Human bronchial epithelial cells differentiate to 3D glandular acini on basement membrane matrix

To create a model system that investigates mechanisms resulting in hyperplasia and hypertrophy of respiratory tract submucosal glands, we developed an in vitro three-dimensional (3D) system wherein normal human bronchial epithelial (HBE) cells differentiated into glandular acini when grown on a basement membrane matrix. The differentiation of primary HBE cells into glandular acini was monitored temporally by light microscopy. Apoptosis-induced lumen formation was observed by immunofluorescence analysis. The acinar cells expressed and secreted MUC5B mucin (marker for glandular mucous cells) and lysozyme, lactoferrin, and zinc-α2-glycoprotein (markers for glandular serous cells) at Day 22. β-Tubulin IV, a marker for ciliated cells, was not detected. Expression of mucous and serous cell markers in HBE glandular acini demonstrated that HBE cells grown on a basement membrane matrix differentiated into acini that exhibit molecular characteristics of respiratory tract glandular acinar cells. Inhibition studies with neutralizing antibodies resulted in a marked decrease in size of the spheroids at Day 7, demonstrating that laminin (a major component of the basement membrane matrix), the cell surface receptor integrin α6, and the cell junction marker E-cadherin have functional roles in HBE acinar morphogenesis. No significant variability was detected in the average size of glandular acini formed by HBE cells from two normal individuals. These results demonstrated that this in vitro model system is reproducible, stable, and potentially useful for studies of glandular differentiation and hyperplasia.

Asthmatic airway epithelium is intrinsically inflammatory and mitotically dyssynchronous

Asthma is an inflammatory condition for which anti-inflammatory glucocorticoids are the standard of care. However, similar efficacy has not been shown for agents targeting inflammatory cells and pathways. This suggests a noninflammatory cell contributor (e.g., epithelium) to asthmatic inflammation. Herein, we sought to define the intrinsic and glucocorticoid-affected properties of asthmatic airway epithelium compared with normal epithelium. Human primary differentiated normal and asthmatic airway epithelia were cultured in glucocorticoid-free medium beginning at -48 hours. They were pulsed with dexamethasone (20 nM) or vehicle for 2 hours at -26, -2, +22, and +46 hours. Cultures were mechanically scrape-wounded at 0 hours and exposed continuously to bromodeoxyuridine (BrdU). Cytokine secretions were analyzed using cytometric bead assays. Wound regeneration/mitosis was analyzed by microscopy and flow cytometry. Quiescent normal (n = 3) and asthmatic (n = 6) epithelia showed similar minimal inflammatory cytokine secretion and mitotic indices. After wounding, asthmatic epithelia secreted more basolateral TGF-β1, IL-10, IL-13, and IL-1β (P < 0.05) and regenerated less efficiently than normal epithelia (+48 h wound area reduction = [mean ± SEM] 50.2 ± 7.5% versus 78.6 ± 7.7%; P = 0.02). Asthmatic epithelia showed 40% fewer BrdU(+) cells at +48 hours (0.32 ± 0.05% versus 0.56 ± 0.07% of total cells; P = 0.03), and those cells were more dyssynchronously distributed along the cell cycle (52 ± 10, 25 ± 4, 23 ± 7% for G1/G0, S, and G2/M, respectively) than normal epithelia (71 ± 1, 12 ± 2, and 17 ± 2% for G1/G0, S, and G2/M, respectively). Dexamethasone pulses improved asthmatic epithelial inflammation and regeneration/mitosis. In summary, we show that inflammatory/fibrogenic cytokine secretions are correlated with dyssynchronous mitosis upon injury. Intermittent glucocorticoids simultaneously decreased epithelial cytokine secretions and resynchronized mitosis. These data, generated in an airway model lacking inflammatory cells, support the concept that epithelium contributes to asthmatic inflammation.

