Contribution of Obstructive Sleep Apnea to Asthmatic Airway Inflammation and Impact of Its Treatment on the Course of Asthma

Asthma and obstructive sleep apnea (OSA) are very common respiratory disorders in the general population. Beyond their high prevalence, shared risk factors, and genetic linkages, bidirectional relationships between asthma and OSA exist, each disorder affecting the other's presence and severity. The author reviews here some of the salient links between constituents of the alternative overlap syndrome, that is, OSA comorbid with asthma, with an emphasis on the effects of OSA or its treatment on inflammation in asthma. In the directional relationship from OSA toward asthma, beyond direct influences, multiple factors and comorbidities seem to contribute.

The Effect of Simulated Obstructive Apneas on Mechanical Characteristics of Lower Airways in Individuals with Asthma

Increased negative intrathoracic pressure that occurs during pharyngeal obstruction can increase thoracic fluid volume that may contribute to lower airway narrowing in individuals with obstructive sleep apnea (OSA) and asthma. Our previous study showed that fluid accumulation in the thorax induced by simulated OSA can increase total respiratory resistance. However, the effect of fluid shift on lower airway narrowing has not been investigated. To examine the effect of fluid accumulation in the thorax on the resistance of the lower airway. Non-asthma participants and individuals with (un)controlled asthma were recruited and underwent a single-day experiment. A catheter with six pressure sensors was inserted through the nose to continuously measure pressure at different sites of the airway, while a pneumotachograph was attached to a mouthpiece to record airflow. To simulate obstructive apneas, participants performed 25 Mueller maneuvers (MMs) while lying supine. Using the recordings of pressure sensor and airflow, total respiratory (RT), lower respiratory components (RL), and upper airway (RUA) resistances were calculated before and after MMs. Generalized estimation equation method was used to find the predictors of RL among variables including age, sex, body mass index, and the effect of MMs and asthma. Eighteen participants were included. Performing MMs significantly increased RT (2.23 ± 2.08 cmH2O/L/s, p = 0.003) and RL (1.52 ± 2.00 cmH2O/L/s, p = 0.023) in participants with asthma, while only RL was increased in non-asthma group (1.96 ± 1.73 cmH2O/L/s, p = 0.039). We found the model with age, and the effect of MMs and asthma severity generated the highest correlation (R2 = 0.69, p < 0.001). We provide evidence that fluid accumulation in the thorax caused by excessive intrathoracic pressure increases RL in both non-asthma and asthma groups. The changes in RL were related to age, having asthma and the effect of simulated OSA. This can explain the interrelationship between OSA and asthma.

One size does not fit all: Perioperative management of patients with heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is recognized as an important risk factor for perioperative complications. However, anesthesia management of HFpEF patients remains a considerable challenge without clear guidance. HFpEF is heterogeneous in its pathophysiological processes, diverse clinical presentations, adverse remodeling of cardiovascular and other organs, and clinical outcomes. It is difficult to manage the disease with one fixed approach because of this. This review phenotypes HFpEF patients by combining their clinical features and anesthesia care issues. Five phenotypes of HFpEF patients are identified: A, O, P, C, and Y. The clinical features, anesthesia implications, and anesthesia management for each phenotype are highlighted and discussed. Such an approach to HFpEF patients in the operating room could deliver safe, high-quality perioperative care.

Obesity and Insulin Resistance in Asthma Pathogenesis and Clinical Outcomes

Common inflammatory ground links obesity, insulin resistance, and asthma. As recognition of their interplay, one worsening the natural course of the other, is recognised, questions remain about how to adequately address them altogether to improve clinical outcomes. The present manuscript sheds light on the problem, describing possible pathophysiological links, clinical views, and therapeutic challenges, raising questions about what remains to be done, and calling for multidisciplinary treatment of these patients to detect diseases early and adequately address them before they become full-blown and deteriorate their health and quality of life.

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.

Asthma and obstructive sleep apnea: Unveiling correlations and treatable traits for comprehensive care

Asthma and obstructive sleep apnea (OSA) are common respiratory disorders. They share characteristics such as airway obstruction, poor sleep quality, and low quality of life. They are often present as comorbidities, along with obesity, gastroesophageal reflux disease (GERD), and allergic rhinitis (AR), which impacts the disease's control. In recent years, there has been discussion about the association between these conditions and their pathophysiological and clinical consequences, resulting in worse health outcomes, increased healthcare resource consumption, prolonged hospital stays, and increased morbidity and mortality. Some studies demonstrate that treatment with continuous positive airway pressure (CPAP) can have a beneficial effect on both pathologies. This review summarizes the existing evidence of the association between asthma and OSA at their pathophysiological, epidemiological, clinical, and therapeutic levels. It intends to raise awareness among healthcare professionals about these conditions and the need for further research.

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.

Chronic intermittent hypoxia increases airway hyperresponsiveness during house dust mites exposures in rats

INTRODUCTION

Accumulating clinical evidence links Obstructive Sleep Apnea (OSA) with worse outcomes of asthma, but impact on airway function remains sparsely studied. We tested effects of Chronic Intermittent Hypoxia (CIH) - a hallmark of OSA - on airway hyperresponsiveness (AHR), in a rat model of chronic allergen-induced inflammation.

METHODS

Brown Norway rats were exposed to six weeks of CIH or normoxia (NORM) concurrent with weekly house dust mites (HDM) or saline (SAL) challenges. At endpoint, we assessed responses to seven Methacholine (Mch) doses (0, 4, 8, 16, 32, 64, 128 mg/mL) on a FlexiVent system (Scireq). Maximal (or plateau) responses (reactivity) for total respiratory system Resistance (R_rs) and Elastance (E_rs), Newtonian airway resistance (R_N, a measure of central airways function) and tissue damping (G, a measure of distal airways function) were plotted.

RESULTS

HDM/CIH-treated animals demonstrated the highest reactivity to Mch in R_rs and E_rs compared to all other groups (HDM/NORM, SAL/CIH and SAL/NORM p < 0.05 for all comparisons, for doses 5-7 for R_rs, and for doses 4-7 for E_rs). The enhanced R_rs response was due to an increase in G (doses 4-7, p < 0.05 for comparisons to all other groups), whereas R_N was not affected by CIH.

CONCLUSIONS

In rats chronically challenged with HDM, concurrent CIH exposure induces AHR primarily in the distal airways, which affects the respiratory system frequency-dependent elastic properties.

Four weeks of repetitive acute hypoxic preconditioning did not alleviate allergen-induced airway dysfunction in rats

Clinical case series suggest beneficial effects of low-dose intermittent hypoxia in asthma. We tested cardiopulmonary effects of repetitive acute hypoxic preconditioning (RAHP) during allergic inflammation. Brown Norway rats were sensitized to house dust mites (HDM) and exposed to 4-week RAHP or normoxia (SHAM), concurrent with weekly HDM or saline (SAL) challenges. We assessed methacholine responses and lung HIF-1α expression at endpoint, and weekly blood pressure (BP). RAHP relative to SHAM: 1) in HDM-challenged rats, showed no protection against HDM-induced airway dysfunction and did not significantly impact BP (week 4 mean BP difference = 10.51 mmHg, p = 0.09) or HIF-1α expression; 2) in SAL-challenged rats, attenuated airway responses to methacholine, reduced BP (week 4 mean BP average difference = -8.72 mmHg, p = 0.04) and amplified HIF-1α expression (p = 0.0086). Four weeks of RAHP did not mitigate the allergen-induced lower airway dysfunction and may detrimentally affect BP. However, it elicited beneficial cardiopulmonary responses in SAL-challenged rats, concurrent with increased HIF-1α expression.

