Sputum interleukin-25 correlates with asthma severity: a preliminary study

Immunotherapeutic implications on targeting the cytokines produced in rhinovirus-induced immunoreactions

Rhinovirus is a widespread virus associated with several respiratory diseases, especially asthma exacerbation. Currently, there are no accurate therapies for rhinovirus. Encouragingly, it is found that during rhinovirus-induced immunoreactions the levels of certain cytokines in patients' serum will alter. These cytokines may have pivotal pro-inflammatory or anti-inflammatory effects via their specific mechanisms. Thus far, studies have shown that inhibitions of cytokines such as IL-1, IL-4, IL-5, IL-6, IL-13, IL-18, IL-25, and IL-33 may attenuate rhinovirus-induced immunoreactions, thereby relieving rhinovirus infection. Furthermore, such therapeutics for rhinovirus infection can be applied to viruses of other species, with certain practicability.

Airway remodelling in asthma and the epithelium: on the edge of a new era

Asthma is a chronic, heterogeneous disease of the airways, often characterised by structural changes known collectively as airway remodelling. In response to environmental insults, including pathogens, allergens and pollutants, the epithelium can initiate remodelling via an inflammatory cascade involving a variety of mediators that have downstream effects on both structural and immune cells. These mediators include the epithelial cytokines thymic stromal lymphopoietin, interleukin (IL)-33 and IL-25, which facilitate airway remodelling through cross-talk between epithelial cells and fibroblasts, and between mast cells and airway smooth muscle cells, as well as through signalling with immune cells such as macrophages. The epithelium can also initiate airway remodelling independently of inflammation in response to the mechanical stress present during bronchoconstriction. Furthermore, genetic and epigenetic alterations to epithelial components are believed to influence remodelling. Here, we review recent advances in our understanding of the roles of the epithelium and epithelial cytokines in driving airway remodelling, facilitated by developments in genetic sequencing and imaging techniques. We also explore how new and existing therapeutics that target the epithelium and epithelial cytokines could modify airway remodelling.

The airway epithelium: an orchestrator of inflammation, a key structural barrier and a therapeutic target in severe asthma

Asthma is a disease of heterogeneous pathology, typically characterised by excessive inflammatory and bronchoconstrictor responses to the environment. The clinical expression of the disease is a consequence of the interaction between environmental factors and host factors over time, including genetic susceptibility, immune dysregulation and airway remodelling. As a critical interface between the host and the environment, the airway epithelium plays an important role in maintaining homeostasis in the face of environmental challenges. Disruption of epithelial integrity is a key factor contributing to multiple processes underlying asthma pathology. In this review, we first discuss the unmet need in asthma management and provide an overview of the structure and function of the airway epithelium. We then focus on key pathophysiological changes that occur in the airway epithelium, including epithelial barrier disruption, immune hyperreactivity, remodelling, mucus hypersecretion and mucus plugging, highlighting how these processes manifest clinically and how they might be targeted by current and novel therapeutics.

Tezepelumab: patient selection and place in therapy in severe asthma

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

Epithelial alarmins: a new target to treat chronic respiratory diseases

INTRODUCTION

In response to injury, epithelial cells release alarmins including thymic stromal lymphopoietin (TSLP), high mobility group-box-1 (HMGB1), interleukin (IL)-33 and -25 that can initiate innate immune responses. These alarmins are recognized as activators of T2-immune responses characteristic for asthma, but recent evidence highlighted their role in non-T2 inflammation, airway remodeling, and pulmonary fibrosis making them an attractive therapeutic target for chronic respiratory diseases (CRD).

AREAS COVERED

In this review, firstly we discuss the role of TSLP, IL-33, IL-25, and HMGB1 in the pathogenesis of asthma, COPD, idiopathic pulmonary fibrosis, and cystic fibrosis according to the published data. In the second part, we summarize the current evidence concerning the efficacy of the antialarmin therapies in CRD. Recent clinical trials showed that anti-TSLP and IL-33/R antibodies can improve severe asthma outcomes. Blocking the IL-33-mediated pathway decreased the exacerbation rate in COPD patients with more important benefit for former-smokers.

EXPERT OPINION

Despite progress in the understanding of the alarmins' role in the pathogenesis of CRD, all their mechanisms of action are not yet identified. Blocking IL-33 and TSLP pathways offers an interesting option to treat severe asthma and COPD, but future investigations are needed to establish their place in the treatment strategies.

Airway remodeling heterogeneity in asthma and its relationship to disease outcomes

