Cooperative effects of Th2 cytokines and allergen on normal and asthmatic bronchial epithelial cells

The airway epithelium: an orchestrator of inflammation, a key structural barrier and a therapeutic target in severe asthma

Asthma is a disease of heterogeneous pathology, typically characterised by excessive inflammatory and bronchoconstrictor responses to the environment. The clinical expression of the disease is a consequence of the interaction between environmental factors and host factors over time, including genetic susceptibility, immune dysregulation and airway remodelling. As a critical interface between the host and the environment, the airway epithelium plays an important role in maintaining homeostasis in the face of environmental challenges. Disruption of epithelial integrity is a key factor contributing to multiple processes underlying asthma pathology. In this review, we first discuss the unmet need in asthma management and provide an overview of the structure and function of the airway epithelium. We then focus on key pathophysiological changes that occur in the airway epithelium, including epithelial barrier disruption, immune hyperreactivity, remodelling, mucus hypersecretion and mucus plugging, highlighting how these processes manifest clinically and how they might be targeted by current and novel therapeutics.

A review of the pathophysiology and the role of ion channels on bronchial asthma

Asthma is one of the main non-communicable chronic diseases and affects a huge portion of the population. It is a multifactorial disease, classified into several phenotypes, being the allergic the most frequent. The pathophysiological mechanism of asthma involves a Th2-type immune response, with high concentrations of allergen-specific immunoglobulin E, eosinophilia, hyperreactivity and airway remodeling. These mechanisms are orchestrated by intracellular signaling from effector cells, such as lymphocytes and eosinophils. Ion channels play a fundamental role in maintaining the inflammatory response on asthma. In particular, transient receptor potential (TRP), stock-operated Ca2+ channels (SOCs), Ca2+-activated K+ channels (IKCa and BKCa), calcium-activated chloride channel (TMEM16A), cystic fibrosis transmembrane conductance regulator (CFTR), piezo-type mechanosensitive ion channel component 1 (PIEZO1) and purinergic P2X receptor (P2X). The recognition of the participation of these channels in the pathological process of asthma is important, as they become pharmacological targets for the discovery of new drugs and/or pharmacological tools that effectively help the pharmacotherapeutic follow-up of this disease, as well as the more specific mechanisms involved in worsening asthma.

Imprinting of bronchial epithelial cells upon in vivo rhinovirus infection in people with asthma

Background

Defective translocation of the translational repressor TIAR (T-cell internal antigen receptor) in bronchial epithelial cells (BECs) from asthma patients underlies epithelial hyperresponsiveness, reflected by an exaggerated production of a select panel of inflammatory cytokines such as CXCL-8, interleukin (IL)-6, granulocyte colony-stimulating factor, CXCL-10, upon exposure to tumour necrosis factor (TNF) and IL-17A. With this study we aimed to clarify whether epithelial hyperresponsiveness is a consistent finding, is changed upon in vivo exposure to rhinovirus (RV)-A16 and applies to the bronchoconstrictor endothelin-1.

Methods

BECs were obtained from asthma patients (n=18) and healthy individuals (n=11), 1 day before and 6 days post-RV-A16 exposure. BECs were cultured and stimulated with TNF and IL-17A and inflammatory mediators were analysed. The bronchoalveolar lavage fluid (BALF) was obtained in parallel with BECs to correlate differential cell counts and inflammatory mediators with epithelial hyperresponsiveness.

Results

Epithelial hyperresponsiveness was confirmed in sequential samples and even increased in BECs from asthma patients after RV-A16 exposure, but not in BECs from healthy individuals. Endothelin-1 tended to increase in BECs from asthma patients collected after RV-A16 exposure, but not in BECs from healthy individuals. In vitro CXCL-8 and endothelin-1 production correlated. In vivo relevance for in vitro CXCL-8 and endothelin-1 production was shown by correlations with forced expiratory volume in 1 s % predicted and CXCL-8 BALF levels.

Conclusion

Epithelial hyperresponsiveness is an intrinsic defect in BECs from asthma patients, which increases upon viral exposure, but not in BECs from healthy individuals. This epithelial hyperresponsiveness also applies to the bronchoconstrictor endothelin-1, which could be involved in airway obstruction.

Epithelial hyperresponsiveness is an intrinsic defect in bronchial epithelium from asthma patients, which increases upon rhinovirus exposure, but not in healthy individualshttps://bit.ly/3xLhjuj

In utero exposure to electronic-cigarette aerosols decreases lung fibrillar collagen content, increases Newtonian resistance and induces sex-specific molecular signatures in neonatal mice

Approximately 7% of pregnant women in the United States use electronic-cigarette (e-cig) devices during pregnancy. There is, however, no scientific evidence to support e-cig use as being 'safe' during pregnancy. Little is known about the effects of fetal exposures to e-cig aerosols on lung alveologenesis. In the present study, we tested the hypothesis that in utero exposure to e-cig aerosol impairs lung alveologenesis and pulmonary function in neonates. Pregnant BALB/c mice were exposed 2 h a day for 20 consecutive days during gestation to either filtered air or cinnamon-flavored e-cig aerosol (36 mg/mL of nicotine). Lung tissue was collected in offspring during lung alveologenesis on postnatal day (PND) 5 and PND11. Lung function was measured at PND11. Exposure to e-cig aerosol in utero led to a significant decrease in body weights at birth which was sustained through PND5. At PND5, in utero e-cig exposures dysregulated genes related to Wnt signaling and epigenetic modifications in both females (~ 120 genes) and males (40 genes). These alterations were accompanied by reduced lung fibrillar collagen content at PND5-a time point when collagen content is close to its peak to support alveoli formation. In utero exposure to e-cig aerosol also increased the Newtonian resistance of offspring at PND11, suggesting a narrowing of the conducting airways. At PND11, in females, transcriptomic dysregulation associated with epigenetic alterations was sustained (17 genes), while WNT signaling dysregulation was largely resolved (10 genes). In males, at PND11, the expression of only 4 genes associated with epigenetics was dysregulated, while 16 Wnt related-genes were altered. These data demonstrate that in utero exposures to cinnamon-flavored e-cig aerosols alter lung structure and function and induce sex-specific molecular signatures during lung alveologenesis in neonatal mice. This may reflect epigenetic programming affecting lung disease development later in life.

Development of a Simple and Robust Whole Blood Assay with Dual Co-Stimulation to Quantify the Release of T-Cellular Signature Cytokines in Response to Aspergillus fumigatus Antigens

Deeper understanding of mold-induced cytokine signatures could promote advances in the diagnosis and treatment of invasive mycoses and mold-associated hypersensitivity syndromes. Currently, most T-cellular immunoassays in medical mycology require the isolation of mononuclear cells and have limited robustness and practicability, hampering their broader applicability in clinical practice. Therefore, we developed a simple, cost-efficient whole blood (WB) assay with dual α-CD28 and α-CD49d co-stimulation to quantify cytokine secretion in response to Aspergillus fumigatus antigens. Dual co-stimulation strongly enhanced A. fumigatus-induced release of T-cellular signature cytokines detectable by enzyme-linked immunosorbent assay (ELISA) or a multiplex cytokine assay. Furthermore, T-cell-dependent activation and cytokine response of innate immune cells was captured by the assay. The protocol consistently showed little technical variation and high robustness to pre-analytic delays of up to 8 h. Stimulation with an A. fumigatus lysate elicited at least 7-fold greater median concentrations of key T-helper cell signature cytokines, including IL-17 and the type 2 T-helper cell cytokines IL-4 and IL-5 in WB samples from patients with Aspergillus-associated lung pathologies versus patients with non-mold-related lung diseases, suggesting high discriminatory power of the assay. These results position WB-ELISA with dual co-stimulation as a simple, accurate, and robust immunoassay for translational applications, encouraging further evaluation as a platform to monitor host immunity to opportunistic pathogens.