Overlaps between obstructive sleep apnoea and other respiratory diseases, including COPD, asthma and interstitial lung disease

In the past, there was limited research relating to the role of sleep in respiratory diseases. Physicians treating these patients tended to focus mainly on the daily disabling symptoms, overlooking the possible significant role of coexisting sleep disorders such as obstructive sleep apnoea (OSA). Nowadays, OSA has been recognised as an important, highly prevalent comorbidity for respiratory diseases such as COPD, asthma and interstitial lung diseases (ILDs). Overlap syndrome refers to the coexistence of chronic respiratory disease and OSA in the same patient. Although, in the past, overlap syndromes have been poorly studied, recent data underline that they result in increased morbidity and mortality compared with either underlying disorder alone. OSA and respiratory disease may be of different severity, and this, along with the existence of various clinical phenotypes, points to the necessity of an individualised therapeutic plan. Early recognition and OSA management could offer key benefits, such as improved sleep, quality of life and disease outcomes.

Educational aims

Describe pathophysiological aspects of OSA in chronic respiratory diseases such as COPD, asthma and ILDs.Understand the bidirectional clinical importance when OSA coexists in chronic respiratory diseases.Review current knowledge of treatment strategies towards an individualised therapeutic plan resulting in patient-centric outcomes.

Intermittent Hypoxia on the Attenuation of Induced Nasal Allergy and Allergic Asthma by MAPK Signaling Pathway Downregulation in a Mice Animal Model

Intermittent hypoxia (IH) has been an issue of considerable research in recent years and triggers a bewildering array of both detrimental and beneficial effects in several physiological systems. However, the mechanisms leading to the effect are not yet clear. Consequently, we investigated the effects of IH on allergen-induced allergic asthma via the mitogen-activated protein kinase (MAPK) signaling pathway. Forty BALB/c mice were dived into four groups. We evaluated the influence of IH on the cell signaling system of the airway during the allergen-induced challenge in an animal model, especially through the MAPK (mitogen-activated protein kinase) pathway. The protein concentrations of p-ERK/ERK, p-JNK/JNK, p-p38/p38, and pMEK/MEK were significantly reduced in the allergen-induced+IH group, compared to the allergen-induced group (p-value < 0.05 as considered statistically significant). The number of eosinophils, neutrophils, macrophages, and lymphocytes in the bronchoalveolar lavage fluid and Dp (Dermatophagoides pteronyssinus)-specific IgG2a and interleukins 4, 5, 13, and 17 were significantly reduced in the Dp+IH group, compared to the Dp group. These findings suggest that the MAPK pathway might be associated with the beneficial effect of IH on the attenuation of allergic response in an allergen-induced mouse model.

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.

Airway Basal Cells Mediate Hypoxia-Induced EMT by Increasing Ribosome Biogenesis

Excessive secretion of airway mucus and fluid accumulation are the common features of many respiratory diseases, which, in turn, induce cell hypoxia in the airway epithelium, resulting in epithelial–mesenchymal transition (EMT) and ultimately fibrosis. However, the mechanisms of EMT induced by hypoxia in the airway are currently unclear. To mimic the status of edematous fluid retention in the airway, we cultured primary mouse tracheal epithelial cells (MTECs) in a liquid–liquid interface (LLI) mode after full differentiation in a classic air–liquid interface (ALI) culture system. The cell hypoxia was verified by the physical characteristics and lactate production in cultured medium as well as HIF expression in MTECs cultured by LLI mode. EMT was evidenced and mainly mediated by basal cells, supported by flow cytometry and immunofluorescence assay. The differently expressed genes of basal and other airway epithelial cells were found to be enriched in the ribosome by our analysis of an MTEC single-cell RNA sequencing data set and Myc, the global regulator of ribosome biogenesis was identified to be highly expressed in basal cells. We next separated basal cells from bulk MTECs by flow cytometry, and the real-time PCR results showed that ribosome biogenesis was significantly upregulated in basal cells, whereas the inhibition of ribosome biogenesis alleviated the phosphorylation of the mammalian target of rapamycin/AKT and abrogated hypoxia-induced EMT in MTECs. Collectively, these observations strongly suggest that basal cells in the airway epithelium may mediate the process of hypoxia-induced EMT, partly through enhancing ribosome biogenesis.

Airway hyperresponsiveness induced by intermittent hypoxia in rats

This study investigated whether intermittent hypoxia (IH) induces airway hyperresponsiveness (AHR) and associated with lung inflammation. Male Brown Norway rats were exposed to 14-day IH or room air (RA) for 6 h/day. One day after the last exposure, total lung resistance to various doses of methacholine was measured as an index of bronchoconstrictive responses. Compared with RA controls, methacholine significantly induced an augmented bronchoconstriction in IH-exposed rats. Moreover, IH exposure evoked lung inflammation which was reflected by increased inflammatory cell infiltration, concentrations of interleukin-6 and prostaglandin E₂ in bronchoalveolar lavage fluid, and lung lipid peroxidation. IH-induced AHR and lung inflammation were completely abolished by daily intraperitoneal injection of N-acetylcysteine (an antioxidant) or ibuprofen (a cyclooxygenase inhibitor), but not by apocynin (an inhibitor of NADPH oxidase) or vehicle. In conclusion, AHR and lung inflammation occur after 14-day IH exposure, with endogenous reactive oxygen species and cyclooxygenase metabolites being responsible for these responses.

Chronic Intermittent Hypoxia Reduces the Effects of Glucosteroid in Asthma via Activating the p38 MAPK Signaling Pathway

Aims

Obstructive sleep apnea (OSA) is a risk factor for steroid-resistant (SR) asthma. However, the underlying mechanism is not well defined. This study aimed to investigate how chronic intermittent hypoxia (CIH), the main pathophysiology of OSA, influenced the effects of glucocorticoids (GCs) on asthma.

Main Methods

The effects of dexamethasone (Dex) were determined using the ovalbumin (OVA)-challenged mouse model of asthma and transforming growth factor (TGF)-β treated airway smooth muscle cells (ASMCs), with or without CIH. The p38 MAPK signaling pathway activity was then detected in the mouse (n = 6) and ASMCs models (n = 6), which were both treated with the p38 MAPK inhibitor SB239063.

Key Findings

Under CIH, mouse pulmonary resistance value, inflammatory cells in bronchoalveolar lavage fluid (BALF), and inflammation scores increased in OVA-challenged combined with CIH exposure mice compared with OVA-challenged mice (p < 0.05). These indicators were similarly raised in the OVA + CIH + Dex group compared with the OVA + Dex group (P < 0.05). CIH exposure enhanced the activation of the p38 MAPK pathway, oxidative stress injury, and the expression of NF-κB both in lung tissue and ASMCs, which were reversed by treatment with Dex and SB239063. In the in vitro study, treatment with Dex and SB239063 decreased ASMCs proliferation induced by TGF-β combined with CIH and suppressed activation of the p38 MAPK pathway, oxidative stress injury, and NF-κB nuclear transcription (p < 0.05).

Significance

These results indicated that CIH decreased GC sensitivity by activating the p38 MAPK signaling pathway.

Asthma and Three Colinear Comorbidities: Obesity, OSA, and GERD

Asthma is a complex disease with heterogeneous phenotypes and endotypes that are incompletely understood. Obesity, obstructive sleep apnea, and gastroesophageal reflux disease co-occur in patients with asthma at higher rates than in those without asthma. Although these diseases share risk factors, there are some data suggesting that these comorbidities have shared inflammatory pathways, drive the development of asthma, or worsen asthma control. This review discusses the epidemiology, pathophysiology, management recommendations, and key knowledge gaps of these common comorbidities.

