The airway epithelium in asthma

Airway epithelial cells as drivers of severe asthma pathogenesis

Our understanding of the airway epithelium's role in driving asthma pathogenesis has evolved over time. From being regarded primarily as a physical barrier that could be damaged via inflammation, the epithelium is now known to actively contribute to asthma development through interactions with the immune system. The airway epithelium contains multiple cell types with specialized functions spanning barrier action, mucociliary clearance, immune cell recruitment, and maintenance of tissue homeostasis. Environmental insults may cause direct or indirect injury to the epithelium leading to impaired barrier function, epithelial remodelling, and increased release of inflammatory mediators. In severe asthma, the epithelial barrier repair process is inhibited and the response to insults is exaggerated, driving downstream inflammation. Genetic and epigenetic mechanisms also maintain dysregulation of the epithelial barrier, adding to disease chronicity. Here, we review the role of the airway epithelium in severe asthma and how targeting the epithelium can contribute to asthma treatment.

Proinflammatory Cytokines in Chronic Respiratory Diseases and Their Management

Pulmonary homeostasis can be agitated either by external environmental insults or endogenous factors produced during respiratory/pulmonary diseases. The lungs counter these insults by initiating mechanisms of inflammation as a localized, non-specific first-line defense response. Cytokines are small signaling glycoprotein molecules that control the immune response. They are formed by numerous categories of cell types and induce the movement, growth, differentiation, and death of cells. During respiratory diseases, multiple proinflammatory cytokines play a crucial role in orchestrating chronic inflammation and structural changes in the respiratory tract by recruiting inflammatory cells and maintaining the release of growth factors to maintain inflammation. The issue aggravates when the inflammatory response is exaggerated and/or cytokine production becomes dysregulated. In such instances, unresolving and chronic inflammatory reactions and cytokine production accelerate airway remodeling and maladaptive outcomes. Pro-inflammatory cytokines generate these deleterious consequences through interactions with receptors, which in turn initiate a signal in the cell, triggering a response. The cytokine profile and inflammatory cascade seen in different pulmonary diseases vary and have become fundamental targets for advancement in new therapeutic strategies for lung diseases. There are considerable therapeutic approaches that target cytokine-mediated inflammation in pulmonary diseases; however, blocking specific cytokines may not contribute to clinical benefit. Alternatively, broad-spectrum anti-inflammatory approaches are more likely to be clinically effective. Herein, this comprehensive review of the literature identifies various cytokines (e.g., interleukins, chemokines, and growth factors) involved in pulmonary inflammation and the pathogenesis of respiratory diseases (e.g., asthma, chronic obstructive pulmonary, lung cancer, pneumonia, and pulmonary fibrosis) and investigates targeted therapeutic treatment approaches.

Surfactant Protein-A and its immunomodulatory roles in infant respiratory syncytial virus infection: a potential for therapeutic intervention?

The vast majority of early-life hospital admissions globally highlight respiratory syncytial virus (RSV), the leading cause of neonatal lower respiratory tract infections, as the major culprit behind the poor neonatal outcomes following respiratory infections. Unlike those of older children and adults, the immune system of neonates looks rather unique, therefore mostly counting on the innate immune system and antibodies of maternal origins. The collaborations between cells and immune compartments during infancy inclines bias toward a T-helper 2 (Th2) immune profile and thereby away from a T-helper 1 (Th1) immune response. What makes it more problematic is that RSV infection also tends to elicit a stronger Th2-biased immune response and drive an aberrant allergy-like inflammation. It is thus evident how RSV infections potentially pave the way for wheezing recurrences and childhood asthma later in life. Surfactant, the essential lung substance for normal breathing processes in mammals, has immunomodulatory properties including lung collectins such as Surfactant Protein-A (SP-A), which is the most abundant protein component of surfactant, and also Surfactant Protein-D (SP-D). Deficiency of SP-A and SP-D has been found to be associated with impaired pathogen clearance and exacerbated immune responses during infections. We therefore conducted a review of the literature to describe pathomechanisms of RSV infections during blunted neonatal immunity potentially facilitating allergy-like inflammatory events within the developing lungs and highlight the potential protective role of the humoral collectin SP-A to mitigate these in the "early in life" pulmonary immune system.

Red cell distribution width to albumin ratio is associated with asthma risk: a population-based study

Background

The red cell distribution width to albumin ratio (RAR), a newly identified biomarker of inflammation, has been linked to a variety of inflammatory diseases. Asthma, a major burden on global health, is an inflammatory airway disease that is profoundly affected by inflammation. This study primarily sought to examine the influence of RAR on the risk of developing asthma.

Methods

Data from 1999 to 2020 was gathered from the NHANES database. The impact of RAR on asthma risk and their non-linear relationship were clarified by multivariate logit and restricted cubic spline (RCS) analyses. Subgroup and interaction analyses collectively formed the sensitivity analysis for this study.

Results

This study was based on an analysis of 54,161 individuals. RAR has been identified as an independent risk factor for asthma, according to logit analysis. The moderate and high RAR groups had a 16% [95% confidence interval (CI): 1.06-1.27] and 43% (95% CI: 1.30-1.58) higher risk, respectively, compared to the lowest group. Every 0.5 unit increase in RAR almost doubled the risk of asthma [odds ratio (OR): 1.82, 95% CI: 1.55-2.12]. There was no non-linear relationship between RAR and asthma risk, based on RCS analysis. Combining subgroup and interaction analyses results, all subgroups in this study showed consistent trends with the overall population.

