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Kang MJ, Ioannou S, Lougheide Q, Dittmar M, Hsu Y, Pastor-Soler NM. The study of intercalated cells using ex vivo techniques: primary cell culture, cell lines, kidney slices, and organoids. Am J Physiol Cell Physiol 2024; 326:C229-C251. [PMID: 37899748 DOI: 10.1152/ajpcell.00479.2022] [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: 10/27/2022] [Revised: 10/23/2023] [Accepted: 10/24/2023] [Indexed: 10/31/2023]
Abstract
This review summarizes methods to study kidney intercalated cell (IC) function ex vivo. While important for acid-base homeostasis, IC dysfunction is often not recognized clinically until it becomes severe. The advantage of using ex vivo techniques is that they allow for the differential evaluation of IC function in controlled environments. Although in vitro kidney tubular perfusion is a classical ex vivo technique to study IC, here we concentrate on primary cell cultures, immortalized cell lines, and ex vivo kidney slices. Ex vivo techniques are useful in evaluating IC signaling pathways that allow rapid responses to extracellular changes in pH, CO2, and bicarbonate (HCO3-). However, these methods for IC work can also be challenging, as cell lines that recapitulate IC do not proliferate easily in culture. Moreover, a "pure" IC population in culture does not necessarily replicate its collecting duct (CD) environment, where ICs are surrounded by the more abundant principal cells (PCs). It is reassuring that many findings obtained in ex vivo IC systems signaling have been largely confirmed in vivo. Some of these newly identified signaling pathways reveal that ICs are important for regulating NaCl reabsorption, thus suggesting new frontiers to target antihypertensive treatments. Moreover, recent single-cell characterization studies of kidney epithelial cells revealed a dual developmental origin of IC, as well as the presence of novel CD cell types with certain IC characteristics. These exciting findings present new opportunities for the study of IC ex vivo and will likely rediscover the importance of available tools in this field.NEW & NOTEWORTHY The study of kidney intercalated cells has been limited by current cell culture and kidney tissue isolation techniques. This review is to be used as a reference to select ex vivo techniques to study intercalated cells. We focused on the use of cell lines and kidney slices as potential useful models to study membrane transport proteins. We also review how novel collecting duct organoids may help better elucidate the role of these intriguing cells.
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Affiliation(s)
- Min Ju Kang
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Silvia Ioannou
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Quinn Lougheide
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Michael Dittmar
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Young Hsu
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Nuria M Pastor-Soler
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
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Liao Z, Liu F, Wang Y, Fan X, Li Y, He J, Buttino I, Yan X, Zhang X, Shi G. Transcriptomic response of Mytilus coruscus mantle to acute sea water acidification and shell damage. Front Physiol 2023; 14:1289655. [PMID: 37954445 PMCID: PMC10639161 DOI: 10.3389/fphys.2023.1289655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 10/16/2023] [Indexed: 11/14/2023] Open
Abstract
Mytilus coruscus is an economically important marine calcifier living in the Yangtze River estuary sea area, where seasonal fluctuations in natural pH occur owing to freshwater input, resulting in a rapid reduction in seawater pH. In addition, Mytilus constantly suffers from shell fracture or injury in the natural environment, and the shell repair mechanisms in mussels have evolved to counteract shell injury. Therefore, we utilized shell-complete and shell-damaged Mytilus coruscus in this study and performed transcriptomic analysis of the mantle to investigate whether the expression of mantle-specific genes can be induced by acute seawater acidification and how the mantle responds to acute acidification during the shell repair process. We found that acute acidification induced more differentially expressed genes than shell damage in the mantle, and the biomineralization-related Gene Ontology terms and KEGG pathways were significantly enriched by these DEGs. Most DEGs were upregulated in enriched pathways, indicating the activation of biomineralization-related processes in the mussel mantle under acute acidification. The expression levels of some shell matrix proteins and antimicrobial peptides increased under acute acidification and/or shell damage, suggesting the molecular modulation of the mantle for the preparation and activation of the shell repairing and anti-infection under adverse environmental conditions. In addition, morphological and microstructural analyses were performed for the mantle edge and shell cross-section, and changes in the mantle secretory capacity and shell inner film system induced by the two stressors were observed. Our findings highlight the adaptation of M. coruscus in estuarine areas with dramatic fluctuations in pH and may prove instrumental in its ability to survive ocean acidification.
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Affiliation(s)
- Zhi Liao
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Fei Liu
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Ying Wang
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Xiaojun Fan
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Yingao Li
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Jianyu He
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Isabella Buttino
- Italian Institute for Environmental Protection and Research (ISPRA), Livorno, Italy
| | - Xiaojun Yan
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Xiaolin Zhang
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
| | - Ge Shi
- Laboratory of Marine Biology Protein Engineering, Marine Science and Technical College, Zhejiang Ocean University, Zhoushan, Zhejiang, China
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Wagner CA, Unwin R, Lopez-Garcia SC, Kleta R, Bockenhauer D, Walsh S. The pathophysiology of distal renal tubular acidosis. Nat Rev Nephrol 2023; 19:384-400. [PMID: 37016093 DOI: 10.1038/s41581-023-00699-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2023] [Indexed: 04/06/2023]
Abstract
The kidneys have a central role in the control of acid-base homeostasis owing to bicarbonate reabsorption and production of ammonia and ammonium in the proximal tubule and active acid secretion along the collecting duct. Impaired acid excretion by the collecting duct system causes distal renal tubular acidosis (dRTA), which is characterized by the failure to acidify urine below pH 5.5. This defect originates from reduced function of acid-secretory type A intercalated cells. Inherited forms of dRTA are caused by variants in SLC4A1, ATP6V1B1, ATP6V0A4, FOXI1, WDR72 and probably in other genes that are yet to be discovered. Inheritance of dRTA follows autosomal-dominant and -recessive patterns. Acquired forms of dRTA are caused by various types of autoimmune diseases or adverse effects of some drugs. Incomplete dRTA is frequently found in patients with and without kidney stone disease. These patients fail to appropriately acidify their urine when challenged, suggesting that incomplete dRTA may represent an intermediate state in the spectrum of the ability to excrete acids. Unrecognized or insufficiently treated dRTA can cause rickets and failure to thrive in children, osteomalacia in adults, nephrolithiasis and nephrocalcinosis. Electrolyte disorders are also often present and poorly controlled dRTA can increase the risk of developing chronic kidney disease.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK.
| | - Robert Unwin
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
| | - Sergio C Lopez-Garcia
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
- Department of Paediatric Nephrology, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - Robert Kleta
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
| | - Detlef Bockenhauer
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
- Department of Paediatric Nephrology, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - Stephen Walsh
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
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The mechanisms of alkali therapy in targeting renal diseases. Biochem Soc Trans 2023; 51:223-232. [PMID: 36744634 DOI: 10.1042/bst20220690] [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: 11/08/2022] [Revised: 12/28/2022] [Accepted: 01/19/2023] [Indexed: 02/07/2023]
Abstract
Chronic kidney disease (CKD) is characterized by progressive reduction in kidney function and treatments aiming at stabilizing or slowing its progression may avoid or delay the necessity of kidney replacement therapy and the increased mortality associated with reduced kidney function. Metabolic acidosis, and less severe stages of the acid stress continuum, are common consequences of CKD and some interventional studies support that its correction slows the progression to end-stage kidney disease. This correction can be achieved with mineral alkali in the form of bicarbonate or citrate salts, ingestion of diets with fewer acid-producing food components or more base-producing food components, or a pharmacological approach. In this mini-review article, we summarize the potential mechanisms involved in the beneficial effects of alkali therapy. We also discuss the perspectives in the field and challenges that must be overcome to advance our understanding of such mechanisms.
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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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Gallic and Hesperidin Ameliorate Electrolyte Imbalances in AlCl3-Induced Nephrotoxicity in Wistar Rats. Biochem Res Int 2022; 2022:6151684. [PMID: 36263197 PMCID: PMC9576448 DOI: 10.1155/2022/6151684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Accepted: 09/06/2022] [Indexed: 11/17/2022] Open
Abstract
Nephrotoxicity is usually characterized by inefficiency of the kidney, thereby causing disruptions to electrolyte balance and blood acidity. This study aimed to evaluate the effect of hesperidin and gallic acid on serum electrolytes and ion pumps in Wistar rats subjected to aluminum chloride (AlCl3)-induced nephrotoxicity. Thirty Wistar rats were randomly divided into six groups of five animals apiece. Group one served as the negative control and received distilled water while the study lasted. Animals in groups 2–4 received 100 mg/kg/day AlCl3 throughout the study. Animals in groups 3 and 4 were also administered 100 mg/kg/day gallic acid and 100 mg/kg/day hesperidin, respectively. Groups 5 and 6 were treated with 100 mg/kg/day gallic acid only and 100 mg/kg/day hesperidin only, respectively. Treatments were administered orally via gavage for 28 days with distilled water as the vehicle. Animals were sacrificed after which levels of potassium, calcium, magnesium, phosphate, chloride, and bicarbonate ions were evaluated in the serum, while activities of Na+/K+ and Ca2+/Mg2+ ATPases were determined in kidney homogenate. Results showed that AlCl3 significantly (p < 0.05) inhibited activities of Na+/K+ and Ca2+/Mg2+ ATPases in addition to increasing serum levels of potassium, calcium, phosphate, and chloride, with concomitant decrease in serum levels of magnesium and bicarbonate. However, coadministration of AlCl3 with either gallic acid or hesperidin ameliorated all the disruptions caused by AlCl3. It could be concluded that gallic acid and hesperidin could be relevant in managing electrolyte imbalances and acidosis occasioned by kidney dysfunction.
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Agarwal S, Sudhini YR, Polat OK, Reiser J, Altintas MM. Renal cell markers: lighthouses for managing renal diseases. Am J Physiol Renal Physiol 2021; 321:F715-F739. [PMID: 34632812 DOI: 10.1152/ajprenal.00182.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Kidneys, one of the vital organs in our body, are responsible for maintaining whole body homeostasis. The complexity of renal function (e.g., filtration, reabsorption, fluid and electrolyte regulation, and urine production) demands diversity not only at the level of cell types but also in their overall distribution and structural framework within the kidney. To gain an in depth molecular-level understanding of the renal system, it is imperative to discern the components of kidney and the types of cells residing in each of the subregions. Recent developments in labeling, tracing, and imaging techniques have enabled us to mark, monitor, and identify these cells in vivo with high efficiency in a minimally invasive manner. In this review, we summarize different cell types, specific markers that are uniquely associated with those cell types, and their distribution in the kidney, which altogether make kidneys so special and different. Cellular sorting based on the presence of certain proteins on the cell surface allowed for the assignment of multiple markers for each cell type. However, different studies using different techniques have found contradictions in cell type-specific markers. Thus, the term "cell marker" might be imprecise and suboptimal, leading to uncertainty when interpreting the data. Therefore, we strongly believe that there is an unmet need to define the best cell markers for a cell type. Although the compendium of renal-selective marker proteins presented in this review is a resource that may be useful to researchers, we acknowledge that the list may not be necessarily exhaustive.