Upregulated Expression of Toll-Like Receptor 7 in Peripheral Blood Basophils of Patients With Allergic Rhinitis

Background

Recently, it has been reported that Toll-like receptor 7 (TLR7) agonists can improve allergic rhinitis (AR) symptoms by up-regulation of Th1 cytokine release and suppression of Th2 cell functions. However, little is known of the expression of TLR7 in basophils of AR.

Objective

To explore the expression of TLR7 in basophils of AR, and influence of allergens on TLR7 expression.

Methods

The expression levels of TLR7 in basophils of patients with AR were determined by flow cytometry, and the influence of allergens on TLR7 expression was examined by real time (q) PCR.

Results

The percentages of TLR7+CCR3+ cells ( P < 0.001 and P = 0.011), TLR7+CD123+HLA-DR− cells ( P = 0 .016 and P = 0.042) and TLR7+CCR3+CD123+HLA-DR− cells ( P = 0.046 and P = 0.035) in blood granulocyte and mononucleated cell populations of the patients with AR were increased, respectively compared with HC subjects. TLR7 MFI on CCR3+ cells ( P = 0.050 and P = 0.043), CD123+HLA-DR− cells ( P < 0.001 and P = 0.002) and CCR3+CD123+HLA-DR− cells ( P < 0.001 and P = 0.003) were enhanced compared with HC subjects. Allergens Der p1 and OVA provoked upregulation of TLR7 expression at both protein and mRNA levels and IL-13 production in KU812 cells. House Dust Mite extract (HDME), Artemisia sieversiana wild allergen extract (ASWE), IL-31, IL-33, IL-37, and TSLP provoked elevation of IL-6 release from KU812 cells following 2 h incubation period.

Conclusions

The percentage of TLR7+ basophils and TLR7 expression intensity in a single basophil are both increased in the blood of patients with AR, indicating that basophils likely contribute to the pathogenesis of AR via TLR7.

Upregulation of epithelial metallothioneins by metal-rich ultrafine particulate matter from an underground railway

Airborne particulate matter (PM) is a leading cause of mortality and morbidity. However, understanding of the range and mechanisms of effects of PM components is poor. PM generated in underground railways is rich in metals, especially iron. In the ultrafine (UFPM; <0.1 μm diameter) fraction, the combination of small size and metal enrichment poses an unknown health risk. This study aimed to analyse transcriptomic responses to underground UFPM in primary bronchial epithelial cells (PBECs), a key site of PM deposition. The oxidation state of iron in UFPM from an underground station was determined by X-ray absorption near edge structure (XANES) spectroscopy. Antioxidant response was assayed using a reporter cell line transfected with an antioxidant response element (ARE)-luciferase construct. Differentiated PBECs were exposed to UFPM for 6 h or 24 h for RNA-Seq and RT-qPCR analysis. XANES showed predominance of redox-active Fe3O4, with ROS generation confirmed by induction of ARE-luciferase expression. 6 h exposure of PBECs to UFPM identified 52 differentially expressed genes (DEGs), especially associated with epithelial maintenance, whereas 24 h exposure yielded 23 DEGs, particularly involved with redox homeostasis and metal binding. At both timepoints, there was upregulation of members of the metallothionein family, low molecular weight proteins with antioxidant activity whose main function is binding and homeostasis of zinc and copper ions, but not iron ions. This upregulation was partially inhibited by metal chelation or ROS scavenging. These data suggest differential regulation of responses to metal-rich UFPM depending on exposure period, and highlight novel pathways and markers of PM exposure, with the role of metallothioneins warranting further investigation.

Proinflammatory Pathways in the Pathogenesis of Asthma

There are multiple proinflammatory pathways in the pathogenesis of asthma. These include both innate and adaptive inflammation, in addition to inflammatory and physiologic responses mediated by eicosanoids. An important component of the innate allergic immune response is ILC2 activated by interleukin (IL)-33, thymic stromal lymphopoietin, and IL-25 to produce IL-5 and IL-13. In terms of the adaptive T-lymphocyte immunity, CD4+ Th2 and IL-17-producing cells are critical in the inflammatory responses in asthma. Last, eicosanoids involved in asthma pathogenesis include prostaglandin D₂ and the cysteinyl leukotrienes that promote smooth muscle constriction and inflammation that propagate allergic responses.

Ezrin, a Membrane Cytoskeleton Cross-Linker Protein, as a Marker of Epithelial Damage in Asthma

RATIONALE

Bronchial epithelial cell damage occurs in patients with bronchial asthma. Ezrin, a membrane-cytoskeleton protein, maintains cellular morphology and intercellular adhesion and protects the barrier function of epithelial cells.

OBJECTIVES

To study the role of ezrin in bronchial epithelial cells injury and correlate its expression with asthma severity.

METHODS

Levels of ezrin were measured in exhaled breath condensate (EBC) and serum in patients with asthma and BAL fluid (BALF) from a mouse model of asthma by ELISA. The regulation of IL-13 on ezrin protein levels was studied in primary bronchial epithelial cells. Ezrin knockdown using shRNA was studied in human bronchial epithelial 16HBE cells.

MEASUREMENTS AND MAIN RESULTS

Ezrin levels were decreased in asthmatic EBC (92.7 ± 34.99 vs. 150.5 ± 10.22 pg/ml, P < 0.0001) and serum (700.7 ± 55.59 vs. 279.2 ± 25.83 pg/ml, P < 0.0001) compared with normal subjects. Levels were much lower in uncontrolled (P < 0.001) and partly controlled patients (P < 0.01) compared with well-controlled subjects. EBC and serum ezrin levels correlated with lung function in patients with asthma and serum ezrin levels were negatively correlated with serum IL-13 and periostin. IL-13-induced downregulation of ezrin expression in primary bronchial epithelial cells was significantly attenuated by the Janus tyrosine kinase 2 inhibitor, TG101348. Ezrin knockdown changed 16HBE cell morphology, enlarged intercellular spaces, and increased their permeability. Ezrin expression was decreased in the lung tissue and BALF of "asthmatic" mice and negatively correlated with BALF IL-13 level.

CONCLUSIONS

Ezrin downregulation is associated with IL-13-induced epithelial damage and might be a potential biomarker of asthma control.

Porous Three-Dimensional Silk Fibroin Scaffolds for Tracheal Epithelial Regeneration in Vitro and in Vivo

The regeneration of functional epithelial lining is critical for artificial grafts to repair tracheal defects. Although silk fibroin (SF) scaffolds have been widely studied for biomedical application (e.g., artificial skin), its potential for tracheal substitute and epithelial regeneration is still unknown. In this study, we fabricated porous three-dimensional (3D) silk fibroin scaffolds and cocultured them with primary human tracheobronchial epithelial cells (HBECs) for 21 days in vitro. Examined by scanning electronic microscopy (SEM) and calcein-AM staining with inverted phase contrast microscopy, the SF scaffolds showed excellent properties of promoting cell growth and proliferation for at least 21 days with good viability. In vivo, the porous 3D SF scaffolds (n = 18) were applied to repair a rabbit anterior tracheal defect. In the control group (n = 18), rabbit autologous pedicled trachea wall without epithelium, an ideal tracheal substitute, was implanted in situ. Observing by endoscopy and computed tomography (CT) scan, the repaired airway segment showed no wall collapse, granuloma formation, or stenosis during an 8-week interval in both groups. SEM and histological examination confirmed the airway epithelial growth on the surface of porous SF scaffolds. Both the epithelium repair speed and the epithelial cell differentiation degree in the SF scaffold group were comparable to those in the control group. Neither severe inflammation nor excessive fibrosis occurred in both groups. In summary, the porous 3D SF scaffold is a promising biomaterial for tracheal repair by successfully supporting tracheal wall contour and promoting tracheal epithelial regeneration.

