Dendritic cells and epithelial cells: linking innate and adaptive immunity in asthma

House dust mite allergen Der f 2 drives IL-6 and GM-CSF expression in airway epithelial cells via p38 MAPK/NF-κB signaling

OBJECTIVE

Der f 2, a major allergen derived from Dermatophagoides farinae, is a leading cause of allergic asthma. IL-6 and GM-CSF play essential roles in the exacerbation of asthma. However, the mechanical act by which Der f 2 mediates the expression of IL-6, IL-8, and GM-CSF in airway epithelial cells remains incompletely elucidated. Herein, we aimed to explore the effect of Der f 2 on IL-6 and GM-CSF expression in the human airway epithelial cell BEAS-2B and A549.

METHODS

Recombinant Der f 2 (rDf2) was acquired using Pichia pastoris. BEAS-2B and A549 cells were used as cell model. The expression of genes and proteins and the involvement of the signaling cascade were assessed using RT-PCR, quantitative real-time PCR (qPCR), Western blotting, and ELISA, respectively.

RESULTS

Our findings showed that rDf2 significantly induced mRNA expression and protein production of IL-6 and GM-CSF in BEAS-2B and A549 cells. In contrast, rDf2 did not influence IL-8 expression or production in both cells. Mechanistic studies revealed that rDf2 triggered activation of the p38 MAPK and JNK. Inhibition of p38, but not JNK, significantly attenuated rDf2-induced IL-6 and GM-CSF expression and production.

CONCLUSION

This study demonstrates that Der f 2 promotes the expression and production of the pro-inflammatory cytokines IL-6 and GM-CSF in airway epithelial cells via activation of the p38 signaling pathway. These findings provide insights into the molecular mechanisms that Der f 2 may exacerbate airway inflammation.

Immunologic aspects of asthma: from molecular mechanisms to disease pathophysiology and clinical translation

In the present review, we focused on recent translational and clinical discoveries in asthma immunology, facilitating phenotyping and stratified or personalized interventions for patients with this condition. The immune processes behind chronic inflammation in asthma exhibit marked heterogeneity, with diverse phenotypes defining discernible features and endotypes illuminating the underlying molecular mechanisms. In particular, two primary endotypes of asthma have been identified: "type 2-high," characterized by increased eosinophil levels in the airways and sputum of patients, and "type 2-low," distinguished by increased neutrophils or a pauci-granulocytic profile. Our review encompasses significant advances in both innate and adaptive immunities, with emphasis on the key cellular and molecular mediators, and delves into innovative biological and targeted therapies for all the asthma endotypes. Recognizing that the immunopathology of asthma is dynamic and continuous, exhibiting spatial and temporal variabilities, is the central theme of this review. This complexity is underscored through the innumerable interactions involved, rather than being driven by a single predominant factor. Integrated efforts to improve our understanding of the pathophysiological characteristics of asthma indicate a trend toward an approach based on disease biology, encompassing the combined examination of the clinical, cellular, and molecular dimensions of the disease to more accurately correlate clinical traits with specific disease mechanisms.

Advances in Dendritic-Cell-Based Vaccines against Respiratory Fungal Infections

Ever since the discovery of dendritic cells by Ralph Steinman and Zanvil Cohn in 1973, it is increasingly evident that dendritic cells are integral for adaptive immune responses, and there is an undeniable focus on them for vaccines development. Fungal infections, often thought to be innocuous, are becoming significant threats due to an increased immunocompromised or immune-suppressed population and climate change. Further, the recent COVID-19 pandemic unraveled the wrath of fungal infections and devastating outcomes. Invasive fungal infections cause significant case fatality rates ranging from 20% to 90%. Regrettably, no licensed fungal vaccines exist, and there is an urgent need for preventive and therapeutic purposes. In this review, we discuss the ontogeny, subsets, tissue distribution, and functions of lung dendritic cells. In the latter part, we summarize and discuss the studies on the DC-based vaccines against pulmonary fungal infections. Finally, we highlight some emerging potential avenues that can be incorporated for DC-based vaccines against fungal infections.

Elevated inflammatory burden index increases mortality in adults with chronic inflammatory airway diseases: a nationwide cohort study

OBJECTIVE

The objective of this study was to investigate the potential association between the inflammatory burden index (IBI) and the prevalence of chronic inflammatory airway diseases (CIAD), as well as mortality rates among individuals diagnosed with CIAD.

METHODS

Participants were sourced from the National Health and Nutrition Examination Survey (NHANES) conducted between 1999 and 2010. The IBI was calculated using the formula: IBI = C-reactive protein * neutrophils / lymphocytes. CIAD comprised self-reported asthma, chronic bronchitis, and chronic obstructive pulmonary disease (COPD). Mortality outcomes, including all-cause and respiratory disease mortality, were determined through linked data from the National Death Index (NDI) up to December 2019.

RESULTS

A total of 27,495 adults were included. IBI was divided into quartiles, with the lowest quartile as the reference group. After adjusting for confounding variables, a positive correlation was observed between higher IBI and increased prevalence of total CIAD (OR = 1.383 [1.215-1.575]), asthma (OR = 1.267 [1.096-1.465]), chronic bronchitis (OR = 1.568 [1.263-1.946]), and COPD (OR = 1.907 [1.311-2.774]). Over a median follow-up of 12.33 [9.92-16.00] years, there were 1221 deaths from all causes and 220 deaths from respiratory disease among 4499 patients with CIAD. Following multivariate adjustments, the fourth quartile was significantly associated with increased risk of all-cause mortality (HR = 2.227 [1.714-2.893]) and respiratory disease mortality (HR = 2.748 [1.383-5.459]) compared to the first quartile of IBI in CIAD participants. Moreover, variable importance analysis using a random survival forest model demonstrated the significance of IBI in predicting mortality from both all-cause and respiratory diseases.

CONCLUSION

IBI exhibited an association with the prevalence of CIAD, with higher IBI levels correlating with elevated all-cause and respiratory disease mortality among individuals with CIAD.

Chemical respiratory sensitization-Current status of mechanistic understanding, knowledge gaps and possible identification methods of sensitizers

Respiratory sensitization is a complex immunological process eventually leading to hypersensitivity following re-exposure to the chemical. A frequent consequence is occupational asthma, which may occur after long latency periods. Although chemical-induced respiratory hypersensitivity has been known for decades, there are currently no comprehensive and validated approaches available for the prospective identification of chemicals that induce respiratory sensitization, while the expectations of new approach methodologies (NAMs) are high. A great hope is that due to a better understanding of the molecular key events, new methods can be developed now. However, this is a big challenge due to the different chemical classes to which respiratory sensitizers belong, as well as because of the complexity of the response and the late manifestation of symptoms. In this review article, the current information on respiratory sensitization related processes is summarized by introducing it in the available adverse outcome pathway (AOP) concept. Potentially useful models for prediction are discussed. Knowledge gaps and gaps of regulatory concern are identified.

Lifestyle Changes and Industrialization in the Development of Allergic Diseases

PURPOSE OF REVIEW

Modernization and Westernization in industrialized and developing nations is associated with a substantial increase in chronic noncommunicable diseases. This transformation has far-reaching effects on lifestyles, impacting areas such as economics, politics, social life, and culture, all of which, in turn, have diverse influences on public health. Loss of contact with nature, alternations in the microbiota, processed food consumption, exposure to environmental pollutants including chemicals, increased stress and decreased physical activity jointly result in increases in the frequency of inflammatory disorders including allergies and many autoimmune and neuropsychiatric diseases. This review aims to investigate the relationship between Western lifestyle and inflammatory disorders.

RECENT FINDINGS

Several hypotheses have been put forth trying to explain the observed increases in these diseases, such as 'Hygiene Hypothesis', 'Old Friends', and 'Biodiversity and Dysbiosis'. The recently introduced 'Epithelial Barrier Theory' incorporates these former hypotheses and suggests that toxic substances in cleaning agents, laundry and dishwasher detergents, shampoos, toothpastes, as well as microplastic, packaged food and air pollution damage the epithelium of our skin, lungs and gastrointestinal system. Epithelial barrier disruption leads to decreased biodiversity of the microbiome and the development of opportunistic pathogen colonization, which upon interaction with the immune system, initiates local and systemic inflammation. Gaining a deeper comprehension of the interplay between the environment, microbiome and the immune system provides the data to assist with legally regulating the usage of toxic substances, to enable nontoxic alternatives and to mitigate these environmental challenges essential for fostering a harmonious and healthy global environment.

