Severe asthma and asthma-COPD overlap: a double agent or identical twins?

Biomarkers in exhaled breath condensate as fingerprints of asthma, chronic obstructive pulmonary disease and asthma-chronic obstructive pulmonary disease overlap: a critical review

Asthma, chronic obstructive pulmonary disease (COPD) and asthma-COPD overlap are the third leading cause of mortality around the world. They share some common features, which can lead to misdiagnosis. To properly manage these conditions, reliable markers for early and accurate diagnosis are needed. Over the past 20 years, many molecules have been investigated in the exhaled breath condensate to better understand inflammation pathways and mechanisms related to these disorders. Recently, more advanced techniques, such as sensitive metabolomic and proteomic profiling, have been used to obtain a more comprehensive understanding. This article reviews the use of targeted and untargeted metabolomic methodology to study asthma, COPD and asthma-COPD overlap.

Metabolomics of asthma, COPD, and asthma-COPD overlap: an overview

The two common progressive lung diseases, asthma and chronic obstructive pulmonary disease (COPD), are the leading causes of morbidity and mortality worldwide. Asthma-COPD overlap, referred to as ACO, is another complex pulmonary disease that manifests itself with features of both asthma and COPD. The disease has no clear diagnostic or therapeutic guidelines, thereby making both diagnosis and treatment challenging. Though a number of studies on ACO have been documented, gaps in knowledge regarding the pathophysiologic mechanism of this disorder exist. Addressing this issue is an urgent need for improved diagnostic and therapeutic management of the disease. Metabolomics, an increasingly popular technique, reveals the pathogenesis of complex diseases and holds promise in biomarker discovery. This comprehensive narrative review, comprising 99 original research articles in the last five years (2017-2022), summarizes the scientific advances in terms of metabolic alterations in patients with asthma, COPD, and ACO. The analytical tools, nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS), commonly used to study the expression of the metabolome, are discussed. Challenges frequently encountered during metabolite identification and quality assessment are highlighted. Bridging the gap between phenotype and metabotype is envisioned in the future.

A unique population of neutrophils generated by air pollutant-induced lung damage exacerbates airway inflammation

BACKGROUND

Diesel exhaust particles (DEPs) are the main component of traffic-related air pollution and have been implicated in the pathogenesis and exacerbation of asthma. However, the mechanism by which DEP exposure aggravates asthma symptoms remains unclear.

OBJECTIVE

This study aimed to identify a key cellular player of air pollutant-induced asthma exacerbation and development.

METHODS

We examined the distribution of innate immune cells in the murine models of asthma induced by house dust mite and DEP. Changes in immune cell profiles caused by DEP exposure were confirmed by flow cytometry and RNA-Seq analysis. The roles of sialic acid-binding, Ig-like lectin F (SiglecF)-positive neutrophils were further evaluated by adoptive transfer experiment and in vitro functional studies.

RESULTS

DEP exposure induced a unique population of lung granulocytes that coexpressed Ly6G and SiglecF. These cells differed phenotypically, morphologically, functionally, and transcriptionally from other SiglecF-expressing cells in the lungs. Our findings with murine models suggest that intratracheal challenge with DEPs induces the local release of adenosine triphosphate, which is a damage-associated molecular pattern signal. Adenosine triphosphate promotes the expression of SiglecF on neutrophils, and these SiglecF⁺ neutrophils worsen type 2 and 3 airway inflammation by producing high levels of cysteinyl leukotrienes and neutrophil extracellular traps. We also found Siglec8- (which corresponds to murine SiglecF) expressing neutrophils, and we found it in patients with asthma-chronic obstructive pulmonary disease overlap.

CONCLUSION

The SiglecF⁺ neutrophil is a novel and critical player in airway inflammation and targeting this population could reverse or ameliorate asthma.

Asthma-COPD overlap: current understanding and the utility of experimental models

Pathological features of both asthma and COPD coexist in some patients and this is termed asthma-COPD overlap (ACO). ACO is heterogeneous and patients exhibit various combinations of asthma and COPD features, making it difficult to characterise the underlying pathogenic mechanisms. There are no controlled studies that define effective therapies for ACO, which arises from the lack of international consensus on the definition and diagnostic criteria for ACO, as well as scant in vitro and in vivo data. There remain unmet needs for experimental models of ACO that accurately recapitulate the hallmark features of ACO in patients. The development and interrogation of such models will identify underlying disease-causing mechanisms, as well as enabling the identification of novel therapeutic targets and providing a platform for assessing new ACO therapies. Here, we review the current understanding of the clinical features of ACO and highlight the approaches that are best suited for developing representative experimental models of ACO.

Understanding the pathogenesis of asthma-COPD overlap is critical for improving therapeutic approaches. We present current knowledge on asthma-COPD overlap and the requirements for developing an optimal animal model of disease.https://bit.ly/3lsjyvm

Characteristics of Specialist-Diagnosed Asthma-COPD Overlap in Severe Asthma: Observations from the Korean Severe Asthma Registry (KoSAR)

BACKGROUND

While the clinical characteristics and outcomes of asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) have been frequently compared with those of COPD or asthma, the prevalence and features of ACO in patients with severe asthma are unclear.

