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Zhao P, Higashijima Y, Sonoda H, Morinaga R, Uema K, Oguchi A, Matsuzaki T, Ikeda M. Glucocorticoid-induced acute diuresis in rats in relation to the reduced renal expression of sodium-dependent cotransporter genes. J Pharmacol Sci 2024; 156:115-124. [PMID: 39179330 DOI: 10.1016/j.jphs.2024.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 07/17/2024] [Accepted: 07/19/2024] [Indexed: 08/26/2024] Open
Abstract
Although several studies have shown that glucocorticoids exert diuretic effects in animals and humans, the underlying mechanism responsible for the acute diuretic effect remains obscure. Here we examined the mechanism in terms of gene-expression. We observed that glucocorticoids, including dexamethasone (Dex) and prednisolone (PSL), acutely induced diuresis in rats in a dose-dependent manner. Free water clearance values were negative after Dex or PSL treatment, similar to those observed after treatment with osmotic diuretics (furosemide and acetazolamide). Dex significantly increased the urinary excretion of sodium, potassium, chloride, glucose, and inorganic phosphorus. Renal microarray analysis revealed that Dex significantly altered the renal expression of genes related to transmembrane transport activity. The mRNA levels of sodium/phosphate (NaPi-2a/Slc34a1, NaPi-2b/Slc34a2, and NaPi-2c/Slc34a3) and sodium/glucose cotransporters (Sglt2/Slc5a2) were significantly reduced in the Dex-treated kidney, being negatively correlated with the urinary excretion of their corresponding solutes. Dex did not affect renal expression of the natriuretic peptide receptor 1 (Npr1) gene, or the expression, localization, and phosphorylation of aquaporin-2 (AQP2), a water channel protein. These findings suggest that the acute diuretic effects of glucocorticoids might be mediated by reduced expression of sodium-dependent cotransporter genes.
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Affiliation(s)
- Peiyan Zhao
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Yoshiki Higashijima
- Institute for Promotion of Tenure Track, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Hiroko Sonoda
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Rio Morinaga
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Keito Uema
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Akane Oguchi
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Toshiyuki Matsuzaki
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Gunma, 371-8511, Japan
| | - Masahiro Ikeda
- Department of Veterinary Pharmacology, University of Miyazaki, Miyazaki, 889-2192, Japan.
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2
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Nickerson AJ, Sheng S, Cox NA, Szekely KG, Marciszyn AL, Lam T, Chen J, Gingras S, Kashlan OB, Kirabo A, Hughey RP, Ray EC, Kleyman TR. Loss of the alpha subunit distal furin cleavage site blunts ENaC activation following Na + restriction. J Physiol 2024; 602:4309-4326. [PMID: 39196791 DOI: 10.1113/jp286559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 07/17/2024] [Indexed: 08/30/2024] Open
Abstract
Epithelial Na+ channels (ENaCs) are activated by proteolysis of the α and γ subunits at specific sites flanking embedded inhibitory tracts. To examine the role of α subunit proteolysis in channel activation in vivo, we generated mice lacking the distal furin cleavage site in the α subunit (αF2M mice). On a normal Na+ control diet, no differences in ENaC protein abundance in kidney or distal colon were noted between wild-type (WT) and αF2M mice. Patch-clamp analyses revealed similar levels of ENaC activity in kidney tubules, while no physiologically relevant differences in blood chemistry or aldosterone levels were detected. Male αF2M mice did exhibit diminished ENaC activity in the distal colon, as measured by amiloride-sensitive short-circuit current (ISC). Following dietary Na+ restriction, WT and αF2M mice had similar natriuretic and colonic ISC responses to amiloride. However, single-channel activity was significantly lower in kidney tubules from Na+-restricted αF2M mice compared with WT littermates. ENaC α and γ subunit expression in kidney and distal colon were also enhanced in Na+-restricted αF2M vs. WT mice, in association with higher aldosterone levels. These data provide evidence that disrupting α subunit proteolysis impairs ENaC activity in vivo, requiring compensation in response to Na+ restriction. KEY POINTS: The epithelial Na+ channel (ENaC) is activated by proteolytic cleavage in vitro, but key questions regarding the role of ENaC proteolysis in terms of whole-animal physiology remain to be addressed. We studied the in vivo importance of this mechanism by generating a mouse model with a genetic disruption to a key cleavage site in the ENaC's α subunit (αF2M mice). We found that αF2M mice did not exhibit a physiologically relevant phenotype under normal dietary conditions, but have impaired ENaC activation (channel open probability) in the kidney during salt restriction. ENaC function at the organ level was preserved in salt-restricted αF2M mice, but this was associated with higher aldosterone levels and increased expression of ENaC subunits, suggesting compensation was required to maintain homeostasis. These results provide the first evidence that ENaC α subunit proteolysis is a key regulator of channel activity in vivo.
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Affiliation(s)
- Andrew J Nickerson
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Shaohu Sheng
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Natalie A Cox
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kennedy G Szekely
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Allison L Marciszyn
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Tracey Lam
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jingxin Chen
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Sebastien Gingras
- Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Ossama B Kashlan
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Annet Kirabo
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Rebecca P Hughey
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Evan C Ray
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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3
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Johnston JG, Welch AK, Cain BD, Sayeski PP, Gumz ML, Wingo CS. Aldosterone: Renal Action and Physiological Effects. Compr Physiol 2023; 13:4409-4491. [PMID: 36994769 DOI: 10.1002/cphy.c190043] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Aldosterone exerts profound effects on renal and cardiovascular physiology. In the kidney, aldosterone acts to preserve electrolyte and acid-base balance in response to changes in dietary sodium (Na+ ) or potassium (K+ ) intake. These physiological actions, principally through activation of mineralocorticoid receptors (MRs), have important effects particularly in patients with renal and cardiovascular disease as demonstrated by multiple clinical trials. Multiple factors, be they genetic, humoral, dietary, or otherwise, can play a role in influencing the rate of aldosterone synthesis and secretion from the adrenal cortex. Normally, aldosterone secretion and action respond to dietary Na+ intake. In the kidney, the distal nephron and collecting duct are the main targets of aldosterone and MR action, which stimulates Na+ absorption in part via the epithelial Na+ channel (ENaC), the principal channel responsible for the fine-tuning of Na+ balance. Our understanding of the regulatory factors that allow aldosterone, via multiple signaling pathways, to function properly clearly implicates this hormone as central to many pathophysiological effects that become dysfunctional in disease states. Numerous pathologies that affect blood pressure (BP), electrolyte balance, and overall cardiovascular health are due to abnormal secretion of aldosterone, mutations in MR, ENaC, or effectors and modulators of their action. Study of the mechanisms of these pathologies has allowed researchers and clinicians to create novel dietary and pharmacological targets to improve human health. This article covers the regulation of aldosterone synthesis and secretion, receptors, effector molecules, and signaling pathways that modulate its action in the kidney. We also consider the role of aldosterone in disease and the benefit of mineralocorticoid antagonists. © 2023 American Physiological Society. Compr Physiol 13:4409-4491, 2023.
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Affiliation(s)
- Jermaine G Johnston
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Amanda K Welch
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Brian D Cain
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
| | - Peter P Sayeski
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
| | - Michelle L Gumz
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
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Shrivastav S, Lee H, Okamoto K, Lu H, Yoshida T, Latt KZ, Wakashin H, Dalgleish JLT, Koritzinsky EH, Xu P, Asico LD, Chung JY, Hewitt S, Gildea JJ, Felder RA, Jose PA, Rosenberg AZ, Knepper MA, Kino T, Kopp JB. HIV-1 Vpr suppresses expression of the thiazide-sensitive sodium chloride co-transporter in the distal convoluted tubule. PLoS One 2022; 17:e0273313. [PMID: 36129874 PMCID: PMC9491550 DOI: 10.1371/journal.pone.0273313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 08/07/2022] [Indexed: 11/19/2022] Open
Abstract
HIV-associated nephropathy (HIVAN) impairs functions of both glomeruli and tubules. Attention has been previously focused on the HIVAN glomerulopathy. Tubular injury has drawn increased attention because sodium wasting is common in hospitalized HIV/AIDS patients. We used viral protein R (Vpr)-transgenic mice to investigate the mechanisms whereby Vpr contributes to urinary sodium wasting. In phosphoenolpyruvate carboxykinase promoter-driven Vpr-transgenic mice, in situ hybridization showed that Vpr mRNA was expressed in all nephron segments, including the distal convoluted tubule. Vpr-transgenic mice, compared with wild-type littermates, markedly increased urinary sodium excretion, despite similar plasma renin activity and aldosterone levels. Kidneys from Vpr-transgenic mice also markedly reduced protein abundance of the Na+-Cl- cotransporter (NCC), while mineralocorticoid receptor (MR) protein expression level was unchanged. In African green monkey kidney cells, Vpr abrogated the aldosterone-mediated stimulation of MR transcriptional activity. Gene expression of Slc12a3 (NCC) in Vpr-transgenic mice was significantly lower compared with wild-type mice, assessed by both qRT-PCR and RNAScope in situ hybridization analysis. Chromatin immunoprecipitation assays identified multiple MR response elements (MRE), located from 5 kb upstream of the transcription start site and extending to the third exon of the SLC12A3 gene. Mutation of MRE and SP1 sites in the SLC12A3 promoter region abrogated the transcriptional responses to aldosterone and Vpr, indicating that functional MRE and SP1 are required for the SLC12A3 gene suppression in response to Vpr. Thus, Vpr attenuates MR transcriptional activity and inhibits Slc12a3 transcription in the distal convoluted tubule and contributes to salt wasting in Vpr-transgenic mice.
