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Pan X, Huang C, Peng A, Zhang Z. Immunohistochemical localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac. J Laryngol Otol 2023; 137:1340-1344. [PMID: 36502818 DOI: 10.1017/s0022215122002444] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE This study aimed to determine the distribution and subcellular localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac. METHODS Ten samples of human endolymphatic sac were collected during acoustic neurinoma removal using the translabyrinthine approach. Immunohistochemistry and immunofluorescence were performed using aquaporin 2 and vasopressin type 2 receptor monoclonal antibodies. RESULTS Confocal microscopy demonstrated that vasopressin type 2 receptor labelling was expressed in both the apical and basolateral plasma membranes, and in the cytoplasm of the endolymphatic sac epithelium, whereas aquaporin 2 was strongly expressed at the basolateral site of the endolymphatic sac epithelium, in both the intraosseous and extraosseous parts of the endolymphatic sac. CONCLUSION Both aquaporin 2 and vasopressin type 2 receptor were detected in the epithelial cells of the human endolymphatic sac, suggesting that this channel may be involved in inner-ear fluid homeostasis. However, strong basolateral expression of aquaporin 2 in endolymphatic sac epithelium suggested that the function of aquaporin 2 may differ between the endolymphatic sac and kidney.
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Affiliation(s)
- X Pan
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - C Huang
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - A Peng
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Z Zhang
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
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2
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Krmar RT, Franzén S, Karlsson L, Strandberg H, Törnroth‐Horsefield S, Andresen JK, Jensen BL, Carlström M, Frithiof R. Effect of controlled hypotensive hemorrhage on plasma sodium levels in anesthetized pigs: An exploratory study. Physiol Rep 2023; 11:e15886. [PMID: 38010195 PMCID: PMC10680582 DOI: 10.14814/phy2.15886] [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: 11/07/2023] [Revised: 11/15/2023] [Accepted: 11/17/2023] [Indexed: 11/29/2023] Open
Abstract
Perioperative hyponatremia, due to non-osmotic release of the antidiuretic hormone arginine vasopressin, is a serious electrolyte disorder observed in connection with many types of surgery. Since blood loss during surgery contributes to the pathogenesis of hyponatremia, we explored the effect of bleeding on plasma sodium using a controlled hypotensive hemorrhage pig model. After 30-min baseline period, hemorrhage was induced by aspiration of blood during 30 min at mean arterial pressure <50 mmHg. Thereafter, the animals were resuscitated with retransfused blood and a near-isotonic balanced crystalloid solution and monitored for 180 min. Electrolyte and water balances, cardiovascular response, renal hemodynamics, and markers of volume regulation and osmoregulation were investigated. All pigs (n = 10) developed hyponatremia. All animals retained hypotonic fluid, and none could excrete net-free water. Urinary excretion of aquaporin 2, a surrogate marker of collecting duct responsiveness to antidiuretic hormone, was significantly reduced at the end of the study, whereas lysine vasopressin, i.e., the pig antidiuretic hormone remained high. In this animal model, hyponatremia developed due to net positive fluid balance and generation of electrolyte-free water by the kidneys. A decreased urinary aquaporin 2 excretion may indicate an escape from antidiuresis.
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Affiliation(s)
- Rafael T. Krmar
- Department of Physiology and PharmacologyKarolinska InstitutetStockholmSweden
| | - Stephanie Franzén
- Department of Surgical Sciences, anesthesiology and Intensive CareUppsala UniversityUppsalaSweden
| | - Leif Karlsson
- Department of Women's and Children's HealthKarolinska Institutet, Pediatric Endocrinology Unit, Karolinska University HospitalStockholmSweden
| | - Helin Strandberg
- Department of Biochemistry and Structural BiologyLund UniversityLundSweden
| | | | - Jesper K. Andresen
- Department of Cardiovascular and Renal ResearchInstitute of Molecular Medicine, University of Southern DenmarkOdenseDenmark
- Department of UrologyOdense University HospitalOdenseDenmark
| | - Boye L. Jensen
- Department of Cardiovascular and Renal ResearchInstitute of Molecular Medicine, University of Southern DenmarkOdenseDenmark
- Department of UrologyOdense University HospitalOdenseDenmark
| | - Mattias Carlström
- Department of Physiology and PharmacologyKarolinska InstitutetStockholmSweden
| | - Robert Frithiof
- Department of Surgical Sciences, anesthesiology and Intensive CareUppsala UniversityUppsalaSweden
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3
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Watts JA, Arroyo JP. Rethinking Vasopressin: New Insights into Vasopressin Signaling and Its Implications. Kidney360 2023; 4:1174-1180. [PMID: 37357355 PMCID: PMC10476687 DOI: 10.34067/kid.0000000000000194] [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] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 06/06/2023] [Indexed: 06/27/2023]
Abstract
Vasopressin is a highly conserved peptide hormone that has been traditionally associated with water homeostasis. There is accumulating evidence in both humans and animal models that vasopressin is implicated in the regulation of metabolism. This review focuses on the effects that vasopressin exerts on the regulation of glucose and fatty acids with a particular emphasis on the potential repercussions of metabolic dysregulation in kidney disease.
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Affiliation(s)
- Jason A. Watts
- Epigenetics and Stem Cell Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina
| | - Juan Pablo Arroyo
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee
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4
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Zuchowski Y, Carty J, Terker AS, Bock F, Trapani JB, Bhave G, Watts JA, Keller S, Zhang M, Zent R, Harris RC, Arroyo JP. Insulin-regulated aminopeptidase is required for water excretion in response to acute hypotonic stress. Am J Physiol Renal Physiol 2023; 324:F521-F531. [PMID: 36995926 PMCID: PMC10202483 DOI: 10.1152/ajprenal.00318.2022] [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: 01/04/2023] [Revised: 03/27/2023] [Accepted: 03/29/2023] [Indexed: 03/31/2023] Open
Abstract
The objective of this study was to understand the response of mice lacking insulin-regulated aminopeptidase (IRAP) to an acute water load. For mammals to respond appropriately to acute water loading, vasopressin activity needs to decrease. IRAP degrades vasopressin in vivo. Therefore, we hypothesized that mice lacking IRAP have an impaired ability to degrade vasopressin and, thus, have persistent urinary concentration. Age-matched 8- to 12-wk-old IRAP wild-type (WT) and knockout (KO) male mice were used for all experiments. Blood electrolytes and urine osmolality were measured before and 1 h after water load (∼2 mL sterile water via intraperitoneal injection). Urine was collected from IRAP WT and KO mice for urine osmolality measurements at baseline and after 1 h administration of the vasopressin type 2 receptor antagonist OPC-31260 (10 mg/kg ip). Immunofluorescence and immunoblot analysis were performed on kidneys at baseline and after 1 h acute water load. IRAP was expressed in the glomerulus, thick ascending loop of Henle, distal tubule, connecting duct, and collecting duct. IRAP KO mice had elevated urine osmolality compared with WT mice due to higher membrane expression of aquaporin 2 (AQP2), which was restored to that of controls after administration of OPC-31260. IRAP KO mice developed hyponatremia after an acute water load because they were unable to increase free water excretion due to increased surface expression of AQP2. In conclusion, IRAP is required to increase water excretion in response to an acute water load due to persistent vasopressin stimulation of AQP2.NEW & NOTEWORTHY Insulin-regulated aminopeptidase (IRAP) degrades vasopressin, but its role in urinary concentration and dilution is unknown. Here, we show that IRAP-deficient mice have a high urinary osmolality at baseline and are unable to excrete free water in response to water loading. These results reveal a novel regulatory role for IRAP in urine concentration and dilution.
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Affiliation(s)
- Yvonne Zuchowski
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Joshua Carty
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Andrew S Terker
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Fabian Bock
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Jonathan B Trapani
- Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Gautam Bhave
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Jason A Watts
- Epigenetics and Stem Cell Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, United States
| | - Susanna Keller
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia, Charlottesville, Virginia, United States
| | - Mingzhi Zhang
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Roy Zent
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, Tennessee, United States
| | - Raymond C Harris
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, Tennessee, United States
| | - Juan Pablo Arroyo
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States
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5
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Min F, Ziming J, Ming W, Bolin F, Xiaoqiao T, Wenhua C, Fanzhong S. Effectiveness of Fuling () and its extracts against spleen deficiency in rats tonifying spleen. J TRADIT CHIN MED 2023; 43:501-506. [PMID: 37147751 PMCID: PMC10133940 DOI: 10.19852/j.cnki.jtcm.2023.03.002] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
OBJECTIVE To observe and explore the effect of Fuling () in alleviating the spleen deficiency symptom pattern (SDSP). METHODS We established an animal model of SDS in Sprague-Dawley () rats by treating them with deficiency-inducing factors, including irregular feeding and tail clamping. Mice were administered Fuling () and its extracts (raw/cooked powder, aqueous/alcohol extract) by gavage once a day for 21 d. The body weight, rectal temperature, and spleen and thymus organ coefficients were calculated. The levels of motilin (MTL), gastrin (GAS), aquaporin 2 (AQP2), interleukin 2 (IL-2), IL-4, and 5-hydroxytryptamine (5-HT) in the serum and the level of AQP2 in the kidneys were evaluated by enzyme-linked immunosorbent assay. RESULTS Fuling () and its extracts did not change the body weight, rectal temperature, and organ coefficients of the spleen and thymus. However, it reduced the levels of MTL and GAS and increased the levels of IL-2 and AQP2. In addition, the levels of IL-4 and 5-HT showed no significant alteration. CONCLUSIONS These results suggested the crucial function of () in SDSP, especially promoting digestive function and water metabolism.