IL-34 regulates IL-6 and IL-8 production in human lung fibroblasts via MAPK, PI3K-Akt, JAK and NF-κB signaling pathways

IL-34 plays diverse roles in disease due to its inflammatory and immunosuppressive properties. Elevated IL-34 expression has been observed in lung cancers and pulmonary infections although its role is unclear. We found that IL-34 addition to primary lung fibroblasts significantly promoted IL-6 and IL-8 expression in a dose and time dependent manner. These effects were reversed when JAK, NF-κB, Akt and p38 inhibitors were included before IL-34 addition. Protein phosphorylation in these pathways was also observed through western-blotting. Stimulation of human lung fibroblasts with IL-34 in combination with TNF-α, IL-17A and IL-4 enhanced inflammatory cytokine production. Our data confirmed the inflammatory effect of IL-34 on human lung fibroblasts and suggested that the IL-34/CSF-1R axis may be a novel therapeutic target in pulmonary disease.

Independent and combined effects of airway remodelling and allergy on airway responsiveness

Airway remodelling and allergic inflammation are key features of airway hyperresponsiveness (AHR) in asthma; however, their interrelationships are unclear. The present study investigated the separate and combined effects of increased airway smooth muscle (ASM) layer thickness and allergy on AHR. We integrated a protocol of ovalbumin (OVA)-induced allergy into a non-inflammatory mouse model of ASM remodelling induced by conditional and airway-specific expression of transforming growth factor-α (TGF-α) in early growth response-1 (Egr-1)-deficient transgenic mice, which produced thickening of the ASM layer following ingestion of doxycycline. Mice were sensitised to OVA and assigned to one of four treatment groups: Allergy - normal chow diet and OVA challenge; Remodelling - doxycycline in chow and saline challenge; Allergy and Remodelling - doxycycline in chow and OVA challenge; and Control - normal chow diet and saline challenge. Airway responsiveness to methacholine (MCh) and histology were assessed. Compared with the Control group, airway responsiveness to MCh was increased in the Allergy group, independent of changes in wall structure, whereas airway responsiveness in the Remodelling group was increased independent of exposure to aeroallergen. The combined effects of allergy and remodelling on airway responsiveness were greater than either of them alone. There was a positive relationship between the thickness of the ASM layer with airway responsiveness, which was shifted upward in the presence of allergy. These findings support allergy and airway remodelling as independent causes of variable and excessive airway narrowing.

Effects of icariin on asthma mouse model are associated with regulation of prostaglandin D2 level

BACKGROUND

We aimed to observe the effect of icariin on an asthma mouse model and explore the potential underlying mechanisms.

METHODS

The asthma mouse model was established by ovalbumin (OVA) sensitisation and respiratory syncytial virus (RSV) infection and then treated with icariin. Airway resistance was assessed by whole body plethysmograph. In addition, pathological slides were stained with haematoxylin-eosin, and the peribronchial inflammation was observed microscopically. The concentration of prostaglandin D2 (PGD2) in serum and bronchoalveolar lavage fluid (BALF) was detected by enzyme-linked immuno sorbent assay (ELISA). The relative level of prostaglandin D2 receptor 2 (CRTH2) mRNA was assessed by real-time quantitative PCR.

RESULTS

Compared with the icariin-untreated group, there was a significant reduction of Penh in the treated group. Total leucocyte amount and all sorts of leukocytes were lower in the treated group than in the untreated group. HE staining results revealed that a large number of inflammatory cells infiltrated into the peribronchial tissues of untreated group, and the degree of airway inflammation decreased significantly in the treated group. PGD2 in serum and BALF, as well as CRTH2 mRNA level in lung tissues were lower in the treated group than in the untreated group.

CONCLUSION

Icariin is a promising therapeutic strategy for asthma, and PGD2 might be a new target for asthma therapy in OVA-induced and RSV-infected asthma model.

Allergen-Specific CD4(+) T Cells in Human Asthma

In allergic asthma, aeroallergen exposure of sensitized individuals mobilizes robust innate and adaptive airway immune responses, stimulating eosinophilic airway inflammation and the activation and infiltration of allergen-specific CD4(+) T cells into the airways. Allergen-specific CD4(+) T cells are thought to be central players in the asthmatic response as they specifically recognize the allergen and initiate and orchestrate the asthmatic inflammatory response. In this article, we briefly review the role of allergen-specific CD4(+) T cells in the pathogenesis of human allergic airway inflammation in allergic individuals, discuss the use of allergen-major histocompatibility complex class II tetramers to characterize allergen-specific CD4(+) T cells, and highlight current gaps in knowledge and directions for future research pertaining to the role of allergen-specific CD4(+) T cells in human asthma.

Human CD8+ T Cells in Asthma: Possible Pathways and Roles for NK-Like Subtypes

Asthma affects approximately 300 million people worldwide and is the most common chronic lung disease, which usually is associated with bronchial inflammation. Most research has focused upon the role of CD4+ T cells, and relatively few studies have addressed the phenotypic and functional roles of CD8+ T cell types and subtypes. Human NK-like CD8+ T cells may involve cells that have been described as CD8+CD28−, CD8+CD28−CD57+, CD8+CD27−, or CD8+ effector memory (TEM) cells, among other. However, most of the data that are available regarding these various cell types were obtained in murine models did not thoroughly characterize these cells with phenotypically or functionally or did not involve asthma-related settings. Nevertheless, one may conceptualize three principal roles for human NK-like CD8+ T cells in asthma: disease-promoting, regulatory, and/or tissue repair. Although evidence for some of these roles is scarce, it is possible to extrapolate some data from overlapping or related CD8+ T cell phenotypes, with caution. Clearly, further research is warranted, namely in terms of thorough functional and phenotypic characterization of human NK-like CD8+ T cells in human asthma of varying severity.

Strategies targeting the IL-4/IL-13 axes in disease

IL-4 and IL-13 are pleiotropic Th2 cytokines produced by a wide variety of different cell types and responsible for a broad range of biology and functions. Physiologically, Th2 cytokines are known to mediate host defense against parasites but they can also trigger disease if their activities are dysregulated. In this review we discuss the rationale for targeting the IL-4/IL-13 axes in asthma, atopic dermatitis, allergic rhinitis, COPD, cancer, inflammatory bowel disease, autoimmune disease and fibrotic disease as well as evaluating the associated clinical data derived from blocking IL-4, IL-13 or IL-4 and IL-13 together.

Airway responses towards allergens - from the airway epithelium to T cells

The prevalence of allergic diseases such as allergic rhinitis is increasing, affecting up to 30% of the human population worldwide. Allergic sensitization arises from complex interactions between environmental exposures and genetic susceptibility, resulting in inflammatory T helper 2 (Th2) cell-derived immune responses towards environmental allergens. Emerging evidence now suggests that an epithelial dysfunction, coupled with inherent properties of environmental allergens, can be responsible for the inflammatory responses towards allergens. Several epithelial-derived cytokines, such as thymic stromal lymphopoietin (TSLP), IL-25 and IL-33, influence tissue-resident dendritic cells (DCs) as well as Th2 effector cells. Exposure to environmental allergens does not elicit Th2 inflammatory responses or any clinical symptoms in nonatopic individuals, and recent findings suggest that a nondamaged, healthy epithelium lowers the DCs' ability to induce inflammatory T-cell responses towards allergens. The purpose of this review was to summarize the current knowledge on which signals from the airway epithelium, from first contact with inhaled allergens all the way to the ensuing Th2-cell responses, influence the pathology of allergic diseases.

