Regulation of IL-1beta-mediated MUC2 gene in NCI-H292 human airway epithelial cells

The gut mucus network: A dynamic liaison between microbes and the immune system

A complex mucus network made up of large polymers of the mucin-family glycoprotein MUC2 exists between the large intestinal microbial mass and epithelial and immune cells. This has long been understood as an innate immune defense barrier against the microbiota and other luminal threats that reinforces the barrier function of the epithelium and limits microbiota contact with the tissues. However, past and recent studies have provided new evidence of how critical the mucus network is to act as a 'liaison' between host and microbe to mediate anti-inflammatory, mutualistic interactions with the microbiota and protection from pathogens. This review summarizes historical and recent insights into the formation of the gut mucus network, how the microbes and immune system influence mucus, and in turn, how the mucus influences immune responses to the microbiota.

Acute infection with Brachyspira hyodysenteriae affects mucin expression, glycosylation, and fecal MUC5AC

Introduction

Infection with strongly β-hemolytic strains of Brachyspira hyodysenteriae leads to swine dysentery (SD), a production-limiting disease that causes mucohemorrhagic diarrhea and typhlocolitis in pigs. This pathogen has strong chemotactic activity toward mucin, and infected pigs often have a disorganized mucus layer and marked de novo expression of MUC5AC, which is not constitutively expressed in the colon. It has been shown that fucose is chemoattractant for B. hyodysenteriae, and a highly fermentable fiber diet can mitigate and delay the onset of SD.

Methods

We used lectins targeting sialic acids in α-2,6 or α-2,3 linkages, N-acetylglucosamine (GlcNAc), α-linked L-fucose, and an immunohistochemical stain targeting N-glycolylneuraminic acid (NeuGc) to investigate the local expression of these mucin glycans in colonic tissues of pigs with acute SD. We used a commercial enzyme-linked immunosorbent assay (ELISA) to quantify fecal MUC5AC in infected pigs and assess its potential as a diagnostic monitoring tool and RNA in situ hybridization to detect IL-17A in the colonic mucosa.

Results

Colonic mucin glycosylation during SD has an overall increase in fucose, a spatially different distribution of GlcNAc with more expression within the crypt lumens of the upper colonic mucosa, and decreased expression or a decreased trend of sialic acids in α-2,6 or α-2,3 linkages, and NeuGc compared to the controls. The degree of increased fucosylation was less in the colonic mucosa of pigs with SD and fed the highly fermentable fiber diet. There was a significant increase in MUC5AC in fecal and colonic samples of pigs with SD at the endpoint compared to the controls, but the predictive value for disease progression was limited.

Discussion

Fucosylation and the impact of dietary fiber may play important roles in the pathogenesis of SD. The lack of predictive value for fecal MUC5AC quantification by ELISA is possibly due to the presence of other non-colonic sources of MUC5AC in the feces. The moderate correlation between IL-17A, neutrophils and MUC5AC confirms its immunoregulatory and mucin stimulatory role. Our study characterizes local alteration of mucin glycosylation in the colonic mucosa of pigs with SD after B. hyodysenteriae infection and may provide insight into host-pathogen interaction.

Alteration of Colonic Mucin Composition and Cytokine Expression in Acute Swine Dysentery

Swine dysentery (SD) is an enteric disease associated with strongly β-hemolytic Brachyspira spp. that cause mucohemorrhagic diarrhea primarily in grower-finisher pigs. We characterized alteration of colonic mucin composition and local cytokine expression in the colon of pigs with acute SD after B. hyodysenteriae (Bhyo) infection and fed either a diet containing 30% distillers dried grains with solubles (DDGS) or a control diet. Colonic tissue samples from 9 noninoculated pigs (Control, N = 4; DDGS, N = 5) and 10 inoculated pigs experiencing acute SD (Bhyo, N = 4; Bhyo-DDGS, N = 6) were evaluated. At the apex of the spiral colon, histochemical staining with high-iron diamine-Alcian blue revealed increased sialomucin (P = .008) and decreased sulfomucin (P = .027) in Bhyo pigs relative to controls, with a dietary effect for sulfomucin. Noninoculated pigs fed DDGS had greater expression of sulfomucin (P = .002) compared to pigs fed the control diet. Immunohistochemically, there was de novo expression of mucin 5AC (MUC5AC) in the Bhyo group while mucin 2 (MUC2) expression was not significantly different between groups. RNA in situ hybridization to detect the pro-inflammatory cytokine IL-1β often showed increased expression in the Bhyo group although without statistical significance, and this was not correlated with MUC5AC or MUC2 expression, suggesting IL-1β is not a major regulator of their secretion in acute SD. Expression of the anti-inflammatory cytokine TGF-β1 was significantly suppressed in the Bhyo group compared to controls (P = .005). This study reveals mucin and cytokine alterations in the colon of pigs with experimentally induced SD and related dietary effects of DDGS.

Elevated adenomatous polyposis coli in goblet cells is associated with inflammation in mouse and human colon

NEW FINDINGS

What is the central question of this study? What is the localization and distribution pattern of adenomatous polyposis coli (APC) in intestinal epithelial cells? Does this distribution change in different regions of the colon or in the condition of inflammation? What is the main finding and its importance? Colonic epithelia from mice and humans contain a subset of goblet cells displaying high APC levels. The number of APC^high goblet cells increases in inflamed tissue, which also displays increased GRP78, indicating potential stress from mucin production. In cultured human colon cells, expression of interleukin 1 pathway components (inducers of MUC2 expression) is reduced upon APC depletion raising the potential for APC participation in an inflammatory response.

