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Sumida TS, Cheru NT, Hafler DA. The regulation and differentiation of regulatory T cells and their dysfunction in autoimmune diseases. Nat Rev Immunol 2024:10.1038/s41577-024-00994-x. [PMID: 38374298 DOI: 10.1038/s41577-024-00994-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2024] [Indexed: 02/21/2024]
Abstract
The discovery of FOXP3+ regulatory T (Treg) cells as a distinct cell lineage with a central role in regulating immune responses provided a deeper understanding of self-tolerance. The transcription factor FOXP3 serves a key role in Treg cell lineage determination and maintenance, but is not sufficient to enable the full potential of Treg cell suppression, indicating that other factors orchestrate the fine-tuning of Treg cell function. Moreover, FOXP3-independent mechanisms have recently been shown to contribute to Treg cell dysfunction. FOXP3 mutations in humans cause lethal fulminant systemic autoinflammation (IPEX syndrome). However, it remains unclear to what degree Treg cell dysfunction is contributing to the pathophysiology of common autoimmune diseases. In this Review, we discuss the origins of Treg cells in the periphery and the multilayered mechanisms by which Treg cells are induced, as well as the FOXP3-dependent and FOXP3-independent cellular programmes that maintain the suppressive function of Treg cells in humans and mice. Further, we examine evidence for Treg cell dysfunction in the context of common autoimmune diseases such as multiple sclerosis, inflammatory bowel disease, systemic lupus erythematosus and rheumatoid arthritis.
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Affiliation(s)
- Tomokazu S Sumida
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA.
| | - Nardos T Cheru
- Department of Immunobiology, Yale School of Medicine, New Haven, CT, USA
| | - David A Hafler
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA.
- Department of Immunobiology, Yale School of Medicine, New Haven, CT, USA.
- Broad Institute of MIT and Harvard, Cambridge, MA, USA.
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2
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Kim GH. Primary Role of the Kidney in Pathogenesis of Hypertension. Life (Basel) 2024; 14:119. [PMID: 38255734 PMCID: PMC10817438 DOI: 10.3390/life14010119] [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: 12/09/2023] [Revised: 01/03/2024] [Accepted: 01/12/2024] [Indexed: 01/24/2024] Open
Abstract
Previous transplantation studies and the concept of 'nephron underdosing' support the idea that the kidney plays a crucial role in the development of essential hypertension. This suggests that there are genetic factors in the kidney that can either elevate or decrease blood pressure. The kidney normally maintains arterial pressure within a narrow range by employing the mechanism of pressure-natriuresis. Hypertension is induced when the pressure-natriuresis mechanism fails due to both subtle and overt kidney abnormalities. The inheritance of hypertension is believed to be polygenic, and essential hypertension may result from a combination of genetic variants that code for renal tubular sodium transporters or proteins involved in regulatory pathways. The renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system (SNS) are the major regulators of renal sodium reabsorption. Hyperactivity of either the RAAS or SNS leads to a rightward shift in the pressure-natriuresis curve. In other words, hypertension is induced when the activity of RAAS and SNS is not suppressed despite increased salt intake. Sodium overload, caused by increased intake and/or reduced renal excretion, not only leads to an expansion of plasma volume but also to an increase in systemic vascular resistance. Endothelial dysfunction is caused by an increased intracellular Na+ concentration, which inhibits endothelial nitric oxide (NO) synthase and reduces NO production. The stiffness of vascular smooth muscle cells is increased by the accumulation of intracellular Na+ and subsequent elevation of cytoplasmic Ca++ concentration. In contrast to the hemodynamic effects of osmotically active Na+, osmotically inactive Na+ stimulates immune cells and produces proinflammatory cytokines, which contribute to hypertension. When this occurs in the gut, the microbiota may become imbalanced, leading to intestinal inflammation and systemic hypertension. In conclusion, the primary cause of hypertension is sodium overload resulting from kidney dysregulation.
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Affiliation(s)
- Gheun-Ho Kim
- Department of Internal Medicine, Hanyang University College of Medicine, Seoul 04763, Republic of Korea
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3
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Kanugula AK, Kaur J, Batra J, Ankireddypalli AR, Velagapudi R. Renin-Angiotensin System: Updated Understanding and Role in Physiological and Pathophysiological States. Cureus 2023; 15:e40725. [PMID: 37350982 PMCID: PMC10283427 DOI: 10.7759/cureus.40725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2023] [Indexed: 06/24/2023] Open
Abstract
The classical view of the renin-angiotensin system (RAS) is that of the circulating hormone pathway involved in salt and water homeostasis and blood pressure regulation. It is also involved in the pathogenesis of cardiac and renal disorders. This led to the creation of drugs blocking the actions of this classical pathway, which improved cardiac and renal outcomes. Our understanding of the RAS has significantly expanded with the discovery of new peptides involved in this complex pathway. Over the last two decades, a counter-regulatory or protective pathway has been discovered that opposes the effects of the classical pathway. Components of RAS are also implicated in the pathogenesis of obesity and its metabolic diseases. The continued discovery of newer molecules also provides novel therapeutic targets to improve disease outcomes. This article aims to provide an overview of an updated understanding of the RAS, its role in physiological and pathological processes, and potential novel therapeutic options from RAS for managing cardiorenal disorders, obesity, and related metabolic disorders.
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Affiliation(s)
- Ashok Kumar Kanugula
- Department of Internal Medicine, Wellstar Health System - Spalding Regional Hospital, Griffin, USA
| | - Jasleen Kaur
- Department of Endocrinology, Diabetes, and Metabolism, HealthPartners, Minneapolis, USA
| | - Jaskaran Batra
- Department of Internal Medicine, Univerity of Pittsburg Medical Center (UPMC) McKeesport, McKeesport, USA
| | | | - Ravikanth Velagapudi
- Department of Pulmonary and Critical Care Medicine, Spectrum Health/Michigan State University, Grand Rapids, USA
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4
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Wynne BM, Samson TK, Moyer HC, van Elst HJ, Moseley AS, Hecht G, Paul O, Al-Khalili O, Gomez-Sanchez C, Ko B, Eaton DC, Hoover RS. Interleukin 6 mediated activation of the mineralocorticoid receptor in the aldosterone-sensitive distal nephron. Am J Physiol Cell Physiol 2022; 323:C1512-C1523. [PMID: 35912993 PMCID: PMC9662807 DOI: 10.1152/ajpcell.00272.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 06/28/2022] [Accepted: 07/11/2022] [Indexed: 11/22/2022]
Abstract
Hypertension is characterized by increased sodium (Na+) reabsorption along the aldosterone-sensitive distal nephron (ASDN) as well as chronic systemic inflammation. Interleukin-6 (IL-6) is thought to be a mediator of this inflammatory process. Interestingly, increased Na+ reabsorption within the ASDN does not always correlate with increases in aldosterone (Aldo), the primary hormone that modulates Na+ reabsorption via the mineralocorticoid receptor (MR). Thus, understanding how increased ASDN Na+ reabsorption may occur independent of Aldo stimulation is critical. Here, we show that IL-6 can activate the MR by activating Rac1 and stimulating the generation of reactive oxygen species (ROS) with a consequent increase in thiazide-sensitive Na+ uptake. Using an in vitro model of the distal convoluted tubule (DCT2), mDCT15 cells, we observed nuclear translocation of eGFP-tagged MR after IL-6 treatment. To confirm the activation of downstream transcription factors, mDCT15 cells were transfected with mineralocorticoid response element (MRE)-luciferase reporter constructs; then treated with vehicle, Aldo, or IL-6. Aldosterone or IL-6 treatment increased luciferase activity that was reversed with MR antagonist cotreatment, but IL-6 treatment was reversed by Rac1 inhibition or ROS reduction. In both mDCT15 and mpkCCD cells, IL-6 increased amiloride-sensitive transepithelial Na+ current. ROS and IL-6 increased 22Na+ uptake via the thiazide-sensitive sodium chloride cotransporter (NCC). These results are the first to demonstrate that IL-6 can activate the MR resulting in MRE activation and that IL-6 increases NCC-mediated Na+ reabsorption, providing evidence for an alternative mechanism for stimulating ASDN Na+ uptake during conditions where Aldo-mediated MR stimulation may not occur.
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Affiliation(s)
- Brandi M Wynne
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
- Department of Internal Medicine, Nephrology & Hypertension, University of Utah, Salt Lake City, Utah
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
- Immunology, Inflammation and Infectious Disease Initiative, University of Utah, Salt Lake City, Utah
| | - Trinity K Samson
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
| | - Hayley C Moyer
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
| | - Henrieke J van Elst
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
- Department of Physiology, Radboud University Medical Center, Nijmegen, Netherlands
| | - Auriel S Moseley
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
| | - Gillian Hecht
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
| | - Oishi Paul
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
| | - Otor Al-Khalili
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
| | - Celso Gomez-Sanchez
- G.V. (Sonny) Montgomery VA Medical Center, Jackson, Mississippi
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Mississippi
| | - Benjamin Ko
- Department of Medicine, Nephrology, University of Chicago, Chicago, Illinois
| | - Douglas C Eaton
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
| | - Robert S Hoover
- Department of Medicine, Nephrology, Emory University, Atlanta, Georgia
- Research Service, Atlanta Veterans Affairs Medical Center, Atlanta, Georgia
- Section of Nephrology and Hypertension, Deming Department of Medicine, Tulane University, New Orleans, Louisiana
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Oezen G, Schentarra EM, Bolten JS, Huwyler J, Fricker G. Sodium arsenite but not aluminum chloride stimulates ABC transporter activity in renal proximal tubules of killifish (Fundulus heteroclitus). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2022; 252:106314. [PMID: 36201872 DOI: 10.1016/j.aquatox.2022.106314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 09/12/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
ABC export proteins including Multidrug resistance-related protein 2 (Mrp2) serve as detoxification mechanism in renal proximal tubules due to active transport of xenobiotics and metabolic waste products into primary urine. The environmental pollutants aluminum and arsenic interfere with a multitude of regulatory mechanisms in the body and here their impact on ABC transporter function was studied. NaAsO2 but not AlCl3 rapidly stimulated Mrp2-mediated Texas Red (TR) transport in isolated renal proximal tubules from killifish, a well-established laboratory model for the determination of efflux transporter activity by utilizing fluorescent substrates for the ABC transporters of interest and confocal microscopy followed by image analysis. This observed stimulation remained unaffected by the translation inhibitor cycloheximide (CHX), but it was abrogated by antagonists and inhibitors of the endothelin receptor type B (ETB)/nitric oxide synthase (NOS)/protein kinase C (PKC) signaling pathway. NaAsO2-triggered effects were abolished as a consequence of PKCα inhibition through Gö6976 and PKCα inhibitor peptide C2-4. Phosphatidylinositol 3-kinase (PI3K) inhibitor LY 294,002 as well as the mammalian target of rapamycin (mTOR) inhibitor rapamycin suppressed NaAsO2-triggered stimulation of luminal TR transport. In addition, the stimulatory effect of NaAsO2 was abolished by GSK650394, an inhibitor of serum- and glucocorticoid-inducible kinase 1 (SGK1), which is an important downstream target. Environmentally relevant concentrations of NaAsO2 further stimulated transport function of P-glycoprotein (P-gp), Multidrug resistance-related protein 4 (Mrp4) and Breast cancer resistance protein (Bcrp) while AlCl3 was ineffective. To our knowledge, this is the first report engaging in the impact of NaAsO2 on efflux transporter signaling and it may contribute to the understanding of defense mechanisms versus this worrying pollutant.
