Obese Individuals with Asthma Preferentially Have a High IL-5/IL-17A/IL-25 Sputum Inflammatory Pattern

Impact of obesity on airway remodeling in asthma: pathophysiological insights and clinical implications

The prevalence of obesity among asthma patients has surged in recent years, posing a significant risk factor for uncontrolled asthma. Beyond its impact on asthma severity and patients' quality of life, obesity is associated with reduced lung function, increased asthma exacerbations, hospitalizations, heightened airway hyperresponsiveness, and elevated asthma-related mortality. Obesity may lead to metabolic dysfunction and immune dysregulation, fostering chronic inflammation characterized by increased pro-inflammatory mediators and adipocytokines, elevated reactive oxygen species, and reduced antioxidant activity. This chronic inflammation holds the potential to induce airway remodeling in individuals with asthma and obesity. Airway remodeling encompasses structural and pathological changes, involving alterations in the airway's epithelial and subepithelial layers, hyperplasia and hypertrophy of airway smooth muscle, and changes in airway vascularity. In individuals with asthma and obesity, airway remodeling may underlie heightened airway hyperresponsiveness and increased asthma severity, ultimately contributing to the development of persistent airflow limitation, declining lung function, and a potential increase in asthma-related mortality. Despite efforts to address the impact of obesity on asthma outcomes, the intricate mechanisms linking obesity to asthma pathophysiology, particularly concerning airway remodeling, remain incompletely understood. This comprehensive review discusses current research investigating the influence of obesity on airway remodeling, to enhance our understanding of obesity's role in the context of asthma airway remodeling.

Obesity-related asthma and its relationship with microbiota

Obesity and asthma are global public health problems. Obesity-related asthma is a special phenotype of asthma with a complex pathogenesis. Its occurrence and development are related to mechanical compression, inflammatory response, metabolic regulation, gene regulation, and vitamin D deficiency. Different treatment strategies used in the process of weight loss have a beneficial impact on asthma. Alterations in gut and airway microbial community structure and their metabolites may also contribute to obesity-related asthma. The role of the Th17/Treg balance in the gut microbiota regulating the immune responses and host metabolism is important. Therapeutic measures associated with the gut microbiota variety may contribute to improving chronic inflammation associated with obesity by regulating the Th17/Treg balance. An early reduction in microbial diversity can predict the development of asthma and lead to allergy through an imbalance of Th2/Th1 responses. Short-chain fatty acids (SCFAs) regulate the differentiation and activation of regulatory T cells, thereby regulating immune homeostasis in the lung to suppress allergic inflammation and weight gain. Therefore, clarifying the microbial mechanism of obesity-related asthma has important guiding significance for clinical treatment. In this review, we used the following terms: "asthma and obesity" and "obesity-related asthma", combining "phenotype", "airway inflammation" and "lung function", and reviewed the characteristics and pathogenesis of obesity-related asthma, the relationship between the gut and airway microbiota and obesity-related asthma, and the current treatment measures for the disease.

Effect of obesity on airway and systemic inflammation in adults with asthma: a systematic review and meta-analysis

BACKGROUND

Obesity is associated with more severe asthma, however, the mechanisms responsible are poorly understood. Obesity is also associated with low-grade systemic inflammation; it is possible that this inflammation extends to the airways of adults with asthma, contributing to worse asthma outcomes. Accordingly, the aim of this review was to examine whether obesity is associated with increased airway and systemic inflammation and adipokines, in adults with asthma.

METHODS

Medline, Embase, CINAHL, Scopus and Current Contents were searched till 11 August 2021. Studies reporting measures of airway inflammation, systemic inflammation and/or adipokines in obese versus non-obese adults with asthma were assessed. We conducted random effects meta-analyses. We assessed heterogeneity using the I2 statistic and publication bias using funnel plots.

RESULTS

We included 40 studies in the meta-analysis. Sputum neutrophils were 5% higher in obese versus non-obese asthmatics (mean difference (MD)=5.0%, 95% CI: 1.2 to 8.9, n=2297, p=0.01, I2=42%). Blood neutrophil count was also higher in obesity. There was no difference in sputum %eosinophils; however, bronchial submucosal eosinophil count (standardised mean difference (SMD)=0.58, 95% CI=0.25 to 0.91, p<0.001, n=181, I2=0%) and sputum interleukin 5 (IL-5) (SMD=0.46, 95% CI=0.17 to 0.75, p<0.002, n=198, I2=0%) were higher in obesity. Conversely, fractional exhaled nitric oxide was 4.5 ppb lower in obesity (MD=-4.5 ppb, 95% CI=-7.1 ppb to -1.8 ppb, p<0.001, n=2601, I2=40%). Blood C reactive protein, IL-6 and leptin were also higher in obesity.

CONCLUSIONS

Obese asthmatics have a different pattern of inflammation to non-obese asthmatics. Mechanistic studies examining the pattern of inflammation in obese asthmatics are warranted. Studies should also investigate the clinical relevance of this altered inflammatory response.

PROSPERO REGISTERATION NUMBER

CRD42021254525.

Lifestyles and the risk of an asthma attack in adult asthma patients: a cross-sectional study using NHANES database

BACKGROUND

The influence of physical activity, diet and sleep on asthma has been well documented by recent studies respectively. However, few studies focus on the relationship between asthma attack and the overall lifestyle, which comprises interrelated lifestyle factors. This study aims to investigate the influence of lifestyles on the ratio of asthma attack. Data were extracted from the NHANES database (2017 to May 2020).

METHODS

A total of 834 asthmatic patients were enrolled and divided into non-asthma attack (N.=460) and asthma attack (N.=374) groups. The risk factors for asthma attacks were preliminarily identified by univariate logistic analysis, then multivariate logistic analysis was employed to select independent risk factors other than lifestyles and further determine the association between lifestyles and asthma attacks.

RESULTS

After multivariate logistic analysis, engagement of vigorous activity (Model 1 P=0.010, Model 2 P=0.016, Model 3 P=0.012), engagement of moderate activity (Model 1 P=0.006, Model 2 P=0.008, Model 3 P=0.003) and sleep disorder (Model1 P=0.001, Model 2 P<0.001, Model 3 P=0.008) were determined as independent risk factors of lifestyles for an asthma attack in the past year.

CONCLUSIONS

This research documented that, for asthmatic patients, engagement of vigorous activity, engagement of moderate activity, and sleep disorder will make an asthma attack more likely to happen.

Adipokines in interstitial lung diseases

Interstitial lung diseases (ILD) are a heterogenic group of respiratory diseases with complex pathogenesis. A growing number of evidence suggests role of adipose tissue and it's hormones (adipokines) in pathogenesis of various disorders, including lung tissue diseases. The aim of this study was to assess the concentrations of selected adipokines and their receptors (apelin, adiponectin, chemerin, chemerin receptor - CMKLR1) in patients with IPF (idiopathic pulmonary fibrosis) and sarcoidosis in comparison to healthy controls. We found changes in adipokines concentrations in ILD. Adiponectin concentrations were higher in all respiratory diseases patients in comparison to healthy controls. Apelin concentration in ILD patients was higher then those in healthy subjects. The trend of chemerin and CMKLR1 concentrations were similar, with highest concentrations seen in sarcoidosis. The study shows a difference of adipokines concentrations between patients with ILD and healthy controls. Adipokines are a potential marker and therapeutic target in patients with IPF and sarcoidosis.

