Mild and moderate asthma is associated with airway goblet cell hyperplasia and abnormalities in mucin gene expression

Lung maturity in esophageal atresia: Experimental and clinical study

INTRODUCTION

Esophageal atresia and tracheoesophageal fistula (EA-TEF) survivors suffer respiratory morbidity of unclear pathogenesis. Defective lung morphogenesis has been described in the rat model. This study examined fetal lung growth and maturity in rats and patients with EA-TEF.

METHODS

Pregnant rats received either adriamycin or vehicle. Control and adriamycin-exposed lungs, with and without EA-TEF, were weighed and processed for RT-PCR, DNA quantification, immunofluorescence and immunoblot analysis of TTF1, VEGF, Sp-B, and α-sma. Twenty human lungs were also processed for immunofluorescence and Alcian-blue staining.

RESULTS

Lungs from fetuses with EA-TEF (E21) showed decreased total DNA; FGF7 and TTF1 mRNA expressions were upregulated at E15 and E18, respectively. Protein expression and immunofluorescent distribution of maturity markers were similar. Lungs from stillborns with EA-TEF showed decreased epithelial expression of Sp-B and VEGF whereas those from newborns tended to have less Sp-B and more VEGF and mucous glands.

DISCUSSION

The lungs of rats with EA-TEF were hypoplastic but achieved near-normal maturity. Stillborns with EA-TEF exhibited an apparently disturbed differentiation of the airway epithelium. Newborns with EA-TEF demonstrated subtle differences in the expression of differentiation markers, and increased number of mucous glands that could influence postnatal respiratory adaptation and explain some respiratory symptoms of EA-TEF survivors.

Epinephrine Activation of the β2-Adrenoceptor Is Required for IL-13-Induced Mucin Production in Human Bronchial Epithelial Cells

Mucus hypersecretion by airway epithelium is a hallmark of inflammation in allergic asthma and results in airway narrowing and obstruction. Others have shown that administration a T_H2 cytokine, IL-13 is sufficient to cause mucus hypersecretion in vivo and in vitro. Asthma therapy often utilizes β₂-adrenoceptor (β₂AR) agonists, which are effective acutely as bronchodilators, however chronic use may lead to a worsening of asthma symptoms. In this study, we asked whether β₂AR signaling in normal human airway epithelial (NHBE) cells affected mucin production in response to IL-13. This cytokine markedly increased mucin production, but only in the presence of epinephrine. Mucin production was blocked by ICI-118,551, a preferential β₂AR antagonist, but not by CGP-20712A, a preferential β₁AR antagonist. Constitutive β₂AR activity was not sufficient for IL-13 induced mucin production and β-agonist-induced signaling is required. A clinically important long-acting β-agonist, formoterol, was as effective as epinephrine in potentiating IL-13 induced MUC5AC transcription. IL-13 induced mucin production in the presence of epinephrine was significantly reduced by treatment with selective inhibitors of ERK1/2 (FR180204), p38 (SB203580) and JNK (SP600125). Replacement of epinephrine with forskolin + IBMX resulted in a marked increase in mucin production in NHBE cells in response to IL-13, and treatment with the inhibitory cAMP analogue Rp-cAMPS decreased mucin levels induced by epinephrine + IL-13. Our findings suggest that β₂AR signaling is required for mucin production in response to IL-13, and that mitogen activated protein kinases and cAMP are necessary for this effect. These data lend support to the notion that β₂AR-agonists may contribute to asthma exacerbations by increasing mucin production via activation of β₂ARs on epithelial cells.

Induction of MUC5AC mucin expression by histamine through the activation of its core promoter region

CONCLUSION

This study provides evidence that histamine induced MUC5AC mRNA expression through the activation of the core region of its promoter. It may also help in approaching new therapeutic strategies in airway mucins hypersecretory diseases.

OBJECTIVE

Mucin hypersecretion characterizes several respiratory diseases. Production of MUC5AC, a major gel forming mucin secreted by airway epithelia, can be induced by various inflammatory mediators. Histamine is associated with MUC5AC up-regulation during the early phase of allergic respiratory diseases. The goal of the present study was to identify whether histamine may induce MUC5AC gene expression both at mRNA and protein levels and to elucidate its mechanism.

METHODS

Guinea pigs were sensitized and challenged with dermatophagoides farinae (Der f) extract. Human lung mucoepidermoid carcinoma cell line (NCI-H292) was used. The regulatory mechanism of MUC5AC by histamine and H1R was investigated using RT-PCR, immunofluorescence, and MUC5AC promoter-driven luciferase reporter assay.

RESULTS

The MUC5AC expression levels were increased by histamine treatment in either nasal tissues of Der f challenged guinea pigs or NCI-H292 cells, whereas the MUC5AC protein over-production induced by histamine administration was significantly inhibited by H1R antagonist chlorpheniramine. It was found that histamine enhanced the activation of the proximal core region of the MUC5AC promoter, which was significantly blocked by chlorpheniramine, as indicated by luciferase reporter assays.

Clinical and laboratory studies of the fate of intranasal allergen

BACKGROUND

The precise way in which allergen is handled by the nose is unknown. The objective of this study was to determine recovery of Der p 1 allergen following nasal administration and to determine whether Der p 1 can be detected in nasal biopsies after natural exposure and nasal challenge to allergen.

METHODS

(1) 20 nonatopic non-rhinitics were challenged with Der p 1 and recovery was measured by ELISA in the nasal wash, nasal mucus and induced sputum up to 30 minutes. Particulate charcoal (<40 μm) served as control. (2) In 8 subjects (5 atopics), 30 to 60 minutes after challenge histological localisation of Der p 1 in the nasal mucosal epithelium, subepithelial mucous glands and lamina propria was performed. Co-localisation of Der p 1 with macrophages and IgE-positive cells was undertaken.

RESULTS

(1) Less than 25% of total allergen was retrievable after aqueous or particulate challenge, most from the nasal mucus during 1-5 min after the challenge. The median of carbon particles recovered was 9%. (2) Prechallenge Der p 1 staining was associated with the epithelium and subepithelial mucous glands. After challenge there was a trend for greater Der p 1 deposition in atopics, but both atopics and nonatopics showed increases in the number of Der p 1 stained cells and stained tissue compartments. In atopics, increased eosinophils, macrophages and IgE positive cells co-localized with Der p 1 staining.

CONCLUSIONS

Der p 1 allergen is detected in nasal tissue independent of atopic status after natural exposure. After challenge the nose effectively retains allergen, which remains mucosally associated; in atopics there is greater Der p 1 deposition and inflammatory response than in nonatopics. These results support the hypothesis that nasal mucus and tissue act as a reservoir for the inhaled Der p 1 allergen leading to a persistent allergic inflammatory response in susceptible individuals.

Poly(inosinic-cytidylic) acid-triggered exacerbation of experimental asthma depends on IL-17A produced by NK cells

Viral infection of the respiratory tract represents the major cause of acute asthma exacerbations. dsRNA is produced as an intermediate during replication of respiratory viruses and triggers immune responses via TLR3. This study aimed at clarifying the mechanisms underlying TLR3 triggered exacerbation of experimental allergic asthma. The TLR3 ligand poly(inosinic-cytidylic) acid was applied intranasally to mice with already established experimental allergic asthma. Airway inflammation, cytokine expression, mucus production, and airway reactivity was assessed in wild-type, IL-17A, or IL-23p19-deficient, and in NK cell-depleted mice. Local application of poly(inosinic-cytidylic) acid exacerbated experimental allergic asthma in mice as characterized by enhanced release of proinflammatory cytokines, aggravated airway inflammation, and increased mucus production together with pronounced airway hyperresponsiveness. This was further associated with augmented production of IL-17 by Th17 cells and NK cells. Whereas experimental exacerbation could be induced in IL-23p19-deficient mice lacking mature, proinflammatory Th17 cells, this was not possible in mice lacking IL-17A or in NK cell-depleted animals. These experiments indicate a central role for IL-17 derived from NK cells but not from Th17 cells in the pathogenesis of virus-triggered exacerbation of experimental asthma.

