C, Parker J, Foster LJ, Laksman Z. Sex-Based Mechanisms of Cardiac Development and Function: Applications for Induced-Pluripotent Stem Cell Derived-Cardiomyocytes. Int J Mol Sci 2024; 25:5964. [PMID: 38892161 PMCID: PMC11172775 DOI: 10.3390/ijms25115964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 05/27/2024] [Accepted: 05/27/2024] [Indexed: 06/21/2024] Open
Abstract
Males and females exhibit intrinsic differences in the structure and function of the heart, while the prevalence and severity of cardiovascular disease vary in the two sexes. However, the mechanisms of this sex-based dimorphism are yet to be elucidated. Sex chromosomes and sex hormones are the main contributors to sex-based differences in cardiac physiology and pathophysiology. In recent years, the advances in induced pluripotent stem cell-derived cardiac models and multi-omic approaches have enabled a more comprehensive understanding of the sex-specific differences in the human heart. Here, we provide an overview of the roles of these two factors throughout cardiac development and explore the sex hormone signaling pathways involved. We will also discuss how the employment of stem cell-based cardiac models and single-cell RNA sequencing help us further investigate sex differences in healthy and diseased hearts.
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Affiliation(s)
- Yinhan Luo
- Centre for Heart Lung Innovation, Department of Medicine, University of British Columbia, Vancouver, BC V6Z 1Y6, Canada; (Y.L.); (J.P.)
| | - Sina Safabakhsh
- Centre for Cardiovascular Innovation, Division of Cardiology, University of British Columbia, Vancouver, BC V6T 2A1, Canada;
| | - Alessia Palumbo
- Michael Smith Laboratories, Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; (A.P.); (L.J.F.)
| | - Céline Fiset
- Research Centre, Montreal Heart Institute, Faculty of Pharmacy, Université de Montréal, Montréal, QC H1T 1C8, Canada;
| | - Carol Shen
- Department of Integrated Sciences, University of British Columbia, Vancouver, BC V6T 1Z2, Canada;
| | - Jeremy Parker
- Centre for Heart Lung Innovation, Department of Medicine, University of British Columbia, Vancouver, BC V6Z 1Y6, Canada; (Y.L.); (J.P.)
| | - Leonard J. Foster
- Michael Smith Laboratories, Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; (A.P.); (L.J.F.)
| | - Zachary Laksman
- Centre for Heart Lung Innovation, Department of Medicine, University of British Columbia, Vancouver, BC V6Z 1Y6, Canada; (Y.L.); (J.P.)
- Centre for Cardiovascular Innovation, Division of Cardiology, University of British Columbia, Vancouver, BC V6T 2A1, Canada;
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2
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Zhang X, Wu Y, Smith C, Louch WE, Morotti S, Dobrev D, Grandi E, Ni H. Enhanced Ca2+-Driven Arrhythmias in Female Patients with Atrial Fibrillation: Insights from Computational Modeling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.04.583217. [PMID: 38496584 PMCID: PMC10942295 DOI: 10.1101/2024.03.04.583217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
BACKGROUND AND AIMS Substantial sex-based differences have been reported in atrial fibrillation (AF), with female patients experiencing worse symptoms, increased complications from drug side effects or ablation, and elevated risk of AF-related stroke and mortality. Recent studies revealed sex-specific alterations in AF-associated Ca2+ dysregulation, whereby female cardiomyocytes more frequently exhibit potentially proarrhythmic Ca2+-driven instabilities compared to male cardiomyocytes. In this study, we aim to gain a mechanistic understanding of the Ca2+-handling disturbances and Ca2+-driven arrhythmogenic events in males vs females and establish their responses to Ca2+-targeted interventions. METHODS AND RESULTS We incorporated known sex differences and AF-associated changes in the expression and phosphorylation of key Ca2+-handling proteins and in ultrastructural properties and dimensions of atrial cardiomyocytes into our recently developed 3D atrial cardiomyocyte model that couples electrophysiology with spatially detailed Ca2+-handling processes. Our simulations of quiescent cardiomyocytes show increased incidence of Ca2+ sparks in female vs male myocytes in AF, in agreement with previous experimental reports. Additionally, our female model exhibited elevated propensity to develop pacing-induced spontaneous Ca2+ releases (SCRs) and augmented beat-to-beat variability in action potential (AP)-elicited Ca2+ transients compared with the male model. Parameter sensitivity analysis uncovered precise arrhythmogenic contributions of each component that was implicated in sex and/or AF alterations. Specifically, increased ryanodine receptor phosphorylation in female AF cardiomyocytes emerged as the major SCR contributor, while reduced L-type Ca2+ current was protective against SCRs for male AF cardiomyocytes. Furthermore, simulations of tentative Ca2+-targeted interventions identified potential strategies to attenuate Ca2+-driven arrhythmogenic events in female atria (e.g., t-tubule restoration, and inhibition of ryanodine receptor and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase), and revealed enhanced efficacy when applied in combination. CONCLUSIONS Our sex-specific computational models of human atrial cardiomyocytes uncover increased propensity to Ca2+-driven arrhythmogenic events in female compared to male atrial cardiomyocytes in AF, and point to combined Ca2+-targeted interventions as promising approaches to treat AF in female patients. Our study establishes that AF treatment may benefit from sex-dependent strategies informed by sex-specific mechanisms.
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3
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Emerson JI, Ariel P, Shi W, Conlon FL. Sex Differences in Mouse Cardiac Electrophysiology Revealed by Simultaneous Imaging of Excitation-Contraction Coupling. J Cardiovasc Dev Dis 2023; 10:479. [PMID: 38132647 PMCID: PMC10743987 DOI: 10.3390/jcdd10120479] [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: 11/06/2023] [Revised: 11/22/2023] [Accepted: 11/27/2023] [Indexed: 12/23/2023] Open
Abstract
Males and females differ in the basic anatomy and physiology of the heart. Sex differences are evident in cardiac repolarization in humans; women have longer corrected QT and JT intervals. However, the molecular mechanisms that lead to these differences are incompletely understood. Here, we present that, like in humans, sex differences in QT and JT intervals exist in mouse models; female mice had longer corrected QT and JT intervals compared with age-matched males. To further understand the molecular underpinning of these sex differences, we developed a novel technology using fluorescent confocal microscopy that allows the simultaneous visualization of action potential, Ca2+ transients, and contractions in isolated cardiomyocytes at a high temporal resolution. From this approach, we uncovered that females at baseline have increased action potential duration, decreased Ca2+ release and reuptake rates, and decreased contraction and relaxation velocities compared with males. Additionally, males had a shorter overall time from action potential onset to peak contraction. In aggregate, our studies uncovered male and female differences in excitation-contraction coupling that account for differences observed in the EKG. Overall, a better understanding of sex differences in electrophysiology is essential for equitably treating cardiac disease.
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Affiliation(s)
- James I. Emerson
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA;
| | - Pablo Ariel
- Microscopy Services Laboratory, Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA;
| | - Wei Shi
- Department of Biology and Genetics, McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA;
| | - Frank L. Conlon
- Department of Biology and Genetics, McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA;
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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4
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Calvet C, Seebeck P. What to consider for ECG in mice-with special emphasis on telemetry. Mamm Genome 2023; 34:166-179. [PMID: 36749381 PMCID: PMC10290603 DOI: 10.1007/s00335-023-09977-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Accepted: 01/16/2023] [Indexed: 02/08/2023]
Abstract
Genetically or surgically altered mice are commonly used as models of human cardiovascular diseases. Electrocardiography (ECG) is the gold standard to assess cardiac electrophysiology as well as to identify cardiac phenotypes and responses to pharmacological and surgical interventions. A variety of methods are used for mouse ECG acquisition under diverse conditions, making it difficult to compare different results. Non-invasive techniques allow only short-term data acquisition and are prone to stress or anesthesia related changes in cardiac activity. Telemetry offers continuous long-term acquisition of ECG data in conscious freely moving mice in their home cage environment. Additionally, it allows acquiring data 24/7 during different activities, can be combined with different challenges and most telemetry systems collect additional physiological parameters simultaneously. However, telemetry transmitters require surgical implantation, the equipment for data acquisition is relatively expensive and analysis of the vast number of ECG data is challenging and time-consuming. This review highlights the limits of non-invasive methods with respect to telemetry. In particular, primary screening using non-invasive methods can give a first hint; however, subtle cardiac phenotypes might be masked or compensated due to anesthesia and stress during these procedures. In addition, we detail the key differences between the mouse and human ECG. It is crucial to consider these differences when analyzing ECG data in order to properly translate the insights gained from murine models to human conditions.
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Affiliation(s)
- Charlotte Calvet
- Zurich Integrative Rodent Physiology (ZIRP), University of Zurich, Zurich, Switzerland
| | - Petra Seebeck
- Zurich Integrative Rodent Physiology (ZIRP), University of Zurich, Zurich, Switzerland
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5
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Prajapati C, Koivumäki J, Pekkanen-Mattila M, Aalto-Setälä K. Sex differences in heart: from basics to clinics. Eur J Med Res 2022; 27:241. [PMID: 36352432 PMCID: PMC9647968 DOI: 10.1186/s40001-022-00880-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 10/24/2022] [Indexed: 11/11/2022] Open
Abstract
Sex differences exist in the structure and function of human heart. The patterns of ventricular repolarization in normal electrocardiograms (ECG) differ in men and women: men ECG pattern displays higher T-wave amplitude and increased ST angle. Generally, women have longer QT duration because of reduced repolarization reserve, and thus, women are more susceptible for the occurrence of torsades de pointes associated with drugs prolonging ventricular repolarization. Sex differences are also observed in the prevalence, penetrance and symptom severity, and also in the prognosis of cardiovascular disease. Generally, women live longer, have less clinical symptoms of cardiac diseases, and later onset of symptoms than men. Sex hormones also play an important role in regulating ventricular repolarization, suggesting that hormones directly influence various cellular functions and adrenergic regulation. From the clinical perspective, sex-based differences in heart physiology are widely recognized, but in daily practice, cardiac diseases are often underdiagnosed and untreated in the women. The underlying mechanisms of sex differences are, however, poorly understood. Here, we summarize sex-dependent differences in normal cardiac physiology, role of sex hormones, and differences in drug responses. Furthermore, we also discuss the importance of human induced pluripotent stem cell-derived cardiomyocytes in further understanding the mechanism of differences in women and men.
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Affiliation(s)
- Chandra Prajapati
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön Katu 34, 33520 Tampere, Finland
| | - Jussi Koivumäki
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön Katu 34, 33520 Tampere, Finland
| | - Mari Pekkanen-Mattila
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön Katu 34, 33520 Tampere, Finland
| | - Katriina Aalto-Setälä
- Faculty of Medicine and Health Technology, Tampere University, Arvo Ylpön Katu 34, 33520 Tampere, Finland
- Heart Center, Tampere University Hospital, Ensitie 4, 33520 Tampere, Finland
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6
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Oknińska M, Mączewski M, Mackiewicz U. Ventricular arrhythmias in acute myocardial ischaemia-Focus on the ageing and sex. Ageing Res Rev 2022; 81:101722. [PMID: 36038114 DOI: 10.1016/j.arr.2022.101722] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 08/17/2022] [Accepted: 08/20/2022] [Indexed: 01/31/2023]
Abstract
Annually, approximately 17 million people die from cardiovascular diseases worldwide, half of them suddenly. The most common direct cause of sudden cardiac death is ventricular arrhythmia triggered by an acute coronary syndrome (ACS). The study summarizes the knowledge of the mechanisms of arrhythmia onset during ACS in humans and in animal models and factors that may influence the susceptibility to life-threatening arrhythmias during ACS with particular focus on the age and sex. The real impact of age and sex on the arrhythmic susceptibility within the setting of acute ischaemia is masked by the fact that ACSs result from coronary artery disease appearing with age much earlier among men than among women. However, results of researches show that in ageing process changes with potential pro-arrhythmic significance, such as increased fibrosis, cardiomyocyte hypertrophy, decrease number of gap junction channels, disturbances of the intracellular Ca2+ signalling or changes in electrophysiological parameters, occur independently of the development of cardiovascular diseases and are more severe in male individuals. A review of the literature also indicates a marked paucity of research in this area in female and elderly individuals. Greater awareness of sex differences in the aging process could help in the development of personalized prevention methods targeting potential pro-arrhythmic factors in patients of both sexes to reduce mortality during the acute phase of myocardial infarction. This is especially important in an era of aging populations in which women will predominate due to their longer lifespan.
