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Roussa E, Juda P, Laue M, Mai-Kolerus O, Meyerhof W, Sjöblom M, Nikolovska K, Seidler U, Kilimann MW. LRBA, a BEACH protein mutated in human immune deficiency, is widely expressed in epithelia, exocrine and endocrine glands, and neurons. Sci Rep 2024; 14:10678. [PMID: 38724551 PMCID: PMC11082223 DOI: 10.1038/s41598-024-60257-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 04/20/2024] [Indexed: 05/12/2024] Open
Abstract
Mutations in LRBA, a BEACH domain protein, cause severe immune deficiency in humans. LRBA is expressed in many tissues and organs according to biochemical analysis, but little is known about its cellular and subcellular localization, and its deficiency phenotype outside the immune system. By LacZ histochemistry of Lrba gene-trap mice, we performed a comprehensive survey of LRBA expression in numerous tissues, detecting it in many if not all epithelia, in exocrine and endocrine cells, and in subpopulations of neurons. Immunofluorescence microscopy of the exocrine and endocrine pancreas, salivary glands, and intestinal segments, confirmed these patterns of cellular expression and provided information on the subcellular localizations of the LRBA protein. Immuno-electron microscopy demonstrated that in neurons and endocrine cells, which co-express LRBA and its closest relative, neurobeachin, both proteins display partial association with endomembranes in complementary, rather than overlapping, subcellular distributions. Prominent manifestations of human LRBA deficiency, such as inflammatory bowel disease or endocrinopathies, are believed to be primarily due to immune dysregulation. However, as essentially all affected tissues also express LRBA, it is possible that LRBA deficiency enhances their vulnerability and contributes to the pathogenesis.
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Affiliation(s)
- Eleni Roussa
- Department Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, Albert-Ludwigs-University Freiburg, Freiburg, Germany
| | - Pavel Juda
- Department of Molecular Neurobiology, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
- Leukocyte Motility Lab, 1st Faculty of Medicine, Charles University of Prague, Vestec, Czech Republic
| | - Michael Laue
- Advanced Light and Electron Microscopy (ZBS 4), Robert Koch Institute, Berlin, Germany
| | - Oliver Mai-Kolerus
- Department of Molecular Genetics, German Institute for Human Nutrition, Potsdam-Rehbruecke, Germany
- Einstein Center for Neurosciences, Charite - Universitätsmedizin Berlin, Berlin, Germany
| | - Wolfgang Meyerhof
- Department of Molecular Genetics, German Institute for Human Nutrition, Potsdam-Rehbruecke, Germany
- Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Markus Sjöblom
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Katerina Nikolovska
- Department of Gastroenterology, Hepatology, Infectiology and Endocrinology, Medical University Hannover, Hannover, Germany
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology, Infectiology and Endocrinology, Medical University Hannover, Hannover, Germany
| | - Manfred W Kilimann
- Department of Molecular Neurobiology, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany.
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Becker HM, Seidler UE. Bicarbonate secretion and acid/base sensing by the intestine. Pflugers Arch 2024; 476:593-610. [PMID: 38374228 PMCID: PMC11006743 DOI: 10.1007/s00424-024-02914-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/15/2024] [Accepted: 01/17/2024] [Indexed: 02/21/2024]
Abstract
The transport of bicarbonate across the enterocyte cell membrane regulates the intracellular as well as the luminal pH and is an essential part of directional fluid movement in the gut. Since the first description of "active" transport of HCO3- ions against a concentration gradient in the 1970s, the fundamental role of HCO3- transport for multiple intestinal functions has been recognized. The ion transport proteins have been identified and molecularly characterized, and knockout mouse models have given insight into their individual role in a variety of functions. This review describes the progress made in the last decade regarding novel techniques and new findings in the molecular regulation of intestinal HCO3- transport in the different segments of the gut. We discuss human diseases with defects in intestinal HCO3- secretion and potential treatment strategies to increase luminal alkalinity. In the last part of the review, the cellular and organismal mechanisms for acid/base sensing in the intestinal tract are highlighted.
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Affiliation(s)
- Holger M Becker
- Department of Gastroenterology, Hannover Medical School, 30625, Hannover, Germany
| | - Ursula E Seidler
- Department of Gastroenterology, Hannover Medical School, 30625, Hannover, Germany.
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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 DOI: 10.1152/ajpcell.00590.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Çelik AT, Barış Z, Aydemir Y, Kocagil S. Late Diagnosis of Congenital Chloride Diarrhea Mimicking Hirschsprung's Disease. Clin Pediatr (Phila) 2024:99228241228116. [PMID: 38303675 DOI: 10.1177/00099228241228116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Affiliation(s)
- Ali Tugay Çelik
- Department of Pediatrics, Faculty of Medicine, Eskisehir Osmangazi University, Eskisehir, Turkey
| | - Zeren Barış
- Department of Pediatric Gastroenterology, Hepatology and Nutrition, Faculty of Medicine, Eskisehir Osmangazi University, Eskisehir, Turkey
| | - Yusuf Aydemir
- Department of Pediatric Gastroenterology, Hepatology and Nutrition, Faculty of Medicine, Eskisehir Osmangazi University, Eskisehir, Turkey
| | - Sinem Kocagil
- Department of Medical Genetics, Faculty of Medicine, Eskisehir Osmangazi University, Eskisehir, Turkey
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Geertsma ER, Oliver D. SLC26 Anion Transporters. Handb Exp Pharmacol 2024; 283:319-360. [PMID: 37947907 DOI: 10.1007/164_2023_698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Solute carrier family 26 (SLC26) is a family of functionally diverse anion transporters found in all kingdoms of life. Anions transported by SLC26 proteins include chloride, bicarbonate, and sulfate, but also small organic dicarboxylates such as fumarate and oxalate. The human genome encodes ten functional homologs, several of which are causally associated with severe human diseases, highlighting their physiological importance. Here, we review novel insights into the structure and function of SLC26 proteins and summarize the physiological relevance of human members.
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Affiliation(s)
- Eric R Geertsma
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
| | - Dominik Oliver
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, Marburg, Germany.
- Center for Mind, Brain and Behavior (CMBB), Universities of Marburg and Giessen, Marburg, Giessen, Germany.
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Zachos NC, Vaughan H, Sarker R, Est-Witte S, Chakraborty M, Baetz NW, Yu H, Yarov-Yarovoy V, McNamara G, Green JJ, Tse CM, Donowitz M. A Novel Peptide Prevents Enterotoxin- and Inflammation-Induced Intestinal Fluid Secretion by Stimulating Sodium-Hydrogen Exchanger 3 Activity. Gastroenterology 2023; 165:986-998.e11. [PMID: 37429363 DOI: 10.1053/j.gastro.2023.06.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/05/2023] [Accepted: 06/09/2023] [Indexed: 07/12/2023]
Abstract
BACKGROUND & AIMS Acute diarrheal diseases are the second most common cause of infant mortality in developing countries. This is contributed to by lack of effective drug therapy that shortens the duration or lessens the volume of diarrhea. The epithelial brush border sodium (Na+)/hydrogen (H+) exchanger 3 (NHE3) accounts for a major component of intestinal Na+ absorption and is inhibited in most diarrheas. Because increased intestinal Na+ absorption can rehydrate patients with diarrhea, NHE3 has been suggested as a potential druggable target for drug therapy for diarrhea. METHODS A peptide (sodium-hydrogen exchanger 3 stimulatory peptide [N3SP]) was synthesized to mimic the part of the NHE3 C-terminus that forms a multiprotein complex that inhibits NHE3 activity. The effect of N3SP on NHE3 activity was evaluated in NHE3-transfected fibroblasts null for other plasma membrane NHEs, a human colon cancer cell line that models intestinal absorptive enterocytes (Caco-2/BBe), human enteroids, and mouse intestine in vitro and in vivo. N3SP was delivered into cells via a hydrophobic fluorescent maleimide or nanoparticles. RESULTS N3SP uptake stimulated NHE3 activity at nmol/L concentrations under basal conditions and partially reversed the reduced NHE3 activity caused by elevated adenosine 3',5'-cyclic monophosphate, guanosine 3',5'-cyclic monophosphate, and Ca2+ in cell lines and in in vitro mouse intestine. N3SP also stimulated intestinal fluid absorption in the mouse small intestine in vivo and prevented cholera toxin-, Escherichia coli heat-stable enterotoxin-, and cluster of differentiation 3 inflammation-induced fluid secretion in a live mouse intestinal loop model. CONCLUSIONS These findings suggest pharmacologic stimulation of NHE3 activity as an efficacious approach for the treatment of moderate/severe diarrheal diseases.
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Affiliation(s)
- Nicholas C Zachos
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
| | - Hannah Vaughan
- Translational Tissue Engineering Center, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Rafiquel Sarker
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Savannah Est-Witte
- Translational Tissue Engineering Center, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Molee Chakraborty
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Nicholas W Baetz
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Hongzhe Yu
- Translational Tissue Engineering Center, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California; Department of Anesthesiology and Pain Medicine, University of California Davis, Davis, California
| | - George McNamara
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Jordan J Green
- Translational Tissue Engineering Center, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Chung-Ming Tse
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Mark Donowitz
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland; Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
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ZHANG QY, GUO Y, JIANG XL, LIU X, ZHAO SG, ZHOU XL, YANG ZW. Intestinal Cckbr-specific knockout mouse as a novel model of salt-sensitive hypertension via sodium over-absorption. J Geriatr Cardiol 2023; 20:538-547. [PMID: 37576480 PMCID: PMC10412539 DOI: 10.26599/1671-5411.2023.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023] Open
Abstract
OBJECTIVES To investigate the value of CCKBRfl/fl villin-Cre mice as a mouse model of salt-sensitive hypertension (SSH). METHODS In the first part, 2-month-old CCKBRfl/fl villin-Cre mice (CKO) and control CCKBRfl/fl mice (WT) were fed with normal diet (0.4% NaCl) or high salt diet (4% NaCl), separately for 6 weeks. In the rescue study, one week of hydrochlorothiazide or saline injection were treated with the CKO mice fed high salt diet. The blood pressure, biochemical indexes, and the expression of small intestinal sodium transporters (NHE3, NKCC1, eNaC) was detected. The organ injury markers (MMP2/MMP9) and the histopathological changes of kidneys were observed, whereas the changes of duodenal sodium absorption were detected by small intestinal perfusion in vivo. RESULTS The CCKBRfl/fl villin-Cre mice with high salt intake exhibited high blood pressure, increased duodenal sodium absorption and urinary sodium excretion, and with renal injury. The protein expression of NHE3, NKCC1 and eNaC were also significant increase in the intestine of CKO-HS mice. Treatment with hydrochlorothiazide remarkably attenuated the elevated blood pressure by high salt absorption in the CCKBRfl/fl villin-Cre mice, but no significant histopathological changes were observed. CONCLUSIONS These results support a crucial role of intestinal Cckbr deficiency on SSH development and the diuretic antihypertension effect in CCKBRfl/fl villin-Cre mice. The CCKBRfl/fl villin-Cre mice with the high salt intake may serve as a stable model of salt-sensitive hypertensive induced by sodium overloading.
