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Nikolovska K, Seidler UE, Stock C. The Role of Plasma Membrane Sodium/Hydrogen Exchangers in Gastrointestinal Functions: Proliferation and Differentiation, Fluid/Electrolyte Transport and Barrier Integrity. Front Physiol 2022; 13:899286. [PMID: 35665228 PMCID: PMC9159811 DOI: 10.3389/fphys.2022.899286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 04/19/2022] [Indexed: 12/11/2022] Open
Abstract
The five plasma membrane Na+/H+ exchanger (NHE) isoforms in the gastrointestinal tract are characterized by distinct cellular localization, tissue distribution, inhibitor sensitivities, and physiological regulation. NHE1 (Slc9a1) is ubiquitously expressed along the gastrointestinal tract in the basolateral membrane of enterocytes, but so far, an exclusive role for NHE1 in enterocyte physiology has remained elusive. NHE2 (Slc9a2) and NHE8 (Slc9a8) are apically expressed isoforms with ubiquitous distribution along the colonic crypt axis. They are involved in pHi regulation of intestinal epithelial cells. Combined use of a knockout mouse model, intestinal organoid technology, and specific inhibitors revealed previously unrecognized actions of NHE2 and NHE8 in enterocyte proliferation and differentiation. NHE3 (Slc9a3), expressed in the apical membrane of differentiated intestinal epithelial cells, functions as the predominant nutrient-independent Na+ absorptive mechanism in the gut. The new selective NHE3 inhibitor (Tenapanor) allowed discovery of novel pathophysiological and drug-targetable NHE3 functions in cystic-fibrosis associated intestinal obstructions. NHE4, expressed in the basolateral membrane of parietal cells, is essential for parietal cell integrity and acid secretory function, through its role in cell volume regulation. This review focuses on the expression, regulation and activity of the five plasma membrane Na+/H+ exchangers in the gastrointestinal tract, emphasizing their role in maintaining intestinal homeostasis, or their impact on disease pathogenesis. We point to major open questions in identifying NHE interacting partners in central cellular pathways and processes and the necessity of determining their physiological role in a system where their endogenous expression/activity is maintained, such as organoids derived from different parts of the gastrointestinal tract.
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Li T, Liu X, Riederer B, Nikolovska K, Singh AK, Mäkelä KA, Seidler A, Liu Y, Gros G, Bartels H, Herzig KH, Seidler U. Genetic ablation of carbonic anhydrase IX disrupts gastric barrier function via claudin-18 downregulation and acid backflux. Acta Physiol (Oxf) 2018; 222:e12923. [PMID: 28748627 PMCID: PMC5901031 DOI: 10.1111/apha.12923] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 11/21/2016] [Accepted: 07/24/2017] [Indexed: 12/28/2022]
Abstract
Aim This study aimed to explore the molecular mechanisms for the parietal cell loss and fundic hyperplasia observed in gastric mucosa of mice lacking the carbonic anhydrase 9 (CAIX). Methods We assessed the ability of CAIX‐knockout and WT gastric surface epithelial cells to withstand a luminal acid load by measuring the pHi of exteriorized gastric mucosa in vivo using two‐photon confocal laser scanning microscopy. Cytokines and claudin‐18A2 expression was analysed by RT‐PCR. Results CAIX‐knockout gastric surface epithelial cells showed significantly faster pHi decline after luminal acid load compared to WT. Increased gastric mucosal IL‐1β and iNOS, but decreased claudin‐18A2 expression (which confer acid resistance) was observed shortly after weaning, prior to the loss of parietal and chief cells. At birth, neither inflammatory cytokines nor claudin‐18 expression were altered between CAIX and WT gastric mucosa. The gradual loss of acid secretory capacity was paralleled by an increase in serum gastrin, IL‐11 and foveolar hyperplasia. Mild chronic proton pump inhibition from the time of weaning did not prevent the claudin‐18 decrease nor the increase in inflammatory markers at 1 month of age, except for IL‐1β. However, the treatment reduced the parietal cell loss in CAIX‐KO mice in the subsequent months. Conclusions We propose that CAIX converts protons that either backflux or are extruded from the cells rapidly to CO2 and H2O, contributing to tight junction protection and gastric epithelial pHi regulation. Lack of CAIX results in persistent acid backflux via claudin‐18 downregulation, causing loss of parietal cells, hypergastrinaemia and foveolar hyperplasia.