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Affiliation(s)
- Shivangi Agarwal
- Department of Internal Medicine, Rush University, Chicago, Illinois
| | | | - Onur K Polat
- Department of Internal Medicine, Rush University, Chicago, Illinois
| | - Jochen Reiser
- Department of Internal Medicine, Rush University, Chicago, Illinois
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Silva PHI, Wiegand A, Daryadel A, Russo G, Ritter A, Gaspert A, Wüthrich RP, Wagner CA, Mohebbi N. Acidosis and alkali therapy in patients with kidney transplant is associated with transcriptional changes and altered abundance of genes involved in cell metabolism and acid-base balance. Nephrol Dial Transplant 2021; 36:1806-1820. [PMID: 34240183 DOI: 10.1093/ndt/gfab210] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Metabolic acidosis occurs frequently in patients with kidney transplant and is associated with higher risk for and accelerated loss of graft function. To date, it is not known whether alkali therapy in these patients improves kidney function and whether acidosis and its therapy is associated with altered expression of proteins involved in renal acid-base metabolism. METHODS We collected retrospectively kidney biopsies from 22 patients. Of these patients, 9 had no acidosis, 9 had metabolic acidosis (plasma HCO3- < 22 mmol/l), and 4 had acidosis and received alkali therapy. We performed transcriptome analysis and immunohistochemistry for proteins involved in renal acid-base handling. RESULTS We found the expression of 40 transcripts significantly changed between kidneys from non-acidotic and acidotic patients. These genes are mostly involved in proximal tubule amino acid and lipid metabolism and energy homeostasis. Three transcripts were fully recovered by alkali therapy: the Kir4.2 K+-channel, an important regulator of proximal tubule HCO3--metabolism and transport, ACADSB and SHMT1, genes involved in beta-oxidation and methionine metabolism. Immunohistochemistry showed reduced staining for the proximal tubule NBCe1 HCO3- transporter in kidneys from acidotic patients that recovered with alkali therapy. In addition, the HCO3-exchanger pendrin was affected by acidosis and alkali therapy. CONCLUSIONS Metabolic acidosis in kidney transplant recipients is associated with alterations in the renal transcriptome that are partly restored by alkali therapy. Acid-base transport proteins mostly from proximal tubule were also affected by acidosis and alkali therapy suggesting that the downregulation of critical players contributes to metabolic acidosis in these patients.
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Affiliation(s)
- Pedro H Imenez Silva
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research NCCR Kidney.CH, Switzerland
| | - Anna Wiegand
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Arezoo Daryadel
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research NCCR Kidney.CH, Switzerland
| | - Giancarlo Russo
- Functional Genomics Center Zürich, University of Zürich and ETH Zürich, Zürich, Switzerland
| | - Alexander Ritter
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Ariana Gaspert
- Department of Pathology and Molecular Pathology, University Hospital Zurich, Zurich, Switzerland
| | - Rudolf P Wüthrich
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research NCCR Kidney.CH, Switzerland
| | - Nilufar Mohebbi
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
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Kidney intercalated cells and the transcription factor FOXi1 drive cystogenesis in tuberous sclerosis complex. Proc Natl Acad Sci U S A 2021; 118:2020190118. [PMID: 33536341 PMCID: PMC8017711 DOI: 10.1073/pnas.2020190118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Tuberous sclerosis complex (TSC) is caused by mutations in TSC1 or TSC2 gene and affects multiple organs, including the kidney, where it presents with angiomyolipomata and cysts that can result in kidney failure. The factors promoting cyst formation and tumor growth in TSC are incompletely understood. Current studies demonstrate that kidney cyst epithelia in TSC mouse models and in humans with TSC are composed of hyperproliferating intercalated cells, along with activation of H+-ATPase and carbonic anhydrase 2. Interfering with intercalated cell proliferation completely inhibited and inactivating carbonic anhydrase 2 significantly protected against cyst formation in TSC. Targeting the acid base and/or electrolyte transporters of intercalated cells may provide a therapeutic approach for the treatment of kidney cysts in TSC. Tuberous sclerosis complex (TSC) is caused by mutations in either TSC1 or TSC2 genes and affects multiple organs, including kidney, lung, and brain. In the kidney, TSC presents with the enlargement of benign tumors (angiomyolipomata) and cysts, which eventually leads to kidney failure. The factors promoting cyst formation and tumor growth in TSC are incompletely understood. Here, we report that mice with principal cell-specific inactivation of Tsc1 develop numerous cortical cysts, which are overwhelmingly composed of hyperproliferating A-intercalated (A-IC) cells. RNA sequencing and confirmatory expression studies demonstrated robust expression of Forkhead Transcription Factor 1 (Foxi1) and its downstream targets, apical H+-ATPase and cytoplasmic carbonic anhydrase 2 (CAII), in cyst epithelia in Tsc1 knockout (KO) mice but not in Pkd1 mutant mice. In addition, the electrogenic 2Cl−/H+ exchanger (CLC-5) is significantly up-regulated and shows remarkable colocalization with H+-ATPase on the apical membrane of cyst epithelia in Tsc1 KO mice. Deletion of Foxi1, which is vital to intercalated cells viability and H+-ATPase expression, completely abrogated the cyst burden in Tsc1 KO mice, as indicated by MRI images and histological analysis in kidneys of Foxi1/Tsc1 double-knockout (dKO) mice. Deletion of CAII, which is critical to H+-ATPase activation, caused significant reduction in cyst burden and increased life expectancy in CAII/Tsc1 dKO mice vs. Tsc1 KO mice. We propose that intercalated cells and their acid/base/electrolyte transport machinery (H+-ATPase/CAII/CLC-5) are critical to cystogenesis, and their inhibition or inactivation is associated with significant protection against cyst generation and/or enlargement in TSC.
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López-González Z, Padilla-Flores T, León-Aparicio D, Gutiérrez-Vásquez E, Salvador C, León-Contreras JC, Hernández-Pando R, Escobar LI. Metabolic acidosis and hyperkalemia differentially regulate cation HCN3 channel in the rat nephron. J Mol Histol 2020; 51:701-716. [PMID: 33070272 DOI: 10.1007/s10735-020-09916-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 10/01/2020] [Indexed: 12/31/2022]
Abstract
The kidney controls body fluids, electrolyte and acid-base balance. Previously, we demonstrated that hyperpolarization-activated and cyclic nucleotide-gated (HCN) cation channels participate in ammonium excretion in the rat kidney. Since acid-base balance is closely linked to potassium metabolism, in the present work we aim to determine the effect of chronic metabolic acidosis (CMA) and hyperkalemia (HK) on protein abundance and localization of HCN3 in the rat kidney. CMA increased HCN3 protein level only in the outer medulla (2.74 ± 0.31) according to immunoblot analysis. However, immunofluorescence assays showed that HCN3 augmented in cortical proximal tubules (1.45 ± 0.11) and medullary thick ascending limb of Henle's loop (4.48 ± 0.45) from the inner stripe of outer medulla. HCN3 was detected in brush border membranes (BBM) and mitochondria of the proximal tubule by immunogold electron and confocal microscopy in control conditions. Acidosis did not alter HCN3 levels in BBM and mitochondria but augmented them in lysosomes. HCN3 was also immuno-detected in mitoautophagosomes. In the distal nephron, HCN3 was expressed in principal and intercalated cells from cortical to medullary collecting ducts. CMA did not change HCN3 abundance in these nephron segments. In contrast, HK doubled HCN3 level in cortical collecting ducts and favored its basolateral localization in principal cells from the inner medullary collecting ducts. These findings further support HCN channels contribution to renal acid-base and potassium balance.
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Affiliation(s)
- Zinaeli López-González
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), 04510, Mexico, Mexico
| | - Teresa Padilla-Flores
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), 04510, Mexico, Mexico
| | - Daniel León-Aparicio
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), 04510, Mexico, Mexico
| | - Erika Gutiérrez-Vásquez
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), 04510, Mexico, Mexico
| | - Carolina Salvador
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), 04510, Mexico, Mexico
| | - Juan C León-Contreras
- Departamento de Patología, Instituto Nacional de Ciencias Médicas Y Nutrición Salvador Zubirán, 14080, Mexico, Mexico
| | - Rogelio Hernández-Pando
- Departamento de Patología, Instituto Nacional de Ciencias Médicas Y Nutrición Salvador Zubirán, 14080, Mexico, Mexico
| | - Laura I Escobar
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), 04510, Mexico, Mexico.
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Abstract
Renal tubular acidosis (RTA) comprises a group of disorders characterized by low capacity for net acid excretion and persistent hyperchloremic metabolic acidosis, despite preserved glomerular filtration rate. RTA are classified into chiefly three types (1, 2 and 4) based on pathophysiology and clinical and laboratory characteristics. Most patients have primary RTA that presents in infancy with polyuria, growth retardation, rickets and/or hypotonia. Diagnosis requires careful evaluation, including exclusion of other entities that can cause acidosis. A variety of tests, administered stepwise, are useful for the diagnosis and characterization of RTA. A genetic or acquired basis can be determined in majority of patients through focused evaluation. Management involves correction of acidosis and dyselectrolytemia; patients with proximal RTA with Fanconi syndrome and rickets require additional supplements of phosphate and vitamin D.
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Affiliation(s)
- Arvind Bagga
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Aditi Sinha
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, 110029, India
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Abstract
Parathyroid hormone is an essential regulator of extracellular calcium and phosphate. PTH enhances calcium reabsorption while inhibiting phosphate reabsorption in the kidneys, increases the synthesis of 1,25-dihydroxyvitamin D, which then increases gastrointestinal absorption of calcium, and increases bone resorption to increase calcium and phosphate. Parathyroid disease can be an isolated endocrine disorder or part of a complex syndrome. Genetic mutations can account for diseases of parathyroid gland formulation, dysregulation of parathyroid hormone synthesis or secretion, and destruction of the parathyroid glands. Over the years, a number of different options are available for the treatment of different types of parathyroid disease. Therapeutic options include surgical removal of hypersecreting parathyroid tissue, administration of parathyroid hormone, vitamin D, activated vitamin D, calcium, phosphate binders, calcium-sensing receptor, and vitamin D receptor activators to name a few. The accurate assessment of parathyroid hormone also provides essential biochemical information to properly diagnose parathyroid disease. Currently available immunoassays may overestimate or underestimate bioactive parathyroid hormone because of interferences from truncated parathyroid hormone fragments, phosphorylation of parathyroid hormone, and oxidation of amino acids of parathyroid hormone.