1-O-alkyl-glycerols from Squid Berryteuthis magister Reduce Inflammation and Modify Fatty Acid and Plasmalogen Metabolism in Asthma Associated with Obesity

Asthma associated with obesity is considered the most severe phenotype and can be challenging to manage with standard medications. Marine-derived 1-O-alkyl-glycerols (AGs), as precursors for plasmalogen synthesis, have high biological activity, making them a promising substance for pharmacology. This study aimed to investigate the effect of AGs from squid Berryteuthis magister on lung function, fatty acid and plasmalogen levels, and cytokine and adipokine production in obese patients with asthma. The investigational trial included 19 patients with mild asthma associated with obesity who received 0.4 g of AGs daily for three months in addition to their standard treatment. The effects of AGs were evaluated at one and three months of treatment. The results of the study demonstrated that intake of AGs increased the FEV1 and FEV1/VC ratios, and significantly decreased the ACQ score in 17 of the 19 patients after three months of treatment. The intake of AGs increased concentration of plasmalogen and n-3 PUFA in plasma, and modified leptin/adiponectin production by adipose tissue. The supplementation of AGs decreased the plasma levels of inflammatory cytokines (TNF-α, IL-4, and IL-17a), and oxylipins (TXB2 and LTB4), suggesting an anti-inflammatory property of AGs. In conclusion, 1-O-alkyl-glycerols could be a promising dietary supplement for improving pulmonary function and reducing inflammation in obese asthma patients, and a natural source for plasmalogen synthesis. The study highlighted that the beneficial effects of AG consumption can be observed after one month of treatment, with gradual improvement after three months of supplementation.

Pediatric obesity and severe asthma: Targeting pathways driving inflammation

Asthma affects more than 300 million people of all ages worldwide, including about 10-15% of school-aged children, and its prevalence is increasing. Severe asthma (SA) is a particular and rare phenotype requiring treatment with high-dose inhaled corticosteroids plus a second controller and/or systemic glucocorticoid courses to achieve symptom control or remaining "uncontrolled" despite this therapy. In SA, other diagnoses have been excluded, and potential exacerbating factors have been addressed. Notably, obese asthmatics are at higher risk of developing SA. Obesity is both a major risk factor and a disease modifier of asthma in children and adults: two main "obese asthma" phenotypes have been described in childhood with high or low levels of Type 2 inflammation biomarkers, respectively, the former characterized by early onset and eosinophilic inflammation and the latter by neutrophilic inflammation and late-onset. Nevertheless, the interplay between obesity and asthma is far more complex and includes obese tissue-driven inflammatory pathways, mechanical factors, comorbidities, and poor response to corticosteroids. This review outlines the most recent findings on SA in obese children, particularly focusing on inflammatory pathways, which are becoming of pivotal importance in order to identify selective targets for specific treatments, such as biological agents.

From Beneath the Skin to the Airway Wall: Understanding the Pathological Role of Adipose Tissue in Comorbid Asthma-Obesity

This article provides a contemporary report on the role of adipose tissue in respiratory dysfunction. Adipose tissue is distributed throughout the body, accumulating beneath the skin (subcutaneous), around organs (visceral), and importantly in the context of respiratory disease, has recently been shown to accumulate within the airway wall: "airway-associated adipose tissue." Excessive adipose tissue deposition compromises respiratory function and increases the severity of diseases such as asthma. The mechanisms of respiratory impairment are inflammatory, structural, and mechanical in nature, vary depending on the anatomical site of deposition and adipose tissue subtype, and likely contribute to different phenotypes of comorbid asthma-obesity. An understanding of adipose tissue-driven pathophysiology provides an opportunity for diagnostic advancement and patient-specific treatment. As an exemplar, the potential impact of airway-associated adipose tissue is highlighted, and how this may change the management of a patient with asthma who is also obese. © 2023 American Physiological Society. Compr Physiol 13:4321-4353, 2023.

Adipose Tissue Inflammation and Pulmonary Dysfunction in Obesity

Obesity is a chronic disease caused by an excess of adipose tissue that may impair health by altering the functionality of various organs, including the lungs. Excessive deposition of fat in the abdominal area can lead to abnormal positioning of the diaphragm and consequent reduction in lung volume, leading to a heightened demand for ventilation and increased exposure to respiratory diseases, such as chronic obstructive pulmonary disease, asthma, and obstructive sleep apnoea. In addition to mechanical ventilatory constraints, excess fat and ectopic deposition in visceral depots can lead to adipose tissue dysfunction, which promotes metabolic disorders. An altered adipokine-secretion profile from dysfunctional adipose tissue in morbid obesity fosters systemic, low-grade inflammation, impairing pulmonary immune response and promoting airway hyperresponsiveness. A potential target of these adipokines could be the NLRP3 inflammasome, a critical component of the innate immune system, the harmful pro-inflammatory effect of which affects both adipose and lung tissue in obesity. In this review, we will investigate the crosstalk between adipose tissue and the lung in obesity, highlighting the main inflammatory mediators and novel therapeutic targets in preventing pulmonary dysfunction.

Differences in Inflammatory Cytokine Profile in Obesity-Associated Asthma: Effects of Weight Loss

Obesity and asthma are associated with systemic inflammation maintained by mediators released by adipose tissue and lung. This study investigated the inflammatory serum mediator profile in obese subjects (O) (n = 35), non-obese asthma (NOA) patients (n = 14), obese asthmatics (OA) (n = 21) and healthy controls (HC) (n = 33). The effect of weight loss after bariatric surgery (BS) was examined in 10 OA and 31 O subjects. We analyzed serum markers including leptin, adiponectin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, ST2, IL-5, IL-9, and IL-18. Compared with HC subjects, the O group showed increased levels of leptin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, and ST2; the OA group presented increased levels of MCP-1, ezrin, YKL-40, and IL-18, and the NOA group had increased levels of ezrin, YKL-40, IL-5, and IL-18. The higher adiponectin/leptin ratio in NOA with respect to OA subjects was the only significant difference between the two groups. IL-9 was the only cytokine with significantly higher levels in OA with respect to O subjects. TNFR2, ezrin, MCP-1, and IL-18 concentrations significantly decreased in O subjects after BS. O, OA, and NOA showed distinct patterns of systemic inflammation. Leptin and adiponectin are regulated in asthma by obesity-dependent and -independent mechanisms. Combination of asthma and obesity does not result in significant additive effects on circulating cytokine levels.

Paucigranulocytic Asthma: Potential Pathogenetic Mechanisms, Clinical Features and Therapeutic Management

Asthma is a heterogeneous disease usually characterized by chronic airway inflammation, in which several phenotypes have been described, related to the age of onset, symptoms, inflammatory characteristics and treatment response. The identification of the inflammatory phenotype in asthma is very useful, since it allows for both the recognition of the asthmatic triggering factor as well as the optimization of treatment The paucigranulocytic phenotype of asthma (PGA) is characterized by sputum eosinophil levels <1−3% and sputum neutrophil levels < 60%. The precise characteristics and the pathobiology of PGA are not fully understood, and, in some cases, it seems to represent a previous eosinophilic phenotype with a good response to anti-inflammatory treatment. However, many patients with PGA remain uncontrolled and experience asthmatic symptoms and exacerbations, irrespective of the low grade of airway inflammation. This observation leads to the hypothesis that PGA might also be either a special phenotype driven by different kinds of cells, such as macrophages or mast cells, or a non-inflammatory phenotype with a low grade of eosinophilic inflammation. In this review, we aim to describe the special characteristics of PGA and the potential therapeutic interventions that could be offered to these patients.

Clinical Characteristics and Management Strategies for Adult Obese Asthma Patients

The rates of asthma and obesity are increasing concurrently in the United States. Epidemiologic studies demonstrate that the incidence of asthma increases with obesity. Furthermore, obese individuals have asthma that is more severe, harder to control, and resistant to standard medications. In fact, specific asthma-obesity phenotypes have been identified. Various pathophysiologic mechanisms, including mechanical, inflammatory, metabolic and microbiome-associated, are at play in promulgating the obese-asthma phenotypes. While standard asthma medications, such as inhaled corticosteroids and biologics, are currently used to treat obese asthmatics, they may have limited effectiveness. Targeting the underlying aberrant processes, such as addressing steroid resistance, microbiome, metabolic and weight loss approaches, may be helpful.

