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Benjamin JI, Pollock DM. Current perspective on circadian function of the kidney. Am J Physiol Renal Physiol 2024; 326:F438-F459. [PMID: 38134232 PMCID: PMC11207578 DOI: 10.1152/ajprenal.00247.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 11/28/2023] [Accepted: 12/18/2023] [Indexed: 12/24/2023] Open
Abstract
Behavior and function of living systems are synchronized by the 24-h rotation of the Earth that guides physiology according to time of day. However, when behavior becomes misaligned from the light-dark cycle, such as in rotating shift work, jet lag, and even unusual eating patterns, adverse health consequences such as cardiovascular or cardiometabolic disease can arise. The discovery of cell-autonomous molecular clocks expanded interest in regulatory systems that control circadian physiology including within the kidney, where function varies along a 24-h cycle. Our understanding of the mechanisms for circadian control of physiology is in the early stages, and so the present review provides an overview of what is known and the many gaps in our current understanding. We include a particular focus on the impact of eating behaviors, especially meal timing. A better understanding of the mechanisms guiding circadian function of the kidney is expected to reveal new insights into causes and consequences of a wide range of disorders involving the kidney, including hypertension, obesity, and chronic kidney disease.
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Affiliation(s)
- Jazmine I Benjamin
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - David M Pollock
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
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2
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Hakimi S, Dutta P, Layton AT. Coupling of renal sodium and calcium transport: a modeling analysis of transporter inhibition and sex differences. Am J Physiol Renal Physiol 2023; 325:F536-F551. [PMID: 37615047 DOI: 10.1152/ajprenal.00145.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 08/17/2023] [Accepted: 08/17/2023] [Indexed: 08/25/2023] Open
Abstract
Ca2+ transport along the nephron occurs via specific transcellular and paracellular pathways and is coupled to the transport of other electrolytes. Notably, Na+ transport establishes an electrochemical gradient to drive Ca2+ reabsorption. Hence, alterations in renal Na+ handling, under pathophysiological conditions or pharmacological manipulations, can have major effects on Ca2+ transport. An important class of pharmacological agent is diuretics, which are commonly prescribed for the management of blood pressure and fluid balance. The pharmacological targets of diuretics generally directly facilitate Na+ transport but also indirectly affect renal Ca2+ handling. To better understand the underlying mechanisms, we developed a computational model of electrolyte transport along the superficial nephron in the kidney of a male and female rat. Sex differences in renal Ca2+ handling are represented. Model simulations predicted in the female rat nephron lower Ca2+ reabsorption in the proximal tubule and thick ascending limb, but higher reabsorption in the late distal convoluted tubule and connecting tubule, compared with the male nephron. The male rat kidney model yielded a higher urinary Ca2+ excretion than the female model, consistent with animal experiments. Model results indicated that along the proximal tubule and thick ascending limb, Ca2+ and Na+ transport occurred in parallel, but those processes were dissociated in the distal convoluted tubule. Additionally, we conducted simulations of inhibition of channels and transporters that play a major role in Na+ and Ca2+ transport. Simulation results revealed alterations in transepithelial Ca2+ transport, with differential effects among nephron segments and between the sexes.NEW & NOTEWORTHY The kidney plays an important role in the maintenance of whole body Ca2+ balance by regulating Ca2+ reabsorption and excretion. This computational modeling study provides insights into how Ca2+ transport along the nephron is coupled to Na+. Model results indicated that along the proximal tubule and thick ascending limb, Ca2+ and Na+ transport occur in parallel, but those processes were dissociated in the distal convoluted tubule. Simulations also revealed sex-specific responses to different pharmacological manipulations.
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Affiliation(s)
- Shervin Hakimi
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Pritha Dutta
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Anita T Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
- Department of Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
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Just A, Mallmann RT, Grossmann S, Sleman F, Klugbauer N. Two-pore channel protein TPC1 is a determining factor for the adaptation of proximal tubular phosphate handling. Acta Physiol (Oxf) 2023; 237:e13914. [PMID: 36599408 DOI: 10.1111/apha.13914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 10/27/2022] [Accepted: 01/02/2023] [Indexed: 01/06/2023]
Abstract
AIM Two-pore channels (TPCs) constitute a small family of cation channels expressed in endo-lysosomal compartments. TPCs have been characterized as critical elements controlling Ca2+ -mediated vesicular membrane fusion and thereby regulating endo-lysosomal vesicle trafficking. Exo- and endocytotic trafficking and lysosomal degradation are major mechanisms of adaption of epithelial transport. A prime example of highly regulated epithelial transport is the tubular system of the kidney. We therefore studied the localization of TPC protein 1 (TPC1) in the kidney and its functional role in the dynamic regulation of tubular transport. METHODS Immunohistochemistry in combination with tubular markers were used to investigate TPC1 expression in proximal and distal tubules. The excretion of phosphate and ammonium, as well as urine volume and pH were studied in vivo, in response to dynamic challenges induced by bolus injection of parathyroid hormone or acid-base transitions via consecutive infusion of NaCl, Na2 CO3 , and NH4 Cl. RESULTS In TPC1-deficient mice, the PTH-induced rise in phosphate excretion was prolonged and exaggerated, and its recovery delayed in comparison with wildtype littermates. In the acid-base transition experiment, TPC1-deficient mice showed an identical rise in phosphate excretion in response to Na2 CO3 compared with wildtypes, but a delayed NH4Cl-induced recovery. Ammonium-excretion decreased with Na2 CO3 , and increased with NH4 Cl, but without differences between genotypes. CONCLUSIONS We conclude that TPC1 is expressed subapically in the proximal but not distal tubule and plays an important role in the dynamic adaptation of proximal tubular phosphate reabsorption towards enhanced, but not reduced absorption.
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Affiliation(s)
- Armin Just
- Institut für Physiologie I, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Robert T Mallmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Sonja Grossmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Faten Sleman
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Norbert Klugbauer
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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4
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Armando I, Cuevas S, Fan C, Kumar M, Izzi Z, Jose PA, Konkalmatt PR. G Protein-Coupled Receptor 37L1 Modulates Epigenetic Changes in Human Renal Proximal Tubule Cells. Int J Mol Sci 2022; 23:ijms232214456. [PMID: 36430934 PMCID: PMC9698582 DOI: 10.3390/ijms232214456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 10/19/2022] [Accepted: 10/31/2022] [Indexed: 11/23/2022] Open
Abstract
Renal luminal sodium transport is essential for physiological blood pressure control, and abnormalities in this process are strongly implicated in the pathogenesis of essential hypertension. Renal G protein-coupled receptors (GPCRs) are critical for the regulation of the reabsorption of essential nutrients, ions, and water from the glomerular filtrate. Recently, we showed that GPCR 37L1 (GPR37L1) is expressed on the apical membrane of renal proximal tubules (RPT) and regulates luminal sodium transport and blood pressure by modulating the function of the sodium proton exchanger 3 (NHE3). However, little is known about GPR37L1 intracellular signaling. Here, we show that GPR37L1 is localized to the nuclear membrane, in addition to the plasma membrane in human RPT cells. Furthermore, GPR37L1 signals via the PI3K/AKT/mTOR pathway to decrease the expression of DNA (cytosine-5)-methyltransferase 1 (DNMT1) and enhance NHE3 transcription. Overall, we demonstrate the direct role of a nuclear membrane GPCR in the regulation of renal sodium through epigenetic gene regulation.
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Poursharif S, Hamza S, Braam B. Changes in Proximal Tubular Reabsorption Modulate Microvascular Regulation via the TGF System. Int J Mol Sci 2022; 23:ijms231911203. [PMID: 36232506 PMCID: PMC9569689 DOI: 10.3390/ijms231911203] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 09/13/2022] [Accepted: 09/14/2022] [Indexed: 11/26/2022] Open
Abstract
This review paper considers the consequences of modulating tubular reabsorption proximal to the macula densa by sodium–glucose co-transporter 2 (SGLT2) inhibitors, acetazolamide, and furosemide in states of glomerular hyperfiltration. SGLT2 inhibitors improve renal function in early and advanced diabetic nephropathy by decreasing the glomerular filtration rate (GFR), presumably by activating the tubuloglomerular feedback (TGF) mechanism. Central in this paper is that the renoprotective effects of SGLT2 inhibitors in diabetic nephropathy can only be partially explained by TGF activation, and there are alternative explanations. The sustained activation of TGF leans on two prerequisites: no or only partial adaptation should occur in reabsorption proximal to macula densa, and no or only partial adaptation should occur in the TGF response. The main proximal tubular and loop of Henle sodium transporters are sodium–hydrogen exchanger 3 (NHE3), SGLT2, and the Na-K-2Cl co-transporter (NKCC2). SGLT2 inhibitors, acetazolamide, and furosemide are the most important compounds; inhibiting these transporters would decrease sodium reabsorption upstream of the macula densa and increase TGF activity. This could directly or indirectly affect TGF responsiveness, which could oppose sustained TGF activation. Only SGLT2 inhibitors can sustainably activate the TGF as there is only partial compensation in tubular reabsorption and TGF response. SGLT2 inhibitors have been shown to preserve GFR in both early and advanced diabetic nephropathy. Other than for early diabetic nephropathy, a solid physiological basis for these effects in advanced nephropathy is lacking. In addition, TGF has hardly been studied in humans, and therefore this role of TGF remains elusive. This review also considers alternative explanations for the renoprotective effects of SGLT2 inhibitors in diabetic patients such as the enhancement of microvascular network function. Furthermore, combination use of SGLT2 inhibitors and angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs). in diabetes can decrease inflammatory pathways, improve renal oxygenation, and delay the progression of diabetic nephropathy.
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Affiliation(s)
- Shayan Poursharif
- Department of Medicine, Division of Nephrology and Immunology, University of Alberta, Edmonton, AB T6G 2G3, Canada
| | - Shereen Hamza
- Department of Physiology, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Branko Braam
- Department of Medicine, Division of Nephrology and Immunology, University of Alberta, Edmonton, AB T6G 2G3, Canada
- Department of Physiology, University of Alberta, Edmonton, AB T6G 2H7, Canada
- Correspondence: ; Tel.: +1-780-492-1867
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Palmer LG. Directing two-way traffic in the kidney: A tale of two ions. J Gen Physiol 2022; 154:213433. [PMID: 36048011 PMCID: PMC9437110 DOI: 10.1085/jgp.202213179] [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] [Indexed: 12/14/2022] Open
Abstract
The kidneys regulate levels of Na+ and K+ in the body by varying urinary excretion of the electrolytes. Since transport of each of the two ions can affect the other, controlling both at the same time is a complex task. The kidneys meet this challenge in two ways. Some tubular segments change the coupling between Na+ and K+ transport. In addition, transport of Na+ can shift between segments where it is coupled to K+ reabsorption and segments where it is coupled to K+ secretion. This permits the kidney to maintain electrolyte balance with large variations in dietary intake.
