Breakdown in epithelial barrier function in patients with asthma: identification of novel therapeutic approaches

Fetal lung growth predicts the risk for early-life respiratory infections and childhood asthma

BACKGROUND

Early-life respiratory infections and asthma are major health burdens during childhood. Markers predicting an increased risk for early-life respiratory diseases are sparse. Here, we identified the predictive value of ultrasound-monitored fetal lung growth for the risk of early-life respiratory infections and asthma.

METHODS

Fetal lung size was serially assessed at standardized time points by transabdominal ultrasound in pregnant women participating in a pregnancy cohort. Correlations between fetal lung growth and respiratory infections in infancy or early-onset asthma at five years were examined. Machine-learning models relying on extreme gradient boosting regressor or classifier algorithms were developed to predict respiratory infection or asthma risk based on fetal lung growth. For model development and validation, study participants were randomly divided into a training and a testing group, respectively, by the employed algorithm.

RESULTS

Enhanced fetal lung growth throughout pregnancy predicted a lower early-life respiratory infection risk. Male sex was associated with a higher risk for respiratory infections in infancy. Fetal lung growth could also predict the risk of asthma at five years of age. We designed three machine-learning models to predict the risk and number of infections in infancy as well as the risk of early-onset asthma. The models' R2 values were 0.92, 0.90 and 0.93, respectively, underscoring a high accuracy and agreement between the actual and predicted values. Influential variables included known risk factors and novel predictors, such as ultrasound-monitored fetal lung growth.

CONCLUSION

Sonographic monitoring of fetal lung growth allows to predict the risk for early-life respiratory infections and asthma.

How does global warming contribute to disorders originating from an impaired epithelial barrier?

The epithelial barrier represents the point of contact between the host and the external environment. It is the first line of defense against external insults in the skin and in the gastrointestinal and upper and lower respiratory tracts. The steep increase in chronic disorders in recent decades, including allergies and autoimmune disorders, has prompted studies to investigate the immune mechanisms of their underlying pathogeneses, all of which point to a thought-provoking shared finding: disrupted epithelial barriers. Climate change with global warming has increased the frequency of unpredictable extreme weather events, such as wildfires, droughts, floods, and aberrant and longer pollination seasons, among many others. These increasingly frequent natural disasters can synergistically damage the epithelial barrier integrity in the presence of environmental pollution. A disrupted epithelial barrier induces proinflammatory activation of epithelial cells and alarmin production, namely, epithelitis. The "opened" epithelial barrier facilitates the entry of the external exposome into and underneath the epithelium, triggering an expulsion response driven by inflammatory cells in the area and chronic inflammation. These changes are associated with microbial dysbiosis with colonizing opportunistic pathogens and decreased commensals. These cellular and molecular events are key mechanisms in the pathogenesis of numerous chronic inflammatory disorders. This review summarizes the impact of global warming on epithelial barrier functions in the context of allergic diseases. Further studies in the impact of climate change on the dysfunction of the epithelial barriers are warranted to improve our understanding of epithelial barrier-related diseases and raise awareness of the environmental insults that pose a threat to our health.

Bisphenol A is more potent than bisphenol S in influencing the physiological and pathological functions of lungs via inducing lung fibrosis and stimulating metastasis

Bisphenol A (BPA) is widely used in the production of plastics, food containers, and receipt ink globally. However, research has identified it as an endocrine disruptor, affecting the hormonal balance in living organisms. Bisphenol S (BPS), one of the alternative substances, was developed, but its effects on human health and the underlying mechanisms remain unclarified. Specifically, research on the effects of oral exposure to bisphenol on the lungs is lacking. We examined the potential differences in toxicity between these compounds in lung cells in vitro and in vivo. Our toxicity mechanism studies on MRC5 and A549 cells exposed to BPA or BPS revealed that BPA induced actin filament abnormalities and activated epithelial-mesenchymal transition (EMT). This finding suggests an increased potential for lung fibrosis and metastasis in lung cancer. However, given that BPS was not detected at the administered dose and under the specific experimental conditions, the probability of these occurrences is considered minimal. Additionally, animal experiments confirmed that oral exposure to BPA activates EMT in the lungs. Our study provides evidence that prolonged oral exposure to BPA can lead to EMT activation in lung tissue, similar to that observed in cell experiments, suggesting the potential to induce lung fibrosis. This research emphasizes the importance of regulating the use of BPA to mitigate its associated pulmonary toxicity. Furthermore, it is significant that within the parameters of our experimental conditions, BPS did not exhibit the toxicological pathways clearly evident in BPA.

Airway epithelial development and function: A key player in asthma pathogenesis?

Though asthma is a common and relatively easy to diagnose disease, attempts at primary or secondary prevention, and cure, have been disappointing. The widespread use of inhaled steroids has dramatically improved asthma control but has offered nothing in terms of altering long-term outcomes or reversing airway remodeling and impairment in lung function. The inability to cure asthma is unsurprising given our limited understanding of the factors that contribute to disease initiation and persistence. New data have focused on the airway epithelium as a potentially key factor orchestrating the different stages of asthma. In this review we summarize for the clinician the current evidence on the central role of the airway epithelium in asthma pathogenesis and the factors that may alter epithelial integrity and functionality.

Serum Zonulin Is a Biomarker for Severe Asthma

Zonulin is a regulator of epithelial and endothelial barrier function. It regulates intestinal permeability through disrupting tight junctions. Defective epithelial barrier function is a hallmark of airway inflammation in asthma. This study aimed to investigate the role of zonulin in the pathogenesis of severe asthma. We enrolled 56 adult patients with asthma (29 severe asthma and 27 mild-to-moderate asthma) and 33 normal controls. The clinical data, sera, and lung tissues of the patients were provided by the Cohort for Reality and Evolution of adult Asthma in Korea (COREA) and the Biobank of Soonchunhyang University Bucheon Hospital, South Korea. Serum zonulin levels were estimated using an enzyme-linked immunosorbent assay, and zonulin expression in the bronchial tissue was evaluated by immunohistochemical staining. The serum zonulin levels were significantly higher in patients with severe asthma (51.98 ± 19.66 ng/mL) than in those with mild-to-moderate asthma and normal controls (26.35 ± 13.70 vs. 17.26 ± 10.29 ng/mL, P < 0.001). They significantly correlated with percent predicted forced expiratory volume in one second (%FEV1) (r = -0.35, P = 0.009). The zonulin expression in the bronchial epithelium was greater in patients with severe asthma. A serum zonulin cutoff value to distinguish between severe and mild-to-moderate asthmatics was 38.83 ng/mL. Zonulin may play an important role in the pathogenesis of severe asthma, and serum zonulin could be a potential biomarker for severe asthma.

IL-4 and IL-13, not eosinophils, drive type 2 airway inflammation, remodeling and lung function decline

RATIONALE

Type 2 (T2) asthma is characterized by airflow limitations and elevated levels of blood and sputum eosinophils, fractional exhaled nitric oxide, IgE, and periostin. While eosinophils are associated with exacerbations, the contribution of eosinophils to lung inflammation, remodeling and function remains largely hypothetical.

OBJECTIVES

To determine the effect of T2 cytokines IL-4, IL-13 and IL-5 on eosinophil biology and compare the impact of depleting just eosinophils versus inhibiting all aspects of T2 inflammation on airway inflammation.

METHODS

Human eosinophils or endothelial cells stimulated with IL-4, IL-13 or IL-5 were assessed for gene changes or chemokine release.Mice exposed to house dust mite extract received anti-IL-4Rα (dupilumab), anti-IL-5 or control antibodies and were assessed for changes in lung histological and inflammatory endpoints.

MEASUREMENTS AND MAIN RESULTS

IL-4 or IL-13 stimulation of human eosinophils and endothelial cells induced gene expression changes related to granulocyte migration; whereas, IL-5 induced changes reflecting granulocyte differentiation.In a mouse model, blocking IL-4Rα improved lung function by impacting multiple effectors of inflammation and remodeling, except peripheral eosinophil counts, thereby disconnecting blood eosinophils from airway inflammation, remodeling and function. Blocking IL-5 globally reduced eosinophil counts but did not impact inflammatory or functional measures of lung pathology. Whole lung transcriptome analysis revealed that IL-5 or IL-4Rα blockade impacted eosinophil associated genes, whereas IL-4Rα blockade also impacted genes associated with multiple cells, cytokines and chemokines, mucus production, cell:cell adhesion and vascular permeability.

CONCLUSIONS

Eosinophils are not the sole contributor to asthma pathophysiology or lung function decline and emphasizes the need to block additional mediators to modify lung inflammation and impact lung function.

