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Richard EM, Brun E, Korchagina J, Crouzier L, Affortit C, Alves S, Cazevieille C, Mausset-Bonnefont AL, Lenoir M, Puel JL, Maurice T, Thiry M, Wang J, Delprat B. Wfs1 E864K knock-in mice illuminate the fundamental role of Wfs1 in endocochlear potential production. Cell Death Dis 2023; 14:387. [PMID: 37386014 PMCID: PMC10310813 DOI: 10.1038/s41419-023-05912-y] [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: 01/11/2023] [Revised: 06/08/2023] [Accepted: 06/20/2023] [Indexed: 07/01/2023]
Abstract
Wolfram syndrome (WS) is a rare neurodegenerative disorder encompassing diabetes mellitus, diabetes insipidus, optic atrophy, hearing loss (HL) as well as neurological disorders. None of the animal models of the pathology are presenting with an early onset HL, impeding the understanding of the role of Wolframin (WFS1), the protein responsible for WS, in the auditory pathway. We generated a knock-in mouse, the Wfs1E864K line, presenting a human mutation leading to severe deafness in affected individuals. The homozygous mice showed a profound post-natal HL and vestibular syndrome, a collapse of the endocochlear potential (EP) and a devastating alteration of the stria vascularis and neurosensory epithelium. The mutant protein prevented the localization to the cell surface of the Na+/K+ATPase β1 subunit, a key protein for the maintenance of the EP. Overall, our data support a key role of WFS1 in the maintenance of the EP and the stria vascularis, via its binding partner, the Na+/K+ATPase β1 subunit.
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Affiliation(s)
| | - Emilie Brun
- INM, Univ Montpellier, INSERM, Montpellier, France
| | | | - Lucie Crouzier
- MMDN, Univ Montpellier, EPHE, INSERM, Montpellier, France
| | | | - Stacy Alves
- MMDN, Univ Montpellier, EPHE, INSERM, Montpellier, France
| | | | | | - Marc Lenoir
- INM, Univ Montpellier, INSERM, Montpellier, France
| | | | - Tangui Maurice
- MMDN, Univ Montpellier, EPHE, INSERM, Montpellier, France
| | - Marc Thiry
- Laboratoire de Biologie Cellulaire, Université de Liège, Liège, Belgique
| | - Jing Wang
- INM, Univ Montpellier, INSERM, Montpellier, France
| | - Benjamin Delprat
- MMDN, Univ Montpellier, EPHE, INSERM, Montpellier, France.
- INM, Univ Montpellier, INSERM, Montpellier, France.
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2
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Mukherji ST, Brambilla L, Stuart KB, Mayes I, Kutz LC, Chen Y, Barbosa LA, Elmadbouh I, McDermott JP, Haller ST, Romero MF, Soleimani M, Liu J, Shapiro JI, Blanco GV, Xie Z, Pierre SV. Na/K-ATPase signaling tonically inhibits sodium reabsorption in the renal proximal tubule. FASEB J 2023; 37:e22835. [PMID: 36856735 PMCID: PMC10028530 DOI: 10.1096/fj.202200785rr] [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: 05/23/2022] [Revised: 02/08/2023] [Accepted: 02/10/2023] [Indexed: 03/02/2023]
Abstract
Through its classic ATP-dependent ion-pumping function, basolateral Na/K-ATPase (NKA) generates the Na+ gradient that drives apical Na+ reabsorption in the renal proximal tubule (RPT), primarily through the Na+ /H+ exchanger (NHE3). Accordingly, activation of NKA-mediated ion transport decreases natriuresis through activation of basolateral (NKA) and apical (NHE3) Na+ reabsorption. In contrast, activation of the more recently discovered NKA signaling function triggers cellular redistribution of RPT NKA and NHE3 and decreases Na+ reabsorption. We used gene targeting to test the respective contributions of NKA signaling and ion pumping to the overall regulation of RPT Na+ reabsorption. Knockdown of RPT NKA in cells and mice increased membrane NHE3 and Na+ /HCO3 - cotransporter (NBCe1A). Urine output and absolute Na+ excretion decreased by 65%, driven by increased RPT Na+ reabsorption (as indicated by decreased lithium clearance and unchanged glomerular filtration rate), and accompanied by elevated blood pressure. This hyper reabsorptive phenotype was rescued upon crossing with RPT NHE3-/- mice, confirming the importance of NKA/NHE3 coupling. Hence, NKA signaling exerts a tonic inhibition on Na+ reabsorption by regulating key apical and basolateral Na+ transporters. This action, lifted upon NKA genetic suppression, tonically counteracts NKA's ATP-driven function of basolateral Na+ reabsorption. Strikingly, NKA signaling is not only physiologically relevant but it also appears to be functionally dominant over NKA ion pumping in the control of RPT reabsorption.
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Affiliation(s)
- Shreya T. Mukherji
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Luca Brambilla
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Kailey B. Stuart
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Isabella Mayes
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Laura C. Kutz
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Yiliang Chen
- Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin
- Blood Research Institute, Versiti, WI
| | - Leandro A Barbosa
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
- Universidade Federal de São João del-Rei, Campus Centro-Oeste Dona Lindu, Divinópolis, MG, Brazil
| | - Ibrahim Elmadbouh
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Jeff P. McDermott
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS
| | - Steven T. Haller
- Department of Medicine, University of Toledo College of Medicine and Life Sciences, Toledo, OH
| | - Michael F. Romero
- Physiology & Biomedical Engineering and Nephrology & Hypertension, Mayo Clinic College of Medicine & Science, Rochester, MN
| | - Manoocher Soleimani
- Department of Medicine, The University of New Mexico Health Sciences Center, Albuquerque, NM
| | - Jiang Liu
- Joan C. Edwards School of Medicine, Marshall University, Huntington, WV
| | - Joseph I. Shapiro
- Joan C. Edwards School of Medicine, Marshall University, Huntington, WV
| | - Gustavo V. Blanco
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS
| | - Zijian Xie
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Sandrine V. Pierre
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
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3
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Xu Y, Marck P, Huang M, Xie JX, Wang T, Shapiro JI, Cai L, Feng F, Xie Z. Biased Effect of Cardiotonic Steroids on Na/K-ATPase-Mediated Signal Transduction. Mol Pharmacol 2021; 99:217-225. [PMID: 33495275 DOI: 10.1124/molpharm.120.000101] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 12/24/2020] [Indexed: 01/13/2023] Open
Abstract
Recent studies have revealed that Na/K-ATPase (NKA) can transmit signals through ion-pumping-independent activation of pathways relayed by distinct intracellular protein/lipid kinases, and endocytosis challenges the traditional definition that cardiotonic steroids (CTS) are NKA inhibitors. Although additional effects of CTS have long been suspected, revealing its agonist impact through the NKA receptor could be a novel mechanism in understanding the basic biology of NKA. In this study, we tested whether different structural CTS could trigger different sets of NKA/effector interactions, resulting in biased signaling responses without compromising ion-pumping capacity. Using purified NKA, we found that ouabain, digitoxigenin, and somalin cause comparable levels of NKA inhibition. However, although endogenous ouabain stimulates both protein kinases and NKA endocytosis, digitoxigenin and somalin bias to protein kinases and endocytosis, respectively, in LLC-PK1 cells. The positive inotropic effects of CTS are traditionally regarded as NKA inhibitors. However, CTS-induced signaling occurs at concentrations at least one order of magnitude lower than that of inotropy, which eliminates their well known toxic actions on the heart. The current study adds a novel mechanism that CTS could exert its biased signaling properties through the NKA signal transducer. SIGNIFICANCE STATEMENT: Although it is now well accepted that NKA has an ion-pumping-independent signaling function, it is still debated whether direct and conformation-dependent NKA/effector interaction is a key to this function. Therefore, this investigation is significant in advancing our understanding of the basic biology of NKA-mediated signal transduction and gaining molecular insight into the structural elements that are important for cardiotonic steroid's biased action.
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Affiliation(s)
- Yunhui Xu
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Pauline Marck
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Minqi Huang
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Jeffrey X Xie
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Tong Wang
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Joseph I Shapiro
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Liquan Cai
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Feng Feng
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
| | - Zijian Xie
- Marshall Institute for Interdisciplinary Research, Huntington, West Virginia (Y.X., P.M., M.H., T.W., L.C., Z.X.); University of Toledo College of Medicine and Life Sciences, Toledo, Ohio (J.X.X.); Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia (J.I.S.); and Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, P. R. China, and Jiangsu Food and Pharmaceutical Science College, Huai'an, P. R. China (F.F.)
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Xu Y, Jiang X, Xu J, Qu W, Xie Z, Jiang RW, Feng F. A previously undescribed phenylethanoid glycoside from Callicarpa kwangtungensis Chun acts as an agonist of the Na/K-ATPase signal transduction pathway. PHYTOCHEMISTRY 2021; 181:112577. [PMID: 33190100 DOI: 10.1016/j.phytochem.2020.112577] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 10/23/2020] [Accepted: 10/24/2020] [Indexed: 06/11/2023]
Abstract
The new concept that Na/K-ATPase acts as a receptor prompted us to look for new ligands from Callicarpa kwangtungensis Chun. Using column chromatography, an undescribed phenethyl alcohol glycoside, callicarpanoside A, and an undescribed benzyl alcohol glycoside, callicarpanoside B, along with twelve known polyphenols were isolated from Callicarpa kwangtungensis Chun. All the isolated compounds were evaluated for their Na/K-ATPase (NKA) inhibitory activities. Using our NKA technology platform-based screening assay protocols, callicarpanoside B was identified as an undescribed Na/K-ATPase agonist. In particular, the newly identified benzyl alcohol glycoside was found to bind NKA and activate the receptor NKA/Src complex, resulting in the activation of protein kinase cascades. These cascades included extracellular signal-regulated kinases and protein kinase C epsilon, as well as NKA α1 endocytosis at nanomolar concentrations. Unlike the class of cardiotonic steroids, callicarpanoside B showed less inhibition of NKA activity and caused less cellular toxicity. Moreover, callicarpanoside B was found to bind NKA at a different site other than the cardiotonic steroids binding site. Thus, we have identified an undescribed NKA α1 agonist that may be used to enhance the physiological processes of NKA α1 signaling.
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Affiliation(s)
- Yunhui Xu
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV, 25701, United States
| | - Xueyang Jiang
- Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, 210009, PR China; Jiangsu Food and Pharmaceutical Science College, Huai'an, 223003, PR China
| | - Jian Xu
- Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, 210009, PR China; Jiangsu Food and Pharmaceutical Science College, Huai'an, 223003, PR China
| | - Wei Qu
- Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, 210009, PR China; Jiangsu Food and Pharmaceutical Science College, Huai'an, 223003, PR China
| | - Zijian Xie
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV, 25701, United States
| | - Ren-Wang Jiang
- Guangdong Province Key Laboratory of Pharmacodynamic Constituents of TCM and New Drugs Research, College of Pharmacy, Jinan University, Guangzhou, 510632, PR China; International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education, College of Pharmacy, Jinan University, Guangzhou, 510632, PR China.
| | - Feng Feng
- Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, 210009, PR China; Jiangsu Food and Pharmaceutical Science College, Huai'an, 223003, PR China.