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Affiliation(s)
- Feng Min
- Hubei Provincial Key Laboratory of Applied Toxicology, Hubei Provincial Center for Disease Control and Prevention, Wuhan 430075, China
| | - Jia Ziming
- Hubei Provincial Key Laboratory of Applied Toxicology, Hubei Provincial Center for Disease Control and Prevention, Wuhan 430075, China
| | - Wan Ming
- Department of pharmaceutical affairs, Hubei Provincial Hospital of TCM, Wuhan 430074, China
| | - Fan Bolin
- Hubei Provincial Key Laboratory of Applied Toxicology, Hubei Provincial Center for Disease Control and Prevention, Wuhan 430075, China
| | - Tang Xiaoqiao
- Hubei Provincial Key Laboratory of Applied Toxicology, Hubei Provincial Center for Disease Control and Prevention, Wuhan 430075, China
| | - Cheng Wenhua
- Hubei Provincial Key Laboratory of Applied Toxicology, Hubei Provincial Center for Disease Control and Prevention, Wuhan 430075, China
| | - Sun Fanzhong
- Hubei Provincial Key Laboratory of Applied Toxicology, Hubei Provincial Center for Disease Control and Prevention, Wuhan 430075, China
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6
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Cheung PW, Boukenna M, Babicz RSE, Mitra S, Kay A, Paunescu TC, Baylor N, Liu CCS, Nair AV, Bouley R, Brown D. Intracellular sites of AQP2 S256 phosphorylation identified using inhibitors of the AQP2 recycling itinerary. Am J Physiol Renal Physiol 2023; 324:F152-F167. [PMID: 36454701 PMCID: PMC9844975 DOI: 10.1152/ajprenal.00123.2022] [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: 05/02/2022] [Revised: 11/23/2022] [Accepted: 11/24/2022] [Indexed: 12/05/2022] Open
Abstract
Vasopressin (VP)-regulated aquaporin-2 (AQP2) trafficking between cytoplasmic vesicles and the plasma membrane of kidney principal cells is essential for water homeostasis. VP affects AQP2 phosphorylation at several serine residues in the COOH-terminus; among them, serine 256 (S256) appears to be a major regulator of AQP2 trafficking. Mutation of this serine to aspartic acid, which mimics phosphorylation, induces constitutive membrane expression of AQP2. However, the intracellular location(s) at which S256 phosphorylation occurs remains elusive. Here, we used strategies to block AQP2 trafficking at different cellular locations in LLC-PK1 cells and monitored VP-stimulated phosphorylation of S256 at these sites by immunofluorescence and Western blot analysis with phospho-specific antibodies. Using methyl-β-cyclodextrin, cold block or bafilomycin, and taxol, we blocked AQP2 at the plasma membrane, in the perinuclear trans-Golgi network, and in scattered cytoplasmic vesicles, respectively. Regardless of its cellular location, VP induced a significant increase in S256 phosphorylation, and this effect was not dependent on a functional microtubule cytoskeleton. To further investigate whether protein kinase A (PKA) was responsible for S256 phosphorylation in these cellular compartments, we created PKA-null cells and blocked AQP2 trafficking using the same procedures. We found that S256 phosphorylation was no longer increased compared with baseline, regardless of AQP2 localization. Taken together, our data indicate that AQP2 S256 phosphorylation can occur at the plasma membrane, in the trans-Golgi network, or in cytoplasmic vesicles and that this event is dependent on the expression of PKA in these cells.NEW & NOTEWORTHY Phosphorylation of aquaporin-2 by PKA at serine 256 (S256) occurs in various subcellular locations during its recycling itinerary, suggesting that the protein complex necessary for AQP2 S256 phosphorylation is present in these different recycling stations. Furthermore, we showed, using PKA-null cells, that PKA activity is required for vasopressin-induced AQP2 phosphorylation. Our data reveal a complex spatial pattern of intracellular AQP2 phosphorylation at S256, shedding new light on the role of phosphorylation in AQP2 membrane accumulation.
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Affiliation(s)
- Pui W Cheung
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Mey Boukenna
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Richard S E Babicz
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Shimontini Mitra
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Anna Kay
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Theodor C Paunescu
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Noah Baylor
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Chen-Chung Steven Liu
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Anil V Nair
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Richard Bouley
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Dennis Brown
- Division of Nephrology, Program in Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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7
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Scorza SI, Milano S, Saponara I, Certini M, De Zio R, Mola MG, Procino G, Carmosino M, Moccia F, Svelto M, Gerbino A. TRPML1-Induced Lysosomal Ca 2+ Signals Activate AQP2 Translocation and Water Flux in Renal Collecting Duct Cells. Int J Mol Sci 2023; 24:ijms24021647. [PMID: 36675161 PMCID: PMC9861594 DOI: 10.3390/ijms24021647] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/04/2023] [Accepted: 01/11/2023] [Indexed: 01/19/2023] Open
Abstract
Lysosomes are acidic Ca2+ storage organelles that actively generate local Ca2+ signaling events to regulate a plethora of cell functions. Here, we characterized lysosomal Ca2+ signals in mouse renal collecting duct (CD) cells and we assessed their putative role in aquaporin 2 (AQP2)-dependent water reabsorption. Bafilomycin A1 and ML-SA1 triggered similar Ca2+ oscillations, in the absence of extracellular Ca2+, by alkalizing the acidic lysosomal pH or activating the lysosomal cation channel mucolipin 1 (TRPML1), respectively. TRPML1-dependent Ca2+ signals were blocked either pharmacologically or by lysosomes' osmotic permeabilization, thus indicating these organelles as primary sources of Ca2+ release. Lysosome-induced Ca2+ oscillations were sustained by endoplasmic reticulum (ER) Ca2+ content, while bafilomycin A1 and ML-SA1 did not directly interfere with ER Ca2+ homeostasis per se. TRPML1 activation strongly increased AQP2 apical expression and depolymerized the actin cytoskeleton, thereby boosting water flux in response to an hypoosmotic stimulus. These effects were strictly dependent on the activation of the Ca2+/calcineurin pathway. Conversely, bafilomycin A1 led to perinuclear accumulation of AQP2 vesicles without affecting water permeability. Overall, lysosomal Ca2+ signaling events can be differently decoded to modulate Ca2+-dependent cellular functions related to the dock/fusion of AQP2-transporting vesicles in principal cells of the CD.
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Affiliation(s)
- Simona Ida Scorza
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Serena Milano
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Ilenia Saponara
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Maira Certini
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Roberta De Zio
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Giuseppe Procino
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Monica Carmosino
- Department of Sciences, University of Basilicata, 85100 Potenza, Italy
| | - Francesco Moccia
- Department of Biology and Biotechnology Lazzaro Spallanzani, University of Pavia, 27100 Pavia, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Andrea Gerbino
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
- Correspondence: ; Tel.: +39-0805443334
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8
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Lu HAJ, He J. Aquaporins in Diabetes Insipidus. Adv Exp Med Biol 2023; 1398:267-279. [PMID: 36717500 DOI: 10.1007/978-981-19-7415-1_18] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Disruption of water and electrolyte balance is frequently encountered in clinical medicine. Regulating water metabolism is critically important. Diabetes insipidus (DI) presented with excessive water loss from the kidney is a major disorder of water metabolism. To understanding the molecular and cellular mechanisms and pathophysiology of DI and rationales of clinical management of DI is important for both research and clinical practice. This chapter will first review various forms of DI focusing on central diabetes insipidus (CDI) and nephrogenic diabetes insipidus (NDI). This is followed by a discussion of regulatory mechanisms underlying CDI and NDI, with a focus on the regulatory axis of vasopressin, vasopressin receptor 2 (V2R) and the water channel molecule, aquaporin 2 (AQP2). The clinical manifestation, diagnosis, and management of various forms of DI will also be discussed with highlights of some of the latest therapeutic strategies that are developed from in vitro experiments and animal studies.
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Affiliation(s)
- H A Jenny Lu
- Program in Membrane Biology, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
| | - Jinzhao He
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
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9
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Maeoka Y, Cornelius RJ, Ferdaus MZ, Sharma A, Nguyen LT, McCormick JA. Cullin 3 mutant causing familial hyperkalemic hypertension lacks normal activity in the kidney. Am J Physiol Renal Physiol 2022; 323:F564-F576. [PMID: 36007890 PMCID: PMC9602935 DOI: 10.1152/ajprenal.00153.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [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: 06/15/2022] [Revised: 07/27/2022] [Accepted: 08/15/2022] [Indexed: 01/07/2023] Open
Abstract
Mutations in the ubiquitin ligase scaffold protein cullin 3 (CUL3) cause the disease familial hyperkalemic hypertension (FHHt). We recently reported that in the kidney, aberrant mutant CUL3 (CUL3-Δ9) activity lowers the abundance of CUL3-Δ9 and Kelch-like 3, the CUL3 substrate adaptor for with-no-lysine kinase 4 (WNK4) and that this is mechanistically important. However, whether CUL3-Δ9 exerts additional effects on other targets that may alter renal function is unclear. Here, we sought to determine 1) whether CUL3-Δ9 expression can rescue the phenotype of renal tubule-specific Cul3 knockout mice, and 2) whether CUL3-Δ9 expression affects other CUL3 substrates. Using an inducible renal tubule-specific system, we studied two CUL3-Δ9-expressing mouse models: Cul3 knockout (Cul3-/-/Δ9) and Cul3 heterozygous background (Cul3+/-/Δ9, FHHt model). The effects of CUL3-Δ9 in these mice were compared with Cul3-/- and Cul3+/- mice. Similar to Cul3-/- mice, Cul3-/-/Δ9 mice displayed polyuria with loss of aquaporin 2 and collecting duct injury; proximal tubule injury also occurred. CUL3-Δ9 did not promote degradation of two CUL3 targets that accumulate in the Cul3-/- kidney: high-molecular-weight (HMW) cyclin E and NAD(P)H:quinone oxidoreductase 1 (NQO1) [a surrogate for the CUL3-Kelch-like ECH-associated protein 1 (KEAP1) substrate nuclear factor erythroid-2-related factor 2]. Since CUL3-Δ9 expression cannot rescue the Cul3-/- phenotype, our data suggest that CUL3-Δ9 cannot normally function in ubiquitin ligase complexes. In Cul3+/-/Δ9 mice, KEAP1 abundance did not differ but NQO1 abundance was higher, suggesting adaptor sequestration by CUL3-Δ9 in vivo. Together, our results provide evidence that in the kidney, CUL3-Δ9 completely lacks normal activity and can trap CUL3 substrate adaptors in inactive complexes.NEW & NOTEWORTHY CUL3 mutation (CUL3-Δ9) causes familial hyperkalemic hypertension (FHHt) by reducing adaptor KLHL3, impairing substrate WNK4 degradation. Whether CUL3-Δ9 affects other targets in kidneys remains unclear. We found that CUL3-Δ9 cannot degrade two CUL3 targets, cyclin E and nuclear factor erythroid-2-related factor 2 (NRF2; using a surrogate marker NQO1), or rescue injury or polyuria caused by Cul3 disruption. In an FHHt model, CUL3-Δ9 impaired NRF2 degradation without reduction of its adaptor KEAP1. Our data provide additional insights into CUL3-Δ9 function in the kidney.