Airway basal stem cells are necessary for the maintenance of functional intraepithelial airway macrophages

Adult stem cells play a crucial role in tissue homeostasis and repair through multiple mechanisms. In addition to being able to replace aged or damaged cells, stem cells provide signals that contribute to the maintenance and function of neighboring cells. In the lung, airway basal stem cells also produce cytokines and chemokines in response to inhaled irritants, allergens, and pathogens, which affect specific immune cell populations and shape the nature of the immune response. However, direct cell-to-cell signaling through contact between airway basal stem cells and immune cells has not been demonstrated. Recently, a unique population of intraepithelial airway macrophages (IAMs) has been identified in the murine trachea. Here, we demonstrate that IAMs require Notch signaling from airway basal stem cells for maintenance of their differentiated state and function. Furthermore, we demonstrate that Notch signaling between airway basal stem cells and IAMs is required for antigen-induced allergic inflammation only in the trachea where the basal stem cells are located whereas allergic responses in distal lung tissues are preserved consistent with a local circuit linking stem cells to proximate immune cells. Finally, we demonstrate that IAM-like cells are present in human conducting airways and that these cells display Notch activation, mirroring their murine counterparts. Since diverse lung stem cells have recently been identified and localized to specific anatomic niches along the proximodistal axis of the respiratory tree, we hypothesize that the direct functional coupling of local stem cell-mediated regeneration and immune responses permits a compartmentalized inflammatory response.

Obesity Enhances Non-Th2 Airway Inflammation in a Murine Model of Allergic Asthma

Obese patients with asthma present with aggravated symptoms that are also harder to treat. Here, we used a mouse model of allergic asthma sensitised and challenged to house dust mite (HDM) extracts to determine whether high-fat-diet consumption would exacerbate the key features of allergic airway inflammation. C57BL/6 mice were intranasally sensitised and challenged with HDM extracts over a duration of 3 weeks. The impact of high-fat-diet (HFD) vs. normal diet (ND) chow was studied on HDM-induced lung inflammation and inflammatory cell infiltration as well as cytokine production. HFD-fed mice had greater inflammatory cell infiltration around airways and blood vessels, and an overall more severe degree of inflammation than in the ND-fed mice (semiquantitative blinded evaluation). Quantitative assessment of HDM-associated Th2 responses (numbers of lung CD4+ T cells, eosinophils, serum levels of allergen-specific IgE as well as the expression of Th2 cytokines (Il5 and Il13)) did not show significant changes between the HFD and ND groups. Interestingly, the HFD group exhibited a more pronounced neutrophilic infiltration within their lung tissues and an increase in non-Th2 cytokines (Il17, Tnfa, Tgf-b, Il-1b). These findings provide additional evidence that obesity triggered by a high-fat-diet regimen may exacerbate asthma by involving non-Th2 and neutrophilic pathways.

Identification of toxicity-induced biomarkers in human non-immune airway cells exposed to respiratory sensitizers: A mechanistic approach

Occupational asthma covers a group of work-related diseases whose clinical manifestations include airway hyperresponsiveness and airflow limitation. Although the chemical respiratory allergy (CRA) induced by Low Molecular Weight (LMW) sensitizers is a major concern, especially in terms of the regulatory framework, to date there are no methods available for preclinically addressing this toxicological outcome, as its mechanistic background is not fully understood at molecular or cellular levels. This paper proposes a mechanistic study applying New Approach Methodologies (NAM) of the pro-inflammatory and functional effects triggered by LMW respiratory allergens in different respiratory tract cell lines, including bronchial epithelial (BEAS-2B), lung fibroblast (MRC-5), and endothelial cells (EA.hy926), and an analysis of the capacity of such chemicals to interact with the mucin protein, to address certain toxicodynamic aspects of such compounds. The results showed that some of the sensitizers evaluated interact with mucin, the main protein mucus component, but the toxicant-mucin complex formation does not seem to be a common feature of different chemical classes of allergens. At a cellular level, sensitizers promoted an increase in IL-8, IL-6, and IL-1β production in the evaluated cell types. It also impaired the MUC1 expression by bronchial cells and activated endothelial cells, thereby increasing the ICAM-I surface expression. Taken together, our results showed that these aforementioned cell types participate in the CRA Adverse Outcome Pathway and must be considered when developing preclinical testing strategies, particularly investigating danger signal production after exposure to LMW sensitizers in different tissue compartments.

A comprehensive review on the role of T cell subsets and CAR-T cell therapy in Aspergillus fumigatus infection

Understanding the immune response to Aspergillus fumigatus, a common cause of invasive fungal infections (IFIs) in immunocompromised individuals, is critical for developing effective treatments. Tcells play a critical role in the immune response to A. fumigatus, with different subsets having distinct functions. Th1 cells are important for controlling fungal growth, while Th2 cells can exacerbate infection. Th17 cells promote the clearance of fungi indirectly by stimulating the production of various antimicrobial peptides from epithelial cells and directly by recruiting and activating neutrophils. Regulatory T cells have varied functions in A.fumigatus infection. They expand after exposure to A. fumigatus conidia and prevent organ injury and fungal sepsis by downregulating inflammation and inhibiting neutrophils or suppressing Th17 cells. Regulatory T cells also block Th2 cells to stop aspergillosis allergies. Immunotherapy with CAR T cells is a promising treatment for fungal infections, including A. fumigatus infections, especially in immunocompromised individuals. However, further research is needed to fully understand the mechanisms underlying the immune response to A. fumigatus and to develop effective immunotherapies with CAR-T cells for this infection. This literature review explores the role of Tcell subsets in A.fumigatus infection, and the effects of CAR-T cell therapy on this fungal infection.

Microbes little helpers and suppliers for therapeutic asthma approaches

Bronchial asthma is a prevalent and increasingly chronic inflammatory lung disease affecting over 300 million people globally. Initially considered an allergic disorder driven by mast cells and eosinophils, asthma is now recognized as a complex syndrome with various clinical phenotypes and immunological endotypes. These encompass type 2 inflammatory endotypes characterized by interleukin (IL)-4, IL-5, and IL-13 dominance, alongside others featuring mixed or non-eosinophilic inflammation. Therapeutic success varies significantly based on asthma phenotypes, with inhaled corticosteroids and beta-2 agonists effective for milder forms, but limited in severe cases. Novel antibody-based therapies have shown promise, primarily for severe allergic and type 2-high asthma. To address this gap, novel treatment strategies are essential for better control of asthma pathology, prevention, and exacerbation reduction. One promising approach involves stimulating endogenous anti-inflammatory responses through regulatory T cells (Tregs). Tregs play a vital role in maintaining immune homeostasis, preventing autoimmunity, and mitigating excessive inflammation after pathogenic encounters. Tregs have demonstrated their ability to control both type 2-high and type 2-low inflammation in murine models and dampen human cell-dependent allergic airway inflammation. Furthermore, microbes, typically associated with disease development, have shown immune-dampening properties that could be harnessed for therapeutic benefits. Both commensal microbiota and pathogenic microbes have demonstrated potential in bacterial-host interactions for therapeutic purposes. This review explores microbe-associated approaches as potential treatments for inflammatory diseases, shedding light on current and future therapeutics.

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.

Regulation of Dendritic Cell Functions by Vitamins as Promising Therapeutic Strategy for Immune System Disorders

A functional immune system is crucial for a healthy life, protecting from infections, tumors, or autoimmune disorders; these are accomplished by the interaction between various immune cells. Nourishment, particularly micronutrients, are very important components in the immune system balance, therefore this review emphasizes the vitamins (D, E, A, C) and Dendritic cells' subsets due to vitamins' roles in immune processes, especially on dendritic cells' functions, maturation, and cytokine production. Current studies reveal significant benefits related to vitamins, including vitamin E, which can contribute to the control of dendritic cells' function and maturation. Furthermore, vitamin D plays an immunoregulatory and anti-inflammatory role in the immune system. Metabolite of vitamin A which is called retinoic acid leads to T cells' differentiation to T helper 1 or T helper 17, so low levels of this vitamin exacerbate the menace of infectious diseases, and vitamin C has anti-oxidant effects on dendritic cells and modulate their activation and differentiation program. Additionally, the correlation between the amount of vitamin and the occurrence or progression of allergic diseases and autoimmunity disorders is discussed according to the results of previous studies.

