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Amiri M, Kaviari MA, Rostaminasab G, Barimani A, Rezakhani L. A novel cell-free therapy using exosomes in the inner ear regeneration. Tissue Cell 2024; 88:102373. [PMID: 38640600 DOI: 10.1016/j.tice.2024.102373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/01/2024] [Accepted: 04/03/2024] [Indexed: 04/21/2024]
Abstract
Cellular and molecular alterations associated with hearing loss are now better understood with advances in molecular biology. These changes indicate the participation of distinct damage and stress pathways that are unlikely to be fully addressed by conventional pharmaceutical treatment. Sensorineural hearing loss is a common and debilitating condition for which comprehensive pharmacologic intervention is not available. The complex and diverse molecular pathology that underlies hearing loss currently limits our ability to intervene with small molecules. The present review focuses on the potential for the use of extracellular vesicles in otology. It examines a variety of inner ear diseases and hearing loss that may be treatable using exosomes (EXOs). The role of EXOs as carriers for the treatment of diseases related to the inner ear as well as EXOs as biomarkers for the recognition of diseases related to the ear is discussed.
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Affiliation(s)
- Masoumeh Amiri
- Faculty of Medicine, Kermanshah University of Medical Science, Kermanshah, Iran
| | - Mohammad Amin Kaviari
- Student Research Committee, Kermanshah University of Medical Sciences, Kermanshah, Iran; Universal Scientific Education and Research Network (USERN) Office, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Gelavizh Rostaminasab
- Clinical Research Development Center, Imam Khomeini and Mohammad Kermanshahi and Farabi Hospitals, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Amir Barimani
- Clinical Research Development Center, Imam Khomeini and Mohammad Kermanshahi and Farabi Hospitals, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Leila Rezakhani
- Fertility and Infertility Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran; Department of Tissue Engineering, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran.
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Su XT, Reyes JV, Lackey AE, Demirci H, Bachmann S, Maeoka Y, Cornelius RJ, McCormick JA, Yang CL, Jung HJ, Welling PA, Nelson JW, Ellison DH. Enriched Single-Nucleus RNA-Sequencing Reveals Unique Attributes of Distal Convoluted Tubule Cells. J Am Soc Nephrol 2024; 35:426-440. [PMID: 38238903 PMCID: PMC11000721 DOI: 10.1681/asn.0000000000000297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Accepted: 12/17/2023] [Indexed: 01/24/2024] Open
Abstract
SIGNIFICANCE STATEMENT High-resolution single-nucleus RNA-sequencing data indicate a clear separation between primary sites of calcium and magnesium handling within distal convoluted tubule (DCT). Both DCT1 and DCT2 express Slc12a3, but these subsegments serve distinctive functions, with more abundant magnesium-handling genes along DCT1 and more calcium-handling genes along DCT2. The data also provide insight into the plasticity of the distal nephron-collecting duct junction, formed from cells of separate embryonic origins. By focusing/changing gradients of gene expression, the DCT can morph into different physiological cell states on demand. BACKGROUND The distal convoluted tubule (DCT) comprises two subsegments, DCT1 and DCT2, with different functional and molecular characteristics. The functional and molecular distinction between these segments, however, has been controversial. METHODS To understand the heterogeneity within the DCT population with better clarity, we enriched for DCT nuclei by using a mouse line combining "Isolation of Nuclei Tagged in specific Cell Types" and sodium chloride cotransporter-driven inducible Cre recombinase. We sorted the fluorescently labeled DCT nuclei using Fluorescence-Activated Nucleus Sorting and performed single-nucleus transcriptomics. RESULTS Among 25,183 DCT cells, 75% were from DCT1 and 25% were from DCT2. In addition, there was a small population (<1%) enriched in proliferation-related genes, such as Top2a , Cenpp , and Mki67 . Although both DCT1 and DCT2 expressed sodium chloride cotransporter, magnesium transport genes were predominantly expressed along DCT1, whereas calcium, electrogenic sodium, and potassium transport genes were more abundant along DCT2. The transition between these two segments was gradual, with a transitional zone in which DCT1 and DCT2 cells were interspersed. The expression of the homeobox genes by DCT cells suggests that they develop along different trajectories. CONCLUSIONS Transcriptomic analysis of an enriched rare cell population using a genetically targeted approach clarifies the function and classification of distal cells. The DCT segment is short, can be separated into two subsegments that serve distinct functions, and is speculated to derive from different origins during development.
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Affiliation(s)
- Xiao-Tong Su
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Jeremiah V. Reyes
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
- Department of Biochemistry and Molecular Biology, College of Medicine, University of the Philippines Manila, Manila, Philippines
| | - Anne E. Lackey
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Hasan Demirci
- Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Sebastian Bachmann
- Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Yujiro Maeoka
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Ryan J. Cornelius
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - James A. McCormick
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Chao-Ling Yang
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Hyun Jun Jung
- Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Paul A. Welling
- Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Jonathan W. Nelson
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - David H. Ellison
- Division of Hypertension and Nephrology, School of Medicine, Oregon Health & Science University, Portland, Oregon
- Oregon Clinical and Translational Research Institute, Oregon Health & Science University, Portland, Oregon
- Renal Section, VA Portland Healthcare System, Portland, Oregon
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Mutchler SM, Hasan M, Murphy CP, Baty CJ, Boyd-Shiwarski C, Kirabo A, Kleyman TR. Dietary sodium alters aldosterone's effect on renal sodium transporter expression and distal convoluted tubule remodelling. J Physiol 2024; 602:967-987. [PMID: 38294810 PMCID: PMC10939779 DOI: 10.1113/jp284041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 12/21/2023] [Indexed: 02/01/2024] Open
Abstract
Aldosterone is responsible for maintaining volume and potassium homeostasis. Although high salt consumption should suppress aldosterone production, individuals with hyperaldosteronism lose this regulation, leading to a state of high aldosterone despite dietary sodium consumption. The present study examines the effects of elevated aldosterone, with or without high salt consumption, on the expression of key Na+ transporters and remodelling in the distal nephron. Epithelial sodium channel (ENaC) α-subunit expression was increased with aldosterone regardless of Na+ intake. However, ENaC β- and γ-subunits unexpectedly increased at both a transcript and protein level with aldosterone when high salt was present. Expression of total and phosphorylated Na+ Cl- cotransporter (NCC) significantly increased with aldosterone, in association with decreased blood [K+ ], but the addition of high salt markedly attenuated the aldosterone-dependent NCC increase, despite equally severe hypokalaemia. We hypothesized this was a result of differences in distal convoluted tubule length when salt was given with aldosterone. Imaging and measurement of the entire pNCC-positive tubule revealed that aldosterone alone caused a shortening of this segment, although the tubule had a larger cross-sectional diameter. This was not true when salt was given with aldosterone because the combination was associated with a lengthening of the tubule in addition to increased diameter, suggesting that differences in the pNCC-positive area are not responsible for differences in NCC expression. Together, our results suggest the actions of aldosterone, and the subsequent changes related to hypokalaemia, are altered in the presence of high dietary Na+ . KEY POINTS: Aldosterone regulates volume and potassium homeostasis through effects on transporters in the kidney; its production can be dysregulated, preventing its suppression by high dietary sodium intake. Here, we examined how chronic high sodium consumption affects aldosterone's regulation of sodium transporters in the distal nephron. Our results suggest that high sodium consumption with aldosterone is associated with increased expression of all three epithelial sodium channel subunits, rather than just the alpha subunit. Aldosterone and its associated decrease in blood [K+ ] lead to an increased expression of Na-Cl cotransporter (NCC); the addition of high sodium consumption with aldosterone partially attenuates this NCC expression, despite similarly low blood [K+ ]. Upstream kinase regulators and tubule remodelling do not explain these results.
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Affiliation(s)
| | | | - Carolyn P Murphy
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Catherine J Baty
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | | | - Annet Kirabo
- Division of Clinical Pharmacology, Department of Medicine, and Department of Molecular Physiology and Biophysics Vanderbilt University, Nashville, TN, USA
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
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Abstract
Aldosterone exerts profound effects on renal and cardiovascular physiology. In the kidney, aldosterone acts to preserve electrolyte and acid-base balance in response to changes in dietary sodium (Na+ ) or potassium (K+ ) intake. These physiological actions, principally through activation of mineralocorticoid receptors (MRs), have important effects particularly in patients with renal and cardiovascular disease as demonstrated by multiple clinical trials. Multiple factors, be they genetic, humoral, dietary, or otherwise, can play a role in influencing the rate of aldosterone synthesis and secretion from the adrenal cortex. Normally, aldosterone secretion and action respond to dietary Na+ intake. In the kidney, the distal nephron and collecting duct are the main targets of aldosterone and MR action, which stimulates Na+ absorption in part via the epithelial Na+ channel (ENaC), the principal channel responsible for the fine-tuning of Na+ balance. Our understanding of the regulatory factors that allow aldosterone, via multiple signaling pathways, to function properly clearly implicates this hormone as central to many pathophysiological effects that become dysfunctional in disease states. Numerous pathologies that affect blood pressure (BP), electrolyte balance, and overall cardiovascular health are due to abnormal secretion of aldosterone, mutations in MR, ENaC, or effectors and modulators of their action. Study of the mechanisms of these pathologies has allowed researchers and clinicians to create novel dietary and pharmacological targets to improve human health. This article covers the regulation of aldosterone synthesis and secretion, receptors, effector molecules, and signaling pathways that modulate its action in the kidney. We also consider the role of aldosterone in disease and the benefit of mineralocorticoid antagonists. © 2023 American Physiological Society. Compr Physiol 13:4409-4491, 2023.
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Affiliation(s)
- Jermaine G Johnston
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Amanda K Welch
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Brian D Cain
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
| | - Peter P Sayeski
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
| | - Michelle L Gumz
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
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Lee SK, Boron WF, Occhipinti R. Potential Novel Role of Membrane-Associated Carbonic Anhydrases in the Kidney. Int J Mol Sci 2023; 24. [PMID: 36835660 DOI: 10.3390/ijms24044251] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 02/06/2023] [Accepted: 02/06/2023] [Indexed: 02/23/2023] Open
Abstract
Carbonic anhydrases (CAs), because they catalyze the interconversion of carbon dioxide (CO2) and water into bicarbonate (HCO3-) and protons (H+), thereby influencing pH, are near the core of virtually all physiological processes in the body. In the kidneys, soluble and membrane-associated CAs and their synergy with acid-base transporters play important roles in urinary acid secretion, the largest component of which is the reabsorption of HCO3- in specific nephron segments. Among these transporters are the Na+-coupled HCO3- transporters (NCBTs) and the Cl--HCO3- exchangers (AEs)-members of the "solute-linked carrier" 4 (SLC4) family. All of these transporters have traditionally been regarded as "HCO3-" transporters. However, recently our group has demonstrated that two of the NCBTs carry CO32- rather than HCO3- and has hypothesized that all NCBTs follow suit. In this review, we examine current knowledge on the role of CAs and "HCO3-" transporters of the SLC4 family in renal acid-base physiology and discuss how our recent findings impact renal acid secretion, including HCO3- reabsorption. Traditionally, investigators have associated CAs with producing or consuming solutes (CO2, HCO3-, and H+) and thus ensuring their efficient transport across cell membranes. In the case of CO32- transport by NCBTs, however, we hypothesize that the role of membrane-associated CAs is not the appreciable production or consumption of substrates but the minimization of pH changes in nanodomains near the membrane.
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Castañeda-Bueno M, Ellison DH. Blood pressure effects of sodium transport along the distal nephron. Kidney Int 2022; 102:1247-1258. [PMID: 36228680 PMCID: PMC9754644 DOI: 10.1016/j.kint.2022.09.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 08/22/2022] [Accepted: 09/01/2022] [Indexed: 11/06/2022]
Abstract
The mammalian distal nephron is a target of highly effective antihypertensive drugs. Genetic variants that alter its transport activity are also inherited causes of high or low blood pressure, clearly establishing its central role in human blood pressure regulation. Much has been learned during the past 25 years about salt transport along this nephron segment, spurred by the cloning of major transport proteins and the discovery of disease-causing genetic variants. Recognition is increasing that substantial cellular and segmental heterogeneity is present along this segment, with electroneutral sodium transport dominating more proximal segments and electrogenic sodium transport dominating more distal segments. Coupled with recent insights into factors that modulate transport along these segments, we now understand one important mechanism by which dietary potassium intake influences sodium excretion and blood pressure. This finding has solved the aldosterone paradox, by demonstrating how aldosterone can be both kaliuretic, when plasma potassium is elevated, and anti-natriuretic, when extracellular fluid volume is low. However, what also has become clear is that aldosterone itself only stimulates a portion of the mineralocorticoid receptors along this segment, with the others being activated by glucocorticoid hormones instead. These recent insights provide an increasingly clear picture of how this short nephron segment contributes to blood pressure homeostasis and have important implications for hypertension prevention and treatment.
