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Abstract
PURPOSE OF REVIEW We recently localized a new K-Cl cotransporters-3 (KCC3) transporter to the apical membrane of type-B intercalated cells. This gives us an opportunity to revisit the roles of the KCC3 in kidney and integrate the new findings to our current knowledge of the biology of the bicarbonate secreting cells. RECENT FINDINGS Here, we review the basic properties of the K-Cl cotransporter with a particular attention to the responsiveness of the transporter to cell swelling. We summarize what is already known about KCC3b and discuss new information gained from our localizing of KCC3a in type-B intercalated cells. We integrate the physiology of KCC3a with the main function of the type-B cell, that is, bicarbonate secretion through the well characterized apical Cl-/HCO3- exchanger and the basolateral Na-HCO3 cotransporter. SUMMARY Both KCC3b and KCC3a seem to be needed for maintaining cell volume during enhanced inward cotransport of Na-glucose in proximal tubule and Na-HCO3 in intercalated cells. In addition, apical KCC3a might couple to pendrin function to recycle Cl-, particularly in conditions of low salt diet and therefore low Cl- delivery to the distal tubule. This function is critical in alkalemia, and KCC3a function in the pendrin-expressing cells may contribute to the K+ loss which is observed in alkalemia.
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Affiliation(s)
- Mohammed Z Ferdaus
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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Ferdaus MZ, Terker AS, Koumangoye R, Delpire E. KCC3a, a Strong Candidate Pathway for K+ Loss in Alkalemia. Front Cell Dev Biol 2022; 10:931326. [PMID: 35874803 PMCID: PMC9301082 DOI: 10.3389/fcell.2022.931326] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 05/24/2022] [Indexed: 11/13/2022] Open
Abstract
Loss-of-function mutations in the human potassium chloride cotransporter-3 (KCC3) cause a hereditary motor sensory neuropathy associated with agenesis of the corpus callosum. While recapitulating the neuropathy, KCC3-knockout mice also exhibit high blood pressure. This phenotype is believed to have neurogenic and/or vascular origins. The role of KCC3 in the kidney is poorly understood. KCC3 is encoded by two major isoforms originating from alternative promoters: KCC3a and KCC3b, with KCC3b being the predominant transcript in the kidney. Although the transporter has previously been localized to the proximal tubule, we show here the unique expression of the KCC3a isoform in the connecting tubule. Using a KCC3a-specific polyclonal antibody validated for both immunofluorescence and immunoblotting, we showed an intense KCC3a signal restricted to cortical intercalated cells. No overlap is detected between KCC3a and sodium chloride cotransporter (NCC), a distal convoluted tubule (DCT) marker; or between KCC3a and ENaC or calbindin, which are both principal cell markers. KCC3a signal was observed in cells expressing the apical V-ATPase and pendrin, establishing a unique expression pattern characteristic of intercalated cells of type-B or type-nonA/nonB. We further show that treatment of wild-type mice with hydrochlorothiazide, amiloride, or fed a K+-deficient diet up-regulates KCC3a level, suggesting that volume depletion increases KCC3a abundance. This hypothesis was confirmed by showing a higher abundance of KCC3a protein after 23-h water restriction or after placing the mice on a low-salt diet. More importantly, abundance of the Cl−/HCO3− exchanger, pendrin, which is known to secrete bicarbonate in alkalotic conditions, was significantly diminished in KCC3-knockout mice. In addition, KCC3a abundance increased significantly alongside pendrin abundance in bicarbonate-treated alkalotic mice, providing a credible mechanism for K+ loss in metabolic alkalosis.
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Affiliation(s)
- Mohammed Zubaerul Ferdaus
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Andrew Scott Terker
- Division of Nephrology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Rainelli Koumangoye
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, United States
- *Correspondence: Eric Delpire,
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Lee JU, Lee HJ, Kim JN, Kim MK, Kim SR, Chang HS, Park CS, Park JS. Effects of Ammonium Chloride on Ozone-induced Airway Inflammation: the Role of Slc26a4 in the Lungs of Mice. J Korean Med Sci 2020; 35:e272. [PMID: 32808511 PMCID: PMC7431289 DOI: 10.3346/jkms.2020.35.e272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Accepted: 06/24/2020] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Exposure to ozone (O₃) induces neutrophilic inflammation and goblet cell hyperplasia in humans and experimental animals. Because the solute carrier family 26-member 4 (Slc26a4; pendrin) gene induces mucin production and intraluminal acidification in the airways, it was hypothesized to be a key molecule in O₃-induced airway injury. Thus, we evaluated the role of Slc26a4 and the protective effects of ammonium chloride (NH₄Cl) in O₃-induced airway injury in mice. METHODS Six-week-old female BALB/c mice were exposed to filtered air or O₃ for 21 days (2 ppm for 3 hr/day). NH₄Cl (0, 0.1, 1, and 10 mM) was administered intratracheally into the airways. Airway resistance was measured using a flexiVent system, and bronchoalveolar lavage fluid (BALF) cells were differentially counted. Slc26a4 and Muc5ac proteins and mRNA were measured via western blotting, real-time polymerase chain reaction, and immunostaining. Tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-17, IL-1β, and caspase-1 were analyzed via western blotting. RESULTS The levels Slc26a4 protein and mRNA significantly increased in lung tissues from Day 7 to Day 21 of O₃ exposure, with concomitant increases in lung resistance, numbers of goblet cells in lung tissues, and inflammatory cells and thiocyanate (SCN-) levels in BALF in a time-dependent manner. Treatment with NH₄Cl significantly reduced these changes to levels similar to those of sham-treated mice, with a concomitant reduction of Slc26a4 proteins in lung lysates and SCN- levels in BALF. Slc26a4 protein was co-expressed with muc5ac protein in the bronchial epithelium, as indicated by immunofluorescence staining. NH₄Cl treatment also significantly attenuated the O₃-induced increases in IFN-γ, TNF-α, IL-17, IL-1β, and p20-activated caspase-1. CONCLUSION Slc26a4 may be involved in O₃-induced inflammatory and epithelial changes in the airways via activation of the inflammasome and the induction of IL-17 and IFN-γ. NH₄Cl shows a potential as a therapeutic agent for controlling O₃-induced airway inflammation and epithelial damage by modulating Slc26a4 expression.
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Affiliation(s)
- Jong Uk Lee
- Division of Allergy and Respiratory Diseases, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
| | - Hyeon Ju Lee
- Division of Allergy and Respiratory Diseases, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
| | - Ji Na Kim
- Division of Allergy and Respiratory Diseases, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
| | - Min Kyung Kim
- Division of Allergy and Respiratory Diseases, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
| | - Sung Roul Kim
- Department of Environmental Health Sciences, Soonchunhyang University, Asan, Korea
| | - Hun Soo Chang
- Division of Allergy and Respiratory Diseases, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
- Soonchunhyang Medical Research Institute, Soonchunhyang University College of Medicine, Cheonan, Korea
| | - Choon Sik Park
- Division of Allergy and Respiratory Diseases, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
| | - Jong Sook Park
- Division of Allergy and Respiratory Diseases, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea.
