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Background: Understanding effects of acute smoke exposure (ASE) on airway epithelial gene expression and their relationship with the effects of chronic smoke exposure may provide biological insights into the development of smoking-related respiratory diseases. Methods: Bronchial airway epithelial cell brushings were collected from 63 individuals without recent cigarette smoke exposure and before and 24 h after smoking three cigarettes. RNA from these samples was profiled on Affymetrix Human Gene 1.0 ST microarrays. Results: We identified 91 genes differentially expressed 24 h after ASE (false discovery rate < 0.25). ASE induced genes involved in xenobiotic metabolism, oxidative stress, and inflammation and repressed genes related to cilium morphogenesis and cell cycle. While many genes altered by ASE are altered similarly in chronic smokers, metallothionein genes are induced by ASE and suppressed in chronic smokers. Metallothioneins are also suppressed in current and former smokers with lung cancer relative to those without lung cancer. Conclusions: Acute exposure to as little as three cigarettes and chronic smoking induce largely concordant changes in airway epithelial gene expression. Differences in short-term and long-term effects of smoking on Kmetallothionein expression and their relationship to lung cancer requires further study given these enzymes' role in the oxidative stress response. [ABSTRACT FROM AUTHOR]

Background: Goblet cell metaplasia, a common feature of chronic obstructive pulmonary disease (COPD), is associated with mucus hypersecretion which contributes to the morbidity and mortality among patients. Transcription factors SAM-pointed domain-containing Ets-like factor (SPDEF) and forkhead box protein A2 (FOXA2) regulate goblet cell differentiation. This study aimed to (1) investigate DNA methylation and expression of SPDEF and FOXA2 during goblet cell differentiation and (2) compare this in airway epithelial cells from patients with COPD and controls during mucociliary differentiation. Methods: To assess DNA methylation and expression of SPDEF and FOXA2 during goblet cell differentiation, primary airway epithelial cells, isolated from trachea (non-COPD controls) and bronchial tissue (patients with COPD), were differentiated by culture at the air-liquid interface (ALI) in the presence of cytokine interleukin (IL)-13 to promote goblet cell differentiation. Results: We found that SPDEF expression was induced during goblet cell differentiation, while FOXA2 expression was decreased. Importantly, CpG number 8 in the SPDEF promoter was hypermethylated upon differentiation, whereas DNA methylation of FOXA2 promoter was not changed. In the absence of IL-13, COPD-derived ALI-cultured cells displayed higher SPDEF expression than control-derived ALI cultures, whereas no difference was found for FOXA2 expression. This was accompanied with hypomethylation of CpG number 6 in the SPDEF promoter and also hypomethylation of CpG numbers 10 and 11 in the FOXA2 promoter. Conclusions: These findings suggest that aberrant DNA methylation of SPDEF and FOXA2 is one of the factors underlying mucus hypersecretion in COPD, opening new avenues for epigenetic-based inhibition of mucus hypersecretion. [ABSTRACT FROM AUTHOR]

Background: COPD patients have a higher risk of pneumonia when treated with fluticasone propionate (FP) than with placebo, and a lower risk with budesonide (BUD). We hypothesized that BUD and FP differentially affect the mucosal barrier in response to viral infection and/or cigarette smoke.Methods: We assessed protective effects of equivalent concentrations of BUD and FP on cytokine production and barrier function (electrical resistance) in human bronchial epithelial 16HBE cells and primary bronchial epithelial cells (PBECs) upon exposure to viral mimetic poly-(I:C) and/or cigarette smoke extract (CSE) or epidermal growth factor (EGF).Results: BUD and FP were equally effective in suppressing poly-(I:C)- and/or CSE-induced IL-8 secretion in 16HBE and PBECs. Poly-(I:C) substantially decreased electrical resistance in 16HBE cells and both BUD and FP fully counteracted this effect. However, FP hardly affected 16HBE barrier dysfunction induced by CSE with/without poly-(I:C), whereas BUD (16 nM) provided full protection, an effect likely mediated by affecting EGFR-downstream target GSK-3β. Similarly, BUD, but not FP, significantly improved CSE-induced barrier dysfunction in PBECs. Finally, BUD, but not FP, exerted a modest but significant protective effect against Streptococcus Pneumoniae-induced barrier dysfunction, and BUD, but not FP, prevented cellular adhesion and/or internalization of these bacteria induced by poly-(I:C) in 16HBE.Conclusions: Collectively, both BUD and FP efficiently control epithelial pro-inflammatory responses and barrier function upon mimicry of viral infection. Of potential clinical relevance, BUD more effectively counteracted CSE-induced barrier dysfunction, reinforcing the epithelial barrier and potentially limiting access of pathogens upon smoking in vivo. [ABSTRACT FROM AUTHOR]

