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Li MT, Du YY, Zhong F, Wang JR, Gu YW, Zhang Y, Huang XT, Deng YZ, Xu ZX. Inhibitory effects of aloperine on voltage-gated Na + channels in rat ventricular myocytes. Naunyn Schmiedebergs Arch Pharmacol 2021; 394:1579-88. [PMID: 33738513 DOI: 10.1007/s00210-021-02076-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 02/28/2021] [Indexed: 12/08/2022]
Abstract
Aloperine (ALO), a quinolizidine alkaloid extracted from Sophora alopecuroides L., modulates hypertension, ventricular remodeling, and myocardial ischemia. However, few studies have evaluated the effects of ALO on other cardiovascular parameters. Accordingly, in this study, we used a rat model of aconitine-induced ventricular arrhythmia to assess the effects of ALO. Notably, ALO pretreatment delayed the onset of ventricular premature and ventricular tachycardia and reduced the incidence of fatal ventricular fibrillation. Moreover, whole-cell patch-clamp assays in rats' ventricular myocyte showed that ALO (3, 10, and 30 μM) significantly reduced the peak sodium current density of voltage-gated Na+ channel currents (INa) in a concentration-dependent manner. The gating kinetics characteristics showed that the steady-state activation and recovery curve were shifted in positive direction along the voltage axis, respectively, and the steady-state inactivation curve was shifted in negative direction along the voltage axis, i.e., which was similar to the inhibitory effects of amiodarone. These results indicated that ALO had anti-arrhythmic effects, partly attributed to INa inhibition. ALO may act as a class I sodium channel anti-arrhythmia agent.
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Hu Q, Ahmad AA, Seidel T, Hunter C, Streiff M, Nikolova L, Spitzer KW, Sachse FB. Location and function of transient receptor potential canonical channel 1 in ventricular myocytes. J Mol Cell Cardiol 2020; 139:113-123. [PMID: 31982426 DOI: 10.1016/j.yjmcc.2020.01.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 12/16/2019] [Accepted: 01/21/2020] [Indexed: 11/17/2022]
Abstract
Transient receptor potential canonical 1 (TRPC1) protein is abundantly expressed in cardiomyocytes. While TRPC1 is supposed to be critically involved in cardiac hypertrophy, its physiological role in cardiomyocytes is poorly understood. We investigated the subcellular location of TRPC1 and its contribution to Ca2+ signaling in mammalian ventricular myocytes. Immunolabeling, three-dimensional scanning confocal microscopy and quantitative colocalization analysis revealed an abundant intracellular location of TRPC1 in neonatal rat ventricular myocytes (NRVMs) and adult rabbit ventricular myocytes. TRPC1 was colocalized with intracellular proteins including sarco/endoplasmic reticulum Ca2+ ATPase 2 in the sarcoplasmic reticulum (SR). Colocalization with wheat germ agglutinin, which labels the glycocalyx and thus marks the sarcolemma including the transverse tubular system, was low. Super-resolution and immunoelectron microscopy supported the intracellular location of TRPC1. We investigated Ca2+ signaling in NRVMs after adenoviral TRPC1 overexpression or silencing. In NRVMs bathed in Na+ and Ca2+ free solution, TRPC1 overexpression and silencing was associated with a decreased and increased SR Ca2+ content, respectively. In isolated rabbit cardiomyocytes bathed in Na+ and Ca2+ free solution, we found an increased decay of the cytosolic Ca2+ concentration [Ca2+]i and increased SR Ca2+ content in the presence of the TRPC channel blocker SKF-96365. In a computational model of rabbit ventricular myocytes at physiological pacing rates, Ca2+ leak through SR TRPC channels increased the systolic and diastolic [Ca2+]i with only minor effects on the action potential and SR Ca2+ content. Our studies suggest that TRPC1 channels are localized in the SR, and not present in the sarcolemma of ventricular myocytes. The studies provide evidence for a role of TRPC1 as a contributor to SR Ca2+ leak in cardiomyocytes, which was previously explained by ryanodine receptors only. We propose that the findings will guide us to an understanding of TRPC1 channels as modulators of [Ca2+]i and contractility in cardiomyocytes.
