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Hwang D, Liu X, Kote A, Reaso J, Andersson T, Shehata MM, Ehdaie A, Wang X, Cingolani E, Ramireddy A, Braunstein ED, Chen LS, Li X, Goldhaber J, Chen PS. Sympathetic toggled paroxysmal atrial fibrillation and recurrent premature atrial contractions in ambulatory patients. Heart Rhythm 2024:S1547-5271(24)02571-2. [PMID: 38762134 DOI: 10.1016/j.hrthm.2024.05.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 05/01/2024] [Accepted: 05/13/2024] [Indexed: 05/20/2024]
Abstract
BACKGROUND Autonomic nerve activity is important in the mechanisms of paroxysmal atrial fibrillation (PAF). OBJECTIVE To test the hypothesis that a single burst of skin sympathetic nerve activity (SKNA) can toggle on and off PAF or premature atrial contraction (PAC) clusters. METHODS We performed neuECG recording over 7 days in patients with PAF. RESULTS In Study 1, we found 8 patients (7 men, 1 woman, 62±8 years) had 124 episodes of PAF. An SKNA burst toggled both on and off PAF in 8 (6.5%) episodes (Type 1), toggled on but not off in 12 (9.7%) episodes (Type 2), and toggled on a PAC cluster, followed by PAF in 4 (3.2%) episodes (Type 3). The duration of these PAF episodes was < 10 min. The remaining 100 (80.6%) episodes were associated with active SKNA bursts throughout PAF (Type 4) and lasted longer than Type 1 (p=0.0185) and Type 2 (p=0.0027) PAF. There were 47 PAC clusters. Among them, 24 (51.1%) were toggled on and off, and 23 (48.9%) were toggled on but not off by an SKNA burst. In Study 2, we found 17 patients (9 men, 8 women, 58±12 years) with < 10 min PAF (4, 8, 0, and 31 of Types 1-4, respectively). There were significant circadian variations of all types of PAF. CONCLUSIONS A single SKNA burst can toggle short-duration PAF and PAC cluster episodes on and off. The absence of continued SKNA after the onset might have affected the maintenance of these arrhythmias.
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Affiliation(s)
- Daerin Hwang
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Xiao Liu
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Anxhela Kote
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Jewel Reaso
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Taiga Andersson
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Michael M Shehata
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Ashkan Ehdaie
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Xunzhang Wang
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Eugenio Cingolani
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Archana Ramireddy
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Eric D Braunstein
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Lan S Chen
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Xiaochun Li
- Department of Biostatistics and Health Data Science, Indiana University, Indianapolis, IN
| | - Joshua Goldhaber
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048; Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095
| | - Peng-Sheng Chen
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048.
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2
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Breves JP, Shaughnessy CA. Endocrine control of gill ionocyte function in euryhaline fishes. J Comp Physiol B 2024:10.1007/s00360-024-01555-3. [PMID: 38739280 DOI: 10.1007/s00360-024-01555-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 02/16/2024] [Accepted: 04/11/2024] [Indexed: 05/14/2024]
Abstract
The endocrine system is an essential regulator of the osmoregulatory organs that enable euryhaline fishes to maintain hydromineral balance in a broad range of environmental salinities. Because branchial ionocytes are the primary site for the active exchange of Na+, Cl-, and Ca2+ with the external environment, their functional regulation is inextricably linked with adaptive responses to changes in salinity. Here, we review the molecular-level processes that connect osmoregulatory hormones with branchial ion transport. We focus on how factors such as prolactin, growth hormone, cortisol, and insulin-like growth-factors operate through their cognate receptors to direct the expression of specific ion transporters/channels, Na+/K+-ATPases, tight-junction proteins, and aquaporins in ion-absorptive (freshwater-type) and ion-secretory (seawater-type) ionocytes. While these connections have historically been deduced in teleost models, more recently, increased attention has been given to understanding the nature of these connections in basal lineages. We conclude our review by proposing areas for future investigation that aim to fill gaps in the collective understanding of how hormonal signaling underlies ionocyte-based processes.
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Affiliation(s)
- Jason P Breves
- Department of Biology, Skidmore College, 815 N. Broadway, Saratoga Springs, NY, 12866, USA.
| | - Ciaran A Shaughnessy
- Department of Integrative Biology, Oklahoma State University, 501 Life Sciences West, Stillwater, OK, 74078, USA
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3
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Bai M, Gallen E, Memarzadeh S, Howie J, Gao X, Kuo CWS, Brown E, Swingler S, Wilson SJ, Shattock MJ, France DJ, Fuller W. Targeted degradation of zDHHC-PATs decreases substrate S-palmitoylation. PLoS One 2024; 19:e0299665. [PMID: 38512906 PMCID: PMC10956751 DOI: 10.1371/journal.pone.0299665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 02/14/2024] [Indexed: 03/23/2024] Open
Abstract
Reversible S-palmitoylation of protein cysteines, catalysed by a family of integral membrane zDHHC-motif containing palmitoyl acyl transferases (zDHHC-PATs), controls the localisation, activity, and interactions of numerous integral and peripheral membrane proteins. There are compelling reasons to want to inhibit the activity of individual zDHHC-PATs in both the laboratory and the clinic, but the specificity of existing tools is poor. Given the extensive conservation of the zDHHC-PAT active site, development of isoform-specific competitive inhibitors is highly challenging. We therefore hypothesised that proteolysis-targeting chimaeras (PROTACs) may offer greater specificity to target this class of enzymes. In proof-of-principle experiments we engineered cell lines expressing tetracycline-inducible Halo-tagged zDHHC5 or zDHHC20, and evaluated the impact of Halo-PROTACs on zDHHC-PAT expression and substrate palmitoylation. In HEK-derived FT-293 cells, Halo-zDHHC5 degradation significantly decreased palmitoylation of its substrate phospholemman, and Halo-zDHHC20 degradation significantly diminished palmitoylation of its substrate IFITM3, but not of the SARS-CoV-2 spike protein. In contrast, in a second kidney derived cell line, Vero E6, Halo-zDHHC20 degradation did not alter palmitoylation of either IFITM3 or SARS-CoV-2 spike. We conclude from these experiments that PROTAC-mediated targeting of zDHHC-PATs to decrease substrate palmitoylation is feasible. However, given the well-established degeneracy in the zDHHC-PAT family, in some settings the activity of non-targeted zDHHC-PATs may substitute and preserve substrate palmitoylation.
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Affiliation(s)
- Mingjie Bai
- School of Cardiovascular & Metabolic Health, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Emily Gallen
- School of Cardiovascular & Metabolic Health, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Sarah Memarzadeh
- School of Chemistry, University of Glasgow, Glasgow, United Kingdom
| | - Jacqueline Howie
- School of Cardiovascular & Metabolic Health, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Xing Gao
- School of Cardiovascular & Metabolic Health, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Chien-Wen S. Kuo
- School of Cardiovascular & Metabolic Health, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Elaine Brown
- School of Cardiovascular & Metabolic Health, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Simon Swingler
- Medical Research Council–University of Glasgow Centre for Virus Research, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Sam J. Wilson
- Medical Research Council–University of Glasgow Centre for Virus Research, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Michael J. Shattock
- School of Cardiovascular and Metabolic Medicine & Sciences, King’s College London, London, United Kingdom
| | - David J. France
- School of Chemistry, University of Glasgow, Glasgow, United Kingdom
| | - William Fuller
- School of Cardiovascular & Metabolic Health, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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4
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Barlow IL, Mackay E, Wheater E, Goel A, Lim S, Zimmerman S, Woods I, Prober DA, Rihel J. The zebrafish mutant dreammist implicates sodium homeostasis in sleep regulation. eLife 2023; 12:RP87521. [PMID: 37548652 PMCID: PMC10406431 DOI: 10.7554/elife.87521] [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] [Indexed: 08/08/2023] Open
Abstract
Sleep is a nearly universal feature of animal behaviour, yet many of the molecular, genetic, and neuronal substrates that orchestrate sleep/wake transitions lie undiscovered. Employing a viral insertion sleep screen in larval zebrafish, we identified a novel gene, dreammist (dmist), whose loss results in behavioural hyperactivity and reduced sleep at night. The neuronally expressed dmist gene is conserved across vertebrates and encodes a small single-pass transmembrane protein that is structurally similar to the Na+,K+-ATPase regulator, FXYD1/Phospholemman. Disruption of either fxyd1 or atp1a3a, a Na+,K+-ATPase alpha-3 subunit associated with several heritable movement disorders in humans, led to decreased night-time sleep. Since atpa1a3a and dmist mutants have elevated intracellular Na+ levels and non-additive effects on sleep amount at night, we propose that Dmist-dependent enhancement of Na+ pump function modulates neuronal excitability to maintain normal sleep behaviour.
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Affiliation(s)
- Ida L Barlow
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Eirinn Mackay
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Emily Wheater
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Aimee Goel
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Sumi Lim
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Steve Zimmerman
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | | | - David A Prober
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
| | - Jason Rihel
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
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5
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Peluffo RD, Hernández JA. The Na +,K +-ATPase and its stoichiometric ratio: some thermodynamic speculations. Biophys Rev 2023; 15:539-552. [PMID: 37681108 PMCID: PMC10480117 DOI: 10.1007/s12551-023-01082-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 06/18/2023] [Indexed: 09/09/2023] Open
Abstract
Almost seventy years after its discovery, the sodium-potassium adenosine triphosphatase (the sodium pump) located in the cell plasma membrane remains a source of novel mechanistic and physiologic findings. A noteworthy feature of this enzyme/transporter is its robust stoichiometric ratio under physiological conditions: it sequentially counter-transports three sodium ions and two potassium ions against their electrochemical potential gradients per each hydrolyzed ATP molecule. Here we summarize some present knowledge about the sodium pump and its physiological roles, and speculate whether energetic constraints may have played a role in the evolutionary selection of its characteristic stoichiometric ratio.
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Affiliation(s)
- R. Daniel Peluffo
- Group of Biophysical Chemistry, Department of Biological Sciences, CENUR Litoral Norte, Universidad de La República, Rivera 1350, CP: 50000 Salto, Uruguay
| | - Julio A. Hernández
- Biophysics and Systems Biology Section, Department of Cell and Molecular Biology, Facultad de Ciencias, Universidad de La República, Iguá 4225, CP: 11400 Montevideo, Uruguay
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6
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Obradovic M, Sudar-Milovanovic E, Gluvic Z, Banjac K, Rizzo M, Isenovic ER. The Na +/K +-ATPase: A potential therapeutic target in cardiometabolic diseases. Front Endocrinol (Lausanne) 2023; 14:1150171. [PMID: 36926029 PMCID: PMC10011626 DOI: 10.3389/fendo.2023.1150171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/14/2023] [Indexed: 03/08/2023] Open
Abstract
Cardiometabolic diseases (CMD) are a direct consequence of modern living and contribute to the development of multisystem diseases such as cardiovascular diseases and diabetes mellitus (DM). CMD has reached epidemic proportions worldwide. A sodium pump (Na+/K+-ATPase) is found in most eukaryotic cells' membrane and controls many essential cellular functions directly or indirectly. This ion transporter and its isoforms are important in the pathogenesis of some pathological processes, including CMD. The structure and function of Na+/K+-ATPase, its expression and distribution in tissues, and its interactions with known ligands such as cardiotonic steroids and other suspected endogenous regulators are discussed in this review. In addition, we reviewed recent literature data related to the involvement of Na+/K+-ATPase activity dysfunction in CMD, focusing on the Na+/K+-ATPase as a potential therapeutic target in CMD.