Most patients with allergic asthma are sensitized to house dust mite (HDM). The allergenicity of HDM largely depends on disruption of the integrity and proinflammatory activation of the airway epithelium. In this study, we hypothesized that Pim1 kinase activity attenuates HDM-induced asthma by preserving airway epithelial integrity. The effects of Pim1 kinase activity on barrier function and release of the proinflammatory mediators IL-1 and CCL20 were studied in vitro in 16HBE and primary bronchial epithelial cells (PBECs). Pim1-proficient and -deficient mice were exposed to a HDM-driven model of allergic asthma, and airway hyperresponsiveness (AHR) was measured upon methacholine challenge. Airway inflammation and proinflammatory mediators in lung tissue and BAL fluid were determined. We observed that inhibition of Pim1 kinase prolongs the HDMinduced loss of barrier function in 16HBE cells and sensitizes PBECs to HDM-induced barrier dysfunction. Additionally, inhibition of Pim1 kinase increased the HDM-induced proinflammatory activity of 16HBE cells as measured by IL-1 secretion. In line herewith, HDM exposure induced an enhanced production of the proinflammatory chemokines CCL17 and CCL20 in Pim1-deficient mice compared with wild-type controls. While we observed a marked increase in eosinophilic and neutrophilic granulocytes as well as mucus cell metaplasia and AHR to methacholine in mice exposed to HDM, these parameters were independent of Pim1 kinase activity. In contrast, levels of the Th2-cytokines IL-5 and IL-10 were significantly augmented in HDM-treated Pim1-deficient mice. Taken together, our study shows that Pim1 kinase activity maintains airway epithelial integrity and protects against HDM-induced proinflammatory activation of the airway epithelium. [ABSTRACT FROM AUTHOR]

Exposure to cigarette smoke (CS) is the main risk factor for developing chronic obstructive pulmonary disease and can induce airway epithelial cell damage, innate immune responses, and airway inflammation. We hypothesized that cell survival factors might decrease the sensitivity of airway epithelial cells to CS-induced damage, thereby protecting the airways against inflammation upon CS exposure. Here, we tested whether Pim survival kinases could protect from CS-induced inflammation. We determined expression of Pim kinases in lung tissue, airway inflammation, and levels of keratinocyte-derived cytokine (KC) and several damage-associated molecular patterns in bronchoalveolar lavage in mice exposed to CS or air. Human bronchial epithelial BEAS-2B cells were treated with CS extract (CSE) in the presence or absence of Pim1 inhibitor and assessed for loss of mitochondrial membrane potential, induction of cell death, and release of heat shock protein 70 (HSP70). We observed increased expression of Pim1, but not of Pim2 and Pim3, in lung tissue after exposure to CS. Pim1- deficient mice displayed a strongly enhanced neutrophilic airway inflammation upon CS exposure compared with wild-type controls. Inhibition of Pim1 activity in BEAS-2B cells increased the loss of mitochondrial membrane potential and reduced cell viability upon CSE treatment, whereas release of HSP70 was enhanced. Interestingly, we observed release of S100A8 but not of double-strand DNA or HSP70 in Pim1-deficient mice compared with wild-type controls upon CS exposure. In conclusion, we show that expression of Pim1 protects against CS-induced cell death in vitro and neutrophilic airway inflammation in vivo. Our data suggest that the underlying mechanism involves CS-induced release of S100A8 and KC. [ABSTRACT FROM AUTHOR]

