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Kong W, Sun X, Yu S, Liu P, Zheng X, Zhang J, Zhu L, Jiang T, Jin M, Gao J, Fan X, Liu X, Liu L. Bile duct ligation increased dopamine levels in the cerebral cortex of rats partly due to induction of tyrosine hydroxylase. Br J Pharmacol 2023. [PMID: 36692417 DOI: 10.1111/bph.16041] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 01/10/2023] [Accepted: 01/18/2023] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND AND PURPOSE Liver failure is associated with psychiatric alterations, partly resulting from the increased brain dopamine levels. We investigated the relationship between increased dopamine levels and mental abnormalities using bile duct ligation (BDL) rats and the mechanism by which liver failure increased dopamine levels in SH-SY5Y cells. Behavioural tests were carried out on day 13 and 27 following BDL, along with measurements of dopamine and metabolites, expressions of enzymes and transporters related to dopamine metabolism, and its transport into the cortex and the hippocampus. SH-SY5Y cells were used to investigate whether NH4 Cl, bile acids and bilirubin affected expression of tyrosine hydroxylase or not. Tyrosine hydroxylase (TH) expression in SH-SY5Y cells co-incubated with bilirubin and signal pathway inhibitors was measured. KEY RESULTS Open-field test results demonstrated BDL rats showed anxiety-like behaviour, accompanied by increased dopamine levels and expression of TH protein in the cortex. Membrane bound long form (MB)-COMT, slightly but significantly decreased. SH-SY5Y cells indicated that increased bilirubin levels was a factor in inducing TH expression. Both inhibitor of NF-κB pathway BAY 11-7082 and silencing NF-κB p65 reversed bilirubin-induced upregulation of TH protein. NF-κB activator TNF-α increased expression of TH protein. Roles of bilirubin in increases of TH protein expressions and dopamine levels were measured using hyperbilirubinemia rats. Anxiety-like behaviour, was associated with increased dopamine levels and TH protein expressions in hyperbilirubinemia rats. CONCLUSION AND IMPLICATIONS BDL significantly increased dopamine levels in rat cortex partly due to bilirubin-mediated TH induction. Increased bilirubin induced TH expression via activating NF-κB signalling pathway.
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Affiliation(s)
- Weimin Kong
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China.,School of Pharmacy, Bengbu Medical College, 2600 Donghai Road, Bengbu, Anhui, China
| | - Xueying Sun
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Siyu Yu
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Peihua Liu
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Xiaoke Zheng
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Jiaxin Zhang
- Hunan Provincial People's Hospital (The first-affiliated hospital of Hunan Normal University), Changsha, China
| | - Liang Zhu
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Tianxin Jiang
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Mengmeng Jin
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Jinghui Gao
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Xiaomin Fan
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Xiaodong Liu
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Li Liu
- Center of Drug Metabolism and Pharmacokinetics, School of Pharmacy, China Pharmaceutical University, Nanjing, China
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Oral Acid Load Down-Regulates Fibroblast Growth Factor 23. Nutrients 2022; 14:nu14051041. [PMID: 35268016 PMCID: PMC8912769 DOI: 10.3390/nu14051041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/25/2022] [Accepted: 02/26/2022] [Indexed: 11/30/2022] Open
Abstract
Increased dietary acid load has a negative impact on health, particularly when renal function is compromised. Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that is elevated during renal failure. The relationship between metabolic acidosis and FGF23 remains unclear. To investigate the effect of dietary acid load on circulating levels of FGF23, rats with normal renal function and with a graded reduction in renal mass (1/2 Nx and 5/6 Nx) received oral NH4Cl for 1 month. Acid intake resulted in a consistent decrease of plasma FGF23 concentrations in all study groups when compared with their non-acidotic control: 239.3 ± 13.5 vs. 295.0 ± 15.8 pg/mL (intact), 346.4 ± 19.7 vs. 522.6 ± 29.3 pg/mL (1/2 Nx) and 988.0 ± 125.5 vs. 2549.4 ± 469.7 pg/mL (5/6 Nx). Acidosis also decreased plasma PTH in all groups, 96.5 ± 22.3 vs. 107.3 ± 19.1 pg/mL, 113.1 ± 17.3 vs. 185.8 ± 22.2 pg/mL and 504.9 ± 75.7 vs. 1255.4 ± 181.1 pg/mL. FGF23 showed a strong positive correlation with PTH (r = 0.877, p < 0.0001) and further studies demonstrated that acidosis did not influence plasma FGF23 concentrations in parathyroidectomized rats, 190.0 ± 31.6 vs. 215 ± 25.6 pg/mL. In conclusion, plasma concentrations of FGF23 are consistently decreased in rats with metabolic acidosis secondary to increased acid intake, both in animals with intact renal function and with decreased renal function. The in vivo effect of metabolic acidosis on FGF23 appears to be related to the simultaneous decrease in PTH.
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Khajah MA, Khushaish S, Luqmani YA. Lactate Dehydrogenase A or B Knockdown Reduces Lactate Production and Inhibits Breast Cancer Cell Motility in vitro. Front Pharmacol 2021; 12:747001. [PMID: 34744727 PMCID: PMC8564068 DOI: 10.3389/fphar.2021.747001] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Accepted: 10/06/2021] [Indexed: 12/20/2022] Open
Abstract
Background: Lactate dehydrogenase (LDH) plays an important role in cancer pathogenesis and enhanced expression/activity of this enzyme has been correlated with poor prognosis. In this study we determined the expression profile of LDH-A and B in normal as well as in endocrine-resistant and -responsive breast cancer cells and the effect of their knockdown on LDH activity, lactate production, proliferation and cell motility. Methods: Knockdown experiments were performed using siRNA and shRNA. The expression profile of LDH and signaling molecules was determined using PCR and western blotting. Intracellular LDH activity and extracellular lactate levels were measured by a biochemical assay. Cell motility was determined using wound healing, while proliferation was determined using MTT assay. Results: LDH-A was expressed in all of the tested cell lines, while LDH-B was specifically expressed only in normal and endocrine-resistant breast cancer cells. This was correlated with significantly enhanced LDH activity and lactate production in endocrine resistant breast cancer cells when compared to normal or endocrine responsive cancer cells. LDH-A or -B knockdown significantly reduced LDH activity and lactate production, which led to reduced cell motility. Exogenous lactate supplementation enhanced cell motility co-incident with enhanced phosphorylation of ERK1/2 and reduced E-cadherin expression. Also, LDH-A or -B knockdown reduced ERK 1/2 phosphorylation. Conclusion: Enhanced cell motility in endocrine resistant breast cancer cells is at least in part mediated by enhanced extracellular lactate levels, and LDH inhibition might be a promising therapeutic target to inhibit cancer cell motility.
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Jabalameli MR, Fitzpatrick FM, Colombo R, Howles SA, Leggatt G, Walker V, Wiberg A, Kunji ERS, Ennis S. Exome sequencing identifies a disease variant of the mitochondrial ATP-Mg/Pi carrier SLC25A25 in two families with kidney stones. Mol Genet Genomic Med 2021; 9:e1749. [PMID: 34346195 PMCID: PMC8683635 DOI: 10.1002/mgg3.1749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 05/13/2021] [Accepted: 07/01/2021] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Calcium kidney stones are common and recurrences are often not preventable by available empiric remedies. Their etiology is multifactorial and polygenic, and an increasing number of genes are implicated. Their identification will enable improved management. METHODS DNA from three stone-formers in a Southampton family (UK) and two from an Italian family were analyzed independently by whole exome sequencing and selected variants were genotyped across all available members of both pedigrees. A disease variant of SLC25A25 (OMIM 608745), encoding the mitochondrial ATP-Mg/Pi carrier 3 (APC3) was identified, and analyzed structurally and functionally with respect to its calcium-regulated transport activity. RESULTS All five patients had a heterozygous dominant SLC25A25 variant (rs140777921; GRCh37.p13: chr 9 130868670 G>C; p.Gln349His; Reference Sequence NM_001006641.3). Non-stone formers also carried the variant indicating incomplete penetrance. Modeling suggests that the variant lacks a conserved polar interaction, which may cause structural instability. Calcium-regulated ATP transport was reduced to ~20% of the wild type, showing a large reduction in function. CONCLUSION The transporter is important in regulating mitochondrial ATP production. This rare variant may increase urine lithogenicity through impaired provision of ATP for solute transport processes in the kidney, and/or for purinergic signaling. Variants found in other genes may compound this abnormality.
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Affiliation(s)
- M Reza Jabalameli
- Department of Human Genetics and Genomic Medicine, University of Southampton, Southampton, UK
| | - Fiona M Fitzpatrick
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Roberto Colombo
- Faculty of Medicine 'Agostino Gemelli', Catholic University of the Sacred Heart, Rome, Italy.,Center for the Study of Rare Inherited Diseases, Niguarda Ca´Granda Metropolitan Hospital, Milan, Italy
| | - Sarah A Howles
- Nuffield Department of Surgical Sciences, University of Oxford, Oxford, UK.,Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Gary Leggatt
- Department of Human Genetics and Genomic Medicine, University of Southampton, Southampton, UK.,Wessex Kidney Centre, Queen Alexandra Hospital, Portsmouth, UK
| | - Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton, Southampton, UK
| | - Akira Wiberg
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - Edmund R S Kunji
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Sarah Ennis
- Department of Human Genetics and Genomic Medicine, University of Southampton, Southampton, UK
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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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Mucosal acidosis elicits a unique molecular signature in epithelia and intestinal tissue mediated by GPR31-induced CREB phosphorylation. Proc Natl Acad Sci U S A 2021; 118:2023871118. [PMID: 33972436 DOI: 10.1073/pnas.2023871118] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Metabolic changes associated with tissue inflammation result in significant extracellular acidosis (EA). Within mucosal tissues, intestinal epithelial cells (IEC) have evolved adaptive strategies to cope with EA through the up-regulation of SLC26A3 to promote pH homeostasis. We hypothesized that EA significantly alters IEC gene expression as an adaptive mechanism to counteract inflammation. Using an unbiased RNA sequencing approach, we defined the impact of EA on IEC gene expression to define molecular mechanisms by which IEC respond to EA. This approach identified a unique gene signature enriched in cyclic AMP response element-binding protein (CREB)-regulated gene targets. Utilizing loss- and gain-of-function approaches in cultured epithelia and murine colonoids, we demonstrate that EA elicits prominent CREB phosphorylation through cyclic AMP-independent mechanisms that requires elements of the mitogen-activated protein kinase signaling pathway. Further analysis revealed that EA signals through the G protein-coupled receptor GPR31 to promote induction of FosB, NR4A1, and DUSP1. These studies were extended to an in vivo murine model in conjunction with colonization of a pH reporter Escherichia coli strain that demonstrated significant mucosal acidification in the TNFΔARE model of murine ileitis. Herein, we observed a strong correlation between the expression of acidosis-associated genes with bacterial reporter sfGFP intensity in the distal ileum. Finally, the expression of this unique EA-associated gene signature was increased during active inflammation in patients with Crohn's disease but not in the patient control samples. These findings establish a mechanism for EA-induced signals during inflammation-associated acidosis in both murine and human ileitis.
