1
|
Ágoston M, Kohajda Z, Virág L, Baláti B, Nagy N, Lengyel C, Bitay M, Bogáts G, Vereckei A, Papp JG, Varró A, Jost N. A Comparative Study of the Rapid (I Kr) and Slow (I Ks) Delayed Rectifier Potassium Currents in Undiseased Human, Dog, Rabbit, and Guinea Pig Cardiac Ventricular Preparations. Pharmaceuticals (Basel) 2024; 17:1091. [PMID: 39204196 PMCID: PMC11357539 DOI: 10.3390/ph17081091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 07/24/2024] [Accepted: 08/09/2024] [Indexed: 09/03/2024] Open
Abstract
To understand the large inter-species variations in drug effects on repolarization, the properties of the rapid (IKr) and the slow (IKs) components of the delayed rectifier potassium currents were compared in myocytes isolated from undiseased human donor (HM), dog (DM), rabbit (RM) and guinea pig (GM) ventricles by applying the patch clamp and conventional microelectrode techniques at 37 °C. The amplitude of the E-4031-sensitive IKr tail current measured at -40 mV after a 1 s long test pulse of 20 mV, which was very similar in HM and DM but significant larger in RM and GM. The L-735,821-sensitive IKs tail current was considerably larger in GM than in RM. In HM, the IKs tail was even smaller than in DM. At 30 mV, the IKr component was activated extremely rapidly and monoexponentially in each studied species. The deactivation of the IKr component in HM, DM, and RM measured at -40 mV. After a 30 mV pulse, it was slow and biexponential, while in GM, the IKr tail current was best fitted triexponentially. At 30 mV, the IKs component activated slowly and had an apparent monoxponential time course in HM, DM, and RM. In contrast, in GM, the activation was clearly biexponential. In HM, DM, and RM, IKs component deactivation measured at -40 mV was fast and monoexponential, while in GM, in addition to the fast component, another slower component was also revealed. These results suggest that the IK in HM resembles that measured in DM and RM and considerably differs from that observed in GM. These findings suggest that the dog and rabbit are more appropriate species than the guinea pig for preclinical evaluation of new potential drugs expected to affect cardiac repolarization.
Collapse
Affiliation(s)
- Márta Ágoston
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
| | - Zsófia Kohajda
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- Interdisciplinary Research and Development and Innovation Centre of Excellence, University of Szeged, 6720 Szeged, Hungary
| | - Beáta Baláti
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
| | - Csaba Lengyel
- Department of Medicine, Albert Szent-Györgyi Medical School, University of Szeged, 6720 Szeged, Hungary
| | - Miklós Bitay
- Department of Cardiac Surgery, Albert Szent-Györgyi Medical School, University of Szeged, 6742 Szeged, Hungary
| | - Gábor Bogáts
- Department of Cardiac Surgery, Albert Szent-Györgyi Medical School, University of Szeged, 6742 Szeged, Hungary
| | - András Vereckei
- Department of Internal Medicine and Haematology, Semmelweis University, 1088 Budapest, Hungary
| | - Julius Gy. Papp
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
- Interdisciplinary Research and Development and Innovation Centre of Excellence, University of Szeged, 6720 Szeged, Hungary
| | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
- Interdisciplinary Research and Development and Innovation Centre of Excellence, University of Szeged, 6720 Szeged, Hungary
| |
Collapse
|
2
|
Oknińska M, Mączewski M, Mackiewicz U. Ventricular arrhythmias in acute myocardial ischaemia-Focus on the ageing and sex. Ageing Res Rev 2022; 81:101722. [PMID: 36038114 DOI: 10.1016/j.arr.2022.101722] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 08/17/2022] [Accepted: 08/20/2022] [Indexed: 01/31/2023]
Abstract
Annually, approximately 17 million people die from cardiovascular diseases worldwide, half of them suddenly. The most common direct cause of sudden cardiac death is ventricular arrhythmia triggered by an acute coronary syndrome (ACS). The study summarizes the knowledge of the mechanisms of arrhythmia onset during ACS in humans and in animal models and factors that may influence the susceptibility to life-threatening arrhythmias during ACS with particular focus on the age and sex. The real impact of age and sex on the arrhythmic susceptibility within the setting of acute ischaemia is masked by the fact that ACSs result from coronary artery disease appearing with age much earlier among men than among women. However, results of researches show that in ageing process changes with potential pro-arrhythmic significance, such as increased fibrosis, cardiomyocyte hypertrophy, decrease number of gap junction channels, disturbances of the intracellular Ca2+ signalling or changes in electrophysiological parameters, occur independently of the development of cardiovascular diseases and are more severe in male individuals. A review of the literature also indicates a marked paucity of research in this area in female and elderly individuals. Greater awareness of sex differences in the aging process could help in the development of personalized prevention methods targeting potential pro-arrhythmic factors in patients of both sexes to reduce mortality during the acute phase of myocardial infarction. This is especially important in an era of aging populations in which women will predominate due to their longer lifespan.
Collapse
Affiliation(s)
- Marta Oknińska
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Marymoncka 99/103, 01-813 Warsaw, Poland
| | - Michał Mączewski
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Marymoncka 99/103, 01-813 Warsaw, Poland
| | - Urszula Mackiewicz
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Marymoncka 99/103, 01-813 Warsaw, Poland.
| |
Collapse
|
3
|
Kim N, Pronto JD, Nickerson DP, Taberner AJ, Hunter PJ. A novel modular modeling approach for understanding different electromechanics between left and right heart in rat. Front Physiol 2022; 13:965054. [PMID: 36176770 PMCID: PMC9513479 DOI: 10.3389/fphys.2022.965054] [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: 06/09/2022] [Accepted: 08/22/2022] [Indexed: 12/01/2022] Open
Abstract
While ion channels and transporters involved in excitation-contraction coupling have been linked and constructed as comprehensive computational models, validation of whether each individual component of a model can be reused has not been previously attempted. Here we address this issue while using a novel modular modeling approach to investigate the underlying mechanism for the differences between left ventricle (LV) and right ventricle (RV). Our model was developed from modules constructed using the module assembly principles of the CellML model markup language. The components of three existing separate models of cardiac function were disassembled as to create smaller modules, validated individually, and then the component parts were combined into a new integrative model of a rat ventricular myocyte. The model was implemented in OpenCOR using the CellML standard in order to ensure reproducibility. Simulated action potential (AP), Ca2+ transient, and tension were in close agreement with our experimental measurements: LV AP showed a prolonged duration and a more prominent plateau compared with RV AP; Ca2+ transient showed prolonged duration and slow decay in LV compared to RV; the peak value and relaxation of tension were larger and slower, respectively, in LV compared to RV. Our novel approach of module-based mathematical modeling has established that the ionic mechanisms underlying the APs and Ca2+ handling play a role in the variation in force production between ventricles. This simulation process also provides a useful way to reuse and elaborate upon existing models in order to develop a new model.
Collapse
Affiliation(s)
- Nari Kim
- NLRL for Innovative Cardiovascular Engineering, Department of Physiology, College of Medicine, Inje University, Busan, South Korea
- Cardiovascular and Metabolic Disease Center, Inje University, Busan, South Korea
- *Correspondence: Nari Kim,
| | - Julius D. Pronto
- NLRL for Innovative Cardiovascular Engineering, Department of Physiology, College of Medicine, Inje University, Busan, South Korea
- Cardiovascular and Metabolic Disease Center, Inje University, Busan, South Korea
| | - David P. Nickerson
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Andrew J. Taberner
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Peter J. Hunter
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| |
Collapse
|
4
|
Canine Myocytes Represent a Good Model for Human Ventricular Cells Regarding Their Electrophysiological Properties. Pharmaceuticals (Basel) 2021; 14:ph14080748. [PMID: 34451845 PMCID: PMC8398821 DOI: 10.3390/ph14080748] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/18/2021] [Accepted: 07/20/2021] [Indexed: 12/19/2022] Open
Abstract
Due to the limited availability of healthy human ventricular tissues, the most suitable animal model has to be applied for electrophysiological and pharmacological studies. This can be best identified by studying the properties of ion currents shaping the action potential in the frequently used laboratory animals, such as dogs, rabbits, guinea pigs, or rats, and comparing them to those of human cardiomyocytes. The authors of this article with the experience of three decades of electrophysiological studies, performed in mammalian and human ventricular tissues and isolated cardiomyocytes, summarize their results obtained regarding the major canine and human cardiac ion currents. Accordingly, L-type Ca2+ current (ICa), late Na+ current (INa-late), rapid and slow components of the delayed rectifier K+ current (IKr and IKs, respectively), inward rectifier K+ current (IK1), transient outward K+ current (Ito1), and Na+/Ca2+ exchange current (INCX) were characterized and compared. Importantly, many of these measurements were performed using the action potential voltage clamp technique allowing for visualization of the actual current profiles flowing during the ventricular action potential. Densities and shapes of these ion currents, as well as the action potential configuration, were similar in human and canine ventricular cells, except for the density of IK1 and the recovery kinetics of Ito. IK1 displayed a largely four-fold larger density in canine than human myocytes, and Ito recovery from inactivation displayed a somewhat different time course in the two species. On the basis of these results, it is concluded that canine ventricular cells represent a reasonably good model for human myocytes for electrophysiological studies, however, it must be borne in mind that due to their stronger IK1, the repolarization reserve is more pronounced in canine cells, and moderate differences in the frequency-dependent repolarization patterns can also be anticipated.