OBJECTIVES

Evaluation of the prevalence and clinical features of ACO using the Korean severe asthma registry.

METHODS

At the time of registration, ACO was determined in patients with severe asthma by attending specialists. Patients were classified into ACO and non-ACO groups, and the demographic and clinical characteristics of these two groups were compared.

RESULTS

Of 482 patients with severe asthma, 23.7% had ACO. Patients in the ACO group were more likely to be male (P < .001), older (P < .001), and ex- or current smokers (P < .001) compared with those in the non-ACO group. Patients in the ACO group had lower mean forced expiratory volume in 1 second (P < .001) and blood eosinophil percentage (P = .006), but higher blood neutrophil percentage (P = .027) than those in the non-ACO group. The ACO group used more inhaled long-acting muscarinic antagonist (P < .001), methylxanthine (P = .001), or sustained systemic corticosteroid (P = .002). In addition, unscheduled emergency department visits due to exacerbation were more frequent in the ACO group (P = .006).

CONCLUSION

Among patients with severe asthma, those with ACO were older, predominantly male, and were more likely to have a smoking history than those with asthma only. Patients with ACO used more systemic corticosteroid and had more frequent exacerbations related to emergency department visits than those with severe asthma only.

Chronic obstructive pulmonary disease phenotypes: imprint on pharmacological and non-pharmacological therapy

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease associated with significant morbidity and mortality. Over the past few years, there has been cumulating interest in describing this heterogeneity and using this information to group patients into different COPD phenotypes. The term phenotype is defined as single or combination of disease attributes that describe differences between individuals with COPD as they relate to clinically meaningful outcomes. It describes also the physical appearance or biochemical characteristics which result from the genotype-environment interaction. Furthermore, it clearly identifies subgroups with a significant impact in the prognosis. Recently, approaches to COPD phenotyping have been significantly enhanced in tandem with developments in understanding the disease’s various pathological, clinical and genetic features. This knowledge inspired the researchers to investigate more tailored therapeutic strategies that could not only give a more potent effect but also help to avoid the traditional therapy’s undesirable side effects. Eventually, it could be said that the phenotypic approach to COPD in the last decade had a huge impact on daily practice and management delivered to COPD patients. In this review, we highlight the impact of pharmacological and non-pharmacological treatment options on COPD outcomes, using a personalized treatment strategy based on different phenotypes.

Oropharyngeal Swallowing Dynamic Findings in People with Asthma

Airflow obstruction in people with asthma, similar to COPD, may interfere with swallowing, increasing the risk of food or liquid entrance into the lower airways, and favoring the uncontrolled disease. To describe the complaints and findings of the oropharyngeal swallowing mechanisms in patients with mild and severe asthma, a cross-sectional study was performed. A total of 135 participants with asthma were studied, of whom 97 had severe asthma and 38 had mild asthma. All subjects answered a questionnaire with demographic information, disease exacerbations, Asthma Control Questionnaire 6 (ACQ6-Juniper 1999), GastroEsophageal Reflux Disease Symptoms Questionnaire (GERD-SQ-Fornari et al. 2004), and Eating Assessment Tool 10 (EAT-10-Gonçalves et al., 2013). The oral and pharyngeal swallowing assessment occurred via videofluoroscopic swallowing evaluation. The age range of the participants was from 19 to 80 years, with a predominance of females (78.6%). Uncontrolled asthma was observed in 50 (52%) of the patients with severe asthma and in 11 (29%) of the patients with mild asthma (ACQ6 > 1.5). The GERD-SQ and EAT-10 scores were similar in both groups. In the bivariate analysis, the group with severe asthma presented with more changes when compared to the group with mild asthma in the following events: atypical lingual movement during the swallowing of liquid in the volumes of 5 ml (p = 0.003) and 10 ml (p = 0.001), and solid (p = 0.009); oral transit time increased in swallowing of liquid in the volumes of 5 ml (p = 0.003) and 20 ml (p = 0.026); beginning of the pharyngeal swallowing phase below the mandibular ramus (p = 0.003); pharyngeal residue (p = 0.017) of solid consistency; laryngeal penetration of 5 ml (p = 0.050) and 20 ml (p = 0.032) of liquid; increased transition time between the oral and pharyngeal swallowing phases (p = 0.035) and increased pharyngeal transit time (p = 0.045) of solid consistency. Tracheal aspiration was observed only in the group with severe asthma. After the multivariate analysis, atypical tongue movement maintained a statistically significant difference between the two groups. Oropharyngeal swallowing alternations were frequent in the studied sample and more markedly present in patients with severe asthma. Multivariate regression revealed atypical lingual movement, which was greater in patients with severe asthma. The clinical significance of these findings should be further investigated.