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Affiliation(s)
- Lawrence G. Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY,Correspondence to Lawrence G. Palmer:
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7
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Oe Y, Vallon V. The Pathophysiological Basis of Diabetic Kidney Protection by Inhibition of SGLT2 and SGLT1. KIDNEY AND DIALYSIS 2022; 2:349-368. [PMID: 36380914 PMCID: PMC9648862 DOI: 10.3390/kidneydial2020032] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
SGLT2 inhibitors can protect the kidneys of patients with and without type 2 diabetes mellitus and slow the progression towards end-stage kidney disease. Blocking tubular SGLT2 and spilling glucose into the urine, which triggers a metabolic counter-regulation similar to fasting, provides unique benefits, not only as an anti-hyperglycemic strategy. These include a low hypoglycemia risk and a shift from carbohydrate to lipid utilization and mild ketogenesis, thereby reducing body weight and providing an additional energy source. SGLT2 inhibitors counteract hyperreabsorption in the early proximal tubule, which acutely lowers glomerular pressure and filtration and thereby reduces the physical stress on the filtration barrier, the filtration of tubule-toxic compounds, and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular gluco-toxicity and improved mitochondrial function and autophagy, can reduce pro-inflammatory, pro-senescence, and pro-fibrotic signaling and preserve tubular function and GFR in the long-term. By shifting transport downstream, SGLT2 inhibitors more equally distribute the transport burden along the nephron and may mimic systemic hypoxia to stimulate erythropoiesis, which improves oxygen delivery to the kidney and other organs. SGLT1 inhibition improves glucose homeostasis by delaying intestinal glucose absorption and by increasing the release of gastrointestinal incretins. Combined SGLT1 and SGLT2 inhibition has additive effects on renal glucose excretion and blood glucose control. SGLT1 in the macula densa senses luminal glucose, which affects glomerular hemodynamics and has implications for blood pressure control. More studies are needed to better define the therapeutic potential of SGLT1 inhibition to protect the kidney, alone or in combination with SGLT2 inhibition.
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Affiliation(s)
- Yuji Oe
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA 92161, USA
- VA San Diego Healthcare System, San Diego, CA 92161, USA
| | - Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA 92161, USA
- VA San Diego Healthcare System, San Diego, CA 92161, USA
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92161, USA
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8
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Bernhardt A, Häberer S, Xu J, Damerau H, Steffen J, Reichardt C, Wolters K, Steffen H, Isermann B, Borucki K, Artelt N, Endlich N, Kozyraki R, Brandt S, Lindquist JA, Mertens PR. High salt diet-induced proximal tubular phenotypic changes and sodium-glucose cotransporter-2 expression are coordinated by cold shock Y-box binding protein-1. FASEB J 2021; 35:e21912. [PMID: 34533842 DOI: 10.1096/fj.202100667rr] [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: 04/23/2021] [Revised: 07/06/2021] [Accepted: 08/25/2021] [Indexed: 11/11/2022]
Abstract
High salt diet (HSD) is a hallmark of blood pressure elevations, weight gain and diabetes onset in the metabolic syndrome. In kidney, compensatory mechanisms are activated to balance salt turnover and maintain homeostasis. Data on the long-term effects of HSD with respect to tubular cell functions and kidney architecture that exclude confounding indirect blood pressure effects are scarce. Additionally we focus on cold shock Y-box binding protein-1 as a tubular cell protective factor. A HSD model (4% NaCl in chow; 1% NaCl in water) was compared to normal salt diet (NSD, standard chow) over 16 months using wild type mice and an inducible conditional whole body knockout for cold shock Y-box binding protein-1 (BL6J/N, Ybx1). HSD induced no difference in blood pressure over 16 months, comparing NSD/HSD and Ybx1 wild type/knockout. Nevertheless, marked phenotypic changes were detected. Glucosuria and subnephrotic albuminuria ensued in wild type animals under HSD, which subsided in Ybx1-deficient animals. At the same time megalin receptors were upregulated. The sodium-glucose cotransporter-2 (SGLT2) was completely downregulated in wild type HSD animals that developed glucosuria. In Ybx1 knockouts, expression of AQP1 and SGLT2 was maintained under HSD; proximal tubular widening and glomerular tubularization developed. Concurrently, amino aciduria of neutral and hydrophobic amino acids was seen. In vitro translation confirmed that YB-1 translationally represses Sglt2 transcripts. Our data reveal profound effects of HSD primarily within glomeruli and proximal tubular segments. YB-1 is regulated by HSD and orchestrates HSD-dependent changes; notably, sets reabsorption thresholds for amino acids, proteins and glucose.
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Affiliation(s)
- Anja Bernhardt
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Saskia Häberer
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - JingJing Xu
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Hannah Damerau
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Johannes Steffen
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Charlotte Reichardt
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Katharina Wolters
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Hannes Steffen
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Berend Isermann
- Institute of Clinical Chemistry and Pathobiochemistry, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Katrin Borucki
- Institute of Clinical Chemistry and Pathobiochemistry, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Nadine Artelt
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany.,NIPOKA GmbH, Greifswald, Germany
| | - Nicole Endlich
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany.,NIPOKA GmbH, Greifswald, Germany
| | - Renata Kozyraki
- Centre de Recherche des Cordeliers, INSERM, UMRS-1138, Université de Paris, Paris, France
| | - Sabine Brandt
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Jonathan A Lindquist
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Peter R Mertens
- Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
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Guerrero A, Visniauskas B, Cárdenas P, Figueroa SM, Vivanco J, Salinas-Parra N, Araos P, Nguyen QM, Kassan M, Amador CA, Prieto MC, Gonzalez AA. α-Ketoglutarate Upregulates Collecting Duct (Pro)renin Receptor Expression, Tubular Angiotensin II Formation, and Na + Reabsorption During High Glucose Conditions. Front Cardiovasc Med 2021; 8:644797. [PMID: 34179130 PMCID: PMC8220822 DOI: 10.3389/fcvm.2021.644797] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 04/13/2021] [Indexed: 11/22/2022] Open
Abstract
Diabetes mellitus (DM) causes high glucose (HG) levels in the plasma and urine. The (pro)renin receptor (PRR) is a key regulator of renal Na+ handling. PRR is expressed in intercalated (IC) cells of the collecting duct (CD) and binds renin to promote angiotensin (Ang) II formation, thereby contributing to Na+ reabsorption. In DM, the Kreb's cycle is in a state of suppression in most tissues. However, in the CD, expression of glucose transporters is augmented, boosting the Kreb's cycle and consequently causing α-ketoglutarate (αKG) accumulation. The αKG receptor 1 (OXGR1) is a Gq-coupled receptor expressed on the apical membrane of IC cells of the CD. We hypothesize that HG causes αKG secretion and activation of OXGR1, which increases PRR expression in CD cells. This effect then promotes intratubular AngII formation and Na+ reabsorption. To test this hypothesis, streptozotocin (STZ)-induced diabetic mice were treated with or without montelukast (ML), an OXGR1 antagonist, for 6 days. STZ mice had higher urinary αKG and PRR expression along with augmented urinary AngII levels and Na+ retention. Treatment with ML prevented all these effects. Similarly, primary cultured inner medullary CD cells treated with HG showed increased PRR expression, while OXGR1 antagonist prevented this effect. αKG increases PRR expression, while treatments with ML, PKC inhibition, or intracellular Ca2+ depletion impair this effect. In silico analysis suggested that αKG binds to mouse OXGR1. These results indicate that HG conditions promote increased levels of intratubular αKG and OXGR1-dependent PRR upregulation, which impact AngII formation and Na+ reabsorption.
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Affiliation(s)
- Aarón Guerrero
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Bruna Visniauskas
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, United States
| | - Pilar Cárdenas
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Stefanny M. Figueroa
- Laboratory of Renal Physiopathology, Institute of Biomedical Sciences, Universidad Autónoma de Chile, Santiago, Chile
| | - Jorge Vivanco
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Nicolas Salinas-Parra
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Patricio Araos
- Laboratory of Renal Physiopathology, Institute of Biomedical Sciences, Universidad Autónoma de Chile, Santiago, Chile
| | - Quynh My Nguyen
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, San Diego, CA, United States
| | - Modar Kassan
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Cristián A. Amador
- Laboratory of Renal Physiopathology, Institute of Biomedical Sciences, Universidad Autónoma de Chile, Santiago, Chile
| | - Minolfa C. Prieto
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, United States
| | - Alexis A. Gonzalez
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
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10
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Sparks MA, Dilmen E, Ralph DL, Rianto F, Hoang TA, Hollis A, Diaz EJ, Adhikari R, Chew G, Petretto EG, Gurley SB, McDonough AA, Coffman TM. Vascular control of kidney epithelial transporters. Am J Physiol Renal Physiol 2021; 320:F1080-F1092. [PMID: 33969697 PMCID: PMC8285646 DOI: 10.1152/ajprenal.00084.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/23/2021] [Accepted: 05/05/2021] [Indexed: 01/03/2023] Open
Abstract
A major pathway in hypertension pathogenesis involves direct activation of ANG II type 1 (AT1) receptors in the kidney, stimulating Na+ reabsorption. AT1 receptors in tubular epithelia control expression and stimulation of Na+ transporters and channels. Recently, we found reduced blood pressure and enhanced natriuresis in mice with cell-specific deletion of AT1 receptors in smooth muscle (SMKO mice). Although impaired vasoconstriction and preserved renal blood flow might contribute to exaggerated urinary Na+ excretion in SMKO mice, we considered whether alterations in Na+ transporter expression might also play a role; therefore, we carried out proteomic analysis of key Na+ transporters and associated proteins. Here, we show that levels of Na+-K+-2Cl- cotransporter isoform 2 (NKCC2) and Na+/H+ exchanger isoform 3 (NHE3) are reduced at baseline in SMKO mice, accompanied by attenuated natriuretic and diuretic responses to furosemide. During ANG II hypertension, we found widespread remodeling of transporter expression in wild-type mice with significant increases in the levels of total NaCl cotransporter, phosphorylated NaCl cotransporter (Ser71), and phosphorylated NKCC2, along with the cleaved, activated forms of the α- and γ-epithelial Na+ channel. However, the increases in α- and γ-epithelial Na+ channel with ANG II were substantially attenuated in SMKO mice. This was accompanied by a reduced natriuretic response to amiloride. Thus, enhanced urinary Na+ excretion observed after cell-specific deletion of AT1 receptors from smooth muscle cells is associated with altered Na+ transporter abundance across epithelia in multiple nephron segments. These findings suggest a system of vascular-epithelial in the kidney, modulating the expression of Na+ transporters and contributing to the regulation of pressure natriuresis.NEW & NOTEWORTHY The use of drugs to block the renin-angiotensin system to reduce blood pressure is common. However, the precise mechanism for how these medications control blood pressure is incompletely understood. Here, we show that mice lacking angiotensin receptors specifically in smooth muscle cells lead to alternation in tubular transporter amount and function. Thus, demonstrating the importance of vascular-tubular cross talk in the control of blood pressure.
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Affiliation(s)
- Matthew A Sparks
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
- Renal Section, Durham Veterans Affairs Health Care System, Durham, North Carolina
| | - Emre Dilmen
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
| | - Donna L Ralph
- Department of Physiology and Neuroscience, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Fitra Rianto
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
| | - Thien A Hoang
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
| | - Alison Hollis
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
| | - Edward J Diaz
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
| | - Rishav Adhikari
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
| | - Gabriel Chew
- Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Enrico G Petretto
- Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Susan B Gurley
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, Oregon
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Thomas M Coffman
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina
- Renal Section, Durham Veterans Affairs Health Care System, Durham, North Carolina
- Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
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11
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Onishi A, Fu Y, Patel R, Darshi M, Crespo-Masip M, Huang W, Song P, Freeman B, Kim YC, Soleimani M, Sharma K, Thomson SC, Vallon V. A role for tubular Na +/H + exchanger NHE3 in the natriuretic effect of the SGLT2 inhibitor empagliflozin. Am J Physiol Renal Physiol 2020; 319:F712-F728. [PMID: 32893663 DOI: 10.1152/ajprenal.00264.2020] [Citation(s) in RCA: 108] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Inhibitors of proximal tubular Na+-glucose cotransporter 2 (SGLT2) are natriuretic, and they lower blood pressure. There are reports that the activities of SGLT2 and Na+-H+ exchanger 3 (NHE3) are coordinated. If so, then part of the natriuretic response to an SGLT2 inhibitor is mediated by suppressing NHE3. To examine this further, we compared the effects of an SGLT2 inhibitor, empagliflozin, on urine composition and systolic blood pressure (SBP) in nondiabetic mice with tubule-specific NHE3 knockdown (NHE3-ko) and wild-type (WT) littermates. A single dose of empagliflozin, titrated to cause minimal glucosuria, increased urinary excretion of Na+ and bicarbonate and raised urine pH in WT mice but not in NHE3-ko mice. Chronic empagliflozin treatment tended to lower SBP despite higher renal renin mRNA expression and lowered the ratio of SBP to renin mRNA, indicating volume loss. This effect of empagliflozin depended on tubular NHE3. In diabetic Akita mice, chronic empagliflozin enhanced phosphorylation of NHE3 (S552/S605), changes previously linked to lesser NHE3-mediated reabsorption. Chronic empagliflozin also increased expression of genes involved with renal gluconeogenesis, bicarbonate regeneration, and ammonium formation. While this could reflect compensatory responses to acidification of proximal tubular cells resulting from reduced NHE3 activity, these effects were at least in part independent of tubular NHE3 and potentially indicated metabolic adaptations to urinary glucose loss. Moreover, empagliflozin increased luminal α-ketoglutarate, which may serve to stimulate compensatory distal NaCl reabsorption, while cogenerated and excreted ammonium balances urine losses of this "potential bicarbonate." The data implicate NHE3 as a determinant of the natriuretic effect of empagliflozin.
