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Teixeira-Fonseca JL, Joviano-Santos JV, da Silva Alcântara F, de Lima Conceição MR, Leal-Silva P, Roman-Campos D. Evaluation of right atrium structure and function in a rat model of monocrotaline-induced pulmonary hypertension: Exploring the possible antiarrhythmic properties of amiodarone. Clin Exp Pharmacol Physiol 2023; 50:893-902. [PMID: 37610053 DOI: 10.1111/1440-1681.13813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 06/02/2023] [Accepted: 07/25/2023] [Indexed: 08/24/2023]
Abstract
Atrial arrhythmias (AA) are common in pulmonary hypertension (PH) and are closely associated with poor clinical outcomes. One of the most studied models to investigate PH is the rat model of monocrotaline (MCT) induced PH (MCT-PH). To date, little is known about right atrium (RA) function in the MCT-PH model and the propensity of RA to develop arrhythmias. Therefore, the aim of the study was to evaluate the function of the RA of control (CTRL) and MCT treated rats, and the ability of amiodarone, a classical antiarrhythmic, to prevent the occurrence of AA in the RA in MCT-PH rats. RA function was studied in MCT-PH rats 20 days after a single subcutaneous injection of MCT 50 mg/kg. The histological results indicated the presence of RA and right ventricular hypertrophy. Surface electrocardiogram demonstrated increased P wave duration, PR wave duration and QT interval in MCT rats. RA from MCT rats were more susceptible to develop ex vivo burst pacing arrhythmias when compared to CTRL. Intriguingly, amiodarone in clinical relevant concentration was not able to prevent the occurrence arrhythmias in RA from MCT-PH animals. Hence, we conclude that the rat model of MCT-PH impairs RA structure and function, and acute exposure of RA to amiodarone in clinical relevant concentration is not able to attenuate the onset of arrhythmias in the ex vivo RA preparation.
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Affiliation(s)
- Jorge Lucas Teixeira-Fonseca
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicine, Federal University of Sao Paulo, São Paulo, Brazil
| | | | - Fabiana da Silva Alcântara
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicine, Federal University of Sao Paulo, São Paulo, Brazil
| | - Michael Ramon de Lima Conceição
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicine, Federal University of Sao Paulo, São Paulo, Brazil
| | - Polyana Leal-Silva
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicine, Federal University of Sao Paulo, São Paulo, Brazil
| | - Danilo Roman-Campos
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicine, Federal University of Sao Paulo, São Paulo, Brazil
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Jiang H, Zhang S, Lu W, Yang F, Bi X, Ma W, Wei Z. In silico assessment of pharmacotherapy for carbon monoxide induced arrhythmias in healthy and failing human hearts. Front Physiol 2022; 13:1018299. [DOI: 10.3389/fphys.2022.1018299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Accepted: 11/16/2022] [Indexed: 11/17/2022] Open
Abstract
Background: Carbon monoxide (CO) is gaining increased attention in air pollution-induced arrhythmias. The severe cardiotoxic consequences of CO urgently require effective pharmacotherapy to treat it. However, existing evidence demonstrates that CO can induce arrhythmias by directly affecting multiple ion channels, which is a pathway distinct from heart ischemia and has received less concern in clinical treatment.Objective: To evaluate the efficacy of some common clinical antiarrhythmic drugs for CO-induced arrhythmias, and to propose a potential pharmacotherapy for CO-induced arrhythmias through the virtual pathological cell and tissue models.Methods: Two pathological models describing CO effects on healthy and failing hearts were constructed as control baseline models. After this, we first assessed the efficacy of some common antiarrhythmic drugs like ranolazine, amiodarone, nifedipine, etc., by incorporating their ion channel-level effects into the cell model. Cellular biomarkers like action potential duration and tissue-level biomarkers such as the QT interval from pseudo-ECGs were obtained to assess the drug efficacy. In addition, we also evaluated multiple specific IKr activators in a similar way to multi-channel blocking drugs, as the IKr activator showed great potency in dealing with CO-induced pathological changes.Results: Simulation results showed that the tested seven antiarrhythmic drugs failed to rescue the heart from CO-induced arrhythmias in terms of the action potential and the ECG manifestation. Some of them even worsened the condition of arrhythmogenesis. In contrast, IKr activators like HW-0168 effectively alleviated the proarrhythmic effects of CO.Conclusion: Current antiarrhythmic drugs including the ranolazine suggested in previous studies did not achieve therapeutic effects for the cardiotoxicity of CO, and we showed that the specific IKr activator is a promising pharmacotherapy for the treatment of CO-induced arrhythmias.
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Bai J, Lu Y, Zhang H. In silico study of the effects of anti-arrhythmic drug treatment on sinoatrial node function for patients with atrial fibrillation. Sci Rep 2020; 10:305. [PMID: 31941982 PMCID: PMC6962222 DOI: 10.1038/s41598-019-57246-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 12/23/2019] [Indexed: 12/21/2022] Open
Abstract
Sinus node dysfunction (SND) is often associated with atrial fibrillation (AF). Amiodarone is the most frequently used agent for maintaining sinus rhythm in patients with AF, but it impairs the sinoatrial node (SAN) function in one-third of AF patients. This study aims to gain mechanistic insights into the effects of the antiarrhythmic agents in the setting of AF-induced SND. We have adapted a human SAN model to characterize the SND conditions by incorporating experimental data on AF-induced electrical remodelling, and then integrated actions of drugs into the modified model to assess their efficacy. Reductions in pacing rate upon the implementation of AF-induced electrical remodelling associated with SND agreed with the clinical observations. And the simulated results showed the reduced funny current (If) in these remodelled targets mainly contributed to the heart rate reduction. Computational drug treatment simulations predicted a further reduction in heart rate during amiodarone administration, indicating that the reduction was the result of actions of amiodarone on INa, IKur, ICaL, ICaT, If and beta-adrenergic receptors. However, the heart rate was increased in the presence of disopyramide. We concluded that disopyramide may be a desirable choice in reversing the AF-induced SND phenotype.
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Affiliation(s)
- Jieyun Bai
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou, China.
| | - Yaosheng Lu
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou, China
| | - Henggui Zhang
- Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom.
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Oyrer J, Maljevic S, Scheffer IE, Berkovic SF, Petrou S, Reid CA. Ion Channels in Genetic Epilepsy: From Genes and Mechanisms to Disease-Targeted Therapies. Pharmacol Rev 2018; 70:142-173. [PMID: 29263209 DOI: 10.1124/pr.117.014456] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 10/02/2017] [Indexed: 12/19/2022] Open
Abstract
Epilepsy is a common and serious neurologic disease with a strong genetic component. Genetic studies have identified an increasing collection of disease-causing genes. The impact of these genetic discoveries is wide reaching-from precise diagnosis and classification of syndromes to the discovery and validation of new drug targets and the development of disease-targeted therapeutic strategies. About 25% of genes identified in epilepsy encode ion channels. Much of our understanding of disease mechanisms comes from work focused on this class of protein. In this study, we review the genetic, molecular, and physiologic evidence supporting the pathogenic role of a number of different voltage- and ligand-activated ion channels in genetic epilepsy. We also review proposed disease mechanisms for each ion channel and highlight targeted therapeutic strategies.
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Affiliation(s)
- Julia Oyrer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Snezana Maljevic
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Ingrid E Scheffer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Samuel F Berkovic
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Christopher A Reid
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
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Yamashita K, Watanabe Y, Kita S, Iwamoto T, Kimura J. Inhibitory effect of YM-244769, a novel Na +/Ca 2+ exchanger inhibitor on Na +/Ca 2+ exchange current in guinea pig cardiac ventricular myocytes. Naunyn Schmiedebergs Arch Pharmacol 2016; 389:1205-1214. [PMID: 27480939 DOI: 10.1007/s00210-016-1282-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 07/21/2016] [Indexed: 11/28/2022]
Abstract
Recently, YM-244769 (N-(3-aminobenzyl)-6-{4-[(3-fluorobenzyl)oxy]phenoxy} nicotinamide) has been reported as a new potent and selective Na+/Ca2+ exchange (NCX) inhibitor by using various cells transfected with NCX using the 45Ca2+ fluorescent technique. However, the electrophysiological study of YM-244769 on NCX had not been performed in the mammalian heart. We examined the effects of YM-244769 on NCX current (INCX) in single cardiac ventricular myocytes of guinea pigs by using the whole-cell voltage clamp technique. YM-244769 suppressed the bidirectional INCX in a concentration-dependent manner. The IC50 values of YM-244769 for the bidirectional outward and inward INCX were both about 0.1 μM. YM-244769 suppressed the unidirectional outward INCX (Ca2+ entry mode) with an IC50 value of 0.05 μM. The effect on the unidirectional inward INCX (Ca2+ exit mode) was less potent, with 10 μM of YM-244769 resulting in the inhibition of only about 50 %. At 5 mM intracellular Na+ concentration, YM-244769 suppressed INCX more potently than it did at 0 mM [Na+]i. Intracellular application of trypsin via the pipette solution did not change the blocking effect of YM-244769. In conclusion, YM-244769 inhibits the Ca2+ entry mode of NCX more potently than the Ca2+ exit mode, and inhibition by YM-244769 is [Na+]i-dependent and trypsin-insensitive. These characteristics are similar to those of other benzyloxyphenyl derivative NCX inhibitors such as KB-R7943, SEA0400, and SN-6. The potency of YM-244769 as an NCX1 inhibitor is higher than those of KB-R7943 and SN-6 and is similar to that of SEA0400.