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Affiliation(s)
- Shashi Shrivastav
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Hewang Lee
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC, United States of America
| | - Koji Okamoto
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Huiyan Lu
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Teruhiko Yoshida
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Khun Zaw Latt
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Hidefumi Wakashin
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - James L. T. Dalgleish
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Erik H. Koritzinsky
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
| | - Peng Xu
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Laureano D. Asico
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC, United States of America
| | - Joon-Yong Chung
- Experimental Pathology Laboratory, Laboratory of Pathology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - Stephen Hewitt
- Experimental Pathology Laboratory, Laboratory of Pathology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - John J. Gildea
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Robin A. Felder
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Pedro A. Jose
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC, United States of America
| | - Avi Z. Rosenberg
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland, United States of America
| | - Mark A. Knepper
- Epithelial Systems Biology Laboratory, Systems Biology Center, Division of Intramural Research, NHLBI, NIH, Bethesda, Maryland, United States of America
| | - Tomoshige Kino
- Laboratory for Molecular and Genomic Endocrinology, Division of Translational Medicine, Sidra Medicine, Doha, Qatar
| | - Jeffrey B. Kopp
- Kidney Disease Section, Kidney Diseases Branch, NIDDK, NIH, Bethesda, Maryland, United States of America
- * E-mail:
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5
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Frindt G, Meyerson JR, Satty A, Scandura JM, Palmer LG. Expression of ENaC subunits in epithelia. J Gen Physiol 2022; 154:213382. [PMID: 35939271 PMCID: PMC9387651 DOI: 10.1085/jgp.202213124] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 05/27/2022] [Accepted: 07/01/2022] [Indexed: 12/14/2022] Open
Abstract
The epithelial Na+ channel (ENaC) is a heterotrimeric protein whose assembly, trafficking, and function are highly regulated. To better understand the biogenesis and activation of the channel, we quantified the expression of individual subunits of ENaC in rat kidneys and colon using calibrated Western blots. The estimated abundance for the three subunits differed by an order of magnitude with the order γENaC ∼ βENaC ≫ αENaC in both organs. Transcript abundance in the kidney, measured with digital-drop PCR and RNAseq, was similar for the three subunits. In both organs, the calculated protein expression of all subunits was much larger than that required to account for maximal Na+ currents measured in these cells, implying a large excess of subunit protein. Whole-kidney biotinylation indicated that at least 5% of β and γ subunits in the kidney and 3% in the colon were expressed on the surface under conditions of salt restriction, which maximizes ENaC-dependent Na+ transport. This indicates a 10- to 100-fold excess of βENaC and γENaC subunits at the surface relative to the requirement for channel activity. We conclude that these epithelia make much more ENaC protein than is required for the physiological function of the channel. This could facilitate rapid regulation of the channels at the cell surface by insuring a large population of inactive, recruitable subunits.
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Affiliation(s)
- Gustavo Frindt
- Departments of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Joel R. Meyerson
- Departments of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Alexandra Satty
- Department of Medicine, Weill-Cornell Medical College, New York, NY
| | | | - Lawrence G. Palmer
- Departments of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY,Correspondence to Lawrence G. Palmer:
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6
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Pearce D, Manis AD, Nesterov V, Korbmacher C. Regulation of distal tubule sodium transport: mechanisms and roles in homeostasis and pathophysiology. Pflugers Arch 2022; 474:869-884. [PMID: 35895103 PMCID: PMC9338908 DOI: 10.1007/s00424-022-02732-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 07/09/2022] [Accepted: 07/11/2022] [Indexed: 02/03/2023]
Abstract
Regulated Na+ transport in the distal nephron is of fundamental importance to fluid and electrolyte homeostasis. Further upstream, Na+ is the principal driver of secondary active transport of numerous organic and inorganic solutes. In the distal nephron, Na+ continues to play a central role in controlling the body levels and concentrations of a more select group of ions, including K+, Ca++, Mg++, Cl-, and HCO3-, as well as water. Also, of paramount importance are transport mechanisms aimed at controlling the total level of Na+ itself in the body, as well as its concentrations in intracellular and extracellular compartments. Over the last several decades, the transporters involved in moving Na+ in the distal nephron, and directly or indirectly coupling its movement to that of other ions have been identified, and their interrelationships brought into focus. Just as importantly, the signaling systems and their components-kinases, ubiquitin ligases, phosphatases, transcription factors, and others-have also been identified and many of their actions elucidated. This review will touch on selected aspects of ion transport regulation, and its impact on fluid and electrolyte homeostasis. A particular focus will be on emerging evidence for site-specific regulation of the epithelial sodium channel (ENaC) and its role in both Na+ and K+ homeostasis. In this context, the critical regulatory roles of aldosterone, the mineralocorticoid receptor (MR), and the kinases SGK1 and mTORC2 will be highlighted. This includes a discussion of the newly established concept that local K+ concentrations are involved in the reciprocal regulation of Na+-Cl- cotransporter (NCC) and ENaC activity to adjust renal K+ secretion to dietary intake.
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Affiliation(s)
- David Pearce
- Department of Medicine, Division of Nephrology, and Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA USA
| | - Anna D. Manis
- Department of Medicine, Division of Nephrology, and Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA USA
| | - Viatcheslav Nesterov
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, Erlangen, Germany
| | - Christoph Korbmacher
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, Erlangen, Germany
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7
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Levanovich PE, Diaczok A, Rossi NF. Clinical and Molecular Perspectives of Monogenic Hypertension. Curr Hypertens Rev 2020; 16:91-107. [PMID: 30963979 PMCID: PMC7499356 DOI: 10.2174/1573402115666190409115330] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 04/02/2019] [Accepted: 04/04/2019] [Indexed: 12/12/2022]
Abstract
Advances in molecular research techniques have enabled a new frontier in discerning the mechanisms responsible for monogenic diseases. In this review, we discuss the current research on the molecular pathways governing blood pressure disorders with a Mendelian inheritance pattern, each presenting with a unique pathophysiology. Glucocorticoid Remediable Aldosteronism (GRA) and Apparent Mineralocorticoid Excess (AME) are caused by mutations in regulatory enzymes that induce increased production of mineralocorticoids or inhibit degradation of glucocorticoids, respectively. Geller syndrome is due to a point mutation in the hormone responsive element of the promotor for the mineralocorticoid receptor, rendering the receptor susceptible to activation by progesterone, leading to hypertension during pregnancy. Pseudohypoaldosteronism type II (PHA-II), also known as Gordon's syndrome or familial hyperkalemic hypertension, is a more variable disorder typically characterized by hypertension, high plasma potassium and metabolic acidosis. Mutations in a variety of intracellular enzymes that lead to enhanced sodium reabsorption have been identified. In contrast, hypertension in Liddle's syndrome, which results from mutations in the Epithelial sodium Channel (ENaC), is associated with low plasma potassium and metabolic alkalosis. In Liddle's syndrome, truncation of one the ENaC protein subunits removes a binding site necessary protein for ubiquitination and degradation, thereby promoting accumulation along the apical membrane and enhanced sodium reabsorption. The myriad effects due to mutation in phosphodiesterase 3A (PDE3A) lead to severe hypertension underlying sodium-independent autosomal dominant hypertension with brachydactyly. How mutations in PDE3A result in the phenotypic features of this disorder are discussed. Understanding the pathologies of these monogenic hypertensive disorders may provide insight into the causes of the more prevalent essential hypertension and new avenues to unravel the complexities of blood pressure regulation.