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Affiliation(s)
- Milan Obradovic
- Department of Radiobiology and Molecular Genetics, “VINČA“ Institute of Nuclear Sciences - National Institute of thе Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Emina Sudar-Milovanovic
- Department of Radiobiology and Molecular Genetics, “VINČA“ Institute of Nuclear Sciences - National Institute of thе Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Zoran Gluvic
- University Clinical-Hospital Centre Zemun-Belgrade, Clinic of Internal medicine, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - Katarina Banjac
- Department of Radiobiology and Molecular Genetics, “VINČA“ Institute of Nuclear Sciences - National Institute of thе Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Manfredi Rizzo
- School of Medicine, Promise Department, University of Palermo, Palermo, Italy
- *Correspondence: Manfredi Rizzo,
| | - Esma R. Isenovic
- Department of Radiobiology and Molecular Genetics, “VINČA“ Institute of Nuclear Sciences - National Institute of thе Republic of Serbia, University of Belgrade, Belgrade, Serbia
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7
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Blaustein MP, Gottlieb SS, Hamlyn JM, Leenen FHH. Whither digitalis? What we can still learn from cardiotonic steroids about heart failure and hypertension. Am J Physiol Heart Circ Physiol 2022; 323:H1281-H1295. [PMID: 36367691 DOI: 10.1152/ajpheart.00362.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Cloning of the "Na+ pump" (Na+,K+-ATPase or NKA) and identification of a circulating ligand, endogenous ouabain (EO), a cardiotonic steroid (CTS), triggered seminal discoveries regarding EO and its NKA receptor in cardiovascular function and the pathophysiology of heart failure (HF) and hypertension. Cardiotonic digitalis preparations were a preferred treatment for HF for two centuries, but digoxin was only marginally effective in a large clinical trial (1997). This led to diminished digoxin use. Missing from the trial, however, was any consideration that endogenous CTS might influence digitalis' efficacy. Digoxin, at therapeutic concentrations, acutely inhibits NKA but, remarkably, antagonizes ouabain's action. Prolonged treatment with ouabain, but not digoxin, causes hypertension in rodents; in this model, digoxin lowers blood pressure (BP). Furthermore, NKA-bound ouabain and digoxin modulate different protein kinase signaling pathways and have disparate long-term cardiovascular effects. Reports of "brain ouabain" led to the elucidation of a new, slow neuromodulatory pathway in the brain; locally generated EO and the α2 NKA isoform help regulate sympathetic drive to the heart and vasculature. The roles of EO and α2 NKA have been studied by EO assay, ouabain-resistant mutation of α2 NKA, and immunoneutralization of EO with ouabain-binding Fab fragments. The NKA α2 CTS binding site and its endogenous ligand are required for BP elevation in many common hypertension models and full expression of cardiac remodeling and dysfunction following pressure overload or myocardial infarction. Understanding how endogenous CTS impact hypertension and HF pathophysiology and therapy should foster reconsideration of digoxin's therapeutic utility.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland.,Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Stephen S Gottlieb
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Frans H H Leenen
- Brain and Heart Research Group, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
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8
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Non-Selective PDE4 Inhibition Induces a Rapid and Transient Decrease of Serum Potassium in Mice. BIOLOGY 2022; 11:biology11111582. [PMID: 36358283 PMCID: PMC9687940 DOI: 10.3390/biology11111582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/24/2022] [Accepted: 10/25/2022] [Indexed: 11/06/2022]
Abstract
Simple Summary Inhibitors of phosphodiesterase 4 (PDE4), a group of isoenzymes that hydrolyze and inactivate the second messenger cAMP, produce promising therapeutic benefits, including anti-inflammatory and memory-enhancing effects. Here, we report that, unexpectedly, PDE4 inhibitors also reduce serum potassium levels in mice. As both the total potassium content of the body, as well as the distribution of potassium between intra- and extracellular compartments, are critical for normal cellular functions, we further explored this observation. Several structurally distinct PDE4 inhibitors reduce serum potassium levels in mice, suggesting it is a class effect of these drugs. Serum potassium levels decrease within 15 min of drug injection, suggesting that PDE4 inhibition lowers serum potassium levels by promoting a transcellular shift of potassium from the blood into cells. This shift is a characteristically fast process, compared to a loss of total-body potassium via the kidneys or digestive tract (e.g., diarrhea). Indeed, stimulating cAMP synthesis with β-adrenoceptor agonists is known to rapidly shift potassium into cells, and PDE4 inhibitors appear to mimic this process by preventing PDE4-mediated cAMP degradation. Our findings reveal that the various acute physiologic effects of PDE4 inhibitors are paralleled and/or may be affected by reduced serum potassium levels. Abstract The analysis of blood samples from mice treated with the PDE4 inhibitor Roflumilast revealed an unexpected reduction in serum potassium levels, while sodium and chloride levels were unaffected. Treatment with several structurally distinct PAN-PDE4 inhibitors, including Roflumilast, Rolipram, RS25344, and YM976 dose-dependently reduced serum potassium levels, indicating the effect is a class-characteristic property. PDE4 inhibition also induces hypothermia and hypokinesia in mice. However, while general anesthesia abrogates these effects of PDE4 inhibitors, potassium levels decrease to similar extents in both awake as well as in fully anesthetized mice. This suggests that the hypokalemic effects of PDE4 inhibitors occur independently of hypothermia and hypokinesia. PDE4 inhibition reduces serum potassium within 15 min of treatment, consistent with a rapid transcellular shift of potassium. Catecholamines promote the uptake of potassium into the cell via increased cAMP signaling. PDE4 appears to modulate these adrenoceptor-mediated effects, as PDE4 inhibition has no additional effects on serum potassium in the presence of saturating doses of the β-adrenoceptor agonist Isoprenaline or the α2-blocker Yohimbine, and is partially blocked by pre-treatment with the β-blocker Propranolol. Together, these data suggest that PDE4 inhibitors reduce serum potassium levels by modulating the adrenergic regulation of cellular potassium uptake.
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9
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Tsumoto K, Kurata Y. Bifurcations and Proarrhythmic Behaviors in Cardiac Electrical Excitations. Biomolecules 2022; 12:biom12030459. [PMID: 35327651 PMCID: PMC8946197 DOI: 10.3390/biom12030459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 03/09/2022] [Accepted: 03/14/2022] [Indexed: 12/23/2022] Open
Abstract
The heart is a hierarchical dynamic system consisting of molecules, cells, and tissues, and acts as a pump for blood circulation. The pumping function depends critically on the preceding electrical activity, and disturbances in the pattern of excitation propagation lead to cardiac arrhythmia and pump failure. Excitation phenomena in cardiomyocytes have been modeled as a nonlinear dynamical system. Because of the nonlinearity of excitation phenomena, the system dynamics could be complex, and various analyses have been performed to understand the complex dynamics. Understanding the mechanisms underlying proarrhythmic responses in the heart is crucial for developing new ways to prevent and control cardiac arrhythmias and resulting contractile dysfunction. When the heart changes to a pathological state over time, the action potential (AP) in cardiomyocytes may also change to a different state in shape and duration, often undergoing a qualitative change in behavior. Such a dynamic change is called bifurcation. In this review, we first summarize the contribution of ion channels and transporters to AP formation and our knowledge of ion-transport molecules, then briefly describe bifurcation theory for nonlinear dynamical systems, and finally detail its recent progress, focusing on the research that attempts to understand the developing mechanisms of abnormal excitations in cardiomyocytes from the perspective of bifurcation phenomena.
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10
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Sirenko ST, Zahanich I, Li Y, Lukyanenko YO, Lyashkov AE, Ziman BD, Tarasov KV, Younes A, Riordon DR, Tarasova YS, Yang D, Vinogradova TM, Maltsev VA, Lakatta EG. Phosphoprotein Phosphatase 1 but Not 2A Activity Modulates Coupled-Clock Mechanisms to Impact on Intrinsic Automaticity of Sinoatrial Nodal Pacemaker Cells. Cells 2021; 10:cells10113106. [PMID: 34831329 PMCID: PMC8623309 DOI: 10.3390/cells10113106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/02/2021] [Accepted: 11/05/2021] [Indexed: 12/02/2022] Open
Abstract
Spontaneous AP (action potential) firing of sinoatrial nodal cells (SANC) is critically dependent on protein kinase A (PKA) and Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent protein phosphorylation, which are required for the generation of spontaneous, diastolic local Ca2+ releases (LCRs). Although phosphoprotein phosphatases (PP) regulate protein phosphorylation, the expression level of PPs and phosphatase inhibitors in SANC and the impact of phosphatase inhibition on the spontaneous LCRs and other players of the oscillatory coupled-clock system is unknown. Here, we show that rabbit SANC express both PP1, PP2A, and endogenous PP inhibitors I-1 (PPI-1), dopamine and cyclic adenosine 3′,5′-monophosphate (cAMP)-regulated phosphoprotein (DARPP-32), kinase C-enhanced PP1 inhibitor (KEPI). Application of Calyculin A, (CyA), a PPs inhibitor, to intact, freshly isolated single SANC: (1) significantly increased phospholamban (PLB) phosphorylation (by 2–3-fold) at both CaMKII-dependent Thr17 and PKA-dependent Ser16 sites, in a time and concentration dependent manner; (2) increased ryanodine receptor (RyR) phosphorylation at the Ser2809 site; (3) substantially increased sarcoplasmic reticulum (SR) Ca2+ load; (4) augmented L-type Ca2+ current amplitude; (5) augmented LCR’s characteristics and decreased LCR period in intact and permeabilized SANC, and (6) increased the spontaneous basal AP firing rate. In contrast, the selective PP2A inhibitor okadaic acid (100 nmol/L) had no significant effect on spontaneous AP firing, LCR parameters, or PLB phosphorylation. Application of purified PP1 to permeabilized SANC suppressed LCR, whereas purified PP2A had no effect on LCR characteristics. Our numerical model simulations demonstrated that PP inhibition increases AP firing rate via a coupled-clock mechanism, including respective increases in the SR Ca2+ pumping rate, L-type Ca2+ current, and Na+/Ca2+-exchanger current. Thus, PP1 and its endogenous inhibitors modulate the basal spontaneous firing rate of cardiac pacemaker cells by suppressing SR Ca2+ cycling protein phosphorylation, the SR Ca2+ load and LCRs, and L-type Ca2+ current.