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Affiliation(s)
- Goezde Oezen
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg 69120, Germany; Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672, United States
| | - Eva-Maria Schentarra
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg 69120, Germany; Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672, United States
| | - Jan Stephan Bolten
- Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672, United States; Department of Pharmaceutical Sciences, University of Basel, Basel 4056, Switzerland
| | - Joerg Huwyler
- Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672, United States; Department of Pharmaceutical Sciences, University of Basel, Basel 4056, Switzerland
| | - Gert Fricker
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg 69120, Germany; Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672, United States.
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Wu A, Wolley MJ, Matthews A, Cowley D, Welling PA, Fenton RA, Stowasser M. In Primary Aldosteronism Acute Potassium Chloride Supplementation Suppresses Abundance and Phosphorylation of the Sodium-Chloride Cotransporter. KIDNEY360 2022; 3:1909-1923. [PMID: 36514401 PMCID: PMC9717638 DOI: 10.34067/kid.0003632022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 08/25/2022] [Indexed: 01/12/2023]
Abstract
Background Elevated abundance of sodium-chloride cotransporter (NCC) and phosphorylated NCC (pNCC) are potential markers of primary aldosteronism (PA), but these effects may be driven by hypokalemia. Methods We measured plasma potassium in patients with PA. If potassium was <4.0 mmol/L, patients were given sufficient oral potassium chloride (KCl) over 24 hours to achieve as close to 4.0 mmol/L as possible. Clinical chemistries were assessed, and urinary extracellular vesicles (uEVs) were examined to investigate effects on NCC. Results Among 21 patients with PA who received a median total dose of 6.0 g (2.4-16.8 g) of KCl, increases were observed in plasma potassium (from 3.4 to 4.0 mmol/L; P<0.001), aldosterone (from 305 to 558 pmol/L; P=0.01), and renin (from 1.2 to 2.5 mIU/L; P<0.001), whereas decreases were detected in uEV levels of NCC (median fold change(post/basal) [FC]=0.71 [0.09-1.99]; P=0.02), pT60-NCC (FC=0.84 [0.06-1.66]; P=0.05), and pT55/60-NCC (FC=0.67 [0.08-2.42]; P=0.02). By contrast, in 10 patients with PA who did not receive KCl, there were no apparent changes in plasma potassium, NCC abundance, and phosphorylation status, but increases were observed in plasma aldosterone (from 178 to 418 pmol/L; P=0.006) and renin (from 2.0 to 3.0 mU/L; P=0.009). Plasma potassium correlated inversely with uEV levels of NCC (R 2=0.11; P=0.01), pT60-NCC (R 2=0.11; P=0.01), and pT55/60-NCC (R 2=0.11; P=0.01). Conclusions Acute oral KCl loading replenished plasma potassium in patients with PA and suppressed NCC abundance and phosphorylation, despite a significant rise in plasma aldosterone. This supports the view that potassium supplementation in humans with PA overrides the aldosterone stimulatory effect on NCC. The increased plasma aldosterone in patients with PA without KCl supplementation may be due to aldosterone response to posture challenge.
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Affiliation(s)
- Aihua Wu
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Martin J. Wolley
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia,Department of Nephrology, Royal Brisbane and Women’s Hospital, Brisbane, Australia
| | - Alexandra Matthews
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Diane Cowley
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Paul A. Welling
- Department of Medicine and Physiology, Johns Hopkins University, Baltimore, Maryland
| | | | - Michael Stowasser
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
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7
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Spencer S, Wheeler‐Jones C, Elliott J. Aldosterone and the mineralocorticoid receptor in renal injury: A potential therapeutic target in feline chronic kidney disease. J Vet Pharmacol Ther 2020; 43:243-267. [PMID: 32128854 PMCID: PMC8614124 DOI: 10.1111/jvp.12848] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 01/20/2020] [Accepted: 02/09/2020] [Indexed: 12/24/2022]
Abstract
There is a growing body of experimental and clinical evidence supporting mineralocorticoid receptor (MR) activation as a powerful mediator of renal damage in laboratory animals and humans. Multiple pathophysiological mechanisms are proposed, with the strongest evidence supporting aldosterone-induced vasculopathy, exacerbation of oxidative stress and inflammation, and increased growth factor signalling promoting fibroblast proliferation and deranged extracellular matrix homeostasis. Further involvement of the MR is supported by extensive animal model experiments where MR antagonists (such as spironolactone and eplerenone) abrogate renal injury, including ischaemia-induced damage. Additionally, clinical trials have shown MR antagonists to be beneficial in human chronic kidney disease (CKD) in terms of reducing proteinuria and cardiovascular events, though current studies have not evaluated primary end points which allow conclusions to made about whether MR antagonists reduce mortality or slow CKD progression. Although differences between human and feline CKD exist, feline CKD shares many characteristics with human disease including tubulointerstitial fibrosis. This review evaluates the evidence for the role of the MR in renal injury and summarizes the literature concerning aldosterone in feline CKD. MR antagonists may represent a promising therapeutic strategy in feline CKD.
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Affiliation(s)
- Sarah Spencer
- Comparative Biomedical SciencesThe Royal Veterinary CollegeLondonUK
| | | | - Jonathan Elliott
- Comparative Biomedical SciencesThe Royal Veterinary CollegeLondonUK
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8
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Mabillard H, Sayer JA. The Molecular Genetics of Gordon Syndrome. Genes (Basel) 2019; 10:genes10120986. [PMID: 31795491 PMCID: PMC6947027 DOI: 10.3390/genes10120986] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/22/2019] [Accepted: 11/25/2019] [Indexed: 12/12/2022] Open
Abstract
Gordon syndrome is a rare inherited monogenic form of hypertension, which is associated with hyperkalaemia and metabolic acidosis. Since the recognition of this predominantly autosomal dominant condition in the 1960s, the study of families with Gordon syndrome has revealed four genes WNK1, WNK4, KLHL3, and CUL3 to be implicated in its pathogenesis after a phenotype–genotype correlation was realised. The encoded proteins Kelch-like 3 and Cullin 3 interact to form a ring-like complex to ubiquitinate WNK-kinase 4, which, in normal circumstances, interacts with the sodium chloride co-symporter (NCC), the epithelial sodium channel (ENaC), and the renal outer medullary potassium channel (ROMK) in an inhibitory manner to maintain normokalaemia and normotension. WNK-kinase 1 has an inhibitory action on WNK-kinase 4. Mutations in WNK1, WNK4, KLHL3, and CUL3 all result in the accumulation of WNK-kinase 4 and subsequent hypertension, hyperkalaemia, and metabolic acidosis. This review explains the clinical aspects, disease mechanisms, and molecular genetics of Gordon syndrome.
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Affiliation(s)
- Holly Mabillard
- Renal Services, The Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne NE7 7DN, UK;
| | - John A. Sayer
- Renal Services, The Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne NE7 7DN, UK;
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Institute of Genetic Medicine, Newcastle University, International Centre for Life, Central Parkway, Newcastle upon Tyne NE1 3BZ, UK
- NIHR Newcastle Biomedical Research Centre, Newcastle University, Newcastle upon Tyne NE4 5PL, UK
- Correspondence: ; Tel.: +44-191-2418608
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9
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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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10
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The interplay of renal potassium and sodium handling in blood pressure regulation: critical role of the WNK-SPAK-NCC pathway. J Hum Hypertens 2019; 33:508-523. [DOI: 10.1038/s41371-019-0170-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 12/18/2018] [Accepted: 01/03/2019] [Indexed: 12/19/2022]
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11
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Feraco A, Armani A, Urbanet R, Nguyen Dinh Cat A, Marzolla V, Jaisser F, Caprio M. Minor role of mature adipocyte mineralocorticoid receptor in high-fat diet-induced obesity. J Endocrinol 2018; 239:229-240. [PMID: 30121579 DOI: 10.1530/joe-18-0314] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 08/07/2018] [Accepted: 08/15/2018] [Indexed: 01/07/2023]
Abstract
Obesity is a major risk factor that contributes to the development of cardiovascular disease and type 2 diabetes. Mineralocorticoid receptor (MR) expression is increased in the adipose tissue of obese patients and several studies provide evidence that MR pharmacological antagonism improves glucose metabolism in genetic and diet-induced mouse models of obesity. In order to investigate whether the lack of adipocyte MR is sufficient to explain these beneficial metabolic effects, we generated a mouse model with inducible adipocyte-specific deletion of Nr3c2 gene encoding MR (adipo-MRKO). We observed a significant, yet not complete, reduction of Nr3c2 transcript and MR protein expression in subcutaneous and visceral adipose depots of adipo-MRKO mice. Notably, only mature adipocyte fraction lacks MR, whereas the stromal vascular fraction maintains normal MR expression in our mouse model. Adipo-MRKO mice fed a 45% high-fat diet for 14 weeks did not show any significant difference in body weight and fat mass compared to control littermates. Glucose and insulin tolerance tests revealed that mature adipocyte MR deficiency did not improve insulin sensitivity in response to a metabolic homeostatic challenge. Accordingly, no significant changes were observed in gene expression profile of adipogenic and inflammatory markers in adipose tissue of adipo-MRKO mice. Moreover, pharmacological MR antagonism in mature primary murine adipocytes, which differentiated ex vivo from WT mice, did not display any effect on adipokine expression. Taken together, these data demonstrate that the depletion of MR in mature adipocytes displays a minor role in diet-induced obesity and metabolic dysfunctions.