Alternative lung cell model systems for toxicology testing strategies: Current knowledge and future outlook

Due to the current relevance of pulmonary toxicology (with focus upon air pollution and the inhalation of hazardous materials), it is important to further develop and implement physiologically relevant models of the entire respiratory tract. Lung model development has the aim to create human relevant systems that may replace animal use whilst balancing cost, laborious nature and regulatory ambition. There is an imperative need to move away from rodent models and implement models that mimic the holistic characteristics important in lung function. The purpose of this review is therefore, to describe and identify the various alternative models that are being applied towards assessing the pulmonary toxicology of inhaled substances, as well as the current and potential developments of various advanced models and how they may be applied towards toxicology testing strategies. These models aim to mimic various regions of the lung, as well as implementing different exposure methods with the addition of various physiologically relevent conditions (such as fluid-flow and dynamic movement). There is further progress in the type of models used with focus on the development of lung-on-a-chip technologies and bioprinting, as well as and the optimization of such models to fill current knowledge gaps within toxicology.

Towards an artificial human lung: modelling organ-like complexity to aid mechanistic understanding

Respiratory diseases account for over 5 million deaths yearly and are a huge burden to healthcare systems worldwide. Murine models have been of paramount importance to decode human lung biology in vivo, but their genetic, anatomical, physiological and immunological differences with humans significantly hamper successful translation of research into clinical practice. Thus, to clearly understand human lung physiology, development, homeostasis and mechanistic dysregulation that may lead to disease, it is essential to develop models that accurately recreate the extraordinary complexity of the human pulmonary architecture and biology. Recent advances in micro-engineering technology and tissue engineering have allowed the development of more sophisticated models intending to bridge the gap between the native lung and its replicates in vitro Alongside advanced culture techniques, remarkable technological growth in downstream analyses has significantly increased the predictive power of human biology-based in vitro models by allowing capture and quantification of complex signals. Refined integrated multi-omics readouts could lead to an acceleration of the translational pipeline from in vitro experimental settings to drug development and clinical testing in the future. This review highlights the range and complexity of state-of-the-art lung models for different areas of the respiratory system, from nasal to large airways, small airways and alveoli, with consideration of various aspects of disease states and their potential applications, including pre-clinical drug testing. We explore how development of optimised physiologically relevant in vitro human lung models could accelerate the identification of novel therapeutics with increased potential to translate successfully from the bench to the patient's bedside.

Nectin4 is a potential therapeutic target for asthma

BACKGROUND

Nectins comprise a family of cellular adhesion molecules involved in Ca2+-independent cellular adhesion. Neither the biological significance nor clinical potential of Nectin4 for asthma has been investigated.

OBJECTIVES

The aims of this study were to elucidate the role of Nectin4 in airway inflammation and to determine the relationship between Nectin4 and clinical variables in patients with asthma.

METHODS

The relationship between Nectin4 levels in the blood of asthmatic patients and clinical variables was examined. Dermatophagoides pteronyssinus 1 (Der p1)-exposed normal human bronchial epithelial (NHBE) cells, and Nectin4-deficient (Nectin4-/-) and wild-type (WT) mice sensitized/challenged with ovalbumin (OVA), were used to investigate the involvement of Nectin4 in the pathogenesis of bronchial asthma via the Src/Rac1 pathway.

RESULTS

Plasma Nectin4 levels were significantly higher in asthmatic patients than controls and correlated with specific IgE D1, D2, lung function. The ROC curves for Nectin4 levels differed between asthma patients and controls. Nectin4/Afadin and Src/Rac1 levels were significantly increased in NHBE cells exposed to Der p1, but decreased in NHBE cells treated with Nectin4 siRNA. Airway obstruction and inflammation, as well as the levels of Th2 cytokines, Nectin4, and Src/Rac1, were increased in WT OVA/OVA mice compared with WT sham mice. Nectin4 knockdown resulted in lower levels of Afadin and Src/Rac1 in Nectin4-/-OVA/OVA than WT OVA/OVA mice.

CONCLUSION

These results suggest that Nectin4 is involved in airway inflammation and may be a therapeutic target in patients with asthma.

Integrating an aerosolized drug delivery device with conventional static cultures and a dynamic airway barrier microphysiological system

Organ on a chip or microphysiological systems (MPSs) aim to resolve current challenges surrounding drug discovery and development resulting from an unrepresentative static cell culture or animal models that are traditionally used by generating a more physiologically relevant environment. Many different airway MPSs have been developed that mimic alveolar or bronchial interfaces, but few methods for aerosol drug delivery at the air-liquid interface exist. This work demonstrates a compact Surface Acoustic Wave (SAW) drug delivery device that generates an aerosol of respirable size for delivery of compounds directly onto polarized or differentiated epithelial cell cultures within an airway barrier MPS and conventional static inserts. As proof of principle, the SAW drug delivery device was used to nebulize viral dsRNA analog poly I:C and steroids fluticasone and dexamethasone without disrupting their biological function.

Role of Obesity in Inflammation and Remodeling of Asthmatic Airway

Obesity is considered as an important risk factor for the onset of asthma and plays a key role in enhancing the disease's severity. Obese asthmatic individuals represent a distinct phenotype of asthma that is associated with additional symptoms, more severe exacerbation, decreased response to standard medication, and poor quality of life. Obesity impairs the function of the lung airway in asthmatic individuals, leading to increased inflammation and severe remodeling of the bronchus; however, the molecular events that trigger such changes are not completely understood. In this manuscript, we review the current findings from studies that focused on understanding the role of obesity in modulating the functions of airway cells, including lung immune cells, epithelial cells, smooth muscle cells, and fibroblasts, leading to airway inflammation and remodeling. Finally, the review sheds light on the current knowledge of different therapeutic approaches for treating obese asthmatic individuals. Given the fact that the prevalence of asthma and obesity has been increasing rapidly in recent years, it is necessary to understand the molecular mechanisms that play a role in the disease pathophysiology of obese asthmatic individuals for developing novel therapies.

A lethal model of Leptospira infection in hamster nasal mucosa

Leptospirosis is a fatal zoonosis caused by contact between skin or a mucosal surface and contaminated soil or water. Hamsters were infected by intraperitoneal injection fto establish experimental leptospirosis, which is not a natural route of infection. There are no reports of nasal mucosal infection in hamsters. In this study, infection of the nasal mucosa was performed to establish a model of natural infection. Both methods of infection can cause lethal models with similar symptoms in the later stages of infection, such as weight loss, blood concentration, increased neutrophils (GRAN), and decreased lymphocytes (LYM) in the blood, severe organ damage and liver function obstruction. The burden of Leptospira in the organs and blood was lower in the mucosal inoculation groups at 1 day after infection. However, mucosal infection induced a higher Leptospira burden in urine than intraperitoneal infection in the late stages of infection. After nasal mucosal infection, antibody levels were higher and lasted longer. These results indicated that the route of nasal mucosal infection is a good choice for studying leptospirosis in hamsters.

The establishment of a leptospirosis experimental model is still key to elucidating the pathogenesis of leptospirosis. Hamsters were infected by intraperitoneal injection to establish experimental leptospirosis, although this is not a natural route of infection. The transmission characteristics of Leptospira and the disease progression in hamsters infected by a natural transmission route (e.g. through mucosal surfaces) had not been explored. In this study, we compared the dynamics of Leptospira infection in hamsters inoculated via the nasal mucosa or by intraperitoneal inoculation, and compared the burden of Leptospira and the level of antibodies produced with disease progression, such as body weight, serology, haematological changes and histopathological changes. Our data suggested that there are significant differences in the dynamics of infection between intraperitoneal and mucosal infection pathways. Although the result was the same in the later stage of infection, the course of mucosal infection was slower, which may better recapitulate the natural history of the disease, assist in studying kidney disease caused by Leptospira, and provide an animal model for the study of leptospirosis mucosal immunity.

Association between serum zonulin level and severity of house dust mite allergic asthma

BACKGROUND

Increased intestinal permeability, either due to the exposure to antigens in asthmatic patients or due to a barrier defect, plays a critical role in susceptibility to environmental allergens. House dust mite allergy occurs more commonly than any other type of allergy among Egyptian asthmatic patients.

AIM

To assess the relation between serum zonulin level as a marker of increased intestinal permeability and the severity of house dust mite allergic asthma.

METHODS

A case-control study which included 48 patients with house dust mite allergic asthma and 48 healthy control subjects attending the Allergy and Immunology Unit, Microbiology and Immunology Department, Faculty of Medicine, Zagazig University.