Conclusion

Notably, this article, the first to examine the relationship between RAR and asthma risk, unveiled a positive linear correlation between them. With an increase in RAR, whether analyzed as a categorical or continuous variable, asthma risk significantly increases. This finding was beneficial for clinicians to anticipate and assess the onset of asthma through stratified or dynamic management. Given RAR's numerous advantages, its application in clinical settings held considerable promise.

Environmental pollutant 3-methyl-4-nitrophenol promotes the expression of oncostatin M to exacerbate airway allergic inflammation

Asthma exacerbation is a common clinical occurrence. The causal factors are not fully understood yet. Environmental pollution is linked to asthma exacerbation. The objective of this study is to elucidate the role of 3-methyl-4-nitrophenol (MNP), an environmental pollutant, in asthma exacerbation. In this study, an airway allergy mouse model was established with ovalbumin as a specific antigen with or without the presence of MNP. The results showed that, in a mouse model, the intensity of airway allergy was significantly increased by exposure to MNP. RNAseq results showed an increase in endoplasmic reticulum (ER) stress-associated molecules and the Osm expression in airway epithelial cells of mice with airway allergy. Exposure of epithelial cells to MNP in culture induced the expression of oncostatin M (OSM) and ER stress associated molecules. The OSM receptor was expressed by macrophages. OSM could drive macrophages to produce tumor necrosis factor-α (TNF-α). Inhibition of PERK, one of the key molecules of ER stress, or depletion of OSM receptor in macrophages, could effectively attenuate the MNP/ovalbumin protocol induced airway allergy. To sum up, by promoting ER stress, environmental pollutant MNP can cause airway epithelial cells to produce OSM. The latter induces macrophages to produce TNF-α, which can exacerbate airway allergy.

Airway epithelial cell response to RSV is mostly impaired in goblet and multiciliated cells in asthma

BACKGROUND

In patients with asthma, respiratory syncytial virus (RSV) infections can cause disease exacerbation by infecting the epithelial layer of the airways, inducing subsequent immune response. The type I interferon antiviral response of epithelial cells upon RSV infection is found to be reduced in asthma in most-but not all-studies. Moreover, the molecular mechanisms causing the differences in the asthmatic bronchial epithelium in response to viral infection are poorly understood.

METHODS

Here, we investigated the transcriptional response to RSV infection of primary bronchial epithelial cells (pBECs) from patients with asthma (n=8) and healthy donors (n=8). The pBECs obtained from bronchial brushes were differentiated in air-liquid interface conditions and infected with RSV. After 3 days, cells were processed for single-cell RNA sequencing.

RESULTS

A strong antiviral response to RSV was observed for all cell types, for all samples (p<1e-48). Most (1045) differentially regulated genes following RSV infection were found in cells transitioning to secretory cells. Goblet cells from patients with asthma showed lower expression of genes involved in the interferon response (false discovery rate <0.05), including OASL, ICAM1 and TNFAIP3. In multiciliated cells, an impairment of the signalling pathways involved in the response to RSV in asthma was observed.

CONCLUSION

Our results highlight that the response to RSV infection of the bronchial epithelium in asthma and healthy airways was largely similar. However, in asthma, the response of goblet and multiciliated cells is impaired, highlighting the need for studying airway epithelial cells at high resolution in the context of asthma exacerbation.

Heme oxygenase-1 alleviates allergic airway inflammation by suppressing NF-κB-mediated pyroptosis of bronchial epithelial cells

Allergic asthma development and pathogenesis are influenced by airway epithelial cells in response to allergens. Heme oxygenase-1 (HO-1), an inducible enzyme responsible for the breakdown of heme, has been considered an appealing target for the treatment of chronic inflammatory diseases. Herein, we report that alleviation of allergic airway inflammation by HO-1-mediated suppression of pyroptosis in airway epithelial cells (AECs). Using house dust mite (HDM)-induced asthma models of mice, we found increased gasdermin D (GSDMD) in the airway epithelium. In vivo administration of disulfiram, a specific inhibitor of pore formation by GSDMD, decreased thymic stromal lymphopoietin (TSLP) release, T helper type 2 immune response, alleviated airway inflammation, and reduced airway hyperresponsiveness (AHR). HO-1 induction by hemin administration reversed these phenotypes. In vitro studies revealed that HO-1 restrained GSDMD-mediated pyroptosis and cytokine TSLP release in AECs by binding Nuclear Factor-Kappa B (NF-κB) p65 RHD domain and thus controlling NF-κB-dependent pyroptosis. These data provide new therapeutic indications for purposing HO-1 to counteract inflammation, which contributes to allergic inflammation control.

