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Zonnefeld AG, Cui CY, Tsitsipatis D, Piao Y, Fan J, Mazan-Mamczarz K, Xue Y, Indig FE, De S, Gorospe M. Characterization of age-associated gene expression changes in mouse sweat glands. Aging (Albany NY) 2024; 16:6717-6730. [PMID: 38637019 PMCID: PMC11087089 DOI: 10.18632/aging.205776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 03/18/2024] [Indexed: 04/20/2024]
Abstract
Evaporation of sweat on the skin surface is the major mechanism for dissipating heat in humans. The secretory capacity of sweat glands (SWGs) declines during aging, leading to heat intolerance in the elderly, but the mechanisms responsible for this decline are poorly understood. We investigated the molecular changes accompanying SWG aging in mice, where sweat tests confirmed a significant reduction of active SWGs in old mice relative to young mice. We first identified SWG-enriched mRNAs by comparing the skin transcriptome of Eda mutant Tabby male mice, which lack SWGs, with that of wild-type control mice by RNA-sequencing analysis. This comparison revealed 171 mRNAs enriched in SWGs, including 47 mRNAs encoding 'core secretory' proteins such as transcription factors, ion channels, ion transporters, and trans-synaptic signaling proteins. Among these, 28 SWG-enriched mRNAs showed significantly altered abundance in the aged male footpad skin, and 11 of them, including Foxa1, Best2, Chrm3, and Foxc1 mRNAs, were found in the 'core secretory' category. Consistent with the changes in mRNA expression levels, immunohistology revealed that higher numbers of secretory cells from old SWGs express the transcription factor FOXC1, the protein product of Foxc1 mRNA. In sum, our study identified mRNAs enriched in SWGs, including those that encode core secretory proteins, and altered abundance of these mRNAs and proteins with aging in mouse SWGs.
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Affiliation(s)
- Alexandra G. Zonnefeld
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Chang-Yi Cui
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Dimitrios Tsitsipatis
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Yulan Piao
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Jinshui Fan
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Krystyna Mazan-Mamczarz
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Yutong Xue
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Fred E. Indig
- Confocal Imaging Core Facility, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Supriyo De
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Myriam Gorospe
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
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Bourgeois S, Houillier P. State of knowledge on ammonia handling by the kidney. Pflugers Arch 2024; 476:517-531. [PMID: 38448728 PMCID: PMC11006756 DOI: 10.1007/s00424-024-02940-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/28/2024] [Accepted: 03/01/2024] [Indexed: 03/08/2024]
Abstract
The disposal of ammonia, the main proton buffer in the urine, is important for acid-base homeostasis. Renal ammonia excretion is the predominant contributor to renal net acid excretion, both under basal condition and in response to acidosis. New insights into the mechanisms of renal ammonia production and transport have been gained in the past decades. Ammonia is the only urinary solute known to be produced in the kidney and selectively transported through the different parts of the nephron. Both molecular forms of total ammonia, NH3 and NH4+, are transported by specific proteins. Proximal tubular ammoniagenesis and the activity of these transport processes determine the eventual fate of total ammonia produced and excreted by the kidney. In this review, we summarized the state of the art of ammonia handling by the kidney and highlighted the newest processes described in the last decade.
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Affiliation(s)
- Soline Bourgeois
- Institut of Physiology, University of Zurich, Zurich, Switzerland.
| | - Pascal Houillier
- Centre de Recherche Des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- Centre National de La Recherche Scientifique (CNRS), EMR 8228, Paris, France
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3
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Sun K, Wang YL, Hou CC, Shang D, Du LJ, Bai L, Zhang XY, Hao CM, Duan SZ. Collecting duct NCOR1 controls blood pressure by regulating mineralocorticoid receptor. J Adv Res 2024:S2090-1232(24)00053-5. [PMID: 38341030 DOI: 10.1016/j.jare.2024.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 11/29/2023] [Accepted: 02/04/2024] [Indexed: 02/12/2024] Open
Abstract
INTRODUCTION Nuclear receptor corepressor 1(NCOR1) is reported to play crucial roles in cardiovascular diseases, but its function in the kidney has remained obscure. OBJECTIVE We aim to elucidate the role of collecting duct NCOR1 in blood pressure (BP) regulation. METHODS AND RESULTS Collecting duct NCOR1 knockout (KO) mice manifested increased BP and aggravated vascular and renal injury in an angiotensin II (Ang II)-induced hypertensive model. KO mice also showed significantly higher BP than littermate control (LC) mice in deoxycorticosterone acetate (DOCA)-salt model. Further study showed that collecting duct NCOR1 deficiency aggravated volume and sodium retention after saline challenge. Among the sodium transporter in the collecting duct, the expression of the three epithelial sodium channel (ENaC) subunits was markedly increased in the renal medulla of KO mice. Consistently, BP in Ang II-infused KO mice decreased significantly to the similar level as those in LC mice after amiloride treatment. ChIP analysis revealed that NCOR1 deficiency increased the enrichment of mineralocorticoid receptor (MR) on the promoters of the three ENaC genes in primary inner medulla collecting duct (IMCD) cells. Co-IP results showed interaction between NCOR1 and MR, and luciferase reporter results demonstrated that NCOR1 inhibited the transcriptional activity of MR. Knockdown of MR eliminated the increased ENaC expression in primary IMCD cells isolated from KO mice. Finally, BP was significantly decreased in Ang II-infused KO mice after treatment of MR antagonist spironolactone and the difference between LC and KO mice was abolished. CONCLUSIONS NCOR1 interacts with MR to control ENaC activity in the collecting duct and to regulate sodium reabsorption and ultimately BP. Targeting NCOR1 might be a promising tactic to interrupt the volume and sodium retention of the collecting duct in hypertension.
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Affiliation(s)
- Ke Sun
- Department of Nephrology, Zhejiang University Medical College Affiliated Sir Run Run Shaw Hospital, Hangzhou, Zhejiang Province 310016, China; Division of Nephrology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Yong-Li Wang
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, China
| | - Chen-Chen Hou
- Department of Respiratory and Critical Care Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China
| | - Da Shang
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Lin-Juan Du
- Laboratory of Oral Microbiota and Systemic Diseases, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China; National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai 200011, China
| | - Lan Bai
- Laboratory of Oral Microbiota and Systemic Diseases, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China; National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai 200011, China
| | - Xing-Yu Zhang
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai 200030, China
| | - Chuan-Ming Hao
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai 200040, China.
| | - Sheng-Zhong Duan
- Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine; State Key Laboratory of Transvascular Implantation Devices, Hangzhou, Zhejiang 310000, China.
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Brady CT, Marshall A, Zhang C, Parker MD. NBCe1-B/C-knockout mice exhibit an impaired respiratory response and an enhanced renal response to metabolic acidosis. Front Physiol 2023; 14:1201034. [PMID: 37405134 PMCID: PMC10315466 DOI: 10.3389/fphys.2023.1201034] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 06/07/2023] [Indexed: 07/06/2023] Open
Abstract
The sodium-bicarbonate cotransporter (NBCe1) has three primary variants: NBCe1-A, -B and -C. NBCe1-A is expressed in renal proximal tubules in the cortical labyrinth, where it is essential for reclaiming filtered bicarbonate, such that NBCe1-A knockout mice are congenitally acidemic. NBCe1-B and -C variants are expressed in chemosensitive regions of the brainstem, while NBCe1-B is also expressed in renal proximal tubules located in the outer medulla. Although mice lacking NBCe1-B/C (KOb/c) exhibit a normal plasma pH at baseline, the distribution of NBCe1-B/C indicates that these variants could play a role in both the rapid respiratory and slower renal responses to metabolic acidosis (MAc). Therefore, in this study we used an integrative physiologic approach to investigate the response of KOb/c mice to MAc. By means of unanesthetized whole-body plethysmography and blood-gas analysis, we demonstrate that the respiratory response to MAc (increase in minute volume, decrease in pCO2) is impaired in KOb/c mice leading to a greater severity of acidemia after 1 day of MAc. Despite this respiratory impairment, the recovery of plasma pH after 3-days of MAc remained intact in KOb/c mice. Using data gathered from mice housed in metabolic cages we demonstrate a greater elevation of renal ammonium excretion and greater downregulation of the ammonia recycling enzyme glutamine synthetase in KOb/c mice on day 2 of MAc, consistent with greater renal acid-excretion. We conclude that KOb/c mice are ultimately able to defend plasma pH during MAc, but that the integrated response is disturbed such that the burden of work shifts from the respiratory system to the kidneys, delaying the recovery of pH.
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Affiliation(s)
- Clayton T. Brady
- Jacobs School of Medicine and Biomedical Sciences, Department of Physiology and Biophysics, The State University of New York: The University at Buffalo, Buffalo, NY, United States
| | - Aniko Marshall
- Jacobs School of Medicine and Biomedical Sciences, Department of Physiology and Biophysics, The State University of New York: The University at Buffalo, Buffalo, NY, United States
| | - Chen Zhang
- Jacobs School of Medicine and Biomedical Sciences, Department of Physiology and Biophysics, The State University of New York: The University at Buffalo, Buffalo, NY, United States
- Department of Biological Sciences, The State University of New York: The University at Buffalo, Buffalo, NY, United States
| | - Mark D. Parker
- Jacobs School of Medicine and Biomedical Sciences, Department of Physiology and Biophysics, The State University of New York: The University at Buffalo, Buffalo, NY, United States
- Jacobs School of Medicine and Biomedical Sciences, Department of Ophthalmology, The State University of New York: The University at Buffalo, Buffalo, NY, United States
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5
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Harris AN, Skankar M, Melanmed M, Batlle D. An Update on Kidney Ammonium Transport Along the Nephron. ADVANCES IN KIDNEY DISEASE AND HEALTH 2023; 30:189-196. [PMID: 36868733 DOI: 10.1053/j.akdh.2022.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 12/14/2022] [Indexed: 03/05/2023]
Abstract
Acid-base homeostasis is critical to the maintenance of normal health. The kidneys have a central role in bicarbonate generation, which occurs through the process of net acid excretion. Renal ammonia excretion is the predominant component of renal net acid excretion under basal conditions and in response to acid-base disturbances. Ammonia produced in the kidney is selectively transported into the urine or the renal vein. The amount of ammonia produced by the kidney that is excreted in the urine varies dramatically in response to physiological stimuli. Recent studies have advanced our understanding of ammonia metabolism's molecular mechanisms and regulation. Ammonia transport has been advanced by recognizing that the specific transport of NH3 and NH4+ by specific membrane proteins is critical to ammonia transport. Other studies show that proximal tubule protein, NBCe1, specifically the A variant, significantly regulates renal ammonia metabolism. This review discusses these critical aspects of the emerging features of ammonia metabolism and transport.
