Airway epithelial barrier function regulates the pathogenesis of allergic asthma

Tezepelumab: patient selection and place in therapy in severe asthma

Asthma is a disease characterised by heterogeneous and multifaceted airway inflammation. Despite the availability of effective treatments, a substantial percentage of patients with the type 2 (T2)-high, but mainly the T2-low, phenotype complain of persistent symptoms, airflow limitation, and poor response to treatments. Currently available biologicals target T2 cytokines, but no monoclonal antibodies or other specific therapeutic options are available for non-T2 asthma. However, targeted therapy against alarmins is radically changing this perspective. The development of alarmin-targeted therapies, of which tezepelumab (TZP) is the first example, may offer broad action on inflammatory pathways as well as an enhanced therapeutic effect on epithelial dysfunction. In this regard, TZP demonstrated positive results not only in patients with severe T2 asthma but also those with non-allergic, non-eosinophilic disease. Therefore, it is necessary to identify clinical features of patients who can benefit from an upstream targeted therapy such as anti-thymic stromal lymphopoietin. The aims of this narrative review are to understand the role of alarmins in asthma pathogenesis and epithelial dysfunction, examine the rationale underlying the indication of TZP treatment in severe asthma, summarise the results of clinical studies, and recognise the specific characteristics of patients potentially eligible for TZP treatment.

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.

Mechanisms and clinical management of eosinophilic oesophagitis: an overview

Since the first description of eosinophilic oesophagitis (EoE) less than three decades ago, we have observed a striking increase in the number of patients diagnosed with EoE and the understanding of its clinical and immunopathogenic background. Nonetheless, a plethora of open questions await elucidation. In this Review, we discuss the current state of knowledge regarding the underlying mechanisms, particularly environmental factors and their interaction with genetic susceptibility. Subsequently, we discuss how to translate these factors into the diagnostic and therapeutic management of this chronic, immune-mediated disorder. Finally, we dissect the still long list of unmet needs, such as reasons for and handling refractory EoE and atypical clinical presentations. These open questions can guide us through future research steps and potentially foster reconsideration of the diagnostic guidelines of EoE.

Destiny of airway disease: interplay between epithelial barrier and the innate immune system

When the organism encounters a foreign substance, it responds with mutual and regular interactions at different stages of the immune system. In airway diseases, the first encounter is at the epithelial level, where innate immune cells and their responses form the first leg of the protective mechanism. The most important barrier for environmental damage is the epithelial barrier. However, the epithelial barrier is not just a mechanical barrier. The formation of the microbiome on the epithelium and the tolerance or intolerance to environmental factors are vital. This vital balance is maintained between the epithelial surface and the subepithelial innate immune system. This is achieved by the epithelial line, which is a mechanical and functional barrier between them. In this respect, epithelial barrier function preservation has an important role in the development and prognosis of airway disease.

Imbalanced IL-37/TNF-α/CTSS signaling disrupts corneal epithelial barrier in a dry eye model in vitro

PURPOSE

To explore novel role and molecular mechanism of a natural anti-inflammatory cytokine interleukin (IL) 37 in preventing corneal epithelial barrier disruption from hyperosmolar stress as can occur in dry eye disease.

METHODS

Primary human corneal epithelial cells (HCECs) were cultured from fresh donor limbal explants. An in vitro dry eye model with hyperosmolar stress was established by switching HCECs from isosmolar (312mOsM) to hyperosmolar medium (350-500 mOsM), and some cells were treated with rhIL-37 or rhTNF-α, for different periods (2-48 h). The expression of cytokines and cathepsin S, and barrier protein integrity were evaluated by RT-qPCR, ELISA, and immunofluorescent staining with confocal microscopy.

RESULTS

The integrity of epithelial barrier was significantly disrupted in HCECs exposed to hyperosmolar medium, as shown by immunofluorescent images of tight junction (TJ, ZO-1, occludin and claudin-1) and adheren junction (E-cadherin) proteins. TNF-α accentuated hyperosmolar-induced disruption of TJ barrier functional integrity whereas exposure to IL-37 blunted or even reversed these changes. Cathepsin S, encoded by CTSS gene, was found to directly disrupt epithelial barrier integrity. Interestingly, CTSS expression was significantly induced by TNF-α and hyperosmolarity, while exogenous rhIL-37 inhibited TNF-α and CTSS expression at mRNA and protein levels following hyperosmolar stress. Furthermore, rhIL-37 restored barrier protein integrity, observed in 2D and 3D confocal immunofluorescent images, in HCECs under hyperosmolar stress.

CONCLUSION

Our findings demonstrate a novel signaling pathway by which anti-inflammatory cytokine IL-37 prevents corneal epithelial barrier disruption under hyperosmotic stress via suppressing TNF-α and CTSS expression. This study provides new insight into mechanisms protecting corneal barrier in dry eye disease.

The Growing Medical Need for Tracheal Replacement: Reconstructive Strategies Should Overcome Their Limits

Breathing, being predominantly an automatic action, is often taken for granted. However, respiratory diseases affect millions of people globally, emerging as one of the major causes of disability and death overall. Among the respiratory dysfunctions, tracheal alterations have always represented a primary challenge for clinicians, biologists, and engineers. Indeed, in the case of wide structural alterations involving more than 50% of the tracheal length in adults or 30% in children, the available medical treatments are ineffective or inapplicable. So far, a plethora of reconstructive approaches have been proposed and clinically applied to face this growing, unmet medical need. Unfortunately, none of them has become a well-established and routinely applied clinical procedure to date. This review summarizes the main clinical reconstructive attempts and classifies them as non-tissue engineering and tissue engineering strategies. The analysis of the achievements and the main difficulties that still hinder this field, together with the evaluation of the forefront preclinical experiences in tracheal repair/replacement, is functional to promote a safer and more effective clinical translation in the near future.

IL-4/IL-13 axis as therapeutic targets in allergic rhinitis and asthma

Allergic rhinitis (AR) is a common disorder of the upper airway, while asthma is a disease affecting the lower airway and both diseases are usually comorbid. Interleukin (IL)-4 and IL-13 are critical cytokines in the induction of the pathogenic Th2 responses in AR and asthma. Targeting the IL-4/IL-13 axis at various levels of its signaling pathway has emerged as promising targeted therapy in both AR and asthma patient populations. In this review, we discuss the biological characteristics of IL-4 and IL-13, their signaling pathways, and therapeutic antibodies against each cytokine as well as their receptors. In particular, the pleiotropic roles of IL-4 and IL-13 in orchestrating Th2 responses in AR and asthma patients indicate that dual IL-4/IL-13 blockade is a promising therapeutic strategy for both diseases.

Allergic Rhinitis: A Clinical and Pathophysiological Overview

Allergic rhinitis (AR) represents a global health concern where it affects approximately 400 million people worldwide. The prevalence of AR has increased over the years along with increased urbanization and environmental pollutants thought to be some of the leading causes of the disease. Understanding the pathophysiology of AR is crucial in the development of novel therapies to treat this incurable disease that often comorbids with other airway diseases. Hence in this mini review, we summarize the well-established yet vital aspects of AR. These include the epidemiology, clinical and laboratory diagnostic criteria, AR in pediatrics, pathophysiology of AR, Th2 responses in the disease, as well as pharmacological and immunomodulating therapies for AR patients.

Extracellular vesicles released by non-small cell lung cancer cells drive invasion and permeability in non-tumorigenic lung epithelial cells

Extracellular vesicles (EVs) released from non-small cell lung cancer (NSCLC) cells are known to promote cancer progression. However, it remains unclear how EVs from various NSCLC cells differ in their secretion profile and their ability to promote phenotypic changes in non-tumorigenic cells. Here, we performed a comparative analysis of EV release from non-tumorigenic cells (HBEC/BEAS-2B) and several NSCLC cell lines (A549, H460, H358, SKMES, and Calu6) and evaluated the potential impact of NSCLC EVs, including EV-encapsulated RNA (EV-RNA), in driving invasion and epithelial barrier impairment in HBEC/BEAS-2B cells. Secretion analysis revealed that cancer cells vary in their secretion level, with some cell lines having relatively low secretion rates. Differential uptake of NSCLC EVs was also observed, with uptake of A549 and SKMES EVs being the highest. Phenotypically, EVs derived from Calu6 and H358 cells significantly enhanced invasion, disrupted an epithelial barrier, and increased barrier permeability through downregulation of E-cadherin and ZO-1. EV-RNA was a key contributing factor in mediating these phenotypes. More nuanced analysis suggests a potential correlation between the aggressiveness of NSCLC subtypes and the ability of their respective EVs to induce cancerous phenotypes.