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Affiliation(s)
- A Feraco
- Laboratory of Cardiovascular Endocrinology, IRCCS San Raffaele Pisana, Rome, Italy
- INSERM, UMR_S 1138, Teams 1, Centre de Recherche des Cordeliers, UPMC Univ Paris 06, Université Paris Descartes, Paris, France
| | - A Armani
- Laboratory of Cardiovascular Endocrinology, IRCCS San Raffaele Pisana, Rome, Italy
| | - R Urbanet
- INSERM, UMR_S 1138, Teams 1, Centre de Recherche des Cordeliers, UPMC Univ Paris 06, Université Paris Descartes, Paris, France
| | - A Nguyen Dinh Cat
- INSERM, UMR_S 1138, Teams 1, Centre de Recherche des Cordeliers, UPMC Univ Paris 06, Université Paris Descartes, Paris, France
| | - V Marzolla
- Laboratory of Cardiovascular Endocrinology, IRCCS San Raffaele Pisana, Rome, Italy
| | - F Jaisser
- INSERM, UMR_S 1138, Teams 1, Centre de Recherche des Cordeliers, UPMC Univ Paris 06, Université Paris Descartes, Paris, France
| | - M Caprio
- Laboratory of Cardiovascular Endocrinology, IRCCS San Raffaele Pisana, Rome, Italy
- Department of Human Sciences and Promotion of the Quality of Life, San Raffaele Roma Open University, Rome, Italy
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12
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Harvey BJ, Thomas W. Aldosterone-induced protein kinase signalling and the control of electrolyte balance. Steroids 2018; 133:67-74. [PMID: 29079406 DOI: 10.1016/j.steroids.2017.10.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 10/18/2017] [Accepted: 10/21/2017] [Indexed: 01/20/2023]
Abstract
Aldosterone acts through the mineralocorticoid receptor (MR) to modulate gene expression in target tissues. In the kidney, the principal action of aldosterone is to promote sodium conservation in the distal nephron and so indirectly enhance water conservation under conditions of hypotension. Over the last twenty years the rapid activation of protein kinase signalling cascades by aldosterone has been described in various tissues. This review describes the integration of rapid protein kinase D signalling responses with the non-genomic actions of aldosterone and transcriptional effects of MR activation.
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Affiliation(s)
- Brian J Harvey
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Education Centre, Beaumont Hospital, Dublin, Ireland
| | - Warren Thomas
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Education Centre, Beaumont Hospital, Dublin, Ireland; Perdana University - Royal College of Surgeons in Ireland School of Medicine, Serdang, Selangor, Malaysia.
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13
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Zinc chloride rapidly stimulates efflux transporters in renal proximal tubules of killifish ( Fundulus heteroclitus ). Toxicol Appl Pharmacol 2017; 334:88-99. [DOI: 10.1016/j.taap.2017.09.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 08/04/2017] [Accepted: 09/01/2017] [Indexed: 12/26/2022]
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McDonough AA, Youn JH. Potassium Homeostasis: The Knowns, the Unknowns, and the Health Benefits. Physiology (Bethesda) 2017; 32:100-111. [PMID: 28202621 PMCID: PMC5337831 DOI: 10.1152/physiol.00022.2016] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Potassium homeostasis has a very high priority because of its importance for membrane potential. Although extracellular K+ is only 2% of total body K+, our physiology was evolutionarily tuned for a high-K+, low-Na+ diet. We review how multiple systems interface to accomplish fine K+ balance and the consequences for health and disease.
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Affiliation(s)
- Alicia A McDonough
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
| | - Jang H Youn
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California
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15
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Liu X, Edinger RS, Klemens CA, Phua YL, Bodnar AJ, LaFramboise WA, Ho J, Butterworth MB. A MicroRNA Cluster miR-23-24-27 Is Upregulated by Aldosterone in the Distal Kidney Nephron Where it Alters Sodium Transport. J Cell Physiol 2017; 232:1306-1317. [PMID: 27636893 DOI: 10.1002/jcp.25599] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 09/14/2016] [Indexed: 01/09/2023]
Abstract
The epithelial sodium channel (ENaC) is expressed in the epithelial cells of the distal convoluted tubules, connecting tubules, and cortical collecting duct (CCD) in the kidney nephron. Under the regulation of the steroid hormone aldosterone, ENaC is a major determinant of sodium (Na+ ) and water balance. The ability of aldosterone to regulate microRNAs (miRs) in the kidney has recently been realized, but the role of miRs in Na+ regulation has not been well established. Here we demonstrate that expression of a miR cluster mmu-miR-23-24-27, is upregulated in the CCD by aldosterone stimulation both in vitro and in vivo. Increasing the expression of these miRs increased Na+ transport in the absence of aldosterone stimulation. Potential miR targets were evaluated and miR-27a/b was verified to bind to the 3'-untranslated region of intersectin-2, a multi-domain protein expressed in the distal kidney nephron and involved in the regulation of membrane trafficking. Expression of Itsn2 mRNA and protein was decreased after aldosterone stimulation. Depletion of Itsn2 expression, mimicking aldosterone regulation, increased ENaC-mediated Na+ transport, while Itsn2 overexpression reduced ENaC's function. These findings reinforce a role for miRs in aldosterone regulation of Na+ transport, and implicate miR-27 in aldosterone's action via a novel target. J. Cell. Physiol. 232: 1306-1317, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Xiaoning Liu
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Robert S Edinger
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Christine A Klemens
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Yu L Phua
- Division of Nephrology in the Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Andrew J Bodnar
- Division of Nephrology in the Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - William A LaFramboise
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Jacqueline Ho
- Division of Nephrology in the Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Michael B Butterworth
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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16
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Grahammer F, Nesterov V, Ahmed A, Steinhardt F, Sandner L, Arnold F, Cordts T, Negrea S, Bertog M, Ruegg MA, Hall MN, Walz G, Korbmacher C, Artunc F, Huber TB. mTORC2 critically regulates renal potassium handling. J Clin Invest 2016; 126:1773-82. [PMID: 27043284 DOI: 10.1172/jci80304] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 02/18/2016] [Indexed: 12/12/2022] Open
Abstract
The mTOR pathway orchestrates cellular homeostasis. The rapamycin-sensitive mTOR complex (mTORC1) in the kidney has been widely studied; however, mTORC2 function in renal tubules is poorly characterized. Here, we generated mice lacking mTORC2 in the distal tubule (Rictorfl/fl Ksp-Cre mice), which were viable and had no obvious phenotype, except for a 2.5-fold increase in plasma aldosterone. Challenged with a low-Na+ diet, these mice adequately reduced Na+ excretion; however, Rictorfl/fl Ksp-Cre mice rapidly developed hyperkalemia on a high-K+ diet, despite a 10-fold increase in serum aldosterone levels, implying that mTORC2 regulates kaliuresis. Phosphorylation of serum- and glucocorticoid-inducible kinase 1 (SGK1) and PKC-α was absent in Rictorfl/fl Ksp-Cre mice, indicating a functional block in K+ secretion activation via ROMK channels. Indeed, patch-clamp experiments on split-open tubular segments from the transition zone of the late connecting tubule and early cortical collecting duct demonstrated that Ba2+-sensitive apical K+ currents were barely detectable in the majority of Rictorfl/fl Ksp-Cre mice. Conversely, epithelial sodium channel (ENaC) activity was largely preserved, suggesting that the reduced ability to maintain K+ homeostasis is the result of impaired apical K+ conductance and not a reduced electrical driving force for K+ secretion. Thus, these data unravel a vital and nonredundant role of mTORC2 for distal tubular K+ handling.
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17
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Rojas-Vega L, Gamba G. Mini-review: regulation of the renal NaCl cotransporter by hormones. Am J Physiol Renal Physiol 2016; 310:F10-4. [DOI: 10.1152/ajprenal.00354.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The renal thiazide-sensitive NaCl cotransporter, NCC, is the major pathway for salt reabsorption in the distal convoluted tubule. The activity of this cotransporter is critical for regulation of several physiological variables such as blood pressure, serum potassium, acid base metabolism, and urinary calcium excretion. Therefore, it is not surprising that numerous hormone-signaling pathways regulate NCC activity to maintain homeostasis. In this review, we will provide an overview of the most recent evidence on NCC modulation by aldosterone, angiotensin II, vasopressin, glucocorticoids, insulin, norepinephrine, estradiol, progesterone, prolactin, and parathyroid hormone.
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Affiliation(s)
- Lorena Rojas-Vega
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico; and
- Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
| | - Gerardo Gamba
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico; and
- Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
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18
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Lu X, Wang F, Liu M, Yang KT, Nau A, Kohan DE, Reese V, Richardson RS, Yang T. Activation of ENaC in collecting duct cells by prorenin and its receptor PRR: involvement of Nox4-derived hydrogen peroxide. Am J Physiol Renal Physiol 2015; 310:F1243-50. [PMID: 26697985 DOI: 10.1152/ajprenal.00492.2015] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 12/15/2015] [Indexed: 11/22/2022] Open
Abstract
The collecting duct (CD) has been recognized as an important source of prorenin/renin, and it also expresses (pro)renin receptor (PRR). The goal of this study was to examine the hypothesis that prorenin or renin via PRR regulates epithelial Na(+) channel (ENaC) activity in mpkCCD cells. Transepithelial Na(+) transport was measured by using a conventional epithelial volt-ohmmeter and was expressed as the calculated equivalent current (Ieq). Amiloride-inhibitable Ieq was used as a reflection of ENaC activity. Administration of prorenin in the nanomolar range induced a significant increase in Ieq that was detectable as early as 1 min, peaked at 5 min, and gradually returned to baseline within 15 min. These changes in Ieq were completely prevented by a newly developed PRR decoy inhibitor, PRO20. Prorenin-induced Ieq was inhibitable by amiloride. Compared with prorenin, renin was less effective in stimulating Ieq Prorenin-induced Ieq was attenuated by apocynin but enhanced by tempol, the latter effect being prevented by catalase. In response to prorenin treatment, the levels of total reactive oxygen species and H2O2 were both increased, as detected by spin-trap analysis and reactive oxygen species (ROS)-Glo H2O2 assay, respectively. Both siRNA-mediated Nox4 knockdown and the dual Nox1/4 inhibitor GKT137892 attenuated prorenin-induced Ieq Overall, our results demonstrate that activation of PRR by prorenin stimulates ENaC activity in CD cells via Nox4-derived H2O2.