Innate Lymphoid Cells Are Required to Induce Airway Hyperreactivity in a Murine Neutrophilic Asthma Model

Rationale

Non-allergic asthma is driven by multiple endotypes of which neutrophilic and pauci-granulocytic asthma have been best established. However, it is still puzzling what drives inflammation and airway hyperreactivity (AHR) in these patients and how it can be treated effectively. Recently, a potential role of the innate immune system and especially the innate lymphoid cells (ILC) has been proposed.

Objective

In this study, we investigated the effects of LPS inhalation on airway inflammation and AHR as a potential model for elucidating the pathogenesis of non-allergic asthma.

Methods

Wild-type (BALB/c), SCID, IL-17A^-/-, and Rag2^-/- γC^-/- mice were endonasally exposed to lipopolysaccharide (LPS, 2 µg) on four consecutive days. Twenty-four hours after the last exposure, AHR to methacholine was assessed. Cytokine levels and ILC subpopulations were determined in lung tissue. Cellular differential analysis was performed in BAL fluid.

Main Results

In this study, we developed a murine model for non-allergic neutrophilic asthma. We found that repeated endonasal applications of low-dose LPS in BALB/c mice led to AHR, BAL neutrophilia, and a significant increase in lung ILC3 as well as a significant increase in lung chemokines KC and MIP-2 and cytokines IL-1β, IL-17A, IL-22, and TNF. The adoptive transfer of ILC in Rag2^-/- γC^-/- mice showed that ILC played a causal role in the induction of AHR in this model. Antagonising IL-1β, but not IL-17A or neutrophils, resulted in a partial reduction in LPS-induced AHR.

Conclusion

In conclusion, we report here a murine model for neutrophilic asthma where ILC are required to induce airway hyperreactivity.

High Insulin in Early Childhood Is Associated with Subsequent Asthma Risk Independent of Body Mass Index

BACKGROUND

Asthma and obesity are major, interconnected public health challenges that usually have their origins in childhood, and for which the relationship is strengthened among those with insulin resistance.

OBJECTIVE

To determine whether high insulin in early life confers increased longitudinal risk for asthma independent of body mass index.

METHODS

The study used data from the Tucson Children's Respiratory Study (TCRS) and the Avon Longitudinal Study of Parents and Children (ALSPAC). Nonfasting insulin was measured in TCRS participants at age 6 years and fasting insulin in ALSPAC participants at age 8 years. Physician-diagnosed active asthma was determined at baseline and at subsequent assessments up to age 36 years in TCRS and 17 years in ALSPAC.

RESULTS

In TCRS, high insulin (upper quartile) at age 6 years was associated with increased odds of having active asthma from ages 8 to 36 years compared with low insulin (odds ratio,1.98; 95% CI, 1.28-3.05; P = .002). Similarly, in ALSPAC, high insulin was associated with a significantly higher risk of active asthma from ages 11 to 17 years compared with low insulin (odds ratio, 1.59; 95% CI, 1.12-2.27; P = .009). These findings were independent of baseline body mass index in both cohorts, and were not related to other demographic and asthma risk factors nor other tested markers of systemic inflammation and metabolic syndrome.

CONCLUSIONS

In 2 separate birth cohorts, higher blood insulin level in early childhood was associated with increased risk of active asthma through adolescence and adulthood, independent of body mass index. High insulin indicates a novel mechanism for asthma development, which may be a target for intervention.

Risankizumab in Severe Asthma - A Phase 2a, Placebo-Controlled Trial

BACKGROUND

Interleukin-23 has been implicated in airway inflammation that is mediated by type 2 and type 17 cytokines. Whether targeting interleukin-23 in the treatment of asthma improves disease control and reduces airway inflammation is unclear.

METHODS

We conducted a phase 2a, multicenter, randomized, double-blind, placebo-controlled, 24-week, parallel-group trial to assess the efficacy and safety of risankizumab, an anti-interleukin-23p19 monoclonal antibody, in adults with severe asthma. Patients were assigned to receive 90 mg of risankizumab or placebo, administered subcutaneously once every 4 weeks. The primary end point was the time to the first asthma worsening. Asthma worsening was defined as deterioration from baseline on 2 or more consecutive days; deterioration was considered to be a decrease of at least 30% in the morning peak expiratory flow or an increase from baseline of at least 50% in the number of puffs of rescue medication in a 24-hour period (equating to at least four additional puffs), a severe asthma exacerbation, or an increase of 0.75 or more points on the 5-item Asthma Control Questionnaire (ACQ-5; scores range from 0 to 6, with higher scores indicating less control). Secondary end points were the annualized rate of asthma worsening, the annualized rate of severe exacerbations, the ACQ-5 score, and the forced expiratory volume in 1 second. Exploratory end points were assessed with the use of sputum cytologic analysis and gene expression analysis, and safety was assessed.

RESULTS

A total of 105 patients received risankizumab and 109 received placebo. The clinical characteristics of the patients were similar in the two groups. The time to the first asthma worsening was shorter with risankizumab than with placebo (median, 40 days vs. 86 days; hazard ratio, 1.46; 95% confidence interval [CI], 1.05 to 2.04; P = 0.03). The rate ratio for annualized asthma worsening with risankizumab as compared with placebo was 1.49 (95% CI, 1.12 to 1.99), and the rate ratio for severe exacerbations was 1.13 (95% CI, 0.75 to 1.70). Sputum transcriptomic pathway analysis showed that genes involved in the activation of natural killer cells and cytotoxic T cells and the activation of the type 1 helper T and type 17 helper T transcription factors were down-regulated by risankizumab. No safety concerns were associated with risankizumab therapy.

CONCLUSIONS

Risankizumab treatment was not beneficial in severe asthma. The time to the first asthma worsening was shorter and the annualized rate of asthma worsening was higher with risankizumab than with placebo. (Funded by AbbVie and Boehringer Ingelheim; ClinicalTrials.gov number, NCT02443298.).

Treatment approaches for the patient with T2 low asthma

OBJECTIVE

To identify treatment approaches that can be used in the management of patients with asthma who lack significant type 2 inflammation, also called T2 low asthma.

DATA SOURCES

Recent expert guideline updates on the management of asthma, recent journal articles and review articles, and foundational journal articles are referenced.

STUDY SELECTIONS

This review cites clinical cohort studies of highly characterized patients with asthma, clinical interventional trials of high impact, mechanistic studies relevant to T2 low asthma, and emerging work in this area.

RESULTS

T2 low asthma accounts for approximately one-third to one-half of individuals with asthma. Characteristics of participants with T2 low asthma include higher body mass index, cigarette smoking/smoke exposure, relative lack of responsiveness to steroids, less bronchodilator reversibility, and often the presence of neutrophilic inflammation. Multiple available interventions target these characteristics, including standard inhalers, azithromycin, and lifestyle interventions of weight loss and smoking cessation.

CONCLUSION

Treatment of T2 low asthma should involve currently available approaches and will benefit from improved definition and understanding of disease pathobiology.

Relationship between type 2 cytokine and inflammasome responses in obesity-associated asthma

BACKGROUND

Obesity is a risk factor for asthma, and obese asthmatic individuals are more likely to have severe, steroid-insensitive disease. How obesity affects the pathogenesis and severity of asthma is poorly understood. Roles for increased inflammasome-mediated neutrophilic responses, type 2 immunity, and eosinophilic inflammation have been described.

OBJECTIVE

We investigated how obesity affects the pathogenesis and severity of asthma and identified effective therapies for obesity-associated disease.

