Exposure to intermittent hypoxia inhibits allergic airway inflammation in a murine model of asthma

Effects of biological therapies on patients with Type-2 high asthma and comorbid obesity

Over 20 million adults and 6 million children in the United States (US) have asthma, a chronic respiratory disease characterized by airway inflammation, bronchoconstriction, and mucus hypersecretion. Obesity, another highly prevalent disease in the US, is a major risk factor for asthma and a significant cause of diminished asthma control, increased submucosal eosinophilia, and reduced quality of life. A large subgroup of these patients experiences severe symptoms and recurrent exacerbations despite maximal dosage of standard asthma therapies. In the past two decades, the development of biological therapies has revolutionized the field and advanced our understanding of type 2 inflammatory biomarkers. However, patients with obesity and comorbid asthma are not principally considered in clinical trials of biologics. Large landmark cluster analyses of patients with asthma have consistently identified specific asthma phenotypes that associate with obesity but may be differentiated by age of asthma onset and inflammatory cell profiles in sputum. These patterns suggest that biologic processes driving asthma pathology are heterogenous among patients with obesity. The biological mechanisms driving pathology in patients with asthma and comorbid obesity are not well understood and likely multifactorial. Future research needs to be done to elicit the cellular and metabolic functions in the relationship of obesity and asthma to yield the best treatment options for this multiplex condition. In this review, we explore the key features of type 2 inflammation in asthma and discuss the effectiveness, safety profile, and research gaps regarding the currently approved biological therapies in asthma patients with obesity.

Co-existence of OSA and respiratory diseases and the influence of gender

INTRODUCTION

Sleep-disordered breathing (SDB), especially obstructive sleep apnea (OSA), is commonly associated with respiratory diseases, such as COPD, asthma and interstitial lung disease.

AREAS COVERED

This narrative review aims to comprehensively synthesize the existing information on SDB in respiratory diseases, investigate the role of gender in this association, and highlight the importance of OSA management in improving sleep, quality of life, and disease prognosis in these specific patient populations.

EXPERT OPINION

Research indicates a synergistic link between OSA and chronic respiratory diseases, which leads to greater morbidity and mortality compared to each disorder alone. Given the lack of an optimal OSA screening tool for these patients, a comprehensive patient approach and overnight diagnostic sleep study are imperative. Despite the limited evidence available, it seems that gender has an impact on the prevalence, severity, and susceptibility of this coexistence. Recognizing the role of gender in the coexistence of OSA and other respiratory diseases can enhance everyday medical practice and enable clinicians to adopt a more personalized approach toward optimal screening and diagnosis of these patients.

The relationship between obstructive sleep apnea and asthma severity and vice versa: a systematic review and meta-analysis

BACKGROUND

There is a great association between the prevalence of obstructive sleep apnea (OSA) and asthma. Nonetheless, whether OSA impacts lung function, symptoms, and control in asthma and whether asthma increases the respiratory events in OSA are unknown. This meta-analysis aimed to examine the relationship between obstructive sleep apnea and asthma severity and vice versa.

METHODS

We carried out a systematic search of PubMed, EMBASE, and Scopus from inception to September 2022. Primary outcomes were lung function, parameters of polysomnography, the risk of OSA in more severe or difficult-to-control asthmatic patients, and the risk of asthma in patients with more severe OSA. Heterogeneity was examined with the Q test and I² statistics. We also performed subgroup analysis, Meta-regression, and Egger's test for bias analysis.

RESULTS

34 studies with 27,912 subjects were totally included. The results showed that the comorbidity of OSA aggravated lung function in asthmatic patients with a consequent decreased forced expiratory volume in one second %predicted (%FEV1) and the effect was particularly evident in children. %FEV1 tended to decrease in adult asthma patients complicated with OSA, but did not reach statistical significance. Interestingly, the risk of asthma seemed to be slightly lower in patients with more severe OSA (OR = 0.87, 95%CI 0.763-0.998). Asthma had no significant effect on polysomnography, but increased daytime sleepiness assessed by the Epworth Sleepiness Scale in OSA patients (WMD = 0.60, 95%CI 0.16-1.04). More severe asthma or difficult-to-control asthma was independently associated with OSA (odds ratio (OR) = 4.36, 95%CI 2.49-7.64).

CONCLUSION

OSA was associated with more severe or difficult-to-control asthma with decreased %FEV₁ in children. The effect of OSA on lung function in adult patients should be further confirmed. Asthma increased daytime sleepiness in OSA patients. More studies are warranted to investigate the effect of asthma on OSA severity and the impact of different OSA severity on the prevalence of asthma. It is strongly recommended that people with moderate-to-severe or difficult-to-control asthma screen for OSA and get the appropriate treatment.

Low oxygen levels decrease adaptive immune responses and ameliorate experimental asthma in mice

BACKGROUND

High-altitude therapy has been used as add-on treatment for allergic asthma with considerable success. However, the underlying mechanisms remain unclear. In order to investigate the possible therapeutic effects of high-altitude therapy on allergic asthma, we utilized a new in vivo mouse model.

METHODS

Mice were treated with house dust mite (HDM) extract over 4 weeks and co-exposed to 10% oxygen (Hyp) or room air for the final 2 weeks. Experimental asthma was assessed by airway hyper-responsiveness, mucus hypersecretion and inflammatory cell recruitment. Isolated immune cells from mouse and allergic patients were stimulated in vitro with HDM under Hyp and normoxia in different co-culture systems to analyse the adaptive immune response.

RESULTS

Compared to HDM-treated mice in room air, HDM-treated Hyp-mice displayed ameliorated mucosal hypersecretion and airway hyper-responsiveness. The attenuated asthma phenotype was associated with strongly reduced activation of antigen-presenting cells (APCs), effector cell infiltration and cytokine secretion. In vitro, hypoxia almost completely suppressed the HDM-induced adaptive immune response in both mouse and human immune cells. While hypoxia did not affect effector T-cell responses per-se, it interfered with antigen-presenting cell (APC) differentiation and APC/effector cell crosstalk.

CONCLUSIONS

Hypoxia-induced reduction in the Th2-response to HDM ameliorates allergic asthma in vivo. Hypoxia interferes with APC/T-cell crosstalk and confers an unresponsive phenotype to APCs.

Asthma and obstructive sleep apnoea in adults and children - an up-to-date review

Obstructive sleep apnoea (OSA) and asthma are two common respiratory disorders in children and adults. Apart from common risk factors, such as obesity, gastroesophageal reflux disease and allergic rhinitis, emerging evidence suggest that the two diseases may complicate the clinical course of each other. On one hand, OSA modifies asthmatic airway inflammation and is associated with poor asthma control. On the other hand, asthma and its medications increase the collapsibility of the upper airways contributing to the development and worsening of OSA. The overnight respiratory symptoms of OSA and asthma are often similar, and an inpatient polysomnography is often necessary for a proper diagnosis, especially in children. Continuous positive pressure, the gold standard treatment for OSA can improve asthma control in patients suffering from both diseases. However, there is limited evidence how anti-asthma medications act in the same patients. Nevertheless, adenotonsillectomy seems to be effective in children with concomitant asthma and OSA. This review summarises the evidence for the bidirectional link between asthma and OSA, focuses on diagnostic and therapeutic challenges and highlights the need for further research.