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Affiliation(s)
- Xiaohan Lu
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Fei Wang
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Mi Liu
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Kevin T Yang
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Adam Nau
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Donald E Kohan
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Van Reese
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Russell S Richardson
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Tianxin Yang
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
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19
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Hernandez AL, Kitz A, Wu C, Lowther DE, Rodriguez DM, Vudattu N, Deng S, Herold KC, Kuchroo VK, Kleinewietfeld M, Hafler DA. Sodium chloride inhibits the suppressive function of FOXP3+ regulatory T cells. J Clin Invest 2015; 125:4212-22. [PMID: 26524592 DOI: 10.1172/jci81151] [Citation(s) in RCA: 224] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 08/20/2015] [Indexed: 12/12/2022] Open
Abstract
FOXP3+ Tregs are central for the maintenance of self-tolerance and can be defective in autoimmunity. In multiple sclerosis and type-1 diabetes, dysfunctional self-tolerance is partially mediated by a population of IFNγ-secreting Tregs. It was previously reported that increased NaCl concentrations promote the induction of proinflammatory Th17 cells and that high-salt diets exacerbate experimental models of autoimmunity. Here, we have shown that increasing NaCl, either in vitro or in murine models via diet, markedly impairs Treg function. NaCl increased IFNγ secretion in Tregs, and reducing IFNγ - either by neutralization with anti-IFNγ antibodies or shRNA-mediated knockdown - restored suppressive activity in Tregs. The heightened IFNγ secretion and loss of Treg function were mediated by the serum/glucocorticoid-regulated kinase (SGK1). A high-salt diet also impaired human Treg function and was associated with the induction of IFNγ-secreting Tregs in a xenogeneic graft-versus-host disease model and in adoptive transfer models of experimental colitis. Our results demonstrate a putative role for an environmental factor that promotes autoimmunity by inducing proinflammatory responses in CD4 effector cells and Treg pathways.
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MESH Headings
- Adoptive Transfer
- Animals
- Antibodies, Neutralizing/immunology
- Autoimmunity/drug effects
- CD4-Positive T-Lymphocytes/immunology
- Cells, Cultured
- Coculture Techniques
- Colitis/immunology
- Cytokines/biosynthesis
- Cytokines/genetics
- Forkhead Transcription Factors/analysis
- Forkhead Transcription Factors/genetics
- Gene Expression Profiling
- Genes, Reporter
- Graft vs Host Disease/immunology
- Heterografts
- Humans
- Immediate-Early Proteins/physiology
- Inflammation
- Interferon-gamma/genetics
- Interferon-gamma/metabolism
- Interferon-gamma/pharmacology
- Leukocytes, Mononuclear/transplantation
- Male
- Mice
- Protein Serine-Threonine Kinases/physiology
- RNA Interference
- RNA, Small Interfering/genetics
- Sodium Chloride/pharmacology
- Sodium Chloride, Dietary/adverse effects
- Sodium Chloride, Dietary/pharmacology
- T-Lymphocytes, Regulatory/drug effects
- T-Lymphocytes, Regulatory/immunology
- T-Lymphocytes, Regulatory/metabolism
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20
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Armani A, Marzolla V, Fabbri A, Caprio M. Cellular mechanisms of MR regulation of adipose tissue physiology and pathophysiology. J Mol Endocrinol 2015; 55:R1-10. [PMID: 26272942 DOI: 10.1530/jme-15-0122] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/13/2015] [Indexed: 12/13/2022]
Abstract
In addition to the well-documented expression and activity of the mineralocorticoid receptor (MR) in the kidney, in the last decade research on MR has also revealed its important role in regulating functions of extrarenal tissues, including adipose tissue, where MR is involved in adipocyte fundamental processes such as differentiation, autophagy and adipokine secretion. MR expression is increased in adipose tissue of murine models of obesity and in obese human subjects, suggesting that over-activation of the mineralocorticoid signaling leads to dysfunctional adipocyte and associated metabolic disorders. Notably, pharmacological blockade of MR prevents metabolic dysfunctions observed in obese mice and suggests a potential therapeutic use of MR antagonists in the treatment of obesity and metabolic syndrome. However, the molecular pathways affected by MR blockade have been poorly investigated. This review summarizes the functions of MR in the adipocyte, discusses potential signaling pathways mediating MR action, and describes post-translational modifications regulating its activity.
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Affiliation(s)
- Andrea Armani
- Laboratory of Cardiovascular Endocrinology IRCCS San Raffaele Pisana, Via di Val Cannuta, 247, Rome, Italy Endocrinology Unit Department of Systems Medicine, S. Eugenio and CTO A. Alesini Hospitals, University Tor Vergata, Rome, Italy University San Raffaele Rome, Italy
| | - Vincenzo Marzolla
- Laboratory of Cardiovascular Endocrinology IRCCS San Raffaele Pisana, Via di Val Cannuta, 247, Rome, Italy Endocrinology Unit Department of Systems Medicine, S. Eugenio and CTO A. Alesini Hospitals, University Tor Vergata, Rome, Italy University San Raffaele Rome, Italy
| | - Andrea Fabbri
- Laboratory of Cardiovascular Endocrinology IRCCS San Raffaele Pisana, Via di Val Cannuta, 247, Rome, Italy Endocrinology Unit Department of Systems Medicine, S. Eugenio and CTO A. Alesini Hospitals, University Tor Vergata, Rome, Italy University San Raffaele Rome, Italy
| | - Massimiliano Caprio
- Laboratory of Cardiovascular Endocrinology IRCCS San Raffaele Pisana, Via di Val Cannuta, 247, Rome, Italy Endocrinology Unit Department of Systems Medicine, S. Eugenio and CTO A. Alesini Hospitals, University Tor Vergata, Rome, Italy University San Raffaele Rome, Italy Laboratory of Cardiovascular Endocrinology IRCCS San Raffaele Pisana, Via di Val Cannuta, 247, Rome, Italy Endocrinology Unit Department of Systems Medicine, S. Eugenio and CTO A. Alesini Hospitals, University Tor Vergata, Rome, Italy University San Raffaele Rome, Italy
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21
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Pearce D, Soundararajan R, Trimpert C, Kashlan OB, Deen PM, Kohan DE. Collecting duct principal cell transport processes and their regulation. Clin J Am Soc Nephrol 2015; 10:135-46. [PMID: 24875192 PMCID: PMC4284417 DOI: 10.2215/cjn.05760513] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The principal cell of the kidney collecting duct is one of the most highly regulated epithelial cell types in vertebrates. The effects of hormonal, autocrine, and paracrine factors to regulate principal cell transport processes are central to the maintenance of fluid and electrolyte balance in the face of wide variations in food and water intake. In marked contrast with the epithelial cells lining the proximal tubule, the collecting duct is electrically tight, and ion and osmotic gradients can be very high. The central role of principal cells in salt and water transport is reflected by their defining transporters-the epithelial Na(+) channel (ENaC), the renal outer medullary K(+) channel, and the aquaporin 2 (AQP2) water channel. The coordinated regulation of ENaC by aldosterone, and AQP2 by arginine vasopressin (AVP) in principal cells is essential for the control of plasma Na(+) and K(+) concentrations, extracellular fluid volume, and BP. In addition to these essential hormones, additional neuronal, physical, and chemical factors influence Na(+), K(+), and water homeostasis. Notably, a variety of secreted paracrine and autocrine agents such as bradykinin, ATP, endothelin, nitric oxide, and prostaglandin E2 counterbalance and limit the natriferic effects of aldosterone and the water-retaining effects of AVP. Considerable recent progress has improved our understanding of the transporters, receptors, second messengers, and signaling events that mediate principal cell responses to changing environments in health and disease. This review primarily addresses the structure and function of the key transporters and the complex interplay of regulatory factors that modulate principal cell ion and water transport.
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Affiliation(s)
- David Pearce
- Division of Nephrology, Department of Medicine, University of California, San Francisco, California
| | - Rama Soundararajan
- Department of Translational Molecular Pathology, MD Anderson Cancer Center, Houston, Texas
| | - Christiane Trimpert
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Ossama B. Kashlan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Peter M.T. Deen
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Donald E. Kohan
- Division of Nephrology, University of Utah Health Sciences Center, Salt Lake City, Utah
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22
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Lu X, Li M, Zhou L, Jiang H, Wang H, Chen J. Urinary serum- and glucocorticoid-inducible kinase SGK1 reflects renal injury in patients with immunoglobulin A nephropathy. Nephrology (Carlton) 2015; 19:307-17. [PMID: 24602173 DOI: 10.1111/nep.12225] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM Serum- and glucocorticoid-inducible kinase SGK1 functions as an important regulator of transepithelial sodium transport by activating epithelial sodium channel in renal tubules. Considerable evidence demonstrated that SGK1 was associated with hypertension and fibrosing diseases, such as diabetic nephropathy and glomerulonephritis. The present study was performed to evaluate the role of SGK1 played in immunoglobulin A (IgA) nephropathy. METHODS Seventy-six patients of biopsy-proven IgA nephropathy and 33 healthy volunteers were enrolled in this study. All patients and healthy volunteers' urinary and serum samples were tested for SGK1 expression by indirect enzyme-linked immunosorbent assay. Meanwhile all patients' renal tissues were semi-quantified for SGK1 expression by immunohistochemistry assay. The relationships between SGK1 expressions and clinical or pathological parameters were also assessed. RESULTS SGK1 expression was upregulated in urine and renal tubules in patients of Oxford classification T1 and T2, whereas its expression in serum did not increase significantly. Relationship analysis indicated that urinary and tissue SGK1 expressions were associated with heavy proteinuria and renal insufficiency in patients with IgA nephropathy. On the other hand, RAS blockades would reduce the SGK1 levels both in urine and renal tissues. CONCLUSION These results suggested that urinary SGK1 should be a good indicator of tubulointerstitial damage in patients of IgA nephropathy. SGK1 expressions in urine and renal tissues were associated with the activity of renin-angiotensin-aldosterone system.