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7
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Egli-Spichtig D, Zhang MYH, Li A, Pastor Arroyo EM, Hernando N, Wagner CA, Chang W, Perwad F. Renal Dnase1 expression is regulated by FGF23 but loss of Dnase1 does not alter renal phosphate handling. Sci Rep 2021; 11:6175. [PMID: 33731726 PMCID: PMC7969776 DOI: 10.1038/s41598-021-84735-3] [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: 07/22/2020] [Accepted: 02/02/2021] [Indexed: 11/16/2022] Open
Abstract
Fibroblast growth factor 23 (FGF23) is a bone-derived endocrine hormone that regulates phosphate and vitamin D metabolism. In models of FGF23 excess, renal deoxyribonuclease 1 (Dnase1) mRNA expression is downregulated. Dnase-1 is an endonuclease which binds monomeric actin. We investigated whether FGF23 suppresses renal Dnase-1 expression to facilitate endocytic retrieval of renal sodium dependent phosphate co-transporters (NaPi-IIa/c) from the brush border membrane by promoting actin polymerization. We showed that wild type mice on low phosphate diet and Fgf23−/− mice with hyperphosphatemia have increased renal Dnase1 mRNA expression while in Hyp mice with FGF23 excess and hypophosphatemia, Dnase1 mRNA expression is decreased. Administration of FGF23 in wild type and Fgf23−/− mice lowered Dnase1 expression. Taken together, our data shows that Dnase1 is regulated by FGF23. In 6-week-old Dnase1−/− mice, plasma phosphate and renal NaPi-IIa protein were significantly lower compared to wild-type mice. However, these changes were transient, normalized by 12 weeks of age and had no impact on bone morphology. Adaptation to low and high phosphate diet were similar in Dnase1−/− and Dnase1+/+ mice, and loss of Dnase1 gene expression did not rescue hyperphosphatemia in Fgf23−/− mice. We conclude that Dnase-1 does not mediate FGF23-induced inhibition of renal tubular phosphate reabsorption.
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Affiliation(s)
- Daniela Egli-Spichtig
- Division of Nephrology, Department of Pediatrics, University of California San Francisco, San Francisco, USA
| | - Martin Y H Zhang
- Division of Nephrology, Department of Pediatrics, University of California San Francisco, San Francisco, USA
| | - Alfred Li
- Department of Medicine, San Francisco Veterans Affairs Medical Center (VAMC), University of California San Francisco, San Francisco, USA
| | - Eva Maria Pastor Arroyo
- Institute of Physiology, University of Zurich, Zurich Switzerland and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Zurich Switzerland and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich Switzerland and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Wenhan Chang
- Department of Medicine, San Francisco Veterans Affairs Medical Center (VAMC), University of California San Francisco, San Francisco, USA
| | - Farzana Perwad
- Division of Nephrology, Department of Pediatrics, University of California San Francisco, San Francisco, USA. .,Children's Renal Center, University of California San Francisco, 550, 16th Street, 5th Floor, MH-5351, San Francisco, CA, 94143-3214, USA.
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8
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Yoo A, Lee H, Jung J, Koh SS, Lee S. Monocarboxylate transporter 9 (MCT9) is down-regulated in renal cell carcinoma. Genes Genomics 2021; 43:351-359. [PMID: 33555501 DOI: 10.1007/s13258-020-01035-2] [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: 10/17/2020] [Accepted: 12/23/2020] [Indexed: 10/22/2022]
Abstract
BACKGROUND The renal cell carcinoma (RCC) incidences are continuously increasing, however, their proper characterization remains difficult. Mammalian kidneys require large amounts of energy, and monocarboxylate transporter (MCT) gene family is responsible for the transport of monocarboxylic compounds across plasma membranes. OBJECTIVE A total of 14 MCT members have been identified in humans, which show highly distinct substrate affinities and tissue distributions. To understand the yet-uncharacterized renal cancer-specific role of MCTs, we identified MCT members that are differentially regulated during the renal tumor progression. METHODS We examined the expression level of MCT members in renal cell tumors and their relationship with survival rate of patients using a public database. Quantitative RT-PCR and northern blotting were performed to validate the expression of MCTs. Anti-MCT9 antiserum was raised in rabbit and used to examine MCT9 expression in normal and tumor tissue arrays. Effect of MCT9 overexpression on cell proliferation was measured using renal cancer cell lines. RESULTS MCT9 was found to be abundantly and exclusively expressed in human kidney cells, and was highly downregulated in renal cancers. Kaplan-Meier plotter analysis revealed an increased survival rate of MCT9 high-expressing RCC patients. MCT9 proteins were detected in normal kidney tissue sections and their overexpression clearly attenuated renal cell proliferation. CONCLUSIONS MCT9 was identified as a novel highly downregulated gene in renal cell cancer, and its overexpression clearly attenuated RCC cell proliferation. Thus, functional analysis of MCT9 may help in deciphering a yet-undiscovered kidney-specific energy metabolism during renal tumor progression.
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Affiliation(s)
- Ara Yoo
- Department of Microbiology and Molecular Biology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Hyeonhee Lee
- Department of Microbiology and Molecular Biology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Jinyoung Jung
- Department of Microbiology and Molecular Biology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Sang Seok Koh
- Department of Biological Sciences, Dong-A University, Busan, 49315, Republic of Korea
| | - Soojin Lee
- Department of Microbiology and Molecular Biology, Chungnam National University, Daejeon, 34134, Republic of Korea.
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Bugarski M, Ghazi S, Polesel M, Martins JR, Hall AM. Changes in NAD and Lipid Metabolism Drive Acidosis-Induced Acute Kidney Injury. J Am Soc Nephrol 2021; 32:342-356. [PMID: 33478973 PMCID: PMC8054907 DOI: 10.1681/asn.2020071003] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 10/30/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The kidney plays an important role in maintaining normal blood pH. Metabolic acidosis (MA) upregulates the pathway that mitochondria in the proximal tubule (PT) use to produce ammonia and bicarbonate from glutamine, and is associated with AKI. However, the extent to which MA causes AKI, and thus whether treating MA would be beneficial, is unclear. METHODS Gavage with ammonium chloride induced acute MA. Multiphoton imaging of mitochondria (NADH/membrane potential) and transport function (dextran/albumin uptake), oxygen consumption rate (OCR) measurements in isolated tubules, histologic analysis, and electron microscopy in fixed tissue, and urinary biomarkers (KIM-1/clara cell 16) assessed tubular cell structure and function in mouse kidney cortex. RESULTS MA induces an acute change in NAD redox state (toward oxidation) in PT mitochondria, without changing the mitochondrial energization state. This change is associated with a switch toward complex I activity and decreased maximal OCR, and a major alteration in normal lipid metabolism, resulting in marked lipid accumulation in PTs and the formation of large multilamellar bodies. These changes, in turn, lead to acute tubular damage and a severe defect in solute uptake. Increasing blood pH with intravenous bicarbonate substantially improves tubular function, whereas preinjection with the NAD precursor nicotinamide (NAM) is highly protective. CONCLUSIONS MA induces AKI via changes in PT NAD and lipid metabolism, which can be reversed or prevented by treatment strategies that are viable in humans. These findings might also help to explain why MA accelerates decline in function in CKD.
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Affiliation(s)
- Milica Bugarski
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Susan Ghazi
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | | | - Joana R. Martins
- Institute of Anatomy, University of Zurich, Zurich, Switzerland,Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Andrew M. Hall
- Institute of Anatomy, University of Zurich, Zurich, Switzerland,Department of Nephrology, University Hospital Zurich, Zurich, Switzerland
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10
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Ugrica M, Bettoni C, Bourgeois S, Daryadel A, Pastor-Arroyo EM, Gehring N, Hernando N, Wagner CA, Rubio-Aliaga I. A chronic high phosphate intake in mice is detrimental for bone health without major renal alterations. Nephrol Dial Transplant 2021; 36:gfab015. [PMID: 33515264 DOI: 10.1093/ndt/gfab015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Phosphate intake has increased in the last decades due to a higher consumption of processed foods. This higher intake is detrimental for patients with chronic kidney disease, increasing mortality and cardiovascular disease risk and accelerating kidney dysfunction. Whether a chronic high phosphate diet is also detrimental for the healthy population is still under debate. METHODS We fed healthy mature adult mice over a period of one year with either a high (1.2% w/w) or a standard (0.6% w/w) phosphate diet, and investigated the impact of a high phosphate diet on mineral homeostasis, kidney function and bone health. RESULTS The high phosphate diet increased plasma phosphate, parathyroid hormone (PTH) and calcitriol levels, with no change in fibroblast growth factor 23 levels. Urinary phosphate, calcium and ammonium excretion were increased. Measured glomerular filtration rate was apparently unaffected, while blood urea was lower and urea clearance was higher in animals fed the high phosphate diet. No change was observed in plasma creatinine levels. Blood and urinary pH were more acidic paralleled by higher bone resorption observed in animals fed a high phosphate diet. Total and cortical bone mineral density was lower in animals fed a high phosphate diet and this effect is independent of the higher PTH levels observed. CONCLUSIONS A chronic high phosphate intake did not cause major renal alterations, but affected negatively bone health, increasing bone resorption and decreasing bone mineral density.
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Affiliation(s)
- Marko Ugrica
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Arezoo Daryadel
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Eva-Maria Pastor-Arroyo
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Nicole Gehring
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Isabel Rubio-Aliaga
- Institute of Physiology, University of Zurich, and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
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Transcriptomic Analysis of Gill and Kidney from Asian Seabass ( Lates calcarifer) Acclimated to Different Salinities Reveals Pathways Involved with Euryhalinity. Genes (Basel) 2020; 11:genes11070733. [PMID: 32630108 PMCID: PMC7397140 DOI: 10.3390/genes11070733] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/29/2020] [Accepted: 06/29/2020] [Indexed: 12/13/2022] Open
Abstract
Asian seabass (or commonly known as barramundi), Lates calcarifer, is a bony euryhaline teleost from the Family Latidae, inhabiting nearshore, estuarine, and marine connected freshwaters throughout the tropical Indo-West Pacific region. The species is catadromous, whereby adults spawn in salinities between 28 and 34 ppt at the mouth of estuaries, with resultant juveniles usually moving into brackish and freshwater systems to mature, before returning to the sea to spawn again as adults. The species lives in both marine and freshwater habitats and can move quickly between the two; thus, the species' ability to tolerate changes in salinity makes it a good candidate for studying the salinity acclimation response in teleosts. In this study, the transcriptome of two major osmoregulatory organs (gills and kidneys) of young juvenile Asian seabass reared in freshwater and seawater were compared. The euryhaline nature of Asian seabass was found to be highly pliable and the moldability of the trait was further confirmed by histological analyses of gills and kidneys. Differences in major expression pathways were observed, with differentially expressed genes including those related to osmoregulation, tissue/organ morphogenesis, and cell volume regulation as central to the osmo-adaptive response. Additionally, genes coding for mucins were upregulated specifically under saline conditions, whereas several genes important for growth and development, as well as circadian entrainment were specifically enriched in fish reared in freshwater. Routing of the circadian rhythm mediated by salinity changes could be the initial step in salinity acclimation and possibly migration in euryhaline fish species such as the Asian seabass.
