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Abstract
The discovery of an inner mucus layer normally impervious to bacteria has changed our way of understanding the interaction between commensal bacteria and the host epithelial cells. This inner colon mucus layer is rapidly renewed and converted into the outer mucus layer by host controlled endogenous proteolytic processing. The mucus characteristics esteem from the properties of the main protein component of these layers, the MUC2 mucin. This forms an enormously large net-like structure that builds the laminated inner mucus layer that largely acts as a size exclusion filter excluding bacteria. In the absence of MUC2 mucin, there is no inner mucus layer and bacteria reach the epithelial cell surface, penetrate the crypts and are also found inside epithelial cells, something that leads to severe inflammation. Other mouse models that spontaneously develop colitis due to different defects, like an absent ion channel (Nhe3) or immunological mediators (Tlr5, IL-10), all also have a defective inner colon mucus layer. Human patients with active ulcerative colitis have this layer penetrable to bacteria and beads the size of bacteria. Some of the ulcerative colitis patients in remission have a normal mucus layer whereas others have a penetrable inner mucus layer. Together, this suggests that the inner mucus layer and its integrity is important for the protection of the colon epithelium and inhibiting activation of the immune system as in ulcerative colitis.
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Affiliation(s)
- Malin E V Johansson
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
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52
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Xu H, Zhang B, Li J, Wang C, Chen H, Ghishan FK. Impaired mucin synthesis and bicarbonate secretion in the colon of NHE8 knockout mice. Am J Physiol Gastrointest Liver Physiol 2012; 303:G335-43. [PMID: 22575219 PMCID: PMC3774248 DOI: 10.1152/ajpgi.00146.2012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Sodium/hydrogen exchanger 8 (NHE8), the newest member of the SLC9 family, is expressed at the apical membrane of the epithelial cells in the intestine and the kidney. Although NHE8 has been shown to be an important player for intestinal sodium absorption early in development, its physiological role in the intestine remains unclear. Here, we successfully created a NHE8 knockout (NHE8(-/-)) mouse model to study the function of this transporter in the intestinal tract. Embryonic stem cells containing interrupted NHE8 gene were injected into mouse blastocyst to produce NHE8(+/-) chimeras. NHE8(-/-) mice showed no lethality during embryonic and fetal development. These mice had normal serum sodium levels and no signs of diarrhea. Apically expressed NHE2 and NHE3 were increased in the small intestine of the NHE8(-/-) mice in compensation. The number of goblet cells and mucin (MUC)-positive cells in the colon was reduced in NHE8(-/-) mice along with mucosal pH, MUC2 expression as well as downregulated in adenoma (DRA) expression. Therefore, the role of NHE8 in the intestine involves both sodium absorption and bicarbonate secretion.
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Affiliation(s)
- Hua Xu
- University of Arizona, Tucson, Arizona
| | - Bo Zhang
- University of Arizona, Tucson, Arizona
| | - Jing Li
- University of Arizona, Tucson, Arizona
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53
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Arshad N, Visweswariah SS. The multiple and enigmatic roles of guanylyl cyclase C in intestinal homeostasis. FEBS Lett 2012; 586:2835-40. [PMID: 22819815 DOI: 10.1016/j.febslet.2012.07.028] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 07/07/2012] [Accepted: 07/09/2012] [Indexed: 12/15/2022]
Abstract
Guanylyl cyclase C (GC-C) is predominantly expressed in intestinal epithelial cells and serves as the receptor for the gastrointestinal hormones guanylin and uroguanylin, and the heat-stable enterotoxin, the causative agent for Travellers' Diarrhea. Activation of GC-C results in an increase in intracellular levels of cGMP, which can regulate fluid and ion secretion, colon cell proliferation, and the gut immune system. This review highlights recent findings arising from studies in the GC-C knock-out mouse, along with enigmatic results obtained from the first descriptions of human disease caused by mutations in the GC-C gene. We provide some insight into these new findings and comment on areas of future study, which may enhance our knowledge of this evolutionarily conserved receptor and signaling system.
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Affiliation(s)
- Najla Arshad
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
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54
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Fiskerstrand T, Arshad N, Haukanes BI, Tronstad RR, Pham KDC, Johansson S, Håvik B, Tønder SL, Levy SE, Brackman D, Boman H, Biswas KH, Apold J, Hovdenak N, Visweswariah SS, Knappskog PM. Familial diarrhea syndrome caused by an activating GUCY2C mutation. N Engl J Med 2012; 366:1586-95. [PMID: 22436048 DOI: 10.1056/nejmoa1110132] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Familial diarrhea disorders are, in most cases, severe and caused by recessive mutations. We describe the cause of a novel dominant disease in 32 members of a Norwegian family. The affected members have chronic diarrhea that is of early onset, is relatively mild, and is associated with increased susceptibility to inflammatory bowel disease, small-bowel obstruction, and esophagitis. METHODS We used linkage analysis, based on arrays with single-nucleotide polymorphisms, to identify a candidate region on chromosome 12 and then sequenced GUCY2C, encoding guanylate cyclase C (GC-C), an intestinal receptor for bacterial heat-stable enterotoxins. We performed exome sequencing of the entire candidate region from three affected family members, to exclude the possibility that mutations in genes other than GUCY2C could cause or contribute to susceptibility to the disease. We carried out functional studies of mutant GC-C using HEK293T cells. RESULTS We identified a heterozygous missense mutation (c.2519G→T) in GUCY2C in all affected family members and observed no other rare variants in the exons of genes in the candidate region. Exposure of the mutant receptor to its ligands resulted in markedly increased production of cyclic guanosine monophosphate (cGMP). This may cause hyperactivation of the cystic fibrosis transmembrane regulator (CFTR), leading to increased chloride and water secretion from the enterocytes, and may thus explain the chronic diarrhea in the affected family members. CONCLUSIONS Increased GC-C signaling disturbs normal bowel function and appears to have a proinflammatory effect, either through increased chloride secretion or additional effects of elevated cellular cGMP. Further investigation of the relevance of genetic variants affecting the GC-C-CFTR pathway to conditions such as Crohn's disease is warranted. (Funded by Helse Vest [Western Norway Regional Health Authority] and the Department of Science and Technology, Government of India.).