Nasal epithelium: new insights and differences of the cytokine profile between normal subjects and subjects with allergic rhinitis

Background: The role of the nasal epithelium in the induction of a proper cytokine response in normal subjects and subjects with allergic rhinitis is still not completely elucidated. Methodology: We aimed to compare nasal epithelial immune responses in allergic rhinitis patients of different ages compared to healthy volunteers. Primary nasal epithelial cells from 47 subjects (33 normal and 17 with allergic rhinitis) were collected and cultured. Their unstimulated supernatants were analysed for 21 cytokines and chemokines. Statistical analysis was performed with the R statistical software and the RStudio interface. Results: Differences of the spontaneous release of epithelial cytokines and chemokines were noticed between the two study groups. The levels of GMCSF, MIP1A, MIP1B, IL28A, TNFA, CCL5 were significantly lower in the allergic rhinitis group compared to healthy volunteers’ group, independent of age. Most differences were noticed in the younger allergic rhinitis group (0-12 years old). Conclusions: Despite the cross-sectional nature of the study and the limited number of subjects, allergic rhinitis appears to be associated with dysfunction of cytokine and chemokine spontaneous release from nasal epithelial cells which may represent an abnormal innate immunity maturation pattern.

Pulmonary Eosinophils at the Center of the Allergic Space-Time Continuum

Eosinophils are typically a minority population of circulating granulocytes being released from the bone-marrow as terminally differentiated cells. Besides their function in the defense against parasites and in promoting allergic airway inflammation, regulatory functions have now been attributed to eosinophils in various organs. Although eosinophils are involved in the inflammatory response to allergens, it remains unclear whether they are drivers of the asthma pathology or merely recruited effector cells. Recent findings highlight the homeostatic and pro-resolving capacity of eosinophils and raise the question at what point in time their function is regulated. Similarly, eosinophils from different physical locations display phenotypic and functional diversity. However, it remains unclear whether eosinophil plasticity remains as they develop and travel from the bone marrow to the tissue, in homeostasis or during inflammation. In the tissue, eosinophils of different ages and origin along the inflammatory trajectory may exhibit functional diversity as circumstances change. Herein, we outline the inflammatory time line of allergic airway inflammation from acute, late, adaptive to chronic processes. We summarize the function of the eosinophils in regards to their resident localization and time of recruitment to the lung, in all stages of the inflammatory response. In all, we argue that immunological differences in eosinophils are a function of time and space as the allergic inflammatory response is initiated and resolved.

Short-Term Preclinical Application of Functional Human Induced Pluripotent Stem Cell-Derived Airway Epithelial Patches

Airway pathologies including cancer, trauma, and stenosis lack effective treatments, meanwhile airway transplantation and available tissue engineering approaches fail due to epithelial dysfunction. Autologous progenitors do not meet the clinical need for regeneration due to their insufficient expansion and differentiation, for which human induced pluripotent stem cells (hiPSCs) are promising alternatives. Airway epithelial patches are engineered by differentiating hiPSC-derived airway progenitors into physiological proportions of ciliated (73.9 ± 5.5%) and goblet (2.1 ± 1.4%) cells on a silk fibroin-collagen vitrigel membrane (SF-CVM) composite biomaterial for transplantation in porcine tracheal defects ex vivo and in vivo. Evaluation of ex vivo tracheal repair using hiPSC-derived SF-CVM patches demonstrate native-like tracheal epithelial metabolism and maintenance of mucociliary epithelium to day 3. In vivo studies demonstrate SF-CVM integration and maintenance of airway patency, showing 80.8 ± 3.6% graft coverage with an hiPSC-derived pseudostratified epithelium and 70.7 ± 2.3% coverage with viable cells, 3 days postoperatively. The utility of bioengineered, hiPSC-derived epithelial patches for airway repair is demonstrated in a short-term preclinical survival model, providing a significant leap for airway reconstruction approaches.

A comparison of three mucus-secreting airway cell lines (Calu-3, SPOC1 and UNCN3T) for use as biopharmaceutical models of the nose and lung

The aim of this work was to compare three existing mucus-secreting airway cell lines for use as models of the airways to study drug transport in the presence of mucus. Each cell line secreted mature, glycosylated mucins, evidenced by the enzyme-linked lectin assay. The secretagogue, adenylyl-imidodiphosphate, increased mucin secretion in SPOC1 (3.5-fold) and UNCN3T (1.5-fold) cells but not in Calu-3 cells. In a novel mucus-depleted (MD) model the amount of mucus in the non-depleted wells was 3-, 8- and 4-fold higher than in the mucus-depleted wells of the Calu-3, SPOC1 and UNCN3T cells respectively. The permeability of 'high mucus' cells to testosterone was significantly less in SPOC1 and UNCN3T cells (P < 0.05) but not Calu-3 cells. Mucin secretion and cytokine release were investigated as indicators of drug irritancy in the SPOC1 and UNCN3T cell lines. A number of inhaled drugs significantly increased mucin secretion at high concentrations and the release of IL-6 and IL-8 from SPOC1 or UNCN3T cells (P < 0.05). SPOC1 and UNCN3T cell lines are better able to model the effect of mucus on drug absorption than the Calu-3 cell line and are proposed for use in assessing drug-mucus interactions in inhaled drug and formulation development.

Inflammation in Asthma Pathogenesis: Role of T cells, Macrophages, Epithelial Cells and Type 2 Inflammation

Asthma is a chronic disease with abnormal inflammatory and immunological responses. The disease initiated by antigens in subjects with genetic susceptibility. However, environmental factors play a role in the initiation and exacerbation of asthma attack. Asthma is T helper 2 (Th2)-cell-mediated disease. Recent studies indicated that asthma is not a single disease entity, but it is with multiple phenotypes and endotypes. The pathophysiological changes in asthma included a series of subsequent continuous vicious circle of cellular activation contributed to induction of chemokines and cytokines that potentiate inflammation. The heterogeneity of asthma influenced the treatment response. The asthma pathogenesis driven by varied set of cells such as eosinophils, basophils, neutrophils, mast cells, macrophages, epithelial cells and T cells. In this review the role of T cells, macrophage, and epithelial cells are discussed.

Oxidized Phosphatidylcholines Induce Multiple Functional Defects in Airway Epithelial Cells

Oxidative stress is a hallmark of numerous airway diseases, contributing to extensive cell and tissue damage. Cell membranes and the airway mucosal lining are rich in phospholipids that are particularly susceptible to oxidative attack, producing bioactive molecules including oxidized phosphatidylcholines (OxPC). With the recent discovery of elevated OxPC in asthmatic patients after allergen challenge, we hypothesized that OxPC directly contribute to disease by inducing airway epithelial cell dysfunction. We found that OxPC induced concentration-dependent cell stress and loss of viability in BEAS-2B and Calu-3 cell lines and primary human epithelial cells. These responses corresponded with significant epithelial barrier dysfunction, which was further compounded when combining OxPC with an epithelial wound. OxPC inhibited DNA synthesis and migration required to re-establish barrier function, but cells recovered if OxPC were washed off soon after treatment. OxPC induced generation of reactive oxygen species, lipid peroxidation and mitochondrial dysfunction, raising the possibility that OxPC cause pathological lipid metabolism in a self-propagating cycle. The oxidative stress induced by OxPC could not be abrogated by putative OxPC receptor blockers, but partial recovery of barrier function, proliferation and lipid peroxidation could be achieved with the antioxidant n-acetyl cysteine. In summary, we have identified OxPC as a group of bioactive molecules that significantly impair multiple facets of epithelial cell function, consistent with pathological features of asthma. Further characterisation of the mechanisms by which OxPC affect epithelial cells could yield new insights into how oxidative stress contributes to the pathogenesis of airway disease.

