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Abstract
OBJECTIVE The aim of the study was to evaluate and compare faecal markers of intestinal inflammation in children with cystic fibrosis (CF), and determine whether intestinal inflammation adversely affects the nutritional phenotype. METHODS Faecal samples for markers of intestinal inflammation, calprotectin, S100A12, and osteoprotegerin, were collected from children with CF, healthy controls (HCs), and Crohn disease (CD). Associations between inflammatory markers and clinical and nutritional indices were determined in subjects with CF. RESULTS Twenty-eight children with CF (mean [standard deviation (SD)] 8.4 [3.3] years old, 22 pancreatic insufficient [PI]), 47 HC, and 30 CD were recruited. Mean (SD) faecal calprotectin in CF (94.3 [100.6] mg/kg) was greater than HC (26.7 [15.4] mg/kg, P < 0.0001), but lower than CD (2133 [2781] mg/kg, P = 0.0003). Abnormal faecal calprotectin was found in subjects only with PI (17/22 (77%), P = 0.001). There was no difference in faecal mean (SD) S100A12 (0.8 [0.9] vs 1.5 [2.2] mg/kg, P = 0.14) and osteoprotegerin concentrations (72.7 [52.2] vs 62.5 [0.0] pg/mL, P = 0.2) between CF and HC. Patients with CD had significantly elevated S100A12 and osteoprotegerin compared with CF and HC. Faecal calprotectin inversely correlated with both weight (r = -0.5, P = 0.003) and height z scores (r = -0.6, P = 0.002) in CF. CONCLUSIONS The pattern of intestinal inflammation in CF is unique and distinct from inflammatory bowel disease, with elevated faecal calprotectin but normal faecal S100A12 and osteoprotegerin concentrations. The severity of intestinal inflammation, based on faecal calprotectin, significantly correlates with poor growth.
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202
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Schultz A, Stick S. Early pulmonary inflammation and lung damage in children with cystic fibrosis. Respirology 2015; 20:569-78. [PMID: 25823858 DOI: 10.1111/resp.12521] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 12/11/2014] [Accepted: 02/17/2015] [Indexed: 12/21/2022]
Abstract
Individuals with cystic fibrosis (CF) suffer progressive airway inflammation, infection and lung damage. Airway inflammation and infection are present from early in life, often before children are symptomatic. CF gene mutations cause changes in the CF transmembrane regulator protein that result in an aberrant airway microenvironment including airway surface liquid (ASL) dehydration, reduced ASL acidity, altered airway mucin and a dysregulated inflammatory response. This review discusses how an altered microenvironment drives CF lung disease before overt airway infection, the response of the CF airway to early infection, and methods to prevent inflammation and early lung disease.
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Affiliation(s)
- André Schultz
- Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth, Western Australia, Australia; School of Paediatric and Child Health, University of Western Australia, Perth, Western Australia, Australia; Telethon Kids Institute, Perth, Western Australia, Australia
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203
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Cantin AM, Hartl D, Konstan MW, Chmiel JF. Inflammation in cystic fibrosis lung disease: Pathogenesis and therapy. J Cyst Fibros 2015; 14:419-30. [PMID: 25814049 DOI: 10.1016/j.jcf.2015.03.003] [Citation(s) in RCA: 308] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/08/2015] [Accepted: 03/08/2015] [Indexed: 11/16/2022]
Abstract
Lung disease is the major cause of morbidity and mortality in patients with cystic fibrosis (CF). Although CF lung disease is primarily an infectious disorder, the associated inflammation is both intense and ineffective at clearing pathogens. Persistent high-intensity inflammation leads to permanent structural damage of the CF airways and impaired lung function that eventually results in respiratory failure and death. Several defective inflammatory responses have been linked to cystic fibrosis transmembrane conductance regulator (CFTR) deficiency including innate and acquired immunity dysregulation, cell membrane lipid abnormalities, various transcription factor signaling defects, as well as altered kinase and toll-like receptor responses. The inflammation of the CF lung is dominated by neutrophils that release oxidants and proteases, particularly elastase. Neutrophil elastase in the CF airway secretions precedes the appearance of bronchiectasis, and correlates with lung function deterioration and respiratory exacerbations. Anti-inflammatory therapies are therefore of particular interest for CF lung disease but must be carefully studied to avoid suppressing critical elements of the inflammatory response and thus worsening infection. This review examines the role of inflammation in the pathogenesis of CF lung disease, summarizes the results of past clinical trials and explores promising new anti-inflammatory options.
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Affiliation(s)
- André M Cantin
- Pulmonary Division, University of Sherbrooke, 3001, 12th Avenue North, Sherbrooke, QC, Canada.
| | - Dominik Hartl
- CF Center, Children's Hospital of the University of Tübingen, Tübingen, Germany
| | - Michael W Konstan
- Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - James F Chmiel
- Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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204
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Kurbatova P, Bessonov N, Volpert V, Tiddens HAWM, Cornu C, Nony P, Caudri D. Model of mucociliary clearance in cystic fibrosis lungs. J Theor Biol 2015; 372:81-8. [PMID: 25746843 DOI: 10.1016/j.jtbi.2015.02.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 02/06/2015] [Accepted: 02/25/2015] [Indexed: 11/19/2022]
Abstract
Mucus clearance is a primary innate defense mechanism in the human airways. Cystic fibrosis (CF) is a genetic disease caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. CF is characterized by dehydration of airway surface liquid and impaired mucociliary clearance. As a result, microorganisms are not efficiently removed from the airways, and patients experience chronic pulmonary infections and inflammation. We propose a new physiologically based mathematical model of muco-ciliary transport consisting of the two major components of the mucociliary clearance system: (i) periciliary liquid layer (PCL) and (ii) mucus layer. We study mucus clearance under normal conditions and in CF patients. Restoring impaired clearance of airway secretions in one of the major goals of therapy in patients with CF. We consider the action of the aerosolized and inhaled medication dornase alfa, which reduces the viscosity of cystic fibrosis mucus, by selectively cleaving the long DNA strands it contains. The results of the model simulations stress the potential relevance of the location of the drug deposition in the central or peripheral airways. Mucus clearance was increased in case the drug was primarily deposited peripherally, i.e. in the small airways.
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Affiliation(s)
- P Kurbatova
- University of Lyon 1, UMR 5558, CRNS Lyon, 8 rue Guillaume Paradin, BP8071, 69376 cedex 08, Lyon, France; UMR 663, Inserm-University Paris Descartes-CEA, Necker Hospital, Paris, France.
| | - N Bessonov
- Institute of Mechanical Engineering Problems, 199178 Saint Petersburg, Russia
| | - V Volpert
- University of Lyon 1, CNRS UMR 5208, Institut Camille Jordan 43 blvd du 11 novembre 1918, F-69622 Villeurbanne-Cedex, France
| | - H A W M Tiddens
- Erasmus University Medical Centre-Sophia Children׳s Hospital, PO Box 2060, 3000 CB Rotterdam, Netherlands
| | - C Cornu
- University of Lyon 1, UMR 5558, CRNS Lyon, 8 rue Guillaume Paradin, BP8071, 69376 cedex 08, Lyon, France; CHU Lyon, Service de Pharmacologie Clinique, 8 rue Guillaume Paradin, BP8071, 69376 cedex 08, Lyon, France; Hôpital Louis Pradel, Centre d׳Investigation Clinique, INSERM CIC201/UMR5558, Bron, France
| | - P Nony
- University of Lyon 1, UMR 5558, CRNS Lyon, 8 rue Guillaume Paradin, BP8071, 69376 cedex 08, Lyon, France; CHU Lyon, Service de Pharmacologie Clinique, 8 rue Guillaume Paradin, BP8071, 69376 cedex 08, Lyon, France
| | - D Caudri
- Erasmus University Medical Centre-Sophia Children׳s Hospital, PO Box 2060, 3000 CB Rotterdam, Netherlands
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205
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Joo NS, Evans IAT, Cho HJ, Park IH, Engelhardt JF, Wine JJ. Proteomic analysis of pure human airway gland mucus reveals a large component of protective proteins. PLoS One 2015; 10:e0116756. [PMID: 25706550 PMCID: PMC4338240 DOI: 10.1371/journal.pone.0116756] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/12/2014] [Indexed: 01/09/2023] Open
Abstract
Airway submucosal glands contribute to innate immunity and protect the lungs by secreting mucus, which is required for mucociliary clearance and which also contains antimicrobial, anti-inflammatory, anti-proteolytic and anti-oxidant proteins. We stimulated glands in tracheal trimmings from three lung donors and collected droplets of uncontaminated mucus as they formed at the gland orifices under an oil layer. We analyzed the mucus using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Analysis identified 5486 peptides and 441 proteins from across the 3 samples (269-319 proteins per subject). We focused on 269 proteins common to at least 2 0f 3 subjects, of which 102 (38%) had protective or innate immunity functions. While many of these have long been known to play such roles, for many others their cellular protective functions have only recently been appreciated in addition to their well-studied biologic functions (e.g. annexins, apolipoproteins, gelsolin, hemoglobin, histones, keratins, and lumican). A minority of the identified proteins are known to be secreted via conventional exocytosis, suggesting that glandular secretion occurs via multiple mechanisms. Two of the observed protective proteins, major vault protein and prohibitin, have not been observed in fluid from human epithelial cultures or in fluid from nasal or bronchoalveolar lavage. Further proteomic analysis of pure gland mucus may help clarify how healthy airways maintain a sterile environment.
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Affiliation(s)
- Nam Soo Joo
- The Cystic Fibrosis Research Laboratory, Stanford University, Stanford, CA, 94305, United States of America
- * E-mail:
| | - Idil Apak T. Evans
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, United States of America
| | - Hyung-Ju Cho
- The Cystic Fibrosis Research Laboratory, Stanford University, Stanford, CA, 94305, United States of America
| | - Il-Ho Park
- The Cystic Fibrosis Research Laboratory, Stanford University, Stanford, CA, 94305, United States of America
| | - John F. Engelhardt
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, United States of America
| | - Jeffrey J. Wine
- The Cystic Fibrosis Research Laboratory, Stanford University, Stanford, CA, 94305, United States of America
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206
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Bodewes FAJA, Verkade HJ, Taminiau JAJM, Borowitz D, Wilschanski M. Cystic fibrosis and the role of gastrointestinal outcome measures in the new era of therapeutic CFTR modulation. J Cyst Fibros 2015; 14:169-77. [PMID: 25677689 DOI: 10.1016/j.jcf.2015.01.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 01/20/2015] [Accepted: 01/20/2015] [Indexed: 01/01/2023]
Abstract
With the development of new drugs that directly affect CFTR protein function, clinical trials are being designed or initiated for a growing number of patients with cystic fibrosis. The currently available and accepted clinical endpoints, FEV1 and BMI, have limitations. The aim of this report is to draw attention to the need and the ample possibilities for the development and validation of relevant gastrointestinal clinical endpoints for scientific evaluation of CFTR modulation treatment, particularly in young children and infants. The gastrointestinal tract offers very good opportunities to measure CFTR protein function and systematically evaluate CF related clinical outcomes based on the principal clinical gastrointestinal manifestations of CF: intestinal pH, intestinal transit time, intestinal bile salt malabsorption, intestinal inflammation, exocrine pancreatic function and intestinal fat malabsorption. We present a descriptive analysis of a variety of gastrointestinal outcome measures for clinical relevance, reliability, validity, responsiveness to interventions, feasibility in particular in young children and the availability of reference values.