Glandular gene expression of sinus mucosa in chronic rhinosinusitis with and without cystic fibrosis

Secretory cells in submucosal glands (SMGs) secrete antibacterial proteins and mucin glycoproteins into the apical lumen of the respiratory tract, and these are critical for innate immune mucosal integrity. Glandular hyperplasia is manifested in diseases with obstructive respiratory pathologies associated with mucous hypersecretion, and is predominant in the sinus mucosa of patients with chronic rhinosinusitis (CRS), cystic fibrosis (CF), and clinical symptoms of CRS. To gain insights into the molecular basis of SMG hyperplasia in CRS, gene expression microarray analyses were performed to identify the differences in global and specific gene expression in the sinus mucosa of control, CRS, and CRS/CF patients. A marked up-regulation of 11 glandular-associated genes in CRS and CRS/CF sinus mucosa was evident. The RNA and protein expressions of the four most highly up-regulated genes (DSG3, KRT14, PTHLH, and OTX2) were evaluated. An increased expression of DSG3, KRT14, and PTHLH was demonstrated at the mRNA and protein levels in both CRS and CRS/CF sinus mucosa, whereas the increased expression of OTX2 was evident only for CRS/CF sinus mucosa, implicating OTX2 as a CF-specific gene. Immunofluorescence analysis localized DSG3, PTHLH, and OTX2 to serous cells, and KRT14 to myoepithelial cells, in SMGs. Because glandular hyperplasia is a central histologic feature of CRS, the identification of overexpressed glandular genes in the sinus mucosa lays the groundwork for future studies of glandular hyperplasia, and may ultimately lead to the development of novel treatments for mucous hypersecretion in patients with CRS.

Increased poly(ADP-ribose) polymerase (PARP)-1 expression and activity are associated with inflammation but not goblet cell metaplasia in murine models of allergen-induced airway inflammation

Inflammation plays a key role in lung injury and in the pathogenesis of asthma. Two murine models of allergic airway inflammation-sensitization and challenge to ovalbumin (OVA) and intratracheal exposure to interleukin-13 (IL13)-were used to evaluate the expression of poly(ADP-ribose) polymerase-1 (PARP-1) in allergic airway inflammation. Inflammation is prominent in OVA-induced allergic asthma, but this inflammation is greatly reduced by a PARP-1 inhibitor and almost eliminated when PARP-1 knockout mice are subjected to the OVA model. The present study temporally evaluated PARP-1 protein expression, localization, and activity, as well as inflammation and goblet cell metaplasia (GCM), in murine lungs following a single OVA challenge or IL13 exposure. Following OVA challenge PARP-1 protein expression and activity were greatly increased, being maximal at 3 to 5 days following OVA exposure and beginning to decrease by day 8. These changes correlated with the timing and degree of inflammation and GCM. In contrast, PARP-1 protein or activity did not change following single IL13 exposure, though GCM was manifested without inflammation. This study demonstrates that both PARP-1 protein and activity are increased by allergen-activated inflammatory mediators, excluding IL13, and that PARP-1 increase does not appear necessary for GCM, one of the characteristic markers of allergic airway inflammation in murine models.

MUC5B Is the predominant mucin glycoprotein in chronic otitis media fluid

Chronic otitis media (COM), e.g. "glue" ear is characterized by middle ear effusion and conductive hearing loss. Although mucous glycoproteins (mucins), which contribute to increased effusion viscosity, have been analyzed in ear tissue specimens, no studies have been reported that characterize the molecular identity of secreted mucin proteins present in actual middle ear fluid. For this study, effusions from children with COM undergoing myringotomy at Children's National Medical Center, Washington, DC were collected. These were solubilized and gel fractionated, and the protein content was identified using a liquid chromatography tandem mass spectrometry (LC-MS/MS) proteomics approach. Western blot analyses with mucin specific antibodies and densitometry were performed to validate the mass spectrometry findings. LC-MS/MS results identified mucin MUC5B by >26 unique peptides in six of six middle ear effusion samples, whereas mucin MUC5AC was only identified in one of six middle ear effusions. These findings were validated by Western blot performed on the same six and on an additional 11 separate samples where densitometry revealed on average a 6.4-fold increased signal in MUC5B when compared with MUC5AC (p = 0.0009). In summary, although both MUC5AC and MUC5B mucins are detected in middle ear effusions, MUC5B seems to be predominant mucin present in COM secretions.

Cigarette smoke alters tissue inhibitor of metalloproteinase 1 and matrix metalloproteinase 9 levels in the basolateral secretions of human asthmatic bronchial epithelium in vitro

BACKGROUND

Asthma, a major cause of chronic lung disease worldwide, has increased in prevalence in all age and ethnic groups, particularly in urban areas where cigarette smoking is common. Cigarette smoke (CS) significantly impacts the development of asthma and is strongly associated with increased asthma-related morbidity.

