Allergen-Induced Increases in Interleukin-25 and Interleukin-25 Receptor Expression in Mature Eosinophils from Atopic Asthmatics

Role of IL-25 on Eosinophils in the Initiation of Th2 Responses in Allergic Asthma

Background

Eosinophils act as a secondary antigen-presenting cell (APC) to stimulate Th cell responses against antigens. IL-25 plays a significant role in eosinophil activation in allergic asthma. The role of IL-25 on the classic APC functions of dendritic cells has been elucidated. However, whether IL-25 facilitates eosinophils for antigen presentation is unknown.

Objective

To elucidate the role of IL-25 on eosinophils antigen presenting function during allergic asthma and its related mechanism.

Methods

Eosinophils from allergic asthma subjects were cultured with IL-25 and HDM to identify the co-stimulator molecules expression. Co-cultures of patient eosinophils and autologous naïve CD4⁺ T cells in the same culture system were to explore whether eosinophils had the capacity to promote Th cell differentiation in response to IL-25 engagement. In asthma mouse model, IL-25^-/- mice were exposed to HDM to investigate the effect of IL-25 on eosinophils during the sensitization phase. The impact of IL-25 on the capacity for eosinophils taking up antigens was evaluated. Mouse bone marrow derived eosinophils (BmEOS) were co-cultured with naïve CD4⁺T cells sorted from spleens under HDM and IL-25 stimulation to identify T cell differentiation.

Results

IL-25 upregulated HLA-DR, PD-L1, and OX-40L expression on eosinophils from allergic asthma patients. IL-25 and HDM co-sensitized eosinophils promoted Th2 differentiation. In mouse model, IL-25^-/- mice experienced restrained allergic pulmonary inflammation and reduced eosinophils recruitment and antigen uptake capacity during the early sensitization phase. In vitro, IL-25 promoted antigen uptake by eosinophils. In BmEOS and naïve CD4⁺T cells co-culture, IL-25 accreted the proportion of CD4⁺Th2 cells, which was absent in CD4⁺T cells culture alone.

Conclusion

Our data identify a novel role of IL-25 in enhancing eosinophils antigen uptake and co-stimulator molecules expression to induce Th2 priming in the context of allergic inflammation.

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.

The Role of Interleukins in the Pathogenesis of Dermatological Immune-Mediated Diseases

Autoimmune inflammatory diseases are primarily characterized by deregulated expression of cytokines, which drive pathogenesis of these diseases. A number of approved and experimental therapies utilize monoclonal antibodies against cytokine proteins. Cytokines can be classified into different families including the interleukins, which are secreted and act on leukocytes, the tumor necrosis factor (TNF) family, as well as chemokine proteins. In this review article, we focus on the interleukin family of cytokines, of which 39 members have been identified to this date. We outline the role of each of these interleukins in the immune system, and various dermatological inflammatory diseases with a focused discussion on the pathogenesis of psoriasis and atopic dermatitis. In addition, we describe the roles of various interleukins in psychiatric, cardiovascular, and gastrointestinal comorbidities. Finally, we review clinical efficacy and safety data from emerging late-phase anti-interleukin therapies under development for psoriasis and atopic dermatitis. Collectively, additional fundamental and clinical research remains necessary to fully elucidate the roles of various interleukin proteins in the pathogenesis of inflammatory dermatologic diseases, and treatment outcomes in patients.

IL-25 promotes trophoblast proliferation and invasion via binding with IL-17RB and associated with PE

INTRODUCTION

Interleukin-25 is a Th2 interleukin and has been shown to influence cell behavior. This study aims to illustrate its affection on extravillous trophoblasts function and association with PE. Methods qPCR and immunohistochemistry demonstrate IL-25 and IL-17RB expression. CCK-8 test and transwell were to access the behavior of HTR8 in the presence or absence of IL-25, IL-25 neutralization antibody. Results EVTs and HTR8 express IL-25 and IL-17RB. IL-25 promotes proliferation and invasion (p< 0.05),which was abolished in the presence of IL-25Ab (p< 0.05). Conclusion: IL-25 may contribute to promote trophoblast invasion and proliferation and abnormal decline of IL-25 might be associated with PE.