Toward primary prevention of asthma. Reviewing the evidence for early-life respiratory viral infections as modifiable risk factors to prevent childhood asthma

A first step in primary disease prevention is identifying common, modifiable risk factors that contribute to a significant proportion of disease development. Infant respiratory viral infection and childhood asthma are the most common acute and chronic diseases of childhood, respectively. Common clinical features and links between these diseases have long been recognized, with early-life respiratory syncytial virus (RSV) and rhinovirus (RV) lower respiratory tract infections (LRTIs) being strongly associated with increased asthma risk. However, there has long been debate over the role of these respiratory viruses in asthma inception. In this article, we systematically review the evidence linking early-life RSV and RV LRTIs with asthma inception and whether they could therefore be targets for primary prevention efforts.

Gene expression in relation to exhaled nitric oxide identifies novel asthma phenotypes with unique biomolecular pathways

RATIONALE

Although asthma is recognized as a heterogeneous disease associated with clinical phenotypes, the molecular basis of these phenotypes remains poorly understood. Although genomic studies have successfully broadened our understanding in diseases such as cancer, they have not been widely used in asthma studies.

OBJECTIVES

To link gene expression patterns to clinical asthma phenotypes.

METHODS

We used a microarray platform to analyze bronchial airway epithelial cell gene expression in relation to the asthma biomarker fractional exhaled nitric oxide (FeNO) in 155 subjects with asthma and healthy control subjects from the Severe Asthma Research Program (SARP).

MEASUREMENTS AND MAIN RESULTS

We first identified a diverse set of 549 genes whose expression correlated with FeNO. We used k-means to cluster the patient samples according to the expression of these genes, identifying five asthma clusters/phenotypes with distinct clinical, physiological, cellular, and gene transcription characteristics-termed "subject clusters" (SCs). To then investigate differences in gene expression between SCs, a total of 1,384 genes were identified that highly differentiated the SCs at an unadjusted P value < 10(-6). Hierarchical clustering of these 1,384 genes identified nine gene clusters or "biclusters," whose coexpression suggested biological characteristics unique to each SC. Although genes related to type 2 inflammation were present, novel pathways, including those related to neuronal function, WNT pathways, and actin cytoskeleton, were noted.

CONCLUSIONS

These findings show that bronchial epithelial cell gene expression, as related to the asthma biomarker FeNO, can identify distinct asthma phenotypes, while also suggesting the presence of underlying novel gene pathways relevant to these phenotypes.

The polymeric mucin Muc5ac is required for allergic airway hyperreactivity

In asthma, airflow obstruction is thought to result primarily from inflammation-triggered airway smooth muscle (ASM) contraction. However, anti-inflammatory and smooth muscle-relaxing treatments are often temporary or ineffective. Overproduction of the mucin MUC5AC is an additional disease feature that, while strongly associated pathologically, is poorly understood functionally. Here we show that Muc5ac is a central effector of allergic inflammation that is required for airway hyperreactivity (AHR) to methacholine (MCh). In mice bred on two well-characterized strain backgrounds (C57BL/6 and BALB/c) and exposed to two separate allergic stimuli (ovalbumin and Aspergillus extract), genetic removal of Muc5ac abolishes AHR. Residual MCh responses are identical to unchallenged controls, and although inflammation remains intact, heterogeneous mucous occlusion decreases by 74%. Thus, whereas inflammatory effects on ASM alone are insufficient for AHR, Muc5ac-mediated plugging is an essential mechanism. Inhibiting MUC5AC may be effective for treating asthma and other lung diseases where it is also overproduced.

S100A8, S100A9 and S100A12 activate airway epithelial cells to produce MUC5AC via extracellular signal-regulated kinase and nuclear factor-κB pathways

Airway mucus hyperproduction is a common feature of chronic airway diseases such as severe asthma, chronic obstructive pulmonary disease and cystic fibrosis, which are closely associated with neutrophilic airway inflammation. S100A8, S100A9 and S100A12 are highly abundant proteins released by neutrophils and have been identified as important biomarkers in many inflammatory diseases. Herein, we report a new role for S100A8, S100A9 and S100A12 for producing MUC5AC, a major mucin protein in the respiratory tract. All three S100 proteins induced MUC5AC mRNA and the protein in normal human bronchial epithelial cells as well as NCI-H292 lung carcinoma cells in a dose-dependent manner. A Toll-like receptor 4 (TLR4) inhibitor almost completely abolished MUC5AC expression by all three S100 proteins, while neutralization of the receptor for advanced glycation end-products (RAGE) inhibited only S100A12-mediated production of MUC5AC. The S100 protein-mediated production of MUC5AC was inhibited by the pharmacological agents that block prominent signalling molecules for MUC5AC expression, such as mitogen-activated protein kinases, nuclear factor-κB (NF-κB) and epidermal growth factor receptor. S100A8, S100A9 and S100A12 equally elicited both phosphorylation of extracellular signal-regulated kinase (ERK) and nuclear translocation of NF-κB/degradation of cytosolic IκB with similar kinetics through TLR4. In contrast, S100A12 preferentially activated the ERK pathway rather than the NF-κB pathway through RAGE. Collectively, these data reveal the capacity of these three S100 proteins to induce MUC5AC production in airway epithelial cells, suggesting that they all serve as key mediators linking neutrophil-dominant airway inflammation to mucin hyperproduction.

Understanding the development of the respiratory glands

BACKGROUND

The submucosal glands (SMGs) of the respiratory system are specialized structures essential for maintaining airway homeostasis. The significance of SMGs is highlighted by their involvement in respiratory diseases such as cystic fibrosis, asthma and chronic bronchitis, where their phenotype and function are severely altered. Uncovering the normal development of the airway SMGs is essential to elucidate their role in these disorders, however, very little is known about the cellular mechanisms and intracellular signals involved in their morphogenesis.

RESULTS

This review describes in detail the embryonic developmental journey of the nasal SMGs and the postnatal development of the tracheal SMGs in the mouse. Current knowledge of the genes and signalling molecules involved in SMG organogenesis is also explored.

CONCLUSION

Here we review the temporal localisation and development of the murine respiratory glands in the hope of stimulating further research into the mechanisms required for successful SMG patterning and function.

Acute nitrogen dioxide (NO2) exposure enhances airway inflammation via modulating Th1/Th2 differentiation and activating JAK-STAT pathway

Nitrogen dioxide (NO2) is an air pollutant associated with poor respiratory health, asthma exacerbation, and an increased likelihood of inhalational allergies. However, the underlying mechanisms are not clear. In the present study, the airway inflammatory response was first assessed in rats exposed to 5mg/m(3) NO2 for seven days. The results showed that NO2 exposure caused the pulmonary pathological alteration, and significantly stimulated MUC5AC expression. Following this, obviously up-regulated changes of pro-inflammatory cytokines (IL-1β, IL-6, and ICAM-1) were observed. Also, NO2 inhalation induced the imbalance in the ratio of Th1/Th2 differentiation (IL-4, IFN-γ, GATA-3 and T-bet) and the activation of following JAK-STAT pathway (JAK1, JAK3 and STAT6). The findings clarify an important mechanism for NO2 inhalation being injurious to the lung and augmenting the degree of allergic airway inflammation.

IL-33 stimulates CXCL8/IL-8 secretion in goblet cells but not normally differentiated airway cells

BACKGROUND

IL-13, a helper T cell type 2 (Th2) cytokine, transforms cultured airway epithelial cells to goblet cells, and this is not inhibited by corticosteroids. IL-33 stimulates Th2 cytokines and is highly expressed in airways of persons with asthma. The effect of IL-33 on goblet cell differentiation and cytokine secretion has not been described.

OBJECTIVE

We examined the effect of IL-33 on CXCL8/IL-8 secretion from goblet or normally differentiated human bronchial epithelial (NHBE) cells and signalling pathways associated with IL-33 activation in these cells.

METHODS

Normal human bronchial epithelial cells were grown to goblet or normally differentiated ciliated cell phenotype at air-liquid interface in the presence or absence of IL-13. After 14 days, differentiated cells were exposed to IL-33 for 24 h.