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Affiliation(s)
- Frank A J A Bodewes
- Pediatric Gastroenterology and Hepatology, University of Groningen, University Medical Center, Groningen, The Netherlands.
| | - Henkjan J Verkade
- Pediatric Gastroenterology and Hepatology, University of Groningen, University Medical Center, Groningen, The Netherlands
| | | | - Drucy Borowitz
- Department of Pediatrics, State University of New York at Buffalo School of Medicine and Biomedical Sciences, Women and Children's Hospital of Buffalo, Buffalo, NY, United States
| | - Michael Wilschanski
- Pediatric Gastroenterology, Hadassah Hebrew University Medical Center, Jerusalem, Israel
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207
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Liu J, Walker NM, Ootani A, Strubberg AM, Clarke LL. Defective goblet cell exocytosis contributes to murine cystic fibrosis-associated intestinal disease. J Clin Invest 2015; 125:1056-68. [PMID: 25642775 DOI: 10.1172/jci73193] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 12/18/2014] [Indexed: 01/12/2023] Open
Abstract
Cystic fibrosis (CF) intestinal disease is associated with the pathological manifestation mucoviscidosis, which is the secretion of tenacious, viscid mucus that plugs ducts and glands of epithelial-lined organs. Goblet cells are the principal cell type involved in exocytosis of mucin granules; however, little is known about the exocytotic process of goblet cells in the CF intestine. Using intestinal organoids from a CF mouse model, we determined that CF goblet cells have altered exocytotic dynamics, which involved intrathecal granule swelling that was abruptly followed by incomplete release of partially decondensated mucus. Some CF goblet cells exhibited an ectopic granule location and distorted cellular morphology, a phenotype that is consistent with retrograde intracellular granule movement during exocytosis. Increasing the luminal concentration of bicarbonate, which mimics CF transmembrane conductance regulator-mediated anion secretion, increased spontaneous degranulation in WT goblet cells and improved exocytotic dynamics in CF goblet cells; however, there was still an apparent incoordination between granule decondensation and exocytosis in the CF goblet cells. Compared with those within WT goblet cells, mucin granules within CF goblet cells had an alkaline pH, which may adversely affect the polyionic composition of the mucins. Together, these findings indicate that goblet cell dysfunction is an epithelial-autonomous defect in the CF intestine that likely contributes to the pathology of mucoviscidosis and the intestinal manifestations of obstruction and inflammation.
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208
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Pelaseyed T, Bergström JH, Gustafsson JK, Ermund A, Birchenough GMH, Schütte A, van der Post S, Svensson F, Rodríguez-Piñeiro AM, Nyström EEL, Wising C, Johansson MEV, Hansson GC. The mucus and mucins of the goblet cells and enterocytes provide the first defense line of the gastrointestinal tract and interact with the immune system. Immunol Rev 2015; 260:8-20. [PMID: 24942678 DOI: 10.1111/imr.12182] [Citation(s) in RCA: 750] [Impact Index Per Article: 83.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The gastrointestinal tract is covered by mucus that has different properties in the stomach, small intestine, and colon. The large highly glycosylated gel-forming mucins MUC2 and MUC5AC are the major components of the mucus in the intestine and stomach, respectively. In the small intestine, mucus limits the number of bacteria that can reach the epithelium and the Peyer's patches. In the large intestine, the inner mucus layer separates the commensal bacteria from the host epithelium. The outer colonic mucus layer is the natural habitat for the commensal bacteria. The intestinal goblet cells secrete not only the MUC2 mucin but also a number of typical mucus components: CLCA1, FCGBP, AGR2, ZG16, and TFF3. The goblet cells have recently been shown to have a novel gate-keeping role for the presentation of oral antigens to the immune system. Goblet cells deliver small intestinal luminal material to the lamina propria dendritic cells of the tolerogenic CD103(+) type. In addition to the gel-forming mucins, the transmembrane mucins MUC3, MUC12, and MUC17 form the enterocyte glycocalyx that can reach about a micrometer out from the brush border. The MUC17 mucin can shuttle from a surface to an intracellular vesicle localization, suggesting that enterocytes might control and report epithelial microbial challenge. There is communication not only from the epithelial cells to the immune system but also in the opposite direction. One example of this is IL10 that can affect and improve the properties of the inner colonic mucus layer. The mucus and epithelial cells of the gastrointestinal tract are the primary gate keepers and controllers of bacterial interactions with the host immune system, but our understanding of this relationship is still in its infancy.
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Affiliation(s)
- Thaher Pelaseyed
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
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209
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Affiliation(s)
- David A Stoltz
- Department of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
- Department of Molecular Physiology and Biophysics, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
- Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa 52242
| | - David K Meyerholz
- Department of Pathology, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Michael J Welsh
- Department of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
- Department of Molecular Physiology and Biophysics, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
- Howard Hughes Medical Institute, Roy J and Lucille A Carver College of Medicine University of Iowa, Iowa City, Iowa 52242
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211
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Jakobsson HE, Rodríguez-Piñeiro AM, Schütte A, Ermund A, Boysen P, Bemark M, Sommer F, Bäckhed F, Hansson GC, Johansson MEV. The composition of the gut microbiota shapes the colon mucus barrier. EMBO Rep 2014; 16:164-77. [PMID: 25525071 PMCID: PMC4328744 DOI: 10.15252/embr.201439263] [Citation(s) in RCA: 441] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Two C57BL/6 mice colonies maintained in two rooms of the same specific pathogen-free (SPF) facility were found to have different gut microbiota and a mucus phenotype that was specific for each colony. The thickness and growth of the colon mucus were similar in the two colonies. However, one colony had mucus that was impenetrable to bacteria or beads the size of bacteria—which is comparable to what we observed in free-living wild mice—whereas the other colony had an inner mucus layer penetrable to bacteria and beads. The different properties of the mucus depended on the microbiota, as they were transmissible by transfer of caecal microbiota to germ-free mice. Mice with an impenetrable mucus layer had increased amounts of Erysipelotrichi, whereas mice with a penetrable mucus layer had higher levels of Proteobacteria and TM7 bacteria in the distal colon mucus. Thus, our study shows that bacteria and their community structure affect mucus barrier properties in ways that can have implications for health and disease. It also highlights that genetically identical animals housed in the same facility can have rather distinct microbiotas and barrier structures.
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Affiliation(s)
- Hedvig E Jakobsson
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
| | | | - André Schütte
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
| | - Anna Ermund
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
| | - Preben Boysen
- Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine and Biosciences Norwegian University of Life Sciences, Oslo, Norway
| | - Mats Bemark
- Department of Microbiology and Immunology, University of Gothenburg, Gothenburg, Sweden Department of Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Felix Sommer
- The Wallenberg Laboratory, Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Fredrik Bäckhed
- The Wallenberg Laboratory, Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Gunnar C Hansson
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
| | - Malin E V Johansson
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
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212
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Abstract
The intestinal epithelium is covered with mucus with the main structural building block being the densely O-glycosylated MUC2 mucin. The intestinal epithelium is exposed to ingested material, our digestive machinery, and large amounts of microorganisms. Mucus is the first line of defense and aids to limit exposure to all these threats to the epithelium. In the small intestine, mucus acts as a matrix, which contains antimicrobial products, such as defensins and immunoglobulin A that limit epithelial exposure to the luminal bacteria. In the colon, the stratified inner mucus layer acts as a physical barrier excluding bacteria from the epithelium. Bacterial penetration of this normally restricted zone is observed in many colitis models and also in patients with ulcerative colitis. Mucus defects that allow bacteria to reach the epithelium and to stimulate an immune system response can lead to the development of intestinal inflammation. The current state of our knowledge concerning the function of the mucus layers and the main mucin component, MUC2, in inflammatory bowel disease is described in this review.
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213
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Chang EH, Tang XX, Shah VS, Launspach JL, Ernst SE, Hilkin B, Karp PH, Abou Alaiwa MH, Graham SM, Hornick DB, Welsh MJ, Stoltz DA, Zabner J. Medical reversal of chronic sinusitis in a cystic fibrosis patient with ivacaftor. Int Forum Allergy Rhinol 2014; 5:178-81. [PMID: 25363320 DOI: 10.1002/alr.21440] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 09/17/2014] [Accepted: 09/25/2014] [Indexed: 01/08/2023]
Abstract
BACKGROUND Chronic sinusitis is universal in cystic fibrosis (CF) and our current treatments are ineffective in reversing sinus disease. The objective of this work was to determine if increasing CF transmembrane conductance regulator (CFTR) activity by ivacaftor could treat CF sinus disease and assess its effect on primary sinus epithelial cultures. METHODS Case report of 1 patient with long-standing chronic sinus disease and a new diagnosis of CF with a mild mutation (P205S) and a severe mutation (G551D). We discuss clinical changes in symptoms, radiographic findings, nasal potential difference testing, and nasal pH values before and after treatment with ivacaftor. We then developed primary sinonasal epithelial cell cultures from a biopsy of the patient to determine changes in airway surface liquid (ASL) pH and ASL viscosity after ivacaftor treatment. RESULTS Ivacaftor treatment reversed CT findings of CF sinus disease, increased nasal voltage and pH, and resolved sinus symptoms after 10 months of therapy. Ivacaftor significantly increased ASL pH and decreased ASL viscosity in primary airway cultures. CONCLUSION This report documents the reversal of CF sinus disease. Based on our in vivo and in vitro results, we speculate that ivacaftor may reverse CF sinusitis by increasing ASL pH and decreasing ASL viscosity. These studies suggest that CFTR modulation may be effective in treating CF and perhaps non-CF sinusitis.
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Affiliation(s)
- Eugene H Chang
- Department of Otolaryngology-Head and Neck Surgery, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA
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214
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Birket SE, Chu KK, Liu L, Houser GH, Diephuis BJ, Wilsterman EJ, Dierksen G, Mazur M, Shastry S, Li Y, Watson JD, Smith AT, Schuster BS, Hanes J, Grizzle WE, Sorscher EJ, Tearney GJ, Rowe SM. A functional anatomic defect of the cystic fibrosis airway. Am J Respir Crit Care Med 2014; 190:421-32. [PMID: 25029666 DOI: 10.1164/rccm.201404-0670oc] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE The mechanisms underlying cystic fibrosis (CF) lung disease pathogenesis are unknown. OBJECTIVES To establish mechanisms linking anion transport with the functional microanatomy, we evaluated normal and CF piglet trachea as well as adult swine trachea in the presence of selective anion inhibitors. METHODS We investigated airway functional microanatomy using microoptical coherence tomography, a new imaging modality that concurrently quantifies multiple functional parameters of airway epithelium in a colocalized fashion. MEASUREMENTS AND MAIN RESULTS Tracheal explants from wild-type swine demonstrated a direct link between periciliary liquid (PCL) hydration and mucociliary transport (MCT) rates, a relationship frequently invoked but never experimentally confirmed. However, in CF airways this relationship was completely disrupted, with greater PCL depths associated with slowest transport rates. This disrupted relationship was recapitulated by selectively inhibiting bicarbonate transport in vitro and ex vivo. CF mucus exhibited increased viscosity in situ due to the absence of bicarbonate transport, explaining defective MCT that occurs even in the presence of adequate PCL hydration. CONCLUSIONS An inherent defect in CF airway surface liquid contributes to delayed MCT beyond that caused by airway dehydration alone and identifies a fundamental mechanism underlying the pathogenesis of CF lung disease in the absence of antecedent infection or inflammation.
