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Teixeira SK, Pontes R, Zuleta LFG, Wang J, Xu D, Hildebrand S, Russell J, Zhan X, Choi M, Tang M, Li X, Ludwig S, Beutler B, Krieger JE. Genetic determinants of blood pressure and heart rate identified through ENU-induced mutagenesis with automated meiotic mapping. SCIENCE ADVANCES 2024; 10:eadj9797. [PMID: 38427739 PMCID: PMC10906923 DOI: 10.1126/sciadv.adj9797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 01/29/2024] [Indexed: 03/03/2024]
Abstract
We used N-ethyl-N-nitrosurea-induced germline mutagenesis combined with automated meiotic mapping to identify specific systolic blood pressure (SBP) and heart rate (HR) determinant loci. We analyzed 43,627 third-generation (G3) mice from 841 pedigrees to assess the effects of 45,378 variant alleles within 15,760 genes, in both heterozygous and homozygous states. We comprehensively tested 23% of all protein-encoding autosomal genes and found 87 SBP and 144 HR (with 7 affecting both) candidates exhibiting detectable hypomorphic characteristics. Unexpectedly, only 18 of the 87 SBP genes were previously known, while 26 of the 144 genes linked to HR were previously identified. Furthermore, we confirmed the influence of two genes on SBP regulation and three genes on HR control through reverse genetics. This underscores the importance of our research in uncovering genes associated with these critical cardiovascular risk factors and illustrate the effectiveness of germline mutagenesis for defining key determinants of polygenic phenotypes that must be studied in an intact organism.
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Affiliation(s)
- Samantha K. Teixeira
- Laboratório de Genética e Cardiologia Molecular, Instituto do Coração, Hospital das Clínicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Roberto Pontes
- Laboratório de Genética e Cardiologia Molecular, Instituto do Coração, Hospital das Clínicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Luiz Fernando G. Zuleta
- Laboratório de Genética e Cardiologia Molecular, Instituto do Coração, Hospital das Clínicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Jianhui Wang
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Darui Xu
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sara Hildebrand
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jamie Russell
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Xiaoming Zhan
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Mihwa Choi
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Miao Tang
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Xiaohong Li
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sara Ludwig
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Bruce Beutler
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jose E. Krieger
- Laboratório de Genética e Cardiologia Molecular, Instituto do Coração, Hospital das Clínicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
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2
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Dimitrov AG. Resting membrane state as an interplay of electrogenic transporters with various pumps. Pflugers Arch 2023; 475:1113-1128. [PMID: 37468808 DOI: 10.1007/s00424-023-02838-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/26/2023] [Accepted: 07/06/2023] [Indexed: 07/21/2023]
Abstract
In this study, a new idea that electrogenic transporters determine cell resting state is presented. The previous assumption was that pumps, especially the sodium one, determine it. The latter meets difficulties, because it violates the law of conservation of energy; also a significant deficit of pump activity is reported. The amount of energy carried by a single ATP molecule reflects the potential of the inner mitochondrial membrane, which is about -200 mV. If pumps enforce a resting membrane potential that is more than twice smaller, then the majority of energy stored in ATP would be dissipated by each pump turning. However, this problem could be solved if control is transferred from pumps to something else, e.g., electrogenic transporters. Then pumps would transfer the energy to the ionic gradient without losses, while the cell surface membrane potential would be associated with the reversal potential of some electrogenic transporters. A minimal scheme of this type would include a sodium-calcium exchanger as well as sodium and calcium pumps. However, note that calcium channels and pumps are positioned along both intracellular organelles and the surface membrane. Therefore, the above-mentioned scheme would involve them as well as possible intercellular communications. Such schemes where various kinds of pumps are assumed to work in parallel may explain, to a great extent, the slow turning rate of the individual members. Interaction of pumps and transporters positioned at distant biological membranes with various forms of energy transfer between them may thus result in hypoxic/reperfusion injury, different kinds of muscle fatigue, and nerve-glia interactions.
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Affiliation(s)
- A G Dimitrov
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 105, 1113, Sofia, Bulgaria.
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3
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Henley T, Goudy J, Easterling M, Donley C, Wirka R, Bressan M. Local tissue mechanics control cardiac pacemaker cell embryonic patterning. Life Sci Alliance 2023; 6:e202201799. [PMID: 36973005 PMCID: PMC10043993 DOI: 10.26508/lsa.202201799] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 03/13/2023] [Accepted: 03/15/2023] [Indexed: 03/29/2023] Open
Abstract
Cardiac pacemaker cells (CPCs) initiate the electric impulses that drive the rhythmic beating of the heart. CPCs reside in a heterogeneous, ECM-rich microenvironment termed the sinoatrial node (SAN). Surprisingly, little is known regarding the biochemical composition or mechanical properties of the SAN, and how the unique structural characteristics present in this region of the heart influence CPC function remains poorly understood. Here, we have identified that SAN development involves the construction of a "soft" macromolecular ECM that specifically encapsulates CPCs. In addition, we demonstrate that subjecting embryonic CPCs to substrate stiffnesses higher than those measured in vivo results in loss of coherent electrical oscillation and dysregulation of the HCN4 and NCX1 ion channels required for CPC automaticity. Collectively, these data indicate that local mechanics play a critical role in maintaining the embryonic CPC function while also quantitatively defining the range of material properties that are optimal for embryonic CPC maturation.
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Affiliation(s)
- Trevor Henley
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Julie Goudy
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Marietta Easterling
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Carrie Donley
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Robert Wirka
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Michael Bressan
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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4
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Manoj P, Kim JA, Kim S, Li T, Sewani M, Chelu MG, Li N. Sinus node dysfunction: current understanding and future directions. Am J Physiol Heart Circ Physiol 2023; 324:H259-H278. [PMID: 36563014 PMCID: PMC9886352 DOI: 10.1152/ajpheart.00618.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 12/20/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022]
Abstract
The sinoatrial node (SAN) is the primary pacemaker of the heart. Normal SAN function is crucial in maintaining proper cardiac rhythm and contraction. Sinus node dysfunction (SND) is due to abnormalities within the SAN, which can affect the heartbeat frequency, regularity, and the propagation of electrical pulses through the cardiac conduction system. As a result, SND often increases the risk of cardiac arrhythmias. SND is most commonly seen as a disease of the elderly given the role of degenerative fibrosis as well as other age-dependent changes in its pathogenesis. Despite the prevalence of SND, current treatment is limited to pacemaker implantation, which is associated with substantial medical costs and complications. Emerging evidence has identified various genetic abnormalities that can cause SND, shedding light on the molecular underpinnings of SND. Identification of these molecular mechanisms and pathways implicated in the pathogenesis of SND is hoped to identify novel therapeutic targets for the development of more effective therapies for this disease. In this review article, we examine the anatomy of the SAN and the pathophysiology and epidemiology of SND. We then discuss in detail the most common genetic mutations correlated with SND and provide our perspectives on future research and therapeutic opportunities in this field.
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Affiliation(s)
- Pavan Manoj
- School of Public Health, Texas A&M University, College Station, Texas
| | - Jitae A Kim
- Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Stephanie Kim
- Department of BioSciences, Rice University, Houston, Texas
| | - Tingting Li
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Maham Sewani
- Department of BioSciences, Rice University, Houston, Texas
| | - Mihail G Chelu
- Division of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Na Li
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas
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5
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Ricci E, Bartolucci C, Severi S. The virtual sinoatrial node: What did computational models tell us about cardiac pacemaking? PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2023; 177:55-79. [PMID: 36374743 DOI: 10.1016/j.pbiomolbio.2022.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 10/17/2022] [Accepted: 10/24/2022] [Indexed: 11/11/2022]
Abstract
Since its discovery, the sinoatrial node (SAN) has represented a fascinating and complex matter of research. Despite over a century of discoveries, a full comprehension of pacemaking has still to be achieved. Experiments often produced conflicting evidence that was used either in support or against alternative theories, originating intense debates. In this context, mathematical descriptions of the phenomena underlying the heartbeat have grown in importance in the last decades since they helped in gaining insights where experimental evaluation could not reach. This review presents the most updated SAN computational models and discusses their contribution to our understanding of cardiac pacemaking. Electrophysiological, structural and pathological aspects - as well as the autonomic control over the SAN - are taken into consideration to reach a holistic view of SAN activity.
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Affiliation(s)
- Eugenio Ricci
- Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi", University of Bologna, Cesena (FC), Italy
| | - Chiara Bartolucci
- Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi", University of Bologna, Cesena (FC), Italy
| | - Stefano Severi
- Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi", University of Bologna, Cesena (FC), Italy.
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6
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Fan W, Sun X, Yang C, Wan J, Luo H, Liao B. Pacemaker activity and ion channels in the sinoatrial node cells: MicroRNAs and arrhythmia. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2023; 177:151-167. [PMID: 36450332 DOI: 10.1016/j.pbiomolbio.2022.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 11/13/2022] [Accepted: 11/25/2022] [Indexed: 11/29/2022]
Abstract
The primary pacemaking activity of the heart is determined by a spontaneous action potential (AP) within sinoatrial node (SAN) cells. This unique AP generation relies on two mechanisms: membrane clocks and calcium clocks. Nonhomologous arrhythmias are caused by several functional and structural changes in the myocardium. MicroRNAs (miRNAs) are essential regulators of gene expression in cardiomyocytes. These miRNAs play a vital role in regulating the stability of cardiac conduction and in the remodeling process that leads to arrhythmias. Although it remains unclear how miRNAs regulate the expression and function of ion channels in the heart, these regulatory mechanisms may support the development of emerging therapies. This study discusses the spread and generation of AP in the SAN as well as the regulation of miRNAs and individual ion channels. Arrhythmogenicity studies on ion channels will provide a research basis for miRNA modulation as a new therapeutic target.
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Affiliation(s)
- Wei Fan
- Department of Cardiovascular Surgery, Affiliated Hospital of Southwest Medical University, 25 Taiping Street, Jiangyang District, Luzhou, Sichuan Province, 646000, China
| | - Xuemei Sun
- Department of Pharmacy, Affiliated Hospital of Southwest Medical University, 25 Taiping Street, Jiangyang District, Luzhou, Sichuan Province, 646000, China
| | - Chao Yang
- Department of Cardiovascular Surgery, Affiliated Hospital of Southwest Medical University, 25 Taiping Street, Jiangyang District, Luzhou, Sichuan Province, 646000, China
| | - Juyi Wan
- Department of Cardiovascular Surgery, Affiliated Hospital of Southwest Medical University, 25 Taiping Street, Jiangyang District, Luzhou, Sichuan Province, 646000, China.
| | - Hongli Luo
- Department of Pharmacy, Affiliated Hospital of Southwest Medical University, 25 Taiping Street, Jiangyang District, Luzhou, Sichuan Province, 646000, China.
| | - Bin Liao
- Department of Cardiovascular Surgery, Affiliated Hospital of Southwest Medical University, 25 Taiping Street, Jiangyang District, Luzhou, Sichuan Province, 646000, China.