RESULTS

CXCL8/IL-8 secretion into the apical (air) side of the goblet cells was greater than from normally differentiated cells (P < 0.01), and IL-33 stimulated apical CXCL8/IL-8 release from goblet cells, but not from normally differentiated cells (P < 0.01). IL-33 increased ERK 1/2 phosphorylation in goblet cells (P < 0.05), and PD98059, a MAPK/ERK kinase inhibitor, attenuated IL-33-stimulated CXCL8/IL-8 secretion from goblet cells (P < 0.001). IL-13 induced ST2 mRNA (P < 0.02) and membrane-bound ST2 protein expression on the apical side surface of goblet cells compared with normally differentiated cells, and neutralization with anti-ST2R antibody attenuated IL-33-induced apical CXCL8/IL-8 secretion from goblet cells (P < 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

Goblet cells secrete CXCL8/IL-8, and this is increased by IL-33 through ST2R-ERK pathway, suggesting a mechanism for enhanced airway inflammation in the asthmatic airway with goblet cell metaplasia.

Submersion and hypoxia inhibit ciliated cell differentiation in a notch-dependent manner

The epithelium that lines the conducting airways is composed of several distinct cell types that differentiate from common progenitor cells. The signals that control fate selection and differentiation of ciliated cells, a major component of the epithelium, are not completely understood. Ciliated cell differentiation can be accomplished in vitro when primary normal human bronchial epithelial (NHBE) cells are cultured at an air-liquid interface, but is inhibited when NHBE cells are cultured under submerged conditions. The mechanism by which submersion prevents ciliogenesis is not understood, but may provide clues to in vivo regulation of ciliated cell differentiation. We hypothesized that submersion creates a hypoxic environment that prevents ciliated cell differentiation by blocking the gene expression program required for ciliogenesis. This was confirmed by showing that expression of multicilin and Forkhead box J1, key factors needed for ciliated cell differentiation, was inhibited when NHBE cells were cultured in submerged and hypoxic conditions. Multicilin and Forkhead box J1 expression and ciliated cell differentiation were restored in submerged and hypoxic cells upon treatment with the γ-secretase inhibitor, N-[(3,5-difluorophenyl)acetyl]-L-alanyl-2-phenyl]glycine-1,1-dimethylethyl ester (DAPT), which suggested that Notch signaling was involved. Overexpression of Notch intracellular domain inhibited differentiation in the presence of DAPT, confirming the role of Notch signaling. These results indicate that submersion and hypoxia prevent ciliated cell differentiation by maintaining Notch signaling, which represses genes necessary for ciliogenesis. These data provide new insights into the molecular mechanisms that control human bronchial differentiation.

Pathobiology of severe asthma

Severe asthma (SA) afflicts a heterogeneous group of asthma patients who exhibit poor responses to traditional asthma medications. SA patients likely represent 5-10% of all asthma patients; however, they have a higher economic burden when compared with milder asthmatics. Considerable research has been performed on pathological pathways and structural changes associated with SA. Although limitations of the pathological approaches, ranging from sampling, to quantitative assessments, to heterogeneity of disease, have prevented a more definitive understanding of the underlying pathobiology, studies linking pathology to molecular markers to targeted therapies are beginning to solidify the identification of select molecular phenotypes. This review addresses the pathobiology of SA and discusses the current limitations of studies, the inflammatory cells and pathways linked to emerging phenotypes, and the structural and remodeling changes associated with severe disease. In all cases, an effort is made to link pathological findings to specific clinical/molecular phenotypes.

Triptolide suppresses airway goblet cell hyperplasia and Muc5ac expression via NF-κB in a murine model of asthma

BACKGROUND

We have reported that triptolide inhibited pulmonary inflammation in patients with steroid-resistant asthma. In the present study, we investigated whether suppresses airway remodeling and goblet cell hyperplasia, studied the mechanism of triptolide on mucin5ac (Muc5ac) expression in a murine model of asthma.

METHODS

BALB/c mice were sensitized to intraperitoneal ovalbumin (OVA) followed by repetitive ovalbumin challenge for 6 weeks. Treatments included triptolide (40 μg/kg) and dexamethasone (2mg/kg). The area of bronchial airway (WAt/Pbm), smooth muscle (WAm/Pbm) and mucus index were assessed 24h after the final OVA challenge. Levels of Muc5ac were assessed by ELISA, immunohistology and real-time PCR. Western blot was performed to analyze the phosphorylation of NF-κB p65.

RESULTS

Triptolide and dexamethasone significantly reduced allergen-induced increases in the thickness of bronchial airway, smooth muscle and goblet cell hyperplasia. Levels of lung Muc5ac and Muc5ac mRNA were significantly reduced in mice treated with triptolide and dexamethasone. Phosphorylation of NF-κB p65 was significantly reduced in mice treated with triptolide and dexamethasone.

CONCLUSION

Triptolide may inhibit airway goblet cell hyperplasia and Muc5ac expression in asthmatic mice via NF-κB. It may be a potential drug for the treatment of patients with severe asthma.

Secretory hyperresponsiveness and pulmonary mucus hypersecretion

The term bronchial hyperresponsiveness is generally used to describe a heightened airway smooth muscle bronchoconstrictor response measured by bronchoprovocation testing. However, the airway also responds to inflammation or bronchoprovocation with increased mucus secretion. We use the term "secretory hyperresponsiveness" to mean increased mucus secretion either intrinsically or in response to bronchoprovocation. This is not the same as retained phlegm or sputum. Unlike smooth muscle contraction, which is rapidly reversible using a bronchodilator, mucus hypersecretion produces airflow limitation that reverses more slowly and depends upon secretion clearance from the airway. Certain groups of patients appear to have greater mucus secretory response, including those with middle lobe syndrome, cough-dominant ("cough-variant") asthma, and severe asthma. Secretory hyperresponsiveness also is a component of forms of lung cancer associated with bronchorrhea. An extreme form of secretory hyperresponsiveness may lead to plastic bronchitis, a disease characterized by rigid branching mucus casts that obstruct the airway. Secretory hyperresponsiveness and mucus hypersecretion appear to be related to activation of the extracellular-regulated kinase 1/2, signaling through the epidermal growth factor receptor, or secretory phospholipases A2. Recognizing secretory hyperresponsiveness as a distinct clinical entity may lead to more effective and targeted therapy for these diseases.

Effects of regular treatment with combination of salmeterol/fluticasone propionate and salmeterol alone in cough variant asthma

OBJECTIVE

Cough variant asthma (CVA) is an important cause of chronic cough, and pathophysiological features of the disease appear to be similar to typical asthma. Because CVA is recognized as a precursor of asthma, early intervention with long-term anti-inflammatory agents may be recommended. However, the role of combination therapy with inhaled corticosteroid and β2-agonist in the treatment of CVA has not been elucidated. To evaluate the effectiveness of the combination therapy, we investigated the clinical impact of regular treatment with salmeterol/fliticasone propionate combination (SFC) and inhaled salmeterol (SAL) alone in patients with CVA.

METHODS

The study was a randomized, controlled, parallel-group multi-center trial. Forty-three CVA patients were assigned to SFC (50/100 µg once daily) or SAL (50 µg twice daily) for 12 weeks. Then, these medications were stopped for the next 24 weeks. Main outcome measures were cough symptoms, pulmonary function and airway inflammation.

RESULTS

Treatment with each of SFC and SAL significantly decreased cough scores and increased FEV1 and PEF, where the efficacy was more pronounced with SFC than SAL. SFC also decreased sputum eosinophil counts and eosinophil cationic protein contents, whereas SAL had no effect. After discontinuation of the treatment, cough scores increased, pulmonary function and eosinophilic airway inflammation were aggravated and returned to the baseline levels.

CONCLUSIONS

Maintenance therapy with SFC provides further improvements in cough symptoms, pulmonary function and airway inflammation, and discontinuation of the therapy causes worsening of the disease, indicating that stopping or interrupting anti-inflammatory therapy may not be advisable in patients with CVA.

The cell biology of asthma

The clinical manifestations of asthma are caused by obstruction of the conducting airways of the lung. Two airway cell types are critical for asthma pathogenesis: epithelial cells and smooth muscle cells. Airway epithelial cells, which are the first line of defense against inhaled pathogens and particles, initiate airway inflammation and produce mucus, an important contributor to airway obstruction. The other main cause of airway obstruction is contraction of airway smooth muscle. Complementary experimental approaches involving cultured cells, animal models, and human clinical studies have provided many insights into diverse mechanisms that contribute to airway epithelial and smooth muscle cell pathology in this complex disease.