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Affiliation(s)
- Kanna Yamashita
- Division of Pharmacological Science, Department of Health Science, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Yasuhide Watanabe
- Division of Pharmacological Science, Department of Health Science, Hamamatsu University School of Medicine, Hamamatsu, Japan.
| | - Satomi Kita
- Department of Pharmacology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Takahiro Iwamoto
- Department of Pharmacology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Junko Kimura
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima, Japan
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Acsai K, Ördög B, Varró A, Nánási PP. Role of the dysfunctional ryanodine receptor - Na(+)-Ca(2+)exchanger axis in progression of cardiovascular diseases: What we can learn from pharmacological studies? Eur J Pharmacol 2016; 779:91-101. [PMID: 26970182 DOI: 10.1016/j.ejphar.2016.03.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 03/04/2016] [Accepted: 03/07/2016] [Indexed: 12/28/2022]
Abstract
Abnormal Ca(2+)homeostasis is often associated with chronic cardiovascular diseases, such as hypertension, heart failure or cardiac arrhythmias, and typically contributes to the basic ethiology of the disease. Pharmacological targeting of cardiac Ca(2+)handling has great therapeutic potential offering invaluable options for the prevention, slowing down the progression or suppression of the harmful outcomes like life threatening cardiac arrhythmias. In this review we outline the existing knowledge on the involvement of malfunction of the ryanodine receptor and the Na(+)-Ca(2+)exchanger in disturbances of Ca(2+)homeostasis and discuss important proof of concept pharmacological studies targeting these mechanisms in context of hypertension, heart failure, atrial fibrillation and ventricular arrhythmias. We emphasize the promising results of preclinical studies underpinning the potential benefits of the therapeutic strategies based on ryanodine receptor or Na(+)-Ca(2+)exchanger inhibition.
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Affiliation(s)
- Károly Acsai
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary
| | - Balázs Ördög
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Faculty of Medicine, Szeged, Hungary
| | - András Varró
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary; Department of Pharmacology and Pharmacotherapy, University of Szeged, Faculty of Medicine, Szeged, Hungary
| | - Péter P Nánási
- Department of Physiology, University of Debrecen, Debrecen, Hungary; Department of Dentistry, University of Debrecen, Debrecen, Hungary.
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Shenoda B. The role of Na+/Ca2+ exchanger subtypes in neuronal ischemic injury. Transl Stroke Res 2015; 6:181-90. [PMID: 25860439 DOI: 10.1007/s12975-015-0395-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 03/09/2015] [Indexed: 01/03/2023]
Abstract
The Na(+)/Ca(2+) exchanger (NCX) plays an important role in the maintenance of Na(+) and Ca(2+) homeostasis in most cells including neurons under physiological and pathological conditions. It exists in three subtypes (NCX1-3) with different tissue distributions but all of them are present in the brain. NCX transports Na(+) and Ca(2+) in either Ca(2+)-efflux (forward) or Ca(2+)-influx (reverse) mode, depending on membrane potential and transmembrane ion gradients. During neuronal ischemia, Na(+) and Ca(2+) ionic disturbances favor NCX to work in reverse mode, giving rise to increased intracellular Ca(2+) levels, while it may regain its forward mode activity on reperfusion. The exact significance of NCX in neuronal ischemic and reperfusion states remains unclear. The differential role of NCX subtypes in ischemic neuronal injury has been extensively investigated using various pharmacological tools as well as genetic models. This review discusses the mode of action of NCX in ischemic and reperfusion states, the differential roles played by NCX subtypes in these states as well as the role of NCX in pre- and postconditioning. NCX subtypes carry variable roles in ischemic injury. Furthermore, the mode of action of each subtype varies in ischemia and reperfusion states. Thus, therapeutic targeting of NCX in stroke should be based on appropriate timing of the administration of NCX subtype-specific strategies.
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Affiliation(s)
- Botros Shenoda
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 North 15th Street, Mail Stop #488, Philadelphia, PA, 19102, USA,
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8
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Majumder R, Pandit R, Panfilov AV. Turbulent electrical activity at sharp-edged inexcitable obstacles in a model for human cardiac tissue. Am J Physiol Heart Circ Physiol 2014; 307:H1024-35. [DOI: 10.1152/ajpheart.00593.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Wave propagation around various geometric expansions, structures, and obstacles in cardiac tissue may result in the formation of unidirectional block of wave propagation and the onset of reentrant arrhythmias in the heart. Therefore, we investigated the conditions under which reentrant spiral waves can be generated by high-frequency stimulation at sharp-edged obstacles in the ten Tusscher-Noble-Noble-Panfilov (TNNP) ionic model for human cardiac tissue. We show that, in a large range of parameters that account for the conductance of major inward and outward ionic currents of the model [fast inward Na+ current ( INa), L—type slow inward Ca2+ current ( ICaL), slow delayed-rectifier current ( IKs), rapid delayed-rectifier current ( IKr), inward rectifier K+ current ( IK1)], the critical period necessary for spiral formation is close to the period of a spiral wave rotating in the same tissue. We also show that there is a minimal size of the obstacle for which formation of spirals is possible; this size is ∼2.5 cm and decreases with a decrease in the excitability of cardiac tissue. We show that other factors, such as the obstacle thickness and direction of wave propagation in relation to the obstacle, are of secondary importance and affect the conditions for spiral wave initiation only slightly. We also perform studies for obstacle shapes derived from experimental measurements of infarction scars and show that the formation of spiral waves there is facilitated by tissue remodeling around it. Overall, we demonstrate that the formation of reentrant sources around inexcitable obstacles is a potential mechanism for the onset of cardiac arrhythmias in the presence of a fast heart rate.
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Affiliation(s)
- Rupamanjari Majumder
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
- Laboratory of Experimental Cardiology, Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Rahul Pandit
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
- Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, India
| | - A. V. Panfilov
- Department of Physics and Astronomy, Gent University, Ghent, Belgium; and
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region, Russia
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9
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Hanafy DA, Chen YC, Chang SL, Lu YY, Lin YK, Kao YH, Chen SA, Chen YJ. Different effects of dronedarone and amiodarone on pulmonary vein electrophysiology, mechanical properties and H2O2-induced arrhythmogenicity. Eur J Pharmacol 2013; 702:103-8. [DOI: 10.1016/j.ejphar.2013.01.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 01/10/2013] [Accepted: 01/16/2013] [Indexed: 11/29/2022]
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10
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Wilhelms M, Rombach C, Scholz EP, Dossel O, Seemann G. Impact of amiodarone and cisapride on simulated human ventricular electrophysiology and electrocardiograms. Europace 2012; 14 Suppl 5:v90-v96. [DOI: 10.1093/europace/eus281] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Brittain MK, Brustovetsky T, Sheets PL, Brittain JM, Khanna R, Cummins TR, Brustovetsky N. Delayed calcium dysregulation in neurons requires both the NMDA receptor and the reverse Na+/Ca2+ exchanger. Neurobiol Dis 2012; 46:109-17. [PMID: 22249110 DOI: 10.1016/j.nbd.2011.12.051] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 12/12/2011] [Accepted: 12/31/2011] [Indexed: 12/20/2022] Open
Abstract
Glutamate-induced delayed calcium dysregulation (DCD) is a causal factor leading to neuronal death. The mechanism of DCD is not clear but Ca2+ influx via N-methyl-d-aspartate receptors (NMDAR) and/or the reverse plasmalemmal Na+/Ca2+ exchanger (NCXrev) could be involved in DCD. However, the extent to which NMDAR and NCX(rev) contribute to glutamate-induced DCD is uncertain. Here, we show that both NMDAR and NCX(rev) are critical for DCD in neurons exposed to excitotoxic glutamate. In rat cultured hippocampal neurons, 25 μM glutamate produced DCD accompanied by sustained increase in cytosolic Na+ ([Na+]c) and plasma membrane depolarization. MK801 and memantine, noncompetitive NMDAR inhibitors, added shortly after glutamate, completely prevented DCD whereas AP-5, a competitive NMDAR inhibitor, failed to protect against DCD. None of the tested inhibitors lowered elevated [Na+]c or restored plasma membrane potential. In the experiments with NCX reversal by gramicidin, MK801 and memantine robustly inhibited NCXrev while AP-5 was much less efficacious. In electrophysiological patch-clamp experiments MK801 and memantine inhibited NCXrev-mediated ion currents whereas AP-5 failed. Thus, MK801 and memantine, in addition to NMDAR, inhibited NCXrev. Inhibition of NCXrev either with KB-R7943, or by collapsing Na+ gradient across the plasma membrane, or by inhibiting Na+/H+ exchanger with 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and thus preventing the increase in [Na+]c failed to preclude DCD. However, NCXrev inhibition combined with NMDAR blockade by AP-5 completely prevented DCD. Overall, our data suggest that both NMDAR and NCXrev are essential for DCD in glutamate-exposed neurons and inhibition of individual mechanism is not sufficient to prevent calcium dysregulation.
