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Reynolds BS, Chetboul V, Elliott J, Laxalde J, Nguyen P, Testault I, Dorso L, Abadie J, Lefebvre HP, Biourge V. Long-term safety of dietary salt: A 5-year ProspEctive rAndomized bliNded and controlled stUdy in healThy aged cats (PEANUT study). J Vet Intern Med 2024; 38:285-299. [PMID: 38084870 PMCID: PMC10800216 DOI: 10.1111/jvim.16952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 11/14/2023] [Indexed: 01/23/2024] Open
Abstract
BACKGROUND High-salt diets promote urine dilution and decrease urolithiasis risk. OBJECTIVE Prospectively evaluate the safety of chronic high dietary salt intake (randomized controlled trial). ANIMALS Twenty research colony neutered, healthy aged cats (11.5 years [10.0-11.6], median [interquartile range]). METHODS Healthy cats were randomized to control or high-salt dry diets (sodium: 1.02 ± 0.16 [mean, SD] and 3.26 ± 0.30 g/Mcal metabolizable energy [ME], respectively; chloride: 2.26 ± 0.33 and 5.71 ± 0.28 g/Mcal ME, respectively), fed for up to 60 months. Assessments included CBC, plasma biochemistry, urinalysis, glomerular filtration rate (GFR), blood pressure, renal and cardiac (conventional Doppler and 2-dimensional color tissue Doppler) imaging, annually. Cats that died or were euthanized underwent necropsy. Diet effects over time were evaluated with linear mixed models. RESULTS Follow-up duration (median [Interquartile range]) was similar between the control (38.7 months [28.6-48.2]) and high-salt group (51.4 months [45.7-59.0]). Diet had no significant effect on changes in GFR, blood pressure, plasma creatinine concentration, end-diastolic left ventricular (LV) wall thicknesses, LV internal diameters, LV systolic function, left atrial size, or systolic and diastolic Doppler variables. One control cat developed hypertension. One high-salt group cat developed persistent azotemia. Serial plasma biochemistry and urine specific gravity suggested early chronic kidney disease in 4 nonazotemic cats (2 per group), consistent with necropsy findings. CONCLUSIONS AND CLINICAL IMPORTANCE In healthy aged cats, a commercial veterinary diet containing 3.26 ± 0.30 g/Mcal ME sodium was safe with regard to renal and cardiac function for up to 5 years.
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Affiliation(s)
| | - Valerie Chetboul
- Unité de cardiologie d'Alfort (UCA), CHUVAEcole Nationale Vétérinare d'AlfortMaisons‐AlfortFrance
- Université Paris‐Est Créteil, INSERM, IMRBCréteilFrance
| | - Jonathan Elliott
- Department of Comparative Biomedical Sciences, Royal Veterinary CollegeUniversity of LondonLondonUK
| | | | - Patrick Nguyen
- Nutrition and Endocrinology Unit, LUNAM UniversitéOnirisNantesFrance
| | | | - Laëticia Dorso
- Centre hospitalier Univesitaire VétérinaireOnirisNantesFrance
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Megwa OF, Pascual LM, Günay C, Pulver SR, Prinz AA. Temporal dynamics of Na/K pump mediated memory traces: insights from conductance-based models of Drosophila neurons. Front Neurosci 2023; 17:1154549. [PMID: 37284663 PMCID: PMC10239822 DOI: 10.3389/fnins.2023.1154549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 04/21/2023] [Indexed: 06/08/2023] Open
Abstract
Sodium potassium ATPases (Na/K pumps) mediate long-lasting, dynamic cellular memories that can last tens of seconds. The mechanisms controlling the dynamics of this type of cellular memory are not well understood and can be counterintuitive. Here, we use computational modeling to examine how Na/K pumps and the ion concentration dynamics they influence shape cellular excitability. In a Drosophila larval motor neuron model, we incorporate a Na/K pump, a dynamic intracellular Na+ concentration, and a dynamic Na+ reversal potential. We probe neuronal excitability with a variety of stimuli, including step currents, ramp currents, and zap currents, then monitor the sub- and suprathreshold voltage responses on a range of time scales. We find that the interactions of a Na+-dependent pump current with a dynamic Na+ concentration and reversal potential endow the neuron with rich response properties that are absent when the role of the pump is reduced to the maintenance of constant ion concentration gradients. In particular, these dynamic pump-Na+ interactions contribute to spike rate adaptation and result in long-lasting excitability changes after spiking and even after sub-threshold voltage fluctuations on multiple time scales. We further show that modulation of pump properties can profoundly alter a neuron's spontaneous activity and response to stimuli by providing a mechanism for bursting oscillations. Our work has implications for experimental studies and computational modeling of the role of Na/K pumps in neuronal activity, information processing in neural circuits, and the neural control of animal behavior.
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Affiliation(s)
- Obinna F. Megwa
- Department of Biology, Emory University, Atlanta, GA, United States
| | | | - Cengiz Günay
- School of Science and Technology, Georgia Gwinnett College, Lawrenceville, GA, United States
| | - Stefan R. Pulver
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom
| | - Astrid A. Prinz
- Department of Biology, Emory University, Atlanta, GA, United States
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Wang S, Cheng Y, Zheng Q, Su X, Deng Y. Evaluating the association between dietary salt intake and the risk of atrial fibrillation using Mendelian randomization. Front Nutr 2023; 10:1073626. [PMID: 37090783 PMCID: PMC10117818 DOI: 10.3389/fnut.2023.1073626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 03/20/2023] [Indexed: 04/08/2023] Open
Abstract
BackgroundPrevious studies have suggested that dietary salt intake affects atrial fibrillation (AF); however, the causal association between them still remains unclear. Thus, we conducted this Mendelian randomization (MR) study to explore the correlation between them.MethodsGenetic instruments for dietary salt intake were from a genome-wide association study (GWAS), which included 462,630 European individuals. Summary-level data for AF were obtained from another published GWAS (22,068 cases and 116,926 controls). The inverse-variance weighting (IVW) method was performed as the primary MR analysis. Multiple MR methods, including Robust Adjusted Profile Score (MR-RAPS), maximum likelihood estimation, and Mendelian randomization pleiotropy residual sum and outlier test (MR-PRESSO) were conducted as complementary analyses. The MR-Egger regression intercept and MR-PRESSO global test were conducted to test potential horizontal pleiotropy. The IVW (Q) method and MR-Egger were performed to detect heterogeneity.ResultsOur results suggested that high dietary salt intake was significantly correlated with increased risk of AF [IVW: odds ratio (OR), 1.36; 95% confidence interval (CI), 1.04–1.77; p = 2.25E-02]. The maximum likelihood estimation (OR, 1.37; 95% CI, 1.05–1.78; p = 2.09E-02), MR-RAPS (OR, 1.37; 95% CI, 1.03–1.81; p = 2.79E-02), and MR-PRESSO method (OR, 1.36; 95% CI, 1.05–1.76; p = 2.37E-02) also showed that dietary salt intake was significantly correlated with the risk of AF.ConclusionThe findings of this study provide robust evidence supporting the correlation between dietary salt intake and the risk of AF. Future studies are required to further clarify this relationship and translate the findings into clinical and public health practice.
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Affiliation(s)
- Sicen Wang
- School of Pharmacy, Health Science Center, Xi’an Jiaotong University, Xi’an, China
| | - Ye Cheng
- School of Pharmacy, Health Science Center, Xi’an Jiaotong University, Xi’an, China
- Department of Cardiology, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
| | - Qi Zheng
- Department of Psychology, Xiamen Xianyue Hospital, Xiamen, China
| | - Xin Su
- Department of Cardiology, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
- *Correspondence: Xin Su,
| | - Yingjian Deng
- Department of Cardiology, Xiamen Cardiovascular Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
- Yingjian Deng,
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Goddard J, Speights CJ, Borganelli M. Salt as a Trigger for Atrial Tachycardia/Fibrillation. Cureus 2022; 14:e26168. [PMID: 35891840 PMCID: PMC9302945 DOI: 10.7759/cureus.26168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2022] [Indexed: 11/18/2022] Open
Abstract
A variety of potential triggers of atrial fibrillation (AF) have been reported, including alcohol consumption, caffeine, exercise, and stress. Vagal AF triggers include gastrointestinal factors such as the amount of food consumed, types of foods, and gas and bloating. In this case report, detailed data of seven dietary and behavioral factors (many vagal) believed to be possible atrial tachycardia (AT) or AF triggers in a single patient with paroxysmal AT/AF were recorded. Episodes of AT and AF were recorded in the patient using a Medtronic loop recorder and analyzed by a cardiac electrophysiologist. To evaluate these potential triggers of AT/AF events, a general linear model with binomial family error distribution was used to fit the data. Then, a stepAIC function from the MASS package in R was used to perform a stepwise model selection using AIC (Akaike information criterion). The analysis only identified the amount of salt intake and the use of polyethylene glycol 3350 as predictors of AT/AF, and high salt intake was the only factor significantly associated with the onset of AT/AF (P < 0.05). Thus, salt intake may trigger AT/AF in ways other than via hypertension.
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Rafaqat S, Rafaqat S, Khurshid H, Rafaqat S. Electrolyte’s imbalance role in atrial fibrillation: Pharmacological management. INTERNATIONAL JOURNAL OF ARRHYTHMIA 2022. [DOI: 10.1186/s42444-022-00065-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
AbstractThe contribution of the perpetuation of atrial fibrillation is caused by electrical remodeling in which calcium, sodium and potassium channels could refer to changes in the ion channel protein expression, development of fibrosis, gene transcription and ion channel redistribution. Calcium and magnesium could influence the risk of atrial fibrillation which is the leading cause of cardiac death, heart failure and ischemic stroke. The elevated serum concentration of calcium had a higher range of in-patient’s mortality, increased total cost of hospitalization and increased length of hospital stay as compared to those without hypercalcemia in atrial fibrillation patients. Moreover, chloride channels could affect homeostasis, atrial myocardial metabolism which may participate in the development of atrial fibrillation. Up to a 50% risk of incidence of AF are higher in which left ventricular hypertrophy, sudden cardiovascular death and overall mortality relate to a low serum magnesium level. Additionally, magnesium prevents the occurrence of AF after cardiac surgery, whereas greater levels of serum phosphorus in the large population-based study and the related calcium–phosphorus products were linked with a greater incidence of AF. Numerous clinical studies had shown the high preoperative risk of AF that is linked with lower serum potassium levels. The conventional risk factor of increased risk of new onset of AF events could independently link with high dietary sodium intake which enhances the fibrosis and inflammation in the atrium but the mechanism remains unknown. Many drugs were used to maintain the electrolyte imbalance in AF patients.