PURPOSE

To evaluate bioinformatic analyses predicting that CS would alter expression of tissue inhibitor of metalloproteinase (TIMP) 1 and matrix metalloproteinase (MMP) 9 in asthmatic epithelium.

METHODS

Primary differentiated normal (n = 4) and asthmatic (n = 4) human respiratory epithelia on collagen-coated Transwells at air-liquid interface were exposed for 1 hour to CS condensate (CSC) or hydrogen peroxide (H2O2). Tissue inhibitor of metalloproteinase 1 and MMP-9 protein levels were measured at 24 hours by enzyme-linked immunosorbent assay in cell lysates and in apical and basolateral secretions.

RESULTS

Tissue inhibitor of metalloproteinase 1 and MMP-9 levels in the apical secretions of normal and asthmatic epithelia were unchanged after exposure to CSC and H2O2. However, CSC increased TIMP-1 levels in the basolateral secretions of both normal and asthmatic epithelia, but decreased MMP-9 levels only in asthmatic basolateral secretions, resulting in a 2.5-fold lower MMP-9/TIMP-1 ratio that corresponded to decreased MMP-9 activity in CS-exposed asthmatic basolateral secretions.

CONCLUSIONS

These data validate our prior bioinformatic analyses predicting that TIMP-1 plays a role in the stress response to CS and indicate that asthmatics exposed to CS may be more susceptible to MMP-9-mediated airway remodeling. This is in agreement with the current paradigm that a reduction in the MMP-9/TIMP-1 ratio is a milieu that favors subepithelial airway remodeling in chronic asthma.

Delineation of a gene network underlying the pulmonary response to oxidative stress in asthma

Cigarette smoke exposure induces a respiratory epithelial response that is mediated in part by oxidative stress. The contribution of oxidative stress to cigarette smoke-induced responses in asthmatic respiratory epithelium is not well understood. We sought to increase this understanding by employing data integration and systems biology approaches to publicly available microarray data deposited over the last several years. In this study, we analyzed 14 publicly available asthma- or tobacco-relevant data series and found 4 (2 mice and 2 human) that fulfilled adequate signal/noise thresholds using unsupervised clustering and F test statistics. Using significance filters and a 4-way Venn diagram approach, we identified 26 overlapping genes in the epithelial transcriptional stress response to cigarette smoke and asthma. This test set corresponded to a 26-member gene/protein network containing 18 members that were highly regulated in a fifth data series of direct lung oxidative stress. Of those network members, 2 stood out (ie, tissue inhibitor of metalloproteinase 1 and thrombospondin 1) owing to central location within the network and marked up-regulation sustained at later times in response to oxidative stress. These analyses identified key relationships and primary hypothetical targets for future studies of cigarette smoke-induced oxidative stress in asthma.

Delineation of a gene network underlying the pulmonary response to oxidative stress in asthma

Cigarette smoke exposure induces a respiratory epithelial response that is mediated in part by oxidative stress. The contribution of oxidative stress to cigarette smoke-induced responses in asthmatic respiratory epithelium is not well understood. We sought to increase this understanding by employing data integration and systems biology approaches to publicly available microarray data deposited over the last several years. In this study, we analyzed 14 publicly available asthma- or tobacco-relevant data series and found 4 (2 mice and 2 human) that fulfilled adequate signal/noise thresholds using unsupervised clustering and F test statistics. Using significance filters and a 4-way Venn diagram approach, we identified 26 overlapping genes in the epithelial transcriptional stress response to cigarette smoke and asthma. This test set corresponded to a 26-member gene/protein network containing 18 members that were highly regulated in a fifth data series of direct lung oxidative stress. Of those network members, 2 stood out (ie, tissue inhibitor of metalloproteinase 1 and thrombospondin 1) owing to central location within the network and marked up-regulation sustained at later times in response to oxidative stress. These analyses identified key relationships and primary hypothetical targets for future studies of cigarette smoke-induced oxidative stress in asthma.

Expression profiling of inflammatory mediators in pediatric sinus mucosa

OBJECTIVE

To evaluate gene expression by microarray analyses of inflammatory mediators in the sinus mucosa of children with and without chronic rhinosinusitis (CRS).

