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Hao S, Zhao H, Hao DH, Ferreri NR. MicroRNA-195a-5p Regulates Blood Pressure by Inhibiting NKCC2A. Hypertension 2023; 80:426-439. [PMID: 36448465 PMCID: PMC9852070 DOI: 10.1161/hypertensionaha.122.19794] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 11/15/2022] [Indexed: 12/05/2022]
Abstract
BACKGROUND Previous studies showed that miR-195a-5p was among the most abundant microRNAs (miRNAs) expressed in the kidney. METHODS Lentivirus silencing of tumor necrosis factor-α (TNF) was performed in vivo and in vitro. Luciferase reporter assays confirmed that bumetanide-sensitive Na+-K+-2Cl- cotransporter isoform A (NKCC2A) mRNA is targeted and repressed by miR-195a-5p. Radiotelemetry was used to measure mean arterial pressure. RESULTS TNF upregulates mmu-miR-195a-5p, and -203 and downregulates mmu-miR-30c and -100 in the medullary thick ascending limb of male mice. miR-195a-5p was >3-fold higher in the renal outer medulla of mice given an intrarenal injection of murine recombinant TNF, whereas silencing TNF inhibited miR-195a-5p expression by ≈51%. Transient transfection of a miR-195a-5p mimic into medullary thick ascending limb cells suppressed NKCC2A mRNA by ≈83%, whereas transfection with Anti-miR-195a-5p increased NKCC2A mRNA. Silencing TNF in medullary thick ascending limb cells prevented increases in miR-195 induced by 400 mosmol/kg H2O medium, an effect reversed by transfection with a miR-195a-5p mimic. Expression of phosphorylated NKCC2 increased 1.5-fold in medullary thick ascending limb cells transfected with Anti-miR-195a-5p and a miR-195a-5p mimic prevented the increase, which was induced by silencing TNF in cells exposed to 400 mosmol/kg H2O medium after osmolality was increased by adding NaCl. Intrarenal injection of TNF suppressed NKCC2A mRNA, whereas injection of miR-195a-5p prevented the increase of NKCC2A mRNA abundance and phosphorylated NKCC2 expression when TNF was silenced. Intrarenal injection with miR-195a-5p markedly attenuated MAP after renal silencing of TNF in mice given 1% NaCl. CONCLUSIONS The study identifies miR-195a-5p as a salt-sensitive and TNF-inducible miRNA that attenuates NaCl-mediated increases in blood pressure by inhibiting NKCC2A.
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Affiliation(s)
- Shoujin Hao
- Department of Pharmacology, New York Medical College, Valhalla
| | - Hong Zhao
- Department of Pharmacology, New York Medical College, Valhalla
| | - David H Hao
- Department of Pharmacology, New York Medical College, Valhalla
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2
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Abstract
The kidney maintains electrolyte, water, and acid-base balance, eliminates foreign and waste compounds, regulates blood pressure, and secretes hormones. There are at least 16 different highly specialized epithelial cell types in the mammalian kidney. The number of specialized endothelial cells, immune cells, and interstitial cell types might even be larger. The concerted interplay between different cell types is critical for kidney function. Traditionally, cells were defined by their function or microscopical morphological appearance. With the advent of new single-cell modalities such as transcriptomics, epigenetics, metabolomics, and proteomics we are entering into a new era of cell type definition. This new technological revolution provides new opportunities to classify cells in the kidney and understand their functions.
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Affiliation(s)
- Michael S Balzer
- Department of Medicine, Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
- Institute of Diabetes Obesity and Metabolism, University of Pennsylvania, Philadelphia, Philadelphia, USA
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Katalin Susztak
- Department of Medicine, Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
- Institute of Diabetes Obesity and Metabolism, University of Pennsylvania, Philadelphia, Philadelphia, USA
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3
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Boder P, Mary S, Mark PB, Leiper J, Dominiczak AF, Padmanabhan S, Rampoldi L, Delles C. Mechanistic interactions of uromodulin with the thick ascending limb: perspectives in physiology and hypertension. J Hypertens 2021; 39:1490-1504. [PMID: 34187999 PMCID: PMC7611110 DOI: 10.1097/hjh.0000000000002861] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hypertension is a significant risk factor for cardiovascular disease and mortality worldwide. The kidney is a major regulator of blood pressure and electrolyte homeostasis, with monogenic disorders indicating a link between abnormal ion transport and salt-sensitive hypertension. However, the association between salt and hypertension remains controversial. Thus, there is continued interest in deciphering the molecular mechanisms behind these processes. Uromodulin (UMOD) is the most abundant protein in the normal urine and is primarily synthesized by the thick ascending limb epithelial cells of the kidney. Genome-wide association studies have linked common UMOD variants with kidney function, susceptibility to chronic kidney disease and hypertension independent of renal excretory function. This review will discuss and provide predictions on the role of the UMOD protein in renal ion transport and hypertension based on current observational, biochemical, genetic, pharmacological and clinical evidence.
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Affiliation(s)
- Philipp Boder
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Sheon Mary
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Patrick B. Mark
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - James Leiper
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Anna F. Dominiczak
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Sandosh Padmanabhan
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Luca Rampoldi
- Molecular Genetics of Renal Disorders Unit, Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Christian Delles
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
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4
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Marcoux A, Tremblay LE, Slimani S, Fiola M, Mac‐Way F, Garneau AP, Isenring P. Molecular characteristics and physiological roles of Na + -K + -Cl - cotransporter 2. J Cell Physiol 2021; 236:1712-1729. [PMID: 32776569 PMCID: PMC7818487 DOI: 10.1002/jcp.29997] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 06/28/2020] [Accepted: 07/24/2020] [Indexed: 12/23/2022]
Abstract
Na+ -K+ -Cl- cotransporter 2 (NKCC2; SLC12A1) is an integral membrane protein that comes as three splice variants and mediates the cotranslocation of Na+ , K+ , and Cl- ions through the apical membrane of the thick ascending loop of Henle (TALH). In doing so, and through the involvement of other ion transport systems, it allows this nephron segment to reclaim a large fraction of the ultrafiltered Na+ , Cl- , Ca2+ , Mg2+ , and HCO3- loads. The functional relevance of NKCC2 in human is illustrated by the many abnormalities that result from the inactivation of this transport system through the use of loop diuretics or in the setting of inherited disorders. The following presentation aims at discussing the physiological roles and molecular characteristics of Na+ -K+ -Cl- cotransport in the TALH and those of the individual NKCC2 splice variants more specifically. Many of the historical and recent data that have emerged from the experiments conducted will be outlined and their larger meaning will also be placed into perspective with the aid of various hypotheses.
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Affiliation(s)
- Andree‐Anne Marcoux
- Department of Medicine, Nephrology Research GroupLaval UniversityQuebec CityQuébecCanada
| | - Laurence E. Tremblay
- Department of Medicine, Nephrology Research GroupLaval UniversityQuebec CityQuébecCanada
| | - Samira Slimani
- Department of Medicine, Nephrology Research GroupLaval UniversityQuebec CityQuébecCanada
| | - Marie‐Jeanne Fiola
- Department of Medicine, Nephrology Research GroupLaval UniversityQuebec CityQuébecCanada
| | - Fabrice Mac‐Way
- Department of Medicine, Nephrology Research GroupLaval UniversityQuebec CityQuébecCanada
| | - Alexandre P. Garneau
- Department of Medicine, Nephrology Research GroupLaval UniversityQuebec CityQuébecCanada
- Cardiometabolic Axis, School of Kinesiology and Physical Activity SciencesUniversity of MontréalMontréalQuebecCanada
| | - Paul Isenring
- Department of Medicine, Nephrology Research GroupLaval UniversityQuebec CityQuébecCanada
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5
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Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2. Int J Mol Sci 2021. [PMID: 33672238 DOI: 10.3390/ijms22042207.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Mutations in the Na-K-2Cl co-transporter NKCC2 lead to type I Bartter syndrome, a life-threatening kidney disease. We previously showed that export from the ER constitutes the limiting step in NKCC2 maturation and cell surface expression. Yet, the molecular mechanisms involved in this process remain obscure. Here, we report the identification of chaperone stress 70 protein (STCH) and the stress-inducible heat shock protein 70 (Hsp70), as two novel binding partners of the ER-resident form of NKCC2. STCH knock-down increased total NKCC2 expression whereas Hsp70 knock-down or its inhibition by YM-01 had the opposite effect. Accordingly, overexpressing of STCH and Hsp70 exerted opposite actions on total protein abundance of NKCC2 and its folding mutants. Cycloheximide chase assay showed that in cells over-expressing STCH, NKCC2 stability and maturation are heavily impaired. In contrast to STCH, Hsp70 co-expression increased NKCC2 maturation. Interestingly, treatment by protein degradation inhibitors revealed that in addition to the proteasome, the ER associated degradation (ERAD) of NKCC2 mediated by STCH, involves also the ER-to-lysosome-associated degradation pathway. In summary, our data are consistent with STCH and Hsp70 having differential and antagonistic effects with regard to NKCC2 biogenesis. These findings may have an impact on our understanding and potential treatment of diseases related to aberrant NKCC2 trafficking and expression.
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6
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Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2. Int J Mol Sci 2021; 22:ijms22042207. [PMID: 33672238 PMCID: PMC7926544 DOI: 10.3390/ijms22042207] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 02/13/2021] [Accepted: 02/20/2021] [Indexed: 12/16/2022] Open
Abstract
Mutations in the Na-K-2Cl co-transporter NKCC2 lead to type I Bartter syndrome, a life-threatening kidney disease. We previously showed that export from the ER constitutes the limiting step in NKCC2 maturation and cell surface expression. Yet, the molecular mechanisms involved in this process remain obscure. Here, we report the identification of chaperone stress 70 protein (STCH) and the stress-inducible heat shock protein 70 (Hsp70), as two novel binding partners of the ER-resident form of NKCC2. STCH knock-down increased total NKCC2 expression whereas Hsp70 knock-down or its inhibition by YM-01 had the opposite effect. Accordingly, overexpressing of STCH and Hsp70 exerted opposite actions on total protein abundance of NKCC2 and its folding mutants. Cycloheximide chase assay showed that in cells over-expressing STCH, NKCC2 stability and maturation are heavily impaired. In contrast to STCH, Hsp70 co-expression increased NKCC2 maturation. Interestingly, treatment by protein degradation inhibitors revealed that in addition to the proteasome, the ER associated degradation (ERAD) of NKCC2 mediated by STCH, involves also the ER-to-lysosome-associated degradation pathway. In summary, our data are consistent with STCH and Hsp70 having differential and antagonistic effects with regard to NKCC2 biogenesis. These findings may have an impact on our understanding and potential treatment of diseases related to aberrant NKCC2 trafficking and expression.
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7
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Garneau AP, Slimani S, Fiola MJ, Tremblay LE, Isenring P. Multiple Facets and Roles of Na+-K+-Cl−Cotransport: Mechanisms and Therapeutic Implications. Physiology (Bethesda) 2020; 35:415-429. [DOI: 10.1152/physiol.00012.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The Na+-K+-Cl−cotransporters play key physiological and pathophysiological roles by regulating the membrane potential of many cell types and the movement of fluid across a variety of epithelial or endothelial structures. As such, they should soon become invaluable targets for the treatment of various disorders including pain, epilepsy, brain edema, and hypertension. This review highlights the nature of these roles, the mechanisms at play, and the unresolved issues in the field.