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Affiliation(s)
- Peter E Levanovich
- Department of Physiology, Wayne State University School of Medicine and the John D. Dingell VA Medical Center, Detroit, Michigan, MI 48201, United States
| | - Alexander Diaczok
- Department of Internal Medicine, Wayne State University School of Medicine and the John D. Dingell VA Medical Center, Detroit, Michigan, MI 48201, United States
| | - Noreen F Rossi
- Department of Physiology, Wayne State University School of Medicine and the John D. Dingell VA Medical Center, Detroit, Michigan, MI 48201, United States
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Yang L, Frindt G, Xu Y, Uchida S, Palmer LG. Aldosterone-dependent and -independent regulation of Na + and K + excretion and ENaC in mouse kidneys. Am J Physiol Renal Physiol 2020; 319:F323-F334. [PMID: 32628540 DOI: 10.1152/ajprenal.00204.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We investigated the regulation of Na+ and K+ excretion and the epithelial Na+ channel (ENaC) in mice lacking the gene for aldosterone synthase (AS) using clearance methods to assess excretion and electrophysiology and Western blot analysis to test for ENaC activity and processing. After 1 day of dietary Na+ restriction, AS-/- mice lost more Na+ in the urine than AS+/+ mice did. After 1 wk on this diet, both genotypes strongly reduced urinary Na+ excretion, but creatinine clearance decreased only in AS-/- mice. Only AS+/+ animals exhibited increased ENaC function, assessed as amiloride-sensitive whole cell currents in collecting ducts or cleavage of αENaC and γENaC in Western blots. To assess the role of aldosterone in the excretion of a K+ load, animals were fasted overnight and refed with high-K+ or low-K+ diets for 5 h. Both AS+/+ and AS-/- mice excreted a large amount of K+ during this period. In both phenotypes the excretion was benzamil sensitive, indicating increased K+ secretion coupled to ENaC-dependent Na+ reabsorption. However, the increase in plasma K+ under these conditions was much larger in AS-/- animals than in AS+/+ animals. In both groups, cleavage of αENaC and γENaC increased. However, Na+ current measured ex vivo in connecting tubules was enhanced only in AS+/+ mice. We conclude that in the absence of aldosterone, mice can conserve Na+ without ENaC activation but at the expense of diminished glomerular filtration rate. Excretion of a K+ load can be accomplished through aldosterone-independent upregulation of ENaC, but aldosterone is required to excrete the excess K+ without hyperkalemia.
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Affiliation(s)
- Lei Yang
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
| | - Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
| | - Yuanyuan Xu
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York.,Department of Cardiology, the Fourth Hospital of Harbin Medical University, Harbin, China
| | - Shinichi Uchida
- Department of Nephrology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
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9
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Sodium Imbalance in Mice Results Primarily in Compensatory Gene Regulatory Responses in Kidney and Colon, but Not in Taste Tissue. Nutrients 2020; 12:nu12040995. [PMID: 32260115 PMCID: PMC7230584 DOI: 10.3390/nu12040995] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 03/27/2020] [Accepted: 03/30/2020] [Indexed: 12/12/2022] Open
Abstract
Renal excretion and sodium appetite provide the basis for sodium homeostasis. In both the kidney and tongue, the epithelial sodium channel (ENaC) is involved in sodium uptake and sensing. The diuretic drug amiloride is known to block ENaC, producing a mild natriuresis. However, amiloride is further reported to induce salt appetite in rodents after prolonged exposure as well as bitter taste impressions in humans. To examine how dietary sodium content and amiloride impact on sodium appetite, mice were subjected to dietary salt and amiloride intervention and subsequently analyzed for ENaC expression and taste reactivity. We observed substantial changes of ENaC expression in the colon and kidney confirming the role of these tissues for sodium homeostasis, whereas effects on lingual ENaC expression and taste preferences were negligible. In comparison, prolonged exposure to amiloride-containing drinking water affected β- and αENaC expression in fungiform and posterior taste papillae, respectively, next to changes in salt taste. However, amiloride did not only change salt taste sensation but also perception of sucrose, glutamate, and citric acid, which might be explained by the fact that amiloride itself activates bitter taste receptors in mice. Accordingly, exposure to amiloride generally affects taste impression and should be evaluated with care.
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10
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Hoorn EJ, Gritter M, Cuevas CA, Fenton RA. Regulation of the Renal NaCl Cotransporter and Its Role in Potassium Homeostasis. Physiol Rev 2020; 100:321-356. [DOI: 10.1152/physrev.00044.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Daily dietary potassium (K+) intake may be as large as the extracellular K+ pool. To avoid acute hyperkalemia, rapid removal of K+ from the extracellular space is essential. This is achieved by translocating K+ into cells and increasing urinary K+ excretion. Emerging data now indicate that the renal thiazide-sensitive NaCl cotransporter (NCC) is critically involved in this homeostatic kaliuretic response. This suggests that the early distal convoluted tubule (DCT) is a K+ sensor that can modify sodium (Na+) delivery to downstream segments to promote or limit K+ secretion. K+ sensing is mediated by the basolateral K+ channels Kir4.1/5.1, a capacity that the DCT likely shares with other nephron segments. Thus, next to K+-induced aldosterone secretion, K+ sensing by renal epithelial cells represents a second feedback mechanism to control K+ balance. NCC’s role in K+ homeostasis has both physiological and pathophysiological implications. During hypovolemia, NCC activation by the renin-angiotensin system stimulates Na+ reabsorption while preventing K+ secretion. Conversely, NCC inactivation by high dietary K+ intake maximizes kaliuresis and limits Na+ retention, despite high aldosterone levels. NCC activation by a low-K+ diet contributes to salt-sensitive hypertension. K+-induced natriuresis through NCC offers a novel explanation for the antihypertensive effects of a high-K+ diet. A possible role for K+ in chronic kidney disease is also emerging, as epidemiological data reveal associations between higher urinary K+ excretion and improved renal outcomes. This comprehensive review will embed these novel insights on NCC regulation into existing concepts of K+ homeostasis in health and disease.
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Affiliation(s)
- Ewout J. Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Catherina A. Cuevas
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Robert A. Fenton
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
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11
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Keppner A, Maric D, Sergi C, Ansermet C, De Bellis D, Kratschmar DV, Canonica J, Klusonova P, Fenton RA, Odermatt A, Crambert G, Hoogewijs D, Hummler E. Deletion of the serine protease CAP2/Tmprss4 leads to dysregulated renal water handling upon dietary potassium depletion. Sci Rep 2019; 9:19540. [PMID: 31863073 PMCID: PMC6925205 DOI: 10.1038/s41598-019-55995-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 12/04/2019] [Indexed: 01/09/2023] Open
Abstract
The kidney needs to adapt daily to variable dietary K+ contents via various mechanisms including diuretic, acid-base and hormonal changes that are still not fully understood. In this study, we demonstrate that following a K+-deficient diet in wildtype mice, the serine protease CAP2/Tmprss4 is upregulated in connecting tubule and cortical collecting duct and also localizes to the medulla and transitional epithelium of the papilla and minor calyx. Male CAP2/Tmprss4 knockout mice display altered water handling and urine osmolality, enhanced vasopressin response leading to upregulated adenylate cyclase 6 expression and cAMP overproduction, and subsequently greater aquaporin 2 (AQP2) and Na+-K+-2Cl− cotransporter 2 (NKCC2) expression following K+-deficient diet. Urinary acidification coincides with significantly increased H+,K+-ATPase type 2 (HKA2) mRNA and protein expression, and decreased calcium and phosphate excretion. This is accompanied by increased glucocorticoid receptor (GR) protein levels and reduced 11β-hydroxysteroid dehydrogenase 2 activity in knockout mice. Strikingly, genetic nephron-specific deletion of GR leads to the mirrored phenotype of CAP2/Tmprss4 knockouts, including increased water intake and urine output, urinary alkalinisation, downregulation of HKA2, AQP2 and NKCC2. Collectively, our data unveil a novel role of the serine protease CAP2/Tmprss4 and GR on renal water handling upon dietary K+ depletion.
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Affiliation(s)
- Anna Keppner
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,Department of Medicine/Physiology, University of Fribourg, Fribourg, Switzerland.,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland
| | - Darko Maric
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,Department of Medicine/Physiology, University of Fribourg, Fribourg, Switzerland.,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland
| | - Chloé Sergi
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Camille Ansermet
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Damien De Bellis
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,Electron Microscopy Facility, University of Lausanne, Lausanne, Switzerland.,Department of Plant Molecular Biology, University of Lausanne, Lausanne, Switzerland
| | - Denise V Kratschmar
- Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland.,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland
| | - Jérémie Canonica
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland.,Ophthalmic Hospital Jules Gonin, University of Lausanne, Lausanne, Switzerland
| | - Petra Klusonova
- Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland.,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Alex Odermatt
- Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland.,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland
| | | | - David Hoogewijs
- Department of Medicine/Physiology, University of Fribourg, Fribourg, Switzerland.,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland
| | - Edith Hummler
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland. .,National Center of Competence in Research Kidney Control of Homeostasis (NCCR Kidney.CH), University of Lausanne, Lausanne, Switzerland.