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Cervantes DO, Pizzo E, Ketkar H, Parambath SP, Tang S, Cianflone E, Cannata A, Vinukonda G, Jain S, Jacobson JT, Rota M. Scn1b expression in the adult mouse heart modulates Na + influx in myocytes and reveals a mechanistic link between Na + entry and diastolic function. Am J Physiol Heart Circ Physiol 2022; 322:H975-H993. [PMID: 35394857 PMCID: PMC9076421 DOI: 10.1152/ajpheart.00465.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 03/09/2022] [Accepted: 03/23/2022] [Indexed: 11/22/2022]
Abstract
Voltage-gated sodium channels (VGSCs) are macromolecular assemblies composed of a number of proteins regulating channel conductance and properties. VGSCs generate Na+ current (INa) in myocytes and play fundamental roles in excitability and impulse conduction in the heart. Moreover, VGSCs condition mechanical properties of the myocardium, a process that appears to involve the late component of INa. Variants in the gene SCN1B, encoding the VGSC β1- and β1B-subunits, result in inherited neurological disorders and cardiac arrhythmias. But the precise contributions of β1/β1B-subunits and VGSC integrity to the overall function of the adult heart remain to be clarified. For this purpose, adult mice with cardiac-restricted, inducible deletion of Scn1b (conditional knockout, cKO) were studied. Myocytes from cKO mice had increased densities of fast (+20%)- and slow (+140%)-inactivating components of INa, with respect to control cells. By echocardiography and invasive hemodynamics, systolic function was preserved in cKO mice, but diastolic properties and ventricular compliance were compromised, with respect to control animals. Importantly, inhibition of late INa with GS967 normalized left ventricular filling pattern and isovolumic relaxation time in cKO mice. At the cellular level, cKO myocytes presented delayed kinetics of Ca2+ transients and cell mechanics, defects that were corrected by inhibition of INa. Collectively, these results document that VGSC β1/β1B-subunits modulate electrical and mechanical function of the heart by regulating, at least in part, Na+ influx in cardiomyocytes.NEW & NOTEWORTHY We have investigated the consequences of deletion of Scn1b, the gene encoding voltage-gated sodium channel β1-subunits, on myocyte and cardiac function. Our findings support the notion that Scn1b expression controls properties of Na+ influx and Ca2+ cycling in cardiomyocytes affecting the modality of cell contraction and relaxation. These effects at the cellular level condition electrical recovery and diastolic function in vivo, substantiating the multifunctional role of β1-subunits in the physiology of the heart.
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Affiliation(s)
| | - Emanuele Pizzo
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Harshada Ketkar
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, New York
| | - Sreema P Parambath
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, New York
| | - Samantha Tang
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, New York
| | - Eleonora Cianflone
- Department of Physiology, New York Medical College, Valhalla, New York
- Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy
| | - Antonio Cannata
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | | | - Sudhir Jain
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, New York
| | - Jason T Jacobson
- Department of Physiology, New York Medical College, Valhalla, New York
- Department of Cardiology, Westchester Medical Center, Valhalla, New York
| | - Marcello Rota
- Department of Physiology, New York Medical College, Valhalla, New York
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Catheter ablation of frequent monomorphic ventricular arrhythmias in Andersen-Tawil syndrome: case report and focused literature review. J Interv Card Electrophysiol 2021; 66:729-736. [PMID: 34665385 DOI: 10.1007/s10840-021-01077-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 10/10/2021] [Indexed: 10/20/2022]
Abstract
BACKGROUND/PURPOSE Andersen-Tawil syndrome type 1 is a rare autosomal dominant disease caused by a KCNJ2 gene mutation and clinically characterized by dysmorphic features, periodic muscular paralysis, and frequent ventricular arrhythmias (VAs). Although polymorphic and bidirectional ventricular tachycardias are prevalent, PVCs are the most frequent VAs. In addition, a "dominant" morphology with RBBB pattern associated with either superior or inferior axis is seen in most of the patients. Due to the limited efficacy of most antiarrhythmic drugs, catheter ablation (CA) is an alternative in patients with monomorphic VAs. Based on our experience, we aimed to review the arrhythmogenic mechanisms and substrates for VAs, and we analyzed the potential reasons for CA failure in this group of patients. METHODS Case report and focused literature review. RESULTS Catheter ablation has been reported to be unsuccessful in all of the few cases published so far. Most of the information suggests that VAs are mainly originated from the left ventricle and probably in the Purkinje network. Although identifying well-established and accepted mapping criteria for successful ablation of a monomorphic ventricular arrhythmia, papillary muscles seem not to be the right target. CONCLUSIONS More research is needed to understand better the precise mechanism and site of origin of VAs in Andersen-Tawil syndrome patients with this particular "dominant" monomorphic ventricular pattern to establish the potential role of CA.
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Wang XC, Jia QZ, Yu YL, Wang HD, Guo HC, Ma XD, Liu CT, Chen XY, Miao QF, Guan BC, Su SW, Wei HM, Wang C. Inhibition of the I Na/K and the activation of peak I Na contribute to the arrhythmogenic effects of aconitine and mesaconitine in guinea pigs. Acta Pharmacol Sin 2021; 42:218-229. [PMID: 32747718 DOI: 10.1038/s41401-020-0467-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Accepted: 06/23/2020] [Indexed: 12/22/2022] Open
Abstract
Aconitine (ACO), a main active ingredient of Aconitum, is well-known for its cardiotoxicity. However, the mechanisms of toxic action of ACO remain unclear. In the current study, we investigated the cardiac effects of ACO and mesaconitine (MACO), a structurally related analog of ACO identified in Aconitum with undocumented cardiotoxicity in guinea pigs. We showed that intravenous administration of ACO or MACO (25 μg/kg) to guinea pigs caused various types of arrhythmias in electrocardiogram (ECG) recording, including ventricular premature beats (VPB), atrioventricular blockade (AVB), ventricular tachycardia (VT), and ventricular fibrillation (VF). MACO displayed more potent arrhythmogenic effect than ACO. We conducted whole-cell patch-clamp recording in isolated guinea pig ventricular myocytes, and observed that treatment with ACO (0.3, 3 μM) or MACO (0.1, 0.3 μM) depolarized the resting membrane potential (RMP) and reduced the action potential amplitude (APA) and durations (APDs) in a concentration-dependent manner. The ACO- and MACO-induced AP remodeling was largely abolished by an INa blocker tetrodotoxin (2 μM) and partly abolished by a specific Na+/K+ pump (NKP) blocker ouabain (0.1 μM). Furthermore, we observed that treatment with ACO or MACO attenuated NKP current (INa/K) and increased peak INa by accelerating the sodium channel activation with the EC50 of 8.36 ± 1.89 and 1.33 ± 0.16 μM, respectively. Incubation of ventricular myocytes with ACO or MACO concentration-dependently increased intracellular Na+ and Ca2+ concentrations. In conclusion, the current study demonstrates strong arrhythmogenic effects of ACO and MACO resulted from increasing the peak INa via accelerating sodium channel activation and inhibiting the INa/K. These results may help to improve our understanding of cardiotoxic mechanisms of ACO and MACO, and identify potential novel therapeutic targets for Aconitum poisoning.
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Nembo EN, Hescheler J, Nguemo F. Stem cells in natural product and medicinal plant drug discovery-An overview of new screening approaches. Biomed Pharmacother 2020; 131:110730. [PMID: 32920519 DOI: 10.1016/j.biopha.2020.110730] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 09/03/2020] [Accepted: 09/04/2020] [Indexed: 01/14/2023] Open
Abstract
Natural products remain a rich source of new drugs, and the search for bioactive molecules from nature continues to play an important role in the development of new medicines. Also, there is increasing use of herbal medicines for the treatment of a plethora of diseases, and demands for more scientific evidence for their efficacy and safety remains a huge challenge. The propensity of stem cells to differentiate into almost every cell type not only holds promise for the delivery of cell-based therapies for currently incurable diseases or a useful tool in studying cell physiology and pathophysiology. Increasingly, stem cells are becoming an important tool in preclinical drug screening and toxicity testing. In this review, we examine the scientific advances made towards the use of pluripotent stem cells as a model for the screening of plant-based medicines. The combination of well-established in vitro electrophysiological and a plethora of toxicogenomic technologies, together with the optimisation of culture methods of herbal plants and pluripotent stem cells can be explored to establish the basis for efficacy, and tissue/organ-based toxicities of many currently used medicinal plants whose efficacies and toxicities remain unknown.
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Affiliation(s)
- Erastus Nembu Nembo
- Institute of Neurophysiology, University of Cologne, 50931, Cologne, Germany
| | - Jürgen Hescheler
- Institute of Neurophysiology, University of Cologne, 50931, Cologne, Germany
| | - Filomain Nguemo
- Institute of Neurophysiology, University of Cologne, 50931, Cologne, Germany.