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Himmerkus N, Svendsen SL, Quintanova C, Bleich M, Von Schwerdtner O, Benzing T, Welling PA, Leipziger J, Rinschen MM. Viewing Cortical Collecting Duct Function Through Phenotype-guided Single-Tubule Proteomics. FUNCTION (OXFORD, ENGLAND) 2020; 1:zqaa007. [PMID: 35330743 PMCID: PMC8788781 DOI: 10.1093/function/zqaa007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 06/26/2020] [Accepted: 06/29/2020] [Indexed: 01/06/2023]
Abstract
The revolution of the omics technologies has enabled profiling of the molecules of any sample. However, the heterogeneity of the kidney with highly specialized nephron segments like the cortical collecting duct (CCD) poses a challenge regarding integration of omics data and functional analysis. We examined function and proteome from the same single CCDs of C57Bl6 mice by investigating them in a double-barreled perfusion system before targeted mass spectrometry. Transepithelial voltage (Vte), transepithelial resistance, as well as amiloride-sensitive voltage (ΔVteamil) were recorded. CCDs were of 400-600 µm of length, showed lumen negative Vte between -8.5 and -32.5 mV and an equivalent short circuit current I'sc between 54 and 192 µA/cm2. On a single-tubule proteome level, intercalated cell (IC) markers strongly correlated with other intercalated cell markers and negatively with principal cell markers. Integration of proteome data with phenotype data revealed that tubular length correlated with actin and Na+-K+-ATPase expression. ΔVte(amil) reflected the expression level of the β-subunit of the epithelial sodium channel. Intriguingly, ΔVte(amil) correlated inversely with the water channel AQP2 and the negative regulator protein NEDD4L (NEDD4-2). In pendrin knockout (KO) mice, the CCD proteome was accompanied by strong downregulation of other IC markers like CLCNKB, BSND (Barttin), and VAA (vH+-ATPase), a configuration that may contribute to the salt-losing phenotype of Pendred syndrome. Proteins normally coexpressed with pendrin were decreased in pendrin KO CCDs. In conclusion, we show that functional proteomics on a single nephron segment scale allows function-proteome correlations, and may potentially help predicting function from omics data.
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Affiliation(s)
- Nina Himmerkus
- Institute of Physiology, Christian Albrechts University Kiel, Kiel, Germany
| | | | | | - Markus Bleich
- Institute of Physiology, Christian Albrechts University Kiel, Kiel, Germany
| | | | - Thomas Benzing
- Center for Molecular Medicine, University of Cologne, Cologne, Germany,Department II of Internal Medicine, University of Cologne, Cologne, Germany
| | - Paul A Welling
- Departments of Physiology and Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Jens Leipziger
- Department of Biomedicine, Aarhus University, Aarhus, Denmark,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
| | - Markus M Rinschen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark,Center for Molecular Medicine, University of Cologne, Cologne, Germany,Department II of Internal Medicine, University of Cologne, Cologne, Germany,Scripps Center for Metabolomics, Scripps Research, San Diego, CA, USA,III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany,Corresponding author. E-mail:
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Wall SM, Verlander JW, Romero CA. The Renal Physiology of Pendrin-Positive Intercalated Cells. Physiol Rev 2020; 100:1119-1147. [PMID: 32347156 PMCID: PMC7474261 DOI: 10.1152/physrev.00011.2019] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 11/06/2019] [Accepted: 11/12/2019] [Indexed: 12/13/2022] Open
Abstract
Intercalated cells (ICs) are found in the connecting tubule and the collecting duct. Of the three IC subtypes identified, type B intercalated cells are one of the best characterized and known to mediate Cl- absorption and HCO3- secretion, largely through the anion exchanger pendrin. This exchanger is thought to act in tandem with the Na+-dependent Cl-/HCO3- exchanger, NDCBE, to mediate net NaCl absorption. Pendrin is stimulated by angiotensin II and aldosterone administration via the angiotensin type 1a and the mineralocorticoid receptors, respectively. It is also stimulated in models of metabolic alkalosis, such as with NaHCO3 administration. In some rodent models, pendrin-mediated HCO3- secretion modulates acid-base balance. However, of probably more physiological or clinical significance is the role of these pendrin-positive ICs in blood pressure regulation, which occurs, at least in part, through pendrin-mediated renal Cl- absorption, as well as their effect on the epithelial Na+ channel, ENaC. Aldosterone stimulates ENaC directly through principal cell mineralocorticoid hormone receptor (ligand) binding and also indirectly through its effect on pendrin expression and function. In so doing, pendrin contributes to the aldosterone pressor response. Pendrin may also modulate blood pressure in part through its action in the adrenal medulla, where it modulates the release of catecholamines, or through an indirect effect on vascular contractile force. In addition to its role in Na+ and Cl- balance, pendrin affects the balance of other ions, such as K+ and I-. This review describes how aldosterone and angiotensin II-induced signaling regulate pendrin and the contribution of pendrin-positive ICs in the kidney to distal nephron function and blood pressure.
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Affiliation(s)
- Susan M Wall
- Departments of Medicine and Physiology, Emory University School of Medicine, Atlanta, Georgia; and Department of Medicine, University of Florida, Gainesville, Florida
| | - Jill W Verlander
- Departments of Medicine and Physiology, Emory University School of Medicine, Atlanta, Georgia; and Department of Medicine, University of Florida, Gainesville, Florida
| | - Cesar A Romero
- Departments of Medicine and Physiology, Emory University School of Medicine, Atlanta, Georgia; and Department of Medicine, University of Florida, Gainesville, Florida
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Abdulnour‐Nakhoul S, Hering‐Smith K, Hamm LL, Nakhoul NL. Effects of chronic hypercapnia on ammonium transport in the mouse kidney. Physiol Rep 2019; 7:e14221. [PMID: 31456326 PMCID: PMC6712239 DOI: 10.14814/phy2.14221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 08/06/2019] [Accepted: 08/07/2019] [Indexed: 11/24/2022] Open
Abstract
Hypercapnia and subsequent respiratory acidosis are serious complications in many patients with respiratory disorders. The acute response to hypercapnia is buffering of H+ by hemoglobin and cellular proteins but this effect is limited. The chronic response is renal compensation that increases HCO3- reabsorption, and stimulates urinary excretion of titratable acids (TA) and NH4+ . However, the main effective pathway is the excretion of NH4+ in the collecting duct. Our hypothesis is that, the renal NH3 /NH4+ transporters, Rhbg and Rhcg, in the collecting duct mediate this response. The effect of hypercapnia on these transporters is unknown. We conducted in vivo experiments on mice subjected to chronic hypercapnia. One group breathed 8% CO2 and the other breathed normal air as control (0.04% CO2 ). After 3 days, the mice were euthanized and kidneys, blood, and urine samples were collected. We used immunohistochemistry and Western blot analysis to determine the effects of high CO2 on localization and expression of the Rh proteins, carbonic anhydrase IV, and pendrin. In hypercapnic animals, there was a significant increase in urinary NH4+ excretion but no change in TA. Western blot analysis showed a significant increase in cortical expression of Rhbg (43%) but not of Rhcg. Expression of CA-IV was increased but pendrin was reduced. These data suggest that hypercapnia leads to compensatory upregulation of Rhbg that contributes to excretion of NH3 /NH4+ in the kidney. These studies are the first to show a link among hypercapnia, NH4+ excretion, and Rh expression.
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Affiliation(s)
- Solange Abdulnour‐Nakhoul
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
| | - Kathleen Hering‐Smith
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
| | - L. Lee Hamm
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
| | - Nazih L. Nakhoul
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
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Abstract
The epithelium of the kidney collecting duct (CD) is composed mainly of two different types of cells with distinct and complementary functions. CD principal cells traditionally have been considered to have a major role in Na+ and water regulation, while intercalated cells (ICs) were thought to largely modulate acid-base homeostasis. In recent years, our understanding of IC function has improved significantly owing to new research findings. Thus, we now have a new model for CD transport that integrates mechanisms of salt and water reabsorption, K+ homeostasis, and acid-base status between principal cells and ICs. There are three main types of ICs (type A, type B, and non-A, non-B), which first appear in the late distal convoluted tubule or in the connecting segment in a species-dependent manner. ICs can be detected in CD from cortex to the initial part of the inner medulla, although some transport proteins that are key components of ICs also are present in medullary CD, cells considered inner medullary. Of the three types of ICs, each has a distinct morphology and expresses different complements of membrane transport proteins that translate into very different functions in homeostasis and contributions to CD luminal pro-urine composition. This review includes recent discoveries in IC intracellular and paracrine signaling that contributes to acid-base regulation as well as Na+, Cl-, K+, and Ca2+ homeostasis. Thus, these new findings highlight the potential role of ICs as targets for potential hypertension treatments.
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Affiliation(s)
- Renee Rao
- University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of University of Southern California, Los Angeles, CA
| | - Vivek Bhalla
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Núria M Pastor-Soler
- University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of University of Southern California, Los Angeles, CA.