Collapse
|
5
|
Elasoru SE, Rhana P, de Oliveira Barreto T, Naves de Souza DL, Menezes-Filho JER, Souza DS, Loes Moreira MV, Gomes Campos MT, Adedosu OT, Roman-Campos D, Melo MM, Cruz JS. Andrographolide protects against isoproterenol-induced myocardial infarction in rats through inhibition of L-type Ca 2+ and increase of cardiac transient outward K + currents. Eur J Pharmacol 2021; 906:174194. [PMID: 34044012 DOI: 10.1016/j.ejphar.2021.174194] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/09/2021] [Accepted: 05/12/2021] [Indexed: 10/21/2022]
Abstract
Myocardial infarction (MI) is the irreversible injury of the myocardium caused by prolonged myocardial ischemia and is a major cause of heart failure and eventual death among ischemic patients. The present study assessed the protective potentials of andrographolide against isoproterenol-induced myocardial infarction in rats. Animals were randomly divided into four groups: Control (Ctr) group received 0.9% saline solution once daily for 21 days, Isoproterenol (Iso) group received 0.9% saline solution once daily for 19 days followed by 80 mg/kg/day of isoproterenol hydrochloride solution on day 20 and 21, Andrographolide (Andro) group received 20 mg/kg/day of andrographolide for 21 days, and Andrographolide plus Isoproterenol (Andro + Iso) group received 20 mg/kg/day of andrographolide for 21 days with co-administration of 80 mg/kg/day of isoproterenol hydrochloride solution on day 20 and 21. After all treatments, cardiac-specific parameters that define cardiac health and early subacute MI were measured in all groups using both biophysical and pharmacological assay methods. Isoproterenol administration significantly (P < 0.05) increased cardiac mass indexes, systemic cardiac biomarkers, infarct size and caused cardiac histological alterations; significantly (P < 0.05) increased heart rate, QRS & QTc intervals and caused ST-segment elevation; significantly (P < 0.05) increased myocytes shortening, action potential duration (APD), L-type Ca2+ current (ICa,L) density and significantly (P < 0.05) decreased transient outward K+ current (Ito) density typical of the early subacute MI. Interestingly, pretreatment with andrographolide prevented and or minimized these anomalies, notably, by reducing ICa,L density and increasing Ito density significantly. Therefore, andrographolide could be seen as a promising therapeutic agent capable of making the heart resistant to early subacute infarction and it could be used as template for the development of semisynthetic drug(s) for cardiac protection against MI.
Collapse
Affiliation(s)
- Seyi Elijah Elasoru
- Department of Biochemistry and Immunology, Institute of Biological Science, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Paula Rhana
- Department of Biochemistry and Immunology, Institute of Biological Science, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Tatiane de Oliveira Barreto
- Department of Biochemistry and Immunology, Institute of Biological Science, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Dayane Lorena Naves de Souza
- Department of Biochemistry and Immunology, Institute of Biological Science, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | | | - Diego Santos Souza
- Department of Biophysics, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Matheus Vilardo Loes Moreira
- Department of Clinical and Veterinary Surgery, School of Veterinary, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Marco Tulio Gomes Campos
- Department of Clinical and Veterinary Surgery, School of Veterinary, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | | | - Danilo Roman-Campos
- Department of Biophysics, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Marilia Martins Melo
- Department of Clinical and Veterinary Surgery, School of Veterinary, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Jader Santos Cruz
- Department of Biochemistry and Immunology, Institute of Biological Science, Federal University of Minas Gerais, Belo Horizonte, Brazil.
| |
Collapse
|
6
|
Song T, Li J, Wang M, Su M, Xu D, Zhou L, Zhang X, Wang H, Hou Y. Analysis of Resibufogenin on Cardiac conduction reveals a species difference in the cardiac electrophysiology: Rats versus guinea pigs. Biomed Pharmacother 2021; 139:111581. [PMID: 33895523 DOI: 10.1016/j.biopha.2021.111581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 03/31/2021] [Accepted: 04/02/2021] [Indexed: 11/29/2022] Open
Abstract
Resibufogenin (RBG) is a chemical ingredient of Chan Su. In our research, we found RBG affected cardiac rhythm in a negative chronotropic way in vivo. The cardiac Mapping system ex vivo and the patch clamp in vitro were used to explore how RBG influenced the cardiac electrophysiological properties. The negative chronotropic action of RBG at 100 μM might be attribute to prolongation in the atrioventricular conduction time and reduction in the ventricular conduction velocity. Using whole-cell patch clamp in ventricular myocytes of adult rats, we found that RBG prolonged the action potential duration (APD) in APD20, APD50, and APD90 at 100 μM and inhibited calcium currents (ICa), total outward potassium currents (IK), and transient outward potassium current (Ito) in a concentration-dependent manner, but not on the inward rectifying potassium current (IK1). Notably, RBG had a potent proarrhythmic action ex vivo in the isolated perfused guinea pig hearts at 10 μM, but not in rats. To avoid the potential cardiotoxicity derived from the distributional differences of ion channels among species, the effect of RGB on IKr in hERG-HEK293 cells was detected. The IC50 of RGB on IKr was more than 100 μM. In summary, all these results indicated that the negative chronotropic action of RBG relied on the blocking activities on multiple ion channels, and the species-difference of proarrhythmic effects might result from lack of the Ito on the myocardial membrane of guinea pigs. Anyhow, the cardiotoxicity observed in guinea pigs required further detailed studies to mitigate the potential risks in the clinical application of Chan Su.
Collapse
Affiliation(s)
- Tao Song
- Shijiazhuang Yiling Pharmaceutical Co., Ltd, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China
| | - Jiajia Li
- Department of Pharmacy, The Fourth Hospital of Shijiazhuang, No.16, the North of Tangu street, Shijiazhuang 050031, Hebei, China
| | - Mingye Wang
- College of Integrated Traditional Chinese and Western Medicine, Hebei Medical University of Chinese Medicine, No.3, Xingyuan Road, Shijiazhuang 050200, Hebei, China
| | - Min Su
- Shijiazhuang Yiling Pharmaceutical Co., Ltd, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China
| | - Dengfeng Xu
- Shijiazhuang Yiling Pharmaceutical Co., Ltd, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China
| | - Luheng Zhou
- Shijiazhuang Yiling Pharmaceutical Co., Ltd, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China
| | - Xiaopei Zhang
- Shijiazhuang Yiling Pharmaceutical Co., Ltd, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China
| | - Hongtao Wang
- Shijiazhuang Yiling Pharmaceutical Co., Ltd, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China
| | - Yunlong Hou
- National Key Laboratory of Collateral Disease Research and Innovative Chinese Medicine, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China; Shijiazhuang Compound Traditional Chinese Medicine Technology Innovation Center, No.238, the South of Tianshan street, Shijiazhuang 050035, Hebei, China; College of Integrated Traditional Chinese and Western Medicine, Hebei Medical University of Chinese Medicine, No.3, Xingyuan Road, Shijiazhuang 050200, Hebei, China.
| |
Collapse
|
7
|
Mann SA, Heide J, Knott T, Airini R, Epureanu FB, Deftu AF, Deftu AT, Radu BM, Amuzescu B. Recording of multiple ion current components and action potentials in human induced pluripotent stem cell-derived cardiomyocytes via automated patch-clamp. J Pharmacol Toxicol Methods 2019; 100:106599. [PMID: 31228558 DOI: 10.1016/j.vascn.2019.106599] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 02/06/2019] [Accepted: 06/14/2019] [Indexed: 12/11/2022]
Abstract
INTRODUCTION The Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative proposes a three-step approach to evaluate proarrhythmogenic liability of drug candidates: effects on individual ion channels in heterologous expression systems, integrating these data into in-silico models of the electrical activity of human cardiomyocytes, and comparison with experiments on human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). Here we introduce patch-clamp electrophysiology techniques on hiPSC-CM to combine two of the CiPA steps in one assay. METHODS We performed automated patch-clamp experiments on hiPSC-CM (Cor.4U®, Ncardia) using the CytoPatch™2 platform in ruptured whole-cell and β-escin-perforated-patch configurations. A combination of three voltage-clamp protocols allowed recording of five distinct ion current components (voltage-gated Na+ current, L-type Ca2+ current, transient outward K+ current, delayed rectifier K+ current, and "funny" hyperpolarization-activated current) from the same cell. We proved their molecular identity by either Na+ replacement with choline or by applying specific blockers: nifedipine, cisapride, chromanol 293B, phrixotoxin-1, ZD7288. We developed a C++ script for automated analysis of voltage-clamp recordings and computation of ion current/conductance surface density for these five cardiac ion currents. RESULTS The distributions from n = 54 hiPSC-CM in "ruptured" patch-clamp vs. n = 35 hiPSC-CM in β-escin-perforated patch-clamp were similar for membrane capacitance, access resistance, and ion current/conductance surface densities. The β-escin-perforated configuration resulted in improved stability of action potential (AP) shape and duration over a 10-min interval, with APD90 decay rate 0.7 ± 1.6%/min (mean ± SD, n = 4) vs. 4.6 ± 1.1%/min. (n = 3) for "ruptured" approach (p = 0.0286, one-tailed Mann-Whitney test). DISCUSSION The improved stability obtained here will allow development of CiPA-compliant automated patch-clamp assays on hiPSC-CM. Future applications include the study of multi ion-channel blocking properties of drugs using dynamic-clamp protocols, adding a valuable new tool to the arsenal of safety-pharmacology.
Collapse
Affiliation(s)
- Stefan A Mann
- Cytocentrics Bioscience GmbH, Nattermannallee 1, 50829 Cologne, Germany
| | - Juliane Heide
- Cytocentrics Bioscience GmbH, Nattermannallee 1, 50829 Cologne, Germany
| | - Thomas Knott
- CytoBioScience Inc., 3463 Magic Drive, San Antonio, TX 78229, USA
| | - Razvan Airini
- Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, 050095 Bucharest, Romania
| | - Florin Bogdan Epureanu
- Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, 050095 Bucharest, Romania
| | - Alexandru-Florian Deftu
- Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, 050095 Bucharest, Romania
| | - Antonia-Teona Deftu
- Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, 050095 Bucharest, Romania
| | - Beatrice Mihaela Radu
- Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, 050095 Bucharest, Romania
| | - Bogdan Amuzescu
- Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, 050095 Bucharest, Romania.
| |
Collapse
|
8
|
Pugsley MK, Yong SL, Goldin AL, Hayes ES, Walker MJA. Molecular charge associated with antiarrhythmic actions in a series of amino-2-cyclohexyl ester derivatives. Eur J Pharmacol 2019; 844:241-252. [PMID: 30571955 DOI: 10.1016/j.ejphar.2018.12.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Revised: 11/12/2018] [Accepted: 12/12/2018] [Indexed: 11/15/2022]
Abstract
A series of amino-2-cyclohexyl ester derivatives were studied for their ion channel blocking and antiarrhythmic actions in the rat and a structure-activity analysis was conducted. The compounds are similar in chemical structure except for ionizable amine groups (pK values 6.1-8.9) and the positional arrangements of aromatic naphthyl moieties. Ventricular arrhythmias were produced in rats by coronary-artery occlusion or electrical stimulation. The electrophysiological effects of these compounds on rat heart sodium channels (Nav1.5) expressed in Xenopus laevis oocytes and transient outward potassium currents (Kv4.3) from isolated rat ventricular myocytes were examined. The compounds reduced the incidence of ischemia-related arrhythmias and increased current threshold for induction of ventricular fibrillo-flutter (VFt) dose-dependently. As pK increased compounds showed a diminished effectiveness against ischemia-induced arrhythmias, and were less selective for ischemia- versus electrically-induced arrhythmias. Where tested, compounds produced a concentration-dependent tonic block of Nav1.5 channels. An increased potency for inhibition of Nav1.5 occurred when the external pH (pHo) was reduced to 6.5. Some compounds inhibited Kv4.3 in a pH-independent manner. Overall, the differences in antiarrhythmic and ion channel blocking properties in this series of compounds can be explained by differences in chemical structure. Antiarrhythmic activity for the amino-2-cyclohexyl ester derivatives is likely a function of mixed ion channel blockade in ischemic myocardium. These studies show that drug inhibition of Nav1.5 occurred at lower concentrations than Kv4.3 and was more sensitive to changes in the ionizable amine groups rather than on positional arrangements of the naphthyl constituents. These results offer insight into antiarrhythmic mechanisms of drug-ion channel interactions.