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Affiliation(s)
- A. P. Garneau
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Canada; and
- Cardiometabolic Axis, School of Kinesiology and Physical Activity Sciences, University of Montréal, Montréal, Canada
| | - S. Slimani
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Canada; and
| | - M. J. Fiola
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Canada; and
| | - L. E. Tremblay
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Canada; and
| | - P. Isenring
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Canada; and
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8
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Abstract
PURPOSE OF REVIEW The apical Na/K/2Cl cotransporter (NKCC2) mediates NaCl reabsorption by the thick ascending limb, contributing to maintenance of blood pressure (BP). Despite effective NKCC2 inhibition by loop diuretics, these agents are not viable for long-term management of BP due to side effects. Novel molecular mechanisms that control NKCC2 activity reveal an increasingly complex picture with interacting layers of NKCC2 regulation. Here, we review the latest developments that shine new light on NKCC2-mediated control of BP and potential new long-term therapies to treat hypertension. RECENT FINDINGS Emerging molecular NKCC2 regulators, often binding partners, reveal a complex overlay of interacting mechanisms aimed at fine tuning NKCC2 activity. Different factors achieve this by shifting the balance between trafficking steps like exocytosis, endocytosis, recycling and protein turnover, or by balancing phosphorylation vs. dephosphorylation. Further molecular details are also emerging on previously known pathways of NKCC2 regulation, and recent in-vivo data continues to place NKCC2 regulation at the center of BP control. SUMMARY Several layers of emerging molecular mechanisms that control NKCC2 activity may operate simultaneously, but they can also be controlled independently. This provides an opportunity to identify new pharmacological targets to fine-tune NKCC2 activity for BP management.
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9
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Natochin YV, Golosova DV. Vasopressin receptor subtypes and renal sodium transport. VITAMINS AND HORMONES 2019; 113:239-258. [PMID: 32138950 DOI: 10.1016/bs.vh.2019.08.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In mammals, three subtypes of V-receptors have been identified in the kidney. The effects of vasopressin, a hormone synthesized in the hypothalamus, are triggered by three distinct receptor isoforms: V2, V1a, and V1b. Stimulation of V2-receptors regulates urine osmotic concentration by increasing sodium reabsorption in the thick ascending limb of the loop of Henle and enhancing osmotic permeability of the epithelium cells in the collecting duct. Stimulation of V1a-receptors inhibits renal sodium reabsorption and induces natriuresis, comparable to the effect of the diuretic furosemide, in the thick ascending limb of the loop of Henle. Stimulation of V1b-receptors induces potassium secretion in the final parts of the distal segments and initial parts of the collecting ducts. In this review, we discuss the role of vasopressin and its interaction with V-receptor subtypes in natriuresis and for stabilizing the physicochemical parameters of the internal environment and water-salt homeostasis in humans. A better understanding of these systems and their regulation is necessary to facilitate identification of additional system components and mechanisms, clarify their contribution during various normal and pathological functional states, and suggest novel strategies for the development of therapeutic interventions.
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Affiliation(s)
- Yu V Natochin
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia.
| | - D V Golosova
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
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10
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Francipane MG, Han B, Oxburgh L, Sims-Lucas S, Li Z, Lagasse E. Kidney-in-a-lymph node: A novel organogenesis assay to model human renal development and test nephron progenitor cell fates. J Tissue Eng Regen Med 2019; 13:1724-1731. [PMID: 31267702 DOI: 10.1002/term.2924] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 04/18/2019] [Accepted: 06/30/2019] [Indexed: 12/12/2022]
Abstract
Stem cell-derived organoids are emerging as sophisticated models for studying development and disease and as potential sources for developing organ substitutes. Unfortunately, although organoids containing renal structures have been generated from mouse and human pluripotent stem cells, there are still critical unanswered questions that are difficult to attain via in vitro systems, including whether these nonvascularized organoids have a stable and physiologically relevant phenotype or whether a suitable transplantation site for long-term in vivo studies can be identified. Even orthotopic engraftment of organoid cultures in the adult does not provide an environment conducive to vascularization and functional differentiation. Previously, we showed that the lymph node offers an alternative transplantation site where mouse metanephroi can differentiate into mature renal structures with excretory, homeostatic, and endocrine functions. Here, we show that the lymph node lends itself well as a niche to also grow human primary kidney rudiments and can additionally be viewed as a platform to interrogate emerging renal organoid cultures. Our study has a wide-ranging impact for tissue engineering approaches to rebuild functional tissues in vivo including-but not limited to-the kidney.
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Affiliation(s)
- Maria Giovanna Francipane
- McGowan Institute for Regenerative Medicine and Pathology Department, University of Pittsburgh, Pittsburgh, Pennsylvania.,Ri.MED Foundation, Palermo, Italy
| | - Bing Han
- McGowan Institute for Regenerative Medicine and Pathology Department, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Leif Oxburgh
- Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, Maine
| | - Sunder Sims-Lucas
- Rangos Research Center, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania
| | - Zhongwei Li
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Eric Lagasse
- McGowan Institute for Regenerative Medicine and Pathology Department, University of Pittsburgh, Pittsburgh, Pennsylvania
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11
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Marcoux AA, Slimani S, Tremblay LE, Frenette-Cotton R, Garneau AP, Isenring P. Regulation of Na +-K +-Cl - cotransporter type 2 by the with no lysine kinase-dependent signaling pathway. Am J Physiol Cell Physiol 2019; 317:C20-C30. [PMID: 30917032 DOI: 10.1152/ajpcell.00041.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Na+-K+-Cl- cotransporter type 2 (NKCC2) is confined to the apical membrane of the thick ascending limb of Henle, where it reabsorbs a substantial fraction of the ultrafiltered NaCl load. It is expressed along this nephron segment as three main splice variants (called NKCC2A, NKCC2B, and NKCC2F) that differ in residue composition along their second transmembrane domain and first intracellular cytosolic connecting segment (CS2). NKCC2 is known to be activated by cell shrinkage and intracellular [Cl-] reduction. Although the with no lysine (WNK) kinases could play a role in this response, the mechanisms involved are ill defined, and the possibility of variant-specific responses has not been tested thus far. In this study, we have used the Xenopus laevis oocyte expression system to gain further insight in these regards. We have found for the first time that cell shrinkage could stimulate NKCC2A- and NKCC2B-mediated ion transport by increasing carrier abundance at the cell surface and that this response was achieved (at least in part) by the enzymatic function of a WNK kinase. Interestingly, we have also found that the activity and cell surface abundance of NKCC2F were less affected by cell shrinkage compared with the other variants and that ion transport by certain variants could be stimulated through WNK kinase expression in the absence of carrier redistribution. Taken together, these results suggest that the WNK kinase-dependent pathway can affect both the trafficking as well as intrinsic activity of NKCC2 and that CS2 plays an important role in carrier regulation.
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Affiliation(s)
- Andrée-Anne Marcoux
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Samira Slimani
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Laurence E Tremblay
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Rachelle Frenette-Cotton
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
| | - Alexandre P Garneau
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada.,Cardiometabolic Research Group, Department of Kinesiology, Faculty of Medicine, University of Montreal , Montreal, Quebec , Canada
| | - Paul Isenring
- Nephrology Research Group, L'Hôtel-Dieu de Québec Research Center, Department of Medicine, Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
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Gonzalez-Vicente A, Saez F, Monzon CM, Asirwatham J, Garvin JL. Thick Ascending Limb Sodium Transport in the Pathogenesis of Hypertension. Physiol Rev 2019; 99:235-309. [PMID: 30354966 DOI: 10.1152/physrev.00055.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The thick ascending limb plays a key role in maintaining water and electrolyte balance. The importance of this segment in regulating blood pressure is evidenced by the effect of loop diuretics or local genetic defects on this parameter. Hormones and factors produced by thick ascending limbs have both autocrine and paracrine effects, which can extend prohypertensive signaling to other structures of the nephron. In this review, we discuss the role of the thick ascending limb in the development of hypertension, not as a sole participant, but one that works within the rich biological context of the renal medulla. We first provide an overview of the basic physiology of the segment and the anatomical considerations necessary to understand its relationship with other renal structures. We explore the physiopathological changes in thick ascending limbs occurring in both genetic and induced animal models of hypertension. We then discuss the racial differences and genetic defects that affect blood pressure in humans through changes in thick ascending limb transport rates. Throughout the text, we scrutinize methodologies and discuss the limitations of research techniques that, when overlooked, can lead investigators to make erroneous conclusions. Thus, in addition to advancing an understanding of the basic mechanisms of physiology, the ultimate goal of this work is to understand our research tools, to make better use of them, and to contextualize research data. Future advances in renal hypertension research will require not only collection of new experimental data, but also integration of our current knowledge.
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Affiliation(s)
| | - Fara Saez
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Casandra M Monzon
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jessica Asirwatham
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jeffrey L Garvin
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
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13
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Ares GR, Kassem KM, Ortiz PA. Fructose acutely stimulates NKCC2 activity in rat thick ascending limbs by increasing surface NKCC2 expression. Am J Physiol Renal Physiol 2018; 316:F550-F557. [PMID: 30516424 DOI: 10.1152/ajprenal.00136.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The thick ascending limb (TAL) reabsorbs 25% of the filtered NaCl through the Na+-K+-2Cl- cotransporter (NKCC2). NKCC2 activity is directly related to surface NKCC2 expression and phosphorylation. Higher NaCl reabsorption by TALs is linked to salt-sensitive hypertension, which is linked to consumption of fructose in the diet. However, little is known about the effects of fructose on renal NaCl reabsorption. We hypothesized that fructose, but not glucose, acutely enhances TAL-dependent NaCl reabsorption by increasing NKCC2 activity via stimulation of surface NKCC2 levels and phosphorylation at Thr96/101. We found that fructose (5 mM) increased transport-related O2 consumption in TALs by 11.1 ± 3.2% ( P < 0.05). The effect of fructose on O2 consumption was blocked by furosemide. To study the effect of fructose on NKCC2 activity, we measured the initial rate of NKCC2-dependent thallium influx. We found that 20 min of treatment with fructose (5 mM) increased NKCC2 activity by 58.5 ± 16.9% ( P < 0.05). We then used surface biotinylation to measure surface NKCC2 levels in rat TALs. Fructose increased surface NKCC2 expression in a concentration-dependent manner (22 ± 5, 49 ± 10, and 101 ± 59% of baseline with 1, 5, and 10 mM fructose, respectively, P < 0.05), whereas glucose or a glucose metabolite did not. Fructose did not change NKCC2 phosphorylation at Thre96/101 or total NKCC2 expression. We concluded that acute fructose treatment increases NKCC2 activity by enhancing surface NKCC2 expression, rather than NKCC2 phosphorylation. Our data suggest that fructose consumption could contribute to salt-sensitive hypertension by stimulating NKCC2-dependent NaCl reabsorption in TALs.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Kamal M Kassem
- Department of Internal Medicine, University of Cincinnati Medical Center , Cincinnati, Ohio
| | - Pablo A Ortiz
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan.,Department of Physiology, Wayne State University , Detroit, Michigan
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14
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Stanevičiūtė J, Juknevičienė M, Palubinskienė J, Balnytė I, Valančiūtė A, Vosyliūtė R, Sužiedėlis K, Lesauskaitė V, Stakišaitis D. Sodium Dichloroacetate Pharmacological Effect as Related to Na-K-2Cl Cotransporter Inhibition in Rats. Dose Response 2018; 16:1559325818811522. [PMID: 30479587 PMCID: PMC6247491 DOI: 10.1177/1559325818811522] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 09/06/2018] [Accepted: 10/09/2018] [Indexed: 01/19/2023] Open
Abstract
The study objective was to investigate a possible sodium dichloroacetate (DCA) pharmacological mechanism causing an increase in diuresis in rats. The aim was to define characteristics of 24-hour urinary Na+, K+, Cl-, Ca2+, and Mg2+ excretion in Wistar male rats and to evaluate effect of a single-dose DCA and repeated DCA dosage on diuresis. Six control and 6 DCA-treated male rats aged 5 to weeks after a single DCA dose and repeated dosage were tested. The single DCA dose treatment caused a significantly higher 24-hour diuresis when compared to control (P < .05), and it was related to increased Cl-, Na+, and K+ urine excretion and a significant increase in Ca2+ and Mg2+ excretion (P < .05); after the repeated 4-week DCA dosage, the diuresis was not increased, but the excretion of the Na+, Cl-, Ca2+, and Mg2+ ions was significantly higher. Kidney immunohistochemistry has revealed that DCA continuous treatment results in an increase in the size of Henle loop thick ascending limb epithelial cells (P < .001). The study results show a significantly reduced RNA expression of Na-K-2Cl co-transporter (NKCC1) in thymus of 4-week DCA-treated rats (P < .03). The study data have indicated a possible mechanism of such pharmacological effect to be NKCC inhibition.