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Affiliation(s)
- Marta Oknińska
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Marymoncka 99/103, 01-813 Warsaw, Poland
| | - Michał Mączewski
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Marymoncka 99/103, 01-813 Warsaw, Poland
| | - Urszula Mackiewicz
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Marymoncka 99/103, 01-813 Warsaw, Poland.
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7
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Thibault S, Ton AT, Huynh F, Fiset C. Connexin Lateralization Contributes to Male Susceptibility to Atrial Fibrillation. Int J Mol Sci 2022; 23:ijms231810696. [PMID: 36142603 PMCID: PMC9506269 DOI: 10.3390/ijms231810696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 09/06/2022] [Accepted: 09/09/2022] [Indexed: 11/16/2022] Open
Abstract
Men have a higher risk of developing atrial fibrillation (AF) than women, though the reason for this is unknown. Here, we compared atrial electrical and structural properties in male and female mice and explored the contribution of sex hormones. Cellular electrophysiological studies revealed that action potential configuration, Na+ and K+ currents were similar in atrial myocytes from male and female mice (4–5 months). Immunofluorescence showed that male atrial myocytes had more lateralization of connexins 40 (63 ± 4%) and 43 (66 ± 4%) than females (Cx40: 45 ± 4%, p = 0.006; Cx43: 44 ± 4%, p = 0.002), with no difference in mRNA expression. Atrial mass was significantly higher in males. Atrial myocyte dimensions were also larger in males. Atrial fibrosis was low and similar between sexes. Orchiectomy (ORC) abolished sex differences in AF susceptibility (M: 65%; ORC: 38%, p = 0.050) by reducing connexin lateralization and myocyte dimensions. Ovariectomy (OVX) did not influence AF susceptibility (F: 42%; OVX: 33%). This study shows that prior to the development of age-related remodeling, male mice have more connexin lateralization and larger atria and atrial myocyte than females. Orchiectomy reduced AF susceptibility in males by decreasing connexin lateralization and atrial myocyte size, supporting a role for androgens. These sex differences in AF substrates may contribute to male predisposition to AF.
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Affiliation(s)
- Simon Thibault
- Research Center, Montreal Heart Institute, Montreal, QC H1T 1C8, Canada
- Faculty of Pharmacy, Université de Montreal, Montreal, QC H3T 1J4, Canada
| | - Anh-Tuan Ton
- Research Center, Montreal Heart Institute, Montreal, QC H1T 1C8, Canada
- Faculty of Pharmacy, Université de Montreal, Montreal, QC H3T 1J4, Canada
| | - François Huynh
- Research Center, Montreal Heart Institute, Montreal, QC H1T 1C8, Canada
- Faculty of Pharmacy, Université de Montreal, Montreal, QC H3T 1J4, Canada
| | - Céline Fiset
- Research Center, Montreal Heart Institute, Montreal, QC H1T 1C8, Canada
- Faculty of Pharmacy, Université de Montreal, Montreal, QC H3T 1J4, Canada
- Correspondence: ; Tel.: +1-514-3763330
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8
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Demers J, Ton A, Huynh F, Thibault S, Ducharme A, Paradis P, Nemer M, Fiset C. Atrial Electrical Remodeling in Mice With Cardiac‐Specific Overexpression of Angiotensin II Type 1 Receptor. J Am Heart Assoc 2022; 11:e023974. [PMID: 35435021 PMCID: PMC9238446 DOI: 10.1161/jaha.121.023974] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background
Elevated angiotensin II levels are thought to play an important role in atrial electrical and structural remodeling associated with atrial fibrillation. However, the mechanisms by which this remodeling occurs are still unclear. Accordingly, we explored the effects of angiotensin II on atrial remodeling using transgenic mice overexpressing angiotensin II type 1 receptor (AT1R) specifically in cardiomyocytes.
Methods and Results
Voltage‐clamp techniques, surface ECG, programmed electrical stimulations along with quantitative polymerase chain reaction, Western blot, and Picrosirius red staining were used to compare the atrial phenotype of AT1R mice and their controls at 50 days and 6 months. Atrial cell capacitance and fibrosis were increased only in AT1R mice at 6 months, indicating the presence of structural remodeling. Ca
2+
(
I
CaL
) and K
+
currents were not altered by AT1R overexpression (AT1R at 50 days). However,
I
CaL
density and Ca
V
1.2 messenger RNA expression were reduced by structural remodeling (AT1R at 6 months). Conversely, Na
+
current (
I
Na
) was reduced (−65%) by AT1R overexpression (AT1R at 50 days) and the presence of structural remodeling (AT1R at 6 months) yields no further effect. The reduced
I
Na
density was not explained by lower Na
V
1.5 expression but was rather associated with an increase in sarcolemmal protein kinase C alpha expression in the atria, suggesting that chronic AT1R activation reduced
I
Na
through protein kinase C alpha activation. Furthermore, connexin 40 expression was reduced in AT1R mice at 50 days and 6 months. These changes were associated with delayed atrial conduction time, as evidenced by prolonged P‐wave duration.
Conclusions
Chronic AT1R activation leads to slower atrial conduction caused by reduced
I
Na
density and connexin 40 expression.
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Affiliation(s)
- Julie Demers
- Research Center Montreal Heart Institute Montréal Québec Canada
- Faculty of Pharmacy Université de Montréal Montréal Québec Canada
| | - Anh‐Tuan Ton
- Research Center Montreal Heart Institute Montréal Québec Canada
- Faculty of Pharmacy Université de Montréal Montréal Québec Canada
| | - François Huynh
- Research Center Montreal Heart Institute Montréal Québec Canada
- Faculty of Pharmacy Université de Montréal Montréal Québec Canada
| | - Simon Thibault
- Research Center Montreal Heart Institute Montréal Québec Canada
- Faculty of Pharmacy Université de Montréal Montréal Québec Canada
| | - Anique Ducharme
- Research Center Montreal Heart Institute Montréal Québec Canada
- Faculty of Medicine Université de Montréal Montréal Québec Canada
| | | | | | - Céline Fiset
- Research Center Montreal Heart Institute Montréal Québec Canada
- Faculty of Pharmacy Université de Montréal Montréal Québec Canada
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9
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Macías Á, Díaz-Larrosa JJ, Blanco Y, Fanjul V, González-Gómez C, Gonzalo P, Andrés-Manzano MJ, da Rocha AM, Ponce-Balbuena D, Allan A, Filgueiras-Rama D, Jalife J, Andrés V. Paclitaxel mitigates structural alterations and cardiac conduction system defects in a mouse model of Hutchinson-Gilford progeria syndrome. Cardiovasc Res 2022; 118:503-516. [PMID: 33624748 PMCID: PMC8803078 DOI: 10.1093/cvr/cvab055] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 11/11/2020] [Accepted: 02/09/2021] [Indexed: 12/12/2022] Open
Abstract
AIMS Hutchinson-Gilford progeria syndrome (HGPS) is an ultrarare laminopathy caused by expression of progerin, a lamin A variant, also present at low levels in non-HGPS individuals. HGPS patients age and die prematurely, predominantly from cardiovascular complications. Progerin-induced cardiac repolarization defects have been described previously, although the underlying mechanisms are unknown. METHODS AND RESULTS We conducted studies in heart tissue from progerin-expressing LmnaG609G/G609G (G609G) mice, including microscopy, intracellular calcium dynamics, patch-clamping, in vivo magnetic resonance imaging, and electrocardiography. G609G mouse cardiomyocytes showed tubulin-cytoskeleton disorganization, t-tubular system disruption, sarcomere shortening, altered excitation-contraction coupling, and reductions in ventricular thickening and cardiac index. G609G mice exhibited severe bradycardia, and significant alterations of atrio-ventricular conduction and repolarization. Most importantly, 50% of G609G mice had altered heart rate variability, and sinoatrial block, both significant signs of premature cardiac aging. G609G cardiomyocytes had electrophysiological alterations, which resulted in an elevated action potential plateau and early afterdepolarization bursting, reflecting slower sodium current inactivation and long Ca+2 transient duration, which may also help explain the mild QT prolongation in some HGPS patients. Chronic treatment with low-dose paclitaxel ameliorated structural and functional alterations in G609G hearts. CONCLUSIONS Our results demonstrate that tubulin-cytoskeleton disorganization in progerin-expressing cardiomyocytes causes structural, cardiac conduction, and excitation-contraction coupling defects, all of which can be partially corrected by chronic treatment with low dose paclitaxel.
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MESH Headings
- Action Potentials/drug effects
- Animals
- Anti-Arrhythmia Agents/pharmacology
- Arrhythmias, Cardiac/drug therapy
- Arrhythmias, Cardiac/genetics
- Arrhythmias, Cardiac/metabolism
- Arrhythmias, Cardiac/physiopathology
- Cytoskeleton/drug effects
- Cytoskeleton/metabolism
- Cytoskeleton/pathology
- Disease Models, Animal
- Excitation Contraction Coupling/drug effects
- Female
- Genetic Predisposition to Disease
- Heart Conduction System/drug effects
- Heart Conduction System/metabolism
- Heart Conduction System/physiopathology
- Heart Rate/drug effects
- Lamin Type A/genetics
- Lamin Type A/metabolism
- Male
- Mice, Mutant Strains
- Mutation
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Paclitaxel/pharmacology
- Progeria/drug therapy
- Progeria/genetics
- Progeria/metabolism
- Progeria/physiopathology
- Refractory Period, Electrophysiological/drug effects
- Swine
- Swine, Miniature
- Tubulin/metabolism
- Mice
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Affiliation(s)
- Álvaro Macías
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - J Jaime Díaz-Larrosa
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Yaazan Blanco
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Víctor Fanjul
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Cristina González-Gómez
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
- CIBER en Enfermedades Cardiovasculares (CIBER-CV), Madrid, Spain
| | - Pilar Gonzalo
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - María Jesús Andrés-Manzano
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
- CIBER en Enfermedades Cardiovasculares (CIBER-CV), Madrid, Spain
| | - Andre Monteiro da Rocha
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109-2800, USA
| | - Daniela Ponce-Balbuena
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109-2800, USA
| | - Andrew Allan
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109-2800, USA
| | - David Filgueiras-Rama
- CIBER en Enfermedades Cardiovasculares (CIBER-CV), Madrid, Spain
- Department of Cardiology, Cardiac Electrophysiology Unit, Hospital Clínico San Carlos, 28040 Madrid, Spain
- Myocardial, Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - José Jalife
- CIBER en Enfermedades Cardiovasculares (CIBER-CV), Madrid, Spain
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48109-2800, USA
- Myocardial, Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Vicente Andrés
- Vascular Pathophysiology Area, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
- CIBER en Enfermedades Cardiovasculares (CIBER-CV), Madrid, Spain
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10
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Wu X, Hoeker GS, Blair GA, King DR, Gourdie RG, Weinberg SH, Poelzing S. Hypernatremia and intercalated disc edema synergistically exacerbate long-QT syndrome type 3 phenotype. Am J Physiol Heart Circ Physiol 2021; 321:H1042-H1055. [PMID: 34623182 DOI: 10.1152/ajpheart.00366.2021] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cardiac voltage-gated sodium channel gain-of-function prolongs repolarization in the long-QT syndrome type 3 (LQT3). Previous studies suggest that narrowing the perinexus within the intercalated disc, leading to rapid sodium depletion, attenuates LQT3-associated action potential duration (APD) prolongation. However, it remains unknown whether extracellular sodium concentration modulates APD prolongation during sodium channel gain-of-function. We hypothesized that elevated extracellular sodium concentration and widened perinexus synergistically prolong APD in LQT3. LQT3 was induced with sea anemone toxin (ATXII) in Langendorff-perfused guinea pig hearts (n = 34). Sodium concentration was increased from 145 to 160 mM. Perinexal expansion was induced with mannitol or the sodium channel β1-subunit adhesion domain antagonist (βadp1). Epicardial ventricular action potentials were optically mapped. Individual and combined effects of varying clefts and sodium concentrations were simulated in a computational model. With ATXII, both mannitol and βadp1 significantly widened the perinexus and prolonged APD, respectively. The elevated sodium concentration alone significantly prolonged APD as well. Importantly, the combination of elevated sodium concentration and perinexal widening synergistically prolonged APD. Computational modeling results were consistent with animal experiments. Concurrently elevating extracellular sodium and increasing intercalated disc edema prolongs repolarization more than the individual interventions alone in LQT3. This synergistic effect suggests an important clinical implication that hypernatremia in the presence of cardiac edema can markedly increase LQT3-associated APD prolongation. Therefore, to our knowledge, this is the first study to provide evidence of a tractable and effective strategy to mitigate LQT3 phenotype by means of managing sodium levels and preventing cardiac edema in patients.NEW & NOTEWORTHY This is the first study to demonstrate that the long-QT syndrome type 3 (LQT3) phenotype can be exacerbated or concealed by regulating extracellular sodium concentrations and/or the intercalated disc separation. The animal experiments and computational modeling in the current study reveal a critically important clinical implication: sodium dysregulation in the presence of edema within the intercalated disc can markedly increase the risk of arrhythmia in LQT3. These findings strongly suggest that maintaining extracellular sodium within normal physiological limits may be an effective and inexpensive therapeutic option for patients with congenital or acquired sodium channel gain-of-function diseases.