DESIGN

Prospective molecular genetics analysis.

SETTING

Children's National Medical Center, Washington, DC.

SUBJECTS

Eleven patients with CRS who underwent endoscopic sinus surgery and 10 control children who underwent craniofacial resection or neurosurgical procedures.

MAIN OUTCOME MEASURES

Gene expression levels of sinus tissue from 6 patients with CRS and 6 controls and messenger RNA expression levels of upregulated inflammatory/immune response genes, as well as cytokines of interest, determined by quantitative reverse transcription-polymerase chain reaction.

RESULTS

Gene expression using the Plier algorithm yielded the most consistent grouping of samples: 96 genes were significantly upregulated more than 2-fold, and 123 genes were downregulated by at least 50% in the CRS sinus tissues compared with controls (P < .05). GeneSpring analysis demonstrated significant changes in several ontology categories in the CRS samples, including inflammatory/immune response genes. The chemokines CXCL13 and CXCL5, serum amyloid A, serpin B4, and defensin beta1 were highly upregulated (> or =5-fold). Increased expression of these genes was validated by quantitative reverse transcription-polymerase chain reaction in an independent set of tissues. Expression levels of interleukins 5, 6, and 8 were similar in both cohorts; these results were validated by reverse transcription-polymerase chain reaction.

CONCLUSIONS

Microarray analyses of sinus mucosa in children with CRS showed an increased expression of inflammatory genes involved in innate and adaptive immune systems. This technology can be successfully used to identify genes implicated in the pathogenesis of pediatric CRS.

Localization and expression of MUC5B and MUC7 mucins in pediatric sinus mucosa

OBJECTIVES

The purpose of this study was to analyze the secretory cell population and distribution of MUC5B and MUC7 mucins in the sinus mucosa of pediatric patients with and without chronic rhinosinusitis (CRS).

METHODS

Sinus mucosal specimens were collected at surgery in a pediatric tertiary care facility. Histologic, immunohistochemical, and morphometric analyses were performed on sinus mucosa of 20 children with CRS and 7 children without CRS.

RESULTS

A significant increase in the area of submucosal glands was evident in the sinus mucosa of children with CRS as compared to controls. MUC5B and MUC7 mucins were expressed in the submucosal glands, as well as in goblet cells, in the sinus mucosa of both populations. No differences in MUC5B or MUC7 expression were observed when mucin expression was normalized to glandular area.

CONCLUSIONS

Children with CRS have an increased number of submucosal glands, indicating that glandular mucins contribute to mucus overproduction in CRS. MUC5B and MUC7 mucins, which have previously been considered only glandular mucins, are also expressed in goblet cells in the sinus mucosa.

Immunohistochemical analyses of MUC5AC mucin expression in sinus mucosa of children with sinusitis and controls

OBJECTIVES

The purpose of this study was to analyze MUC5AC protein expression in sinus mucosal specimens of children with and without chronic sinusitis.

METHODS

Morphometric, histologic, and immunohistochemical analyses were carried out on sinus mucosa of 7 children with chronic sinusitis and 6 children without sinusitis.

RESULTS

MUC5AC protein was expressed in a subset of goblet cells in the surface epithelium, but not in the submucosal glands in either pediatric population. The number of goblet cells that expressed MUC5AC mucin was not significantly different in patients with and without chronic sinusitis. All specimens had similar numbers of goblet cells in the surface epithelium.

CONCLUSIONS

The data demonstrate that neither goblet cell hyperplasia nor increased MUC5AC expression occurs in the sinus mucosa of children with chronic sinusitis. This suggests that in contrast to asthma, in which goblet cell hyperplasia is present in the lower respiratory tract, mucus hypersecretion in pediatric chronic sinusitis may involve other secretory cells, eg, submucosal glandular cells, and mucins secreted by these glandular cells.

Regulation of mucin genes in chronic inflammatory airway diseases

In this review, we summarize work over the past 15 years on mucin gene expression and regulation in the lung, as well as how mucin gene expression is altered in chronic lung diseases. This field owes a great debt to Carol Basbaum for her pioneering work in dissecting signaling pathways regulating mucin gene expression and for her tremendous energy in promoting the importance of understanding the basic pathogenic mechanisms that drive mucus overproduction in cystic fibrosis, chronic obstructive pulmonary disease, and asthma.