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Affiliation(s)
- Jūratė Stanevičiūtė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Milda Juknevičienė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Jolita Palubinskienė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Ingrida Balnytė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Angelija Valančiūtė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Rūta Vosyliūtė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Kęstutis Sužiedėlis
- Laboratory of Molecular Oncology, National Cancer Institute, Vilnius, Lithuania
| | - Vaiva Lesauskaitė
- Institute of Cardiology of Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Donatas Stakišaitis
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania.,Laboratory of Molecular Oncology, National Cancer Institute, Vilnius, Lithuania
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15
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Nawata CM, Pannabecker TL. Mammalian urine concentration: a review of renal medullary architecture and membrane transporters. J Comp Physiol B 2018; 188:899-918. [PMID: 29797052 PMCID: PMC6186196 DOI: 10.1007/s00360-018-1164-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 04/23/2018] [Accepted: 05/14/2018] [Indexed: 01/10/2023]
Abstract
Mammalian kidneys play an essential role in balancing internal water and salt concentrations. When water needs to be conserved, the renal medulla produces concentrated urine. Central to this process of urine concentration is an osmotic gradient that increases from the corticomedullary boundary to the inner medullary tip. How this gradient is generated and maintained has been the subject of study since the 1940s. While it is generally accepted that the outer medulla contributes to the gradient by means of an active process involving countercurrent multiplication, the source of the gradient in the inner medulla is unclear. The last two decades have witnessed advances in our understanding of the urine-concentrating mechanism. Details of medullary architecture and permeability properties of the tubules and vessels suggest that the functional and anatomic relationships of these structures may contribute to the osmotic gradient necessary to concentrate urine. Additionally, we are learning more about the membrane transporters involved and their regulatory mechanisms. The role of medullary architecture and membrane transporters in the mammalian urine-concentrating mechanism are the focus of this review.
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Affiliation(s)
- C Michele Nawata
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA.
| | - Thomas L Pannabecker
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA
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16
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Wang F, Liu Q, Jin L, Hu S, Luo R, Han M, Zhai Y, Wang W, Li C. Combination exposure of melamine and cyanuric acid is associated with polyuria and activation of NLRP3 inflammasome in rats. Am J Physiol Renal Physiol 2018; 315:F199-F210. [DOI: 10.1152/ajprenal.00609.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The molecular mechanisms of melamine-induced renal toxicity have not been fully understood. The purpose of the study aimed to investigate whether melamine and cyanuric acid induced NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation in the kidney, which may contribute to abnormal water and sodium handling in a rat model. Wistar rats received melamine (Mel; 200 mg·kg body wt−1·day−1), cyanuric acid (CA; 200 mg·kg body wt−1·day−1), or Mel plus CA (Mel + CA; 100 mg·kg body wt−1·day−1, each) for 2 wk. Mel + CA caused damaged tubular epithelial structure and organelles, dilated tubular lumen, and inflammatory responses. Crystals were observed in urine and serum specimen, also in the lumen of dilated distal renal tubules. The combined ingestion of Mel and CA in rats caused a markedly impaired urinary concentration, which was associated with reduced protein expression of aquaporin (AQP)1, 2, and 3 in inner medulla and α-Na-K-ATPase and Na-K-2Cl transporters in cortex and outer medulla. Mel + CA treatment was associated with increased protein expression of CD3 and mRNA levels of CD68 and F4/80 as well as phosphorylation of NF-κB in the kidney. Mel + CA treatment increased protein and mRNA expression of NLRP3 inflammasome components apoptosis-associated speck-like protein containing a caspase recruitment domain, caspase-1, and IL-1β in the inner medulla of rats. NF-κB inhibitor Bay 11-7082 reduced IL-1β expression induced by Mel + CA and prevented downregulation of AQP2 in inner medullary collecting duct cell suspensions. In conclusion, Mel + CA treatment caused urinary-concentrating defects and reduced expression of renal AQPs and key sodium transporters, which is likely due to the inflammatory responses and activation of NLRP3 inflammasome induced by crystals formed in the kidney.
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Affiliation(s)
- Feifei Wang
- 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
| | - Lizi Jin
- Department of Cardiology, The 5th Affiliated Hospital, Sun Yat-sen University, Zhuhai, China
| | - Shan Hu
- 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
| | - Mengke Han
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Yonggong Zhai
- Life Sciences College, Beijing Normal University, Beijing, People’s Republic of China
| | - Weidong Wang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Chunling Li
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
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17
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Tingskov SJ, Kwon TH, Frøkiær J, Nørregaard R. Tamoxifen Decreases Lithium-Induced Natriuresis in Rats With Nephrogenic Diabetes Insipidus. Front Physiol 2018; 9:903. [PMID: 30050465 PMCID: PMC6052323 DOI: 10.3389/fphys.2018.00903] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 06/21/2018] [Indexed: 11/13/2022] Open
Abstract
Lithium is widely used in the treatment of bipolar affective disorders, but often causes nephrogenic diabetes insipidus (NDI), a condition characterized by a severe urinary concentrating defect. Lithium-induced NDI is associated with dysregulation of the amiloride-sensitive epithelial sodium channel (ENaC), which is essential for renal sodium reabsorption. Sex hormones have been shown to affect the expression of aquaporin-2 (AQP2) and sodium transporters. Therefore, we evaluated whether tamoxifen (TAM), a selective estrogen receptor modulator (SERM), would affect lithium-induced dysregulation of ENaC subunits and natriuresis. Rats were fed with lithium-containing food for 2 weeks to induce NDI and natriuresis. TAM was administered daily via gastric gavage after 1 week of lithium administration. Lithium treatment alone resulted in increased urinary sodium excretion and significant reduction of βENaC and γENaC at both RNA and protein levels. In addition, the plasma sodium level reduced after lithium treatment. Administration of TAM prevented increased urinary sodium excretion as well as attenuated the downregulation of βENaC and γENaC. Consistent with these findings, immunohistochemistry (IHC) showed stronger labeling of βENaC and γENaC subunits in the apical domain of the collecting duct cells in the cortical tissue of lithium-fed rats treated with TAM. Other major sodium transporters including NaPi-2, NKCC2, Na/K-ATPase, and NHE3, are believed not to have an effect on the increased urinary sodium excretion since their expression increased or was unchanged after treatment with lithium. In conclusion, the results demonstrated that TAM rescued the adverse effects of the lithium-induced increase in fractional excretion of sodium after the establishment of lithium-induced NDI.
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Affiliation(s)
| | - Tae-Hwan Kwon
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Daegu, South Korea
| | - Jørgen Frøkiær
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Rikke Nørregaard
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
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18
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Zacchia M, Capolongo G, Rinaldi L, Capasso G. The importance of the thick ascending limb of Henle's loop in renal physiology and pathophysiology. Int J Nephrol Renovasc Dis 2018; 11:81-92. [PMID: 29497325 PMCID: PMC5818843 DOI: 10.2147/ijnrd.s154000] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The thick ascending limb (TAL) of Henle’s loop is a crucial segment for many tasks of the nephron. Indeed, the TAL is not only a mainstay for reabsorption of sodium (Na+), potassium (K+), and divalent cations such as calcium (Ca2+) and magnesium (Mg2+) from the luminal fluid, but also has an important role in urine concentration, overall acid–base homeostasis, and ammonia cycle. Transcellular Na+ transport along the TAL is a prerequisite for Na+, K+, Ca2+, Mg2+ homeostasis, and water reabsorption, the latter through its contribution in the generation of the cortico-medullar osmotic gradient. The role of this nephron site in acid–base balance, via bicarbonate reabsorption and acid secretion, is sometimes misunderstood by clinicians. This review describes in detail these functions, reporting in addition to the well-known molecular mechanisms, some novel findings from the current literature; moreover, the pathophysiology and the clinical relevance of primary or acquired conditions caused by TAL dysfunction are discussed. Knowing the physiology of the TAL is fundamental for clinicians, for a better understanding and management of rare and common conditions, such as tubulopathies, hypertension, and loop diuretics abuse.
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Affiliation(s)
- Miriam Zacchia
- Division of Nephrology, Department of Cardio-Thoracic and Respiratory Sciences, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Giovanna Capolongo
- Division of Nephrology, Department of Cardio-Thoracic and Respiratory Sciences, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Luca Rinaldi
- Division of Nephrology, Department of Cardio-Thoracic and Respiratory Sciences, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Giovambattista Capasso
- Division of Nephrology, Department of Cardio-Thoracic and Respiratory Sciences, Università della Campania "Luigi Vanvitelli", Naples, Italy
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19
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Singh R, Kursan S, Almiahoub MY, Almutairi MM, Garzón-Muvdi T, Alvarez-Leefmans FJ, Di Fulvio M. Plasma Membrane Targeting of Endogenous NKCC2 in COS7 Cells Bypasses Functional Golgi Cisternae and Complex N-Glycosylation. Front Cell Dev Biol 2017; 4:150. [PMID: 28101499 PMCID: PMC5209364 DOI: 10.3389/fcell.2016.00150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 12/14/2016] [Indexed: 12/04/2022] Open
Abstract
Na+K+2Cl− co-transporters (NKCCs) effect the electroneutral movement of Na+-K+ and 2Cl− ions across the plasma membrane of vertebrate cells. There are two known NKCC isoforms, NKCC1 (Slc12a2) and NKCC2 (Slc12a1). NKCC1 is a ubiquitously expressed transporter involved in cell volume regulation, Cl− homeostasis and epithelial salt secretion, whereas NKCC2 is abundantly expressed in kidney epithelial cells of the thick ascending loop of Henle, where it plays key roles in NaCl reabsorption and electrolyte homeostasis. Although NKCC1 and NKCC2 co-transport the same ions with identical stoichiometry, NKCC1 actively co-transports water whereas NKCC2 does not. There is growing evidence showing that NKCC2 is expressed outside the kidney, but its function in extra-renal tissues remains unknown. The present study shows molecular and functional evidence of endogenous NKCC2 expression in COS7 cells, a widely used mammalian cell model. Endogenous NKCC2 is primarily found in recycling endosomes, Golgi cisternae, Golgi-derived vesicles, and to a lesser extent in the endoplasmic reticulum. Unlike NKCC1, NKCC2 is minimally hybrid/complex N-glycosylated under basal conditions and yet it is trafficked to the plasma membrane region of hyper-osmotically challenged cells through mechanisms that require minimal complex N-glycosylation or functional Golgi cisternae. Control COS7 cells exposed to slightly hyperosmotic (~6.7%) solutions for 16 h were not shrunken, suggesting that either one or both NKCC1 and NKCC2 may participate in cell volume recovery. However, NKCC2 targeted to the plasma membrane region or transient over-expression of NKCC2 failed to rescue NKCC1 in COS7 cells where NKCC1 had been silenced. Further, COS7 cells in which NKCC1, but not NKCC2, was silenced exhibited reduced cell size compared to control cells. Altogether, these results suggest that NKCC2 does not participate in cell volume recovery and therefore, NKCC1 and NKCC2 are functionally different Na+K+2Cl− co-transporters.
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Affiliation(s)
- Richa Singh
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Shams Kursan
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Mohamed Y Almiahoub
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Mohammed M Almutairi
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Tomás Garzón-Muvdi
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Francisco J Alvarez-Leefmans
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
| | - Mauricio Di Fulvio
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University Dayton, OH, USA
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20
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Caceres PS, Mendez M, Haque MZ, Ortiz PA. Vesicle-associated Membrane Protein 3 (VAMP3) Mediates Constitutive Trafficking of the Renal Co-transporter NKCC2 in Thick Ascending Limbs: ROLE IN RENAL FUNCTION AND BLOOD PRESSURE. J Biol Chem 2016; 291:22063-22073. [PMID: 27551042 PMCID: PMC5063989 DOI: 10.1074/jbc.m116.735167] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Indexed: 02/04/2023] Open
Abstract
Renal cells of the thick ascending limb (TAL) reabsorb NaCl via the apical Na+/K+/2Cl- co-transporter NKCC2. Trafficking of NKCC2 to the apical surface regulates NKCC2-mediated NaCl absorption and blood pressure. The molecular mechanisms by which NKCC2 reaches the apical surface and their role in renal function and maintenance of blood pressure are poorly characterized. Here we report that NKCC2 interacts with the vesicle fusion protein VAMP3, and they co-localize at the TAL apical surface. We observed that silencing VAMP3 in vivo blocks constitutive NKCC2 exocytic delivery, decreasing the amount of NKCC2 at the TAL apical surface. VAMP3 is not required for cAMP-stimulated NKCC2 exocytic delivery. Additionally, genetic deletion of VAMP3 in mice decreased total expression of NKCC2 in the TAL and lowered blood pressure. Consistent with these results, urinary excretion of water and electrolytes was higher in VAMP3 knock-out mice, which produced more diluted urine. We conclude that VAMP3 interacts with NKCC2 and mediates its constitutive exocytic delivery to the apical surface. Additionally, VAMP3 is required for normal NKCC2 expression, renal function, and blood pressure.