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Affiliation(s)
- Xiaobo Wu
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Gregory S Hoeker
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Grace A Blair
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - D Ryan King
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Robert G Gourdie
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Seth H Weinberg
- Department of Biomedical Engineering, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
| | - Steven Poelzing
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
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11
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Naumenko N, Mutikainen M, Holappa L, Ruas JL, Tuomainen T, Tavi P. PGC-1α deficiency reveals sex-specific links between cardiac energy metabolism and EC-coupling during development of heart failure in mice. Cardiovasc Res 2021; 118:1520-1534. [PMID: 34086875 PMCID: PMC9074965 DOI: 10.1093/cvr/cvab188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 06/03/2021] [Indexed: 12/24/2022] Open
Abstract
Aims Biological sex has fundamental effects on mammalian heart physiology and pathogenesis. While it has been established that female sex is a protective factor against most cardiovascular diseases (CVDs), this beneficial effect may involve pathways associated with cardiac energy metabolism. Our aim was to elucidate the role of transcriptional coactivator PGC-1α in sex dimorphism of heart failure (HF) development. Methods and results Here, we show that mice deficient in cardiac expression of the peroxisome proliferator-activated receptor gamma (PPAR-γ) coactivator-1α (PGC-1α) develop dilated HF associated with changes in aerobic and anaerobic metabolism, calcium handling, cell structure, electrophysiology, as well as gene expression. These cardiac changes occur in both sexes, but female mice develop an earlier and more severe structural and functional phenotype associated with dyssynchronous local calcium release resulting from disruption of t-tubular structures of the cardiomyocytes. Conclusions These data reveal that the integrity of the subcellular Ca2+ release and uptake machinery is dependent on energy metabolism and that female hearts are more prone to suffer from contractile dysfunction in conditions with compromised production of cellular energy. Furthermore, these findings suggest that PGC-1α is a central mediator of sex-specific differences in heart function and CVD susceptibility.
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Affiliation(s)
- Nikolay Naumenko
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Maija Mutikainen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Lari Holappa
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Jorge L Ruas
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Tomi Tuomainen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Pasi Tavi
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
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12
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Rodgers JL, Vanthenapalli S, Panguluri SK. Electrical remodeling and cardiotoxicity precedes structural and functional remodeling of mouse hearts under hyperoxia treatment. J Cell Physiol 2021; 236:4482-4495. [PMID: 33230829 DOI: 10.1002/jcp.30165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 10/27/2020] [Accepted: 11/05/2020] [Indexed: 01/16/2023]
Abstract
Clinical reports suggest a high incidence of ICU mortality with the use of hyperoxia during mechanical ventilation in patients. Our laboratory is pioneer in studying effect of hyperoxia on cardiac pathophysiology. In this study for the first time, we are reporting the sequence of cardiac pathophysiological events in mice under hyperoxic conditions in time-dependent manner. C57BL/6J male mice, aged 8-10 weeks, were treated with either normal air or >90% oxygen for 24, 48, and 72 h. Following normal air or hyperoxia treatment, physical, biochemical, functional, electrical, and molecular parameters were analyzed. Our data showed that significant reduction of body weight observed as early as 24 h hyperoxia treatment, whereas, no significant changes in heart weight until 72 h. Although we do not see any fibrosis in these hearts, but observed significant increase in cardiomyocyte size with hyperoxia treatment in time-dependent manner. Our data also demonstrated that arrhythmias were present in mice at 24 h hyperoxia, and worsened comparatively after 48 and 72 h. Echocardiogram data confirmed cardiac dysfunction in time-dependent manner. Dysregulation of ion channels such as Kv4.2 and KChIP2; and serum cardiac markers confirmed that hyperoxia-induced effects worsen with each time point. From these observations, it is evident that electrical remodeling precedes structural remodeling, both of which gets worse with length of hyperoxia exposure, therefore shorter periods of hyperoxia exposure is always beneficial for better outcome in ICU/critical care units.
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Affiliation(s)
- Jennifer L Rodgers
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida, USA
| | - Sahit Vanthenapalli
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida, USA
| | - Siva K Panguluri
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida, USA
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13
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Costa S, Saguner AM, Gasperetti A, Akdis D, Brunckhorst C, Duru F. The Link Between Sex Hormones and Susceptibility to Cardiac Arrhythmias: From Molecular Basis to Clinical Implications. Front Cardiovasc Med 2021; 8:644279. [PMID: 33681311 PMCID: PMC7925388 DOI: 10.3389/fcvm.2021.644279] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 01/27/2021] [Indexed: 12/30/2022] Open
Abstract
It is well-known that gender is an independent risk factor for some types of cardiac arrhythmias. For example, males have a greater prevalence of atrial fibrillation and the Brugada Syndrome. In contrast, females are at increased risk for the Long QT Syndrome. However, the underlying mechanisms of these gender differences have not been fully identified. Recently, there has been accumulating evidence indicating that sex hormones may have a significant impact on the cardiac rhythm. In this review, we describe in-depth the molecular interactions between sex hormones and the cardiac ion channels, as well as the clinical implications of these interactions on the cardiac conduction system, in order to understand the link between these hormones and the susceptibility to arrhythmias.
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Affiliation(s)
- Sarah Costa
- Arrhythmia and Electrophysiology, Department of Cardiology, University Heart Center, Zurich, Switzerland
| | - Ardan M Saguner
- Arrhythmia and Electrophysiology, Department of Cardiology, University Heart Center, Zurich, Switzerland
| | - Alessio Gasperetti
- Arrhythmia and Electrophysiology, Department of Cardiology, University Heart Center, Zurich, Switzerland.,Cardiac Arrhythmia Service, Department of Cardiology, Johns Hopkins Hospital, Baltimore, MD, United States
| | - Deniz Akdis
- Arrhythmia and Electrophysiology, Department of Cardiology, University Heart Center, Zurich, Switzerland
| | - Corinna Brunckhorst
- Arrhythmia and Electrophysiology, Department of Cardiology, University Heart Center, Zurich, Switzerland
| | - Firat Duru
- Arrhythmia and Electrophysiology, Department of Cardiology, University Heart Center, Zurich, Switzerland.,Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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14
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Bozdogan O, Bozcaarmutlu A, Kaya ST, Sapmaz C, Ozarslan TO, Eksioglu D, Yasar S. Decreasing myocardial estrogen receptors and antioxidant activity may be responsible for increasing ischemia- and reperfusion-induced ventricular arrhythmia in older female rats. Life Sci 2021; 271:119190. [PMID: 33571518 DOI: 10.1016/j.lfs.2021.119190] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 01/21/2021] [Accepted: 02/06/2021] [Indexed: 11/18/2022]
Abstract
AIMS This study aimed to investigate the relationship between ischemia- and reperfusion-induced arrhythmia and blood serum estrogen levels, myocardial estrogen receptor levels, antioxidant enzyme activities, and the effects of the estrogen receptor blocker, fulvestrant (ICI 182 780). MAIN METHODS A total of 102 female Sprague-Dawley rats of different ages (2-3, 6-7, 14-15, and 20-21 months) were used in this study. Myocardial ischemia was produced by ligation of the descending branch of the left anterior descending coronary artery, and reperfusion was produced by releasing this artery. An electrocardiogram (ECG) and blood pressure were recorded for 6 min of ischemia and 6 min of reperfusion. The levels of superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT), estrogen receptor α (ERα), and estrogen receptor β (ERβ) in myocardial tissue and 17 beta-estradiol (E2) in blood serum were measured via enzyme-linked immunosorbent assay (ELISA). The results were compared using a Mann-Whitney U test, one-way analysis of variance (ANOVA), and a student's t-test. KEY FINDINGS It is not the changes in serum estrogen levels but the decreasing myocardial estrogen receptors and antioxidant activities that could be responsible for the occurrence of more severe arrhythmia in response to reperfusion in older female rats. SIGNIFICANCE The death rate due to a heart attack in younger men is higher than in women. However, it equalizes after the menopausal stage in women. In this study, the reason for the increasing sudden post-menopausal death rate in women was investigated experimentally.
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Affiliation(s)
- Omer Bozdogan
- Department of Biology, Faculty of Arts and Science, Bolu Abant Izzet Baysal University, Bolu, Turkey.
| | - Azra Bozcaarmutlu
- Department of Chemistry, Faculty of Arts and Science, Bolu Abant Izzet Baysal University, Bolu, Turkey
| | - Salih Tunc Kaya
- Department of Biology, Faculty of Arts and Science, Düzce University, Düzce, Turkey
| | - Canan Sapmaz
- Department of Chemistry, Faculty of Arts and Science, Bolu Abant Izzet Baysal University, Bolu, Turkey
| | - Talat Ogulcan Ozarslan
- Department of Infectious Diseases and Clinical Microbiology, Institute of Health Sciences, Bolu Abant Izzet Baysal University, Bolu, Turkey
| | - Didem Eksioglu
- Department of Biology, Faculty of Arts and Science, Bolu Abant Izzet Baysal University, Bolu, Turkey
| | - Selcuk Yasar
- Program of Medical Laboratory Techniques, Vocational School of Health Services, Istanbul Esenyurt University, Istanbul, Turkey
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15
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Long V, Fiset C. Contribution of estrogen to the pregnancy-induced increase in cardiac automaticity. J Mol Cell Cardiol 2020; 147:27-34. [PMID: 32798536 DOI: 10.1016/j.yjmcc.2020.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 07/21/2020] [Accepted: 08/06/2020] [Indexed: 12/21/2022]
Abstract
BACKGROUND The heart rate progressively increases throughout pregnancy, reaching a maximum in the third trimester. This elevated heart rate is also present in pregnant mice and is associated with accelerated automaticity, higher density of the pacemaker current If and changes in Ca2+ homeostasis in sinoatrial node (SAN) cells. Strong evidence has also been provided showing that 17β-estradiol (E2) and estrogen receptor α (ERα) regulate heart rate. Accordingly, we sought to determine whether E2 levels found in late pregnancy cause the increased cardiac automaticity associated with pregnancy. METHODS AND RESULTS Voltage- and current-clamp experiments were carried out on SAN cells isolated from female mice lacking estrogen receptor alpha (ERKOα) or beta (ERKOβ) receiving chronic E2 treatment mimicking late pregnancy concentrations. E2 treatment significantly increased the action potential rate (284 ± 24 bpm, +E2 354 ± 23 bpm, p = 0.040) and the density of If (+52%) in SAN cells from ERKOβ mice. However, If density remains unchanged in SAN cells from E2-treated ERKOα mice. Additionally, E2 also increased If density (+67%) in nodal-like human-induced pluripotent stem cell-derived cardiomyocytes (N-hiPSC-CM), recapitulating in a human SAN cell model the effect produced in mice. However, the L-type calcium current (ICaL) and Ca2+ transients, examined using N-hiPSC-CM and SAN cells respectively, were not affected by E2, indicating that other mechanisms contribute to changes observed in these parameters during pregnancy. CONCLUSION The accelerated SAN automaticity observed in E2-treated ERKOβ mice is explained by an increased If density mediated by ERα, demonstrating that E2 plays a major role in regulating SAN function during pregnancy.
