1
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Chakraborty P, Massé S, Azam MA, Thollon C, Niri A, Lai PFH, Bouly M, Riazi S, Nanthakumar K. Effects of azumolene on arrhythmia substrate in a model of recurrent long-duration ventricular fibrillation. Biochem Biophys Res Commun 2022; 600:123-129. [PMID: 35219100 DOI: 10.1016/j.bbrc.2022.02.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 02/09/2022] [Indexed: 11/17/2022]
Abstract
BACKGROUND Proarrhythmic risk of conventional anti-arrhythmic agents is linked to unintended modulation of membrane voltage dynamics. We have demonstrated that the anti-fibrillatory effect of azumolene is mediated via stabilization of the hyperphosphorylated ryanodine receptor (RyR2), leading to attenuation of diastolic calcium leak. However, the concomitant effects on membrane voltage dynamics have not been evaluated yet. METHODS After baseline optical mapping, Langendorff-perfused rabbit hearts treated with azumolene, or vehicle, were subjected to global ischemia-reperfusion (I/R) followed by two episodes of long-duration ventricular fibrillation (LDVF). Simultaneous dual epicardial calcium transient (CaT) and voltage dynamics were studied optically. RESULTS Pre-treatment with azumolene was associated with higher CaT amplitude alternans ratios (0.94 ± 0.02 vs. 0.78 ± 0.03 in control hearts, at 6 Hz; p = 0.005; and action potential amplitude alternans ratio (0.95 ± 0.02 vs. 0.78 ± 0.04 at 6.0 Hz; p = 0.02), and reduction of action potential duration (APD80) dispersion (9.0 ± 4.8 msec vs. 19.3 ± 6.6 msec at 6.0 Hz p = 0.02) and optical action potential upstroke rise time (26.3 ± 2.6 msec in control vs. 13.8 ± 0.6 msec at 6.0 Hz, p = 0.02) after LDVF. No change in action potential duration (APD) was noted with azumolene treatment. CONCLUSION In a model of ischemic recurrent LDVF, treatment with azumolene led to reduction of cardiac alternans, i.e., calcium and voltage alternans. Unlike conventional anti-arrhythmic agents, reduction of action potential upstroke rise time and preservation of action potential duration following azumolene treatment may reduce the proarrhythmia risk.
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Affiliation(s)
- Praloy Chakraborty
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Stéphane Massé
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Mohammed Ali Azam
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | | | - Ahmed Niri
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Patrick F H Lai
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada
| | - Muriel Bouly
- Institut de Recherches Internationales Servier (IRIS), Suresnes, France
| | - Sheila Riazi
- Malignant Hyperthermia Investigation Unit, Department of Anesthesia and Pain Management, University Health Network, Toronto, Ontario, Canada
| | - Kumaraswamy Nanthakumar
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada.
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2
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Ji X, Bradley JL, Zheng G, Ge W, Xu J, Hu J, He F, Shabnam R, Peberdy MA, Ornato JP, Chen Q, Lesnefsky EJ, Tang W. Cerebral and myocardial mitochondrial injury differ in a rat model of cardiac arrest and cardiopulmonary resuscitation. Biomed Pharmacother 2021; 140:111743. [PMID: 34020243 DOI: 10.1016/j.biopha.2021.111743] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 05/11/2021] [Accepted: 05/13/2021] [Indexed: 11/18/2022] Open
Abstract
Brain mitochondria are more sensitive to global ischemia compared to heart mitochondria. Complex I in the electron transport chain (ETC) is sensitive to ischemic injury and is a major control point of the rate of ADP stimulated oxygen consumption. The purpose of this study was to explore whether changes in cerebral and myocardial mitochondria differ after cardiac arrest. Animals were randomized into 4 groups (n = 6): 1) Sham 2) VF 3) VF+CPR 4) ROSC 1hr. Ventricular Fibrillation (VF) was induced through a guide wire advanced from the right jugular vein into the ventricle and untreated for 8 min. Resuscitation was attempted with a 4J defibrillation after 8 min of cardiopulmonary resuscitation (CPR). Brain mitochondria and cardiac mitochondrial subpopulations were isolated. Calcium retention capacity was measured to assess susceptibility to mitochondrial permeability transition pore opening. ADP stimulated oxygen consumption and ETC activity assays were performed. Brain mitochondria are far more sensitive to injury during cardiac arrest and resuscitation compared to cardiac mitochondria. Complex I is highly sensitive to injury in brain mitochondria. With markedly decreased calcium retention capacity, mitochondria contribute to cerebral reperfusion injury. Therapeutic preservation of cerebral mitochondrial activity and mitochondrial function during cardiac arrest may improve post-resuscitation neurologic function.
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Affiliation(s)
- Xianfei Ji
- Department of Emergency, Shandong Provincial Hospital affiliated to Shandong First Medical University, Jinan, China; Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA.
| | - Jennifer L Bradley
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA; Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA, USA.
| | - Guanghui Zheng
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA.
| | - Weiwei Ge
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA.
| | - Jing Xu
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA.
| | - Juntao Hu
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA.
| | - Fenglian He
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA.
| | | | - Mary Ann Peberdy
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA; Departments of Internal Medicine and Emergency Medicine, Virginia Commonwealth University Health System, Richmond, VA, USA; Division of Cardiology, Department of Internal Medicine, Virginia Commonwealth University Health System, Richmond, VA, USA.
| | - Joseph P Ornato
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA; Department of Emergency Medicine, Virginia Commonwealth University Health System, Richmond, VA, USA.
| | - Qun Chen
- Division of Cardiology, Department of Internal Medicine, Virginia Commonwealth University Health System, Richmond, VA, USA.
| | - Edward J Lesnefsky
- Division of Cardiology, Department of Internal Medicine, Virginia Commonwealth University Health System, Richmond, VA, USA; Medical Service, McGuire Department of Veterans Affairs Medical Center, Richmond, VA, USA; McGuire Research Institute, Richmond, VA, USA.
| | - Wanchun Tang
- Weil Institute of Emergency and Critical Care Research, Virginia Commonwealth University, Richmond, VA, USA; Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA, USA; Department of Emergency Medicine, Virginia Commonwealth University Health System, Richmond, VA, USA.
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3
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Guo WH, Wang X, Shang MS, Chen Z, Guo Q, Li L, Wang HY, Yu RH, Ma CS. Crosstalk between PKC and MAPK pathway activation in cardiac fibroblasts in a rat model of atrial fibrillation. Biotechnol Lett 2020; 42:1219-1227. [PMID: 32095918 DOI: 10.1007/s10529-020-02843-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 02/19/2020] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Atrial fibrillation (AF) is the most frequent form of cardiac arrhythmia and major cause of cardiac ischemia. Defective calcium homeostasis due to anomalous expression of ryanodine receptor type 2 (RyR2) or its hyperactivation by phosphorylation by serine threonine kinases has been implicated as a central mechanism of AF pathogenesis. Given the role of protein kinase C (PKC) isoforms in cardiac function we investigated role of PKC in AF using a rat model. RESULTS PMA induced global increase in protein synthesis in cardiac fibroblasts isolated from AF rats, but not healthy controls, and the increase was inhibited by PKC inhibition. PMA mediated activation of both PKC and ERK and either inhibition of PKC by Go6983 or ERK by the MEK inhibitor Trametinib attenuated both P-ERK and P-PKC in both cardiac fibroblasts isolated from AF rats or from healthy rats but transduced with PKC-delta. The PKC and ERK mediated induction of global protein synthesis was found to be mediated by increased phosphorylation of the ribosomal protein S6. CONCLUSION Our findings provide a foundation for future testing of PKC and MEK inhibitors to treat AF in pre-clinical models. It also needs to be determined if PKC and MAPK pathway activation is functioning via RyR2 or some yet undefined substrates.
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Affiliation(s)
- Wei-Hua Guo
- Department of Cardiology, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, 100700, China
| | - Xian Wang
- Department of Cardiology, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, 100700, China
| | - Mei-Sheng Shang
- Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, No.2, Anzhen Road, Chaoyang District, Beijing, 100029, China
| | - Zhe Chen
- Department of Cardiology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Qi Guo
- Department of Cardiology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Li Li
- Department of Cardiology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Hai-Ying Wang
- Department of Cardiology, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, 100700, China
| | - Rong-Hui Yu
- Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, No.2, Anzhen Road, Chaoyang District, Beijing, 100029, China
| | - Chang-Sheng Ma
- Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, No.2, Anzhen Road, Chaoyang District, Beijing, 100029, China.
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4
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Ke HY, Chin LH, Tsai CS, Lin FZ, Chen YH, Chang YL, Huang SM, Chen YC, Lin CY. Cardiac calcium dysregulation in mice with chronic kidney disease. J Cell Mol Med 2020; 24:3669-3677. [PMID: 32064746 PMCID: PMC7131917 DOI: 10.1111/jcmm.15066] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 01/14/2020] [Accepted: 01/23/2020] [Indexed: 12/30/2022] Open
Abstract
Cardiovascular complications are leading causes of morbidity and mortality in patients with chronic kidney disease (CKD). CKD significantly affects cardiac calcium (Ca2+) regulation, but the underlying mechanisms are not clear. The present study investigated the modulation of Ca2+ homeostasis in CKD mice. Echocardiography revealed impaired fractional shortening (FS) and stroke volume (SV) in CKD mice. Electrocardiography showed that CKD mice exhibited longer QT interval, corrected QT (QTc) prolongation, faster spontaneous activities, shorter action potential duration (APD) and increased ventricle arrhythmogenesis, and ranolazine (10 µmol/L) blocked these effects. Conventional microelectrodes and the Fluo‐3 fluorometric ratio techniques indicated that CKD ventricular cardiomyocytes exhibited higher Ca2+ decay time, Ca2+ sparks, and Ca2+ leakage but lower [Ca2+]i transients and sarcoplasmic reticulum Ca2+ contents. The CaMKII inhibitor KN93 and ranolazine (RAN; late sodium current inhibitor) reversed the deterioration in Ca2+ handling. Western blots revealed that CKD ventricles exhibited higher phosphorylated RyR2 and CaMKII and reduced phosphorylated SERCA2 and SERCA2 and the ratio of PLB‐Thr17 to PLB. In conclusions, the modulation of CaMKII, PLB and late Na+ current in CKD significantly altered cardiac Ca2+ regulation and electrophysiological characteristics. These findings may apply on future clinical therapies.