Cell-type-specific role of P2Y2 receptor in HDM-driven model of allergic airway inflammation

Allergic airway inflammation (AAI) is a chronic respiratory disease that is considered a severe restriction in daily life and is accompanied by a constant risk of acute aggravation. It is characterized by IgE-dependent activation of mast cells, infiltration of eosinophils, and activated T-helper cell type 2 (Th2) lymphocytes into airway mucosa. Purinergic receptor signaling is known to play a crucial role in inducing and maintaining allergic airway inflammation. Previous studies in an ovalbumin (OVA)-alum mouse model demonstrated a contribution of the P2Y2 purinergic receptor subtype (P2RY2) in allergic airway inflammation. However, conflicting data concerning the mechanism by which P2RY2 triggers AAI has been reported. Thus, we aimed at elucidating the cell-type-specific role of P2RY2 signaling in house dust mite (HDM)-driven model of allergic airway inflammation. Thereupon, HDM-driven AAI was induced in conditional knockout mice, deficient or intact for P2ry2 in either alveolar epithelial cells, hematopoietic cells, myeloid cells, helper T cells, or dendritic cells. To analyze the functional role of P2RY2 in these mice models, flow cytometry of bronchoalveolar lavage fluid (BALF), cytokine measurement of BALF, invasive lung function measurement, HDM re-stimulation of mediastinal lymph node (MLN) cells, and lung histology were performed. Mice that were subjected to an HDM-based model of allergic airway inflammation resulted in reduced signs of acute airway inflammation including eosinophilia in BALF, peribronchial inflammation, Th2 cytokine production, and bronchial hyperresponsiveness in mice deficient for P2ry2 in alveolar epithelial cells, hematopoietic cells, myeloid cells, or dendritic cells. Furthermore, the migration of bone-marrow-derived dendritic cells and bone-marrow-derived monocytes, both deficient in P2ry2, towards ATP was impaired. Additionally, we found reduced levels of MCP-1/CCL2 and IL-8 homologues in the BALF of mice deficient in P2ry2 in myeloid cells and lower concentrations of IL-33 in the lung tissue of mice deficient in P2ry2 in alveolar epithelial cells. In summary, our results show that P2RY2 contributes to HDM-induced airway inflammation by mediating proinflammatory cytokine production in airway epithelial cells, monocytes, and dendritic cells and drives the recruitment of lung dendritic cells and monocytes.

A comprehensive review on glycation and its potential application to reduce food allergenicity

Food allergens are a major concern for individuals who are susceptible to food allergies and may experience various health issues due to allergens in their food. Most allergenic foods are subjected to heat treatment before being consumed. However, thermal processing and prolonged storage can cause glycation reactions to occur in food. The glycation reaction is a common processing method requiring no special chemicals or equipment. It may affect the allergenicity of proteins by altering the structure of the epitope, revealing hidden epitopes, concealing linear epitopes, or creating new ones. Changes in food allergenicity following glycation processing depend on several factors, including the allergen's characteristics, processing parameters, and matrix, and are therefore hard to predict. This review examines how glycation reactions affect the allergenicity of different allergen groups in allergenic foods.

Biological effects triggered by chemical respiratory sensitizers on THP-1 monocytic cells

Respiratory sensitization encompasses a group of diseases that manifest through airway hyperresponsiveness and airflow limitation. Although the concerns regarding human health, to date there are still no validated methods for preclinical assessment of this class of toxicants once the chemical respiratory allergy mechanistic framework is not fully understood. As Dendritic Cells (DCs) are the bridging elements between innate and adaptative immune responses, we preliminarily investigated the biological alterations triggered by seven different LMW respiratory allergens in the DC model THP-1. The results have shown that exposure to respiratory allergens promoted alterations in DCs maturation/activation status and triggered pro-inflammatory changes in these cells through increased expression for the CD86/HLA-DR/CD11c surface biomarkers and enhancement in IL-8 and IL-6 production by exposed THP-1 cells. Therefore, evidence was found to support the startpoint for chemical respiratory allergy pathogenesis elucidation, subsidizing the contribution of dendritic cells in such pathomechanisms.

Treatment of allergy: Overview of synthetic anti-allergy small molecules in medicinal chemistry

The prevalence of allergic diseases has been continuously increasing over the past few decades, affecting approximately 20-30% of the global population. Allergic reactions to infection of respiratory tract, digestive tract, and skin system involve multiple different targets. The main difficulty of anti-allergy research is how to develop drugs with good curative effect and less side effects by adopting new multi-targets and mechanisms according to the clinical characteristics of different allergic populations and different allergens. This review focuses on information concerning potential therapeutic targets as well as the synthetic anti-allergy small molecules with respect to their medicinal chemistry. The structure-activity relationship and the mechanism of compound-target interaction were highlighted with perspective to histamine-1/4 receptor antagonists, leukotriene biosynthesis, Th2 cytokines inhibitors, and calcium channel blockers. We hope that the study of chemical scaffold modification and optimization for different lead compounds summarized in this review not only lays the foundation for improvement of success rate and efficiency of virtual screening of antiallergic drugs, but also can provide valuable reference for the drug design of related promising research such as allergy, inflammation, and cancer.

Airway Epithelium: A Neglected but Crucial Cell Type in Asthma Pathobiology

The features of allergic asthma are believed to be mediated mostly through the Th2 immune response. In this Th2-dominant concept, the airway epithelium is presented as the helpless victim of Th2 cytokines. However, this Th2-dominant concept is inadequate to fill some of the vital knowledge gaps in asthma pathogenesis, like the poor correlation between airway inflammation and airway remodeling and severe asthma endotypes, including Th2-low asthma, therapy resistance, etc. Since the discovery of type 2 innate lymphoid cells in 2010, asthma researchers started believing in that the airway epithelium played a crucial role, as alarmins, which are the inducers of ILC2, are almost exclusively secreted by the airway epithelium. This underscores the eminence of airway epithelium in asthma pathogenesis. However, the airway epithelium has a bipartite functionality in sustaining healthy lung homeostasis and asthmatic lungs. On the one hand, the airway epithelium maintains lung homeostasis against environmental irritants/pollutants with the aid of its various armamentaria, including its chemosensory apparatus and detoxification system. Alternatively, it induces an ILC2-mediated type 2 immune response through alarmins to amplify the inflammatory response. However, the available evidence indicates that restoring epithelial health may attenuate asthmatic features. Thus, we conjecture that an epithelium-driven concept in asthma pathogenesis could fill most of the gaps in current asthma knowledge, and the incorporation of epithelial-protective agents to enhance the robustness of the epithelial barrier and the combative capacity of the airway epithelium against exogenous irritants/allergens may mitigate asthma incidence and severity, resulting in better asthma control.

The innate immune brakes of the lung

Respiratory mucosal surfaces are continuously exposed to not only innocuous non-self antigens but also pathogen-associated molecular patterns (PAMPs) originating from environmental or symbiotic microbes. According to either "self/non-self" or "danger" models, this should systematically result in homeostasis breakdown and the development of immune responses directed to inhaled harmless antigens, such as T helper type (Th)2-mediated asthmatic reactions, which is fortunately not the case in most people. This discrepancy implies the existence, in the lung, of regulatory mechanisms that tightly control immune homeostasis. Although such mechanisms have been poorly investigated in comparison to the ones that trigger immune responses, a better understanding of them could be useful in the development of new therapeutic strategies against lung diseases (e.g., asthma). Here, we review current knowledge on innate immune cells that prevent the development of aberrant immune responses in the lung, thereby contributing to mucosal homeostasis.