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Affiliation(s)
- Valérie Long
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal H1T 1C8, Québec, Canada; Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.
| | - Céline Fiset
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal H1T 1C8, Québec, Canada; Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.
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16
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Jiao L, Machuki JO, Wu Q, Shi M, Fu L, Adekunle AO, Tao X, Xu C, Hu X, Yin Z, Sun H. Estrogen and calcium handling proteins: new discoveries and mechanisms in cardiovascular diseases. Am J Physiol Heart Circ Physiol 2020; 318:H820-H829. [PMID: 32083972 DOI: 10.1152/ajpheart.00734.2019] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Estrogen deficiency is considered to be an important factor leading to cardiovascular diseases (CVDs). Indeed, the prevalence of CVDs in postmenopausal women exceeds that of premenopausal women and men of the same age. Recent research findings provide evidence that estrogen plays a pivotal role in the regulation of calcium homeostasis and therefore fine-tunes normal cardiomyocyte contraction and relaxation processes. Disruption of calcium homeostasis is closely associated with the pathological mechanism of CVDs. Thus, this paper maps out and summarizes the effects and mechanisms of estrogen on calcium handling proteins in cardiac myocytes, including L-type Ca2+ channel, the sarcoplasmic reticulum Ca2+ release channel named ryanodine receptor, sarco(endo)plasmic reticulum Ca2+-ATPase, and sodium-calcium exchanger. In so doing, we provide theoretical and experimental evidence for the successful design of estrogen-based prevention and treatment therapies for CVDs.
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Affiliation(s)
- Lijuan Jiao
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | | | - Qi Wu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Mingjin Shi
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Lu Fu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | | | - Xi Tao
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Chenxi Xu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Xide Hu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Zeyuan Yin
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Hong Sun
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
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17
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Okajima T, Imai H, Murase Y, Ogawa Y, Kawaguchi K. The efficacy of radiofrequency catheter ablation for menstruation-dependent incessant ventricular tachycardia: A case report. HeartRhythm Case Rep 2019; 6:158-162. [PMID: 32181136 PMCID: PMC7064799 DOI: 10.1016/j.hrcr.2019.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Affiliation(s)
| | | | - Yosuke Murase
- Address reprint requests and correspondence: Dr Yosuke Murase, Department of Cardiology, Komaki City Hospital, 1-20 Joubushi, Komaki, Aichi, 485-8520, Japan.
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18
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Wells SP, Waddell HM, Sim CB, Lim SY, Bernasochi GB, Pavlovic D, Kirchhof P, Porrello ER, Delbridge LMD, Bell JR. Cardiomyocyte functional screening: interrogating comparative electrophysiology of high-throughput model cell systems. Am J Physiol Cell Physiol 2019; 317:C1256-C1267. [PMID: 31577512 DOI: 10.1152/ajpcell.00306.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cardiac arrhythmias of both atrial and ventricular origin are an important feature of cardiovascular disease. Novel antiarrhythmic therapies are required to overcome current drug limitations related to effectiveness and pro-arrhythmia risk in some contexts. Cardiomyocyte culture models provide a high-throughput platform for screening antiarrhythmic compounds, but comparative information about electrophysiological properties of commonly used types of cardiomyocyte preparations is lacking. Standardization of cultured cardiomyocyte microelectrode array (MEA) experimentation is required for its application as a high-throughput platform for antiarrhythmic drug development. The aim of this study was to directly compare the electrophysiological properties and responses to isoproterenol of three commonly used cardiac cultures. Neonatal rat ventricular myocytes (NRVMs), immortalized atrial HL-1 cells, and custom-generated human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were cultured on microelectrode arrays for 48-120 h. Extracellular field potentials were recorded, and conduction velocity was mapped in the presence/absence of the β-adrenoceptor agonist isoproterenol (1 µM). Field potential amplitude and conduction velocity were greatest in NRVMs and did not differ in cardiomyocytes isolated from male/female hearts. Both NRVMs and hiPSC-CMs exhibited longer field potential durations with rate dependence and were responsive to isoproterenol. In contrast, HL-1 cells exhibited slower conduction and shorter field potential durations and did not respond to 1 µM isoproterenol. This is the first study to compare the intrinsic electrophysiologic properties of cultured cardiomyocyte preparations commonly used for in vitro electrophysiology assessment. These findings offer important comparative data to inform methodological approaches in the use of MEA and other techniques relating to cardiomyocyte functional screening investigations of particular relevance to arrhythmogenesis.
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Affiliation(s)
- Simon P Wells
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia.,Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, United Kingdom
| | - Helen M Waddell
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Choon Boon Sim
- Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Shiang Y Lim
- St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.,Departments of Medicine and Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - Gabriel B Bernasochi
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Davor Pavlovic
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, United Kingdom
| | - Paulus Kirchhof
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, United Kingdom.,Departments of Cardiology, University Hospitals Birmingham and Sandwell and West Birmingham Hospitals National Health Service Trusts, Birmingham, United Kingdom
| | - Enzo R Porrello
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Lea M D Delbridge
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - James R Bell
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia.,Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, Victoria, Australia
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19
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Association Between HDL Cholesterol and QTc Interval: A Population-Based Epidemiological Study. J Clin Med 2019; 8:jcm8101527. [PMID: 31547597 PMCID: PMC6832837 DOI: 10.3390/jcm8101527] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/16/2019] [Accepted: 09/18/2019] [Indexed: 01/06/2023] Open
Abstract
Previous experimental studies showed that increasing high-density lipoprotein cholesterol (HDL) cholesterol shortens cardiac ventricular repolarization and the QT interval corrected for heart rate (QTc). However, little is known about the epidemiological relationship between HDL and QTc. The potential antiarrhythmic effect of HDL cholesterol remains a speculative hypothesis. In this cross-sectional population based study in adults living in the Italian-speaking part of Switzerland, we aimed to explore the association between HDL cholesterol and the QTc interval in the general population. A total of 1202 subjects were screened. electrocardiogram (ECG) recordings, measurements of lipid parameters and other laboratory tests were performed. QTc was corrected using Bazett’s (QTcBaz) and Framingham (QTcFram) formulas. HDL was categorized according to percentile distributions: <25th (HDL-1; ≤1.39 mmol/L); 25th–<50th (HDL-2; 1.40–1.69 mmol/L); 50th–<75th (HDL-3; 1.69–1.99 mmol/L); and ≥75th (HDL-4; ≥2.0 mmol/L). After exclusion procedures, data of 1085 subjects were analyzed. Compared with the HDL reference group (HDL-1), HDL-2 and HDL-3 were associated with a reduction of QTcBaz and QTcFram duration in crude (HDL-2, QTcBaz/QTcFram: β-11.306/–10.186, SE 4.625/4.016; p = 0.016/0.012; HDL-3, β-12.347/–12.048, SE 4.875/4.233, p = 0.012/<0.001) and adjusted (HDL-2: β-11.697/–10.908, SE 4.333/4.151, p < 0.001/0.010; HDL-3 β-11.786/–11.002, SE 4.719/4.521, p = 0.014/0.016) linear regression models in women. In adjusted logistic regression models higher HDL, were also associated with lower risk of prolonged QTcBaz/QTcFram (HDL-2: OR 0.16/0.17, CI 0.03–0.83/0.47–0.65; HDL-3: OR 0.10/0.14, CI 0.10–0.64/0.03–0.63) in women. Restricted cubic spline analysis confirmed a non linear association (p < 0.001). The present findings indicate an epidemiological association between HDL cholesterol and QTc duration. To draw firm conclusions, further investigations in other populations and with a prospective cohort design are needed.
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20
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Peter AK, Rossi AC, Buvoli M, Ozeroff CD, Crocini C, Perry AR, Buvoli AE, Lee LA, Leinwand LA. Expression of Normally Repressed Myosin Heavy Chain 7b in the Mammalian Heart Induces Dilated Cardiomyopathy. J Am Heart Assoc 2019; 8:e013318. [PMID: 31364453 PMCID: PMC6761648 DOI: 10.1161/jaha.119.013318] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background In mammals, muscle contraction is controlled by a family of 10 sarcomeric myosin motors. The expression of one of its members, MYH7b, is regulated by alternative splicing, and while the protein is restricted to specialized muscles such as extraocular muscles or muscle spindles, RNA that cannot encode protein is expressed in most skeletal muscles and in the heart. Remarkably, birds and snakes express MYH7b protein in both heart and skeletal muscles. This observation suggests that in the mammalian heart, the motor activity of MYH7b may only be needed during development since its expression is prevented in adult tissue, possibly because it could promote disease by unbalancing myocardial contractility. Methods and Results We have analyzed MYH7b null mice to determine the potential role of MYH7b during cardiac development and also generated transgenic mice with cardiac myocyte expression of MYH7b protein to measure its impact on cardiomyocyte function and contractility. We found that MYH7b null mice are born at expected Mendelian ratios and do not have a baseline cardiac phenotype as adults. In contrast, transgenic cardiac MYH7b protein expression induced early cardiac dilation in males with significantly increased left ventricular mass in both sexes. Cardiac dilation is progressive, leading to early cardiac dysfunction in males, but later dysfunction in females. Conclusions The data presented show that the expression of MYH7b protein in the mammalian heart has been inhibited during the evolution of mammals most likely to prevent the development of a severe cardiomyopathy that is sexually dimorphic.
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Affiliation(s)
- Angela K Peter
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Alberto C Rossi
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Massimo Buvoli
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Christopher D Ozeroff
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Claudia Crocini
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Amy R Perry
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Ada E Buvoli
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Lindsey A Lee
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
| | - Leslie A Leinwand
- Department of Molecular, Cellular and Developmental Biology Biofrontiers Institute University of Colorado Boulder CO
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21
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Novielli-Kuntz NM, Jelen M, Barr K, DeLalio LJ, Feng Q, Isakson BE, Gros R, Laird DW. Ablation of both Cx40 and Panx1 results in similar cardiovascular phenotypes exhibited in Cx40 knockout mice. Biosci Rep 2019; 39:BSR20182350. [PMID: 30745457 PMCID: PMC6393227 DOI: 10.1042/bsr20182350] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 01/10/2019] [Accepted: 02/05/2019] [Indexed: 11/30/2022] Open
Abstract
Connexins (Cxs) and pannexins (Panxs) are highly regulated large-pore channel-forming proteins that participate in cellular communication via small molecular exchange with the extracellular microenvironment, or in the case of connexins, directly between cells. Given the putative functional overlap between single membrane-spanning connexin hemichannels and Panx channels, and cardiovascular system prevalence, we generated the first Cx40-/-Panx1-/- mouse with the anticipation that this genetic modification would lead to a severe cardiovascular phenotype. Mice null for both Cx40 and Panx1 produced litter sizes and adult growth progression similar to wild-type (WT), Cx40-/- and Panx1-/- mice. Akin to Cx40-/- mice, Cx40-/-Panx1-/- mice exhibited cardiac hypertrophy and elevated systolic, diastolic, and mean arterial blood pressure compared with WT and Panx1-/- mice; however assessment of left ventricular ejection fraction and fractional shortening revealed no evidence of cardiac dysfunction between groups. Furthermore, Cx40-/-, Panx1-/-, and Cx40-/-Panx1-/- mice demonstrated impaired endothelial-mediated vasodilation of aortic segments to increasing concentrations of methacholine (MCh) compared with WT, highlighting roles for both Cx40 and Panx1 in vascular endothelial cell (EC) function. Surprisingly, elevated kidney renin mRNA expression, plasma renin activity, and extraglomerular renin-producing cell populations found in Cx40-/- mice was further exaggerated in double knockout mice. Thus, while gestation and gross development were conserved in Cx40-/-Panx1-/- mice, they exhibit cardiac hypertrophy, hypertension, and impaired endothelial-mediated vasodilation that phenocopies Cx40-/- mice. Nevertheless, the augmented renin homeostasis observed in the double knockout mice suggests that both Cx40 and Panx1 may play an integrative role.