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Affiliation(s)
- Akira Onishi
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Yiling Fu
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Rohit Patel
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Manjula Darshi
- Center for Renal Precision Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Maria Crespo-Masip
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California.,Biomedical Research Institute, University of Lleida, Lleida, Spain
| | - Winnie Huang
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Panai Song
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Brent Freeman
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Young Chul Kim
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | | | - Kumar Sharma
- Center for Renal Precision Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Scott Culver Thomson
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Volker Vallon
- Department of Medicine, University of California-San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
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12
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Hu R, McDonough AA, Layton AT. Sex differences in solute transport along the nephrons: effects of Na + transport inhibition. Am J Physiol Renal Physiol 2020; 319:F487-F505. [PMID: 32744084 DOI: 10.1152/ajprenal.00240.2020] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Each day, ~1.7 kg of NaCl and 180 liters of water are reabsorbed by nephron segments in humans, with urinary excretion fine tuned to meet homeostatic requirements. These tasks are coordinated by a spectrum of renal Na+ transporters and channels. The goal of the present study was to investigate the extent to which inhibitors of transepithelial Na+ transport (TNa) along the nephron alter urinary solute excretion and how those effects may vary between male and female subjects. To accomplish that goal, we developed sex-specific multinephron models that represent detailed transcellular and paracellular transport processes along the nephrons of male and female rat kidneys. We simulated inhibition of Na+/H+ exchanger 3 (NHE3), bumetanide-sensitive Na+-K+-2Cl- cotransporter (NKCC2), Na+-Cl- cotransporter (NCC), and amiloride-sensitive epithelial Na+ channel (ENaC). NHE3 inhibition simulations predicted a substantially reduced proximal tubule TNa, and NKCC2 inhibition substantially reduced thick ascending limb TNa. Both gave rise to diuresis, natriuresis, and kaliuresis, with those effects stronger in female rats. While NCC inhibition was predicted to have only minor impact on renal TNa, it nonetheless had a notable effect of enhancing excretion of Na+, K+, and Cl-, particularly in female rats. Inhibition of ENaC was predicted to have opposite effects on the excretion of Na+ (increased) and K+ (decreased) and to have only a minor impact on whole kidney TNa. Unlike inhibition of other transporters, ENaC inhibition induced stronger natriuresis and diuresis in male rats than female rats. Overall, model predictions agreed well with measured changes in Na+ and K+ excretion in response to diuretics and Na+ transporter mutations.
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Affiliation(s)
- Rui Hu
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Anita T Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada.,Department of Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
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13
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An inducible intestinal epithelial cell-specific NHE3 knockout mouse model mimicking congenital sodium diarrhea. Clin Sci (Lond) 2020; 134:941-953. [PMID: 32227118 PMCID: PMC8819665 DOI: 10.1042/cs20200065] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 12/13/2022]
Abstract
The sodium–hydrogen exchanger isoform 3 (NHE3, SLC9A3) is abundantly expressed in the gastrointestinal tract and is proposed to play essential roles in Na+ and fluid absorption as well as acid–base homeostasis. Mutations in the SLC9A3 gene can cause congenital sodium diarrhea (CSD). However, understanding the precise role of intestinal NHE3 has been severely hampered due to the lack of a suitable animal model. To navigate this problem and better understand the role of intestinal NHE3, we generated a tamoxifen-inducible intestinal epithelial cell-specific NHE3 knockout mouse model (NHE3IEC-KO). Before tamoxifen administration, the phenotype and blood parameters of NHE3IEC-KO were unremarkable compared with control mice. After tamoxifen administration, NHE3IEC-KO mice have undetectable levels of NHE3 in the intestine. NHE3IEC-KO mice develop watery, alkaline diarrhea in combination with a swollen small intestine, cecum and colon. The persistent diarrhea results in higher fluid intake. After 3 weeks, NHE3IEC-KO mice show a ~25% mortality rate. The contribution of intestinal NHE3 to acid–base and Na+ homeostasis under normal conditions becomes evident in NHE3IEC-KO mice that have metabolic acidosis, lower blood bicarbonate levels, hyponatremia and hyperkalemia associated with drastically elevated plasma aldosterone levels. These results demonstrate that intestinal NHE3 has a significant contribution to acid–base, Na+ and volume homeostasis, and lack of intestinal NHE3 has consequences on intestinal structural integrity. This mouse model mimics and explains the phenotype of individuals with CSD carrying SLC9A3 mutations.
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14
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Boyd-Shiwarski CR, Weaver CJ, Beacham RT, Shiwarski DJ, Connolly KA, Nkashama LJ, Mutchler SM, Griffiths SE, Knoell SA, Sebastiani RS, Ray EC, Marciszyn AL, Subramanya AR. Effects of extreme potassium stress on blood pressure and renal tubular sodium transport. Am J Physiol Renal Physiol 2020; 318:F1341-F1356. [PMID: 32281415 PMCID: PMC7311711 DOI: 10.1152/ajprenal.00527.2019] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We characterized mouse blood pressure and ion transport in the setting of commonly used rodent diets that drive K+ intake to the extremes of deficiency and excess. Male 129S2/Sv mice were fed either K+-deficient, control, high-K+ basic, or high-KCl diets for 10 days. Mice maintained on a K+-deficient diet exhibited no change in blood pressure, whereas K+-loaded mice developed an ~10-mmHg blood pressure increase. Following challenge with NaCl, K+-deficient mice developed a salt-sensitive 8 mmHg increase in blood pressure, whereas blood pressure was unchanged in mice fed high-K+ diets. Notably, 10 days of K+ depletion induced diabetes insipidus and upregulation of phosphorylated NaCl cotransporter, proximal Na+ transporters, and pendrin, likely contributing to the K+-deficient NaCl sensitivity. While the anionic content with high-K+ diets had distinct effects on transporter expression along the nephron, both K+ basic and KCl diets had a similar increase in blood pressure. The blood pressure elevation on high-K+ diets correlated with increased Na+-K+-2Cl- cotransporter and γ-epithelial Na+ channel expression and increased urinary response to furosemide and amiloride. We conclude that the dietary K+ maneuvers used here did not recapitulate the inverse effects of K+ on blood pressure observed in human epidemiological studies. This may be due to the extreme degree of K+ stress, the low-Na+-to-K+ ratio, the duration of treatment, and the development of other coinciding events, such as diabetes insipidus. These factors must be taken into consideration when studying the physiological effects of dietary K+ loading and depletion.
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Affiliation(s)
- Cary R. Boyd-Shiwarski
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Claire J. Weaver
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Rebecca T. Beacham
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Daniel J. Shiwarski
- 2Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Kelly A. Connolly
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Lubika J. Nkashama
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Stephanie M. Mutchler
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Shawn E. Griffiths
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Sophia A. Knoell
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Romano S. Sebastiani
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Evan C. Ray
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Allison L. Marciszyn
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Arohan R. Subramanya
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania,3Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania,4Veterans Administration, Pittsburgh Healthcare System, Pittsburgh Pennsylvania
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15
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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16
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Yanda MK, Cha B, Cebotaru CV, Cebotaru L. Pharmacological reversal of renal cysts from secretion to absorption suggests a potential therapeutic strategy for managing autosomal dominant polycystic kidney disease. J Biol Chem 2019; 294:17090-17104. [PMID: 31570523 DOI: 10.1074/jbc.ra119.010320] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 09/26/2019] [Indexed: 12/19/2022] Open
Abstract
Autosomal-dominant polycystic kidney disease (ADPKD) induces a secretory phenotype, resulting in multiple fluid-filled cysts. We have previously demonstrated that VX-809, a corrector of the cystic fibrosis transmembrane conductance regulator (CFTR), reduces cyst growth. Here, we show that in normal mice CFTR is located within the cells and also at the apical and basolateral membranes. However, in polycystic kidney disease (pkd1)-knockout mice, CFTR was located at the plasma membrane, consistent with its role in cAMP-dependent fluid secretion. In cystic mice, VX-809 treatment increased CFTR levels at the apical membrane and reduced its association with the endoplasmic reticulum. Surprisingly, VX-809 treatment significantly increased CFTR's co-localization with the basolateral membrane in cystic mice. Na+/H+ exchanger 3 (NHE3) is present in pkd1-knockout and normal mice and in proximal tubule-derived, cultured pkd1-knockout cells. VX-809 increased the expression, activity, and apical plasma membrane localization of NHE3. Co-localization of epithelial sodium channel (ENaC) with the plasma membrane was reduced in cysts in pkd1-knockout mice, consistent with an inability of the cysts to absorb fluid. Interestingly, in the cystic mice, VX-809 treatment increased ENaC levels at the apical plasma membrane consistent with fluid absorption. Thus, VX-809 treatment of pkd1-null mouse kidneys significantly affected CFTR, NHE3, and ENaC, altering the cyst phenotype from one poised toward fluid secretion toward one more favorable for absorption. VX-809 also altered the location of CFTR but not of NHE3 or ENaC in normal mice. Given that VX-809 administration is safe, it may have potential utility for treating patients with ADPKD.
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Affiliation(s)
- Murali K Yanda
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Boyoung Cha
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Cristina V Cebotaru
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Liudmila Cebotaru
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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17
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Onishi A, Fu Y, Darshi M, Crespo-Masip M, Huang W, Song P, Patel R, Kim YC, Nespoux J, Freeman B, Soleimani M, Thomson S, Sharma K, Vallon V. Effect of renal tubule-specific knockdown of the Na +/H + exchanger NHE3 in Akita diabetic mice. Am J Physiol Renal Physiol 2019; 317:F419-F434. [PMID: 31166707 PMCID: PMC6732454 DOI: 10.1152/ajprenal.00497.2018] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 05/21/2019] [Accepted: 05/27/2019] [Indexed: 01/03/2023] Open
Abstract
Na+/H+ exchanger isoform 3 (NHE3) contributes to Na+/bicarbonate reabsorption and ammonium secretion in early proximal tubules. To determine its role in the diabetic kidney, type 1 diabetic Akita mice with tubular NHE3 knockdown [Pax8-Cre; NHE3-knockout (KO) mice] were generated. NHE3-KO mice had higher urine pH, more bicarbonaturia, and compensating increases in renal mRNA expression for genes associated with generation of ammonium, bicarbonate, and glucose (phosphoenolpyruvate carboxykinase) in proximal tubules and H+ and ammonia secretion and glycolysis in distal tubules. This left blood pH and bicarbonate unaffected in nondiabetic and diabetic NHE3-KO versus wild-type mice but was associated with renal upregulation of proinflammatory markers. Higher renal phosphoenolpyruvate carboxykinase expression in NHE3-KO mice was associated with lower Na+-glucose cotransporter (SGLT)2 and higher SGLT1 expression, indicating a downward tubular shift in Na+ and glucose reabsorption. NHE3-KO was associated with lesser kidney weight and glomerular filtration rate (GFR) independent of diabetes and prevented diabetes-associated albuminuria. NHE3-KO, however, did not attenuate hyperglycemia or prevent diabetes from increasing kidney weight and GFR. Higher renal gluconeogenesis may explain similar hyperglycemia despite lower SGLT2 expression and higher glucosuria in diabetic NHE3-KO versus wild-type mice; stronger SGLT1 engagement could have affected kidney weight and GFR responses. Chronic kidney disease in humans is associated with reduced urinary excretion of metabolites of branched-chain amino acids and the tricarboxylic acid cycle, a pattern mimicked in diabetic wild-type mice. This pattern was reversed in nondiabetic NHE3-KO mice, possibly reflecting branched-chain amino acids use for ammoniagenesis and tricarboxylic acid cycle upregulation to support formation of ammonia, bicarbonate, and glucose in proximal tubule. NHE3-KO, however, did not prevent the diabetes-induced urinary downregulation in these metabolites.