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Affiliation(s)
- Paulo S Caceres
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202, the Department of Physiology, Wayne State University, Detroit, Michigan 48202, and
| | - Mariela Mendez
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202
| | - Mohammed Z Haque
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202, the Interim Translational Research Institute, Academic Health System, Hamad Medical Corporation, 16060 Doha, Qatar
| | - Pablo A Ortiz
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202, the Department of Physiology, Wayne State University, Detroit, Michigan 48202, and
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21
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Zazzeron L, Ottolina D, Scotti E, Ferrari M, Bruzzone P, Sibilla S, Marenghi C, Gattinoni L, Caironi P. Real-time urinary electrolyte monitoring after furosemide administration in surgical ICU patients with normal renal function. Ann Intensive Care 2016; 6:72. [PMID: 27447787 PMCID: PMC4958084 DOI: 10.1186/s13613-016-0168-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 06/28/2016] [Indexed: 11/29/2022] Open
Abstract
Background Although the loop-diuretic furosemide is widely employed in critically ill patients with known long-term effects on plasma electrolytes, accurate data describing its acute effects on renal electrolyte handling and the generation of plasma electrolyte alterations are lacking. We hypothesized that the long-term effects of furosemide on plasma electrolytes and acid–base depend on its immediate effects on electrolyte excretion rate and patient clinical baseline characteristics. By monitoring urinary electrolytes quasi-continuously, we aimed to verify this hypothesis in a cohort of surgical ICU patients with normal renal function. Methods We retrospectively enrolled 39 consecutive patients admitted to a postoperative ICU after major surgery, and receiving single low-dose intravenous administration of furosemide. Urinary output, pH, sodium [Na+], potassium [K+], chloride [Cl−] and ammonium [NH4+] concentrations were measured every 10 min for three to 8 h. Urinary anion gap (AG), electrolyte excretion rate, fractional excretion (Fe) and time constant of urinary [Na+] variation (τNa+) were calculated. Results Ten minutes after furosemide administration (12 ± 5 mg), urinary [Na+] and [Cl−], and their excretion rates, increased to similar levels (P < 0.001). After the first hour, urinary [Cl−] decreased less rapidly than [Na+], leading to a reduction in urinary AG and pH and an increment in urinary [NH4+] (P < 0.001). Median urinary [Cl−] over the first 3-h period was higher than baseline urinary and plasmatic [Cl−] (P < 0.001). During the first 2 h, difference between FeCl− and FeNa+ increased (P < 0.05). Baseline higher values of central venous pressure and FeNa+ were associated with greater increases in FeNa+ after furosemide (P = 0.03 and P = 0.007), whereas higher values of mean arterial and central venous pressures were associated with a longer τNa+ (P < 0.05). In patients receiving multiple administrations (n = 11), arterial pH, base excess and strong ion difference increased, due to a decrease in plasmatic [Cl−]. Conclusions Low-dose furosemide administration immediately modifies urinary electrolyte excretion rates, likely in relation to the ongoing proximal tubular activity, unveiled by its inhibitory action on Henle’s loop. Such effects, when cumulative, found the bases for the long-term alterations observed. Real-time urinary electrolyte monitoring may help in tailoring patient diuretic and hemodynamic therapies. Electronic supplementary material The online version of this article (doi:10.1186/s13613-016-0168-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Luca Zazzeron
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Università degli Studi di Milano, Via F. Sforza 35, 20122, Milan, Italy
| | - Davide Ottolina
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Università degli Studi di Milano, Via F. Sforza 35, 20122, Milan, Italy
| | - Eleonora Scotti
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Università degli Studi di Milano, Via F. Sforza 35, 20122, Milan, Italy
| | - Michele Ferrari
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Università degli Studi di Milano, Via F. Sforza 35, 20122, Milan, Italy
| | - Paola Bruzzone
- Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milan, Italy
| | - Silvio Sibilla
- Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milan, Italy
| | - Cristina Marenghi
- Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milan, Italy
| | - Luciano Gattinoni
- Department of Anesthesiology and Intensive Care Medicine, Georg-August-University Göttingen, Göttingen, Germany
| | - Pietro Caironi
- Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Università degli Studi di Milano, Via F. Sforza 35, 20122, Milan, Italy. .,Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milan, Italy.
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22
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Jaykumar AB, Caceres PS, Sablaban I, Tannous BA, Ortiz PA. Real-time monitoring of NKCC2 endocytosis by total internal reflection fluorescence (TIRF) microscopy. Am J Physiol Renal Physiol 2015; 310:F183-91. [PMID: 26538436 DOI: 10.1152/ajprenal.00104.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 10/30/2015] [Indexed: 11/22/2022] Open
Abstract
The apical Na-K-2Cl cotransporter (NKCC2) mediates NaCl reabsorption by the thick ascending limb (TAL). The amount of NKCC2 at the apical membrane of TAL cells is determined by exocytic delivery, recycling, and endocytosis. Surface biotinylation allows measurement of NKCC2 endocytosis, but it has low time resolution and does not allow imaging of the dynamic process of endocytosis. We hypothesized that total internal reflection fluorescence (TIRF) microscopy imaging of labeled NKCC2 would allow monitoring of NKCC2 endocytosis in polarized Madin-Darby canine kidney (MDCK) and TAL cells. Thus we generated a NKCC2 construct containing a biotin acceptor domain (BAD) sequence between the transmembrane domains 5 and 6. Once expressed in polarized MDCK or TAL cells, surface NKCC2 was specifically biotinylated by exogenous biotin ligase (BirA). We also demonstrate that expression of a secretory form of BirA in TAL cells induces metabolic biotinylation of NKCC2. Labeling biotinylated surface NKCC2 with fluorescent streptavidin showed that most apical NKCC2 was located within small discrete domains or clusters referred to as "puncta" on the TIRF field. NKCC2 puncta were observed to disappear from the TIRF field, indicating an endocytic event which led to a decrease in the number of surface puncta at a rate of 1.18 ± 0.16%/min in MDCK cells, and a rate 1.09 ± 0.08%/min in TAL cells (n = 5). Treating cells with a cholesterol-chelating agent (methyl-β-cyclodextrin) completely blocked NKCC2 endocytosis. We conclude that TIRF microscopy of labeled NKCC2 allows the dynamic imaging of individual endocytic events at the apical membrane of TAL cells.
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Affiliation(s)
- Ankita Bachhawat Jaykumar
- Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan; Department of Physiology, Wayne State University, Detroit, Michigan; and
| | - Paulo S Caceres
- Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan; Department of Physiology, Wayne State University, Detroit, Michigan; and
| | - Ibrahim Sablaban
- Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan
| | - Bakhos A Tannous
- Experimental Therapeutics and Molecular Imaging Laboratory, Neuroscience Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Pablo A Ortiz
- Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan; Department of Physiology, Wayne State University, Detroit, Michigan; and
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23
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Kortenoeven MLA, Pedersen NB, Rosenbaek LL, Fenton RA. Vasopressin regulation of sodium transport in the distal nephron and collecting duct. Am J Physiol Renal Physiol 2015; 309:F280-99. [DOI: 10.1152/ajprenal.00093.2015] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 05/27/2015] [Indexed: 12/22/2022] Open
Abstract
Arginine vasopressin (AVP) is released from the posterior pituitary gland during states of hyperosmolality or hypovolemia. AVP is a peptide hormone, with antidiuretic and antinatriuretic properties. It allows the kidneys to increase body water retention predominantly by increasing the cell surface expression of aquaporin water channels in the collecting duct alongside increasing the osmotic driving forces for water reabsorption. The antinatriuretic effects of AVP are mediated by the regulation of sodium transport throughout the distal nephron, from the thick ascending limb through to the collecting duct, which in turn partially facilitates osmotic movement of water. In this review, we will discuss the regulatory role of AVP in sodium transport and summarize the effects of AVP on various molecular targets, including the sodium-potassium-chloride cotransporter NKCC2, the thiazide-sensitive sodium-chloride cotransporter NCC, and the epithelial sodium channel ENaC.
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Affiliation(s)
- M. L. A. Kortenoeven
- Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark
| | - N. B. Pedersen
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark; and
| | - L. L. Rosenbaek
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - R. A. Fenton
- Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark
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24
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Orlov SN, Koltsova SV, Kapilevich LV, Gusakova SV, Dulin NO. NKCC1 and NKCC2: The pathogenetic role of cation-chloride cotransporters in hypertension. Genes Dis 2015; 2:186-196. [PMID: 26114157 PMCID: PMC4477834 DOI: 10.1016/j.gendis.2015.02.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 02/16/2015] [Indexed: 11/17/2022] Open
Abstract
This review summarizes the data on the functional significance of ubiquitous (NKCC1) and renal-specific (NKCC2) isoforms of electroneutral sodium, potassium and chloride cotransporters. These carriers contribute to the pathogenesis of hypertension via regulation of intracellular chloride concentration in vascular smooth muscle and neuronal cells and via sensing chloride concentration in the renal tubular fluid, respectively. Both NKCC1 and NKCC2 are inhibited by furosemide and other high-ceiling diuretics widely used for attenuation of extracellular fluid volume. However, the chronic usage of these compounds for the treatment of hypertension and other volume-expanded disorders may have diverse side-effects due to suppression of myogenic response in microcirculatory beds.
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Affiliation(s)
- Sergei N. Orlov
- Faculty of Biology, M.V. Lomonosov Moscow State University, Russia
- Тomsk State University, Russia
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25
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Abstract
The thick ascending limb occupies a central anatomic and functional position in human renal physiology, with critical roles in the defense of the extracellular fluid volume, the urinary concentrating mechanism, calcium and magnesium homeostasis, bicarbonate and ammonium homeostasis, and urinary protein composition. The last decade has witnessed tremendous progress in the understanding of the molecular physiology and pathophysiology of this nephron segment. These advances are the subject of this review, with emphasis on particularly recent developments.
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Affiliation(s)
- David B Mount
- Renal Division, Brigham and Women's Hospital, Veterans Affairs Boston Healthcare System, Boston, Massachusetts
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Caceres PS, Mendez M, Ortiz PA. Vesicle-associated membrane protein 2 (VAMP2) but Not VAMP3 mediates cAMP-stimulated trafficking of the renal Na+-K+-2Cl- co-transporter NKCC2 in thick ascending limbs. J Biol Chem 2014; 289:23951-62. [PMID: 25008321 PMCID: PMC4156046 DOI: 10.1074/jbc.m114.589333] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
In the kidney, epithelial cells of the thick ascending limb (TAL) reabsorb NaCl via the apical Na+/K+/2Cl− co-transporter NKCC2. Steady-state surface NKCC2 levels in the apical membrane are maintained by a balance between exocytic delivery, endocytosis, and recycling. cAMP is the second messenger of hormones that enhance NaCl absorption. cAMP stimulates NKCC2 exocytic delivery via protein kinase A (PKA), increasing steady-state surface NKCC2. However, the molecular mechanism involved has not been studied. We found that several members of the SNARE family of membrane fusion proteins are expressed in TALs. Here we report that NKCC2 co-immunoprecipitates with VAMP2 in rat TALs, and they co-localize in discrete domains at the apical surface. cAMP stimulation enhanced VAMP2 exocytic delivery to the plasma membrane of renal cells, and stimulation of PKA enhanced VAMP2-NKCC2 co-immunoprecipitation in TALs. In vivo silencing of VAMP2 but not VAMP3 in TALs blunted cAMP-stimulated steady-state surface NKCC2 expression and completely blocked cAMP-stimulated NKCC2 exocytic delivery. VAMP2 was not involved in constitutive NKCC2 delivery. We concluded that VAMP2 but not VAMP3 selectively mediates cAMP-stimulated NKCC2 exocytic delivery and surface expression in TALs. We also demonstrated that cAMP stimulation enhances VAMP2 exocytosis and promotes VAMP2 interaction with NKCC2.