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Affiliation(s)
- Matthew K Brittain
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Yamakawa T, Watanabe Y, Watanabe H, Kimura J. Inhibitory Effect of Cibenzoline on Na+/Ca2+ Exchange Current in Guinea-Pig Cardiac Ventricular Myocytes. J Pharmacol Sci 2012; 120:59-62. [DOI: 10.1254/jphs.12050sc] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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Mahmood Q, Rashid A, Ahmad SS, Azim MR, Bilal M. Current Status of Toxic Metals Addition to Environment and Its Consequences. THE PLANT FAMILY BRASSICACEAE 2012. [DOI: 10.1007/978-94-007-3913-0_2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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Brustovetsky T, Brittain MK, Sheets PL, Cummins TR, Pinelis V, Brustovetsky N. KB-R7943, an inhibitor of the reverse Na+ /Ca2+ exchanger, blocks N-methyl-D-aspartate receptor and inhibits mitochondrial complex I. Br J Pharmacol 2011; 162:255-70. [PMID: 20883473 DOI: 10.1111/j.1476-5381.2010.01054.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE An isothiourea derivative (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methane sulfonate (KB-R7943), a widely used inhibitor of the reverse Na(+) /Ca(2+) exchanger (NCX(rev)), was instrumental in establishing the role of NCX(rev) in glutamate-induced Ca(2+) deregulation in neurons. Here, the effects of KB-R7943 on N-methyl-D-aspartate (NMDA) receptors and mitochondrial complex I were tested. EXPERIMENTAL APPROACH Fluorescence microscopy, electrophysiological patch-clamp techniques and cellular respirometry with Seahorse XF24 analyzer were used with cultured hippocampal neurons; membrane potential imaging, respirometry and Ca(2+) flux measurements were made in isolated rat brain mitochondria. KEY RESULTS KB-R7943 inhibited NCX(rev) with IC(50) = 5.7 ± 2.1 µM, blocked NMDAR-mediated ion currents, and inhibited NMDA-induced increase in cytosolic Ca(2+) with IC(50) = 13.4 ± 3.6 µM but accelerated calcium deregulation and mitochondrial depolarization in glutamate-treated neurons. KB-R7943 depolarized mitochondria in a Ca(2+) -independent manner. Stimulation of NMDA receptors caused NAD(P)H oxidation that was coupled or uncoupled from ATP synthesis depending on the presence of Ca(2+) in the bath solution. KB-R7943, or rotenone, increased NAD(P)H autofluorescence under resting conditions and suppressed NAD(P)H oxidation following glutamate application. KB-R7943 inhibited 2,4-dinitrophenol-stimulated respiration of cultured neurons with IC(50) = 11.4 ± 2.4 µM. With isolated brain mitochondria, KB-R7943 inhibited respiration, depolarized organelles and suppressed Ca(2+) uptake when mitochondria oxidized complex I substrates but was ineffective when mitochondria were supplied with succinate, a complex II substrate. CONCLUSIONS AND IMPLICATIONS KB-R7943, in addition to NCX(rev) , blocked NMDA receptors in cultured hippocampal neurons and inhibited complex I in the mitochondrial respiratory chain. These findings are critical for the correct interpretation of experimental results obtained with KB-R7943 and a better understanding of its neuroprotective action.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology and Toxicology Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA.
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Zidan RA. Effect of long-term administration of amiodarone on rat lung and the possible protective role of vitamin E. ACTA ACUST UNITED AC 2011. [DOI: 10.1097/01.ehx.0000395190.66459.04] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Watanabe Y, Kimura J. Inhibitory effect of azimilide on Na+/Ca2+ exchange current in guinea-pig cardiac myocytes. J Pharmacol Sci 2010; 114:111-4. [PMID: 20710119 DOI: 10.1254/jphs.10066sc] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
We examined the effect of azimilide, a class III antiarrhythmic drug, on Na(+)/Ca(2+) exchange current (I(NCX)) in guinea-pig cardiac single ventricular cells. External application of azimilide suppressed bi-directional I(NCX) in a concentration-dependent manner. IC(50) values for outward and inward I(NCX) were 45 and 40 µM, respectively, with Hill coefficients of 1. Azimilide attenuated I(NCX) in the presence of trypsin in the patch pipette, indicating that azimilide is a trypsin-insensitive NCX inhibitor. Delayed afterdepolarization induced by electrical stimulation with ouabain disappeared in the presence of 30 µM azimilide. We conclude that azimilide inhibits NCX at supratherapeutic concentrations.
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Affiliation(s)
- Yasuhide Watanabe
- Division of Pharmacological Science, Department of Health Science, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu, Japan.
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Li EC, Esterly JS, Pohl S, Scott SD, McBride BF. Drug-Induced QT-Interval Prolongation: Considerations for Clinicians. Pharmacotherapy 2010; 30:684-701. [DOI: 10.1592/phco.30.7.684] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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18
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Samantaray A, Chandra A, Panigrahi S. Amiodarone for the prevention of reperfusion ventricular fibrillation. J Cardiothorac Vasc Anesth 2009; 24:239-43. [PMID: 19800815 DOI: 10.1053/j.jvca.2009.07.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The purpose of this study was to evaluate the efficacy of prophylactic single-dose amiodarone administered through the pump circuit before releasing the aortic cross-clamp (ACC) in preventing the occurrence of reperfusion ventricular fibrillation (RVF). DESIGN A prospective, randomized double-blind, placebo-controlled efficacy study. SETTING A tertiary level teaching hospital. INTERVENTION Seventeen patients received 150 mg of amiodarone in 10 mL of normal saline by way of the pump 3 minutes before releasing the ACC, and a control group of 17 patients received 10 mL of normal saline. MEASUREMENT AND MAIN RESULTS The primary outcome of the study was the incidence of ventricular fibrillation requiring defibrillation during the 30-minute period after myocardial reperfusion. A large decrease in RVF (65% to 18%) was observed in the amiodarone-treated group with the number needed to treat only 2.1.The myocardial performance in terms of cardiac output was better in the amiodarone group; this could be attributed to the lower incidence of RVF and subsequent direct current shock therapy. CONCLUSIONS The observations showed that single-dose prophylactic amiodarone administered through the pump circuit 3 minutes before ACC release was an effective therapy to reduce the incidence of post-ACC release ventricular arrhythmias.
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Affiliation(s)
- Aloka Samantaray
- Department of Anesthesiology and Critical Care, Sri Venkateswara Institute of Medical Sciences, Andhra Pradesh, India.
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19
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Tamura A, Ogura T, Uemura H, Reien Y, Kishimoto T, Nagai T, Komuro I, Miyazaki M, Nakaya H. Effects of Antiarrhythmic Drugs on the Hyperpolarization-Activated Cyclic Nucleotide–Gated Channel Current. J Pharmacol Sci 2009; 110:150-9. [DOI: 10.1254/jphs.08312fp] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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20
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Noble D. Computational models of the heart and their use in assessing the actions of drugs. J Pharmacol Sci 2008; 107:107-17. [PMID: 18566519 DOI: 10.1254/jphs.cr0070042] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Models of cardiac cells are sufficiently well developed to answer questions concerning the actions of drugs on repolarization and the initiation of arrhythmias. These models can be used to characterize drug-receptor action profiles that would be expected to avoid arrhythmia and so help to identify drugs that may be safer. Several examples of such action profiles are presented here, including a recently-developed blocker of persistent sodium current, ranolazine. The models have also been incorporated into tissue and organ models that enable arrhythmia to be modelled also at these levels. Work at these levels can reproduce both re-entrant arrhythmia and fibrillation.
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Affiliation(s)
- Denis Noble
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
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Li L, Watanabe Y, Matsuoka I, Kimura J. Acidic preconditioning inhibits Na+/H+ and Na+/Ca2+ exchanger interaction via PKCepsilon in guinea-pig ventricular myocytes. J Pharmacol Sci 2008; 107:309-16. [PMID: 18603829 DOI: 10.1254/jphs.08049fp] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
An interaction between the Na(+)/Ca(2+) exchanger (NCX) and the Na(+)/H(+) exchanger (NHE) induces reperfusion injury. We investigated the effect of brief repetitive acidosis as acidic preconditioning on NCX and NHE interaction during recovery from acidosis. NCX current with the reversal potential was measured in guinea-pig ventricular myocytes using the whole-cell voltage clamp. The cells were exposed to 5 min of acidosis preceded by two episodes of brief acidosis as acidic preconditioning. Acidosis inhibited NCX current and upon recovery shifted its reversal potential in the negative direction. The shift was prevented by cariporide, but was augmented by a high concentration of phorbol 13-myristate acetate (PMA). Acidic preconditioning prevented the shift, but not in the presence of a selective PKCepsilon inhibitor. A low concentration of PMA, which activates PKCepsilon selectively, prevented the shift, but together with PKCepsilon inhibitor (epsilonV1-2) restored the shift during recovery. 5-Hydroxydecanoate inhibited the effects of acidic preconditioning and those of both low and high concentrations of PMA. The negative shift of NCX reversal potential during recovery from acidosis may be due to [Na(+)](i) accumulation by the NHE. Acidic preconditioning prevented the shift most likely by activating PKCepsilon, which in turn inhibited the NHE. The NHE-NCX interaction may be one of the important end-effectors of preconditioning.
