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Blaustein MP, Hamlyn JM. Sensational site: the sodium pump ouabain-binding site and its ligands. Am J Physiol Cell Physiol 2024; 326:C1120-C1177. [PMID: 38223926 PMCID: PMC11193536 DOI: 10.1152/ajpcell.00273.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 01/16/2024]
Abstract
Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
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2
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Staehr C, Aalkjaer C, Matchkov V. The vascular Na,K-ATPase: clinical implications in stroke, migraine, and hypertension. Clin Sci (Lond) 2023; 137:1595-1618. [PMID: 37877226 PMCID: PMC10600256 DOI: 10.1042/cs20220796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 10/05/2023] [Accepted: 10/09/2023] [Indexed: 10/26/2023]
Abstract
In the vascular wall, the Na,K-ATPase plays an important role in the control of arterial tone. Through cSrc signaling, it contributes to the modulation of Ca2+ sensitivity in vascular smooth muscle cells. This review focuses on the potential implication of Na,K-ATPase-dependent intracellular signaling pathways in severe vascular disorders; ischemic stroke, familial migraine, and arterial hypertension. We propose similarity in the detrimental Na,K-ATPase-dependent signaling seen in these pathological conditions. The review includes a retrospective proteomics analysis investigating temporal changes after ischemic stroke. The analysis revealed that the expression of Na,K-ATPase α isoforms is down-regulated in the days and weeks following reperfusion, while downstream Na,K-ATPase-dependent cSrc kinase is up-regulated. These results are important since previous studies have linked the Na,K-ATPase-dependent cSrc signaling to futile recanalization and vasospasm after stroke. The review also explores a link between the Na,K-ATPase and migraine with aura, as reduced expression or pharmacological inhibition of the Na,K-ATPase leads to cSrc kinase signaling up-regulation and cerebral hypoperfusion. The review discusses the role of an endogenous cardiotonic steroid-like compound, ouabain, which binds to the Na,K-ATPase and initiates the intracellular cSrc signaling, in the pathophysiology of arterial hypertension. Currently, our understanding of the precise control mechanisms governing the Na,K-ATPase/cSrc kinase regulation in the vascular wall is limited. Understanding the role of vascular Na,K-ATPase signaling is essential for developing targeted treatments for cerebrovascular disorders and hypertension, as the Na,K-ATPase is implicated in the pathogenesis of these conditions and may contribute to their comorbidity.
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Affiliation(s)
- Christian Staehr
- Department of Biomedicine, Aarhus University, Høegh-Guldbergsgade 10, 8000 Aarhus, Denmark
- Department of Renal Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 35, Aarhus, Denmark
| | - Christian Aalkjaer
- Department of Biomedicine, Aarhus University, Høegh-Guldbergsgade 10, 8000 Aarhus, Denmark
- Danish Cardiovascular Academy, Høegh-Guldbergsgade 10, 8000 Aarhus, Denmark
| | - Vladimir V. Matchkov
- Department of Biomedicine, Aarhus University, Høegh-Guldbergsgade 10, 8000 Aarhus, Denmark
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3
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Gurler B, Gencay G, Baloglu E. Hypoxia and HIF-1α Regulate the Activity and Expression of Na,K-ATPase Subunits in H9c2 Cardiomyoblasts. Curr Issues Mol Biol 2023; 45:8277-8288. [PMID: 37886965 PMCID: PMC10605391 DOI: 10.3390/cimb45100522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 10/08/2023] [Accepted: 10/10/2023] [Indexed: 10/28/2023] Open
Abstract
The optimal function of the Na,K-ATPase (NKA) pump is essential for the heart. In ischemic heart disease, NKA activity decreases due to the decreased expression of the pump subunits. Here, we tested whether the hypoxia-inducible transcription factor (HIF-1α), the key signaling molecule regulating the adaptation of cells to hypoxia, is involved in controlling the expression and cellular dynamics of α1- and β1-NKA isoforms and of NKA activity in in-vitro hypoxic H9c2 cardiomyoblasts. HIF-1α was silenced through adenoviral infection, and cells were kept in normoxia (19% O2) or hypoxia (1% O2) for 24 h. We investigated the mRNA and protein expression of α1-, β1-NKA using RT-qPCR and Western blot in whole-cell lysates, cell membranes, and cytoplasmic fractions after labeling the cell surface with NHS-SS-biotin and immunoprecipitation. NKA activity and intracellular ATP levels were also measured. We found that in hypoxia, silencing HIF-1α prevented the decreased mRNA expression of α1-NKA but not of β1-NKA. Hypoxia decreased the plasma membrane expression of α1-NKA and β1- NKA compared to normoxic cells. In hypoxic cells, HIF-1α silencing prevented this effect by inhibiting the internalization of α1-NKA. Total protein expression was not affected. The decreased activity of NKA in hypoxic cells was fully prevented by silencing HIF-1α independent of cellular ATP levels. This study is the first to show that in hypoxic H9c2 cardiomyoblasts, HIF-1α controls the internalization and membrane insertion of α1-NKA subunit and of NKA activity. The mechanism behind this regulation needs further investigation.
