Biomarkers for Severe Asthma: Lessons From Longitudinal Cohort Studies

Regional challenges to optimize the management of patients with severe asthma type 2 inflammation: a Delphi consensus in seven countries

Objective:Severe asthma burdens patients and presents clinical management challenges for healthcare professionals. Biologics are crucial interventions for severe type two (T2) patients with high eosinophil counts. We conducted a Delphi consensus in seven developing or typically underrepresented countries to understand expert agreement on managing severe asthma with type two (T2) inflammation.

Methods:The study comprised two online survey rounds and a participant meeting, involving 21 and 20 respiratory experts in the first and second survey, respectively. We developed a 70-statement questionnaire after literature review. Responses were recorded on a Likert scale (0-9) with 75% consensus threshold.

Results:Consensus was reached on 37/60 closed-ended questions, including subtypes, in survey-1 and 20/47 closed-ended questions in survey-2. 95% of participants agreed on biomarker use for biologic treatment selection. 100% agreed timely biologic treatment leads to improvement in patients with severe asthma and an eosinophilic phenotype. 90% agreed to avoid maintenance oral corticosteroids (OCS) and start biologic therapy directly. Experts defined clinical remission on treatment as no exacerbations, no OCS use, Asthma Control Questionnaire (ACQ)-5 score < 1.5, and lung function optimization (forced expiratory volume in one second [FEV1] ≥ 80% of predicted or pre-bronchodilator FEV1 increase ≥ 100 mL from baseline). In survey-1, 81% agreed these outcomes are achievable in practice. All referral statements achieved consensus.

Conclusions:This Delphi study focused on understanding patients with severe asthma and T2 inflammation in developing/underrepresented countries. Appropriately utilizing biomarkers, timely treatment interventions for best outcomes, expert consensus on clinical remission, and referral are crucial for improving patient management.

Bryostatins 1 and 3 inhibit TRPM8 and modify TRPM8- and TRPV1-mediated lung epithelial cell responses to a proinflammatory stimulus via protein kinase C

Bryostatin 1 is a protein kinase C (PKC α, β, δ) activator with anti-inflammatory effects. We hypothesized that bryostatins 1 and 3 could modulate transient receptor potential (TRP) channels via PKC and alter TRP-mediated proinflammatory signaling in lung epithelial cells challenged with a proinflammatory stimulus, coal fly ash (CFA). Bryostatins 1 and 3 inhibited icilin-induced calcium flux in HEK-293 cells overexpressing full-length human transient receptor potential melastatin-8 (TRPM8) but did not inhibit activation by menthol or the activities of human transient receptor potential ankyrin 1, transient receptor potential vanilloid 1 (TRPV1), TRPV3, or TRPV4; mouse and rat TRPM8 were less sensitive to inhibition. TRPM8 inhibition was transient (<24 hours), PKC-dependent, and involved differential phosphorylation of amino acids T17, S27, S850, and S1040. CFA particles stimulate interleukin-8 (IL8) and C-X-C motif chemokine ligand 1 (CXCL1) expression by human bronchial epithelial cells via activation of truncated TRPM8 (TRPM8-Δ801) and TRPV1. However, bryostatins 1 and 3 altered IL8 and CXCL1 mRNA expression with and without CFA treatment. At 4 hours, the bryostatins also suppressed TRPM8 mRNA and induced TRPV1 mRNA, which reversed at 24 hours. These effects were reversed by pharmacological inhibition of PKC isoforms (α, ζ, ε, or η) but not δ, implying a network comprised of presumably PKCα, TRPM8-Δ801, and TRPV1 that regulates IL8 and CXCL1 expression by airway epithelial cells. Finally, an unexpected interaction between TRPV1 and TRPM8, but not TRPM8-Δ801, was also identified. Specifically, the coexpression of TRPM8 and TRPV1 reduced TRPM8 expression and activity, which was reversed by TRPV1 inhibition, revealing novel mechanisms by which bryostatins and PKC affect TRP channel signaling in lung epithelial and potentially other cell types. SIGNIFICANCE STATEMENT: Bryostatins 1 and 3 selectively and transiently inhibit human TRPM8 activity via protein kinase C-dependent phosphorylation and temporally modify the expression and induction of interleukin-8 and C-X-C motif chemokine ligand 1 in lung epithelial cells by regulating TRPV1 and TRPM8 expression. This regulatory nexus may have therapeutic potential for treating airway inflammation.

Bacterial Extracellular Vesicles: Potential Therapeutic Applications, Challenges, and Future Prospects

Almost all cell types naturally secret extracellular vesicles (EVs) in the extracellular space with variable metabolic cargo facilitating intracellular communication, posing immune-modulation capacity. Thus, "bacterial extracellular vesicles" (BEVs), with their great immunoregulatory, immune response stimulation and disease condition-altering potential, have gained importance in the medical and therapeutic industry. Various subtypes of BEVs were observed and reported in the literature, such as exosomes (30-150 nm), microvesicles (100-1000 nm), apoptotic bodies (1000-5000 nm), and oncosomes (1000-10,000 nm). As biological systems are complex entities, inserting BEVs requires extra high purity. Various techniques for BEV isolation have been employed alone or with other strategies, such as ultracentrifugation, precipitation, size-exclusion chromatography, affinity-based separation, ultrafiltration, and field-flow fractionation. But to date, no BEV isolation method is considered perfect as the lack of standard protocols limits their scale-up. Medical research has focused on BEVs to explore their diverse therapeutic potential. This review particularly focused on the recent advancements in the potential medical application of BEVs, current challenges, and prospects associated with their scale-up.

Update on Inflammatory Biomarkers for Defining Asthma Phenotype

Asthma is a chronic heterogeneous disease characterized by various symptoms and persistent airway inflammation, resulting in progressive lung function decline. Classifying asthma phenotypes/endotypes is crucial because the underlying mechanisms and long-term outcomes vary from patient to patient. Recent trials have identified several biomarkers for classifying asthma phenotypes/endotypes, and current treatments have been developed on the basis of these biomarkers. Conventional biomarkers, including immunoglobulin E, blood/sputum eosinophil counts, airway obstruction or reversibility, and fractional exhaled nitric oxide, are widely used to diagnose asthma. However, these markers have some limitations, necessitating the discovery of additional biomarkers. Therefore, this review summarizes recently suggested biomarkers for representing type 2-high (eosinophilic) vs. type 2-low (neutrophilic) asthma, non-steroidal anti-inflammatory drug-exacerbated respiratory disease, and severe asthma. Additionally, we discuss the potential benefits of these biomarkers in classifying specific phenotypes/endotypes and managing asthmatic patients.

