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MUC1: The First Respiratory Mucin with an Anti-Inflammatory Function. J Clin Med 2017; 6:jcm6120110. [PMID: 29186029 PMCID: PMC5742799 DOI: 10.3390/jcm6120110] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/22/2017] [Accepted: 11/24/2017] [Indexed: 02/07/2023] Open
Abstract
MUC1 is a membrane-bound mucin expressed on the apical surfaces of most mucosal epithelial cells. In normal lung epithelia, MUC1 is a binding site for Pseudomonas aeruginosa, an opportunistic human pathogen of great clinical importance. It has now been established that MUC1 also serves an anti-inflammatory role in the airways that is initiated late in the course of a bacterial infection and is mediated through inhibition of Toll-like receptor (TLR) signaling. MUC1 expression was initially shown to interfere with TLR5 signaling in response to P. aeruginosa flagellin, but has since been extended to other TLRs. These new findings point to an immunomodulatory role for MUC1 during P. aeruginosa lung infection, particularly during the resolution phase of inflammation. This review briefly summarizes the recent characterization of MUC1’s anti-inflammatory properties in both the respiratory tract and extrapulmonary tissues.
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2
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Kumar S, Cruz E, Joshi S, Patel A, Jahan R, Batra SK, Jain M. Genetic variants of mucins: unexplored conundrum. Carcinogenesis 2017; 38:671-679. [PMID: 27838635 DOI: 10.1093/carcin/bgw120] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 11/10/2016] [Indexed: 12/12/2022] Open
Abstract
Alternative gene splicing, occurring ubiquitously in multicellular organisms can produce several protein isoforms with putatively different functions. The enormously extended genomic structure of mucin genes characterized by the presence of multiple exons encoding various domains may result in functionally diverse repertoire of mucin proteins due to alternative splicing. Splice variants (Svs) and mutations in mucin genes have been observed in various cancers and shown to participate in cancer progression and metastasis. Although several mucin Svs have been identified, their potential functions remain largely unexplored with the exception of the Svs of MUC1 and MUC4. A few studies have examined the expression of MUC1 and MUC4 Svs in cancer and indicated their potential involvement in promoting cancer cell proliferation, invasion, migration, angiogenesis and inflammation. Herein we review the current understanding of mucin Svs in cancer and inflammation and discuss the potential impact of splicing in generating a functionally diverse repertoire of mucin gene products. We also performed mutational analysis of mucin genes across five major cancer types in International Cancer Genome Consortium database and found unequal mutational rates across the panel of cancer-associated mucins. Although the functional role of mucins in the pathobiology of various malignancies and their utility as diagnostic and therapeutic targets remain undisputed, these attributes need to be reevaluated in light of the potentially unique functions of disease-specific genetic variants of mucins. Thus, the expressional and functional characterization of the genetic variants of mucins may provide avenues to fully exploit their potential as novel biomarkers and therapeutic targets.
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Affiliation(s)
- Sushil Kumar
- Department of Biochemistry and Molecular Biology
| | - Eric Cruz
- Department of Biochemistry and Molecular Biology
| | | | - Asish Patel
- Department of Biochemistry and Molecular Biology
| | - Rahat Jahan
- Department of Biochemistry and Molecular Biology
| | - Surinder K Batra
- Department of Biochemistry and Molecular Biology.,Eppley Institute for Research in Cancer and Allied Diseases.,Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Maneesh Jain
- Department of Biochemistry and Molecular Biology.,Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
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3
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van Putten JPM, Strijbis K. Transmembrane Mucins: Signaling Receptors at the Intersection of Inflammation and Cancer. J Innate Immun 2017; 9:281-299. [PMID: 28052300 DOI: 10.1159/000453594] [Citation(s) in RCA: 170] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 11/19/2016] [Indexed: 12/18/2022] Open
Abstract
Mucosal surfaces line our body cavities and provide the interaction surface between commensal and pathogenic microbiota and the host. The barrier function of the mucosal layer is largely maintained by gel-forming mucin proteins that are secreted by goblet cells. In addition, mucosal epithelial cells express cell-bound mucins that have both barrier and signaling functions. The family of transmembrane mucins consists of diverse members that share a few characteristics. The highly glycosylated extracellular mucin domains inhibit invasion by pathogenic bacteria and can form a tight mesh structure that protects cells in harmful conditions. The intracellular tails of transmembrane mucins can be phosphorylated and connect to signaling pathways that regulate inflammation, cell-cell interactions, differentiation, and apoptosis. Transmembrane mucins play important roles in preventing infection at mucosal surfaces, but are also renowned for their contributions to the development, progression, and metastasis of adenocarcinomas. In general, transmembrane mucins seem to have evolved to monitor and repair damaged epithelia, but these functions can be highjacked by cancer cells to yield a survival advantage. This review presents an overview of the current knowledge of the functions of transmembrane mucins in inflammatory processes and carcinogenesis in order to better understand the diverse functions of these multifunctional proteins.