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Affiliation(s)
- Edward Ki Yun Leung
- Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, CA, United States; Department of Pathology, Keck School of Medicine of University of Southern California, Los Angeles, CA, United States.
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Genini A, Mohebbi N, Daryadel A, Bettoni C, Wagner CA. Adaptive response of the murine collecting duct to alkali loading. Pflugers Arch 2020; 472:1079-1092. [DOI: 10.1007/s00424-020-02423-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/31/2020] [Accepted: 06/19/2020] [Indexed: 01/14/2023]
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14
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Rao R, Bhalla V, Pastor-Soler NM. Intercalated Cells of the Kidney Collecting Duct in Kidney Physiology. Semin Nephrol 2020; 39:353-367. [PMID: 31300091 DOI: 10.1016/j.semnephrol.2019.04.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The epithelium of the kidney collecting duct (CD) is composed mainly of two different types of cells with distinct and complementary functions. CD principal cells traditionally have been considered to have a major role in Na+ and water regulation, while intercalated cells (ICs) were thought to largely modulate acid-base homeostasis. In recent years, our understanding of IC function has improved significantly owing to new research findings. Thus, we now have a new model for CD transport that integrates mechanisms of salt and water reabsorption, K+ homeostasis, and acid-base status between principal cells and ICs. There are three main types of ICs (type A, type B, and non-A, non-B), which first appear in the late distal convoluted tubule or in the connecting segment in a species-dependent manner. ICs can be detected in CD from cortex to the initial part of the inner medulla, although some transport proteins that are key components of ICs also are present in medullary CD, cells considered inner medullary. Of the three types of ICs, each has a distinct morphology and expresses different complements of membrane transport proteins that translate into very different functions in homeostasis and contributions to CD luminal pro-urine composition. This review includes recent discoveries in IC intracellular and paracrine signaling that contributes to acid-base regulation as well as Na+, Cl-, K+, and Ca2+ homeostasis. Thus, these new findings highlight the potential role of ICs as targets for potential hypertension treatments.
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Affiliation(s)
- Renee Rao
- University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of University of Southern California, Los Angeles, CA
| | - Vivek Bhalla
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Núria M Pastor-Soler
- University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of University of Southern California, Los Angeles, CA.
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15
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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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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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Distal renal tubular acidosis: genetic causes and management. World J Pediatr 2019; 15:422-431. [PMID: 31079338 DOI: 10.1007/s12519-019-00260-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 04/12/2019] [Indexed: 12/11/2022]
Abstract
BACKGROUND Distal renal tubular acidosis (dRTA) is a kidney tubulopathy that causes a state of normal anion gap metabolic acidosis due to impairment of urine acidification. This review aims to summarize the etiology, pathophysiology, clinical findings, diagnosis and therapeutic approach of dRTA, with emphasis on genetic causes of dRTA. DATA SOURCES Literature reviews and original research articles from databases, including PubMed and Google Scholar. Manual searching was performed to identify additional studies about dRTA. RESULTS dRTA is characterized as the dysfunction of the distal urinary acidification, leading to metabolic acidosis. In pediatric patients, the most frequent etiology of dRTA is the genetic alteration of genes responsible for the codification of distal tubule channels, whereas, in adult patients, dRTA is more commonly secondary to autoimmune diseases, use of medications and uropathies. Patients with dRTA exhibit failure to thrive and important laboratory alterations, which are used to define the diagnosis. The oral alkali and potassium supplementation can correct the biochemical defects, improve clinical manifestations and avoid nephrolithiasis and nephrocalcinosis. CONCLUSIONS dRTA is a multifactorial disease leading to several clinical manifestations. Clinical and laboratory alterations can be corrected by alkali replacement therapy.
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18
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Ueda Y, Ookawara S, Miyazawa H, Ito K, Hirai K, Hoshino T, Morishita Y. Changes in Serum and Urinary Potassium Handling Associated with Renin-Angiotensin-Aldosterone System Inhibitors in Advanced Chronic Kidney Disease Patients. Cureus 2019; 11:e5561. [PMID: 31695981 PMCID: PMC6820673 DOI: 10.7759/cureus.5561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Objective This study aimed to (i) compare the extent of urinary potassium (K+) excretion in addition to the changes in serum K+ concentration: and (ii) clarify the association between changes in serum K+ concentration, urinary K+ excretion, and acid-base status with or without renin-angiotensin-aldosterone system (RAAS) inhibitors in patients with advanced chronic kidney disease (CKD) stages. Methods Six hundred and ninety-one patients with advanced CKD (CKD G3b, 161; G4, 271; G5, 259) were retrospectively evaluated. Differences in serum K+ concentration, urinary K+ excretion, and serum sodium and chloride differences (Na+−Cl-) were compared among patients with RAAS inhibitors, RAAS inhibitors and diuretic agents, and without either medication in each CKD stage. Results Serum K+ concentrations in patients with RAAS inhibitors were significantly higher than in those with RAAS inhibitors and diuretics in CKD stage G3b and the other two treatment groups in CKD stage G4. Urinary K+ excretion among the three groups did not differ significantly in each CKD stage. Serum Na+−Cl- differences in patients with RAAS inhibitors were significantly smaller than in those with RAAS inhibitors and diuretics in CKD stages G3b (p = 0.006) and the other two groups in CKD stage G4 (vs. RAAS inhibitors and diuretics, p <0.001; vs. without either medication, p = 0.008). Conclusion Our study demonstrated that RAAS inhibitor use might be associated with hyperkalemia via not decreased urinary K+ excretion but rather K+ redistribution from intracellular to extracellular fluid induced by the progression of metabolic acidosis in patients with advanced CKD, particularly stages G3b and G4.
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Affiliation(s)
- Yuichiro Ueda
- Internal Medicine, First Department of Integrated Medicine, Saitama Medical Center, Saitama, JPN
| | - Susumu Ookawara
- Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, Saitama, JPN
| | - Haruhisa Miyazawa
- Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Saitama, JPN
| | - Kiyonori Ito
- Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Saitama, JPN
| | - Keiji Hirai
- Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, Saitama, JPN
| | - Taro Hoshino
- Nephrology, Department of Internal Medicine, Saitama Red-Cross Hospital, Saitama, JPN
| | - Yoshiyuki Morishita
- Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Saitama, JPN
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19
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Gordon WE, Espinoza JA, Leerberg DM, Yelon D, Hamdoun A. Xenobiotic transporter activity in zebrafish embryo ionocytes. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2019; 212:88-97. [PMID: 31077970 PMCID: PMC6561644 DOI: 10.1016/j.aquatox.2019.04.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/14/2019] [Accepted: 04/16/2019] [Indexed: 06/09/2023]
Abstract
Ionocytes are specialized cells in the epidermis of embryonic zebrafish (Danio rerio) that play important roles in ion homeostasis and have functional similarities to mammalian renal cells. Here, we examined whether these cells might also share another functional similarity with renal cells, which is the presence of efflux transporter activities useful for elimination of toxic small molecules. Xenobiotic transporters (XTs), including the ATP-Binding Cassette (ABC) family, are a major defense mechanism against diffusible toxic molecules in aquatic embryos, including zebrafish, but their activity in the ionocytes has not previously been studied. Using fluorescent small molecule substrates of XT, we observed that specific populations of ionocytes uptake and efflux fluorescent small molecules in a manner consistent with active transport. We specifically identified a P-gp/ABCB1 inhibitor-sensitive efflux activity in the H+-ATPase-rich (HR) ionocytes, and show that these cells exhibit enriched expression of the ABCB gene, abcb5. The results extend our understanding of the functional significance of zebrafish ionocytes and indicate that these cells could play an important role in protection of the fish embryo from harmful small molecules.
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Affiliation(s)
- Wei E Gordon
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA; Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Jose A Espinoza
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Dena M Leerberg
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Deborah Yelon
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Amro Hamdoun
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.
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20
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Walsh PA, O'Donovan DJ. An appraisal of the in vivo role of phosphate as a modulator of urinary ammonium and titratable acid excretion in the acidotic rabbit. J Anim Physiol Anim Nutr (Berl) 2019; 103:1571-1577. [PMID: 31241230 DOI: 10.1111/jpn.13143] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 04/18/2019] [Accepted: 05/26/2019] [Indexed: 01/07/2023]
Abstract
Previous studies have shown that the intravenous infusion of inorganic phosphate increased urinary ammonium excretion 8- to 10-fold in the acidotic rabbit. This was considered to be a very important observation at the time and to be unique to the rabbit. While investigating this finding, we discovered that the formol titration procedure, used to measure urinary ammonium by this research group, is subject to interference by phosphate, casting doubt on the validity of the urinary ammonium excretion data reported by them in the literature. In order to re-assess the importance of phosphate as a potential modulator of urinary ammonium excretion in the acidotic rabbit, renal net acid excretion studies were carried out in phosphate-loaded acidotic animals. We observed that while urinary ammonium excretion increased significantly (p < 0.05) after 50 min of phosphate infusion, the maximum concentrations excreted were substantially less than previously reported in the literature. However, through its urinary buffering capacity, we observed that inorganic phosphate, via an experimentally induced phosphaturia, could substantially enhance titratable acid excretion. Contrary to earlier reports, we demonstrated that phosphate plays a relatively minor in vivo modulator role in enhancing renal net acid excretion through the vehicle of ammonium during acute metabolic acidosis in the hyperphosphataemic rabbit. The findings reported in this study constitute an important update on ammonia metabolism in the acidotic rabbit.
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Affiliation(s)
- Patrick A Walsh
- Department of Physiology, School of Medicine, RCSI Bahrain, Manama, Bahrain
| | - Daniel J O'Donovan
- Department of Physiology, National University of Ireland Galway, Galway, Ireland
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21
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Abstract
Parathyroid hormone (PTH) is the major secretory product of the parathyroid glands, and in hypocalcemic conditions, can enhance renal calcium reabsorption, increase active vitamin D production to increase intestinal calcium absorption, and mobilize calcium from bone by increasing turnover, mainly but not exclusively in cortical bone. PTH has therefore found clinical use as replacement therapy in hypoparathyroidism. PTH also may have a physiologic role in augmenting bone formation, particularly in trabecular and to some extent in cortical bone. This action has been applied to the clinic to provide anabolic therapy for osteoporosis.
