Bronchial hyperresponsiveness to histamine correlates with airway remodelling in adults with asthma

New phosphodiesterase-4 inhibitors present airways relaxant activity in a guinea pig acute asthma model

Asthma is a disease characterized by chronic inflammation and hyper responsiveness of airways. We aimed to assess the relaxant potential of phosphodiesterase-4 (PDE4) inhibitors N-sulfonilhidrazonic derivatives on non-asthmatic and asthmatic guinea pig trachea. Firstly, guinea pigs were sensitized and challenged with ovalbumin, and then morphological, and contractile changes were evaluated resulting from asthma, followed by evaluation of relaxant effect of derivatives on guinea pig trachea and the cAMP levels measurement by ELISA. It has been evidenced hypertrophy of airway smooth muscle, inflammatory infiltrate, and vascular abnormalities. Moreover, only sensitized tracheal rings were responsive to OVA. Contractile response to histamine, but not to carbachol, was greater in sensitized animals, however the relaxant response to aminophylline and isoprenaline were the same in non-asthmatics and asthmatics. N-sulfonilhidrazonic derivatives presented equipotent relaxant action independent of epithelium, with exception of LASSBio-1850 that presented a low efficacy (< 50%) and LASSBio-1847 with a 4-fold higher potency on asthmatics. LASSBio-1847 relaxant curve was impaired in the presence of propranolol and potentiated by isoprenaline in both groups. Furthermore, relaxation was potentiated 54- and 4-fold by forskolin in non-asthmatics and asthmatics, respectively. Likewise, LASSBio-1847 potentiated relaxant curve of aminophylline 147- and 4-fold in both groups. The PKA inhibitor H-89 impaired the relaxant potency of the derivative. Finally, LASSBio-1847 increased tracheal intracellular cAMP levels similarly to rolipram, selective PDE4 inhibitor, in both animals. LASSBio-1847 showed to be promising to relax guinea pig trachea from non-sensitized and sensitized guinea pigs by activation of β2-adrenergic receptors/AC/cAMP pathway.

The contribution of reticular basement membrane proteins to basal airway epithelial attachment, spreading and barrier formation: implications for airway remodeling in asthma

Rationale

In the healthy lung, the pseudostratified conducting airway epithelium is anchored to the reticular basement membrane (RBM) via hemidesmosome junction complexes formed between basal cells and the extracellular matrix (ECM). The RBM within the healthy lung is composed of the ECM proteins laminin and collagen-IV. In patients with asthma, the RBM is remodeled with collagen-I, -III and fibronectin deposition. The goal of this study was to assess the effect of RBM ECM proteins on basal airway epithelial cell attachment, spreading and barrier formation using real-time electrical cell-substrate impedance sensing (ECIS).

Methods

ECIS 8-well arrays were coated with 50 μg/mL of fibronectin, collagen-I, collagen-III, collagen-IV, or laminin and compared to bovine serum albumin (BSA) or uncoated controls. The airway epithelial cell line (1HAEo-) was seeded 40, 50, 60, and 70 k cells/well and continuously monitored over 70 h to assess cell attachment, spreading and barrier formation using high (64 k Hz) and low (500 Hz) frequency resistance and capacitance. Data were analyzed using a one-phase decay model from which half-life (time cells cover half of the electrode area) and rate-constant (cell-spreading rate/h) were determined and a generalized additive mixed effect model (GAMM) was used to assess ECM proteins over the entire experiment.

Results

High-frequency (64 kHz) capacitance measures demonstrated the half-life for 1HAEo-cells to attach was fastest when grown on fibronectin (6.5 h), followed by collagen-I (7.2 h) and collagen-III (8.1 h), compared to collagen-IV (11.3 h), then laminin (13.2 h) compared to BSA (12.4 h) and uncoated (13.9 h) controls. High-frequency (64 kHz) resistance measures demonstrated that the rate of 1HAEo- cell spreading was significantly faster on fibronectin and collagen-I compared to collagen-III, collagen-IV, laminin, BSA and the uncoated control. Low-frequency (500 Hz) resistance measures demonstrated that 1HAEo-cells formed a functional barrier fastest when grown on fibronectin and collagen-I, compared to the other ECM conditions. Lastly, the distance of 1HAEo-cells from the ECM substrates was the smallest when grown on fibronectin reflecting high cell-matrix adhesion.

Conclusion

Airway epithelial cells attach, spread and form a barrier fastest on fibronectin, and collagen-I and these reticular basement membrane ECM proteins may play a protective role in preserving the epithelial barrier during airway remodeling in asthma.

Epithelial-Mesenchymal Transition Mechanisms in Chronic Airway Diseases: A Common Process to Target?