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12
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Gottier Nwafor J, Nowik M, Anzai N, Endou H, Wagner CA. Metabolic Acidosis Alters Expression of Slc22 Transporters in Mouse Kidney. Kidney Blood Press Res 2020; 45:263-274. [PMID: 32062662 DOI: 10.1159/000506052] [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: 11/16/2019] [Accepted: 01/20/2020] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION The kidneys play a central role in eliminating metabolic waste products and drugs through transporter-mediated excretion along the proximal tubule. This task is mostly achieved through a variety of transporters from the solute carrier family 22 (SLC22) family of organic cation and anion transporters. Metabolic acidosis modulates metabolic and renal functions and also affects the clearance of metabolites and drugs from the body. We had previously shown that induction of metabolic acidosis in mice alters a large set of transcripts, among them also many transporters including transporters from the Slc22 family. OBJECTIVE Here we further investigated the impact of acidosis on Slc22 family members. METHODS Metabolic acidosis was induced for 2 or 7 days with NH4Cl, some animals also received the uricase inhibitor oxonic acid for comparison. Expression of transporters was studied by qPCR and immunoblotting. RESULTS NH4Cl induced no significant changes in plasma or urine uric acid levels but caused downregulation of Slc22a1 (Oct1), Slc22a6 (Oat1), Slc22a19 (Oat5), and -Slc22a12 (Urat1) at mRNA level. In contrast, Slc22a4 mRNA (Octn1) was upregulated. On protein level, NH4Cl increased Octn1 (after 7 days) and Urat1 (after 2 days) abundance and decreased Oat1 (after 2 days) and Urat1 (after 7 days). Oxonic acid had no impact on protein abundance of any of the transporters tested. CONCLUSION In summary, metabolic acidosis alters expression of several transporters involved in renal excretion of metabolic waste products and drugs. This may have implications for drug kinetics and clearance of waste metabolites.
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Affiliation(s)
- Janine Gottier Nwafor
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Marta Nowik
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Naohiko Anzai
- Department of Pharmacology, Chiba University Graduate School of Medicine, Chiba, Japan
| | - Hitoshi Endou
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Tokyo, Japan
| | - Carsten A Wagner
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland,
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13
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Wesson DE, Buysse JM, Bushinsky DA. Mechanisms of Metabolic Acidosis-Induced Kidney Injury in Chronic Kidney Disease. J Am Soc Nephrol 2020; 31:469-482. [PMID: 31988269 DOI: 10.1681/asn.2019070677] [Citation(s) in RCA: 104] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Retrospective analyses and single-center prospective studies identify chronic metabolic acidosis as an independent and modifiable risk factor for progression of CKD. In patients with CKD, untreated chronic metabolic acidosis often leads to an accelerated reduction in GFR. Mechanisms responsible for this reduction include adaptive responses that increase acid excretion but lead to a decline in kidney function. Metabolic acidosis in CKD stimulates production of intrakidney paracrine hormones including angiotensin II, aldosterone, and endothelin-1 (ET-1) that mediate the immediate benefit of increased kidney acid excretion, but their chronic upregulation promotes inflammation and fibrosis. Chronic metabolic acidosis also stimulates ammoniagenesis that increases acid excretion but also leads to ammonia-induced complement activation and deposition of C3 and C5b-9 that can cause tubule-interstitial damage, further worsening disease progression. These effects, along with acid accumulation in kidney tissue, combine to accelerate progression of kidney disease. Treatment of chronic metabolic acidosis attenuates these adaptive responses; reduces levels of angiotensin II, aldosterone, and ET-1; reduces ammoniagenesis; and diminishes inflammation and fibrosis that may lead to slowing of CKD progression.
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Affiliation(s)
- Donald E Wesson
- Baylor Scott & White Health and Wellness Center, Dallas, Texas; .,Department of Internal Medicine, Texas A&M College of Medicine, Bryan, Texas
| | | | - David A Bushinsky
- Division of Nephrology, University of Rochester School of Medicine, Rochester, New York
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Monosodium Glutamate (MSG) Renders Alkalinizing Properties and Its Urinary Metabolic Markers of MSG Consumption in Rats. Biomolecules 2019; 9:biom9100542. [PMID: 31569818 PMCID: PMC6843139 DOI: 10.3390/biom9100542] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 09/25/2019] [Accepted: 09/26/2019] [Indexed: 12/12/2022] Open
Abstract
Monosodium glutamate (MSG) is widely used as a flavor enhancer and its effects on human health are still debated. We aimed to investigate whether MSG can act as alkalinizing agent in murine models and if its metabolites are biomarkers of MSG consumption. For this purpose, adult male Wistar rats were given water added with 1 g% MSG or three types of control water, including sodium chloride (NaCl) and sodium bicarbonate (NaHCO3). At 14 days, urinary pH, electrolytes, urinary metabolites and ion-exchanger gene expression were determined. The results revealed that MSG-treated rats had significantly more alkaline urine and higher levels of urinary sodium and bicarbonate similar to NaHCO3 controls. These changes correlated with a lower expression of ion-exchanger genes, namely, CAII, NBC1, and AE1, which are involved in bicarbonate kidney reabsorption. The urinary metabolic profiles also revealed similar patterns for the MSG and NaHCO3 groups. In conclusion, MSG exhibits similar properties to NaHCO3, an alkalinizing agent, with regard to inducing alkaline urine, reducing bicarbonate kidney reabsorption, and generating a specific urinary metabolic pattern. We believe that these observations will be useful to further study the MSG effects in humans.
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15
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Yang OCY, Loh SH. Acidic Stress Triggers Sodium-Coupled Bicarbonate Transport and Promotes Survival in A375 Human Melanoma Cells. Sci Rep 2019; 9:6858. [PMID: 31048755 PMCID: PMC6497716 DOI: 10.1038/s41598-019-43262-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/18/2019] [Indexed: 12/27/2022] Open
Abstract
Melanoma cells preserve intracellular pH (pHi) within a viable range despite an acidic ambient pH that typically falls below pH 7.0. The molecular mechanisms underlying this form of acidic preservation in melanoma remain poorly understood. Previous studies had demonstrated that proton transporters including the monocarboxylate transporter (MCT), the sodium hydrogen exchanger (NHE), and V-Type ATPase mediate acid extrusion to counter intracellular acidification in melanoma cells. In this report, the expression and function of the Sodium-Coupled Bicarbonate Transporter (NCBT) family of base loaders were further characterized in melanoma cell lines. NCBT family members were found to be expressed in three different melanoma cell lines – A375, MeWo, and HS695T – and included the electrogenic sodium-bicarbonate cotransporter isoforms 1 and 2 (NBCe1 and NBCe2), the electroneutral sodium-bicarbonate cotransporter (NBCn1), and the sodium-dependent chloride-bicarbonate exchanger (NDCBE). These transporters facilitated 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS)-dependent pHi recovery in melanoma cells, in response to intracellular acidification induced by ammonium chloride prepulse. Furthermore, the expression of NCBTs were upregulated via chronic exposure to extracellular acidification. Given the current research interest in the NCBTs as a molecular driver of tumourigenesis, characterising NCBT in melanoma provides impetus for developing novel therapeutic targets for melanoma treatment.
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Affiliation(s)
- Oscar C Y Yang
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, United Kingdom.,Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Shih-Hurng Loh
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, United Kingdom. .,Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan. .,Department of Pharmacy Practice, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
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16
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Hering-Smith KS, Hamm LL. Acidosis and citrate: provocative interactions. ANNALS OF TRANSLATIONAL MEDICINE 2018; 6:374. [PMID: 30370301 DOI: 10.21037/atm.2018.07.37] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | - L Lee Hamm
- Department of Medicine, Tulane University School of Medicine, New Orleans, LA, USA
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17
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Dreffs A, Henderson D, Dmitriev AV, Antonetti DA, Linsenmeier RA. Retinal pH and Acid Regulation During Metabolic Acidosis. Curr Eye Res 2018; 43:902-912. [PMID: 29641914 PMCID: PMC6095710 DOI: 10.1080/02713683.2018.1458882] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE Changes in retinal pH may contribute to a variety of eye diseases. To study the effect of acidosis alone, we induced systemic metabolic acidosis and hypothesized that the retina would respond with altered expression of genes involved in acid/base regulation. METHODS Systemic metabolic acidosis was induced in Long-Evans rats for up to 2 weeks by adding NH4Cl to the drinking water. After 2 weeks, venous pH was 7.25 ± 0.08 (SD) and [HCO3-] was 21.4 ± 4.6 mM in acidotic animals; pH was 7.41 ± 0.03 and [HCO3-] was 30.5 ± 1.0 mM in controls. Retinal mRNAs were quantified by quantitative reverse transcription polymerase chain reaction. Protein was quantified with Western blots and localized by confocal microscopy. Retinal [H+]o was measured in vivo with pH microelectrodes in animals subjected to metabolic acidosis and in controls. RESULTS NH4Cl in drinking water or given intravenous was effective in acidifying the retina. Cariporide, a blocker of Na+/H+ exchange, further acidified the retina. Metabolic acidosis for 2 weeks led to increases of 40-100% in mRNA for carbonic anhydrase isoforms II (CA-II) and XIV (CA-XIV) and acid-sensing ion channels 1 and 4 (ASIC1 and ASIC4) (all p < 0.005). Expression of anion exchange protein 3 (AEP-3) and Na+/H+ exchanger (NHE)-1 also increased by ≥50% (both p < 0.0001). Changes were similar after 1 week of acidosis. Protein for AEP-3 doubled. NHE-1 co-localized with vascular markers, particularly in the outer plexiform layer. CA-II was located in the neural parenchyma of the ganglion cell layer and diffusely in the rest of the inner retina. CONCLUSIONS The retina responds to systemic acidosis with increased expression of proton and bicarbonate exchangers, carbonic anhydrase, and ASICs. While responses to acidosis are usually associated with renal regulation, these studies suggest that the retina responds to changes in local pH presumably to control its acid/base environment in response to systemic acidosis.