Airway inflammation in asthma is orchestrated by recruitment of T helper (Th)2 lymphocytes to the lung and subsequent production of Th2-like cytokines upon allergen challenge. To examine whether allergen-induced dysfunction of the β2-adrenergic receptor (β2-AR) contributes to the enhanced T(h2) cell activity in asthma. β2-adrenergic regulation of cytokine mRNA expression was studied in α-CD3/α-CD28-activated peripheral blood lymphocytes from seven asthma patients before and 6 h after allergen challenge, in conjunction with the effects of β2-agonist fenoterol on T cell chemotaxis and signalling pathways. A complete loss of β2-AR control over expression of the Th2 cytokines IL-4, IL-5 and IL-13, but not of the Th1 cytokine IFN-γ, was observed after allergen challenge. Furthermore, we found impaired β2-AR regulation of T cell migration as well as signal transduction pathways, i.e. the phosphorylation of cyclic adenosine monophosphate-responsive element binding protein and the inhibition of the mitogen-activated protein kinase pathway. The loss of β2-AR control was associated with increased β-adrenergic receptor kinase expression, which might be involved in β2-AR desensitization. In addition, we demonstrate for the first time that T cells exposed to the chemokine thymus and activation-regulated chemokine show hyporesponsiveness to fenoterol. Our results suggest that allergen-induced loss of β2-AR control, possibly mediated by chemokine release, plays an important role in enhanced Th2-like activity in asthma. [ABSTRACT FROM AUTHOR]

Abstract Background Cigarette smoke, the major risk factor for COPD, is known to activate matrix metalloproteinases in airway epithelium. We investigated whether metalloproteinases, particularly A Disintegrin and Metalloproteinase (ADAM)17, contribute to increased pro-inflammatory epithelial responses with respect to the release of IL-8 and TGF-α, cytokines implicated in COPD pathogenesis. Methods We studied the effects of cigarette smoke extract (CSE) and metalloproteinase inhibitors on TGF-α and IL-8 release in primary bronchial epithelial cells (PBECs) from COPD patients, healthy smokers and non-smokers. Results We observed that TGF-α was mainly shed by ADAM17 in PBECs from all groups. Interestingly, IL-8 production occurred independently from ADAM17 and TGF-α shedding, but was significantly inhibited by broad-spectrum metalloproteinase inhibitor TAPI-2. CSE did not induce ADAM17-dependent TGF-α shedding, while it slightly augmented the production of IL-8. This was accompanied by reduced endogenous inhibitor of metalloproteinase (TIMP)-3 levels, suggesting that CSE does not directly but rather indirectly alter activity of ADAM17 through the regulation of its endogenous inhibitor. Furthermore, whereas baseline TGF-α shedding was lower in COPD PBECs, the early release of IL-8 (likely due to its shedding) was higher in PBECs from COPD than healthy smokers. Importantly, this was accompanied by lower TIMP-2 levels in COPD PBECs, while baseline TIMP-3 levels were similar between groups. Conclusions Our data indicate that IL-8 secretion is regulated independently from ADAM17 activity and TGF-α shedding and that particularly its early release is differentially regulated in PBECs from COPD and healthy smokers. Since TIMP-2-sensitive metalloproteinases could potentially contribute to IL-8 release, these may be interesting targets to further investigate novel therapeutic strategies in COPD.