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11
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Cellini A, Höfler D, Arias-Loza PA, Bandleon S, Langsenlehner T, Kohlhaas M, Maack C, Bauer WR, Eder-Negrin P. The α2-isoform of the Na +/K +-ATPase protects against pathological remodeling and β-adrenergic desensitization after myocardial infarction. Am J Physiol Heart Circ Physiol 2021; 321:H650-H662. [PMID: 34448639 DOI: 10.1152/ajpheart.00808.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The role of the Na+/K+-ATPase (NKA) in heart failure associated with myocardial infarction (MI) is poorly understood. The elucidation of its precise function is hampered by the existence of two catalytic NKA isoforms (NKA-α1 and NKA-α2). Our aim was to analyze the effects of an increased NKA-α2 expression on functional deterioration and remodeling during long-term MI treatment in mice and its impact on Ca2+ handling and inotropy of the failing heart. Wild-type (WT) and NKA-α2 transgenic (TG) mice (TG-α2) with a cardiac-specific overexpression of NKA-α2 were subjected to MI injury for 8 wk. As examined by echocardiography, gravimetry, and histology, TG-α2 mice were protected from functional deterioration and adverse cardiac remodeling. Contractility and Ca2+ transients (Fura 2-AM) in cardiomyocytes from MI-treated TG-α2 animals showed reduced Ca2+ amplitudes during pacing or after caffeine application. Ca2+ efflux in cardiomyocytes from TG-α2 mice was accelerated and diastolic Ca2+ levels were decreased. Based on these alterations, sarcomeres exhibited an enhanced sensitization and thus increased contractility. After the acute stimulation with the β-adrenergic agonist isoproterenol (ISO), cardiomyocytes from MI-treated TG-α2 mice responded with increased sarcomere shortenings and Ca2+ peak amplitudes. This positive inotropic response was absent in cardiomyocytes from WT-MI animals. Cardiomyocytes with NKA-α2 as predominant isoform minimize Ca2+ cycling but respond to β-adrenergic stimulation more efficiently during chronic cardiac stress. These mechanisms might improve the β-adrenergic reserve and contribute to functional preservation in heart failure.NEW & NOTEWORTHY Reduced systolic and diastolic calcium levels in cardiomyocytes from NKA-α2 transgenic mice minimize the desensitization of the β-adrenergic signaling system. These effects result in an improved β-adrenergic reserve and prevent functional deterioration and cardiac remodeling.
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Affiliation(s)
- Antonella Cellini
- Comprehensive Heart Failure Center, Würzburg, Germany.,Department of Internal Medicine I, University Hospital, Würzburg, Germany
| | - Dorina Höfler
- Comprehensive Heart Failure Center, Würzburg, Germany.,Department of Internal Medicine I, University Hospital, Würzburg, Germany
| | - Paula A Arias-Loza
- Comprehensive Heart Failure Center, Würzburg, Germany.,Department of Nuclear Medicine I, University Hospital, Würzburg, Germany
| | - Sandra Bandleon
- Comprehensive Heart Failure Center, Würzburg, Germany.,Department of Internal Medicine I, University Hospital, Würzburg, Germany
| | - Tanja Langsenlehner
- Department of Therapeutic Radiology and Oncology, Medical University of Graz, Graz, Austria
| | | | | | - Wolfgang R Bauer
- Department of Internal Medicine I, University Hospital, Würzburg, Germany
| | - Petra Eder-Negrin
- Comprehensive Heart Failure Center, Würzburg, Germany.,Department of Internal Medicine I, University Hospital, Würzburg, Germany
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12
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With a grain of salt: Sodium elevation and metabolic remodelling in heart failure. J Mol Cell Cardiol 2021; 161:106-115. [PMID: 34371034 PMCID: PMC7611640 DOI: 10.1016/j.yjmcc.2021.08.003] [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] [Received: 02/05/2021] [Revised: 07/09/2021] [Accepted: 08/03/2021] [Indexed: 12/14/2022]
Abstract
Elevated intracellular Na (Nai) and metabolic impairment are interrelated pathophysiological features of the failing heart (HF). There have been a number of studies showing that myocardial sodium elevation subtly affects mitochondrial function. During contraction, mitochondrial calcium (Camito) stimulates a variety of TCA cycle enzymes, thereby providing reducing equivalents to maintain ATP supply. Nai elevation has been shown to impact Camito; however, whether metabolic remodelling in HF is caused by increased Nai has only been recently demonstrated. This novel insight may help to elucidate the contribution of metabolic remodelling in the pathophysiology of HF, the lack of efficacy of current HF therapies and a rationale for the development of future metabolism-targeting treatments. Here we review the relationship between Na pump inhibition, elevated Nai, and altered metabolic profile in the context of HF and their link to metabolic (in)flexibility and mitochondrial reprogramming.
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13
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Yap JQ, Seflova J, Sweazey R, Artigas P, Robia SL. FXYD proteins and sodium pump regulatory mechanisms. J Gen Physiol 2021; 153:211866. [PMID: 33688925 PMCID: PMC7953255 DOI: 10.1085/jgp.202012633] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 02/03/2021] [Indexed: 12/12/2022] Open
Abstract
The sodium/potassium-ATPase (NKA) is the enzyme that establishes gradients of sodium and potassium across the plasma membrane. NKA activity is tightly regulated for different physiological contexts through interactions with single-span transmembrane peptides, the FXYD proteins. This diverse family of regulators has in common a domain containing a Phe-X-Tyr-Asp (FXYD) motif, two conserved glycines, and one serine residue. In humans, there are seven tissue-specific FXYD proteins that differentially modulate NKA kinetics as appropriate for each system, providing dynamic responsiveness to changing physiological conditions. Our understanding of how FXYD proteins contribute to homeostasis has benefitted from recent advances described in this review: biochemical and biophysical studies have provided insight into regulatory mechanisms, genetic models have uncovered remarkable complexity of FXYD function in integrated physiological systems, new posttranslational modifications have been identified, high-resolution structural studies have revealed new details of the regulatory interaction with NKA, and new clinical correlations have been uncovered. In this review, we address the structural determinants of diverse FXYD functions and the special roles of FXYDs in various physiological systems. We also discuss the possible roles of FXYDs in protein trafficking and regulation of non-NKA targets.
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Affiliation(s)
- John Q Yap
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Jaroslava Seflova
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Ryan Sweazey
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Seth L Robia
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
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14
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RNAseq shows an all-pervasive day-night rhythm in the transcriptome of the pacemaker of the heart. Sci Rep 2021; 11:3565. [PMID: 33574422 PMCID: PMC7878777 DOI: 10.1038/s41598-021-82202-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 01/01/2021] [Indexed: 12/12/2022] Open
Abstract
Physiological systems vary in a day-night manner anticipating increased demand at a particular time. Heart is no exception. Cardiac output is primarily determined by heart rate and unsurprisingly this varies in a day-night manner and is higher during the day in the human (anticipating increased day-time demand). Although this is attributed to a day-night rhythm in post-translational ion channel regulation in the heart's pacemaker, the sinus node, by the autonomic nervous system, we investigated whether there is a day-night rhythm in transcription. RNAseq revealed that ~ 44% of the sinus node transcriptome (7134 of 16,387 transcripts) has a significant day-night rhythm. The data revealed the oscillating components of an intrinsic circadian clock. Presumably this clock (or perhaps the master circadian clock in the suprachiasmatic nucleus) is responsible for the rhythm observed in the transcriptional machinery, which in turn is responsible for the rhythm observed in the transcriptome. For example, there is a rhythm in transcripts responsible for the two principal pacemaker mechanisms (membrane and Ca2+ clocks), transcripts responsible for receptors and signalling pathways known to control pacemaking, transcripts from genes identified by GWAS as determinants of resting heart rate, and transcripts from genes responsible for familial and acquired sick sinus syndrome.
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15
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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16
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Petrushanko IY, Mitkevich VA, Makarov AA. Molecular Mechanisms of the Redox Regulation of the Na,K-ATPase. Biophysics (Nagoya-shi) 2020. [DOI: 10.1134/s0006350920050139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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17
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Intracellular sodium elevation reprograms cardiac metabolism. Nat Commun 2020; 11:4337. [PMID: 32859897 PMCID: PMC7455741 DOI: 10.1038/s41467-020-18160-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 07/10/2020] [Indexed: 12/12/2022] Open
Abstract
Intracellular Na elevation in the heart is a hallmark of pathologies where both acute and chronic metabolic remodelling occurs. Here, we assess whether acute (75 μM ouabain 100 nM blebbistatin) or chronic myocardial Nai load (PLM3SA mouse) are causally linked to metabolic remodelling and whether the failing heart shares a common Na-mediated metabolic ‘fingerprint’. Control (PLMWT), transgenic (PLM3SA), ouabain-treated and hypertrophied Langendorff-perfused mouse hearts are studied by 23Na, 31P, 13C NMR followed by 1H-NMR metabolomic profiling. Elevated Nai leads to common adaptive metabolic alterations preceding energetic impairment: a switch from fatty acid to carbohydrate metabolism and changes in steady-state metabolite concentrations (glycolytic, anaplerotic, Krebs cycle intermediates). Inhibition of mitochondrial Na/Ca exchanger by CGP37157 ameliorates the metabolic changes. In silico modelling indicates altered metabolic fluxes (Krebs cycle, fatty acid, carbohydrate, amino acid metabolism). Prevention of Nai overload or inhibition of Na/Camito may be a new approach to ameliorate metabolic dysregulation in heart failure. The failing heart is characterised by both alterations in mitochondrial metabolism and an elevation of cytosolic sodium. Here, the authors use 23Na NMR and metabolic profiling to show these are related, and that elevation in intracellular Na reprograms cardiac substrate utilisation via effects on mitochondrial Na/Ca exchange.
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18
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Cardiomyocyte calcium handling in health and disease: Insights from in vitro and in silico studies. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 157:54-75. [PMID: 32188566 DOI: 10.1016/j.pbiomolbio.2020.02.008] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/31/2019] [Accepted: 02/29/2020] [Indexed: 02/07/2023]
Abstract
Calcium (Ca2+) plays a central role in cardiomyocyte excitation-contraction coupling. To ensure an optimal electrical impulse propagation and cardiac contraction, Ca2+ levels are regulated by a variety of Ca2+-handling proteins. In turn, Ca2+ modulates numerous electrophysiological processes. Accordingly, Ca2+-handling abnormalities can promote cardiac arrhythmias via various mechanisms, including the promotion of afterdepolarizations, ion-channel modulation and structural remodeling. In the last 30 years, significant improvements have been made in the computational modeling of cardiomyocyte Ca2+ handling under physiological and pathological conditions. However, numerous questions involving the Ca2+-dependent regulation of different macromolecular complexes, cross-talk between Ca2+-dependent regulatory pathways operating over a wide range of time scales, and bidirectional interactions between electrophysiology and mechanics remain to be addressed by in vitro and in silico studies. A better understanding of disease-specific Ca2+-dependent proarrhythmic mechanisms may facilitate the development of improved therapeutic strategies. In this review, we describe the fundamental mechanisms of cardiomyocyte Ca2+ handling in health and disease, and provide an overview of currently available computational models for cardiomyocyte Ca2+ handling. Finally, we discuss important uncertainties and open questions about cardiomyocyte Ca2+ handling and highlight how synergy between in vitro and in silico studies may help to answer several of these issues.
