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Abe K, Nishizawa T, Artigas P. An unusual conformation from Na +-sensitive non-gastric proton pump mutants reveals molecular mechanisms of cooperative Na +-binding. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119543. [PMID: 37482134 DOI: 10.1016/j.bbamcr.2023.119543] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 06/29/2023] [Accepted: 07/14/2023] [Indexed: 07/25/2023]
Abstract
The Na+,K+-ATPase (NKA) and non-gastric H+,K+- ATPase (ngHKA) share ~65 % sequence identity, and nearly identical catalytic cycles. These pumps alternate between inward-facing (E1) and outward-facing (E2) conformations and differ in their exported substrate (Na+ or H+) and stoichiometries (3 Na+:2 K+ or 1 H+:1 K+). We reported that structures of the NKA-mimetic ngHKA mutant K794S/A797P/W940/R949C (SPWC) with 2 K+ occluded in E2-Pi and 3 Na+-bound in E1·ATP states were nearly identical to NKA structures in equivalent states. Here we report the cryo-EM structures of K794A and K794S, two poorly-selective ngHKA mutants, under conditions to stabilize the E1·ATP state. Unexpectedly, the structures show a hybrid with both E1- and E2-like structural features. While transmembrane segments TM1-TM3 and TM4's extracellular half adopted an E2-like conformation, the rest of the protein assumed an E1 configuration. Two spherical densities, likely bound Na+, were observed at cation-binding sites I and III, without density at site II. This explains the E2-like conformation of TM4's exoplasmic half. In NKA, oxygen atoms derived from the unwound portion of TM4 coordinated Na+ at site II. Thus, the lack of Na+ at site II of K794A/S prevents the luminal portion of TM4 from taking an E1-like position. The K794A structure also suggests that incomplete coordination of Na+ at site III induces the halfway rotation of TM6, which impairs Na+-binding at the site II. Thus, our observations provide insight into the molecular mechanism of E2-E1 transition and cooperative Na+-binding in the NKA and other related cation pumps.
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Affiliation(s)
- Kazuhiro Abe
- Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya 464-8601, Japan; Cellular and Structural Physiology Institute, Nagoya University, Nagoya 464-8601, Japan; Center for One Medicine Innovative Translational Research, Gifu University Institute for Advanced Study, Japan.
| | - Tomohiro Nishizawa
- Graduate School of Medical Life Sciences, Yokohama City University, Tsurumi, Yokohama 230-0045, Japan
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA
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2
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Lasaad S, Walter C, Rafael C, Morla L, Doucet A, Picard N, Blanchard A, Fromes Y, Matot B, Crambert G, Cheval L. GDF15 mediates renal cell plasticity in response to potassium depletion in mice. Acta Physiol (Oxf) 2023; 239:e14046. [PMID: 37665159 DOI: 10.1111/apha.14046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 08/17/2023] [Accepted: 08/23/2023] [Indexed: 09/05/2023]
Abstract
OBJECTIVE To understand the mechanisms involved in the response to a low-K+ diet (LK), we investigated the role of the growth factor GDF15 and the ion pump H,K-ATPase type 2 (HKA2) in this process. METHODS Male mice of different genotypes (WT, GDF15-KO, and HKA2-KO) were fed an LK diet for different periods of time. We analyzed GDF15 levels, metabolic and physiological parameters, and the cellular composition of collecting ducts. RESULTS Mice fed an LK diet showed a 2-4-fold increase in plasma and urine GDF15 levels. Compared to WT mice, GDF15-KO mice rapidly developed hypokalemia due to impaired renal adaptation. This is related to their 1/ inability to increase the number of type A intercalated cells (AIC) and 2/ absence of upregulation of H,K-ATPase type 2 (HKA2), the two processes responsible for K+ retention. Interestingly, we showed that the GDF15-mediated proliferative effect on AIC was dependent on the ErbB2 receptor and required the presence of HKA2. Finally, renal leakage of K+ induced a reduction in muscle mass in GDF15-KO mice fed LK diet. CONCLUSIONS In this study, we showed that GDF15 and HKA2 are linked and play a central role in the response to K+ restriction by orchestrating the modification of the cellular composition of the collecting duct.
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Affiliation(s)
- Samia Lasaad
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
| | - Christine Walter
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
| | - Chloé Rafael
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
| | - Luciana Morla
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
| | - Alain Doucet
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
| | - Nicolas Picard
- Laboratory of Tissue Biology and Therapeutic Engineering, UMR 5305 CNRS, University Lyon 1, Lyon, France
| | - Anne Blanchard
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
- Assistance Publique Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Centre d'Investigation Clinique, Paris, France
| | - Yves Fromes
- NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology, Paris, France
| | - Béatrice Matot
- NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology, Paris, France
| | - Gilles Crambert
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
| | - Lydie Cheval
- Laboratoire de Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- CNRS EMR 8228 - Unité Métabolisme et Physiologie Rénale, Paris, France
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3
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Lasaad S, Crambert G. Renal K + retention in physiological circumstances: focus on adaptation of the distal nephron and cross-talk with Na + transport systems. Front Physiol 2023; 14:1264296. [PMID: 37719462 PMCID: PMC10500064 DOI: 10.3389/fphys.2023.1264296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 08/18/2023] [Indexed: 09/19/2023] Open
Abstract
Consumption of salt (NaCl) and potassium (K+) has been completely modified, switching from a rich-K+/low-NaCl diet in the hunter-gatherer population to the opposite in the modern, westernized population. The ability to conserve K+ is crucial to maintain the plasma K+ concentration in a physiological range when dietary K+ intake is decreased. Moreover, a chronic reduction in the K+ intake is correlated with an increased blood pressure, an effect worsened by a high-Na+ diet. The renal adaptation to a low-K+ diet in order to maintain the plasma K+ level in the normal range is complex and interconnected with the mechanisms of the Na+ balance. In this short review, we will recapitulate the general mechanisms allowing the plasma K+ value to remain in the normal range, when there is a necessity to retain K+ (response to low-K+ diet and adaptation to gestation), by focusing on the processes occurring in the most distal part of the nephron. We will particularly outline the mechanisms of K+ reabsorption and discuss the consequences of its absence on the Na+ transport systems and the regulation of the extracellular compartment volume and blood pressure.
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Affiliation(s)
- Samia Lasaad
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Université Paris Cité, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France
- CNRS EMR 8228—Unité Métabolisme et Physiologie Rénale, Paris, France
| | - Gilles Crambert
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Université Paris Cité, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France
- CNRS EMR 8228—Unité Métabolisme et Physiologie Rénale, Paris, France
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4
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Structure and function of H +/K + pump mutants reveal Na +/K + pump mechanisms. Nat Commun 2022; 13:5270. [PMID: 36085139 PMCID: PMC9463140 DOI: 10.1038/s41467-022-32793-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/17/2022] [Indexed: 11/09/2022] Open
Abstract
Ion-transport mechanisms evolve by changing ion-selectivity, such as switching from Na+ to H+ selectivity in secondary-active transporters or P-type-ATPases. Here we study primary-active transport via P-type ATPases using functional and structural analyses to demonstrate that four simultaneous residue substitutions transform the non-gastric H+/K+ pump, a strict H+-dependent electroneutral P-type ATPase, into a bona fide Na+-dependent electrogenic Na+/K+ pump. Conversion of a H+-dependent primary-active transporter into a Na+-dependent one provides a prototype for similar studies of ion-transport proteins. Moreover, we solve the structures of the wild-type non-gastric H+/K+ pump, a suitable drug target to treat cystic fibrosis, and of its Na+/K+ pump-mimicking mutant in two major conformations, providing insight on how Na+ binding drives a concerted mechanism leading to Na+/K+ pump phosphorylation.
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5
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Ayasse N, Berg P, Andersen JF, Svendsen SL, Sørensen MV, Fedosova NU, Lynch IJ, Wingo CS, Leipziger J. Benzamil-mediated urine alkalization is caused by the inhibition of H +-K +-ATPases. Am J Physiol Renal Physiol 2021; 320:F596-F607. [PMID: 33554781 DOI: 10.1152/ajprenal.00444.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Epithelial Na+ channel (ENaC) blockers elicit acute and substantial increases of urinary pH. The underlying mechanism remains to be understood. Here, we evaluated if benzamil-induced urine alkalization is mediated by an acute reduction in H+ secretion via renal H+-K+-ATPases (HKAs). Experiments were performed in vivo on HKA double-knockout and wild-type mice. Alterations in dietary K+ intake were used to change renal HKA and ENaC activity. The acute effects of benzamil (0.2 µg/g body wt, sufficient to block ENaC) on urine flow rate and urinary electrolyte and acid excretion were monitored in anesthetized, bladder-catheterized animals. We observed that benzamil acutely increased urinary pH (ΔpH: 0.33 ± 0.07) and reduced NH4+ and titratable acid excretion and that these effects were distinctly enhanced in animals fed a low-K+ diet (ΔpH: 0.74 ± 0.12), a condition when ENaC activity is low. In contrast, benzamil did not affect urine acid excretion in animals kept on a high-K+ diet (i.e., during high ENaC activity). Thus, urine alkalization appeared completely uncoupled from ENaC function. The absence of benzamil-induced urinary alkalization in HKA double-knockout mice confirmed the direct involvement of these enzymes. The inhibitory effect of benzamil was also shown in vitro for the pig α1-isoform of HKA. These results suggest a revised explanation of the benzamil effect on renal acid-base excretion. Considering the conditions used here, we suggest that it is caused by a direct inhibition of HKAs in the collecting duct and not by inhibition of the ENaC function.NEW & NOTEWORTHY Bolus application of epithelial Na+ channel (EnaC) blockers causes marked and acute increases of urine pH. Here, we provide evidence that the underlying mechanism involves direct inhibition of the H+-K+ pump in the collecting duct. This could provide a fundamental revision of the previously assumed mechanism that suggested a key role of ENaC inhibition in this response.
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Affiliation(s)
- Niklas Ayasse
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - Peder Berg
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | | | | | - Mads V Sørensen
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - Natalya U Fedosova
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - I Jeanette Lynch
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida, Gainesville, Florida.,North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida, Gainesville, Florida.,North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Jens Leipziger
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark.,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
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6
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Increased colonic K + excretion through inhibition of the H,K-ATPase type 2 helps reduce plasma K + level in a murine model of nephronic reduction. Sci Rep 2021; 11:1833. [PMID: 33469051 PMCID: PMC7815745 DOI: 10.1038/s41598-021-81388-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 12/21/2020] [Indexed: 11/09/2022] Open
Abstract
Hyperkalemia is frequently observed in patients at the end-stage of chronic kidney disease (CKD), and has possible harmful consequences on cardiac function. Many strategies are currently used to manage hyperkalemia, one consisting of increasing fecal K+ excretion through the administration of cation-exchange resins. In this study, we explored another more specific method of increasing intestinal K+ secretion by inhibiting the H,K-ATPase type 2 (HKA2), which is the main colonic K+ reabsorptive pathway. We hypothetised that the absence of this pump could impede the increase of plasma K+ levels following nephronic reduction (N5/6) by favoring fecal K+ secretion. In N5/6 WT and HKA2KO mice under normal K+ intake, the plasma K+ level remained within the normal range, however, a load of K+ induced strong hyperkalemia in N5/6 WT mice (9.1 ± 0.5 mM), which was significantly less pronounced in N5/6 HKA2KO mice (7.9 ± 0.4 mM, p < 0.01). This was correlated to a higher capacity of HKA2KO mice to excrete K+ in their feces. The absence of HKA2 also increased fecal Na+ excretion by inhibiting its colonic ENaC-dependent absorption. We also showed that angiotensin-converting-enzyme inhibitor like enalapril, used to treat hypertension during CKD, induced a less severe hyperkalemia in N5/6 HKA2KO than in N5/6 WT mice. This study therefore provides the proof of concept that the targeted inhibition of HKA2 could be a specific therapeutic maneuver to reduce plasma K+ levels in CKD patients.