Collapse
Affiliation(s)
- Michael K Pugsley
- Safety Pharmacology & Toxicology, Fairfield, CT 06825, USA; Department of Pharmacology & Therapeutics, Faculty of Medicine, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3.
| | - Sandro L Yong
- Department of Pharmacology & Therapeutics, Faculty of Medicine, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3
| | - Alan L Goldin
- Department of Microbiology & Molecular Genetics, University of California, Irvine, California, CA 92697-4025, USA
| | - Eric S Hayes
- BioCurate Pty Ltd., Parkville, Victoria, Australia
| | - Michael J A Walker
- Department of Pharmacology & Therapeutics, Faculty of Medicine, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3
| |
Collapse
|
9
|
Golovko VA, Kosevich IA, Gonotkov MA. Pharmacological analysis of the transmembrane action potential configuration in myoepithelial cells of the spontaneously beating heart of the ascidian Styela rustica in vitro. ACTA ACUST UNITED AC 2017; 220:4589-4599. [PMID: 28982967 DOI: 10.1242/jeb.154641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Accepted: 09/28/2017] [Indexed: 11/20/2022]
Abstract
The mechanisms of action potential (AP) generation in the myoepithelial cells of the tunicate heart are not yet well understood. Here, an attempt was made to elucidate these mechanisms by analyzing the effects of specific blockers of K+, Na+ and Ca2+ currents on the configuration of transmembrane APs and their frequency in the spontaneously beating ascidian heart. In addition, an immunocytochemical analysis of heart myoepithelial cells was performed. Staining with anti-FMRF-amide and anti-tubulin antibodies did not reveal any nerve elements within the heart tube. Treatment with 1 mmol l-1 TEA (IK blocker) resulted in depolarization of heart cell sarcolemma by 10 mV, and inhibition of APs generation was recorded after 3 min of exposure. Prior to this moment, the frequency of AP generation in a burst decreased from 16-18 to 2 beats min-1 owing to prolongation of the diastole. After application of ivabradine (3 or 10 µmol l-1), the spontaneous APs generation frequency decreased by 24%. Based on these results and published data, it is concluded that the key role in the automaticity of the ascidian heart is played by the outward K+ currents, Na+ currents, activated hyperpolarization current If and a current of unknown nature IX.
Collapse
Affiliation(s)
- Vladimir A Golovko
- Institute of Physiology, Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya St., Syktyvkar 167982, Russia
| | - Igor A Kosevich
- Faculty of Biology, M.Lomonosov Moscow State University, Moscow 119991, Russia
| | - Mikhail A Gonotkov
- Institute of Physiology, Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya St., Syktyvkar 167982, Russia
| |
Collapse
|
10
|
β-adrenergic stimulation augments transmural dispersion of repolarization via modulation of delayed rectifier currents I Ks and I Kr in the human ventricle. Sci Rep 2017; 7:15922. [PMID: 29162896 PMCID: PMC5698468 DOI: 10.1038/s41598-017-16218-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 11/09/2017] [Indexed: 12/23/2022] Open
Abstract
Long QT syndrome (LQTS) is an inherited or drug induced condition associated with delayed repolarization and sudden cardiac death. The cardiac potassium channel, IKr, and the adrenergic-sensitive cardiac potassium current, IKs, are two primary contributors to cardiac repolarization. This study aimed to elucidate the role of β-adrenergic (β-AR) stimulation in mediating the contributions of IKr and IKs to repolarizing the human left ventricle (n = 18). Optical mapping was used to measure action potential durations (APDs) in the presence of the IKs blocker JNJ-303 and the IKr blocker E-4031. We found that JNJ-303 alone did not increase APD. However, under isoprenaline (ISO), both the application of JNJ-303 and additional E-4031 significantly increased APD. With JNJ-303, ISO decreased APD significantly more in the epicardium as compared to the endocardium, with subsequent application E-4031 increasing mid- and endocardial APD80 more significantly than in the epicardium. We found that β-AR stimulation significantly augmented the effect of IKs blocker JNJ-303, in contrast to the reduced effect of IKr blocker E-4031. We also observed synergistic augmentation of transmural repolarization gradient by the combination of ISO and E-4031. Our results suggest β-AR-mediated increase of transmural dispersion of repolarization, which could pose arrhythmogenic risk in LQTS patients.
Collapse
|
11
|
The IK1/Kir2.1 channel agonist zacopride prevents and cures acute ischemic arrhythmias in the rat. PLoS One 2017; 12:e0177600. [PMID: 28542320 PMCID: PMC5436763 DOI: 10.1371/journal.pone.0177600] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 04/20/2017] [Indexed: 12/13/2022] Open
Abstract
Arrhythmogenesis in acute myocardial infarction (MI) is associated with depolarization of resting membraine potential (RMP) and decrease of inward rectifier potassium current (IK1) in cardiomyocytes. However, clinical anti-arrhythmic agents that primarily act on RMP by enhancing the IK1 channel are not currently available. We hypothesized that zacopride, a selective and moderate agonist of the IK1/Kir2.1 channels, prevents and cures acute ischemic arrhythmias. To test this viewpoint, adult Sprague-Dawley (SD) rats were subjected to MI by ligating the left main coronary artery. The antiarrhythmic effects of zacopride (i.v. infusion) were observed in the settings of pre-treatment (zacopride given 3 min prior to coronary occlusion), post-treatment (zacopride given 3 min after coronary occlusion) and therapeutic treatment (zacopride given 30 s after the onset of the first sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) post MI). In all the three treatment modes, zacopride (15 μg/kg) inhibited MI-induced ventricular tachyarrhythmias, as shown by significant decreases in the premature ventricular contraction (PVC) and the duration and incidence of VT or VF. In Langendorff perfused rat hearts, the antiarrhythmic effect of 1 μmol/L zacopride were reversed by 1 μmol/L BaCl2, a blocker of IK1 channel. Patch clamp results in freshly isolated rat ventricular myocytes indicated that zacopride activated the IK1 channel and thereby reversed hypoxia-induced RMP depolarization and action potential duration (APD) prolongation. In addition, zacopride (1 μmol/L) suppressed hypoxia- or isoproterenol- induced delayed afterdepolarizations (DADs). In Kir2.x transfected Chinese hamster ovary (CHO) cells, zacopride activated the Kir2.1 homomeric channel but not the Kir2.2 or Kir2.3 channels. These results support our hypothesis that moderately enhancing IK1/Kir2.1 currents as by zacopride rescues ischemia- and hypoxia- induced RMP depolarization, and thereby prevents and cures acute ischemic arrhythmias. This study brings a new viewpoint to antiarrhythmic theories and provides a promising target for the treatment of acute ischemic arrhythmias.
Collapse
|
12
|
Hundahl LA, Tfelt-Hansen J, Jespersen T. Rat Models of Ventricular Fibrillation Following Acute Myocardial Infarction. J Cardiovasc Pharmacol Ther 2017; 22:514-528. [PMID: 28381093 DOI: 10.1177/1074248417702894] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A number of animal models have been designed in order to unravel the underlying mechanisms of acute ischemia-induced arrhythmias and to test compounds and interventions for antiarrhythmic therapy. This is important as acute myocardial infarction (AMI) continues to be the major cause of sudden cardiac death, and we are yet to discover safe and effective treatments of the lethal arrhythmias occurring in the acute setting. Animal models therefore continue to be relevant for our understanding and treatment of acute ischemic arrhythmias. This review discusses the applicability of the rat as a model for ventricular arrhythmias occurring during the acute phase of AMI. It provides a description of models developed, advantages and disadvantages of rats, as well as an overview of the most important interventions investigated and the relevance for human pathophysiology.
Collapse
Affiliation(s)
- Laura A Hundahl
- 1 Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Tfelt-Hansen
- 2 Department of Cardiology, Heart Centre, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Thomas Jespersen
- 1 Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
13
|
Aguilar-Sanchez Y, Fainstein D, Mejia-Alvarez R, Escobar AL. Local Field Fluorescence Microscopy: Imaging Cellular Signals in Intact Hearts. J Vis Exp 2017. [PMID: 28362405 DOI: 10.3791/55202] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
In the heart, molecular signaling studies are usually performed in isolated myocytes. However, many pathological situations such as ischemia and arrhythmias can only be fully understood at the whole organ level. Here, we present the spectroscopic technique of local field fluorescence microscopy (LFFM) that allows the measurement of cellular signals in the intact heart. The technique is based on a combination of a Langendorff perfused heart and optical fibers to record fluorescent signals. LFFM has various applications in the field of cardiovascular physiology to study the heart under normal and pathological conditions. Multiple cardiac variables can be monitored using different fluorescent indicators. These include cytosolic [Ca2+], intra-sarcoplasmic reticulum [Ca2+] and membrane potentials. The exogenous fluorescent probes are excited and the emitted fluorescence detected with three different arrangements of LFFM epifluorescence techniques presented in this paper. The central differences among these techniques are the type of light source used for excitation and on the way the excitation light is modulated. The pulsed LFFM (PLFFM) uses laser light pulses while continuous wave LFFM (CLFFM) uses continuous laser light for excitation. Finally, light-emitting diodes (LEDs) were used as a third light source. This non-coherent arrangement is called pulsed LED fluorescence microscopy (PLEDFM).
