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Gao H, Wang Z, Yang F, Wang X, Wang S, Zhang Q, Liu X, Sun Y, Kong J, Yao J. Graphene-integrated mesh electronics with converged multifunctionality for tracking multimodal excitation-contraction dynamics in cardiac microtissues. Nat Commun 2024; 15:2321. [PMID: 38485708 PMCID: PMC10940632 DOI: 10.1038/s41467-024-46636-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 03/05/2024] [Indexed: 03/18/2024] Open
Abstract
Cardiac microtissues provide a promising platform for disease modeling and developmental studies, which require the close monitoring of the multimodal excitation-contraction dynamics. However, no existing assessing tool can track these multimodal dynamics across the live tissue. We develop a tissue-like mesh bioelectronic system to track these multimodal dynamics. The mesh system has tissue-level softness and cell-level dimensions to enable stable embedment in the tissue. It is integrated with an array of graphene sensors, which uniquely converges both bioelectrical and biomechanical sensing functionalities in one device. The system achieves stable tracking of the excitation-contraction dynamics across the tissue and throughout the developmental process, offering comprehensive assessments for tissue maturation, drug effects, and disease modeling. It holds the promise to provide more accurate quantification of the functional, developmental, and pathophysiological states in cardiac tissues, creating an instrumental tool for improving tissue engineering and studies.
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Affiliation(s)
- Hongyan Gao
- Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, 01003, USA
| | - Zhien Wang
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Feiyu Yang
- Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA, 01003, USA
| | - Xiaoyu Wang
- Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, 01003, USA
| | - Siqi Wang
- Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, 01003, USA
| | - Quan Zhang
- Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, 01003, USA
| | - Xiaomeng Liu
- Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, 01003, USA
| | - Yubing Sun
- Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA, 01003, USA
- Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, 01003, USA
- Department of Biomedical Engineering, University of Massachusetts, Amherst, MA, 01003, USA
| | - Jing Kong
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Jun Yao
- Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, 01003, USA.
- Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, 01003, USA.
- Department of Biomedical Engineering, University of Massachusetts, Amherst, MA, 01003, USA.
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Gaballah M, Penttinen K, Kreutzer J, Mäki AJ, Kallio P, Aalto-Setälä K. Cardiac Ischemia On-a-Chip: Antiarrhythmic Effect of Levosimendan on Ischemic Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes. Cells 2022; 11:cells11061045. [PMID: 35326497 PMCID: PMC8947267 DOI: 10.3390/cells11061045] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 03/15/2022] [Accepted: 03/17/2022] [Indexed: 02/05/2023] Open
Abstract
Ischemic heart disease (IHD) is one of the leading causes of mortality worldwide. Preserving functionality and preventing arrhythmias of the heart are key principles in the management of patients with IHD. Levosimendan, a unique calcium (Ca2+) enhancer with inotropic activity, has been introduced into clinical usage for heart failure treatment. Human-induced pluripotent cell-derived cardiomyocytes (hiPSC-CMs) offer an opportunity to better understand the pathophysiological mechanisms of the disease as well as to serve as a platform for drug screening. Here, we developed an in vitro IHD model using hiPSC-CMs in hypoxic conditions and defined the effects of the subsequent hypoxic stress on CMs functionality. Furthermore, the effect of levosimendan on hiPSC-CMs functionality was evaluated during and after hypoxic stress. The morphology, contractile, Ca2+-handling, and gene expression properties of hiPSC-CMs were investigated in response to hypoxia. Hypoxia resulted in significant cardiac arrhythmia and decreased Ca2+ transient amplitude. In addition, disorganization of sarcomere structure was observed after hypoxia induction. Interestingly, levosimendan presented significant antiarrhythmic properties, as the arrhythmia was abolished or markedly reduced with levosimendan treatment either during or after the hypoxic stress. Moreover, levosimendan presented significant protection from the sarcomere alterations induced by hypoxia. In conclusion, this chip model appears to be a suitable preclinical representation of IHD. With this hypoxia platform, detailed knowledge of the disease pathophysiology can be obtained. The antiarrhythmic effect of levosimendan was clearly observed, suggesting a possible new clinical use for the drug.
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Affiliation(s)
- Mahmoud Gaballah
- Heart Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland; (K.P.); (K.A.-S.)
- Department of Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, University of Sadat City, Menoufia 32897, Egypt
- Correspondence: ; Tel.: +358-402574148
| | - Kirsi Penttinen
- Heart Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland; (K.P.); (K.A.-S.)
| | - Joose Kreutzer
- Micro- and Nanosystems Research Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland; (J.K.); (A.-J.M.); (P.K.)
| | - Antti-Juhana Mäki
- Micro- and Nanosystems Research Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland; (J.K.); (A.-J.M.); (P.K.)
| | - Pasi Kallio
- Micro- and Nanosystems Research Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland; (J.K.); (A.-J.M.); (P.K.)
| | - Katriina Aalto-Setälä
- Heart Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland; (K.P.); (K.A.-S.)
- Heart Hospital, Tampere University Hospital, 33520 Tampere, Finland
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Plant LD, Xiong D, Romero J, Dai H, Goldstein SAN. Hypoxia Produces Pro-arrhythmic Late Sodium Current in Cardiac Myocytes by SUMOylation of Na V1.5 Channels. Cell Rep 2021; 30:2225-2236.e4. [PMID: 32075761 PMCID: PMC7054841 DOI: 10.1016/j.celrep.2020.01.025] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 12/03/2019] [Accepted: 01/07/2020] [Indexed: 01/08/2023] Open
Abstract
Acute cardiac hypoxia produces life-threatening elevations in late sodium current (ILATE) in the human heart. Here, we show the underlying mechanism: hypoxia induces rapid SUMOylation of NaV1.5 channels so they reopen when normally inactive, late in the action potential. NaV1.5 is SUMOylated only on lysine 442, and the mutation of that residue, or application of a deSUMOylating enzyme, prevents hypoxic reopenings. The time course of SUMOylation of single channels in response to hypoxia coincides with the increase in ILATE, a reaction that is complete in under 100 s. In human cardiac myocytes derived from pluripotent stem cells, hypoxia-induced ILATE is confirmed to be SUMO-dependent and to produce action potential prolongation, the pro-arrhythmic change observed in patients. The cardiac channel NaV1.5 passes pro-arrhythmic late sodium currents in response to hypoxia. Plant et al. demonstrate the pathophysiological mechanism to be rapid, hypoxia-induced monoSUMOylation of NaV1.5 channels. Blocking SUMOylation of lysine442 prevents hypoxia-induced late currents and attendant prolongation of the action potential in human cardiomyocytes derived from pluripotent stem cells.
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Affiliation(s)
- Leigh D Plant
- Department of Pharmaceutical Sciences, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
| | - Dazhi Xiong
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA
| | - Jesus Romero
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA
| | - Hui Dai
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA
| | - Steve A N Goldstein
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA.
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Eleutheroside B, a selective late sodium current inhibitor, suppresses atrial fibrillation induced by sea anemone toxin II in rabbit hearts. Acta Pharmacol Sin 2021; 42:209-217. [PMID: 32612277 DOI: 10.1038/s41401-020-0453-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 06/01/2020] [Indexed: 11/09/2022] Open
Abstract
Eleutheroside B (EB) is the main active constituent derived from the Chinese herb Acanthopanax senticosus (AS) that has been reported to possess cardioprotective effects. In this study we investigated the effects of EB on cardiac electrophysiology and its suppression on atrial fibrillation (AF). Whole-cell recording was conducted in isolated rabbit atrial myocytes. The intracellular calcium ([Ca2+]i) concentration was measured using calcium indicator Fura-2/AM fluorescence. Monophasic action potential (MAP) and electrocardiogram (ECG) synchronous recordings were conducted in Langendorff-perfused rabbit hearts using ECG signal sampling and analysis system. We showed that EB dose-dependently inhibited late sodium current (INaL), transient sodium current (INaT), and sea anemone toxin II (ATX II)-increased INaL with IC50 values of 167, 1582, and 181 μM, respectively. On the other hand, EB (800 μM) did not affect L-type calcium current (ICaL), inward rectifier potassium channel current (IK), and action potential duration (APD). Furthermore, EB (300 μM) markedly decreased ATX II-prolonged the APD at 90% repolarization (APD90) and eliminated ATX II-induced early afterdepolarizations (EADs), delayed afterdepolarizations (DADs), and triggered activities (TAs). Moreover, EB (200 μM) significantly suppressed ATX II-induced Na+-dependent [Ca2+]i overload in atrial myocytes. In the Langendorff-perfused rabbit hearts, application of EB (200 μM) or TTX (2 μM) substantially decreased ATX II-induced incidences of atrial fibrillation (AF), ventricular fibrillation (VF), and heart death. These results suggest that augmented INaL alone is sufficient to induce AF, and EB exerts anti-AF actions mainly via blocking INaL, which put forward the basis of pharmacology for new clinical application of EB.