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Affiliation(s)
- Qiong-Yu ZHANG
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yan GUO
- Emergency Department, Taihe County People’s Hospital, Taihe County, Anhui Province, China
| | - Xiao-Liang JIANG
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical Collage (PUMC), Beijing, China
| | - Xing LIU
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical Collage (PUMC), Beijing, China
| | - Shu-Guang ZHAO
- Emergency Department, Taihe County People’s Hospital, Taihe County, Anhui Province, China
| | - Xian-Liang ZHOU
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Zhi-Wei YANG
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical Collage (PUMC), Beijing, China
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Fan W, Tan Q. Application of the steady-state intestinal perfusion system in measuring intestinal fluid absorption and bicarbonate secretion in vivo. Front Physiol 2023; 14:1163888. [PMID: 37497438 PMCID: PMC10366686 DOI: 10.3389/fphys.2023.1163888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 06/26/2023] [Indexed: 07/28/2023] Open
Abstract
Background: The steady-state intestinal perfusion system represents a tool used in measuring intestinal fluid absorption and bicarbonate secretion in vivo; however, detailed procedures and parameters were not elucidated fully. Aim: We focused on the methods of the steady-state intestinal perfusion system comprehensively including the blood pressure, hematocrit, blood gas, and heart rate of mouse. Methods: Anesthetized, tracheally intubated, and artificially ventilated mice were used for this system. The blood pressure, hematocrit, blood gas, heart rate, and rate of fluid absorption and HCO3 - secretion of the small intestine and colon at different time points were evaluated. Results: Blood pressure, hematocrit, blood gas, and heart rate became stable at the 30 min time point after completion of surgery and could be maintained for 2 h. Rates of fluid absorption and bicarbonate secretion were also kept stable during the period of steady state of mice. Rates of fluid absorption and bicarbonate secretion were different among the jejunum, ileum, proximal, and mid-distal colon. Conclusion: The steady-state intestinal perfusion system is a reliable system for measuring intestinal fluid absorption and bicarbonate secretion in vivo.
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Tse CM, Zhang Z, Lin R, Sarker R, Donowitz M, Singh V. The Air-Liquid Interface Reorganizes Membrane Lipids and Enhances the Recruitment of Slc26a3 to Lipid-Rich Domains in Human Colonoid Monolayers. Int J Mol Sci 2023; 24:ijms24098273. [PMID: 37175979 PMCID: PMC10179158 DOI: 10.3390/ijms24098273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/15/2023] Open
Abstract
Cholesterol-rich membrane domains, also called lipid rafts (LRs), are specialized membrane domains that provide a platform for intracellular signal transduction. Membrane proteins often cluster in LRs that further aggregate into larger platform-like structures that are enriched in ceramides and are called ceramide-rich platforms (CRPs). The role of CRPs in the regulation of intestinal epithelial functions remains unknown. Down-regulated in adenoma (DRA) is an intestinal Cl-/HCO3- antiporter that is enriched in LRs. However, little is known regarding the mechanisms involved in the regulation of DRA activity. The air-liquid interface (ALI) was created by removing apical media for a specified number of days; from 12-14 days post-confluency, Caco-2/BBe cells or a colonoid monolayer were grown as submerged cultures. Confocal imaging was used to examine the dimensions of membrane microdomains that contained DRA. DRA expression and activity were enhanced in Caco-2/BBe cells and human colonoids using an ALI culture method. ALI causes an increase in acid sphingomyelinase (ASMase) activity, an enzyme responsible for enhancing ceramide content in the plasma membrane. ALI cultures expressed a larger number of DRA-containing platforms with dimensions >2 µm compared to cells grown as submerged cultures. ASMase inhibitor, desipramine, disrupted CRPs and reduced the ALI-induced increase in DRA expression in the apical membrane. Exposing normal human colonoid monolayers to ALI increased the ASMase activity and enhanced the differentiation of colonoids along with basal and forskolin-stimulated DRA activities. ALI increases DRA activity and expression by increasing ASMase activity and platform formation in Caco-2/BBe cells and by enhancing the differentiation of colonoids.
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Affiliation(s)
- C Ming Tse
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Zixin Zhang
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Ruxian Lin
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Rafiquel Sarker
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
| | - Mark Donowitz
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
- Department of Cellular and Molecular Physiology, School of Medicine, The Johns Hopkins University, Baltimore, MD 21205, USA
| | - Varsha Singh
- Division of Gastroenterology & Hepatology, Department of Medicine, School of Medicine, The Johns Hopkins University, 720 Rutland Avenue, 933 Ross Research Building, Baltimore, MD 21205, USA
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Guo Y, Li X, Geng C, Song S, Xie X, Wang C. Vitamin D receptor involves in the protection of intestinal epithelial barrier function via up-regulating SLC26A3. J Steroid Biochem Mol Biol 2023; 227:106231. [PMID: 36462760 DOI: 10.1016/j.jsbmb.2022.106231] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 05/13/2022] [Accepted: 07/15/2022] [Indexed: 12/05/2022]
Abstract
BACKGROUND Vitamin D receptor (VDR) and SLC26A3 (DRA) have been identified as pivotal protective factors in maintaining gut homeostasis in IBD patients. However, the specific mechanism underlying the increased intestinal susceptibility to inflammation induced by the loss of VDR and whether DRA participates in the role of VDR regulating intestinal epithelial barrier function are undefined. AIM The current study is undertaken to elucidate the regulatory effects of VDR on DRA and VDR prevents intestinal epithelial barrier dysfunction via up-regulating the expression of DRA. METHODS WT and VDR-/- mice are used as models for intestinal epithelial response. Paracellular permeability is measured by TEER and FD-4 assays. Immunohistochemistry, immunofluorescence, qPCR and immunoblotting are performed to determine the effects of VDR and DRA on gut epithelial barrier function. RESULTS VDR-/- mice exhibits significant hyperpermeability of intestine with greatly decreased levels of ZO-1 and Claudin1 proteins. DRA is located on the intestinal epithelial apical membrane and is tightly modulated by VDR in vivo and in vitro via activating ERK1/2 MAPK signaling pathway. Notably, the current study for the first time demonstrates that VDR maintains intestinal epithelial barrier integrity via up-regulating DRA expression and the lack of DRA induced by VDR knockdown leads to a more susceptive condition for intestine to DSS-induced colitis. CONCLUSION Our study provides evidence and deep comprehension regarding the role of VDR in modulating DRA expression in gut homeostasis and makes novel contributions to better generally understanding the links between VDR, DRA and intestinal epithelial barrier function.
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Affiliation(s)
- Yaoyu Guo
- Department of Gastroenterology, West China Hospital of Sichuan University, Chengdu, China
| | - Xiao Li
- Department of Gastroenterology, West China Hospital of Sichuan University, Chengdu, China
| | - Chong Geng
- Department of Gastroenterology, West China Hospital of Sichuan University, Chengdu, China
| | - Shuailing Song
- Department of Gastroenterology, West China Hospital of Sichuan University, Chengdu, China
| | - Xiaoxi Xie
- Department of Gastroenterology, West China Hospital of Sichuan University, Chengdu, China
| | - Chunhui Wang
- Department of Gastroenterology, West China Hospital of Sichuan University, Chengdu, China.
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Whittamore JM, Hatch M. Oxalate secretion is stimulated by a cAMP-dependent pathway in the mouse cecum. Pflugers Arch 2023; 475:249-266. [PMID: 36044064 PMCID: PMC9851989 DOI: 10.1007/s00424-022-02742-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 08/06/2022] [Accepted: 08/18/2022] [Indexed: 02/01/2023]
Abstract
Elevated levels of the intracellular second messenger cAMP can stimulate intestinal oxalate secretion however the membrane transporters responsible are unclear. Oxalate transport by the chloride/bicarbonate (Cl-/HCO3-) exchanger Slc26a6 or PAT-1 (Putative Anion Transporter 1), is regulated via cAMP when expressed in Xenopus oocytes and cultured cells but whether this translates to the native epithelia is unknown. This study investigated the regulation of oxalate transport by the mouse intestine focusing on transport at the apical membrane hypothesizing PAT-1 is the target of a cAMP-dependent signaling pathway. Adopting the Ussing chamber technique we measured unidirectional 14C-oxalate and 36Cl- flux ([Formula: see text] and [Formula: see text]) across distal ileum, cecum and distal colon, employing forskolin (FSK) and 3-isobutyl-1-methylxanthine (IBMX) to trigger cAMP production. FSK/IBMX initiated a robust secretory response by all segments but the stimulation of net oxalate secretion was confined to the cecum only involving activation of [Formula: see text] and distinct from net Cl- secretion produced by inhibiting [Formula: see text]. Using the PAT-1 knockout (KO) mouse we determined cAMP-stimulated [Formula: see text] was not directly dependent on PAT-1, but it was sensitive to mucosal DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid), although unlikely to be another Cl-/HCO3- exchanger given the lack of trans-stimulation or cis-inhibition by luminal Cl- or HCO3-. The cAMP-activated oxalate efflux was reliant on CFTR (Cystic Fibrosis Transmembrane conductance Regulator) activity, but only in the presence of PAT-1, leading to speculation on the involvement of a multi-transporter regulatory complex. Further investigations at the cellular and molecular level are necessary to define the mechanism and transporter(s) responsible.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA.
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research | Internal Medicine, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-8885, USA.
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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Nylander O, Sjöblom M, Sedin J, Dahlgren D. Effects of α2-adrenoceptor stimulation on luminal alkalinisation and net fluid flux in rat duodenum. PLoS One 2022; 17:e0273208. [PMID: 36006975 PMCID: PMC9409570 DOI: 10.1371/journal.pone.0273208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 08/03/2022] [Indexed: 12/03/2022] Open
Abstract
The sympathetic nervous system is highly involved in the regulation of gastrointestinal functions such as luminal alkalinisation and fluid absorption. However, the exact mechanisms are not clear. This study aimed to delineate how α2-adrenergic receptor stimulation reduces duodenal luminal alkalinisation and induces net fluid absorption. This was tested by perfusing the duodenum of anesthetized rats with isotonic solutions devoid of Cl- and/or Na+, in the absence and presence of the α2-adrenoceptor agonist clonidine. The clonidine was also studied in rats treated with dimethylamiloride (a Na+/H+ exchange inhibitor), vasoactive intestinal peptide, and the nicotinic receptor antagonist hexamethonium. Clonidine reduced luminal alkalinisation and induced net fluid absorption. The Cl--free solution decreased luminal alkalinisation and abolished net fluid absorption, but did not prevent clonidine from doing so. Both the Na+-free solution and luminal dimethylamiloride increased luminal alkalinisation and abolished net fluid absorption, effects counteracted by clonidine. The NaCl-free solution (D-mannitol) did not affect luminal alkalinisation, but reduced net fluid absorption. Clonidine reduced luminal alkalinisation and induced net fluid absorption in rats perfused luminally with mannitol. However, clonidine did not affect the vasoactive intestinal peptide-induced increase in luminal alkalinisation or fluid secretion. Pre-treatment with hexamethonium abolished the effects of clonidine on luminal alkalinisation and net fluid flux. In summary, our in vivo experiments showed that clonidine-induced reduction in luminal alkalinisation and induction of net fluid absorption was unrelated to luminal Na+ and Cl-, or to apical Na+/H+ or Cl-/HCO3- exchangers. Instead, clonidine seems to exert its effects via suppression of nicotinic receptor-activated acetylcholine secretomotor neurons.