Dexamethasone-mediated repression of MUC5AC gene expression in human lung epithelial cells

Glucocorticoids regulate gene expression via binding of the ligand-activated glucocorticoid receptor (GR) to glucocorticoid-responsive elements (GRE) in target gene promoters. The MUC5AC gene, which encodes the protein backbone of an abundant secreted airway mucin, has several putative GRE cis-elements in its 5' sequence. Mechanism(s) whereby glucocorticoids regulate mucin genes have not previously been described. In this study, the glucocorticoid dexamethasone (Dex) decreased MUC5AC mRNA abundance in A549 and NCI-H292 cell lines and primary differentiated normal bronchial epithelial cells by 50-80%, suggesting a common mechanism of MUC5AC gene repression in human lung epithelial cells. Kinetic analyses showed that MUC5AC mRNA was not significantly decreased until 6 h after Dex exposure, and that nuclear translocation of GR was biphasic, suggesting that Dex-mediated cis-repression of MUC5AC gene expression was a delayed response of GR translocation. Transfection analyses demonstrated that Dex transcriptionally repressed the MUC5AC promoter. Electrophoretic mobility shift assays with wild-type and mutant oligonucleotide probes showed that GR bound to two GRE cis-sites (nucleotides -930 to -912 and -369 to -351) in the MUC5AC promoter. Analyses of mutated MUC5AC promoter constructs demonstrated that NF-kappaB cis-sites were not involved in Dex-mediated repression of MUC5AC. Dex did not alter mRNA stability of MUC5AC transcripts. Taken together, the data indicate that Dex transcriptionally mediates repression of MUC5AC gene expression in human lung epithelial cells at quiescent states after binding of GR to one or more GRE cis-elements in the MUC5AC promoter.

Temporal analysis of goblet cells and mucin gene expression in murine models of allergic asthma

In murine models of allergic asthma, mice repeatedly exposed to allergens or interleukin (IL)13 have numerous goblet cells in their airway epithelium, in contrast to healthy naïve mice. This study evaluated whether a single airway exposure of ovalbumin or IL13 would produce goblet cell metaplasia. Following ovalbumin challenge, airway goblet cells were present by 1 day, increased further by day 2 and day 3, and decreased by day 8. Following IL13 exposure, some goblet cells were detected at 6 hours and increased by 18 and 48 hours. Goblet transition cells, which are morphologically but not histologically similar to goblet cells, were observed at 6 and 18 hours following IL13 exposure and day 1 following ovalbumin challenge. Increased Muc5ac and Muc2 mRNA expression occurred following ovalbumin or IL13, but not saline, exposure. Mucin transcripts were localized to goblet cells in the surface airway epithelium. Muc5ac protein was expressed in some goblet transition and goblet cells. Overall, these data demonstrated that a single airway exposure to ovalbumin or IL13 is sufficient to generate goblet cell metaplasia and thus increase mucin gene expression in two strains of mice.