Epithelial-to-mesenchymal transition (EMT) is a reversible process, in which epithelial cells lose their epithelial traits and acquire a mesenchymal phenotype. This transformation has been described in different lung diseases, such as lung cancer, interstitial lung diseases, asthma, chronic obstructive pulmonary disease and other muco-obstructive lung diseases, such as cystic fibrosis and non-cystic fibrosis bronchiectasis. The exaggerated chronic inflammation typical of these pulmonary diseases can induce molecular reprogramming with subsequent self-sustaining aberrant and excessive profibrotic tissue repair. Over time this process leads to structural changes with progressive organ dysfunction and lung function impairment. Although having common signalling pathways, specific triggers and regulation mechanisms might be present in each disease. This review aims to describe the various mechanisms associated with fibrotic changes and airway remodelling involved in chronic airway diseases. Having better knowledge of the mechanisms underlying the EMT process may help us to identify specific targets and thus lead to the development of novel therapeutic strategies to prevent or limit the onset of irreversible structural changes.

Airway remodeling heterogeneity in asthma and its relationship to disease outcomes

Asthma affects an estimated 262 million people worldwide and caused over 461,000 deaths in 2019. The disease is characterized by chronic airway inflammation, reversible bronchoconstriction, and airway remodeling. Longitudinal studies have shown that current treatments for asthma (inhaled bronchodilators and corticosteroids) can reduce the frequency of exacerbations, but do not modify disease outcomes over time. Further, longitudinal studies in children to adulthood have shown that these treatments do not improve asthma severity or fixed airflow obstruction over time. In asthma, fixed airflow obstruction is caused by remodeling of the airway wall, but such airway remodeling also significantly contributes to airway closure during bronchoconstriction in acute asthmatic episodes. The goal of the current review is to understand what is known about the heterogeneity of airway remodeling in asthma and how this contributes to the disease process. We provide an overview of the existing knowledge on airway remodeling features observed in asthma, including loss of epithelial integrity, mucous cell metaplasia, extracellular matrix remodeling in both the airways and vessels, angiogenesis, and increased smooth muscle mass. While such studies have provided extensive knowledge on different aspects of airway remodeling, they have relied on biopsy sampling or pathological assessment of lungs from fatal asthma patients, which have limitations for understanding airway heterogeneity and the entire asthma syndrome. To further understand the heterogeneity of airway remodeling in asthma, we highlight the potential of in vivo imaging tools such as computed tomography and magnetic resonance imaging. Such volumetric imaging tools provide the opportunity to assess the heterogeneity of airway remodeling within the whole lung and have led to the novel identification of heterogenous gas trapping and mucus plugging as important predictors of patient outcomes. Lastly, we summarize the current knowledge of modification of airway remodeling with available asthma therapeutics to highlight the need for future studies that use in vivo imaging tools to assess airway remodeling outcomes.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Airway wall thickness and airflow limitations in asthma assessed in quantitative computed tomography

Background:

Asthma is a frequent chronic disease of the airways. In spite of the fact that symptoms of asthma are well known, the pathogenesis has not yet been fully understood. Quantitative computed tomography (qCT) of the lung allows for the measurment of a set of parameters. The aim of this study was to evaluate the usefulness of quantitative computed tomography in the assessment of airway wall thickness in asthma.

Methods:

The prospective study was performed on a group of 83 patients with well-defined, long-term asthma between 2016 and 2018. The control group was composed of 30 healthy volunteers. All examined subjects were non-smokers. All computed tomography (CT) studies were performed using a 128 multi-slice CT scanner with no contrast, following a chest scanning protocol in the supine position, at full inspiration and breath-holds.

Results:

Quantitative bronchial tree measurements were obtained from the third up to the ninth generation of the posterior basal bronchi (B10) of the right lung in a blinded fashion. The value of the wall thickness in patients with asthma was significantly higher in all measured generations of the bronchial tree (third to ninth generation). The lumen area and the inner diameter significantly correlated with the lung function tests and were substantially smaller in the examined group from the seventh to the ninth generation of the bronchi (p < 0.05).

Conclusions:

We conclude that airway remodelling occurs in most patients with long-term asthma and is associated mainly with the medium and small airways. Imaging techniques, especially qCT can be useful in the diagnosis and management of asthma.

The reviews of this paper are available via the supplemental material section.

Airway hyperresponsiveness, remodeling and inflammation in infants with wheeze

BACKGROUND

The relationship of airway hyperresponsiveness to airway remodeling and inflammation in infants with wheeze is unclear.

OBJECTIVE

To investigate airway hyperresponsiveness, remodeling and inflammation in infants with wheeze and troublesome breathing.

METHODS

Inclusion criteria were as follows: full-term, 3-23 months of age; doctor -diagnosed wheeze and persistent recurrent troublesome breathing; without obvious structural defect, suspicion of ciliary dyskinesia, cystic fibrosis, immune deficiency or specified use of corticosteroids. Airway hyperresponsiveness (AHR) was evaluated by performing a methacholine bronchial challenge test combined with whole body plethysmography and rapid thoracoabdominal compression. Endobronchial biopsies were analysed for remodeling (thickness of reticular basement membrane and amount of airway smooth muscle) and for inflammation (numbers of inflammatory cells). Correlation analyses were performed.