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215
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Hoegger MJ, Fischer AJ, McMenimen JD, Ostedgaard LS, Tucker AJ, Awadalla MA, Moninger TO, Michalski AS, Hoffman EA, Zabner J, Stoltz DA, Welsh MJ. Impaired mucus detachment disrupts mucociliary transport in a piglet model of cystic fibrosis. Science 2014; 345:818-22. [PMID: 25124441 DOI: 10.1126/science.1255825] [Citation(s) in RCA: 292] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Lung disease in people with cystic fibrosis (CF) is initiated by defective host defense that predisposes airways to bacterial infection. Advanced CF is characterized by a deficit in mucociliary transport (MCT), a process that traps and propels bacteria out of the lungs, but whether this deficit occurs first or is secondary to airway remodeling has been unclear. To assess MCT, we tracked movement of radiodense microdisks in airways of newborn piglets with CF. Cholinergic stimulation, which elicits mucus secretion, substantially reduced microdisk movement. Impaired MCT was not due to periciliary liquid depletion; rather, CF submucosal glands secreted mucus strands that remained tethered to gland ducts. Inhibiting anion secretion in non-CF airways replicated CF abnormalities. Thus, impaired MCT is a primary defect in CF, suggesting that submucosal glands and tethered mucus may be targets for early CF treatment.
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Affiliation(s)
- Mark J Hoegger
- Department of Molecular Physiology and Biophysics, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Anthony J Fischer
- Department of Pediatrics, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - James D McMenimen
- Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Lynda S Ostedgaard
- Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Alex J Tucker
- Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Maged A Awadalla
- Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Thomas O Moninger
- Central Microscopy Research Facility, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Andrew S Michalski
- Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Eric A Hoffman
- Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA. Department of Radiology, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA. Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA
| | - Joseph Zabner
- Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - David A Stoltz
- Department of Molecular Physiology and Biophysics, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA. Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA. Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA.
| | - Michael J Welsh
- Department of Molecular Physiology and Biophysics, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA. Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA. Howard Hughes Medical Institute (HHMI), University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA.
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Rowe SM, Heltshe SL, Gonska T, Donaldson SH, Borowitz D, Gelfond D, Sagel SD, Khan U, Mayer-Hamblett N, Van Dalfsen JM, Joseloff E, Ramsey BW. Clinical mechanism of the cystic fibrosis transmembrane conductance regulator potentiator ivacaftor in G551D-mediated cystic fibrosis. Am J Respir Crit Care Med 2014; 190:175-84. [PMID: 24927234 DOI: 10.1164/rccm.201404-0703oc] [Citation(s) in RCA: 391] [Impact Index Per Article: 39.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
RATIONALE Ivacaftor is a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator recently approved for patients with CF age 6 and older with the G551D mutation. OBJECTIVES To evaluate ivacaftor in a postapproval setting and determine mechanism of action and response of clinically relevant markers. METHODS We conducted a longitudinal cohort study in 2012-2013 in G551D CF patients age 6 and older with no prior exposure to ivacaftor. Study assessments were performed at baseline, 1, 3, and 6 months after ivacaftor initiation. Substudies evaluated mucociliary clearance, β-adrenergic sweat secretion rate, gastrointestinal pH, and sputum inflammation and microbiology Measurements and Main Results: A total of 151 of 153 subjects were prescribed ivacaftor and 88% completed the study through 6 months. FEV1 % predicted improved from baseline to 6 months (mean absolute change, 6.7%; P < 0.001). Similarly, body mass index improved from baseline to 6 months (mean change, 0.8 kg/m(2); P < 0.001). Sweat chloride decreased from baseline to 6 months (mean change, -53.8 mmol/L; 95% confidence interval, -57.7 to -49.9; P < 0.001), reflecting augmented CFTR function. There was significant improvement in hospitalization rate (P < 0.001) and Pseudomonas aeruginosa burden (P < 0.01). Significant improvements in mucociliary clearance (P < 0.001), gastrointestinal pH (P = 0.001), and microbiome were also observed, providing clinical mechanisms underlying the therapeutic benefit of ivacaftor. CONCLUSIONS Significant clinical and physiologic improvements were observed on initiation of ivacaftor in a broad patient population, including reduced infection with P. aeruginosa. Biomarker studies substantially improve the understanding of the mechanistic consequences of CFTR modulation on pulmonary and gastrointestinal physiology.
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Affiliation(s)
- Steven M Rowe
- 1 Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
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217
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Gustafsson JK, Lindén SK, Alwan AH, Scholte BJ, Hansson GC, Sjövall H. Carbachol-induced colonic mucus formation requires transport via NKCC1, K⁺ channels and CFTR. Pflugers Arch 2014; 467:1403-1415. [PMID: 25139191 DOI: 10.1007/s00424-014-1595-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 08/01/2014] [Accepted: 08/06/2014] [Indexed: 12/26/2022]
Abstract
The colonic mucosa protects itself from the luminal content by secreting mucus that keeps the bacteria at a distance from the epithelium. For this barrier to be effective, the mucus has to be constantly replenished which involves exocytosis and expansion of the secreted mucins. Mechanisms involved in regulation of mucus exocytosis and expansion are poorly understood, and the aim of this study was to investigate whether epithelial anion secretion regulates mucus formation in the colon. The muscarinic agonist carbachol was used to induce parallel secretion of anions and mucus, and by using established inhibitors of ion transport, we studied how inhibition of epithelial transport affected mucus formation in mouse colon. Anion secretion and mucin exocytosis were measured by changes in membrane current and epithelial capacitance, respectively. Mucus thickness measurements were used to determine the carbachol effect on mucus growth. The results showed that the carbachol-induced increase in membrane current was dependent on NKCC1 co-transport, basolateral K(+) channels and Cftr activity. In contrast, the carbachol-induced increase in capacitance was partially dependent on NKCC1 and K(+) channel activity, but did not require Cftr activity. Carbachol also induced an increase in mucus thickness that was inhibited by the NKCC1 blocker bumetanide. However, mice that lacked a functional Cftr channel did not respond to carbachol with an increase in mucus thickness, suggesting that carbachol-induced mucin expansion requires Cftr channel activity. In conclusion, these findings suggest that colonic epithelial transport regulates mucus formation by affecting both exocytosis and expansion of the mucin molecules.
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Affiliation(s)
- Jenny K Gustafsson
- Department of Medical Biochemistry, University of Gothenburg, Medicinaregatan 9A, Box 440, Gothenburg, 405 30, Sweden.
| | - Sara K Lindén
- Department of Medical Biochemistry, University of Gothenburg, Medicinaregatan 9A, Box 440, Gothenburg, 405 30, Sweden
| | - Ala H Alwan
- Department of Medical Biochemistry, University of Gothenburg, Medicinaregatan 9A, Box 440, Gothenburg, 405 30, Sweden
| | - Bob J Scholte
- Department of Cell Biology, Erasmus MC, Rotterdam, The Netherlands
| | - Gunnar C Hansson
- Department of Medical Biochemistry, University of Gothenburg, Medicinaregatan 9A, Box 440, Gothenburg, 405 30, Sweden
| | - Henrik Sjövall
- Department of Internal Medicine, University of Gothenburg, Gothenburg, Sweden
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218
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Microbial-induced meprin β cleavage in MUC2 mucin and a functional CFTR channel are required to release anchored small intestinal mucus. Proc Natl Acad Sci U S A 2014; 111:12396-401. [PMID: 25114233 DOI: 10.1073/pnas.1407597111] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The mucus that covers and protects the epithelium of the intestine is built around its major structural component, the gel-forming MUC2 mucin. The gel-forming mucins have traditionally been assumed to be secreted as nonattached. The colon has a two-layered mucus system where the inner mucus is attached to the epithelium, whereas the small intestine normally has a nonattached mucus. However, the mucus of the small intestine of meprin β-deficient mice was now found to be attached. Meprin β is an endogenous zinc-dependent metalloprotease now shown to cleave the N-terminal region of the MUC2 mucin at two specific sites. When recombinant meprin β was added to the attached mucus of meprin β-deficient mice, the mucus was detached from the epithelium. Similar to meprin β-deficient mice, germ-free mice have attached mucus as they did not shed the membrane-anchored meprin β into the luminal mucus. The ileal mucus of cystic fibrosis (CF) mice with a nonfunctional cystic fibrosis transmembrane conductance regulator (CFTR) channel was recently shown to be attached to the epithelium. Addition of recombinant meprin β to CF mucus did not release the mucus, but further addition of bicarbonate rendered the CF mucus normal, suggesting that MUC2 unfolding exposed the meprin β cleavage sites. Mucus is thus secreted attached to the goblet cells and requires an enzyme, meprin β in the small intestine, to be detached and released into the intestinal lumen. This process regulates mucus properties, can be triggered by bacterial contact, and is nonfunctional in CF due to poor mucin unfolding.
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219
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Campylobacter jejuni infection suppressed Cl⁻ secretion induced by CFTR activation in T-84 cells. J Infect Chemother 2014; 20:682-8. [PMID: 25107576 DOI: 10.1016/j.jiac.2014.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 04/26/2014] [Accepted: 07/08/2014] [Indexed: 11/22/2022]
Abstract
Campylobacter jejuni causes foodborne disease associated with abdominal pain, gastroenteritis, and diarrhea. These symptoms are induced by bacterial adherence and invasion of host epithelial cells. C. jejuni infection can occur with a low infective dose, suggesting that C. jejuni may have evolved strategies to cope with the bacterial clearance system in the gastrointestinal tract. The mucosa layer is the first line of defense against bacteria. Mucus conditions are maintained by water and anion (especially Cl(-)) movement. Cystic fibrosis transmembrane conductance regulator (CFTR) is the main Cl(-) channel transporting Cl(-) to the lumen. Mutations in CFTR result in dehydrated secreted mucus and bacterial accumulation in the lungs, and recent studies suggest that closely related pathogenic bacteria also may survive in the intestine. However, the relationship between C. jejuni infection and CFTR has been little studied. Here, we used an (125)I(-) efflux assay and measurement of short-circuit current to measure Cl(-) secretion in C. jejuni-infected T-84 human intestinal epithelial cells. The basic state of Cl(-) secretion was unchanged by C. jejuni infection, but CFTR activator was observed to induce Cl(-) secretion suppressed in C. jejuni-infected T-84 cells. The suppression of activated Cl(-) secretion was bacterial dose-dependent and duration-dependent. A similar result was observed during infection with other C. jejuni strains. The mechanism of suppression may occur by affecting water movement or mucus condition in the intestinal tract. A failure of mucus barrier function may promote bacterial adhesion or invasion of host intestinal epithelial cells, thereby causing bacterial preservation in the host intestinal tract.
