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Shen J, Fu H, Ding Y, Yuan Z, Xiang Z, Ding M, Huang M, Peng Y, Li T, Zha K, Ye Q. The role of iron overload and ferroptosis in arrhythmia pathogenesis. IJC HEART & VASCULATURE 2024; 52:101414. [PMID: 38694269 PMCID: PMC11060960 DOI: 10.1016/j.ijcha.2024.101414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 04/20/2024] [Accepted: 04/23/2024] [Indexed: 05/04/2024]
Abstract
Ferroptosis is a newly discovered form of programmed cell death triggered by intracellular iron overload, which leads to the accumulation of lipid peroxides in various cells. It has been implicated in the pathogenesis and progression of various diseases, including tumors, neurological disorders, and cardiovascular diseases. The intricate mechanism underlying ferroptosis involves an imbalance between the oxidation and antioxidant systems, disturbances in iron metabolism, membrane lipid peroxidation, and dysregulation of amino acid metabolism. We highlight the key molecular mechanisms governing iron overload and ferroptosis, and discuss potential molecular pathways linking ferroptosis with arrhythmias.
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Affiliation(s)
- Jingsong Shen
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Hengsong Fu
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Yanling Ding
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Ziyang Yuan
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Zeming Xiang
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Miao Ding
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Min Huang
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Yongquan Peng
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Tao Li
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou 646000, China
| | - Kelan Zha
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Qiang Ye
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
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Chang GJ, Yeh YH, Chen WJ, Ko YS, Lai YJ, Lee YS. Candesartan Cilexetil Attenuates Arrhythmogenicity Following Pressure Overload in Rats via the Modulation of Cardiac Electrical and Structural Remodeling and Calcium Handling Dysfunction. J Am Heart Assoc 2022; 11:e024285. [PMID: 35862154 PMCID: PMC9375482 DOI: 10.1161/jaha.121.024285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Background Cardiac hypertrophy is associated with abnormal electrophysiology and increased arrhythmia risk. This study assessed whether candesartan cilexetil, an angiotensin II type 1 receptor blocker, could suppress arrhythmogenecity by attenuating cardiac electrical remodeling and calcium mishandling in rats with pressure‐overload hypertrophy. Methods and Results Male Sprague‐Dawley rats were randomly subjected to abdominal aorta banding or sham procedure and received either candesartan cilexetil (3.0 mg/kg per day) or vehicle by gavage for 5 weeks. Pressure overload was characterized by compensated left ventricular (LV) hypertrophy and fibrosis, increased LV pressure and its decay time, and prolonged corrected QT interval, all of which were attenuated by candesartan cilexetil treatment. Candesartan cilexetil–treated banded rat hearts displayed shorter QT intervals and lower vulnerability to atrial and ventricular tachyarrhythmias than vehicle‐treated banded hearts. Candesartan cilexetil prevented banding‐induced prolonged action potential duration and reduced the occurrence of triggered activity in LV papillary muscles. In addition, the prolonged time to 50% cell relengthening and calcium transient decay time were normalized in LV myocytes from candesartan cilexetil–treated banded rats, along with a normalization of decreased SERCA2a (sarco[endo]plasmic reticulum calcium‐ATPase) expression in LV tissues. Furthermore, candesartan cilexetil normalized depressed transient outward potassium current densities and protein and mRNA levels of both voltage‐gated potassium 4.2 and 4.3 channel subunits (Kv4.2 and Kv4.3) in banded rats. Conclusions Candesartan cilexetil protects the heart from pressure overload‐induced adverse electrical remodeling by preserving potassium channel densities. In addition, calcium handling and its molecular regulation also improved after treatment. These beneficial effects may contribute to a lower susceptibility to arrhythmias in hearts from candesartan cilexetil–treated pressure‐overloaded rats.
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Affiliation(s)
- Gwo-Jyh Chang
- Graduate Institute of Clinical Medicinal Sciences College of Medicine Chang Gung University Tao-Yuan Taiwan.,Cardiovascular Division of Medicine Chang Gung Memorial Hospital Tao-Yuan Taiwan
| | - Yung-Hsin Yeh
- Cardiovascular Division of Medicine Chang Gung Memorial Hospital Tao-Yuan Taiwan
| | - Wei-Jan Chen
- Cardiovascular Division of Medicine Chang Gung Memorial Hospital Tao-Yuan Taiwan
| | - Yu-Shien Ko
- Cardiovascular Division of Medicine Chang Gung Memorial Hospital Tao-Yuan Taiwan
| | - Ying-Ju Lai
- Cardiovascular Division of Medicine Chang Gung Memorial Hospital Tao-Yuan Taiwan.,Department of Respiratory Therapy College of Medicine Chang Gung University Tao-Yuan Taiwan
| | - Yun-Shien Lee
- Genomic Medicine Research Core Laboratory Chang Gung Memorial Hospital Tao-Yuan Taiwan.,Department of Biotechnology Ming Chuan University Tao-Yuan Taiwan
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Jing Y, Yang R, Chen W, Ye Q. Anti-Arrhythmic Effects of Sodium-Glucose Co-Transporter 2 Inhibitors. Front Pharmacol 2022; 13:898718. [PMID: 35814223 PMCID: PMC9263384 DOI: 10.3389/fphar.2022.898718] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/04/2022] [Indexed: 12/11/2022] Open
Abstract
Arrhythmias are clinically prevalent with a high mortality rate. They impose a huge economic burden, thereby substantially affecting the quality of life. Sodium-glucose co-transporter 2 inhibitor (SGLT2i) is a new type of hypoglycemic drug, which can regulate blood glucose level safely and effectively. Additionally, it reduces the occurrence and progression of heart failure and cardiovascular events significantly. Recently, studies have found that SGLT2i can alleviate the occurrence and progression of cardiac arrhythmias; however, the exact mechanism remains unclear. In this review, we aimed to discuss and summarize new literature on different modes in which SGLT2i ameliorates the occurrence and development of cardiac arrhythmias.
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Kim KH, Oh Y, Liu J, Dababneh S, Xia Y, Kim RY, Kim DK, Ban K, Husain M, Hui CC, Backx PH. Irx5 and transient outward K + currents contribute to transmural contractile heterogeneities in the mouse ventricle. Am J Physiol Heart Circ Physiol 2022; 322:H725-H741. [PMID: 35245131 DOI: 10.1152/ajpheart.00572.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have established that fast transmural gradients of transient outward K+ current (Ito,f) correlate with regional differences in action potential (AP) profile and excitation-contraction coupling (ECC) with high Ito,f expression in the epimyocardium (EPI) being associated with short APs and low contractility and vice versa. Herein, we investigated the effects of disrupted Ito,f gradient on contractile properties using mouse models of Irx5 knockout (Irx5-KO) for selective Ito,f elevation in the endomyocardium (ENDO) of the left ventricle (LV) and Kcnd2 ablation (KV4.2-KO) for selective Ito,freduction in the EPI. Irx5-KO mice exhibited decreased global LV contractility in association with reductions in cell shortening and Ca2+ transient amplitudes in isolated ENDO but not EPI cardiomyocytes. Moreover, transcriptional profiling revealed that the primary effect of Irx5 ablation on ECC-related genes was to increase Ito,f gene expression (i.e. Kcnd2 and Kcnip2) in the ENDO, but not the EPI. Indeed, KV4.2-KO mice showed selective increases in cell shortening and Ca2+ transients in isolated EPI cardiomyocytes, leading to enhanced ventricular contractility and mice lacking both Irx5 and Kcnd2 displayed elevated ventricular contractility comparable to KV4.2-KO mice. Our findings demonstrate that the transmural electromechanical heterogeneities in the healthy ventricles depend on the Irx5-dependent Ito,f gradients. These observations provide a useful framework for assessing the molecular mechanisms underlying the alterations in contractile heterogeneity seen in the diseased heart.
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Affiliation(s)
- Kyoung-Han Kim
- University of Ottawa Heart Institute, Ottawa, ON, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Yena Oh
- University of Ottawa Heart Institute, Ottawa, ON, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Jie Liu
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Saif Dababneh
- University of Ottawa Heart Institute, Ottawa, ON, Canada
| | - Ying Xia
- University of Ottawa Heart Institute, Ottawa, ON, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Ri Youn Kim
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Dae-Kyum Kim
- University of Ottawa Heart Institute, Ottawa, ON, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Kiwon Ban
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | - Mansoor Husain
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Toronto General Research Institute, University Health Network, Toronto, ON, Canada
| | - Chi-Chung Hui
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Peter H Backx
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Biology, Faculty of Science, York University, Toronto, ON, Canada.,Toronto General Research Institute, University Health Network, Toronto, ON, Canada
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Alyu F, Olgar Y, Degirmenci S, Turan B, Ozturk Y. Interrelated In Vitro Mechanisms of Sibutramine-Induced Cardiotoxicity. Cardiovasc Toxicol 2021; 21:322-335. [PMID: 33389602 DOI: 10.1007/s12012-020-09622-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Accepted: 11/24/2020] [Indexed: 11/26/2022]
Abstract
Consumption of illicit pharmaceutical products containing sibutramine has been reported to cause cardiovascular toxicity problems. This study aimed to demonstrate the toxicity profile of sibutramine, and thereby provide important implications for the development of more effective strategies in both clinical approaches and drug design studies. Action potentials (APs) were determined from freshly isolated ventricular cardiomyocytes with whole-cell configuration of current clamp as online. The maximum amplitude of APs (MAPs), the resting membrane potential (RMP), and AP duration from the repolarization phases were calculated from original records. The voltage-dependent K+-channel currents (IK) were recorded in the presence of external Cd2+ and both inward and outward parts of the current were calculated, while their expression levels were determined with qPCR. The levels of intracellular free Ca2+ and H+ (pHi) as well as reactive oxygen species (ROS) were measured using either a ratiometric micro-spectrofluorometer or confocal microscope. The mechanical activity of isolated hearts was observed with Langendorff-perfusion system. Acute sibutramine applications (10-8-10-5 M) induced significant alterations in both MAPs and RMP as well as the repolarization phases of APs and IK in a concentration-dependent manner. Sibutramine (10 μM) induced Ca2+-release from the sarcoplasmic reticulum under either electrical or caffeine stimulation, whereas it depressed left ventricular developed pressure with a marked decrease in the end-diastolic pressure. pHi inhibition by sibutramine supports the observed negative alterations in contractility. Changes in mRNA levels of different IK subunits are consistent with the acute inhibition of the repolarizing IK, affecting AP parameters, and provoke the cardiotoxicity.
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Affiliation(s)
- Feyza Alyu
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, Yunus Emre Campus, 26470, Eskisehir, Turkey
| | - Yusuf Olgar
- Department of Biophysics, Faculty of Medicine, Ankara University, 06230, Ankara, Turkey
| | - Sinan Degirmenci
- Department of Biophysics, Faculty of Medicine, Ankara University, 06230, Ankara, Turkey
| | - Belma Turan
- Department of Biophysics, Faculty of Medicine, Ankara University, 06230, Ankara, Turkey
- Department of Biophysics, Faculty of Medicine, Lokman Hekim University, 06230, Ankara, Turkey
| | - Yusuf Ozturk
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, Yunus Emre Campus, 26470, Eskisehir, Turkey.