RESULTS

A statistically significant difference was detected between the two studied groups with respect to serum IgE and serum zonulin levels (p ˂ 0.001 and ˂ 0.001, respectively). The mean serum zonulin was equal to 258.3 ± 153.01 ng/ml in the asthmatic group and 80 ± 13 ng/ml in the control group. Serum zonulin level significantly increased with the increase of asthma severity (p ˂ 0.001). The cut off value of serum zonulin was ≥ 198 ng/ml, and the area under the curve was 0.76. It displayed sensitivity equal to 80% and specificity equal to 71.4%. Its negative predictive value was equal to 83.3%.

CONCLUSION

Intestinal barrier dysfunction contributes to the pathogenesis of allergic asthma. Serum zonulin level reflects an increase in intestinal permeability. Zonulin acts as prognostic factor of severity in asthma. Correction of the gut barrier defect may have a potential positive prognostic effect in asthma.

Environmental factors in epithelial barrier dysfunction

The main interfaces controlling and attempting to homeostatically balance communications between the host and the environment are the epithelial barriers of the skin, gastrointestinal system, and airways. The epithelial barrier constitutes the first line of physical, chemical, and immunologic defenses and provides a protective wall against environmental factors. Following the industrial revolution in the 19th century, urbanization and socioeconomic development have led to an increase in energy consumption, and waste discharge, leading to increased exposure to air pollution and chemical hazards. Particularly after the 1960s, biological and chemical insults from the surrounding environment-the exposome-have been disrupting the physical integrity of the barrier by degrading the intercellular barrier proteins at tight and adherens junctions, triggering epithelial alarmin cytokine responses such as IL-25, IL-33, and thymic stromal lymphopoietin, and increasing the epithelial barrier permeability. A typical type 2 immune response develops in affected organs in asthma, rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, food allergy, and atopic dermatitis. The aim of this article was to discuss the effects of environmental factors such as protease enzymes of allergens, detergents, tobacco, ozone, particulate matter, diesel exhaust, nanoparticles, and microplastic on the integrity of the epithelial barriers in the context of epithelial barrier hypothesis.

Pulsatile contractions promote apoptotic cell extrusion in epithelial tissues

Extrusion is a mechanism used to eliminate unfit, excess, or dying cells from epithelial tissues. The initial events guiding which cells will be selectively extruded from the epithelium are not well understood. Here, we induced damage in a subset of epithelial cells in the developing zebrafish and used time-lapse imaging to examine cell and cytoskeletal dynamics leading to extrusion. We show that cell extrusion is preceded by actomyosin contractions that are pulsatile. Our data show that pulsatile contractions are induced by a junctional to medial re-localization of myosin. Analysis of cell area during contractions revealed that cells pulsing with the longest duration and highest amplitude undergo progressive area loss and extrude. Although pulses were driven by local increases in tension, damage to many cells promoted an overall decrease in the tensile state of the epithelium. We demonstrate that caspase activation leads to sphingosine-1-phosphate enrichment that controls both tissue tension and pulses to dictate areas of extrusion. These data suggest that the kinetics of pulsatile contractions define a key behavioral difference between extruding and non-extruding cells and are predictive of extrusion. Altogether, our study provides mechanistic insight into how localized changes in physical forces are coordinated to remove defective cells for homeostatic maintenance of living epithelial tissues.

Variant-to-Gene-Mapping Analyses Reveal a Role for the Hypothalamus in Genetic Susceptibility to Inflammatory Bowel Disease

BACKGROUND & AIMS

Inflammatory bowel disease (IBD) is a polygenic disorder characterized principally by dysregulated inflammation impacting the gastrointestinal tract. However, there also is increasing evidence for a clinical association with stress and depression. Given the role of the hypothalamus in stress responses and in the pathogenesis of depression, useful insights could be gleaned from understanding its genetic role in IBD.

METHODS

We conducted genetic correlation analyses on publicly available genome-wide association study summary statistics for depression and IBD traits to identify genetic commonalities. We used partitioned linkage disequilibrium score regression, leveraging our ATAC sequencing and promoter-focused Capture C data, to measure enrichment of IBD single-nucleotide polymorphisms within promoter-interacting open chromatin regions of human embryonic stem cell-derived hypothalamic-like neurons (HNs). Using the same data sets, we performed variant-to-gene mapping to implicate putative IBD effector genes in HNs. To contrast these results, we similarly analyzed 3-dimensional genomic data generated in epithelium-derived colonoids from rectal biopsy specimens from donors without pathologic disease noted at the time of colonoscopy. Finally, we conducted enrichment pathway analyses on the implicated genes to identify putative IBD dysfunctional pathways.

RESULTS

We found significant genetic correlations (rg) of 0.122 with an adjusted P (Padj) = 1.4 × 10-4 for IBD: rg = 0.122; Padj = 2.5 × 10-3 for ulcerative colitis and genetic correlation (rg) = 0.094; Padj = 2.5 × 10-3 for Crohn's disease, and significant approximately 4-fold (P = .005) and approximately 7-fold (P = .03) enrichment of IBD single-nucleotide polymorphisms in HNs and colonoids, respectively. We implicated 25 associated genes in HNs, among which CREM, CNTF, and RHOA encode key regulators of stress. Seven genes also additionally were implicated in the colonoids. We observed an overall enrichment for immune and hormonal signaling pathways, and a colonoid-specific enrichment for microbiota-relevant terms.

CONCLUSIONS

Our results suggest that the hypothalamus warrants further study in the context of IBD pathogenesis.

Bidirectional interaction of airway epithelial remodeling and inflammation in asthma

Asthma is a chronic disease of the airways that has long been viewed predominately as an inflammatory condition. Accordingly, current therapeutic interventions focus primarily on resolving inflammation. However, the mainstay of asthma therapy neither fully improves lung function nor prevents disease exacerbations, suggesting involvement of other factors. An emerging concept now holds that airway remodeling, another major pathological feature of asthma, is as important as inflammation in asthma pathogenesis. Structural changes associated with asthma include disrupted epithelial integrity, subepithelial fibrosis, goblet cell hyperplasia/metaplasia, smooth muscle hypertrophy/hyperplasia, and enhanced vascularity. These alterations are hypothesized to contribute to airway hyperresponsiveness, airway obstruction, airflow limitation, and progressive decline of lung function in asthmatic individuals. Consequently, targeting inflammation alone does not suffice to provide optimal clinical benefits. Here we review asthmatic airway remodeling, focusing on airway epithelium, which is critical to maintaining a healthy respiratory system, and is the primary defense against inhaled irritants. In asthma, airway epithelium is both a mediator and target of inflammation, manifesting remodeling and resulting obstruction among its downstream effects. We also highlight the potential benefits of therapeutically targeting airway structural alterations. Since pathological tissue remodeling is likewise observed in other injury- and inflammation-prone tissues and organs, our discussion may have implications beyond asthma and lung disease.

Airway Remodeling in Asthma

Asthma is an inflammatory disease of the airways that may result from exposure to allergens or other environmental irritants, resulting in bronchoconstriction, wheezing, and shortness of breath. The structural changes of the airways associated with asthma, broadly referred to as airway remodeling, is a pathological feature of chronic asthma that contributes to the clinical manifestations of the disease. Airway remodeling in asthma constitutes cellular and extracellular matrix changes in the large and small airways, epithelial cell apoptosis, airway smooth muscle cell proliferation, and fibroblast activation. These pathological changes in the airway are orchestrated by crosstalk of different cell types within the airway wall and submucosa. Environmental exposures to dust, chemicals, and cigarette smoke can initiate the cascade of pro-inflammatory responses that trigger airway remodeling through paracrine signaling and mechanostimulatory cues that drive airway remodeling. In this review, we explore three integrated and dynamic processes in airway remodeling: (1) initiation by epithelial cells; (2) amplification by immune cells; and (3) mesenchymal effector functions. Furthermore, we explore the role of inflammaging in the dysregulated and persistent inflammatory response that perpetuates airway remodeling in elderly asthmatics.

In-air EIS sensor for in situ and real-time monitoring of in vitro epithelial cells under air-exposure

This paper reports in-air monitoring of in vitro monolayer cells under air-exposure utilizing electrochemical impedance spectroscopy (EIS). In-air impedance measurement was performed by placing integrated electrodes laterally, instead of vertically, to a cell membrane, avoiding electrical disconnection, unlike conventional transepithelial-electrical-resistance (TEER). The in-air EIS sensor platform mainly consisted of two chambers, separated by a porous membrane where cells were cultured, that enabled cell exposure to both air (apical side) and liquid (basal side) for long-term measurement. On top of the membrane, EIS interdigitated electrodes were patterned and lung epithelial cells (A549 type II) were cultured with air exposure on one side. The fabricated in-air EIS sensor successfully demonstrated in situ real-time measurement of cell populations in confluency in the range of 7.8 × 104 and 9.6 × 105 cells per cm2 at a sensitivity of 3.0 × 10-2 Ω per cell in impedance and in the range of 1.0 × 104 and 9.6 × 105 cells per cm2 at a sensitivity of 0.17 × 10-15 F per cell in capacitance under AC frequencies of 100 kHz and 1 MHz, respectively. It also successfully monitored transient modulation of tight-junctions that collectively began to open in 30 minutes after the injection of 100 ng ml-1 TNF-α (a relaxation agent), reached maximum relaxation with a 12.6% increase in impedance value and a 12% decrease in capacitance in 60 minutes, and recovered back to its original junction status after 720 minutes, which confirmed the observation in animal models in the literature. Note that the opposite trends in impedance and capacitance allowed the in-air EIS sensor to distinguish cell population changes from tight junction modulation. It was concluded that the developed in-air EIS sensor in an in vitro platform can enable in situ and real-time monitoring of the population of the 'air-exposed' cells as well as the modulation of tight-junctions, which has not been demonstrated yet.