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220
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Kim D, Kim J, Burghardt B, Best L, Steward MC. Role of anion exchangers in Cl− and HCO3− secretion by the human airway epithelial cell line Calu-3. Am J Physiol Cell Physiol 2014; 307:C208-19. [DOI: 10.1152/ajpcell.00083.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Despite the importance of airway surface liquid pH in the lung's defenses against infection, the mechanism of airway HCO3− secretion remains unclear. Our aim was to assess the contribution of apical and basolateral Cl−/HCO3− exchangers to Cl− and HCO3− transport in the Calu-3 cell line, derived from human airway submucosal glands. Changes in intracellular pH (pHi) were measured following substitution of Cl− with gluconate. Apical Cl− substitution led to an alkalinization in forskolin-stimulated cells, indicative of Cl−/HCO3− exchange. This was unaffected by the anion exchange inhibitor DIDS but inhibited by the CFTR blocker CFTRinh-172, suggesting that the HCO3− influx might occur via CFTR, rather than a solute carrier family 26 (SLC26) exchanger, as recently proposed. The anion selectivity of the recovery process more closely resembled that of CFTR than an SLC26 exchanger, and quantitative RT-PCR showed only low levels of SLC26 exchanger transcripts relative to CFTR and anion exchanger 2 (AE2). For pHi to rise to observed values (∼7.8) through HCO3− entry via CFTR, the apical membrane potential must reverse to at least +20 mV following Cl− substitution; this was confirmed by perforated-patch recordings. Substitution of basolateral Cl− evoked a DIDS-sensitive alkalinization, attributed to Cl−/HCO3− exchange via AE2. This appeared to be abolished in forskolin-stimulated cells but was unmasked by blocking apical efflux of HCO3− via CFTR. We conclude that Calu-3 cells secrete HCO3− predominantly via CFTR, and, contrary to previous reports, the basolateral anion exchanger AE2 remains active during stimulation, providing an important pathway for basolateral Cl− uptake.
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Affiliation(s)
- Dusik Kim
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Juyeon Kim
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Beáta Burghardt
- Department of Oral Biology, Semmelweis University, Budapest, Hungary; and
| | - Len Best
- Faculty of Medicine and Human Sciences, University of Manchester, Manchester, United Kingdom
| | - Martin C. Steward
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
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221
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Abstract
Macromolecular structures embedded in the cell plasma membrane called ‘porosomes’, are involved in the regulated fractional release of intravesicular contents from cells during secretion. Porosomes range in size from 15 nm in neurons and astrocytes to 100-180 nm in the exocrine pancreas and neuroendocrine cells. Porosomes have been isolated from a number of cells, and their morphology, composition, and functional reconstitution well documented. The 3D contour map of the assembly of proteins within the porosome complex, and its native X-ray solution structure at sub-nm resolution has also advanced. This understanding now provides a platform to address diseases that may result from secretory defects. Water and ion binding to mucin impart hydration, critical for regulating viscosity of the mucus in the airways epithelia. Appropriate viscosity is required for the movement of mucus by the underlying cilia. Hence secretion of more viscous mucus prevents its proper transport, resulting in chronic and fatal airways disease such as cystic fibrosis (CF). CF is caused by the malfunction of CF transmembrane conductance regulator (CFTR), a chloride channel transporter, resulting in viscous mucus in the airways. Studies in mice lacking functional CFTR secrete highly viscous mucous that adhered to the epithelium. Since CFTR is known to interact with the t-SNARE protein syntaxin-1A, and with the chloride channel CLC-3, which are also components of the porosome complex, the interactions between CFTR and the porosome complex in the mucin-secreting human airway epithelial cell line Calu-3 was hypothesized and tested. Results from the study demonstrate the presence of approximately 100 nm in size porosome complex composed of 34 proteins at the cell plasma membrane in Calu-3 cells, and the association of CFTR with the complex. In comparison, the nuclear pore complex measures 120 nm and is comprised of over 500 protein molecules. The involvement of CFTR in porosome-mediated mucin secretion is hypothesized, and is currently being tested.
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Affiliation(s)
- Bhanu P Jena
- Wayne State University School of Medicine, Department of Physiology, Detroit, MI, USA
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222
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Sondo E, Caci E, Galietta LJ. The TMEM16A chloride channel as an alternative therapeutic target in cystic fibrosis. Int J Biochem Cell Biol 2014; 52:73-6. [DOI: 10.1016/j.biocel.2014.03.022] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 03/20/2014] [Accepted: 03/21/2014] [Indexed: 01/12/2023]
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223
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Shamsuddin AKM, Quinton PM. Native small airways secrete bicarbonate. Am J Respir Cell Mol Biol 2014; 50:796-804. [PMID: 24224935 DOI: 10.1165/rcmb.2013-0418oc] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Since the discovery of Cl(-) impermeability in cystic fibrosis (CF) and the cloning of the responsible channel, CF pathology has been widely attributed to a defect in epithelial Cl(-) transport. However, loss of bicarbonate (HCO3(-)) transport also plays a major, possibly more critical role in CF pathogenesis. Even though HCO3(-) transport is severely affected in the native pancreas, liver, and intestines in CF, we know very little about HCO3(-) secretion in small airways, the principle site of morbidity in CF. We used a novel, mini-Ussing chamber system to investigate the properties of HCO3(-) transport in native porcine small airways (∼ 1 mm φ). We assayed HCO3(-) transport across small airway epithelia as reflected by the transepithelial voltage, conductance, and equivalent short-circuit current with bilateral 25-mM HCO3(-) plus 125-mM NaGlu Ringer's solution in the presence of luminal amiloride (10 μM). Under these conditions, because no major transportable anions other than HCO3(-) were present, we took the equivalent short-circuit current to be a direct measure of active HCO3(-) secretion. Applying selective agonists and inhibitors, we show constitutive HCO3(-) secretion in small airways, which can be stimulated significantly by β-adrenergic- (cAMP) and purinergic (Ca(2+)) -mediated agonists, independently. These results indicate that two separate components for HCO3(-) secretion, likely via CFTR- and calcium-activated chloride channel-dependent processes, are physiologically regulated for likely roles in mucus clearance and antimicrobial innate defenses of small airways.
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Affiliation(s)
- A K M Shamsuddin
- 1 Department of Pediatrics, University of California San Diego, La Jolla, California; and
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224
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Abstract
Cystic fibrosis (CF) remains the most common fatal hereditary lung disease. The discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene 25 years ago set the stage for: 1) unravelling the molecular and cellular basis of CF lung disease; 2) the generation of animal models to study in vivo pathogenesis; and 3) the development of mutation-specific therapies that are now becoming available for a subgroup of patients with CF. This article highlights major advances in our understanding of how CFTR dysfunction causes chronic mucus obstruction, neutrophilic inflammation and bacterial infection in CF airways. Furthermore, we focus on recent breakthroughs and remaining challenges of novel therapies targeting the basic CF defect, and discuss the next steps to be taken to make disease-modifying therapies available to a larger group of patients with CF, including those carrying the most common mutation ΔF508-CFTR. Finally, we will summarise emerging evidence indicating that acquired CFTR dysfunction may be implicated in the pathogenesis of chronic obstructive pulmonary disease, suggesting that lessons learned from CF may be applicable to common airway diseases associated with mucus plugging.
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Affiliation(s)
- Marcus A Mall
- Dept of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), University of Heidelberg, Member of the German Center for Lung Research (DZL), Heidelberg, Germany Division of Paediatric Pulmonology and Allergy and Cystic Fibrosis Center, Dept of Paediatrics, University of Heidelberg, Member of the German Center for Lung Research (DZL), Heidelberg, Germany
| | - Dominik Hartl
- Paediatric Infectiology and Immunology, Dept of Pediatrics, University of Tübingen, Tübingen, Germany
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225
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Meconium ileus in cystic fibrosis is not linked to central repetitive region length variation in MUC1, MUC2, and MUC5AC. J Cyst Fibros 2014; 13:613-6. [PMID: 24920497 DOI: 10.1016/j.jcf.2014.05.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 05/01/2014] [Accepted: 05/03/2014] [Indexed: 01/08/2023]
Abstract
BACKGROUND Mucins are excellent candidates for contributing to the presence of meconium ileus (MI) in cystic fibrosis (CF) due to their extensive genetic variation and known function in intestinal physiology. The length of variants in mucin central repetitive regions has not been explored as "risk" factors for MI in CF. METHODS We investigated the length polymorphisms in the central repetitive regions of MUC1, MUC2, and MUC5AC by Southern blot and tested for association with MI in CF subjects. RESULTS No significant associations were found for the allele sizes of any of the genes with respect to the prevalence of MI (p values=0.33, 0.16, and 0.71 for MUC1, MUC2, and MUC5AC, respectively). CONCLUSIONS The genetic length variants in the central repetitive region of three MUC genes studied are not associated with MI in subjects with CF.
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226
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Ridley C, Kouvatsos N, Raynal BD, Howard M, Collins RF, Desseyn JL, Jowitt TA, Baldock C, Davis CW, Hardingham TE, Thornton DJ. Assembly of the respiratory mucin MUC5B: a new model for a gel-forming mucin. J Biol Chem 2014; 289:16409-20. [PMID: 24778189 PMCID: PMC4047408 DOI: 10.1074/jbc.m114.566679] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 04/17/2014] [Indexed: 12/17/2022] Open
Abstract
Mucins are essential components in mucus gels that form protective barriers at all epithelial surfaces, but much remains unknown about their assembly, intragranular organization, and post-secretion unfurling to form mucus. MUC5B is a major polymeric mucin expressed by respiratory epithelia, and we investigated the molecular mechanisms involved during its assembly. Studies of intact polymeric MUC5B revealed a single high affinity calcium-binding site, distinct from multiple low affinity sites on each MUC5B monomer. Self-diffusion studies with intact MUC5B showed that calcium binding at the protein site catalyzed reversible cross-links between MUC5B chains to form networks. The site of cross-linking was identified in the MUC5B D3-domain as it was specifically blocked by D3 peptide antibodies. Biophysical analysis and single particle EM of recombinant MUC5B N terminus (D1D2D'D3; NT5B) and subdomains (D1, D1-D2, D2-D'-D3, and D3) generated structural models of monomers and disulfide-linked dimers and suggested that MUC5B multimerizes by disulfide linkage between D3-domains to form linear polymer chains. Moreover, these analyses revealed reversible homotypic interactions of NT5B at low pH and in high calcium, between disulfide-linked NT5B dimers, but not monomers. These results enable a model of MUC5B to be derived, which predicts mechanisms of mucin intracellular assembly and storage, which may be common to the other major gel-forming polymeric mucins.
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Affiliation(s)
- Caroline Ridley
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Nikos Kouvatsos
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Bertrand D Raynal
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Marj Howard
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Richard F Collins
- the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Jean-Luc Desseyn
- the INSERM U995, University of Lille, F-59045 Lille, France, and
| | - Thomas A Jowitt
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Clair Baldock
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - C William Davis
- the Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina 27517-7248
| | - Timothy E Hardingham
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - David J Thornton
- From the Wellcome Trust Centre for Cell-Matrix Research and the Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom,
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227
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Abstract
PURPOSE OF REVIEW The article reviews advances in gastrointestinal aspects of cystic fibrosis (CF) published in the literature over the past year, and highlights new and interesting research. RECENT FINDINGS Animal models can be used to understand the pathophysiology of gastrointestinal complications in CF. The CF mouse is useful for studying distal intestinal obstruction, dysmotility and dysbiosis, and the CF pig model has helped us better understand meconium ileus and pancreatic and hepatobiliary secretory problems. Studies in humans help elucidate the evolution of pancreatic insufficiency, how reflux may lead to lung disease, problems with intestinal dysmotility, mechanisms leading to pancreatitis and the increased prevalence of gastrointestinal cancer. Biomarkers are shedding light on CF-related liver disease. Rectal biopsies can help in diagnosis and in studying new drugs for CF. SUMMARY Gastrointestinal complications of CF are likely to be seen with increasing frequency as patients with CF lead longer lives. CF animal models and modern research techniques are providing new insights into extrapulmonary complications. CF clinicians should be familiar with diagnosis and management of common gastrointestinal complications and should build bridges with specialists so that referrals can be made when needed.