Serum Galectin-10: A biomarker for persistent airflow limitation in adult asthmatics

Background

Inhaled corticosteroids (ICS) are primary anti-inflammatory medications to control eosinophilic airway inflammation, and prevent asthma exacerbation. However, persistent airflow limitation (PAL) presents in some asthmatics even on ICS treatment, leading to lung function decline. Thus, we evaluated clinical associations of serum galectin-10 (Gal10) and galectin-3 (Gal3) levels in adult asthmatics who had maintained anti-asthma medication.

Methods

Sixty-seven asthmatics and 78 healthy controls (HCs) were recruited. Serum Gal10 and Gal3 levels were measured by enzyme-linked immunosorbent assay, and their clinical relevance with inflammatory and lung function parameters was evaluated. Spirometry was performed to assess PAL and small airway dysfunction (SAD). Airway epithelial cells were cocultured with eosinophils/neutrophils, and were exposed to house dust mites to assess the production of Gal10 and Gal3.

Results

Serum Gal10 (not Gal3) levels were significantly higher in asthmatics than in HCs (P < 0.001), in asthmatics with PAL than in those without PAL (P = 0.005), and in those with SAD than in those without SAD (P = 0.004). The Gal10-high group had significantly higher levels of peripheral CD66+ neutrophil counts, serum periostin and Gal3, and lower values of FEV1% and MMEF% than the Gal10-low group (P < 0.050 for all). The production of Gal10 and Gal3 was increased in eosinophilic airway model, while Gal10 (not Gal3) levels were increased in neutrophilic airway model as well as house dust mite stimulation.

Conclusion

Our findings suggest that serum Gal10 level may be a potential biomarker for PAL in adult asthmatics.

The Cytochrome P450 2C8*3 Variant (rs11572080) Is Associated with Improved Asthma Symptom Control in Children and Altered Lipid Mediator Production and Inflammatory Response in Human Bronchial Epithelial Cells

This study investigated an association between the cytochrome P450 (CYP) 2C8*3 polymorphism with asthma symptom control in children and changes in lipid metabolism and pro-inflammatory signaling by human bronchial epithelial cells (HBECs) treated with cigarette smoke condensate (CSC). CYP genes are inherently variable in sequence, and while such variations are known to produce clinically relevant effects on drug pharmacokinetics and pharmacodynamics, the effects on endogenous substrate metabolism and associated physiologic processes are less understood. In this study, CYP2C8*3 was associated with improved asthma symptom control among children: Mean asthma control scores were 3.68 (n = 207) for patients with one or more copies of the CYP2C8*3 allele versus 4.42 (n = 965) for CYP2C8*1/*1 (P = 0.0133). In vitro, CYP2C8*3 was associated with an increase in montelukast 36-hydroxylation and a decrease in linoleic acid metabolism despite lower mRNA and protein expression. Additionally, CYP2C8*3 was associated with reduced mRNA expression of interleukin-6 (IL-6) and C-X-C motif chemokine ligand 8 (CXCL-8) by HBECs in response to CSC, which was replicated using the soluble epoxide hydrolase inhibitor, 12-[[(tricyclo[3.3.1.13,7]dec-1-ylamino)carbonyl]amino]-dodecanoic acid. Interestingly, 9(10)- and 12(13)- dihydroxyoctadecenoic acid, the hydrolyzed metabolites of 9(10)- and 12(13)- epoxyoctadecenoic acid, increased the expression of IL-6 and CXCL-8 mRNA by HBECs. This study reveals previously undocumented effects of the CYP2C8*3 variant on the response of HBECs to exogenous stimuli. SIGNIFICANCE STATEMENT: These findings suggest a role for CYP2C8 in regulating the epoxyoctadecenoic acid:dihydroxyoctadecenoic acid ratio leading to a change in cellular inflammatory responses elicited by environmental stimuli that exacerbate asthma.

8-Iso-prostaglandin F2α as a biomarker of type 2 low airway inflammation and remodeling in adult asthma

BACKGROUND

Although 8-iso-prostaglandin F2a has been proposed as a potential biomarker for oxidative stress in airway diseases, its specific role in asthma remains poorly understood.

OBJECTIVE

To evaluate the diagnostic potential of 8-iso-prostaglandin F2a in assessing airway inflammation, airway remodeling, airway hyperresponsiveness, and oxidative stress in asthma.

METHODS

Blood and urine concentrations of 8-iso-prostaglandin F2a were quantified using liquid chromatography-tandem mass spectrometry in 128 adults with asthma who had maintained antiasthma medications. Their correlations with clinical data, sputum cell counts, lung function parameters, and serum markers of epithelial/neutrophil activity and airway remodeling were then analyzed.

RESULTS

The urinary 8-iso-prostaglandin F2a concentrations were significantly higher in patients with noneosinophilic asthma than in those with eosinophilic asthma (P < .05). The area under the curve was 0.678, indicating moderate diagnostic accuracy for noneosinophilic asthma. There were significant correlations with neutrophilic inflammation markers and airway remodeling markers (all P < .05). Negative correlations were observed with forced expiratory volume in 1 second (%), forced expiratory volume in 1 second/forced vital capacity, forced expiratory flow at 25% to 75% of forced vital capacity, and serum club cell protein 16 levels (all P < .05). High 8-iso-prostaglandin F2a concentrations were also noted in obese and smoking subgroups (all P < .05). However, the serum 8-iso-prostaglandin F2a concentrations were not correlated with these asthma-related parameters.

CONCLUSION

Urinary 8-iso-prostaglandin F2a concentrations are a potential biomarker for phenotyping severe asthma, particularly noneosinophilic asthma, offering oxidative stress-induced epithelial inflammation/remodeling as an additional target in asthma management.

Lactobacillus paracasei-derived extracellular vesicles alleviate neutrophilic asthma by inhibiting the JNK pathway in airway epithelium

BACKGROUND

Lactobacillus paracasei has been known to reduce airway resistance and inflammation in asthma. However, the therapeutic effect of its extracellular vesicles (EVs) in patients with asthma remains unclear.

METHODS

To validate the clinical relevance of L. paracasei-derived EVs (LpEV) in asthma, the composition of gut microbial EVs was verified by metagenomics in LPS-induced C57BL/6 mice. The components of proteins and metabolites in LpEV were identified by peptide mass fingerprinting and metabolomic analysis. The serum levels of specific IgG1 or IgG4 antibodies to LpEV were compared by ELISA between patients with eosinophilic asthma (EA, n = 10) and those with neutrophilic asthma (NA, n = 10) as well as with healthy controls (HCs, n = 10). Finally, therapeutic effects of LpEV and their metabolites in asthma were validated in vivo/in vitro.

