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Sibarov DA, Zhuravleva ZD, Ilina MA, Boikov SI, Stepanenko YD, Karelina TV, Antonov SM. Unveiling the Role of Cholesterol in Subnanomolar Ouabain Rescue of Cortical Neurons from Calcium Overload Caused by Excitotoxic Insults. Cells 2023; 12:2011. [PMID: 37566090 PMCID: PMC10417153 DOI: 10.3390/cells12152011] [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: 07/12/2023] [Revised: 07/31/2023] [Accepted: 08/04/2023] [Indexed: 08/12/2023] Open
Abstract
Na/K-ATPase maintains transmembrane ionic gradients and acts as a signal transducer when bound to endogenous cardiotonic steroids. At subnanomolar concentrations, ouabain induces neuroprotection against calcium overload and apoptosis of neurons during excitotoxic stress. Here, the role of lipid rafts in interactions between Na/K-ATPase, sodium-calcium exchanger (NCX), and N-methy-D-aspartate receptors (NMDARs) was investigated. We analyzed 0.5-1-nanometer ouabain's effects on calcium responses and miniature post-synaptic current (mEPSCs) frequencies of cortical neurons during the action of NMDA in rat primary culture and brain slices. In both objects, ouabain attenuated NMDA-evoked calcium responses and prevented an increase in mEPSC frequency, while the cholesterol extraction by methyl-β-cyclodextrin prevented the effects. The data support the conclusions that (i) ouabain-induced inhibition of NMDA-elicited calcium response involves both pre- and post-synapse, (ii) the presence of astrocytes in the tripartite synapse is not critical for the ouabain effects, which are found to be similar in cell cultures and brain slices, and (iii) ouabain action requires the integrity of cholesterol-rich membrane microdomains in which the colocalization and functional interaction of NMDAR-transferred calcium influx, calcium extrusion by NCX, and Na/K-ATPase modulation of the exchanger occur. This regulation of the molecules by cardiotonic steroids may influence synaptic transmission, prevent excitotoxic neuronal death, and interfere with the pharmacological actions of neurological medicines.
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Affiliation(s)
| | | | | | | | | | | | - Sergei M. Antonov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Torez pr. 44, 194223 Saint-Petersburg, Russia; (D.A.S.); (Z.D.Z.); (M.A.I.); (S.I.B.); (Y.D.S.); (T.V.K.)
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2
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Circulating Ouabain Modulates Expression of Claudins in Rat Intestine and Cerebral Blood Vessels. Int J Mol Sci 2020; 21:ijms21145067. [PMID: 32709081 PMCID: PMC7404321 DOI: 10.3390/ijms21145067] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 07/13/2020] [Accepted: 07/14/2020] [Indexed: 12/20/2022] Open
Abstract
The ability of exogenous low ouabain concentrations to affect claudin expression and therefore epithelial barrier properties was demonstrated previously in cultured cell studies. We hypothesized that chronic elevation of circulating ouabain in vivo can affect the expression of claudins and tight junction permeability in different tissues. We tested this hypothesis in rats intraperitoneally injected with ouabain (1 μg/kg) for 4 days. Rat jejunum, colon and brain frontal lobes, which are variable in the expressed claudins and tight junction permeability, were examined. Moreover, the porcine jejunum cell line IPEC-J2 was studied. In IPEC-J2-cells, ouabain (10 nM, 19 days of incubation) stimulated epithelial barrier formation, increased transepithelial resistance and the level of cSrc-kinase activation by phosphorylation, accompanied with an increased expression of claudin-1, -5 and down-regulation of claudin-12; the expression of claudin-3, -4, -8 and tricellulin was not changed. In the jejunum, chronic ouabain increased the expression of claudin-1, -3 and -5 without an effect on claudin-2 and -4 expression. In the colon, only down-regulation of claudin-3 was observed. Chronic ouabain protected the intestine transepithelial resistance against functional injury induced by lipopolysaccharide treatment or by modeled acute microgravity; this regulation was most pronounced in the jejunum. Claudin-1 was also up-regulated in cerebral blood vessels. This was associated with reduction of claudin-3 expression while the expression of claudin-5 and occludin was not affected. Altogether, our results confirm that circulating ouabain can functionally and tissue-specifically affect barrier properties of epithelial and endothelial tissues via Na,K-ATPase-mediated modulation of claudins expression.
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Akkuratov EE, Westin L, Vazquez-Juarez E, de Marothy M, Melnikova AK, Blom H, Lindskog M, Brismar H, Aperia A. Ouabain Modulates the Functional Interaction Between Na,K-ATPase and NMDA Receptor. Mol Neurobiol 2020; 57:4018-4030. [PMID: 32651756 PMCID: PMC7467916 DOI: 10.1007/s12035-020-01984-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 06/08/2020] [Indexed: 12/18/2022]
Abstract
The N-methyl-D-aspartate (NMDA) receptor plays an essential role in glutamatergic transmission and synaptic plasticity and researchers are seeking for different modulators of NMDA receptor function. One possible mechanism for its regulation could be through adjacent membrane proteins. NMDA receptors coprecipitate with Na,K-ATPase, indicating a potential interaction of these two proteins. Ouabain, a mammalian cardiotonic steroid that specifically binds to Na,K-ATPase and affects its conformation, can protect from some toxic effects of NMDA receptor activation. Here we have examined whether NMDA receptor activity and downstream effects can be modulated by physiological ouabain concentrations. The spatial colocalization between NMDA receptors and the Na,K-ATPase catalytic subunits on dendrites of cultured rat hippocampal neurons was analyzed with super-resolution dSTORM microscopy. The functional interaction was analyzed with calcium imaging of single hippocampal neurons exposed to 10 μM NMDA in presence and absence of ouabain and by determination of the ouabain effect on NMDA receptor–dependent long-term potentiation. We show that NMDA receptors and the Na,K-ATPase catalytic subunits alpha1 and alpha3 exist in same protein complex and that ouabain in nanomolar concentration consistently reduces the calcium response to NMDA. Downregulation of the NMDA response is not associated with internalization of the receptor or with alterations in its state of Src phosphorylation. Ouabain in nanomolar concentration elicits a long-term potentiation response. Our findings suggest that ouabain binding to a fraction of Na,K-ATPase molecules that cluster with the NMDA receptors will, via a conformational effect on the NMDA receptors, cause moderate but consistent reduction of NMDA receptor response at synaptic activation.
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Affiliation(s)
- Evgeny E Akkuratov
- Science for Life Laboratory, Department of Applied Physics, Kungliga Tekniska Högskolan, Stockholm, Sweden
| | - Linda Westin
- Science for Life Laboratory, Department of Women's and Children's health, Karolinska Institutet, Stockholm, Sweden
| | - Erika Vazquez-Juarez
- Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Minttu de Marothy
- Science for Life Laboratory, Department of Women's and Children's health, Karolinska Institutet, Stockholm, Sweden
| | - Aleksandra K Melnikova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia, 119234
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Kungliga Tekniska Högskolan, Stockholm, Sweden
| | - Maria Lindskog
- Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Kungliga Tekniska Högskolan, Stockholm, Sweden.
| | - Anita Aperia
- Science for Life Laboratory, Department of Women's and Children's health, Karolinska Institutet, Stockholm, Sweden
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Shi M, Cao L, Cao X, Zhu M, Zhang X, Wu Z, Xiong S, Xie Z, Yang Y, Chen J, Wong PTH, Bian JS. DR-region of Na +/K + ATPase is a target to treat excitotoxicity and stroke. Cell Death Dis 2018; 10:6. [PMID: 30584244 PMCID: PMC6315034 DOI: 10.1038/s41419-018-1230-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 11/20/2018] [Accepted: 11/21/2018] [Indexed: 12/13/2022]
Abstract
Na+/K+ ATPase (NKA) is important in maintaining cellular functions. We found that loss of NKA activities in NKAα1+/− mice is associated with increased susceptibility to ischemic injuries following transient middle cerebral artery occlusion (tMCAO). This is corroborated by the neuroprotective effects of an antibody raised against an extracellular DR region (897DVEDSYGQQWTYEQR911, sequence number as in rat) of NKAα subunit (DR-Ab) in both preventive and therapeutic settings. DR-Ab protects cortical neurons against glutamate-induced toxicity by stimulating activities of NKA and Na+/Ca2+ exchanger (NCX), which resulted in accelerated Ca2+ extrusion. DR-Ab also enhanced the association between NKA and GluR2 and therefore reduced the internalization of both proteins from membrane induced by glutamate toxicity. The mechanism appears to involve suppression of GluR2 phosphorylation through PKCα/PICK pathway. Our data indicate that DR-region of NKA may be a novel therapeutic target for drug development for the treatment of ischemic stroke.