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Luo Q, Wu T, Wu W, Chen G, Luo X, Jiang L, Tao H, Rong M, Kang S, Deng M. The Functional Role of Voltage-Gated Sodium Channel Nav1.5 in Metastatic Breast Cancer. Front Pharmacol 2020; 11:1111. [PMID: 32792949 PMCID: PMC7393602 DOI: 10.3389/fphar.2020.01111] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 07/08/2020] [Indexed: 12/12/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs), which are abnormally expressed in various types of cancers such as breast cancer, prostate cancer, lung cancer, and cervical cancer, are involved in the metastatic process of invasion and migration. Nav1.5 is a pore-forming α subunit of VGSC encoded by SCN5A. Various studies have demonstrated that Nav1.5, often as its neonatal splice form, is highly expressed in metastatic breast cancer cells. Abnormal activation and expression of Nav1.5 trigger a variety of cellular mechanisms, including changing H+ efflux, promoting epithelial-to-mesenchymal transition (EMT) and the expression of cysteine cathepsin, to potentiate the metastasis and invasiveness of breast cancer cells in vitro and in vivo. Here, we systematically review the latest available data on the pro-metastatic effect of Nav1.5 and its underlying mechanisms in breast cancer. We summarize the factors affecting Nav1.5 expression in breast cancer cells, and discuss the potential of Nav1.5 blockers serving as candidates for breast cancer treatment.
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Affiliation(s)
- Qianxuan Luo
- Department of Biochemistry and Molecular Biology & Hunan Province Key Laboratory of Basic and Applied Hematology, School of Life Sciences, Central South University, Changsha, China
- Hunan Key Laboratory of Animal Models for Human Diseases & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China
| | - Ting Wu
- Department of Biochemistry and Molecular Biology & Hunan Province Key Laboratory of Basic and Applied Hematology, School of Life Sciences, Central South University, Changsha, China
- Xiangya School of Medicine, Central South University, Changsha, China
| | - Wenfang Wu
- Department of Biochemistry and Molecular Biology & Hunan Province Key Laboratory of Basic and Applied Hematology, School of Life Sciences, Central South University, Changsha, China
| | - Gong Chen
- Department of Biochemistry and Molecular Biology & Hunan Province Key Laboratory of Basic and Applied Hematology, School of Life Sciences, Central South University, Changsha, China
| | - Xuan Luo
- Department of Biochemistry and Molecular Biology, Hunan Normal University, Changsha, China
| | - Liping Jiang
- Xiangya School of Medicine, Central South University, Changsha, China
| | - Huai Tao
- Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, China
| | - Mingqiang Rong
- Department of Biochemistry and Molecular Biology, Hunan Normal University, Changsha, China
| | - Shuntong Kang
- Department of Biochemistry and Molecular Biology & Hunan Province Key Laboratory of Basic and Applied Hematology, School of Life Sciences, Central South University, Changsha, China
- Xiangya School of Medicine, Central South University, Changsha, China
| | - Meichun Deng
- Department of Biochemistry and Molecular Biology & Hunan Province Key Laboratory of Basic and Applied Hematology, School of Life Sciences, Central South University, Changsha, China
- Hunan Key Laboratory of Animal Models for Human Diseases & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China
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Guo D, Jenkinson S. Simultaneous assessment of compound activity on cardiac Nav1.5 peak and late currents in an automated patch clamp platform. J Pharmacol Toxicol Methods 2019; 99:106575. [PMID: 30999054 DOI: 10.1016/j.vascn.2019.04.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/22/2019] [Accepted: 04/12/2019] [Indexed: 01/04/2023]
Abstract
INTRODUCTION High throughput in vitro profiling of the cardiac Nav1.5 peak sodium current (INa) is widely used in cardiac safety screening. However, there is no standardized high throughput method to measure late INa. This study assessed the pharmacological and biophysical properties of veratridine and ATX-II, as well as the channel mutation (Nav1.5-∆KPQ) on the late INa. We describe a method for simultaneous measurement of both peak and late INa. METHODS The planar patch clamp technique (QPatch) was applied to record the peak and late INa. RESULTS The Nav1.5-∆KPQ mutant produced a small late INa (41.9 ± 5.4 pA) not large enough to enable compound profiling. In contrast in wild type Nav1.5 expressing cells veratridine (100 μM) and ATX-II (100 nM) enhanced concentration-dependent increases in the late INa (maximum responses of 1162.2 ± 258.5 pA and 392.4 ± 71.3 pA, respectively). Veratridine inhibited, whereas, ATX-II had a minimal effect, on the peak INa and preserved the current-voltage curve. Peak and late INa inhibition was characterized for 25 clinical INa blockers in the presence of ATX-II. Compound IC50 values for peak INa generated in the absence or presence of ATX-II correlated. The potency of the late INa block was found to be dependent on whether it was measured at the end of the depolarizing pulse or during the ramp. DISCUSSION In the presence of ATX-II, both peak and late INa could be assessed simultaneously. Late INa may be best assessed using the maximum response obtained during the ramp of the voltage protocol.
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Affiliation(s)
- Donglin Guo
- Drug Safety Research and Development, Pfizer Inc., La Jolla, CA 92121, United States of America.
| | - Stephen Jenkinson
- Drug Safety Research and Development, Pfizer Inc., La Jolla, CA 92121, United States of America
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Mačianskienė R, Martišienė I, Navalinskas A, Treinys R, Andriulė I, Jurevičius J. Mechanism of Action Potential Prolongation During Metabolic Inhibition in the Whole Rabbit Heart. Front Physiol 2018; 9:1077. [PMID: 30140239 PMCID: PMC6095129 DOI: 10.3389/fphys.2018.01077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 07/19/2018] [Indexed: 11/24/2022] Open
Abstract
Myocardial ischemia is associated with significant changes in action potential (AP) duration, which has a biphasic response to metabolic inhibition. Here, we investigated the mechanism of initial AP prolongation in whole Langendorff-perfused rabbit heart. We used glass microelectrodes to record APs transmurally. Simultaneously, optical AP, calcium transient (CaT), intracellular pH, and magnesium concentration changes were recorded using fluorescent dyes. The fluorescence signals were recorded using an EMCCD camera equipped with emission filters; excitation was induced by LEDs. We demonstrated that metabolic inhibition by carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) resulted in AP shortening preceded by an initial prolongation and that there were no important differences in the response throughout the wall of the heart and in the apical/basal direction. AP prolongation was reduced by blocking the ICaL and transient outward potassium current (Ito) with diltiazem (DTZ) and 4-aminopyridine (4-AP), respectively. FCCP, an uncoupler of oxidative phosphorylation, induced reductions in CaTs and intracellular pH and increased the intracellular Mg2+ concentration. In addition, resting potential depolarization was observed, clearly indicating a decrease in the inward rectifier K+ current (IK1) that can retard AP repolarization. Thus, we suggest that the main currents responsible for AP prolongation during metabolic inhibition are the ICaL, Ito, and IK1, the activities of which are modulated mainly by changes in intracellular ATP, calcium, magnesium, and pH.
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Affiliation(s)
- Regina Mačianskienė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Irma Martišienė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Antanas Navalinskas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Rimantas Treinys
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Inga Andriulė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Jonas Jurevičius
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
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Na V Channels: Assaying Biosynthesis, Trafficking, Function. Methods Mol Biol 2017. [PMID: 29264805 DOI: 10.1007/978-1-4939-7553-2_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Integral to the cell surface is channels, pumps, and exchanger proteins that facilitate the movement of ions across the membrane. Ion channels facilitate the passive movement of ions down an electrochemical gradient. Ion pumps actively use energy to actively translocate ions, often against concentration or voltage gradients, while ion exchangers utilize energy to couple the transport of different ion species such that one ion moves down its gradient and the released free energy is used to drive the movement of a different ion against its electrochemical gradient. Some ion pumps and exchangers may be electrogenic, i.e., the ion transport they support is not electrically neutral and generates a current. Functions of these pore-forming membrane proteins include the establishment of membrane potentials, gating of ions flows across the cell membrane to elicit action potentials and other electrical signals, as well as the regulation of cell volumes. The major forms of ion channels include voltage-, ligand-, and signal-gated channels. In this review, we describe mammalian voltage dependent Na (NaV) channels.
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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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Wang K, Li L, Wu Y, Yang Y, Chen J, Zhang D, Liu Z, Xu J, Cao M, Mao X, Liu C. Increased serum gamma-glutamyltransferase levels are associated with ventricular instability in type 2 diabetes. Endocrine 2016; 52:63-72. [PMID: 26433737 DOI: 10.1007/s12020-015-0760-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 09/23/2015] [Indexed: 12/26/2022]
Abstract
The purpose of our study is to examine the association between serum GGT levels and ventricular instability in Chinese patients with T2DM. We conducted a cross-sectional, community-based study in Nanjing, China from June to November 2011. Among 10,050 patients aged 40-79 years, we enrolled 2444 with pre-diabetes, 2496 with T2DM, and 4521 without diabetes (non-diabetes). Electrocardiograms were performed to measure the QT interval corrected for heart rate (QTc) and QT interval dispersion (QTd). Serum GGT levels, metabolic parameters, body mass index, and blood pressure were also measured. We found that there were no significant associations of increased QTc/QTd with serum GGT levels in participants with pre-existing T2DM and non-diabetes, after adjusting for age, duration of diabetes, and metabolic parameters. Even after adjustment, higher risks of QTc ≥ 440 ms/√s and QTd ≥ 58 ms were found in participants with serum GGT levels ≥49 U/L compared with those with <15 U/L in the pre-diabetes (QTc: OR 1.96, 95 % CI 1.23-2.47; QTd: OR 1.34, 95 % CI 1.07-1.94) and newly diagnosed T2DM (QTc: OR 2.01, 95 % CI 1.39-2.51; QTd: OR 1.53, 95 % CI 1.03-1.99) groups. We conclude that Increased serum GGT levels are associated with some markers of ventricular repolarization abnormalities in the early stage of T2DM.