ABSTRACT

Adenomatous polyposis coli (APC) serves as a gatekeeper of intestinal homeostasis by promoting cellular differentiation and maintaining crypt architecture. Although appreciated as a critical colon tumour suppressor, roles for APC in disease states such as inflammation have yet to be fully delineated. This study aimed to characterize the localization of APC protein in gastrointestinal tissues from human patients with active inflammatory bowel disease and mice with dextran sodium sulfate (DSS)-induced colitis. Fluorescence immunohistochemistry revealed a subset of goblet cells with elevated Apc staining intensity in the small intestines and proximal/medial colons of mice. Upon induction of colitis with DSS, these 'APC^high ' goblet cells remained in the proximal and medial colon, but now were also observed in the distal colon. This phenotype was recapitulated in humans, with APC^high goblet cells observed only in the descending colons of patients with active ulcerative colitis. In cultured human colon cells derived from normal tissue, APC depletion reduced expression of mRNAs encoding the interleukin 1 (IL1) signalling pathway components IL1β and interleukin-1 receptor (IL1R), known regulators of Muc2 expression. Treating cancer cells lacking wild-type APC with IL1β, or induction of full-length APC in these cells led to increases in IL1R and MUC2 expression. Combining IL1β treatment with APC induction led to an increase of MUC2 expression greater than expected for additive affects, suggesting that APC sensitizes cells to IL1 signalling. These findings suggest that APC has novel roles in maintaining proper goblet cell function, thus providing further evidence for APC as an important factor in intestinal tissue homeostasis and disease.

Mometasone Furoate Suppresses PMA-Induced MUC-5AC and MUC-2 Production in Human Airway Epithelial Cells

BACKGROUND

Mucus hypersecretion from airway epithelium is a characteristic feature of airway inflammatory diseases. Tumor necrosis factor α (TNF-α) regulates mucin synthesis. Glucocorticoids including mometasone fuorate (MF) have been used to attenuate airway inflammation. However, effects of MF on mucin production have not been reported.

METHODS

Effects of MF and budesonide (BUD) on the phorbol-12-myristate-13-acetate (PMA)-induction of mucin and TNF-α in human airway epithelial cells (NCI-H292) were investigated in the present study. Confluent NCI-H292 cells were pretreated with PMA (200 nM) for 2 hours. Subsequently, the cells were stimulated with MF (1-500 ng/mL) or BUD (21.5 ng/mL) for 8 hours. Dexamethasone (1 µg/mL) was used as the positive control. Real-time polymerase chain reaction was used to determine MUC2 and MUC5AC mRNA levels. The level of total mucin, MUC2, MUC5AC, and TNF-α in culture supernatants were measured using enzyme-linked immunosorbent assay.

RESULTS

MF and BUD significantly suppressed MUC2 and MUC5AC gene expression in PMA-stimulated NCI-H292 cells. The inhibitory effects of the two steroid drugs were also observed in the production of total mucin, MUC2 and MUC5AC proteins, and TNF-α.

CONCLUSION

Our findings demonstrated that MF and BUD attenuated mucin and TNF-α production in PMA-induced human airway epithelial cells.

Secreted mucins in pseudomyxoma peritonei: pathophysiological significance and potential therapeutic prospects

Pseudomyxoma peritonei (PMP, ORPHA26790) is a clinical syndrome characterized by progressive dissemination of mucinous tumors and mucinous ascites in the abdomen and pelvis. PMP is a rare disease with an estimated incidence of 1-2 out of a million. Clinically, PMP usually presents with a variety of unspecific signs and symptoms, including abdominal pain and distention, ascites or even bowel obstruction. It is also diagnosed incidentally at surgical or non-surgical investigations of the abdominopelvic viscera. PMP is a neoplastic disease originating from a primary mucinous tumor of the appendix with a distinctive pattern of the peritoneal spread. Computed tomography and histopathology are the most reliable diagnostic modalities. The differential diagnosis of the disease includes secondary peritoneal carcinomatoses and some rare peritoneal conditions. Optimal elimination of mucin and the mucin-secreting tumor comprises the current standard of care for PMP offered in specialized centers as visceral resections and peritonectomy combined with intraperitoneal chemotherapy. This multidisciplinary approach has reportedly provided a median survival rate of 16.3 years, a median progression-free survival rate of 8.2 years and 10- and 15-year survival rates of 63% and 59%, respectively. Despite its indolent, bland nature as a neoplasm, PMP is a debilitating condition that severely impacts quality of life. It tends to be diagnosed at advanced stages and frequently recurs after treatment. Being ignored in research, however, PMP remains a challenging, enigmatic entity. Clinicopathological features of the PMP syndrome and its morbid complications closely correspond with the multifocal distribution of the secreted mucin collections and mucin-secreting implants. Novel strategies are thus required to facilitate macroscopic, as well as microscopic, elimination of mucin and its source as the key components of the disease. In this regard, MUC2, MUC5AC and MUC5B have been found as the secreted mucins of relevance in PMP. Development of mucin-targeted therapies could be a promising avenue for future research which is addressed in this article.

Virulent Shigella flexneri affects secretion, expression, and glycosylation of gel-forming mucins in mucus-producing cells

Mucin glycoproteins are secreted in large amounts by the intestinal epithelium and constitute an efficient component of innate immune defenses to promote homeostasis and protect against enteric pathogens. In this study, our objective was to investigate how the bacterial enteropathogen Shigella flexneri, which causes bacillary dysentery, copes with the mucin defense barrier. We report that upon in vitro infection of mucin-producing polarized human intestinal epithelial cells, virulent S. flexneri manipulates the secretion of gel-forming mucins. This phenomenon, which is triggered only by virulent strains, results in accumulation of mucins at the cell apical surface, leading to the appearance of a gel-like structure that favors access of bacteria to the cell surface and the subsequent invasion process. We identify MUC5AC, a gel-forming mucin, as a component of this structure. Formation of this gel does not depend on modifications of electrolyte concentrations, induction of trefoil factor expression, endoplasmic reticulum stress, or response to unfolded proteins. In addition, transcriptional and biochemical analyses of infected cells reveal modulations of mucin gene expression and modifications of mucin glycosylation patterns, both of which are induced by virulent bacteria in a type III secretion system-dependent manner. Thus, S. flexneri has developed a dedicated strategy to alter the mucus barrier by targeting key elements of the gel-forming capacity of mucins: gene transcription, protein glycosylation, and secretion.

