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Fu C, Hao J, Zeng M, Song Y, Jiang W, Zhang P, Luo A, Cao Z, Belardinelli L, Ma J. Modulation of late sodium current by Ca2+-calmodulin-dependent protein kinase II, protein kinase C and Ca2+during hypoxia in rabbit ventricular myocytes. Exp Physiol 2017; 102:818-834. [DOI: 10.1113/ep085990] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 04/13/2017] [Indexed: 01/05/2023]
Affiliation(s)
- Chen Fu
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
- Department of Cardiovascular Medicine; Tianyou Hospital, affiliated to Wuhan University of Science and Technology; Wuhan China
| | - Jie Hao
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
| | - Mengliu Zeng
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
| | - Yejia Song
- Division of Cardiovascular Medicine; University of Florida College of Medicine; Gainesville FL USA
| | - Wanzhen Jiang
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
| | - Peihua Zhang
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
| | - Antao Luo
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
| | - Zhenzhen Cao
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
| | | | - Jihua Ma
- Cardio-Electrophysiological Research Laboratory; Medical College of Wuhan University of Science and Technology; Wuhan China
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Ronchi C, Torre E, Rizzetto R, Bernardi J, Rocchetti M, Zaza A. Late sodium current and intracellular ionic homeostasis in acute ischemia. Basic Res Cardiol 2017; 112:12. [PMID: 28101642 DOI: 10.1007/s00395-017-0602-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 01/03/2017] [Indexed: 11/25/2022]
Abstract
Blockade of the late Na+ current (I NaL) protects from ischemia/reperfusion damage; nevertheless, information on changes in I NaL during acute ischemia and their effect on intracellular milieu is missing. I NaL, cytosolic Na+ and Ca2+ activities (Nacyt, Cacyt) were measured in isolated rat ventricular myocytes during 7 min of simulated ischemia (ISC); in all the conditions tested, effects consistently exerted by ranolazine (RAN) and tetrodotoxin (TTX) were interpreted as due to I NaL blockade. The results indicate that I NaL was enhanced during ISC in spite of changes in action potential (AP) contour; I NaL significantly contributed to Nacyt rise, but only marginally to Cacyt rise. The impact of I NaL on Cacyt was markedly enhanced by blockade of the sarcolemmal(s) Na+/Ca2+ exchanger (NCX) and was due to the presence of (Na+-sensitive) Ca2+ efflux through mitochondrial NCX (mNCX). sNCX blockade increased Cacyt and decreased Nacyt, thus indicating that, throughout ISC, sNCX operated in the forward mode, in spite of the substantial Nacyt increment. Thus, a robust Ca2+ source, other than sNCX and including mitochondria, contributed to Cacyt during ISC. Most, but not all, of RAN effects were shared by TTX. (1) The paradigm that attributes Cacyt accumulation during acute ischemia to decrease/reversal of sNCX transport may not be of general applicability; (2) I NaL is enhanced during ISC, when the effect of Nacyt on mitochondrial Ca2+ transport may substantially contribute to I NaL impact on Cacyt; (3) RAN may act mostly, but not exclusively, through I NaL blockade during ISC.
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Affiliation(s)
- Carlotta Ronchi
- Department of Biotechnologies and Biosciences, University Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Eleonora Torre
- Department of Biotechnologies and Biosciences, University Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Riccardo Rizzetto
- Department of Biotechnologies and Biosciences, University Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Joyce Bernardi
- Department of Biotechnologies and Biosciences, University Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Marcella Rocchetti
- Department of Biotechnologies and Biosciences, University Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Antonio Zaza
- Department of Biotechnologies and Biosciences, University Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy.