Collapse
Affiliation(s)
| | - Diego Fainstein
- Centro de Investigaciones Cardiovasculares, Universidad de la Plata and Conicet; Facultad de Ingenieria, Universidad Nacional de Entre Rios
| | | | | |
Collapse
|
14
|
Devenyi RA, Sobie EA. There and back again: Iterating between population-based modeling and experiments reveals surprising regulation of calcium transients in rat cardiac myocytes. J Mol Cell Cardiol 2016; 96:38-48. [PMID: 26235057 PMCID: PMC4733425 DOI: 10.1016/j.yjmcc.2015.07.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 07/08/2015] [Accepted: 07/22/2015] [Indexed: 01/17/2023]
Abstract
While many ion channels and transporters involved in cardiac cellular physiology have been identified and described, the relative importance of each in determining emergent cellular behaviors remains unclear. Here we address this issue with a novel approach that combines population-based mathematical modeling with experimental tests to systematically quantify the relative contributions of different ion channels and transporters to the amplitude of the cellular Ca(2+) transient. Sensitivity analysis of a mathematical model of the rat ventricular cardiomyocyte quantified the response of cell behaviors to changes in the level of each ion channel and transporter, and experimental tests of these predictions were performed to validate or invalidate the predictions. The model analysis found that partial inhibition of the transient outward current in rat ventricular epicardial myocytes was predicted to have a greater impact on Ca(2+) transient amplitude than either: (1) inhibition of the same current in endocardial myocytes, or (2) comparable inhibition of the sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA). Experimental tests confirmed the model predictions qualitatively but showed some quantitative disagreement. This guided us to recalibrate the model by adjusting the relative importance of several Ca(2+) fluxes, thereby improving the consistency with experimental data and producing a more predictive model. Analysis of human cardiomyocyte models suggests that the relative importance of outward currents to Ca(2+) transporters is generalizable to human atrial cardiomyocytes, but not ventricular cardiomyocytes. Overall, our novel approach of combining population-based mathematical modeling with experimental tests has yielded new insight into the relative importance of different determinants of cell behavior.
Collapse
Affiliation(s)
- Ryan A Devenyi
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, 1 Gustave L Levy Place, New York, NY, USA
| | - Eric A Sobie
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, 1 Gustave L Levy Place, New York, NY, USA.
| |
Collapse
|
15
|
Gattoni S, Røe ÅT, Frisk M, Louch WE, Niederer SA, Smith NP. The calcium-frequency response in the rat ventricular myocyte: an experimental and modelling study. J Physiol 2016; 594:4193-224. [PMID: 26916026 DOI: 10.1113/jp272011] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/22/2016] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS In the majority of species, including humans, increased heart rate increases cardiac contractility. This change is known as the force-frequency response (FFR). The majority of mammals have a positive force-frequency relationship (FFR). In rat the FFR is controversial. We derive a species- and temperature-specific data-driven model of the rat ventricular myocyte. As a measure of the FFR, we test the effects of changes in frequency and extracellular calcium on the calcium-frequency response (CFR) in our model and three altered models. The results show a biphasic peak calcium-frequency response, due to biphasic behaviour of the ryanodine receptor and the combined effect of the rapid calmodulin buffer and the frequency-dependent increase in diastolic calcium. Alterations to the model reveal that inclusion of Ca(2+) /calmodulin-dependent protein kinase II (CAMKII)-mediated L-type channel and transient outward K(+) current activity enhances the positive magnitude calcium-frequency response, and the absence of CAMKII-mediated increase in activity of the sarco/endoplasmic reticulum Ca(2+) -ATPase induces a negative magnitude calcium-frequency response. ABSTRACT An increase in heart rate affects the strength of cardiac contraction by altering the Ca(2+) transient as a response to physiological demands. This is described by the force-frequency response (FFR), a change in developed force with pacing frequency. The majority of mammals, including humans, have a positive FFR, and cardiac contraction strength increases with heart rate. However, the rat and mouse are exceptions, with the majority of studies reporting a negative FFR, while others report either a biphasic or a positive FFR. Understanding the differences in the FFR between humans and rats is fundamental to interpreting rat-based experimental findings in the context of human physiology. We have developed a novel model of rat ventricular electrophysiology and calcium dynamics, derived predominantly from experimental data recorded under physiological conditions. As a measure of FFR, we tested the effects of changes in stimulation frequency and extracellular calcium concentration on the simulated Ca(2+) transient characteristics and showed a biphasic peak calcium-frequency relationship, consistent with recent observations of a shift from negative to positive FFR when approaching the rat physiological frequency range. We tested the hypotheses that (1) inhibition of Ca(2+) /calmodulin-dependent protein kinase II (CAMKII)-mediated increase in sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) activity, (2) CAMKII modulation of SERCA, L-type channel and transient outward K(+) current activity and (3) Na(+) /K(+) pump dynamics play a significant role in the rat FFR. The results reveal a major role for CAMKII modulation of SERCA in the peak Ca(2+) -frequency response, driven most significantly by the cytosolic calcium buffering system and changes in diastolic Ca(2+) .
Collapse
Affiliation(s)
- Sara Gattoni
- King's College London, Department of Biomedical Engineering and Imaging Sciences, St. Thomas' Hospital, London, UK
| | - Åsmund Treu Røe
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Steven A Niederer
- King's College London, Department of Biomedical Engineering and Imaging Sciences, St. Thomas' Hospital, London, UK
| | - Nicolas P Smith
- King's College London, Department of Biomedical Engineering and Imaging Sciences, St. Thomas' Hospital, London, UK.,University of Auckland, Engineering School Block 1, Level 5, 20 Symonds St, Auckland, 101, New Zealand
| |
Collapse
|
16
|
Abstract
Cardiac delayed rectifier potassium channels conduct outward potassium currents during the plateau phase of action potentials and play pivotal roles in cardiac repolarization. These include IKs, IKr and the atrial specific IKur channels. In this article, we will review their molecular identities and biophysical properties. Mutations in the genes encoding delayed rectifiers lead to loss- or gain-of-function phenotypes, disrupt normal cardiac repolarization and result in various cardiac rhythm disorders, including congenital Long QT Syndrome, Short QT Syndrome and familial atrial fibrillation. We will also discuss the prospect of using delayed rectifier channels as therapeutic targets to manage cardiac arrhythmia.
Collapse
Affiliation(s)
- Lei Chen
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Kevin J Sampson
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Robert S Kass
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA.
| |
Collapse
|
17
|
Dubó S, Gallegos D, Cabrera L, Sobrevia L, Zúñiga L, González M. Cardiovascular Action of Insulin in Health and Disease: Endothelial L-Arginine Transport and Cardiac Voltage-Dependent Potassium Channels. Front Physiol 2016; 7:74. [PMID: 27014078 PMCID: PMC4791397 DOI: 10.3389/fphys.2016.00074] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 02/15/2016] [Indexed: 12/19/2022] Open
Abstract
Impairment of insulin signaling on diabetes mellitus has been related to cardiovascular dysfunction, heart failure, and sudden death. In human endothelium, cationic amino acid transporter 1 (hCAT-1) is related to the synthesis of nitric oxide (NO) and insulin has a vascular effect in endothelial cells through a signaling pathway that involves increases in hCAT-1 expression and L-arginine transport. This mechanism is disrupted in diabetes, a phenomenon potentiated by excessive accumulation of reactive oxygen species (ROS), which contribute to lower availability of NO and endothelial dysfunction. On the other hand, electrical remodeling in cardiomyocytes is considered a key factor in heart failure progression associated to diabetes mellitus. This generates a challenge to understand the specific role of insulin and the pathways involved in cardiac function. Studies on isolated mammalian cardiomyocytes have shown prolongated action potential in ventricular repolarization phase that produces a long QT interval, which is well explained by attenuation in the repolarizing potassium currents in cardiac ventricles. Impaired insulin signaling causes specific changes in these currents, such a decrease amplitude of the transient outward K(+) (Ito) and the ultra-rapid delayed rectifier (IKur) currents where, together, a reduction of mRNA and protein expression levels of α-subunits (Ito, fast; Kv 4.2 and IKs; Kv 1.5) or β-subunits (KChIP2 and MiRP) of K(+) channels involved in these currents in a MAPK mediated pathway process have been described. These results support the hypothesis that lack of insulin signaling can produce an abnormal repolarization in cardiomyocytes. Furthermore, the arrhythmogenic potential due to reduced Ito current can contribute to an increase in the incidence of sudden death in heart failure. This review aims to show, based on pathophysiological models, the regulatory function that would have insulin in vascular system and in cardiac electrophysiology.
Collapse
Affiliation(s)
- Sebastián Dubó
- Department of Kinesiology, Faculty of Medicine, Universidad de Concepción Concepción, Chile
| | - David Gallegos
- Vascular Physiology Laboratory, Department of Physiology, Faculty of Biological Sciences, Universidad de Concepción Concepción, Chile
| | - Lissette Cabrera
- Vascular Physiology Laboratory, Department of Physiology, Faculty of Biological Sciences, Universidad de ConcepciónConcepción, Chile; Department of Morphophysiology, Faculty of Medicine, Universidad Diego PortalesSantiago, Chile
| | - Luis Sobrevia
- Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynecology, Faculty of Medicine, School of Medicine, Pontificia Universidad Católica de ChileSantiago, Chile; Department of Physiology, Faculty of Pharmacy, Universidad de SevillaSeville, Spain; Faculty of Medicine and Biomedical Sciences, University of Queensland Centre for Clinical Research (UQCCR), University of QueenslandHerston, QLD, Queensland, Australia
| | - Leandro Zúñiga
- Centro de Investigaciones Médicas, Escuela de Medicina, Universidad de Talca Talca, Chile
| | - Marcelo González
- Vascular Physiology Laboratory, Department of Physiology, Faculty of Biological Sciences, Universidad de ConcepciónConcepción, Chile; Group of Research and Innovation in Vascular Health (GRIVAS-Health)Chillán, Chile
| |
Collapse
|
18
|
Martínez-Ladrón de Guevara E, Pérez-Hernández N, Villalobos-López MÁ, Pérez-Ishiwara DG, Salas-Benito JS, Martínez Martínez A, Hernández-García V. The Actions of Lyophilized Apple Peel on the Electrical Activity and Organization of the Ventricular Syncytium of the Hearts of Diabetic Rats. J Diabetes Res 2016; 2016:8178936. [PMID: 26839897 PMCID: PMC4709627 DOI: 10.1155/2016/8178936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 09/27/2015] [Accepted: 09/29/2015] [Indexed: 11/17/2022] Open
Abstract
This study was designed to examine the effects of lyophilized red delicious apple peel (RDP) on the action potentials (APs) and the input resistance-threshold current relationship. The experiments were performed on isolated papillary heart muscles from healthy male rats, healthy male rats treated with RDP, diabetic male rats, and diabetic male rats treated with RDP. The preparation was superfused with oxygenated Tyrode's solution at 37°C. The stimulation and the recording of the APs, the input resistance, and the threshold current were made using conventional electrophysiological methods. The RDP presented no significant effect in normal rats. Equivalent doses in diabetic rats reduced the APD and ARP. The relationship between input resistance and threshold current established an inverse correlation. The results indicate the following: (1) The functional structure of the cardiac ventricular syncytium in healthy rats is heterogeneous, in terms of input resistance and threshold current. Diabetes further accentuates the heterogeneity. (2) As a consequence, conduction block occurs and increases the possibility of reentrant arrhythmias. (3) These modifications in the ventricular syncytium, coupled with the increase in the ARP, are the adequate substrate so that, with diabetes, the heart becomes more arrhythmogenic. (4) RDP decreases the APD, the ARP, and most syncytium irregularity caused by diabetes.