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Affiliation(s)
- Autumn N Harris
- Department of Small Animal Clinical Science, University of Florida College of Veterinary Medicine, Gainesville, FL; Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL.
| | - Mythri Skankar
- Department of Nephrology, Institute of Nephro-urology, Bengaluru, India
| | - Michal Melanmed
- Albert Einstein College of Medicine/ Montefiore Medical Center, Bronx, NY
| | - Daniel Batlle
- Northwestern University Feinberg School of Medicine, Chicago, IL
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Verlander JW, Lee HW, Wall SM, Harris AN, Weiner ID. The proximal tubule through an NBCe1-dependent mechanism regulates collecting duct phenotypic and remodeling responses to acidosis. Am J Physiol Renal Physiol 2023; 324:F12-F29. [PMID: 36264886 PMCID: PMC9762982 DOI: 10.1152/ajprenal.00175.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 10/12/2022] [Accepted: 10/13/2022] [Indexed: 02/04/2023] Open
Abstract
The renal response to acid-base disturbances involves phenotypic and remodeling changes in the collecting duct. This study examines whether the proximal tubule controls these responses. We examined mice with genetic deletion of proteins present only in the proximal tubule, either the A variant or both A and B variants of isoform 1 of the electrogenic Na+-bicarbonate cotransporter (NBCe1). Both knockout (KO) mice have spontaneous metabolic acidosis. We then determined the collecting duct phenotypic responses to this acidosis and the remodeling responses to exogenous acid loading. Despite the spontaneous acidosis in NBCe1-A KO mice, type A intercalated cells in the inner stripe of the outer medullary collecting duct (OMCDis) exhibited decreased height and reduced expression of H+-ATPase, anion exchanger 1, Rhesus B glycoprotein, and Rhesus C glycoprotein. Combined kidney-specific NBCe1-A/B deletion induced similar changes. Ultrastructural imaging showed decreased apical plasma membrane and increased vesicular H+-ATPase in OMCDis type A intercalated cell in NBCe1-A KO mice. Next, we examined the collecting duct remodeling response to acidosis. In wild-type mice, acid loading increased the proportion of type A intercalated cells in the connecting tubule (CNT) and OMCDis, and it decreased the proportion of non-A, non-B intercalated cells in the connecting tubule, and type B intercalated cells in the cortical collecting duct (CCD). These changes were absent in NBCe1-A KO mice. We conclude that the collecting duct phenotypic and remodeling responses depend on proximal tubule-dependent signaling mechanisms blocked by constitutive deletion of proximal tubule NBCe1 proteins.NEW & NOTEWORTHY This study shows that the proximal tubule regulates collecting duct phenotypic and remodeling responses to acidosis.
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Affiliation(s)
- Jill W Verlander
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Susan M Wall
- Renal Division, Emory University, Atlanta, Georgia
| | - Autumn N Harris
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
- Deparment of Small Animal Clinical Science, University of Florida College of Veterinary Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
- Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center, Gainesville, Florida
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7
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A Novel Form of Renal Tubular Acidosis Associated With Immune Checkpoint Inhibitors. Kidney Int Rep 2022; 8:197-201. [PMID: 36644354 PMCID: PMC9831939 DOI: 10.1016/j.ekir.2022.10.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 10/16/2022] [Accepted: 10/18/2022] [Indexed: 11/07/2022] Open
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8
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Purkerson JM, Everett CA, Schwartz GJ. Ammonium chloride-induced acidosis exacerbates cystitis and pyelonephritis caused by uropathogenic E. coli. Physiol Rep 2022; 10:e15471. [PMID: 36151614 PMCID: PMC9508385 DOI: 10.14814/phy2.15471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 06/16/2023] Open
Abstract
Acute pyelonephritis caused by uropathogenic E. coli (UPEC) can cause renal scarring and lead to development of chronic kidney disease. Prevention of kidney injury requires an understanding of host factors and/or UPEC adaptive responses that are permissive for UPEC colonization of the urinary tract. Although some studies have suggested urine acidification limits UPEC growth in culture, other studies have described acid-resistance mechanisms (AR) in E. coli such as the CadC/CadBA module that promotes adaptation to acid and nitrosative stress. Herein we confirm and extend our previous study by demonstrating that despite urine acidification, metabolic acidosis induced by dietary ammonium chloride (NH4 Cl-A) exacerbates cystitis and pyelonephritis in innate immune competent (C3H-HeN) mice characterized by: (1) markedly elevated UPEC burden and increased chemokine/cytokine and NOS2 mRNA expression, (2) accumulation of intravesicular debris noninvasively detected by Power Doppler Ultrasound (PDUS), and (3) collecting duct (CD) dysfunction that manifests as a urine concentration defect. Bladder debris and CD dysfunction were due to the inflammatory response, as neither was observed in Tlr4-deficient (C3H-HeJ) mice. The effect of NH4 Cl-A was unrelated to acidosis as dietary administration of hydrochloric acid (HCl-A) yielded a comparable acid-base status yet did not increase UPEC burden. NH4 Cl-A increased polyamines and decreased nitric oxide (NO) metabolites in urine indicating that excess dietary ammonium shifts arginine metabolism toward polyamines at the expense of NO synthesis. Furthermore, despite increased expression of NOS2, NO production post UPEC infection was attenuated in NH4 Cl-A mice compared to controls. Thus, in addition to induction of metabolic acidosis and urine acidification, excess dietary ammonium alters the polyamine:NO balance and thereby compromises NOS2-mediated innate immune defense.
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Affiliation(s)
- Jeffrey M. Purkerson
- Pediatric NephrologyUniversity of Rochester Medical CenterRochesterNew YorkUSA
- Strong Children's Research CenterUniversity of Rochester Medical CenterRochesterNew YorkUSA
| | - Coralee A. Everett
- Pediatric NephrologyUniversity of Rochester Medical CenterRochesterNew YorkUSA
- Strong Children's Research CenterUniversity of Rochester Medical CenterRochesterNew YorkUSA
| | - George J. Schwartz
- Pediatric NephrologyUniversity of Rochester Medical CenterRochesterNew YorkUSA
- Strong Children's Research CenterUniversity of Rochester Medical CenterRochesterNew YorkUSA
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9
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Han Z, Ma K, Tao H, Liu H, Zhang J, Sai X, Li Y, Chi M, Nian Q, Song L, Liu C. A Deep Insight Into Regulatory T Cell Metabolism in Renal Disease: Facts and Perspectives. Front Immunol 2022; 13:826732. [PMID: 35251009 PMCID: PMC8892604 DOI: 10.3389/fimmu.2022.826732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 01/24/2022] [Indexed: 11/29/2022] Open
Abstract
Kidney disease encompasses a complex set of diseases that can aggravate or start systemic pathophysiological processes through their complex metabolic mechanisms and effects on body homoeostasis. The prevalence of kidney disease has increased dramatically over the last two decades. CD4+CD25+ regulatory T (Treg) cells that express the transcription factor forkhead box protein 3 (Foxp3) are critical for maintaining immune homeostasis and preventing autoimmune disease and tissue damage caused by excessive or unnecessary immune activation, including autoimmune kidney diseases. Recent studies have highlighted the critical role of metabolic reprogramming in controlling the plasticity, stability, and function of Treg cells. They are also likely to play a vital role in limiting kidney transplant rejection and potentially promoting transplant tolerance. Metabolic pathways, such as mitochondrial function, glycolysis, lipid synthesis, glutaminolysis, and mammalian target of rapamycin (mTOR) activation, are involved in the development of renal diseases by modulating the function and proliferation of Treg cells. Targeting metabolic pathways to alter Treg cells can offer a promising method for renal disease therapy. In this review, we provide a new perspective on the role of Treg cell metabolism in renal diseases by presenting the renal microenvironment、relevant metabolites of Treg cell metabolism, and the role of Treg cell metabolism in various kidney diseases.
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Affiliation(s)
- Zhongyu Han
- Department of Nephrology, Sichuan Academy of Medical Science and Sichuan Provincial People's Hospital, Sichuan Renal Disease Clinical Research Center, University of Electronic Science and Technology of China, Chengdu, China.,Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, China.,Reproductive & Women-Children Hospital, School of Medical and Life Sciences, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Kuai Ma
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hongxia Tao
- Reproductive & Women-Children Hospital, School of Medical and Life Sciences, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Hongli Liu
- Reproductive & Women-Children Hospital, School of Medical and Life Sciences, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Jiong Zhang
- Department of Nephrology, Sichuan Academy of Medical Science and Sichuan Provincial People's Hospital, Sichuan Renal Disease Clinical Research Center, University of Electronic Science and Technology of China, Chengdu, China.,Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, China
| | - Xiyalatu Sai
- Affiliated Hospital of Inner Mongolia University for the Nationalities, Tongliao, China
| | - Yunlong Li
- Reproductive & Women-Children Hospital, School of Medical and Life Sciences, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Mingxuan Chi
- Department of Nephrology, Sichuan Academy of Medical Science and Sichuan Provincial People's Hospital, Sichuan Renal Disease Clinical Research Center, University of Electronic Science and Technology of China, Chengdu, China.,Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, China
| | - Qing Nian
- Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, China.,Department of Blood Transfusion Sicuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Linjiang Song
- Reproductive & Women-Children Hospital, School of Medical and Life Sciences, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Chi Liu
- Department of Nephrology, Sichuan Academy of Medical Science and Sichuan Provincial People's Hospital, Sichuan Renal Disease Clinical Research Center, University of Electronic Science and Technology of China, Chengdu, China.,Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, China
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10
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Lee HW, Verlander JW, Shull GE, Harris AN, Weiner ID. Acid-base effects of combined renal deletion of NBCe1-A and NBCe1-B. Am J Physiol Renal Physiol 2022; 322:F208-F224. [PMID: 35001662 PMCID: PMC8836747 DOI: 10.1152/ajprenal.00358.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 01/05/2022] [Accepted: 01/06/2022] [Indexed: 02/03/2023] Open
Abstract
The molecular mechanisms regulating ammonia metabolism are fundamental to acid-base homeostasis. Deletion of the A splice variant of Na+-bicarbonate cotransporter, electrogenic, isoform 1 (NBCe1-A) partially blocks the effect of acidosis to increase urinary ammonia excretion, and this appears to involve the dysregulated expression of ammoniagenic enzymes in the proximal tubule (PT) in the cortex but not in the outer medulla (OM). A second NBCe1 splice variant, NBCe1-B, is present throughout the PT, including the OM, where NBCe1-A is not present. The purpose of the present study was to determine the effect of combined renal deletion of NBCe1-A and NBCe1-B on systemic and PT ammonia metabolism. We generated NBCe1-A/B deletion using Cre-loxP techniques and used Cre-negative mice as controls. As renal NBCe1-A and NBCe1-B expression is limited to the PT, Cre-positive mice had PT NBCe1-A/B deletion [PT-NBCe1-A/B knockout (KO)]. Although on a basal diet, PT-NBCe1-A/B KO mice had severe metabolic acidosis, yet urinary ammonia excretion was not changed significantly. PT-NBCe1-A/B KO decreased the expression of phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase and increased the expression of glutamine synthetase, an ammonia-recycling enzyme, in PTs in both the cortex and OM. Exogenous acid loading increased ammonia excretion in control mice, but PT-NBCe1-A/B KO prevented any increase. PT-NBCe1-A/B KO significantly blunted acid loading-induced changes in phosphate-dependent glutaminase, phosphoenolpyruvate carboxykinase, and glutamine synthetase expression in PTs in both the cortex and OM. We conclude that NBCe1-B, at least in the presence of NBCe1-A deletion, contributes to PT ammonia metabolism in the OM and thereby to systemic acid-base regulation.NEW & NOTEWORTHY The results of the present study show that combined deletion of both A and B splice variants of electrogenic Na+-bicarbonate cotransporter 1 from the proximal tubule impairs acid-base homeostasis and completely blocks changes in ammonia excretion in response to acidosis, indicating that both proteins are critical to acid-base homeostasis.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Gary E Shull
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Autumn N Harris
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
- Deparment of Small Animal Clinical Science, University of Florida College of Veterinary Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
- Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center, Gainesville, Florida
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11
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Eguchi K, Izumi Y, Yasuoka Y, Nakagawa T, Ono M, Maruyama K, Matsuo N, Hiramatsu A, Inoue H, Nakayama Y, Nonoguchi H, Lee HW, Weiner ID, Kakizoe Y, Kuwabara T, Mukoyama M. Regulation of Rhcg, an ammonia transporter, by aldosterone in the kidney. J Endocrinol 2021; 249:95-112. [PMID: 33705345 PMCID: PMC9428946 DOI: 10.1530/joe-20-0267] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 03/09/2021] [Indexed: 11/08/2022]
Abstract
Rhesus C glycoprotein (Rhcg), an ammonia transporter, is a key molecule in urinary acid excretion and is expressed mainly in the intercalated cells (ICs) of the renal collecting duct. In the present study we investigated the role of aldosterone in the regulation of Rhcg expression. In in vivo experiments using C57BL/6J mice, Western blot analysis showed that continuous subcutaneous administration of aldosterone increased the expression of Rhcg in membrane fraction of the kidney. Supplementation of potassium inhibited the effect of aldosterone on the Rhcg. Next, mice were subjected to adrenalectomy with or without administration of aldosterone, and then ad libitum 0.14 M NH4Cl containing water was given. NH4Cl load increased the expression of Rhcg in membrane fraction. Adrenalectomy decreased NH4Cl-induced Rhcg expression, which was restored by administration of aldosterone. Immunohistochemical studies revealed that NH4Cl load induced the localization of Rhcg at the apical membrane of ICs in the outer medullary collecting duct. Adrenalectomy decreased NH4Cl-induced membrane localization of Rhcg, which was restored by administration of aldosterone. For in vitro experiments, IN-IC cells, an immortalized cell line stably expressing Flag-tagged Rhcg (Rhcg-Flag), were used. Western blot analysis showed that aldosterone increased the expression of Rhcg-Flag in membrane fraction, while the increase in extracellular potassium level inhibited the effect of aldosterone. Both spironolactone and Gӧ6983, a PKC inhibitor, inhibited the expression of Rhcg-Flag in the membrane fraction. These results suggest that aldosterone regulates the membrane expression of Rhcg through the mineralocorticoid receptor and PKC pathways, which is modulated by extracellular potassium level.