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5
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The Na/K-ATPase α1 and c-Src form signaling complex under native condition: A crosslinking approach. Sci Rep 2020; 10:6006. [PMID: 32265464 PMCID: PMC7138855 DOI: 10.1038/s41598-020-61920-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 03/04/2020] [Indexed: 11/09/2022] Open
Abstract
The protein-protein interactions amongst the Na/K-ATPase α1 subunit, c-Src, and caveolin-1 (cav-1) are essential for the Na/K-ATPase signaling functions. However, there are arguments concerning the interaction model. The present study aims to clarify the interactions amongst the endogenous native proteins in live cells under native resting condition. Under native condition, Blue Native-PAGE and Blue Native-PAGE/SDS-PAGE 2D analyses demonstrated co-existence of the α1 subunit and c-Src in same protein complex, as well as a direct interaction between the α1 subunit and c-Src. By comparison of cleavable and non-cleavable cysteine-cysteine crosslinked samples, capillary immunoblotting analysis demonstrated that depletion of Src kinase family members (c-Src, Yes, and Fyn) or cav-1 clearly reduced the interactions of the α1 subunit with proteins, but depletion of cav-1 did not affect the interaction of c-Src with the α1 subunit. The data indicated that there are direct interactions between the α1 subunit and c-Src as well as between the α1 subunit and cav-1, but argued about the interaction between c-Src and cav-1 under the condition. Furthermore, the data also indicated the existence of different protein complexes containing the α1 subunit and c-Src, which might have different signaling functions.
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Pavlovic D. Endogenous cardiotonic steroids and cardiovascular disease, where to next? Cell Calcium 2019; 86:102156. [PMID: 31896530 PMCID: PMC7031694 DOI: 10.1016/j.ceca.2019.102156] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/24/2019] [Accepted: 12/24/2019] [Indexed: 11/18/2022]
Abstract
Ever since British Physician William Withering first described the use of foxglove extract for treatment of patients with congestive heart failure in 1785, cardiotonic steroids have been used clinically to treat heart failure and more recently atrial fibrillation. Due to their ability to bind and inhibit the ubiquitous transport enzyme sodium potassium pump, thus regulating intracellular Na+ concentration in every living cell, they are also an essential tool for research into the sodium potassium pump structure and function. Exogenous CTS have been clearly demonstrated to affect cardiovascular system through modulation of vagal tone, cardiac contraction (via ionic changes) and altered natriuresis. Reports of a number of endogenous CTS, since the 1980s, have intensified research into their physiologic and pathophysiologic roles and opened up novel therapeutic targets. Substantive evidence pointing to the role of endogenous ouabain and marinobufagenin, the two most prominent CTS, in development of cardiovascular disease has accumulated. Nevertheless, their presence, structure, biosynthesis pathways and even mechanism of action remain unclear or controversial. In this review the current state-of-the-art, the controversies and the remaining questions surrounding the role of endogenous cardiotonic steroids in health and disease are discussed.
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Affiliation(s)
- Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
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Eleftheriadis T, Pissas G, Antoniadi G, Golfinopoulos S, Liakopoulos V, Stefanidis I. Energy handling in renal tubular epithelial cells of the hamster, a native hibernator, under warm anoxia or reoxygenation. Biomed Rep 2018; 9:503-510. [PMID: 30546878 DOI: 10.3892/br.2018.1157] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 10/10/2018] [Indexed: 12/12/2022] Open
Abstract
Ischemia-reperfusion (I-R) injury causes several diseases, including acute kidney injury. Hibernating mammals survive periods of torpor with a marked drop in tissue perfusion, interspersed with periods of arousal, and consequently I-R injury. In the present study, sensitivity to anoxia and/or reoxygenation and alterations in cellular ATP and homeostasis of the two most energy consuming processes, protein translation and Na+-K+-ATPase function, were evaluated in renal proximal tubular epithelial cells of mouse or native hibernator hamster origin. Compared with the mouse cells, the hamster cells were less sensitive to anoxia and reoxygenation and ATP was preserved under anoxia. Anoxia triggered mechanisms that suppress protein translation in both species. However, under anoxia, the activity of ATPase, which is mostly attributed to Na+-K+-ATPase function, remained stable in the hamster cells but decreased in the mouse cells. In normoxia, ATPase activity in hamster cells was considerably lower than that in mouse cells. As the Na+-K+-ATPase pump preserves the ion gradient against passive leakage through ion channels, the lower energy demand for the function of this pump in hamster cells may indicate less ion leakage due to fewer ion channels. In accordance with this hypothesis, ouabain-treated hamster cells had a higher survival rate than mouse cells, indicating fewer ion channels and consequently slower deregulation of intracellular ion concentration and cell death due to Na+-K+-ATPase inhibition. Therefore, it is likely that the conserved energy from the suppression of protein translation is adequate enough to support the lower energy demand for Na+-K+-ATPase function and cell survival of hamster cells under anoxia. Clarifying how cells of a native hibernator manage energy under warm I-R may reveal novel and possible clinically applicable pathways for preventing I-R injury.
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Affiliation(s)
- Theodoros Eleftheriadis
- Department of Nephrology, Faculty of Medicine, University of Thessaly, 41110 Larissa, Greece
| | - Georgios Pissas
- Department of Nephrology, Faculty of Medicine, University of Thessaly, 41110 Larissa, Greece
| | - Georgia Antoniadi
- Department of Nephrology, Faculty of Medicine, University of Thessaly, 41110 Larissa, Greece
| | - Spyridon Golfinopoulos
- Department of Nephrology, Faculty of Medicine, University of Thessaly, 41110 Larissa, Greece
| | - Vassilios Liakopoulos
- Department of Nephrology, Faculty of Medicine, University of Thessaly, 41110 Larissa, Greece
| | - Ioannis Stefanidis
- Department of Nephrology, Faculty of Medicine, University of Thessaly, 41110 Larissa, Greece
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The Na/K-ATPase Signaling: From Specific Ligands to General Reactive Oxygen Species. Int J Mol Sci 2018; 19:ijms19092600. [PMID: 30200500 PMCID: PMC6163532 DOI: 10.3390/ijms19092600] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 08/10/2018] [Accepted: 08/28/2018] [Indexed: 12/16/2022] Open
Abstract
The signaling function of the Na/K-ATPase has been established for 20 years and is widely accepted in the field, with many excellent reports and reviews not cited here. Even though there is debate about the underlying mechanism, the signaling function is unquestioned. This short review looks back at the evolution of Na/K-ATPase signaling, from stimulation by cardiotonic steroids (also known as digitalis-like substances) as specific ligands to stimulation by reactive oxygen species (ROS) in general. The interplay of cardiotonic steroids and ROS in Na/K-ATPase signaling forms a positive-feedback oxidant amplification loop that has been implicated in some pathophysiological conditions.
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Quantum Modeling: A Bridge between the Pumping and Signaling Functions of Na/K-ATPase. Int J Mol Sci 2018; 19:ijms19082347. [PMID: 30096926 PMCID: PMC6121303 DOI: 10.3390/ijms19082347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 08/06/2018] [Accepted: 08/07/2018] [Indexed: 12/15/2022] Open
Abstract
Although the signaling function of Na/K-ATPase has been studied for decades, the chasm between the pumping function and the signaling function of Na/K-ATPase is still an open issue. This article explores the relationship between ion pumping and signaling with attention to the amplification of oxidants through this signaling function. We specifically consider the Na/K-ATPase with respect to its signaling function as a superposition of different states described for its pumping function. We then examine how alterations in the relative amounts of these states could alter signaling through the Src-EGFR-ROS pathway. Using assumptions based on some experimental observations published by our laboratories and others, we develop some predictions regarding cellular oxidant stress.
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10
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Abstract
As aging involves oxidant injury, we examined the role of the recently described Na/K-ATPase oxidant amplification loop (NKAL). First, C57Bl6 old mice were given a western diet to stimulate oxidant injury or pNaKtide to antagonize the NKAL. The western diet accelerated functional and morphological evidence for aging whereas pNaKtide attenuated these changes. Next, human dermal fibroblasts (HDFs) were exposed to different types of oxidant stress in vitro each of which increased expression of senescence markers, cell-injury, and apoptosis as well as stimulated the NKAL. Further stimulation of the NKAL with ouabain augmented cellular senescence whereas treatment with pNaKtide attenuated it. Although N-Acetyl Cysteine and Vitamin E also ameliorated overall oxidant stress to a similar degree as pNaKtide, the pNaKtide produced protection against senescence that was substantially greater than that seen with either antioxidant. In particular, pNaKtide appeared to specifically ameliorate nuclear oxidant stress to a greater degree. These data demonstrate that the NKAL is intimately involved in the aging process and may serve as a target for anti-aging interventions.
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Na⁺ i,K⁺ i-Dependent and -Independent Signaling Triggered by Cardiotonic Steroids: Facts and Artifacts. Molecules 2017; 22:molecules22040635. [PMID: 28420099 PMCID: PMC6153942 DOI: 10.3390/molecules22040635] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 03/31/2017] [Accepted: 04/11/2017] [Indexed: 11/17/2022] Open
Abstract
Na⁺,K⁺-ATPase is the only known receptor of cardiotonic steroids (CTS) whose interaction with catalytic α-subunits leads to inhibition of this enzyme. As predicted, CTS affect numerous cellular functions related to the maintenance of the transmembrane gradient of monovalent cations, such as electrical membrane potential, cell volume, transepithelial movement of salt and osmotically-obliged water, symport of Na⁺ with inorganic phosphate, glucose, amino acids, nucleotides, etc. During the last two decades, it was shown that side-by-side with these canonical Na⁺i/K⁺i-dependent cellular responses, long-term exposure to CTS affects transcription, translation, tight junction, cell adhesion and exhibits tissue-specific impact on cell survival and death. It was also shown that CTS trigger diverse signaling cascades via conformational transitions of the Na⁺,K⁺-ATPase α-subunit that, in turn, results in the activation of membrane-associated non-receptor tyrosine kinase Src, phosphatidylinositol 3-kinase and the inositol 1,4,5-triphosphate receptor. These findings allowed researchers to propose that endogenous CTS might be considered as a novel class of steroid hormones. We focus our review on the analysis of the relative impact Na⁺i,K⁺i-mediated and -independent pathways in cellular responses evoked by CTS.