Collapse
Affiliation(s)
| | - Nury Pérez-Hernández
- National School of Medicine and Homeopathy, National Polytechnic Institute, 07320 Mexico City, DF, Mexico
| | | | | | - Juan Santiago Salas-Benito
- National School of Medicine and Homeopathy, National Polytechnic Institute, 07320 Mexico City, DF, Mexico
| | | | - Vicente Hernández-García
- Institute of Biomedical Sciences, Autonomous University of Ciudad Juárez, 32310 Ciudad Juárez, CHIH, Mexico
- *Vicente Hernández-García:
| |
Collapse
|
19
|
Ramos-Franco J, Aguilar-Sanchez Y, Escobar AL. Intact Heart Loose Patch Photolysis Reveals Ionic Current Kinetics During Ventricular Action Potentials. Circ Res 2015; 118:203-15. [PMID: 26565013 DOI: 10.1161/circresaha.115.307399] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 11/12/2015] [Indexed: 12/16/2022]
Abstract
RATIONALE Assessing the underlying ionic currents during a triggered action potential (AP) in intact perfused hearts offers the opportunity to link molecular mechanisms with pathophysiological problems in cardiovascular research. The developed loose patch photolysis technique can provide striking new insights into cardiac function at the whole heart level during health and disease. OBJECTIVE To measure transmembrane ionic currents during an AP to determine how and when surface Ca(2+) influx that triggers Ca(2+)-induced Ca(2+) release occurs and how Ca(2+)-activated conductances can contribute to the genesis of AP phase 2. METHODS AND RESULTS Loose patch photolysis allows the measurement of transmembrane ionic currents in intact hearts. During a triggered AP, a voltage-dependent Ca(2+) conductance was fractionally activated (dis-inhibited) by rapidly photo-degrading nifedipine, the Ca(2+) channel blocker. The ionic currents during a mouse ventricular AP showed a fast early component and a slower late component. Pharmacological studies established that the molecular basis underlying the early component was driven by an influx of Ca(2+) through the L-type channel, CaV 1.2. The late component was identified as an Na(+)-Ca(2+) exchanger current mediated by Ca(2+) released from the sarcoplasmic reticulum. CONCLUSIONS The novel loose patch photolysis technique allowed the dissection of transmembrane ionic currents in the intact heart. We were able to determine that during an AP, L-type Ca(2+) current contributes to phase 1, whereas Na(+)-Ca(2+) exchanger contributes to phase 2. In addition, loose patch photolysis revealed that the influx of Ca(2+) through L-type Ca(2+) channels terminates because of voltage-dependent deactivation and not by Ca(2+)-dependent inactivation, as commonly believed.
Collapse
Affiliation(s)
- Josefina Ramos-Franco
- From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (J.R.-F.); and Quantitative Systems Biology Program, School of Natural Sciences (Y.A.-S.) and Biological Engineering and Small Scale Technologies Program, School of Engineering (A.L.E.), University of California, Merced, CA
| | - Yuriana Aguilar-Sanchez
- From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (J.R.-F.); and Quantitative Systems Biology Program, School of Natural Sciences (Y.A.-S.) and Biological Engineering and Small Scale Technologies Program, School of Engineering (A.L.E.), University of California, Merced, CA
| | - Ariel L Escobar
- From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (J.R.-F.); and Quantitative Systems Biology Program, School of Natural Sciences (Y.A.-S.) and Biological Engineering and Small Scale Technologies Program, School of Engineering (A.L.E.), University of California, Merced, CA.
| |
Collapse
|
20
|
Liu WJ, Deng JX, Wang G, Gao KP, Lin ZX, Liu SY, Wang YH, Liu J. Manipulation of KCNE2 expression modulates action potential duration and Ito and IK in rat and mouse ventricular myocytes. Am J Physiol Heart Circ Physiol 2015; 309:H1288-302. [PMID: 26297229 DOI: 10.1152/ajpheart.00757.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 08/19/2015] [Indexed: 11/22/2022]
Abstract
In heterologous expression systems, KCNE2 has been demonstrated to interact with multiple α-subunits of voltage-dependent cation channels and modulate their functions. However, the physiological and pathological roles of KCNE2 in cardiomyocytes are poorly understood. The present study aimed to investigate the effects of bidirectional modulation of KCNE2 expression on action potential (AP) duration (APD) and voltage-dependent K+ channels in cardiomyocytes. Adenoviral gene delivery and RNA interference were used to either increase or decrease KCNE2 expression in cultured neonatal and adult rat or neonatal mouse ventricular myocytes. Knockdown of KCNE2 prolonged APD in both neonatal and adult myocytes, whereas overexpression of KCNE2 shortened APD in neonatal but not adult myocytes. Consistent with the alterations in APD, KCNE2 knockdown decreased transient outward K+ current ( Ito) densities in neonatal and adult myocytes, whereas KCNE2 overexpression increased Ito densities in neonatal but not adult myocytes. Furthermore, KCNE2 knockdown accelerated the rates of Ito activation and inactivation, whereas KCNE2 overexpression slowed Ito gating kinetics in neonatal but not adult myocytes. Delayed rectifier K+ current densities were remarkably affected by manipulation of KCNE2 expression in mouse but not rat cardiomyocytes. Simulation of the AP of a rat ventricular myocyte with a mathematical model showed that alterations in Ito densities and gating properties can result in similar APD alterations in KCNE2 overexpression and knockdown cells. In conclusion, endogenous KCNE2 in cardiomyocytes is important in maintaining cardiac electrical stability mainly by regulating Ito and APD. Perturbation of KCNE2 expression may predispose the heart to ventricular arrhythmia by prolonging APD.
Collapse
Affiliation(s)
- Wen-juan Liu
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China; and
| | - Jian-xin Deng
- Department of Endocrinology, The First Affiliated Hospital of Shenzhen University, Shenzhen No. 2 People's Hospital, Shenzhen, China
| | - Gang Wang
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China; and
| | - Kai-ping Gao
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China; and
| | - Ze-xun Lin
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China; and
| | - Shuai-ye Liu
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China; and
| | - Yong-hui Wang
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China; and
| | - Jie Liu
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen, China; and
| |
Collapse
|
21
|
Abstract
Optimal cardiac function depends on proper timing of excitation and contraction in various regions of the heart, as well as on appropriate heart rate. This is accomplished via specialized electrical properties of various components of the system, including the sinoatrial node, atria, atrioventricular node, His-Purkinje system, and ventricles. Here we review the major regionally determined electrical properties of these cardiac regions and present the available data regarding the molecular and ionic bases of regional cardiac function and dysfunction. Understanding these differences is of fundamental importance for the investigation of arrhythmia mechanisms and pharmacotherapy.
Collapse
Affiliation(s)
- Daniel C Bartos
- Department of Pharmacology, University of California Davis, Davis, California, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, California, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California Davis, Davis, California, USA
| |
Collapse
|
22
|
|
23
|
Arrhythmia and thyroid dysfunction. Herz 2014; 40 Suppl 2:101-9. [DOI: 10.1007/s00059-014-4123-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 05/20/2014] [Accepted: 05/27/2014] [Indexed: 10/25/2022]
|
24
|
Localization of Kv4.2 and KChIP2 in lipid rafts and modulation of outward K+ currents by membrane cholesterol content in rat left ventricular myocytes. Pflugers Arch 2014; 467:299-309. [DOI: 10.1007/s00424-014-1521-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 04/11/2014] [Accepted: 04/15/2014] [Indexed: 02/03/2023]
|
25
|
Epac activator critically regulates action potential duration by decreasing potassium current in rat adult ventricle. J Mol Cell Cardiol 2013; 57:96-105. [PMID: 23376036 DOI: 10.1016/j.yjmcc.2013.01.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 12/21/2012] [Accepted: 01/17/2013] [Indexed: 02/08/2023]
Abstract
Sympathetic stimulation is an important modulator of cardiac function via the classic cAMP-dependent signaling pathway, PKA. Recently, this paradigm has been challenged by the discovery of a family of guanine nucleotide exchange proteins directly activated by cAMP (Epac), acting in parallel to the classic signaling pathway. In cardiac myocytes, Epac activation is known to modulate Ca(2+) cycling yet their actions on cardiac ionic currents remain poorly characterized. This study attempts to address this paucity of information using the patch clamp technique to record action potential (AP) and ionic currents on rat ventricular myocytes. Epac was selectively activated by 8-CPT-AM (acetoxymethyl ester form of 8-CPT). AP amplitude, maximum depolarization rate and resting membrane amplitude were unaltered by 8-CPT-AM, strongly suggesting that Na(+) current and inward rectifier K(+) current are not regulated by Epac. In contrast, AP duration was significantly increased by 8-CPT-AM (prolongation of duration at 50% and 90% of repolarization by 41±10% and 43±8% respectively, n=11). L-type Ca(2+) current density was unaltered by 8-CPT-AM (n=16) so this cannot explain the action potential lengthening. However, the steady state component of K(+) current was significantly inhibited by 8-CPT-AM (-38±6%, n=15), while the transient outward K(+) current was unaffected by 8-CPT-AM. These effects were PKA-independent since they were observed in the presence of PKA inhibitor KT5720. Isoprenaline (100nM) induced a significant prolongation of AP duration, even in the presence of KT5720. This study provides the first evidence that the cAMP-binding protein Epac critically modulates cardiac AP duration by decreasing steady state K(+) current. These observations may be relevant to diseases in which Epac is upregulated, like cardiac hypertrophy.