RESULTS

Significantly lower proportions of EVs derived from Lactobacillus at the genus level were noted in mice with NA than in control mice. Moreover, the serum levels of LpEV-specific IgG4, but not IgG1, were lower in patients with NA than in those with EA or in HCs and positively correlated with FEV1 (%) values. In addition, oral administration of LpEV reduced airway resistance and inflammation in mice with NA. Finally, LpEV and their 3 metabolites (dodecanoic acid, palmitoleic acid, and D-(-)-tagatose) significantly inhibited JNK phosphorylation/IL-8 production in airway epithelium in vitro.

CONCLUSIONS

These findings suggest that LpEV may have a therapeutic potential targeting NA by suppressing the JNK pathway and proinflammatory cytokine production in airway epithelium.

Phenotyping of Severe Asthma in the Era of Broad-Acting Anti-Asthma Biologics

Severe asthma is associated with significant morbidity and mortality despite the maximal use of inhaled corticosteroids and additional controller medications, and has a high economic burden. Biologic therapies are recommended for the management of severe, uncontrolled asthma to help to prevent exacerbations and to improve symptoms and health-related quality of life. The effective management of severe asthma requires consideration of clinical heterogeneity that is driven by varying clinical and inflammatory phenotypes, which are reflective of distinct underlying disease mechanisms. Phenotyping patients using a combination of clinical characteristics such as the age of onset or comorbidities and biomarker profiles, including blood eosinophil counts and levels of fractional exhaled nitric oxide and serum total immunoglobulin E, is important for the differential diagnosis of asthma. In addition, phenotyping is beneficial for risk assessment, selection of treatment, and monitoring of the treatment response in patients with asthma. This review describes the clinical and inflammatory phenotypes of asthma, provides an overview of biomarkers routinely used in clinical practice and those that have recently been explored for phenotyping, and aims to assess the value of phenotyping in severe asthma management in the current era of biologics.

ST2-Mediated Neutrophilic Airway Inflammation: A Therapeutic Target for Patients With Uncontrolled Asthma

PURPOSE

Suppression of tumorigenicity 2 (ST2) has been proposed as the receptor contributing to neutrophilic inflammation in patients with type 2-low asthma. However, the exact role of ST2 in neutrophil activation remains poorly understood.

METHODS

A total of 105 asthmatic patients (classified into 3 groups according to control status: the controlled asthma [CA], partly-controlled asthma [PA], and uncontrolled asthma [UA] groups), and 104 healthy controls were enrolled to compare serum levels of soluble ST2 (sST2) and interleukin (IL)-33. Moreover, the functions of ST2 in neutrophils and macrophages (Mϕ) were evaluated ex vivo and in vivo.

RESULTS

Serum sST2 levels were significantly higher in the UA group than in the CA or PA groups (P < 0.05 for all) with a negative correlation between serum sST2 and forced expiratory volume in 1 second % (r = -0.203, P = 0.038). Significantly higher expression of ST2 receptors on peripheral neutrophils was noted in the UA group than in the PA or CA groups. IL-33 exerted its effects on the production of reactive oxygen species, the formation of extracellular traps from neutrophils, and Mϕ polarization/activation. In neutrophilic asthmatic mice, treatment with anti-ST2 antibody significantly suppressed proinflammatory cytokines (tumor necrosis factor-alpha and IL-17A) as well as the numbers of immune cells (neutrophils, Mϕ, and group 3 innate lymphoid cells) in the lungs.

CONCLUSIONS

These results suggest that IL-33 induces the activation of neutrophils and Mϕ via ST2 receptors, leading to neutrophilic airway inflammation and poor control status of asthma. ST2 could be a therapeutic target for neutrophilic airway inflammation in patients with UA.

Association between asthma, rhinitis and atopic dermatitis with leprosy: A case-control study

Background Considering the cross-regulation of Th1 and Th2 responses, we hypothesised that atopic diseases (Th2) inhibit the protective Th1 immune response to Mycobacterium leprae and exacerbates leprosy. Objective In this study, we aimed to evaluate the association between leprosy and atopic diseases. Methods To evaluate the association of atopic diseases with leprosy, we conducted a case-control study that included leprosy patients (n = 333) and their household contacts (n = 93). The questionnaire from the International Study of Asthma and Allergies in Childhood, which is validated in several countries for epidemiological diagnosis of atopic diseases, was applied to determine the occurrence of atopic diseases, allergic rhinitis, asthma, and atopic dermatitis among leprosy patients and the household contacts. Results Considering clinical and epidemiological data, among the leprosy group 51.6% (n = 172) were determined to have at least one atopic disease, while atopy was observed less frequently at 40.86% among household contacts (n = 38). When two or more atopic diseases were assessed, the frequency was significantly higher among the leprosy patients than in the household contacts (21.9% vs. 11.8%; P-value = 0.03). Likewise, the frequency of asthma was significantly higher among leprosy patients (21%) than in the household contacts (10.8%; P-value = 0.02). Thus, our analyses revealed an association of atopic diseases with leprosy, with a significant linear increase in the occurrence of leprosy with an increase in the number of atopic diseases (P-value = 0.01). Limitation Due to the difficulties in recruiting household contacts that have prolonged contact with patients, but are not genetically related to the patient, the household contacts group is smaller than the leprosy patient group. Conclusion The data reveal an association between atopic diseases and leprosy outcomes. This knowledge could improve the treatment of leprosy patients with co-incident atopic diseases.

Eosinophil extracellular traps in asthma: implications for pathogenesis and therapy

Asthma is a common, chronic inflammatory disease of the airways that affects millions of people worldwide and is associated with significant healthcare costs. Eosinophils, a type of immune cell, play a critical role in the development and progression of asthma. Eosinophil extracellular traps (EETs) are reticular structures composed of DNA, histones, and granulins that eosinophils form and release into the extracellular space as part of the innate immune response. EETs have a protective effect by limiting the migration of pathogens and antimicrobial activity to a controlled range. However, chronic inflammation can lead to the overproduction of EETs, which can trigger and exacerbate allergic asthma. In this review, we examine the role of EETs in asthma.