[Obstructive sleep apnea and asthma: Clinical implications]

Obstructive sleep apnea (OSA) and asthma are common respiratory diseases that can coexist in the same patient. Epidemiological and pathophysiological data suggest an independent link between these two diseases. Specially, OSA is frequently associated with non-eosinophilic and with poorly-controlled asthma. Common comorbidities including obesity, gastroesophageal reflux and rhinitis may promote this association. The impact of OSA treatment on the clinical and functional control of asthma has been extensively investigated. Numerous non-randomized studies suggest that continuous positive pressure treatment is likely to improve asthma symptoms, the control of the disease and quality of life in asthmatics with OSA. However, this impact has not been confirmed in the limited randomized trial available. To date, the optimal treatment approach in asthmatics with OSA is the best treatment of each disease separately and the recognition and treatment of comorbidities. When indicated, obesity surgery has a major impact on both diseases.

Impact of obstructive sleep apnea on assisted ventilation in children with asthma exacerbation

OBJECTIVE

To determine the impact of obstructive sleep apnea (OSA) on asthma exacerbation severity in children hospitalized for asthma exacerbation.

HYPOTHESIS

OSA is associated with greater use of invasive mechanical ventilation (IMV) and noninvasive mechanical ventilation (NIMV) in children hospitalized for asthma exacerbation.

STUDY DESIGN

A retrospective cohort study.

PATIENT-SUBJECT SELECTION

Hospitalization records of children aged 2-18 years admitted for acute asthma exacerbation were obtained for 2000, 2003, 2006, 2009, and 2012 from the Kids' Inpatient Database.

METHODOLOGY

The primary exposure was OSA, the primary outcome was IMV, and secondary outcomes were NIMV, length of hospital stay (LOS), and inflation-adjusted cost of hospitalization. Multivariable logistic regression, negative binomial, and linear regression were conducted to ascertain the impact of OSA on primary and secondary outcomes. Exploratory analyses investigated the impact of obesity on primary and secondary outcomes.

RESULTS

Among 564,467 hospitalizations for acute asthma exacerbation, 4209 (0.75%) had OSA. Multivariable regression indicated that OSA was associated with IMV (adjusted odds ratio [OR], 5.33 [95% confidence interval, CI: 4.35-6.54], p < .0001), NIMV (adjusted OR, 8.30 [95% CI: 6.56-10.51], p < .0001), longer LOS (adjusted incidence rate ratio, 1.34 [95% CI 1.28-1.43], p < .0001), and greater inflation-adjusted cost of hospitalization (adjusted β, 0.38 [95% CI: 0.33-0.43], p < .0001). Obesity was also significantly associated IMV, NIMV, longer LOS, and greater inflation-adjusted cost of hospitalization. There was no interaction between OSA and obesity.

CONCLUSION

OSA is an independent risk factor for IMV, NIMV, longer LOS, and elevated inflation-adjusted costs of hospitalization in children hospitalized for asthma exacerbation.

Contribution of comorbidities to obesity-related asthma in children

Children with obesity are at increased risk for developing asthma that is difficult to control. A complicating factor to asthma management among these children is likely the commonplace co-morbidities that also result from obesity. We discuss three common obesity-related comorbidities which appear to complicate the effective management of asthma, including hypovitaminosis D, obstructive sleep apnea and gastro-esophageal reflux. Each conditions requires more research to understand their effects on asthma management.

Lung oxidative stress and transcriptional regulations induced by estradiol and intermittent hypoxia

We determined the effects of chronic intermittent hypoxia (CIH) and estradiol (E₂) on oxidative stress and gene expression in the lungs. Female Sprague-Dawley rats were left intact (sham) or ovariectomized (OVX) and implanted with pumps delivering vehicle or E₂ (0.5 mg/kg/day). Two weeks following surgery, the rats were exposed to room air (RA) or CIH for 7 days (10% O₂, 10 cycles/hour, 8 h/day). Lung samples were used to measure the activities of pro- (NADPH and xanthine oxidases) and antioxidant (superoxide dismutase, catalase and glutathione peroxidase) enzymes, and concentrations of advanced oxidation of protein products (AOPP). We determined gene expression with an RNA microarray and enrichment analysis of differentially expressed genes. In rats exposed to RA, OVX and E₂ supplementation increased pro- and antioxidant activities and AOPP concentration. In rats exposed to CIH, AOPP concentration, pro- and antioxidant enzymes activities increased in sham, did not changed in OVX-Veh rats, and were reduced in OVX-E₂ rats. In rats exposed to RA, genes involved in extracellular matrix were up-regulated by OVX and down-regulated by E₂, while E₂ up-regulated genes involved in cell mobility/adherence and leukocytes migration. OVX downregulated expression of roughly 200 olfactory receptor genes without effect of E₂. CIH altered gene expression in sham and OVX-E₂, but not in OVX-Veh rats. Enrichment analysis confirmed the antioxidant effects of E₂ under CIH. There are important interactions between ovarian hormones and CIH that can be relevant to better understand the consequences of sleep apnea (i.e. CIH) on the occurrence of lung pathologies in women.

Effects of allergic airway inflammation and chronic intermittent hypoxia on systemic blood pressure

Asthma and obstructive sleep apnea (OSA) are highly prevalent chronic conditions, and both are associated with systemic hypertension. Additionally, asthma and OSA reciprocally interact, mutually exacerbating each other. In this study, we tested the effect of allergen-induced lower airway inflammation and concurrent chronic intermittent hypoxia (CIH) on systemic blood pressure (BP), pulmonary function, and proinflammatory cytokines, in a rat model. Brown Norway rats were exposed to 43 days of normoxia (NORM) or CIH, concurrent with weekly house dust mite (HDM) challenges. BP was measured 1 day after the last HDM challenge. On day 44, pulmonary function was tested, and blood for Th-2 and Th-1 cytokine levels was collected. HDM significantly increased mean (P = 0.002), systolic (P = 0.003), and diastolic (P = 0.004) BP compared with saline-challenged controls. Higher mean BP significantly correlated to increased total respiratory system resistance (R² = 0.266, P = 0.002), driven by an association with parenchymal tissue dampening (R² = 0.166, P = 0.016). HDM relative to saline-challenged controls increased the expression of serum IL-6 (P = 0.008), but no relationships of systemic BP with IL-6 or any other cytokines were found. CIH did not alter the allergen-induced responses on BP, although it tended to increase the expression of serum IL-6 (P = 0.06) and monocyte chemoattractant protein-1 (MCP-1, P = 0.09), regardless of HDM challenge. Chronic allergen-induced airway inflammation results in systemic hypertension that is correlated to the degree of distal airway obstruction induced by the allergen. These effects do not appear to be explained by the associated systemic inflammation.