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Affiliation(s)
- Libing Li
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima, Japan
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22
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Szentandrássy N, Birinyi P, Szigeti G, Farkas A, Magyar J, Tóth A, Csernoch L, Varró A, Nánási PP. SEA0400 fails to alter the magnitude of intracellular Ca2+ transients and contractions in Langendorff-perfused guinea pig heart. Naunyn Schmiedebergs Arch Pharmacol 2008; 378:65-71. [PMID: 18458877 DOI: 10.1007/s00210-008-0296-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 04/03/2008] [Indexed: 12/01/2022]
Abstract
SEA0400 is a recently developed inhibitor of the Na+/Ca2+ exchanger (NCX) shown to suppress both forward and reverse mode operation of NCX. Present experiments were designed to study the effect of partial blockade of NCX on Ca handling and contractility in Langendorff-perfused guinea pig hearts loaded with the fluorescent Ca-sensitive dye fura-2. Left ventricular pressure and intracellular calcium concentration ([Ca2+]i) were synchronously recorded before and after cumulative superfusion with 0.3 and 1 muM SEA0400. SEA0400 caused no significant change in the systolic and diastolic values of left ventricular pressure and [Ca2+]i. Accordingly, pulse pressure and amplitude of the [Ca2+]i transient also remained unchanged in the presence of SEA0400. SEA0400 had no influence either on the time required to reach peak values of pressure and [Ca2+)]i or on half relaxation time. On the other hand, both 0.3 and 1 microM SEA0400 significantly increased the decay time constant of [Ca2+]i transients, obtained by fitting its descending limb between 30% and 90% of relaxation, from 127 +/- 7 to 165 +/- 7 and 177 +/- 14 ms, respectively (P < 0.05, n=6). In contrast to the guinea pig hearts, rat hearts responded to SEA0400 treatment with increased [Ca2+]i transients and contractility. These interspecies differences observed in the effect of SEA0400 can be explained by the known differences in calcium handling between the two species.
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Affiliation(s)
- Norbert Szentandrássy
- Department of Physiology, University of Debrecen, 4012, Debrecen, P.O. Box 22, Hungary
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Watanabe Y, Kimura J. Acute inhibitory effect of dronedarone, a noniodinated benzofuran analogue of amiodarone, on Na+/Ca2+ exchange current in guinea pig cardiac ventricular myocytes. Naunyn Schmiedebergs Arch Pharmacol 2008; 377:371-6. [PMID: 18392809 DOI: 10.1007/s00210-008-0270-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 01/31/2008] [Indexed: 11/27/2022]
Abstract
Using the whole-cell voltage-clamp method, we examined an acute effect of dronedarone, a noniodinated benzofuran analogue of amiodarone, on Na+/Ca2+ exchange current (INCX) in guinea pig cardiac ventricular cells. The INCX was recorded by ramp pulses with a holding potential of -60 mV using a pipette solution containing 226 nM free Ca2+ (20 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and 10 mM Ca2+) and 20 mM Na+. The external solution contained 140 mM Na+, 1 mM Ca2+, and blockers of other currents and pumps such as Cs+, nifedipine, ryanodine, and ouabain. A selective potent NCX inhibitor, KB-R7943 (100 microM), was used to completely inhibit INCX. Dronedarone inhibited INCX in a concentration-dependent manner. The IC50 values for the outward and inward INCX inhibition were about 33 and 28 microM, respectively, with the Hill coefficient of 1 for both. The inhibitory effect of dronedarone at 50 microM on INCX did not change in the presence of trypsin in the pipette solution. Therefore, dronedarone is classified as a trypsin-insensitive NCX inhibitor and distinct from amiodarone which is a trypsin sensitive. We conclude that dronedarone inhibits INCX but the potency is tenfold less than that of amiodarone. Dronedarone may modestly inhibit INCX in a therapeutic concentration range.
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Affiliation(s)
- Yasuhide Watanabe
- Division of Pharmacological Science, Department of Health Science, Hamamatsu University School of Medicine, 1-20-1 Handa-yama, Higashi-ku, Hamamatsu, 431-3192, Japan.
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24
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Niu CF, Watanabe Y, Ono K, Iwamoto T, Yamashita K, Satoh H, Urushida T, Hayashi H, Kimura J. Characterization of SN-6, a novel Na+/Ca2+ exchange inhibitor in guinea pig cardiac ventricular myocytes. Eur J Pharmacol 2007; 573:161-9. [PMID: 17644086 DOI: 10.1016/j.ejphar.2007.06.033] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2007] [Revised: 06/11/2007] [Accepted: 06/12/2007] [Indexed: 10/23/2022]
Abstract
We examined the effect of SN-6, a new benzyloxyphenyl Na(+)/Ca(2+) exchange (NCX) inhibitor on the Na(+)/Ca(2+) exchange current (I(NCX)) and other membrane currents in isolated guinea pig ventricular myocytes using the whole-cell voltage-clamp technique. SN-6 suppressed I(NCX) in a concentration-dependent manner. The IC(50) values of SN-6 were 2.3 microM and 1.9 microM for the outward and inward components of the bi-directional I(NCX), respectively. On the other hand, SN-6 suppressed the outward uni-directional I(NCX) more potently (IC(50) value of 0.6 microM) than the inward uni-directional I(NCX). SN-6 at 10 microM inhibited the uni-directional inward I(NCX) by only 22.4+/-3.1%. SN-6 and KB-R7943 suppressed I(NCX) more potently when intracellular Na(+) concentration was higher. Thus, both drugs inhibit NCX in an intracellular Na(+) concentration-dependent manner. Intracellular application of trypsin via a pipette solution did not change the blocking effect of SN-6 on I(NCX). Therefore, SN-6 is categorized as an intracellular-trypsin-insensitive NCX inhibitor. SN-6 at 10 microM inhibited I(Na), I(Ca), I(K) and I(K1) by about 13%, 34%, 33% and 13%, respectively. SN-6 at 10 microM shortened the action potential duration at 50% repolarization (APD(50)) by about 34%, and that at 90% repolarization (APD(90)) by about 25%. These results indicate that SN-6 inhibits NCX in a similar manner to that of KB-R7943. However, SN-6 at 10 microM affected other membrane currents less potently than KB-R7943.
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Affiliation(s)
- Chun-Feng Niu
- Department of Internal Medicine III, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
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25
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Niu CF, Watanabe Y, Iwamoto T, Yamashita K, Satoh H, Urushida T, Hayashi H, Kimura J. Electrophysiological effects of SN-6, a novel Na+/Ca2+ exchange inhibitor on membrane currents in guinea pig ventricular myocytes. Ann N Y Acad Sci 2007; 1099:534-9. [PMID: 17446498 DOI: 10.1196/annals.1387.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We examined the effect of SN-6 on the Na+/Ca2+ exchanger (NCX) current (I(NCX)) and other membrane currents in isolated guinea pig ventricular myocytes using the whole-cell voltage clamp technique. SN-6 suppressed the bidirectional I(NCX) in a concentration-dependent manner. The IC50 values of SN-6 were 2.3 microM and 1.9 microM for the outward and inward components of the bidirectional I(NCX), respectively. On the other hand, SN-6 suppressed the unidirectional outward I(NCX) more potently than the inward I(NCX), with an IC(50) value of 0.6 microM. SN-6 at 10 microM inhibited the unidirectional inward I(NCX) by only 22.4 +/- 3.1%. SN-6 suppressed I(NCX) more potentially when intracellular Na+ concentration became higher. SN-6 inhibited I(Na), I(Ca), I(Kr), I(Ks), and I(K1) by about 13%, 34%, 33%, 18%, and 13%, respectively. SN-6 shortened the action potential duration (APD) by about 34% and 25% at APD(50) and APD(90), respectively. These results indicate that SN-6 inhibits NCX in a similar manner to that of KB-R7943. SN-6 and KB-R7943 inhibit the unidirectional outward I(NCX) more potently than the unidirectional inward I(NCX). Both drugs inhibit NCX in an intracellular Na+ concentration-dependent manner. However, SN-6 affected other membrane currents less potently than KB-R7943.