Aeroparticles, Composition, and Lung Diseases

Urban air pollution is a serious worldwide problem due to its impact on human health. In the past 60 years, growing evidence established a correlation between exposure to air pollutants and the developing of severe respiratory diseases. Recently particulate matter (PM) is drawing more public attention to various aspects including historical backgrounds, physicochemical characteristics, and its pathological role. Therefore, this review is focused on these aspects. The most famous air pollution disaster happened in London on December 1952; it has been calculated that more than 4,000 deaths occurred during this event. Air pollution is a complex mix of gases and particles. Gaseous pollutants disseminate deeply into the alveoli, allowing its diffusion through the blood–air barrier to several organs. Meanwhile, PM is a mix of solid or liquid particles suspended in the air. PM is deposited at different levels of the respiratory tract, depending on its size: coarse particles (PM₁₀) in upper airways and fine particles (PM_2.5) can be accumulated in the lung parenchyma, inducing several respiratory diseases. Additionally to size, the composition of PM has been associated with different toxicological outcomes on clinical and epidemiological, as well as in vivo and in vitro animal and human studies. PM can be constituted by organic, inorganic, and biological compounds. All these compounds are capable of modifying several biological activities, including alterations in cytokine production, coagulation factors balance, pulmonary function, respiratory symptoms, and cardiac function. It can also generate different modifications during its passage through the airways, like inflammatory cells recruitment, with the release of cytokines and reactive oxygen species (ROS). These inflammatory mediators can activate different pathways, such as MAP kinases, NF-κB, and Stat-1, or induce DNA adducts. All these alterations can mediate obstructive or restrictive respiratory diseases like asthma, COPD, pulmonary fibrosis, and even cancer. In 2013, outdoor air pollution was classified as Group 1 by IARC based on all research studies data about air pollution effects. Therefore, it is important to understand how PM composition can generate several pulmonary pathologies.

A novel lung explant model for the ex vivo study of efficacy and mechanisms of anti-influenza drugs

Influenza A virus causes considerable morbidity and mortality largely because of a lack of effective antiviral drugs. Viral neuraminidase inhibitors, which inhibit viral release from the infected cell, are currently the only approved drugs for influenza, but have recently been shown to be less effective than previously thought. Growing resistance to therapies that target viral proteins has led to increased urgency in the search for novel anti-influenza compounds. However, discovery and development of new drugs have been restricted because of differences in susceptibility to influenza between animal models and humans and a lack of translation between cell culture and in vivo measures of efficacy. To circumvent these limitations, we developed an experimental approach based on ex vivo infection of human bronchial tissue explants and optimized a method of flow cytometric analysis to directly quantify infection rates in bronchial epithelial tissues. This allowed testing of the effectiveness of TVB024, a vATPase inhibitor that inhibits viral replication rather than virus release, and to compare efficacy with the current frontline neuraminidase inhibitor, oseltamivir. The study showed that the vATPase inhibitor completely abrogated epithelial cell infection, virus shedding, and the associated induction of proinflammatory mediators, whereas oseltamivir was only partially effective at reducing these mediators and ineffective against innate responses. We propose, therefore, that this explant model could be used to predict the efficacy of novel anti-influenza compounds targeting diverse stages of the viral replication cycle, thereby complementing animal models and facilitating progression of new drugs into clinical trials.

Airway epithelium interactions with aeroallergens: role of secreted cytokines and chemokines in innate immunity

Airway epithelial cells are the first line of defense against the constituents of the inhaled air, which include allergens, pathogens, pollutants, and toxic compounds. The epithelium not only prevents the penetration of these foreign substances into the interstitium, but also senses their presence and informs the organism’s immune system of the impending assault. The epithelium accomplishes the latter through the release of inflammatory cytokines and chemokines that recruit and activate innate immune cells at the site of assault. These epithelial responses aim to eliminate the inhaled foreign substances and minimize their detrimental effects to the organism. Quite frequently, however, the innate immune responses of the epithelium to inhaled substances lead to chronic and high level release of pro-inflammatory mediators that may mediate the lung pathology seen in asthma. The interactions of airway epithelial cells with allergens will be discussed with particular focus on interactions-mediated epithelial release of cytokines and chemokines and their role in the immune response. As pollutants are other major constituents of inhaled air, we will also discuss how pollutants may alter the responses of airway epithelial cells to allergens.

The effects on bronchial epithelial mucociliary cultures of coarse, fine, and ultrafine particulate matter from an underground railway station

We have previously shown that underground railway particulate matter (PM) is rich in iron and other transition metals across coarse (PM_10–2.5), fine (PM_2.5), and quasi-ultrafine (PM_0.18) fractions and is able to generate reactive oxygen species (ROS). However, there is little knowledge of whether the metal-rich nature of such particles exerts toxic effects in mucus-covered airway epithelial cell cultures or whether there is an increased risk posed by the ultrafine fraction. Monolayer and mucociliary air-liquid interface (ALI) cultures of primary bronchial epithelial cells (PBECs) were exposed to size-fractionated underground railway PM (1.1–11.1 µg/cm²) and release of lactate dehydrogenase and IL-8 was assayed. ROS generation was measured, and the mechanism of generation studied using desferrioxamine (DFX) and N-acetylcysteine (NAC). Expression of heme oxygenase-1 (HO-1) was determined by RT-qPCR. Particle uptake was studied by transmission electron microscopy. Underground PM increased IL-8 release from PBECs, but this was diminished in mucus-secreting ALI cultures. Fine and ultrafine PM generated a greater level of ROS than coarse PM. ROS generation by ultrafine PM was ameliorated by DFX and NAC, suggesting an iron-dependent mechanism. Despite the presence of mucus, ALI cultures displayed increased HO-1 expression. Intracellular PM was observed within vesicles, mitochondria, and free in the cytosol. The results indicate that, although the mucous layer appears to confer some protection against underground PM, ALI PBECs nonetheless detect PM and mount an antioxidant response. The combination of increased ROS-generating ability of the metal-rich ultrafine fraction and ability of PM to penetrate the mucous layer merits further research.

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.

The bovine lung in biomedical research: visually guided bronchoscopy, intrabronchial inoculation and in vivo sampling techniques

There is an ongoing search for alternative animal models in research of respiratory medicine. Depending on the goal of the research, large animals as models of pulmonary disease often resemble the situation of the human lung much better than mice do. Working with large animals also offers the opportunity to sample the same animal repeatedly over a certain course of time, which allows long-term studies without sacrificing the animals.

The aim was to establish in vivo sampling methods for the use in a bovine model of a respiratory Chlamydia psittaci infection. Sampling should be performed at various time points in each animal during the study, and the samples should be suitable to study the host response, as well as the pathogen under experimental conditions.

Bronchoscopy is a valuable diagnostic tool in human and veterinary medicine. It is a safe and minimally invasive procedure. This article describes the intrabronchial inoculation of calves as well as sampling methods for the lower respiratory tract. Videoendoscopic, intrabronchial inoculation leads to very consistent clinical and pathological findings in all inoculated animals and is, therefore, well-suited for use in models of infectious lung disease. The sampling methods described are bronchoalveolar lavage, bronchial brushing and transbronchial lung biopsy. All of these are valuable diagnostic tools in human medicine and could be adapted for experimental purposes to calves aged 6-8 weeks. The samples obtained were suitable for both pathogen detection and characterization of the severity of lung inflammation in the host.