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228
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Nilsson HE, Ambort D, Bäckström M, Thomsson E, Koeck PJB, Hansson GC, Hebert H. Intestinal MUC2 mucin supramolecular topology by packing and release resting on D3 domain assembly. J Mol Biol 2014; 426:2567-2579. [PMID: 24816392 DOI: 10.1016/j.jmb.2014.04.027] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 04/12/2014] [Accepted: 04/23/2014] [Indexed: 11/25/2022]
Abstract
MUC2 is the major gel-forming mucin of the colon forming a protective gel barrier organized into an inner stratified and an outer loose layer. The MUC2 N-terminus (D1-D2-D'D3 domains) has a dual function in building a net-like structure by disulfide-bonded trimerization and packing the MUC2 polymer into an N-terminal concatenated polygonal platform with the C-termini extending perpendicularly by pH- and calcium-dependent interactions. We studied the N-terminal D'D3 domain by producing three recombinant variants, with or without Myc tag and GFP (green fluorescent protein), and analyzed these by gel filtration, electron microscopy and single particle image processing. The three variants were all trimers when analyzed upon denaturing conditions but eluted as hexamers upon gel filtration under native conditions. Studies by electron microscopy and three-dimensional maps revealed cage-like structures with 2- and 3-fold symmetries. The structure of the MUC2 D3 domain confirms that the MUC2 mucin forms branched net-like structures. This suggests that the MUC2 mucin is stored with two N-terminal concatenated ring platforms turned by 180° against each other, implicating that every second unfolded MUC2 net in mature mucus is turned upside down.
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Affiliation(s)
- Harriet E Nilsson
- Department of Biosciences and Nutrition, Karolinska Institutet, and School of Technology and Health, KTH Royal Institute of Technology, Novum, SE-141 57 Huddinge, Sweden.,Department of Medical Biochemistry, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Daniel Ambort
- Department of Medical Biochemistry, University of Gothenburg, SE-405 30 Gothenburg, Sweden.,Mammalian Protein Expression Core Facility, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Malin Bäckström
- Department of Medical Biochemistry, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Elisabeth Thomsson
- Mammalian Protein Expression Core Facility, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Philip J B Koeck
- Department of Biosciences and Nutrition, Karolinska Institutet, and School of Technology and Health, KTH Royal Institute of Technology, Novum, SE-141 57 Huddinge, Sweden
| | - Gunnar C Hansson
- Department of Medical Biochemistry, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Hans Hebert
- Department of Biosciences and Nutrition, Karolinska Institutet, and School of Technology and Health, KTH Royal Institute of Technology, Novum, SE-141 57 Huddinge, Sweden
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229
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Jeong JH, Joo NS, Hwang PH, Wine JJ. Mucociliary clearance and submucosal gland secretion in the ex vivo ferret trachea. Am J Physiol Lung Cell Mol Physiol 2014; 307:L83-93. [PMID: 24793168 DOI: 10.1152/ajplung.00009.2014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In many species submucosal glands are an important source of tracheal mucus, but the extent to which mucociliary clearance (MCC) depends on gland secretion is unknown. To explore this relationship, we measured basal and agonist-stimulated MCC velocities in ex vivo tracheas from adult ferrets and compared the velocities with previously measured rates of ferret glandular mucus secretion (Cho HJ, Joo NS, Wine JJ. Am J Physiol Lung Cell Mol Physiol 299: L124-L136, 2010). Stimulated MCC velocities (mm/min, means ± SE for 10- to 35-min period poststimulation) were as follows: 1 μM carbachol: 19.1 ± 3.3 > 10 μM phenylephrine: 15.3 ± 2.4 ≈ 10 μM isoproterenol: 15.0 ± 1.9 ≈ 10 μM forskolin: 14.6 ± 3.1 > 1 μM vasoactive intestinal peptide (VIP): 10.2 ± 2.2 >> basal (t15): 1.8 ± 0.3; n = 5-10 for each condition. Synergistic stimulation of MCC was observed between low concentrations of carbachol (100 nM) and isoproterenol (300 nM). Bumetanide inhibited carbachol-stimulated MCC by ~70% and abolished the increase in MCC stimulated by forskolin + VIP, whereas HCO3 (-)-free solutions did not significantly inhibit MCC to either intracellular Ca(2+) concentration or intracellular cAMP concentration ([cAMP]i)-elevating agonists. Stimulation and inhibition of MCC and gland secretion differed in several respects: most importantly, elevating [cAMP]i increased MCC much more effectively than expected from its effects on gland secretion, and bumetanide almost completely inhibited [cAMP]i-stimulated MCC while it had a smaller effect on gland secretion. We conclude that changes in glandular fluid secretion are complexly related to MCC and discuss possible reasons for this.
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Affiliation(s)
- Jin Hyeok Jeong
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California; Department of Otolaryngology-Head and Neck Surgery, Hanyang University School of Medicine, Seoul, Korea; and
| | - Nam Soo Joo
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California
| | - Peter H Hwang
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - Jeffrey J Wine
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California;
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230
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Ehre C, Ridley C, Thornton DJ. Cystic fibrosis: an inherited disease affecting mucin-producing organs. Int J Biochem Cell Biol 2014; 52:136-45. [PMID: 24685676 DOI: 10.1016/j.biocel.2014.03.011] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 02/28/2014] [Accepted: 03/17/2014] [Indexed: 02/01/2023]
Abstract
Our current understanding of cystic fibrosis (CF) has revealed that the biophysical properties of mucus play a considerable role in the pathogenesis of the disease in view of the fact that most mucus-producing organs are affected in CF patients. In this review, we discuss the potential causal relationship between altered cystic fibrosis transmembrane conductance regulator (CFTR) function and the production of mucus with abnormal biophysical properties in the intestine and lungs, highlighting what has been learned from cell cultures and animal models that mimic CF pathogenesis. A similar cascade of events, including mucus obstruction, infection and inflammation, is common to all epithelia affected by impaired surface hydration. Hence, the main structural components of mucus, namely the polymeric, gel-forming mucins, are critical to the onset of the disease. Defective CFTR leads to epithelial surface dehydration, altered pH/electrolyte composition and mucin concentration. Further, it can influence mucin transition from the intracellular to extracellular environment, potentially resulting in aberrant mucus gel formation. While defective HCO3(-) production has long been identified as a feature of CF, it has only recently been considered as a key player in the transition phase of mucins. We conclude by examining the influence of mucins on the biophysical properties of CF sputum and discuss existing and novel therapies aimed at removing mucus from the lungs. This article is part of a Directed Issue entitled: Cystic Fibrosis: From o-mics to cell biology, physiology, and therapeutic advances.
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Affiliation(s)
- Camille Ehre
- CF/Pulmonary Research & Treatment Centre, The University of North Carolina at Chapel Hill, USA.
| | - Caroline Ridley
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, UK
| | - David J Thornton
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, UK
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231
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Shumilov D, Popov A, Fudala R, Akopova I, Gryczynski I, Borejdo J, Gryczynski Z, Grygorczyk R. Real-time imaging of exocytotic mucin release and swelling in Calu-3 cells using acridine orange. Methods 2014; 66:312-24. [PMID: 24055436 PMCID: PMC4780354 DOI: 10.1016/j.ymeth.2013.09.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 09/05/2013] [Indexed: 11/17/2022] Open
Abstract
Mucus secretion is the first-line of defence against the barrage of irritants inhaled into human lungs, but abnormally thick and viscous mucus results in many respiratory diseases. Understanding the processes underlying mucus pathology is hampered, in part, by lack of appropriate experimental tools for labeling and studying mucin granule secretion from live cells with high sensitivity and temporal resolution. In this report we present original spectroscopic properties of acridine orange (AO) which could be utilized to study granule release and mucin swelling with various advanced fluorescence imaging approaches. Low concentration (<200 μM) AO solutions presented absorption maximum at 494 nm, emission maximum at 525 nm and only ∼1.76 ns fluorescence lifetime. By contrast at high concentrations (4-30 mM) favoring formation of AO aggregates, a very different absorption with maximum at ∼440 nm, dramatically red-shifted emission with maximum at 630 nm, and over 10-fold increased fluorescence lifetime (∼20 ns) was observed. To verify potential utility of AO for real-time imaging we have performed confocal, total internal reflection fluorescence (TIRF) and fluorescence lifetime imaging (FLIM) of AO-stained Calu-3 cells. We found similar red-shifted fluorescence spectra and long fluorescence lifetime in intracellular granules as compared to that in the cytoplasm consistent with granular AO accumulation. Mechanical stimulation of Calu-3 cells resulted in multiple exocytotic secretory events of AO-stained granules followed by post-exocytotic swelling of their fluorescently-labeled content that was seen in single-line TIRF images as rapidly-expanding bright-fluorescence patches. The rate of their size expansion followed first-order kinetics with diffusivity of 3.98±0.07×10(-7)c m(2)/s, as expected for mucus gel swelling. This was followed by fluorescence decrease due to diffusional loss of AO that was ∼10-fold slower in the secreted mucus compared to bulk aqueous solution. In summary, we showed that AO-staining could be utilized for real-time TIRF imaging of mucin granule exocytosis and mucin swelling with high sensitivity and temporal resolution. Considering unique AO fluorescence properties that permit selective excitation of AO monomers versus aggregates, our study lays the groundwork for future development of two-color excitation scheme and two-color fluorescence FLIM live-cell imaging assay with potentially many biological applications.
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Affiliation(s)
- Dmytro Shumilov
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, USA
| | - Alexander Popov
- Research Centre, Centre hospitalier de l'Université de Montréal (CRCHUM) - Hôtel-Dieu, and Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Rafal Fudala
- Center for Commercialization of Fluorescence Technologies, Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Irina Akopova
- Center for Commercialization of Fluorescence Technologies, Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Ignacy Gryczynski
- Center for Commercialization of Fluorescence Technologies, Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, USA; Department of Cell Biology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Julian Borejdo
- Center for Commercialization of Fluorescence Technologies, Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, USA; Center for Commercialization of Fluorescence Technologies, Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, USA.
| | - Ryszard Grygorczyk
- Research Centre, Centre hospitalier de l'Université de Montréal (CRCHUM) - Hôtel-Dieu, and Department of Medicine, Université de Montréal, Montreal, Quebec, Canada.
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232
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Clancy JP, Johnson SG, Yee SW, McDonagh EM, Caudle KE, Klein TE, Cannavo M, Giacomini KM. Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for ivacaftor therapy in the context of CFTR genotype. Clin Pharmacol Ther 2014; 95:592-7. [PMID: 24598717 DOI: 10.1038/clpt.2014.54] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 02/24/2014] [Indexed: 01/19/2023]
Abstract
Cystic fibrosis (CF) is a life-shortening disease arising as a consequence of mutations within the CFTR gene. Novel therapeutics for CF are emerging that target CF transmembrane conductance regulator protein (CFTR) defects resulting from specific CFTR variants. Ivacaftor is a drug that potentiates CFTR gating function and is specifically indicated for CF patients with a particular CFTR variant, G551D-CFTR (rs75527207). Here, we provide therapeutic recommendations for ivacaftor based on preemptive CFTR genotype results.