Mechanical bacterial lysate enhances antimicrobial barrier mechanisms in human airway epithelial cells

Polyvalent mechanical bacterial lysate is effective in the prevention of respiratory tract infections, although its mechanism of action is not entirely elucidated. Because epithelial cells constitute the frontline defense against infections, we investigated the molecular mechanisms of innate response exerted by bronchial epithelial cells in the presence of polyvalent mechanical bacterial lysate. By using primary human bronchial epithelial cells, we observed that polyvalent mechanical bacterial lysate was able to increase the expression of cellular adhesion molecules such as ICAM-1 and E-cadherin, as well as the expression of amphiregulin, a growth factor able to support human bronchial epithelial cell proliferation. Remarkably, polyvalent mechanical bacterial lysate promoted in human bronchial epithelial cells the de novo expression of human β-defensin-2, a major antimicrobial peptide, conferring them a direct antimicrobial activity. Moreover, polyvalent mechanical bacterial lysate-stimulated human bronchial epithelial cells provided signals for increased IL-22 production by innate lymphoid cells via IL-23, which could further contribute to the release of antimicrobial peptides by epithelial cells. In agreement with these in vitro data, the concentration of both IL-23 and antimicrobial peptides (human β-defensin-2 and LL-37) increased in the saliva of healthy volunteers after sublingual administration of polyvalent mechanical bacterial lysate. Altogether, these results indicate that polyvalent mechanical bacterial lysate administration might support mucosal barrier integrity and promote mechanisms of antimicrobial activity in airway epithelial cells.

Effects of mesenchymal stem cell-derived nanovesicles in experimental allergic airway inflammation

BACKGROUND

Allergic asthma is associated with airflow obstruction and hyper-responsiveness that arises from airway inflammation and remodeling. Cell therapy with mesenchymal stem cells (MSC) has been shown to attenuate inflammation in asthma models, and similar effects have recently been observed using extracellular vesicles (EV) obtained from these cells. Biologically functional vesicles can also be artificially generated from MSC by extruding cells through membranes to produce EV-mimetic nanovesicles (NV). In this study, we aimed to determine the effects of different MSC-derived vesicles in a murine model of allergic airway inflammation.

METHODS

EV were obtained through sequential centrifugation of serum-free media conditioned by human bone marrow MSC for 24 h. NV were produced through serial extrusion of the whole cells through filters. Both types of vesicles underwent density gradient purification and were quantified through nanoparticle tracking analysis. C57BL/6 mice were sensitized to ovalbumin (OVA, 8 µg), and then randomly divided into the OVA group (intranasally exposed to 100 µg OVA for 5 days) and control group (exposed to PBS). The mice were then further divided into groups that received 2 × 10⁹ EV or NV (intranasally or intraperitoneally) or PBS immediately following the first OVA exposure.

RESULTS

Administration of EV and NV reduced cellularity and eosinophilia in bronchoalveolar lavage (BAL) fluid in OVA-sensitized and OVA-exposed mice. In addition, NV treatment resulted in decreased numbers of inflammatory cells within the lung tissue, and this was associated with lower levels of Eotaxin-2 in both BAL fluid and lung tissue. Furthermore, both intranasal and systemic administration of NV were effective in reducing inflammatory cells; however, systemic delivery resulted in a greater reduction of eosinophilia in the lung tissue.

CONCLUSIONS

Taken together, our results indicate that MSC-derived NV significantly reduce OVA-induced allergic airway inflammation to a level comparable to EV. Thus, cell-derived NV may be a novel EV-mimetic therapeutic candidate for treating allergic diseases such as asthma.

Nanotherapeutics for immune network modulation in tumor microenvironments

Immunotherapy has shown promise in cancer treatment, and is thus drawing increasing interest in this field. While the standard chemotherapy- and/or radiotherapy-based cancer treatments aim to directly kill cancer cells, immunotherapy uses host immune cell surveillance to fight cancer. In the tumor environment, there is a close relationship between tumor cells and the adjacent immune cells, which are largely suppressed by cancer-related regulation of immune checkpoints, immune-suppressive cytokines, and metabolic factors. The immune modulators currently approved for cancer treatment remain limited by issues with dose tolerance and insufficient efficacy. Researchers have developed and tested various nano-delivery systems with the goal of improving the treatment outcome of these drugs. By encapsulating immune modulators in particles and directing their tissue accumulation, some such systems have decreased immune-related toxicity while sharpening the antitumor response. Surface-ligand modification of nanoparticles has allowed drugs to be delivered to specific immune cells types. Researchers have also studied strategies for depleting or reprogramming the immune-suppressive cells to recover the immune environment. Combining a nanomaterial with an external stimulus has been used to induce immunogenic cell death; this favors the inflammatory environment found in tumor tissues to promote antitumor immunity. The present review covers the most recent strategies aimed at modulating the tumor immune environment, and discusses the challenges and future perspectives in developing nanoparticles for cancer immunotherapy.

Langerin-expressing dendritic cells in pulmonary immune-related diseases

Dendritic cells (DCs) are “frontline” immune cells dedicated to antigen presentation. They serve as an important bridge connecting innate and adaptive immunity, and express various receptors for antigen capture. DCs are divided into various subclasses according to their differential expression of cell surface receptors and different subclasses of DCs exhibit specific immunological characteristics. Exploring the common features of each sub-category has became the focus of many studies. There are certain amounts of DCs expressing langerin in airways and peripheral lungs while the precise mechanism by which langerin⁺ DCs drive pulmonary disease is unclear. Langerin-expressing DCs can be further subdivided into numerous subtypes based on the co-expressed receptors, but here, we identify commonalities across these subtypes that point to the major role of langerin. Better understanding is required to clarify key disease pathways and determine potential new therapeutic approaches.

Suppression of Allergic Asthma by Loss of Function of Miz1-Mediated Th1 Skewing

Asthma is the most prevalent chronic respiratory disease worldwide. There is currently no cure, and it remains an important cause of morbidity and mortality. Here we report that lung-specific loss of function of the transcription factor c-Myc-interacting zinc finger protein-1 (Miz1) upregulates the pro-T helper 1 (Th1) cytokine interleukin 12 (IL-12). Upregulation of IL-12 in turn stimulates a Th1 response, thereby counteracting T helper 2 (Th2) response and preventing the allergic response in mouse models of house dust mite (HDM)- and ovalbumin (OVA)-induced asthma. Using transgenic mice expressing Cre under a cell-specific promoter, we demonstrate that Miz1 acts in lung epithelial cells and dendritic cells in asthma. Chromatin immunoprecipitation (ChIP) coupled with high-throughput DNA sequencing (ChIP-seq) or quantitative PCR (ChIP-qPCR) reveals the binding of Miz1 on the Il12 promoter indicating direct repression of IL-12 by Miz1. Additionally, histone deacetylase 1 (HDAC1) is recruited to the Il12 promoter in a Miz1-depdenent manner, suggesting epigenetic repression of Il12 by Miz1. Furthermore, Miz1 is upregulated in human asthmatic samples as well as in asthmatic mice. Our data together suggest that Miz1 is upregulated during asthma, which in turn promotes asthma pathogenesis by preventing Th1 skewing through the transcriptional repression of IL-12.

Circulating SSEA-1+ stem cell-mediated tissue repair in allergic airway inflammation

Structural changes known as airway remodeling characterize chronic/severe asthma and contribute to lung dysfunction. We previously reported that neonatal SSEA-1⁺ pulmonary stem/progenitor cells (PSCs) ameliorated airway inflammation in asthmatic mice. However, the molecular mechanisms by which endogenous SSEA-1⁺ PSC of adult mice afford beneficial effects in alveolar homeostasis and lung repair after allergen challenge remain incompletely understood. To analyze the expression profile and clarify the biological significance of endogenous adult lung SSEA-1⁺ cells in asthmatic mice. Lung SSEA-1⁺ cells and circulating SSEA-1⁺ cells in peripheral blood were determined by confocal microscopy and cytometric analysis. GFP chimeric mice were used to trace cell lineage in vivo. The roles of circulating SSEA-1⁺ cells were verified in ovalbumin-induced and house dust mite-induced allergic asthmatic models. In asthmatic mice, endogenous lung SSEA-1⁺ cells almost disappeared; however, a unique population of circulating SSEA-1⁺ cells was enriched after the challenge phase. In asthmatic mice, adoptive transfer of circulating SSEA-1⁺ cells had a specific homing preference for the lung in response to inhaled antigen through upregulating CXCR7–CXCL11 chemokine axis. Circulating SSEA-1⁺ cells can transdifferentiate in the alveolar space and ameliorate lung inflammation and structural damage through inhibiting the infiltration of inflammatory cells into peribronchovascular and goblet cell hyperplasia areas, reducing the thickened smooth muscle layers and PAS-positive mucus-containing goblet cells. Reinforcing bone marrow-derived circulating SSEA-1⁺ cells from peripheral blood into lung tissue which create a rescue mechanism in maintaining alveolar homeostasis and tissue repair to mediate lung protection for emergency responses after allergen challenge in asthmatic conditions.