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19
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Essandoh K, Philippe JM, Jenkins PM, Brody MJ. Palmitoylation: A Fatty Regulator of Myocardial Electrophysiology. Front Physiol 2020; 11:108. [PMID: 32140110 PMCID: PMC7042378 DOI: 10.3389/fphys.2020.00108] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 01/30/2020] [Indexed: 01/02/2023] Open
Abstract
Regulation of cardiac physiology is well known to occur through the action of kinases that reversibly phosphorylate ion channels, calcium handling machinery, and signaling effectors. However, it is becoming increasingly apparent that palmitoylation or S-acylation, the post-translational modification of cysteines with saturated fatty acids, plays instrumental roles in regulating the localization, activity, stability, sorting, and function of numerous proteins, including proteins known to have essential functions in cardiomyocytes. However, the impact of this modification on cardiac physiology requires further investigation. S-acylation is catalyzed by the zDHHC family of S-acyl transferases that localize to intracellular organelle membranes or the sarcolemma. Recent work has begun to uncover functions of S-acylation in the heart, particularly in the regulation of cardiac electrophysiology, including modification of the sodium-calcium exchanger, phospholemman and the cardiac sodium pump, as well as the voltage-gated sodium channel. Elucidating the regulatory functions of zDHHC enzymes in cardiomyocytes and determination of how S-acylation is altered in the diseased heart will shed light on how these modifications participate in cardiac pathogenesis and potentially identify novel targets for the treatment of cardiovascular disease. Indeed, proteins with critical signaling roles in the heart are also S-acylated, including receptors and G-proteins, yet the dynamics and functions of these modifications in myocardial physiology have not been interrogated. Here, we will review what is known about zDHHC enzymes and substrate S-acylation in myocardial physiology and highlight future areas of investigation that will uncover novel functions of S-acylation in cardiac homeostasis and pathophysiology.
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Affiliation(s)
- Kobina Essandoh
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, United States
| | - Julie M Philippe
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, United States
| | - Paul M Jenkins
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, United States.,Department of Psychiatry, University of Michigan, Ann Arbor, MI, United States
| | - Matthew J Brody
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, United States.,Department of Internal Medicine, University of Michigan, Ann Arbor, MI, United States
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20
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Pavlovic D. Endogenous cardiotonic steroids and cardiovascular disease, where to next? Cell Calcium 2019; 86:102156. [PMID: 31896530 PMCID: PMC7031694 DOI: 10.1016/j.ceca.2019.102156] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/24/2019] [Accepted: 12/24/2019] [Indexed: 11/18/2022]
Abstract
Ever since British Physician William Withering first described the use of foxglove extract for treatment of patients with congestive heart failure in 1785, cardiotonic steroids have been used clinically to treat heart failure and more recently atrial fibrillation. Due to their ability to bind and inhibit the ubiquitous transport enzyme sodium potassium pump, thus regulating intracellular Na+ concentration in every living cell, they are also an essential tool for research into the sodium potassium pump structure and function. Exogenous CTS have been clearly demonstrated to affect cardiovascular system through modulation of vagal tone, cardiac contraction (via ionic changes) and altered natriuresis. Reports of a number of endogenous CTS, since the 1980s, have intensified research into their physiologic and pathophysiologic roles and opened up novel therapeutic targets. Substantive evidence pointing to the role of endogenous ouabain and marinobufagenin, the two most prominent CTS, in development of cardiovascular disease has accumulated. Nevertheless, their presence, structure, biosynthesis pathways and even mechanism of action remain unclear or controversial. In this review the current state-of-the-art, the controversies and the remaining questions surrounding the role of endogenous cardiotonic steroids in health and disease are discussed.
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Affiliation(s)
- Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
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21
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Ke HY, Yang HY, Francis AJ, Collins TP, Surendran H, Alvarez-Laviada A, Firth JM, MacLeod KT. Changes in cellular Ca 2+ and Na + regulation during the progression towards heart failure in the guinea pig. J Physiol 2019; 598:1339-1359. [PMID: 30811606 PMCID: PMC7187457 DOI: 10.1113/jp277038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 02/26/2019] [Indexed: 12/19/2022] Open
Abstract
Key points During compensated hypertrophy in vivo fractional shortening (FS) remains constant until heart failure (HF) develops, when FS decreases from 70% to 39%. Compensated hypertrophy is accompanied by an increase in INa,late and a decrease in Na+,K+‐ATPase current. These changes persist as HF develops. SR Ca2+ content increases during compensated hypertrophy then decreases in HF. In healthy cells, increases in SR Ca2+ content and Ca2+ transients can be achieved by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant during compensated hypertrophy then decreases in HF, when there is also an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment.
Abstract We followed changes in cardiac myocyte Ca2+ and Na+ regulation from the formation of compensated hypertrophy (CH) until signs of heart failure (HF) are apparent using a trans‐aortic pressure overload (TAC) model. In this model, in vivo fractional shortening (FS) remained constant despite HW:BW ratio increasing by 39% (CH) until HF developed 150 days post‐TAC when FS decreased from 70% to 39%. Using live and fixed fluorescence imaging and electrophysiological techniques, we found an increase in INa,late from –0.34 to –0.59 A F−1 and a decrease in Na+,K+‐ATPase current from 1.09 A F−1 to 0.54 A F−1 during CH. These changes persisted as HF developed (INa,late increased to –0.82 A F−1 and Na+,K+‐ATPase current decreased to 0.51 A F−1). Sarcoplasmic reticulum (SR) Ca2+ content increased during CH then decreased in HF (from 32 to 15 μm l−1) potentially supporting the maintenance of FS in the whole heart and Ca2+ transients in single myocytes during the former stage. We showed using glycoside blockade in healthy myocytes that increases in SR Ca2+ content and Ca2+ transients can be driven by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant in CH but decreases (τ for SERCA‐mediated Ca2+ removal changed from 6.3 to 3.0 s−1) in HF. In HF there was an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment. During compensated hypertrophy in vivo fractional shortening (FS) remains constant until heart failure (HF) develops, when FS decreases from 70% to 39%. Compensated hypertrophy is accompanied by an increase in INa,late and a decrease in Na+,K+‐ATPase current. These changes persist as HF develops. SR Ca2+ content increases during compensated hypertrophy then decreases in HF. In healthy cells, increases in SR Ca2+ content and Ca2+ transients can be achieved by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant during compensated hypertrophy then decreases in HF, when there is also an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment.
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Affiliation(s)
- H-Y Ke
- Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (ROC)
| | - H-Y Yang
- Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (ROC)
| | - A J Francis
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - T P Collins
- The Wellcome Trust, Gibbs Building, 215 Euston Road, London, NW1 2BE, UK
| | - H Surendran
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - A Alvarez-Laviada
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - J M Firth
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - K T MacLeod
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
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22
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Hormonal regulation of Na +-K +-ATPase from the evolutionary perspective. CURRENT TOPICS IN MEMBRANES 2019; 83:315-351. [PMID: 31196608 DOI: 10.1016/bs.ctm.2019.01.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Na+-K+-ATPase, an α/β heterodimer, is an ancient enzyme that maintains Na+ and K+ gradients, thus preserving cellular ion homeostasis. In multicellular organisms, this basic housekeeping function is integrated to fulfill the needs of specialized organs and preserve whole-body homeostasis. In vertebrates, Na+-K+-ATPase is essential for many fundamental physiological processes, such as nerve conduction, muscle contraction, nutrient absorption, and urine excretion. During vertebrate evolution, three key developments contributed to diversification and integration of Na+-K+-ATPase functions. Generation of novel α- and β-subunits led to formation of multiple Na+-K+-ATPase isoenyzmes with distinct functional characteristics. Development of a complex endocrine system enabled efficient coordination of diverse Na+-K+-ATPase functions. Emergence of FXYDs, small transmembrane proteins that regulate Na+-K+-ATPase, opened new ways to modulate its function. FXYDs are a vertebrate innovation and an important site of hormonal action, suggesting they played an especially prominent role in evolving interaction between Na+-K+-ATPase and the endocrine system in vertebrates.
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23
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Skogestad J, Aronsen JM. Hypokalemia-Induced Arrhythmias and Heart Failure: New Insights and Implications for Therapy. Front Physiol 2018; 9:1500. [PMID: 30464746 PMCID: PMC6234658 DOI: 10.3389/fphys.2018.01500] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 10/05/2018] [Indexed: 12/18/2022] Open
Abstract
Routine use of diuretics and neurohumoral activation make hypokalemia (serum K+ < 3. 5 mM) a prevalent electrolyte disorder among heart failure patients, contributing to the increased risk of ventricular arrhythmias and sudden cardiac death in heart failure. Recent experimental studies have suggested that hypokalemia-induced arrhythmias are initiated by the reduced activity of the Na+/K+-ATPase (NKA), subsequently leading to Ca2+ overload, Ca2+/Calmodulin-dependent kinase II (CaMKII) activation, and development of afterdepolarizations. In this article, we review the current mechanistic evidence of hypokalemia-induced triggered arrhythmias and discuss how molecular changes in heart failure might lower the threshold for these arrhythmias. Finally, we discuss how recent insights into hypokalemia-induced arrhythmias could have potential implications for future antiarrhythmic treatment strategies.
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Affiliation(s)
- Jonas Skogestad
- Division of Cardiovascular and Pulmonary Diseases, Institute of Experimental Medical Research, University of Oslo and Oslo University Hospital, Oslo, Norway
| | - Jan Magnus Aronsen
- Department of Pharmacology, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway.,Bjørknes College, Oslo, Norway
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24
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Câmara DR, Kastelic JP, Thundathil JC. Role of the Na +/K +-ATPase ion pump in male reproduction and embryo development. Reprod Fertil Dev 2018; 29:1457-1467. [PMID: 27456939 DOI: 10.1071/rd16091] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 06/19/2016] [Indexed: 12/18/2022] Open
Abstract
Na+/K+-ATPase was one of the first ion pumps studied because of its importance in maintaining osmotic and ionic balances between intracellular and extracellular environments, through the exchange of three Na+ ions out and two K+ ions into a cell. This enzyme, which comprises two main subunits (α and β), with or without an auxiliary polypeptide (γ), can have specific biochemical properties depending on the expression of associated isoforms (α1β1 and/or α2β1) in the cell. In addition to the importance of Na+/K+-ATPase in ensuring the function of many tissues (e.g. brain, heart and kidney), in the reproductive tract this protein is essential for embryo development because of its roles in blastocoel formation and embryo hatching. In the context of male reproduction, the discovery of a very specific subunit (α4), apparently restricted to male germ cells, only expressed after puberty and able to influence sperm function (e.g. motility and capacitation), opened a remarkable field for further investigations regarding sperm biology. Therefore, the present review focuses on the importance of Na+/K+-ATPase on male reproduction and embryo development.
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Affiliation(s)
- D R Câmara
- Faculdade de Medicina Veterinária, Universidade Federal de Alagoas, Fazenda São Luiz, s/n, Zona Rural do Município de Viçosa, Viçosa-AL, CEP: 57700-000, Brazil
| | - J P Kastelic
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB T2N 4N1, Canada
| | - J C Thundathil
- Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB T2N 4N1, Canada
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25
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Hu G, Song Y, Ke S, Cao H, Zhang C, Deng G, Yang F, Zhou S, Liu P, Guo X, Liu P. Tanshinone IIA protects against pulmonary arterial hypertension in broilers. Poult Sci 2018; 96:1132-1138. [PMID: 27702914 DOI: 10.3382/ps/pew322] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 07/31/2016] [Indexed: 12/30/2022] Open
Abstract
This investigation was conducted to study the effects of tanshinone IIA (TIIA) on pulmonary arterial hypertension (PAH) in broilers. Two-hundred newly hatched Arbor Acre commercial broilers were randomly divided into 3 groups. All groups, with the exception of the control group (tap water), were given NaCl water (0.3%) starting on the d 15, and broilers in the protected group were fed a diet supplemented with TIIA (2.5 g/kg) starting on the d 15. On d 28, 35, 42, and 49, the ratio of the right ventricular weight to the total ventricular weight (RV: TV) and the values of other biochemical indicators for each group chickens were determined. The concentrations of interleukin-6 (IL-6), interleukin-1β (IL-1β), nuclear factor kappa (NF-κB), and P38 (a mitogen-activated protein kinase) were measured using enzyme-linked immune sorbent assays (ELISA). The results showed that the proportion of chickens in the diseased group with an RV:TV ratio in the range of 0.250 to 0.299 (10%) was significantly higher (25 to 30%) compared to that of the other groups (P < 0.05), and the proportion in all chickens was 28%. In addition, the IL-6, IL-1β, NF-κB, and P38 protein concentrations were higher in the diseased group, whereas there were no differences between the control group and the protected group. Moreover, the measurements of body weight, liver function, kidney function and electrolytes showed significant differences between the diseased group and the other groups. These findings suggest that tanshinone IIA may protect broilers from PAH, which is an important piece of information for the poultry industry.