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Affiliation(s)
- Koji Eguchi
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Yuichiro Izumi
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Yukiko Yasuoka
- Department of Physiology, Kitasato University School of Medicine, Minami-ku, Sagamihara, Kanagawa, Japan
| | - Terumasa Nakagawa
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Makoto Ono
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Kosuke Maruyama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Naomi Matsuo
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Akiko Hiramatsu
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Hideki Inoue
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Yushi Nakayama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Hiroshi Nonoguchi
- Division of Internal Medicine, Kitasato University Medical Center, Kitamoto, Saitama, Japan
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension, and Transplantation, University of Florida College of Medicine, Gainesville, Florida, USA
| | - I David Weiner
- Division of Nephrology, Hypertension, and Transplantation, University of Florida College of Medicine, Gainesville, Florida, USA
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida, USA
| | - Yutaka Kakizoe
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Takashige Kuwabara
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
| | - Masashi Mukoyama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Chuo-ku, Kumamoto, Japan
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12
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Grishin D, Kasap E, Izotov A, Lisitsa A. Multifaceted ammonia transporters. ALL LIFE 2020. [DOI: 10.1080/26895293.2020.1812443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Affiliation(s)
- D.V. Grishin
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - E.Y. Kasap
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - A.A. Izotov
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - A.V. Lisitsa
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
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13
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Weiner ID, Verlander JW. Emerging Features of Ammonia Metabolism and Transport in Acid-Base Balance. Semin Nephrol 2020; 39:394-405. [PMID: 31300094 DOI: 10.1016/j.semnephrol.2019.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ammonia metabolism has a critical role in acid-base homeostasis and in other cellular functions. Kidneys have a central role in bicarbonate generation, which occurs through the process of net acid excretion; ammonia metabolism is the quantitatively greatest component of net acid excretion, both under basal conditions and in response to acid-base disturbances. Several recent studies have advanced our understanding substantially of the molecular mechanisms and regulation of ammonia metabolism. First, the previous paradigm that ammonia transport could be explained by passive NH3 diffusion and NH4+ trapping has been advanced by the recognition that specific transport of NH3 and of NH4+ by specific membrane proteins is critical to ammonia transport. Second, significant advances have been made in the understanding of the regulation of ammonia metabolism. Novel studies have shown that hyperkalemia directly inhibits ammonia metabolism, thereby leading to the metabolic acidosis present in type IV renal tubular acidosis. Other studies have shown that the proximal tubule protein NBCe1, specifically the A variant NBCe1-A, has a major role in regulating renal ammonia metabolism. Third, there are important sex differences in ammonia metabolism that involve structural and functional differences in the kidney. This review addresses these important aspects of ammonia metabolism and transport.
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Affiliation(s)
- I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL; Nephrology and Hypertension Section, Gainesville Veterans Affairs Medical Center, Gainesville, FL.
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL
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14
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Abstract
Acid-base balance is critical for normal life. Acute and chronic disturbances impact cellular energy metabolism, endocrine signaling, ion channel activity, neuronal activity, and cardiovascular functions such as cardiac contractility and vascular blood flow. Maintenance and adaptation of acid-base homeostasis are mostly controlled by respiration and kidney. The kidney contributes to acid-base balance by reabsorbing filtered bicarbonate, regenerating bicarbonate through ammoniagenesis and generation of protons, and by excreting acid. This review focuses on acid-base disorders caused by renal processes, both inherited and acquired. Distinct rare inherited monogenic diseases affecting acid-base handling in the proximal tubule and collecting duct have been identified. In the proximal tubule, mutations of solute carrier 4A4 (SLC4A4) (electrogenic Na+/HCO3--cotransporter Na+/bicarbonate cotransporter e1 [NBCe1]) and other genes such as CLCN5 (Cl-/H+-antiporter), SLC2A2 (GLUT2 glucose transporter), or EHHADH (enoyl-CoA, hydratase/3-hydroxyacyl CoA dehydrogenase) causing more generalized proximal tubule dysfunction can cause proximal renal tubular acidosis resulting from bicarbonate wasting and reduced ammoniagenesis. Mutations in adenosine triphosphate ATP6V1 (B1 H+-ATPase subunit), ATPV0A4 (a4 H+-ATPase subunit), SLC4A1 (anion exchanger 1), and FOXI1 (forkhead transcription factor) cause distal renal tubular acidosis type I. Carbonic anhydrase II mutations affect several nephron segments and give rise to a mixed proximal and distal phenotype. Finally, mutations in genes affecting aldosterone synthesis, signaling, or downstream targets can lead to hyperkalemic variants of renal tubular acidosis (type IV). More common forms of renal acidosis are found in patients with advanced stages of chronic kidney disease and are owing, at least in part, to a reduced capacity for ammoniagenesis.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center for Competence in Research Kidney, Switzerland.
| | - Pedro H Imenez Silva
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center for Competence in Research Kidney, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center for Competence in Research Kidney, Switzerland
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15
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Harris AN, Lee HW, Verlander JW, Weiner ID. Testosterone modulates renal ammonia metabolism. Am J Physiol Renal Physiol 2020; 318:F922-F935. [PMID: 32116019 DOI: 10.1152/ajprenal.00560.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
There are substantial sex differences in renal structure and ammonia metabolism that correlate with differences in expression of proteins involved in ammonia generation and transport. This study determined the role of testis-derived testosterone in these differences. We studied 4-mo-old male C57BL/6 mice 4 and 8 wk after either bilateral orchiectomy (ORCH) or sham-operated control surgery and determined the effect of testosterone replacement to reverse the effects of ORCH. Finally, we determined the cellular expression of androgen receptor (AR), testosterone's canonical target receptor. ORCH decreased kidney and proximal tubule size, and testosterone replacement reversed this effect. ORCH increased ammonia excretion in a testosterone-dependent fashion; this occurred despite similar food intake, which is the primary component of endogenous acid production. ORCH increased expression of both phosphoenolpyruvate, a major ammonia-generating protein, and Na+-K+-2Cl- cotransporter, which mediates thick ascending limb ammonia reabsorption; these changes were reversed with testosterone replacement. Orchiectomy also decreased expression of Na+/H+ exchanger isoform 3, which mediates proximal tubule ammonia secretion, in a testosterone-dependent pattern. Finally, ARs are expressed throughout the proximal tubule in both the male and female kidney. Testosterone, possibly acting through ARs, has dramatic effects on kidney and proximal tubule size and decreases ammonia excretion through its effects on several key proteins involved in ammonia metabolism.
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Affiliation(s)
- Autumn N Harris
- Deparment of Small Animal Clinical Science, University of Florida College of Veterinary Medicine, Gainesville, Florida.,Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida.,Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center, Gainesville, Florida
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16
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Lee HW, Harris AN, Romero MF, Welling PA, Wingo CS, Verlander JW, Weiner ID. NBCe1-A is required for the renal ammonia and K + response to hypokalemia. Am J Physiol Renal Physiol 2019; 318:F402-F421. [PMID: 31841393 DOI: 10.1152/ajprenal.00481.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Hypokalemia increases ammonia excretion and decreases K+ excretion. The present study examined the role of the proximal tubule protein NBCe1-A in these responses. We studied mice with Na+-bicarbonate cotransporter electrogenic, isoform 1, splice variant A (NBCe1-A) deletion [knockout (KO) mice] and their wild-type (WT) littermates were provided either K+ control or K+-free diet. We also used tissue sections to determine the effect of extracellular ammonia on NaCl cotransporter (NCC) phosphorylation. The K+-free diet significantly increased proximal tubule NBCe1-A and ammonia excretion in WT mice, and NBCe1-A deletion blunted the ammonia excretion response. NBCe1-A deletion inhibited the ammoniagenic/ammonia recycling enzyme response in the cortical proximal tubule (PT), where NBCe1-A is present in WT mice. In the outer medulla, where NBCe1-A is not present, the PT ammonia metabolism response was accentuated by NBCe1-A deletion. KO mice developed more severe hypokalemia and had greater urinary K+ excretion during the K+-free diet than did WT mice. This was associated with blunting of the hypokalemia-induced change in NCC phosphorylation. NBCe1-A KO mice have systemic metabolic acidosis, but experimentally induced metabolic acidosis did not alter NCC phosphorylation. Although KO mice have impaired ammonia metabolism, experiments in tissue sections showed that lack of ammonia does impair NCC phosphorylation. Finally, urinary aldosterone was greater in KO mice than in WT mice, but neither expression of epithelial Na+ channel α-, β-, and γ-subunits nor of H+-K+-ATPase α1- or α2-subunits correlated with changes in urinary K+. We conclude that NBCe1-A is critical for the effect of diet-induced hypokalemia to increase cortical proximal tubule ammonia generation and for the expected decrease in urinary K+ excretion.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Autumn N Harris
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Paul A Welling
- Nephrology Division, Departments of Medicine and Physiology, Johns Hopkins Medical School, Baltimore, Maryland
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida.,Nephrology and Hypertension Section, Gainesville Veterans Affairs Medical Center, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida.,Nephrology and Hypertension Section, Gainesville Veterans Affairs Medical Center, Gainesville, Florida
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17
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Harris AN, Lee HW, Fang L, Verlander JW, Weiner ID. Differences in acidosis-stimulated renal ammonia metabolism in the male and female kidney. Am J Physiol Renal Physiol 2019; 317:F890-F905. [PMID: 31390234 DOI: 10.1152/ajprenal.00244.2019] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Renal ammonia excretion is a critical component of acid-base homeostasis, and changes in ammonia excretion are the predominant component of increased net acid excretion in response to metabolic acidosis. We recently reported substantial sex-dependent differences in basal ammonia metabolism that correlate with sex-dependent differences in renal structure and expression of key proteins involved in ammonia metabolism. The purpose of the present study was to investigate the effect of sex on the renal ammonia response to an exogenous acid load. We studied 4-mo-old C57BL/6 mice. Ammonia excretion, which was less in male mice under basal conditions, increased in response to acid loading to a greater extent in male mice, such that maximal ammonia excretion did not differ between the sexes. Fundamental structural sex differences in the nonacid-loaded kidney persisted after acid loading, with less cortical proximal tubule volume density in the female kidney than in the male kidney, whereas collecting duct volume density was greater in the female kidney. To further investigate sex-dependent differences in the response to acid loading, we examined the expression of proteins involved in ammonia metabolism. The change in expression of phosphoenolpyruvate carboxykinase and Rh family B glycoprotein with acid loading was greater in male mice than in female mice, whereas Na+-K+-2Cl- cotransporter and inner stripe of the outer medulla intercalated cell Rh family C glycoprotein expression were significantly greater in female mice than in male mice. There was no significant sex difference in glutamine synthetase, Na+/H+ exchanger isoform 3, or electrogenic Na+-bicarbonate cotransporter 1 variant A protein expression in response to acid loading. We conclude that substantial sex-dependent differences in the renal ammonia response to acid loading enable a similar maximum ammonia excretion response.