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12
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Li Q, Fung E. Multifaceted Functions of Epithelial Na + Channel in Modulating Blood Pressure. Hypertension 2019; 73:273-281. [PMID: 30580685 DOI: 10.1161/hypertensionaha.118.12330] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Qi Li
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
| | - Erik Fung
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Gerald Choa Cardiac Research Centre, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Lui Che Woo Institute of Innovative Medicine, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
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13
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The role of distal tubule and collecting duct sodium reabsorption in sunitinib-induced hypertension. J Hypertens 2019; 36:892-903. [PMID: 29283974 DOI: 10.1097/hjh.0000000000001650] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Antiangiogenic receptor tyrosine kinase inhibitors (RTKI) induce arterial hypertension which may limit their use. Renal fractional sodium excretion (FENa) is reduced in early RTKI-induced hypertension, whereas fractional lithium excretion is unaltered. Therefore, we tested the hypothesis that activated distal tubule and collecting duct sodium reabsorption contributes to RTKI-induced hypertension. METHODS Amiloride-sensitive and hydrochlorothiazide (HCTZ)-sensitive fractional sodium reabsorption (FRNa) and renal epithelial sodium channel (ENaC) as well as sodium chloride cotransporter (NCC) abundances were determined in sunitinib-treated and control rats. The antihypertensive effects of amiloride and HCTZ were investigated by radiotelemery. RESULTS After 4 days of treatment, mean arterial pressure was 20 mmHg higher, FENa was lower (0.32 ± 0.08% vs. 0.65 ± 0.14%; P < 0.05), and renal medullary-ENaC protein abundance was higher in sunitinib-treated rats than in controls. Amiloride-sensitive FRNa was 2.37 ± 0.52% in sunitinib-treated rats vs. 2.66 ± 0.44% in controls (n.s.). HCTZ increased FENa by a similar magnitude without affecting amiloride-sensitive FRNa in both groups. After 14 days of treatment, renal medullary β-ENaC protein abundance was higher in rats that received sunitinib than in controls, whereas α-ENaC, γ-ENaC, and NCC abundances were similar in both groups. Amiloride and HCTZ reduced the sunitinib-induced mean arterial pressure rise by 8 ± 3 mmHg (P < 0.05) and 12 ± 2 mmHg (P < 0.05), respectively, without additive effects when combined. CONCLUSION ENaC-dependent and thiazide-sensitive sodium-retaining mechanisms are not overactive in sunitinib-induced hypertension but ENaC blockers and in particular thiazides may be suitable for its treatment.
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14
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Sánchez-Solís CN, Cuevas-Romero E, Munoz A, Cervantes-Rodríguez M, Rodríguez-Antolín J, Nicolás-Toledo L. Morphometric changes and AQP2 expression in kidneys of young male rats exposed to chronic stress and a high-sucrose diet. Biomed Pharmacother 2018; 105:1098-1105. [PMID: 30021346 DOI: 10.1016/j.biopha.2018.06.086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 06/13/2018] [Accepted: 06/14/2018] [Indexed: 02/06/2023] Open
Abstract
OBJECTIVE Consumption of a cafeteria-like diet and chronic stress have a negative impact on kidney function and morphology in adult rats. However, the interaction between chronic restraint stress and high-sucrose diet on renal morphology in young rats is unknown. A high-sucrose diet does not modify serum glucose levels but reduces serum corticosterone levels in stressed young rats, in this way it is confusing a possible potentiate or protector effect of this diet on kidney damage induced by stress. METHODS Wistar male rats at 4 weeks of age were randomly assigned into 4 groups: control (C), stressed (St), high-sucrose diet (S30), and chronic restraint stress plus a 30% sucrose diet (St + S30). Rats were fed with a standard chow and tap water (C group) or 30% sucrose diluted in water (S30 group). Chronic restraint stress consisted of 1-h daily placement into a plastic cylinder, 5 days per week, and for 4 weeks. RESULTS Stressed rats exhibited a low number of corpuscles, glomeruli, high number of mesangial cells, major deposition of mesangial matrix and aquaporin-2 protein (AQP-2) expression, and low creatinine levels. Meanwhile, high-sucrose diet ameliorated AQP-2 expression and avoided the reduction of creatinine levels induced by chronic stress. The combination of stress and high-sucrose diet maintained similar effects on the kidney as stress alone, although it induced a greater reduction in the area of proximal tubules. CONCLUSIONS Our results show that both chronic stress and a high-sucrose diet induce histological changes, but chronic stress may generate an accelerated glomerular hypertrophy associated with functional changes before puberty.
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Affiliation(s)
| | - Estela Cuevas-Romero
- Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico
| | - Alvaro Munoz
- Centro Universitario del Norte, Universidad de Guadalajara, Jalisco, Mexico
| | | | - Jorge Rodríguez-Antolín
- Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico
| | - Leticia Nicolás-Toledo
- Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico.
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15
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Frindt G, Yang L, Bamberg K, Palmer LG. Na restriction activates epithelial Na channels in rat kidney through two mechanisms and decreases distal Na + delivery. J Physiol 2018; 596:3585-3602. [PMID: 29737520 DOI: 10.1113/jp275988] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 05/03/2018] [Indexed: 12/15/2022] Open
Abstract
KEY POINTS Dietary Na restriction, through the mineralocorticoid aldosterone, acts on epithelial Na channels via both fast (24 h) and slow (5-7 days) mechanisms in the kidney. The fast effect entails increased proteolytic processing and trafficking of channel protein to the apical membrane. It is rapidly reversible by the mineralocorticoid receptor antagonist eplerenone and is largely lost when tubules are studied ex vivo. The slow effect does not require increased processing or surface expression, is refractory to acute eplerenone treatment, and is preserved ex vivo. Both slow and fast effects contribute to Na retention in vivo. Increased Na+ reabsorption in the proximal tubule also promotes Na conservation under conditions of chronic dietary Na restriction, reducing Na+ delivery to the distal nephron. ABSTRACT Changes in the activity of the epithelial Na channel (ENaC) help to conserve extracellular fluid volume. In rats fed a low-salt diet, proteolytic processing of ENaC increased within 1 day, and was almost maximal after 3 days. The rapid increase in the abundance of cleaved αENaC and γENaC correlated with decreased urinary Na+ excretion and with increased ENaC surface expression. By contrast, ENaC activity, measured ex vivo in isolated cortical collecting ducts, increased modestly after 3 days and required 5 days to reach maximal levels. The mineralocorticoid receptor antagonist eplerenone reversed the increase in cleaved γENaC and induced natriuresis after 1 or 3 days but failed to alter either ENaC currents or Na+ excretion after 7 days of Na restriction. We conclude that Na depletion, through aldosterone, stimulates ENaC via independent fast and slow mechanisms. In vivo, amiloride-induced natriuresis increased after 1 day of Na depletion. By contrast, hydrochlorothiazide (HCTZ)-induced natriuresis decreased gradually over 7 days, consistent with increased ability of ENaC activity to compensate for decreased Na+ reabsorption in the distal convoluted tubule. Administration of amiloride and HCTZ together increased Na+ excretion less in Na-depleted compared to control animals, indicating decreased delivery of Na+ to the distal nephron when dietary Na is restricted. Measurements of creatinine and Li+ clearances indicated that increased Na reabsorption by the proximal tubules is responsible for the decreased delivery. Thus, Na conservation during chronic dietary salt restriction entails enhanced transport by both proximal and distal nephron segments.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA
| | - Lei Yang
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA
| | - Krister Bamberg
- Cardiovascular, Renal and Metabolism, Innovative Medicines and Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA
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16
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Shashikanth N, Yeruva S, Ong MLDM, Odenwald MA, Pavlyuk R, Turner JR. Epithelial Organization: The Gut and Beyond. Compr Physiol 2017; 7:1497-1518. [DOI: 10.1002/cphy.c170003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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17
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You L, Li W, Chen T, Tang D, You J, Zhang X. A retrospective analysis of postoperative hypokalemia in pituitary adenomas after transsphenoidal surgery. PeerJ 2017; 5:e3337. [PMID: 28560099 PMCID: PMC5444367 DOI: 10.7717/peerj.3337] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 04/20/2017] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Pituitary adenoma is one of the most common intracranial neoplasms, and its primary treatment is endoscopic endonasal transsphenoidal tumorectomy. Postoperative hypokalemia in these patients is a common complication, and is associated with morbidity and mortality. This study aimed to analyze the etiopathology of postoperative hypokalemia in pituitary adenomas after endoscopic transsphenoidal surgery. METHODS AND MATERIALS This retrospective study included 181 pituitary adenomas confirmed by histopathology. Unconditional logistic regression analysis was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Repeated measures ANOVA was used to analyze change in serum potassium levels at different time points. RESULTS Multiple Logistic regression analysis revealed that only ACTH-pituitary adenoma (OR = 4.92, 95% CI [1.18-20.48], P = 0.029) had a significant association with postoperative hypokalemia. Moreover, the overall mean serum potassium concentration was significantly lower in the ACTH versus the non-ACTH group (3.34 mmol/L vs. 3.79 mmol/L, P = 0.001). Postoperative hypokalemia was predominantly found in patients with ACTH-pituitary adenoma (P = 0.033). CONCLUSIONS ACTH-pituitary adenomas may be an independent factor related postoperative hypokalemia in patients despite conventional potassium supplementation in the immediate postoperative period.
