Airway Hyperresponsiveness Levels Research Articles

Airway hyperresponsiveness correlates with airway TSLP in asthma independent of eosinophilic inflammation

BackgroundThymic stromal lymphopoietin (TSLP) is released from the airway epithelium in response to various environmental triggers, inducing a Type-2 inflammatory response, and is associated with airway inflammation, airway hyperresponsiveness (AHR) and exacerbations. TSLP may also induce AHR via a direct effect on airway smooth muscle and mast cells, independently of Type-2 inflammation, although association between airway TSLP and AHR across asthma phenotypes only has been described sparsely. ObjectiveTo investigate the association between AHR and levels of TSLP in serum, sputum and BAL in patients with asthma with and without Type-2 inflammation. MethodsA novel ultra-sensitive MSD S-plex assay was used to measure levels of TSLP in patients with asthma (serum n=182, sputum n=81, BAL n=85) and healthy controls (serum n=47). The distribution and association between airway and systemic TSLP, measures of AHR, Type-2 inflammation and severity of disease were assessed. ResultsTSLP in sputum was associated with AHR independently of levels of eosinophils and fractional exhaled nitric oxide, ρ=0.49, p=0.005. Serum TSLP (geo.mean (95% CI)) was higher in both eosinophil-high and eosinophil-low asthma compared to healthy controls: 1600 fg/ml (1468-1744) and 1294 fg/ml (1167-1435) vs. 846 fg/ml (661-1082), but did not correlate with the level of AHR. Increasing age, male sex and eosinophils in blood were associated with higher levels of TSLP in serum, whereas lung function, ICS dose and symptom score were not. ConclusionThe association between TSLP in sputum and AHR to mannitol irrespective of markers of type-2 inflammation further supports a role of TSLP in AHR that is partially independent of eosinophilic inflammation.

Airway hyperresponsiveness and inflammation in Japanese patients with human immunodeficiency virus 1 infection

IntroductionDespite the growing population of long-term survivors with human immunodeficiency virus 1 (HIV) exhibiting asthma-like features worldwide, the pathogenesis underlying airway hyperresponsiveness (AHR) and airway inflammation remains unclear. We aimed to investigate AHR and airway inflammation in an HIV-infected Japanese population. MethodsOf 94 Japanese participants, 10 HIV-infected participants with asthma were excluded from the study. We compared the characteristics of HIV-infected (n = 34) and non-HIV-infected participants (n = 50). Eosinophilic, neutrophilic, mixed (eosinophilic and neutrophilic), and paucigranulocytic airway inflammatory phenotypes were classified based on induced sputum characteristics. ResultsThe prevalence of AHR in HIV-infected participants (32.4%) was significantly higher than that in their non-HIV-infected counterparts (10.0%) (P = 0.0213). The multivariate nominal logistic regression analysis revealed HIV as an independent risk factor for AHR. HIV-infected participants were significantly more likely to have a neutrophilic airway inflammatory phenotype than non-HIV-infected participants (P = 0.0358). Furthermore, HIV-infected participants with AHR demonstrated a significant correlation between AHR levels and the percentage of sputum neutrophils (r = −0.65, P = 0.0316). The percentage of sputum neutrophils was negatively associated with the blood CD4 cell count (r = −0.66, P = 0.0266). ConclusionsWe observed the high prevalence of AHR and neutrophilic airway inflammatory phenotype in Japanese participants with stable HIV infection. Our findings provide insight into the mechanisms of AHR and may facilitate the development of novel treatment for individuals with AHR and HIV infection.

Environmental allergens house dust mite-induced asthma is associated with ferroptosis in the lungs.