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Affiliation(s)
- Meimei Shi
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Lei Cao
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Xu Cao
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Mengyuan Zhu
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Xingzhou Zhang
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Zhiyuan Wu
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Siping Xiong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Zhizhong Xie
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Yong Yang
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, Center for New Drug Safety Evaluation and Research, China Pharmaceutical University, Nanjing, 211198, China
| | - Jingyu Chen
- Lung Transplant Group, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, 214021, Jiangsu, PR China
| | - Peter T H Wong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore
| | - Jin-Song Bian
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117600, Singapore. .,National University of Singapore (Suzhou) Research Institute, Suzhou, 215123, China.
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Hu HJ, Song M. Disrupted Ionic Homeostasis in Ischemic Stroke and New Therapeutic Targets. J Stroke Cerebrovasc Dis 2017; 26:2706-2719. [PMID: 29054733 DOI: 10.1016/j.jstrokecerebrovasdis.2017.09.011] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 08/30/2017] [Accepted: 09/06/2017] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Stroke is a leading cause of long-term disability. All neuroprotectants targeting excitotoxicity have failed to become stroke medications. In order to explore and identify new therapeutic targets for stroke, we here reviewed present studies of ionic transporters and channels that are involved in ischemic brain damage. METHOD We surveyed recent literature from animal experiments and clinical reports in the databases of PubMed and Elsevier ScienceDirect to analyze ionic mechanisms underlying ischemic cell damage and suggest promising ideas for stroke therapy. RESULTS Dysfunction of ionic transporters and disrupted ionic homeostasis are most early changes that underlie ischemic brain injury, thus receiving sustained attention in translational stroke research. The Na+/K+-ATPase, Na+/Ca2+ Exchanger, ionotropic glutamate receptor, acid-sensing ion channels (ASICs), sulfonylurea receptor isoform 1 (SUR1)-regulated NCCa-ATP channels, and transient receptor potential (TRP) channels are critically involved in ischemia-induced cellular degenerating processes such as cytotoxic edema, excitotoxicity, necrosis, apoptosis, and autophagic cell death. Some ionic transporters/channels also act as signalosomes to regulate cell death signaling. For acute stroke treatment, glutamate-mediated excitotoxicity must be interfered within 2 hours after stroke. The SUR1-regulated NCCa-ATP channels, Na+/K+-ATPase, ASICs, and TRP channels have a much longer therapeutic window, providing new therapeutic targets for developing feasible pharmacological treatments toward acute ischemic stroke. CONCLUSION The next generation of stroke therapy can apply a polypharmacology strategy for which drugs are designed to target multiple ion transporters/channels or their interaction with neurotoxic signaling pathways. But a successful translation of neuroprotectants relies on in-depth analyses of cell death mechanisms and suitable animal models resembling human stroke.
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Affiliation(s)
- Hui-Jie Hu
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Mingke Song
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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6
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Dorard E, Chasseigneaux S, Gorisse-Hussonnois L, Broussard C, Pillot T, Allinquant B. Soluble Amyloid Precursor Protein Alpha Interacts with alpha3-Na, K-ATPAse to Induce Axonal Outgrowth but Not Neuroprotection: Evidence for Distinct Mechanisms Underlying these Properties. Mol Neurobiol 2017; 55:5594-5610. [PMID: 28983842 DOI: 10.1007/s12035-017-0783-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 09/20/2017] [Indexed: 01/09/2023]
Abstract
Amyloid precursor protein (APP) is cleaved not only to generate the amyloid peptide (Aß), involved in neurodegenerative processes, but can also be metabolized by alpha secretase to produce and release soluble N-terminal APP (sAPPα), which has many properties including the induction of axonal elongation and neuroprotection. The mechanisms underlying the properties of sAPPα are not known. Here, we used proteomic analysis of mouse cortico-hippocampal membranes to identify the neuronal specific alpha3 (α3)-subunit of the plasma membrane enzyme Na, K-ATPase (NKA) as a new binding partner of sAPPα. We showed that sAPPα recruits very rapidly clusters of α3-NKA at neuronal surface, and its binding triggers a cascade of events promoting sAPPα-induced axonal outgrowth. The binding of sAPPα with α3-NKA was not observed for sAPPα-induced Aß1-42 oligomers neuroprotection, neither the downstream events particularly the interaction of sAPPα with APP before endocytosis, ERK signaling, and the translocation of SET from the nucleus to the plasma membrane. These data suggest that the mechanisms of the axonal growth promoting and neuroprotective properties of sAPPα appear to be specific and independent. The signals at the cell surface specific to trigger these mechanisms require further study.
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Affiliation(s)
- Emilie Dorard
- UMR_S894 INSERM, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, 75014, Paris, France.,SynAging, 54500, Vandoeuvre-les, Nancy, France
| | - Stéphanie Chasseigneaux
- UMR_S894 INSERM, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, 75014, Paris, France.,INSERM U1144, Université Paris Descartes and Université Paris Diderot UMR-S 1144, 75006, Paris, France
| | - Lucie Gorisse-Hussonnois
- UMR_S894 INSERM, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, 75014, Paris, France
| | - Cédric Broussard
- Plate-forme Protéomique, Université Paris Descartes 3P5, Institut Cochin, 75014, Paris, France
| | | | - Bernadette Allinquant
- UMR_S894 INSERM, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, 75014, Paris, France.
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7
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Alpha 2 Na +,K +-ATPase silencing induces loss of inflammatory response and ouabain protection in glial cells. Sci Rep 2017; 7:4894. [PMID: 28687727 PMCID: PMC5501845 DOI: 10.1038/s41598-017-05075-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 05/24/2017] [Indexed: 12/12/2022] Open
Abstract
Ouabain (OUA) is a cardiac glycoside that binds to Na+,K+-ATPase (NKA), a conserved membrane protein that controls cell transmembrane ionic concentrations and requires ATP hydrolysis. At nM concentrations, OUA activates signaling pathways that are not related to its typical inhibitory effect on the NKA pump. Activation of these signaling pathways protects against some types of injury of the kidneys and central nervous system. There are 4 isoforms of the alpha subunit of NKA, which are differentially distributed across tissues and may have different physiological roles. Glial cells are important regulators of injury and inflammation in the brain and express the α1 and α2 NKA isoforms. This study investigated the role of α2 NKA in OUA modulation of the neuroinflammatory response induced by lipopolysaccharide (LPS) in mouse primary glial cell cultures. LPS treatment increased lactate dehydrogenase release, while OUA did not decrease cell viability and blocked LPS-induced NF-κB activation. Silencing α2 NKA prevented ERK and NF-κB activation by LPS. α2 NKA also regulates TNF-α and IL-1β levels. The data reported here indicate a significant role of α2 NKA in regulating central LPS effects, with implications in the associated neuroinflammatory processes.