Model systems for investigating mucin gene expression in airway diseases

Overproduction of mucus and of mucin glycoproteins and goblet cell hyperplasia occurs in chronic obstructive airway diseases, including asthma and cystic fibrosis. Mucus overproduction results from alterations in several cellular processes, including altered regulation of airway mucin genes on exposure to environmental and infectious agents and to inflammatory mediators. Seven of the nine identified MUC genes (which encode the protein backbone of mucins) are normally expressed in human respiratory tract tissues. Several inflammatory mediators have now been shown to regulate expression of MUC2, MUC5AC, and MUC5B genes. Importantly, mucin gene expression can be regulated both transcriptionally and posttranscriptionally. Current information on airway mucin gene expression is summarized in this review along with an overview of airway epithelial model systems. In vitro model systems include airway epithelial carcinoma cell lines and primary normal human bronchial epithelial (NHBE) cells. In vivo systems include human respiratory tract tissues and rodent airways. Our laboratory has begun to investigate the role of cytokines on mucin gene expression in vitro and in vivo and on goblet cell metaplasia in vivo. Because cytokines can alter cell proliferation, we characterized the effect of interleukin (IL)-4 and IL-13 on the proliferation of NHBE cells and three human lung carcinoma cell lines--A549, NCI-H292, and Calu-3--that are frequently used for analyses of airway mucin gene expression. Both IL-4 and IL-13 had cell-specific effects. They increased proliferation moderately (1.2-3.0-fold) in NHBE and Calu-3 cells, but markedly inhibited proliferation of A549 cells in a dose-dependent manner. IL-4 increased proliferation of NCI-H292 cells moderately, although IL-13 had no significant effect. We also examined the role of IL-13 and IL-4 on MUC5AC messenger RNA (mRNA) expression in A549, Calu-3, and H292 cell lines and did not observe any significant effect. However, we recently showed an increase in Muc-5ac mRNA and protein expression in a murine model of ovalbumin-induced allergic asthma and in murine airways when IL-13 was delivered intranasally (Alimam, N.Z., et al. Am J. Respir. Cell Mol. Biol. 22:253--260). Thus, we speculate that IL-13 plays a role in the differentiation of murine airway epithelial cells into goblet cells, which then express Muc-5ac mRNA. A detailed analysis of the role of cytokines in airway cell differentiation and mucin gene expression both in vitro and in vivo is required to elucidate the roles of mucins in airway health and diseases. Identification of Muc-5ac as a major gene and gene product in goblet cell metaplasia should facilitate delineation of the molecular mechanisms underlying the induction and reversal of airway goblet cell metaplasia and goblet cell hyperplasia.

Muc-5/5ac mucin messenger RNA and protein expression is a marker of goblet cell metaplasia in murine airways

Airway inflammation, hyperreactivity, increased number of goblet cells, and mucus overproduction characterize asthma. Respiratory challenge with ovalbumin (OVA) of sensitized mice has been shown by several laboratories to cause pulmonary pathology similar to that observed in human allergic asthma. Recently, interleukin (IL)-13 has been shown to be a central mediator in this process. Because the airways of healthy mice have few, if any, mucus-producing cells, an increase in the number of these cells likely reflects induction of mucin-gene expression. The purpose of this study was to identify mucin genes induced as a result of airway goblet-cell metaplasia (GCM) in mice sensitized and challenged with OVA or in mice treated with IL-13 alone. BALB/c mice were sensitized by intraperitoneal injection (Days 0, 4, 7, 11, and 14) and intranasal instillation (Day 14) of 100 microg of OVA in saline, and then challenged by intranasal instillation (Days 25, 26, and 27) of the same. IL-13-treated mice received 5 microg of IL-13 by intranasal instillation on three consecutive days. Control mice were given saline alone. All mice were studied 24 h after the last challenge. Histologic analysis of the lungs revealed both a striking peribronchial and perivascular lymphocytic and eosinophilic inflammation and airway GCM in OVA-treated mice, and also airway GCM without inflammation in IL-13-treated mice. Northern blot analysis of lung RNA demonstrated (1) expression of Muc-5/5ac messenger RNA (mRNA) in OVA-treated and IL-13-treated mice, but not in control mice; (2) expression of Muc-1 mRNA at comparable levels in all mice regardless of treatment; and (3) no expression of Muc-2 or Muc-3 mRNA in control or treated mice. Western blot analysis demonstrated the expression of Muc-5/5ac protein (both apomucin and glycosylated mucin) in lung lysates of OVA-treated (but not control) mice, and also the expression of Muc-5/5ac mucins in the bronchoalveolar lavage fluid of OVA-treated and IL-13-treated mice. These findings demonstrate that airway GCM is associated with the induction of pulmonary expression of Muc-5/5ac mRNA and mucin in murine models of allergic asthma.

Neutrophil elastase increases MUC5AC mRNA and protein expression in respiratory epithelial cells

Chronic neutrophil-predominant inflammation and hypersecretion of mucus are common pathophysiological features of cystic fibrosis, chronic bronchitis, and viral- or pollution-triggered asthma. Neutrophils release elastase, a serine protease, that causes increased mucin production and secretion. The molecular mechanisms of elastase-induced mucin production are unknown. We hypothesized that as part of this mechanism, elastase upregulates expression of a major respiratory mucin gene, MUC5AC. A549, a human lung carcinoma cell line that expresses MUC5AC mRNA and protein, and normal human bronchial epithelial cells in an air-liquid interface culture were stimulated with neutrophil elastase. Neutrophil elastase increased MUC5AC mRNA levels in a time-dependent manner in both cell culture systems. Neutrophil elastase treatment also increased MUC5AC protein levels in A549 cells. The mechanism of MUC5AC gene regulation by elastase was determined in A549 cells. The induction of MUC5AC gene expression required serine protease activity; other classes of proteases had no effect on MUC5AC gene expression. Neutrophil elastase increased MUC5AC mRNA levels by enhancing mRNA stability. This is the first report of mucin gene regulation by this mechanism.