Previous studies have indicated that allergens such as house dust mites (HDM) in the environment can induce allergic asthma. Ferroptosis is a newly discovered form of regulatory cell death characterized by aberrant lipid peroxidation and the accumulation of reactive oxygen species (ROS) in cells. However, whether ferroptosis participates in the pathological process of asthma remains to be elucidated. The present study used a HDM-induced mouse asthma model to determine the effect of HDM exposure on allergic asthma and its underlying mechanisms. Female BALB/c mice were intranasally exposed to HDM to induce allergic asthma. Airway hyperresponsiveness (AHR), lung inflammation, mucus secretion, IgE levels, cytokine levels and inflammatory cell counts in bronchoalveolar lavage fluid (BALF) were investigated. In addition, the morphological changes of mitochondria, ROS levels, glutathione (GSH) levels and changes in ferroptosis pathway proteins were also determined in murine lungs. As a result, HDM exposure significantly increased AHR, inflammatory cell infiltration and mucus secretion around the airways. Furthermore, elevated IgE levels in the BALF, lung eosinophilia and a concomitant increase in IL-13 and IL-5 levels in BALF were observed. HDM inhalation increased ROS and decreased GSH levels in the lungs. HDM inhalation induced dysmorphic small mitochondria with decreased crista, as well as condensed, ruptured outer membranes. Western blotting demonstrated that the activities of glutathione peroxidase 4 and catalytic subunit solute carrier family 7 member 11 were significantly decreased, and that protein expression levels of acyl-CoA synthetase long-chain family member 4 and 15 lipoxygenase 1 were upregulated compared with mice in the normal control group. Overall, these results indicated that the AHR, airway inflammation, lipid peroxidation and ROS levels increased in HDM-induced asthma, and that HDM inhalation induced ferroptosis in the lungs, which helped to form an improved understanding of the pathogenesis of allergic asthma.

Airway Hyperresponsiveness to Inhaled Mannitol Identifies a Cluster of Noneosinophilic Asthma Patients with High Symptom Burden

Patients with asthma are heterogeneous in clinical presentation and in response to treatment. Despite this, tools to guide treatment are limited and include mainly measures of eosinophilic inflammation and symptoms. Airway hyperresponsiveness (AHR) to mannitol is present in patients across inflammatory phenotypes and improve with inhaled corticosteroids. To investigate whether measuring AHR to mannitol in addition to eosinophilic inflammation and symptoms adds information to the phenotypic characterization of patients with asthma. A total of 317 patients with asthma from 6 different cohorts were included in the analysis. All patients had measures of AHR to mannitol, blood eosinophils, and Asthma Control Questionnaire 5 available. A cluster analysis using Ward minimum variance method was performed. The distribution of fraction of exhaled nitric oxide, immunoglobulin E, lung function, induced sputum inflammatory cell count, age of onset, and severity of disease was compared between clusters. Four clusters were identified. Three of the clusters had proportionate levels of AHR, eosinophilic inflammation, and symptoms, but 1 cluster presented with low levels of eosinophilic inflammation and a significant symptom burden. Half of the subjects in this cluster presented with AHR to inhaled mannitol. Lung function, fraction of exhaled nitric oxide, body mass index, and immunoglobulin E were normal. Information on AHR to mannitol in addition to blood eosinophils and symptoms identifies a subgroup of asthma patients with symptomatic, noneosinophilic disease. Airway hyperresponsiveness to mannitol may provide a treatable trait in a subgroup of patients with noneosinophilic asthma.

Long noncoding RNA LINC-PINT retards the abnormal growth of airway smooth muscle cells via regulating the microRNA-26a-5p/PTEN axis in asthma

BackgroundAsthma is a chronic respiratory disease worldwide. This study aimed to explore the functions of the long noncoding RNA LINC-PINT (LINC-PINT) in asthma and to determine its underlying molecular mechanisms. MethodsRat asthma model was established with ovalbumin sensitization and challenge. The serum level of IgE, airway hyperresponsiveness (AHR), airway inflammation, and pathological changes of lung were evaluated. Airway smooth muscle cells (ASMCs) were stimulated with platelet-derived growth factor-BB (PDGF-BB) to mimic the asthma-like condition at cellular level. QRT-PCR was performed to detect the expression of LINC-PINT, microRNA-26a-5p (miR-26a-5p), and PTEN. MTT and transwell assays were performed to measure the viability and migration of ASMCs. The protein expression of airway remodelling marker MMP-1 and MMP-9 was measured by western blot. The interactions among LINC-PINT, miR-26a-5p, and PTEN were determined by dual-luciferase reporter assay. ResultsThe expression of LINC-PINT and PTEN was decreased, while miR-26a-5p expression was increased in PDGF-BB-stimulated ASMCs. In vivo, overexpression of LINC-PINT decreased the serum level of IgE, AHR, airway inflammation, and pathological changes of lung in asthma rat model. In vitro, up-regulation of LINC-PINT decreased the viability, migration, and MMP-1 and MMP-9 protein expression in PDGF-BB-stimulated ASMCs. Dual-luciferase reporter assay determined that LINC-PINT targeted miR-26a-5p, and miR-26a-5p targeted PTEN in ASMCs. Feedback approaches confirmed that miR-26a-5p up-regulation or PTEN down-regulation reversed the suppressive effect of LINC-PINT overexpression on the abnormal growth of ASMCs. ConclusionsLINC-PINT overexpression retarded the abnormal growth of ASMCs by regulating the miR-26a-5p/PTEN axis, offering a potential therapeutic target for asthma.