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Affiliation(s)
- Jos P M van Putten
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
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4
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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: 809] [Impact Index Per Article: 89.9] [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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5
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Wilberts BL, Arruda PH, Kinyon JM, Madson DM, Frana TS, Burrough ER. Comparison of Lesion Severity, Distribution, and Colonic Mucin Expression in Pigs With Acute Swine Dysentery Following Oral Inoculation With “Brachyspira hampsonii” or Brachyspira hyodysenteriae. Vet Pathol 2014; 51:1096-108. [DOI: 10.1177/0300985813516646] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Swine dysentery is classically associated with infection by Brachyspira hyodysenteriae, the only current officially recognized Brachyspira sp. that consistently imparts strong beta-hemolysis on blood agar. Recently, several strongly beta-hemolytic Brachyspira have been isolated from swine with clinical dysentery that are not identified as B. hyodysenteriae by PCR including the recently proposed species “ Brachyspira hampsonii.” In this study, 6-week-old pigs were inoculated with either a clinical isolate of “ B. hampsonii” (EB107; n = 10) clade II or a classic strain of B. hyodysenteriae (B204; n = 10) to compare gross and microscopic lesions and alterations in colonic mucin expression in pigs with clinical disease versus controls ( n = 6). Gross lesions were similar between infected groups. No histologic difference was observed between infected groups with regard to neutrophilic inflammation, colonic crypt depth, mucosal ulceration, or hemorrhage. Histochemical and immunohistochemical evaluation of the apex of the spiral colon revealed decreased expression of sulphated mucins, decreased expression of MUC4, and increased expression of MUC5AC in diseased pigs compared to controls. No difference was observed between diseased pigs in inoculated groups. This study reveals significant alterations in colonic mucin expression in pigs with acute swine dysentery and further reveals that these and other microscopic changes are similar following infection with “ B. hampsonii” clade II or B. hyodysenteriae.
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Affiliation(s)
- B. L. Wilberts
- Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, IA
| | - P. H. Arruda
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA
| | - J. M. Kinyon
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA
| | - D. M. Madson
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA
| | - T. S. Frana
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA
| | - E. R. Burrough
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA
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6
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Pelaseyed T, Zäch M, Petersson AC, Svensson F, Johansson DGA, Hansson GC. Unfolding dynamics of the mucin SEA domain probed by force spectroscopy suggest that it acts as a cell-protective device. FEBS J 2013; 280:1491-501. [PMID: 23331320 DOI: 10.1111/febs.12144] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Revised: 01/16/2013] [Accepted: 01/18/2013] [Indexed: 11/28/2022]
Abstract
MUC1 and other membrane-associated mucins harbor long, up to 1 μm, extended highly glycosylated mucin domains and sea urchin sperm protein, enterokinase and agrin (SEA) domains situated on their extracellular parts. These mucins line luminal tracts and organs, and are anchored to the apical cell membrane by a transmembrane domain. The SEA domain is highly conserved and undergoes a molecular strain-dependent autocatalytic cleavage during folding in the endoplasmic reticulum, a process required for apical plasma membrane expression. To date, no specific function has been designated for the SEA domain. Here, we constructed a recombinant protein consisting of three SEA domains in tandem and used force spectroscopy to assess the dissociation force required to unfold individual, folded SEA domains. Force-distance curves revealed three peaks, each representing unfolding of a single SEA domain. Fitting the observed unfolding events to a worm-like chain model yielded an average contour length of 32 nm per SEA domain. Analysis of forces applied on the recombinant protein revealed an average unfolding force of 168 pN for each SEA domain at a loading rate of 25 nN·s(-1). Thus, the SEA domain may act as a breaking point that can dissociate before the plasma membrane is breached when mechanical forces are applied to cell surfaces.
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Affiliation(s)
- Thaher Pelaseyed
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
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Lillehoj EP, Kato K, Lu W, Kim KC. Cellular and molecular biology of airway mucins. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 303:139-202. [PMID: 23445810 PMCID: PMC5593132 DOI: 10.1016/b978-0-12-407697-6.00004-0] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Airway mucus constitutes a thin layer of airway surface liquid with component macromolecules that covers the luminal surface of the respiratory tract. The major function of mucus is to protect the lungs through mucociliary clearance of inhaled foreign particles and noxious chemicals. Mucus is comprised of water, ions, mucin glycoproteins, and a variety of other macromolecules, some of which possess anti-microbial, anti-protease, and anti-oxidant activities. Mucins comprise the major protein component of mucus and exist as secreted and cell-associated glycoproteins. Secreted, gel-forming mucins are mainly responsible for the viscoelastic property of mucus, which is crucial for effective mucociliary clearance. Cell-associated mucins shield the epithelial surface from pathogens through their extracellular domains and regulate intracellular signaling through their cytoplasmic regions. However, neither the exact structures of mucin glycoproteins, nor the manner through which their expression is regulated, are completely understood. This chapter reviews what is currently known about the cellular and molecular properties of airway mucins.