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Affiliation(s)
- Chun-Feng Niu
- Department of Internal Medicine III, Hamamatsu University School of Medicine, 1-20-1 Hondayama, Hamamatsu, Shizuoka, 431-3192, Japan
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26
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Sermsappasuk P, Abdelrahman O, Weiss M. Modeling Cardiac Uptake and Negative Inotropic Response of Verapamil in Rat Heart: Effect of Amiodarone. Pharm Res 2006; 24:48-57. [PMID: 16969694 DOI: 10.1007/s11095-006-9117-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Accepted: 07/10/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE To determine the effect of the P-glycoprotein (Pgp) modulator amiodarone on the pharmacokinetics and pharmacodynamics (PK/PD) of Pgp substrate verapamil in the perfused rat heart. METHODS In Langendorff-perfused rat hearts, the outflow concentration-time curve and inotropic response data were measured after a 1.5 nmol dose of [3H]-verapamil (infused within 1 min) in the absence and presence of the amiodarone (1 microM) in perfusate, as well as using a double dosing regimen (0.75 nmol in a 10 min interval). These data were analyzed by a PK/PD model. RESULTS Amiodarone failed to influence the rapid uptake and equilibrium partitioning of verapamil into the heart. The time course of the negative inotropic effect of verapamil, including the 'rebound' above the original baseline after the infusion of verapamil was stopped, could be described by a PK/PD tolerance model. Tolerance development (mean delay time, 12 min) led to a reduction in predicted steady-state effect (16%). The EC50 and Emax values as estimated in single dose experiments were 16.4+/-4.1 nM and 50.5+/-18.9 mmHg, respectively. CONCLUSIONS The result does not support the hypothesis that Pgp inhibition by amiodarone increases cardiac uptake of the Pgp substrate verapamil.
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Affiliation(s)
- Pakawadee Sermsappasuk
- Section of Pharmacokinetics, Department of Pharmacology, Martin Luther University Halle-Wittenberg, D-06097, Halle, Germany
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27
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Sermsappasuk P, Baek M, Weiss M. Kinetic analysis of myocardial uptake and negative inotropic effect of amiodarone in rat heart. Eur J Pharm Sci 2006; 28:243-8. [PMID: 16574386 DOI: 10.1016/j.ejps.2006.02.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Revised: 02/02/2006] [Accepted: 02/20/2006] [Indexed: 10/24/2022]
Abstract
The distribution kinetics of the highly lipophilic antiarrhythmic agent amiodarone is not well understood. The purpose of the present investigation was to develop a pharmacokinetic-pharmacodynamic (PK/PD) model to describe cardiac uptake and the negative inotropic effect of amiodarone in the isolated perfused rat heart. Amiodarone (10 microM) was infused for 15 min to 6 hearts. The time course of outflow concentration and left ventricular developed pressure were measured and analyzed by the model. The uptake of amiodarone by the heart was flow limited and characterized by an extremely high partition coefficient with a predicted tissue washout half-live of 17 h. Only 36.8% of input amount to heart recovered within 45 min after start of the 15 min infusion. The negative inotropic effect was delayed with a time constant of 11 min and the maximal decrease in left ventricular developed pressure was described by a sigmoid E(max) model with an E(max) of 37.7% and an EC(50) of 0.53 microM. Our results suggest a rapid tissue uptake and a moderate negative inotropic effect of amiodarone after intravenous injection.
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Affiliation(s)
- Pakawadee Sermsappasuk
- Section of Pharmacokinetics, Department of Pharmacology, Martin Luther University Halle-Wittenberg, D-06097 Halle, Germany
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28
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Isomoto S, Kawakami A, Arakaki T, Yamashita S, Yano K, Ono K. Effects of Antiarrhythmic Drugs on Apoptotic Pathways in H9c2 Cardiac Cells. J Pharmacol Sci 2006; 101:318-24. [PMID: 16891766 DOI: 10.1254/jphs.fp0050951] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Antiarrhythmic drugs may induce cellular apoptosis in the heart. By using representatives of 5 different categories of antiarrhythmic drugs, that is, pilsicainide, propranolol, nifekalant, verapamil, and amiodarone, we investigated whether these ion channel blockers or beta-antagonists affect cardiac apoptosis in cell cultures. Cultured H9c2 cells were treated with the drugs at varying concentrations. To determine the degree of apoptosis, the percentage of hypodiploid cells, mitochondrial transmembrane potential (DeltaPsi(m)), and activities of caspases were measured quantitatively. At 24 h after administration, only amiodarone induced apoptosis in the H9c2 cells. Amiodarone at a concentration of 14.8 microM or higher decreased DeltaPsi(m) and activated caspase-2 within 3 h of administration, and it caused the appearance of hypodiploid cells and activation of caspases-3 and -9 at 6 h or later. Thus, amiodarone, but none of the other antiarrhythmic drugs tested, possesses a pro-apoptotic effect, mainly via the mitochondrial pathway, suggesting that this effect is distinct from the blocking action of Na+, K+, and Ca2+ channels or the beta-adrenergic receptor. Furthermore, induction of apoptosis in a dose-dependent manner by amiodarone indicates the importance of monitoring the serum concentration in order to avoid its adverse effects.
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Affiliation(s)
- Shojiro Isomoto
- Department of Cardiovascular Science, Oita University School of Medicine, Hasama, Yufu, Japan.
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Watanabe Y, Koide Y, Kimura J. Topics on the Na+/Ca2+ Exchanger: Pharmacological Characterization of Na+/Ca2+ Exchanger Inhibitors. J Pharmacol Sci 2006; 102:7-16. [PMID: 16990699 DOI: 10.1254/jphs.fmj06002x2] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Using the whole-cell voltage clamp, we examined acute effects of various agents on Na(+)/Ca(2+) exchange current (I(NCX)) in guinea-pig cardiac ventricular cells and transfected cells. Among the antiarrhythmic drugs, amiodarone, bepridil, dronedarone, cibenzoline, azimilide, and aprindine inhibited I(NCX) in a concentration-dependent manner. We also investigated the effects on NCX of 2,3-buanedione monoxim (BDM) and selective NCX inhibitors such as KB-R7943, SEA0400, and SN-6. The presence of trypsin in the pipette solution attenuated the inhibitory effects on NCX of amiodarone, bepridil, and BDM, suggesting that these drugs inhibit NCX from the cytosolic side. In contrast, the trypsin-insensitive NCX inhibitors were aprindine, azimilide, dronedarone, cibenzoline, KB-R7943, SEA0400, and SN-6. KB-R7943, SEA0400, and SN-6 suppressed the uni-directional outward I(NCX) more potently than the uni-directional inward I(NCX). The mechanism of this mode-dependency is unknown, but is suggested to be related to intracellular Na(+) concentration.
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Affiliation(s)
- Yasuhide Watanabe
- Division of Pathophysiology, Basic Nursing, Hamamatsu University School of Medicine, Japan.
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Abstract
Despite recent advances in preventing sudden cardiac death (SCD) due to cardiac arrhythmia, its incidence in the population at large has remained unacceptably high. Better understanding of the interaction among various functional, structural, and genetic factors underlying the susceptibility to, and initiation of, fatal arrhythmias is a major goal and will provide new tools for the prediction, prevention, and therapy of SCD. Here, we review the role of aberrant intracellular Ca handling, ionic imbalances associated with acute myocardial ischemia, neurohumoral changes, and genetic predisposition in the pathogenesis of SCD due to cardiac arrhythmia. Therapeutic measures to prevent SCD are also discussed.
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Affiliation(s)
- Michael Rubart
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5225, USA.
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31
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Birinyi P, Acsai K, Bányász T, Tóth A, Horváth B, Virág L, Szentandrássy N, Magyar J, Varró A, Fülöp F, Nánási PP. Effects of SEA0400 and KB-R7943 on Na+/Ca2+ exchange current and L-type Ca2+ current in canine ventricular cardiomyocytes. Naunyn Schmiedebergs Arch Pharmacol 2005; 372:63-70. [PMID: 16086157 DOI: 10.1007/s00210-005-1079-x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2005] [Accepted: 06/28/2005] [Indexed: 10/25/2022]
Abstract
SEA0400 and KB-R7943 are compounds synthesised to block transsarcolemmal Na+/Ca2+ exchange current (I(Na/Ca)); however, they have also been shown to inhibit L-type Ca2+ current (I(Ca)). The potential value of these compounds depends critically on their relative selectivity for I(Na/Ca) over I(Ca). In the present work, therefore, the concentration-dependent effects of SEA0400 and KB-R7943 on I(Na/Ca) and I(Ca) were studied and compared in canine ventricular cardiomyocytes using the whole-cell configuration of the patch clamp technique. SEA0400 and KB-R7943 decreased I(Na/Ca) in a concentration-dependent manner, having EC50 values of 111+/-43 nM and 3.35+/-0.82 microM, when suppressing inward currents, while the respective EC50 values were estimated at 108+/-18 nM and 4.74+/-0.69 microM in the case of outward current block. SEA0400 and KB-R7943 also blocked I(Ca), having comparable EC50 values (3.6 microM and 3.2 microM, respectively). At higher concentrations (10 microM) both drugs accelerated inactivation of I(Ca), retarded recovery from inactivation and shifted the voltage dependence of inactivation towards more negative voltages. The voltage dependence of activation was slightly modified by SEA0400, but not by KB-R7943. Based on the relatively good selectivity of submicromolar concentrations of SEA0400--but not KB-R7943--for I(Na/Ca) over I(Ca), SEA0400 appears to be a suitable tool to study the role of I(Na/Ca) in Ca2+ handling in canine cardiac cells. At concentrations higher than 1 microM, however, I(Ca) is progressively suppressed by the compound.