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Affiliation(s)
- Autumn N Harris
- Department of Small Animal Clinical Sciences, University of Florida College of Veterinary Medicine, Gainesville, Florida.,Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Lijuan Fang
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida.,Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center, Gainesville, Florida
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18
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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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19
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Osis G, Webster KL, Harris AN, Lee HW, Chen C, Fang L, Romero MF, Khattri RB, Merritt ME, Verlander JW, Weiner ID. Regulation of renal NaDC1 expression and citrate excretion by NBCe1-A. Am J Physiol Renal Physiol 2019; 317:F489-F501. [PMID: 31188034 PMCID: PMC6732450 DOI: 10.1152/ajprenal.00015.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 05/20/2019] [Accepted: 06/07/2019] [Indexed: 11/22/2022] Open
Abstract
Citrate is critical for acid-base homeostasis and to prevent calcium nephrolithiasis. Both metabolic acidosis and hypokalemia decrease citrate excretion and increase expression of Na+-dicarboxylate cotransporter 1 (NaDC1; SLC13A2), the primary protein involved in citrate reabsorption. However, the mechanisms transducing extracellular signals and mediating these responses are incompletely understood. The purpose of the present study was to determine the role of the Na+-coupled electrogenic bicarbonate cotransporter (NBCe1) A variant (NBCe1-A) in citrate metabolism under basal conditions and in response to acid loading and hypokalemia. NBCe1-A deletion increased citrate excretion and decreased NaDC1 expression in the proximal convoluted tubules (PCT) and proximal straight tubules (PST) in the medullary ray (PST-MR) but not in the PST in the outer medulla (PST-OM). Acid loading wild-type (WT) mice decreased citrate excretion. NaDC1 expression increased only in the PCT and PST-MR and not in the PST-MR. In NBCe1-A knockout (KO) mice, the acid loading change in citrate excretion was unaffected, changes in PCT NaDC1 expression were blocked, and there was an adaptive increase in PST-MR. Hypokalemia in WT mice decreased citrate excretion; NaDC1 expression increased only in the PCT and PST-MR. NBCe1-A KO blocked both the citrate and NaDC1 changes. We conclude that 1) adaptive changes in NaDC1 expression in response to metabolic acidosis and hypokalemia occur specifically in the PCT and PST-MR, i.e., in cortical proximal tubule segments; 2) NBCe1-A is necessary for normal basal, metabolic acidosis and hypokalemia-stimulated citrate metabolism and does so by regulating NaDC1 expression in cortical proximal tubule segments; and 3) adaptive increases in PST-OM NaDC1 expression occur in NBCe1-A KO mice in response to acid loading that do not occur in WT mice.
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Affiliation(s)
- Gunars Osis
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Kierstin L Webster
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Autumn N Harris
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
- Department of Small Animal Clinical Sciences, University of Florida College of Veterinary Medicine, Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Chao Chen
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Lijuan Fang
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Ram B Khattri
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida
| | - Matthew E Merritt
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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20
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Fang L, Lee HW, Chen C, Harris AN, Romero MF, Verlander JW, Weiner ID. Expression of the B splice variant of NBCe1 (SLC4A4) in the mouse kidney. Am J Physiol Renal Physiol 2018; 315:F417-F428. [PMID: 29631353 PMCID: PMC6172571 DOI: 10.1152/ajprenal.00515.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 03/07/2018] [Accepted: 03/29/2018] [Indexed: 01/10/2023] Open
Abstract
Sodium-coupled bicarbonate transporters are critical for renal electrolyte transport. The electrogenic, sodium-coupled bicarbonate cotransporter, isoform 1 (NBCe1), encoded by the SLC4A4 geneencoded by the SLC4A4 gene has five multiple splice variants; the A splice variant, NBCe1-A, is the primary basolateral bicarbonate transporter in the proximal convoluted tubule. This study's purpose was to determine if there is expression of additional NBCe1 splice variants in the mouse kidney, their cellular distribution, and their regulation by metabolic acidosis. In wild-type mice, an antibody reactive only to NBCe1-A showed basolateral immunolabel only in cortical proximal tubule (PT) segments, whereas an antibody reactive to all NBCe1 splice variants (pan-NBCe1) showed basolateral immunolabel in PT segments in both the cortex and outer medulla. In mice with NBCe1-A deletion, the pan-NBCe1 antibody showed basolateral PT immunolabel in both the renal cortex and outer stripe of the outer medulla, and immunoblot analysis showed expression of a ~121-kDa protein. RT-PCR of mRNA from NBCe1-A knockout mice directed at splice variant-specific regions showed expression of only NBCe1-B mRNA. In wild-type kidney, RT-PCR confirmed expression of mRNA for the NBCe1-B splice variant and absence of mRNA for the C, D, and E splice variants. Finally, exogenous acid loading increased expression in the proximal straight tubule in the outer stripe of the outer medulla. These studies demonstrate that the NBCe1-B splice variant is present in the PT, and its expression increases in response to exogenous acid loading, suggesting it participates in the PT contribution to acid-base homeostasis.
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Affiliation(s)
- Lijuan Fang
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Chao Chen
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Autumn N Harris
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine , Gainesville, Florida
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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21
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Harris AN, Lee HW, Osis G, Fang L, Webster KL, Verlander JW, Weiner ID. Differences in renal ammonia metabolism in male and female kidney. Am J Physiol Renal Physiol 2018; 315:F211-F222. [PMID: 29561185 DOI: 10.1152/ajprenal.00084.2018] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Renal ammonia metabolism has a major role in the maintenance of acid-base homeostasis. Sex differences are well recognized as an important biological variable in many aspects of renal function, including fluid and electrolyte metabolism. However, sex differences in renal ammonia metabolism have not been previously reported. Therefore, the purpose of the current study was to investigate sex differences in renal ammonia metabolism. We studied 4-mo-old wild-type C57BL/6 mice fed a normal diet. Despite similar levels of food intake, and, thus, protein intake, which is the primary determinant of endogenous acid production, female mice excreted greater amounts of ammonia, but not titratable acids, than did male mice. This difference in ammonia metabolism was associated with fundamental structural differences between the female and male kidney. In the female mouse kidney, proximal tubules account for a lower percentage of the renal cortical parenchyma compared with the male kidney, whereas collecting ducts account for a greater percentage of the renal parenchyma than in male kidneys. To further investigate the mechanism(s) behind the greater ammonia excretion in female mice, we examined differences in the expression of proteins involved in renal ammonia metabolism and transport. Greater basal ammonia excretion in females was associated with greater expression of PEPCK, glutamine synthetase, NKCC2, Rhbg, and Rhcg than was observed in male mice. We conclude that there are sex differences in basal ammonia metabolism that involve both renal structural differences and differences in expression of proteins involved in ammonia metabolism.
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Affiliation(s)
- Autumn N Harris
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Gunars Osis
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Lijuan Fang
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Kierstin L Webster
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine , Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine , Gainesville, Florida.,Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center , Gainesville, Florida
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22
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Lee HW, Osis G, Harris AN, Fang L, Romero MF, Handlogten ME, Verlander JW, Weiner ID. NBCe1-A Regulates Proximal Tubule Ammonia Metabolism under Basal Conditions and in Response to Metabolic Acidosis. J Am Soc Nephrol 2018; 29:1182-1197. [PMID: 29483156 DOI: 10.1681/asn.2017080935] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 01/10/2018] [Indexed: 12/16/2022] Open
Abstract
Renal ammonia metabolism is the primary mechanism through which the kidneys maintain acid-base homeostasis, but the molecular mechanisms regulating renal ammonia generation are unclear. In these studies, we evaluated the role of the proximal tubule basolateral plasma membrane electrogenic sodium bicarbonate cotransporter 1 variant A (NBCe1-A) in this process. Deletion of the NBCe1-A gene caused severe spontaneous metabolic acidosis in mice. Despite this metabolic acidosis, which normally causes a dramatic increase in ammonia excretion, absolute urinary ammonia concentration was unaltered. Additionally, NBCe1-A deletion almost completely blocked the ability to increase ammonia excretion after exogenous acid loading. Under basal conditions and during acid loading, urine pH was more acidic in mice with NBCe1-A deletion than in wild-type controls, indicating that the abnormal ammonia excretion was not caused by a primary failure of urine acidification. Instead, NBCe1-A deletion altered the expression levels of multiple enzymes involved in proximal tubule ammonia generation, including phosphate-dependent glutaminase, phosphoenolpyruvate carboxykinase, and glutamine synthetase, under basal conditions and after exogenous acid loading. Deletion of NBCe1-A did not impair expression of key proteins involved in collecting duct ammonia secretion. These studies demonstrate that the integral membrane protein NBCe1-A has a critical role in basal and acidosis-stimulated ammonia metabolism through the regulation of proximal tubule ammonia-metabolizing enzymes.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Gunars Osis
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Autumn N Harris
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Lijuan Fang
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Mary E Handlogten
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida; .,Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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23
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Harris AN, Grimm PR, Lee HW, Delpire E, Fang L, Verlander JW, Welling PA, Weiner ID. Mechanism of Hyperkalemia-Induced Metabolic Acidosis. J Am Soc Nephrol 2018; 29:1411-1425. [PMID: 29483157 DOI: 10.1681/asn.2017111163] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 02/03/2018] [Indexed: 12/22/2022] Open
Abstract
Background Hyperkalemia in association with metabolic acidosis that are out of proportion to changes in glomerular filtration rate defines type 4 renal tubular acidosis (RTA), the most common RTA observed, but the molecular mechanisms underlying the associated metabolic acidosis are incompletely understood. We sought to determine whether hyperkalemia directly causes metabolic acidosis and, if so, the mechanisms through which this occurs.Methods We studied a genetic model of hyperkalemia that results from early distal convoluted tubule (DCT)-specific overexpression of constitutively active Ste20/SPS1-related proline-alanine-rich kinase (DCT-CA-SPAK).Results DCT-CA-SPAK mice developed hyperkalemia in association with metabolic acidosis and suppressed ammonia excretion; however, titratable acid excretion and urine pH were unchanged compared with those in wild-type mice. Abnormal ammonia excretion in DCT-CA-SPAK mice associated with decreased proximal tubule expression of the ammonia-generating enzymes phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase and overexpression of the ammonia-recycling enzyme glutamine synthetase. These mice also had decreased expression of the ammonia transporter family member Rhcg and decreased apical polarization of H+-ATPase in the inner stripe of the outer medullary collecting duct. Correcting the hyperkalemia by treatment with hydrochlorothiazide corrected the metabolic acidosis, increased ammonia excretion, and normalized ammoniagenic enzyme and Rhcg expression in DCT-CA-SPAK mice. In wild-type mice, induction of hyperkalemia by administration of the epithelial sodium channel blocker benzamil caused hyperkalemia and suppressed ammonia excretion.Conclusions Hyperkalemia decreases proximal tubule ammonia generation and collecting duct ammonia transport, leading to impaired ammonia excretion that causes metabolic acidosis.