Angiotensin-(1-7) Rescues Chronic Intermittent Hypoxia-Aggravated Transforming Growth Factor-β-Mediated Airway Remodeling in Murine and Cellular Models of Asthma

Renin-angiotensin system (RAS) is involved in TGF-β-mediated epithelial-to-mesenchymal transition (EMT) and is responsible for airway remodeling in refractory asthma. Obstructive sleep apnea (OSA), which affects RAS activity, is a risk factor for refractory asthma. We aimed to investigate how chronic intermittent hypoxia (IH), the main pathophysiology of OSA, exacerbates asthma and whether Ang-(1-7) protects against chronic IH-induced airway remodeling in asthma. We exposed ovalbumin (OVA)-challenged asthma mice to chronic IH and observed that chronic IH aggravated airway inflammation and collagen deposit in OVA-challenged mice. Compared with the OVA group, the OVA + chronic IH group had a lower expression level of epithelial marker E-cadherin and higher expression levels of mesenchymal markers α-smooth muscle actin and collagen IV in airway epithelia, accompanied with activation of TGF-β/Smad pathway. These changes were reversed by the administration of Ang-(1-7). Consistently, Ang-(1-7) mitigated chronic IH-induced activation of TGF-β-mediated EMT in lipopolysaccharide-treated bronchial epithelial cells in a dose-dependent manner, which was blocked by Ang-(1-7)-specific Mas receptor antagonist A779. Taken together, Ang-(1-7) rescued chronic IH-aggravated TGF-β-mediated EMT to suppress airway remodeling, implying that RAS activity is involved in the mechanisms of OSA-related airway dysfunction in asthma. SIGNIFICANCE STATEMENT: OSA is a risk factor for refractory asthma. In this study, we aimed to explore the mechanisms of how OSA exacerbates refractory asthma. We found that chronic IH induces TGF-β-mediated EMT and aggravates airway collagen deposit. We also found that Ang-(1-7) erased the aggravation of TGF-β-mediated EMT and epithelial fibrosis upon chronic IH exposure. These findings provided new insights that the ACE2/Ang-(1-7)/Mas axis might be considered as a potential therapeutic target for patients with asthma and OSA.

Asthma and Obstructive Sleep Apnea Overlap: What Has the Evidence Taught Us?

Obstructive sleep apnea (OSA) and asthma are highly prevalent chronic respiratory disorders. Beyond their frequent coexistence arising from their high prevalence and shared risk factors, these disorders feature a reciprocal interaction whereby each disease impacts the severity of the other. Emerging evidence implicates airway and systemic inflammation, neuroimmune interactions, and effects of asthma-controlling medications (corticosteroids) as factors that predispose patients with asthma to OSA. Conversely, undiagnosed or inadequately treated OSA adversely affects asthma control, partly via effects of intermittent hypoxia on airway inflammation and tissue remodeling. In this article, we review multiple lines of recently published evidence supporting this interaction. We provide a set of recommendations for clinicians involved in the care of adults with asthma, and identify critical gaps in our knowledge about this overlap.

Serum periostin and TNF-α levels in patients with obstructive sleep apnea-hypopnea syndrome

PURPOSE

Obstructive sleep apnea-hypopnea syndrome (OSAHS) may cause pulmonary diseases, and periostin plays an important role on the development of pulmonary diseases. In addition, periostin and pro-inflammatory cytokine TNF-α can regulate each other in vivo. This study aimed to observe the changes of serum periostin and TNF-α levels in patients with OSAHS compared with healthy volunteers and to investigate their correlation.

METHODS

A convenience sample of 67 patients with OSAHS in our hospital from December 2018 to December 2019 was selected and categorized into mild, moderate, and severe groups according to apnea-hypopnea index by polysomnography. In addition, 21 healthy volunteers were selected as the control group. Serum levels of periostin and TNF-α were determined by enzyme-linked immunosorbent assay (ELISA). Results were analyzed using the SPSS software.

RESULTS

Both serum periostin and TNF-α levels in all the three OSAHS groups were higher than those of the control group and increased with severity of OSAHS. The severe group had significantly higher serum periostin and TNF-α levels than the mild and moderate groups (p < 0.05). For patients with OSAHS, serum periostin and TNF-α levels positively correlated with the apnea-hypopnea index (AHI) (p < 0.01) and negatively correlated with the lowest saturation oxygen (LSaO₂) and mean saturation oxygen (MSaO₂) (both p < 0.01). In addition, there was a positive correlation between serum periostin and TNF-α levels in patients with OSAHS (p < 0.001).

CONCLUSIONS

Serum periostin and TNF-α levels were significantly increased in patients with OSAHS and may serve as a potential biomarker for severity of OSAHS. These findings suggest that it may be fruitful to study the role of periostin and TNF-α in OSAHS-induced pulmonary diseases.

Vulnerability of the developing airway

Longer term respiratory morbidity is a frequent concern for former preterm infants. Increased airway reactivity and wheezing disorders are extremely common in this population, both in infants who meet diagnostic criteria for bronchopulmonary dysplasia [BPD], and in the absence of this diagnosis. It is, therefore, imperative to gain a better understanding of normal and abnormal postnatal development of the immature airway. Airway hyperreactivity may be secondary to abnormal bronchoalveolar attachments in the face of parenchymal lung injury, or secondary to an imbalance between constrictor and dilator neural pathways. Finally, the airway itself may undergo functional and/or structural changes, including increased airway smooth muscle mass, and changes in airway extracellular matrix which may, in turn, modulate downstream signaling pathways to hyperoxia or pressure exposed vulnerable airways.

Impact of sleep opportunity on asthma outcomes in adolescents

RATIONALE

Insufficient sleep is associated with a number of negative health outcomes; as most adolescents obtain <7 h of sleep per night, it is important to understand how sleep impacts asthma among adolescents.

OBJECTIVES

To examine the impact of sleep opportunity on asthma in adolescents.

METHODS

In this study, 54 adolescents with asthma (12-17 years, 69% female, 65% Caucasian) participated in a randomized, cross-over sleep manipulation trial, including a sleep stabilization week, five nights of a "Short" sleep opportunity (time in bed: 6.5 h/night), and five nights of a "Long" sleep opportunity (time in bed: 9.5 h/night). Wake times were consistent across all three study weeks. Primary outcomes were lung function (daily peak expiratory flow rate, weekly spirometry) and functional asthma outcomes (daily asthma symptoms, Asthma Control Questionnaire, PROMIS Asthma Impact Scale). Markers of inflammation were also explored.

MEASUREMENTS AND MAIN RESULTS

Compared to the Long sleep week, during the Short sleep week, morning FEV1 was lower (p = 0.006), while asthma symptoms and albuterol use was higher (p < 0.05), and asthma showed a trend towards greater negative impact on daily life (p = 0.07). No differences were found for weekly measures of lung function or inflammation.

CONCLUSIONS

An insufficient sleep opportunity negatively impacts objective and subjective daily symptoms of asthma in adolescents, as well as health related quality of life. As most adolescents are significantly sleep deprived, it is important to target sleep health in the treatment of asthma.

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

PURPOSE

Obesity increases the severity of asthma, and patients with severe asthma are often complicated with obstructive sleep apnea syndrome (OSAS), a concomitant disease of obesity. We investigated whether intermittent hypoxia (IH), which is a physiological feature of OSAS, modifies allergic airway inflammation in a murine model of asthma.

METHODS

Balb/c mice were sensitized by ovalbumin (OVA) intraperitoneally twice (days 1 and 14) and challenged with intranasal OVA three times (days 21, 22, and 23). The mice were exposed to IH either from days 1 to 24 (long exposure) or only from days 21 to 24 (short exposure). The impact of IH exposure to allergic airway inflammation was investigated using these mice models by histologic, morphometric, and molecular techniques. Additionally, the airway responsiveness to acetylcholine was also assessed.

RESULTS

OVA-sensitized and OVA-challenged mice exposed to room air (RA) showed increased total cell and eosinophil numbers in the BALF. The levels of interleukin (IL)-5 and IL-13 in the BALF also increased and goblet cell metaplasia was induced. In contrast, both long and short exposure to IH inhibited the increased total cell and eosinophil numbers. The levels of IL-5 and IL-13 in the BALF also decreased on exposure to IH. Moreover, the goblet cell hyperplasia and airway hyperresponsiveness were significantly reduced in mice exposed to IH compared to those exposed to RA.