The Dual Role of the Airway Epithelium in Asthma: Active Barrier and Regulator of Inflammation

Chronic airway inflammation is the cornerstone on which bronchial asthma arises, and in turn, chronic inflammation arises from a complex interplay between environmental factors such as allergens and pathogens and immune cells as well as structural cells constituting the airway mucosa. Airway epithelial cells (AECs) are at the center of these processes. On the one hand, they represent the borderline separating the body from its environment in order to keep inner homeostasis. The airway epithelium forms a multi-tiered, self-cleaning barrier that involves an unstirred, discontinuous mucous layer, the dense and rigid mesh of the glycocalyx, and the cellular layer itself, consisting of multiple, densely interconnected cell types. On the other hand, the airway epithelium represents an immunologically highly active tissue once its barrier has been penetrated: AECs play a pivotal role in releasing protective immunoglobulin A. They express a broad spectrum of pattern recognition receptors, enabling them to react to environmental stressors that overcome the mucosal barrier. By releasing alarmins-proinflammatory and regulatory cytokines-AECs play an active role in the formation, strategic orientation, and control of the subsequent defense reaction. Consequently, the airway epithelium is of vital importance to chronic inflammatory diseases, such as asthma.

Long-term clinical outcomes of aspirin-exacerbated respiratory disease: Real-world data from an adult asthma cohort

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is a phenotype of severe asthma, but its disease course has not been well documented compared with that of aspirin-tolerant asthma (ATA).

OBJECTIVES

This study aimed to investigate the long-term clinical outcomes between AERD and ATA.

METHODS

AERD patients were identified by the diagnostic code and positive bronchoprovocation test in a real-world database. Longitudinal changes in lung function, blood eosinophil/neutrophil counts, and annual numbers of severe asthma exacerbations (AEx) were compared between the AERD and the ATA groups. Within a year after baseline, two or more severe AEx events indicated severe AERD, whereas less than two AEx events indicated nonsevere AERD.

RESULTS

Among asthmatics, 353 had AERD in which 166 and 187 patients had severe and nonsevere AERD, respectively, and 717 had ATA. AERD patients had significantly lower FEV1%, higher blood neutrophil counts, and higher sputum eosinophils (%) (all p < .05) as well as higher levels of urinary LTE4 and serum periostin, and lower levels of serum myeloperoxidase and surfactant protein D (all p < .01) than those with ATA. In a 10-year follow-up, the severe AERD group maintained lower FEV1% with more severe AEs than the nonsevere AERD group.

CONCLUSION AND CLINICAL RELEVANCE

We demonstrated that AERD patients presented poorer long-term clinical outcomes than ATA patients in real-world data analyses.

Tissue Inhibitor of Metalloproteinase-1 Enhances Eosinophilic Airway Inflammation in Severe Asthma

PURPOSE

Severe asthma (SA) is characterized by persistent airway inflammation and remodeling, followed by lung function decline. The present study aimed to evaluate the role of tissue inhibitor of metalloproteinase-1 (TIMP-1) in the pathogenesis of SA.

METHODS

We enrolled 250 adult asthmatics (54 with SA and 196 with non-SA) and 140 healthy controls (HCs). Serum TIMP-1 levels were determined by enzyme-linked immunosorbent assay. The release of TIMP-1 from airway epithelial cells (AECs) in response to stimuli as well as the effects of TIMP-1 on the activations of eosinophils and macrophages were evaluated in vitro and in vivo.

RESULTS

Significantly higher levels of serum TIMP-1 were noted in asthmatics than in HCs, in the SA group than in non-SA group, and in the type 2 SA group than in non-type 2 SA group (P < 0.01 for all). A negative correlation between serum TIMP-1 and FEV₁% values (r = -0.400, P = 0.003) was noted in the SA group. In vitro study demonstrated that TIMP-1 was released from AECs in response to poly I:C, IL-13, eosinophil extracellular traps (EETs) and in coculture with eosinophils. TIMP-1-stimulated mice showed eosinophilic airway inflammation, which was not completely suppressed by steroid treatment. In vitro and in vivo functional studies showed that TIMP-1 directly activated eosinophils and macrophages, and induced the release of EETs and macrophages to polarize toward M2 subset, which was suppressed by anti-TIMP-1 antibody.

CONCLUSIONS

These findings suggest that TIMP-1 enhances eosinophilic airway inflammation and that serum TIMP-1 may be a potential biomarker and/or therapeutic target for type 2 SA.

Eosinophilic Airway Diseases: From Pathophysiological Mechanisms to Clinical Practice

Eosinophils play a key role in airway inflammation in many diseases, such as allergic and non-allergic asthma, chronic rhinosinusitis with nasal polyps, and chronic obstructive pulmonary disease. In these chronic disabling conditions, eosinophils contribute to tissue damage, repair, remodeling, and disease persistence through the production a variety of mediators. With the introduction of biological drugs for the treatment of these respiratory diseases, the classification of patients based on clinical characteristics (phenotype) and pathobiological mechanisms (endotype) has become mandatory. This need is particularly evident in severe asthma, where, despite the great scientific efforts to understand the immunological pathways underlying clinical phenotypes, the identification of specific biomarkers defining endotypes or predicting pharmacological response remains unsatisfied. In addition, a significant heterogeneity also exists among patients with other airway diseases. In this review, we describe some of the immunological differences in eosinophilic airway inflammation associated with severe asthma and other airway diseases and how these factors might influence the clinical presentation, with the aim of clarifying when eosinophils play a key pathogenic role and, therefore, represent the preferred therapeutic target.

Baseline Characteristics of Patients Enrolled in Clinical Trials of Biologics for Severe Asthma as Potential Predictors of Outcomes

(1) Background: Over the past 20 years, monoclonal antibodies have been developed for the treatment of severe asthma, with numerous randomised controlled trials (RCTs) conducted to define their safety and efficacy. The growing availability of biologics, which until now have only been available for T2-high asthma, has been further enriched by the arrival of tezepelumab. (2) Methods: This review aims to evaluate the baseline characteristics of patients enrolled in RCTs of biologics for severe asthma to understand how they could potentially predict outcomes and how they can help differentiate between available options. (3) Results: The studies reviewed demonstrated that all biologic agents are effective in improving asthma control, especially with regard to reducing exacerbation rates and OCS use. As we have seen, in this regard, there are few data on omalizumab and none yet on tezepelumab. In analysing exacerbations and average doses of OCSs, pivotal studies on benralizumab have enrolled more seriously ill patients. Secondary outcomes, such as improvement in lung function and quality of life, showed better results-especially for dupilumab and tezepelumab. (4) Conclusion: Biologics are all effective, albeit with important differences. What fundamentally guides the choice is the patient's clinical history, the endotype represented by biomarkers (especially blood eosinophils), and comorbidities (especially nasal polyposis).