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Affiliation(s)
- Hung-Yen Ke
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Department and Graduate Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Li-Han Chin
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Chien-Sung Tsai
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Department and Graduate Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Feng-Zhi Lin
- Grade institute of life sciences, National Defense Medical Center, Taipei, Taiwan
| | - Yen-Hui Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yung-Lung Chang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
| | - Shih-Ming Huang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
| | - Yao-Chang Chen
- Department of Biomedical Engineering and Institute of Physiology, National Defense Medical Center, Taipei, Taiwan
| | - Chih-Yuan Lin
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
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5
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Increased expression of ryanodine receptor type-2 during atrial fibrillation by miR-106-25 cluster independent mechanism. Exp Cell Res 2019; 375:113-117. [DOI: 10.1016/j.yexcr.2018.11.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 11/15/2018] [Accepted: 11/26/2018] [Indexed: 11/23/2022]
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6
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Knezl V, Sotníková R, Brnoliaková Z, Stankovičová T, Bauer V, Bezek Š. Monotherapy of experimental metabolic syndrome: II. Study of cardiovascular effects. Interdiscip Toxicol 2017; 10:86-92. [PMID: 30174531 PMCID: PMC6107648 DOI: 10.1515/intox-2017-0014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/16/2017] [Indexed: 01/01/2023] Open
Abstract
Metabolic syndrome belongs to the most important risk factors of cardiovascular diseases. The aim of this study was to investigate changes in cardiovascular system induced by high cholesterol and high fat diet (HCHF) in HTG rats and their influence by a pyridoindole antioxidant - SMe1EC2 (S). The effects of S were compared with those of atorvastatin (A). Male HTG rats were fed HCHF (1% cholesterol + 7.5% lard) for 4 weeks. S and A were administered p.o., 50 mg/kg b.w. Following experimental groups were used: Wistar rats (W), hypertriglyceridemic rats (HTG), HTG rats fed HCHF (CHOL), HTG+S (S-HTG), CHOL+S (S-CHOL), and CHOL+A (A-CHOL). Values of blood pressure (BP) and selected ECG parameters were monitored in conscious animals, functions of the isolated heart and aorta were analyzed ex vivo. At the end of the experiment, systolic (sBP) and diastolic (dBP) blood pressure was increased in HTG and CHOL. S and A decreased BP in all treated groups. Accordingly with BP changes, the aortic endothelial function of CHOL was damaged. Both S and A administration ameliorated the endothelium-dependent relaxation to values of W. PQ and QTc intervals were prolonged in CHOL, while the treatment with S or A improved ECG findings. Prodysrhythmogenic threshold was decreased significantly in CHOL and both treatments returned it to the control values. In conclusion, HCHF increased BP, impaired endothelial relaxation of the aorta and potentiated susceptibility of myocardium to dysrhythmias. The effect of S on the changes induced by HCHF diet was more pronounced than that of A.
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Affiliation(s)
- Vladimír Knezl
- Institute of Experimental Pharmacology and Toxicology, Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava, Slovakia
| | - Ružena Sotníková
- Institute of Experimental Pharmacology and Toxicology, Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava, Slovakia
| | - Zuzana Brnoliaková
- Institute of Experimental Pharmacology and Toxicology, Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava, Slovakia
| | - Tatiana Stankovičová
- Department of Pharmacology and Toxicology, Comenius University in Bratislava, Faculty of Pharmacy, Odbojárov 10, 832 32 Bratislava 3, Slovakia
| | - Viktor Bauer
- Institute of Experimental Pharmacology and Toxicology, Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava, Slovakia
| | - Štefan Bezek
- Institute of Experimental Pharmacology and Toxicology, Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava, Slovakia
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7
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Jiang W, Zeng M, Cao Z, Liu Z, Hao J, Zhang P, Tian Y, Zhang P, Ma J. Icariin, a Novel Blocker of Sodium and Calcium Channels, Eliminates Early and Delayed Afterdepolarizations, As Well As Triggered Activity, in Rabbit Cardiomyocytes. Front Physiol 2017; 8:342. [PMID: 28611679 PMCID: PMC5447092 DOI: 10.3389/fphys.2017.00342] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/09/2017] [Indexed: 11/13/2022] Open
Abstract
Icariin, a flavonoid monomer from Herba Epimedii, has confirmed pharmacological and biological effects. However, its effects on arrhythmias and cardiac electrophysiology remain unclear. Here we investigate the effects of icariin on ion currents and action potentials (APs) in the rabbit myocardium. Furthermore, the effects of icariin on aconitine-induced arrhythmias were assessed in whole rabbits. Ion currents and APs were recorded in voltage-clamp and current-clamp mode in rabbit left ventricular myocytes (LVMs) and left atrial myocytes (LAMs), respectively. Icariin significantly shortened action potential durations (APDs) at 50 and 90% repolarization (APD50 and APD90) and reduced AP amplitude (APA) and the maximum upstroke velocity (Vmax) of APs in LAMs and LVMs; however, icariin had no effect on resting membrane potential (RMP) in these cells. Icariin decreased the rate-dependence of the APD and completely abolished anemonia toxin II (ATX-II)-induced early afterdepolarizations (EADs). Moreover, icariin significantly suppressed delayed afterdepolarizations (DADs) and triggered activities (TAs) elicited by isoproterenol (ISO, 1 μM) and high extracellular calcium concentrations ([Ca2+]o, 3.6 mM) in LVMs. Icariin also decreased INaT in a concentration-dependent manner in LAMs and LVMs, with IC50 values of 12.28 ± 0.29 μM (n = 8 cells/4 rabbits) and 11.83 ± 0.92 μM (n = 10 cells/6 rabbits; p > 0.05 vs. LAMs), respectively, and reversed ATX-II-induced INaL in a concentration-dependent manner in LVMs. Furthermore, icariin attenuated ICaL in a dose-dependent manner in LVMs. The corresponding IC50 value was 4.78 ± 0.89 μM (n = 8 cells/4 rabbits), indicating that the aforementioned current in LVMs was 2.8-fold more sensitive to icariin than ICaL in LAMs (13.43 ± 2.73 μM; n = 9 cells/5 rabbits). Icariin induced leftward shifts in the steady-state inactivation curves of INaT and ICaL in LAMs and LVMs but did not have a significant effect on their activation processes. Moreover, icariin had no effects on IK1 and IKr in LVMs or Ito and IKur in LAMs. These results revealed for the first time that icariin is a multichannel blocker that affects INaT, INaL and ICaL in the myocardium and that the drug had significant inhibitory effects on aconitine-induced arrhythmias in whole rabbits. Therefore, icariin has potential as a class I and IV antiarrhythmic drug.
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Affiliation(s)
- Wanzhen Jiang
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Mengliu Zeng
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Zhenzhen Cao
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Zhipei Liu
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Jie Hao
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Peipei Zhang
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Youjia Tian
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Peihua Zhang
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
| | - Jihua Ma
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and TechnologyHubei, China
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8
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Vornanen M. Electrical Excitability of the Fish Heart and Its Autonomic Regulation. FISH PHYSIOLOGY 2017. [DOI: 10.1016/bs.fp.2017.04.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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9
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Lee BK, Kim MJ, Jeung KW, Choi SS, Park SW, Yun SW, Lee SM, Lee DH, Min YI. 2,3-Butanedione monoxime facilitates successful resuscitation in a dose-dependent fashion in a pig model of cardiac arrest. Am J Emerg Med 2016; 34:1053-8. [DOI: 10.1016/j.ajem.2016.03.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 03/07/2016] [Accepted: 03/07/2016] [Indexed: 11/17/2022] Open
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10
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Antiarrhythmic Effect of Either Negative Modulation or Blockade of Small Conductance Ca2+-activated K+ Channels on Ventricular Fibrillation in Guinea Pig Langendorff-perfused Heart. J Cardiovasc Pharmacol 2015; 66:294-9. [DOI: 10.1097/fjc.0000000000000278] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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11
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El-Ani D, Philipchik I, Stav H, Levi M, Zerbib J, Shainberg A. Tumor necrosis factor alpha protects heart cultures against hypoxic damage via activation of PKA and phospholamban to prevent calcium overload. Can J Physiol Pharmacol 2014; 92:917-25. [PMID: 25349921 DOI: 10.1139/cjpp-2014-0092] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
This study aims to elucidate the mechanisms by which tumor necrosis factor alpha (TNFα) provides protection from hypoxic damage to neonatal rat cardiomyocyte cultures. We show that when intracellular Ca(2+) ([Ca(2+)]i) levels are elevated by extracellular Ca(2+) ([Ca(2+)]o) or by hypoxia, then TNFα decreased [Ca(2+)]i in individual cardiomyocytes. However, TNFα did not reduce [Ca(2+)]i after its increase by thapsigargin, (a SERCA2a inhibitor), indicating that TNFα attenuates Ca(2+) overload through Ca(2+) uptake by SERCA2a. TNFα did not reduce [Ca(2+)]i, following its elevation when [Ca(2+)]o levels were elevated in TNFα receptor knock-out mice. H-89, a protein kinase A (PKA) inhibitor, attenuated the protective effect of TNFα when the cardiomyoctyes were subjected to hypoxia, as determined by lactate dehydrogenase (LDH) and creatine kinase (CK) released and from the cardiomyocytes. Moreover, when the levels of [Ca(2+)]i were increased by hypoxia, H-89, but not KN93, (a calmodulin kinase II inhibitor), prevented the reduction in [Ca(2+)]i by TNFα. TNFα increased the phosphorylation of PKA in normoxic and hypoxic cardiomyoctes, indicating that the cardioprotective effect of TNFα against hypoxic damage was via PKA activation. Hypoxia decreased phosphorylated phospholamban levels; however, TNFα attenuated this decrease following hypoxia. It is suggested that TNFα activates phospholamban phosphorylation in hypoxic heart cultures via PKA to stimulate SERCA2a activity to limit Ca(2+) overload.
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Affiliation(s)
- Dalia El-Ani
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
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Brief endocardial surge of Ca2+ transient but monotonic suppression of action potential occurs during acute ischemia in canine ventricular tissue. Heart Rhythm 2013; 10:1201-8. [DOI: 10.1016/j.hrthm.2013.05.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Indexed: 11/22/2022]
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13
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Li XC, Wei L, Zhang GQ, Bai ZL, Hu YY, Zhou P, Bai SH, Chai Z, Lakatta EG, Hao XM, Wang SQ. Ca2+ cycling in heart cells from ground squirrels: adaptive strategies for intracellular Ca2+ homeostasis. PLoS One 2011; 6:e24787. [PMID: 21935466 PMCID: PMC3173481 DOI: 10.1371/journal.pone.0024787] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 08/17/2011] [Indexed: 12/21/2022] Open
Abstract
Heart tissues from hibernating mammals, such as ground squirrels, are able to endure hypothermia, hypoxia and other extreme insulting factors that are fatal for human and nonhibernating mammals. This study was designed to understand adaptive mechanisms involved in intracellular Ca2+ homeostasis in cardiomyocytes from the mammalian hibernator, ground squirrel, compared to rat. Electrophysiological and confocal imaging experiments showed that the voltage-dependence of L-type Ca2+ current (ICa) was shifted to higher potentials in ventricular myocytes from ground squirrels vs. rats. The elevated threshold of ICa did not compromise the Ca2+-induced Ca2+ release, because a higher depolarization rate and a longer duration of action potential compensated the voltage shift of ICa. Both the caffeine-sensitive and caffeine-resistant components of cytosolic Ca2+ removal were more rapid in ground squirrels. Ca2+ sparks in ground squirrels exhibited larger amplitude/size and much lower frequency than in rats. Due to the high ICa threshold, low SR Ca2+ leak and rapid cytosolic Ca2+ clearance, heart cells from ground squirrels exhibited better capability in maintaining intracellular Ca2+ homeostasis than those from rats and other nonhibernating mammals. These findings not only reveal adaptive mechanisms of hibernation, but also provide novel strategies against Ca2+ overload-related heart diseases.