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Affiliation(s)
- María Castañeda-Bueno
- Department of Nephrology and Mineral Metabolism, National Institute of Medical Sciences and Nutrition, Salvador Zubirán, Tlalpan, Mexico City, Mexico
| | - David H Ellison
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon, USA; Oregon Clinical & Translational Research Institute, Oregon Health & Science University, Portland, Oregon, USA; LeDucq Transatlantic Network of Excellence, Portland, Oregon, USA; Renal Section, VA Portland Healthcare System, Portland, Oregon, USA.
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Frindt G, Meyerson JR, Satty A, Scandura JM, Palmer LG. Expression of ENaC subunits in epithelia. J Gen Physiol 2022; 154:213382. [PMID: 35939271 PMCID: PMC9387651 DOI: 10.1085/jgp.202213124] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 05/27/2022] [Accepted: 07/01/2022] [Indexed: 12/14/2022] Open
Abstract
The epithelial Na+ channel (ENaC) is a heterotrimeric protein whose assembly, trafficking, and function are highly regulated. To better understand the biogenesis and activation of the channel, we quantified the expression of individual subunits of ENaC in rat kidneys and colon using calibrated Western blots. The estimated abundance for the three subunits differed by an order of magnitude with the order γENaC ∼ βENaC ≫ αENaC in both organs. Transcript abundance in the kidney, measured with digital-drop PCR and RNAseq, was similar for the three subunits. In both organs, the calculated protein expression of all subunits was much larger than that required to account for maximal Na+ currents measured in these cells, implying a large excess of subunit protein. Whole-kidney biotinylation indicated that at least 5% of β and γ subunits in the kidney and 3% in the colon were expressed on the surface under conditions of salt restriction, which maximizes ENaC-dependent Na+ transport. This indicates a 10- to 100-fold excess of βENaC and γENaC subunits at the surface relative to the requirement for channel activity. We conclude that these epithelia make much more ENaC protein than is required for the physiological function of the channel. This could facilitate rapid regulation of the channels at the cell surface by insuring a large population of inactive, recruitable subunits.
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Affiliation(s)
- Gustavo Frindt
- Departments of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Joel R. Meyerson
- Departments of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Alexandra Satty
- Department of Medicine, Weill-Cornell Medical College, New York, NY
| | | | - Lawrence G. Palmer
- Departments of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY,Correspondence to Lawrence G. Palmer:
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Yang L, Xu Y, Gravotta D, Frindt G, Weinstein AM, Palmer LG. ENaC and ROMK channels in the connecting tubule regulate renal K+ secretion. J Gen Physiol 2021; 153:212401. [PMID: 34143184 PMCID: PMC8217949 DOI: 10.1085/jgp.202112902] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/24/2021] [Indexed: 12/15/2022] Open
Abstract
We measured the activities of epithelial Na channels (ENaC) and ROMK channels in the distal nephron of the mouse kidney and assessed their role in the process of K+ secretion under different physiological conditions. Under basal dietary conditions (0.5% K), ENaC activity, measured as amiloride-sensitive currents, was high in cells at the distal end of the distal convoluted tubule (DCT) and proximal end of the connecting tubule (CNT), a region we call the early CNT (CNTe). In more distal parts of the CNT (aldosterone-sensitive portion [CNTas]), these currents were minimal. This functional difference correlated with alterations in the intracellular location of ENaC, which was at or near the apical membrane in CNTe and more cytoplasmic in the CNTas. ROMK activity, measured as TPNQ-sensitive currents, was substantial in both segments. A mathematical model of the rat nephron suggested that K+ secretion by the CNTe predicted from these currents provides much of the urinary K+ required for K balance on this diet. In animals fed a K-deficient diet (0.1% K), both ENaC and ROMK currents in the CNTe decreased by ∼50%, predicting a 50% decline in K+ secretion. Enhanced reabsorption by a separate mechanism is required to avoid excessive urinary K+ losses. In animals fed a diet supplemented with 3% K, ENaC currents increased modestly in the CNTe but strongly in the CNTas, while ROMK currents tripled in both segments. The enhanced secretion of K+ by the CNTe and the recruitment of secretion by the CNTas account for the additional transport required for K balance. Therefore, adaptation to increased K+ intake involves the extension of robust K+ secretion to more distal parts of the nephron.
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Affiliation(s)
- Lei Yang
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Yuanyuan Xu
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Diego Gravotta
- Department of Ophthalmology, Weill-Cornell Medical College, New York, NY
| | - Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Alan M Weinstein
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
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Abstract
The Epithelial Na+ Channel, ENaC, comprised of 3 subunits (αβγ, or sometimes δβγENaC), plays a critical role in regulating salt and fluid homeostasis in the body. It regulates fluid reabsorption into the blood stream from the kidney to control blood volume and pressure, fluid absorption in the lung to control alveolar fluid clearance at birth and maintenance of normal airway surface liquid throughout life, and fluid absorption in the distal colon and other epithelial tissues. Moreover, recent studies have also revealed a role for sodium movement via ENaC in nonepithelial cells/tissues, such as endothelial cells in blood vessels and neurons. Over the past 25 years, major advances have been made in our understanding of ENaC structure, function, regulation, and role in human disease. These include the recently solved three-dimensional structure of ENaC, ENaC function in various tissues, and mutations in ENaC that cause a hereditary form of hypertension (Liddle syndrome), salt-wasting hypotension (PHA1), or polymorphism in ENaC that contributes to other diseases (such as cystic fibrosis). Moreover, great strides have been made in deciphering the regulation of ENaC by hormones (e.g., the mineralocorticoid aldosterone, glucocorticoids, vasopressin), ions (e.g., Na+ ), proteins (e.g., the ubiquitin-protein ligase NEDD4-2, the kinases SGK1, AKT, AMPK, WNKs & mTORC2, and proteases), and posttranslational modifications [e.g., (de)ubiquitylation, glycosylation, phosphorylation, acetylation, palmitoylation]. Characterization of ENaC structure, function, regulation, and role in human disease, including using animal models, are described in this article, with a special emphasis on recent advances in the field. © 2021 American Physiological Society. Compr Physiol 11:1-29, 2021.
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Affiliation(s)
- Daniela Rotin
- The Hospital for Sick Children, and The University of Toronto, Toronto, Canada
| | - Olivier Staub
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
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Sholokh A, Klussmann E. Local cyclic adenosine monophosphate signalling cascades-Roles and targets in chronic kidney disease. Acta Physiol (Oxf) 2021; 232:e13641. [PMID: 33660401 DOI: 10.1111/apha.13641] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 02/26/2021] [Accepted: 03/01/2021] [Indexed: 12/20/2022]
Abstract
The molecular mechanisms underlying chronic kidney disease (CKD) are poorly understood and treatment options are limited, a situation underpinning the need for elucidating the causative molecular mechanisms and for identifying innovative treatment options. It is emerging that cyclic 3',5'-adenosine monophosphate (cAMP) signalling occurs in defined cellular compartments within nanometre dimensions in processes whose dysregulation is associated with CKD. cAMP compartmentalization is tightly controlled by a specific set of proteins, including A-kinase anchoring proteins (AKAPs) and phosphodiesterases (PDEs). AKAPs such as AKAP18, AKAP220, AKAP-Lbc and STUB1, and PDE4 coordinate arginine-vasopressin (AVP)-induced water reabsorption by collecting duct principal cells. However, hyperactivation of the AVP system is associated with kidney damage and CKD. Podocyte injury involves aberrant AKAP signalling. cAMP signalling in immune cells can be local and slow the progression of inflammatory processes typical for CKD. A major risk factor of CKD is hypertension. cAMP directs the release of the blood pressure regulator, renin, from juxtaglomerular cells, and plays a role in Na+ reabsorption through ENaC, NKCC2 and NCC in the kidney. Mutations in the cAMP hydrolysing PDE3A that cause lowering of cAMP lead to hypertension. Another major risk factor of CKD is diabetes mellitus. AKAP18 and AKAP150 and several PDEs are involved in insulin release. Despite the increasing amount of data, an understanding of functions of compartmentalized cAMP signalling with relevance for CKD is fragmentary. Uncovering functions will improve the understanding of physiological processes and identification of disease-relevant aberrations may guide towards new therapeutic concepts for the treatment of CKD.
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Affiliation(s)
- Anastasiia Sholokh
- Max‐Delbrück‐Center for Molecular Medicine (MDC) Helmholtz Association Berlin Germany
| | - Enno Klussmann
- Max‐Delbrück‐Center for Molecular Medicine (MDC) Helmholtz Association Berlin Germany
- DZHK (German Centre for Cardiovascular Research) Berlin Germany
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11
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Essigke D, Ilyaskin AV, Wörn M, Bohnert BN, Xiao M, Daniel C, Amann K, Birkenfeld AL, Szabo R, Bugge TH, Korbmacher C, Artunc F. Zymogen-locked mutant prostasin (Prss8) leads to incomplete proteolytic activation of the epithelial sodium channel (ENaC) and severely compromises triamterene tolerance in mice. Acta Physiol (Oxf) 2021; 232:e13640. [PMID: 33650216 DOI: 10.1111/apha.13640] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 02/15/2021] [Accepted: 02/26/2021] [Indexed: 02/06/2023]
Abstract
AIM The serine protease prostasin (Prss8) is expressed in the distal tubule and stimulates proteolytic activation of the epithelial sodium channel (ENaC) in co-expression experiments in vitro. The aim of this study was to explore the role of prostasin in proteolytic ENaC activation in the kidney in vivo. METHODS We used genetically modified knockin mice carrying a Prss8 mutation abolishing proteolytic activity (Prss8-S238A) or a mutation leading to a zymogen-locked state (Prss8-R44Q). Mice were challenged with low sodium diet and diuretics. Regulation of ENaC activity by Prss8-S238A and Prss8-R44Q was studied in vitro using the Xenopus laevis oocyte expression system. RESULTS Co-expression of murine ENaC with Prss8-wt or Prss8-S238A in oocytes caused maximal proteolytic ENaC activation, whereas ENaC was activated only partially in oocytes co-expressing Prss8-R44Q. This was paralleled by a reduced proteolytic activity at the cell surface of Prss8-R44Q expressing oocytes. Sodium conservation under low sodium diet was preserved in Prss8-S238A and Prss8-R44Q mice but with higher plasma aldosterone concentrations in Prss8-R44Q mice. Treatment with the ENaC inhibitor triamterene over four days was tolerated in Prss8-wt and Prss8-S238A mice, whereas Prss8-R44Q mice developed salt wasting and severe weight loss associated with hyperkalemia and acidosis consistent with impaired ENaC function and renal failure. CONCLUSION Unlike proteolytically inactive Prss8-S238A, zymogen-locked Prss8-R44Q produces incomplete proteolytic ENaC activation in vitro and causes a severe renal phenotype in mice treated with the ENaC inhibitor triamterene. This indicates that Prss8 plays a role in proteolytic ENaC activation and renal function independent of its proteolytic activity.