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Affiliation(s)
- David Goltzman
- Department of Medicine and Research Institute of the McGill University Health Centre, 1001 Decarie Boulevard, Montreal, Quebec H4A 3J1, Canada; Departments of Medicine and of Physiology, McGill University, 845 Sherbrooke St West, Montreal, Quebec H3A 0B9, Canada.
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22
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Adenylyl cyclase 6 in acid-base balance - adding complexity. Clin Sci (Lond) 2018; 132:1995-1997. [PMID: 30220652 DOI: 10.1042/cs20180572] [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: 08/02/2018] [Revised: 08/14/2018] [Accepted: 08/16/2018] [Indexed: 11/17/2022]
Abstract
Systemic acid-base balance is tightly controlled within a narrow range of pH. Disturbances in systemic acid-base homeostasis are associated with diverse detrimental effects. The kidney is a key regulator of acid-base balance, capable of excreting HCO3- or H+, and chronic kidney disease invariably leads to acidosis. However, the regulatory pathways underlying the fine-tuned acid-base sensing and regulatory mechanisms are still incompletely understood. In the article published recently in Clinical Science (vol 132 (16) 1779-1796), Poulson and colleagues investigated the role of adenylyl cyclase 6 (AC6) in acid-base homeostasis. They uncovered a complex role of AC6, specifically affecting acid-base balance during HCO3- load, which causes pronounced alkalosis in AC6-deficient mice. However, the phenotype of AC6-deficient mice appears much more complex, involving systemic effects associated with increased energy expenditure. These observations remind us that there is much to be learned about the intricate signaling pathways involved in renal control of acid-base balance and the complex ramifications of acid-base regulation.
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23
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Lewis L, Kwong RWM. Zebrafish as a Model System for Investigating the Compensatory Regulation of Ionic Balance during Metabolic Acidosis. Int J Mol Sci 2018; 19:E1087. [PMID: 29621145 PMCID: PMC5979485 DOI: 10.3390/ijms19041087] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 03/25/2018] [Accepted: 04/02/2018] [Indexed: 12/16/2022] Open
Abstract
Zebrafish (Danio rerio) have become an important model for integrative physiological research. Zebrafish inhabit a hypo-osmotic environment; to maintain ionic and acid-base homeostasis, they must actively take up ions and secrete acid to the water. The gills in the adult and the skin at larval stage are the primary sites of ionic regulation in zebrafish. The uptake of ions in zebrafish is mediated by specific ion transporting cells termed ionocytes. Similarly, in mammals, ion reabsorption and acid excretion occur in specific cell types in the terminal region of the renal tubules (distal convoluted tubule and collecting duct). Previous studies have suggested that functional regulation of several ion transporters/channels in the zebrafish ionocytes resembles that in the mammalian renal cells. Additionally, several mechanisms involved in regulating the epithelial ion transport during metabolic acidosis are found to be similar between zebrafish and mammals. In this article, we systemically review the similarities and differences in ionic regulation between zebrafish and mammals during metabolic acidosis. We summarize the available information on the regulation of epithelial ion transporters during acidosis, with a focus on epithelial Na⁺, Cl- and Ca2+ transporters in zebrafish ionocytes and mammalian renal cells. We also discuss the neuroendocrine responses to acid exposure, and their potential role in ionic compensation. Finally, we identify several knowledge gaps that would benefit from further study.
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Affiliation(s)
- Lletta Lewis
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada.
| | - Raymond W M Kwong
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada.
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24
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Lister A, Bourgeois S, Imenez Silva PH, Rubio-Aliaga I, Marbet P, Walsh J, Shelton LM, Keller B, Verrey F, Devuyst O, Giesbertz P, Daniel H, Goldring CE, Copple IM, Wagner CA, Odermatt A. NRF2 regulates the glutamine transporter Slc38a3 (SNAT3) in kidney in response to metabolic acidosis. Sci Rep 2018; 8:5629. [PMID: 29618784 PMCID: PMC5884861 DOI: 10.1038/s41598-018-24000-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 03/19/2018] [Indexed: 12/28/2022] Open
Abstract
Expression of the glutamine transporter SNAT3 increases in kidney during metabolic acidosis, suggesting a role during ammoniagenesis. Microarray analysis of Nrf2 knock-out (KO) mouse kidney identified Snat3 as the most significantly down-regulated transcript compared to wild-type (WT). We hypothesized that in the absence of NRF2 the kidney would be unable to induce SNAT3 under conditions of metabolic acidosis and therefore reduce the availability of glutamine for ammoniagenesis. Metabolic acidosis was induced for 7 days in WT and Nrf2 KO mice. Nrf2 KO mice failed to induce Snat3 mRNA and protein expression during metabolic acidosis. However, there were no differences in blood pH, bicarbonate, pCO2, chloride and calcium or urinary pH, ammonium and phosphate levels. Normal induction of ammoniagenic enzymes was observed whereas several amino acid transporters showed differential regulation. Moreover, Nrf2 KO mice during acidosis showed increased expression of renal markers of oxidative stress and injury and NRF2 activity was increased during metabolic acidosis in WT kidney. We conclude that NRF2 is required to adapt the levels of SNAT3 in response to metabolic acidosis. In the absence of NRF2 and SNAT3, the kidney does not have any major acid handling defect; however, increased oxidative stress and renal injury may occur.
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Affiliation(s)
- Adam Lister
- Department of Pharmaceutical Sciences, Division of Molecular and Systems Toxicology, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland.,National Center for Competence in Research Kidney.CH, Zürich, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, Zürich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland.,National Center for Competence in Research Kidney.CH, Zürich, Switzerland
| | - Pedro H Imenez Silva
- Institute of Physiology, Zürich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland.,National Center for Competence in Research Kidney.CH, Zürich, Switzerland
| | - Isabel Rubio-Aliaga
- Institute of Physiology, Zürich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland.,National Center for Competence in Research Kidney.CH, Zürich, Switzerland
| | - Philippe Marbet
- Department of Pharmaceutical Sciences, Division of Molecular and Systems Toxicology, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland.,National Center for Competence in Research Kidney.CH, Zürich, Switzerland
| | - Joanne Walsh
- Department of Molecular and Clinical Pharmacology, MRC Centre for Drug Safety Science, University of Liverpool, Liverpool, L69 3GE, UK
| | - Luke M Shelton
- Department of Molecular and Clinical Pharmacology, MRC Centre for Drug Safety Science, University of Liverpool, Liverpool, L69 3GE, UK
| | - Bettina Keller
- Institute of Physiology, Zürich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
| | - Francois Verrey
- Institute of Physiology, Zürich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland.,National Center for Competence in Research Kidney.CH, Zürich, Switzerland
| | - Olivier Devuyst
- Institute of Physiology, Zürich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland.,National Center for Competence in Research Kidney.CH, Zürich, Switzerland
| | - Pieter Giesbertz
- Department of Biochemistry, ZIEL Research Center of Nutrition and Food Sciences, Technische Universität München, Freising, Germany
| | - Hannelore Daniel
- Department of Biochemistry, ZIEL Research Center of Nutrition and Food Sciences, Technische Universität München, Freising, Germany
| | - Christopher E Goldring
- Department of Molecular and Clinical Pharmacology, MRC Centre for Drug Safety Science, University of Liverpool, Liverpool, L69 3GE, UK
| | - Ian M Copple
- Department of Molecular and Clinical Pharmacology, MRC Centre for Drug Safety Science, University of Liverpool, Liverpool, L69 3GE, UK
| | - Carsten A Wagner
- Institute of Physiology, Zürich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland. .,National Center for Competence in Research Kidney.CH, Zürich, Switzerland.
| | - Alex Odermatt
- Department of Pharmaceutical Sciences, Division of Molecular and Systems Toxicology, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland. .,National Center for Competence in Research Kidney.CH, Zürich, Switzerland.
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25
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Bourgeois S, Bounoure L, Mouro-Chanteloup I, Colin Y, Brown D, Wagner CA. The ammonia transporter RhCG modulates urinary acidification by interacting with the vacuolar proton-ATPases in renal intercalated cells. Kidney Int 2018; 93:390-402. [PMID: 29054531 PMCID: PMC6166241 DOI: 10.1016/j.kint.2017.07.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 07/08/2017] [Accepted: 07/27/2017] [Indexed: 12/19/2022]
Abstract
Ammonium, stemming from renal ammoniagenesis, is a major urinary proton buffer and is excreted along the collecting duct. This process depends on the concomitant secretion of ammonia by the ammonia channel RhCG and of protons by the vacuolar-type proton-ATPase pump. Thus, urinary ammonium content and urinary acidification are tightly linked. However, mice lacking Rhcg excrete more alkaline urine despite lower urinary ammonium, suggesting an unexpected role of Rhcg in urinary acidification. RhCG and the B1 and B2 proton-ATPase subunits could be co-immunoprecipitated from kidney. In ex vivo microperfused cortical collecting ducts (CCD) proton-ATPase activity was drastically reduced in the absence of Rhcg. Conversely, overexpression of RhCG in HEK293 cells resulted in higher proton secretion rates and increased B1 proton-ATPase mRNA expression. However, in kidneys from Rhcg-/- mice the expression of only B1 and B2 subunits was altered. Immunolocalization of proton-ATPase subunits together with immuno-gold detection of the A proton-ATPase subunit showed similar localization and density of staining in kidneys from Rhcg+/+ and Rhcg-/-mice. In order to test for a reciprocal effect of intercalated cell proton-ATPases on Rhcg activity, we assessed Rhcg and proton-ATPase activities in microperfused CCD from Atp6v1b1-/- mice and showed reduced proton-ATPase activity without altering Rhcg activity. Thus, RhCG and proton-ATPase are located within the same cellular protein complex. RhCG may modulate proton-ATPase function and urinary acidification, whereas proton-ATPase activity does not affect RhCG function. This mechanism may help to coordinate ammonia and proton secretion beyond physicochemical driving forces.