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Dilaveris P, Antoniou CK, Manolakou P, Tsiamis E, Gatzoulis K, Tousoulis D. Biomarkers Associated with Atrial Fibrosis and Remodeling. Curr Med Chem 2019; 26:780-802. [PMID: 28925871 DOI: 10.2174/0929867324666170918122502] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 12/16/2016] [Accepted: 12/23/2016] [Indexed: 12/22/2022]
Abstract
Atrial fibrillation is the most common rhythm disturbance encountered in clinical practice. Although often considered as solely arrhythmic in nature, current evidence has established that atrial myopathy constitutes both the substrate and the outcome of atrial fibrillation, thus initiating a vicious, self-perpetuating cycle. This myopathy is triggered by stress-induced (including pressure/volume overload, inflammation, oxidative stress) responses of atrial tissue, which in the long term become maladaptive, and combine elements of both structural, especially fibrosis, and electrical remodeling, with contemporary approaches yielding potentially useful biomarkers of these processes. Biomarker value becomes greater given the fact that they can both predict atrial fibrillation occurrence and treatment outcome. This mini-review will focus on the biomarkers of atrial remodeling (both electrical and structural) and fibrosis that have been validated in human studies, including biochemical, histological and imaging approaches.
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Affiliation(s)
- Polychronis Dilaveris
- First Department of Cardiology, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
| | | | - Panagiota Manolakou
- First Department of Cardiology, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
| | - Eleftherios Tsiamis
- First Department of Cardiology, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
| | - Konstantinos Gatzoulis
- First Department of Cardiology, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
| | - Dimitris Tousoulis
- First Department of Cardiology, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
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Wei W, Peng J, Shen T. Rosuvastatin Alleviates Ischemia/Reperfusion Injury in Cardiomyocytes by Downregulating Hsa-miR-24-3p to Target Upregulated Uncoupling Protein 2. Cell Reprogram 2019; 21:99-107. [PMID: 30835496 DOI: 10.1089/cell.2018.0039] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Statins could reduce the risks of coronary heart disease death and ischemic cardiovascular events. In this study, we aim to explore the role of rosuvastatin in ischemia/reperfusion (I/R)-injured cardiomyocytes and the possible mechanism. An I/R model was established by oxygen-glucose deprivation/reperfusion (OGD/R). The protective effects of rosuvastatin pretreatment on OGD/R-injured cardiomyocytes were performed using MTT assay, lactate dehydrogenase (LDH) release assay, and quantitative real-time polymerase chain reaction (qRT-PCR). Bioinformatics software TargetScan and miRTarBase were used to predict the targeted miRNAs with uncoupling protein (UCP)2. Furthermore, verify the binding capacity of hsa-miR-24-3p and UCP2 with qRT-PCR and dual-luciferase reporter assay. The expression of UCP2, cell viability, LDH level, and apoptosis level affected by downregulated hsa-miR-24-3p were assessed using qRT-PCR, western blotting, MTT, the LDH kit, and flow cytometry. Pretreatment with rosuvastatin could significantly augment cell viability, reduce LDH level, increase the expression of UCP2, and downregulate hsa-miR-24-3p in OGD/R-injured H9c2 cells. miR-24-3p was closely connected with UCP2, and downregulated miR-24-3p could promote UCP2 expression, which presented cell viability increasing, LDH release and cell apoptosis inhibition in OGD/R condition. Moreover, it decreased the protein expression of Cleaved-Caspase-9 and Cyto C. This is the first time our study suggests that rosuvastatin pretreatment protects cardiomyocytes from OGD/R through upregulating UCP2 through downregulation of hsa-miR-24-3p.
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Affiliation(s)
- Wenjuan Wei
- 1 Department of Cardiovascular Medicine, The First People's Hospital of Xiaoshan Hangzhou, Hangzhou, China
| | - Jun Peng
- 1 Department of Cardiovascular Medicine, The First People's Hospital of Xiaoshan Hangzhou, Hangzhou, China
| | - Ting Shen
- 2 Electrocardiogram Room of Department of Functional Examination, Zhejiang Province Tongde Hospital, Hangzhou, China
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Mora MT, Ferrero JM, Romero L, Trenor B. Sensitivity analysis revealing the effect of modulating ionic mechanisms on calcium dynamics in simulated human heart failure. PLoS One 2017; 12:e0187739. [PMID: 29117223 PMCID: PMC5678731 DOI: 10.1371/journal.pone.0187739] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 10/25/2017] [Indexed: 12/27/2022] Open
Abstract
Abnormal intracellular Ca2+ handling is the major contributor to the depressed cardiac contractility observed in heart failure. The electrophysiological remodeling associated with this pathology alters both the action potential and the Ca2+ dynamics, leading to a defective excitation-contraction coupling that ends in mechanical dysfunction. The importance of maintaining a correct intracellular Ca2+ concentration requires a better understanding of its regulation by ionic mechanisms. To study the electrical activity and ionic homeostasis of failing myocytes, a modified version of the O’Hara et al. human action potential model was used, including electrophysiological remodeling. The impact of the main ionic transport mechanisms was analyzed using single-parameter sensitivity analyses, the first of which explored the modulation of electrophysiological characteristics related to Ca2+ exerted by the remodeled parameters. The second sensitivity analysis compared the potential consequences of modulating individual channel conductivities, as one of the main effects of potential drugs, on Ca2+ dynamic properties under both normal conditions and in heart failure. The first analysis revealed the important contribution of the sarcoplasmic reticulum Ca2+-ATPase (SERCA) dysfunction to the altered Ca2+ homeostasis, with the Na+/Ca2+ exchanger (NCX) and other Ca2+ cycling proteins also playing a significant role. Our results highlight the importance of improving the SR uptake function to increase Ca2+ content and restore Ca2+ homeostasis and contractility. The second sensitivity analysis highlights the different response of the failing myocyte versus the healthy myocyte to potential pharmacological actions on single channels. The result of modifying the conductances of the remodeled proteins such as SERCA and NCX in heart failure has less impact on Ca2+ modulation. These differences should be taken into account when designing drug therapies.
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Affiliation(s)
- Maria T. Mora
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
| | - Jose M. Ferrero
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
| | - Lucia Romero
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
| | - Beatriz Trenor
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
- * E-mail:
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14
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Ton AT, Biet M, Delabre JF, Morin N, Dumaine R. In-utero exposure to nicotine alters the development of the rabbit cardiac conduction system and provides a potential mechanism for sudden infant death syndrome. Arch Toxicol 2017; 91:3947-3960. [PMID: 28593499 DOI: 10.1007/s00204-017-2006-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 06/01/2017] [Indexed: 01/06/2023]
Abstract
In-utero exposure to tobacco smoke remains the highest risk factor for sudden infant death syndrome (SIDS). To alleviate the risks, nicotine replacement therapies are often prescribed to women who wish to quit smoking during their pregnancy. Cardiac arrhythmias is considered the final outcome leading to sudden death. Our goal in this study was to determine if exposing rabbit fetus to nicotine altered the cardiac conduction system of newborn kittens in a manner susceptible to cause SIDS. Using neuronal markers and a series of immunohistological and electrophysiological techniques we found that nicotine delayed the development of the cardiac pacemaker center (sinoatrial node) and decreased its innervation. At the molecular level, nicotine favored the expression of cardiac sodium channels with biophysical properties that will tend to slow heart rate and diminish electrical conduction. Our results show that alterations of the cardiac sodium current may contribute to the bradycardia, conduction disturbances and other cardiac arrhythmias often associated to SIDS and raise awareness on the use of replacement therapy during pregnancy.
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Affiliation(s)
- Anh Tuan Ton
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
- Montreal Heart Institute, University of Montreal, Montréal, QC, Canada
| | - Michael Biet
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
| | - Jean-Francois Delabre
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
| | - Nathalie Morin
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
| | - Robert Dumaine
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada.
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Wang C, Wang LL, Zhang C, Cao ZZ, Luo AT, Zhang PH, Fan XR, Ma JH. Tolterodine reduces veratridine-augmented late I Na, reverse-I NCX and early afterdepolarizations in isolated rabbit ventricular myocytes. Acta Pharmacol Sin 2016; 37:1432-1441. [PMID: 27569391 DOI: 10.1038/aps.2016.76] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/12/2016] [Indexed: 12/19/2022] Open
Abstract
AIM The augmentation of late sodium current (INa.L) not only causes intracellular Na+ accumulation, which results in intracellular Ca2+ overload via the reverse mode of the Na+/Ca2+ exchange current (reverse-INCX), but also prolongs APD and induces early afterdepolarizations (EAD), which can lead to arrhythmia and cardiac dysfunction. Thus, the inhibition of INa.L is considered to be a potential way for therapeutic intervention in ischemia and heart failure. In this study we investigated the effects of tolterodine (Tol), a competitive muscarinic receptor antagonist, on normal and veratridine (Ver)-augmented INa.L, reverse-INCX and APD in isolated rabbit ventricular myocytes, which might contribute to its cardioprotective activity. METHODS Rabbit ventricular myocytes were prepared. The INa.L and reverse-INCX were recorded in voltage clamp mode, whereas action potentials and Ver-induced early afterdepolarizations (EADs) were recorded in current clamp mode. Drugs were applied via superfusion. RESULTS Tol (3-120 nmol/L) concentration-dependently inhibited the normal and Ver-augmented INa.L with IC50 values of 32.08 nmol/L and 42.47 nmol/L, respectively. Atropine (100 μmol/L) did not affect the inhibitory effects of Tol (30 nmol/L) on Ver-augmented INa.L. In contrast, much high concentrations of Tol was needed to inhibit the transient sodium current (INa.T) with an IC50 value of 183.03 μmol/L. In addition, Tol (30 nmol/L) significantly shifted the inactivation curve of INa.T toward a more depolarizing membrane potential without affecting its activation characteristics. Moreover, Tol (30 nmol/L) significantly decreased Ver-augmented reverse-INCX. Tol (30 nmol/L) increased the action potential duration (APD) by 16% under the basal conditions. Ver (20 μmol/L) considerably extended the APD and evoked EADs in 18/24 cells (75%). In the presence of Ver, Tol (30 nmol/L) markedly decreased the APD and eliminated EADs (0/24 cells). CONCLUSION Tol inhibits normal and Ver-augmented INaL and decreases Ver-augmented reverse-INCX. In addition, Tol reverses the prolongation of the APD and eliminates the EADs induced by Ver, thus prevents Ver-induced arrhythmia.