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Affiliation(s)
- Alyssa Dreffs
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI
| | - Desmond Henderson
- Department of Biomedical Engineering, Northwestern University, Evanston and Chicago, IL
| | - Andrey V. Dmitriev
- Department of Biomedical Engineering, Northwestern University, Evanston and Chicago, IL
| | - David A. Antonetti
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI
| | - Robert A. Linsenmeier
- Department of Biomedical Engineering, Northwestern University, Evanston and Chicago, IL
- Department of Neurobiology, Northwestern University, Evanston and Chicago, IL
- Department of Ophthalmology, Northwestern University, Evanston and Chicago, IL
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18
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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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19
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Izumi Y, Inoue H, Nakayama Y, Eguchi K, Yasuoka Y, Matsuo N, Nonoguchi H, Kakizoe Y, Kuwabara T, Mukoyama M. TSS-Seq analysis of low pH-induced gene expression in intercalated cells in the renal collecting duct. PLoS One 2017; 12:e0184185. [PMID: 28859164 PMCID: PMC5578634 DOI: 10.1371/journal.pone.0184185] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 08/18/2017] [Indexed: 12/24/2022] Open
Abstract
Metabolic acidosis often results from chronic kidney disease; in turn, metabolic acidosis accelerates the progression of kidney injury. The mechanisms for how acidosis facilitates kidney injury are not fully understood. To investigate whether low pH directly affects the expression of genes controlling local homeostasis in renal tubules, we performed transcription start site sequencing (TSS-Seq) using IN-IC cells, a cell line derived from rat renal collecting duct intercalated cells, with acid loading for 24 h. Peak calling identified 651 up-regulated and 128 down-regulated TSSs at pH 7.0 compared with those at pH 7.4. Among them, 424 and 38 TSSs were ≥ 1.0 and ≤ -1.0 in Log2 fold change, which were annotated to 193 up-regulated and 34 down-regulated genes, respectively. We used gene ontology analysis and manual curation to profile the up-regulated genes. The analysis revealed that many up-regulated genes are involved in renal fibrosis, implying potential molecular mechanisms induced by metabolic acidosis. To verify the activity of the ubiquitin-proteasome system (UPS), a candidate pathway activated by acidosis, we examined the expression of proteins from cells treated with a proteasome inhibitor, MG132. The expression of ubiquitinated proteins was greater at pH 7.0 than at pH 7.4, suggesting that low pH activates the UPS. The in vivo study demonstrated that acid loading increased the expression of ubiquitin proteins in the collecting duct cells in mouse kidneys. Motif analysis revealed Egr1, the mRNA expression of which was increased at low pH, as a candidate factor that possibly stimulates gene expression in response to low pH. In conclusion, metabolic acidosis can facilitate renal injury and fibrosis during kidney disease by locally activating various pathways in the renal tubules.
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Affiliation(s)
- Yuichiro Izumi
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Hideki Inoue
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Yushi Nakayama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
- * E-mail:
| | - Koji Eguchi
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Yukiko Yasuoka
- Department of Physiology, Kitasato University School of Medicine, Sagamihara, Japan
| | - Naomi Matsuo
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Hiroshi Nonoguchi
- Department of Internal Medicine and Education & Research Center, Kitasato University Medical Center, Kitamoto, Japan
| | - Yutaka Kakizoe
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Takashige Kuwabara
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Masashi Mukoyama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
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20
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Knöpfel T, Atanassoff A, Hernando N, Biber J, Wagner CA. Renal localization and regulation by dietary phosphate of the MCT14 orphan transporter. PLoS One 2017; 12:e0177942. [PMID: 28662032 PMCID: PMC5490967 DOI: 10.1371/journal.pone.0177942] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 05/05/2017] [Indexed: 01/15/2023] Open
Abstract
MCT14 is an orphan transporter belonging to the SLC16 transporter family mediating the transport of monocarboxylates, aromatic amino acids, creatine, and thyroid hormones. The expression, tissue localization, regulation, and function of MCT14 are unknown. In mouse MCT14 mRNA abundance is highest in kidney. Using a newly developed and validated antibody, MCT14 was localized to the luminal membrane of the thick ascending limb of the loop of Henle colocalizing in the same cells with uromodulin and NKCC2. MCT14 mRNA and protein was found to be highly regulated by dietary phosphate intake in mice being increased by high dietary phosphate intake at both mRNA and protein level. In order to identify the transport substrate(s), we expressed MCT14 in Xenopus laevis oocytes where MCT14 was integrated into the plasma membrane. However, no transport was discovered for the classic substrates of the SLC16 family nor for phosphate. In summary, MCT14 is an orphan transporter regulated by phosphate and highly enriched in kidney localizing to the luminal membrane of one specific nephron segment.
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Affiliation(s)
- Thomas Knöpfel
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- NCCR Kidney.CH, Switzerland
| | - Alexander Atanassoff
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- NCCR Kidney.CH, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- NCCR Kidney.CH, Switzerland
| | - Jürg Biber
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- NCCR Kidney.CH, Switzerland
| | - Carsten A. Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- NCCR Kidney.CH, Switzerland
- * E-mail:
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21
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Rubio-Aliaga I, Wagner CA. Regulation and function of the SLC38A3/SNAT3 glutamine transporter. Channels (Austin) 2016; 10:440-52. [PMID: 27362266 DOI: 10.1080/19336950.2016.1207024] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- Isabel Rubio-Aliaga
- a Institute of Physiology, the National Center for Competence in Research NCCR Kidney, University of Zurich , Zurich , Switzerland
| | - Carsten A Wagner
- a Institute of Physiology, the National Center for Competence in Research NCCR Kidney, University of Zurich , Zurich , Switzerland
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22
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Lee HW, Osis G, Handlogten ME, Lamers WH, Chaudhry FA, Verlander JW, Weiner ID. Proximal tubule-specific glutamine synthetase deletion alters basal and acidosis-stimulated ammonia metabolism. Am J Physiol Renal Physiol 2016; 310:F1229-42. [PMID: 27009341 PMCID: PMC4935770 DOI: 10.1152/ajprenal.00547.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 03/13/2016] [Indexed: 02/07/2023] Open
Abstract
Glutamine synthetase (GS) catalyzes the recycling of NH4 (+) with glutamate to form glutamine. GS is highly expressed in the renal proximal tubule (PT), suggesting ammonia recycling via GS could decrease net ammoniagenesis and thereby limit ammonia available for net acid excretion. The purpose of the present study was to determine the role of PT GS in ammonia metabolism under basal conditions and during metabolic acidosis. We generated mice with PT-specific GS deletion (PT-GS-KO) using Cre-loxP techniques. Under basal conditions, PT-GS-KO increased urinary ammonia excretion significantly. Increased ammonia excretion occurred despite decreased expression of key proteins involved in renal ammonia generation. After the induction of metabolic acidosis, the ability to increase ammonia excretion was impaired significantly by PT-GS-KO. The blunted increase in ammonia excretion occurred despite greater expression of multiple components of ammonia generation, including SN1 (Slc38a3), phosphate-dependent glutaminase, phosphoenolpyruvate carboxykinase, and Na(+)-coupled electrogenic bicarbonate cotransporter. We conclude that 1) GS-mediated ammonia recycling in the PT contributes to both basal and acidosis-stimulated ammonia metabolism and 2) adaptive changes in other proteins involved in ammonia metabolism occur in response to PT-GS-KO and cause an underestimation of the role of PT GS expression.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Gunars Osis
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Mary E Handlogten
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Wouter H Lamers
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Farrukh A Chaudhry
- Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway; and
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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23
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Zhou Y, Skelton LA, Xu L, Chandler MP, Berthiaume JM, Boron WF. Role of Receptor Protein Tyrosine Phosphatase γ in Sensing Extracellular CO2 and HCO3. J Am Soc Nephrol 2016; 27:2616-21. [PMID: 26839367 DOI: 10.1681/asn.2015040439] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 12/17/2015] [Indexed: 01/06/2023] Open
Abstract
Regulation of blood pH-critical for virtually every facet of life-requires that the renal proximal tubule (PT) adjust its rate of H(+) secretion (nearly the same as the rate of HCO3 (-) reabsorption, JHCO3 ) in response to changes in blood [CO2] and [HCO3 (-)]. Yet CO2/HCO3 (-) sensing mechanisms remain poorly characterized. Because receptor tyrosine kinase inhibitors render JHCO3 in the PT insensitive to changes in CO2 concentration, we hypothesized that the structural features of receptor protein tyrosine phosphatase-γ (RPTPγ) that are consistent with binding of extracellular CO2 or HCO3 (-) facilitate monitoring of blood CO2/HCO3 (-) concentrations. We now report that PTs express RPTPγ on blood-facing membranes. Moreover, RPTPγ deletion in mice eliminated the CO2 and HCO3 (-) sensitivities of JHCO3 as well as the normal defense of blood pH during whole-body acidosis. Thus, RPTPγ appears to be a novel extracellular CO2/HCO3 (-) sensor critical for pH homeostasis.
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Affiliation(s)
- Yuehan Zhou
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Lara A Skelton
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Lumei Xu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Margaret P Chandler
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Jessica M Berthiaume
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
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Daryadel A, Bourgeois S, Figueiredo MFL, Gomes Moreira A, Kampik NB, Oberli L, Mohebbi N, Lu X, Meima ME, Danser AHJ, Wagner CA. Colocalization of the (Pro)renin Receptor/Atp6ap2 with H+-ATPases in Mouse Kidney but Prorenin Does Not Acutely Regulate Intercalated Cell H+-ATPase Activity. PLoS One 2016; 11:e0147831. [PMID: 26824839 PMCID: PMC4732657 DOI: 10.1371/journal.pone.0147831] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 01/08/2016] [Indexed: 12/11/2022] Open
Abstract
The (Pro)renin receptor (P)RR/Atp6ap2 is a cell surface protein capable of binding and non-proteolytically activate prorenin. Additionally, (P)RR is associated with H+-ATPases and alternative functions in H+-ATPase regulation as well as in Wnt signalling have been reported. Kidneys express very high levels of H+-ATPases which are involved in multiple functions such as endocytosis, membrane protein recycling as well as urinary acidification, bicarbonate reabsorption, and salt absorption. Here, we wanted to localize the (P)RR/Atp6ap2 along the murine nephron, exmaine whether the (P)RR/Atp6ap2 is coregulated with other H+-ATPase subunits, and whether acute stimulation of the (P)RR/Atp6ap2 with prorenin regulates H+-ATPase activity in intercalated cells in freshly isolated collecting ducts. We localized (P)PR/Atp6ap2 along the murine nephron by qPCR and immunohistochemistry. (P)RR/Atp6ap2 mRNA was detected in all nephron segments with highest levels in the collecting system coinciding with H+-ATPases. Further experiments demonstrated expression at the brush border membrane of proximal tubules and in all types of intercalated cells colocalizing with H+-ATPases. In mice treated with NH4Cl, NaHCO3, KHCO3, NaCl, or the mineralocorticoid DOCA for 7 days, (P)RR/Atp6ap2 and H+-ATPase subunits were regulated but not co-regulated at protein and mRNA levels. Immunolocalization in kidneys from control, NH4Cl or NaHCO3 treated mice demonstrated always colocalization of PRR/Atp6ap2 with H+-ATPase subunits at the brush border membrane of proximal tubules, the apical pole of type A intercalated cells, and at basolateral and/or apical membranes of non-type A intercalated cells. Microperfusion of isolated cortical collecting ducts and luminal application of prorenin did not acutely stimulate H+-ATPase activity. However, incubation of isolated collecting ducts with prorenin non-significantly increased ERK1/2 phosphorylation. Our results suggest that the PRR/Atp6ap2 may form a complex with H+-ATPases in proximal tubule and intercalated cells but that prorenin has no acute effect on H+-ATPase activity in intercalated cells.