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Affiliation(s)
- Daniel Essigke
- Department of Internal Medicine Division of Endocrinology, Diabetology and Nephrology University Hospital Tübingen Tuebingen Germany
| | - Alexandr V. Ilyaskin
- Institute of Cellular and Molecular Physiology Friedrich‐Alexander University Erlangen‐Nürnberg (FAU) Erlangen Germany
| | - Matthias Wörn
- Department of Internal Medicine Division of Endocrinology, Diabetology and Nephrology University Hospital Tübingen Tuebingen Germany
| | - Bernhard N. Bohnert
- Department of Internal Medicine Division of Endocrinology, Diabetology and Nephrology University Hospital Tübingen Tuebingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tuebingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tuebingen Germany
| | - Mengyun Xiao
- Department of Internal Medicine Division of Endocrinology, Diabetology and Nephrology University Hospital Tübingen Tuebingen Germany
| | - Christoph Daniel
- Institute of Pathology Department of Nephropathology Friedrich‐Alexander University Erlangen‐Nürnberg (FAU) Erlangen Germany
| | - Kerstin Amann
- Institute of Pathology Department of Nephropathology Friedrich‐Alexander University Erlangen‐Nürnberg (FAU) Erlangen Germany
| | - Andreas L. Birkenfeld
- Department of Internal Medicine Division of Endocrinology, Diabetology and Nephrology University Hospital Tübingen Tuebingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tuebingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tuebingen Germany
| | - Roman Szabo
- Proteases and Tissue Remodeling Section National Institute of Dental and Craniofacial ResearchNational Institutes of Health Bethesda MD USA
| | - Thomas H. Bugge
- Proteases and Tissue Remodeling Section National Institute of Dental and Craniofacial ResearchNational Institutes of Health Bethesda MD USA
| | - Christoph Korbmacher
- Institute of Cellular and Molecular Physiology Friedrich‐Alexander University Erlangen‐Nürnberg (FAU) Erlangen Germany
| | - Ferruh Artunc
- Department of Internal Medicine Division of Endocrinology, Diabetology and Nephrology University Hospital Tübingen Tuebingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tuebingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tuebingen Germany
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12
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Zhang DD, Duan XP, Xiao Y, Wu P, Gao ZX, Wang WH, Lin DH. Deletion of renal Nedd4-2 abolishes the effect of high sodium intake (HS) on Kir4.1, ENaC, and NCC and causes hypokalemia during high HS. Am J Physiol Renal Physiol 2021; 320:F883-F896. [PMID: 33818128 DOI: 10.1152/ajprenal.00555.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Neural precursor cell expressed developmentally downregulated protein 4-2 (Nedd4-2) regulates the expression of Kir4.1, thiazide-sensitive NaCl cotransporter (NCC), and epithelial Na+ channel (ENaC) in the aldosterone-sensitive distal nephron (ASDN), and Nedd4-2 deletion causes salt-sensitive hypertension. We now examined whether Nedd4-2 deletion compromises the effect of high-salt (HS) diet on Kir4.1, NCC, ENaC, and renal K+ excretion. Immunoblot analysis showed that HS diet decreased the expression of Kir4.1, Ca2+-activated large-conductance K+ channel subunit-α (BKα), ENaCβ, ENaCγ, total NCC, and phospho-NCC (at Thr53) in floxed neural precursor cell expressed developmentally downregulated gene 4-like (Nedd4lfl/fl) mice, whereas these effects were absent in kidney-specific Nedd4-2 knockout (Ks-Nedd4-2 KO) mice. Renal clearance experiments also demonstrated that Nedd4-2 deletion abolished the inhibitory effect of HS diet on hydrochlorothiazide-induced natriuresis. Patch-clamp experiments showed that neither HS diet nor low-salt diet had an effect on Kir4.1/Kir5.1 currents of the distal convoluted tubule in Nedd4-2-deficient mice, whereas we confirmed that HS diet inhibited and low-salt diet increased Kir4.1/Kir5.1 activity in Nedd4lflox/flox mice. Nedd4-2 deletion increased ENaC currents in the ASDN, and this increase was more robust in the cortical collecting duct than in the distal convoluted tubule. Also, HS-induced inhibition of ENaC currents in the ASDN was absent in Nedd4-2-deficient mice. Renal clearance experiments showed that HS intake for 2 wk increased the basal level of renal K+ excretion and caused hypokalemia in Ks-Nedd4-2-KO mice but not in Nedd4lflox/flox mice. In contrast, plasma Na+ concentrations were similar in Nedd4lflox/flox and Ks-Nedd4-2 KO mice on HS diet. We conclude that Nedd4-2 plays an important role in mediating the inhibitory effect of HS diet on Kir4.1, ENaC, and NCC and is essential for maintaining normal renal K+ excretion and plasma K+ ranges during long-term HS diet.NEW & NOTEWORTHY The present study suggests that Nedd4-2 is involved in mediating the inhibitory effect of high salt (HS) diet on Kir4.1/kir5.1 in the distal convoluted tubule, NaCl cotransporter function, and epithelial Na+ channel activity and that Nedd4-2 plays an essential role in maintaining K+ homeostasis in response to a long-term HS diet. This suggests the possibility that HS intake could lead to hypokalemia in subjects lacking proper Nedd4-2 E3 ubiquitin ligase activity in aldosterone-sensitive distal nephron.
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Affiliation(s)
- Dan-Dan Zhang
- Guangdong-Hong Kong Joint Laboratory on Immunological and Genetic Kidney Diseases, Guangdong Academy of Medical Sciences, Guangdong Provincial People's Hospital, Guangzhou, China.,Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Xin-Peng Duan
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Yu Xiao
- Department of Physiology, Qiqihar Medical College, Heilongjiang, China.,Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Peng Wu
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Zhong-Xiuzi Gao
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
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13
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Wang MX, Wang LJ, Xiao Y, Zhang DD, Duan XP, Wang WH. Epoxyeicosatrienoic acid metabolites inhibit Kir4.1/Kir5.1 in the distal convoluted tubule. Am J Physiol Renal Physiol 2020; 318:F1369-F1376. [PMID: 32308018 PMCID: PMC7311705 DOI: 10.1152/ajprenal.00018.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/12/2020] [Accepted: 04/13/2020] [Indexed: 11/22/2022] Open
Abstract
Cytochrome P-450 (Cyp) epoxygenase-dependent metabolites of arachidonic acid (AA) have been shown to inhibit renal Na+ transport, and inhibition of Cyp-epoxygenase is associated with salt-sensitive hypertension. We used the patch-clamp technique to examine whether Cyp-epoxygenase-dependent AA metabolites inhibited the basolateral 40-pS K+ channel (Kir4.1/Kir5.1) in the distal convoluted tubule (DCT). Application of AA inhibited the basolateral 40-pS K+ channel in the DCT. The inhibitory effect of AA on the 40-pS K+ channel was specific because neither linoleic nor oleic acid was able to mimic the effect of AA on the K+ channel. Inhibition of Cyp-monooxygenase with N-methylsulfonyl-12,12-dibromododec-11-enamide or inhibition of cyclooxygenase with indomethacin failed to abolish the inhibitory effect of AA on the 40-pS K+ channel. However, the inhibition of Cyp-epoxygenase with N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide abolished the effect of AA on the 40-pS K+ channel in the DCT. Moreover, addition of either 11,12-epoxyeicosatrienoic acid (EET) or 14,15-EET also inhibited the 40-pS K+ channel in the DCT. Whole cell recording demonstrated that application of AA decreased, whereas N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide treatment increased, Ba2+-sensitive K+ currents in the DCT. Finally, application of 14,15-EET but not AA was able to inhibit the basolateral 40-pS K+ channel in the DCT of Cyp2c44-/- mice. We conclude that Cyp-epoxygenase-dependent AA metabolites inhibit the basolateral Kir4.1/Kir5.1 in the DCT and that Cyp2c44-epoxygenase plays a role in the regulation of the basolateral K+ channel in the mouse DCT.
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MESH Headings
- 8,11,14-Eicosatrienoic Acid/analogs & derivatives
- 8,11,14-Eicosatrienoic Acid/metabolism
- 8,11,14-Eicosatrienoic Acid/pharmacology
- Amides/pharmacology
- Animals
- Arachidonic Acid/metabolism
- Arachidonic Acid/pharmacology
- Cytochrome P450 Family 2/antagonists & inhibitors
- Cytochrome P450 Family 2/genetics
- Cytochrome P450 Family 2/metabolism
- Enzyme Inhibitors/pharmacology
- Kidney Tubules, Distal/drug effects
- Kidney Tubules, Distal/metabolism
- Male
- Membrane Potentials
- Mice, 129 Strain
- Mice, Knockout
- Potassium Channel Blockers/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Inwardly Rectifying/antagonists & inhibitors
- Potassium Channels, Inwardly Rectifying/metabolism
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Affiliation(s)
- Ming-Xiao Wang
- Department of Physiology, Zhuhai Campus of Zunyi Medical University, Zunyi, Guizhou, China
| | - Li-Jun Wang
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Yu Xiao
- Department of Physiology, Qiqihar Medical College, Heilongjiang, China
| | - Dan-Dan Zhang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Xin-Peng Duan
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
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14
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Shi S, Montalbetti N, Wang X, Rush BM, Marciszyn AL, Baty CJ, Tan RJ, Carattino MD, Kleyman TR. Paraoxonase 3 functions as a chaperone to decrease functional expression of the epithelial sodium channel. J Biol Chem 2020; 295:4950-4962. [PMID: 32079677 DOI: 10.1074/jbc.ra119.011789] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/17/2020] [Indexed: 01/11/2023] Open
Abstract
The paraoxonase (PON) family comprises three highly conserved members: PON1, PON2, and PON3. They are orthologs of Caenorhabditis elegans MEC-6, an endoplasmic reticulum-resident chaperone that has a critical role in proper assembly and surface expression of the touch-sensing degenerin channel in nematodes. We have shown recently that MEC-6 and PON2 negatively regulate functional expression of the epithelial Na+ channel (ENaC), suggesting that the chaperone function is conserved within this family. We hypothesized that other PON family members also modulate ion channel expression. Pon3 is specifically expressed in the aldosterone-sensitive distal tubules in the mouse kidney. We found here that knocking down endogenous Pon3 in mouse cortical collecting duct cells enhanced Na+ transport, which was associated with increased γENaC abundance. We further examined Pon3 regulation of ENaC in two heterologous expression systems, Fisher rat thyroid cells and Xenopus oocytes. Pon3 coimmunoprecipitated with each of the three ENaC subunits in Fisher rat thyroid cells. As a result of this interaction, the whole-cell and surface abundance of ENaC α and γ subunits was reduced by Pon3. When expressed in oocytes, Pon3 inhibited ENaC-mediated amiloride-sensitive Na+ currents, in part by reducing the surface expression of ENaC. In contrast, Pon3 did not alter the response of ENaC to chymotrypsin-mediated proteolytic activation or [2-(trimethylammonium)ethyl]methanethiosulfonate-induced activation of αβS518Cγ, suggesting that Pon3 does not affect channel open probability. Together, our results suggest that PON3 regulates ENaC expression by inhibiting its biogenesis and/or trafficking.
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Affiliation(s)
- Shujie Shi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Xueqi Wang
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Nephrology, Second Xiangya Hospital of Central South University, Changsha 410011, Hunan, China
| | - Brittney M Rush
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Allison L Marciszyn
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Catherine J Baty
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Roderick J Tan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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15
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Wu P, Gao Z, Zhang D, Duan X, Terker AS, Lin D, Ellison DH, Wang W. Effect of Angiotensin II on ENaC in the Distal Convoluted Tubule and in the Cortical Collecting Duct of Mineralocorticoid Receptor Deficient Mice. J Am Heart Assoc 2020; 9:e014996. [PMID: 32208832 PMCID: PMC7428622 DOI: 10.1161/jaha.119.014996] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 02/18/2020] [Indexed: 12/02/2022]
Abstract
Background Angiotensin II stimulates epithelial Na+ channel (ENaC) by aldosterone-independent mechanism. We now test the effect of angiotensin II on ENaC in the distal convoluted tubule (DCT) and cortical collecting duct (CCD) of wild-type (WT) and kidney-specific mineralocorticoid receptor knockout mice (KS-MR-KO). Methods and Results We used electrophysiological, immunoblotting and renal-clearance methods to examine the effect of angiotensin II on ENaC in KS-MR-KO and wild-type mice. High K+ intake stimulated ENaC in the late DCT/early connecting tubule (DCT2/CNT) and in the CCD whereas low sodium intake stimulated ENaC in the CCD but not in the DCT2/CNT. The deletion of MR abolished the stimulatory effect of high K+ and low sodium intake on ENaC, partially inhibited ENaC in DCT2/CNT but almost abolished ENaC activity in the CCD. Application of losartan inhibited ENaC only in DCT2/CNT of both wild-type and KS-MR-KO mice but not in the CCD. Angiotensin II infusion for 3 days has a larger stimulatory effect on ENaC in the DCT2/CNT than in the CCD. Three lines of evidence indicate that angiotensin II can stimulate ENaC by MR-independent mechanism: (1) angiotensin II perfusion augmented ENaC expression in KS-MR-KO mice; (2) angiotensin II stimulated ENaC in the DCT2/CNT but to a lesser degree in the CCD in KS-MR-KO mice; (3) angiotensin II infusion augmented benzamil-induced natriuresis, increased the renal K+ excretion and corrected hyperkalemia of KS-MR-KO mice. Conclusions Angiotensin II-induced stimulation of ENaC occurs mainly in the DCT2/CNT and to a lesser degree in the CCD and MR plays a dominant role in determining ENaC activity in the CCD but to a lesser degree in the DCT2/CNT.