Inhibition of β-Catenin/CREB Binding Protein Signaling Attenuates House Dust Mite-Induced Goblet Cell Metaplasia in Mice

Excessive mucus production is a major feature of allergic asthma. Disruption of epithelial junctions by allergens such as house dust mite (HDM) results in the activation of β-catenin signaling, which has been reported to stimulate goblet cell differentiation. β-catenin interacts with various co-activators including CREB binding protein (CBP) and p300, thereby regulating the expression of genes involved in cell proliferation and differentiation, respectively. We specifically investigated the role of the β-catenin/CBP signaling pathway in goblet cell metaplasia in a HDM-induced allergic airway disease model in mice using ICG-001, a small molecule inhibitor that blocks the binding of CBP to β-catenin. Female 6- 8-week-old BALB/c mice were sensitized to HDM/saline on days 0, 1, and 2, followed by intranasal challenge with HDM/saline with or without subcutaneous ICG-001/vehicle treatment from days 14 to 17, and samples harvested 24 h after the last challenge/treatment. Differential inflammatory cells in bronchoalveolar lavage (BAL) fluid were enumerated. Alcian blue (AB)/Periodic acid–Schiff (PAS) staining was used to identify goblet cells/mucus production, and airway hyperresponsiveness (AHR) was assessed using invasive plethysmography. Exposure to HDM induced airway inflammation, goblet cell metaplasia and increased AHR, with increased airway resistance in response to the non-specific spasmogen methacholine. Inhibition of the β-catenin/CBP pathway using treatment with ICG-001 significantly attenuated the HDM-induced goblet cell metaplasia and infiltration of macrophages, but had no effect on eosinophils, neutrophils, lymphocytes or AHR. Increased β-catenin/CBP signaling may promote HDM-induced goblet cell metaplasia in mice.

Epithelium-derived IL17A Promotes Cigarette Smoke-induced Inflammation and Mucus Hyperproduction

Airway epithelium is a central modulator of innate and adaptive immunity in the lung. Interleukin (IL)17A expression was found to be increased in airway epithelium; however, the role of epithelial-derived IL17A in chronic obstructive pulmonary disease (COPD) remains unclear. In this study, we aim to determine whether epithelial-derived IL17A regulates inflammation and mucus hyperproduction in COPD using a cultured human bronchial epithelial (HBE) cell line in vitro and airway epithelium IL17A-specific knockout mouse in vivo. Increased IL17A expression was observed in mouse airway epithelium upon cigarette smoke (CS) exposure or in a COPD mouse model that was induced by CS and elastin. CS extract (CSE) also triggered IL17A expression in HBE cells. Blocking IL17A or IL17RA effectively attenuated CSE-induced MUC5AC and the inflammatory cytokines IL6, tumor necrosis factor (TNF)-α, and IL1β in HBE cells, suggesting that IL17A mediates CSE-induced inflammation and mucin production in an autocrine manner. CSE activated p-JUN and p-JNK, which were also reduced by IL17RA-siRNA, and JUN-siRNA attenuated CSE-induced IL6 and MUC5AC. In vivo, selective knockout of IL17A in airway epithelium markedly reduced the neutrophilic infiltration in Bronchoalveolar Lavage Fluid (BALF), peribronchial inflammation, pro-inflammatory mediators (CXCL1 and CXCL2), and mucus production in a COPD mouse model. We showed a novel function of airway epithelium-derived IL17A, which can act locally in an autocrine manner to amplify inflammation and increase mucus production in COPD pathogenesis.

Revisiting the controversy: The role of fungi in chronic rhinosinusitis

In the last two decades, the development of culture-independent genomic techniques has facilitated an increased appreciation of the microbiota-immunity interactions and their role in a multitude of chronic inflammatory diseases such as chronic rhinosinusitis (CRS), asthma, inflammatory bowel disease and dermatitis. While the pathologic role of bacteria in chronic inflammatory diseases is generally accepted, the understanding of the role of fungi remains controversial. Chronic rhinosinusitis, specifically the phenotype linked to nasal polyps, represents a spectrum of chronic inflammatory diseases typically characterized by a type 2 immune response. Studies on the microbiota within sinus cavities from healthy and diseased patients have focused on the bacterial community, mainly highlighting the loss of diversity associated with sinus inflammation. Within the various CRS with nasal polyps (CRSwNP) phenotypes, allergic fungal rhinosinusitis presents an opportunity to investigate the role of fungi in chronic type 2 immune responses as well as the antifungal immune pathways designed to prevent invasive fungal diseases. In this review, we examine the spectrum of fungi-associated sinus diseases highlighting the interaction between fungal species and host immune status on disease presentation. With a focus on fungi and type 2 immune response, we highlight the current knowledge and its limitations of the sinus mycobiota along with cellular interactions and activated molecular pathways linked to fungi.

Nasal Epithelial Barrier Integrity and Tight Junctions Disruption in Allergic Rhinitis: Overview and Pathogenic Insights

Allergic rhinitis (AR) is a common disorder affecting up to 40% of the population worldwide and it usually persists throughout life. Nasal epithelial barrier constitutes the first line of defense against invasion of harmful pathogens or aeroallergens. Cell junctions comprising of tight junctions (TJs), adherens junctions, desmosomes and hemidesmosomes form the nasal epithelial barrier. Impairment of TJ molecules plays causative roles in the pathogenesis of AR. In this review, we describe and discuss the components of TJs and their disruption leading to development of AR, as well as regulation of TJs expression by epigenetic changes, neuro-immune interaction, epithelial-derived cytokines (thymic stromal lymphopoietin, IL-25 and IL-33), T helper 2 (Th2) cytokines (IL-4, IL-5, IL-6 and IL-13) and innate lymphoid cells. These growing evidence support the development of novel therapeutic approaches to restore nasal epithelial TJs expression in AR patients.

Implications for Extracellular Matrix Interactions With Human Lung Basal Stem Cells in Lung Development, Disease, and Airway Modeling

The extracellular matrix (ECM) is not simply a quiescent scaffold. This three-dimensional network of extracellular macromolecules provides structural, mechanical, and biochemical support for the cells of the lung. Throughout life, the ECM forms a critical component of the pulmonary stem cell niche. Basal cells (BCs), the primary stem cells of the airways capable of differentiating to all luminal cell types, reside in close proximity to the basolateral ECM. Studying BC-ECM interactions is important for the development of therapies for chronic lung diseases in which ECM alterations are accompanied by an apparent loss of the lung's regenerative capacity. The complexity and importance of the native ECM in the regulation of BCs is highlighted as we have yet to create an in vitro culture model that is capable of supporting the long-term expansion of multipotent BCs. The interactions between the pulmonary ECM and BCs are, therefore, a vital component for understanding the mechanisms regulating BC stemness during health and disease. If we are able to replicate these interactions in airway models, we could significantly improve our ability to maintain basal cell stemness ex vivo for use in in vitro models and with prospects for cellular therapies. Furthermore, successful, and sustained airway regeneration in an aged or diseased lung by small molecules, novel compounds or via cellular therapy will rely upon both manipulation of the airway stem cells and their immediate niche within the lung. This review will focus on the current understanding of how the pulmonary ECM regulates the basal stem cell function, how this relationship changes in chronic disease, and how replicating native conditions poses challenges for ex vivo cell culture.