Decreased expression of airway epithelial Axl is associated with eosinophilic inflammation in severe asthma

BACKGROUND

Airway epithelium-derived cytokines are critical to provoke and perpetuate type 2 inflammation in asthma. Yet it is poorly understood how this epithelial cell-driven inflammatory response is negatively regulated. We previously reported that Axl receptor tyrosine kinase was expressed by basal cells in the airway epithelium and had a role in defining their stem cell identity. However, whether and how Axl regulates airway type 2 inflammation remains unknown.

METHODS

We performed immunofluorescence staining to compare Axl expression in airway epithelium between non-asthmatic subjects, mild-moderate asthma and severe asthma. We confirmed this result by interrogating public databases of global gene expression in endobronchial biopsies. We then quantified eosinophil numbers infiltrating into the trachea of wild-type or Axl-knockout mice that were intranasally treated with house dust mite extracts (HDM). Cell-based assays using siRNA targeting Axl were further performed to identify molecules involved in Axl-mediated regulation of inflammation.

RESULTS

Histological assessments and transcriptome analyses revealed decreases in protein and mRNA of Axl in airway basal cells of severe asthmatics. This reduction of Axl expression was correlated with infiltration of eosinophils and mast cells in severe asthmatics. Eosinophil infiltration was more evident in the trachea of Axl-knockout mice in response to repetitive HDM administration. siRNA-mediated knockdown of Axl increased mRNA and protein expression of granulocyte macrophage-colony stimulating factor (GM-CSF) in human bronchial epithelial cells.

CONCLUSIONS

Axl kinase expressed by basal cells may suppress excessive eosinophilic inflammation via inhibition of GM-CSF in the airway. Axl reduction has clinical implications for the pathogenesis of severe asthma.

The Role of Defective Epithelial Barriers in Allergic Lung Disease and Asthma Development

The respiratory epithelium constitutes the physical barrier between the human body and the environment, thus providing functional and immunological protection. It is often exposed to allergens, microbial substances, pathogens, pollutants, and environmental toxins, which lead to dysregulation of the epithelial barrier and result in the chronic inflammation seen in allergic diseases and asthma. This epithelial barrier dysfunction results from the disturbed tight junction formation, which are multi-protein subunits that promote cell-cell adhesion and barrier integrity. The increasing interest and evidence of the role of impaired epithelial barrier function in allergy and asthma highlight the need for innovative approaches that can provide new knowledge in this area. Here, we review and discuss the current role and mechanism of epithelial barrier dysfunction in developing allergic diseases and the effect of current allergy therapies on epithelial barrier restoration.

The Role of Airway Epithelial Cell Alarmins in Asthma

The airway epithelium is the first line of defense for the lungs, detecting inhaled environmental threats through pattern recognition receptors expressed transmembrane or intracellularly. Activation of pattern recognition receptors triggers the release of alarmin cytokines IL-25, IL-33, and TSLP. These alarmins are important mediators of inflammation, with receptors widely expressed in structural cells as well as innate and adaptive immune cells. Many of the key effector cells in the allergic cascade also produce alarmins, thereby contributing to the airways disease by driving downstream type 2 inflammatory processes. Randomized controlled clinical trials have demonstrated benefit when blockade of TSLP and IL-33 were added to standard of care medications, suggesting these are important new targets for treatment of asthma. With genome-wide association studies demonstrating associations between single-nucleotide polymorphisms of the TSLP and IL-33 gene and risk of asthma, it will be important to understand which subsets of asthma patients will benefit most from anti-alarmin therapy.

Role of Secretoglobin+ (club cell) NFκB/RelA-TGFβ signaling in aero-allergen-induced epithelial plasticity and subepithelial myofibroblast transdifferentiation

Repetitive aeroallergen exposure is linked to sensitization and airway remodeling through incompletely understood mechanisms. In this study, we examine the dynamic mucosal response to cat dander extract (CDE), a ubiquitous aero-allergen linked to remodeling, sensitization and asthma. We find that daily exposure of CDE in naïve C57BL/6 mice activates innate neutrophilic inflammation followed by transition to a lymphocytic response associated with waves of mucosal transforming growth factor (TGF) isoform expression. In parallel, enhanced bronchiolar Smad3 expression and accumulation of phospho-SMAD3 was observed, indicating paracrine activation of canonical TGFβR signaling. CDE exposure similarly triggered epithelial cell plasticity, associated with expression of mesenchymal regulatory factors (Snai1 and Zeb1), reduction of epithelial markers (Cdh1) and activation of the NFκB/RelA transcriptional activator. To determine whether NFκB functionally mediates CDE-induced growth factor response, mice were stimulated with CDE in the absence or presence of a selective IKK inhibitor. IKK inhibition substantially reduced the level of CDE-induced TGFβ1 expression, pSMAD3 accumulation, Snai1 and Zeb1 expression. Activation of epithelial plasticity was demonstrated by flow cytometry in whole lung homogenates, where CDE induces accumulation of SMA⁺Epcam⁺ population. Club cells are important sources of cytokine and growth factor production. To determine whether Club cell innate signaling through NFκB/RelA mediated CDE induced TGFβ signaling, we depleted RelA in Secretoglobin (Scgb1a1)-expressing bronchiolar cells. Immunofluorescence-optical clearing light sheet microscopy showed a punctate distribution of Scgb1a1 progenitors throughout the small airway. We found that RelA depletion in Secretoglobin⁺ cells results in inhibition of the mucosal TGFβ response, blockade of EMT and reduced subepithelial myofibroblast expansion. We conclude that the Secretoglobin—derived bronchiolar cell is central to coordinating the innate response required for mucosal TGFβ1 response, EMT and myofibroblast expansion. These data have important mechanistic implications for how aero-allergens trigger mucosal injury response and remodeling in the small airway.

Hemagglutinin Nanoparticulate Vaccine with Controlled Photochemical Immunomodulation for Pathogenic Influenza-Specific Immunity

Recently, viral infectious diseases, including COVID-19 and Influenza, are the subjects of major concerns worldwide. One strategy for addressing these concerns focuses on nasal vaccines, which have great potential for achieving successful immunization via safe, easy, and affordable approaches. However, conventional nasal vaccines have major limitations resulting from fast removal when pass through nasal mucosa and mucociliary clearance hindering their effectiveness. Herein a nanoparticulate vaccine (NanoVac) exhibiting photochemical immunomodulation and constituting a new self-assembled immunization system of a photoactivatable polymeric adjuvant with influenza virus hemagglutinin for efficient nasal delivery and antigen-specific immunity against pathogenic influenza viruses is described. NanoVac increases the residence period of antigens and further enhances by spatiotemporal photochemical modulation in the nasal cavity. As a consequence, photochemical immunomodulation of NanoVacs successfully induces humoral and cellular immune responses followed by stimulation of mature dendritic cells, plasma cells, memory B cells, and CD4+ and CD8+ T cells, resulting in secretion of antigen-specific immunoglobulins, cytokines, and CD8+ T cells. Notably, challenge with influenza virus after nasal immunization with NanoVacs demonstrates robust prevention of viral infection. Thus, this newly designed vaccine system can serve as a promising strategy for developing vaccines that are active against current hazardous pathogen outbreaks and pandemics.