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Affiliation(s)
- T. Li
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
| | - X. Liu
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
- Department of Department of Gastroenterology; Affiliated Hospital of Zunyi Medical College; Zunyi China
| | - B. Riederer
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
| | - K. Nikolovska
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
| | - A. K. Singh
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
| | - K. A. Mäkelä
- Institute of Biomedicine and Biocenter of Oulu; Oulu University; Finland
| | - A. Seidler
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
| | - Y. Liu
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
| | - G. Gros
- Department of Physiology; Hannover Medical School; Hannover Germany
| | - H. Bartels
- Department of Anatomy; Hannover Medical School; Hannover Germany
| | - K. H. Herzig
- Institute of Biomedicine and Biocenter of Oulu; Oulu University; Finland
| | - U. Seidler
- Department of Gastroenterology; Hannover Medical School; Hannover Germany
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Kirchhoff P, Wagner CA, Gaetzschmann F, Radebold K, Geibel JP. Demonstration of a functional apical sodium hydrogen exchanger in isolated rat gastric glands. Am J Physiol Gastrointest Liver Physiol 2003; 285:G1242-8. [PMID: 12907430 DOI: 10.1152/ajpgi.00165.2003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Previous studies have shown that gastric glands express at least sodium-hydrogen exchanger (NHE) isoforms 1-4. Our aim was to study NHE-3 localization in rat parietal cells and to investigate the functional activity of an apical membrane NHE-3 isoform in parietal cells of rats. Western blot analysis and immunohistochemistry showed expression of NHE-3 in rat stomach colocalizing the protein in parietal cells together with the beta-subunit of the H(+)-K(+)-ATPase. Functional studies in luminally perfused gastric glands demonstrated the presence of an apical NHE isoform sensitive to low concentrations of 5-ethylisopropyl amiloride (EIPA). Intracellular pH measurements in parietal cells conducted in omeprazole-pretreated superfused gastric glands showed an Na+-dependent proton extrusion pathway that was inhibited both by low concentrations of EIPA and by the NHE-3 specific inhibitor S3226. This pathway for proton extrusion had a higher activity in resting glands and was inhibited on stimulation of histamine-induced H(+)-K(+)-ATPase proton extrusion. We conclude that the NHE-3 isoform located on the apical membrane of parietal cells offers an additional pathway for proton secretion under resting conditions. Furthermore, the gastric NHE-3 appears to work under resting conditions and inactivates during periods of H(+)-K(+)-ATPase activity.
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Affiliation(s)
- Philipp Kirchhoff
- Department of Surgery, Yale University School of Medicine, New Haven, Connecticut 06511, USA
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Caroppo R, Gerbino A, Debellis L, Kifor O, Soybel DI, Brown EM, Hofer AM, Curci S. Asymmetrical, agonist-induced fluctuations in local extracellular [Ca(2+)] in intact polarized epithelia. EMBO J 2001; 20:6316-26. [PMID: 11707403 PMCID: PMC125728 DOI: 10.1093/emboj/20.22.6316] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We recently proposed that extracellular Ca(2+) ions participate in a novel form of intercellular communication involving the extracellular Ca(2+)-sensing receptor (CaR). Here, using Ca(2+)-selective microelectrodes, we directly measured the profile of agonist-induced [Ca(2+)]ext changes in restricted domains near the basolateral or luminal membranes of polarized gastric acid-secreting cells. The Ca(2+)-mobilizing agonist carbachol elicited a transient, La(3+)-sensitive decrease in basolateral [Ca(2+)] (average approximately 250 microM, but as large as 530 microM). Conversely, carbachol evoked an HgCl2-sensitive increase in [Ca(2+)] (average approximately 400 microM, but as large as 520 microM) in the lumen of single gastric glands. Both responses were significantly reduced by pre-treatment with sarco-endoplasmic reticulum Ca(2+) ATPase (SERCA) pump inhibitors or with the intracellular Ca(2+) chelator BAPTA-AM. Immunofluorescence experiments demonstrated an asymmetric localization of plasma membrane Ca(2+) ATPase (PMCA), which appeared to be partially co-localized with CaR and the gastric H(+)/K(+)-ATPase in the apical membrane of the acid-secreting cells. Our data indicate that agonist stimulation results in local fluctuations in [Ca(2+)]ext that would be sufficient to modulate the activity of the CaR on neighboring cells.