Prioritizing Molecular Biomarkers in Asthma and Respiratory Allergy Using Systems Biology

Highly prevalent respiratory diseases such as asthma and allergy remain a pressing health challenge. Currently, there is an unmet need for precise diagnostic tools capable of predicting the great heterogeneity of these illnesses. In a previous study of 94 asthma/respiratory allergy biomarker candidates, we defined a group of potential biomarkers to distinguish clinical phenotypes (i.e. nonallergic asthma, allergic asthma, respiratory allergy without asthma) and disease severity. Here, we analyze our experimental results using complex algorithmic approaches that establish holistic disease models (systems biology), combining these insights with information available in specialized databases developed worldwide. With this approach, we aim to prioritize the most relevant biomarkers according to their specificity and mechanistic implication with molecular motifs of the diseases. The Therapeutic Performance Mapping System (Anaxomics’ TPMS technology) was used to generate one mathematical model per disease: allergic asthma (AA), non-allergic asthma (NA), and respiratory allergy (RA), defining specific molecular motifs for each. The relationship of our molecular biomarker candidates and each disease was analyzed by artificial neural networks (ANNs) scores. These analyses prioritized molecular biomarkers specific to the diseases and to particular molecular motifs. As a first step, molecular characterization of the pathophysiological processes of AA defined 16 molecular motifs: 2 specific for AA, 2 shared with RA, and 12 shared with NA. Mechanistic analysis showed 17 proteins that were strongly related to AA. Eleven proteins were associated with RA and 16 proteins with NA. Specificity analysis showed that 12 proteins were specific to AA, 7 were specific to RA, and 2 to NA. Finally, a triggering analysis revealed a relevant role for AKT1, STAT1, and MAPK13 in all three conditions and for TLR4 in asthmatic diseases (AA and NA). In conclusion, this study has enabled us to prioritize biomarkers depending on the functionality associated with each disease and with specific molecular motifs, which could improve the definition and usefulness of new molecular biomarkers.

Galectin-7 overexpression destroys airway epithelial barrier in transgenic mice

When the integrity of airway epithelium is destroyed, the ordered airway barrier no longer exists and increases sensitivity to viral infections and allergens, leading to the occurrence of airway inflammation such as asthma. Here, we found that galectin-7 transgenic(+) mice exhibited abnormal airway structures as embryos and after birth. These abnormalities included absent or substantially reduced pseudostratified columnar ciliated epithelium and increased monolayer cells with irregular arrangement and widening of intercellular spaces. Moreover, airway tissue from galectin-7 transgenic(+) mice showed evidence of impaired cell-cell junctions and decreased expression of zonula occludens-1(ZO-1) and E-cadherin. When treated with respiratory syncytial virus (RSV) or ovalbumin (OVA), galectin-7 transgenic(+) mice developed substantially increased bronchial epithelial detachment and apoptosis, airway smooth muscle and basement membrane thickening, and enhanced airway responsiveness. We found that Galectin-7 localized in the cytoplasm and nucleus of bronchial epithelial cells, and that increased apoptosis was mediated through mitochondrial release of cytochrome c and upregulated JNK1 activation and expression of caspase-3 in galectin-7 Tg(+) mice. These findings suggested that Galectin-7 causes airway structural defects and destroys airway epithelium barrier, which predispose the airways to RSV or OVA-induced epithelial apoptosis, injury, and other asthma responses.

Periostin: contributor to abnormal airway epithelial function in asthma?

Periostin (POSTN) may serve as a biomarker for Type-2 mediated eosinophilic airway inflammation in asthma. We hypothesised that a Type-2 cytokine, interleukin (IL)-13, induces airway epithelial expression of POSTN, which in turn contributes to epithelial changes observed in asthma.We studied the effect of IL-13 on POSTN expression in BEAS-2B and air-liquid interface differentiated primary bronchial epithelial cells (PBECs). Additionally, the effects of recombinant human POSTN on epithelial-to-mesenchymal transition (EMT) markers and mucin genes were assessed. POSTN single cell gene expression and protein levels were analysed in bronchial biopsies and induced sputum from asthma patients and healthy controls.IL-13 increased POSTN expression in both cell types and this was accompanied by EMT-related features in BEAS-2B. In air-liquid interface differentiated PBECs, IL-13 increased POSTN basolateral and apical release. Apical administration of POSTN increased the expression of MMP-9, MUC5B and MUC5AC In bronchial biopsies, POSTN expression was mainly confined to basal epithelial cells, ionocytes, endothelial cells and fibroblasts, showing higher expression in basal epithelial cells from asthma patients versus those from controls. A higher level of POSTN protein expression in epithelial and subepithelial layers was confirmed in bronchial biopsies from asthma patients when compared to healthy controls. Although sputum POSTN levels were not higher in asthma, levels correlated with eosinophil numbers and with the coughing-up of mucus.POSTN expression is increased by IL-13 in bronchial epithelial cells and is higher in bronchial biopsies from asthma patients. This may have important consequences, as administration of POSTN increases epithelial expression of mucin genes, supporting the relationship of POSTN with Type-2 mediated asthma and mucus secretion.

Airway epithelial integrin β4 suppresses allergic inflammation by decreasing CCL17 production

Airway epithelial cells (AECs) play a key role in asthma susceptibility and severity. Integrin β4 (ITGB4) is a structural adhesion molecule that is down-regulated in the airway epithelium of asthma patients. Although a few studies hint toward the role of ITGB4 in asthmatic inflammation pathogenesis, their specific resultant effects remain unexplored. In the present study, we determined the role of ITGB4 of AECs in the regulation of Th2 response and identified the underpinning molecular mechanisms. We found that ITGB4 deficiency led to exaggerated lung inflammation and AHR with higher production of CCL17 in house dust mite (HDM)-treated mice. ITGB4 regulated CCL17 production in AECs through EGFR, ERK and NF-κB pathways. EFGR-antagonist treatment or the neutralization of CCL17 both inhibited exaggerated pathological marks in HDM-challenged ITGB4-deficient mice. Together, these results demonstrated the involvement of ITGB4 deficiency in the development of Th2 responses of allergic asthma by down-regulation of EGFR and CCL17 pathway in AECs.

Cross-reactive antibodies against dust mite-derived enolase induce neutrophilic airway inflammation

BACKGROUND AND AIMS

Neutrophilic inflammation is a hallmark of some specific asthma phenotypes; its aetiology is not yet fully understood. House dust mite (HDM) is the most common factor in the pathogenesis of airway inflammation. This study aims to elucidate the role of cross-antibodies against HDM-derived factors in the development of neutrophilic inflammation in the airway.

METHODS

Blood samples were collected from asthma patients with chronic neutrophilic asthma for analysis of HDM-specific cross-reactive antibodies. The role of an antibody against HDM-derived enolase (EnoAb) in the impairment of airway epithelial barrier function and induction of airway inflammation was assessed in a cell culture model and an animal model.

RESULTS

High similarity (72%) of the enolase gene sequences was identified between HDM and human. Serum EnoAb was detected in patients with chronic neutrophilic asthma. The EnoAb bound to airway epithelial cells to form complexes with enolase, which activated complement, impaired airway epithelial barrier functions and induced neutrophilic inflammation in the airway tissues.

CONCLUSIONS

HDM-derived enolase can induce specific cross-antibodies in humans, which induce neutrophilic inflammation in the airway.

Titanium dioxide nanoparticles exaggerate respiratory syncytial virus-induced airway epithelial barrier dysfunction

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in children worldwide. While most develop a mild, self-limiting illness, some develop severe acute lower respiratory infection and persistent airway disease. Exposure to ambient particulate matter has been linked to asthma, bronchitis, and viral infection in multiple epidemiological studies. We hypothesized that coexposure to nanoparticles worsens RSV-induced airway epithelial barrier dysfunction. Bronchial epithelial cells were incubated with titanium dioxide nanoparticles (TiO2-NP) or a combination of TiO2-NP and RSV. Structure and function of epithelial cell barrier were analyzed. Viral titer and the role of reactive oxygen species (ROS) generation were evaluated. In vivo, mice were intranasally incubated with TiO2-NP, RSV, or a combination. Lungs and bronchoalveolar lavage (BAL) fluid were harvested for analysis of airway inflammation and apical junctional complex (AJC) disruption. RSV-induced AJC disruption was amplified by TiO2-NP. Nanoparticle exposure increased viral infection in epithelial cells. TiO2-NP induced generation of ROS, and pretreatment with antioxidant, N-acetylcysteine, reversed said barrier dysfunction. In vivo, RSV-induced injury and AJC disruption were augmented in the lungs of mice given TiO2-NP. Airway inflammation was exacerbated, as evidenced by increased white blood cell infiltration into the BAL, along with exaggeration of peribronchial inflammation and AJC disruption. These data demonstrate that TiO2-NP exposure exacerbates RSV-induced AJC dysfunction and increases inflammation by mechanisms involving generation of ROS. Further studies are required to determine whether NP exposure plays a role in the health disparities of asthma and other lung diseases, and why some children experience more severe airway disease with RSV infection.