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Affiliation(s)
- Qinghua Hu
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA; Department of Cardiovascular Surgery, Xiangya Hospital, Central-South University, Changsha, Hunan 410078, China
| | - Azmi A Ahmad
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA
| | - Thomas Seidel
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Chris Hunter
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Molly Streiff
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA
| | - Linda Nikolova
- Core Research Facilities, Health Sciences Center, University of Utah, Salt Lake City, UT 84112, USA
| | - Kenneth W Spitzer
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Frank B Sachse
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA.
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Liu S, Gao X, Wu X, Yu Y, Yu Z, Zhao S, Zhao H. BK channels regulate calcium oscillations in ventricular myocytes on different substrate stiffness. Life Sci 2019; 235:116802. [PMID: 31472150 DOI: 10.1016/j.lfs.2019.116802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 08/26/2019] [Accepted: 08/28/2019] [Indexed: 01/29/2023]
Abstract
Substrate stiffness is essential for cell functions, but the mechanisms by which cell sense mechanical cues are still unclear. Here we show that the frequency and the amplitude of spontaneous Ca2+ oscillations were greater in chick cardiomyocytes cultured on the stiff substrates than that on the soft substrates. The spontaneous Ca2+ oscillations were increased on stiff substrates. However, an eliminated dependence of the Ca2+ oscillations on substrate stiffness was observed after applying blocker of the large-conductance Ca2+-activated K+ (BK) channels. In addition, the activity of BK channels in cardiomyocytes cultured on the stiff substrates was decreased. These results provide compelling evidences to show that BK channels are crucial in substrate stiffness-dependent regulation of the Ca2+ oscillation in cardiomyocytes.
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Affiliation(s)
- Sisi Liu
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China
| | - Xiaohui Gao
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Xiaoan Wu
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Yang Yu
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China
| | - Zhang Yu
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China
| | - Sui Zhao
- Affiliated High School of Tsinghua University, Beijing 100084, PR China
| | - Hucheng Zhao
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China.
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Belevych AE, Ho HT, Bonilla IM, Terentyeva R, Schober KE, Terentyev D, Carnes CA, Györke S. The role of spatial organization of Ca 2+ release sites in the generation of arrhythmogenic diastolic Ca 2+ release in myocytes from failing hearts. Basic Res Cardiol 2017; 112:44. [PMID: 28612155 DOI: 10.1007/s00395-017-0633-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 06/06/2017] [Indexed: 01/20/2023]
Abstract
In heart failure (HF), dysregulated cardiac ryanodine receptors (RyR2) contribute to the generation of diastolic Ca2+ waves (DCWs), thereby predisposing adrenergically stressed failing hearts to life-threatening arrhythmias. However, the specific cellular, subcellular, and molecular defects that account for cardiac arrhythmia in HF remain to be elucidated. Patch-clamp techniques and confocal Ca2+ imaging were applied to study spatially defined Ca2+ handling in ventricular myocytes isolated from normal (control) and failing canine hearts. Based on their activation time upon electrical stimulation, Ca2+ release sites were categorized as coupled, located in close proximity to the sarcolemmal Ca2+ channels, and uncoupled, the Ca2+ channel-free non-junctional Ca2+ release units. In control myocytes, stimulation of β-adrenergic receptors with isoproterenol (Iso) resulted in a preferential increase in Ca2+ spark rate at uncoupled sites. This site-specific effect of Iso was eliminated by the phosphatase inhibitor okadaic acid, which caused similar facilitation of Ca2+ sparks at coupled and uncoupled sites. Iso-challenged HF myocytes exhibited increased predisposition to DCWs compared to control myocytes. In addition, the overall frequency of Ca2+ sparks was increased in HF cells due to preferential stimulation of coupled sites. Furthermore, coupled sites exhibited accelerated recovery from functional refractoriness in HF myocytes compared to control myocytes. Spatially resolved subcellular Ca2+ mapping revealed that DCWs predominantly originated from coupled sites. Inhibition of CaMKII suppressed DCWs and prevented preferential stimulation of coupled sites in Iso-challenged HF myocytes. These results suggest that CaMKII- (and phosphatase)-dependent dysregulation of junctional Ca2+ release sites contributes to Ca2+-dependent arrhythmogenesis in HF.