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7
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Ren L, Thai PN, Gopireddy RR, Timofeyev V, Ledford HA, Woltz RL, Park S, Puglisi JL, Moreno CM, Santana LF, Conti AC, Kotlikoff MI, Xiang YK, Yarov-Yarovoy V, Zaccolo M, Zhang XD, Yamoah EN, Navedo MF, Chiamvimonvat N. Adenylyl cyclase isoform 1 contributes to sinoatrial node automaticity via functional microdomains. JCI Insight 2022; 7:e162602. [PMID: 36509290 PMCID: PMC9746826 DOI: 10.1172/jci.insight.162602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 10/05/2022] [Indexed: 11/22/2022] Open
Abstract
Sinoatrial node (SAN) cells are the heart's primary pacemaker. Their activity is tightly regulated by β-adrenergic receptor (β-AR) signaling. Adenylyl cyclase (AC) is a key enzyme in the β-AR pathway that catalyzes the production of cAMP. There are current gaps in our knowledge regarding the dominant AC isoforms and the specific roles of Ca2+-activated ACs in the SAN. The current study tests the hypothesis that distinct AC isoforms are preferentially expressed in the SAN and compartmentalize within microdomains to orchestrate heart rate regulation during β-AR signaling. In contrast to atrial and ventricular myocytes, SAN cells express a diverse repertoire of ACs, with ACI as the predominant Ca2+-activated isoform. Although ACI-KO (ACI-/-) mice exhibit normal cardiac systolic or diastolic function, they experience SAN dysfunction. Similarly, SAN-specific CRISPR/Cas9-mediated gene silencing of ACI results in sinus node dysfunction. Mechanistically, hyperpolarization-activated cyclic nucleotide-gated 4 (HCN4) channels form functional microdomains almost exclusively with ACI, while ryanodine receptor and L-type Ca2+ channels likely compartmentalize with ACI and other AC isoforms. In contrast, there were no significant differences in T-type Ca2+ and Na+ currents at baseline or after β-AR stimulation between WT and ACI-/- SAN cells. Due to its central characteristic feature as a Ca2+-activated isoform, ACI plays a unique role in sustaining the rise of local cAMP and heart rates during β-AR stimulation. The findings provide insights into the critical roles of the Ca2+-activated isoform of AC in sustaining SAN automaticity that is distinct from contractile cardiomyocytes.
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Affiliation(s)
- Lu Ren
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California, USA
| | - Phung N. Thai
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
| | | | - Valeriy Timofeyev
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
| | - Hannah A. Ledford
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
| | - Ryan L. Woltz
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
| | - Seojin Park
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, Nevada, USA
- Prestige Biopharma Korea, Myongjigukje 7-ro, Gangseo-gu, Busan, South Korea
| | - Jose L. Puglisi
- College of Medicine. California North State University, Sacramento, California, USA
| | - Claudia M. Moreno
- Department of Physiology and Membrane Biology, UCD, Davis, California, USA
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington, USA
| | | | - Alana C. Conti
- Research & Development Service, John D. Dingell VA Medical Center, and
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA
| | | | - Yang Kevin Xiang
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
- Department of Pharmacology, UCD, Davis, California, USA
| | | | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, United Kingdom
| | - Xiao-Dong Zhang
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, Nevada, USA
| | | | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiovascular Medicine, UCD, Davis, California, USA
- Department of Veteran Affairs, Northern California Health Care System, Sacramento, California, USA
- Department of Pharmacology, UCD, Davis, California, USA
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8
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Peters CH, Rickert C, Morotti S, Grandi E, Aronow KA, Beam KG, Proenza C. The funny current If is essential for the fight-or-flight response in cardiac pacemaker cells. J Gen Physiol 2022; 154:213619. [PMID: 36305844 PMCID: PMC9812006 DOI: 10.1085/jgp.202213193] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 08/22/2022] [Accepted: 10/04/2022] [Indexed: 01/07/2023] Open
Abstract
The sympathetic nervous system fight-or-flight response is characterized by a rapid increase in heart rate, which is mediated by an increase in the spontaneous action potential (AP) firing rate of pacemaker cells in the sinoatrial node. Sympathetic neurons stimulate sinoatrial myocytes (SAMs) by activating β adrenergic receptors (βARs) and increasing cAMP. The funny current (If) is among the cAMP-sensitive currents in SAMs. If is critical for pacemaker activity, however, its role in the fight-or-flight response remains controversial. In this study, we used AP waveform analysis, machine learning, and dynamic clamp experiments in acutely isolated SAMs from mice to quantitatively define the AP waveform changes and role of If in the fight-or-flight increase in AP firing rate. We found that while βAR stimulation significantly altered nearly all AP waveform parameters, the increase in firing rate was only correlated with changes in a subset of parameters (diastolic duration, late AP duration, and diastolic depolarization rate). Dynamic clamp injection of the βAR-sensitive component of If showed that it accounts for ∼41% of the fight-or-flight increase in AP firing rate and 60% of the decrease in the interval between APs. Thus, If is an essential contributor to the fight-or-flight increase in heart rate.
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Affiliation(s)
- Colin H. Peters
- Department of Physiology & Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Christian Rickert
- Department of Physiology & Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Stefano Morotti
- Department of Pharmacology, University of California, Davis, School of Medicine, Davis, CA
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, School of Medicine, Davis, CA
| | | | - Kurt G. Beam
- Department of Physiology & Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Catherine Proenza
- Department of Physiology & Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO,Division of Cardiology, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO,Correspondence to Catherine Proenza:
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9
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Glutamate drives 'local Ca 2+ release' in cardiac pacemaker cells. Cell Res 2022; 32:843-854. [PMID: 35840807 PMCID: PMC9437105 DOI: 10.1038/s41422-022-00693-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Accepted: 06/27/2022] [Indexed: 11/30/2022] Open
Abstract
The sinoatrial node (SAN) is the origin of the electrical signals for rhythmic heartbeats in mammals. The spontaneous firing of SAN pacemaker cells (SANPCs) triggers cardiac contraction. ‘Local Ca2+ release’ (LCR), a unique cellular activity, acts as the ‘engine’ of the spontaneous firing of SANPCs. However, the mechanism of LCR initiation remains unclear. Here, we report that endogenous glutamate drives LCRs in SANPCs. Using a glutamate sensor, we unraveled a tight correlation between glutamate accumulation and LCR occurrence, indicating a potential relationship between glutamate and LCRs. Intracellular application of glutamate significantly enhanced the LCRs in both intact and permeabilized SANPCs. Mechanistically, we revealed that mitochondrial excitatory amino acid transporter 1 (EAAT1)-dependent mitochondrial glutamate import promoted ROS generation, which in turn led to the oxidation of Ca2+-handling proteins, ultimately resulting in enhanced LCRs. Importantly, EAAT1 depletion reduced both the spontaneous firing rates of isolated SANPCs and the heart rate in vitro and in vivo, suggesting the central role of EAAT1 as a glutamate transporter in the regulation of cardiac autonomic rhythm. In conclusion, our results indicate that glutamate serves as an LCR igniter in SANPCs, adding a potentially important element to the coupled-clock theory that explains the origin of spontaneous firing. These findings shed new light on the future prevention and treatment of cardiac pacemaker cell-related arrhythmias.
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10
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Intracellular Ca2+-Mediated Mechanisms for the Pacemaker Depolarization of the Mouse and Guinea Pig Sinus Node Tissue. Biomolecules 2022; 12:biom12030377. [PMID: 35327569 PMCID: PMC8945042 DOI: 10.3390/biom12030377] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/24/2022] [Accepted: 02/11/2022] [Indexed: 11/17/2022] Open
Abstract
Intracellular Ca2+-mediated mechanisms for pacemaker depolarization were studied in sinus node tissue preparations from mice and guinea pigs. Microelectrode recordings revealed that the sinus node of the mouse, which had a higher beating rate, had a steeper slope of the pacemaker depolarization than that of the guinea pig. BAPTA and ryanodine, agents that interfere with intracellular Ca2+, significantly decreased the slope of the pacemaker depolarization in both species. In contrast, SEA0400, a specific inhibitor of the Na+-Ca2+ exchanger (NCX), as well as change to low Na+ extracellular solution, significantly decreased the slope in the mouse, but not in the guinea pig. Niflumic acid, a blocker of the Ca2+ activated Cl− channel, decreased the slope in both species. Confocal microscopy revealed the presence of spontaneous Ca2+ oscillations during the interval between Ca2+ transients; such phenomenon was more pronounced in the mouse than in the guinea pig. Thus, although intracellular Ca2+-mediated mechanisms were involved in the pacemaker depolarization of the sinus node in both species, the NCX current was involved in the mouse but not in the guinea pig.
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11
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Ottolia M, John S, Hazan A, Goldhaber JI. The Cardiac Na + -Ca 2+ Exchanger: From Structure to Function. Compr Physiol 2021; 12:2681-2717. [PMID: 34964124 DOI: 10.1002/cphy.c200031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Ca2+ homeostasis is essential for cell function and survival. As such, the cytosolic Ca2+ concentration is tightly controlled by a wide number of specialized Ca2+ handling proteins. One among them is the Na+ -Ca2+ exchanger (NCX), a ubiquitous plasma membrane transporter that exploits the electrochemical gradient of Na+ to drive Ca2+ out of the cell, against its concentration gradient. In this critical role, this secondary transporter guides vital physiological processes such as Ca2+ homeostasis, muscle contraction, bone formation, and memory to name a few. Herein, we review the progress made in recent years about the structure of the mammalian NCX and how it relates to function. Particular emphasis will be given to the mammalian cardiac isoform, NCX1.1, due to the extensive studies conducted on this protein. Given the degree of conservation among the eukaryotic exchangers, the information highlighted herein will provide a foundation for our understanding of this transporter family. We will discuss gene structure, alternative splicing, topology, regulatory mechanisms, and NCX's functional role on cardiac physiology. Throughout this article, we will attempt to highlight important milestones in the field and controversial topics where future studies are required. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.
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Affiliation(s)
- Michela Ottolia
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Scott John
- Department of Medicine (Cardiology), UCLA, Los Angeles, California, USA
| | - Adina Hazan
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
| | - Joshua I Goldhaber
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
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12
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Lotteau S, Zhang R, Hazan A, Grabar C, Gonzalez D, Aynaszyan S, Philipson KD, Ottolia M, Goldhaber JI. Acute Genetic Ablation of Cardiac Sodium/Calcium Exchange in Adult Mice: Implications for Cardiomyocyte Calcium Regulation, Cardioprotection, and Arrhythmia. J Am Heart Assoc 2021; 10:e019273. [PMID: 34472363 PMCID: PMC8649274 DOI: 10.1161/jaha.120.019273] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Background Sodium‐calcium (Ca2+) exchanger isoform 1 (NCX1) is the dominant Ca2+ efflux mechanism in cardiomyocytes and is critical to maintaining Ca2+ homeostasis during excitation‐contraction coupling. NCX1 activity has been implicated in the pathogenesis of cardiovascular diseases, but a lack of specific NCX1 blockers complicates experimental interpretation. Our aim was to develop a tamoxifen‐inducible NCX1 knockout (KO) mouse to investigate compensatory adaptations of acute ablation of NCX1 on excitation‐contraction coupling and intracellular Ca2+ regulation, and to examine whether acute KO of NCX1 confers resistance to triggered arrhythmia and ischemia/reperfusion injury. Methods and Results We used the α‐myosin heavy chain promoter (Myh6)‐MerCreMer promoter to create a tamoxifen‐inducible cardiac‐specific NCX1 KO mouse. Within 1 week of tamoxifen injection, NCX1 protein expression and current were dramatically reduced. Diastolic Ca2+ increased despite adaptive reductions in Ca2+ current and action potential duration and compensatory increases in excitation‐contraction coupling gain, sarcoplasmic reticulum Ca2+ ATPase 2 and plasma membrane Ca2+ ATPase. As these adaptations progressed over 4 weeks, diastolic Ca2+ normalized and SR Ca2+ load increased. Left ventricular function remained normal, but mild fibrosis and hypertrophy developed. Transcriptomics revealed modification of cardiovascular‐related gene networks including cell growth and fibrosis. NCX1 KO reduced spontaneous action potentials triggered by delayed afterdepolarizations and reduced scar size in response to ischemia/reperfusion. Conclusions Tamoxifen‐inducible NCX1 KO mice adapt to acute genetic ablation of NCX1 by reducing Ca2+ influx, increasing alternative Ca2+ efflux pathways, and increasing excitation‐contraction coupling gain to maintain contractility at the cost of mild Ca2+‐activated hypertrophy and fibrosis and decreased survival. Nevertheless, KO myocytes are protected against spontaneous action potentials and ischemia/reperfusion injury.