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Affiliation(s)
- Torunn Fiskerstrand
- Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, 5021 Bergen, Norway.
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55
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Larmonier CB, Laubitz D, Thurston RD, Bucknam AL, Hill FM, Midura-Kiela M, Ramalingam R, Kiela PR, Ghishan FK. NHE3 modulates the severity of colitis in IL-10-deficient mice. Am J Physiol Gastrointest Liver Physiol 2011; 300:G998-G1009. [PMID: 21415416 PMCID: PMC3119112 DOI: 10.1152/ajpgi.00073.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
NHE3, the major intestinal Na(+)/H(+) exchanger, was shown to be downregulated and/or inhibited in patients with inflammatory bowel disease (IBD), a phenomenon believed to contribute to inflammation-associated diarrhea. NHE3(-/-) mice spontaneously develop colitis and demonstrate high susceptibility to dextran sulfate-induced mucosal injury. We investigated the effects of NHE3 deficiency on the development of chronic colitis in an IL-10 knockout (KO) mouse model of Crohn's disease. NHE3(-/-) mice were first backcrossed to 129/SvEv mice for >10 generations, with no apparent changes in their survival or phenotype. These mice were crossed with IL-10(-/-) mice on the same genetic background, and the phenotypes of 10-wk-old wild-type (WT), IL-10(-/-), NHE3(-/-), and IL-10(-/-)/NHE3(-/-) (double-KO) mice were studied. Histological and immunohistochemical examination of the colon established important architectural alterations, including increased neutrophilic and mononuclear cell infiltration in double- compared with single-KO mice. Double-KO mice demonstrated increased colonic expression of neutrophil collagenase matrix metalloproteinase-8 and the chemokines macrophage inflammatory protein-2, CXCL1, CXCL10, and CXCL11. Colonic IFNγ, IL-17, and IL-12/23 p40 protein secretion was significantly increased in double- compared with single-KO mice. IL-10(-/-)/NHE3(-/-) mouse colonic epithelium exhibited increased hallmarks of apoptosis, including a significantly increased number of cleaved caspase-3-positive surface epithelial cells. These results highlight the importance of NHE3 in the maintenance of intestinal barrier integrity and in modulating the inflammatory process in IL-10-deficient mice. Chronic NHE3 inhibition or underexpression observed in IBD may therefore contribute to the pathogenesis of IBD by influencing the extent of the epithelial barrier defect and affect the ultimate degree of inflammation.
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Affiliation(s)
- C. B. Larmonier
- 1Department of Pediatrics, Steele Children's Research Center,
| | - D. Laubitz
- 1Department of Pediatrics, Steele Children's Research Center, ,3Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - R. D. Thurston
- 1Department of Pediatrics, Steele Children's Research Center,
| | - A. L. Bucknam
- 2Department of Immunobiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - F. M. Hill
- 1Department of Pediatrics, Steele Children's Research Center,
| | - M. Midura-Kiela
- 1Department of Pediatrics, Steele Children's Research Center,
| | - R. Ramalingam
- 1Department of Pediatrics, Steele Children's Research Center,
| | - P. R. Kiela
- 1Department of Pediatrics, Steele Children's Research Center, ,2Department of Immunobiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - F. K. Ghishan
- 1Department of Pediatrics, Steele Children's Research Center,
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56
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Coordinate activation of inflammatory gene networks, alveolar destruction and neonatal death in AKNA deficient mice. Cell Res 2011; 21:1564-77. [PMID: 21606955 DOI: 10.1038/cr.2011.84] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Gene expression can be regulated by chromatin modifiers, transcription factors and proteins that modulate DNA architecture. Among the latter, AT-hook transcription factors have emerged as multifaceted regulators that can activate or repress broad A/T-rich gene networks. Thus, alterations of AT-hook genes could affect the transcription of multiple genes causing global cell dysfunction. Here we report that targeted deletions of mouse AKNA, a hypothetical AT-hook-like transcription factor, sensitize mice to pathogen-induced inflammation and cause sudden neonatal death. Compared with wild-type littermates, AKNA KO mice appeared weak, failed to thrive and most died by postnatal day 10. Systemic inflammation, predominantly in the lungs, was accompanied by enhanced leukocyte infiltration and alveolar destruction. Cytologic, immunohistochemical and molecular analyses revealed CD11b(+)Gr1(+) neutrophils as major tissue infiltrators, neutrophilic granule protein, cathelin-related antimicrobial peptide and S100A8/9 as neutrophil-specific chemoattracting factors, interleukin-1β and interferon-γ as proinflammatory mediators, and matrix metalloprotease 9 as a plausible proteolytic trigger of alveolar damage. AKNA KO bone marrow transplants in wild-type recipients reproduced the severe pathogen-induced reactions and confirmed the involvement of neutrophils in acute inflammation. Moreover, promoter/reporter experiments showed that AKNA could act as a gene repressor. Our results support the concept of coordinated pathway-specific gene regulation functions modulating the intensity of inflammatory responses, reveal neutrophils as prominent mediators of acute inflammation and suggest mechanisms underlying the triggering of acute and potentially fatal immune reactions.