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Affiliation(s)
- Andriy E Belevych
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, 43210, USA. .,Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH, 43210, USA.
| | - Hsiang-Ting Ho
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, 43210, USA.,Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH, 43210, USA
| | - Ingrid M Bonilla
- Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH, 43210, USA.,College of Pharmacy, The Ohio State University, Columbus, OH, 43210, USA
| | - Radmila Terentyeva
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Karsten E Schober
- College of Veterinary Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - Dmitry Terentyev
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Cynthia A Carnes
- Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH, 43210, USA.,College of Pharmacy, The Ohio State University, Columbus, OH, 43210, USA
| | - Sándor Györke
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, 43210, USA. .,Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH, 43210, USA.
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Cao F, Wang T, Ding W, Li Z, Shi S, Wang X. Effects of diacetyl-liensinine on electrophysiology in rabbit ventricular myocytes. BMC Pharmacol Toxicol 2017; 18:33. [PMID: 28476169 PMCID: PMC5420095 DOI: 10.1186/s40360-017-0137-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 04/27/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Diacetyl-liensinine is a chemosynthetic derivative of liensinine, extracted from the seed embryo of Nelumbo nucifera Gaertn, in China. It has been found to have extensive anti- arrhythmic actions. The present study was designed to investigate the effects of diacetyl-liensinine on electro- physiology of myocytes. METHODS We exposed rabbit ventricular myocytes to diacetyl-liensinine using standard whole-cell patch-clamp technique and measured the action potential, L-type calcium current (I Ca-L), delayed rectifier potassium current (I K), transient outward potassium current (I to) and inward rectifier potassium current (I K1). RESULTS Our results showed that diacetyl-liensinine significantly prolonged action potential duration at 50 and 90% repolarization (APD50, APD90), at 10 and 30 μM, while shortened APD50 and APD90 at 100 μM. In addition, diacetyl-liensinine inhibited the ICa-L, IK, I to and IK1 in a concentration-dependent manner. CONCLUSIONS The results suggest that diacetyl-liensinine might be a potential anti-arrhythmic agent.
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Affiliation(s)
- Feng Cao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, People's Republic of China.
- Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, People's Republic of China.
- Hubei Key Laboratory of Cardiology, Wuhan, 430060, People's Republic of China.
| | - Teng Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, People's Republic of China
- Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan, 430060, People's Republic of China
| | - Wenmao Ding
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, People's Republic of China
- Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan, 430060, People's Republic of China
| | - Zhe Li
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, People's Republic of China
- Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan, 430060, People's Republic of China
| | - Shaobo Shi
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, People's Republic of China
- Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan, 430060, People's Republic of China
| | - Xiaozhan Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, People's Republic of China
- Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan, 430060, People's Republic of China
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Abstract
It is now well established that the slowly inactivating component of the Na(+) current (INa-L) in the mammalian heart is a significant regulator of the action potential waveform. This insight has led to detailed studies of the role of INa-L in a number of important and challenging pathophysiological settings. These include genetically based ventricular arrhythmias (LQT 1, 2, and 3), ventricular arrhythmias arising from progressive cardiomyopathies (including diabetic), and proarrhythmic abnormalities that develop during local or global ventricular ischemia. Inhibition of INa-L may also be a useful strategy for management of atrial flutter and fibrillation. Many important biophysical parameters that characterize INa-L have been identified; and INa-L as an antiarrhythmia drug target has been studied extensively. However, relatively little information is available regarding (1) the ion transfer or current-voltage relationship for INa-L or (2) the time course of its reactivation at membrane potentials similar to the resting or diastolic membrane potential in mammalian ventricle. This chapter is based on our preliminary findings concerning these two very important physiological/biophysical descriptors for INa-L. Our results were obtained using whole-cell voltage clamp methods applied to enzymatically isolated rat ventricular myocytes. A chemical agent, BDF 9148, which was once considered to be a drug candidate in the Na(+)-dependent inotropic agent category has been used to markedly enhance INa-L current. BDF acts in a potent, selective, and reversible fashion. These BDF 9148 effects are compared and contrasted with the prototypical activator of INa-L, a sea anemone toxin, ATX II.