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Affiliation(s)
- Sabine Lotteau
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Rui Zhang
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Adina Hazan
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Christina Grabar
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Devina Gonzalez
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | | | - Kenneth D Philipson
- Department of Physiology David Geffen School of Medicine at UCLA Los Angeles CA
| | - Michela Ottolia
- Division of Molecular Medicine Department of Anesthesiology and Perioperative Medicine David Geffen School of Medicine at UCLA Los Angeles CA
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13
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Peters CH, Liu PW, Morotti S, Gantz SC, Grandi E, Bean BP, Proenza C. Bidirectional flow of the funny current (I f) during the pacemaking cycle in murine sinoatrial node myocytes. Proc Natl Acad Sci U S A 2021; 118:e2104668118. [PMID: 34260402 PMCID: PMC8285948 DOI: 10.1073/pnas.2104668118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Sinoatrial node myocytes (SAMs) act as cardiac pacemaker cells by firing spontaneous action potentials (APs) that initiate each heartbeat. The funny current (If) is critical for the generation of these spontaneous APs; however, its precise role during the pacemaking cycle remains unresolved. Here, we used the AP-clamp technique to quantify If during the cardiac cycle in mouse SAMs. We found that If is persistently active throughout the sinoatrial AP, with surprisingly little voltage-dependent gating. As a consequence, it carries both inward and outward current around its reversal potential of -30 mV. Despite operating at only 2 to 5% of its maximal conductance, If carries a substantial fraction of both depolarizing and repolarizing net charge movement during the firing cycle. We also show that β-adrenergic receptor stimulation increases the percentage of net depolarizing charge moved by If, consistent with a contribution of If to the fight-or-flight increase in heart rate. These properties were confirmed by heterologously expressed HCN4 channels and by mathematical models of If Modeling further suggested that the slow rates of activation and deactivation of the HCN4 isoform underlie the persistent activity of If during the sinoatrial AP. These results establish a new conceptual framework for the role of If in pacemaking, in which it operates at a very small fraction of maximal activation but nevertheless drives membrane potential oscillations in SAMs by providing substantial driving force in both inward and outward directions.
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Affiliation(s)
- Colin H Peters
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Pin W Liu
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115
| | - Stefano Morotti
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Stephanie C Gantz
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Bruce P Bean
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045;
- Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
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14
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DiFrancesco ML, Mesirca P, Bidaud I, Isbrandt D, Mangoni ME. The funny current in genetically modified mice. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:39-50. [PMID: 34129872 DOI: 10.1016/j.pbiomolbio.2021.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/18/2021] [Accepted: 06/07/2021] [Indexed: 12/27/2022]
Abstract
Since its first description in 1979, the hyperpolarization-activated funny current (If) has been the object of intensive research aimed at understanding its role in cardiac pacemaker activity and its modulation by the sympathetic and parasympathetic branches of the autonomic nervous system. If was described in isolated tissue strips of the rabbit sinoatrial node using the double-electrode voltage-clamp technique. Since then, the rabbit has been the principal animal model for studying pacemaker activity and If for more than 20 years. In 2001, the first study describing the electrophysiological properties of mouse sinoatrial pacemaker myocytes and those of If was published. It was soon followed by the description of murine myocytes of the atrioventricular node and the Purkinje fibres. The sinoatrial node of genetically modified mice has become a very popular model for studying the mechanisms of cardiac pacemaker activity. This field of research benefits from the impressive advancement of in-vivo exploration techniques of physiological parameters, imaging, genetics, and large-scale genomic approaches. The present review discusses the influence of mouse genetic on the most recent knowledge of the funny current's role in the physiology and pathophysiology of cardiac pacemaker activity. Genetically modified mice have provided important insights into the role of If in determining intrinsic automaticity in vivo and in myocytes of the conduction system. In addition, gene targeting of f-(HCN) channel isoforms have contributed to elucidating the current's role in the regulation of heart rate by the parasympathetic nervous system. This review is dedicated to Dario DiFrancesco on his retirement.
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Affiliation(s)
- Mattia L DiFrancesco
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genoa, Italy; IRCCS Ospedale Policlinico San Martino, Genoa, Italy; Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France.
| | - Pietro Mesirca
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France
| | - Isabelle Bidaud
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France
| | - Dirk Isbrandt
- Deutsches Zentrum für Neurodegenerative Erktankungen (DZNE), Bonn, Germany; University of Cologne, Institute for Molecular and Behavioral Neuroscience, Cologne, Germany
| | - Matteo E Mangoni
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France.
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15
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Hennis K, Rötzer RD, Piantoni C, Biel M, Wahl-Schott C, Fenske S. Speeding Up the Heart? Traditional and New Perspectives on HCN4 Function. Front Physiol 2021; 12:669029. [PMID: 34122140 PMCID: PMC8191466 DOI: 10.3389/fphys.2021.669029] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/19/2021] [Indexed: 01/20/2023] Open
Abstract
The sinoatrial node (SAN) is the primary pacemaker of the heart and is responsible for generating the intrinsic heartbeat. Within the SAN, spontaneously active pacemaker cells initiate the electrical activity that causes the contraction of all cardiomyocytes. The firing rate of pacemaker cells depends on the slow diastolic depolarization (SDD) and determines the intrinsic heart rate (HR). To adapt cardiac output to varying physical demands, HR is regulated by the autonomic nervous system (ANS). The sympathetic and parasympathetic branches of the ANS innervate the SAN and regulate the firing rate of pacemaker cells by accelerating or decelerating SDD-a process well-known as the chronotropic effect. Although this process is of fundamental physiological relevance, it is still incompletely understood how it is mediated at the subcellular level. Over the past 20 years, most of the work to resolve the underlying cellular mechanisms has made use of genetically engineered mouse models. In this review, we focus on the findings from these mouse studies regarding the cellular mechanisms involved in the generation and regulation of the heartbeat, with particular focus on the highly debated role of the hyperpolarization-activated cyclic nucleotide-gated cation channel HCN4 in mediating the chronotropic effect. By focusing on experimental data obtained in mice and humans, but not in other species, we outline how findings obtained in mice relate to human physiology and pathophysiology and provide specific information on how dysfunction or loss of HCN4 channels leads to human SAN disease.
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Affiliation(s)
- Konstantin Hennis
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - René D. Rötzer
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Chiara Piantoni
- Institute for Neurophysiology, Hannover Medical School, Hanover, Germany
| | - Martin Biel
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Christian Wahl-Schott
- Institute for Neurophysiology, Hannover Medical School, Hanover, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Stefanie Fenske
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
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16
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Wallace MJ, El Refaey M, Mesirca P, Hund TJ, Mangoni ME, Mohler PJ. Genetic Complexity of Sinoatrial Node Dysfunction. Front Genet 2021; 12:654925. [PMID: 33868385 PMCID: PMC8047474 DOI: 10.3389/fgene.2021.654925] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Accepted: 03/01/2021] [Indexed: 12/13/2022] Open
Abstract
The pacemaker cells of the cardiac sinoatrial node (SAN) are essential for normal cardiac automaticity. Dysfunction in cardiac pacemaking results in human sinoatrial node dysfunction (SND). SND more generally occurs in the elderly population and is associated with impaired pacemaker function causing abnormal heart rhythm. Individuals with SND have a variety of symptoms including sinus bradycardia, sinus arrest, SAN block, bradycardia/tachycardia syndrome, and syncope. Importantly, individuals with SND report chronotropic incompetence in response to stress and/or exercise. SND may be genetic or secondary to systemic or cardiovascular conditions. Current management of patients with SND is limited to the relief of arrhythmia symptoms and pacemaker implantation if indicated. Lack of effective therapeutic measures that target the underlying causes of SND renders management of these patients challenging due to its progressive nature and has highlighted a critical need to improve our understanding of its underlying mechanistic basis of SND. This review focuses on current information on the genetics underlying SND, followed by future implications of this knowledge in the management of individuals with SND.
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Affiliation(s)
- Michael J. Wallace
- Frick Center for Heart Failure and Arrhythmia Research, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States
| | - Mona El Refaey
- Frick Center for Heart Failure and Arrhythmia Research, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States
| | - Pietro Mesirca
- CNRS, INSERM, Institut de Génomique Fonctionnelle, Université de Montpellier, Montpellier, France
- Laboratory of Excellence ICST, Montpellier, France
| | - Thomas J. Hund
- Frick Center for Heart Failure and Arrhythmia Research, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH, United States
| | - Matteo E. Mangoni
- CNRS, INSERM, Institut de Génomique Fonctionnelle, Université de Montpellier, Montpellier, France
- Laboratory of Excellence ICST, Montpellier, France
| | - Peter J. Mohler
- Frick Center for Heart Failure and Arrhythmia Research, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States
- Division of Cardiovascular Medicine, Department of Internal Medicine, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States
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17
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Pelat M, Barbe F, Daveu C, Ly-Nguyen L, Lartigue T, Marque S, Tavares G, Ballet V, Guillon JM, Steinmeyer K, Wirth K, Gögelein H, Arndt P, Rackelmann N, Weston J, Bellevergue P, McCort G, Trellu M, Lucats L, Beauverger P, Pruniaux-Harnist MP, Janiak P, Chézalviel-Guilbert F. SAR340835, a Novel Selective Na +/Ca 2+ Exchanger Inhibitor, Improves Cardiac Function and Restores Sympathovagal Balance in Heart Failure. J Pharmacol Exp Ther 2021; 377:293-304. [PMID: 33602875 DOI: 10.1124/jpet.120.000238] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 02/08/2021] [Indexed: 11/22/2022] Open
Abstract
In failing hearts, Na+/Ca2+ exchanger (NCX) overactivity contributes to Ca2+ depletion, leading to contractile dysfunction. Inhibition of NCX is expected to normalize Ca2+ mishandling, to limit afterdepolarization-related arrhythmias, and to improve cardiac function in heart failure (HF). SAR340835/SAR296968 is a selective NCX inhibitor for all NCX isoforms across species, including human, with no effect on the native voltage-dependent calcium and sodium currents in vitro. Additionally, it showed in vitro and in vivo antiarrhythmic properties in several models of early and delayed afterdepolarization-related arrhythmias. Its effect on cardiac function was studied under intravenous infusion at 250,750 or 1500 µg/kg per hour in dogs, which were either normal or submitted to chronic ventricular pacing at 240 bpm (HF dogs). HF dogs were infused with the reference inotrope dobutamine (10 µg/kg per minute, i.v.). In normal dogs, NCX inhibitor increased cardiac contractility (dP/dtmax) and stroke volume (SV) and tended to reduce heart rate (HR). In HF dogs, NCX inhibitor significantly and dose-dependently increased SV from the first dose (+28.5%, +48.8%, and +62% at 250, 750, and 1500 µg/kg per hour, respectively) while significantly increasing dP/dtmax only at 1500 (+33%). Furthermore, NCX inhibitor significantly restored sympathovagal balance and spontaneous baroreflex sensitivity (BRS) from the first dose and reduced HR at the highest dose. In HF dogs, dobutamine significantly increased dP/dtmax and SV (+68.8%) but did not change HR, sympathovagal balance, or BRS. Overall, SAR340835, a selective potent NCX inhibitor, displayed a unique therapeutic profile, combining antiarrhythmic properties, capacity to restore systolic function, sympathovagal balance, and BRS in HF dogs. NCX inhibitors may offer new therapeutic options for acute HF treatment. SIGNIFICANCE STATEMENT: HF is facing growing health and economic burden. Moreover, patients hospitalized for acute heart failure are at high risk of decompensation recurrence, and no current acute decompensated HF therapy definitively improved outcomes. A new potent, Na+/Ca2+ exchanger inhibitor SAR340835 with antiarrhythmic properties improved systolic function of failing hearts without creating hypotension, while reducing heart rate and restoring sympathovagal balance. SAR340835 may offer a unique and attractive pharmacological profile for patients with acute heart failure as compared with current inotrope, such as dobutamine.