RESULTS

Forty-nine infants fulfilled the inclusion criteria for the present study. Median age was 1.06 years (IQR 0.6; 1.5). Lung function was impaired in 39/49 (80%) children, at the median age of 1.1 years. Methacholine challenge was successfully performed in 38/49 children. Impaired baseline lung function was correlated with AHR (P = .047, Spearman). In children with the most sensitive quartile of AHR, the percentage of median bronchial airway smooth muscle % and the number of bronchial mast cells in airway smooth muscle were not significantly higher compared to others (P = .057 and 0.056, respectively). No association was found between AHR and thickness of reticular basement membrane or inflammatory cells. Only a small group of children with both atopy and AHR (the most reactive quartile) had thicker airway smooth muscle area than non-atopics with AHR (P = .031).

CONCLUSIONS AND CLINICAL RELEVANCE

These findings do not support the concept that AHR in very young children with wheeze is determined by eosinophilic inflammation or clear-cut remodeling although it is associated with impaired baseline lung function. The possible association of increased airway smooth muscle area among atopic children with AHR remains to be confirmed.

Lung Sound Analysis Provides A Useful Index For Both Airway Narrowing And Airway Inflammation In Patients With Bronchial Asthma

Background

The expiration-to-inspiration sound power ratio in a midfrequency range (E/I MF), a parameter of lung sound analysis (LSA), has been reported to be useful as an index of airway inflammation in patients with bronchial asthma. However, the E/I MF reflects airway narrowing caused by airway inflammation, and there is thus concern that it may not be an index of airway eosinophilic inflammation itself.

Methods

A total of 131 patients with bronchial asthma were classified into four groups according to the presence or absence of airway narrowing and airway inflammation to examine whether the E/I MF could serve as an index of airway inflammation.

Results

The E/I MF was significantly higher in patients with a normal forced expiratory volume in one second (FEV₁) and high fractional exhaled nitric oxide (FeNO), those with a low FEV₁ and normal FeNO, and those with a low FEV₁ and high FeNO than in those with a normal FEV₁ and normal FeNO (p < 0.05–0.01). In particular, the E/I MF was high even in the patients who had no airway narrowing but had airway inflammation (p < 0.01). The results of multivariate analysis of factors involved in FeNO in patients with a normal FEV₁ revealed that the E/I MF was an independent factor (p = 0.0281).

Conclusion

The E/I MF is a useful index of airway inflammation in the treatment of asthma, regardless of the presence or absence of airway narrowing.

Microfibrillar-associated protein 4 in serum is associated with asthma in Danish adolescents and young adults

Background

Microfibrillar‐associated protein 4 (MFAP4) is an extracellular matrix protein belonging to the fibrinogen‐related protein superfamily, which plays multifaceted roles in innate immunity and normal endothelial function. It has been proposed that MFAP4 promotes the development of asthma in vivo and proasthmatic pathways of bronchial smooth muscle cells in vitro. The aim of this study was to investigate the significance of serum MFAP4 in adolescents and young adolescents with persistent asthma.

Methods

Prospective, observational study including adolescents and young adults (age 11‐27 years) previously diagnosed with asthma during childhood 2003 to 2005 (0‐15 years) at the four pediatric outpatient clinics in the Region of Southern Denmark (n = 449). Healthy controls were recruited at follow‐up (n = 314). Detection of serum MFAP4 was performed by AlphaLISA technique.

Results

Current asthma was associated to a 14% higher mean level of serum MFAP4 compared with controls (expβ 1.14, 95% confidence intervals [CI], 1.05‐1.23) and a 6% higher mean level compared with subjects with no current asthma (expβ 1.06, 95% CI, 0.99‐1.13). No association was found at follow‐up between serum MFAP4 and self‐reported atopic symptoms (other than asthma), Asthma Control Test‐score, fractional exhaled nitric oxide (FeNO), nor to flow rate at 1 second, forced vital capacity, and forced expiratory flow 25% to 75%, response to short‐acting beta 2 agonist or mannitol.

Conclusions

We found a significantly higher mean level of serum MFAP4 in adolescent and young adults with mild to moderate asthma compared with healthy controls but no association to FeNO and lung function nor to the response to short‐acting beta 2 agonist or mannitol. The result supports the hypothesis that MFAP4 plays a role in the pathogenesis of asthma although the marker did not demonstrate any obvious potential as an asthma biomarker in adolescents and young adults with asthma. To understand the possible proasthmatic functions of MFAP4, further investigation in specific asthma phenotypes and the underlying molecular mechanisms is warranted.

Phenotype classification using the combination of lung sound analysis and fractional exhaled nitric oxide for evaluating asthma treatment

BACKGROUND

We report the utility of combining lung sound analysis and fractional exhaled nitric oxide (FeNO) for phenotype classification of airway inflammation in patients with bronchial asthma. We investigated the usefulness of the combination of the expiration-to-inspiration sound power ratio in the mid-frequency range (E/I MF) of 200-400 Hz and FeNO for comprehensively classifying disease type and evaluating asthma treatment.

