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Amiri M, Jiang M, Salari A, Xiu R, Alper SL, Seidler UE. Reduced surface pH and upregulated AE2 anion exchange in SLC26A3-deleted polarized intestinal epithelial cells. Am J Physiol Cell Physiol 2024; 326:C829-C842. [PMID: 38223928 PMCID: PMC11193482 DOI: 10.1152/ajpcell.00590.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 12/21/2023] [Accepted: 01/02/2024] [Indexed: 01/16/2024]
Abstract
Loss of function mutations in the SLC26A3 gene cause chloride-losing diarrhea in mice and humans. Although systemic adaptive changes have been documented in these patients and in the corresponding knockout mice, how colonic enterocytes adapt to loss of this highly expressed and highly regulated luminal membrane anion exchanger remains unclear. To address this question, SLC26A3 was deleted in the self-differentiating Caco2BBe colonic cell line by the CRISPR/Cas9 technique. We selected a clone with loss of SLC26A3 protein expression and morphological features indistinguishable from those of the native cell line. Neither growth curves nor development of transepithelial electrical resistance (TEER) differed between wild-type (WT) and SLC26A3 knockout (KO) cells. Real-time qPCR and Western analysis in SLC26A3-KO cells revealed an increase in AE2 expression without significant change in NHE3 expression or localization. Steady-state pHi and apical and basolateral Cl-/HCO3- exchange activities were assessed fluorometrically in a dual perfusion chamber with independent perfusion of luminal and serosal baths. Apical Cl-/HCO3- exchange rates were strongly reduced in SLC26A3-KO cells, accompanied by a surface pH more acidic than that of WT cells. Steady-state pHi was not significantly different from that of WT cells, but basolateral Cl-/HCO3- exchange rates were higher in SLC26A3-KO than in WT cells. The data show that CRISPR/Cas9-mediated SLC26A3 deletion strongly reduced apical Cl-/HCO3- exchange rate and apical surface pH, but sustained a normal steady-state pHi due to increased expression and function of basolateral AE2. The low apical surface pH resulted in functional inhibition of NHE-mediated fluid absorption despite normal expression of NHE3 polypeptide.NEW & NOTEWORTHY SLC26A3 gene mutations cause chloride-losing diarrhea. To understand how colonic enterocytes adapt, SLC26A3 was deleted in Caco2BBe cells using CRISPR/Cas9. In comparison to the wild-type cells, SLC26A3 knockout cells showed similar growth and transepithelial resistance but substantially reduced apical Cl-/HCO3- exchange rates, and an acidic surface pH. Steady-state intracellular pH was comparable between the WT and KO cells due to increased basolateral AE2 expression and function.
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Affiliation(s)
- Mahdi Amiri
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Min Jiang
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Azam Salari
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Renjie Xiu
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Seth L Alper
- Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States
| | - Ursula E Seidler
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
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Guo Y, Li Y, Tang Z, Geng C, Xie X, Song S, Wang C, Li X. Compromised NHE8 Expression Is Responsible for Vitamin D-Deficiency Induced Intestinal Barrier Dysfunction. Nutrients 2023; 15:4834. [PMID: 38004229 PMCID: PMC10674576 DOI: 10.3390/nu15224834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/15/2023] [Accepted: 11/16/2023] [Indexed: 11/26/2023] Open
Abstract
Objectives: Vitamin D (VitD) and Vitamin D receptor (VDR) are suggested to play protective roles in the intestinal barrier in ulcerative colitis (UC). However, the underlying mechanisms remain elusive. Evidence demonstrates that Na+/H+ exchanger isoform 8 (NHE8, SLC9A8) is essential in maintaining intestinal homeostasis, regarded as a promising target for UC therapy. Thus, this study aims to investigate the effects of VitD/VDR on NHE8 in intestinal protection. Methods: VitD-deficient mice, VDR-/- mice and NHE8-/- mice were employed in this study. Colitis mice were established by supplementing DSS-containing water. Caco-2 cells and 3D-enteroids were used for in vitro studies. VDR siRNA (siVDR), VDR over-expression plasmid (pVDR), TNF-α and NF-κb p65 inhibitor QNZ were used for mechanical studies. The expression of interested proteins was detected by multiple techniques. Results: In colitis mice, paricalcitol upregulated NHE8 expression was accompanied by restoring colonic mucosal injury. In VitD-deficient and VDR-/- colitis mice, NHE8 expression was compromised with more serious mucosal damage. Noteworthily, paricalcitol could not prevent intestinal barrier dysfunction and histological destruction in NHE8-/- mice. In Caco-2 cells and enteroids, siVDR downregulated NHE8 expression, further promoted TNF-α-induced NHE8 downregulation and stimulated TNF-α-induced NF-κb p65 phosphorylation. Conversely, QNZ blocked TNF-α-induced NHE8 downregulation in the absence or presence of siVDR. Conclusions: Our study indicates depressed NHE8 expression is responsible for VitD-deficient-induced colitis aggravation. These findings provide novel insights into the molecular mechanisms of VitD/VDR in intestine protection in UC.