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Liu J, Yan Y, Nie Y, Shapiro JI. Na/K-ATPase Signaling and Salt Sensitivity: The Role of Oxidative Stress. Antioxidants (Basel) 2017; 6:E18. [PMID: 28257114 PMCID: PMC5384181 DOI: 10.3390/antiox6010018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 02/10/2017] [Accepted: 02/22/2017] [Indexed: 02/07/2023] Open
Abstract
Other than genetic regulation of salt sensitivity of blood pressure, many factors have been shown to regulate renal sodium handling which contributes to long-term blood pressure regulation and have been extensively reviewed. Here we present our progress on the Na/K-ATPase signaling mediated sodium reabsorption in renal proximal tubules, from cardiotonic steroids-mediated to reactive oxygen species (ROS)-mediated Na/K-ATPase signaling that contributes to experimental salt sensitivity.
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Affiliation(s)
- Jiang Liu
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA.
| | - Yanling Yan
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA.
| | - Ying Nie
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA.
| | - Joseph I Shapiro
- Department of Medicine, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25701, USA
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13
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Madan N, Xu Y, Duan Q, Banerjee M, Larre I, Pierre SV, Xie Z. Src-independent ERK signaling through the rat α3 isoform of Na/K-ATPase. Am J Physiol Cell Physiol 2017; 312:C222-C232. [PMID: 27903584 PMCID: PMC5401946 DOI: 10.1152/ajpcell.00199.2016] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 11/30/2016] [Accepted: 11/30/2016] [Indexed: 01/10/2023]
Abstract
The Na/K-ATPase α1 polypeptide supports both ion-pumping and signaling functions. The Na/K-ATPase α3 polypeptide differs from α1 in both its primary structure and its tissue distribution. The expression of α3 seems particularly important in neurons, and recent clinical evidence supports a unique role of this isoform in normal brain function. The nature of this specific role of α3 has remained elusive, because the ubiquitous presence of α1 has hindered efforts to characterize α3-specific functions in mammalian cell systems. Using Na/K-ATPase α1 knockdown pig kidney cells (PY-17), we generated the first stable mammalian cell line expressing a ouabain-resistant form of rat Na/K-ATPase α3 in the absence of endogenous pig α1 detectable by Western blotting. In these cells, Na/K-ATPase α3 formed a functional ion-pumping enzyme and rescued the expression of Na/K-ATPase β1 and caveolin-1 to levels comparable with those observed in PY-17 cells rescued with a rat Na/K-ATPase α1 (AAC-19). The α3-containing enzymes had lower Na+ affinity and lower ouabain-sensitive transport activity than their α1-containing counterparts under basal conditions, but showed a greater capacity to be activated when intracellular Na+ was increased. In contrast to Na/K-ATPase α1, α3 could not regulate Src. Upon exposure to ouabain, Src activation did not occur, yet ERK was activated through Src-independent pathways involving PI3K and PKC. Hence, α3 expression confers signaling and pumping properties that are clearly distinct from that of cells expressing Na/K-ATPase α1.
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Affiliation(s)
- Namrata Madan
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia
| | - Yunhui Xu
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia
- Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, China; and
| | - Qiming Duan
- Gladstone Institute of Cardiovascular Disease, San Francisco, California
| | - Moumita Banerjee
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia
| | - Isabel Larre
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia
| | - Sandrine V Pierre
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia
| | - Zijian Xie
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia;
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14
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Yan Y, Shapiro AP, Mopidevi BR, Chaudhry MA, Maxwell K, Haller ST, Drummond CA, Kennedy DJ, Tian J, Malhotra D, Xie ZJ, Shapiro JI, Liu J. Protein Carbonylation of an Amino Acid Residue of the Na/K-ATPase α1 Subunit Determines Na/K-ATPase Signaling and Sodium Transport in Renal Proximal Tubular Cells. J Am Heart Assoc 2016; 5:e003675. [PMID: 27613772 PMCID: PMC5079028 DOI: 10.1161/jaha.116.003675] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 08/12/2016] [Indexed: 01/12/2023]
Abstract
BACKGROUND We have demonstrated that cardiotonic steroids, such as ouabain, signaling through the Na/K-ATPase, regulate sodium reabsorption in the renal proximal tubule. By direct carbonylation modification of the Pro222 residue in the actuator (A) domain of pig Na/K-ATPase α1 subunit, reactive oxygen species are required for ouabain-stimulated Na/K-ATPase/c-Src signaling and subsequent regulation of active transepithelial (22)Na(+) transport. In the present study we sought to determine the functional role of Pro222 carbonylation in Na/K-ATPase signaling and sodium handling. METHODS AND RESULTS Stable pig α1 knockdown LLC-PK1-originated PY-17 cells were rescued by expressing wild-type rat α1 and rat α1 with a single mutation of Pro224 (corresponding to pig Pro222) to Ala. This mutation does not affect ouabain-induced inhibition of Na/K-ATPase activity, but abolishes the effects of ouabain on Na/K-ATPase/c-Src signaling, protein carbonylation, Na/K-ATPase endocytosis, and active transepithelial (22)Na(+) transport. CONCLUSIONS Direct carbonylation modification of Pro224 in the rat α1 subunit determines ouabain-mediated Na/K-ATPase signal transduction and subsequent regulation of renal proximal tubule sodium transport.
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Affiliation(s)
- Yanling Yan
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine, Marshall University, Huntington, WV
| | - Anna P Shapiro
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH
| | - Brahma R Mopidevi
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH
| | - Muhammad A Chaudhry
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine, Marshall University, Huntington, WV
| | - Kyle Maxwell
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine, Marshall University, Huntington, WV
| | - Steven T Haller
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH
| | | | - David J Kennedy
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH
| | - Jiang Tian
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH
| | - Deepak Malhotra
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH
| | - Zi-Jian Xie
- Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
| | - Joseph I Shapiro
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine, Marshall University, Huntington, WV Department of Medicine, University of Toledo College of Medicine, Toledo, OH
| | - Jiang Liu
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine, Marshall University, Huntington, WV Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, WV
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15
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Abstract
Endocytosis can be separated into the categories of phagocytosis and pinocytosis. Phagocytosis can be distinguished from pinocytosis primarily by the size of particle ingested and by its dependence on actin polymerization as a key step in particle ingestion. Several specific forms of pinocytosis have been identified that can be distinguished based on their dependence on clathrin or caveolin. Both clathrin and caveolin-dependent pinocytosis appear to require the participation of dynamin to internalize the plasma membrane. Other, less well-characterized forms of pinocytosis have also been described. Although endocytosis has long been known to affect receptor density, recent studies have demonstrated that endocytosis through clathrin- and caveolin-dependent processes plays a key role in receptor-mediated signal transduction. In some cases, blockade of these processes attenuates, or even prevents, signal transduction from taking place. This information, coupled with a better understanding of endocytosis mechanisms, will help advance the field of cell biology as well as present new targets for drug development and disease treatment.
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Affiliation(s)
- Jiang Liu
- Department of Medicine, Room 12, Ruppert Center, 3120 Glendale Avenue, Toledo, OH 43614, USA.
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16
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Shah PT, Martin R, Yan Y, Shapiro JI, Liu J. Carbonylation Modification Regulates Na/K-ATPase Signaling and Salt Sensitivity: A Review and a Hypothesis. Front Physiol 2016; 7:256. [PMID: 27445847 PMCID: PMC4923243 DOI: 10.3389/fphys.2016.00256] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 06/11/2016] [Indexed: 01/01/2023] Open
Abstract
Na/K-ATPase signaling has been implicated in different physiological and pathophysiological conditions. Accumulating evidence indicates that oxidative stress not only regulates the Na/K-ATPase enzymatic activity, but also regulates its signaling and other functions. While cardiotonic steroids (CTS)-induced increase in reactive oxygen species (ROS) generation is an intermediate step in CTS-mediated Na/K-ATPase signaling, increase in ROS alone also stimulates Na/K-ATPase signaling. Based on literature and our observations, we hypothesize that ROS have biphasic effects on Na/K-ATPase signaling, transcellular sodium transport, and urinary sodium excretion. Oxidative modulation, in particular site specific carbonylation of the Na/K-ATPase α1 subunit, is a critical step in proximal tubular Na/K-ATPase signaling and decreased transcellular sodium transport leading to increases in urinary sodium excretion. However, once this system is overstimulated, the signaling, and associated changes in sodium excretion are blunted. This review aims to evaluate ROS-mediated carbonylation of the Na/K-ATPase, and its potential role in the regulation of pump signaling and sodium reabsorption in the renal proximal tubule (RPT).
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Affiliation(s)
- Preeya T Shah
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University Huntington, WV, USA
| | - Rebecca Martin
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University Huntington, WV, USA
| | - Yanling Yan
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University Huntington, WV, USA
| | - Joseph I Shapiro
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University Huntington, WV, USA
| | - Jiang Liu
- Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University Huntington, WV, USA
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17
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Yan Y, Shapiro JI. The physiological and clinical importance of sodium potassium ATPase in cardiovascular diseases. Curr Opin Pharmacol 2016; 27:43-9. [PMID: 26891193 PMCID: PMC5161351 DOI: 10.1016/j.coph.2016.01.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 01/14/2016] [Accepted: 01/29/2016] [Indexed: 12/14/2022]
Abstract
The Na/K-ATPase has been extensively studied, but it is only recently that its role as a scaffolding and signaling protein has been identified. It has been identified that cardiotonic steroids (CTS) such as digitalis mediate signal transduction through the Na/K-ATPase in a process found to result in the generation of reactive oxygen species (ROS). As these ROS also appear capable of initiating this signal cascade, a feed forward amplification process has been postulated and subsequently implicated in some disease pathways including uremic cardiomyopathy.
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Affiliation(s)
- Yanling Yan
- Joan C. Edwards School of Medicine, Marshall University, Department of Medicine, USA
| | - Joseph I Shapiro
- Joan C. Edwards School of Medicine, Marshall University, Department of Medicine, USA.