Chronic anti-inflammatory drug therapy inhibits gel-forming mucin production in a murine xenograft model of human pseudomyxoma peritonei

BACKGROUND

Intraperitoneal accumulation of mucinous ascites in pseudomyxoma peritonei (PMP) promotes an inflammatory/fibrotic reaction that progresses to bowel obstruction and eventual patient demise. Cytokines and inflammation-associated transcription factor binding sites, such as glucocorticoid response elements and COX-2, regulate secretory mucin, specifically MUC2, production. We hypothesized that anti-inflammatory drugs targeting inflammation-associated pathways may reduce mucin production and subsequent disease morbidity in PMP.

METHODS

The effects of dexamethasone and Celebrex were assessed in mucin-secreting human colon cancer LS174T cells in vitro and murine xenograft models of LS174T and human appendiceal PMP in vivo by serial parametric measurements, MUC2 transcripts via real-time RT-PCR, and MUC2 protein expression via immunofluorescence assays.

RESULTS

Dexamethasone significantly inhibited basal MUC2 mRNA levels in LS174T cells, inhibited mucinous tumor accumulation in an intraperitoneal PMP xenograft model, and prolonged survival in a subcutaneous LS174T xenograft model. Celebrex significantly inhibited sodium butyrate-stimulated MUC2 mRNA levels in LS174T cells and demonstrated a statistically nonsignificant trend toward reduced mucinous tumor growth and prolonged survival in the xenograft models. MUC2 protein analysis by immunofluorescence demonstrated a dual effect of dexamethasone on mucin production and tumor cell count.

CONCLUSIONS

Inflammatory mediators are known to regulate mucin production and may promote overexpression of MUC2 by neoplastic cells with goblet cell phenotype in PMP. Anti-inflammatory drugs, dexamethasone and Celebrex, could inhibit extracellular mucin production in PMP by targeting inflammatory cascades and, therefore, may decrease compressive symptoms, increase the disease-free interval, and reduce the extent or frequency of morbid cytoreductive surgeries.

Mucin as a therapeutic target in pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is characterized by intraperitoneal dissemination of mucinous ascites. This malignancy frequently recurs despite aggressive locoregional therapies, demonstrates chemo-insensitivity and lacks targeted therapies. This review addresses some intriguing questions in PMP; what role does mucin play in this malignancy?; what genetic alterations and dysregulated signaling pathways lead to a putative goblet cell-lineage differentiation or mucin overexpression?; are targeted therapies against known transcriptional pathways for mucin production a novel therapeutic strategy in this malignancy?

Differential expression of gastric MUC5AC in colonic epithelial cells: TFF3-wired IL1 β/Akt crosstalk-induced mucosal immune response against Shigella dysenteriae infection

An understanding of the signaling mechanism(s) that regulate the differential expression of gastric mucin MUC5AC in colonic epithelial cells would contribute significantly to investigations of its role in colonic mucosa infected with the bacterial pathogen Shigella dysenteriae. Here we show that S. dysenteriae-Sinduced expression of interleukin-1β upregulates MUC2 expression and the differential expression of MUC5AC. Differential expression of MUC5AC involves crosstalk between interleukin-1β and Akt, whereby the trefoil factor family peptide TFF3 activates Akt by phosphorylation of EGFR. TFF3 also downregulates E-cadherin expression, causing accumulation of β-catenin in the cytosol. Phosphorylation of GSK-3β (inactivated) by activated Akt inhibits ubiquitylation of β-catenin, leading to its nuclear translocation, which then induces the expression of MUC5AC and cyclin D1. Accumulation of cyclin D1 alters the cell cycle, promoting cell survival and proliferation. Human colon HT29MTX cells, which overexpress MUC5AC, were resistant to adherence and invasion of S. dysenteriae when compared with other mucin-secreting HT29 cell types. Thus, during infection with S. dysenteriae, crosstalk between interleukin-1β and Akt wired by TFF3 induces expression of MUC5AC in colonic epithelial cells. Differentially expressed gastric MUC5AC aids in mucosal clearance of S. dysenteriae, inhibiting adherence and invasion of the pathogen to colonic epithelial cells, which protects the host.

Mucins in inflammatory bowel diseases and colorectal cancer

The gastrointestinal tract is protected by a mucus barrier with both secreted and cell-surface mucins contributing to the exclusion of luminal microbes and toxins. Alterations in the structure and/or quantity of mucins alter the barrier function of mucus and could play roles in initiating and maintaining mucosal inflammation in inflammatory bowel diseases (IBD), and in driving cancer development in the intestine. The aim of this review is to focus on the roles of the mucins in IBD. The polymorphisms of mucin genes that have been associated with susceptibility to IBD, and alterations in mucin expression as well as factors that regulate production of the mucins in IBD, are summarized. Data from animal models of intestinal inflammation, which support the importance of mucins in IBD and cancer development, are also discussed.

Up-regulation of MUC2 and IL-1β expression in human colonic epithelial cells by Shigella and its interaction with mucins

BACKGROUND

The entire gastrointestinal tract is protected by a mucous layer, which contains complex glycoproteins called mucins. MUC2 is one such mucin that protects the colonic mucosa from invading microbes. The initial interaction between microbes and mucins is an important step for microbial pathogenesis. Hence, it was of interest to investigate the relationship between host (mucin) and pathogen interaction, including Shigella induced expression of MUC2 and IL-1β during shigellosis.