Inhaled environmental allergens and toxicants as determinants of the asthma phenotype

The driving environmental factors behind the development of the asthma phenotype remain incompletely studied and understood. Here, we present an overview of inhaled allergic/atopic and mainly nonallergic/nonatopic or toxicant shapers of the asthma phenotype, which are present in both the indoor and outdoor environment around us. The inhaled allergic/atopic factors include fungus, mold, animal dander, cockroach, dust mites, and pollen; these allergic triggers and shapers of the asthma phenotype are considered in the context of their ability to drive the immunologic IgE response and potentially induce interactions between the innate and adaptive immune responses, with special emphasis on the NADPH-dependent reactive oxygen-species-associated mechanism of pollen-associated allergy induction. The inhaled nonallergic/nonatopic, toxicant factors include gaseous and volatile agents, such as sulfur dioxide, ozone, acrolein, and butadiene, as well as particulate agents, such as rubber tire breakdown particles, and diesel exhaust particles. These toxicants are reviewed in terms of their relevant chemical characteristics and hazard potential, ability to induce airway dysfunction, and potential for driving the asthma phenotype. Special emphasis is placed on their interactive nature with other triggers and drivers, with regard to driving the asthma phenotype. Overall, both allergic and nonallergic environmental factors can interact to acutely exacerbate the asthma phenotype; some may also promote its development over prolonged periods of untreated exposure, or possibly indirectly through effects on the genome. Further therapeutic considerations should be given to these environmental factors when determining the best course of personalized medicine for individuals with asthma.

Rhinovirus-16 induced release of IP-10 and IL-8 is augmented by Th2 cytokines in a pediatric bronchial epithelial cell model

Background

In response to viral infection, bronchial epithelial cells increase inflammatory cytokine release to activate the immune response and curtail viral replication. In atopic asthma, enhanced expression of Th2 cytokines is observed and we postulated that Th2 cytokines may augment the effects of rhinovirus-induced inflammation.

Methods

Primary bronchial epithelial cell cultures from pediatric subjects were treated with Th2 cytokines for 24 h before infection with RV16. Release of IL-8, IP-10 and GM-CSF was measured by ELISA. Infection was quantified using RTqPCR and TCID₅₀. Phosphatidyl inositol 3-kinase (PI3K) and P38 mitogen activated protein kinase (MAPK) inhibitors and dexamethasone were used to investigate differences in signaling pathways.

Results

The presence of Th2 cytokines did not affect RV replication or viral titre, yet there was a synergistic increase in IP-10 release from virally infected cells in the presence of Th2 cytokines. Release of IL-8 and GM-CSF was also augmented. IP-10 release was blocked by a PI3K inhibitor and IL-8 by dexamethasone.

Conclusion

Th2 cytokines increase release of inflammatory cytokines in the presence of rhinovirus infection. This increase is independent of effects of virus replication. Inhibition of the PI3K pathway inhibits IP-10 expression.

Caveolin-1 controls airway epithelial barrier function. Implications for asthma

The molecular basis for airway epithelial fragility in asthma has remained unclear. We investigated whether the loss of caveolin-1, the major component of caveolae and a known stabilizer of adherens junctions, contributes to epithelial barrier dysfunction in asthma. We studied the expression of caveolin-1 and adhesion molecules E-cadherin and β-catenin in airway sections, and we cultured bronchial epithelial cells from patients with asthma and from healthy control subjects. To determine the functional role of caveolin-1, we investigated the effects of caveolin-1 up-regulation and down-regulation on E-cadherin expression, barrier function, and proallergic activity in the human bronchial epithelial cell lines 16HBE and BEAS-2B. The membrane expression of caveolin-1 was significantly lower in airway epithelia from patients with asthma than from subjects without asthma, and this lower expression was maintained in vitro upon air-liquid interface and submerged culturing. Importantly, reduced caveolin-1 expression was accompanied by a loss of junctional E-cadherin and β-catenin expression, disrupted epithelial barrier function, and increased levels of the proallergic cytokine thymic stromal lymphopoietin (TSLP). Furthermore, E-cadherin redistribution upon exposure to epidermal growth factor or house dust mite was paralleled by the internalization of caveolin-1 in 16HBE cells. These effects appear to be causally related, because the short, interfering RNA down-regulation of caveolin-1 resulted in the delocalization of E-cadherin and barrier dysfunction in 16HBE cells. Moreover, caveolin-1 overexpression improved barrier function and reduced TSLP expression in BEAS-2B cells. Together, our data demonstrate a crucial role for caveolin-1 in epithelial cell-cell adhesion, with important consequences for epithelial barrier function and the promotion of Th2 responses in asthma.

Lipopolysaccharide induces up-regulation of TGF-α through HDAC2 in a rat model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification with decreased alveolar number and increased airspace. Previous studies suggested that transforming growth factor-α (TGF-α) may contribute to arrested alveolar development in BPD. Histone deacetylases (HDACs) control cellular signaling and gene expression. HDAC2 is crucial for suppression of inflammatory gene expression. Here we investigated whether HDAC2 was involved in the arrest of alveolarization, as well as the ability of HDAC2 to regulate TGF-α expression in a rat model of BPD induced by intra-amniotic injection of lipopolysaccharide (LPS). Results showed that LPS exposure led to a suppression of both HDAC1 and HDAC2 expression and activity, induced TGF-α expression, and disrupted alveolar morphology. Mechanistic studies showed that overexpression of HDAC2, but not HDAC1, suppressed LPS-induced TGF-α expression. Moreover, the HDAC inhibitor TSA or downregulation of HDAC2 by siRNA both significantly increased TGF-α expression in cultured myofibroblasts. Finally, preservation of HDAC activity by theophylline treatment improved alveolar development and attenuated TGF-α release. Together, these findings indicate that attenuation of TGF-α-mediated effects in the lung by enhancing HDAC2 may have a therapeutic effect on treating BPD.

Nasal epithelial cells can act as a physiological surrogate for paediatric asthma studies

Introduction

Differentiated paediatric epithelial cells can be used to study the role of epithelial cells in asthma. Nasal epithelial cells are easier to obtain and may act as a surrogate for bronchial epithelium in asthma studies. We assessed the suitability of nasal epithelium from asthmatic children to be a surrogate for bronchial epithelium using air-liquid interface cultures.

Methods

Paired nasal and bronchial epithelial cells from asthmatic children (n = 9) were differentiated for 28 days under unstimulated and IL-13-stimulated conditions. Morphological and physiological markers were analysed using immunocytochemistry, transepithelial-electrical-resistance, Quantitative Real-time-PCR, ELISA and multiplex cytokine/chemokine analysis.

Results

Physiologically, nasal epithelial cells from asthmatic children exhibit similar cytokine responses to stimulation with IL-13 compared with paired bronchial epithelial cells. Morphologically however, nasal epithelial cells differed significantly from bronchial epithelial cells from asthmatic patients under unstimulated and IL-13-stimulated conditions. Nasal epithelial cells exhibited lower proliferation/differentiation rates and lower percentages of goblet and ciliated cells when unstimulated, while exhibiting a diminished and varied response to IL-13.

Conclusions

We conclude that morphologically, nasal epithelial cells would not be a suitable surrogate due to a significantly lower rate of proliferation and differentiation of goblet and ciliated cells. Physiologically, nasal epithelial cells respond similarly to exogenous stimulation with IL-13 in cytokine production and could be used as a physiological surrogate in the event that bronchial epithelial cells are not available.

Innate immune response to LPS in airway epithelium is dependent on chronological age and antecedent exposures

The immune mechanisms for neonatal susceptibility to respiratory pathogens are poorly understood. Given that mucosal surfaces serve as a first line of host defense, we hypothesized that the innate immune response to infectious agents may be developmentally regulated in airway epithelium. To test this hypothesis, we determined whether the expression of IL-8 and IL-6 in airway epithelium after LPS exposure is dependent on chronological age. Tracheas from infant, juvenile, and adult rhesus monkeys were first exposed to LPS ex vivo, and then processed for air-liquid interface primary airway epithelial cell cultures and secondary LPS treatment in vitro. Compared with adult cultures, infant and juvenile cultures expressed significantly reduced concentrations of IL-8 after LPS treatment. IL-8 protein in cultures increased with animal age, whereas LPS-induced IL-6 protein was predominantly associated with juvenile cultures. Toll-like receptor (TLR) pathway RT-PCR arrays showed differential expressions of multiple mRNAs in infant cultures relative to adult cultures, including IL-1α, TLR10, and the peptidoglycan recognition protein PGLYRP2. To determine whether the age-dependent cytokine response to LPS is reflective of antecedent exposures, we assessed primary airway epithelial cell cultures established from juvenile monkeys housed in filtered air since birth. Filtered air-housed animal cultures exhibited LPS-induced IL-8 and IL-6 expression that was discordant with age-matched ambient air-housed animals. A single LPS aerosol in vivo also affected this cytokine profile. Cumulatively, our findings demonstrate that the innate immune response to LPS in airway epithelium is variable with age, and may be modulated by previous environmental exposures.