Micrococcus luteus-derived extracellular vesicles attenuate neutrophilic asthma by regulating miRNAs in airway epithelial cells

Bacterial extracellular vesicles (EVs) have been shown to regulate various pulmonary diseases, but their functions in asthma remain uncertain. To demonstrate the clinical significance of Micrococcus luteus-derived EVs (MlEVs) in asthma, we enrolled 45 asthmatic patients (20 patients with neutrophilic asthma [NA], 25 patients with eosinophilic asthma [EA]) and 40 healthy controls (HCs). When the prevalence of IgG1 and IgG4 specific to MlEVs was evaluated in serum by ELISA, lower levels of MlEV-specific IgG4 (but not IgG1) were noted in asthmatic patients than in HCs. Among asthmatic patients, significantly lower levels of MIEV-specific IgG4 were noted in patients with NA than in those with EA. Moreover, there was a positive correlation between serum MlEV-specific IgG4 levels and FEV₁ (%) values. In asthmatic C57BL/6 mice, MlEVs significantly attenuated neutrophilic airway inflammation by reducing the production of IL-1β and IL-17 in bronchoalveolar lavage fluid as well as the number of group 3 innate lymphoid cells (ILC3s) in lung tissues. To clarify the functional mechanism of MlEVs in NA, the effect of MlEVs on airway epithelial cells (AECs) and immune cells was investigated ex vivo. According to microarray analysis, MlEVs upregulated hsa-miR-4517 expression in AECs. Moreover, this miRNA could suppress IL-1β production by monocytes, resulting in the inhibition of ILC3 activation and neutrophil recruitment. These findings suggest that MlEVs could be a novel therapeutic agent for managing unresolved NA by regulating miRNA expression in AECs.

Calcium ionophore-activated platelets induce eosinophil extracellular trap formation

BACKGROUND

Platelets play a modulatory role in inflammatory response by secreting a vast array of granules and disintegrating into membrane-bound microparticles upon activation. The interplay between eosinophils and platelets is postulated to be implicated in the pathology of allergic airway inflammation. In this study, we investigated whether activated platelets can induce eosinophil extracellular trap (EET) formation, a cellular process by which activated eosinophils release net-like DNA fibers.

METHODS

Platelets were stimulated with the calcium ionophore, A23187, and the platelet agonists, thrombin and adenosine diphosphate (ADP). Platelet cultures were fractionated into conditioned medium (CM) and pellet, which were then overlaid on eosinophils to examine EET formation.

RESULTS

The CM and pellet from A23187-activated platelets stimulated eosinophils to generate EET, whereas those from thrombin- or ADP-activated platelets failed to induce such generation. The EET-inducing activity of the A23187-activated platelet culture was linearly proportional to the number of activated platelets. Interestingly, while EET formation induced by the direct stimulation of eosinophils with A23187 was NADPH oxidase (NOX)-dependent, EET formation induced by A23187-activated platelets was NOX-independent and significantly inhibited by necroptosis pathway inhibitors.

CONCLUSIONS

Activated platelets and their products may induce EET formation, thereby potentiating their role in eosinophilic airway inflammation.

Immunologic Basis of Type 2 Biologics for Severe Asthma

Asthma is a chronic airway inflammatory disease characterized by reversible airway obstruction and airway hyperreactivity to various environmental stimuli, leading to recurrent cough, dyspnea, and wheezing episodes. Regarding inflammatory mechanisms, type 2/eosinophilic inflammation along with activated mast cells is the major one; however, diverse mechanisms, including structural cells-derived and non-type 2/neutrophilic inflammations are involved, presenting heterogenous phenotypes. Although most asthmatic patients could be properly controlled by the guided treatment, patients with severe asthma (SA; classified as a treatment-refractory group) suffer from uncontrolled symptoms with frequent asthma exacerbations even on regular anti-inflammatory medications, raising needs for additional controllers, including biologics that target specific molecules found in asthmatic airway, and achieving the precision medicine for asthma. This review summarizes the immunologic basis of airway inflammatory mechanisms and current biologics for SA in order to address unmet needs for future targets.

Comparison between clinical trials and real-world evidence studies on biologics for severe asthma

In recent years, the more widespread availability of biological drugs with specific mechanisms of action has led to significant breakthroughs in the management of severe asthma. Over time, numerous randomised clinical trials have been conducted to evaluate the efficacy and safety of these biologics and define the eligibility criteria of patients suitable for various therapeutic options. These studies were conducted under controlled conditions not always applicable to real life. For this and other reasons, real-world evidence and pragmatic studies are required to provide useful information on the effectiveness of biological drugs and their safety, even in the long term. Because differences in outcomes have sometimes emerged between clinical trials and real-life studies, it is important to clarify the causes of these discrepancies and define the significance of the results of studies conducted in the course of daily clinical practice. Thus, a scientific debate is ongoing, and no consensus has been reached. The purpose of this narrative review is to analyse the differences between randomised trials and real-world evidence studies, focusing on their roles in guiding clinicians among different therapeutic options and understanding the reasons for the large discrepancies often found in the results obtained.

Down-regulated surfactant protein B in obese asthmatics

BACKGROUND

Obesity is a common comorbid condition in adult asthmatics and known as a feature of asthma severity. However, the molecular mechanism under obesity-induced inflammation has not yet been fully understood.

OBJECTIVE

Considering the essential role of hydrophobic surfactant protein B (SP-B) in lung function, SP-B was targeted to examine its involvement in the development of obesity-induced airway inflammation in asthmatics.

METHODS

The aim was to examine an alteration in circulating SP-B according to obesity in adult asthmatics, 129 asthmatics were enrolled and classified into 3 groups (obese, overweight and normal-weight groups) according to body mass index (BMI). Circulating SP-B levels were determined by enzyme-linked immunosorbent assay. Four single nucleotide polymorphisms of SFTPB gene were genotyped. Serum ceramide levels were measured by liquid chromatography-tandem mass spectrometry.

RESULTS

Significantly lower serum SP-B levels were noted in the obese group than in the overweight or normal-weight group (p = .002). The serum SP-B level was significantly correlated with serum levels of C18:0 ceramide and transforming growth factor beta 1 as well as BMI (r = -0.200; r = -0.215; r = -0.332, p < .050 for all). An inverse correlation was noted between serum SP-B and fractional exhaled nitric oxide levels in female asthmatics (r = -0.287, p = .009). Genetic predisposition of the SFTPB gene at 9306 A>G to the obese and overweight groups was noted.

CONCLUSION

Obesity altered ceramide metabolism leading to pulmonary surfactant dysfunction and impaired resolution of airway inflammation, finally contributing to the phenotypes of obese asthmatics.