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Wang C, Wang LL, Zhang C, Cao ZZ, Luo AT, Zhang PH, Fan XR, Ma JH. Tolterodine reduces veratridine-augmented late I Na, reverse-I NCX and early afterdepolarizations in isolated rabbit ventricular myocytes. Acta Pharmacol Sin 2016; 37:1432-1441. [PMID: 27569391 DOI: 10.1038/aps.2016.76] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/12/2016] [Indexed: 12/19/2022] Open
Abstract
AIM The augmentation of late sodium current (INa.L) not only causes intracellular Na+ accumulation, which results in intracellular Ca2+ overload via the reverse mode of the Na+/Ca2+ exchange current (reverse-INCX), but also prolongs APD and induces early afterdepolarizations (EAD), which can lead to arrhythmia and cardiac dysfunction. Thus, the inhibition of INa.L is considered to be a potential way for therapeutic intervention in ischemia and heart failure. In this study we investigated the effects of tolterodine (Tol), a competitive muscarinic receptor antagonist, on normal and veratridine (Ver)-augmented INa.L, reverse-INCX and APD in isolated rabbit ventricular myocytes, which might contribute to its cardioprotective activity. METHODS Rabbit ventricular myocytes were prepared. The INa.L and reverse-INCX were recorded in voltage clamp mode, whereas action potentials and Ver-induced early afterdepolarizations (EADs) were recorded in current clamp mode. Drugs were applied via superfusion. RESULTS Tol (3-120 nmol/L) concentration-dependently inhibited the normal and Ver-augmented INa.L with IC50 values of 32.08 nmol/L and 42.47 nmol/L, respectively. Atropine (100 μmol/L) did not affect the inhibitory effects of Tol (30 nmol/L) on Ver-augmented INa.L. In contrast, much high concentrations of Tol was needed to inhibit the transient sodium current (INa.T) with an IC50 value of 183.03 μmol/L. In addition, Tol (30 nmol/L) significantly shifted the inactivation curve of INa.T toward a more depolarizing membrane potential without affecting its activation characteristics. Moreover, Tol (30 nmol/L) significantly decreased Ver-augmented reverse-INCX. Tol (30 nmol/L) increased the action potential duration (APD) by 16% under the basal conditions. Ver (20 μmol/L) considerably extended the APD and evoked EADs in 18/24 cells (75%). In the presence of Ver, Tol (30 nmol/L) markedly decreased the APD and eliminated EADs (0/24 cells). CONCLUSION Tol inhibits normal and Ver-augmented INaL and decreases Ver-augmented reverse-INCX. In addition, Tol reverses the prolongation of the APD and eliminates the EADs induced by Ver, thus prevents Ver-induced arrhythmia.
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Azuma YT, Hayashi S, Nishiyama K, Kita S, Mukai K, Nakajima H, Iwamoto T, Takeuchi T. Na(+) /Ca(2+) exchanger-heterozygote knockout mice display increased relaxation in gastric fundus and accelerated gastric transit in vivo. Neurogastroenterol Motil 2016; 28:827-36. [PMID: 26787195 DOI: 10.1111/nmo.12779] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 12/25/2015] [Indexed: 01/31/2023]
Abstract
BACKGROUND For the contraction and relaxation of gastric smooth muscles to occur, the intracellular Ca(2+) concentration must be increased and decreased, respectively. The Na(+) /Ca(2+) exchanger (NCX) is a plasma membrane transporter that is involved in regulating intracellular Ca(2+) concentrations. METHODS To determine the role of NCX in gastrointestinal tissues, we examined electric field stimulation (EFS)-induced relaxations in the circular muscles of the gastric fundus in NCX1 and NCX2 heterozygote knockout mice (HET). KEY RESULTS The myenteric plexus layers and the longitudinal and circular muscle layers in the gastric fundus of wild-type mice (WT) were strongly immunoreactive to NCX1 and NCX2. EFS induced a transient relaxation that was apparent during the stimulus and a sustained relaxation that persisted after the end of the stimulus. The amplitudes of EFS-induced transient relaxation and sustained relaxation were greater in NCX1 HET and NCX2 HET than in WT. When an inhibitor of nitric oxide synthase was added following the EFS, neither NCX1 HET nor NCX2 HET exhibited transient relaxation, similar to WT. Furthermore, when a PACAP antagonist was added following the EFS, sustained relaxation in NCX1 HET and NCX2 HET was not observed, similar to WT. Next, we examined the effect of NCX heterozygous deficiency on relaxation in response to NO and PACAP in smooth muscles. The magnitude of NOR-1- and PACAP-induced relaxations in NCX1 HET and NCX2 HET was similar to that of WT. CONCLUSIONS & INFERENCES In this study, we demonstrate that NCX1 and NCX2 expressed in neurons regulate the motility in the gastric fundus.