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16
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Altamirano F, Wang ZV, Hill JA. Cardioprotection in ischaemia-reperfusion injury: novel mechanisms and clinical translation. J Physiol 2015; 593:3773-88. [PMID: 26173176 PMCID: PMC4575567 DOI: 10.1113/jp270953] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Accepted: 06/23/2015] [Indexed: 12/29/2022] Open
Abstract
In recent decades, robust successes have been achieved in conquering the acutely lethal manifestations of heart disease. Nevertheless, the prevalence of heart disease, especially heart failure, continues to rise. Among the precipitating aetiologies, ischaemic disease is a leading cause of heart failure. In the context of ischaemia, the myocardium is deprived of oxygen and nutrients, which elicits a cascade of events that provokes cell death. This ischaemic insult is typically coupled with reperfusion, either spontaneous or therapeutically imposed, wherein blood supply is restored to the previously ischaemic tissue. While this intervention limits ischaemic injury, it triggers a new cascade of events that is also harmful, viz. reperfusion injury. In recent years, novel insights have emerged regarding mechanisms of ischaemia-reperfusion injury, and some hold promise as targets of therapeutic relevance. Here, we review a select number of these pathways, focusing on recent discoveries and highlighting prospects for therapeutic manipulation for clinical benefit.
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Affiliation(s)
- Francisco Altamirano
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical CenterDallas, TX, 75390, USA
| | - Zhao V Wang
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical CenterDallas, TX, 75390, USA
| | - Joseph A Hill
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical CenterDallas, TX, 75390, USA
- Department of Molecular Biology, University of Texas Southwestern Medical CenterDallas, TX, 75390, USA
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17
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Li W, Wang X, He M, Wang C, Qiao Z, Wang Q, Ren S, Yu Q. Activating Na+-K+ ATPase: a potential cardioprotective therapy during early hemorrhagic shock. Med Hypotheses 2014; 83:685-7. [PMID: 25459134 DOI: 10.1016/j.mehy.2014.09.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 09/22/2014] [Indexed: 11/16/2022]
Abstract
Cell volume and resting potential are heavily affected by the activity of Na+-K+ ATPase (NKA, Na+-K+ pump), an essential membrane protein that regulates plasma K+ and Na+ levels. It is generally accepted that the ineffective perfusion of body tissues inhibits NKA activity and that NKA activity and heart failure are closely related. Recently, research has proven that the activation of NKA provides significant cardioprotection against ischemic injury. Based on these data, we propose that NKA stimulation could attenuate the development of heart arrhythmia during the early phase of hemorrhagic shock.
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Affiliation(s)
- Weijing Li
- Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Xuanlin Wang
- Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Min He
- Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Chunyan Wang
- Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Zhixin Qiao
- Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Qingjun Wang
- Shenzhou Biology & Technology Co., Ltd., Hohhot, Inner Mongolia 010206, China
| | - Suping Ren
- Beijing Institute of Transfusion Medicine, Beijing 100850, China.
| | - Qun Yu
- Beijing Institute of Transfusion Medicine, Beijing 100850, China.
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18
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Mijares A, Altamirano F, Kolster J, Adams JA, López JR. Age-dependent changes in diastolic Ca(2+) and Na(+) concentrations in dystrophic cardiomyopathy: Role of Ca(2+) entry and IP3. Biochem Biophys Res Commun 2014; 452:1054-9. [PMID: 25242522 DOI: 10.1016/j.bbrc.2014.09.045] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 09/11/2014] [Indexed: 01/01/2023]
Abstract
Duchenne muscular dystrophy (DMD) is a lethal X-inherited disease caused by dystrophin deficiency. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with a dilated cardiomyopathy that leads to progressive heart failure at the end of the second decade. The aim of the present study was to characterize the diastolic Ca(2+) concentration ([Ca(2+)]d) and diastolic Na(+) concentration ([Na(+)]d) abnormalities in cardiomyocytes isolated from 3-, 6-, 9-, and 12-month old mdx mice using ion-selective microelectrodes. In addition, the contributions of gadolinium (Gd(3+))-sensitive Ca(2+) entry and inositol triphosphate (IP3) signaling pathways in abnormal [Ca(2+)]d and [Na(+)]d were investigated. Our results showed an age-dependent increase in both [Ca(2+)]d and [Na(+)]d in dystrophic cardiomyocytes compared to those isolated from age-matched wt mice. Gd(3+) treatment significantly reduced both [Ca(2+)]d and [Na(+)]d at all ages. In addition, blockade of the IP3-pathway with either U-73122 or xestospongin C significantly reduced ion concentrations in dystrophic cardiomyocytes. Co-treatment with U-73122 and Gd(3+) normalized both [Ca(2+)]d and [Na(+)]d at all ages in dystrophic cardiomyocytes. These data showed that loss of dystrophin in mdx cardiomyocytes produced an age-dependent intracellular Ca(2+) and Na(+) overload mediated at least in part by enhanced Ca(2+) entry through Gd(3+) sensitive transient receptor potential channels (TRPC), and by IP3 receptors.
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Affiliation(s)
- Alfredo Mijares
- Instituto Venezolano de Investigaciones Científicas, Centro de Biofísica y Bioquímica, Caracas, Venezuela
| | - Francisco Altamirano
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
| | - Juan Kolster
- Centro de Investigaciones Biomédicas, México D.F., Mexico
| | - José A Adams
- Division of Neonatology, Mount Sinai Medical Center, Miami, FL 33140, USA
| | - José R López
- Instituto Venezolano de Investigaciones Científicas, Centro de Biofísica y Bioquímica, Caracas, Venezuela; Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
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Suzuki K, Matsumoto A, Nishida H, Reien Y, Maruyama H, Nakaya H. Termination of Aconitine-Induced Atrial Fibrillation by the KACh-Channel Blocker Tertiapin: Underlying Electrophysiological Mechanism. J Pharmacol Sci 2014; 125:406-14. [DOI: 10.1254/jphs.14023fp] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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20
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Shryock JC, Song Y, Rajamani S, Antzelevitch C, Belardinelli L. The arrhythmogenic consequences of increasing late INa in the cardiomyocyte. Cardiovasc Res 2013; 99:600-11. [PMID: 23752976 DOI: 10.1093/cvr/cvt145] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This review presents the roles of cardiac sodium channel NaV1.5 late current (late INa) in generation of arrhythmic activity. The assumption of the authors is that proper Na(+) channel function is necessary to the maintenance of the transmembrane electrochemical gradient of Na(+) and regulation of cardiac electrical activity. Myocyte Na(+) channels' openings during the brief action potential upstroke contribute to peak INa and initiate excitation-contraction coupling. Openings of Na(+) channels outside the upstroke contribute to late INa, a depolarizing current that persists throughout the action potential plateau. The small, physiological late INa does not appear to be critical for normal electrical or contractile function in the heart. Late INa does, however, reduce the net repolarizing current, prolongs action potential duration, and increases cellular Na(+) loading. An increase of late INa, due to acquired conditions (e.g. heart failure) or inherited Na(+) channelopathies, facilitates the formation of early and delayed afterpolarizations and triggered arrhythmias, spontaneous diastolic depolarization, and cellular Ca(2+) loading. These in turn increase the spatial and temporal dispersion of repolarization time and may lead to reentrant arrhythmias.
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Affiliation(s)
- John C Shryock
- Department of Biology, Cardiovascular Therapeutic Area, Gilead Sciences, Foster City, CA, USA
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21
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Sophocarpine Attenuates the Na+-dependent Ca2+ Overload Induced by Anemonia Sulcata Toxin—Increased Late Sodium Current in Rabbit Ventricular Myocytes. J Cardiovasc Pharmacol 2012; 60:357-66. [DOI: 10.1097/fjc.0b013e318262c932] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Trenor B, Cardona K, Gomez JF, Rajamani S, Ferrero JM, Belardinelli L, Saiz J. Simulation and mechanistic investigation of the arrhythmogenic role of the late sodium current in human heart failure. PLoS One 2012; 7:e32659. [PMID: 22427860 PMCID: PMC3299678 DOI: 10.1371/journal.pone.0032659] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 02/02/2012] [Indexed: 11/18/2022] Open
Abstract
Heart failure constitutes a major public health problem worldwide. The electrophysiological remodeling of failing hearts sets the stage for malignant arrhythmias, in which the role of the late Na+ current (INaL) is relevant and is currently under investigation. In this study we examined the role of INaL in the electrophysiological phenotype of ventricular myocytes, and its proarrhythmic effects in the failing heart. A model for cellular heart failure was proposed using a modified version of Grandi et al. model for human ventricular action potential that incorporates the formulation of INaL. A sensitivity analysis of the model was performed and simulations of the pathological electrical activity of the cell were conducted. The proposed model for the human INaL and the electrophysiological remodeling of myocytes from failing hearts accurately reproduce experimental observations. The sensitivity analysis of the modulation of electrophysiological parameters of myocytes from failing hearts due to ion channels remodeling, revealed a role for INaL in the prolongation of action potential duration (APD), triangulation of the shape of the AP, and changes in Ca2+ transient. A mechanistic investigation of intracellular Na+ accumulation and APD shortening with increasing frequency of stimulation of failing myocytes revealed a role for the Na+/K+ pump, the Na+/Ca2+ exchanger and INaL. The results of the simulations also showed that in failing myocytes, the enhancement of INaL increased the reverse rate-dependent APD prolongation and the probability of initiating early afterdepolarizations. The electrophysiological remodeling of failing hearts and especially the enhancement of the INaL prolong APD and alter Ca2+ transient facilitating the development of early afterdepolarizations. An enhanced INaL appears to be an important contributor to the electrophysiological phenotype and to the dysregulation of [Ca2+]i homeostasis of failing myocytes.
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Affiliation(s)
- Beatriz Trenor
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano, Universitat Politècnica de València, Valencia, Spain.