METHODS

A total of 233 patients with bronchial asthma were included. The cutoff values of FeNO and E/I MF were set to 38 ppb and 0.36, respectively, according to a previous study. The patients were divided into 4 subgroups based on the FeNO and E/I MF cutoff values. Respiratory function, the percentages of sputum eosinophils and neutrophils, and patient background characteristics were compared among groups.

RESULTS

Respiratory function was well controlled in the FeNO low/E/I MF low group (good control). Sputum neutrophil was higher and FEV₁,%pred was lower in the FeNO low/E/I MF high group (poor control). History of childhood asthma and atopic asthma were associated with the FeNO high/E/I MF low group (insufficient control). The FeNO high/E/I MF high group corresponded to a longer disease duration, increased blood or sputum eosinophils, and lower FEV₁/FVC (poor control).

CONCLUSIONS

The combination of FeNO and E/I MF assessed by lung sound analysis allows the condition of airway narrowing and the degree of airway inflammation to be assessed in patients with asthma and is useful for evaluating bronchial asthma treatments.

Low Variability in Peak Expiratory Flow Predicts Successful Inhaled Corticosteroid Step-Down in Adults with Asthma

BACKGROUND

The prognosis for patients beyond 1 year after reduction of their inhaled corticosteroid (ICS) dose remains unknown. Predictive factors that can be evaluated before the initiation of asthma treatment or at ICS dose reduction are unknown.

METHODS

We prospectively studied 223 patients in 6 hospitals in the National Hospital Organization of Japan during the 36 months after 50% reduction of their daily ICS dose. All patients recorded their morning and evening peak expiratory flows (PEFs) in their diaries. Lung function, bronchial hyperresponsiveness, fractional nitric oxide levels, number of eosinophils in sputum, and serum IgE levels were measured in most patients. Serum levels of IL-10, IL-33, and thymic stromal lymphopoietin before ICS dose reduction were measured in all patients.

RESULTS

During the 36-month study period, asthma control was retained in 127 (59.6%) of the 213 enrolled patients who underwent ICS dose reduction. Multivariate logistic regression analysis revealed that, at the initiation of dose reduction, the factors most predictive of maintenance of asthma control after ICS dose reduction were a low serum IL-33 level (P < .01), low PEF variability over 1 week (P = .014), childhood onset of asthma (at age <10 years) (P = .03), and high serum IL-10 level (P = .035).

CONCLUSIONS

We demonstrated that low PEF variability over 1 week, high serum IL-10 level, and low serum IL-33 concentration were useful factors for predicting that an adult's asthma will remain in control for months to years after a 50% reduction in the daily ICS dose.

Airway Evaluation with Multidetector Computed Tomography Post-Processing Methods in Asthmatic Patients

Asthma is a chronic inflammatory obstructive airways disease. The disease occurs regardless of age and manifests with cough, attacks of breathlessness, and tightness in the chest. The pathophysiology of asthma is complex and still not fully understood. It is essential to find answers concerning the role of each part of the bronchial tree in asthma, especially the role of small bronchioles. With the development of newer generations of multidetector computed tomography (MDCT) and advanced post-processing methods it is possible to obtain more detailed images and gain insight into further aspects of asthma. MDCT post-processing methods can be divided into two-dimensional (2D) and three-dimensional (3D). In 2D projections, visualized hypodense regions correspond to the airway flow limitations. With the more advanced methods, such as multi planar reconstructions (MPR), images in different planes (axial, coronal, or sagittal) can be created. In the MPR technique only the voxels which are adjacent to each other in the predetermined plane can be extracted from the data set. Using the minimal/maximal intensity projections and shaded surface display, the volume of interest (VOI) can be extracted. High resolution CT scans can be used to create a more advanced imaging tool - the virtual bronchoscopy (VB). Using the VB makes it possible to visualize regions of obturation in the bronchi of up to the 5-8th generation. The MDCT with advanced post-processing methods is likely to assume an important role in the differential diagnosis of asthma, particularly when the diagnosis is dubious or hard to settle due to accompanying other lung diseases.

Immunohistology and remodeling in fatal pediatric and adolescent asthma

Background

Thickening of reticular basement membrane, increased airway smooth muscle mass and eosinophilic inflammation are found in adult fatal asthma. At the present study the histopathology of fatal paediatric and adolescent asthma is evaluated.

Methods

Post-mortem lung autopsies from 12 fatal asthma cases and 8 non-asthmatic control subjects were examined. Thickness of reticular basement membrane (RBM) and percentage of airway smooth muscle (ASM%) mass area were measured and inflammatory cells were counted. Patient records were reviewed for clinical history.