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8
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Plössl K, Royer M, Bernklau S, Tavraz NN, Friedrich T, Wild J, Weber BHF, Friedrich U. Retinoschisin is linked to retinal Na/K-ATPase signaling and localization. Mol Biol Cell 2017; 28:2178-2189. [PMID: 28615319 PMCID: PMC5531734 DOI: 10.1091/mbc.e17-01-0064] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 06/02/2017] [Accepted: 06/06/2017] [Indexed: 01/30/2023] Open
Abstract
Retinoschisin binds to the extracellular domain of Na/K-ATPase subunit β2. Retinoschisin inhibits Na/K-ATPase–associated signaling cascades and affects Na/K-ATPase localization. The retinoschisin-Na/K-ATPase complex overlaps with signaling mediators. Defective Na/K-ATPase signaling by retinoschisin deficiency may promote retinal dystrophy. Mutations in the RS1 gene cause X-linked juvenile retinoschisis (XLRS), a hereditary retinal dystrophy. We recently showed that retinoschisin, the protein encoded by RS1, regulates ERK signaling and apoptosis in retinal cells. In this study, we explored an influence of retinoschisin on the functionality of the Na/K-ATPase, its interaction partner at retinal plasma membranes. We show that retinoschisin binding requires the β2-subunit of the Na/K-ATPase, whereas the α-subunit is exchangeable. Our investigations revealed no effect of retinoschisin on Na/K-ATPase–mediated ATP hydrolysis and ion transport. However, we identified an influence of retinoschisin on Na/K-ATPase–regulated signaling cascades and Na/K-ATPase localization. In addition to the known ERK deactivation, retinoschisin treatment of retinoschisin-deficient (Rs1h-/Y) murine retinal explants decreased activation of Src, an initial transmitter in Na/K-ATPase signal transduction, and of Ca2+ signaling marker Camk2. Immunohistochemistry on murine retinae revealed an overlap of the retinoschisin–Na/K-ATPase complex with proteins involved in Na/K-ATPase signaling, such as caveolin, phospholipase C, Src, and the IP3 receptor. Finally, retinoschisin treatment altered Na/K-ATPase localization in photoreceptors of Rs1h-/Y retinae. Taken together, our results suggest a regulatory effect of retinoschisin on Na/K-ATPase signaling and localization, whereas Na/K-ATPase-dysregulation caused by retinoschisin deficiency could represent an initial step in XLRS pathogenesis.
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Affiliation(s)
- Karolina Plössl
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Melanie Royer
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Sarah Bernklau
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Neslihan N Tavraz
- Institute of Chemistry, Technical University of Berlin, 10623 Berlin, Germany
| | - Thomas Friedrich
- Institute of Chemistry, Technical University of Berlin, 10623 Berlin, Germany
| | - Jens Wild
- Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg, University of Regensburg, 93053 Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Ulrike Friedrich
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
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9
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Cui X, Xie Z. Protein Interaction and Na/K-ATPase-Mediated Signal Transduction. Molecules 2017; 22:molecules22060990. [PMID: 28613263 PMCID: PMC6152704 DOI: 10.3390/molecules22060990] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 06/01/2017] [Accepted: 06/02/2017] [Indexed: 02/05/2023] Open
Abstract
The Na/K-ATPase (NKA), or Na pump, is a member of the P-type ATPase superfamily. In addition to pumping ions across cell membrane, it is engaged in assembly of multiple protein complexes in the plasma membrane. This assembly allows NKA to perform many non-pumping functions including signal transduction that are important for animal physiology and disease progression. This article will focus on the role of protein interaction in NKA-mediated signal transduction, and its potential utility as target for developing new therapeutics.
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Affiliation(s)
- Xiaoyu Cui
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV 25703, USA.
| | - Zijian Xie
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV 25703, USA.
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10
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Lopachev AV, Lopacheva OM, Osipova EA, Vladychenskaya EA, Smolyaninova LV, Fedorova TN, Koroleva OV, Akkuratov EE. Ouabain-induced changes in MAP kinase phosphorylation in primary culture of rat cerebellar cells. Cell Biochem Funct 2017; 34:367-77. [PMID: 27338714 DOI: 10.1002/cbf.3199] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 05/21/2016] [Accepted: 05/23/2016] [Indexed: 02/06/2023]
Abstract
Cardiotonic steroid (CTS) ouabain is a well-established inhibitor of Na,K-ATPase capable of inducing signalling processes including changes in the activity of the mitogen activated protein kinases (MAPK) in various cell types. With increasing evidence of endogenous CTS in the blood and cerebrospinal fluid, it is of particular interest to study ouabain-induced signalling in neurons, especially the activation of MAPK, because they are the key kinases activated in response to extracellular signals and regulating cell survival, proliferation and apoptosis. In this study we investigated the effect of ouabain on the level of phosphorylation of three MAPK (ERK1/2, JNK and p38) and on cell survival in the primary culture of rat cerebellar cells. Using Western blotting we described the time course and concentration dependence of phosphorylation for ERK1/2, JNK and p38 in response to ouabain. We discovered that ouabain at a concentration of 1 μM does not cause cell death in cultured neurons while it changes the phosphorylation level of the three MAPK: ERK1/2 is phosphorylated transiently, p38 shows sustained phosphorylation, and JNK is dephosphorylated after a long-term incubation. We showed that ERK1/2 phosphorylation increase does not depend on ouabain-induced calcium increase and p38 activation. Changes in p38 phosphorylation, which is independent from ERK1/2 activation, are calcium dependent. Changes in JNK phosphorylation are calcium dependent and also depend on ERK1/2 and p38 activation. Ten-micromolar ouabain leads to cell death, and we conclude that different effects of 1-μM and 10-μM ouabain depend on different ERK1/2 and p38 phosphorylation profiles. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Alexander V Lopachev
- Research Center of Neurology, Moscow, Russia.,Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Olga M Lopacheva
- Research Center of Neurology, Moscow, Russia.,Lomonosov Moscow State University, International Biotechnological Center, Moscow, Russia
| | - Ekaterina A Osipova
- Lomonosov Moscow State University, International Biotechnological Center, Moscow, Russia.,Lomonosov Moscow State University, Faculty of Chemistry, Department of Chemical Enzymology, Moscow, Russia
| | | | - Larisa V Smolyaninova
- Lomonosov Moscow State University, International Biotechnological Center, Moscow, Russia.,Lomonosov Moscow State University, Faculty of Biology, Department of Biochemistry, Moscow, Russia
| | | | - Olga V Koroleva
- Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Evgeny E Akkuratov
- St. Petersburg State University, Institute of Translational Biomedicine, St. Petersburg, Russia
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11
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Kinoshita PF, Leite JA, Orellana AMM, Vasconcelos AR, Quintas LEM, Kawamoto EM, Scavone C. The Influence of Na(+), K(+)-ATPase on Glutamate Signaling in Neurodegenerative Diseases and Senescence. Front Physiol 2016; 7:195. [PMID: 27313535 PMCID: PMC4890531 DOI: 10.3389/fphys.2016.00195] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 05/17/2016] [Indexed: 12/17/2022] Open
Abstract
Decreased Na(+), K(+)-ATPase (NKA) activity causes energy deficiency, which is commonly observed in neurodegenerative diseases. The NKA is constituted of three subunits: α, β, and γ, with four distinct isoforms of the catalytic α subunit (α1-4). Genetic mutations in the ATP1A2 gene and ATP1A3 gene, encoding the α2 and α3 subunit isoforms, respectively can cause distinct neurological disorders, concurrent to impaired NKA activity. Within the central nervous system (CNS), the α2 isoform is expressed mostly in glial cells and the α3 isoform is neuron-specific. Mutations in ATP1A2 gene can result in familial hemiplegic migraine (FHM2), while mutations in the ATP1A3 gene can cause Rapid-onset dystonia-Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC), as well as the cerebellar ataxia, areflexia, pescavus, optic atrophy and sensorineural hearing loss (CAPOS) syndrome. Data indicates that the central glutamatergic system is affected by mutations in the α2 isoform, however further investigations are required to establish a connection to mutations in the α3 isoform, especially given the diagnostic confusion and overlap with glutamate transporter disease. The age-related decline in brain α2∕3 activity may arise from changes in the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase (PKG) pathway. Glutamate, through nitric oxide synthase (NOS), cGMP and PKG, stimulates brain α2∕3 activity, with the glutamatergic N-methyl-D-aspartate (NMDA) receptor cascade able to drive an adaptive, neuroprotective response to inflammatory and challenging stimuli, including amyloid-β. Here we review the NKA, both as an ion pump as well as a receptor that interacts with NMDA, including the role of NKA subunits mutations. Failure of the NKA-associated adaptive response mechanisms may render neurons more susceptible to degeneration over the course of aging.