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Affiliation(s)
- Yujiro Maeoka
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon
| | - Ryan J Cornelius
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon
| | - Mohammed Zubaerul Ferdaus
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon
| | - Avika Sharma
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon
| | - Luan T Nguyen
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon
| | - James A McCormick
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon
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10
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Wu A, Wolley MJ, Wu Q, Cowley D, Palmfeldt J, Welling PA, Fenton RA, Stowasser M. Acute Intravenous NaCl and Volume Expansion Reduces Sodium-Chloride Cotransporter Abundance and Phosphorylation in Urinary Extracellular Vesicles. Kidney360 2022; 3:910-921. [PMID: 36128481 PMCID: PMC9438418 DOI: 10.34067/kid.0000362022] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 02/28/2022] [Indexed: 01/12/2023]
Abstract
Background Sodium chloride (NaCl) loading and volume expansion suppress the renin-angiotensin-aldosterone system to reduce renal tubular reabsorption of NaCl and water, but effects on the sodium-chloride cotransporter (NCC) and relevant renal transmembrane proteins that are responsible for this modulation in humans are less well investigated. Methods We used urinary extracellular vesicles (uEVs) as an indirect readout to assess renal transmembrane proteins involved in NaCl and water homeostasis in 44 patients with hypertension who had repeatedly raised aldosterone/renin ratios undergoing infusion of 2 L of 0.9% saline over 4 hours. Results When measured by mass spectrometry in 13 patients, significant decreases were observed in NCC (median fold change [FC]=0.70); pendrin (FC=0.84); AQP2 (FC=0.62); and uEV markers, including ALIX (FC=0.65) and TSG101 (FC=0.66). Immunoblotting reproduced the reduction in NCC (FC=0.54), AQP2 (FC=0.42), ALIX (FC=0.52), and TSG101 (FC=0.55) in the remaining 31 patients, and demonstrated a significant decrease in phosphorylated NCC (pNCC; FC=0.49). However, after correction for ALIX, the reductions in NCC (FC=0.90) and pNCC (FC=1.00) were no longer apparent, whereas the significant decrease in AQP2 persisted (FC=0.62). Conclusion We conclude that (1) decreases in NCC and pNCC, induced by acute NaCl loading and volume expansion, may be due to diluted post-test urines; (2) the lack of change of NCC and pNCC when corrected for ALIX, despite a fall in plasma aldosterone, may be due to the lack of change in plasma K+; and (3) the decrease in AQP2 may be due to a decrease in vasopressin in response to volume expansion.
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Affiliation(s)
- Aihua Wu
- Endocrine Hypertension Research Centre, University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Martin J. Wolley
- Endocrine Hypertension Research Centre, University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia,Department of Nephrology, Royal Brisbane and Women’s Hospital, Brisbane, Australia
| | - Qi Wu
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Diane Cowley
- Endocrine Hypertension Research Centre, University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Johan Palmfeldt
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Paul A. Welling
- Department of Medicine and Physiology, Johns Hopkins University, Baltimore, Maryland
| | | | - Michael Stowasser
- Endocrine Hypertension Research Centre, University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
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11
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Matchimakul P, Pongkan W, Kongtung P, Mektrirat R. Comparative quantitation of aquaporin-2 and arginine vasopressin receptor-2 localizations among chronic kidney disease and healthy kidney in dogs. Vet World 2021; 14:2773-2781. [PMID: 34903939 PMCID: PMC8654747 DOI: 10.14202/vetworld.2021.2773-2781] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 09/09/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND AND AIM Aquaporin-2 (AQP2) and arginine vasopressin receptor-2 (AVPR2) are proteins that control water homeostasis in principal cells. Chronic kidney disease (CKD) is defined as the impairment and irreversible loss of kidney function and/or structure, which causes water imbalances and polyuria. The study aimed to know the expression of AQPs and AVPR2 in the kidneys of a canine with CKD. MATERIALS AND METHODS The kidneys were collected from two dog carcasses from Small Animal Teaching Hospital, Faculty of Veterinary Medicine, Chiang Mai University. The kidney tissue was prepared for immunohistochemistry and investigated the expression and localization of tissue's AQP2 and AVPR2. For statistical analysis, the Mann-Whitney U-test was applied to the data. RESULTS By immunohistochemistry, AQP2 was expressed strongly in the basolateral and apical membranes of the principal cells, whereas AVPR2 was localized in the principal cell's basolateral membrane in both renal cortex and renal medulla. In the normal kidney, the semi-quantitative immunohistochemistry for the percentage of protein expression of AQP2 and AVPR2 was 5.062±0.4587 and 4.306±0.7695, respectively. In contrast, protein expression of AQP2 and AVPR2 in CKD was found to be 1.218±0.1719 and 0.8536±0.1396, respectively. The data shows that the percentage of AQP2 and AVPR2 expression was decreased, corresponding to a 4-fold and 5-fold in CKD (p<0.001). CONCLUSION Our findings revealed that CKD was a marked decrease in AQP2 and AVPR2 expression. The central role of specific AQP2 and AVPR2 in regulating water homeostasis will provide correlations in case of CKD with polyuria.
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Affiliation(s)
- Pitchaya Matchimakul
- Department of Veterinary Bioscience and Veterinary Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
- Integrative Research Center for Veterinary Circulatory Sciences, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
| | - Wanpitak Pongkan
- Department of Veterinary Bioscience and Veterinary Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
- Integrative Research Center for Veterinary Circulatory Sciences, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
| | - Piyamat Kongtung
- Central Laboratory, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
| | - Raktham Mektrirat
- Department of Veterinary Bioscience and Veterinary Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
- Integrative Research Center for Veterinary Circulatory Sciences, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
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12
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Li Q, Lu B, Yang J, Li C, Li Y, Chen H, Li N, Duan L, Gu F, Zhang J, Xia W. Molecular Characterization of an Aquaporin-2 Mutation Causing Nephrogenic Diabetes Insipidus. Front Endocrinol (Lausanne) 2021; 12:665145. [PMID: 34512542 PMCID: PMC8429928 DOI: 10.3389/fendo.2021.665145] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 07/06/2021] [Indexed: 11/30/2022] Open
Abstract
The aquaporin 2 (AQP2) plays a critical role in water reabsorption to maintain water homeostasis. AQP2 mutation leads to nephrogenic diabetes insipidus (NDI), characterized by polyuria, polydipsia, and hypernatremia. We previously reported that a novel AQP2 mutation (G215S) caused NDI in a boy. In this study, we aimed to elucidate the cell biological consequences of this mutation on AQP2 function and clarify the molecular pathogenic mechanism for NDI in this patient. First, we analyzed AQP2 expression in Madin-Darby canine kidney (MDCK) cells by AQP2-G215S or AQP2-WT plasmid transfection and found significantly decreased AQP2-G215S expression in cytoplasmic membrane compared with AQP2-WT, independent of forskolin treatment. Further, we found co-localization of endoplasmic reticulum (ER) marker (Calnexin) with AQP2-G215S rather than AQP2-WT in MDCK cells by immunocytochemistry. The functional analysis showed that MDCK cells transfected with AQP2-G215S displayed reduced water permeability compared with AQP2-WT. Visualization of AQP2 structure implied that AQP2-G215S mutation might interrupt the folding of the sixth transmembrane α-helix and/or the packing of α-helices, resulting in the misfolding of monomer and further impaired formation of tetramer. Taken together, these findings suggested that AQP2-G215S was misfolded and retained in the ER and could not be translocated to the apical membrane to function as a water channel, which revealed the molecular pathogenic mechanism of AQP2-G215S mutation and explained for the phenotype of NDI in this patient.