A prenatally disrupted airway epithelium orchestrates the fetal origin of asthma in mice

BACKGROUND

Prenatal challenges such as maternal stress perception increase the risk and severity of asthma during childhood. However, insights into the trajectories and targets underlying the pathogenesis of prenatally triggered asthma are largely unknown. The developing lung and immune system may constitute such targets.

OBJECTIVE

Here we have aimed to identify the differential sex-specific effects of prenatal challenges on lung function, immune response, and asthma severity in mice.

METHODS

We generated bone marrow chimeric (BMC) mice harboring either prenatally stress-exposed lungs or a prenatally stress-exposed immune (hematopoietic) system and induced allergic asthma via ovalbumin. Next-generation sequencing (RNA sequencing) of lungs and assessment of airway epithelial barrier function in ovalbumin-sensitized control and prenatally stressed offspring was also performed.

RESULTS

Profoundly enhanced airway hyperresponsiveness, inflammation, and fibrosis were exclusively present in female BMC mice with prenatally stress-exposed lungs. These effects were significantly perpetuated if both the lungs and the immune system had been exposed to prenatal stress. A prenatally stress-exposed immune system alone did not suffice to increase the severity of these asthma features. RNA sequencing analysis of lungs from prenatally stressed, non-BMC, ovalbumin-sensitized females unveiled a deregulated expression of genes involved in asthma pathogenesis, tissue remodeling, and tight junction formation. It was also possible to independently confirm a tight junction disruption. In line with this, we identified an altered perinatal and/or postnatal expression of genes involved in lung development along with an impaired alveolarization in female prenatally stressed mice.

CONCLUSION

Here we have shown that the fetal origin of asthma is orchestrated by a disrupted airway epithelium and further perpetuated by a predisposed immune system.

Comparison of Normal and Metaplastic Epithelium in Patients with Stable versus Persistently Symptomatic Severe Asthma Using Laser-Capture Microdissection and Data-Independent Acquisition-Mass Spectrometry

A proportion of patients with severe asthma (SA) show poor responses to traditional asthma medications; however, it remains unknown why some patients remain persistently symptomatic. Our objective was to explore the use of laser-capture microdissection of specific epithelial structures combined with quantitative data-independent acquisition mass spectrometry to elucidate differences in protein composition in patients with SA with varying symptom control. Unbiased label-free quantitative proteome analyses were performed on laser-capture-microdissected areas of specific epithelial structures from patients with SA with varying degrees of symptom control. A total of 1993 stable SA and 1652 symptomatic SA proteins in normal epithelium and 1458 stable SA and 1647 symptomatic SA proteins in metaplastic epithelium were quantified. When comparing proteome profiles based on symptom control, 33 proteins in patients with stable SA (≥twofold change; P ≤ 0.05) and 13 proteins in patients with persistently symptomatic SA (≥twofold change; P ≤ 0.05) were enriched significantly. When comparing proteome profiles based on epithelial status, 21 proteins in normal epithelium (≥twofold change; P ≤ 0.05) and 6 proteins in metaplastic epithelium (≥twofold change; P ≤ 0.05) were enriched significantly. New treatment strategies are needed for patients with severe asthma and exploratory studies of unbiased nature such as this may help when searching for new mechanisms and potential targets involved in the disease pathology.

A Novel Serine Protease Inhibitor PE-BBI Ameliorates Cockroach Extract-Mediated Airway Epithelial Barrier Dysfunction

Epithelial barrier dysfunction, characteristic of allergic airway disease may be, at least in part, due to the action of allergen-associated protease activities. Cockroach allergy is a major global health issue, with cockroaches containing considerable serine trypsin-like protease (TLP) activity. The present study sought to evaluate two novel protease inhibitors (PE-BBI and pLR-HL), recently isolated from amphibian skin secretions, for their potential to neutralise cockroach TLP activity and to determine any protective effect on cockroach-induced airway epithelial barrier disruption. Inhibitor potencies against the cockroach-associated activities were determined using a fluorogenic peptide substrate-based activity assay. 16HBE14o^- cells (16HBE; a bronchial epithelial cell line) were treated with cockroach extract (CRE) in the presence or absence of the compounds in order to assess cell viability (RealTime Glo luminescent assay) and epithelial barrier disruption (transepithelial resistance and paracellular dextran flux). PE-BBI potently and selectively inhibited CRE TLP activity (pIC₅₀ -8), but not host (16HBE) cell surface activity, which conferred protection of 16HBE cells from CRE-induced cell damage and barrier disruption. Novel protease inhibitor strategies such as PE-BBI may be useful for the treatment of allergic airway disease caused by cockroach proteases.

DP2 antagonism reduces airway smooth muscle mass in asthma by decreasing eosinophilia and myofibroblast recruitment

Increased airway smooth muscle mass, a feature of airway remodeling in asthma, is the strongest predictor of airflow limitation and contributes to asthma-associated morbidity and mortality. No current drug therapy for asthma is known to affect airway smooth muscle mass. Although there is increasing evidence that prostaglandin D₂ type 2 receptor (DP₂) is expressed in airway structural and inflammatory cells, few studies have addressed the expression and function of DP₂ in airway smooth muscle cells. We report that the DP₂ antagonist fevipiprant reduced airway smooth muscle mass in bronchial biopsies from patients with asthma who had participated in a previous randomized placebo-controlled trial. We developed a computational model to capture airway remodeling. Our model predicted that a reduction in airway eosinophilia alone was insufficient to explain the clinically observed decrease in airway smooth muscle mass without a concomitant reduction in the recruitment of airway smooth muscle cells or their precursors to airway smooth muscle bundles that comprise the airway smooth muscle layer. We experimentally confirmed that airway smooth muscle migration could be inhibited in vitro using DP₂-specific antagonists in an airway smooth muscle cell culture model. Our analyses suggest that fevipiprant, through antagonism of DP₂, reduced airway smooth muscle mass in patients with asthma by decreasing airway eosinophilia in concert with reduced recruitment of myofibroblasts and fibrocytes to the airway smooth muscle bundle. Fevipiprant may thus represent a potential therapy to ameliorate airway remodeling in asthma.

Serum Levels of Epithelial-Derived Cytokines as Interleukin-25 and Thymic Stromal Lymphopoietin after a Single Dose of Mepolizumab in Patients with Severe Non-Allergic Eosinophilic Asthma: A Short Report

The bronchial epithelium has continuous contact with environmental agents initiating and maintaining airway type 2 inflammation in asthma. However, there is a lack of data on whether reduced airway eosinophilic inflammation can affect the production of epithelial-derived mediators, such as interleukin-25 (IL-25) and thymic stromal lymphopoietin (TSLP). The aim of this study was to investigate the changes in serum levels of IL-25 and TSLP after a single dose of mepolizumab, a humanized monoclonal antibody to interleukin-5 (IL-5), in patients with severe non-allergic eosinophilic asthma (SNEA). We examined 9 SNEA patients before and four weeks after administration of 100 mg mepolizumab subcutaneously. The fractional exhaled nitric oxide (FeNO) level was analysed using an electrochemical assay (NIOX VERO®, Circassia, UK). Serum IL-25 and TSLP levels were measured by ELISA. Four weeks after the single dose of mepolizumab, blood eosinophil count significantly decreased from 0.55 ± 0.20 × 109/l to 0.14 ± 0.04 × 109/l (p = 0.01) and FEV1 increased from 2.1 ± 0.5 l (65.4 ± 8.8% of predicted) to 2.6 ± 0.4 l (76.4 ± 9.1% of predicted) (p = 0.04), while FeNO level has not changed (32.3 ± 8.4 vs 42.9 ± 12.6 ppb). Serum IL-25 level significantly decreased from 48.0 ± 17.2 pg/mL to 34.8 ± 17.1 pg/mL (p = 0.02) with same tendency in TSLP level: from 359.8 ± 71.3 pg/mL to 275.6 ± 47.8 pg/mL (p = 0.02). It has also been noticed a significant relation between changes in the blood eosinophil count and serum IL-25 level (r = 0.81, p = 0.008), as well as between changes in serum IL-25 and TSLP levels (r = 0.93, p = 0.004) after a single dose of mepolizumab. Thus, anti-IL-5 treatment with mepolizumab might diminish the production of bronchial epithelial-derived cytokines IL-25 and TSLP in patients with SNEA which is potentially related to reduced eosinophilic inflammation. This trial is registered in ClinicalTrial.gov with identifier NCT03388359.