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Cagiltay E, Pouwels S, Erbas O, Taskiran D, Kalkanli Tas S, Aslan I. The Prophylactic Effects of Metoprolol, Diltiazem, and Pilocarpine on Hypoglycemia-Induced Prolongation of QT Interval. Cureus 2021; 13:e14058. [PMID: 33898141 PMCID: PMC8061426 DOI: 10.7759/cureus.14058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/23/2021] [Indexed: 01/08/2023] Open
Abstract
Background Insulin-induced hypoglycemia has been demonstrated to prolong the corrected QT (QTc) interval. Prolongation of the QTc interval, especially in diabetic patients using insulin, can cause fatal ventricular arrhythmias. The aim of this study was to evaluate the effects of metoprolol, diltiazem, and pilocarpine on hypoglycemia-induced QTc prolongation. Methods Thirty male rats were randomly distributed into the following five groups: Group 1 (1 mL/kg saline, n=6), Group 2 (40 U/kg crystalline insulin + saline, n=6), Group 3 (40 U/kg crystalline insulin + 1 mg/kg metoprolol, n=6), Group 4 (40 U/kg crystalline insulin + 0.8 mg/kg pilocarpine, n=6), and Group 5 (40 U/kg crystalline insulin + 2 mg/kg diltiazem, n=6). Three hours after insulin injection, the blood glucose level was measured in all groups. Blood glucose <40 mg/dl was defined as hypoglycemia. Electrocardiograms (ECG) were taken in lead I (DI), and QTc was calculated by using Bazett's formula. Results Group 2 (insulin + saline) showed that it had a significantly prolonged QTc interval as compared to the control group (p<0.0001). However, treatments of the rats with metoprolol, pilocarpine, and diltiazem significantly prevented prolongation of the QTc interval as compared to the insulin + saline group (p<0.005, p<0.005, and p<0.01, respectively). Conclusion The findings of the present study demonstrated the efficacy of metoprolol, pilocarpine, and diltiazem in the prevention of hypoglycemia-induced QTc prolongation in male rats.
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Affiliation(s)
- Eylem Cagiltay
- Department of Physiology, Istanbul Bilim University School of Medicine, Istanbul, TUR
| | - Sjaak Pouwels
- Intensive Care Medicine, Elisabeth-Tweesteden Hospital, Tilburg, NLD
| | - Oytun Erbas
- Department of Physiology, Istanbul Bilim University School of Medicine, Istanbul, TUR
| | - Dilek Taskiran
- Department of Physiology, Ege University School of Medicine, Izmir, TUR
| | - Sevgi Kalkanli Tas
- Department of Immunology, University of Health Sciences, Faculty of Medicine, Istanbul, TUR
| | - Ismael Aslan
- Department of Pharmacy, University of Health Sciences, Institute of Health Sciences, Istanbul, TUR
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7
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Zhang MW, Shen YJ, Shi J, Yu JG. MiR-223-3p in Cardiovascular Diseases: A Biomarker and Potential Therapeutic Target. Front Cardiovasc Med 2021; 7:610561. [PMID: 33553260 PMCID: PMC7854547 DOI: 10.3389/fcvm.2020.610561] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Accepted: 12/23/2020] [Indexed: 12/20/2022] Open
Abstract
Cardiovascular diseases, involving vasculopathy, cardiac dysfunction, or circulatory disturbance, have become the major cause of death globally and brought heavy social burdens. The complexity and diversity of the pathogenic factors add difficulties to diagnosis and treatment, as well as lead to poor prognosis of these diseases. MicroRNAs are short non-coding RNAs to modulate gene expression through directly binding to the 3′-untranslated regions of mRNAs of target genes and thereby to downregulate the protein levels post-transcriptionally. The multiple regulatory effects of microRNAs have been investigated extensively in cardiovascular diseases. MiR-223-3p, expressed in multiple cells such as macrophages, platelets, hepatocytes, and cardiomyocytes to modulate their cellular activities through targeting a variety of genes, is involved in the pathological progression of many cardiovascular diseases. It participates in regulation of several crucial signaling pathways such as phosphatidylinositol 3-kinase/protein kinase B, insulin-like growth factor 1, nuclear factor kappa B, mitogen-activated protein kinase, NOD-like receptor family pyrin domain containing 3 inflammasome, and ribosomal protein S6 kinase B1/hypoxia inducible factor 1 α pathways to affect cell proliferation, migration, apoptosis, hypertrophy, and polarization, as well as electrophysiology, resulting in dysfunction of cardiovascular system. Here, in this review, we will discuss the role of miR-223-3p in cardiovascular diseases, involving its verified targets, influenced signaling pathways, and regulation of cell function. In addition, the potential of miR-223-3p as therapeutic target and biomarker for diagnosis and prediction of cardiovascular diseases will be further discussed, providing clues for clinicians.
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Affiliation(s)
- Meng-Wan Zhang
- Department of Pharmacy, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Yun-Jie Shen
- Department of Pharmacy, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Jing Shi
- Department of Pharmacy, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Jian-Guang Yu
- Department of Pharmacy, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
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Wacker C, Dams N, Schauer A, Ritzer A, Volk T, Wagner M. Region-specific mechanisms of corticosteroid-mediated inotropy in rat cardiomyocytes. Sci Rep 2020; 10:11604. [PMID: 32665640 PMCID: PMC7360564 DOI: 10.1038/s41598-020-68308-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 06/23/2020] [Indexed: 11/09/2022] Open
Abstract
Regional differences in ion channel activity in the heart control the sequence of repolarization and may contribute to differences in contraction. Corticosteroids such as aldosterone or corticosterone increase the L-type Ca2+ current (ICaL) in the heart via the mineralocorticoid receptor (MR). Here, we investigate the differential impact of corticosteroid-mediated increase in ICaL on action potentials (AP), ion currents, intracellular Ca2+ handling and contractility in endo- and epicardial myocytes of the rat left ventricle. Dexamethasone led to a similar increase in ICaL in endocardial and epicardial myocytes, while the K+ currents Ito and IK were unaffected. However, AP duration (APD) and AP-induced Ca2+ influx (QCa) significantly increased exclusively in epicardial myocytes, thus abrogating the normal differences between the groups. Dexamethasone increased Ca2+ transients, contractility and SERCA activity in both regions, the latter possibly due to a decrease in total phospholamban (PLB) and an increase PLBpThr17. These results suggest that corticosteroids are powerful modulators of ICaL, Ca2+ transients and contractility in both endo- and epicardial myocytes, while APD and QCa are increased in epicardial myocytes only. This indicates that increased ICaL and SERCA activity rather than QCa are the primary drivers of contractility by adrenocorticoids.
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Affiliation(s)
- Caroline Wacker
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Niklas Dams
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Alexander Schauer
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Anne Ritzer
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Tilmann Volk
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany. .,Muscle Research Center Erlangen (MURCE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
| | - Michael Wagner
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany. .,Abteilung für Rhythmologie, Herzzentrum Dresden, Fetscherstraße 76, 01307, Dresden, Germany.
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9
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Chen X, Qin M, Jiang W, Zhang Y, Liu X. Electrophysiological characteristics of pressure overload-induced cardiac hypertrophy and its influence on ventricular arrhythmias. PLoS One 2017; 12:e0183671. [PMID: 28863155 PMCID: PMC5580922 DOI: 10.1371/journal.pone.0183671] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 08/03/2017] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE To explore the cardiac electrophysiological characteristics of cardiac hypertrophy and its influence on the occurrence of ventricular tachyarrhythmias. METHODS Adult C57BL6 mice were randomly divided into a surgery group and a control group. Thoracic aortic constriction was performed on mice in the surgery group, and cardiac anatomical and ultrasonic evaluations were performed to confirm the success of the cardiac hypertrophy model 4 weeks after the operation. Using the Langendorff method of isolated heart perfusion, monophasic action potentials (MAPs) and the effective refractory period (ERP) at different parts of the heart (including the epi- and endo-myocardium of the left and right ventricles) were measured, and the induction rate of ventricular tachyarrhythmias was observed under programmed electrical stimulus (PES) and burst stimulus. Whole-cell patch-clamp was used to obtain the I-V characteristics of voltage-gated potassium channels in cardiomyocytes of different parts of the heart (including the epi- and endo-myocardium of the left and right ventricles) as well as the channels' properties of steady-state inactivation and recovery from inactivation. RESULTS The ratio of heart weight to body weight and the ratio of left ventricular weight to body weight in the surgery group were significantly higher than those in the control group (P < 0.05). Ultrasonic evaluation revealed that both interventricular septal diameter (IVSD) and left ventricle posterior wall diameter (LVPWD) in the surgery group were significantly larger than those in the control group (P < 0.05). Under PES and burst stimuli, the induction rates of arrhythmias in the surgery group significantly increased, reaching 41.2% and 23.5%, respectively. Both the QT interval and action potential duration (APD) in the surgery group were significantly longer than in the control group (P<0.01), and the changes showed obvious spatial heterogeneity. Whole-cell patch-clamp recordings demonstrated that the surgery group had significantly lower potassium current densities (IPeak, Ito, IKur, Iss, and IK1) at different parts of the heart than the control group (P < 0.01), and there were significant differences in the half-inactivation voltage (V1/2) and the inactivation-recovery time constant (τ) of Ito and IKur at different parts of the heart (P < 0.01) between the surgery group and the control group. In addition, the surgery group had significantly lower densities of IPeak, Ito, and IKur in cells of the endo-myocardium (P < 0.05), and the changes showed obvious spatial heterogeneity. CONCLUSION Changes in the current density and function of potassium channels contributed to irregular repolarization in cardiac hypertrophy, and the spatially heterogeneous changes of the channels may increase the occurrence of ventricular arrhythmias that accompany cardiac hypertrophy.
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Affiliation(s)
- Xiaowei Chen
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Mu Qin
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
- * E-mail: (XL); (MQ)
| | - Weifeng Jiang
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Yu Zhang
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Xu Liu
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
- * E-mail: (XL); (MQ)
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10
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Osadchii OE. Role of abnormal repolarization in the mechanism of cardiac arrhythmia. Acta Physiol (Oxf) 2017; 220 Suppl 712:1-71. [PMID: 28707396 DOI: 10.1111/apha.12902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K+ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca2+ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na+ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K+ channel (dofetilide).
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Affiliation(s)
- O. E. Osadchii
- Department of Health Science and Technology; University of Aalborg; Aalborg Denmark
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11
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Kharin SN, Krandycheva VV, Tsvetkova AS, Shumikhin KV. Remodeling of ventricular repolarization in experimental right ventricular hypertrophy. J Electrocardiol 2017; 50:626-633. [PMID: 28554514 DOI: 10.1016/j.jelectrocard.2017.05.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Indexed: 01/30/2023]
Abstract
BACKGROUND To understand electrophysiological mechanisms that underlie the progression of compensated right ventricular hypertrophy (RVH) to heart failure, the purpose of the study was to evaluate remodeling of ventricular repolarization in connection with hemodynamic abnormalities and vulnerability of the heart ventricles to arrhythmias in RVH rats with pulmonary arterial hypertension (PAH) and heart failure. METHODS PAH followed by heart failure was induced by monocrotaline in adult female Wistar rats. Unipolar epicardial electrograms and cardiac hemodynamic parameters were recorded in situ. Vulnerability to ventricular arrhythmias was measured as the threshold dose of aconitine required to produce sustained ventricular tachycardia. Histological examination of the heart ventricles was performed. Activation-recovery intervals (ARIs) and ARI dispersions were used as indices of durations and heterogeneity of repolarization respectively to assess ventricular repolarization. RESULTS AND CONCLUSIONS The development of compensated RVH was characterized by the dramatic prolongation of repolarization against the less expressed increase in repolarization heterogeneity, whereas the dramatic increase in repolarization heterogeneity against the less expressed but inhomogeneous prolongation of repolarization occurred in the progression of compensated RVH to heart failure. These changes increased vulnerability of the failing heart but not the compensated heart to aconitine-induced ventricular arrhythmias.