CONCLUSIONS

These results suggest that IH may not deteriorate the asthmatic condition in a murine model of asthma.

Associations of variants In the hexokinase 1 and interleukin 18 receptor regions with oxyhemoglobin saturation during sleep

Sleep disordered breathing (SDB)-related overnight hypoxemia is associated with cardiometabolic disease and other comorbidities. Understanding the genetic bases for variations in nocturnal hypoxemia may help understand mechanisms influencing oxygenation and SDB-related mortality. We conducted genome-wide association tests across 10 cohorts and 4 populations to identify genetic variants associated with three correlated measures of overnight oxyhemoglobin saturation: average and minimum oxyhemoglobin saturation during sleep and the percent of sleep with oxyhemoglobin saturation under 90%. The discovery sample consisted of 8,326 individuals. Variants with p < 1 × 10(-6) were analyzed in a replication group of 14,410 individuals. We identified 3 significantly associated regions, including 2 regions in multi-ethnic analyses (2q12, 10q22). SNPs in the 2q12 region associated with minimum SpO2 (rs78136548 p = 2.70 × 10(-10)). SNPs at 10q22 were associated with all three traits including average SpO2 (rs72805692 p = 4.58 × 10(-8)). SNPs in both regions were associated in over 20,000 individuals and are supported by prior associations or functional evidence. Four additional significant regions were detected in secondary sex-stratified and combined discovery and replication analyses, including a region overlapping Reelin, a known marker of respiratory complex neurons.These are the first genome-wide significant findings reported for oxyhemoglobin saturation during sleep, a phenotype of high clinical interest. Our replicated associations with HK1 and IL18R1 suggest that variants in inflammatory pathways, such as the biologically-plausible NLRP3 inflammasome, may contribute to nocturnal hypoxemia.

Obstructive sleep apnoea and comorbidity - an overview of the association and impact of continuous positive airway pressure therapy

INTRODUCTION

Obstructive sleep apnoea (OSA) is highly prevalent and there is considerable evidence supporting an independent association with a wide range of co-morbidities including cardiovascular, endocrine and metabolic, neuropsychiatric, pulmonary, and renal. Areas covered: A PubMed search of all the recent literature relating to OSA and co-morbidities was undertaken to critically evaluate the potential relationships and possible benefit of continuous positive airway pressure (CPAP) therapy. Expert commentary: The evidence supporting an independent association is stronger for some co-morbidities than others and in cardiovascular diseases is strongest for hypertension and atrial fibrillation. Potential mechanisms include intermittent hypoxia, fluctuating intrathoracic pressure, and recurring micro-arousals that trigger cell and molecular consequences including sympathetic excitation, systemic inflammation and oxidative stress, in addition to metabolic and endothelial dysfunction. Different mechanisms may predominate in individual co-morbidities. Recent long term randomised controlled trials have cast doubt on benefits to co-morbidities from CPAP therapy of OSA, especially where co-morbidities are already established. However, benefits may result in patients who are compliant with therapy and further research is required to clearly establish the role of OSA therapy in both primary and secondary prevention of co-morbidities.

Gas Partial Pressure in Cultured Cells: Patho-Physiological Importance and Methodological Approaches

Gas partial pressures within the cell microenvironment are one of the key modulators of cell pathophysiology. Indeed, respiratory gases (O2 and CO2) are usually altered in respiratory diseases and gasotransmitters (CO, NO, H2S) have been proposed as potential therapeutic agents. Investigating the pathophysiology of respiratory diseases in vitro mandates that cultured cells are subjected to gas partial pressures similar to those experienced by each cell type in its native microenvironment. For instance, O2 partial pressures range from ∼13% in the arterial endothelium to values as low as 2-5% in cells of other healthy tissues and to less than 1% in solid tumor cells, clearly much lower values than those used in conventional cell culture research settings (∼19%). Moreover, actual cell O2 partial pressure in vivo changes with time, at considerably different timescales as illustrated by tumors, sleep apnea, or mechanical ventilation. Unfortunately, the conventional approach to modify gas concentrations at the above culture medium precludes the tight and exact control of intra-cellular gas levels to realistically mimic the natural cell microenvironment. Interestingly, well-controlled cellular application of gas partial pressures is currently possible through commercially available silicone-like material (PDMS) membranes, which are biocompatible and have a high permeability to gases. Cells are seeded on one side of the membrane and tailored gas concentrations are circulated on the other side of the membrane. Using thin membranes (50-100 μm) the value of gas concentration is instantaneously (<0.5 s) transmitted to the cell microenvironment. As PDMS is transparent, cells can be concurrently observed by conventional or advanced microscopy. This procedure can be implemented in specific-purpose microfluidic devices and in settings that do not require expensive or complex technologies, thus making the procedure readily implementable in any cell biology laboratory. This review describes the gas composition requirements for a cell culture in respiratory research, the limitations of current experimental settings, and also suggests new approaches to better control gas partial pressures in a cell culture.

Inherent vs. Induced Loop Gain Abnormalities in Obstructive Sleep Apnea

Unstable ventilatory chemoreflex control, quantified as loop gain, is recognized as one of four key pathophysiological traits that contribute to cause obstructive sleep apnea (OSA). Novel treatments aimed at reducing loop gain are being investigated, with the intention that future OSA treatment may be tailored to the individual's specific cause of apnea. However, few studies have evaluated loop gain in OSA and non-OSA controls and those that have provide little evidence to support an inherent abnormality in either overall chemical loop gain in OSA patients vs. non-OSA controls, or its components (controller and plant gain). However, intermittent hypoxia may induce high controller gain through neuroplastic changes to chemoreflex control, and may also decrease plant gain via oxidative stress induced inflammation and reduced lung function. The inherent difficulties and limitations with loop gain measurements are discussed and areas where further research are required are highlighted, as only by understanding the mechanisms underlying OSA are new therapeutic approaches likely to emerge in OSA.

Chronic intermittent hypoxia worsens bleomycin-induced lung fibrosis in rats

Obstructive sleep apnea (OSA) has been linked to increased mortality in pulmonary fibrosis. Its key feature, chronic intermittent hypoxia (CIH), can lead to oxidative stress and inflammation, known to lead to fibrotic pathology in other organs. We tested the effects of CIH in an animal model of bleomycin-induced lung fibrosis. Sprague Dawley rats were instilled intratracheally with bleomycin (Blm) or saline (Sal), and exposed to CIH or normal air (Norm) for 9 or 30 days. Pulmonary function was tested and lungs were harvested for histological and molecular analyses. In Blm-treated animals, 30days of CIH compared to Norm increased total lung collagen content (p=0.008) and reduced Quasi-static lung compliance (p=0.04). CIH upregulated lipid peroxidation and increased NF-κB activation, IL-17 mRNA and Col1α1 mRNA expression. Our results indicate that following Blm-induced lung injury, CIH amplifies collagen deposition via oxidative and inflammatory pathways, culminating in stiffer lungs. Thus, OSA may augment fibrosis in patients with interstitial lung disease.