Qi-Xian Decoction Upregulated E-cadherin Expression in Human Lung Epithelial Cells and Ovalbumin-Challenged Mice by Inhibiting Reactive Oxygen Species-Mediated Extracellular-Signal-Regulated Kinase (ERK) Activation

Background

Loss of the epithelial barrier is characterized by a reduction in E-cadherin expression and is a hallmark of asthma. Qi-xian decoction (QXT) is a Chinese medicinal formula that has been used to effectively treat asthma. This study aimed to investigate the effect of QXT on E-cadherin expression in human lung epithelial 16HBE cells and ovalbumin-challenged mice and to explore the underlying molecular mechanism.

Material/Methods

Ovalbumin (OVA)-induced mice were used as a model of asthma. Real-time PCR and Western blotting were utilized to examine mRNA and protein levels. Lung tissue reactive oxygen species (ROS) levels were evaluated using dichloro-dihydro-fluorescein diacetate (DCFH-DA). Serum superoxide dismutase (SOD) and the total antioxidant capacity (TAOC) were measured via enzyme-linked immunosorbent assay (ELISA)-based analyses. 16HBE cells were utilized to explore the effect of QXT or hydrogen peroxide (H₂O₂) on the expression of E-cadherin in vitro.

Results

We found that QXT treatment increased E-cadherin expression and decreased extracellular-signal-regulated kinase (ERK) phosphorylation levels in the lung tissues of OVA-challenged mice. QXT also downregulated ROS levels and increased serum SOD and TAOC levels in OVA-challenged mice. In vitro studies demonstrated that increased ROS generation induced by H₂O₂ resulted in decreased E-cadherin expression levels in 16HBE cells, which was attenuated by inhibition of ERK signaling. Moreover, the H₂O₂-induced downregulation of E-cadherin expression, increased ROS generation, and ERK activation in 16HBE cells were restored by treatment with QXT water or ethanol extract.

Conclusions

These data demonstrate that one mechanism by which QXT protects against asthma is to restore E-cadherin expression in vivo and in vitro by inhibiting ROS-mediated ERK activation.

Host-microbe cross-talk in the lung microenvironment: implications for understanding and treating chronic lung disease

Chronic respiratory diseases are highly prevalent worldwide and will continue to rise in the foreseeable future. Despite intensive efforts over recent decades, the development of novel and effective therapeutic approaches has been slow. However, there is new and increasing evidence that communities of micro-organisms in our body, the human microbiome, are crucially involved in the development and progression of chronic respiratory diseases. Understanding the detailed mechanisms underlying this cross-talk between host and microbiota is critical for development of microbiome- or host-targeted therapeutics and prevention strategies. Here we review and discuss the most recent knowledge on the continuous reciprocal interaction between the host and microbes in health and respiratory disease. Furthermore, we highlight promising developments in microbiome-based therapies and discuss the need to employ more holistic approaches of restoring both the pulmonary niche and the microbial community.

The reciprocal interaction between microbes and host in the lung is increasingly recognised as an important determinant of health. The complexity of this cross-talk needs to be taken into account when studying diseases and developing future new therapies.https://bit.ly/2VKYUfT

Epithelial cell dysfunction, a major driver of asthma development

Airway epithelial barrier dysfunction is frequently observed in asthma and may have important implications. The physical barrier function of the airway epithelium is tightly interwoven with its immunomodulatory actions, while abnormal epithelial repair responses may contribute to remodelling of the airway wall. We propose that abnormalities in the airway epithelial barrier play a crucial role in the sensitization to allergens and pathogenesis of asthma. Many of the identified susceptibility genes for asthma are expressed in the airway epithelium, supporting the notion that events at the airway epithelial surface are critical for the development of the disease. However, the exact mechanisms by which the expression of epithelial susceptibility genes translates into a functionally altered response to environmental risk factors of asthma are still unknown. Interactions between genetic factors and epigenetic regulatory mechanisms may be crucial for asthma susceptibility. Understanding these mechanisms may lead to identification of novel targets for asthma intervention by targeting the airway epithelium. Moreover, exciting new insights have come from recent studies using single‐cell RNA sequencing (scRNA‐Seq) to study the airway epithelium in asthma. This review focuses on the role of airway epithelial barrier function in the susceptibility to develop asthma and novel insights in the modulation of epithelial cell dysfunction in asthma.

Impact of the Local Inflammatory Environment on Mucosal Vitamin D Metabolism and Signaling in Chronic Inflammatory Lung Diseases

Vitamin D plays an active role in the modulation of innate and adaptive immune responses as well as in the protection against respiratory pathogens. Evidence for this immunomodulatory and protective role is derived from observational studies showing an association between vitamin D deficiency, chronic airway diseases and respiratory infections, and is supported by a range of experimental studies using cell culture and animal models. Furthermore, recent intervention studies have now shown that vitamin D supplementation reduces exacerbation rates in vitamin D-deficient patients with chronic obstructive pulmonary disease (COPD) or asthma and decreases the incidence of acute respiratory tract infections. The active vitamin D metabolite, 1,25-dihydroxy-vitamin D (1,25(OH)₂D), is known to contribute to the integrity of the mucosal barrier, promote killing of pathogens (via the induction of antimicrobial peptides), and to modulate inflammation and immune responses. These mechanisms may partly explain its protective role against infections and exacerbations in COPD and asthma patients. The respiratory mucosa is an important site of local 1,25(OH)₂D synthesis, degradation and signaling, a process that can be affected by exposure to inflammatory mediators. As a consequence, mucosal inflammation and other disease-associated factors, as observed in e.g., COPD and asthma, may modulate the protective actions of 1,25(OH)₂D. Here, we discuss the potential consequences of various disease-associated processes such as inflammation and exposure to pathogens and inhaled toxicants on vitamin D metabolism and local responses to 1,25(OH)₂D in both immune- and epithelial cells. We furthermore discuss potential consequences of disturbed local levels of 25(OH)D and 1,25(OH)₂D for chronic lung diseases. Additional insight into the relationship between disease-associated mechanisms and local effects of 1,25(OH)₂D is expected to contribute to the design of future strategies aimed at improving local levels of 1,25(OH)₂D and signaling in chronic inflammatory lung diseases.

Significant Changes in Trans-Epithelial Barrier Proteins of Adenoid Tissue with Atopic Status in Children

OBJECTIVES

Adenoid tissue is important in local immune response and epithelial barrier dysfunction of this tissue may contribute to allergies. The aim of this study was to evaluate the relationship between the status of cross-epithelial barrier elements in adenoid tissue lymphoepithelium and inhalant allergen sensitization.

MATERIALS AND METHODS

Children aged 5-15 years, who underwent adenotonsillectomy, participated in this study. All subjects underwent skin prick testing with environmental inhalant allergens. Occludin, ZO1, e-cadherin, β-catenin, desmoglein, desmoplakin, and connexon-43 were stained immunohistochemically in the adenoid tissues obtained and scored by H-score.

RESULTS

We enrolled 76 children, 14 among whom were sensitized to environmental allergens. Among the zonula occludens proteins, median H-scores for occludin, claudin, and ZO-1 were significantly lower in the atopic compared to the nonatopic group respectively (p<0.001). Similarly, median H-scores for e-cadherin and β catenin proteins of the zonula adherens were significantly lower in the atopic group (p<0.001). Both desmoglein and desmoplakin H-scores were significantly lower in the atopic group [60 (50-100) vs 280 (260-300), p<0.001 and 105 (87.5-120) vs 280 (67.25-300), p<0.001 respectively]. Moreover, connexin-43 protein of the gap junction was significantly lower in the atopic group (p<0.001).

CONCLUSION

Adenoid tissue, which is the initial point of contact of inhalant allergens demonstrates epithelial barrier junctional protein, changes in children with inhalant allergen sensitization without clinical allergic disease symptoms. Therefore, it may be concluded that epithelial barrier function plays an important role in the development of allergen sensitization versus tolerance.