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MESH Headings
- Ammonium Chloride/pharmacology
- Animals
- Anion Transport Proteins/genetics
- Anion Transport Proteins/metabolism
- Aquaporin 2/genetics
- Aquaporin 2/metabolism
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Dogs
- Gene Expression Regulation
- Kidney Cortex/cytology
- Kidney Cortex/drug effects
- Kidney Cortex/metabolism
- Kidney Medulla/cytology
- Kidney Medulla/drug effects
- Kidney Medulla/metabolism
- Kidney Tubules, Collecting/cytology
- Kidney Tubules, Collecting/drug effects
- Kidney Tubules, Collecting/metabolism
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Madin Darby Canine Kidney Cells
- Male
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Mice, Inbred C57BL
- Proton-Translocating ATPases/genetics
- Proton-Translocating ATPases/metabolism
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Renin/pharmacology
- Renin-Angiotensin System/drug effects
- Signal Transduction
- Sodium Bicarbonate/pharmacology
- Sodium Chloride/pharmacology
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
- Solute Carrier Family 12, Member 1/genetics
- Solute Carrier Family 12, Member 1/metabolism
- Solute Carrier Family 12, Member 3/genetics
- Solute Carrier Family 12, Member 3/metabolism
- Sulfate Transporters
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Affiliation(s)
- Arezoo Daryadel
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | | | | | - Nicole B. Kampik
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Lisa Oberli
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Nilufar Mohebbi
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Divison of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Xifeng Lu
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Marcel E. Meima
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - A. H. Jan Danser
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Carsten A. Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- * E-mail:
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Edge J, Mündel T, Pilegaard H, Hawke E, Leikis M, Lopez-Villalobos N, Oliveira RSF, Bishop DJ. Ammonium Chloride Ingestion Attenuates Exercise-Induced mRNA Levels in Human Muscle. PLoS One 2015; 10:e0141317. [PMID: 26656911 PMCID: PMC4686080 DOI: 10.1371/journal.pone.0141317] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 10/07/2015] [Indexed: 01/17/2023] Open
Abstract
Minimizing the decrease in intracellular pH during high-intensity exercise training promotes greater improvements in mitochondrial respiration. This raises the intriguing hypothesis that pH may affect the exercise-induced transcription of genes that regulate mitochondrial biogenesis. Eight males performed 10x2-min cycle intervals at 80% V˙O2peak intensity on two occasions separated by ~2 weeks. Participants ingested either ammonium chloride (ACID) or calcium carbonate (PLA) the day before and on the day of the exercise trial in a randomized, counterbalanced order, using a crossover design. Biopsies were taken from the vastus lateralis muscle before and after exercise. The mRNA level of peroxisome proliferator-activated receptor co-activator 1α (PGC-1α), citrate synthase, cytochome c and FOXO1 was elevated at rest following ACID (P<0.05). During the PLA condition, the mRNA content of mitochondrial- and glucose-regulating proteins was elevated immediately following exercise (P<0.05). In the early phase (0–2 h) of post-exercise recovery during ACID, PGC-1α, citrate synthase, cytochome C, FOXO1, GLUT4, and HKII mRNA levels were not different from resting levels (P>0.05); the difference in PGC-1α mRNA content 2 h post-exercise between ACID and PLA was not significant (P = 0.08). Thus, metabolic acidosis abolished the early post-exercise increase of PGC-1α mRNA and the mRNA of downstream mitochondrial and glucose-regulating proteins. These findings indicate that metabolic acidosis may affect mitochondrial biogenesis, with divergent responses in resting and post-exercise skeletal muscle.
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Affiliation(s)
- Johann Edge
- Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand
- School of Sport and Exercise, Massey University, Palmerston North, New Zealand
| | - Toby Mündel
- School of Sport and Exercise, Massey University, Palmerston North, New Zealand
| | - Henriette Pilegaard
- Centre of Inflammation and Metabolism (CIM), Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Emma Hawke
- Centre of Inflammation and Metabolism (CIM), Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Murray Leikis
- Department of Renal Medicine, Wellington Hospital, Newtown, New Zealand
| | - Nicolas Lopez-Villalobos
- Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
| | - Rodrigo S. F. Oliveira
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Australia
| | - David J. Bishop
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Australia
- * E-mail:
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Loss of function mutation of the Slc38a3 glutamine transporter reveals its critical role for amino acid metabolism in the liver, brain, and kidney. Pflugers Arch 2015; 468:213-27. [PMID: 26490457 DOI: 10.1007/s00424-015-1742-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 09/29/2015] [Accepted: 10/02/2015] [Indexed: 01/10/2023]
Abstract
Glutamine, the most abundant amino acid in mammals, is critical for cell and organ functions. Its metabolism depends on the ability of cells to take up or release glutamine by transporters located in the plasma membrane. Several solute carrier (SLC) families transport glutamine, but the SLC38 family has been thought to be mostly responsible for glutamine transport. We demonstrate that despite the large number of glutamine transporters, the loss of Snat3/Slc38a3 glutamine transporter has a major impact on the function of organs expressing it. Snat3 mutant mice were generated by N-ethyl-N-nitrosurea (ENU) mutagenesis and showed stunted growth, altered amino acid levels, hypoglycemia, and died around 20 days after birth. Hepatic concentrations of glutamine, glutamate, leucine, phenylalanine, and tryptophan were highly reduced paralleled by downregulation of the mTOR pathway possibly linking reduced amino acid availability to impaired growth and glucose homeostasis. Snat3-deficient mice had altered urea levels paralleled by dysregulation of the urea cycle, gluconeogenesis, and glutamine synthesis. Mice were ataxic with higher glutamine but reduced glutamate and gamma-aminobutyric acid (GABA) levels in brain consistent with a major role of Snat3 in the glutamine-glutamate cycle. Renal ammonium excretion was lower, and the expression of enzymes and amino acid transporters involved in ammoniagenesis were altered. Thus, SNAT3 is a glutamine transporter required for amino acid homeostasis and determines critical functions in various organs. Despite the large number of glutamine transporters, loss of Snat3 cannot be compensated, suggesting that this transporter is a major route of glutamine transport in the liver, brain, and kidney.
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Integrated transcriptomic and proteomic analyses uncover regulatory roles of Nrf2 in the kidney. Kidney Int 2015; 88:1261-1273. [PMID: 26422507 PMCID: PMC4676083 DOI: 10.1038/ki.2015.286] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 07/07/2015] [Accepted: 07/31/2015] [Indexed: 12/26/2022]
Abstract
The transcription factor Nrf2 exerts protective effects in numerous experimental models of acute kidney injury, and is a promising therapeutic target in chronic kidney disease. To provide a detailed insight into the regulatory roles of Nrf2 in the kidney, we performed integrated transcriptomic and proteomic analyses of kidney tissue from wild-type and Nrf2 knockout mice treated with the Nrf2 inducer methyl-2-cyano-3,12-dioxooleano-1,9-dien-28-oate (CDDO-Me, also known as bardoxolone methyl). After 24 hours, analyses identified 2561 transcripts and 240 proteins that were differentially expressed in the kidneys of Nrf2 knockout mice, compared to wild-type counterparts, and 3122 transcripts and 68 proteins that were differentially expressed in wild-type mice treated with CDDO-Me, compared to vehicle control. In light of their sensitivity to genetic and pharmacological modulation of renal Nrf2 activity, genes/proteins that regulate xenobiotic disposition, redox balance, the intra/extracellular transport of small molecules, and the supply of NADPH and other cellular fuels were found to be positively regulated by Nrf2 in the kidney. This was verified by qPCR, immunoblotting, pathway analysis and immunohistochemistry. In addition, the levels of NADPH and glutathione were found to be significantly decreased in the kidneys of Nrf2 knockout mice. Thus, Nrf2 regulates genes that coordinate homeostatic processes in the kidney, highlighting its potential as a novel therapeutic target.
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Molinas SM, Soria LR, Marrone J, Danielli M, Trumper L, Marinelli RA. Acidosis-induced downregulation of hepatocyte mitochondrial aquaporin-8 and ureagenesis from ammonia. Biochem Cell Biol 2015; 93:417-20. [PMID: 26194146 DOI: 10.1139/bcb-2014-0168] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has been proposed that, during metabolic acidosis, the liver downregulates mitochondrial ammonia detoxification via ureagenesis, a bicarbonate-consuming process. Since we previously demonstrated that hepatocyte mitochondrial aquaporin-8 channels (mtAQP8) facilitate the uptake of ammonia and its metabolism into urea, we studied whether mtAQP8 is involved in the liver adaptive response to acidosis. Primary cultured rat hepatocytes were adapted to acidosis by exposing them to culture medium at pH 7.0 for 40 h. Control cells were exposed to pH 7.4. Hepatocytes exposed to acid medium showed a decrease in mtAQP8 protein expression (-30%, p < 0.05). Ureagenesis from ammonia was assessed by incubating the cells with (15)N-labeled ammonia and measuring (15)N-labeled urea synthesis by nuclear magnetic resonance. Reduced ureagenesis was found in acidified hepatocytes (-31%, p < 0.05). In vivo studies in rats subjected to 7 days acidosis also showed decreased protein expression of hepatic mtAQP8 (-50%, p < 0.05) and reduced liver urea content (-35%; p < 0.05). In conclusion, our in vitro and in vivo data suggest that hepatic mtAQP8 expression is downregulated in acidosis, a mechanism that may contribute to decreased ureagenesis from ammonia in response to acidosis.
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Affiliation(s)
- Sara M Molinas
- a Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, (2000) Rosario, Argentina.,b Farmacología. Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, (2000) Rosario, Argentina
| | - Leandro R Soria
- a Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, (2000) Rosario, Argentina
| | - Julieta Marrone
- a Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, (2000) Rosario, Argentina
| | - Mauro Danielli
- a Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, (2000) Rosario, Argentina
| | - Laura Trumper
- b Farmacología. Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, (2000) Rosario, Argentina.,c Consejo de Investigaciones de la Universidad Nacional de Rosario (CIUNR)
| | - Raúl A Marinelli
- a Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, (2000) Rosario, Argentina
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29
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Lawrence MJ, Wright PA, Wood CM. Physiological and molecular responses of the goldfish (Carassius auratus) kidney to metabolic acidosis, and potential mechanisms of renal ammonia transport. ACTA ACUST UNITED AC 2015; 218:2124-35. [PMID: 25987732 DOI: 10.1242/jeb.117689] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 05/05/2015] [Indexed: 01/20/2023]
Abstract
Relative to the gills, the mechanisms by which the kidney contributes to ammonia and acid-base homeostasis in fish are poorly understood. Goldfish were exposed to a low pH environment (pH 4.0, 48 h), which induced a characteristic metabolic acidosis and an increase in total plasma [ammonia] but reduced plasma ammonia partial pressure (PNH3). In the kidney tissue, total ammonia, lactate and intracellular pH remained unchanged. The urinary excretion rate of net base under control conditions changed to net acid excretion under low pH, with contributions from both the NH4 (+) (∼30%) and titratable acidity minus bicarbonate (∼70%; TA-HCO3 (-)) components. Inorganic phosphate (Pi), urea and Na(+) excretion rates were also elevated while Cl(-) excretion rates were unchanged. Renal alanine aminotransferase activity increased under acidosis. The increase in renal ammonia excretion was due to significant increases in both the glomerular filtration and the tubular secretion rates of ammonia, with the latter accounting for ∼75% of the increase. There was also a 3.5-fold increase in the mRNA expression of renal Rhcg-b (Rhcg1) mRNA. There was no relationship between ammonia secretion and Na(+) reabsorption. These data indicate that increased renal ammonia secretion during acidosis is probably mediated through Rhesus (Rh) glycoproteins and occurs independently of Na(+) transport, in contrast to branchial and epidermal models of Na(+)-dependent ammonia transport in freshwater fish. Rather, we propose a model of parallel H(+)/NH3 transport as the primary mechanism of renal tubular ammonia secretion that is dependent on renal amino acid catabolism.