Collapse
|
26
|
Ren AJ, Liang Q, Wang R, Ji HY, Wu Y, Shi JS, Lin L, Yuan WJ. Effects of Salusin-β on action potential and ionic currents in ventricular myocytes of rats. Acta Physiol (Oxf) 2013; 207:166-72. [PMID: 22846709 DOI: 10.1111/j.1748-1716.2012.02475.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 06/17/2012] [Accepted: 07/23/2012] [Indexed: 12/01/2022]
Abstract
AIM Salusin-β is a regulatory peptide that exerts negative inotropic effect on ventricular muscle, but its electrophysiological effects on ventricular myocytes are still unknown. METHODS Action potential and channel currents such as sodium current (I(N) (a) ), transient outward potassium current (I(to) ), steady-state potassium current (I(sus) ), sodium-calcium exchange current (I(N) (aCa) ) and inward rectifier potassium current (I(K) (1) ) were measured in ventricular myocytes isolated from 12 to 16 weeks rats by whole-cell voltage-clamp techniques. RESULTS Salusin-β dose-dependently shortened the duration of action potential in rat ventricular myocytes. Furthermore, salusin-β significantly inhibited I(N) (aCa) and increased I(to) , but did not affect I(N) (a) , I(sus) and I(K) (1) . CONCLUSION These results suggest that the effect of salusin-β on action potential may be partly attributed to a decrease in inward currents and an increase in outward currents.
Collapse
Affiliation(s)
- An-Jing Ren
- Department of Pathophysiology; Second Military Medical University; Shanghai; China
| | | | - Rong Wang
- Department of Physiology and Neurobiology; Ningxia Medical University; Yinchuan; China
| | - Hai-Yu Ji
- Department of Physiology and Neurobiology; Ningxia Medical University; Yinchuan; China
| | - Yi Wu
- Department of Physiology and Neurobiology; Ningxia Medical University; Yinchuan; China
| | - Jing-Song Shi
- Department of Endocrinology; Nanjing Military General Hospital; Nanjing; China
| | - Li Lin
- Department of Physiology; Second Military Medical University; Shanghai; China
| | | |
Collapse
|
27
|
Kavak S. Effects of Insulin on Altered Mechanical and Electrical Papillary Muscle Activities of Diabetic Rats. J Membr Biol 2012; 246:31-7. [DOI: 10.1007/s00232-012-9499-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 08/18/2012] [Indexed: 10/27/2022]
|
28
|
Chae JE, Kim HS, Ahn DS, Park WK. Ionic mechanisms of desflurane on prolongation of action potential duration in rat ventricular myocytes. Yonsei Med J 2012; 53:204-12. [PMID: 22187254 PMCID: PMC3250338 DOI: 10.3349/ymj.2012.53.1.204] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
PURPOSE Despite the fact that desflurane prolongs the QTC interval in humans, little is known about the mechanisms that underlie these actions. We investigated the effects of desflurane on action potential (AP) duration and underlying electrophysiological mechanisms in rat ventricular myocytes. MATERIALS AND METHODS Rat ventricular myocytes were enzymatically isolated and studied at room temperature. AP was measured using a current clamp technique. The effects of 6% (0.78 mM) and 12% (1.23 mM) desflurane on transient outward K⁺ current (I(to)), sustained outward current (I(sus)), inward rectifier K⁺ current (I(KI)), and L-type Ca²⁺ current were determined using a whole cell voltage clamp. RESULTS Desflurane prolonged AP duration, while the amplitude and resting membrane potential remained unchanged. Desflurane at 0.78 mM and 1.23 mM significantly reduced the peak I(to) by 20 ± 8% and 32 ± 7%, respectively, at +60 mV. Desflurane (1.23 mM) shifted the steady-state inactivation curve in a hyperpolarizing direction and accelerated inactivation of the current. While desflurane (1.23 mM) had no effects on I(sus) and I(KI), it reduced the L-type Ca²⁺ current by 40 ± 6% (p<0.05). CONCLUSION Clinically relevant concentrations of desflurane appear to prolong AP duration by suppressing I(to) in rat ventricular myocytes.
Collapse
Affiliation(s)
- Jee Eun Chae
- Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Hyun Soo Kim
- Department of Life Science, College of Natural Sciences, Ewha Woman's University, Seoul, Korea
| | - Duck Sun Ahn
- Department of Physiology, Yonsei University College of Medicine, Seoul, Korea
| | - Wyun Kon Park
- Department of Anesthesiology and Pain Medicine, Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
| |
Collapse
|
29
|
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.
Collapse
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
| | | | | | | | | | | | | |
Collapse
|
30
|
Abstract
Ventricular fibrillation (VF) is the leading cause of sudden cardiac death. This brief review addresses issues relevant to the dynamics of the rotors responsible for functional reentry and VF. It also makes an attempt to summarize present-day knowledge of the manner in which the dynamic interplay between inward and outward transmembrane currents and the heterogeneous cardiac structure establish a substrate for the initiation and maintenance of rotors and VF. The fragmentary nature of our current understanding of ionic VF mechanisms does not even allow an approach toward a "Theory of VF". Yet some hope is provided by recently obtained insight into the roles played in VF by some of the sarcolemmal ion channels that control the excitation-recovery process. For example, strong evidence supports the idea that the interplay between the rapid-inward sodium current and the inward-rectifier potassium current controls rotor formation, as well as rotor stability and frequency. Solid evidence also exists for an involvement of L-type calcium current in the control of rotor frequency and in determining VF-to-ventricular tachycardia conversion. Less clear, however, is whether or not time dependent outward currents through voltage-gated potassium channels affect the fibrillatory process. Hopefully, taking advantage of currently available approaches of structural, molecular and cellular biology, together with computational and imaging techniques, will afford us the opportunity to further advance knowledge on VF mechanisms.
Collapse
Affiliation(s)
- Sami F Noujaim
- Department of Pharmacology and Institute for Cardiovascular Research, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | | | | |
Collapse
|
31
|
Serum positive for the autoantibody against the β(1)-adrenoceptor from Chinese patients with congestive heart failure decreases I(ss) in mouse cardiac myocytes. Clin Dev Immunol 2011; 2011:143517. [PMID: 21716722 PMCID: PMC3119415 DOI: 10.1155/2011/143517] [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: 11/05/2010] [Accepted: 04/07/2011] [Indexed: 11/17/2022]
Abstract
Autoantibodies targeting the β1-adrenergic receptor (AAB-β1) display agonist-like effects, which may have a pathogenic role in the progression of heart failure. Here, we used the electrophysiological recordings to explore the effects of AAB-β1-positive serum from Chinese patients with heart failure on the activity of the peak transient outward potassium current (Ito) and the end 50 ms steady-state potassium current (Iss) in mouse cardiac myocytes. We found that the AAB-β1-positive serum had no effect on the activity of Ito, but it produced a decrease in the currents of Iss. A low concentration of positive serum (1/100) had a small inhibitory effect on Iss. However, positive serum at 1 : 10, 1 : 20, and 1 : 50 significantly decreased Iss. The concentration-dependence analysis showed that the EC50 of AAB-β1-positive serum was 1/60.24 and its nH was 2.86. It indicated that the AAB-β1 could inhibit Iss in mouse cardiomyocyte in a concentration-dependent manner.
Collapse
|
32
|
Cazorla O, Lacampagne A. Regional variation in myofilament length-dependent activation. Pflugers Arch 2011; 462:15-28. [DOI: 10.1007/s00424-011-0933-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 02/01/2011] [Accepted: 02/03/2011] [Indexed: 12/17/2022]
|
33
|
Nerbonne JM. Molecular Analysis of Voltage‐Gated K
+
Channel Diversity and Functioning in the Mammalian Heart. Compr Physiol 2011. [DOI: 10.1002/cphy.cp020115] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
34
|
Ravens U, Wettwer E. Ultra-rapid delayed rectifier channels: molecular basis and therapeutic implications. Cardiovasc Res 2010; 89:776-85. [DOI: 10.1093/cvr/cvq398] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
|
35
|
Roman-Campos D, Duarte HL, Gomes ER, Castro CH, Guatimosim S, Natali AJ, Almeida AP, Pesquero JB, Pesquero JL, Cruz JS. Investigation of the cardiomyocyte dysfunction in bradykinin type 2 receptor knockout mice. Life Sci 2010; 87:715-23. [DOI: 10.1016/j.lfs.2010.10.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 09/28/2010] [Accepted: 10/08/2010] [Indexed: 12/28/2022]
|
36
|
Kim N, Cannell MB, Hunter PJ. Changes in the calcium current among different transmural regions contributes to action potential heterogeneity in rat heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 103:28-34. [PMID: 20553743 DOI: 10.1016/j.pbiomolbio.2010.05.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 03/16/2010] [Accepted: 05/19/2010] [Indexed: 11/15/2022]
Abstract
To clarify the transmural heterogeneity of action potential (AP) time course, we examined the regulation of L-type Ca(2+) current (I(Ca,L)) by voltage and Ca(2+)-dependent mechanisms. Currents were recorded using patch clamp of single rat subepicardial (EPI) and subendocardial (ENDO) of left ventricular, right ventricular (RV) and septal (SEP) cardiomyocytes. Voltage clamp commands were derived from ENDO and EPI APs or rectangular voltage pulses. During rectangular pulses, peak I(Ca,L) was significantly greater in EPI than in other cells. The inactivation of I(Ca,L) by Ca(2+)-dependent mechanisms (suppressed by ryanodine and BAPTA) was present in all cells but greater in extent in ENDO and SEP cells. Activation and inactivation curves for all regions show subtle differences that are Ca(2+) sensitive, with Ca(2+) inactivation shifting the activation variables negative by approximately 7 mV and inactivation variables positive by 2-7 mV (EPI being least, RV greatest). In AP-clamps, the peak I(Ca,L) was significantly smaller in ENDO than in EPI cells, while the integrated current was significantly larger in ENDO than in EPI cells. The results are discussed with regard to the interplay of AP time course and net Ca(2+) influx.