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Affiliation(s)
- Olof Nylander
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Markus Sjöblom
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - John Sedin
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - David Dahlgren
- Division of Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
- * E-mail:
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Kim S, Vaidya B, Cho SY, Kwon J, Kim D. Human Norovirus-Induced Gene Expression Biomarkers in Zebrafish. J Food Prot 2022; 85:924-929. [PMID: 35333356 DOI: 10.4315/jfp-21-419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 03/16/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT The challenges associated with development of an animal model system to replicate human norovirus (HuNoV) has hampered the study of the pathogenesis and therapeutic interventions for this virus. In this study, we replicated HuNoV GII.4 and evaluated virus gene expression in infected zebrafish. Three doses of inoculation resulted in successful virus replication. Genes for transmembrane transporters (tfa, cftr, slc26a3, and slc26a6), a heat shock chaperone (hspa8), and immune response cytokines (ifng1 and il1b) were highly expressed in HuNoV-infected zebrafish; however, expression levels of genes were reduced in zebrafish infected with thermally inactivated HuNoV. These results confirm HuNoV replication in juvenile zebrafish and will facilitate the investigation of biomarker gene expression during HuNoV infection. HIGHLIGHTS
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Affiliation(s)
- Songhak Kim
- Department of Food Science and Technology and Foodborne Virus Research Center, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Bipin Vaidya
- Department of Food Science and Technology and Foodborne Virus Research Center, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Se-Young Cho
- Department of Food Science and Technology and Foodborne Virus Research Center, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Joseph Kwon
- Department of BioChemical Analysis, Korea Basic Science Institute, Daejeon 34133, Republic of Korea
| | - Duwoon Kim
- Department of Food Science and Technology and Foodborne Virus Research Center, Chonnam National University, Gwangju 61186, Republic of Korea
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Kini A, Zhao B, Basic M, Roy U, Iljazovic A, Odak I, Ye Z, Riederer B, Di Stefano G, Römermann D, Koenecke C, Bleich A, Strowig T, Seidler U. Upregulation of antimicrobial peptide expression in slc26a3-/- mice with colonic dysbiosis and barrier defect. Gut Microbes 2022; 14:2041943. [PMID: 35230892 PMCID: PMC8890434 DOI: 10.1080/19490976.2022.2041943] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Genetic defects in SLC26A3 (DRA), an intestinal Cl-/HCO3- exchanger, result in congenital chloride diarrhea (CLD), marked by lifelong acidic diarrhea and a high risk of inflammatory bowel disease. Slc26a3-/- mice serve as a model to understand the pathophysiology of CLD and search for treatment options. This study investigates the microbiota changes in slc26a3-/- colon, the genotype-related causes for the observed microbiota alterations, its inflammatory potential, as well as the corresponding host responses. The luminal and the mucosa-adherent cecal and colonic microbiota of cohoused slc26a3-/- and wt littermates were analyzed by 16S rRNA gene sequencing. Fecal microbiota transfer from cohoused slc26a3-/- and wt littermates to germ-free wt mice was performed to analyze the stability and the inflammatory potential of the communities.The cecal and colonic luminal and mucosa-adherent microbiota of slc26a3-/- mice was abnormal from an early age, with a loss of diversity, of short-chain fatty acid producers, and an increase of pathobionts. The transfer of slc26a3-/- microbiota did not result in intestinal inflammation and the microbial diversity in the recipient mice normalized over time. A strong increase in the expression of Il22, Reg3β/γ, Relmβ, and other proteins with antimicrobial functions was observed in slc26a3-/- colon from juvenile age, while the mucosal and systemic inflammatory signature was surprisingly mild. The dysbiotic microbiota, low mucosal pH, and mucus barrier defect in slc26a3-/- colon are accompanied by a stark upregulation of the expression of a panel of antimicrobial proteins. This may explain the low inflammatory burden in the gut of these mice.
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Affiliation(s)
| | - Bei Zhao
- Microbial Immune Regulation Research Group, Helmholtz Center for Infection Research, Braunschweig, Germany
| | | | - Urmi Roy
- Microbial Immune Regulation Research Group, Helmholtz Center for Infection Research, Braunschweig, Germany
| | - Aida Iljazovic
- Microbial Immune Regulation Research Group, Helmholtz Center for Infection Research, Braunschweig, Germany
| | - Ivan Odak
- Institute of Immunology Hannover Medical School Hannover, Germany
| | | | | | | | | | | | | | - Till Strowig
- Microbial Immune Regulation Research Group, Helmholtz Center for Infection Research, Braunschweig, Germany
| | - Ursula Seidler
- Department of Gastroenterology,CONTACT Ursula Seidler Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl Neuberg Straße 1, D30625, Hannover.de, Germany
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16
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Nikolovska K, Cao L, Hensel I, Di Stefano G, Seidler A, Zhou K, Qian J, Singh AK, Riederer B, Seidler U. Sodium/hydrogen-exchanger-2 modulates colonocyte lineage differentiation. Acta Physiol (Oxf) 2022; 234:e13774. [PMID: 34985202 DOI: 10.1111/apha.13774] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 10/12/2021] [Accepted: 01/01/2022] [Indexed: 12/11/2022]
Abstract
AIM The sodium/hydrogen exchanger 2 (NHE2) is an intestinal acid extruder with crypt-predominant localization and unresolved physiological significance. Our aim was to decipher its role in colonic epithelial cell proliferation, differentiation and electrolyte transport. METHODS Alterations induced by NHE2-deficiency were addressed in murine nhe2-/- and nhe2+/+ colonic crypts and colonoids, and NHE2-knockdown and control Caco2Bbe cells using pH-fluorometry, gene expression analysis and immunofluorescence. RESULTS pHi -measurements along the colonic cryptal axis revealed significantly decreased intracellular pH (pHi ) in the middle segment of nhe2-/- compared to nhe2+/+ crypts. Increased Nhe2 mRNA expression was detected in murine colonoids in the transiently amplifying/progenitor cell stage (TA/PE). Lack of Nhe2 altered the differentiation programme of colonic epithelial cells with reduced expression of absorptive lineage markers alkaline phosphatase (iAlp), Slc26a3 and transcription factor hairy and enhancer-of-split 1 (Hes1), but increased expression of secretory lineage markers Mucin 2, trefoil factor 3 (Tff3), enteroendocrine marker chromogranin A and murine atonal homolog 1 (Math1). Enterocyte differentiation was found to be pHi dependent with acidic pHi reducing, and alkaline pHi stimulating the expression of enterocyte differentiation markers in Caco2Bbe cells. A thicker mucus layer, longer crypts and an expanded brush border membrane zone of sodium/hydrogen exchanger 3 (NHE3) abundance may explain the lack of inflammation and the normal fluid absorptive rate in nhe2-/- colon. CONCLUSIONS The results suggest that NHE2 expression is activated when colonocytes emerge from the stem cell niche. Its activity increases progenitor cell pHi and thereby supports absorptive enterocyte differentiation.
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Affiliation(s)
- Katerina Nikolovska
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
| | - Li Cao
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
- Department of Gastroenterology Tongji Hospital Huazhong University Wuhan China
| | - Inga Hensel
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
| | - Gabriella Di Stefano
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
| | - Anna Elisabeth Seidler
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
| | - Kunyan Zhou
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
| | - Jiajie Qian
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
- Department of Transplantation and Hepatobiliary Surgery First Affiliated Hospital of Zheijang University Hangzhou China
| | - Anurag Kumar Singh
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
- Department of Physiological Chemistry University of Halle Halle (Saale) Germany
| | - Brigitte Riederer
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology and Endocrinology Hannover Medical School Hannover Germany
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Abstract
Epithelial oxalate transport is fundamental to the role occupied by the gastrointestinal (GI) tract in oxalate homeostasis. The absorption of dietary oxalate, together with its secretion into the intestine, and degradation by the gut microbiota, can all influence the excretion of this nonfunctional terminal metabolite in the urine. Knowledge of the transport mechanisms is relevant to understanding the pathophysiology of hyperoxaluria, a risk factor in kidney stone formation, for which the intestine also offers a potential means of treatment. The following discussion presents an expansive review of intestinal oxalate transport. We begin with an overview of the fate of oxalate, focusing on the sources, rates, and locations of absorption and secretion along the GI tract. We then consider the mechanisms and pathways of transport across the epithelial barrier, discussing the transcellular, and paracellular components. There is an emphasis on the membrane-bound anion transporters, in particular, those belonging to the large multifunctional Slc26 gene family, many of which are expressed throughout the GI tract, and we summarize what is currently known about their participation in oxalate transport. In the final section, we examine the physiological stimuli proposed to be involved in regulating some of these pathways, encompassing intestinal adaptations in response to chronic kidney disease, metabolic acid-base disorders, obesity, and following gastric bypass surgery. There is also an update on research into the probiotic, Oxalobacter formigenes, and the basis of its unique interaction with the gut epithelium. © 2021 American Physiological Society. Compr Physiol 11:1-41, 2021.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
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18
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Zhou K, Amiri M, Salari A, Yu Y, Xu H, Seidler U, Nikolovska K. Functional characterization of the sodium/hydrogen exchanger 8 and its role in proliferation of colonic epithelial cells. Am J Physiol Cell Physiol 2021; 321:C471-C488. [PMID: 34288721 DOI: 10.1152/ajpcell.00582.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Intestinal NaCl, HCO3-, and fluid absorption are strongly dependent on apical Na+/H+ exchange. The intestine expresses three presumably apical sodium-hydrogen exchanger (NHE) isoforms: NHE2, NHE3, and NHE8. We addressed the role of NHE8 [solute carrier 9A8 (SLC9A8)] and its interplay with NHE2 (SLC9A2) in luminal proton extrusion during acute and chronic enterocyte acidosis and studied the differential effects of NHE8 and NHE2 on enterocyte proliferation. In contrast to NHE3, which was upregulated in differentiated versus undifferentiated colonoids, the expression of NHE2 and NHE8 remained constant during differentiation of colonoids and Caco2Bbe cells. Heterogeneously expressed Flag-tagged rat (r)Nhe8 and human (h)NHE8 translocated to the apical membrane of Caco2Bbe cells. rNhe8 and hNHE8, when expressed in NHE-deficient PS120 fibroblasts showed higher sensitivity to HOE642 compared to NHE2. Lentiviral shRNA knockdown of endogenous NHE2 in Caco2Bbe cells (C2Bbe/shNHE2) resulted in a decreased steady-state intracellular pH (pHi), an increased NHE8 mRNA expression, and augmented NHE8-mediated apical NHE activity. Lentiviral shRNA knockdown of endogenous NHE8 in Caco2Bbe cells (C2Bbe/shNHE8) resulted in a decreased steady-state pHi as well, accompanied by decreased NHE2 mRNA expression and activity, which together contributed to reduced apical NHE activity in the NHE8-knockdown cells. Chronic acidosis increased NHE8 but not NHE2 mRNA expression. Alterations in NHE2 and NHE8 expression/activity affected proliferation, with C2Bbe/shNHE2 cells having lower and C2Bbe/shNHE8 having higher proliferative capacity, accompanied by amplified ERK1/2 signaling pathway and increased EGFR expression in the latter cell line. Thus, both Na+/H+ exchangers have distinct functions during cellular homeostasis by triggering different signaling pathways to regulate cellular proliferation and pHi control.