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Affiliation(s)
- Kun Wang
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Ling Li
- Department of Endocrinology, Zhongda Hospital, School of Medicine, Southeast University, 87, Dingjiaqiao Road, Nanjing, 210009, China
| | - Yang Wu
- Department of Endocrinology, The First People's Hospital of Changzhou, Third Affiliated Hospital of Suzhou University, 185, Juqian Road, Changzhou, 213003, China
| | - Yu Yang
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Jie Chen
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Danyu Zhang
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Zhoujun Liu
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Juan Xu
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Meng Cao
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Xiaodong Mao
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China
| | - Chao Liu
- Department of Endocrinology, Affiliated Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, 100, Hongshan Road, Nanjing, 210028, China.
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Hou JW, Li W, Guo K, Chen XM, Chen YH, Li CY, Zhao BC, Zhao J, Wang H, Wang YP, Li YG. Antiarrhythmic effects and potential mechanism of WenXin KeLi in cardiac Purkinje cells. Heart Rhythm 2016; 13:973-82. [DOI: 10.1016/j.hrthm.2015.12.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Indexed: 10/22/2022]
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12
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Inhibition of the cardiac Na⁺ channel α-subunit Nav1.5 by propofol and dexmedetomidine. Naunyn Schmiedebergs Arch Pharmacol 2015; 389:315-25. [PMID: 26667357 DOI: 10.1007/s00210-015-1195-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 11/26/2015] [Indexed: 12/19/2022]
Abstract
Propofol and dexmedetomidine are very commonly used sedative agents. However, several case reports demonstrated cardiovascular adverse effects of these two sedatives. Both substances were previously demonstrated to quite potently inhibit neuronal voltage-gated Na(+) channels. Thus, a possible molecular mechanism for some of their cardiac side effects is an inhibition of cardiac voltage gated Na(+) channels. In this study, we therefore explored the effects of propofol and dexmedetomidine on the cardiac predominant Na(+) channel α-subunit Nav1.5. Effects of propofol and dexmedetomidine were investigated on constructs of the human α-subunit Nav1.5 stably expressed in HEK-293 cells by means of whole-cell patch clamp recordings. Both agents induced a concentration-dependent tonic inhibition of Nav1.5. The calculated IC50 value for propofol was 228 ± 10 μM, and for dexmedetomidine 170 ± 20 μM. Tonic block only marginally increased on inactivated channels, and a weak use-dependent block at 10 Hz was observed for dexmedetomidine (16 ± 2 % by 100 μM). The voltage dependencies of fast and slow inactivation as well as the time course of recovery from inactivation were shifted by both propofol and dexmedetomidine. Propofol (IC50 126 ± 47 μM) and dexmedetomidine (IC50 182 ± 27 μM) blocked the persistent sodium current induced by veratradine. Finally, the local-anesthetic (LA)-insensitive mutant Nav1.5-F1760A exhibited reduced tonic and use-dependent block by both substances. Dexmedetomidine was generally more potent as compared to propofol. Propofol and dexmedetomidine seem to interact with the LA-binding site to inhibit the cardiac Na(+) channel Nav1.5 in a state-dependent manner. These data suggest that Nav1.5 is a hitherto unrecognized molecular component of some cardiovascular side effects of these sedative agents.
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Cui C, Zhou T, Li J, Wang H, Li X, Xiong J, Xu P, Xue M. Proteomic analysis of the mouse brain after repetitive exposure to hypoxia. Chem Biol Interact 2015; 236:57-66. [PMID: 25937538 DOI: 10.1016/j.cbi.2015.04.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Revised: 02/04/2015] [Accepted: 04/09/2015] [Indexed: 10/23/2022]
Abstract
Hypoxic preconditioning (HPC) is known to have a protective effect against hypoxic damage; however, the precise mechanisms involved remain unknown. In this study, an acute and repetitive hypoxia mouse model, two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) coupled with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/TOF-MS), and Western blot experiments were used to identify the differential expression of key proteins in the mouse brain during HPC. Approximately 2100 2D-DIGE spots were observed following gel imaging and spot detection. Significant differences (p < 0.05) in the expression of 66 proteins were observed between the 3× HPC treatment group and the control group, 45 proteins were observed between the 6× HPC treatment group and the control group, and 70 proteins were observed between the 3× HPC treatment group and the 6× HPC group. Consistent results among Western blot, 2D-DIGE and MS methods were observed for the proteins, ATP synthase subunit alpha, malate dehydrogenase, guanine nucleotide-binding protein subunit beta-1 and proteasome subunit alpha type-2. The proteins associated with ATP synthesis and the citric acid cycle were down-regulated, while those linked to glycolysis and oxygen-binding were up-regulated. This proteomic analysis of the mouse brain after HPC furthers understanding of the molecular pathways involved in the protective effect of HPC and these findings provide new insight into the mechanisms of hypoxia and HPC.
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Affiliation(s)
- Can Cui
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China
| | - Tao Zhou
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China
| | - Jingyi Li
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China
| | - Hong Wang
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China
| | - Xiaorong Li
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China; Beijing Laboratory for Biomedical Detection Technology and Instrument, Beijing 100069, China
| | - Jie Xiong
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China; Beijing Laboratory for Biomedical Detection Technology and Instrument, Beijing 100069, China
| | - Pingxiang Xu
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China; Beijing Laboratory for Biomedical Detection Technology and Instrument, Beijing 100069, China
| | - Ming Xue
- Department of Pharmacology, School of Basic Medical Sciences, Capital Medical University, Beijing 10069, China; Beijing Laboratory for Biomedical Detection Technology and Instrument, Beijing 100069, China.
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Mattiazzi A, Argenziano M, Aguilar-Sanchez Y, Mazzocchi G, Escobar AL. Ca2+ Sparks and Ca2+ waves are the subcellular events underlying Ca2+ overload during ischemia and reperfusion in perfused intact hearts. J Mol Cell Cardiol 2015; 79:69-78. [PMID: 25451173 PMCID: PMC4302011 DOI: 10.1016/j.yjmcc.2014.10.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/08/2014] [Accepted: 10/20/2014] [Indexed: 11/27/2022]
Abstract
Abnormal intracellular Ca(2+) cycling plays a key role in cardiac dysfunction, particularly during the setting of ischemia/reperfusion (I/R). During ischemia, there is an increase in cytosolic and sarcoplasmic reticulum (SR) Ca(2+). At the onset of reperfusion, there is a transient and abrupt increase in cytosolic Ca(2++), which occurs timely associated with reperfusion arrhythmias. However, little is known about the subcellular dynamics of Ca(2+) increase during I/R, and a possible role of the SR as a mechanism underlying this increase has been previously overlooked. The aim of the present work is to test two main hypotheses: (1) An increase diastolic Ca(2+) sparks frequency (cspf) constitutes a mayor substrate for the ischemia-induced diastolic Ca(2+) increase; (2) an increase in cytosolic Ca(2+) pro-arrhythmogenic events (Ca(2+) waves), mediates the abrupt diastolic Ca(2+) rise at the onset of reperfusion. We used confocal microscopy on mouse intact hearts loaded with Fluo-4. Hearts were submitted to global I/R (12/30 min) to assess epicardial Ca(2+) sparks in the whole heart. Intact heart sparks were faster than in isolated myocytes whereas cspf was not different. During ischemia, cspf significantly increased relative to preischemia (2.07±0.33 vs. 1.13±0.20 sp/s/100 μm, n=29/34, 7 hearts). Reperfusion significantly changed Ca(2+) sparks kinetics, by prolonging Ca(2+) sparks rise time and decreased cspf. However, it significantly increased Ca(2+) wave frequency relative to ischemia (0.71±0.14 vs. 0.38±0.06 w/s/100 μm, n=32/33, 7 hearts). The results show for the first time the assessment of intact perfused heart Ca(2+) sparks and provides direct evidence of increased Ca(2+) sparks in ischemia that transform into Ca(2+) waves during reperfusion. These waves may constitute a main trigger for reperfusion arrhythmias.
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Affiliation(s)
- Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, UNLP, Argentina
| | - Mariana Argenziano
- Universidad Nacional de San Martin, San Martin, Argentina; Biological Engineering and Small Scale Technologies, School of Engineering, University of California, Merced, CA, USA
| | - Yuriana Aguilar-Sanchez
- Biological Engineering and Small Scale Technologies, School of Engineering, University of California, Merced, CA, USA
| | - Gabriela Mazzocchi
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, UNLP, Argentina
| | - Ariel L Escobar
- Biological Engineering and Small Scale Technologies, School of Engineering, University of California, Merced, CA, USA.