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Affiliation(s)
- Paula F. Kinoshita
- Department of Pharmacology, Institute of Biomedical Science, University of São PauloSão Paulo, Brazil
| | - Jacqueline A. Leite
- Department of Pharmacology, Institute of Biomedical Science, University of São PauloSão Paulo, Brazil
| | - Ana Maria M. Orellana
- Department of Pharmacology, Institute of Biomedical Science, University of São PauloSão Paulo, Brazil
| | - Andrea R. Vasconcelos
- Department of Pharmacology, Institute of Biomedical Science, University of São PauloSão Paulo, Brazil
| | - Luis E. M. Quintas
- Laboratory of Biochemical and Molecular Pharmacology, Institute of Biomedical Sciences, Federal University of Rio de JaneiroRio de Janeiro, Brazil
| | - Elisa M. Kawamoto
- Department of Pharmacology, Institute of Biomedical Science, University of São PauloSão Paulo, Brazil
| | - Cristoforo Scavone
- Department of Pharmacology, Institute of Biomedical Science, University of São PauloSão Paulo, Brazil
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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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Garcia IJP, Kinoshita PF, Scavone C, Mignaco JA, de Oliveira Barbosa LA, de Lima Santos H. Ouabain Modulates the Lipid Composition of Hippocampal Plasma Membranes from Rats with LPS-induced Neuroinflammation. J Membr Biol 2015; 248:1191-8. [DOI: 10.1007/s00232-015-9840-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 09/04/2015] [Indexed: 12/21/2022]
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Kinoshita PF, Yshii LM, Vasconcelos AR, Orellana AMM, Lima LDS, Davel APC, Rossoni LV, Kawamoto EM, Scavone C. Signaling function of Na,K-ATPase induced by ouabain against LPS as an inflammation model in hippocampus. J Neuroinflammation 2014; 11:218. [PMID: 25551197 PMCID: PMC4307894 DOI: 10.1186/s12974-014-0218-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Accepted: 12/08/2014] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Ouabain (OUA) is a newly recognized hormone that is synthesized in the adrenal cortex and hypothalamus. Low doses of OUA can activate a signaling pathway by interaction with Na,K-ATPase, which is protective against a number of insults. OUA has central and peripheral anti-inflammatory effects. Lipopolysaccharide (LPS), via toll-like receptor 4 activation, is a widely used model to induce systemic inflammation. This study used a low OUA dose to evaluate its effects on inflammation induced by LPS injection in rats. METHODS Adult male Wistar rats received acute intraperitoneal (ip) OUA (1.8 μg/kg) or saline 20 minutes before LPS (200 μg/kg, ip) or saline injection. Some of the animals had their femoral artery catheterized in order to assess arterial blood pressure values before and after OUA administration. Na,K-ATPase activity, cytokine mRNA levels, apoptosis-related proteins, NF-κB activation brain-derived neurotrophic factor BDNF, corticosterone and TNF-α levels were measured. RESULTS OUA pretreatment decreased mRNA levels of the pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and IL-1β, which are activated by LPS in the hippocampus, but with no effect on serum measures of these factors. None of these OUA effects were linked to Na,K-ATPase activity. The involvement of the inflammatory transcription factor NF-κB in the OUA effect was indicated by its prevention of LPS-induced nuclear translocation of the NF-κB subunit, RELA (p65), as well as the decreased cytosol levels of the NF-κB inhibitor, IKB, in the hippocampus. OUA pretreatment reversed the LPS-induced glial fibrillary acidic protein (GFAP) activation and associated inflammation in the dentate gyrus. OUA also prevented LPS-induced increases in the hippocampal Bax/Bcl2 ratio suggesting an anti-apoptotic action in the brain. CONCLUSION Our results suggest that a low dose of OUA has an important anti-inflammatory effect in the rat hippocampus. This effect was associated with decreased GFAP induction by LPS in the dentate gyrus, a brain area linked to adult neurogenesis.
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Affiliation(s)
- Paula Fernanda Kinoshita
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil.
| | - Lidia Mitiko Yshii
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil.
| | - Andrea Rodrigues Vasconcelos
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil.
| | - Ana Maria Marques Orellana
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil.
| | - Larissa de Sá Lima
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil.
| | - Ana Paula Couto Davel
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
| | - Luciana Venturini Rossoni
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
| | - Elisa Mitiko Kawamoto
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil.
| | - Cristoforo Scavone
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil.
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Krivoi II. Functional interactions of Na,K-ATPase with molecular environment. Biophysics (Nagoya-shi) 2014. [DOI: 10.1134/s000635091405011x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
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Takechi M, Wada T, Yagi H, Masuko T, Kawabata A. Ouabain exerts cytoprotection by diminishing the intracellular K(+) concentration increase caused by distinct stimuli in human leukemic cells. J Pharm Pharmacol 2014; 67:126-32. [PMID: 25208542 DOI: 10.1111/jphp.12317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 08/03/2014] [Indexed: 11/30/2022]
Abstract
OBJECTIVES We tested if modulation of cytosolic K(+) levels by ouabain, an inhibitor of Na(+) /K(+) -ATPase, exerts cytoprotection against distinct stressful stimuli in human leukemic cells. METHODS The cytosolic K(+) , Na(+) or Ca(2+) levels and the cytotoxicity were evaluated by flow cytometry. KEY FINDINGS Various cytotoxic chemicals and ultraviolet irradiation induced cell death and increased intracellular concentrations of K(+) , Na(+) or Ca(2+) . Ouabain reduced the cytotoxicity and the elevation of cytosolic levels of K(+) but not those of Na(+) or Ca(2+) . CONCLUSIONS Our data thus suggest that elevated cytosolic K(+) levels are associated with the cytotoxicity in response to distinct stressful stimuli and that ouabain exerts cytoprotection most probably by regulating intracellular K(+) levels.