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Affiliation(s)
- Paulo S Caceres
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202 and the Department of Physiology, Wayne State University, Detroit, Michigan 48202
| | - Mariela Mendez
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202 and
| | - Pablo A Ortiz
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan 48202 and the Department of Physiology, Wayne State University, Detroit, Michigan 48202
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Miranda CA, Lee JW, Chou CL, Knepper MA. Tolvaptan as a tool in renal physiology. Am J Physiol Renal Physiol 2013; 306:F359-66. [PMID: 24305472 DOI: 10.1152/ajprenal.00330.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
For decades, the Brattleboro rat has been a useful model in kidney physiology. These animals manifest central diabetes insipidus (lack of circulating vasopressin) due to a mutation in the vasopressin-neurophysin gene. V2 receptor-mediated vasopressin actions in the kidney can be assessed in these animals by infusing the V2-selective vasopressin analog 1-desamino-8-D-arginine vasopressin (dDAVP). However, the major commercial supplier in the United States has ceased production, creating the need for another reliable experimental model of V2 receptor-mediated vasopressin action in rodents. We designed an in vivo protocol to investigate vasopressin responses in the rat kidney using osmotic minipumps loaded with tolvaptan, a nonpeptide competitive inhibitor of the vasopressin V2 receptor. Tolvaptan-infused rats had a mean urinary osmolality of <300 vs. >2,000 mosmol/kgH₂O in vehicle-infused rats. The tolvaptan infusion produced large decreases in the renal abundance of aquaporin-2 (AQP2), aquaporin-3 (AQP3), the β-subunit of the epithelial sodium channel (β-ENaC), and γ-ENaC that were comparable to the differences seen in vehicle-infused vs. vasopressin-infused Brattleboro rats. Thus we conclude that tolvaptan infusion in rats provides an additional model (besides dDAVP-infusion in the Brattleboro rat) for the assessment of V2 receptor-mediated vasopressin actions in the kidney. We also provide ancillary in vitro data in rat inner-medullary-collecting-duct suspensions showing that tolvaptan can block vasopressin's effects on phosphorylation of the water channel AQP2 in vitro. Specifically, tolvaptan almost completely inhibited the ability of vasopressin to increase AQP2 phosphorylation at Ser256, Ser264, and Ser269, while strongly inhibiting a vasopressin-induced decrease in AQP2 phosphorylation at Ser261.
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Affiliation(s)
- Carlos A Miranda
- National Institutes of Health, Bldg. 10, Rm. 6N260, 10 Center Dr., MSC-1603, Bethesda, MD 20892-1603.
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Ares GR, Ortiz PA. Dynamin2, clathrin, and lipid rafts mediate endocytosis of the apical Na/K/2Cl cotransporter NKCC2 in thick ascending limbs. J Biol Chem 2012; 287:37824-34. [PMID: 22977238 DOI: 10.1074/jbc.m112.386425] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Steady-state surface levels of the apical Na/K/2Cl cotransporter NKCC2 regulate NaCl reabsorption by epithelial cells of the renal thick ascending limb (THAL). We reported that constitutive endocytosis of NKCC2 controls NaCl absorption in native THALs; however, the pathways involved in NKCC2 endocytosis are unknown. We hypothesized that NKCC2 endocytosis at the apical surface depends on dynamin-2 and clathrin. Measurements of steady-state surface NKCC2 and the rate of NKCC2 endocytosis in freshly isolated rat THALs showed that inhibition of endogenous dynamin-2 with dynasore blunted NKCC2 endocytosis by 56 ± 11% and increased steady-state surface NKCC2 by 67 ± 27% (p < 0.05). Expression of the dominant negative Dyn2K44A in THALs slowed the rate of NKCC2 endocytosis by 38 ± 8% and increased steady-state surface NKCC2 by 37 ± 8%, without changing total NKCC2 expression. Inhibition of clathrin-mediated endocytosis with chlorpromazine blunted NKCC2 endocytosis by 54 ± 6%, while preventing clathrin from interacting with synaptojanin also blunted NKCC2 endocytosis by 52 ± 5%. Disruption of lipid rafts blunted NKCC2 endocytosis by 39 ± 4% and silencing caveolin-1 by 29 ± 4%. Simultaneous inhibition of clathrin- and lipid raft-mediated endocytosis completely blocked NKCC2 internalization. We concluded that dynamin-2, clathrin, and lipid rafts mediate NKCC2 endocytosis and maintain steady-state apical surface NKCC2 in native THALs. These are the first data identifying the endocytic pathway for apical NKCC2 endocytosis.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Wayne State University, Detroit, Michigan 48202, USA
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Ferreri NR, Hao S, Pedraza PL, Escalante B, Vio CP. Eicosanoids and tumor necrosis factor-alpha in the kidney. Prostaglandins Other Lipid Mediat 2011; 98:101-6. [PMID: 22101002 DOI: 10.1016/j.prostaglandins.2011.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 10/31/2011] [Accepted: 11/03/2011] [Indexed: 12/14/2022]
Abstract
The thick ascending limb of Henle's loop (TAL) is capable of metabolizing arachidonic acid (AA) by cytochrome P450 (CYP450) and cyclooxygenase (COX) pathways and has been identified as a nephron segment that contributes to salt-sensitive hypertension. Previous studies demonstrated a prominent role for CYP450-dependent metabolism of AA to products that inhibited ion transport pathways in the TAL. However, COX-2 is constitutively expressed along all segments of the TAL and is increased in response to diverse stimuli. The ability of Tamm-Horsfall glycoprotein, a selective marker of cortical TAL (cTAL) and medullary (mTAL), to bind TNF and localize it to this nephron segment prompted studies to determine the capacity of mTAL cells to produce TNF and determine its effects on mTAL function. The colocalization of calcium-sensing receptor (CaR) and COX-2 in the TAL supports the notion that activation of CaR induces TNF-dependent COX-2 expression and PGE₂ synthesis in mTAL cells. Additional studies showed that TNF produced by mTAL cells inhibits ⁸⁶Rb uptake, an in vitro correlate of natriuresis, in an autocrine- and COX-2-dependent manner. The molecular mechanism for these effects likely includes inhibition of Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) expression and trafficking.
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Affiliation(s)
- Nicholas R Ferreri
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA.
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Pisitkun T, Hoffert JD, Saeed F, Knepper MA. NHLBI-AbDesigner: an online tool for design of peptide-directed antibodies. Am J Physiol Cell Physiol 2011; 302:C154-64. [PMID: 21956165 DOI: 10.1152/ajpcell.00325.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Investigation of physiological mechanisms at a cellular level often requires production of high-quality antibodies, frequently using synthetic peptides as immunogens. Here we describe a new, web-based software tool called NHLBI-AbDesigner that allows the user to visualize the information needed to choose optimal peptide sequences for peptide-directed antibody production (http://helixweb.nih.gov/AbDesigner/). The choice of an immunizing peptide is generally based on a need to optimize immunogenicity, antibody specificity, multispecies conservation, and robustness in the face of posttranslational modifications (PTMs). AbDesigner displays information relevant to these criteria as follows: 1) "Immunogenicity Score," based on hydropathy and secondary structure prediction; 2) "Uniqueness Score," a predictor of specificity of an antibody against all proteins expressed in the same species; 3) "Conservation Score," a predictor of ability of the antibody to recognize orthologs in other animal species; and 4) "Protein Features" that show structural domains, variable regions, and annotated PTMs that may affect antibody performance. AbDesigner displays the information online in an interactive graphical user interface, which allows the user to recognize the trade-offs that exist for alternative synthetic peptide choices and to choose the one that is best for a proposed application. Several examples of the use of AbDesigner for the display of such trade-offs are presented, including production of a new antibody to Slc9a3. We also used the program in large-scale mode to create a database listing the 15-amino acid peptides with the highest Immunogenicity Scores for all known proteins in five animal species, one plant species (Arabidopsis thaliana), and Saccharomyces cerevisiae.
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Affiliation(s)
- Trairak Pisitkun
- Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1603, USA
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Ares GR, Caceres PS, Ortiz PA. Molecular regulation of NKCC2 in the thick ascending limb. Am J Physiol Renal Physiol 2011; 301:F1143-59. [PMID: 21900458 DOI: 10.1152/ajprenal.00396.2011] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The kidney plays an essential role in blood pressure regulation by controlling short-term and long-term NaCl and water balance. The thick ascending limb of the loop of Henle (TAL) reabsorbs 25-30% of the NaCl filtered by the glomeruli in a process mediated by the apical Na(+)-K(+)-2Cl(-) cotransporter NKCC2, which allows Na(+) and Cl(-) entry from the tubule lumen into TAL cells. In humans, mutations in the gene coding for NKCC2 result in decreased or absent activity characterized by severe salt and volume loss and decreased blood pressure (Bartter syndrome type 1). Opposite to Bartter's syndrome, enhanced NaCl absorption by the TAL is associated with human hypertension and animal models of salt-sensitive hypertension. TAL NaCl reabsorption is subject to exquisite control by hormones like vasopressin, parathyroid, glucagon, and adrenergic agonists (epinephrine and norepinephrine) that stimulate NaCl reabsorption. Atrial natriuretic peptides or autacoids like nitric oxide and prostaglandins inhibit NaCl reabsorption, promoting salt excretion. In general, the mechanism by which hormones control NaCl reabsorption is mediated directly or indirectly by altering the activity of NKCC2 in the TAL. Despite the importance of NKCC2 in renal physiology, the molecular mechanisms by which hormones, autacoids, physical factors, and intracellular ions regulate NKCC2 activity are largely unknown. During the last 5 years, it has become apparent that at least three molecular mechanisms determine NKCC2 activity. As such, membrane trafficking, phosphorylation, and protein-protein interactions have recently been described in TALs and heterologous expression systems as mechanisms that modulate NKCC2 activity. The focus of this review is to summarize recent data regarding NKCC2 regulation and discuss their potential implications in physiological control of TAL function, renal physiology, and blood pressure regulation.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Dept. of Internal Medicine, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA
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Mutig K, Kahl T, Saritas T, Godes M, Persson P, Bates J, Raffi H, Rampoldi L, Uchida S, Hille C, Dosche C, Kumar S, Castañeda-Bueno M, Gamba G, Bachmann S. Activation of the bumetanide-sensitive Na+,K+,2Cl- cotransporter (NKCC2) is facilitated by Tamm-Horsfall protein in a chloride-sensitive manner. J Biol Chem 2011; 286:30200-10. [PMID: 21737451 DOI: 10.1074/jbc.m111.222968] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Active transport of NaCl across thick ascending limb (TAL) epithelium is accomplished by Na(+),K(+),2Cl(-) cotransporter (NKCC2). The activity of NKCC2 is determined by vasopressin (AVP) or intracellular chloride concentration and includes its amino-terminal phosphorylation. Co-expressed Tamm-Horsfall protein (THP) has been proposed to interact with NKCC2. We hypothesized that THP modulates NKCC2 activity in TAL. THP-deficient mice (THP(-/-)) showed an increased abundance of intracellular NKCC2 located in subapical vesicles (+47% compared with wild type (WT) mice), whereas base-line phosphorylation of NKCC2 was significantly decreased (-49% compared with WT mice), suggesting reduced activity of the transporter in the absence of THP. Cultured TAL cells with low endogenous THP levels and low base-line phosphorylation of NKCC2 displayed sharp increases in NKCC2 phosphorylation (+38%) along with a significant change of intracellular chloride concentration upon transfection with THP. In NKCC2-expressing frog oocytes, co-injection with THP cRNA significantly enhanced the activation of NKCC2 under low chloride hypotonic stress (+112% versus +235%). Short term (30 min) stimulation of the vasopressin V2 receptor pathway by V2 receptor agonist (deamino-cis-D-Arg vasopressin) resulted in enhanced NKCC2 phosphorylation in WT mice and cultured TAL cells transfected with THP, whereas in the absence of THP, NKCC2 phosphorylation upon deamino-cis-D-Arg vasopressin was blunted in both systems. Attenuated effects of furosemide along with functional and structural adaptation of the distal convoluted tubule in THP(-/-) mice supported the notion that NaCl reabsorption was impaired in TAL lacking THP. In summary, these results are compatible with a permissive role for THP in the modulation of NKCC2-dependent TAL salt reabsorptive function.