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Affiliation(s)
- Xiaoqian Lu
- Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China; Kidney Disease Immunology Laboratory, The Third Grade Laboratory, State Administration of Traditional Chinese Medicine of China, Hangzhou, China; Key Laboratory of Multiple Organ Transplantation, Ministry of Health of China, Hangzhou, China; Key Laboratory of Nephropathy of Zhejiang Province, Hangzhou, China
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23
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Abstract
The distal convoluted tubule (DCT) is a short nephron segment, interposed between the macula densa and collecting duct. Even though it is short, it plays a key role in regulating extracellular fluid volume and electrolyte homeostasis. DCT cells are rich in mitochondria, and possess the highest density of Na+/K+-ATPase along the nephron, where it is expressed on the highly amplified basolateral membranes. DCT cells are largely water impermeable, and reabsorb sodium and chloride across the apical membrane via electroneurtral pathways. Prominent among this is the thiazide-sensitive sodium chloride cotransporter, target of widely used diuretic drugs. These cells also play a key role in magnesium reabsorption, which occurs predominantly, via a transient receptor potential channel (TRPM6). Human genetic diseases in which DCT function is perturbed have provided critical insights into the physiological role of the DCT, and how transport is regulated. These include Familial Hyperkalemic Hypertension, the salt-wasting diseases Gitelman syndrome and EAST syndrome, and hereditary hypomagnesemias. The DCT is also established as an important target for the hormones angiotensin II and aldosterone; it also appears to respond to sympathetic-nerve stimulation and changes in plasma potassium. Here, we discuss what is currently known about DCT physiology. Early studies that determined transport rates of ions by the DCT are described, as are the channels and transporters expressed along the DCT with the advent of molecular cloning. Regulation of expression and activity of these channels and transporters is also described; particular emphasis is placed on the contribution of genetic forms of DCT dysregulation to our understanding.
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Affiliation(s)
- James A McCormick
- Division of Nephrology & Hypertension, Oregon Health & Science University, & VA Medical Center, Portland, Oregon, United States
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24
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Gleason CE, Frindt G, Cheng CJ, Ng M, Kidwai A, Rashmi P, Lang F, Baum M, Palmer LG, Pearce D. mTORC2 regulates renal tubule sodium uptake by promoting ENaC activity. J Clin Invest 2014; 125:117-28. [PMID: 25415435 DOI: 10.1172/jci73935] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 10/23/2014] [Indexed: 12/17/2022] Open
Abstract
The epithelial Na+ channel (ENaC) is essential for Na+ homeostasis, and dysregulation of this channel underlies many forms of hypertension. Recent studies suggest that mTOR regulates phosphorylation and activation of serum/glucocorticoid regulated kinase 1 (SGK1), which is known to inhibit ENaC internalization and degradation; however, it is not clear whether mTOR contributes to the regulation of renal tubule ion transport. Here, we evaluated the effect of selective mTOR inhibitors on kidney tubule Na+ and K+ transport in WT and Sgk1-/- mice, as well as in isolated collecting tubules. We found that 2 structurally distinct competitive inhibitors (PP242 and AZD8055), both of which prevent all mTOR-dependent phosphorylation, including that of SGK1, caused substantial natriuresis, but not kaliuresis, in WT mice, which indicates that mTOR preferentially influences ENaC function. PP242 also substantially inhibited Na+ currents in isolated perfused cortical collecting tubules. Accordingly, patch clamp studies on cortical tubule apical membranes revealed that mTOR inhibition markedly reduces ENaC activity, but does not alter activity of K+ inwardly rectifying channels (ROMK channels). Together, these results demonstrate that mTOR regulates kidney tubule ion handling and suggest that mTOR regulates Na+ homeostasis through SGK1-dependent modulation of ENaC activity.
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25
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Edinger RS, Coronnello C, Bodnar AJ, Labarca M, Bhalla V, LaFramboise WA, Benos PV, Ho J, Johnson JP, Butterworth MB. Aldosterone regulates microRNAs in the cortical collecting duct to alter sodium transport. J Am Soc Nephrol 2014; 25:2445-57. [PMID: 24744440 PMCID: PMC4214524 DOI: 10.1681/asn.2013090931] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 02/05/2014] [Indexed: 12/26/2022] Open
Abstract
A role for microRNAs (miRs) in the physiologic regulation of sodium transport in the kidney has not been established. In this study, we investigated the potential of aldosterone to alter miR expression in mouse cortical collecting duct (mCCD) epithelial cells. Microarray studies demonstrated the regulation of miR expression by aldosterone in both cultured mCCD and isolated primary distal nephron principal cells. Aldosterone regulation of the most significantly downregulated miRs, mmu-miR-335-3p, mmu-miR-290-5p, and mmu-miR-1983 was confirmed by quantitative RT-PCR. Reducing the expression of these miRs separately or in combination increased epithelial sodium channel (ENaC)-mediated sodium transport in mCCD cells, without mineralocorticoid supplementation. Artificially increasing the expression of these miRs by transfection with plasmid precursors or miR mimic constructs blunted aldosterone stimulation of ENaC transport. Using a newly developed computational approach, termed ComiR, we predicted potential gene targets for the aldosterone-regulated miRs and confirmed ankyrin 3 (Ank3) as a novel aldosterone and miR-regulated protein. A dual-luciferase assay demonstrated direct binding of the miRs with the Ank3-3' untranslated region. Overexpression of Ank3 increased and depletion of Ank3 decreased ENaC-mediated sodium transport in mCCD cells. These findings implicate miRs as intermediaries in aldosterone signaling in principal cells of the distal kidney nephron.
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Affiliation(s)
| | | | | | | | | | | | | | | | - John P Johnson
- Renal-Electrolyte Division, Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Michael B Butterworth
- Renal-Electrolyte Division, Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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26
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Wolfsdorf JI, Allgrove J, Craig ME, Edge J, Glaser N, Jain V, Lee WWR, Mungai LNW, Rosenbloom AL, Sperling MA, Hanas R. ISPAD Clinical Practice Consensus Guidelines 2014. Diabetic ketoacidosis and hyperglycemic hyperosmolar state. Pediatr Diabetes 2014; 15 Suppl 20:154-79. [PMID: 25041509 DOI: 10.1111/pedi.12165] [Citation(s) in RCA: 214] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 05/21/2014] [Indexed: 12/16/2022] Open
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27
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Abstract
Liddle syndrome is monogenic hypertension caused by mutations in the epithelial Na+ channel (ENaC) that interfere with its ubiquitylation by Nedd4-2. In this issue, Ronzaud and colleagues found that deleting Nedd4-2 from kidney tubules in adult mice led to ENaC accumulation, but not at the plasma membrane, as predicted from current models. Instead, abundance of the sodium chloride transporter NCC increased at the plasma membrane, and the mice have some features of increased NCC activity. Together, the results suggest that defective ubiquitylation of ENaC by Nedd4-2 may not fully explain Liddle syndrome and that Nedd4-2 modulates NCC more strongly.
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Affiliation(s)
- David H Ellison
- Division of Nephrology and Hypertension, CH12R, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, USA.
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28
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Raikwar NS, Liu KZ, Thomas CP. A regulated NH2-terminal Sgk1 variant with enhanced function is expressed in the collecting duct. Am J Physiol Renal Physiol 2012; 303:F1527-33. [PMID: 23034940 DOI: 10.1152/ajprenal.00191.2012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sgk1 is a relatively unstable kinase that regulates epithelial Na(+) transport in the distal nephron of the kidney. We identified a 5' variant alternate transcript of human Sgk1 (Sgk1_v3) that is expressed in the connecting tubule and collecting duct, is regulated by aldosterone and insulin, and is predicted to encode an NH(2)-terminal variant Sgk1 isoform, Sgk1_i3. Sgk1_i3 contains a polybasic motif, KKR, in its NH(2) terminus that regulates ubiquitination and stability of the expressed protein in HEK293 cells. In Fisher rat thyroid, and mpkCCD(c14) cells, Sgk1_i3 had a significantly greater effect on Na(+) transport compared with Sgk1 and its stimulatory effect was dependent on the kinase domain. Sgk1_i3 increased the abundance of cleaved epithelial Na(+) channel (ENaC) subunits at the cell surface, which was inhibited by coexpression of Nedd4-2. Together, the data demonstrate that a renally expressed Sgk1 isoform, Sgk1_i3, shows improved stability, is regulated by insulin and aldosterone, and stimulates ENaC activity when heterologously expressed in collecting duct cells.
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Soundararajan R, Lu M, Pearce D. Organization of the ENaC-regulatory machinery. Crit Rev Biochem Mol Biol 2012; 47:349-59. [PMID: 22506713 DOI: 10.3109/10409238.2012.678285] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The control of fluid and electrolyte homeostasis in vertebrates requires the integration of a diverse set of signaling inputs, which control epithelial Na(+) transport, the principal ionic component of extracellular fluid. The key site of regulation is a segment of the kidney tubules, frequently termed the aldosterone-sensitive distal nephron, wherein the epithelial Na(+) channel (or ENaC) mediates apical ion entry. Na(+) transport in this segment is strongly regulated by the salt-retaining hormone, aldosterone, which acts through the mineralocorticoid receptor (MR) to influence the expression of a selected set of target genes, most notably the serine-threonine kinase SGK1, which phosphorylates and inhibits the E3 ubiquitin ligase Nedd4-2. It has long been known that ENaC activity is tightly regulated in vertebrate epithelia. Recent evidence suggests that SGK1 and Nedd4-2, along with other ENaC-regulatory proteins, physically associate with each other and with ENaC in a multi-protein complex. The various components of the complex are regulated by diverse signaling networks, including steroid receptor-, PI3-kinase-, mTOR-, and Raf-MEK-ERK-dependent pathways. In this review, we focus on the organization of the targets of these pathways by multi-domain scaffold proteins and lipid platforms into a unified complex, thereby providing a molecular basis for signal integration in the control of ENaC.
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Affiliation(s)
- Rama Soundararajan
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, CA 94143, USA
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Abstract
The central goal of this overview article is to summarize recent findings in renal epithelial transport,focusing chiefly on the connecting tubule (CNT) and the cortical collecting duct (CCD).Mammalian CCD and CNT are involved in fine-tuning of electrolyte and fluid balance through reabsorption and secretion. Specific transporters and channels mediate vectorial movements of water and solutes in these segments. Although only a small percent of the glomerular filtrate reaches the CNT and CCD, these segments are critical for water and electrolyte homeostasis since several hormones, for example, aldosterone and arginine vasopressin, exert their main effects in these nephron sites. Importantly, hormones regulate the function of the entire nephron and kidney by affecting channels and transporters in the CNT and CCD. Knowledge about the physiological and pathophysiological regulation of transport in the CNT and CCD and particular roles of specific channels/transporters has increased tremendously over the last two decades.Recent studies shed new light on several key questions concerning the regulation of renal transport.Precise distribution patterns of transport proteins in the CCD and CNT will be reviewed, and their physiological roles and mechanisms mediating ion transport in these segments will also be covered. Special emphasis will be given to pathophysiological conditions appearing as a result of abnormalities in renal transport in the CNT and CCD.