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7
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Baratta VM, Norz V, Barahona MJ, Gisinger TM, Mulligan D, Geibel JP. Penicillin G Induces H+, K+-ATPase via a Nitric Oxide-Dependent Mechanism in the Rat Colonic Crypt. Cell Physiol Biochem 2020; 54:1132-1142. [PMID: 33175479 PMCID: PMC8095381 DOI: 10.33594/000000305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2020] [Indexed: 11/21/2022] Open
Abstract
Background/Aims: The colonic H+, K+ ATPase (HKA2) is a heterodimeric membrane protein that exchanges luminal K+ for intracellular H+ and is involved in maintaining potassium homeostasis. Under homeostatic conditions, the colonic HKA2 remains inactive, since most of the potassium is absorbed by the small intestine. In diarrheal states, potassium is secreted and compensatory potassium absorption becomes necessary. This study proposes a novel mechanism whereby the addition of penicillin G sodium salt (penG) to colonic crypts stimulates potassium uptake in the presence of intracellular nitric oxide (NO), under sodium-free (0-Na+) conditions. Methods: Sprague Dawley rat colonic crypts were isolated and pHi changes were monitored through the ammonium prepulse technique. Increased proton extrusion in 0-Na+ conditions reflected heightened H+, K+ ATPase activity. Colonic crypts were exposed to penG, L-arginine (a NO precursor), and N-nitro l-arginine methyl ester (L-NAME, a NO synthase inhibitor). Results: Isolated administration of penG significantly increased H+, K+ ATPase activity from baseline, p 0.0067. Co-administration of arginine and penG in 0-Na+ conditions further upregulated H+, K+ ATPase activity, p <0.0001. Crypt perfusion with L-NAME and penG demonstrated a significant reduction in H+, K+ ATPase activity, p 0.0058. Conclusion: Overall, acute exposure of colonic crypts to penG activates the H+, K+ ATPase in the presence of NO. This study provides new insights into colonic potassium homeostasis.
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Affiliation(s)
- Vanessa M Baratta
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA
| | - Valentina Norz
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA.,Paracelsus Medical University, School of Medicine, Salzburg, Austria
| | - Maria J Barahona
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA
| | - Teresa M Gisinger
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA.,Paracelsus Medical University, School of Medicine, Salzburg, Austria
| | - David Mulligan
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA
| | - John P Geibel
- Yale University, School of Medicine, Department of Surgery, New Haven, CT, USA, .,Yale University School of Medicine, Department of Cellular and Molecular Physiology, New Haven, CT, USA
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8
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McFarlin BE, Chen Y, Priver TS, Ralph DL, Mercado A, Gamba G, Madhur MS, McDonough AA. Coordinate adaptations of skeletal muscle and kidney to maintain extracellular [K +] during K +-deficient diet. Am J Physiol Cell Physiol 2020; 319:C757-C770. [PMID: 32845718 PMCID: PMC7654654 DOI: 10.1152/ajpcell.00362.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/17/2020] [Accepted: 08/19/2020] [Indexed: 12/16/2022]
Abstract
Extracellular fluid (ECF) potassium concentration ([K+]) is maintained by adaptations of kidney and skeletal muscle, responses heretofore studied separately. We aimed to determine how these organ systems work in concert to preserve ECF [K+] in male C57BL/6J mice fed a K+-deficient diet (0K) versus 1% K+ diet (1K) for 10 days (n = 5-6/group). During 0K feeding, plasma [K+] fell from 4.5 to 2 mM; hindlimb muscle (gastrocnemius and soleus) lost 28 mM K+ (from 115 ± 2 to 87 ± 2 mM) and gained 27 mM Na+ (from 27 ± 0.4 to 54 ± 2 mM). Doubling of muscle tissue [Na+] was not associated with inflammation, cytokine production or hypertension as reported by others. Muscle transporter adaptations in 0K- versus 1K-fed mice, assessed by immunoblot, included decreased sodium pump α2-β2 subunits, decreased K+-Cl- cotransporter isoform 3, and increased phosphorylated (p) Na+,K+,2Cl- cotransporter isoform 1 (NKCC1p), Ste20/SPS-1-related proline-alanine rich kinase (SPAKp), and oxidative stress-responsive kinase 1 (OSR1p) consistent with intracellular fluid (ICF) K+ loss and Na+ gain. Renal transporters' adaptations, effecting a 98% reduction in K+ excretion, included two- to threefold increased phosphorylated Na+-Cl- cotransporter (NCCp), SPAKp, and OSR1p abundance, limiting Na+ delivery to epithelial Na+ channels where Na+ reabsorption drives K+ secretion; and renal K sensor Kir 4.1 abundance fell 25%. Mass balance estimations indicate that over 10 days of 0K feeding, mice lose ~48 μmol K+ into the urine and muscle shifts ~47 μmol K+ from ICF to ECF, illustrating the importance of the concerted responses during K+ deficiency.
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Affiliation(s)
- Brandon E McFarlin
- Department of Physiology and Neuroscience, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Yuhan Chen
- Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
- Department of Cardiology, Nanjing University Medical School, Nanjing, China
| | - Taylor S Priver
- Department of Physiology and Neuroscience, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Donna L Ralph
- Department of Physiology and Neuroscience, Keck School of Medicine of the University of Southern California, Los Angeles, California
| | - Adriana Mercado
- Department of Nephrology, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico
| | - Gerardo Gamba
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México and Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
| | - Meena S Madhur
- Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine of the University of Southern California, Los Angeles, California
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9
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Chokeshaiusaha K, Puthier D, Sananmuang T, Olanratmanee EO, Nguyen C, Kedkovid R. Differential DNA methylation analysis across the promoter regions using methylated DNA immunoprecipitation sequencing profiling of porcine loin muscle. Vet World 2020; 13:1113-1125. [PMID: 32801562 PMCID: PMC7396332 DOI: 10.14202/vetworld.2020.1113-1125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 05/05/2020] [Indexed: 12/15/2022] Open
Abstract
Background and Aim: Pork leanness and marbling are among the essential traits of consumer preference. To acquire knowledge about universal epigenetic regulations for improving breed selection, a meta-analysis of methylated DNA immunoprecipitation sequencing (MeDIP-seq) profiling data of mixed loin muscle types was performed in this study. Materials and Methods: MeDIP-seq profiling datasets of longissimus dorsi muscle and psoas major muscles from male and female pigs of Landrace and Tibetan breeds were preprocessed and aligned to the porcine genome. Analysis of differential methylated DNA regions (DMRs) between the breeds was performed by focusing on transcription start sites (TSSs) of known genes (−20,000-3000 bases from TSS). All associated genes were further reviewed for their functions and predicted for transcription factors (TF) possibly associated with their TSSs. Results: When the methylation levels of DMRs in TSS regions of Landrace breed were compared to those of Tibetan breed, 10 DMRs were hypomethylated (Landrace < Tibetan), and 19 DMRs were hypermethylated (Landrace > Tibetan), accordingly (p≤0.001). According to the reviews about gene functions, all associated genes were pieces of evidence for their roles in a variety of muscle and lipid metabolisms. Prediction of the binding TFs revealed the six most abundant binding TFs to such DMRs-associated TSS (p≤0.0001) as follows: ZNF384, Foxd3, IRF1, KLF9, EWSR1-FLI1, HES5, and TFAP2A. Conclusion: Common DMRs-associated TSS between the lean-type and the marbled-type loin muscles were identified in this study. Interestingly, the genes associated with such regions were strongly evidenced for their possible roles on the muscle trait characteristics by which further novel research topics could be focused on them in the future.
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Affiliation(s)
- Kaj Chokeshaiusaha
- Department of Veterinary Science, Faculty of Veterinary Medicine, Rajamangala University of Technology Tawan-OK, Chon Buri, Thailand
| | - Denis Puthier
- Aix-Marseille University, INSERM UMR 1090, TAGC, Marseille, France
| | - Thanida Sananmuang
- Department of Veterinary Science, Faculty of Veterinary Medicine, Rajamangala University of Technology Tawan-OK, Chon Buri, Thailand
| | - Em-On Olanratmanee
- Department of Veterinary Science, Faculty of Veterinary Medicine, Rajamangala University of Technology Tawan-OK, Chon Buri, Thailand
| | - Catherine Nguyen
- Aix-Marseille University, INSERM UMR 1090, TAGC, Marseille, France
| | - Roongtham Kedkovid
- Department of Veterinary Medicine, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.,Swine Reproduction Research Unit, Chulalongkorn University, Bangkok, Thailand
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10
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Walter C, Rafael C, Lasaad S, Baron S, Salhi A, Crambert G. H,K-ATPase type 2 regulates gestational extracellular compartment expansion and blood pressure in mice. Am J Physiol Regul Integr Comp Physiol 2020; 318:R320-R328. [PMID: 31913688 DOI: 10.1152/ajpregu.00067.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The modifications of the hemodynamic system and hydromineral metabolism are physiological features characterizing a normal gestation. Thus, the ability to expand plasma volume without increasing the level of blood pressure is necessary for the correct perfusion of the placenta. The kidney is essential in this adaptation by reabsorbing avidly sodium and fluid. In this study, we observed that the H,K-ATPase type 2 (HKA2), an ion pump expressed in kidney and colon and already involved in the control of the K+ balance during gestation, is also required for the correct plasma volume expansion and to maintain normal blood pressure. Indeed, compared with WT pregnant mice that exhibit a 1.6-fold increase of their plasma volume, pregnant HKA2-null mice (HKA2KO) only modestly expand their extracellular volume (×1.2). The renal expression of the epithelial Na channel (ENaC) α- and γ-subunits and that of the pendrin are stimulated in gravid WT mice, whereas the Na/Cl- cotransporter (NCC) expression is downregulated. These modifications are all blunted in HKA2KO mice. This impeded renal adaptation to gestation is accompanied by the development of hypotension in the pregnant HKA2KO mice. Altogether, our results showed that the absence of the HKA2 during gestation leads to an "underfilled" situation and has established this transporter as a key player of the renal control of salt and potassium metabolism during gestation.