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Affiliation(s)
- Akira Onishi
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Yiling Fu
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Manjula Darshi
- Center for Renal Precision Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Maria Crespo-Masip
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
- Biomedical Research Institute (IRBLleida), University of Lleida, Lleida, Spain
| | - Winnie Huang
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Panai Song
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Rohit Patel
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Young Chul Kim
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Josselin Nespoux
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Brent Freeman
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | | | - Scott Thomson
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Kumar Sharma
- Center for Renal Precision Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Volker Vallon
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
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18
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Abstract
Metabolic acidosis is defined as a pathologic process that, when unopposed, increases the concentration of hydrogen ions (H+) in the body and reduces the bicarbonate (HCO3-) concentration. Metabolic acidosis can be of a kidney origin or an extrarenal cause. Assessment of urinary ammonium excretion by calculating the urine anion gap or osmolal gap is a useful method to distinguish between these two causes. Extrarenal processes include increased endogenous acid production and accelerated loss of bicarbonate from the body. Metabolic acidosis of renal origin is due to a primary defect in renal acidification with no increase in extrarenal hydrogen ion production. This situation can occur because either the renal input of new bicarbonate is insufficient to regenerate the bicarbonate lost in buffering endogenous acid as with distal renal tubular acidosis (RTA) or the RTA of renal insufficiency, or the filtered bicarbonate is lost by kidney wasting as in proximal RTA. In either condition, because of loss of either NaHCO3 (proximal RTA) or NaA (distal RTA), effective extracellular volume is reduced and as a result the avidity for chloride reabsorption derived from the diet is increased and results in a hyperchloremic normal gap metabolic acidosis. The RTA of renal insufficiency is also characterized by a normal gap acidosis, however, with severe reductions in the glomerular filtration rate an anion gap metabolic acidosis eventually develops.
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Affiliation(s)
- Biff F Palmer
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA -
| | - Deborah J Clegg
- Department of Health Studies, College of Arts and Sciences, American University, Washington, DC, USA.,Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, University of California Los Angeles (UCLA), Los Angeles, CA, USA
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19
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Spires D, Manis AD, Staruschenko A. Ion channels and transporters in diabetic kidney disease. CURRENT TOPICS IN MEMBRANES 2019; 83:353-396. [PMID: 31196609 PMCID: PMC6815098 DOI: 10.1016/bs.ctm.2019.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Type 1 and 2 diabetes mellitus are major medical epidemics affecting millions of patients worldwide. Diabetes mellitus is the leading cause of diabetic kidney disease (DKD), which is the most common cause of end-stage renal disease (ESRD). DKD is associated with significant changes in renal hemodynamics and electrolyte transport. Alterations in renal ion transport triggered by pathophysiological conditions in diabetes can exacerbate hypertension, accelerate renal injury, and are integral to the development of DKD. Renal ion transporters and electrolyte homeostasis play a fundamental role in functional changes and injury to the kidney during DKD. With the large number of ion transporters involved in DKD, understanding the roles of individual transporters as well as the complex cascades through which they interact is essential in the development of effective treatments for patients suffering from this disease. This chapter aims to gather current knowledge of the major renal ion transporters with altered expression and activity under diabetic conditions, and provide a comprehensive overview of their interactions and collective functions in DKD.
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Affiliation(s)
- Denisha Spires
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Anna D Manis
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States; Clement J. Zablocki VA Medical Center, Milwaukee, WI, United States.
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20
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Babich V, Vadnagara K, Di Sole F. Adenosine A 2A receptor blocks the A 1 receptor inhibition of renal Na + transport and oxygen consumption. J Cell Physiol 2019; 234:13917-13930. [PMID: 30633335 DOI: 10.1002/jcp.28074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Accepted: 12/18/2018] [Indexed: 11/11/2022]
Abstract
A high renal oxygen (O2 ) need is primarily associated with the renal tubular O2 consumption (VO2 ) necessary for a high rate of sodium (Na+ ) transport. Limited O2 availability leads to increased levels of adenosine, which regulates the kidney via activation of both A1 and A2A adenosine receptors (A1R and A2AR, respectively). The relative contributions of A1R and A2AR to the regulation of renal Na+ transport and VO2 have not been determined. We demonstrated that A1R activation has a dose-dependent biphasic effect on both renal Na+ /H+ exchanger-3 (NHE3), a major player in Na+ transport, and VO2 . Here, we report concentration-dependent effects of adenosine: less than 5 × 10-7 M adenosine-stimulated NHE3 activity; between 5 × 10-7 M and 10-5 M adenosine-inhibited NHE3 activity; and greater than 10-5 M adenosine reversed the change in NHE3 activity (returned to baseline). A1R activation mediated the activation and inhibition of NHE3 activity, whereas 10-4 M adenosine had no effect on the NHE3 activity due to A2AR activation. The following occurred when A1R and A2AR were activated: (a) Blockade of the A2AR receptor restored the NHE3 inhibition mediated by A1R activation, (b) the NHE-dependent effect on VO2 mediated by A1R activation became NHE independent, and (c) A2AR bound to A1R. In summary, A1R affects VO2 via NHE-dependent mechanisms, whereas A2AR acts via NHE-independent mechanisms. When both A1R and A2AR are activated, the A2AR effect on NHE3 and VO2 predominates, possibly via an A1R-A2AR protein interaction. A2AR-A1R heterodimerization is proposed as the molecular mechanism enabling the NHE-independent control of renal VO2 .
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Affiliation(s)
- Victor Babich
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, Iowa.,School of Liberal Arts and Sciences, Mercy College of Health Sciences, Des Moines, Iowa.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Komal Vadnagara
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Francesca Di Sole
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, Iowa.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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21
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Zheng X, Asico LD, Ma X, Konkalmatt PR. G protein-coupled receptor 37L1 regulates renal sodium transport and blood pressure. Am J Physiol Renal Physiol 2018; 316:F506-F516. [PMID: 30566002 DOI: 10.1152/ajprenal.00289.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
G protein-coupled receptors (GPCRs) in the kidney regulate the reabsorption of essential nutrients, ions, and water from the glomerular filtrate. Abnormalities in renal epithelial ion transport play important roles in the pathogenesis of essential hypertension. The orphan G protein-coupled receptor 37L1 (GPR37L1), also known as endothelin receptor type B-like protein (ETBR-LP2), is expressed in several regions in the brain, but its expression profile and function in peripheral tissues are poorly understood. We found that GPR37L1 mRNA expression is highest in the brain, followed by the stomach, heart, testis, and ovary, with moderate expression in the kidney, pancreas, skeletal muscle, liver, lung, and spleen. Immunofluorescence analyses revealed the expression of GPR37L1 in specific regions within some organs. In the kidney, GPR37L1 is expressed in the apical membrane of renal proximal tubule cells. In human renal proximal tubule cells, the transient expression of GPR37LI increased intracellular sodium, whereas the silencing of GPR37LI decreased intracellular sodium. Inhibition of Na+/H+ exchanger isoform 3 (NHE3) activity abrogated the GPR37L1-mediated increase in intracellular sodium. Renal-selective silencing of Gpr37l1 in mice increased urine output and sodium excretion and decreased systolic and diastolic blood pressures. The renal-selective silencing of GPR37L1 decreased the protein expression of NHE3 but not the expression of Na+-K+-ATPase or sodium-glucose cotransporter 2. Our findings show that in the kidney, GPR37L1 participates in renal proximal tubule luminal sodium transport and regulation of blood pressure by increasing the renal expression and function of NHE3 by decreasing cAMP production. The role of GPR37L1, expressed in specific cell types in organs other than the kidney, remains to be determined.
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Affiliation(s)
- Xiaoxu Zheng
- Department of Medicine, The George Washington University , Washington, District of Columbia
| | - Laureano D Asico
- Department of Medicine, The George Washington University , Washington, District of Columbia
| | - Xiaobo Ma
- Department of Medicine, The George Washington University , Washington, District of Columbia
| | - Prasad R Konkalmatt
- Department of Medicine, The George Washington University , Washington, District of Columbia
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22
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Kamel KS, Schreiber M, Halperin ML. Renal potassium physiology: integration of the renal response to dietary potassium depletion. Kidney Int 2018; 93:41-53. [PMID: 29102372 DOI: 10.1016/j.kint.2017.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/31/2017] [Accepted: 08/03/2017] [Indexed: 01/30/2023]
Abstract
We summarize the current understanding of the physiology of the renal handling of potassium (K+), and present an integrative view of the renal response to K+ depletion caused by dietary K+ restriction. This renal response involves contributions from different nephron segments, and aims to diminish the rate of excretion of K+ as a result of: decreasing the rate of electrogenic (and increasing the rate of electroneutral) reabsorption of sodium in the aldosterone-sensitive distal nephron (ASDN), decreasing the abundance of renal outer medullary K+ channels in the luminal membrane of principal cells in the ASDN, decreasing the flow rate in the ASDN, and increasing the reabsorption of K+ in the cortical and medullary collecting ducts. The implications of this physiology for the association between K+ depletion and hypertension, and K+ depletion and formation of calcium kidney stones are discussed.
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Affiliation(s)
- Kamel S Kamel
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
| | - Martin Schreiber
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Mitchell L Halperin
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
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23
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Tonneijck L, Muskiet MHA, Blijdorp CJ, Smits MM, Twisk JW, Kramer MHH, Danser AHJ, Diamant M, Joles JA, Hoorn EJ, van Raalte DH. Renal tubular effects of prolonged therapy with the GLP-1 receptor agonist lixisenatide in patients with type 2 diabetes mellitus. Am J Physiol Renal Physiol 2018; 316:F231-F240. [PMID: 30353743 DOI: 10.1152/ajprenal.00432.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) are well-established glucose-lowering drugs for type 2 diabetes mellitus (T2DM) management. Acute GLP-1RA administration increases urinary excretion of sodium and other electrolytes. However, the renal tubular effects of prolonged GLP-1RA treatment are largely unknown. In this secondary analysis of a randomized trial, we determined the renal tubular effects of 8-wk treatment with 20 μg lixisenatide, a short-acting (prandial) GLP-1RA, versus titrated once-daily insulin glulisine in 35 overweight T2DM-patients on stable insulin glargine background therapy (age: 62 ± 7 yr, glycated hemoglobin: 8.0 ± 0.9%, estimated glomerular filtration rate: >60 ml·min-1·1.73 m-2). After a standardized breakfast, lixisenatide increased absolute and fractional excretions of sodium, chloride, and potassium and increased urinary pH. In contrast, lixisenatide reduced absolute and fractional excretions of magnesium, calcium, and phosphate. At week 8, patients treated with lixisenatide had significantly more phosphorylated sodium-hydrogen exchanger isoform 3 (NHE3) in urinary extracellular vesicles than those on insulin glulisine treatment, which suggested decreased NHE3 activity in the proximal tubule. A rise in postprandial blood pressure with lixisenatide partly explained the changes in the urinary excretion of sodium, potassium, magnesium, and phosphate and the changes in urinary pH. In conclusion, lixisenatide affects postprandial urinary excretion of several electrolytes and increases urinary pH compared with insulin glulisine in T2DM patients after 8 wk of treatment. This is most likely explained by a drug-induced rise in blood pressure or direct inhibitory effects on NHE3 in the proximal tubule.