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MESH Headings
- Angiotensin II/pharmacology
- Animals
- Epithelial Sodium Channels/metabolism
- Hyperkalemia/drug therapy
- Hyperkalemia/genetics
- Hyperkalemia/metabolism
- Hyperkalemia/physiopathology
- Kidney Tubules, Collecting/drug effects
- Kidney Tubules, Collecting/metabolism
- Kidney Tubules, Collecting/physiopathology
- Kidney Tubules, Distal/drug effects
- Kidney Tubules, Distal/metabolism
- Kidney Tubules, Distal/physiopathology
- Membrane Potentials
- Mice, Knockout
- Natriuresis/drug effects
- Potassium/urine
- Receptor, Angiotensin, Type 1/agonists
- Receptor, Angiotensin, Type 1/metabolism
- Receptors, Mineralocorticoid/deficiency
- Receptors, Mineralocorticoid/genetics
- Renal Elimination/drug effects
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Affiliation(s)
- Peng Wu
- Institute of Hypertension and Kidney DiseaseThe First Affiliated Hospital of Zhengzhou UniversityZhengzhouChina
| | - Zhong‐Xiuzi Gao
- Institute of Hypertension and Kidney DiseaseThe First Affiliated Hospital of Zhengzhou UniversityZhengzhouChina
| | - Dan‐Dan Zhang
- Department of PharmacologyNew York Medical CollegeValhallaNY
| | - Xin‐Peng Duan
- Department of PharmacologyNew York Medical CollegeValhallaNY
| | - Andrew S. Terker
- Department of MedicineOregon Health & Science UniversityVA Portland Health Care SystemPortlandOR
| | - Dao‐Hong Lin
- Department of PharmacologyNew York Medical CollegeValhallaNY
| | - David H. Ellison
- Department of MedicineOregon Health & Science UniversityVA Portland Health Care SystemPortlandOR
| | - Wen‐Hui Wang
- Department of PharmacologyNew York Medical CollegeValhallaNY
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16
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Lossow K, Meyerhof W, Behrens M. Sodium Imbalance in Mice Results Primarily in Compensatory Gene Regulatory Responses in Kidney and Colon, but Not in Taste Tissue. Nutrients 2020; 12:E995. [PMID: 32260115 DOI: 10.3390/nu12040995] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 03/27/2020] [Accepted: 03/30/2020] [Indexed: 12/12/2022] Open
Abstract
Renal excretion and sodium appetite provide the basis for sodium homeostasis. In both the kidney and tongue, the epithelial sodium channel (ENaC) is involved in sodium uptake and sensing. The diuretic drug amiloride is known to block ENaC, producing a mild natriuresis. However, amiloride is further reported to induce salt appetite in rodents after prolonged exposure as well as bitter taste impressions in humans. To examine how dietary sodium content and amiloride impact on sodium appetite, mice were subjected to dietary salt and amiloride intervention and subsequently analyzed for ENaC expression and taste reactivity. We observed substantial changes of ENaC expression in the colon and kidney confirming the role of these tissues for sodium homeostasis, whereas effects on lingual ENaC expression and taste preferences were negligible. In comparison, prolonged exposure to amiloride-containing drinking water affected β- and αENaC expression in fungiform and posterior taste papillae, respectively, next to changes in salt taste. However, amiloride did not only change salt taste sensation but also perception of sucrose, glutamate, and citric acid, which might be explained by the fact that amiloride itself activates bitter taste receptors in mice. Accordingly, exposure to amiloride generally affects taste impression and should be evaluated with care.
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17
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Abstract
Ubiquitination of the epithelial Na+ channel (ENaC) in epithelial cells may influence trafficking and hormonal regulation of the channels. We assessed ENaC ubiquitination (ub-ENaC) in mouse and rat kidneys using affinity beads to capture ubiquitinated proteins from tissue homogenates and Western blot analysis with anti-ENaC antibodies. Ub-αENaC was observed primarily as a series of proteins of apparent molecular mass of 40-70 kDa, consistent with the addition of variable numbers of ubiquitin molecules primarily to the NH2-terminal cleaved fragment (~30 kDa) of the subunit. No significant Ub-βENaC was detected, indicating that ubiquitination of this subunit is minimal. For γENaC, the protein eluted from the affinity beads had the same apparent molecular mass as the cleaved COOH-terminal fragment of the subunit (~65 kDa). This suggests that the ubiquitinated NH2 terminus remains attached to the COOH-terminal moiety during isolation through disulfide bonds. Consistent with this, under nonreducing conditions, eluates contained material with increased molecular mass (90-150 kDa). In mice with a Liddle syndrome mutation (β566X) deleting a putative binding site for the ubiquitin ligase neural precursor cell expressed developmentally downregulated 4-2, the amount of ub-γENaC was reduced as expected. To assess aldosterone dependence of ubiquitination, we fed rats either control or low-Na+ diets for 7 days before kidney harvest. Na+ depletion increased the amounts of ub-αENaC and ub-γENaC by three- to fivefold, probably reflecting increased amounts of fully cleaved ENaC. We conclude that ubiquitination occurs after complete proteolytic processing of the subunits, contributing to retrieval and/or disposal of channels expressed at the cell surface. Diminished ubiquitination does not appear to be a major factor in aldosterone-dependent ENaC upregulation.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
| | - Marko Bertog
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Christoph Korbmacher
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
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18
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Abstract
Daily dietary potassium (K+) intake may be as large as the extracellular K+ pool. To avoid acute hyperkalemia, rapid removal of K+ from the extracellular space is essential. This is achieved by translocating K+ into cells and increasing urinary K+ excretion. Emerging data now indicate that the renal thiazide-sensitive NaCl cotransporter (NCC) is critically involved in this homeostatic kaliuretic response. This suggests that the early distal convoluted tubule (DCT) is a K+ sensor that can modify sodium (Na+) delivery to downstream segments to promote or limit K+ secretion. K+ sensing is mediated by the basolateral K+ channels Kir4.1/5.1, a capacity that the DCT likely shares with other nephron segments. Thus, next to K+-induced aldosterone secretion, K+ sensing by renal epithelial cells represents a second feedback mechanism to control K+ balance. NCC’s role in K+ homeostasis has both physiological and pathophysiological implications. During hypovolemia, NCC activation by the renin-angiotensin system stimulates Na+ reabsorption while preventing K+ secretion. Conversely, NCC inactivation by high dietary K+ intake maximizes kaliuresis and limits Na+ retention, despite high aldosterone levels. NCC activation by a low-K+ diet contributes to salt-sensitive hypertension. K+-induced natriuresis through NCC offers a novel explanation for the antihypertensive effects of a high-K+ diet. A possible role for K+ in chronic kidney disease is also emerging, as epidemiological data reveal associations between higher urinary K+ excretion and improved renal outcomes. This comprehensive review will embed these novel insights on NCC regulation into existing concepts of K+ homeostasis in health and disease.
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Affiliation(s)
- Ewout J. Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Catherina A. Cuevas
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Robert A. Fenton
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
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19
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Zachar R, Mikkelsen MK, Skjødt K, Marcussen N, Zamani R, Jensen BL, Svenningsen P. The epithelial Na+ channel α- and γ-subunits are cleaved at predicted furin-cleavage sites, glycosylated and membrane associated in human kidney. Pflugers Arch 2019; 471:1383-1396. [DOI: 10.1007/s00424-019-02321-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 10/02/2019] [Accepted: 10/07/2019] [Indexed: 01/28/2023]
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20
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Chen L, Clark JZ, Nelson JW, Kaissling B, Ellison DH, Knepper MA. Renal-Tubule Epithelial Cell Nomenclature for Single-Cell RNA-Sequencing Studies. J Am Soc Nephrol 2019; 30:1358-1364. [PMID: 31253652 DOI: 10.1681/asn.2019040415] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Affiliation(s)
- Lihe Chen
- Epithelial Systems Biology Laboratory, Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Jevin Z Clark
- Epithelial Systems Biology Laboratory, Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Jonathan W Nelson
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, Oregon; and
| | | | - David H Ellison
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, Oregon; and
| | - Mark A Knepper
- Epithelial Systems Biology Laboratory, Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland;
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21
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Affiliation(s)
- Rawad Lashhab
- Department of Physiology and Membrane Protein and Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada
- Department of Physiology and Membrane Protein and Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - A.K.M. Shahid Ullah
- Department of Physiology and Membrane Protein and Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada
- Department of Physiology and Membrane Protein and Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Emmanuelle Cordat
- Department of Physiology and Membrane Protein and Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada
- Department of Physiology and Membrane Protein and Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada
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22
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Lu TJ, Kan WC, Yang SS, Jiang ST, Wu SN, Ling P, Bao BY, Lin CY, Yang ZY, Weng YP, Chan CH, Lu TL. MST3 is involved in ENaC-mediated hypertension. Am J Physiol Renal Physiol 2019; 317:F30-F42. [PMID: 30969802 DOI: 10.1152/ajprenal.00455.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Liddle syndrome is an inherited form of human hypertension caused by increasing epithelial Na+ channel (ENaC) expression. Increased Na+ retention through ENaC with subsequent volume expansion causes hypertension. In addition to ENaC, the Na+-K+-Cl- cotransporter (NKCC) and Na+-Cl- symporter (NCC) are responsible for Na+ reabsorption in the kidneys. Several Na+ transporters are evolutionarily regulated by the Ste20 kinase family. Ste20-related proline/alanine-rich kinase and oxidative stress-responsive kinase-1 phosphorylate downstream NKCC2 and NCC to maintain Na+ and blood pressure (BP) homeostasis. Mammalian Ste20 kinase 3 (MST3) is another member of the Ste20 family. We previously reported that reduced MST3 levels were found in the kidneys in spontaneously hypertensive rats and that MST3 was involved in Na+ regulation. To determine whether MST3 is involved in BP stability through Na+ regulation, we generated a MST3 hypomorphic mutation and designated MST3+/- and MST3-/- mice to examine BP and serum Na+ and K+ concentrations. MST3-/- mice exhibited hypernatremia, hypokalemia, and hypertension. The increased ENaC in the kidney played roles in hypernatremia. The reabsorption of more Na+ promoted more K+ secretion in the kidney and caused hypokalemia. The hypernatremia and hypokalemia in MST3-/- mice were significantly reversed by the ENaC inhibitor amiloride, indicating that MST3-/- mice reabsorbed more Na+ through ENaC. Furthermore, Madin-Darby canine kidney cells stably expressing kinase-dead MST3 displayed elevated ENaC currents. Both the in vivo and in vitro results indicated that MST3 maintained Na+ homeostasis through ENaC regulation. We are the first to report that MST3 maintains BP stability through ENaC regulation.
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Affiliation(s)
- Te-Jung Lu
- Department of Medical Laboratory Science and Biotechnology, Chung Hwa University of Medical Technology , Tainan , Taiwan
| | - Wei-Chih Kan
- Department of Nephrology, Chi-Mei Medical Center , Tainan , Taiwan.,Department of Biological Science and Technology, Chung Hwa University of Medical Technology , Tainan , Taiwan
| | - Sung-Sen Yang
- Division of Nephrology, Department of Medicine, Tri-service General Hospital, Graduate Institute of Medical Sciences, National Defense Medical Center , Taipei , Taiwan
| | - Si-Tse Jiang
- Department of Research and Development, National Laboratory Animal Center, National Applied Research Laboratories , Tainan , Taiwan
| | - Sheng-Nan Wu
- Department of Physiology, College of Medicine, National Cheng Kung University , Tainan , Taiwan
| | - Pin Ling
- Department of Physiology, College of Medicine, National Cheng Kung University , Tainan , Taiwan.,Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University , Tainan , Taiwan
| | - Bo-Ying Bao
- School of Pharmacy, China Medical University , Taichung , Taiwan
| | - Chia-Yu Lin
- Department of Medical Laboratory Science and Biotechnology, China Medical University , Taichung , Taiwan
| | - Zin-Ya Yang
- Department of Medical Laboratory Science and Biotechnology, China Medical University , Taichung , Taiwan
| | - Yui-Ping Weng
- Department of Biological Science and Technology, Chung Hwa University of Medical Technology , Tainan , Taiwan
| | - Chee-Hong Chan
- Department of Nephrology, Chang Bing Show Chwan Memorial Hospital, Lukang, Changhua, Taiwan
| | - Te Ling Lu
- School of Pharmacy, China Medical University , Taichung , Taiwan
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23
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Murillo-de-Ozores AR, Gamba G, Castañeda-Bueno M. Molecular mechanisms for the regulation of blood pressure by potassium. Curr Top Membr 2019; 83:285-313. [PMID: 31196607 DOI: 10.1016/bs.ctm.2019.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
It has been well documented that the amount of potassium in the diet is associated with blood pressure levels in the population: the higher the potassium consumption, the lower the blood pressure and the cardiovascular mortality. In the last few years certain mechanisms for potassium regulation of salt reabsorption in the kidney have been elucidated at the molecular level. In this work we discuss the evidence demonstrating the relationship between potassium intake and blood pressure levels in human populations and in animal models, as well as the experimental data that reveal the effects of potassium on transepithelial Na+ reabsorption in different nephron segments. We also discuss the physiological relevance of K+-induced natriuresis, and finally, we focus on the molecular mechanisms by which extracellular potassium modulates the activity of the renal NaCl cotransporter, which is the mechanism that has been best dissected so far.