METHODS

The mucin-Shigella interaction was revealed by an in vitro mucin-binding assay. Invasion of Shigella dysenteriae into HT-29 cells was analyzed by Transmission electron microscopy. Shigella induced mucin and IL-1β expression were analyzed by RT-PCR and Immunofluorescence.

RESULTS

The clinical isolates of Shigella were found to be virulent by a congo-red binding assay. The in vitro mucin-binding assay revealed both Shigella dysenteriae and Shigella flexneri have binding affinity in the increasing order of: guinea pig small intestinal mucin

CONCLUSIONS

Our study concludes that the Shigella species specifically binds to guinea pig colonic mucin, but not to guinea pig small intestinal mucin. The guinea pig colonic mucin showed a greater binding parameter (R), and more saturable binding, suggesting the presence of a finite number of receptor binding sites in the colonic mucin of the host. In addition, modification of mucins with TFMS and sodium metaperiodate significantly reduced mucin-bacterial binding; suggesting that the mucin-Shigella interaction occurs through carbohydrate epitopes on the mucin backbones. Overproduction of MUC2 may alter adherence and invasion of Shigella dysenteriae into human colonic epithelial cells.

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MESH Headings

• Animals
• Base Sequence
• Cell Line
• Colon/cytology
• Colon/metabolism
• DNA Primers
• Enzyme-Linked Immunosorbent Assay
• Epithelial Cells/metabolism
• Guinea Pigs
• Humans
• Interleukin-1beta/metabolism
• Microscopy, Electron, Transmission
• Mucin-2/metabolism
• Reverse Transcriptase Polymerase Chain Reaction
• Shigella dysenteriae/pathogenicity
• Shigella dysenteriae/physiology
• Up-Regulation
• Virulence

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Affiliation(s)

Radhakrishnan Prakash Department of Biochemistry, University of Madras, Guindy Campus, Chennai, Tamilnadu, India
Subramaniya Bharathi Raja Department of Biochemistry, University of Madras, Guindy Campus, Chennai, Tamilnadu, India
Halagowder Devaraj Unit of Biochemistry, Department of Zoology, University of Madras, Guindy Campus, Chennai, Tamilnadu, India
Sivasitambaram Niranjali Devaraj Department of Biochemistry, University of Madras, Guindy Campus, Chennai, Tamilnadu, India

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Mucin dynamics and enteric pathogens

The extracellular secreted mucus and the cell surface glycocalyx prevent infection by the vast numbers of microorganisms that live in the healthy gut. Mucin glycoproteins are the major component of these barriers. In this Review, we describe the components of the secreted and cell surface mucosal barriers and the evidence that they form an effective barricade against potential pathogens. However, successful enteric pathogens have evolved strategies to circumvent these barriers. We discuss the interactions between enteric pathogens and mucins, and the mechanisms that these pathogens use to disrupt and avoid mucosal barriers. In addition, we describe dynamic alterations in the mucin barrier that are driven by host innate and adaptive immune responses to infection.

Dietary polyphenols affect MUC5AC expression and ciliary movement in respiratory cells and nasal mucosa

BACKGROUND

Dietary polyphenols have been widely consumed in food, and their anti-inflammatory and anticancer activities have been recently studied. Although the effects of dietary polyphenols on mucin hypersecretion have been studied to some extent, the effects of mucociliary movement have not been elucidated thus far. Therefore, we investigated whether dietary polyphenols inhibit MUC5AC gene expression in NCI-H292 cells, and, if so, whether they would have an effect on ciliary beat frequency (CBF) of human nasal mucosa.

METHODS

NCI-H292 cells were pretreated with four different dietary polyphenols ([6]-gingerol, epigallocatechin gallate (EGCG), curcumin, and quercetin) and were treated with IL-1beta (10 ng/mL). Proliferation of NCI-H292 cells was analyzed. The mRNA expression of MUC5AC was determined by real-time polymerase chain reaction. CBF of normal nasal mucosa, which was obtained from the ethmoid sinus and treated with the polyphenols, was assessed via inverted microscope and computerized program.

RESULTS

Minimal inhibitory concentration (MIC) of MUC5AC expression of each polyphenol was found as follows: [6]-gingerol, 1 microM; EGCG, 20 microM; quercetin, 40 microM; and curcumin, 10 microM. No polyphenol influenced cell proliferation at this MIC. CBF was not affected by [6]-gingerol, quercetin, or EGCG, but ciliary movement decreased in curcumin.

CONCLUSION

[6]-Gingerol, quercetin, and EGCG may be considered as antihypersecretory agents because they effectively inhibit mucus secretion of respiratory epithelial cells while maintaining normal nasal ciliary movement.

Expression of glutaredoxin-1 in nasal polyps and airway epithelial cells

BACKGROUND

Glutaredoxins (GRX)-1 is glutathione-dependent oxidoreductase. However, the role of these enzymes remains unknown in airway inflammatory diseases. Therefore, we aimed to establish the expression pattern of GRX-1 in the nasal polyps (NPs) and to assess the regulatory mechanisms associated with GRX-1 expression in interleukin (IL)-1 beta-treated airway epithelial cells.

METHODS

The expression of GRX-1 in NPs and normal nasal mucosa were analyzed by reverse-transcription polymerase chain reaction and immunohistochemical staining. IL-1 beta-induced reactive oxygen species (ROS) formation and GRX-1 expression in the airway epithelial cells was determined by flow cytometry and immunoassay.