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Affiliation(s)
- Péter Birinyi
- Department of Physiology, University Medical School of Debrecen, P.O. Box 22, 4012, Debrecen, Hungary
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Watanabe Y, Iwamoto T, Matsuoka I, Ono T, Shigekawa M, Kimura J. Effects of amiodarone on mutant Na+/Ca2+ exchangers expressed in CCL 39 cells. Eur J Pharmacol 2005; 496:49-54. [PMID: 15288574 DOI: 10.1016/j.ejphar.2004.06.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Revised: 05/27/2004] [Accepted: 06/08/2004] [Indexed: 11/20/2022]
Abstract
Using the whole cell voltage clamp, we reported previously that amiodarone acutely inhibits Na+/Ca2+ exchange current (INCX) in guinea pig cardiac ventricular myocytes. Intracellular application of trypsin via the patch pipette attenuated the blocking effect of amiodarone, suggesting that amiodarone affects the Na+/Ca2+ exchanger (NCX) from the cytoplasmic side. Here, we attempted to detect the site of amiodarone inhibition using wild type NCX1, mutants, and NCX3 expressed in CCL39 fibroblasts. INCX was recorded by ramp pulses. Amiodarone at 30 microM inhibited INCX by 80% in cells expressing wild type NCX1. However, 30 microM amiodarone inhibited INCX by about 55% in cells expressing mutant NCX1 with amino acids 217-671 (DeltaXIP) or 247-671 (Delta247-671) deleted in the long intracellular loop between the transmembrane segments (TM) 5 and 6. INCXs from NCX mutants deleted of cytoplasmic TM1-2, TM3-4 or the C-terminus were inhibited by amiodarone to a similar extent as the wild type. Amiodarone also inhibited INCX of NCX3 by 76%. These results suggest that a long intracellular loop may be involved in the inhibition of NCX1 by amiodarone, but that other intracellular loops, XIP region or C terminus are not involved in the amiodarone inhibition of NCX1.
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Affiliation(s)
- Yasuhide Watanabe
- Department of Ecology and Clinical Therapeutics, School of Nursing, Fukushima Medical University, Fukushima 960-1295, Japan.
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Nagasawa Y, Chen J, Hashimoto K. Antiarrhythmic Properties of a Prior Oral Loading of Amiodarone in In Vivo Canine Coronary Ligation/Reperfusion-Induced Arrhythmia Model: Comparison With Other Class III Antiarrhythmic Drugs. J Pharmacol Sci 2005; 97:393-9. [PMID: 15764841 DOI: 10.1254/jphs.fp0040512] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Amiodarone, which is generally classified as class III antiarrhythmic drug in the Vaughan Williams classification, is widely used for the treatments of refractory arrhythmias. However, we previously reported that intravenous infusion of amiodarone (6.67 mg/kg per hour) did not suppress arrhythmias induced by coronary ligation/reperfusion in dogs. In this study, we examined effects of a prior oral loading of amiodarone on arrhythmias induced by coronary ligation/reperfusion. Sixteen female beagle dogs (8.5 - 12.5 kg) were divided into two groups; one group was given amiodarone (40 mg/kg, orally, n = 8), and the other was given empty gelatin capsules (n = 8) 2 h before the operation. Dogs were anesthetized with pentobarbital and artificially ventilated. The left chest was opened, and the left anterior descending coronary artery was ligated for 30 min and then reperfused. The mean plasma concentration of amiodarone was over 1.3 mug/ml. Although the prior oral loading of amiodarone did not change the QT interval, amiodarone suppressed the number of ectopic beats during coronary ligation and the incidence of ventricular fibrillation during coronary ligation and reperfusion periods (P<0.05 vs control group). In conclusion, a prior oral loading of amiodarone suppressed arrhythmias induced by coronary ligation/reperfusion with a dose that did not prolong the QT interval. This antiarrhythmic property of amiodarone is different from those of the other class III drugs in that antiarrhythmic effects were accompanied by QT prolongation in our all previous studies.
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Affiliation(s)
- Yoshinobu Nagasawa
- Department of Pharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi.
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Annunziato L, Pignataro G, Di Renzo GF. Pharmacology of Brain Na+/Ca2+Exchanger: From Molecular Biology to Therapeutic Perspectives. Pharmacol Rev 2004; 56:633-54. [PMID: 15602012 DOI: 10.1124/pr.56.4.5] [Citation(s) in RCA: 254] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
In the last two decades, there has been a growing interest in unraveling the role that the Na+/Ca2+ exchanger (NCX) plays in the function and regulation of several cellular activities. Molecular biology, electrophysiology, genetically modified mice, and molecular pharmacology have helped to delve deeper and more successfully into the physiological and pathophysiological role of this exchanger. In fact, this nine-transmembrane protein, widely distributed in the brain and in the heart, works in a bidirectional way. Specifically, when it operates in the forward mode of operation, it couples the extrusion of one Ca2+ ion with the influx of three Na+ ions. In contrast, when it operates in the reverse mode of operation, while three Na+ ions are extruded, one Ca2+ enters into the cells. Different isoforms of NCX, named NCX1, NCX2, and NCX3, have been described in the brain, whereas only one, NCX1, has been found in the heart. The hypothesis that NCX can play a relevant role in several pathophysiological conditions, including hypoxia-anoxia, white matter degeneration after spinal cord injury, brain trauma and optical nerve injury, neuronal apoptosis, brain aging, and Alzheimer's disease, stems from the observation that NCX, in parallel with selective ion channels and ATP-dependent pumps, is efficient at maintaining intracellular Ca2+ and Na+ homeostasis. In conclusion, although studies concerning the involvement of NCX in the pathological mechanisms underlying brain injury during neurodegenerative diseases started later than those related to heart disease, the availability of pharmacological agents able to selectively modulate each NCX subtype activity and antiporter mode of operation will provide a better understanding of its pathophysiological role and, consequently, more promising approaches to treat these neurological disorders.
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Affiliation(s)
- L Annunziato
- Division of Pharmacology, Department of Neuroscience, School of Medicine, Federico II University of Naples, Via S. Pansini, 5-80131 Naples, Italy.
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Ohtsuka M, Takano H, Suzuki M, Zou Y, Akazawa H, Tamagawa M, Wakimoto K, Nakaya H, Komuro I. Role of Na+-Ca2+ exchanger in myocardial ischemia/reperfusion injury: evaluation using a heterozygous Na+-Ca2+ exchanger knockout mouse model. Biochem Biophys Res Commun 2004; 314:849-53. [PMID: 14741714 DOI: 10.1016/j.bbrc.2003.12.165] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We used Na(+)-Ca(2+) exchanger (NCX) knockout mice to evaluate the effects of NCX in cardiac function and the infarct size after ischemia/reperfusion injury. The contractile function in NCX KO mice hearts was significantly better than that in wild type (WT) mice hearts after ischemia/reperfusion and the infarct size was significantly small in NCX KO mice hearts compared with that in WT mice hearts. NCX is critically involved in the development of ischemia/reperfusion-induced myocardial injury and therefore the inhibition of NCX function may contribute to cardioprotection against ischemia/reperfusion injury.
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Affiliation(s)
- Masashi Ohtsuka
- Department of Cardiovascular Science and Medicine, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, 260-8670, Chiba, Japan
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Mubagwa K, Macianskiene R, Viappiani S, Gendviliene V, Carlsson B, Brandts B. KB130015, a new amiodarone derivative with multiple effects on cardiac ion channels. CARDIOVASCULAR DRUG REVIEWS 2004; 21:216-35. [PMID: 12931255 DOI: 10.1111/j.1527-3466.2003.tb00117.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
KB130015 (KB015), a new drug structurally related to amiodarone, has been proposed to have antiarrhythmic properties. In contrast to amiodarone, KB015 markedly slows the kinetics of inactivation of Na(+) channels by enhancing concentration-dependently (K(0.5) asymptotically equal to 2 microM) a slow-inactivating I(Na) component (tau(slow) asymptotically equal to 50 ms) at the expense of the normal, fast-inactivating component (tau(fast) asymptotically equal to 2 to 3 ms). However, like amiodarone, KB015 slows the recovery from inactivation and causes a shift (K(0.5) asymptotically equal to 6.9 microM) of the steady-state voltage-dependent inactivation to more negative potentials. Despite prolonging the opening of Na(+) channels KB015 does not lengthen but often shortens the action potential duration (APD) in pig myocytes or in multicellular preparations. Only short APDs in mouse are markedly prolonged by KB015, which frequently induces early afterdepolarizations. KB015 has also an effect on other ion channels. It decreases the amplitude of the L-type Ca(2+) current (I(Ca-L)) without changing its time course, and it inhibits G-protein gated and ATP-gated K(+) channels. Both the receptor-activated I(K(ACh)) (induced in atrial myocytes by either ACh, adenosine or sphingosylphosphorylcholine) and the receptor-independent (GTPgammaS-induced or background) I(K(ACh)) are concentration-dependently (K(0.5) asymptotically equal to 0.6 - 0.9 microM) inhibited by KB015. I(K(ATP)), induced in atrial myocytes during metabolic inhibition with 2,4-dinitrophenol (DNP), is equally suppressed. However, KB015 has no effect on I(K1) or on I(to). Consistent with the effects in K(+) currents, KB015 does not depolarize the resting potential but antagonizes the APD shortening by muscarinic receptor activation or by DNP. Intracellular cell dialysis with KB015 has marginal or no effect on Na(+) or K(+) channels and does not prevent the effect of extracellularly applied drug, suggesting that KB015 interacts directly with channels at sites more easily accessible from the extracellular than the intracellular side of the membrane. At high concentrations KB015 exerts a positive inotropic action. It also interacts with thyroid hormone nuclear receptors. Its toxic effects remain largely unexplored, but it is well tolerated during chronic administration.