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Affiliation(s)
- Erik P. Lillehoj
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Kosuke Kato
- Center for Inflammation, Translational and Clinical Lung Research and Department of Physiology, Temple University School of Medicine, Philadelphia, PA, USA
| | - Wenju Lu
- Guangzhou Institute of Respiratory Diseases, State Key Laboratory of Respiratory Diseases, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, PR China
| | - Kwang C. Kim
- Center for Inflammation, Translational and Clinical Lung Research and Department of Physiology, Temple University School of Medicine, Philadelphia, PA, USA
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8
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The MUC1 extracellular domain subunit is found in nuclear speckles and associates with spliceosomes. PLoS One 2012; 7:e42712. [PMID: 22905162 PMCID: PMC3414450 DOI: 10.1371/journal.pone.0042712] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 07/11/2012] [Indexed: 02/04/2023] Open
Abstract
MUC1 is a large transmembrane glycoprotein and oncogene expressed by epithelial cells and overexpressed and underglycosylated in cancer cells. The MUC1 cytoplasmic subunit (MUC1-C) can translocate to the nucleus and regulate gene expression. It is frequently assumed that the MUC1 extracellular subunit (MUC1-N) does not enter the nucleus. Based on an unexpected observation that MUC1 extracellular domain antibody produced an apparently nucleus-associated staining pattern in trophoblasts, we have tested the hypothesis that MUC1-N is expressed inside the nucleus. Three different antibodies were used to identify MUC1-N in normal epithelial cells and tissues as well as in several cancer cell lines. The results of immunofluorescence and confocal microscopy analyses as well as subcellular fractionation, Western blotting, and siRNA/shRNA studies, confirm that MUC1-N is found within nuclei of all cell types examined. More detailed examination of its intranuclear distribution using a proximity ligation assay, subcellular fractionation, and immunoprecipitation suggests that MUC1-N is located in nuclear speckles (interchromatin granule clusters) and closely associates with the spliceosome protein U2AF65. Nuclear localization of MUC1-N was abolished when cells were treated with RNase A and nuclear localization was altered when cells were incubated with the transcription inhibitor 5,6-dichloro-1-b-d-ribofuranosylbenzimidazole (DRB). While MUC1-N predominantly associated with speckles, MUC1-C was present in the nuclear matrix, nucleoli, and the nuclear periphery. In some nuclei, confocal microscopic analysis suggest that MUC1-C staining is located close to, but only partially overlaps, MUC1-N in speckles. However, only MUC1-N was found in isolated speckles by Western blotting. Also, MUC1-C and MUC1-N distributed differently during mitosis. These results suggest that MUC1-N translocates to the nucleus where it is expressed in nuclear speckles and that MUC1-N and MUC1-C have dissimilar intranuclear distribution patterns.
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9
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Petersson J, Schreiber O, Hansson GC, Gendler SJ, Velcich A, Lundberg JO, Roos S, Holm L, Phillipson M. Importance and regulation of the colonic mucus barrier in a mouse model of colitis. Am J Physiol Gastrointest Liver Physiol 2011; 300:G327-33. [PMID: 21109593 PMCID: PMC3302190 DOI: 10.1152/ajpgi.00422.2010] [Citation(s) in RCA: 259] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The colonic mucus layer serves as an important barrier and prevents colonic bacteria from invading the mucosa and cause inflammation. The regulation of colonic mucus secretion is poorly understood. The aim of this study was to investigate the role of the mucus barrier in induction of colitis. Furthermore, regulation of mucus secretion by luminal bacterial products was studied. The colon of anesthetized Muc2(-/-), Muc1(-/-), wild-type (wt), and germ-free mice was exteriorized, the mucosal surface was visualized, and mucus thickness was measured with micropipettes. Colitis was induced by DSS (dextran sodium sulfate, 3%, in drinking water), and disease activity index (DAI) was assessed daily. The colonic mucosa of germ-free and conventionally housed mice was exposed to the bacterial products LPS (lipopolysaccharide) and PGN (peptidoglycan). After DSS induction of colitis, the thickness of the firmly adherent mucus layer was significantly thinner after 5 days and onward, which paralleled the increment of DAI. Muc2(-/-) mice, which lacked firmly adherent mucus, were predisposed to colitis, whereas Muc1(-/-) mice were protected with significantly lower DAI by DSS compared with wt mice. The mucus barrier increased in Muc1(-/-) mice in response to DSS, whereas significantly fewer T cells were recruited to the inflamed colon. Mice housed under germ-free conditions had an extremely thin adherent colonic mucus layer, but when exposed to bacterial products (PGN or LPS) the thickness of the adherent mucus layer was quickly restored to levels observed in conventionally housed mice. This study demonstrates a correlation between decreasing mucus barrier and increasing clinical symptoms during onset of colitis. Mice lacking colonic mucus (Muc2(-/-)) were hypersensitive to DSS-induced colitis, whereas Muc1(-/-) were protected, probably through the ability to increase the mucus barrier but also by decreased T cell recruitment to the afflicted site. Furthermore, the ability of bacteria to regulate the thickness of the colonic mucus was demonstrated.