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Affiliation(s)
- Kunyan Zhou
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Mahdi Amiri
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Azam Salari
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Yan Yu
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Hua Xu
- Department of Pediatrics, University of Arizona Health Science Center, Tucson, Arizona
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Katerina Nikolovska
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
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19
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Di Meglio L, Castaldo G, Mosca C, Paonessa A, Gelzo M, Esposito MV, Berni Canani R. Congenital chloride diarrhea clinical features and management: a systematic review. Pediatr Res 2021; 90:23-29. [PMID: 33173177 DOI: 10.1038/s41390-020-01251-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 10/06/2020] [Indexed: 11/09/2022]
Abstract
INTRODUCTION Congenital chloride diarrhea (CLD) is a rare autosomal recessive disorder characterized by watery diarrhea with a high level of fecal Cl-, metabolic alkalosis, and electrolyte alterations. Several intestinal and extraintestinal complications and even death can occur. An optimal knowledge of the clinical features and best therapeutic strategies is mandatory for an effective management. METHODS Articles published between 1 January 1965 and 31 December 2019, reported in PUBMED and EMBASE, were evaluated for a systematic review analyzing four categories: anamnestic features, clinical features, management, and follow-up strategies. RESULTS Fifty-seven papers reporting information on 193 CLD patients were included. The most common anamnestic features were positive family anamnesis for chronic diarrhea (44.4%), consanguinity (75%), polyhydramnios (98.3%), preterm delivery (78.6%), and failure to pass meconium (60.7%). Mean age at diarrhea onset was 6.63 days. Median diagnostic delay was 60 days. Prenatal diagnosis, based on molecular analysis, was described in 40/172 (23.3%). All patients received NaCl/KCl-substitutive therapy. An improvement of diarrhea during adulthood was reported in 91.3% of cases. Failure to thrive (21.6%) and chronic kidney disease (17.7%) were the most common complications. CONCLUSIONS This analysis of a large population suggests the necessity of better strategies for the management of CLD. A close follow-up and a multidisciplinary approach is mandatory to manage this condition characterized by heterogeneous and multisystemic complications. IMPACT In this systematic review, we describe data regarding anamnestic features, clinical features, management, and follow-up of CLD patients obtained from the largest population of patients ever described to date. The results of our investigation could provide useful insights for the diagnostic approach and the management of this condition.
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Affiliation(s)
- Lavinia Di Meglio
- Department of Translational Medical Science, University Federico II, Naples, Italy.,Diagnostica Ecografica e Prenatale di A.Di Meglio, Naples, Italy
| | - Giuseppe Castaldo
- CEINGE Advanced Biotechnologies Research Center, University Federico II, Naples, Italy
| | - Caterina Mosca
- Department of Translational Medical Science, University Federico II, Naples, Italy
| | - Andrea Paonessa
- Department of Translational Medical Science, University Federico II, Naples, Italy
| | - Monica Gelzo
- CEINGE Advanced Biotechnologies Research Center, University Federico II, Naples, Italy.,Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | | | - Roberto Berni Canani
- Department of Translational Medical Science, University Federico II, Naples, Italy. .,CEINGE Advanced Biotechnologies Research Center, University Federico II, Naples, Italy.
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Cil O, Haggie PM, Tan JAT, Rivera AA, Verkman AS. SLC26A6-selective inhibitor identified in a small-molecule screen blocks fluid absorption in small intestine. JCI Insight 2021; 6:e147699. [PMID: 34100381 PMCID: PMC8262356 DOI: 10.1172/jci.insight.147699] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 04/21/2021] [Indexed: 12/14/2022] Open
Abstract
SLC26A6 (also known as putative anion transporter 1 [PAT1]) is a Cl–/HCO3– exchanger expressed at the luminal membrane of enterocytes where it facilitates intestinal Cl– and fluid absorption. Here, high-throughput screening of 50,000 synthetic small molecules in cells expressing PAT1 and a halide-sensing fluorescent protein identified several classes of inhibitors. The most potent compound, the pyrazolo-pyrido-pyrimidinone PAT1inh-B01, fully inhibited PAT1-mediated anion exchange (IC50 ~350 nM), without inhibition of the related intestinal transporter SLC26A3 (also known as DRA). In closed midjejunal loops in mice, PAT1inh-B01 inhibited fluid absorption by 50%, which increased to >90% when coadministered with DRA inhibitor DRAinh-A270. In ileal loops, PAT1inh-B01 blocked fluid absorption by >80%, whereas DRAinh-A270 was without effect. In colonic loops, PAT1inh-B01 was without effect, whereas DRAinh-A270 completely blocked fluid absorption. In a loperamide constipation model, coadministration of PAT1inh-B01 with DRAinh-A270 increased stool output compared with DRAinh-A270 alone. These results provide functional evidence for complementary and region-specific roles of PAT1 and DRA in intestinal fluid absorption, with PAT1 as the predominant anion exchanger in mouse ileum. We believe that PAT1inh-B01 is a novel tool to study intestinal ion and fluid transport and perhaps a drug candidate for small intestinal hyposecretory disorders such as cystic fibrosis–related meconium ileus and distal intestinal obstruction syndrome.
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Affiliation(s)
| | - Peter M Haggie
- Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California, USA
| | - Joseph-Anthony Tapia Tan
- Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California, USA
| | - Amber A Rivera
- Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California, USA
| | - Alan S Verkman
- Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California, USA
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21
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Stephens CE, Whittamore JM, Hatch M. The role of NHE3 (Slc9a3) in oxalate and sodium transport by mouse intestine and regulation by cAMP. Physiol Rep 2021; 9:e14828. [PMID: 33904662 PMCID: PMC8077127 DOI: 10.14814/phy2.14828] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/01/2021] [Accepted: 03/09/2021] [Indexed: 12/14/2022] Open
Abstract
Intestinal oxalate transport involves Cl−/HCO3− exchangers but how this transport is regulated is not currently known. NHE3 (Slc9a3), an apical Na+/H+ exchanger, is an established target for regulation of electroneutral NaCl absorption working in concert with Cl−/HCO3− exchangers. To test whether NHE3 could be involved in regulation of intestinal oxalate transport and renal oxalate handling we compared urinary oxalate excretion rates and intestinal transepithelial fluxes of 14C‐oxalate and 22Na+ between NHE3 KO and wild‐type (WT) mice. NHE3 KO kidneys had lower creatinine clearance suggesting reduced GFR, but urinary oxalate excretion rates (µmol/24 h) were similar compared to the WT but doubled when expressed as a ratio of creatinine. Intestinal transepithelial fluxes of 14C‐oxalate and 22Na+ were measured in the distal ileum, cecum, and distal colon. The absence of NHE3 did not affect basal net transport rates of oxalate or sodium across any intestinal section examined. Stimulation of intracellular cAMP with forskolin (FSK) and 3‐isobutyl‐1‐methylxanthine (IBMX) led to an increase in net oxalate secretion in the WT distal ileum and cecum and inhibition of sodium absorption in the cecum and distal colon. In NHE3 KO cecum, cAMP stimulation of oxalate secretion was impaired suggesting the possibility of a role for NHE3 in this process. Although, there is little evidence for a role of NHE3 in basal intestinal oxalate fluxes, NHE3 may be important for cAMP stimulation of oxalate in the cecum and for renal handling of oxalate.
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Affiliation(s)
- Christine E Stephens
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Jonathan M Whittamore
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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22
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Yu Q. Slc26a3 (DRA) in the Gut: Expression, Function, Regulation, Role in Infectious Diarrhea and Inflammatory Bowel Disease. Inflamm Bowel Dis 2021; 27:575-584. [PMID: 32989468 DOI: 10.1093/ibd/izaa256] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Indexed: 12/12/2022]
Abstract
BACKGROUND The transport of transepithelial Cl- and HCO3- is crucial for the function of the intestinal epithelium and maintains the acid-based homeostasis. Slc26a3 (DRA), as a key chloride-bicarbonate exchanger protein in the intestinal epithelial luminal membrane, participates in the electroneutral NaCl absorption of intestine, together with Na+/H+ exchangers. Increasing recent evidence supports the essential role of decreased DRA function or expression in infectious diarrhea and inflammatory bowel disease (IBD). METHOD In this review, we give an overview of the current knowledge of Slc26a3, including its cloning and expression, function, roles in infectious diarrhea and IBD, and mechanisms of actions. A better understanding of the physiological and pathophysiological relevance of Slc26a3 in infectious diarrhea and IBD may reveal novel targets for future therapy. CONCLUSION Understanding the physiological function, regulatory interactions, and the potential mechanisms of Slc26a3 in the pathophysiology of infectious diarrhea and IBD will define novel therapeutic approaches in future.
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Affiliation(s)
- Qin Yu
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan City, China
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Whittamore JM, Hatch M. The anion exchanger PAT-1 (Slc26a6) does not participate in oxalate or chloride transport by mouse large intestine. Pflugers Arch 2021; 473:95-106. [PMID: 33205229 DOI: 10.1007/s00424-020-02495-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 10/23/2020] [Accepted: 11/10/2020] [Indexed: 01/20/2023]
Abstract
The membrane-bound transport proteins responsible for oxalate secretion across the large intestine remain unidentified. The apical chloride/bicarbonate (Cl-/HCO3-) exchanger encoded by Slc26a6, known as PAT-1 (putative anion transporter 1), is a potential candidate. In the small intestine, PAT-1 makes a major contribution to oxalate secretion but whether this role extends into the large intestine has not been directly tested. Using the PAT-1 knockout (KO) mouse, we compared the unidirectional absorptive ([Formula: see text]) and secretory ([Formula: see text]) flux of oxalate and Cl- across cecum, proximal colon, and distal colon from wild-type (WT) and KO mice in vitro. We also utilized the non-specific inhibitor DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid) to confirm a role for PAT-1 in WT large intestine and (in KO tissues) highlight any other apical anion exchangers involved. Under symmetrical, short-circuit conditions the cecum and proximal colon did not transport oxalate on a net basis, whereas the distal colon supported net secretion. We found no evidence for the participation of PAT-1, or indeed any other DIDS-sensitive transport mechanism, in oxalate or Cl- by the large intestine. Most unexpectedly, mucosal DIDS concurrently stimulated [Formula: see text] and [Formula: see text] by 25-68% across each segment without impacting net transport. For the colon, these changes were directly proportional to increased transepithelial conductance suggesting this response was the result of bidirectional paracellular flux. In conclusion, PAT-1 does not contribute to oxalate or Cl- transport by the large intestine, and we urge caution when using DIDS with mouse colonic epithelium.