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Affiliation(s)
- Beyza Gurler
- Department of Medical Biotechnology, Institute of Health Sciences, Acibadem Mehmet Ali Aydinlar University, Istanbul 34752, Turkey;
| | - Gizem Gencay
- Department of Molecular and Translational Biomedicine, Institute of Natural and Applied Sciences, Acibadem Mehmet Ali Aydinlar University, Istanbul 34752, Turkey;
| | - Emel Baloglu
- Department of Medical Pharmacology, School of Medicine, Acibadem Mehmet Ali Aydinlar University, Istanbul 34752, Turkey
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Baloglu E. Hypoxic Stress-Dependent Regulation of Na,K-ATPase in Ischemic Heart Disease. Int J Mol Sci 2023; 24:ijms24097855. [PMID: 37175562 PMCID: PMC10177966 DOI: 10.3390/ijms24097855] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Revised: 04/19/2023] [Accepted: 04/20/2023] [Indexed: 05/15/2023] Open
Abstract
In cardiomyocytes, regular activity of the Na,K-ATPase (NKA) and its Na/K pump activity is essential for maintaining ion gradients, excitability, propagation of action potentials, electro-mechanical coupling, trans-membrane Na+ and Ca2+ gradients and, thus, contractility. The activity of NKA is impaired in ischemic heart disease and heart failure, which has been attributed to decreased expression of the NKA subunits. Decreased NKA activity leads to intracellular Na+ and Ca2+ overload, diastolic dysfunction and arrhythmias. One signal likely related to these events is hypoxia, where hypoxia-inducible factors (HIF) play a critical role in the adaptation of cells to low oxygen tension. HIF activity increases in ischemic heart, hypertension, heart failure and cardiac fibrosis; thus, it might contribute to the impaired function of NKA. This review will mainly focus on the regulation of NKA in ischemic heart disease in the context of stressed myocardium and the hypoxia-HIF axis and argue on possible consequences of treatment.
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Affiliation(s)
- Emel Baloglu
- Department of Medical Pharmacology, School of Medicine, Acibadem Mehmet Ali Aydinlar University, 34752 Istanbul, Turkey
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Rajanathan R, Riera CVI, Pedersen TM, Staehr C, Bouzinova EV, Nyengaard JR, Thomsen MB, Bøtker HE, Matchkov VV. Hypercontractile Cardiac Phenotype in Mice with Migraine-Associated Mutation in the Na +,K +-ATPase α 2-Isoform. Cells 2023; 12:cells12081108. [PMID: 37190017 DOI: 10.3390/cells12081108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 05/17/2023] Open
Abstract
Two α-isoforms of the Na+,K+-ATPase (α1 and α2) are expressed in the cardiovascular system, and it is unclear which isoform is the preferential regulator of contractility. Mice heterozygous for the familial hemiplegic migraine type 2 (FHM2) associated mutation in the α2-isoform (G301R; α2+/G301R mice) have decreased expression of cardiac α2-isoform but elevated expression of the α1-isoform. We aimed to investigate the contribution of the α2-isoform function to the cardiac phenotype of α2+/G301R hearts. We hypothesized that α2+/G301R hearts exhibit greater contractility due to reduced expression of cardiac α2-isoform. Variables for contractility and relaxation of isolated hearts were assessed in the Langendorff system without and in the presence of ouabain (1 µM). Atrial pacing was performed to investigate rate-dependent changes. The α2+/G301R hearts displayed greater contractility than WT hearts during sinus rhythm, which was rate-dependent. The inotropic effect of ouabain was more augmented in α2+/G301R hearts than in WT hearts during sinus rhythm and atrial pacing. In conclusion, cardiac contractility was greater in α2+/G301R hearts than in WT hearts under resting conditions. The inotropic effect of ouabain was rate-independent and enhanced in α2+/G301R hearts, which was associated with increased systolic work.