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Affiliation(s)
- J P Clancy
- 1] Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA [2] Department of Pediatrics, University of Cincinnati, Cincinnati, Ohio, USA
| | - S G Johnson
- 1] Department of Clinical Pharmacy, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Denver, Colorado, USA [2] Clinical Pharmacy Services, Kaiser Permanente Colorado, Denver, Colorado, USA
| | - S W Yee
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA
| | - E M McDonagh
- Department of Genetics, Stanford University Medical Center, Stanford, California, USA
| | - K E Caudle
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - T E Klein
- Department of Genetics, Stanford University Medical Center, Stanford, California, USA
| | - M Cannavo
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - K M Giacomini
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA
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233
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Berkebile AR, McCray PB. Effects of airway surface liquid pH on host defense in cystic fibrosis. Int J Biochem Cell Biol 2014; 52:124-9. [PMID: 24560894 DOI: 10.1016/j.biocel.2014.02.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 02/01/2014] [Accepted: 02/11/2014] [Indexed: 01/27/2023]
Abstract
Cystic fibrosis is a lethal genetic disorder characterized by viscous mucus and bacterial colonization of the airways. Airway surface liquid represents a first line of pulmonary defense. Studies in humans and animal models of cystic fibrosis indicate that the pH of airway surface liquid is reduced in the absence of cystic fibrosis transmembrane conductance regulator function. Many aspects of the innate host defense system of the airways are pH sensitive, including antimicrobial peptide/protein activity, the rheological properties of secreted mucins, mucociliary clearance, and the activity of proteases. This review will focus on how changes in airway surface liquid pH may contribute to the host defense defect in cystic fibrosis soon after birth. Understanding how changes in pH impact mucosal immunity may lead to new therapies that can modify the airway surface liquid environment, improve airway defenses, and alter the disease course.
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Affiliation(s)
- Abigail R Berkebile
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Paul B McCray
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA; Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
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234
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Johansson MEV, Gustafsson JK, Holmén-Larsson J, Jabbar KS, Xia L, Xu H, Ghishan FK, Carvalho FA, Gewirtz AT, Sjövall H, Hansson GC. Bacteria penetrate the normally impenetrable inner colon mucus layer in both murine colitis models and patients with ulcerative colitis. Gut 2014; 63:281-91. [PMID: 23426893 PMCID: PMC3740207 DOI: 10.1136/gutjnl-2012-303207] [Citation(s) in RCA: 653] [Impact Index Per Article: 65.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE The inner mucus layer in mouse colon normally separates bacteria from the epithelium. Do humans have a similar inner mucus layer and are defects in this mucus layer a common denominator for spontaneous colitis in mice models and ulcerative colitis (UC)? METHODS AND RESULTS The colon mucus layer from mice deficient in Muc2 mucin, Core 1 O-glycans, Tlr5, interleukin 10 (IL-10) and Slc9a3 (Nhe3) together with that from dextran sodium sulfate-treated mice was immunostained for Muc2, and bacterial localisation in the mucus was analysed. All murine colitis models revealed bacteria in contact with the epithelium. Additional analysis of the less inflamed IL-10(-/-) mice revealed a thicker mucus layer than wild-type, but the properties were different, as the inner mucus layer could be penetrated both by bacteria in vivo and by fluorescent beads the size of bacteria ex vivo. Clear separation between bacteria or fluorescent beads and the epithelium mediated by the inner mucus layer was also evident in normal human sigmoid colon biopsy samples. In contrast, mucus on colon biopsy specimens from patients with UC with acute inflammation was highly penetrable. Most patients with UC in remission had an impenetrable mucus layer similar to that of controls. CONCLUSIONS Normal human sigmoid colon has an inner mucus layer that is impenetrable to bacteria. The colon mucus in animal models that spontaneously develop colitis and in patients with active UC allows bacteria to penetrate and reach the epithelium. Thus colon mucus properties can be modulated, and this suggests a novel model of UC pathophysiology.
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Affiliation(s)
- Malin E V Johansson
- Department of Medical Biochemistry, University of Gothenburg, , Gothenburg, Sweden
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235
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Dynamic changes in mucus thickness and ion secretion during Citrobacter rodentium infection and clearance. PLoS One 2013; 8:e84430. [PMID: 24386378 PMCID: PMC3875541 DOI: 10.1371/journal.pone.0084430] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/22/2013] [Indexed: 11/19/2022] Open
Abstract
Citrobacter rodentium is an attaching and effacing pathogen used as a murine model for enteropathogenic Escherichia coli. The mucus layers are a complex matrix of molecules, and mucus swelling, hydration and permeability are affected by many factors, including ion composition. Here, we used the C. rodentium model to investigate mucus dynamics during infection. By measuring the mucus layer thickness in tissue explants during infection, we demonstrated that the thickness changes dynamically during the course of infection and that its thickest stage coincides with the start of a decrease of bacterial density at day 14 after infection. Although quantitative PCR analysis demonstrated that mucin mRNA increases during early infection, the increased mucus layer thickness late in infection was not explained by increased mRNA levels. Proteomic analysis of mucus did not demonstrate the appearance of additional mucins, but revealed an increased number of proteins involved in defense responses. Ussing chamber-based electrical measurements demonstrated that ion secretion was dynamically altered during the infection phases. Furthermore, the bicarbonate ion channel Bestrophin-2 mRNA nominally increased, whereas the Cftr mRNA decreased during the late infection clearance phase. Microscopy of Muc2 immunostained tissues suggested that the inner striated mucus layer present in the healthy colon was scarce during the time point of most severe infection (10 days post infection), but then expanded, albeit with a less structured appearance, during the expulsion phase. Together with previously published literature, the data implies a model for clearance where a change in secretion allows reformation of the mucus layer, displacing the pathogen to the outer mucus layer, where it is then outcompeted by the returning commensal flora. In conclusion, mucus and ion secretion are dynamically altered during the C. rodentium infection cycle.
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236
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Ermund A, Gustafsson JK, Hansson GC, Keita ÅV. Mucus properties and goblet cell quantification in mouse, rat and human ileal Peyer's patches. PLoS One 2013; 8:e83688. [PMID: 24358305 PMCID: PMC3865249 DOI: 10.1371/journal.pone.0083688] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 11/15/2013] [Indexed: 02/08/2023] Open
Abstract
Peyer's patches (PPs) are collections of lymphoid follicles in the small intestine, responsible for scanning the intestinal content for foreign antigens such as soluble molecules, particulate matter as well as intact bacteria and viruses. The immune cells of the patch are separated from the intestinal lumen by a single layer of epithelial cells, the follicle-associated epithelium (FAE). This epithelium covers the dome of the follicle and contains enterocyte-like cells and M cells, which are particularly specialized in taking up antigens from the gut. However, the presence and number of goblet cells as well as the presence of mucus on top of the FAE is controversial. When mouse ileal PPs were mounted in a horizontal Ussing-type chamber, we could observe a continuous mucus layer at mounting and new, easily removable mucus was released from the villi on the patch upon stimulation. Confocal imaging using fluorescent beads revealed a penetrable mucus layer covering the domes. Furthermore, immunostaining of FAE from mice, rats and humans with a specific antibody against the main component of intestinal mucus, the MUC2 mucin, clearly identify mucin-containing goblet cells. Transmission electron micrographs further support the identification of mucus releasing goblet cells on the domes of PPs in these species.
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Affiliation(s)
- Anna Ermund
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
| | - Jenny K. Gustafsson
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
| | - Gunnar C. Hansson
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
| | - Åsa V. Keita
- Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University and County Council of Östergötland, Linköping, Sweden
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237
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Hou X, Lewis KT, Wu Q, Wang S, Chen X, Flack A, Mao G, Taatjes DJ, Sun F, Jena BP. Proteome of the porosome complex in human airway epithelia: interaction with the cystic fibrosis transmembrane conductance regulator (CFTR). J Proteomics 2013; 96:82-91. [PMID: 24220302 DOI: 10.1016/j.jprot.2013.10.041] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 10/20/2013] [Accepted: 10/31/2013] [Indexed: 01/11/2023]
Abstract
UNLABELLED The surface of the airways is coated with a thin film of mucus composed primarily of mucin, which is under continuous motion via ciliary action. Mucin not only serves to lubricate the airways epithelia, but also functions as a trap for foreign particles and pathogens, thereby assisting in keeping the airways clean and free of particulate matter and infections. Altered mucin secretion especially increased mucin viscosity, results in mucin stagnation due to the inability of the cilia to propel them, leading to infections and diseases such as cystic fibrosis (CF). Since porosomes have been demonstrated to be the secretory portals at the cell plasma membrane in cells, their presence, structure, and composition in the mucin-secreting human airway epithelial cell line Calu-3 expressing CF transmembrane receptor (CFTR), were investigated. Atomic force microscopy (AFM) of Calu-3 cells demonstrates the presence of approximately 100nm in diameter porosome openings at the plasma membrane surface. Electron microscopy confirms the AFM results, and tandem mass spectrometry and immunoanalysis performed on isolated Calu-3 porosomes, reveal the association of CFTR with the porosome complex. These new findings will facilitate understanding of CFTR-porosome interactions influencing mucous secretion, and provide critical insights into the etiology of CF disease. BIOLOGICAL SIGNIFICANCE In the present study, the porosome proteome in human airway epithelia has been determined. The interaction between the cystic fibrosis transmembrane conductance regulator (CFTR) and the porosome complex in the human airway epithelia is further demonstrated. The possible regulation by CFTR on the quality of mucus secretion via the porosome complex at the cell plasma membrane is hypothesized. These new findings will facilitate understanding of CFTR-porosome interactions influencing mucous secretion, and provide critical insights into the etiology of CF disease.
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Affiliation(s)
- Xia Hou
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Kenneth T Lewis
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Qingtian Wu
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Sunxi Wang
- Department of Chemical Engineering & Materials Science, College of Engineering, Wayne State University, MI 48202, USA
| | - Xuequn Chen
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Amanda Flack
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Guangzhao Mao
- Department of Chemical Engineering & Materials Science, College of Engineering, Wayne State University, MI 48202, USA
| | - Douglas J Taatjes
- Department of Pathology, Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, VT 05405, USA
| | - Fei Sun
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Bhanu P Jena
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201, USA; Department of Chemical Engineering & Materials Science, College of Engineering, Wayne State University, MI 48202, USA.