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Affiliation(s)
- Lili You
- Department of Clinical Epidemiology, First Hospital of Jilin University, Changchun, China
| | - Wenpeng Li
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, China
| | - Tang Chen
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, China
| | - Dongfang Tang
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, China
| | - Jinliang You
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, China
| | - Xianfeng Zhang
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, China
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18
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Afsar B, Vaziri ND, Aslan G, Tarim K, Kanbay M. Gut hormones and gut microbiota: implications for kidney function and hypertension. ACTA ACUST UNITED AC 2016; 10:954-961. [PMID: 27865823 DOI: 10.1016/j.jash.2016.10.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 10/25/2016] [Indexed: 02/07/2023]
Abstract
Increased blood pressure (BP) and chronic kidney disease are two leading risk factors for cardiovascular disease. Increased sodium intake is one of the most important risk factors for development of hypertension. Recent data have shown that gut influences kidney function and BP by variety of mechanisms. Various hormones and peptides secreted from gut such as gastrin, glucocorticoids, Glucagon-like peptide-1 impact on kidney function and BP especially influencing sodium absorption from gut. These findings stimulate scientist to find new therapeutic options such as tenapanor for treatment of hypertension by blocking sodium absorption from gut. The gastrointestinal tract is also occupied by a huge community of microbes (microbiome) that under normal condition has a symbiotic relationship with the host. Alterations in the structure and function of the gut microbiota have been shown to play a key role in the pathogenesis and complications of numerous diseases including hypertension. Based on these data, in this review, we provide a summary of the available data on the role of gut and gut microbiota in regulation of BP and kidney function.
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Affiliation(s)
- Baris Afsar
- Division of Nephrology, Department of Medicine, Konya Numune State Hospital, Konya, Turkey
| | - Nosratola D Vaziri
- Division of Nephrology and Hypertension, Department of Medicine, Schools of Medicine and Biological Science, University of California, Irvine, CA, USA
| | - Gamze Aslan
- Department of Cardiology, Koc University School of Medicine, Istanbul, Turkey
| | - Kayhan Tarim
- Department of Medicine, Koc University School of Medicine, Istanbul, Turkey
| | - Mehmet Kanbay
- Division of Nephrology, Department of Medicine, Koc University School of Medicine, Istanbul, Turkey.
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19
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Yang L, Frindt G, Lang F, Kuhl D, Vallon V, Palmer LG. SGK1-dependent ENaC processing and trafficking in mice with high dietary K intake and elevated aldosterone. Am J Physiol Renal Physiol 2016; 312:F65-F76. [PMID: 27413200 DOI: 10.1152/ajprenal.00257.2016] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 07/06/2016] [Indexed: 02/04/2023] Open
Abstract
We examined renal Na and K transporters in mice with deletions in the gene encoding the aldosterone-induced protein SGK1. The knockout mice were hyperkalemic, and had altered expression of the subunits of the epithelial Na channel (ENaC). The kidneys showed decreased expression of the cleaved forms of the γENaC subunit, and the fully glycosylated form of the βENaC subunits when animals were fed a high-K diet. Knockout animals treated with exogenous aldosterone also had reduced subunit processing and diminished surface expression of βENaC and γENaC. Expression of the three upstream Na transporters NHE3, NKCC2, and NCC was reduced in both wild-type and knockout mice in response to K loading. The activity of ENaC measured as whole cell amiloride-sensitive current (INa) in principal cells of the cortical collecting duct (CCD) was minimal under control conditions but was increased by a high-K diet to a similar extent in knockout and wild-type animals. INa in the connecting tubule also increased similarly in the two genotypes in response to exogenous aldosterone administration. The activities of both ROMK channels in principal cells and BK channels in intercalated cells of the CCD were unaffected by the deletion of SGK1. Acute treatment of animals with amiloride produced similar increases in Na excretion and decreases in K excretion in the two genotypes. The absence of changes in ENaC activity suggests compensation for decreased surface expression. Altered K balance in animals lacking SGK1 may reflect defects in ENaC-independent K excretion.
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Affiliation(s)
- Lei Yang
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York.,Department of Physiology, Harbin Medical University, Harbin, China
| | - Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
| | - Florian Lang
- Department of Cardiology, Vascular Medicine and Physiology, University of Tübingen, Tübingen, Germany
| | - Dietmar Kuhl
- Institute for Molecular and Cellular Cognition, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; and
| | - Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York;
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20
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Frindt G, Gravotta D, Palmer LG. Regulation of ENaC trafficking in rat kidney. ACTA ACUST UNITED AC 2016; 147:217-27. [PMID: 26880754 PMCID: PMC4772376 DOI: 10.1085/jgp.201511533] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 01/11/2016] [Indexed: 12/16/2022]
Abstract
The epithelial Na channel (ENaC) forms a pathway for Na(+) reabsorption in the distal nephron, and regulation of these channels is essential for salt homeostasis. In the rat kidney, ENaC subunits reached the plasma membrane in both immature and fully processed forms, the latter defined by either endoglycosidase H-insensitive glycosylation or proteolytic cleavage. Animals adapted to a low-salt diet have increased ENaC surface expression that is specific for the mature forms of the subunit proteins and is similar (three- to fourfold) for α, β, and γENaC. Kidney membranes were fractionated using differential centrifugation, sucrose-gradient separation, and immunoabsorption. Endoplasmic reticulum membranes, isolated using an antibody against calnexin, expressed immature γENaC, and the content decreased with Na depletion. Golgi membranes, isolated with an antibody against the cis-Golgi protein GM130, expressed both immature and processed γENaC; Na depletion increased the content of processed γENaC in this fraction by 3.8-fold. An endosomal compartment isolated using an antibody against Rab11 contained both immature and processed γENaC; the content of processed subunit increased 2.4-fold with Na depletion. Finally, we assessed the content of γENaC in the late endocytic compartments indirectly using urinary exosomes. All of the γENaC in these exosomes was in the fully cleaved form, and its content increased by 4.5-fold with Na depletion. These results imply that stimulation of ENaC surface expression results at least in part from increased rates of formation of fully processed subunits in the Golgi and subsequent trafficking to the apical membrane.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics and Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Diego Gravotta
- Department of Physiology and Biophysics and Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Lawrence G Palmer
- Department of Physiology and Biophysics and Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
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21
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Christensen TH, Bailey MA, Kenyon CJ, Jensen BL, Hunter RW. Sodium homeostasis is preserved in a global 11β-hydroxysteroid dehydrogenase type 1 knockout mouse model. Exp Physiol 2015; 100:1362-78. [PMID: 26337786 DOI: 10.1113/ep085177] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Accepted: 08/27/2015] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Glucocorticoids act in the kidney to promote salt and water retention. Renal 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), by increasing local concentrations of glucocorticoids, may exert an antinatriuretic effect. We hypothesized that global deletion of 11βHSD1 in the mouse would give rise to a salt-wasting renal phenotype. What is the main finding and its importance? We subjected a mouse model of global 11βHSD1 deletion to studies of water and electrolyte balance, renal clearance, urinary steroid excretion, renin-angiotensin system activation and renal sodium transporter expression. We found no significant effects on renal sodium or water excretion. Any effect of renal 11βHSD1 on sodium homeostasis is subtle. Glucocorticoids act in the kidney to regulate glomerular haemodynamics and tubular sodium transport; the net effect favours sodium retention. 11β-Hydroxysteroid dehydrogenase type 1 (11βHSD1) is expressed in the renal tubules and the interstitial cells of the medulla, where it is likely to regenerate active glucocorticoids from inert 11-keto forms. The physiological function of renal 11βHSD1 is largely unknown. We hypothesized that loss of renal 11βHSD1 would result in salt wasting and tested this in a knockout mouse model in which 11βHSD1 was deleted in all body tissues. In balance studies, 11βHSD1 deletion had no effect on water, sodium or potassium metabolism; transition to a low-sodium diet did not reveal a natriuretic phenotype. Renal clearance studies demonstrated identical haemodynamic parameters (arterial blood pressure, renal blood flow and glomerular filtration rate) in knockout and wild-type mice, but revealed an augmented kaliuretic response to thiazides in 11βHSD1 knockout animals. There was no effect on the natriuretic response to the amiloride analogue benzamil. Urinary excretion of deoxycorticosterone was higher in 11βHSD1 knockout mice, and there was hypertrophy of cells in the zona fasciculata of the adrenal cortex. There was no difference in the activity of the renin-angiotensin and nitric oxide systems, no difference in renal histology and no difference in the abundance of key tubular transporter proteins. We conclude that any effect of 11βHSD1 on renal sodium excretion is subtle.