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Affiliation(s)
- Xiao-Chen Li
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Ling Wei
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Guang-Qin Zhang
- Research Division of Pharmacology, China Pharmaceutical University, Nanjing, China
| | - Zai-Ling Bai
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Ying-Ying Hu
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Peng Zhou
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Shu-Hua Bai
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Zhen Chai
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Edward G. Lakatta
- Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, Maryland, United States of America
| | - Xue-Mei Hao
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
| | - Shi-Qiang Wang
- State Key Lab of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China
- * E-mail:
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Katsnelson LB, Solovyova O, Balakin A, Lookin O, Konovalov P, Protsenko Y, Sulman T, Markhasin VS. Contribution of mechanical factors to arrhythmogenesis in calcium overloaded cardiomyocytes: model predictions and experiments. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:81-9. [PMID: 21699912 DOI: 10.1016/j.pbiomolbio.2011.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 06/06/2011] [Indexed: 10/18/2022]
Abstract
It is well-known that Ca²⁺ overload in cardiomyocytes may underlie arrhythmias. However, the possible contribution of mechanical factors to rhythm disturbances in Ca²⁺ overloaded myocytes has not been sufficiently investigated. We used a mathematical model of the electrical and mechanical activity of cardiomyocytes to reveal an essential role of the mechanisms of cardiac mechano-electric feedback in arrhythmogenesis in Ca²⁺ overloaded myocardium. In the model, the following mechanical factors increased Ca²⁺ overload in contracting cardiomyocytes and promoted rhythm disturbances: i) a decrease in the mechanical load for afterloaded contractions; and ii) a decrease in the initial length of sarcomeres for isometric twitches. In exact accordance with the model predictions, in experiments on papillary muscles from the right ventricle of guinea pigs with Ca²⁺ overloaded cardiomyocytes (using 0.5-1 μM of ouabain), we found that emergence of rhythm disturbances and extrasystoles depends on the mechanical conditions of muscle contraction.
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Affiliation(s)
- Leonid B Katsnelson
- Institute of Immunology and Physiology, Ural Branch of the Russian Academy of Sciences, 106 Pervomayskaya str, Ekaterinburg 620049, Russian Federation.
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15
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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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16
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Tribulova N, Seki S, Radosinska J, Kaplan P, Babusikova E, Knezl V, Mochizuki S. Myocardial Ca2+ handling and cell-to-cell coupling, key factors in prevention of sudden cardiac deathThis article is one of a selection of papers published in a special issue on Advances in Cardiovascular Research. Can J Physiol Pharmacol 2009; 87:1120-9. [DOI: 10.1139/y09-106] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Using whole-heart preparations, we tested our hypothesis that Ca2+ handling is closely related to cell-to-cell coupling at the gap junctions and that both are critical for the development and particularly the termination of ventricular fibrillation (VF) and hence the prevention of sudden arrhythmic death. Intracellular free calcium concentration ([Ca2+]i), ECG, and left ventricular pressure were continuously monitored in isolated guinea pig hearts before and during development of low K+-induced sustained VF and during its conversion into sinus rhythm facilitated by stobadine. We also examined myocardial ultrastructure to detect cell-to-cell coupling alterations. We demonstrated that VF occurrence was preceded by a 55.9% ± 6.2% increase in diastolic [Ca2+]i, which was associated with subcellular alterations indicating Ca2+ overload of the cardiomyocytes and disorders in coupling among the cells. Moreover, VF itself further increased [Ca2+]i by 58.2% ± 3.4% and deteriorated subcellular and cell-to-cell coupling abnormalities that were heterogeneously distributed throughout the myocardium. In contrast, termination of VF and its conversion into sinus rhythm was marked by restoration of basal [Ca2+]i, resulting in recovery of intercellular coupling linked with synchronous contraction. Furthermore, we have shown that hearts exhibiting lower SERCA2a (sarcoplasmic reticulum Ca2+-ATPase) activity and abnormal intercellular coupling (as in older guinea pigs) are more prone to develop Ca2+ overload associated with cell-to-cell uncoupling than hearts with higher SERCA2a activity (as in young guinea pigs). Consequently, young animals are better able to terminate VF spontaneously. These findings indicate the crucial role of Ca2+ handling in relation to cell-to-cell coupling in both the occurrence and termination of malignant arrhythmia.
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Affiliation(s)
- Narcis Tribulova
- Institute for Heart Research, Slovak Academy of Sciences, Dubravska cesta 9, PO Box 104, 840 05 Bratislava, Slovak Republic
- Division of Cardiology, Department of Internal Medicine, Jikei University, Tokyo, Japan
- Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
- Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Shingo Seki
- Institute for Heart Research, Slovak Academy of Sciences, Dubravska cesta 9, PO Box 104, 840 05 Bratislava, Slovak Republic
- Division of Cardiology, Department of Internal Medicine, Jikei University, Tokyo, Japan
- Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
- Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Jana Radosinska
- Institute for Heart Research, Slovak Academy of Sciences, Dubravska cesta 9, PO Box 104, 840 05 Bratislava, Slovak Republic
- Division of Cardiology, Department of Internal Medicine, Jikei University, Tokyo, Japan
- Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
- Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Peter Kaplan
- Institute for Heart Research, Slovak Academy of Sciences, Dubravska cesta 9, PO Box 104, 840 05 Bratislava, Slovak Republic
- Division of Cardiology, Department of Internal Medicine, Jikei University, Tokyo, Japan
- Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
- Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Eva Babusikova
- Institute for Heart Research, Slovak Academy of Sciences, Dubravska cesta 9, PO Box 104, 840 05 Bratislava, Slovak Republic
- Division of Cardiology, Department of Internal Medicine, Jikei University, Tokyo, Japan
- Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
- Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Vladimir Knezl
- Institute for Heart Research, Slovak Academy of Sciences, Dubravska cesta 9, PO Box 104, 840 05 Bratislava, Slovak Republic
- Division of Cardiology, Department of Internal Medicine, Jikei University, Tokyo, Japan
- Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
- Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Seibu Mochizuki
- Institute for Heart Research, Slovak Academy of Sciences, Dubravska cesta 9, PO Box 104, 840 05 Bratislava, Slovak Republic
- Division of Cardiology, Department of Internal Medicine, Jikei University, Tokyo, Japan
- Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
- Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovak Republic
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Abstract
Oxysterols are biologically active molecules that result from the oxidation of cholesterol. Several oxysterols are found in macrophages and macrophage-derived 'foam cells' in atherosclerotic tissue. Lipophilic oxysterols penetrate cell membranes and, therefore, their concentrations can reach harmful levels in endothelial and smooth muscle cells located in close proximity to the atherosclerotic plaques or inflammatory zones. New findings suggest that the effects of oxysterols on cardiomyocytes can lead to cell hypertrophy and death. This may make oxysterols one of the major factors precipitating morbidity in atherosclerosis-induced cardiac diseases and inflammation-induced heart complications. The pathological actions of oxysterols on muscle cells were shown to depend on dysfunctional Ca(2+) signaling; however, the mechanisms of the effects remain to be elucidated. Understanding the effects of oxysterols could lead to therapies that modulate malfunction of cardiomyocytes. This review discusses the experimental findings and the relevance of oxysterols to heart failure, and suggests strategies for important future investigations.
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Affiliation(s)
- Valeriy Lukyanenko
- Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, MD 21201, USA.
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18
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Thyroid hormones and cardiac arrhythmias. Vascul Pharmacol 2009; 52:102-12. [PMID: 19850152 DOI: 10.1016/j.vph.2009.10.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 10/05/2009] [Indexed: 01/09/2023]
Abstract
Thyroid hormone plays an important role in cardiac electrophysiology and Ca2+ handling through both genomic and nongenomic mechanisms of action, while both actions can interfere. Chronic changes in the amount of circulating thyroid hormone due to thyroid dysfunction or systemic disease result in structural, electrophysiological and Ca2+ handling remodeling, while acute changes may affect basal activity of cardiac cells membrane systems. Consequently, long-term or rapid modulation of sarcolemmal ion channels, Ca2+ cycling proteins and intercellular communicating channels by thyroid hormone may affect heart function as well as susceptibility of the heart to arrhythmias. This aspect including pro- and anti-arrhythmic potential of thyroid hormone is highlighted in this review.
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Lukyanenko V, Chikando A, Lederer WJ. Mitochondria in cardiomyocyte Ca2+ signaling. Int J Biochem Cell Biol 2009; 41:1957-71. [PMID: 19703657 PMCID: PMC3522519 DOI: 10.1016/j.biocel.2009.03.011] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 03/20/2009] [Accepted: 03/26/2009] [Indexed: 10/20/2022]
Abstract
Ca(2+) signaling is of vital importance to cardiac cell function and plays an important role in heart failure. It is based on sarcolemmal, sarcoplasmic reticulum and mitochondrial Ca(2+) cycling. While the first two are well characterized, the latter remains unclear, controversial and technically challenging. In mammalian cardiac myocytes, Ca(2+) influx through L-type calcium channels in the sarcolemmal membrane triggers Ca(2+) release from the nearby junctional sarcoplasmic reticulum to produce Ca(2+) sparks. When this triggering is synchronized by the cardiac action potential, a global [Ca(2+)](i) transient arises from coordinated Ca(2+) release events. The ends of intermyofibrillar mitochondria are located within 20 nm of the junctional sarcoplasmic reticulum and thereby experience a high local [Ca(2+)] during the Ca(2+) release process. Both local and global Ca(2+) signals may thus influence calcium signaling in mitochondria and, reciprocally, mitochondria may contribute to the local control of calcium signaling. In addition to the intermyofibrillar mitochondria, morphologically distinct mitochondria are also located in the perinuclear and subsarcolemmal regions of the cardiomyocyte and thus experience a different local [Ca(2+)]. Here we review the literature in regard to several issues of broad interest: (1) the ultrastructural basis for mitochondrion - sarcoplasmic reticulum cross-signaling; (2) mechanisms of sarcoplasmic reticulum signaling; (3) mitochondrial calcium signaling; and (4) the possible interplay of calcium signaling between the sarcoplasmic reticulum and adjacent mitochondria. Finally, this review discusses experimental findings and mathematical models of cardiac calcium signaling between the sarcoplasmic reticulum and mitochondria, identifies weaknesses in these models, and suggests strategies and approaches for future investigations.
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Affiliation(s)
- Valeriy Lukyanenko
- Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, MD 21201, USA.
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20
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Sulman T, Katsnelson LB, Solovyova O, Markhasin VS. Mathematical modeling of mechanically modulated rhythm disturbances in homogeneous and heterogeneous myocardium with attenuated activity of na+ -k+ pump. Bull Math Biol 2008; 70:910-49. [PMID: 18259823 DOI: 10.1007/s11538-007-9285-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Accepted: 10/03/2007] [Indexed: 10/22/2022]
Abstract
A mathematical model of the cardiomyocyte electromechanical function is used to study contribution of mechanical factors to rhythm disturbances in the case of the cardiomyocyte calcium overload. Particular attention is paid to the overload caused by diminished activity of the sodium-potassium pump. It is shown in the framework of the model, where mechano-calcium feedback is accounted for that myocardium mechanics may significantly enhance arrhythmogenicity of the calcium overload. Specifically, a role of cross-bridge attachment/detachment processes, a role of mechanical conditions of myocardium contractions (length, load), and a role of myocardium viscosity in the case of simulated calcium overload have been revealed. Underlying mechanisms are analyzed. Several approaches are designed in the model and compared to each other for recovery of the valid myocardium electrical and mechanical performance in the case of the partially suppressed sodium-potassium pump.