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Affiliation(s)
- Qian Li
- Department of Endocrinology, Key Laboratory of Endocrinology, NHC, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Bichao Lu
- Department of Immunology, Research Center on Pediatric Development and Diseases, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, State Key Laboratory of Medical Molecular Biology, Beijing, China
| | - Jia Yang
- Department of Immunology, Research Center on Pediatric Development and Diseases, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, State Key Laboratory of Medical Molecular Biology, Beijing, China
| | - Chao Li
- Department of Immunology, Research Center on Pediatric Development and Diseases, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, State Key Laboratory of Medical Molecular Biology, Beijing, China
| | - Yanchun Li
- Department of Radiation Oncology, Stanford University, School of Medicine, Stanford, CA, United States
| | - Hui Chen
- Department of Immunology, Research Center on Pediatric Development and Diseases, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, State Key Laboratory of Medical Molecular Biology, Beijing, China
| | - Naishi Li
- Department of Endocrinology, Key Laboratory of Endocrinology, NHC, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Lian Duan
- Department of Endocrinology, Key Laboratory of Endocrinology, NHC, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Feng Gu
- Department of Endocrinology, Key Laboratory of Endocrinology, NHC, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Jianmin Zhang
- Department of Immunology, Research Center on Pediatric Development and Diseases, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, State Key Laboratory of Medical Molecular Biology, Beijing, China
| | - Weibo Xia
- Department of Endocrinology, Key Laboratory of Endocrinology, NHC, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
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13
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Han M, Li S, Xie H, Liu Q, Wang A, Hu S, Zhao X, Kong Y, Wang W, Li C. Activation of TGR5 restores AQP2 expression via the HIF pathway in renal ischemia-reperfusion injury. Am J Physiol Renal Physiol 2021; 320:F308-F321. [PMID: 33427060 DOI: 10.1152/ajprenal.00577.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 12/22/2020] [Indexed: 12/28/2022] Open
Abstract
Renal ischemia-reperfusion (I/R) injury is associated with markedly reduced protein expression of aquaporins (AQPs). Membrane G protein-coupled bile acid receptor-1 (TGR5) has shown protective roles in some kidney diseases. The purpose of the current study was to investigate whether activation of TGR5 prevented the decreased protein expression of AQPs in rodents with renal I/R injury and potential mechanisms. TGR5 agonist lithocholic acid (LCA) treatment reduced polyuria after renal I/R injury in rats. LCA prevented the decreased abundance of AQP2 protein and upregulated hypoxia-inducible factor (HIF)-1α protein expression, which were associated with decreased protein abundance of NF-κB p65 and IL-1β. After renal I/R, mice with tgr5 gene deficiency exhibited further decreases in AQP2 and HIF-1α protein abundance and increases of IL-1β and NF-κB p65 protein expression compared with wild-type mice. In primary cultured inner medullary collecting duct cells with hypoxia/reoxygenation, LCA induced markedly increased protein expression of AQP2 and HIF-1α, which were partially prevented by the PKA inhibitor H89. FG4592, a prolyl-4-hydroxylase domain-containing protein inhibitor, increased HIF-1α and AQP2 protein abundance in association with decreased NF-κB p65 protein expression in inner medullary collecting duct cells with hypoxia/reoxygenation. In conclusion, TGR5 stimulation by LCA prevented downregulation of renal AQPs in kidney with I/R injury, likely through activating HIF-1α signaling and suppressing inflammatory responses.NEW & NOTEWORTHY Stimulation of the membrane G protein-coupled bile acid receptor TGR5 by lithocholic acid (LCA) reduced polyuria in rats with renal ischemia-reperfusion (I/R) injury. LCA increased abundance of aquaporin-2 (AQP2) protein and upregulated hypoxia-inducible factor (HIF)-1α protein expression in association with decreased NF-κB p65 and IL-1β. After I/R, mice with tgr5 gene deficiency exhibited more severe decreases in AQP2 and HIF-1α protein abundance and inflammatory responses. TGR5 activation exhibits a protective role in acute renal injury induced by I/R.
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Affiliation(s)
- Mengke Han
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Suchun Li
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Haixia Xie
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Qiaojuan Liu
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Ani Wang
- Cardiovascular Center, The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, China
| | - Shan Hu
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Xiaoduo Zhao
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Yonglun Kong
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Weidong Wang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
- Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
- Department of Nephrology, the Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
| | - Chunling Li
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
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14
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Zhao G, Wu X, Wang W, Yang CS, Zhang J. Tea Drinking Alleviates Diabetic Symptoms via Upregulating Renal Water Reabsorption Proteins and Downregulating Renal Gluconeogenic Enzymes in db/db Mice. Mol Nutr Food Res 2020; 64:e2000505. [PMID: 33052021 DOI: 10.1002/mnfr.202000505] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 09/19/2020] [Indexed: 01/01/2023]
Abstract
SCOPE Tea, made from the plant Camellia sinensis, is known to have anti-diabetes effects and different mechanisms of action are proposed. Kidney is a vital organ in managing water reabsorption and glucose metabolism, and is greatly influenced by diabetes. The present study investigates the effects of tea administration on water reabsorption and gluconeogenesis in the kidney of diabetic mice. METHODS AND RESULTS Db/db mice are given tea infusion as drinking fluid when they begin to exhibit hyperglycemia. It is found that green tea or black tea infusion potently elevates renal proteins vital for water reabsorption, including protein kinase C-α, aquaporin 2, and urea transporter-A1, as well as increases trafficking of these proteins to apical plasma membrane where they exert water reabsorption function. The treatment also downregulates renal gluconeogenic enzymes, including glucose-6-phosphatase-α and phosphoenolpyruvate carboxykinase. Associated with these biochemical changes are the rectified polyuria, polydipsia, polyphagia, and hyperglycemia, all symptoms of diabetes. CONCLUSIONS For the first time, the present study demonstrates that tea has robust effects in enhancing kidney water reabsorption proteins and downregulating gluconeogenic enzymes in db/db mice. It remains to be investigated whether such beneficial effects of tea occur in humans.
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Affiliation(s)
- Guangshan Zhao
- State Key Laboratory of Tea Plant Biology and Utilization, School of Tea & Food Science, Anhui Agricultural University, Hefei, Anhui, 230036, China
- Biology Postdoctoral Research Station, Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou, Guangdong, 510632, China
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, Guangdong, 510632, China
| | - Ximing Wu
- State Key Laboratory of Tea Plant Biology and Utilization, School of Tea & Food Science, Anhui Agricultural University, Hefei, Anhui, 230036, China
| | - Wenping Wang
- State Key Laboratory of Tea Plant Biology and Utilization, School of Tea & Food Science, Anhui Agricultural University, Hefei, Anhui, 230036, China
| | - Chung S Yang
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854-8020, USA
- International Joint Research Laboratory of Tea Chemistry and Health Effects, Anhui Agricultural University, Hefei, Anhui, 230036, China
| | - Jinsong Zhang
- State Key Laboratory of Tea Plant Biology and Utilization, School of Tea & Food Science, Anhui Agricultural University, Hefei, Anhui, 230036, China
- International Joint Research Laboratory of Tea Chemistry and Health Effects, Anhui Agricultural University, Hefei, Anhui, 230036, China
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15
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Sánchez-Solís CN, Cuevas Romero E, Soto-Rodríguez I, de Lourdes Arteaga-Castañeda M, De León-Ramírez YM, Rodríguez-Antolín J, Nicolás-Toledo L. High-sucrose diet potentiates hyperaldosteronism and renal injury induced by stress in young adult rats. Clin Exp Pharmacol Physiol 2020; 47:1985-1994. [PMID: 32911579 DOI: 10.1111/1440-1681.13394] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 07/27/2020] [Accepted: 08/04/2020] [Indexed: 11/27/2022]
Abstract
Analyze the effect of stress and high-sucrose diet on serum aldosterone levels and the morphometric characteristics of the kidney in young adult rats. Wistar male rats aged 21 days old weaned were randomly assigned into four groups: control (C), stressed (St), high-sucrose diet (S30), and chronic restraint stress plus a 30% sucrose diet (St + S30). Rats were fed with a standard chow and tap water ad libitum (C group) or 30% sucrose diluted in water (S30 group) during eight weeks. The St and St + S30 groups were subject to restraint stress (1-hour daily in a plastic cylinder, 5 days per week), four weeks before euthanasia. At 81 days old, all animals were killed and blood samples and kidneys were collected. Stressed rats had an increase in the serum aldosterone and renal triacylglycerol, a decrease in the area of the renal corpuscle, glomeruli, proximal tubules, and aquaporin 2 expressions with loss of glomeruli. For its part, the high-sucrose diet decreased the area of the renal corpuscle, glomeruli, and aquaporin 2 expressions in the cortex. The combination of stress and high- sucrose diet maintained similar effects on the kidney as the stress alone, although it induced an increase in the creatinine levels and renal glycogen. Our results showed that chronic stress induces hyperaldosteronism and kidney injury. The intake of a high-sucrose diet may potentiate the renal injury promoted by stress.
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Affiliation(s)
| | - Estela Cuevas Romero
- Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, México
| | | | | | | | - Jorge Rodríguez-Antolín
- Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, México
| | - Leticia Nicolás-Toledo
- Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, México
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16
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Abstract
Congenital nephrogenic diabetes insipidus (CNDI) is a rare renal disorder caused by mutations in arginine vasopressin receptor 2 (AVPR2) or aquaporin 2 (AQP2). The clinical signs of CNDI include polyuria, compensatory polydipsia, dehydration, electrolyte disorder, and developmental retardation without prompt treatment. In this study we report a rare case of CNDI caused by a single base transition in AQP2 gene. A 4.5 years old male patient suffered from oral dryness, polydipsia, and polyuria for more than 3 years. Laboratory examinations showed hypernatremia, hyperchloremia, and decreased urine osmolality and specific gravity. Ultrasound and MRI found bilateral upper ureteral dilatation and hydronephrosis. Furthermore, sequencing analysis found a C>T transition leading to a T108M missense mutation of AQP2. The patient was given low sodium diet and treated with hydrochlorothiazide followed by amiloride with indomethacin. The patient's clinical course improved remarkably after 1 year of treatment. This study reports the first case of CNDI featuring T108M missense mutation alone. These findings demonstrate a causative role of T108M mutation for CNDI and contribute to the mechanistic understanding of CNDI disease process.