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57
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Steinbrecher KA, Harmel-Laws E, Garin-Laflam MP, Mann EA, Bezerra LD, Hogan SP, Cohen MB. Murine guanylate cyclase C regulates colonic injury and inflammation. THE JOURNAL OF IMMUNOLOGY 2011; 186:7205-14. [PMID: 21555532 DOI: 10.4049/jimmunol.1002469] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Guanylate cyclase C (GUCY2C or GC-C) and its ligands, guanylin (GUCA2A or Gn) and uroguanylin (GUCA2B or Ugn), are expressed in intestinal epithelial cells and regulate ion secretion, intestinal barrier function, and epithelial monolayer homeostasis via cGMP-dependent signaling pathways. The aim of this study was to determine whether GC-C and its ligands direct the course of intestinal inflammation. In this article, we show that dextran sodium sulfate (DSS)-induced clinical disease and histological damage to the colonic mucosa were significantly less severe in GC-C(-/-) mice and moderately reduced in Gn(-/-) animals. Relative to wild-type controls, GC-C(-/-) and Gn(-/-) mice had reduced apoptosis and increased proliferation of intestinal epithelial cells during DSS colitis. Basal and DSS-induced production of resistin-like molecule β (RELMβ) was substantially diminished in GC-C(-/-) mice. RELMβ is thought to stimulate cytokine production in macrophages in this disease model and, consistent with this, TNF-α and IFN-γ production was minimal in GC-C(-/-) animals. RELMβ and cytokine levels were similar to wild-type in Gn(-/-) mice, however. Colonic instillation of recombinant RELMβ by enema into GC-C(-/-) mice restores sensitivity to DSS-mediated mucosal injury. These findings demonstrate a novel role for GC-C signaling in facilitating mucosal wounding and inflammation, and further suggest that this may be mediated, in part, through control of RELMβ production.
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Affiliation(s)
- Kris A Steinbrecher
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA.
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58
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Stappenbeck TS, Rioux JD, Mizoguchi A, Saitoh T, Huett A, Darfeuille-Michaud A, Wileman T, Mizushima N, Carding S, Akira S, Parkes M, Xavier RJ. Crohn disease: a current perspective on genetics, autophagy and immunity. Autophagy 2011; 7:355-74. [PMID: 20729636 PMCID: PMC3842289 DOI: 10.4161/auto.7.2.13074] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 04/17/2010] [Indexed: 12/13/2022] Open
Abstract
Crohn disease (CD) is a chronic and debilitating inflammatory condition of the gastrointestinal tract. Prevalence in Western populations is 100-150/100,000 and somewhat higher in Ashkenazi Jews. Peak incidence is in early adult life, although any age can be affected and a majority of affected individuals progress to relapsing and chronic disease. Medical treatments rely significantly on empirical corticosteroid therapy and immunosuppression, and intestinal resectional surgery is frequently required. Thus, 80% of patients with CD come to surgery for refractory disease or complications. It is hoped that an improved understanding of pathogenic mechanisms, for example by studying the genetic basis of CD and other forms of inflammatory bowel diseases (IBD), will lead to improved therapies and possibly preventative strategies in individuals identified as being at risk.