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Affiliation(s)
- Christine Walter
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Sorbonne Paris Cité Université, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France
| | - Chloé Rafael
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Sorbonne Paris Cité Université, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France
| | - Samia Lasaad
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Sorbonne Paris Cité Université, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France
| | - Stéphanie Baron
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Sorbonne Paris Cité Université, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France.,Hôpital Européen Georges Pompidou, Laboratoire de Physiologie, Paris, France
| | - Amel Salhi
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Sorbonne Paris Cité Université, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France
| | - Gilles Crambert
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Sorbonne Paris Cité Université, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Laboratoire de Physiologie Rénale et Tubulopathies, Paris, France
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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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Rao MC. Physiology of Electrolyte Transport in the Gut: Implications for Disease. Compr Physiol 2019; 9:947-1023. [PMID: 31187895 DOI: 10.1002/cphy.c180011] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We now have an increased understanding of the genetics, cell biology, and physiology of electrolyte transport processes in the mammalian intestine, due to the availability of sophisticated methodologies ranging from genome wide association studies to CRISPR-CAS technology, stem cell-derived organoids, 3D microscopy, electron cryomicroscopy, single cell RNA sequencing, transgenic methodologies, and tools to manipulate cellular processes at a molecular level. This knowledge has simultaneously underscored the complexity of biological systems and the interdependence of multiple regulatory systems. In addition to the plethora of mammalian neurohumoral factors and their cross talk, advances in pyrosequencing and metagenomic analyses have highlighted the relevance of the microbiome to intestinal regulation. This article provides an overview of our current understanding of electrolyte transport processes in the small and large intestine, their regulation in health and how dysregulation at multiple levels can result in disease. Intestinal electrolyte transport is a balance of ion secretory and ion absorptive processes, all exquisitely dependent on the basolateral Na+ /K+ ATPase; when this balance goes awry, it can result in diarrhea or in constipation. The key transporters involved in secretion are the apical membrane Cl- channels and the basolateral Na+ -K+ -2Cl- cotransporter, NKCC1 and K+ channels. Absorption chiefly involves apical membrane Na+ /H+ exchangers and Cl- /HCO3 - exchangers in the small intestine and proximal colon and Na+ channels in the distal colon. Key examples of our current understanding of infectious, inflammatory, and genetic diarrheal diseases and of constipation are provided. © 2019 American Physiological Society. Compr Physiol 9:947-1023, 2019.
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Affiliation(s)
- Mrinalini C Rao
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA
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13
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Cheval L, Bakouh N, Walter C, Tembely D, Morla L, Escher G, Vogt B, Crambert G, Planelles G, Doucet A. ANP-stimulated Na + secretion in the collecting duct prevents Na + retention in the renal adaptation to acid load. Am J Physiol Renal Physiol 2019; 317:F435-F443. [PMID: 31188029 DOI: 10.1152/ajprenal.00059.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have recently reported that type A intercalated cells of the collecting duct secrete Na+ by a mechanism coupling the basolateral type 1 Na+-K+-2Cl- cotransporter with apical type 2 H+-K+-ATPase (HKA2) functioning under its Na+/K+ exchange mode. The first aim of the present study was to evaluate whether this secretory pathway is a target of atrial natriuretic peptide (ANP). Despite hyperaldosteronemia, metabolic acidosis is not associated with Na+ retention. The second aim of the present study was to evaluate whether ANP-induced stimulation of Na+ secretion by type A intercalated cells might account for mineralocorticoid escape during metabolic acidosis. In Xenopus oocytes expressing HKA2, cGMP, the second messenger of ANP, increased the membrane expression, activity, and Na+-transporting rate of HKA2. Feeding mice with a NH4Cl-enriched diet increased urinary excretion of aldosterone and induced a transient Na+ retention that reversed within 3 days. At that time, expression of ANP mRNA in the collecting duct and urinary excretion of cGMP were increased. Reversion of Na+ retention was prevented by treatment with an inhibitor of ANP receptors and was absent in HKA2-null mice. In conclusion, paracrine stimulation of HKA2 by ANP is responsible for the escape of the Na+-retaining effect of aldosterone during metabolic acidosis.
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Affiliation(s)
- Lydie Cheval
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
| | - Naziha Bakouh
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
| | - Christine Walter
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
| | - Dignê Tembely
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
| | - Luciana Morla
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
| | - Geneviève Escher
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Bruno Vogt
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Gilles Crambert
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
| | - Gabrielle Planelles
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
| | - Alain Doucet
- Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Université Sorbonne Paris Cité, Université Paris Descartes, Université Paris Diderot, Paris, France.,Centre National de la Recherche Scientifique, ERL 8228, Paris, France
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14
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Yeung SMH, Vogt L, Rotmans JI, Hoorn EJ, de Borst MH. Potassium: poison or panacea in chronic kidney disease? Nephrol Dial Transplant 2018; 34:175-180. [DOI: 10.1093/ndt/gfy329] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 09/20/2018] [Indexed: 11/15/2022] Open
Affiliation(s)
- Stanley M H Yeung
- Department of Internal Medicine, Division of Nephrology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Liffert Vogt
- Department of Internal Medicine, Section of Nephrology, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Joris I Rotmans
- Department of Internal Medicine (Nephrology), Leiden University Medical Center, Leiden, The Netherlands
| | - Ewout J Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Martin H de Borst
- Department of Internal Medicine, Division of Nephrology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
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15
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Scudieri P, Musante I, Caci E, Venturini A, Morelli P, Walter C, Tosi D, Palleschi A, Martin-Vasallo P, Sermet-Gaudelus I, Planelles G, Crambert G, Galietta LJ. Increased expression of ATP12A proton pump in cystic fibrosis airways. JCI Insight 2018; 3:123616. [PMID: 30333310 DOI: 10.1172/jci.insight.123616] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 08/29/2018] [Indexed: 11/17/2022] Open
Abstract
Proton secretion mediated by ATP12A protein on the surface of the airway epithelium may contribute to cystic fibrosis (CF) lung disease by favoring bacterial infection and airway obstruction. We studied ATP12A in fresh bronchial samples and in cultured epithelial cells. In vivo, ATP12A expression was found almost exclusively at the apical side of nonciliated cells of airway epithelium and in submucosal glands, with much higher expression in CF samples. This could be due to bacterial infection and inflammation, since treating cultured cells with bacterial supernatants or with IL-4 (a cytokine that induces goblet cell hyperplasia) increased the expression of ATP12A in nonciliated cells. This observation was associated with upregulation and translocation of ATP1B1 protein from the basal to apical epithelial side, where it colocalizes with ATP12A. ATP12A function was evaluated by measuring the pH of the apical fluid in cultured epithelia. Under resting conditions, CF epithelia showed more acidic values. This abnormality was minimized by inhibiting ATP12A with ouabain. Following treatment with IL-4, ATP12A function was markedly increased, as indicated by strong acidification occurring under bicarbonate-free conditions. Our study reveals potentially novel aspects of ATP12A and remarks its importance as a possible therapeutic target in CF and other respiratory diseases.
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Affiliation(s)
- Paolo Scudieri
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli NA, Italy
| | - Ilaria Musante
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli NA, Italy
| | - Emanuela Caci
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, Italy
| | - Arianna Venturini
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli NA, Italy
| | - Patrizia Morelli
- U.O.C. Laboratorio Analisi, Istituto Giannina Gaslini, Genova, Italy
| | - Christine Walter
- CNRS ERL 8228 - Centre de Recherche des Cordeliers - Laboratoire de Métabolisme et Physiologie Rénale, Paris, France.,Sorbonne Université, UPMC Univ Paris 06, INSERM, Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, Paris, France
| | - Davide Tosi
- Thoracic Surgery and Lung Transplantation Unit, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milano, Italy
| | - Alessandro Palleschi
- Thoracic Surgery and Lung Transplantation Unit, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milano, Italy
| | - Pablo Martin-Vasallo
- UD de Bioquímica y Biología Molecular and Centro de Investigaciones Biomédicas de Canarias (CIBICAN), Universidad de La Laguna, La Laguna, Tenerife, Spain
| | | | - Gabrielle Planelles
- CNRS ERL 8228 - Centre de Recherche des Cordeliers - Laboratoire de Métabolisme et Physiologie Rénale, Paris, France.,Sorbonne Université, UPMC Univ Paris 06, INSERM, Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, Paris, France
| | - Gilles Crambert
- CNRS ERL 8228 - Centre de Recherche des Cordeliers - Laboratoire de Métabolisme et Physiologie Rénale, Paris, France.,Sorbonne Université, UPMC Univ Paris 06, INSERM, Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, Paris, France
| | - Luis Jv Galietta
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli NA, Italy
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16
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Rajendran VM, Sandle GI. Colonic Potassium Absorption and Secretion in Health and Disease. Compr Physiol 2018; 8:1513-1536. [PMID: 30215859 PMCID: PMC9769410 DOI: 10.1002/cphy.c170030] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The colon has large capacities for K+ absorption and K+ secretion, but its role in maintaining K+ homeostasis is often overlooked. For many years, passive diffusion and/or solvent drag were thought to be the primary mechanisms for K+ absorption in human and animal colon. However, it is now clear that apical H+ ,K+ -ATPase, in coordination with basolateral K+ -Cl- cotransport and/or K+ and Cl- channels operating in parallel, mediate electroneutral K+ absorption in animal colon. We now know that K+ absorption in rat colon reflects ouabain-sensitive and ouabain-insensitive apical H+ ,K+ -ATPase activities. Ouabain-insensitive and ouabain-sensitive H+ ,K+ -ATPases are localized in surface and crypt cells, respectively. Colonic H+ ,K+ -ATPase consists of α- (HKCα ) and β- (HKCβ ) subunits which, when coexpressed, exhibit ouabain-insensitive H+ ,K+ -ATPase activity in HEK293 cells, while HKCα coexpressed with the gastric β-subunit exhibits ouabain-sensitive H+ ,K+ -ATPase activity in Xenopus oocytes. Aldosterone enhances apical H+ ,K+ -ATPase activity, HKCα specific mRNA and protein expression, and K+ absorption. Active K+ secretion, on the other hand, is mediated by apical K+ channels operating in a coordinated way with the basolateral Na+ -K+ -2Cl- cotransporter. Both Ca2+ -activated intermediate conductance K+ (IK) and large conductance K+ (BK) channels are located in the apical membrane of colonic epithelia. IK channel-mediated K+ efflux provides the driving force for Cl- secretion, while BK channels mediate active (e.g., cAMP-activated) K+ secretion. BK channel expression and activity are increased in patients with end-stage renal disease and ulcerative colitis. This review summarizes the role of apical H+ ,K+ -ATPase in K+ absorption, and apical BK channel function in K+ secretion in health and disease. © 2018 American Physiological Society. Compr Physiol 8:1513-1536, 2018.
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Affiliation(s)
| | - Geoffrey I. Sandle
- Leeds Institute of Biomedical and Clinical Sciences, St James’s University Hospital, Leeds LS9 7TF, UK
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17
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Malik S, Lambert E, Zhang J, Wang T, Clark HL, Cypress M, Goldman BI, Porter GA, Pena S, Nino W, Gray DA. Potassium conservation is impaired in mice with reduced renal expression of Kir4.1. Am J Physiol Renal Physiol 2018; 315:F1271-F1282. [PMID: 30110571 DOI: 10.1152/ajprenal.00022.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To better understand the role of the inward-rectifying K channel Kir4.1 (KCNJ10) in the distal nephron, we initially studied a global Kir4.1 knockout mouse (gKO), which demonstrated the hypokalemia and hypomagnesemia seen in SeSAME/EAST syndrome and was associated with reduced Na/Cl cotransporter (NCC) expression. Lethality by ~3 wk, however, limits the usefulness of this model, so we developed a kidney-specific Kir4.1 "knockdown" mouse (ksKD) using a cadherin 16 promoter and Cre-loxP methodology. These mice appeared normal and survived to adulthood. Kir4.1 protein expression was decreased ~50% vs. wild-type (WT) mice by immunoblotting, and immunofluorescence showed moderately reduced Kir4.1 staining in distal convoluted tubule that was minimal or absent in connecting tubule and cortical collecting duct. Under control conditions, the ksKD mice showed metabolic alkalosis and relative hypercalcemia but were normokalemic and mildly hypermagnesemic despite decreased NCC expression. In addition, the mice had a severe urinary concentrating defect associated with hypernatremia, enlarged kidneys with tubulocystic dilations, and reduced aquaporin-3 expression. On a K/Mg-free diet for 1 wk, however, ksKD mice showed marked hypokalemia (serum K: 1.5 ± 0.1 vs. 3.0 ± 0.1 mEq/l for WT), which was associated with renal K wasting (transtubular K gradient: 11.4 ± 0.8 vs. 1.6 ± 0.4 in WT). Phosphorylated-NCC expression increased in WT but not ksKD mice on the K/Mg-free diet, suggesting that loss of NCC adaptation underlies the hypokalemia. In conclusion, even modest reduction in Kir4.1 expression results in impaired K conservation, which appears to be mediated by reduced expression of activated NCC.