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Affiliation(s)
- J. Petersson
- 1Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden;
| | - O. Schreiber
- 1Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden;
| | - G. C. Hansson
- 2Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden;
| | - S. J. Gendler
- 3Mayo Clinic College of Medicine, Mayo Clinic Arizona, Scottsdale, Arizona;
| | - A. Velcich
- 4Montefiore Medical Center, Bronx, New York;
| | - J. O. Lundberg
- 5Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden; and
| | - S. Roos
- 6Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - L. Holm
- 1Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden;
| | - M. Phillipson
- 1Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden;
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Guang W, Ding H, Czinn SJ, Kim KC, Blanchard TG, Lillehoj EP. Muc1 cell surface mucin attenuates epithelial inflammation in response to a common mucosal pathogen. J Biol Chem 2010; 285:20547-57. [PMID: 20430889 DOI: 10.1074/jbc.m110.121319] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Helicobacter pylori infection of the gastric mucosa causes an active-chronic inflammation that is strongly linked to the development of duodenal and gastric ulcers and stomach cancer. However, greater than 80% of individuals infected with H. pylori are asymptomatic beyond histologic inflammation, and it is unknown what factors influence the incidence and character of bacterial-associated gastritis and related disorders. Because previous studies demonstrated that the Muc1 epithelial glycoprotein inhibited inflammation during acute lung infection by Pseudomonas aeruginosa, we asked whether Muc1 might also counter-regulate gastric inflammation in response to H. pylori infection. Muc1(-/-) mice displayed increased bacterial colonization of the stomach and greater TNF-alpha and keratinocyte chemoattractant transcript levels compared with Muc1(+/+) mice after experimental H. pylori infection. Knockdown of Muc1 expression in AGS human gastric epithelial cells by RNA interference was associated with increased phosphorylation of IkappaBalpha, augmented activation and nuclear translocation of NF-kappaB, and enhanced production of interleulin-8 compared with Muc1-expressing cells. Conversely, Muc1 overexpression was correlated with decreased NF-kappaB activation, reduced interleulin-8 production, and diminished IkappaB kinase beta (IKKbeta)/IKKgamma coimmunoprecipitation compared with cells expressing Muc1 endogenously. Cotransfection of AGS cells with Muc1 plus IKKbeta, but not a catalytically inactive IKKbeta mutant, reversed the Muc1 inhibitory effect. Finally, Muc1 formed a coimmunoprecipitation complex with IKKgamma but not with IKKbeta. These results are consistent with the hypothesis that Muc1 binds to IKKgamma, thereby inhibiting formation of the catalytically active IKK complex and blocking the ability of H. pylori to stimulate IkappaBalpha phosphorylation, NF-kappaB activation, and downstream inflammatory responses.
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Affiliation(s)
- Wei Guang
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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11
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Singh AK, Riederer B, Chen M, Xiao F, Krabbenhöft A, Engelhardt R, Nylander O, Soleimani M, Seidler U. The switch of intestinal Slc26 exchangers from anion absorptive to HCOFormula secretory mode is dependent on CFTR anion channel function. Am J Physiol Cell Physiol 2010; 298:C1057-65. [PMID: 20164375 DOI: 10.1152/ajpcell.00454.2009] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
CFTR has been recognized to function as both an anion channel and a key regulator of Slc26 anion transporters in heterologous expression systems. Whether this regulatory relationship between CFTR and Slc26 transporters is seen in native intestine, and whether this effect is coupled to CFTR transport function or other features of this protein, has not been studied. The duodena of anesthetized CFTR-, NHE3-, Slc26a6-, and Scl26a3-deficient mice and wild-type (WT) littermates were perfused, and duodenal bicarbonate (HCO(3)(-)) secretion (DBS) and fluid absorptive or secretory rates were measured. The selective NHE3 inhibitor S1611 or genetic ablation of NHE3 significantly reduced fluid absorptive rates and increased DBS. Slc26a6 (PAT1) or Slc26a3 (DRA) ablation reduced the S1611-induced DBS increase and reduced fluid absorptive rates, suggesting that the effect of S1611 or NHE3 ablation on HCO(3)(-) secretion may be an unmasking of Slc26a6- and Slc26a3-mediated Cl(-)/HCO(3)(-) exchange activity. In the absence of CFTR expression or after application of the CFTR(inh)-172, fluid absorptive rates were similar to those of WT, but S1611 induced virtually no increase in DBS, demonstrating that CFTR transport activity, and not just its presence, is required for Slc26-mediated duodenal HCO(3)(-) secretion. A functionally active CFTR is an absolute requirement for Slc26-mediated duodenal HCO(3)(-) secretion, but not for Slc26-mediated fluid absorption, in which these transporters operate in conjunction with the Na(+)/H(+) exchanger NHE3. This suggests that Slc26a6 and Slc26a3 need proton recycling via NHE3 to operate in the Cl(-) absorptive mode and Cl(-) exit via CFTR to operate in the HCO(3)(-) secretory mode.