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Affiliation(s)
- Autumn N Harris
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - P Richard Grimm
- Department of Physiology and Maryland Center for Kidney Discovery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee; and
| | - Lijuan Fang
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Paul A Welling
- Department of Physiology and Maryland Center for Kidney Discovery, University of Maryland School of Medicine, Baltimore, Maryland
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; .,Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center, Gainesville, Florida
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24
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Douma LG, Holzworth MR, Solocinski K, Masten SH, Miller AH, Cheng KY, Lynch IJ, Cain BD, Wingo CS, Gumz ML. Renal Na-handling defect associated with PER1-dependent nondipping hypertension in male mice. Am J Physiol Renal Physiol 2018; 314:F1138-F1144. [PMID: 29357420 DOI: 10.1152/ajprenal.00546.2017] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Many physiological functions have a circadian rhythm, including blood pressure (BP). BP is highest during the active phase, whereas during the rest period, BP dips 10-20%. Patients that do not experience this dip at night are termed "nondippers." Nondipping hypertension is associated with increased risk of cardiovascular disease. The mechanisms underlying nondipping hypertension are not understood. Without the circadian clock gene Per1, C57BL/6J mice develop nondipping hypertension on a high-salt diet plus mineralocorticoid treatment (HS/DOCP). Our laboratory has shown that PER1 regulates expression of several genes related to sodium (Na) transport in the kidney, including epithelial Na channel (ENaC) and Na chloride cotransporter (NCC). Urinary Na excretion also demonstrates a circadian pattern with a peak during active periods. We hypothesized that PER1 contributes to circadian regulation of BP via a renal Na-handling-dependent mechanism. Na-handling genes from the distal nephron were inappropriately regulated in KO mice on HS/DOCP. Additionally, the night/day ratio of Na urinary excretion by Per1 KO mice is decreased compared with WT (4 × vs. 7×, P < 0.001, n = 6 per group). Distal nephron-specific Per1 KO mice also show an inappropriate increase in expression of Na transporter genes αENaC and NCC. These results support the hypothesis that PER1 mediates control of circadian BP rhythms via the regulation of distal nephron Na transport genes. These findings have implications for the understanding of the etiology of nondipping hypertension and the subsequent development of novel therapies for this dangerous pathophysiological condition.
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Affiliation(s)
- Lauren G Douma
- Department of Medicine, University of Florida , Gainesville, Florida.,Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida
| | | | - Kristen Solocinski
- Department of Medicine, University of Florida , Gainesville, Florida.,Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida
| | - Sarah H Masten
- Department of Medicine, University of Florida , Gainesville, Florida
| | - Amber H Miller
- Department of Medicine, University of Florida , Gainesville, Florida
| | - Kit-Yan Cheng
- Department of Medicine, University of Florida , Gainesville, Florida
| | - I Jeanette Lynch
- Department of Medicine, University of Florida , Gainesville, Florida.,Research, North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Brian D Cain
- Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida
| | - Charles S Wingo
- Department of Medicine, University of Florida , Gainesville, Florida.,Research, North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Michelle L Gumz
- Department of Medicine, University of Florida , Gainesville, Florida.,Department of Biochemistry and Molecular Biology, University of Florida , Gainesville, Florida.,Research, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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25
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Rajkumar P, Cha B, Yin J, Arend LJ, Păunescu TG, Hirabayashi Y, Donowitz M, Pluznick JL. Identifying the localization and exploring a functional role for Gprc5c in the kidney. FASEB J 2018; 32:2046-2059. [PMID: 29196502 DOI: 10.1096/fj.201700610rr] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The investigation of orphan GPCRs (GPRs) has the potential to uncover novel insights into whole animal physiology. In this study, our goal was to determine the renal localization of Gprc5c, a receptor that we previously reported to be highly expressed in murine whole kidney, and to examine physiologic parameters in Gprc5c knockout (KO) mice to gain insight into function. Gprc5c localized to the apical membrane of renal proximal tubules (PTs) in mice, rats, and humans. With the comparison of Gprc5c wild-type (WT) and KO mice, we found that Gprc5c KO mice have altered acid-base homeostasis. Specifically, Gprc5c KO mice have lower blood pH and higher urine pH compared with WT mice, with a reduced level of titratable acids in their urine. In an in vitro GPCR internalization assay, we observed that Gprc5c internalization (an index of activation) was triggered by alkaline extracellular pH. Furthermore, with the use of an in vitro BCECF assay, we observed that Gprc5c increases Na+/H+ exchanger 3 (NHE3) activity at alkaline pH. We also find that the NHE3 activity is reduced in Gprc5c KO mice by 2 photon imaging in seminaphthorhodafluors (SNARF)-4F-loaded kidney sections. NHE3 is a primary contributor to apical transport of H+ in the renal PT. Together, these data imply that Gprc5c modulates the renal contribution to systemic pH homeostasis, at least in part, by taking part in the regulation of NHE3.-Rajkumar, P., Cha, B., Yin, J., Arend, L. J., Păunescu, T. G., Hirabayashi, Y., Donowitz, M., Pluznick, J. L. Identifying the localization and exploring a functional role for Gprc5c in the kidney.
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Affiliation(s)
- Premraj Rajkumar
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Boyoung Cha
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jianyi Yin
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Lois J Arend
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Teodor G Păunescu
- Division of Nephrology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Yoshio Hirabayashi
- Laboratory for Molecular Membrane Neuroscience, RIKEN Brain Science Institute, Saitama, Japan
| | - Mark Donowitz
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jennifer L Pluznick
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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26
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Alsady M, de Groot T, Kortenoeven MLA, Carmone C, Neijman K, Bekkenkamp-Grovenstein M, Engelke U, Wevers R, Baumgarten R, Korstanje R, Deen PMT. Lithium induces aerobic glycolysis and glutaminolysis in collecting duct principal cells. Am J Physiol Renal Physiol 2017; 314:F230-F239. [PMID: 29070571 DOI: 10.1152/ajprenal.00297.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Lithium, given to bipolar disorder patients, causes nephrogenic diabetes insipidus (Li-NDI), a urinary-concentrating defect. Li-NDI occurs due to downregulation of principal cell AQP2 expression, which coincides with principal cell proliferation. The metabolic effect of lithium on principal cells, however, is unknown and investigated here. In earlier studies, we showed that the carbonic anhydrase (CA) inhibitor acetazolamide attenuated Li-induced downregulation in mouse-collecting duct (mpkCCD) cells. Of the eight CAs present in mpkCCD cells, siRNA and drug treatments showed that downregulation of CA9 and to some extent CA12 attenuated Li-induced AQP2 downregulation. Moreover, lithium induced cell proliferation and increased the secretion of lactate. Lithium also increased urinary lactate levels in wild-type mice that developed Li-NDI but not in lithium-treated mice lacking ENaC, the principal cell entry site for lithium. Inhibition of aerobic glycolysis with 2-deoxyglucose (2DG) attenuated lithium-induced AQP2 downregulation in mpkCCD cells but did not attenuate Li-NDI in mice. Interestingly, NMR analysis demonstrated that lithium also increased the urinary succinate, fumarate, citrate, and NH4+ levels, which were, in contrast to lactate, not decreased by 2DG. Together, our data reveal that lithium induces aerobic glycolysis and glutaminolysis in principal cells and that inhibition of aerobic glycolysis, but not the glutaminolysis, does not attenuate Li-NDI.
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Affiliation(s)
- Mohammad Alsady
- Department of Physiology, Radboud University Medical Center , Nijmegen , The Netherlands
| | - Theun de Groot
- Department of Physiology, Radboud University Medical Center , Nijmegen , The Netherlands.,The Jackson Laboratory, Nathan Shock Center of Excellence in the Basic Biology of Aging, The Jackson Laboratory , Bar Harbor, Maine
| | | | - Claudia Carmone
- Department of Physiology, Radboud University Medical Center , Nijmegen , The Netherlands
| | - Kim Neijman
- Department of Physiology, Radboud University Medical Center , Nijmegen , The Netherlands
| | | | - Udo Engelke
- Department of Laboratory Medicine, Radboud University Medical Center , Nijmegen , The Netherlands
| | - Ron Wevers
- Department of Laboratory Medicine, Radboud University Medical Center , Nijmegen , The Netherlands
| | - Ruben Baumgarten
- Society of Experimental Laboratory Medicine , Amersfoort , The Netherlands
| | - Ron Korstanje
- The Jackson Laboratory, Nathan Shock Center of Excellence in the Basic Biology of Aging, The Jackson Laboratory , Bar Harbor, Maine
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27
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TELOH JK, WAACK IN, DE GROOT H. Prompt Rise in Urinary Ammonium Excretion Suffices To Mitigate Metabolic Acidosis in an Experimental Animal Model of Severe Normovolemic Hemodilution. Physiol Res 2017; 66:615-620. [DOI: 10.33549/physiolres.933491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Recently, we have established a model of severe stepwise normovolemic hemodilution to a hematocrit of 10 % in rats employing three different colloidal volume replacement solutions (Voluven, Volulyte and Gelafundin) that are routinely used in clinical practice at present. We did not see severe dilutional acidosis as to be expected, but a decline in urinary pH. We here looked on further mechanisms of renal acid excretion during normovolemic hemodilution. Bicarbonate, which had been removed during normovolemic hemodilution, was calculated with the help of the Henderson-Hasselbalch equation. The urinary amount of ammonium as well as phosphate was determined in residual probes. The absolute amount of free protons in urine was obtained from the pH of the respective samples. The amount of protons generated during normovolemic hemodilution was approximately 0.6 mmol. During experimental time (5.5 h), distinct urinary ammonium excretion occurred (Voluven 0.52 mmol, Volulyte 0.39 mmol and Gelafundin 0.77 mmol). Proton excretion via the phosphate buffer constituted 0.04 mmol in every experimental group. Excretion of free protons was in the range of 10-6 mmol. The present data prove that the prompt rise in urinary ammonium excretion is also valid for acute metabolic acidosis originating from severe normovolemic hemodilution.
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Affiliation(s)
- J. K. TELOH
- Institute of Physiological Chemistry, University of Duisburg-Essen, University Hospital Essen, Essen, Germany
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28
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Polymorphisms in Renal Ammonia Metabolism Genes Correlate With 24-Hour Urine pH. Kidney Int Rep 2017; 2:1111-1121. [PMID: 29270519 PMCID: PMC5733879 DOI: 10.1016/j.ekir.2017.06.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 05/23/2017] [Accepted: 06/14/2017] [Indexed: 11/24/2022] Open
Abstract
Introduction Urine pH is critical for net acid and solute excretion, but the genetic factors that contribute to its regulation are incompletely understood. Methods We tested the association of single nucleotide polymorphisms (SNPs) from 16 genes related to ammonia (NH3) metabolism (15 biological candidates selected a priori, 1 selected from a previous genome-wide association study analysis) to that of 24-hour urine pH in 2493 individuals of European descent across 2 different cohorts using linear regression, adjusting for age, sex, and body mass index. Results Of 2871 total SNPs in these genes, 13 SNPs in ATP6V0A4 (a4 subunit of hydrogen− adenosine triphosphatase), SLC9A3 (sodium/hydrogen exchanger, isoform 3), and RHCG (Rhesus C glycoprotein), and 12 SNPs from insulin-like growth factor binding protein 7 (IGFBP7) had a meta-analysis P value <0.01 in the joint analysis plus a consistent direction of effect and at a least suggestive association (P < 0.1) in both cohorts. The maximal effect size (in pH units) for each additional minor allele of the identified SNPs was −0.13 for IGFBP7, −0.08 for ATP6V0A4, 0.06 for RHCG, and −0.06 for SLC9A3; SNP rs34447434 in IGFBP7 had the lowest meta-analysis P value (P = 7.1 × 10−8). After adjusting for net alkali absorption, urine pH remained suggestively associated with multiple SNPs in IGFBP, 1 SNP in ATP6V0A4, and a new SNP in GLS (phosphate-dependent glutaminase). Discussion Overall, these findings suggest that variants in common genes involved in ammonia metabolism may substantively contribute to basal urine pH regulation. These variations might influence the likelihood of developing disease conditions associated with altered urine pH, such as uric acid or calcium phosphate kidney stones.
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29
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Postoperative Compensatory Ammonium Excretion Subsequent to Systemic Acidosis in Cardiac Patients. BIOMED RESEARCH INTERNATIONAL 2017; 2017:5383574. [PMID: 28612026 PMCID: PMC5458371 DOI: 10.1155/2017/5383574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 03/01/2017] [Accepted: 04/26/2017] [Indexed: 11/18/2022]
Abstract
Background Postoperative acid-base imbalances, usually acidosis, frequently occur after cardiac surgery. In most cases, the human body, not suffering from any severe preexisting illnesses regarding lung, liver, and kidney, is capable of transient compensation and final correction. The aim of this study was to correlate the appearance of postoperatively occurring acidosis with renal ammonium excretion. Materials and Methods Between 07/2014 and 10/2014, a total of 25 consecutive patients scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass were enrolled in this prospective observational study. During the operative procedure and the first two postoperative days, blood gas analyses were carried out and urine samples collected. Urine samples were analyzed for the absolute amount of ammonium. Results Of all patients, thirteen patients developed acidosis as an initial disturbance in the postoperative period: five of respiratory and eight of metabolic origin. Four patients with respiratory acidosis but none of those with metabolic acidosis subsequently developed a base excess > +2 mEq/L. Conclusion Ammonium excretion correlated with the increase in base excess. The acidosis origin seems to have a large influence on renal compensation in terms of ammonium excretion and the possibility of an overcorrection.