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Affiliation(s)
- Lennart Tonneijck
- Diabetes Center, Department of Internal Medicine, VU University Medical Center , Amsterdam , The Netherlands
| | - Marcel H A Muskiet
- Diabetes Center, Department of Internal Medicine, VU University Medical Center , Amsterdam , The Netherlands
| | - Charles J Blijdorp
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus University Medical Center , Rotterdam , The Netherlands
| | - Mark M Smits
- Diabetes Center, Department of Internal Medicine, VU University Medical Center , Amsterdam , The Netherlands
| | - Jos W Twisk
- Department of Health Sciences and the EMGO Institute for Health and Care Research, VU University Amsterdam , Amsterdam , The Netherlands ; Department of Epidemiology and Biostatistics, VU University Medical Center , Amsterdam , The Netherlands
| | - Mark H H Kramer
- Diabetes Center, Department of Internal Medicine, VU University Medical Center , Amsterdam , The Netherlands
| | - A H J Danser
- Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus University Medical Center , Rotterdam , The Netherlands
| | - Michaela Diamant
- Diabetes Center, Department of Internal Medicine, VU University Medical Center , Amsterdam , The Netherlands
| | - Jaap A Joles
- Department of Nephrology and Hypertension, University Medical Center Utrecht , Utrecht , The Netherlands
| | - Ewout J Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus University Medical Center , Rotterdam , The Netherlands
| | - Daniël H van Raalte
- Diabetes Center, Department of Internal Medicine, VU University Medical Center , Amsterdam , The Netherlands
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24
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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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25
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Yang L, Xu S, Guo X, Uchida S, Weinstein AM, Wang T, Palmer LG. Regulation of renal Na transporters in response to dietary K. Am J Physiol Renal Physiol 2018; 315:F1032-F1041. [PMID: 29923764 DOI: 10.1152/ajprenal.00117.2018] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Changes in the expression of Na transport proteins were measured in the kidneys of mice with increased dietary K intake for 1 wk. The epithelial Na channel (ENaC) was upregulated, with enhanced expression of full-length and cleaved forms of α-ENaC and cleaved γ-ENaC. At the same time, the amount of the NaCl cotransporter NCC and its phosphorylated form decreased by ~50% and ~80%, respectively. The expression of the phosphorylated form of the Na-K-2Cl cotransporter NKCC2 also decreased, despite an increase in overall protein content. The effect was stronger in males (80%) than in females (40%). This implies that less Na+ is reabsorbed in the thick ascending limb of Henle's loop and distal convoluted tubule along with Cl-, whereas more is reabsorbed in the aldosterone-sensitive distal nephron in exchange for secreted K+. The abundance of the proximal tubule Na/H exchanger NHE3 decreased by ~40%, with similar effects in males and females. Time-course studies indicated that NCC and NHE3 proteins decreased progressively over 7 days on a high-K diet. Expression of mRNA encoding these proteins increased, implying that the decreased protein levels resulted from decreased rates of synthesis or increased rates of degradation. The potential importance of changes in NHE3, NKCC2, and NCC in promoting K+ excretion was assessed with a mathematical model. Simulations indicated that decreased NHE3 produced the largest effect. Regulation of proximal tubule Na+ transport may play a significant role in achieving K homeostasis.
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Affiliation(s)
- Lei Yang
- Department of Physiology and Biophysics, Weill Medical College of Cornell University , New York, New York
| | - Shuhua Xu
- Department of Cellular and Molecular Physiology, Yale University , New Haven, Connecticut
| | - Xiaoyun Guo
- Department of Cellular and Molecular Physiology, Yale University , New Haven, Connecticut
| | - Shinichi Uchida
- Department of Nephrology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Alan M Weinstein
- Department of Physiology and Biophysics, Weill Medical College of Cornell University , New York, New York
| | - Tong Wang
- Department of Cellular and Molecular Physiology, Yale University , New Haven, Connecticut
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill Medical College of Cornell University , New York, New York
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26
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Effects of Nitric Oxide on Renal Proximal Tubular Na + Transport. BIOMED RESEARCH INTERNATIONAL 2017; 2017:6871081. [PMID: 29181400 PMCID: PMC5664255 DOI: 10.1155/2017/6871081] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/14/2017] [Indexed: 12/28/2022]
Abstract
Nitric oxide (NO) has a wide variety of physiological functions in the kidney. Besides the regulatory effects in intrarenal haemodynamics and glomerular microcirculation, in vivo studies reported the diuretic and natriuretic effects of NO. However, opposite results showing the stimulatory effect of NO on Na+ reabsorption in the proximal tubule led to an intense debate on its physiological roles. Animal studies have showed the biphasic effect of angiotensin II (Ang II) and the overall inhibitory effect of NO on the activity of proximal tubular Na+ transporters, the apical Na+/H+ exchanger isoform 3, basolateral Na+/K+ ATPase, and the Na+/HCO3− cotransporter. However, whether these effects could be reproduced in humans remained unclear. Notably, our recent functional analysis of isolated proximal tubules demonstrated that Ang II dose-dependently stimulated human proximal tubular Na+ transport through the NO/guanosine 3′,5′-cyclic monophosphate (cGMP) pathway, confirming the human-specific regulation of proximal tubular transport via NO and Ang II. Of particular importance for this newly identified pathway is its possibility of being a human-specific therapeutic target for hypertension. In this review, we focus on NO-mediated regulation of proximal tubular Na+ transport, with emphasis on the interaction with individual Na+ transporters and the crosstalk with Ang II signalling.
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27
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Hu MC, Bobulescu IA, Quiñones H, Gisler SM, Moe OW. Dopamine reduces cell surface Na +/H + exchanger-3 protein by decreasing NHE3 exocytosis and cell membrane recycling. Am J Physiol Renal Physiol 2017; 313:F1018-F1025. [PMID: 28768665 DOI: 10.1152/ajprenal.00251.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 07/14/2017] [Accepted: 07/24/2017] [Indexed: 01/06/2023] Open
Abstract
The intrarenal autocrine-paracrine dopamine (DA) system mediates a significant fraction of the natriuresis in response to a salt load. DA inhibits a number of Na+ transporters to effect sodium excretion, including the proximal tubule Na+/H+ exchanger-3 (NHE3). DA represent a single hormone that regulates NHE3 at multiple levels, including translation, degradation, endocytosis, and protein phosphorylation. Because cell surface NHE3 protein is determined by the balance between exocytotic insertion and endocytotic retrieval, we examined whether DA acutely affects the rate of NHE3 exocytosis in a cell culture model. DA inhibited NHE3 exocytosis at a dose-dependent manner with a half maximal around 10-6 M. The DA effect on NHE3 exocytosis was blocked by inhibition of protein kinase A and by brefeldin A, which inhibits endoplasmic reticulum-to-Golgi transport. NHE3 directly interacts with the ε-subunit of coatomer protein based on yeast-two-hybrid and coimmunoprecipitation. Because NHE3 has been shown to be recycled back to the cell membrane after endocytosis, we measured NHE3 recycling using a biochemical reinsertion assay and showed that reinsertion of NHE3 back to the membrane is also inhibited by DA. In conclusion, among the many mechanisms by which DA reduces apical membrane NHE3 and induces proximal tubule natriuresis, one additional mechanism is inhibition of exocytotic insertion and reinsertion of NHE3 in the apical cell surface.
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Affiliation(s)
- Ming Chang Hu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; .,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - I Alexandru Bobulescu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Henry Quiñones
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Serge M Gisler
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Orson W Moe
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas; and.,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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28
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Godinho AN, Costa GT, Oliveira NO, Cardi BA, Uchoa DEA, Silveira ER, Quintas LEM, Noël FG, Fonteles MC, Carvalho KM, Santos CF, Lessa LMA, do Nascimento NRF. Effects of cardiotonic steroids on isolated perfused kidney and NHE3 activity in renal proximal tubules. Biochim Biophys Acta Gen Subj 2017; 1861:1943-1950. [PMID: 28506883 DOI: 10.1016/j.bbagen.2017.05.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 05/07/2017] [Accepted: 05/11/2017] [Indexed: 12/11/2022]
Abstract
Cardiotonic steroids (CS) are known as modulators of sodium and water homeostasis. These compounds contribute to the excretion of sodium under overload conditions due to its natriuretic property related to the inhibition of the renal Na+/K+-ATPase (NKA) pump α1 isoform. NHE3, the main route for Na+ reabsorption in the proximal tubule, depends on the Na+ gradient generated by the NKA pump. In the present study we aimed to investigate the effects of marinobufagin (MBG) and telocinobufagin (TBG) on the renal function of isolated perfused rat kidney and on the inhibition of NKA activity. Furthermore, we investigated the mechanisms for the cardiotonic steroid-mediated natriuretic effect, by evaluating and comparing the effects of bufalin (BUF), ouabain (OUA), MBG and TBG on NHE3 activity in the renal proximal tubule in vivo. TBG significantly increased GFR, UF, natriuresis and kaliuresis in isolated perfused rat kidney, and inhibits the activity of NKA at a much higher rate than MBG. By stationary microperfusion technique, the perfusion with BUF, OUA, TBG or MBG promoted an inhibitory effect on NHE3 activity, whereas BUF was the most effective agent, and demonstrated a dose-dependent response, with maximal inhibition at 50nM. Furthermore, our data showed the role of NKA-Src kinase pathway in the inhibition of NHE3 by CS. Finally, a downstream step, MEK1/2-ERK1/2 was also investigated, and, similar to Src inhibition, the MEK1/2 inhibitor (U0126) suppressed the BUF effect. Our findings indicate the involvement of NKA-SRc-Kinase-Ras-Raf-ERK1/2 pathway in the downregulation of NHE3 by cardiotonic steroids in the renal proximal tubule, promoting a reduction of proximal sodium reabsorption and natriuresis.