Mulberroside F improves airway hyperresponsiveness and inflammation in asthmatic mice

Mulberroside F is isolated from the leaves and roots of Morus alba L. Here, we investigated whether mulberroside F could alleviate airway inflammation and eosinophil infiltration in the lungs of asthmatic mice. We also examined whether mulberroside F attenuated inflammatory responses in human tracheal epithelial BEAS-2B cells. Female BALB/c mice were sensitized and challenged with ovalbumin (OVA), and administered different doses of mulberroside F via intraperitoneal injection. Additionally, tumor necrosis factor (TNF)-α-stimulated BEAS-2B cells were treated with various doses of mulberroside F, followed by detection of the expressions of inflammatory cytokines and chemokines. The results demonstrated that mulberroside F mitigated the levels of proinflammatory cytokines and chemokines, and CCL11, in inflammatory BEAS-2B cells. Mulberroside F also suppressed reactive oxygen species (ROS) production and ICAM-1 expression in TNF-α-stimulated BEAS-2B cells, which effectively suppressed monocyte cell adherence. In an animal model of asthma, mulberroside F treatment attenuated airway hyperresponsiveness, eosinophil infiltration, and goblet cell hyperplasia. Mulberroside F treatment also decreased lung fibrosis and airway inflammation in OVA-sensitized mice. Moreover, mulberroside F significantly reduced expressions of Th2-associated cytokines (including interleukin(IL)-4, IL-5, and IL-13) in bronchoalveolar lavage fluid compared to OVA-sensitized mice. Our results confirmed that mulberroside F is a novel bioactive compound that can effectively reduce airway inflammation and eosinophil infiltration in asthmatic mice via inhibition of Th2-cell activation.

3D in vitro hydrogel models to study the human lung extracellular matrix and fibroblast function

The pulmonary extracellular matrix (ECM) is a macromolecular structure that provides mechanical support, stability and elastic recoil for different pulmonary cells including the lung fibroblasts. The ECM plays an important role in lung development, remodeling, repair, and the maintenance of tissue homeostasis. Biomechanical and biochemical signals produced by the ECM regulate the phenotype and function of various cells including fibroblasts in the lungs. Fibroblasts are important lung structural cells responsible for the production and repair of different ECM proteins (e.g., collagen and fibronectin). During lung injury and in chronic lung diseases such as asthma, idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD), an abnormal feedback between fibroblasts and the altered ECM disrupts tissue homeostasis and leads to a vicious cycle of fibrotic changes resulting in tissue remodeling. In line with this, using 3D hydrogel culture models with embedded lung fibroblasts have enabled the assessment of the various mechanisms involved in driving defective (fibrotic) fibroblast function in the lung's 3D ECM environment. In this review, we provide a summary of various studies that used these 3D hydrogel models to assess the regulation of the ECM on lung fibroblast phenotype and function in altered lung ECM homeostasis in health and in chronic respiratory disease.

Macrophages Orchestrate Airway Inflammation, Remodeling, and Resolution in Asthma

Asthma is a heterogenous chronic inflammatory lung disease with endotypes that manifest different immune system profiles, severity, and responses to current therapies. Regardless of endotype, asthma features increased immune cell infiltration, inflammatory cytokine release, and airway remodeling. Lung macrophages are also heterogenous in that there are separate subsets and, depending on the environment, different effector functions. Lung macrophages are important in recruitment of immune cells such as eosinophils, neutrophils, and monocytes that enhance allergic inflammation and initiate T helper cell responses. Persistent lung remodeling including mucus hypersecretion, increased airway smooth muscle mass, and airway fibrosis contributes to progressive lung function decline that is insensitive to current asthma treatments. Macrophages secrete inflammatory mediators that induce airway inflammation and remodeling. Additionally, lung macrophages are instrumental in protecting against pathogens and play a critical role in resolution of inflammation and return to homeostasis. This review summarizes current literature detailing the roles and existing knowledge gaps for macrophages as key inflammatory orchestrators in asthma pathogenesis. We also raise the idea that modulating inflammatory responses in lung macrophages is important for alleviating asthma.

A scoping review: What are the cellular mechanisms that drive the allergic inflammatory response to fungal allergens in the lung epithelium?

Allergic airway disease (AAD) is a collective term for respiratory disorders that can be exacerbated upon exposure to airborne allergens. The contribution of fungal allergens to AAD has become well established over recent years. We conducted a comprehensive review of the literature using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to better understand the mechanisms involved in the allergic response to fungi in airway epithelia, identify knowledge gaps and make recommendations for future research. The search resulted in 61 studies for final analysis. Despite heterogeneity in the models and methods used, we identified major pathways involved in fungal allergy. These included the activation of protease-activated receptor 2, the EGFR pathway, adenosine triphosphate and purinergic receptor-dependent release of IL33, and oxidative stress, which drove mucin expression and goblet cell metaplasia, Th2 cytokine production, reduced barrier integrity, eosinophil recruitment, and airway hyperresponsiveness. However, there were several knowledge gaps and therefore we recommend future research should focus on the use of more physiologically relevant methods to directly compare key allergenic fungal species, clarify specific mechanisms of fungal allergy, and assess the fungal allergy in disease models. This will inform disease management and future interventions, ultimately reducing the burden of disease.

Low-intensity diode laser combined with nasal glucocorticoids in the treatment of recurrent epistaxis in children: a randomized controlled trail

BACKGROUND

A painless and effective treatment of childhood epistaxis is needed.