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238
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Ito G, Okamoto R, Murano T, Shimizu H, Fujii S, Nakata T, Mizutani T, Yui S, Akiyama-Morio J, Nemoto Y, Okada E, Araki A, Ohtsuka K, Tsuchiya K, Nakamura T, Watanabe M. Lineage-specific expression of bestrophin-2 and bestrophin-4 in human intestinal epithelial cells. PLoS One 2013; 8:e79693. [PMID: 24223998 PMCID: PMC3818177 DOI: 10.1371/journal.pone.0079693] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Accepted: 09/24/2013] [Indexed: 01/21/2023] Open
Abstract
Intestinal epithelial cells (IECs) regulate the absorption and secretion of anions, such as HCO3- or Cl-. Bestrophin genes represent a newly identified group of calcium-activated Cl- channels (CaCCs). Studies have suggested that, among the four human bestrophin-family genes, bestrophin-2 (BEST2) and bestrophin-4 (BEST4) might be expressed within the intestinal tissue. Consistently, a study showed that BEST2 is expressed by human colonic goblet cells. However, their precise expression pattern along the gastrointestinal tract, or the lineage specificity of the cells expressing these genes, remains largely unknown. Here, we show that BEST2 and BEST4 are expressed in vivo, each in a distinct, lineage-specific manner, in human IECs. While BEST2 was expressed exclusively in colonic goblet cells, BEST4 was expressed in the absorptive cells of both the small intestine and the colon. In addition, we found that BEST2 expression is significantly down-regulated in the active lesions of ulcerative colitis, where goblet cells were depleted, suggesting that BEST2 expression is restricted to goblet cells under both normal and pathologic conditions. Consistently, the induction of goblet cell differentiation by a Notch inhibitor, LY411575, significantly up-regulated the expression of not BEST4 but BEST2 in MUC2-positive HT-29 cells. Conversely, the induction of absorptive cell differentiation up-regulated the expression of BEST4 in villin-positive Caco-2 cells. In addition, we found that the up- or down-regulation of Notch activity leads to the preferential expression of either BEST4 or BEST2, respectively, in LS174T cells. These results collectively confirmed that BEST2 and BEST4 could be added to the lineage-specific genes of humans IECs due to their abilities to clearly identify goblet cells of colonic origin and a distinct subset of absorptive cells, respectively.
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Affiliation(s)
- Go Ito
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ryuichi Okamoto
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
- Department of Advanced GI therapeutics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
- * E-mail:
| | - Tatsuro Murano
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hiromichi Shimizu
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Satoru Fujii
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Toru Nakata
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tomohiro Mizutani
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Shiro Yui
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Junko Akiyama-Morio
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yasuhiro Nemoto
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Eriko Okada
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Akihiro Araki
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kazuo Ohtsuka
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kiichiro Tsuchiya
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
- Department of Advanced GI therapeutics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tetsuya Nakamura
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
- Department of Advanced GI therapeutics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Mamoru Watanabe
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
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239
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Gastrointestinal HCO3- transport and epithelial protection in the gut: new techniques, transport pathways and regulatory pathways. Curr Opin Pharmacol 2013; 13:900-8. [PMID: 24280619 DOI: 10.1016/j.coph.2013.10.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/29/2013] [Accepted: 10/01/2013] [Indexed: 02/07/2023]
Abstract
The concept of a protective alkaline gastric and duodenal mucus layer is a century old, yet it is amazing how much new information on HCO3(-) transport pathways has emerged recently, made possible by the extensive utilization of gene-deleted and transgenic mice and novel techniques to study HCO3(-) transport. This review highlights recent findings regarding the importance of HCO3(-) for mucosal protection of duodenum and other gastrointestinal epithelia against luminal acid and other damaging factors. Recently, methods have been developed to visualize HCO3(-) transport in vivo by assessing the surface pH in the mucus layer, as well as the epithelial pH. New information about HCO3(-) transport pathways, and emerging concepts about the intricate regulatory network that governs duodenal HCO3(-) secretion are described, and new perspectives for drug therapy discussed.
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240
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Garnett JP, Turner MJ. Controversies surrounding the role of CFTR in airway bicarbonate secretion. J Physiol 2013; 591:2241-2. [PMID: 23740884 DOI: 10.1113/jphysiol.2013.251199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- James P Garnett
- Division of Biomedical Sciences, St George's, University of London, London, UK.
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241
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Galietta LJV. Managing the underlying cause of cystic fibrosis: a future role for potentiators and correctors. Paediatr Drugs 2013; 15:393-402. [PMID: 23757197 DOI: 10.1007/s40272-013-0035-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Cystic fibrosis (CF), a severe genetic disease, is caused by mutations that alter the structure and function of CFTR, a plasma membrane channel permeable to chloride and bicarbonate. Defective anion transport in CF irreversibly damages the lungs, pancreas, liver, and other organs. CF mutations cause loss of CFTR function in multiple ways. In particular, class 3 mutations such as p.Gly551Asp strongly decrease the time spent by CFTR in the open state (gating defect). Instead, class 2 mutations impair the maturation of CFTR protein and its transport from the endoplasmic reticulum to the plasma membrane (trafficking defect). The deletion of phenylalanine 508 (p.Phe508del), the most frequent mutation among CF patients (70-90 %), destabilizes the CFTR protein, thus causing both a trafficking and a gating defect. These two defects can be overcome with drug-like molecules generically called correctors and potentiators, respectively. The potentiator Kalydeco™ (also known as Ivacaftor or VX-770), developed by Vertex Pharmaceuticals, has been recently approved by the US FDA and the European Medicines Agency (EMA) for the treatment of CF patients carrying at least one CFTR allele with the p.Gly551Asp mutation (2-5 % of all patients). In contrast, the corrector VX-809, which significantly improves p.Phe508del-CFTR trafficking in vitro, is still under study in clinical trials. Because of multiple defects caused by the p.Phe508del mutation, it is probable that rescue of the mutant protein will require combined treatment with correctors having different mechanisms of action. This review evaluates the status of experimental and clinical research in pharmacotherapy for the CF basic defect.
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Affiliation(s)
- Luis J V Galietta
- Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, Via Gerolamo Gaslini 5, 16147, Genova, Italy,
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242
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Adler KB, Tuvim MJ, Dickey BF. Regulated mucin secretion from airway epithelial cells. Front Endocrinol (Lausanne) 2013; 4:129. [PMID: 24065956 PMCID: PMC3776272 DOI: 10.3389/fendo.2013.00129] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 09/03/2013] [Indexed: 12/18/2022] Open
Abstract
Secretory epithelial cells of the proximal airways synthesize and secrete gel-forming polymeric mucins. The secreted mucins adsorb water to form mucus that is propelled by neighboring ciliated cells, providing a mobile barrier which removes inhaled particles and pathogens from the lungs. Several features of the intracellular trafficking of mucins make the airway secretory cell an interesting comparator for the cell biology of regulated exocytosis. Polymeric mucins are exceedingly large molecules (up to 3 × 10(6) Da per monomer) whose folding and initial polymerization in the ER requires the protein disulfide isomerase Agr2. In the Golgi, mucins further polymerize to form chains and possibly branched networks comprising more than 20 monomers. The large size of mucin polymers imposes constraints on their packaging into transport vesicles along the secretory pathway. Sugar side chains account for >70% of the mass of mucins, and their attachment to the protein core by O-glycosylation occurs in the Golgi. Mature polymeric mucins are stored in large secretory granules ∼1 μm in diameter. These are translocated to the apical membrane to be positioned for exocytosis by cooperative interactions among myristoylated alanine-rich C kinase substrate, cysteine string protein, heat shock protein 70, and the cytoskeleton. Mucin granules undergo exocytic fusion with the plasma membrane at a low basal rate and a high stimulated rate. Both rates are mediated by a regulated exocytic mechanism as indicated by phenotypes in both basal and stimulated secretion in mice lacking Munc13-2, a sensor of the second messengers calcium and diacylglycerol (DAG). Basal secretion is induced by low levels of activation of P2Y2 purinergic and A3 adenosine receptors by extracellular ATP released in paracrine fashion and its metabolite adenosine. Stimulated secretion is induced by high levels of the same ligands, and possibly by inflammatory mediators as well. Activated receptors are coupled to phospholipase C by Gq, resulting in the generation of DAG and of IP3 that releases calcium from apical ER. Stimulated secretion requires activation of the low affinity calcium sensor Synaptotagmin-2, while a corresponding high affinity calcium sensor in basal secretion is not known. The core exocytic machinery is comprised of the SNARE proteins VAMP8, SNAP23, and an unknown Syntaxin protein, together with the scaffolding protein Munc18b. Common and distinct features of this exocytic system in comparison to neuroendocrine cells and neurons are highlighted.
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Affiliation(s)
- Kenneth B. Adler
- Department of Molecular Biomedical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, NC, USA
| | - Michael J. Tuvim
- Department of Pulmonary Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Burton F. Dickey
- Department of Pulmonary Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- *Correspondence: Burton F. Dickey, Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Unit 1462, 1515 Holcombe Boulevard, Houston, TX 77030-4009, USA e-mail:
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243
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Jakab RL, Collaco AM, Ameen NA. Characterization of CFTR High Expresser cells in the intestine. Am J Physiol Gastrointest Liver Physiol 2013; 305:G453-65. [PMID: 23868408 PMCID: PMC3761243 DOI: 10.1152/ajpgi.00094.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The CFTR High Expresser (CHE) cells express eightfold higher levels of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel compared with neighboring enterocytes and were first identified by our laboratory (Ameen et al., Gastroenterology 108: 1016, 1995). We used double-label immunofluorescence microscopy to further study these enigmatic epithelial cells in rat intestine in vivo or ex vivo. CHE cells were found in duodenum, most frequent in proximal jejunum, and absent in ileum and colon. CFTR abundance increased in CHE cells along the crypt-villus axis. The basolateral Na(+)K(+)Cl(-) cotransporter NKCC1, a key transporter involved in Cl(-) secretion, was detected at similar levels in CHE cells and neighboring enterocytes at steady state. Microvilli appeared shorter in CHE cells, with low levels of Myosin 1a, a villus enterocyte-specific motor that retains sucrase/isomaltase in the brush-border membrane (BBM). CHE cells lacked alkaline phosphatase and absorptive villus enterocyte BBM proteins, including Na(+)H(+) exchanger NHE3, Cl(-)/HCO3(-) exchanger SLC26A6 (putative anion exchanger 1), and sucrase/isomaltase. High levels of the vacuolar-ATPase proton pump were observed in the apical domain of CHE cells. Levels of the NHE regulatory factor NHERF1, Na-K-ATPase, and Syntaxin 3 were similar to that of neighboring enterocytes. cAMP or acetylcholine stimulation robustly increased apical CFTR and basolateral NKCC1 disproportionately in CHE cells relative to neighboring enterocytes. These data strongly argue for a specialized role of CHE cells in Cl(-)-mediated "high-volume" fluid secretion on the villi of the proximal small intestine.
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Affiliation(s)
- Robert L. Jakab
- Departments of 1Pediatrics/Gastroenterology and Hepatology, and
| | - Anne M. Collaco
- Departments of 1Pediatrics/Gastroenterology and Hepatology, and
| | - Nadia A. Ameen
- Departments of 1Pediatrics/Gastroenterology and Hepatology, and ,2Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
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Kotha K, Clancy JP. Ivacaftor treatment of cystic fibrosis patients with the G551D mutation: a review of the evidence. Ther Adv Respir Dis 2013; 7:288-96. [DOI: 10.1177/1753465813502115] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cystic fibrosis (CF) is a recessive disorder caused by mutations in the gene that encodes the CF transmembrane conductance regulator (CFTR) protein. CFTR protein is a chloride and bicarbonate channel that is critical for normal epithelial ion transport and hydration of epithelial surfaces. Current CF care is supportive, but recent breakthroughs have occurred with the advent of novel therapeutic strategies that assist the function of mutant CFTR proteins. The development and key clinical trial results of ivacaftor, a small molecule that targets gating defects in disease-causing CFTR mutations including G551D CFTR, are summarized in this review. The G551D mutation is reasonably common in the CF patient population and produces a CFTR protein that localizes normally to the plasma membrane, but fails to open in response to cellular cues. Ivacaftor treatment produces dramatic improvements in lung function, weight, lung disease stability, patient-reported outcomes, and CFTR biomarkers in patients with CF harboring the G551D CFTR mutation compared with placebo controls and patients with two copies of the common F508del CFTR mutation. The unprecedented success of ivacaftor treatment for the G551D CF patient population has generated excitement in the CF care community regarding the expansion of its use to other CF patient populations with primary or secondary gating defects.