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Affiliation(s)
- Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Lisa Bounoure
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | | | - Yves Colin
- UMR_S1134, INSERM, Université Paris Diderot, INTS, Labex GR-Ex, Paris, France
| | - Dennis Brown
- Center for Systems Biology, Program in Membrane Biology, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
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26
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Yang ZK, Gao F. The systematic analysis of ultraconserved genomic regions in the budding yeast. Bioinformatics 2018; 34:361-366. [PMID: 29028909 DOI: 10.1093/bioinformatics/btx619] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 09/26/2017] [Indexed: 11/12/2022] Open
Abstract
Motivation In the evolution of species, a kind of special sequences, termed ultraconserved sequences (UCSs), have been inherited without any change, which strongly suggests those sequences should be crucial for the species to survive or adapt to the environment. However, the UCSs are still regarded as mysterious genetic sequences so far. Here, we present a systematic study of ultraconserved genomic regions in the budding yeast based on the publicly available genome sequences, in order to reveal their relationship with the adaptability or fitness advantages of the budding yeast. Results Our results indicate that, in addition to some fundamental biological functions, the UCSs play an important role in the adaptation of Saccharomyces cerevisiae to the acidic environment, which is backed up by the previous observation. Besides that, we also find the highly unchanged genes are enriched in some other pathways, such as the nutrient-sensitive signaling pathway. To facilitate the investigation of unique UCSs, the UCSC Genome Browser was utilized to visualize the chromosomal position and related annotations of UCSs in S.cerevisiae genome. Availability and implementation For more details on UCSs, please refer to the Supplementary information online, and the custom code is available on request. Contact fgao@tju.edu.cn. Supplementary information Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Zhi-Kai Yang
- Department of Physics, Tianjin University, Tianjin 300072, China.,SinoGenoMax Co., Ltd./Chinese National Human Genome Center, Beijing 100176, China
| | - Feng Gao
- Department of Physics, Tianjin University, Tianjin 300072, China.,Key Laboratory of Systems Bioengineering (Ministry of Education).,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin 300072, China
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27
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Pathare G, Dhayat NA, Mohebbi N, Wagner CA, Bobulescu IA, Moe OW, Fuster DG. Changes in V-ATPase subunits of human urinary exosomes reflect the renal response to acute acid/alkali loading and the defects in distal renal tubular acidosis. Kidney Int 2018; 93:871-880. [PMID: 29310826 DOI: 10.1016/j.kint.2017.10.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 10/02/2017] [Accepted: 10/05/2017] [Indexed: 12/26/2022]
Abstract
In the kidney, final urinary acidification is achieved by V-ATPases expressed in type A intercalated cells. The B1 subunit of the V-ATPase is required for maximal urinary acidification, while the role of the homologous B2 subunit is less clear. Here we examined the effect of acute acid/alkali loading in humans on B1 and B2 subunit abundance in urinary exosomes in normal individuals and of acid loading in patients with distal renal tubular acidosis (dRTA). Specificities of B1 and B2 subunit antibodies were verified by yeast heterologously expressing human B1 and B2 subunits, and murine wild-type and B1-deleted kidney lysates. Acute ammonium chloride loading elicited systemic acidemia, a drop in urinary pH, and increased urinary ammonium excretion. Nadir urinary pH was achieved at four to five hours, and exosomal B1 abundance was significantly increased at two through six hours after ammonium chloride loading. After acute equimolar sodium bicarbonate loading, blood and urinary pH rose rapidly, with a concomitant reduction of exosomal B1 abundance within two hours, which remained lower throughout the test. In contrast, no change in exosomal B2 abundance was found following acid or alkali loading. In patients with inherited or acquired distal RTA, the urinary B1 subunit was extremely low or undetectable and did not respond to acid loading in urine, whereas no change in B2 subunit was found. Thus, both B1 and B2 subunits of the V-ATPase are detectable in human urinary exosomes, and acid and alkali loading or distal RTA cause changes in the B1 but not B2 subunit abundance in urinary exosomes.
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Affiliation(s)
- Ganesh Pathare
- Division of Nephrology and Hypertension, Bern University Hospital, University of Bern, Bern, Switzerland; Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland; National Centre of Competence in Research Transcure, University of Bern, Bern, Switzerland
| | - Nasser A Dhayat
- Division of Nephrology and Hypertension, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Nilufar Mohebbi
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center for Competence in Research Kidney.CH, Zurich, Switzerland
| | - Ion A Bobulescu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Orson W Moe
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Daniel G Fuster
- Division of Nephrology and Hypertension, Bern University Hospital, University of Bern, Bern, Switzerland; Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland; National Centre of Competence in Research Transcure, University of Bern, Bern, Switzerland.
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28
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Enerbäck S, Nilsson D, Edwards N, Heglind M, Alkanderi S, Ashton E, Deeb A, Kokash FEB, Bakhsh ARA, Van't Hoff W, Walsh SB, D'Arco F, Daryadel A, Bourgeois S, Wagner CA, Kleta R, Bockenhauer D, Sayer JA. Acidosis and Deafness in Patients with Recessive Mutations in FOXI1. J Am Soc Nephrol 2017; 29:1041-1048. [PMID: 29242249 DOI: 10.1681/asn.2017080840] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 11/15/2017] [Indexed: 11/03/2022] Open
Abstract
Maintenance of the composition of inner ear fluid and regulation of electrolytes and acid-base homeostasis in the collecting duct system of the kidney require an overlapping set of membrane transport proteins regulated by the forkhead transcription factor FOXI1. In two unrelated consanguineous families, we identified three patients with novel homozygous missense mutations in FOXI1 (p.L146F and p.R213P) predicted to affect the highly conserved DNA binding domain. Patients presented with early-onset sensorineural deafness and distal renal tubular acidosis. In cultured cells, the mutations reduced the DNA binding affinity of FOXI1, which hence, failed to adequately activate genes crucial for normal inner ear function and acid-base regulation in the kidney. A substantial proportion of patients with a clinical diagnosis of inherited distal renal tubular acidosis has no identified causative mutations in currently known disease genes. Our data suggest that recessive mutations in FOXI1 can explain the disease in a subset of these patients.
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Affiliation(s)
- Sven Enerbäck
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden;
| | - Daniel Nilsson
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Noel Edwards
- Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Mikael Heglind
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Sumaya Alkanderi
- Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Emma Ashton
- North East Thames Regional Genetic Service Laboratories, London, United Kingdom
| | - Asma Deeb
- Pediatric Services, Mafraq Hospital, Abu Dhabi, United Arab Emirates
| | - Feras E B Kokash
- College of Medicine, Gulf Medical University, Ajman, United Arab Emirates
| | - Abdul R A Bakhsh
- College of Medicine, Gulf Medical University, Ajman, United Arab Emirates
| | - William Van't Hoff
- Great Ormond Street Hospital for Children, National Health Service Foundation Trust, London, United Kingdom
| | - Stephen B Walsh
- University College London Centre for Nephrology, London, United Kingdom
| | - Felice D'Arco
- College of Medicine, Gulf Medical University, Ajman, United Arab Emirates
| | - Arezoo Daryadel
- Institute of Physiology, University of Zürich, Zurich, Switzerland; and.,National Center for Competence in Research, National Center in Competence in Research Kidney.CH, Zurich, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zürich, Zurich, Switzerland; and.,National Center for Competence in Research, National Center in Competence in Research Kidney.CH, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zürich, Zurich, Switzerland; and.,National Center for Competence in Research, National Center in Competence in Research Kidney.CH, Zurich, Switzerland
| | - Robert Kleta
- Great Ormond Street Hospital for Children, National Health Service Foundation Trust, London, United Kingdom.,University College London Centre for Nephrology, London, United Kingdom
| | - Detlef Bockenhauer
- Great Ormond Street Hospital for Children, National Health Service Foundation Trust, London, United Kingdom.,University College London Centre for Nephrology, London, United Kingdom
| | - John A Sayer
- Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, United Kingdom
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29
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Pathophysiology, diagnosis and treatment of inherited distal renal tubular acidosis. J Nephrol 2017; 31:511-522. [DOI: 10.1007/s40620-017-0447-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 09/21/2017] [Indexed: 10/18/2022]
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30
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Complicated pregnancies in inherited distal renal tubular acidosis: importance of acid-base balance. J Nephrol 2016; 30:455-460. [DOI: 10.1007/s40620-016-0370-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 12/06/2016] [Indexed: 01/08/2023]
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31
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Mohebbi N, Ferraro PM, Gambaro G, Unwin R. Tubular and genetic disorders associated with kidney stones. Urolithiasis 2016; 45:127-137. [DOI: 10.1007/s00240-016-0945-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 11/22/2016] [Indexed: 02/08/2023]
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32
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Schulze Blasum B, Schröter R, Neugebauer U, Hofschröer V, Pavenstädt H, Ciarimboli G, Schlatter E, Edemir B. The kidney-specific expression of genes can be modulated by the extracellular osmolality. FASEB J 2016; 30:3588-3597. [PMID: 27464968 DOI: 10.1096/fj.201600319r] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 07/05/2016] [Indexed: 12/29/2022]
Abstract
With this study, we wanted to prove the hypothesis that the unique extracellular osmolality within the renal medulla modulates a specific gene expression pattern. The physiologic functions of the kidneys are mediated by the segment-specific expression of key proteins. So far, we have limited knowledge about the mechanisms that control this gene expression pattern. The hyperosmolality in the renal medullary interstitium is of major importance as a driving force for urine concentration. We made use of primarily cultured rat renal inner medullary collecting-duct cells and microarray analysis to identify genes affected by the environmental osmolality of the culture medium. We identified hundreds of genes that were either induced or repressed in expression by hyperosmolality in a time- and osmolality-dependent fashion. Further analysis demonstrated that many of them, physiologically, showed a kidney- and even collecting-duct-specific expression, including secreted proteins, kinases, and transcription factors. On the other hand, we identified factors, down-regulated in expression, that have a diuretic effect. In conclusion, the kidney is the only organ that has such a hyperosmotic environment, and study provides an excellent method for controlling tissue-specific gene expression.-Schulze Blasum, B., Schröter, R., Neugebauer, U., Hofschröer, V., Pavenstädt, H., Ciarimboli, G., Schlatter E., Edemir, B. The kidney-specific expression of genes can be modulated by the extracellular osmolality.