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Affiliation(s)
- Michael J Lawrence
- Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1 Department of Biology, Carleton University, Ottawa, ON, Canada K1S 5B6
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Chris M Wood
- Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1 Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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30
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IWANAGA T, KISHIMOTO A. Cellular distributions of monocarboxylate transporters: a review . Biomed Res 2015; 36:279-301. [DOI: 10.2220/biomedres.36.279] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Toshihiko IWANAGA
- Laboratory of Histology and Cytology, Graduate School of Medicine, Hokkaido University
| | - Ayuko KISHIMOTO
- Laboratory of Histology and Cytology, Graduate School of Medicine, Hokkaido University
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31
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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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32
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Katt WP, Antonyak MA, Cerione RA. Simultaneously targeting tissue transglutaminase and kidney type glutaminase sensitizes cancer cells to acid toxicity and offers new opportunities for therapeutic intervention. Mol Pharm 2014; 12:46-55. [PMID: 25426679 PMCID: PMC4291776 DOI: 10.1021/mp500405h] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Most cancer cells undergo characteristic metabolic changes that are commonly referred to as the Warburg effect, with one of the hallmarks being a dramatic increase in the rate of lactic acid fermentation. This leads to the production of protons, which in turn acidifies the microenvironment surrounding tumors. Cancer cells have acquired resistance to acid toxicity, allowing them to survive and grow under these detrimental conditions. Kidney type glutaminase (GLS1), which is responsible for the conversion of glutamine to glutamate, produces ammonia as part of its catalytic activities and has been shown to modulate cellular acidity. In this study, we show that tissue, or type 2, transglutaminase (TG2), a γ-glutamyl transferase that is highly expressed in metastatic cancers and produces ammonia as a byproduct of its catalytic activity, is up-regulated by decreases in cellular pH and helps protect cells from acid-induced cell death. Since both TG2 and GLS1 can similarly function to protect cancer cells, we then proceeded to demonstrate that treatment of a variety of cancer cell types with inhibitors of each of these proteins results in synthetic lethality. The combination doses of the inhibitors induce cell death, while individual treatment with each compound shows little or no ability to kill cells. These results suggest that combination drug treatments that simultaneously target TG2 and GLS1 might provide an effective strategy for killing cancer cells.
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Affiliation(s)
- William P Katt
- Department of Molecular Medicine and Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853-6401, United States
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Wei Y, Liao Y, Zavilowitz B, Ren J, Liu W, Chan P, Rohatgi R, Estilo G, Jackson EK, Wang WH, Satlin LM. Angiotensin II type 2 receptor regulates ROMK-like K⁺ channel activity in the renal cortical collecting duct during high dietary K⁺ adaptation. Am J Physiol Renal Physiol 2014; 307:F833-43. [PMID: 25100281 DOI: 10.1152/ajprenal.00141.2014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The kidney adjusts K⁺ excretion to match intake in part by regulation of the activity of apical K⁺ secretory channels, including renal outer medullary K⁺ (ROMK)-like K⁺ channels, in the cortical collecting duct (CCD). ANG II inhibits ROMK channels via the ANG II type 1 receptor (AT1R) during dietary K⁺ restriction. Because AT1Rs and ANG II type 2 receptors (AT2Rs) generally function in an antagonistic manner, we sought to characterize the regulation of ROMK channels by the AT2R. Patch-clamp experiments revealed that ANG II increased ROMK channel activity in CCDs isolated from high-K⁺ (HK)-fed but not normal K⁺ (NK)-fed rats. This response was blocked by PD-123319, an AT2R antagonist, but not by losartan, an AT1R antagonist, and was mimicked by the AT2R agonist CGP-42112. Nitric oxide (NO) synthase is present in CCD cells that express ROMK channels. Blockade of NO synthase with N-nitro-l-arginine methyl ester and free NO with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt completely abolished ANG II-stimulated ROMK channel activity. NO enhances the synthesis of cGMP, which inhibits phosphodiesterases (PDEs) that normally degrade cAMP; cAMP increases ROMK channel activity. Pretreatment of CCDs with IBMX, a broad-spectrum PDE inhibitor, or cilostamide, a PDE3 inhibitor, abolished the stimulatory effect of ANG II on ROMK channels. Furthermore, PKA inhibitor peptide, but not an activator of the exchange protein directly activated by cAMP (Epac), also prevented the stimulatory effect of ANG II. We conclude that ANG II acts at the AT2R to stimulate ROMK channel activity in CCDs from HK-fed rats, a response opposite to that mediated by the AT1R in dietary K⁺-restricted animals, via a NO/cGMP pathway linked to a cAMP-PKA pathway.
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Affiliation(s)
- Yuan Wei
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Pharmacology, New York Medical College, Valhalla, New York; Department of Cell Biology, New York University Medical Center, New York, New York
| | - Yi Liao
- Department of Cell Biology, New York University Medical Center, New York, New York
| | - Beth Zavilowitz
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jin Ren
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Wen Liu
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Pokman Chan
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Rajeev Rohatgi
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Medicine, James J. Peters Veterans Affairs Medical Center, Bronx, New York; and
| | - Genevieve Estilo
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Edwin K Jackson
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Lisa M Satlin
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
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34
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Abstract
Gene Ontology (GO) provides dynamic controlled vocabularies to aid in the description of the functional biological attributes and subcellular locations of gene products from all taxonomic groups (www.geneontology.org). Here we describe collaboration between the renal biomedical research community and the GO Consortium to improve the quality and quantity of GO terms describing renal development. In the associated annotation activity, the new and revised terms were associated with gene products involved in renal development and function. This project resulted in a total of 522 GO terms being added to the ontology and the creation of approximately 9,600 kidney-related GO term associations to 940 UniProt Knowledgebase (UniProtKB) entries, covering 66 taxonomic groups. We demonstrate the impact of these improvements on the interpretation of GO term analyses performed on genes differentially expressed in kidney glomeruli affected by diabetic nephropathy. In summary, we have produced a resource that can be utilized in the interpretation of data from small- and large-scale experiments investigating molecular mechanisms of kidney function and development and thereby help towards alleviating renal disease.
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35
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Altintas MM, Moriwaki K, Wei C, Möller CC, Flesche J, Li J, Yaddanapudi S, Faridi MH, Gödel M, Huber TB, Preston RA, Jiang JX, Kerjaschki D, Sever S, Reiser J. Reduction of proteinuria through podocyte alkalinization. J Biol Chem 2014; 289:17454-67. [PMID: 24817115 DOI: 10.1074/jbc.m114.568998] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Podocytes are highly differentiated cells and critical elements for the filtration barrier of the kidney. Loss of their foot process (FP) architecture (FP effacement) results in urinary protein loss. Here we show a novel role for the neutral amino acid glutamine in structural and functional regulation of the kidney filtration barrier. Metabolic flux analysis of cultured podocytes using genetic, toxic, and immunologic injury models identified increased glutamine utilization pathways. We show that glutamine uptake is increased in diseased podocytes to couple nutrient support to increased demand during the disease state of FP effacement. This feature can be utilized to transport increased amounts of glutamine into damaged podocytes. The availability of glutamine determines the regulation of podocyte intracellular pH (pHi). Podocyte alkalinization reduces cytosolic cathepsin L protease activity and protects the podocyte cytoskeleton. Podocyte glutamine supplementation reduces proteinuria in LPS-treated mice, whereas acidification increases glomerular injury. In summary, our data provide a metabolic opportunity to combat urinary protein loss through modulation of podocyte amino acid utilization and pHi.
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Affiliation(s)
- Mehmet M Altintas
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Kumiko Moriwaki
- the Department of Medicine, Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Changli Wei
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Clemens C Möller
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Jan Flesche
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Jing Li
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Suma Yaddanapudi
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Mohd Hafeez Faridi
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Markus Gödel
- the Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany
| | - Tobias B Huber
- the Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany, the BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs University, 79106 Freiburg, Germany
| | - Richard A Preston
- the Department of Medicine, Division of Clinical Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Jean X Jiang
- the Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229, and
| | - Dontscho Kerjaschki
- the Clinical Institute of Pathology, Medical University of Vienna, 1090 Vienna, Austria
| | - Sanja Sever
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Jochen Reiser
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035,
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36
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Namba T, Takabatake Y, Kimura T, Takahashi A, Yamamoto T, Matsuda J, Kitamura H, Niimura F, Matsusaka T, Iwatani H, Matsui I, Kaimori J, Kioka H, Isaka Y, Rakugi H. Autophagic clearance of mitochondria in the kidney copes with metabolic acidosis. J Am Soc Nephrol 2014; 25:2254-66. [PMID: 24700866 DOI: 10.1681/asn.2013090986] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Metabolic acidosis, a common complication of CKD, causes mitochondrial stress by undefined mechanisms. Selective autophagy of impaired mitochondria, called mitophagy, contributes toward maintaining cellular homeostasis in various settings. We hypothesized that mitophagy is involved in proximal tubular cell adaptations to chronic metabolic acidosis. In transgenic mice expressing green fluorescent protein-tagged microtubule-associated protein 1 light chain 3 (GFP-LC3), NH4Cl loading increased the number of GFP puncta exclusively in the proximal tubule. In vitro, culture in acidic medium produced similar results in proximal tubular cell lines stably expressing GFP-LC3 and facilitated the degradation of SQSTM1/p62 in wild-type cells, indicating enhanced autophagic flux. Upon acid loading, proximal tubule-specific autophagy-deficient (Atg5-deficient) mice displayed significantly reduced ammonium production and severe metabolic acidosis compared with wild-type mice. In vitro and in vivo, acid loading caused Atg5-deficient proximal tubular cells to exhibit reduced mitochondrial respiratory chain activity, reduced mitochondrial membrane potential, and fragmented morphology with marked swelling in mitochondria. GFP-LC3-tagged autophagosomes colocalized with ubiquitinated mitochondria in proximal tubular cells cultured in acidic medium, suggesting that metabolic acidosis induces mitophagy. Furthermore, restoration of Atg5-intact nuclei in Atg5-deficient proximal tubular cells increased mitochondrial membrane potential and ammoniagenesis. In conclusion, metabolic acidosis induces autophagy in proximal tubular cells, which is indispensable for maintaining proper mitochondrial functions including ammoniagenesis, and thus for adapted urinary acid excretion. Our results provide a rationale for the beneficial effect of alkali supplementation in CKD, a condition in which autophagy may be reduced, and suggest a new therapeutic option for acidosis by modulating autophagy.