Respiratory carcinoma cell lines. MUC genes and glycoconjugates

Lung carcinoma cell lines are being used in many laboratories to study various airway epithelial functions, including mucin gene expression. To identify model systems for investigating regulation of MUC5/5AC gene expression and secretion of MUC5/5AC mucins in airway epithelial cells, we evaluated the expression of several mucin genes in six carcinoma cell lines of respiratory tract origin. RNA was extracted from A549, Calu-3, NCI H292, Calu-6, RPMI 2650, and A-427 cells; MUC1, MUC2, MUC4, MUC5/5AC, and MUC5B messenger RNA (mRNA) expression was determined. By Northern analyses, all cell lines expressed MUC1 mRNA, whereas MUC2 mRNA was not detectable in any of the cell lines. RPMI 2650 cell lines expressed only MUC1 mRNA. NCI-H292 cells expressed MUC4 and low levels of MUC5/5AC mRNA. Calu-3 and A549 cells expressed MUC5/5AC mRNA; A549 cells also expressed MUC5B mRNA. Glycoconjugates secreted by lung carcinoma cells were also examined. By wheat germ lectin analysis, Calu-3, H292, and A549 cells secreted high molecular weight glycoproteins having N-acetylglucosamine and/or sialic acid moieties. Western blot analyses with an anti-MUC5:TR-3A antibody demonstrated that Calu-3 and A549 cells secreted MUC5/5AC mucins. All six carcinoma cell lines secreted large, radiolabeled, sulfated macromolecules; the majority were proteoglycans that were digested by hyaluronidase. However, Calu-3 cells also secreted sulfated high molecular-weight glycoproteins that were immunoprecipitated by anti-MUC5:TR-3A antibody. These studies demonstrated that Calu-3 and A549 cell lines expressed high and moderate amounts of MUC5/5AC mRNA and MUC5/5AC mucins, whereas H292 cells expressed lesser amounts. These cell lines should prove useful for studies of MUC5/5AC gene expression and MUC5/5AC biosynthesis, trafficking, and secretions in airway epithelial cells.

Mucin gene expression (MUC1, MUC2, and MUC5/5AC) in nasal epithelial cells of cystic fibrosis, allergic rhinitis, and normal individuals

The early pathogenic events in cystic fibrosis (CF) include colonization of Pseudomonas in the lung, airway inflammation, and mucus hypersecretion with airway obstruction. The primary mechanisms leading to chronic infection and inflammation are not well understood. One possible explanation for this cascade of events is increased or altered expression of one or more mucin (MUC) genes by CF cells in the respiratory tract. We compared expression levels of three mucin genes, MUC1, MUC2, and MUC5/5AC, known to be expressed in the respiratory tract of CF, allergic rhinitis, and normal individuals. Mucin transcript levels in nasal epithelial cells free from inflammation were quantitated by an MUC mRNA slot-blot method. This study revealed three major findings: (1) MUC5/5AC mRNA was expressed at five- to tenfold greater levels than MUC2 or MUC1 for all subjects. (2) MUC2 mRNA levels were similar among all subject groups. (3) In CF subjects, there was a trend toward reduced MUC5/5AC expression. When normalized to the levels of MUC2 expression in individual specimens, MUC5/5AC expression was reduced significantly in CF cells compared with normal cells. These data suggest that mucin gene expression is altered in noninflamed CF nasal cells.

Factitious post traumatic stress disorder: a case report

A 24-year-old man presented with a convincing history of Post Traumatic Stress Disorder (PTSD). He claimed to be the victim of a widely publicized 'human bomb' attack by the IRA in Northern Ireland when he was serving with the armed forces. Psychometric tests for PTSD confirmed his symptoms. A subsequent check of public and military records demonstrated that he was a serviceman at that time, but showed conclusively that he could not have been present at the terrorist incident.