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23
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Bilirubin Attenuates Bufadienolide-Induced Ventricular Arrhythmias and Cardiac Dysfunction in Guinea-Pigs by Reducing Elevated Intracellular Na+ Levels. Cardiovasc Toxicol 2011; 12:83-9. [DOI: 10.1007/s12012-011-9142-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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24
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Carro J, Rodríguez JF, Laguna P, Pueyo E. A human ventricular cell model for investigation of cardiac arrhythmias under hyperkalaemic conditions. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:4205-32. [PMID: 21969673 DOI: 10.1098/rsta.2011.0127] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In this study, several modifications were introduced to a recently proposed human ventricular action potential (AP) model so as to render it suitable for the study of ventricular arrhythmias. These modifications were driven by new sets of experimental data available from the literature and the analysis of several well-established cellular arrhythmic risk biomarkers, namely AP duration at 90 per cent repolarization (APD(90)), AP triangulation, calcium dynamics, restitution properties, APD(90) adaptation to abrupt heart rate changes, and rate dependence of intracellular sodium and calcium concentrations. The proposed methodology represents a novel framework for the development of cardiac cell models. Five stimulation protocols were applied to the original model and the ventricular AP model developed here to compute the described arrhythmic risk biomarkers. In addition, those models were tested in a one-dimensional fibre in which hyperkalaemia was simulated by increasing the extracellular potassium concentration, [K(+)](o). The effective refractory period (ERP), conduction velocity (CV) and the occurrence of APD alternans were investigated. Results show that modifications improved model behaviour as verified by: (i) AP triangulation well within experimental limits (the difference between APD at 50 and 90 per cent repolarization being 78.1 ms); (ii) APD(90) rate adaptation dynamics characterized by fast and slow time constants within physiological ranges (10.1 and 105.9 s); and (iii) maximum S1S2 restitution slope in accordance with experimental data (S(S1S2)=1.0). In simulated tissues under hyperkalaemic conditions, APD(90) progressively shortened with the degree of hyperkalaemia, whereas ERP increased once a threshold in [K(+)](o) was reached ([K(+)](o)≈6 mM). CV decreased with [K(+)](o), and conduction was blocked for [K(+)](o)>10.4 mM. APD(90) alternans were observed for [K(+)](o)>9.8 mM. Those results adequately reproduce experimental observations. This study demonstrated the value of basing the development of AP models on the computation of arrhythmic risk biomarkers, as opposed to joining together independently derived ion channel descriptions to produce a whole-cell AP model, with the new framework providing a better picture of the model performance under a variety of stimulation conditions. On top of replicating experimental data at single-cell level, the model developed here was able to predict the occurrence of APD(90) alternans and areas of conduction block associated with high [K(+)](o) in tissue, which is of relevance for the investigation of the arrhythmogenic substrate in ischaemic hearts.
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Affiliation(s)
- Jesús Carro
- Aragón Institute of Engineering Research (I3A), IIS Aragón, Universidad de Zaragoza, Spain
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Abstract
Proline-rich tyrosine kinase 2 (Pyk2) is a nonreceptor protein kinase regulated by intracellular Ca2+, CaMK, and PKC and can be activated by different stress signals involved in heart failure. However, Pyk2 has not been investigated in the human heart, and the functional role of Pyk2 signaling at the whole heart level has not been elucidated. We hypothesize that Ca2+-dependent activation of Pyk2 is involved in cardiac electrophysiology. We examined the expression of Pyk2 in nonfailing versus ischemic and nonischemic failing human hearts ( n = 6 hearts/group). To investigate Pyk2 function, we optically mapped perfused hearts from wild-type (WT; n = 7) and knockout (Pyk2−/−; n = 8) mice during autonomic stimulation. Experiments were done in control mice and after 1 wk of transverse aortic constriction. We used the Illumina beadarray approach for transcriptional profiling of WT and Pyk2−/− mouse ventricles. Western blot analysis revealed a doubling of Pyk2 activation in nonischemic failing versus nonfailing human hearts. In mouse hearts, we observed a much higher probability of ventricular tachyarrhythmia during ACh perfusion in Pyk2−/− versus WT mice. Parasympathetic stimulation resulted in a dose-dependent decrease of atrial action potential duration (APD) in both WT and Pyk2−/− mice, whereas in ventricles it induced APD shortening in Pyk2−/− mice but not in WT mice. Deficiency of Pyk2 abolished ACh-induced prolongation of atrioventricular delay in Pyk2−/− mouse hearts but did not affect heart rate. Lower mRNA and protein levels of sarco(endo)plasmic reticulum Ca2+-ATPase 2 and higher mRNA levels of Na+/Ca2+ exchanger 1 were detected in Pyk2−/− hearts compared with WT hearts. The transverse aortic constriction protocol did not change the phenotype. In conclusion, our results indicate a protective role of Pyk2 with respect to ventricular tachyarrhythmia during parasympathetic stimulation by regulation of gene expression related to Ca2+ handling. We hypothesize that activation of Pyk2 in the human heart during heart failure may contribute to protection against arrhythmia.
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Affiliation(s)
- Di Lang
- Department of Biomedical Engineering, Washington University, St. Louis, Missouri; and
| | - Alexey V. Glukhov
- Department of Biomedical Engineering, Washington University, St. Louis, Missouri; and
| | - Tatiana Efimova
- Division of Dermatology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Igor R. Efimov
- Department of Biomedical Engineering, Washington University, St. Louis, Missouri; and
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Thireau J, Pasquié JL, Martel E, Le Guennec JY, Richard S. New drugs vs. old concepts: a fresh look at antiarrhythmics. Pharmacol Ther 2011; 132:125-45. [PMID: 21420430 DOI: 10.1016/j.pharmthera.2011.03.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 03/01/2011] [Indexed: 01/10/2023]
Abstract
Common arrhythmias, particularly atrial fibrillation (AF) and ventricular tachycardia/fibrillation (VT/VF) are a major public health concern. Classic antiarrhythmic (AA) drugs for AF are of limited effectiveness, and pose the risk of life-threatening VT/VF. For VT/VF, implantable cardiac defibrillators appear to be the unique, yet unsatisfactory, solution. Very few AA drugs have been successful in the last few decades, due to safety concerns or limited benefits in comparison to existing therapy. The Vaughan-Williams classification (one drug for one molecular target) appears too restrictive in light of current knowledge of molecular and cellular mechanisms. New AA drugs such as atrial-specific and/or multichannel blockers, upstream therapy and anti-remodeling drugs, are emerging. We focus on the cellular mechanisms related to abnormal Na⁺ and Ca²⁺ handling in AF, heart failure, and inherited arrhythmias, and on novel strategies aimed at normalizing ionic homeostasis. Drugs that prevent excessive Na⁺ entry (ranolazine) and aberrant diastolic Ca²⁺ release via the ryanodine receptor RyR2 (rycals, dantrolene, and flecainide) exhibit very interesting antiarrhythmic properties. These drugs act by normalizing, rather than blocking, channel activity. Ranolazine preferentially blocks abnormal persistent (vs. normal peak) Na⁺ currents, with minimal effects on normal channel function (cell excitability, and conduction). A similar "normalization" concept also applies to RyR2 stabilizers, which only prevent aberrant opening and diastolic Ca²⁺ leakage in diseased tissues, with no effect on normal function during systole. The different mechanisms of action of AA drugs may increase the therapeutic options available for the safe treatment of arrhythmias in a wide variety of pathophysiological situations.
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Affiliation(s)
- Jérôme Thireau
- Inserm U1046 Physiologie & Médecine Expérimentale du Cœur et des Muscles, Université Montpellier-1, Université Montpellier-2, 34295 Montpellier Cedex 5, France
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27
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Fan X, Ma J, Wan W, Zhang P, Wang C, Wu L. Increased intracellular calcium concentration causes electrical turbulence in guinea pig ventricular myocytes. SCIENCE CHINA-LIFE SCIENCES 2011; 54:240-7. [PMID: 21416323 DOI: 10.1007/s11427-011-4146-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 12/21/2010] [Indexed: 01/25/2023]
Abstract
Dysregulation of intracellular Ca(2+) homeostasis is associated with various pathological conditions and arrhythmogenesis of the heart. The objective of this study was to investigate the effects of an acute increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) on the electrophysiology of ventricular myocytes by mimicking intracellular Ca(2+) overload. The [Ca(2+)](i) was clamped to either a controlled (65-100 nmol L(-1)) or increased (1 μmol L(-1)) level. The transmembrane action potentials and ionic currents were recorded using whole-cell patch clamp techniques. We found that the acute increase in [Ca(2+)](i) shortened the action potential duration, reduced the action potential amplitude, maximum depolarization velocity and resting membrane potential, caused delayed after-depolarizations (DADs), and triggered activity-compared with these parameters in the control. The increased [Ca(2+)](i) augmented late I (Na) in a time-dependent manner, reduced I (CaL) and I (K1), and increased I (Kr) but not I (Ks). The results of this study can be used to explain calcium overload-induced ventricular arrhythmias.
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Affiliation(s)
- Xinrong Fan
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan 430081, China
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Les effets pro-arythmiques des médicaments. ARCHIVES OF CARDIOVASCULAR DISEASES SUPPLEMENTS 2010. [DOI: 10.1016/s1878-6480(10)70373-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Gawarammana I, Mohamed F, Bowe SJ, Rathnathilake A, Narangoda SK, Azher S, Dawson AH, Buckley NA. Fructose-1, 6-diphosphate (FDP) as a novel antidote for yellow oleander-induced cardiac toxicity: a randomized controlled double blind study. BMC Emerg Med 2010; 10:15. [PMID: 20587052 PMCID: PMC2912827 DOI: 10.1186/1471-227x-10-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Accepted: 06/29/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cardiac toxicity due to ingestion of oleander plant seeds in Sri Lanka and some other South Asian countries is very common. At present symptomatic oleander seed poisoning carries a mortality of 10% in Sri Lanka and treatment of yellow oleander poisoning is limited to gastric decontamination and atropine administration. The only proven effective antidote is digoxin antibodies but these are not available for routine use because of the high cost. The main objective of this study is to investigate the effectiveness of a new and inexpensive antidote for patients with life threatening arrhythmias due oleander poisoning. METHOD/DESIGN We set up a randomised double blind clinical trial to assess the effectiveness of Fructose 1, 6 diphosphate (FDP) in acute yellow oleander poisoning patients admitted to the adult medical wards of a tertiary hospital in Sri Lanka. Patients will be initially resuscitated following the national guidelines and eligible patients will be randomised to receive either FDP or an equal amount of normal saline. The primary outcome measure for this study is the sustained reversion to sinus rhythm with a heart rate greater than 50/min within 2 hours of completion of FDP/placebo bolus. Secondary outcomes include death, reversal of hyperkalaemia on the 6, 12, 18 and 24 hour samples and maintenance of sinus rhythm on the holter monitor. Analysis will be on intention-to-treat. DISCUSSION This trial will provide information on the effectiveness of FDP in yellow oleander poisoning. If FDP is effective in cardiac glycoside toxicity, it would provide substantial benefit to the patients in rural Asia. The drug is inexpensive and thus could be made available at primary care hospitals if proven to be effective. TRIAL REGISTRATION Current Controlled trial ISRCTN71018309.