Blood eosinophils, FeNO and small airways dysfunction in predicting airway hyperresponsiveness in patients with asthma-like symptoms

Purpose In patients with suspected asthma and no airflow limitation in spirometry, methacholine challenge testing (MCT) for airway hyperresponsiveness (AHR) is an option of documenting variable airflow limitation. The goal of the study was to assess the ability of blood eosinophils, fractional concentration of exhaled nitric oxide (FeNO) and distal airways function to discriminate patients with AHR from those with normal airway responsiveness (AR). Methods We analyzed baseline data from 42 participants who underwent MCT because of asthma-like symptoms and no airflow limitation in spirometry. Results Eosinophil count was higher among participants with borderline AHR comparing to those with normal AR (340 cells/µL, IQR 285-995 vs. 125 cells/µL, IQR 75-180, post-hoc p = 0.041). FeNO and percent predicted of functional residual volume (FRC%pred) were higher in participants with moderate-marked AHR compared to those with normal AR (40 ppb, IQR 30.5-100.5 vs. 18 ppb, IQR 13-50, post-hoc p = 0.008; 140.1%±17.0% vs. 107.3%±20.7%, post-hoc p < 0.001, respectively). Percentage predicted of the maximal expiratory flow at 25% of the forced vital capacity (MEF25%pred) was lower in participants with mild AHR and borderline AHR compared to those with normal AR (72.9%±16.9% vs. 113.0%±36.8%, post-hoc p = 0.017; 73.3%±15.9% vs. 113.0%±36.8%, post-hoc p = 0.045; respectively). Level of AHR correlated with eosinophil count, FeNO, MEF25%pred, forced expiratory flow between 25% and 75% of vital capacity (FEF25-75%pred), FRC%pred and specific airway resistance (sRaw). Conclusions Blood eosinophils, FeNO and small airways dysfunction markers are related to the level of AR to methacholine in patients with asthma-like symptoms and no airflow limitation in spirometry.

Establishment and characterization of murine models of asthma and subcutaneous immunotherapy for Humulus pollen allergy.

Introduction Humulus pollen is an important cause of allergic asthma in East Asia. There have been some murine models for Humulus pollen allergy established by intraperitoneal (IP) sensitization and nasal drip stimulation, but they were not comprehensive enough. Here, we used atomized inhalation for challenge and compared the subcutaneous (SC) and IP sensitization routes to determine the optimal method to establish a model of asthma induced by Humulus pollen. Subsequently, we tried to develop a rapid subcutaneous immunotherapy (SCIT) model for Humulus allergy.MethodsBALB/c Mice were sensitized through the SC or IP route, with respective reference to previously established sensitization methods and allergen dosing, and challenged with nebulized Humulus pollen extract to induce asthma. To compare the two sensitization methods, airway hyperresponsiveness (AHR), inflammatory cell infiltration, allergen‐specific serum immunoglobulin (Ig)E (sIgE) levels, cytokine levels, and lung histopathology were assessed. The effects of SCIT (once every other day for 16 days) on airway inflammation, AHR, sIgE, and allergen‐specific serum IgG2a (sIgG2a) levels were evaluated by using the model established in this study.ResultsAlthough mice sensitized by the SC or IP routes both showed AHR and airway inflammation, the SC route elicited significantly higher levels of sIgE, eosinophil inflammation, and T helper type 2 cytokines, compared with the IP route. SCIT in the treatment group significantly reduced the titers of sIgE, enhanced the titers of sIgG2a, and effectively alleviated pulmonary inflammation and AHR, compared with the vehicle group.ConclusionsThe SC route can be used to establish a murine model of Humulus pollen allergy that recapitulates the characteristics of clinical allergic asthma. Short‐term SCIT can significantly improve symptoms and pathophysiology in asthmatic mice.