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30
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Lee HW, Osis G, Handlogten ME, Verlander JW, Weiner ID. Proximal tubule glutamine synthetase expression is necessary for the normal response to dietary protein restriction. Am J Physiol Renal Physiol 2017; 313:F116-F125. [PMID: 28331060 DOI: 10.1152/ajprenal.00048.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/15/2017] [Accepted: 03/20/2017] [Indexed: 01/15/2023] Open
Abstract
Dietary protein restriction has multiple benefits in kidney disease. Because protein intake is a major determinant of endogenous acid production, it is important that net acid excretion changes in parallel during changes in dietary protein intake. Dietary protein restriction decreases endogenous acid production and decreases urinary ammonia excretion, a major component of net acid excretion. Glutamine synthetase (GS) catalyzes the reaction of [Formula: see text] and glutamate, which regenerates the essential amino acid glutamine and decreases net ammonia generation. Because renal proximal tubule GS expression increases during dietary protein restriction, this could contribute to the decreased ammonia excretion. The purpose of the current study was to determine the role of proximal tubule GS in the renal response to protein restriction. We generated mice with proximal tubule-specific GS deletion (PT-GS-KO) using Cre-loxP techniques. Cre-negative (Control) and PT-GS-KO mice in metabolic cages were provided 20% protein diet for 2 days and were then changed to low-protein (6%) diet for the next 7 days. Additional PT-GS-KO mice were maintained on 20% protein diet. Dietary protein restriction caused a rapid decrease in urinary ammonia excretion in both genotypes, but PT-GS-KO blunted this adaptive response significantly. This occurred despite no significant genotype-dependent differences in urinary pH or in serum electrolytes. There were no significant differences between Control and PT-GS-KO mice in expression of multiple other proteins involved in renal ammonia handling. We conclude that proximal tubule GS expression is necessary for the appropriate decrease in ammonia excretion during dietary protein restriction.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida; and
| | - Gunars Osis
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida; and
| | - Mary E Handlogten
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida; and
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida; and
| | - I David Weiner
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida; and .,Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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31
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Abstract
Acid-base homeostasis is critical to maintenance of normal health. Renal ammonia excretion is the quantitatively predominant component of renal net acid excretion, both under basal conditions and in response to acid-base disturbances. Although titratable acid excretion also contributes to renal net acid excretion, the quantitative contribution of titratable acid excretion is less than that of ammonia under basal conditions and is only a minor component of the adaptive response to acid-base disturbances. In contrast to other urinary solutes, ammonia is produced in the kidney and then is selectively transported either into the urine or the renal vein. The proportion of ammonia that the kidney produces that is excreted in the urine varies dramatically in response to physiological stimuli, and only urinary ammonia excretion contributes to acid-base homeostasis. As a result, selective and regulated renal ammonia transport by renal epithelial cells is central to acid-base homeostasis. Both molecular forms of ammonia, NH3 and NH4+, are transported by specific proteins, and regulation of these transport processes determines the eventual fate of the ammonia produced. In this review, we discuss these issues, and then discuss in detail the specific proteins involved in renal epithelial cell ammonia transport.
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Affiliation(s)
- I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; and Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; and Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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32
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Osis G, Handlogten ME, Lee HW, Hering-Smith KS, Huang W, Romero MF, Verlander JW, Weiner ID. Effect of NBCe1 deletion on renal citrate and 2-oxoglutarate handling. Physiol Rep 2016; 4:4/8/e12778. [PMID: 27117802 PMCID: PMC4848728 DOI: 10.14814/phy2.12778] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 04/01/2016] [Indexed: 12/03/2022] Open
Abstract
The bicarbonate transporter, NBCe1 (SLC4A4), is necessary for at least two components of the proximal tubule contribution to acid‐base homeostasis, filtered bicarbonate reabsorption, and ammonia metabolism. This study's purpose was to determine NBCe1's role in a third component of acid‐base homeostasis, organic anion metabolism, by studying mice with NBCe1 deletion. Because NBCe1 deletion causes metabolic acidosis, we also examined acid‐loaded wild‐type adult mice to determine if the effects of NBCe1 deletion were specific to NBCe1 deletion or were a non‐specific effect of the associated metabolic acidosis. Both NBCe1 KO and acid‐loading decreased citrate excretion, but in contrast to metabolic acidosis alone, NBCe1 KO decreased expression of the apical citrate transporter, NaDC‐1. Thus, NBCe1 expression is necessary for normal NaDC‐1 expression, and NBCe1 deletion induces a novel citrate reabsorptive pathway. Second, NBCe1 KO increased 2‐oxoglutarate excretion. This could not be attributed to the metabolic acidosis as experimental acidosis decreased excretion. Increased 2‐oxoglutarate excretion could not be explained by changes in plasma 2‐oxoglutarate levels, the glutaminase I or the glutaminase II generation pathways, 2‐oxoglutarate metabolism, its putative apical 2‐oxoglutarate transporter, OAT10, or its basolateral transporter, NaDC‐3. In summary: (1) NBCe1 is necessary for normal proximal tubule NaDC‐1 expression; (2) NBCe1 deletion results in stimulation of a novel citrate reabsorptive pathway; and (3) NBCe1 is necessary for normal 2‐oxoglutarate metabolism through mechanisms independent of expression of known transport and metabolic pathways.
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Affiliation(s)
- Gunars Osis
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Mary E Handlogten
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | | | - Weitao Huang
- Renal Division, Tulane University College of Medicine, New Orleans, Louisiana
| | - Michael F Romero
- Department of Physiology & Biomedical Engineering and Nephrology & Hypertension, Mayo Clinic College Of Medicine, Rochester, Minnesota
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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Weiner ID, Verlander JW. Recent advances in understanding renal ammonia metabolism and transport. Curr Opin Nephrol Hypertens 2016; 25:436-43. [PMID: 27367914 PMCID: PMC4974126 DOI: 10.1097/mnh.0000000000000255] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PURPOSE OF REVIEW The purpose of this review is to provide a succinct description of the recent findings that advance our understanding of the fundamental renal process of ammonia metabolism and transport in conditions relevant to the clinician. RECENT FINDINGS Recent studies advance our understanding of renal ammonia metabolism. Mechanisms through which chronic kidney disease and altered dietary protein intake alter ammonia excretion have been identified. Lithium, although it can acutely cause distal renal tubular acidosis, was shown with long-term use to increase urinary ammonia excretion, and this appeared to be mediated, at least in part, by increased Rhcg expression. Gene deletion studies showed that the ammonia recycling enzyme, glutamine synthetase, has a critical role in normal-stimulated and acidosis-stimulated ammonia metabolism and that the proximal tubule basolateral bicarbonate transporter, NBCe1, is necessary for normal ammonia metabolism. Finally, our understanding of the molecular ammonia species, NH3 versus NH4, transported by Rh glycoproteins continues to be advanced. SUMMARY Fundamental studies have been recently published that advance our understanding of the regulation of ammonia metabolism in clinically important circumstances, and our understanding of the mechanisms and regulation of proximal tubule ammonia generation, and the mechanisms through which Rh glycoproteins contribute to ammonia secretion.
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Affiliation(s)
- I. David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL 32610
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, FL 32611
| | - Jill W. Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL 32610
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Lee HW, Osis G, Handlogten ME, Lamers WH, Chaudhry FA, Verlander JW, Weiner ID. Proximal tubule-specific glutamine synthetase deletion alters basal and acidosis-stimulated ammonia metabolism. Am J Physiol Renal Physiol 2016; 310:F1229-42. [PMID: 27009341 PMCID: PMC4935770 DOI: 10.1152/ajprenal.00547.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 03/13/2016] [Indexed: 02/07/2023] Open
Abstract
Glutamine synthetase (GS) catalyzes the recycling of NH4 (+) with glutamate to form glutamine. GS is highly expressed in the renal proximal tubule (PT), suggesting ammonia recycling via GS could decrease net ammoniagenesis and thereby limit ammonia available for net acid excretion. The purpose of the present study was to determine the role of PT GS in ammonia metabolism under basal conditions and during metabolic acidosis. We generated mice with PT-specific GS deletion (PT-GS-KO) using Cre-loxP techniques. Under basal conditions, PT-GS-KO increased urinary ammonia excretion significantly. Increased ammonia excretion occurred despite decreased expression of key proteins involved in renal ammonia generation. After the induction of metabolic acidosis, the ability to increase ammonia excretion was impaired significantly by PT-GS-KO. The blunted increase in ammonia excretion occurred despite greater expression of multiple components of ammonia generation, including SN1 (Slc38a3), phosphate-dependent glutaminase, phosphoenolpyruvate carboxykinase, and Na(+)-coupled electrogenic bicarbonate cotransporter. We conclude that 1) GS-mediated ammonia recycling in the PT contributes to both basal and acidosis-stimulated ammonia metabolism and 2) adaptive changes in other proteins involved in ammonia metabolism occur in response to PT-GS-KO and cause an underestimation of the role of PT GS expression.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Gunars Osis
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Mary E Handlogten
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Wouter H Lamers
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Farrukh A Chaudhry
- Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway; and
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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Handlogten ME, Osis G, Lee HW, Romero MF, Verlander JW, Weiner ID. NBCe1 expression is required for normal renal ammonia metabolism. Am J Physiol Renal Physiol 2015; 309:F658-66. [PMID: 26224717 PMCID: PMC4593816 DOI: 10.1152/ajprenal.00219.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 07/26/2015] [Indexed: 11/22/2022] Open
Abstract
The mechanisms regulating proximal tubule ammonia metabolism are incompletely understood. The present study addressed the role of the proximal tubule basolateral electrogenic Na(+)-coupled bicarbonate cotransporter (NBCe1; Slc4a4) in renal ammonia metabolism. We used mice with heterozygous and homozygous NBCe1 gene deletion and compared these mice with their wild-type littermates. Because homozygous NBCe1 gene deletion causes 100% mortality before day 25, we studied mice at day 8 (±1 day). Both heterozygous and homozygous gene deletion caused a gene dose-related decrease in serum bicarbonate. The ability to lower urinary pH was intact, and even accentuated, with NBCe1 deletion. However, in contrast to the well-known effect of metabolic acidosis to increase urinary ammonia excretion, NBCe1 deletion caused a gene dose-related decrease in ammonia excretion. There was no identifiable change in proximal tubule structure by light microscopy. Examination of proteins involved in renal ammonia metabolism showed decreased expression of phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase, key enzymes in proximal tubule ammonia generation, and increased expression of glutamine synthetase, which recycles intrarenal ammonia and regenerates glutamine. Expression of key proteins involved in ammonia transport outside of the proximal tubule (rhesus B glycoprotein and rhesus C glycoprotein) was not significantly changed by NBCe1 deletion. We conclude from these findings that NBCe1 expression is necessary for normal proximal tubule ammonia metabolism.