Daytime and Nighttime Visual Analog Scales May Be Useful in Assessing Asthma Control Levels Before and After Treatment

PURPOSE

Few questionnaires evaluate daytime and nighttime symptoms separately, although these assessments could contribute to the improvement of disease control levels and prevention of future risks in asthma. The purpose of this retrospective study was to investigate whether daytime and nighttime visual analog scales (VAS) are useful in measuring the perception of symptoms, assessing disease control levels, and evaluating the treatment effects in asthma.

PATIENTS AND METHODS

Self-reporting asthma control tests (ACT) before and after treatment are standardized tests used to determine disease control levels. A multiple regression analysis was performed to determine the correlation between daytime and nighttime VAS and the characteristics of patients before treatment, as well as the changes in VAS and lung functions and fractional exhaled nitrogen oxide after treatment in 55 treatment-naïve symptomatic adult patients with asthma.

RESULTS

Both daytime (r = -0.57, P < 0.0001) and nighttime (r = -0.46, P < 0.0001) VAS correlated well with ACT scores, and there was a correlation between daytime and nighttime VAS (r = 0.33, P = 0.0148) before treatment. In addition, the changes in daytime (r = -0.65, P < 0.0001) and nighttime (r = -0.44, P < 0.0001) VAS were significantly associated with changes in the ACT scores. The multiple regression analysis (β [95% confidence interval]) revealed that improvements in the daytime (-2.33 [-4.55 to -0.11], P = 0.0405) and nighttime (-3.09 [-6.25 to 0.07], P = 0.0505) VAS were associated with an increased forced vital capacity after treatment, although there was no correlation between the VAS and characteristics before treatment.

CONCLUSION

Our study demonstrated that daytime and nighttime VAS were useful in assessing disease control levels and evaluating the treatment effects in asthma.

Effects of Asthma Medication Type on Asthma Exacerbation in a Real-World Setting

PURPOSE

Currently, there are multiple options for the pharmacological treatment of asthma. This study aimed to compare the effects of different asthma medications on exacerbation in a real-world setting.

MATERIALS AND METHODS

We retrospectively reviewed electronic medical records of asthma patients who visited the hospital from November 1, 2016 to October 31, 2019. The number of asthma exacerbations requiring administration of systemic steroids was the primary outcome. A time-varying Cox regression analysis was used to reflect the real-world setting: variable usage times, discontinuation, and switching of medication.

RESULTS

Among 937 patients with asthma, 228 (24.3%) experienced asthma exacerbation during the study period. Asthma exacerbation was observed in patients using short-acting β₂-agonists (SABA) alone (50.4% vs. 28.6%, p<0.001) as well as in patients not using inhaled corticosteroids (ICS) (58.8% vs. 40.3%, p<0.001), long-acting β₂-agonists (LABA) (54.8% vs. 36.1%, p<0.001), and leukotriene receptor antagonists (71.5% vs. 50.8%, p<0.001). A time-varying Cox regression analysis of asthma exacerbations according to the duration of asthma medication showed that SABA alone increased the risk of asthma exacerbation [hazard ratio (HR), 1.834; 95% confidence interval (CI), 1.299-2.588; p=0.001], whereas ICS-LABA decreased the risk (HR, 0.733; 95% CI, 0.538-0.997; p=0.048). However, in the subgroup analysis according to medication type, specific ingredients showed no significant differences.

CONCLUSION

In the real world, asthma medications affect asthma exacerbation variably according to the medication type.

Efficacy, safety, and tolerability of lebrikizumab in adolescent patients with uncontrolled asthma (ACOUSTICS)

Background

Lebrikizumab is a monoclonal antibody that modulates activity of interleukin-13. The Phase 3 ACOUSTICS study assessed lebrikizumab efficacy and safety in adolescents with uncontrolled asthma despite standard-of-care treatment.

Methods

Adolescents (aged 12-17 years) with uncontrolled asthma, prebronchodilator forced expiratory volume in 1 s 40%-90% predicted, and stable background therapy were randomised 1:1:1 to receive lebrikizumab 125 or 37.5 mg or placebo subcutaneously once every 4 weeks. Primary efficacy endpoint was asthma exacerbation rate over 52 weeks.

Results

Between August 2013 and July 2016, 579 patients were screened and 346 were randomised; 224 (65%) completed the study with 52 weeks of treatment. Lebrikizumab 125 mg (n = 116) reduced the exacerbation rate at 52 weeks versus placebo (n = 117; adjusted rate ratio [RR] 0.49 [95% CI 0.28-0.83]; 51% rate reduction). Lebrikizumab 37.5 mg (n = 113) was less effective at reducing exacerbations (RR 0.60 [95% CI 0.35-1.03]; 40% rate reduction). In patients with blood eosinophil counts ≥300 cells/μl, both lebrikizumab doses reduced exacerbations (125 mg: RR 0.44 [95% CI 0.21-0.89]; 37.5 mg: 0.42 [95% CI 0.19-0.93]). Treatment-emergent adverse events, serious adverse events, and adverse events leading to study discontinuation occurred in 155 (68%), 7 (3%), and 5 (2%) of 229 patients who received lebrikizumab (both 125 and 37.5 mg doses) and in 72 (62%), 4 (3%), and 1 (1%) of 117 who received placebo, respectively. No deaths occurred.

Conclusion

Lebrikizumab 125 mg reduced asthma exacerbation rates in adolescents with uncontrolled asthma. However, the study was prematurely terminated (sponsor's decision) potentially limiting interpretation of results.

Clinical trial registration

NCT01875003 (www.ClinicalTrials.gov).

Extracellular Traps: A Novel Therapeutic Target for Severe Asthma

Asthma is a complicated disease defined by a combination of clinical symptoms and physiological characteristics. Typically, asthma is diagnosed by the presence of episodic cough, wheezing, or dyspnea triggered by variable environmental factors (allergens and respiratory infections), and reversible airflow obstruction. To date, the majority of asthmatic patients have been adequately controlled by anti-inflammatory/bronchodilating agents, but those with severe asthma (SA) have not been sufficiently controlled by high-dose inhaled corticosteroids-long-acting beta-agonists plus additional controllers including leukotriene modifiers. Accordingly, these uncontrolled patients provoke a special issue, because they consume high healthcare resources, requiring innovative precision medicine solutions. Recently, phenotyping based on biomarkers of airway inflammation has led to elucidating the pathophysiological mechanism of SA, where emerging evidence has highlighted the significance of eosinophil or neutrophil extracellular traps contributing to the development of SA. Here, we aimed to provide current findings about extracellular traps as a novel therapeutic target for asthma to address medical unmet needs.