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Affiliation(s)
- Y T Azuma
- Laboratory of Veterinary Pharmacology, Division of Veterinary Science, Osaka Prefecture University Graduate School of Life and Environmental Science, Osaka, Japan
| | - S Hayashi
- Laboratory of Veterinary Pharmacology, Division of Veterinary Science, Osaka Prefecture University Graduate School of Life and Environmental Science, Osaka, Japan
| | - K Nishiyama
- Laboratory of Veterinary Pharmacology, Division of Veterinary Science, Osaka Prefecture University Graduate School of Life and Environmental Science, Osaka, Japan
| | - S Kita
- Department of Pharmacology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - K Mukai
- Laboratory of Veterinary Pharmacology, Division of Veterinary Science, Osaka Prefecture University Graduate School of Life and Environmental Science, Osaka, Japan
| | - H Nakajima
- Laboratory of Veterinary Pharmacology, Division of Veterinary Science, Osaka Prefecture University Graduate School of Life and Environmental Science, Osaka, Japan
| | - T Iwamoto
- Department of Pharmacology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - T Takeuchi
- Laboratory of Veterinary Pharmacology, Division of Veterinary Science, Osaka Prefecture University Graduate School of Life and Environmental Science, Osaka, Japan
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Fan X, Wang C, Wang N, Ou X, Liu H, Yang Y, Dang X, Zeng X, Cai L. Atrial-selective block of sodium channels by acehytisine in rabbit myocardium. J Pharmacol Sci 2016; 132:235-243. [PMID: 27107824 DOI: 10.1016/j.jphs.2016.03.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 03/15/2016] [Accepted: 03/29/2016] [Indexed: 11/28/2022] Open
Abstract
Acehytisine, a multi-ion channel blocker, can markedly inhibit INa, ICa, IKur, If at various concentrations and effectively terminate and prevent atrial fibrillation (AF) in patients and animal models, but the molecular mechanism underlying its blockage remains elusive. In this study, we investigated the effects of acehytisine on action potentials and sodium channels of atrial and ventricular myocytes isolated from rabbit, using whole-cell recording system. We found that acehytisine exerted stronger blocking effects on sodium channels in atria than in ventricles, especially at depolarization (IC50: 48.48 ± 7.75 μmol/L in atria vs. 560.17 ± 63.98 μmol/L in ventricles). It also significantly shifted steady state inactivation curves toward negative potentials in atrial myocytes, without affecting the recovery kinetics from inactivation of sodium channels in the same cells. In addition, acehytisine inhibited INa in a use-dependent manner and regulated slow inactivation kinetics by different gating configurations. These findings indicate that acehytisine selectively blocks atrial sodium channels and possesses affinity to sodium channel in certain states, which provides additional evidence for the anti-AF of acehytisine.
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Affiliation(s)
- Xinrong Fan
- Department of Cardiology, Institute of Cardiovascular Disease of Chengdu, The Third People's Hospital of Chengdu, Chengdu, China; The Key Laboratory of Medical Electrophysiology, Ministry of Education of China, and the Institute of Cardiovascular Research, Sichuan Medical University, Luzhou, China
| | - Chao Wang
- Department of Cardiology, Institute of Cardiovascular Disease of Chengdu, The Third People's Hospital of Chengdu, Chengdu, China
| | - Na Wang
- The Key Laboratory of Medical Electrophysiology, Ministry of Education of China, and the Institute of Cardiovascular Research, Sichuan Medical University, Luzhou, China
| | - Xianhong Ou
- The Key Laboratory of Medical Electrophysiology, Ministry of Education of China, and the Institute of Cardiovascular Research, Sichuan Medical University, Luzhou, China
| | - Hanxiong Liu
- Department of Cardiology, Institute of Cardiovascular Disease of Chengdu, The Third People's Hospital of Chengdu, Chengdu, China
| | - Yan Yang
- The Key Laboratory of Medical Electrophysiology, Ministry of Education of China, and the Institute of Cardiovascular Research, Sichuan Medical University, Luzhou, China
| | - Xitong Dang
- The Key Laboratory of Medical Electrophysiology, Ministry of Education of China, and the Institute of Cardiovascular Research, Sichuan Medical University, Luzhou, China
| | - Xiaorong Zeng
- The Key Laboratory of Medical Electrophysiology, Ministry of Education of China, and the Institute of Cardiovascular Research, Sichuan Medical University, Luzhou, China.
| | - Lin Cai
- Department of Cardiology, Institute of Cardiovascular Disease of Chengdu, The Third People's Hospital of Chengdu, Chengdu, China.