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Affiliation(s)
- S N Kharin
- Laboratory of Cardiac Physiology, Institute of Physiology of the Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, 50 Pervomayskaya Street, GSP-2, Syktyvkar, Komi Republic, Russian Federation; Department of Physiology, Medical Institute, Federal State Budget Educational Institution of Higher Education «Syktyvkar State University named after Pitirim Sorokin», 11 Babushkin Street, Syktyvkar, Komi Republic, Russian Federation.
| | - V V Krandycheva
- Laboratory of Cardiac Physiology, Institute of Physiology of the Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, 50 Pervomayskaya Street, GSP-2, Syktyvkar, Komi Republic, Russian Federation; Department of Physiology, Medical Institute, Federal State Budget Educational Institution of Higher Education «Syktyvkar State University named after Pitirim Sorokin», 11 Babushkin Street, Syktyvkar, Komi Republic, Russian Federation
| | - A S Tsvetkova
- Laboratory of Cardiac Physiology, Institute of Physiology of the Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, 50 Pervomayskaya Street, GSP-2, Syktyvkar, Komi Republic, Russian Federation
| | - K V Shumikhin
- Department of Physiology, Medical Institute, Federal State Budget Educational Institution of Higher Education «Syktyvkar State University named after Pitirim Sorokin», 11 Babushkin Street, Syktyvkar, Komi Republic, Russian Federation
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12
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McKinnon D, Rosati B. Transmural gradients in ion channel and auxiliary subunit expression. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 122:165-186. [PMID: 27702655 DOI: 10.1016/j.pbiomolbio.2016.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 09/30/2016] [Indexed: 12/11/2022]
Abstract
Evolution has acted to shape the action potential in different regions of the heart in order to produce a maximally stable and efficient pump. This has been achieved by creating regional differences in ion channel expression levels within the heart as well as differences between equivalent cardiac tissues in different species. These region- and species-dependent differences in channel expression are established by regulatory evolution, evolution of the regulatory mechanisms that control channel expression levels. Ion channel auxiliary subunits are obvious targets for regulatory evolution, in order to change channel expression levels and/or modify channel function. This review focuses on the transmural gradients of ion channel expression in the heart and the role that regulation of auxiliary subunit expression plays in generating and shaping these gradients.
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Affiliation(s)
- David McKinnon
- Department of Veterans Affairs Medical Center, Northport, NY, USA; Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA; Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Barbara Rosati
- Department of Veterans Affairs Medical Center, Northport, NY, USA; Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA; Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, 11794, USA.
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13
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Abstract
Heart disease produces substantial remodeling of K(+) channels that in general promotes arrhythmia occurrence. In the case of ventricular arrhythmias, K(+) channel remodeling contributes to the arrhythmic risk and increases vulnerability to torsades de pointes with K(+) channel inhibiting drugs. Atrial K(+) channel remodeling caused by atrial fibrillation promotes arrhythmia stability and presents opportunities for the development of new drugs targeting atrial inward rectifier K(+) currents. A better understanding of K(+) channel remodeling will help clinicians to appreciate arrhythmia mechanisms and determinants in a variety of clinical situations and to better manage arrhythmia therapy in patients with heart disease.
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Affiliation(s)
- Vincent Algalarrondo
- Department of Medicine, Research Center, Montreal Heart Institute, University of Montreal, 5000 Belanger Street East, Montreal, Quebec H1T 1C8, Canada; Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler, Montréal, Québec H3G 1Y6, Canada; Faculty of Medicine, University Duisburg-Essen, Hufelandstr. 55, Essen 45122, Germany
| | - Stanley Nattel
- Department of Medicine, Research Center, Montreal Heart Institute, University of Montreal, 5000 Belanger Street East, Montreal, Quebec H1T 1C8, Canada; Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler, Montréal, Québec H3G 1Y6, Canada; Faculty of Medicine, University Duisburg-Essen, Hufelandstr. 55, Essen 45122, Germany.
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14
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Meo M, Meste O, Signore S, Sorrentino A, Cannata A, Zhou Y, Matsuda A, Luciani M, Kannappan R, Goichberg P, Leri A, Anversa P, Rota M. Reduction in Kv Current Enhances the Temporal Dispersion of the Action Potential in Diabetic Myocytes: Insights From a Novel Repolarization Algorithm. J Am Heart Assoc 2016; 5:e003078. [PMID: 26896476 PMCID: PMC4802457 DOI: 10.1161/jaha.115.003078] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Accepted: 01/02/2016] [Indexed: 02/06/2023]
Abstract
BACKGROUND Diabetes is associated with prolongation of the QT interval of the electrocardiogram and enhanced dispersion of ventricular repolarization, factors that, together with atherosclerosis and myocardial ischemia, may promote the occurrence of electrical disorders. Thus, we tested the possibility that alterations in transmembrane ionic currents reduce the repolarization reserve of myocytes, leading to action potential (AP) prolongation and enhanced beat-to-beat variability of repolarization. METHODS AND RESULTS Diabetes was induced in mice with streptozotocin (STZ), and effects of hyperglycemia on electrical properties of whole heart and myocytes were studied with respect to an untreated control group (Ctrl) using electrocardiographic recordings in vivo, ex vivo perfused hearts, and single-cell patch-clamp analysis. Additionally, a newly developed algorithm was introduced to obtain detailed information of the impact of high glucose on AP profile. Compared to Ctrl, hyperglycemia in STZ-treated animals was coupled with prolongation of the QT interval, enhanced temporal dispersion of electrical recovery, and susceptibility to ventricular arrhythmias, defects observed, in part, in the Akita mutant mouse model of type I diabetes. AP was prolonged and beat-to-beat variability of repolarization was enhanced in diabetic myocytes, with respect to Ctrl cells. Density of Kv K(+) and L-type Ca(2+) currents were decreased in STZ myocytes, in comparison to cells from normoglycemic mice. Pharmacological reduction of Kv currents in Ctrl cells lengthened AP duration and increased temporal dispersion of repolarization, reiterating features identified in diabetic myocytes. CONCLUSIONS Reductions in the repolarizing K(+) currents may contribute to electrical disturbances of the diabetic heart.
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Affiliation(s)
- Marianna Meo
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Olivier Meste
- Laboratoire d'Informatique, Signaux et Systèmes de Sophia Antipolis (I3S), Université Nice Sophia Antipolis, CNRS, Nice, France
| | - Sergio Signore
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Andrea Sorrentino
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Antonio Cannata
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Yu Zhou
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Alex Matsuda
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA Fondazione Cardiocentro Ticino, University of Zurich, Lugano, Switzerland
| | - Marco Luciani
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Ramaswamy Kannappan
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Polina Goichberg
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Annarosa Leri
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA Fondazione Cardiocentro Ticino, University of Zurich, Lugano, Switzerland
| | - Piero Anversa
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA Fondazione Cardiocentro Ticino, University of Zurich, Lugano, Switzerland
| | - Marcello Rota
- Division of Cardiovascular Medicine, Departments of Anesthesia and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA Department of Physiology, New York Medical College, Valhalla, NY
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15
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Yang KC, Nerbonne JM. Mechanisms contributing to myocardial potassium channel diversity, regulation and remodeling. Trends Cardiovasc Med 2015; 26:209-18. [PMID: 26391345 DOI: 10.1016/j.tcm.2015.07.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 07/11/2015] [Accepted: 07/12/2015] [Indexed: 01/19/2023]
Abstract
In the mammalian heart, multiple types of K(+) channels contribute to the control of cardiac electrical and mechanical functioning through the regulation of resting membrane potentials, action potential waveforms and refractoriness. There are similarly vast arrays of K(+) channel pore-forming and accessory subunits that contribute to the generation of functional myocardial K(+) channel diversity. Maladaptive remodeling of K(+) channels associated with cardiac and systemic diseases results in impaired repolarization and increased propensity for arrhythmias. Here, we review the diverse transcriptional, post-transcriptional, post-translational, and epigenetic mechanisms contributing to regulating the expression, distribution, and remodeling of cardiac K(+) channels under physiological and pathological conditions.
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Affiliation(s)
- Kai-Chien Yang
- Department of Pharmacology, National Taiwan University, Taipei, Taiwan; Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Jeanne M Nerbonne
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO; Internal Medicine, Washington University School of Medicine, St. Louis, MO; Cardiovascular Division, Washington University School of Medicine, St. Louis, MO.
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16
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17
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Hsueh CH, Chen NX, Lin SF, Chen PS, Gattone VH, Allen MR, Fishbein MC, Moe SM. Pathogenesis of arrhythmias in a model of CKD. J Am Soc Nephrol 2014; 25:2812-21. [PMID: 24854269 DOI: 10.1681/asn.2013121343] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Patients with CKD have an increased risk of cardiovascular mortality from arrhythmias and sudden cardiac death. We used a rat model of CKD (Cy/+) to study potential mechanisms of increased ventricular arrhythmias. Rats with CKD showed normal ejection fraction but hypertrophic myocardium. Premature ventricular complexes occurred more frequently in CKD rats than normal rats (42% versus 11%, P=0.18). By optical mapping techniques, action potential duration (APD) at 80% of repolarization was longer in CKD rats (78±4ms) than normal rats (63±3 ms, P<0.05) at a 200-ms pacing cycle length. Calcium transient (CaT) duration was comparable. Pacing cycle length thresholds to induce CaT alternans or APD alternans were longer in CKD rats than normal rats (100±7 versus 80±3 ms and 93±6 versus 76±4 ms for CaT and APD alternans, respectively, P<0.05), suggesting increased vulnerability to ventricular arrhythmia. Ventricular fibrillation was induced in 9 of 12 CKD rats and 2 of 9 normal rats (P<0.05); early afterdepolarization occurred in two CKD rats but not normal rats. The mRNA levels of TGF-β, microRNA-21, and sodium calcium-exchanger type 1 were upregulated, whereas the levels of microRNA-29, L-type calcium channel, sarco/endoplasmic reticulum calcium-ATPase type 2a, Kv1.4, and Kv4.3 were downregulated in CKD rats. Cardiac fibrosis was mild and not different between groups. We conclude that cardiac ion channel and calcium handling are abnormal in CKD rats, leading to increased vulnerability to early afterdepolarization, triggered activity, and ventricular arrhythmias.