Idiopathic pulmonary fibrosis (IPF) is one of the most aggressive forms of idiopathic interstitial pneumonias, characterized by chronic and progressive fibrosis subverting the lung's architecture, pulmonary functional decline, progressive respiratory failure, and high mortality (median survival 3 years after diagnosis). Among the mechanisms associated with disease onset and progression, it has been hypothesized that IPF lungs might be affected either by a regenerative deficit of the alveolar epithelium or by a dysregulation of repair mechanisms in response to alveolar and vascular damage. This latter might be related to the progressive dysfunction and exhaustion of the resident stem cells together with a process of cellular and tissue senescence. The role of endogenous mesenchymal stromal/stem cells (MSCs) resident in the lung in the homeostasis of these mechanisms is still a matter of debate. Although endogenous MSCs may play a critical role in lung repair, they are also involved in cellular senescence and tissue ageing processes with loss of lung regenerative potential. In addition, MSCs have immunomodulatory properties and can secrete anti-fibrotic factors. Thus, MSCs obtained from other sources administered systemically or directly into the lung have been investigated for lung epithelial repair and have been explored as a potential therapy for the treatment of lung diseases including IPF. Given these multiple potential roles of MSCs, this review aims both at elucidating the role of resident lung MSCs in IPF pathogenesis and the role of administered MSCs from other sources for potential IPF therapies., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Samarelli, Tonelli, Heijink, Martin Medina, Marchioni, Bruzzi, Castaniere, Andrisani, Gozzi, Manicardi, Moretti, Cerri, Fantini, Tabbì, Nani, Mastrolia, Weiss, Dominici and Clini.)

Background and Objective: Cigarette smoking is one of the most prevalent causes of preventable deaths worldwide, leading to chronic diseases, including chronic obstructive pulmonary disease (COPD). Cigarette smoke is known to induce significant transcriptional modifications throughout the respiratory tract. However, it is largely unknown how genetic profiles influence the smoking-related transcriptional changes and how changes in gene expression translate into altered alveolar epithelial repair responses., Methods: We performed a candidate-based acute cigarette smoke-induced eQTL study, investigating the association between SNP and differential gene expression of FPR family members in bronchial epithelial cells isolated 24 h after smoking and after 48 h without smoking. The effects FPR1 on lung epithelial integrity and repair upon damage in the presence and absence of cigarette smoke were studied in CRISPR-Cas9-generated lung epithelial knockout cells., Results: One significant (FDR < 0.05) inducible eQTL (rs3212855) was identified that induced a >2-fold change in gene expression. The minor allele of rs3212855 was associated with significantly higher gene expression of FPR1, FPR2 and FPR3 upon smoking. Importantly, the minor allele of rs3212855 was also associated with lower lung function. Alveolar epithelial FPR1 knockout cells were protected against CSE-induced reduction in repair capacity upon wounding., Conclusion: We identified a novel smoking-related inducible eQTL that is associated with a smoke-induced increase in the expression of FPR1, FPR2 and FPR3, and with lowered lung function. in vitro FPR1 down-regulation protects against smoke-induced reduction in lung epithelial repair., (© 2020 The Authors. Respirology published by John Wiley & Sons Australia, Ltd on behalf of Asian Pacific Society of Respirology.)

Background: COPD patients have increased risk of pneumonia when treated with fluticasone propionate (FP), whereas this is generally not the case with budesonide (BUD) treatment. We hypothesized that BUD and FP differentially affect the expression of immune defense genes., Methods: Human bronchial epithelial 16HBE cells and air-liquid interface (ALI)-cultured primary bronchial epithelial cells (PBECs) were pre-treated with clinically equipotent concentrations of BUD or FP (0.16-16 nM BUD and 0.1-10 nM FP), and the expression of immune defense genes was studied at baseline and after exposure to rhinovirus (RV16)., Results: Using microfluidic cards, we observed that both BUD and FP significantly suppressed CXCL8, IFNB1 and S100A8 mRNA expression in unstimulated 16HBE cells. Interestingly, BUD, but not FP, significantly increased lactotransferrin (LTF) expression. The difference between the effect of BUD and FP on LTF expression was statistically significant and confirmed by qPCR and at the protein level by western blotting. RV16 infection of ALI-cultured PBECs significantly increased the expression of CCL20, IFNB1 and S100A8, but not of LTF or CAMP/LL-37. In these RV16-exposed cells, LTF expression was again significantly higher upon pre-treatment with BUD than with FP. The same was observed for S100A8, but not for CCL20, IFNB1 or CAMP/LL-37 expression., Conclusions: Treatment of human bronchial epithelial cells with BUD results in significantly higher expression of specific immune defense genes than treatment with FP. The differential regulation of these immune defense genes may help to explain the clinical observation that BUD and FP treatment differ with respect to the risk of developing pneumonia in COPD., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: The asthma gene PCDH1 encodes Protocadherin-1, a putative adhesion molecule of unknown function expressed in the airway epithelium. Here, we characterize the localization, differential expression, homotypic adhesion specificity and function of PCDH1 in airway epithelial cells in asthma., Methods: We performed confocal fluorescence microscopy to determine subcellular localization of PCDH1 in 16HBE cells and primary bronchial epithelial cells (PBECs) grown at air-liquid interface. Next, to compare PCDH1 expression and localization in asthma and controls we performed qRT-PCR and fluorescence microscopy in PBECs and immunohistochemistry on airway wall biopsies. We examined homotypic adhesion specificity of HEK293T clones overexpressing fluorescently tagged-PCDH1 isoforms. Finally, to evaluate the role for PCDH1 in epithelial barrier formation and repair, we performed siRNA knockdown-studies and measured epithelial resistance., Results: PCDH1 localized to the cell membrane at cell-cell contact sites, baso-lateral to adherens junctions, with increasing expression during epithelial differentiation. No differences in gene expression or localization of PCDH1 isoforms expressing the extracellular domain were observed in either PBECs or airway wall biopsies between asthma patients and controls. Overexpression of PCDH1 mediated homotypic interaction, whereas downregulation of PCDH1 reduced epithelial barrier formation, and impaired repair after wounding., Conclusions: In conclusion, PCDH1 is localized to the cell membrane of bronchial epithelial cells baso-lateral to the adherens junction. Expression of PCDH1 is not reduced nor delocalized in asthma even though PCDH1 contributes to homotypic adhesion, epithelial barrier formation and repair., Competing Interests: The authors have declared that no competing interests exist.