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18
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Shattock MJ, Ottolia M, Bers DM, Blaustein MP, Boguslavskyi A, Bossuyt J, Bridge JHB, Chen-Izu Y, Clancy CE, Edwards A, Goldhaber J, Kaplan J, Lingrel JB, Pavlovic D, Philipson K, Sipido KR, Xie ZJ. Na+/Ca2+ exchange and Na+/K+-ATPase in the heart. J Physiol 2015; 593:1361-82. [PMID: 25772291 PMCID: PMC4376416 DOI: 10.1113/jphysiol.2014.282319] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 10/30/2014] [Indexed: 12/17/2022] Open
Abstract
This paper is the third in a series of reviews published in this issue resulting from the University of California Davis Cardiovascular Symposium 2014: Systems approach to understanding cardiac excitation–contraction coupling and arrhythmias: Na+ channel and Na+ transport. The goal of the symposium was to bring together experts in the field to discuss points of consensus and controversy on the topic of sodium in the heart. The present review focuses on cardiac Na+/Ca2+ exchange (NCX) and Na+/K+-ATPase (NKA). While the relevance of Ca2+ homeostasis in cardiac function has been extensively investigated, the role of Na+ regulation in shaping heart function is often overlooked. Small changes in the cytoplasmic Na+ content have multiple effects on the heart by influencing intracellular Ca2+ and pH levels thereby modulating heart contractility. Therefore it is essential for heart cells to maintain Na+ homeostasis. Among the proteins that accomplish this task are the Na+/Ca2+ exchanger (NCX) and the Na+/K+ pump (NKA). By transporting three Na+ ions into the cytoplasm in exchange for one Ca2+ moved out, NCX is one of the main Na+ influx mechanisms in cardiomyocytes. Acting in the opposite direction, NKA moves Na+ ions from the cytoplasm to the extracellular space against their gradient by utilizing the energy released from ATP hydrolysis. A fine balance between these two processes controls the net amount of intracellular Na+ and aberrations in either of these two systems can have a large impact on cardiac contractility. Due to the relevant role of these two proteins in Na+ homeostasis, the emphasis of this review is on recent developments regarding the cardiac Na+/Ca2+ exchanger (NCX1) and Na+/K+ pump and the controversies that still persist in the field.
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Affiliation(s)
- Michael J Shattock
- King's College London BHF Centre of Excellence, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
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19
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Pavlovic D. The role of cardiotonic steroids in the pathogenesis of cardiomyopathy in chronic kidney disease. Nephron Clin Pract 2014; 128:11-21. [PMID: 25341357 DOI: 10.1159/000363301] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Cardiotonic steroids (CTS) are a new class of hormones that circulate in the blood and are divided into two distinct groups, cardenolides, such as ouabain and digoxin, and bufadienolides, such as marinobufagenin, telocinobufagin and bufalin. They have the ability to bind and inhibit the ubiquitous transport enzyme sodium potassium pump, thus regulating intracellular Na(+) concentration in every living cell. Although digoxin has been prescribed to heart failure patients for at least 200 years, the realization that CTS are endogenously produced has intensified research into their physiological and pathophysiological roles. Over the last two decades, substantial evidence has accumulated demonstrating the effects of endogenously synthesised CTS on the kidneys, vasculature and the heart. In this review, the current state of art and the controversies surrounding the manner in which CTS mediate their pathophysiological effects are discussed. Several potential therapeutic strategies have emerged as a result of our increased understanding of the role CTS play in health and disease.
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Affiliation(s)
- Davor Pavlovic
- Cardiovascular Division, King's College London, Rayne Institute, St. Thomas' Hospital, London, UK
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20
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Su Y, Al-Lamki RS, Blake-Palmer KG, Best A, Golder ZJ, Zhou A, Karet Frankl FE. Physical and functional links between anion exchanger-1 and sodium pump. J Am Soc Nephrol 2014; 26:400-9. [PMID: 25012180 DOI: 10.1681/asn.2013101063] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Anion exchanger-1 (AE1) mediates chloride-bicarbonate exchange across the plasma membranes of erythrocytes and, via a slightly shorter transcript, kidney epithelial cells. On an omnivorous human diet, kidney AE1 is mainly active basolaterally in α-intercalated cells of the collecting duct, where it is functionally coupled with apical proton pumps to maintain normal acid-base homeostasis. The C-terminal tail of AE1 has an important role in its polarized membrane residency. We have identified the β1 subunit of Na(+),K(+)-ATPase (sodium pump) as a binding partner for AE1 in the human kidney. Kidney AE1 and β1 colocalized in renal α-intercalated cells and coimmunoprecipitated (together with the catalytic α1 subunit of the sodium pump) from human kidney membrane fractions. ELISA and fluorescence titration assays confirmed that AE1 and β1 interact directly, with a Kd value of 0.81 μM. GST-AE1 pull-down assays using human kidney membrane proteins showed that the last 11 residues of AE1 are important for β1 binding. siRNA-induced knockdown of β1 in cell culture resulted in a significant reduction in kidney AE1 levels at the cell membrane, whereas overexpression of kidney AE1 increased cell surface sodium pump levels. Notably, membrane staining of β1 was reduced throughout collecting ducts of AE1-null mouse kidney, where increased fractional excretion of sodium has been reported. These data suggest a requirement of β1 for proper kidney AE1 membrane residency, and that activities of AE1 and the sodium pump are coregulated in kidney.
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Affiliation(s)
- Ya Su
- Departments of Medical Genetics and
| | - Rafia S Al-Lamki
- Division of Renal Medicine, University of Cambridge, Cambridge, United Kingdom
| | | | | | | | | | - Fiona E Karet Frankl
- Departments of Medical Genetics and Division of Renal Medicine, University of Cambridge, Cambridge, United Kingdom
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21
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Wang Y, Ye Q, Liu C, Xie JX, Yan Y, Lai F, Duan Q, Li X, Tian J, Xie Z. Involvement of Na/K-ATPase in hydrogen peroxide-induced activation of the Src/ERK pathway in LLC-PK1 cells. Free Radic Biol Med 2014; 71:415-426. [PMID: 24703895 PMCID: PMC6779055 DOI: 10.1016/j.freeradbiomed.2014.03.036] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 03/25/2014] [Accepted: 03/25/2014] [Indexed: 11/17/2022]
Abstract
We have shown that Na/K-ATPase interacts with Src. Here, we test the role of this interaction in H2O2-induced activation of Src and ERK. We found that exposure of LLC-PK1 cells to H2O2 generated by the addition of glucose oxidase into the culture medium activated Src and ERK1/2. It also caused a modest reduction in the number of surface Na/K-ATPases and in ouabain-sensitive Rb(+) uptake. These effects of H2O2 seem similar to those induced by ouabain, a specific ligand of Na/K-ATPase, in LLC-PK1 cells. In accordance, we found that the effects of H2O2 on Src and ERK1/2 were inhibited in α1 Na/K-ATPase-knockdown PY-17 cells. Whereas expression of wild-type α1 or the A420P mutant α1 defective in Src regulation rescued the pumping activity in PY-17 cells, only α1, and not the A420P mutant, was able to restore the H2O2-induced activation of protein kinases. Consistent with this, disrupting the formation of the Na/K-ATPase/Src complex with pNaKtide attenuated the effects of H2O2 on the kinases. Moreover, a direct effect of H2O2 on Na/K-ATPase-mediated regulation of Src was demonstrated. Finally, H2O2 reduced the expression of E-cadherin through the Na/K-ATPase/Src-mediated signaling pathway. Taken together, the data suggest that the Na/K-ATPase/Src complex may serve as one of the receptor mechanisms for H2O2 to regulate Src/ERK protein kinases and consequently the phenotype of renal epithelial cells.
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Affiliation(s)
- Yu Wang
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China
| | - Qiqi Ye
- Department of Physiology and Department of Pharmacology and Medicine, College of Medicine, University of Toledo, Toledo, OH 43614, USA
| | - Changxuan Liu
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China
| | - Jeffrey X Xie
- Department of Physiology and Department of Pharmacology and Medicine, College of Medicine, University of Toledo, Toledo, OH 43614, USA
| | - Yanling Yan
- Department of Physiology and Department of Pharmacology and Medicine, College of Medicine, University of Toledo, Toledo, OH 43614, USA
| | - Fangfang Lai
- Department of Physiology and Department of Pharmacology and Medicine, College of Medicine, University of Toledo, Toledo, OH 43614, USA
| | - Qiming Duan
- Department of Physiology and Department of Pharmacology and Medicine, College of Medicine, University of Toledo, Toledo, OH 43614, USA
| | - Xiaomei Li
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China
| | - Jiang Tian
- Department of Physiology and Department of Pharmacology and Medicine, College of Medicine, University of Toledo, Toledo, OH 43614, USA
| | - Zijian Xie
- Department of Physiology and Department of Pharmacology and Medicine, College of Medicine, University of Toledo, Toledo, OH 43614, USA.
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22
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Xie JX, Shapiro AP, Shapiro JI. The Trade-Off between Dietary Salt and Cardiovascular Disease; A Role for Na/K-ATPase Signaling? Front Endocrinol (Lausanne) 2014; 5:97. [PMID: 25101054 PMCID: PMC4101451 DOI: 10.3389/fendo.2014.00097] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 06/07/2014] [Indexed: 12/12/2022] Open
Abstract
It has been postulated for some time that endogenous digitalis-like substances, also called cardiotonic steroids (CTS), exist, and that these substances are involved in sodium handling. Within the past 20 years, these substances have been unequivocally identified and measurements of circulating and tissue concentrations have been made. More recently, it has been identified that CTS also mediate signal transduction through the Na/K-ATPase, and consequently been implicated in profibrotic pathways. This review will discuss the mechanism of CTS in renal sodium handling and a potential "trade-off" effect from their role in inducing tissue fibrosis.
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Affiliation(s)
- Joe X. Xie
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO, USA
| | - Anna Pearl Shapiro
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH, USA
| | - Joseph Isaac Shapiro
- Department of Medicine, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, USA
- *Correspondence: Joseph Isaac Shapiro, Department of Medicine, Joan C. Edwards School of Medicine, Marshall University, 1600 Medical Center Drive Suite 3408, Huntington, WV 25701, USA e-mail:
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23
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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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24
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Yan Y, Shapiro AP, Haller S, Katragadda V, Liu L, Tian J, Basrur V, Malhotra D, Xie ZJ, Abraham NG, Shapiro JI, Liu J. Involvement of reactive oxygen species in a feed-forward mechanism of Na/K-ATPase-mediated signaling transduction. J Biol Chem 2013; 288:34249-34258. [PMID: 24121502 DOI: 10.1074/jbc.m113.461020] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cardiotonic steroids (such as ouabain) signaling through Na/K-ATPase regulate sodium reabsorption in the renal proximal tubule. We report here that reactive oxygen species are required to initiate ouabain-stimulated Na/K-ATPase·c-Src signaling. Pretreatment with the antioxidant N-acetyl-L-cysteine prevented ouabain-stimulated Na/K-ATPase·c-Src signaling, protein carbonylation, redistribution of Na/K-ATPase and sodium/proton exchanger isoform 3, and inhibition of active transepithelial (22)Na(+) transport. Disruption of the Na/K-ATPase·c-Src signaling complex attenuated ouabain-stimulated protein carbonylation. Ouabain-stimulated protein carbonylation is reversed after removal of ouabain, and this reversibility is largely independent of de novo protein synthesis and degradation by either the lysosome or the proteasome pathways. Furthermore, ouabain stimulated direct carbonylation of two amino acid residues in the actuator domain of the Na/K-ATPase α1 subunit. Taken together, the data indicate that carbonylation modification of the Na/K-ATPase α1 subunit is involved in a feed-forward mechanism of regulation of ouabain-mediated renal proximal tubule Na/K-ATPase signal transduction and subsequent sodium transport.