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Affiliation(s)
| | - Neal X Chen
- Division of Nephrology, Department of Medicine, and
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology
| | | | - Vincent H Gattone
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Matthew R Allen
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Michael C Fishbein
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California; and
| | - Sharon M Moe
- Division of Nephrology, Department of Medicine, and Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana; Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, Indiana
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18
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Huang ZB, Fang C, Lin MH, Yuan GY, Zhou SX, Wu W. Effect of fosinopril on the transient outward potassium current of hypertrophied left ventricular myocardium in the spontaneously hypertensive rat. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2014; 387:419-25. [PMID: 24441766 DOI: 10.1007/s00210-014-0956-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 01/02/2014] [Indexed: 11/26/2022]
Abstract
To investigate fosinopril's effect on the transient outward potassium current (Ito) of differing degrees of hypertrophied myocytes in the spontaneously hypertensive rat (SHR). Ten- and 24-week-old SHRs were used as models for cardiac hypertrophy. Hypertrophied ventricular myocytes were exposed to 1, 10, and 100 μmol/L fosinopril; the whole-cell patch-clamp technique was used to study the effects on the transient outward potassium current. Ito current density was decreased in SHR myocytes relative to controls (14.17 ± 0.31 and 11.62 ± 0.08 pA/pF in 10- and 24-week-old SHR versus 16.73 ± 0.15 pA/pF, p < 0.01). Higher concentrations of fosinopril (10 and 100 μmol/L) increased Ito peak current density in 10-week-old SHR myocytes compared with controls (14.92 ± 0.14 and 15.27 ± 0.13 pA/pF versus 14.17 ± 0.31 pA/pF, p < 0.01). Fosinopril increased Ito peak current density in 24-week-old SHR myocytes at all doses (12.70 ± 0.07, 13.74 ± 0.10, and 14.53 ± 0.13 versus 11.62 ± 0.08 pA/pF for controls, p < 0.01). Fosinopril had a greater Ito elevation potential on hypertrophied myocytes in 24-week-old compared with 10-week-old SHR for each dose (1.08 ± 0.09 versus 0.37 ± 0.26 pA/pF, p < 0.01; 2.13 ± 0.05 versus 0.75 ± 0.35 pA/pF, p < 0.01; 2.92 ± 0.07 versus 1.10 ± 0.40 pA/pF, p < 0.01). Fosinopril increased Ito current density in hypertrophied myocytes. This effect was more pronounced in myocytes with a greater degree of hypertrophy.
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Affiliation(s)
- Zhi-Bin Huang
- Department of Cardiology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510080, China
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19
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Schwoerer AP, Neef S, Broichhausen I, Jacubeit J, Tiburcy M, Wagner M, Biermann D, Didié M, Vettel C, Maier LS, Zimmermann WH, Carrier L, Eschenhagen T, Volk T, El-Armouche A, Ehmke H. Enhanced Ca²+ influx through cardiac L-type Ca²+ channels maintains the systolic Ca²+ transient in early cardiac atrophy induced by mechanical unloading. Pflugers Arch 2013; 465:1763-73. [PMID: 23842739 PMCID: PMC3898408 DOI: 10.1007/s00424-013-1316-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 06/13/2013] [Accepted: 06/18/2013] [Indexed: 11/04/2022]
Abstract
Cardiac atrophy as a consequence of mechanical unloading develops following exposure to microgravity or prolonged bed rest. It also plays a central role in the reverse remodelling induced by left ventricular unloading in patients with heart failure. Surprisingly, the intracellular Ca2+ transients which are pivotal to electromechanical coupling and to cardiac plasticity were repeatedly found to remain unaffected in early cardiac atrophy. To elucidate the mechanisms underlying the preservation of the Ca2+ transients, we investigated Ca2+ cycling in cardiomyocytes from mechanically unloaded (heterotopic abdominal heart transplantation) and control (orthotopic) hearts in syngeneic Lewis rats. Following 2 weeks of unloading, sarcoplasmic reticulum (SR) Ca2+ content was reduced by ~55 %. Atrophic cardiac myocytes also showed a much lower frequency of spontaneous diastolic Ca2+ sparks and a diminished systolic Ca2+ release, even though the expression of ryanodine receptors was increased by ~30 %. In contrast, current clamp recordings revealed prolonged action potentials in endocardial as well as epicardial myocytes which were associated with a two to fourfold higher sarcolemmal Ca2+ influx under action potential clamp. In addition, Cav1.2 subunits which form the pore of L-type Ca2+ channels (LTCC) were upregulated in atrophic myocardium. These data suggest that in early cardiac atrophy induced by mechanical unloading, an augmented sarcolemmal Ca2+ influx through LTCC fully compensates for a reduced systolic SR Ca2+ release to preserve the Ca2+ transient. This interplay involves an electrophysiological remodelling as well as changes in the expression of cardiac ion channels.
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Affiliation(s)
- A. P. Schwoerer
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
| | - S. Neef
- Department of Cardiology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
| | - I. Broichhausen
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
| | - J. Jacubeit
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
| | - M. Tiburcy
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - M. Wagner
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - D. Biermann
- Department of Cardiovascular Surgery, Center for Cardiology and Cardiovascular Surgery, University Heart Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
| | - M. Didié
- Department of Cardiology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - C. Vettel
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - L. S. Maier
- Department of Cardiology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - W. H. Zimmermann
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - L. Carrier
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- Inserm, U974; CNRS, UMR7215; UPMC UM76, Institut de Myologie, Paris, 75013 France
| | - T. Eschenhagen
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
| | - T. Volk
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - A. El-Armouche
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - H. Ehmke
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
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REN YANPING, ZHANG MINGJUAN, ZHANG TING, HUANG RUOWEN. Effect of ouabain on myocardial remodeling in rats. Exp Ther Med 2013; 6:65-70. [PMID: 23935720 PMCID: PMC3735870 DOI: 10.3892/etm.2013.1098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 04/03/2013] [Indexed: 11/20/2022] Open
Abstract
The aim of this study was to investigate the effect of ouabain (EO) on myocardial remodeling. Twenty-two adult male Sprague-Dawley rats were randomly divided into two groups: the rats in the EO group (n=12) were intraperitoneally injected with EO daily and those in the control group (n=10) were injected with physiological saline daily. After 8 weeks the rats were sacrificed. The ultrastructural changes in the myocardium were observed. The expression levels of voltage-gated potassium channel 4.2 (KV4.2) were detected by real-time quantitative reverse transcription-polymerase chain reaction. The effects of EO on the myocardial action potential and transient potassium efflux (Ito) were measured by patch clamping. The systolic blood pressure (SBP) of 10 of the 12 rats in the EO group, designated as the EO-sensitive (OS) rats, began to increase from the fifth week of treatment and was significantly higher compared with that of the control group 6 weeks later (P<0.01). The remaining 2 rats in the EO group that presented no increase in SBP following 8 weeks of treatment (P>0.05) were designated as EO-resistant (OR) rats. Pathological ultrastructural changes were significant in the apical mid-myocardium of the OS rats. No significant differences in KV4.2 expression were observed among the OS, OR and control rats. The patch clamp results revealed that EO prolongs the action potential duration, reduces Ito and triggers the electrical remodeling of the myocardium. EO induces a blood pressure increase and triggers structural and electrical remodeling.
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Krandycheva V, Kharin S, Strelkova M, Shumikhin K, Sobolev A, Shmakov D. Ventricular repolarization in a rat model of global heart failure. Clin Exp Pharmacol Physiol 2013; 40:431-7. [DOI: 10.1111/1440-1681.12104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 04/02/2013] [Accepted: 04/29/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Valeria Krandycheva
- Laboratory of Cardiac Physiology; Institute of Physiology of the Komi Science Centre of the Ural Branch of the Russian Academy of Sciences; Syktyvkar; Russia
| | - Sergey Kharin
- Laboratory of Cardiac Physiology; Institute of Physiology of the Komi Science Centre of the Ural Branch of the Russian Academy of Sciences; Syktyvkar; Russia
| | - Marina Strelkova
- Laboratory of Cardiac Physiology; Institute of Physiology of the Komi Science Centre of the Ural Branch of the Russian Academy of Sciences; Syktyvkar; Russia
| | - Konstantin Shumikhin
- Department of Biomedical Disciplines; Komi Branch of Kirov State Medical Academy; Syktyvkar; Russia
| | - Aleksey Sobolev
- Department of Physiology; Komi Branch of Kirov State Medical Academy; Syktyvkar; Russia
| | - Dmitry Shmakov
- Laboratory of Cardiac Physiology; Institute of Physiology of the Komi Science Centre of the Ural Branch of the Russian Academy of Sciences; Syktyvkar; Russia
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Shi C, Wang X, Dong F, Wang Y, Hui J, Lin Z, Yang J, Xu Y. Temporal alterations and cellular mechanisms of transmural repolarization during progression of mouse cardiac hypertrophy and failure. Acta Physiol (Oxf) 2013; 208:95-110. [PMID: 23356774 DOI: 10.1111/apha.12071] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 10/29/2012] [Accepted: 01/23/2013] [Indexed: 01/02/2023]
Abstract
AIM The remodelling of transmural dispersion of repolarization (TDR) in human heart failure (HF) and in different animal models of cardiac hypertrophy or HF remains a controversial topic. We hypothesize that TDR may exhibit temporal alterations, depending on the stage of the disease. METHODS We systematically investigated the temporal alterations of TDR during the development of cardiac hypertrophy and HF in the mouse pressure-overload model using electrophysiological and molecular biology techniques. RESULTS A progressive prolongation of QT interval and changes in the amplitude of the J wave at 2, 5, 9 and 13 weeks were found in anesthetized aorta-banded mice. Action potential duration (APD) at 90% repolarization (APD90) in subendocardial myocytes of the left ventricular free wall remained unchanged at the hypertrophic stage (2 and 5 weeks), but was significantly prolonged in HF mice at 9 and 13 weeks. However, APD90 in subepicardial myocytes exhibited a significant prolongation at 2 weeks and did not progressively extend from 2 weeks to 13 weeks in banded mice. Thus, non-parallel prolongation of APD in subendocardial and subepicardial myocytes led to a reduction in TDR at hypertrophic stage and an amplification of TDR at HF stage. Further experiments revealed that asynchronous down-regulation of voltage-dependent potassium currents (I(to,f), I(K,slow) and I(ss)) and L-type calcium currents (I(Ca-L)) in subendocardial and subepicardial myocytes may contribute to the dynamic remodelling of transmural APD. CONCLUSION The two distinct TDR modes were revealed during the progression of mouse cardiac hypertrophy and failure, indicating that the remodelling of TDR depends on the stage of the disease.
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Affiliation(s)
| | - X. Wang
- The Third Hospital of Hebei Medical University; Shijiazhuang; China
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23
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Bealer SL, Little JG. Seizures following hippocampal kindling induce QT interval prolongation and increased susceptibility to arrhythmias in rats. Epilepsy Res 2013; 105:216-9. [PMID: 23352222 DOI: 10.1016/j.eplepsyres.2013.01.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 12/18/2012] [Accepted: 01/03/2013] [Indexed: 12/28/2022]
Abstract
The prolonged seizures of status epilepticus produce chronic arrhythmogenic changes in cardiac function. This study was designed to determine if repeated, self-limiting seizures administered to kindled rats induce similar cardiac dysfunction. Multiple seizures administered to rats following hippocampal kindling resulted in cardiac QT interval prolongation and increased susceptibility to experimental arrhythmias. These data suggest that multiple, self-limiting seizures of intractable epilepsy may have cardiac effects that can contribute to sudden unexpected death in epilepsy (SUDEP).