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Affiliation(s)
- Tomoko Namba
- Departments of Geriatric Medicine and Nephrology (B6)
| | | | - Tomonori Kimura
- Departments of Geriatric Medicine and Nephrology (B6), Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico; and
| | | | | | - Jun Matsuda
- Departments of Geriatric Medicine and Nephrology (B6)
| | | | | | - Taiji Matsusaka
- Institute of Medical Science and Department of Internal Medicine, Tokai University School of Medicine, Isehara, Kanagawa, Japan
| | | | - Isao Matsui
- Departments of Geriatric Medicine and Nephrology (B6)
| | | | - Hidetaka Kioka
- Medical Biochemistry, and Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | | | - Hiromi Rakugi
- Departments of Geriatric Medicine and Nephrology (B6)
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Everything you need to know about distal renal tubular acidosis in autoimmune disease. Rheumatol Int 2014; 34:1037-45. [PMID: 24682397 PMCID: PMC4107275 DOI: 10.1007/s00296-014-2993-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 03/14/2014] [Indexed: 11/24/2022]
Abstract
Renal acid–base homeostasis is a complex process, effectuated by bicarbonate reabsorption and acid secretion. Impairment of urinary acidification is called renal tubular acidosis (RTA). Distal renal tubular acidosis (dRTA) is the most common form of the RTA syndromes. Multiple pathophysiologic mechanisms, each associated with various etiologies, can lead to dRTA. The most important consequence of dRTA is (recurrent) nephrolithiasis. The diagnosis is based on a urinary acidification test. Potassium citrate is the treatment of choice.
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38
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Heterogeneous Cellular Distribution of Glutamate Dehydrogenase in Brain and in Non-neural Tissues. Neurochem Res 2014; 39:500-15. [DOI: 10.1007/s11064-013-1235-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2013] [Revised: 12/27/2013] [Accepted: 12/30/2013] [Indexed: 01/30/2023]
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Renal expression of FGF23 and peripheral resistance to elevated FGF23 in rodent models of polycystic kidney disease. Kidney Int 2014; 85:1340-50. [PMID: 24402093 DOI: 10.1038/ki.2013.526] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Revised: 09/11/2013] [Accepted: 10/17/2013] [Indexed: 11/08/2022]
Abstract
Fibroblast growth factor 23 (FGF23) regulates phosphate homeostasis and is linked to cardiovascular disease and all-cause mortality in chronic kidney disease. FGF23 rises in patients with CKD stages 2-3, but in patients with autosomal dominant polycystic kidney disease, the increase of FGF23 precedes the first measurable decline in renal function. The mechanisms governing FGF23 production and effects in kidney disease are largely unknown. Here we studied the relation between FGF23 and mineral homeostasis in two animal models of PKD. Plasma FGF23 levels were increased 10-fold in 4-week-old cy/+ Han:SPRD rats, whereas plasma urea and creatinine concentrations were similar to controls. Plasma calcium and phosphate levels as well as TmP/GFR were similar in PKD and control rats at all time points examined. Expression and activity of renal phosphate transporters, the vitamin D3-metabolizing enzymes, and the FGF23 co-ligand Klotho in the kidney were similar in PKD and control rats through 8 weeks of age, indicating resistance to FGF23, although phosphorylation of the FGF receptor substrate 2α protein was enhanced. In the kidneys of rats with PKD, FGF23 mRNA was highly expressed and FGF23 protein was detected in cells lining renal cysts. FGF23 expression in bone and spleen was similar in control rats and rats with PKD. Similarly, in an inducible Pkd1 knockout mouse model, plasma FGF23 levels were elevated, FGF23 was expressed in kidneys, but renal phosphate excretion was normal. Thus, the polycystic kidney produces FGF23 but is resistant to its action.
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Lee HW, Verlander JW, Handlogten ME, Han KH, Weiner ID. Effect of collecting duct-specific deletion of both Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg) on renal response to metabolic acidosis. Am J Physiol Renal Physiol 2013; 306:F389-400. [PMID: 24338819 DOI: 10.1152/ajprenal.00176.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Rhesus (Rh) glycoproteins, Rh B and Rh C Glycoprotein (Rhbg and Rhcg, respectively), are ammonia-specific transporters expressed in renal distal nephron and collecting duct sites that are necessary for normal rates of ammonia excretion. The purpose of the current studies was to determine the effect of their combined deletion from the renal collecting duct (CD-Rhbg/Rhcg-KO) on basal and acidosis-stimulated acid-base homeostasis. Under basal conditions, urine pH and ammonia excretion and serum HCO3(-) were similar in control (C) and CD-Rhbg/Rhcg-KO mice. After acid-loading for 7 days, CD-Rhbg/Rhcg-KO mice developed significantly more severe metabolic acidosis than did C mice. Acid loading increased ammonia excretion, but ammonia excretion increased more slowly in CD-Rhbg/Rhcg-KO and it was significantly less than in C mice on days 1-5. Urine pH was significantly more acidic in CD-Rhbg/Rhcg-KO mice on days 1, 3, and 5 of acid loading. Metabolic acidosis increased phosphenolpyruvate carboxykinase (PEPCK) and Na(+)/H(+) exchanger NHE-3 and decreased glutamine synthetase (GS) expression in both genotypes, and these changes were significantly greater in CD-Rhbg/Rhcg-KO than in C mice. We conclude that 1) Rhbg and Rhcg are critically important in the renal response to metabolic acidosis; 2) the significantly greater changes in PEPCK, NHE-3, and GS expression in acid-loaded CD-Rhbg/Rhcg-KO compared with acid-loaded C mice cause the role of Rhbg and Rhcg to be underestimated quantitatively; and 3) in mice with intact Rhbg and Rhcg expression, metabolic acidosis does not induce maximal changes in PEPCK, NHE-3, and GS expression despite the presence of persistent metabolic acidosis.
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Affiliation(s)
- Hyun-Wook Lee
- Div. of Nephrology, Hypertension, and Transplantation, Univ. of Florida College of Medicine, PO Box 100224, Gainesville, FL 32610.
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42
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Sodium-coupled dicarboxylate and citrate transporters from the SLC13 family. Pflugers Arch 2013; 466:119-30. [PMID: 24114175 DOI: 10.1007/s00424-013-1369-y] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/19/2013] [Accepted: 09/23/2013] [Indexed: 12/30/2022]
Abstract
The SLC13 family in humans and other mammals consists of sodium-coupled transporters for anionic substrates: three transporters for dicarboxylates/citrate and two transporters for sulfate. This review will focus on the di- and tricarboxylate transporters: NaDC1 (SLC13A2), NaDC3 (SLC13A3), and NaCT (SLC13A5). The substrates of these transporters are metabolic intermediates of the citric acid cycle, including citrate, succinate, and α-ketoglutarate, which can exert signaling effects through specific receptors or can affect metabolic enzymes directly. The SLC13 transporters are important for regulating plasma, urinary and tissue levels of these metabolites. NaDC1, primarily found on the apical membranes of renal proximal tubule and small intestinal cells, is involved in regulating urinary levels of citrate and plays a role in kidney stone development. NaDC3 has a wider tissue distribution and high substrate affinity compared with NaDC1. NaDC3 participates in drug and xenobiotic excretion through interactions with organic anion transporters. NaCT is primarily a citrate transporter located in the liver and brain, and its activity may regulate metabolic processes. The recent crystal structure of the Vibrio cholerae homolog, VcINDY, provides a new framework for understanding the mechanism of transport in this family. This review summarizes current knowledge of the structure, function, and regulation of the di- and tricarboxylate transporters of the SLC13 family.
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43
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Schauer KL, Freund DM, Prenni JE, Curthoys NP. Proteomic profiling and pathway analysis of the response of rat renal proximal convoluted tubules to metabolic acidosis. Am J Physiol Renal Physiol 2013; 305:F628-40. [PMID: 23804448 PMCID: PMC3761203 DOI: 10.1152/ajprenal.00210.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 06/13/2013] [Indexed: 01/10/2023] Open
Abstract
Metabolic acidosis is a relatively common pathological condition that is defined as a decrease in blood pH and bicarbonate concentration. The renal proximal convoluted tubule responds to this condition by increasing the extraction of plasma glutamine and activating ammoniagenesis and gluconeogenesis. The combined processes increase the excretion of acid and produce bicarbonate ions that are added to the blood to partially restore acid-base homeostasis. Only a few cytosolic proteins, such as phosphoenolpyruvate carboxykinase, have been determined to play a role in the renal response to metabolic acidosis. Therefore, further analysis was performed to better characterize the response of the cytosolic proteome. Proximal convoluted tubule cells were isolated from rat kidney cortex at various times after onset of acidosis and fractionated to separate the soluble cytosolic proteins from the remainder of the cellular components. The cytosolic proteins were analyzed using two-dimensional liquid chromatography and tandem mass spectrometry (MS/MS). Spectral counting along with average MS/MS total ion current were used to quantify temporal changes in relative protein abundance. In all, 461 proteins were confidently identified, of which 24 exhibited statistically significant changes in abundance. To validate these techniques, several of the observed abundance changes were confirmed by Western blotting. Data from the cytosolic fractions were then combined with previous proteomic data, and pathway analyses were performed to identify the primary pathways that are activated or inhibited in the proximal convoluted tubule during the onset of metabolic acidosis.
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Affiliation(s)
- Kevin L Schauer
- Dept. of Biochemistry and Molecular Biology, Colorado State Univ., Campus Delivery 1870, Ft. Collins, CO 80523-1870, USA
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44
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Dong L, Li Z, Leffler NR, Asch AS, Chi JT, Yang LV. Acidosis activation of the proton-sensing GPR4 receptor stimulates vascular endothelial cell inflammatory responses revealed by transcriptome analysis. PLoS One 2013; 8:e61991. [PMID: 23613998 PMCID: PMC3628782 DOI: 10.1371/journal.pone.0061991] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Accepted: 03/18/2013] [Indexed: 12/13/2022] Open
Abstract
Acidic tissue microenvironment commonly exists in inflammatory diseases, tumors, ischemic organs, sickle cell disease, and many other pathological conditions due to hypoxia, glycolytic cell metabolism and deficient blood perfusion. However, the molecular mechanisms by which cells sense and respond to the acidic microenvironment are not well understood. GPR4 is a proton-sensing receptor expressed in endothelial cells and other cell types. The receptor is fully activated by acidic extracellular pH but exhibits lesser activity at the physiological pH 7.4 and minimal activity at more alkaline pH. To delineate the function and signaling pathways of GPR4 activation by acidosis in endothelial cells, we compared the global gene expression of the acidosis response in primary human umbilical vein endothelial cells (HUVEC) with varying level of GPR4. The results demonstrated that acidosis activation of GPR4 in HUVEC substantially increased the expression of a number of inflammatory genes such as chemokines, cytokines, adhesion molecules, NF-κB pathway genes, and prostaglandin-endoperoxidase synthase 2 (PTGS2 or COX-2) and stress response genes such as ATF3 and DDIT3 (CHOP). Similar GPR4-mediated acidosis induction of the inflammatory genes was also noted in other types of endothelial cells including human lung microvascular endothelial cells and pulmonary artery endothelial cells. Further analyses indicated that the NF-κB pathway was important for the acidosis/GPR4-induced inflammatory gene expression. Moreover, acidosis activation of GPR4 increased the adhesion of HUVEC to U937 monocytic cells under a flow condition. Importantly, treatment with a recently identified GPR4 antagonist significantly reduced the acidosis/GPR4-mediated endothelial cell inflammatory response. Taken together, these results show that activation of GPR4 by acidosis stimulates the expression of a wide range of inflammatory genes in endothelial cells. Such inflammatory response can be suppressed by GPR4 small molecule inhibitors and hold potential therapeutic value.