OBJECTIVE

To observe the effectiveness of low-intensity diode (Lid) laser in treating epistaxis complicated with allergic rhinitis in children.

METHODS

Our study is a prospective, randomized, controlled, registry trial (NO. 202001201) involving 44 recurrent epistaxis children (<14 years old) with or without Allergic Rhinitis (AR) in our hospital. They were divided randomly into the Laser and Control groups. The Laser group was treated with Lid laser (wavelength 635 nm, power 15mW) for 10 min after nasal mucosa was moistened with normal saline (NS). The Control group moistened their nasal cavities with NS only. Children in two groups complicated with AR were given nasal glucocorticoids for 2 weeks. The effectiveness of Lid laser in treating epistaxis and AR were compared between the two groups after treatment.

RESULTS

After treatment, the effective rate of the Laser group in epistaxis (23/24, 95.8%) was higher than the Control group (16/20, 80%) (p < .05). The VAS scores of the children complicated with AR in the two groups both improved after treatment, however, the variation of VAS score (3.02 ± 1.50) in the Laser group was greater than the Control group (1.83 ± 1.56) (p < .05).

CONCLUSION

As a safe and efficient method, Lid laser treatment can effectively alleviate epistaxis and inhibit symptoms of AR in children.

Asthma Management in Adults

Management of asthma in adults has advanced in the past 10 years. Central to these advances has been further clarification of type (T) 2 mechanisms of airway inflammation and utilization of T2 biomarkers, that is, eosinophils and fractional exhaled nitric oxide. In addition, epithelial cells are emerging as significant contributors to inflammation through generation of alarmins to initiate local injury as well as downstream pathways. Five new biologics, mepolizumab, benralizumab, reslizumab, dupilumab, and tezepelumab, were approved to join omalizumab and revolutionize severe asthma treatment. These biologics significantly prevent exacerbations to spare systemic corticosteroids use and their side effects. Guidelines attest to the effectiveness of inhaled corticosteroids/long-acting β-agonists (formoterol) for both maintenance and rescue therapy. Focused updates to the Expert Panel Report addressed limited but specific questions relevant to asthma control. Future guidelines should include phenotype/endotype-directed therapeutics to gain more precision-directed treatment.

Role of Chemokines and Inflammatory Cells in Respiratory Allergy

The idea of "one airway, one disease" has been gaining importance in the last decade. In the upper and lower airways, allergic mechanisms interact with each other. In the initial stage of respiratory allergic inflammation, allergens contact the respiratory epithelium, which produces chemokines and inflammatory factors, which cause allergic reactions by binding to the corresponding receptors and chemotactic various inflammatory cells to reach the epithelium and tissues. It also drives inflammatory cells to activate and produce more inflammatory factors, thus producing a cascade amplification effect. Inflammatory cell aggregation and activation are very complex and interact with each other in a lattice structure. By blocking the action of various chemokines, inflammatory cell aggregation is reduced, and ultimately the symptoms of respiratory allergy are alleviated. Chemokines can serve as cues for coordinated recruitment of immune cells into and out of tissues, as well as directing the spatial organization of immune cells within tissues and cellular interactions. Chemokines are critical in directing immune cell migration and thus have an important role in the direction of respiratory allergy: however, chemokines are also involved in the production and recruitment of immune cells that contribute to respiratory allergy. In this article, linking the upper and lower respiratory tracts. We review the role of the chemokine system in the respiratory immune response and discuss how respiratory disease modulates overall chemokines to shape the type and outcome of the immune response to the treatment of respiratory allergic disease so that we can further deepen our knowledge of chemokines in the direction of respiratory allergy. In the future, we can do drug research and development based on this network structure and explore new research directions.

Airway Inflammation Before and After Bronchial Thermoplasty in Severe Asthma

Background

Bronchial thermoplasty (BT) is a bronchoscopic treatment for severe asthma, of which the working mechanism and responder profile are partly unknown. The aim of this study is to analyse whether BT alters airway inflammation by epithelial gene expression, inflammatory cell counts and cytokines, and whether this relates to treatment response.

Methods

In this clinical trial, 28 severe asthma patients underwent bronchoscopy before and after treatment to obtain bronchial brushes and bronchoalveolar lavage fluid (BALF) from treated and untreated airways. RNA was extracted from bronchial brushes for transcriptome analysis, and BALF cells and cytokines were analysed. Asthma quality of life questionnaires were used to distinguish responders from non-responders. We compared results before and after treatment, between treated and untreated airways, and between responders and non-responders.

Results

Gene expression of airway epithelium related to airway inflammation gene set was significantly downregulated in treated airways compared to untreated airways, although this did not differ for patients before and after treatment. No differences were observed in cell counts and cytokines, neither from the untreated compared to treated airways, nor before and after treatment. At baseline, compared to non-responders, the expression of genes related to glycolysis in bronchial epithelium was downregulated and both BALF and blood eosinophil counts were higher in responders.

Conclusion

Local differences in gene sets pertaining to epithelial inflammatory status were identified between treated and untreated airways after treatment, not resulting in changes in differential cell counts and cytokine analyses in BALF. Secondly, baseline epithelial glycolysis genes and eosinophil counts in BALF and blood were different between responders and non-responders. The observations from this study demonstrate the potential impact of BT on epithelial gene expression related to airway inflammation while also identifying a possible responder profile.