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Affiliation(s)
- Lina Ma
- Department of Pediatric Nephrology, Lanzhou University Second Hospital, Lanzhou, China.,Department of Nephrology, Gansu Children's Hospital, Lanzhou, China
| | - Dengyan Wu
- Department of Pediatric Nephrology, Lanzhou University Second Hospital, Lanzhou, China.,Department of Nephrology, Gansu Children's Hospital, Lanzhou, China
| | - Xingmin Wang
- Nantong Institute of Genetics and Reproductive Medicine, Nantong Maternity and Child Healthcare Hospital, Nantong University, Nantong, China.,School of Medicine, Jiangsu University, Zhenjiang, China
| | - Yonghong Yang
- Department of Pediatric Nephrology, Lanzhou University Second Hospital, Lanzhou, China.,Department of Nephrology, Gansu Children's Hospital, Lanzhou, China
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17
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Somparn P, Boonkrai C, Charngkaew K, Chomanee N, Hodge KG, Fenton RA, Pisitkun T, Khositseth S. Bilateral ureteral obstruction is rapidly accompanied by ER stress and activation of autophagic degradation of IMCD proteins, including AQP2. Am J Physiol Renal Physiol 2020; 318:F135-F147. [PMID: 31736351 PMCID: PMC7054639 DOI: 10.1152/ajprenal.00113.2019] [Citation(s) in RCA: 4] [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] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
After the release of bilateral ureteral obstruction (BUO), postobstructive diuresis from an impaired urine concentration mechanism is associated with reduced aquaporin 2 (AQP2) abundance in the inner medullary collecting duct (IMCD). However, the underlying molecular mechanism of this AQP2 reduction is incompletely understood. To elucidate the mechanisms responsible for this phenomenon, we studied molecular changes in IMCDs isolated from rats with 4-h BUO or sham operation at the early onset of AQP2 downregulation using mass spectrometry-based proteomic analysis. Two-hundred fifteen proteins had significant changes in abundances, with 65% of them downregulated in the IMCD of 4-h BUO rats compared with sham rats. Bioinformatic analysis revealed that significantly changed proteins were associated with functional Gene Ontology terms, including “cell-cell adhesion,” “cell-cell adherens junction,” “mitochondrial inner membrane,” “endoplasmic reticulum chaperone complex,” and the KEGG pathway of glycolysis/gluconeogenesis. Targeted liquid chromatography-tandem mass spectrometry or immunoblot analysis confirmed the changes in 19 proteins representative of each predominant cluster, including AQP2. Electron microscopy demonstrated disrupted tight junctions, disorganized adherens junctions, swollen mitochondria, enlargement of the endoplasmic reticulum lumen, and numerous autophagosomes/lysosomes in the IMCD of rats with 4-h BUO. AQP2 and seven proteins chosen as representative of the significantly altered clusters had a significant increase in immunofluorescence-based colocalization with autophagosomes/lysosomes. Immunogold electron microscopy confirmed colocalization of AQP2 with the autophagosome marker microtubule-associated protein 1A/1B-light chain 3 and the lysosomal marker cathepsin D in IMCD cells of rats with 4-h BUO. We conclude that enhanced autophagic degradation of AQP2 and other critical proteins, as well as endoplasmic reticulum stress in the IMCD, are initiated shortly after BUO.
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Affiliation(s)
- Poorichaya Somparn
- Center of Excellent in Systems Biology, Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.,Translational Research in Inflammation and Immunology Research Unit, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Chatikorn Boonkrai
- Center of Excellent in Systems Biology, Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Komgrid Charngkaew
- Department of Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Thailand
| | - Nusara Chomanee
- Department of Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Thailand
| | - Kenneth G Hodge
- Center of Excellent in Systems Biology, Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Robert A Fenton
- Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport, Aarhus University, Aarhus, Denmark
| | - Trairak Pisitkun
- Center of Excellent in Systems Biology, Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.,Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, Bethesda, Maryland
| | - Sookkasem Khositseth
- Department of Pediatrics, Faculty of Medicine, Thammasat University, Pathumthani, Thailand
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18
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Roche JV, Nesverova V, Olsson C, Deen PM, Törnroth-Horsefield S. Structural Insights into AQP2 Targeting to Multivesicular Bodies. Int J Mol Sci 2019; 20:ijms20215351. [PMID: 31661793 PMCID: PMC6862464 DOI: 10.3390/ijms20215351] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 10/21/2019] [Accepted: 10/24/2019] [Indexed: 12/16/2022] Open
Abstract
Vasopressin-dependent trafficking of AQP2 in the renal collecting duct is crucial for the regulation of water homeostasis. This process involves the targeting of AQP2 to the apical membrane during dehydration as well as its removal when hydration levels have been restored. The latter involves AQP2 endocytosis and sorting into multivesicular bodies (MVB), from where it may be recycled, degraded in lysosomes, or released into urine via exosomes. The lysosomal trafficking regulator-interacting protein 5 (LIP5) plays a crucial role in this by coordinating the actions of the endosomal sorting complex required for transport III (ESCRT-III) and vacuolar protein sorting 4 (Vps4) ATPase, resulting in the insertion of AQP2 into MVB inner vesicles. While the interaction between LIP5 and the ESCRT-III complex and Vps4 is well characterized, very little is known about how LIP5 interacts with AQP2 or any other membrane protein cargo. Here, we use a combination of fluorescence spectroscopy and computer modeling to provide a structural model of how LIP5 interacts with human AQP2. We demonstrate that, the AQP2 tetramer binds up to two LIP5 molecules and that the interaction is similar to that seen in the complex between LIP5 and the ESCRT-III component, charged multivesicular body protein 1B (CHMP1B). These studies give the very first structural insights into how LIP5 enables membrane protein insertion into MVB inner vesicles and significantly increase our understanding of the AQP2 trafficking mechanism.
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Affiliation(s)
- Jennifer Virginia Roche
- Department of Biochemistry and Structural Biology, Lund University, PO Box 124, 221 00, Lund, Sweden.
| | - Veronika Nesverova
- Department of Biochemistry and Structural Biology, Lund University, PO Box 124, 221 00, Lund, Sweden.
| | - Caroline Olsson
- Department of Biochemistry and Structural Biology, Lund University, PO Box 124, 221 00, Lund, Sweden.
| | - Peter Mt Deen
- Department of Physiology, Radboud University Medical Centre, Geert Grooteplein-Zuid 10, 6525 GA Nijmegen, The Netherlands.
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Zhou XJ, Bao YT, Chen HS, Xuan L, Chen XM, Zhang JY, Yang YX, Li CY. [Effect of Zhenwu Tang on regulating of "AVP-V2R-AQP2" pathway in NRK-52E cells]. Zhongguo Zhong Yao Za Zhi 2018; 43:603-608. [PMID: 29600629 DOI: 10.19540/j.cnki.cjcmm.20171113.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Indexed: 11/18/2022]
Abstract
This study was aimed to investigate the effect and mechanism of Zhenwu Tang on AVP-V2R-AQP2 pathway in NRK-52E cells in vitro. Forty eight male SD rats were randomly divided into eight groups with 6 animals in each group. Distilled water or 22.68 g·kg⁻¹·d⁻¹ Zhenwu Tang(calculated by raw drug dosage meter) was given by gavage. Blood samples were collected by cardiac puncture, and the medicated serum was centrifuged from the blood by 3 000 r·min⁻¹. NRK-52E cells were treated with different medicated serum or dDAVP. The condition of cell proliferation was detected by RTCA. The distribution of V2R and AQP2 in cells were detected by immunofluorescence. The expression of V2R, PKA and AQP2 were detected by Western blot and AQP2 mRNA level was detected by real-time PCR. Results showed that the level of AQP2 mRNA(P<0.01) and protein expression of V2R, PKA and AQP2(P<0.05, P<0.01, P<0.05) of Z7d group which was treated with Zhenwu Tang medicated serum for 24 h were significantly higher than that of normal rat serum group. And the expression level of V2R, p-AQP2 and AQP2(P<0.01, P<0.05, P<0.01) of Z7d+dDAVP group were significantly increased comparing to normal rat serum group. The results indicate that the applying of Zhenwu Tang medicated serum could increase the expression level of V2R, PKA and AQP2 which exist in AVP-V2R-AQP2 pathway in NRK-52E, and there is synergistic effect between Zhenwu Tang medicated serum and dDAVP. So the pathway of AVP-V2R-AQP2 may be one of the mechanism for which Zhenwu Tang regulate balance of water transportation.
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Affiliation(s)
- Xiao-Jie Zhou
- Zhejiang Chinese Medicine University, Hangzhou 310053, China
| | - Yu-Ting Bao
- Zhejiang Chinese Medicine University, Hangzhou 310053, China
| | - Hong-Shu Chen
- Affiliated First Hospital of Zhejiang Chinese Medical University, Hangzhou 310006, China
| | - Ling Xuan
- Zhejiang Chinese Medicine University, Hangzhou 310053, China
| | - Xue-Ming Chen
- Zhejiang Chinese Medicine University, Hangzhou 310053, China
| | - Jie-Ying Zhang
- Zhejiang Chinese Medicine University, Hangzhou 310053, China
| | | | - Chang-Yu Li
- Zhejiang Chinese Medicine University, Hangzhou 310053, China
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Ishikawa SE. Is Exaggerated Release of Arginine Vasopressin an Endocrine Disorder? Pathophysiology and Treatment. J Clin Med 2017; 6:jcm6110102. [PMID: 29088071 PMCID: PMC5704119 DOI: 10.3390/jcm6110102] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 10/27/2017] [Accepted: 10/30/2017] [Indexed: 12/05/2022] Open
Abstract
Exaggerated release of arginine vasopressin (AVP) is profoundly involved in impaired water excretion and related hyponatremia. Such disorders underlie syndromes of inappropriate secretion of antidiuretic hormone (SIADH) and edematous diseases, such as congestive heart failure and decompensated liver cirrhosis. All the causes are fundamentally from non-endocrine diseases. AVP-induced water retention could produce hyponatremia, and further accelerate poor long-term outcome of edematous diseases. Administration of AVP V2 receptor antagonists verifies how much AVP is involved in the pathogenesis of the impaired water excretion. The present paper demonstrated that exaggerated release of AVP plays a crucial role as an accessory endocrine disorder in pathological states of water retention and dilutional hyponatremia in non-endocrine disorders.
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Affiliation(s)
- San-E Ishikawa
- Department of Endocrinology and Metabolism, International University of Health and Welfare Hospital, Nasushiobara 329-2763, Tochigi, Japan.