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Affiliation(s)
- Thaddeus S. Stappenbeck
- Departments of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO USA
| | - John D. Rioux
- Université de Montréal; Montréal, Québec Canada
- Montreal Heart Institute; Montréal, Québec Canada
| | - Atsushi Mizoguchi
- Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital and Harvard Medical School; Boston, MA USA
- Department of Pathology; Massachusetts General Hospital and Harvard Medical School; Boston, MA USA
| | - Tatsuya Saitoh
- Laboratory of Host Defense; WPI Immunology Frontier Research Center; Osaka University; Suita, Osaka Japan
- Department of Host Defense Osaka; Japan
| | - Alan Huett
- Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital and Harvard Medical School; Boston, MA USA
| | | | - Tom Wileman
- Infection and Immunity; School of Medicine; Faculty of Health; University of East Anglia; East Anglia, Norfolk UK
| | - Noboru Mizushima
- Department of Physiology and Cell Biology at Tokyo Medical and Dental University; Bunkyo-ku, Tokyo Japan
| | | | - Shizuo Akira
- Laboratory of Host Defense; WPI Immunology Frontier Research Center; Osaka University; Suita, Osaka Japan
- Department of Host Defense Osaka; Japan
| | - Miles Parkes
- IBD Research Group; Addenbrooke’s Hospital; University of Cambridge; Cambridge UK
| | - Ramnik J. Xavier
- Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital and Harvard Medical School; Boston, MA USA
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59
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Farkas K, Yeruva S, Rakonczay Z, Ludolph L, Molnár T, Nagy F, Szepes Z, Schnúr A, Wittmann T, Hubricht J, Riederer B, Venglovecz V, Lázár G, Király M, Zsembery Á, Varga G, Seidler U, Hegyi P. New therapeutic targets in ulcerative colitis: the importance of ion transporters in the human colon. Inflamm Bowel Dis 2011; 17:884-98. [PMID: 20722063 DOI: 10.1002/ibd.21432] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 06/22/2010] [Indexed: 12/12/2022]
Abstract
BACKGROUND The absorption of water and ions (especially Na(+) and Cl(-)) is an important function of colonic epithelial cells in both physiological and pathophysiological conditions. Despite the comprehensive animal studies, there are only scarce available data on the ion transporter activities of the normal and inflamed human colon. METHODS In this study, 128 healthy controls and 69 patients suffering from ulcerative colitis (UC) were involved. We investigated the expressional and functional characteristics of the Na(+)/H(+) exchangers (NHE) 1-3, the epithelial sodium channel (ENaC), and the SLC26A3 Cl(-)/HCO 3- exchanger downregulated in adenoma (DRA) in primary colonic crypts isolated from human biopsy and surgical samples using microfluorometry, patch clamp, and real-time reverse-transcription polymerase chain reaction (RT-PCR) techniques. RESULTS Data collected from colonic crypts showed that the activities of electroneutral (via NHE3) and the electrogenic Na(+) absorption (via ENaC) are in inverse ratio to each other in the proximal and distal colon. We found no significant differences in the activity of NHE2 in different segments of the colon. Surface cell Cl(-)/HCO 3- exchange is more active in the distal part of the colon. Importantly, both sodium and chloride absorptions are damaged in UC, whereas NHE1, which has been shown to promote immune response, is upregulated by 6-fold. CONCLUSIONS These results open up new therapeutic targets in UC.
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Affiliation(s)
- Klaudia Farkas
- First Department of Medicine, University of Szeged, Szeged, Hungary
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60
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Stappenbeck TS, Rioux JD, Mizoguchi A, Saitoh T, Huett A, Darfeuille-Michaud A, Wileman T, Mizushima N, Carding S, Akira S, Parkes M, Xavier RJ. Crohn disease: a current perspective on genetics, autophagy and immunity. Autophagy 2011. [PMID: 20729636 DOI: 10.4161/auto.7.4.13074] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Crohn disease (CD) is a chronic and debilitating inflammatory condition of the gastrointestinal tract. Prevalence in Western populations is 100-150/100,000 and somewhat higher in Ashkenazi Jews. Peak incidence is in early adult life, although any age can be affected and a majority of affected individuals progress to relapsing and chronic disease. Medical treatments rely significantly on empirical corticosteroid therapy and immunosuppression, and intestinal resectional surgery is frequently required. Thus, 80% of patients with CD come to surgery for refractory disease or complications. It is hoped that an improved understanding of pathogenic mechanisms, for example by studying the genetic basis of CD and other forms of inflammatory bowel diseases (IBD), will lead to improved therapies and possibly preventative strategies in individuals identified as being at risk.
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Affiliation(s)
- Thaddeus S Stappenbeck
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.
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61
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Dorfman R, Taylor C, Lin F, Sun L, Sandford A, Paré P, Berthiaume Y, Corey M, Durie P, Zielenski J. Modulatory effect of the SLC9A3 gene on susceptibility to infections and pulmonary function in children with cystic fibrosis. Pediatr Pulmonol 2011; 46:385-92. [PMID: 20967843 DOI: 10.1002/ppul.21372] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 08/10/2010] [Accepted: 09/04/2010] [Indexed: 11/10/2022]
Abstract
In cystic fibrosis (CF), CFTR dysfunction leads to salt and water imbalance across airway epithelia, depleted surface liquid layer, and impaired mucociliary clearance. This provides optimal conditions for chronic bacterial infections leading to excessive inflammation and progressive obstructive lung disease. We hypothesized that other epithelial channels affecting salt balance across the airways may play a role in the susceptibility to bacterial infections and modulate severity of CF lung disease. The SLC9A3 gene encoding a Na(+) /H(+) exchanger was demonstrated to be a modifier intestinal disease in a murine model of CF. We examined the potential role of SLC9A3 as a modifier of CF lung disease severity. We analyzed 11 SLC9A3 gene variants for association with age of first Pseudomonas aeruginosa infection and lung function in children with CF. The T allele of an intronic variant in the SLC9A3 gene (rs4957061) was significantly (P = 0.02) associated with earlier acquisition of Pseudomonas infection in a cohort of 1,004 pediatric patients. Analysis of lung function in a subset of these patients (752) revealed that patients homozygous for the T allele had substantially reduced lung function and accelerated rate of decline. Although the functional basis for the modulatory effects of this SLC9A3 variant on CF lung disease remains to be elucidated, altered function of the Na(+) /H(+) exchanger may further deplete the airway liquid surface, thereby enhancing susceptibility to Pseudomonas infections and worsening the severity of lung disease.