Respiratory Symptoms, Allergies, and Environmental Exposures in Children with and without Asthma

BACKGROUND

Epidemiological data concerning the level of asthma morbidity indicate that in Poland, asthma is diagnosed in 5-10% of the pediatric population. Aim The purpose of this study was to compare the prevalence of respiratory symptoms and allergies in a group of children with and without asthma and to evaluate the association between exposure to environmental factors and the prevalence of bronchial asthma in a pediatric population.

MATERIAL AND METHODS

A cross-sectional study was conducted on a group of 995 children attending primary schools in the province of Silesia in 2018-2019. The research tool was an anonymous questionnaire developed based on the form used in The International Study of Asthma and Allergies in Childhood (ISAAC). Children's health status, the prevalence of bronchial asthma, and the performance of allergic skin tests were assessed based on parents' indications in a questionnaire. Environmental exposures such as mold and dampness in apartments or ETS were similarly assessed. Analyses were performed using Statistica 13.0; p < 0.05.

RESULTS

A total of 88 subjects (8.8%) suffered from bronchial asthma. Parents of children with asthma, compared to parents of children without the disease, were more likely to rate their children's health as rather good (43.2% vs. 38.0%) or average (21.6% vs. 3.1%). All analyzed respiratory symptoms, as well as allergies, were statistically more frequent in children with bronchial asthma.

CONCLUSIONS

The parent's subjective assessment of the child's health varied significantly according to the asthma diagnosis. Asthma is also associated with other diseases: allergic reactions to pollen, house dust, hay fever, and AD (atopic dermatitis) were statistically significantly more frequent among children diagnosed with bronchial asthma.

The Pioneer Transcription Factor Foxa2 Modulates T Helper Differentiation to Reduce Mouse Allergic Airway Disease

Foxa2, a member of the Forkhead box (Fox) family of transcription factors, plays an important role in the regulation of lung function and lung tissue homeostasis. FOXA2 expression is reduced in the lung and airways epithelium of asthmatic patients and in mice absence of Foxa2 from the lung epithelium contributes to airway inflammation and goblet cell hyperplasia. Here we demonstrate a novel role for Foxa2 in the regulation of T helper differentiation and investigate its impact on lung inflammation. Conditional deletion of Foxa2 from T-cells led to increased Th2 cytokine secretion and differentiation, but decreased Th1 differentiation and IFN-γ expression in vitro. Induction of mouse allergic airway inflammation resulted in more severe disease in the conditional Foxa2 knockout than in control mice, with increased cellular infiltration to the lung, characterized by the recruitment of eosinophils and basophils, increased mucus production and increased production of Th2 cytokines and serum IgE. Thus, these experiments suggest that Foxa2 expression in T-cells is required to protect against the Th2 inflammatory response in allergic airway inflammation and that Foxa2 is important in T-cells to maintain the balance of effector cell differentiation and function in the lung.

Gypenoside A from Gynostemma pentaphyllum Attenuates Airway Inflammation and Th2 Cell Activities in a Murine Asthma Model

Our previous study found that oral administration of Gynostemma pentaphyllum extract can attenuate airway hyperresponsiveness (AHR) and reduce eosinophil infiltration in the lungs of asthmatic mice. Gypenoside A is isolated from G. pentaphyllum. In this study, we investigated whether gypenoside A can effectively reduce asthma in mice. Asthma was induced in BALB/c mice by ovalbumin injection. Asthmatic mice were treated with gypenoside A via intraperitoneal injection to assess airway inflammation, AHR, and immunomodulatory effects. In vitro, gypenoside A reduced inflammatory and oxidative responses in inflammatory tracheal epithelial cells. Experimental results showed that gypenoside A treatment can suppress eosinophil infiltration in the lungs, reduce tracheal goblet cell hyperplasia, and attenuate AHR. Gypenoside A significantly reduced Th2 cytokine expression and also inhibited the expression of inflammatory genes and proteins in the lung and bronchoalveolar lavage fluid. In addition, gypenoside A also significantly inhibited the secretion of inflammatory cytokines and chemokines and reduced oxidative expression in inflammatory tracheal epithelial cells. The experimental results suggested that gypenoside A is a natural compound that can effectively reduce airway inflammation and AHR in asthma, mainly by reducing Th2 cell activation.

Exploration of induced sputum BIRC3 levels and clinical implications in asthma

BACKGROUND

Baculoviral IAP repeat-containing 3 (BIRC3) which encodes a member of the IAP family of proteins upregulated in the asthma expression profile dataset. However, there was few research on studying the clinical implication of BIRC3 in asthma.

OBJECTIVE

To validate BIRC3 expression and its clinical implications in induced sputum of asthma.

METHODS

Based on the GSE76262 (118 asthma cases and 21 healthy controls) dataset, differentially expressed genes were screened using R software. Subsequently, BIRC3 mRNA and protein were clinically verified in induced sputum samples through quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). Besides, the correlations between BIRC3 expression and asthmatic eosinophilic/allergic inflammation indicators (FeNO, IgE, and EOS%), pulmonary function (FEV₁, FEV₁% pred, FVC% pred, and FEV₁/FVC), and inflammatory cytokines (IL-4, IL-5, IL-13, IL-25, IL-10, IL-33, and TSLP) were analyzed. Finally, BIRC3 mRNA was detected in human primary bronchial epithelial cells stimulated by cytokines (IL-4 or IL-13).