Hydroxysafflor Yellow A Alleviates Ovalbumin-Induced Asthma in a Guinea Pig Model by Attenuateing the Expression of Inflammatory Cytokines and Signal Transduction

Hydroxysafflor yellow A (HSYA) is an effective ingredient of the Chinese herb Carthamus tinctorius L. In this study, we aimed to evaluate the effects of HSYA on ovalbumin (OVA)-induced asthma in guinea pigs, and to elucidate the underlying mechanisms. We established a guinea pig asthma model by intraperitoneal injection and atomized administration OVA. Guinea pigs were injected intraperitoneally with HSYA (50, 75, 112.5 mg/kg) once daily from days 2 to 22 before OVA administration. We examined biomarkers including lung function, pulmonary histopathology, immunoglobulin E (IgE), Th1/Th2 relative inflammatory mediators, and related pathways. Pathological changes in lung tissues were detected by hematoxylin and eosin and periodic acid-Schiff staining. Phosphorylation levels of JNK mitogen-activated protein kinase (MAPK), p38 MAPK, ERK MAPK, and inhibitor of nuclear factor κBα (IκBα) were detected by western blot. plasma levels of total IgE, platelet-activating factor (PAF), and interleukin (IL)-3 were detected by enzyme-linked immunosorbent assay (ELISA). Expression levels of tumor necrosis factor (TNF)-α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-13, and interferon (IFN)-γ were detected by ELISA and real-time quantitative polymerase chain reaction. HSYA significantly reduced airway resistance, improved dynamic lung compliance, and attenuated the pathologic changes. HSYA also inhibited the phosphorylation of JNK MAPK, p38 MAPK, ERK MAPK, and IκBα, and inhibited the OVA-induced elevations of IgE, PAF, IL-1β, IL-6, IL-4, IL-5, and IL-13 and the decreases in TNF-α, IFN-γ, IL-2, and IL-3. These findings suggest that HSYA has a protective effect on OVA-induced asthma through inhibiting the Th1/Th2 cell imbalance and inhibiting activation of the MAPK signaling pathway.

Estrogen reinforces barrier formation and protects against tumor necrosis factor alpha-induced barrier dysfunction in oral epithelial cells

Purpose

Epithelial barrier dysfunction is involved in the pathophysiology of periodontitis and oral lichen planus. Estrogens have been shown to enhance the physical barrier function of intestinal and esophageal epithelia, and we aimed to investigate the effect of estradiol (E2) on the regulation of physical barrier and tight junction (TJ) proteins in human oral epithelial cell monolayers.

Methods

HOK-16B cell monolayers cultured on transwells were treated with E2, an estrogen receptor (ER) antagonist (ICI 182,780), tumor necrosis factor alpha (TNFα), or dexamethasone (Dexa), and the transepithelial electrical resistance (TER) was then measured. Cell proliferation was measured by the cell counting kit (CCK)-8 assay. The levels of TJ proteins and nuclear translocation of nuclear factor (NF)-κB were examined by confocal microscopy.

Results

E2 treatment increased the TER and the levels of junctional adhesion molecule (JAM)-A and zonula occludens (ZO)-1 in a dose-dependent manner, without affecting cell proliferation during barrier formation. Treatment of the tight-junctioned cell monolayers with TNFα induced decreases in the TER and the levels of ZO-1 and nuclear translocation of NF-κB. These TNFα-induced changes were inhibited by E2, and this effect was completely reversed by co-treatment with ICI 182,780. Furthermore, E2 and Dexa presented an additive effect on the epithelial barrier function.

Conclusions

E2 reinforces the physical barrier of oral epithelial cells through the nuclear ER-dependent upregulation of TJ proteins. The protective effect of E2 on the TNFα-induced impairment of the epithelial barrier and its additive effect with Dexa suggest its potential use to treat oral inflammatory diseases involving epithelial barrier dysfunction.

Effects of microRNA-19b on airway remodeling, airway inflammation and degree of oxidative stress by targeting TSLP through the Stat3 signaling pathway in a mouse model of asthma

This study explored the effects of microRNA-19b (miR-19b) on airway remodeling, airway inflammation, and degree of oxidative stress in a mouse model of asthma. Bioinformatics analyses and dual luciferase reporter gene assays revealed that thymic stromal lymphopoietin (TSLP) is a direct target of miR-19b. An asthma model was established via ovalbumin (OVA) sensitization and challenge in 72 female BALB/c mice. Mice were then assigned to saline, OVA-sensitized, saline+miR-19b mimics, saline+anti-TSLP, OVA-sensitized+miR-19b mimics, OVA-sensitized+mimics scramble, OVA-sensitized+anti-TSLP, and OVA-sensitized+IgG2a groups. Pathological morphology changes were detected through hematoxylin/eosin, Masson, and periodic acid-Schiff staining. miR-19b was downregulated while TSLP and Stat3 were upregulated in the OVA-sensitized group compared with the saline group. Bronchoalveolar lavage fluid samples from OVA-sensitized mice showed increased total protein, IL-4, IL-5 and IL-6 levels, numbers of inflammatory cells, eosinophils, neutrophils, mononuclear macrophages and lymphocytes, and eosinophil% compared to controls. Lung tissues from sensitized mice exhibited decreased superoxide dismutase activity and increased methane dicarboxylic aldehyde levels. The effects of OVA sensitization were reversed in the OVA-sensitized+miR-19b mimics and OVA-sensitized+anti-TSLP groups. These findings suggest miR-19b reduces airway remodeling, airway inflammation, and degree of oxidative stress by inhibiting Stat3 signaling through TSLP downregulation in a mouse asthma model.

Does atopy affect the course of viral pneumonia?

Background

The presence of atopy is considered as a risk factor for severe respiratory symptoms in children. The objective of this study was to examine the effect of atopy on the course of disease in children hospitalised with viral pneumonia.

Methods

Children between the ages of 1 and 6 years hospitalised due to viral pneumonia between the years of 2013 and 2016 were included to this multicentre study. Patients were classified into two groups as mild–moderate and severe according to the course of pneumonia. Presence of atopy was evaluated with skin prick tests. Groups were compared to evaluate the risk factors associated with severe viral pneumonia.

Results

A total of 280 patients from nine centres were included in the study. Of these patients, 163 (58.2%) were male. Respiratory syncytial virus (29.7%), Influenza A (20.5%), rhinovirus (18.9%), adenovirus (10%), human metapneumovirus (8%), parainfluenza (5.2%), coronavirus (6%), and bocavirus (1.6%) were isolated from respiratory samples. Eighty-five (30.4%) children had severe pneumonia. Atopic sensitisation was found in 21.4% of the patients. Ever wheezing (RR: 1.6, 95% CI: 1.1–2.4), parental asthma (RR: 1.5, 95% CI: 1.1–2.2), other allergic diseases in the family (RR: 1.8, 95% CI: 1.2–2.9) and environmental tobacco smoke (RR: 1.6, 95% CI: 1.1–3.5) were more common in the severe pneumonia group.

Conclusions

When patients with mild–moderate pneumonia were compared to patients with severe pneumonia, frequency of atopy was not different between the two groups. However, parental asthma, ever wheezing and environmental tobacco smoke exposure are risk factors for severe viral pneumonia in children.

Airway epithelial barrier dysfunction in the pathogenesis and prognosis of respiratory tract diseases in childhood and adulthood

The lungs are in direct contact with the environment through the tubular structure that constitutes the airway. Starting from the nasal orifice, the airway is exposed to foreign particles including infectious agents, allergens, and other substances that can damage the airways. Therefore, the airway must have a functional epithelial barrier both in the upper and lower airways to protect against these threats. As with the skin, it is likely that the pathogenesis of respiratory diseases is a consequence of epithelial barrier defects in these airways. The characteristics of this system, starting from the beginning of life and extending into maturing and aging, determine the prognosis of respiratory diseases. In this article, we discuss the pathogenesis, clinical phenotype, and prognosis of respiratory diseases from newborns to adulthood in the context of epithelial barrier function and dysfunction.