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Nanami M, Pham TD, Kim YH, Yang B, Sutliff RL, Staub O, Klein JD, Lopez-Cayuqueo KI, Chambrey R, Park AY, Wang X, Pech V, Verlander JW, Wall SM. The Role of Intercalated Cell Nedd4-2 in BP Regulation, Ion Transport, and Transporter Expression. J Am Soc Nephrol 2018; 29:1706-1719. [PMID: 29773687 DOI: 10.1681/asn.2017080826] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 03/29/2018] [Indexed: 12/23/2022] Open
Abstract
BackgroundNedd4-2 is an E3 ubiquitin-protein ligase that associates with transport proteins, causing their ubiquitylation, and then internalization and degradation. Previous research has suggested a correlation between Nedd4-2 and BP. In this study, we explored the effect of intercalated cell (IC) Nedd4-2 gene ablation on IC transporter abundance and function and on BP.Methods We generated IC Nedd4-2 knockout mice using Cre-lox technology and produced global pendrin/Nedd4-2 null mice by breeding global Nedd4-2 null (Nedd4-2-/- ) mice with global pendrin null (Slc26a4-/- ) mice. Mice ate a diet with 1%-4% NaCl; BP was measured by tail cuff and radiotelemetry. We measured transepithelial transport of Cl- and total CO2 and transepithelial voltage in cortical collecting ducts perfused in vitro Transporter abundance was detected with immunoblots, immunohistochemistry, and immunogold cytochemistry.Results IC Nedd4-2 gene ablation markedly increased electroneutral Cl-/HCO3- exchange in the cortical collecting duct, although benzamil-, thiazide-, and bafilomycin-sensitive ion flux changed very little. IC Nedd4-2 gene ablation did not increase the abundance of type B IC transporters, such as AE4 (Slc4a9), H+-ATPase, barttin, or the Na+-dependent Cl-/HCO3- exchanger (Slc4a8). However, IC Nedd4-2 gene ablation increased CIC-5 total protein abundance, apical plasma membrane pendrin abundance, and the ratio of pendrin expression on the apical membrane to the cytoplasm. IC Nedd4-2 gene ablation increased BP by approximately 10 mm Hg. Moreover, pendrin gene ablation eliminated the increase in BP observed in global Nedd4-2 knockout mice.Conclusions IC Nedd4-2 regulates Cl-/HCO3- exchange in ICs., Nedd4-2 gene ablation increases BP in part through its action in these cells.
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Affiliation(s)
| | | | | | - Baoli Yang
- Department of Obstetrics and Gynecology, University of Iowa, Iowa City, Iowa
| | | | - Olivier Staub
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,National Centre of Competence in Research "Kidney.ch," Zurich, Switzerland
| | | | - Karen I Lopez-Cayuqueo
- Centro de Estudios Cientificos, Valdivia, Chile.,Institut National de la Santé et de la Recherche Médicale U970, Paris Cardiovascular Research Center, Université Paris-Descartes, Paris, France
| | - Regine Chambrey
- Institut National de la Santé et de la Recherche Médicale U1188, Universite de la Reunion, Plateforme Cyclotron Réunion Océan Indien, St. Denis, Ile de la Reunion, France; and
| | | | | | | | - Jill W Verlander
- Renal Division, Department of Medicine, University of Florida at Gainesville, Gainesville, Florida
| | - Susan M Wall
- Renal and .,Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
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Wall SM. Renal intercalated cells and blood pressure regulation. Kidney Res Clin Pract 2017; 36:305-317. [PMID: 29285423 PMCID: PMC5743040 DOI: 10.23876/j.krcp.2017.36.4.305] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 11/17/2017] [Accepted: 11/20/2017] [Indexed: 12/12/2022] Open
Abstract
Type B and non-A, non-B intercalated cells are found within the connecting tubule and the cortical collecting duct. Of these cell types, type B intercalated cells are known to mediate Cl- absorption and HCO3- secretion largely through pendrin-dependent Cl-/HCO3- exchange. This exchange is stimulated by angiotensin II administration and is also stimulated in models of metabolic alkalosis, for instance after aldosterone or NaHCO3 administration. In some rodent models, pendrin-mediated HCO3- secretion modulates acid-base balance. However, the role of pendrin in blood pressure regulation is likely of more physiological or clinical significance. Pendrin regulates blood pressure not only by mediating aldosterone-sensitive Cl- absorption, but also by modulating the aldosterone response for epithelial Na+ channel (ENaC)-mediated Na+ absorption. Pendrin regulates ENaC through changes in open channel of probability, channel surface density, and channels subunit total protein abundance. Thus, aldosterone stimulates ENaC activity through both direct and indirect effects, the latter occurring through its stimulation of pendrin expression and function. Therefore, pendrin contributes to the aldosterone pressor response. Pendrin may also modulate blood pressure in part through its action in the adrenal medulla, where it modulates the release of catecholamines, or through an indirect effect on vascular contractile force. This review describes how aldosterone and angiotensin II-induced signaling regulate pendrin and the contributory role of pendrin in distal nephron function and blood pressure.
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Affiliation(s)
- Susan M. Wall
- Departments of Medicine, Emory University School of Medicine, Atlanta, GA,
USA
- Physiology, Emory University School of Medicine, Atlanta, GA,
USA
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Edwards A, Crambert G. Versatility of NaCl transport mechanisms in the cortical collecting duct. Am J Physiol Renal Physiol 2017; 313:F1254-F1263. [PMID: 28877883 DOI: 10.1152/ajprenal.00369.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 08/16/2017] [Accepted: 08/31/2017] [Indexed: 12/16/2022] Open
Abstract
The cortical collecting duct (CCD) forms part of the aldosterone-sensitive distal nephron and plays an essential role in maintaining the NaCl balance and acid-base status. The CCD epithelium comprises principal cells as well as different types of intercalated cells. Until recently, transcellular Na+ transport was thought to be restricted to principal cells, whereas (acid-secreting) type A and (bicarbonate-secreting) type B intercalated cells were associated with the regulation of acid-base homeostasis. This review describes how this traditional view has been upended by several discoveries in the past decade. A series of studies has shown that type B intercalated cells can mediate electroneutral NaCl reabsorption by a mechanism involving Na+-dependent and Na+-independent Cl-/[Formula: see text] exchange, and that is energetically driven by basolateral vacuolar H+-ATPase pumps. Other research indicates that type A intercalated cells can mediate NaCl secretion, through a bumetanide-sensitive pathway that is energized by apical H+,K+-ATPase type 2 pumps operating as Na+/K+ exchangers. We also review recent findings on the contribution of the paracellular route to NaCl transport in the CCD. Last, we describe cross-talk processes, by which one CCD cell type impacts Na+/Cl- transport in another cell type. The mechanisms that have been identified to date demonstrate clearly the interdependence of NaCl and acid-base transport systems in the CCD. They also highlight the remarkable versatility of this nephron segment.
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Affiliation(s)
- Aurélie Edwards
- Sorbonne Universités, UPMC Univ Paris 06, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and .,Department of Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Gilles Crambert
- Sorbonne Universités, UPMC Univ Paris 06, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and
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Abstract
Pendrin is a Na(+)-independent Cl(-)/HCO3(-) exchanger found in the apical regions of type B and non-A, non-B intercalated cells within the aldosterone-sensitive region of the nephron, i.e., the distal convoluted tubule (DCT), the connecting tubule (CNT), and the cortical collecting duct (CCD). Type B intercalated cells mediate Cl(-) absorption and HCO3(-) secretion primarily through pendrin-mediated Cl(-)/HCO3(-) exchange. This exchanger is upregulated with angiotensin II administration and in models of metabolic alkalosis, such as following administration of aldosterone or NaHCO3. In the absence of pendrin-mediated HCO3(-) secretion, an enhanced alkalosis is observed following aldosterone or NaHCO3 administration. However, probably of more significance is the role of pendrin in the pressor response to aldosterone. Pendrin mediates Cl(-) absorption and modulates aldosterone-induced Na(+) absorption mediated by the epithelial Na channel (ENaC). Pendrin changes ENaC activity by changing both channel open probability (Po) and surface density (N), at least partly by altering luminal HCO3(-) and ATP concentration. Thus aldosterone and angiotensin II stimulate pendrin expression and function, which stimulates ENaC activity, thereby contributing to the pressor response of these hormones. However, pendrin may modulate blood pressure partly through its extrarenal effects. For example, pendrin is expressed in the adrenal medulla, where it modulates catecholamine release. The increase in catecholamine release observed with pendrin gene ablation likely contributes to the increment in vascular contractile force observed in the pendrin null mouse. This review summarizes the signaling mechanisms that regulate pendrin abundance and function as well as the contribution of pendrin to distal nephron function.