Chronic obstructive pulmonary disease (COPD) is currently the fourth leading cause of death worldwide and, in contrast to the trend for cardiovascular diseases, mortality rates still continue to climb. This increase is in part due to an aging population, being expanded by the "Baby boomer" generation who grew up when smoking rates were at their peak and by people in developing countries living longer. Sadly, there has been a disheartening lack of new therapeutic approaches to counteract the progressive decline in lung function associated with the disease that leads to disability and death. COPD is characterized by irreversible chronic airflow limitation that is caused by emphysematous destruction of lung elastic tissue and/or obstruction in the small airways due to occlusion of their lumen by inflammatory mucus exudates, narrowing and obliteration. These lesions are mainly produced by the response of the tissue to the repetitive inhalational injury inflicted by noxious gases, including cigarette smoke, which involves interaction between infiltrating inflammatory immune cells, resident cells (e.g. epithelial cells and fibroblasts) and the extra cellular matrix. This interaction leads to tissue destruction and airway remodeling with changes in elastin and collagen, such that the epithelial-mesenchymal trophic unit is dysregulated in both the disease pathologies. This review focuses on: 1--novel inflammatory and remodeling factors that are altered in COPD; 2--in vitro and in vivo models to understand the mechanism whereby the extra cellular matrix environment in altered in COPD; and 3--COPD in the context of wound-repair tissue responses, with a focus on the regulation of mesenchymal cell fate and phenotype., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: We hypothesised that increased oxidative stress, as present in the airways of asthma and chronic obstructive pulmonary disease (COPD) patients, induces epithelial damage and reduces epithelial responsiveness to suppressive effects of corticosteroids on proinflammatory cytokine production and barrier function., Methods: We induced oxidative stress by H2O2 and/or cigarette smoke extract (CSE) in human bronchial epithelial 16HBE cells and primary bronchial epithelial cells (PBEC) derived by brushings from asthma patients, COPD patients, and smoking and non-smoking control individuals. We investigated effects of budesonide on barrier function (electrical resistance) and TNF-α-induced proinflammatory cytokine production (IL-8/CXCL8, granulocyte macrophage-colony stimulating factor (GM-CSF))., Results: We observed that H2O2 and CSE reduce epithelial resistance. Budesonide significantly counteracted this effect, likely by protection against epidermal growth factor receptor-dependent cell-cell contact disruption. Furthermore, budesonide suppressed proinflammatory cytokine production. H2O2 pretreatment reduced this effect of budesonide on cytokine production in both 16HBE cells and PBECs. Importantly, PBECs from asthma and COPD patients were less sensitive to budesonide with respect to cytokine production and barrier function than PBECs from control subjects., Conclusions: Together, our data indicate that budesonide suppresses epithelial proinflammatory responses and barrier dysfunction and that oxidative stress reduces these effects in airway epithelium from asthma and COPD patients. Therefore, restoration of corticosteroid responsiveness in asthma and COPD may act to improve the airway epithelial barrier.