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Affiliation(s)
- Alana N Godinho
- Biomedical Sciences Superior Institute, State University of Ceará, Fortaleza, Brazil
| | - Graciana T Costa
- Biomedical Sciences Superior Institute, State University of Ceará, Fortaleza, Brazil
| | - Nádia O Oliveira
- Biomedical Sciences Superior Institute, State University of Ceará, Fortaleza, Brazil
| | - Bruno A Cardi
- Biomedical Sciences Superior Institute, State University of Ceará, Fortaleza, Brazil
| | | | | | - Luis Eduardo M Quintas
- Biomedical Sciences Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - François G Noël
- Biomedical Sciences Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Manassés C Fonteles
- Biomedical Sciences Superior Institute, State University of Ceará, Fortaleza, Brazil
| | | | - Cláudia F Santos
- Biomedical Sciences Superior Institute, State University of Ceará, Fortaleza, Brazil
| | - Lucília M A Lessa
- Biomedical Sciences Superior Institute, State University of Ceará, Fortaleza, Brazil
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29
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Eiam-Ong S, Chaipipat M, Manotham K, Eiam-Ong S. Rapid Action of Aldosterone on Protein Levels of Sodium-Hydrogen Exchangers and Protein Kinase C Beta Isoforms in Rat Kidney. Int J Endocrinol 2017; 2017:2975853. [PMID: 29201052 PMCID: PMC5671724 DOI: 10.1155/2017/2975853] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 06/23/2017] [Accepted: 08/06/2017] [Indexed: 12/22/2022] Open
Abstract
Previous in vitro studies demonstrated that aldosterone rapidly activates sodium-hydrogen exchangers 1 and 3 (NHE 1 and 3). In vitro investigations revealed that protein kinase C (PKC) regulates NHE properties. We previously demonstrated that aldosterone rapidly enhances PKCα protein abundance in the rat kidney. There are no reports of renal PKCβ (I and II) protein levels related to the regulation by aldosterone. There are also no in vivo data regarding the rapid effects of aldosterone on renal protein levels of NHE (1 and 3) and PKCβ (I and II), simultaneously. In the current study, rats received normal saline solution or aldosterone (150 μg/kg BW, i.p.). After 30 minutes, abundance and immunoreactivity of these proteins were determined by Western blot analysis and immunohistochemistry, respectively. Aldosterone increased NHE1 and NHE3 protein abundance to 152% and 134%, respectively (P < 0.05). PKCβI protein level was enhanced by 30%, whereas PKCβII declined slightly. Aldosterone increased NHE protein expression mostly in the medulla. PKCβI immunostaining intensity was increased in the glomeruli, renal vasculature, and thin limb of the loop of Henle, while PKCβII was reduced. This is the first in vivo study to simultaneously demonstrate that aldosterone rapidly elevates PKCβI and NHE (1 and 3) protein abundance in the rat kidney. Aldosterone-induced NHE (1 and 3) protein levels may be related to PKCβI activation.
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Affiliation(s)
- Somchit Eiam-Ong
- Department of Physiology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
| | - Mookda Chaipipat
- Department of Pathology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
| | | | - Somchai Eiam-Ong
- Department of Medicine (Division of Nephrology), Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
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30
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Layton AT, Laghmani K, Vallon V, Edwards A. Solute transport and oxygen consumption along the nephrons: effects of Na+ transport inhibitors. Am J Physiol Renal Physiol 2016; 311:F1217-F1229. [PMID: 27707706 DOI: 10.1152/ajprenal.00294.2016] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 09/28/2016] [Indexed: 01/11/2023] Open
Abstract
Sodium and its associated anions are the major determinant of extracellular fluid volume, and the reabsorption of Na+ by the kidney plays a crucial role in long-term blood pressure control. The goal of this study was to investigate the extent to which inhibitors of transepithelial Na+ transport (TNa) along the nephron alter urinary solute excretion and TNa efficiency and how those effects may vary along different nephron segments. To accomplish that goal, we used the multinephron model developed in the companion study (28). That model represents detailed transcellular and paracellular transport processes along the nephrons of a rat kidney. We simulated the inhibition of the Na+/H+ exchanger (NHE3), the bumetanide-sensitive Na+-K+-2Cl- transporter (NKCC2), the Na+-Cl- cotransporter (NCC), and the amiloride-sensitive Na+ channel (ENaC). Under baseline conditions, NHE3, NKCC2, NCC, and ENaC reabsorb 36, 22, 4, and 7%, respectively, of filtered Na+ The model predicted that inhibition of NHE3 substantially reduced proximal tubule TNa and oxygen consumption (QO2 ). Whole-kidney TNa efficiency, as reflected by the number of moles of Na+ reabsorbed per moles of O2 consumed (denoted by the ratio TNa/QO2 ), decreased by ∼20% with 80% inhibition of NHE3. NKCC2 inhibition simulations predicted a substantial reduction in thick ascending limb TNa and QO2 ; however, the effect on whole-kidney TNa/QO2 was minor. Tubular K+ transport was also substantially impaired, resulting in elevated urinary K+ excretion. The most notable effect of NCC inhibition was to increase the excretion of Na+, K+, and Cl-; its impact on whole-kidney TNa and its efficiency was minor. Inhibition of ENaC was predicted to have opposite effects on the excretion of Na+ (increased) and K+ (decreased) and to have only a minor impact on whole-kidney TNa and TNa/QO2 Overall, model predictions agree well with measured changes in Na+ and K+ excretion in response to diuretics and Na+ transporter mutations.
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Affiliation(s)
- Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina;
| | - Kamel Laghmani
- Sorbonne Universités, UPMC Univ Paris 06, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and
| | - Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego, La Jolla, California, and San Diego Veterans Affairs Healthcare System, San Diego, California
| | - Aurélie Edwards
- Sorbonne Universités, UPMC Univ Paris 06, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and
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31
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Kutina AV, Marina AS, Natochin YV. Effects of exenatide on glycemia and renal water and ion excretion differ in frogs and rats. J EVOL BIOCHEM PHYS+ 2016. [DOI: 10.1134/s0022093016030054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Morla L, Edwards A, Crambert G. New insights into sodium transport regulation in the distal nephron: Role of G-protein coupled receptors. World J Biol Chem 2016; 7:44-63. [PMID: 26981195 PMCID: PMC4768124 DOI: 10.4331/wjbc.v7.i1.44] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 10/02/2015] [Accepted: 11/25/2015] [Indexed: 02/05/2023] Open
Abstract
The renal handling of Na+ balance is a major determinant of the blood pressure (BP) level. The inability of the kidney to excrete the daily load of Na+ represents the primary cause of chronic hypertension. Among the different segments that constitute the nephron, those present in the distal part (i.e., the cortical thick ascending limb, the distal convoluted tubule, the connecting and collecting tubules) play a central role in the fine-tuning of renal Na+ excretion and are the target of many different regulatory processes that modulate Na+ retention more or less efficiently. G-protein coupled receptors (GPCRs) are crucially involved in this regulation and could represent efficient pharmacological targets to control BP levels. In this review, we describe both classical and novel GPCR-dependent regulatory systems that have been shown to modulate renal Na+ absorption in the distal nephron. In addition to the multiplicity of the GPCR that regulate Na+ excretion, this review also highlights the complexity of these different pathways, and the connections between them.
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33
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Hatanaka M, Kaimori JY, Yamamoto S, Matsui I, Hamano T, Takabatake Y, Ecelbarger CM, Takahara S, Isaka Y, Rakugi H. Azilsartan Improves Salt Sensitivity by Modulating the Proximal Tubular Na+-H+ Exchanger-3 in Mice. PLoS One 2016; 11:e0147786. [PMID: 26807585 PMCID: PMC4725961 DOI: 10.1371/journal.pone.0147786] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 01/10/2016] [Indexed: 12/27/2022] Open
Abstract
A potent angiotensin II type-1 receptor blocker, azilsartan, has been reported to reduce blood pressure more effectively than candesartan. Interestingly, azilsartan can also restore the circadian rhythm of blood pressure. We hypothesized that azilsartan could also improve salt sensitivity; thus, we examined the effect of azilsartan on sodium handling in renal tubules. Subtotal nephrectomized C57BL/6 mice received azilsartan (1.0 mg/kg/day), candesartan (0.3 mg/kg/day), or vehicle via the oral route in conjunction with a normal- (0.3%) or high-salt (8.0%) diet. Two weeks later, the azilsartan group showed significantly lower blood pressure during the light period than the candesartan and vehicle groups (azilsartan: 103.1 ± 1.0; candesartan: 111.7 ± 2.7; vehicle: 125.5 ± 2.5 mmHg; P < 0.05; azilsartan or candesartan vs. vehicle). The azilsartan group also showed higher urinary fractional excretion of sodium during the dark period than the candesartan and vehicle groups (azilsartan: 21.37 ± 3.69%; candesartan: 14.17 ± 1.42%; vehicle: 13.85 ± 5.30%; P < 0.05 azilsartan vs. candesartan or vehicle). A pressure—natriuresis curve demonstrated that azilsartan treatment restored salt sensitivity. Immunofluorescence and western blotting showed lower levels of Na+-H+ exchanger-3 (NHE3) protein (the major sodium transporter in renal proximal tubules) in the azilsartan group, but not in the candesartan or vehicle groups. However, azilsartan did not affect NHE3 transcription levels. Interestingly, we did not observe increased expression of downstream sodium transporters, which would have compensated for the increased flow of sodium and water due to non-absorption by NHE3. We also confirmed the mechanism stated above using cultured opossum kidney proximal tubular cells. Results revealed that a proteasomal inhibitor (but not a lysosomal inhibitor) blocked the azilsartan-induced decrease in NHE3 protein expression, suggesting that azilsartan increases NHE3 ubiquitination. In conclusion, azilsartan (but not candesartan) improved salt sensitivity possibly by decreasing NHE3 expression via ubiquitin—proteasomal degradation.
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Affiliation(s)
- Masaki Hatanaka
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Jun-Ya Kaimori
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
- Department of Advanced Technology for Transplantation, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
- * E-mail:
| | - Satoko Yamamoto
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Isao Matsui
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Takayuki Hamano
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
- Department of Comprehensive Kidney Disease Research, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Yoshitsugu Takabatake
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Carolyn M. Ecelbarger
- Department of Medicine, Division of Endocrinology and Metabolism, Georgetown University, Washington D.C., United States of America
| | - Shiro Takahara
- Department of Advanced Technology for Transplantation, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Yoshitaka Isaka
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Hiromi Rakugi
- Department of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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34
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Sodium-Proton (Na+/H+) Antiporters: Properties and Roles in Health and Disease. Met Ions Life Sci 2016; 16:391-458. [DOI: 10.1007/978-3-319-21756-7_12] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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35
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Abstract
PURPOSE OF REVIEW NEDD4-2 is an ubiquitin-protein ligase that was originally identified as an interactor of the epithelial Na+ channel (ENaC); this interaction is defective in Liddle's syndrome, causing elevated ENaC activity and salt-sensitive hypertension. In this review we aim to highlight progress achieved in recent years demonstrating that NEDD4-2 is involved in the control of Na+ transporters that are different from ENaC, but which also play a role in salt-sensitive hypertension. RECENT FINDINGS It has been shown that NEDD4-2 interacts with ubiquitylates and negatively regulates the thiazide-sensitive NCC (Na+,Cl- -cotransporter), both in vitro and in vivo in inducible, nephron-specific Nedd4-2 knockout mice. Moreover, evidence has been provided that NEDD4-2 is also involved in the regulation of human NHE3 (Na+,H+-exchanger 3) and NKCC2 (Na+,K+,2Cl- -cotransporter 2). SUMMARY The emerging role of NEDD4-2 in the regulation of different Na+ transporters along the nephron and the identification of human polymorphisms in the NEDD4-2 gene (Nedd4L) related to salt-sensitive hypertension makes this ubiquitin-protein ligase an interesting target for the development of antihypertensive drugs.
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Handlogten ME, Osis G, Lee HW, Romero MF, Verlander JW, Weiner ID. NBCe1 expression is required for normal renal ammonia metabolism. Am J Physiol Renal Physiol 2015; 309:F658-66. [PMID: 26224717 PMCID: PMC4593816 DOI: 10.1152/ajprenal.00219.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 07/26/2015] [Indexed: 11/22/2022] Open
Abstract
The mechanisms regulating proximal tubule ammonia metabolism are incompletely understood. The present study addressed the role of the proximal tubule basolateral electrogenic Na(+)-coupled bicarbonate cotransporter (NBCe1; Slc4a4) in renal ammonia metabolism. We used mice with heterozygous and homozygous NBCe1 gene deletion and compared these mice with their wild-type littermates. Because homozygous NBCe1 gene deletion causes 100% mortality before day 25, we studied mice at day 8 (±1 day). Both heterozygous and homozygous gene deletion caused a gene dose-related decrease in serum bicarbonate. The ability to lower urinary pH was intact, and even accentuated, with NBCe1 deletion. However, in contrast to the well-known effect of metabolic acidosis to increase urinary ammonia excretion, NBCe1 deletion caused a gene dose-related decrease in ammonia excretion. There was no identifiable change in proximal tubule structure by light microscopy. Examination of proteins involved in renal ammonia metabolism showed decreased expression of phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase, key enzymes in proximal tubule ammonia generation, and increased expression of glutamine synthetase, which recycles intrarenal ammonia and regenerates glutamine. Expression of key proteins involved in ammonia transport outside of the proximal tubule (rhesus B glycoprotein and rhesus C glycoprotein) was not significantly changed by NBCe1 deletion. We conclude from these findings that NBCe1 expression is necessary for normal proximal tubule ammonia metabolism.