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21
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Ren H, Yang B, Ruiz JA, Efe O, Ilori TO, Sands JM, Klein JD. Phosphatase inhibition increases AQP2 accumulation in the rat IMCD apical plasma membrane. Am J Physiol Renal Physiol 2016; 311:F1189-F1197. [PMID: 27488997 PMCID: PMC5210195 DOI: 10.1152/ajprenal.00150.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [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: 03/10/2016] [Accepted: 08/01/2016] [Indexed: 01/11/2023] Open
Abstract
Vasopressin triggers the phosphorylation and apical plasma membrane accumulation of aquaporin 2 (AQP2), and it plays an essential role in urine concentration. Vasopressin, acting through protein kinase A, phosphorylates AQP2. However, the phosphorylation state of AQP2 could also be affected by the action of protein phosphatases (PPs). Rat inner medullas (IM) were incubated with calyculin (PP1 and PP2A inhibitor, 50 nM) or tacrolimus (PP2B inhibitor, 100 nM). Calyculin did not affect total AQP2 protein abundance (by Western blot) but did significantly increase the abundances of pS256-AQP2 and pS264-AQP2. It did not change pS261-AQP2 or pS269-AQP2. Calyculin significantly enhanced the membrane accumulation (by biotinylation) of total AQP2, pS256-AQP2, and pS264-AQP2. Likewise, immunohistochemistry showed an increase in the apical plasma membrane association of pS256-AQP2 and pS264-AQP2 in calyculin-treated rat IM. Tacrolimus also did not change total AQP2 abundance but significantly increased the abundances of pS261-AQP2 and pS264-AQP2. In contrast to calyculin, tacrolimus did not change the amount of total AQP2 in the plasma membrane (by biotinylation and immunohistochemistry). Tacrolimus did increase the expression of pS264-AQP2 in the apical plasma membrane (by immunohistochemistry). In conclusion, PP1/PP2A regulates the phosphorylation and apical plasma membrane accumulation of AQP2 differently than PP2B. Serine-264 of AQP2 is a phosphorylation site that is regulated by both PP1/PP2A and PP2B. This dual regulatory pathway may suggest a previously unappreciated role for multiple phosphatases in the regulation of urine concentration.
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Affiliation(s)
- Huiwen Ren
- Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, Georgia
- Department of Pharmacology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China; and
| | - Baoxue Yang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China; and
| | - Joseph A Ruiz
- Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, Georgia
| | - Orhan Efe
- Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, Georgia
| | - Titilayo O Ilori
- Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, Georgia
| | - Jeff M Sands
- Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, Georgia
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Janet D Klein
- Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, Georgia;
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
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22
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Rahman SS, Boesen EI. Outside the mainstream: novel collecting duct proteins regulating water balance. Am J Physiol Renal Physiol 2016; 311:F1341-F1345. [PMID: 27784697 DOI: 10.1152/ajprenal.00488.2016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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: 09/02/2016] [Revised: 10/06/2016] [Accepted: 10/18/2016] [Indexed: 12/26/2022] Open
Abstract
Body water balance is critical to survival and, therefore, very tightly regulated by the hypothalamus and kidney. A key mechanism involved in this process, the arginine vasopressin-mediated phosphorylation and apical membrane insertion of aquaporin 2 in the collecting duct, has been extensively studied; however, with the increased availability of conditional knockout animals, several novel collecting duct proteins have recently been implicated in water homeostasis. In this Mini-Review, we briefly discuss these novel proteins and their roles in the regulation of water homeostasis.
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Affiliation(s)
- Shamma S Rahman
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Erika I Boesen
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
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23
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Sands JM, Klein JD. Physiological insights into novel therapies for nephrogenic diabetes insipidus. Am J Physiol Renal Physiol 2016; 311:F1149-F1152. [PMID: 27534996 DOI: 10.1152/ajprenal.00418.2016] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [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: 07/27/2016] [Accepted: 08/16/2016] [Indexed: 12/11/2022] Open
Abstract
Fundamental kidney physiology research can provide important insight into how the kidney works and suggest novel therapeutic opportunities to treat human diseases. This is especially true for nephrogenic diabetes insipidus (NDI). Over the past decade, studies elucidating the molecular physiology and signaling pathways regulating water transport have suggested novel therapeutic possibilities. In patients with congenital NDI due to mutations in the type 2 vasopressin receptor (V2R) or acquired NDI due to lithium (or other medications), there are no functional abnormalities in the aquaporin-2 (AQP2) water channel, or in another key inner medullary transport protein, the UT-A1 urea transporter. If it is possible to phosphorylate and/or increase the apical membrane accumulation of these proteins, independent of vasopressin or cAMP, one may be able to treat NDI. Sildenifil (through cGMP), erlotinib, and simvastatin each stimulate AQP2 insertion into the apical plasma membrane. Some recent human data suggest that sildenafil and simvastatin may improve urine concentrating ability. ONO-AE1-329 (ONO) stimulates the EP4 prostanoid receptor (EP4), which stimulates kinases that in turn phosphorylate AQP2 and UT-A1. Clopidogrel is a P2Y12-R antagonist that potentiates the effect of vasopressin and increases AQP2 abundance. Metformin stimulates AMPK to phosphorylate and activate AQP2 and UT-A1, and it increases urine concentrating ability in two rodent models of NDI. Since metformin, sildenafil, and simvastatin are commercially available and have excellent safety records, the potential for rapidly advancing them into clinical trials is high.
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Affiliation(s)
- Jeff M Sands
- Renal Division, Department of Medicine, and Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Janet D Klein
- Renal Division, Department of Medicine, and Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
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Wang W, Luo R, Lin Y, Wang F, Zheng P, Levi M, Yang T, Li C. Aliskiren restores renal AQP2 expression during unilateral ureteral obstruction by inhibiting the inflammasome. Am J Physiol Renal Physiol 2015; 308:F910-22. [PMID: 25694485 DOI: 10.1152/ajprenal.00649.2014] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [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: 12/09/2014] [Accepted: 02/11/2015] [Indexed: 12/17/2022] Open
Abstract
Ureteral obstruction is associated with reduced expression of renal aquaporins (AQPs), urinary concentrating defects, and an enhanced inflammatory response, in which the renin-angiotensin system (RAS) may play an important role. We evaluated whether RAS blockade by a direct renin inhibitor, aliskiren, would prevent the decreased renal protein expression of AQPs in a unilateral ureteral obstruction (UUO) model and what potential mechanisms may be involved. UUO was performed for 3 days (3UUO) and 7 days (7UUO) in C57BL/6 mice with or without aliskiren injection. In 3UUO and 7UUO mice, aliskiren abolished the reduction of AQP2 protein expression but not AQP1, AQP3, and AQP4. mRNA levels of renal AQP2 and vasopressin type 2 receptor were decreased in obstructed kidneys of 7UUO mice, which were prevented by aliskiren treatment. Aliskiren treatment was also associated with a reduced inflammatory response in obstructed kidneys of UUO mice. Aliskiren significantly decreased mRNA levels of several proinflammatory factors, such as transforming growth factor-β and tumor necrosis factor-α, seen in obstructed kidneys of UUO mice. Interestingly, mRNA and protein levels of the NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome components apoptosis-associated speck-like protein containing a caspase recruitment domain, caspase-1, and IL-1β were dramatically increased in obstructed kidneys of 7UUO mice, which were significantly suppressed by aliskiren. In primary cultured inner medullary collecting duct cells, IL-1β significantly decreased AQP2 expression. In conclusions, RAS blockade with the direct renin inhibitor aliskiren increased water channel AQP2 expression in obstructed kidneys of UUO mice, at least partially by preventing NLRP3 inflammasome activation in association with ureteral obstruction.
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Affiliation(s)
- Weidong Wang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Renfei Luo
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Yu Lin
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Feifei Wang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Peili Zheng
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Moshe Levi
- Division of Renal Diseases and Hypertension, Anschutz Medical Campus, University of Colorado, Aurora, Colorado; and
| | - Tianxin Yang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China; Department of Medicine, University of Utah, and Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Chunling Li
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China;
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25
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Fujimoto M, Okada SI, Kawashima Y, Nishimura R, Miyahara N, Kawaba Y, Hanaki K, Nanba E, Kondo Y, Igarashi T, Kanzaki S. Clinical overview of nephrogenic diabetes insipidus based on a nationwide survey in Japan. Yonago Acta Med 2014; 57:85-91. [PMID: 25324589 PMCID: PMC4198574] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 01/31/2014] [Indexed: 06/04/2023]
Abstract
BACKGROUND Nephrogenic diabetes insipidus (NDI) is a rare disease whose complications include polyuria, renal dysfunction, growth disorder and mental retardation. The details of NDI's clinical course have been unclear. To address this uncertainty, we performed a large investigation of the clinical course of NDI in Japan. METHODS Between December 2009 and March 2011, we provided a primary questionnaire to 26,282 members of the Japan Endocrine Society, the Japanese Urological Association, the Japanese Society for Pediatric Endocrinology, the Japanese Society for Pediatric Nephrology, the Japanese Society of Nephrology, the Japanese Society of Neurology and the Japanese Society of Pediatric Urology. In addition, we provided a secondary questionnaire to 121 members who reported experience with cases of NDI. We asked about patient's age at onset, diagnosis, complications, effect of treatment and patient's genotype. RESULTS We enrolled 173 patients with NDI in our study. Of these NDI patients, 143 were congenital and 30 were acquired. Of the 173, 73 patients (42%) experienced urologic complications. Among the 143 with congenital NDI, 20 patients (14%) had mental retardation. Patients with NDI mainly received thiazide diuretics, and some patients responded to treatment with desmopressin acetate (DDAVP). Gene analyses were performed in 87 patients (61%) with congenital NDI, revealing that 65 patients had an arginine vasopressin receptor type 2 (AVPR2) gene mutation and that 8 patients (9.2%) had an aquaporin 2 (AQP2) gene mutation. Patients with the AVPR2 mutation (D85N) generally showed a mild phenotype, and we found that DDAVP was generally an effective treatment for NDI among these patients. CONCLUSION We suggest that adequate diagnosis and treatment are the most important factors for improving prognoses. We further suggest that gene analysis should be performed for optimal treatment selection and the early detection of NDI among siblings.