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Affiliation(s)
- Yanling Yan
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine at Marshall University, Huntington, West Virginia 25755; Institute of Biomedical Engineering, Yanshan University, Qinhuangdao 066004, China
| | - Anna P Shapiro
- Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Steven Haller
- Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Vinai Katragadda
- Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Lijun Liu
- Department of Pharmacology, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Jiang Tian
- Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614; Department of Pharmacology, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Venkatesha Basrur
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109
| | - Deepak Malhotra
- Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Zi-Jian Xie
- Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614; Department of Pharmacology, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Nader G Abraham
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine at Marshall University, Huntington, West Virginia 25755
| | - Joseph I Shapiro
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine at Marshall University, Huntington, West Virginia 25755; Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Jiang Liu
- Department of Pharmacology, Physiology and Toxicology, JCE School of Medicine at Marshall University, Huntington, West Virginia 25755.
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25
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Lai F, Madan N, Ye Q, Duan Q, Li Z, Wang S, Si S, Xie Z. Identification of a mutant α1 Na/K-ATPase that pumps but is defective in signal transduction. J Biol Chem 2013; 288:13295-304. [PMID: 23532853 DOI: 10.1074/jbc.m113.467381] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND It has not been possible to study the pumping and signaling functions of Na/K-ATPase independently in live cells. RESULTS Both cell-free and cell-based assays indicate that the A420P mutation abolishes the Src regulatory function of Na/K-ATPase. CONCLUSION A420P mutant has normal pumping but not signaling function. SIGNIFICANCE Identification of Src regulation-null mutants is crucial for addressing physiological role of Na/K-ATPase. The α1 Na/K-ATPase possesses both pumping and signaling functions. However, it has not been possible to study these functions independently in live cells. We have identified a 20-amino acid peptide (Ser-415 to Gln-434) (NaKtide) from the nucleotide binding domain of α1 Na/K-ATPase that binds and inhibits Src in vitro. The N terminus of NaKtide adapts a helical structure. In vitro kinase assays showed that replacement of residues that contain a bulky side chain in the helical structure of NaKtide by alanine abolished the inhibitory effect of the peptide on Src. Similarly, disruption of helical structure by proline replacement, either single or in combination, reduced the inhibitory potency of NaKtide on Src. To identify mutant α1 that retains normal pumping function but is defective in Src regulation, we transfected Na/K-ATPase α1 knockdown PY-17 cells with expression vectors of wild type or mutant α1 carrying Ala to Pro mutations in the region of NaKtide helical structure and generated several stable cell lines. We found that expression of either A416P or A420P or A425P mutant fully restored the α1 content and consequently the pumping capacity of cells. However, in contrast to A416P, either A420P or A425P mutant was incapable of interacting and regulating cellular Src. Consequently, expression of these two mutants caused significant inhibition of ouabain-activated signal transduction and cell growth. Thus we have identified α1 mutant that has normal pumping function but is defective in signal transduction.
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Affiliation(s)
- Fangfang Lai
- Department of Physiology, Pharmacology, and Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
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Gopalakrishnan K, Kumarasamy S, Yan Y, Liu J, Kalinoski A, Kothandapani A, Farms P, Joe B. Increased Expression of Rififylin in A < 330 Kb Congenic Strain is Linked to Impaired Endosomal Recycling in Proximal Tubules. Front Genet 2012; 3:138. [PMID: 22891072 PMCID: PMC3413941 DOI: 10.3389/fgene.2012.00138] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Accepted: 07/11/2012] [Indexed: 11/13/2022] Open
Abstract
Cell surface proteins are internalized into the cell through endocytosis and either degraded within lysosomes or recycled back to the plasma membrane. While perturbations in endosomal internalization are known to modulate renal function, it is not known whether similar alterations in recycling affect renal function. Rififylin is a known regulator of endocytic recycling with E3 ubiquitin protein ligase activity. In this study, using two genetically similar strains, the Dahl Salt-sensitive rat and an S.LEW congenic strain, which had allelic variants within a < 330 kb segment containing rififylin, we tested the hypothesis that alterations in endosomal recycling affect renal function. The congenic strain had 1.59-fold higher renal expression of rififylin. Transcriptome analysis indicated that components of both endocytosis and recycling were upregulated in the congenic strain. Transcription of Atp1a1 and cell surface content of the protein product of Atp1a1, the alpha subunit of Na+K+ATPase were increased in the proximal tubules from the congenic strain. Because rififylin does not directly regulate endocytosis and it is also a differentially expressed gene within the congenic segment, we reasoned that the observed alterations in the transcriptome of the congenic strain constitute a feedback response to the primary functional alteration of recycling caused by rififylin. To test this, recycling of transferrin was studied in isolated proximal tubules. Recycling was significantly delayed within isolated proximal tubules of the congenic strain, which also had a higher level of polyubiquitinated proteins and proteinuria compared with S. These data provide evidence to suggest that delayed endosomal recycling caused by excess of rififylin indirectly affects endocytosis, enhances intracellular protein polyubiquitination and contributes to proteinuria.
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Affiliation(s)
- Kathirvel Gopalakrishnan
- Center for Hypertension and Personalized Medicine, University of Toledo College of Medicine and Life Sciences Toledo, OH, USA
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Cytosolic organelles shape calcium signals and exo–endocytotic responses of chromaffin cells. Cell Calcium 2012; 51:309-20. [DOI: 10.1016/j.ceca.2011.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 12/02/2011] [Accepted: 12/05/2011] [Indexed: 01/09/2023]
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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: 47] [Impact Index Per Article: 3.9] [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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Gupta S, Yan Y, Malhotra D, Liu J, Xie Z, Najjar SM, Shapiro JI. Ouabain and insulin induce sodium pump endocytosis in renal epithelium. Hypertension 2012; 59:665-72. [PMID: 22311908 DOI: 10.1161/hypertensionaha.111.176727] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cardiotonic steroids signaling through the basolateral sodium pump (Na/K-ATPase) have been shown to alter renal salt handling in intact animals. Because the relationship between renal salt handling and blood pressure is a key determinant of hypertension, and patients with insulin resistance are frequently hypertensive, we chose to examine whether there might be competition for resources necessary for receptor-mediated endocytosis. In LLC-PK1 cells, the Na/K-ATPase-α1 and carcinoembryonic antigen cell adhesion molecule 1, a plasma membrane protein that promotes receptor-mediated endocytosis, colocalized in the plasma membranes and translocated to the intracellular region in response to ouabain. Either ouabain or insulin alone caused accumulation of and carcinoembryonic antigen cell adhesion molecule, as well as insulin receptor-β, and epidermal growth factor receptor in early endosomes, but no synergy was demonstrable. Like ouabain, insulin also caused c-Src activation. When caveolin or Na/K-ATPase-α1 expression was knocked down with small interfering RNA, insulin but not ouabain induced carcinoembryonic antigen cell adhesion molecule 1, insulin receptor-β, and epidermal growth factor receptor endocytosis. To determine whether this might be relevant to salt handling in vivo, we examined salt loading in mice with null renal carcinoembryonic antigen cell adhesion molecule 2 expression. The null renal carcinoembryonic antigen cell adhesion molecule 2 animals demonstrated greater increases in blood pressure with increases in dietary salt than control animals. These data demonstrate that cardiotonic steroids and insulin compete for cellular endocytosis resources and suggest that, under conditions where circulating insulin concentrations are high, cardiotonic steroid-mediated natriuresis could be impaired.
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Affiliation(s)
- Shalini Gupta
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH 43614-2598, USA
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New Insights into the Regulation of Na+,K+-ATPase by Ouabain. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:99-132. [DOI: 10.1016/b978-0-12-394305-7.00002-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Milla J, Montesinos MS, Machado JD, Borges R, Alonso E, Moreno-Ortega AJ, Cano-Abad MF, García AG, Ruiz-Nuño A. Ouabain enhances exocytosis through the regulation of calcium handling by the endoplasmic reticulum of chromaffin cells. Cell Calcium 2011; 50:332-42. [PMID: 21741086 DOI: 10.1016/j.ceca.2011.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 05/23/2011] [Accepted: 06/09/2011] [Indexed: 11/18/2022]
Abstract
The augmentation of neurotransmitter and hormone release produced by ouabain inhibition of plasmalemmal Na+/K+-ATPase (NKA) is well established. However, the mechanism underlying this action is still controversial. Here we have shown that in bovine adrenal chromaffin cells ouabain diminished the mobility of chromaffin vesicles, an indication of greater number of docked vesicles at subplasmalemmal exocytotic sites. On the other hand, ouabain augmented the number of vesicles undergoing exocytosis in response to a K+ pulse, rather than the quantal size of single vesicles. Furthermore, ouabain produced a tiny and slow Ca2+ release from the endoplasmic reticulum (ER) and gradually augmented the transient elevations of the cytosolic Ca2+ concentrations ([Ca2+]c) triggered by K+ pulses. These effects were paralleled by gradual increments of the transient catecholamine release responses triggered by sequential K+ pulses applied to chromaffin cell populations treated with ouabain. Both, the increases of K+-elicited [Ca2+]c and secretion in ouabain-treated cells were blocked by thapsigargin (THAPSI), 2-aminoethoxydiphenyl borate (2-APB) and caffeine. These results are compatible with the view that ouabain may enhance the ER Ca2+ load and facilitate the Ca2+-induced-Ca2+ release (CICR) component of the [Ca2+]c signal generated during K+ depolarisation. This could explain the potentiating effects of ouabain on exocytosis.
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Affiliation(s)
- Juan Milla
- Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, and Servicio de Farmacología Clínica, Instituto de Investigación Sanitaria, Hospital Universitario de la Princesa, Madrid, Spain
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Koleganova N, Piecha G, Ritz E, Becker LE, Müller A, Weckbach M, Nyengaard JR, Schirmacher P, Gross-Weissmann ML. Both high and low maternal salt intake in pregnancy alter kidney development in the offspring. Am J Physiol Renal Physiol 2011; 301:F344-54. [PMID: 21593188 DOI: 10.1152/ajprenal.00626.2010] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In humans, low glomerular numbers are related to hypertension, cardiovascular, and renal disease in adult life. The present study was designed 1) to explore whether above- or below-normal dietary salt intake during pregnancy influences nephron number and blood pressure in the offspring and 2) to identify potential mechanisms in kidney development modified by maternal sodium intake. Sprague-Dawley rats were fed low (0.07%)-, intermediate (0.51%)-, or high (3.0%)-sodium diets during pregnancy and lactation. The offspring were weaned at 4 wk and subsequently kept on a 0.51% sodium diet. The kidney structure was assessed at postnatal weeks 1 and 12 and the expression of proteins of interest at term and at week 1. Blood pressure was measured in male offspring by telemetry from postnatal month 2 to postnatal month 9. The numbers of glomeruli at weeks 1 and 12 were significantly lower and, in males, telemetrically measured mean arterial blood pressure after month 5 was higher in offspring of dams on a high- or low- compared with intermediate-sodium diet. A high-salt diet was paralleled by higher concentrations of marinobufagenin in the amniotic fluid and an increase in the expression of both sprouty-1 and glial cell-derived neutrophic factor in the offspring's kidney. The expression of FGF-10 was lower in offspring of dams on a low-sodium diet, and the expression of Pax-2 and FGF-2 was lower in offspring of dams on a high-sodium diet. Both excessively high and excessively low sodium intakes during pregnancy modify protein expression in offspring kidneys and reduce the final number of glomeruli, predisposing the risk of hypertension later in life.