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Effects of a new antiarrhythmic drug SS-68 on electrical activity in working atrial and ventricular myocardium of mouse and their ionic mechanisms. J Pharmacol Sci 2015; 128:202-7. [PMID: 26255591 DOI: 10.1016/j.jphs.2015.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 07/12/2015] [Accepted: 07/20/2015] [Indexed: 11/22/2022] Open
Abstract
SS-68 is a derivative of indole, which demonstrated strong antiarrhythmic effects not associated with significant QT prolongation in dog models of atrial fibrillation. Therefore, SS-68 was proposed as a new antiarrhythmic drug and the present study is the first describing its effects on action potentials (APs) configuration and elucidating the ionic mechanisms of these effects. Sharp microelectrodes were used to record APs in isolated preparations of mouse atrial and ventricular myocardium. In both types of myocardium 10(-6) M SS-68 produced reduction of AP duration, 3 × 10(-6) M failed to alter AP waveform and 10(-5) - 3 × 10(-5) M prolonged APs. Sensitivity of main ionic currents to SS-68 was determined using whole-cell patch clamp. Transient potassium current Ito was slightly inhibited by SS-68 with IC50 = 1.43 × 10(-4) M. IKur was more sensitive with IC50 = 1.84 × 10(-5) M. Background inward rectifier showed very low sensitivity to SS-68 - only 10(-4) M SS-68 caused significant reduction of IK1. ICaL was significantly inhibited by 10(-6)M - 3 × 10(-5) M SS-68. The IC50 value for the ICaL was 1.84 × 10(-6) M. Thus, main ionic currents of mouse cardiomyocytes are inhibited by SS-68 in the following order of potency: ICaL > IKur > Ito > IK1. While lower concentration of SS-68 shorten APs via suppression of ICaL, higher concentrations inhibit K(+)-currents leading to APs prolongation.
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Wu Y, Wang L, Ma J, Song Y, Zhang P, Luo A, Fu C, Cao Z, Wang X, Shryock JC, Belardinelli L. Protein kinase C and Ca(2+) -calmodulin-dependent protein kinase II mediate the enlarged reverse INCX induced by ouabain-increased late sodium current in rabbit ventricular myocytes. Exp Physiol 2015; 100:399-409. [PMID: 25641541 DOI: 10.1113/expphysiol.2014.083972] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 01/23/2015] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? What are the effects of protein kinase C (PKC) and Ca(2+) -calmodulin-dependent protein kinase II (CaMKII) on late sodium current (INaL ), reverse Na(+) -Ca(2+) exchange current (reverse INCX ) or intracellular Ca(2+) levels changed by ouabain? What is the main finding and its importance? Ouabain, even at low concentrations (0.5-8.0 μm), can increase INaL and reverse INCX , and these effects may contribute to the effect of the glycoside to increase Ca(2+) transients and contractility. Both PKC and CaMKII activities may mediate or modulate these processes. It has been reported that the cardiac glycoside ouabain can increase the late sodium current (INaL ), as well as the diastolic intracellular calcium concentration and contractile shortening. Whether an increase of INaL participates in a pathway that can mediate the positive inotropic response to ouabain is unknown. We therefore determined the effects of ouabain on INaL , reverse Na(+) -Ca(2+) exchange current (reverse INCX ), intracellular Ca(2+) ([Ca(2+) ]i ) levels and contractile shortening in rabbit isolated ventricular myocytes. Ouabain (0.1-8 μm) markedly increased INaL and reverse INCX in a concentration-dependent manner, with significant effects at concentrations as low as 0.5 and 1 μm. These effects of ouabain were suppressed by the INaL inhibitors TTX and ranolazine, the protein kinase C inhibitor bisindolylmaleimide and the Ca(2+) -calmodulin-dependent protein kinase II inhibitor KN-93. The enhancement by 0.5 μm ouabain of ventricular myocyte contractility and intracellular Ca(2+) transients was suppressed by 2.0 μm TTX. We conclude that ouabain, even at low concentrations (0.5-8.0 μm), can increase INaL and reverse INCX , and these effects may contribute to the effect of the glycoside to increase Ca(2+) transients and contractility. Both protein kinase C and Ca(2+) -calmodulin-dependent protein kinase II activities may mediate or modulate these processes.
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Affiliation(s)
- Ying Wu
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, China
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