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Affiliation(s)
- Susan M Wall
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; and Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
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Abstract
Pendrin is a Na(+)-independent Cl(-)/HCO3(-) exchanger that localizes to type B and non-A, non-B intercalated cells, which are expressed within the aldosterone-sensitive region of the nephron, i.e., the distal convoluted tubule, the connecting tubule, and the cortical collecting duct. Type B cells mediate Cl(-) absorption and HCO3(-) secretion primarily through pendrin-mediated Cl(-)/HCO3(-) exchange. At least in some treatment models, pendrin acts in tandem with the Na(+)-dependent Cl(-)/HCO3(-) exchanger (NDCBE) encoded by Slc4a8 to mediate NaCl absorption. The pendrin-mediated Cl(-)/HCO3(-) exchange process is greatly upregulated in models of metabolic alkalosis, such as following aldosterone administration or dietary NaHCO3 loading. It is also upregulated by angiotensin II. In the absence of pendrin [Slc26a4 (-/-) or pendrin null mice], aldosterone-stimulated NaCl absorption is reduced, which lowers the blood pressure response to aldosterone and enhances the alkalosis that follows the administration of this steroid hormone. Pendrin modulates aldosterone-induced Na(+) absorption by changing ENaC abundance and function through a kidney-specific mechanism that does not involve changes in the concentration of a circulating hormone. Instead, pendrin changes ENaC abundance and function at least in part by altering luminal HCO3(-) and ATP concentrations. Thus, aldosterone and angiotensin II also stimulate pendrin expression and function, which likely contributes to the pressor response of these hormones. This review summarizes the contribution of the Cl(-)/HCO3(-) exchanger pendrin in distal nephron function.
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Lazo-Fernandez Y, Aguilera G, Pham TD, Park AY, Beierwaltes WH, Sutliff RL, Verlander JW, Pacak K, Osunkoya AO, Ellis CL, Kim YH, Shipley GL, Wynne BM, Hoover RS, Sen SK, Plotsky PM, Wall SM. Pendrin localizes to the adrenal medulla and modulates catecholamine release. Am J Physiol Endocrinol Metab 2015; 309:E534-45. [PMID: 26173457 PMCID: PMC4572452 DOI: 10.1152/ajpendo.00035.2015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 07/09/2015] [Indexed: 02/02/2023]
Abstract
Pendrin (Slc26a4) is a Cl(-)/HCO3 (-) exchanger expressed in renal intercalated cells and mediates renal Cl(-) absorption. With pendrin gene ablation, blood pressure and vascular volume fall, which increases plasma renin concentration. However, serum aldosterone does not significantly increase in pendrin-null mice, suggesting that pendrin regulates adrenal zona glomerulosa aldosterone production. Therefore, we examined pendrin expression in the adrenal gland using PCR, immunoblots, and immunohistochemistry. Pendrin protein was detected in adrenal lysates from wild-type but not pendrin-null mice. However, immunohistochemistry and qPCR of microdissected adrenal zones showed that pendrin was expressed in the adrenal medulla, rather than in cortex. Within the adrenal medulla, pendrin localizes to both epinephrine- and norepinephrine-producing chromaffin cells. Therefore, we examined plasma catecholamine concentration and blood pressure in wild-type and pendrin-null mice under basal conditions and then after 5 and 20 min of immobilization stress. Under basal conditions, blood pressure was lower in the mutant than in the wild-type mice, although epinephrine and norepinephrine concentrations were similar. Catecholamine concentration and blood pressure increased markedly in both groups with stress. With 20 min of immobilization stress, epinephrine and norepinephrine concentrations increased more in pendrin-null than in wild-type mice, although stress produced a similar increase in blood pressure in both groups. We conclude that pendrin is expressed in the adrenal medulla, where it blunts stress-induced catecholamine release.
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Affiliation(s)
| | - Greti Aguilera
- Section on Endocrine Physiology, Developmental Endocrinology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Truyen D Pham
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Annie Y Park
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - William H Beierwaltes
- Hypertension and Vascular Research Division, Henry Ford Hospital and Wayne State School of Medicine, Detroit, Michigan
| | - Roy L Sutliff
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Atlanta Veterans Affairs Hospital, Atlanta, Georgia
| | - Jill W Verlander
- Department of Medicine, University of Florida, Gainesville, Florida
| | - Karel Pacak
- Program in Reproductive and Adult Endocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Adeboye O Osunkoya
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia
| | - Carla L Ellis
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia
| | - Young Hee Kim
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Gregory L Shipley
- Department of Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas
| | - Brandi M Wynne
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Robert S Hoover
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Atlanta Veterans Affairs Hospital, Atlanta, Georgia; Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Shurjo K Sen
- Cardiovascular Disease Section, and National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Paul M Plotsky
- Department of Psychiatry, Emory University School of Medicine, Atlanta, Georgia; and
| | - Susan M Wall
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
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Abstract
The H(+) concentration in human blood is kept within very narrow limits, ~40 nmol/L, despite the fact that dietary metabolism generates acid and base loads that are added to the systemic circulation throughout the life of mammals. One of the primary functions of the kidney is to maintain the constancy of systemic acid-base chemistry. The kidney has evolved the capacity to regulate blood acidity by performing three key functions: (i) reabsorb HCO3(-) that is filtered through the glomeruli to prevent its excretion in the urine; (ii) generate a sufficient quantity of new HCO3(-) to compensate for the loss of HCO3(-) resulting from dietary metabolic H(+) loads and loss of HCO3(-) in the urea cycle; and (iii) excrete HCO3(-) (or metabolizable organic anions) following a systemic base load. The ability of the kidney to perform these functions requires that various cell types throughout the nephron respond to changes in acid-base chemistry by modulating specific ion transport and/or metabolic processes in a coordinated fashion such that the urine and renal vein chemistry is altered appropriately. The purpose of the article is to provide the interested reader with a broad review of a field that began historically ~60 years ago with whole animal studies, and has evolved to where we are currently addressing questions related to kidney acid-base regulation at the single protein structure/function level.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA
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15
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Roy A, Al-bataineh MM, Pastor-Soler NM. Collecting duct intercalated cell function and regulation. Clin J Am Soc Nephrol 2015; 10:305-24. [PMID: 25632105 DOI: 10.2215/cjn.08880914] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Intercalated cells are kidney tubule epithelial cells with important roles in the regulation of acid-base homeostasis. However, in recent years the understanding of the function of the intercalated cell has become greatly enhanced and has shaped a new model for how the distal segments of the kidney tubule integrate salt and water reabsorption, potassium homeostasis, and acid-base status. These cells appear in the late distal convoluted tubule or in the connecting segment, depending on the species. They are most abundant in the collecting duct, where they can be detected all the way from the cortex to the initial part of the inner medulla. Intercalated cells are interspersed among the more numerous segment-specific principal cells. There are three types of intercalated cells, each having distinct structures and expressing different ensembles of transport proteins that translate into very different functions in the processing of the urine. This review includes recent findings on how intercalated cells regulate their intracellular milieu and contribute to acid-base regulation and sodium, chloride, and potassium homeostasis, thus highlighting their potential role as targets for the treatment of hypertension. Their novel regulation by paracrine signals in the collecting duct is also discussed. Finally, this article addresses their role as part of the innate immune system of the kidney tubule.
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Affiliation(s)
- Ankita Roy
- Renal-Electrolyte Division, Department of Medicine; and
| | | | - Núria M Pastor-Soler
- Renal-Electrolyte Division, Department of Medicine; and Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania A.R. and M.M.A. contributed equally to this work.