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Affiliation(s)
- Steven L Bealer
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt Lake City, UT 84112-5820, USA.
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Santulli G, Cipolletta E, Sorriento D, Del Giudice C, Anastasio A, Monaco S, Maione AS, Condorelli G, Puca A, Trimarco B, Illario M, Iaccarino G. CaMK4 Gene Deletion Induces Hypertension. J Am Heart Assoc 2012; 1:e001081. [PMID: 23130158 PMCID: PMC3487344 DOI: 10.1161/jaha.112.001081] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/21/2012] [Indexed: 11/16/2022]
Abstract
Background The expression of calcium/calmodulin-dependent kinase IV (CaMKIV) was hitherto thought to be confined to the nervous system. However, a recent genome-wide analysis indicated an association between hypertension and a single-nucleotide polymorphism (rs10491334) of the human CaMKIV gene (CaMK4), which suggests a role for this kinase in the regulation of vascular tone. Methods and Results To directly assess the role of CaMKIV in hypertension, we characterized the cardiovascular phenotype of CaMK4−/− mice. They displayed a typical hypertensive phenotype, including high blood pressure levels, cardiac hypertrophy, vascular and kidney damage, and reduced tolerance to chronic ischemia and myocardial infarction compared with wild-type littermates. Interestingly, in vitro experiments showed the ability of this kinase to activate endothelial nitric oxide synthase. Eventually, in a population study, we found that the rs10491334 variant associates with a reduction in the expression levels of CaMKIV in lymphocytes from hypertensive patients. Conclusions Taken together, our results provide evidence that CaMKIV plays a pivotal role in blood pressure regulation through the control of endothelial nitric oxide synthase activity. (J Am Heart Assoc. 2012;1:e001081 doi: 10.1161/JAHA.112.001081.)
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Affiliation(s)
- Gaetano Santulli
- Department of Clinical Medicine, Cardiovascular and Immunologic Sciences, "Federico II" University of Naples, Naples, Italy (G.S., E.C., D.S., C.D.G., A.A., B.T.)
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N-acetylcysteine prevents electrical remodeling and attenuates cellular hypertrophy in epicardial myocytes of rats with ascending aortic stenosis. Basic Res Cardiol 2012; 107:290. [PMID: 22855324 DOI: 10.1007/s00395-012-0290-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 05/22/2012] [Accepted: 07/18/2012] [Indexed: 02/07/2023]
Abstract
Pressure overload is associated with cardiac hypertrophy and electrical remodeling. Here, we investigate the effects of the antioxidant N-acetylcysteine (NAC) on the cellular cardiac electrophysiology of female Sprague-Dawley rats with ascending aortic stenosis (AS). Rats were treated with NAC (1 g/kg body weight) or control solution 1 week before the intervention and in the week following AS or sham operation. Seven days after the operation, blood pressure and left ventricular pressure were measured before the heart was excised. Single cells were isolated from epicardial and endocardial layers of the left ventricular free wall and investigated using the whole-cell patch-clamp technique. Systolic blood pressure and left ventricular peak pressure were not significantly altered in the NAC group. NAC reduced the increase (p < 0.001) in the relative left ventricular weight (p < 0.05) as well as the increase (p < 0.001) in cell capacitance in epicardial (p < 0.05), but not in endocardial myocytes of AS animals. The L-type Ca(2+) current (I (CaL)) was significantly increased by AS in epicardial (+19 % at 0 mV, p < 0.01) but not in endocardial myocytes. NAC completely prevented this increase in I (CaL) (p < 0.01). The current density of the transient outward K(+) current (I (to)) was not affected by AS or NAC. Action potential duration to 90 % repolarization was significantly prolonged in epicardial (p < 0.01) as well as in endocardial (p < 0.001) cells of AS animals. NAC prevented the AP prolongation in epicardial myocytes only (p < 0.05). We conclude that reducing oxidative stress in pressure overload can prevent electrical remodeling and ameliorate hypertrophy in epicardial but not in endocardial myocytes.
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Tao W, Shi J, Dorn GW, Wei L, Rubart M. Spatial variability in T-tubule and electrical remodeling of left ventricular epicardium in mouse hearts with transgenic Gαq overexpression-induced pathological hypertrophy. J Mol Cell Cardiol 2012; 53:409-19. [PMID: 22728217 DOI: 10.1016/j.yjmcc.2012.06.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Revised: 05/18/2012] [Accepted: 06/13/2012] [Indexed: 10/28/2022]
Abstract
Pathological left ventricular hypertrophy (LVH) is consistently associated with prolongation of the ventricular action potentials. A number of previous studies, employing various experimental models of hypertrophy, have revealed marked differences in the effects of hypertrophy on action potential duration (APD) between myocytes from endocardial and epicardial layers of the LV free wall. It is not known, however, whether pathological LVH is also accompanied by redistribution of APD among myocytes from the same layer in the LV free wall. In the experiments here, LV epicardial action potential remodeling was examined in a mouse model of decompensated LVH, produced by cardiac-restricted transgenic Gαq overexpression. Confocal linescanning-based optical recordings of propagated action potentials from individual in situ cardiomyocytes across the outer layer of the anterior LV epicardium demonstrated spatially non-uniform action potential prolongation in transgenic hearts, giving rise to alterations in spatial dispersion of epicardial repolarization. Local density and distribution of anti-Cx43 mmune reactivity in Gαq hearts were unchanged compared to wild-type hearts, suggesting preservation of intercellular coupling. Confocal microscopy also revealed heterogeneous disorganization of T-tubules in epicardial cardiomyocytes in situ. These data provide evidence of the existence of significant electrical and structural heterogeneity within the LV epicardial layer of hearts with transgenic Gαq overexpression-induced hypertrophy, and further support the notion that a small portion of electrically well connected LV tissue can maintain dispersion of action potential duration through heterogeneity in the activities of sarcolemmal ionic currents that control repolarization. It remains to be examined whether other experimental models of pathological LVH, including pressure overload LVH, similarly exhibit alterations in T-tubule organization and/or dispersion of repolarization within distinct layers of LV myocardium.
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Affiliation(s)
- Wen Tao
- Riley Heart Research Center, Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202-5225, USA
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Kharin S, Krandycheva V, Tsvetkova A, Strelkova M, Shmakov D. Remodeling of ventricular repolarization in a chronic doxorubicin cardiotoxicity rat model. Fundam Clin Pharmacol 2012; 27:364-72. [DOI: 10.1111/j.1472-8206.2012.01037.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Su F, Shi M, Yan Z, Ou D, Li J, Lu Z, Zheng Q. Simvastatin modulates remodeling of Kv4.3 expression in rat hypertrophied cardiomyocytes. Int J Biol Sci 2012; 8:236-48. [PMID: 22253567 PMCID: PMC3258563 DOI: 10.7150/ijbs.8.236] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 12/31/2011] [Indexed: 12/17/2022] Open
Abstract
Objectives: Hypertrophy has been shown to be associated with arrhythmias which can be caused by abnormal remodeling of the Kv4-family of transient potassium channels. Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) have recently been shown to exert pleiotropic protective effects in cardiovascular diseases, including anti-arrhythmias. It is hypothesized that remodeling of Kv4.3 occurs in rat hypertrophied cardiomyocytes and is regulated by simvastatin. Methods: Male Sprague-Dawley rats and neonatal rat ventricular myocytes (NRVMs) underwent abdominal aortic banding (AAB) for 7 weeks and angiotensin II (AngII) treatment, respectively, to induce cardiac hypertrophy. Kv4.3 expression by NRVMs and myocardium (subepicardial and subendocardial) in the left ventricle was measured. The transient outward potassium current (Ito) of NRVMs was recorded using a whole-cell patch-clamp method. Results: Expression of the Kv4.3 transcript and protein was significantly reduced in myocardium (subepicardial and subendocardial) in the left ventricle and in NRVMs. Simvastatin partially prevented the reduction of Kv4.3 expression in NRVMs and subepicardial myocardium but not in the subendocardial myocardium. Hypertrophied NRVMs exhibited a significant reduction in the Ito current and this effect was partially reversed by simvastatin. Conclusions: Simvastatin alleviated the reduction of Kv4.3 expression, Ito currents in hypertrophied NRVMs and alleviated the reduced Kv4.3 expression in subepicardial myocardium from the hypertrophied left ventricle. It can be speculated that among the pleiotropic effects of simvastatin, the anti-arrhythmia effect is partly mediated by its effect on Kv4.3.
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Affiliation(s)
- Feifei Su
- Department of Cardiology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China.
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Little JG, Bealer SL. β adrenergic blockade prevents cardiac dysfunction following status epilepticus in rats. Epilepsy Res 2011; 99:233-9. [PMID: 22209271 DOI: 10.1016/j.eplepsyres.2011.12.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 10/27/2011] [Accepted: 12/01/2011] [Indexed: 10/14/2022]
Abstract
Status epilepticus (SE) can result in temporary cardiac dysfunction in patients, characterized by reduced ejection fraction, decreased ventricular contractility, and alterations in electrical activity of the heart. Although reversible, the cardiac effects of seizures are acutely life threatening, and may contribute to the delayed mortality following SE. The precise mechanisms mediating acute cardiac dysfunctions are not known. These studies evaluated effects of self-sustaining limbic SE in rats on cardiac performance 24h following seizures, and determined if sympathetic nervous system activation during seizures contributed to cardiac dysfunction. Rats subjected to SE received either vehicle (saline) or the B1 adrenergic antagonist atenolol (AT) prior to and during 90 min of seizure activity. Control rats were similarly treated, except they did not undergo seizures. Twenty-four hours after SE, animals were anesthetized and catheterized for measurement of cardiac performance variables. Animals undergoing SE demonstrated significantly reduced cardiac output, decreased ventricular contractility and relaxation, increased blood pressure, and prolonged QT interval. However, heart rate was not altered. Treatment with AT prevented all changes in cardiac performance due to SE, and attenuated the increase in QT interval. These data demonstrate that SE in the rat results in cardiac dysfunction 24h following seizures, mediated by the sympathetic nervous system.
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Affiliation(s)
- Jason G Little
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt Lake City, UT 84112, United States
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Yang KC, Jay PY, McMullen JR, Nerbonne JM. Enhanced cardiac PI3Kα signalling mitigates arrhythmogenic electrical remodelling in pathological hypertrophy and heart failure. Cardiovasc Res 2011; 93:252-62. [PMID: 22038742 DOI: 10.1093/cvr/cvr283] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
AIMS Cardiac hypertrophy and heart failure are associated with QT prolongation and lethal ventricular arrhythmias resulting from decreased K(+) current densities and impaired repolarization. Recent studies in mouse models of physiological cardiac hypertrophy revealed that increased phosphoinositide-3-kinase-α (PI3Kα) signalling results in the up-regulation of K(+) channels and the normalization of ventricular repolarization. The experiments here were undertaken to test the hypothesis that increased PI3Kα signalling will counteract the adverse electrophysiological remodelling associated with pathological hypertrophy and heart failure. METHODS AND RESULTS In contrast to wild-type mice, left ventricular (LV) hypertrophy, induced by transverse aortic constriction (TAC), did not result in prolongation of ventricular action potentials or QT intervals in mice with cardiac-specific expression of constitutively active PI3Kα (caPI3Kα). Indeed, repolarizing K(+) currents and K(+) channel subunit transcripts were increased in caPI3Kα + TAC LV myocytes in proportion to the TAC-induced cellular hypertrophy. Congestive heart failure in a transgenic model of dilated cardiomyopathy model is accompanied by prolonged QT intervals and ventricular action potentials, reduced K(+) currents and K(+) channel transcripts. Increased PI3Kα signalling, but not renin-angiotensin system blockade, in this model also results in increased K(+) currents and improved ventricular repolarization. CONCLUSION In the setting of pathological hypertrophy or heart failure, enhanced PI3Kα signalling results in the up-regulation of K(+) channel subunits, normalization of K(+) current densities and preserved ventricular function. Augmentation of PI3Kα signalling, therefore, may be a useful and unique strategy to protect against the increased risk of ventricular arrhythmias and sudden death associated with cardiomyopathy.