METHODS

We assessed associations between body mass index and inflammasome responses with type 2 (T2) immune responses in the sputum of 25 subjects with asthma. Functional roles for NLR family, pyrin domain-containing (NLRP) 3 inflammasome and T2 cytokine responses in driving key features of disease were examined in experimental high-fat diet-induced obesity and asthma.

RESULTS

Body mass index and inflammasome responses positively correlated with increased IL-5 and IL-13 expression as well as C-C chemokine receptor type 3 expression in the sputum of subjects with asthma. High-fat diet-induced obesity resulted in steroid-insensitive airway hyperresponsiveness in both the presence and absence of experimental asthma. High-fat diet-induced obesity was also associated with increased NLRP3 inflammasome responses and eosinophilic inflammation in airway tissue, but not lumen, in experimental asthma. Inhibition of NLRP3 inflammasome responses reduced steroid-insensitive airway hyperresponsiveness but had no effect on IL-5 or IL-13 responses in experimental asthma. Depletion of IL-5 and IL-13 reduced obesity-induced NLRP3 inflammasome responses and steroid-insensitive airway hyperresponsiveness in experimental asthma.

CONCLUSION

We found a relationship between T2 cytokine and NLRP3 inflammasome responses in obesity-associated asthma, highlighting the potential utility of T2 cytokine-targeted biologics and inflammasome inhibitors.

Management Strategies to Reduce Exacerbations in non-T2 Asthma

There have been considerable advances in our understanding of asthmatic airway inflammation, resulting in a paradigm shift of classifying individuals on the basis of either the presence or the absence of type 2 (T2) inflammatory markers. Several novel monoclonal antibody therapies targeting T2 cytokines have demonstrated significant clinical effects including reductions in acute exacerbations and improvements in asthma-related quality of life and lung function for individuals with T2-high asthma. However, there have been fewer advancements in developing therapies for those without evidence of T2 airway inflammation (so-called non-T2 asthma). Here, we review the heterogeneity of molecular mechanisms responsible for initiation and regulation of non-T2 inflammation and discuss both current and potential future therapeutic options for individuals with non-T2 asthma.

Associations of TNFA, IL17A, and RORC mRNA expression levels in peripheral blood leukocytes with obesity-related asthma in adolescents

Obesity is associated with a unique non-T2 asthma phenotype, characterised by a Th17 immune response. Retinoid-related orphan receptor C (RORC) is the master transcription factor for Th17 polarisation. We investigated the association of TNFA, IL17A, and RORC mRNA expression levels with the non-T2 phenotype. We conducted a cross-sectional study in adolescents, subdivided as follows: healthy (HA), allergic asthma without obesity (AA), obesity without asthma (OB), and non-allergic asthma with obesity (NAO). TNFA, IL17A, and RORC mRNA expression in peripheral blood leukocytes were assessed by RT-PCR. NAO exhibited higher TNFA mRNA expression levels than HA or OB, as well as the highest IL17A and RORC mRNA expression levels among the four groups. The best biomarker for discriminating non-allergic asthma among obese adolescents was RORC mRNA expression levels (area under the curve: 0.95). RORC mRNA expression levels were associated with the non-T2 asthma phenotype, hinting at a therapeutic target in obesity-related asthma.

Lipid metabolism in asthma: Immune regulation and potential therapeutic target

Asthma is a chronic inflammatory disease of the lungs that poses a considerable health and socioeconomic burden. Several risk factors work synergistically to affect the progression of asthma. Lipid metabolism, especially in distinct cells such as T cells, macrophages, granulocytes, and non-immune cells, plays an essential role in the pathogenesis of asthma, as lipids are potent signaling molecules that regulate a multitude of cellular response. In this review, we focused on the metabolic pathways of lipid molecules, especially fatty acids and their derivatives, and summarized their roles in various cells during the pathogenesis of asthma along with the current pharmacological agents targeting lipid metabolism.

Asthma and Obesity: Two Diseases on the Rise and Bridged by Inflammation

Asthma and obesity are two epidemics affecting the developed world. The relationship between obesity and both asthma and severe asthma appears to be weight-dependent, causal, partly genetic, and probably bidirectional. There are two distinct phenotypes: 1. Allergic asthma in children with obesity, which worsens a pre-existing asthma, and 2. An often non allergic, late-onset asthma developing as a consequence of obesity. In obesity, infiltration of adipose tissue by macrophages M1, together with an increased expression of multiple mediators that amplify and propagate inflammation, is considered as the culprit of obesity-related inflammation. Adipose tissue is an important source of adipokines, such as pro-inflammatory leptin, produced in excess in obesity, and adiponectin with anti-inflammatory effects with reduced synthesis. The inflammatory process also involves the synthesis of pro-inflammatory cytokines such as IL-1β, IL-6, TNFα, and TGFβ, which also contribute to asthma pathogenesis. In contrast, asthma pro-inflammatory cytokines such as IL-4, IL-5, IL-13, and IL-33 contribute to maintain the lean state. The resulting regulatory effects of the immunomodulatory pathways underlying both diseases have been hypothesized to be one of the mechanisms by which obesity increases asthma risk and severity. Reduction of weight by diet, exercise, or bariatric surgery reduces inflammatory activity and improves asthma and lung function.

IL-17A and TNF-α as potential biomarkers for acute respiratory distress syndrome and mortality in patients with obesity and COVID-19

Coronavirus disease 2019 (COVID-19) was declared a pandemic and international health emergency by the World Health Organization. Patients with obesity with COVID-19 are 7 times more likely to need invasive mechanical ventilation than are patients without obesity (OR 7.36; 95% CI: 1.63–33.14, p = 0.021). Acute respiratory distress syndrome (ARDS) is one of the main causes of death related to COVID-19 and is triggered by a cytokine storm that damages the respiratory epithelium. Interleukins that cause the chronic low-grade inflammatory state of obesity, such as interleukin (IL)-1β, IL-6, monocyte chemoattractant peptide (MCP)-1, and, in particular, IL-17A and tumour necrosis factor alpha (TNF-α), also play very important roles in lung damage in ARDS. Therefore, obesity is associated with an immune state favourable to a cytokine storm. Our hypothesis is that serum concentrations of TNF-α and IL-17A are more elevated in patients with obesity and COVID-19, and consequently, they have a greater probability of developing ARDS and death. The immunobiology of IL-17A and TNF-α opens a new fascinating field of research for COVID-19.

How to apply the personalized medicine in obesity-associated asthma?

INTRODUCTION

Obesity-associated asthma (OA) is frequently severe, with an increased rate of hospitalizations, numerous comorbidities and low response to corticosteroids. Despite progress in applying for personalized medicine in asthma, no specific recommendations exist for the management of OA.

AREAS COVERED

The aim of this review is to summarize recent data about the relationship obesity-asthma, describe clinical characteristics, potential mechanisms involved and possible therapeutic interventions to improve OA outcomes. Extensive research in the PubMed was performed using the following terms: "asthma and obesity" and "obese asthma" in combination with "phenotypes", "airway inflammation", "biomarkers", "lung function", "weight loss", "lifestyle interventions", "therapies" Currently two phenotypes are described. Early-onset atopic asthma is conventional allergic asthma aggravated by the pro-inflammatory properties of adipose tissue in excess, while late-onset non-atopic asthma is due to airway dysfunction as a consequence of the chronic lung compression caused by the obese chest walls. Previous data showed that different therapeutic strategies used in weight loss have a positive impact on OA outcomes.

EXPERT OPINION

The presence of a multidisciplinary team (chest physician, nutritionist, exercise physiologist, physiotherapist, psychologist, bariatric surgeon) and the collaboration between different specialists are mandatory to optimize the management and to apply the personalized medicine in OA.