Statin use and markers of immunity in the Doetinchem cohort study

It has been suggested that statins can both stimulate and suppress the immune system, and thereby, may influence autoimmune diseases. Therefore, we studied effects of statins on innate and adaptive immunity, and self-tolerance by measuring serological levels of C-reactive protein (CRP), neopterin, immunoglobulin E (IgE) antibodies and the presence of autoantibodies (antinuclear antibodies (ANA) and IgM rheumatoid factor (RF)) in the general population. We conducted a nested case-control study within the population-based Doetinchem cohort. Data from health questionnaires, serological measurements and information on medication from linkage to pharmacy-dispensing records were available. We selected 332 statin users (cases) and 331 non-users (controls), matched by age, sex, date of serum collection, history of cardiovascular diseases, diabetes mellitus type II and stroke. Multivariate regression analyses were performed to estimate effect of statins on the immune system. The median level of CRP in statin users (1.28 mg/L, interquartile range (IQR): 0.59-2.79) was lower than in non-users (1.62 mg/L, IQR: 0.79-3.35), which after adjustment was estimated to be a 28% lower level. We observed an inverse association between duration of statin use and CRP levels. Elevated levels of IgE (>100 IU/mL) were more prevalent in statin users compared to non-users. A trend towards increased levels of IgE antibodies in statin users was observed, whereas no associations were found between statin use and levels of neopterin or the presence of autoantibodies. In this general population sub-sample, we observed an anti-inflammatory effect of statin use and a trend towards an increase of IgE levels, an surrogate marker for Th (helper) 2 responses without a decrease in neopterin levels, a surrogate marker for Th1 response and/or self-tolerance. We postulate that the observed decreased inflammatory response during statin therapy may be important but is insufficient to induce loss of self-tolerance.

Comparison of TNF antagonism by etanercept and dexamethasone on airway epithelium and remodeling in an experimental model of asthma

BACKGROUND

The aim of the study was to compare the influence of TNF antagonism and corticosteroid treatment on epithelial, smooth muscle and basement membrane component of airway remodeling in an experimental murine model of chronic asthma.

METHODS

We used 30 BALB/c mice. Group 1 not exposed to ovalbumin or any medication was designated as control group. Chronic asthma model was achieved in the other three groups with intraperitoneal (IP) and inhaled ovalbumin. Then, Group 2 received IP saline, Group 3 received IP dexamethasone and Group 4 received IP etanercept. Epithelial, subepithelial smooth muscle and basement membrane thickness as well as goblet cells and mast cells were examined on samples isolated from left lung.

RESULTS

Etanercept treatment led to thinner epithelial and basement membrane layer and lower goblet and mast cell number than untreated asthmatic mice (p<0.001, p=0.001, p=0.005 and p=0.03 respectively). Neither epithelial and basement membrane thickness nor mast cell number was different among mice treated with etanercept and dexamethasone (p=0.38, p=0.79 and p=0.51 respectively). However, etanercept group was associated with thicker subepithelial muscle layer but lower goblet cell number (p<0.001 and p=0.04 respectively) than dexamethasone group.

CONCLUSIONS

Corticosteroids are more effective in decreasing smooth muscle mass while TNF antagonists in reducing goblet cell number in animal model of asthma. Therefore, further research is needed to assess the synergistic use of TNF antagonism and dexamethasone for more rational remodeling control.

The innate antiviral response upregulates IL-13 receptor α2 in bronchial fibroblasts

BACKGROUND

IL-13 is key mediator of allergic inflammation in asthmatic patients. We have previously shown that the decoy receptor IL-13 receptor (IL-13R) α2 attenuates responses of fibroblasts to IL-13. Because the expression of IL-13Rα2 can be regulated by IFN-γ, a type II interferon, we hypothesized that innate antiviral responses characterized by type I interferon expression can also induce IL-13Rα2 expression.

OBJECTIVE

We sought to induce an innate antiviral response in primary fibroblasts using exposure to double-stranded RNA (dsRNA) and to examine the expression and function of IL-13Rα2.

METHODS

Primary human fibroblasts were cultured from endobronchial biopsy specimens obtained from healthy or asthmatic volunteers and challenged with dsRNA. Upregulation of IL-13Rα2 mRNA was measured by using real-time quantitative PCR, and cell-surface IL-13Rα2 protein expression was measured by using fluorescence-activated cell sorting. Eotaxin release was determined by means of ELISA.

RESULTS

Direct treatment with IFN-β led to an upregulation of IL-13Rα2. Exposure to dsRNA rapidly induced IFN-β mRNA in fibroblasts, and this was followed by significant induction of IL-13Rα2 mRNA and cell-surface protein expression, which was dependent on de novo protein synthesis. A neutralizing antibody to the IFN-α/β receptor blocked cell-surface expression of IL-13Rα2 in the presence of dsRNA. Pretreatment of fibroblasts with dsRNA led to attenuation of IL-13-stimulated eotaxin production. However, the presence of an IL-13Rα2 neutralizing antibody restored IL-13-stimulated eotaxin production in dsRNA-treated cells.

CONCLUSION

IFN-β induces IL-13Rα2 expression, leading to a consequential suppression of responsiveness to IL-13. These data suggest cross-talk between TH1 and TH2 pathways and point to an immunomodulatory role for IL-13Rα2 in human bronchial fibroblasts during viral infection.

Role of aberrant WNT signalling in the airway epithelial response to cigarette smoke in chronic obstructive pulmonary disease

BACKGROUND

WNT signalling is activated during lung tissue damage and inflammation. We investigated whether lung epithelial expression of WNT ligands, receptors (frizzled; FZD) or target genes is dysregulated on cigarette smoking and/or in chronic obstructive pulmonary disease (COPD).

METHODS

We studied this in human lung epithelial cell lines and primary bronchial epithelial cells (PBEC) from COPD patients and control (non-)smokers, at baseline and on cigarette smoke extract (CSE) exposure.

RESULTS

CSE significantly decreased WNT-4, WNT-10B and FZD2 and increased WNT-5B mRNA expression in 16HBE, but did not affect WNT-4 protein. The mRNA expression of WNT-4, but not other WNT ligands, was lower in PBEC from smokers than non-smokers and downregulated by CSE in PBEC from all groups, yet higher in PBEC from COPD patients than control smokers. Moreover, PBEC from COPD patients displayed higher WNT-4 protein expression than both smokers and non-smokers. Exogenously added WNT-4 significantly increased CXCL8/IL-8, IL-6, CCL5/RANTES, CCL2/MCP-1 and vascular endothelial growth factor (VEGF) secretion in 16HBE, but did not affect the canonical WNT target genes MMP-2, MMP-9, fibronectin, β-catenin, Dickkopf and axin-2, and induced activation of the non-canonical signalling molecule p38. Moreover, WNT-4 potentiated the CSE-induced upregulation of IL-8 and VEGF.

CONCLUSIONS

WNT-4 mRNA and protein levels are higher in PBEC from COPD patients than control (non-)smokers, while cigarette smoke downregulates airway epithelial WNT-4 mRNA, but not protein expression. As WNT-4 further increases CSE-induced pro-inflammatory cytokine release in bronchial epithelium, we propose that higher epithelial WNT-4 levels in combination with cigarette smoking may have important implications for the development of airway inflammation in COPD.