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Affiliation(s)
- Masayuki Takechi
- Faculty of Pharmacy, Kinki University, Higashiosaka, Osaka, Japan
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Changes in the Distribution of the α 3 Na(+)/K(+) ATPase Subunit in Heterozygous Lurcher Purkinje Cells as a Genetic Model of Chronic Depolarization during Development. Int J Cell Biol 2014; 2014:152645. [PMID: 24719618 PMCID: PMC3955620 DOI: 10.1155/2014/152645] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 12/28/2013] [Accepted: 01/13/2014] [Indexed: 11/30/2022] Open
Abstract
A common assumption of excitotoxic mechanisms in the nervous system is that the ionic imbalance resulting from overstimulation of glutamate receptors and increased Na+ and Ca++ influx overwhelms cellular energy metabolic systems leading to cell death. The goal of this study was to examine how a chronic Na+ channel leak current in developing Purkinje cells in the heterozygous Lurcher mutant (+/Lc) affects the expression and distribution of the α3 subunit of the Na+/K+ ATPase pump, a key component of the homeostasis system that maintains ionic equilibrium in neurons. The expression pattern of the catalytic α3 Na+/K+ ATPase subunit was analyzed by immunohistochemistry, histochemistry, and Western Blots in wild type (WT) and +/Lc cerebella at postnatal days P10, P15, and P25 to determine if there are changes in the distribution of active Na+/K+ ATPase subunits in degenerating Purkinje cells. The results suggest that the expression of the catalytic α3 subunit is altered in chronically depolarized +/Lc Purkinje cells, although the density of active Na+/K+ ATPase pumps is not significantly altered compared with WT in the cerebellar cortex at P15, and then declines from P15 to P25 in the +/Lc cerebellum as the +/Lc Purkinje cells degenerate.
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Xie JX, Li X, Xie Z. Regulation of renal function and structure by the signaling Na/K-ATPase. IUBMB Life 2013; 65:991-8. [PMID: 24323927 PMCID: PMC5375025 DOI: 10.1002/iub.1229] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 11/08/2013] [Indexed: 12/23/2022]
Abstract
The Na/K-ATPase as an essential ion pump was discovered more than 50 years ago (Skou (1989) Biochim. Biophys. Acta 1000, 439-446; Feraille and Doucet (2001) Physiol. Rev. 81, 345-418). The signaling function of Na/K-ATPase has been gradually appreciated over the last 20 years, first from the studies of regulatory effects of ouabain on cardiac cell growth. Several reviews on this topic have been written during the last few years (Schoner and Scheiner-Bobis (2007) Am. J. Physiol. Cell. Physiol. 293, C509-C536; Xie and Cai (2003) Mol. Interv. 3, 157 - 168; Bagrov et al. (2009) Pharmacol. Rev. 61, 9-38; Tian and Xie (2008) Physiology 23, 205-211; Fontana et al. (2013) FEBS J. 280, 5450-5455; Blanco and Wallace (2013) Am. J. Physiol. Renal Physiol. 305, F797-F812). This article will focus on the molecular mechanism of Na/K-ATPase-mediated signal transduction and its potential regulatory role in renal physiology and diseases.
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Affiliation(s)
- Jeffrey X Xie
- Department of Physiology and Pharmacology, University of Toledo College of Medicine, Toledo, OH, USA
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Ouabain-induced apoptosis in cochlear hair cells and spiral ganglion neurons in vitro. BIOMED RESEARCH INTERNATIONAL 2013; 2013:628064. [PMID: 24228256 PMCID: PMC3818842 DOI: 10.1155/2013/628064] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 08/16/2013] [Indexed: 11/20/2022]
Abstract
Ouabain is a common tool to explore the pathophysiological changes in adult mammalian cochlea in vivo. In prior studies, locally administering ouabain via round window membrane demonstrated that the ototoxic effects of ouabain in vivo varied among mammalian species. Little is known about the ototoxic effects in vitro. Thus, we prepared cochlear organotypic cultures from postnatal day-3 rats and treated these cultures with ouabain at 50, 500, and 1000 μM for different time to elucidate the ototoxic effects of ouabain in vitro and to provide insights that could explain the comparative ototoxic effects of ouabain in vivo. Degeneration of cochlear hair cells and spiral ganglion neurons was evaluated by hair-cell staining and neurofilament labeling, respectively. Annexin V staining was used to detect apoptotic cells. A quantitative RT-PCR apoptosis-focused gene array determined changes in apoptosis-related genes. The results showed that ouabain-induced damage in vitro was dose and time dependent. 500 μM ouabain and 1000 μM ouabain were destructively traumatic to both spiral ganglion neurons and cochlear hair cells in an apoptotic signal-dependent pathway. The major apoptotic pathways in ouabain-induced spiral ganglion neuron apoptosis culminated in the stimulation of the p53 pathway and triggering of apoptosis by a network of proapoptotic signaling pathways.
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Ouabain activates NFκB through an NMDA signaling pathway in cultured cerebellar cells. Neuropharmacology 2013; 73:327-36. [DOI: 10.1016/j.neuropharm.2013.06.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 06/01/2013] [Accepted: 06/03/2013] [Indexed: 11/21/2022]
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Abushik PA, Sibarov DA, Eaton MJ, Skatchkov SN, Antonov SM. Kainate-induced calcium overload of cortical neurons in vitro: Dependence on expression of AMPAR GluA2-subunit and down-regulation by subnanomolar ouabain. Cell Calcium 2013; 54:95-104. [PMID: 23721822 DOI: 10.1016/j.ceca.2013.05.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 04/25/2013] [Accepted: 05/02/2013] [Indexed: 01/03/2023]
Abstract
Whereas kainate (KA)-induced neurodegeneration has been intensively investigated, the contribution of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) in neuronal Ca2+ overload ([Ca2+]i) is still controversial. Using Ca2+ imaging and patch-clamp techniques, we found different types of Ca2+ entry in cultured rat cortical neurons. The presence of Ca2+ in the extracellular solution was required to generate the [Ca2+]i responses to 30 μM N-methyl-d-aspartate (NMDA) or KA. The dynamics of NMDA-induced [Ca2+]i responses were fast, while KA-induced responses developed slower reaching high [Ca2+]i. Ifenprodil, a specific inhibitor of the GluN2B subunit of NMDARs, reduced NMDA-induced [Ca2+]i responses suggesting expression of GluN1/GluN2B receptors. Using IEM-1460, a selective blocker of Ca(2+)-permeable GluA2-subunit lacking AMPARs, we found three neuronal responses to KA: (i) IEM-1460 resistant neurons which are similar to pyramidal neurons expressing Ca(2+)-impermeable GluA2-rich AMPARs; (ii) Neurons exhibiting nearly complete block of both KA-induced currents and [Ca2+]i signals by IEM-1460 may represent interneurons expressing GluA2-lacking AMPARs and (iii) neurons with moderate sensitivity to IEM-1460. Ouabain at 1 nM prevented the neuronal Ca2+ overload induced by KA. The data suggest, that cultured rat cortical neurons maintain functional phenotypes of the adult brain cortex, and demonstrate the key contribution of the Na/K-ATPase in neuroprotection against KA excitotoxicity.