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Affiliation(s)
- Kerim Mutig
- Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany
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Haque MZ, Ares GR, Caceres PS, Ortiz PA. High salt differentially regulates surface NKCC2 expression in thick ascending limbs of Dahl salt-sensitive and salt-resistant rats. Am J Physiol Renal Physiol 2011; 300:F1096-104. [PMID: 21307126 DOI: 10.1152/ajprenal.00600.2010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
NaCl reabsorption by the thick ascending limb of the loop of Henle (THAL) occurs via the apical Na-K-2Cl cotransporter, NKCC2. Overall, NKCC2 activity and NaCl reabsorption are regulated by the amount of NKCC2 at the apical surface, and also by phosphorylation. Dahl salt-sensitive rats (SS) exhibit higher NaCl reabsorption by the THAL compared with Dahl salt-resistant rats (SR), and they become hypertensive during high-salt (HS) intake. However, the effect of HS on THAL transport, surface NKCC2 expression, and NKCC2 NH(2)-terminus phosphorylation has not been studied. We hypothesized that HS enhances surface NKCC2 and its phosphorylation in THALs from Dahl SS. THAL suspensions were obtained from a group of SS and SR rats on normal-salt (NS) or HS intake. In SR rats THAL NaCl transport measured as furosemide-sensitive oxygen consumption was decreased by HS (-34%, P < 0.05). In contrast, HS did not affect THAL transport in SS rats. As expected, HS increased systolic blood pressure only in SS rats (Δ 23 ± 2 mmHg, P < 0.002) but not in SR rats (Δ 5 ± 3 mmHg). We next tested the effect of HS intake on apical surface NKCC2 and its NH(2)-terminus threonine phosphorylation (P-NKCC2) in SS and SR rats. HS intake decreased surface NKCC2 by 15 ± 2% (P < 0.03) in THALs from SR without affecting total NKCC2 or NH(2)-terminus P-NKCC2. In contrast, in SS rats HS intake increased surface NKCC2 by 54 ± 6% (P < 0.01) without affecting total NKCC2 expression or P-NKCC2. We conclude that HS intake causes different effects on surface NKCC2 in SS and SR rats. Our data suggest that enhanced surface NKCC2 in SS rats might contribute to enhanced NaCl reabsorption in SS rats during HS intake.
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Affiliation(s)
- Mohammed Ziaul Haque
- Department of Internal Medicine, Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA
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Hao S, Zhao H, Darzynkiewicz Z, Battula S, Ferreri NR. Differential regulation of NFAT5 by NKCC2 isoforms in medullary thick ascending limb (mTAL) cells. Am J Physiol Renal Physiol 2011; 300:F966-75. [PMID: 21228109 DOI: 10.1152/ajprenal.00408.2010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The effects of Na(+)-K(+)-2Cl(-) cotransporter type 2 (NKCC2) isoforms on the regulation of nuclear factor of activated T cells isoform 5 (NFAT5) were determined in mouse medullary thick ascending limb (mTAL) cells exposed to high NaCl concentration. Primary cultures of mTAL cells and freshly isolated mTAL tubules, both derived from the outer medulla (outer stripe>inner stripe), express NKCC2 isoforms A and F. The relative expression of NKCC2A mRNA was approximately twofold greater than NKCC2F in these preparations. The abundance of NKCC2A mRNA, but not NKCC2F mRNA, increased approximately twofold when mTAL cells were exposed for 2 h to a change in osmolality from 300 to 500 mosmol/kgH₂O, produced with NaCl. Total NKCC2 protein expression also increased. Moreover, a 2.5-fold increase in NFAT5 mRNA accumulation was observed after cells were exposed to 500 mosmol/kgH₂O for 4 h. Laser-scanning cytometry detected a twofold increase in endogenous NFAT5 protein expression in response to high NaCl concentration. Pretreatment with the loop diuretic bumetanide dramatically reduced transcriptional activity of the NFAT5-specific reporter construct TonE-Luc in mTAL cells exposed to high NaCl. Transient transfection of mTAL cells with shRNA vectors targeting NKCC2A prevented increases in NFAT5 mRNA abundance and protein expression and inhibited NFAT5 transcriptional activity in response to hypertonic stress. Silencing of NKCC2F mRNA did not affect NFAT5 mRNA accumulation but partially inhibited NFAT5 transcriptional activity. These findings suggest that NKCC2A and NKCC2F exhibit differential effects on NFAT5 expression and transcriptional activity in response to hypertonicity produced by high NaCl concentration.
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Affiliation(s)
- Shoujin Hao
- Department of Pharmacology, New York Medical College, Valhalla, New York, USA
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35
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Feric M, Zhao B, Hoffert JD, Pisitkun T, Knepper MA. Large-scale phosphoproteomic analysis of membrane proteins in renal proximal and distal tubule. Am J Physiol Cell Physiol 2011; 300:C755-70. [PMID: 21209370 DOI: 10.1152/ajpcell.00360.2010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Recent advances in mass spectrometry (MS) have provided means for large-scale phosphoproteomic profiling of specific tissues. Here, we report results from large-scale tandem MS [liquid chromatography (LC)-MS/MS]-based phosphoproteomic profiling of biochemically isolated membranes from the renal cortex, with focus on transporters and regulatory proteins. Data sets were filtered (by target-decoy analysis) to limit false-positive identifications to <2%. A total of 7,125 unique nonphosphorylated and 743 unique phosphorylated peptides were identified. Among the phosphopeptides identified were sites on transporter proteins, i.e., solute carrier (Slc, n = 63), ATP-binding cassette (Abc, n = 4), and aquaporin (Aqp, n = 3) family proteins. Database searches reveal that a majority of the phosphorylation sites identified in transporter proteins were previously unreported. Most of the Slc family proteins are apical or basolateral transporters expressed in proximal tubule cells, including proteins known to mediate transport of glucose, amino acids, organic ions, and inorganic ions. In addition, we identified potentially important phosphorylation sites for transport proteins from distal nephron segments, including the bumetanide-sensitive Na-K-2Cl cotransporter (Slc12a1 or NKCC2) at Ser(87), Thr(101), and Ser(126) and the thiazide-sensitive Na-Cl cotransporter (Slc12a3 or NCC) at Ser(71) and Ser(124). A subset of phosphorylation sites in regulatory proteins coincided with known functional motifs, suggesting specific regulatory roles. An online database from this study (http://dir.nhlbi.nih.gov/papers/lkem/rcmpd/) provides a resource for future studies of transporter regulation.
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Affiliation(s)
- Marina Feric
- Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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Zaarour N, Defontaine N, Demaretz S, Azroyan A, Cheval L, Laghmani K. Secretory carrier membrane protein 2 regulates exocytic insertion of NKCC2 into the cell membrane. J Biol Chem 2011; 286:9489-502. [PMID: 21205824 DOI: 10.1074/jbc.m110.166546] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The renal-specific Na-K-2Cl co-transporter, NKCC2, plays a pivotal role in regulating body salt levels and blood pressure. NKCC2 mutations lead to type I Bartter syndrome, a life-threatening kidney disease. Regulation of NKCC2 trafficking behavior serves as a major mechanism in controlling NKCC2 activity across the plasma membrane. However, the identities of the protein partners involved in cell surface targeting of NKCC2 are largely unknown. To gain insight into these processes, we used a yeast two-hybrid system to screen a kidney cDNA library for proteins that interact with the NKCC2 C terminus. One binding partner we identified was SCAMP2 (secretory carrier membrane protein 2). Microscopic confocal imaging and co-immunoprecipitation assays confirmed NKCC2-SCAMP2 interaction in renal cells. SCAMP2 associated also with the structurally related co-transporter NCC, suggesting that the interaction with SCAMP2 is a common feature of sodium-dependent chloride co-transporters. Heterologous expression of SCAMP2 specifically decreased cell surface abundance as well as transport activity of NKCC2 across the plasma membrane. Co-immunolocalization experiments revealed that intracellularly retained NKCC2 co-localizes with SCAMP2 in recycling endosomes. The rate of NKCC2 endocytic retrieval, assessed by the sodium 2-mercaptoethane sulfonate cleavage assay, was not affected by SCAMP2. The surface-biotinylatable fraction of newly inserted NKCC2 in the plasma membrane was reduced by SCAMP2, demonstrating that SCAMP2-induced decrease in surface NKCC2 is due to decreased exocytotic trafficking. Finally, a single amino acid mutation, cysteine 201 to alanine, within the conserved cytoplasmic E peptide of SCAMP2, which is believed to regulate exocytosis, abolished SCAMP2-mediated down-regulation of the co-transporter. Taken together, these data are consistent with a model whereby SCAMP2 regulates NKCC2 transit through recycling endosomes and limits the cell surface targeting of the co-transporter by interfering with its exocytotic trafficking.
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Affiliation(s)
- Nancy Zaarour
- INSERM, Centre de Recherche des Cordeliers, UMRS 872, CNRS, ERL7226, 75006 Paris, France
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Ares GR, Ortiz PA. Constitutive endocytosis and recycling of NKCC2 in rat thick ascending limbs. Am J Physiol Renal Physiol 2010; 299:F1193-202. [PMID: 20719977 DOI: 10.1152/ajprenal.00307.2010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The Na-K-2Cl cotransporter (NKCC2) mediates NaCl absorption by the thick ascending limb of Henle's loop (THAL). Exocytosis and endocytosis regulates surface expression of most transporters. However, little is known about the mechanism of NKCC2 trafficking in the absence of stimulating hormones and whether this mechanism contributes to regulation of steady-state surface expression of apical NKCC2 in the THAL. We tested whether NKCC2 undergoes constitutive endocytosis that regulates steady-state surface NKCC2 and NaCl reabsorption in THALs. We measured steady-state surface NKCC2 levels and the rate of NKCC2 endocytosis by surface biotinylation and Western blot and confocal microscopy of isolated perfused rat THALs. We observed constitutive NKCC2 endocytosis over 30 min that averaged 21.5 ± 2.7% of the surface pool. We then tested whether methyl-β-cyclodextrin (MβCD), a compound that inhibits endocytosis by chelating membrane cholesterol, blocked NKCC2 endocytic retrieval. We found that 30-min treatment with MβCD (5 mM) blocked NKCC2 endocytosis by 81% (P < 0.01). Blockade of endocytosis by MβCD induced accumulation of NKCC2 at the apical membrane as demonstrated by a 60 ± 16% (P < 0.05) increase in steady-state surface expression and enhanced apical surface NKCC2 immunostaining in isolated, perfused THALs. Acute treatment with MβCD did not change the total pool of NKCC2. MβCD did not affect NKCC2 trafficking when it was complexed with cholesterol before treatment. Inhibition endocytosis with MβCD enhanced NKCC2-dependent NaCl entry by 57 ± 16% (P < 0.05). Finally, we observed that a fraction of retrieved NKCC2 recycles back to the plasma membrane (36 ± 7%) over 30 min. We concluded that constitutive NKCC2 trafficking maintains steady-state surface NKCC2 and regulates NaCl reabsorption in THALs. These are the first data showing an increase in apical membrane NKCC2 in THALs by altering the rates of constitutive NKCC2 trafficking, rather than by stimulation of hormone-dependent signaling.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Div., Dept. of Internal Medicine, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA
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Tresguerres M, Levin LR, Buck J, Grosell M. Modulation of NaCl absorption by [HCO(3)(-)] in the marine teleost intestine is mediated by soluble adenylyl cyclase. Am J Physiol Regul Integr Comp Physiol 2010; 299:R62-71. [PMID: 20410468 DOI: 10.1152/ajpregu.00761.2009] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intestinal HCO(3)(-) secretion and NaCl absorption are essential for counteracting dehydration in marine teleost fish. We investigated how these two processes are coordinated in toadfish. HCO(3)(-) stimulated a luminal positive short-circuit current (I(sc)) in intestine mounted in Ussing chamber, bathed with the same saline solution on the external and internal sides of the epithelium. The I(sc) increased proportionally to the [HCO(3)(-)] in the bath up to 80 mM NaHCO(3), and it did not occur when NaHCO(3) was replaced with Na(+)-gluconate or with NaHCO(3) in Cl(-)-free saline. HCO(3)(-) (20 mM) induced a approximately 2.5-fold stimulation of I(sc), and this [HCO(3)(-)] was used in all subsequent experiments. The HCO(3)(-)-stimulated I(sc) was prevented or abolished by apical application of 10 muM bumetanide (a specific inhibitor of NKCC) and by 30 microM 4-catechol estrogen [CE; an inhibitor of soluble adenylyl cyclase (sAC)]. The inhibitory effects of bumetanide and CE were not additive. The HCO(3)(-)-stimulated I(sc) was prevented by apical bafilomycin (1 microM) and etoxolamide (1 mM), indicating involvement of V-H(+)-ATPase and carbonic anhydrases, respectively. Immunohistochemistry and Western blot analysis confirmed the presence of an NKCC2-like protein in the apical membrane and subapical area of epithelial intestinal cells, of Na(+)/K(+)-ATPase in basolateral membranes, and of an sAC-like protein in the cytoplasm. We propose that sAC regulates NKCC activity in response to luminal HCO(3)(-), and that V-H(+)-ATPase and intracellular carbonic anhydrase are essential for transducing luminal HCO(3)(-) into the cell by CO(2)/HCO(3)(-) hydration/dehydration. This mechanism putatively coordinates HCO(3)(-) secretion with NaCl and water absorption in toadfish intestine.