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Affiliation(s)
- Sundeep Malik
- Department of Pharmacology and Physiology, School of Medicine, University of Rochester , Rochester, New York
| | - Emily Lambert
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Junhui Zhang
- Department of Cellular and Molecular Physiology, Yale University School of Medicine , New Haven, Connecticut
| | - Tong Wang
- Department of Cellular and Molecular Physiology, Yale University School of Medicine , New Haven, Connecticut
| | - Heather L Clark
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Michael Cypress
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Bruce I Goldman
- Pathology and Laboratory Medicine, University of Rochester , Rochester, New York
| | - George A Porter
- Cardiology Division, Department of Pediatrics, University of Rochester , Rochester, New York
| | - Salvador Pena
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Wilson Nino
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
| | - Daniel A Gray
- Nephrology Division, Department of Medicine, University of Rochester , Rochester, New York
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18
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Nakamura T, Kurihara I, Kobayashi S, Yokota K, Murai-Takeda A, Mitsuishi Y, Morisaki M, Kohata N, Oshima Y, Minami Y, Shibata H, Itoh H. Intestinal Mineralocorticoid Receptor Contributes to Epithelial Sodium Channel-Mediated Intestinal Sodium Absorption and Blood Pressure Regulation. J Am Heart Assoc 2018; 7:JAHA.117.008259. [PMID: 29929989 PMCID: PMC6064907 DOI: 10.1161/jaha.117.008259] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Background Mineralocorticoid receptor (MR) has pathological roles in various cell types, including renal tubule cells, myocytes, and smooth muscle cells; however, the role of MR in intestinal epithelial cells (IECs) has not been sufficiently evaluated. The intestine is the sensing organ of ingested sodium; accordingly, intestinal MR is expected to have essential roles in blood pressure (BP) regulation. Methods and Results We generated IEC‐specific MR knockout (IEC‐MR‐KO) mice. With a standard diet, fecal sodium excretion was 1.5‐fold higher in IEC‐MR‐KO mice, with markedly decreased colonic expression of β‐ and γ‐epithelial sodium channel, than in control mice. Urinary sodium excretion in IEC‐MR‐KO mice decreased by 30%, maintaining sodium balance; however, a low‐salt diet caused significant reductions in body weight and BP in IEC‐MR‐KO mice, and plasma aldosterone exhibited a compensatory increase. With a high‐salt diet, intestinal sodium absorption markedly increased to similar levels in both genotypes, without an elevation in BP. Deoxycorticosterone/salt treatment elevated BP and increased intestinal sodium absorption in both genotypes. Notably, the increase in BP was significantly smaller in IEC‐MR‐KO mice than in control mice. The addition of the MR antagonist spironolactone to deoxycorticosterone/salt treatment eliminated the differences in BP and intestinal sodium absorption between genotypes. Conclusions Intestinal MR regulates intestinal sodium absorption in the colon and contributes to BP regulation. These regulatory effects are associated with variation in epithelial sodium channel expression. These findings suggest that intestinal MR is a new target for studying the molecular mechanism of hypertension and cardiovascular diseases.
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Affiliation(s)
- Toshifumi Nakamura
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Isao Kurihara
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Sakiko Kobayashi
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Kenichi Yokota
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Ayano Murai-Takeda
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Yuko Mitsuishi
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Mitsuha Morisaki
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Nao Kohata
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Yosuke Oshima
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Yukiko Minami
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Hirotaka Shibata
- Department of Endocrinology, Metabolism, Rheumatology and Nephrology, Faculty of Medicine, Oita University, Oita, Japan
| | - Hiroshi Itoh
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
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19
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Han J, Lee SH, Giebisch G, Wang T. Potassium Channelopathies and Gastrointestinal Ulceration. Gut Liver 2017; 10:881-889. [PMID: 27784845 PMCID: PMC5087926 DOI: 10.5009/gnl15414] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/14/2015] [Accepted: 10/20/2015] [Indexed: 12/13/2022] Open
Abstract
Potassium channels and transporters maintain potassium homeostasis and play significant roles in several different biological actions via potassium ion regulation. In previous decades, the key revelations that potassium channels and transporters are involved in the production of gastric acid and the regulation of secretion in the stomach have been recognized. Drugs used to treat peptic ulceration are often potassium transporter inhibitors. It has also been reported that potassium channels are involved in ulcerative colitis. Direct toxicity to the intestines from nonsteroidal anti-inflammatory drugs has been associated with altered potassium channel activities. Several reports have indicated that the long-term use of the antianginal drug Nicorandil, an adenosine triphosphate-sensitive potassium channel opener, increases the chances of ulceration and perforation from the oral to anal regions throughout the gastrointestinal (GI) tract. Several of these drug features provide further insights into the role of potassium channels in the occurrence of ulceration in the GI tract. The purpose of this review is to investigate whether potassium channelopathies are involved in the mechanisms responsible for ulceration that occurs throughout the GI tract.
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Affiliation(s)
- Jaeyong Han
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
| | - Seung Hun Lee
- Department of Internal Medicine, Section of Nephrology, Yale University, New Haven, CT, USA
| | - Gerhard Giebisch
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
| | - Tong Wang
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
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McDonough AA, Youn JH. Potassium Homeostasis: The Knowns, the Unknowns, and the Health Benefits. Physiology (Bethesda) 2017; 32:100-111. [PMID: 28202621 PMCID: PMC5337831 DOI: 10.1152/physiol.00022.2016] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Potassium homeostasis has a very high priority because of its importance for membrane potential. Although extracellular K+ is only 2% of total body K+, our physiology was evolutionarily tuned for a high-K+, low-Na+ diet. We review how multiple systems interface to accomplish fine K+ balance and the consequences for health and disease.
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Affiliation(s)
- Alicia A McDonough
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
| | - Jang H Youn
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California
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21
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Turck D, Bresson JL, Burlingame B, Dean T, Fairweather-Tait S, Heinonen M, Hirsch-Ernst KI, Mangelsdorf I, McArdle H, Neuhäuser-Berthold M, Nowicka G, Pentieva K, Sanz Y, Siani A, Sjödin A, Stern M, Tomé D, Van Loveren H, Vinceti M, Willatts P, Aggett P, Martin A, Przyrembel H, Brönstrup A, Ciok J, Gómez Ruiz JÁ, de Sesmaisons-Lecarré A, Naska A. Dietary reference values for potassium. EFSA J 2016. [DOI: 10.2903/j.efsa.2016.4592] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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22
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Morla L, Doucet A, Lamouroux C, Crambert G, Edwards A. The renal cortical collecting duct: a secreting epithelium? J Physiol 2016; 594:5991-6008. [PMID: 27412964 PMCID: PMC5063930 DOI: 10.1113/jp272877] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/07/2016] [Indexed: 01/01/2023] Open
Abstract
KEY POINTS The cortical collecting duct (CCD) plays an essential role in sodium homeostasis by fine-tuning the amount of sodium that is excreted in the urine. Ex vivo, the microperfused CCD reabsorbs sodium in the absence of lumen-to-bath concentration gradients. In the present study, we show that, in the presence of physiological lumen-to-bath concentration gradients, and in the absence of endocrine, paracrine and neural regulation, the mouse CCD secretes sodium, which represents a paradigm shift. This secretion occurs via the paracellular route, as well as a transcellular pathway that is energized by apical H+ /K+ -ATPase type 2 pumps operating as Na+ /K+ exchangers. The newly identified transcellular secretory pathway represents a physiological target for the regulation of sodium handling and for anti-hypertensive therapeutic agents. ABSTRACT In vitro microperfusion experiments have demonstrated that cortical collecting ducts (CCDs) reabsorb sodium via principal and type B intercalated cells under sodium-depleted conditions and thereby contribute to sodium and blood pressure homeostasis. However, these experiments were performed in the absence of the transepithelial ion concentration gradients that prevail in vivo and determine paracellular transport. The present study aimed to characterize Na+ , K+ and Cl- fluxes in the mouse CCD in the presence of physiological transepithelial concentration gradients. For this purpose, we combined in vitro measurements of ion fluxes across microperfused CCDs of sodium-depleted mice with the predictions of a mathematical model. When NaCl transport was inhibited in all cells, CCDs secreted Na+ and reabsorbed K+ ; Cl- transport was negligible. Removing inhibitors of type A and B intercalated cells increased Na+ secretion in wild-type (WT) mice but not in H+ /K+ -ATPase type 2 (HKA2) knockout mice. Further inhibition of basolateral NaCl entry via the Na+ -K+ -2Cl- cotransporter in type A intercalated cells reduced Na+ secretion in WT mice to the levels observed in HKA2-/- mice. With no inhibitors, WT mouse CCDs still secreted Na+ and reabsorbed K+ . In vivo, HKA2-/- mice excreted less Na+ than WT mice after switching to a high-salt diet. Taken together, our results indicate that type A intercalated cells secrete Na+ via basolateral Na+ -K+ -2Cl- cotransporters in tandem with apical HKA2 pumps. They also suggest that the CCD can mediate overall Na+ secretion, and that its ability to reabsorb NaCl in vivo depends on the presence of acute regulatory factors.
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Affiliation(s)
- Luciana Morla
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, CNRS, ERL 8228, Centre de Recherche des Cordeliers, Paris, France
| | - Alain Doucet
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, CNRS, ERL 8228, Centre de Recherche des Cordeliers, Paris, France
| | - Christine Lamouroux
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, CNRS, ERL 8228, Centre de Recherche des Cordeliers, Paris, France
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23
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Walter C, Tanfous MB, Igoudjil K, Salhi A, Escher G, Crambert G. H,K-ATPase type 2 contributes to salt-sensitive hypertension induced by K(+) restriction. Pflugers Arch 2016; 468:1673-83. [PMID: 27562425 DOI: 10.1007/s00424-016-1872-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 08/15/2016] [Accepted: 08/17/2016] [Indexed: 01/24/2023]
Abstract
In industrialized countries, a large part of the population is daily exposed to low K(+) intake, a situation correlated with the development of salt-sensitive hypertension. Among many processes, adaptation to K(+)-restriction involves the stimulation of H,K-ATPase type 2 (HKA2) in the kidney and colon and, in this study, we have investigated whether HKA2 also contributes to the determination of blood pressure (BP). By using wild-type (WT) and HKA2-null mice (HKA2 KO), we showed that after 4 days of K(+) restriction, WT remain normokalemic and normotensive (112 ± 3 mmHg) whereas HKA2 KO mice exhibit hypokalemia and hypotension (104 ± 2 mmHg). The decrease of BP in HKA2 KO is due to the absence of NaCl-cotransporter (NCC) stimulation, leading to renal loss of salt and decreased extracellular volume (by 20 %). These effects are likely related to the renal resistance to vasopressin observed in HKA2 KO that may be explained, in part by the increased production of prostaglandin E2 (PGE2). In WT, the stimulation of NCC induced by K(+)-restriction is responsible for the elevation in BP when salt intake increases, an effect blunted in HKA2-null mice. The presence of an activated HKA2 is therefore required to limit the decrease in plasma [K(+)] but also contributes to the development of salt-sensitive hypertension.