Introduction: Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease with pulmonary and extra-pulmonary manifestations. Although COPD is a complex disease, diagnosis and staging are still based on simple spirometry measurements. Different COPD phenotypes exist based on clinical, physiological, immunological and radiological observations. Cigarette smoking is the most important risk factor for COPD, but only 15-20% of smokers develop the disease, suggesting a genetic predisposition. Unfortunately, little is known about the pathogenesis of COPD, and even less on the very first steps that are associated with an aberrant response to smoke exposure. This study aims to investigate the underlying local and systemic inflammation of different clinical COPD phenotypes, and acute effects of cigarette smoke exposure in individuals susceptible and non-susceptible for the development of COPD. Furthermore, we will investigate mechanisms associated with corticosteroid insensitivity. Our study will provide valuable information regarding the pathogenetic mechanisms underlying the natural course of COPD., Methods and Analysis: This cross-sectional study will include young and old individuals susceptible or non-susceptible to develop COPD. At a young age (18-40 years) 60 'party smokers' will be included who are called susceptible or non-susceptible based on COPD prevalence in smoking family members. In addition, 30 healthy smokers (age 40-75 years) and 110 COPD patients will be included. Measurements will include questionnaires, pulmonary function, low-dose CT scanning of the lung, body composition, 6 min walking distance and biomarkers in peripheral blood, sputum, urine, exhaled breath condensate, epithelial lining fluid, bronchial brushes and biopsies. Non-biased approaches such as proteomics will be performed in blood and epithelial lining fluid., Ethics and Dissemination: This multicentre study was approved by the medical ethical committees of UMC Groningen and Utrecht, the Netherlands. The study findings will be presented at conferences and will be reported in peer-reviewed journals., Trial Registration: ClinicalTrials.gov, NCT00807469 (study 1) and NCT00850863 (study 2).

Cigarette smoking, the major cause of chronic obstructive pulmonary disease (COPD), induces aberrant airway epithelial structure and function. The underlying mechanisms are unresolved so far. We studied effects of cigarette smoke extract (CSE) on epithelial barrier function and wound regeneration in human bronchial epithelial 16HBE cells and primary bronchial epithelial cells (PBECs) from COPD patients, nonsmokers and healthy smokers. We demonstrate that CSE rapidly and transiently impairs 16HBE barrier function, largely due to disruption of cell-cell contacts. CSE induced a similar, but stronger and more sustained, defect in PBECs. Application of the specific epidermal growth factor receptor (EGFR) inhibitor AG1478 showed that EGFR activation contributes to the CSE-induced defects in both 16HBE cells and PBECs. Furthermore, our data indicate that the endogenous protease calpain mediates these defects through tight junction protein degradation. CSE also delayed the reconstitution of 16HBE intercellular contacts during wound healing and attenuated PBEC barrier function upon wound regeneration. These findings were comparable between PBECs from smokers, healthy smokers and COPD patients. In conclusion, we demonstrate for the first time that CSE reduces epithelial integrity, probably by EGFR and calpain-dependent disruption of intercellular contacts. This may increase susceptibility to environmental insults, e.g. inhaled pathogens. Thus, EGFR may be a promising target for therapeutic strategies to improve mucosal barrier function in cigarette smoking-related disease.