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Affiliation(s)
- Alexander Staruschenko
- Department of Physiology and Kidney Disease Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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Soundararajan R, Pearce D, Ziera T. The role of the ENaC-regulatory complex in aldosterone-mediated sodium transport. Mol Cell Endocrinol 2012; 350:242-7. [PMID: 22101317 PMCID: PMC3270213 DOI: 10.1016/j.mce.2011.11.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 10/11/2011] [Accepted: 11/03/2011] [Indexed: 12/29/2022]
Abstract
The mineralocorticoid aldosterone is indispensable for the control of blood pressure and fluid volume in mammals. It acts in large part to increase the abundance and activity of the epithelial Na(+) channel (ENaC), which mediates apical Na(+) entry in the distal parts of the kidney tubules. Aldosterone acts through the mineralocorticoid receptor to alter the transcription of specific genes, including SGK1 and GILZ1. Recent evidence suggests that these key aldosterone-regulated factors function within a unique multi-protein ENaC-regulatory-complex that governs the net cell surface expression and activity of the channel. Another aldosterone-induced protein, CNK3 (connector enhancer of kinase suppressor of Ras 3), also stimulates ENaC and has all of the features of a scaffolding protein. With these observations in mind, we discuss the possibility that CNK3 coordinates the dynamic assembly of the ENaC-regulatory-complex, and promotes context-appropriate aldosterone signal transduction in the regulation of epithelial Na(+) transport.
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Affiliation(s)
- Rama Soundararajan
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94143
| | - David Pearce
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94143
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California 94143
| | - Tim Ziera
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94143
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Arroyo JP, Lagnaz D, Ronzaud C, Vázquez N, Ko BS, Moddes L, Ruffieux-Daidié D, Hausel P, Koesters R, Yang B, Stokes JB, Hoover RS, Gamba G, Staub O. Nedd4-2 modulates renal Na+-Cl- cotransporter via the aldosterone-SGK1-Nedd4-2 pathway. J Am Soc Nephrol 2011; 22:1707-19. [PMID: 21852580 DOI: 10.1681/asn.2011020132] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Regulation of renal Na(+) transport is essential for controlling blood pressure, as well as Na(+) and K(+) homeostasis. Aldosterone stimulates Na(+) reabsorption by the Na(+)-Cl(-) cotransporter (NCC) in the distal convoluted tubule (DCT) and by the epithelial Na(+) channel (ENaC) in the late DCT, connecting tubule, and collecting duct. Aldosterone increases ENaC expression by inhibiting the channel's ubiquitylation and degradation; aldosterone promotes serum-glucocorticoid-regulated kinase SGK1-mediated phosphorylation of the ubiquitin-protein ligase Nedd4-2 on serine 328, which prevents the Nedd4-2/ENaC interaction. It is important to note that aldosterone increases NCC protein expression by an unknown post-translational mechanism. Here, we present evidence that Nedd4-2 coimmunoprecipitated with NCC and stimulated NCC ubiquitylation at the surface of transfected HEK293 cells. In Xenopus laevis oocytes, coexpression of NCC with wild-type Nedd4-2, but not its catalytically inactive mutant, strongly decreased NCC activity and surface expression. SGK1 prevented this inhibition in a kinase-dependent manner. Furthermore, deficiency of Nedd4-2 in the renal tubules of mice and in cultured mDCT(15) cells upregulated NCC. In contrast to ENaC, Nedd4-2-mediated inhibition of NCC did not require the PY-like motif of NCC. Moreover, the mutation of Nedd4-2 at either serine 328 or 222 did not affect SGK1 action, and mutation at both sites enhanced Nedd4-2 activity and abolished SGK1-dependent inhibition. Taken together, these results suggest that aldosterone modulates NCC protein expression via a pathway involving SGK1 and Nedd4-2 and provides an explanation for the well-known aldosterone-induced increase in NCC protein expression.
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Affiliation(s)
- Juan Pablo Arroyo
- Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Instituto Mexico City, Mexico
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Arroyo JP, Ronzaud C, Lagnaz D, Staub O, Gamba G. Aldosterone paradox: differential regulation of ion transport in distal nephron. Physiology (Bethesda) 2011; 26:115-23. [PMID: 21487030 DOI: 10.1152/physiol.00049.2010] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The mechanisms through which aldosterone promotes apparently opposite effects like salt reabsorption and K(+) secretion remain poorly understood. The identification, localization, and physiological analysis of ion transport systems in distal nephron have revealed an intricate network of interactions between several players, revealing the complex mechanism behind the aldosterone paradox. We review the mechanisms involved in differential regulation of ion transport that allow the fine tuning of salt and K(+) balance.
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Affiliation(s)
- Juan Pablo Arroyo
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
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McCormick JA, Ellison DH. The WNKs: atypical protein kinases with pleiotropic actions. Physiol Rev 2011; 91:177-219. [PMID: 21248166 DOI: 10.1152/physrev.00017.2010] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
WNKs are serine/threonine kinases that comprise a unique branch of the kinome. They are so-named owing to the unusual placement of an essential catalytic lysine. WNKs have now been identified in diverse organisms. In humans and other mammals, four genes encode WNKs. WNKs are widely expressed at the message level, although data on protein expression is more limited. Soon after the WNKs were identified, mutations in genes encoding WNK1 and -4 were determined to cause the human disease familial hyperkalemic hypertension (also known as pseudohypoaldosteronism II, or Gordon's Syndrome). For this reason, a major focus of investigation has been to dissect the role of WNK kinases in renal regulation of ion transport. More recently, a different mutation in WNK1 was identified as the cause of hereditary sensory and autonomic neuropathy type II, an early-onset autosomal disease of peripheral sensory nerves. Thus the WNKs represent an important family of potential targets for the treatment of human disease, and further elucidation of their physiological actions outside of the kidney and brain is necessary. In this review, we describe the gene structure and mechanisms regulating expression and activity of the WNKs. Subsequently, we outline substrates and targets of WNKs as well as effects of WNKs on cellular physiology, both in the kidney and elsewhere. Next, consequences of these effects on integrated physiological function are outlined. Finally, we discuss the known and putative pathophysiological relevance of the WNKs.
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Affiliation(s)
- James A McCormick
- Division of Nephrology and Hypertension, Oregon Health and Science University and Veterans Affairs Medical Center, Portland, Oregon 97239, USA.
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Cheng CJ, Huang CL. Activation of PI3-kinase stimulates endocytosis of ROMK via Akt1/SGK1-dependent phosphorylation of WNK1. J Am Soc Nephrol 2011; 22:460-71. [PMID: 21355052 DOI: 10.1681/asn.2010060681] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
WNK kinases stimulate endocytosis of ROMK channels to regulate renal K+ handling. Phosphatidylinositol 3-kinase (PI3K)-activating hormones, such as insulin and IGF 1, phosphorylate WNK1, but how this affects the regulation of ROMK abundance is unknown. Here, serum starvation of ROMK-transfected HEK cells led to an increase of ROMK current density; subsequent addition of insulin or IGF1 inhibited ROMK currents in a PI3K-dependent manner. Serum and insulin also increased phosphorylation of the downstream kinases Akt1 and SGK1 as well as WNK1. A biotinylation assay suggested that insulin and IGF1 inhibit ROMK by enhancing its endocytosis, a process that WNK1 may mediate. Knockdown of WNK1 with siRNA or expression of a phospho-deficient WNK1 mutant (T58A) both prevented insulin-induced inhibition of ROMK currents, suggesting that phosphorylation at Threonine-58 of WNK1 is important to mediate the inhibition of ROMK by PI3K-activating hormones or growth factors. In vitro and in vivo kinase assays supported the notion that Akt1 and SGK1 can phosphorylate WNK1 at this site, and we established that Akt1 and SGK1 synergistically inhibit ROMK through WNK1. We used dominant-negative intersectin and dynamin constructs to show that SGK1-mediated phosphorylation of WNK1 inhibits ROMK by promoting its endocytosis. Taken together, these results suggest that PI3K-activating hormones inhibit ROMK by enhancing its endocytosis via a mechanism that involves phosphorylation of WNK1 by Akt1 and SGK1.
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Affiliation(s)
- Chih-Jen Cheng
- Department of Medicine, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-8856, USA
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Soundararajan R, Wang J, Melters D, Pearce D. Glucocorticoid-induced Leucine zipper 1 stimulates the epithelial sodium channel by regulating serum- and glucocorticoid-induced kinase 1 stability and subcellular localization. J Biol Chem 2010; 285:39905-13. [PMID: 20947508 DOI: 10.1074/jbc.m110.161133] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Serum- and glucocorticoid-induced kinase 1 (SGK1) is a multifunctional protein kinase that markedly influences various cellular processes such as proliferation, apoptosis, glucose metabolism, and sodium (Na(+)) transport via the epithelial Na(+) channel, ENaC. SGK1 is a short-lived protein, which is predominantly targeted to the endoplasmic reticulum (ER) to undergo rapid proteasome-mediated degradation through the ER-associated degradation (ERAD) system. We show here that the aldosterone-induced chaperone, GILZ1 (glucocorticoid-induced leucine zipper protein-1) selectively decreases SGK1 localization to ER as well as its interaction with ER-associated E3 ubiquitin ligases, HRD1 and CHIP. GILZ1 inhibits SGK1 ubiquitinylation and subsequent proteasome-mediated degradation, thereby prolonging its half-life and increasing its steady-state expression. Furthermore, comparison of the effect of GILZ1 with that of proteasome inhibition (by MG-132) supports the idea that these effects of GILZ1 are secondary to physical interaction of GILZ1 with SGK1 and enhanced recruitment of SGK1 to targets within an "ENaC regulatory complex," thus making less SGK1 available to the ERAD machinery. Finally, effects of GILZ1 knockdown and overexpression strongly support the idea that these effects of GILZ1 are functionally important for ENaC regulation. These data provide new insight into how the manifold activities of SGK1 are selectively deployed and strengthened through modulation of its molecular interactions, subcellular localization, and stability.