Clinical presentation of patients with suspected obstructive sleep apnea and self-reported physician-diagnosed asthma in the ESADA cohort

Obstructive sleep apnea (OSA) and asthma are often associated and several studies suggest a bidirectional relationship between asthma and OSA. This study analyzed the characteristics of patients with suspected OSA from the European Sleep Apnea Database according to presence/absence of physician-diagnosed asthma. Cross-sectional data in 16,236 patients (29.1% female) referred for suspected OSA were analyzed according to occurrence of physician-diagnosed asthma for anthropometrics, OSA severity and sleepiness. Sleep structure was assessed in patients studied by polysomnography (i.e. 48% of the sample). The prevalence of physician-diagnosed asthma in the entire cohort was 4.8% (7.9% in women, 3.7% in men, p < 0.0001), and decreased from subjects without OSA to patients with mild-moderate and severe OSA (p = 0.02). Obesity was highly prevalent in asthmatic women, whereas BMI distribution was similar in men with and without physician-diagnosed asthma. Distribution of OSA severity was similar in patients with and without physician-diagnosed asthma, and unaffected by treatment for asthma or gastroesophageal reflux. Asthma was associated with poor sleep quality and sleepiness. Physician-diagnosed asthma was less common in a sleep clinic population than expected from the results of studies in the general population. Obesity appears as the major factor raising suspicion of OSA in asthmatic women, whereas complaints of poor sleep quality were the likely reason for referral in asthmatic men.

Challenges and perspectives in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is a major challenge for physicians and healthcare systems throughout the world. The high prevalence and the impact on daily life of OSA oblige clinicians to offer effective and acceptable treatment options. However, recent evidence has raised questions about the benefits of positive airway pressure therapy in ameliorating comorbidities.

An international expert group considered the current state of knowledge based on the most relevant publications in the previous 5 years, discussed the current challenges in the field, and proposed topics for future research on epidemiology, phenotyping, underlying mechanisms, prognostic implications and optimal treatment of patients with OSA.

The group concluded that a revision to the diagnostic criteria for OSA is required to include factors that reflect different clinical and pathophysiological phenotypes and relevant comorbidities (e.g.nondipping nocturnal blood pressure). Furthermore, current severity thresholds require revision to reflect factors such as the disparity in the apnoea–hypopnoea index (AHI) between polysomnography and sleep studies that do not include sleep stage measurements, in addition to the poor correlation between AHI and daytime symptoms such as sleepiness. Management decisions should be linked to the underlying phenotype and consider outcomes beyond AHI.

Therapeutic effects of telomerase in mice with pulmonary fibrosis induced by damage to the lungs and short telomeres

Pulmonary fibrosis is a fatal lung disease characterized by fibrotic foci and inflammatory infiltrates. Short telomeres can impair tissue regeneration and are found both in hereditary and sporadic cases. We show here that telomerase expression using AAV9 vectors shows therapeutic effects in a mouse model of pulmonary fibrosis owing to a low-dose bleomycin insult and short telomeres. AAV9 preferentially targets regenerative alveolar type II cells (ATII). AAV9-Tert-treated mice show improved lung function and lower inflammation and fibrosis at 1–3 weeks after viral treatment, and improvement or disappearance of the fibrosis at 8 weeks after treatment. AAV9-Tert treatment leads to longer telomeres and increased proliferation of ATII cells, as well as lower DNA damage, apoptosis, and senescence. Transcriptome analysis of ATII cells confirms downregulation of fibrosis and inflammation pathways. We provide a proof-of-principle that telomerase activation may represent an effective treatment for pulmonary fibrosis provoked or associated with short telomeres.

Idiopathic pulmonary fibrosis (or IPF for short) is a rare disease that scars the lungs. The condition gets worse over time, making it harder and harder to breathe, and eventually leading to death. Patients typically only survive for a few years after being diagnosed with IPF. This is because, as yet, there is no cure; the available treatments only act to lessen the symptoms.

Several risk factors have linked to the development of IPF, among them, the presence of short telomeres. Like the plastic tips on shoelaces, telomeres are protective structures at the ends of chromosomes. Telomeres shorten with age, and when they become too short the cell stops dividing and often dies in a process known as apoptosis. IPF can develop when the telomeres in the cells that repair everyday wear and tear in the lungs (known as ATII cells) become too short. This means that the damage goes unrepaired, triggering an immune reaction and uncontrolled scarring.

Telomerase is an enzyme that can lengthen short telomeres, and Povedano, Martínez et al. set out to develop a new treatment approach that would use this enzyme to correct the short telomeres, and cure the scarring seen in IPF. Gene therapy was used to introduce the gene for telomerase into mice that had scarring in their lungs due to short telomeres.

Povedano, Martínez et al. found that, when injected into the mice, the telomerase gene therapy was able to reach ATII cells and could help to heal the lungs. At the level of individual cells, mice treated with telomerase had longer telomeres, meaning that more of their ATII cells stayed alive and kept dividing to regenerate the lung tissue. Consistent with previous studies, the telomerase gene therapy caused no negative side effects in the mice; for example, there was no increased risk of cancer.

These findings may possibly lead to new treatments for those patients suffering from IPF associated with short telomeres. Developing this approach into a clinical trial could in the future benefit many IPF patients who currently have very limited treatment options.

Role of Sleep Apnea and Gastroesophageal Reflux in Severe Asthma

Gastroesophageal reflux and obstructive sleep apnea syndrome are conditions that practitioners have been encouraged to evaluate and treat as part of a comprehensive approach to achieving asthma control. In this review, the author looks at the evidence linking these two conditions as factors that may impact difficult-to-control asthma and looks critically at the evidence suggesting that evaluation and treatment of these conditions when present impacts asthma control.

Role of lung volume and airway inflammation in obstructive sleep apnea

Obstructive sleep apnea (OSA) is a prevalent disorder that affects not only the upper airways but also the intrathoracic airways. In this review, we summarize the results of studies on lung function and airway inflammation. We provide evidence that the alterations in intrathoracic airways observed in OSA are not purely consequences of mechanical trauma and oxidative stress during apneic events but have a causal role in the structural changes associated with OSA and increasing severity of this disorder.

Downregulation of semaphorin 3E promotes hallmarks of experimental chronic allergic asthma

Guidance cues such as semaphorins are attractive novel therapeutic targets for allergic disorders. We have previously described an inhibitory effect of semaphorin 3E (Sema3E) on human airway smooth muscle cell function. We have further addressed a canonical role for Sema3E in acute model of allergic asthma in vivo. Considering the chronic nature of the disease, the potential implication of Sema3E to alleviate long-lasting deficits should be investigated. Expression of Sema3E in a chronic model of allergic asthma was assessed after exposure to house dust mite (HDM) as a clinically relevant allergen. Chronic features of allergic asthma including airway hyper-responsiveness (AHR), inflammation, and remodeling were studied in Sema3E-deficient mice. Additionally, the effect of exogenous Sema3E treatment was evaluated in prophylactic and therapeutic experimental models. We have demonstrated that expression of Sema3E is robustly suppressed in the airways upon chronic HDM exposure. Chronic allergic airway disease was significantly augmented in Sema3E-deficient mouse model which was associated with an increased AHR, remodeling, and Th2/Th17 inflammation. Intranasal Sema3E administration restored chronic deficits of allergic asthma in mice. Data from this study unveil a key regulatory role of Sema3E in chronic course of asthma via orchestration of impaired inflammatory and remodeling responses.

Alteration of Inflammatory Mediators in the Upper and Lower Airways under Chronic Intermittent Hypoxia: Preliminary Animal Study

Purpose

We hypothesized that CIH may affect the upper airway immune system and aimed to verify whether CIH can induce airway inflammation in a murine obstructive sleep apnea (OSA) model.

Methods

C57BL6 male mice were exposed to intermittent hypoxia (CIH group; 5 ~ 21% FiO₂, 120 sec cycles, 12 h/d, n = 6) or room air (Sham group, n = 6) for up to 4 weeks in identical chambers. Nasal and lung tissues and lavage fluid were collected and analyzed by multiplex assay. Lung lavage fluid was also utilized for FACS analysis to determine eosinophil count.