Results

The age range of the cases was from 0.9 to 19.5 years, eight were males and five had received inhaled corticosteroids. Thickened RBM was detected in majority of the cases without any correlation to treatment delay, age at onset of symptoms or diagnosis. In the large airways ASM was clearly increased in one third of the cases whereas the median ASM% did not differ from that in healthy controls (14.0% vs. 14.0%). In small airways no increase of ASM was found, instead mucous plugs were seen in fatal asthma. The number of eosinophils, plasmacytoid dendritic cells, macrophages, and B-cells were significantly increased in fatal asthma cases compared with controls and the two latter correlated with the length of the fatal exacerbation.

Conclusions

The findings highlight the strong presence of eosinophils and mucous plugs even in small airways in children and adolescents with fatal asthma. Thickened RBM was obvious in majority of the patients. Contrary to our hypothesis, increased ASM% was detected in only one third of the patients.

Bitter taste receptor agonists alter mitochondrial function and induce autophagy in airway smooth muscle cells

Airway remodeling, including increased airway smooth muscle (ASM) mass, is a hallmark feature of asthma and COPD. We previously identified the expression of bitter taste receptors (TAS2Rs) on human ASM cells and demonstrated that known TAS2R agonists could promote ASM relaxation and bronchodilation and inhibit mitogen-induced ASM growth. In this study, we explored cellular mechanisms mediating the antimitogenic effect of TAS2R agonists on human ASM cells. Pretreatment of ASM cells with TAS2R agonists chloroquine and quinine resulted in inhibition of cell survival, which was largely reversed by bafilomycin A1, an autophagy inhibitor. Transmission electron microscope studies demonstrated the presence of double-membrane autophagosomes and deformed mitochondria. In ASM cells, TAS2R agonists decreased mitochondrial membrane potential and increased mitochondrial ROS and mitochondrial fragmentation. Inhibiting dynamin-like protein 1 (DLP1) reversed TAS2R agonist-induced mitochondrial membrane potential change and attenuated mitochondrial fragmentation and cell death. Furthermore, the expression of mitochondrial protein BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 (Bnip3) and mitochondrial localization of DLP1 were significantly upregulated by TAS2R agonists. More importantly, inhibiting Bnip3 mitochondrial localization by dominant-negative Bnip3 significantly attenuated cell death induced by TAS2R agonist. Collectively the TAS2R agonists chloroquine and quinine modulate mitochondrial structure and function, resulting in ASM cell death. Furthermore, Bnip3 plays a central role in TAS2R agonist-induced ASM functional changes via a mitochondrial pathway. These findings further establish the cellular mechanisms of antimitogenic effects of TAS2R agonists and identify a novel class of receptors and pathways that can be targeted to mitigate airway remodeling as well as bronchoconstriction in obstructive airway diseases.

Bitter Taste Receptor Agonists Mitigate Features of Allergic Asthma in Mice

Asthma is characterized by airway inflammation, mucus secretion, remodeling and hyperresponsiveness (AHR). Recent research has established the bronchodilatory effect of bitter taste receptor (TAS2R) agonists in various models. Comprehensive pre-clinical studies aimed at establishing effectiveness of TAS2R agonists in disease models are lacking. Here we aimed to determine the effect of TAS2R agonists on features of asthma. Further, we elucidated a mechanism by which TAS2R agonists mitigate features of asthma. Asthma was induced in mice using intranasal house dust mite or aerosol ova-albumin challenge, and chloroquine or quinine were tested in both prophylactic and treatment models. Allergen challenge resulted in airway inflammation as evidenced by increased immune cells infiltration and release of cytokines and chemokines in the lungs, which were significantly attenuated in TAS2R agonists treated mice. TAS2R agonists attenuated features of airway remodeling including smooth muscle mass, extracellular matrix deposition and pro-fibrotic signaling, and also prevented mucus accumulation and development of AHR in mice. Mechanistic studies using human neutrophils demonstrated that inhibition of immune cell chemotaxis is a key mechanism by which TAS2R agonists blocked allergic airway inflammation and exerted anti-asthma effects. Our comprehensive studies establish the effectiveness of TAS2R agonists in mitigating multiple features of allergic asthma.

Peripheral bronchial obstruction evaluation in patients with asthma by lung sound analysis and impulse oscillometry

BACKGROUND

Computer-aided lung sound analysis (LSA) has been reported to be useful for evaluating airway inflammation and obstruction in asthma patients. We investigated the relation between LSA and impulse oscillometry with the evaluation of peripheral airway obstruction.

METHODS

A total of 49 inhaled corticosteroid-naive bronchial asthma patients underwent LSA, spirometry, impulse oscillometry, and airway hyperresponsiveness testing. The data were analyzed to assess correlations between the expiration: inspiration lung sound power ratio (dB) at low frequencies between 100 and 195 Hz (E/I LF) and various parameters.

