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Dixon RE. Nanoscale Organization, Regulation, and Dynamic Reorganization of Cardiac Calcium Channels. Front Physiol 2022; 12:810408. [PMID: 35069264 PMCID: PMC8769284 DOI: 10.3389/fphys.2021.810408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Accepted: 11/30/2021] [Indexed: 12/19/2022] Open
Abstract
The architectural specializations and targeted delivery pathways of cardiomyocytes ensure that L-type Ca2+ channels (CaV1.2) are concentrated on the t-tubule sarcolemma within nanometers of their intracellular partners the type 2 ryanodine receptors (RyR2) which cluster on the junctional sarcoplasmic reticulum (jSR). The organization and distribution of these two groups of cardiac calcium channel clusters critically underlies the uniform contraction of the myocardium. Ca2+ signaling between these two sets of adjacent clusters produces Ca2+ sparks that in health, cannot escalate into Ca2+ waves because there is sufficient separation of adjacent clusters so that the release of Ca2+ from one RyR2 cluster or supercluster, cannot activate and sustain the release of Ca2+ from neighboring clusters. Instead, thousands of these Ca2+ release units (CRUs) generate near simultaneous Ca2+ sparks across every cardiomyocyte during the action potential when calcium induced calcium release from RyR2 is stimulated by depolarization induced Ca2+ influx through voltage dependent CaV1.2 channel clusters. These sparks summate to generate a global Ca2+ transient that activates the myofilaments and thus the electrical signal of the action potential is transduced into a functional output, myocardial contraction. To generate more, or less contractile force to match the hemodynamic and metabolic demands of the body, the heart responds to β-adrenergic signaling by altering activity of calcium channels to tune excitation-contraction coupling accordingly. Recent accumulating evidence suggests that this tuning process also involves altered expression, and dynamic reorganization of CaV1.2 and RyR2 channels on their respective membranes to control the amplitude of Ca2+ entry, SR Ca2+ release and myocardial function. In heart failure and aging, altered distribution and reorganization of these key Ca2+ signaling proteins occurs alongside architectural remodeling and is thought to contribute to impaired contractile function. In the present review we discuss these latest developments, their implications, and future questions to be addressed.
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Affiliation(s)
- Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA, United States
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Hamilton S, Terentyev D. Altered Intracellular Calcium Homeostasis and Arrhythmogenesis in the Aged Heart. Int J Mol Sci 2019; 20:ijms20102386. [PMID: 31091723 PMCID: PMC6566636 DOI: 10.3390/ijms20102386] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 04/29/2019] [Accepted: 05/08/2019] [Indexed: 12/17/2022] Open
Abstract
Aging of the heart is associated with a blunted response to sympathetic stimulation, reduced contractility, and increased propensity for arrhythmias, with the risk of sudden cardiac death significantly increased in the elderly population. The altered cardiac structural and functional phenotype, as well as age-associated prevalent comorbidities including hypertension and atherosclerosis, predispose the heart to atrial fibrillation, heart failure, and ventricular tachyarrhythmias. At the cellular level, perturbations in mitochondrial function, excitation-contraction coupling, and calcium homeostasis contribute to this electrical and contractile dysfunction. Major determinants of cardiac contractility are the intracellular release of Ca2+ from the sarcoplasmic reticulum by the ryanodine receptors (RyR2), and the following sequestration of Ca2+ by the sarco/endoplasmic Ca2+-ATPase (SERCa2a). Activity of RyR2 and SERCa2a in myocytes is not only dependent on expression levels and interacting accessory proteins, but on fine-tuned regulation via post-translational modifications. In this paper, we review how aberrant changes in intracellular Ca2+ cycling via these proteins contributes to arrhythmogenesis in the aged heart.
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Affiliation(s)
- Shanna Hamilton
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210, USA.
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA.
| | - Dmitry Terentyev
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210, USA.
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA.