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Affiliation(s)
- Ruslan Dorfman
- Program in Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada
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62
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Al-Shamali A, Khan I. Expression of Na-H exchanger-8 isoform is suppressed in experimental colitis in adult rat: lack of reversibility by dexamethasone. Scand J Gastroenterol 2011; 46:20-9. [PMID: 20950207 DOI: 10.3109/00365521.2010.521890] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVES Mechanism of the apical transporter Na-H exchanger-8 (NHE-8) regulation was investigated by examining the effects of anti-inflammatory dexamethasone in experimental colitis. In addition, its localization was investigated in the lipid rich membrane domain called membrane rafts. MATERIAL AND METHODS Colitis was induced by trinitrobenzene sulfonic acid (TNBS) and colon segments were removed from 5 day post-TNBS and used to estimate the levels of NHE-8 protein and mRNA using ECL western blot analysis and a competitive RT-PCR method. Myeloperoxidase activity, malondialdehyde levels and histologic changes were evaluated. RESULTS NHE-8 protein level was decreased in inflamed colon and was not reversed by dexamethasone. However, mRNA levels remained unchanged in inflamed colon. The levels of NHE-8 protein and mRNA were not significantly different in non-colitic control as compared to dexamethasone treated non-colitis. Elevation of myeloperoxidase activity, malondialdehyde and infiltration of inflammatory cells in inflamed colon were suppressed by dexamethasone treatment of colitis significantly. Furthermore, NHE-8 protein was not detected in the detergent resistant membrane (DRM) or lipid rafts, but was present in the detergent sensitive membrane (DRS) fractions. Actin showed its partition similar to NHE-8. On the contrary, NHE-3 was present in both DRM and DRS fractions. Flotillin-1 and caveolin were enriched in the fractions designated as lipid rafts. CONCLUSIONS These findings demonstrate the suppression of NHE-8 protein in inflamed adult rat colon, which seems to be regulated post-transcriptionally. Furthermore, the absence of NHE-8 in lipid rafts suggests its regulation independent of cAMP or recycling through endocytosis unlike NHE-3 isoform.
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Affiliation(s)
- Amna Al-Shamali
- Department of Biochemistry, Faculty of Medicine, Kuwait University, Kuwait
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63
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Westbrook AM, Szakmary A, Schiestl RH. Mechanisms of intestinal inflammation and development of associated cancers: lessons learned from mouse models. Mutat Res 2010; 705:40-59. [PMID: 20298806 PMCID: PMC2878867 DOI: 10.1016/j.mrrev.2010.03.001] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 02/21/2010] [Accepted: 03/08/2010] [Indexed: 12/15/2022]
Abstract
Chronic inflammation is strongly associated with approximately 1/5th of all human cancers. Arising from combinations of factors such as environmental exposures, diet, inherited gene polymorphisms, infections, or from dysfunctions of the immune response, chronic inflammation begins as an attempt of the body to remove injurious stimuli; however, over time, this results in continuous tissue destruction and promotion and maintenance of carcinogenesis. Here we focus on intestinal inflammation and its associated cancers, a group of diseases on the rise and affecting millions of people worldwide. Intestinal inflammation can be widely grouped into inflammatory bowel diseases (ulcerative colitis and Crohn's disease) and celiac disease. Long-standing intestinal inflammation is associated with colorectal cancer and small-bowel adenocarcinoma, as well as extraintestinal manifestations, including lymphomas and autoimmune diseases. This article highlights potential mechanisms of pathogenesis in inflammatory bowel diseases and celiac disease, as well as those involved in the progression to associated cancers, most of which have been identified from studies utilizing mouse models of intestinal inflammation. Mouse models of intestinal inflammation can be widely grouped into chemically induced models; genetic models, which make up the bulk of the studied models; adoptive transfer models; and spontaneous models. Studies in these models have lead to the understanding that persistent antigen exposure in the intestinal lumen, in combination with loss of epithelial barrier function, and dysfunction and dysregulation of the innate and adaptive immune responses lead to chronic intestinal inflammation. Transcriptional changes in this environment leading to cell survival, hyperplasia, promotion of angiogenesis, persistent DNA damage, or insufficient repair of DNA damage due to an excess of proinflammatory mediators are then thought to lead to sustained malignant transformation. With regards to extraintestinal manifestations such as lymphoma, however, more suitable models are required to further investigate the complex and heterogeneous mechanisms that may be at play.