Epithelial-interleukin-1 inhibits collagen formation by airway fibroblasts: Implications for asthma

In asthma, the airway epithelium has an impaired capacity to differentiate and plays a key role in the development of airway inflammation and remodeling through mediator release. The study objective was to investigate the release of (IL)-1 family members from primary airway epithelial-cells during differentiation, and how they affect primary airway fibroblast (PAF)-induced inflammation, extracellular matrix (ECM) production, and collagen I remodeling. The release of IL-1α/β and IL-33 during airway epithelial differentiation was assessed over 20-days using air-liquid interface cultures. The effect of IL-1 family cytokines on airway fibroblasts grown on collagen-coated well-plates and 3-dimensional collagen gels was assessed by measurement of inflammatory mediators and ECM proteins by ELISA and western blot, as well as collagen fiber formation using non-linear optical microscopy after 24-hours. The production of IL-1α is elevated in undifferentiated asthmatic-PAECs compared to controls. IL-1α/β induced fibroblast pro-inflammatory responses (CXCL8/IL-8, IL-6, TSLP, GM-CSF) and suppressed ECM-production (collagen, fibronectin, periostin) and the cell’s ability to repair and remodel fibrillar collagen I via LOX, LOXL1 and LOXL2 activity, as confirmed by inhibition with β-aminopropionitrile. These data support a role for epithelial-derived-IL-1 in the dysregulated repair of the asthmatic-EMTU and provides new insights into the contribution of airway fibroblasts in inflammation and airway remodeling in asthma.

Phenotypic and functional translation of IL33 genetics in asthma

BACKGROUND

Asthma is a complex disease with multiple phenotypes that may differ in disease pathobiology and treatment response. IL33 single nucleotide polymorphisms (SNPs) have been reproducibly associated with asthma. IL33 levels are elevated in sputum and bronchial biopsies of patients with asthma. The functional consequences of IL33 asthma SNPs remain unknown.

OBJECTIVE

This study sought to determine whether IL33 SNPs associate with asthma-related phenotypes and with IL33 expression in lung or bronchial epithelium. This study investigated the effect of increased IL33 expression on human bronchial epithelial cell (HBEC) function.

METHODS

Association between IL33 SNPs (Chr9: 5,815,786-6,657,983) and asthma phenotypes (Lifelines/DAG [Dutch Asthma GWAS]/GASP [Genetics of Asthma Severity & Phenotypes] cohorts) and between SNPs and expression (lung tissue, bronchial brushes, HBECs) was done using regression modeling. Lentiviral overexpression was used to study IL33 effects on HBECs.

RESULTS

We found that 161 SNPs spanning the IL33 region associated with 1 or more asthma phenotypes after correction for multiple testing. We report a main independent signal tagged by rs992969 associating with blood eosinophil levels, asthma, and eosinophilic asthma. A second, independent signal tagged by rs4008366 presented modest association with eosinophilic asthma. Neither signal associated with FEV₁, FEV₁/forced vital capacity, atopy, and age of asthma onset. The 2 IL33 signals are expression quantitative loci in bronchial brushes and cultured HBECs, but not in lung tissue. IL33 overexpression in vitro resulted in reduced viability and reactive oxygen species-capturing of HBECs, without influencing epithelial cell count, metabolic activity, or barrier function.

CONCLUSIONS

We identify IL33 as an epithelial susceptibility gene for eosinophilia and asthma, provide mechanistic insight, and implicate targeting of the IL33 pathway specifically in eosinophilic asthma.

Current strategies and opportunities to manufacture cells for modeling human lungs

Chronic lung diseases remain major healthcare burdens, for which the only curative treatment is lung transplantation. In vitro human models are promising platforms for identifying and testing novel compounds to potentially decrease this burden. Directed differentiation of pluripotent stem cells is an important strategy to generate lung cells to create such models. Current lung directed differentiation protocols are limited as they do not 1) recapitulate the diversity of respiratory epithelium, 2) generate consistent or sufficient cell numbers for drug discovery platforms, and 3) establish the histologic tissue-level organization critical for modeling lung function. In this review, we describe how lung development has formed the basis for directed differentiation protocols, and discuss the utility of available protocols for lung epithelial cell generation and drug development. We further highlight tissue engineering strategies for manipulating biophysical signals during directed differentiation such that future protocols can recapitulate both chemical and physical cues present during lung development.

Identification of urban particulate matter-induced disruption of human respiratory mucosa integrity using whole transcriptome analysis and organ-on-a chip

Background

Exposure to air particulate matter (PM) is associated with various diseases in the human respiratory system. To date, most in vitro studies showing cellular responses to PM have been performed in cell culture using a single cell type. There are few studies considering how multicellular networks communicate in a tissue microenvironment when responding to the presence of PM. Here, an in vitro three-dimensional (3D) respiratory mucosa-on-a-chip, composed of human nasal epithelial cells, fibroblasts, and endothelial cells, is used to recapitulate and better understand the effects of urban particulate matter (UPM) on human respiratory mucosa.

Results

We hypothesized that the first cells to contact with UPM, the nasal epithelial cells, would respond similar to the tissue microenvironment, and the 3D respiratory mucosa model would be a suitable platform to capture these events. First, whole transcriptome analysis revealed that UPM induced gene expression alterations in inflammatory and adhesion-related genes in human nasal epithelial cells. Next, we developed an in vitro 3D respiratory mucosa model composed of human nasal epithelial cells, fibroblasts, and endothelial cells and demonstrated that the model is structurally and functionally compatible with the respiratory mucosa. Finally, we used our model to expose human nasal epithelial cells to UPM, which led to a disruption in the integrity of the respiratory mucosa by decreasing the expression of zonula occludens-1 in both the epithelium and endothelium, while also reducing vascular endothelial cadherin expression in the endothelium.

Conclusions

We demonstrate the potential of the 3D respiratory mucosa model as a valuable tool for the simultaneous evaluation of multicellular responses caused by external stimuli in the human respiratory mucosa. We believe that the evaluation strategy proposed in the study will move us toward a better understanding of the detailed molecular mechanisms associated with pathological changes in the human respiratory system.

MIF signaling blocking alleviates airway inflammation and airway epithelial barrier disruption in a HDM-induced asthma model

Recent studies have indicated that Macrophage migration inhibitory factor (MIF) plays an important role in the prevention and treatment of asthma. However the role of MIF in airway inflammation and airway epithelial barrier disruption in house dust mite (HDM)-induced asthma has not been addressed. We hypothesized that MIF contributed to HDM-induced the production of Th2-associated cytokines and E-cadherin dysfunction in asthmatic mice and 16HBE cells. In vivo, a HDM-induced asthma mouse model was set up and mice treated with MIF antagonist ISO-1 after HDM. The mice treated with the ISO-1 ameliorated airway hyper-reactivity, airway inflammation, increased serum IgE levels, the aberrant arrangement of E-cadherin as well as the release of Th2 cytokines induced by HDM. In vitro, the exposure of 16HBE cells to HDM and rhMIF resulted in airway epithelial barrier disruption, inflammatory cytokine production and enhanced glycolytic flux. While these changes were attenuated by MIF siRNA treatment. Sequentially, treatment of 16HBE cells with PFKFB3 antagonist PFK15 significantly lowered rhMIF-induced these changes in 16HBE cells. Therefore, these results indicate that MIF may be an important contributor in airway inflammation and airway epithelial barrier disruption of HDM-induced asthma. Moreover, HDM specifically induces airway inflammation and airway epithelial barrier disruption of 16HBE cells through MIF-mediated enhancement of aerobic glycolysis.

Pathway analysis of a genome-wide gene by air pollution interaction study in asthmatic children

OBJECTIVES

We aimed to investigate the role of genetics in the respiratory response of asthmatic children to air pollution, with a genome-wide level analysis of gene by nitrogen dioxide (NO2) and carbon monoxide (CO) interaction on lung function and to identify biological pathways involved.

METHODS

We used a two-step method for fast linear mixed model computations for genome-wide association studies, exploring whether variants modify the longitudinal relationship between 4-month average pollution and post-bronchodilator FEV1 in 522 Caucasian and 88 African-American asthmatic children. Top hits were confirmed with classic linear mixed-effect models. We used the improved gene set enrichment analysis for GWAS (i-GSEA4GWAS) to identify plausible pathways.