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Dong B, Li C, Zhang X, Wang S, Cheng Z, Rong P. Electroacupuncture of neiguan (PC 6) inhibits enhanced voltage-gated sodium currents in ischemic ventricular myocytes. J TRADIT CHIN MED 2015; 34:710-5. [PMID: 25618976 DOI: 10.1016/s0254-6272(15)30086-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To examine the effect of electroacupuncture (EA) at bilateral Neiguan (PC 6) on voltage-gated Na+ currents (I(Na)) and channels (Na(v)) in ischemic ventricular myocytes. METHODS EA serum was prepared from six male adult Sprague-Dawley rats that had received EA at bilateral Neiguan (PC 6). Eighteen ventricular myocytes were prepared from six SD rats using an enzymolysis approach. Myocardial ischemia was mimicked by perfusion of ischemic solution. Whole-cell patch-clamping was used to record three currents evoked from isolated cells. The first current was the control, and recorded in absence of ischemic solution current. The second was the ischemic current, and recorded after perfusion of ischemic solution for 5 min, while the EA current was last, and recorded after perfusion of EA serum for 5 min. Na(v) kinetic curves were fitted using related formulas. RESULTS Compared with those in controls, in the presence of ischemic solution, peak amplitudes of I(Na) significantly increased from - 40 mV to +30 mV, and half-maximal inactivation potentials of Na(v) increased significantly, while half-maximal activation potentials, slope factors and the recovery time from inactivation to activation of Na(v) were unchanged. Compared with those in the ischemic solution, in the presence of EA serum, peak ischemic current amplitudes significantly reduced from - 40 mV to +40 mV, and half-maximal inactivation potentials were restored, while half-maximal activation potentials, slope factors and the recovery time from inactivation to activation of Na(v) were unchanged. CONCLUSION EA at bilateral Neiguan (PC 6) can reduce enhanced I(Na) via restoration of delayed Na(v) inactivation in ischemic ventricular myocytes.
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Ma J, Song Y, Shryock JC, Hu L, Wang W, Yan X, Zhang P, Belardinelli L. Ranolazine Attenuates Hypoxia- and Hydrogen Peroxide-induced Increases in Sodium Channel Late Openings in Ventricular Myocytes. J Cardiovasc Pharmacol 2014; 64:60-8. [DOI: 10.1097/fjc.0000000000000090] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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17
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Di Diego JM, Antzelevitch C. Acute myocardial ischemia: cellular mechanisms underlying ST segment elevation. J Electrocardiol 2014; 47:486-90. [PMID: 24742586 DOI: 10.1016/j.jelectrocard.2014.02.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Indexed: 10/25/2022]
Abstract
The electrocardiogram (ECG) is an essential tool for the diagnosis of acute myocardial ischemia in the emergency department, as well as for that of an evolving acute myocardial infarction (AMI). Changes in the surface ECG in leads whose positive poles face the ischemic region are known to be related to injury currents flowing across the boundaries between the ischemic and the surrounding normal myocardium. Although experimental studies have also shown an endocardium to epicardium differential sensitivity to the effect of acute ischemia, the important contribution of this transmural heterogeneous response to the changes observed in the surface ECG is less appreciated by the clinical cardiologist. This review briefly discusses our current knowledge regarding the electrophysiology of the ischemic myocardium focusing primarily on the electrophysiologic changes underlying the ECG alterations observed at the onset of a transmural AMI.
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18
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Jones DK, Ruben PC. Proton modulation of cardiac I Na: a potential arrhythmogenic trigger. Handb Exp Pharmacol 2014; 221:169-81. [PMID: 24737236 DOI: 10.1007/978-3-642-41588-3_8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Voltage-gated sodium (NaV) channels generate the upstroke and mediate duration of the ventricular action potential, thus they play a critical role in mediating cardiac excitability. Cardiac ischemia triggers extracellular pH to drop as low as pH 6.0, within just 10 min of its onset. Heightened proton concentrations reduce sodium conductance and alter the gating parameters of the cardiac-specific voltage-gated sodium channel, NaV1.5. Most notably, acidosis destabilizes fast inactivation, which plays a critical role in regulating action potential duration. The changes in NaV1.5 channel gating contribute to cardiac dysfunction during ischemia that can cause syncope, cardiac arrhythmia, and even sudden cardiac death. Understanding NaV channel modulation by protons is paramount to treatment and prevention of the deleterious effects of cardiac ischemia and other triggers of cardiac acidosis.
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Abstract
Late I Na is an integral part of the sodium current, which persists long after the fast-inactivating component. The magnitude of the late I Na is relatively small in all species and in all types of cardiomyocytes as compared with the amplitude of the fast sodium current, but it contributes significantly to the shape and duration of the action potential. This late component had been shown to increase in several acquired or congenital conditions, including hypoxia, oxidative stress, and heart failure, or due to mutations in SCN5A, which encodes the α-subunit of the sodium channel, as well as in channel-interacting proteins, including multiple β subunits and anchoring proteins. Patients with enhanced late I Na exhibit the type-3 long QT syndrome (LQT3) characterized by high propensity for the life-threatening ventricular arrhythmias, such as Torsade de Pointes (TdP), as well as for atrial fibrillation. There are several distinct mechanisms of arrhythmogenesis due to abnormal late I Na, including abnormal automaticity, early and delayed after depolarization-induced triggered activity, and dramatic increase of ventricular dispersion of repolarization. Many local anesthetic and antiarrhythmic agents have a higher potency to block late I Na as compared with fast I Na. Several novel compounds, including ranolazine, GS-458967, and F15845, appear to be the most selective inhibitors of cardiac late I Na reported to date. Selective inhibition of late I Na is expected to be an effective strategy for correcting these acquired and congenital channelopathies.
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20
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Clanton TL, Hogan MC, Gladden LB. Regulation of cellular gas exchange, oxygen sensing, and metabolic control. Compr Physiol 2013; 3:1135-90. [PMID: 23897683 DOI: 10.1002/cphy.c120030] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells must continuously monitor and couple their metabolic requirements for ATP utilization with their ability to take up O2 for mitochondrial respiration. When O2 uptake and delivery move out of homeostasis, cells have elaborate and diverse sensing and response systems to compensate. In this review, we explore the biophysics of O2 and gas diffusion in the cell, how intracellular O2 is regulated, how intracellular O2 levels are sensed and how sensing systems impact mitochondrial respiration and shifts in metabolic pathways. Particular attention is paid to how O2 affects the redox state of the cell, as well as the NO, H2S, and CO concentrations. We also explore how these agents can affect various aspects of gas exchange and activate acute signaling pathways that promote survival. Two kinds of challenges to gas exchange are also discussed in detail: when insufficient O2 is available for respiration (hypoxia) and when metabolic requirements test the limits of gas exchange (exercising skeletal muscle). This review also focuses on responses to acute hypoxia in the context of the original "unifying theory of hypoxia tolerance" as expressed by Hochachka and colleagues. It includes discourse on the regulation of mitochondrial electron transport, metabolic suppression, shifts in metabolic pathways, and recruitment of cell survival pathways preventing collapse of membrane potential and nuclear apoptosis. Regarding exercise, the issues discussed relate to the O2 sensitivity of metabolic rate, O2 kinetics in exercise, and influences of available O2 on glycolysis and lactate production.
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Affiliation(s)
- T L Clanton
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.
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Coppini R, Ferrantini C, Mazzoni L, Sartiani L, Olivotto I, Poggesi C, Cerbai E, Mugelli A. Regulation of intracellular Na(+) in health and disease: pathophysiological mechanisms and implications for treatment. Glob Cardiol Sci Pract 2013; 2013:222-42. [PMID: 24689024 PMCID: PMC3963757 DOI: 10.5339/gcsp.2013.30] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 09/01/2013] [Indexed: 12/19/2022] Open
Abstract
Transmembrane sodium (Na+) fluxes and intracellular sodium homeostasis are central players in the physiology of the cardiac myocyte, since they are crucial for both cell excitability and for the regulation of the intracellular calcium concentration. Furthermore, Na+ fluxes across the membrane of mitochondria affect the concentration of protons and calcium in the matrix, regulating mitochondrial function. In this review we first analyze the main molecular determinants of sodium fluxes across the sarcolemma and the mitochondrial membrane and describe their role in the physiology of the healthy myocyte. In particular we focus on the interplay between intracellular Ca2+ and Na+. A large part of the review is dedicated to discuss the changes of Na+ fluxes and intracellular Na+ concentration([Na+]i) occurring in cardiac disease; we specifically focus on heart failure and hypertrophic cardiomyopathy, where increased intracellular [Na+]i is an established determinant of myocardial dysfunction. We review experimental evidence attributing the increase of [Na+]i to either decreased Na+ efflux (e.g. via the Na+/K+ pump) or increased Na+ influx into the myocyte (e.g. via Na+ channels). In particular, we focus on the role of the “late sodium current” (INaL), a sustained component of the fast Na+ current of cardiac myocytes, which is abnormally enhanced in cardiac diseases and contributes to both electrical and contractile dysfunction. We analyze the pathophysiological role of INaL enhancement in heart failure and hypertrophic cardiomyopathy and the consequences of its pharmacological modulation, highlighting the clinical implications. The central role of Na+ fluxes and intracellular Na+ physiology and pathophysiology of cardiac myocytes has been highlighted by a large number of recent works. The possibility of modulating Na+ inward fluxes and [Na+]i with specific INaL inhibitors, such as ranolazine, has made Na+a novel suitable target for cardiac therapy, potentially capable of addressing arrhythmogenesis and diastolic dysfunction in severe conditions such as heart failure and hypertrophic cardiomyopathy.