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Affiliation(s)
- Rama Soundararajan
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94143, USA
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Butterworth MB. Regulation of the epithelial sodium channel (ENaC) by membrane trafficking. Biochim Biophys Acta Mol Basis Dis 2010; 1802:1166-77. [PMID: 20347969 DOI: 10.1016/j.bbadis.2010.03.010] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 03/15/2010] [Accepted: 03/20/2010] [Indexed: 02/07/2023]
Abstract
The epithelial Na(+) channel (ENaC) is a major regulator of salt and water reabsorption in a number of epithelial tissues. Abnormalities in ENaC function have been directly linked to several human disease states including Liddle syndrome, psuedohypoaldosteronism, and cystic fibrosis and may be implicated in salt-sensitive hypertension. ENaC activity in epithelial cells is regulated both by open probability and channel number. This review focuses on the regulation of ENaC in the cells of the kidney cortical collecting duct by trafficking and recycling. The trafficking of ENaC is discussed in the broader context of epithelial cell vesicle trafficking. Well-characterized pathways and protein interactions elucidated using epithelial model cells are discussed, and the known overlap with ENaC regulation is highlighted. In following the life of ENaC in CCD epithelial cells the apical delivery, internalization, recycling, and destruction of the channel will be discussed. While a number of pathways presented still need to be linked to ENaC regulation and many details of the regulation of ENaC trafficking remain to be elucidated, knowledge of these mechanisms may provide further insights into ENaC activity in normal and disease states.
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Affiliation(s)
- Michael B Butterworth
- Department Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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38
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Jia Z, Aoyagi T, Kohan DE, Yang T. mPGES-1 deletion impairs aldosterone escape and enhances sodium appetite. Am J Physiol Renal Physiol 2010; 299:F155-66. [PMID: 20335314 DOI: 10.1152/ajprenal.90702.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aldosterone (Aldo) is a major sodium-retaining hormone that reduces renal sodium excretion and also stimulates sodium appetite. In the face of excess Aldo, the sodium-retaining action of this steroid is overridden by an adaptive regulatory mechanism, a phenomenon termed Aldo escape. The underlying mechanism of this phenomenon is not well defined but appeared to involve a number of natriuretic factors such prostaglandins (PGs). Here, we investigated the role of microsomal prostaglandin E synthase-1 (mPGES-1) in the response to excess Aldo. A 14-day Aldo infusion at 0.35 mg x kg(-1) x day(-1) via an osmotic minipump in conjunction with normal salt intake did not produce obvious disturbances in fluid metabolism in WT mice as suggested by normal sodium and water balance, plasma sodium concentration, hematocrit, and body weight, despite the evidence of a transient sodium accumulation on days 1 or 2. In a sharp contrast, the 14-day Aldo treatment in mPGES-1 knockoute (KO) mice led to increased sodium and water balance, persistent reduction of hematocrit, hypernatremia, and body weight gain, all evidence of fluid retention. The escaped wild-type (WT) mice displayed a remarkable increase in urinary PGE(2) excretion in parallel with coinduction of mPGES-1 in the proximal tubules, accompanied by a remarkable, widespread downregulation of renal sodium and water transporters. The increase in urinary PGE(2) excretion together with the downregulation of renal sodium and water transporters were all significantly blocked in the KO mice. Interestingly, compared with WT controls, the KO mice exhibited consistent increases in sodium and water intake during Aldo infusion. Together, these results suggest an important role of mPGES-1 in antagonizing the sodium-retaining action of Aldo at the levels of both the central nervous system and the kidney.
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Affiliation(s)
- Zhanjun Jia
- Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah 84132, USA
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Viengchareun S, Kamenicky P, Teixeira M, Butlen D, Meduri G, Blanchard-Gutton N, Kurschat C, Lanel A, Martinerie L, Sztal-Mazer S, Blot-Chabaud M, Ferrary E, Cherradi N, Lombès M. Osmotic stress regulates mineralocorticoid receptor expression in a novel aldosterone-sensitive cortical collecting duct cell line. Mol Endocrinol 2009; 23:1948-62. [PMID: 19846540 DOI: 10.1210/me.2009-0095] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Aldosterone effects are mediated by the mineralocorticoid receptor (MR), a transcription factor highly expressed in the distal nephron. Given that MR expression level constitutes a key element controlling hormone responsiveness, there is much interest in elucidating the molecular mechanisms governing MR expression. To investigate whether hyper- or hypotonicity could affect MR abundance, we established by targeted oncogenesis a novel immortalized cortical collecting duct (CCD) cell line and examined the impact of osmotic stress on MR expression. KC3AC1 cells form domes, exhibit a high transepithelial resistance, express 11beta-hydroxysteroid dehydrogenase 2 and functional endogenous MR, which mediates aldosterone-stimulated Na(+) reabsorption through the epithelial sodium channel activation. MR expression is tightly regulated by osmotic stress. Hypertonic conditions induce expression of tonicity-responsive enhancer binding protein, an osmoregulatory transcription factor capable of binding tonicity-responsive enhancer response elements located in MR regulatory sequences. Surprisingly, hypertonicity leads to a severe reduction in MR transcript and protein levels. This is accompanied by a concomitant tonicity-induced expression of Tis11b, a mRNA-destabilizing protein that, by binding to the AU-rich sequences of the 3'-untranslated region of MR mRNA, may favor hypertonicity-dependent degradation of labile MR transcripts. In sharp contrast, hypotonicity causes a strong increase in MR transcript and protein levels. Collectively, we demonstrate for the first time that optimal adaptation of CCD cells to changes in extracellular fluid composition is accompanied by drastic modification in MR abundance via transcriptional and posttranscriptional mechanisms. Osmotic stress-regulated MR expression may represent an important molecular determinant for cell-specific MR action, most notably in renal failure, hypertension, or mineralocorticoid resistance.
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Gabor A, Leenen FHH. Mechanisms in the PVN mediating local and central sodium-induced hypertension in Wistar rats. Am J Physiol Regul Integr Comp Physiol 2008; 296:R618-30. [PMID: 19109373 DOI: 10.1152/ajpregu.90417.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sympathoexcitatory and hypertensive responses to central infusion of Na(+)-rich artificial cerebrospinal fluid (aCSF) are enhanced by aldosterone and mediated by mineralocorticoid receptors (MRs) and benzamil-blockable Na(+) influx, leading to "ouabain" release and ANG II type 1 (AT(1)) receptor stimulation. The present study evaluated the functional role of these mechanisms in the paraventricular nucleus (PVN). In conscious Wistar rats, Na(+)-rich aCSF was infused either directly into the PVN or intracerebroventricularly preceded by aldosterone and blockers. Infusion of Na(+)-rich aCSF in the PVN caused gradual increases in blood pressure (BP) and heart rate (HR). Aldosterone and a subpressor dose of ouabain in the PVN alone did not affect BP and HR but enhanced responses to Na(+). Eplerenone, benzamil, and "ouabain"-binding Fab fragments only blocked the enhancement by aldosterone, whereas losartan blocked all responses to Na(+)-rich aCSF in the PVN. Increases in BP and HR by intracerebroventricular infusion of Na(+)-rich aCSF were enhanced by aldosterone infused intracerebroventricularly, but not in the PVN. Telmisartan in the PVN again blocked all responses. In contrast, both eplerenone and benzamil in the PVN did not change the pressor responses to intracerebroventricular infusion of aldosterone and Na(+)-rich aCSF. These findings indicate that AT(1) receptors in the PVN mediate the responses to Na(+)-rich aCSF and their enhancement by aldosterone, both locally in the PVN or in the general CSF. MRs, benzamil-blockable Na(+) channels or transporters, and "ouabain" can be functionally active in the PVN, but in Wistar rats appear not to contribute to the pressor responses to short-term increases in CSF [Na(+)].
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Paradoxical mineralocorticoid receptor activation and left ventricular diastolic dysfunction under high oxidative stress conditions. J Hypertens 2008; 26:1453-62. [PMID: 18551023 DOI: 10.1097/hjh.0b013e328300a232] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Salt status plays a pivotal role in angiotensin-II-induced organ damage by regulating reactive oxygen species status, and it is reported that reactive oxygen species activate mineralocorticoid receptors. METHOD To clarify the role of reactive oxygen species-related mineralocorticoid receptor activation in angiotensin-II-induced cardiac dysfunction, we examined the effect of the following: salt status; an MR antagonist, eplerenone; and an antioxidant, tempol in angiotensin-II-loaded Sprague-Dawley rats. RESULTS Angiotensin-II/salt-loading elevated blood pressure, and neither eplerenone nor tempol antagonized the rise in blood pressure significantly. Left ventricular diastolic function was monitored by measuring peak velocity of a mitral early inflow (E), the ratio of mitral early inflow to atrial contraction related flow (E/A), deceleration time of mitral early inflow and -dP/dt, the time constant (T), and filling pressure (left ventricular end-diastolic pressure) by echocardiography or cardiac catheterization. Despite the suppressed serum aldosterone, left ventricular diastolic function was deteriorated with angiotensin II/high salt, but not affected by angiotensin II/low salt. However, angiotensin-II/salt-induced cardiac dysfunction was restored by eplerenone and tempol. Nicotinamide adenine dinucleotide phosphateoxidase-derived superoxide formation was greater in the hearts of the angiotensin II/high-salt rats than of the angiotensin II/low-salt rats. The expression of the Na(+) -H(+) exchanger isoform 1, a target of mineralocorticoid receptor activation, was significantly increased in the angiotensin II/high-salt group. Both tempol and eplerenone inhibited the angiotensin-II/salt-induced upregulation of Na(+) -H(+) exchanger isoform 1. CONCLUSION These findings demonstrate that mineralocorticoid receptor activation by oxidative stress can cause left ventricular diastolic dysfunction in a rat model of mild hypertension.
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Wang J, Knight ZA, Fiedler D, Williams O, Shokat KM, Pearce D. Activity of the p110-alpha subunit of phosphatidylinositol-3-kinase is required for activation of epithelial sodium transport. Am J Physiol Renal Physiol 2008; 295:F843-50. [PMID: 18653476 DOI: 10.1152/ajprenal.90348.2008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The pathways implicated in the control of epithelial Na(+) channel (ENaC)-dependent Na(+) transport in renal collecting duct cells share substantial parallels with those implicated in insulin-regulated glucose metabolism. Notably, both are inhibited by wortmannin and LY294002 and signal through phosphatidylinositol-3-kinase (PI3K)-dependent kinases SGK1 and Akt. The inhibitor pattern is thought to reflect dependence on PI3K activity since wortmannin and LY294002 are both effective inhibitors of this kinase. However, these inhibitors block a variety of kinases from different families and lack specificity within the PI3K family. To begin to dissect more precisely the pathways required for signaling and for control of Na(+) transport in renal collecting duct cells, we have examined the effect of a set of PI3K inhibitors, which selectively block distinct subsets of PI3K catalytic subunit isoforms. We have found that ENaC-dependent Na(+) transport was blocked by inhibitors of the p110-alpha isoform of PI3K, but not by inhibitors of p110-beta, -gamma, or -delta. Inhibitors that block Na(+) current also blocked SGK1 and Akt phosphorylation. In contrast to insulin-stimulated glucose uptake in muscle cells, p110-beta inhibition did not enhance sensitivity to p110-alpha inhibition. These data support the conclusion that ENaC-dependent Na(+) current is controlled exclusively by p110-alpha, the same isoform that is the principal mediator of insulin effects on glucose metabolism, and lacks any dependence on p110-beta. These findings further underscore the extent to which Na(+) and glucose regulation are intertwined and provide additional insight into the interconnections between diabetes and hypertension.