Results

We determined the protein level of 24 different cytokines, chemokines, and inflammatory mediators. Among various cytokines, levels of IL-1α, IL-1β, IL-4, IL-6, and IL-13 were significantly elevated in nose or lung tissue from the CIH group. In addition, MCP-1 and periostin were elevated in nose and lung tissue and lavage fluid from the CIH group.

Conclusions

CIH for 4 weeks altered the levels of inflammatory mediators in both the nose and lungs of mouse model. We suggest that the airway immune system may be deteriorated by CIH and allergic inflammation in the upper or lower airway could be worsened by sleep apnea.

Hypoxia-induced ADAM 17 expression is mediated by RSK1-dependent C/EBPβ activation in human lung fibroblasts

Hypoxia was identified as a mediator of lung fibrosis in patients with chronic obstructive asthma (COA). Overexpression of a disintegrin and metalloproteinase 17 (ADAM 17) and connective tissue growth factor (CTGF) leads to development of tissue fibrosis. However, the signaling pathway in hypoxia-induced ADAM 17 expression remains poorly defined. In this study, we investigated the roles that ribosomal S-6 kinase 1 (RSK1)/CCAAT/enhancer-binding protein β (C/EBPβ)-dependent ADAM 17 expression plays in hypoxia-induced CTGF expression in human lung fibroblasts. We observed that hypoxia caused increases in ADAM 17 expression and ADAM 17-luciferase activity in WI-38 cells. Hypoxia-induced CTGF-luciferase activity and CTGF expression were reduced in cells transfected with small interfering (si)RNA of ADAM 17 in WI-38 cells. Moreover, hypoxia-induced ADAM 17 expression was reduced by RSK1 siRNA and C/EBPβ siRNA. Hypoxia caused time-dependent increases in RSK1 phosphorylation at Thr359/Ser363. Exposure of cells to hypoxia resulted in increased C/EBPβ phosphorylation at Thr266 and C/EBPβ-luciferase activity in time-dependent manners, and these effects were suppressed by RSK1 siRNA. Hypoxia induced recruitment of C/EBPβ to the ADAM 17 promoter. Furthermore, CTGF-luciferase activity induced by hypoxia was attenuated by RSK1 siRNA and C/EBPβ siRNA. These results suggest that hypoxia instigates the RSK1-dependent C/EBPβ signaling pathway, which in turn initiates binding of C/EBPβ to the ADAM 17 promoter and ultimately induces ADAM 17 expression in human lung fibroblasts. Moreover, RSK1/C/EBPβ-dependent ADAM 17 expression is involved in hypoxia-induced CTGF expression. Our results suggest possible therapeutic approaches for treating hypoxia-mediated lung fibrosis in COA.

Long-term effects of recurrent intermittent hypoxia and hyperoxia on respiratory system mechanics in neonatal mice

BACKGROUND

Premature infants are at increased risk for wheezing disorders. Clinically, these neonates experience recurrent episodes of apnea and desaturation often treated by increasing the fraction of inspired oxygen (FIO₂). We developed a novel paradigm of neonatal intermittent hypoxia with subsequent hyperoxia overshoots (CIH_O/E) and hypothesized that CIH_O/E elicits long-term changes on pulmonary mechanics in mice.

METHODS

Neonatal C57BL/6 mice received CIH_O/E, which consisted of 10% O2 (1 min) followed by a transient exposure to 50% FIO₂, on 10-min repeating cycles 24 h/d from birth to P7. Baseline respiratory mechanics, methacholine challenge, RT-PCR for pro and antioxidants, radial alveolar counts, and airway smooth muscle actin were assessed at P21 after 2-wk room air recovery. Control groups were mice exposed to normoxia, chronic intermittent hyperoxia (CIH_E), and chronic intermittent hypoxia (CIH_O).

RESULTS

CIH_O/E and CIH_E increased airway resistance at higher doses of methacholine and decreased baseline compliance compared with normoxia mice. Lung mRNA for NOX2 was increased by CIH_O/E. Radial alveolar counts and airway smooth muscle actin was not different between groups.

CONCLUSION

Neonatal intermittent hypoxia/hyperoxia exposure results in long-term changes in respiratory mechanics. We speculate that recurrent desaturation with hyperoxia overshoot may increase oxidative stress and contribute to wheezing in former preterm infants.

Heliox-Driven Nebulization Has a Positive Effect on the Lung Function in Lipopolysaccharide-Induced Chronic Obstructive Pulmonary Disease Rat Model

Background

Chronic obstructive pulmonary disease (COPD) is a serious lung disease that severely threatens people’s health. This study aimed to investigate the effects of heliox-driven nebulization (HDN) on lung function and arterial blood gases in a COPD rat model.

Material/Methods

Twelve healthy male Wistar rats were selected as controls and 34 rats were used to establish a COPD model induced by lipopolysaccharide. Then 6 rats each from the control and model groups were selected for their symptoms to be observed. The remaining 6 normal rats were used as control group (group A) and the remaining 28 experimental COPD rats were randomly assigned to 4 groups: experimental COPD group (group B), medical oxygen group (group C), and heliox groups (group D, He/O₂=63%/37%; group E, He/O₂=71%/29%). The lung function indicators and arterial blood gases were analyzed to evaluate the effects of different driving gases on COPD rats.

Results

The COPD model was successfully established with slow growth and severe lung dysfunction. Inspiratory resistance, expiratory resistance, and forced expiratory volume at 0.10 s (FEV0.10)/FVC were significantly decreased, whereas dynamic lung compliance was significantly increased in groups D and E, compared with the experimental COPD group (group B; P<0.05). Meanwhile, compared with the model group, the values of partial pressure of carbon dioxide in arterial blood were significantly higher, whereas the potential of hydrogen values were significantly lower after atomization in groups C and D but not in group E (P<0.05). The obvious increase in arterial oxygen saturation was found only in group E (P<0.05).

Conclusions

HDN improved the lung function and arterial blood gas analysis results in experimental COPD rats, with an optimal percentage of He/O₂=71%/29%.

Intermittent Hypoxia Contributes to the Lung Damage by Increased Oxidative Stress, Inflammation, and Disbalance in Protease/Antiprotease System

INTRODUCTION

Intermittent hypoxia as a surrogate of obstructive sleep apnea is associated with different cardiovascular complications. However, the effects of intermittent hypoxia on the lung tissue are less known. Therefore, the aim of our present study was to investigate if intermittent hypoxia may influence oxidative stress, inflammation, and protease/antiprotease system in the lung. Additionally, potential protective properties of anti-inflammatory and anti-oxidative drugs have been evaluated.

METHODS

32 mice were divided into four groups: (1) intermittent hypoxia, (2) intermittent hypoxia with infliximab, (3) intermittent hypoxia with L-glutathione, and (4) normoxia. After 4 weeks, lungs and blood were collected. Levels of reactive oxygen species in the lung were calculated by L-O12-enhanced chemiluminescence. CD68-positive lung macrophages were detected by immunofluorescence. Concentrations of elastase and desmosine in lung and of alpha-1-antitrypsin in blood were calculated by means of enzyme-linked immunosorbent assay.

RESULTS

Compared to a control, intermittent hypoxia augmented the release of free oxygen radicals, expression of CD68+ macrophages, and concentration of elastase in the lung tissue. Despite increased blood levels of protective alpha-1-antitrypsin, concentrations of desmosine-degradation product of elastin were higher versus control. The application of anti-inflammatory infliximab und anti-oxidative L-glutathione prevented at least partly the above-observed hypoxia-associated changes.

CONCLUSIONS

Intermittent hypoxia contributes to the lung damage by increased oxidative stress, inflammation, and disbalance in protease/antiprotease system. Infliximab and L-glutathione may prevent adverse hypoxia-induced lung alternations.