Collapse
Affiliation(s)
- Nari Kim
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | | | | |
Collapse
|
37
|
Weber dos Santos R, Nygren A, Otaviano Campos F, Koch H, Giles WR. Experimental and theoretical ventricular electrograms and their relation to electrophysiological gradients in the adult rat heart. Am J Physiol Heart Circ Physiol 2009; 297:H1521-34. [DOI: 10.1152/ajpheart.01066.2008] [Citation(s) in RCA: 16] [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 electrical activity of adult mouse and rat hearts has been analyzed extensively, often as a prerequisite for genetic engineering studies or for the development of rodent models of human diseases. Some aspects of the initiation and conduction of the cardiac action potential in rodents closely resemble those in large mammals. However, rodents have a much higher heart rate and their ventricular action potential is triangular and very short. As a consequence, an interpretation of the electrocardiogram in the mouse and rat remains difficult and controversial. In this study, optical mapping techniques have been applied to an in vitro left ventricular adult rat preparation to obtain patterns of conduction and action potential duration measurements from the epicardial surface. This information has been combined with previously published mathematical models of the rat ventricular myocyte to develop a bidomain model for action potential propagation and electrogram formation in the rat left ventricle. Important insights into the basis for the repolarization waveform in the ventricular electrogram of the adult rat have been obtained. Notably, our model demonstrated that the biphasic shape of the rat ventricular repolarization wave can be explained in terms of the transmural and apex-to-base gradients in action potential duration that exist in the rat left ventricle.
Collapse
Affiliation(s)
| | - Anders Nygren
- Department of Physiology and Biophysics,
- Department of Electrical and Computer Engineering,
- Centre for Bioengineering Research and Education, and
| | - Fernando Otaviano Campos
- Department of Computer Science, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil
- Institute of Biophysics, Medical University of Graz, Graz, Austria; and
| | - Hans Koch
- Department of Biosignals, Physikalisch-Technische Bundesanstalt, Berlin, Germany
| | - Wayne R. Giles
- Department of Physiology and Biophysics,
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| |
Collapse
|
38
|
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.
Collapse
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
| | | |
Collapse
|
39
|
Roman-Campos D, Campos AC, Gioda CR, Campos PP, Medeiros MAA, Cruz JS. Cardiac structural changes and electrical remodeling in a thiamine-deficiency model in rats. Life Sci 2009; 84:817-24. [PMID: 19345230 DOI: 10.1016/j.lfs.2009.03.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Revised: 01/26/2009] [Accepted: 03/25/2009] [Indexed: 01/29/2023]
Abstract
AIMS Thiamine is an important cofactor present in many biochemical reactions, and its deprivation can lead to heart dysfunction. Little is known about the influence of thiamine deprivation on the electrophysiological behavior of the isolated heart cells and information about thiamine deficiency in heart morphology is controversial. Thus, we decided to investigate the major repolarizing conductances and their influence in the action potential (AP) waveform as well as the changes in the heart structure in a set of thiamine deficiency in rats. MAIN METHODS Using the patch-clamp technique, we investigated inward (I(K1)) and outward K(+) currents (I(to)), T-type and L-type Ca(2+) currents and APs. To evaluate heart morphology we used hematoxylin and eosin in transversal heart sections. KEY FINDINGS Thiamine deficiency caused a marked decrease in left ventricle thickness, cardiomyocyte number, cell length and width, and membrane capacitance. When evaluating I(to) we did not find difference in current amplitude; however an acceleration of I(to) inactivation was observed. I(K1) showed a reduction in the amplitude and slope conductance, which implicated a less negative resting membrane potential in cardiac myocytes isolated from thiamine-deficient rats. We did not find any difference in L-type Ca(2+) current density. T-type Ca(2+) current was not observed. In addition, we did not observe significant changes in AP repolarization. SIGNIFICANCE Based on our study we can conclude that thiamine deficiency causes heart hypotrophy and not heart hypertrophy. Moreover, we provided evidence that there is no major electrical remodeling during thiamine deficiency, a feature of heart failure models.
Collapse
Affiliation(s)
- D Roman-Campos
- Laboratório de Membranas Excitáveis e de Biologia Cardiovascular, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31970-901, Belo Horizonte-MG, Brazil
| | | | | | | | | | | |
Collapse
|
40
|
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]
|
41
|
Overholser BR, Zheng X, Tisdale JE. Catecholaminergic Effects on Ventricular Repolarization During Inhibition of the Rapid Component of the Delayed Rectifier Potassium Current in a Perfused Heart Model. Pharmacotherapy 2008; 28:1315-24. [DOI: 10.1592/phco.28.11.1315] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
42
|
Kontogeorgis A, Li X, Kang EY, Feig JE, Ponzio M, Kang G, Kaba RA, Wit AL, Fisher EA, Morley GE, Peters NS, Coetzee WA, Gutstein DE. Decreased connexin43 expression in the mouse heart potentiates pacing-induced remodeling of repolarizing currents. Am J Physiol Heart Circ Physiol 2008; 295:H1905-16. [PMID: 18757477 PMCID: PMC2614590 DOI: 10.1152/ajpheart.590.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Gap junction redistribution and reduced expression, a phenomenon termed gap junction remodeling (GJR), is often seen in diseased hearts and may predispose toward arrhythmias. We have recently shown that short-term pacing in the mouse is associated with changes in connexin43 (Cx43) expression and localization but not with increased inducibility into sustained arrhythmias. We hypothesized that short-term pacing, if imposed on murine hearts with decreased Cx43 abundance, could serve as a model for evaluating the electrophysiological effects of GJR. We paced wild-type (normal Cx43 abundance) and heterozygous Cx43 knockout (Cx43+/−; 66% mean reduction in Cx43) mice for 6 h at 10–15% above their average sinus rate. We investigated the electrophysiological effects of pacing on the whole animal using programmed electrical stimulation and in isolated ventricular myocytes with patch-clamp studies. Cx43+/− myocytes had significantly shorter action potential durations (APD) and increased steady-state (Iss) and inward rectifier (IK1) potassium currents compared with those of wild-type littermate cells. In Cx43+/− hearts, pacing resulted in a significant prolongation of ventricular effective refractory period and APD and significant diminution of Iss compared with unpaced Cx43+/− hearts. However, these changes were not seen in paced wild-type mice. These data suggest that Cx43 abundance plays a critical role in regulating currents involved in myocardial repolarization and their response to pacing. Our study may aid in understanding how dyssynchronous activation of diseased, Cx43-deficient myocardial tissue can lead to electrophysiological changes, which may contribute to the worsened prognosis often associated with pacing in the failing heart.
Collapse
Affiliation(s)
- Andrianos Kontogeorgis
- Leon H. Charney Division of Cardiology, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Barbosa EC, Bomfim ADS, Benchimol-Barbosa PR, Ginefra P. Ionic mechanisms and vectorial model of early repolarization pattern in the surface electrocardiogram of the athlete. Ann Noninvasive Electrocardiol 2008; 13:301-7. [PMID: 18713332 PMCID: PMC6932540 DOI: 10.1111/j.1542-474x.2008.00235.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The electrocardiogram (ECG) of the athlete displays particular characteristics as a consequence of both electrophysiological and autonomic remodeling of the heart that follows continued physical training. However, doubts persist on how these changes directly interact during ventricular activation and repolarization ultimately affecting surface ECG waveforms in athletes. OBJECTIVE This article considers an in deep rationale for the electrocardiographic pattern known as early repolarization based on both electrophysiological mechanisms at cellular level and the vectorial theory of the cardiac activation. METHODS The mechanism by which the autonomic remodeling influences the cardiac electrical activation is reviewed and an insight model of the ventricular repolarization based on ionic models and the vectorial theory of the cardiac activation is proposed. RESULTS Considering the underlying processes related to ventricular electrical remodeling, we propose that, in athletes' heart: 1) vagal modulation increases regional electrophysiological differences in action potential phases 1 and 2 amplitudes, thus enhancing a voltage gradient between epicardial and endocardial fibers; 2) this gradient affects depolarization and repolarization timing sequences; 3) repolarization wave front starts earlier on ventricular wall and partially overcomes the end of depolarization causing an upward displacement of the J-point, ST segment elevation, and inscription of magnified T-waves amplitudes leading to characteristic surface ECG waveform patterns. CONCLUSIONS In athletes, the association between epicardial to endocardial electrophysiological differences and early repolarization ECG pattern can be demonstrated by the vectorial theory of the ventricular activation and repolarization.
Collapse
Affiliation(s)
- Eduardo C Barbosa
- Department of Cardiology, State University of Rio de Janeiro, Rio de Janeiro, Brazil.
| | | | | | | |
Collapse
|
44
|
Lee AS, Chen WP, Su MJ. Comparison of the cardiac electrophysiological effects between doxazosin and bunazosin. J Biomed Sci 2008; 15:519-28. [PMID: 18427952 DOI: 10.1007/s11373-008-9249-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Accepted: 04/01/2008] [Indexed: 11/29/2022] Open
Abstract
In Langendorff-perfused adult rat heart with constant pressure at 80 mmHg, we found doxazosin, an alpha(1) adrenoceptor blocker, at 10 muM prolonged PR interval and induced occasional arrhythmia followed by complete inhibition of the sinus rhythm, whereas bunazosin, another alpha(1)-blocker, at same concentration did not. The results of voltage-clamp study showed that, at the concentration of 10 muM, doxazosin inhibited I (Na), I ( (Ca,L) ), I (to), and Iss without changing I (k1) but bunazosin only inhibited I ( (Ca,L) ) about 30%. Doxazosin also caused markedly negative shift of the I (Na) inactivation curve. In current-clamp study, doxazosin prolonged action potential duration in association with the decreased action potential amplitude and upstroke velocity, whereas bunazosin did not. We hypothesize that doxazosin-induced arrhythmia may result from the heterogeneous or different level of I ( (Ca,L) ) blockade of AV nodal tissue. In conclusion, the present study suggests that bunazosin is safer than doxazosin for long-term treatment in view of electrophysiological effect. However, the underlying mechanism of doxazosin induced nodal arrhythmia is still needed to be determined.