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Affiliation(s)
- Masanobu Fujimoto
- Division of Pediatrics & Perinatology, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Shin-Ichi Okada
- Division of Pediatrics & Perinatology, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Yuki Kawashima
- Division of Pediatrics & Perinatology, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Rei Nishimura
- Division of Pediatrics & Perinatology, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Naoki Miyahara
- Division of Pediatrics & Perinatology, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Yasuo Kawaba
- Division of Pediatrics & Perinatology, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Keiichi Hanaki
- †Department of Women's and Children's Family Nursing, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
| | - Eiji Nanba
- ‡Division of Functional Genomics, Research Center for Bioscience and Technology, Tottori University, Yonago 683-8504, Japan
| | - Yoshiaki Kondo
- §Health Care Services Management, Nihon University School of Medicine, Tokyo 173-0032, Japan
| | - Takashi Igarashi
- ‖Department of Pediatrics, Graduate School of Medicine, University of Tokyo, Tokyo 113-8655, Japan
| | - Susumu Kanzaki
- Division of Pediatrics & Perinatology, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
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Abstract
We investigated the influence of sex and puberty stage on circadian urine production and levels of antidiuretic hormone [arginine vasopressin (AVP)] in healthy children. Thirty-nine volunteers (9 prepuberty boys, 10 prepuberty girls, 10 midpuberty boys, and 10 midpuberty girls) were included. All participants underwent a 24-h circadian inpatient study under standardized conditions regarding Na(+) and fluid intake. Blood samples were drawn every 4 h for measurements of plasma AVP, serum 17-β-estradiol, and testosterone, and urine was fractionally collected for measurements of electrolytes, aquaporin (AQP)2, and PGE2. We found a marked nighttime decrease in diuresis (from 1.69 ± 0.08 to 0.86 ± 0.06 ml·kg(-1)·h(-1), P < 0.001) caused by a significant nighttime increase in solute-free water reabsorption (TcH2O; day-to-night ratio: 0.64 ± 0.07, P < 0.001) concurrent with a significant decrease in osmotic excretion (day-to-night ratio: 1.23 ± 0.06, P < 0.001). Plasma AVP expressed a circadian rhythm (P < 0.01) with a nighttime increase and peak levels at midnight (0.49 ± 0.05 pg/ml). The circadian plasma AVP rhythm was not influenced by sex (P = 0.56) or puberty stage (P = 0.73). There was significantly higher nighttime TcH2O in prepuberty children. This concurred with increased nighttime urinary AQP2 excretion in prepuberty children. Urinary PGE2 exhibited a circadian rhythm independent of sex or puberty stage. Levels of serum 17β-estradiol and testosterone were as expected for sex and puberty stage, and no effect on the AVP-AQP2-TcH2O axis was observed. This study found a circadian rhythm of plasma AVP independent of sex and puberty stage, although nighttime TcH2O was higher and AQP2 excretion was more pronounced in prepuberty children, suggesting higher prepuberty renal AVP sensitivity.
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Affiliation(s)
- B Mahler
- Dept. of Pediatrics, Regionshospitalet Randers, Skovlyvej 1, Randers 8930, Denmark.
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27
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Michałek K, Laszczyńska M, Ciechanowicz AK, Herosimczyk A, Rotter I, Oganowska M, Lepczyński A, Dratwa-Chałupnik A. Immunohistochemical identification of aquaporin 2 in the kidneys of young beef cattle. Biotech Histochem 2013; 89:342-7. [PMID: 24325682 DOI: 10.3109/10520295.2013.858828] [Citation(s) in RCA: 6] [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] [Indexed: 11/13/2022] Open
Abstract
Aquaporin 2 (AQP2) is a small, integral tetrameric plasma membrane protein that is expressed in mammalian kidneys. The specific constitution of this protein and its selective permeability to water means that AQP2 plays an important role in hypertonic urine production. Immunolocalization of AQP2 has been studied in humans, monkeys, sheep, dogs, rabbits, rats, mice and adult cattle. We analyzed the expression of AQP2 in kidneys of 7-month-old Polish-Friesian var. black and white male calves. AQP2 was localized in the principal cells of collecting ducts in medullary rays penetrating the renal cortex and in the collecting ducts of renal medulla. AQP2 was expressed most strongly in the apical plasma membrane, but expression was observed also in the intracellular vesicles and basolateral plasma membrane. Our study provides new information concerning the immunolocalization of AQP2 in calf kidneys.
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Affiliation(s)
- K Michałek
- Department of Physiology, Cytobiology and Proteomics, Faculty of Biotechnology and Animal Husbandry, West Pomeranian University of Technology , Doktora Judyma Str. 6, 71-466
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Kortenoeven MLA, Sinke AP, Hadrup N, Trimpert C, Wetzels JFM, Fenton RA, Deen PMT. Demeclocycline attenuates hyponatremia by reducing aquaporin-2 expression in the renal inner medulla. Am J Physiol Renal Physiol 2013; 305:F1705-18. [PMID: 24154696 DOI: 10.1152/ajprenal.00723.2012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Binding of vasopressin to its type 2 receptor in renal collecting ducts induces cAMP signaling, transcription and translocation of aquaporin (AQP)2 water channels to the plasma membrane, and water reabsorption from the prourine. Demeclocycline is currently used to treat hyponatremia in patients with the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Demeclocycline's mechanism of action, which is poorly understood, is studied here. In mouse cortical collecting duct (mpkCCD) cells, which exhibit deamino-8-D-arginine vasopressin (dDAVP)-dependent expression of endogenous AQP2, demeclocycline decreased AQP2 abundance and gene transcription but not its protein stability. Demeclocycline did not affect vasopressin type 2 receptor localization but decreased dDAVP-induced cAMP generation and the abundance of adenylate cyclase 3 and 5/6. The addition of exogenous cAMP partially corrected the demeclocycline effect. As in patients, demeclocycline increased urine volume, decreased urine osmolality, and reverted hyponatremia in an SIADH rat model. AQP2 and adenylate cyclase 5/6 abundances were reduced in the inner medulla but increased in the cortex and outer medulla, in the absence of any sign of toxicity. In conclusion, our in vitro and in vivo data indicate that demeclocycline mainly attenuates hyponatremia in SIADH by reducing adenylate cyclase 5/6 expression and, consequently, cAMP generation, AQP2 gene transcription, and AQP2 abundance in the renal inner medulla, coinciding with a reduced vasopressin escape response in other collecting duct segments.
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Affiliation(s)
- Marleen L A Kortenoeven
- no. 286, Dept. of Physiology, Radboud Univ. Medical Centre, PO Box 9101, Nijmegen 6500 HB, The Netherlands.
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29
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Jung HJ, Kwon TH. Membrane Trafficking of Collecting Duct Water Channel Protein AQP2 Regulated by Akt/AS160. Electrolyte Blood Press 2010; 8:59-65. [PMID: 21468198 PMCID: PMC3043758 DOI: 10.5049/ebp.2010.8.2.59] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [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: 11/15/2010] [Accepted: 12/06/2010] [Indexed: 11/25/2022] Open
Abstract
Akt (protein kinase B (PKB)) is a serine/threonine kinase that acts in the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. The PI3K/Akt signaling pathway, triggered by growth factors and hormones including vasopressin, is an important pathway that is widely involved in cellular mechanisms regulating transcription, translation, cell growth and death, cell proliferation, migration, and cell cycles. In particular, Akt and Akt substrate protein of 160 kDa (AS160) are likely to participate in the trafficking of aquaporin-2 (AQP2) in the kidney collecting duct. In this study, we demonstrated that 1) small interfering RNA (siRNA)-mediated gene silencing of Akt1 significantly decreased Akt1 and phospho-AS160 protein expression; and 2) confocal laser scanning microscopy of AQP2 in mouse cortical collecting duct cells (M-1 cells) revealed AS160 knockdown by siRNA increased AQP2 expression in the plasma membrane compared with controls, despite the absence of dDAVP stimulation. Thus, the results suggest that PI3K/Akt pathways could play a role in AQP2 trafficking via the AS160 protein.
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Affiliation(s)
- Hyun Jun Jung
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Daegu, Korea
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30
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Martinerie L, Viengchareun S, Delezoïde AL, Jaubert F, Sinico M, Prevot S, Boileau P, Meduri G, Lombès M. Low renal mineralocorticoid receptor expression at birth contributes to partial aldosterone resistance in neonates. Endocrinology 2009; 150:4414-24. [PMID: 19477942 PMCID: PMC3201843 DOI: 10.1210/en.2008-1498] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The human neonatal period is characterized by renal immaturity with impaired capacity to regulate water and sodium homeostasis, resembling partial aldosterone resistance. Because aldosterone effects are mediated by the mineralocorticoid receptor (MR), we postulated that this hormonal unresponsiveness could be related to low MR expression in the distal nephron. We measured aldosterone and renin levels in umbilical cord blood of healthy newborns. We used quantitative real-time PCR and immunohistochemistry to analyze the expression of MR and key players of the mineralocorticoid signaling pathway during human and mouse renal development. High aldosterone and renin levels were found at birth. MR mRNA was detected in mouse kidney at d 16 postcoitum, peaking at d 18 postcoitum, but its expression was surprisingly very low at birth, rising progressively afterward. Similar biphasic temporal expression was observed during human renal embryogenesis, with a transient expression between 15 and 24 wk of gestation but an undetectable immunoreactive MR in late gestational and neonatal kidneys. This cyclic MR expression was tightly correlated with the evolution of the 11beta-hydroxysteroid dehydrogenase type 2 and the epithelial sodium channel alpha-subunit. In contrast, glucocorticoid and vasopressin receptors and aquaporin 2 followed a progressive and sustained evolution during renal maturation. Our study provides the first evidence for a low renal MR expression level at birth, despite high aldosterone levels, which could account for compromised postnatal sodium handling. Elucidation of regulatory mechanisms governing MR expression should lead to new strategies for the management of sodium waste in preterms and neonates.