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Affiliation(s)
- Michel Pelat
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Fabrice Barbe
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Cyril Daveu
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Laetitia Ly-Nguyen
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Thomas Lartigue
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Suzanne Marque
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Georges Tavares
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Véronique Ballet
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Jean-Michel Guillon
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Klaus Steinmeyer
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Klaus Wirth
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Heinz Gögelein
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Petra Arndt
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Nils Rackelmann
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - John Weston
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Patrice Bellevergue
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Gary McCort
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Marc Trellu
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Laurence Lucats
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Philippe Beauverger
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Marie-Pierre Pruniaux-Harnist
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Philip Janiak
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
| | - Frédérique Chézalviel-Guilbert
- Cardiovascular and Metabolism TSU (M.P., F.B., C.D., T.L., S.M., G.T., L.L., Ph.B., M.-P.P.-H., P.J., F.C.-G.) and Integrated Drug Discovery (Pa.B.), Sanofi R&D, Chilly Mazarin, France; Preclinical Safety, Sanofi R&D, Alfortville, France (L.L.-N., V.B., J.-M.G., M.T.); Sanofi R&D, Industriepark Höchst, Frankfurt, Germany (K.S., K.W., H.G., P.A., N.R., J.W.); and Integrated Drug Discovery, Sanofi R&D, Vitry sur Seine, France (G.M.)
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18
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Izumi Y, Mennerick SJ, Doherty JJ, Zorumski CF. Oxysterols Modulate the Acute Effects of Ethanol on Hippocampal N-Methyl-d-Aspartate Receptors, Long-Term Potentiation, and Learning. J Pharmacol Exp Ther 2021; 377:181-188. [PMID: 33441369 PMCID: PMC8051516 DOI: 10.1124/jpet.120.000376] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 01/08/2021] [Indexed: 12/29/2022] Open
Abstract
Ethanol is a noncompetitive inhibitor of N-methyl-d-aspartate receptors (NMDARs) and acutely disrupts hippocampal synaptic plasticity and learning. In the present study, we examined the effects of oxysterol positive allosteric modulators (PAMs) of NMDARs on ethanol-mediated inhibition of NMDARs, block of long-term potentiation (LTP) and long-term depression (LTD) in rat hippocampal slices, and defects in one-trial learning in vivo. We found that 24S-hydroxycholesterol and a synthetic oxysterol analog, SGE-301, overcame effects of ethanol on NMDAR-mediated synaptic responses in the CA1 region but did not alter acute effects of ethanol on LTD; the synthetic oxysterol, however, overcame acute inhibition of LTP. In addition, both oxysterols overcame persistent effects of ethanol on LTP in vitro, and the synthetic analog reversed defects in one-trial inhibitory avoidance learning in vivo. These results indicate that effects of ethanol on both LTP and LTD arise by complex mechanisms beyond NMDAR antagonism and that oxysterol NMDAR PAMS may represent a novel approach for preventing and reversing acute ethanol-mediated changes in cognition.
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Affiliation(s)
- Yukitoshi Izumi
- Department of Psychiatry and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (Y.I., S.J.M., C.F.Z.); and Sage Therapeutics, Cambridge, Massachusetts (J.J.D.)
| | - Steven J Mennerick
- Department of Psychiatry and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (Y.I., S.J.M., C.F.Z.); and Sage Therapeutics, Cambridge, Massachusetts (J.J.D.)
| | - James J Doherty
- Department of Psychiatry and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (Y.I., S.J.M., C.F.Z.); and Sage Therapeutics, Cambridge, Massachusetts (J.J.D.)
| | - Charles F Zorumski
- Department of Psychiatry and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (Y.I., S.J.M., C.F.Z.); and Sage Therapeutics, Cambridge, Massachusetts (J.J.D.)
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19
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Otsomaa L, Levijoki J, Wohlfahrt G, Chapman H, Koivisto AP, Syrjänen K, Koskelainen T, Peltokorpi SE, Finckenberg P, Heikkilä A, Abi-Gerges N, Ghetti A, Miller PE, Page G, Mervaala E, Nagy N, Kohajda Z, Jost N, Virág L, Varró A, Papp JG. Discovery and characterization of ORM-11372, a novel inhibitor of the sodium-calcium exchanger with positive inotropic activity. Br J Pharmacol 2020; 177:5534-5554. [PMID: 32959887 PMCID: PMC7707092 DOI: 10.1111/bph.15257] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 08/14/2020] [Accepted: 09/03/2020] [Indexed: 11/29/2022] Open
Abstract
Background and Purpose The lack of selective sodium–calcium exchanger (NCX) inhibitors has hampered the exploration of physiological and pathophysiological roles of cardiac NCX 1.1. We aimed to discover more potent and selective drug like NCX 1.1 inhibitor. Experimental Approach A flavan series‐based pharmacophore model was constructed. Virtual screening helped us identify a novel scaffold for NCX inhibition. A distinctively different NCX 1.1 inhibitor, ORM‐11372, was discovered after lead optimization. Its potency against human and rat NCX 1.1 and selectivity against other ion channels was assessed. The cardiovascular effects of ORM‐11372 were studied in normal and infarcted rats and rabbits. Human cardiac safety was studied ex vivo using human ventricular trabeculae. Key Results ORM‐11372 inhibited human NCX 1.1 reverse and forward currents; IC50 values were 5 and 6 nM respectively. ORM‐11372 inhibited human cardiac sodium 1.5 (INa) and hERG KV11.1 currents (IhERG) in a concentration‐dependent manner; IC50 values were 23.2 and 10.0 μM. ORM‐11372 caused no changes in action potential duration; short‐term variability and triangulation were observed for concentrations of up to 10 μM. ORM‐11372 induced positive inotropic effects of 18 ± 6% and 35 ± 8% in anaesthetized rats with myocardial infarctions and in healthy rabbits respectively; no other haemodynamic effects were observed, except improved relaxation at the lowest dose. Conclusion and Implications ORM‐11372, a unique, novel, and potent inhibitor of human and rat NCX 1.1, is a positive inotropic compound. NCX inhibition can induce clinically relevant improvements in left ventricular contractions without affecting relaxation, heart rate, or BP, without pro‐arrhythmic risk.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Piet Finckenberg
- Department of Pharmacology, Faculty of Medicine, Helsinki, Finland
| | | | | | | | | | - Guy Page
- R&D, AnaBios Corporation, San Diego, CA, USA
| | - Eero Mervaala
- Department of Pharmacology, Faculty of Medicine, Helsinki, Finland
| | - Norbert Nagy
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Zsófia Kohajda
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Norbert Jost
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - András Varró
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Julius Gy Papp
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, Faculty of Medicine, University of Szeged, Szeged, Hungary
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20
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Tsai WC, Guo S, Olaopa MA, Field LJ, Yang J, Shen C, Chang CP, Chen PS, Rubart M. Complex Arrhythmia Syndrome in a Knock-In Mouse Model Carrier of the N98S Calm1 Mutation. Circulation 2020; 142:1937-1955. [PMID: 32929985 DOI: 10.1161/circulationaha.120.046450] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Calmodulin mutations are associated with arrhythmia syndromes in humans. Exome sequencing previously identified a de novo mutation in CALM1 resulting in a p.N98S substitution in a patient with sinus bradycardia and stress-induced bidirectional ventricular ectopy. The objectives of the present study were to determine if mice carrying the N98S mutation knocked into Calm1 replicate the human arrhythmia phenotype and to examine arrhythmia mechanisms. METHODS Mouse lines heterozygous for the Calm1N98S allele (Calm1N98S/+) were generated using CRISPR/Cas9 technology. Adult mutant mice and their wildtype littermates (Calm1+/+) underwent electrocardiographic monitoring. Ventricular de- and repolarization was assessed in isolated hearts using optical voltage mapping. Action potentials and whole-cell currents and [Ca2+]i, as well, were measured in single ventricular myocytes using the patch-clamp technique and fluorescence microscopy, respectively. The microelectrode technique was used for in situ membrane voltage monitoring of ventricular conduction fibers. RESULTS Two biologically independent knock-in mouse lines heterozygous for the Calm1N98S allele were generated. Calm1N98S/+ mice of either sex and line exhibited sinus bradycardia, QTc interval prolongation, and catecholaminergic bidirectional ventricular tachycardia. Male mutant mice also showed QRS widening. Pharmacological blockade and activation of β-adrenergic receptors rescued and exacerbated, respectively, the long-QT phenotype of Calm1N98S/+ mice. Optical and electric assessment of membrane potential in isolated hearts and single left ventricular myocytes, respectively, revealed β-adrenergically induced delay of repolarization. β-Adrenergic stimulation increased peak density, slowed inactivation, and left-shifted the activation curve of ICa.L significantly more in Calm1N98S/+ versus Calm1+/+ ventricular myocytes, increasing late ICa.L in the former. Rapidly paced Calm1N98S/+ ventricular myocytes showed increased propensity to delayed afterdepolarization-induced triggered activity, whereas in situ His-Purkinje fibers exhibited increased susceptibility for pause-dependent early afterdepolarizations. Epicardial mapping of Calm1N98S/+ hearts showed that both reentry and focal mechanisms contribute to arrhythmogenesis. CONCLUSIONS Heterozygosity for the Calm1N98S mutation is causative of an arrhythmia syndrome characterized by sinus bradycardia, QRS widening, adrenergically mediated QTc interval prolongation, and bidirectional ventricular tachycardia. β-Adrenergically induced ICa.L dysregulation contributes to the long-QT phenotype. Pause-dependent early afterdepolarizations and tachycardia-induced delayed afterdepolarizations originating in the His-Purkinje network and ventricular myocytes, respectively, constitute potential sources of arrhythmia in Calm1N98S/+ hearts.