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Bround MJ, Wambolt R, Cen H, Asghari P, Albu RF, Han J, McAfee D, Pourrier M, Scott NE, Bohunek L, Kulpa JE, Chen SRW, Fedida D, Brownsey RW, Borchers CH, Foster LJ, Mayor T, Moore EDW, Allard MF, Johnson JD. Cardiac Ryanodine Receptor (Ryr2)-mediated Calcium Signals Specifically Promote Glucose Oxidation via Pyruvate Dehydrogenase. J Biol Chem 2016; 291:23490-23505. [PMID: 27621312 DOI: 10.1074/jbc.m116.756973] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Indexed: 11/06/2022] Open
Abstract
Cardiac ryanodine receptor (Ryr2) Ca2+ release channels and cellular metabolism are both disrupted in heart disease. Recently, we demonstrated that total loss of Ryr2 leads to cardiomyocyte contractile dysfunction, arrhythmia, and reduced heart rate. Acute total Ryr2 ablation also impaired metabolism, but it was not clear whether this was a cause or consequence of heart failure. Previous in vitro studies revealed that Ca2+ flux into the mitochondria helps pace oxidative metabolism, but there is limited in vivo evidence supporting this concept. Here, we studied heart-specific, inducible Ryr2 haploinsufficient (cRyr2Δ50) mice with a stable 50% reduction in Ryr2 protein. This manipulation decreased the amplitude and frequency of cytosolic and mitochondrial Ca2+ signals in isolated cardiomyocytes, without changes in cardiomyocyte contraction. Remarkably, in the context of well preserved contractile function in perfused hearts, we observed decreased glucose oxidation, but not fat oxidation, with increased glycolysis. cRyr2Δ50 hearts exhibited hyperphosphorylation and inhibition of pyruvate dehydrogenase, the key Ca2+-sensitive gatekeeper to glucose oxidation. Metabolomic, proteomic, and transcriptomic analyses revealed additional functional networks associated with altered metabolism in this model. These results demonstrate that Ryr2 controls mitochondrial Ca2+ dynamics and plays a specific, critical role in promoting glucose oxidation in cardiomyocytes. Our findings indicate that partial RYR2 loss is sufficient to cause metabolic abnormalities seen in heart disease.
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Affiliation(s)
- Michael J Bround
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Rich Wambolt
- From the Cardiovascular Research Group, Life Sciences Institute and.,the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | - Haoning Cen
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Parisa Asghari
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Razvan F Albu
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Jun Han
- the University of Victoria-Genome British Columbia Proteomics Centre, Victoria, British Columbia V8Z 7X8, and
| | - Donald McAfee
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | - Marc Pourrier
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | - Nichollas E Scott
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Lubos Bohunek
- the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | | | - S R Wayne Chen
- the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 2T9, Canada
| | - David Fedida
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | | | - Christoph H Borchers
- the University of Victoria-Genome British Columbia Proteomics Centre, Victoria, British Columbia V8Z 7X8, and
| | - Leonard J Foster
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Thibault Mayor
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Edwin D W Moore
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Michael F Allard
- From the Cardiovascular Research Group, Life Sciences Institute and.,the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | - James D Johnson
- From the Cardiovascular Research Group, Life Sciences Institute and .,Departments of Cellular and Physiological Sciences
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Cardioprotective effect of selenium via modulation of cardiac ryanodine receptor calcium release channels in diabetic rat cardiomyocytes through thioredoxin system. J Nutr Biochem 2013; 24:2110-8. [PMID: 24183307 DOI: 10.1016/j.jnutbio.2013.08.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 07/29/2013] [Accepted: 08/01/2013] [Indexed: 11/21/2022]