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16
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Ladsous M, Vlaeminck-Guillem V, Dumur V, Vincent C, Dubrulle F, Dhaenens CM, Wémeau JL. Analysis of the thyroid phenotype in 42 patients with Pendred syndrome and nonsyndromic enlargement of the vestibular aqueduct. Thyroid 2014; 24:639-48. [PMID: 24224479 DOI: 10.1089/thy.2013.0164] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Pendred syndrome (PS), a recessive disorder caused by mutations in the SLC26A4 (PDS) gene, is associated with deafness and goiter. SLC26A4 mutations have also been identified in patients exhibiting isolated sensorineural hearing loss without apparent thyroid abnormality (nonsyndromic enlargement of the vestibular aqueduct; nonsyndromic EVA). Our aim was to describe systematically the thyroidal phenotypes and the SLC26A4 genotypes of patients presenting with PS or nonsyndromic EVA. METHODS Nineteen patients with PS and 23 patients with nonsyndromic EVA, aged 5-53 years, were included. They underwent thyroid evaluation (physical examination, biological thyroid function tests, measurement of thyroglobulin level, thyroid ultrasonography, and thyroid (123)I scintigraphy with perchlorate discharge test), otological evaluation, and SLC26A4 mutation screening. RESULTS In 19 patients with PS, goiter was identified in 15 (79%) and hypothyroidism in 15 (79%); hypothyroidism was subclinical in four patients and congenital in six patients. The perchlorate discharge test (PDT) was positive in 10/16 (63%). Morphological evaluation of the inner ear using MRI and/or CT showed bilateral EVA in 15/15 PS patients. Mutation screening revealed two SLC26A4 mutant alleles in all 19 PS patients that were homozygous in two families and compound heterozygous in 12 families. In the 23 patients with nonsyndromic EVA, systematic thyroid evaluation found no abnormalities except for slightly increased thyroglobulin levels in two patients. SLC26A4 mutations were identified in 9/23 (39%). Mutations were biallelic in two (compound heterozygous) and monoallelic in seven patients. CONCLUSION The thyroid phenotype is widely variable in PS. SLC26A4 mutation screening is needed in patients exhibiting PS or nonsyndromic EVA. PS is associated with biallelic SLC26A4 mutations and nonsyndromic EVA with no, monoallelic, or biallelic SLC26A4 mutations. Systematic thyroid evaluation is recommended in patients with nonsyndromic EVA associated with one or two SLC26A4 mutations. We propose using a combination of three parameters to define and diagnose PS: (i) sensorineural deafness with bilateral EVA; (ii) thyroid abnormality comprising goiter and/or hypothyroidism and/or a positive PDT; (iii) biallelic SLC26A4 mutations.
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Affiliation(s)
- Miriam Ladsous
- 1 Department of Endocrinology, Regional University Hospital Center (CHRU) of Lille, Lille, France
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17
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Vijayakumar S, Peng H, Schwartz GJ. Galectin-3 mediates oligomerization of secreted hensin using its carbohydrate-recognition domain. Am J Physiol Renal Physiol 2013; 305:F90-9. [PMID: 23657851 DOI: 10.1152/ajprenal.00498.2012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A multidomain, multifunctional 230-kDa extracellular matrix (ECM) protein, hensin, regulates the adaptation of rabbit kidney to metabolic acidosis by remodeling collecting duct intercalated cells. Conditional deletion of hensin in intercalated cells of the mouse kidney leads to distal renal tubular acidosis and to a significant reduction in the number of cells expressing the basolateral chloride-bicarbonate exchanger kAE1, a characteristic marker of α-intercalated cells. Although hensin is secreted as a monomer, its polymerization and ECM assembly are essential for its role in the adaptation of the kidney to metabolic acidosis. Galectin-3, a unique lectin with specific affinity for β-galactoside glycoconjugates, directly interacts with hensin. Acidotic rabbits had a significant increase in the number of cells expressing galectin-3 in the collecting duct and exhibited colocalization of galectin-3 with hensin in the ECM of microdissected tubules. In this study, we confirmed the increased expression of galectin-3 in acidotic rabbit kidneys by real-time RT-PCR. Galectin-3 interacted with hensin in vitro via its carbohydrate-binding COOH-terminal domain, and the interaction was competitively inhibited by lactose, removal of the COOH-terminal domain of galectin-3, and deglycosylation of hensin. Galectin-9, a lectin with two carbohydrate-recognition domains, is also present in the rabbit kidney; galectin-9 partially oligomerized hensin in vitro. Our results demonstrate that galectin-3 plays a critical role in hensin ECM assembly by oligomerizing secreted monomeric hensin. Both the NH₂-terminal and COOH-terminal domains are required for this function. We suggest that in the case of galectin-3-null mice galectin-9 may partially substitute for the function of galectin-3.
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Affiliation(s)
- Soundarapandian Vijayakumar
- Department of Pediatrics (Pediatric Nephrology), University of Rochester School of Medicine, Rochester, NY, USA
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18
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Parker MD, Boron WF. The divergence, actions, roles, and relatives of sodium-coupled bicarbonate transporters. Physiol Rev 2013; 93:803-959. [PMID: 23589833 PMCID: PMC3768104 DOI: 10.1152/physrev.00023.2012] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.
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Affiliation(s)
- Mark D Parker
- Dept. of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4970, USA.
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19
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Abstract
Renal ammonia metabolism and transport mediates a central role in acid-base homeostasis. In contrast to most renal solutes, the majority of renal ammonia excretion derives from intrarenal production, not from glomerular filtration. Renal ammoniagenesis predominantly results from glutamine metabolism, which produces 2 NH4(+) and 2 HCO3(-) for each glutamine metabolized. The proximal tubule is the primary site for ammoniagenesis, but there is evidence for ammoniagenesis by most renal epithelial cells. Ammonia produced in the kidney is either excreted into the urine or returned to the systemic circulation through the renal veins. Ammonia excreted in the urine promotes acid excretion; ammonia returned to the systemic circulation is metabolized in the liver in a HCO3(-)-consuming process, resulting in no net benefit to acid-base homeostasis. Highly regulated ammonia transport by renal epithelial cells determines the proportion of ammonia excreted in the urine versus returned to the systemic circulation. The traditional paradigm of ammonia transport involving passive NH3 diffusion, protonation in the lumen and NH4(+) trapping due to an inability to cross plasma membranes is being replaced by the recognition of limited plasma membrane NH3 permeability in combination with the presence of specific NH3-transporting and NH4(+)-transporting proteins in specific renal epithelial cells. Ammonia production and transport are regulated by a variety of factors, including extracellular pH and K(+), and by several hormones, such as mineralocorticoids, glucocorticoids and angiotensin II. This coordinated process of regulated ammonia production and transport is critical for the effective maintenance of acid-base homeostasis.
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Affiliation(s)
- I David Weiner
- Nephrology and Hypertension Section, NF/SGVHS, Gainesville, Florida, USA.
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20
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Pech V, Thumova M, Kim YH, Agazatian D, Hummler E, Rossier BC, Weinstein AM, Nanami M, Wall SM. ENaC inhibition stimulates Cl- secretion in the mouse cortical collecting duct through an NKCC1-dependent mechanism. Am J Physiol Renal Physiol 2012; 303:F45-55. [PMID: 22496413 DOI: 10.1152/ajprenal.00030.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In cortical collecting ducts (CCDs) perfused in vitro, inhibiting the epithelial Na(+) channel (ENaC) reduces Cl(-) absorption. Since ENaC does not transport Cl(-), the purpose of this study was to determine how ENaC modulates Cl(-) absorption. Thus, Cl(-) absorption was measured in CCDs perfused in vitro that were taken from mice given aldosterone for 7 days. In wild-type mice, we observed no effect of luminal hydrochlorothiazide on either Cl(-) absorption or transepithelial voltage (V(T)). However, application of an ENaC inhibitor [benzamil (3 μM)] to the luminal fluid or application of a Na(+)-K(+)-ATPase inhibitor to the bath reduced Cl(-) absorption by ∼66-75% and nearly obliterated lumen-negative V(T). In contrast, ENaC inhibition had no effect in CCDs from collecting duct-specific ENaC-null mice (Hoxb7:CRE, Scnn1a(loxlox)). Whereas benzamil-sensitive Cl(-) absorption did not depend on CFTR, application of a Na(+)-K(+)-2Cl(-) cotransport inhibitor (bumetanide) to the bath or ablation of the gene encoding Na(+)-K(+)-2Cl(-) cotransporter 1 (NKCC1) blunted benzamil-sensitive Cl(-) absorption, although the benzamil-sensitive component of V(T) was unaffected. In conclusion, first, in CCDs from aldosterone-treated mice, most Cl(-) absorption is benzamil sensitive, whereas thiazide-sensitive Cl(-) absorption is undetectable. Second, benzamil-sensitive Cl(-) absorption occurs by inhibition of ENaC, possibly due to elimination of lumen-negative V(T). Finally, benzamil-sensitive Cl(-) flux occurs, at least in part, through transcellular transport through a pathway that depends on NKCC1.