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Affiliation(s)
- Britta Schulze Blasum
- Department of Internal Medicine D, Experimental Nephrology, University of Münster, Münster, Germany
| | - Rita Schröter
- Department of Internal Medicine D, Experimental Nephrology, University of Münster, Münster, Germany
| | - Ute Neugebauer
- Department of Internal Medicine D, Experimental Nephrology, University of Münster, Münster, Germany
| | - Verena Hofschröer
- Institute of Physiology II, University of Münster, Münster, Germany; and
| | - Hermann Pavenstädt
- Department of Internal Medicine D, Experimental Nephrology, University of Münster, Münster, Germany
| | - Guiliano Ciarimboli
- Department of Internal Medicine D, Experimental Nephrology, University of Münster, Münster, Germany
| | - Eberhard Schlatter
- Department of Internal Medicine D, Experimental Nephrology, University of Münster, Münster, Germany
| | - Bayram Edemir
- Department of Internal Medicine D, Experimental Nephrology, University of Münster, Münster, Germany; Faculty of Medicine, Department of Hematology and Oncology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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33
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Shavit L, Chen L, Ahmed F, Ferraro PM, Moochhala S, Walsh SB, Unwin R. Selective screening for distal renal tubular acidosis in recurrent kidney stone formers: initial experience and comparison of the simultaneous furosemide and fludrocortisone test with the short ammonium chloride test. Nephrol Dial Transplant 2016; 31:1870-1876. [PMID: 26961999 DOI: 10.1093/ndt/gfv423] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 11/10/2015] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Distal renal tubular acidosis (dRTA) is associated with renal stone disease, and it often needs to be considered and excluded in some recurrent calcium kidney stone formers (KSFs). However, a diagnosis of dRTA, especially when 'incomplete', can be missed and needs to be confirmed by a urinary acidification (UA) test. The gold standard reference test is still the short ammonium chloride (NH4Cl) test, but it is limited by gastrointestinal side effects and occasionally failure to ingest sufficient NH4Cl. For this reason, the furosemide plus fludrocortisone (F+F) test has been proposed as an easier and better-tolerated screening test. The aim of the present study was to assess the usefulness of the F+F test as a clinical screening tool for dRTA in a renal stone clinic. METHODS We studied 124 patients retrospectively in whom incomplete dRTA was suspected: 71 had kidney stones only, 9 had nephrocalcinosis only and 44 had both. A total of 158 UA tests were performed: 124 F+F and 34 NH4Cl; both tests were completed in 34 patients. RESULTS The mean age was 45.4 ± 15 years, and 49% of patients were male. The prevalence of complete and incomplete dRTAs was 7 and 13.7%, respectively. Of the 34 patients tested using both tests, 17 (50%) were abnormal and 4 (12%) were normal. Thirteen (39%) patients were abnormal by F+F, but normal by NH4Cl [sensitivity 100% (95% CI 80-100), specificity 24% (95% CI 7-50), positive predictive value 57% (95% CI 37-75), negative predictive value 100% (95% CI 40-100)]. CONCLUSIONS The F+F test is characterized by an excellent sensitivity and negative predictive value, and the diagnosis of incomplete dRTA can be excluded reliably in a patient who acidifies their urine normally with this test. However, its lack of specificity is a drawback, and if there is any doubt, an abnormal F+F test may need to be confirmed by a follow-up NH4Cl test. Ideally, a prospective blinded study in unselected KSFs is needed to accurately assess the reliability of the F+F test in diagnosing, rather than excluding, dRTA.
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Affiliation(s)
- Linda Shavit
- UCL Centre for Nephrology, University College London Medical School, Royal Free Campus and Hospital, London, UK
- Adult Nephrology Unit, Shaare Zedek Medical Center, Jerusalem, Israel
| | - Lucia Chen
- UCL Centre for Nephrology, University College London Medical School, Royal Free Campus and Hospital, London, UK
| | - Fayha Ahmed
- Department of Clinical Biochemistry, Royal Free Hospital, London, UK
| | | | - Shabbir Moochhala
- UCL Centre for Nephrology, University College London Medical School, Royal Free Campus and Hospital, London, UK
| | - Steven B Walsh
- UCL Centre for Nephrology, University College London Medical School, Royal Free Campus and Hospital, London, UK
| | - Robert Unwin
- UCL Centre for Nephrology, University College London Medical School, Royal Free Campus and Hospital, London, UK
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34
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Guh YJ, Yang CY, Liu ST, Huang CJ, Hwang PP. Oestrogen-related receptor α is required for transepithelial H+ secretion in zebrafish. Proc Biol Sci 2016; 283:20152582. [PMID: 26911965 PMCID: PMC4810828 DOI: 10.1098/rspb.2015.2582] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 02/02/2016] [Indexed: 01/22/2023] Open
Abstract
Oestrogen-related receptor α (ERRα) is an orphan nuclear receptor which is important for adaptive metabolic responses under conditions of increased energy demand, such as cold, exercise and fasting. Importantly, metabolism under these conditions is usually accompanied by elevated production of organic acids, which may threaten the body acid-base status. Although ERRα is known to help regulate ion transport by the renal epithelia, its role in the transport of acid-base equivalents remains unknown. Here, we tested the hypothesis that ERRα is involved in acid-base regulation mechanisms by using zebrafish as the model to examine the effects of ERRα on transepithelial H(+) secretion. ERRα is abundantly expressed in H(+)-pump-rich cells (HR cells), a group of ionocytes responsible for H(+) secretion in the skin of developing embryos, and its expression is stimulated by acidic (pH 4) environments. Knockdown of ERRα impairs both basal and low pH-induced H(+) secretion in the yolk-sac skin, which is accompanied by decreased expression of H(+)-secreting-related transporters. The effect of ERRα on H(+) secretion is achieved through regulating both the total number of HR cells and the function of individual HR cells. These results demonstrate, for the first time, that ERRα is required for transepithelial H(+) secretion for systemic acid-base homeostasis.
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Affiliation(s)
- Ying-Jey Guh
- Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan, Republic of China Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan, Republic of China
| | - Chao-Yew Yang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan, Republic of China
| | - Sian-Tai Liu
- Department of Life Science, National Taiwan Normal University, Taipei 11677, Taiwan, Republic of China
| | - Chang-Jen Huang
- Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan, Republic of China
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan, Republic of China
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35
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Cornelius RJ, Wang B, Wang-France J, Sansom SC. Maintaining K + balance on the low-Na +, high-K + diet. Am J Physiol Renal Physiol 2016; 310:F581-F595. [PMID: 26739887 DOI: 10.1152/ajprenal.00330.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 12/29/2015] [Indexed: 02/07/2023] Open
Abstract
A low-Na+, high-K+ diet (LNaHK) is considered a healthier alternative to the "Western" high-Na+ diet. Because the mechanism for K+ secretion involves Na+ reabsorptive exchange for secreted K+ in the distal nephron, it is not understood how K+ is eliminated with such low Na+ intake. Animals on a LNaHK diet produce an alkaline load, high urinary flows, and markedly elevated plasma ANG II and aldosterone levels to maintain their K+ balance. Recent studies have revealed a potential mechanism involving the actions of alkalosis, urinary flow, elevated ANG II, and aldosterone on two types of K+ channels, renal outer medullary K+ and large-conductance K+ channels, located in principal and intercalated cells. Here, we review these recent advances.
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Affiliation(s)
- Ryan J Cornelius
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon; and
| | - Bangchen Wang
- Department of Cellular/Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Jun Wang-France
- Department of Cellular/Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Steven C Sansom
- Department of Cellular/Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
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36
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Abstract
Metabolic acidosis could emerge from diseases disrupting acid-base equilibrium or from drugs that induce similar derangements. Occurrences are usually accompanied by comorbid conditions of drug-induced metabolic acidosis, and clinical outcomes may range from mild to fatal. It is imperative that clinicians not only are fully aware of the list of drugs that may lead to metabolic acidosis but also understand the underlying pathogenic mechanisms. In this review, we categorized drug-induced metabolic acidosis in terms of pathophysiological mechanisms, as well as individual drugs’ characteristics.
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Affiliation(s)
- Amy Quynh Trang Pham
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-8885, USA; Departments of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-8885, USA; Baylor Family Medicine Residency at Garland, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-8885, USA
| | - Li Hao Richie Xu
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-8885, USA
| | - Orson W Moe
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-8885, USA; Departments of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-8885, USA; Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-8885, USA
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37
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Pezzotti G, Puppulin L, La Rosa A, Boffelli M, Zhu W, McEntire BJ, Hosogi S, Nakahari T, Marunaka Y. Effect of pH and monovalent cations on the Raman spectrum of water: Basics revisited and application to measure concentration gradients at water/solid interface in Si3N4 biomaterial. Chem Phys 2015. [DOI: 10.1016/j.chemphys.2015.10.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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38
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Abstract
Acid-base homeostasis and pH regulation are critical for both normal physiology and cell metabolism and function. The importance of this regulation is evidenced by a variety of physiologic derangements that occur when plasma pH is either high or low. The kidneys have the predominant role in regulating the systemic bicarbonate concentration and hence, the metabolic component of acid-base balance. This function of the kidneys has two components: reabsorption of virtually all of the filtered HCO3(-) and production of new bicarbonate to replace that consumed by normal or pathologic acids. This production or generation of new HCO3(-) is done by net acid excretion. Under normal conditions, approximately one-third to one-half of net acid excretion by the kidneys is in the form of titratable acid. The other one-half to two-thirds is the excretion of ammonium. The capacity to excrete ammonium under conditions of acid loads is quantitatively much greater than the capacity to increase titratable acid. Multiple, often redundant pathways and processes exist to regulate these renal functions. Derangements in acid-base homeostasis, however, are common in clinical medicine and can often be related to the systems involved in acid-base transport in the kidneys.
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Affiliation(s)
- L Lee Hamm
- Department of Medicine, Section of Nephrology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana; and Medicine Service, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana
| | - Nazih Nakhoul
- Department of Medicine, Section of Nephrology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana; and Medicine Service, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana
| | - Kathleen S Hering-Smith
- Department of Medicine, Section of Nephrology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana; and Medicine Service, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana
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39
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Lin CH, Shih TH, Liu ST, Hsu HH, Hwang PP. Cortisol Regulates Acid Secretion of H(+)-ATPase-rich Ionocytes in Zebrafish (Danio rerio) Embryos. Front Physiol 2015; 6:328. [PMID: 26635615 PMCID: PMC4646979 DOI: 10.3389/fphys.2015.00328] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 10/29/2015] [Indexed: 01/01/2023] Open
Abstract
Systemic acid-base regulation is vital for physiological processes in vertebrates. Freshwater (FW) fish live in an inconstant environment, and thus frequently face ambient acid stress. FW fish have to efficiently modulate their acid secretion processes for body fluid acid-base homeostasis during ambient acid challenge; hormonal control plays an important role in such physiological regulation. The hormone cortisol was previously proposed to be associated with acid base regulation in FW fish; however, the underlying mechanism has not been fully described. In the present study, mRNA expression of acid-secreting related transporters and cyp11b (encoding an enzyme involved in cortisol synthesis) in zebrafish embryos was stimulated by treatment with acidic FW (AFW, pH 4.0) for 3 d. Exogenous cortisol treatment (20 mg/L, 3 d) resulted in upregulated expression of transporters related to acid secretion and increased acid secretion function at the organism level in zebrafish embryos. Moreover, cortisol treatment also significantly increased the acid secretion capacity of H(+)-ATPase-rich cells (HRCs) at the cellular level. In loss-of-function experiments, microinjection of glucocorticoid receptor (GR) morpholino (MO) suppressed the expression of acid-secreting related transporters, and decreased acid secretion function at both the organism and cellular levels; on the other hand, mineralocorticoid receptor (MR) MO did not induce any effects. Such evidence supports the hypothesized role of cortisol in fish acid-base regulation, and provides new insights into the roles of cortisol; cortisol-GR signaling stimulates zebrafish acid secretion function through transcriptional/translational regulation of the transporters and upregulation of acid secretion capacity in each acid-secreting ionocyte.