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Affiliation(s)
- Polina A Abushik
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint-Petersburg, Russian Federation
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22
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Natural products inspired synthesis of neuroprotective agents against H2O2-induced cell death. Bioorg Med Chem Lett 2013; 23:1232-7. [DOI: 10.1016/j.bmcl.2013.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 12/27/2012] [Accepted: 01/02/2013] [Indexed: 11/22/2022]
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Sibarov DA, Bolshakov AE, Abushik PA, Krivoi II, Antonov SM. Na+,K+-ATPase Functionally Interacts with the Plasma Membrane Na+,Ca2+ Exchanger to Prevent Ca2+ Overload and Neuronal Apoptosis in Excitotoxic Stress. J Pharmacol Exp Ther 2012; 343:596-607. [DOI: 10.1124/jpet.112.198341] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
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Abstract
Based on a wealth of mechanistic evidence supported by the fact that ouabain mimics the spleen-liver effect in this article, the hypothesis is established that the endogenous hormone ouabain not only mimics the effects of ischemic preconditioning but also may be an ideal drug for the prevention of ischemic diseases. Moreover, it is argued that the spleen-liver effect may represent a general protective mechanism for the protection of organisms against oxygen deficiency. Investigating the spleen-liver mechanism offers a new approach to decipher the secrets of ischemic conditioning. Preconditioning represents a basic mechanism to protect a wide variety of cells against stressful stimuli such as ischemia. The ability to undergo preconditioning is almost ubiquitous in tissues and is highly conserved across species. Reinvestigation of the "spleen-liver mechanism" will allow the study of metabolic inhibitors and hormone mimics that all could help to transform ischemic preconditioning into a cure of the epidemic ischemic heart disease. Ouabain mimics the effects of the spleen factor. Cardioprotection induced by ouabain is due to the activation of pathways that are also activated in ischemic preconditioning. Just like ischemic preconditioning, ouabain activates the reperfusion injury salvage kinase pathway. Activation of nuclear factor kappa B and other transcription factors contribute to the long lasting effects of ouabain. The endogenous hormone ouabain just like preconditioning offers multiorgan protection based on innate mechanisms, which warrants clinical investigation. Clinical studies with ouabain that correspond to current standards are warranted.
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Reactive Oxygen Species Modulation of Na/K-ATPase Regulates Fibrosis and Renal Proximal Tubular Sodium Handling. Int J Nephrol 2012; 2012:381320. [PMID: 22518311 PMCID: PMC3299271 DOI: 10.1155/2012/381320] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 11/07/2011] [Indexed: 01/11/2023] Open
Abstract
The Na/K-ATPase is the primary force regulating renal sodium handling and plays a key role in both ion homeostasis and blood pressure regulation. Recently, cardiotonic steroids (CTS)-mediated Na/K-ATPase signaling has been shown to regulate fibrosis, renal proximal tubule (RPT) sodium reabsorption, and experimental Dahl salt-sensitive hypertension in response to a high-salt diet. Reactive oxygen species (ROS) are an important modulator of nephron ion transport. As there is limited knowledge regarding the role of ROS-mediated fibrosis and RPT sodium reabsorption through the Na/K-ATPase, the focus of this review is to examine the possible role of ROS in the regulation of Na/K-ATPase activity, its signaling, fibrosis, and RPT sodium reabsorption.
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Fridman E, Lichtstein D, Rosen H. Formation of new high density glycogen-microtubule structures is induced by cardiac steroids. J Biol Chem 2012; 287:6518-29. [PMID: 22228762 DOI: 10.1074/jbc.m111.273698] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cardiac steroids (CS), an important class of naturally occurring compounds, are synthesized in plants and animals. The only established receptor for CS is the ubiquitous Na(+),K(+)-ATPase, a major plasma membrane transporter. The binding of CS to Na(+),K(+)-ATPase causes the inhibition of Na(+) and K(+) transport and elicits cell-specific activation of several intracellular signaling mechanisms. It is well documented that the interaction of CS with Na(+),K(+)-ATPase is responsible for numerous changes in basic cellular physiological properties, such as electrical plasma membrane potential, cell volume, intracellular [Ca(2+)] and pH, endocytosed membrane traffic, and the transport of other solutes. In the present study we show that CS induces the formation of dark structures adjacent to the nucleus in human NT2 and ACHN cells. These structures, which are not surrounded by membranes, are clusters of glycogen and a distorted microtubule network. Formation of these clusters results from a relocation of glycogen and microtubules in the cells, two processes that are independent of one another. The molecular mechanisms underlying the formation of the clusters are mediated by the Na(+),K(+)-ATPase, ERK1/2 signaling pathway, and an additional unknown factor. Similar glycogen clusters are induced by hypoxia, suggesting that the CS-induced structural change, described in this study, may be part of a new type of cellular stress response.
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Affiliation(s)
- Eleonora Fridman
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, the Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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Kawamoto EM, Lima LS, Munhoz CD, Yshii LM, Kinoshita PF, Amara FG, Pestana RRF, Orellana AMM, Cipolla-Neto J, Britto LRG, Avellar MCW, Rossoni LV, Scavone C. Influence of N-methyl-D-aspartate receptors on ouabain activation of nuclear factor-κB in the rat hippocampus. J Neurosci Res 2011; 90:213-28. [PMID: 22006678 DOI: 10.1002/jnr.22745] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Revised: 06/25/2011] [Accepted: 06/27/2011] [Indexed: 02/06/2023]
Abstract
It has been shown that ouabain (OUA) can activate the Na,K-ATPase complex and mediate intracellular signaling in the central nervous system (CNS). Inflammatory stimulus increases glutamatergic transmission, especially at N-methyl-D-aspartate (NMDA) receptors, which are usually coupled to the activation of nitric oxide synthase (NOS). Nuclear factor-κB (NF-κB) activation modulates the expression of genes involved in development, plasticity, and inflammation. The present work investigated the effects of OUA on NF-κB binding activity in rat hippocampus and the influence of this OUA-Na,K-ATPase signaling cascade in NMDA-mediated NF-κB activation. The findings presented here are the first report indicating that intrahippocampal administration of OUA, in a concentration that did not alter Na,K-ATPase or NOS activity, induced an activation of NF-κB, leading to increases in brain-derived neurotrophic factor (Bdnf), inducible NOS (iNos), tumor necrosis factor-α (Tnf-α), and B-cell leukemia/lymphoma 2 (Bcl2) mRNA levels. This response was not linked to any significant signs of neurodegeneration as showed via Fluoro-Jade B and Nissl stain. Intrahippocampal administration of NMDA induced NF-κB activation and increased NOS and α(2/3) -Na,K-ATPase activities. NMDA treatment further increased OUA-induced NF-κB activation, which was partially blocked by MK-801, an antagonist of NMDA receptor. These results suggest that OUA-induced NF-κB activation is at least in part dependent on Na,K-ATPase modulatory action of NMDA receptor in hippocampus. The interaction of these signaling pathways could be associated with biological mechanisms that may underlie the basal homeostatic state linked to the inflammatory signaling cascade in the brain.
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Affiliation(s)
- E M Kawamoto
- Molecular Neuropharmacology Laboratory, Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
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Panayiotidis MI, Franco R, Bortner CD, Cidlowski JA. Ouabain-induced perturbations in intracellular ionic homeostasis regulate death receptor-mediated apoptosis. Apoptosis 2010; 15:834-49. [PMID: 20422450 DOI: 10.1007/s10495-010-0494-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Apoptosis is defined by specific morphological and biochemical characteristics including cell shrinkage (termed apoptotic volume decrease), a process that results from the regulation of ion channels and plasma membrane transporter activity. The Na(+)-K(+)-ATPase is the predominant pump that controls cell volume and plasma membrane potential in cells and alterations in its function have been suggested to be associated with apoptosis. We report here that the Na(+)-K(+)-ATPase inhibitor ouabain, potentiates apoptosis in the human lymphoma Jurkat cells exposed to Fas ligand (FasL) or tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) but not other apoptotic agents such as H(2)O(2), thapsigargin or UV-C implicating a role for the Na(+)-K(+)-ATPase in death receptor-induced apoptosis. Interestingly, ouabain also potentiated perturbations in cell Ca(2+) homeostasis only in conjunction with the apoptotic inducer FasL but not TRAIL. Ouabain did not affect alterations in the intracellular Ca(2+) levels in response to H(2)O(2), thapsigargin or UV-C. FasL-induced alterations in Ca(2+) were not abolished in Ca(2+)-free medium but incubation of cells with BAPTA-AM inhibited both Ca(2+) perturbations and the ouabain-induced potentiation of FasL-induced apoptosis. Our data suggest that the impairment of the Na(+)-K(+)-ATPase activity during apoptosis is linked to perturbations in cell Ca(2+) homeostasis that modulate apoptosis induced by the activation of Fas by FasL.