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Affiliation(s)
- Mary E Handlogten
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Gunars Osis
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering and Nephrology and Hypertension, Mayo Clinic College Of Medicine, Rochester, Minnesota; and
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; Nephrology and Hypertension Section, Gainesville Veterans Administration Medical Center, Gainesville, Florida
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Abstract
The H(+) concentration in human blood is kept within very narrow limits, ~40 nmol/L, despite the fact that dietary metabolism generates acid and base loads that are added to the systemic circulation throughout the life of mammals. One of the primary functions of the kidney is to maintain the constancy of systemic acid-base chemistry. The kidney has evolved the capacity to regulate blood acidity by performing three key functions: (i) reabsorb HCO3(-) that is filtered through the glomeruli to prevent its excretion in the urine; (ii) generate a sufficient quantity of new HCO3(-) to compensate for the loss of HCO3(-) resulting from dietary metabolic H(+) loads and loss of HCO3(-) in the urea cycle; and (iii) excrete HCO3(-) (or metabolizable organic anions) following a systemic base load. The ability of the kidney to perform these functions requires that various cell types throughout the nephron respond to changes in acid-base chemistry by modulating specific ion transport and/or metabolic processes in a coordinated fashion such that the urine and renal vein chemistry is altered appropriately. The purpose of the article is to provide the interested reader with a broad review of a field that began historically ~60 years ago with whole animal studies, and has evolved to where we are currently addressing questions related to kidney acid-base regulation at the single protein structure/function level.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA
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Parathyroid hormone inhibition of Na+/H+ exchanger 3 transcription: Intracellular signaling pathways and transcription factor expression. Biochem Biophys Res Commun 2015; 461:582-8. [DOI: 10.1016/j.bbrc.2015.04.049] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 04/07/2015] [Indexed: 11/18/2022]
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Pontes RB, Crajoinas RO, Nishi EE, Oliveira-Sales EB, Girardi AC, Campos RR, Bergamaschi CT. Renal nerve stimulation leads to the activation of the Na+/H+ exchanger isoform 3 via angiotensin II type I receptor. Am J Physiol Renal Physiol 2015; 308:F848-56. [PMID: 25656367 DOI: 10.1152/ajprenal.00515.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 01/29/2015] [Indexed: 01/13/2023] Open
Abstract
Renal nerve stimulation at a low frequency (below 2 Hz) causes water and sodium reabsorption via α1-adrenoreceptor tubular activation, a process independent of changes in systemic blood pressure, renal blood flow, or glomerular filtration rate. However, the underlying mechanism of the reabsorption of sodium is not fully understood. Since the sympathetic nervous system and intrarenal ANG II appear to act synergistically to mediate the process of sodium reabsorption, we hypothesized that low-frequency acute electrical stimulation of the renal nerve (ESRN) activates NHE3-mediated sodium reabsorption via ANG II AT1 receptor activation in Wistar rats. We found that ESRN significantly increased urinary angiotensinogen excretion and renal cortical ANG II content, but not the circulating angiotensinogen levels, and also decreased urinary flow and pH and sodium excretion via mechanisms independent of alterations in creatinine clearance. Urinary cAMP excretion was reduced, as was renal cortical PKA activity. ESRN significantly increased NHE3 activity and abundance in the apical microvillar domain of the proximal tubule, decreased the ratio of phosphorylated NHE3 at serine 552/total NHE3, but did not alter total cortical NHE3 abundance. All responses mediated by ESRN were completely abolished by a losartan-mediated AT1 receptor blockade. Taken together, our results demonstrate that higher NHE3-mediated proximal tubular sodium reabsorption induced by ESRN occurs via intrarenal renin angiotensin system activation and triggering of the AT1 receptor/inhibitory G-protein signaling pathway, which leads to inhibition of cAMP formation and reduction of PKA activity.
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Affiliation(s)
- Roberto B Pontes
- Departamento de Fisiologia, Disciplina de Fisiologia Cardiovascular, Universidade Federal de São Paulo, São Paulo, Brazil; and
| | - Renato O Crajoinas
- Laboratory of Genetics and Molecular Cardiology, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Erika E Nishi
- Departamento de Fisiologia, Disciplina de Fisiologia Cardiovascular, Universidade Federal de São Paulo, São Paulo, Brazil; and
| | - Elizabeth B Oliveira-Sales
- Departamento de Fisiologia, Disciplina de Fisiologia Cardiovascular, Universidade Federal de São Paulo, São Paulo, Brazil; and
| | - Adriana C Girardi
- Laboratory of Genetics and Molecular Cardiology, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Ruy R Campos
- Departamento de Fisiologia, Disciplina de Fisiologia Cardiovascular, Universidade Federal de São Paulo, São Paulo, Brazil; and
| | - Cássia T Bergamaschi
- Departamento de Fisiologia, Disciplina de Fisiologia Cardiovascular, Universidade Federal de São Paulo, São Paulo, Brazil; and
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Ruan R, Guo AH, Hao YJ, Zheng JS, Wang D. De novo assembly and characterization of narrow-ridged finless porpoise renal transcriptome and identification of candidate genes involved in osmoregulation. Int J Mol Sci 2015; 16:2220-38. [PMID: 25608655 PMCID: PMC4307359 DOI: 10.3390/ijms16012220] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 12/08/2014] [Accepted: 01/13/2015] [Indexed: 02/04/2023] Open
Abstract
During the evolutionary transition from land to water, cetaceans have undergone numerous critical challenges, with osmoregulation being the major one. Two subspecies of the narrow-ridged finless porpoise (Neophocaena asiaeorientalis), the freshwater Yangtze finless porpoise (N. a. asiaeorientalis, NAA) and the marine East Asian finless porpoise (N. a. sunameri, NAS), provide excellent subjects to understand the genetic basis of osmoregulatory divergence between freshwater and marine mammals. The kidney plays an important and well-established role in osmoregulation in marine mammals and thus, herein, we utilized RNA-seq to characterize the renal transcriptome and preliminarily analyze the divergence between the NAA and the NAS. Approximately 48.98 million clean reads from NAS and 49.40 million clean reads from NAA were obtained by RNA-Seq. And 73,449 (NAS) and 68,073 (NAA) unigenes were assembled. Among these annotations, 22,231 (NAS) and 21,849 (NAA) unigenes were annotated against the NCBI nr protein database. The ion channel complex GO term and four pathways were detected as relevant to osmoregulation by GO and KEGG pathway classification of these annotated unigenes. Although the endangered status of the study species prevented analysis of biological replicates, we identified nine differentially expressed genes (DEGs) that may be vital in the osmoregulation of the narrow-ridged finless porpoise and worthwhile for future studies. Of these DEGs, the differential expression and distribution of the aquaporin-2 (AQP2) in the collecting duct were verified using immunohistochemical experiments. Together, this work is the first report of renal transcriptome sequencing in cetaceans, and it will provide a valuable resource for future molecular genetics studies on cetacean osmoregulation.
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Affiliation(s)
- Rui Ruan
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology of Chinese Academy of Sciences, Wuhan 430072, China.
| | - Ai-Huan Guo
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology of Chinese Academy of Sciences, Wuhan 430072, China.
| | - Yu-Jiang Hao
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology of Chinese Academy of Sciences, Wuhan 430072, China.
| | - Jin-Song Zheng
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology of Chinese Academy of Sciences, Wuhan 430072, China.
| | - Ding Wang
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology of Chinese Academy of Sciences, Wuhan 430072, China.
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Li H, Klett DE, Littleton R, Elder JS, Sammon JD. Role of insulin resistance in uric acid nephrolithiasis. World J Nephrol 2014; 3:237-242. [PMID: 25374817 PMCID: PMC4220356 DOI: 10.5527/wjn.v3.i4.237] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 07/21/2014] [Accepted: 09/10/2014] [Indexed: 02/05/2023] Open
Abstract
Metabolic syndrome has been implicated in the pathogenesis of uric acid stones. Although not completely understood, its role is supported by many studies demonstrating increased prevalence of uric acid stones in patients with metabolic syndrome and in particular insulin resistance, a major component of metabolic syndrome. This review presents epidemiologic studies demonstrating the association between metabolic syndrome and nephrolithiasis in general as well as the relationship between insulin resistance and uric acid stone formation, in particular. We also review studies that explore the pathophysiologic relationship between insulin resistance and uric acid nephrolithiasis.
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42
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Glover M, O'Shaughnessy KM. Molecular insights from dysregulation of the thiazide-sensitive WNK/SPAK/NCC pathway in the kidney: Gordon syndrome and thiazide-induced hyponatraemia. Clin Exp Pharmacol Physiol 2014; 40:876-84. [PMID: 23683032 DOI: 10.1111/1440-1681.12115] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 05/10/2013] [Accepted: 05/14/2013] [Indexed: 12/11/2022]
Abstract
Human blood pressure is dependent on balancing dietary salt intake with its excretion by the kidney. Mendelian syndromes of altered blood pressure demonstrate the importance of the distal nephron in this process and of the thiazide-sensitive pathway in particular. Gordon syndrome (GS), the phenotypic inverse of the salt-wasting Gitelman syndrome, is a condition of hyperkalaemic hypertension that is reversed by low-dose thiazide diuretics or a low-salt diet. Variants within at least four genes [i.e. with-no-lysine(K) kinase 1 (WNK1), WNK4, kelch-like family member 3 (KLHL3) and cullin 3 (CUL3)] can cause the phenotype of GS. Details are still emerging for some of these genes, but it is likely that they all cause a gain-of-function in the thiazide-sensitive Na(+) -Cl(-) cotransporter (NCC) and hence salt retention. Herein, we discuss the key role of STE20/sporulation-specific protein 1 (SPS1)-related proline/alanine-rich kinase (SPAK), which functions as an intermediary between the WNKs and NCC and for which a loss-of-function mutation produces a Gitelman-type phenotype in a mouse model. In addition to Mendelian blood pressure syndromes, the study of patients who develop thiazide-induced-hyponatraemia (TIH) may give further molecular insights into the role of the thiazide-sensitive pathway for salt reabsorption. In the present paper we discuss the key features of TIH, including its high degree of reproducibility on rechallenge, possible genetic predisposition and mechanisms involving excessive saliuresis and water retention. Together, studies of Gordon syndrome and TIH may increase our understanding of the molecular regulation of sodium trafficking via the thiazide-sensitive pathway and have important implications for hypertensive patients, both in the identification of new antihypertensive drug targets and avoidance of hyponatraemic side-effects.