Human leukocyte antigen-G expression in differentiated human airway epithelial cells: lack of modulation by Th2-associated cytokines

Background

Human leukocyte antigen (HLA)-G is a nonclassical class I antigen with immunomodulatory roles including up-regulation of suppressor T regulatory lymphocytes. HLA-G was recently identified as an asthma susceptibility gene, and expression of a soluble isoform, HLA-G5, has been demonstrated in human airway epithelium. Increased presence of HLA-G5 has been demonstrated in bronchoalveolar lavage fluid recovered from patients with mild asthma; this suggests a role for this isoform in modulating airway inflammation though the mechanisms by which this occurs is unclear. Airway inflammation associated with Th2 cytokines such as IL-4 and IL-13 is a principal feature of asthma, but whether these cytokines elicit expression of HLA-G is not known.

Methods

We examined gene and protein expression of both soluble (G5) and membrane-bound (G1) HLA-G isoforms in primary differentiated human airway epithelial cells collected from normal lungs and grown in air-liquid interface culture. Cells were treated with up to 10 ng/ml of either IL-4, IL-5, or IL-13, or 100 ng/ml of the immunomodulatory cytokine IL-10, or 10,000 U/ml of the Th1-associated cytokine interferon-beta, for 24 hr, after which RNA was isolated for evaluation by quantitative PCR and protein was collected for Western blot analysis.

Results

HLA-G5 but not G1 was present in dAEC as demonstrated by quantitative PCR, western blot and confocal microscopy. Neither G5 nor G1 expression was increased by the Th2-associated cytokines IL-4, IL-5 or IL-13 over 24 hr, nor after treatment with IL-10, but was increased 4.5 ± 1.4 fold after treatment with 10,000 U/ml interferon-beta.

Conclusions

These data demonstrate the constitutive expression of a T lymphocyte regulatory molecule in differentiated human airway epithelial cells that is not modulated by Th2-associated cytokines.

Leukotriene D4 and interleukin-13 cooperate to increase the release of eotaxin-3 by airway epithelial cells

INTRODUCTION

Airway epithelial cells play a central role in the physiopathology of asthma. They release eotaxins when treated with T(H)2 cytokines such as interleukin (IL)-4 or IL-13, and these chemokines attract eosinophils and potentiate the biosynthesis of cysteinyl leukotrienes (cysLTs), which in turn induce bronchoconstriction and mucus secretion. These effects of cysLTs mainly mediated by CysLT(1) and CysLT(2) receptors on epithelial cell functions remain largely undefined. Because the release of inflammatory cytokines, eotaxins, and cysLTs occur relatively at the same time and location in the lung tissue, we hypothesized that they regulate inflammation cooperatively rather than redundantly. We therefore investigated whether cysLTs and the T(H)2 cytokines would act in concert to augment the release of eotaxins by airway epithelial cells.

METHODS

A549 cells or human primary bronchial epithelial cells were incubated with or without IL-4, IL-13, and/or LTD(4). The release of eotaxin-3 and the expression of cysLT receptors were assessed by ELISA, RT-PCR, and flow cytometry, respectively.

RESULTS

IL-4 and IL-13 induced the release of eotaxin-3 by airway epithelial cells. LTD(4) weakly induced the release of eotaxin-3 but clearly potentiated the IL-13-induced eotaxin-3 release. LTD(4) had no effect on IL-4-stimulated cells. Epithelial cells expressed CysLT(1) but not CysLT(2). CysLT(1) expression was increased by IL-13 but not by IL-4 and/or LTD(4). Importantly, the upregulation of CysLT(1) by IL-13 preceded eotaxin-3 release.

CONCLUSIONS

These results demonstrate a stepwise cooperation between IL-13 and LTD(4). IL-13 upregulates CysLT(1) expression and consequently the response to cysLTs This results in an increased release of eotaxin-3 by epithelial cells which at its turn increases the recruitment of leukocytes and their biosynthesis of cysLTs. This positive amplification loop involving epithelial cells and leukocytes could be implicated in the recruitment of eosinophils observed in asthmatics.

IL-13 in asthma and allergic disease: asthma phenotypes and targeted therapies

Decades of research in animal models have provided abundant evidence to show that IL-13 is a key T(H)2 cytokine that directs many of the important features of airway inflammation and remodeling in patients with allergic asthma. Several promising focused therapies for asthma that target the IL-13/IL-4/signal transducer and activator of transcription 6 pathway are in development, including anti-IL-13 mAbs and IL-4 receptor antagonists. The efficacy of these new potential asthma therapies depends on the responsiveness of patients. However, an understanding of how IL-13-directed therapies might benefit asthmatic patients is confounded by the complex heterogeneity of the disease. Recent efforts to classify subphenotypes of asthma have focused on sputum cellular inflammation profiles, as well as cluster analyses of clinical variables and molecular and genetic signatures. Researchers and clinicians can now evaluate biomarkers of T(H)2-driven airway inflammation in asthmatic patients, such as serum IgE levels, sputum eosinophil counts, fraction of exhaled nitric oxide levels, and serum periostin levels, to aid decision making in clinical trials and drug development and to identify subsets of patients who might benefit from therapies. Although it is unlikely that these therapies will benefit all asthmatic patients with this heterogeneous disease, advances in understanding asthma subphenotypes in relation to clinical variables and T(H)2 cytokine responses offer the opportunity to improve the efficacy and safety of proposed therapies for asthma.

Molecular mechanisms of IgE mediated food allergy

The purpose of this review is to collate current knowledge and recent advances in molecular mechanism behind the immediate type hypersensitivity of foods. Food allergy is a growing concern of human health in developed as well as developing countries now days. Food allergic reactions are mostly IgE mediated and also known as immediate type hypersensitivity or type I reaction. This review encompasses a wide range of molecular events during IgE mediated reactions like primary exposure of allergens, processing of allergens by antigen presenting cells, role of transcription factors like GATA-3, STAT-6, NF-AT, c-maf, c-kit and NF-κB, Treg cells, toll like receptors, cytokines and chemokines, class switch to IgE, FcεR1 receptor, priming of IgE on mast cells or basophils, signaling events followed by secondary exposure of allergens, degranulation and release of mediators like leukotrienes, histamines, prostaglandins, β-hexosaminidase and ultimately anaphylaxis. This review may be helpful to beginners as well as experts working in the field of allergy and immunology because of the stepwise explanations of molecular mechanisms involved in IgE mediated reactions.

The airway epithelium in asthma

Asthma is a T lymphocyte-controlled disease of the airway wall caused by inflammation, overproduction of mucus and airway wall remodeling leading to bronchial hyperreactivity and airway obstruction. The airway epithelium is considered an essential controller of inflammatory, immune and regenerative responses to allergens, viruses and environmental pollutants that contribute to asthma pathogenesis. Epithelial cells express pattern recognition receptors that detect environmental stimuli and secrete endogenous danger signals, thereby activating dendritic cells and bridging innate and adaptive immunity. Improved understanding of the epithelium's function in maintaining the integrity of the airways and its dysfunction in asthma has provided important mechanistic insight into how asthma is initiated and perpetuated and could provide a framework by which to select new therapeutic strategies that prevent exacerbations and alter the natural course of the disease.