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Affiliation(s)
- Anurag Kumar Singh
- Dept. of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Germany
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12
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Horn G, Gaziel A, Wreschner DH, Smorodinsky NI, Ehrlich M. ERK and PI3K regulate different aspects of the epithelial to mesenchymal transition of mammary tumor cells induced by truncated MUC1. Exp Cell Res 2009; 315:1490-504. [PMID: 19245809 DOI: 10.1016/j.yexcr.2009.02.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 01/26/2009] [Accepted: 02/11/2009] [Indexed: 02/06/2023]
Abstract
Epithelial to mesenchymal transition (EMT) integrates changes to cell morphology and signaling pathways resulting from modifications to the cell's transcriptional response. Different combinations of stimuli ignite this process in the contexts of development or tumor progression. The human MUC1 gene encodes multiple alternatively spliced forms of a polymorphic oncoprotein that is aberrantly expressed in epithelial malignancies. MUC1 is endowed with various signaling modules and has the potential to mediate proliferative and morphological changes characteristic of the progression of epithelial tumors. The tyrosine-rich cytoplasmic domain and the heavily glycosylated extracellular domain both play a role in MUC1-mediated signal transduction. However, the attribution of function to specific domains of MUC1 is difficult due to the concomitant presence of multiple forms of the protein, which stem from alternative splicing and proteolytic cleavage. Here we show that DA3 mouse mammary tumor cells stably transfected with a truncated genomic fragment of human MUC1 undergo EMT. In their EMT, these cells demonstrate altered [i] morphology, [ii] signaling pathways and [iii] expression of epithelial and mesenchymal markers. Similarly to well characterized human breast cancer cell lines, cells transfected with truncated MUC1 show an ERK-dependent increased spreading on fibronectin, and a PI3K-dependent enhancement of their proliferative rate.
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Affiliation(s)
- Galit Horn
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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13
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Baldus SE, Engelmann K, Hanisch FG. MUC1 and the MUCs: A Family of Human Mucins with Impact in Cancer Biology. Crit Rev Clin Lab Sci 2008; 41:189-231. [PMID: 15270554 DOI: 10.1080/10408360490452040] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Mucins represent a family of glycoproteins characterized by repeat domains and a dense O-glycosylation. During the last two decades, the gene and peptide structures of various mucins as well as their glycosylation states were partly elucidated. Characteristic tumor-associated alterations of the expression patterns and glycosylation profiles were observed in biochemical, immunochemical, and histological studies and are discussed in the light of efforts to use the most prominent member in this family, MUC1, as a tumor target in anti-tumor strategies. Within this context the present review, focusing on MUC1, describes recent work on the regulation of mucin biosynthesis by cytokines and hormones, the role of mucins in cell adhesion, and their interaction with the immune system. Important aspects of clinical diagnostics based on mucin antigens are discussed, including the application of tumor serum assays and the significance of numerous studies revealing correlations between the expression of peptide cores or mucin-associated carbohydrates and clinicopathological parameters like tumor progression and prognosis.
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Affiliation(s)
- Stephan E Baldus
- Institute of Pathology and Center of Biochemistry, University of Cologne, Cologne, Germany.
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14
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Abstract
Cell surface mucins are large transmembrane glycoproteins involved in diverse functions ranging from shielding the airway epithelium against pathogenic infection to regulating cellular signaling and transcription. Although hampered by the relatively recent characterization of cell surface mucins and the difficulties inherent in working with molecules of their size, numerous studies have placed the tethered mucins in the thick of normal and diseased lung physiology. This review focuses on the three best-characterized cell surface mucins expressed in the respiratory tract: MUC1, MUC4, and MUC16.