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Affiliation(s)
- Aya M. Westbrook
- Molecular Toxicology Interdepartmental Program, UCLA School of Medicine and School of Public Health, University of California at Los Angeles, Los Angeles, CA 90095
- Department of Pathology and Lab Medicine, UCLA School of Medicine and School of Public Health, University of California at Los Angeles, Los Angeles, CA 90095
| | - Akos Szakmary
- Institute for Cancer Research, Medical University of Vienna, Austria
| | - Robert H. Schiestl
- Molecular Toxicology Interdepartmental Program, UCLA School of Medicine and School of Public Health, University of California at Los Angeles, Los Angeles, CA 90095
- Department of Pathology and Lab Medicine, UCLA School of Medicine and School of Public Health, University of California at Los Angeles, Los Angeles, CA 90095
- Institute for Cancer Research, Medical University of Vienna, Austria
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Alex P, Ye M, Zachos NC, Sipes J, Nguyen T, Suhodrev M, Gonzales L, Arora Z, Zhang T, Centola M, Guggino SE, Li X. Clcn5 knockout mice exhibit novel immunomodulatory effects and are more susceptible to dextran sulfate sodium-induced colitis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2010; 184:3988-96. [PMID: 20181886 PMCID: PMC4460988 DOI: 10.4049/jimmunol.0901657] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Although the intracellular Cl(-)/H(+) exchanger Clc-5 is expressed in apical intestinal endocytic compartments, its pathophysiological role in the gastrointestinal tract is unknown. In light of recent findings that CLC-5 is downregulated in active ulcerative colitis (UC), we tested the hypothesis that loss of CLC-5 modulates the immune response, thereby inducing susceptibility to UC. Acute dextran sulfate sodium (DSS) colitis was induced in Clcn5 knockout (KO) and wild-type (WT) mice. Colitis, monitored by disease activity index, histological activity index, and myeloperoxidase activity were significantly elevated in DSS-induced Clcn5 KO mice compared with those in WT mice. Comprehensive serum multiplex cytokine profiling demonstrated a heightened Th1-Th17 profile (increased TNF-alpha, IL-6, and IL-17) in DSS-induced Clcn5 KO mice compared with that in WT DSS colitis mice. Interestingly, Clcn5 KO mice maintained on a high vitamin D diet attenuated DSS-induced colitis. Immunofluorescence and Western blot analyses of colonic mucosa validated the systemic cytokine patterns and further revealed enhanced activation of the NF-kappaB pathway in DSS-induced Clcn5 KO mice compared with those in WT mice. Intriguingly, high baseline levels of IL-6 and phospho-IkappaB were observed in Clcn5 KO mice, suggesting a novel immunopathogenic role for the functional defects that result from the loss of Clc-5. Our studies demonstrate that the loss of Clc-5 1) exhibits IL-6-mediated immunopathogenesis, 2) significantly exacerbated DSS-induced colitis, which is influenced by dietary factors, including vitamin D, and 3) portrays distinct NF-kappaB-modulated Th1-Th17 immune dysregulation, implying a role for CLC-5 in the immunopathogenesis of UC.
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Affiliation(s)
- Philip Alex
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Mei Ye
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Department of Internal Medicine and Geriatrics, Zhongnan Hospital, Wuhan University, Wuhan, China
| | - Nicholas C. Zachos
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Jennifer Sipes
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Thuan Nguyen
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Maxim Suhodrev
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Liberty Gonzales
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Zubin Arora
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Ting Zhang
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Michael Centola
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Sandra E. Guggino
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Xuhang Li
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
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Mechanisms of the regulation of the intestinal Na+/H+ exchanger NHE3. J Biomed Biotechnol 2010; 2010:238080. [PMID: 20011065 PMCID: PMC2789519 DOI: 10.1155/2010/238080] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 09/11/2009] [Indexed: 01/25/2023] Open
Abstract
A major of Na+ absorptive process in the proximal part of intestine and kidney is electroneutral exchange of Na+ and H+ by Na+/H+ exchanger type 3 (NHE3). During the past decade, significant advance has been achieved in the mechanisms of NHE3 regulation. A bulk of the current knowledge on Na+/H+ exchanger regulation is based on heterologous expression of mammalian Na+/H+ exchangers in Na+/H+ exchanger deficient fibroblasts, renal epithelial, and intestinal epithelial cells. Based on the reductionist's approach, an understanding of NHE3 regulation has been greatly advanced. More recently, confirmations of in vitro studies have been made using animals deficient in one or more proteins but in some cases unexpected findings have emerged. The purpose of this paper is to provide a brief overview of recent progress in the regulation and functions of NHE3 present in the luminal membrane of the intestinal tract.
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Darsigny M, Babeu JP, Dupuis AA, Furth EE, Seidman EG, Lévy É, Verdu EF, Gendron FP, Boudreau F. Loss of hepatocyte-nuclear-factor-4alpha affects colonic ion transport and causes chronic inflammation resembling inflammatory bowel disease in mice. PLoS One 2009; 4:e7609. [PMID: 19898610 PMCID: PMC2764139 DOI: 10.1371/journal.pone.0007609] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 10/02/2009] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Hnf4alpha, an epithelial specific transcriptional regulator, is decreased in inflammatory bowel disease and protects against chemically-induced colitis in mice. However, the precise role of this factor in maintaining normal inflammatory homeostasis of the intestine remains unclear. The aim of this study was to evaluate the sole role of epithelial Hnf4alpha in the maintenance of gut inflammatory homeostasis in mice. METHODOLOGY/PRINCIPAL FINDINGS We show here that specific epithelial deletion of Hnf4alpha in mice causes spontaneous chronic intestinal inflammation leading to focal areas of crypt dropout, increased cytokines and chemokines secretion, immune cell infiltrates and crypt hyperplasia. A gene profiling analysis in diseased Hnf4alpha null colon confirms profound genetic changes in cell death and proliferative behaviour related to cancer. Among the genes involved in the immune protection through epithelial barrier function, we identify the ion transporter claudin-15 to be down-modulated early in the colon of Hnf4alpha mutants. This coincides with a significant decrease of mucosal ion transport but not of barrier permeability in young animals prior to the manifestation of the disease. We confirm that claudin-15 is a direct Hnf4alpha gene target in the intestinal epithelial context and is down-modulated in mouse experimental colitis and inflammatory bowel disease. CONCLUSION Our results highlight the critical role of Hnf4alpha to maintain intestinal inflammatory homeostasis during mouse adult life and uncover a novel function for Hnf4alpha in the regulation of claudin-15 expression. This establishes Hnf4alpha as a mediator of ion epithelial transport, an important process for the maintenance of gut inflammatory homeostasis.