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24
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Eckhard AH, Zhu M, O'Malley JT, Williams GH, Loffing J, Rauch SD, Nadol JB, Liberman MC, Adams JC. Inner ear pathologies impair sodium-regulated ion transport in Meniere's disease. Acta Neuropathol 2019; 137:343-357. [PMID: 30390121 PMCID: PMC6513907 DOI: 10.1007/s00401-018-1927-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 10/26/2018] [Accepted: 10/26/2018] [Indexed: 11/17/2022]
Abstract
Meniere's disease (MD), a syndromal inner ear disease, is commonly associated with a pathological accumulation of endolymphatic fluid in the inner ear, termed "idiopathic" endolymphatic hydrops (iEH). Although numerous precipitating/exacerbating factors have been proposed for MD, its etiology remains elusive. Here, using immunohistochemistry and in situ protein-protein interaction detection assays, we demonstrate mineralocorticoid-controlled sodium transport mechanisms in the epithelium of the extraosseous portion of the endolymphatic sac (eES) in the murine and human inner ears. Histological analysis of the eES in an extensive series of human temporal bones consistently revealed pathological changes in the eES in cases with iEH and a clinical history of MD, but no such changes were found in cases with "secondary" EH due to other otological diseases or in healthy controls. Notably, two etiologically different pathologies-degeneration and developmental hypoplasia-that selectively affect the eES in MD were distinguished. Clinical records from MD cases with degenerative and hypoplastic eES pathology revealed distinct intergroup differences in clinical disease presentation. Overall, we have identified for the first time two inner ear pathologies that are consistently present in MD and can be directly linked to the pathogenesis of EH, and which potentially affect the phenotypical presentation of MD.
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Affiliation(s)
- Andreas H Eckhard
- Otopathology Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
- Department of Otorhinolaryngology, University Hospital Zurich, Frauenklinikstrasse 24, 8091, Zurich, Switzerland.
| | - MengYu Zhu
- Otopathology Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
| | - Jennifer T O'Malley
- Otopathology Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
| | - Gordon H Williams
- Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | | | - Steven D Rauch
- Otopathology Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA
- Vestibular Division, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, USA
- Massachusetts General Hospital, Boston, MA, USA
| | - Joe B Nadol
- Otopathology Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA
| | - Joe C Adams
- Otopathology Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA
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25
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Wu P, Gao ZX, Su XT, Wang MX, Wang WH, Lin DH. Kir4.1/Kir5.1 Activity Is Essential for Dietary Sodium Intake-Induced Modulation of Na-Cl Cotransporter. J Am Soc Nephrol 2018; 30:216-227. [PMID: 30559144 DOI: 10.1681/asn.2018080799] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 11/13/2018] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Dietary sodium intake regulates the thiazide-sensitive Na-Cl cotransporter (NCC) in the distal convoluted tubule (DCT). Whether the basolateral, inwardly rectifying potassium channel Kir4.1/Kir5.1 (a heterotetramer of Kir4.1/Kir5.1) in the DCT is essential for mediating the effect of dietary sodium intake on NCC activity is unknown. METHODS We used electrophysiology, renal clearance techniques, and immunoblotting to examine effects of Kir4.1/Kir5.1 in the DCT and NCC in wild-type and kidney-specific Kir4.1 knockout mice. RESULTS Low sodium intake stimulated basolateral Kir4.1/Kir5.1 activity, increased basolateral K+ conductance, and hyperpolarized the membrane. Conversely, high sodium intake inhibited the potassium channel, decreased basolateral K+ currents, and depolarized the membrane. Low sodium intake increased total and phosphorylated NCC expression and augmented hydrochlorothiazide-induced natriuresis; high sodium intake had opposite effects. Thus, elevated NCC activity induced by low sodium intake was associated with upregulation of Kir4.1/Kir5.1 activity in the DCT, whereas inhibition of NCC activity by high sodium intake was associated with diminished Kir4.1/Kir5.1 activity. In contrast, dietary sodium intake did not affect NCC activity in knockout mice. Further, Kir4.1 deletion not only abolished basolateral K+ conductance and depolarized the DCT membrane, but also abrogated the stimulating effects induced by low sodium intake on basolateral K+ conductance and hyperpolarization. Finally, dietary sodium intake did not alter urinary potassium excretion rate in hypokalemic knockout and wild-type mice. CONCLUSIONS Stimulation of Kir4.1/Kir5.1 by low intake of dietary sodium is essential for NCC upregulation, and inhibition of Kir4.1/Kir5.1 induced by high sodium intake is a key step for downregulation of NCC.
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Affiliation(s)
- Peng Wu
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Zhong-Xiuzi Gao
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Ming-Xiao Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
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26
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Kamel KS, Schreiber M, Halperin ML. Renal potassium physiology: integration of the renal response to dietary potassium depletion. Kidney Int 2018; 93:41-53. [PMID: 29102372 DOI: 10.1016/j.kint.2017.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/31/2017] [Accepted: 08/03/2017] [Indexed: 01/30/2023]
Abstract
We summarize the current understanding of the physiology of the renal handling of potassium (K+), and present an integrative view of the renal response to K+ depletion caused by dietary K+ restriction. This renal response involves contributions from different nephron segments, and aims to diminish the rate of excretion of K+ as a result of: decreasing the rate of electrogenic (and increasing the rate of electroneutral) reabsorption of sodium in the aldosterone-sensitive distal nephron (ASDN), decreasing the abundance of renal outer medullary K+ channels in the luminal membrane of principal cells in the ASDN, decreasing the flow rate in the ASDN, and increasing the reabsorption of K+ in the cortical and medullary collecting ducts. The implications of this physiology for the association between K+ depletion and hypertension, and K+ depletion and formation of calcium kidney stones are discussed.
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Affiliation(s)
- Kamel S Kamel
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
| | - Martin Schreiber
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Mitchell L Halperin
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
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27
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Wang WH. Basolateral Kir4.1 activity in the distal convoluted tubule regulates K secretion by determining NaCl cotransporter activity. Curr Opin Nephrol Hypertens 2016; 25:429-35. [PMID: 27306796 DOI: 10.1097/MNH.0000000000000248] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PURPOSE OF REVIEW Renal potassium (K) secretion plays a key role in maintaining K homeostasis. The classic mechanism of renal K secretion is focused on the connecting tubule and cortical collecting duct, in which K is uptaken by basolateral Na-K-ATPase and is secreted into the lumen by apical ROMK (Kir1.1) and Ca-activated big conductance K channel. Recently, genetic studies and animal models have indicated that inwardly rectifying K channel 4.1 (Kir4.1 or Kcnj10) in the distal convoluted tubule (DCT) may play a role in the regulation of K secretion in the aldosterone-sensitive distal nephron by targeting the NaCl cotransporter (NCC). This review summarizes recent progresses regarding the role of Kir4.1 in the regulation of NCC and K secretion. RECENT FINDINGS Kir4.1 is expressed in the basolateral membrane of the DCT, and plays a predominant role in contributing to the basolateral K conductance and in participating in the generation of negative membrane potential. Kir4.1 is also the substrate of src-family tyrosine kinase and the stimulation of src-family tyrosine kinase activates Kir4.1 activity in the DCT. The genetic deletion or functional inhibition of Kir4.1 depolarizes the membrane of the DCT, inhibits ste20-proline-alanine rich kinase, and suppresses NCC activity. Moreover, the downregulation of Kir4.1 increases epithelial Na channel expression in the collecting duct and urinary K excretion. Finally, mice with low Kir4.1 activity in the DCT are hypomagnesemia and hypokalemia. SUMMARY Recent progress in exploring the regulation and the function of Kir4.1 in the DCT strongly indicates that Kir4.1plays an important role in initiating the regulation of renal K secretion by targeting NCC and it may serves as a K sensor in the kidney.
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28
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Udwan K, Abed A, Roth I, Dizin E, Maillard M, Bettoni C, Loffing J, Wagner CA, Edwards A, Feraille E. Dietary sodium induces a redistribution of the tubular metabolic workload. J Physiol 2017; 595:6905-6922. [PMID: 28940314 PMCID: PMC5685825 DOI: 10.1113/jp274927] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/11/2017] [Indexed: 01/11/2023] Open
Abstract
Key points Body Na+ content is tightly controlled by regulated urinary Na+ excretion. The intrarenal mechanisms mediating adaptation to variations in dietary Na+ intake are incompletely characterized. We confirmed and expanded observations in mice that variations in dietary Na+ intake do not alter the glomerular filtration rate but alter the total and cell‐surface expression of major Na+ transporters all along the kidney tubule. Low dietary Na+ intake increased Na+ reabsorption in the proximal tubule and decreased it in more distal kidney tubule segments. High dietary Na+ intake decreased Na+ reabsorption in the proximal tubule and increased it in distal segments with lower energetic efficiency. The abundance of apical transporters and Na+ delivery are the main determinants of Na+ reabsorption along the kidney tubule. Tubular O2 consumption and the efficiency of sodium reabsorption are dependent on sodium diet.
Abstract Na+ excretion by the kidney varies according to dietary Na+ intake. We undertook a systematic study of the effects of dietary salt intake on glomerular filtration rate (GFR) and tubular Na+ reabsorption. We examined the renal adaptive response in mice subjected to 7 days of a low sodium diet (LSD) containing 0.01% Na+, a normal sodium diet (NSD) containing 0.18% Na+ and a moderately high sodium diet (HSD) containing 1.25% Na+. As expected, LSD did not alter measured GFR and increased the abundance of total and cell‐surface NHE3, NKCC2, NCC, α‐ENaC and cleaved γ‐ENaC compared to NSD. Mathematical modelling predicted that tubular Na+ reabsorption increased in the proximal tubule but decreased in the distal nephron because of diminished Na+ delivery. This prediction was confirmed by the natriuretic response to diuretics targeting the thick ascending limb, the distal convoluted tubule or the collecting system. On the other hand, HSD did not alter measured GFR but decreased the abundance of the aforementioned transporters compared to NSD. Mathematical modelling predicted that tubular Na+ reabsorption decreased in the proximal tubule but increased in distal segments with lower transport efficiency with respect to O2 consumption. This prediction was confirmed by the natriuretic response to diuretics. The activity of the metabolic sensor adenosine monophosphate‐activated protein kinase (AMPK) was related to the changes in tubular Na+ reabsorption. Our data show that fractional Na+ reabsorption is distributed differently according to dietary Na+ intake and induces changes in tubular O2 consumption and sodium transport efficiency. Body Na+ content is tightly controlled by regulated urinary Na+ excretion. The intrarenal mechanisms mediating adaptation to variations in dietary Na+ intake are incompletely characterized. We confirmed and expanded observations in mice that variations in dietary Na+ intake do not alter the glomerular filtration rate but alter the total and cell‐surface expression of major Na+ transporters all along the kidney tubule. Low dietary Na+ intake increased Na+ reabsorption in the proximal tubule and decreased it in more distal kidney tubule segments. High dietary Na+ intake decreased Na+ reabsorption in the proximal tubule and increased it in distal segments with lower energetic efficiency. The abundance of apical transporters and Na+ delivery are the main determinants of Na+ reabsorption along the kidney tubule. Tubular O2 consumption and the efficiency of sodium reabsorption are dependent on sodium diet.
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Affiliation(s)
- Khalil Udwan
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Ahmed Abed
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Isabelle Roth
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland
| | - Eva Dizin
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Marc Maillard
- Centre hospitalier universitaire Vaudois, Service de néphrologie, CH-1011, Lausanne, Switzerland
| | - Carla Bettoni
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - Johannes Loffing
- Institute of Anatomy, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Aurélie Edwards
- Centre de Recherche des Cordeliers, INSERM UMRS1138 and CNRS ERL8228, 15 rue de l'Ecole de Médecine, F-75006, Paris, France.,Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Eric Feraille
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
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29
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Poulsen SB, Christensen BM. Long-term aldosterone administration increases renal Na+-Cl− cotransporter abundance in late distal convoluted tubule. Am J Physiol Renal Physiol 2017; 313:F756-F766. [DOI: 10.1152/ajprenal.00352.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 10/04/2016] [Accepted: 10/07/2016] [Indexed: 11/22/2022] Open
Abstract
Renal Na+-Cl− cotransporter (NCC) is expressed in early distal convoluted tubule (DCT) 1 and late DCT (DCT2). NCC activity can be stimulated by aldosterone administration, and the mechanism is assumed to depend on the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which inactivates glucocorticoids that would otherwise occupy aldosterone receptors. Because 11β-HSD2 in rat may only be abundantly expressed in DCT2 cells and not in DCT1 cells, it has been speculated that aldosterone specifically stimulates NCC activity in DCT2 cells. In mice, however, it is debated if 11β-HSD2 is expressed in DCT2 cells. The present study examined whether aldosterone administration in mice stimulates NCC abundance and phosphorylation in DCT2 cells but not in DCT1 cells. B6/C57 male mice were administered 100 µg aldosterone·kg body weight−1·24 h−1 for 6 days and euthanized during isoflurane inhalation. Western blotting of whole kidney homogenate showed that aldosterone administration stimulated NCC and pT58-NCC abundances ( P < 0.001). In DCT1 cells, confocal microscopy detected no effect of the aldosterone administration on NCC and pT58-NCC abundances. By contrast, NCC and pT58-NCC abundances were stimulated by aldosterone administration in the middle of DCT2 ( P < 0.001 and <0.01, respectively) and at the junction between DCT2 and CNT ( P < 0.001 and <0.05, respectively). In contrast to rat, immunohistochemistry in mouse showed no/very weak 11β-HSD2 expression in DCT2 cells. Collectively, long-term aldosterone administration stimulates mouse NCC and pT58-NCC abundances in DCT2 cells and presumably not in DCT1 cells.