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Affiliation(s)
- Christine L Hattrup
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, Scottsdale, AR 85259, USA
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15
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De Lisle RC, Roach E, Jansson K. Effects of laxative and N-acetylcysteine on mucus accumulation, bacterial load, transit, and inflammation in the cystic fibrosis mouse small intestine. Am J Physiol Gastrointest Liver Physiol 2007; 293:G577-84. [PMID: 17615175 DOI: 10.1152/ajpgi.00195.2007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The accumulation of mucus in affected organs is characteristic of cystic fibrosis (CF). The CF mouse small intestine has dramatic mucus accumulation and exhibits slower interdigestive intestinal transit. These factors are proposed to play cooperative roles that foster small intestinal bacterial overgrowth (SIBO) and contribute to the innate immune response of the CF intestine. It was hypothesized that decreasing the mucus accumulation would reduce SIBO and might improve other aspects of the CF intestinal phenotype. To test this, solid chow-fed CF mice were treated with an osmotic laxative to improve gut hydration or liquid-fed mice were treated orally with N-acetylcysteine (NAC) to break mucin disulfide bonds. Treatment with laxative or NAC reduced mucus accumulation by 43% and 50%, respectively, as measured histologically as dilation of the intestinal crypts. Laxative and NAC also reduced bacterial overgrowth in the CF intestine by 92% and 63%, respectively. Treatment with laxative normalized small intestinal transit in CF mice, whereas NAC did not. The expression of innate immune response-related genes was significantly reduced in laxative-treated CF mice, whereas there was no significant effect in NAC-treated CF mice. In summary, laxative and NAC treatments of CF mice reduced mucus accumulation to a similar extent, but laxative was more effective than NAC at reducing bacterial load. Eradication of bacterial overgrowth by laxative treatment was associated with normalized intestinal transit and a reduction in the innate immune response. These results suggest that both mucus accumulation and slowed interdigestive small intestinal transit contribute to SIBO in the CF intestine.
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MESH Headings
- Acetylcysteine/pharmacology
- Acetylcysteine/therapeutic use
- Animals
- Bacteria/drug effects
- Bacteria/genetics
- Bacteria/growth & development
- Body Weight/drug effects
- Cathartics/pharmacology
- Cathartics/therapeutic use
- Cystic Fibrosis/drug therapy
- Cystic Fibrosis/metabolism
- Cystic Fibrosis/microbiology
- Cystic Fibrosis/physiopathology
- Disease Models, Animal
- Expectorants/pharmacology
- Expectorants/therapeutic use
- Gastric Emptying/drug effects
- Gastrointestinal Transit/drug effects
- Gene Expression Regulation/drug effects
- Immunity, Innate/drug effects
- Immunity, Innate/genetics
- Inflammation/drug therapy
- Inflammation/metabolism
- Inflammation/microbiology
- Inflammation/physiopathology
- Intestine, Small/drug effects
- Intestine, Small/metabolism
- Intestine, Small/microbiology
- Intestine, Small/physiopathology
- Mice
- Mice, Inbred CFTR
- Mucus/metabolism
- Polyethylene Glycols/pharmacology
- Polyethylene Glycols/therapeutic use
- RNA, Bacterial/metabolism
- RNA, Ribosomal, 16S/metabolism
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Affiliation(s)
- Robert C De Lisle
- Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS 66160, USA.
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16
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Hansson GC, Johansson MEV, Lidell ME. Biosynthesis and Secretion of Mucins, Especially the MUC2 Mucin, in Relation to Cystic Fibrosis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007. [DOI: 10.1007/0-387-23250-8_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Kuver R, Wong T, Klinkspoor JH, Lee SP. Absence of CFTR is associated with pleiotropic effects on mucins in mouse gallbladder epithelial cells. Am J Physiol Gastrointest Liver Physiol 2006; 291:G1148-54. [PMID: 16825704 DOI: 10.1152/ajpgi.00547.2005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mucus of cystic fibrosis patients exhibits altered biochemical composition and biophysical behavior, but the causal relationships between altered cystic fibrosis transmembrane conductance regulator (CFTR) function and the abnormal mucus seen in various organ systems remain unclear. We used cultured gallbladder epithelial cells (GBEC) from wild-type and Cftr((-/-)) mice to investigate mucin gene and protein expression, kinetics of postexocytotic mucous granule content expansion, and biochemical and ionic compositions of secreted mucins. Muc1, Muc3, Muc4, Muc5ac, and Muc5b mRNA levels were significantly lower in Cftr((-/-)) GBEC compared with wild-type cells, whereas Muc2 mRNA levels were higher in Cftr((-/-)) cells. Quantitative immunoblotting demonstrated a trend toward lower MUC1, MUC2, MUC3, MUC5AC, and MUC5B mucin levels in Cftr((-/-)) cells compared with cells from wild-type mice. In contrast, the levels of secreted MUC1, MUC3, MUC5B, and MUC6 mucins were significantly higher from Cftr((-/-)) cells; a trend toward higher levels of secreted MUC2 and MUC5AC was also noted from Cftr((-/-)) cells. Cftr((-/-)) cells demonstrated slower postexocytotic mucous granule content expansion. Calcium concentration was significantly elevated in the mucous gel secreted by Cftr((-/-)) cells compared with wild-type cells. Secreted mucins from Cftr((-/-)) cells contained higher sulfate concentrations. Thus absence of CFTR is associated with pleiotropic effects on mucins in murine GBEC.
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Affiliation(s)
- Rahul Kuver
- Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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18
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Abstract
Colonic mucus is a key element of colonic barrier as it is located at the frontier between luminal microflora and colonic mucosa itself. Colonic mucus is mainly composed of high molecular weight glycoproteins called mucins that can be either secreted or membrane-linked. The expression of various colonic mucins is altered in colorectal cancers or inflammations. The aim of this review is to highlight the crucial role played by colonic mucins in the maintenance of colonic barrier integrity, both because they are part of the protective mucus layer, and because they individually exert specific functions involved in epithelial barrier, like cell growth and differentiation, immunomodulation, signal transduction or cell adhesion.