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Affiliation(s)
| | - Meghan Jelen
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Canada
| | - Kevin Barr
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Canada
| | - Leon J DeLalio
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, U.S.A
| | - Qingping Feng
- Department of Physiology and Pharmacology London, ON, Canada
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, U.S.A
| | - Robert Gros
- Department of Physiology and Pharmacology London, ON, Canada
- Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Canada
- Department of Physiology and Pharmacology London, ON, Canada
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22
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Rodgers JL, Iyer D, Rodgers LE, Vanthenapalli S, Panguluri SK. Impact of hyperoxia on cardiac pathophysiology. J Cell Physiol 2019; 234:12595-12603. [PMID: 30652312 DOI: 10.1002/jcp.28136] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 12/20/2018] [Indexed: 01/09/2023]
Abstract
Mechanical ventilation with high oxygen therapy (hyperoxia) is widely implemented in critical care and ICU settings. Although supplemental oxygen is beneficial to treat hypoxia, its use is also associated with poor outcomes and high mortality in patients. Lung injury due to hyperoxia exposure has been well-documented in patients, including in adults and neonates. Thus, lung injury due to hyperoxia has been extensively researched in both preclinical and clinical studies. However, hyperoxia has also been shown to be associated with hemodynamic changes in patients in ICU, including reductions in heart rate, stroke volume, and cardiac output. In addition, certain experimental studies report that hyperoxia exposure in neonates results in cardiac dysfunction in later adult life. Despite this, until recently, the impact of hyperoxia within the heart has not been well studied, or reported, specifically in adult experimental models. To close this significant gap, our lab has sought to clarify hyperoxia-induced cardiac pathophysiology in adult murine models. This review discusses the current findings regarding the cardiovascular impact of hyperoxia exposure.
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Affiliation(s)
- Jennifer L Rodgers
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida
| | - Drishya Iyer
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida
| | - Lydia E Rodgers
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida
| | - Sahit Vanthenapalli
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida
| | - Siva K Panguluri
- Department of Pharmaceutical Sciences, College of Pharmacy, University of South Florida, Tampa, Florida
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23
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Masuda K, Takanari H, Morishima M, Ma F, Wang Y, Takahashi N, Ono K. Testosterone-mediated upregulation of delayed rectifier potassium channel in cardiomyocytes causes abbreviation of QT intervals in rats. J Physiol Sci 2018; 68:759-767. [PMID: 29332211 PMCID: PMC10717990 DOI: 10.1007/s12576-017-0590-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 12/26/2017] [Indexed: 12/01/2022]
Abstract
Men have shorter rate-corrected QT intervals (QTc) than women, especially at the period of adolescence or later. The aim of this study was to elucidate the long-term effects of testosterone on cardiac excitability parameters including electrocardiogram (ECG) and potassium channel current. Testosterone shortened QT intervals in ECG in castrated male rats, not immediately after, but on day 2 or later. Expression of Kv7.1 (KCNQ1) mRNA was significantly upregulated by testosterone in cardiomyocytes of male and female rats. Short-term application of testosterone was without effect on delayed rectifier potassium channel current (IKs), whereas IKs was significantly increased in cardiomyocytes treated with dihydrotestosterone for 24 h, which was mimicked by isoproterenol (24 h). Gene-selective inhibitors of a transcription factor SP1, mithramycin, abolished the effects of testosterone on Kv7.1. Testosterone increases Kv7.1-IKs possibly through a pathway related to a transcription factor SP1, suggesting a genomic effect of testosterone as an active factor for cardiac excitability.
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Affiliation(s)
- Kimiko Masuda
- Department of Cardiology and Clinical Examination, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
- Department of Pathophysiology, Oita University School of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita, 879-5593, Japan
| | - Hiroki Takanari
- Department of Pathophysiology, Oita University School of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita, 879-5593, Japan
| | - Masaki Morishima
- Department of Pathophysiology, Oita University School of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita, 879-5593, Japan
| | - FangFang Ma
- Department of Pathophysiology, Oita University School of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita, 879-5593, Japan
| | - Yan Wang
- Department of Cardiology and Clinical Examination, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
- Department of Pathophysiology, Oita University School of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita, 879-5593, Japan
| | - Naohiko Takahashi
- Department of Cardiology and Clinical Examination, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
| | - Katsushige Ono
- Department of Pathophysiology, Oita University School of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita, 879-5593, Japan.
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24
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Bernardo BC, Ooi JYY, Weeks KL, Patterson NL, McMullen JR. Understanding Key Mechanisms of Exercise-Induced Cardiac Protection to Mitigate Disease: Current Knowledge and Emerging Concepts. Physiol Rev 2018; 98:419-475. [PMID: 29351515 DOI: 10.1152/physrev.00043.2016] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The benefits of exercise on the heart are well recognized, and clinical studies have demonstrated that exercise is an intervention that can improve cardiac function in heart failure patients. This has led to significant research into understanding the key mechanisms responsible for exercise-induced cardiac protection. Here, we summarize molecular mechanisms that regulate exercise-induced cardiac myocyte growth and proliferation. We discuss in detail the effects of exercise on other cardiac cells, organelles, and systems that have received less or little attention and require further investigation. This includes cardiac excitation and contraction, mitochondrial adaptations, cellular stress responses to promote survival (heat shock response, ubiquitin-proteasome system, autophagy-lysosomal system, endoplasmic reticulum unfolded protein response, DNA damage response), extracellular matrix, inflammatory response, and organ-to-organ crosstalk. We summarize therapeutic strategies targeting known regulators of exercise-induced protection and the challenges translating findings from bench to bedside. We conclude that technological advancements that allow for in-depth profiling of the genome, transcriptome, proteome and metabolome, combined with animal and human studies, provide new opportunities for comprehensively defining the signaling and regulatory aspects of cell/organelle functions that underpin the protective properties of exercise. This is likely to lead to the identification of novel biomarkers and therapeutic targets for heart disease.
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Affiliation(s)
- Bianca C Bernardo
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Jenny Y Y Ooi
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Kate L Weeks
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Natalie L Patterson
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
| | - Julie R McMullen
- Baker Heart and Diabetes Institute , Melbourne , Australia ; Department of Paediatrics, University of Melbourne , Victoria , Australia ; Department of Diabetes, Central Clinical School, Monash University , Victoria , Australia ; Department of Medicine, Central Clinical School, Monash University , Victoria , Australia ; and Department of Physiology, School of Biomedical Sciences , Victoria , Australia
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25
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Tamayo M, Martin-Nunes L, Val-Blasco A, Piedras MJ, Larriba MJ, Gómez-Hurtado N, Fernández-Velasco M, Delgado C. Calcitriol, the Bioactive Metabolite of Vitamin D, Increases Ventricular K + Currents in Isolated Mouse Cardiomyocytes. Front Physiol 2018; 9:1186. [PMID: 30197603 PMCID: PMC6117532 DOI: 10.3389/fphys.2018.01186] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/07/2018] [Indexed: 01/20/2023] Open
Abstract
Calcitriol, the bioactive metabolite of vitamin D, interacts with the ubiquitously expressed nuclear vitamin D receptor (VDR) to induce genomic effects, but it can also elicit rapid responses via membrane-associated VDR through mechanisms that are poorly understood. The down-regulation of K+ currents is the main origin of electrophysiological remodeling in pathological hypertrophy and heart failure (HF), which can contribute to action potential prolongation and subsequently increase the risk of triggered arrhythmias. Adult mouse ventricular myocytes were isolated and treated with 10 nM calcitriol or vehicle for 15–30 min. In some experiments, cardiomyocytes were pretreated with the Akt inhibitor triciribine. In the adult mouse ventricle, outward K+ currents involved in cardiac repolarization are comprised of three components: the fast transient outward current (Itof), the ultrarapid delayed rectifier K+ current (Ikur), and the non-inactivating steady-state outward current (Iss). K+ currents were investigated using the whole-cell or the perforated patch-clamp technique and normalized to cell capacitance to obtain current densities. Calcitriol treatment of cardiomyocytes induced an increase in the density of Itof and Ikur, which was lost in myocytes isolated from VDR-knockout mice. In addition, calcitriol activated Akt in cardiomyocytes and pretreatment with triciribine prevented the calcitriol-induced increase of outward K+ currents. In conclusion, we demonstrate that calcitriol via VDR and Akt increases both Itof and Ikur densities in mouse ventricular cardiomyocytes. Our findings may provide new mechanistics clues for the cardioprotective role of this hormone in the heart.
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Affiliation(s)
- María Tamayo
- Biomedical Research Institute "Alberto Sols" CSIC-UAM/CIBER-CV, Madrid, Spain
| | - Laura Martin-Nunes
- Biomedical Research Institute "Alberto Sols" CSIC-UAM/CIBER-CV, Madrid, Spain
| | - Almudena Val-Blasco
- Innate Immune Response Group, IdiPAZ/CIBER-CV, La Paz University Hospital, Madrid, Spain
| | - Maria J Piedras
- Biomedical Research Institute "Alberto Sols" CSIC-UAM/CIBER-CV, Madrid, Spain.,University Francisco de Vitoria, Madrid, Spain
| | - María J Larriba
- Biomedical Research Institute "Alberto Sols" CSIC-UAM/CIBERONC, Madrid, Spain
| | | | | | - Carmen Delgado
- Biomedical Research Institute "Alberto Sols" CSIC-UAM/CIBER-CV, Madrid, Spain
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Mathieu S, El Khoury N, Rivard K, Paradis P, Nemer M, Fiset C. Angiotensin II Overstimulation Leads to an Increased Susceptibility to Dilated Cardiomyopathy and Higher Mortality in Female Mice. Sci Rep 2018; 8:952. [PMID: 29343862 PMCID: PMC5772611 DOI: 10.1038/s41598-018-19436-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 11/15/2017] [Indexed: 11/09/2022] Open
Abstract
Heart failure (HF) is associated with high mortality and affects men and women differently. The underlying mechanisms for these sex-related differences remain largely unexplored. Accordingly, using mice with cardiac-specific overexpression of the angiotensin II (ANGII) type 1 receptor (AT1R), we explored male-female differences in the manifestations of hypertrophy and HF. AT1R mice of both sexes feature electrical and Ca2+ handling alterations, systolic dysfunction, hypertrophy and develop HF. However, females had much higher mortality (21.0%) rate than males (5.5%). In females, AT1R stimulation leads to more pronounced eccentric hypertrophy (larger increase in LV mass/body weight ratio [+31%], in cell length [+27%], in LV internal end-diastolic [LVIDd, +34%] and systolic [LVIDs, +67%] diameter) and dilation (larger decrease in LV posterior wall thickness, +17%) than males. In addition, in female AT1R mice the cytosolic Ca2+ extrusion mechanisms were more severely compromised and were associated with a specific increased in Ca2+ sparks (by 187%) and evidence of SR Ca2+ leak. Altogether, these results suggest that female AT1R mice have more severe eccentric hypertrophy, dysfunction and compromised Ca2+ dynamics. These findings indicate that females are more susceptible to the adverse effects of AT1R stimulation than males favouring the development of HF and increased mortality.
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Affiliation(s)
- Sophie Mathieu
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec, Canada.,Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada
| | - Nabil El Khoury
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada
| | - Katy Rivard
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec, Canada.,Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada
| | - Pierre Paradis
- Lady Davis Institute, McGill University, Montreal, Québec, Canada
| | - Mona Nemer
- Ottawa University, Ottawa, Ontario, Canada
| | - Céline Fiset
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec, Canada. .,Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.
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Katsi V, Georgiopoulos G, Marketou M, Oikonomou D, Parthenakis F, Makris T, Nihoyannopoulos P, Vardas P, Tousoulis D. Atrial fibrillation in pregnancy: a growing challenge. Curr Med Res Opin 2017; 33:1497-1504. [PMID: 28498066 DOI: 10.1080/03007995.2017.1330257] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
BACKGROUND Atrial fibrillation (AF) constitutes a relatively infrequent pregnancy complication, which may be a therapeutic Gordian knot. Indeed, sparse data exist regarding the prevalence, prognosis, and management of AF during pregnancy. In general, AF occurs as a benign, self-limited arrhythmia, but occasionally may have severe hemodynamic consequences in pregnant patients suffering from heart failure, congenital heart disease, or other comorbidities. Extra-cardiac causes of AF should always be meticulously excluded. REVIEW Treatment decisions are difficult, since medications may cross the placental barrier and potentially affect fetal growth and organogenesis, or even result in fetal bradyarrhythmias. Treatment goals are not differentiated in comparison to those regarding AF occurring in the general population. Still, while maternal treatment is prioritized, issues regarding fetal health must deliberately be considered. Consequently, hemodynamic instability is to be promptly treated with synchronized electrical cardioversion. In contrast, in stable patients, pharmacologic cardioversion, under appropriate antithrombotic regimen, should be attempted. Selection of appropriate antithrombotic therapy, including novel oral anticoagulants, imposes further difficulties on therapeutic decision-making. Further clinical trials are warranted in order to assess the pathophysiology and prognosis of AF in pregnancy and ameliorate the evidence-based therapeutic strategy in this specific group of the population.