Secondhand tobacco smoke and severity in wheezing children: Nasal oxidant stress and inflammation

OBJECTIVES

Prenatal and postnatal smoke exposures are associated with many lung diseases in children due to impaired lung function, increased inflammation, and oxidative stress. We aimed to determine the influence of secondhand tobacco smoke exposure on the levels of nasal glutathione, IL-8, IL-17, MMP-9, and TIMP-1, as well as serum surfactant protein-D (SP-D) in wheezy children.

METHODS

We enrolled 150 children with recurrent wheezing and recorded wheezing characteristics at enrollment. We measured the levels of serum cotinine, SP-D, nasal glutathione, IL-8, IL-17, MMP-9, and TIMP-1. Serum cotinine levels between 3 and 12 ng/mL, and above 12 ng/mL were defined as lower and higher level secondhand tobacco smoke exposure, respectively. The ANOVA test, Pearson's correlation analysis and multivariate analysis with a linear regression test were used for the statistical analysis.

RESULTS

Ninety-one children had been exposed to lower level secondhand tobacco smoke, while 24 children were exposed to higher level secondhand tobacco smoke. Thirty-five children were not exposed to cigarette smoke. Wheezing symptom scores were higher in exposed children (p = 0.03). Levels of other biomarkers showed no significant difference.

CONCLUSIONS

Secondhand tobacco smoke exposure is associated with more severe respiratory symptoms in wheezing children. However, levels of nasal or serum inflammatory markers fail to explain this association, either because of different mechanical factors in the process or due to low levels of the biomarkers especially in nasal secretions.

Phenotypic and genetic aspects of epithelial barrier function in asthmatic patients

The bronchial epithelium is continuously exposed to a multitude of noxious challenges in inhaled air. Cellular contact with most damaging agents is reduced by the action of the mucociliary apparatus and by formation of a physical barrier that controls passage of ions and macromolecules. In conjunction with these defensive barrier functions, immunomodulatory cross-talk between the bronchial epithelium and tissue-resident immune cells controls the tissue microenvironment and barrier homeostasis. This is achieved by expression of an array of sensors that detect a wide variety of viral, bacterial, and nonmicrobial (toxins and irritants) agents, resulting in production of many different soluble and cell-surface molecules that signal to cells of the immune system. The ability of the bronchial epithelium to control the balance of inhibitory and activating signals is essential for orchestrating appropriate inflammatory and immune responses and for temporally modulating these responses to limit tissue injury and control the resolution of inflammation during tissue repair. In asthmatic patients abnormalities in many aspects of epithelial barrier function have been identified. We postulate that such abnormalities play a causal role in immune dysregulation in the airways by translating gene-environment interactions that underpin disease pathogenesis and exacerbation.

Airway Epithelial Cells Are Crucial Targets of Glucocorticoids in a Mouse Model of Allergic Asthma

Although glucocorticoids (GCs) are a mainstay in the clinical management of asthma, the target cells that mediate their therapeutic effects are unknown. Contrary to our expectation, we found that GC receptor (GR) expression in immune cells was dispensable for successful therapy of allergic airway inflammation (AAI) with dexamethasone. Instead, GC treatment was compromised in mice expressing a defective GR in the nonhematopoietic compartment or selectively lacking the GR in airway epithelial cells. Further, we found that an intact GR dimerization interface was a prerequisite for the suppression of AAI and airway hyperresponsiveness by GCs. Our observation that the ability of dexamethasone to modulate gene expression in airway epithelial cells coincided with its potency to resolve AAI supports a crucial role for transcriptional regulation by the GR in this cell type. Taken together, we identified an unknown mode of GC action in the treatment of allergic asthma that might help to develop more specific therapies in the future.

Cockroach protease allergen induces allergic airway inflammation via epithelial cell activation

Protease allergens are known to enhance allergic inflammation but their exact role in initiation of allergic reactions at mucosal surfaces still remains elusive. This study was aimed at deciphering the role of serine protease activity of Per a 10, a major cockroach allergen in initiation of allergic inflammation at mucosal surfaces. We demonstrate that Per a 10 increases epithelial permeability by disruption of tight junction proteins, ZO-1 and occludin, and enhances the migration of Monocyte derived dendritic cell precursors towards epithelial layer as exhibited by trans-well studies. Per a 10 exposure also leads to secretion of IL-33, TSLP and intracellular Ca²⁺ dependent increase in ATP levels. Further, in vivo experiments revealed that Per a 10 administration in mice elevated allergic inflammatory parameters along with high levels of IL-33, TSLP, IL-1α and uric acid in the mice lungs. We next demonstrated that Per a 10 cleaves CD23 (low affinity IgE receptor) from the surface of PBMCs and purified B cells and CD25 (IL-2 receptor) from the surface of PBMCs and purified T cells in an activity dependent manner, which might favour Th2 responses. In conclusion, protease activity of Per a 10 plays a significant role in initiation of allergic airway inflammation at the mucosal surfaces.

Functional Effects of Cigarette Smoke-Induced Changes in Airway Smooth Muscle Mitochondrial Morphology

Long-term exposure to cigarette smoke (CS) triggers airway hyperreactivity and remodeling, effects that involve airway smooth muscle (ASM). We previously showed that CS destabilizes the networked morphology of mitochondria in human ASM by regulating the expression of mitochondrial fission and fusion proteins via multiple signaling mechanisms. Emerging data link regulation of mitochondrial morphology to cellular structure and function. We hypothesized that CS-induced changes in ASM mitochondrial morphology detrimentally affect mitochondrial function, leading to CS effects on contractility and remodeling. Here, ASM cells were exposed to 1% cigarette smoke extract (CSE) for 48 h to alter mitochondrial fission/fusion, or by inhibiting the fission protein Drp1 or the fusion protein Mfn2. Mitochondrial function was assessed via changes in bioenergetics or altered rates of proliferation and apoptosis. Our results indicate that both exposure to CS and inhibition of mitochondrial fission/fusion proteins affect mitochondrial function (i.e., energy metabolism, proliferation, and apoptosis) in ASM cells. In vivo, the airways in mice chronically exposed to CS are thickened and fibrotic, and the expression of proteins involved in mitochondrial function is dramatically altered in the ASM of these mice. We conclude that CS-induced changes in mitochondrial morphology (fission/fusion balance) correlate with mitochondrial function, and thus may control ASM proliferation, which plays a central role in airway health. J. Cell. Physiol. 232: 1053-1068, 2017. © 2016 Wiley Periodicals, Inc.

IL-1α mediates cellular cross-talk in the airway epithelial mesenchymal trophic unit

The bronchial epithelium and underlying fibroblasts form an epithelial mesenchymal trophic unit (EMTU) which controls the airway microenvironment. We hypothesized that cell-cell communication within the EMTU propagates and amplifies the innate immune response to respiratory viral infections.

EMTU co-culture models incorporating polarized (16HBE14o-) or differentiated primary human bronchial epithelial cells (HBECs) and fibroblasts were challenged with double-stranded RNA (dsRNA) or rhinovirus.

In the polarized EMTU model, dsRNA affected ionic but not macromolecular permeability or cell viability. Compared with epithelial monocultures, dsRNA-stimulated pro-inflammatory mediator release was synergistically enhanced in the basolateral compartment of the EMTU model, with the exception of IL-1α which was unaffected by the presence of fibroblasts. Blockade of IL-1 signaling with IL-1 receptor antagonist (IL-1Ra) completely abrogated dsRNA-induced basolateral release of mediators except CXCL10. Fibroblasts were the main responders to epithelial-derived IL-1 since exogenous IL-1α induced pro-inflammatory mediator release from fibroblast but not epithelial monocultures. Our findings were confirmed in a differentiated EMTU model where rhinovirus infection of primary HBECs and fibroblasts resulted in synergistic induction of basolateral IL-6 that was significantly abrogated by IL-1Ra. This study provides the first direct evidence of integrated IL-1 signaling within the EMTU to propagate inflammatory responses to viral infection.

Epithelial cell extrusion: Pathways and pathologies

To remove dying or unwanted cells from an epithelium while preserving the barrier function of the layer, epithelia use a unique process called cell extrusion. To extrude, the cell fated to die emits the lipid Sphingosine 1 Phosphate (S1P), which binds the G-protein-coupled receptor Sphingosine 1 Phosphate receptor 2 (S1P₂) in the neighboring cells that activates Rho-mediated contraction of an actomyosin ring circumferentially and basally. This contraction acts to squeeze the cell out apically while drawing together neighboring cells and preventing any gaps to the epithelial barrier. Epithelia can extrude out cells targeted to die by apoptotic stimuli to repair the barrier in the face of death or extrude live cells to promote cell death when epithelial cells become too crowded. Indeed, because epithelial cells naturally turn over by cell death and division at some of the highest rates in the body, epithelia depend on crowding-induced live cell extrusion to preserve constant cell numbers. If extrusion is defective, epithelial cells rapidly lose contact inhibition and form masses. Additionally, because epithelia act as the first line of defense in innate immunity, preservation of this barrier is critical for preventing pathogens from invading the body. Given its role in controlling constant cell numbers and maintaining barrier function, a number of different pathologies can result when extrusion is disrupted. Here, we review mechanisms and signaling pathways that control epithelial extrusion and discuss how defects in these mechanisms can lead to multiple diseases. We also discuss tactics pathogens have devised to hijack the extrusion process to infect and colonize epithelia.