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Affiliation(s)
- Estelle Gaudier
- UMR, Physiologie des Adaptations Nutrionnelles, Centre de recherche en Nutrition Humaine, INRA, 44316 Nantes
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Malmberg EK, Noaksson KA, Phillipson M, Johansson MEV, Hinojosa-Kurtzberg M, Holm L, Gendler SJ, Hansson GC. Increased levels of mucins in the cystic fibrosis mouse small intestine, and modulator effects of the Muc1 mucin expression. Am J Physiol Gastrointest Liver Physiol 2006; 291:G203-10. [PMID: 16500918 DOI: 10.1152/ajpgi.00491.2005] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mouse model (Cftr(tm1UNC)/Cftr(tm1UNC)) for cystic fibrosis (CF) shows mucus accumulation and increased Muc1 mucin mRNA levels due to altered splicing (Hinojosa-Kurtzberg AM, Johansson MEV, Madsen CS, Hansson GC, and Gendler SJ. Am J Physiol Gastrointest Liver Physiol 284: G853-G862, 2003). However, it is not known whether Muc1 is a major mucin contributing to the increased mucus and why CF/Muc1-/- mice show lower mucus accumulation. To address this, we have purified mucins from the small intestine of CF mice using guanidinium chloride extraction, ultracentrifugation, and gel filtration and analyzed them by slot blot, gel electrophoresis, proteomics, and immunoblotting. Normal and CF mice with wild-type (WT) Muc1 or Muc1-/- or that are transgenic for human MUC1 (MUC1.Tg, on a Muc1-/- background) were analyzed. The total amount of mucins, both soluble and insoluble in guanidinium chloride, increased up to 10-fold in the CF mice compared with non-CF animals, whereas the CF mice lacking Muc1 showed intermediate levels between the CF and non-CF mice. However, the levels of Muc3 (orthologue of human MUC17) were increased in the CF/Muc1-/- mice compared with the CF/MUC1.Tg animals. The amount of MUC1 mucin was increased several magnitudes in the CF mice, but MUC1 did still not appear to be a major mucin. The amount of insoluble mucus of the large intestine was also increased in the CF mice, an effect that was partially restored in the CF/Muc1-/- mice. The thickness of the firmly adherent mucus layer of colon in the Muc1-/- mice was significantly lower than that of WT mice. The results suggest that MUC1 is not a major component in the accumulated mucus of CF mice and that MUC1 can influence the amount of other mucins in a still unknown way.
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Affiliation(s)
- Emily K Malmberg
- Department of Medical Biochemistry, Göteborg University, Gothenburg, Sweden
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20
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Singh AP, Chauhan SC, Andrianifahanana M, Moniaux N, Meza JL, Copin MC, van Seuningen I, Hollingsworth MA, Aubert JP, Batra SK. MUC4 expression is regulated by cystic fibrosis transmembrane conductance regulator in pancreatic adenocarcinoma cells via transcriptional and post-translational mechanisms. Oncogene 2006; 26:30-41. [PMID: 16799633 DOI: 10.1038/sj.onc.1209764] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
MUC4 mucin is a high molecular weight transmembrane glycoprotein that plays important roles in tumour biology. It is aberrantly expressed in pancreatic adenocarcinoma, while not being detectable in the normal pancreas. Previous studies have demonstrated that the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel that is defective in CF, is implicated in multiple cellular functions, including gene regulation. In the present study, using a CFTR-defective pancreatic cancer cell line and its derived subline expressing functional CFTR, we report that MUC4 expression is negatively regulated by CFTR. Short-interfering RNA (siRNA)-mediated silencing of CFTR also leads to an increased expression of MUC4. Additionally, our results suggest that CFTR-mediated regulation of MUC4 is cell density-dependent and is achieved by transcriptional and posttranslational mechanisms. Moreover, in a panel of pancreatic cancer cell lines and normal pancreas, we observed that CFTR was downregulated in pancreatic cancer cells and negatively correlated with MUC4 in most cases. An aberrant expression of MUC4 was also detected in the CF pancreas. Downregulation of CFTR in pancreatic adenocarcinoma and its inverse association with the tumour-linked mucin, MUC4, indicate novel function(s) of CFTR in pancreatic tumour biology and suggest the implication of new signalling pathway(s) in MUC4 regulation.