RESULTS

The expression level of GRX-1 in NPs was significantly higher than in the normal nasal mucosa (p < 0.05). GRX-1 was highly expressed in the surface epithelial cells and the submucosal glandular cells in the NPs. IL-1 beta increased the intracellular ROS formation and GRX-1 expression in airway epithelial cells. The inhibition of IL-1 beta-induced ROS production by N-acetyl-cystein, an ROS scavenger, reduced GRX-1 expression. Diphenyleneiodonium and apocynin, NADPH oxidase inhibitors, did not abolish IL-1 beta-induced ROS formation and GRX-1 expression, whereas budesonide attenuated it.

CONCLUSION

High GRX-1 expression in NPs might be a primary defense against chronic inflammatory oxidative stress in nasal mucosa. IL-1 beta-induced up-regulation of GRX-1 in airway epithelial cells is probably mediated by ROS. Glucocorticoids can regulate IL-1 beta-induced ROS formation and GRX-1 expression.

The symplekin/ZONAB complex inhibits intestinal cell differentiation by the repression of AML1/Runx1

BACKGROUND & AIMS

Symplekin is a ubiquitously expressed protein involved in RNA polyadenylation and transcriptional regulation that localizes at tight junctions in epithelial cells. The association between symplekin and the Y-box transcription factor ZONAB activates proliferation in intestinal and kidney cells. We analyzed symplekin expression in human colonic crypts and investigated its function in differentiation.

METHODS

Expression of differentiation markers and transcription factors was assessed in HT29-Cl.16E cells that expressed inducible symplekin short hairpin RNA or were transfected with ZONAB small interfering RNAs. Intestines of AML1(Delta/Delta) mice were stained with alcian blue and analyzed for expression of AML1/Runx1, GAPDH, KLF-4, and Muc-2. Mobility shift and chromatin immunoprecipitation were used to detect AML1 and ZONAB/DbpA binding to promoter regions of the Krüppel-like factor 4 (KLF4) and acute myeloid leukemia-1 (AML1) genes, respectively.

RESULTS

The gradient of nuclear symplekin expression decreased from the proliferative toward the differentiated compartment of colonic crypts; symplekin down-regulation promoted the differentiation of HT29-Cl.16E colorectal carcinoma cells into goblet cells. Down-regulation of symplekin or ZONAB/Dbpa induced de novo expression of the transcription factor AML1/Runx1, thereby increasing the expression of KLF4 and promoting goblet cell differentiation. Furthermore, increased AML1 expression was required for the induction of goblet cell differentiation after symplekin down-regulation. KLF4 expression and goblet cell numbers were reduced in the intestines of AML1(Delta/Delta) mice, confirming the role of AML1 as a promoter of intestinal differentiation in vivo.

CONCLUSIONS

Symplekin cooperates with ZONAB to negatively regulate intestinal goblet cell differentiation, acting by repression of AML1 and KLF4.

[6]-Gingerol suppresses interleukin-1 beta-induced MUC5AC gene expression in human airway epithelial cells

BACKGROUND

[6]-Gingerol is a major active component of ginger and a natural polyphenol compound. The present study investigated whether [6]-gingerol suppresses interleukin (IL)-1 beta-induced MUC5AC gene expression in human airway epithelial cells and, if so, examined whether the suppression of MUC5AC gene expression is mediated via the mitogen-activated protein kinase (MAPK) signal transduction pathway.

METHODS

MUC5AC mRNA and protein were measured using reverse transcription-polymerase chain reaction (PCR), real-time PCR, and Western blot analysis in cultured NCI-H292 human airway epithelial cells. Extracellular signal-regulated kinase (ERK) and p38 MAPK protein levels were analyzed by Western blot.

RESULTS

Expression of MUC5AC mRNA increased in NCI-H292 cells upon treatment with 10 ng/mL of IL-1 beta for 24 hours. When the cells were pretreated with 10 microM of [6]-gingerol, expression of IL-1 beta-induced MUC5AC mRNA and protein was significantly suppressed. Suppression of IL-1 beta-induced MUC5AC mRNA was also observed in cells pretreated with ERK- or p38 MAPK-specific inhibitors, suggesting that [6]-gingerol-mediated suppression of IL-1 beta-induced MUC5AC mRNA operated via the ERK- and p38 MAPK-dependent pathways.

CONCLUSIONS

[6]-Gingerol suppresses IL-1 beta -induced MUC5AC gene expression in human airway epithelial cells via the ERK- and p38 MAPK-dependent pathways; therefore, [6]-gingerol may be considered a possible anti-hypersecretory agent.

CREB mediates prostaglandin F2alpha-induced MUC5AC overexpression

Mucus secretion is an important protective mechanism for the luminal lining of open tubular organs, but mucin overproduction in the respiratory tract can exacerbate the inflammatory process and cause airway obstruction. Production of MUC5AC, a predominant gel-forming mucin secreted by airway epithelia, can be induced by various inflammatory mediators such as prostaglandins. The two major prostaglandins involved in inflammation are PGE(2) and PGF(2alpha). PGE(2)-induced mucin production has been well studied, but the effect of PGF(2alpha) on mucin production remains poorly understood. To elucidate the effect and underlying mechanism of PGF(2alpha) on MUC5AC production, we investigated the signal transduction of PGF(2alpha) associated with this effect using normal human tracheobronchial epithelial cells. Our results demonstrated that PGF(2alpha) induces MUC5AC overproduction via a signaling cascade involving protein kinase C, ERK, p90 ribosomal S6 protein kinase, and CREB. The regulation of PGF(2alpha)-induced MUC5AC expression by CREB was further confirmed by cAMP response element-dependent MUC5AC promoter activity and by interaction between CREB and MUC5AC promoter. The abrogation of all downstream signaling activities via suppression of each signaling molecule along the pathway indicates that a single pathway from PGF(2alpha) receptor to CREB is responsible for inducing MUC5AC overproduction. As CREB also mediates mucin overproduction induced by PGE(2) and other inflammatory mediators, our findings have important clinical implications for the management of airway mucus hypersecretion.