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Affiliation(s)
- R B Clark
- University of Calgary, Calgary, AB, Canada
| | - W R Giles
- University of Calgary, Calgary, AB, Canada
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Zhao XJ, Lin K, Zhang Y, Xu B, Liu L, Fu YC, Chen X, Cai ZQ, Wu ZJ, Huang Y, Li Y. Effects of allitridum on the transient outward potassium current in rats with heart failure. J Geriatr Cardiol 2016; 13:783-8. [PMID: 27899943 DOI: 10.11909/j.issn.1671-5411.2016.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
OBJECTIVE To study the effect of allitridum on the transient outward potassium current (Ito) of ventricular myocytes in heart failure (HF). METHODS The dual enzymatic method was used to separate single ventricular myocytes from Sprague Dawley rats. Patch-clamping was used to record Ito and analyze the effect of allitridum on the current. RESULTS The Ito current had a significant decrease in the HF group, compared with the control group. The density of Ito in the HF group was increased after treatment of allitridum (30 µmol/L). The peak current densities of Ito were enhanced in the HF group from 6.01 ± 0.30 pA/pF to 8.41 ± 0.54 pA/pF (P < 0.01) at +50 mV after treatment with allitridum (30 µmol/L). We also determined the effect of allitridum on the gating mechanism of the Ito in the HF group. CONCLUSIONS We found that allitridum increased the Ito by accelerating the activation of channels and shortened the time constants of inactivation, and allitridum decreased the remodeling of Ito in ventricular myocytes of rats with HF.
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Markandeya YS, Tsubouchi T, Hacker TA, Wolff MR, Belardinelli L, Balijepalli RC. Inhibition of late sodium current attenuates ionic arrhythmia mechanism in ventricular myocytes expressing LaminA-N195K mutation. Heart Rhythm 2016; 13:2228-2236. [PMID: 27498076 DOI: 10.1016/j.hrthm.2016.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND Lamin A and C are nuclear filament proteins encoded by the LMNA gene. Mutations in the LMNA gene cause many congenital diseases known as laminopathies, including Emery-Dreifuss muscular dystrophy, Hutchinson-Gilford progeria syndrome, and familial dilated cardiomyopathy (DCM) with conduction disease. A missense mutation (N195K) in the A-type lamins results in familial DCM and sudden arrhythmic death. OBJECTIVE The purpose of this study was to investigate the ion current mechanism of arrhythmia and DCM caused by the LaminA-N195K variant. METHODS A homozygous mouse line expressing the Lmna-N195K mutation (LmnaN195K/N195K) that exhibited arrhythmia, DCM, and sudden death was used. Using whole cell patch-clamp technique, we measured action potential duration (APD), Na+ currents (INa) in ventricular myocytes isolated from LmnaN195K/N195K, and wild-type mice. RESULTS Both peak and late INa were significantly (P <.05) increased in LmnaN195K/N195K ventricular myocytes. Similarly, LmnaN195K/N195K ventricular myocytes exhibited significant (P <.005) prolongation of APD (time to 50% [APD50] and 90% [APD90] repolarization) and triggered activity. Acute application of ranolazine inhibited late INa, shortened APD, and abolished triggered activity in LmnaN195K/N195K ventricular myocytes. CONCLUSION Inhibition of late INa may be an effective therapy in preventing arrhythmia in patients with LmnaN195K mutation-related DCM.
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Affiliation(s)
- Yogananda S Markandeya
- Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison, Wisconsin
| | - Tadashi Tsubouchi
- Preclinical Research Laboratories, Sumitomo Dainippon Pharma Co. Ltd., Osaka, Japan
| | - Timothy A Hacker
- Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison, Wisconsin
| | - Matthew R Wolff
- Meriter UnityPoint Heart and Vascular Institute, Madison, Wisconsin
| | | | - Ravi C Balijepalli
- Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison, Wisconsin.