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Affiliation(s)
- Wen-Chin Tsai
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (W.-C.T., S.G., M.A.O., J.Y., C.-P.C. P.-S.C., M.R.), Indiana University School of Medicine, Indianapolis.,Department of Cardiology, Cardiovascular Research Center, Buddhist Tzu Chi General Hospital and Tzu Chi University, Hualien, Taiwan (W.-C.T.)
| | - Shuai Guo
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (W.-C.T., S.G., M.A.O., J.Y., C.-P.C. P.-S.C., M.R.), Indiana University School of Medicine, Indianapolis.,Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, China (S.G.)
| | - Michael A Olaopa
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (W.-C.T., S.G., M.A.O., J.Y., C.-P.C. P.-S.C., M.R.), Indiana University School of Medicine, Indianapolis
| | - Loren J Field
- Wells Center for Pediatric Research, Department of Pediatrics (L.J.F., M.R.), Indiana University School of Medicine, Indianapolis
| | - Jin Yang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (W.-C.T., S.G., M.A.O., J.Y., C.-P.C. P.-S.C., M.R.), Indiana University School of Medicine, Indianapolis
| | - Changyu Shen
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (C.S.)
| | - Ching-Pin Chang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (W.-C.T., S.G., M.A.O., J.Y., C.-P.C. P.-S.C., M.R.), Indiana University School of Medicine, Indianapolis
| | - Peng-Sheng Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (W.-C.T., S.G., M.A.O., J.Y., C.-P.C. P.-S.C., M.R.), Indiana University School of Medicine, Indianapolis
| | - Michael Rubart
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (W.-C.T., S.G., M.A.O., J.Y., C.-P.C. P.-S.C., M.R.), Indiana University School of Medicine, Indianapolis.,Wells Center for Pediatric Research, Department of Pediatrics (L.J.F., M.R.), Indiana University School of Medicine, Indianapolis
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21
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Kohajda Z, Loewe A, Tóth N, Varró A, Nagy N. The Cardiac Pacemaker Story-Fundamental Role of the Na +/Ca 2+ Exchanger in Spontaneous Automaticity. Front Pharmacol 2020; 11:516. [PMID: 32410993 PMCID: PMC7199655 DOI: 10.3389/fphar.2020.00516] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 04/01/2020] [Indexed: 01/01/2023] Open
Abstract
The electrophysiological mechanism of the sinus node automaticity was previously considered exclusively regulated by the so-called "funny current". However, parallel investigations increasingly emphasized the importance of the Ca2+-homeostasis and Na+/Ca2+ exchanger (NCX). Recently, increasing experimental evidence, as well as insight through mechanistic in silico modeling demonstrates the crucial role of the exchanger in sinus node pacemaking. NCX had a key role in the exciting story of discovery of sinus node pacemaking mechanisms, which recently settled with a consensus on the coupled-clock mechanism after decades of debate. This review focuses on the role of the Na+/Ca2+ exchanger from the early results and concepts to recent advances and attempts to give a balanced summary of the characteristics of the local, spontaneous, and rhythmic Ca2+ releases, the molecular control of the NCX and its role in the fight-or-flight response. Transgenic animal models and pharmacological manipulation of intracellular Ca2+ concentration and/or NCX demonstrate the pivotal function of the exchanger in sinus node automaticity. We also highlight where specific hypotheses regarding NCX function have been derived from computational modeling and require experimental validation. Nonselectivity of NCX inhibitors and the complex interplay of processes involved in Ca2+ handling render the design and interpretation of these experiments challenging.
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Affiliation(s)
- Zsófia Kohajda
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Axel Loewe
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - András Varró
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Norbert Nagy
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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22
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Kohajda Z, Tóth N, Szlovák J, Loewe A, Bitay G, Gazdag P, Prorok J, Jost N, Levijoki J, Pollesello P, Papp JG, Varró A, Nagy N. Novel Na +/Ca 2+ Exchanger Inhibitor ORM-10962 Supports Coupled Function of Funny-Current and Na +/Ca 2+ Exchanger in Pacemaking of Rabbit Sinus Node Tissue. Front Pharmacol 2020; 10:1632. [PMID: 32063850 PMCID: PMC7000430 DOI: 10.3389/fphar.2019.01632] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 12/13/2019] [Indexed: 01/01/2023] Open
Abstract
Background and Purpose The exact mechanism of spontaneous pacemaking is not fully understood. Recent results suggest tight cooperation between intracellular Ca2+ handling and sarcolemmal ion channels. An important player of this crosstalk is the Na+/Ca2+ exchanger (NCX), however, direct pharmacological evidence was unavailable so far because of the lack of a selective inhibitor. We investigated the role of the NCX current in pacemaking and analyzed the functional consequences of the If-NCX coupling by applying the novel selective NCX inhibitor ORM-10962 on the sinus node (SAN). Experimental Approach Currents were measured by patch-clamp, Ca2+-transients were monitored by fluorescent optical method in rabbit SAN cells. Action potentials (AP) were recorded from rabbit SAN tissue preparations. Mechanistic computational data were obtained using the Yaniv et al. SAN model. Key Results ORM-10962 (ORM) marginally reduced the SAN pacemaking cycle length with a marked increase in the diastolic Ca2+ level as well as the transient amplitude. The bradycardic effect of NCX inhibition was augmented when the funny-current (If) was previously inhibited and vice versa, the effect of If was augmented when the Ca2+ handling was suppressed. Conclusion and Implications We confirmed the contribution of the NCX current to cardiac pacemaking using a novel NCX inhibitor. Our experimental and modeling data support a close cooperation between If and NCX providing an important functional consequence: these currents together establish a strong depolarization capacity providing important safety factor for stable pacemaking. Thus, after individual inhibition of If or NCX, excessive bradycardia or instability cannot be expected because each of these currents may compensate for the reduction of the other providing safe and rhythmic SAN pacemaking.
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Affiliation(s)
- Zsófia Kohajda
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Jozefina Szlovák
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Axel Loewe
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Gergő Bitay
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Péter Gazdag
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - János Prorok
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Norbert Jost
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | | | | | - Julius Gy Papp
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - András Varró
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Norbert Nagy
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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23
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Lariccia V, Macrì ML, Matteucci A, Maiolino M, Amoroso S, Magi S. Effects of ticagrelor on the sodium/calcium exchanger 1 (NCX1) in cardiac derived H9c2 cells. Eur J Pharmacol 2019; 850:158-166. [PMID: 30721704 DOI: 10.1016/j.ejphar.2019.01.067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 01/08/2019] [Accepted: 01/17/2019] [Indexed: 12/15/2022]
Abstract
Ticagrelor is a direct acting and reversibly binding P2Y12 antagonist approved for the prevention of thromboembolic events. Clinical effects of ticagrelor cannot be simply accounted for by pure platelet inhibition, and off-target mechanisms can potentially play a role. In particular, recent evidence suggests that ticagrelor may also influence heart function and improve the evolution of myocardial ischemic injury by more direct effects on myocytes. The cardiac sodium/calcium exchanger 1 (NCX1) is a critical player in the generation and control of calcium (Ca2+) signals, which orchestrate multiple myocyte activities in health and disease. Altered expression and/or activity of NCX1 can have profound consequences for the function and fate of myocytes. Whether ticagrelor affects cardiac NCX1 has not been investigated yet. To explore this hypothesis, we analyzed the expression, localization and activity of NCX1 in the heart derived H9c2-NCX1 cells following ticagrelor exposure. We found that ticagrelor concentration- and time-dependently reduced the activity of the cardiac NCX1 in H9c2 cells. In particular, the inhibitory effect of ticagrelor on the Ca2+-influx mode of NCX1 was evident within 1 h and further developed after 24 h, when NCX1 activity was suppressed by about 55% in cells treated with 1 μM ticagrelor. Ticagrelor-induced inhibition of exchanger activity was reached at clinically relevant concentrations, without affecting the expression levels and subcellular distribution of NCX1. Collectively, these findings suggest that cardiac NCX1 is a new downstream target of ticagrelor, which may contribute to the therapeutic profile of ticagrelor in clinical practice.
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Affiliation(s)
- Vincenzo Lariccia
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126 Ancona, Italy.
| | - Maria Loredana Macrì
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126 Ancona, Italy
| | - Alessandra Matteucci
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126 Ancona, Italy
| | - Marta Maiolino
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126 Ancona, Italy
| | - Salvatore Amoroso
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126 Ancona, Italy
| | - Simona Magi
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126 Ancona, Italy
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24
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Holdt LM, Kohlmaier A, Teupser D. Molecular functions and specific roles of circRNAs in the cardiovascular system. Noncoding RNA Res 2018; 3:75-98. [PMID: 30159442 PMCID: PMC6096412 DOI: 10.1016/j.ncrna.2018.05.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 05/11/2018] [Accepted: 05/11/2018] [Indexed: 12/25/2022] Open
Abstract
As part of the superfamily of long noncoding RNAs, circular RNAs (circRNAs) are emerging as a new type of regulatory molecules that partake in gene expression control. Here, we review the current knowledge about circRNAs in cardiovascular disease. CircRNAs are not only associated with different types of cardiovascular disease, but they have also been identified as intracellular effector molecules for pathophysiological changes in cardiovascular tissues, and as cardiovascular biomarkers. This evidence is put in the context of the current understanding of general circRNA biogenesis and of known interactions of circRNAs with DNA, RNA, and proteins.
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Affiliation(s)
- Lesca M. Holdt
- Institute of Laboratory Medicine, University Hospital, LMU Munich, Germany
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Ca V1.3 L-type Ca 2+ channel contributes to the heartbeat by generating a dihydropyridine-sensitive persistent Na + current. Sci Rep 2017; 7:7869. [PMID: 28801600 PMCID: PMC5554211 DOI: 10.1038/s41598-017-08191-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 07/07/2017] [Indexed: 11/22/2022] Open
Abstract
The spontaneous activity of sinoatrial node (SAN) pacemaker cells is generated by a functional interplay between the activity of ionic currents of the plasma membrane and intracellular Ca2+ dynamics. The molecular correlate of a dihydropyridine (DHP)-sensitive sustained inward Na+ current (Ist), a key player in SAN automaticity, is still unknown. Here we show that Ist and the L-type Ca2+ current (ICa,L) share CaV1.3 as a common molecular determinant. Patch-clamp recordings of mouse SAN cells showed that Ist is activated in the diastolic depolarization range, and displays Na+ permeability and minimal inactivation and sensitivity to ICa,L activators and blockers. Both CaV1.3-mediated ICa,L and Ist were abolished in CaV1.3-deficient (CaV1.3−/−) SAN cells but the CaV1.2-mediated ICa,L current component was preserved. In SAN cells isolated from mice expressing DHP-insensitive CaV1.2 channels (CaV1.2DHP−/−), Ist and CaV1.3-mediated ICa,L displayed overlapping sensitivity and concentration–response relationships to the DHP blocker nifedipine. Consistent with the hypothesis that CaV1.3 rather than CaV1.2 underlies Ist, a considerable fraction of ICa,L was resistant to nifedipine inhibition in CaV1.2DHP−/− SAN cells. These findings identify CaV1.3 channels as essential molecular components of the voltage-dependent, DHP-sensitive Ist Na+ current in the SAN.
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Increased sodium/calcium exchanger activity enhances beta-adrenergic-mediated increase in heart rate: Whole-heart study in a homozygous sodium/calcium exchanger overexpressor mouse model. Heart Rhythm 2017; 14:1247-1253. [PMID: 28495655 DOI: 10.1016/j.hrthm.2017.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Indexed: 11/23/2022]
Abstract
BACKGROUND The cardiac sodium/calcium (Na+/Ca2+) exchanger (NCX) contributes to diastolic depolarization in cardiac pacemaker cells. Increased NCX activity has been found in heart failure and atrial fibrillation. The influence of increased NCX activity on resting heart rate, beta-adrenergic-mediated increase in heart rate, and cardiac conduction properties is unknown. OBJECTIVE The purpose of this study was to investigate the influence of NCX overexpression in a homozygous transgenic whole-heart mouse model (NCX-OE) on sinus and AV nodal function. METHODS Langendorff-perfused, beating whole hearts of NCX-OE and the corresponding wild-type (WT) were studied ± isoproterenol (ISO; 0.2 μM). Epicardial ECG, AV nodal Wenckebach cycle length (AVN-WCL), and retrograde AVN-WCL were obtained. RESULTS At baseline, basal heart rate was unaltered between NCX-OE and WT (WT: cycle length [CL] 177.6 ± 40.0 ms, no. of hearts [n] = 20; NCX-OE: CL 185.9 ± 30.5 ms, n = 18; P = .21). In the presence of ISO, NCX-OE exhibited a significantly higher heart rate compared to WT (WT: CL 133.4 ± 13.4 ms, n = 20; NCX-OE: CL 117.7 ± 14.2 ms, n = 18; P <.001). ISO led to a significant shortening of the anterograde and retrograde AVN-WCL without differences between NCX-OE and WT. CONCLUSION This study is the first to demonstrate that increased NCX activity enhances beta-adrenergic increase of heart rate. Mechanistically, increased NCX inward mode activity may promote acceleration of diastolic depolarization in sinus nodal pacemaker cells, thus enhancing chronotropy in NCX-OE. These findings suggest a novel potential therapeutic target for heart rate control in the presence of increased NCX activity, such as heart failure.