The relationship between eosinophilia and airway remodelling in mild asthma

BACKGROUND

Eosinophilia is a marker of corticosteroid responsiveness and risk of exacerbation in asthma; although it has been linked to submucosal matrix deposition, its relationship with other features of airway remodelling is less clear.

OBJECTIVE

The aim of this study was to investigate the relationship between airway eosinophilia and airway remodelling.

METHODS

Bronchial biopsies from subjects (n = 20 in each group) with mild steroid-naïve asthma, with either low (0-0.45 mm(-2)) ) or high submucosal eosinophil (23.43-46.28 mm(-2) ) counts and healthy controls were assessed for in vivo epithelial damage (using epidermal growth factor receptor staining), mucin expression, airway smooth muscle (ASM) hypertrophy and inflammatory cells within ASM.

RESULTS

The proportion of in vivo damaged epithelium was significantly greater (P = 0.02) in the high-eosinophil (27.37%) than the low-eosinophil (4.14%) group. Mucin expression and goblet cell numbers were similar in the two eosinophil groups; however, MUC-2 expression was increased (P = 0.002) in the high-eosinophil group compared with controls. The proportion of submucosa occupied by ASM was higher in both asthma groups (P = 0.021 and P = 0.046) compared with controls. In the ASM, eosinophil and T-lymphocyte numbers were higher (P < 0.05) in the high-eosinophil group than both the low-eosinophil group and the controls, whereas the numbers of mast cells were increased in the high-eosinophil group (P = 0.01) compared with controls.

CONCLUSION

Submucosal eosinophilia is a marker (and possibly a cause) of epithelial damage and is related to infiltration of ASM with eosinophils and T lymphocytes, but is unrelated to mucus metaplasia or smooth muscle hypertrophy.

Aerosolized montelukast polymeric particles-an alternative to oral montelukast-alleviate symptoms of asthma in a rodent model

PURPOSE

Cysteinyl leukotrienes (CysLTs) propagate inflammatory reactions that result from allergen exposure in asthma. Montelukast, a CysLT type-1 receptor antagonist, disrupts mediator-receptor interactions and minimizes inflammatory response. In this study, we have evaluated anti-asthmatic efficacy of inhalable montelukast-loaded large porous particulate formulations in ovalbumin-induced rat airway inflammation model that mimics asthma.

METHODS

The anti-inflammatory effects of a montelukast-loaded formulation were investigated in rats by measuring the total protein content, levels of injury markers and number of inflammatory cells in the bronchoalveolar lavage fluid (BALF). The histopathological studies assessed the morphological and structural changes that occur in asthmatic lungs. Animals were also challenged with methacholine to examine the airway hyper-reactivity.

RESULTS

Compared with healthy animals, asthmatic animals showed a 3.8- and 4.77-fold increase in the protein content and number of inflammatory cells in BALF, respectively. Intratracheal montelukast particles reduced the protein content by 3.3-fold and the number of inflammatory cells by 2.62-fold. Also, montelukast particles reduced the lactate dehydrogenase (LDH) and myeloperoxidase (MPO) levels by a 4.87- and 6.8-fold in BALF, respectively. Montelukast particles reduced the airway wall thickness by 2.5-fold compared with untreated asthmatic lungs. Further, particulate formulation protected the lungs against methacholine-induced bronchial provocation (p < 0.05).

CONCLUSIONS

Respirable large porous particles containing montelukast alleviated allergen-induced inflammatory response in an animal model and prevented histological changes associated with asthma. Thus montelukast-loaded large porous polylactic acid (PLA) particles could be an aerosolized delivery approach for administration of currently available oral montelukast.

Genetics and early detection in idiopathic pulmonary fibrosis

Genetic studies hold promise in helping to identify patients with early idiopathic pulmonary fibrosis (IPF). Recent studies using chest computed tomograms (CTs) in smokers and in the general population have demonstrated that imaging abnormalities suggestive of an early stage of pulmonary fibrosis are not uncommon and are associated with respiratory symptoms, physical examination abnormalities, and physiologic decrements expected, but less severe than those noted in patients with IPF. Similarly, recent genetic studies have demonstrated strong and replicable associations between a common promoter polymorphism in the mucin 5B gene (MUC5B) and both IPF and the presence of abnormal imaging findings in the general population. Despite these findings, it is important to note that the definition of early-stage IPF remains unclear, limited data exist to definitively connect abnormal imaging findings to IPF, and genetic studies assessing early-stage pulmonary fibrosis remain in their infancy. In this perspective we provide updated information on interstitial lung abnormalities and their connection to IPF. We summarize information on the genetics of pulmonary fibrosis by focusing on the recent genetic findings of MUC5B. Finally, we discuss the implications of these findings and suggest a roadmap for the use of genetics in the detection of early IPF.

Lung epithelial stem cells and their niches: Fgf10 takes center stage

Throughout life adult animals crucially depend on stem cell populations to maintain and repair their tissues to ensure life-long organ function. Stem cells are characterized by their capacity to extensively self-renew and give rise to one or more differentiated cell types. These powerful stem cell properties are key to meet the changing demand for tissue replacement during normal lung homeostasis and regeneration after lung injury. Great strides have been made over the last few years to identify and characterize lung epithelial stem cells as well as their lineage relationships. Unfortunately, knowledge on what regulates the behavior and fate specification of lung epithelial stem cells is still limited, but involves communication with their microenvironment or niche, a local tissue environment that hosts and influences the behaviors or characteristics of stem cells and that comprises other cell types and extracellular matrix. As such, an intimate and dynamic epithelial-mesenchymal cross-talk, which is also essential during lung development, is required for normal homeostasis and to mount an appropriate regenerative response after lung injury. Fibroblast growth factor 10 (Fgf10) signaling in particular seems to be a well-conserved signaling pathway governing epithelial-mesenchymal interactions during lung development as well as between different adult lung epithelial stem cells and their niches. On the other hand, disruption of these reciprocal interactions leads to a dysfunctional epithelial stem cell-niche unit, which may culminate in chronic lung diseases such as chronic obstructive pulmonary disease (COPD), chronic asthma and idiopathic pulmonary fibrosis (IPF).

IL-1β induction of MUC5AC gene expression is mediated by CREB and NF-κB and repressed by dexamethasone

Chronic airway diseases are characterized by inflammation and mucus overproduction. The MUC5AC mucin gene is upregulated by the proinflammatory cytokine interleukin-1 β (IL-1β) via activation of cAMP response element-binding protein (CREB) in the NCI-H292 cancer cell line and nuclear factor-κB (NF-κB) in the HBE1 transformed cell line, with each transcription factor binding to a cognate cis site in the proximal or distal region, respectively, of the MUC5AC promoter. We utilized primary differentiated human bronchial epithelial (HBE) and A549 lung adenocarcinoma cells to further investigate the contributions of CREB and NF-κB subunits to the IL-1β-induced upregulation of MUC5AC. Data show that ligand binding of IL-1β to the IL-1β receptor is required to increase MUC5AC mRNA abundance. Chromatin immunoprecipitation analyses show direct binding of CREB to the previously identified cAMP response element site and binding of p65 and p50 subunits to a novel NF-κB site in a mucin-regulatory domain in the proximal promoter and to a previously identified NF-κB site in the distal promoter. P50 binds to both NF-κB sites at 1 h following IL-1β exposure, but is replaced at 2 h by p65 in A549 cells and by a p50/p65 heterodimer in HBE cells. Thus IL-1β activates multiple domains in the MUC5AC promoter but exhibits some cell-specific responses, highlighting the complexity of MUC5AC transcriptional regulation. Data show that dexamethasone, a glucocorticoid that transcriptionally represses MUC5AC gene expression under constitutive conditions, also represses IL-1β-mediated upregulation of MUC5AC gene expression. A further understanding of mechanisms mediating MUC5AC regulation should lead to a honing of therapeutic approaches for the treatment of mucus overproduction in inflammatory lung diseases.