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Affiliation(s)
- Laetitia Martinerie
- Récepteurs stéroïdiens : physiopathologie endocrinienne et métabolique
INSERM : U693IFR93Université Paris Sud - Paris XIFaculté de médecine 63, Rue Gabriel Peri 94276 LE KREMLIN BICETRE,FR
| | - Say Viengchareun
- Récepteurs stéroïdiens : physiopathologie endocrinienne et métabolique
INSERM : U693IFR93Université Paris Sud - Paris XIFaculté de médecine 63, Rue Gabriel Peri 94276 LE KREMLIN BICETRE,FR
| | - Anne-Lise Delezoïde
- Service de Biologie du Développement
Assistance publique - Hôpitaux de Paris (AP-HP)Hôpital Robert DebréUniversité Paris Diderot - Paris 775019 Paris,FR
| | - Francis Jaubert
- Service d'AnatomoPathologie
Assistance publique - Hôpitaux de Paris (AP-HP)Hôpital Necker - Enfants MaladesUniversité Paris DescartesParis 75015,FR
| | - Martine Sinico
- Service d'AnatomoPathologie
CHIC CréteilCréteil 94010,FR
| | - Sophie Prevot
- Service d'AnatomoPathologie
Assistance publique - Hôpitaux de Paris (AP-HP)Hôpital Antoine BéclèreUniversité Paris Sud - Paris XIClamart 92141,FR
| | - Pascal Boileau
- Service de Pédiatrie et Réanimations néonatales
Université Paris Sud - Paris XIAssistance publique - Hôpitaux de Paris (AP-HP)Hôpital Antoine Béclère92141 Clamart,FR
| | - Géri Meduri
- Récepteurs stéroïdiens : physiopathologie endocrinienne et métabolique
INSERM : U693IFR93Université Paris Sud - Paris XIFaculté de médecine 63, Rue Gabriel Peri 94276 LE KREMLIN BICETRE,FR
- Service de génétique moléculaire, pharmacogénétique et hormonologie
Assistance publique - Hôpitaux de Paris (AP-HP)Hôpital BicêtreUniversité Paris Sud - Paris XI78, rue du Général Leclerc 94275 Le Kremlin Bicêtre,FR
| | - Marc Lombès
- Récepteurs stéroïdiens : physiopathologie endocrinienne et métabolique
INSERM : U693IFR93Université Paris Sud - Paris XIFaculté de médecine 63, Rue Gabriel Peri 94276 LE KREMLIN BICETRE,FR
- Service d'Endocrinologie et Maladies de la reproduction
Assistance publique - Hôpitaux de Paris (AP-HP)Hôpital Bicêtre78 rue du général Leclerc, Le Kremlin Bicêtre 94275,FR
- Correspondence should be adressed to: Marc Lombès
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Abstract
Ubiquitination is known to be important for endocytosis and lysosomal degradation of aquaporin-2 (AQP2). Ubiquitin (Ub) is covalently attached to the lysine residue of the substrate proteins and activation and attachment of Ub to a target protein is mediated by the action of three enzymes (i.e., E1, E2, and E3). In particular, E3 Ub-protein ligases are known to have substrate specificity. This minireview will discuss the ubiquitination of AQP2 and identification of potential E3 Ub-protein ligases for 1-deamino-8-D-arginine vasopressin (dDAVP)-dependent AQP2 regulation.
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Affiliation(s)
- Yu-Jung Lee
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Daegu, Korea
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32
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Abstract
Vasopressin, a neurohypophyseal peptide hormone, is the endogenous agonist at V1a, V1b, and V2 receptors. The most important physiological function of vasopressin is the maintenance of water homeostasis through interaction with V2 receptors in the kidney. Vasopressin binds to V2 receptor and increases the number of aquaporin-2 at the apical plasma membrane of collecting duct principal cells. That induces high water permeability across the membrane. Several non-peptide vasopressin receptor antagonists have been developed and are being studied primarily for treating conditions characterized by hyponatremia and fluid overload. Further studies are needed to determine how they are best used in these situations.
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Affiliation(s)
- Yun Kyu Oh
- Department of Internal Medicine, Seoul National University Boramae Hospital, Seoul National University College of Medicine, Seoul, Korea
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33
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Shimizu MHM, Danilovic A, Andrade L, Volpini RA, Libório AB, Sanches TRC, Seguro AC. N-acetylcysteine protects against renal injury following bilateral ureteral obstruction. Nephrol Dial Transplant 2008; 23:3067-73. [PMID: 18469310 PMCID: PMC2542407 DOI: 10.1093/ndt/gfn237] [Citation(s) in RCA: 32] [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] [Indexed: 02/07/2023] Open
Abstract
Background. Obstructive nephropathy decreases renal blood flow (RBF) and glomerular filtration rate (GFR), causing tubular abnormalities, such as urinary concentrating defect, as well as increasing oxidative stress. This study aimed to evaluate the effects of N-acetylcysteine (NAC) on renal function, as well as on the protein expression of aquaporin 2 (AQP2) and endothelial nitric oxide synthase (eNOS), after the relief of bilateral ureteral obstruction (BUO). Methods. Adult male Wistar rats were divided into four groups: sham (sham operated); sham operated + 440 mg/kg body weight (BW) of NAC daily in drinking water, started 2 days before and maintained until 48 h after the surgery; BUO (24-h BUO only); BUO + NAC-pre (24-h BUO plus 440 mg/kg BW of NAC daily in drinking water started 2 days before BUO); and BUO + NAC-post (24-h BUO plus 440 mg/kg BW of NAC daily in drinking water started on the day of BUO relief). Experiments were conducted 48 h after BUO relief. Results. Serum levels of thiobarbituric reactive substances, which are markers of lipid peroxidation, were significantly lower in NAC-treated rats than in the BUO group rats. The administration of NAC provided significant protection against post-BUO GFR drops and reductions in RBF. Renal cortices and BUO rats presented decreased eNOS protein expression of eNOS in the renal cortex of BUO group rats, whereas it was partially recovered in BUO + NAC-pre group rats. Urine osmolality was significantly lower in BUO rats than in sham group rats or NAC-treated rats, the last also presenting less interstitial fibrosis. Post-BUO downregulation of AQP2 protein expression was averted in the BUO + NAC-pre group rats. Conclusions. This study demonstrates that NAC administration ameliorates the renal function impairment observed 48 h after the relief of 24-h BUO. Oxidative stress is important for the suppression of GFR, RBF, tissue AQP2 and eNOS in the polyuric phase after the release of BUO.
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34
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Abstract
Congenital nephrogenic diabetes insipidus (CNDI) is a rare inherited disorder characterized by insensitivity of the kidney to the antidiuretic effect of vasopressin. There are three inheritance patterns of CNDI: the X-linked recessive form associated with vasopressin V2 receptor gene mutations, and the autosomal recessive and dominant forms associated with aquaporin-2 gene (AQP2) mutations. The evaluation for polyuria and polydipsia in a one-month-old Korean girl revealed no response to vasopressin and confirmed the diagnosis of CNDI. Because the child was female without family history of CNDI, her disease was thought to be an autosomal recessive form. We analyzed the AQP2 gene and detected a compound heterozygous missense point mutation: 70Ala (GCC) to Asp (GAC) in exon 1 inherited from her father and 187Arg (CGC) to His (CAC) in exon 3 inherited from her mother. The first mutation is located within the first NPA motif of the AQP2 molecule and the second one right after the second NPA motif. This is the first report to characterize AQP2 mutations in Korean patients with autosomal recessive CNDI, and expands the spectrum of AQP2 mutations by reporting two novel mutation, 70Ala (GCC) to Asp (GAC) and 187Arg (CGC) to His (CAC).
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Affiliation(s)
- Hae Il Cheong
- Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Korea.
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35
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Abstract
BACKGROUND AND AIM Water retention is a major clinical problem in patients with liver cirrhosis. Recent research suggests that renal aquaporins may be pathophysiologically involved in this condition. The aim of the present cross sectional study of patients with liver cirrhosis was to determine if 24 hour urinary excretion of renal aquaporin 2 (AQP2) differed from that of healthy control subjects and if such excretion was related to the severity of liver disease and to the patient's water balance. RESULTS Twenty four hour urinary excretion of AQP2 and free water clearance were measured in 33 stable cirrhosis patients on usual medication and in eight healthy subjects. AQP2 excretion, quantitated by immunoblotting, was eight times higher in cirrhosis patients than in controls (0.167 (0.270) U/day v 0.021 (0.017); p<0.05). Stratification according to clinical manifestations (Child- Pugh classes) revealed that it increased with the clinical severity of cirrhosis (class A 0.04 (0.04); class B 0.09 (0.16); class C 0.31 (0.35); p<0.05) but was not related to liver function, as measured by galactose elimination capacity. Excretion correlated inversely with free water clearance (rho=-0.57, p<0.01). It was higher in patients with oesophagogastric varices but not in those with ascites. Plasma vasopressin concentrations were not related to AQP2 excretion and there was no relation to dose or type of diuretic treatment. CONCLUSIONS Urinary AQP2 excretion was increased in patients with cirrhosis. Moreover, urinary AQP2 excretion increased with severity of cirrhosis in parallel with impairment of free water clearance. This suggests a functional association between increased AQP2 excretion and increased renal reabsorption of water in cirrhosis.
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Affiliation(s)
- P Ivarsen
- Department of Medicine V, Aarhus University Hospital, Denmark.
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