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Kini A, Singh AK, Riederer B, Yang I, Tan X, Stefano G, Tan Q, Xiao F, Xia W, Suerbaum S, Seidler U. Slc26a3 deletion alters pH-microclimate, mucin biosynthesis, microbiome composition and increases the TNFα expression in murine colon. Acta Physiol (Oxf) 2020; 230:e13498. [PMID: 32415725 DOI: 10.1111/apha.13498] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 05/07/2020] [Accepted: 05/08/2020] [Indexed: 12/24/2022]
Abstract
AIM SLC26A3 (DRA) mediates the absorption of luminal Cl- in exchange for HCO3 - in the distal intestine. Its expression is lost in congenital chloride diarrhoea (CLD) and strongly decreased in the presence of intestinal inflammation. To characterize the consequences of a loss of Slc26a3 beyond disturbed electrolyte transport, colonic mucus synthesis, surface accumulation and composition, pH microclimate, microbiome composition and development of inflammation was studied in slc26a3-/- mice. METHODS The epithelial surface pH microclimate and the surface mucus accumulation in vivo was assessed by two photon microscopy in exteriorized mid colon of anaesthetized slc26a3-/- and wt littermates. Mucus synthesis, composition and inflammatory markers were studied by qPCR and immunohistochemistry and microbiome composition by 16S rRNA sequencing. RESULTS Colonic pH microclimate was significantly more acidic in slc26a3-/- and to a lesser extent in cftr-/- than in wt mice. Goblet cell thecae per crypt were decreased in slc26a3-/- and increased in cftr-/- colon. Mucus accumulation in vivo was reduced, but much less so than in cftr-/- colon, which is possibly related to the different colonic fluid balance. Slc26a3-/- colonic luminal microbiome displayed strong decrease in diversity. These alterations preceded and maybe causally related to increased mucosal TNFα mRNA expression levels and leucocyte infiltration in the mid-distal colon of slc26a3-/- but not of cftr-/- mice. CONCLUSIONS These findings may explain the strong increase in the susceptibility of slc26a3-/- mice to DSS damage, and offer insight into the mechanisms leading to an increased incidence of intestinal inflammation in CLD patients.
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Affiliation(s)
- Archana Kini
- Department of GastroenterologyHannover Medical School Hannover Germany
| | - Anurag K. Singh
- Department of GastroenterologyHannover Medical School Hannover Germany
- Institute for Physiological Chemistry Martin‐Luther University Halle (Saale) Germany
| | - Brigitte Riederer
- Department of GastroenterologyHannover Medical School Hannover Germany
| | - Ines Yang
- Institute of Medical Microbiology and Hospital EpidemiologyHannover Medical School Hannover Germany
| | - Xinjie Tan
- Department of GastroenterologyHannover Medical School Hannover Germany
| | - Gabriella Stefano
- Department of GastroenterologyHannover Medical School Hannover Germany
| | - Qinghai Tan
- Department of GastroenterologyHannover Medical School Hannover Germany
| | - Fang Xiao
- Department of GastroenterologyHannover Medical School Hannover Germany
- Department of Gastroenterology Tongji HospitalHuazhou University of Technology and Science Wuhan China
| | - Weiliang Xia
- Department of GastroenterologyHannover Medical School Hannover Germany
- Department of Hepatobiliary and Transplantation Surgery First affiliated Hospital Zheijang University Hangzhou China
| | - Sebastian Suerbaum
- Institute of Medical Microbiology and Hospital EpidemiologyHannover Medical School Hannover Germany
- Faculty of Medicine Max von Pettenkofer InstituteLMU Munich Munchen Germany
| | - Ursula Seidler
- Department of GastroenterologyHannover Medical School Hannover Germany
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Liu Y, Tan Q, Riederer B, di Stefano G, Römermann D, Qian J, Reiner J, Seidler U. Deciphering ion transporters, kinases and PDZ-adaptor molecules that mediate guanylate cyclase C agonist-dependent intestinal fluid loss in vivo. Biochem Pharmacol 2020; 178:114040. [DOI: 10.1016/j.bcp.2020.114040] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 05/13/2020] [Indexed: 01/12/2023]
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Xue J, Thomas L, Tahmasbi M, Valdez A, Dominguez Rieg JA, Fenton RA, Rieg T. An inducible intestinal epithelial cell-specific NHE3 knockout mouse model mimicking congenital sodium diarrhea. Clin Sci (Lond) 2020; 134:941-53. [PMID: 32227118 DOI: 10.1042/CS20200065] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 12/13/2022]
Abstract
The sodium–hydrogen exchanger isoform 3 (NHE3, SLC9A3) is abundantly expressed in the gastrointestinal tract and is proposed to play essential roles in Na+ and fluid absorption as well as acid–base homeostasis. Mutations in the SLC9A3 gene can cause congenital sodium diarrhea (CSD). However, understanding the precise role of intestinal NHE3 has been severely hampered due to the lack of a suitable animal model. To navigate this problem and better understand the role of intestinal NHE3, we generated a tamoxifen-inducible intestinal epithelial cell-specific NHE3 knockout mouse model (NHE3IEC-KO). Before tamoxifen administration, the phenotype and blood parameters of NHE3IEC-KO were unremarkable compared with control mice. After tamoxifen administration, NHE3IEC-KO mice have undetectable levels of NHE3 in the intestine. NHE3IEC-KO mice develop watery, alkaline diarrhea in combination with a swollen small intestine, cecum and colon. The persistent diarrhea results in higher fluid intake. After 3 weeks, NHE3IEC-KO mice show a ~25% mortality rate. The contribution of intestinal NHE3 to acid–base and Na+ homeostasis under normal conditions becomes evident in NHE3IEC-KO mice that have metabolic acidosis, lower blood bicarbonate levels, hyponatremia and hyperkalemia associated with drastically elevated plasma aldosterone levels. These results demonstrate that intestinal NHE3 has a significant contribution to acid–base, Na+ and volume homeostasis, and lack of intestinal NHE3 has consequences on intestinal structural integrity. This mouse model mimics and explains the phenotype of individuals with CSD carrying SLC9A3 mutations.
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Jayawardena D, Tyagi S, Nazmi A, Olivares-Villagómez D, Dudeja PK. Ion Transport Basis of Diarrhea in a Mouse Model of Adoptive T Cell Transfer Colitis. Dig Dis Sci 2020; 65:1700-9. [PMID: 31741140 DOI: 10.1007/s10620-019-05945-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 11/06/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND Diarrhea, a major pathological hallmark of inflammatory bowel disease, is characterized by a significant reduction in the expression and function of key intestinal ion transporters. The adoptive naïve CD4+ T cell transfer colitis is an immune-based, chronic colitis mouse model which resembles human Crohn's disease. Although mice with T cell transfer colitis demonstrate diarrhea, the ion transporter basis of this phenotype has not been explored. AIMS/METHODS In the current studies, we aimed to determine the mRNA and protein levels of the key NaCl transporters DRA and NHE3 along with the mRNA expression of other transporters in the inflamed intestine. RESULTS Naïve CD4+ T cells, transferred to Rag2 knockout mice, induced severe colonic inflammation characterized by histological damage and increased mRNA levels of cytokines in the colon with no effect in the ileum. Diarrheal phenotype was a key feature of the excised colons of mice where loose stools were evident. Our results demonstrated that the key chloride transporter DRA, mRNA, and protein levels were significantly reduced in the inflamed colon. However, expression of the key sodium hydrogen exchanger NHE3 was unaffected. The mRNA expression of other important transporters was also determined; in this regard, the sodium channel ENACα and the monocarboxylate transporters MCT1 and SMCT1 mRNA levels were also significantly lower compared to control mice. However, CFTR mRNA was not altered in the colon or ileum. CONCLUSIONS The studies conducted herein for the first time demonstrate the downregulation of important intestinal ion transporters in proximal and distal colon in T cell transfer colitis mouse model, providing valuable evidence for the ion transporter basis of diarrhea in this chronic model of inflammation.
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Abstract
Na+/H+ exchangers (NHEs) are expressed in virtually all human tissues and organs. Two major tasks of those NHE isoforms that are located in plasma membranes are cell volume control by Na+-uptake and cellular pH regulation by H+-extrusion. Several NHEs, particularly NHE 1–4 and 8, are involved in the pathogenesis of diseases of the digestive system such as inflammatory bowel disease (ulcerative colitis, Crohn’s disease) and gastric and colorectal tumorigenesis. In the present review, we describe the physiological purposes, possible malfunctions and pathophysiological effects of the different NHE isoforms along the alimentary canal from esophagus to colon, including pancreas, liver and gallbladder. Particular attention is paid to the functions of NHEs in injury repair and to the role of NHE1 in Barrett’s esophagus. The impact of NHEs on gut microbiota and intestinal mucosal integrity is also dealt with. As the hitherto existing findings are not always consistent, sometimes even controversial, they are compared and critically discussed.
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Affiliation(s)
- Li Cao
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhenglin Yuan
- Department of Stomatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Mei Liu
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Christian Stock
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hanover, Germany
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Gao J, Yin J, Xu K, Li T, Yin Y. What Is the Impact of Diet on Nutritional Diarrhea Associated with Gut Microbiota in Weaning Piglets: A System Review. Biomed Res Int 2019; 2019:6916189. [PMID: 31976326 DOI: 10.1155/2019/6916189] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 11/19/2019] [Accepted: 12/03/2019] [Indexed: 12/11/2022]
Abstract
Piglets experience severe growth challenges and diarrhea after weaning due to nutritional, social, psychological, environmental, and physiological changes. Among these changes, the nutritional factor plays a key role in postweaning health. Dietary protein, fibre, starch, and electrolyte levels are highly associated with postweaning nutrition diarrhea (PWND). In this review, we mainly discuss the high protein, fibre, resistant starch, and electrolyte imbalance in diets that induce PWND, with a focus on potential mechanisms in weaned piglets.
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Wang JL, Zhao L, Zhu J, Wang DK, Ren MJ, Wang M, Liu Y, Boron WF, Chen LM. Expression, Localization, and Effect of High Salt Intake on Electroneutral Na +/HCO 3 - Cotransporter NBCn2 in Rat Small Intestine: Implication in Intestinal NaCl Absorption. Front Physiol 2019; 10:1334. [PMID: 31736772 PMCID: PMC6828735 DOI: 10.3389/fphys.2019.01334] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 10/07/2019] [Indexed: 12/20/2022] Open
Abstract
The electroneutral Na+/HCO3 - cotransporter NBCn2 (SLC4A10) of solute carrier family 4 (SLC4) plays important physiological and pathological roles in the body. Our previous study showed that NBCn2 is expressed on the protein level in the small intestine of rat. Here, by reverse-transcription polymerase chain reaction (PCR), we identified a novel full-length NBCn2 variant, i.e., NBCn2-K, from rat small intestine. By pHi measurement with Xenopus oocytes, the activity of NBCn2-K is not significantly different from NBCn2-G. By western blotting, NBCn2 and the Na+/H+ exchanger NHE3 (SLC9A3) are predominantly expressed in the jejunum of rat small intestine. By immunofluorescence, NBCn2 and NHE3 are localized at the apical domain of the jejunum. NaCl overload decreases the expression of NBCn2 by 56% and that of NHE3 by 40% in the small intestine. We propose that NBCn2 is involved in the transepithelial NaCl absorption in the small intestine, and that the down-regulation of NBCn2 by NaCl represents an adaptive response to high salt intake in rat.