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26
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Is there a causal link between intracellular Na elevation and metabolic remodelling in cardiac hypertrophy? Biochem Soc Trans 2018; 46:817-827. [PMID: 29970448 PMCID: PMC6103460 DOI: 10.1042/bst20170508] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/23/2018] [Accepted: 05/24/2018] [Indexed: 01/23/2023]
Abstract
Alterations in excitation–contraction coupling and elevated intracellular sodium (Nai) are hallmarks of pathological cardiac remodelling that underline contractile dysfunction. In addition, changes in cardiac metabolism are observed in cardiac hypertrophy and heart failure (HF) that lead to a mismatch in ATP supply and demand, contributing to poor prognosis. A link between Nai and altered metabolism has been proposed but is not well understood. Many mitochondrial enzymes are stimulated by mitochondrial calcium (Camito) during contraction, thereby sustaining production of reducing equivalents to maintain ATP supply. This stimulation is thought to be perturbed when cytosolic Nai is high due to increased Camito efflux, potentially compromising ATPmito production and leading to metabolic dysregulation. Increased Nai has been previously shown to affect Camito; however, whether Nai elevation plays a causative role in energetic mismatching in the hypertrophied and failing heart remains unknown. In this review, we discuss the relationship between elevated Nai, NaK ATPase dysregulation and the metabolic phenotype in the contexts of pathological hypertrophy and HF and their link to metabolic flexibility, capacity (reserve) and efficiency that are governed by intracellular ion homeostasis. The development of non-invasive analytical techniques using nuclear magnetic resonance able to probe metabolism in situ in the functioning heart will enable a better understanding of the underlying mechanisms of Nai overload in cardiac pathophysiology. They will lead to novel insights that help to explain the metabolic contribution towards these diseases, the incomplete rescue observed with current therapies and a rationale for future energy-targeted therapies.
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Howie J, Wypijewski KJ, Plain F, Tulloch LB, Fraser NJ, Fuller W. Greasing the wheels or a spanner in the works? Regulation of the cardiac sodium pump by palmitoylation. Crit Rev Biochem Mol Biol 2018; 53:175-191. [PMID: 29424237 DOI: 10.1080/10409238.2018.1432560] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The ubiquitous sodium/potassium ATPase (Na pump) is the most abundant primary active transporter at the cell surface of multiple cell types, including ventricular myocytes in the heart. The activity of the Na pump establishes transmembrane ion gradients that control numerous events at the cell surface, positioning it as a key regulator of the contractile and metabolic state of the myocardium. Defects in Na pump activity and regulation elevate intracellular Na in cardiac muscle, playing a causal role in the development of cardiac hypertrophy, diastolic dysfunction, arrhythmias and heart failure. Palmitoylation is the reversible conjugation of the fatty acid palmitate to specific protein cysteine residues; all subunits of the cardiac Na pump are palmitoylated. Palmitoylation of the pump's accessory subunit phospholemman (PLM) by the cell surface palmitoyl acyl transferase DHHC5 leads to pump inhibition, possibly by altering the relationship between the pump catalytic α subunit and specifically bound membrane lipids. In this review, we discuss the functional impact of PLM palmitoylation on the cardiac Na pump and the molecular basis of recognition of PLM by its palmitoylating enzyme DHHC5, as well as effects of palmitoylation on Na pump cell surface abundance in the cardiac muscle. We also highlight the numerous unanswered questions regarding the cellular control of this fundamentally important regulatory process.
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Affiliation(s)
- Jacqueline Howie
- a Institute of Cardiovascular and Medical Sciences , University of Glasgow , Glasgow , UK
| | | | - Fiona Plain
- b Molecular and Clinical Medicine , University of Dundee , Dundee , UK
| | - Lindsay B Tulloch
- b Molecular and Clinical Medicine , University of Dundee , Dundee , UK
| | - Niall J Fraser
- b Molecular and Clinical Medicine , University of Dundee , Dundee , UK
| | - William Fuller
- a Institute of Cardiovascular and Medical Sciences , University of Glasgow , Glasgow , UK
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Arystarkhova E, Bouley R, Liu YB, Sweadner KJ. Impaired AQP2 trafficking in Fxyd1 knockout mice: A role for FXYD1 in regulated vesicular transport. PLoS One 2017; 12:e0188006. [PMID: 29155857 PMCID: PMC5695786 DOI: 10.1371/journal.pone.0188006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 10/30/2017] [Indexed: 01/08/2023] Open
Abstract
The final adjustment of urine volume occurs in the inner medullary collecting duct (IMCD), chiefly mediated by the water channel aquaporin 2 (AQP2). With vasopressin stimulation, AQP2 accumulation in the apical plasma membrane of principal cells allows water reabsorption from the lumen. We report that FXYD1 (phospholemman), better known as a regulator of Na,K-ATPase, has a role in AQP2 trafficking. Daytime urine of Fxyd1 knockout mice was more dilute than WT despite similar serum vasopressin, but both genotypes could concentrate urine during water deprivation. FXYD1 was found in IMCD. In WT mice, phosphorylated FXYD1 was detected intracellularly, and vasopressin induced its dephosphorylation. We tested the hypothesis that the dilute urine in knockouts was caused by alteration of AQP2 trafficking. In WT mice at baseline, FXYD1 and AQP2 were not strongly co-localized, but elevation of vasopressin produced translocation of both FXYD1 and AQP2 to the apical plasma membrane. In kidney slices, baseline AQP2 distribution was more scattered in the Fxyd1 knockout than in WT. Apical recruitment of AQP2 occurred in vasopressin-treated Fxyd1 knockout slices, but upon vasopressin washout, there was more rapid reversal of apical AQP2 localization and more heterogeneous cytoplasmic distribution of AQP2. Notably, in sucrose gradients, AQP2 was present in a detergent-resistant membrane domain that had lower sedimentation density in the knockout than in WT, and vasopressin treatment normalized its density. We propose that FXYD1 plays a role in regulating AQP2 retention in apical membrane, and that this involves transfers between raft-like membrane domains in endosomes and plasma membranes.
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Affiliation(s)
- Elena Arystarkhova
- Laboratory of Membrane Biology, Dept. of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, Unites States of America
- * E-mail: (EA); (KJS)
| | - Richard Bouley
- Center for Systems Biology, Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Yi Bessie Liu
- Laboratory of Membrane Biology, Dept. of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, Unites States of America
| | - Kathleen J. Sweadner
- Laboratory of Membrane Biology, Dept. of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, Unites States of America
- * E-mail: (EA); (KJS)
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Blaustein MP. How does pressure overload cause cardiac hypertrophy and dysfunction? High-ouabain affinity cardiac Na + pumps are crucial. Am J Physiol Heart Circ Physiol 2017; 313:H919-H930. [PMID: 28733446 PMCID: PMC5792198 DOI: 10.1152/ajpheart.00131.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 07/18/2017] [Accepted: 07/18/2017] [Indexed: 12/17/2022]
Abstract
Left ventricular hypertrophy is frequently observed in hypertensive patients and is believed to be due to the pressure overload and cardiomyocyte stretch. Three recent reports on mice with genetically engineered Na+ pumps, however, have demonstrated that cardiac ouabain-sensitive α2-Na+ pumps play a key role in the pathogenesis of transaortic constriction-induced hypertrophy. Hypertrophy was delayed/attenuated in mice with mutant, ouabain-resistant α2-Na+ pumps and in mice with cardiac-selective knockout or transgenic overexpression of α2-Na+ pumps. The latter, seemingly paradoxical, findings can be explained by comparing the numbers of available (ouabain-free) high-affinity (α2) ouabain-binding sites in wild-type, knockout, and transgenic hearts. Conversely, hypertrophy was accelerated in α2-ouabain-resistant (R) mice in which the normally ouabain-resistant α1-Na+ pumps were mutated to an ouabain-sensitive (S) form (α1S/Sα2R/R or "SWAP" vs. wild-type or α1R/R α2S/S mice). Furthermore, transaortic constriction-induced hypertrophy in SWAP mice was prevented/reversed by immunoneutralizing circulating endogenous ouabain (EO). These findings show that EO and its receptor, ouabain-sensitive α2, are critical factors in pressure overload-induced cardiac hypertrophy. This complements reports linking elevated plasma EO to hypertension, cardiac hypertrophy, and failure in humans and elucidates the underappreciated role of the EO-Na+ pump pathway in cardiovascular disease.
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Affiliation(s)
- Mordecai P. Blaustein
- Departments of Physiology and Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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Regulation of hepatic Na+/K+-ATPase in obese female and male rats: involvement of ERK1/2, AMPK, and Rho/ROCK. Mol Cell Biochem 2017; 440:77-88. [DOI: 10.1007/s11010-017-3157-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 08/05/2017] [Indexed: 12/22/2022]
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Eleftheriadou O, Boguslavskyi A, Longman MR, Cowan J, Francois A, Heads RJ, Wadzinski BE, Ryan A, Shattock MJ, Snabaitis AK. Expression and regulation of type 2A protein phosphatases and alpha4 signalling in cardiac health and hypertrophy. Basic Res Cardiol 2017; 112:37. [PMID: 28526910 PMCID: PMC5438423 DOI: 10.1007/s00395-017-0625-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 05/02/2017] [Indexed: 01/25/2023]
Abstract
Cardiac physiology and hypertrophy are regulated by the phosphorylation status of many proteins, which is partly controlled by a poorly defined type 2A protein phosphatase-alpha4 intracellular signalling axis. Quantitative PCR analysis revealed that mRNA levels of the type 2A catalytic subunits were differentially expressed in H9c2 cardiomyocytes (PP2ACβ > PP2ACα > PP4C > PP6C), NRVM (PP2ACβ > PP2ACα = PP4C = PP6C), and adult rat ventricular myocytes (PP2ACα > PP2ACβ > PP6C > PP4C). Western analysis confirmed that all type 2A catalytic subunits were expressed in H9c2 cardiomyocytes; however, PP4C protein was absent in adult myocytes and only detectable following 26S proteasome inhibition. Short-term knockdown of alpha4 protein expression attenuated expression of all type 2A catalytic subunits. Pressure overload-induced left ventricular (LV) hypertrophy was associated with an increase in both PP2AC and alpha4 protein expression. Although PP6C expression was unchanged, expression of PP6C regulatory subunits (1) Sit4-associated protein 1 (SAP1) and (2) ankyrin repeat domain (ANKRD) 28 and 44 proteins was elevated, whereas SAP2 expression was reduced in hypertrophied LV tissue. Co-immunoprecipitation studies demonstrated that the interaction between alpha4 and PP2AC or PP6C subunits was either unchanged or reduced in hypertrophied LV tissue, respectively. Phosphorylation status of phospholemman (Ser63 and Ser68) was significantly increased by knockdown of PP2ACα, PP2ACβ, or PP4C protein expression. DNA damage assessed by histone H2A.X phosphorylation (γH2A.X) in hypertrophied tissue remained unchanged. However, exposure of cardiomyocytes to H2O2 increased levels of γH2A.X which was unaffected by knockdown of PP6C expression, but was abolished by the short-term knockdown of alpha4 expression. This study illustrates the significance and altered activity of the type 2A protein phosphatase-alpha4 complex in healthy and hypertrophied myocardium.