The Nonantibiotic Macrolide EM900 Attenuates House Dust Mite-Induced Airway Inflammation in a Mouse Model of Obesity-Associated Asthma

INTRODUCTION

Obesity-associated asthma is characterized by type 2-low airway inflammation. We previously showed that EM900, which is a 12-membered nonantibiotic macrolide, suppressed airway inflammation in a mouse model of asthma exacerbation. The aim of this study was to clarify the effects of EM900 in obesity-associated asthma.

METHODS

BALB/c mice were fed a low-fat diet (LFD) or high-fat diet (HFD). Mice were intranasally sensitized and challenged with house dust mites (HDMs) and were orally administered EM900. Airway inflammation was assessed using inflammatory cells in bronchoalveolar lavage (BALF). Cytokines were examined by ELISA in lung tissues. Lung interstitial macrophages (CD45+, CD11clow, CD11b+, and Ly6c-) were counted by flow cytometry in single cells from lung tissues.

RESULTS

Body weight increased significantly in the HFD compared with the LFD group. The total cell count and numbers of neutrophils and eosinophils in BALF were significantly suppressed by EM900 administration in the HFD-HDM group. The levels of interleukin (IL)-17A were increased in the HFD-HDM group compared with the LFD-HDM group, although the difference did not reach statistical significance. The levels of IL-17A, macrophage inflammatory protein 2, IL-1β, IL-5, and regulated on activation, normal T cell expressed and secreted in lung tissue were significantly suppressed by EM900 administration in the HFD-HDM group. The percentage of interstitial macrophages in lungs was significantly decreased by EM900 administration in the HFD-HDM group.

CONCLUSION

Both type 2 and type 2-low airway inflammation were attenuated by EM900 in this obesity-associated asthma model. These results show that EM900 might be a candidate agent for the treatment of obesity-associated asthma.

Mechanisms and therapeutic strategies for non-T2 asthma

Non-T2 asthma is traditionally defined as asthma without features of T2 asthma. The definition is arbitrary and is generally based on the presence of neutrophils in sputum, or the absence (or normal levels) of eosinophils or other T2 markers in sputum (paucigranulocytic), airway biopsies or in blood. This definition may be imprecise as we gain more knowledge from applying transcriptomics and proteomics to blood and airway samples. The prevalence of non-T2 asthma is also difficult to estimate as most studies are cross-sectional and influenced by concomitant treatment with glucocorticosteroids, and by the presence of recognized or unrecognized airway infections. No specific therapies have shown any clinical benefits in patients with asthma that is associated with a non-T2 inflammatory process. It remains to be seen if such an endotype truly exists and to identify treatments to target that endotype. Meanwhile, identifying intense airway neutrophilia as an indicator of airway infection and airway hyperresponsiveness as an indicator of smooth muscle dysfunction, and treating them appropriately, and not increasing glucocorticosteroids in patients who do not have obvious T2 inflammation, seem reasonable.

New insights in neutrophilic asthma

PURPOSE OF REVIEW

Recent advances in both murine models and clinical research of neutrophilic asthma are improving our understanding on the etiology and pathophysiology of this enigmatic endotype of asthma. We here aim at providing an overview of our current and latest insights on the pathophysiology and treatment of neutrophilic asthma.

RECENT FINDINGS

Activation of the NLRP3 inflammasome pathway with increased IL-1β has been demonstrated in various studies involving patients with asthma. It has been suggested that type 3 innate lymphoid cells are implicated in the inflammatory cascade leading to neutrophilic inflammation. The role of neutrophil extracellular traps is only at the start of being understood and might be an attractive novel therapeutic target. A diverse panel of nonallergic stimuli, such as cigarette smoke, intensive exercise, cold air or saturated fatty acids, have been linked with neutrophilic airway inflammation. Azithromycin treatment could reduce asthma exacerbations and quality of life in patients with persistent asthma.

SUMMARY

Research of the last few years has accelerated our insights in mechanisms underlying neutrophilic asthma. This is in stark contrast with the lack of efficacy of different therapies targeting neutrophil chemotaxis and/or signalling cascade, such as IL-17A or CXCR2. Macrolide therapy might be a useful add-on therapy for patients with persistent asthma.

Toward clinically applicable biomarkers for asthma: An EAACI position paper

Inflammation, structural, and functional abnormalities within the airways are key features of asthma. Although these processes are well documented, their expression varies across the heterogeneous spectrum of asthma. Type 2 inflammatory responses are characterized by increased levels of eosinophils, FeNO, and type 2 cytokines in blood and/or airways. Presently, type 2 asthma is the best-defined endotype, typically found in patients with allergic asthma, but surprisingly also in nonallergic patients with (severe) asthma. The etiology of asthma with non-type 2 inflammation is less clear. During the past decade, targeted therapies, including biologicals and small molecules, have been increasingly integrated into treatment strategies of severe asthma. These treatments block specific inflammatory pathways or single mediators. Single or composite biomarkers help to identify patients who will benefit from these treatments. So far, only a few inflammatory biomarkers have been validated for clinical application. The European Academy of Allergy & Clinical Immunology Task Force on Biomarkers in Asthma was initiated to review different biomarker sampling methods and to investigate clinical applicability of new and existing inflammatory biomarkers (point-of-care) to support diagnosis, targeted treatment, and monitoring of severe asthma. Subsequently, we discuss existing and novel targeted therapies for asthma as well as applicable biomarkers.

Role of IL-17 in asthma pathogenesis and its implications for the clinic

Introduction: Asthma is a respiratory disorder typically characterized by T-helper type 2 (Th2) inflammation that is mediated by cytokines, including IL-4, IL-5, and IL-13. Pathophysiologically, airway inflammation involving prominent eosinophilia, elevated IgE synthesis, airway hyperresponsiveness, mucus hypersecretion, and airway remodeling manifest clinically in patients as wheezing, breathlessness, chest tightness and episodic coughing. However, the Th2 paradigm falls short in interpreting the full spectrum of asthma severity. Areas covered: Severe asthmatics represent a distinct phenotype with their mixed pattern of neutrophilic-eosinophilic infiltration and glucocorticoid insensitivity making them refractory to currently available therapies. Th17 cells and their signature cytokine, IL-17, have been implicated in the development of severe asthma. Here, we review the contribution of IL-17 in the pathological features of asthma, gathered from both human and animal studies published in Pubmed during the past 10 years, and briefly discuss the clinical implications of targeting IL-17 imbalance in asthmatic patients. Expert opinion: With advancement in our understanding of the role of IL-17 in asthma pathology, it is clear that IL-17 is a targetable pathway which may lead to improvement in clinical symptoms of asthma. However, further elucidation of the complex interactions unfurled by IL-17 is essential in the empirical development of effective therapeutic options for refractory asthmatics.

Obesity and severe asthma

Obesity is an important global health issue for both children and adults. Obesity increases the prevalence and incidence of asthma and also increases the risk for severe asthma. Here we describe the features of severe asthma phenotypes for which obesity is a defining characteristic, including steroid resistance, airway inflammation, and co-morbidities. We also review current concepts regarding the mechanistic basis for the impact of obesity in severe asthma, including possible roles for vitamin D deficiency, systemic inflammation, and the microbiome. Finally, we describe data indicating a role for diet, weight loss, and exercise in the treatment of severe asthma with obesity. Better understanding of the mechanistic basis for the role of obesity in severe asthma could lead to new therapeutic options for this population.