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Affiliation(s)
- Mihalis I Panayiotidis
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health, Research Triangle Park, NC, 27709, USA.
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Li SY, Sun WG, Jia YH, Wu GS, An GS, Ni JH, Jia HT. Calcium signal-initiated early activation of NF-kappaB in neurons is a neuroprotective event in response to kainic acid-induced excitotoxicity. BIOCHEMISTRY (MOSCOW) 2010; 75:101-9. [PMID: 20331430 DOI: 10.1134/s000629791001013x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We demonstrate that activation of nuclear factor kappaB (NF-kappaB) in neurons is neuroprotective in response to kainic acid (KA)-induced excitotoxicity. Combination of Western blotting, immunocytochemistry, and electrophoresis mobility shift assay showed that KA exposure induced a fast but transient nuclear translocation of the NF-kappaB p65 subunit and increased DNA-binding activity of NF-kappaB in primary cultured cortical neurons. The transient NF-kappaB activity was associated with upregulation of antiapoptotic Bcl-xL and XIAP gene products revealed by real-time PCR. Knockdown of p65 decreased neuronal viability and antiapoptotic gene expression. In addition, we showed that KA-stimulated DNA-binding activity of NF-kappaB was associated with reactive oxygen species and calcium signals, using AMPA/KA receptor antagonist, calcium chelator, and antioxidant. These results suggest that the fast and transient activation of NF-kappaB initiated by calcium signals is one of the important proximal events in response to KA-induced excitotoxicity, which has neuroprotective effect against KA-induced apoptosis.
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Affiliation(s)
- Shu-Yan Li
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing, 100191, PR China.
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de Rezende Corrêa G, da Silva Cunha KC, dos Santos AA, de Araujo EG. The Trophic Effect of Ouabain on Retinal Ganglion Cell is Mediated by EGF Receptor and PKC δ Activation. Neurochem Res 2010; 35:1343-52. [DOI: 10.1007/s11064-010-0190-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/11/2010] [Indexed: 01/11/2023]
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Karpova LV, Bulygina ER, Boldyrev AA. Different neuronal Na+/K+-ATPase isoforms are involved in diverse signaling pathways. Cell Biochem Funct 2010; 28:135-41. [DOI: 10.1002/cbf.1632] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Antonov SM, Krivoi II, Drabkina TM, Mironova EV, Evstratova AA. Neuroprotective effect of ouabain and Bcl-2 peptide expression during hyperactivation of NMDA receptors in rat brain cortical neurons in vitro. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2009; 426:207-9. [PMID: 19650317 DOI: 10.1134/s0012496609030041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- S M Antonov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, pr Toreza 44, St. Petersburg, 194223 Russia
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Ferguson AL, Stone TW. Adenosine preconditions against ouabain but not against glutamate on CA1-evoked potentials in rat hippocampal slices. Eur J Neurosci 2009; 28:2084-98. [PMID: 19046389 DOI: 10.1111/j.1460-9568.2008.06490.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Hypoxic and ischaemic brain damage are believed to involve excessive release of glutamate, and recent work shows that glutamate-induced damage in brain slices can be reduced by preconditioning with hypoxia or glutamate itself. Because adenosine is a powerful preconditioning agent, we have investigated whether adenosine could precondition against glutamate in vitro. In rat hippocampal slices, glutamate depolarization reduced the amplitudes of antidromic- and orthodromic-evoked potentials, with only partial recovery. Applying adenosine before these insults failed to increase that recovery. Ouabain also produced depolarization with partial reversibility, but adenosine pretreatment increased the extent of recovery. The preconditioning effect of adenosine on ouabain responses was prevented by blocking receptors for N-methyl-D-aspartate (NMDA), but not receptors for kainate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and was blocked by inhibiting nitric oxide synthase. Preconditioning was also abolished by the ATP-dependent potassium channel blockers, glibenclamide (cytoplasmic) or 5-hydroxydecanoate (mitochondrial). We conclude that adenosine does not precondition against glutamate in hippocampal slices, but that it does precondition against ouabain with a pharmacology similar to studies in vivo. Ischaemic neuronal damage is a complex of many factors, and because adenosine can precondition against ischaemic neuronal damage, its failure to protect against glutamate highlights limitations of using glutamate alone as a model for ischaemia. Because damage following ischaemia, trauma or excitotoxicity also involves reduced Na(+),K(+)-ATPase activity, and adenosine can precondition against ouabain, we propose that ouabain-induced damage represents an additional or alternative model for the contribution to cell damage of Na(+),K(+)-ATPase loss, this being more relevant to the mechanisms of preconditioning.
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Affiliation(s)
- Alexandra L Ferguson
- Faculty of Biomedical & Life Sciences, West Medical Building, University of Glasgow, Glasgow, UK
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Li Z, Xie Z. The Na/K-ATPase/Src complex and cardiotonic steroid-activated protein kinase cascades. Pflugers Arch 2008; 457:635-44. [DOI: 10.1007/s00424-008-0470-0] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 01/24/2008] [Accepted: 01/29/2008] [Indexed: 01/01/2023]
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Kulikov A, Eva A, Kirch U, Boldyrev A, Scheiner-Bobis G. Ouabain activates signaling pathways associated with cell death in human neuroblastoma. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1691-702. [PMID: 17524349 DOI: 10.1016/j.bbamem.2007.04.012] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 03/29/2007] [Accepted: 04/03/2007] [Indexed: 10/23/2022]
Abstract
Cardiotonic steroids (CTS) like ouabain are not only specific inhibitors of the sodium pump (Na(+),K(+)-ATPase), they also can influence various cytosolic signaling events in a hormone-like manner. In the neuroblastoma cell line SH-SY5Y ouabain triggers multiple signaling pathways. Within 30 min of incubation with 1 or 10 microM ouabain, SH-SY5Y cells generate reactive oxygen species to a level approximately 50% above control and show a modest but significant elevation in cytosolic [Ca(2+)] of about 25%. After 6 h of exposure, ouabain stimulates a series of anti-apoptotic actions in SH-SY5Y cells, including concentration-dependent phosphorylation of Erk1/2, Akt, and Bad. Nevertheless, at the same time this CTS also induces a series of events that inhibit retinoic acid-induced neuritogenesis and promote cell death. Both of these latter phenomena are possibly associated with the observed ouabain-induced reduction in the abundance of the anti-apoptotic proteins Bcl-XL and Bcl-2. In addition, ouabain treatment results in cytochrome c release into the cytosol and induces activation of caspase 3, events that point towards the stimulation of apoptotic pathways that are probably enhanced by the stimulation of p53 phosphorylation at Ser15 also observed in this study. These pathways may eventually lead to cell death: treatment with 10 nM ouabain results in a 20% decrease in cell number after 4 days of incubation and treatment with 1 microM ouabain decreases cells number by about 75%. The results obtained here emphasize the importance of further research in order to elucidate the various signalling cascades triggered by ouabain and possibly other CTS that are used in the treatment of heart failure and to identify their primary receptor(s).