RESULTS

BIRC3 was screened as a candidate gene in the GSE76262, which was highly expressed in asthma. Highly expressed BIRC3 was positively correlated with eosinophilic and allergic indicators, including FeNO, blood eosinophil, and serum IgE. Moreover, BIRC3 protein was positively associated with inflammation cytokines, like IL-4, IL-5, IL-13, IL-25, IL-10, IL-33, and TSLP, while negatively correlated with FEV1, FEV1%pred, FVC% pred, and FEV1/FVC. Furthermore, the expression of BIRC3 could be induced in primary bronchial epithelial cells treated by cytokines IL-4 or IL-13.

CONCLUSIONS

BIRC3 significantly increased in induced sputum of asthma and positively correlated with airway eosinophilic and peripheral blood allergic inflammation, type 2 cytokines, and airway obstruction. Increased BIRC3 might be involved in the pathogenesis of asthma by affecting the eosinophilic and allergic inflammation.

The Rho kinase (ROCK) inhibitor Y-27632 reduces the β2-adrenoceptor density but enhance cAMP formation in primary equine bronchial epithelial cells

The present study addresses the effect of the Rho-kinase (ROCK) inhibitor Y-27632 on the β2-adrenoceptor density and β-agonist-stimulated intracellular second messenger cAMP formation in primary equine bronchial epithelial cells (EBEC). Y-27632 significantly decreased the β2-adrenoceptor number (Bmax) without markedly affecting the receptor affinity (dissociation constant, KD) to the radioligand [125I]-iodocyanopindolol (ICYP). In contrast, Y-27632 augmented the β-agonist-stimulated intracellular cAMP production. Herein, Y-27632 markedly increased the maximal cAMP responses (Emax) (isoproterenol > epinephrine > norepinephrine) but did not shift the β-agonist concentration-effect curves to the left. The β2-selective antagonist ICI 118.551 and the β1/β2-antagonsit propranolol but not the β1-selctive antagonist CGP 20712A reversed the isoproterenol-induced cAMP formation equally in Y-27632-treated and control EBEC, suggesting the effect was merely related to the β2-subtype. These results show that Y-27632 differentially regulates the receptor density and function. Thus, these findings provide the first evidence that the functional interaction of the β2-adrenoceptor and Rho-kinase (ROCK) signaling pathways decreases the receptor expression but enhances receptor downstream cAMP formation. This differential regulation of the receptor density and function by Y-27632 should be further reconsidered with regard to the beneficial effect of the drug in asthma therapy.

Blocking ATP-releasing channels prevents high extracellular ATP levels and airway hyperreactivity in an asthmatic mouse model

Allergic asthma is a chronic airway inflammatory response to different triggers like inhaled allergens. Excessive ATP in fluids from patients with asthma is considered an inflammatory signal and an important autocrine/paracrine modulator of airway physiology. Here, we investigated the deleterious effect of increased extracellular ATP (eATP) concentration on the mucociliary clearance (MCC) effectiveness and determined the role of ATP releasing channels during airway inflammation in an ovalbumin (OVA)-sensitized mouse model. Our allergic mouse model exhibited high levels of eATP measured in the tracheal fluid with a luciferin-luciferase assay and reduced MCC velocity determined by microspheres tracking in the trachea ex vivo. Addition of ATP had a dual effect on MCC, where lower ATP concentration (µM) increased microspheres velocity, whereas higher concentration (mM) transiently stopped microspheres movement. Also, an augmented ethidium bromide uptake by the allergic tracheal airway epithelium suggests an increase in ATP release channel functionality during inflammatory conditions. The use of carbenoxolone, a nonspecific inhibitor of connexin and pannexin1 channels reduced the eATP concentration in the allergic mouse tracheal fluid and dye uptake by the airway epithelium, providing evidence that these ATP release channels are facilitating the net flux of ATP to the lumen during airway inflammation. However, only the specific inhibition of pannexin1 with ¹⁰Panx peptide significantly reduced eATP in bronchoalveolar lavage and decreased airway hyperresponsiveness in OVA-allergic mouse model. These data provide evidence that blocking eATP may be a pharmacological alternative to be explored in rescue therapy during episodes of airflow restriction in patients with asthma.

Response to Mepolizumab Treatment in Patients with Severe Eosinophilic Asthma and Atopic Phenotypes

Purpose

Improved understanding of characteristics that may influence treatment response across phenotypes may help guide treatment decisions.

Patients and Methods

This was a post hoc analysis of MENSA, a multicenter, randomized, double-blind, placebo-controlled trial (NCT01691521). Patients aged ≥12 years with severe eosinophilic asthma received mepolizumab (75 mg intravenously or 100 mg subcutaneously) or placebo, plus standard of care, every 4 weeks for 32 weeks. Outcomes assessed were the annualized rate of clinically significant exacerbations and change from baseline in Asthma Control Questionnaire (ACQ)-5 score. Subgroup analyses were performed by baseline blood eosinophil count (<150, ≥150–300, ≥300 cells/μL) within atopic subgroups (non-atopic [specific immunoglobulin E <0.35 kU/L], atopic [≥0.35–17.5 kU/L], strongly atopic [>17.5 kU/L]), and by house dust mite (HDM) sensitivity.