Epithelial injury and repair in airways diseases

Asthma is a common chronic disease characterized by variable respiratory distress with underlying airway inflammation and airflow obstruction. The incidence of asthma has risen inexorably over the past 50 years, suggesting that environmental factors are important in its etiology. All inhaled environmental stimuli interact with the lung at the respiratory epithelium, and it is a testament to the effectiveness of the airway innate defenses that the majority of inhaled substances are cleared without the need to elicit an inflammatory response. However, once this barrier is breached, effective communication with immune and inflammatory cells is required to protect the internal milieu of the lung. In asthma, the respiratory epithelium is known to be structurally and functionally abnormal. Structurally, the epithelium shows evidence of damage and has more mucus-producing cells than normal airways. Functionally, the airway epithelial barrier can be more permeable and more sensitive to oxidants and show a deficient innate immune response to respiratory virus infection compared with that in normal individuals. The potential of a susceptible epithelium and the underlying mesenchyme to create a microenvironment that enables deviation of immune and inflammatory responses to external stimuli may be crucial in the development and progression of asthma. In this review, we consider three important groups of environmental stimuli on the epithelium in asthma: oxidants, such as environmental pollution and acetaminophen; viruses, including rhinovirus; and agents that cause barrier disruption, such as house dust mite allergens. The pathology associated with each stimulus is considered, and potential future treatments arising from research on their effects are presented.

Allergic asthma biomarkers using systems approaches

Asthma is characterized by lung inflammation caused by complex interaction between the immune system and environmental factors such as allergens and inorganic pollutants. Recent research in this field is focused on discovering new biomarkers associated with asthma pathogenesis. This review illustrates updated research associating biomarkers of allergic asthma and their potential use in systems biology of the disease. We focus on biomolecules with altered expression, which may serve as inflammatory, diagnostic and therapeutic biomarkers of asthma discovered in human or experimental asthma model using genomic, proteomic and epigenomic approaches for gene and protein expression profiling. These include high-throughput technologies such as state of the art microarray and proteomics Mass Spectrometry (MS) platforms. Emerging concepts of molecular interactions and pathways may provide new insights in searching potential clinical biomarkers. We summarized certain pathways with significant linkage to asthma pathophysiology by analyzing the compiled biomarkers. Systems approaches with this data can identify the regulating networks, which will eventually identify the key biomarkers to be used for diagnostics and drug discovery.

Modulation of conjunctival goblet cell function by inflammatory cytokines

Ocular surface inflammation associated with Sjögren's syndrome is characterized by a loss of secretory function and alteration in numbers of mucin secreting goblet cells. Such changes are a prominent feature of ocular surface inflammatory diseases and are attributed to inflammation; however, the exact effect of the inflammatory cytokines on conjunctival goblet cell function remains largely unknown. In this study, we developed a primary culture of mouse goblet cells from conjunctival tissue and evaluated the effects on their function by inflammatory cytokines detected in the conjunctiva of mouse model of Sjögren's syndrome (Thrombospondin-1 deficient mice). We found that apoptosis of goblet cells was primarily induced by TNF-α and IFN-γ. These two cytokines also inhibited mucin secretion by goblet cells in response to cholinergic stimulation, whereas IL-6 enhanced such secretion. No changes in secretory response were detected in the presence of IL-13 or IL-17. Goblet cells proliferated to varying degrees in response to all the tested cytokines with the greatest response to IL-13 followed by IL-6. Our results therefore reveal that inflammatory cytokines expressed in the conjunctiva during an ocular surface disease directly disrupt conjunctival goblet cell functions, compromising the protective function of tears, thereby contributing to ocular surface damage.

Bronchial thermoplasty: interventional therapy in asthma

Bronchial thermoplasty is a new treatment option for patients with severe bronchial asthma who remain symptomatic despite maximal medical therapy. The aim of this interventional therapy option is the reduction of smooth muscle in the central and peripheral airways in order to reduce symptomatic bronchoconstriction via the application of heat. A full treatment with bronchial thermoplasty is divided into three bronchoscopies. Randomized, controlled clinical trials have shown an increase in quality of life, a reduction in severe exacerbations, and decreases in emergency department visits as well as days lost from school or work. The trials did not show a reduction in hyperresponsiveness or improvement in forced expiratory volume in 1 s. Short-term adverse effects include an increase in exacerbation rate, an increase in respiratory infections and an increase in hospitalizations. In the 5-year follow up of the studies available there was evidence of clinical and functional stability of the treated patients. Further studies are necessary to identify an asthma phenotype that responds well to this treatment.

Muc5b is required for airway defence

Respiratory surfaces are exposed to billions of particulates and pathogens daily. A protective mucus barrier traps and eliminates them through mucociliary clearance (MCC). However, excessive mucus contributes to transient respiratory infections and to the pathogenesis of numerous respiratory diseases. MUC5AC and MUC5B are evolutionarily conserved genes that encode structurally related mucin glycoproteins, the principal macromolecules in airway mucus. Genetic variants are linked to diverse lung diseases, but specific roles for MUC5AC and MUC5B in MCC, and the lasting effects of their inhibition, are unknown. Here we show that mouse Muc5b (but not Muc5ac) is required for MCC, for controlling infections in the airways and middle ear, and for maintaining immune homeostasis in mouse lungs, whereas Muc5ac is dispensable. Muc5b deficiency caused materials to accumulate in upper and lower airways. This defect led to chronic infection by multiple bacterial species, including Staphylococcus aureus, and to inflammation that failed to resolve normally. Apoptotic macrophages accumulated, phagocytosis was impaired, and interleukin-23 (IL-23) production was reduced in Muc5b(-/-) mice. By contrast, in mice that transgenically overexpress Muc5b, macrophage functions improved. Existing dogma defines mucous phenotypes in asthma and chronic obstructive pulmonary disease (COPD) as driven by increased MUC5AC, with MUC5B levels either unaffected or increased in expectorated sputum. However, in many patients, MUC5B production at airway surfaces decreases by as much as 90%. By distinguishing a specific role for Muc5b in MCC, and by determining its impact on bacterial infections and inflammation in mice, our results provide a refined framework for designing targeted therapies to control mucin secretion and restore MCC.

Low-molecular-weight heparin (LMWH)-loaded large porous PEG-PLGA particles for the treatment of asthma

BACKGROUND

Heparin-like compounds interrupt leukocyte adhesion and migration, and prevent release of chemical mediators during the process of inflammation. However, little is known whether the anti-inflammatory property of smaller heparin fragments, low-molecular-weight heparin (LMWH), plays any role in the process of airway inflammation. In this study, we sought to evaluate the efficacy of LMWH-loaded large porous polyethylene glycol-poly(D,L-lactide-co-glycolide) (PEG-PLGA) particulate formulations in alleviating the cellular and biochemical changes associated with asthma.

METHODS

To study the pharmacological efficacy of LMWH for the treatment of asthma, we have used a previously optimized polymeric formulation of LMWH. The anti-asthmatic efficacy of the optimized formulation was studied in an ovalbumin-sensitized rat model of asthma. The influence of the formulation on asthmatic lungs was assessed by measuring the total protein content and number of inflammatory cells in the bronchoalveolar lavage fluid (BALF). Lungs were also examined for morphological and structural changes that may occur in asthmatic lungs.

RESULTS

Compared with healthy animals, asthmatic animals showed a seven- and threefold increase in the protein content and number of inflammatory cells in BALF, respectively. However, intratracheal LMWH particles reduced the protein content by 2.5-fold and the number of inflammatory cells by 1.8-fold-comparable to those of sham animals. Similarly, LMWH particles reduced the lactate dehydrogenase levels by 2.8- and threefold in BALF and plasma, respectively. The airway wall thickness also decreased from 47.37±6.02 μm to 21.35±3.60 μm upon treatment with PEG-PLGA particles of LMWH. Goblet cell hyperplasia was also reduced in asthmatic rats treated with LMWH particles.

CONCLUSION

PLGA particles of LMWH were efficacious in improving cellular and histological changes associated with asthma, and thus this polymeric formulation has the potential for further development into a clinically viable anti-asthma therapy.