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Affiliation(s)
| | - Clàudia Vilaseca I Riera
- Department of Basic Science, School of Medicine and Health Sciences, International University of Catalonia, 08195 Barcelona, Spain
| | | | - Christian Staehr
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
| | | | - Jens Randel Nyengaard
- Department of Clinical Medicine, Core Center for Molecular Morphology, Section for Stereology and Microscopy, Aarhus University, 8000 Aarhus, Denmark
- Department of Pathology, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Morten B Thomsen
- Biomedical Sciences, University of Copenhagen, 1168 Copenhagen, Denmark
| | - Hans Erik Bøtker
- Department of Cardiology, Aarhus University Hospital, 8200 Aarhus, Denmark
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Rognant S, Kravtsova VV, Bouzinova EV, Melnikova EV, Krivoi II, Pierre SV, Aalkjaer C, Jepps TA, Matchkov VV. The microtubule network enables Src kinase interaction with the Na,K-ATPase to generate Ca2+ flashes in smooth muscle cells. Front Physiol 2022; 13:1007340. [PMID: 36213229 PMCID: PMC9538378 DOI: 10.3389/fphys.2022.1007340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 09/05/2022] [Indexed: 12/03/2022] Open
Abstract
Background: Several local Ca2+ events are characterized in smooth muscle cells. We have previously shown that an inhibitor of the Na,K-ATPase, ouabain induces spatially restricted intracellular Ca2+ transients near the plasma membrane, and suggested the importance of this signaling for regulation of intercellular coupling and smooth muscle cell contraction. The mechanism behind these Na,K-ATPase-dependent “Ca2+ flashes” remains to be elucidated. In addition to its conventional ion transport function, the Na,K-ATPase is proposed to contribute to intracellular pathways, including Src kinase activation. The microtubule network is important for intracellular signaling, but its role in the Na,K-ATPase-Src kinase interaction is not known. We hypothesized the microtubule network was responsible for maintaining the Na,K-ATPase-Src kinase interaction, which enables Ca2+ flashes. Methods: We characterized Ca2+ flashes in cultured smooth muscle cells, A7r5, and freshly isolated smooth muscle cells from rat mesenteric artery. Cells were loaded with Ca2+-sensitive fluorescent dyes, Calcium Green-1/AM and Fura Red/AM, for ratiometric measurements of intracellular Ca2+. The Na,K-ATPase α2 isoform was knocked down with siRNA and the microtubule network was disrupted with nocodazole. An involvement of the Src signaling was tested pharmacologically and with Western blot. Protein interactions were validated with proximity ligation assays. Results: The Ca2+ flashes were induced by micromolar concentrations of ouabain. Knockdown of the α2 isoform Na,K-ATPase abolished Ca2+ flashes, as did inhibition of tyrosine phosphorylation with genistein and PP2, and the inhibitor of the Na,K-ATPase-dependent Src activation, pNaKtide. Ouabain-induced Ca2+ flashes were associated with Src kinase activation by phosphorylation. The α2 isoform Na,K-ATPase and Src kinase colocalized in the cells. Disruption of microtubule with nocodazole inhibited Ca2+ flashes, reduced Na,K-ATPase/Src interaction and Src activation. Conclusion: We demonstrate that the Na,K-ATPase-dependent Ca2+ flashes in smooth muscle cells require an interaction between the α2 isoform Na, K-ATPase and Src kinase, which is maintained by the microtubule network.