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Affiliation(s)
- Kanigula Mubagwa
- Centre for Experimental Surgery and Anaesthesiology, University of Leuven, Belgium.
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Komuro I, Ohtsuka M. Forefront of Na+/Ca2+ Exchanger Studies: Role of Na+/Ca2+ Exchanger – Lessons From Knockout Mice. J Pharmacol Sci 2004; 96:23-6. [PMID: 15359083 DOI: 10.1254/jphs.fmj04002x5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
We used Na+/Ca2+ exchanger (NCX) knockout mice to evaluate the effects of NCX in cardiac function and the infarct size after ischemia/reperfusion injury. The contractile function in NCX KO mice hearts was significantly better than that in wild type (WT) mouse hearts after ischemia/reperfusion and the infracted size was significantly smaller in NCX KO mice hearts compared with that in WT mice hearts. NCX is critically involved in the development of ischemia/reperfusion-induced myocardial injury, and therefore the inhibition of NCX function may contribute to cardioprotection against ischemia/reperfusion injury.
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Affiliation(s)
- Issei Komuro
- Department of Cardiovascular Science and Medicine, Chiba University Graduate School of Medicine, Inohana, Chuo-ku, Japan.
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Abstract
The successful identification of drug targets requires an understanding of the high-level functional interactions between the key components of cells, organs and systems, and how these interactions change in disease states. This information does not reside in the genome, or in the individual proteins that genes code for, it is to be found at a higher level. Genomics will succeed in revolutionising pharmaceutical research and development only if these interactions are also understood by determining the logic of healthy and diseased states. The rapid growth in biological databases, models of cells, tissues and organs, and in computing power has made it possible to explore functionality all the way from the level of genes to whole organs and systems. Combined with genomic and proteomic data, in silico simulation technology is set to transform all stages of drug discovery and development. The major obstacle to achieving this will be obtaining the relevant experimental data at levels higher than genomics and proteomics.
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Affiliation(s)
- Denis Noble
- University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK.
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Doggrell SA, Hancox JC. Is timing everything? Therapeutic potential of modulators of cardiac Na(+) transporters. Expert Opin Investig Drugs 2003; 12:1123-42. [PMID: 12831348 DOI: 10.1517/13543784.12.7.1123] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Sodium ion (Na(+)) transporters have roles in the modulation of cardiomyocyte pH and Na(+) and Ca(2+) handling. Activation of the cardiac Na(+)-H(+) exchanger 1 (NHE1) during ischaemia induces arrhythmias, myocardial stunning and irreversible cell injury. As the benefits of NHE1 inhibitors (e.g., amiloride, cariporide) in models of myocardial infarction are usually much greater when used as pretreatment, rather than during or after ischaemia, it is probably not surprising that clinical trials with cariporide in ischaemia have shown little shortterm benefit. NHE1 inhibitors have been shown to be beneficial in animal models of ventricular fibrillation and resuscitation, cardioplegia, hypertrophy and heart failure, and their therapeutic potential in these conditions should be further developed. The Na(+)-HCO(3)(-) cotransporter (NBC) is also stimulated by intracellular acidification, and part of the benefit of angiotensin-converting enzyme inhibitors after myocardial infarction may be due to inhibition of the NBC. Selective inhibitors of the NBC are required to determine the therapeutic potential of this mechanism. The Na(+)-Ca(2+) exchanger (NCX) has a major role in cardiac Na(+) and Ca(2+) homeostasis and influences cardiac electrical activity. The NCX also has a role in ischaemia/infarction, arrhythmias, hypertrophy and heart failure. NCX inhibitors may have beneficial effects in animal models of ischaemia and reperfusion injury and the therapeutic benefit of these should be further studied in animal models.
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Affiliation(s)
- Sheila A Doggrell
- School of Biomedical Sciences, The University of Queensland, QLD 4072, Australia.
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Abstract
KB-R7943 inhibits the Na(+)/Ca(2+) exchanger in an independent manner or in a manner dependent on the direction of the current. This effect may be due to the experimental protocols bawed on the competition between the drug and external substrate ions. Some antiarrhythmic drugs inhibit NCX. A new column of NCX was added in Sicilian Gambit.
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Affiliation(s)
- Junko Kimura
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima, Japan.
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Watanabe Y, Matsuoka I, Kimura J. Chronic administration of amiodarone does not affect Na+/Ca2+ exchange current in guinea pig cardiac ventricular myocytes. JAPANESE JOURNAL OF PHARMACOLOGY 2002; 90:21-7. [PMID: 12396024 DOI: 10.1254/jjp.90.21] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We investigated chronic effects of amiodarone on Na+/Ca2+ exchange current (INCX) and on the level of Na+/Ca2+ exchanger (NCX1) mRNA in guinea pig ventricular myocytes using the whole-cell clamp technique and RT-PCR analysis, respectively. Guinea pigs were intraperitoneally injected with 80 mg/kg per day of amiodarone or the vehicle (saline) for 1 or 4 weeks. Single ventricular cells were isolated from the hearts of both groups of animals. Action potential duration at 90% repolarization level was prolonged to 143% and 165% of the control values by treatment with amiodarone for 1 and 4 weeks, respectively. INCX density and the level of NCX1 mRNA were not significantly changed by chronic treatment with amiodarone. The level of thyroid hormone (T4) within the blood was not changed by the treatments. These results suggest that chronic treatment with amiodarone does not affect the Na+/Ca2+ exchanger, with respect to the level of its mRNA and current density in guinea pig ventricular myocytes.
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Affiliation(s)
- Yasuhide Watanabe
- Department of Ecology and Clinical Therapeutics, School of Nursing, Fukushima Medical University, Japan.
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Abstract
The year 2001 saw a remarkable burst of interest in biological simulation, with several international meetings on the subject, and the inclusion, by journals, of web site references from which published models can be downloaded. So, why has all this happened so suddenly?
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Affiliation(s)
- Denis Noble
- Department of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
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Watanabe Y, Iwamoto T, Shigekawa M, Kimura J. Inhibitory effect of aprindine on Na+/Ca2+ exchange current in guinea-pig cardiac ventricular myocytes. Br J Pharmacol 2002; 136:361-6. [PMID: 12023938 PMCID: PMC1573359 DOI: 10.1038/sj.bjp.0704721] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Using the whole-cell voltage clamp technique, the effect of aprindine on Na+/Ca2+ exchange current (I(NCX)) was examined in guinea-pig single cardiac ventricular myocytes and CCL39 fibroblasts expressing a dog cardiac Na+/Ca2+ exchanger (NCX1). 2. I(NCX) was recorded by ramp pulses from the holding potential of -60 mV with the external solution containing 140 mM Na+ and 1 mM Ca2+, and the pipette solution containing 20 mM Na+, 20 mM BAPTA and 13 mM Ca2+ (433 nM free Ca2+). 3. External application of aprindine suppressed I(NCX) in a concentration-dependent manner. The IC50 values of outward (measured at 50 mV) and inward (measured at -100 mV) I(NCX) components were 48.8 and 51.8 microM with Hill coefficients of 1.3 and 1, respectively. 4. Intracellular application of trypsin via the pipette solution did not change the blocking effect of aprindine, suggesting that aprindine does not affect the exchanger from the cytoplasmic side. 5. Aprindine inhibited I(NCX) of a mutant NCX1 with a deletion of amino acids 247 - 671 in the large intracellular domain between the transmembrane segments 5 and 6 in a similar manner to that of the wild-type, suggesting that the site of aprindine inhibition is not in the large intracellular domain of NCX1. 6. A kinetic study indicated that aprindine was cooperatively competitive with KB-R7943, another inhibitor of NCX and that aprindine was a competitive inhibitor with respect to external Ca2+. 7. We conclude that aprindine may modestly inhibit I(NCX) in a therapeutic range of concentrations (around 2.5 approximately 6.9 microM) possibly at an external or intra-membranous site of the exchanger.
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Affiliation(s)
- Yasuhide Watanabe
- Department of Ecology and Clinical Therapeutics, School of Nursing, Fukushima Medical University, Fukushima 960-1295, Japan.