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Affiliation(s)
- Kai-Chien Yang
- Department of Developmental Biology, Washington University Medical School, 660 South Euclid Avenue Box 8103, St Louis, MO 63110-1093, USA
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Youm JB, Choi SW, Jang CH, Kim HK, Leem CH, Kim N, Han J. A computational model of cytosolic and mitochondrial [ca] in paced rat ventricular myocytes. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2011; 15:217-39. [PMID: 21994480 DOI: 10.4196/kjpp.2011.15.4.217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 08/09/2011] [Accepted: 08/09/2011] [Indexed: 11/15/2022]
Abstract
We carried out a series of experiment demonstrating the role of mitochondria in the cytosolic and mitochondrial Ca(2+) transients and compared the results with those from computer simulation. In rat ventricular myocytes, increasing the rate of stimulation (1~3 Hz) made both the diastolic and systolic [Ca(2+)] bigger in mitochondria as well as in cytosol. As L-type Ca(2+) channel has key influence on the amplitude of Ca(2+)-induced Ca(2+) release, the relation between stimulus frequency and the amplitude of Ca(2+) transients was examined under the low density (1/10 of control) of L-type Ca(2+) channel in model simulation, where the relation was reversed. In experiment, block of Ca(2+) uniporter on mitochondrial inner membrane significantly reduced the amplitude of mitochondrial Ca(2+) transients, while it failed to affect the cytosolic Ca(2+) transients. In computer simulation, the amplitude of cytosolic Ca(2+) transients was not affected by removal of Ca(2+) uniporter. The application of carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) known as a protonophore on mitochondrial membrane to rat ventricular myocytes gradually increased the diastolic [Ca(2+)] in cytosol and eventually abolished the Ca(2+) transients, which was similarly reproduced in computer simulation. The model study suggests that the relative contribution of L-type Ca(2+) channel to total transsarcolemmal Ca(2+) flux could determine whether the cytosolic Ca(2+) transients become bigger or smaller with higher stimulus frequency. The present study also suggests that cytosolic Ca(2+) affects mitochondrial Ca(2+) in a beat-to-beat manner, however, removal of Ca(2+) influx mechanism into mitochondria does not affect the amplitude of cytosolic Ca(2+) transients.
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Affiliation(s)
- Jae Boum Youm
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan 614-735, Korea
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Soltysinska E, Olesen SP, Osadchii OE. Myocardial structural, contractile and electrophysiological changes in the guinea-pig heart failure model induced by chronic sympathetic activation. Exp Physiol 2011; 96:647-63. [DOI: 10.1113/expphysiol.2011.058503] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Rondelet B, Dewachter C, Kerbaul F, Kang X, Fesler P, Brimioulle S, Naeije R, Dewachter L. Prolonged overcirculation-induced pulmonary arterial hypertension as a cause of right ventricular failure. Eur Heart J 2011; 33:1017-26. [PMID: 21606077 DOI: 10.1093/eurheartj/ehr111] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
AIMS Three-month chronic systemic-to-pulmonary shunting in growing piglets has been reported as an early pulmonary arterial hypertension (PAH) model with preserved right ventricular (RV) function. We sought to determine whether prolonged shunting might be associated with more severe PAH and RV failure. METHODS AND RESULTS Fourteen growing piglets were randomized to a sham operation or the anastomosis of the left innominate artery to the pulmonary arterial trunk. Six months later, the shunt was closed and the animals underwent haemodynamic evaluation followed by tissue sampling for pathobiological assessment. Prolonged shunting had resulted in increased mean pulmonary artery pressure (22 ± 2 versus 17 ± 1 mmHg) and pulmonary arteriolar medial thickness, while cardiac output was decreased. However, RV-arterial coupling was markedly deteriorated, with a ~50% decrease in the ratio of end-systolic to pulmonary arterial elastances (Ees/Ea). Lung tissue expressions of endothelin-1, angiopoietin-1, and bone morphogenetic protein receptor-2 were similarly altered compared with previously observed after 3-month shunting. At the RV tissue level, pro-apoptotic ratio of Bax-to-Bcl-2 expressions and caspase-3 activation were increased, along with an increase in cardiomyocyte size, while expressions in voltage-gated potassium channels (Kv1.5 and Kv2.1) and angiogenic factors (angiopoietin-2 and vascular endothelial growth factor) were decreased. Right ventricular expressions of pro-inflammatory cytokines [interleukin (IL)-1α, IL-1β, tumour necrosis factor-α (TNF-α)] and natriuretic peptide precursors (NPPA and NPPB) were increased. There was an inverse correlation between RV Ees/Ea and pro-apoptotic Bax/Bcl-2 ratios. CONCLUSIONS Prolonged left-to-right shunting in piglets does not further aggravate pulmonary vasculopathy, but is a cause of RV failure, which appears related to an activation of apoptosis and inflammation.
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Affiliation(s)
- Benoit Rondelet
- Physiology Laboratory, Faculty of Medicine, Université Libre de Bruxelles, 808 Lennik Road, 1070 Brussels, Belgium
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Liu J, Kim KH, London B, Morales MJ, Backx PH. Dissection of the voltage-activated potassium outward currents in adult mouse ventricular myocytes: I to,f, I to,s, I K,slow1, I K,slow2, and I ss. Basic Res Cardiol 2011; 106:189-204. [DOI: 10.1007/s00395-010-0134-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 10/27/2010] [Accepted: 11/04/2010] [Indexed: 11/30/2022]
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Bealer SL, Little JG, Metcalf CS, Brewster AL, Anderson AE. Autonomic and cellular mechanisms mediating detrimental cardiac effects of status epilepticus. Epilepsy Res 2010; 91:66-73. [PMID: 20650612 PMCID: PMC3212408 DOI: 10.1016/j.eplepsyres.2010.06.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 06/09/2010] [Accepted: 06/23/2010] [Indexed: 11/22/2022]
Abstract
Prolonged seizure activity (status epilepticus; SE) can result in increased susceptibility to lethal ventricular arrhythmias for an extended period of time following seizure termination. SE is accompanied by acute, intense activation of the sympathetic nervous system (SymNS) and results in myocyte myofilament damage, arrhythmogenic alterations in cardiac electrical activity, and increased susceptibility to ventricular arrhythmias. However, the mechanisms mediating the changes in cardiac function, and the specific arrhythmogenic substrate produced during SE are unknown. To determine if detrimental cardiac effects of SE are mediated by SymNS stimulation of the heart, we examined the effects of B-adrenergic blockade (atenolol) during seizure activity on blood pressure, heart rate, myocyte myofilament injury (cardiac troponin I, cTnI), electrocardiographic activity, and susceptibility to arrhythmias. Furthermore, we determined if SE was associated with altered expression of the Kv4.x potassium channels, which are critical for action potential repolarization and thereby contribute significantly to normal cardiac electrical activity. Lithium-pilocarpine induced SE was associated with acute tachycardia, hypertension, and cardiomyocyte damage. Arrhythmogenic alterations in cardiac electrical activity accompanied by increased susceptibility to experimentally induced arrhythmias were evident during the first 2 weeks following SE. Both were prevented by atenolol treatment during seizures. Furthermore, one and two weeks after SE, myocyte ion channel remodeling, characterized by a decreased expression of cardiac Kv4.2 potassium channels, was evident. These data suggest that the cardiac effects of prolonged and intense SymNS activation during SE induce myofilament damage and downregulation of Kv4.2 channels, which alter cardiac electrical activity and increase susceptibility to lethal arrhythmias.
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Affiliation(s)
- Steven L Bealer
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt Lake City, UT 84121, United States.
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Kmecova J, Klimas J. Heart rate correction of the QT duration in rats. Eur J Pharmacol 2010; 641:187-92. [DOI: 10.1016/j.ejphar.2010.05.038] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2010] [Revised: 05/14/2010] [Accepted: 05/28/2010] [Indexed: 11/16/2022]
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Open channel block of the fast transient outward K+ current by primaquine and chloroquine in rat left ventricular cardiomyocytes. Eur J Pharmacol 2010; 647:13-20. [PMID: 20807529 DOI: 10.1016/j.ejphar.2010.08.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 07/02/2010] [Accepted: 08/12/2010] [Indexed: 12/25/2022]
Abstract
Anti-malarial drugs may have severe adverse cardiac effects as a result of their ion channel blocking properties. Here we investigate the effect of the aminoquinolines primaquine and chloroquine on the fast transient outward K(+) current (I(to)) of single epicardial myocytes isolated from the left ventricular free wall of female Wistar rats. The ruptured-patch whole-cell configuration of the patch-clamp technique was used to investigate I(to). At +60 mV, primaquine blocked I(to) amplitude (defined as the current inactivating during a test pulse of 600 ms duration) with an IC(50) of 118±8 μM. I(to) charge was blocked with an IC(50) of 33±2 μM (n=42), indicating open channel block. Chloroquine blocked I(to) amplitude with an IC(50) of 4.6±0.9 mM, while the IC(50) for I(to) charge was 439±63 μM (n=23). The kinetic analysis of the onset of block revealed K(d) values of 52±8 μM (n=18) and 520±60μM (n=11) for primaquine and chloroquine, respectively. Both drugs significantly accelerated the apparent inactivation time constant of I(to). Steady-state inactivation of I(to) was not altered by 30 μM primaquine. In contrast, I(to) recovery from inactivation was prolonged with the appearance of an additional long time constant without a change of the short time constant. Exposure to 1mM chloroquine resulted in a right shift of steady-state inactivation, whereas recovery from inactivation was only mildly affected. Both substances exhibited considerable use dependence. In X. laevis oocytes heterologously expressing hKv4.2+hKChIP2b channels the block by the aminoquinolines was voltage dependent. We conclude that primaquine and chloroquine are open-channel blockers of I(to).