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Affiliation(s)
- Jin-Lin Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Lei Zhao
- Department of Obstetrics, Maternal and Child Health Hospital of Hubei Province, Wuhan, China
| | - Jun Zhu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Deng-Ke Wang
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Mei-Juan Ren
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Meng Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Ying Liu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Walter F. Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Li-Ming Chen
- Key Laboratory of Molecular Biophysics of the Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
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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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33
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Zhang N, Heruth DP, Wu W, Zhang LQ, Nsumu MN, Shortt K, Li K, Jiang X, Wang B, Friesen C, Li DY, Ye SQ. Functional characterization of SLC26A3 c.392C>G (p.P131R) mutation in intestinal barrier function using CRISPR/CAS9-created cell models. Cell Biosci 2019; 9:40. [PMID: 31114672 PMCID: PMC6518688 DOI: 10.1186/s13578-019-0303-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 05/07/2019] [Indexed: 12/11/2022] Open
Abstract
Background Congenital chloride diarrhea (CCD) in a newborn is a rare autosomal recessive disorder with life-threatening complications, requiring early diagnostics and treatment to prevent severe dehydration and infant mortality. SLC26A3 rs386833481 (c.392C>G; p.P131R) gene polymorphism is an important genetic determinant of CCD. Here, we report the influence of the non-synonymous SLC26A3 variant rs386833481 gene polymorphism on the function of the epithelial barrier and the potential mechanisms of these effects. Results We found that P131R-SLC26A3 increased dysfunction of the epithelial barrier compared with wild type SLC26A3 in human colonic Caco-2 and mouse colonic CMT-93 cells. When P131R-SLC26A3 was subsequently reverted to wild type, the epithelial barrier function was restored similar to wild type cells. Further study demonstrated that variant P131R-SLC26A3 disrupts function of epithelial barrier through two distinct molecular mechanisms: (a) decreasing SLC26A3 expression through a ubiquitination pathway and (b) disrupting a key interaction with its partner ZO-1/CFTR, thereby increasing the epithelial permeability. Conclusion Our study provides an important insight of SLC26A3 SNPs in the regulation of the epithelial permeability and indicates that SLC26A3 rs386833481 is likely a causative mutation in the dysfunction of epithelial barrier of CCD, and correction of this SNP or increasing SLC26A3 function could be therapeutically beneficial for chronic diarrhea diseases.
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Affiliation(s)
- Nini Zhang
- 1Division of Gastroenterology, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA.,2Division of Experimental and Translational Genetics, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA.,3Department of Biomedical and Health Informatics, University of Missouri Kansas City School of Medicine, Kansas City, MO USA.,4Department of Pediatrics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi China
| | - Daniel P Heruth
- 2Division of Experimental and Translational Genetics, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA
| | - Weibin Wu
- 2Division of Experimental and Translational Genetics, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA.,3Department of Biomedical and Health Informatics, University of Missouri Kansas City School of Medicine, Kansas City, MO USA.,8Department of Neonatology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Li Qin Zhang
- 2Division of Experimental and Translational Genetics, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA.,5Department of Biomedical Sciences, University of Missouri Kansas City School of Medicine, Kansas City, MO USA
| | - Marianne N Nsumu
- 2Division of Experimental and Translational Genetics, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA.,3Department of Biomedical and Health Informatics, University of Missouri Kansas City School of Medicine, Kansas City, MO USA
| | - Katherine Shortt
- 2Division of Experimental and Translational Genetics, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA.,6Division of Cell Biology & Biophysics, University of Missouri Kansas City School of Biological Sciences, Kansas City, MO USA
| | - Kelvin Li
- 7Department of Global Biostatistics and Data Science, Center for Bioinformatics and Genomics, Tulane University, New Orleans, LA USA
| | - Xun Jiang
- 4Department of Pediatrics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi China
| | - Baoxi Wang
- 4Department of Pediatrics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi China
| | - Craig Friesen
- 1Division of Gastroenterology, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA
| | - Ding-You Li
- 1Division of Gastroenterology, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA
| | - Shui Qing Ye
- 2Division of Experimental and Translational Genetics, Department of Pediatrics, Children's Mercy Hospitals and Clinics, Kansas City, MO USA.,3Department of Biomedical and Health Informatics, University of Missouri Kansas City School of Medicine, Kansas City, MO USA.,6Division of Cell Biology & Biophysics, University of Missouri Kansas City School of Biological Sciences, Kansas City, MO USA
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Yu Y, Seidler A, Zhou K, Yuan Z, Yeruva S, Amiri M, Yun CC, Nikolovska K, Seidler U. Expression, Localization and Functional Activity of the Major Na⁺/H⁺ Exchange Isoforms Expressed in the Intestinal Cell Line Caco-2BBe. Cell Physiol Biochem 2019; 52:1017-1038. [PMID: 30977986 PMCID: PMC7104346 DOI: 10.33594/000000070] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 02/25/2019] [Indexed: 12/15/2022] Open
Abstract
Background/Aims Enterocytes express a number of NHE isoforms with presumed localization in the apical (NHE2, 3 and 8) or basolateral (NHE1) membrane. Functional activity and localization of enterocyte NHE isoforms were assessed using fully differentiated Caco-2BBe cells, whose genetic expression profile closely resembles mature enterocytes. Methods The activity of the different NHEs was analyzed by fluorometric pHi-metry in a perfusion chamber with separate apical and basolateral perfusion, using specific inhibitors and shRNA knockdown of NHE2. The expression of the NHEs and of other relevant acid extrusion transporters was quantified by qPCR. Results Quantitative comparison of the mRNA expression levels of the different NHE isoforms in 14 day-differentiated Caco-2BBe cells showed the following order: NHE2>NHE8>NHE3>NHE1. Acid-activated NHE exchange rates in the basolateral membrane were >6-fold higher than in the apical membrane. 79 ± 3 % of the acid-activated basolateral Na+/H+ exchange rate displayed a NHE1-typical inhibitor profile, and no NHE2/3/8 typical activity could be observed. Analysis of the apical Na+/H+ exchange rates revealed that approximately 51 ± 3 % of the total apical activity displayed a NHE2/8-typical inhibitor profile and 31 ± 6 % a NHE3-typical inhibitor profile. Because no selective NHE2 inhibitor is available, a stable NHE2 knockdown cell line (C2NHE2KD) was generated. C2NHE2KD displayed a reduced NHE2-typical apical Na+/H+ exchange rate and maintained a lower steady-state pHi, despite high expression levels of other acid extruders, in particular NBCn1 (Slc4a7). Conclusion Differentiated Caco-2BBe cells display particularly high mRNA expression levels of NHE2, which can be functionally identified in the apical membrane. Although at low intracellular pH, NHE2 transport rate was far lower than that of NHE1. NHE2 activity was nevertheless essential for the maintenance of the steady-state pHi of these cells.
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Affiliation(s)
- Yan Yu
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Anna Seidler
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Kunyan Zhou
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Zhenglin Yuan
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Sunil Yeruva
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Mahdi Amiri
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
| | - Chris C Yun
- Division of Digestive Diseases, Department of Medicine, Emory University, Atlanta, GA, USA
| | | | - Ursula Seidler
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany,
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Seidler U, Nikolovska K. Slc26 Family of Anion Transporters in the Gastrointestinal Tract: Expression, Function, Regulation, and Role in Disease. Compr Physiol 2019; 9:839-872. [DOI: 10.1002/cphy.c180027] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Stephens CE, Whittamore JM, Hatch M. 125 Iodide as a surrogate tracer for epithelial chloride transport by the mouse large intestine in vitro. Exp Physiol 2019; 104:334-344. [PMID: 30615234 PMCID: PMC6397055 DOI: 10.1113/ep087445] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/02/2019] [Indexed: 12/25/2022]
Abstract
NEW FINDINGS What is the central question of this study? The tracer 36 Cl- , currently used to measure transepithelial Cl- fluxes, has become prohibitively expensive, threatening its future use. 125 Iodide, previously validated alongside 36 Cl- as a tracer of Cl- efflux by cells, has not been tested as a surrogate for 36 Cl- across epithelia. What is the main finding and its importance? We demonstrate that 125 I- can serve as an inexpensive replacement for measuring Cl- transport across mouse large intestine, tracking Cl- transport in response to cAMP stimulation (inducing Cl- secretion) in the presence and absence of the main gastrointestinal Cl- -HCO3- exchanger, DRA. ABSTRACT Chloride transport is important for driving fluid secretion and absorption by the large intestine, with dysregulation resulting in diarrhoea-associated pathologies. The radioisotope 36 Cl- has long been used as a tracer to measure epithelial Cl- transport but is prohibitively expensive. 125 Iodide has been used as an alternative to 36 Cl- in some transport assays but has never been validated as an alternative for tracing bidirectional transepithelial Cl- fluxes. The goal of this study was to validate 125 I- as an alternative to 36 Cl- for measurement of Cl- transport by the intestine. Simultaneous fluxes of 36 Cl- and 125 I- were measured across the mouse caecum and distal colon. Net Cl- secretion was induced by the stimulation of cAMP with a cocktail of forskolin (FSK) and 3-isobutyl-1-methylxanthine (IBMX). Unidirectional fluxes of 125 I- correlated well with 36 Cl- fluxes after cAMP-induced net Cl- secretion, occurring predominantly through a reduction in the absorptive mucosal-to-serosal Cl- flux rather than by stimulation of the secretory serosal-to-mucosal Cl- flux. Correlations between 125 I- fluxes and 36 Cl- fluxes were maintained in epithelia from mice lacking DRA (Slc26a3), the main Cl- -HCO3- exchanger responsible for Cl- absorption by the large intestine. Lower rates of Cl- and I- absorption in the DRA knockout intestine suggest that DRA might have a previously unrecognized role in iodide uptake. This study validates that 125 I- traces transepithelial Cl- fluxes across the mouse large intestine, provides insights into the mechanism of net Cl- secretion and suggests that DRA might be involved in intestinal iodide absorption.
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Affiliation(s)
- Christine E Stephens
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Jonathan M Whittamore
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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Lenzen H, Qian J, Manns MP, Seidler U, Jörns A. Restoration of mucosal integrity and epithelial transport function by concomitant anti-TNFα treatment in chronic DSS-induced colitis. J Mol Med (Berl) 2018; 96:831-843. [DOI: 10.1007/s00109-018-1658-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 05/27/2018] [Accepted: 06/01/2018] [Indexed: 12/25/2022]
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Ding X, Li D, Li M, Wang H, He Q, Wang Y, Yu H, Tian D, Yu Q. SLC26A3 (DRA) prevents TNF-alpha-induced barrier dysfunction and dextran sulfate sodium-induced acute colitis. J Transl Med 2018; 98:462-76. [PMID: 29330471 DOI: 10.1038/s41374-017-0005-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 11/08/2017] [Accepted: 11/15/2017] [Indexed: 12/24/2022] Open
Abstract
SLC26A3 encodes a Cl-/HCO3- ion transporter that is also known as downregulated in adenoma (DRA) and is involved in HCO3-/mucus formation. The role of DRA in the epithelial barrier has not been previously established. In this study, we investigated the in vivo and in vitro mechanisms of DRA in the colon epithelial barrier. Immunofluorescence (IF) and co-immunoprecipitation (co-IP) studies reveal that DRA binds directly to tight junction (TJ) proteins and affects the expression of TJ proteins in polarized Caco-2BBe cells. Similarly, DRA colocalizes with ZO-1 in the intestinal epithelium. Knockdown or overexpression of DRA leads to alterations in TJ proteins and epithelial permeability. In addition, TNF-α treatment downregulates DRA by activating NF-кB and subsequently affecting intestinal epithelial barrier integrity. Furthermore, overexpression of DRA partly reverses the TNF-α-induced damage by stabilizing TJ proteins. Neutralization of TNF-α in dextran sulfate sodium (DSS)-induced colitis mice demonstrates improved the outcomes, and the therapeutic effect of the TNF-α neutralizing mAb is mediated in part by the preservation of DRA expression. These data suggest that DRA may be one of the therapeutic targets of TNF-α. Moreover, DRA delivered by adenovirus vector significantly prevents the exacerbation of colitis and improves epithelial barrier function by promoting the recovery of TJ proteins in DSS-treated mice. In conclusion, DRA plays a role in protecting the epithelial barrier and may be a therapeutic target in gut homeostasis.