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Affiliation(s)
- Indika Gawarammana
- South Asian Clinical Toxicology Research Collaboration, Department of Clinical Medicine, University of Peradeniya, Sri Lanka
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Kir 2.1 channelopathies: the Andersen-Tawil syndrome. Pflugers Arch 2010; 460:289-94. [PMID: 20306271 DOI: 10.1007/s00424-010-0820-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 02/25/2010] [Accepted: 02/28/2010] [Indexed: 10/19/2022]
Abstract
As a multisystem disorder, Andersen-Tawil syndrome (ATS) is rather unique in the family of channelopathies. The full spectrum of the disease is characterized by ventricular arrhythmias, dysmorphic features, and periodic paralysis. Most ATS patients have a mutation in the ion channel gene, KCNJ2, which encodes the inward rectifier K+ channel Kir2.1, a component of the inward rectifier IK1.IK1 provides repolarizing current during the most terminal phase of repolarization and is the primary conductance controlling the diastolic membrane potential. Thus, ATS is a disorder of cardiac repolarization. The chapter will discuss the most recent data concerning the genetic, cellular, and clinical data underlying this unique disorder.
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HASDEMIR CAN, AYDIN HIKMETH, CELIK HANDANA, SIMSEK EVRIM, PAYZIN SERDAR, KAYIKCIOGLU MERAL, AYDIN MEHMET, KULTURSAY HAKAN, CAN LEVENTH. Transcriptional Profiling of Septal Wall of the Right Ventricular Outflow Tract in Patients with Idiopathic Ventricular Arrhythmias. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2010; 33:159-67. [DOI: 10.1111/j.1540-8159.2009.02606.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Romero L, Pueyo E, Fink M, Rodríguez B. Impact of ionic current variability on human ventricular cellular electrophysiology. Am J Physiol Heart Circ Physiol 2009; 297:H1436-45. [PMID: 19648254 DOI: 10.1152/ajpheart.00263.2009] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Abnormalities in repolarization and its rate dependence are known to be related to increased proarrhythmic risk. A number of repolarization-related electrophysiological properties are commonly used as preclinical biomarkers of arrhythmic risk. However, the variability and complexity of repolarization mechanisms make the use of cellular biomarkers to predict arrhythmic risk preclinically challenging. Our goal is to investigate the role of ionic current properties and their variability in modulating cellular biomarkers of arrhythmic risk to improve risk stratification and identification in humans. A systematic investigation into the sensitivity of the main preclinical biomarkers of arrhythmic risk to changes in ionic current conductances and kinetics was performed using computer simulations. Four stimulation protocols were applied to the ten Tusscher and Panfilov human ventricular model to quantify the impact of +/-15 and +/-30% variations in key model parameters on action potential (AP) properties, Ca(2+) and Na(+) dynamics, and their rate dependence. Simulations show that, in humans, AP duration is moderately sensitive to changes in all repolarization current conductances and in L-type Ca(2+) current (I(CaL)) and slow component of the delayed rectifier current (I(Ks)) inactivation kinetics. AP triangulation, however, is strongly dependent only on inward rectifier K(+) current (I(K1)) and delayed rectifier current (I(Kr)) conductances. Furthermore, AP rate dependence (i.e., AP duration rate adaptation and restitution properties) and intracellular Ca(2+) and Na(+) levels are highly sensitive to both I(CaL) and Na(+)/K(+) pump current (I(NaK)) properties. This study provides quantitative insights into the sensitivity of preclinical biomarkers of arrhythmic risk to variations in ionic current properties in humans. The results show the importance of sensitivity analysis as a powerful method for the in-depth validation of mathematical models in cardiac electrophysiology.
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Affiliation(s)
- Lucía Romero
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano, Universidad Politécnica de Valencia, Valencia, Spain.
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Zheng J, Ma J, Zhang P, Hu L, Fan X, Tang Q. Milrinone inhibits hypoxia or hydrogen dioxide-induced persistent sodium current in ventricular myocytes. Eur J Pharmacol 2009; 616:206-12. [PMID: 19549513 DOI: 10.1016/j.ejphar.2009.06.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Revised: 05/28/2009] [Accepted: 06/09/2009] [Indexed: 12/19/2022]
Abstract
Much evidence indicates that increased persistent sodium current (I(Na.P)) is associated with cellular calcium overload and I(Na.P) is considered to be a potential target for therapeutic intervention in ischaemia and heart failure. By inhibiting type III phosphodiesterase, milrinone increases intracellular cyclic adenosine monophosphate (cAMP), with a positive inotropic effect. However, the effect of milrinone on increased I(Na.P) under pathological conditions remains unknown. Accordingly, we investigated the effect of milrinone on increased I(Na.P) induced by hypoxia or hydrogen dioxide in guinea pig ventricular myocytes. While milrinone (0.01 mM or 0.1mM) or cAMP (0.1 mM) decreased I(Na.P) respectively in control condition, application of 1 microM H-89, a selective cAMP-dependant protein kinase inhibitor, prevented the effect of 0.1mM milrinone in control condition. Milrinone (0.1 mM) reduced the increased I(Na.P) induced by hypoxia. Furthermore, 0.01 mM or 0.1mM milrinone reduced the enhanced I(Na.P) induced by 0.3 mM hydrogen peroxide. In addition, 0.01 mM or 0.1 mM milrinone shortened action potential duration at 90% repolarization (APD(90)). Bath application of 0.3 mM hydrogen dioxide markedly prolonged APD(90), while 2 microM tetrodotoxin (TTX) reversed the prolonged APD(90). In the other two groups, 0.01 mM or 0.1 mM milrinone shortened the prolonged APD(90) induced by 0.3 mM hydrogen peroxide, ultimately 2 microM TTX causing a further decurtation of APD(90). These findings demonstrate that milrinone inhibited I(Na.P) under normal condition, hypoxia or hydrogen dioxide-induced I(Na.P), and the APD(90) prolonged by hydrogen dioxide-induced I(Na.P) in ventricular myocytes, which is associated with the mechanism of milrinone increasing intracellular cAMP.
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Affiliation(s)
- Jie Zheng
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan, Hubei, China
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Pasquié JL, Richard S. Prolongation in QT interval is not predictive of Ca2+-dependent arrhythmias: implications for drug safety. Expert Opin Drug Saf 2009; 8:57-72. [DOI: 10.1517/14740330802655454] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Alternative splicing of Nav1.5: An electrophysiological comparison of ‘neonatal’ and ‘adult’ isoforms and critical involvement of a lysine residue. J Cell Physiol 2008; 216:716-26. [DOI: 10.1002/jcp.21451] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Pathophysiology and pharmacology of the cardiac “late sodium current”. Pharmacol Ther 2008; 119:326-39. [DOI: 10.1016/j.pharmthera.2008.06.001] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2008] [Accepted: 06/04/2008] [Indexed: 12/19/2022]
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Incerpi S, Davis PJ, De Vito P, Farias RN, Lin HY, Davis FB. Nongenomic Actions of Thyroid Hormone and Intracellular Calcium Metabolism. Clin Rev Bone Miner Metab 2008. [DOI: 10.1007/s12018-008-9019-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Christé G, Chahine M, Chevalier P, Pásek M. Changes in action potentials and intracellular ionic homeostasis in a ventricular cell model related to a persistent sodium current in SCN5A mutations underlying LQT3. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2007; 96:281-93. [PMID: 17892895 DOI: 10.1016/j.pbiomolbio.2007.07.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
In LQT3 patients, SCN5A mutations induce ultraslow inactivation of a small fraction of the hNav1.5 current, i.e. persistent Na+ current (IpNa). We explored the time course of effects of such a change on the intracellular ionic homeostasis in a model of guinea-pig cardiac ventricular cell [Pasek, M., Simurda, J., Orchard, C.H., Christé, G., 2007b. A model of the guinea-pig ventricular cardiomyocyte incorporating a transverse-axial tubular system. Prog. Biophys. Mol. Biol., this issue]. Sudden addition of IpNa prevented action potential (AP) repolarization when its conductance (gpNa) exceeded 0.12% of the maximal conductance of fast INa (gNa). With gpNa at 0.1% gNa, the AP duration at 90% repolarization (APD90) was initially lengthened to 2.6-fold that in control. Under regular stimulation at 1 Hz it shortened progressively to 1.37-fold control APD90, and intracellular [Na+]i increased by 6% with a time constant of 106 s. Further increasing gpNa to 0.2% gNa caused an immediate increase in APD90 to 5.7-fold that in control, which decreased to 2.2-fold that in control in 30s stimulation at 1 Hz. At this time diastolic [Na+]i and [Ca2+]i were, respectively, 34% and 52% higher than in control and spontaneous erratic SR Ca release occurred. In the presence of IpNa causing 46% lengthening of APD90, the model cell displayed arrhythmogenic behaviour when external [K+] was lowered to 5 mM from an initial value at 5.4 mM. By contrast, when K+ currents IKr and IKs were lowered in the model cell to produce the same lengthening of APD90, no proarrhythmic behaviour was observed, even when external [K+] was lowered to 2.5 mM.