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30
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Sharma K, Haque M, Guidry R, Ueta Y, Teruyama R. Effect of dietary salt intake on epithelial Na + channels (ENaC) in vasopressin magnocellular neurosecretory neurons in the rat supraoptic nucleus. J Physiol 2017; 595:5857-5874. [PMID: 28714095 PMCID: PMC5577521 DOI: 10.1113/jp274856] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 07/11/2017] [Indexed: 01/18/2023] Open
Abstract
KEY POINTS A growing body of evidence suggests that epithelial Na+ channels (ENaCs) in the brain play a significant role in the regulation of blood pressure; however, the brain structures that mediate the effect are not well understood. Because vasopressin (VP) neurons play a pivotal role in coordinating neuroendocrine and autonomic responses to maintain cardiovascular homeostasis, a basic understanding of the regulation and activity of ENaC in VP neurons is of great interest. We show that high dietary salt intake caused an increase in the expression and activity of ENaC which resulted in the steady state depolarization of VP neurons. The results help us understand one of the mechanisms underlying how dietary salt intake affects the activity of VP neurons via ENaC activity. ABSTRACT All three epithelial Na+ channel (ENaC) subunits (α, β and γ) are located in vasopressin (VP) magnocellular neurons in the hypothalamic supraoptic (SON) and paraventricular nuclei. Our previous study demonstrated that ENaC mediates a Na+ leak current that affects the steady state membrane potential in VP neurons. In the present study, we evaluated the effect of dietary salt intake on ENaC regulation and activity in VP neurons. High dietary salt intake for 7 days caused an increase in expression of β- and γENaC subunits in the SON and the translocation of αENaC immunoreactivity towards the plasma membrane. Patch clamp experiments on hypothalamic slices showed that the mean amplitude of the putative ENaC currents was significantly greater in VP neurons from animals that were fed a high salt diet compared with controls. The enhanced ENaC current contributed to the more depolarized basal membrane potential observed in VP neurons in the high salt diet group. These findings indicate that high dietary NaCl intake enhances the expression and activity of ENaCs, which augments synaptic drive by depolarizing the basal membrane potential close to the action potential threshold during hormonal demand. However, ENaCs appear to have only a minor role in the regulation of the firing activity of VP neurons in the absence of synaptic inputs as neither the mean intraburst frequency, burst duration, nor interspike interval variability of phasic bursting activity was affected. Moreover, ENaC activity did not affect the initiation, sustention, or termination of the phasic bursting generated in an intrinsic manner without synaptic inputs.
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Affiliation(s)
- Kaustubh Sharma
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Masudul Haque
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Richard Guidry
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Yoichi Ueta
- Department of Physiology, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan
| | - Ryoichi Teruyama
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
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31
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Abstract
Distal sodium transport is a final step in the regulation of blood pressure. As such, understanding how the two main sodium transport proteins, the thiazide-sensitive sodium chloride cotransporter (NCC) and the epithelial sodium channel (ENaC), are regulated is paramount. Both are expressed in the late distal nephron; however, no evidence has suggested that these two sodium transport proteins interact. Recently, we established that these two sodium transport proteins functionally interact in the second part of the distal nephron (DCT2). Given their co-localization within the DCT2, we hypothesized that NCC and ENaC interactions might be modulated by aldosterone (Aldo). Aldo treatment increased NCC and αENaC colocalization (electron microscopy) and interaction (coimmunoprecipitation). Finally, with co-expression of the Aldo-induced protein serum- and glucocorticoid-inducible kinase 1 (SGK1), NCC and αENaC interactions were increased. These data demonstrate that Aldo promotes increased interaction of NCC and ENaC, within the DCT2 revealing a novel method of regulation for distal sodium reabsorption.
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Affiliation(s)
- Brandi M Wynne
- Division of Nephrology, Department of Medicine, Emory University, Atlanta, GA, 30322, USA. .,Center for Cell and Molecular Signaling, Emory University, Atlanta, GA, 30322, USA.
| | - Abinash C Mistry
- Division of Nephrology, Department of Medicine, Emory University, Atlanta, GA, 30322, USA
| | - Otor Al-Khalili
- Department of Physiology, Emory University, Atlanta, GA, 30322, USA
| | - Rickta Mallick
- Division of Nephrology, Department of Medicine, Emory University, Atlanta, GA, 30322, USA
| | - Franziska Theilig
- Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - Douglas C Eaton
- Department of Physiology, Emory University, Atlanta, GA, 30322, USA.,Center for Cell and Molecular Signaling, Emory University, Atlanta, GA, 30322, USA
| | - Robert S Hoover
- Division of Nephrology, Department of Medicine, Emory University, Atlanta, GA, 30322, USA.,Department of Physiology, Emory University, Atlanta, GA, 30322, USA.,Research Service, Atlanta Veteran's Administration Medical Center, Decatur, GA, 30033, USA
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32
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Fenton RA, Poulsen SB, de la Mora Chavez S, Soleimani M, Dominguez Rieg JA, Rieg T. Renal tubular NHE3 is required in the maintenance of water and sodium chloride homeostasis. Kidney Int 2017; 92:397-414. [PMID: 28385297 DOI: 10.1016/j.kint.2017.02.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 01/25/2017] [Accepted: 02/02/2017] [Indexed: 11/30/2022]
Abstract
The sodium/proton exchanger isoform 3 (NHE3) is expressed in the intestine and the kidney, where it facilitates sodium (re)absorption and proton secretion. The importance of NHE3 in the kidney for sodium chloride homeostasis, relative to the intestine, is unknown. Constitutive tubule-specific NHE3 knockout mice (NHE3loxloxCre) did not show significant differences compared to control mice in body weight, blood pH or bicarbonate and plasma sodium, potassium, or aldosterone levels. Fluid intake, urinary flow rate, urinary sodium/creatinine, and pH were significantly elevated in NHE3loxloxCre mice, while urine osmolality and GFR were significantly lower. Water deprivation revealed a small urinary concentrating defect in NHE3loxloxCre mice on a control diet, exaggerated on low sodium chloride. Ten days of low or high sodium chloride diet did not affect plasma sodium in control mice; however, NHE3loxloxCre mice were susceptible to low sodium chloride (about -4 mM) or high sodium chloride intake (about +2 mM) versus baseline, effects without differences in plasma aldosterone between groups. Blood pressure was significantly lower in NHE3loxloxCre mice and was sodium chloride sensitive. In control mice, the expression of the sodium/phosphate co-transporter Npt2c was sodium chloride sensitive. However, lack of tubular NHE3 blunted Npt2c expression. Alterations in the abundances of sodium/chloride cotransporter and its phosphorylation at threonine 58 as well as the abundances of the α-subunit of the epithelial sodium channel, and its cleaved form, were also apparent in NHE3loxloxCre mice. Thus, renal NHE3 is required to maintain blood pressure and steady-state plasma sodium levels when dietary sodium chloride intake is modified.
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Affiliation(s)
- Robert A Fenton
- InterPrET Center, Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Søren B Poulsen
- InterPrET Center, Department of Biomedicine, Aarhus University, Aarhus, Denmark; VA San Diego Healthcare System, San Diego, California, USA
| | | | - Manoocher Soleimani
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio, USA; Research Services, Veterans Affairs Medical Center, Cincinnati, Ohio, USA
| | - Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida, USA
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida, USA.
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33
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Frindt G, Yang L, Uchida S, Weinstein AM, Palmer LG. Responses of distal nephron Na + transporters to acute volume depletion and hyperkalemia. Am J Physiol Renal Physiol 2017; 313:F62-F73. [PMID: 28356292 DOI: 10.1152/ajprenal.00668.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 03/21/2017] [Accepted: 03/21/2017] [Indexed: 01/01/2023] Open
Abstract
We assessed effects of acute volume reductions induced by administration of diuretics in rats. Direct block of Na+ transport produced changes in urinary electrolyte excretion. Adaptations to these effects appeared as alterations in the expression of protein for the distal nephron Na+ transporters NCC and ENaC. Two hours after a single injection of furosemide (6 mg/kg) or hydrochlorothiazide (HCTZ; 30 mg/kg) Na+ and K+ excretion increased but no changes in the content of activated forms of NCC (phosphorylated on residue T53) or ENaC (cleaved γ-subunit) were detected. In contrast, amiloride (0.6 mg/kg) evoked a similar natriuresis that coincided with decreased pT53NCC and increased cleaved γENaC. Alterations in posttranslational membrane protein processing correlated with an increase in plasma K+ of 0.6-0.8 mM. Decreased pT53NCC occurred within 1 h after amiloride injection, whereas changes in γENaC were slower and were blocked by the mineralocorticoid receptor antagonist spironolactone. Increased γENaC cleavage correlated with elevation of the surface expression of the subunit as assessed by in situ biotinylation. Na depletion induced by 2 h of furosemide or HCTZ treatment increases total NCC expression without affecting ENaC protein. However, restriction of Na intake for 10 h (during the day) or 18 h (overnight) increased the abundance of both total NCC and of cleaved α- and γENaC. We conclude that the kidneys respond acutely to hyperkalemic challenges by decreasing the activity of NCC while increasing that of ENaC. They respond to hypovolemia more slowly, increasing Na+ reabsorptive capacities of both of these transporters.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
| | - Lei Yang
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York.,Department of Physiology, Harbin University School of Medicine, Harbin, China; and
| | - Shinichi Uchida
- Department of Nephrology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Alan M Weinstein
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York.,Department of Medicine, Weill Cornell Medical College, New York, New York
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York;
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34
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Wang L, Zhang C, Su XT, Lin DH, Wu P, Schwartzman ML, Wang WH. PGF 2α regulates the basolateral K channels in the distal convoluted tubule. Am J Physiol Renal Physiol 2017; 313:F254-F261. [PMID: 28356287 PMCID: PMC5582901 DOI: 10.1152/ajprenal.00102.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 03/17/2017] [Accepted: 03/23/2017] [Indexed: 11/22/2022] Open
Abstract
Our aim is to examine the role of PGF2α receptor (FP), a highly expressed prostaglandin receptor in the distal convoluted tubule (DCT) in regulating the basolateral 40-pS K channel. The single-channel studies demonstrated that PGF2α had a biphasic effect on the 40-pS K channel in the DCT-PGF2α stimulated at low concentrations (less than 500 nM), while at high concentrations (above 1 µM), it inhibited the 40-pS K channels. Moreover, neither 13,14-dihydro-15-keto-PGF2α (a metabolite of PGF2α) nor PGE2 was able to mimic the effect of PGF2α on the 40-pS K channel in the DCT. The inhibition of PKC had no significant effect on the 40-pS K channel; however, it abrogated the inhibitory effect of 5 µM PGF2α on the K channel. Moreover, stimulation of PKC inhibited the 40-pS K channel in the DCT, suggesting that PKC mediates the inhibitory effect of PGF2α on the 40-pS K channel. Conversely, the stimulatory effect of PGF2α on the 40-pS K channel was absent in the DCT treated with DPI, a NADPH oxidase (NOX) inhibitor. Also, adding 100 µM H2O2 mimicked the stimulatory effect of PGF2α and increased the 40-pS K channel activity in DCT. Moreover, the stimulatory effect of 500 nM PGF2α and H2O2 was not additive, suggesting the role of superoxide-related species in mediating the stimulatory effect of PGF2α on the 40-pS K channel. The inhibition of Src family tyrosine protein kinase (SFK) not only inhibited the 40-pS K channel in the DCT but also completely abolished the stimulatory effects of PGF2α and H2O2 on the 40-pS K channel. We conclude that PGF2α at low doses stimulates the basolateral 40-pS K channel by a NOX- and SFK-dependent mechanism, while at high concentrations, it inhibits the K channel by a PKC-dependent pathway.
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Affiliation(s)
- Lijun Wang
- Department of Physiology, Harbin Medical University, Harbin, China; and.,Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Chengbiao Zhang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Peng Wu
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | | | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
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35
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Jiang C, Kawabe H, Rotin D. The Ubiquitin Ligase Nedd4L Regulates the Na/K/2Cl Co-transporter NKCC1/SLC12A2 in the Colon. J Biol Chem 2017; 292:3137-3145. [PMID: 28087701 DOI: 10.1074/jbc.m116.770065] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/03/2017] [Indexed: 01/06/2023] Open
Abstract
The ubiquitin ligase Nedd4-like (Nedd4L, or Nedd4-2) binds to and regulates stability of the epithelial Na+ channel (ENaC) in salt-absorbing epithelia in the kidney, lung, and other tissues. Its role in the distal colon, which also absorbs salt and fluid and expresses ENaC, is unknown. Using a conditional knock-out approach to knock out Nedd4L in mice intestinal epithelium (Nedd4Lf/f ;Vil-CreERT2 ) we show here that Nedd4L depletion leads to a higher steady-state short circuit current (Isc) in mouse distal colon tissue relative to controls. This higher Isc was partially reduced by the addition of apical amiloride and strongly reduced by basolateral bumetanide as well as by depletion of basolateral Cl-, suggesting that Na+/K+/2Cl- (NKCC1/SLC12A2) co-transporter and ENaC are targets of Nedd4L in the colon. In accordance, NKCC1 (and γENaC) protein abundance in the colon of the Nedd4L knock-out animals was increased, indicating that Nedd4L normally suppresses these proteins. However, we did not observe co-immunoprecipitation between Nedd4L and NKCC1, suggesting that Nedd4L indirectly suppresses NKCC1 expression. Low salt diet resulted in a strong increase in β and γ (but not α) ENaC mRNA and protein expression and ENaC activity. Although salt restriction also increased NKCC1 protein and mRNA abundance, it did not lead to its elevated activity (Isc). These results identify NKCC1 as a novel target for Nedd4L-mediated down-regulation in vivo, which modulates ion and fluid transport in the distal colon together with ENaC.