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Affiliation(s)
- Mary E Handlogten
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Gunars Osis
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering and Nephrology and Hypertension, Mayo Clinic College Of Medicine, Rochester, Minnesota; and
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center, Gainesville, Florida
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Noiret L, Baigent S, Jalan R, Thomas SR. Mathematical Model of Ammonia Handling in the Rat Renal Medulla. PLoS One 2015; 10:e0134477. [PMID: 26280830 PMCID: PMC4539222 DOI: 10.1371/journal.pone.0134477] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 07/10/2015] [Indexed: 01/19/2023] Open
Abstract
The kidney is one of the main organs that produces ammonia and release it into the circulation. Under normal conditions, between 30 and 50% of the ammonia produced in the kidney is excreted in the urine, the rest being absorbed into the systemic circulation via the renal vein. In acidosis and in some pathological conditions, the proportion of urinary excretion can increase to 70% of the ammonia produced in the kidney. Mechanisms regulating the balance between urinary excretion and renal vein release are not fully understood. We developed a mathematical model that reflects current thinking about renal ammonia handling in order to investigate the role of each tubular segment and identify some of the components which might control this balance. The model treats the movements of water, sodium chloride, urea, NH3 and NH4+, and non-reabsorbable solute in an idealized renal medulla of the rat at steady state. A parameter study was performed to identify the transport parameters and microenvironmental conditions that most affect the rate of urinary ammonia excretion. Our results suggest that urinary ammonia excretion is mainly determined by those parameters that affect ammonia recycling in the loops of Henle. In particular, our results suggest a critical role for interstitial pH in the outer medulla and for luminal pH along the inner medullary collecting ducts.
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Affiliation(s)
- Lorette Noiret
- CoMPLEX, University College London (UCL), London, United Kingdom
- * E-mail:
| | - Stephen Baigent
- CoMPLEX, University College London (UCL), London, United Kingdom
- Mathematics, UCL, London, United Kingdom
| | - Rajiv Jalan
- Institute of Hepatology, UCL Medical School, London, United Kingdom
| | - S. Randall Thomas
- IR4M (UMR8081), Université Paris-Sud, Centre National de la Recherche Scientifique, Orsay, France
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Weiner ID, Mitch WE, Sands JM. Urea and Ammonia Metabolism and the Control of Renal Nitrogen Excretion. Clin J Am Soc Nephrol 2015; 10:1444-58. [PMID: 25078422 PMCID: PMC4527031 DOI: 10.2215/cjn.10311013] [Citation(s) in RCA: 234] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Renal nitrogen metabolism primarily involves urea and ammonia metabolism, and is essential to normal health. Urea is the largest circulating pool of nitrogen, excluding nitrogen in circulating proteins, and its production changes in parallel to the degradation of dietary and endogenous proteins. In addition to serving as a way to excrete nitrogen, urea transport, mediated through specific urea transport proteins, mediates a central role in the urine concentrating mechanism. Renal ammonia excretion, although often considered only in the context of acid-base homeostasis, accounts for approximately 10% of total renal nitrogen excretion under basal conditions, but can increase substantially in a variety of clinical conditions. Because renal ammonia metabolism requires intrarenal ammoniagenesis from glutamine, changes in factors regulating renal ammonia metabolism can have important effects on glutamine in addition to nitrogen balance. This review covers aspects of protein metabolism and the control of the two major molecules involved in renal nitrogen excretion: urea and ammonia. Both urea and ammonia transport can be altered by glucocorticoids and hypokalemia, two conditions that also affect protein metabolism. Clinical conditions associated with altered urine concentrating ability or water homeostasis can result in changes in urea excretion and urea transporters. Clinical conditions associated with altered ammonia excretion can have important effects on nitrogen balance.
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Affiliation(s)
- I David Weiner
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida; Division of Nephrology, Hypertension, and Transplantation, University of Florida College of Medicine, Gainesville, Florida;
| | - William E Mitch
- Nephrology Division, Baylor College of Medicine, Houston, Texas; and
| | - Jeff M Sands
- Nephrology Division, 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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Lawrence MJ, Wright PA, Wood CM. Physiological and molecular responses of the goldfish (Carassius auratus) kidney to metabolic acidosis, and potential mechanisms of renal ammonia transport. ACTA ACUST UNITED AC 2015; 218:2124-35. [PMID: 25987732 DOI: 10.1242/jeb.117689] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 05/05/2015] [Indexed: 01/20/2023]
Abstract
Relative to the gills, the mechanisms by which the kidney contributes to ammonia and acid-base homeostasis in fish are poorly understood. Goldfish were exposed to a low pH environment (pH 4.0, 48 h), which induced a characteristic metabolic acidosis and an increase in total plasma [ammonia] but reduced plasma ammonia partial pressure (PNH3). In the kidney tissue, total ammonia, lactate and intracellular pH remained unchanged. The urinary excretion rate of net base under control conditions changed to net acid excretion under low pH, with contributions from both the NH4 (+) (∼30%) and titratable acidity minus bicarbonate (∼70%; TA-HCO3 (-)) components. Inorganic phosphate (Pi), urea and Na(+) excretion rates were also elevated while Cl(-) excretion rates were unchanged. Renal alanine aminotransferase activity increased under acidosis. The increase in renal ammonia excretion was due to significant increases in both the glomerular filtration and the tubular secretion rates of ammonia, with the latter accounting for ∼75% of the increase. There was also a 3.5-fold increase in the mRNA expression of renal Rhcg-b (Rhcg1) mRNA. There was no relationship between ammonia secretion and Na(+) reabsorption. These data indicate that increased renal ammonia secretion during acidosis is probably mediated through Rhesus (Rh) glycoproteins and occurs independently of Na(+) transport, in contrast to branchial and epidermal models of Na(+)-dependent ammonia transport in freshwater fish. Rather, we propose a model of parallel H(+)/NH3 transport as the primary mechanism of renal tubular ammonia secretion that is dependent on renal amino acid catabolism.
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Affiliation(s)
- Michael J Lawrence
- Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1 Department of Biology, Carleton University, Ottawa, ON, Canada K1S 5B6
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Chris M Wood
- Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1 Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Lee HW, Osis G, Handlogten ME, Guo H, Verlander JW, Weiner ID. Effect of dietary protein restriction on renal ammonia metabolism. Am J Physiol Renal Physiol 2015; 308:F1463-73. [PMID: 25925252 DOI: 10.1152/ajprenal.00077.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 04/20/2015] [Indexed: 11/22/2022] Open
Abstract
Dietary protein restriction has multiple benefits in kidney disease. Because protein intake is a major determinant of endogenous acid production, it is important that net acid excretion change in parallel during protein restriction. Ammonia is the primary component of net acid excretion, and inappropriate ammonia excretion can lead to negative nitrogen balance. Accordingly, we examined ammonia excretion in response to protein restriction and then we determined the molecular mechanism of the changes observed. Wild-type C57Bl/6 mice fed a 20% protein diet and then changed to 6% protein developed an 85% reduction in ammonia excretion within 2 days, which persisted during a 10-day study. The expression of multiple proteins involved in renal ammonia metabolism was altered, including the ammonia-generating enzymes phosphate-dependent glutaminase (PDG) and phosphoenolpyruvate carboxykinase (PEPCK) and the ammonia-metabolizing enzyme glutamine synthetase. Rhbg, an ammonia transporter, increased in expression in the inner stripe of outer medullary collecting duct intercalated cell (OMCDis-IC). However, collecting duct-specific Rhbg deletion did not alter the response to protein restriction. Rhcg deletion did not alter ammonia excretion in response to dietary protein restriction. These results indicate 1) dietary protein restriction decreases renal ammonia excretion through coordinated regulation of multiple components of ammonia metabolism; 2) increased Rhbg expression in the OMCDis-IC may indicate a biological role in addition to ammonia transport; and 3) Rhcg expression is not necessary to decrease ammonia excretion during dietary protein restriction.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Gunars Osis
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Mary E Handlogten
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Hui Guo
- Division of Nephrology, Second Hospital of Shanxi Medical University, Yaiyuan, Shanxi, Peoples Republic of China; and
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville, Florida, Nephrology and Hypertension Section, Medical Service, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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Renal acid-base regulation: new insights from animal models. Pflugers Arch 2014; 467:1623-41. [PMID: 25515081 DOI: 10.1007/s00424-014-1669-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 12/16/2022]
Abstract
Because majority of biological processes are dependent on pH, maintaining systemic acid-base balance is critical. The kidney contributes to systemic acid-base regulation, by reabsorbing HCO3 (-) (both filtered by glomeruli and generated within a nephron) and acidifying urine. Abnormalities in those processes will eventually lead to a disruption in systemic acid-base balance and provoke metabolic acid-base disorders. Research over the past 30 years advanced our understanding on cellular and molecular mechanisms responsible for those processes. In particular, a variety of transgenic animal models, where target genes are deleted either globally or conditionally, provided significant insights into how specific transporters are contributing to the renal acid-base regulation. Here, we broadly overview the mechanisms of renal ion transport participating to acid-base regulation, with emphasis on data obtained from transgenic mice models.
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Weiner ID, Leader JP, Bedford JJ, Verlander JW, Ellis G, Kalita P, Vos F, de Jong S, Walker RJ. Effects of chronic lithium administration on renal acid excretion in humans and rats. Physiol Rep 2014; 2:2/12/e12242. [PMID: 25501430 PMCID: PMC4332220 DOI: 10.14814/phy2.12242] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Lithium therapy's most common side effects affecting the kidney are nephrogenic diabetes insipidus (NDI) and chronic kidney disease. Lithium may also induce a distal renal tubular acidosis. This study investigated the effect of chronic lithium exposure on renal acid–base homeostasis, with emphasis on ammonia and citrate excretion. We compared 11 individuals on long‐term lithium therapy with six healthy individuals. Under basal conditions, lithium‐treated individuals excreted significantly more urinary ammonia than did control subjects. Following an acute acid load, urinary ammonia excretion increased approximately twofold above basal rates in both lithium‐treated and control humans. There were no significant differences between lithium‐treated and control subjects in urinary pH or urinary citrate excretion. To elucidate possible mechanisms, rats were randomized to diets containing lithium or regular diet for 6 months. Similar to humans, basal ammonia excretion was significantly higher in lithium‐treated rats; in addition, urinary citrate excretion was also significantly greater. There were no differences in urinary pH. Expression of the critical ammonia transporter, Rhesus C Glycoprotein (Rhcg), was substantially greater in lithium‐treated rats than in control rats. We conclude that chronic lithium exposure increases renal ammonia excretion through mechanisms independent of urinary pH and likely to involve increased collecting duct ammonia secretion via the ammonia transporter, Rhcg. This study investigated the effect of chronic lithium exposure on renal acid–base homeostasis, with emphasis on ammonia and citrate excretion. Chronic lithium exposure increases renal ammonia excretion through mechanisms independent of urinary pH and likely to involve increased collecting duct ammonia secretion via the ammonia transporter, Rhcg.
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Affiliation(s)
- I David Weiner
- Nephrology and Hypertension Section, NF/SGVHS, Gainesville, Florida Department of Medicine, University of Florida College of Medicine, Gainesville, Florida
| | - John P Leader
- Department of Medicine, University of Otago, Dunedin, New Zealand
| | | | - Jill W Verlander
- Department of Medicine, University of Florida College of Medicine, Gainesville, Florida
| | - Gaye Ellis
- Department of Medicine, University of Otago, Dunedin, New Zealand
| | - Priyakshi Kalita
- Department of Medicine, University of Otago, Dunedin, New Zealand
| | - Frederiek Vos
- Department of Medicine, University of Otago, Dunedin, New Zealand
| | - Sylvia de Jong
- Department of Medicine, University of Otago, Dunedin, New Zealand
| | - Robert J Walker
- Department of Medicine, University of Otago, Dunedin, New Zealand
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Moss DM, Neary M, Owen A. The role of drug transporters in the kidney: lessons from tenofovir. Front Pharmacol 2014; 5:248. [PMID: 25426075 PMCID: PMC4227492 DOI: 10.3389/fphar.2014.00248] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 10/24/2014] [Indexed: 12/15/2022] Open
Abstract
Tenofovir disoproxil fumarate, the prodrug of nucleotide reverse transcriptase inhibitor tenofovir, shows high efficacy and relatively low toxicity in HIV patients. However, long-term kidney toxicity is now acknowledged as a modest but significant risk for tenofovir-containing regimens, and continuous use of tenofovir in HIV therapy is currently under question by practitioners and researchers. Co-morbidities (hepatitis C, diabetes), low body weight, older age, concomitant administration of potentially nephrotoxic drugs, low CD4 count, and duration of therapy are all risk factors associated with tenofovir-associated tubular dysfunction. Tenofovir is predominantly eliminated via the proximal tubules of the kidney, therefore drug transporters expressed in renal proximal tubule cells are believed to influence tenofovir plasma concentration and toxicity in the kidney. We review here the current evidence that the actions, pharmacogenetics, and drug interactions of drug transporters are relevant factors for tenofovir-associated tubular dysfunction. The use of creatinine and novel biomarkers for kidney damage, and the role that drug transporters play in biomarker disposition, are discussed. The lessons learnt from investigating the role of transporters in tenofovir kidney elimination and toxicity can be utilized for future drug development and clinical management programs.