Annexin II mediates the neutrophil elastase-stimulated exocytosis of mucin 5ac

The overexpression and hypersecretion of mucus is a hallmark of several chronic pulmonary inflammatory diseases, including chronic obstructive pulmonary disease (COPD), asthma and cystic fibrosis. Mucin 5ac (MUC5AC) is a major component of airway mucus. Annexin II (ANXII) has been reported to be expressed in various cells and is associated with the fusion of secretory vesicles. Neutrophil elastase (NE) is present at high concentrations in the airway surface fluid in patients with cystic fibrosis and various other severe diseases. However, the role of ANXII in NE-induced secretion of MUC5AC granules remains unclear. It was determined that NE upregulates the transcription and protein synthesis of ANXII in 16HBE human bronchial epithelial cells. Following stimulation with NE, ANXII is recruited to the cell membrane, as visualised by cell immunochemistry and laser confocal microscopy, and the redistribution of ANXII is inhibited by the protein kinase-C (PKC) inhibitor bisindolylmaleimide I. Conversely, depleting endogenous ANXII decreases MUC5AC secretion into the cell culture supernatant and increases the levels of intracellular MUC5AC protein. The data indicated that ANXII is associated with the secretion of MUC5AC granules.

Characterization of reactive nitrogen species in allergic asthma

OBJECTIVE

To investigate the molecular mechanism of reactive nitrogen species (RNS) in the pathogenesis of asthma and examine the use of fractional exhaled nitric oxide (FENO) measurements in close conjunction with standard clinical assessments of asthma.

DATA SOURCES

Through PubMed, Google Scholar, and Medline databases, a broad medical literature review was performed in the following areas of asthma pathobiology and management: allergic asthma, RNS, nitric oxide (NO), airway inflammation, and FENO.

STUDY SELECTIONS

Studies were selected based on the physiologic and pathophysiologic roles of RNS in relation to allergic asthma. Current evaluations on clinical applications of FENO in asthma treatment also were selected.

RESULTS

At the onset of an asthma attack, an enhanced production of NO strongly correlates with increase inducible NO synthase (NOS) activity, whereas endothelial NOS and neuronal NOS regulate primarily normal metabolic functions in the central and peripheral airways. During allergic inflammatory responses, NO and superoxide form peroxynitrite, which has deleterious effects in the respiratory tract. RNS directly accentuates airway inflammation and cytotoxicity through nitrosative stress. Moreover, the use of FENO to monitor eosinophilic-mediated airway inflammation is a potentially valuable assessment that supplements standard procedures to monitor the progression of asthma.

CONCLUSION

This review examines recent evidence implicating the molecular mechanisms of NO and NO-derived RNS in the pathobiology of asthma and suggests that monitoring FENO may markedly contribute to asthma diagnosis.

Differences in respiratory syncytial virus and influenza infection in a house-dust-mite-induced asthma mouse model: consequences for steroid sensitivity

A significant number of clinical asthma exacerbations are triggered by viral infection. We aimed to characterize the effect of virus infection in an HDM (house dust mite) mouse model of asthma and assess the effect of oral corticosteroids. HDM alone significantly increased eosinophils, lymphocytes, neutrophils, macrophages and a number of cytokines in BAL (bronchoalveolar lavage), all of which were sensitive to treatment with prednisolone (with the exception of neutrophils). Virus infection also induced cell infiltration and cytokines. RSV (respiratory syncytial virus) infection in HDM-treated animals further increased all cell types in BAL (except eosinophils, which declined), but induced no further increase in HDM-elicited cytokines. However, while HDM-elicited TNF-α (tumour necrosis factor-α), IFN-γ (interferon-γ), IL (interleukin)-2, IL-5 and IL-10 were sensitive to prednisolone treatment, concomitant infection with RSV blocked the sensitivity towards steroid. In contrast, influenza infection in HDM- challenged animals resulted in increased BAL lymphocytes, neutrophils, IFN-γ, IL-1β, IL-4, IL-5, IL-10 and IL-12, but all were attenuated by prednisolone treatment. HDM also increased eNO (exhaled NO), which was further increased by concomitant virus infection. This increase was only partially attenuated by prednisolone. RSV infection alone increased BAL mucin. However, BAL mucin was increased in HDM animals with virus infection. Chronic HDM challenge in mice elicits a broad inflammatory response that shares many characteristics with clinical asthma. Concomitant influenza or RSV infection elicits differing inflammatory profiles that differ in their sensitivity towards steroids. This model may be suitable for the assessment of novel pharmacological interventions for asthmatic exacerbation.

Abr, a negative regulator of Rac, attenuates cockroach allergen-induced asthma in a mouse model

Abr deactivates Ras-related C3 botulinum toxin substrate (Rac), a master molecular switch that positively regulates many immune cell functions, by converting it to its GDP-bound conformation. In this article, we report that, in the absence of Abr function, cockroach allergen (CRA)-immunized mice experienced a fatal asthma attack when challenged with CRA. The asthma in abr(-/-) mice was characterized by increased pulmonary mucus production, elevated serum IgE, and leukocyte airway infiltration. Decreased pulmonary compliance was further documented by increased airway resistance upon methacholine challenge. Peribronchial and bronchoalveolar lavage eosinophils, key cells associated with allergic asthma, were increased in abr(-/-) mice, but adoptive transfer of this cell type from immunized mice to naive controls, followed by CRA challenge, showed that eosinophils are not primarily responsible for differences in airway resistance between controls and abr-null mutants. CD4(+) T cell numbers in the airways of CRA-challenged abr(-/-) mice also were significantly increased compared with controls, as were the Th2 T cell-secreted cytokines IL-4 and IL-5 in total lung. Interestingly, when control and abr(-/-) CD4(+) T cells from CRA-immunized mice were transferred to wild-type animals, airway resistance upon challenge with CRA was significantly higher in mice transplanted with T cells lacking Abr function. CD4(+) T cells from CRA-immunized and challenged abr(-/-) mice contained elevated levels of activated GTP-bound Rac compared with wild-type controls. Functionally, abr(-/-) CD4(+) T cells from CRA-exposed mice showed significantly enhanced chemotaxis toward CCL21. These results identify Abr-regulated CD4(+) T cell migration as an important component of severe CRA-evoked allergic asthma in mice.

Synthetic response of stimulated respiratory epithelium: modulation by prednisolone and iKK2 inhibition

Background:

The airway epithelium plays a central role in wound repair and host defense and is implicated in the immunopathogenesis of asthma. Whether there are intrinsic differences between the synthetic capacity of epithelial cells derived from subjects with asthma and healthy control subjects and how this mediator release is modulated by antiinflammatory therapy remains uncertain. We sought to examine the synthetic function of epithelial cells from different locations in the airway tree from subjects with and without asthma and to determine the effects of antiinflammatory therapies upon this synthetic capacity.

Methods:

Primary epithelial cells were derived from 17 subjects with asthma and 16 control subjects. The release of 13 cytokines and chemokines from nasal, bronchial basal, and air-liquid interface differentiated epithelial cells before and after stimulation with IL-1β, IL-1β and interferon-γ, or Poly-IC (Toll-like receptor 3 agonist) was measured using MesoScale discovery or enzyme-linked immunosorbent assay, and the effects of prednisolone and an inhibitor of nuclear factor κ-B2 (IKK2i) were determined.

Results:

The pattern of release of cytokines and chemokines was significantly different between nasal, bronchial basal, and differentiated epithelial cells but not between health and disease. Stimulation of the epithelial cells caused marked upregulation of most mediators, which were broadly corticosteroid unresponsive but attenuated by IKK2i.

Conclusion:

Synthetic capacity of primary airway epithelial cells varied between location and degree of differentiation but was not disease specific. Activation of epithelial cells by proinflammatory cytokines and toll-like receptor 3 agonism is attenuated by IKK2i, but not corticosteroids, suggesting that IKK2i may represent an important novel therapy for asthma.

Chronic cough and sputum production are associated with worse clinical outcomes in stable asthma

BACKGROUND

Chronic cough and sputum production (chronic mucus hypersecretion) is a poorly described clinical feature of asthma. Our objective was to identify clinical, immunological and computed tomography (CT) measures of airway wall dimensions associated with these symptoms in smokers and never smokers with asthma.