RESULTS

Two SNPs near the EPHA3 (rs13090972 and rs958144) and one in TXNDC8 (rs7041938) showed significant interactions with NO2 in Caucasians but we did not replicate this locus in African-Americans. SNP-CO interactions did not reach genome-wide significance. The i-GSEA4GWAS showed a pathway linked to the HO-1/CO system to be associated with CO-related FEV1 changes. For NO2-related FEV1 responses, we identified pathways involved in cellular adhesion, oxidative stress, inflammation, and metabolic responses.

CONCLUSION

The host lung function response to long-term exposure to pollution is linked to genes involved in cellular adhesion, oxidative stress, inflammatory, and metabolic pathways.

ITGB4 deficiency induces senescence of airway epithelial cells through p53 activation

Aging is characterized by a progressive loss of physiological integrity, leading to impaired organ function and, ultimately, increased vulnerability to death. Many complex diseases are related to aging, including asthma. In the lung, the airway epithelium serves as the first barrier to prevent the access of inspired external stimuli and dictates the initial stress responses. Notably, in the airway mucosa of asthma patients, an increase in senescent airway epithelial cells has been detected. Although it has been speculated that the senescence of airway epithelial cells could increase asthma susceptibility and aggravate asthma severity, the role of cell senescence in the development of asthma remains unclear. Integrin β4 (ITGB4) is a structural adhesion molecule with complex physiological functions that is downregulated in airway epithelial cells of asthma patients. This study demonstrates that the expression of ITGB4 in airway epithelial cells is downregulated significantly under oxidative stress or upon inflammatory stimulation. Moreover, we show that ITGB4 deficiency induces the senescence of airway epithelial cells through the activation of the p53 pathway both in vitro and in vivo. Together, our results demonstrate that airway epithelial senescence induced by ITGB4 deficiency after oxidative stress or inflammatory stimulation may be involved in the pathogenesis of asthma. Understanding the contribution of ITGB4 deficiency to the senescence of airway epithelial cells in asthma patients may provide new therapeutic approaches for the treatment of asthma.

Extra-adrenal glucocorticoid synthesis at epithelial barriers

Epithelial barriers play an important role in the exchange of nutrients, gases, and other signals between our body and the outside world. However, they protect it also from invasion by potential pathogens. Defective epithelial barriers and associated overshooting immune responses are the basis of many different inflammatory disorders of the skin, the lung, and the intestinal mucosa. The anti-inflammatory activity of glucocorticoids has been efficiently used for the treatment of these diseases. Interestingly, epithelia in these tissues are also a rich source of endogenous glucocorticoids, suggesting that local glucocorticoid synthesis is part of a tissue-specific regulatory circuit. In this review, we summarize current knowledge about the extra-adrenal glucocorticoid synthesis at the epithelial barriers of the intestine, lung and the skin, and discuss their relevance in the pathogenesis of inflammatory diseases and as therapeutic targets.

Jin Gui Shen Qi Wan, a traditional Chinese medicine, alleviated allergic airway hypersensitivity and inflammatory cell infiltration in a chronic asthma mouse model

ETHNOPHARMACOLOGICAL RELEVANCE

In Asia, Jin Gui Shen Qi Wan (JGSQW) has been used for hundreds of years to treat asthma.

AIM OF THE STUDY

The traditional Chinese medicine JGSQW is composed of Rehmannia glutinosa, Dioscorea opposita, Cornus officinalis, Poria cocos, Paeonia suffruticosa, Alisma orientalis, Aconitum carmichaelii and Cinnamomum cassia. However, the immunological mechanism underlying the effect of JGSQW treatment on asthma remains unclear. This study examined whether JGSQW has the potential to reduce asthma symptoms in mice with chronic asthma induced by recurrent Dermatophagoides pteronyssinus (Der p) stimulation, as well as its immunoregulatory mechanisms.

MATERIALS AND METHODS

The airways of BALB/c mice were stimulated with Der p (i.t.) once per week (50 μL, 1 mg/mL) for 6 consecutive weeks, and the mice were fed JGSQW (1 g/kg) 30 min prior to the Der p stimulation. Three days after the last stimulation, the mice were sacrificed to evaluate the airway remodelling, infiltration of inflammatory cells, lung histological features, and total IgE in the blood. Additionally, after A549 cells were treated with JGSQW, loganin, or paeoniflorin for 30 min, 10 ng/mL IL-1β was added to stimulate the A549 cells to evaluate the effect of the medicine on the ICAM-1 gene expression after IL-1β stimulation.

RESULTS

JGSQW significantly reduced the Der p-induced infiltration of inflammatory cells into airways and decreased the total IgE and Der p-specific IgG1 in serum. Collagen assays and histopathological examinations showed that JGSQW reduced lung airway remodelling. Additionally, an electrophoretic mobility shift assay and immunohistochemical staining verified that JGSQW inhibited the NF-kB expression in airway epithelial cell nuclei. JGSQW, loganin, and paeoniflorin inhibited the ICAM-1 gene expression caused by the IL-1β stimulation of A549 cells, and loganin and paeoniflorin had the maximum inhibitory effect when mixed according to the combination of doses in JGSQW.

CONCLUSION

These results indicated that in the chronic asthma mouse model, JGSQW inhibits the infiltration of inflammatory cells into the airways and airway remodelling and exhibits specific immunoregulatory effects. JGSQW with certain doses of loganin and paeoniflorin inhibited ICAM-1 gene expression in epithelial cells.

TSLP promotes asthmatic airway remodeling via p38-STAT3 signaling pathway in human lung fibroblast

PURPOSE

Thymic stromal lymphopoietin (TSLP) acts as a critical cytokine involved in asthmatic airway remodeling. Our study aimed to characterize the crosstalk between airway epithelial cells and fibroblasts regulated by TSLP through the signaling pathways of Mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3).

MATERIALS AND METHODS

Human biopsy specimens and lung tissues from mice were stained with hematoxylin and eosin (H&E) and immunohistochemistry. Human lung fibroblasts were stimulated with human recombinant TSLP. The protein expression of phosphorylation of STAT3 (p-STAT3) and phosphorylation of MAPK as well as the expression of collagen I and alpha-smooth muscle actin (α-SMA) were detected by Western blotting and immunofluorescence. Co-culture was performed to detect the influence of TSLP secreted by airway epithelial cells on fibroblasts. An ovalbumin (OVA)-induced asthmatic murine model was established with or without intraperitoneal injection of SB203580 (inhibitor of p-38). Protein expression in lung tissue was detected by immunohistochemistry and western blotting.

RESULT

TSLP could activate MAPK in HLF-1. SB203580 could inhibit the activation of p38, attenuate phosphorylation of STAT3, and decrease the expression of collagen I and α-SMA consequently in human fibroblasts. Co-culture demonstrated that TSLP secreted by epithelial cells could promote the expression of collagen I and α-SMA and aggravates airway remodeling in fibroblasts. In vivo, expression of TSLP, collagen I, α-SMA, p-p38 and p-STAT3 was upregulated in airway tissue of OVA-challenged mice and downregulated in mice which were treated by SB203580. The tissue staining showed that airway structure change was attenuated by SB203580 compared with OVA challenged mice as well.

CONCLUSIONS

TSLP might promote asthmatic airway remodeling via p38 MAPK-STAT3 axis activation and the crosstalk between airway epithelial cells and fibroblasts could aggravate remodeling. Blockade of p38 could alleviate airway remodeling which might provide a new therapeutic target for asthma.