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Affiliation(s)
- Chia-Hao Lin
- Institute of Cellular and Organismic Biology, Academia SinicaTaipei, Taiwan
- National Institute for Basic Biology, National Institutes of Natural SciencesOkazaki, Japan
| | - Tin-Han Shih
- Biodiversity Research Center, Academia SinicaTaipei, Taiwan
| | - Sian-Tai Liu
- Department of Life Science, National Taiwan Normal UniversityTaipei, Taiwan
| | - Hao-Hsuan Hsu
- Institute of Cellular and Organismic Biology, Academia SinicaTaipei, Taiwan
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia SinicaTaipei, Taiwan
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40
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Aquaporin 2-labeled cells differentiate to intercalated cells in response to potassium depletion. Histochem Cell Biol 2015; 145:17-24. [PMID: 26496924 DOI: 10.1007/s00418-015-1372-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2015] [Indexed: 10/22/2022]
Abstract
The mammalian renal collecting duct consists of principal cells (PCs) and intercalated cells (ICs). Both PCs and ICs are involved in potassium (K(+)) homeostasis, PCs through their role in K(+) secretion and ICs through their ability to facilitate K(+) resorption. We previously hypothesized that PCs may differentiate into ICs upon K(+) depletion. However, no direct evidence has yet been obtained to conclusively demonstrate that PCs differentiate into ICs in response to K(+) depletion. Here, we present direct evidence for the differentiation of PCs into ICs by cell lineage tracing using aquaporin 2 (AQP2)-Cre mice and R26R-EYFP transgenic mice. In control mice, AQP2-EYFP(+) cells exhibited mainly a PC phenotype (AQP2-positive/H(+)-ATPase-negative). Interestingly, some AQP2-EYFP(+) cells exhibited an IC phenotype (H(+)-ATPase-positive/AQP2-negative); these cells accounted for 1.7 %. After K(+) depletion, the proportion of AQP2-EYFP(+) cells with an IC phenotype was increased to 4.1 %. Furthermore, some AQP2-EYFP(+) cells exhibited a "null cell" phenotype (AQP2-negative/H(+)-ATPase-negative) after K(+) depletion. Collectively, our data demonstrate that AQP2-labeled cells can differentiate into ICs, as well as null cells, in response to K(+) depletion. This finding indicates that some of AQP2-labeled cells possess properties of progenitor cells and that they can differentiate into ICs in the adult mouse kidney.
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Dhayat NA, Schaller A, Albano G, Poindexter J, Griffith C, Pasch A, Gallati S, Vogt B, Moe OW, Fuster DG. The Vacuolar H+-ATPase B1 Subunit Polymorphism p.E161K Associates with Impaired Urinary Acidification in Recurrent Stone Formers. J Am Soc Nephrol 2015; 27:1544-54. [PMID: 26453614 DOI: 10.1681/asn.2015040367] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 09/02/2015] [Indexed: 11/03/2022] Open
Abstract
Mutations in the vacuolar-type H(+)-ATPase B1 subunit gene ATP6V1B1 cause autosomal-recessive distal renal tubular acidosis (dRTA). We previously identified a single-nucleotide polymorphism (SNP) in the human B1 subunit (c.481G>A; p.E161K) that causes greatly diminished pump function in vitro To investigate the effect of this SNP on urinary acidification, we conducted a genotype-phenotype analysis of recurrent stone formers in the Dallas and Bern kidney stone registries. Of 555 patients examined, 32 (5.8%) were heterozygous for the p.E161K SNP, and the remaining 523 (94.2%) carried two wild-type alleles. After adjustment for sex, age, body mass index, and dietary acid and alkali intake, p.E161K SNP carriers had a nonsignificant tendency to higher urinary pH on a random diet (6.31 versus 6.09; P=0.09). Under an instructed low-Ca and low-Na diet, urinary pH was higher in p.E161K SNP carriers (6.56 versus 6.01; P<0.01). Kidney stones of p.E161K carriers were more likely to contain calcium phosphate than stones of wild-type patients. In acute NH4Cl loading, p.E161K carriers displayed a higher trough urinary pH (5.34 versus 4.89; P=0.01) than wild-type patients. Overall, 14.6% of wild-type patients and 52.4% of p.E161K carriers were unable to acidify their urine below pH 5.3 and thus, can be considered to have incomplete dRTA. In summary, our data indicate that recurrent stone formers with the vacuolar H(+)-ATPase B1 subunit p.E161K SNP exhibit a urinary acidification deficit with an increased prevalence of calcium phosphate-containing kidney stones. The burden of E161K heterozygosity may be a forme fruste of dRTA.
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Affiliation(s)
- Nasser A Dhayat
- Swiss National Centres of Competence in Research Kidney.CH and TransCure and Divisions of Nephrology, Hypertension and Clinical Pharmacology, Clinical Research, Bern University Hospital, University of Bern, Switzerland; and
| | - Andre Schaller
- Clinical Research, Bern University Hospital, University of Bern, Switzerland; and Human Genetics, and Departments of Pediatrics and
| | - Giuseppe Albano
- Swiss National Centres of Competence in Research Kidney.CH and TransCure and Divisions of Nephrology, Hypertension and Clinical Pharmacology, Clinical Research, Bern University Hospital, University of Bern, Switzerland; and Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - John Poindexter
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, and
| | - Carolyn Griffith
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, and
| | - Andreas Pasch
- Swiss National Centres of Competence in Research Kidney.CH and TransCure and Divisions of Nephrology, Hypertension and Clinical Pharmacology, Clinical Research, Bern University Hospital, University of Bern, Switzerland; and
| | - Sabina Gallati
- Clinical Research, Bern University Hospital, University of Bern, Switzerland; and Human Genetics, and Departments of Pediatrics and
| | - Bruno Vogt
- Swiss National Centres of Competence in Research Kidney.CH and TransCure and Divisions of Nephrology, Hypertension and Clinical Pharmacology, Clinical Research, Bern University Hospital, University of Bern, Switzerland; and
| | - Orson W Moe
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, and Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Daniel G Fuster
- Swiss National Centres of Competence in Research Kidney.CH and TransCure and Divisions of Nephrology, Hypertension and Clinical Pharmacology, Clinical Research, Bern University Hospital, University of Bern, Switzerland; and Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland;
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Aquaporin 1 Is Involved in Acid Secretion by Ionocytes of Zebrafish Embryos through Facilitating CO2 Transport. PLoS One 2015; 10:e0136440. [PMID: 26287615 PMCID: PMC4546062 DOI: 10.1371/journal.pone.0136440] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 08/04/2015] [Indexed: 12/29/2022] Open
Abstract
Mammalian aquaporin 1 (AQP1) is well known to function as a membrane channel for H2O and CO2 transport. Zebrafish AQP1a.1 (the homologue of mammalian AQP1) was recently identified in ionocytes of embryos; however its role in ionocytes is still unclear. In this study, we hypothesized that zebrafish AQP1a.1 is involved in the acid secretion by ionocytes through facilitating H2O and CO2 diffusion. A real-time PCR showed that mRNA levels of AQP1a.1 in embryos were induced by exposure to 1% CO2 hypercapnia for 3 days. In situ hybridization and immunohistochemistry showed that the AQP1a.1 transcript was highly expressed by acid-secreting ionocytes, i.e., H+-ATPase-rich (HR) cells. A scanning ion-selective electrode technique (SIET) was applied to analyze CO2-induced H+ secretion by individual ionocytes in embryos. H+ secretion by HR cells remarkably increased after a transient loading of CO2 (1% for 10 min). AQP1a.1 knockdown with morpholino oligonucleotides decreased the H+ secretion of HR cells by about half and limited the CO2 stimulated increase. In addition, exposure to an AQP inhibitor (PCMB) for 10 min also suppressed CO2-induced H+ secretion. Results from this study support our hypothesis and provide in vivo evidence of the physiological role of AQP1 in CO2 transport.
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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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Guh YJ, Lin CH, Hwang PP. Osmoregulation in zebrafish: ion transport mechanisms and functional regulation. EXCLI JOURNAL 2015; 14:627-59. [PMID: 26600749 PMCID: PMC4650948 DOI: 10.17179/excli2015-246] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 04/21/2015] [Indexed: 12/21/2022]
Abstract
Fish, like mammals, have to maintain their body fluid ionic and osmotic homeostasis through sophisticated iono-/osmoregulation mechanisms, which are conducted mainly by ionocytes of the gill (the skin in embryonic stages), instead of the renal tubular cells in mammals. Given the advantages in terms of genetic database availability and manipulation, zebrafish is an emerging model for research into regulatory and integrative physiology. At least five types of ionocytes, HR, NaR, NCC, SLC26, and KS cells, have been identified to carry out Na(+) uptake/H(+) secretion/NH4 (+) excretion, Ca(2+) uptake, Na(+)/Cl(-) uptake, K(+) secretion, and Cl(-) uptake/HCO3 (-) secretion, respectively, through distinct sets of transporters. Several hormones, namely isotocin, prolactin, cortisol, stanniocalcin-1, calcitonin, endothelin-1, vitamin D, parathyorid hormone 1, catecholamines, and the renin-angiotensin-system, have been demonstrated to positively or negatively regulate ion transport through specific receptors at different ionocytes stages, at either the transcriptional/translational or posttranslational level. The knowledge obtained using zebrafish answered many long-term contentious or unknown issues in the field of fish iono-/osmoregulation. The homology of ion transport pathways and hormone systems also means that the zebrafish model informs studies on mammals or other animal species, thereby providing insights into related fields.