Effect of glucocorticoid on the MUC4 gene in nasal polyps

OBJECTIVES/HYPOTHESIS

Among the airway mucin genes, the MUC4 gene is an important gene in its response to inflammatory diseases of the upper airway. However, the expression and regulation of the MUC4 gene in the nasal polyps remains unclear.

STUDY DESIGN

The purpose of this study was to evaluate the expression of MUC4 mRNA and synthesis of mucin glycoprotein in the nasal polyps before and after treatment with a topical steroid in vivo and in vitro.

METHODS

Nasal polyps were obtained from 20 patients with chronic rhinosinusitis and were subsequently cultured. The level of MUC4 mRNA was measured by reverse-transcription polymerase chain reaction, and the amount of the MUC4 mucin glycoprotein was estimated by the enzyme-linked immunosorbent assay method.

RESULTS

The expression of MUC4 mRNA was found to be significantly higher in the nasal polyps than in the inferior turbinate (P < .05). The addition of interleukin (IL)-1 beta and lipopolysaccharide (LPS) increased the expression of MUC4 mRNA and mucin glycoprotein synthesis in cultured nasal polyp epithelial cells. Treatment with glucocorticoid inhibited the expression of MUC4 mRNA in the nasal polyps; it also inhibited the expression of IL-1 beta and LPS-induced MUC4 mRNA and mucin glycoprotein synthesis in cultured nasal polyp epithelial cells. The inhibitory effects of glucocorticoid were restored by treatment with a glucocorticoid receptor antagonist (RU-486).

CONCLUSIONS

These results suggest that the MUC4 gene is expressed in the nasal polyps and that glucocorticoid can control the expression of the MUC4 gene and mucin glycoprotein synthesis.

Regulation of airway mucin gene expression

Mucins are important components that exert a variety of functions in cell-cell interaction, epidermal growth factor receptor signaling, and airways protection. In the conducting airways of the lungs, mucins are the major contributor to the viscoelastic property of mucous secretion, which is the major barrier to trapping inhaled microbial organism, particulates, and oxidative pollutants. The homeostasis of mucin production is an important feature in conducting airways for the maintenance of mucociliary function. Aberrant mucin secretion and accumulation in airway lumen are clinical hallmarks associated with various lung diseases, such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, emphysema, and lung cancer. Among 20 known mucin genes identified, 11 of them have been verified at either the mRNA and/or protein level in airways. The regulation of mucin genes is complicated, as are the mediators and signaling pathways. This review summarizes the current view on the mediators, the signaling pathways, and the transcriptional units that are involved in the regulation of airway mucin gene expression. In addition, we also point out essential features of epigenetic mechanisms for the regulation of these genes.

Mucins in the mucosal barrier to infection

The mucosal tissues of the gastrointestinal, respiratory, reproductive, and urinary tracts, and the surface of the eye present an enormous surface area to the exterior environment. All of these tissues are covered with resident microbial flora, which vary considerably in composition and complexity. Mucosal tissues represent the site of infection or route of access for the majority of viruses, bacteria, yeast, protozoa, and multicellular parasites that cause human disease. Mucin glycoproteins are secreted in large quantities by mucosal epithelia, and cell surface mucins are a prominent feature of the apical glycocalyx of all mucosal epithelia. In this review, we highlight the central role played by mucins in accommodating the resident commensal flora and limiting infectious disease, interplay between underlying innate and adaptive immunity and mucins, and the strategies used by successful mucosal pathogens to subvert or avoid the mucin barrier, with a particular focus on bacteria.

Phosphoinositide 3-kinase signalling in lung disease: leucocytes and beyond

The family of lipid kinases termed phosphoinositide-3-kinase (PI3K) is known to contribute at multiple levels to innate and adaptive immune responses, and is hence an attractive target for drug discovery in inflammatory and autoimmune disease, including respiratory diseases. The development of isoform-selective pharmacological inhibitors, targeted gene manipulation and short interfering RNA (siRNA) target validation have facilitated a better understanding of the role that each member of this family of kinases plays in the physiology and pathology of the respiratory system. In this review, we will evaluate the evidence for the roles of specific PI3K isoforms in the lung and airways, and discuss their potential as targets for novel drug therapies.

Mucin overproduction in chronic inflammatory lung disease

Mucus overproduction and hypersecretion are commonly observed in chronic inflammatory lung disease. Mucins are gel-forming glycoproteins that can be stimulated by a variety of mediators. The present review addresses the mechanisms involved in the upregulation of secreted mucins. Mucin induction by neutrophil elastase, bacteria, cytokines, growth factors, smoke and cystic fibrosis transmembrane conductance regulator malfunction are also discussed.

The inhibitory effect of the leukotriene receptor antagonist on leukotriene D4-induced MUC2/5AC gene expression and mucin secretion in human airway epithelial cells

OBJECTIVES

Mucin gene expression and mucin production are markedly increased in inflammatory airway disorders such as asthma, chronic bronchitis and rhinosinusitis. Cytokines, lipopolysaccharides and other inflammatory mediators such as prostaglandin and leukotriene are related to the secretion and production of mucin. However, the relationship of leukotrienes with mucin genes expression is not clear. The aim of this study is to evaluate MUC2/5AC gene expression and mucin secretion by the leukotriene receptor in human airway epithelial cells.

METHODS

The effect of leukotriene D(4) and the leukotriene receptor antagonist, pranlukast hydrate (ONO-1078) on the regulation of MUC2/5AC gene expression and mucin secretion were observed in human airway NCI-H292 epithelial cells. The mRNA levels of MUC2/5AC and the amount of mucin were determined by reverse transcription-polymerase chain reaction (RT-PCR) and immunoassay.