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Affiliation(s)
- Chong Jiang
- Hospital for Sick Children and University of Toronto, Toronto, Ontario M5G 0A4, Canada
| | - Hiroshi Kawabe
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3D, 37075 Goettingen, Germany
| | - Daniela Rotin
- Hospital for Sick Children and University of Toronto, Toronto, Ontario M5G 0A4, Canada.
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Giani JF, Eriguchi M, Bernstein EA, Katsumata M, Shen XZ, Li L, McDonough AA, Fuchs S, Bernstein KE, Gonzalez-Villalobos RA. Renal tubular angiotensin converting enzyme is responsible for nitro-L-arginine methyl ester (L-NAME)-induced salt sensitivity. Kidney Int 2016; 91:856-867. [PMID: 27988209 DOI: 10.1016/j.kint.2016.10.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 09/29/2016] [Accepted: 10/06/2016] [Indexed: 01/13/2023]
Abstract
Renal parenchymal injury predisposes to salt-sensitive hypertension, but how this occurs is not known. Here we tested whether renal tubular angiotensin converting enzyme (ACE), the main site of kidney ACE expression, is central to the development of salt sensitivity in this setting. Two mouse models were used: it-ACE mice in which ACE expression is selectively eliminated from renal tubular epithelial cells; and ACE 3/9 mice, a compound heterozygous mouse model that makes ACE only in renal tubular epithelium from the ACE 9 allele, and in liver hepatocytes from the ACE 3 allele. Salt sensitivity was induced using a post L-NAME salt challenge. While both wild-type and ACE 3/9 mice developed arterial hypertension following three weeks of high salt administration, it-ACE mice remained normotensive with low levels of renal angiotensin II. These mice displayed increased sodium excretion, lower sodium accumulation, and an exaggerated reduction in distal sodium transporters. Thus, in mice with renal injury induced by L-NAME pretreatment, renal tubular epithelial ACE, and not ACE expression by renal endothelium, lung, brain, or plasma, is essential for renal angiotensin II accumulation and salt-sensitive hypertension.
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Affiliation(s)
- Jorge F Giani
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Masahiro Eriguchi
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Ellen A Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Makoto Katsumata
- Cedars-Sinai Animal Models Core, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Xiao Z Shen
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Liang Li
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Alicia A McDonough
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Sebastien Fuchs
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, California, USA
| | - Kenneth E Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Romer A Gonzalez-Villalobos
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA; CVMET Research Unit, Pfizer, Inc., Cambridge, Massachusetts, USA.
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Xu C, Lu A, Wang H, Fang H, Zhou L, Sun P, Yang T. (Pro)Renin receptor regulates potassium homeostasis through a local mechanism. Am J Physiol Renal Physiol 2016; 313:F641-F656. [PMID: 27440776 DOI: 10.1152/ajprenal.00043.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 07/12/2016] [Accepted: 07/18/2016] [Indexed: 11/22/2022] Open
Abstract
(Pro)renin receptor (PRR) is highly expressed in the distal nephron, but it has an unclear functional implication. The present study was conducted to explore a potential role of renal PRR during high K+ (HK) loading. In normal Sprague-Dawley rats, a 1-wk HK intake increased renal expression of full-length PRR and urinary excretion of soluble PRR (sPRR). Administration of PRO20, a decoy peptide antagonist of PRR, in K+-loaded animals elevated plasma K+ level and decreased urinary K+ excretion, accompanied with suppressed urinary aldosterone excretion and intrarenal aldosterone levels. HK downregulated Na+-Cl- cotransporter (NCC) expression but upregulated CYP11B2 (cytochrome P-450, family 11, subfamily B, polypeptide 2), renal outer medullary K+ channel (ROMK), calcium-activated potassium channel subunit α1 (α-BK), α-Na+-K+-ATPase (α-NKA), and epithelial Na+ channel subunit β (β-ENaC), all of which were blunted by PRO20. After HK loading was completed, urinary, but not plasma renin, was upregulated, which was blunted by PRO20. The same experiments that were performed using adrenalectomized (ADX) rats yielded similar results. Interestingly, spironolactone treatment in HK-loaded ADX rats attenuated kaliuresis but promoted natriuresis, which was associated with the suppressed responses of β-ENaC, α-NKA, ROMK, and α-BK protein expression. Taken together, we discovered a novel role of renal PRR in regulation of K+ homeostasis through a local mechanism involving intrarenal renin-angiotensin-aldosterone system and coordinated regulation of membrane Na+- and K+-transporting proteins.
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Affiliation(s)
- Chuanming Xu
- Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
| | - Aihua Lu
- Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
| | - Hong Wang
- Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
| | - Hui Fang
- Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
| | - Li Zhou
- Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China
| | - Peng Sun
- Anesthesiology, Sun Yat-sen University Cancer Center, Guangzhou, China; and
| | - Tianxin Yang
- Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China; .,Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
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Mistry AC, Wynne BM, Yu L, Tomilin V, Yue Q, Zhou Y, Al-Khalili O, Mallick R, Cai H, Alli AA, Ko B, Mattheyses A, Bao HF, Pochynyuk O, Theilig F, Eaton DC, Hoover RS. The sodium chloride cotransporter (NCC) and epithelial sodium channel (ENaC) associate. Biochem J 2016; 473:3237-52. [PMID: 27422782 DOI: 10.1042/BCJ20160312] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/11/2016] [Indexed: 11/17/2022]
Abstract
The thiazide-sensitive sodium chloride cotransporter (NCC) and the epithelial sodium channel (ENaC) are two of the most important determinants of salt balance and thus systemic blood pressure. Abnormalities in either result in profound changes in blood pressure. There is one segment of the nephron where these two sodium transporters are coexpressed, the second part of the distal convoluted tubule. This is a key part of the aldosterone-sensitive distal nephron, the final regulator of salt handling in the kidney. Aldosterone is the key hormonal regulator for both of these proteins. Despite these shared regulators and coexpression in a key nephron segment, associations between these proteins have not been investigated. After confirming apical localization of these proteins, we demonstrated the presence of functional transport proteins and native association by blue native PAGE. Extensive coimmunoprecipitation experiments demonstrated a consistent interaction of NCC with α- and γ-ENaC. Mammalian two-hybrid studies demonstrated direct binding of NCC to ENaC subunits. Fluorescence resonance energy transfer and immunogold EM studies confirmed that these transport proteins are within appropriate proximity for direct binding. Additionally, we demonstrate that there are functional consequences of this interaction, with inhibition of NCC affecting the function of ENaC. This novel finding of an association between ENaC and NCC could alter our understanding of salt transport in the distal tubule.
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Nesterov V, Krueger B, Bertog M, Dahlmann A, Palmisano R, Korbmacher C. In Liddle Syndrome, Epithelial Sodium Channel Is Hyperactive Mainly in the Early Part of the Aldosterone-Sensitive Distal Nephron. Hypertension 2016; 67:1256-62. [DOI: 10.1161/hypertensionaha.115.07061] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 03/16/2016] [Indexed: 11/16/2022]
Affiliation(s)
- Viatcheslav Nesterov
- From the Institut für Zelluläre und Molekulare Physiologie (V.N., B.K., M.B., C.K.), Universitätsklinikum Erlangen, Medizinische Klinik 4–Nephrologie und Hypertensiologie (A.D.), and Optical Imaging Center Erlangen (OICE) (R.P.), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Bettina Krueger
- From the Institut für Zelluläre und Molekulare Physiologie (V.N., B.K., M.B., C.K.), Universitätsklinikum Erlangen, Medizinische Klinik 4–Nephrologie und Hypertensiologie (A.D.), and Optical Imaging Center Erlangen (OICE) (R.P.), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Marko Bertog
- From the Institut für Zelluläre und Molekulare Physiologie (V.N., B.K., M.B., C.K.), Universitätsklinikum Erlangen, Medizinische Klinik 4–Nephrologie und Hypertensiologie (A.D.), and Optical Imaging Center Erlangen (OICE) (R.P.), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Anke Dahlmann
- From the Institut für Zelluläre und Molekulare Physiologie (V.N., B.K., M.B., C.K.), Universitätsklinikum Erlangen, Medizinische Klinik 4–Nephrologie und Hypertensiologie (A.D.), and Optical Imaging Center Erlangen (OICE) (R.P.), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Ralf Palmisano
- From the Institut für Zelluläre und Molekulare Physiologie (V.N., B.K., M.B., C.K.), Universitätsklinikum Erlangen, Medizinische Klinik 4–Nephrologie und Hypertensiologie (A.D.), and Optical Imaging Center Erlangen (OICE) (R.P.), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Christoph Korbmacher
- From the Institut für Zelluläre und Molekulare Physiologie (V.N., B.K., M.B., C.K.), Universitätsklinikum Erlangen, Medizinische Klinik 4–Nephrologie und Hypertensiologie (A.D.), and Optical Imaging Center Erlangen (OICE) (R.P.), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
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40
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Abstract
The epithelial Na channel (ENaC) forms a pathway for Na(+) reabsorption in the distal nephron, and regulation of these channels is essential for salt homeostasis. In the rat kidney, ENaC subunits reached the plasma membrane in both immature and fully processed forms, the latter defined by either endoglycosidase H-insensitive glycosylation or proteolytic cleavage. Animals adapted to a low-salt diet have increased ENaC surface expression that is specific for the mature forms of the subunit proteins and is similar (three- to fourfold) for α, β, and γENaC. Kidney membranes were fractionated using differential centrifugation, sucrose-gradient separation, and immunoabsorption. Endoplasmic reticulum membranes, isolated using an antibody against calnexin, expressed immature γENaC, and the content decreased with Na depletion. Golgi membranes, isolated with an antibody against the cis-Golgi protein GM130, expressed both immature and processed γENaC; Na depletion increased the content of processed γENaC in this fraction by 3.8-fold. An endosomal compartment isolated using an antibody against Rab11 contained both immature and processed γENaC; the content of processed subunit increased 2.4-fold with Na depletion. Finally, we assessed the content of γENaC in the late endocytic compartments indirectly using urinary exosomes. All of the γENaC in these exosomes was in the fully cleaved form, and its content increased by 4.5-fold with Na depletion. These results imply that stimulation of ENaC surface expression results at least in part from increased rates of formation of fully processed subunits in the Golgi and subsequent trafficking to the apical membrane.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics and Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Diego Gravotta
- Department of Physiology and Biophysics and Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Lawrence G Palmer
- Department of Physiology and Biophysics and Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
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Chambrey R, Trepiccione F. Relative roles of principal and intercalated cells in the regulation of sodium balance and blood pressure. Curr Hypertens Rep 2015; 17:538. [PMID: 25794953 DOI: 10.1007/s11906-015-0538-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The kidney continuously adapts daily renal excretion of NaCl to match dietary intakes in order to maintain the NaCl content of the body, and keep vascular volume constant. Any situation that leads to NaCl retention favors a rise in blood pressure. The aldosterone-sensitive distal nephron, which contains two main types of cells, principal (PC) and intercalated (IC) cells, is an important site for the final regulation of urinary Na(+) excretion. Research over the past 20 years established a paradigm in which PCs are the exclusive site of Na(+) absorption while ICs are solely dedicated to acid-base transport. Recent studies have revealed the unexpected importance of ICs for NaCl reabsorption. Here, we review the mechanisms of Na(+) and Cl(-) transport in the aldosterone-sensitive distal nephron, with emphasis on the role of ICs in maintaining NaCl balance and normal blood pressure.
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Abstract
Hyperkalemia is common in patients with impaired kidney function or who take drugs that inhibit the renin-angiotensin-aldosterone axis. During the past decade, substantial advances in understanding how the body controls potassium excretion have been made, which may lead to improved standard of care for these patients. Renal potassium disposition is primarily handled by a short segment of the nephron, comprising part of the distal convoluted tubule and the connecting tubule, and regulation results from the interplay between aldosterone and plasma potassium. When dietary potassium intake and plasma potassium are low, the electroneutral sodium chloride cotransporter is activated, leading to salt retention. This effect limits sodium delivery to potassium secretory segments, limiting potassium losses. In contrast, when dietary potassium intake is high, aldosterone is stimulated. Simultaneously, potassium inhibits the sodium chloride cotransporter. Because more sodium is then delivered to potassium secretory segments, primed by aldosterone, kaliuresis results. When these processes are disrupted, hyperkalemia results. Recently, new agents capable of removing potassium from the body and treating hyperkalemia have been tested in clinical trials. This development suggests that more effective and safer approaches to the prevention and treatment of hyperkalemia may be on the horizon.