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Affiliation(s)
- Raffaele Coppini
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Cecilia Ferrantini
- Department of Clinical and Experimental Medicine, division of Physiology, University of Florence, Italy
| | - Luca Mazzoni
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Laura Sartiani
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Iacopo Olivotto
- Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy
| | - Corrado Poggesi
- Department of Clinical and Experimental Medicine, division of Physiology, University of Florence, Italy
| | - Elisabetta Cerbai
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Alessandro Mugelli
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
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22
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Shryock JC, Song Y, Rajamani S, Antzelevitch C, Belardinelli L. The arrhythmogenic consequences of increasing late INa in the cardiomyocyte. Cardiovasc Res 2013; 99:600-11. [PMID: 23752976 DOI: 10.1093/cvr/cvt145] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This review presents the roles of cardiac sodium channel NaV1.5 late current (late INa) in generation of arrhythmic activity. The assumption of the authors is that proper Na(+) channel function is necessary to the maintenance of the transmembrane electrochemical gradient of Na(+) and regulation of cardiac electrical activity. Myocyte Na(+) channels' openings during the brief action potential upstroke contribute to peak INa and initiate excitation-contraction coupling. Openings of Na(+) channels outside the upstroke contribute to late INa, a depolarizing current that persists throughout the action potential plateau. The small, physiological late INa does not appear to be critical for normal electrical or contractile function in the heart. Late INa does, however, reduce the net repolarizing current, prolongs action potential duration, and increases cellular Na(+) loading. An increase of late INa, due to acquired conditions (e.g. heart failure) or inherited Na(+) channelopathies, facilitates the formation of early and delayed afterpolarizations and triggered arrhythmias, spontaneous diastolic depolarization, and cellular Ca(2+) loading. These in turn increase the spatial and temporal dispersion of repolarization time and may lead to reentrant arrhythmias.
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Affiliation(s)
- John C Shryock
- Department of Biology, Cardiovascular Therapeutic Area, Gilead Sciences, Foster City, CA, USA
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23
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Despa S, Bers DM. Na⁺ transport in the normal and failing heart - remember the balance. J Mol Cell Cardiol 2013; 61:2-10. [PMID: 23608603 DOI: 10.1016/j.yjmcc.2013.04.011] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 03/22/2013] [Accepted: 04/11/2013] [Indexed: 12/12/2022]
Abstract
In the heart, intracellular Na(+) concentration ([Na(+)]i) is a key modulator of Ca(2+) cycling, contractility and cardiac myocyte metabolism. Several Na(+) transporters are electrogenic, thus they both contribute to shaping the cardiac action potential and at the same time are affected by it. [Na(+)]i is controlled by the balance between Na(+) influx through various pathways, including the Na(+)/Ca(2+) exchanger and Na(+) channels, and Na(+) extrusion via the Na(+)/K(+)-ATPase. [Na(+)]i is elevated in HF due to a combination of increased entry through Na(+) channels and/or Na(+)/H(+) exchanger and reduced activity of the Na(+)/K(+)-ATPase. Here we review the major Na(+) transport pathways in cardiac myocytes and how they participate in regulating [Na(+)]i in normal and failing hearts. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes."
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Affiliation(s)
- Sanda Despa
- Department of Pharmacology, University of California, Davis, CA, USA.
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24
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Qian C, Ma J, Zhang P, Luo A, Wang C, Ren Z, Kong L, Zhang S, Wang X, Wu Y. Resveratrol attenuates the Na(+)-dependent intracellular Ca(2+) overload by inhibiting H(2)O(2)-induced increase in late sodium current in ventricular myocytes. PLoS One 2012; 7:e51358. [PMID: 23272101 PMCID: PMC3521760 DOI: 10.1371/journal.pone.0051358] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 11/01/2012] [Indexed: 12/19/2022] Open
Abstract
Background/Aims Resveratrol has been demonstrated to be protective in the cardiovascular system. The aim of this study was to assess the effects of resveratrol on hydrogen peroxide (H2O2)-induced increase in late sodium current (INa.L) which augmented the reverse Na+-Ca2+ exchanger current (INCX), and the diastolic intracellular Ca2+ concentration in ventricular myocytes. Methods INa.L, INCX, L-type Ca2+ current (ICa.L) and intracellular Ca2+ properties were determined using whole-cell patch-clamp techniques and dual-excitation fluorescence photomultiplier system (IonOptix), respectively, in rabbit ventricular myocytes. Results Resveratrol (10, 20, 40 and 80 µM) decreased INa.L in myocytes both in the absence and presence of H2O2 (300 µM) in a concentration dependent manner. Ranolazine (3–9 µM) and tetrodotoxin (TTX, 4 µM), INa.L inhibitors, decreased INa.L in cardiomyocytes in the presence of 300 µM H2O2. H2O2 (300 µM) increased the reverse INCX and this increase was significantly attenuated by either 20 µM resveratrol or 4 µM ranolazine or 4 µM TTX. In addition, 10 µM resveratrol and 2 µM TTX significantly depressed the increase by 150 µM H2O2 of the diastolic intracellular Ca2+ fura-2 fluorescence intensity (FFI), fura-fluorescence intensity change (△FFI), maximal velocity of intracellular Ca2+ transient rise and decay. As expected, 2 µM TTX had no effect on ICa.L. Conclusion Resveratrol protects the cardiomyocytes by inhibiting the H2O2-induced augmentation of INa.L.and may contribute to the reduction of ischemia-induced lethal arrhythmias.
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Affiliation(s)
- Chunping Qian
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan, Hubei, People's Republic of China
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25
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Vandenberg JI, Perry MD, Perrin MJ, Mann SA, Ke Y, Hill AP. hERG K+ Channels: Structure, Function, and Clinical Significance. Physiol Rev 2012; 92:1393-478. [DOI: 10.1152/physrev.00036.2011] [Citation(s) in RCA: 463] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.
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Affiliation(s)
- Jamie I. Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Matthew D. Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Mark J. Perrin
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Stefan A. Mann
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Ying Ke
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Adam P. Hill
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
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26
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Tang Q, Ma J, Zhang P, Wan W, Kong L, Wu L. Persistent sodium current and Na+/H+ exchange contributes to the augmentation of the reverse Na+/Ca2+ exchange during hypoxia or acute ischemia in ventricular myocytes. Pflugers Arch 2012; 463:513-22. [PMID: 22234427 DOI: 10.1007/s00424-011-1070-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 12/22/2011] [Indexed: 12/19/2022]
Abstract
The increases in persistent sodium currents (I (Na.P)) and Na(+)/H(+) exchange (NHE) causes intracellular Ca(2+) overload. The objective of this study was to determine the contribution of I (Na.P) and NHE on the hypoxia- or acute ischemia-induced increase in the reverse Na(+)/Ca(2+) exchange current (HIR- or AIR-I (NCX)). I (Na.P) and I (NCX) in rabbit ventricular myocytes were recorded during hypoxia or acute ischemia, combination of acidosis (pH values were 6.0 intracellularly and 6.8 extracellularly) and hypoxia, using whole-cell patch-clamp techniques. The results indicate that (1) under hypoxic condition, the augmentation of both HIR-I (NCX) and I (Na.P) was inhibited by TTX (2 to 8 μM) in a concentration-dependent manner. The inhibitions of I (Na,P) and HIR-I (NCX) reached maximum in the presence of either 4 μM TTX or 10 μM KR-32568 (a NHE inhibitor), respectively. The maximal inhibitions of HIR-I (NCX) by 4 μM TTX and 10 μM KR-32568 were 72.54% and 16.89%, respectively. (2) Administration of 2 μM TTX and 10 μM KR-32568 in either order in the same cells decreased HIR-I (NCX) by 64.83% and 16.94%, respectively. (3) I (Na.P) and the reverse I (NCX) were augmented during acute ischemia. TTX (4 μM) and KR-32568 (10 μM) reduced AIR-I (NCX) by 73.39% and 24.13%, respectively. (4) Under normoxic condition, veratridine (20 μM) significantly increased I (Na.P) and the reverse I (NCX), which was reversed by 4 μM TTX. In conclusion, during hypoxia or acute ischemia, both increased I (Na.P) and NHE contribute to the HIR- or AIR-I (NCX) with the former playing a major role comparing with the latter.
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Affiliation(s)
- Qiong Tang
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan, Hubei, China
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27
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Ma J, Luo A, Wu L, Wan W, Zhang P, Ren Z, Zhang S, Qian C, Shryock JC, Belardinelli L. Calmodulin kinase II and protein kinase C mediate the effect of increased intracellular calcium to augment late sodium current in rabbit ventricular myocytes. Am J Physiol Cell Physiol 2011; 302:C1141-51. [PMID: 22189558 DOI: 10.1152/ajpcell.00374.2011] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) augments late sodium current (I(Na.L)) in cardiomyocytes. This study tests the hypothesis that both Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) and protein kinase C (PKC) mediate the effect of increased [Ca(2+)](i) to increase I(Na.L). Whole cell and open cell-attached patch clamp techniques were used to record I(Na.L) in rabbit ventricular myocytes dialyzed with solutions containing various concentrations of [Ca(2+)](i). Dialysis of cells with [Ca(2+)](i) from 0.1 to 0.3, 0.6, and 1.0 μM increased I(Na.L) in a concentration-dependent manner from 0.221 ± 0.038 to 0.554 ± 0.045 pA/pF (n = 10, P < 0.01) and was associated with an increase in mean Na(+) channel open probability and prolongation of channel mean open-time (n = 7, P < 0.01). In the presence of 0.6 μM [Ca(2+)](i), KN-93 (10 μM) and bisindolylmaleimide (BIM, 2 μM) decreased I(Na.L) by 45.2 and 54.8%, respectively. The effects of KN-93 and autocamtide-2-related inhibitory peptide II (2 μM) were not different. A combination of KN-93 and BIM completely reversed the increase in I(Na.L) as well as the Ca(2+)-induced changes in Na(+) channel mean open probability and mean open-time induced by 0.6 μM [Ca(2+)](i). Phorbol myristoyl acetate increased I(Na.L) in myocytes dialyzed with 0.1 μM [Ca(2+)](i); the effect was abolished by Gö-6976. In summary, both CaMKII and PKC are involved in [Ca(2+)](i)-mediated augmentation of I(Na.L) in ventricular myocytes. Inhibition of CaMKII and/or PKC pathways may be a therapeutic target to reduce myocardial dysfunction and cardiac arrhythmias caused by calcium overload.