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Affiliation(s)
- Salomé Rognant
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Violetta V. Kravtsova
- Department of General Physiology, St. Petersburg State University, St. Petersburg, Russia
| | | | | | - Igor I. Krivoi
- Department of General Physiology, St. Petersburg State University, St. Petersburg, Russia
| | - Sandrine V. Pierre
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV, United States
| | | | - Thomas A. Jepps
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Vladimir V. Matchkov
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- *Correspondence: Vladimir V. Matchkov,
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Guldbrandsen HO, Staehr C, Iversen NK, Postnov DD, Matchkov VV. Does Src Kinase Mediated Vasoconstriction Impair Penumbral Reperfusion? Stroke 2021; 52:e250-e258. [PMID: 33947213 DOI: 10.1161/strokeaha.120.032737] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Despite successful recanalization, a significant number of patients with ischemic stroke experience impaired local brain tissue reperfusion with adverse clinical outcome. The cause and mechanism of this multifactorial complication are yet to be understood. At the current moment, major attention is given to dysfunction in blood-brain barrier and capillary blood flow but contribution of exaggerated constriction of cerebral arterioles has also been suggested. In the brain, arterioles significantly contribute to vascular resistance and thus control of perfusion. Accordingly, pathological changes in arteriolar wall function can, therefore, limit sufficient reperfusion in ischemic stroke, but this has not yet received sufficient attention. Although an increased vascular tone after reperfusion has been demonstrated in several studies, the mechanism behind it remains to be characterized. Importantly, the majority of conventional mechanisms controlling vascular contraction failed to explain elevated cerebrovascular tone after reperfusion. We propose here that the Na,K-ATPase-dependent Src kinase activation are the key mechanisms responsible for elevation of cerebrovascular tone after reperfusion. The Na,K-ATPase, which is essential to control intracellular ion homeostasis, also executes numerous signaling functions. Under hypoxic conditions, the Na,K-ATPase is endocytosed from the membrane of vascular smooth muscle cells. This initiates the Src kinase signaling pathway that sensitizes the contractile machinery to intracellular Ca2+ resulting in hypercontractility of vascular smooth muscle cells and, thus, elevated cerebrovascular tone that can contribute to impaired reperfusion after stroke. This mechanism integrates with cerebral edema that was suggested to underlie impaired reperfusion and is further supported by several studies, which are discussed in this article. However, final demonstration of the molecular mechanism behind Src kinase-associated arteriolar hypercontractility in stroke remains to be done.
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Affiliation(s)
| | - Christian Staehr
- Department of Biomedicine, MEMBRANES, Health (H.O.G., C.S., V.V.M.), Aarhus University, Denmark
| | - Nina Kerting Iversen
- Center of Functionally Integrative Neuroscience, Institute for Clinical Medicine (N.K.I.), Aarhus University, Denmark
| | - Dmitry D Postnov
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, Copenhagen University, Denmark (D.D.P.)
| | - Vladimir V Matchkov
- Department of Biomedicine, MEMBRANES, Health (H.O.G., C.S., V.V.M.), Aarhus University, Denmark
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Teggi R, Colombo B, Zagato L, Filippi M. Could ionic regulation disorders explain the overlap between meniere's disease and migraine? J Vestib Res 2021; 31:297-301. [PMID: 33579883 DOI: 10.3233/ves-200788] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Ménière's disease (MD) is an inner ear disorder characterized by a burden of symptoms and comorbidities, including migraine. In both disorders, ionic dysregulation may play a role as a predisposing factor. In recent years. aquaporins have been widely investigated, but the results are far from conclusive. We recently studied the genetics of ionic transporters and the hormone endogenous ouabain as predisposing factors for development of MD. In particular, we found two genetic polymorphisms associated with MD: 1) rs3746951, a missense variant (Gly180Ser) in the salt-inducible kinase-1 (SIK1) gene encoding a Na+, K+ ATPase; 2) rs487119, an intronic variant of gene SLC8A1 coding for a Na+, Ca++ exchanger (NCX-1). Ionic concentration in the brain also plays a role in the pathophysiology of migraine. In this brief review we summarize what has been published on MD and migraine.