Human lung cDC1 drive increased perforin-mediated NK cytotoxicity in Chronic Obstructive Pulmonary Disease

In chronic obstructive pulmonary disease (COPD), lung natural killer cells (NKs) lyse autologous lung epithelial cells in vitro, but underlying mechanisms and their relationship to epithelial cell apoptosis in vivo are undefined. Although this cytolytic capacity of lung NKs depends on priming by dendritic cells (DC), whether priming correlates with DC maturation or is limited to a specific DC subset are also unknown. We recruited ever-smokers (≥10 pack-years) (n=96) undergoing clinically-indicated lung resections. We analyzed lung NKs for cytotoxic molecule transcripts and for cytotoxicity, which we correlated with in situ detection of activated Caspase-3/7+ airway epithelial cells. To investigate DC priming, we measured lung DC expression of CCR2, CCR7, and CX3CR1, and co-cultured peripheral blood NKs with autologous lung DC, either matured using LPS (non-obstructed smokers) or separated into conventional DC type-1 (cDC1) versus cDC type-2 (cDC2) (COPD). Lung NKs in COPD expressed more perforin (p<0.02) and granzyme B (p<0.03) transcripts; inhibiting perforin blocked in vitro killing by lung NKs. Cytotoxicity in vitro correlated significantly (S_r=0.68, p=0.0043) with numbers of apoptotic epithelial cells per airway. In non-obstructed smokers, LPS-induced maturation enhanced DC-mediated priming of blood NKs, reflected by greater epithelial cell death. Although CCR7 expression was greater in COPD in both cDC1 (p<0.03) and cDC2 (p=0.009), only lung cDC1 primed NK killing. Thus, rather than being intrinsic to those with COPD, NK priming is a capacity of human lung DC that is inducible by recognition of bacterial (and possibly other) danger signals and restricted to the cDC1 subset.

Enzymatic crosslinking and food allergenicity: A comprehensive review

Food allergy has become a major global public health concern. In the past decades, enzymatic crosslinking technique has been employed to mitigate the immunoreactivity of food allergens. It is an emerging non-thermal technique that can serve as a great alternative to conventional food processing approaches in developing hypoallergenic food products, owing to their benefits of high specificity and selectivity. Enzymatic crosslinking via tyrosinase (TYR), laccase (LAC), peroxidase (PO), and transglutaminase (TG) modifies the structural and biochemical properties of food allergens that subsequently cause denaturation and masking of the antigenic epitopes. LAC, TYR, and PO catalyze the oxidation of tyrosine side chains to initiate protein crosslinking, while TG initiates isopeptide bonding between lysine and glutamine residues. Enzymatic treatment produces a high molecular weight crosslinked polymer with reduced immunoreactivity and IgE-binding potential. Crosslinked allergens further inhibit mast cell degranulation due to the lower immunostimulatory potential that assists in the equilibration of T-helper (Th)1/Th2 immunobalance. This review provides an updated overview of the studies carried out in the last decade on the potential application of enzymatic crosslinking for mitigating food allergenicity that can be of importance in the context of developing hypoallergenic/non-allergenic food products.

Targeting immune dysfunction in aging

Human aging is a multifactorial phenomenon that affects numerous organ systems and cellular processes, with the immune system being one of the most dysregulated. Immunosenescence, the gradual deterioration of the immune system, and inflammaging, a chronic inflammatory state that persists in the elderly, are among the plethora of immune changes that occur during aging. Almost all populations of immune cells change with age in terms of numbers and/or activity. These alterations are in general highly detrimental, resulting in an increased susceptibility to infections, reduced healing abilities, and altered homeostasis that promote the emergence of age-associated diseases such as cancer, diabetes, and other diseases associated with inflammation. Thanks to recent developments, several strategies have been proposed to target central immunological processes or specific immune subpopulations affected by aging. These therapeutic approaches could soon be applied in the clinic to slow down or even reverse specific age-induced immune changes in order to rejuvenate the immune system and prevent or reduce the impact of various diseases. Due to its systemic nature and interconnection with all the other systems in the body, the immune system is an attractive target for aging intervention because relatively targeted modifications to a small set of cells have the potential to improve the health of multiple organ systems. Therefore, anti-aging immune targeting therapies could represent a potent approach for improving healthspan. Here, we review aging changes in the major components of the immune system, we summarize the current immune-targeting therapeutic approaches in the context of aging and discuss the future directions in the field of immune rejuvenation.

The Induction of Alpha-1 Antitrypsin by Vitamin D in Human T Cells Is TGF-β Dependent: A Proposed Anti-inflammatory Role in Airway Disease

Background: Vitamin D upregulates anti-inflammatory and antimicrobial pathways that promote respiratory health. Vitamin D synthesis is initiated following skin exposure to sunlight, however nutritional supplementation can be required to address deficiency, for example during the winter months or due to cultural constraints. We recently reported that 1α,25-dihydroxyvitamin D3 (1,25(OH)₂D3) treatment induced alpha-1 antitrypsin (AAT) expression in CD4+, but not CD8+ T cells, with evidence supporting an immunoregulatory role.

Research Question: To understand the relationship between vitamin D, lung AAT levels and T lymphocytes further we investigated whether TGF-β is required as a co-factor for 1,25(OH)₂D3-induced upregulation of AAT by vitamin D in CD8+ T cells in vitro and correlated circulating vitamin D levels with lung AAT levels in vivo.

Results: 1,25(OH)₂D3 in combination with TGF-β1 increased AAT expression by CD8+ T cells, as well as VDR and RXRα gene expression, which may partly explain the requirement for TGF-β. CD4+ T cells may also require autocrine stimulation with TGF-β as a co-factor since 1,25(OH)₂D3 was associated with increased TGF-β bioactivity and neutralisation of TGF-β partially abrogated 1,25(OH)₂D3-induced SERPINA1 gene expression. Neither CD4+ nor CD8+ T cells responded to the circulating vitamin D precursor, 25-hydroxyvitamin D3 for induction of SERPINA1, suggesting that local generation of 1,25(OH)₂D3 is required. Transcriptional gene profiling studies previously demonstrated that human bronchial epithelial cells rapidly increased TGF-β2 gene expression in response to 1,25(OH)₂D3. Here, human epithelial cells responded to precursor 25(OH)D3 to increase bioactive TGF-β synthesis. CD8+ T cells responded comparably to TGF-β1 and TGF-β2 to increase 1,25(OH)₂D3-induced AAT. However, CD8+ T cells from adults with AAT-deficiency, homozygous for the Z allele of SERPINA1, were unable to mount this response. AAT levels in the airways of children with asthma and controls correlated with circulating 25(OH)D3.

Conclusions: Vitamin D increases AAT expression in human T cells and this response is impaired in T cells from individuals homozygous for the Z allele of SERPINA1 in a clinic population. Furthermore, a correlation between circulating vitamin D and airway AAT is reported. We propose that vitamin D-induced AAT contributes to local immunomodulation and airway health effects previously attributed to vitamin D.

Beyond dermal exposure: The respiratory tract as a target organ in hazard assessments of cosmetic ingredients

Dermal contact is the main route of exposure for most cosmetics; however, inhalation exposure could be significant for some formulations (e.g., aerosols, powders). Current cosmetic regulations do not require specific tests addressing respiratory irritation and sensitisation, and despite the prohibition of animal testing for cosmetics, no alternative methods have been validated to assess these endpoints to date. Inhalation hazard is mainly determined based on existing human and animal evidence, read-across, and extrapolation of data from different target organs or tissues, such as the skin. However, because of mechanistic differences, effects on the skin cannot predict effects on the respiratory tract, which indicates a substantial need for the development of new approach methodologies addressing respiratory endpoints for inhalable chemicals in general. Cosmetics might present a particularly significant need for risk assessments of inhalation exposure to provide a more accurate toxicological evaluation and ensure consumer safety. This review describes the differences in the mechanisms of irritation and sensitisation between the skin and the respiratory tract, the progress that has already been made, and what still needs to be done to fill the gap in the inhalation risk assessment of cosmetic ingredients.