METHODS

Cross-sectional data was analysed from 120 smokers and never smokers with asthma. Participants with and without a history of chronic mucus hypersecretion were compared for clinical outcomes, sputum differential cell counts and CT measures of airway dimensions (wall thickness, luminal area and percent wall area).

RESULTS

Chronic mucus hypersecretion occurred in a higher proportion of smokers with asthma (56%) than never smokers with asthma (20%), (p < 0.001) and the proportion of patients with these symptoms increased with asthma severity (p = 0.003). Smokers with asthma and chronic mucus hypersecretion had worse current clinical control than smokers without those symptoms [ACQ score 2.3 versus 1.6, p = 0.002]. A greater proportion of never smokers with chronic mucus hypersecretion required short courses of oral corticosteroids in the last year (58% versus 19%, p = 0.011). Sputum neutrophil and eosinophil counts were similar in asthma patients with or without chronic mucus hypersecretion. Of those with severe asthma and chronic mucus hypersecretion, a CT measure of airway lumen area was reduced in smokers compared to never smokers (11.4 mm(2) versus 18.4 mm(2); p = 0.017).

CONCLUSIONS

Chronic mucus hypersecretion occurs frequently in adults with stable asthma, particularly in smokers with severe disease and is associated with worse current clinical control in smokers and more exacerbations in never smokers.

Notch signaling downregulates MUC5AC expression in airway epithelial cells through Hes1-dependent mechanisms

BACKGROUND

Mucus overproduction is one of the major pathological features of asthma, and MUC5AC is the major mucin component of airway mucus. However, whether Notch signaling is implicated in the regulation of MUC5AC expression in airway secretary cells is still undetermined.

OBJECTIVE

The aim of this study is to examine whether Notch signaling can regulate MUC5AC expression and explore the molecular mechanisms.

METHODS

Mouse mtCC1-2 cells and human NCI-H292 cells were transfected with NIC, and MUC5AC expression was examined. Using gene reporter assays, site-directed mutagenesis, and ChIP assays, the activity of both mouse and human MUC5AC promoter was analyzed.

RESULTS

Notch signaling regulated MUC5AC expression both in mouse mtCC1-2 cells and in human NCI-H292 cells. Several Hes-binding site N-boxes were identified in the 5' region of both mouse and human MUC5AC promoters. Overexpression of NIC resulted in activation of the MUC5AC promoter. Site-directed mutagenesis report assays revealed that Hes proteins might repress both mouse and human MUC5AC promoter activity. Furthermore, ChIP assays confirmed that Hes1 binds to the MUC5AC promoter both in mouse mtCC1-2 cells and in human NCI-H292 cells.

CONCLUSIONS

Notch signaling can directly downregulate MUC5AC promoter activity through Hes1-dependent mechanisms, which may be identified as possible targets for pharmacotherapy of airway mucus hypersecretion in asthma.

Endobronchial biopsy: a guide for asthma therapy selection in the era of bronchial thermoplasty

OBJECTIVE

Bronchial thermoplasty (BT) reduces airway smooth muscle in patients with severe asthma. We developed a novel standardized histologic grading system assessing inflammation and structural remodeling on endobronchial biopsy (EBBx) in severe persistent asthma and evaluated airway structure before and after BT. In addition, we correlated invasive and non-invasive inflammatory markers in severe persistent asthma.

METHODS

Thirty-three patients with severe persistent asthma underwent bronchoscopy, including bronchoalveolar lavage (BAL) and diagnostic EBBx. The control group (N = 41) underwent EBBx for other clinical indications. Biopsies were graded for airway inflammation and epithelial and submucosal structural features. We also evaluated airway histology in three patients before and after BT.

RESULTS

Compared to the control group, patients with severe persistent asthma more often had intraepithelial eosinophils and lymphocytes (67% vs. 17% and 61% vs. 27%; p < .001 and p = .005, respectively) and prominent smooth muscle and goblet cell hyperplasia (88% vs. 29% and 47% vs. 22%, p < .001 and p = .004, respectively). Other features including epithelial denudation and basement membrane thickening were not significantly different. Following BT, airway smooth muscle was no longer prominent due to partial replacement by fibrosis. Increased submucosal eosinophilic inflammation and BAL eosinophilia correlated with exhaled nitric oxide (eNO, p = .05 for both).

CONCLUSIONS

We developed a clinically applicable standardized histologic grading system which identified structural but not inflammatory changes before and after BT in severe persistent asthmatics. Additionally, we demonstrated that eNO is representative of submucosal eosinophilia in this population. This semi-quantitative assessment will be useful for practicing pathologists assessing EBBx from severe persistent asthma patients for diagnostic and clinical research purposes.

CD8(+) T cells characterize early smoking-related airway pathology in patients with asthma

BACKGROUND

Smoking in asthma occurs frequently and is associated with increased symptom severity, an impaired response to corticosteroids, and accelerated lung function decline. Airway pathology in smoking asthmatics is characterized by neutrophilia and epithelial changes such as goblet cell hyperplasia and increased proliferation. Bronchial CD8(+) T cells are implicated in lung function decline in asthma and COPD. We hypothesized that smoking modifies airway inflammation in asthma by increasing the number of CD8(+) T cells at an early stage.

OBJECTIVES & METHODS

To study effects of smoking on airway pathology in bronchial biopsies from atopic patients with controlled intermittent or mild persistent asthma (12 smokers, 9.7 py and 11 never-smokers, 0.0 py; 20-50 yrs; FEV1 > 70% predicted; PC20MCh < 8 mg/mL, no ICS) using immunohistochemistry.

RESULTS

Smoking asthmatics showed higher numbers of bronchial CD8(+) T cells (55.8 vs 23.9 cells/0.1 mm(2); p = 0.001) and CD68(+) macrophages (7.5 vs 4.6 cells/0.1 mm(2), p = 0.012), and a lower CD4(+)/CD8(+) cell ratio (0.16 vs 0.40; p = 0.007) compared with non-smoking asthmatics, but no difference in neutrophils. Furthermore, the % intact epithelium was higher in smoking asthmatics (49.3 vs 23.3, p = 0.001).

CONCLUSION

Smoking asthmatics with a limited smoking history show a distinct pattern of airway pathology characterized by a bronchial infiltrate of CD8(+) T cells and CD68(+) macrophages, and epithelial remodelling resembling COPD-like features. This raises the hypothesis that early presence of CD8(+) T cells contributes to disease progression in smoking asthmatics.

Towards multiscale modeling of influenza infection

Aided by recent advances in computational power, algorithms, and higher fidelity data, increasingly detailed theoretical models of infection with influenza A virus are being developed. We review single scale models as they describe influenza infection from intracellular to global scales, and, in particular, we consider those models that capture details specific to influenza and can be used to link different scales. We discuss the few multiscale models of influenza infection that have been developed in this emerging field. In addition to discussing modeling approaches, we also survey biological data on influenza infection and transmission that is relevant for constructing influenza infection models. We envision that, in the future, multiscale models that capitalize on technical advances in experimental biology and high performance computing could be used to describe the large spatial scale epidemiology of influenza infection, evolution of the virus, and transmission between hosts more accurately.

Role of Epithelial Cells in Chronic Inflammatory Lung Disease

Airborne pathogens entering the lungs first encounter the mucus layer overlaying epithelial cells as a first line of host defense [1, 2]. In addition to serving as the physical barrier to these toxic agents, intact epithelia also are major sources of various macromolecules including antimicrobial agents, antioxidants and antiproteases [3, 4] as well as proinflammatory cytokines and chemokines that initiate and amplify host defensive responses to these toxic agents [5]. Airway epithelial cells can be categorized as either ciliated or secretory [6]. Secretory cells, such as goblet cells and Clara cells, are responsible for the production and secretion of mucus along the apical epithelial surface and, in conjunction with ciliated cells, for the regulation of airway surface liquid viscosity. In addition, submucosal mucus glands connect to the airway lumen through a ciliated duct that propels mucins outward. These glands are present in the larger airways between bands of smooth muscle and cartilage. See Fig. 1.