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Affiliation(s)
| | | | | | - Olga Kifor
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - David I. Soybel
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - Edward M. Brown
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - Aldebaran M. Hofer
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - Silvana Curci
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
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Rossmann H, Sonnentag T, Heinzmann A, Seidler B, Bachmann O, Vieillard-Baron D, Gregor M, Seidler U. Differential expression and regulation of Na(+)/H(+) exchanger isoforms in rabbit parietal and mucous cells. Am J Physiol Gastrointest Liver Physiol 2001; 281:G447-58. [PMID: 11447025 DOI: 10.1152/ajpgi.2001.281.2.g447] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Several Na(+)/H(+) exchanger (NHE) isoforms are expressed in the stomach, and NHE1 and NHE2 knockout mice display gastric mucosal atrophy. This study investigated the cellular distribution of the NHE isoforms NHE1, NHE2, NHE3, and NHE4 in rabbit gastric epithelial cells and their regulation by intracellular pH (pH(i)), hyperosmolarity, and an increase in cAMP. Semiquantitative RT-PCR and Northern blot experiments showed high NHE1 and NHE2 mRNA levels in mucous cells and high NHE4 mRNA levels in parietal and chief cells. Fluorescence optical measurements in cultured rabbit parietal and mucous cells using the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein and NHE isoform-specific inhibitors demonstrated that in both cell types, intracellular acidification activates NHE1 and NHE2, whereas hyperosmolarity activates NHE1 and NHE4. The relative contribution of the different isoforms to pH(i)- and hyperosmolarity-activated Na(+)/H(+) exchange in the different cell types paralleled their relative expression levels. cAMP elevation also stimulated NHE4, whereas an increase in osmolarity above a certain threshold further increased NHE1 and not NHE4 activity. We conclude that in rabbit gastric epithelium, NHE1 and NHE4 regulate cell volume and NHE1 and NHE2 regulate pH(i). The high NHE1 and NHE2 expression levels in mucous cells may reflect their special need for pH(i) regulation during high gastric acidity. NHE4 is likely involved in volume regulation during acid secretion.
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Affiliation(s)
- H Rossmann
- First Department of Medicine, Eberhard-Karls University Tübingen, D-72076 Tübingen, Germany
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Shull GE, Miller ML, Schultheis PJ. Lessons from genetically engineered animal models VIII. Absorption and secretion of ions in the gastrointestinal tract. Am J Physiol Gastrointest Liver Physiol 2000; 278:G185-90. [PMID: 10666041 DOI: 10.1152/ajpgi.2000.278.2.g185] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Absorption and secretion of ions in gastrointestinal and other epithelial tissues require the concerted activities of ion pumps, channels, symporters, and exchangers, which operate in coupled systems to mediate transepithelial transport. Our understanding of the identities, membrane locations, and biochemical activities of epithelial ion transporters has advanced significantly in recent years, but major gaps and uncertainties remain in our understanding of their physiological functions. Increasingly, this problem is being addressed by the analysis of mutant mouse models developed by gene targeting. In this review, we discuss gene knockout studies of the secretory isoform of the Na(+)-K(+)-2Cl(-) cotransporter, isoforms 1, 2, and 3 of the Na(+)/H(+) exchanger, and the colonic H(+)-K(+)-ATPase. This approach is leading to a clearer understanding of the functions of these transporters in the living animal.
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Affiliation(s)
- G E Shull
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA.
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