Crosstalk of the IκB Kinase with Spliced X-Box Binding Protein 1 Couples Inflammation with Glucose Metabolic Reprogramming in Epithelial-Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) plays a critical role in airway injury, repair, and structural remodeling. IκB kinase (IKK)-NFκB signaling regulates late EMT-associated gene expression. However, IKK-mediated mesenchymal transition occurs earlier than NFκB/RelA subunit-dependent EMT gene expression, leading us to investigate the hypothesis that IKK plays an independent mechanism in transforming growth factor-β (TGFβ)-induced EMT. Time-resolved dissection of early proteome and phosphoproteome changes in response to TGFβ and a specific IKK inhibitor, BMS-345541, revealed that IKK regulates cascades of 23 signaling pathways essential in EMT, including TGFβ signaling, p38 mitogen associate protein kinase (MAPK), Toll receptor signaling, and integrin pathways. We identified early IKK-dependent phosphorylation of core regulatory proteins in essential EMT signaling cassettes, including ATF2, JUN, NFKB1/p105, and others. Interestingly, we found that IKKβ directly complexes with and phosphorylates the spliced X-box-binding protein 1 (XBP1s). XBP1s is an arm of the unfolded protein response (UPR) that activates the hexosamine biosynthetic pathway (HBP), a pathway that mediates protein N-glycosylation and survival from ER stress-induced apoptosis in EMT. We found that inhibition of IKK activity abolishes the phosphorylation of XBP1-T48, blocks XBP1s nuclear translocation, and inhibits the activation of HBP. Our study elucidates a previously unrecognized IKKβ-XBP1s-HBP crosstalk pathway that couples inflammation and glucose metabolic reprogramming in ETM. Because XBP1-HBP controls N-glycosylation of the extracellular matrix (ECM) in EMT, this novel IKKβ-XBP1-HBP pathway may contain therapeutic targets whose inhibition could prevent ECM remodeling in lung fibrosis or other airway remodeling diseases.

A new approach for activation of the kiwifruit cysteine protease for usage in in-vitro testing

Actinidin (Act d 1), a highly abundant cysteine protease from kiwifruit, is one of the major contributors to the development of kiwifruit allergy. Many studies have focused on the optimization of Act d 1 purification and its role in the development of food allergies. Testing on cell culture monolayers is a common step in the elucidation of food allergen sensitization. In the case of cysteine proteases, an additional activation step with L-cysteine is required before the testing. Hence, we aimed to evaluate whether L-cysteine already present in commonly used cell culture media would suffice for Act d 1 activation. Successfully activated Act d 1 (98.1% of proteolytic activity, as compared to L-cysteine activated Act d 1) was further tested in two commonly used 2D model systems (Caco-2 and HEK293 cells) to evaluate its role on the mRNA expression of cytokines involved in the innate immunity (IL-1β, IL-6, TNFα, TSLP). Furthermore, the contribution of Act d 1 in the promotion of inflammation through regulation of inducible nitric oxide synthase (iNOS) mRNA expression was also examined. These results demonstrate that activation of cysteine proteases can be achieved without previous enzyme incubation in L-cysteine -containing solution. Act d 1 incubated in cell culture medium was able to modulate gene expression of pro-inflammatory cytokines when tested on two model systems of the epithelial barrier.

Trained immunity induced by in vivo peptide-based STAT6 inhibition prevents ragweed allergy in mice

BACKGROUND

Trained immunity is the ability of the innate immune system to form immune memory responses to provide support the formation of appropriate adaptive responses. Allergic airways disease (AAD) is a maladapted immune response to allergens, initiated and maintained by the type 2 (T2) inflammatory pathway. It is predicated by the elaboration of cytokines IL-4 and IL-13 and follows activation of the STAT6 transcription factor.

OBJECTIVE

To investigate the role of trained immunity in mucosal immune responses following neonatal vaccination with the STAT6 inhibitory peptide (STAT6-IP), in preventing the development of ragweed-induced AAD.

METHODS

We demonstrate that transfer of CD4⁺ T cells or dendritic cells (DC) from STAT6-IP vaccinated wild-type BALB/c mice to naïve mice, that were subsequently chronically exposed to sensitizing doses of ragweed allergen, is sufficient to prevent development of T2 responses in recipients.

RESULTS

Our results demonstrate significant reductions in; airways hyperresponsiveness (AHR); ragweed-specific IgE; pulmonary inflammation; T2 cytokines; and inflammatory gene expressions in recipient mice. Expression of IDO, TGFβ and T regulatory cells were all significantly increased. Anti-TGFβ treatment during the ragweed sensitization phase re-constituted the pro-inflammatory T2 immune response. We show that tolerance can be attained via DC trained in the STAT6-IP-mediated tolerant milieu. This effect is not restricted to a particular allergen and does not require antigen-mediated T cell activation prior to transfer.

CONCLUSION

Adoptive transfer experiments suggest that STAT6-IP treatment trains dendritic and cells to mediate tolerant immunity to chronic ragweed exposure in the airways. This indicates that early transient STAT6-inhibition constitutes an effective immunomodulatory airways allergy preventative strategy.

Old Friends with Unexploited Perspectives: Current Advances in Mesenchymal Stem Cell-Based Therapies in Asthma

Mesenchymal stem cells (MSCs) have a great regenerative and immunomodulatory potential that was successfully tested in numerous pre-clinical and clinical studies of various degenerative, hematological and inflammatory disorders. Over the last few decades, substantial immunoregulatory effects of MSC treatment were widely observed in different experimental models of asthma. Therefore, it is tempting to speculate that stem cell-based treatment could become an attractive means to better suppress asthmatic airway inflammation, especially in subjects resistant to currently available anti-inflammatory therapies. In this review, we discuss mechanisms accounting for potent immunosuppressive properties of MSCs and the rationale for their use in asthma. We describe in detail an intriguing interplay between MSCs and other crucial players in the immune system as well as lung microenvironment. Finally, we reveal the potential of MSCs in maintaining airway epithelial integrity and alleviating lung remodeling.

Non-Musculoskeletal Benefits of Vitamin D beyond the Musculoskeletal System

Vitamin D, a fat-soluble prohormone, is endogenously synthesized in response to sunlight or taken from dietary supplements. Since vitamin D receptors are present in most tissues and cells in the body, the mounting understanding of the role of vitamin D in humans indicates that it does not only play an important role in the musculoskeletal system, but has beneficial effects elsewhere as well. This review summarizes the metabolism of vitamin D, the research regarding the possible risk factors leading to vitamin D deficiency, and the relationships between vitamin D deficiency and numerous illnesses, including rickets, osteoporosis and osteomalacia, muscle weakness and falls, autoimmune disorders, infectious diseases, cardiovascular diseases (CVDs), cancers, and neurological disorders. The system-wide effects of vitamin D and the mechanisms of the diseases are also discussed. Although accumulating evidence supports associations of vitamin D deficiency with physical and mental disorders and beneficial effects of vitamin D with health maintenance and disease prevention, there continue to be controversies over the beneficial effects of vitamin D. Thus, more well-designed and statistically powered trials are required to enable the assessment of vitamin D’s role in optimizing health and preventing disease.

The Anti-inflammatory Potential of Selected Plant-derived Compounds in Respiratory Diseases

Inflammation plays a major role in chronic airway diseases like asthma, COPD, and cystic fibrosis. Inflammation plays a crucial role in the worsening of the lung function resulting in worsening symptoms. The inflammatory process is very complexed, therefore the strategies for developing an effective treatment for inflammatory airway diseases would benefit from the use of natural substances. Plant products have demonstrated anti-inflammatory properties on various lung disease models and numerous natural plant agents have successfully been used to treat inflammation. Naturally occurring substances may exert some anti-inflammatory effects by modulating some of the inflammatory pathways. These agents have been used in different cultures for thousands of years and have proven to be relatively safe. Parthenolide, apocynin, proanthocyanidins, and boswellic acid present different mechanisms of actions - among others, through NF-kB or NADPH oxidase inhibition, therefore showing a wide range of applications in various inflammatory diseases. Moreover, some of them have also antioxidant properties. This review provides an overview of the anti-inflammatory effects of some of the natural agents and illustrates their great potential as sources of drugs to cover an extensive range of pharmacological effects.

Involvement of Innate Lymphoid Cells and Dendritic Cells in a Mouse Model of Chemical-induced Asthma

PURPOSE

Exposure to low concentrations of toluene diisocyanate (TDI) leads to immune-mediated chemical-induced asthma. The role of the adaptive immune system has already been thoroughly investigated; nevertheless, the involvement of innate immune cells in the pathophysiology of chemical-induced asthma is still unresolved. The aim of the study is to investigate the role of innate lymphoid cells (ILCs) and dendritic cells (DCs) in a mouse model for chemical-induced asthma.