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Affiliation(s)
- Christine Walter
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, Université Paris Descartes, F-75006, Paris, France.,CNRS ERL 8228 - Centre de Recherche des Cordeliers - Laboratoire de Métabolisme et Physiologie Rénale, F-75006, Paris, France
| | - Mariem Ben Tanfous
- Faculté des Sciences de Tunis El Manar, Campus Universitaire 2092, El Manar Tunis, Tunisie
| | - Katia Igoudjil
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, Université Paris Descartes, F-75006, Paris, France.,CNRS ERL 8228 - Centre de Recherche des Cordeliers - Laboratoire de Métabolisme et Physiologie Rénale, F-75006, Paris, France
| | - Amel Salhi
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, Université Paris Descartes, F-75006, Paris, France.,CNRS ERL 8228 - Centre de Recherche des Cordeliers - Laboratoire de Métabolisme et Physiologie Rénale, F-75006, Paris, France
| | - Geneviève Escher
- Departement für Nephrologie, Hypertonie und klinische Pharmakologie, Universitätsspital Bern - Inselspital, CH-3010, Bern, Switzerland
| | - Gilles Crambert
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, Université Paris Descartes, F-75006, Paris, France. .,CNRS ERL 8228 - Centre de Recherche des Cordeliers - Laboratoire de Métabolisme et Physiologie Rénale, F-75006, Paris, France.
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24
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Su G, Letcher RJ, Crump D, Farmahin R, Giesy JP, Kennedy SW. Sunlight Irradiation of Highly Brominated Polyphenyl Ethers Generates Polybenzofuran Products That Alter Dioxin-responsive mRNA Expression in Chicken Hepatocytes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:2318-2327. [PMID: 26854739 DOI: 10.1021/acs.est.5b04939] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report on two highly brominated polyphenyl ether flame retardants, tetradecabromo-1,4- diphenoxybenzene (TeDB-DiPhOBz) and 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209), that formed photolytic degradation products in tetrahydrofuran (THF)/hexane solvent after 21 days of natural sunlight irradiation (SI). These degradation products of SI-TeDB-DiPhOBz and SI-BDE-209 included the numerous polybrominated homologue groups of polybenzofurans and dibenzofurans, respectively. Formation of similar polybenzofuran and dibenzofuran products was also observed following a 3 month exposure of the solid powder forms of TeDB-DiPhOBz and BDE-209 to natural SI. These resulting degradation product mixtures were administered to chicken embryonic hepatocytes (CEH) to determine effects on mRNA expression levels of 27 dioxin-responsive genes. For the solvent-based SI study, equivalent concentrations of 1 or 25 μM of SI-TeDB-DiPhOBz or 1 or 10 μM of SI-BDE-209 resulted in gene expression profiles that were similar to those of the most potent dioxin-like compound, 2,3,7,8-tetrachlorodibenzo-p-dioxin. In addition, a concentration-dependent induction of CYP1A4 and CYP1A5 mRNA was observed following exposure to SI-TeDB-DiPhOBz and SI-BDE-209. Based on ECthreshold values for CYP1A4/5 mRNA expression, relative potency (ReP) values were 1 × 10(-6) and 1 × 10(-5) for SI-TeDB-DiPhOBz and SI-BDE-209, respectively. The SI TeDB-DiPhOBz and BDE-209 powder degradation product mixture also significantly induced CYP1A4 mRNA levels in CEH. Our findings clearly show that the environmental stability of TeDB-DiPhOBz and BDE-209, and possibly other highly brominated polyphenyl ethers, is of great concern from a dioxin-like degradation products and toxicity perspective.
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Affiliation(s)
- Guanyong Su
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada
- Department of Chemistry, Carleton University , Ottawa, Ontario K1S 5B6, Canada
| | - Robert J Letcher
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada
- Department of Chemistry, Carleton University , Ottawa, Ontario K1S 5B6, Canada
| | - Doug Crump
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada
| | - Reza Farmahin
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada
- Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa , Ottawa, Ontario K1N 6N5, Canada
| | - John P Giesy
- Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan , Saskatoon, Saskatchewan S7N 5B3, Canada
- Department of Zoology and Center for Integrative Toxicology, Michigan State University , East Lansing, Michigan 48824, United States
| | - Sean W Kennedy
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada
- Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa , Ottawa, Ontario K1N 6N5, Canada
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25
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Abstract
The H(+) concentration in human blood is kept within very narrow limits, ~40 nmol/L, despite the fact that dietary metabolism generates acid and base loads that are added to the systemic circulation throughout the life of mammals. One of the primary functions of the kidney is to maintain the constancy of systemic acid-base chemistry. The kidney has evolved the capacity to regulate blood acidity by performing three key functions: (i) reabsorb HCO3(-) that is filtered through the glomeruli to prevent its excretion in the urine; (ii) generate a sufficient quantity of new HCO3(-) to compensate for the loss of HCO3(-) resulting from dietary metabolic H(+) loads and loss of HCO3(-) in the urea cycle; and (iii) excrete HCO3(-) (or metabolizable organic anions) following a systemic base load. The ability of the kidney to perform these functions requires that various cell types throughout the nephron respond to changes in acid-base chemistry by modulating specific ion transport and/or metabolic processes in a coordinated fashion such that the urine and renal vein chemistry is altered appropriately. The purpose of the article is to provide the interested reader with a broad review of a field that began historically ~60 years ago with whole animal studies, and has evolved to where we are currently addressing questions related to kidney acid-base regulation at the single protein structure/function level.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA
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26
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Penton D, Czogalla J, Loffing J. Dietary potassium and the renal control of salt balance and blood pressure. Pflugers Arch 2015; 467:513-30. [PMID: 25559844 DOI: 10.1007/s00424-014-1673-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 12/10/2014] [Accepted: 12/11/2014] [Indexed: 01/09/2023]
Abstract
Dietary potassium (K(+)) intake has antihypertensive effects, prevents strokes, and improves cardiovascular outcomes. The underlying mechanism for these beneficial effects of high K(+) diets may include vasodilation, enhanced urine flow, reduced renal renin release, and negative sodium (Na(+)) balance. Indeed, several studies demonstrate that dietary K(+) intake induces renal Na(+) loss despite elevated plasma aldosterone. This review briefly highlights the epidemiological and experimental evidences for the effects of dietary K(+) on arterial blood pressure. It discusses the pivotal role of the renal distal tubule for the regulation of urinary K(+) and Na(+) excretion and blood pressure and highlights that it depends on the coordinated interaction of different nephron portions, epithelial cell types, and various ion channels, transporters, and ATPases. Moreover, we discuss the relevance of aldosterone and aldosterone-independent factors in mediating the effects of an altered K(+) intake on renal K(+) and Na(+) handling. Particular focus is given to findings suggesting that an aldosterone-independent downregulation of the thiazide-sensitive NaCl cotransporter significantly contributes to the natriuretic and antihypertensive effect of a K(+)-rich diet. Last but not least, we refer to the complex signaling pathways enabling the kidney to adapt its function to the homeostatic needs in response to an altered K(+) intake. Future work will have to further address the underlying cellular and molecular mechanism and to elucidate, among others, how an altered dietary K(+) intake is sensed and how this signal is transmitted to the different epithelial cells lining the distal tubule.
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Affiliation(s)
- David Penton
- Institute of Anatomy, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
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27
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Malsure S, Wang Q, Charles RP, Sergi C, Perrier R, Christensen BM, Maillard M, Rossier BC, Hummler E. Colon-specific deletion of epithelial sodium channel causes sodium loss and aldosterone resistance. J Am Soc Nephrol 2014; 25:1453-64. [PMID: 24480829 DOI: 10.1681/asn.2013090936] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Aldosterone promotes electrogenic sodium reabsorption through the amiloride-sensitive epithelial sodium channel (ENaC). Here, we investigated the importance of ENaC and its positive regulator channel-activating protease 1 (CAP1/Prss8) in colon. Mice lacking the αENaC subunit in colonic superficial cells (Scnn1a(KO)) were viable, without fetal or perinatal lethality. Control mice fed a regular or low-salt diet had a significantly higher amiloride-sensitive rectal potential difference (∆PDamil) than control mice fed a high-salt diet. In Scnn1a(KO) mice, however, this salt restriction-induced increase in ∆PDamil did not occur, and the circadian rhythm of ∆PDamil was blunted. Plasma and urinary sodium and potassium did not change with regular or high-salt diets or potassium loading in control or Scnn1a(KO) mice. However, Scnn1a(KO) mice fed a low-salt diet lost significant amounts of sodium in their feces and exhibited high plasma aldosterone and increased urinary sodium retention. Mice lacking the CAP1/Prss8 in colonic superficial cells (Prss8(KO)) were viable, without fetal or perinatal lethality. Compared with controls, Prss8(KO) mice fed regular or low-salt diets exhibited significantly reduced ∆PDamil in the afternoon, but the circadian rhythm was maintained. Prss8(KO) mice fed a low-salt diet also exhibited sodium loss through feces and higher plasma aldosterone levels. Thus, we identified CAP1/Prss8 as an in vivo regulator of ENaC in colon. We conclude that, under salt restriction, activation of the renin-angiotensin-aldosterone system in the kidney compensated for the absence of ENaC in colonic surface epithelium, leading to colon-specific pseudohypoaldosteronism type 1 with mineralocorticoid resistance without evidence of impaired potassium balance.
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Affiliation(s)
- Sumedha Malsure
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Qing Wang
- Service of Nephrology, University Hospital of Lausanne (CHUV), Lausanne, Switzerland; and Division of Physiology, Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - Roch-Philippe Charles
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Chloe Sergi
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Romain Perrier
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | | | - Marc Maillard
- Service of Nephrology, University Hospital of Lausanne (CHUV), Lausanne, Switzerland; and
| | - Bernard C Rossier
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Edith Hummler
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland;
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28
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Abstract
H-K-ATPase type 2 (HKA2), also known as the "nongastric" or "colonic" H-K-ATPase, is broadly expressed, and its presence in the kidney has puzzled experts in the field of renal ion transport systems for many years. One of the most important and robust characteristics of this transporter is that it is strongly stimulated after dietary K(+) restriction. This result prompted many investigators to propose that it should play a role in allowing the kidney to efficiently retain K(+) under K(+) depletion. However, the apparent absence of a clear renal phenotype in HKA2-null mice has led to the idea that this transporter is an epiphenomenon. This review summarizes past and recent findings regarding the functional, structural and physiological characteristics of H-K-ATPase type 2. The findings discussed in this review suggest that, as in the famous story, the ugly duckling of the X-K-ATPase family is actually a swan.
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Affiliation(s)
- Gilles Crambert
- INSERM/UPMC Paris 6/CNRS, Centre de Recherche des Cordeliers Génomique, Physiologie et Physiopathologie Rénales, Equipe 3 U1138, ERL 8228, 15 rue de l'Ecole de Médecine, 75270 Paris Cedex, France.