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Affiliation(s)
- Vasiliki Katsi
- a First Department of Cardiology , Hippokration Hospital, University of Athens , Athens , Greece
| | - Georgios Georgiopoulos
- a First Department of Cardiology , Hippokration Hospital, University of Athens , Athens , Greece
| | - Maria Marketou
- b Cardiology Department , Heraklion University Hospital , Crete , Greece
| | - Dimitrios Oikonomou
- a First Department of Cardiology , Hippokration Hospital, University of Athens , Athens , Greece
| | | | - Thomas Makris
- c Cardiology Department , Helena Venizelou Hospital , Athens , Greece
| | - Petros Nihoyannopoulos
- a First Department of Cardiology , Hippokration Hospital, University of Athens , Athens , Greece
| | - P Vardas
- b Cardiology Department , Heraklion University Hospital , Crete , Greece
| | - Dimitris Tousoulis
- a First Department of Cardiology , Hippokration Hospital, University of Athens , Athens , Greece
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28
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Kaese S, Larbig R, Rohrbeck M, Frommeyer G, Dechering D, Olligs J, Schönhofer-Merl S, Wessely R, Klingel K, Seebohm G, Eckardt L. Electrophysiological alterations in a murine model of chronic coxsackievirus B3 myocarditis. PLoS One 2017. [PMID: 28644868 PMCID: PMC5482483 DOI: 10.1371/journal.pone.0180029] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION Coxsackievirus B3 (CVB3) is known to induce acute and chronic myocarditis. Most infections are clinically unapparent but some patients suffer from ventricular arrhythmias (VA) and sudden cardiac death (SCD). Studies showed that acute CVB3 infection may cause impaired function of cardiac ion channels, creating a proarrhythmic substrate. However, it is unknown whether low level CVB3+ expression in myocytes may cause altered cardiac electrophysiology leading to VA. METHODS Cellular electrophysiology was used to analyze cellular action potentials (APs) and occurrence of afterdepolarizations from isolated cardiomyocytes of wildtype (WT) and transgenic CVB3ΔVP0 (CVB3+) mice. Further, we studied surface ECGs, monophasic APs, ventricular effective refractory period (VERP) and inducibility of VAs in Langendorff-perfused whole hearts. All used cardiomyocytes and whole hearts originated from male mice. RESULTS Cellular action potential duration (APD) in WT and CVB3+ myocytes was unchanged. No difference in mean occurrence or amplitude of afterdepolarizations in WT and CVB3+ myocytes was found. Interestingly, resting membrane potential in CVB3+ myocytes was significantly hyperpolarized (WT: -90.0±2.2 mV, n = 7; CVB3+: -114.1±3.0 mV, n = 14; p<0.005). Consistently, in Langendorff-perfused hearts, APDs were also not different between WT and CVB3+ whole hearts. Within both groups, we found a heart rate dependent shortening of ADP90 with increasing heart rate in Langendorff-perfused hearts. VERP was significantly prolonged in CVB3+ hearts compared to WT (WT: 36.0±2.7 ms, n = 5; CVB3+: 47.0±2.0 ms, n = 7; p = 0.018). Resting heart rate (HR) in Langendorff-perfused hearts was not significantly different between both genotypes. Electrical pacing protocols induced no VA in WT and CVB3+ hearts. CONCLUSION In CVB3+ mice, prolonged ventricular refractoriness and hyperpolarized resting membrane potentials in presence of unchanged APD were observed, suggesting that low level CVB3 expression does not promote VA by altered cardiac electrophysiology in this type of chronic myocarditis. These findings may suggest that other mechanisms such as chronic myocardial inflammation or fibrosis may account for arrhythmias observed in patients with chronic enteroviral myocarditis.
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Affiliation(s)
- Sven Kaese
- Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
- * E-mail:
| | - Robert Larbig
- Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
| | - Matthias Rohrbeck
- The IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
- Interdisciplinary Centre for Clinical Research (IZKF), Faculty of Medicine, University of Münster, Münster, Germany
| | - Gerrit Frommeyer
- Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
| | - Dirk Dechering
- Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
| | - Jan Olligs
- Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
| | - Sabine Schönhofer-Merl
- Deutsches Herzzentrum and Medizinische Klinik, Klinikum rechts der Isar, University of Technology, Munich, Germany
| | - Rainer Wessely
- Deutsches Herzzentrum and Medizinische Klinik, Klinikum rechts der Isar, University of Technology, Munich, Germany
- Zentrum für Herz- und Gefäßmedizin, Im Mediapark 2, Köln, Germany
| | - Karin Klingel
- Department of Molecular Pathology, University of Tübingen, Tübingen, Germany
| | - Guiscard Seebohm
- The IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
- Interdisciplinary Centre for Clinical Research (IZKF), Faculty of Medicine, University of Münster, Münster, Germany
| | - Lars Eckardt
- Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
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Hormones and sex differences: changes in cardiac electrophysiology with pregnancy. Clin Sci (Lond) 2017; 130:747-59. [PMID: 27128800 DOI: 10.1042/cs20150710] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 02/01/2016] [Indexed: 11/17/2022]
Abstract
Disruption of cardiac electrical activity resulting in palpitations and syncope is often an early symptom of pregnancy. Pregnancy is a time of dramatic and dynamic physiological and hormonal changes during which numerous demands are placed on the heart. These changes result in electrical remodelling which can be detected as changes in the electrocardiogram (ECG). This gestational remodelling is a very under-researched area. There are no systematic large studies powered to determine changes in the ECG from pre-pregnancy, through gestation, and into the postpartum period. The large variability between patients and the dynamic nature of pregnancy hampers interpretation of smaller studies, but some facts are consistent. Gestational cardiac hypertrophy and a physical shift of the heart contribute to changes in the ECG. There are also electrical changes such as an increased heart rate and lengthening of the QT interval. There is an increased susceptibility to arrhythmias during pregnancy and the postpartum period. Some changes in the ECG are clearly the result of changes in ion channel expression and behaviour, but little is known about the ionic basis for this electrical remodelling. Most information comes from animal models, and implicates changes in the delayed-rectifier channels. However, it is likely that there are additional roles for sodium channels as well as changes in calcium homoeostasis. The changes in the electrical profile of the heart during pregnancy and the postpartum period have clear implications for the safety of pregnant women, but the field remains relatively undeveloped.
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Waldschmidt L, Junkereit V, Bähring R. KChIP2 genotype dependence of transient outward current (Ito) properties in cardiomyocytes isolated from male and female mice. PLoS One 2017; 12:e0171213. [PMID: 28141821 PMCID: PMC5283746 DOI: 10.1371/journal.pone.0171213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 01/18/2017] [Indexed: 11/19/2022] Open
Abstract
The transient outward current (Ito) in cardiomyocytes is largely mediated by Kv4 channels associated with Kv Channel Interacting Protein 2 (KChIP2). A knockout model has documented the critical role of KChIP2 in Ito expression. The present study was conducted to characterize in both sexes the dependence of Ito properties, including current magnitude, inactivation kinetics, recovery from inactivation and voltage dependence of inactivation, on the number of functional KChIP2 alleles. For this purpose we performed whole-cell patch-clamp experiments on isolated left ventricular cardiomyocytes from male and female mice which had different KChIP2 genotypes; i.e., wild-type (KChIP2+/+), heterozygous knockout (KChIP2+/-) or complete knockout of KChIP2 (KChIP2-/-). We found in both sexes a KChIP2 gene dosage effect (i.e., a proportionality between number of alleles and phenotype) on Ito magnitude, however, concerning other Ito properties, KChIP2+/- resembled KChIP2+/+. Only in the total absence of KChIP2 (KChIP2-/-) we observed a slowing of Ito kinetics, a slowing of recovery from inactivation and a negative shift of a portion of the voltage dependence of inactivation. In a minor fraction of KChIP2-/- myocytes Ito was completely lost. The distinct KChIP2 genotype dependences of Ito magnitude and inactivation kinetics, respectively, seen in cardiomyocytes were reproduced with two-electrode voltage-clamp experiments on Xenopus oocytes expressing Kv4.2 and different amounts of KChIP2. Our results corroborate the critical role of KChIP2 in controlling Ito properties. They demonstrate that the Kv4.2/KChIP2 interaction in cardiomyocytes is highly dynamic, with a clear KChIP2 gene dosage effect on Kv4 channel surface expression but not on inactivation gating.
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Affiliation(s)
- Lara Waldschmidt
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Vera Junkereit
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Robert Bähring
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
- * E-mail:
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31
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Mathieu S, El Khoury N, Rivard K, Gélinas R, Goyette P, Paradis P, Nemer M, Fiset C. Reduction in Na(+) current by angiotensin II is mediated by PKCα in mouse and human-induced pluripotent stem cell-derived cardiomyocytes. Heart Rhythm 2016; 13:1346-54. [PMID: 26921763 DOI: 10.1016/j.hrthm.2016.02.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Indexed: 10/22/2022]
Abstract
BACKGROUND Ventricular arrhythmias and sudden cardiac deaths are among the leading causes of mortality in patients with heart failure, and the underlying mechanisms remain incompletely understood. Chronic elevation of angiotensin II (ANGII) is known to be one of the main contributors to heart failure. OBJECTIVE We tested whether ANGII can alter ventricular conduction and Na(+) current using transgenic mice with cardiomyocyte-restricted overexpression of ANGII type 1 receptor (AT1R). METHODS We used surface electrocardiograms along with current- and voltage-clamp techniques to characterize the electrophysiological properties of AT1R mice while the underlying regulatory mechanisms were explored using reverse transcription/quantitative polymerase chain reaction, Western blots, and immunofluorescence techniques. RESULTS Electrophysiological data indicated that chronic AT1R activation in ventricular myocytes caused a 60% reduction in Na(+) current density that slowed the maximal velocity of the action potential upstroke, leading to a prolongation of the QRS complex. These changes occur independently of cardiac hypertrophy, suggesting a direct role for ANGII/AT1R in slowing ventricular conduction. Western blots demonstrated a selective increase in sarcolemmal protein kinase Cα (PKCα) in AT1R mice, indicating PKCα activation. Furthermore, immunofluorescence analysis showed reorganization of PKCα expression to sarcolemma and colocalization with NaV1.5 in AT1R myocytes. The involvement of PKCα in regulating Na(+) current was subsequently demonstrated in human-induced pluripotent stem cell-derived cardiomyocytes where ANGII treatment reduced Na(+) current density. Concomitant treatment with αV5-3, a PKCα translocation inhibitor peptide, blocked the ANGII effect. CONCLUSION Overall, this study suggests that in mouse and human cardiomyocytes, PKCα is an important mediator of the ANGII-induced reduction in Na(+) current and may contribute to ventricular arrhythmias.
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Affiliation(s)
- Sophie Mathieu
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Faculty of Pharmacy, Université de Montréal, Montreal, Quebec, Canada
| | - Nabil El Khoury
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Katy Rivard
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Faculty of Pharmacy, Université de Montréal, Montreal, Quebec, Canada
| | - Roselle Gélinas
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada
| | - Philippe Goyette
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada
| | - Pierre Paradis
- Lady Davis Institute, Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montreal, Quebec, Canada
| | - Mona Nemer
- Ottawa University, Ottawa, Ontario, Canada
| | - Céline Fiset
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Faculty of Pharmacy, Université de Montréal, Montreal, Quebec, Canada.