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Affiliation(s)
- Jihua Ma
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, China.
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28
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Murphy L, Renodin D, Antzelevitch C, Di Diego JM, Cordeiro JM. Extracellular proton depression of peak and late Na⁺ current in the canine left ventricle. Am J Physiol Heart Circ Physiol 2011; 301:H936-44. [PMID: 21685271 PMCID: PMC3191105 DOI: 10.1152/ajpheart.00204.2011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 06/12/2011] [Indexed: 11/22/2022]
Abstract
Cardiac ischemia reduces excitability in ventricular tissue. Acidosis (one component of ischemia) affects a number of ion currents. We examined the effects of extracellular acidosis (pH 6.6) on peak and late Na(+) current (I(Na)) in canine ventricular cells. Epicardial and endocardial myocytes were isolated, and patch-clamp techniques were used to record I(Na). Action potential recordings from left ventricular wedges exposed to acidic Tyrode solution showed a widening of the QRS complex, indicating slowing of transmural conduction. In myocytes, exposure to acidic conditions resulted in a 17.3 ± 0.9% reduction in upstroke velocity. Analysis of fast I(Na) showed that current density was similar in epicardial and endocardial cells at normal pH (68.1 ± 7.0 vs. 63.2 ± 7.1 pA/pF, respectively). Extracellular acidosis reduced the fast I(Na) magnitude by 22.7% in epicardial cells and 23.1% in endocardial cells. In addition, a significant slowing of the decay (time constant) of fast I(Na) was observed at pH 6.6. Acidosis did not affect steady-state inactivation of I(Na) or recovery from inactivation. Analysis of late I(Na) during a 500-ms pulse showed that the acidosis significantly reduced late I(Na) at 250 and 500 ms into the pulse. Using action potential clamp techniques, application of an epicardial waveform resulted in a larger late I(Na) compared with when an endocardial waveform was applied to the same cell. Acidosis caused a greater decrease in late I(Na) when an epicardial waveform was applied. These results suggest acidosis reduces both peak and late I(Na) in both cell types and contributes to the depression in cardiac excitability observed under ischemic conditions.
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Affiliation(s)
- Lisa Murphy
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, Utica, New York 13501, USA
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29
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Onkal R, Djamgoz MB. Molecular pharmacology of voltage-gated sodium channel expression in metastatic disease: Clinical potential of neonatal Nav1.5 in breast cancer. Eur J Pharmacol 2009; 625:206-19. [DOI: 10.1016/j.ejphar.2009.08.040] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 08/04/2009] [Accepted: 08/19/2009] [Indexed: 10/20/2022]
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30
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Du Y, Zhang S, Wu H, Zou A, Lei M, Cheng L, Liao Y. Glycyrretinic acid blocks cardiac sodium channels expressed in Xenopus oocytes. JOURNAL OF ETHNOPHARMACOLOGY 2009; 125:318-323. [PMID: 19559778 DOI: 10.1016/j.jep.2009.06.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Revised: 04/23/2009] [Accepted: 06/17/2009] [Indexed: 05/28/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Licorice has been used to treat many ailments including cardiovascular disorders in China for long time. Recent studies have shown that the cardiac actions of licorice have been attributed to its active component, glycyrretinic acid (GA). However, its mechanism remains poorly understood. AIM OF THE STUDY The effects of GA on the cardiac sodium currents (I(Na)), L-type calcium currents (I(Ca,L)) and hyperpolarization-activated inward currents (I(f)) were investigated. MATERIALS AND METHODS Human isoforms of wild-type and DeltaKPQ-mutant type sodium channels were expressed in Xenopus oocytes, and the resulting currents (peak and late I(Na)) were recorded using a two-microelectrode voltage-clamp technique. A perforated patch clamp technique was employed to record I(Ca,L) and I(f) from isolated rabbit sinoatrial node pacemaker cells. RESULTS GA inhibited peak I(Na) (33% at 90 microM) and late I(Na) (72% at 90 microM), but caused no significant effects on I(Ca,L) and I(f). CONCLUSION GA blocked cardiac sodium currents, particularly late I(Na.) Our findings might help to understand the traditional use of licorice in the treatment of cardiovascular disorders, because reduction of sodium currents (particularly late I(Na)) would be expected to provide protection from Na(+)-induced Ca(2+) overload and cell damage.
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Affiliation(s)
- Yimei Du
- Ion Channelopathy Research Center, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, PR China
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Zheng J, Ma J, Zhang P, Hu L, Fan X, Tang Q. Milrinone inhibits hypoxia or hydrogen dioxide-induced persistent sodium current in ventricular myocytes. Eur J Pharmacol 2009; 616:206-12. [PMID: 19549513 DOI: 10.1016/j.ejphar.2009.06.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Revised: 05/28/2009] [Accepted: 06/09/2009] [Indexed: 12/19/2022]
Abstract
Much evidence indicates that increased persistent sodium current (I(Na.P)) is associated with cellular calcium overload and I(Na.P) is considered to be a potential target for therapeutic intervention in ischaemia and heart failure. By inhibiting type III phosphodiesterase, milrinone increases intracellular cyclic adenosine monophosphate (cAMP), with a positive inotropic effect. However, the effect of milrinone on increased I(Na.P) under pathological conditions remains unknown. Accordingly, we investigated the effect of milrinone on increased I(Na.P) induced by hypoxia or hydrogen dioxide in guinea pig ventricular myocytes. While milrinone (0.01 mM or 0.1mM) or cAMP (0.1 mM) decreased I(Na.P) respectively in control condition, application of 1 microM H-89, a selective cAMP-dependant protein kinase inhibitor, prevented the effect of 0.1mM milrinone in control condition. Milrinone (0.1 mM) reduced the increased I(Na.P) induced by hypoxia. Furthermore, 0.01 mM or 0.1mM milrinone reduced the enhanced I(Na.P) induced by 0.3 mM hydrogen peroxide. In addition, 0.01 mM or 0.1 mM milrinone shortened action potential duration at 90% repolarization (APD(90)). Bath application of 0.3 mM hydrogen dioxide markedly prolonged APD(90), while 2 microM tetrodotoxin (TTX) reversed the prolonged APD(90). In the other two groups, 0.01 mM or 0.1 mM milrinone shortened the prolonged APD(90) induced by 0.3 mM hydrogen peroxide, ultimately 2 microM TTX causing a further decurtation of APD(90). These findings demonstrate that milrinone inhibited I(Na.P) under normal condition, hypoxia or hydrogen dioxide-induced I(Na.P), and the APD(90) prolonged by hydrogen dioxide-induced I(Na.P) in ventricular myocytes, which is associated with the mechanism of milrinone increasing intracellular cAMP.
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Affiliation(s)
- Jie Zheng
- Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan, Hubei, China
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32
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To establish a pharmacological experimental platform for the study of cardiac hypoxia using the microelectrode array. J Pharmacol Toxicol Methods 2009; 59:146-52. [DOI: 10.1016/j.vascn.2009.02.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Accepted: 02/17/2009] [Indexed: 11/19/2022]
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Clements-Jewery H, Andrag E, Curtis MJ. Druggable targets for sudden cardiac death prevention: lessons from the past and strategies for the future. Curr Opin Pharmacol 2009; 9:146-53. [PMID: 19167272 DOI: 10.1016/j.coph.2008.12.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 12/02/2008] [Accepted: 12/04/2008] [Indexed: 12/19/2022]
Abstract
Sudden cardiac death (SCD) is most commonly caused by ventricular fibrillation (VF). The single largest cohort of victims is the population with little or no prior overt heart disease. Effective prevention will require long-term prophylaxis by drugs in large numbers of people identified by risk factors. This means that safe as well as effective drugs are required. Drugs with overt effects on cardiac electrophysiology have failed in the clinic owing to poor effectiveness and/or adverse effects. This article examines possible new drug targets. We have focused on acute myocardial ischaemia as it is the most strikingly proarrhythmic pathology, and the most common cause of coronary artery disease-related VF and SCD according to inferences from epidemiology, drug trials and decades of animal research. To set the scene we have briefly explored drugs that have failed in the clinic in order to identify possible targets that have been overlooked or underexploited. We conclude that the best strategy is identification of pathology-specific targets that render drugs active only where and when their action is required.