Asthma affects an estimated 262 million people worldwide and caused over 461,000 deaths in 2019. The disease is characterized by chronic airway inflammation, reversible bronchoconstriction, and airway remodeling. Longitudinal studies have shown that current treatments for asthma (inhaled bronchodilators and corticosteroids) can reduce the frequency of exacerbations, but do not modify disease outcomes over time. Further, longitudinal studies in children to adulthood have shown that these treatments do not improve asthma severity or fixed airflow obstruction over time. In asthma, fixed airflow obstruction is caused by remodeling of the airway wall, but such airway remodeling also significantly contributes to airway closure during bronchoconstriction in acute asthmatic episodes. The goal of the current review is to understand what is known about the heterogeneity of airway remodeling in asthma and how this contributes to the disease process. We provide an overview of the existing knowledge on airway remodeling features observed in asthma, including loss of epithelial integrity, mucous cell metaplasia, extracellular matrix remodeling in both the airways and vessels, angiogenesis, and increased smooth muscle mass. While such studies have provided extensive knowledge on different aspects of airway remodeling, they have relied on biopsy sampling or pathological assessment of lungs from fatal asthma patients, which have limitations for understanding airway heterogeneity and the entire asthma syndrome. To further understand the heterogeneity of airway remodeling in asthma, we highlight the potential of in vivo imaging tools such as computed tomography and magnetic resonance imaging. Such volumetric imaging tools provide the opportunity to assess the heterogeneity of airway remodeling within the whole lung and have led to the novel identification of heterogenous gas trapping and mucus plugging as important predictors of patient outcomes. Lastly, we summarize the current knowledge of modification of airway remodeling with available asthma therapeutics to highlight the need for future studies that use in vivo imaging tools to assess airway remodeling outcomes.

IL-17 Cytokines and Chronic Lung Diseases

IL-17 cytokines are expressed by numerous cells (e.g., gamma delta (γδ) T, innate lymphoid (ILC), Th17, epithelial cells). They contribute to the elimination of bacteria through the induction of cytokines and chemokines which mediate the recruitment of inflammatory cells to the site of infection. However, IL-17-driven inflammation also likely promotes the progression of chronic lung diseases, such as chronic obstructive pulmonary disease (COPD), lung cancer, cystic fibrosis, and asthma. In this review, we highlight the role of IL-17 cytokines in chronic lung diseases.

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.

The expression of IL17RA on sputum macrophages in asthma patients

IL-17A and IL-25 (IL-17 cytokines family) play an important role in the development of asthma, and allergy. Both cytokines act by binding to heterodimeric receptors with IL17RA as a common subunit. This receptor is found on macrophages, and some other cell types. The aim of the study was to determine the expression of IL17RA on asthmatic and control macrophages from induced sputum (IS) with the regard to IL-17/IL-25 background and relation to clinical features of the disease. We found an elevated expression of IL17RA on sputum macrophages in asthma patients vs controls. A characteristic sputum profile of atopic asthmatic was as follows: high CD206 + IL17RA + macrophage percentage, elevated IL-25 level and low CD206 + IL17RA- macrophage percentage. Based on the above results, it seems that CD206 + sputum macrophages are the effector cells that express common subunit of the receptor for IL-17A and IL-25 in asthma. This may be related to the Th2-dependent environment in asthma and increased concentrations of IL-25 and IL-13 as well as eosinophils in the airways. To our knowledge, our study provides the first data on a possible link between immunological reaction orchestrating CD206 + expressing sputum macrophages and IL-25 via IL17RA pathway in the asthmatic airways.

Sputum IL-25, IL-33 and TSLP, IL-23 and IL-36 in airway obstructive diseases. Reduced levels of IL-36 in eosinophilic phenotype

INTRODUCTION

Alarmins ((IL-25, IL-33 and thymic stromal lymphopoietin (TSLP)) are known to promote Th2 inflammation and could be associated with eosinophilic airway infiltration. They may also play a role in airway remodeling in chronic airway obstructive diseases such as asthma and chronic obstructive pulmonary disease (COPD). IL-23 and IL-36 were shown to mediate the neutrophilic airway inflammation as seen in chronic airway obstructive diseases.

OBJECTIVES

The purpose of this project was to determine the expression and the production of these cytokines from induced sputum (IS) in patients with chronic airway obstructive diseases including asthmatics and COPD. The relationship of the mediators with sputum inflammatory cellular profile and the severity of airway obstruction was assessed.

METHODS

The alarmins (IL-25, IL-33 and TSLP) as well as IL-23 and IL-36 concentrations were measured in IS from 24 asthmatics and 20 COPD patients compared to 25 healthy volunteers. The cytokines were assessed by ELISA in the IS supernatant and by RT-qPCR in the IS cells.

RESULTS

At protein level, no difference was observed between controls and patients suffering from airway obstructive diseases regarding the different mediators. IL-36 protein level was negatively correlated with sputum eosinophil and appeared significantly decreased in patients with an eosinophilic airway inflammation compared to those with a neutrophilic profile and controls. At gene level, only IL-36, IL-23 and TSLP were measurable but none differed between controls and patients with airway obstructive diseases. IL-36 and IL-23 were significantly increased in patients with an neutrophilic inflammatory profile compared to those with an eosinophilic inflammation and were correlated with sputum neutrophil proportions. None of the mediators were linked to airway obstruction.

CONCLUSIONS

The main finding of our study is that patients with eosinophilic airway inflammation exhibited a reduced IL-36 level which could make them more susceptible to airway infections as IL-36 is implicated in antimicrobial defense. This study showed also an implication of IL-36 and IL-23 in airway neutrophilic inflammation in chronic airway obstructive diseases.

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.

Blocking epithelial alarmins, upstream mediators triggered early in the asthma inflammatory response that orchestrate broad inflammatory effects, is a promising alternative approach to asthma treatment, which may be effective in a broad patient population https://bit.ly/2zqoXAw

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

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