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Affiliation(s)
- Tatiana Sulman
- Institute of Immunology and Physiology, Ural Division of the Russian Academy of Sciences, Bldg. 91, Pervomayskaya str., 620041, Ekaterinburg, Russia
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21
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Rickover O, Zinman T, Kaplan D, Shainberg A. Exogenous nitric oxide triggers classic ischemic preconditioning by preventing intracellular Ca2+ overload in cardiomyocytes. Cell Calcium 2007; 43:324-33. [PMID: 17692373 DOI: 10.1016/j.ceca.2007.06.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 06/20/2007] [Accepted: 06/20/2007] [Indexed: 11/28/2022]
Abstract
The involvement of nitric oxide (NO) in the late phase of ischemic preconditioning is well established. However, the role of NO as a trigger or mediator of "classic preconditioning" remains to be determined. The present study was designed to investigate the effects of NO on calcium homeostasis in cultured newborn rat cardiomyocytes in normoxia and hypoxia. We found that treatment with the NO donor, sodium nitroprusside (SNP) induced a sustained elevation of intracellular calcium level ([Ca(2+)](i)) followed by a decrease to control levels. Elevation of extracellular calcium, which generally occurs during ischemia, caused an immediate increase in [Ca(2+)](i) and arrhythmia in cultures of newborn cardiomyocytes. Treatment with SNP decreased [Ca(2+)](i) to control levels and re-established synchronized beating of cardiomyocytes. A decrease in extracellular [Na(+)], which inhibits the Na(+)/Ca(2+) exchanger, did not prevent [Ca(2+)](i) reduction by SNP. In contrast, application of thapsigargin, an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a), increased [Ca(2+)](i), and in its presence, SNP did not reduce [Ca(2+)](i), indicating that Ca(2+) reduction is achieved via activation of SERCA2a. The results obtained suggest that activation of SERCA2a by SNP increases Ca(2+) uptake into the sarcoplasmic reticulum (SR) and prevents cytosolic Ca(2+) overload, which might explain the protective effect of SNP from hypoxic damage.
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Affiliation(s)
- Ophra Rickover
- Gonda (Goldschmied) Medical Diagnostic Research Center, The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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Bonnemeier H, Schäfer U, Ortak J, Kurz T, Katus HA, Richardt G, Schunkert H. Low doses of intracoronary enalaprilat suppress reperfusion-associated ventricular arrhythmias after primary percutaneous coronary interventions for acute myocardial infarction. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2007; 30 Suppl 1:S160-5. [PMID: 17302696 DOI: 10.1111/j.1540-8159.2007.00629.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND In the era of early reperfusion therapy, life-threatening ventricular arrhythmias (VA) remain common after recanalization of an occluded coronary artery. Experimental studies reported that angiotensin-converting (ACE) inhibitors suppress reperfusion-induced VA. However, whether ACE inhibitors lower the incidence of reperfusion clinical VA is unknown. We examined the effects of low doses of intracoronary (i.c.) enalaprilat (EN) as an adjunct to direct percutaneous coronary interventions (PCI) on reperfusion VA in the acute phase of myocardial infarction (MI). METHODS We randomly assigned 22 patients with a first acute MI, who underwent successful direct PCI, to EN, 50 mug, i.c., or placebo (PL), administered immediately after reperfusion. VA were manually edited and counted from 24-hour Holter recordings begun upon hospital admission. RESULTS There were no significant between-groups differences in clinical characteristics. Mean RR interval before and after PCI, and the incidence of VA before PCI were similar in both groups. After PCI the incidence of reperfusion-induced VA was significantly lower in the EN-treated group (VPB/h: PL 29.9 +/- 12 vs EN 43.2 +/- 42, P < 0.05; couplets/h: EN 0.9 +/- 0.7 vs PL 4.1 +/- 5.0, P < 0.01; triplets/h: EN 0.3 +/- 0.2 vs PL 1.2 +/- 1.5, P < 0.05; ventricular tachycardia/h: EN 0.3 +/- 0.1 vs PL 0.8 +/- 0.5, P < 0.01). CONCLUSIONS Compared with PL, i.c. EN significantly lowered the incidence of reperfusion-associated VA. This previously unrecognized antiarrhythmic effect might be an important therapeutic benefit conferred by ACE inhibitors, beyond limitation of infarct size.
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Affiliation(s)
- Hendrik Bonnemeier
- Medizinische Klinik II, Universitätsklinikum Schleswig-Holstein Campus Lübeck, Lübeck, Germany.
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23
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Bonnemeier H, Schäfer U, Kurz T, Ortak J, Hartmann F, Katus HA, Richardt G, Schunkert H. Effects of Intracoronary Low-Dose Enalaprilat on Ventricular Repolarization Dynamics After Direct Percutaneous Intervention for Acute Myocardial Infarction. Pacing Clin Electrophysiol 2007; 30:631-7. [PMID: 17461873 DOI: 10.1111/j.1540-8159.2007.00724.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Data from animal models suggest that inhibition of angiotensin converting enzymes result in an increased ventricular electrical stability after reperfusion in acute myocardial infarction (MI). As electrical stability is largely dependent on ventricular repolarization, we sought to determine the impact of low-dose intracoronary (i.c.) application of enalaprilat (EN) as an adjunct to direct primary coronary intervention (PCI) on QT dynamics in the acute phase of MI. METHODS Twenty-two consecutive patients with a first acute MI who underwent successful direct PCI (TIMI 3 flow) were randomized to i.c. EN (50 microg) or placebo/saline (PL), given immediately after reopening of the infarct vessel. On hospital admission, a 24-hour-Holter-electrocardiogram (ECG) was initiated. Slopes of the linear QT/RR regression were determined for the time intervals before reperfusion and after reperfusion. RESULTS A total of 7 patients in the EN group and 8 patients in the PL group had valid ECG recordings for beat-to-beat QT analysis. Mean RR interval and mean QT interval were not significantly different between the EN and the PL groups both before and after PCI. There were also no significant differences regarding QT/RR slopes between EN and PL groups before PCI. After PCI, QT/RR slopes significantly decreased in the EN group (0.169 +/- 0.04 to 0.121 +/- 0.03; P < 0.01), whereas there were no significant alterations in the PL group (0.175 +/- 0.04 to 0.171 +/- 0.03; P = ns). CONCLUSIONS Intracoronary EN therapy as an adjunct to direct PCI significantly decreases QT/RR slopes, suggesting a normalization of the coupling between heart rate and repolarization by improving electrical restitution. Thus, our findings offer new insights into possible beneficial effects of ACE inhibition on cardiac electrical stability in acute MI.
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24
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Zinman T, Shneyvays V, Tribulova N, Manoach M, Shainberg A. Acute, nongenomic effect of thyroid hormones in preventing calcium overload in newborn rat cardiocytes. J Cell Physiol 2006; 207:220-31. [PMID: 16331687 DOI: 10.1002/jcp.20562] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In this study, we examined the acute effects of thyroid hormones (TH) T(3) and T(4), leading to improvement of myocardial function through activation of Ca(2+) extrusion mechanisms and, consequently, prevention of intracellular calcium overload. Extracellular calcium elevation from 1.8 to 3.8 mM caused immediate increase in intracellular calcium level ([Ca(2+)](i)) in newborn cardiomyocyte cultures. Administration of 10 or 100 nM T(3) or T(4) rapidly (within 10 sec) decreased [Ca(2+)](i) to its control level. Similar results were obtained when [Ca(2+)](i) was elevated by decreasing extracellular Na(+) concentration, causing backward influx of Ca(2+) through Na(+)/Ca(2+) exchanger, or by administration of caffeine, releasing Ca(2+) from the sarcoplasmic reticulum (SR). Under these conditions, T(3) or T(4) decreased [Ca(2+)](i). T(3) and T(4) also exhibited protective effects during ischemia. T(3) or T(4) presence during hypoxia for 120 min in culture medium restricted the increase of [Ca(2+)](i) and prevented the pathological effects of its overload. An inhibitor of SR Ca(2+)-ATPase (SERCA2a), thapsigargin, increases [Ca(2+)](i) and in its presence neither T(3) nor T(4) had any effect on the [Ca(2+)](i) level. The reduction of [Ca(2+)](i) level by T(3) and T(4) was also blocked in the presence of H-89 (a PKA inhibitor), and by calmodulin inhibitors. The effect of TH on the reduction of [Ca(2+)](i) was prevented by propranolol, indicating that the hormones exert their effect through interaction with adrenergic receptors. These results support our hypothesis that TH prevent calcium overload in newborn rat cardiomyocytes, most likely by a direct, acute, and nongenomic effect on Ca(2+) transport into the SR.
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Affiliation(s)
- T Zinman
- Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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25
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Nagai H, Minatoguchi S, Chen XH, Wang N, Arai M, Uno Y, Lu C, Misao Y, Onogi H, Kobayashi H, Takemura G, Maruyama R, Fujiwara T, Fujiwara H. Cilnidipine, an N+L-Type Dihydropyridine Ca Channel Blocker, Suppresses the Occurrence of Ischemia/Reperfusion Arrhythmia in a Rabbit Model of Myocardial Infarction. Hypertens Res 2005; 28:361-8. [PMID: 16138567 DOI: 10.1291/hypres.28.361] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Dihydropyridine Ca channel blockers are widely prescribed for the treatment of hypertension and coronary artery diseases, but it remains unknown whether these agents protect against arrhythmias. We investigated whether cilnidipine, an N+L-type Ca channel blocker, reduces the incidences of ventricular premature beats (VPBs) and, if so, via what mechanisms. Japanese white rabbits underwent 30 min of ischemia and 48 h of reperfusion. Cilnidipine (0.5 or 1.0 microg/kg/min, i.v.) or saline (i.v.) was administered from 30 min before ischemia to 30 min after reperfusion. Electrocardiogram and blood pressure were monitored and the incidences of VPBs were measured. At 48 h after reperfusion, myocardial infarct was measured. Myocardial interstitial noradrenaline levels were determined before, during and after 30 min of ischemia with cilnidipine (0.5 and 1.0 microg/kg/min) or saline. The incidences of VPBs during ischemia and reperfusion were significantly attenuated in the cilnidipine 0.5 group (15.6 +/- 3.1 and 6.8 +/- 1.9 beats/30 min) and in the cilnidipine 1.0 group (10.4 +/- 4.9 and 3.5 +/- 1.0 beats/30 min) compared to the control group (27.2 +/- 4.5 and 24.2 +/- 3.1 beats/30 min), respectively. Myocardial interstitial noradrenaline levels were significantly reduced in the cilnidipine 0.5 and 1.0 groups compared to the control group during ischemia and reperfusion. The antiarrhythmic effect of cilnidipine may be related to the attenuation of cardiac sympathetic nerve activity. This finding may provide new insight into therapeutic strategies for hypertensive patients with ventricular arrhythmias.