A toolbox to study epidermal cell types in zebrafish

Epithelia provide a crucial protective barrier for our organs and are also the sites where the majority of carcinomas form. Most studies on epithelia and carcinomas use cell culture or organisms where high-resolution live imaging is inaccessible without invasive techniques. Here, we introduce the developing zebrafish epidermis as an excellent in vivo model system for studying a living epithelium. We developed tools to fluorescently tag specific epithelial cell types and express genes in a mosaic fashion using five Gal4 lines identified from an enhancer trap screen. When crossed to a variety of UAS effector lines, we can now track, ablate or monitor single cells at sub-cellular resolution. Using photo-cleavable morpholino oligonucleotides that target gal4, we can also express genes in a mosaic fashion at specific times during development. Together, this system provides an excellent in vivo alternative to tissue culture cells, without the intrinsic concerns of culture conditions or transformation, and enables the investigation of distinct cell types within living epithelial tissues.

Claudin-18 deficiency is associated with airway epithelial barrier dysfunction and asthma

BACKGROUND

Epithelial barrier dysfunction and increased permeability may contribute to antigen sensitization and disease progression in asthma. Claudin-18.1 is the only known lung-specific tight junction protein, but its contribution to airway barrier function or asthma is unclear.

OBJECTIVES

We sought to test the hypotheses that claudin-18 is a determinant of airway epithelial barrier function that is downregulated by IL-13 and that claudin-18 deficiency results in increased aeroantigen sensitization and airway hyperresponsiveness.

METHODS

Claudin-18.1 mRNA levels were measured in airway epithelial brushings from healthy controls and patients with asthma. In patients with asthma, claudin-18 levels were compared with a three-gene-mean marker of T_H2 inflammation. Airway epithelial permeability changes due to claudin-18 deficiency were measured in 16HBE cells and claudin-18 null mice. The effect of IL-13 on claudin expression was determined in primary human airway epithelial cells and in mice. Airway hyperresponsiveness and serum IgE levels were compared in claudin-18 null and wild-type mice following aspergillus sensitization.

RESULTS

Epithelial brushings from patients with asthma (n = 67) had significantly lower claudin-18 mRNA levels than did those from healthy controls (n = 42). Claudin-18 levels were lowest among T_H2-high patients with asthma. Loss of claudin-18 was sufficient to impair epithelial barrier function in 16HBE cells and in mouse airways. IL-13 decreased claudin-18 expression in primary human cells and in mice. Claudin-18 null mice had significantly higher serum IgE levels and increased airway responsiveness following intranasal aspergillus sensitization.

CONCLUSIONS

These data support the hypothesis that claudin-18 is an essential contributor to the airway epithelial barrier to aeroantigens. Furthermore, T_H2 inflammation suppresses claudin-18 expression, potentially promoting sensitization and airway hyperresponsiveness.

Rhinosinusal Inflammation and High Mobility Group Box 1 Protein: A New Target for Therapy

BACKGROUND/AIMS

High mobility group box 1 (HMGB1) is a protein belonging to the class of damage-associated molecular pattern molecules, which activates innate immunity and powerful inflammatory factors. The aim of this review is to show the importance of HMGB1 in the pathogenesis of nasal inflammatory diseases and to suggest that inhibition of HMGB1 may be an innovative therapeutic target.

METHODS

We used immunohistochemistry to study whether HMGB1 increases in chronic rhinosinusitis with nasal polyps and whether its expression is associated with eosinophils and inflammatory cytokines. Using primary cultures of human nasal epithelial cells, we localised lipopolysaccharide-induced active translocation and release of HMGB1 by immunofluorescence assay and Western blot.

RESULTS

Patients with severe symptoms have the highest HMGB1 serum levels. Glycyrrhetic acid inhibits the chemotactic and mitogenic function of HMGB1, binding to the hydrophobic residues that delimit the pockets in box A and B.

CONCLUSIONS

Chronic inflammatory diseases of the nose and paranasal sinuses are increasingly prevalent and are a financial burden for society. HMGB1 has been shown to play a role in several inflammatory diseases of otolaryngological interest. The inhibition of HMGB1 may be an innovative therapeutic target for patients with chronic upper airway inflammatory diseases having nasal obstruction as a major symptom.

Epithelial barrier function and immunity in asthma

The bronchial epithelium is constantly exposed to a wide range of environmental materials present in inhaled air, including noxious gases and anthropogenic and natural particulates, such as gas and particles from car emissions, tobacco smoke, pollens, animal dander, and pathogens. As a fully differentiated, pseudostratified mucociliary epithelium, the bronchial epithelium protects the internal milieu of the lung from these agents by forming a physical barrier involving adhesive complexes and a chemical barrier involving secretion of mucus, which traps inhaled particles that can be cleared by the mucociliary escalator. It is a testament to the effectiveness of these two barriers that most environmental challenges are largely overcome without the need to develop an inflammatory response. However, as the initial cell of contact with the environment, the bronchial epithelium also plays a pivotal role in immune surveillance and appropriate activation of immune effector cells and antigen presenting cells in the presence of pathogens or other danger signals. Thus, the bronchial epithelium plays a central role in controlling tissue homeostasis and innate immunity. This review will discuss these barrier properties and how dysregulation of these homeostatic mechanisms can contribute to disease pathologies such as asthma.

Low molecular weight components of pollen alter bronchial epithelial barrier functions

The bronchial epithelium plays a key role in providing a protective barrier against many environmental substances of anthropogenic or natural origin which enter the lungs during breathing. Appropriate responses to these agents are critical for regulation of tissue homeostasis, while inappropriate responses may contribute to disease pathogenesis. Here, we compared epithelial barrier responses to different pollen species, characterized the active pollen components and the signaling pathways leading to epithelial activation. Polarized bronchial cells were exposed to extracts of timothy grass (Phleum pratense), ragweed (Ambrosia artemisifolia), mugwort (Artemisia vulgaris), birch (Betula alba) and pine (Pinus sylvestris) pollens. All pollen species caused a decrease in ionic permeability as monitored trans-epithelial electrical resistance (TER) and induced polarized release of mediators analyzed by ELISA, with grass pollen showing the highest activity. Ultrafiltration showed that the responses were due to components <3kDa. However, lipid mediators, including phytoprostane E1, had no effect on TER, and caused only modest induction of mediator release. Reverse-phase chromatography separated 2 active fractions: the most hydrophilic maximally affected cytokine release whereas the other only affected TER. Inhibitor studies revealed that JNK played a more dominant role in regulation of barrier permeability in response to grass pollen exposure, whereas ERK and p38 controlled cytokine release. Adenosine and the flavonoid isorhamnetin present in grass pollen contributed to the overall effect on airway epithelial barrier responses. In conclusion, bronchial epithelial barrier functions are differentially affected by several low molecular weight components released by pollen. Furthermore, ionic permeability and innate cytokine production are differentially regulated.

Epithelial function and dysfunction in asthma

Asthma was previously defined as an allergic Th2-mediated inflammatory immune disorder. Recently, this paradigm has been challenged because not all pathological changes observed in the asthmatic airways are adequately explained simply as a result of Th2-mediated processes. Contemporary thought holds that asthma is a complex immune disorder involving innate as well as adaptive immune responses, with the clinical heterogeneity of asthma perhaps a result of the different relative contribution of these two systems to the disease. Epidemiological studies show that exposure to certain environmental substances is strongly associated with the risk of developing asthma. The airway epithelium is first barrier to interact with, and respond to, environmental agents (pollution, viral infection, allergens), suggesting that it is a key player in the pathology of asthma. Epithelial cells play a key role in the regulation of tissue homeostasis by the modulation of numerous molecules, from antioxidants and lipid mediators to growth factors, cytokines, and chemokines. Additionally, the epithelium is also able to suppress mechanisms involved in, for example, inflammation in order to maintain homeostasis. An intrinsic alteration or defect in these regulation mechanisms compromises the epithelial barrier, and therefore, the barrier may be more prone to environmental substances and thus more likely to exhibit an asthmatic phenotype. In support of this, polymorphisms in a number of genes that are expressed in the bronchial epithelium have been linked to asthma susceptibility, while environmental factors may affect epigenetic mechanisms that can alter epithelial function and response to environmental insults. A detailed understanding of the regulatory role of the airway epithelium is required to develop new therapeutic strategies for asthma that not only address the symptoms but also the underlining pathogenic mechanism(s) and prevent airway remodelling.