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Affiliation(s)
- Vladimir Pech
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
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21
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Gennari FJ. Pathophysiology of Metabolic Alkalosis: A New Classification Based on the Centrality of Stimulated Collecting Duct Ion Transport. Am J Kidney Dis 2011; 58:626-36. [DOI: 10.1053/j.ajkd.2011.06.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 06/14/2011] [Indexed: 11/11/2022]
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22
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Weiner ID, Verlander JW. Role of NH3 and NH4+ transporters in renal acid-base transport. Am J Physiol Renal Physiol 2011; 300:F11-23. [PMID: 21048022 PMCID: PMC3023229 DOI: 10.1152/ajprenal.00554.2010] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 11/01/2010] [Indexed: 11/22/2022] Open
Abstract
Renal ammonia excretion is the predominant component of renal net acid excretion. The majority of ammonia excretion is produced in the kidney and then undergoes regulated transport in a number of renal epithelial segments. Recent findings have substantially altered our understanding of renal ammonia transport. In particular, the classic model of passive, diffusive NH3 movement coupled with NH4+ "trapping" is being replaced by a model in which specific proteins mediate regulated transport of NH3 and NH4+ across plasma membranes. In the proximal tubule, the apical Na+/H+ exchanger, NHE-3, is a major mechanism of preferential NH4+ secretion. In the thick ascending limb of Henle's loop, the apical Na+-K+-2Cl- cotransporter, NKCC2, is a major contributor to ammonia reabsorption and the basolateral Na+/H+ exchanger, NHE-4, appears to be important for basolateral NH4+ exit. The collecting duct is a major site for renal ammonia secretion, involving parallel H+ secretion and NH3 secretion. The Rhesus glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), are recently recognized ammonia transporters in the distal tubule and collecting duct. Rhcg is present in both the apical and basolateral plasma membrane, is expressed in parallel with renal ammonia excretion, and mediates a critical role in renal ammonia excretion and collecting duct ammonia transport. Rhbg is expressed specifically in the basolateral plasma membrane, and its role in renal acid-base homeostasis is controversial. In the inner medullary collecting duct (IMCD), basolateral Na+-K+-ATPase enables active basolateral NH4+ uptake. In addition to these proteins, several other proteins also contribute to renal NH3/NH4+ transport. The role and mechanisms of these proteins are discussed in depth in this review.
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Affiliation(s)
- I David Weiner
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, FL 32610, USA.
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23
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Hotta K, Sho M, Yamato I, Shimada K, Harada H, Akahori T, Nakamura S, Konishi N, Yagita H, Nonomura K, Nakajima Y. Direct targeting of fibroblast growth factor-inducible 14 protein protects against renal ischemia reperfusion injury. Kidney Int 2011; 79:179-88. [DOI: 10.1038/ki.2010.379] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
PURPOSE OF REVIEW Recent studies have identified a new family of ammonia-specific transporters, Rh glycoproteins, which enable NH3-specific transport. The purpose of this review is to summarize recent evidence regarding the role of Rh glycoproteins in renal ammonia transport. RECENT FINDINGS The Rh glycoproteins, RhAG/Rhag, RhBG/Rhbg and RhCG/Rhcg, transport ammonia in the form of molecular NH3, although there is some evidence suggesting the possibility of NH4 transport. RhAG/Rhag is expressed only in erythrocytes, and not in the kidney. Rhbg and Rhcg are expressed in distal nephron sites, from the distal convoluted tubule through the inner medullary collecting duct, with basolateral Rhbg expression and both apical and basolateral Rhcg expression. Whether Rhbg contributes to renal ammonia transport remains controversial. Rhcg expression parallels ammonia excretion in multiple experimental models and genetic deletion studies, both global and collecting duct-specific, demonstrate a critical role for Rhcg in both basal and acidosis-stimulated renal ammonia excretion. X-ray crystallography has defined critical structural elements in Rh glycoprotein-mediated ammonia transport. Finally, Rh glycoproteins may also function as CO2 transporters. SUMMARY No longer can NH3 transport be considered to occur only through diffusive NH3 movement. Transporter-mediated NH3 movement is fundamental to ammonia metabolism.
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Pech V, Pham TD, Hong S, Weinstein AM, Spencer KB, Duke BJ, Walp E, Kim YH, Sutliff RL, Bao HF, Eaton DC, Wall SM. Pendrin modulates ENaC function by changing luminal HCO3-. J Am Soc Nephrol 2010; 21:1928-41. [PMID: 20966128 DOI: 10.1681/asn.2009121257] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The epithelial Na(+) channel, ENaC, and the Cl(-)/HCO(3)(-) exchanger, pendrin, mediate NaCl absorption within the cortical collecting duct and the connecting tubule. Although pendrin and ENaC localize to different cell types, ENaC subunit abundance and activity are lower in aldosterone-treated pendrin-null mice relative to wild-type mice. Because pendrin mediates HCO(3)(-) secretion, we asked if increasing distal delivery of HCO(3)(-) through a pendrin-independent mechanism "rescues" ENaC function in pendrin-null mice. We gave aldosterone and NaHCO(3) to increase pendrin-dependent HCO(3)(-) secretion within the connecting tubule and cortical collecting duct, or gave aldosterone and NaHCO(3) plus acetazolamide to increase luminal HCO(3)(-) concentration, [HCO(3)(-)], independent of pendrin. Following treatment with aldosterone and NaHCO(3), pendrin-null mice had lower urinary pH and [HCO(3)(-)] as well as lower renal ENaC abundance and function than wild-type mice. With the addition of acetazolamide, however, acid-base balance as well as ENaC subunit abundance and function was similar in pendrin-null and wild-type mice. We explored whether [HCO(3)(-)] directly alters ENaC abundance and function in cultured mouse principal cells (mpkCCD). Amiloride-sensitive current and ENaC abundance rose with increased [HCO(3)(-)] on the apical or the basolateral side, independent of the substituting anion. However, ENaC was more sensitive to changes in [HCO(3)(-)] on the basolateral side of the monolayer. Moreover, increasing [HCO(3)(-)] on the apical and basolateral side of Xenopus kidney cells increased both ENaC channel density and channel activity. We conclude that pendrin modulates ENaC abundance and function, at least in part by increasing luminal [HCO(3)(-)] and/or pH.