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Affiliation(s)
- Thorbjørn H Christensen
- University/British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK.,Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Matthew A Bailey
- University/British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
| | - Christopher J Kenyon
- University/British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
| | - Boye L Jensen
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Robert W Hunter
- University/British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
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22
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Jeggle P, Hofschröer V, Maase M, Bertog M, Kusche‐Vihrog K. Aldosterone synthase knockout mouse as a model for sodium‐induced endothelial sodium channel up‐regulation in vascular endothelium. FASEB J 2015; 30:45-53. [DOI: 10.1096/fj.14-259606] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 08/13/2015] [Indexed: 12/31/2022]
Affiliation(s)
- Pia Jeggle
- Institute of Physiology II, University of MunsterMunsterGermany
| | | | - Martina Maase
- Institute of Physiology II, University of MunsterMunsterGermany
| | - Marko Bertog
- Institut für Zelluläre und Molekulare Physiologie, Friedrich‐Alexander Universität Erlangen‐NürnbergErlangenGermany
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23
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Mordasini D, Loffing-Cueni D, Loffing J, Beatrice R, Maillard MP, Hummler E, Burnier M, Escher G, Vogt B. ENaC activity in collecting ducts modulates NCC in cirrhotic mice. Pflugers Arch 2015; 467:2529-39. [PMID: 26055235 DOI: 10.1007/s00424-015-1711-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 04/24/2015] [Accepted: 05/18/2015] [Indexed: 01/07/2023]
Abstract
Cirrhosis is a frequent and severe disease, complicated by renal sodium retention leading to ascites and oedema. A better understanding of the complex mechanisms responsible for renal sodium handling could improve clinical management of sodium retention. Our aim was to determine the importance of the amiloride-sensitive epithelial sodium channel (ENaC) in collecting ducts in compensate and decompensate cirrhosis. Bile duct ligation was performed in control mice (CTL) and collecting duct-specific αENaC knockout (KO) mice, and ascites development, aldosterone plasma concentration, urinary sodium/potassium ratio and sodium transporter expression were compared. Disruption of ENaC in collecting ducts (CDs) did not alter ascites development, urinary sodium/potassium ratio, plasma aldosterone concentrations or Na,K-ATPase abundance in CCDs. Total αENaC abundance in whole kidney increased in cirrhotic mice of both genotypes and cleaved forms of α and γ ENaC increased only in ascitic mice of both genotypes. The sodium chloride cotransporter (NCC) abundance was lower in non-ascitic KO, compared to non-ascitic CTL, and increased when ascites appeared. In ascitic mice, the lack of αENaC in CDs induced an upregulation of total ENaC and NCC and correlated with the cleavage of ENaC subunits. This revealed compensatory mechanisms which could also take place when treating the patients with diuretics. These compensatory mechanisms should be considered for future development of therapeutic strategies.
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Affiliation(s)
- David Mordasini
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland. .,Department of Clinical Research, University of Bern, Bern, Switzerland.
| | | | | | - Rohrbach Beatrice
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland.,Department of Clinical Research, University of Bern, Bern, Switzerland
| | - Marc P Maillard
- Service of Nephrology and Hypertension, CHUV, Rue du Bugnon 17, CH-1005, Lausanne, Switzerland
| | - Edith Hummler
- Department of Pharmacology and Toxicology, University of Lausanne, Rue du Bugnon 27, CH-1005, Lausanne, Switzerland
| | - Michel Burnier
- Service of Nephrology and Hypertension, CHUV, Rue du Bugnon 17, CH-1005, Lausanne, Switzerland
| | - Geneviève Escher
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland.,Department of Clinical Research, University of Bern, Bern, Switzerland
| | - Bruno Vogt
- Department of Nephrology, Hypertension and Clinical Pharmacology, Inselspital, Bern University Hospital, Bern, Switzerland.,Department of Clinical Research, University of Bern, Bern, Switzerland
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24
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Frindt G, Palmer LG. Acute effects of aldosterone on the epithelial Na channel in rat kidney. Am J Physiol Renal Physiol 2014; 308:F572-8. [PMID: 25520012 DOI: 10.1152/ajprenal.00585.2014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The acute effects of aldosterone administration on epithelial Na channels (ENaC) in rat kidney were examined using electrophysiology and immunodetection. Animals received a single injection of aldosterone (20 μg/kg body wt), which reduced Na excretion over the next 3 h. Channel activity was assessed in principal cells of cortical collecting ducts as amiloride-sensitive whole cell clamp current (INa). INa averaged 100 pA/cell, 20-30% of that reported for the same preparation under conditions of chronic stimulation. INa was negligible in control animals that did not receive hormone. The acute physiological response correlated with changes in ENaC processing and trafficking. These effects included increases in the cleaved forms of α-ENaC and γ-ENaC, assessed by Western blot, and increases in the surface expression of β-ENaC and γ-ENaC measured after surface protein biotinylation. These changes were qualitatively and quantitatively similar to those of chronic stimulation. This suggests that altered trafficking to or from the apical membrane is an early response to the hormone and that later increases in channel activity require stimulation of channels residing at the surface.
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Affiliation(s)
- Gustavo Frindt
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, New York
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25
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Kellenberger S, Schild L. International Union of Basic and Clinical Pharmacology. XCI. Structure, Function, and Pharmacology of Acid-Sensing Ion Channels and the Epithelial Na+ Channel. Pharmacol Rev 2014; 67:1-35. [DOI: 10.1124/pr.114.009225] [Citation(s) in RCA: 193] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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26
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Rossier BC. Epithelial sodium channel (ENaC) and the control of blood pressure. Curr Opin Pharmacol 2014; 15:33-46. [DOI: 10.1016/j.coph.2013.11.010] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 11/18/2013] [Accepted: 11/18/2013] [Indexed: 11/29/2022]
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27
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Hunter RW, Ivy JR, Bailey MA. Glucocorticoids and renal Na+ transport: implications for hypertension and salt sensitivity. J Physiol 2014; 592:1731-44. [PMID: 24535442 PMCID: PMC4001748 DOI: 10.1113/jphysiol.2013.267609] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The clinical manifestations of glucocorticoid excess include central obesity, hyperglycaemia, dyslipidaemia, electrolyte abnormalities and hypertension. A century on from Cushing's original case study, these cardinal features are prevalent in industrialized nations. Hypertension is the major modifiable risk factor for cardiovascular and renal disease and reflects underlying abnormalities of Na+ homeostasis. Aldosterone is a master regulator of renal Na+ transport but here we argue that glucocorticoids are also influential, particularly during moderate excess. The hypothalamic–pituitary–adrenal axis can affect renal Na+ homeostasis on multiple levels, systemically by increasing mineralocorticoid synthesis and locally by actions on both the mineralocorticoid and glucocorticoid receptors, both of which are expressed in the kidney. The kidney also expresses both of the 11β-hydroxysteroid dehydrogenase (11βHSD) enzymes. The intrarenal generation of active glucocorticoid by 11βHSD1 stimulates Na+ reabsorption; failure to downregulate the enzyme during adaption to high dietary salt causes salt-sensitive hypertension. The deactivation of glucocorticoid by 11βHSD2 underpins the regulatory dominance for Na+ transport of mineralocorticoids and defines the ‘aldosterone-sensitive distal nephron’. In summary, glucocorticoids can stimulate renal transport processes conventionally attributed to the renin–angiotensin–aldosterone system. Importantly, Na+ and volume homeostasis do not exert negative feedback on the hypothalamic–pituitary–adrenal axis. These actions are therefore clinically relevant and may contribute to the pathogenesis of hypertension in conditions associated with elevated glucocorticoid levels, such as the metabolic syndrome and chronic stress.
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Affiliation(s)
- Robert W Hunter
- University/BHF Centre for Cardiovascular Science, The Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, UK.
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28
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Warnock DG, Kusche-Vihrog K, Tarjus A, Sheng S, Oberleithner H, Kleyman TR, Jaisser F. Blood pressure and amiloride-sensitive sodium channels in vascular and renal cells. Nat Rev Nephrol 2014; 10:146-57. [PMID: 24419567 DOI: 10.1038/nrneph.2013.275] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sodium transport in the distal nephron is mediated by epithelial sodium channel activity. Proteolytic processing of external domains and inhibition with increased sodium concentrations are important regulatory features of epithelial sodium channel complexes expressed in the distal nephron. By contrast, sodium channels expressed in the vascular system are activated by increased external sodium concentrations, which results in changes in the mechanical properties and function of endothelial cells. Mechanosensitivity and shear stress affect both epithelial and vascular sodium channel activity. Guyton's hypothesis stated that blood pressure control is critically dependent on vascular tone and fluid handling by the kidney. The synergistic effects, and complementary regulation, of the epithelial and vascular systems are consistent with the Guytonian model of volume and blood pressure regulation, and probably reflect sequential evolution of the two systems. The integration of vascular tone, renal perfusion and regulation of renal sodium reabsorption is the central underpinning of the Guytonian model. In this Review, we focus on the expression and regulation of sodium channels, and we outline the emerging evidence that describes the central role of amiloride-sensitive sodium channels in the efferent (vascular) and afferent (epithelial) arms of this homeostatic system.