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29
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Beierwaltes WH, Harrison-Bernard LM, Sullivan JC, Mattson DL. Assessment of renal function; clearance, the renal microcirculation, renal blood flow, and metabolic balance. Compr Physiol 2013; 3:165-200. [PMID: 23720284 DOI: 10.1002/cphy.c120008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Historically, tools to assess renal function have been developed to investigate the physiology of the kidney in an experimental setting, and certain of these techniques have utility in evaluating renal function in the clinical setting. The following work will survey a spectrum of these tools, their applications and limitations in four general sections. The first is clearance, including evaluation of exogenous and endogenous markers for determining glomerular filtration rate, the adaptation of estimated glomerular filtration rate in the clinical arena, and additional clearance techniques to assess various other parameters of renal function. The second section deals with in vivo and in vitro approaches to the study of the renal microvasculature. This section surveys a number of experimental techniques including corticotomy, the hydronephrotic kidney, vascular casting, intravital charge coupled device videomicroscopy, multiphoton fluorescent microscopy, synchrotron-based angiography, laser speckle contrast imaging, isolated renal microvessels, and the perfused juxtamedullary nephron microvasculature. The third section addresses in vivo and in vitro approaches to the study of renal blood flow. These include ultrasonic flowmetry, laser-Doppler flowmetry, magnetic resonance imaging (MRI), phase contrast MRI, cine phase contrast MRI, dynamic contrast-enhanced MRI, blood oxygen level dependent MRI, arterial spin labeling MRI, x-ray computed tomography, and positron emission tomography. The final section addresses the methodologies of metabolic balance studies. These are described for humans, large experimental animals as well as for rodents. Overall, the various in vitro and in vivo topics and applications to evaluate renal function should provide a guide for the investigator or physician to understand and to implement the techniques in the laboratory or clinic setting.
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Affiliation(s)
- William H Beierwaltes
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, and Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
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30
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Partial genetic deficiency in tissue kallikrein impairs adaptation to high potassium intake in humans. Kidney Int 2013; 84:1271-7. [PMID: 23760292 DOI: 10.1038/ki.2013.224] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 04/16/2013] [Accepted: 04/18/2013] [Indexed: 12/14/2022]
Abstract
Inactivation of the tissue kallikrein gene in mice impairs renal handling of potassium due to enhanced H, K-ATPase activity, and induces hyperkalemia. We investigated whether the R53H loss-of-function polymorphism of the human tissue kallikrein gene affects renal potassium handling. In a crossover study, 30 R53R homozygous and 10 R53H heterozygous healthy males were randomly assigned to a low-sodium/high-potassium or a high-sodium/low-potassium diet to modulate tissue kallikrein synthesis. On the seventh day of each diet, participants were studied before and during a 2-h infusion of furosemide to stimulate distal potassium secretion. Urinary kallikrein activity was significantly lower in R53H than in R53R subjects on the low-sodium/high-potassium diet and was similarly reduced in both genotypes on high-sodium/low-potassium. Plasma potassium and renal potassium reabsorption were similar in both genotypes on an ad libitum sodium/potassium diet or after 7 days of a high-sodium/low-potassium diet. However, the median plasma potassium was significantly higher after 7 days of low-sodium/high-potassium diet in R53H than in R53R individuals. Urine potassium excretion and plasma aldosterone concentrations were similar. On the low-sodium/high-potassium diet, furosemide-induced decrease in plasma potassium was significantly larger in R53H than in R53R subjects. Thus, impaired tissue kallikrein stimulation by a low-sodium/high-potassium diet in R53H subjects with partial tissue kallikrein deficiency highlights an inappropriate renal adaptation to potassium load, consistent with experimental data in mice.
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31
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Wall SM, Weinstein AM. Cortical distal nephron Cl(-) transport in volume homeostasis and blood pressure regulation. Am J Physiol Renal Physiol 2013; 305:F427-38. [PMID: 23637202 DOI: 10.1152/ajprenal.00022.2013] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Renal intercalated cells mediate the secretion or absorption of Cl(-) and OH(-)/H(+) equivalents in the connecting segment (CNT) and cortical collecting duct (CCD). In so doing, they regulate acid-base balance, vascular volume, and blood pressure. Cl(-) absorption is either electrogenic and amiloride-sensitive or electroneutral and thiazide-sensitive. However, which Cl(-) transporter(s) are targeted by these diuretics is debated. While epithelial Na(+) channel (ENaC) does not transport Cl(-), it modulates Cl(-) transport probably by generating a lumen-negative voltage, which drives Cl(-) flux across tight junctions. In addition, recent evidence indicates that ENaC inhibition increases electrogenic Cl(-) secretion via a type A intercalated cells. During ENaC blockade, Cl(-) is taken up across the basolateral membrane through the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1) and then secreted across the apical membrane through a conductive pathway (a Cl(-) channel or an electrogenic exchanger). The mechanism of this apical Cl(-) secretion is unresolved. In contrast, thiazide diuretics inhibit electroneutral Cl(-) absorption mediated by a Na(+)-dependent Cl(-)/HCO3(-) exchanger. The relative contribution of the thiazide and the amiloride-sensitive components of Cl(-) absorption varies between studies and probably depends on the treatment model employed. Cl(-) absorption increases markedly with angiotensin and aldosterone administration, largely by upregulating the Na(+)-independent Cl(-)/HCO3(-) exchanger pendrin. In the absence of pendrin [Slc26a4((-/-)) or pendrin null mice], aldosterone-stimulated Cl(-) absorption is significantly reduced, which attenuates the pressor response to this steroid hormone. Pendrin also modulates aldosterone-induced changes in ENaC abundance and function through a kidney-specific mechanism that does not involve changes in the concentration of a circulating hormone. Instead, pendrin changes ENaC abundance and function, at least in part, by altering luminal HCO3(-). This review summarizes mechanisms of Cl(-) transport in CNT and CCD and how these transporters contribute to the regulation of extracellular volume and blood pressure.
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Affiliation(s)
- Susan M Wall
- Renal Division, WMB Rm. 338, 1639 Pierce Dr., NE, Atlanta, GA 30322.
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32
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A link between fertility and K+ homeostasis: role of the renal H,K-ATPase type 2. Pflugers Arch 2013; 465:1149-58. [DOI: 10.1007/s00424-013-1252-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 02/11/2013] [Accepted: 02/12/2013] [Indexed: 11/25/2022]
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33
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Nguyen MTX, Yang LE, Fletcher NK, Lee DH, Kocinsky H, Bachmann S, Delpire E, McDonough AA. Effects of K+-deficient diets with and without NaCl supplementation on Na+, K+, and H2O transporters' abundance along the nephron. Am J Physiol Renal Physiol 2012; 303:F92-104. [PMID: 22496411 DOI: 10.1152/ajprenal.00032.2012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Dietary potassium (K(+)) restriction and hypokalemia have been reported to change the abundance of most renal Na(+) and K(+) transporters and aquaporin-2 isoform, but results have not been consistent. The aim of this study was to reexamine Na(+), K(+) and H(2)O transporters' pool size regulation in response to removing K(+) from a diet containing 0.74% NaCl, as well as from a diet containing 2% NaCl (as found in American diets) to blunt reducing total diet electrolytes. Sprague-Dawley rats (n = 5-6) were fed for 6 days with one of these diets: 2% KCl, 0.74% NaCl (2K1Na, control chow) compared with 0.03% KCl, 0.74% NaCl (0K1Na); or 2% KCl, 2%NaCl (2K2Na) compared with 0.03% KCl, 2% NaCl (0K2Na, Na(+) replete). In both 0K1Na and 0K2Na there were significant decreases in: 1) plasma [K(+)] (<2.5 mM); 2) urinary K(+) excretion (<5% of control); 3) urine osmolality and plasma [aldosterone], as well as 4) an increase in urine volume and medullary hypertrophy. The 0K2Na group had the lowest [aldosterone] (172.0 ± 17.4 pg/ml) and lower blood pressure (93.2 ± 4.9 vs. 112.0 ± 3.1 mmHg in 2K2Na). Transporter pool size regulation was determined by quantitative immunoblotting of renal cortex and medulla homogenates. The only differences measured in both 0K1Na and 0K2Na groups were a 20-30% decrease in cortical β-ENaC, 30-40% increases in kidney-specific Ste20/SPS1-related proline/alanine-rich kinase, and a 40% increase in medullary sodium pump abundance. The following proteins were not significantly changed in both the 0 K groups: Na(+)/H(+) exchanger isoform 3; Na(+)-K(+)-Cl(-) cotransporter; Na(+)-Cl(-) cotransporter, oxidative stress response kinase-1; renal outer medullary K(+) channel; autosomal recessive hypercholesterolemia; c-Src, aquaporin 2 isoform; or renin. Thus, despite profound hypokalemia and renal K(+) conservation, we did not confirm many of the changes that were previously reported. We predict that changes in transporter distribution and activity are likely more important for conserving K(+) than changes in total abundance.
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Affiliation(s)
- Mien T X Nguyen
- Department of Cell and Neurobiology, Keck School of Medicine of University of Southern California, Los Angeles, California, USA
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Salhi A, Centeno G, Firsov D, Crambert G. Circadian expression of H,K-ATPase type 2 contributes to the stability of plasma K⁺ levels. FASEB J 2012; 26:2859-67. [PMID: 22459151 DOI: 10.1096/fj.11-199711] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Maintenance by the kidney of stable plasma K(+) values is crucial, as plasma K(+) controls muscle and nerve activity. Since renal K(+) excretion is regulated by the circadian clock, we aimed to identify the ion transporters involved in this process. In control mice, the renal mRNA expression of H,K-ATPase type 2 (HKA2) is 25% higher during rest compared to the activity period. Conversely, under dietary K(+) restriction, HKA2 expression is ∼40% higher during the activity period. This reversal suggests that HKA2 contributes to the circadian regulation of K(+) homeostasis. Compared to their wild-type (WT) littermates, HKA2-null mice fed a normal diet have 2-fold higher K(+) renal excretion during rest. Under K(+) restriction, their urinary K(+) loss is 40% higher during the activity period. This inability to excrete K(+) "on time" is reflected in plasma K(+) values, which vary by 12% between activity and rest periods in HKA2-null mice but remain stable in WT mice. Analysis of the circadian expression of HKA2 regulators suggests that Nrf2, but not progesterone, contributes to its rhythmicity. Therefore, HKA2 acts to maintain the circadian rhythm of urinary K(+) excretion and preserve stable plasma K(+) values throughout the day.
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Affiliation(s)
- Amel Salhi
- Université Pierre et Marie Curie Paris 6, Institut National de Santé et de Recherche Médicale (INSERM), Centre National Recherche Scientifique (CNRS) Unité Mixte de Recherche en Santé 872, Equipe 3, Laboratoire de Génomique, Physiologie et Physiopathologie Rénales ERL Paris, France
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Abstract
The distal nephron plays a critical role in the renal control of homeostasis. Until very recently most studies focused on the control of Na(+), K(+), and water balance by principal cells of the collecting duct and the regulation of solute and water by hormones from the renin-angiotensin-aldosterone system and by antidiuretic hormone. However, recent studies have revealed the unexpected importance of renal intercalated cells, a subtype of cells present in the connecting tubule and collecting ducts. Such cells were thought initially to be involved exclusively in acid-base regulation. However, it is clear now that intercalated cells absorb NaCl and K(+) and hence may participate in the regulation of blood pressure and potassium balance. The second paradigm-challenging concept we highlight is the emerging importance of local paracrine factors that play a critical role in the renal control of water and electrolyte balance.