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Affiliation(s)
- Mark Glover
- Division of Therapeutics and Molecular Medicine, University of Nottingham, Nottingham, UK
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43
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De S, Kuwahara S, Saito A. The endocytic receptor megalin and its associated proteins in proximal tubule epithelial cells. MEMBRANES 2014; 4:333-55. [PMID: 25019425 PMCID: PMC4194038 DOI: 10.3390/membranes4030333] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 06/23/2014] [Accepted: 07/01/2014] [Indexed: 02/08/2023]
Abstract
Receptor-mediated endocytosis in renal proximal tubule epithelial cells (PTECs) is important for the reabsorption and metabolization of proteins and other substances, including carrier-bound vitamins and trace elements, in glomerular filtrates. Impairment of this endocytic process results in the loss of such substances and development of proteinuria, which is an important clinical indicator of kidney diseases and is also a risk marker for cardiovascular disease. Megalin, a member of the low-density lipoprotein receptor gene family, is a multiligand receptor expressed in the apical membrane of PTECs and plays a central role in the endocytic process. Megalin interacts with various intracellular adaptor proteins for intracellular trafficking and cooperatively functions with other membrane molecules, including the cubilin-amnionless complex. Evidence suggests that megalin and the cubilin-amnionless complex are involved in the uptake of toxic substances into PTECs, which leads to the development of kidney disease. Studies of megalin and its associated molecules will be useful for future development of novel strategies for the diagnosis and treatment of kidney diseases.
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Affiliation(s)
- Shankhajit De
- Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan.
| | - Shoji Kuwahara
- Department of Applied Molecular Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan.
| | - Akihiko Saito
- Department of Applied Molecular Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan.
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44
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No YR, He P, Yoo BK, Yun CC. Unique regulation of human Na+/H+ exchanger 3 (NHE3) by Nedd4-2 ligase that differs from non-primate NHE3s. J Biol Chem 2014; 289:18360-72. [PMID: 24831004 DOI: 10.1074/jbc.m113.541706] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Na(+)/H(+) exchanger NHE3 expressed in the intestine and kidney plays a major role in NaCl and HCO3 (-) absorption that is closely linked to fluid absorption and blood pressure regulation. The Nedd4 family of E3 ubiquitin ligases interacts with a number of transporters and channels via PY motifs. A comparison of NHE3 sequences revealed the presence of PY motifs in NHE3s from human and several non-human primates but not in non-primate NHE3s. In this study we evaluated the differences between human and non-primate NHE3s in ubiquitination and interaction with Nedd4-2. We found that Nedd4-2 ubiquitinated human NHE3 (hNHE3) and altered its expression and activity. Surprisingly, rat NHE3 co-immunoprecipitated Nedd4-2, but its expression and activity were not altered by silencing of Nedd4-2. Ubiquitination by Nedd4-2 rendered hNHE3 to undergo internalization at a significantly greater rate than non-primate NHE3s without altering protein stability. Insertion of a PY motif in rabbit NHE3 recapitulated the interaction with Nedd4-2 and enhanced internalization. Thus, we propose a new model where disruption of Nedd4-2 interaction elevates hNHE3 expression and activity.
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Affiliation(s)
- Yi Ran No
- From the Division of Digestive Diseases, Department of Medicine and
| | - Peijian He
- From the Division of Digestive Diseases, Department of Medicine and
| | - Byong Kwon Yoo
- From the Division of Digestive Diseases, Department of Medicine and
| | - C Chris Yun
- From the Division of Digestive Diseases, Department of Medicine and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322
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45
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Kim S, Lee J, Heo NJ, Lee JW, Han JS. Alkali therapy attenuates the progression of kidney injury via Na/H exchanger inhibition in 5/6 nephrectomized rats. J Korean Med Sci 2014; 29:691-8. [PMID: 24851027 PMCID: PMC4024946 DOI: 10.3346/jkms.2014.29.5.691] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 03/21/2014] [Indexed: 11/20/2022] Open
Abstract
Metabolic acidosis is a cause of renal disease progression, and alkali therapy ameliorates its progression. However, there are few reports on the role of renal acid-base transporters during alkali therapy. We evaluated the effect of sodium bicarbonate therapy and the role of acid-base transporters on renal disease progression in rats with a remnant kidney. Sprague-Dawley rats consumed dietary sodium bicarbonate (NaHCO3) or sodium chloride (NaCl) with 20% casein after a 5/6 nephrectomy. After being provided with a casein diet, the NaHCO3-treated group had higher levels of serum bicarbonate than the control group. At week 4, the glomerular filtration rate in the NaHCO3 group was higher than that in the NaCl group, and the difference became prominent at week 10. The glomerulosclerosis and tubulointerstitial damage indices in the NaHCO3 group were less severe compared with controls at week 4 and 10. The expression of the Na/H exchanger (NHE) was decreased, and apical reactivity was decreased in the NaHCO3 group, compared with the NaCl group. Endothelin-1 levels in the kidney were also decreased in the NaHCO3 group. Dietary sodium bicarbonate has the effects of ameliorating renal disease progression, which may be related to the altered expression of NHE in the remaining kidney.
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Affiliation(s)
- Sejoong Kim
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Jeonghwan Lee
- Department of Internal Medicine, Hallym University Hangang Sacred Heart Hospital, Seoul, Korea
| | - Nam Ju Heo
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
- Department of Internal Medicine, Healthcare System Gangnam Center, Seoul National University Hospital, Seoul, Korea
| | - Jae Wook Lee
- Epithelial Systems Biology Laboratory, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jin Suk Han
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
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Healy V, Thompson C, Johns EJ. The adrenergic regulation of proximal tubular Na⁺/H⁺ exchanger 3 in the rat. Acta Physiol (Oxf) 2014; 210:678-89. [PMID: 24118769 DOI: 10.1111/apha.12181] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 08/29/2013] [Accepted: 10/06/2013] [Indexed: 11/27/2022]
Abstract
AIM This study in the anaesthetized rat investigated how renal sympathetic nerve activity and catecholamine release influenced NHE3 abundance and activity in proximal tubular brush border membranes using both in vivo and in vitro approaches. METHODS Renal excretory function and brush border NHE3 abundance and activity were measured in rat kidneys which underwent renal denervation, renal nerve electrical stimulation and renal infusion of phenylephrine and the NHE3 inhibitor S1661. NHE3 activity and cell surface abundance were also measured in primary cultures of proximal tubular cells treated with noradrenaline and prazosin. RESULTS Acute renal denervation caused a natriuresis and diuresis, which occurred with a reduction in NHE3 abundance and activity in the brush border membranes. By contrast, low-level electrical stimulation of the renal innervation causing an antinatriuresis and antidiuresis increased NHE3 activity in the brush border membranes. Intrarenal infusion of phenylephrine caused an antinatriuresis and antidiuresis, while blockade of NHE3 activity, using local infusion of the blocker S1661, caused a natriuresis and diuresis. Exposure of primary cultures of proximal tubular cells to noradrenaline increased brush border NHE3 abundance and activity which was blocked by prior exposure to prazosin, indicating it as an α1 -adrenoceptor-mediated mechanism. CONCLUSION Together, these findings demonstrate that the renal sympathetic nerves not only have a direct action to modulate tubular sodium reabsorption via stimulation of the NHE transporter, but also have an indirect effect, whereby NHE3 abundance is increased within the brush border membrane, thereby increasing the capacity for fluid reabsorption.
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Affiliation(s)
- V. Healy
- Department of Physiology; University College Cork; Cork Ireland
| | - C. Thompson
- Department of Physiology; University College Cork; Cork Ireland
| | - E. J. Johns
- Department of Physiology; University College Cork; Cork Ireland
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Abstract
Tightly coupled exchange of Na(+) for H(+) occurs across the surface membrane of virtually all living cells. For years, the underlying molecular entity was unknown and the full physiological significance of the exchange process was not appreciated, but much knowledge has been gained in the last two decades. We now realize that, unlike most of the other transporters that specialize in supporting one specific function, Na(+)/H(+) exchangers (NHE) participate in a remarkable assortment of physiological processes, ranging from pH homeostasis and epithelial salt transport, to systemic and cellular volume regulation. In parallel, we have learned a great deal about the biochemistry and molecular biology of Na(+)/H(+) exchange. Indeed, it has now become apparent that exchange is mediated not by one, but by a diverse family of related yet distinct carriers (antiporters) sometimes present in different cell types and located in various intracellular compartments. Each one of these has unique structural features that dictate its functional role and mode of regulation. The biological relevance of Na(+)/H(+) exchange is emphasized by its evolutionary conservation; analogous exchangers are present from bacteria to man. Because of its wide distribution and versatile function, Na(+)/H(+) exchange has attracted an enormous amount of interest and therefore generated a vast literature. The vastness and complexity of the field has been compounded by the multiplicity of NHE isoforms. For reasons of space and in the spirit of this series, this overview is restricted to the family of mammalian NHEs.
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Affiliation(s)
- John Orlowski
- Department of Physiology, McGill University, Montreal, Canada
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48
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Xie JX, Li X, Xie Z. Regulation of renal function and structure by the signaling Na/K-ATPase. IUBMB Life 2013; 65:991-8. [PMID: 24323927 PMCID: PMC5375025 DOI: 10.1002/iub.1229] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 11/08/2013] [Indexed: 12/23/2022]
Abstract
The Na/K-ATPase as an essential ion pump was discovered more than 50 years ago (Skou (1989) Biochim. Biophys. Acta 1000, 439-446; Feraille and Doucet (2001) Physiol. Rev. 81, 345-418). The signaling function of Na/K-ATPase has been gradually appreciated over the last 20 years, first from the studies of regulatory effects of ouabain on cardiac cell growth. Several reviews on this topic have been written during the last few years (Schoner and Scheiner-Bobis (2007) Am. J. Physiol. Cell. Physiol. 293, C509-C536; Xie and Cai (2003) Mol. Interv. 3, 157 - 168; Bagrov et al. (2009) Pharmacol. Rev. 61, 9-38; Tian and Xie (2008) Physiology 23, 205-211; Fontana et al. (2013) FEBS J. 280, 5450-5455; Blanco and Wallace (2013) Am. J. Physiol. Renal Physiol. 305, F797-F812). This article will focus on the molecular mechanism of Na/K-ATPase-mediated signal transduction and its potential regulatory role in renal physiology and diseases.
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Affiliation(s)
- Jeffrey X Xie
- Department of Physiology and Pharmacology, University of Toledo College of Medicine, Toledo, OH, USA
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Christensen EI, Wagner CA, Kaissling B. Uriniferous tubule: structural and functional organization. Compr Physiol 2013; 2:805-61. [PMID: 23961562 DOI: 10.1002/cphy.c100073] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The uriniferous tubule is divided into the proximal tubule, the intermediate (thin) tubule, the distal tubule and the collecting duct. The present chapter is based on the chapters by Maunsbach and Christensen on the proximal tubule, and by Kaissling and Kriz on the distal tubule and collecting duct in the 1992 edition of the Handbook of Physiology, Renal Physiology. It describes the fine structure (light and electron microscopy) of the entire mammalian uriniferous tubule, mainly in rats, mice, and rabbits. The structural data are complemented by recent data on the location of the major transport- and transport-regulating proteins, revealed by morphological means(immunohistochemistry, immunofluorescence, and/or mRNA in situ hybridization). The structural differences along the uriniferous tubule strictly coincide with the distribution of the major luminal and basolateral transport proteins and receptors and both together provide the basis for the subdivision of the uriniferous tubule into functional subunits. Data on structural adaptation to defined functional changes in vivo and to genetical alterations of specified proteins involved in transepithelial transport importantly deepen our comprehension of the correlation of structure and function in the kidney, of the role of each segment or cell type in the overall renal function,and our understanding of renal pathophysiology.
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50
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Abstract
Chloride transport along the nephron is one of the key actions of the kidney that regulates extracellular volume and blood pressure. To maintain steady state, the kidney needs to reabsorb the vast majority of the filtered load of chloride. This is accomplished by the integrated function of sequential chloride transport activities along the nephron. The detailed mechanisms of transport in each segment generate unique patterns of interactions between chloride and numerous other individual components that are transported by the kidney. Consequently, chloride transport is inextricably intertwined with that of sodium, potassium, protons, calcium, and water. These interactions not only allow for exquisitely precise regulation but also determine the particular patterns in which the system can fail in disease states.
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Affiliation(s)
- John C Edwards
- UNC Kidney Center and the Departments of Medicine and Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
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