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Affiliation(s)
- David G Warnock
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, 1720 2nd Avenue South, Birmingham, AL 34294-0007, USA
| | - Kristina Kusche-Vihrog
- Institut für Physiologie II, Westfälische Wilhelms Universität, Robert-Koch-Straße 27, 48149 Münster, Germany
| | - Antoine Tarjus
- INSERM U872 Team 1, Centre de Recherche des Cordeliers, Université René Descartes, Université Pierre et Marie Curie, 15 rue de l'Ecole de Médecine, 75006 Paris, France
| | - Shaohu Sheng
- Renal and Electrolyte Division, Department of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA 15261, USA
| | - Hans Oberleithner
- Institut für Physiologie II, Westfälische Wilhelms Universität, Robert-Koch-Straße 27, 48149 Münster, Germany
| | - Thomas R Kleyman
- Renal and Electrolyte Division, Department of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA 15261, USA
| | - Frederic Jaisser
- INSERM U872 Team 1, Centre de Recherche des Cordeliers, Université René Descartes, Université Pierre et Marie Curie, 15 rue de l'Ecole de Médecine, 75006 Paris, France
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29
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Cruz SA, Lin CH, Chao PL, Hwang PP. Glucocorticoid receptor, but not mineralocorticoid receptor, mediates cortisol regulation of epidermal ionocyte development and ion transport in zebrafish (danio rerio). PLoS One 2013; 8:e77997. [PMID: 24205060 PMCID: PMC3812134 DOI: 10.1371/journal.pone.0077997] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 09/08/2013] [Indexed: 12/25/2022] Open
Abstract
Cortisol is the major endogenous glucocorticoid (GC) both in human and fish, mediated by corticosteroid receptors. Due to the absence of aldosterone production in teleost fish, cortisol is also traditionally accepted to function as mineralocorticoid (MC); but whether it acts through the glucocorticoid receptor (GR) or the mineralocorticoid receptor (MR) remains a subject of debate. Here, we used loss-of-function and rescue assays to determine whether cortisol affects zebrafish epidermal ionocyte development and function via the GR and/or the MR. GR knockdown morphants displayed a significant decrease in the major ionocytes, namely Na(+)-K(+)-ATPase-rich cells (NaRCs) and H(+)-ATPase-rich cells (HRCs), as well as other cells, including epidermal stem cells (ESCs), keratinocytes, and mucus cells; conversely, cell numbers were unaffected in MR knockdown morphants. In agreement, GR morphants, but not MR morphants, exhibited decreased NaRC-mediated Ca(2+) uptake and HRC-mediated H(+) secretion. Rescue via GR capped mRNA injection or exogenous cortisol incubation normalized the number of epidermal ionocytes in GR morphants. We also provide evidence for GR localization in epidermal cells. At the transcript level, GR mRNA is ubiquitously expressed in gill sections and present in both NaRCs and HRCs, supporting the knockdown and functional assay results in embryo. Altogether, we have provided solid molecular evidence that GR is indeed present on ionocytes, where it mediates the effects of cortisol on ionocyte development and function. Hence, cortisol-GR axis performs the roles of both GC and MC in zebrafish skin and gills.
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Affiliation(s)
- Shelly Abad Cruz
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan, R. O. C
| | - Chia-Hao Lin
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan, R. O. C
| | - Pei-Lin Chao
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan, R. O. C
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan, R. O. C
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30
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Kim BG, Kim JY, Kim M, Kim CH, Choi JY, Kim SH. Gene regulation by glucocorticoid in ENaC-mediated Na⁺ transport by middle ear epithelial cells. Laryngoscope 2013; 124:E27-33. [PMID: 24114932 DOI: 10.1002/lary.24397] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 08/02/2013] [Accepted: 08/19/2013] [Indexed: 11/11/2022]
Abstract
OBJECTIVES/HYPOTHESIS The epithelial sodium channel (ENaC) is a Na(+) transport channel located in the apical membrane of the human middle ear epithelium. Although ENaC-mediated sodium transport has been reported to be upregulated by dexamethasone in human middle ear epithelium, there has been no study of the downstream pathways for increased ENaC expression mediated by glucocorticoids in this tissue. We investigated the effect of dexamethasone on the expression of ENaC and glucocorticoid regulatory genes for ENaC expression in human middle ear epithelial cells (HMEECs). STUDY DESIGN In vitro investigation. METHODS Real-time RT-PCR and Western blot analysis were used to determine the expression level of ENaC and its regulatory genes in HMEECs. RESULTS The transcript and protein expression of the α-, β-, and γ-ENaC subunits were all upregulated by dexamethasone (100 nM) in HMEECs. Dexamethasone treatment also increased the transcript expression of serum/glucocorticoid-regulated kinase1 (SGK1) and neural precursor cell-expressed developmentally downregulated (Nedd) 4-2, and decreased the transcript expression of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). ENaC transcript expression was not changed after mifepristone (a glucocorticoid antagonist, 100 nM) + dexamethasone treatment when compared to the control, but increased after spironolactone (a mineralocorticoid antagonist, 100 nM) + dexamethasone treatment. CONCLUSIONS These findings indicate that dexamethasone increases the transcript and protein expression of the α-, β-, and γ-ENaC subunits via the GR-SGK1-Nedd4-2 pathway and provides insight into the molecular mechanism of the increased sodium transport mediated by ENaC with steroid treatment in HMEECs. LEVEL OF EVIDENCE N/A.
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Affiliation(s)
- Bo G Kim
- Department of Otorhinolaryngology, Yonsei University, College of Medicine, Seoul
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31
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Mamenko M, Zaika O, Prieto MC, Jensen VB, Doris PA, Navar LG, Pochynyuk O. Chronic angiotensin II infusion drives extensive aldosterone-independent epithelial Na+ channel activation. Hypertension 2013; 62:1111-1122. [PMID: 24060890 DOI: 10.1161/hypertensionaha.113.01797] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The inability of mineralocorticoid receptor (MR) blockade to reduce hypertension associated with high angiotensin (Ang) II suggests direct actions of Ang II to regulate tubular sodium reabsorption via the epithelial Na(+) channel (ENaC) in the aldosterone-sensitive distal nephron. We used freshly isolated aldosterone-sensitive distal nephron from mice to delineate the synergism and primacy between aldosterone and Ang II in controlling functional ENaC activity. Inhibition of MR specifically prevented the increased number of functionally active ENaC, but not ENaC open probability elicited by a low sodium diet. In contrast, we found no functional role of glucocorticoid receptors in the regulation of ENaC activity by dietary salt intake. Simultaneous inhibition of MR and Ang II type 1 receptors ameliorated the enhanced ENaC activity caused by low dietary salt intake and produced significantly greater natriuresis than either inhibitor alone. Chronic systemic Ang II infusion induced more than 2 times greater increase in ENaC activity than observed during dietary sodium restriction. Importantly, ENaC activity remained greatly above control levels during maximal MR inhibition. We conclude that during variations in dietary salt intake both aldosterone and Ang II contribute complementarily to the regulation of ENaC activity in the aldosterone-sensitive distal nephron. In contrast, in the setting of Ang II-dependent hypertension, ENaC activity is upregulated well above the physiological range and is not effectively suppressed by inhibition of the aldosterone-MR axis. This provides a mechanistic explanation for the resistance to MR inhibition that occurs in hypertensive subjects having elevated intrarenal Ang II levels.