Cellular and molecular biology of airway mucins

Airway mucus constitutes a thin layer of airway surface liquid with component macromolecules that covers the luminal surface of the respiratory tract. The major function of mucus is to protect the lungs through mucociliary clearance of inhaled foreign particles and noxious chemicals. Mucus is comprised of water, ions, mucin glycoproteins, and a variety of other macromolecules, some of which possess anti-microbial, anti-protease, and anti-oxidant activities. Mucins comprise the major protein component of mucus and exist as secreted and cell-associated glycoproteins. Secreted, gel-forming mucins are mainly responsible for the viscoelastic property of mucus, which is crucial for effective mucociliary clearance. Cell-associated mucins shield the epithelial surface from pathogens through their extracellular domains and regulate intracellular signaling through their cytoplasmic regions. However, neither the exact structures of mucin glycoproteins, nor the manner through which their expression is regulated, are completely understood. This chapter reviews what is currently known about the cellular and molecular properties of airway mucins.

TGF-β₂ decreases baseline and IL-13-stimulated mucin production by primary human bronchial epithelial cells

INTRODUCTION

Mucus hypersecretion is a major contributor to asthma pathology and occurs as part of a spectrum of structural changes termed airway wall remodeling. Transforming growth factor (TGF)-β is proposed to play a key role in regulating airway matrix remodeling although less is known about the specific action of TGF-β isoforms in regulating mucus production.

METHODS

Primary human bronchial epithelial (HBE) cells cultured at air-liquid interface were treated with exogenous TGF-β(1), TGF-β(2), and/or a Th2 cytokine, interleukin (IL)-13. Expression and production of respiratory mucins, MUC5AC and MUC5B, were analyzed by real-time PCR, agarose gel electrophoresis, and western blotting. A murine-transformed Clara cell line (mtCC1-2) transfected with a luciferase reporter driven by the Muc5ac promoter containing Smad4 site-mutated cis sequences was used to determine whether exogenous TGF-β(2) affects Muc5ac promoter function.

RESULTS

Surprisingly, TGF-β(1) showed no measurable effect on MUC5AC or MUC5B production by HBE cells whereas TGF-β(2) caused a decrease in both MUC5AC and MUC5B mRNA and protein. Dual treatment with TGF-β(2) and IL-13 partially attenuated the increase in mucin production found with IL-13 alone. This effect was confirmed by using mtCC1-2 cells where addition of TGF-β(2) reduced the ability of IL-13/EGF to induce Muc5ac promoter expression in wild-type cells; however, this decrease was absent in mutant promoter-transfected cells.

DISCUSSION AND CONCLUSION

Findings suggest that normal regulation of MUC5AC and MUC5B production by HBE cells is TGF-β isoform-specific and that TGF-β(2) downregulates both MUC5AC and MUC5B. Furthermore, TGF-β(2) controls baseline and IL-13-driven Muc5ac promoter function in murine Clara cells via an endogenous Smad4 recognition motif.

Changes in water channel aquaporin 1 and aquaporin 5 in the small airways and the alveoli in a rat asthma model

OBJECTIVES

To examine changes in aquaporin 1 (AQP1) and aquaporin 5 (AQP5) in the small airways and alveoli in a rat asthma model.

METHOD

Forty Wistar rats were randomly divided into a control group and an ovalbumin (OVA) sensitization asthma model group. The distribution and expression of AQP1 and AQP5 in lung tissues were analyzed using immunohistochemistry (IHC), quantified the staining intensity by assessing integrated optical densities (IOD), and Western blotting (WB).

RESULTS

IHC showed AQP1 was mainly distributed in sub-epithelial microvascular endothelial cells (MECs) and red blood cells. IOD values showed, in the asthma model group, the expression of AQP1 in alveolar MECs was lower than that in the control group (P<0.05); However, AQP1 expression in small airways sub-epithelial was higher than in the control group (P<0.05). The WB indicated that AQP1 expression in the asthma model group was 57% lower than in the control group (P<0.05). AQP5 was mainly distributed in the non-ciliated epithelial cells of the small airways and the apical membranes of type I and type II epithelial cells. IOD values showed, in asthma model group, the expression of AQP5 increased in small airways epithelium (P<0.05), and decreased in alveolar epithelium (P<0.05). The WB showed a 36% reduction in AQP5 expression compared with the control group (P<0.05).

CONCLUSION

AQP1 and AQP5 increased in small airways in rats with experimentally induced asthma, indicating that they may be involved in the formation of submucosal edema and mucus hypersecretion. Decreased AQP1 and AQP5 in pulmonary alveoli may be related to increased alveolar liquid viscosity and the formation of mucus plugs.

Glucocorticoid receptor and histone deacetylase-2 mediate dexamethasone-induced repression of MUC5AC gene expression

Airway occlusion in obstructive airway diseases is caused in part by the overproduction of secretory mucin glycoproteins through the up-regulation of mucin (MUC) genes by inflammatory mediators. Some pharmacological agents, including the glucocorticoid dexamethasone (Dex), repress mucin concentrations in lung epithelial cancer cells. Here, we show that Dex reduces the expression of MUC5AC, a major airway mucin gene, in primary differentiated normal human bronchial epithelial (NHBE) cells in a dose-dependent and time-dependent manner, and that the Dex-induced repression is mediated by the glucocorticoid receptor (GR) and two glucocorticoid response elements (GREs) in the MUC5AC promoter. The pre-exposure of cells to RU486, a GR antagonist, and mutations in either the GRE3 or GRE5 cis-sites abolished the Dex-induced repression. Chromatin immunoprecipitation (ChIP) assays showed a rapid temporal recruitment of GR to the GRE3 and GRE5 cis-elements in the MUC5AC promoter in NHBE and in A549 cells. Immunofluorescence showed nuclear colocalization of GR and histone deacetylase-2 (HDAC2) in MUC5AC-expressing NHBE cells. ChIP also showed a rapid temporal recruitment of HDAC2 to the GRE3 and GRE5 cis-elements in the MUC5AC promoter in both cell types. The knockdown of HDAC2 by HDAC2-specific short interfering RNA prevented the Dex-induced repression of MUC5AC in NHBE and A549 cells. These data demonstrate that GR and HDAC2 are recruited to the GRE3 and GRE5 cis-sites in the MUC5AC promoter and mediate the Dex-induced cis repression of MUC5AC gene expression. A better understanding of the mechanisms whereby glucocorticoids repress MUC5AC gene expression may be useful in formulating therapeutic interventions in chronic lung diseases.

The pharmacological modulation of allergen-induced asthma

Aeroallergens are the most common triggers for the development of asthma. Recent birth cohort studies have identified viral infections occurring against a background of aeroallergen sensitization as a potent risk factor for initiation of asthma. Viral infection enhances immunopathogenic potential of pre-existing inhalant allergy via modulating airway mucosal dendritic cells. By using an allergen inhalation challenge clinical model, studies have shown that the late asthma response (LAR) is associated with more pronounced allergen-induced airway inflammation and airway hyperresponsiveness. The degree of airway eosinophilia, regulated by bone marrow progenitor cells and interleukin-5 level, correlates with the magnitude of the LAR and the increase in hyperresponsiveness. Both myeloid and plasmacytoid dendritic cell subsets have been involved in the pathogenesis of allergen-induced LAR. Myeloid dendritic cells are responsible for the allergen presentation and induction of inflammation and plasmacytoid dendritic cells play a role in the resolution of allergen-induced inflammation. A variety of potential new classes of asthma medication has also been evaluated with the allergen inhalation challenge in mild asthmatic subjects. Examples are TPI ASM8, an inhaled anti-sense oligonucleotide drug product, which attenuated both early and LARs via inhibition of the target gene mRNA of chemokine receptor 3, and the common β chain of interleukin-3, interleukin-5 and granulocyte-macrophage colony-stimulating factor receptor. Anti-human antibody interleukin-13 (IM-638) significantly attenuated both early and late allergen-induced asthma response. Pitrakinra, which targets both interleukin-4 and interleukin-13, substantially diminishes allergen-induced airway responses. Allergen-induced airway responses are a valuable way to evaluate the activity of possible new therapies in asthmatic airways.