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Affiliation(s)
- Dominique Eladari
- Centre de Recherche des Cordeliers, Université Paris Descartes, INSERM UMRS 872, Equipe 3, F-75006, Paris, France; ,
- Université Pierre et Marie Curie, CNRS ERL7226, F-75006, Paris, France
- Département de Physiologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, F-75015, Paris, France
| | - Régine Chambrey
- Centre de Recherche des Cordeliers, Université Paris Descartes, INSERM UMRS 872, Equipe 3, F-75006, Paris, France; ,
- Université Pierre et Marie Curie, CNRS ERL7226, F-75006, Paris, France
| | - Janos Peti-Peterdi
- Department of Physiology and Biophysics, Keck School of Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033;
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Elabida B, Edwards A, Salhi A, Azroyan A, Fodstad H, Meneton P, Doucet A, Bloch-Faure M, Crambert G. Chronic potassium depletion increases adrenal progesterone production that is necessary for efficient renal retention of potassium. Kidney Int 2011; 80:256-62. [DOI: 10.1038/ki.2011.15] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Fenton RA, Praetorius J. Molecular Physiology of the Medullary Collecting Duct. Compr Physiol 2011; 1:1031-56. [DOI: 10.1002/cphy.c100064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Greenlee MM, Lynch IJ, Gumz ML, Cain BD, Wingo CS. Mineralocorticoids stimulate the activity and expression of renal H+,K+-ATPases. J Am Soc Nephrol 2010; 22:49-58. [PMID: 21164026 DOI: 10.1681/asn.2010030311] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
In the renal collecting duct, mineralocorticoids drive Na(+) reabsorption, K(+) secretion, and H(+) secretion through coordinated actions on apical and basolateral transporters. Whether mineralocorticoids act through H(+),K(+)-ATPases to maintain K(+) and acid-base homeostasis is unknown. Here, treatment of mice with the mineralocorticoid desoxycorticosterone pivalate (DOCP) resulted in weight gain, a decrease in blood [K(+)] and [Cl(-)], and an increase in blood [Na(+)] and [HCO(3)(-)]. DOCP treatment increased the rate of H(+),K(+)-ATPase-mediated H(+) secretion in intercalated cells of the inner cortical collecting duct. mRNA expression of the catalytic subunit HKα(1) did not significantly change, whereas HKα(2) mRNA expression dramatically increased in the outer and inner medulla of DOCP-treated mice. A high-K(+) diet abrogated this increase in renal HKα(2) expression, showing that DOCP-mediated stimulation of HKα(2) expression depends on dietary K(+) intake. DOCP treatment of mice lacking HKα(1) (HKα(1)(-/-)) resulted in greater urinary Na(+) retention than observed in either wild-type mice or mice lacking both HKα(1) and HKα(2) (HKα(1,2)(-/-)). DOCP-treated HKα(1,2)(-/-) mice exhibited a lower blood [HCO(3)(-)] and less Na(+) and K(+) retention than either wild-type or HKα(1)(-/-) mice. Taken together, these results indicate that H(+),K(+)-ATPases-especially the HKα(2)-containing H(+),K(+)-ATPases-play an important role in the effects of mineralocorticoids on K(+), acid-base, and Na(+) balance.
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Affiliation(s)
- Megan M Greenlee
- Research Service, North Florida/South Georgia Veterans Health System, 1601 SW Archer Road, Gainesville, FL 32608, USA
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Abstract
PURPOSE OF REVIEW We integrate recent evidence that demonstrates the importance of the gastric (HKalpha1) and nongastric (HKalpha2)-containing hydrogen potassium adenosine triphosphatases (H,K-ATPases) on physiological function and their role in potassium (K), sodium (Na), and acid-base balance. RECENT FINDINGS Previous studies focused on the primary role of H,K-ATPases as a mechanism of K conservation during states of K deprivation. Both isoforms function in H secretion and K absorption in vivo during K deprivation, but recent findings show that these pumps also function in acid secretion in animals fed normal K-replete diets. The complicated pharmacological inhibition of both pumps is reviewed. Interestingly, HKalpha2-null mice have a reduced expression and activity of the renal epithelial Na channel alpha subunit in the colon. When the human nongastric isoform was studied in a heterologous expression system with its cognate beta subunit (NaKbeta1), the pump exhibited substantial Na affinity at the 'K'-binding site. Evidence cited herein raises the possibility that either directly or indirectly the renal HKalpha2-containing H,K-ATPase may affect Na balance. SUMMARY Both H,K-ATPase isoforms are active in normal animals and not just under conditions of K depletion. The possibility that either one or both isoforms contribute to Na absorption, particularly in humans, raises important clinical implications for these pumps in the kidney.
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Tissue kallikrein permits early renal adaptation to potassium load. Proc Natl Acad Sci U S A 2010; 107:13526-31. [PMID: 20624970 DOI: 10.1073/pnas.0913070107] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Tissue kallikrein (TK) is a serine protease synthetized in renal tubular cells located upstream from the collecting duct where renal potassium balance is regulated. Because secretion of TK is promoted by K+ intake, we hypothesized that this enzyme might regulate plasma K+ concentration ([K+]). We showed in wild-type mice that renal K+ and TK excretion increase in parallel after a single meal, representing an acute K+ load, whereas aldosterone secretion is not modified. Using aldosterone synthase-deficient mice, we confirmed that the control of TK secretion is aldosterone-independent. Mice with TK gene disruption (TK-/-) were used to assess the impact of the enzyme on plasma [K+]. A single large feeding did not lead to any significant change in plasma [K+] in TK+/+, whereas TK-/- mice became hyperkalemic. We next examined the impact of TK disruption on K+ transport in isolated cortical collecting ducts (CCDs) microperfused in vitro. We found that CCDs isolated from TK-/- mice exhibit net transepithelial K+ absorption because of abnormal activation of the colonic H+,K+-ATPase in the intercalated cells. Finally, in CCDs isolated from TK-/- mice and microperfused in vitro, the addition of TK to the perfusate but not to the peritubular bath caused a 70% inhibition of H+,K+-ATPase activity. In conclusion, we have identified the serine protease TK as a unique kalliuretic factor that protects against hyperkalemia after a dietary K+ load.
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Shao J, Gumz ML, Cain BD, Xia SL, Shull GE, van Driel IR, Wingo CS. Pharmacological profiles of the murine gastric and colonic H,K-ATPases. Biochim Biophys Acta Gen Subj 2010; 1800:906-11. [PMID: 20594946 DOI: 10.1016/j.bbagen.2010.05.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 04/23/2010] [Accepted: 05/03/2010] [Indexed: 10/19/2022]
Abstract
BACKGROUND The H,K-ATPase, consisting of α and ß subunits, belongs to the P-type ATPase family. There are two isoforms of the α subunit, HKα₁ and HKα₂ encoded by different genes. The ouabain-resistant gastric HKα₁-H,K-ATPase is Sch28080-sensitive. However, the colonic HKα₂-H,K-ATPase from different species shows poor primary structure conservation of the HKα₂ subunit between species and diverse pharmacological sensitivity to ouabain and Sch28080. This study sought to determine the contribution of each gene to functional activity and its pharmacological profile using mouse models with targeted disruption of HKα₁, HKα₂, or HKbeta genes. METHODS Membrane vesicles from gastric mucosa and distal colon in wild-type (WT), HKα₁, HKα₂, or HKß knockout (KO) mice were extracted. K-ATPase activity and pharmacological profiles were examined. RESULTS The colonic H,K-ATPase demonstrated slightly greater affinity for K(+) than the gastric H,K-ATPase. This K-ATPase activity was not detected in the colon of HKα₂ KO but was observed in HKß KO with properties indistinguishable from WT. Neither ouabain nor Sch28080 had a significant effect on the WT colonic K-ATPase activity, but orthovanadate abolished this activity. Amiloride and its analogs benzamil and 5-N-ethyl-N-isopropylamiloride inhibited K-ATPase activity of HKα₁-containing H,K-ATPase; the dose dependence of inhibition was similar for all three inhibitors. In contrast, the colonic HKα₂-H,K-ATPase was not inhibited by these compounds. CONCLUSIONS These data demonstrate that the mouse colonic H,K-ATPase exhibits a ouabain- and Sch28080-insensitive, orthovanadate-sensitive K-ATPase activity. Interestingly, pharmacological studies suggested that the mouse gastric H,K-ATPase is sensitive to amiloride. GENERAL SIGNIFICANCE Characterization of the pharmacological profiles of the H,K-ATPases is important for understanding the relevant knockout animals and for considering the specificity of the inhibitors.
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Affiliation(s)
- Jiahong Shao
- Department of Medicine, University of Florida College of Medicine, Gainesville, FL 32610, USA
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Colonic potassium handling. Pflugers Arch 2010; 459:645-56. [PMID: 20143237 DOI: 10.1007/s00424-009-0781-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 12/23/2009] [Accepted: 12/25/2009] [Indexed: 10/19/2022]
Abstract
Homeostatic control of plasma K+ is a necessary physiological function. The daily dietary K+ intake of approximately 100 mmol is excreted predominantly by the distal tubules of the kidney. About 10% of the ingested K+ is excreted via the intestine. K+ handling in both organs is specifically regulated by hormones and adapts readily to changes in dietary K+ intake, aldosterone and multiple local paracrine agonists. In chronic renal insufficiency, colonic K+ secretion is greatly enhanced and becomes an important accessory K+ excretory pathway. During severe diarrheal diseases of different causes, intestinal K+ losses caused by activated ion secretion may become life threatening. This topical review provides an update of the molecular mechanisms and the regulation of mammalian colonic K+ absorption and secretion. It is motivated by recent results, which have identified the K+ secretory ion channel in the apical membrane of distal colonic enterocytes. The directed focus therefore covers the role of the apical Ca2+ and cAMP-activated BK channel (KCa1.1) as the apparently only secretory K+ channel in the distal colon.
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Gumz ML, Lynch IJ, Greenlee MM, Cain BD, Wingo CS. The renal H+-K+-ATPases: physiology, regulation, and structure. Am J Physiol Renal Physiol 2009; 298:F12-21. [PMID: 19640897 DOI: 10.1152/ajprenal.90723.2008] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The H(+)-K(+)-ATPases are ion pumps that use the energy of ATP hydrolysis to transport protons (H(+)) in exchange for potassium ions (K(+)). These enzymes consist of a catalytic alpha-subunit and a regulatory beta-subunit. There are two catalytic subunits present in the kidney, the gastric or HKalpha(1) isoform and the colonic or HKalpha(2) isoform. In this review we discuss new information on the physiological function, regulation, and structure of the renal H(+)-K(+)-ATPases. Evaluation of enzymatic functions along the nephron and collecting duct and studies in HKalpha(1) and HKalpha(2) knockout mice suggest that the H(+)-K(+)-ATPases may function to transport ions other than protons and potassium. These reports and recent studies in mice lacking both HKalpha(1) and HKalpha(2) suggest important roles for the renal H(+)-K(+)-ATPases in acid/base balance as well as potassium and sodium homeostasis. Molecular modeling studies based on the crystal structure of a related enzyme have made it possible to evaluate the structures of HKalpha(1) and HKalpha(2) and provide a means to study the specific cation transport properties of H(+)-K(+)-ATPases. Studies to characterize the cation specificity of these enzymes under different physiological conditions are necessary to fully understand the role of the H(+)-K(+) ATPases in renal physiology.