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Affiliation(s)
- Vladimir Pech
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
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26
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Amlal H, Petrovic S, Xu J, Wang Z, Sun X, Barone S, Soleimani M. Deletion of the anion exchanger Slc26a4 (pendrin) decreases apical Cl(-)/HCO3(-) exchanger activity and impairs bicarbonate secretion in kidney collecting duct. Am J Physiol Cell Physiol 2010; 299:C33-41. [PMID: 20375274 DOI: 10.1152/ajpcell.00033.2010] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The anion exchanger Pendrin, which is encoded by SLC26A4 (human)/Slc26a4 (mouse) gene, is localized on the apical membrane of non-acid-secreting intercalated (IC) cells in the kidney cortical collecting duct (CCD). To examine its role in the mediation of bicarbonate secretion in vivo and the apical Cl(-)/HCO(3)(-) exchanger in the kidney CCD, mice with genetic deletion of pendrin were generated. The mutant mice show the complete absence of pendrin expression in their kidneys as assessed by Northern blot hybridization, Western blot, and immunofluorescence labeling. Pendrin knockout (KO) mice display significantly acidic urine at baseline [pH 5.20 in KO vs. 6.01 in wild type (WT); P < 0.0001] along with elevated serum HCO(3)(-) concentration (27.4 vs. 24 meq/l in KO vs. WT, respectively; P < 0.02), consistent with decreased bicarbonate secretion in vivo. The urine chloride excretion was comparable in WT and KO mice. For functional studies, CCDs were microperfused and IC cells were identified by their ability to trap the pH fluorescent dye BCECF. The apical Cl(-)/HCO(3)(-) exchanger activity in B-IC and non-A, non-B-IC cells, as assessed by intracellular pH monitoring, was significantly reduced in pendrin-null mice. The basolateral Cl(-)/HCO(3)(-) exchanger activity in A-IC cells and in non-A, non-B-IC cells, was not different in pendrin KO mice relative to WT animals. Urine NH(4)(+) (ammonium) excretion increased significantly, consistent with increased trapping of NH(3) in the collecting duct in pendrin KO mice. We conclude that Slc26a4 (pendrin) deletion impairs the secretion of bicarbonate in vivo and reduces apical Cl(-)/HCO(3)(-) exchanger activity in B-IC and non-A, non-B-IC cells in CCD. Additional apical Cl(-)/HCO(3)(-) exchanger(s) is (are) present in the CCD.
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Affiliation(s)
- Hassane Amlal
- Research Services, Cincinnati Department of Veterans Affairs Medical Center, Cincinnati, OH, USA
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Lee HW, Verlander JW, Bishop JM, Igarashi P, Handlogten ME, Weiner ID. Collecting duct-specific Rh C glycoprotein deletion alters basal and acidosis-stimulated renal ammonia excretion. Am J Physiol Renal Physiol 2009; 296:F1364-75. [PMID: 19321595 PMCID: PMC2692449 DOI: 10.1152/ajprenal.90667.2008] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2008] [Accepted: 03/24/2009] [Indexed: 11/22/2022] Open
Abstract
NH3 movement across plasma membranes has traditionally been ascribed to passive, lipid-phase diffusion. However, ammonia-specific transporters, Mep/Amt proteins, are present in primitive organisms and mammals express orthologs of Mep/Amt proteins, the Rh glycoproteins. These findings suggest that the mechanisms of NH3 movement in mammalian tissues should be reexamined. Rh C glycoprotein (Rhcg) is expressed in the collecting duct, where NH3 secretion is necessary for both basal and acidosis-stimulated ammonia transport. To determine whether the collecting duct secretes NH3 via Rhcg or via lipid-phase diffusion, we generated mice with collecting duct-specific Rhcg deletion (CD-KO). CD-KO mice had loxP sites flanking exons 5 and 9 of the Rhcg gene (Rhcg(fl/fl)) and expressed Cre-recombinase under control of the Ksp-cadherin promoter (Ksp-Cre). Control (C) mice were Rhcg(fl/fl) but Ksp-Cre negative. We confirmed kidney-specific genomic recombination using PCR analysis and collecting duct-specific Rhcg deletion using immunohistochemistry. Under basal conditions, urinary ammonia excretion was less in KO vs. C mice; urine pH was unchanged. After acid-loading for 7 days, CD-KO mice developed more severe metabolic acidosis than did C mice. Urinary ammonia excretion did not increase significantly on the first day of acidosis in CD-KO mice, despite an intact ability to increase urine acidification, whereas it increased significantly in C mice. On subsequent days, urinary ammonia excretion slowly increased in CD-KO mice, but was always significantly less than in C mice. We conclude that collecting duct Rhcg expression contributes to both basal and acidosis-stimulated renal ammonia excretion, indicating that collecting duct ammonia secretion is, at least in part, mediated by Rhcg and not solely by lipid diffusion.
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Affiliation(s)
- Hyun-Wook Lee
- University of Florida College of Medicine, PO Box 100224, Gainesville, FL 32610, USA
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Abstract
The family of mammalian bicarbonate transport proteins are involved in a wide-range of physiological processes. The importance of bicarbonate transport follows from the biochemistry of HCO(3)(-) itself. Bicarbonate is the waste product of mitochondrial respiration. HCO(3)(-) undergoes pH-dependent conversion into CO(2) and in doing so converts from a membrane impermeant anion into a gas that can diffuse across membranes. The CO(2)-HCO(3)(-) equilibrium forms the most important pH buffering system of our bodies. Bicarbonate transport proteins facilitate the movement of membrane-impermeant HCO(3)(-) across membranes to accelerate disposal of waste CO(2), control cellular and whole-body pH, and to regulate fluid movement and acid/base secretion. Defects of bicarbonate transport proteins manifest in diseases of most organ systems. Fourteen gene products facilitate mammalian bicarbonate transport, whose physiology and pathophysiology is discussed in the present review.
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Pech V, Zheng W, Pham TD, Verlander JW, Wall SM. Angiotensin II activates H+-ATPase in type A intercalated cells. J Am Soc Nephrol 2008; 19:84-91. [PMID: 18178800 DOI: 10.1681/asn.2007030277] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
We reported previously that angiotensin II (AngII) increases net Cl(-) absorption in mouse cortical collecting duct (CCD) by transcellular transport across type B intercalated cells (IC) via an H(+)-ATPase-and pendrin-dependent mechanism. Because intracellular trafficking regulates both pendrin and H(+)-ATPase, we hypothesized that AngII induces the subcellular redistribution of one or both of these exchangers. To answer this question, CCD from furosemide-treated mice were perfused in vitro, and the subcellular distributions of pendrin and the H(+)-ATPase were quantified using immunogold cytochemistry and morphometric analysis. Addition of AngII in vitro did not change the distribution of pendrin or H(+)-ATPase within type B IC but within type A IC increased the ratio of apical plasma membrane to cytoplasmic H(+)-ATPase three-fold. Moreover, CCDs secreted bicarbonate under basal conditions but absorbed bicarbonate in response to AngII. In summary, angiotensin II stimulates H(+) secretion into the lumen, which drives Cl(-) absorption mediated by apical Cl(-)/HCO(3)(-) exchange as well as generates more favorable electrochemical gradient for ENaC-mediated Na(+) absorption.
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Affiliation(s)
- Vladimír Pech
- Emory University School of Medicine, Renal Division, 1639 Pierce Drive, NE, WMB Room 338, Atlanta, GA 30322, USA.
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Kim YH, Pech V, Spencer KB, Beierwaltes WH, Everett LA, Green ED, Shin W, Verlander JW, Sutliff RL, Wall SM. Reduced ENaC protein abundance contributes to the lower blood pressure observed in pendrin-null mice. Am J Physiol Renal Physiol 2007; 293:F1314-24. [PMID: 17686956 DOI: 10.1152/ajprenal.00155.2007] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pendrin (encoded by Pds, Slc26a4) is a Cl(-)/HCO(3)(-) exchanger expressed in the apical regions of type B and non-A, non-B intercalated cells of kidney and mediates renal Cl(-) absorption, particularly when upregulated. Aldosterone increases blood pressure by increasing absorption of both Na(+) and Cl(-) through increased protein abundance and function of Na(+) transporters, such as the epithelial Na(+) channel (ENaC) and the Na(+)-Cl(-) cotransporter (NCC), as well as Cl(-) transporters, such as pendrin. Because aldosterone analogs do not increase blood pressure in Slc26a4(-/-) mice, we asked whether Na(+) excretion and Na(+) transporter protein abundance are altered in kidneys from these mutant mice. Thus wild-type and Slc26a4-null mice were given a NaCl-replete, a NaCl-restricted, or NaCl-replete diet and aldosterone or aldosterone analogs. Abundance of the major renal Na(+) transporters was examined with immunoblots and immunohistochemistry. Slc26a4-null mice showed an impaired ability to conserve Na(+) during dietary NaCl restriction. Under treatment conditions in which circulating aldosterone is increased, alpha-, beta-, and 85-kDa gamma-ENaC subunit protein abundances were reduced 15-35%, whereas abundance of the 70-kDa fragment of gamma-ENaC was reduced approximately 70% in Slc26a4-null relative to wild-type mice. Moreover, ENaC-dependent changes in transepithelial voltage were much lower in cortical collecting ducts from Slc26a4-null than from wild-type mice. Thus, in kidney, ENaC protein abundance and function are modulated by pendrin or through a pendrin-dependent downstream event. The reduced ENaC protein abundance and function observed in Slc26a4-null mice contribute to their lower blood pressure and reduced ability to conserve Na(+) during NaCl restriction.