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Affiliation(s)
- Lixue Dong
- Department of Oncology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Zhigang Li
- Department of Oncology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Nancy R. Leffler
- Department of Oncology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Adam S. Asch
- Department of Oncology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina, United States of America
| | - Jen-Tsan Chi
- Institute for Genome Sciences and Policy, Duke University, Durham, North Carolina, United States of America
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, United States of America
| | - Li V. Yang
- Department of Oncology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina, United States of America
- * E-mail:
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45
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Parker MD, Boron WF. The divergence, actions, roles, and relatives of sodium-coupled bicarbonate transporters. Physiol Rev 2013; 93:803-959. [PMID: 23589833 PMCID: PMC3768104 DOI: 10.1152/physrev.00023.2012] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.
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Affiliation(s)
- Mark D Parker
- Dept. of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4970, USA.
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46
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Mohebbi N, Perna A, van der Wijst J, Becker HM, Capasso G, Wagner CA. Regulation of two renal chloride transporters, AE1 and pendrin, by electrolytes and aldosterone. PLoS One 2013; 8:e55286. [PMID: 23383138 PMCID: PMC3561381 DOI: 10.1371/journal.pone.0055286] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Accepted: 12/21/2012] [Indexed: 01/14/2023] Open
Abstract
The renal handling of salt and protons and bicarbonate are intricately linked through shared transport mechanisms for sodium, chloride, protons, and bicarbonate. In the collecting duct, the regulated fine-tuning of salt and acid-base homeostasis is achieved by a series of transport proteins located in different cell types, intercalated and principal cells. Intercalated cells are considered to be of less importance for salt handling but recent evidence has suggested that the anion exchanger pendrin may participate in salt reabsorption and blood pressure regulation. Here, we examined the regulated expression of two functionally related but differentially expressed anion exchangers, AE1 and pendrin, by dietary electrolyte intake and aldosterone. Cortical expression of pendrin was regulated on mRNA and protein level. The combination of NaHCO3 and DOCA enhanced pendrin mRNA and protein levels, whereas DOCA or NaHCO3 alone had no effect. NaCl or KHCO3 increased pendrin mRNA, KCl decreased its mRNA abundance. On protein level, NH4Cl, NaCl, and KCl reduced pendrin expression, the other treatments were without effect. In contrast, AE1 mRNA or protein expression in kidney cortex was regulated by none of these treatments. In kidney medulla, NaHCO3/DOCA or NaHCO3 alone enhanced AE1 mRNA levels. AE1 protein abundance was increased by NH4Cl, NaHCO3/DOCA, and NaCl. Immunolocalization showed that during NH4Cl treatment the relative number of AE1 positive cells was increased and pendrin expressing cells reduced. Thus, pendrin and AE1 are differentially regulated with distinct mechanisms that separately affect mRNA and protein levels. Pendrin is regulated by acidosis and chloride intake, whereas AE1 is enhanced by acidosis, NaCl, and the combination of DOCA and NaHCO3.
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Affiliation(s)
- Nilufar Mohebbi
- Institute of Physiology and Zurich Center for Integrative Human Physiology-ZIHP, Zurich, Switzerland
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47
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Raj S, Scott DR, Nguyen T, Sachs G, Kraut JA. Acid stress increases gene expression of proinflammatory cytokines in Madin-Darby canine kidney cells. Am J Physiol Renal Physiol 2013; 304:F41-8. [DOI: 10.1152/ajprenal.00128.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metabolic acidosis is thought to exacerbate chronic kidney disease in part by stimulating the release of potentially injurious substances. To define the genes whose expression is affected by exposure to an acidic milieus, we examined the effect of exposure of MDCK cells to pH 7.4 and pH 7.0 for 24 h on gene expression using a canine derived microarray. Exposure to this pH stress for 24 h led to increased expression of 278 genes (2.2% of the transcriptome) by at least 2-fold and 60 of these (21%) were upregulated by >3-fold. On the other hand, 186 genes (1.5% of the transcriptome) were downregulated by at least 2-fold and 16 of these (9%) were downregulated by 3-fold or more. Ten percent of the genes upregulated by at least threefold encode proinflammatory cytokine proteins, including colony stimulating factor 2, chemokine ligand 7, chemokine ligand 20, chemokine ligand 8, and interleukin-1α. Two others encode metallopeptidases. The most highly upregulated gene encodes a protein, lubricin, shown to be important in preventing cartilage damage and in tissue injury or repair. Upregulation of four genes was confirmed by quantitative PCR. Housekeeping genes were not increased. To examine the effect of decreasing medium pH, we measured intracellular pH (pHi) using 2,7-bis (2-carboxyethyl)5-carboxyfluorescein. With extracellular pH (pHo) of 7.0, pHi fell and remained depressed. These findings suggest that a pH stress alone can increase renal expression of proinflammatory and other genes that contribute to renal injury.
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Affiliation(s)
- Suraja Raj
- Medical Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Research Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
| | - David R. Scott
- Research Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Thomas Nguyen
- Medical Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Research Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Division of Nephrology, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
| | - George Sachs
- Medical Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Research Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; and
| | - Jeffrey A. Kraut
- Medical Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Research Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; and
- Division of Nephrology, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California
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48
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Freund DM, Prenni JE, Curthoys NP. Response of the mitochondrial proteome of rat renal proximal convoluted tubules to chronic metabolic acidosis. Am J Physiol Renal Physiol 2012; 304:F145-55. [PMID: 23136003 DOI: 10.1152/ajprenal.00526.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Metabolic acidosis is a common clinical condition that is caused by a decrease in blood pH and bicarbonate concentration. Increased extraction and mitochondrial catabolism of plasma glutamine within the renal proximal convoluted tubule generates ammonium and bicarbonate ions that facilitate the excretion of acid and partially restore acid-base balance. Previous studies identified only a few mitochondrial proteins, including two key enzymes of glutamine metabolism, which are increased during chronic acidosis. A workflow was developed to characterize the mitochondrial proteome of the proximal convoluted tubule. Based upon the increase in specific activity of cytochrome c oxidase, the isolated mitochondria were enriched eightfold. Two-dimensional liquid chromatography coupled with mass spectrometry was utilized to compare mitochondrial-enriched samples from control and chronic acidotic rats. Proteomic analysis identified 901 proteins in the control and acidotic samples. Further analysis identified 37 peptides that contain an N-ε-acetyl-lysine; of these, 22 are novel sites. Spectral counting analysis revealed 33 proteins that are significantly altered in abundance in response to chronic metabolic acidosis. Western blot analysis was performed to validate the calculated changes in abundance. Thus the current study represents the first comprehensive analysis of the mitochondrial proteome of the rat renal proximal convoluted tubule and its response to metabolic acidosis.
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Affiliation(s)
- Dana M Freund
- Dept. of Biochemistry and Molecular Biology, Colorado State Univ., Ft. Collins, CO 80523-1870, USA
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49
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Alam-Faruque Y, Dimmer EC, Huntley RP, O'Donovan C, Scambler P, Apweiler R. The Renal Gene Ontology Annotation Initiative. Organogenesis 2012; 6:71-5. [PMID: 20885853 DOI: 10.4161/org.6.2.11294] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 12/18/2009] [Accepted: 01/22/2010] [Indexed: 12/26/2022] Open
Abstract
The gene ontology (go) resource provides dynamic controlled vocabularies to aid in the description of the functional attributes and subcellular locations of gene products from all taxonomic groups (www.geneontology.org). A renal-focused curation initiative, funded by Kidney Research UK and supported by the GO Consortium, has started at the European Bioinformatics Institute and aims to provide a detailed GO resource for mammalian proteins implicated in renal development and function. This report outlines the aims of this initiative and explains how the renal community can become involved to help improve the availability, quality and quantity of GO terms and their association to specific proteins.
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Molinas SM, Trumper L, Marinelli RA. Mitochondrial aquaporin-8 in renal proximal tubule cells: evidence for a role in the response to metabolic acidosis. Am J Physiol Renal Physiol 2012; 303:F458-66. [PMID: 22622463 DOI: 10.1152/ajprenal.00226.2012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial ammonia synthesis in proximal tubules and its urinary excretion are key components of the renal response to maintain acid-base balance during metabolic acidosis. Since aquaporin-8 (AQP8) facilitates transport of ammonia and is localized in inner mitochondrial membrane (IMM) of renal proximal cells, we hypothesized that AQP8-facilitated mitochondrial ammonia transport in these cells plays a role in the response to acidosis. We evaluated whether mitochondrial AQP8 (mtAQP8) knockdown by RNA interference is able to impair ammonia excretion in the human renal proximal tubule cell line, HK-2. By RT-PCR and immunoblotting, we found that AQP8 is expressed in these cells and is localized in IMM. HK-2 cells were transfected with short-interfering RNA targeting human AQP8. After 48 h, the levels of mtAQP8 protein decreased by 53% (P < 0.05). mtAQP8 knockdown decreased the rate of ammonia released into culture medium in cells grown at pH 7.4 (-31%, P < 0.05) as well as in cells exposed to acid (-90%, P < 0.05). We also evaluated mtAQP8 protein expression in HK-2 cells exposed to acidic medium. After 48 h, upregulation of mtAQP8 (+74%, P < 0.05) was observed, together with higher ammonia excretion rate (+73%, P < 0.05). In vivo studies in NH(4)Cl-loaded rats showed that mtAQP8 protein expression was also upregulated after 7 days of acidosis in renal cortex (+51%, P < 0.05). These data suggest that mtAQP8 plays an important role in the adaptive response of proximal tubule to acidosis possibly facilitating mitochondrial ammonia transport.
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Affiliation(s)
- Sara M Molinas
- Instituto de Fisiología Experimental. Facultad de Ciencias Bioquímicas y Farmacéuticas. Universidad Nacional de Rosario, Suipacha 570, 2000 Rosario, Santa Fe, Argentina.
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