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Hashimoto N, Yamashita T, Fujikura N, Tsuruzoe N. NIP-141, a multiple ion channel blocker, terminates aconitine-induced atrial fibrillation and prevents the rapid pacing-induced atrial effective refractory period shortening in dogs. ACTA ACUST UNITED AC 2007; 9:246-51. [PMID: 17350982 DOI: 10.1093/europace/eum018] [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: 11/12/2022]
Abstract
AIMS NIP-141 is a novel multiple ion channel blocker with atrial selective effects. In this study, we examined the effects of NIP-141 on aconitine-induced atrial fibrillation (AF) and rapid atrial pacing-induced atrial effective refractory period (ERP) shortening in dogs. METHODS AND RESULTS Aconitine AF was induced by the application of aconitine on the right appendage. NIP-141 (10 mg/kg) converted AF to sinus rhythm in 5 of 6 dogs. The Na(+) channel blockers disopyramide (1 mg/kg) and phenytoin (10 mg/kg) also terminated AF, but the I(Kr) blocker (d-sotalol; 4 mg/kg) and a Ca(2+) channel blocker (verapamil; 0.3 mg/kg) did not terminate AF in this model. To clarify the mechanism of AF termination, we examined the effects on ERP and conduction time, but NIP-141 (10 mg/kg) had no significant effects. In a short-term rapid atrial pacing model, NIP-141 (2.5 mg/kg/10 min, followed by 0.033 mg/kg/min) prevented atrial ERP shortening. We also found NIP-141 bound to Na(+) channel site 2 receptor and L-type Ca(2+) channel, but not to Na(+) channel site 1 receptor using radioligands binding assay. CONCLUSION NIP-141 terminated AF in aconitine-induced AF and prevented the atrial remodelling by short-term rapid pacing in dogs, possibly via the blocking of Na(+) and Ca(2+) channels.
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Affiliation(s)
- Norio Hashimoto
- Biological Research Laboratories, Nissan Chemical Industries Ltd, 1470 Shiraoka, Minamisaitama, Saitama 349-0294, Japan.
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Zhou H, Ma JH, Zhang PH, Luo AT. Vitamin C Pretreatment Attenuates Hypoxia-Induced Disturbance of Sodium Currents in Guinea Pig Ventricular Myocytes. J Membr Biol 2006; 211:81-7. [PMID: 17041784 DOI: 10.1007/s00232-005-7014-8] [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] [Received: 11/04/2005] [Revised: 03/30/2006] [Indexed: 10/24/2022]
Abstract
As an important in vivo antioxidant, vitamin C is commonly used clinically to alleviate hypoxia-induced heart symptoms. To approach the protective mechanisms of vitamin C on hearts during hypoxia, we investigated the electrophysiological effects of vitamin C (1 mM: , pretreated before hypoxia) on Na(+) currents (including transient and persistent Na(+) currents) in guinea pig ventricular myocytes during hypoxia by the whole-cell and single-channel patch-clamp techniques. Whole-cell recordings showed that the mean current density of I (NaT) in the hypoxia group decreased from the control value of 40.2142 +/- 1.7735 to 27.1663 +/- 1.8441 pA/pF and current density of I (NaP) increased from 0.3987 +/- 0.0474 to 1.1854 +/- 01994 pA/pF (n = 9, P < 0.05 vs. control) at 15 min. However, when vitamin C was administered before hypoxia as pretreatment, I (NaT )and I (NaP )varied moderately (mean current density of I (NaT) decreasing from 41.6038 +/- 2.9762 to 34.6341 +/- 1.9651 pA/pF and current density of I (NaP) increasing from 0.3843 +/- 0.0636 to 0.6734 +/- 0.1057 pA/pF; n = 9, P < 0.05 vs. hypoxia group). Single-channel recordings (cell-patched) showed that the mean open probability and open time of I (NaP) increased significantly in both groups at hypoxia 15 min. However, the increased current values of the hypoxia group were still marked at hypoxia 15 min (n = 9, P < 0.05 vs. vitamin C + hypoxia group). Our results indicate that vitamin C can attenuate the disturbed effects of hypoxia on Na(+) currents (I (NaT) and I (NaP)) of cardiac myocytes in guinea pigs effectively.
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Affiliation(s)
- Hao Zhou
- Cardio-Electrophysiological Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan, PR China
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Lee SY, Lee CO. Inhibition of Na+-K+ pump and L-type Ca2+ channel by glibenclamide in Guinea pig ventricular myocytes. J Pharmacol Exp Ther 2004; 312:61-8. [PMID: 15365090 DOI: 10.1124/jpet.104.074369] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glibenclamide, a potent cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel blocker, is frequently used to study function and regulation of CFTR Cl(-) channels. In this study, the effects of glibenclamide on intracellular Na(+) concentration ([Na(+)](i)), contraction, Ca(2+) transient, and membrane potential were investigated in isolated guinea pig ventricular myocytes. Glibenclamide increased [Na(+)](i) and decreased contraction and Ca(2+) transient. However, glibenclamide did not change membrane potential. To determine whether inhibition of Na(+)-K(+) pumps and L-type Ca(2+) channels is responsible for the increase of [Na(+)](i) and the decrease of contraction, we tested the effects of glibenclamide on Na(+)-K(+) pump current and L-type Ca(2+) current (I(Ca,L)). Glibenclamide decreased Na(+)-K(+) pump current and I(Ca,L) in a concentration-dependent manner. In the presence of Cl(-) channel inhibitors, glibenclamide depolarized diastolic membrane potential and reduced action potential duration. This result suggests that the reason for lack of effect of glibenclamide on membrane potential might be due to its combined inhibitory effects on the Na(+)-K(+) pump, the L-type Ca(2+) channel, and Cl(-) channels, which may have opposing effects on membrane potential. These results indicate that glibenclamide increases [Na(+)(i)] by inhibiting the Na(+)-K(+) pump and decreases contraction and Ca(2+) transient, in addition, by blocking the L-type Ca(2+) channel.
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Affiliation(s)
- So-Young Lee
- Department of Life Science, Pohang University of Science and Technology, Pohang, Kyung-buk, 790-784, Republic of Korea
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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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Tristani-Firouzi M, Jensen JL, Donaldson MR, Sansone V, Meola G, Hahn A, Bendahhou S, Kwiecinski H, Fidzianska A, Plaster N, Fu YH, Ptacek LJ, Tawil R. Functional and clinical characterization of KCNJ2 mutations associated with LQT7 (Andersen syndrome). J Clin Invest 2002; 110:381-8. [PMID: 12163457 PMCID: PMC151085 DOI: 10.1172/jci15183] [Citation(s) in RCA: 329] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Andersen syndrome (AS) is a rare, inherited disorder characterized by periodic paralysis, long QT (LQT) with ventricular arrhythmias, and skeletal developmental abnormalities. We recently established that AS is caused by mutations in KCNJ2, which encodes the inward rectifier K(+) channel Kir2.1. In this report, we characterized the functional consequences of three novel and seven previously described KCNJ2 mutations using a two-microelectrode voltage-clamp technique and correlated the findings with the clinical phenotype. All mutations resulted in loss of function and dominant-negative suppression of Kir2.1 channel function. In mutation carriers, the frequency of periodic paralysis was 64% and dysmorphic features 78%. LQT was the primary cardiac manifestation, present in 71% of KCNJ2 mutation carriers, with ventricular arrhythmias present in 64%. While arrhythmias were common, none of our subjects suffered sudden cardiac death. To gain insight into the mechanism of arrhythmia susceptibility, we simulated the effect of reduced Kir2.1 using a ventricular myocyte model. A reduction in Kir2.1 prolonged the terminal phase of the cardiac action potential, and in the setting of reduced extracellular K(+), induced Na(+)/Ca(2+) exchanger-dependent delayed afterdepolarizations and spontaneous arrhythmias. These findings suggest that the substrate for arrhythmia susceptibility in AS is distinct from the other forms of inherited LQT syndrome.
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Jo SH, Cho CH, Chae SW, Lee CO. Role of protein kinase C in alpha(1)-adrenergic regulation of a(Na)(i) in guinea pig ventricular myocytes. Am J Physiol Heart Circ Physiol 2000; 279:H1661-8. [PMID: 11009453 DOI: 10.1152/ajpheart.2000.279.4.h1661] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the role of protein kinase C (PKC) in alpha(1)-adrenergic regulation of intracellular Na(+) activity (a(Na)(i)) in single guinea pig ventricular myocytes. a(Na)(i) and membrane potentials were measured with the Na(+)-sensitive indicator sodium-binding benzofuran isophthalate and conventional microelectrodes, respectively, at room temperature (24-26 degrees C) while myocytes were stimulated at a rate of 0.25-0.3 Hz. The PKC activator 4beta-phorbol 12-myristate 13-acetate (PMA) decreased a(Na)(i) in a concentration-dependent manner. PMA (100 nM) produced a maximal decrease in a(Na)(i) of 1.5 mM from 6.5 +/- 0.4 to 5.0 +/- 0.4 mM (means +/- SE, n = 12, P < 0.01). The PMA concentration required for a half-maximal decrease in a(Na)(i) was 0.46 +/- 0.13 nM (n = 3, P < 0.01). An inactive phorbol, 4alpha-phorbol 12-myristate 13-acetate, did not decrease a(Na)(i). The decrease caused by PMA could be blocked by the PKC inhibitors staurosporine and bisindolylmaleimide I (GF-109203X). Stimulation of the alpha(1)-adrenoceptor with 50 microM phenylephrine decreased a(Na)(i) from 6.1 +/- 0.3 to 4.6 +/- 0.3 mM (n = 11, P < 0.01). The decrease in a(Na)(i) produced by phenylephrine was blocked by pretreatment with staurosporine, GF-109203X, or PMA. The decrease in a(Na)(i) produced by PMA was not prevented by pretreatment with tetrodotoxin but was blocked by pretreatment with strophanthidin or high extracellular K(+) concentration. The results suggest that alpha(1)-adrenergic receptor activation results in a decrease in a(Na)(i) via PKC-induced stimulation of the Na(+)-K(+) pump in cardiac myocytes.