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Liu J, Yan Y, Liu L, Xie Z, Malhotra D, Joe B, Shapiro JI. Impairment of Na/K-ATPase signaling in renal proximal tubule contributes to Dahl salt-sensitive hypertension. J Biol Chem 2011; 286:22806-13. [PMID: 21555512 DOI: 10.1074/jbc.m111.246249] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We have observed that, in renal proximal tubular cells, cardiotonic steroids such as ouabain in vitro signal through Na/K-ATPase, which results in inhibition of transepithelial (22)Na(+) transport by redistributing Na/K-ATPase and NHE3. In the present study, we investigate the role of Na/K-ATPase signaling in renal sodium excretion and blood pressure regulation in vivo. In Sprague-Dawley rats, high salt diet activated c-Src and induced redistribution of Na/K-ATPase and NHE3 in renal proximal tubules. In Dahl salt sensitive (S) and resistant (R) rats given high dietary salt, we found different effects on blood pressure but, more interestingly, different effects on renal salt handling. These differences could be explained by different signaling through the proximal tubular Na/K-ATPase. Specifically, in Dahl R rats, high salt diet significantly stimulated phosphorylation of c-Src and ERK1/2, reduced Na/K-ATPase activity and NHE3 activity, and caused redistribution of Na/K-ATPase and NHE3. In contrast, these adaptations were either much less effective or not seen in the Dahl S rats. We also studied the primary culture of renal proximal tubule isolated from Dahl S and R rats fed a low salt diet. In this system, ouabain induced Na/K-ATPase/c-Src signaling and redistribution of Na/K-ATPase and NHE3 in the Dahl R rats, but not in the Dahl S rats. Our data suggested that impairment of Na/K-ATPase signaling and consequent regulation of Na/K-ATPase and NHE3 in renal proximal tubule may contribute to salt-induced hypertension in the Dahl S rat.
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Affiliation(s)
- Jiang Liu
- Department of Medicine, University of Toledo College of Medicine, Toledo, Ohio 43614, USA.
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Silva E, Serrão M, Soares-da-Silva P. Age-dependent effect of ouabain on renal Na+,K+-ATPase. Life Sci 2011; 88:719-24. [DOI: 10.1016/j.lfs.2011.02.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 01/16/2011] [Accepted: 02/02/2011] [Indexed: 01/06/2023]
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Oshiro N, Dostanic-Larson I, Neumann JC, Lingrel JB. The ouabain-binding site of the α2 isoform of Na,K-ATPase plays a role in blood pressure regulation during pregnancy. Am J Hypertens 2010; 23:1279-85. [PMID: 20940714 DOI: 10.1038/ajh.2010.195] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The cardiotonic steroid/ouabain-binding site of the α subunit of Na,K-ATPase is thought to play an important role in cardiovascular homeostasis. Previously, we demonstrated the cardiotonic steroid-binding site of the α2 Na,K-ATPase is involved in adrenocorticotropic hormone (ACTH)-induced hypertension by using gene-modified α2(R/R) mice in which the cardiotonic steroid-binding site is relatively resistant to ouabain compared to the ouabain-sensitive wild-type α2(S/S) mice. To further explore the importance of this site in the cardiovascular system, we investigated blood pressure regulation during pregnancy in mice with the α2(R/R) isoform. METHODS The systolic blood pressure (SBP) of the α2(S/S) and α2(R/R) mice was measured before and during pregnancy by tail-cuff. The expression of the α isoforms of Na, K-ATPase in various tissues and plasma endogenous ouabain contents were assessed prior to pregnancy as well as days 7 and 17 of gestation. RESULTS The α2(S/S) mice showed a gradual decrease in the SBP during the first two trimesters, followed by an increase above the preconceptional level in the third trimester. However, the α2(R/R) mice exhibited a lower blood pressure in the third trimester. The cardiac expression of the α2 Na,K-ATPase in the α2(S/S) mice was significantly less than that of the α2(R/R) mice throughout the pregnancy. The plasma endogenous ouabain concentration significantly increased by twofold at day 17 of pregnancy in the α2(R/R) mice but not in the α2(S/S) mice. CONCLUSIONS The cardiotonic steroid-binding site of the α2 Na,K-ATPase plays a role in maintaining normal SBP during pregnancy.
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Ward JBJ, Lawler K, Amu S, Taylor CT, Fallon PG, Keely SJ. Hydroxylase inhibition attenuates colonic epithelial secretory function and ameliorates experimental diarrhea. FASEB J 2010; 25:535-43. [PMID: 20944011 DOI: 10.1096/fj.10-166983] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hydroxylases are oxygen-sensing enzymes that regulate cellular responses to hypoxia. Transepithelial Cl(-) secretion, the driving force for fluid secretion, is dependent on O(2) availability for generation of cellular energy. Here, we investigated the role of hydroxylases in regulating epithelial secretion and the potential for targeting these enzymes in treatment of diarrheal disorders. Ion transport was measured as short-circuit current changes across voltage-clamped monolayers of T(84) cells and mouse colon. The antidiarrheal efficacy of dimethyloxallyl glycine (DMOG) was tested in a mouse model of allergic disease. Hydroxylase inhibition with DMOG attenuated Ca(2+)- and cAMP-dependent secretory responses in voltage-clamped T(84) cells to 20.2 ± 2.6 and 38.8 ± 6.7% (n=16; P≤0.001) of those in control cells, respectively. Antisecretory actions of DMOG were time and concentration dependent, being maximal after 18 h of DMOG (1 mM) treatment. DMOG specifically inhibited Na(+)/K(+)-ATPase pump activity without altering its expression or membrane localization. In mice, DMOG inhibited agonist-induced secretory responses ex vivo and prevented allergic diarrhea in vivo. In conclusion, hydroxylases are important regulators of epithelial Cl(-) and fluid secretion and present a promising target for development of new drugs to treat transport disorders.
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Affiliation(s)
- Joseph B J Ward
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin, Ireland
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Tian J, Haller S, Periyasamy S, Brewster P, Zhang H, Adlakha S, Fedorova OV, Xie ZJ, Bagrov AY, Shapiro JI, Cooper CJ. Renal ischemia regulates marinobufagenin release in humans. Hypertension 2010; 56:914-9. [PMID: 20823380 DOI: 10.1161/hypertensionaha.110.155564] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiotonic steroids, including marinobufagenin, are a group of new steroid hormones found in plasma and urine of patients with congestive heart failure, myocardial infarction, and chronic renal failure. In animal studies, partial nephrectomy induces marinobufagenin elevation, cardiac hypertrophy, and fibrosis. The objective of this study is to test the effect of renal ischemia on marinobufagenin levels in humans with renal artery stenosis (RAS). To test this, plasma marinobufagenin levels were measured in patients with RAS of the Prospective Randomized Study Comparing Renal Artery Stenting With or Without Distal Protection, non-RAS patient controls who were scheduled for coronary angiography, and normal healthy individuals. Marinobufagenin levels were significantly higher in patients with RAS compared with those of the other 2 groups. Multivariate analysis shows that occurrence of RAS is independently related to marinobufagenin levels. In addition, renal artery revascularization by stenting partially reversed marinobufagenin levels in the patients with RAS (0.77±0.06 nmol/L at baseline; 0.66±0.06 nmol/L at 24 hours; and 0.61±0.05 nmol/L at 1 month). In conclusion, we have found that marinobufagenin levels are increased in patients with RAS, whereas reversal of renal ischemia by stenting treatment reduces marinobufagenin levels. These results suggest that RAS-induced renal ischemia may be a major cause of marinobufagenin release.
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Affiliation(s)
- Jiang Tian
- Department of Medicine Cardiovascular Division, University of Toledo, Toledo, OH 43614, USA.
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Fedorova OV, Shapiro JI, Bagrov AY. Endogenous cardiotonic steroids and salt-sensitive hypertension. Biochim Biophys Acta Mol Basis Dis 2010; 1802:1230-6. [PMID: 20347967 DOI: 10.1016/j.bbadis.2010.03.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 03/18/2010] [Accepted: 03/20/2010] [Indexed: 12/12/2022]
Abstract
Endogenous cardiotonic steroids (CTS), also called digitalis like factors, have been postulated to play important roles in pathogenesis of hypertension for nearly half of a century. For the past 50 years biomedical scientists have been in quest of an unidentified factor or hormone that both increases blood pressure and renal sodium excretion; this "natriuretic hormone" was, in fact, postulated to interact with the Na/K-ATPase. Recent discoveries have led to the identification of steroid molecules which are present in humans, rodents and amphibians, and which, in a complex manner, interact with each other and with the other systems that regulate renal salt handling and contribute to the salt-sensitivity of blood pressure. Recent findings include the specific identification of endogenous cardenolide (endogenous ouabain) and bufadienolide (marinobufagenin) CTS in humans along with the delineation of mechanisms by which CTS can signal through the Na/K-ATPase. Although CTS were first considered important in the regulation of renal sodium transport and arterial pressure, more recent work implicates these hormones in the central regulation of blood pressure and regulation of cell growth, and development of cardiovascular and renal fibrosis in particular.