RESULTS

E/I LF and X5 were identified as independent factors that affect V˙_{50,%predicted}. E/I LF showed a positive correlation with R5 (r = 0.34, p = 0.017), R20 (r = 0.34, p = 0.018), reactance area (AX, r = 0.40, p = 0.005), and resonant frequency of reactance (Fres, r = 0.32, p = 0.024). A negative correlation was found between E/I LF and X5 (r = -0.47, p = 0.0006). E/I LF showed a negative correlation with FEV₁/FVC(%), FEV_1,%predicted, V˙_{50,%predicted}, and V˙_{25,%predicted} (r = -0.41, p = 0.003; r = -0.44, p = 0.002; r = -0.49, p = 0.0004; and r = -0.30, p = 0.024, respectively). E/I LF was negatively correlated with log PC₂₀ (r = -0.30, p = 0.024). Log PC₂₀, X5, and past smoking were identified as independent factors that affected E/I LF level.

CONCLUSIONS

E/I LF as with X5 can be an indicator of central and peripheral airway obstruction in bronchial asthma patients.

Pheretima aspergillum decoction suppresses inflammation and relieves asthma in a mouse model of bronchial asthma by NF-κB inhibition

ETHNOPHARMACOLOGICAL RELEVANCE AND AIM OF THE STUDY

Guang-Pheretima, the live form of the earthworm Pheretima aspergillum, is a traditional Chinese medicine commonly used for the treatment of asthma, cough, stroke, epilepsy and other diseases due to its anti-inflammatory, anti-asthmatic, anti-seizure, thrombolytic and diuretic properties. Although Guang-Pheretima is effective in the relief of asthma, its pharmacological activity and the underlying molecular mechanisms are not fully understood. Hence, we investigated the effects of a Pheretima aspergillum decoction (PAD) against inflammation in a model of ovalbumin (OVA)-induced asthma in BALB/c mice, as well as the nuclear factor-κB (NF-κB) pathway involved in this process.

MATERIALS AND METHODS

OVA was used to sensitize and challenge the airway of the mice, and PAD was administrated by gavage. We measured airway hyperresponsiveness (AHR) in the mice 24h following a final methacholine challenge with whole-body plethysmography. The bronchoalveolar lavage fluid (BALF), serum and pulmonary tissues were collected 48h after the last challenge. The levels of inflammatory factors and the related mRNAs were determined by enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR), respectively. The number of differential inflammatory cells in the BALF was counted. Serum total and OVA-specific IgE levels were measured with ELISA. The activation of NF-κB signaling in the lung was detected by western blotting. In addition, the lung tissues were stained with hematoxylin and eosin or periodic acid Schiff stain for histopathological examination.

RESULTS

PAD treatment significantly alleviated AHR in the asthmatic mice, decreased the mRNA and protein levels of IL-4, IL-5 and IL-13 and downregulated IgE. In addition, PAD treatment attenuated mucus secretion and infiltration of inflammatory cells in the lung while inhibiting the activation of NF-κB signaling.

CONCLUSIONS

PAD effectively inhibited the activation of NF-κB signaling in the lungs of mice with OVA-induced asthma, and mitigated AHR and Th2 type inflammatory reactions. Therefore, PAD may serve as a drug candidate for asthma treatment.

The effects of in utero vitamin D deficiency on airway smooth muscle mass and lung function

We have previously demonstrated increased airway smooth muscle (ASM) mass and airway hyperresponsiveness in whole-life vitamin D-deficient female mice. In this study, we aimed to uncover the molecular mechanisms contributing to altered lung structure and function. RNA was extracted from lung tissue of whole-life vitamin D-deficient and -replete female mice, and gene expression patterns were profiled by RNA sequencing. The data showed that genes involved in embryonic organ development, pattern formation, branching morphogenesis, Wingless/Int signaling, and inflammation were differentially expressed in vitamin D-deficient mice. Network analysis suggested that differentially expressed genes were connected by the hubs matrix metallopeptidase 9; NF-κ light polypeptide gene enhancer in B cells inhibitor, α; epidermal growth factor receptor; and E1A binding protein p300. Given our findings that developmental pathways may be altered, we investigated if the timing of vitamin D exposure (in utero vs. postnatal) had an impact on lung health outcomes. Gene expression was measured in in utero or postnatal vitamin D-deficient mice, as well as whole-life vitamin D-deficient and -replete mice at 8 weeks of age. Baseline lung function, airway hyperresponsiveness, and airway inflammation were measured and lungs fixed for lung structure assessment using stereological methods and quantification of ASM mass. In utero vitamin D deficiency was sufficient to increase ASM mass and baseline airway resistance and alter lung structure. There were increased neutrophils but decreased lymphocytes in bronchoalveolar lavage. Expression of inflammatory molecules S100A9 and S100A8 was mainly increased in postnatal vitamin D-deficient mice. These observations suggest that in utero vitamin D deficiency can alter lung structure and function and increase inflammation, contributing to symptoms in chronic diseases, such as asthma.