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Nordin C. The case for hypoglycaemia as a proarrhythmic event: basic and clinical evidence. Diabetologia 2010; 53:1552-61. [PMID: 20407743 DOI: 10.1007/s00125-010-1752-6] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Accepted: 02/03/2010] [Indexed: 12/21/2022]
Abstract
Recent clinical studies show that hypoglycaemia is associated with increased risk of death, especially in patients with coronary artery disease or acute myocardial infarction. This paper reviews data from cellular and clinical research supporting the hypothesis that acute hypoglycaemia increases the risk of malignant ventricular arrhythmias and death in patients with diabetes by generating the two classic abnormalities responsible for the proarrhythmic effect of medications, i.e. QT prolongation and Ca(2+) overload. Acute hypoglycaemia causes QT prolongation and the risk of ventricular tachycardia by directly suppressing K(+) currents activated during repolarisation, a proarrhythmic effect of many medications. Since diabetes itself, myocardial infarction, hypertrophy, autonomic neuropathy and congestive heart failure also cause QT prolongation, the arrhythmogenic effect of hypoglycaemia is likely to be greatest in patients with pre-existent cardiac disease and diabetes. Furthermore, the catecholamine surge during hypoglycaemia raises intracellular Ca(2+), thereby increasing the risk of ventricular tachycardia and fibrillation by the same mechanism as that activated by sympathomimetic inotropic agents and digoxin. Diabetes itself may sensitise myocardium to the arrhythmogenic effect of Ca(2+) overload. In humans, noradrenaline (norepinephrine) also lengthens action potential duration and causes further QT prolongation. Finally, both hypoglycaemia and the catecholamine response acutely lower serum K(+), which leads to QT prolongation and Ca(2+) loading. Thus, hypoglycaemia and the subsequent catecholamine surge provoke multiple, interactive, synergistic responses that are known to be proarrhythmic when associated with medications and other electrolyte abnormalities. Patients with diabetes and pre-existing cardiac disease may therefore have increased risk of ventricular tachycardia and fibrillation during hypoglycaemic episodes.
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Affiliation(s)
- C Nordin
- Division of Cardiology, Montefiore Medical Center, 111 E. 210th Street, Bronx, NY 10467, USA.
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Zhang L, Xu CQ, Hong Y, Zhang JL, Liu Y, Zhao M, Cao YX, Lu YJ, Yang BF, Shan HL. Propranolol regulates cardiac transient outward potassium channel in rat myocardium via cAMP/PKA after short-term but not after long-term ischemia. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:63-71. [PMID: 20499050 DOI: 10.1007/s00210-010-0520-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 04/25/2010] [Indexed: 10/19/2022]
Abstract
It was recently suggested that the antiarrhythmic effect of propranolol, a ss-adrenoceptor antagonist, on ischemic myocardium includes restoration of I(K1) current and Cx43 conductance; however, little is known whether effects on the transient outward current I(to) contribute. A model of myocardial infarction (MI) by ligating the left anterior descending coronary artery was established. Propranolol was given 1 h or daily for 3 months, whole-cell patch-clamp techniques were used to measure I(to). Kv4.2 and PKA levels were analyzed by Western blot and cAMP level was determined by radioimmunoassay. The results showed that propranolol decreased the incidence of arrhythmias induced by acute ischemia and mortality in 3 month MI rats. Propranolol restored the diminished I(to) density and Kv4.2 protein in MI hearts. In addition, neonatal cardiomyocyte pretreatment with propranolol or administrated after hypoxia can resume I(to) density. cAMP/PKA was enhanced in acute MI, the reason of decreased Kv4.2 expression. Treatment with propranolol prevented the increased cAMP/PKA in 1 h MI, whereas propranolol had little effect on decreased cAMP/PKA in 3 months MI. This study demonstrated that both short- and long-term propranolol administrations protect cardiomyocytes against arrhythmias and mortality caused by cardiac ischemia; the involvement of cAMP/PKA signal pathway in the regulation of propranolol on I(to) acted differently along with the ischemic progression.
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Affiliation(s)
- Li Zhang
- Department of Pharmacology, the State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
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Molecular and functional remodeling of Ito by angiotensin II in the mouse left ventricle. J Mol Cell Cardiol 2010; 48:140-51. [DOI: 10.1016/j.yjmcc.2009.08.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 08/20/2009] [Accepted: 08/27/2009] [Indexed: 11/18/2022]
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Larger transient outward K(+) current and shorter action potential duration in Galpha(11) mutant mice. Pflugers Arch 2009; 459:607-18. [PMID: 19953263 DOI: 10.1007/s00424-009-0762-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 10/05/2009] [Accepted: 11/11/2009] [Indexed: 10/20/2022]
Abstract
The alpha(1)-adrenoceptor as well as the AT(1)- and the ET(A)-receptor couple to G-proteins of the Galpha(q/11) family and contribute to the regulation of the transient outward K(+) current (I(to,f)) under pathological conditions such as cardiac hypertrophy or failure. This suggests an important role of Galpha(q/11)-signalling in the physiological regulation of I(to,f). Here, we investigate mice deficient of the Galpha(11) protein (gna11(-/-)) to clarify the physiological role of Galpha(11) signalling in cardiac ion channel regulation. Myocytes from endocardial and epicardial layers were isolated from the left ventricular free wall and investigated using the ruptured-patch whole-cell patch-clamp technique. At +40 mV, epicardial myocytes from gna11(-/-) mice displayed a 23% larger I(to,f) than controls (52.6 + or - 4.1 pApF(-1), n = 20 vs 42.7 + or - 2.8 pApF(-1), n = 26, p < 0.05). Endocardial I(to,f) was similar in gna11(-/-) mice and controls. With the except of minor changes in endocardial myocytes, I(to,f) kinetics were similar in both groups. In the epicardial layer, western blot analysis revealed a 19% higher expression of the K(+)-channel alpha-subunit Kv4.2 in gna11(-/-) mice than in wild type (wt; p < 0.05). The beta-subunit KChIP2b was upregulated by 102% in epicardial myocytes of gna11(-/-) mice (p < 0.01, n = 4). Consistent with the difference in I(to,f), action potential duration was shorter in epicardial cells of gna11(-/-) mice than in wt (p < 0.05), while no difference was found in endocardial myocytes. These results suggest that Galpha(11)-coupled signalling is a central pathway in the regulation of I(to,f). It physiologically exerts a tonic inhibitory influence on the expression of I(to,f) and thereby contributes to the regulation of cardiac repolarisation.
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Stones R, Billeter R, Zhang H, Harrison S, White E. The role of transient outward K+ current in electrical remodelling induced by voluntary exercise in female rat hearts. Basic Res Cardiol 2009; 104:643-52. [PMID: 19415411 PMCID: PMC2758204 DOI: 10.1007/s00395-009-0030-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 03/21/2009] [Accepted: 04/08/2009] [Indexed: 12/24/2022]
Abstract
Regular exercise can lead to electrical remodelling of the heart. The cellular mechanisms associated with these changes are not well understood, and are difficult to study in human tissue but are important given that exercise is recommended to the general population. We have investigated the role played by the transient outward K+ current (I(to)) in the changes in electrical activity seen in response to voluntary exercise training in rats. Female rats undertook 6 weeks of voluntary wheel running exercise (TRN) or were sedentary controls (SED). Monophasic action potentials (MAPs) were recorded from the surface of whole hearts. Whole cell patch clamp recordings of I(to); mRNA and protein levels of selected targets in sub-epicardial (EPI) and sub-endocardial myocardium of SED and TRN hearts were compared. In TRN rats, heart weight:body weight was significantly increased and epicardial MAPs significantly prolonged. I(to) density was reduced in TRN EPI myocytes, such that the transmural gradient of I(to) was significantly reduced (P < 0.05). Computer modelling of these changes in I(to) predicted the observed changes in action potential profile. However, transmural gradients in mRNA and protein expression for Kv4.2 or mRNA levels of the Kv4.2 regulators; KChIP2 and Irx-5 were not significantly altered by voluntary exercise. We conclude that voluntary exercise electrical remodelling is caused, at least in part, by a decrease in EPI I(to), possibly because of fewer functional channels in the membrane, which results in a fall in the transmural action potential duration gradient.
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Affiliation(s)
- Rachel Stones
- Institute of Membrane and Systems Biology and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Garstang Building, Leeds, LS29JT UK
| | - Rudolf Billeter
- Centre for Integrated Systems Biology and Medicine, University of Nottingham, Nottingham, UK
| | - Henggui Zhang
- School of Physics and Astronomy, University of Manchester, Manchester, UK
| | - Simon Harrison
- Institute of Membrane and Systems Biology and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Garstang Building, Leeds, LS29JT UK
| | - Ed White
- Institute of Membrane and Systems Biology and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Garstang Building, Leeds, LS29JT UK
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Metcalf CS, Poelzing S, Little JG, Bealer SL. Status epilepticus induces cardiac myofilament damage and increased susceptibility to arrhythmias in rats. Am J Physiol Heart Circ Physiol 2009; 297:H2120-7. [PMID: 19820194 DOI: 10.1152/ajpheart.00724.2009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Status epilepticus (SE) is a seizure or series of seizures that persist for >30 min and often results in mortality. Death rarely occurs during or immediately following seizure activity, but usually within 30 days. Although ventricular arrhythmias have been implicated in SE-related mortality, the effects of this prolonged seizure activity on the cardiac function and susceptibility to arrhythmias have not been directly investigated. We evaluated myocardial damage, alterations in cardiac electrical activity, and susceptibility to experimentally induced arrhythmias produced by SE in rats. SE resulted in seizure-related increases in blood pressure, heart rate, and the first derivative of pressure, as well as modest, diffuse myocyte damage assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining. Ten to twelve days following seizures, electrocardiographic recordings showed arrhythmogenic alterations in cardiac electrical activity, denoted by prolonged QT interval corrected for heart rate and QT dispersion. Finally, SE increased susceptibility to experimentally induced (intravenous aconitine) cardiac arrhythmias. These data suggest that SE produces tachycardic ischemia following the activation of the sympathetic nervous system, resulting in cardiac myofilament damage, arrhythmogenic alterations in cardiac electrical activity, and increased susceptibility to ventricular arrhythmias.
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Affiliation(s)
- Cameron S Metcalf
- Department of Pharmacology and Toxicology, University of Utah, 30 S. 2000 East Rm. 201, Salt Lake City, UT 84112, USA
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Niwa N, Nerbonne JM. Molecular determinants of cardiac transient outward potassium current (I(to)) expression and regulation. J Mol Cell Cardiol 2009; 48:12-25. [PMID: 19619557 DOI: 10.1016/j.yjmcc.2009.07.013] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 06/25/2009] [Accepted: 07/10/2009] [Indexed: 12/21/2022]
Abstract
Rapidly activating and inactivating cardiac transient outward K(+) currents, I(to), are expressed in most mammalian cardiomyocytes, and contribute importantly to the early phase of action potential repolarization and to plateau potentials. The rapidly recovering (I(t)(o,f)) and slowly recovering (I(t)(o,s)) components are differentially expressed in the myocardium, contributing to regional heterogeneities in action potential waveforms. Consistent with the marked differences in biophysical properties, distinct pore-forming (alpha) subunits underlie the two I(t)(o) components: Kv4.3/Kv4.2 subunits encode I(t)(o,f), whereas Kv1.4 encodes I(t)(o,s), channels. It has also become increasingly clear that cardiac I(t)(o) channels function as components of macromolecular protein complexes, comprising (four) Kvalpha subunits and a variety of accessory subunits and regulatory proteins that influence channel expression, biophysical properties and interactions with the actin cytoskeleton, and contribute to the generation of normal cardiac rhythms. Derangements in the expression or the regulation of I(t)(o) channels in inherited or acquired cardiac diseases would be expected to increase the risk of potentially life-threatening cardiac arrhythmias. Indeed, a recently identified Brugada syndrome mutation in KCNE3 (MiRP2) has been suggested to result in increased I(t)(o,f) densities. Continued focus in this area seems certain to provide new and fundamentally important insights into the molecular determinants of functional I(t)(o) channels and into the molecular mechanisms involved in the dynamic regulation of I(t)(o) channel functioning in the normal and diseased myocardium.