Optimal biomaterials for tracheal epithelial grafts: An in vitro systematic comparative analysis

Tracheal injury, stenosis, and malignancy demand tracheal reconstruction, which often fails due to the lack of a functioning epithelium. We performed an extensive comparative analysis to determine optimal biomaterials for developing tracheal epithelial grafts with mucociliary function. We screened Hyaluronan-Poly(Ethylene Glycol), Chitosan-Collagen, Collagen Vitrigel Membrane, Fibrin Glue, Silk Fibroin, and Gelatin based on various parameters including mechanical strength, bulk degradation, cell attachment, spreading, metabolic activity, focal adhesion formation, and differentiation into ciliated and goblet cells. Silk Fibroin had significantly higher tensile strength (21.23 ± 4.42 MPa), retained 50% of its mass across 5 weeks, allowed 80-100% cell spreading and increasing metabolic activity across 10 days, focal adhesion formation within 2 h, and differentiation into 5.9 ± 2.6% goblet cells. Silk Fibroin, however, led to poor ciliation, producing 5.5 ± 3.9% ciliated cells, whereas Collagen Vitrigel Membrane promoted excellent ciliation. To capitalize on the mechanical and differentiation benefits of its respective components, we developed a composite biomaterial of Silk Fibroin and Collagen Vitrigel Membrane (SF-CVM), which demonstrated enhanced maturation into 20.6 ± 1.7% ciliated and 5.6 ± 1.0% goblet cells. Development of biomaterials-based airway epithelial grafts that provide desirable mechanics and differentiation is a major step towards treatment of airway disease. STATEMENT OF SIGNIFICANCE: Tracheal blockage, injury, and malignancy greater than 50% of the adult tracheal length cannot be safely resected. Tracheal replacement is one approach, but a major cause of transplant failure is the lack of a functioning epithelium. While tissue engineering for tracheal regeneration using biomaterials is promising, there is currently no gold standard. Therefore, we performed a systematic comparative study to characterize relevant materials for generating a biomaterials-based airway epithelial graft. We developed a composite biomaterial intended for surgical implantation providing tensile strength, slow biodegradation, and optimal support for differentiation of mature epithelia. This is a significant step augmenting current state-of-the-art methods for airway surgeries, laryngeal reconstruction, and tracheal tissue engineering.

Role of PCDH 1 Gene in the Development of Childhood Asthma and Other Related Phenotypes: A Literature Review

The asthma gene PCDH 1, encoding protocadherin-1, is a cellular adhesion molecule which plays an important role in epithelial barrier formation and repair. PCDH 1 is a novel susceptible gene not only in childhood asthma but also in eczema and other atopic phenotypes. In this article, we reviewed relevant articles from PubMed, Google Scholar, Science Direct and included all available significant pieces of information about the PCDH 1 association with asthma and other atopic or non-atopic phenotypes. It is very interesting that cigarette smoking can induce changes in PCDH 1 expression but how the changes in PCDH 1 induce asthma is still not clear. PCDH 1 gene polymorphism also sometimes plays role in asthma and bronchial hyperresponsiveness (BHR) pathogenesis as well as in allergic dermatitis.

The Cell Research Trends of Asthma: A Stem Frequency Analysis of the Literature

Objective

This study summarized asthma literature indexed in the Medical Literature Analysis and Retrieval System Online (MEDLINE) and explored the history and present trends of asthma cell research by stem frequency ranking to forecast the prospect of future work.

Methods

Literature was obtained from MEDLINE for the past 30 years and divided into three groups by decade as the retrieval time. The frequency of stemmed words in each group was calculated using Python with Apache Spark and the Natural Language Tool Kit for ranking. The unique stems or shared stems of 3 decades were summarized.

Results

A total of 1331, 4393, and 7215 records were retrieved from 3 decades chronologically, and the stem ranking of the top 50 were listed by frequency. The number of stems shared with 3 decades was 26 and with the first and last 2 decades was 5 and 13.

Conclusions

The number of cell research studies of asthma has increased rapidly, and scholars have paid more attentions on experimental research, especially on mechanistic research. Eosinophils, mast cells, and T cells are the hot spots of immunocyte research, while epithelia and smooth muscle cells are the hot spots of structural cell research. The research trend is closely linked with the development of experimental technology, including animal models. Early studies featured basic research, but immunity research has dominated in recent decades. The distinct definition of asthma phenotypes associated with genetic characteristics, immunity research, and the introduction of new cells will be the hot spots in future work.

Poly-L-Arginine Induces Apoptosis of NCI-H292 Cells via ERK1/2 Signaling Pathway

Cationic protein is a cytotoxic protein secreted by eosinophils and takes part in the damage of airway epithelium in asthma. Poly-L-arginine (PLA), a synthetic cationic protein, is widely used to mimic the biological function of the natural cationic protein in vitro. Previous studies demonstrated the damage of the airway epithelial cells by cationic protein, but the molecular mechanism is unclear. The purpose of this study aimed at exploring whether PLA could induce apoptosis of human airway epithelial cells (NCI-H292) and the underlying mechanism. Methods. The morphology of apoptotic cells was observed by transmission electron microscopy. The rate of apoptosis was analyzed by flow cytometry (FCM). The expressions of the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), Bcl-2/Bax, and cleaved caspase-3 were assessed by western blot. Results. PLA can induce apoptosis in NCI-H292 cells in a concentration-dependent manner. Moreover, the phosphorylation of the ERK1/2 and the unbalance of Bcl2/Bax, as well as the activation of caspase-3, were involved in the PLA-induced apoptosis. Conclusions. PLA can induce the apoptosis in NCI-H292 cells, and this process at least involved the ERK1/2 and mitochondrial pathway. The results could have some indications in revealing the apoptotic damage of the airway epithelial cells. Besides, inhibition of cationic protein-induced apoptotic death in airway epithelial cells could be considered as a potential target of anti-injury or antiremodeling in asthmatics.

The nutrition-gut microbiome-physiology axis and allergic diseases

Dietary and bacterial metabolites influence immune responses. This raises the question whether the increased incidence of allergies, asthma, some autoimmune diseases, cardiovascular disease, and others might relate to intake of unhealthy foods, and the decreased intake of dietary fiber. In recent years, new knowledge on the molecular mechanisms underpinning a 'diet-gut microbiota-physiology axis' has emerged to substantiate this idea. Fiber is fermented to short chain fatty acids (SCFAs), particularly acetate, butyrate, and propionate. These metabolites bind 'metabolite-sensing' G-protein-coupled receptors such as GPR43, GPR41, and GPR109A. These receptors play fundamental roles in the promotion of gut homeostasis and the regulation of inflammatory responses. For instance, these receptors and their metabolites influence Treg biology, epithelial integrity, gut homeostasis, DC biology, and IgA antibody responses. The SCFAs also influence gene transcription in many cells and tissues, through their inhibition of histone deacetylase expression or function. Contained in this mix is the gut microbiome, as commensal bacteria in the gut have the necessary enzymes to digest dietary fiber to SCFAs, and dysbiosis in the gut may affect the production of SCFAs and their distribution to tissues throughout the body. SCFAs can epigenetically modify DNA, and so may be one mechanism to account for diseases with a 'developmental origin', whereby in utero or post-natal exposure to environmental factors (such as nutrition of the mother) may account for disease later in life. If the nutrition-gut microbiome-physiology axis does underpin at least some of the Western lifestyle influence on asthma and allergies, then there is tremendous scope to correct this with healthy foodstuffs, probiotics, and prebiotics.

Knob protein enhances epithelial barrier integrity and attenuates airway inflammation

BACKGROUND

Altered epithelial physical and functional barrier properties along with T_H1/T_H2 immune dysregulation are features of allergic asthma. Regulation of junction proteins to improve barrier function of airway epithelial cells has the potential for alleviation of allergic airway inflammation.

OBJECTIVE

We sought to determine the immunomodulatory effect of knob protein of the adenoviral capsid on allergic asthma and to investigate its mechanism of action on airway epithelial junction proteins and barrier function.

METHODS

Airway inflammation, including junction protein expression, was evaluated in allergen-challenged mice with and without treatment with knob. Human bronchial epithelial cells were exposed to knob, and its effects on expression of junction proteins and barrier integrity were determined.

RESULTS

Administration of knob to allergen-challenged mice suppressed airway inflammation (eosinophilia, airway hyperresponsiveness, and IL-5 levels) and prevented allergen-induced loss of airway epithelial occludin and E-cadherin expression. Additionally, knob decreased expression of T_H2-promoting inflammatory mediators, specifically IL-33, by murine lung epithelial cells. At a cellular level, treatment of human bronchial epithelial cells with knob activated c-Jun N-terminal kinase, increased expression of occludin and E-cadherin, and enhanced epithelial barrier integrity.

CONCLUSION

Increased expression of junction proteins mediated by knob leading to enhanced epithelial barrier function might mitigate the allergen-induced airway inflammatory response, including asthma.