Level of Fatty Acid Binding Protein 5 (FABP5) Is Increased in Sputum of Allergic Asthmatics and Links to Airway Remodeling and Inflammation

BACKGROUND

The inflammatory processes in the upper and lower airways in allergic rhinitis and asthma are similar. Induced sputum and nasal lavage fluid provide a non-invasive way to examine proteins involved in airway inflammation in these conditions.

OBJECTIVES

We conducted proteomic analyses of sputum and nasal lavage fluid samples to reveal differences in protein abundances and compositions between the asthma and rhinitis patients and to investigate potential underlying mechanisms.

METHODS

Induced sputum and nasal lavage fluid samples were collected from 172 subjects with 1) allergic rhinitis, 2) asthma combined with allergic rhinitis, 3) nonallergic rhinitis and 4) healthy controls. Proteome changes in 21 sputum samples were analysed with two-dimensional difference gel electrophoresis (2D-DIGE), and the found differentially regulated proteins identified with mass spectrometry. Immunological validation of identified proteins in the sputum and nasal lavage fluid samples was performed with Western blot and ELISA.

RESULTS

Altogether 31 different proteins were identified in the sputum proteome analysis, most of these were found also in the nasal lavage fluid. Fatty acid binding protein 5 (FABP5) was up-regulated in the sputum of asthmatics. Immunological validation in the whole study population confirmed the higher abundance levels of FABP5 in asthmatic subjects in both the sputum and nasal lavage fluid samples. In addition, the vascular endothelial growth factor (VEGF) level was increased in the nasal lavage fluid of asthmatics and there were positive correlations between FABP5 and VEGF levels (r=0.660, p<0.001) and concentrations of FABP5 and cysteinyl leukotriene (CysLT) (r=0.535, p<0.001) in the nasal lavage fluid.

CONCLUSIONS

FABP5 may contribute to the airway remodeling and inflammation in asthma by fine-tuning the levels of CysLTs, which induce VEGF production.

Nrf2 reduces allergic asthma in mice through enhanced airway epithelial cytoprotective function

Asthma development and pathogenesis are influenced by the interactions of airway epithelial cells and innate and adaptive immune cells in response to allergens. Oxidative stress is an important mediator of asthmatic phenotypes in these cell types. Nuclear erythroid 2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that is the key regulator of the response to oxidative and environmental stress. We previously demonstrated that Nrf2-deficient mice have heightened susceptibility to asthma, including elevated oxidative stress, inflammation, mucus, and airway hyperresponsiveness (AHR) (Rangasamy T, Guo J, Mitzner WA, Roman J, Singh A, Fryer AD, Yamamoto M, Kensler TW, Tuder RM, Georas SN, Biswal S. J Exp Med 202: 47-59, 2005). Here we dissected the role of Nrf2 in lung epithelial cells and tested whether genetic or pharmacological activation of Nrf2 reduces allergic asthma in mice. Cell-specific activation of Nrf2 in club cells of the airway epithelium significantly reduced allergen-induced AHR, inflammation, mucus, Th2 cytokine secretion, oxidative stress, and airway leakiness and increased airway levels of tight junction proteins zonula occludens-1 and E-cadherin. In isolated airway epithelial cells, Nrf2 enhanced epithelial barrier function and increased localization of zonula occludens-1 to the cell surface. Pharmacological activation of Nrf2 by 2-trifluoromethyl-2'-methoxychalone during the allergen challenge was sufficient to reduce allergic inflammation and AHR. New therapeutic options are needed for asthma, and this study demonstrates that activation of Nrf2 in lung epithelial cells is a novel potential therapeutic target to reduce asthma susceptibility.

Cigarette smoke causes caspase-independent apoptosis of bronchial epithelial cells from asthmatic donors

BACKGROUND

Epidemiologic studies have demonstrated important links between air pollution and asthma. Amongst these pollutants, environmental cigarette smoke is a risk factor both for asthma pathogenesis and exacerbation. As the barrier to the inhaled environment, the bronchial epithelium is a key structure that is exposed to cigarette smoke.

OBJECTIVES

Since primary bronchial epithelial cells (PBECs) from asthmatic donors are more susceptible to oxidant-induced apoptosis, we hypothesized that they would be susceptible to cigarette smoke-induced cell death.

METHODS

PBECs from normal and asthmatic donors were exposed to cigarette smoke extract (CSE); cell survival and apoptosis were assessed by fluorescence-activated cell sorting, and protective effects of antioxidants evaluated. The mechanism of cell death was evaluated using caspase inhibitors and immunofluorescent staining for apoptosis-inducing factor (AIF).

RESULTS

Exposure of PBEC cultures to CSE resulted in a dose-dependent increase in cell death. At 20% CSE, PBECs from asthmatic donors exhibited significantly more apoptosis than cells from non-asthmatic controls. Reduced glutathione (GSH), but not ascorbic acid (AA), protected against CSE-induced apoptosis. To investigate mechanisms of CSE-induced apoptosis, caspase-3 or -9 inhibitors were tested, but these failed to prevent apoptosis; in contrast, CSE promoted nuclear translocation of AIF from the mitochondria. GSH reduced the number of nuclear-AIF positive cells whereas AA was ineffective.

CONCLUSION

Our results show that PBECs from asthmatic donors are more susceptible to CSE-induced apoptosis. This response involves AIF, which has been implicated in DNA damage and ROS-mediated cell-death. Epithelial susceptibility to CSE may contribute to the impact of environmental tobacco smoke in asthma.

Regulation of TWIK-related potassium channel-1 (Trek1) restitutes intestinal epithelial barrier function

The disruption of epithelial barrier integrity is an important factor in the pathogenesis of various immune disorders. However, the restitution of the compromised barrier functions is difficult. This study investigates the regulation of TWIK-related potassium channel-1 (Trek1) in the restitution of intestinal epithelial barrier functions. The human colon epithelial cell line T84 was cultured in monolayers and used to observe epithelial barrier functions in vitro. An intestinal allergy mouse model was created. Cytokine levels were determined by enzyme-linked immunosorbent assay and western blotting. The results showed that Trek1 deficiency induced T84 monolayer barrier disruption. Allergic responses markedly suppressed the expression of Trek1 in the intestinal epithelia via activating the mitogen-activated protein kinase pathways and increasing the expression of histone deacetylase-1. The inhibition of histone deacetylase-1 by sodium butyrate or the administration of a butyrate-producing probiotic (Clostridium butyricum) restored the intestinal epithelial barrier functions and markedly enhanced the effect of antigen-specific immunotherapy. The data suggest that Trek1 is required for the maintenance of intestinal epithelial barrier integrity. Allergic responses induce an insufficiency of Trek1 expression in the intestinal epithelia. Trek1 expression facilitates the restoration of intestinal epithelial barrier functions in an allergic environment.

Respiratory syncytial virus can infect basal cells and alter human airway epithelial differentiation

Respiratory syncytial virus (RSV) is a major cause of morbidity and mortality worldwide, causing severe respiratory illness in infants and immune compromised patients. The ciliated cells of the human airway epithelium have been considered to be the exclusive target of RSV, although recent data have suggested that basal cells, the progenitors for the conducting airway epithelium, may also become infected in vivo. Using either mechanical or chemical injury models, we have demonstrated a robust RSV infection of p63+ basal cells in air-liquid interface (ALI) cultures of human bronchial epithelial cells. In addition, proliferating basal cells in 2D culture were also susceptible to RSV infection. We therefore tested the hypothesis that RSV infection of this progenitor cell would influence the differentiation status of the airway epithelium. RSV infection of basal cells on the day of seeding (MOI≤0.0001), resulted in the formation of an epithelium that showed a profound loss of ciliated cells and gain of secretory cells as assessed by acetylated α-tubulin and MUC5AC/MUC5B immunostaining, respectively. The mechanism driving the switch in epithelial phenotype is in part driven by the induced type I and type III interferon response that we demonstrate is triggered early following RSV infection. Neutralization of this response attenuates the RSV-induced loss of ciliated cells. Together, these data show that through infection of proliferating airway basal cells, RSV has the potential to influence the cellular composition of the airway epithelium. The resulting phenotype might be expected to contribute towards both the severity of acute infection, as well as to the longer-term consequences of viral exacerbations in patients with pre-existing respiratory diseases.