METHODS

On days 1 and 8, BALB/c mice were dermally treated (20 μL/ear) with 0.5% TDI or the vehicle acetone olive oil (AOO; 2:3). On days 15, 17, 19, 22 and 24, the mice received an oropharyngeal challenge with 0.01% TDI or AOO (1:4). One day after the last challenge, airway hyperreactivity (AHR) to methacholine was assessed, followed by an evaluation of pulmonary inflammation and immune-related parameters, including the cytokine pattern in bronchoalveolar lavage fluid, lymphocyte subpopulations of the lymph nodes and their ex vivo cytokine production profile, blood immunoglobulins and DC and ILC subpopulations in the lungs.

RESULTS

Both DC and ILC2 were recruited to the lungs after multiple airway exposures to TDI, regardless of the prior dermal sensitization. However, prior dermal sensitization with TDI alone results in AHR and predominant eosinophilic airway inflammation, accompanied by a typical type 2 helper T (Th2) cytokine profile.

CONCLUSIONS

TDI-induced asthma is mediated by a predominant type 2 immune response, with the involvement of adaptive Th2 cells. However, from our study we suggest that the innate ILC2 cells are important additional players in the development of TDI-induced asthma.

Der p 2.1 Peptide Abrogates House Dust Mites-Induced Asthma Features in Mice and Humanized Mice by Inhibiting DC-Mediated T Cell Polarization

Asthma is a chronic airway disease often due to sensitization to aeroallergens, especially house dust mite allergens (HDMs). The Dermatophagoides pteronyssinus group 2 (Der p 2), is one of the most representative HDM allergens and is recognized by more than 90% of HDM-allergic patients. In mouse models, all asthma-related features can be prevented by prophylactic administration of Dermatophagoides pteronyssinus 2-derived peptide (Der p 2.1). However, it is unknown whether it is able to treat well-established asthma in mice and humans. We aimed here to evaluate the efficacy of Der p 2.1 immunotherapy in a mouse, humanized mouse, and asthmatic patients. Asthma related-features were analyzed through airway hyperresponsiveness (AHR), allergen-specific IgE, and lung histology in mice and humanized mice. Immune profile was analyzed using lung and blood from mice and severe asthmatic patients respectively. T cell and dendritic cell (DC) polarization was evaluated using co-culture of bone marrow derived cells (BMDCs) and naïve T cell from naïve mice. Mice and humanized mice both have a reduced AHR, lung tissue alteration, and HDM-specific IgE under Der p 2.1 treatment. Concerning the immune profile, T helper 2 cells (Th2) and T helper 17 cells (Th17) were significantly reduced in both mice and humanized mice lung and in peripheral blood mononuclear cells (PBMCs) from severe asthmatic patients after Der p 2.1 incubation. The downregulation of T cell polarization seems to be linked to an increase of IL-10-secreting DC under Der p 2.1 treatment in both mice and severe asthmatic patients. This study shows that allergen-derived peptide immunotherapy abrogates asthma-related features in mice and humanized mice by reducing Th2 and Th17 cells polarization via IL-10-secreting DC. These results suggest that Der p 2.1 peptide immunotherapy could be a promising approach to treat both Th2 and Th17 immunity in asthma.

Association between asthma and invasive pneumococcal disease risk: a systematic review and meta-analysis

Purpose

Asthma has been shown to be related to an increased risk of invasive pneumococcal disease (IPD), although the results remain inconclusive. Therefore, we performed a meta-analysis to determine whether asthma increases the risk of IPD. This meta-analysis was performed to validate and strengthen the association between asthma and IPD.

Methods

PubMed, EMBASE, Web of Science, and the reference lists of all relevant articles and books were screened until May 2019. Two authors independently assessed eligibility and study quality and extracted data. A common odds ratio was estimated using a random-effects meta-analysis model of aggregated published data.

Results

A total of eight studies with 8877 IPD cases and 78,366 controls were included. Our meta-analysis showed that asthma was significantly associated with the increased risk of IPD (OR 2.44 [95% CI, 2.02–2.96]). The children with asthma (0–17 years old) (OR 2.86 [95% CI 1.80–4.55]) had a higher risk of IPD susceptibility compared with the adult patients (≥ 18 years old) (OR 2.45 [95% CI 1.98–3.03]).

Conclusions

Results of this meta-analysis indicated that the patients with asthma had a higher risk of IPD susceptibility, especially among the children with asthma.

Influenza A virus enhances ciliary activity and mucociliary clearance via TLR3 in airway epithelium

Background

Viral respiratory tract infections, such as influenza A virus (IAV), are common and life-threatening illnesses worldwide. The mechanisms by which viruses are removed from the respiratory tract are indispensable for airway host defense. Mucociliary clearance is an airway defense mechanism that removes pathogens from the respiratory tract. The coordination and modulation of the ciliary beating of airway epithelial cells play key roles in maintaining effective mucociliary clearance. However, the impact of respiratory virus infection on ciliary activity and mucociliary clearance remains unclear.

Methods

Tracheal samples were taken from wild-type (WT) and Toll-like receptor 3 (TLR3)-knockout (KO) mice. Transient organ culture of murine trachea was performed in the presence or absence of IAV, polyI:C, a synthetic TLR3 ligand, and/or reagents. Subsequently, cilia-driven flow and ciliary motility were analyzed. To evaluate cilia-driven flow, red fluorescent beads were loaded into culture media and movements of the beads onto the tracheal surface were observed using a fluorescence microscope. To evaluate ciliary motility, cilia tips were labeled with Indian ink diluted with culture medium. The motility of ink-labeled cilia tips was recorded by high-speed cameras.

Results

Short-term IAV infection significantly increased cilia-driven flow and ciliary beat frequency (CBF) compared with the control level in WT culture. Whereas IAV infection did not elicit any increases of cilia-driven flow and CBF in TLR3-KO culture, indicating that TLR3 was essential to elicit an increase of cilia-driven flow and CBF in response to IAV infection. TLR3 activation by polyI:C readily induced adenosine triphosphate (ATP) release from the trachea and increases of cilia-driven flow and CBF in WT culture, but not in TLR3-KO culture. Moreover, blockade of purinergic P2 receptors (P2Rs) signaling using P2R antagonist, suramin, suppressed polyI:C-mediated increases of cilia-driven flow and CBF, indicating that TLR3-mediated ciliary activation depended on released extracellular ATP and the autocrine ATP-P2R loop.

Conclusions

IAV infection readily increases ciliary activity and cilia-driven flow via TLR3 activation in the airway epithelium, thereby hastening mucociliary clearance and “sweeping” viruses from the airway as an initial host defense response. Mechanically, extracellular ATP release in response to TLR3 activation promotes ciliary activity through autocrine ATP-P2R loop.

Developments in the mechanisms of allergy in 2018 through the eyes of Clinical and Experimental Allergy, Part I

In the first of two linked articles, we describe the development in the mechanisms underlying allergy as described by Clinical & Experimental Allergy and other journals in 2018. Experimental models of allergic disease, basic mechanisms and clinical mechanisms are all covered.

Degradation of bacterial permeability family member A1 (BPIFA1) by house dust mite (HDM) cysteine protease Der p 1 abrogates immune modulator function

Bacterial permeability family member A1 (BPIFA1) is one of the most abundant proteins present in normal airway surface liquid (ASL). It is known to be diminished in asthmatic patients' sputum, which causes airway hyperresponsiveness (AHR). What is currently unclear is how environmental factors, such as allergens' impact on BPIFA1's abundance and functions in the context of allergic asthma. House dust mite (HDM) is a predominant domestic source of aeroallergens. The group of proteases found in HDM is thought to cleave multiple cellular protective mechanisms, and therefore foster the development of allergic asthma. Here, we show that BPIFA1 is cleaved by HDM proteases in a time-, dose-, and temperature-dependent manner. We have also shown the main component in HDM that is responsible for BPIFA1's degradation is Der p1. Fragmented BPIFA1 failed to bind E. coli lipopolysaccharide (LPS), and hence elevated TNFα and IL-6 secretion in human whole blood. BPIFA1 degradation is also observed in vivo in bronchoalveolar fluid (BALF) of mice which are intranasally instilled with HDM. These data suggest that proteases associated with environmental allergens such as HDM cleave BPIFA1 and therefore impair its immune modulator function.