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Wu Y, Valdivia HH, Wehrens XHT, Anderson ME. A Single Protein Kinase A or Calmodulin Kinase II Site Does Not Control the Cardiac Pacemaker Ca2+ Clock. Circ Arrhythm Electrophysiol 2016; 9:e003180. [PMID: 26857906 DOI: 10.1161/circep.115.003180] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND Fight or flight heart rate (HR) increases depend on protein kinase A (PKA)- and calmodulin kinase II (CaMKII)-mediated enhancement of Ca(2+) uptake and release from sarcoplasmic reticulum (SR) in sinoatrial nodal cells (SANC). However, the impact of specific PKA and CaMKII phosphorylation sites on HR is unknown. METHODS AND RESULTS We systematically evaluated validated PKA and CaMKII target sites on phospholamban and the ryanodine receptor using genetically modified mice. We found that knockin alanine replacement of ryanodine receptor PKA (S2808) or CaMKII (S2814) target sites failed to affect HR responses to isoproterenol or spontaneous activity in vivo or in SANC. Similarly, selective mutation of phospholamban amino acids critical for enhancing SR Ca(2+) uptake by PKA (S16) or CaMKII (T17) to alanines did not affect HR in vivo or in SANC. In contrast, CaMKII inhibition by expression of AC3-I has been shown to slow SANC rate responses to isoproterenol and decrease SR Ca(2+) content. Phospholamban deficiency rescued SR Ca(2+) content and SANC rate responses to isoproterenol in mice with AC3-I expression, suggesting that CaMKII affects HR by modulation of SR Ca(2+) content. Consistent with this, mice expressing a superinhibitory phospholamban mutant had low SR Ca(2+) content and slow HR in vivo and in SANC. CONCLUSIONS SR Ca(2+) depletion reduces HR and SR Ca(2+) repletion restores physiological SANC rate responses, despite CaMKII inhibition. PKA and CaMKII do not affect HR by a unique target site governing SR Ca(2+) uptake or release. HR acceleration may require an SR Ca(2+) content threshold.
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Affiliation(s)
- Yuejin Wu
- From the Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD (Y.W., M.E.A.); Center for Arrhythmia Research, Cardiovascular Division, Department of Internal Medicine, University of Michigan, Ann Arbor (H.H.V.); and Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine, Pediatrics, Baylor College of Medicine, Houston, TX (X.H.T.W.).
| | - Héctor H Valdivia
- From the Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD (Y.W., M.E.A.); Center for Arrhythmia Research, Cardiovascular Division, Department of Internal Medicine, University of Michigan, Ann Arbor (H.H.V.); and Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine, Pediatrics, Baylor College of Medicine, Houston, TX (X.H.T.W.)
| | - Xander H T Wehrens
- From the Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD (Y.W., M.E.A.); Center for Arrhythmia Research, Cardiovascular Division, Department of Internal Medicine, University of Michigan, Ann Arbor (H.H.V.); and Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine, Pediatrics, Baylor College of Medicine, Houston, TX (X.H.T.W.)
| | - Mark E Anderson
- From the Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD (Y.W., M.E.A.); Center for Arrhythmia Research, Cardiovascular Division, Department of Internal Medicine, University of Michigan, Ann Arbor (H.H.V.); and Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine, Pediatrics, Baylor College of Medicine, Houston, TX (X.H.T.W.).
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Unudurthi SD, Wu X, Qian L, Amari F, Onal B, Li N, Makara MA, Smith SA, Snyder J, Fedorov VV, Coppola V, Anderson ME, Mohler PJ, Hund TJ. Two-Pore K+ Channel TREK-1 Regulates Sinoatrial Node Membrane Excitability. J Am Heart Assoc 2016; 5:e002865. [PMID: 27098968 PMCID: PMC4859279 DOI: 10.1161/jaha.115.002865] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background Two‐pore K+ channels have emerged as potential targets to selectively regulate cardiac cell membrane excitability; however, lack of specific inhibitors and relevant animal models has impeded the effort to understand the role of 2‐pore K+ channels in the heart and their potential as a therapeutic target. The objective of this study was to determine the role of mechanosensitive 2‐pore K+ channel family member TREK‐1 in control of cardiac excitability. Methods and Results Cardiac‐specific TREK‐1–deficient mice (αMHC‐Kcnkf/f) were generated and found to have a prevalent sinoatrial phenotype characterized by bradycardia with frequent episodes of sinus pause following stress. Action potential measurements from isolated αMHC‐Kcnk2f/f sinoatrial node cells demonstrated decreased background K+ current and abnormal sinoatrial cell membrane excitability. To identify novel pathways for regulating TREK‐1 activity and sinoatrial node excitability, mice expressing a truncated allele of the TREK‐1–associated cytoskeletal protein βIV‐spectrin (qv4J mice) were analyzed and found to display defects in cell electrophysiology as well as loss of normal TREK‐1 membrane localization. Finally, the βIV‐spectrin/TREK‐1 complex was found to be downregulated in the right atrium from a canine model of sinoatrial node dysfunction and in human cardiac disease. Conclusions These findings identify a TREK‐1–dependent pathway essential for normal sinoatrial node cell excitability that serves as a potential target for selectively regulating sinoatrial node cell function.
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Affiliation(s)
- Sathya D Unudurthi
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH
| | - Xiangqiong Wu
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH
| | - Lan Qian
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH
| | - Foued Amari
- Department of Molecular Virology, Immunology & Medical Genetics, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Birce Onal
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH
| | - Ning Li
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Michael A Makara
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Sakima A Smith
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Jedidiah Snyder
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH
| | - Vadim V Fedorov
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Vincenzo Coppola
- Department of Molecular Virology, Immunology & Medical Genetics, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Mark E Anderson
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD
| | - Peter J Mohler
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Physiology & Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Thomas J Hund
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH
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Spontaneous inward currents reflecting oscillatory activation of Na+/Ca2+ exchangers in human embryonic stem cell-derived cardiomyocytes. Pflugers Arch 2015; 468:609-22. [DOI: 10.1007/s00424-015-1769-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Revised: 11/30/2015] [Accepted: 12/03/2015] [Indexed: 11/25/2022]
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Shattock MJ, Ottolia M, Bers DM, Blaustein MP, Boguslavskyi A, Bossuyt J, Bridge JHB, Chen-Izu Y, Clancy CE, Edwards A, Goldhaber J, Kaplan J, Lingrel JB, Pavlovic D, Philipson K, Sipido KR, Xie ZJ. Na+/Ca2+ exchange and Na+/K+-ATPase in the heart. J Physiol 2015; 593:1361-82. [PMID: 25772291 PMCID: PMC4376416 DOI: 10.1113/jphysiol.2014.282319] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 10/30/2014] [Indexed: 12/17/2022] Open
Abstract
This paper is the third in a series of reviews published in this issue resulting from the University of California Davis Cardiovascular Symposium 2014: Systems approach to understanding cardiac excitation–contraction coupling and arrhythmias: Na+ channel and Na+ transport. The goal of the symposium was to bring together experts in the field to discuss points of consensus and controversy on the topic of sodium in the heart. The present review focuses on cardiac Na+/Ca2+ exchange (NCX) and Na+/K+-ATPase (NKA). While the relevance of Ca2+ homeostasis in cardiac function has been extensively investigated, the role of Na+ regulation in shaping heart function is often overlooked. Small changes in the cytoplasmic Na+ content have multiple effects on the heart by influencing intracellular Ca2+ and pH levels thereby modulating heart contractility. Therefore it is essential for heart cells to maintain Na+ homeostasis. Among the proteins that accomplish this task are the Na+/Ca2+ exchanger (NCX) and the Na+/K+ pump (NKA). By transporting three Na+ ions into the cytoplasm in exchange for one Ca2+ moved out, NCX is one of the main Na+ influx mechanisms in cardiomyocytes. Acting in the opposite direction, NKA moves Na+ ions from the cytoplasm to the extracellular space against their gradient by utilizing the energy released from ATP hydrolysis. A fine balance between these two processes controls the net amount of intracellular Na+ and aberrations in either of these two systems can have a large impact on cardiac contractility. Due to the relevant role of these two proteins in Na+ homeostasis, the emphasis of this review is on recent developments regarding the cardiac Na+/Ca2+ exchanger (NCX1) and Na+/K+ pump and the controversies that still persist in the field.
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Affiliation(s)
- Michael J Shattock
- King's College London BHF Centre of Excellence, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
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Burst pacemaker activity of the sinoatrial node in sodium-calcium exchanger knockout mice. Proc Natl Acad Sci U S A 2015. [PMID: 26195795 DOI: 10.1073/pnas.1505670112] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In sinoatrial node (SAN) cells, electrogenic sodium-calcium exchange (NCX) is the dominant calcium (Ca) efflux mechanism. However, the role of NCX in the generation of SAN automaticity is controversial. To investigate the contribution of NCX to pacemaking in the SAN, we performed optical voltage mapping and high-speed 2D laser scanning confocal microscopy (LSCM) of Ca dynamics in an ex vivo intact SAN/atrial tissue preparation from atrial-specific NCX knockout (KO) mice. These mice lack P waves on electrocardiograms, and isolated NCX KO SAN cells are quiescent. Voltage mapping revealed disorganized and arrhythmic depolarizations within the NCX KO SAN that failed to propagate into the atria. LSCM revealed intermittent bursts of Ca transients. Bursts were accompanied by rising diastolic Ca, culminating in long pauses dominated by Ca waves. The L-type Ca channel agonist BayK8644 reduced the rate of Ca transients and inhibited burst generation in the NCX KO SAN whereas the Ca buffer 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (acetoxymethyl ester) (BAPTA AM) did the opposite. These results suggest that cellular Ca accumulation hinders spontaneous depolarization in the NCX KO SAN, possibly by inhibiting L-type Ca currents. The funny current (If) blocker ivabradine also suppressed NCX KO SAN automaticity. We conclude that pacemaker activity is present in the NCX KO SAN, generated by a mechanism that depends upon If. However, the absence of NCX-mediated depolarization in combination with impaired Ca efflux results in intermittent bursts of pacemaker activity, reminiscent of human sinus node dysfunction and "tachy-brady" syndrome.
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The genetic basis for inherited forms of sinoatrial dysfunction and atrioventricular node dysfunction. J Interv Card Electrophysiol 2015; 43:121-34. [PMID: 25863800 PMCID: PMC4486151 DOI: 10.1007/s10840-015-9998-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 03/13/2015] [Indexed: 01/01/2023]
Abstract
The sinoatrial node (SAN) and the atrioventricular node (AVN) are the anatomical and functional regions of the heart which play critical roles in the generation and conduction of the electrical impulse. Their functions are ensured by peculiar structural cytological properties and specific collections of ion channels. Impairment of SAN and AVN activity is generally acquired,but in some cases familial inheritance has been established and therefore a genetic cause is involved. In recent years, combined efforts of clinical practice and experimental basic science studies have identified and characterized several causative gene mutations associated with the nodal syndromes. Channelopathies, i.e., diseases associated with defective ion channels, remain the major cause of genetically determined nodal arrhythmias; however, it is becoming increasingly evident that mutations in other classes of regulatory and structural proteins also have profound pathophysiological roles. In this review, we will present some aspects of the genetic identification of the molecular mechanism underlying both SAN and AVN dysfunctions with a particular focus on mutations of the Na, pacemaker (HCN), and Ca channels. Genetic defects in regulatory proteins and calcium-handling proteins will be also considered. In conclusion, the identification of the genetic defects associated with familial nodal dysfunction is an essential step for implementing an appropriate therapeutic treatment.