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Affiliation(s)
- Kavitha Kotha
- Division of Pulmonary Medicine, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center and the University of Cincinnati, Cincinnati, OH, USA
| | - John P. Clancy
- Division of Pulmonary Medicine, Cincinnati Children’s Hospital Medical Center, ML 2021, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA
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245
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Ermund A, Schütte A, Johansson MEV, Gustafsson JK, Hansson GC. Studies of mucus in mouse stomach, small intestine, and colon. I. Gastrointestinal mucus layers have different properties depending on location as well as over the Peyer's patches. Am J Physiol Gastrointest Liver Physiol 2013; 305:G341-7. [PMID: 23832518 PMCID: PMC3761247 DOI: 10.1152/ajpgi.00046.2013] [Citation(s) in RCA: 250] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Colon has been shown to have a two-layered mucus system where the inner layer is devoid of bacteria. However, a complete overview of the mouse gastrointestinal mucus system is lacking. We now characterize mucus release, thickness, growth over time, adhesive properties, and penetrability to fluorescent beads from stomach to distal colon. Colon displayed spontaneous mucus release and all regions released mucus in response to carbachol and PGE2, except the distal colon and domes of Peyer's patches. Stomach and colon had an inner mucus layer that was adherent to the epithelium. In contrast, the small intestine and Peyer's patches had a single mucus layer that was easily aspirated. The inner mucus layer of the distal colon was not penetrable to beads the size of bacteria and the inner layer of the proximal colon was only partly penetrable. In contrast, the inner mucus layer of stomach was fully penetrable, as was the small intestinal mucus. This suggests a functional organization of the intestinal mucus system, where the small intestine has loose and penetrable mucus that may allow easy penetration of nutrients, in contrast to the stomach, where the mucus provides physical protection, and the colon, where the mucus separates bacteria from the epithelium. This knowledge of the mucus system and its organization improves our understanding of the gastrointestinal tract physiology.
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Affiliation(s)
- Anna Ermund
- Dept. Medical Biochemistry, Univ. of Gothenburg, Box 440, 40530 Gothenburg, Sweden.
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246
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Collaco AM, Jakab RL, Hoekstra NE, Mitchell KA, Brooks A, Ameen NA. Regulated traffic of anion transporters in mammalian Brunner's glands: a role for water and fluid transport. Am J Physiol Gastrointest Liver Physiol 2013; 305:G258-75. [PMID: 23744739 PMCID: PMC3742856 DOI: 10.1152/ajpgi.00485.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The Brunner's glands of the proximal duodenum exert barrier functions through secretion of glycoproteins and antimicrobial peptides. However, ion transporter localization, function, and regulation in the glands are less clear. Mapping the subcellular distribution of transporters is an important step toward elucidating trafficking mechanisms of fluid transport in the gland. The present study examined 1) changes in the distribution of intestinal anion transporters and the aquaporin 5 (AQP5) water channel in rat Brunner's glands following second messenger activation and 2) anion transporter distribution in Brunner's glands from healthy and disease-affected human tissues. Cystic fibrosis transmembrane conductance regulator (CFTR), AQP5, sodium-potassium-coupled chloride cotransporter 1 (NKCC1), sodium-bicarbonate cotransporter (NBCe1), and the proton pump vacuolar ATPase (V-ATPase) were localized to distinct membrane domains and in endosomes at steady state. Carbachol and cAMP redistributed CFTR to the apical membrane. cAMP-dependent recruitment of CFTR to the apical membrane was accompanied by recruitment of AQP5 that was reversed by a PKA inhibitor. cAMP also induced apical trafficking of V-ATPase and redistribution of NKCC1 and NBCe1 to the basolateral membranes. The steady-state distribution of AQP5, CFTR, NBCe1, NKCC1, and V-ATPase in human Brunner's glands from healthy controls, cystic fibrosis, and celiac disease resembled that of rat; however, the distribution profiles were markedly attenuated in the disease-affected duodenum. These data support functional transport of chloride, bicarbonate, water, and protons by second messenger-regulated traffic in mammalian Brunner's glands under physiological and pathophysiological conditions.
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Affiliation(s)
- Anne M. Collaco
- 1Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut;
| | - Robert L. Jakab
- 1Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut;
| | - Nadia E. Hoekstra
- 1Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut;
| | - Kisha A. Mitchell
- 2Department of Pathology, Yale University School of Medicine, New Haven, Connecticut; and
| | - Amos Brooks
- 2Department of Pathology, Yale University School of Medicine, New Haven, Connecticut; and
| | - Nadia A. Ameen
- 1Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut; ,3Department Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
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247
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Yang N, Garcia MAS, Quinton PM. Normal mucus formation requires cAMP-dependent HCO3- secretion and Ca2+-mediated mucin exocytosis. J Physiol 2013; 591:4581-93. [PMID: 23818690 DOI: 10.1113/jphysiol.2013.257436] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Evidence from the pathology in cystic fibrosis (CF) and recent results in vitro indicate that HCO3- is required for gel-forming mucins to form the mucus that protects epithelial surfaces. Mucus formation and release is a complex process that begins with an initial intracellular phase of synthesis, packaging and apical granule exocytosis that is followed by an extracellular phase of mucin swelling, transport and discharge into a lumen. Exactly where HCO3- becomes crucial in these processes is unknown, but we observed that in the presence of HCO3-, stimulating dissected segments of native mouse intestine with 5-hydroxytryptamine (5-HT) and prostaglandin E2 (PGE2) induced goblet cell exocytosis followed by normal mucin discharge in wild-type (WT) intestines. CF intestines that inherently lack cystic fibrosis transmembrane conductance regulator (CFTR)-dependent HCO3- secretion also demonstrated apparently normal goblet cell exocytosis, but in contrast, this was not followed by similar mucin discharge. Moreover, we found that even in the presence of HCO3-, when WT intestines were stimulated only with a Ca2+-mediated agonist (carbachol), exocytosis was followed by poor discharge as with CF intestines. However, when the Ca2+-mediated agonist was combined with a cAMP-mediated agonist (isoproterenol (isoprenaline) or vasoactive intestinal peptide) in the presence of HCO3- both normal exocytosis and normal discharge was observed. These results indicate that normal mucus formation requires concurrent activation of a Ca2+-mediated exocytosis of mucin granules and an independent cAMP-mediated, CFTR-dependent, HCO3- secretion that appears to mainly enhance the extracellular phases of mucus excretion.
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Affiliation(s)
- Ning Yang
- N. Yang: Division of Respiratory Medicine, Department of Pediatrics, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0830, USA.
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248
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Tiklová K, Tsarouhas V, Samakovlis C. Control of airway tube diameter and integrity by secreted chitin-binding proteins in Drosophila. PLoS One 2013; 8:e67415. [PMID: 23826295 PMCID: PMC3691276 DOI: 10.1371/journal.pone.0067415] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 05/18/2013] [Indexed: 01/08/2023] Open
Abstract
The transporting function of many branched tubular networks like our lungs and circulatory system depend on the sizes and shapes of their branches. Understanding the mechanisms of tube size control during organ development may offer new insights into a variety of human pathologies associated with stenoses or cystic dilations in tubular organs. Here, we present the first secreted luminal proteins involved in tube diametric expansion in the Drosophila airways. obst-A and gasp are conserved among insect species and encode secreted proteins with chitin binding domains. We show that the widely used tracheal marker 2A12, recognizes the Gasp protein. Analysis of obst-A and gasp single mutants and obst-A; gasp double mutant shows that both genes are primarily required for airway tube dilation. Similarly, Obst-A and Gasp control epidermal cuticle integrity and larval growth. The assembly of the apical chitinous matrix of the airway tubes is defective in gasp and obst-A mutants. The defects become exaggerated in double mutants indicating that the genes have partially redundant functions in chitin structure modification. The phenotypes in luminal chitin assembly in the airway tubes are accompanied by a corresponding reduction in tube diameter in the mutants. Conversely, overexpression of Obst-A and Gasp causes irregular tube expansion and interferes with tube maturation. Our results suggest that the luminal levels of matrix binding proteins determine the extent of diametric growth. We propose that Obst-A and Gasp organize luminal matrix assembly, which in turn controls the apical shapes of adjacent cells during tube diameter expansion.
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Affiliation(s)
- Katarína Tiklová
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Vasilios Tsarouhas
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Christos Samakovlis
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
- * E-mail:
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249
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Pelaseyed T, Gustafsson JK, Gustafsson IJ, Ermund A, Hansson GC. Carbachol-induced MUC17 endocytosis is concomitant with NHE3 internalization and CFTR membrane recruitment in enterocytes. Am J Physiol Cell Physiol 2013; 305:C457-67. [PMID: 23784542 DOI: 10.1152/ajpcell.00141.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have reported that transmembrane mucin MUC17 binds PDZ protein PDZK1, which retains MUC17 apically in enterocytes. MUC17 and transmembrane mucins MUC3 and MUC12 are suggested to build the enterocyte apical glycocalyx. Carbachol (CCh) stimulation of the small intestine results in gel-forming mucin secretion from goblet cells, something that requires adjacent enterocytes to secrete chloride and bicarbonate for proper mucin formation. Surface labeling and confocal imaging demonstrated that apically expressed MUC17 in Caco-2 cells and Muc3(17) in murine enterocytes were endocytosed upon stimulation with CCh. Relocation of MUC17 in response to CCh was specific as MUC3 and MUC12 did not relocate following CCh stimulation. MUC17 colocalized with PDZK1 under basal conditions, while MUC17 relocated to the terminal web and into early endosomes after CCh stimulation. CCh stimulation concomitantly internalized the Na(+/)H(+) exchanger 3 (NHE3) and recruited cystic fibrosis transmembrane conductance regulator (CFTR) to the apical membranes, a process that was important for CFTR-mediated bicarbonate secretion necessary for proper gel-forming mucin unfolding. The reason for the specific internalization of MUC17 is not understood, but it could limit the diffusion barrier for ion secretion caused by the apical enterocyte glycocalyx or alternatively act to sample luminal bacteria. Our results reveal well-orchestrated mucus secretion and trafficking of ion channels and the MUC17 mucin.
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Affiliation(s)
- Thaher Pelaseyed
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
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250
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Abstract
Mucins--large, highly glycosylated proteins--are important for the luminal protection of the gastrointestinal tract. Enterocytes have their apical surface covered by transmembrane mucins and goblet cells produce the secreted gel-forming mucins that form mucus. The small intestine has a single unattached mucus layer, which in cystic fibrosis becomes attached, accounting for the intestinal manifestations of this disease. The stomach and colon have two layers of mucus; the inner layer is attached and the outer layer is less dense and unattached. In the colon, the outer mucus layer is the habitat for commensal bacteria. The inner mucus layer is impervious to bacteria and is renewed every hour by surface goblet cells. The crypt goblet cells have the ability to restitute the mucus layer by secretion, for example after an ischaemic challenge. Proteases of certain parasites and some bacteria can cleave mucins and dissolve the mucus as part of their pathogenicity. The inner mucus layer can, however, also become penetrable to bacteria by several other mechanisms, including aberrations in the immune system. When bacteria reach the epithelial surface, the immune system is activated and inflammation is triggered. This mechanism might occur in some types of ulcerative colitis.
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