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Affiliation(s)
- Hiroshi Nagai
- Second Department of Internal Medicine, Gifu University School of Medicine, Gifu, Japan
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26
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Omichi C, Lamp ST, Lin SF, Yang J, Baher A, Zhou S, Attin M, Lee MH, Karagueuzian HS, Kogan B, Qu Z, Garfinkel A, Chen PS, Weiss JN. Intracellular Ca dynamics in ventricular fibrillation. Am J Physiol Heart Circ Physiol 2004; 286:H1836-44. [PMID: 14704235 DOI: 10.1152/ajpheart.00123.2003] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the heart, membrane voltage ( Vm) and intracellular Ca (Cai) are bidirectionally coupled, so that ionic membrane currents regulate Cai cycling and Cai affects ionic currents regulating action potential duration (APD). Although Cai reliably and consistently tracks Vm at normal heart rates, it is possible that at very rapid rates, sarcoplasmic reticulum Cai cycling may exhibit intrinsic dynamics. Non-voltage-gated Cai release might cause local alternations in APD and refractoriness that influence wavebreak during ventricular fibrillation (VF). In this study, we tested this hypothesis by examining the extent to which Cai is associated with Vm during VF. Cai transients were mapped optically in isolated arterially perfused swine right ventricles using the fluorescent dye rhod 2 AM while intracellular membrane potential was simultaneously recorded either locally with a microelectrode (5 preparations) or globally with the voltage-sensitive dye RH-237 (5 preparations). Mutual information (MI) is a quantitative statistical measure of the extent to which knowledge of one variable ( Vm) predicts the value of a second variable (Cai). MI was high during pacing and ventricular tachycardia (VT; 1.13 ± 0.21 and 1.69 ± 0.18, respectively) but fell dramatically during VF (0.28 ± 0.06, P < 0.001). Cai at sites 4–6 mm apart also showed decreased MI during VF (0.63 ± 0.13) compared with pacing (1.59 ± 0.34, P < 0.001) or VT (2.05 ± 0.67, P < 0.001). Spatially, Cai waves usually bore no relationship to membrane depolarization waves during nonreentrant fractionated waves typical of VF, whereas they tracked each other closely during pacing and VT. The dominant frequencies of Vm and Cai signals analyzed by fast Fourier transform were similar during VT but differed significantly during VF. Cai is closely associated with Vm closely during pacing and VT but not during VF. These findings suggest that during VF, non-voltage-gated Cai release events occur and may influence wavebreak by altering Vm and APD locally.
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Affiliation(s)
- Chikaya Omichi
- Division of Cardiology, Cedars-Sinai Medical Center and Center for Health Sciences, University of California-Los Angeles Cardiovascular Research Laboratory, David Geffen School of Medicine, UCLA, Los Angeles, California 90095-1760, USA
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27
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Seki S, Tribulova N, Manoach M, Mochizuki S. Modulation of intracellular Ca(2+) concentration by tedisamil, a class III antiarrhythmic agent, in isolated heart preparation. Life Sci 2003; 73:1805-11. [PMID: 12888119 DOI: 10.1016/s0024-3205(03)00538-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
New class III antiarrhythmic/defibrillating compound tedisamil was shown to facilitate termination of atrial and ventricular fibrillation in experimental as well as clinical conditions. However, class III-related inhibition of K(+) current associated with prolongation of repolarization can not solely explain its defibrillating ability. Following recent findings it was hypothesized that defibrillating effect of tedisamil is likely due to its sympathomimetic feature linked with modulation of intracellular calcium. Results of this study obtained in isolated heart preparation showed that elevated intracellular Ca(2+) free concentration was decreased by administration of tedisamil in concentration that did not induce Q-T interval prolongation. Due to species differences the effective concentration was in rat 10(-7) M, while in guinea pig 10(-5) M. On the contrary, further dramatic increase of elevated Ca(2+) was detected upon administration of tedisamil in concentration that markedly prolonged Q-T interval (10(-5) M in rat). It is concluded that defibrillating ability of tedisamil is most likely associated with attenuation of abnormal and harmful intracellular Ca(2+) elevation (that is highly arrhythmogenic) than with prolongation of APD or Q-T interval.
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Affiliation(s)
- S Seki
- Division of Cardiology, Department of Internal Medicine, Jikei University School of Medicine, Tokyo, Japan
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Structural Substrates Involved in the Development of Severe Arrhythmias in Hypertensive Rat and Aged Guinea Pig Hearts. ACTA ACUST UNITED AC 2003. [DOI: 10.1007/978-1-4419-9262-8_27] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
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Marks AR, Priori S, Memmi M, Kontula K, Laitinen PJ. Involvement of the cardiac ryanodine receptor/calcium release channel in catecholaminergic polymorphic ventricular tachycardia. J Cell Physiol 2002; 190:1-6. [PMID: 11807805 DOI: 10.1002/jcp.10031] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The cardiac ryanodine receptor (RyR2), the major calcium release channel on the sarcoplasmic reticulum (SR) in cardiomyocytes, has recently been shown to be involved in at least two forms of sudden cardiac death (SCD): (1) Catecholaminergic polymorphic ventricular tachycardia (CPVT) or familial polymorphic VT (FPVT); and (2) Arrhythmogenic right ventricular dysplasia type 2 (ARVD2). Eleven RyR2 missense mutations have been linked to these diseases. All eleven RyR2 mutations cluster into 3 regions of RyR2 that are homologous to the three malignant hyperthermia (MH)/central core disease (CCD) mutation regions of the skeletal muscle ryanodine receptor/calcium release channel RyR1. MH/CCD RyR1 mutations have been shown to alter calcium-induced calcium release. Sympathetic nervous system stimulation leads to phosphorylation of RyR2 by protein kinase A (PKA). PKA phosphorylation of RyR2 activates the channel. In conditions associated with high rates of SCD such as heart failure RyR2 is PKA hyperphosphorylated resulting in "leaky" channels. SR calcium leak during diastole can generate "delayed after depolarizations" that can trigger fatal cardiac arrhythmias (e.g., VT). We propose that RyR2 mutations linked to genetic forms of catecholaminergic-induced SCD may alter the regulation of the channel resulting in increased SR calcium leak during sympathetic stimulation.
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Affiliation(s)
- Andrew R Marks
- Center for Molecular Cardiology, Department of Pharmacology, Box 65, Columbia University College of Physicians and Surgeons, 630 West 168th Street, New York, NY 10032, USA.
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Min JY, Ding B, Wang JF, Sullivan MF, Morgan JP. Metoprolol attenuates postischemic depressed myocardial function in papillary muscles isolated from normal and postinfarction rat hearts. Eur J Pharmacol 2001; 422:115-25. [PMID: 11430922 DOI: 10.1016/s0014-2999(01)01050-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The present study was designed to test the hypothesis that metoprolol treatment may enhance tolerance to ischemia in normal and postinfarction rat myocardium. Myocardial infarction was induced by permanent ligation of the left coronary artery in adult rats. Animals were divided into sham-operated and infarction groups with or without metoprolol treatment. Metoprolol treatment (60 mg/kg/day via gastric gavage) was started on the second day after surgery and continued until sacrifice at 6 weeks after myocardial infarction. Isometric force and intracellular Ca(2+) ([Ca(2+)](i)) transients were simultaneously recorded in isolated left ventricular papillary muscles. Ischemia was simulated by immersing the muscles into fluorocarbon with hypoxia. Metoprolol treatment induced a significant improvement of isometric force and ameliorated diastolic [Ca(2+)](i) overload in postinfarction rat myocardium at baseline. Metoprolol treatment also reduced diastolic [Ca(2+)](i), ameliorated the depression of developed tension during ischemia, and enhanced recovery of postischemic depressed myocardial function in sham-operated and postinfarction rat papillary muscles. Protein levels of the sarcoplasmic reticulum Ca(2+) ATPase of left ventricles and postischemic papillary muscles from metoprolol-treated rats were higher than those in placebo-treated animals. We concluded, therefore, that metoprolol treatment produced appreciable improvement of intracellular Ca(2+) handling during ischemia-reoxygenation cycles, and enhanced recovery of postischemic depressed myocardial function in both normal and postinfarction rat myocardium.
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Affiliation(s)
- J Y Min
- The Charles A. Dana Research Institute and the Harvard-Thorndike Laboratory, Cardiovascular Division, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
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31
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Abstract
Calcium (Ca2+) ions are second messengers in signaling pathways in all types of cells. They regulate muscle contraction, electrical signals which determine the cardiac rhythm and cell growth pathways in the heart. In the past decade cDNA cloning has provided clues as to the molecular structure of the intracellular Ca2+ release channels (ryanodine receptors, RyR, and inositol 1,4,5-trisphosphate receptors, IP3R) on the sarcoplasmic and endoplasmic reticulum (SR/ER) and an understanding of how these molecules regulate Ca2+ homeostasis in the heart is beginning to emerge. The intracellular Ca2+ release channels form a distinct class of ion channels distinguished by their structure, size, and function. Both RyRs and IP3Rs have gigantic cytoplasmic domains that serve as scaffolds for modulatory proteins that regulate the channel pore located in the carboxy terminal 10% of the channel sequence. The channels are tetramers comprised of four RyR or IP3R subunits. RyR2 is required for excitation-contraction (EC) coupling in the heart. Using co-sedimentation and co-immunoprecipitation we have defined a macromolecular complex comprised of RyR2, FKBP12.6, PKA, the protein phosphatases PP1 and PP2A, and an anchoring protein mAKAP. We have shown that protein kinase A (PKA) phosphorylation of RyR2 dissociates FKBP12.6 and regulates the channel open probability (P(o)). In failing human hearts RyR2 is PKA hyperphosphorylated resulting in defective channel function due to increased sensitivity to Ca2+-induced activation.
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Affiliation(s)
- A R Marks
- Center for Molecular Cardiology, Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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Amitzur G, Pogatz V, Novikov I, Kaplinsky E, Eldar M. Modulation of ventricular fibrillation in the isolated heart: the role of slow calcium channel activity under continuous perfusion. J Cardiovasc Pharmacol 2000; 35:16-28. [PMID: 10630729 DOI: 10.1097/00005344-200001000-00003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The individual activities of sodium versus calcium channels in the initiation and maintenance of ventricular fibrillation (VF) have not been fully elucidated. Therefore we studied in isolated heart under nonischemic conditions (a) VF characteristics in untreated hearts, (b) initiation and maintenance of VF during attenuation and blockade of slow calcium channel activity by verapamil, (c) the effect of these interventions on the characteristics of the induced arrhythmia, and (d) the impact of heart weight on the observed results. Measurements were carried out in both ventricles of isolated feline hearts during ventricular pacing and 8 min of electrically induced tachyarrhythmias. Measurements during ventricular pacing included epicardial conduction time (CON), refractoriness (VRP), and all tissue resistivity (ATR; an indirect measure of changes in intercellular electrical coupling). Measurements during arrhythmia included ATR, peak frequency [PKF; a measure of the prevailing frequency based on Fast Fourier Transform (FFT) analysis], and normalized entropy (ENTROP; a measure of the degree of arrhythmia organization). Measurements during sinus rhythm and arrhythmia were repeated after blocking of calcium channel activity by verapamil at a high concentration (1.8x10(-4) M; n = 8) and at two low concentrations (1.5 and 3.0x10(-7) M; n = 8). In untreated hearts, mainly VF episodes were induced, exhibiting a low degree of organization with no significant change in this parameter throughout the arrhythmia (8 min). In the left ventricle (LV; and to a much smaller extent in the right ventricle; RV), a gradual increase in PKF was observed throughout the arrhythmia, with no significant change in ATR. Verapamil at a high concentration increased CON, but did not affect VRP. These findings were similar in both ventricles. In lower verapamil concentrations, CON was not affected, and VRP was slightly shortened. After treatment with a high verapamil concentration, VF could not be induced in small hearts but was always inducible in large hearts. Transient arrhythmia episodes appeared in 9% of untreated hearts, in 25% with "high" verapamil, and in 25-37% with "low" verapamil. With all verapamil concentrations, the induced arrhythmia was modulated from a predominantly VF to PVT or MVT type, manifested by a decrease in ENTROP. This effect was less pronounced with increasing heart weight. No significant change in PKF and in ATR was obtained with verapamil throughout the arrhythmia. It is suggested that verapamil modulation of arrhythmia organization is associated mainly with a direct blockade of calcium channel activity (perhaps by causing reduction in the safety factor for conduction), rather than with indirect modulation of electrophysiological parameters.