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Affiliation(s)
- Ying-Jey Guh
- Institute of Cellular and Organismic Biology, Academia Sinica, Nakang, Taipei, Taiwan ; Institute of Biological Chemistry, Academia Sinica, Nakang, Taipei, Taiwan
| | - Chia-Hao Lin
- National Institute for Basic Biology, Myodaiji-cho, Okazaki, 444-8787, Japan
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Nakang, Taipei, Taiwan
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Furukawa F, Tseng YC, Liu ST, Chou YL, Lin CC, Sung PH, Uchida K, Lin LY, Hwang PP. Induction of Phosphoenolpyruvate Carboxykinase (PEPCK) during Acute Acidosis and Its Role in Acid Secretion by V-ATPase-Expressing Ionocytes. Int J Biol Sci 2015; 11:712-25. [PMID: 25999794 PMCID: PMC4440261 DOI: 10.7150/ijbs.11827] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 04/09/2015] [Indexed: 12/21/2022] Open
Abstract
Vacuolar-Type H+-ATPase (V-ATPase) takes the central role in pumping H+ through cell membranes of diverse organisms, which is essential for surviving acid-base fluctuating lifestyles or environments. In mammals, although glucose is believed to be an important energy source to drive V-ATPase, and phosphoenolpyruvate carboxykinase (PEPCK), a key enzyme for gluconeogenesis, is known to be activated in response to acidosis, the link between acid secretion and PEPCK activation remains unclear. In the present study, we used zebrafish larva as an in vivo model to show the role of acid-inducible PEPCK activity in glucose production to support higher rate of H+ secretion via V-ATPase, by utilizing gene knockdown, glucose supplementation, and non-invasive scanning ion-selective electrode technique (SIET). Zebrafish larvae increased V-ATPase-mediated acid secretion and transiently expression of Pck1, a zebrafish homolog of PEPCK, in response to acid stress. When pck1 gene was knocked down by specific morpholino, the H+ secretion via V-ATPase decreased, but this effect was rescued by supplementation of glucose into the yolk. By assessing changes in amino acid content and gene expression of respective enzymes, glutamine and glutamate appeared to be the major source for replenishment of Krebs cycle intermediates, which are subtracted by Pck1 activity. Unexpectedly, pck1 knockdown did not affect glutamine/glutamate catalysis, which implies that Pck1 does not necessarily drive this process. The present study provides the first in vivo evidence that acid-induced PEPCK provides glucose for acid-base homeostasis at an individual level, which is supported by rapid pumping of H+ via V-ATPase at the cellular level.
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Affiliation(s)
- Fumiya Furukawa
- 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan ; 2. Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
| | - Yung-Che Tseng
- 3. Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Sian-Tai Liu
- 3. Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Yi-Ling Chou
- 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan
| | - Ching-Chun Lin
- 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan
| | - Po-Hsuan Sung
- 4. Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Katsuhisa Uchida
- 2. Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
| | - Li-Yih Lin
- 3. Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Pung-Pung Hwang
- 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan
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Lin YH, Hung GY, Wu LC, Chen SW, Lin LY, Horng JL. Anion exchanger 1b in stereocilia is required for the functioning of mechanotransducer channels in lateral-line hair cells of zebrafish. PLoS One 2015; 10:e0117041. [PMID: 25679789 PMCID: PMC4332475 DOI: 10.1371/journal.pone.0117041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/18/2014] [Indexed: 11/19/2022] Open
Abstract
The anion exchanger (AE) plays critical roles in physiological processes including CO2 transport and volume regulation in erythrocytes and acid-base regulation in renal tubules. Although expression of the AE in inner-ear hair cells was reported, its specific localization and function are still unclear. Using in situ hybridization, we found that the AE1b transcript is expressed in lateral-line hair cells of zebrafish larvae. An immunohistochemical analysis with a zebrafish-specific antibody localized AE1b to stereocilia of hair cells, and the expression was eliminated by morpholino knockdown of AE1b. A non-invasive, scanning ion-selective electrode technique was applied to analyze mechanotransducer (MET) channel-mediated Ca2+ influx at stereocilia of hair cells of intact fish. Ca2+ influx was effectively suppressed by AE1b morpholino knockdown and inhibitor (DIDS) treatment. Elevating external Ca2+ (0.2 to 2 mM) neutralized the inhibition of DIDS. Taken together, this study provides solid evidence to show that AE1b in stereocilia is required for the proper functioning of MET channels.
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Affiliation(s)
- Yuan-Hsiang Lin
- Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, ROC
| | - Giun-Yi Hung
- Department of Pediatrics, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
- Department of Pediatrics, Faculty of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
| | - Liang-Chun Wu
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan, ROC
| | - Sheng-Wen Chen
- Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan, ROC
| | - Li-Yih Lin
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan, ROC
- * E-mail:
| | - Jiun-Lin Horng
- Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan, ROC
- * E-mail:
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Roy A, Al-bataineh MM, Pastor-Soler NM. Collecting duct intercalated cell function and regulation. Clin J Am Soc Nephrol 2015; 10:305-24. [PMID: 25632105 DOI: 10.2215/cjn.08880914] [Citation(s) in RCA: 149] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Intercalated cells are kidney tubule epithelial cells with important roles in the regulation of acid-base homeostasis. However, in recent years the understanding of the function of the intercalated cell has become greatly enhanced and has shaped a new model for how the distal segments of the kidney tubule integrate salt and water reabsorption, potassium homeostasis, and acid-base status. These cells appear in the late distal convoluted tubule or in the connecting segment, depending on the species. They are most abundant in the collecting duct, where they can be detected all the way from the cortex to the initial part of the inner medulla. Intercalated cells are interspersed among the more numerous segment-specific principal cells. There are three types of intercalated cells, each having distinct structures and expressing different ensembles of transport proteins that translate into very different functions in the processing of the urine. This review includes recent findings on how intercalated cells regulate their intracellular milieu and contribute to acid-base regulation and sodium, chloride, and potassium homeostasis, thus highlighting their potential role as targets for the treatment of hypertension. Their novel regulation by paracrine signals in the collecting duct is also discussed. Finally, this article addresses their role as part of the innate immune system of the kidney tubule.
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Affiliation(s)
- Ankita Roy
- Renal-Electrolyte Division, Department of Medicine; and
| | | | - Núria M Pastor-Soler
- Renal-Electrolyte Division, Department of Medicine; and Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania A.R. and M.M.A. contributed equally to this work.
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Bürki R, Mohebbi N, Bettoni C, Wang X, Serra AL, Wagner CA. Impaired expression of key molecules of ammoniagenesis underlies renal acidosis in a rat model of chronic kidney disease. Nephrol Dial Transplant 2014; 30:770-81. [PMID: 25523450 DOI: 10.1093/ndt/gfu384] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 11/19/2014] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Advanced chronic kidney disease (CKD) is associated with the development of renal metabolic acidosis. Metabolic acidosis per se may represent a trigger for progression of CKD. Renal acidosis of CKD is characterized by low urinary ammonium excretion with preserved urinary acidification indicating a defect in renal ammoniagenesis, ammonia excretion or both. The underlying molecular mechanisms, however, have not been addressed to date. METHODS We examined the Han:SPRD rat model and used a combination of metabolic studies, mRNA and protein analysis of renal molecules involved in acid-base handling. RESULTS We demonstrate that rats with reduced kidney function as evident from lower creatinine clearance, lower haematocrit, higher plasma blood urea nitrogen, creatinine, phosphate and potassium had metabolic acidosis that could be aggravated by HCl acid loading. Urinary ammonium excretion was highly reduced whereas urinary pH was more acidic in CKD compared with control animals. The abundance of key enzymes and transporters of proximal tubular ammoniagenesis (phosphate-dependent glutaminase, PEPCK and SNAT3) and bicarbonate transport (NBCe1) was reduced in CKD compared with control animals. In the collecting duct, normal expression of the B1 H(+)-ATPase subunit is in agreement with low urinary pH. In contrast, the RhCG ammonia transporter, critical for the final secretion of ammonia into urine was strongly down-regulated in CKD animals. CONCLUSION In the Han:SPRD rat model for CKD, key molecules required for renal ammoniagenesis and ammonia excretion are highly down-regulated providing a possible molecular explanation for the development and maintenance of renal acidosis in CKD patients.
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Affiliation(s)
- Remy Bürki
- Institute of Physiology and ZIHP, University of Zurich, Zurich, Switzerland
| | - Nilufar Mohebbi
- Institute of Physiology and ZIHP, University of Zurich, Zurich, Switzerland Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology and ZIHP, University of Zurich, Zurich, Switzerland
| | - Xueqi Wang
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland Department of Nephrology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Andreas L Serra
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology and ZIHP, University of Zurich, Zurich, Switzerland
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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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Kartner N, Manolson MF. Novel techniques in the development of osteoporosis drug therapy: the osteoclast ruffled-border vacuolar H(+)-ATPase as an emerging target. Expert Opin Drug Discov 2014; 9:505-22. [PMID: 24749538 DOI: 10.1517/17460441.2014.902155] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
INTRODUCTION Bone loss occurs in many diseases, including osteoporosis, rheumatoid arthritis and periodontal disease. For osteoporosis alone, it is estimated that 75 million people are afflicted worldwide, with high risks of fractures and increased morbidity and mortality. The demand for treatment consumes an ever-increasing share of healthcare resources. Successive generations of antiresorptive bisphosphonate drugs have reduced side effects, minimized frequency of dosing, and increased efficacy in halting osteoporotic bone loss, but their shortcomings have remained significant to the extent that a monoclonal antibody antiresorptive has recently taken a significant market share. Yet this latter, paradigm-shifting approach has its own drawbacks. AREAS COVERED This review summarizes recent literature on bone-remodeling cell and molecular biology and the background for existing approaches and emerging therapeutics and targets for treating osteoporosis. The authors discuss vacuolar H(+)-ATPase (V-ATPase) molecular biology and the recent advances in targeting the osteoclast ruffled-border V-ATPase (ORV) for the development of novel antiresorptive drugs. They also cover examples from the V-ATPase-targeted drug discovery literature, including conventional molecular biology methods, in silico drug discovery, and gene therapy in more detail as proofs of concept. EXPERT OPINION Existing therapeutic options for osteoporosis have limitations and inherent drawbacks. Thus, the search for novel approaches to osteoporosis drug discovery remains relevant. Targeting the ORV may be one of the more selective means of regulating bone resorption. Furthermore, this approach may be effective without removing active osteoclasts from the finely balanced osteoclast-osteoblast coupling required for normal bone remodeling.
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Affiliation(s)
- Norbert Kartner
- University of Toronto , 124 Edward Street, Toronto, Ontario M5G 1G6 , Canada
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