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Affiliation(s)
- Yaoyu Guo
- Department of Gastroenterology and Hepatology, West China Hospital, Sichuan University, Chengdu 610041, China; (Y.G.); (Y.L.); (X.X.); (S.S.)
| | - Yanni Li
- Department of Gastroenterology and Hepatology, West China Hospital, Sichuan University, Chengdu 610041, China; (Y.G.); (Y.L.); (X.X.); (S.S.)
| | - Zeya Tang
- Department of Outpatient, West China Hospital, Sichuan University, Chengdu 610041, China;
| | - Chong Geng
- Laboratory of Gastroenterology and Hepatology, West China Hospital, Sichuan University, Chengdu 610041, China;
| | - Xiaoxi Xie
- Department of Gastroenterology and Hepatology, West China Hospital, Sichuan University, Chengdu 610041, China; (Y.G.); (Y.L.); (X.X.); (S.S.)
| | - Shuailing Song
- Department of Gastroenterology and Hepatology, West China Hospital, Sichuan University, Chengdu 610041, China; (Y.G.); (Y.L.); (X.X.); (S.S.)
| | - Chunhui Wang
- Department of Gastroenterology and Hepatology, West China Hospital, Sichuan University, Chengdu 610041, China; (Y.G.); (Y.L.); (X.X.); (S.S.)
| | - Xiao Li
- Department of Gastroenterology and Hepatology, West China Hospital, Sichuan University, Chengdu 610041, China; (Y.G.); (Y.L.); (X.X.); (S.S.)
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Gardner CC, James PF. Na +/H + Exchangers (NHEs) in Mammalian Sperm: Essential Contributors to Male Fertility. Int J Mol Sci 2023; 24:14981. [PMID: 37834431 PMCID: PMC10573352 DOI: 10.3390/ijms241914981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 10/03/2023] [Accepted: 10/04/2023] [Indexed: 10/15/2023] Open
Abstract
Na+/H+ exchangers (NHEs) are known to be important regulators of pH in multiple intracellular compartments of eukaryotic cells. Sperm function is especially dependent on changes in pH and thus it has been postulated that NHEs play important roles in regulating the intracellular pH of these cells. For example, in order to achieve fertilization, mature sperm must maintain a basal pH in the male reproductive tract and then alkalize in response to specific signals in the female reproductive tract during the capacitation process. Eight NHE isoforms are expressed in mammalian testis/sperm: NHE1, NHE3, NHE5, NHE8, NHA1, NHA2, NHE10, and NHE11. These NHE isoforms are expressed at varying times during spermatogenesis and localize to different subcellular structures in developing and mature sperm where they contribute to multiple aspects of sperm physiology and male fertility including proper sperm development/morphogenesis, motility, capacitation, and the acrosome reaction. Previous work has provided evidence for NHE3, NHE8, NHA1, NHA2, and NHE10 being critical for male fertility in mice and NHE10 has recently been shown to be essential for male fertility in humans. In this article we review what is known about each NHE isoform expressed in mammalian sperm and discuss the physiological significance of each NHE isoform with respect to male fertility.