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Affiliation(s)
- Noriko Niwa
- Department of Developmental Biology, Washington University School of Medicine, 660 South Euclid Avenue, Box 8103, St. Louis, MO 63110-1093, USA
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Boukens BJD, Christoffels VM, Coronel R, Moorman AFM. Developmental basis for electrophysiological heterogeneity in the ventricular and outflow tract myocardium as a substrate for life-threatening ventricular arrhythmias. Circ Res 2009; 104:19-31. [PMID: 19118284 DOI: 10.1161/circresaha.108.188698] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Reentry is the main mechanism of life-threatening ventricular arrhythmias, including ventricular fibrillation and tachycardia. Its occurrence depends on the simultaneous presence of an arrhythmogenic substrate (a preexisting condition) and a "trigger," and is favored by electrophysiological heterogeneities. In the adult heart, electrophysiological heterogeneities of the ventricle exist along the apicobasal, left-right, and transmural axes. Also, conduction is preferentially slowed in the right ventricular outflow tract, especially during pharmacological sodium channel blockade. We propose that the origin of electrophysiological heterogeneities of the adult heart lies in early heart development. The heart is formed from several progenitor regions: the first heart field predominantly forms the left ventricle, whereas the second heart field forms the right ventricle and outflow tract. Furthermore, the embryonic outflow tract consists of slowly conducting tissue until it is incorporated into the ventricles and develops rapidly conducting properties. The subepicardial myocytes and subendocardial myocytes run distinctive gene programs from their formation onwards. This review discusses the hypothesis that electrophysiological heterogeneities in the adult heart result from persisting patterns in gene expression and function along the craniocaudal and epicardial-endocardial axes of the developing heart. Understanding the developmental origins of electrophysiological heterogeneity contributing to ventricular arrhythmias may give rise to new therapies.
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Affiliation(s)
- Bastiaan J D Boukens
- Heart Failure Research Center, Academic Medical Center, Amsterdam, The Netherlands
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Altered expression of Na+ transporters at the mRNA level in rat normal and hypertrophic myocardium. Heart Vessels 2009; 24:54-62. [PMID: 19165570 DOI: 10.1007/s00380-008-1071-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Accepted: 05/16/2008] [Indexed: 10/21/2022]
Abstract
Intracellular Na(+) ([Na(+)](i)) regulation plays a crucial role in the structural, mechanical, and electrical properties of myocardium. It is assumed that the [Na(+)](i) handling system may differ not only between normal and diseased hearts but also regionally within a heart. To gain new insight concerning disease- and region-dependent differences in the [Na(+)](i)-regulatory system, we investigated mRNA expression of Na+ transporters, the principal determinants of [Na(+)](i). Nonischemic pressure-overloaded hypertrophy was created by suprarenal abdominal aortic constriction of 50% for 7 weeks. mRNA abundances of Na(+)-Ca(2+) exchanger (NCX1), Na(+)-H(+) exchanger (NHE1), Na(+)-K(+)-2Cl(-) exchanger (NKCC1) and Na(+), K(+)-ATPase multigene family(alpha(1), alpha(2), alpha(3), and beta(1) isoforms) were measured by the real-time quantitative polymerase chain reaction method. mRNA abundance of all transporters mediating Na(+) influx (NCX1, NHE1, and NKCC1) was significantly upregulated as compared to normal. In contrast, Na(+)-efflux-mediating transporter (Na(+), K(+)-ATPase) mRNA expression was unaltered between normal and hypertrophic hearts. Losartan, an angiotensin II AT1 receptor antagonist, significantly attenuated upregulation of Na(+)-influx-mediating transporters induced by aortic constriction. The onset of Na(+)-influx-mediating transporter upregulation occurred within 5 days following constriction. In normal and hypertrophied hearts, mRNA of all Na(+)-influx-mediating transporters was expressed in order of abundance as: apex > septum approximately free wall of left ventricles. A transmural gradient in expression was also evident in normal hearts (midcardium > endo- and epicardium), which was attenuated under hypertrophic development. Myocardial hypertrophy is associated with significant changes in the spatial distribution and expression levels of Na(+) transporters. The upregulation of Na influx transporters during hypertrophy may contribute to the remodeling process, modulate contractility and promote arrhythmias.
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NFATc3-dependent loss of I(to) gradient across the left ventricular wall during chronic beta adrenergic stimulation. J Mol Cell Cardiol 2008; 46:249-56. [PMID: 19027024 DOI: 10.1016/j.yjmcc.2008.10.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 09/26/2008] [Accepted: 10/09/2008] [Indexed: 01/08/2023]
Abstract
In heart, pore-forming Kv4 alpha channel subunits underlie the K(+) transient outward current (I(to)). Expression of Kv4 is greater in left ventricular epicardial (EPI) than in endocardial (ENDO) cells, resulting in larger I(to) in EPI than in ENDO cells. In adult ventricular myocytes, the transcription factor NFATc3 suppresses Kv4 expression. NFATc3 activity is higher in ENDO than in EPI cells and this has been proposed to contribute to heterogeneous Kv4 expression across the left ventricular free wall. Here, we tested the hypothesis that regional activation of NFATc3 signaling dissipates the gradient of I(to) density across the mouse left ventricle during chronic activation of beta adrenergic signaling. [Ca(2+)](i), calcineurin, and NFAT activity were larger in ENDO than in EPI myocytes. Infusion of the beta adrenergic receptor agonist isoproterenol increased [Ca(2+)](i), calcineurin, and NFAT activity in EPI, but not in ENDO myocytes, leading to equalization of these parameters in EPI and ENDO cells. This was accompanied by dissipation of the transmural gradient in Kv4.2 expression and I(to) density. Unlike wild type, ENDO or EPI myocytes from beta1 adrenergic receptor-null and NFATc3-null mice did not undergo changes in I(to) density during isoproterenol infusion. Collectively, these data suggest that calcineurin and NFATc3 signaling contributes to the loss of heterogeneous Kv4 expression, and hence I(to) density, in the mouse left ventricle during chronic beta adrenergic stimulation.
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Schwoerer AP, Melnychenko I, Goltz D, Hedinger N, Broichhausen I, El-Armouche A, Eschenhagen T, Volk T, Ehmke H. Unloaded rat hearts in vivo express a hypertrophic phenotype of cardiac repolarization. J Mol Cell Cardiol 2008; 45:633-41. [DOI: 10.1016/j.yjmcc.2008.02.271] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 02/11/2008] [Accepted: 02/12/2008] [Indexed: 11/25/2022]
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Teos LY, Zhao A, Alvin Z, Laurence GG, Li C, Haddad GE. Basal and IGF-I-dependent regulation of potassium channels by MAP kinases and PI3-kinase during eccentric cardiac hypertrophy. Am J Physiol Heart Circ Physiol 2008; 295:H1834-45. [PMID: 18757484 DOI: 10.1152/ajpheart.321.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The potassium channels I(K) and I(K1), responsible for the action potential repolarization and resting potential respectively, are altered during cardiac hypertrophy. The activation of insulin-like growth factor-I (IGF-I) during hypertrophy may affect channel activity. The aim was to examine the modulatory effects of IGF-I on I(K) and I(K1) through mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways during hypertrophy. With the use of specific inhibitors for ERK1/2 (PD98059), p38 MAPK (SB203580) and PI3K/Akt (LY294002), Western blot and whole cell patch-clamp were conducted on sham and aorto-caval shunt-induced hypertrophy adult rat myocytes. Basal activation levels of MAPKs and Akt were increased during hypertrophy. Acute IGF-I (10(-8) M) enhanced basal activation levels of these kinases in normal hearts but only those of Akt in hypertrophied ones. I(K) and I(K1) activities were lowered by IGF-I. Inhibition of ERK1/2, p38 MAPK, or Akt reduced basal I(K) activity by 70, 32, or 50%, respectively, in normal cardiomyocytes vs. 53, 34, or 52% in hypertrophied ones. However, basal activity of I(K1) was reduced by 45, 48, or 45% in the former vs. 63, 43, or 24% in the latter. The inhibition of either MAPKs or Akt alleviated IGF-I effects on I(K) and I(K1). We conclude that basal I(K) and I(K1) are positively maintained by steady-state Akt and ERK activities. K+ channels seem to be regulated in a dichotomic manner by acutely stimulated MAPKs and Akt. Eccentric cardiac hypertrophy may be associated with a change in the regulation of the steady-state basal activities of K+ channels towards MAPKs, while that of the acute IGF-I-stimulated ones toward Akt.
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Affiliation(s)
- Leyla Y Teos
- Department of Physiology and Biophysics, College of Medicine, Howard University, Washington, DC 20059, USA
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50
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Wagner M, Rudakova E, Volk T. Aldosterone-induced changes in the cardiac L-type Ca(2+) current can be prevented by antioxidants in vitro and are absent in rats on low salt diet. Pflugers Arch 2008; 457:339-49. [PMID: 18504604 DOI: 10.1007/s00424-008-0518-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Revised: 03/18/2008] [Accepted: 04/12/2008] [Indexed: 12/21/2022]
Abstract
Mineralocorticoid receptor (MR) activation modulates cardiac L-type Ca(2+) current (I (CaL)) and transient outward K(+) current (I (to)). The exact circumstances of MR activation, however, remain elusive. Here, we investigate the influence of corticosteroids on MR-mediated changes in cellular electrophysiology. In vitro incubation of adult rat ventricular myocytes with the MR agonist aldosterone (100 nM, 24 h) increased I (CaL) density by 34% (n = 16; p < 0.01). This effect was abrogated by co-incubation with the MR antagonist spironolactone (10 muM). To investigate whether an increase in serum aldosterone concentration is sufficient for an increase in I (CaL) in vivo, rats were subjected to low Na(+) diet (LSD, 0.013% Na(+)) for 28 days. This increased serum aldosterone concentration from 0.19 +/- 0.04 nM (n = 6) in control animals (0.3% Na(+), CSD) to 16.1 +/- 2.1 nM (n = 6; p < 0.0001). Strikingly, I (CaL) density was similar in both CSD and LSD rats (-12.9 +/- 0.9 pA pF(-1), n = 18 and -13.7 +/- 1.1 pA pF(-1), n = 16, respectively), as was I (to) density. In vitro, the glucocorticoid corticosterone (1 microM) also increased I (CaL) and this effect was blocked by spironolactone (10 microM). Co-incubation with corticosterone (1 microM, the normal serum concentration) and aldosterone (100 nM, mimicking low Na(+) intake) did not further increase I (CaL) compared to corticosterone alone. Moreover, co-incubation of myocytes with N-acetylcysteine (10 mM) prevented the aldosterone (100 nM) or corticosterone (1 microM)-induced increase in I (CaL). In conclusion, an increase in serum aldosterone concentration in response to LSD is not sufficient for an increase in I (CaL) density in cardiomyocytes in vivo. This is supported in vitro by the absence of an effect of aldosterone on I (CaL) in the presence of a physiological concentration of corticosterone. Moreover, the cellular redox state may modulate MR activation.
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Affiliation(s)
- Michael Wagner
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstrasse 6, 91054, Erlangen, Germany
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