IgE induces proliferation in human airway smooth muscle cells: role of MAPK and STAT3 pathways

Airway remodeling is not specifically targeted by current asthma medications, partly owing to the lack of understanding of remodeling mechanisms, altogether posing great challenges in asthma treatment. Increased airway smooth muscle (ASM) mass due to hyperplasia/hypertrophy contributes significantly to overall airway remodeling and correlates with decline in lung function. Recent evidence suggests that IgE sensitization can enhance the survival and mediator release in inflammatory cells. Human ASM (HASM) cells express both low affinity (FcεRII/CD23) and high affinity IgE Fc receptors (FcεRI), and IgE can modulate the contractile and synthetic function of HASM cells. IgE was recently shown to induce HASM cell proliferation but the detailed mechanisms remain unknown. We report here that IgE sensitization induces HASM cell proliferation, as measured by ³H-thymidine, EdU incorporation, and manual cell counting. As an upstream signature component of FcεRI signaling, inhibition of spleen tyrosine kinase (Syk) abrogated the IgE-induced HASM proliferation. Further analysis of IgE-induced signaling depicted an IgE-mediated activation of Erk 1/2, p38, JNK MAPK, and Akt kinases. Lastly, lentiviral-shRNA-mediated STAT3 silencing completely abolished the IgE-mediated HASM cell proliferation. Collectively, our data provide mechanisms of a novel function of IgE which may contribute, at least in part, to airway remodeling observed in allergic asthma by directly inducing HASM cell proliferation.

Remodeling, inflammation and airway responsiveness in early childhood asthma

PURPOSE OF REVIEW

Remodeling and inflammation together with airway hyperresponsiveness are essential components of asthma but their role in development of the disease is still obscure.

RECENT FINDINGS

Recent data imply that remodeling can occur early in childhood, not necessarily subsequent to but rather, in parallel with inflammation. The assumption of thickening of the reticular basement membrane being a prerequirement for chronic asthma is questioned but development of airway responsiveness is a significant factor. Airway responsiveness is at least partially linked to bronchial inflammation but there are several other genes and pathways regulating airway responsiveness. Increased airway smooth muscle in early childhood is associated with later development of asthma and may be one link between inflammation and airway responsiveness. Novel findings on genetic variation in genes regulating lung growth and remodeling in early childhood shed light on the pathophysiological mechanisms leading to chronic asthma.

SUMMARY

Even young children with chronic asthma have detectable elements of airway remodeling, inflammation and increased airway responsiveness, which all contribute to impaired lung function.

Increased airway smooth muscle in preschool wheezers who have asthma at school age

BACKGROUND

Increased airway smooth muscle (ASM) is a feature of established asthma in schoolchildren, but nothing is known about ASM in preschool wheezers.

OBJECTIVE

We sought to determine endobronchial biopsy specimen ASM area fraction in preschool wheezers and its association with asthma at school age.

METHODS

ASM area, reticular basement membrane thickness, and mucosal eosinophil and ASM mast cell values were quantified in endobronchial biopsy specimens previously obtained from preschool children undergoing clinically indicated bronchoscopy: severe recurrent wheezers (n=47; median age, 26 months) and nonwheezing control subjects (n=21; median age, 15 months). Children were followed up, and asthma status was established at age 6 to 11 years. Preschool airway pathology was examined in relation to asthma at school age.

RESULTS

Forty-two (62%) of 68 children had 1 or more evaluable biopsy specimens for ASM. At school age, 51 of 68 children were followed up, and 15 (40%) of 37 preschool wheezers had asthma. Children who had asthma and an evaluable biopsy specimen had increased preschool ASM area fraction (n=8; median age, 8.2 years [range, 6-10.4 years]; median ASM, 0.12 [range, 0.08-0.16]) compared with that seen in children without asthma (n=24; median age, 7.3 years [range, 5.9-11 years]; median ASM, 0.07 [range, 0.02-0.23]; P=.007). However, preschool reticular basement membrane thickness and mucosal eosinophil or ASM mast cell values were not different between those who did or did not have asthma at school age.

CONCLUSION

Increased preschool ASM is associated with those children who have asthma at school age. Thus a focus on early changes in ASM might be important in understanding the subsequent development of childhood asthma.

Markers for step-down of inhaled corticosteroid therapy in adult asthmatics

BACKGROUND

Treatment guidelines recommend the use of inhaled corticosteroids (ICS) as first-line therapy for all stages of persistent asthma. However, it is unknown whether ICS dose reduction in adult asthmatics is compatible with maintaining asthma control. Moreover, there are no predictors of efficacy in maintaining asthma control upon ICS reduction.

METHODS

We recruited 90 adult patients with moderate or severe asthma but no clinical symptoms of asthma for at least 6 months. All patients reduced their ICS doses by half but continued taking other asthma-related medications. As a primary outcome, we measured asthma exacerbations during the 12 months following ICS reduction. We also further monitored patients from the above study who had maintained total asthma control for 12 months after ICS reduction and who had continued on their reduced doses of ICS or had further reduced, or stopped, their ICS.