Diagnostic Accuracy of Liquid Biomarkers in Airway Diseases: Toward Point-of-Care Applications

Background

Liquid biomarkers have shown increasing utility in the clinical management of airway diseases. Salivary and blood samples are particularly amenable to point-of-care (POC) testing due to simple specimen collection and processing. However, very few POC tests have successfully progressed to clinical application due to the uncertainty and unpredictability surrounding their diagnostic accuracy.

Objective

To review liquid biomarkers of airway diseases with well-established diagnostic accuracies and discuss their prospects for future POC applications.

Methodology

A literature review of publications indexed in Medline or Embase was performed to evaluate the diagnostic accuracy of liquid biomarkers for chronic obstructive pulmonary disease (COPD), asthma, laryngopharyngeal reflux (LPR), and COVID-19.

Results

Of 3,628 studies, 71 fulfilled the inclusion criteria. Sputum and blood eosinophils were the most frequently investigated biomarkers for the management of asthma and COPD. Salivary pepsin was the only biomarker with a well-documented accuracy for the diagnosis of LPR. Inflammatory blood biomarkers (e.g., CRP, D-dimers, ferritin) were found to be useful to predict the severity, complications, and mortality related to COVID-19 infection.

Conclusion

Multiple liquid biomarkers have well-established diagnostic accuracies and are thus amenable to POC testing in clinical settings.

Immunobiology of Steroid-Unresponsive Severe Asthma

Asthma is a heterogeneous respiratory disease characterized by airflow obstruction, bronchial hyperresponsiveness and airway inflammation. Approximately 10% of asthma patients suffer from uncontrolled severe asthma (SA). A major difference between patients with SA from those with mild-to-moderate asthma is the resistance to common glucocorticoid treatments. Thus, steroid-unresponsive uncontrolled asthma is a hallmark of SA. An impediment in the development of new therapies for SA is a limited understanding of the range of immune responses and molecular networks that can contribute to the disease process. Typically SA is thought to be characterized by a Th2-low and Th17-high immunophenotype, accompanied by neutrophilic airway inflammation. However, Th2-mediated eosinophilic inflammation, as well as mixed Th1/Th17-mediated inflammation, is also described in SA. Thus, existing studies indicate that the immunophenotype of SA is diverse. This review attempts to summarize the interplay of different immune mediators and related mechanisms that are associated with airway inflammation and the immunobiology of SA.

Allergic and eosinophilic asthma in the era of biomarkers and biologics: similarities, differences and misconceptions

OBJECTIVE

Severe asthma is associated with substantial personal and economic burden; maintaining disease control is the key management goal. Increased understanding of asthma heterogeneity and development of type 2 (T2)-targeting biologics has substantially advanced disease management and outcomes; however, despite both being driven by T2 inflammation, allergic and eosinophilic asthma have different treatment recommendations. We sought to better understand the similarities and differences between allergic and eosinophilic asthma and highlight where misconceptions may arise.

DATA SOURCES

Published articles, pivotal trials, post hoc analyses, and asthma clinical guidelines sourced from PubMed.

STUDY SELECTIONS

Sources reporting allergic and eosinophilic asthma classifications, disease mechanisms, and biomarkers associated with treatment response.

RESULTS

This review highlights that severe allergic and eosinophilic asthma are both driven by T2 inflammation with eosinophils playing a cardinal role. Despite this overlap, treatment recommendations differ based on asthma classification. T2 cytokine gene expression is a reasonably well-established research tool, but not a well-established biomarker in clinical practice, unlike blood eosinophil counts, fractional exhaled nitric oxide, and immunoglobulin E; the clinical relevance of immunoglobulin E as a predictive biomarker remains unclear.

CONCLUSION

Asthma classifications that can be easily characterized at patient level to ensure accurate diagnosis, predict disease trajectory, and treatment response are required. The current dichotomy of allergic and eosinophilic asthma classifications is likely too simplistic, given the similar eosinophil-mediated disease pathophysiology in both classifications. Our results provide future directions to guide clinically meaningful interpretation of asthma endophenotypes, which may improve understanding of severe asthma characterization and aid future advances in defining responders more precisely with personalized medicine approaches.

Role of Thymus and Activation-Regulated Chemokine in Allergic Asthma

Background

Objective

Methods

Results

Conclusion

Evolving Concept of Severe Asthma: Transition From Diagnosis to Treatable Traits

In recent decades, the concept of severe asthma has evolved from an umbrella term encompassing patients with high-intensity treatment needs to a clinical syndrome with heterogeneous, albeit distinct, pathophysiological processes. Biased and unbiased cluster approaches have been used to identify several clinical phenotypes. In parallel, cellular and molecular approaches allow for the development of biological therapies, especially targeting type 2 (T2) cytokine pathways. Although T2-biologics have significantly improved clinical outcomes for patients with severe asthma in real-world practice, questions on the proper use of biologics remain open. Furthermore, a subset of severe asthma patients remains poorly controlled. The unmet needs require a new approach. The “treatable traits” concept has been suggested to address a diversity of pathophysiological factors in severe asthma and overcome the limitations of existing treatment strategies. With a tailored therapy that targets the treatable traits in individual patients, better personalized medical care and outcomes should be achieved.

Serum Amyloid A1: A Biomarker for Neutrophilic Airway Inflammation in Adult Asthmatic Patients

Purpose

We evaluated the role of serum amyloid A1 (SAA1) in the pathogenesis of airway inflammation according to the phenotype of asthma.

Methods

One hundred twenty-two asthmatic patients and 60 healthy control subjects (HCs) were enrolled to measure SAA1 levels. The production of SAA1 from airway epithelial cells (AECs) and its effects on macrophages and neutrophils were investigated in vitro and in vivo.

Results

The SAA1 levels were significantly higher in sera of asthmatic patients than in those of HCs (P = 0.014); among asthmatics, patients with neutrophilic asthma (NA) showed significantly higher SAA1 levels than those with non-NA (P < 0.001). In vitro, polyinosinic:polycytidylic acid (Poly I-C) treatment markedly enhanced the production of SAA1 from AECs, which was further augmented by neutrophils; SAA1 could induce the production of interleukin (IL)-6, IL-8, and S100 calcium-binding protein A9 from AECs. Additionally, SAA1 activated neutrophils and macrophages isolated from peripheral blood of asthmatics, releasing neutrophil extracellular traps (NETs) and secreting proinflammatory cytokines presenting M1 phenotype, respectively. In ovalbumin-induced asthma mice, Poly I-C treatment significantly increased SAA1 levels as well as IL-17A/interferon-gamma/IL-33 levels in bronchoalveolar lavage fluid (BALF), leading to airway hyperresponsiveness and inflammation. The highest levels of SAA1 and neutrophilia were noted in the BALF and sera of the NA mouse model, followed by the mixed granulocytic asthma (MA) model. Especially, SAA1 induced IL-17/retinoic acid receptor-related orphan receptor γt expression from activated CD4+ T lymphocytes in asthmatic mice.