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Vacher B, Pignier C, Létienne R, Verscheure Y, Le Grand B. F 15845 inhibits persistent sodium current in the heart and prevents angina in animal models. Br J Pharmacol 2009; 156:214-25. [PMID: 19133985 DOI: 10.1111/j.1476-5381.2008.00062.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Activation of the persistent sodium current in ischaemic myocardium results in calcium overload which is toxic for the cardiomyocyte. Thus, the activity of 3-(R)-[3-(2-methoxyphenylthio-2-(S)-methylpropyl]amino-3,4-dihydro-2H-1,5 benzoxathiepine bromhydrate (F 15845), a new selective persistent sodium current blocker, in protecting against the effects of cardiac ischaemia was examined, in both in vitro and in vivo models. EXPERIMENTAL APPROACH Electrophysiological studies using patch-clamp and conventional microlelectrode techniques, isolated perfused hearts and models of angina in anaesthetized animals were used to assess the protection afforded by F 15845 against ischaemia-induced changes. KEY RESULTS F 15845 reduced the persistent sodium current activated by veratridine (IC(50) 1.58 x 10(-6) mol.L(-1)). F 15845 blocked voltage-gated human cardiac sodium channels in a novel, voltage-dependent manner, selectively affecting steady-state inactivation. F 15845 did not affect action potential shape and basal function of guinea pig isolated perfused hearts but did reduce ischaemia-induced diastolic contracture in this model (IC(50) 0.64 x 10(-6) mol.L(-1)). In rabbits, F 15845 given i.v. (ED(50) 0.05 mg.kg(-1)) or orally (ED(50) 0.13 mg.kg(-1)) dose-dependently and powerfully inhibited regional myocardial ischaemia-induced ST segment elevation in the absence of haemodynamic effects, implying direct cardiac activity. In dogs, F 15845 dose-dependently inhibited epicardial ST segment changes (70 +/- 8% at 0.63 mg.kg(-1)) in an experimental angina model of demand ischaemia, again without haemodynamic effects, confirming a direct anti-anginal activity. CONCLUSIONS AND IMPLICATIONS F 15845 is a selective, potent blocker of the persistent sodium current, generated by the human Na(v)1.5 channel isoforms, and prevents cardiac angina in animal models.
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Affiliation(s)
- B Vacher
- Centre de Recherche Pierre Fabre, 17 Avenue Jean Moulin, Castres Cedex, France
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35
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Chevalier M, Ben-Mabrouk F, Tryba AK. Background sodium current underlying respiratory rhythm regularity. Eur J Neurosci 2008; 28:2423-33. [PMID: 19032590 DOI: 10.1111/j.1460-9568.2008.06537.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rhythm-generating neural circuits underlying diverse behaviors such as locomotion, sleep states, digestion and respiration play critical roles in our lives. Irregularities in these rhythmic behaviors characterize disease states--thus, it is essential that we identify the ionic and/or cellular mechanisms that are necessary for triggering these rhythmic behaviors on a regular basis. Here, we examine which ionic conductances underlie regular or 'stable' respiratory activities, which are proposed to underlie eupnea, or normal quiet breathing. We used a mouse in vitro medullary slice preparation containing the rhythmogenic respiratory neural circuit, called the preBötzinger complex (preBötC), that underlies inspiratory respiratory activity. We varied either [K(+)](o) or [Na(+)](o), or blocked voltage-gated calcium channels, while recording from synaptically isolated respiratory pacemakers, and examined which of these manipulations resulted in their endogenous bursting becoming more irregular. Of these, lowering [Na(+)](o) increased the irregularity of endogenous bursting by synaptically isolated pacemakers. Lowering [Na(+)](o) also decreased the regularity of fictive eupneic activity generated by the ventral respiratory group (VRG) population and hypoglossal motor output. Voltage clamp data indicate that lowering [Na(+)](o), in a range that results in irregular population rhythm generation, decreased persistent sodium currents, but not transient sodium currents underlying action potentials. Our data suggest that background sodium currents play a major role in determining the regularity of the fictive eupneic respiratory rhythm.
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Affiliation(s)
- Marc Chevalier
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI 53226, USA
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36
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Pathophysiology and pharmacology of the cardiac “late sodium current”. Pharmacol Ther 2008; 119:326-39. [DOI: 10.1016/j.pharmthera.2008.06.001] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2008] [Accepted: 06/04/2008] [Indexed: 12/19/2022]
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37
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Pignier C, Le Grand B. Letter by Pignier and Le Grand regarding article "Acute administration of fish oil inhibits triggered activity in isolated myocytes from rabbits and patients with heart failure". Circulation 2008; 118:e69; author reply e70. [PMID: 18625900 DOI: 10.1161/circulationaha.108.778373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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38
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Hale SL, Shryock JC, Belardinelli L, Sweeney M, Kloner RA. Late sodium current inhibition as a new cardioprotective approach. J Mol Cell Cardiol 2008; 44:954-967. [PMID: 18462746 DOI: 10.1016/j.yjmcc.2008.03.019] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Revised: 03/05/2008] [Accepted: 03/21/2008] [Indexed: 12/19/2022]
Abstract
There is increasing evidence that the late sodium current of the sodium channel in myocytes plays a critical role in the pathophysiology of myocardial ischemia and thus is a potential therapeutic target in patients with ischemic heart disease. Ranolazine, an inhibitor of the late sodium current, reduces the frequency and severity of anginal attacks and ST-segment depression in humans, and unlike other antianginal drugs, ranolazine does not alter heart rate or blood pressure. In experimental animal models, ranolazine has been shown to reduce myocardial infarct size and to improve left ventricular function after acute ischemia and chronic heart failure. This article reviews published data describing the role of late sodium current and its inhibition by ranolazine in clinical and experimental studies of myocardial ischemia.
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Affiliation(s)
- Sharon L Hale
- The Heart Institute of Good Samaritan Hospital, Los Angeles, CA 90017, USA; The Keck School of Medicine, Division of Cardiovascular Medicine, University of Southern California, Los Angeles, CA 90017, USA
| | - John C Shryock
- Cardiovascular Therapeutics, Inc, 1651 Page Mill Road, Palo Alto, CA 94304, USA.
| | - Luiz Belardinelli
- Cardiovascular Therapeutics, Inc, 1651 Page Mill Road, Palo Alto, CA 94304, USA
| | - Michael Sweeney
- Depomed, Inc., 1360 O'Brien Drive, Menlo Park, CA 94025, USA
| | - Robert A Kloner
- The Heart Institute of Good Samaritan Hospital, Los Angeles, CA 90017, USA; The Keck School of Medicine, Division of Cardiovascular Medicine, University of Southern California, Los Angeles, CA 90017, USA
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Pinet C, Algalarrondo V, Sablayrolles S, Le Grand B, Pignier C, Cussac D, Perez M, Hatem SN, Coulombe A. Protease-activated receptor-1 mediates thrombin-induced persistent sodium current in human cardiomyocytes. Mol Pharmacol 2008; 73:1622-31. [PMID: 18326052 DOI: 10.1124/mol.107.043182] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
After the thrombus formation in cardiac cavities or coronaries, the serine protease thrombin is produced and can therefore reach the myocardial tissue by the active process of extravasation and binds to the G protein-coupled protease-activated receptor-1 (PAR1) expressed in human myocardium. The role of PAR1 was investigated in the thrombin effect on sodium current (I(Na)). I(Na) was recorded in freshly isolated human atrial myocytes by the whole-cell patch-clamp method. Action potentials (AP) were recorded in guinea pig ventricular tissue by the conventional glass microelectrode technique. Thrombin-activated PAR1 induced a tetrodotoxin-blocked persistent sodium current, I(NaP), in a concentration-dependent manner with an apparent EC(50) of 28 U/ml. The PAR1 agonist peptide SFLLR-NH(2) (50 microM) was able to mimic PAR1-thrombin action, whereas PAR1 antagonists N(3)-cyclopropyl-7-((4-(1-methylethyl)-phenyl)methyl)-7H-pyrrolo(3,2-f)quinazoline-1,3-diamine (SCH 203099; 10 microM) and 1-(3,5-di-tert-butyl-4-hydroxy-phenyl)-2-[3-(3-ethyl-3-hydroxy-pentyl)-2-imino-2,3-dihydro-imidazol-1-yl]-ethanone (ER 112787) (1 microM), completely inhibited it. The activated PAR1 involves the calcium-independent phospholipase-A(2) signaling pathway because two inhibitors of this cascade, bromoenol lactone (50 microM) and haloenol lactone suicide substrate (50 microM), block PAR1-thrombin-induced I(NaP).Asa consequence of I(NaP) activation, in guinea pig right ventricle papillary muscle, action potential duration (APD) were significantly increased by 20% and 15% under the respective action of 32 U/ml thrombin and 50 microM SFLLR-NH(2), and these increases in APD were prevented by 1 microM tetrodotoxin or markedly reduced by application of 1 microM SCH 203099 or ER 112787. Thrombin, through PAR1 activation, increases persistent component of the Na(+) current resulting in an uncontrolled sodium influx into the cardiomyocyte, which can contribute to cellular injuries observed during cardiac ischemia.
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Affiliation(s)
- Caroline Pinet
- Centre National de la Recherche Scientifique, Unité 8162, Université de Paris XI, and Laboratoire de Recherches Médicales, Hôpital Marie Lannelongue, Le Plessis-Robinson, France
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Saint DA. The cardiac persistent sodium current: an appealing therapeutic target? Br J Pharmacol 2008; 153:1133-42. [PMID: 18071303 PMCID: PMC2275458 DOI: 10.1038/sj.bjp.0707492] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 08/20/2007] [Accepted: 08/28/2007] [Indexed: 12/19/2022] Open
Abstract
The sodium current in the heart is not a single current with a mono-exponential decay but rather a mixture of currents with different kinetics. It is not clear whether these arise from distinct populations of channels, or from modulation of a single population. A very slowly inactivating component, [(INa(P))] I(Na(P)) is usually about 1% of the size of the peak transient current [I(Na(T))], but is enhanced by hypoxia. It contributes to Na(+) loading and cellular damage in ischaemia and re-perfusion, and perhaps to ischaemic arrhythmias. Class I antiarrhythmic agents such as flecainide, lidocaine and mexiletine generally block I(NA(P)) more potently than block of I(Na(T)) and have been used clinically to treat LQT3 syndrome, which arises because mutations in SCN5A produce defective inactivation of the cardiac sodium channel. The same approach may be useful in some pathological situations, such as ischaemic arrhythmias or diastolic dysfunction, and newer agents are being developed with this goal. For example, ranolazine blocks I(Na(P)) about 10 times more potently than I(Na(T)) and has shown promise in the treatment of angina. Alternatively, the combination of I(Na(P)) block with K(+) channel block may provide protection from the induction of Torsades de Pointe when these agents are used to treat atrial arrhythmias (eg Vernakalant). In all of these scenarios, an understanding of the role of I(Na(P)) in cardiac pathophysiology, the mechanisms by which it may affect cardiac electrophysiology and the potential side effects of blocking I(Na(P)) in the heart and elsewhere will become increasingly important.