Dendritic cell-derived tumor necrosis factor α modifies airway epithelial cell responses

Mucosal dendritic cells (DC) are intimately associated with the airway epithelium and thus are ideally situated to be first responders to pathogens. We hypothesize that DC drive innate immune responses through early release of tumor necrosis factor (TNF) α, which drives airway epithelial cell responses. In a mouse model, TNFα release was significantly increased following a single exposure to German cockroach (GC) frass, an event independent of neutrophil recruitment into the airways. While lung epithelial cells and alveolar macrophages failed to release TNFα following GC frass exposure, bone marrow-derived DC (BMDC) produced substantial amounts of TNFα suggesting their importance as early responding cells. This was confirmed by flow cytometry of pulmonary myeloid DC. Addition of GC frass-pulsed BMDC or conditioned media from GC frass-pulsed BMDC to primary mouse tracheal epithelial cells (MTEC) or MLE-15 cells induced chemokine (C-C) motif ligand (CCL) 20 and granulocyte macrophage (GM) colony-stimulating factor (CSF), both of which are important for DC recruitment, survival and differentiation. Importantly, DC do not produce CCL20 or GM-CSF following allergen exposure. Blocking TNFα receptor 1 (TNFR1) completely abolished chemokine production, suggesting that BMDC-derived TNFα induced airway epithelial cell activation and enhancement of the innate immune response. Lastly, blocking TNFR1 in vivo resulted in significantly decreased CCL20 and GM-CSF production in the lungs of mice. Together, our data strongly suggest that DC-derived TNFα plays a crucial role in the initiation of innate immune responses through the modification of airway epithelial cell responses.

Chronic Aspergillus fumigatus exposure upregulates the expression of mucin 5AC in the airways of asthmatic rats

BACKGROUND

Airway mucus hypersecretion is associated with increased morbidity and mortality in patients with asthma. Chronic Aspergillus fumigatus (A. fumigatus) exposure leads to aggravation of airway inflammation and remodeling, including goblet cell hyperplasia (GCH) and mucus hypersecretion in a rat model of asthma. The effects of chronic A. fumigatus exposure on the expression of airway mucin 5AC (MUC5AC) are unknown.

METHODS

The rat model of chronic asthma was set up by systemic sensitization and repeated challenge to ovalbumin (OVA). The asthmatic rats were exposed to chronic intranasal inhalation of A. fumigatus spores. The changes of MUC5AC expression, the extent of GCH, and airway hyperreactivity (AHR) were measured after exposure to the fungus.

RESULTS AND CONCLUSIONS

Chronic exposure to A. fumigatus upregulates the expression of MUC5AC, and induces GCH in the airways of asthma rats, and the remodeling changes of the airway epithelium was positively correlated with AHR. Upregulation of MUC5AC and induction of GCH may be mechanisms by which chronic A. fumigatus exposure promotes the progression of asthma.

Bronchial brushings for investigating airway inflammation and remodelling

Asthma is the commonest medical cause for hospital admission for children in Australia, affects more than 300 million people worldwide, and is incurable, severe in large number and refractory to treatment in many. However, there have been no new significant treatments despite intense research and billions of dollars. The advancement in our understanding in this disease has been limited due to its heterogeneity, genetic complexity and has severely been hampered particularly in children by the difficulty in obtaining relevant target organ tissue. This review attempts to provide an overview of the currently used and recently developed/adapted techniques used to obtain lung tissue with specific reference to the airway epithelium.

Accelerated and progressive and lethal liver fibrosis in mice that lack interleukin (IL)-10, IL-12p40, and IL-13Rα2

BACKGROUND & AIMS

Progressive fibrosis contributes to the morbidity of several chronic diseases; it typically develops slowly, so the mechanisms that control its progression and resolution have been difficult to model. The proteins interleukin (IL)-10, IL-12p40, and IL-13Rα2 regulate hepatic fibrosis following infection with the helminth parasite Schistosoma mansoni. We examined whether these mediators interact to slow the progression of hepatic fibrosis in mice with schistosomiasis.

METHODS

IL-10(-/-), IL-12/23(p40)(-/-), and IL-13Rα2(-/-) mice were crossed to generate triple knockout (TKO) mice. We studied these mice to determine whether the simultaneous deletion of these 3 negative regulators of the immune response accelerated mortality from liver fibrosis following infection with S mansoni.

RESULTS

Induction of inflammation by S mansoni, liver fibrosis, and mortality increased greatly in TKO mice compared with wild-type mice; 100% of the TKO mice died by 10 weeks after infection. Morbidity and mortality were associated with the development of portal hypertension, hepatosplenomegaly, gastrointestinal bleeding, ascites, thrombocytopenia, esophageal and gastric varices, anemia, and increased levels of liver enzymes, all features of advanced liver disease. IL-10, IL-12p40, and IL-13Rα2 reduced the production and activity of the profibrotic cytokine IL-13. A neutralizing antibody against IL-13 reduced the morbidity and mortality of the TKO mice following S mansoni infection.

CONCLUSIONS

IL-10, IL-12p40, and IL-13Rα2 act cooperatively to suppress liver fibrosis in mice following infection with S mansoni. This model rapidly reproduces many of the complications observed in patients with advanced cirrhosis, so it might be used to evaluate the efficacy of antifibrotic reagents being developed for schistosomiasis or other fibrotic diseases associated with a T-helper 2 cell-mediated immune response.

Responses of airway epithelium to environmental injury: role in the induction phase of childhood asthma

The pathogenesis of allergic asthma in childhood remains poorly understood. Environmental factors which appear to contribute to allergic sensitisation, with development of a Th2-biased immunological response in genetically predisposed individuals, include wheezing lower respiratory viral infections in early life and exposure to airborne environmental pollutants. These may activate pattern recognition receptors and/or cause oxidant injury to airway epithelial cells (AECs). In turn, this may promote Th2 polarisation via a "final common pathway" involving interaction between AEC, dendritic cells, and CD4+ T lymphocytes. Potentially important cytokines produced by AEC include thymic stromal lymphopoietin and interleukin-25. Their role is supported by in vitro studies using human AEC, as well as by experiments in animal models. To date, however, few investigations have employed models of the induction phase of childhood asthma. Further research may help to identify interventions that could reduce the risk of allergic asthma.

IL-13-induced MUC5AC production and goblet cell differentiation is steroid resistant in human airway cells

BACKGROUND

Glucocorticosteroids (GCS) are used to treat bronchial asthma, but are not uniformly effective, especially in severe asthma. IL-13 is a T helper type 2 cytokine implicated in the pathogenesis of asthma, and IL-13 induces mucus production and goblet cell hyperplasia in airway epithelial cells. The effect of GCS on IL-13-induced mucin production is not well characterized.

OBJECTIVE

The aim of this study was to evaluate the effect of dexamethasone (Dex), a potent synthetic GCS, on IL-13-induced MUC5AC mucin expression and goblet cell proliferation in differentiated normal human bronchial epithelial cells (NHBECs).

METHODS

NHBECs were cultured for 14 days at an air-liquid interface with IL-13, with or without Dex. MUC5AC protein secretion and mRNA expression was determined using ELISA and quantitative real-time PCR. IL-8 production was assayed using ELISA. Histochemical analysis was performed using H&E and periodic acid-Schiff stain, and MUC5AC immunostaining.

RESULTS

Although Dex dose dependently inhibited IL-8 release induced by 5 ng/mL IL-13, Dex 0.001-1 μg/mL had no effect on IL-13 induced MUC5AC protein secretion or mRNA expression. Dex paradoxically increased MUC5AC induced by IL-13 at 0.5 and 1 ng/mL, but had no effect alone or with IL-13 at 0.1 ng/mL. Dex 0.001-1 μg/mL did not inhibit the differentiation of cells into goblet cells and MUC5AC-positive cells induced by IL-13.

CONCLUSION AND CLINICAL RELEVANCE

Dex at therapeutic concentrations did not inhibit the effects of IL-13 on goblet cell differentiation, characteristic of severe asthma. Paradoxically, MUC5AC production was increased with lower dose IL-13 exposure. This may lead to airway mucus obstruction commonly seen in life-threatening asthma.