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Affiliation(s)
- Mykola Mamenko
- Department of Integrative Biology and Pharmacology; The University of Texas Health Science Center at Houston, USA
| | - Oleg Zaika
- Department of Integrative Biology and Pharmacology; The University of Texas Health Science Center at Houston, USA
| | - Minolfa C Prieto
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, USA
| | - V Behrana Jensen
- Center for Laboratory Animal Medicine and Care The University of Texas Health Science Center at Houston, USA
| | - Peter A Doris
- Institute of Molecular Medicine, The University of Texas Health Science Center at Houston, USA
| | - L Gabriel Navar
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, USA
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology; The University of Texas Health Science Center at Houston, USA
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32
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Gray C, Al-Dujaili EA, Sparrow AJ, Gardiner SM, Craigon J, Welham SJ, Gardner DS. Excess maternal salt intake produces sex-specific hypertension in offspring: putative roles for kidney and gastrointestinal sodium handling. PLoS One 2013; 8:e72682. [PMID: 23991143 PMCID: PMC3749995 DOI: 10.1371/journal.pone.0072682] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 07/17/2013] [Indexed: 12/21/2022] Open
Abstract
Hypertension is common and contributes, via cardiovascular disease, towards a large proportion of adult deaths in the Western World. High salt intake leads to high blood pressure, even when occurring prior to birth – a mechanism purported to reside in altered kidney development and later function. Using a combination of in vitro and in vivo approaches we tested whether increased maternal salt intake influences fetal kidney development to render the adult individual more susceptible to salt retention and hypertension. We found that salt-loaded pregnant rat dams were hypernatraemic at day 20 gestation (147±5 vs. 128±5 mmoles/L). Increased extracellular salt impeded murine kidney development in vitro, but had little effect in vivo. Kidneys of the adult offspring had few structural or functional abnormalities, but male and female offspring were hypernatraemic (166±4 vs. 149±2 mmoles/L), with a marked increase in plasma corticosterone (e.g. male offspring; 11.9 [9.3–14.8] vs. 2.8 [2.0–8.3] nmol/L median [IQR]). Furthermore, adult male, but not female, offspring had higher mean arterial blood pressure (effect size, +16 [9–21] mm Hg; mean [95% C.I.]. With no clear indication that the kidneys of salt-exposed offspring retained more sodium per se, we conducted a preliminary investigation of their gastrointestinal electrolyte handling and found increased expression of proximal colon solute carrier family 9 (sodium/hydrogen exchanger), member 3 (SLC9A3) together with altered faecal characteristics and electrolyte handling, relative to control offspring. On the basis of these data we suggest that excess salt exposure, via maternal diet, at a vulnerable period of brain and gut development in the rat neonate lays the foundation for sustained increases in blood pressure later in life. Hence, our evidence further supports the argument that excess dietary salt should be avoided per se, particularly in the range of foods consumed by physiologically immature young.
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Affiliation(s)
- Clint Gray
- School of Veterinary Medicine and Science, University of Nottingham, Nottingham, United Kingdom
- * E-mail: (CG); (SW); (DG)
| | | | | | - Sheila M. Gardiner
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Jim Craigon
- School of Biosciences, University of Nottingham, Nottingham, United Kingdom
| | - Simon J.M. Welham
- School of Biosciences, University of Nottingham, Nottingham, United Kingdom
- * E-mail: (CG); (SW); (DG)
| | - David S. Gardner
- School of Veterinary Medicine and Science, University of Nottingham, Nottingham, United Kingdom
- * E-mail: (CG); (SW); (DG)
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Hwang PP, Chou MY. Zebrafish as an animal model to study ion homeostasis. Pflugers Arch 2013; 465:1233-47. [PMID: 23568368 PMCID: PMC3745619 DOI: 10.1007/s00424-013-1269-1] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/11/2013] [Accepted: 03/12/2013] [Indexed: 01/27/2023]
Abstract
Zebrafish (Danio rerio) possesses several advantages as an experimental organism, including the applicability of molecular tools, ease of in vivo cellular observation and functional analysis, and rapid embryonic development, making it an emerging model for the study of integrative and regulatory physiology and, in particular, the epithelial transport associated with body fluid ionic homeostasis. Zebrafish inhabits a hypotonic freshwater environment, and as such, the gills (or the skin, during embryonic stages) assume the role of the kidney in body fluid ionic homeostasis. Four types of ionocyte expressing distinct sets of transporters have been identified in these organs: H+-ATPase-rich, Na+-K+-ATPase-rich, Na+-Cl− cotransporter-expressing and K+-secreting cells; these ionocytes perform transepithelial H+ secretion/Na+ uptake/NH4+ excretion, Ca2+ uptake, Na+/Cl− uptake, and K+ secretion, respectively. Zebrafish ionocytes are analogous to various renal tubular cells, in terms of ion transporter expression and function. During embryonic development, ionocyte progenitors develop from epidermal stem cells and then differentiate into different types of ionocyte through a positive regulatory loop of Foxi3a/-3b and other transcription factors. Several hormones, including cortisol, vitamin D, stanniocalcin-1, calcitonin, and isotocin, were found to participate in the control pathways of ionic homeostasis by precisely studying the target ion transport pathways, ion transporters, or ionocytes of the hormonal actions. In conclusion, the zebrafish model not only enhances our understanding of body fluid ion homeostasis and hormonal control in fish but also informs studies on mammals and other animal species, thereby providing new insights into related fields.
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Affiliation(s)
- Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan.
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Nesterov V, Dahlmann A, Krueger B, Bertog M, Loffing J, Korbmacher C. Aldosterone-dependent and -independent regulation of the epithelial sodium channel (ENaC) in mouse distal nephron. Am J Physiol Renal Physiol 2012; 303:F1289-99. [DOI: 10.1152/ajprenal.00247.2012] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Aldosterone is thought to be the main hormone to stimulate the epithelial sodium channel (ENaC) in the aldosterone-sensitive distal nephron (ASDN) comprising the late distal convoluted tubule (DCT2), the connecting tubule (CNT) and the entire collecting duct (CD). There is immunohistochemical evidence for an axial gradient of ENaC expression along the ASDN with highest expression in the DCT2 and CNT. However, most of our knowledge about renal ENaC function stems from studies in the cortical collecting duct (CCD). Here we investigated ENaC function in the transition zone of DCT2/CNT or CNT/CCD microdissected from mice maintained on different sodium diets to vary plasma aldosterone levels. Single-channel recordings demonstrated amiloride-sensitive Na+ channels in DCT2/CNT with biophysical properties typical for ENaC previously described in CNT/CCD. In animals maintained on a standard salt diet, the average ENaC-mediated whole cell current (Δ Iami) was higher in DCT2/CNT than in CNT/CCD. A low salt diet increased Δ Iami in CNT/CCD but had little effect on Δ Iami in DCT2/CNT. To investigate whether aldosterone is necessary for ENaC activity in the DCT2/CNT, we used aldosterone synthase knockout (AS−/−) mice that lack aldosterone. In CNT/CCD of AS−/− mice, Δ Iami was lower than that in wild-type (WT) animals and was not stimulated by a low salt diet. In contrast, in DCT2/CNT of AS−/− mice, Δ Iami was similar to that in DCT2/CNT of WT animals both on a standard and on a low salt diet. We conclude that ENaC function in the DCT2/CNT is largely independent of aldosterone which is in contrast to its known aldosterone sensitivity in CNT/CCD.
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Affiliation(s)
- Viatcheslav Nesterov
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
| | - Anke Dahlmann
- Universitätsklinikum Erlangen, Medizinische Klinik 4–Nephrologie und Hypertensiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; and
| | - Bettina Krueger
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
| | - Marko Bertog
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
| | | | - Christoph Korbmacher
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
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35
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Current world literature. Curr Opin Nephrol Hypertens 2012; 21:557-66. [PMID: 22874470 DOI: 10.1097/mnh.0b013e3283574c3b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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36
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Craigie E, Evans LC, Mullins JJ, Bailey MA. Failure to downregulate the epithelial sodium channel causes salt sensitivity in Hsd11b2 heterozygote mice. Hypertension 2012; 60:684-90. [PMID: 22777941 DOI: 10.1161/hypertensionaha.112.196410] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In vivo, the enzyme 11β-hydroxysteroid dehydrogenase type 2 influences ligand access to the mineralocorticoid receptor. Ablation of the encoding gene, HSD11B2, causes the hypertensive syndrome of apparent mineralocorticoid excess. Studies in humans and experimental animals have linked reduced 11β-hydroxysteroid dehydrogenase type 2 activity and salt sensitivity of blood pressure. In the present study, renal mechanisms underpinning salt sensitivity were investigated in Hsd11b2(+/-) mice fed low-, standard-, and high-sodium diets. In wild-type mice, there was a strong correlation between dietary sodium content and fractional sodium excretion but not blood pressure. High sodium feeding abolished amiloride-sensitive sodium reabsorption, consistent with downregulation of the epithelial sodium channel. In Hsd11b2(+/-) mice, the natriuretic response to increased dietary sodium content was blunted, and epithelial sodium channel activity persisted. High-sodium diet also reduced renal blood flow and increased blood pressure in Hsd11b2(+/-) mice. Aldosterone was modulated by dietary sodium in both genotypes, and salt sensitivity in Hsd11b2(+/-) mice was associated with increased plasma corticosterone levels. Chronic administration of an epithelial sodium channel blocker or a glucocorticoid receptor antagonist prevented salt sensitivity in Hsd11b2(+/-) mice, whereas mineralocorticoid receptor blockade with spironolactone did not. This study shows that reduced 11β-hydroxysteroid dehydrogenase type 2 causes salt sensitivity of blood pressure because of impaired renal natriuretic capacity. This reflects deregulation of epithelial sodium channels and increased renal vascular resistance. The phenotype is not caused by illicit activation of mineralocorticoid receptors by glucocorticoids but by direct activation of glucocorticoid receptors.
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Affiliation(s)
- Eilidh Craigie
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, United Kingdom
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