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Drum BML, Dixon RE, Yuan C, Cheng EP, Santana LF. Cellular mechanisms of ventricular arrhythmias in a mouse model of Timothy syndrome (long QT syndrome 8). J Mol Cell Cardiol 2013; 66:63-71. [PMID: 24215710 DOI: 10.1016/j.yjmcc.2013.10.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 10/29/2013] [Accepted: 10/31/2013] [Indexed: 11/17/2022]
Abstract
Ca(2+) flux through l-type CaV1.2 channels shapes the waveform of the ventricular action potential (AP) and is essential for excitation-contraction (EC) coupling. Timothy syndrome (TS) is a disease caused by a gain-of-function mutation in the CaV1.2 channel (CaV1.2-TS) that decreases inactivation of the channel, which increases Ca(2+) influx, prolongs APs, and causes lethal arrhythmias. Although many details of the CaV1.2-TS channels are known, the cellular mechanisms by which they induce arrhythmogenic changes in intracellular Ca(2+) remain unclear. We found that expression of CaV1.2-TS channels increased sarcolemmal Ca(2+) "leak" in resting TS ventricular myocytes. This resulted in higher diastolic [Ca(2+)]i in TS ventricular myocytes compared to WT. Accordingly, TS myocytes had higher sarcoplasmic reticulum (SR) Ca(2+) load and Ca(2+) spark activity, larger amplitude [Ca(2+)]i transients, and augmented frequency of Ca(2+) waves. The large SR Ca(2+) release in TS myocytes had a profound effect on the kinetics of CaV1.2 current in these cells, increasing the rate of inactivation to a high, persistent level. This limited the amount of influx during EC coupling in TS myocytes. The relationship between the level of expression of CaV1.2-TS channels and the probability of Ca(2+) wave occurrence was non-linear, suggesting that even low levels of these channels were sufficient to induce maximal changes in [Ca(2+)]i. Depolarization of WT cardiomyocytes with a TS AP waveform increased, but did not equalize [Ca(2+)]i, compared to depolarization of TS myocytes with the same waveform. We propose that CaV1.2-TS channels increase [Ca(2+)] in the cytosol and the SR, creating a Ca(2+)overloaded state that increases the probability of arrhythmogenic spontaneous SR Ca(2+) release.
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Affiliation(s)
- Benjamin M L Drum
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Rose E Dixon
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Can Yuan
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Edward P Cheng
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Luis F Santana
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA.
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Park WS, Son YK, Ko EA, Choi SW, Kim N, Choi TH, Youn HJ, Jo SH, Hong DH, Han J. A Carbohydrate Fraction, AIP1, from Artemisia Iwayomogi Reduces the Action Potential Duration by Activation of Rapidly Activating Delayed Rectifier K Channels in Rabbit Ventricular Myocytes. Korean J Physiol Pharmacol 2010; 14:119-25. [PMID: 20631882 DOI: 10.4196/kjpp.2010.14.3.119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/04/2010] [Accepted: 05/10/2010] [Indexed: 11/15/2022]
Abstract
We investigated the effects of a hot-water extract of Artemisia iwayomogi, a plant belonging to family Compositae, on cardiac ventricular delayed rectifier K(+) current (I(K)) using the patch clamp technique. The carbohydrate fraction AIP1 dose-dependently increased the heart rate with an apparent EC(50) value of 56.1+/-5.5 microg/ml. Application of AIP1 reduced the action potential duration (APD) in concentration-dependent fashion by activating I(K) without significantly altering the resting membrane potential (IC(50) value of APD(50): 54.80+/-2.24, IC(50) value of APD(90): 57.45+/-3.47 microg/ml). Based on the results, all experiments were performed with 50 microg/ml of AIP1. Pre-treatment with the rapidly activating delayed rectifier K(+) current (I(Kr)) inhibitor, E-4031 prolonged APD. However, additional application of AIP1 did not reduce APD. The inhibition of slowly activating delayed rectifier K(+) current (I(Ks)) by chromanol 293B did not change the effect of AIP1. AIP1 did not significantly affect coronary arterial tone or ion channels, even at the highest concentration of AIP1. In summary, AIP1 reduces APD by activating I(Kr) but not I(Ks). These results suggest that the natural product AIP1 may provide an adjunctive therapy of long QT syndrome.
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Affiliation(s)
- Won Sun Park
- Department of Physiology, Institute of Medical Science, Kangwon National University School of Medicine, Chuncheon 200-701, Korea
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