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Affiliation(s)
- Darren M Moss
- Department of Molecular and Clinical Pharmacology, University of Liverpool Liverpool, UK
| | - Megan Neary
- Department of Molecular and Clinical Pharmacology, University of Liverpool Liverpool, UK
| | - Andrew Owen
- Department of Molecular and Clinical Pharmacology, University of Liverpool Liverpool, UK
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Geyer RR, Parker MD, Toye AM, Boron WF, Musa-Aziz R. Relative CO₂/NH₃ permeabilities of human RhAG, RhBG and RhCG. J Membr Biol 2014; 246:915-26. [PMID: 24077989 DOI: 10.1007/s00232-013-9593-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 09/05/2013] [Indexed: 10/26/2022]
Abstract
Mammalian glycosylated rhesus (Rh) proteins include the erythroid RhAG and the nonerythroid RhBG and RhCG. RhBG and RhCG are expressed in multiple tissues, including hepatocytes and the collecting duct (CD) of the kidney. Here, we expressed human RhAG, RhBG and RhCG in Xenopus oocytes (vs. H2O-injected control oocytes) and used microelectrodes to monitor the maximum transient change in surface pH (DpHS) caused by exposing the same oocyte to 5 % CO₂/33 mM HCO₃⁻ (an increase) or 0.5 mM NH₃/NH₄⁺ (a decrease). Subtracting the respective values for day-matched, H₂O-injected control oocytes yielded channel-specific values (*). (ΔpH*(S))(CO₂) and (-ΔpH*(S))(NH₃) were each significantly >0 for all channels, indicating that RhBG and RhCG--like RhAG--can carry CO₂ and NH₃. We also investigated the role of a conserved aspartate residue, which was reported to inhibit NH₃ transport. However, surface biotinylation experiments indicate the mutants RhBG(D178N) and RhCG(D177N) have at most a very low abundance in the oocyte plasma membrane. We demonstrate for the first time that RhBG and RhCG--like RhAG--have significant CO₂ permeability, and we confirm that RhAG, RhBG and RhCG all have significant NH₃ permeability. However, as evidenced by (ΔpH*(S))(CO₂)/ (-ΔpH*(S))(NH₃) values, we could not distinguish among the CO₂/ NH₃ permeability ratios for RhAG, RhBG and RhCG. Finally, we propose a mechanism whereby RhBG and RhCG contribute to acid secretion in the CD by enhancing the transport of not only NH₃ but also CO₂ across the membranes of CD cells.
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Weiner ID, Verlander JW. Ammonia transport in the kidney by Rhesus glycoproteins. Am J Physiol Renal Physiol 2014; 306:F1107-20. [PMID: 24647713 PMCID: PMC4024734 DOI: 10.1152/ajprenal.00013.2014] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 03/14/2014] [Indexed: 12/26/2022] Open
Abstract
Renal ammonia metabolism is a fundamental element of acid-base homeostasis, comprising a major component of both basal and physiologically altered renal net acid excretion. Over the past several years, a fundamental change in our understanding of the mechanisms of renal epithelial cell ammonia transport has occurred, replacing the previous model which was based upon diffusion equilibrium for NH3 and trapping of NH4(+) with a new model in which specific and regulated transport of both NH3 and NH4(+) across renal epithelial cell membranes via specific membrane proteins is required for normal ammonia metabolism. A major advance has been the recognition that members of a recently recognized transporter family, the Rhesus glycoprotein family, mediate critical roles in renal and extrarenal ammonia transport. The erythroid-specific Rhesus glycoprotein, Rh A Glycoprotein (Rhag), was the first Rhesus glycoprotein recognized as an ammonia-specific transporter. Subsequently, the nonerythroid Rh glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), were cloned and identified as ammonia transporters. They are expressed in specific cell populations and membrane domains in distal renal epithelial cells, where they facilitate ammonia secretion. In this review, we discuss the distribution of Rhbg and Rhcg in the kidney, the regulation of their expression and activity in physiological disturbances, the effects of genetic deletion on renal ammonia metabolism, and the molecular mechanisms of Rh glycoprotein-mediated ammonia transport.
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Affiliation(s)
- I David Weiner
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville Florida; and Division of Nephrology, Hypertension, and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville Florida; and
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46
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Nakhoul NL, Lee Hamm L. The challenge of determining the role of Rh glycoproteins in transport of NH3and NH4+. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/wmts.105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Nazih L. Nakhoul
- Department of Physiology; Tulane University Medical School; New Orleans LA USA
- Department of Medicine, Section of Nephrology; Tulane University Medical School; New Orleans LA USA
| | - L. Lee Hamm
- Department of Medicine, Section of Nephrology; Tulane University Medical School; New Orleans LA USA
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Bounoure L, Ruffoni D, Müller R, Kuhn GA, Bourgeois S, Devuyst O, Wagner CA. The role of the renal ammonia transporter Rhcg in metabolic responses to dietary protein. J Am Soc Nephrol 2014; 25:2040-52. [PMID: 24652796 DOI: 10.1681/asn.2013050466] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
High dietary protein imposes a metabolic acid load requiring excretion and buffering by the kidney. Impaired acid excretion in CKD, with potential metabolic acidosis, may contribute to the progression of CKD. Here, we investigated the renal adaptive response of acid excretory pathways in mice to high-protein diets containing normal or low amounts of acid-producing sulfur amino acids (SAA) and examined how this adaption requires the RhCG ammonia transporter. Diets rich in SAA stimulated expression of enzymes and transporters involved in mediating NH4 (+) reabsorption in the thick ascending limb of the loop of Henle. The SAA-rich diet increased diuresis paralleled by downregulation of aquaporin-2 (AQP2) water channels. The absence of Rhcg transiently reduced NH4 (+) excretion, stimulated the ammoniagenic pathway more strongly, and further enhanced diuresis by exacerbating the downregulation of the Na(+)/K(+)/2Cl(-) cotransporter (NKCC2) and AQP2, with less phosphorylation of AQP2 at serine 256. The high protein acid load affected bone turnover, as indicated by higher Ca(2+) and deoxypyridinoline excretion, phenomena exaggerated in the absence of Rhcg. In animals receiving a high-protein diet with low SAA content, the kidney excreted alkaline urine, with low levels of NH4 (+) and no change in bone metabolism. Thus, the acid load associated with high-protein diets causes a concerted response of various nephron segments to excrete acid, mostly in the form of NH4 (+), that requires Rhcg. Furthermore, bone metabolism is altered by a high-protein acidogenic diet, presumably to buffer the acid load.
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Affiliation(s)
- Lisa Bounoure
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland; and
| | - Davide Ruffoni
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Ralph Müller
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | | | - Soline Bourgeois
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland; and
| | - Olivier Devuyst
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland; and
| | - Carsten A Wagner
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland; and
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Lee HW, Verlander JW, Handlogten ME, Han KH, Weiner ID. Effect of collecting duct-specific deletion of both Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg) on renal response to metabolic acidosis. Am J Physiol Renal Physiol 2013; 306:F389-400. [PMID: 24338819 DOI: 10.1152/ajprenal.00176.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Rhesus (Rh) glycoproteins, Rh B and Rh C Glycoprotein (Rhbg and Rhcg, respectively), are ammonia-specific transporters expressed in renal distal nephron and collecting duct sites that are necessary for normal rates of ammonia excretion. The purpose of the current studies was to determine the effect of their combined deletion from the renal collecting duct (CD-Rhbg/Rhcg-KO) on basal and acidosis-stimulated acid-base homeostasis. Under basal conditions, urine pH and ammonia excretion and serum HCO3(-) were similar in control (C) and CD-Rhbg/Rhcg-KO mice. After acid-loading for 7 days, CD-Rhbg/Rhcg-KO mice developed significantly more severe metabolic acidosis than did C mice. Acid loading increased ammonia excretion, but ammonia excretion increased more slowly in CD-Rhbg/Rhcg-KO and it was significantly less than in C mice on days 1-5. Urine pH was significantly more acidic in CD-Rhbg/Rhcg-KO mice on days 1, 3, and 5 of acid loading. Metabolic acidosis increased phosphenolpyruvate carboxykinase (PEPCK) and Na(+)/H(+) exchanger NHE-3 and decreased glutamine synthetase (GS) expression in both genotypes, and these changes were significantly greater in CD-Rhbg/Rhcg-KO than in C mice. We conclude that 1) Rhbg and Rhcg are critically important in the renal response to metabolic acidosis; 2) the significantly greater changes in PEPCK, NHE-3, and GS expression in acid-loaded CD-Rhbg/Rhcg-KO compared with acid-loaded C mice cause the role of Rhbg and Rhcg to be underestimated quantitatively; and 3) in mice with intact Rhbg and Rhcg expression, metabolic acidosis does not induce maximal changes in PEPCK, NHE-3, and GS expression despite the presence of persistent metabolic acidosis.
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Affiliation(s)
- Hyun-Wook Lee
- Div. of Nephrology, Hypertension, and Transplantation, Univ. of Florida College of Medicine, PO Box 100224, Gainesville, FL 32610.
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Christensen EI, Wagner CA, Kaissling B. Uriniferous tubule: structural and functional organization. Compr Physiol 2013; 2:805-61. [PMID: 23961562 DOI: 10.1002/cphy.c100073] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The uriniferous tubule is divided into the proximal tubule, the intermediate (thin) tubule, the distal tubule and the collecting duct. The present chapter is based on the chapters by Maunsbach and Christensen on the proximal tubule, and by Kaissling and Kriz on the distal tubule and collecting duct in the 1992 edition of the Handbook of Physiology, Renal Physiology. It describes the fine structure (light and electron microscopy) of the entire mammalian uriniferous tubule, mainly in rats, mice, and rabbits. The structural data are complemented by recent data on the location of the major transport- and transport-regulating proteins, revealed by morphological means(immunohistochemistry, immunofluorescence, and/or mRNA in situ hybridization). The structural differences along the uriniferous tubule strictly coincide with the distribution of the major luminal and basolateral transport proteins and receptors and both together provide the basis for the subdivision of the uriniferous tubule into functional subunits. Data on structural adaptation to defined functional changes in vivo and to genetical alterations of specified proteins involved in transepithelial transport importantly deepen our comprehension of the correlation of structure and function in the kidney, of the role of each segment or cell type in the overall renal function,and our understanding of renal pathophysiology.
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Characteristics of mammalian Rh glycoproteins (SLC42 transporters) and their role in acid-base transport. Mol Aspects Med 2013; 34:629-37. [PMID: 23506896 DOI: 10.1016/j.mam.2012.05.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 04/16/2012] [Indexed: 01/06/2023]
Abstract
The mammalian Rh glycoproteins belong to the solute transporter family SLC42 and include RhAG, present in red blood cells, and two non-erythroid members RhBG and RhCG that are expressed in various tissues, including kidney, liver, skin and the GI tract. The Rh proteins in the red blood cell form an "Rh complex" made up of one D-subunit, one CE-subunit and two RhAG subunits. The Rh complex has a well-known antigenic effect but also contributes to the stability of the red cell membrane. RhBG and RhCG are related to the NH4(+) transporters of the yeast and bacteria but their exact function is yet to be determined. This review describes the expression and molecular properties of these membrane proteins and their potential role as NH3/NH4(+) and CO2 transporters. The likelihood that these proteins transport gases such as CO2 or NH3 is novel and significant. The review also describes the physiological importance of these proteins and their relevance to human disease.
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