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Affiliation(s)
- David H Ellison
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon; Renal Section, Veterans Affairs Portland Health Care System, Portland, Oregon; and
| | - Andrew S Terker
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon
| | - Gerardo Gamba
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, Mexico
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43
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Kortenoeven MLA, Pedersen NB, Rosenbaek LL, Fenton RA. Vasopressin regulation of sodium transport in the distal nephron and collecting duct. Am J Physiol Renal Physiol 2015; 309:F280-99. [DOI: 10.1152/ajprenal.00093.2015] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 05/27/2015] [Indexed: 12/22/2022] Open
Abstract
Arginine vasopressin (AVP) is released from the posterior pituitary gland during states of hyperosmolality or hypovolemia. AVP is a peptide hormone, with antidiuretic and antinatriuretic properties. It allows the kidneys to increase body water retention predominantly by increasing the cell surface expression of aquaporin water channels in the collecting duct alongside increasing the osmotic driving forces for water reabsorption. The antinatriuretic effects of AVP are mediated by the regulation of sodium transport throughout the distal nephron, from the thick ascending limb through to the collecting duct, which in turn partially facilitates osmotic movement of water. In this review, we will discuss the regulatory role of AVP in sodium transport and summarize the effects of AVP on various molecular targets, including the sodium-potassium-chloride cotransporter NKCC2, the thiazide-sensitive sodium-chloride cotransporter NCC, and the epithelial sodium channel ENaC.
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Affiliation(s)
- M. L. A. Kortenoeven
- Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark
| | - N. B. Pedersen
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark; and
| | - L. L. Rosenbaek
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - R. A. Fenton
- Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark
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Mordasini D, Loffing-Cueni D, Loffing J, Beatrice R, Maillard MP, Hummler E, Burnier M, Escher G, Vogt B. ENaC activity in collecting ducts modulates NCC in cirrhotic mice. Pflugers Arch 2015; 467:2529-39. [PMID: 26055235 DOI: 10.1007/s00424-015-1711-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 04/24/2015] [Accepted: 05/18/2015] [Indexed: 01/07/2023]
Abstract
Cirrhosis is a frequent and severe disease, complicated by renal sodium retention leading to ascites and oedema. A better understanding of the complex mechanisms responsible for renal sodium handling could improve clinical management of sodium retention. Our aim was to determine the importance of the amiloride-sensitive epithelial sodium channel (ENaC) in collecting ducts in compensate and decompensate cirrhosis. Bile duct ligation was performed in control mice (CTL) and collecting duct-specific αENaC knockout (KO) mice, and ascites development, aldosterone plasma concentration, urinary sodium/potassium ratio and sodium transporter expression were compared. Disruption of ENaC in collecting ducts (CDs) did not alter ascites development, urinary sodium/potassium ratio, plasma aldosterone concentrations or Na,K-ATPase abundance in CCDs. Total αENaC abundance in whole kidney increased in cirrhotic mice of both genotypes and cleaved forms of α and γ ENaC increased only in ascitic mice of both genotypes. The sodium chloride cotransporter (NCC) abundance was lower in non-ascitic KO, compared to non-ascitic CTL, and increased when ascites appeared. In ascitic mice, the lack of αENaC in CDs induced an upregulation of total ENaC and NCC and correlated with the cleavage of ENaC subunits. This revealed compensatory mechanisms which could also take place when treating the patients with diuretics. These compensatory mechanisms should be considered for future development of therapeutic strategies.
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Affiliation(s)
- David Mordasini
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland. .,Department of Clinical Research, University of Bern, Bern, Switzerland.
| | | | | | - Rohrbach Beatrice
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland.,Department of Clinical Research, University of Bern, Bern, Switzerland
| | - Marc P Maillard
- Service of Nephrology and Hypertension, CHUV, Rue du Bugnon 17, CH-1005, Lausanne, Switzerland
| | - Edith Hummler
- Department of Pharmacology and Toxicology, University of Lausanne, Rue du Bugnon 27, CH-1005, Lausanne, Switzerland
| | - Michel Burnier
- Service of Nephrology and Hypertension, CHUV, Rue du Bugnon 17, CH-1005, Lausanne, Switzerland
| | - Geneviève Escher
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland.,Department of Clinical Research, University of Bern, Bern, Switzerland
| | - Bruno Vogt
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland.,Department of Clinical Research, University of Bern, Bern, Switzerland
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Abstract
The kidney filters vast quantities of Na at the glomerulus but excretes a very small fraction of this Na in the final urine. Although almost every nephron segment participates in the reabsorption of Na in the normal kidney, the proximal segments (from the glomerulus to the macula densa) and the distal segments (past the macula densa) play different roles. The proximal tubule and the thick ascending limb of the loop of Henle interact with the filtration apparatus to deliver Na to the distal nephron at a rather constant rate. This involves regulation of both filtration and reabsorption through the processes of glomerulotubular balance and tubuloglomerular feedback. The more distal segments, including the distal convoluted tubule (DCT), connecting tubule, and collecting duct, regulate Na reabsorption to match the excretion with dietary intake. The relative amounts of Na reabsorbed in the DCT, which mainly reabsorbs NaCl, and by more downstream segments that exchange Na for K are variable, allowing the simultaneous regulation of both Na and K excretion.
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Affiliation(s)
- Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York; and
| | - Jürgen Schnermann
- Kidney Disease Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
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46
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Abstract
Aldosterone is a major regulator of Na(+) absorption and acts primarily by controlling the epithelial Na(+) channel (ENaC) function at multiple levels including transcription. ENaC consists of α, β, and γ subunits. In the classical model, aldosterone enhances transcription primarily by activating mineralocorticoid receptor (MR). However, how aldosterone induces chromatin alternation and thus leads to gene activation or repression remains largely unknown. Emerging evidence suggests that Dot1a-Af9 complex plays an important role in repression of αENaC by directly binding and modulating targeted histone H3 K79 hypermethylation at the specific subregions of αENaC promoter. Aldosterone impairs Dot1a-Af9 formation by decreasing expression of Dot1a and Af9 and by inducing Sgk1, which, in turn, phosphorylates Af9 at S435 to weaken Dot1a-Af9 interaction. MR counterbalances Dot1a-Af9 action by competing with Dot1a for binding Af9. Af17 derepresses αENaC by competitively interacting with Dot1a and facilitating Dot1a nuclear export. Consistently, MR(-/-) mice have impaired ENaC expression at day 5 after birth, which may contribute to progressive development of pseudohypoaldosteronism type 1 in a later stage. Af17(-/-) mice have decreased ENaC expression, renal Na(+) retention, and blood pressure. In contrast, Dot1l(AC) mice have increased αENaC expression, despite a 20% reduction of the principal cells. This chapter reviews these findings linking aldosterone action to ENaC transcription through chromatin modification. Future direction toward the understanding the role of Dot1a-Af9 complex beyond ENaC regulation, in particular, in renal fibrosis is also briefly discussed.
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Affiliation(s)
- Lihe Chen
- Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, Texas, USA; Division of Renal Diseases and Hypertension, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Xi Zhang
- Division of Renal Diseases and Hypertension, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Wenzheng Zhang
- Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, Texas, USA; Division of Renal Diseases and Hypertension, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA.
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Abstract
The distal convoluted tubule (DCT) is a short nephron segment, interposed between the macula densa and collecting duct. Even though it is short, it plays a key role in regulating extracellular fluid volume and electrolyte homeostasis. DCT cells are rich in mitochondria, and possess the highest density of Na+/K+-ATPase along the nephron, where it is expressed on the highly amplified basolateral membranes. DCT cells are largely water impermeable, and reabsorb sodium and chloride across the apical membrane via electroneurtral pathways. Prominent among this is the thiazide-sensitive sodium chloride cotransporter, target of widely used diuretic drugs. These cells also play a key role in magnesium reabsorption, which occurs predominantly, via a transient receptor potential channel (TRPM6). Human genetic diseases in which DCT function is perturbed have provided critical insights into the physiological role of the DCT, and how transport is regulated. These include Familial Hyperkalemic Hypertension, the salt-wasting diseases Gitelman syndrome and EAST syndrome, and hereditary hypomagnesemias. The DCT is also established as an important target for the hormones angiotensin II and aldosterone; it also appears to respond to sympathetic-nerve stimulation and changes in plasma potassium. Here, we discuss what is currently known about DCT physiology. Early studies that determined transport rates of ions by the DCT are described, as are the channels and transporters expressed along the DCT with the advent of molecular cloning. Regulation of expression and activity of these channels and transporters is also described; particular emphasis is placed on the contribution of genetic forms of DCT dysregulation to our understanding.
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Affiliation(s)
- James A McCormick
- Division of Nephrology & Hypertension, Oregon Health & Science University, & VA Medical Center, Portland, Oregon, United States
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48
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Abstract
The acute effects of aldosterone administration on epithelial Na channels (ENaC) in rat kidney were examined using electrophysiology and immunodetection. Animals received a single injection of aldosterone (20 μg/kg body wt), which reduced Na excretion over the next 3 h. Channel activity was assessed in principal cells of cortical collecting ducts as amiloride-sensitive whole cell clamp current (INa). INa averaged 100 pA/cell, 20-30% of that reported for the same preparation under conditions of chronic stimulation. INa was negligible in control animals that did not receive hormone. The acute physiological response correlated with changes in ENaC processing and trafficking. These effects included increases in the cleaved forms of α-ENaC and γ-ENaC, assessed by Western blot, and increases in the surface expression of β-ENaC and γ-ENaC measured after surface protein biotinylation. These changes were qualitatively and quantitatively similar to those of chronic stimulation. This suggests that altered trafficking to or from the apical membrane is an early response to the hormone and that later increases in channel activity require stimulation of channels residing at the surface.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
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Kellenberger S, Schild L. International Union of Basic and Clinical Pharmacology. XCI. Structure, Function, and Pharmacology of Acid-Sensing Ion Channels and the Epithelial Na+ Channel. Pharmacol Rev 2014; 67:1-35. [DOI: 10.1124/pr.114.009225] [Citation(s) in RCA: 193] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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50
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Todkar A, Picard N, Loffing-Cueni D, Sorensen MV, Mihailova M, Nesterov V, Makhanova N, Korbmacher C, Wagner CA, Loffing J. Mechanisms of renal control of potassium homeostasis in complete aldosterone deficiency. J Am Soc Nephrol 2014; 26:425-38. [PMID: 25071088 DOI: 10.1681/asn.2013111156] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Aldosterone-independent mechanisms may contribute to K(+) homeostasis. We studied aldosterone synthase knockout (AS(-/-)) mice to define renal control mechanisms of K(+) homeostasis in complete aldosterone deficiency. AS(-/-) mice were normokalemic and tolerated a physiologic dietary K(+) load (2% K(+), 2 days) without signs of illness, except some degree of polyuria. With supraphysiologic K(+) intake (5% K(+)), AS(-/-) mice decompensated and became hyperkalemic. High-K(+) diets induced upregulation of the renal outer medullary K(+) channel in AS(-/-) mice, whereas upregulation of the epithelial sodium channel (ENaC) sufficient to increase the electrochemical driving force for K(+) excretion was detected only with a 2% K(+) diet. Phosphorylation of the thiazide-sensitive NaCl cotransporter was consistently lower in AS(-/-) mice than in AS(+/+) mice and was downregulated in mice of both genotypes in response to increased K(+) intake. Inhibition of the angiotensin II type 1 receptor reduced renal creatinine clearance and apical ENaC localization, and caused severe hyperkalemia in AS(-/-) mice. In contrast with the kidney, the distal colon of AS(-/-) mice did not respond to dietary K(+) loading, as indicated by Ussing-type chamber experiments. Thus, renal adaptation to a physiologic, but not supraphysiologic, K(+) load can be achieved in aldosterone deficiency by aldosterone-independent activation of the renal outer medullary K(+) channel and ENaC, to which angiotensin II may contribute. Enhanced urinary flow and reduced activity of the thiazide-sensitive NaCl cotransporter may support renal adaptation by activation of flow-dependent K(+) secretion and increased intratubular availability of Na(+) that can be reabsorbed in exchange for K(+) secreted.
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Affiliation(s)
- Abhijeet Todkar
- Institutes of Anatomy and Physiology, and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | | | | | | | | | - Viatcheslav Nesterov
- Institute for Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany; and
| | - Natalia Makhanova
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Christoph Korbmacher
- Institute for Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany; and
| | - Carsten A Wagner
- Physiology, and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Johannes Loffing
- Institutes of Anatomy and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland;
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