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Affiliation(s)
- Olga Eleftheriadou
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Andrii Boguslavskyi
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Michael R Longman
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Jonathan Cowan
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Asvi Francois
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Richard J Heads
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Brian E Wadzinski
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Ali Ryan
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Michael J Shattock
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Andrew K Snabaitis
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK.
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Skovgaard C, Almquist NW, Bangsbo J. Effect of increased and maintained frequency of speed endurance training on performance and muscle adaptations in runners. J Appl Physiol (1985) 2017; 122:48-59. [DOI: 10.1152/japplphysiol.00537.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 10/05/2016] [Accepted: 11/07/2016] [Indexed: 01/04/2023] Open
Abstract
The aim of the study was, in runners accustomed to speed endurance training (SET), to examine the effect of increased and maintained frequency of SET on performance and muscular adaptations. After familiarization (FAM) to SET, 18 male ( n = 14) and female ( n = 4) runners (V̇o2max: 57.3 ± 3.4 ml/min; means ± SD) completed 20 sessions of maintained low-frequency (LF; every fourth day; n = 7) or high-frequency (HF; every second day; n = 11) SET. Before FAM as well as before and after an intervention period (INT), subjects completed a series of running tests and a biopsy from m. vastus lateralis was collected. Ten-kilometer performance improved ( P < 0.05) ~3.5% during FAM with no further change during INT. Time to exhaustion at 90% vV̇o2max was 15 and 22% longer ( P < 0.05) during FAM and a further 12 and 16% longer ( P < 0.05) during INT in HF and LF, respectively. During FAM, muscle expression of NHE1 and maximal activity of citrate synthase (CS) and phosphofructokinase (PFK) increased ( P < 0.05), running economy (RE) improved ( P < 0.05), and V̇o2max was unchanged. During INT, both HF and LF increased ( P < 0.05) muscle expression of NKAβ1, whereas maximal activity of CS and PFK, RE, and V̇o2max were unchanged. Furthermore, during INT, muscle expression of FXYD1 and SERCA1, and FXYD1 activity increased ( P < 0.05) in HF, while muscle expression of SERCA2 decreased ( P < 0.05) in LF. Thus increased or maintained frequency of SET leads to further improvements in short-term exercise capacity, but not in 10-km running performance. The better short-term exercise capacity may be associated with elevated expression of muscle proteins related to Na+/K+ transportation and Ca2+ reuptake. NEW & NOTEWORTHY Ten speed endurance training (SET) sessions improved short-term exercise capacity and 10-km performance, which was followed by further improved short-term exercise capacity, but unchanged 10-km performance after 20 SET sessions performed with either high frequency (4 per 8 days) or continued low frequency (2 per 8 days) in trained runners. The further gain in short-term exercise capacity was associated with changes in muscle expression of proteins of importance for the development of fatigue.
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Affiliation(s)
- Casper Skovgaard
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark; and
- Team Danmark (Danish Elite Sports Organization), Copenhagen, Denmark
| | - Nicki Winfield Almquist
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark; and
| | - Jens Bangsbo
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark; and
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Habeck M, Tokhtaeva E, Nadav Y, Ben Zeev E, Ferris SP, Kaufman RJ, Bab-Dinitz E, Kaplan JH, Dada LA, Farfel Z, Tal DM, Katz A, Sachs G, Vagin O, Karlish SJD. Selective Assembly of Na,K-ATPase α2β2 Heterodimers in the Heart: DISTINCT FUNCTIONAL PROPERTIES AND ISOFORM-SELECTIVE INHIBITORS. J Biol Chem 2016; 291:23159-23174. [PMID: 27624940 DOI: 10.1074/jbc.m116.751735] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Indexed: 12/31/2022] Open
Abstract
The Na,K-ATPase α2 subunit plays a key role in cardiac muscle contraction by regulating intracellular Ca2+, whereas α1 has a more conventional role of maintaining ion homeostasis. The β subunit differentially regulates maturation, trafficking, and activity of α-β heterodimers. It is not known whether the distinct role of α2 in the heart is related to selective assembly with a particular one of the three β isoforms. We show here by immunofluorescence and co-immunoprecipitation that α2 is preferentially expressed with β2 in T-tubules of cardiac myocytes, forming α2β2 heterodimers. We have expressed human α1β1, α2β1, α2β2, and α2β3 in Pichia pastoris, purified the complexes, and compared their functional properties. α2β2 and α2β3 differ significantly from both α2β1 and α1β1 in having a higher K0.5K+ and lower K0.5Na+ for activating Na,K-ATPase. These features are the result of a large reduction in binding affinity for extracellular K+ and shift of the E1P-E2P conformational equilibrium toward E1P. A screen of perhydro-1,4-oxazepine derivatives of digoxin identified several derivatives (e.g. cyclobutyl) with strongly increased selectivity for inhibition of α2β2 and α2β3 over α1β1 (range 22-33-fold). Molecular modeling suggests a possible basis for isoform selectivity. The preferential assembly, specific T-tubular localization, and low K+ affinity of α2β2 could allow an acute response to raised ambient K+ concentrations in physiological conditions and explain the importance of α2β2 for cardiac muscle contractility. The high sensitivity of α2β2 to digoxin derivatives explains beneficial effects of cardiac glycosides for treatment of heart failure and potential of α2β2-selective digoxin derivatives for reducing cardiotoxicity.
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Affiliation(s)
| | - Elmira Tokhtaeva
- the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073
| | - Yotam Nadav
- From the Department of Biomolecular Sciences and
| | - Efrat Ben Zeev
- Israel National Centre for Personalized Medicine, Weizmann Institute of Science, Rehovoth 7610001, Israel
| | - Sean P Ferris
- the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | - Randal J Kaufman
- the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | | | - Jack H Kaplan
- the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607, and
| | - Laura A Dada
- the Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Zvi Farfel
- From the Department of Biomolecular Sciences and.,the School of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Daniel M Tal
- From the Department of Biomolecular Sciences and
| | - Adriana Katz
- From the Department of Biomolecular Sciences and
| | - George Sachs
- the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073
| | - Olga Vagin
- the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073,
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Blaustein MP, Chen L, Hamlyn JM, Leenen FHH, Lingrel JB, Wier WG, Zhang J. Pivotal role of α2 Na + pumps and their high affinity ouabain binding site in cardiovascular health and disease. J Physiol 2016; 594:6079-6103. [PMID: 27350568 DOI: 10.1113/jp272419] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 06/18/2016] [Indexed: 12/13/2022] Open
Abstract
Reduced smooth muscle (SM)-specific α2 Na+ pump expression elevates basal blood pressure (BP) and increases BP sensitivity to angiotensin II (Ang II) and dietary NaCl, whilst SM-α2 overexpression lowers basal BP and decreases Ang II/salt sensitivity. Prolonged ouabain infusion induces hypertension in rodents, and ouabain-resistant mutation of the α2 ouabain binding site (α2R/R mice) confers resistance to several forms of hypertension. Pressure overload-induced heart hypertrophy and failure are attenuated in cardio-specific α2 knockout, cardio-specific α2 overexpression and α2R/R mice. We propose a unifying hypothesis that reconciles these apparently disparate findings: brain mechanisms, activated by Ang II and high NaCl, regulate sympathetic drive and a novel neurohumoral pathway mediated by both brain and circulating endogenous ouabain (EO). Circulating EO modulates ouabain-sensitive α2 Na+ pump activity and Ca2+ transporter expression and, via Na+ /Ca2+ exchange, Ca2+ homeostasis. This regulates sensitivity to sympathetic activity, Ca2+ signalling and arterial and cardiac contraction.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA. .,Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, 21201, USA.
| | - Ling Chen
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA.,Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Frans H H Leenen
- Hypertension Unit, University of Ottawa Heart Institute, Ottawa, ON, Canada, K1Y 4W7
| | - Jerry B Lingrel
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267-0524, USA
| | - W Gil Wier
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Jin Zhang
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
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Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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Matchkov VV, Krivoi II. Specialized Functional Diversity and Interactions of the Na,K-ATPase. Front Physiol 2016; 7:179. [PMID: 27252653 PMCID: PMC4879863 DOI: 10.3389/fphys.2016.00179] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 05/04/2016] [Indexed: 12/22/2022] Open
Abstract
Na,K-ATPase is a protein ubiquitously expressed in the plasma membrane of all animal cells and vitally essential for their functions. A specialized functional diversity of the Na,K-ATPase isozymes is provided by molecular heterogeneity, distinct subcellular localizations, and functional interactions with molecular environment. Studies over the last decades clearly demonstrated complex and isoform-specific reciprocal functional interactions between the Na,K-ATPase and neighboring proteins and lipids. These interactions are enabled by a spatially restricted ion homeostasis, direct protein-protein/lipid interactions, and protein kinase signaling pathways. In addition to its "classical" function in ion translocation, the Na,K-ATPase is now considered as one of the most important signaling molecules in neuronal, epithelial, skeletal, cardiac and vascular tissues. Accordingly, the Na,K-ATPase forms specialized sub-cellular multimolecular microdomains which act as receptors to circulating endogenous cardiotonic steroids (CTS) triggering a number of signaling pathways. Changes in these endogenous cardiotonic steroid levels and initiated signaling responses have significant adaptive values for tissues and whole organisms under numerous physiological and pathophysiological conditions. This review discusses recent progress in the studies of functional interactions between the Na,K-ATPase and molecular microenvironment, the Na,K-ATPase-dependent signaling pathways and their significance for diversity of cell function.