Abstract
Increased oxidative stress contributes to heart dysfunction via impaired Ca(2+) homeostasis in diabetes. Abnormal RyR2 function related with altered cellular redox state is an important factor in the pathogenesis of diabetic cardiomyopathy, while its underlying mechanisms remain poorly understood. In the present study, we used a streptozotocin-induced rat model of diabetic cardiomyopathy and tested a hypothesis that diabetes-related alteration in RyR2 function is related with ROS-induced posttranslational modifications. For this, we used heart preparations from either a diabetic rat or a sodium selenate (NaSe)-treated (0.3 mg/kg for 4 weeks) diabetic rat as well as either NaSe- (100 nmol/L) or thioredoxin (Trx; 5 μmol/L)-incubated (30 min) diabetic cardiomyocytes. Experimental approaches included imaging of intracellular free-Ca(2+) ([Ca(2+)]i) under both electrically stimulated and resting Fluo-3-loaded cardiomyocytes. RyR2-mediated SR-Ca(2+) leak was significantly enhanced in diabetic cardiomyocytes, resulting in reduced amplitude and prolonged time courses of [Ca(2+)]i transients compared to those of controls. Both SR-Ca(2+) leak and [Ca(2+)]i transients were normalized by treating diabetic rats with NaSe or by incubating diabetic myocytes with NaSe or Trx. Moreover, exposure of diabetic cardiomyocytes to antioxidants significantly improved [Ca(2+)]i handling factors such as phosphorylation/protein levels of RyR2, amount of RyR2-bound FKBP12.6 and activities of both protein kinase A and CaMKII. NaSe treatment also normalized the oxidative stress/antioxidant defense biomarkers in plasma as well as Trx activity and nuclear factor-κB phosphorylation in the diabetic rat heart. Collectively, these findings suggest that redox modification through Trx-system besides the glutathione system contributes to abnormal function of RyR2s in hyperglycemic cardiomyocytes, presenting a potential therapeutic target for treating diabetics to preserve cardiac function.
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Boissière J, Maufrais C, Baquet G, Schuster I, Dauzat M, Doucende G, Obert P, Berthoin S, Nottin S. Specific left ventricular twist-untwist mechanics during exercise in children. J Am Soc Echocardiogr 2013; 26:1298-305. [PMID: 23972490 DOI: 10.1016/j.echo.2013.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Indexed: 10/26/2022]
Abstract
BACKGROUND In adults, left ventricular (LV) systolic twist is an important factor that determines LV filling, both at rest and during exercise. In children, lower LV twist has been demonstrated at rest, but its adaptation during exercise and its functional consequences on LV filling are unknown. METHODS Using speckle-tracking echocardiography, LV twist-untwist mechanics were studied in 25 children (aged 10-12 years) and 20 young adults (aged 18-44 years) at rest and during three exercise workloads performed at 20%, 30%, and 40% of their maximal aerobic power. RESULTS At rest, LV twist was lower in children, because of a higher temporal dispersion of peak rotation between base and apex. During exercise, the increase of basal rotation was blunted in children compared with adults (-6.7 ± 2.7° vs -9.0 ± 2.0° at 40% of maximal aerobic power, P < .05). Consequently, LV twist increased to a lesser extent (13.0 ± 5.0° vs 15.8 ± 4.5° at 40% of maximal aerobic power, P < .05). The increase in LV untwisting rates during exercise was also lower in children, leading to a lower percentage of untwisting during early diastole (8 ± 8% vs 29 ± 20% at 40% of maximal aerobic power, P < .001). Consequently, during early diastole, the normal timing of diastolic events observed in young adults, with untwist occurring before radial displacement, was blunted in children. Nevertheless, children exhibited normal LV filling due to higher diastolic radial and longitudinal strain rates. CONCLUSIONS Twist-untwist mechanics may evolve with advancing age. In children, early diastolic LV untwisting appears to be less important than in adults. Their better LV intrinsic myocardial relaxation may ensure adequate LV filling during exercise without dependence on the additional effect of suction resulting from LV energy recoil.