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Capel RA, Terrar DA. The importance of Ca(2+)-dependent mechanisms for the initiation of the heartbeat. Front Physiol 2015; 6:80. [PMID: 25859219 PMCID: PMC4373508 DOI: 10.3389/fphys.2015.00080] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/02/2015] [Indexed: 01/01/2023] Open
Abstract
Mechanisms underlying pacemaker activity in the sinus node remain controversial, with some ascribing a dominant role to timing events in the surface membrane (“membrane clock”) and others to uptake and release of calcium from the sarcoplasmic reticulum (SR) (“calcium clock”). Here we discuss recent evidence on mechanisms underlying pacemaker activity with a particular emphasis on the many roles of calcium. There are particular areas of controversy concerning the contribution of calcium spark-like events and the importance of I(f) to spontaneous diastolic depolarisation, though it will be suggested that neither of these is essential for pacemaking. Sodium-calcium exchange (NCX) is most often considered in the context of mediating membrane depolarisation after spark-like events. We present evidence for a broader role of this electrogenic exchanger which need not always depend upon these spark-like events. Short (milliseconds or seconds) and long (minutes) term influences of calcium are discussed including direct regulation of ion channels and NCX, and control of the activity of calcium-dependent enzymes (including CaMKII, AC1, and AC8). The balance between the many contributory factors to pacemaker activity may well alter with experimental and clinical conditions, and potentially redundant mechanisms are desirable to ensure the regular spontaneous heart rate that is essential for life. This review presents evidence that calcium is central to the normal control of pacemaking across a range of temporal scales and seeks to broaden the accepted description of the “calcium clock” to cover these important influences.
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Affiliation(s)
- Rebecca A Capel
- British Heart Foundation Centre of Research Excellence, Department of Pharmacology, University of Oxford Oxford, UK
| | - Derek A Terrar
- British Heart Foundation Centre of Research Excellence, Department of Pharmacology, University of Oxford Oxford, UK
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Kaestner L, Scholz A, Lipp P. Conceptual and technical aspects of transfection and gene delivery. Bioorg Med Chem Lett 2015; 25:1171-6. [DOI: 10.1016/j.bmcl.2015.01.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Revised: 12/30/2014] [Accepted: 01/09/2015] [Indexed: 12/22/2022]
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Vakrou S, Abraham MR. Hypertrophic cardiomyopathy: a heart in need of an energy bar? Front Physiol 2014; 5:309. [PMID: 25191275 PMCID: PMC4137386 DOI: 10.3389/fphys.2014.00309] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 07/30/2014] [Indexed: 01/08/2023] Open
Abstract
Hypertrophic cardiomyopathy (HCM) has been recently recognized as the most common inherited cardiovascular disorder, affecting 1 in 500 adults worldwide. HCM is characterized by myocyte hypertrophy resulting in thickening of the ventricular wall, myocyte disarray, interstitial and/or replacement fibrosis, decreased ventricular cavity volume and diastolic dysfunction. HCM is also the most common cause of sudden death in the young. A large proportion of patients diagnosed with HCM have mutations in sarcomeric proteins. However, it is unclear how these mutations lead to the cardiac phenotype, which is variable even in patients carrying the same causal mutation. Abnormalities in calcium cycling, oxidative stress, mitochondrial dysfunction and energetic deficiency have been described constituting the basis of therapies in experimental models of HCM and HCM patients. This review focuses on evidence supporting the role of cellular metabolism and mitochondria in HCM.
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Affiliation(s)
- Styliani Vakrou
- Division of Cardiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
| | - M Roselle Abraham
- Division of Cardiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
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Kaestner L, Scholz A, Tian Q, Ruppenthal S, Tabellion W, Wiesen K, Katus HA, Müller OJ, Kotlikoff MI, Lipp P. Genetically encoded Ca2+ indicators in cardiac myocytes. Circ Res 2014; 114:1623-39. [PMID: 24812351 DOI: 10.1161/circresaha.114.303475] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Genetically encoded Ca(2+) indicators constitute a powerful set of tools to investigate functional aspects of Ca(2+) signaling in isolated cardiomyocytes, cardiac tissue, and whole hearts. Here, we provide an overview of the concepts, experiences, state of the art, and ongoing developments in the use of genetically encoded Ca(2+) indicators for cardiac cells and heart tissue. This review is supplemented with in vivo viral gene transfer experiments and comparisons of available genetically encoded Ca(2+) indicators with each other and with the small molecule dye Fura-2. In the context of cardiac myocytes, we provide guidelines for selecting a genetically encoded Ca(2+) indicator. For future developments, we discuss improvements of a broad range of properties, including photophysical properties such as spectral spread and biocompatibility, as well as cellular and in vivo applications.
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Affiliation(s)
- Lars Kaestner
- From the Institute for Molecular Cell Biology and Research Center for Molecular Imaging and Screening, School of Medicine, Saarland University, Homburg-Saar, Germany (L.K., A.S., Q.T., S.R., W.T., K.W., P.L.); Department of Internal Medicine III, University of Heidelberg, Heidelberg, Germany (H.A.K., O.J.M.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Germany (H.A.K., O.J.M.); and Biomedical Sciences Department, College of Veterinary Medicine, Cornell University, Ithaca, NY (M.I.K.)
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Curran J, Makara MA, Little SC, Musa H, Liu B, Wu X, Polina I, Alecusan JS, Wright P, Li J, Billman GE, Boyden PA, Gyorke S, Band H, Hund TJ, Mohler PJ. EHD3-dependent endosome pathway regulates cardiac membrane excitability and physiology. Circ Res 2014; 115:68-78. [PMID: 24759929 DOI: 10.1161/circresaha.115.304149] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Cardiac function is dependent on the coordinate activities of membrane ion channels, transporters, pumps, and hormone receptors to tune the membrane electrochemical gradient dynamically in response to acute and chronic stress. Although our knowledge of membrane proteins has rapidly advanced during the past decade, our understanding of the subcellular pathways governing the trafficking and localization of integral membrane proteins is limited and essentially unstudied in vivo. In the heart, to our knowledge, there are no in vivo mechanistic studies that directly link endosome-based machinery with cardiac physiology. OBJECTIVE To define the in vivo roles of endosome-based cellular machinery for cardiac membrane protein trafficking, myocyte excitability, and cardiac physiology. METHODS AND RESULTS We identify the endosome-based Eps15 homology domain 3 (EHD3) pathway as essential for cardiac physiology. EHD3-deficient hearts display structural and functional defects including bradycardia and rate variability, conduction block, and blunted response to adrenergic stimulation. Mechanistically, EHD3 is critical for membrane protein trafficking, because EHD3-deficient myocytes display reduced expression/localization of Na/Ca exchanger and L-type Ca channel type 1.2 with a parallel reduction in Na/Ca exchanger-mediated membrane current and Cav1.2-mediated membrane current. Functionally, EHD3-deficient myocytes show increased sarcoplasmic reticulum [Ca], increased spark frequency, and reduced expression/localization of ankyrin-B, a binding partner for EHD3 and Na/Ca exchanger. Finally, we show that in vivo EHD3-deficient defects are attributable to cardiac-specific roles of EHD3 because mice with cardiac-selective EHD3 deficiency demonstrate both structural and electric phenotypes. CONCLUSIONS These data provide new insight into the critical role of endosome-based pathways in membrane protein targeting and cardiac physiology. EHD3 is a critical component of protein trafficking in heart and is essential for the proper membrane targeting of select cellular proteins that maintain excitability.
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Affiliation(s)
- Jerry Curran
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.).
| | - Michael A Makara
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Sean C Little
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Hassan Musa
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Bin Liu
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Xiangqiong Wu
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Iuliia Polina
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Joseph S Alecusan
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Patrick Wright
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Jingdong Li
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - George E Billman
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Penelope A Boyden
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Sandor Gyorke
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Hamid Band
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Thomas J Hund
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
| | - Peter J Mohler
- From The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus (J.C., M.A.M., S.C.L., H.M., B.L., X.W., I.P., J.S.A., P.W., J.L., G.E.B., S.G., T.J.H., P.J.M.); Departments of Internal Medicine (P.J.M.) and Physiology and Cell Biology (J.C., M.A.M., S.C.L., H.M., B.L., P.W., G.E.B., S.G., P.J.M.), The Ohio State University, Columbus; Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus (T.J.H.); Department of Pharmacology and Center for Molecular Therapeutics, Columbia University Medical Center, New York, NY (P.A.B.); and The Eppley Institute and UNMC-Eppley Cancer Center, University of Nebraska Medical Center, Omaha (H.B.)
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Maltsev VA, Yaniv Y, Maltsev AV, Stern MD, Lakatta EG. Modern perspectives on numerical modeling of cardiac pacemaker cell. J Pharmacol Sci 2014; 125:6-38. [PMID: 24748434 DOI: 10.1254/jphs.13r04cr] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Cardiac pacemaking is a complex phenomenon that is still not completely understood. Together with experimental studies, numerical modeling has been traditionally used to acquire mechanistic insights in this research area. This review summarizes the present state of numerical modeling of the cardiac pacemaker, including approaches to resolve present paradoxes and controversies. Specifically we discuss the requirement for realistic modeling to consider symmetrical importance of both intracellular and cell membrane processes (within a recent "coupled-clock" theory). Promising future developments of the complex pacemaker system models include the introduction of local calcium control, mitochondria function, and biochemical regulation of protein phosphorylation and cAMP production. Modern numerical and theoretical methods such as multi-parameter sensitivity analyses within extended populations of models and bifurcation analyses are also important for the definition of the most realistic parameters that describe a robust, yet simultaneously flexible operation of the coupled-clock pacemaker cell system. The systems approach to exploring cardiac pacemaker function will guide development of new therapies such as biological pacemakers for treating insufficient cardiac pacemaker function that becomes especially prevalent with advancing age.
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Affiliation(s)
- Victor A Maltsev
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, USA
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Maltsev AV, Yaniv Y, Stern MD, Lakatta EG, Maltsev VA. RyR-NCX-SERCA local cross-talk ensures pacemaker cell function at rest and during the fight-or-flight reflex. Circ Res 2014; 113:e94-e100. [PMID: 24158576 DOI: 10.1161/circresaha.113.302465] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
RATIONALE A recent study published in Circulation Research by Gao et al used sinoatrial node (SAN)-targeted, incomplete Ncx1 knockout in mice to explore the role of the Na(+)/Ca(2+) exchanger (NCX) in cardiac pacemaker. The authors concluded that NCX is required for increasing sinus rates, but not for maintaining resting heart rate. This conclusion was based, in part, on numeric model simulations performed by Gao et al that reproduced their experimental results of unchanged action potentials in the knockout SAN cells. The authors, however, did not simulate the NCX current (INCX), that is, the subject of the study. OBJECTIVE We extended numeric examinations to simulate INCX in their incomplete knockout SAN cells that is crucial to interpret the study results. METHODS AND RESULTS INCX and Ca(2+) dynamics were simulated using different contemporary numeric models of SAN cells. We found that minimum diastolic Ca(2+) levels and INCX amplitudes generated by remaining NCX molecules (only 20% of control) remained almost unchanged. Simulations using a new local Ca(2+) control model indicate that these powerful compensatory mechanisms involve complex local cross-talk of Ca(2+) cycling proteins and NCX. Specifically, lower NCX expression facilitates Ca(2+)-induced Ca(2+) release and larger local Ca(2+) releases that stabilize diastolic INCX. Further reduction of NCX expression results in arrhythmia and halt of automaticity. CONCLUSIONS Remaining NCX molecules in the incomplete knockout model likely produce almost the same diastolic INCX as in wild-type cells. INCX contribution is crucially important for both basal automaticity of SAN cells and during the fight-or-flight reflex.