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Affiliation(s)
- Roberto Teggi
- Division of Otolaryngology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Bruno Colombo
- Units of Neurology and Neurophysiology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Laura Zagato
- Genomics of Renal Diseases and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Massimo Filippi
- Units of Neurology and Neurophysiology, IRCCS San Raffaele Scientific Institute, Milan, Italy.,Neuroimaging Research Unit, INSPE, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy; Vita-SaluteSan Raffaele University, Milan, Italy
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9
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Blaustein MP, Hamlyn JM. Ouabain, endogenous ouabain and ouabain-like factors: The Na + pump/ouabain receptor, its linkage to NCX, and its myriad functions. Cell Calcium 2020; 86:102159. [PMID: 31986323 DOI: 10.1016/j.ceca.2020.102159] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 01/01/2020] [Accepted: 01/03/2020] [Indexed: 12/12/2022]
Abstract
In this brief review we discuss some aspects of the Na+ pump and its roles in mediating the effects of ouabain and endogenous ouabain (EO): i) in regulating the cytosolic Ca2+ concentration ([Ca2+]CYT) via Na/Ca exchange (NCX), and ii) in activating a number of protein kinase (PK) signaling cascades that control a myriad of cell functions. Importantly, [Ca2+]CYT and the other signaling pathways intersect at numerous points because of the influence of Ca2+ and calmodulin in modulating some steps in those other pathways. While both mechanisms operate in virtually all cells and tissues, this article focuses primarily on their functions in the cardiovascular system, the central nervous system (CNS) and the kidneys.
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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.
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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10
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Erratum. Acta Physiol (Oxf) 2019; 227:e13343. [PMID: 31402596 DOI: 10.1111/apha.13343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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11
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Endolymphatic hydrops and ionic transporters: genetic and biohumoral aspects. J Neurol 2019; 266:47-51. [DOI: 10.1007/s00415-019-09399-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 05/18/2019] [Accepted: 05/23/2019] [Indexed: 12/15/2022]
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12
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Staehr C, Rajanathan R, Matchkov VV. Involvement of the Na + ,K + -ATPase isoforms in control of cerebral perfusion. Exp Physiol 2019; 104:1023-1028. [PMID: 30768809 DOI: 10.1113/ep087519] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/11/2019] [Indexed: 12/11/2022]
Abstract
NEW FINDINGS What is the topic of this review? In this review, we consider the role of the Na+ ,K+ -ATPase in cerebrovascular function and how it might be changed in familial hemiplegic migraine type 2 (FHM2). The primary focus is involvement of the Na+ ,K+ -ATPase isoforms in regulation of cerebrovascular tone. What advances does it highlight? In this review, we discuss three overall distinct mechanisms whereby the Na+ ,K+ -ATPase might be capable of regulating cerebrovascular tone. Furthermore, we discuss how changes in the Na+ ,K+ -ATPase in cerebral arteries might affect brain perfusion and thereby be involved in the pathology of FHM2. ABSTRACT Familial hemiplegic migraine type 2 (FHM2) has been characterized by biphasic changes in cerebral blood flow during a migraine attack, with initial hypoperfusion followed by abnormal hyperperfusion of the affected hemisphere. We suggested that FHM2-associated loss-of-function mutation(s) in the Na+ ,K+ -ATPase α2 isoform might be responsible for these biphasic changes in several ways. We found that reduced expression of the α2 isoform leads to sensitization of the contractile machinery to [Ca2+ ]i via Src kinase-dependent signal transduction. This change in sensitivity might be the underlying mechanism for both abnormally potentiated vasoconstriction and exaggerated vasorelaxation. Moreover, the functional significance of the Na+ ,K+ -ATPase α2 isoform in astrocytes provides for the possibility of elevated extracellular potassium signalling from astrocytic endfeet to the vascular wall in neurovascular coupling.