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Influence of Gender on the Tolerability, Safety, and Efficacy of Quinidine Used for Treatment of Supraventricular and Ventricular Arrhythmias. Am J Cardiol 2015; 116:1845-51. [PMID: 26514302 DOI: 10.1016/j.amjcard.2015.09.042] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 09/06/2015] [Accepted: 09/06/2015] [Indexed: 11/23/2022]
Abstract
Quinidine, a class IA antiarrhythmic drug (AAD), has been used for the treatment of arrhythmias since the early 1900s. Use has decreased recently because of the availability of newer AADs and concerns about side effects and safety. Quinidine can cause QT prolongation, and women have longer QT intervals and are more susceptible to torsades de pointes (TdP) than are men. We sought to evaluate the influence of gender on quinidine tolerability, safety, and efficacy. We performed retrospective analyses of patients at our institution prescribed quinidine as an AAD between 2000 and 2012. Time to quinidine discontinuation and arrhythmia recurrence were evaluated using Cox proportional hazards models. In 179 patients, 23.5% were women and median age was 65.8 years. Quinidine indication was supraventricular arrhythmias in 68.7% and ventricular arrhythmias in 27.9% of patients. At 3 years after quinidine initiation, Kaplan-Meier probability of quinidine discontinuation was 65.7% for men and 82.4% for women (p = 0.015). Women were more likely than men to discontinue quinidine for QT prolongation (14.3 vs 4.4%, p = 0.036) and TdP (4.8 vs 0%, p = 0.054). After multivariate adjustment, female gender remained independently associated with quinidine discontinuation (adjusted hazard ratio 1.97, p = 0.014). Gender had no influence on arrhythmia recurrence: 1 year after quinidine initiation, Kaplan-Meier probability of freedom from recurrent arrhythmia was 62.4% in men and 57.9% in women (p = 0.33). Quinidine is highly effective in both genders. However, women are more likely than men to experience QT prolongation and TdP on quinidine and are more likely to discontinue quinidine independent of these side effects.
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El Gebeily G, El Khoury N, Mathieu S, Brouillette J, Fiset C. Estrogen regulation of the transient outward K(+) current involves estrogen receptor α in mouse heart. J Mol Cell Cardiol 2015. [PMID: 26205295 DOI: 10.1016/j.yjmcc.2015.07.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
BACKGROUND AND OBJECTIVE We have previously shown that androgens upregulate cardiac K(+) channels and shorten repolarization. However, the effects that estrogens (E2) and estrogen receptors (ER) might have on the various repolarizing K(+) currents and underlying ion channels remain incompletely understood. Accordingly, our objective was to verify whether and how E2 and its ERs subtypes influence these K(+) currents. METHODS AND RESULTS In order to examine the influence of E2 and ERs on K(+) currents we drastically lowered the E2 level through ovariectomy (OVX; 74% reduction vs CTL) and in parallel, we used female mice lacking either ERα (ERαKO) or ERβ (ERβKO). In OVX mice, results showed a specific increase of 35% in the density of the Ca(2+)-independent transient outward K(+) current (Ito) compared to CTL. Western blots showed increase in Kv4.2 and Kv4.3 sarcolemmal protein expression while qPCR revealed higher mRNA expression of only Kv4.3 in OVX mice. This upregulation of Ito was correlated with a shorter ventricular action potential duration and QTc interval. In ERαKO but not ERβKO mice, the mRNA of Kv4.3 was selectively increased. Furthermore, when ventricular myocytes obtained from ERαKO and ERβKO were cultured in the presence of E2, results showed that E2 reduced Ito density only in ERβKO myocytes confirming the repressive role of E2-ERα in regulating Ito. CONCLUSION Altogether, these results suggest that E2 negatively regulates the density of Ito through ERα, this highlights a potential role for this female hormone and its α-subtype receptor in modulating cardiac electrical activity.
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Affiliation(s)
- Gracia El Gebeily
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec H1T 1C8, Canada; Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.
| | - Nabil El Khoury
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec H1T 1C8, Canada; Department of Physiology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada.
| | - Sophie Mathieu
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec H1T 1C8, Canada; Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.
| | - Judith Brouillette
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec H1T 1C8, Canada; Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.
| | - Céline Fiset
- Research Center, Montreal Heart Institute, 5000 Bélanger, Montréal, Québec H1T 1C8, Canada; Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.
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Cardiac safety profile of etamicastat, a novel peripheral selective dopamine-β-hydroxylase inhibitor in non-human primates, human young and elderly healthy volunteers and hypertensive patients. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.ijcme.2015.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Cardiovascular safety pharmacology profile of etamicastat, a novel peripheral selective dopamine-ß-hydroxylase inhibitor. Eur J Pharmacol 2015; 750:98-107. [DOI: 10.1016/j.ejphar.2015.01.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Revised: 01/18/2015] [Accepted: 01/20/2015] [Indexed: 11/24/2022]
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Hoeker GS, Hood AR, Katra RP, Poelzing S, Pogwizd SM. Sex differences in β-adrenergic responsiveness of action potentials and intracellular calcium handling in isolated rabbit hearts. PLoS One 2014; 9:e111411. [PMID: 25340795 PMCID: PMC4207827 DOI: 10.1371/journal.pone.0111411] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 10/02/2014] [Indexed: 11/20/2022] Open
Abstract
Cardioprotection in females, as observed in the setting of heart failure, has been attributed to sex differences in intracellular calcium handling and its modulation by β-adrenergic signaling. However, further studies examining sex differences in β-adrenergic responsiveness have yielded inconsistent results and have mostly been limited to studies of contractility, ion channel function, or calcium handling alone. Given the close interaction of the action potential (AP) and intracellular calcium transient (CaT) through the process of excitation-contraction coupling, the need for studies exploring the relationship between agonist-induced AP and calcium handling changes in female and male hearts is evident. Thus, the aim of this study was to use optical mapping to examine sex differences in ventricular APs and CaTs measured simultaneously from Langendorff-perfused hearts isolated from naïve adult rabbits during β-adrenergic stimulation. The non-selective β-agonist isoproterenol (Iso) decreased AP duration (APD90), CaT duration (CaD80), and the decay constant of the CaT (τ) in a dose-dependent manner (1–316.2 nM), with a plateau at doses ≥31.6 nM. The Iso-induced changes in APD90 and τ (but not CaD80) were significantly smaller in female than male hearts. These sex differences were more significant at faster (5.5 Hz) than resting rates (3 Hz). Treatment with Iso led to the development of spontaneous calcium release (SCR) with a dose threshold of 31.6 nM. While SCR occurrence was similar in female (49%) and male (53%) hearts, the associated ectopic beats had a lower frequency of occurrence (16% versus 40%) and higher threshold (100 nM versus 31.6 nM) in female than male hearts (p<0.05). In conclusion, female hearts had a decreased capacity to respond to β-adrenergic stimulation, particularly under conditions of increased demand (i.e. faster pacing rates and “maximal” levels of Iso effects), however this reduced β-adrenergic responsiveness of female hearts was associated with reduced arrhythmic activity.
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Affiliation(s)
- Gregory S. Hoeker
- Departments of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Ashleigh R. Hood
- Departments of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Rodolphe P. Katra
- Departments of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Steven Poelzing
- Department of Biomedical Engineering, Virginia Tech Carilion Research Institute, Roanoke, Virginia, United States of America
| | - Steven M. Pogwizd
- Departments of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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Sex Differences in Cardiac Electrophysiology and Clinical Arrhythmias: Epidemiology, Therapeutics, and Mechanisms. Can J Cardiol 2014; 30:783-92. [DOI: 10.1016/j.cjca.2014.03.032] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 03/23/2014] [Indexed: 11/30/2022] Open
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Abstract
Sexual dimorphism is a well-established phenomenon, but its degree varies tremendously among species. Since the early days of Einthoven's development of the three-lead galvanometer ECG, we have known there are marked differences in QT intervals of men and women. It required over a century to appreciate the profound implications of sex-based electrophysiological differences in QT interval on the panoply of sex differences with respect to arrhythmia risk, drug sensitivity, and treatment modalities. Little is known about the fundamental mechanism responsible for sex differences in electrical substrate of the human heart, in large part due to the lack of tissue availability. Animal models are an important research tool, but species differences in the sexual dimorphism of the QT interval, the ionic currents underlying the cardiac repolarization, and effects of sex steroids make it difficult to interpolate animal to human sex differences. In addition, in some species, different strains of the same animal model yield conflicting data. Each model has its strengths, such as ease of genetic manipulation in mice or size in dogs. However, many animals do not reproduce the sexual dimorphism of QT seen in humans. To match sex linked prolongation of QT interval and arrhythmogenic phenotype, the current data suggest that the rabbit may be best suited to provide insight into sex differences in humans. In the future, emerging technologies such as induced pluripotent stem cell derived cardiac myocyte systems may offer the opportunity to study sex differences in a controlled hormonal situation in the context of a sex specific human model system.
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Affiliation(s)
- Guy Salama
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania; University of Pittsburgh Medical Center Heart and Vascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Glenna C L Bett
- Center for Cellular and Systems Electrophysiology, University at Buffalo, State University of New York, Buffalo, New York; Department of Obstetrics and Gynecology, University at Buffalo, State University of New York, Buffalo, New York; and Department of Physiology and Biophysics, University at Buffalo, State University of New York, Buffalo, New York
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Abstract
Control and modulation of electrical signaling is vital to normal physiology, particularly in neurons, cardiac myocytes, and skeletal muscle. The orchestrated activities of variable sets of ion channels and transporters, including voltage-gated ion channels (VGICs), are responsible for initiation, conduction, and termination of the action potential (AP) in excitable cells. Slight changes in VGIC activity can lead to severe pathologies including arrhythmias, epilepsies, and paralyses, while normal excitability depends on the precise tuning of the AP waveform. VGICs are heavily posttranslationally modified, with upward of 30% of the mature channel mass consisting of N- and O-glycans. These glycans are terminated typically by negatively charged sialic acid residues that modulate voltage-dependent channel gating directly. The data indicate that sialic acids alter VGIC activity in isoform-specific manners, dependent in part, on the number/location of channel sialic acids attached to the pore-forming alpha and/or auxiliary subunits that often act through saturating electrostatic mechanisms. Additionally, cell-specific regulation of sialylation can affect VGIC gating distinctly. Thus, channel sialylation is likely regulated through two mechanisms that together contribute to a dynamic spectrum of possible gating motifs: a subunit-specific mechanism and regulated (aberrant) changes in the ability of the cell to glycosylate. Recent studies showed that neuronal and cardiac excitability is modulated through regulated changes in voltage-gated Na(+) channel sialylation, suggesting that both mechanisms of differential VGIC sialylation contribute to electrical signaling in the brain and heart. Together, the data provide insight into an important and novel paradigm involved in the control and modulation of electrical signaling.
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Affiliation(s)
- Andrew R Ednie
- Programs in Cardiovascular Research and Neuroscience, Department of Molecular Pharmacology & Physiology, College of Medicine, University of South Florida, Tampa, Florida, USA
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Sex differences in mechanisms of cardiac excitation-contraction coupling. Pflugers Arch 2013; 465:747-63. [PMID: 23417603 PMCID: PMC3651827 DOI: 10.1007/s00424-013-1233-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 01/29/2013] [Accepted: 01/30/2013] [Indexed: 11/25/2022]
Abstract
The incidence and expression of cardiovascular diseases differs between the sexes. This is not surprising, as cardiac physiology differs between men and women. Clinical and basic science investigations have shown important sex differences in cardiac structure and function. The pervasiveness of sex differences suggests that such differences must be fundamental, likely operating at a cellular level. Indeed, studies have shown that isolated ventricular myocytes from female animals have smaller and slower contractions and underlying calcium transients compared to males. Recent evidence suggests that this arises from sex differences in components of the cardiac excitation–contraction coupling pathway, the sequence of events linking myocyte depolarization to calcium release from the sarcoplasmic reticulum and subsequent contraction. The concept that sex hormones may regulate intracellular calcium at the level of the cardiomyocyte is important, as levels of these hormones decline in both men and women as the incidence of cardiovascular disease rises. This review focuses on the impact of sex on cardiac contraction, in particular at the cellular level, and highlights specific components of the excitation–contraction coupling pathway that differ between the sexes. Understanding sex hormone regulation of calcium homeostasis in the heart may reveal new avenues for therapeutic strategies to treat cardiac dysfunction and cardiovascular diseases.