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Affiliation(s)
- Martin Tresguerres
- Department of Pharmacology, Weill Cornell Medical College, New York, New York 10065, USA.
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Dong B, Nishimura N, Vogel CF, Tohyama C, Matsumura F. TCDD-induced cyclooxygenase-2 expression is mediated by the nongenomic pathway in mouse MMDD1 macula densa cells and kidneys. Biochem Pharmacol 2009; 79:487-97. [PMID: 19782052 DOI: 10.1016/j.bcp.2009.08.031] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 08/21/2009] [Accepted: 08/24/2009] [Indexed: 01/15/2023]
Abstract
Cyclooxygenase-2 (Cox-2) plays a critical role in TCDD-induced hydronephrosis in mouse neonates. In this study we found that induction of Cox-2 by TCDD in MMDD1, a mouse macula densa cell line, is accompanied with a rapid increase in the enzymatic activity of cytosolic phospholipase A2 (cPLA2) as well as activation of protein kinases. Calcium serves as a trigger for such an action of TCDD in this cell line. These observations indicate that the basic mode of action of TCDD to induce the rapid inflammatory response in MMDD1 is remarkably similar to those mediated by the nongenomic pathway of aryl hydrocarbon receptor (AhR) found in other types of cells. Such an action of TCDD to induce Cox-2 in MMDD1 was not affected by "DRE decoy oligonucleotides" treatment or by introduction of a mutation on the DRE site of Cox-2 promoter, suggesting that this route of action of TCDD is clearly different from that mediated by the classical genomic pathway. An in vivo study with Ahr(nls) mouse model has shown that TCDD-induces Cox-2 and renin expression in the kidneys of the Ahr(nls) mice as well as Ahr(+/-) mice, but not in the Ahr(-/-) mice, indicating that this initial action of TCDD in mouse kidney does not require the translocation of AhR into the nucleus, supporting our conclusion that induction of Cox-2 by TCDD in mouse kidney is largely mediated by the nongenomic pathway of TCDD-activated AhR.
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Affiliation(s)
- Bin Dong
- Department of Environmental Toxicology, University of California, 4245 Meyer Hall, Davis, CA 95616, USA
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Caceres PS, Ares GR, Ortiz PA. cAMP stimulates apical exocytosis of the renal Na(+)-K(+)-2Cl(-) cotransporter NKCC2 in the thick ascending limb: role of protein kinase A. J Biol Chem 2009; 284:24965-71. [PMID: 19592485 PMCID: PMC2757200 DOI: 10.1074/jbc.m109.037135] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The apical renal Na(+)-K(+)-2Cl(-) cotransporter NKCC2 mediates NaCl absorption by the thick ascending limb (TAL) of Henle's loop. cAMP stimulates NKCC2 by enhancing steady-state apical membrane levels of this protein; however, the trafficking and signaling mechanisms by which this occurs have not been studied. Here, we report that stimulation of endogenous cAMP levels with either forskolin/3-isobutyl-1-methylxanthine (IBMX) or the V2 receptor agonist [deamino-Cys(1),d-Arg(8)]vasopressin increases steady-state surface NKCC2 and that the protein kinase A (PKA) inhibitor H-89 blocks this effect. Confocal imaging of apical surface NKCC2 in isolated perfused TALs confirmed a stimulatory effect of cAMP on apical trafficking that was blocked by PKA inhibition. Selective stimulation of PKA with the agonist N(6)-benzoyl-cAMP (500 microm) stimulated steady-state surface NKCC2, whereas the Epac-selective agonist 8-p-chlorophenylthio-2'-O-methyl-cAMP (100 and 250 microm) had no effect. To explore the trafficking mechanism by which cAMP increases apical NKCC2, we measured cumulative apical membrane exocytosis and NKCC2 exocytic insertion in TALs. By monitoring apical FM1-43 fluorescence, we observed rapid stimulation of apical exocytosis (2 min) by forskolin/IBMX. We also found constitutive exocytic insertion of NKCC2 in TALs over time, which was increased by 3-fold in the presence of forskolin/IBMX. PKA inhibition blunted cAMP-stimulated exocytic insertion but did not affect the rate of constitutive exocytosis. We conclude that cAMP stimulates steady-state apical surface NKCC2 by stimulating exocytic insertion and that this process is highly dependent on PKA but not Epac.
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Affiliation(s)
- Paulo S Caceres
- Hypertension and Vascular Research Division, Henry Ford Hospital, Wayne State University, Detroit, Michigan 48202, USA
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Welker P, Böhlick A, Mutig K, Salanova M, Kahl T, Schlüter H, Blottner D, Ponce-Coria J, Gamba G, Bachmann S. Renal Na+-K+-Cl- cotransporter activity and vasopressin-induced trafficking are lipid raft-dependent. Am J Physiol Renal Physiol 2008; 295:F789-802. [PMID: 18579701 PMCID: PMC2536870 DOI: 10.1152/ajprenal.90227.2008] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 06/17/2008] [Indexed: 11/22/2022] Open
Abstract
Apical bumetanide-sensitive Na(+)-K(+)-2Cl(-) cotransporter (NKCC2), the kidney-specific member of a cation-chloride cotransporter superfamily, is an integral membrane protein responsible for the transepithelial reabsorption of NaCl. The role of NKCC2 is essential for renal volume regulation. Vasopressin (AVP) controls NKCC2 surface expression in cells of the thick ascending limb of the loop of Henle (TAL). We found that 40-70% of Triton X-100-insoluble NKCC2 was present in cholesterol-enriched lipid rafts (LR) in rat kidney and cultured TAL cells. The related Na(+)-Cl(-) cotransporter (NCC) from rat kidney was distributed in LR as well. NKCC2-containing LR were detected both intracellularly and in the plasma membrane. Bumetanide-sensitive transport of NKCC2 as analyzed by (86)Rb(+) influx in Xenopus laevis oocytes was markedly reduced by methyl-beta-cyclodextrin (MbetaCD)-induced cholesterol depletion. In TAL, short-term AVP application induced apical vesicular trafficking along with a shift of NKCC2 from non-raft to LR fractions. In parallel, increased colocalization of NKCC2 with the LR ganglioside GM1 and their polar translocation were assessed by confocal analysis. Apical biotinylation showed twofold increases in NKCC2 surface expression. These effects were blunted by mevalonate-lovastatin/MbetaCD-induced cholesterol deprivation. Collectively, these findings demonstrate that a pool of NKCC2 distributes in rafts. Results are consistent with a model in which LR mediate polar insertion, activity, and AVP-induced trafficking of NKCC2 in the control of transepithelial NaCl transport.
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Affiliation(s)
- Pia Welker
- Institute of Anatomy, Charité-Universitätsmedizin Berlin, Philippstrasse 12, Berlin, Germany
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43
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Ares GR, Caceres P, Alvarez-Leefmans FJ, Ortiz PA. cGMP decreases surface NKCC2 levels in the thick ascending limb: role of phosphodiesterase 2 (PDE2). Am J Physiol Renal Physiol 2008; 295:F877-87. [PMID: 18684888 DOI: 10.1152/ajprenal.00449.2007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
NaCl absorption in the medullary thick ascending limb of the loop of Henle (THAL) is mediated by the apical Na/K/2Cl cotransporter (NKCC2). Hormones that increase cGMP, such as nitric oxide (NO) and natriuretic peptides, decrease NaCl absorption by the THAL. However, the mechanism by which cGMP decreases NaCl absorption in THALs is not known. We hypothesized that cGMP decreases surface NKCC2 levels in the THAL. We used surface biotinylation to measure surface NKCC2 levels in rat THAL suspensions. We tested the effect of the membrane-permeant cGMP analog dibutyryl-cGMP (db-cGMP) on surface NKCC2 levels. Incubating THALs with db-cGMP for 20 min decreased surface NKCC2 levels in a concentration-dependent manner (basal=100%; db-cGMP 100 microM=77+/-7%; 500 microM=54+/-10% and 1,000 microM=61+/-8%). A different cGMP analog 8-bromo-cGMP (8-Br-cGMP) also decreased surface NKCC2 levels by 25%, (basal=100%; 8-Br-cGMP=75+/-5%). Incubation of isolated, perfused THALs with db-cGMP decreased apical surface NKCC2 labeling levels as measured by immunofluorescence and confocal microscopy. cGMP-stimulated phosphodiesterase 2 (PDE2) mediates the inhibitory effect of NO on NaCl absorption by THALs. Thus we examined the role of PDE2 and found that PDE2 inhibitors blocked the effect of db-cGMP on surface NKCC2. Also, a nonstimulatory concentration of db-cAMP blocked the cGMP-induced decrease in surface NKCC2. Finally, db-cGMP inhibited THAL net Cl absorption by 48+/-4%, and this effect was completely blocked by PDE2 inhibition. We conclude that cGMP decreases NKCC2 levels in the apical membrane of THALs and that this effect is mediated by PDE2. This is an important mechanism by which cGMP inhibits NaCl absorption by the THAL.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, and Department of Physiology, Wayne State University, 2799 West Grand Blvd., Detroit, MI 48202, USA
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Welker P, Böhlick A, Mutig K, Salanova M, Kahl T, Schlüter H, Blottner D, Ponce-Coria J, Gamba G, Bachmann S. Renal Na+-K+-Cl- cotransporter activity and vasopressin-induced trafficking are lipid raft-dependent. Am J Physiol Renal Physiol 2008. [PMID: 18579701 DOI: 10.1152/ajprenal.90227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Apical bumetanide-sensitive Na(+)-K(+)-2Cl(-) cotransporter (NKCC2), the kidney-specific member of a cation-chloride cotransporter superfamily, is an integral membrane protein responsible for the transepithelial reabsorption of NaCl. The role of NKCC2 is essential for renal volume regulation. Vasopressin (AVP) controls NKCC2 surface expression in cells of the thick ascending limb of the loop of Henle (TAL). We found that 40-70% of Triton X-100-insoluble NKCC2 was present in cholesterol-enriched lipid rafts (LR) in rat kidney and cultured TAL cells. The related Na(+)-Cl(-) cotransporter (NCC) from rat kidney was distributed in LR as well. NKCC2-containing LR were detected both intracellularly and in the plasma membrane. Bumetanide-sensitive transport of NKCC2 as analyzed by (86)Rb(+) influx in Xenopus laevis oocytes was markedly reduced by methyl-beta-cyclodextrin (MbetaCD)-induced cholesterol depletion. In TAL, short-term AVP application induced apical vesicular trafficking along with a shift of NKCC2 from non-raft to LR fractions. In parallel, increased colocalization of NKCC2 with the LR ganglioside GM1 and their polar translocation were assessed by confocal analysis. Apical biotinylation showed twofold increases in NKCC2 surface expression. These effects were blunted by mevalonate-lovastatin/MbetaCD-induced cholesterol deprivation. Collectively, these findings demonstrate that a pool of NKCC2 distributes in rafts. Results are consistent with a model in which LR mediate polar insertion, activity, and AVP-induced trafficking of NKCC2 in the control of transepithelial NaCl transport.