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Affiliation(s)
| | - Paul F. James
- Department of Biology, Miami University, Oxford, OH 45056, USA;
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Li Y, Hook JS, Ding Q, Xiao X, Chung SS, Mettlen M, Xu L, Moreland JG, Agathocleous M. Neutrophil metabolomics in severe COVID-19 reveal GAPDH as a suppressor of neutrophil extracellular trap formation. Nat Commun 2023; 14:2610. [PMID: 37147288 PMCID: PMC10162006 DOI: 10.1038/s41467-023-37567-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 03/20/2023] [Indexed: 05/07/2023] Open
Abstract
Severe COVID-19 is characterized by an increase in the number and changes in the function of innate immune cells including neutrophils. However, it is not known how the metabolome of immune cells changes in patients with COVID-19. To address these questions, we analyzed the metabolome of neutrophils from patients with severe or mild COVID-19 and healthy controls. We identified widespread dysregulation of neutrophil metabolism with disease progression including in amino acid, redox, and central carbon metabolism. Metabolic changes in neutrophils from patients with severe COVID-19 were consistent with reduced activity of the glycolytic enzyme GAPDH. Inhibition of GAPDH blocked glycolysis and promoted pentose phosphate pathway activity but blunted the neutrophil respiratory burst. Inhibition of GAPDH was sufficient to cause neutrophil extracellular trap (NET) formation which required neutrophil elastase activity. GAPDH inhibition increased neutrophil pH, and blocking this increase prevented cell death and NET formation. These findings indicate that neutrophils in severe COVID-19 have an aberrant metabolism which can contribute to their dysfunction. Our work also shows that NET formation, a pathogenic feature of many inflammatory diseases, is actively suppressed in neutrophils by a cell-intrinsic mechanism controlled by GAPDH.
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Affiliation(s)
- Yafeng Li
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jessica S Hook
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Qing Ding
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Xue Xiao
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Quantitative Biomedical Research Center, Department of Population and Data Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Stephen S Chung
- Department of Internal Medicine, Division of Hematology and Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Marcel Mettlen
- Department of Cell Biology, Quantitative Light Microscopy Core, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Lin Xu
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Quantitative Biomedical Research Center, Department of Population and Data Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jessica G Moreland
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Michalis Agathocleous
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Salari A, Zhou K, Nikolovska K, Seidler U, Amiri M. Human Colonoid-Myofibroblast Coculture for Study of Apical Na +/H + Exchangers of the Lower Cryptal Neck Region. Int J Mol Sci 2023; 24:ijms24054266. [PMID: 36901695 PMCID: PMC10001859 DOI: 10.3390/ijms24054266] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/17/2023] [Accepted: 02/18/2023] [Indexed: 02/25/2023] Open
Abstract
Cation and anion transport in the colonocyte apical membrane is highly spatially organized along the cryptal axis. Because of lack of experimental accessibility, information about the functionality of ion transporters in the colonocyte apical membrane in the lower part of the crypt is scarce. The aim of this study was to establish an in vitro model of the colonic lower crypt compartment, which expresses the transit amplifying/progenitor (TA/PE) cells, with accessibility of the apical membrane for functional study of lower crypt-expressed Na+/H+ exchangers (NHEs). Colonic crypts and myofibroblasts were isolated from human transverse colonic biopsies, expanded as three-dimensional (3D) colonoids and myofibroblast monolayers, and characterized. Filter-grown colonic myofibroblast-colonic epithelial cell (CM-CE) cocultures (myofibroblasts on the bottom of the transwell and colonocytes on the filter) were established. The expression pattern for ion transport/junctional/stem cell markers of the CM-CE monolayers was compared with that of nondifferentiated (EM) and differentiated (DM) colonoid monolayers. Fluorometric pHi measurements were performed to characterize apical NHEs. CM-CE cocultures displayed a rapid increase in transepithelial electrical resistance (TEER), paralleled by downregulation of claudin-2. They maintained proliferative activity and an expression pattern resembling TA/PE cells. The CM-CE monolayers displayed high apical Na+/H+ exchange activity, mediated to >80% by NHE2. Human colonoid-myofibroblast cocultures allow the study of ion transporters that are expressed in the apical membrane of the nondifferentiated colonocytes of the cryptal neck region. The NHE2 isoform is the predominant apical Na+/H+ exchanger in this epithelial compartment.
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Affiliation(s)
- Azam Salari
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, 30625 Hannover, Germany
| | - Kunyan Zhou
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, 30625 Hannover, Germany
- Department of Thyroid Surgery, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310027, China
| | - Katerina Nikolovska
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, 30625 Hannover, Germany
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, 30625 Hannover, Germany
- Correspondence: (U.S.); (M.A.); Tel.: +49-511-532-9427 (U.S.); Fax: +49-511-532-8428 (U.S.)
| | - Mahdi Amiri
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, 30625 Hannover, Germany
- Correspondence: (U.S.); (M.A.); Tel.: +49-511-532-9427 (U.S.); Fax: +49-511-532-8428 (U.S.)
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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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