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Affiliation(s)
- S H Jo
- Department of Life Science, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
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Yuill KH, Convery MK, Dooley PC, Doggrell SA, Hancox JC. Effects of BDF 9198 on action potentials and ionic currents from guinea-pig isolated ventricular myocytes. Br J Pharmacol 2000; 130:1753-66. [PMID: 10952663 PMCID: PMC1572251 DOI: 10.1038/sj.bjp.0703476] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2000] [Accepted: 05/12/2000] [Indexed: 11/09/2022] Open
Abstract
BDF 9198 (a congener of DPI 201 - 106 and BDF 9148) was found to be a positive inotrope on guinea-pig isolated ventricular muscle strips. The effects of BDF 9198 on action potentials and ionic currents from guinea-pig isolated ventricular myocytes were studied using the whole cell patch clamp method. In normal external solution, at 37 degrees C, action potential duration at 50% repolarization (APD(50)) was 167.4+/-8.36 ms (n=37). BDF 9198 produced a concentration-dependent increase in APD(50) (no significant increase at 1x10(-10) M; and APD(50) values of 273.03+/-35.8 ms at 1x10(-9) M; n=6, P<0.01 and 694.7+/-86.3 ms at 1x10(-7) M; P<0.001, n=7). At higher concentrations in the range tested, BDF 9198 also induced early and delayed and after-depolarizations. Qualitative measurements of I(Na) with physiological [Na](o) showed prolongation of the current by BDF 9198, and the appearance of transient oscillatory inward currents at high concentrations. Quantitative recording conditions for I(Na) were established using low external [Na] and by making measurements at room temperature. The current - voltage relation, activation parameters and time-course of I(Na) were similar before and after a partial blocking dose of Tetrodotoxin (TTX, 1 microM), despite a 2 fold difference in current amplitude. This suggests that voltage-clamp during flow of I(Na) was adequately maintained under our conditions. Selective measurements of I(Na) at room temperature showed that BDF 9198 induced a concentration-dependent, sustained component of I(Na) (I(Late)) and caused a slight left-ward shift in the current - voltage relation for peak current. The drug-induced I(Late) showed a similar voltage dependence to peak current in the presence of BDF 9198. Both peak current and I(Late) were abolished by 30 microM TTX and were sensitive to external [Na]. Inactivation of control I(Na) during a 200 ms test pulse to -30 mV followed a bi-exponential time-course. In addition to inducing a sustained current component, BDF 9198 left the magnitude of the fast inactivation time-constant unchanged, but increased the magnitude of the slow inactivation time-constant. Additional experiments with a longer pulse (1 s) raised the possibility that in the presence of BDF 9198, I(Na) inactivation may be comprised of more than two phases. No significant effects of 1x10(-6) M BDF 9198 were observed on the L-type calcium current, or delayed and inward rectifying potassium currents measured at 37 degrees C. It is concluded that the prolongation of APD(50) by BDF 9198 resulted from selective modulation of I(Na). Reduced current inactivation induced a persistent I(Na), increasing the net depolarizing current during the action potential. This action of the drug indicates a potential for 'QT prolongation' of the ECG. The observation of after-depolarizations suggests a potential for proarrhythmia at some drug concentrations.
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Affiliation(s)
- K H Yuill
- Department of Physiology and Cardiovascular Research Laboratories, School of Medical Sciences, University Walk, Bristol, BS8 1TD
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Bian JS, Pei JM, Cheung CS, Zhang WM, Wong TM. kappa -opioid receptor stimulation induces arrhythmia in the isolated rat heart via the protein kinase C/Na(+)-H(+)exchange pathway. J Mol Cell Cardiol 2000; 32:1415-27. [PMID: 10900168 DOI: 10.1006/jmcc.2000.1175] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study attempted to determine whether the protein kinase C (PKC)/Na(+)-H(+)exchange (NHE) pathway would mediate the arrhythmogenic action of kappa -opioid receptor (OR) stimulation. We first determined the effects of U50,488H, a selective kappa -OR agonist, on PKC activity and cardiac rhythm in the isolated perfused rat heart, and intracellular pH (pH(i)), and Ca(2+)([Ca(2+)](i)) and Na(+)([Na(+)](i)) concentrations in the isolated ventricular myocyte. At 5-40 microm U50,488H concentration dependently increased the particulate PKC activity and pH(i), and induced arrhythmia. 40 microm U50,488H also increased [Na(+)](i)and [Ca(2+)](i). The arrhythmogenic effects of 40 microm U50,488H were abolished by nor-binaltorphimine, a selective kappa -OR antagonist. Blockade of PKC and NHE with respective blockers, 1 microm bisindolylmaleimide I or 0.5 microm calphostin C, and 1 microm 5-[N -methyl- N -isobutyl]amiloride or 1 microm 5-([N -ethyl- N -isopropopyl]amiloride, abolished and significantly attenuated, respectively, the effects of kappa -OR stimulation on pH(i), [Na(+)](i)and [Ca(2+)](i), and arrhythmia. To determine the role of pH(i), we observed U50,488H-induced arrhythmia at pH(i)6.8. At this pH(i), the pH(i)increased gradually both in the presence and absence of 40 microm U50,488H to a similar extent. While the increase in response to U50,488H was significantly less at pH(i)6.8 (from 0.09 to 0.10) than that at pH(i)7.1 (from 0.01 to 0.18), the arrhythmia induced by the agonist was the same at both high and low pHs. On the other hand, 5 microm monensin, a sodium ionophore, increased [Na(+)](i)and [Ca(2+)](i), and induced arrhythmia to similar extents as U50,488H. PKC and NHE inhibitors, that significantly attenuated the effects induced by U50,488H, had no effect on those induced by monensin. In conclusion, kappa -OR stimulation induces arrhythmia via PKC/NHE. [Na(+)](i)and [Ca(2+)](i), but not pH(i), may be directly responsible for arrhythmia induced by kappa -OR stimulation.
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Affiliation(s)
- J S Bian
- Department of Physiology and Institute of Cardiovascular Science and Medicine, The University of Hong Kong, Hong Kong, China
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Faber GM, Rudy Y. Action potential and contractility changes in [Na(+)](i) overloaded cardiac myocytes: a simulation study. Biophys J 2000; 78:2392-404. [PMID: 10777735 PMCID: PMC1300828 DOI: 10.1016/s0006-3495(00)76783-x] [Citation(s) in RCA: 334] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Sodium overload of cardiac cells can accompany various pathologies and induce fatal cardiac arrhythmias. We investigate effects of elevated intracellular sodium on the cardiac action potential (AP) and on intracellular calcium using the Luo-Rudy model of a mammalian ventricular myocyte. The results are: 1) During rapid pacing, AP duration (APD) shortens in two phases, a rapid phase without Na(+) accumulation and a slower phase that depends on [Na(+)](i). 2) The rapid APD shortening is due to incomplete deactivation (accumulation) of I(Ks). 3) The slow phase is due to increased repolarizing currents I(NaK) and reverse-mode I(NaCa), secondary to elevated [Na(+)](i). 4) Na(+)-overload slows the rate of AP depolarization, allowing time for greater I(Ca(L)) activation; it also enhances reverse-mode I(NaCa). The resulting increased Ca(2+) influx triggers a greater [Ca(2+)](i) transient. 5) Reverse-mode I(NaCa) alone can trigger Ca(2+) release in a voltage and [Na(+)](i)-dependent manner. 6) During I(NaK) block, Na(+) and Ca(2+) accumulate and APD shortens due to enhanced reverse-mode I(NaCa); contribution of I(K(Na)) to APD shortening is negligible. By slowing AP depolarization (hence velocity) and shortening APD, Na(+)-overload acts to enhance inducibility of reentrant arrhythmias. Shortened APD with elevated [Ca(2+)](i) (secondary to Na(+)-overload) also predisposes the myocardium to arrhythmogenic delayed afterdepolarizations.
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Affiliation(s)
- G M Faber
- Cardiac Bioelectricity Research and Training Center and Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7207 USA
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Jayachandran JV, Zipes DP, Weksler J, Olgin JE. Role of the Na(+)/H(+) exchanger in short-term atrial electrophysiological remodeling. Circulation 2000; 101:1861-6. [PMID: 10769289 DOI: 10.1161/01.cir.101.15.1861] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The pathophysiology underlying electrophysiological remodeling (ER) from rapid atrial rates is unknown. We tested the hypothesis that activation of the Na(+)/H(+) exchanger (NHE) by ischemia contributes to ER. METHODS AND RESULTS Twenty-eight dogs were studied under autonomic blockade. In 15 closed-chest dogs, atrial fibrillation was simulated by right atrial pacing at 600 bpm over 5 hours. Of these, 9 (pace/NHEI) received HOE642, a selective inhibitor of the NHE, and 6 (pace/control) received saline. In pace/controls, atrial effective refractory period (AERP) at a drive cycle length (DCL) of 400 ms shortened from 143+/-7 to 118+/-5 ms (1 hour) and to 122+/-17 ms (5 hours). Shortening of AERP was prevented in the pace/NHEI group (P=0.02 compared with pace/controls). At baseline in all 15 dogs, pacing at shorter DCL resulted in shortening of AERP (physiological rate adaptation), which was lost at 5 hours in pace/controls. In pace/NHEI animals, rate adaptation was maintained despite 5 hours of pacing (P=0.02). In 13 other open-chest dogs, right atrial ERP was determined before and after occlusion of the right coronary artery. Five received HOE642 (ischemia/NHEI), 5 saline (ischemia/control), and 3 intravenous glibenclamide. In ischemia/controls, AERP(400) decreased (156+/-30 to 130+/-32 ms). Shortening of AERP was not prevented by glibenclamide (180+/-20 to 153+/-33 ms) but was prevented in ischemia/NHEI dogs (169+/-12 to 184+/-19 ms, P=0.001 compared with ischemia/controls and ischemia/glibenclamide). Rate adaptation was lost in ischemia/controls and preserved in ischemia/NHEI dogs (P=0. 02). CONCLUSIONS Activation of the NHE is one mechanism underlying short-term ER.
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Affiliation(s)
- J V Jayachandran
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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