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Affiliation(s)
- Andrey Kulikov
- Institut für Biochemie und Endokrinologie, Fachbereich Veterinärmedizin, Justus-Liebig-Universität Frankfurter Str. 100, D-35392 Giessen, Germany
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Schoner W, Scheiner-Bobis G. Endogenous and exogenous cardiac glycosides: their roles in hypertension, salt metabolism, and cell growth. Am J Physiol Cell Physiol 2007; 293:C509-36. [PMID: 17494630 DOI: 10.1152/ajpcell.00098.2007] [Citation(s) in RCA: 341] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cardiotonic steroids (CTS), long used to treat heart failure, are endogenously produced in mammals. Among them are the hydrophilic cardenolide ouabain and the more hydrophobic cardenolide digoxin, as well as the bufadienolides marinobufagenin and telecinobufagin. The physiological effects of endogenous ouabain on blood pressure and cardiac activity are consistent with the "Na(+)-lag" hypothesis. This hypothesis assumes that, in cardiac and arterial myocytes, a CTS-induced local increase of Na(+) concentration due to inhibition of Na(+)/K(+)-ATPase leads to an increase of intracellular Ca(2+) concentration ([Ca(2+)](i)) via a backward-running Na(+)/Ca(2+) exchanger. The increase in [Ca(2+)](i) then activates muscle contraction. The Na(+)-lag hypothesis may best explain short-term and inotropic actions of CTS. Yet all data on the CTS-induced alteration of gene expression are consistent with another hypothesis, based on the Na(+)/K(+)-ATPase "signalosome," that describes the interaction of cardiac glycosides with the Na(+) pump as machinery activating various signaling pathways via intramembrane and cytosolic protein-protein interactions. These pathways, which may be activated simultaneously or selectively, elevate [Ca(2+)](i), activate Src and the ERK1/2 kinase pathways, and activate phosphoinositide 3-kinase and protein kinase B (Akt), NF-kappaB, and reactive oxygen species. A recent development indicates that new pharmaceuticals with antihypertensive and anticancer activities may be found among CTS and their derivatives: the antihypertensive rostafuroxin suppresses Na(+) resorption and the Src-epidermal growth factor receptor-ERK pathway in kidney tubule cells. It may be the parent compound of a new principle of antihypertensive therapy. Bufalin and oleandrin or the cardenolide analog UNBS-1450 block tumor cell proliferation and induce apoptosis at low concentrations in tumors with constitutive activation of NF-kappaB.
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Affiliation(s)
- Wilhelm Schoner
- Institut für Biochemie und Endokrinologie, Fachbereich Veterinärmedizin, Justus-Liebig-Universität Giessen, Frankfurter Str 100, Giessen, Germany.
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Martin LJ, Liu Z, Chen K, Price AC, Pan Y, Swaby JA, Golden WC. Motor neuron degeneration in amyotrophic lateral sclerosis mutant superoxide dismutase-1 transgenic mice: mechanisms of mitochondriopathy and cell death. J Comp Neurol 2007; 500:20-46. [PMID: 17099894 DOI: 10.1002/cne.21160] [Citation(s) in RCA: 211] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The mechanisms of human mutant superoxide dismutase-1 (mSOD1) toxicity to motor neurons (MNs) are unresolved. We show that MNs in G93A-mSOD1 transgenic mice undergo slow degeneration lacking similarity to apoptosis structurally and biochemically. It is characterized by somal and mitochondrial swelling and formation of DNA single-strand breaks prior to double-strand breaks occurring in nuclear and mitochondrial DNA. p53 and p73 are activated in degenerating MNs, but without nuclear import. The MN death is independent of activation of caspases-1, -3, and -8 or apoptosis-inducing factor within MNs, with a blockade of apoptosis possibly mediated by Aven up-regulation. MN swelling is associated with compromised Na,K-ATPase activity and aggregation. mSOD1 mouse MNs accumulate mitochondria from the axon terminals and generate higher levels of superoxide, nitric oxide, and peroxynitrite than MNs in control mice. Nitrated and aggregated cytochrome c oxidase subunit-I and alpha-synuclein as well as nitrated SOD2 accumulate in mSOD1 mouse spinal cord. Mitochondria in mSOD1 mouse MNs accumulate NADPH diaphorase and inducible nitric oxide synthase (iNOS)-like immunoreactivity, and iNOS gene deletion extends significantly the life span of G93A-mSOD1 mice. Prior to MN loss, spinal interneurons degenerate. These results identify novel mechanisms for mitochondriopathy and MN degeneration in amyotrophic lateral sclerosis (ALS) mice involving blockade of apoptosis, accumulation of MN mitochondria with enhanced toxic potential from distal terminals, NOS localization in MN mitochondria and peroxynitrite damage, and early degeneration of alpha-synuclein(+) interneurons. The data support roles for oxidative stress, protein nitration and aggregation, and excitotoxicity as participants in the process of MN degeneration caused by mSOD1.
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Affiliation(s)
- Lee J Martin
- Department of Pathology, Division of Neuropathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2196, USA.
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Abstract
Cardiac glycosides have been used for decades to treat congestive heart failure. The recent identification of cardiotonic steroids such as ouabain, digoxin, marinobufagenin, and telocinobufagin in blood plasma, adrenal glands, and hypothalamus of mammals led to exciting new perspectives in the pathology of heart failure and arterial hypertension. Biosynthesis of ouabain and digoxin occurs in adrenal glands and is under the control of angiotensin II, endothelin, and epinephrine released from cells of the midbrain upon stimulation of brain areas sensing cerebrospinal Na(+) concentration and, apparently, the body's K(+) content. Rapid changes of endogenous ouabain upon physical exercise may favor the economy of the heart by a rise of intracellular Ca(2)(+) levels in cardiac and atrial muscle cells. According to the sodium pump lag hypothesis, this may be accomplished by partial inhibition of the sodium pump and Ca(2+) influx via the Na(+)/Ca(2+) exchanger working in reverse mode or via activation of the Na(+)/K(+)-ATPase signalosome complex, generating intracellular calcium oscillations, reactive oxygen species, and gene activation via nuclear factor-kappaB or extracellular signal-regulated kinases 1 and 2. Elevated concentrations of endogenous ouabain and marinobufagenin in the subnanomolar concentration range were found to stimulate proliferation and differentiation of cardiac and smooth muscle cells. They may have a primary role in the development of cardiac dysfunction and failure because (i) offspring of hypertensive patients evidently inherit elevated plasma concentrations of endogenous ouabain; (ii) such elevated concentrations correlate positively with cardiac dysfunction, hypertrophy, and arterial hypertension; (iii) about 40% of Europeans with uncomplicated essential hypertension show increased concentrations of endogenous ouabain associated with reduced heart rate and cardiac hypertrophy; (iv) in patients with advanced arterial hypertension, circulating levels of endogenous ouabain correlate with BP and total peripheral resistance; (v) among patients with idiopathic dilated cardiomyopathy, high circulating levels of endogenous ouabain and marinobufagenin identify those individuals who are predisposed to progressing more rapidly to heart failure, suggesting that endogenous ouabain (and marinobufagenin) may contribute to toxicity upon digoxin therapy. In contrast to endogenous ouabain, endogenous marinobufagenin may act as a natriuretic substance as well. It shows a higher affinity for the ouabain-insensitive alpha(1) isoform of Na(+)/K(+)-ATPase of rat kidney tubular cells and its levels are increased in volume expansion and pre-eclampsia. Digoxin, which is synthesized in adrenal glands, seems to counteract the hypertensinogenic action of ouabain in rats, as do antibodies against ouabain, for example, (Digibind) and rostafuroxin (PST 2238), a selective ouabain antagonist. It lowers BP in ouabain- and adducin-dependent hypertension in rats and is a promising new class of antihypertensive medication in humans.
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Affiliation(s)
- Wilhelm Schoner
- Institute of Biochemistry and Endocrinology, Justus-Liebig-University Giessen, Giessen, Germany.
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