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Affiliation(s)
- Young Hee Kim
- Department of Medicine, Emory University, Atlanta, Georgia, USA
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Nakaya K, Harbidge DG, Wangemann P, Schultz BD, Green ED, Wall SM, Marcus DC. Lack of pendrin HCO3- transport elevates vestibular endolymphatic [Ca2+] by inhibition of acid-sensitive TRPV5 and TRPV6 channels. Am J Physiol Renal Physiol 2007; 292:F1314-21. [PMID: 17200157 PMCID: PMC2515270 DOI: 10.1152/ajprenal.00432.2006] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The low Ca(2+) concentration ([Ca(2+)]) of mammalian endolymph in the inner ear is required for normal hearing and balance. We reported (Yamauchi et al., Biochem Biophys Res Commun 331: 1353-1357, 2005) that the epithelial Ca(2+) channels TRPV5 and TRPV6 (transient receptor potential types 5 and 6) are expressed in the vestibular system and that TRPV5 expression is stimulated by 1,25-dihydroxyvitamin D(3), as also reported in kidney. TRPV5/6 channels are known to be inhibited by extracellular acidic pH. Endolymphatic pH, [Ca(2+)], and transepithelial potential of the utricle were measured in Cl(-)/HCO(3)(-) exchanger pendrin (SLC26A4) knockout mice in vivo. Slc26a4(-/-) mice exhibit reduced pH and utricular endolymphatic potential and increased [Ca(2+)]. Monolayers of primary cultures of rat semicircular canal duct cells were grown on permeable supports, and cellular uptake of (45)Ca(2+) was measured individually from the apical and basolateral sides. Net uptake of (45)Ca(2+) was greater after incubation with 1,25-dihydroxyvitamin D(3). Net (45)Ca(2+) absorption was dramatically inhibited by low apical pH and was stimulated by apical alkaline pH. Gadolinium, lanthanum, and ruthenium red reduced apical uptake. These observations support the notion that one aspect of vestibular dysfunction in Pendred syndrome is a pathological elevation of endolymphatic [Ca(2+)] due to luminal acidification and consequent inhibition of TRPV5/6-mediated Ca(2+) absorption.
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Affiliation(s)
- Kazuhiro Nakaya
- Cellular Biophysics Laboratory, Dept. Anatomy & Physiology, Kansas State University, Manhattan, KS 66506
- Dept. of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Donald G. Harbidge
- Cellular Biophysics Laboratory, Dept. Anatomy & Physiology, Kansas State University, Manhattan, KS 66506
| | - Philine Wangemann
- Cell Physiology Laboratory, Dept. Anatomy & Physiology, Kansas State University, Manhattan, KS 66506
| | - Bruce D. Schultz
- Epithelial Cell Biology Laboratory, Dept. Anatomy & Physiology, Kansas State University, Manhattan, KS 66506
| | - Eric D. Green
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892
| | - Susan M. Wall
- Renal Division, Emory University School of Medicine, 1639 Pierce Drive NE, Atlanta, GA 30322
| | - Daniel C. Marcus
- Cellular Biophysics Laboratory, Dept. Anatomy & Physiology, Kansas State University, Manhattan, KS 66506
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Abstract
Acid-base homeostasis to a great extent relies on renal ammonia metabolism. In the past several years, seminal studies have generated important new insights into the mechanisms of renal ammonia transport. In particular, the theory that ammonia transport occurs almost exclusively through nonionic NH(3) diffusion and NH(4)(+) trapping has given way to a model postulating that a variety of proteins specifically transport NH(3) and NH(4)(+) and that this transport is critical for normal ammonia metabolism. Many of these proteins transport primarily H(+) or K(+) but also transport NH(4)(+). Nonerythroid Rh glycoproteins transport ammonia and may represent critical facilitators of ammonia transport in the kidney. This review discusses the underlying aspects of renal ammonia transport as well as specific proteins with important roles in renal ammonia transport.
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Affiliation(s)
- I. David Weiner
- Nephrology Section, North Florida/South Georgia Veterans Health System, University of Florida, Gainesville, Florida 32608
- Division of Nephrology, Hypertension and Transplantation, University of Florida, Gainesville, Florida 32608
| | - L. Lee Hamm
- Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana 70112
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Macrophage invasion contributes to degeneration of stria vascularis in Pendred syndrome mouse model. BMC Med 2006; 4:37. [PMID: 17187680 PMCID: PMC1796619 DOI: 10.1186/1741-7015-4-37] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Accepted: 12/22/2006] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Pendred syndrome, an autosomal-recessive disorder characterized by deafness and goiter, is caused by a mutation of SLC26A4, which codes for the anion exchanger pendrin. We investigated the relationship between pendrin expression and deafness using mice that have (Slc26a4+/+ or Slc26a4+/-) or lack (Slc26a4-/-) a complete Slc26a4 gene. Previously, we reported that stria vascularis of adult Slc26a4-/- mice is hyperpigmented and that marginal cells appear disorganized. Here we determine the time course of hyperpigmentation and marginal cell disorganization, and test the hypothesis that inflammation contributes to this tissue degeneration. METHODS Slc26a4-/- and age-matched control (Slc26a4+/+ or Slc26a4+/-) mice were studied at four postnatal (P) developmental stages: before and after the age that marks the onset of hearing (P10 and P15, respectively), after weaning (P28-41) and adult (P74-170). Degeneration and hyperpigmentation stria vascularis was evaluated by confocal microscopy. Gene expression in stria vascularis was analyzed by microarray and quantitative RT-PCR. In addition, the expression of a select group of genes was quantified in spiral ligament, spleen and liver to evaluate whether expression changes seen in stria vascularis are specific for stria vascularis or systemic in nature. RESULTS Degeneration of stria vascularis defined as hyperpigmentation and marginal cells disorganization was not seen at P10 or P15, but occurred after weaning and was associated with staining for CD68, a marker for macrophages. Marginal cells in Slc26a4-/-, however, had a larger apical surface area at P10 and P15. No difference in the expression of Lyzs, C3 and Cd45 was found in stria vascularis of P15 Slc26a4+/- and Slc26a4-/- mice. However, differences in expression were found after weaning and in adult mice. No difference in the expression of markers for acute inflammation, including Il1a, Il6, Il12a, Nos2 and Nos3 were found at P15, after weaning or in adults. The expression of macrophage markers including Ptprc (= Cd45), Cd68, Cd83, Lyzs, Lgals3 (= Mac2 antigen), Msr2, Cathepsins B, S, and K (Ctsb, Ctss, Ctsk) and complement components C1r, C3 and C4 was significantly increased in stria vascularis of adult Slc26a4-/- mice compared to Slc26a4+/+ mice. Expression of macrophage markers Cd45 and Cd84 and complement components C1r and C3 was increased in stria vascularis but not in spiral ligament, liver or spleen of Slc26a4-/- compared to Slc26a4+/- mice. The expression of Lyzs was increased in stria vascularis and spiral ligament but not in liver or spleen. CONCLUSION The data demonstrate that hyperpigmentation of stria vascularis and marginal cell reorganization in Slc26a4-/- mice occur after weaning, coinciding with an invasion of macrophages. The data suggest that macrophage invasion contributes to tissue degeneration in stria vascularis, and that macrophage invasion is restricted to stria vascularis and is not systemic in nature. The delayed onset of degeneration of stria vascularis suggests that a window of opportunity exists to restore/preserve hearing in mice and therefore possibly in humans suffering from Pendred syndrome.
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