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Affiliation(s)
- Mathieu Darsigny
- Canadian Institutes of Health Research Team on Digestive Epithelium, Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Jean-Philippe Babeu
- Canadian Institutes of Health Research Team on Digestive Epithelium, Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Andrée-Anne Dupuis
- Canadian Institutes of Health Research Team on Digestive Epithelium, Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Emma E. Furth
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Ernest G. Seidman
- Canadian Institutes of Health Research Team on Digestive Epithelium, Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Research Institute, McGill University Health Center, Montréal, Quebec, Canada
| | - Émile Lévy
- Canadian Institutes of Health Research Team on Digestive Epithelium, Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Department of Nutrition, CHU Ste-Justine, Université de Montréal, Quebec, Canada
| | - Elena F. Verdu
- Division of Gastroenterology, McMaster University, Hamilton, Ontario, Canada
| | - Fernand-Pierre Gendron
- Canadian Institutes of Health Research Team on Digestive Epithelium, Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - François Boudreau
- Canadian Institutes of Health Research Team on Digestive Epithelium, Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Département d'anatomie et biologie cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- * E-mail:
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Donowitz M, Mohan S, Zhu CX, Chen TE, Lin R, Cha B, Zachos NC, Murtazina R, Sarker R, Li X. NHE3 regulatory complexes. ACTA ACUST UNITED AC 2009; 212:1638-46. [PMID: 19448074 DOI: 10.1242/jeb.028605] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The epithelial brush border Na/H exchanger NHE3 is active under basal conditions and functions as part of neutral NaCl absorption in the intestine and renal proximal tubule, where it accounts for the majority of total Na absorbed. NHE3 is highly regulated. Both stimulation and inhibition occur post-prandially. This digestion related regulation of NHE3 is mimicked by multiple extracellular agonists and intracellular second messengers. The regulation of NHE3 depends on its C-terminal cytoplasmic domain, which acts as a scaffold to bind multiple regulatory proteins and links NHE3 to the cytoskeleton. The cytoskeletal association occurs by both direct binding to ezrin and by indirect binding via ezrin binding to the C-terminus of the multi-PDZ domain containing proteins NHERF1 and NHERF2. This is a review of the domain structure of NHE3 and of the scaffolding function and role in the regulation of NHE3 of the NHE3 C-terminal domain.
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Affiliation(s)
- Mark Donowitz
- Johns Hopkins University School of Medicine, 720 Rutland Avenue Baltimore, MD 21205, USA.
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Kiela PR, Laubitz D, Larmonier CB, Midura-Kiela MT, Lipko MA, Janikashvili N, Bai A, Thurston R, Ghishan FK. Changes in mucosal homeostasis predispose NHE3 knockout mice to increased susceptibility to DSS-induced epithelial injury. Gastroenterology 2009; 137:965-75, 975.e1-10. [PMID: 19450596 PMCID: PMC3454522 DOI: 10.1053/j.gastro.2009.05.043] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 05/04/2009] [Accepted: 05/14/2009] [Indexed: 12/27/2022]
Abstract
BACKGROUND & AIMS NHE3 is a target of inhibition by proinflammatory cytokines and pathogenic bacteria, an event contributing to diarrhea in infectious and idiopathic colitis. In mice, NHE3 deficiency leads to mild diarrhea, increased intestinal expression of interferon (IFN)-gamma, and distal colitis, suggesting its role in epithelial barrier homeostasis. Our aim was to investigate the role of NHE3 in maintaining mucosal integrity. METHODS Control or dextran sulfate sodium (DSS)-treated, 6- to 8-week-old wild-type (WT) and NHE3(-/-) mice were used for the experiments. Small intestines were dissected for further analysis. RESULTS NHE3(-/-) mice have elevated numbers of CD8alpha(+) T and natural killer cells in the intraepithelial lymphocytes and lamina propria lymphocytes compartments, representing the source of IFN-gamma. NHE3(-/-) mice display alterations in epithelial gene and protein expression patterns that predispose them to a high susceptibility to DSS, with accelerated mortality resulting from intestinal bleeding, hypovolemic shock, and sepsis, even at a very low DSS concentration. Microarray analysis and intestinal hemorrhage indicate that NHE3 deficiency predisposes mice to DSS-induced small intestinal injury, a segment never reported as affected by DSS, and demonstrate major differences in the colonic response to DSS challenge in WT and NHE3(-/-) mice. In NHE3(-/-) mice, broad-spectrum oral antibiotics or anti-asialo GM1 antibodies reduce the expression of IFN-gamma and iNOS to basal levels and delay but do not prevent severe mortality in response to DSS treatment. CONCLUSIONS These results suggest that NHE3 participates in mucosal responses to epithelial damage, acting as a modifier gene determining the extent of the gut inflammatory responses in the face of intestinal injury.