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Affiliation(s)
- Jian Wang
- Division of Nephrology, Department of Medicine, San Francisco General Hospital, 1001 Potrero Avenue, San Francisco, CA 94110, USA
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Fejes-Tóth G, Frindt G, Náray-Fejes-Tóth A, Palmer LG. Epithelial Na+channel activation and processing in mice lacking SGK1. Am J Physiol Renal Physiol 2008; 294:F1298-305. [DOI: 10.1152/ajprenal.00579.2007] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Amiloride-sensitive Na+channel activity was examined in the cortical collecting ducts of a mouse line (SGK1−/−) deficient in the serum- and glucocorticoid-dependent protein kinase SGK1. This activity was correlated with changes in renal Na handling and in the maturation of epithelial Na+channel (ENaC) protein. Neither SGK1−/−mice nor paired SGK1+/+animals expressed detectable channel activity, measured as amiloride-sensitive whole-cell current ( INa), under control conditions with standard chow. Administration of aldosterone (0.5 μg/h via osmotic minipump for 7 days) increased INato a similar extent in SGK1+/+(378 ± 61 pA/cell at −100 mV) and in SGK1−/−(350 ± 57 pA/cell) animals. However, the maturation of ENaC, assessed as the ratio of cleaved to full-length forms of γ-ENaC, was more pronounced in SGK+/+mice. The SGK1−/−animals exhibited a salt-wasting phenotype when kept on a low-Na diet for up to 2 days, losing significantly more Na in the urine than wild-type mice. Under these conditions, INawas enhanced more in SGK1−/−(94 ± 14 pA/cell) than in SGK+/+(23 ± 5 pA/cell) genotypes. Despite the larger currents, the ratio of cleaved to full-length γ-ENaC was lower in the knockout animals. The mice also expressed a smaller amount of Na+-Cl−cotransporter protein under Na-depleted conditions. These results indicated that SGK1 is essential for optimal processing of ENaC but is not required for activation of the channel by aldosterone.
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McCormick JA, Yang CL, Ellison DH. WNK kinases and renal sodium transport in health and disease: an integrated view. Hypertension 2008; 51:588-96. [PMID: 18212265 DOI: 10.1161/hypertensionaha.107.103788] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- James A McCormick
- Division of Nephrology and Hypertension and Heart Research Center, Department of Medicine, Oregon Health and Science University, Portland, OR 97239, USA
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Klaus F, Palmada M, Lindner R, Laufer J, Jeyaraj S, Lang F, Boehmer C. Up-regulation of hypertonicity-activated myo-inositol transporter SMIT1 by the cell volume-sensitive protein kinase SGK1. J Physiol 2008; 586:1539-47. [PMID: 18202099 DOI: 10.1113/jphysiol.2007.146191] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Mechanisms of regulatory cell volume increase following cell shrinkage include accumulation of organic osmolytes such as betaine, taurine, sorbitol, glycerophosphorylcholine (GPC) and myo-inositol. Myo-inositol is taken up by the sodium-myo-inositol-transporter SMIT1 (SLC5A3) expressed in a wide variety of cell types. Hypertonicity induces the transcription of the SMIT1 gene upon binding of the transcription factor tonicity enhancer binding protein (TonEBP) to tonicity responsive enhancers (TonE) in the SMIT1 promoter region. However, little is known about post-translational regulation of the carrier protein. In this study we show that SMIT1 is modulated by the serum- and glucocorticoid-inducible kinase SGK1, a protein genomically up-regulated by hypertonicity. As demonstrated by two-electrode voltage-clamp in the Xenopus oocyte expression system, SMIT1-mediated myo-inositol-induced currents are up-regulated by coexpression of wild type SGK1 and constitutively active (S422D)SGK1 but not by inactive (K127N)SGK1. The increase in SMIT1 activity is due to an elevated cell surface expression of the carrier while its kinetic properties remain unaffected. According to the decay of SMIT1 activity in the presence of brefeldin A, SGK1 stabilizes the SMIT1 protein in the plasma membrane. The SGK isoforms SGK2, SGK3 and the closely related protein kinase B (PKB) are similarly capable of activating SMIT1 activity. SMIT1-mediated currents are decreased by coexpression of the ubiquitin-ligase Nedd4-2, an effect counteracted by additional coexpression of SGK1. In conclusion, the present observations disclose SGK isoforms and protein kinase B as novel regulators of SMIT1 activity.
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Affiliation(s)
- F Klaus
- Physiologisches Institut der Universität Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany
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Affiliation(s)
- Friedrich C Luft
- Franz Volhard Clinic, HELIOS Kliniken Berlin, Medical Faculty of the Charité, Humboldt University, Wiltbergstrasse 50, 13125, Berlin-Buch, Germany.
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Lang F, Böhmer C, Palmada M, Seebohm G, Strutz-Seebohm N, Vallon V. (Patho)physiological significance of the serum- and glucocorticoid-inducible kinase isoforms. Physiol Rev 2006; 86:1151-78. [PMID: 17015487 DOI: 10.1152/physrev.00050.2005] [Citation(s) in RCA: 509] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The serum- and glucocorticoid-inducible kinase-1 (SGK1) is ubiquitously expressed and under genomic control by cell stress (including cell shrinkage) and hormones (including gluco- and mineralocorticoids). Similar to its isoforms SGK2 and SGK3, SGK1 is activated by insulin and growth factors via phosphatidylinositol 3-kinase and the 3-phosphoinositide-dependent kinase PDK1. SGKs activate ion channels (e.g., ENaC, TRPV5, ROMK, Kv1.3, KCNE1/KCNQ1, GluR1, GluR6), carriers (e.g., NHE3, GLUT1, SGLT1, EAAT1-5), and the Na+-K+-ATPase. They regulate the activity of enzymes (e.g., glycogen synthase kinase-3, ubiquitin ligase Nedd4-2, phosphomannose mutase-2) and transcription factors (e.g., forkhead transcription factor FKHRL1, beta-catenin, nuclear factor kappaB). SGKs participate in the regulation of transport, hormone release, neuroexcitability, cell proliferation, and apoptosis. SGK1 contributes to Na+ retention and K+ elimination of the kidney, mineralocorticoid stimulation of salt appetite, glucocorticoid stimulation of intestinal Na+/H+ exchanger and nutrient transport, insulin-dependent salt sensitivity of blood pressure and salt sensitivity of peripheral glucose uptake, memory consolidation, and cardiac repolarization. A common ( approximately 5% prevalence) SGK1 gene variant is associated with increased blood pressure and body weight. SGK1 may thus contribute to metabolic syndrome. SGK1 may further participate in tumor growth, neurodegeneration, fibrosing disease, and the sequelae of ischemia. SGK3 is required for adequate hair growth and maintenance of intestinal nutrient transport and influences locomotive behavior. In conclusion, the SGKs cover a wide variety of physiological functions and may play an active role in a multitude of pathophysiological conditions. There is little doubt that further targets will be identified that are modulated by the SGK isoforms and that further SGK-dependent in vivo physiological functions and pathophysiological conditions will be defined.
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Affiliation(s)
- Florian Lang
- Department of Physiology, University of Tuebingen, Tuebingen, Germany.
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Proctor G, Linas S. Type 2 pseudohypoaldosteronism: new insights into renal potassium, sodium, and chloride handling. Am J Kidney Dis 2006; 48:674-93. [PMID: 16997066 DOI: 10.1053/j.ajkd.2006.06.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Accepted: 06/12/2006] [Indexed: 11/11/2022]
Affiliation(s)
- Gregory Proctor
- Division of Nephrology, University of Colorado Health Sciences Center, Denver, CO, USA.
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Nielsen J, Kwon TH, Frøkiaer J, Knepper MA, Nielsen S. Maintained ENaC trafficking in aldosterone-infused rats during mineralocorticoid and glucocorticoid receptor blockade. Am J Physiol Renal Physiol 2006; 292:F382-94. [PMID: 16912064 DOI: 10.1152/ajprenal.00212.2005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aldosterone induces redistribution of epithelial sodium channel (ENaC) to the apical plasma membrane from intracellular vesicles in renal connecting tubule (CNT) and cortical collecting duct (CCD). The role of the classical mineralocorticoid receptor (MR) in ENaC trafficking is still debated. We examined whether the MR antagonist spironolactone affects ENaC regulation in the kidney cortex of aldosterone-infused rats. Aldosterone infusion for 7 days resulted in a plasma aldosterone concentration in the high physiological range (3 to 4 nM). Aldosterone infusion decreased plasma K(+) concentration compared with untreated control rats. Cotreatment with spironolactone completely blocked the aldosterone-induced decrease in plasma K(+). Immunoblotting and immunohistochemistry showed increased protein abundance of Na-K-ATPase alpha(1)-subunit and NCC in the kidney cortex, in response to aldosterone infusion that was blocked by spironolactone. In contrast, aldosterone-induced redistribution of ENaC subunits from the cytoplasm to the apical plasma membrane domain in CNT and CCD was unaffected by spironolactone. Immunoblotting of alphaENaC showed increased protein abundance in aldosterone-infused rats that was not blocked by spironolactone treatment. To exclude possible glucocorticoid receptor (GR)-mediated effects of aldosterone, we treated aldosterone-infused rats with both spironolactone and the GR antagonist RU486. Combined MR and GR blockade prevented neither ENaC trafficking nor the upregulation of alphaENaC protein abundance in aldosterone-infused rats. We provide new evidence for ENaC trafficking occurring independent of MR and GR activation in aldosterone-infused rats.
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Affiliation(s)
- Jakob Nielsen
- The Water and Salt Research Center, Institute of Anatomy, Aarhus, Denmark
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Luft FC. The serum- and glucocorticoid-induced kinase in DOCA-salt hypertension. J Mol Med (Berl) 2006; 84:709-11. [PMID: 16897073 DOI: 10.1007/s00109-006-0086-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Indexed: 10/24/2022]
Affiliation(s)
- Friedrich C Luft
- Franz Volhard Clinic, HELIOS Kliniken Berlin, Medical Faculty of the Charité, Humboldt University, Wiltbergstrasse 50, 13125, Berlin-Buch, Germany.
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