Augmented Responses to Ozone in Obese Mice Require IL-17A and Gastrin-Releasing Peptide

Ozone and obesity both increase IL-17A in the lungs. In mice, obesity augments the airway hyperresponsiveness and neutrophil recruitment induced by acute ozone exposure. Therefore, we examined the role of IL-17A in obesity-related increases in the response to ozone observed in obese mice. Lean wild-type and obese db/db mice were pretreated with IL-17A-blocking or isotype antibodies, exposed to air or ozone (2 ppm for 3 h), and evaluated 24 hours later. Microarray analysis of lung tissue gene expression was used to examine the mechanistic basis for effects of anti-IL-17A. Compared with lean mice, ozone-exposed obese mice had greater concentrations of BAL IL-17A and greater numbers of pulmonary IL-17A⁺ cells. Ozone-induced increases in BAL IL-23 and CCL20, cytokines important for IL-17A⁺ cell recruitment and activation, were also greater in obese mice. Anti-IL-17A treatment reduced ozone-induced airway hyperresponsiveness toward levels observed in lean mice. Anti-IL-17A treatment also reduced BAL neutrophils in both lean and obese mice, possibly because of reductions in CXCL1. Microarray analysis identified gastrin-releasing peptide (GRP) receptor (Grpr) among those genes that were both elevated in the lungs of obese mice after ozone exposure and reduced after anti-IL-17A treatment. Furthermore, ozone exposure increased BAL GRP to a greater extent in obese than in lean mice, and GRP-neutralizing antibody treatment reduced obesity-related increases in ozone-induced airway hyperresponsiveness and neutrophil recruitment. Our data indicate that IL-17A contributes to augmented responses to ozone in db/db mice. Furthermore, IL-17A appears to act at least in part by inducing expression of Grpr.

Saturated fatty acids, obesity, and the nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in asthmatic patients

BACKGROUND

Both obesity and high dietary fat intake activate the nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome.

OBJECTIVE

We aimed to examine NLRP3 inflammasome activity in the airways of obese asthmatic patients after macronutrient overload and in immune cells challenged by inflammasome triggers.

METHODS

Study 1 was a cross-sectional observational study of nonobese (n = 51) and obese (n = 76) asthmatic adults. Study 2 was a randomized, crossover, acute feeding study in 23 asthmatic adults (n = 12 nonobese and n = 11 obese subjects). Subjects consumed 3 isocaloric meals on 3 separate occasions (ie, saturated fatty acid, n-6 polyunsaturated fatty acid, and carbohydrate) and were assessed at 0 and 4 hours. For Studies 1 and 2, airway inflammation was measured based on sputum differential cell counts, IL-1β protein levels (ELISA), and sputum cell gene expression (Nanostring nCounter). In Study 3 peripheral blood neutrophils and monocytes were isolated by using Ficoll density gradient and magnetic bead separation and incubated with or without palmitic acid, LPS, or TNF-α for 24 hours, and IL-1β release was measured (ELISA).

RESULTS

In Study 1 NLRP3 and nucleotide oligomerization domain 1 (NOD1) gene expression was upregulated, and sputum IL-1β protein levels were greater in obese versus nonobese asthmatic patients. In Study 2 the saturated fatty acid meal led to increases in sputum neutrophil percentages and sputum cell gene expression of Toll-like receptor 4 (TLR4) and NLRP3 at 4 hours in nonobese asthmatic patients. In Study 3 neutrophils and monocytes released IL-1β when challenged with a combination of palmitic acid and LPS or TNF-α.

CONCLUSION

The NLRP3 inflammasome is a potential therapeutic target in asthmatic patients. Behavioral interventions that reduce fatty acid exposure, such as weight loss and dietary saturated fat restriction, warrant further exploration.

Role of sputum biomarkers in the management of asthma

PURPOSE OF REVIEW

Airway inflammation is considered to be a cardinal feature of asthma. However, the type of airway inflammation is heterogeneous and airway inflammation may even be absent. Biomarkers may help to identify the inflammatory phenotype or endotype, especially now the time has come that targeted therapies enter daily practice.

RECENT FINDINGS

Sputum biomarkers have increased our insights into the different inflammatory asthma phenotypes, their response to treatment and their association with progression of disease. New endotypes of type 2 driven inflammation were identified using a multidimensional approach. A specific mast cell subtype has been linked with type 2 driven inflammation and response to inhaled corticosteroids. Advances have been made with regard to sputum cytokine analysis and might also help to guide future treatment of severe asthma.

SUMMARY

Identifying the target population for biological therapies will not be possible without the use of biomarkers. Optimized, easy-to-apply, automated methods for sputum analysis (cellular content or soluble markers) need to be developed for implementation of sputum biomarkers in daily clinical practice.

Innate lymphoid cells at the interface between obesity and asthma

Obesity and asthma prevalence has dramatically and concomitantly increased over the last 25 years, and many epidemiological studies have highlighted obesity as an important risk factor for asthma. Although many studies have been performed, the underlying mechanisms remain poorly understood. Innate mechanisms have been involved in both diseases, in particular through the recently described innate lymphoid cells (ILCs). ILCs are subdivided into three groups that are defined by their cytokine production and by their master transcription factor expression, in sharp correlation with their T helper counterparts. However, unlike T helper cells, ILCs do not express antigen-specific receptors, but respond to damage-induced signals. ILCs have been found in target tissues of both diseases, and data have implicated these cells in the pathogenesis of both diseases. In particular group 2 ILCs (ILC2) are activated in both the adipose and lung tissues under the effect of interleukin-33 and interleukin-25 expression. However, counter-intuitively to the well-known association between obesity and asthma, ILC2 are beneficial for obesity but deleterious for asthma. This review will examine the roles of ILCs in each disease and recent data highlighting ILCs as a putative link between obesity and asthma.

Effect of obesity on sinonasal disease in asthma

OBJECTIVE

Sinonasal disease can contribute to poor asthma control. There are reports that link obesity with an increased prevalence of sinonasal disease, but no studies evaluating the severity of sinonasal disease in obese asthmatics, and how this impacts asthma control. The purpose of the current study was to determine if obesity is associated with increased severity of sinonasal disease, and/or affects response to nasal corticosteroid treatment in asthma.

METHODS

This study included 236 adults participating in a 24-week randomized, double-masked, placebo-controlled study of nasal mometasone for the treatment of poorly controlled asthma. Sinonasal disease severity was assessed using validated questionnaires, and compared in participants of differing BMIs. Eosinophilic inflammation was assessed using markers in nasal lavage, serum and exhaled nitric oxide. Response to treatment was compared in different BMI groups.

RESULTS

Obesity had no effect on the severity of sinonasal disease symptoms in asthmatics (Sino-Nasal Outcome Test 22 (SNOT 22) score [mean ± SD] 35.4 ± 18.5, 40.2 ± 22.8, and 39.1 ± 21.7, p = 0.43, in lean, overweight and obese participants), nor on nasal, bronchial or systemic markers of allergic inflammation. Nasal steroids had some limited effects on symptoms, lung function and inflammatory markers in lean participants, but no detectable effect was found in obese patients.

CONCLUSIONS

Obesity does not affect severity of sinonasal disease in patients with asthma; the association of sinonasal disease symptoms with increased asthma severity and markers of Type 2 inflammation are consistent across all BMI groups. The response of obese patients to nasal corticosteroids requires further study.

Mechanisms of Asthma in Obesity. Pleiotropic Aspects of Obesity Produce Distinct Asthma Phenotypes

The majority of patients with severe or difficult-to-control asthma in the United States are obese. Epidemiological studies have clearly established that obese patients tend to have worse asthma control and increased hospitalizations and do not respond to standard controller therapy as well as lean patients with asthma. Less clear are the mechanistic underpinnings for the striking clinical differences between lean and obese patients with asthma. Because obesity is principally a disorder of metabolism and energy regulation, processes fundamental to the function of every cell and system within the body, it is not surprising that it affects the respiratory system; it is perhaps surprising that it has taken so long to appreciate how dysfunctional metabolism and energy regulation lead to severe airway disease. Although early investigations focused on identifying a common factor in obesity that could promote airway disease, an appreciation has emerged that the asthma of obesity is a manifestation of multiple anomalies related to obesity affecting all the different pathways that cause asthma, and likely also to de novo airway dysfunction. Consequently, all the phenotypes of asthma currently recognized in lean patients (which are profoundly modified by obesity), as well as those unique to one's obesity endotype, likely contribute to obese asthma in a particular individual. This perspective reviews what we have learned from clinical studies and animal models about the phenotypes of asthma in obesity, which show how specific aspects of obesity and altered metabolism might lead to de novo airway disease and profoundly modify existing airway disease.