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Affiliation(s)
| | - Igor I Krivoi
- Department of General Physiology, St. Petersburg State University St. Petersburg, Russia
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Sirenko SG, Maltsev VA, Yaniv Y, Bychkov R, Yaeger D, Vinogradova T, Spurgeon HA, Lakatta EG. Electrochemical Na+ and Ca2+ gradients drive coupled-clock regulation of automaticity of isolated rabbit sinoatrial nodal pacemaker cells. Am J Physiol Heart Circ Physiol 2016; 311:H251-67. [PMID: 27208164 DOI: 10.1152/ajpheart.00667.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 05/11/2016] [Indexed: 11/22/2022]
Abstract
Coupling of an intracellular Ca(2+) clock to surface membrane ion channels, i.e., a "membrane clock, " via coupling of electrochemical Na(+) and Ca(2+) gradients (ENa and ECa, respectively) has been theorized to regulate sinoatrial nodal cell (SANC) normal automaticity. To test this hypothesis, we measured responses of [Na(+)]i, [Ca(2+)]i, membrane potential, action potential cycle length (APCL), and rhythm in rabbit SANCs to Na(+)/K(+) pump inhibition by the digitalis glycoside, digoxigenin (DG, 10-20 μmol/l). Initial small but significant increases in [Na(+)]i and [Ca(2+)]i and reductions in ENa and ECa in response to DG led to a small reduction in maximum diastolic potential (MDP), significantly enhanced local diastolic Ca(2+) releases (LCRs), and reduced the average APCL. As [Na(+)]i and [Ca(2+)]i continued to increase at longer times following DG exposure, further significant reductions in MDP, ENa, and ECa occurred; LCRs became significantly reduced, and APCL became progressively and significantly prolonged. This was accompanied by increased APCL variability. We also employed a coupled-clock numerical model to simulate changes in ENa and ECa simultaneously with ion currents not measured experimentally. Numerical modeling predicted that, as the ENa and ECa monotonically reduced over time in response to DG, ion currents (ICaL, ICaT, If, IKr, and IbNa) monotonically decreased. In parallel with the biphasic APCL, diastolic INCX manifested biphasic changes; initial INCX increase attributable to enhanced LCR ensemble Ca(2+) signal was followed by INCX reduction as ENCX (ENCX = 3ENa - 2ECa) decreased. Thus SANC automaticity is tightly regulated by ENa, ECa, and ENCX via a complex interplay of numerous key clock components that regulate SANC clock coupling.
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Affiliation(s)
- Syevda G Sirenko
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland
| | - Victor A Maltsev
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland
| | - Yael Yaniv
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland; Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel
| | - Rostislav Bychkov
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland; Universidad Central del Caribe, Santa Juanita, Bayamon Puerto Rico
| | - Daniel Yaeger
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland
| | - Tatiana Vinogradova
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland
| | - Harold A Spurgeon
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, National Institutes of Health, National Institute on Aging, Intramural Research Program, Baltimore, Maryland;
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Yan Y, Shapiro JI. The physiological and clinical importance of sodium potassium ATPase in cardiovascular diseases. Curr Opin Pharmacol 2016; 27:43-9. [PMID: 26891193 PMCID: PMC5161351 DOI: 10.1016/j.coph.2016.01.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 01/14/2016] [Accepted: 01/29/2016] [Indexed: 12/14/2022]
Abstract
The Na/K-ATPase has been extensively studied, but it is only recently that its role as a scaffolding and signaling protein has been identified. It has been identified that cardiotonic steroids (CTS) such as digitalis mediate signal transduction through the Na/K-ATPase in a process found to result in the generation of reactive oxygen species (ROS). As these ROS also appear capable of initiating this signal cascade, a feed forward amplification process has been postulated and subsequently implicated in some disease pathways including uremic cardiomyopathy.
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Affiliation(s)
- Yanling Yan
- Joan C. Edwards School of Medicine, Marshall University, Department of Medicine, USA
| | - Joseph I Shapiro
- Joan C. Edwards School of Medicine, Marshall University, Department of Medicine, USA.
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Thomassen M, Gunnarsson TP, Christensen PM, Pavlovic D, Shattock MJ, Bangsbo J. Intensive training and reduced volume increases muscle FXYD1 expression and phosphorylation at rest and during exercise in athletes. Am J Physiol Regul Integr Comp Physiol 2016; 310:R659-69. [PMID: 26791827 DOI: 10.1152/ajpregu.00081.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 01/18/2016] [Indexed: 01/10/2023]
Abstract
The present study examined the effect of intensive training in combination with marked reduction in training volume on phospholemman (FXYD1) expression and phosphorylation at rest and during exercise. Eight well-trained cyclists replaced their regular training with speed-endurance training (10-12 × ∼30-s sprints) two or three times per week and aerobic high-intensity training (4-5 × 3-4 min at 90-95% of peak aerobic power output) 1-2 times per week for 7 wk and reduced the training volume by 70%. Muscle biopsies were obtained before and during a repeated high-intensity exercise protocol, and protein expression and phosphorylation were determined by Western blot analysis. Expression of FXYD1 (30%), actin (40%), mammalian target of rapamycin (mTOR) (12%), phospholamban (PLN) (16%), and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) γ/δ (25%) was higher (P < 0.05) than before the training intervention. In addition, after the intervention, nonspecific FXYD1 phosphorylation was higher (P < 0.05) at rest and during exercise, mainly achieved by an increased FXYD1 Ser-68 phosphorylation, compared with before the intervention. CaMKII, Thr-287, and eukaryotic elongation factor 2 Thr-56 phosphorylation at rest and during exercise, overall PKCα/β, Thr-638/641, and mTOR Ser-2448 phosphorylation during repeated intense exercise as well as resting PLN Thr-17 phosphorylation were also higher (P < 0.05) compared with before the intervention period. Thus, a period of high-intensity training with reduced training volume increases expression and phosphorylation levels of FXYD1, which may affect Na(+)/K(+) pump activity and muscle K(+) homeostasis during intense exercise. Furthermore, higher expression of CaMKII and PLN, as well as increased phosphorylation of CaMKII Thr-287 may have improved intracellular Ca(2+) handling.
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Affiliation(s)
- Martin Thomassen
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark; and
| | - Thomas P Gunnarsson
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark; and
| | - Peter M Christensen
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark; and
| | - Davor Pavlovic
- Cardiovascular Division, King's College London, The Rayne Institute, St. Thomas' Hospital, London, United Kingdom
| | - Michael J Shattock
- Cardiovascular Division, King's College London, The Rayne Institute, St. Thomas' Hospital, London, United Kingdom
| | - Jens Bangsbo
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark; and
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Kravtsova VV, Petrov AM, Matchkov VV, Bouzinova EV, Vasiliev AN, Benziane B, Zefirov AL, Chibalin AV, Heiny JA, Krivoi II. Distinct α2 Na,K-ATPase membrane pools are differently involved in early skeletal muscle remodeling during disuse. ACTA ACUST UNITED AC 2016; 147:175-88. [PMID: 26755774 PMCID: PMC4727944 DOI: 10.1085/jgp.201511494] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 12/22/2015] [Indexed: 11/29/2022]
Abstract
Location, location, location. The Na-K pump of skeletal muscle is regulated differently at neuromuscular junctions. The Na,K-ATPase is essential for the contractile function of skeletal muscle, which expresses the α1 and α2 subunit isoforms of Na,K-ATPase. The α2 isozyme is predominant in adult skeletal muscles and makes a greater contribution in working compared with noncontracting muscles. Hindlimb suspension (HS) is a widely used model of muscle disuse that leads to progressive atrophy of postural skeletal muscles. This study examines the consequences of acute (6–12 h) HS on the functioning of the Na,K-ATPase α1 and α2 isozymes in rat soleus (disused) and diaphragm (contracting) muscles. Acute disuse dynamically and isoform-specifically regulates the electrogenic activity, protein, and mRNA content of Na,K-ATPase α2 isozyme in rat soleus muscle. Earlier disuse-induced remodeling events also include phospholemman phosphorylation as well as its increased abundance and association with α2 Na,K-ATPase. The loss of α2 Na,K-ATPase activity results in reduced electrogenic pump transport and depolarized resting membrane potential. The decreased α2 Na,K-ATPase activity is caused by a decrease in enzyme activity rather than by altered protein and mRNA content, localization in the sarcolemma, or functional interaction with the nicotinic acetylcholine receptors. The loss of extrajunctional α2 Na,K-ATPase activity depends strongly on muscle use, and even the increased protein and mRNA content as well as enhanced α2 Na,K-ATPase abundance at this membrane region after 12 h of HS cannot counteract this sustained inhibition. In contrast, additional factors may regulate the subset of junctional α2 Na,K-ATPase pool that is able to recover during HS. Notably, acute, low-intensity muscle workload restores functioning of both α2 Na,K-ATPase pools. These results demonstrate that the α2 Na,K-ATPase in rat skeletal muscle is dynamically and acutely regulated by muscle use and provide the first evidence that the junctional and extrajunctional pools of the α2 Na,K-ATPase are regulated differently.
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Affiliation(s)
- Violetta V Kravtsova
- Department of General Physiology, St. Petersburg State University, St. Petersburg 199034, Russia
| | - Alexey M Petrov
- Department of Normal Physiology, Kazan State Medical University, Kazan 420012, Russia
| | | | - Elena V Bouzinova
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, 8240 Risskov, Denmark
| | - Alexander N Vasiliev
- Department of General Physiology, St. Petersburg State University, St. Petersburg 199034, Russia
| | - Boubacar Benziane
- Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Andrey L Zefirov
- Department of Normal Physiology, Kazan State Medical University, Kazan 420012, Russia
| | - Alexander V Chibalin
- Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Judith A Heiny
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Igor I Krivoi
- Department of General Physiology, St. Petersburg State University, St. Petersburg 199034, Russia
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Mishra NK, Habeck M, Kirchner C, Haviv H, Peleg Y, Eisenstein M, Apell HJ, Karlish SJD. Molecular Mechanisms and Kinetic Effects of FXYD1 and Phosphomimetic Mutants on Purified Human Na,K-ATPase. J Biol Chem 2015; 290:28746-59. [PMID: 26429909 DOI: 10.1074/jbc.m115.687913] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Indexed: 11/06/2022] Open
Abstract
Phospholemman (FXYD1) is a single-transmembrane protein regulator of Na,K-ATPase, expressed strongly in heart, skeletal muscle, and brain and phosphorylated by protein kinases A and C at Ser-68 and Ser-63, respectively. Binding of FXYD1 reduces Na,K-ATPase activity, and phosphorylation at Ser-68 or Ser-63 relieves the inhibition. Despite the accumulated information on physiological effects, whole cell studies provide only limited information on molecular mechanisms. As a complementary approach, we utilized purified human Na,K-ATPase (α1β1 and α2β1) reconstituted with FXYD1 or mutants S63E, S68E, and S63E,S68E that mimic phosphorylation at Ser-63 and Ser-68. Compared with control α1β1, FXYD1 reduces Vmax and turnover rate and raises K0.5Na. The phosphomimetic mutants reverse these effects and reduce K0.5Na below control K0.5Na. Effects on α2β1 are similar but smaller. Experiments in proteoliposomes reconstituted with α1β1 show analogous effects of FXYD1 on K0.5Na, which are abolished by phosphomimetic mutants and also by increasing mole fractions of DOPS in the proteoliposomes. Stopped-flow experiments using the dye RH421 show that FXYD1 slows the conformational transition E2(2K)ATP → E1(3Na)ATP but does not affect 3NaE1P → E2P3Na. This regulatory effect is explained simply by molecular modeling, which indicates that a cytoplasmic helix (residues 60-70) docks between the αN and αP domains in the E2 conformation, but docking is weaker in E1 (also for phosphomimetic mutants). Taken together with previous work showing that FXYD1 also raises binding affinity for the Na(+)-selective site III, these results provide a rather comprehensive picture of the regulatory mechanism of FXYD1 that complements the physiological studies.