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Affiliation(s)
- Anna V Maltsev
- From the Department of Mathematics, University of Bristol, Bristol, United Kingdom
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Khananshvili D. Sodium-calcium exchangers (NCX): molecular hallmarks underlying the tissue-specific and systemic functions. Pflugers Arch 2013; 466:43-60. [PMID: 24281864 DOI: 10.1007/s00424-013-1405-y] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Revised: 11/06/2013] [Accepted: 11/09/2013] [Indexed: 12/19/2022]
Abstract
NCX proteins explore the electrochemical gradient of Na(+) to mediate Ca(2+)-fluxes in exchange with Na(+) either in the Ca(2+)-efflux (forward) or Ca(2+)-influx (reverse) mode, whereas the directionality depends on ionic concentrations and membrane potential. Mammalian NCX variants (NCX1-3) and their splice variants are expressed in a tissue-specific manner to modulate the heartbeat rate and contractile force, the brain's long-term potentiation and learning, blood pressure, renal Ca(2+) reabsorption, the immune response, neurotransmitter and insulin secretion, apoptosis and proliferation, mitochondrial bioenergetics, etc. Although the forward mode of NCX represents a major physiological module, a transient reversal of NCX may contribute to EC-coupling, vascular constriction, and synaptic transmission. Notably, the reverse mode of NCX becomes predominant in pathological settings. Since the expression levels of NCX variants are disease-related, the selective pharmacological targeting of tissue-specific NCX variants could be beneficial, thereby representing a challenge. Recent structural and biophysical studies revealed a common module for decoding the Ca(2+)-induced allosteric signal in eukaryotic NCX variants, although the phenotype variances in response to regulatory Ca(2+) remain unclear. The breakthrough discovery of the archaebacterial NCX structure may serve as a template for eukaryotic NCX, although the turnover rates of the transport cycle may differ ~10(3)-fold among NCX variants to fulfill the physiological demands for the Ca(2+) flux rates. Further elucidation of ion-transport and regulatory mechanisms may lead to selective pharmacological targeting of NCX variants under disease conditions.
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Affiliation(s)
- Daniel Khananshvili
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Ramat-Aviv, Tel-Aviv, 69978, Israel,
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Groenke S, Larson ED, Alber S, Zhang R, Lamp ST, Ren X, Nakano H, Jordan MC, Karagueuzian HS, Roos KP, Nakano A, Proenza C, Philipson KD, Goldhaber JI. Complete atrial-specific knockout of sodium-calcium exchange eliminates sinoatrial node pacemaker activity. PLoS One 2013; 8:e81633. [PMID: 24278453 PMCID: PMC3836769 DOI: 10.1371/journal.pone.0081633] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 10/25/2013] [Indexed: 11/18/2022] Open
Abstract
The origin of sinoatrial node (SAN) pacemaker activity in the heart is controversial. The leading candidates are diastolic depolarization by "funny" current (If) through HCN4 channels (the "Membrane Clock" hypothesis), depolarization by cardiac Na-Ca exchange (NCX1) in response to intracellular Ca cycling (the "Calcium Clock" hypothesis), and a combination of the two ("Coupled Clock"). To address this controversy, we used Cre/loxP technology to generate atrial-specific NCX1 KO mice. NCX1 protein was undetectable in KO atrial tissue, including the SAN. Surface ECG and intracardiac electrograms showed no atrial depolarization and a slow junctional escape rhythm in KO that responded appropriately to β-adrenergic and muscarinic stimulation. Although KO atria were quiescent they could be stimulated by external pacing suggesting that electrical coupling between cells remained intact. Despite normal electrophysiological properties of If in isolated patch clamped KO SAN cells, pacemaker activity was absent. Recurring Ca sparks were present in all KO SAN cells, suggesting that Ca cycling persists but is uncoupled from the sarcolemma. We conclude that NCX1 is required for normal pacemaker activity in murine SAN.
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Affiliation(s)
- Sabine Groenke
- Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Eric D. Larson
- Department of Physiology & Biophysics, University of Colorado School of Medicine, Denver, Colorado, United States of America
| | - Sarah Alber
- Department of Physiology & Biophysics, University of Colorado School of Medicine, Denver, Colorado, United States of America
| | - Rui Zhang
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Scott T. Lamp
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Xiaoyan Ren
- Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Haruko Nakano
- Department of Molecular, Cell and Developmental Biology, Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California Los Angeles, Los Angeles, California, United States of America
| | - Maria C. Jordan
- Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Hrayr S. Karagueuzian
- Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Kenneth P. Roos
- Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Atsushi Nakano
- Department of Molecular, Cell and Developmental Biology, Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California Los Angeles, Los Angeles, California, United States of America
| | - Catherine Proenza
- Department of Physiology & Biophysics, University of Colorado School of Medicine, Denver, Colorado, United States of America
| | - Kenneth D. Philipson
- Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Joshua I. Goldhaber
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
- * E-mail:
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Depressed pacemaker activity of sinoatrial node myocytes contributes to the age-dependent decline in maximum heart rate. Proc Natl Acad Sci U S A 2013; 110:18011-6. [PMID: 24128759 DOI: 10.1073/pnas.1308477110] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
An inexorable decline in maximum heart rate (mHR) progressively limits human aerobic capacity with advancing age. This decrease in mHR results from an age-dependent reduction in "intrinsic heart rate" (iHR), which is measured during autonomic blockade. The reduced iHR indicates, by definition, that pacemaker function of the sinoatrial node is compromised during aging. However, little is known about the properties of pacemaker myocytes in the aged sinoatrial node. Here, we show that depressed excitability of individual sinoatrial node myocytes (SAMs) contributes to reductions in heart rate with advancing age. We found that age-dependent declines in mHR and iHR in ECG recordings from mice were paralleled by declines in spontaneous action potential (AP) firing rates (FRs) in patch-clamp recordings from acutely isolated SAMs. The slower FR of aged SAMs resulted from changes in the AP waveform that were limited to hyperpolarization of the maximum diastolic potential and slowing of the early part of the diastolic depolarization. These AP waveform changes were associated with cellular hypertrophy, reduced current densities for L- and T-type Ca(2+) currents and the "funny current" (If), and a hyperpolarizing shift in the voltage dependence of If. The age-dependent reduction in sinoatrial node function was not associated with changes in β-adrenergic responsiveness, which was preserved during aging for heart rate, SAM FR, L- and T-type Ca(2+) currents, and If. Our results indicate that depressed excitability of individual SAMs due to altered ion channel activity contributes to the decline in mHR, and thus aerobic capacity, during normal aging.
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Herrmann S, Lipp P, Wiesen K, Stieber J, Nguyen H, Kaiser E, Ludwig A. The cardiac sodium-calcium exchanger NCX1 is a key player in the initiation and maintenance of a stable heart rhythm. Cardiovasc Res 2013; 99:780-8. [PMID: 23761399 DOI: 10.1093/cvr/cvt154] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
AIMS The complex molecular mechanisms underlying spontaneous cardiac pacemaking are not fully understood. Recent findings point to a co-ordinated interplay between intracellular Ca(2+) cycling and plasma membrane-localized cation transport determining the origin and periodicity of pacemaker potentials. The sodium-calcium exchanger (NCX1) is a key sarcolemmal protein for the maintenance of calcium homeostasis in the heart. Here, we investigated the contribution of NCX1 to cardiac pacemaking. METHODS AND RESULTS We used an inducible and sinoatrial node-specific Cre transgene to create micelacking NCX1 selectively in cells of the cardiac pacemaking and conduction system (cpNCX1KO). RT-PCR and immunolabeling experiments confirmed the precise tissue-specific and temporally controlled deletion. Ablation of NCX1 resulted in a progressive slowing of heart rate accompanied by severe arrhythmias. Isolated sinoatrial tissue strips displayed a significantly decreased and irregular contraction rate underpinning a disturbed intrinsic pacemaker activity. Mutant animals displayed a gradual increase in the heart-to-body weight ratio and developed ventricular dilatation; however, their ventricular contractile performance was not significantly affected. Pacemaker cells from cpNCX1KO showed no NCX1 activity in response to caffeine-induced Ca(2+) release, determined by Ca(2+) imaging. Regular spontaneous Ca(2+) discharges were frequently seen in control, but only sporadically in knockout (KO) cells. The majority of NCX1KO cells displayed an irregular and a significantly reduced frequency of spontaneous Ca(2+) signals. Furthermore, Ca(2+) transients measured during electrical field stimulation were of smaller magnitude and decelerated kinetics in KO cells. CONCLUSIONS Our results establish NCX1 as a critical target for the proper function of cardiac pacemaking.
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Affiliation(s)
- Stefan Herrmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
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Simrick S, Schindler RF, Poon KL, Brand T. Popeye domain-containing proteins and stress-mediated modulation of cardiac pacemaking. Trends Cardiovasc Med 2013; 23:257-63. [PMID: 23562093 DOI: 10.1016/j.tcm.2013.02.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 02/05/2013] [Accepted: 02/06/2013] [Indexed: 10/27/2022]
Abstract
An intricate network of ion channels and pumps are involved in generating a diastolic pacemaker potential, which is transmitted to the working myocardium with the help of the cardiac conduction system. The principles of cardiac pacemaking are reasonably well understood, however, the mechanism by which the heart increases its beating frequency in response to adrenergic stimulation has not been fully worked out. The Popeye domain-containing (Popdc) genes encode plasma membrane-localized proteins that are able to bind cAMP with high affinity; mice with null mutations in Popdc1 or 2 have a stress-induced pacemaker dysfunction. The phenotype in both mutants develops in an age-dependent manner and thus may model pacemaker dysfunction in man, as well as provide novel mechanistic insights into the process of pacemaker adaptation to stress.
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Affiliation(s)
- Subreena Simrick
- Heart Science Centre, National Heart and Lung Institute, Imperial College London, Harefield UB9 6JH, United Kingdom
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Santulli G, Iaccarino G. Pinpointing beta adrenergic receptor in ageing pathophysiology: victim or executioner? Evidence from crime scenes. IMMUNITY & AGEING 2013; 10:10. [PMID: 23497413 PMCID: PMC3763845 DOI: 10.1186/1742-4933-10-10] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/10/2013] [Indexed: 02/07/2023]
Abstract
G protein-coupled receptors (GPCRs) play a key role in cellular communication, allowing human cells to sense external cues or to talk each other through hormones or neurotransmitters. Research in this field has been recently awarded with the Nobel Prize in chemistry to Robert J. Lefkowitz and Brian K. Kobilka, for their pioneering work on beta adrenergic receptors (βARs), a prototype GPCR. Such receptors, and β2AR in particular, which is extensively distributed throughout the body, are involved in a number of pathophysiological processes. Moreover, a large amount of studies has demonstrated their participation in ageing process. Reciprocally, age-related changes in regulation of receptor responses have been observed in numerous tissues and include modifications of βAR responses. Impaired sympathetic nervous system function has been indeed evoked as at least a partial explanation for several modifications that occur with ageing. This article represents an updated presentation of the current knowledge in the field, summarizing in a systematic way the major findings of research on ageing in several organs and tissues (crime scenes) expressing βARs: heart, vessels, skeletal muscle, respiratory system, brain, immune system, pancreatic islets, liver, kidney and bone.
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Affiliation(s)
- Gaetano Santulli
- Departments of Translational Medical Sciences and Advanced Biomedical Sciences, "Federico II" University, Naples, Italy.
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Electrical storm: recent pathophysiological insights and therapeutic consequences. Basic Res Cardiol 2013; 108:336. [DOI: 10.1007/s00395-013-0336-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/29/2013] [Accepted: 02/04/2013] [Indexed: 01/01/2023]
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