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Affiliation(s)
- Christian Staehr
- Department of Biomedicine, Health, Aarhus University, Aarhus C, Denmark
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13
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Abstract
The Na,K-ATPase is an enzyme essential for ion homeostasis in all cells. Over the last decades, it has been well-established that in addition to the transport of Na+/K+ over the cell membrane, the Na,K-ATPase acts as a receptor transducing humoral signals intracellularly. It has been suggested that ouabain-like compounds serve as endogenous modulators of this Na,K-ATPase signal transduction. The molecular mechanisms underlying Na,K-ATPase signaling are complicated and suggest the confluence of divergent biological pathways. This review discusses recent updates on the Na,K-ATPase signaling pathways characterized or suggested in vascular smooth muscle cells. The conventional view on this signaling is based on a microdomain structure where the Na,K-ATPase controls the Na,Ca-exchanger activity via modulation of intracellular Na+ in the spatially restricted submembrane space. This, in turn, affects intracellular Ca2+ and Ca2+ load in the sarcoplasmic reticulum leading to modulation of contractility as well as gene expression. An ion-transport-independent signal transduction from the Na,K-ATPase is based on molecular interactions. This was primarily characterized in other cell types but recently also demonstrated in vascular smooth muscles. The downstream signaling from the Na,K-ATPase includes Src and phosphatidylinositol-4,5-bisphosphate 3 kinase signaling pathways and generation of reactive oxygen species. Moreover, in vascular smooth muscle cells the interaction between the Na,K-ATPase and proteins responsible for Ca2+ homeostasis, e.g., phospholipase C and inositol triphosphate receptors, contributes to an integration of the signaling pathways. Recent update on the Na,K-ATPase dependent intracellular signaling and the significance for physiological functions and pathophysiological changes are discussed in this review.
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14
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Schubert R. The second life of ion transporters as signal transducers. Acta Physiol (Oxf) 2018; 224:e13155. [PMID: 29938912 DOI: 10.1111/apha.13155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- R Schubert
- Cardiovascular Physiology, Centre for Biomedicine and Medical Technology Mannheim (CBTM), European Center of Angioscience (ECAS), Ruprecht-Karls-University Heidelberg, Mannheim, Germany
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15
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The Na,K-ATPase-Dependent Src Kinase Signaling Changes with Mesenteric Artery Diameter. Int J Mol Sci 2018; 19:ijms19092489. [PMID: 30142894 PMCID: PMC6164810 DOI: 10.3390/ijms19092489] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 08/17/2018] [Accepted: 08/21/2018] [Indexed: 01/09/2023] Open
Abstract
Inhibition of the Na,K-ATPase by ouabain potentiates vascular tone and agonist-induced contraction. These effects of ouabain varies between different reports. In this study, we assessed whether the pro-contractile effect of ouabain changes with arterial diameter and the molecular mechanism behind it. Rat mesenteric small arteries of different diameters (150–350 µm) were studied for noradrenaline-induced changes of isometric force and intracellular Ca2+ in smooth muscle cells. These functional changes were correlated to total Src kinase and Src phosphorylation assessed immunohistochemically. High-affinity ouabain-binding sites were semi-quantified with fluorescent ouabain. We found that potentiation of noradrenaline-sensitivity by ouabain correlates positively with an increase in arterial diameter. This was not due to differences in intracellular Ca2+ responses but due to sensitization of smooth muscle cell contractile machinery to Ca2+. This was associated with ouabain-induced Src activation, which increases with increasing arterial diameter. Total Src expression was similar in arteries of different diameters but the density of high-affinity ouabain binding sites increased with increasing arterial diameters. We suggested that ouabain binding induces more Src kinase activity in mesenteric small arteries with larger diameter leading to enhanced sensitization of the contractile machinery to Ca2+.
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