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Affiliation(s)
- Michelle L Gumz
- Research Service, North Florida/South Georgia Veterans Health System, Gainesville, Florida, USA
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Yu Z, Li M, Zhang D, Xu W, Kone BC. Sp1 trans-activates the murine H(+)-K(+)-ATPase alpha(2)-subunit gene. Am J Physiol Renal Physiol 2009; 297:F63-70. [PMID: 19420113 DOI: 10.1152/ajprenal.00039.2009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The H(+)-K(+)-ATPase alpha(2) (HKalpha2) gene of the renal collecting duct and distal colon plays a central role in potassium and acid-base homeostasis, yet its transcriptional control remains poorly characterized. We previously demonstrated that the proximal 177 bp of its 5'-flanking region confers basal transcriptional activity in murine inner medullary collecting duct (mIMCD3) cells and that NF-kappaB and CREB-1 bind this region to alter transcription. In the present study, we sought to determine whether the -144/-135 Sp element influences basal HKalpha2 gene transcription in these cells. Electrophoretic mobility shift and supershift assays using probes for -154/-127 revealed Sp1-containing DNA-protein complexes in nuclear extracts of mIMCD3 cells. Chromatin immunoprecipitation (ChIP) assays demonstrated that Sp1, but not Sp3, binds to this promoter region of the HKalpha2 gene in mIMCD3 cells in vivo. HKalpha2 minimal promoter-luciferase constructs with point mutations in the -144/-135 Sp element exhibited much lower activity than the wild-type promoter in transient transfection assays. Overexpression of Sp1, but not Sp3, trans-activated an HKalpha2 proximal promoter-luciferase construct in mIMCD3 cells as well as in SL2 insect cells, which lack Sp factors. Conversely, small interfering RNA knockdown of Sp1 inhibited endogenous HKalpha2 mRNA expression, and binding of Sp1 to chromatin associated with the proximal HKalpha2 promoter without altering the binding or regulatory influence of NF-kappaB p65 or CREB-1 on the proximal HKalpha2 promoter. We conclude that Sp1 plays an important and positive role in controlling basal HKalpha2 gene expression in mIMCD3 cells in vivo and in vitro.
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Affiliation(s)
- Zhiyuan Yu
- Departments of Medicine and of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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Wang WH, Giebisch G. Regulation of potassium (K) handling in the renal collecting duct. Pflugers Arch 2009; 458:157-68. [PMID: 18839206 PMCID: PMC2730119 DOI: 10.1007/s00424-008-0593-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 09/20/2008] [Indexed: 12/13/2022]
Abstract
This review provides an overview of the molecular mechanisms of K transport in the mammalian connecting tubule (CNT) and cortical collecting duct (CCD), both nephron segments responsible for the regulation of renal K secretion. Aldosterone and dietary K intake are two of the most important factors regulating K secretion in the CNT and CCD. Recently, angiotensin II (AngII) has also been shown to play a role in the regulation of K secretion. In addition, genetic and molecular biological approaches have further identified new mechanisms by which aldosterone and dietary K intake regulate K transport. Thus, the interaction between serum-glucocorticoid-induced kinase 1 (SGK1) and with-no-lysine kinase 4 (WNK4) plays a significant role in mediating the effect of aldosterone on ROMK (Kir1.1), an important apical K channel modulating K secretion. Recent evidence suggests that WNK1, mitogen-activated protein kinases such as P38, ERK, and Src family protein tyrosine kinase are involved in mediating the effect of low K intake on apical K secretory channels.
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Affiliation(s)
- Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, 10595, USA.
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Cermak R, Evelgünne A, Scharrer E. Influence of the dietary potassium content on transepithelial potassium transport in rat jejunum. J Anim Physiol Anim Nutr (Berl) 2008. [DOI: 10.1046/j.1439-0396.2000.00260.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Heitzmann D, Warth R. Physiology and pathophysiology of potassium channels in gastrointestinal epithelia. Physiol Rev 2008; 88:1119-82. [PMID: 18626068 DOI: 10.1152/physrev.00020.2007] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Epithelial cells of the gastrointestinal tract are an important barrier between the "milieu interne" and the luminal content of the gut. They perform transport of nutrients, salts, and water, which is essential for the maintenance of body homeostasis. In these epithelia, a variety of K(+) channels are expressed, allowing adaptation to different needs. This review provides an overview of the current literature that has led to a better understanding of the multifaceted function of gastrointestinal K(+) channels, thereby shedding light on pathophysiological implications of impaired channel function. For instance, in gastric mucosa, K(+) channel function is a prerequisite for acid secretion of parietal cells. In epithelial cells of small intestine, K(+) channels provide the driving force for electrogenic transport processes across the plasma membrane, and they are involved in cell volume regulation. Fine tuning of salt and water transport and of K(+) homeostasis occurs in colonic epithelia cells, where K(+) channels are involved in secretory and reabsorptive processes. Furthermore, there is growing evidence for changes in epithelial K(+) channel expression during cell proliferation, differentiation, apoptosis, and, under pathological conditions, carcinogenesis. In the future, integrative approaches using functional and postgenomic/proteomic techniques will help us to gain comprehensive insights into the role of K(+) channels of the gastrointestinal tract.
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Affiliation(s)
- Dirk Heitzmann
- Institute of Physiology and Clinic and Policlinic for Internal Medicine II, Regensburg, Germany
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Borenshtein D, Fry RC, Groff EB, Nambiar PR, Carey VJ, Fox JG, Schauer DB. Diarrhea as a cause of mortality in a mouse model of infectious colitis. Genome Biol 2008; 9:R122. [PMID: 18680595 PMCID: PMC2575512 DOI: 10.1186/gb-2008-9-8-r122] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 05/01/2008] [Accepted: 08/04/2008] [Indexed: 02/03/2023] Open
Abstract
Analysis of gene expression in the colons of Citrobacter rodentium-infected susceptible and resistant mice suggests that mortality is associated with impaired intestinal ion transport. Background Comparative characterization of genome-wide transcriptional changes during infection can help elucidate the mechanisms underlying host susceptibility. In this study, transcriptional profiling of the mouse colon was carried out in two cognate lines of mice that differ in their response to Citrobacter rodentium infection; susceptible inbred FVB/N and resistant outbred Swiss Webster mice. Gene expression in the distal colon was determined prior to infection, and at four and nine days post-inoculation using a whole mouse genome Affymetrix array. Results Computational analysis identified 462 probe sets more than 2-fold differentially expressed between uninoculated resistant and susceptible mice. In response to C. rodentium infection, 5,123 probe sets were differentially expressed in one or both lines of mice. Microarray data were validated by quantitative real-time RT-PCR for 35 selected genes and were found to have a 94% concordance rate. Transcripts represented by 1,547 probe sets were differentially expressed between susceptible and resistant mice regardless of infection status, a host effect. Genes associated with transport were over-represented to a greater extent than even immune response-related genes. Electrolyte analysis revealed reduction in serum levels of chloride and sodium in susceptible animals. Conclusion The results support the hypothesis that mortality in C. rodentium-infected susceptible mice is associated with impaired intestinal ion transport and development of fatal fluid loss and dehydration. These studies contribute to our understanding of the pathogenesis of C. rodentium and suggest novel strategies for the prevention and treatment of diarrhea associated with intestinal bacterial infections.
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Affiliation(s)
- Diana Borenshtein
- Department of Biological Engineering, Massachusetts Institute of Technology, Massachusetts Avenue, Cambridge, MA 02139, USA
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Aw S, Adams DS, Qiu D, Levin M. H,K-ATPase protein localization and Kir4.1 function reveal concordance of three axes during early determination of left-right asymmetry. Mech Dev 2008; 125:353-72. [PMID: 18160269 PMCID: PMC2346612 DOI: 10.1016/j.mod.2007.10.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 10/05/2007] [Accepted: 10/24/2007] [Indexed: 12/23/2022]
Abstract
Consistent laterality is a fascinating problem, and study of the Xenopus embryo has led to molecular characterization of extremely early steps in left-right patterning: bioelectrical signals produced by ion pumps functioning upstream of asymmetric gene expression. Here, we reveal a number of novel aspects of the H+/K+-ATPase module in chick and frog embryos. Maternal H+/K+-ATPase subunits are asymmetrically localized along the left-right, dorso-ventral, and animal-vegetal axes during the first cleavage stages, in a process dependent on cytoskeletal organization. Using a reporter domain fused to molecular motors, we show that the cytoskeleton of the early frog embryo can provide asymmetric, directional information for subcellular transport along all three axes. Moreover, we show that the Kir4.1 potassium channel, while symmetrically expressed in a dynamic fashion during early cleavages, is required for normal LR asymmetry of frog embryos. Thus, Kir4.1 is an ideal candidate for the K+ ion exit path needed to allow the electroneutral H+/K+-ATPase to generate voltage gradients. In the chick embryo, we show that H+/K+-ATPase and Kir4.1 are expressed in the primitive streak, and that the known requirement for H+/K+-ATPase function in chick asymmetry does not function through effects on the circumferential expression pattern of Connexin43. These data provide details crucial for the mechanistic modeling of the physiological events linking subcellular processes to large-scale patterning and suggest a model where the early cytoskeleton sets up asymmetric ion flux along the left-right axis as a system of planar polarity functioning orthogonal to the apical-basal polarity of the early blastomeres.
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Affiliation(s)
- Sherry Aw
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dany S. Adams
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dayong Qiu
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Michael Levin
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
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Lynch IJ, Rudin A, Xia SL, Stow LR, Shull GE, Weiner ID, Cain BD, Wingo CS. Impaired acid secretion in cortical collecting duct intercalated cells from H-K-ATPase-deficient mice: role of HKalpha isoforms. Am J Physiol Renal Physiol 2007; 294:F621-7. [PMID: 18057185 DOI: 10.1152/ajprenal.00412.2007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Two classes of H pumps, H-K-ATPase and H-ATPase, contribute to luminal acidification and HCO(3) transport in the collecting duct (CD). At least two H-K-ATPase alpha-subunits are expressed in the CD: HKalpha(1) and HKalpha(2). Both exhibit K dependence but have different inhibitor sensitivities. The HKalpha(1) H-K-ATPase is Sch-28080 sensitive, whereas the pharmacological profile of the HKalpha(2) H-K-ATPase is not completely understood. The present study used a nonpharmacological, genetic approach to determine the contribution of HKalpha(1) and HKalpha(2) to cortical CD (CCD) intercalated cell (IC) proton transport in mice fed a normal diet. Intracellular pH (pH(i)) recovery was determined in ICs using in vitro microperfusion of CCD after an acute intracellular acid load in wild-type mice and mice of the same strain lacking expression of HKalpha(1), HKalpha(2), or both H-K-ATPases (HKalpha(1,2)). A-type and B-type ICs were differentiated by luminal loading with BCECF-AM and peritubular chloride removal from CO(2)/HCO(3)-buffered solutions to identify the membrane locations of Cl/HCO(3) exchange activity. H-ATPase- and Na/H exchange-mediated H transport were inhibited with bafilomycin A(1) (100 nM) and EIPA (10 microM), respectively. Here, we report 1) initial pH(i) and buffering capacity were not significantly altered in the ICs of HKalpha-deficient mice, 2) either HKalpha(1) or HKalpha(2) deficiency resulted in slower acid extrusion, and 3) A-type ICs from HKalpha(1,2)-deficient mice had significantly slower acid extrusion compared with A-type ICs from HKalpha(1)-deficient mice alone. These studies are the first nonpharmacological demonstration that both HKalpha(1) and HKalpha(2) contribute to H secretion in both A-type and B-type ICs in animals fed a normal diet.
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Affiliation(s)
- I Jeanette Lynch
- North Florida/South Georgia Veterans Health System, University of Florida, Gainesville, Florida, USA.
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