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Affiliation(s)
- Olga V Fedorova
- National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
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Liu J, Xie ZJ. The sodium pump and cardiotonic steroids-induced signal transduction protein kinases and calcium-signaling microdomain in regulation of transporter trafficking. Biochim Biophys Acta Mol Basis Dis 2010; 1802:1237-45. [PMID: 20144708 DOI: 10.1016/j.bbadis.2010.01.013] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 01/28/2010] [Accepted: 01/30/2010] [Indexed: 12/12/2022]
Abstract
The Na/K-ATPase was discovered as an energy transducing ion pump. A major difference between the Na/K-ATPase and other P-type ATPases is its ability to bind a group of chemicals called cardiotonic steroids (CTS). The plant-derived CTS such as digoxin are valuable drugs for the management of cardiac diseases, whereas ouabain and marinobufagenin (MBG) have been identified as a new class of endogenous hormones. Recent studies have demonstrated that the endogenous CTS are important regulators of renal Na(+) excretion and blood pressure. The Na/K-ATPase is not only an ion pump, but also an important receptor that can transduce the ligand-like effect of CTS on intracellular protein kinases and Ca(2+) signaling. Significantly, these CTS-provoked signaling events are capable of reducing the surface expression of apical NHE3 (Na/H exchanger isoform 3) and basolateral Na/K-ATPase in renal proximal tubular cells. These findings suggest that endogenous CTS may play an important role in regulation of tubular Na(+) excretion under physiological conditions; conversely, a defect at either the receptor level (Na/K-ATPase) or receptor-effector coupling would reduce the ability of renal proximal tubular cells to excrete Na(+), thus culminating/resulting in salt-sensitive hypertension.
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Affiliation(s)
- Jiang Liu
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH, USA
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Kozikowski TA, Magdesian KG, Puschner B. Oleander intoxication in New World camelids: 12 cases (1995-2006). J Am Vet Med Assoc 2009; 235:305-10. [PMID: 19650704 DOI: 10.2460/javma.235.3.305] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To characterize the clinical and clinicopathologic effects and evaluate outcome associated with oleander toxicosis in New World camelids. DESIGN Retrospective case series. ANIMALS 11 llamas and 1 alpaca. PROCEDURES Medical records from a veterinary medical teaching hospital from January 1, 1995, to December 31, 2006, were reviewed. Records of all New World camelids that had detectable amounts of oleandrin in samples of serum, urine, or gastrointestinal fluid were included in the study. Descriptive statistics were used to evaluate the history, physical examination findings, clinicopathologic data, and outcome of affected camelids. RESULTS 11 llamas and 1 alpaca met the inclusion criteria of the study. Either oleander plants were present where the camelids resided (n = 7) or oleander plant material was identified in the hay fed to the camelids (5). One llama was dead on arrival at the hospital, and another was euthanized upon admission because of financial concerns. Of the 10 treated camelids, 9 had evidence of acute renal failure, 7 had gastrointestinal signs, and 4 had cardiac dysrhythmias on initial evaluation. The overall mortality rate was 25%, but the mortality rate for the 10 camelids that were medically treated was 10%. CONCLUSIONS AND CLINICAL RELEVANCE In New World camelids, oleander intoxication was associated with a triad of clinical effects (ie, renal, gastrointestinal, and cardiovascular dysfunction). Oleander intoxication often represented a herd problem but carried a fair to good prognosis if treated promptly. Oleander toxicosis should be considered a differential diagnosis in sick camelids.
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Affiliation(s)
- Tania A Kozikowski
- Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
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Bagrov AY, Shapiro JI, Fedorova OV. Endogenous cardiotonic steroids: physiology, pharmacology, and novel therapeutic targets. Pharmacol Rev 2009; 61:9-38. [PMID: 19325075 PMCID: PMC2763610 DOI: 10.1124/pr.108.000711] [Citation(s) in RCA: 384] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Endogenous cardiotonic steroids (CTS), also called digitalis-like factors, have been postulated to play important roles in health and disease for nearly half a century. Recent discoveries, which include the specific identification of endogenous cardenolide (endogenous ouabain) and bufadienolide (marinobufagenin) CTS in humans along with the delineation of an alternative mechanism by which CTS can signal through the Na(+)/K(+)-ATPase, have increased the interest in this field substantially. Although CTS were first considered important in the regulation of renal sodium transport and arterial pressure, more recent work implicates these hormones in the regulation of cell growth, differentiation, apoptosis, and fibrosis, the modulation of immunity and of carbohydrate metabolism, and the control of various central nervous functions and even behavior. This review focuses on the physiological interactions between CTS and other regulatory systems that may be important in the pathophysiology of essential hypertension, preeclampsia, end-stage renal disease, congestive heart failure, and diabetes mellitus. Based on our increasing understanding of the regulation of CTS as well as the molecular mechanisms of these hormone increases, we also discuss potential therapeutic strategies.
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Affiliation(s)
- Alexei Y Bagrov
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Dr., Baltimore, MD 21224, USA.
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Monoclonal antibody to an endogenous bufadienolide, marinobufagenin, reverses preeclampsia-induced Na/K-ATPase inhibition and lowers blood pressure in NaCl-sensitive hypertension. J Hypertens 2009; 26:2414-25. [PMID: 19008721 DOI: 10.1097/hjh.0b013e328312c86a] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Levels of marinobufagenin (MBG), an endogenous bufadienolide Na/K-ATPase (NKA) inhibitor, increase in preeclampsia and in NaCl-sensitive hypertension. METHODS We tested a 3E9 monoclonal anti-MBG antibody (mAb) for the ability to lower blood pressure (BP) in NaCl-sensitive hypertension and to reverse the preeclampsia-induced inhibition of erythrocyte NKA. Measurements of MBG were performed via immunoassay based on 4G4 anti-MBG mAb. RESULTS In hypertensive Dahl-S rats, intraperitoneal administration of 50 microg/kg 3E9 mAb lowered BP by 32 mmHg and activated the Na/K-pump in the thoracic aorta by 51%. NaCl supplementation of pregnant rats (n = 16) produced a 37 mmHg increase in BP, a 3.5-fold rise in MBG excretion, and a 25% inhibition of the Na/K-pump in the thoracic aorta, compared with pregnant rats on a normal NaCl intake. In eight pregnant hypertensive rats, 3E9 mAb reduced the BP (21 mmHg) and restored the vascular Na/K-pump. In 14 patients with preeclampsia (mean BP, 126 +/- 3 mmHg; 26.9 +/- 1.4 years; gestational age, 37 +/- 0.8 weeks), plasma MBG was increased three-fold and erythrocyte NKA was inhibited compared with that of 12 normotensive pregnant women (mean BP, 71 +/- 3 mmHg) (1.5 +/- 0.1 vs. 3.1 +/- 0.2 micromol Pi/ml/h, respectively; P < 0.01). Ex-vivo 3E9 mAb restored NKA activity in erythrocytes from patients with preeclampsia. As compared with 3E9 mAb, Digibind, an affinity-purified antidigoxin antibody, was less active with respect to lowering BP in both hypertensive models and to restoration of NKA from erythrocytes from patients with preeclampsia. CONCLUSION Anti-MBG mAbs may be a useful tool in studies of MBG in vitro and in vivo and may offer treatment of preeclampsia.
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Fedorova LV, Raju V, El-Okdi N, Shidyak A, Kennedy DJ, Vetteth S, Giovannucci DR, Bagrov AY, Fedorova OV, Shapiro JI, Malhotra D. The cardiotonic steroid hormone marinobufagenin induces renal fibrosis: implication of epithelial-to-mesenchymal transition. Am J Physiol Renal Physiol 2009; 296:F922-34. [PMID: 19176701 DOI: 10.1152/ajprenal.90605.2008] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We recently demonstrated that the cardiotonic steroid marinobufagenin (MBG) induced fibrosis in rat hearts through direct stimulation of collagen I secretion by cardiac fibroblasts. This stimulation was also responsible for the cardiac fibrosis seen in experimental renal failure. In this study, the effect of MBG on the development of renal fibrosis in rats was investigated. Four weeks of MBG infusion triggered mild periglomerular and peritubular fibrosis in the cortex and the appearance of fibrotic scars in the corticomedullary junction of the kidney. MBG also significantly increased the protein levels and nuclear localization of the transcription factor Snail in the tubular epithelia. It is known that activation of Snail is associated with epithelial-to-mesenchymal transition (EMT) during renal fibrosis. To examine whether MBG alone can trigger EMT, we used the porcine proximal tubular cell line LLC-PK1. MBG (100 nM) caused LLC-PK1 cells grown to confluence to acquire a fibroblast-like shape and have an invasive motility. The expressions of the mesenchymal proteins collagen I, fibronectin, and vimentin were increased twofold. However, the total level of E-cadherin remained unchanged. These alterations in LLC-PK1 cells in the presence of MBG were accompanied by elevated expression and nuclear translocation of Snail. During the time course of EMT, MBG did not have measurable inhibitory effects on the ion pumping activity of its natural ligand, Na(+)-K(+)-ATPase. Our data suggest that the MBG may be an important factor in inducing EMT and, through this mechanism, elevated levels of MBG in chronic renal failure may play a role in the progressive fibrosis.
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Affiliation(s)
- Larisa V Fedorova
- Division of Nephrology, Dept. of Medicine, Univ. of Toledo College of Medicine, 3000 Arlington Ave., Toledo Ohio, 43614-2598, USA
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Pereyra-Alfonso S, Del Valle Armanino M, Vázquez C, Peña C, Rodríguez de Lores Arnaiz G. High-affinity neurotensin receptor is involved in phosphoinositide turnover increase by inhibition of sodium pump in neonatal rat brain. Neurochem Res 2008; 33:2206-13. [PMID: 18758956 DOI: 10.1007/s11064-008-9672-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2007] [Accepted: 03/13/2008] [Indexed: 10/21/2022]
Abstract
Phosphoinositide (PI) metabolism is enhanced in neonatal brain by activation of neurotransmitter receptors and by inhibition of the sodium pump with ouabain or endogenous inhibitor termed endobain E. Peptide neurotensin inhibits synaptosomal membrane Na(+), K(+)-ATPase activity, an effect blocked by SR 48692, a selective antagonist for high-affinity neurotensin receptor (NTS1). The purpose of this study was to evaluate potential participation of NTS1 receptor on PI hydrolysis enhancement by sodium pump inhibition. Cerebral cortex miniprisms from neonatal Wistar rats were preloaded with [(3)H]myoinositol in buffer during 60 min and further preincubated for 0 min or 30 min in the absence or presence of SR 48692. Then, ouabain or endobain E were added and incubation proceeded during 20 or 60 min. Reaction was stopped with chloroform/methanol and [(3)H]inositol-phosphates (IPs) accumulation was quantified in the water phase. After 60-min incubation with ouabain, IPs accumulation values reached roughly 500% or 860% in comparison with basal values (100%), if the preincubation was omitted or lasted 30 min, respectively. Values were reduced 50% in the presence of SR 48692. In 20-min incubation experiments, IPs accumulation by ouabain versus basal was 300% or 410% if preincubation was 0 min or 30 min, respectively, an effect blocked 23% or 32% with SR 48692. PI hydrolysis enhancement by endobain E was similarly blocked by SR 48692, being this effect higher when sample incubation with the endogenous inhibitor lasted 60 min versus 20 min. Present results indicate that PI hydrolysis increase by sodium pump inhibition with ouabain or endobain E is partially diminished by SR 48692. It is therefore suggested that NTS1 receptor may be involved in cell signaling system mediated by PI turnover.