METHODS

qPCR and immunohistochemistry (IHC) were used to demonstrate IL-25 and its receptor IL-17RB expression in primary human trophoblasts of normal first- and third- trimester, as well as third-trimester of PE. CCK-8 test and transwell invasion system in vitro were applied separately to access the behavior of trophoblast cell line (HTR8) in the presence or absence of IL-25, IL-25 neutralization antibody (IL-25 Ab).

RESULTS

EVTs and HTR8 express IL-25 and IL-17RB. The expressions increase in third-trimester during normal pregnancy. In PE, both of IL-25 and IL-17RB expressions decrease (p< 0.05). IL-25 for 24 h promoted HTR8 proliferation and invasion (p< 0.05). The effect was abolished in the presence of IL-25Ab (p< 0.05).

CONCLUSION

This study demonstrates that IL-25 may contribute to promote trophoblast invasion and proliferation and abnormal decline of IL-25 might be associated with PE.

Evaluation of Sensitivity and Specificity of Interleukins 25 and 33 in Diagnosis of Pediatric Asthma

The roles of interleukin 25 (a member of the interleukin 17 family) and interleukin 33 (a member of the interleukin 1 family) in asthma and airway hyperresponsiveness are yet to be fully understood. The aim of this study was to investigate the roles of IL- 25 and IL- 33 in the diagnosis of pediatric asthma and their association with severity and treatment of the disease. This was a case-control study comprising 74 children with asthma as the patient group and 75 healthy children as the control group. The age of the participants ranged from 1 to 15 years. Levels of IL- 25 and IL- 33 in the serum were measured using ELISA kits. The highest positive predictive values (88.9%) occurred in IL- 25 with sensitivity and specificity of about 97.3% and 88.0% respectively, while the sensitivity and specificity of IL- 33 were about 51.4% and 66.0% respectively, with a positive predictive value of about (60.3%). The present study thus found that IL- 25 had higher diagnostic sensitivity and specificity values than IL- 33 in children with asthma. In addition, both interleukins were found to have a statistical significance regarding treatment of the disease in children.

Anti-alarmin approaches entering clinical trials

PURPOSE OF REVIEW

The alarmins, thymic stromal lymphopoietin (TSLP), interleukin (IL)-25 and IL-33, are upstream regulators of T2 (type 2) inflammation and found to be expressed at high levels in airway epithelium of patients with T2 asthma. This review will summarize how alarmins regulate the inflamed asthmatic airways through previously described and newly identified mechanisms.

RECENT FINDINGS

Alarmins drive allergic and nonallergic asthma through activation of innate lymphoid cell 2 (ILC2), which are a rich source of cytokines such as IL-5 and IL-13, with resulting effects on eosinophilopoeisis and remodelling, respectively. Findings from bronchial allergen challenges have illustrated widespread expression of alarmins and their receptors across many effector cells in airways, and recent studies have emphasized alarmin regulation of CD4 T lymphocytes, eosinophils and basophils, and their progenitors. Furthermore, a link between alarmins and lipid mediators is being uncovered.

SUMMARY

Alarmins can drive well defined inflammatory pathways through activation of dendritic cells and polarizing T cells to produce type 2 cytokines, as well as they can directly activate many other effector cells that play a central role in allergic and nonallergic asthma. Clinical trials support a central role for TSLP in driving airway inflammation and asthma exacerbations, while ongoing trials blocking IL-33 and IL-25 will help to define their respective role in asthma.

Allergen bronchoprovocation test: an important research tool supporting precision medicine

PURPOSE OF REVIEW

Allergen bronchoprovocation test (ABT) has been used to study asthma pathophysiology and as a disease-modelling tool to assess the properties and efficacy of new asthma drugs. In view of the complexity and heterogeneity of asthma, which has driven the definition of several phenotypes and endotypes, we aim to discuss the role of ABT in the era of precision medicine and provide guidance for clinicians how to interpret and use available data to understand the implications for the benefits of asthma treatment.