RESULTS

Leukotriene D(4) upregulated MUC2/5AC gene expression and mucin secretion in a dose dependent pattern. Pranlukast hydrate (ONO-1078, 100 microM) downregulated the leukotriene D(4)-induced MUC2/5AC gene expression and mucin secretion.

CONCLUSION

These results suggest that the leukotriene receptor system is one of the mechanisms related to MUC2/5AC gene expression and mucin secretion in the human airway epithelium.

IL-9 modulated MUC4 gene and glycoprotein expression in airway epithelial cells

Compromised epithelial cell integrity is a common feature associated with chronic lung inflammatory states such as asthma. While epithelial cell damage is largely due to sustained effects of inflammatory mediators localized to airways, the subsequent process of epithelial cell differentiation is attributed to members of the transmembrane receptor tyrosine kinase family called the ErbB's. MUC4, a large molecular weight membrane-bound glycoprotein, has recently been identified as a potential ligand for the ErbB-2 receptor. In this study, we investigated the possible role of interleukin-9 (IL-9), a Th2 cytokine, on MUC4 expression using a lung cancer cell line, NCI-H650. We determined that IL-9 up-regulates MUC4 expression in a time and concentration-dependent fashion. Nuclear run-on assays indicated transcriptional regulation of MUC4 while no post-transcriptional mRNA stabilization was observed by actinomycin D chase experiments. IL-9 also increased MUC4 glycoprotein expression as determined by Western blots using a monoclonal antibody specific for a non-tandem repeat region on ASGP-2 region of MUC4. Furthermore, a JAK3-selective inhibitor 4-(4'-hydroxyphenyl) amino-6, 7-dimethoxyquinazoline (WHI-P131), substantially reduced IL-9-induced MUC4 mRNA expression in a dose-dependent fashion. These results implicate a potential role for IL-9 upon MUC4 expression in human airway epithelial cells.

IL-4 induced MUC4 enhancement in respiratory epithelial cells in vitro is mediated through JAK-3 selective signaling

BACKGROUND

Recent studies have identified MUC4 mucin as a ligand for activation of ErbB2, a receptor tyrosine kinase that modulates epithelial cell proliferation following epithelial damage in airways of asthmatics. In this study, we investigated the potential role of IL-4, one of the Th2 inflammatory cytokines persistent in asthmatic airways, in regulating MUC4 expression using a cell line NCI-H650.

METHODS

Real time PCR analysis was performed to determine concentration and time dependent effects of IL-4 upon MUC4 expression. Nuclear run on experiments were carried out to explore potential transcriptional modulation. Western blotting experiments using a monoclonal antibody specific to ASGP-2 domain of MUC4 were performed to analyze MUC4 glycoprotein levels in plasma membrane fractions. To analyze potential signal transduction cascades, IL-4 treated confluent cultures were co-incubated, separately with a pan-JAK inhibitor, a JAK-3 selective inhibitor or a MEK-1, 2 (MAPK) inhibitor at various concentrations before MUC4 transcript analysis. Corresponding transcription factor activation was tested by western blotting using a monoclonal p-STAT-6 antibody.

RESULTS

MUC4 levels increased in a concentration and time specific fashion reaching peak expression at 2.5 ng/ml and 8 h. Nuclear run on experiments revealed transcriptional enhancement. Corresponding increases in MUC4 glycoprotein levels were observed in plasma membrane fractions. Pan-JAK inhibitor revealed marked reduction in IL-4 stimulated MUC4 levels and JAK3 selective inhibitor down-regulated MUC4 mRNA expression in a concentration-dependent fashion. In accordance with the above observations, STAT-6 activation was detected within 5 minutes of IL-4 stimulus. No effect in MUC4 levels was observed on using a MAPK inhibitor.

CONCLUSION

These observations signify a potential role for IL-4 in MUC4 up-regulation in airway epithelia.

MUC4 mucin expression in human pancreatic tumours is affected by organ environment: the possible role of TGFbeta2

MUC4 is highly expressed in human pancreatic tumours and pancreatic tumour cell lines, but is minimally or not expressed in normal pancreas or chronic pancreatitis. Here, we investigated the aberrant regulation of MUC4 expression in vivo using clonal human pancreatic tumour cells (CD18/HPAF) grown either orthotopically in the pancreas (OT) or ectopically in subcutaneous tissue (SC) in the nude mice. Histological examination of the OT and SC tumours showed moderately differentiated and anaplastic morphology, respectively. The OT tumour cells showed metastases to distant lymph nodes and faster tumour growth (P<0.01) compared to the SC tumours. The MUC4 transcripts in OT tumours were very high compared to the undetectable levels in SC tumours. The SC tumour cells regained their ability to express MUC4 transcripts after in vitro culture. Immunohistochemical analysis using MUC4-specific polyclonal antiserum confirmed the results obtained by Northern blot analysis. Interestingly, the OT tumours showed expression of TGFβ2 compared to no expression in SC, suggesting a possible link between MUC4 and TGFβ2. The MUC4 expression, morphology, and metastasis of human pancreatic tumour cells are regulated by a local host microenvironment. TGFβ2 may serve as an interim regulator of this function.