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Affiliation(s)
- Julien Boissière
- EA 4488-Activité Physique-Muscle-Santé, Université Lille Nord de France, Faculté des Sciences du Sport et de l'Education Physique, Lille, France
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Martinelli V, Cellot G, Toma FM, Long CS, Caldwell JH, Zentilin L, Giacca M, Turco A, Prato M, Ballerini L, Mestroni L. Carbon nanotubes instruct physiological growth and functionally mature syncytia: nongenetic engineering of cardiac myocytes. ACS NANO 2013; 7:5746-56. [PMID: 23734857 DOI: 10.1021/nn4002193] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Myocardial tissue engineering currently represents one of the most realistic strategies for cardiac repair. We have recently discovered the ability of carbon nanotube scaffolds to promote cell division and maturation in cardiomyocytes. Here, we test the hypothesis that carbon nanotube scaffolds promote cardiomyocyte growth and maturation by altering the gene expression program, implementing the cell electrophysiological properties and improving networking and maturation of functional syncytia. In our study, we combine microscopy, biological and electrophysiological methodologies, and calcium imaging, to verify whether neonatal rat ventricular myocytes cultured on substrates of multiwall carbon nanotubes acquire a physiologically more mature phenotype compared to control (gelatin). We show that the carbon nanotube substrate stimulates the induction of a gene expression profile characteristic of terminal differentiation and physiological growth, with a 2-fold increase of α-myosin heavy chain (P < 0.001) and upregulation of sarcoplasmic reticulum Ca(2+) ATPase 2a. In contrast, markers of pathological hypertrophy remain unchanged (β-myosin heavy chain, skeletal α-actin, atrial natriuretic peptide). These modifications are paralleled by an increase of connexin-43 gene expression, gap junctions and functional syncytia. Moreover, carbon nanotubes appear to exert a protective effect against the pathologic stimulus of phenylephrine. Finally, cardiomyocytes on carbon nanotubes demonstrate a more mature electrophysiological phenotype of syncytia and intracellular calcium signaling. Thus, carbon nanotubes interacting with cardiomyocytes have the ability to promote physiological growth and functional maturation. These properties are unique in the current vexing field of tissue engineering, and offer unprecedented perspectives in the development of innovative therapies for cardiac repair.
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Bround MJ, Wambolt R, Luciani DS, Kulpa JE, Rodrigues B, Brownsey RW, Allard MF, Johnson JD. Cardiomyocyte ATP production, metabolic flexibility, and survival require calcium flux through cardiac ryanodine receptors in vivo. J Biol Chem 2013; 288:18975-86. [PMID: 23678000 DOI: 10.1074/jbc.m112.427062] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Ca(2+) fluxes between adjacent organelles are thought to control many cellular processes, including metabolism and cell survival. In vitro evidence has been presented that constitutive Ca(2+) flux from intracellular stores into mitochondria is required for basal cellular metabolism, but these observations have not been made in vivo. We report that controlled in vivo depletion of cardiac RYR2, using a conditional gene knock-out strategy (cRyr2KO mice), is sufficient to reduce mitochondrial Ca(2+) and oxidative metabolism, and to establish a pseudohypoxic state with increased autophagy. Dramatic metabolic reprogramming was evident at the transcriptional level via Sirt1/Foxo1/Pgc1α, Atf3, and Klf15 gene networks. Ryr2 loss also induced a non-apoptotic form of programmed cell death associated with increased calpain-10 but not caspase-3 activation or endoplasmic reticulum stress. Remarkably, cRyr2KO mice rapidly exhibited many of the structural, metabolic, and molecular characteristics of heart failure at a time when RYR2 protein was reduced 50%, a similar degree to that which has been reported in heart failure. RYR2-mediated Ca(2+) fluxes are therefore proximal controllers of mitochondrial Ca(2+), ATP levels, and a cascade of transcription factors controlling metabolism and survival.
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Affiliation(s)
- Michael J Bround
- Cardiovascular Research Group, Life Sciences Institute, University of British Columbia, Vancouver V6T 1Z3, Canada
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Cardioprotective effect of propranolol on diabetes-induced altered intracellular Ca2+ signaling in rat. J Bioenerg Biomembr 2011; 43:747-56. [DOI: 10.1007/s10863-011-9400-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Accepted: 10/12/2011] [Indexed: 10/15/2022]
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