Obesity's effect on asthma extends to diagnostic criteria

BACKGROUND

The use of inflammatory biomarkers to delineate the type of lung inflammation present in asthmatic subjects is increasingly common. However, the effect of obesity on these markers is unknown.

OBJECTIVES

We aimed to determine the effect of obesity on conventional markers of inflammation in asthmatic subjects.

METHODS

We performed secondary analysis of data from 652 subjects previously enrolled in 2 Asthma Clinical Research Network trials. We performed linear correlations between biomarkers and logistic regression analysis to determine the predictive value of IgE levels, blood eosinophil counts, and fraction of exhaled nitric oxide values in relationship to sputum eosinophil counts (>2%), as well as to determine whether cut points existed that would maximize the sensitivity and specificity for predicting sputum eosinophilia in the 3 weight groups.

RESULTS

Overall, statistically significant but relatively weak correlations were observed among all 4 markers of inflammation. Within obese subjects, the only significant correlation found was between IgE levels and blood eosinophil counts (r = 0.33, P < .001); furthermore, all other correlations between inflammatory markers were approximately 0, including correlations with sputum eosinophil counts. In addition, the predictive value of each biomarker alone or in combination was poor in obese subjects. In fact, in obese subjects none of the biomarkers of inflammation significantly predicted the presence of high sputum eosinophil counts. Obese asthmatic subjects have lower cut points for IgE levels (268 IU), fraction of exhaled nitric oxide values (14.5 ppb), and blood eosinophil counts (96 cells/μL) than all other groups.

CONCLUSIONS

In obese asthmatic subjects conventional biomarkers of inflammation are poorly predictive of eosinophilic airway inflammation. As such, biomarkers currently used to delineate eosinophilic inflammation in asthmatic subjects should be approached with caution in these subjects.

Precision medicine in patients with allergic diseases: Airway diseases and atopic dermatitis-PRACTALL document of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology

In this consensus document we summarize the current knowledge on major asthma, rhinitis, and atopic dermatitis endotypes under the auspices of the PRACTALL collaboration platform. PRACTALL is an initiative of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology aiming to harmonize the European and American approaches to best allergy practice and science. Precision medicine is of broad relevance for the management of asthma, rhinitis, and atopic dermatitis in the context of a better selection of treatment responders, risk prediction, and design of disease-modifying strategies. Progress has been made in profiling the type 2 immune response-driven asthma. The endotype driven approach for non-type 2 immune response asthma, rhinitis, and atopic dermatitis is lagging behind. Validation and qualification of biomarkers are needed to facilitate their translation into pathway-specific diagnostic tests. Wide consensus between academia, governmental regulators, and industry for further development and application of precision medicine in management of allergic diseases is of utmost importance. Improved knowledge of disease pathogenesis together with defining validated and qualified biomarkers are key approaches to precision medicine.

Cluster analysis of sputum cytokine-high profiles reveals diversity in T(h)2-high asthma patients

Background

Asthma is characterized by a heterogeneous inflammatory profile and can be subdivided into T(h)2-high and T(h)2-low airway inflammation. Profiling of a broader panel of airway cytokines in large unselected patient cohorts is lacking.

Methods

Patients (n = 205) were defined as being “cytokine-low/high” if sputum mRNA expression of a particular cytokine was outside the respective 10^th/90^th percentile range of the control group (n = 80). Unsupervised hierarchical clustering was used to determine clusters based on sputum cytokine profiles.

Results

Half of patients (n = 108; 52.6%) had a classical T(h)2-high (“IL-4-, IL-5- and/or IL-13-high”) sputum cytokine profile. Unsupervised cluster analysis revealed 5 clusters. Patients with an “IL-4- and/or IL-13-high” pattern surprisingly did not cluster but were equally distributed among the 5 clusters. Patients with an “IL-5-, IL-17A-/F- and IL-25- high” profile were restricted to cluster 1 (n = 24) with increased sputum eosinophil as well as neutrophil counts and poor lung function parameters at baseline and 2 years later. Four other clusters were identified: “IL-5-high or IL-10-high” (n = 16), “IL-6-high” (n = 8), “IL-22-high” (n = 25). Cluster 5 (n = 132) consists of patients without “cytokine-high” pattern or patients with only high IL-4 and/or IL-13.

Conclusion

We identified 5 unique asthma molecular phenotypes by biological clustering. Type 2 cytokines cluster with non-type 2 cytokines in 4 out of 5 clusters. Unsupervised analysis thus not supports a priori type 2 versus non-type 2 molecular phenotypes. www.clinicaltrials.gov NCT01224938. Registered 18 October 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0524-y) contains supplementary material, which is available to authorized users.

IL-17 protein levels in both induced sputum and plasma are increased in stable but not acute asthma individuals with obesity

BACKGROUND

Obesity worsens asthma control partly through enhanced airway neutrophilia, altered lung mechanics and comorbidities, including obstructive sleep apnea syndrome, gastroesophageal reflux disease and depression. Although controversial, obesity may also cause poorer outcomes in acute asthma. IL-17 is associated with neutrophilic inflammation, steroid resistance and severe asthma, but its importance in the association between asthma and obesity is unknown.

OBJECTIVE

To investigate the role of IL-17 in obese asthma in both acute and stable settings.

METHODS

Both stable (n = 177) and acute (n = 78) asthmatics were recruited and categorized into lean (n = 77 and 39 respectively), overweight (n = 41 and 17 respectively) and obese (n = 59 and 22 respectively) groups and compared for clinical characteristics, including sputum and plasma IL-17 protein concentrations, sputum cellularity, spirometry and comorbidities. Correlations of IL-17 expression with other measures were explored.

RESULTS

In stable subjects, airway neutrophilia and IL-17 concentrations were most prominent in the obese, and correlated positively with each other. Significant increase in plasma IL-17 levels was also noted and associated with elevated depressive symptoms in obesity. In acute asthma, IL-17 expression, like most other clinical measures, was similar among lean, overweight and obese groups, but was higher in acute versus stable asthma subjects, with sputum IL-17 correlating positively with sputum neutrophils and negatively with FEV₁ and plasma IL-17 showing a positive connection to airway eosinophilia during exacerbation.

CONCLUSIONS

IL-17 contributes to worse disease control in obese asthma through enhancing airway neutrophilia and depression, and may implicate in asthma exacerbations. Effects of adiposity on acute asthma remain uncertain.

Urinary metabolomic profiling of asthmatics can be related to clinical characteristics

Metabolomics has been increasingly explored to achieve an improved understanding of asthma. In the current observational and exploratory study, the first to have examined the relationship between oxidative stress extension, eosinophilic inflammation, and disease severity in asthmatic patients, metabolomics (using target aliphatic aldehydes and alkanes) was carried out using solid-phase microextraction (SPME) followed by a comprehensive two-dimensional gas chromatography coupled to mass spectrometry with a high-resolution time-of-flight analyzer (GC×GC-ToFMS). We were able to demonstrate that metabolomics can give valuable insights into asthma mechanisms once lipidic peroxidation assessed by urinary metabolomics is related to the clinical characteristics of nonobese asthmatics, such as disease severity, lung function, and eosinophilic inflammation. Nevertheless, considering our sample size, the obtained results require further validation using a much larger sample cohort.