RECENT FINDINGS

In this review, we summarize background knowledge and applications of ABT and provide an update with recent publications on this topic. In the past years, several studies have been published on ABT in combination with non-invasive and invasive airway samplings and innovative detection techniques allowing to study several inflammatory mechanisms linked to Th2-pathway and allergen-induced pathophysiology throughout the airways.

SUMMARY

ABT is a valuable research tool, which has strongly contributed to precision medicine by helping to define allergen-triggered key inflammatory pathways and airway pathophysiology, and thus helped to shape our understanding of allergen-driven asthma phenotypes and endotypes. In addition, ABT has been instrumental to assess the interactions and effects of new-targeted asthma treatments along these pathways.

Anti-alarmins in asthma: targeting the airway epithelium with next-generation biologics

Monoclonal antibody therapies have significantly improved treatment outcomes for patients with severe asthma; however, a significant disease burden remains. Available biologic treatments, including anti-immunoglobulin (Ig)E, anti-interleukin (IL)-5, anti-IL-5Rα and anti-IL-4Rα, reduce exacerbation rates in study populations by approximately 50% only. Furthermore, there are currently no effective treatments for patients with severe, type 2-low asthma. Existing biologics target immunological pathways that are downstream in the type 2 inflammatory cascade, which may explain why exacerbations are only partly abrogated. For example, type 2 airway inflammation results from several inflammatory signals in addition to IL-5. Clinically, this can be observed in how fractional exhaled nitric oxide (F eNO), which is driven by IL-13, may remain unchanged during anti-IL-5 treatment despite reduction in eosinophils, and how eosinophils may remain unchanged during anti-IL-4Rα treatment despite reduction in F eNO The broad inflammatory response involving cytokines including IL-4, IL-5 and IL-13 that ultimately results in the classic features of exacerbations (eosinophilic inflammation, mucus production and bronchospasm) is initiated by release of "alarmins" thymic stromal lymphopoietin (TSLP), IL-33 and IL-25 from the airway epithelium in response to triggers. The central, upstream role of these epithelial cytokines has identified them as strong potential therapeutic targets to prevent exacerbations and improve lung function in patients with type 2-high and type 2-low asthma. This article describes the effects of alarmins and discusses the potential role of anti-alarmins in the context of existing biologics. Clinical phenotypes of patients who may benefit from these treatments are also discussed, including how biomarkers may help identify potential responders.

Serum levels of epithelial-derived mediators and interleukin-4/interleukin-13 signaling after bronchial challenge with Dermatophagoides pteronyssinus in patients with allergic asthma

Allergens are the main trigger that enhances airway type 2 inflammation, and the epithelium is the first line of defense that reacts to its exposure. Therefore, epithelial-derived mediators, such as interleukin (IL)-25, IL-33, thymic stromal lymphopoietin (TSLP) and ezrin, may play a role as alarmins in IL-4/IL-13 signaling in allergic asthma (AA). We investigated the serum levels of IL-25, IL-33, TSLP, ezrin, IL-4 and IL-13, after bronchial challenge with Dermatophagoides pteronyssinus in patients with AA. We examined 18 subjects: nine steroid-free stable patients with AA sensitized to D. pteronyssinus and nine non-atopic healthy subjects (HS). Bronchial allergen challenge was performed using inhaled D. pteronyssinus allergen. IL-4, IL-13, IL-25, IL-33, TSLP and ezrin levels in serum were measured by ELISA at two time points - before and 24 hours after bronchial allergen challenge. The serum levels of IL-25, TSLP and ezrin did not differ between AA and HS groups at baseline. However, after allergen exposure, significant increases in serum levels of IL-25, TSLP and ezrin were observed only in patients with AA. The serum level of IL-33 at baseline was significantly higher in the AA group compared with HS, but the allergen challenge did not provoke an increase of this cytokine in any group. IL-4 and IL-13 levels were significantly higher at baseline in the AA group compared with HS and, after allergen exposure, were significantly increased in the AA group, with no effect on HS. Thus, the epithelial-derived mediators IL-25, TSLP and ezrin, via IL4/IL13 signaling, enhance type 2 inflammation after bronchial challenge with D. pteronyssinus in AA.