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Affiliation(s)
- Pia Welker
- Institute of Anatomy, Charité-Universitätsmedizin Berlin, Philippstrasse 12, Berlin, Germany
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45
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Wang G, Li C, Kim SW, Ring T, Wen J, Djurhuus JC, Wang W, Nielsen S, Frøkiaer J. Ureter obstruction alters expression of renal acid-base transport proteins in rat kidney. Am J Physiol Renal Physiol 2008; 295:F497-506. [PMID: 18508879 DOI: 10.1152/ajprenal.00425.2007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Urinary tract obstruction impairs renal function and is often associated with a urinary acidification defect caused by diminished net H+ secretion and/or HCO3- reabsorption. To identify the molecular mechanisms of these defects, protein expression of key acid-base transporters were examined along the renal nephron and collecting duct of kidneys from rats subjected to 24-h bilateral ureteral obstruction (BUO), 4 days after release of BUO (BUO-R), or BUO-R rats with experimentally induced metabolic acidosis (BUO-A). Semiquantitative immunoblotting revealed that BUO caused a significant reduction in the expression of the type 3 Na+/H+ exchanger (NHE3) in the cortex (21 +/- 4%), electrogenic Na+/HCO3- cotransporter (NBC1; 71 +/- 5%), type 1 bumetanide-sensitive Na+-K+-2Cl- cotransporter (NKCC2; 3 +/- 1%), electroneutral Na+/HCO3- cotransporter (NBCn1; 46 +/- 7%), and anion exchanger (pendrin; 87 +/- 2%). The expression of H+-ATPase increased in the inner medullary collecting duct (152 +/- 13%). These changes were confirmed by immunocytochemistry. In BUO-R rats, there was a persistent downregulation of all the acid-base transporters including H+-ATPase. Two days of NH4Cl loading reduced plasma pH and HCO3- levels in BUO-A rats. The results demonstrate that the expression of multiple renal acid-base transporters are markedly altered in response to BUO, which may be responsible for development of metabolic acidosis and contribute to the urinary acidification defect after release of the obstruction.
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Affiliation(s)
- Guixian Wang
- The Water and Salt Research Center, Aarhus University, Aarhus, Denmark
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Castrop H, Schnermann J. Isoforms of renal Na-K-2Cl cotransporter NKCC2: expression and functional significance. Am J Physiol Renal Physiol 2008; 295:F859-66. [PMID: 18495801 DOI: 10.1152/ajprenal.00106.2008] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The renal Na-K-2Cl cotransporter (NKCC2, BSC1) is selectively expressed in the apical membrane of cells of the thick ascending limb of the loop of Henle (TAL) and macula densa. NKCC2-dependent salt transport constitutes the major apical entry pathway for transepithelial salt reabsorption in the TAL. Although NKCC2 is encoded by a single gene (Slc12a1), differential splicing of the NKCC2 pre-mRNA results in the formation of several alternate transcripts. Thus three full-length splice isoforms of NKCC2 differ in their variable exon 4, resulting in transcripts for NKCC2B, NKCC2A, and NKCC2F. In addition to full-length isoforms, variants with truncated COOH-terminal ends have been described. The various splice isoforms of NKCC2 differ in their localization along the TAL and in their transport characteristics. Data in the literature are reviewed to assess the principles of NKCC2 differential splicing, the localization of NKCC2 splice isoforms along the TAL in various species, and the functional characteristics of the splice isoforms. In addition, we discuss the functional significance of NKCC2 isoforms for TAL salt retrieval and for the specific salt sensor function of macula densa cells based on studies using isoform-specific NKCC2-knockout mice. We suggest that different NKCC2 splice variants cooperate in salt retrieval along the TAL and that the coexpression of two splice variants (NKCC2B and NKCC2A) in the macula densa cells facilitates efficient salt sensing over wide ranges of fluctuating salt concentrations.
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Affiliation(s)
- Hayo Castrop
- Physiologisches Institut der Universität Regensburg, Universitätsstr. 31, D-93040 Regensburg, Germany.
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47
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Chalfoun AT, Kreydiyyeh SI. Involvement of the cytoskeleton in the effect of PGE2 on ion transport in the rat distal colon. Prostaglandins Other Lipid Mediat 2007; 85:58-64. [PMID: 18096422 DOI: 10.1016/j.prostaglandins.2007.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2007] [Revised: 08/23/2007] [Accepted: 10/26/2007] [Indexed: 10/22/2022]
Abstract
This work aimed at studying the effect of PGE2 on water and chloride absorption from the rat distal colon and at investigating the involvement of the cytoskeleton in the modulation of colonic transporters. PGE2 increased significantly net water and chloride absorption. It increased also the activity of the Na+K+-ATPase and the expression of the Na+K+2Cl- cotransporter. The increase in pump activity was ascribed to its phosphorylation by PKA or PKC when activated upon binding of PGE2 to its receptors, and was deemed responsible for the increase in Cl- absorption. Cytochalasin B (CytoB), a disrupter of microfilaments, decreased net water and chloride absorption in presence or absence of PGE2. Furthermore it down-regulated both pump and cotransporter, and lowered Na+K+-ATPase activity. It was suggested that an intact actin cytoskeleton is required for the basal and the PGE2-elicited trafficking of both transporters. On the other hand, colchicine, an inhibitor of microtubule polymerization, had no effect on the absorption of water and chloride but abrogated the stimulatory effect of PGE2. Colchicine exerted a similar effect to that of cytochlasin on the expression of both pump and cotransporter in presence or absence of PGE2 except for the basal activity of the pump which was not altered by microtubule disruption. It was concluded that both microfilament and microtubular networks are involved in the basal and PGE2-elicited increase in colonic ion absorption.
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Affiliation(s)
- Antoine T Chalfoun
- Department of Biology, Faculty of Arts & Sciences, American University of Beirut, Bliss Street, Beirut, Lebanon
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Fenton RA, Knepper MA. Mouse models and the urinary concentrating mechanism in the new millennium. Physiol Rev 2007; 87:1083-112. [PMID: 17928581 DOI: 10.1152/physrev.00053.2006] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our understanding of urinary concentrating and diluting mechanisms at the end of the 20th century was based largely on data from renal micropuncture studies, isolated perfused tubule studies, tissue analysis studies and anatomical studies, combined with mathematical modeling. Despite extensive data, several key questions remained to be answered. With the advent of the 21st century, a new approach, transgenic and knockout mouse technology, is providing critical new information about urinary concentrating processes. The central goal of this review is to summarize findings in transgenic and knockout mice pertinent to our understanding of the urinary concentrating mechanism, focusing chiefly on mice in which expression of specific renal transporters or receptors has been deleted. These include the major renal water channels (aquaporins), urea transporters, ion transporters and channels (NHE3, NKCC2, NCC, ENaC, ROMK, ClC-K1), G protein-coupled receptors (type 2 vasopressin receptor, prostaglandin receptors, endothelin receptors, angiotensin II receptors), and signaling molecules. These studies shed new light on several key questions concerning the urinary concentrating mechanism including: 1) elucidation of the role of water absorption from the descending limb of Henle in countercurrent multiplication, 2) an evaluation of the feasibility of the passive model of Kokko-Rector and Stephenson, 3) explication of the role of inner medullary collecting duct urea transport in water conservation, 4) an evaluation of the role of tubuloglomerular feedback in maintenance of appropriate distal delivery rates for effective regulation of urinary water excretion, and 5) elucidation of the importance of water reabsorption in the connecting tubule versus the collecting duct for maintenance of water balance.
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Affiliation(s)
- Robert A Fenton
- Water and Salt Research Center, Institute of Anatomy, University of Aarhus, Aarhus, Denmark.
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Wingert RA, Selleck R, Yu J, Song HD, Chen Z, Song A, Zhou Y, Thisse B, Thisse C, McMahon AP, Davidson AJ. The cdx genes and retinoic acid control the positioning and segmentation of the zebrafish pronephros. PLoS Genet 2007; 3:1922-38. [PMID: 17953490 PMCID: PMC2042002 DOI: 10.1371/journal.pgen.0030189] [Citation(s) in RCA: 252] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 09/11/2007] [Indexed: 12/11/2022] Open
Abstract
Kidney function depends on the nephron, which comprises a blood filter, a tubule that is subdivided into functionally distinct segments, and a collecting duct. How these regions arise during development is poorly understood. The zebrafish pronephros consists of two linear nephrons that develop from the intermediate mesoderm along the length of the trunk. Here we show that, contrary to current dogma, these nephrons possess multiple proximal and distal tubule domains that resemble the organization of the mammalian nephron. We examined whether pronephric segmentation is mediated by retinoic acid (RA) and the caudal (cdx) transcription factors, which are known regulators of segmental identity during development. Inhibition of RA signaling resulted in a loss of the proximal segments and an expansion of the distal segments, while exogenous RA treatment induced proximal segment fates at the expense of distal fates. Loss of cdx function caused abrogation of distal segments, a posterior shift in the position of the pronephros, and alterations in the expression boundaries of raldh2 and cyp26a1, which encode enzymes that synthesize and degrade RA, respectively. These results suggest that the cdx genes act to localize the activity of RA along the axis, thereby determining where the pronephros forms. Consistent with this, the pronephric-positioning defect and the loss of distal tubule fate were rescued in embryos doubly-deficient for cdx and RA. These findings reveal a novel link between the RA and cdx pathways and provide a model for how pronephric nephrons are segmented and positioned along the embryonic axis.
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Affiliation(s)
- Rebecca A Wingert
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Rori Selleck
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Jing Yu
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Huai-Dong Song
- Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Second Medical University, Shanghai, China
| | - Zhu Chen
- Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Second Medical University, Shanghai, China
| | - Anhua Song
- Department of Medicine, Division of Hematology/Oncology, Children's Hospital, Boston, Massachusetts, United States of America
- Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Yi Zhou
- Department of Medicine, Division of Hematology/Oncology, Children's Hospital, Boston, Massachusetts, United States of America
- Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Bernard Thisse
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
| | - Christine Thisse
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
| | - Andrew P McMahon
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Alan J Davidson
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts, United States of America
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Abstract
High salt consumption contributes to the development of hypertension and is considered an independent risk factor for vascular remodeling, cardiac hypertrophy, and stroke incidence. In this review, we discuss the molecular origins of primary sensors involved in the phenomenon of salt sensitivity. Based on the analysis of literature data, we conclude that the kidneys and central nervous system (CNS) are two major sites for salt sensing via several distinct mechanisms: 1) [Cl(-)] sensing in renal tubular fluids, primarily by Na(+)-K(+)-Cl(-) cotransporter (NKCC) isoforms NKCC2B and NKCC2A, whose expression is mainly limited to macula densa cells; 2) [Na(+)] sensing in cerebrospinal fluid (CSF) by a novel isoform of Na(+) channels, Na(x), expressed in subfornical organs; 3) sensing of CSF osmolality by mechanosensitive, nonselective cation channels (transient receptor potential vanilloid type 1 channels), expressed in neuronal cells of supraoptic and paraventricular nuclei; and 4) osmolarity sensing by volume-regulated anion channels in glial cells of supraoptic and paraventricular nuclei. Such multiplicity of salt-sensing mechanisms likely explains the differential effects of Na(+) and Cl(-) loading on the long-term maintenance of elevated blood pressure that is documented in experimental models of salt-sensitive hypertension.
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Affiliation(s)
- Sergei N Orlov
- Department of Medicine and Centre Hospitalier de l'Université de Montréal, Montreal, Quebec, Canada.
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