Conclusions

The results show that SAA1 could induce neutrophilic airway inflammation by activating neutrophils along with NET formation, M1 macrophages, and Th2/Th17 predominant cells, contributing to the phenotype of NA or MA.

Strategies Targeting Type 2 Inflammation: From Monoclonal Antibodies to JAK-Inhibitors

Bronchial asthma and its frequent comorbidity chronic rhinosinusitis (CRS), are characterized by an inflammatory process at lower and upper respiratory tract, with a variability in terms of clinical presentations (phenotypes) and distinct underpin pathophysiological mechanisms (endotypes). Based on the characteristics of inflammation, bronchial asthma can be distinguished into type 2 (eosinophilic) or nontype 2 (noneosinophilic) endotypes. In type 2 asthma endotype, the pathogenic mechanism is sustained by an inflammatory process driven by Th2 cells, type 2 innate lymphoid cells (ILC2) and type 2 cytokines, which include interleukin (IL)-4, IL-5, IL-9 and IL-13. The definition of asthma and chronic rhinusinusitis phenotype/endotype is crucial, taking into account the availability of novel biologic agents, such as monoclonal antibodies targeting the classical type 2 cytokines. Recently, new therapeutic strategies have been proposed and analyzed in preliminary clinical trials. Among them Janus kinase (JAK) inhibitors, now largely used for the treatment of other chronic inflammatory diseases such as rheumatoid arthritis and inflammatory bowel diseases, is receiving great relevance. The rationale of this strategy derives from the data that JAK is a tyrosine kinase involved in the signaling of T cell receptor and of several cytokines that play a role in allergic respiratory disease, such as IL-2, IL-4 and IL-9. In this review, we discuss whether treatment with biological agents and JAK inhibitors may be equally effective in controlling type 2 inflammatory process in both asthma and CRS.

The Impact of Monoclonal Antibodies on Airway Smooth Muscle Contractility in Asthma: A Systematic Review

Airway hyperresponsiveness (AHR) represents a central pathophysiological hallmark of asthma, with airway smooth muscle (ASM) being the effector tissue implicated in the onset of AHR. ASM also exerts pro-inflammatory and immunomodulatory actions, by secreting a wide range of cytokines and chemokines. In asthma pathogenesis, the overexpression of several type 2 inflammatory mediators including IgE, IL-4, IL-5, IL-13, and TSLP has been associated with ASM hyperreactivity, all of which can be targeted by humanized monoclonal antibodies (mAbs). Therefore, the aim of this review was to systematically assess evidence across the literature on mAbs for the treatment of asthma with respect to their impact on the ASM contractile tone. Omalizumab, mepolizumab, benralizumab, dupilumab, and tezepelumab were found to be effective in modulating the contractility of the ASM and preventing the AHR, but no available studies concerning the impact of reslizumab on the ASM were identified from the literature search. Omalizumab, dupilumab, and tezepelumab can directly modulate the ASM in asthma, by specifically blocking the interaction between IgE, IL-4, and TSLP, and their receptors are located on the surface of ASM cells. Conversely, mepolizumab and benralizumab have prevalently indirect impacts against AHR by targeting eosinophils and other immunomodulatory effector cells promoting inflammatory processes. AHR has been suggested as the main treatable trait towards precision medicine in patients suffering from eosinophilic asthma, therefore, well-designed head-to-head trials are needed to compare the efficacy of those mAbs that directly target ASM contractility specifically against the AHR in severe asthma, namely omalizumab, dupilumab, and tezepelumab.

Metabolic Phenotypes in Asthmatic Adults: Relationship with Inflammatory and Clinical Phenotypes and Prognostic Implications

Bronchial asthma is a chronic disease that affects individuals of all ages. It has a high prevalence and is associated with high morbidity and considerable levels of mortality. However, asthma is not a single disease, and multiple subtypes or phenotypes (clinical, inflammatory or combinations thereof) can be detected, namely in aggregated clusters. Most studies have characterised asthma phenotypes and clusters of phenotypes using mainly clinical and inflammatory parameters. These studies are important because they may have clinical and prognostic implications and may also help to tailor personalised treatment approaches. In addition, various metabolomics studies have helped to further define the metabolic features of asthma, using electronic noses or targeted and untargeted approaches. Besides discriminating between asthma and a healthy state, metabolomics can detect the metabolic signatures associated with some asthma subtypes, namely eosinophilic and non-eosinophilic phenotypes or the obese asthma phenotype, and this may prove very useful in point-of-care application. Furthermore, metabolomics also discriminates between asthma and other “phenotypes” of chronic obstructive airway diseases, such as chronic obstructive pulmonary disease (COPD) or Asthma–COPD Overlap (ACO). However, there are still various aspects that need to be more thoroughly investigated in the context of asthma phenotypes in adequately designed, homogeneous, multicentre studies, using adequate tools and integrating metabolomics into a multiple-level approach.

Neutrophil extracellular traps and neutrophil-derived mediators as possible biomarkers in bronchial asthma

Neutrophils (PMNs) contain and release a powerful arsenal of mediators, including several granular enzymes, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs). Although airway neutrophilia is associated with severity, poor response to glucocorticoids and exacerbations, the pathophysiological role of neutrophils in asthma remains poorly understood. Twenty-four patients with asthma and 22 healthy controls (HCs) were prospectively recruited. Highly purified peripheral blood neutrophils (> 99%) were evaluated for ROS production and activation status upon stimulation with lipopolysaccharide (LPS), N-formylmethionyl-leucyl-phenylalanine (fMLP) and phorbol 12-myristate 13-acetate (PMA). Plasma levels of myeloperoxidase (MPO), CXCL8, matrix metalloproteinase-9 (MMP-9), granulocyte–monocyte colony-stimulating factor (GM-CSF) and vascular endothelial growth factor (VEGF-A) were measured by ELISA. Plasma concentrations of citrullinated histone H3 (CitH3) and circulating free DNA (dsDNA) were evaluated as NET biomarkers. Activated PMNs from asthmatics displayed reduced ROS production and activation status compared to HCs. Plasma levels of MPO, MMP-9 and CXCL8 were increased in asthmatics compared to HCs. CitH3 and dsDNA plasma levels were increased in asthmatics compared to controls and the CitH3 concentrations were inversely correlated to the % decrease in FEV₁/FVC in asthmatics. These findings indicate that neutrophils and their mediators could have an active role in asthma pathophysiology.