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Beaume J, Braconnier A, Dolley-hitze T, Bertocchio J. Bicarbonate : de la physiologie aux applications thérapeutiques pour tout clinicien. Nephrol Ther 2018; 14:13-23. [DOI: 10.1016/j.nephro.2017.02.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 02/22/2017] [Indexed: 11/17/2022]
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Stumpff F. A look at the smelly side of physiology: transport of short chain fatty acids. Pflugers Arch 2018; 470:571-598. [PMID: 29305650 DOI: 10.1007/s00424-017-2105-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 12/19/2017] [Accepted: 12/20/2017] [Indexed: 12/14/2022]
Abstract
Fermentative organs such as the caecum, the colon, and the rumen have evolved to produce and absorb energy rich short chain fatty acids (SCFA) from otherwise indigestible substrates. Classical models postulate diffusional uptake of the undissociated acid (HSCFA). However, in net terms, a major part of SCFA absorption occurs with uptake of Na+ and resembles classical, coupled electroneutral NaCl transport. Considerable evidence suggests that the anion transporting proteins expressed by epithelia of fermentative organs are poorly selective and that their main function may be to transport acetate-, propionate-, butyrate- and HCO3- as the physiologically relevant anions. Apical uptake of SCFA thus involves non-saturable diffusion of the undissociated acid (HSCFA), SCFA-/HCO3- exchange via DRA (SLC26A3) and/or SCFA--H+ symport (MCT1, SLC16A1). All mechanisms lead to cytosolic acidification with stimulation of Na+/H+ exchange via NHE (SLC9A2/3). Basolaterally, Na+ leaves via the Na+/K+-ATPase with recirculation of K+. Na+ efflux drives the transport of SCFA- anions through volume-regulated anion channels, such as maxi-anion channels (possibly SLCO2A1), LRRC8, anoctamins, or uncoupled exchangers. When luminal buffering is inadequate, basolateral efflux will increasingly involve SCFA-/ HCO3- exchange (AE1/2, SCL4A1/2), or efflux of SCFA- with H+ (MCT1/4, SLC16A1/3). Furthermore, protons can be basolaterally removed by NHE1 (SCL9A1) or NBCe1 (SLC4A4). The purpose of these transport proteins is to maximize the amount of SCFA transported from the tightly buffered ingesta while minimizing acid transport through the epithelium. As known from the rumen for many decades, a disturbance of these processes is likely to cause severe colonic disease.
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Affiliation(s)
- Friederike Stumpff
- Institute of Veterinary Physiology, Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany.
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Ding X, Li D, Li M, Tian D, Yu H, Yu Q. Tumor necrosis factor-α acts reciprocally with solute carrier family 26, member 3, (downregulated-in-adenoma) and reduces its expression, leading to intestinal inflammation. Int J Mol Med 2017; 41:1224-1232. [PMID: 29286110 PMCID: PMC5819926 DOI: 10.3892/ijmm.2017.3347] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 12/18/2017] [Indexed: 12/12/2022] Open
Abstract
Solute carrier family 26, member 3 (Slc26a3), also termed downregulated-in-adenoma (DRA) is a member of the Slc26 family of anion transporters and is mutated in congenital chloride diarrhea. Our previous study demonstrated that DRA deficiency is associated with severely reduced colonic HCO3‑ secretion, a loss of colonic fluid absorption, a lack of a firmly adherent mucus layer and a severely reduced colonic mucosal resistance to dextran sodium sulfate (DSS) damage. However, the direct effect of mediators that trigger intestinal inflammatory factors on DRA has not been fully investigated. Tumor necrosis factor (TNF)‑α is a central mediator of intestinal inflammation in inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease. However, to the best of our knowledge, whether TNF‑α acts reciprocally with DRA leading to the development of gut inflammation in IBD has not been reported. The present study identified that the expression level of DRA was reduced in active UC patients and DSS‑induced colitis mice with high expression levels of TNF‑α identified in the peripheral blood serum. In addition, TNF‑α may affect the expression level of DRA in human colonic Caco2BBE cells in a dose‑dependent manner, including in DRA overexpressed Caco2BBE cells. Furthermore, knockdown of TNF‑α in Caco2BBE cells led to a higher expression level of DRA and a markedly reduced secretion of TNF‑α in the culture media. In addition, knockdown of DRA in Caco2BBE cells led to a higher secretion of TNF‑α in the culture media compared with the control cells, which could be reversed by overexpression of DRA. Overall, these results indicate that TNF‑α may act reciprocally with DRA, leading to the development of intestinal inflammation. Based on the pivotal position of TNF‑α in IBD, DRA is hypothesized to have therapeutic potential against colitis serving as an important target.
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Affiliation(s)
- Xiangming Ding
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Dongxiao Li
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Mengke Li
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Dean Tian
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Hongbing Yu
- Department of Pediatrics, BC Children's Hospital and The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Qin Yu
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
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Chao PC, Butt AG. cAMP-dependent secretagogues stimulate the NaHCO 3 cotransporter in the villous epithelium of the brushtail possum, Trichosurus vulpecula. J Comp Physiol B 2017; 187:1019-1028. [PMID: 28247055 DOI: 10.1007/s00360-017-1063-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/30/2017] [Accepted: 02/05/2017] [Indexed: 12/22/2022]
Abstract
In the ileum of the brushtail possum, Trichosurus vulpecula, fluid secretion appears to be driven by electrogenic HCO3- secretion. Consistent with this, the cystic fibrosis transmembrane conductance regulator is expressed in the apical membrane of the ileal epithelial cells and the pancreatic or secretory variant of the NaHCO3 cotransporter in the basolateral membrane. This suggests that in the possum ileum, electrogenic HCO3- secretion is driven by basolateral NaHCO3 cotransporter (NBC) activity. To determine if the NBC contributes to HCO3- secretion in the possum ileum, intracellular pH (pHi) measurements in isolated villi were used to demonstrate NBC activity in the ileal epithelial cells and investigate the effect of cAMP-dependent secretagogues. In CO2/HCO3--free solutions, recovery of the epithelial cells from an acid load was Na+-dependent and ≈80% inhibited by ethyl-isopropyl-amiloride (EIPA, 10 µmol L-1), indicative of the presence of an Na+/H+ exchanger, most likely NHE1. However, in the presence of CO2/HCO3-, EIPA only inhibited ≈ 50% of the recovery, the remainder was inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS, 500 µmol L-1), indicative of NBC activity. Under steady-state conditions, NHE1 inhibition by EIPA had little effect on pHi in the presence or absence of secretagogues, but NBC inhibition with DIDS resulted in a rapid acidification of the cells, which was increased fivefold by secretagogues. These data demonstrate the functional activity of an NaHCO3 cotransporter in the ileal epithelial cells. Furthermore, the stimulation of NBC activity by secretagogues is consistent with the involvement of an NaHCO3 cotransporter in electrogenic HCO3- secretion.
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Affiliation(s)
- Pin-Chun Chao
- Department of Physiology, School of Biomedical Sciences, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - A Grant Butt
- Department of Physiology, School of Biomedical Sciences, University of Otago, PO Box 56, Dunedin, 9054, New Zealand.
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Paehler Vor der Nolte A, Chodisetti G, Yuan Z, Busch F, Riederer B, Luo M, Yu Y, Menon MB, Schneider A, Stripecke R, Nikolovska K, Yeruva S, Seidler U. Na + /H + exchanger NHE1 and NHE2 have opposite effects on migration velocity in rat gastric surface cells. J Cell Physiol 2017; 232:1669-1680. [PMID: 28019659 PMCID: PMC5396337 DOI: 10.1002/jcp.25758] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 12/21/2016] [Accepted: 12/22/2016] [Indexed: 12/13/2022]
Abstract
Following superficial injury, neighbouring gastric epithelial cells close the wound by rapid cell migration, a process called epithelial restitution. Na+/H+ exchange (NHE) inhibitors interfere with restitution, but the role of the different NHE isoforms expressed in gastric pit cells has remained elusive. The role of the basolaterally expressed NHE1 (Slc9a1) and the presumably apically expressed NHE2 (Slc9a2) in epithelial restitution was investigated in the nontransformed rat gastric surface cell line RGM1. Migration velocity was assessed by loading the cells with the fluorescent dye DiR and following closure of an experimental wound over time. Since RGM1 cells expressed very low NHE2 mRNA and have low transport activity, NHE2 was introduced by lentiviral gene transfer. In medium with pH 7.4, RGM1 cells displayed slow wound healing even in the absence of growth factors and independently of NHE activity. Growth factors accelerated wound healing in a partly NHE1‐dependent fashion. Preincubation with acidic pH 7.1 stimulated restitution in a NHE1‐dependent fashion. When pH 7.1 was maintained during the restitution period, migratory speed was reduced to ∼10% of the speed at pH 7,4, and the residual restitution was further inhibited by NHE1 inhibition. Lentiviral NHE2 expression increased the steady‐state pHi and reduced the restitution velocity after low pH preincubation, which was reversible by pharmacological NHE2 inhibition. The results demonstrate that in RGM1 cells, migratory velocity is increased by NHE1 activation, while NHE2 activity inhibit this process. A differential activation of NHE1 and NHE2 may therefore, play a role in the initiation and completion of the epithelial restitution process.
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Affiliation(s)
- Anja Paehler Vor der Nolte
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Giriprakash Chodisetti
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Zhenglin Yuan
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Florian Busch
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Brigitte Riederer
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Min Luo
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Yan Yu
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Manoj B Menon
- Departments of Biochemistry, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Andreas Schneider
- Departments of Hematology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Renata Stripecke
- Departments of Hematology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Katerina Nikolovska
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Sunil Yeruva
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
| | - Ursula Seidler
- Departments of Gastroenterology, Hemostatsis, Oncology and Stem Cell Transplantation, Medical School of Hannover, Germany
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Whittamore JM, Hatch M. The role of intestinal oxalate transport in hyperoxaluria and the formation of kidney stones in animals and man. Urolithiasis 2017; 45:89-108. [PMID: 27913853 DOI: 10.1007/s00240-016-0952-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 11/22/2016] [Indexed: 12/26/2022]
Abstract
The intestine exerts a considerable influence over urinary oxalate in two ways, through the absorption of dietary oxalate and by serving as an adaptive extra-renal pathway for elimination of this waste metabolite. Knowledge of the mechanisms responsible for oxalate absorption and secretion by the intestine therefore have significant implications for understanding the etiology of hyperoxaluria, as well as offering potential targets for future treatment strategies for calcium oxalate kidney stone disease. In this review, we present the recent developments and advances in this area over the past 10 years, and put to the test some of the new ideas that have emerged during this time, using human and mouse models. A key focus for our discussion are the membrane-bound anion exchangers, belonging to the SLC26 gene family, some of which have been shown to participate in transcellular oxalate absorption and secretion. This has offered the opportunity to not only examine the roles of these specific transporters, revealing their importance to oxalate homeostasis, but to also probe the relative contributions made by the active transcellular and passive paracellular components of oxalate transport across the intestine. We also discuss some of the various physiological stimuli and signaling pathways which have been suggested to participate in the adaptation and regulation of intestinal oxalate transport. Finally, we offer an update on research into Oxalobacter formigenes, alongside recent investigations of other oxalate-degrading gut bacteria, in both laboratory animals and humans.