RESULTS

Forty of ninety patients (44.4%) experienced exacerbations after ICS reduction (time to first exacerbation: 6.4 ± 3.6 months). Multivariate logistic regression modeling revealed a rank order of predictors of success in ICS reduction while retaining asthma control: acetylcholine (ACh) PC(20) (p < 0.01); length of time with no clinical symptoms before ICS reduction (p < 0.01); FeNO (p = 0.028); and forced expiratory volume in 1 s (FEV(1); % predicted) (p = 0.03). Finally thirty-nine of 50 patients maintained total asthma control for at least 2 years after the initial ICS reduction.

CONCLUSIONS

In asthma patients with normalized AChPC(20) of 20mg/mL or 10mg/mL and no clinical symptoms for at least 12 or 24 months it may be possible to successfully reduce ICS without increasing exacerbations for long time.

Allergen challenge differentially affects the number of circulating monocyte subsets

Peripheral blood monocyte (PBM) subsets play different roles in inflammatory response and tissue remodelling. The aim of this study was to investigate how allergen challenge affects the number of circulating PBMs in Dermatophagoides pteronyssinus (Dp) allergic patients (Dp-APs). Among 34 Dp-APs challenged, in 22 patients significant bronchoconstriction was demonstrated [responders (Rs)], while in 12, only upper respiratory symptoms were seen [non-responders (NRs)]. Twelve healthy, non-atopic subjects were used as controls (HCs). Expression of CD14, CD16 and CCR4 was evaluated by flow cytometry on the whole-blood samples before (T(0) ), 6 h (T(6) ) and 24 h (T(24) ) after the challenge. Plasma concentrations of CCL2, CX3CL1 and CCL17 were evaluated using ELISA. At T(0) , the mean percentage of CD14++ CD16+ PBMs in Rs (35.4%; 95%CI 26.9-43.9%) was significantly greater than in HCs (14.6%; 95%CI 7.3-21.8%; P = 0.006) and in NRs (17.5%; 95%CI 9.6-25.4%; P = 0.001). The baseline number of CD14++ CD16+ PBMs correlated with airway hyper responsiveness (AHR) (r = -0.507; 95%CI -0.834 to -0.432, P < 0.001). At T(24) , the number of CD14++ CD16+ PBMs significantly decreased in Rs but not in NRs and the numbers inversely correlated with plasma CCL17 concentration. Changes in the number of circulating CD14++ CD16+ cells after Dp challenge correlated with AHR (r = 0.706, 95%CI 0.43-0.861; P < 0.001). In all subjects, the greatest expression of CCR4 was found on CD14++ CD16+ PBMs. Expansion of CD14++ CD16+ monocytes in the peripheral blood with subsequent mobilization of those cells after allergen challenge may facilitate the development of AHR in Dp-APs.

Is there a regulatory role of immunoglobulins on tissue forming cells relevant in chronic inflammatory lung diseases?

Epithelial cells, fibroblasts and smooth muscle cells together form and give structure to the airway wall. These three tissue forming cell types are structure giving elements and participate in the immune response to inhaled particles including allergens and dust. All three cell types actively contribute to the pathogenesis of chronic inflammatory lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). Tissue forming cells respond directly to allergens through activated immunoglobulins which then bind to their corresponding cell surface receptors. It was only recently reported that allergens and particles traffic through epithelial cells without modification and bind to the immunoglobulin receptors on the surface of sub-epithelial mesenchymal cells. In consequence, these cells secrete pro-inflammatory cytokines, thereby extending the local inflammation. Furthermore, activation of the immunoglobulin receptors can induce proliferation and tissue remodeling of the tissue forming cells. New studies using anti-IgE antibody therapy indicate that the inhibition of immunoglobulins reduces the response of tissue forming cells. The unmeasured questions are: (i) why do tissue forming cells express immunoglobulin receptors and (ii) do tissue forming cells process immunoglobulin receptor bound particles? The focus of this review is to provide an overview of the expression and function of various immunoglobulin receptors.

Evidence of a genetic contribution to lung function decline in asthma

There has been great progress in identifying new asthma susceptibility genes. In asthmatic subjects there is variable airway remodeling that includes features such as smooth muscle hypertrophy/hyperplasia, basement membrane thickening, and increased extracellular matrix deposition. Does airway remodeling have a genetic contribution in asthma? Data from different murine strains suggest there is a genetic contribution to the development and progression of airway remodeling. In human subjects it is important to consider what surrogate markers of remodeling have been used in genetic studies. Baseline FEV(1) and airway hyperresponsiveness are determined by a complex interplay of factors, including nonremodeling mechanisms; however, we consider a decline in FEV(1) as a robust marker of remodeling. To date, single nucleotide polymorphisms spanning ADAM33, ESR1, PLAUR, and VEGF have been associated with an excess decline in lung function in asthmatic subjects carrying the rare alleles (FEV(1), -13.0 to 55.2 mL/y excess). Interestingly these genes have overlapping functions in proteolytic pathways in the airways. There is accumulating evidence that genetic factors are important in the development of airway remodeling in asthmatic subjects, and further longitudinal studies with additional remodeling phenotypes and genome-wide association studies will identify novel susceptibility genes, leading to new approaches to target remodeling in asthmatic subjects.