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Abstract
Successful physiological analysis requires an understanding of the functional interactions between the key components of cells, organs, and systems, as well as how these interactions change in disease states. This information resides neither in the genome nor even in the individual proteins that genes code for. It lies at the level of protein interactions within the context of subcellular, cellular, tissue, organ, and system structures. There is therefore no alternative to copying nature and computing these interactions to determine the logic of healthy and diseased states. The rapid growth in biological databases; models of cells, tissues, and organs; and the development of powerful computing hardware and algorithms have made it possible to explore functionality in a quantitative manner all the way from the level of genes to the physiological function of whole organs and regulatory systems. This review illustrates this development in the case of the heart. Systems physiology of the 21st century is set to become highly quantitative and, therefore, one of the most computer-intensive disciplines.
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Affiliation(s)
- Denis Noble
- University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK.
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Weiss M, Kang W. P-glycoprotein inhibitors enhance saturable uptake of idarubicin in rat heart: pharmacokinetic/pharmacodynamic modeling. J Pharmacol Exp Ther 2002; 300:688-94. [PMID: 11805234 DOI: 10.1124/jpet.300.2.688] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Little is known about cardiac uptake kinetics of idarubicin, including a possible protective role of P-glycoprotein (Pgp)-mediated transport. This study therefore investigated uptake and negative inotropic action of idarubicin in the single-pass isolated perfused rat heart by using a pharmacokinetic/pharmacodynamic modeling approach. Idarubicin was administered as a 10-min constant infusion of 0.5 mg followed by a 70-min washout period in the absence and presence of the Pgp antagonists verapamil or amiodarone. Outflow concentration and left ventricular developed pressure were measured and the model parameters were estimated by simultaneous nonlinear regression. The results indicate the existence of a saturable, Michaelis-Menten type uptake process into the heart (K(m) = 3.06 microM, V(max) = 46.0 microM/min). Verapamil and amiodarone significantly enhanced the influx rate (V(max) increased 1.8-fold), suggesting that idarubicin is transported by Pgp directly out of the membrane before it gets into the cell. Verapamil and amiodarone attenuated the negative inotropic action of idarubicin, which was linked to the intracellular concentration of idarubicin.
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Affiliation(s)
- Michael Weiss
- Section of Pharmacokinetics, Department of Pharmacology, Martin Luther University Halle-Wittenberg, Halle, Germany.
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Abstract
Amiodarone has been used as an anti-arrhythmic drug since the 1970s and has an established role in the treatment of ventricular tachyarrhythmias. Although considered to be a class III anti-arrhythmic, amiodarone also has class I, II and IV actions, which gives it a unique pharmacological and anti-arrhythmic profile. Amiodarone is a structural analogue of thyroid hormone and some of its anti-arrhythmic properties and toxicity may be attributable to interactions with nuclear thyroid hormone receptors. The lipid solubility of amiodarone gives it an exceptionally long half-life. Oral amiodarone takes days to work in ventricular tachyarrhythmias, but iv. amiodarone has immediate effect and can be used in life threatening ventricular arrhythmias. Intravenous amiodarone administered after out-of-hospital cardiac arrest due to ventricular fibrillation improves survival to hospital admission. Many survivors of myocardial infarction (MI) die during the subsequent year, probably due to ventricular arrhythmia. Amiodarone reduces sudden death after MI and this benefit is predominantly observed in patients with preserved cardiac function. Sudden cardiac death, predominantly due to ventricular arrhythmias, is also commonly seen in patients with heart failure. The Grupo de Estudio de la Sobrevida en lsuficiencia Cardiaca en Argentina (GESICA) and Estudio Piloto Argentino de Muerte Subita y Amiodarona (EPAMSA) trials showed survival benefit of amiodarone in heart failure, whereas Congestive Heart Failure-Survival Trial of Anti-arrhythmic Therapy (CHF-STAT) did not. Subsequent meta-analysis established a survival benefit of amiodarone in heart failure. Implanted Cardioverter Def ibrillators (ICDs) also give survival benefit to patients at risk of sudden death. In patients with a history of ventricular fibrillation or haemodynamically-compromising ventricular tachycardia, ICDs have been shown to be superior to anti-arrhythmic drugs, principally amiodarone. Further analysis has been undertaken to ascertain which patients are most likely to benefit from ICDs, as these are more expensive than treatment with amiodarone. Patients with severely depressed ejection fractions should be the first to be considered for ICDs. A new indication for amiodarone is atrial fibrillation or flutter. Amiodarone is effective in chronic and recent onset atrial fibrillation and orally or iv. for atrial fibrillation after heart surgery. In atrial fibrillation amiodarone is more than or equi-effective with flecainide, quinidine, racemic sotalol, propafenone and diltiazem and therefore should be considered for first line therapy. Amiodarone is also safe and effective in controlling refractory tachyarrhythmias in infants and is safe after cardiac surgery.
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Affiliation(s)
- S A Doggrell
- Department of Physiology and Pharmacology, University of Queensland, Brisbane, 4072 Australia.
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Watanabe Y, Kimura J. Blocking effect of bepridil on Na+/Ca2+ exchange current in guinea pig cardiac ventricular myocytes. JAPANESE JOURNAL OF PHARMACOLOGY 2001; 85:370-5. [PMID: 11388640 DOI: 10.1254/jjp.85.370] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We examined the effect of bepridil, a class IV antiarrhythmic drug, on Na+/Ca2+ exchange current (I(NCX)) in single guinea pig cardiac ventricular cells using the whole-cell voltage clamp technique. I(NCX) was recorded by ramp pulses from the holding potential of -60 mV in the presence of 140 mM Na+ and 1 mM Ca2+ in the external solution and 20 mM Na+ and 119 nM free Ca2+ (7 mM Ca2+ and 20 mM BAPTA) in the internal solution. Bepridil suppressed I(NCX) in a concentration-dependent manner. The IC50 value was 8.1 microM with a Hill coefficient of 0.8. Intracellular treatment with trypsin via the pipette solution attenuated the blocking effect of bepridil, suggesting that the inhibitory site is on the cytosolic side of the Na+/Ca2+ exchanger. In the absence of albumin in the external solution, 10 microM bepridil inhibited I(NCX) by 46+/-7% (n = 8), while bepridil blocked it by 28+/-8% (n = 6) in the presence of albumin. Bepridil inhibited I(NCX) in a supra-therapeutic concentration range.
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Affiliation(s)
- Y Watanabe
- Department of Ecology and Clinical Therapeutics, School of Nursing, Fukushima Medical University, Japan.
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Watanabe Y, Iwamoto T, Matsuoka I, Ohkubo S, Ono T, Watano T, Shigekawa M, Kimura J. Inhibitory effect of 2,3-butanedione monoxime (BDM) on Na(+)/Ca(2+) exchange current in guinea-pig cardiac ventricular myocytes. Br J Pharmacol 2001; 132:1317-25. [PMID: 11250883 PMCID: PMC1572662 DOI: 10.1038/sj.bjp.0703926] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The effect of 2,3-butanedione monoxime (BDM), a 'chemical phosphatase', on Na(+)/Ca(2+) exchange current (I(NCX)) was investigated using the whole-cell voltage-clamp technique in single guinea-pig cardiac ventricular myocytes and in CCL39 fibroblast cells expressing canine NCX1. 2. I(NCX) was identified as a current sensitive to KB-R7943, a relatively selective NCX inhibitor, at 140 mM Na(+) and 2 mM Ca(2+) in the external solution and 20 mM Na(+) and 433 nM free Ca(2+) in the pipette solution. 3. In guinea-pig ventricular cells, BDM inhibited I(NCX) in a concentration-dependent manner. The IC(50) value was 2.4 mM with a Hill coefficients of 1. The average time for 50% inhibition by 10 mM BDM was 124+/-31 s (n=5). 4. The effect of BDM was not affected by 1 microM okadaic acid in the pipette solution, indicating that the inhibition was not via activation of okadaic acid-sensitive protein phosphatases. 5. Intracellular trypsin treatment via the pipette solution significantly suppressed the inhibitory effect of BDM, implicating an intracellular site of action of BDM. 6. PAM (pralidoxime), another oxime compound, also inhibited I(NCX) in a manner similar to BDM. 7. Isoprenaline at 50 microM and phorbol 12-myristate 13-acetate (PMA) at 8 microM did not reverse the inhibition of I(NCX) by BDM. 8. BDM inhibited I(NCX) in CCL39 cells expressing NCX1 and in its mutant in which its three major phosphorylatable serine residues were replaced with alanines. 9. We conclude that BDM inhibits I(NCX) but the mechanism of inhibition is not by dephosphorylation of the Na(+)/Ca(2+) exchanger as a 'chemical phosphatase'.
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Affiliation(s)
- Yasuhide Watanabe
- Department of Ecology and Clinical Therapeutics, School of Nursing, Fukushima Medical University, Fukushima 960-1295, Japan
| | - Takahiro Iwamoto
- Department of Molecular Physiology, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
| | - Isao Matsuoka
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima 960-1295, Japan
| | | | - Tomoyuki Ono
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima 960-1295, Japan
| | - Tomokazu Watano
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima 960-1295, Japan
| | - Munekazu Shigekawa
- Department of Molecular Physiology, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
| | - Junko Kimura
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima 960-1295, Japan
- Author for correspondence:
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