Intermittent hypoxia initiated plasticity in humans: A multipronged therapeutic approach to treat sleep apnea and overlapping co-morbidities

Over the past three decades exposure to intermittent hypoxia (IH) has generally been considered a stimulus associated with a number of detrimental outcomes. However, there is sufficient evidence to link IH to many beneficial outcomes but they have largely been ignored, particularly in the field of sleep medicine in the United States. Recent reviews have postulated that this apparent contradiction is related to the severity and duration of exposure to IH; mild forms of IH initiate beneficial outcomes while severe forms of IH are coupled to detrimental consequences. In the present review we explore the role that IH has in initiating respiratory plasticity and the potential this form of plasticity has to mitigate obstructive sleep apnea (OSA) in humans. In taking this approach, we address the possibility that IH could serve as an adjunct therapy coupled with continuous positive airway pressure (CPAP) to treat OSA. Our working hypothesis is that exposure to mild IH leads to respiratory plasticity that manifests in increased stability of the upper airway, which could ultimately reduce the CPAP required to treat OSA. In turn, this reduction could increase CPAP compliance and extend the length of treatment each night, which might improve the magnitude of outcome measures. Improved treatment compliance coupled with the direct effect that IH has on numerous overlapping conditions (i.e. asthma, chronic obstructive pulmonary disease, spinal cord injury) may well lead to substantial improvements that exceed outcomes following treatment with CPAP alone. Overall, this review will consider evidence from the published literature which suggests that IH could serve as an effective multipronged therapeutic approach to treat sleep apnea and its overlapping co-morbidities.

Obstructive Sleep Apnoea Modulates Airway Inflammation and Remodelling in Severe Asthma

Background

Obstructive sleep apnoea (OSA) is frequently observed in severe asthma but the causal link between the 2 diseases remains hypothetical. The role of OSA-related systemic and airway neutrophilic inflammation in asthma bronchial inflammation or remodelling has been rarely investigated. The aim of this study was to compare hallmarks of inflammation in induced sputum and features of airway remodelling in bronchial biopsies from adult patients with severe asthma with and without OSA.

Materials and Methods

An overnight polygraphy was performed in 55 patients referred for difficult-to-treat asthma, who complained of nocturnal respiratory symptoms, poor sleep quality or fatigue. We compared sputum analysis, reticular basement membrane (RBM) thickness, smooth muscle area, vascular density and inflammatory cell infiltration in bronchial biopsies.

Results

In total, 27/55 patients (49%) had OSA diagnosed by overnight polygraphy. Despite a moderate increase in apnoea-hypopnoea index (AHI; 14.2±1.6 event/h [5–35]), the proportion of sputum neutrophils was higher and that of macrophages lower in OSA than non-OSA patients, with higher levels of interleukin 8 and matrix metalloproteinase 9. The RBM was significantly thinner in OSA than non-OSA patients (5.8±0.4 vs. 7.8±0.4 μm, p<0.05). RBM thickness and OSA severity assessed by the AHI were negatively correlated (rho = -0.65, p<0.05). OSA and non-OSA patients did not differ in age, sex, BMI, lung function, asthma control findings or treatment.

Conclusion

Mild OSA in patients with severe asthma is associated with increased proportion of neutrophils in sputum and changes in airway remodelling.

Assessment of the Mechanistic Role of Cinnarizine in Modulating Experimentally-Induced Bronchial Asthma in Rats

BACKGROUND/AIMS

Calcium influx, inflammatory infiltration, cytokine production, immunoglobulin E activation and oxidative stress play coordinated roles in bronchial asthma pathogenesis. We aim to assess the protective effect of cinnarizine against experimentally induced bronchial asthma.

METHODS

Bronchial asthma was induced by ovalbumin sensitization and challenge. Rats were allocated into a normal control, an asthma control, a dexamethasone (standard) treatment, and 2 cinnarizine treatment groups. The respiratory functions tidal volume (TV) and peak expiratory flow rate (PEFR), the inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-5 (IL-5) in lung tissue, the allergic immunoglobulin IgE in serum, the absolute eosinophil count (AEC) in bronchoalveolar lavage fluid (BALF), as well as the oxidative and nitrosative markers glutathione reduced (GSH) and superoxide dismutase (SOD) in lung tissue and nitric oxide end products (NOx) in BALF were assessed, followed by a histopathological study.

RESULTS

Cinnarizine administration significantly restored TV, PEFR, TNF-α, IL-5, IgE, AEC, GSH, SOD and NOx values back to normal levels, and significantly decreased perivascular and peribronchiolar inflammatory scores.

CONCLUSION

Cinnarizine may protect against experimental bronchial asthma. Suppressant effect of cinnarizine on pro-inflammatory cytokines release, IgE antibody production, eosinophil infiltration as well as oxidative and nitrosative stress may explain its anti-asthmatic potential.

Mice with Pulmonary Fibrosis Driven by Telomere Dysfunction

Idiopathic pulmonary fibrosis (IPF) is a degenerative disease of the lungs with an average survival post-diagnosis of 2-3 years. New therapeutic targets and treatments are necessary. Mutations in components of the telomere-maintenance enzyme telomerase or in proteins important for telomere protection are found in both familial and sporadic IPF cases. However, the lack of mouse models that faithfully recapitulate the human disease has hampered new advances. Here, we generate two independent mouse models that develop IPF owing to either critically short telomeres (telomerase-deficient mice) or severe telomere dysfunction in the absence of telomere shortening (mice with Trf1 deletion in type II alveolar cells). We show that both mouse models develop pulmonary fibrosis through induction of telomere damage, thus providing proof of principle of the causal role of DNA damage stemming from dysfunctional telomeres in IPF development and identifying telomeres as promising targets for new treatments.

Obstructive Sleep Apnea Risk, Asthma Burden, and Lower Airway Inflammation in Adults in the Severe Asthma Research Program (SARP) II

BACKGROUND

Obstructive sleep apnea (OSA) may worsen asthma, but large studies are lacking and the underlying mechanisms are unknown.

OBJECTIVE

The objective of this study was to determine the prevalence of OSA risk among patients with asthma of different severity compared with normal controls (NC), and among asthmatics, to test the relationship of OSA risk with asthma burden and airway inflammation.

METHODS

Subjects with severe (SA, n = 94) and nonsevere asthma (NSA, n = 161), and NC (n = 146) were recruited in an add-on substudy, to the observational Severe Asthma Research Program (SARP) II; subjects completed sleep quality, sleepiness and OSA risk (Sleep Apnea scale of the Sleep Disorders Questionnaire [SA-SDQ]) questionnaires, and clinical assessments. Sputum was induced in a subset of asthmatics.

RESULTS

Relative to NC, despite similar sleep duration, the subjects with SA and NSA had worse sleep quality, were sleepier, and had higher SA-SDQ scores. Among asthmatics, higher SA-SDQ was associated with increased asthma symptoms, β-agonist use, health care utilization, and worse asthma quality of life. A significant association of SA-SDQ with sputum polymorphonuclear cells% was noted: each increase in SA-SDQ by its standard deviation (6.85 units) was associated with a rise in % sputum neutrophils of 7.78 (95% CI 2.33-13.22, P = .0006), independent of obesity and other confounders.

CONCLUSIONS

OSA symptoms are more prevalent among asthmatics, in whom they are associated with higher disease burden. OSA risk is associated with a neutrophilic airway inflammation in asthma, which suggests that OSA may be an important contributor to the neutrophilic asthma. Further studies are necessary to confirm these findings and better understand the mechanistic underpinnings of this relationship.