A subset of asthma patients suffer from glucocorticoid (GC) insensitivity. T-helper cell type 17 cells have an emerging role in GC insensitivity, although the mechanisms are still poorly understood. We investigated whether interleukin (IL)-17A induces GC insensitivity in airway epithelium by studying its effects on responsiveness of tumour necrosis factor (TNF)-α-induced IL-8 production to budesonide in human bronchial epithelial 16HBE cells. We unravelled the underlying mechanism by the use of specific pathway inhibitors, reporter and overexpression constructs and a histone deacetylase (HDAC) activity assay. We demonstrated that IL-17A-induced IL-8 production is normally sensitive to GCs, while IL-17A pre-treatment significantly reduced the sensitivity of TNF-α-induced IL-8 production to budesonide. IL-17A activated the p38, extracellular signal-related kinase (ERK) and phosphoinositide-3-kinase (PI3K) pathways, and the latter appeared to be involved in IL-17A-induced GC insensitivity. Furthermore, IL-17A reduced HDAC activity, and overexpression of HDAC2 reversed IL-17A-induced GC insensitivity. In contrast, IL-17A did not affect budesonide-induced transcriptional activity of the GC receptor, suggesting that IL-17A does not impair the actions of the ligated GC receptor. In conclusion, we have shown for the first time that IL-17A induces GC insensitivity in airway epithelium, which is probably mediated by PI3K activation and subsequent reduction of HDAC2 activity. Thus, blockade of IL-17A or downstream signalling molecule PI3K may offer new strategies for therapeutic intervention in GC-insensitive asthma.

Impaired airway epithelial barrier function has emerged as a key factor in the pathogenesis of allergic asthma. We aimed to discern the involvement of the epidermal growth factor receptor (EGFR) in allergen-induced epithelial barrier impairment, as we previously observed that house dust mite (HDM) signals through EGFR. We investigated the junctional integrity of human bronchial epithelial cells using electric cell-substrate impedance sensing and immunofluorescent staining. HDM induced a rapid, transient fall in epithelial resistance, concomitant with delocalisation of E-cadherin and zona occludens (ZO)-1, and proteolytic cleavage of the latter. EGFR inhibition by AG1478 reduced the HDM-triggered decrease in epithelial resistance and improved restoration of epithelial junctions. Similarly, AG1478 increased epithelial barrier recovery upon electroporation-induced injury, although it delayed the migration phase of the wound healing response. HDM-promoted redistribution of E-cadherin was mediated via EGFR-dependent activation of protease-activated receptor (PAR)-2, while the concomitant ZO-1 degradation was PAR-2/EGFR-independent. Importantly, the fibrogenic cytokine transforming growth factor (TGF)-β prolonged HDM-induced EGFR phosphorylation and inhibited ligand-induced EGFR internalisation/degradation, which resulted in sustained E-cadherin and ZO-1 redistribution. Thus, allergen-induced, PAR-2/EGFR-mediated signalling decreases epithelial resistance and promotes junction disassembly. The TGF-β-enhanced EGFR signalling may be an important contributor to barrier dysfunction and increased epithelial vulnerability in response to HDM.

Research on epithelial cell lines and primary epithelium is required to dissect the mechanisms underlying the structural abnormalities in airway epithelium observed for respiratory diseases, including asthma and chronic obstructive pulmonary disease. The novel electric cell-substrate impedance sensing technique was used to monitor cell adhesion/spreading, barrier function and wound healing. Primary bronchial epithelium was compared with airway epithelial cell lines 16HBE14o-, BEAS-2B, NCI-H292 and A549. BEAS-2B, A549 and primary cells form a confluent monolayer more rapidly than do 16HBE14o- cells. In contrast, 16HBE14o- cells form stronger intercellular contacts, with a 10-fold higher resistance than BEAS-2B, A549 and NCI-H292 cells and a five-fold increase over primary cells. Accordingly, expression of the adhesion molecules zona occludens-1 and E-cadherin was highest in 16HBE14o- cells. These molecules were localised in intercellular junctions in both 16HBE14o- and primary cells. Finally, restoration of barrier function upon injury was impaired in BEAS-2B compared to 16HBE14o- cells. In conclusion, epithelial cell types display remarkable phenotypic differences and should, accordingly, be used to address specific research questions. 16HBE14o- cells appear most suitable for studies on barrier formation, whereas resemblance in attachment of primary and BEAS-2B and A549 cells makes the latter more important for translational research on cell-matrix contact.