Endotypes of allergic diseases and asthma: An important step in building blocks for the future of precision medicine

Discoveries from basic science research in the last decade have brought significant progress in knowledge of pathophysiologic processes of allergic diseases, with a compelling impact on understanding of the natural history, risk prediction, treatment selection or mechanism-specific prevention strategies. The view of the pathophysiology of allergic diseases developed from a mechanistic approach, with a focus on symptoms and organ function, to the recognition of a complex network of immunological pathways. Several subtypes of inflammation and complex immune-regulatory networks and the reasons for their failure are now described, that open the way for the development of new diagnostic tools and innovative targeted-treatments. An endotype is a subtype of a disease condition, which is defined by a distinct pathophysiological mechanism, whereas a disease phenotype defines any observable characteristic of a disease without any implication of a mechanism. Another key word linked to disease endotyping is biomarker that is measured and evaluated to examine any biological or pathogenic processes, including response to a therapeutic intervention. These three keywords will be discussed more and more in the future with the upcoming efforts to revolutionize patient care in the direction of precision medicine and precision health. The understanding of disease endotypes based on pathophysiological principles and their validation across clinically meaningful outcomes in asthma, allergic rhinitis, chronic rhinosinusitis, atopic dermatitis and food allergy will be crucial for the success of precision medicine as a new approach to patient management.

Sex hormones and systemic inflammation are modulators of the obese-asthma phenotype

BACKGROUND

Both systemic inflammation and sex hormones have been proposed as potential mediators of the obese-asthma phenotype. The aim of this study was to examine the associations between sex hormones, oral contraceptive pill (OCP) use, systemic inflammation and airway inflammation in adults with asthma.

METHODS

Obese (n = 39) and nonobese (n = 42) females and obese (n = 24) and nonobese (n = 25) males with asthma were recruited. Females were further categorized as reproductive-aged (<50 years old; n = 36) or older (>50 years old; n = 45). Thirteen (36.1%) reproductive-aged females were using the OCP. Participants had induced sputum cell counts measured and blood analysed for sex hormones and inflammatory markers.

RESULTS

Obese reproductive-aged females had higher sputum %neutrophils than nonobese reproductive-aged females (45.4 ± 24.3% vs 27.5 ± 17.5%, P = 0.016); however, there was no difference in sputum neutrophils in obese compared with nonobese males (P = 0.620) or older females (P = 0.087). Multiple linear regression analysis found testosterone and OCP use to be negative predictors of sputum %neutrophils, while C-reactive protein and IL-6 were positive predictors of sputum %neutrophils. BMI and age were not significant predictors in the multivariate model. Reproductive-aged females using the OCP had significantly lower sputum %neutrophils than those not using the OCP (23.2 ± 12.6% vs 42.1 ± 23.8%, P = 0.015).

CONCLUSIONS

This study suggests that sex hormones and systemic inflammation may be mediating the obese-asthma phenotype. The observation that OCP use was associated with lower sputum %neutrophils in reproductive-aged females warrants further investigation.

Prolonged allergen exposure is associated with increased thymic stromal lymphopoietin expression and Th2-skewing in mouse models of chronic rhinosinusitis

OBJECTIVES/HYPOTHESIS

Chronic rhinosinusitis (CRS) is characterized by a dysfunctional host-environment interaction at the nasal mucosa. Contributions of host susceptibility factors such as atopy and aspirin sensitivity to CRS pathophysiology are well established. However, clinical studies on the effects of environmental factors are limited. This study investigates the histological and immunological effects of allergen exposure duration in animal models.

STUDY DESIGN

Animal study.

METHODS

A murine model for CRS with nasal polypoid lesions was induced by instilling ovalbumin/staphylococcal enterotoxin B (SEB) into murine nasal cavities for 12 (short term) or 24 weeks (long term). Histopathological changes were observed. Interleukin (IL)-4, IL-17A, IL-10, and interferon (INF)-γ levels from nasal lavage fluid were measured using enzyme-linked immunosorbent assay. Gene expressions of IL-25, thymic stromal lymphopoietin (TSLP), IL-4, IL-5, INF-γ, C-C motif chemokine ligand (CCL)-11, CCL-24, C-X-C motif chemokine ligand (CXCL)-1, CXCL-2, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, matrix metallopeptidase (MMP)-7, and tissue inhibitor of metalloproteinase (TIMP)-3 were analyzed from the nasal mucosa.

RESULTS

Long-term CRS models exhibited increased polypoid lesions, edematous mucosal thickness, and eosinophil infiltration compared with short-term models and showed a higher IL-10 level but lower IFN-γ and IL-17A protein levels. Moreover, CCL-24 and MMP-7 gene expressions increased whereas TIMP-3 expression decreased in long-term models compared to controls and short-term models. IL-25 and TSLP expressions were upregulated at mRNA and protein levels in short-term and long-term CRS models, respectively. Furthermore, TSLP mRNA expression was positively associated with IL-5 (r = 0.8754) and inversely correlated to IFN-γ (r = -0.7212) in CRS models.

CONCLUSIONS

Prolonged allergen exposure in ovalbumin/SEB-induced CRS models maintains Th2 inflammation and reduces Th1 inflammation, which was associated with upregulation of TSLP.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:E265-E272, 2016.

Obesity, Asthma, and the Microbiome

Obesity is a risk factor for asthma, but standard asthma drugs have reduced efficacy in the obese. Obesity alters the gastrointestinal microbial community structure. This change in structure contributes to some obesity-related conditions and also could be contributing to obesity-related asthma. Although currently unexplored, obesity may also be altering lung microbiota. Understanding the role of microbiota in obesity-related asthma could lead to novel treatments for these patients.

IL-25 as a novel therapeutic target in nasal polyps of patients with chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) with nasal polyps (NPs) in Western populations is associated with TH2 cytokine polarization. IL-25, an IL-17 family cytokine, was recently reported to induce TH2-type immune responses and to contribute to several allergic diseases, such as atopic dermatitis and asthma. However, the role of IL-25 in Asian patients with nasal polyposis remains unclear.

OBJECTIVE

We sought to determine the role of IL-25 in Asian patients with nasal polyposis and CRS.

METHODS

We investigated IL-25 expression and its cellular origins in NPs of human subjects using immunohistochemistry (IHC), quantitative RT-PCR, and ELISA of NP tissues. Correlations between IL-25 expression and expression of other inflammatory markers in NP tissues were also explored. Anti-IL-25 neutralizing antibody was administered in an ovalbumin- and staphylococcal enterotoxin B-induced murine NP model to confirm the function of IL-25 during nasal polypogenesis.

RESULTS

IL-25 expression was upregulated in NP mucosa from patients with CRS with NPs compared with uncinate process tissue from control subjects and those with CRS without NPs. Overexpression of epithelial IL-25 was confirmed by using IHC, and double IHC staining showed that tryptase-positive cells were one of the main sources of IL-25 among immune cells. Furthermore, IL-17 receptor B levels were also increased in immune cells of patients with NPs compared with those in control subjects. In NPs IL-25 mRNA expression positively correlated with the expression of several inflammatory markers, including T-box transcription factor, RAR-related orphan receptor C, GATA3, eosinophil cationic protein, TGF-β1, and TGF-β2. IL-25 was more abundant in the murine NP model compared with control mice, and similar correlations between IL-25 and inflammatory markers were observed in murine models. Anti-IL-25 treatment reduced the number of polyps, mucosal edema thickness, collagen deposition, and infiltration of inflammatory cells, such as eosinophils and neutrophils. This treatment also inhibited expression of local inflammatory cytokines, such as IL-4 and IFN-γ. Furthermore, expression of CCL11, CXCL2, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 in the nasal mucosa was suppressed in the anti-IL-25-treated group.

CONCLUSION

Our results suggest that IL-25 secreted from the sinonasal epithelia and infiltrating mast cells plays a crucial role in the pathogenesis of CRS with NPs in Asian patients. In addition, our results suggest the novel possibility of treating nasal polyposis with anti-IL-25 therapy.