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Affiliation(s)
- G Amitzur
- Neufeld Cardiac Research Institute, Sackler School of Medicine, Tel Aviv University, Sheba Medical Center, Tel Hashomer, Israel
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Ohara F, Sugimoto T, Yamamoto N, Ohkubo K, Maeda K, Ozaki T, Seki J, Goto T. Preischemic and postischemic treatment with a new Na+/H+-exchange inhibitor, FR183998, shows cardioprotective effects in rats with cardiac ischemia and reperfusion. J Cardiovasc Pharmacol 1999; 34:848-56. [PMID: 10598129 DOI: 10.1097/00005344-199912000-00012] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study describes the pharmacologic profile of a new Na+/H(+)-exchange inhibitor, FR183998, in anesthetized rats. FR183998 had a potent inhibitory effect on Na+/H+ exchange of rat lymphocytes with median inhibitory (IC50) value of 0.3 nM. Treatment with FR183998 (0.01-0.32 mg/kg, i.v.) reduced or completely abolished ventricular fibrillation and mortality induced by 5-min ischemia followed by reperfusion, when it was administered not only 5 min before ischemia but also 1 min before reperfusion. Myocardial infarct size induced by 30-min ischemia and 60-min reperfusion was reduced significantly in a dose-dependent manner by FR183998 (0.1-1.0 mg/kg, i.v.) when the drug was administered preischemically or at an early phase of ischemia. The ventricular tachycardia and the ventricular fibrillation observed during the ischemic period also were suppressed significantly. These results indicate that FR183998 has a strong inhibitory effect on Na+/H+ exchange and suggest that treatment with FR183998 either before or immediately after the onset of ischemia can prevent the occurrence of arrhythmias and myocardial cell necrosis in situations of ischemia and reperfusion.
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Affiliation(s)
- F Ohara
- Department of Cardiovascular Diseases, Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co., Ltd, Osaka, Japan
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Ohkusa T, Ueyama T, Yamada J, Yano M, Fujumura Y, Esato K, Matsuzaki M. Alterations in cardiac sarcoplasmic reticulum Ca2+ regulatory proteins in the atrial tissue of patients with chronic atrial fibrillation. J Am Coll Cardiol 1999; 34:255-63. [PMID: 10400019 DOI: 10.1016/s0735-1097(99)00169-2] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES Our purpose was to determine whether atrial fibrillation (AF) patients have alterations in sarcoplasmic reticulum (SR) Ca2+ regulatory proteins in the atrial myocardium. BACKGROUND Clinically, AF is the most frequently encountered arrhythmia. Recent studies indicate that an inability to maintain intracellular Ca2+ homeostasis with a consequent increase in membrane-triggered activity could be the primary initiating factor in some circumstances, and that cytosolic Ca2+ abnormalities are an important mediator of sustained AF. METHODS We measured the maximum number of [3H]ryanodine binding sites (Bmax) and the expression levels of ryanodine receptor (RyR) mRNA and calcium-adenosine triphosphatase (Ca2+-ATPase) mRNA in atrial myocardial tissue from 13 patients with AF due to mitral valvular disease (MVD) and 9 patients with normal sinus rhythm (NSR). RESULTS In AF patients, 1) Bmax was significantly lower in each atrium (0.21+/-0.03 pmol/mg [right], 0.16+/-0.04 pmol/mg [left]) than in the right atrium (0.26+/-0.08 pmol/mg) of NSR patients; 2) Bmax was significantly lower in the left atrium than in the right atrium; 3) Bmax in the left atrium was significantly lower at higher levels of pulmonary capillary wedge pressure; 4) the expression level of RyR mRNA was significantly lower in both the left (1.24 x 10(-2)+/-1.28 x 10(-2)) and right (1.70 x 10(-2)+/-1.78 x 10(-2)) atrium than in the right atrium of NSR patients (6.11 x 10(-2)+/-2.79 x 10(-2)); and 5) the expression level of Ca2+-ATPase mRNA was significantly lower in both the left (5.67 x 10(-2)+/-4.01 x 10(-2)) and right (7.71 x 10(-2)+/-3.56 x 10(-2)) atrium than in the right atrium (12.60 x 10(-2)+/-3.92 x 10(-2)) of NSR patients. CONCLUSIONS These results provide the first direct evidence of abnormalities in the Ca2+ regulatory proteins of the atrial myocardium in chronic AF patients. Conceivably, such abnormalities may be involved in the initiation and/or perpetuation of AF.
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Affiliation(s)
- T Ohkusa
- Second Department of Internal Medicine, Yamaguchi University School of Medicine, Ube, Japan.
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35
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Abstract
The aim of this review is to provide basic information on the electrophysiological changes during acute ischemia and reperfusion from the level of ion channels up to the level of multicellular preparations. After an introduction, section II provides a general description of the ion channels and electrogenic transporters present in the heart, more specifically in the plasma membrane, in intracellular organelles of the sarcoplasmic reticulum and mitochondria, and in the gap junctions. The description is restricted to activation and permeation characterisitics, while modulation is incorporated in section III. This section (ischemic syndromes) describes the biochemical (lipids, radicals, hormones, neurotransmitters, metabolites) and ion concentration changes, the mechanisms involved, and the effect on channels and cells. Section IV (electrical changes and arrhythmias) is subdivided in two parts, with first a description of the electrical changes at the cellular and multicellular level, followed by an analysis of arrhythmias during ischemia and reperfusion. The last short section suggests possible developments in the study of ischemia-related phenomena.
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Affiliation(s)
- E Carmeliet
- Centre for Experimental Surgery and Anesthesiology, University of Leuven, Leuven, Belgium
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36
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Conradie S, Coetzee A, Coetzee J. Anesthetic modulation of myocardial ischemia and reperfusion injury in pigs: comparison between halothane and sevoflurane. Can J Anaesth 1999; 46:71-81. [PMID: 10078408 DOI: 10.1007/bf03012519] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE Halothane offers protection against the reperfusion injury of the myocardium. This study compared sevoflurane with halothane in its potential to modulate the effects of acute severe ischemia and reperfusion on the myocardium. METHODS Experiments were conducted on 25 pigs. Anesthesia consisted of thiopental, vecuronium and fentanyl. The lungs were mechanically ventilated with oxygen and nitrogen. Animals were randomly allocated to receive either I MAC halothane or sevoflurane. A control group received fentanyl and pentobarbital. Regional myocardial function was measured with sonomicrometers. The left anterior descending coronary artery was occluded for 15 min followed by 60 min reperfusion. RESULTS Neither halothane nor sevoflurane protected the heart against the effects of acute and severe regional myocardial ischemia. During reperfusion, 89% of the animals receiving sevoflurane suffered from ventricular fibrillation compared with 30% in the halothane group (P < 0.005). Five minutes into the reperfusion period the animals subjected to halothane anesthesia demonstrated an 88% recovery in regional myocardial systolic function while in the sevoflurane group the recovery was 40% of pre-ischemic control (P < 0.05). CONCLUSION Halothane is associated with less reperfusion arrhythmias and, in addition, recovery of regional myocardial function during reperfusion was more rapid in the presence of halothane than with sevoflurane.
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Affiliation(s)
- S Conradie
- Department of Anesthesiology, University of Stellenbosch Medical School, Tygerberg, South Africa
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Muller CA, Opie LH, McCarthy J, Hofmann D, Pineda CA, Peisach M. Effects of mibefradil, a novel calcium channel blocking agent with T-type activity, in acute experimental myocardial ischemia: maintenance of ventricular fibrillation threshold without inotropic compromise. J Am Coll Cardiol 1998; 32:268-74. [PMID: 9669280 DOI: 10.1016/s0735-1097(98)00182-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES We tested whether mibefradil, a selective T-type calcium channel blocking agent, could differentially inhibit experimental ventricular arrhythmogenesis more than contractility during acute regional ischemia and reperfusion compared with that during L-channel blockade by verapamil. BACKGROUND T-type calcium channels are found in nodal and conduction tissue and in vascular smooth muscle, but in much lower density in contractile myocardium. The potential role of mibefradil in ventricular arrhythmogenesis remains unclear. METHODS Mibefradil (Ro 40-5967, 1 mg/kg body weight intravenously [i.v.]) was given as a bolus 30 min before anterior descending coronary artery ligation, followed by 2 mg/kg per h i.v. during 20 min of ischemia and 25 min of reperfusion in open chest pigs. In a second group, mibefradil was given in a dose twice as high. A third group received verapamil (0.3 mg/kg i.v.), followed by an infusion of 0.6 mg/kg per h. RESULTS During the ischemic period, the low (clinically relevant) dose of mibefradil prevented the fall of the ventricular fibrillation threshold, without depressing the maximal rate of pressure development of the left ventricle (LVmax dP/dt). This low dose increased left ventricular blood flow, whereas peripheral arterial pressure remained unchanged. The higher dose of both mibefradil and verapamil was antiarrhythmic during ischemia, at the cost of depressed contractile activity. During reperfusion, only the higher dose of mibefradil and verapamil was antiarrhythmic but both depressed contractile activity. CONCLUSIONS Mibefradil is antiarrhythmic, without inotropic compromise. Speculatively, both T-type and L-type calcium channel blockade are involved in these effects.
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Affiliation(s)
- C A Muller
- Medical Research Council Heart Research Group, Cape Heart Centre, University of Cape Town, South Africa.