Results

Of 576 patients analyzed, 272 were non-atopic, 181 were atopic and 94 were strongly atopic; 29 had missing atopy data. In patients with blood eosinophil counts ≥300 cells/µL, mepolizumab versus placebo reduced clinically significant exacerbations by 74%, 43% and 25% in the non-atopic, atopic and strongly atopic subgroups. Similar reductions were observed in all atopic subgroups in other blood eosinophil count categories where there were sufficient patient numbers for analysis, except for non-atopic patients with baseline blood eosinophil counts of <150 cells/μL. Improvements in ACQ-5 scores of –0.75, –0.73 and –0.78 with mepolizumab versus placebo were observed in non-atopic, atopic and strongly atopic patients with blood eosinophil counts ≥300 cells/µL; consistent improvements in ACQ-5 were not observed in patients with blood eosinophil counts <150 or ≥150–300 cells/μL. Reductions in clinically significant exacerbations with mepolizumab versus placebo were also observed irrespective of sensitivity to HDMs.

Conclusion

Mepolizumab was associated with a trend for reductions in clinically significant exacerbations and improved asthma control versus placebo in patients with severe eosinophilic asthma, irrespective of atopic status or HDM sensitivity.

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Mechanisms and biomarkers of airway epithelial cell damage in asthma: A review

Bronchial asthma is a heterogeneous disease with complex pathological mechanisms representing different phenotypes, including severe asthma. The airway epithelium is a major site of complex pathological changes in severe asthma due, in part, to activation of inflammatory and immune mechanisms in response to noxious agents. Current imaging procedures are unable to accurately measure epithelial and airway remodeling. Damage of airway epithelial cells occurs is linked to specific phenotypes and endotypes which provides an opportunity for the identification of biomarkers reflecting epithelial, and airway, remodeling. Identification of patients with more severe epithelial disruption using biomarkers may also provide personalised therapeutic opportunities and/or markers of successful therapeutic intervention. Here, we review the evidence for ongoing epithelial cell dysregulation in the pathogenesis of asthma, the sentinel role of the airway epithelium and how understanding these molecular mechanisms provides the basis for the identification of candidate biomarkers for asthma prediction, prevention, diagnosis, treatment and monitoring.

The airway epithelium during infancy and childhood: A complex multicellular immune barrier. Basic review for clinicians

The airway epithelium is a complex multicellular layer that extends from the nasopharynx to the small airways. It functions as an immune respiratory barrier during early life that develops, matures, and regenerates to adapt to the changes in the environment. While airway epithelial abnormalities have been identified in several clinical disorders, there is increasing interest in understanding its basic regulation and structure in humans. Indeed, recent advances in technology (e.g. single-cell analysis and new human airway epithelial cell models) have allowed us to identify additional cellular subtypes and functions that overall have greatly improved our understanding of the airway epithelium during health and disease. In this review we summarize key features of the airway epithelium including: 1) multilayer structure and cell heterogeneity; 2) adaptability to different environmental and developmental stimuli; 3) innate recognition; and 4) orchestration of immune responses. We discuss these features with a translational and clinical prospective focusing on the development of human respiratory immunity, particularly during early life.

Flow-Cytometric Analysis and Purification of Airway Epithelial-Cell Subsets

The human airway epithelium is essential in homeostasis, and epithelial dysfunction contributes to chronic airway disease. Development of flow-cytometric methods to characterize subsets of airway epithelial cells will enable further dissection of airway epithelial biology. Leveraging single-cell RNA-sequencing data in combination with known cell type-specific markers, we developed panels of antibodies to characterize and isolate the major airway epithelial subsets (basal, ciliated, and secretory cells) from human bronchial epithelial-cell cultures. We also identified molecularly distinct subpopulations of secretory cells and demonstrated cell subset-specific expression of low-abundance transcripts and microRNAs that are challenging to analyze with current single-cell RNA-sequencing methods. These new tools will be valuable for analyzing and separating airway epithelial subsets and interrogating airway epithelial biology.

Lung organoids, useful tools for investigating epithelial repair after lung injury

Organoids are derived from stem cells or organ-specific progenitors. They display structures and functions consistent with organs in vivo. Multiple types of organoids, including lung organoids, can be generated. Organoids are applied widely in development, disease modelling, regenerative medicine, and other multiple aspects. Various human pulmonary diseases caused by several factors can be induced and lead to different degrees of lung epithelial injury. Epithelial repair involves the participation of multiple cells and signalling pathways. Lung organoids provide an excellent platform to model injury to and repair of lungs. Here, we review the recent methods of cultivating lung organoids, applications of lung organoids in epithelial repair after injury, and understanding the mechanisms of epithelial repair investigated using lung organoids. By using lung organoids, we can discover the regulatory mechanisms related to the repair of lung epithelia. This strategy could provide new insights for more effective management of lung diseases and the development of new drugs.