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Sex differences in cardiac autonomic regulation and in repolarisation electrocardiography. Pflugers Arch 2013; 465:699-717. [PMID: 23404618 DOI: 10.1007/s00424-013-1228-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Accepted: 01/28/2013] [Indexed: 12/16/2022]
Abstract
The review summarises the present knowledge on the sex differences in cardiac autonomic regulations and in related aspects of electrocardiography with particular attention to myocardial repolarisation. Although some of the sex differences are far from fully established, multitude of observations show consistent differences between women and men. Despite more pronounced parasympathetic cardiac regulation, women have higher resting heart rate and lower baroreflex sensitivity. Of the electrocardiographic phenomena, women have longer QT interval duration, repolarisation sequence more synchronised with the inverse of the depolarisation sequence, and likely increased regional heterogeneity of myocardial repolarisation. Studies investigating the relationship of these sex disparities to hormonal differences led frequently to conflicting results. Although sex hormones seem to play a key role by influencing both autonomic tone and electrophysiological properties at the cellular level, neither the truly relevant hormones nor their detailed actions are known. Physiologic usefulness of the described sex differences is also unknown. The review suggests that new studies are needed to advance the understanding of the physiologic mechanisms responsible for these inequalities between women and men and provides key methodological suggestions that need to be followed in future research.
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Abstract
Hyperpolarization-activated cyclic nucleotide gated (HCN) channels pass a cationic current (I(h)/I(f)) that crucially contributes to the slow diastolic depolarization (SDD) of sinoatrial pacemaker cells and, hence, is a key determinant of cardiac automaticity and the generation of the heartbeat. However, there is growing evidence that HCN channels are not restricted to the spontaneously active cells of the sinoatrial node and the conduction system but are also present in ventricular cardiomyocytes that produce an action potential lacking SDD. This observation raises the question of the principal function(s) of HCN channels in working myocardium. Our recent analysis of an HCN3-deficient (HCN3-/-) mouse line has shed new light on this central question. We propose that HCN channels contribute to the ventricular action potential waveform, specifically during late repolarization. In this review, we outline this new concept.
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Affiliation(s)
- Stefanie Fenske
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung-Department Pharmazie, Ludwig-Maximilians-Universität München, Munich, Germany
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Fares E, Parks RJ, MacDonald JK, Egar JM, Howlett SE. Ovariectomy enhances SR Ca2+ release and increases Ca2+ spark amplitudes in isolated ventricular myocytes. J Mol Cell Cardiol 2012; 52:32-42. [DOI: 10.1016/j.yjmcc.2011.09.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 08/18/2011] [Accepted: 09/02/2011] [Indexed: 11/24/2022]
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Rivard K, Grandy SA, Douillette A, Paradis P, Nemer M, Allen BG, Fiset C. Overexpression of type 1 angiotensin II receptors impairs excitation-contraction coupling in the mouse heart. Am J Physiol Heart Circ Physiol 2011; 301:H2018-27. [DOI: 10.1152/ajpheart.01092.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transgenic mice that overexpress human type 1 angiotensin II receptor (AT1R) in the heart develop cardiac hypertrophy. Previously, we have shown that in 6-mo AT1R mice, which exhibit significant cardiac remodeling, fractional shortening is decreased. However, it is not clear whether altered contractility is attributable to AT1R overexpression or is secondary to cardiac hypertrophy/remodeling. Thus the present study characterized the effects of AT1R overexpression on ventricular L-type Ca2+ currents ( ICaL), cell shortening, and Ca2+ handling in 50-day and 6-mo-old male AT1R mice. Echocardiography showed there was no evidence of cardiac hypertrophy in 50-day AT1R mice but that fractional shortening was decreased. Cellular experiments showed that cell shortening, ICaL, and Cav1.2 mRNA expression were significantly reduced in 50-day and 6-mo-old AT1R mice compared with controls. In addition, Ca2+ transients and caffeine-induced Ca2+ transients were reduced whereas the time to 90% Ca2+ transient decay was prolonged in both age groups of AT1R mice. Western blot analysis revealed that sarcoplasmic reticulum Ca2+-ATPase and Na+/Ca2+ exchanger protein expression was significantly decreased in 50-day and 6-mo AT1R mice. Overall, the data show that cardiac contractility and the mechanisms that underlie excitation-contraction coupling are altered in AT1R mice. Furthermore, since the alterations in contractility occur before the development of cardiac hypertrophy, it is likely that these changes are attributable to the increased activity of the renin-angiotensin system brought about by AT1R overexpression. Thus it is possible that AT1R blockade may help maintain cardiac contractility in individuals with heart disease.
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Affiliation(s)
- Katy Rivard
- Research Centre, Montreal Heart Institute, Montreal,
- Faculty of Pharmacy, Université de Montréal, Montreal,
| | - Scott A. Grandy
- Research Centre, Montreal Heart Institute, Montreal,
- Faculty of Pharmacy, Université de Montréal, Montreal,
| | - Annie Douillette
- Research Centre, Montreal Heart Institute, Montreal,
- Faculty of Pharmacy, Université de Montréal, Montreal,
| | | | | | | | - Céline Fiset
- Research Centre, Montreal Heart Institute, Montreal,
- Faculty of Pharmacy, Université de Montréal, Montreal,
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Abstract
BACKGROUND Gender disparities in the incidence of torsade de pointes (TdP) ventricular tachycardia exist, but the mechanisms in humans are unresolved. We addressed this issue using a mathematical model of a human ventricular cell. METHODS We implemented gender differences in the Priebe-Beuckelmann model cell by modifying the amplitudes of the L-type Ca(2+) current (I(Ca,L)), transient outward K(+) current (I(to)), and rapid component of the delayed rectifier K(+)current (I(Kr)), according to experimental data from animal male and female hearts. Gender disparities in electrical heterogeneity between transmural layers (subepicardium, midmyocardium, subendocardium) were implemented by modifying various ion currents according to experimental data. RESULTS Action potentials in female cells have longer durations and steeper duration versus frequency relationships than male cells. In the female cells, electrical heterogeneity between transmural layers is larger and the susceptibility to early afterdepolarisations is higher than in male cells. CONCLUSION Gender-related differences in I(Ca,L), I(to), and I(Kr )may explain the gender disparities in human cardiac electrophysiology. Female cells have an increased susceptibility to early afterdepolarisations following mild reductions in net repolarising forces. Combined with their greater electrical heterogeneity, this renders them more vulnerable to TdP. (Neth Heart J 2007;15:405-11.).
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Synergic Effects of β-Estradiol and Erythromycin on hERG Currents. J Membr Biol 2011; 241:31-8. [DOI: 10.1007/s00232-011-9360-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 03/21/2011] [Indexed: 11/25/2022]
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Tanaka Y, Tada H, Ito S, Naito S, Higuchi K, Kumagai K, Hachiya H, Hirao K, Oshima S, Taniguchi K, Aonuma K, Isobe M. Gender and Age Differences in Candidates for Radiofrequency Catheter Ablation of Idiopathic Ventricular Arrhythmias. Circ J 2011; 75:1585-91. [DOI: 10.1253/circj.cj-10-0941] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yasuaki Tanaka
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University
| | - Hiroshi Tada
- Cardiovascular Division, Institute of Clinical Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba
| | - Sachiko Ito
- Division of Cardiology, Gunma Prefectural Cardiovascular Center
| | - Shigeto Naito
- Division of Cardiology, Gunma Prefectural Cardiovascular Center
| | - Koji Higuchi
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University
| | - Koji Kumagai
- Division of Cardiology, Gunma Prefectural Cardiovascular Center
| | - Hitoshi Hachiya
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University
| | - Kenzo Hirao
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University
| | - Shigeru Oshima
- Division of Cardiology, Gunma Prefectural Cardiovascular Center
| | | | - Kazutaka Aonuma
- Cardiovascular Division, Institute of Clinical Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba
| | - Mitsuaki Isobe
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University
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El Gebeily G, Fiset C. Upregulation of ventricular potassium channels by chronic tamoxifen treatment. Cardiovasc Res 2010; 90:68-76. [PMID: 21131637 DOI: 10.1093/cvr/cvq384] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Tamoxifen is a selective oestrogen receptor modulator widely used in the prevention and treatment of breast cancer. Women receiving long-term tamoxifen therapy do not experience cardiac arrhythmias although acute perfusion of tamoxifen has been shown to inhibit cardiac K(+) currents. This observation suggests that chronic tamoxifen treatment does not negatively modulate cardiac K(+) currents. Therefore, we investigated the chronic effects of tamoxifen on K(+) currents and channels in mouse and guinea pig ventricles. METHODS AND RESULTS Female mice and guinea pigs were treated with placebo or tamoxifen pellets for 60 days. Voltage-clamp experiments showed that the density of the Ca²(+)-independent transient outward (I(to)), the ultrarapid delayed rectifier (I(Kur)), the steady-state (I(ss)), and the inward rectifier (I(K1)) K(+) currents were increased in tamoxifen-treated mice ventricle. Western blot analysis revealed that protein expression of the underlying K(+) channels Kv4.3 (I(to)), Kv1.5 (I(Kur)), Kv2.1 (I(ss)), and Kir2.1 (I(K1)) were significantly higher in the ventricle of tamoxifen-treated mice. Protein expression of the K(+) channel subunits encoding I(Kr) and I(Ks) (ERG1, KCNQ1, and KCNE1) was also increased in tamoxifen-treated guinea pig ventricle. CONCLUSION Conditions with high oestrogen levels are associated with reduced K(+) currents. Thus, conceivably, tamoxifen might prevent the inhibitory effects of oestrogen on K(+) channels by blocking the oestrogen receptors, which would explain the reported increase in K(+) currents. These findings could contribute to explain the absence of cardiac arrhythmia with long-term tamoxifen therapy.
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Affiliation(s)
- Gracia El Gebeily
- Research Center, Montreal Heart Institute, Montréal, Québec, Canada H1T 1C8
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50
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Farrell SR, Ross JL, Howlett SE. Sex differences in mechanisms of cardiac excitation-contraction coupling in rat ventricular myocytes. Am J Physiol Heart Circ Physiol 2010; 299:H36-45. [DOI: 10.1152/ajpheart.00299.2010] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Components of excitation-contraction (E-C) coupling were compared in ventricular myocytes isolated from 3-mo-old male and female rats. Ca2+ concentrations (fura-2) and cell shortening (edge detector) were measured simultaneously (37°C). Membrane potential and ionic currents were measured with microelectrodes. Action potentials were similar in male and female myocytes, but contractions were smaller and slower in females. In voltage-clamped cells, peak contractions were smaller in females than in males (5.1 ± 0.7% vs. 7.7 ± 0.8% diastolic length, P < 0.05). Similarly, Ca2+ transients were smaller in females than in males and the rate of rise of the Ca2+ transient was slower in females. Despite smaller contractions and Ca2+ transients in females, Ca2+ current density was similar in both groups. Sarcoplasmic reticulum Ca2+ content, assessed with caffeine, did not differ between the sexes. However, E-C coupling gain (rate of Ca2+ release/Ca2+ current) was smaller in females than in males (157.0 ± 15.6 vs. 338.4 ± 54.3 (nM/s)/(pA/pF), P < 0.05). To determine whether the reduced gain in female cells was due to changes in unitary Ca2+ release, spontaneous Ca2+ sparks were evaluated (fluo-4, 37°C). Spark frequencies and widths were similar in both groups, but spark amplitudes were smaller in females than in males (0.56 ± 0.01 vs. 0.64 ± 0.01 ΔF/F0, P < 0.05). Spark durations also were shorter in females than in males (full duration at half-maximum = 14.86 ± 0.17 vs. 16.25 ± 0.27 ms, P < 0.05). These observations suggest that decreases in the size and duration of Ca2+ sparks contributes to the decrease in E-C coupling gain in female myocytes. Thus, differences in cardiac contractile function arise, in part, from differences in unitary Ca2+ release between the sexes.
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Affiliation(s)
| | | | - Susan E. Howlett
- Departments of 1Pharmacology and
- Medicine (Geriatric Medicine), Dalhousie University, Halifax, Nova Scotia, Canada
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