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Yu Q, Liu X, Liu Y, Riederer B, Li T, Tian DA, Tuo B, Shull G, Seidler U. Defective small intestinal anion secretion, dipeptide absorption, and intestinal failure in suckling NBCe1-deficient mice. Pflugers Arch 2016; 468:1419-32. [PMID: 27228994 PMCID: PMC4951514 DOI: 10.1007/s00424-016-1836-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 11/27/2022]
Abstract
The electrogenic Na+HCO3− cotransporter NBCe1 (Slc4a4) is strongly expressed in the basolateral enterocyte membrane in a villous/surface predominant fashion. In order to better understand its physiological function in the intestine, isolated mucosae in miniaturized Ussing chambers and microdissected intestinal villi or crypts loaded with the fluorescent pH-indicator BCECF were studied from the duodenum, jejunum, and colon of 14- to 17-days-old slc4a4-deficient (KO) and WT mice. NBCe1 was active in the basal state in all intestinal segments under study, most likely to compensate for acid loads imposed upon the enterocytes. Upregulation of other basolateral base uptake mechanism occurs, but in a segment-specific fashion. Loss of NBCe1 resulted in severely impaired Cl− and fluid secretory response, but not HCO3− secretory response to agonist stimulation. In addition, NBCe1 was found to be active during transport processes that load the surface enterocytes with acid, such as Slc26a3 (DRA)-mediated luminal Cl−/HCO3− exchange or PEPT1-mediated H+/dipeptide uptake. Possibly because of the high energy demand for hyperventilation in conjunction with the fluid secretory and nutrient absorptive defects and the relative scarcity of compensatory mechanisms, NBCe1-deficient mice developed progressive jejunal failure, worsening of metabolic acidosis, and death in the third week of life. Our data suggest that the electrogenic influx of base via NBCe1 maintains enterocyte anion homeostasis and pHi control. Its loss impairs small intestinal Cl− and fluid secretion as well as the neutralization of acid loads imposed on the enterocytes during nutrient and electrolyte absorption.
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Affiliation(s)
- Qin Yu
- Department of Gastroenterology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.,Department of Gastroenterology, Tongji Hospital, Huazhong University of Science & Technology, Wuhan, People's Republic of China
| | - Xuemei Liu
- Department of Gastroenterology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.,Department of Gastroenterology, Zunyi Medical College, Zunyi, China
| | - Yongjian Liu
- Department of Gastroenterology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - Brigitte Riederer
- Department of Gastroenterology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - Taolang Li
- Department of Gastroenterology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.,Department of Gastrointestinal Surgery, Zunyi Medical College, Zunyi, China
| | - De-An Tian
- Department of Gastroenterology, Tongji Hospital, Huazhong University of Science & Technology, Wuhan, People's Republic of China
| | - Biguang Tuo
- Department of Gastroenterology, Zunyi Medical College, Zunyi, China
| | - Gary Shull
- Department of of Molecular Genetics, University of Cincinnati, Cincinnati, OH, USA
| | - Ursula Seidler
- Department of Gastroenterology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
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Jalali R, Zandieh-Doulabi B, DenBesten PK, Seidler U, Riederer B, Wedenoja S, Micha D, Bronckers ALJJ. Slc26a3/Dra and Slc26a6 in Murine Ameloblasts. J Dent Res 2015; 94:1732-9. [PMID: 26394631 DOI: 10.1177/0022034515606873] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Formation of apatite crystals during enamel development generates protons. To sustain mineral accretion, maturation ameloblasts need to buffer these protons. The presence of cytosolic carbonic anhydrases, the basolateral Na(+) bicarbonate cotransporter Nbce1, and the basolateral anion exchanger Ae2a,b in maturation ameloblasts suggests that these cells secrete bicarbonates into the forming enamel, but it is unknown by which mechanism. Solute carrier (Slc) family 26A encodes different anion exchangers that exchange Cl(-)/HCO3 (-), including Slc26a3/Dra, Slc26a6/Pat-1, and Slc26a4/pendrin. Previously, we showed that pendrin is expressed in ameloblasts but is not critical for enamel formation. In this study, we tested the hypothesis that maturation ameloblasts express Dra and Slc26a6 to secrete bicarbonate into the enamel space in exchange for Cl(-). Real-time polymerase chain reaction detected mRNA transcripts for Dra and Slc26a6 in mouse incisor enamel organs, and Western blotting confirmed their translation into protein. Both isoforms were immunolocalized in ameloblasts, principally at maturation stage. Mice with null mutation of either Dra or Slc26a6 had a normal dental or skeletal phenotype without changes in mineral density, as measured by micro-computed tomography. In enamel organs of Slc26a6-null mice, Dra and pendrin protein levels were both elevated by 52% and 55%, respectively. The amount of Slc26a6 protein was unchanged in enamel organs of Ae2a,b- and Cftr-null mice but reduced in Dra-null mice by 36%. Our data show that ameloblasts express Dra, pendrin, or Slc26a6 but each of these separately is not critical for formation of dental enamel. The data suggest that in ameloblasts, Slc26a isoforms can functionally compensate for one another.
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Affiliation(s)
- R Jalali
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - B Zandieh-Doulabi
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - P K DenBesten
- Department of Oral Sciences, University of California, San Francisco, CA, USA
| | - U Seidler
- Abteilung Gastroenterologie, Hepatologie und Endokrinologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - B Riederer
- Abteilung Gastroenterologie, Hepatologie und Endokrinologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - S Wedenoja
- Department of Medical Genetics, Biomedicum Helsinki, University of Helsinki, Finland
| | - D Micha
- Department of Clinical Genetics, Vrije Universiteit Medical Center, Amsterdam, Netherlands
| | - A L J J Bronckers
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
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Abstract
Diarrhoeal disease remains a major health burden worldwide. Secretory diarrhoeas are caused by certain bacterial and viral infections, inflammatory processes, drugs and genetic disorders. Fluid secretion across the intestinal epithelium in secretory diarrhoeas involves multiple ion and solute transporters, as well as activation of cyclic nucleotide and Ca(2+) signalling pathways. In many secretory diarrhoeas, activation of Cl(-) channels in the apical membrane of enterocytes, including the cystic fibrosis transmembrane conductance regulator and Ca(2+)-activated Cl(-) channels, increases fluid secretion, while inhibition of Na(+) transport reduces fluid absorption. Current treatment of diarrhoea includes replacement of fluid and electrolyte losses using oral rehydration solutions, and drugs targeting intestinal motility or fluid secretion. Therapeutics in the development pipeline target intestinal ion channels and transporters, regulatory proteins and cell surface receptors. This Review describes pathogenic mechanisms of secretory diarrhoea, current and emerging therapeutics, and the challenges in developing antidiarrhoeal therapeutics.
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Affiliation(s)
- Jay R Thiagarajah
- Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Mark Donowitz
- Departments of Physiology and Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Ross 925, 720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Alan S Verkman
- Departments of Medicine and Physiology, 1246 Health Sciences East Tower, University of California, 500 Parnassus Avenue, San Francisco, CA 94143, USA
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Whittamore JM, Frost SC, Hatch M. Effects of acid-base variables and the role of carbonic anhydrase on oxalate secretion by the mouse intestine in vitro. Physiol Rep 2015; 3:e12282. [PMID: 25716924 PMCID: PMC4393191 DOI: 10.14814/phy2.12282] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 12/06/2014] [Accepted: 12/30/2014] [Indexed: 12/15/2022] Open
Abstract
Hyperoxaluria is a major risk factor for calcium oxalate kidney stones and the intestine is recognized as an important extra-renal pathway for eliminating oxalate. The membrane-bound chloride/bicarbonate (Cl(-)/) exchangers are involved in the transcellular movement of oxalate, but little is understood about how they might be regulated. , CO2, and pH are established modulators of intestinal NaCl cotransport, involving Na(+)/H(+) and Cl(-)/ exchange, but their influence on oxalate transport is unknown. Measuring (14)C-oxalate and (36)Cl fluxes across isolated, short-circuited segments of the mouse distal ileum and distal colon we examined the role of these acid-base variables and carbonic anhydrase (CA) in oxalate and Cl(-) transport. In standard buffer both segments performed net oxalate secretion (and Cl(-) absorption), but only the colon, and the secretory pathway were responsive to and CO2. Ethoxzolamide abolished net oxalate secretion by the distal colon, and when used in tandem with an impermeant CA inhibitor, signaled an intracellular CA isozyme was required for secretion. There was a clear dependence on as their removal eliminated secretion, while at 42 mmol/L was also decreased and eradicated. Independent of pH, raising Pco2 from 28 to 64 mmHg acutely stimulated net oxalate secretion 41%. In summary, oxalate secretion by the distal colon was dependent on , CA and specifically modulated by CO2, whereas the ileum was remarkably unresponsive. These findings highlight the distinct segmental heterogeneity along the intestine, providing new insights into the oxalate transport mechanism and how it might be regulated.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of FloridaGainesville, Florida, USA
| | - Susan C Frost
- Department of Biochemistry and Molecular Biology, College of Medicine, University of FloridaGainesville, Florida, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of FloridaGainesville, Florida, USA
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Sultan A, Luo M, Yu Q, Riederer B, Xia W, Chen M, Lissner S, Gessner JE, Donowitz M, Yun CC, deJonge H, Lamprecht G, Seidler U. Differential association of the Na+/H+ Exchanger Regulatory Factor (NHERF) family of adaptor proteins with the raft- and the non-raft brush border membrane fractions of NHE3. Cell Physiol Biochem 2014; 32:1386-402. [PMID: 24297041 DOI: 10.1159/000356577] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2013] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND/AIMS Trafficking, brush border membrane (BBM) retention, and signal-specific regulation of the Na+/H+ exchanger NHE3 is regulated by the Na+/H+ Exchanger Regulatory Factor (NHERF) family of PDZ-adaptor proteins, which enable the formation of multiprotein complexes. It is unclear, however, what determines signal specificity of these NHERFs. Thus, we studied the association of NHE3, NHERF1 (EBP50), NHERF2 (E3KARP), and NHERF3 (PDZK1) with lipid rafts in murine small intestinal BBM. METHODS Detergent resistant membranes ("lipid rafts") were isolated by floatation of Triton X-incubated small intestinal BBM from a variety of knockout mouse strains in an Optiprep step gradient. Acid-activated NHE3 activity was measured fluorometrically in BCECF-loaded microdissected villi, or by assessment of CO2/HCO3(-) mediated increase in fluid absorption in perfused jejunal loops of anethetized mice. RESULTS NHE3 was found to partially associate with lipid rafts in the native BBM, and NHE3 raft association had an impact on NHE3 transport activity and regulation in vivo. NHERF1, 2 and 3 were differentially distributed to rafts and non-rafts, with NHERF2 being most raft-associated and NHERF3 entirely non-raft associated. NHERF2 expression enhanced the localization of NHE3 to membrane rafts. The use of acid sphingomyelinase-deficient mice, which have altered membrane lipid as well as lipid raft composition, allowed us to test the validity of the lipid raft concept in vivo. CONCLUSIONS The differential association of the NHERFs with the raft-associated and the non-raft fraction of NHE3 in the brush border membrane is one component of the differential and signal-specific NHE3 regulation by the different NHERFs.
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