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38
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Bjerneroth G. Alkaline buffers for correction of metabolic acidosis during cardiopulmonary resuscitation with focus on Tribonat--a review. Resuscitation 1998; 37:161-71. [PMID: 9715776 DOI: 10.1016/s0300-9572(98)00051-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A combined hypercarbic and metabolic acidosis develops during the low flow state of cardiac arrest treated with cardiopulmonary resuscitation. Several negative consequences of the acidosis have been demonstrated, two of the most important being reduced contractility of the ischaemic but still beating myocardium and impaired resuscitability of the arrested heart. Even though interventions to re-establish a spontaneous circulation should be the number one priority during cardiopulmonary resuscitation, attempts to treat the acidosis are often carried out in order to avoid the reported negative inotropic effect. Different alkaline buffers have been used, but it has been demonstrated over the years that such treatment may aggravate the situation due to a variety of deleterious side-effects of the buffers. A mixture of THAM, acetate, sodium bicarbonate and phosphate registered as Tribonat has been suggested as a suitable alternative to conventional buffer substances. The problems preceding the designation of Tribonat as well as studies evaluating its effects are reviewed in this article. Tribonat seems to offer a more well-balanced buffering without any major disadvantages compared with previously used alkaline buffers, even though improved survival has not been reported.
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Affiliation(s)
- G Bjerneroth
- Department of Anaesthesiology, Uppsala University Hospital, Sweden
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Manoach M, Varon D, Shainberg A, Zinman T, Isaack A, Rutman IH, Kaplan D, Tribulova N. The protective effect of class III antiarrhythmic agents against calcium overload in cultured myocytes. Life Sci 1997; 61:PL 227-34. [PMID: 9353172 DOI: 10.1016/s0024-3205(97)00742-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Calcium ions have been implicated in the mechanisms of ventricular arrhythmias. Impairment of intercellular coupling by calcium overload is considered to facilitate ventricular fibrillation (VF) and to sup-press its self termination. According to our hypothesis, any compound that decreases intracellular calcium concentration [Ca2+]i during VF can serve as defibrillating drug. In this study, we examined the effect of d-sotalol and tedisamil on calcium overload in cultured, spontaneously beating rat cardiomyocytes. The changes of [Ca2+]i were measured by indo-1 method and the intercellular synchronization by image analysis. The results showed that increase in [Ca2+]o from 1.9 mM to 3.9 mM increased [Ca2+]i from 100 nM to 320 nM and transformed the synchronized cell movement to an asynchronous one. Administration of 5 x 10(-6) M d-sotalol or 10(-6) M tedisamil, decreased the [Ca2+]i to its basic level and restored the synchronized activity. In summary: Our results showed that increase in [Ca2+]i known to cause inhibition of intercellular coupling, that could lead to arrhythmia and fibrillation while d-sotalol or tedisamil prevented this effect. These results support our hypothesis, that class III antiarrhythmic compounds with positive inotropic effect, increase intercellular synchronization, by decreasing free [Ca2+]i, most probably by increasing the Ca2+ uptake by the sarcoplasmic reticulum, and therefore act as a defibrillating compound.
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Affiliation(s)
- M Manoach
- Department of Physiology, Tel Aviv Medical School, Israel
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Aoyagi T, Sugiura S, Eto Y, Yonekura K, Matsumoto A, Yokoyama I, Kobayakawa N, Omata M, Kirimoto T, Hayashi Y, Momomura S. Inhibition of carnitine synthesis protects against left ventricular dysfunction in rats with myocardial ischemia. J Cardiovasc Pharmacol 1997; 30:468-74. [PMID: 9335406 DOI: 10.1097/00005344-199710000-00010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
During myocardial ischemia, inhibition of the carnitine-mediated transportation of fatty acid may be beneficial because it facilitates glucose utilization and prevents an accumulation of fatty acid metabolites. We orally administered 3-(2,2,2-trimethyl hydrazinium) propionate (MET), an inhibitor of carnitine synthesis, for 20 days to rats. Then we evaluated left ventricular (LV) function during brief ischemia by using a buffer-perfused isovolumic heart model. After 15 min of reoxygenation after the transient ischemia, LV peak systolic pressure (PSP) almost completely returned to the baseline level in rats given MET (96 +/- 4%), whereas it was only partially (77 +/- 16%) recovered in the placebo-treated rats. We induced myocardial infarction in other rats by ligating the left anterior descending coronary artery. Then the animals were given MET for 20 days, and LV function was compared. In the placebo-treated rats (with myocardial infarction, but without drug treatment), LVPSP was lower than that in the sham group [108 +/- 19 (n = 10) vs. 136 +/- 15 mm Hg (n = 13); p < 0.05], and the time constant (T) of LV pressure decay was elongated (36 +/- 4 vs. 30 +/- 7 ms; p < 0.05). In MET-treated groups, however, neither PSP nor T differed from those in the sham group. In conclusion, inhibition of the carnitine-mediated transportation of fatty acid by MET protected against left ventricular dysfunction in acute and chronic myocardial ischemia.
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Ehlert FA, Goldberger JJ. Cellular and pathophysiological mechanisms of ventricular arrhythmias in acute ischemia and infarction. Pacing Clin Electrophysiol 1997; 20:966-75. [PMID: 9127403 DOI: 10.1111/j.1540-8159.1997.tb05501.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ventricular arrhythmias in the setting of acute myocardial ischemia and infarction remain a serious health problem because of their sudden and unpredictable nature and their potentially grave results. Electrophysiological changes that may be responsible for these arrhythmias have been described in cardiac cells and in ischemic tissue. Experimental models have played a major role in elucidating the diversity of potential mechanisms for these arrhythmias. Increases in extracellular K+, the presence of toxic metabolites, and the accumulation of catecholamines in ischemic tissue all appear to have a role in arrhythmogenesis. The autonomic nervous system also appears to play a major role in these arrhythmias. With increased understanding of the pathophysiology underlying these arrhythmias, prevention can be enhanced and therapy can be better targeted.
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Affiliation(s)
- F A Ehlert
- Department of Medicine, Northwestern University Medical School, Chicago, Illinois, USA
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42
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Meissner A, Szymanska G, Morgan JP. Effects of dantrolene sodium on intracellular Ca2(+)-handling in normal and Ca2(+)-overloaded cardiac muscle. Eur J Pharmacol 1996; 316:333-42. [PMID: 8982705 DOI: 10.1016/s0014-2999(96)00678-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We investigated the effects of dantrolene sodium on intracellular Ca2+ homeostasis in normal and Ca2+ overloaded rat cardiac muscle. In isometrically contracting rat papillary muscles loaded with the Ca2+ indicator aequorin, dantrolene (50 microM) produced a mild negative inotropic effect (28 +/- 1.8 to 21 +/- 1.1 mN/mm2; mean +/- S.E.; n = 6; P < 0.01), which was paralleled by a decrease in peak systolic [Ca2+]i (0.81 +/- 0.04 to 0.67 +/- 0.04 microM; P < 0.01). In isolated cardiac sarcoplasmic reticulum, dantrolene (50 microM) increased the initial Ca2+ uptake rate by 23% as compared to control preparations (at pCa 6.2: 46.9 +/- 1.6 to 61.1 +/- 2.2 nmol/mg per min; n = 4; P < 0.001). Intracellular Ca2+ overload was provoked in isoproterenol-pretreated (100 microM) preparations with [Ca2+]o = 5.0 mM at a stimulation rate of 1.0 Hz (n = 12). Diastolic Ca2+ oscillations and aftercontractions increased mean diastolic [Ca2+]i (0.33 +/- 0.1 to 0.56 +/- 0.1 microM) and tension (9.5 +/- 1.8 to 15.3 +/- 2.1 mN/mm2), respectively. Addition of dantrolene (50 microM) reduced the amplitude of Ca2+ oscillations and aftercontractions; mean diastolic [Ca2+]i decreased to 0.44 +/- 0.1 microM and diastolic tension to 13.5 +/- 2.2 mN/mm2. We conclude, therefore, that dantrolene sodium modifies Ca2+ handling by the myocardial sarcoplasmic reticulum, an effect that might be useful in cardiac disorders with impaired [Ca2+]i homeostasis.
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Affiliation(s)
- A Meissner
- Department of Cardiology, University of Kiel, Germany
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Bjerneroth G, Li YC, Wiklund L, Ridefelt P. Effect of tris buffer on free cytosolic calcium in myocardial cells. Crit Care Med 1996; 24:1713-8. [PMID: 8874311 DOI: 10.1097/00003246-199610000-00019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To study the effect of tris buffer on free cytosolic calcium in vitro. DESIGN Open, randomized, control trial of dispersed rat myocardial cells. SETTING Experimental laboratory in a large university hospital. SUBJECTS Dispersed myocardial cells from Sprague-Dawley rats. INTERVENTIONS The influences of pure trometamol (tris) and a tris butter mixture, as well as conventional sodium bicarbonate on free cytosolic calcium in suspended rat myocardial cells were studied with the fluorescent intracellular probe fura-2. MEASUREMENTS AND MAIN RESULTS Addition of pure trometamol (tris) resulted in a significant increase of free cytosolic calcium in myocardial cells suspended in a buffer containing 1.25 mM of ionized calcium. The actions of trometamol display a dose-dependency in relation to the concentration of external ionized calcium since the ionized calcium response was reduced in a buffer with 0.5 mM of extracellular ionized calcium. Furthermore, removal of external ionized calcium totally prevented trometamol induced increases of ionized calcium, indicating that this increase is dependent on transmembrane ionized calcium fluxes. When tris buffer mixture was investigated in 1.25 mM of calcium, as well as 0.5 mM of external ionized calcium, a decrease of ionized calcium was noted initially, followed by an increase during the observation period. Addition of sodium bicarbonate to the two experimental settings resulted in a more prominent initial decrease of ionized calcium, followed by a slower increase which did not reach the initial values during the 20-min observation period. Extracellular pH was also included as a variable. When the cells were suspended in a buffer containing 1.25 mM of ionized calcium with a pH of 6.80 instead of 7.40 (as above), addition of pure trometamol also resulted in an increase of ionized calcium; however, after 20 mins this increase was smaller as compared with the results above. When tris buffer mixture as well as sodium bicarbonate was added, initial decreases of ionized calcium were recorded, followed by smaller increases during the observation period, compared with the increase in buffers with a pH of 7.40. CONCLUSIONS Pure trometamol (tris) induces an increase in free cytosolic calcium in suspended myocardial cells.
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Affiliation(s)
- G Bjerneroth
- Department of Anaesthesiology, Uppsala University Hospital, Sweden
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Ebihara Y, Tani M, Shinmura K, Nakamura Y, Asakura Y. Effect of stepwise normalization of perfusate pH on post-ischemic functional recovery and Ca2+ overload in isolated rat hearts. JAPANESE CIRCULATION JOURNAL 1996; 60:683-90. [PMID: 8902586 DOI: 10.1253/jcj.60.683] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The purpose of this study was to examine whether initial acidic reperfusion after ischemia followed by stepwise normalization of perfusate pH could improve functional recovery and to assess whether this is associated with a reduction in Ca2+ overload. Isolated rat hearts were subjected to global ischemia for 25 min, followed by 30 min of reperfusion. In the control group (Group C), the perfusate pH was 7.4 throughout reperfusion. In the acidic groups, the perfusate pH was 6.8 for the first 5 min, 7.1 for the second 5 min, and 7.4 for the remainder of reperfusion. Acidic buffer was produced either by adding HCl (metabolic acidosis, Group MA) or by bubbling with gas containing 12 to 24% CO2 (respiratory acidosis, Group RA). The recovery of ventricular function, Ca2+ uptake, and energy metabolites were analyzed. Thirteen of the 15 hearts in Group C, 14 of the 15 in MA and 8 of the 15 in RA recovered regular cardiac rhythm at the end of reperfusion. In these hearts which exhibited normal rhythm, the percent recovery in developed pressure was higher (MA: 73 +/- 8, RA: 68 +/- 6, C: 51 +/- 5%, p < 0.05) and left ventricular end-diastolic pressure was lower (MA: 5.1 +/- 1.4, RA: 5.9 +/- 1.3, C: 14.2 +/- 2.7 mmHg, p < 0.05) in the acidic groups. The improved recovery was associated with a significant reduction in Ca2+ uptake which persisted with the restoration of normal pH. These results demonstrate that early acidic reperfusion enhances contractile recovery and diminishes Ca2+ overload. Moreover, these salutary effects are maintained after stepwise normalization of the perfusate pH to physiological values.