The Enhanced Adhesion of Eosinophils Is Associated with Their Prolonged Viability and Pro-Proliferative Effect in Asthma

Before eosinophils migrate into the bronchial lumen, they promote airway structural changes after contact with pulmonary cells and extracellular matrix components. We aimed to investigate the impact of eosinophil adhesion to their viability and pro-proliferative effect on airway smooth muscle (ASM) cells and pulmonary fibroblasts during different asthma phenotypes. A total of 39 individuals were included: 14 steroid-free non-severe allergic asthma (AA) patients, 10 severe non-allergic eosinophilic asthma (SNEA) patients, and 15 healthy control subjects (HS). For AA patients and HS groups, a bronchial allergen challenge with Dermatophagoides pteronysinnus was performed. Individual combined cells cultures were prepared between isolated peripheral blood eosinophils and ASM cells or pulmonary fibroblasts. Eosinophil adhesion was measured by evaluating their peroxidase activity, cell viability was performed by annexin V and propidium iodide staining, and proliferation by Alamar blue assay. We found that increased adhesion of eosinophils was associated with prolonged viability (p < 0.05) and an enhanced pro-proliferative effect on ASM cells and pulmonary fibroblasts in asthma (p < 0.05). However, eosinophils from SNEA patients demonstrated higher viability and inhibition of pulmonary structural cell apoptosis, compared to the AA group (p < 0.05), while their adhesive and pro-proliferative properties were similar. Finally, in the AA group, in vivo allergen-activated eosinophils demonstrated a higher adhesion, viability, and pro-proliferative effect on pulmonary structural cells compared to non-activated eosinophils (p < 0.05).

Recent Advances in Clinical Allergy and Immunology

Allergic diseases are of great concern because of their high prevalence, which is still rising in several regions, their impact on patients' physical and psychological health, the huge burden they place on patients' quality of life, as well as the socioeconomic consequences that they cause. Recent research has provided new data on both genetic and environmental risk factors of atopic/allergic diseases. The application of new technologies such as "omics" has allowed a better understanding of the pathogenesis and has helped with the identification of therapeutic targets. Immense progress has been made in developing and applying novel, targeted therapies, for example for asthma and urticaria. Intensive efforts are being made to find biomarkers that help to classify patients, to identify their potential responsiveness to specific therapies, and to monitor the disease severity. Based on recent insights in the pathogenesis of food allergy and drug hypersensitivity, novel strategies for diagnostics, allergen avoidance, and induction of tolerance have been developed. Here, we summarize important findings in the field of clinical allergy and immunology with a special focus on asthma, allergic rhinitis, atopic dermatitis, food allergy, urticaria, angioedema, and drug hypersensitivity.

Biological Properties and the Role of IL-25 in Disease Pathogenesis

The interleukin- (IL-) 17 superfamily, a T cell-derived cytokine, consists of 6 ligands (IL-17A-IL-17F) and 5 receptors (IL-17RA-IL-17RE). IL-17A, a prototype member of this family, is involved in the pathogenesis of allergies, autoimmune diseases, allograft transplantations, and malignancies. By contrast, IL-17B is reported to be closely related to certain diseases, particularly tumors such as breast cancer, gastric cancer, and pancreatic cancer. Recently, the biological function of IL-17E (also called IL-25) in disease, particularly airway diseases, has attracted the attention of researchers. However, studies on IL-25 are scant. In this review, we detail the structural characteristics, expression patterns, responder cells, biological properties, and role of IL-25 in disease pathogenesis.

Antialarmins for treatment of asthma: future perspectives

PURPOSE OF REVIEW

Recent studies have highlighted the role of alarmins in asthma pathophysiology and tested the roles of these cytokines in asthmatic patients. This review will discuss the recent advances in the role of alarmins in asthma and the potential of future targeted therapies in asthma.