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Affiliation(s)
| | | | - Corinna Kirchner
- the Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Haim Haviv
- From the Department of Biological Chemistry
| | - Yoav Peleg
- Israel Structural Proteomics Center, Weizmann Institute of Science, Rehovot 7610001, Israel and
| | | | - Hans Juergen Apell
- the Department of Biology, University of Konstanz, 78464 Konstanz, Germany
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Sárközy M, Szűcs G, Pipicz M, Zvara Á, Éder K, Fekete V, Szűcs C, Bárkányi J, Csonka C, Puskás LG, Kónya C, Ferdinandy P, Csont T. The effect of a preparation of minerals, vitamins and trace elements on the cardiac gene expression pattern in male diabetic rats. Cardiovasc Diabetol 2015; 14:85. [PMID: 26126619 PMCID: PMC4499218 DOI: 10.1186/s12933-015-0248-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 06/17/2015] [Indexed: 02/06/2023] Open
Abstract
Background Diabetic patients have an increased risk of developing cardiovascular diseases, which are the leading cause of death in developed countries. Although multivitamin products are widely used as dietary supplements, the effects of these products have not been investigated in the diabetic heart yet. Therefore, here we investigated if a preparation of different minerals, vitamins, and trace elements (MVT) affects the cardiac gene expression pattern in experimental diabetes. Methods Two-day old male Wistar rats were injected with streptozotocin (i.p. 100 mg/kg) or citrate buffer to induce diabetes. From weeks 4 to 12, rats were fed with a vehicle or a MVT preparation. Fasting blood glucose measurement and oral glucose tolerance test were performed at week 12, and then total RNA was isolated from the myocardium and assayed by rat oligonucleotide microarray for 41012 oligonucleotides. Results Significantly elevated fasting blood glucose concentration and impaired glucose tolerance were markedly improved by MVT-treatment in diabetic rats at week 12. Genes with significantly altered expression due to diabetes include functional clusters related to cardiac hypertrophy (e.g. caspase recruitment domain family, member 9; cytochrome P450, family 26, subfamily B, polypeptide; FXYD domain containing ion transport regulator 3), stress response (e.g. metallothionein 1a; metallothionein 2a; interleukin-6 receptor; heme oxygenase (decycling) 1; and glutathione S-transferase, theta 3), and hormones associated with insulin resistance (e.g. resistin; FK506 binding protein 5; galanin/GMAP prepropeptide). Moreover the expression of some other genes with no definite cardiac function was also changed such as e.g. similar to apolipoprotein L2; brain expressed X-linked 1; prostaglandin b2 synthase (brain). MVT-treatment in diabetic rats showed opposite gene expression changes in the cases of 19 genes associated with diabetic cardiomyopathy. In healthy hearts, MVT-treatment resulted in cardiac gene expression changes mostly related to immune response (e.g. complement factor B; complement component 4a; interferon regulatory factor 7; hepcidin). Conclusions MVT-treatment improved diagnostic markers of diabetes. This is the first demonstration that MVT-treatment significantly alters cardiac gene expression profile in both control and diabetic rats. Our results and further studies exploring the mechanistic role of individual genes may contribute to the prevention or diagnosis of cardiac complications in diabetes. Electronic supplementary material The online version of this article (doi:10.1186/s12933-015-0248-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Márta Sárközy
- Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary.
| | - Gergő Szűcs
- Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary.
| | - Márton Pipicz
- Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary.
| | - Ágnes Zvara
- Institute of Genetics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, Hungary.
| | - Katalin Éder
- Department of Genetics, Cell- and Immunobiology, Semmelweis University, Budapest, Hungary.
| | - Veronika Fekete
- Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary.
| | | | | | - Csaba Csonka
- Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary.
| | - László G Puskás
- Institute of Genetics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, Hungary.
| | - Csaba Kónya
- Béres Pharmaceuticals Ltd, Budapest, Hungary.
| | - Péter Ferdinandy
- Pharmahungary Group, Szeged, Hungary. .,Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.
| | - Tamás Csont
- Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary.
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44
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Smith LE, White MY. The role of post-translational modifications in acute and chronic cardiovascular disease. Proteomics Clin Appl 2015; 8:506-21. [PMID: 24961403 DOI: 10.1002/prca.201400052] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 05/27/2014] [Accepted: 06/17/2014] [Indexed: 12/22/2022]
Abstract
Cardiovascular disease (CVD) in one of the leading causes of mortality and morbidity worldwide, accounting for both primary diseases of the heart and vasculature and arising as a co-morbidity with numerous pathologies, including type 2 diabetes mellitus (T2DM). There has been significant emphasis on the role of the genome in CVD, aiding in the definition of 'at-risk' patients. The extent of disease penetrance however, can be influenced by environmental factors that are not detectable by investigating the genome alone. By targeting the transcriptome in response to CVD, the interplay between genome and environment is more apparent, however this implies the level of protein expression without reference to proteolytic turnover, or potentially more importantly, without defining the role of PTMs in the development of disease. Here, we discuss the role of both brief and irreversible PTMs in the setting of myocardial ischemia/reperfusion injury. Key proteins involved in calcium regulation have been observed as differentially modified by phosphorylation/O-GlcNAcylation or phosphorylation/redox modifications, with the level of interplay dependent on the physiological or pathophysiological state. The ability to modify crucial sites to produce the desired functional output is modulated by the presence of other PTMs as exemplified in the T2DM heart, where hyperglycemia results in aberrant O-GlcNAcylation and advanced glycation end products. By using the signalling events predicted to be critical to post-conditioning, an intervention with great promise for the cardioprotection of the ischemia/reperfusion injured heart, as an example, we discuss the level of PTMs and their interplay. The inability of post-conditioning to protect the diabetic heart may be regulated by aberrant PTMs influencing those sites necessary for protection.
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Affiliation(s)
- Lauren E Smith
- Discipline of Pathology, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia
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45
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Pavlovic D. The role of cardiotonic steroids in the pathogenesis of cardiomyopathy in chronic kidney disease. Nephron Clin Pract 2014; 128:11-21. [PMID: 25341357 DOI: 10.1159/000363301] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Cardiotonic steroids (CTS) are a new class of hormones that circulate in the blood and are divided into two distinct groups, cardenolides, such as ouabain and digoxin, and bufadienolides, such as marinobufagenin, telocinobufagin and bufalin. They have the ability to bind and inhibit the ubiquitous transport enzyme sodium potassium pump, thus regulating intracellular Na(+) concentration in every living cell. Although digoxin has been prescribed to heart failure patients for at least 200 years, the realization that CTS are endogenously produced has intensified research into their physiological and pathophysiological roles. Over the last two decades, substantial evidence has accumulated demonstrating the effects of endogenously synthesised CTS on the kidneys, vasculature and the heart. In this review, the current state of art and the controversies surrounding the manner in which CTS mediate their pathophysiological effects are discussed. Several potential therapeutic strategies have emerged as a result of our increased understanding of the role CTS play in health and disease.
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Affiliation(s)
- Davor Pavlovic
- Cardiovascular Division, King's College London, Rayne Institute, St. Thomas' Hospital, London, UK
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46
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Boguslavskyi A, Pavlovic D, Aughton K, Clark JE, Howie J, Fuller W, Shattock MJ. Cardiac hypertrophy in mice expressing unphosphorylatable phospholemman. Cardiovasc Res 2014; 104:72-82. [PMID: 25103111 PMCID: PMC4174889 DOI: 10.1093/cvr/cvu182] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
AIMS Elevation of intracellular Na in the failing myocardium contributes to contractile dysfunction, the negative force-frequency relationship, and arrhythmias. Although phospholemman (PLM) is recognized to form the link between signalling pathways and Na/K pump activity, the possibility that defects in its regulation contribute to elevation of intracellular Na has not been investigated. Our aim was to test the hypothesis that the prevention of PLM phosphorylation in a PLM(3SA) knock-in mouse (in which PLM has been rendered unphosphorylatable) will exacerbate cardiac hypertrophy and cellular Na overload. Testing this hypothesis should determine whether changes in PLM phosphorylation are simply bystander effects or are causally involved in disease progression. METHODS AND RESULTS In wild-type (WT) mice, aortic constriction resulted in hypophosphorylation of PLM with no change in Na/K pump expression. This under-phosphorylation of PLM occurred at 3 days post-banding and was associated with a progressive decline in Na/K pump current and elevation of [Na]i. Echocardiography, morphometry, and pressure-volume (PV) catheterization confirmed remodelling, dilation, and contractile dysfunction, respectively. In PLM(3SA) mice, expression of Na/K ATPase was increased and PLM decreased such that net Na/K pump current under quiescent conditions was unchanged (cf. WT myocytes); [Na(+)]i was increased and forward-mode Na/Ca exchanger was reduced in paced PLM(3SA) myocytes. Cardiac hypertrophy and Na/K pump inhibition were significantly exacerbated in banded PLM(3SA) mice compared with banded WT. CONCLUSIONS Decreased phosphorylation of PLM reduces Na/K pump activity and exacerbates Na overload, contractile dysfunction, and adverse remodelling following aortic constriction in mice. This suggests a novel therapeutic target for the treatment of heart failure.
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Affiliation(s)
| | - Davor Pavlovic
- Cardiovascular Division, King's College London, London, UK
| | - Karen Aughton
- Cardiovascular Division, King's College London, London, UK
| | - James E Clark
- Cardiovascular Division, King's College London, London, UK
| | - Jacqueline Howie
- Division of Cardiovascular and Diabetes Medicine, University of Dundee, Dundee, UK
| | - William Fuller
- Division of Cardiovascular and Diabetes Medicine, University of Dundee, Dundee, UK
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Breves JP, McCormick SD, Karlstrom RO. Prolactin and teleost ionocytes: new insights into cellular and molecular targets of prolactin in vertebrate epithelia. Gen Comp Endocrinol 2014; 203:21-8. [PMID: 24434597 PMCID: PMC4096611 DOI: 10.1016/j.ygcen.2013.12.014] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 12/20/2013] [Accepted: 12/29/2013] [Indexed: 11/30/2022]
Abstract
The peptide hormone prolactin is a functionally versatile hormone produced by the vertebrate pituitary. Comparative studies over the last six decades have revealed that a conserved function for prolactin across vertebrates is the regulation of ion and water transport in a variety of tissues including those responsible for whole-organism ion homeostasis. In teleost fishes, prolactin was identified as the "freshwater-adapting hormone", promoting ion-conserving and water-secreting processes by acting on the gill, kidney, gut and urinary bladder. In mammals, prolactin is known to regulate renal, intestinal, mammary and amniotic epithelia, with dysfunction linked to hypogonadism, infertility, and metabolic disorders. Until recently, our understanding of the cellular mechanisms of prolactin action in fishes has been hampered by a paucity of molecular tools to define and study ionocytes, specialized cells that control active ion transport across branchial and epidermal epithelia. Here we review work in teleost models indicating that prolactin regulates ion balance through action on ion transporters, tight-junction proteins, and water channels in ionocytes, and discuss recent advances in our understanding of ionocyte function in the genetically and embryonically accessible zebrafish (Danio rerio). Given the high degree of evolutionary conservation in endocrine and osmoregulatory systems, these studies in teleost models are contributing novel mechanistic insight into how prolactin participates in the development, function, and dysfunction of osmoregulatory systems across the vertebrate lineage.
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Affiliation(s)
- Jason P Breves
- Department of Biology & Center for Neuroendocrine Studies, University of Massachusetts, Amherst, MA 01003, USA.
| | - Stephen D McCormick
- Department of Biology & Center for Neuroendocrine Studies, University of Massachusetts, Amherst, MA 01003, USA; USGS, Conte Anadromous Fish Research Center, Turners Falls, MA 01376, USA
| | - Rolf O Karlstrom
- Department of Biology & Center for Neuroendocrine Studies, University of Massachusetts, Amherst, MA 01003, USA
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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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