Collapse
Affiliation(s)
- An-Sheng Lee
- Institute of Pharmacology, College of Medicine, National Taiwan University, No.1, Sec.1, Jen-Ai Rd., Taipei 100, Taiwan, ROC
| | | | | |
Collapse
|
45
|
Crescioli C, Squecco R, Cosmi L, Sottili M, Gelmini S, Borgogni E, Sarchielli E, Scolletta S, Francini F, Annunziato F, Vannelli GB, Serio M. Immunosuppression in cardiac graft rejection: a human in vitro model to study the potential use of new immunomodulatory drugs. Exp Cell Res 2008; 314:1337-50. [PMID: 18291365 DOI: 10.1016/j.yexcr.2007.12.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Revised: 12/20/2007] [Accepted: 12/20/2007] [Indexed: 10/22/2022]
Abstract
CXCL10-CXCR3 axis plays a pivotal role in cardiac allograft rejection, so that targeting CXCL10 without inducing generalized immunosuppression may be of therapeutic significance in allotransplantation. Since the role of resident cells in cardiac rejection is still unclear, we aimed to establish reliable human cardiomyocyte cultures to investigate Th1 cytokine-mediated response in allograft rejection. We used human fetal cardiomyocytes (Hfcm) isolated from fetal hearts, obtained after legal abortions. Hfcm expressed specific cardiac lineage markers, specific cardiac structural proteins, typical cardiac currents and generated ventricular action potentials. Thus, Hfcm represent a reliable in vitro tool for allograft rejection research, since they resemble the features of mature cells. Hfcm secreted CXCL10 in response to IFNgamma and TNFalphaalpha; this effect was magnified by cytokine combination. Cytokine synergy was associated to a significant TNFalpha-induced up-regulation of IFNgammaR. The response of Hfcm to some currently used immunosuppressive drugs compared to rosiglitazone, a peroxisome proliferator-activated receptor gamma agonist and Th1-mediated response inhibitor, was also evaluated. Only micophenolic acid and rosiglitazone halved CXCL10 secretion by Hfcm. Given the pivotal role of IFNgamma-induced chemokines in Th1-mediated allograft rejection, these preliminary results suggest that the combined effects of immunosuppressive agents and rosiglitazone could be potentially beneficial to patients receiving heart transplants.
Collapse
Affiliation(s)
- Clara Crescioli
- Center for Research Transfer and High Education DENOthe, University of Florence, Florence, Italy.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Sallé L, Kharche S, Zhang H, Brette F. Mechanisms underlying adaptation of action potential duration by pacing rate in rat myocytes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 96:305-20. [PMID: 17869329 DOI: 10.1016/j.pbiomolbio.2007.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Heart rate is an essential determinant of cardiac performance. In rat ventricular myocytes, a sudden increase in rate yields to a prolongation of the action potential duration (APD). The mechanism underlying this prolongation is controversial: it has been proposed that the longer APD is due to either: (1) a decrease in K+ currents only or (2) an increase in Ca2+ current only. The aim of this study was to quantitatively investigate the contribution of Ca2+ and K+ currents in the adaptation of APD to pacing rate. Simulation using a mathematical model of ventricular rat cardiac cell model [Pandit, S.V., Clark, R.B., Giles, W.R., Demir, S.S., 2001. A mathematical model of action potential heterogeneity in adult rat left ventricular myocytes. Biophys. J. 81, 3029-3051] predicted a role in the prolongation of APD for K+ currents only. In patch clamp experiments, increasing the pacing rate leads to a significant increase in APD in both control and detubulated myocytes, although it was more marked in control than detubulated myocytes. Supporting the model prediction, we observed that increasing stimulation frequency leads to a decrease in K+ currents in voltage clamped rat ventricular myocytes (square and action potential waveforms), and to a similar extent in both cell types. We have also observed that frequency-dependent facilitation of Ca2+ current occurred in control cells but not in detubulated cells (square and action potential waveforms). From these experiments, we calculated that the relative contribution of Ca2+ and K+ currents to the longer APD following an increase in pacing rate is approximately 65% and approximately 35%, respectively. Therefore, in contrast to the model prediction, Ca2+ current has a significant role in the adaptation of APD to pacing rate. Finally, we have introduced a simplistic modification to the Pandit's model to account for the frequency-dependent facilitation of Ca2+ current.
Collapse
Affiliation(s)
- Laurent Sallé
- Laboratoire de Physiologie Cellulaire, EA3212, Université de Caen, 14032 Caen, France
| | | | | | | |
Collapse
|
47
|
Effects of rosiglitazone on altered electrical left ventricular papillary muscle activities of diabetic rat. Naunyn Schmiedebergs Arch Pharmacol 2007; 376:415-21. [DOI: 10.1007/s00210-007-0234-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Accepted: 11/23/2007] [Indexed: 10/22/2022]
|
48
|
Strutz-Seebohm N, Gutcher I, Decher N, Steinmeyer K, Lang F, Seebohm G. Comparison of potent Kv1.5 potassium channel inhibitors reveals the molecular basis for blocking kinetics and binding mode. Cell Physiol Biochem 2007; 20:791-800. [PMID: 17982261 DOI: 10.1159/000110439] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2007] [Indexed: 12/14/2022] Open
Abstract
In this study, we analysed the inhibitory potency, blocking characteristics and putative binding sites of three structurally distinct Kv1.5 channel inhibitors on cloned human Kv1.5 channels. Obtained IC(50) values for S9947, MSD-D and ICAGEN-4 were 0.7 microM, 0.5 microM, and 1.6 microM, respectively. The Hill-coefficients were close to 1 for S9947 and approximately 2 for MSD-D and ICAGEN-4. All three compounds inhibited Kv1.5 channels preferentially in the open state, with Kv1.5 block displaying positive frequency dependence, but no clear voltage and potassium dependence. In contrast to slow on- and off-rates of apparent binding of MSD-D and ICAGEN-4, S9947 had fast on- and off-rates resulting in faster adaptation to changes in pulse frequency. Utilizing Alanine-scanning and in silico modeling we suggest binding of the compounds to the central cavity with crucial residues Ile508 and Val512 in the S6-segment. Residue Thr480 located at the base of the selectivity filter is important for ICAGEN-4 and S9947 inhibition, but less so for MSD-D binding. Our docking models suggest that the innermost potassium ion in the selectivity filter may form a tertiary complex with oxygens of S9947 and ICAGEN-4 and residue Thr480. This binding component is absent in the MSD-D block. As S9947 and ICAGEN-4 show faster block with proceeding channel openings, formation of this tertiary complex may increasingly stabilise binding of S9947 and ICAGEN-4, thereby explaining open channel block kinetics of these compounds.
Collapse
|
49
|
Mertens A, Stiedl O, Steinlechner S, Meyer M. Cardiac dynamics during daily torpor in the Djungarian hamster (Phodopus sungorus). Am J Physiol Regul Integr Comp Physiol 2007; 294:R639-50. [PMID: 18032471 DOI: 10.1152/ajpregu.00496.2007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Djungarian or Siberian hamsters (Phodopus sungorus) acclimated to short photoperiod display episodes of spontaneous daily torpor with metabolic rate depressed by approximately 70% and body temperature (T(b)) reduced by approximately 20 degrees C. To study the cardiovascular adjustment to daily torpor in Phodopus, electrocardiogram (ECG) and T(b) were continuously recorded by telemetry during entrance into torpor, in deep torpor, and during arousal from torpor. Minimum T(b) during torpor bouts was approximately 21 degrees C, and heart rate, approximately 349 beats/min at euthermy, displayed marked sinus bradyarrhythmia at approximately 70 beats/min. Arousal was typically completed within approximately 40 min, followed by a sustained post-torpor inactivity tachycardia ( approximately 540 beats/min). The absence of episodes of conduction block, tachyarrhythmia, or other forms of ectopy throughout the torpor cycle demonstrates a remarkable resistance to arrhythmogenesis. The ECG morphology lacks a distinct isoelectric interval following the QRS complex, and the ST segment resembles the ECG pattern in mice, with a prominent fast transient outward K(+) current (I(to,f)) determining the early phase of ventricular repolarization. During low-temperature torpor, the amplitudes of the QRS complex substantially increased, suggesting that in the euthermic state the terminal portion of ventricular depolarization is fused with the beginning of repolarization, low T(b) acting to decorrelate the superposition between depolarization and repolarization by delaying the repolarization onset. Atrioventricular and ventricular conduction times were prolonged as function of T(b). In contrast, the QT vs. T(b) relationship showed marked hysteresis indicating the operation of nonlinear control mechanisms whereby the rapid QT shortening during arousal results from additional mechanisms (probably sympathetic stimulation) other than temperature alone.
Collapse
Affiliation(s)
- Alexander Mertens
- Fractal Physiology, Max Planck Institute for Experimental Medicine, Hermann Rein Strasse 3, Göttingen, Germany
| | | | | | | |
Collapse
|
50
|
Low JC, Wasan KM, Fazli L, Eberding A, Adomat H, Guns ES. Assessing the therapeutic and toxicological effects of cesium chloride following administration to nude mice bearing PC-3 or LNCaP prostate cancer xenografts. Cancer Chemother Pharmacol 2007; 60:821-9. [PMID: 17294190 DOI: 10.1007/s00280-007-0429-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The purpose of this study was to assess the therapeutic and toxicological effects of cesium chloride (CsCl) administration in mice bearing prostate cancer tumors. METHODS Three CsCl dose titration studies were completed in tumor-bearing and non-tumor-bearing athymic nude mice. All mice were administered either vehicle (controls), 150, 300, 600, 800, 1,000, or 1,200 mg/kg of CsCl once daily by oral gavage for 30 consecutive days. Body mass was measured daily, food and water consumption were measured every 2 days, and tumor volume was measured twice weekly. Histopathological analysis was conducted on tissues collected from each of the studies. Serum AST/ALT and creatinine were also measured. RESULTS Administration of 800-1,200 mg/kg CsCl reduced PC-3 tumor growth but had no effect on LNCaP tumors. Administration of 800-1,200 mg/kg CsCl also resulted in increased water consumption, bladder crystal development, and higher prevalence of cardiac fibrin clots. An observed loss in body mass was dependent on the xenograft type and concentration of CsCl administered. CsCl did not affect serum AST/ALT and creatinine levels. CONCLUSIONS CsCl may have a therapeutic effect against prostate cancer, but one cannot overlook the acute toxicities also described.
Collapse
Affiliation(s)
- Jonathan C Low
- Urologic Sciences, The Prostate Center at Vancouver General Hospital, 2660 Oak Street, Vancouver, BC, Canada V6H 3Z4.
| | | | | | | | | | | |
Collapse
|