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Affiliation(s)
- Susana Pereyra-Alfonso
- Instituto de Biología Celular y Neurociencias "Prof. E. De Robertis", Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, 1121, Buenos Aires, Argentina
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Bagrov AY, Shapiro JI. Endogenous digitalis: pathophysiologic roles and therapeutic applications. NATURE CLINICAL PRACTICE. NEPHROLOGY 2008; 4:378-92. [PMID: 18542120 PMCID: PMC2574729 DOI: 10.1038/ncpneph0848] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 04/29/2008] [Indexed: 12/22/2022]
Abstract
Endogenous digitalis-like factors, also called cardiotonic steroids, have been thought for nearly half a century to have important roles in health and disease. The endogenous cardiotonic steroids ouabain and marinobufagenin have been identified in humans, and an effector mechanism has been delineated by which these hormones signal through the sodium/potassium-transporting ATPase. These findings have increased interest in this field substantially. Although cardiotonic steroids were first considered important in the regulation of renal sodium transport and arterial pressure, subsequent work has implicated these hormones in the control of cell growth, apoptosis and fibrosis, among other processes. This Review focuses on the role of endogenous cardiotonic steroids in the pathophysiology of essential hypertension, congestive heart failure, end-stage renal disease and pre-eclampsia. We also discuss potential therapeutic strategies that have emerged as a result of the increased understanding of the regulation and actions of cardiotonic steroids.
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Affiliation(s)
- Alexei Y Bagrov
- Hypertension Unit at Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, Baltimore 21224, MD, USA.
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Novel interactions of CLN3 protein link Batten disease to dysregulation of fodrin-Na+, K+ ATPase complex. Exp Cell Res 2008; 314:2895-905. [PMID: 18621045 DOI: 10.1016/j.yexcr.2008.06.016] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 05/22/2008] [Accepted: 06/13/2008] [Indexed: 01/15/2023]
Abstract
Juvenile neuronal ceroid lipofuscinosis (JNCL, Batten disease) is the most common progressive neurodegenerative disorder of childhood. CLN3, the transmembrane protein underlying JNCL, is proposed to participate in multiple cellular events including membrane trafficking and cytoskeletal functions. We demonstrate here that CLN3 interacts with the plasma membrane-associated cytoskeletal and endocytic fodrin and the associated Na(+), K(+) ATPase. The ion pumping activity of Na(+), K(+) ATPase was unchanged in Cln3(-/-) mouse primary neurons. However, the immunostaining pattern of fodrin appeared abnormal in JNCL fibroblasts and Cln3(-/-) mouse brains suggesting disturbances in the fodrin cytoskeleton. Furthermore, the basal subcellular distribution as well as ouabain-induced endocytosis of neuron-specific Na(+), K(+) ATPase were remarkably affected in Cln3(-/-) mouse primary neurons. These data suggest that CLN3 is involved in the regulation of plasma membrane fodrin cytoskeleton and consequently, the plasma membrane association of Na(+), K(+) ATPase. Most of the processes regulated by multifunctional fodrin and Na(+), K(+) ATPase are also affected in JNCL and Cln3-deficiency implicating that dysregulation of fodrin cytoskeleton and non-pumping functions of Na(+), K(+) ATPase may play a role in the neuronal degeneration in JNCL.
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Torielli L, Tivodar S, Montella RC, Iacone R, Padoani G, Tarsini P, Russo O, Sarnataro D, Strazzullo P, Ferrari P, Bianchi G, Zurzolo C. alpha-Adducin mutations increase Na/K pump activity in renal cells by affecting constitutive endocytosis: implications for tubular Na reabsorption. Am J Physiol Renal Physiol 2008; 295:F478-87. [PMID: 18524856 DOI: 10.1152/ajprenal.90226.2008] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Genetic variation in alpha-adducin cytoskeletal protein is implicated in the polymerization and bundling of actin and alteration of the Na/K pump, resulting in abnormal renal sodium transport and hypertension in Milan hypertensive rats and humans. To investigate the molecular involvement of alpha-adducin in controlling Na/K pump activity, wild-type or mutated rat and human alpha-adducin forms were, respectively, transfected into several renal cell lines. Through multiple experimental approaches (microscopy, enzymatic assays, coimmunoprecipitation), we showed that rat and human mutated forms increased Na/K pump activity and the number of pump units; moreover, both variants coimmunoprecipitate with Na/K pump. The increased Na/K pump activity was not due to changes in its basolateral localization, but to an alteration of Na/K pump residential time on the plasma membrane. Indeed, both rat and human mutated variants reduced constitutive Na/K pump endocytosis and similarly affected transferrin receptor trafficking and fluid-phase endocytosis. In fact, alpha-adducin was detected in clathrin-coated vesicles and coimmunoprecipitated with clathrin. These results indicate that adducin, besides its modulatory effects on actin cytoskeleton dynamics, might play a direct role in clathrin-dependent endocytosis. The constitutive reduction of the Na/K pump endocytic rate induced by mutated adducin variants may be relevant in Na-dependent hypertension.
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Cai H, Wu L, Qu W, Malhotra D, Xie Z, Shapiro JI, Liu J. Regulation of apical NHE3 trafficking by ouabain-induced activation of the basolateral Na+-K+-ATPase receptor complex. Am J Physiol Cell Physiol 2007; 294:C555-63. [PMID: 18077602 DOI: 10.1152/ajpcell.00475.2007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The long-term effects of ouabain on transepithelial Na(+) transport involve transcriptional downregulation of apical Na(+)/H(+) exchanger isoform 3 (NHE3). The aim of this study was to determine whether ouabain could acutely regulate NHE3 via a posttranscriptional mechanism in LLC-PK1 cells. We observed that the basolateral, but not apical, application of ouabain for 1 h significantly reduced transepithelial Na(+) transport. This effect was not due to changes in the integrity of tight junctions or increases in the intracellular Na(+) concentration. Ouabain regulated the trafficking of NHE3 and subsequently inhibited its activity, a process independent of intracellular Na(+) concentration. Ouabain-induced NHE3 trafficking was abolished by either cholesterol depletion or Src inhibition. Moreover, ouabain increased the intracellular Ca(2+) concentration. Pretreatment of cells with the intracellular Ca(2+) chelator BAPTA-AM blocked ouabain-induced trafficking of NHE3. Also, blockade of Na(+)-K(+)-ATPase endocytosis by a phosphatidylinositol 3-kinase inhibitor was equally effective in attenuating ouabain-induced NHE3 trafficking. These data indicate that ouabain acutely stimulates NHE3 trafficking by activating the basolateral Na(+)-K(+)-ATPase signaling complex. Taken together with our previous observations, we propose that ouabain can simultaneously regulate basolateral Na(+)-K(+)-ATPase and apical NHE3, leading to inhibition of transepithelial Na(+) transport. This mechanism may be relevant to proximal tubular Na(+) handling during conditions associated with increases in circulating endogenous cardiotonic steroids.
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Affiliation(s)
- Haiping Cai
- Department of Medicine, University of Toledo College of Medicine, 3120 Glendale Ave., Toledo, OH 43614-5089, USA
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Regulation of sodium pump endocytosis by cardiotonic steroids: Molecular mechanisms and physiological implications. ACTA ACUST UNITED AC 2007; 14:171-81. [PMID: 17961998 DOI: 10.1016/j.pathophys.2007.09.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have previously shown that ouabain and other cardiotonic steroids interact with the plasmalemmal Na/K-ATPase and cause a time and dose dependent endocytosis of the Na/K-ATPase. This endocytosis is demonstrable using fluorescence imaging as well as conventional biochemical and biophysical cell separation methods. In proximal tubule cells, this process appears to regulate the density of basolateral Na/K-ATPase expression directly as well as indirectly modulate transepithelial sodium transport. Work with genetic manipulations, as well as pharmacological agents with cell culture models, have demonstrated that the cardiotonic steroid stimulated endocytosis of the plasmalemmal Na/K-ATPase requires caveolin and clathrin as well as the activation of c-Src, transactivation of the EGFR and activation of PI3K. Interestingly c-Src, EGFR and ERK1/2 all appear to be endocytosed along with the plasmalemmal Na/K-ATPase. These observations suggest a close analogy between a subset of plasmalemmal Na/K-ATPase and signaling companions with conventional receptor tyrosine kinases. While further studies are necessary to delineate the role of this endocytosis in the generation as well as the limit of signal transduction through the Na/K-ATPase signal cascade, we propose that it has an important role in the regulation of renal sodium handling as well as other important processes.
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Akimova OA, Hamet P, Orlov SN. [Na+]i/[K+]i -independent death of ouabain-treated renal epithelial cells is not mediated by Na+,K+ -ATPase internalization and de novo gene expression. Pflugers Arch 2007; 455:711-9. [PMID: 17622553 DOI: 10.1007/s00424-007-0283-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Accepted: 05/02/2007] [Indexed: 10/23/2022]
Abstract
The cytotoxic effect of long-term exposure of renal epithelial cells to ouabain and other cardiotonic steroids (CTS) is mediated by the interaction of these compounds with Na(+),K(+)-ATPase but is independent of the inhibition of Na(+),K(+)-ATPase-mediated ion fluxes. Sustained application of CTS also leads to Na(+),K(+)-ATPase endocytosis and its translocation into the nuclei that might trigger the cell death machinery via the regulation of gene expression. This study examines the role of Na(+),K(+)-ATPase internalization and de novo gene expression in the death of ouabain-treated C7-Madin-Darby canine kidney (MDCK) cells derived from distal tubules of the MDCK. In these cells, 6-h exposure to 3 microM ouabain led to the internalization of approximately 50% of plasmalemmal Na(+),K(+)-ATPase. Prolonged incubation in a K(+)-free medium abolished ouabain-induced Na(+),K(+)-ATPase internalization but did not affect the cytotoxic action of ouabain seen after 18-h incubation. Previously, it was shown that CTS-induced Na(+),K(+)-ATPase internalization is mediated by its interaction with Src within caveolae. Neither caveolae damage by cholesterol depletion with methyl-beta-cyclodextrin nor Src inhibition with 4-amino-5(4-chlorophenyl)-7-(t-butyl)pyrazol[3,4-d]pyridine affected the death of ouabain-treated C7-MDCK cells. Actinomycin D at the 0.1-microg/ml concentration almost completely abolished ribonucleic acid synthesis but did not protect C7-MDCK cells from the cytotoxic action of ouabain. Our results show that neither Na(+),K(+)-ATPase endocytosis nor de novo gene expression contributes to Na(+)(i), K(+)(i)-independent cell death signaling evoked by prolonged exposure to CTS.
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Affiliation(s)
- Olga A Akimova
- Research Centre, Centre Hospitalier de l'Université de Montréal, Technôpole Angus, 2901 Rachel East, Montreal, Quebec H1W 4A4, Canada
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