Airway mucus: its components and function

The airway surface liquid (ASL), often referred to as mucus, is a thin layer of fluid covering the luminal surface of the airway. The major function of mucus is to protect the lung through mucociliary clearance against foreign particles and chemicals entering the lung. The mucus is comprised of water, ions, and various kinds of macromolecules some of which possess the protective functions such as anti-microbial, anti-protease, and anti-oxidant activity. Mucus glycoproteins or mucins are mainly responsible for the viscoelastic property of mucus, which is crucial for the effective mucociliary clearance. There are at least eight mucin genes identified in the human airways, which will potentially generate various kinds of mucin molecules. At present, neither the exact structures of mucin proteins nor their regulation are understood although it seems likely that different types of mucins are involved in different functions and might also be associated with certain airway diseases. The fact that mucins are tightly associated with various macromolecules present in ASL seems to suggest that the defensive role of ASL is determined not only by these individual components but rather by a combination of these components. Collectively, mucins in ASL may be compared to aircraft carriers carrying various types of weapons in defense of airbome enemies.

Interleukin-1beta induces MUC2 and MUC5AC synthesis through cyclooxygenase-2 in NCI-H292 cells

Interleukin-1beta (IL-1beta) has been implicated in the pathogenesis of inflammatory diseases of the airway. In this study, we investigated the regulation of MUC2 and MUC5AC expression and of their regulatory mechanisms through cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)). Cells activated by IL-1beta showed increased COX-2, MUC2, and MUC5AC expressions at both the mRNA and protein levels. Mucin production was blocked by the selective COX-2 inhibitor NS398, and PGE(2) directly induced MUC2 and MUC5AC expression at both the mRNA and protein levels in a dose-dependent manner. These results suggest a role for PGE(2) in IL-1beta-induced mucin synthesis in NCI-H292 cells. To investigate the roles of molecules upstream of COX-2 in mucin regulation, we examined the role of mitogen-activated protein kinases (MAPKs). Cells activated by IL-1beta showed increased extracellular signal-regulated kinase (ERK)1/2 and p38 phosphorylation, and IL-1beta-induced MUC2 and MUC5AC production was blocked by the ERK pathway inhibitor PD98059 or the p38 inhibitor SB203580. The inhibition of both MAPKs reduced IL-1beta-induced COX-2 expression and PGE(2) synthesis. Furthermore, the addition of PGE(2) to cells overcame the inhibitory effects of both MAPK inhibitors in IL-1beta-induced mucin production. These results indicate that in human pulmonary epithelial cells, IL-1beta activates ERK or p38 to induce COX-2 production, which in turn induces MUC2 and MUC5AC production.

Induction of MUC2 and MUC5AC mucins by factors of the epidermal growth factor (EGF) family is mediated by EGF receptor/Ras/Raf/extracellular signal-regulated kinase cascade and Sp1

The 11p15 mucin genes (MUC2, MUC5AC, MUC5B and MUC6) possess a cell-specific pattern of expression in normal lung that is altered during carcinogenesis. Growth factors of the epidermal growth factor family are known to target key genes that in turn may affect the homeostasis of lung mucosae. Our aim was to study the regulation of the 11p15 mucin genes both at the promoter and protein levels to assess whether their altered expression may represent a key event during lung carcinogenesis. Studies were performed in the mucoepidermoid NCI-H292 lung cancer cell line. Cell treatment with epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), or tumor necrosis factor alpha (TNF-alpha) resulted in a dramatic increase of MUC2 and MUC5AC mRNAs levels, promoter activity, and apomucin expression, whereas those of MUC5B and MUC6 were unchanged. pGL3 deletion mutants of MUC2, MUC5AC, and MUC5B promoters were constructed and used in transient transfection assays to characterize EGF- and TGF-alpha-responsive regulatory regions within the promoters. They were located in the -2627/-2097 and -202/-1 regions of MUC2 and MUC5AC promoters, respectively. Finally, we demonstrate that transcription factor Sp1 not only binds and activates MUC2 and MUC5AC promoters but also participates to their EGF- and TGF-alpha-mediated up-regulation. We also show that Sp3 is a strong inhibitor of 11p15 mucin gene transcription. In conclusion, MUC2 and MUC5AC are two target genes of EGFR ligands in lung cancer cells, and up-regulation of these two genes goes through concomitant activation of the EGFR/Ras/Raf/Extracellular Signal-regulated Kinase-signaling pathway and Sp1 binding to their promoters.

Mucin apoprotein expression in COPD

Mucins, which are complex glycoproteins that provide the viscoelastic properties of mucus that are essential for the protection of the airways, are characterized by a variable-number tandem repeats (VNTR) region that may undergo alternate splicing during transcription. Such transcripts may yield multiple proteins via diverse post-translational modifications involving glycosylation (within each VNTR). Fifteen distinct mucin genes have been identified, with several mapping to chromosomal clusters (ie, 7q22 and 11p15.5), possibly having evolved by gene duplication. The deduced protein sequences can be subdivided into both membrane-associated mucins and secreted mucins. Membrane-associated mucins consist of cytoplasmic, transmembrane, and extracellular domains. The membrane-associated mucins MUC1, MUC4, and MUC11 have been localized to the lung. In addition to VNTRs, secreted mucins possess repeated cysteine-rich D-domains (which are important in polymerization). Secreted mucins that are localized to the lung include MUC2 (in cells with and without secretory granules), MUC5AC (in surface and submucosal mucous cells), MUC5B and MUC8 (in submucosal mucous cells), and MUC7 (in submucosal serous cells). Currently, little is known about the regulation of mucins in COPD patients. Recent studies with acrolein and cigarette smoke have suggested that MUC5AC is inducible (accompanied by epidermal growth factor [EGF] ligand formation and the activation of EGF receptor-dependent pathways), whereas MUC5B is constitutively expressed (increasing through gland enlargement). Similarly, little is known about the genetic determinants that control mucus hypersecretion, but preliminary findings in animal models suggest that intrastrain differences in acrolein-induced mucin formation are amenable to genetic analysis. As our understanding of the functional genomics of mucin biology increases, further clinical targets and therapeutic strategies are likely to emerge.