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Affiliation(s)
- D A Saint
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA, Australia.
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41
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Fang KM, Lee AS, Su MJ, Lin CL, Chien CL, Wu ML. Free fatty acids act as endogenous ionophores, resulting in Na+ and Ca2+ influx and myocyte apoptosis. Cardiovasc Res 2008; 78:533-45. [PMID: 18267958 DOI: 10.1093/cvr/cvn030] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIMS Disturbances in lipid metabolism have been suggested to play an important role in myocardial damage. Marked accumulation of free fatty acids (FFAs), including arachidonic acid (AA), palmitic acid, oleic acid, and linoleic acid, occurs during post-ischaemia and reperfusion (post-I/R). Possible cellular mechanisms of AA/FFAs-induced myocyte apoptosis were investigated. METHODS AND RESULTS In neonatal rat ventricular myocytes, AA/FFAs activate a novel non-selective cation conductance (NSCC), resulting in both intracellular Ca(2+) and Na(+) overload. AA caused sustained cytosolic [Na(+)](cyt) and [Ca(2+)](cyt) overload, resulting in mitochondrial [Na(+)](m) and [Ca(2+)](m) overload, which induced caspase-3-mediated apoptosis. Similar apoptotic effects were seen using Na(+) ionophore cocktail/Ca(2+)-free medium, which induced [Na(+)](cyt) and [Na(+)](m), but not [Ca(2+)](cyt) and [Ca(2+)](m) overload. Electron microscopy showed that inhibition of [Na(+)](m) overload prevented disruption of the mitochondrial membrane, showing that [Na(+)](m) overload is an important upstream signal in AA- and FFA-induced myocyte apoptosis. CONCLUSION AA and FFAs, which accumulate in the myocardium during post-I/R, may therefore act as naturally occurring endogenous ionophores and contribute to the myocyte death seen during post-I/R.
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Affiliation(s)
- Kwang-Ming Fang
- Institute of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
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Shryock JC, Belardinelli L. Inhibition of late sodium current to reduce electrical and mechanical dysfunction of ischaemic myocardium. Br J Pharmacol 2007; 153:1128-32. [PMID: 18071302 DOI: 10.1038/sj.bjp.0707522] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
This commentary on the review by DA Saint in the current issue of the British Journal of Pharmacology focuses on the pathological role of late I(Na) in the heart, the evidence supporting inhibition of late I(Na) as a therapeutic target in ischaemic heart disease, and the therapeutic applications and challenges for development of new late I(Na) inhibitors. Recent reports from a large clinical outcome trial (MERLIN) of ranolazine, a drug known to inhibit late I(Na), indicated that it was safe and reduced recurrent ischaemia and arrhythmic activity. In combination with other results indicating that inhibition of late I(Na) reduces ischaemia, myocardial Ca(2+) overload, and electrical and mechanical dysfunction when late I(Na) is increased, the new clinical trial results suggest that reduction of cardiac late I(Na) is safe and therapeutically beneficial.
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Affiliation(s)
- J C Shryock
- CV Therapeutics Inc, Palo Alto, CA 94304, USA
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43
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Shang LL, Sanyal S, Pfahnl AE, Jiao Z, Allen J, Liu H, Dudley SC. NF-kappaB-dependent transcriptional regulation of the cardiac scn5a sodium channel by angiotensin II. Am J Physiol Cell Physiol 2007; 294:C372-9. [PMID: 18032528 DOI: 10.1152/ajpcell.00186.2007] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Angiotensin II (ANG II) increases oxidative stress and is associated with increased risk of sudden cardiac death. The cardiac Na(+) channel promoter contains elements that confer redox sensitivity. We tested the hypothesis that ANG II-mediated oxidative stress may modulate Na(+) channel current through altering channel transcription. In H9c2 myocytes treated for 48 h with ANG II (100 nmol/l) or H(2)O(2) (10 micromol/l) showed delayed macroscopic inactivation, increased late current, and 59.6% and 53.8% reductions in Na(+) current, respectively (P < or = 0.01). By quantitative real-time RT-PCR, the cardiac Na(+) channel (scn5a) mRNA abundance declined by 47.3% (P < 0.01) in H9c2 myocytes treated for 48 h with 100 nmol/l ANG II. A similar change occurred with 20 micromol/l H(2)O(2) (46.9%, P < 0.01) after 48 h. Comparable effects were seen in acutely isolated ventricular myocytes. The effects of ANG II could be inhibited by prior treatment of H9c2 cells with scavengers of reactive oxygen species or an inhibitor of the NADPH oxidase. Mutation of the scn5a promoter NF-kappaB binding site prevented decreased activity in response to ANG II and H(2)O(2). Gel shift and chromosomal immunoprecipitation assays confirmed that nuclear factor (NF)-kappaB bound to the scn5a promoter in response to ANG II and H(2)O(2). Overexpression of the p50 subunit of NF-kappaB in H9c2 cells reduced scn5a mRNA (77.3%, P < 0.01). In conclusion, ANG II can decrease scn5a transcription and current. This effect appears to be through production of H(2)O(2) resulting in NF-kappaB binding to the Na(+) channel promoter.
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Affiliation(s)
- Lijuan L Shang
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, Georgia, USA
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Pignier C, Revenaz C, Rauly-Lestienne I, Cussac D, Delhon A, Gardette J, Le Grand B. Direct protective effects of poly-unsaturated fatty acids, DHA and EPA, against activation of cardiac late sodium current. Basic Res Cardiol 2007; 102:553-64. [PMID: 17891522 DOI: 10.1007/s00395-007-0676-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 08/17/2007] [Accepted: 08/22/2007] [Indexed: 10/22/2022]
Abstract
Polyunsaturated fatty acids (PUFAs) such as docosahexaenoic and eicosapentaenoic acids (DHA, EPA) exert ischemic anti-arrhythmic effects. However, their mechanism of action remains unknown. The present study was designed to investigate their potential effect on the regulation of the late sodium current as the basis for their ischemic anti-arrhythmic activity. Human isoforms of wild-type SCN5A and DeltaKPQ-mutated cardiac sodium channels were stably transfected in HEK 293 cells and, the resulting currents were recorded using the patch clamp technique in whole cell configuration. In addition to their effect to inhibit peak I(Na), acute application of DHA and EPA blocked veratridine-induced late sodium current (late I(Na-Verat)) in a concentration--dependent manner with IC(50) values of 2.1 +/- 0.5 microM and 5.2 +/- 0.8 microM,for DHA and EPA, respectively. Channels availability was reduced, resulting in a significant leftward shift of the steadystate inactivation curve by -10.0 +/- 2.1 mV and -8.5 +/- 0.2 mV for DHA and EPA, respectively. Similar inhibitory effects of DHA and EPA were also observed on late I(Na-KPQ). In addition to their role as blocking agents of peak I(Na), DHA and EPA reduced human late I(Na). These results could explain the antiarrhythmic properties of DHA and EPA during ischemia or following ischemia-reperfusion.
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Affiliation(s)
- Christophe Pignier
- Division des Maladies Cardiovasculaires II, Centre de Recherche Pierre Fabre, Castres cedex, France.
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Abstract
All mammals and birds must develop effective strategies to cope with reduced oxygen availability. These animals achieve tolerance to acute and chronic hypoxia by (a) reductions in metabolism, (b) the prevention of cellular injury, and (c) the maintenance of functional integrity. Failure to meet any one of these tasks is detrimental. Birds and mammals accomplish this triple task through a highly coordinated, systems-level reconfiguration involving the partial shutdown of some but not all organs. This reconfiguration is achieved through a similarly complex reconfiguration at the cellular and molecular levels. Reconfiguration at these various levels depends on numerous factors that include the environment, the degree of hypoxic stress, and developmental, behavioral, and ecological conditions. Although common molecular strategies exist, the cellular and molecular changes in any given cell are very diverse. Some cells remain metabolically active, whereas others shut down or rely on anaerobic metabolism. This cellular shutdown is temporarily regulated, and during hypoxic exposure, active cellular networks must continue to control vital functions. The challenge for future research is to explore the cellular mechanisms and conditions that transform an organ or a cellular network into a hypometabolic state, without loss of functional integrity. Much can be learned in this respect from nature: Diving, burrowing, and hibernating animals living in diverse environments are masters of adaptation and can teach us how to deal with hypoxia, an issue of great clinical significance.
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Affiliation(s)
- Jan-Marino Ramirez
- Department of Organismal Biology & Anatomy, University of Chicago, Chicago, Illinois 60637, USA.
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