RECENT FINDINGS

Epithelial-derived cytokines can be released upon exposure to external stimuli, causing damage to the epithelial barrier and resulting in tissue inflammation. Of these cytokines, IL-25, IL-33 and thymic stromal lymphopoeitin (TSLP), have been associated with asthma. These alarmins are all not only overexpressed in asthmatic airways, particularly in airway epithelial cells, but also in other structural and immune cells. Furthermore, all three alarmins drive type-2 pro-inflammatory responses in several immune cells that have been identified as key players in the pathogenesis of asthma, including innate lymphoid type-2 cells. Clinical trials testing therapeutics that block pathways of the alarmins are in progress.

SUMMARY

To-date, only TSLP blockade has been reported in human clinical trials, and this approach has shown efficacy in asthmatic patients. Current body of evidence suggests that alarmins are useful upstream targets for treatment of asthma.

Interleukin-25 and eosinophils progenitor cell mobilization in allergic asthma

Background

Eosinophil-lineage committed progenitor cells (EoP) migrate from the bone marrow and differentiate locally to provide an ongoing source of mature eosinophils in asthmatic inflammatory responses in the airways. Sputum levels of EoP are increased in asthmatics compared to normal controls suggesting an exaggerated eosinophilopoietic environment in the airways. Understanding what factors promote EoP traffic to the airways is important to understand the diathesis of asthma pathology. Interleukin (IL)-25, is an epithelial-derived cytokine that promotes type 2 inflammatory responses. We have previously shown that levels of IL-25 and expression of the IL-25 receptor (IL-17RA and IL-17RB) on mature eosinophils are greater in allergic asthmatics compared to atopic non-asthmatics and non-atopic normal controls. In addition, these levels were increased significantly increased following allergen inhalation challenge and physiologically relevant levels of IL-25 stimulated eosinophil degranulation, intracellular IL-5 and IL-13 expression and primed migration to eotaxin. The current study, examined the role of IL-25 on allergen-induced trafficking of EoP in atopic asthmatics.

Methods

Asthmatics (n = 14) who developed allergen-induced early and late responses were enrolled in the study. Blood was collected at pre- and 24 h post-challenge. At each time point, surface expression of IL-17RA and IL-17RB on EoP was evaluated by flow cytometry. Migration assays examined the effect of IL-25 on EoP chemotactic responses, in vitro. In addition, IL-25 knockout ovalbumin (OVA) sensitized and challenged mice were studied to evaluate in vivo mobilization effects of IL-25 on newly formed EoP and mature eosinophils.

Results

There was a significant increase in numbers of blood EoP expressing IL-17RB, 24 h post-allergen inhalation challenge in allergic asthmatics. Pre-exposure to IL-25 primed the migrational responsiveness of EoP to stromal cell-derived factor 1α. In OVA-sensitized mice, knocking out IL-25 significantly alleviated OVA-induced eosinophil infiltration in the airway and newly formed eosinophils were reduced in the lung.

Conclusions

The findings of this study indicate a potential role for IL-25 in allergen-induced trafficking of EoP to the airways and local differentiation promoting tissue eosiniophilia in asthmatic responses.

Asthma Biomarkers: Do They Bring Precision Medicine Closer to the Clinic?

Measurement of biomarkers has been incorporated within clinical research of asthma to characterize the population and to associate the disease with environmental and therapeutic effects. Regrettably, at present, there are no specific biomarkers, none is validated or qualified, and endotype-driven choices overlap. Biomarkers have not yet reached clinical practice and are not included in current asthma guidelines. Last but not least, the choice of the outcome upholding the value of the biomarkers is extremely difficult, since it has to reflect the mechanistic intervention while being relevant to both the disease and the particular person. On the verge of a new age of asthma healthcare standard, we must embrace and adapt to the key drivers of change. Disease endotypes, biomarkers, and precision medicine represent an emerging model of patient care building on large-scale biologic databases, omics and diverse cellular assays, health information technology, and computational tools for analyzing sizable sets of data. A profound transformation of clinical and research pattern from population to individual risk and from investigator-imposed subjective disease clustering (hypothesis driven) to unbiased, data-driven models is facilitated by the endotype/biomarker-driven approach.