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Affiliation(s)
- Pawel R. Kiela
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
- Department of Immunobiology, University of Arizona Health Sciences Center, 1656 E. Mabel Street, Tucson, Arizona, 85724
| | - Daniel Laubitz
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Claire B. Larmonier
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Monica T. Midura-Kiela
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Maciej A. Lipko
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Nona Janikashvili
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Aiping Bai
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Robert Thurston
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
| | - Fayez K. Ghishan
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona Health Sciences Center 1501 N. Campbell Ave, Tucson, AZ 85724
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The protein disulfide isomerase AGR2 is essential for production of intestinal mucus. Proc Natl Acad Sci U S A 2009; 106:6950-5. [PMID: 19359471 DOI: 10.1073/pnas.0808722106] [Citation(s) in RCA: 298] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Protein disulfide isomerases (PDIs) aid protein folding and assembly by catalyzing formation and shuffling of cysteine disulfide bonds in the endoplasmic reticulum (ER). Many members of the PDI family are expressed in mammals, but the roles of specific PDIs in vivo are poorly understood. A recent homology-based search for additional PDI family members identified anterior gradient homolog 2 (AGR2), a protein originally presumed to be secreted by intestinal epithelial cells. Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2, a large, cysteine-rich glycoprotein that forms the protective mucus gel lining the intestine. A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. Mice lacking AGR2 were viable but were highly susceptible to colitis, indicating a critical role for AGR2 in protection from disease. We conclude that AGR2 is a unique member of the PDI family, with a specialized and nonredundant role in intestinal mucus production.
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Abstract
PURPOSE OF REVIEW In recent years, the field of intestinal physiology has witnessed significant progress in our understanding of the expression and function of ion transport proteins and their genes under physiological and pathophysiological conditions. This review will present some of these most recent advances in the small intestinal ion transport mechanisms. RECENT FINDINGS One of the new and exciting aspects of this field has been the integration of function and structure of several intestinal transport processes. This is well exemplified by the discussed intricacies of intestinal bicarbonate secretion as well as the role of scaffolding PDZ proteins interacting with several transporters. We also discuss some of the most recent data pointing to the role of ion transporters in the pathogenesis of inflammation-associated diarrhea and their potential role in the maintenance of epithelial integrity. SUMMARY Mouse models deficient in some of the key genes encoding ion transporters and their adapter proteins continue to provide important clues into intestinal transport processes. Several of the new in-vivo findings revise or complement past paradigms, many of which were derived from in-vitro approaches. New data on the interdependent functions of multiple transporters, as exemplified here by intestinal bicarbonate secretion, increase the complexity of the intestinal ion transport mechanisms and continue to contribute to a more integrated view of the transport phenomena in the gut. Data from patients and mouse models of intestinal inflammation also increase our understanding of the pathophysiology of inflammation-associated diarrhea.
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Sullivan S, Alex P, Dassopoulos T, Zachos NC, Iacobuzio-Donahue C, Donowitz M, Brant SR, Cuffari C, Harris ML, Datta LW, Conklin A, Chen Y, Li X. Downregulation of sodium transporters and NHERF proteins in IBD patients and mouse colitis models: potential contributors to IBD-associated diarrhea. Inflamm Bowel Dis 2009; 15:261-74. [PMID: 18942765 PMCID: PMC2627787 DOI: 10.1002/ibd.20743] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND One of the most common symptoms among patients with inflammatory bowel disease (IBD) is diarrhea, which is thought to be contributed by changes in electrolyte transport associated with intestinal inflammation. This study was designed to test the hypothesis that intestinal Na(+)-related transporters/channels and their regulatory proteins may be downregulated as a potential contributor to IBD-associated diarrhea. METHODS SDS-PAGE and Western blotting and/or confocal immunomicroscopy were used to examine the expression of Na(+)/H(+)-exchangers 1-3 (NHE1-3), epithelial Na(+) channel (ENaC), Na(+)/K(+)-ATPase, the intracellular Cl(-) channel 5 (ClC-5), and NHE3 regulatory factors (NHERF1,2) in ileal and colonic pinch biopsies from IBD patients and noninflammatory controls, as well as from colonic mucosa of dextran sodium sulfate (DSS)- and TNBS-induced acute murine IBD models. RESULTS NHE1,3 (but not NHE2), beta-ENaC, Na(+)/K(+)-ATPase-alpha, ClC-5, and NHERF1 were all downregulated in sigmoid mucosal biopsies from most cases of active UC and/or CD compared to controls. NHE3 was also decreased in ileal mucosal biopsies of active CD, as well as in approximately 50% of sigmoid biopsies from inactive UC or CD. Importantly, similar downregulation of NHE1,3, beta-ENaC, and NHERF1,2 was also observed in the mouse colon (but not ileum) of DSS- and TNBS-induced colitis. CONCLUSIONS IBD-associated diarrhea may be due to a coordinated downregulation of multiple Na(+) transporter and related regulatory proteins, including NHE1,3, Na(+)/K(+)-ATPase, and ENaC, as well as NHERF1,2, and ClC-5, all of which are involved directly or indirectly in intestinal Na(+) absorption.
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Affiliation(s)
- Sean Sullivan
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205,Dept of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Philip Alex
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | | | - Nicholas C. Zachos
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | | | - Mark Donowitz
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Steven R. Brant
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Carmen Cuffari
- Dept of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Mary L. Harris
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Lisa Wu Datta
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - aurie Conklin
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205,Dept of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Yueping Chen
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Xuhang Li
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205,Address correspondence to: Xuhang Li, Ph.D. 720 Rutland Ave, 918 Ross Research Bldg GI Division, Department of Medicine Johns Hopkins University School of Medicine Baltimore, MD 21205 Tel. 443-287-4804 Fax. 410-955-9677 E-mail:
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