Clinical and histopathologic predictors of therapeutic response to bronchial thermoplasty in severe refractory asthma

BACKGROUND

Phenotypes and endotypes predicting optimal response to bronchial thermoplasty (BT) in patients with severe asthma remain elusive.

OBJECTIVE

Our aim was to compare the clinical characteristics and hallmarks of airway inflammation and remodeling before and after BT in responder and partial responder patients with severe asthma refractory to oral steroids and to omalizumab.

METHODS

In all, 23 patients with severe refractory asthma were divided into BT responders (n = 15) and BT partial responders (n = 8), according to the decrease in asthma exacerbations at 12 months after BT. Clinical parameters were compared at baseline and 12 months after BT, and hallmarks of airway inflammation and remodeling were analyzed by immunohistochemistry in bronchial biopsy specimens before and 3 months after BT.

RESULTS

At baseline, the BT responders were around 8 years younger than the BT partial responders (P = .02) and they had a greater incidence of atopy, higher numbers of blood eosinophils (both P = .03) and IgE levels, higher epithelial IFN-α expression, and higher numbers of mucosal eosinophils and IL-33-positive cells (P ≤ .05). A reduction in blood eosinophil count, serum IgE level, type 2 airway inflammation, and numbers of mucosal IL-33-positive cells and mast cells associated with augmented epithelial MUC5AC and IFN-α/β immunostaining was noted after BT in responders, whereas the numbers of mucosal IL-33-positive cells were augmented in BT partial responders. Most of these changes were correlated with clinical parameters. Subepithelial membrane thickening and airway smooth muscle area were similar in the 2 patient groups at baseline and after BT.

CONCLUSION

By reducing allergic type 2 inflammation and increasing epithelial MUC5AC and anti-viral IFN-α/β expression, BT may enhance host immune responses and thus attenuate exacerbations and symptoms in BT responders. Instead, targeting IL-33 may provide a clinical benefit in BT partial responders.

Bronchoconstriction: a potential missing link in airway remodelling

In asthma, progressive structural changes of the airway wall are collectively termed airway remodelling. Despite its deleterious effect on lung function, airway remodelling is incompletely understood. As one of the important causes leading to airway remodelling, here we discuss the significance of mechanical forces that are produced in the narrowed airway during asthma exacerbation, as a driving force of airway remodelling. We cover in vitro, ex vivo and in vivo work in this field, and discuss up-to-date literature supporting the idea that bronchoconstriction may be the missing link in a comprehensive understanding of airway remodelling in asthma.

IL-17C expression and its correlation with pediatric adenoids: a preliminary study

Objective: Interleukin-17 (IL-17) C is a cytokine expressed by epithelial cells in response to bacterial stimulation. In contrast to other members of the IL-17 family of cytokines, IL-17C is upregulated early during infection, maintains integrity of the epithelial layer barrier, and mediates the innate immune response. We investigated the expression profile of IL-17C in pediatric adenoids. Methods: Pediatric adenoid tissues and lavage fluids were collected from a total of 38 subjects. The Limulus amebocyte lysate test and real-time PCR using Staphylococcus aureus primers were performed to evaluate bacterial contents in adenoids. Expression of IL-17RE in adenoids was analyzed using real-time polymerase chain reaction and western blot. The expression of IL-17C was evaluated by western blot and immunohistochemistry and compared between allergic rhinitis (AR) and control subjects. The levels of Hsp27, Hsp70, and IL-17C in adenoid lavage fluids were evaluated by enzyme-linked immunosorbent assay, and the correlation between these molecules was statistically analyzed. Results: The pediatric adenoids were found to be exposed to bacteria and had a normal flora comprising both gram-negative and -positive bacteria. IL-17RE, an IL-17C specific receptor, was highly expressed in the epithelium of adenoids. IL-17C was expressed in all evaluated adenoid tissue samples, irrespective of the allergic status of the patient. IL-17C secretion was detected in half of the adenoid lavage fluid samples and was associated with Hsp70 level. Conclusion: Our findings indicate the possible role of pediatric adenoids in innate immunity modulation via an innate immunity-associated cytokine.

Cell-Specific DNA Methylation Signatures in Asthma

Asthma is a complex trait, often associated with atopy. The genetic contribution has been evidenced by familial occurrence. Genome-wide association studies allowed for associating numerous genes with asthma, as well as identifying new loci that have a minor contribution to its phenotype. Considering the role of environmental exposure on asthma development, an increasing amount of literature has been published on epigenetic modifications associated with this pathology and especially on DNA methylation, in an attempt to better understand its missing heritability. These studies have been conducted in different tissues, but mainly in blood or its peripheral mononuclear cells. However, there is growing evidence that epigenetic changes that occur in one cell type cannot be directly translated into another one. In this review, we compare alterations in DNA methylation from different cells of the immune system and of the respiratory tract. The cell types in which data are obtained influences the global status of alteration of DNA methylation in asthmatic individuals compared to control (an increased or a decreased DNA methylation). Given that several genes were cell-type-specific, there is a great need for comparative studies on DNA methylation from different cells, but from the same individuals in order to better understand the role of epigenetics in asthma pathophysiology.