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Affiliation(s)
- A P Singh
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198-5870, USA
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Imbert Y, Darling DS, Jumblatt MM, Foulks GN, Couzin EG, Steele PS, Young WW. MUC1 splice variants in human ocular surface tissues: possible differences between dry eye patients and normal controls. Exp Eye Res 2006; 83:493-501. [PMID: 16631167 DOI: 10.1016/j.exer.2006.01.031] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 01/16/2006] [Accepted: 01/23/2006] [Indexed: 11/28/2022]
Abstract
Mucins are highly glycosylated proteins that are vital to the maintenance of healthy epithelial surfaces including the ocular surface. Mucins act as lubricants, protectants, and mediators of signal transduction. The majority of the O-glycosylation sites on the transmembrane mucin MUC1 are found in a highly polymorphic core region containing a variable number of tandem repeats (VNTR). MUC1 alleles can be divided into size classes that contain small (30-45) or large (60-90) numbers of repeats. Although at least 12 splice variants of MUC1 have been found in other tissues, no splice variants have been reported in human ocular surface tissues. We have used RT-PCR to identify MUC1 splice variants that were then confirmed by sequencing. We here report the presence in some samples of human cornea, conjunctiva, and lacrimal gland of MUC1/B which features canonical splicing between exons 1 and 2 and MUC1/A, a transcript that retains 27bp from the 3' end of intron 1 and is predicted to add 9 amino acids to the MUC1 sequence upstream of the tandem repeat region. Cornea and conjunctiva both contain the MUC1/SEC splice variant that lacks the transmembrane domain and, therefore, results in a soluble, secreted form of MUC1. Cornea and conjunctiva also contain MUC1/Y and MUC1/Z(X) variants that lack the tandem repeat region. Cornea, conjunctiva, and lacrimal gland also contain a previously undescribed MUC1 variant transcript, termed MUC1/YI, that retains 99bp from the 5' end and 27bp from the 3' end of the first intron, resulting in a frame shift and premature stop codon. This transcript is predicted to produce a novel 27 amino acid peptide after signal peptidase cleavage. Analysis of brush cytology samples revealed that the percentage of dry eye patients expressing the MUC1/A variant in the conjunctival epithelium is lower than in normal control donors. Western blotting confirmed that MUC1/A is associated with alleles containing the large size class of tandem repeats. Therefore, we propose that one factor in susceptibility to dry eye disease may be the lengths of the MUC1 VNTR in conjunctival epithelium based on the rationale that longer VNTR provide better lubrication and greater protection of the ocular surface against inflammation.
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Affiliation(s)
- Yoannis Imbert
- Department of Molecular, Cellular & Craniofacial Biology, School of Dentistry, University of Louisville, 501 S. Preston St., Louisville, KY 40292, USA
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De Lisle RC, Roach EA, Norkina O. Eradication of small intestinal bacterial overgrowth in the cystic fibrosis mouse reduces mucus accumulation. J Pediatr Gastroenterol Nutr 2006; 42:46-52. [PMID: 16385253 DOI: 10.1097/01.mpg.0000189322.34582.3e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES Mucus accumulation in cystic fibrosis (CF) is involved in blockage of the distal small intestine. Because expression of mucin genes and mucus secretion can be increased by infection and previous work indicated that small intestinal bacterial overgrowth occurs in CF, we tested whether reduction of bacterial load by antibiotic treatment would reduce mucin gene expression and mucus accumulation in the CF mouse small intestine. METHODS CF transmembrane conductance regulator null (cftr (tm1UNC)) and wild type littermates were treated with ciprofloxacin and metronidazole for 3 weeks. Muc2 and Muc3 gene expression were measured by quantitative reverse-transcriptase polymerase chain reaction. Periodic acid Schiff (PAS) staining and morphometry were used to measure the size of mucus droplets within goblet cells and dilation of the intestinal crypt lumen, as estimates of mucus secretion and accumulation. RESULTS Antibiotic treatment did not significantly affect Muc2 and Muc3 gene expression in CF mice. In untreated CF mice, the crypt lumen was almost sevenfold wider than wild type. Antibiotic treatment of CF mice reduced the intensity of PAS crypt lumen staining, and the lumen width was decreased by approximately 25%. The area occupied by PAS-positive material in goblet cells was significantly greater in tissues from antibiotic treated mice. CONCLUSIONS Eradication of bacterial overgrowth in CF mice significantly decreased mucus secretion and accumulation in intestinal crypts without an effect on mucin gene expression. It is proposed that bacterial overgrowth stimulates mucus secretion, which contributes to its accumulation in the small intestine. Control of bacterial overgrowth is expected to reduce mucus accumulation and may improve intestinal function and overall health in CF.
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Affiliation(s)
- Robert C De Lisle
- Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas 66160, USA.
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Abstract
Cystic fibrosis (CF) is a progressive disease in which the lung is perceived to be normal at birth and is injured by recurrent infection. However, there is increasing evidence that the lung is functionally and structurally abnormal prior to the appearance of clinical infection. The cystic fibrosis transmembrane regulator (CFTR) is highly expressed in fetal tissues, and this review examines the role of CFTR in regulatory cascades during lung development. Early changes in the CF lung are examined from a perspective of disrupted fetal development, explaining a number of paradoxes seen with the disease.
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