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Affiliation(s)
- Y Ebihara
- Department of Geriatric Medicine, School of Medicine, Keio University, Tokyo, Japan
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Tani M, Shinmura K, Hasegawa H, Nakamura Y. Effect of methylisobutyl amiloride on [Na+]i, reperfusion arrhythmias, and function in ischemic rat hearts. J Cardiovasc Pharmacol 1996; 27:794-801. [PMID: 8761845 DOI: 10.1097/00005344-199606000-00005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
With 2 microM methylisobutyl amiloride (MIA), an inhibitor of Na+/H+ exchange, we tested the hypothesis that ion imbalance due to H+/Na+/Ca2+ exchange exacerbates reperfusion injury and arrhythmias. Isolated rat hearts were subjected to 25-min global ischemia and 30-min reperfusion. In the MIA-treated group, MIA was added throughout the perfusion protocol. Left ventricular pressure (LVP), arrhythmias, myocardial Na+ and K+ content, 45Ca2+ uptake, and the levels of energy metabolites were analyzed. The recovery of LV developed pressure (LVDP) and +dP/dt and -dP/dt were improved in the MIA group (53 vs. 80, 71 vs. 86, 77 vs. 94%: each p < 0.05). MIA inhibited the increase in Na+ content and the decrease in K+ content that occurred at the end of the ischemic phase and reduced 45Ca2+ uptake after reperfusion (28.6 vs. 17.1, 248 vs. 296, 2.79 vs. 1.36 microM/g dry weight of tissue; each p < 0.05). The incidence of ventricular tachycardia (VT) or ventricular fibrillation (VF) was lower in the MIA group [VT 11 of 20 (55%) vs. 4 of 20 (20%), p < 0.05; VF 13 of 20, (65%) vs. 6 of 20 (30%), 0.05 < p < 0.1], although the incidence of VF just escaped statistical significance. ATP level was higher in the MIA group after the ischemic phase and reperfusion (5.3 vs. 9.9, 12.3 vs. 14.7 microM/g dry weight of tissue; each p < 0.05). Our results suggest that MIA reduced reperfusion arrhythmias and improved functional recovery in isolated rat hearts subjected to global ischemia apparently by preserving high-energy phosphates during ischemia and by inhibiting Na+/H+ exchange, with attenuated cellular imbalance between Na+ and Ca2+.
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Affiliation(s)
- M Tani
- Department of Geriatric Medicine, Keio University School of Medicine, Tokyo, Japan
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Kihara Y, Inoko M, Hatakeyama N, Momose Y, Sasayama S. Mechanisms of negative inotropic effects of class Ic antiarrhythmic agents: comparative study of the effects of flecainide and pilsicainide on intracellular calcium handling in dog ventricular myocardium. J Cardiovasc Pharmacol 1996; 27:42-51. [PMID: 8656657 DOI: 10.1097/00005344-199601000-00008] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We studied the subcellular mechanisms responsible for the negative inotropic effects of the two Ic drugs flecainide and pilsicainide. Aequorin luminescence (Ca2+i) and isometric tension were recorded simultaneously in isolated trabeculae from the dog ventricle. In isolated myocytes from the same ventricle, the slow inward current (ICa) was recorded. Both flecainide and pilsicainide decreased peak Ca2+i, peak tension, and peak ICa concentration dependently. Each effect with flecainide was more marked than that with pilsicainide; however, Ca2+i and ICa paralleled each other in changes in tension, and the tension-Ca2+i-ICa relationship showed the same curve for each drug. We conclude that the difference in negative inotropic effects of these class Ic drugs are primarily related to their effects on L-type Ca2+ channels and the subsequent decreases in the amount of Ca2+ released from the sarcoplasmic reticulum (SR) during each cardiac cycle. Therefore, their negative inotropic effects may not be directly correlated with the essential mechanisms responsible for their antiarrhythmic action.
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Affiliation(s)
- Y Kihara
- Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University School of Medicine, Japan
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Hata T, Noda T, Nishimura M, Watanabe Y. The role of Ca2+ release from sarcoplasmic reticulum in the regulation of sinoatrial node automaticity. Heart Vessels 1996; 11:234-41. [PMID: 9129243 DOI: 10.1007/bf01746203] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The role of Ca2+ release channels in the sarcoplasmic reticulum in modulating physiological automaticity of the sinoatrial (SA) node was studied by recording transmembrane action potentials and membrane ionic currents in small preparations of the rabbit SA node. Ryanodine, which modifies the conductance and gating behavior of the Ca2+ release channels, was used to block Ca2+ release from the sarcoplasmic reticulum. Superfusion of 1-mM ryanodine decreased the spontaneous firing frequency as well as the maximal rate of depolarization of the SA, and these reductions reached a steady state within approximately 5 min. The action potential recordings revealed that the latter part of diastolic depolarization was depressed and that the take-off potential became less negative. This suggested that the negative chronotropic effect of ryanodine resulted from the blockade of physiological Ca2+ release from the sarcoplasmic reticulum. In voltage clamp experiments, using double-microelectrode techniques, ryanodine did not markedly reduce the Ca2+ current (ICa) but decreased the delayed rectifying K+ current (IK), the steady-state inward current (Iss), and the hyperpolarization-activated inward current (Ih). These observations suggest that, even when the function of C2+ channels in the cell membrane is normally maintained, depression of Ca2+ release channels in the sarcoplasmic reticulum would prevent sufficient elevation of the Ca2+ concentration in SA node cells for the activation of various ionic currents, and, thus adversely affect the physiological automaticity of this primary cardiac pacemaker.
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Affiliation(s)
- T Hata
- Cardiovascular Institute, Fujita Health University School of Medicine, Aichi, Japan
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Guarini S, Martini MC, Bertolini A. Reperfusion-induced arrhythmias and lethality are reduced by a 2KDa heparin fragment. Life Sci 1995; 57:967-72. [PMID: 7643721 DOI: 10.1016/0024-3205(95)02031-d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The influence of a low molecular weight heparin (Oligo-H, m.w. 2KDa) on ventricular arrhythmias and lethality induced by heart reperfusion following a 5 min coronary occlusion was studied in anesthetized rats. Both intravenous (i.v.) and subcutaneous (s.c.) injection of the compound dose- and time-dependently prevented the reperfusion syndrome: in all saline-pretreated animals post-ischemic reperfusion induced ventricular tachycardia (VT), which degenerated into ventricular fibrillation (VF) in 25 out of 30 rats, with a mortality rate of 73%; on the other hand, in rats i.v. or s.c. pretreated with Oligo-H (20 mg/kg, 30 and 90 min, respectively, before coronary occlusion), VT occurred in 4 out of 10-11 animals and degenerated into VF in 2-3 out of 10-11 animals, with a mortality rate of 18-20%. Even more effective was a low molecular weight dermatan sulfate (Oligo-DS, m.w. 2.1KDa). In rats treated with lidocaine, used as reference compound, at the dose of 5 mg/kg i.v. 10 min before coronary occlusion, VT occurred in 2 out of 10 animals and degenerated into VF in 1 out of 10 animals, with a mortality rate of 10%. It is concluded that low molecular weight glycosaminoglycans significantly reduce the consequences of heart reperfusion.
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Affiliation(s)
- S Guarini
- Department of Biomedical Sciences, University of Modena, Italy
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Abstract
Since their first description five years ago, knowledge about human atrial 5-HT4 receptors has increased considerably. Progress has been facilitated by the advent of selective antagonists with high affinity for human atrial 5-HT4 receptors. The receptors have been detected in both right and left atrium where they mediate increases in contractile force. Human sinoatrial 5-HT4 receptors may mediate the tachycardia caused by 5-HT and cisapride, and 5-HT elicits arrhythmias via 5-HT4 receptors in human atrium. In this article, Alberto Kaumann suggests that 5-HT may be involved in the genesis of atrial fibrillation and associated thromboembolic stroke and that both the arrhythmia and stroke could be prevented by inhibiting 5-HT4 receptors.
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Affiliation(s)
- A J Kaumann
- Human Pharmacology Laboratory, Babraham Institute, Cambridge, UK
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du Toit EF, Opie LH. Antiarrhythmic properties of specific inhibitors of sarcoplasmic reticulum calcium ATPase in the isolated perfused rat heart after coronary artery ligation. J Am Coll Cardiol 1994; 23:1505-10. [PMID: 8176114 DOI: 10.1016/0735-1097(94)90399-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVES The hypothesis tested was that sequestration of calcium by the sarcoplasmic reticulum and internal calcium oscillations may play a role in the genesis of ischemic and reperfusion ventricular arrhythmias. BACKGROUND Previous data suggest that inhibition of the release of intracellular calcium from the sarcoplasmic reticulum by ryanodine may prevent ventricular fibrillation. METHODS The isolated Langendorff perfused rat heart was treated with two specific inhibitors of the calcium ATPase pump of the sarcoplasmic reticulum (thapsigargin [10(-6) mol/liter] or cyclopiazonic acid [10(-7) mol/liter]) for 5 min before left anterior descending coronary artery ligation was performed. One group of hearts was subject to 30 min of coronary artery ligation, and ischemic arrhythmias were monitored. In a second group, the incidence of reperfusion arrhythmias was measured after 10, 15, 20, 25 and 30 min of coronary artery ligation. RESULTS Thapsigargin treatment during ischemia and reperfusion decreased the incidence of reperfusion ventricular fibrillation after 10 min of coronary artery ligation from 67% (n = 6) to 0% (n = 6) (p < 0.05), after 15 min from 81% (n = 16) to 25% (n = 20) (p < 0.002) and after 20 min of ischemia from 90% (n = 10) to 46% (n = 13) (p < 0.05). Thapsigargin treatment also decreased the incidence of ischemic ventricular fibrillation from 83% (n = 12) to 0% (n = 12) (p < 0.002). Cyclopiazonic acid treatment during ischemia and reperfusion likewise decreased the incidence of ischemic and reperfusion arrhythmias. CONCLUSIONS The highly specific inhibitors of the calcium uptake pump of the sarcoplasmic reticulum--thapsigargin and cyclopiazonic acid--have antifibrillatory properties in the isolated perfused rat heart. They appear to act by restriction of calcium oscillations between the sarcoplasmic reticulum and the cytosol.
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Affiliation(s)
- E F du Toit
- Ischaemic Heart Disease Research Unit, University of Cape Town, South Africa
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