LPS aggravates lung inflammation induced by RSV by promoting the ERK-MMP-12 signaling pathway in mice

BackgroundRSV can lead to persistent airway inflammation and airway hyperresponsiveness (AHR), and is intimately associated with childhood recurrent wheezing and asthma, but the underlying mechanisms remain unclear. Lipopolysaccharide (LPS) is also implicated in the onset and exacerbation of asthma. However, whether inhalation of LPS can boost airway inflammation induced by RSV is not clear. In this study, we utilized an LPS- and RSV-superinfected mouse model to explore underlying pathogenesis.MethodsMice were infected with RSV on day 0 and inoculated with LPS from day 35 to day 41, samples were collected on day 42. Inflammatory cells, lung histopathology and AHR were measured. Cytokines were detected by ELISA and ERK, JNK, p38 was determined by western blot. MMP408, PD98059, SP600125 and SB203580 were used to inhibit MMP-12, ERK, JNK and p38 respectively.ResultsLPS exposure superimposed on RSV-infected lungs could lead to more vigorous cellular influx, lung structures damage, augmented AHR and higher MMP-12 levels. Inhibition of MMP-12 or ERK signaling pathway in vivo both diminished LPS-driven airway inflammation and AHR.ConclusionsExposure to LPS in RSV-infected mice is associated with enhanced increases in ERK-MMP-12 expression that translates into increased lung inflammation and AHR. These findings contribute novel information to the field investigating the onset of post-RSV bronchiolitis recurrent wheezing as a result of LPS exposure.

Resp-Aid in Ova-challenged mice decreased airway inflammatory cell infiltration, AHR and IL-13 cytokine expression levels

Abstract Introduction Asthma is an inflammatory disease caused by repeated immediate phase hypersensitivity and late-phase allergic reactions in the lungs. Resp-Aid is a formula composed of 9 medicinal herbs that supports in the resolution of respiratory disorders (Coltsfoot, Marshamallow, Plantain, Mullein, Horehound, Licorice, Lobelia, Ginger, and Myrrh). These herbs, alone, have shown positive effects in reducing symptoms associated with asthma. However, the effects of the combination of these herbs on asthma is not well understood. Therefore, we conducted a series of studies to explore the mechanism of action of Resp-Aid. Material and Methods C57Bl/6 male mice (n = 7 each group) were challenged with or without ovalbumin (OVA). After the challenge, they were divided into 4 groups where 2 groups received 1 drop of Resp-Aid twice daily for 7 days and 2 groups acted as control. On day 5 of the treatment with Resp-Aid the airway hyperresponsiveness (AHR) was measured. After the treatment with Resp-Aid, lungs and bronchoalveolar lavage (BAL) fluid were collected and the cytokines (IL-4, IL-5, IL-13, IL-17a, IFNy), MPO and EPO were quantified. Results All OVA-challenged mice had increased AHR, leukocytes and cytokine levels compared to their respective controls showing the development of an asthmatic response. The Resp-Aid asthmatic groups had decreased AHR, IL-13, neutrophils and EPO levels compared to asthmatic mice. Conclusion This data show that Resp-Aid changed the immune response related to asthma, and it may be a potential target for therapeutic intervention in allergic lung disease or asthma.

Treatment of Allergic Asthma with Fenretinide Formulation (LAU-7b) Downregulates ORMDL Sphingolipid Biosynthesis Regulator 3 (Ormdl3) Expression and Normalizes Ceramide Imbalance.

Zona pellucida binding protein 2 (Zpbp2) and ORMDL sphingolipid biosynthesis regulator 3 (Ormdl3), mapped downstream of Zpbp2, were identified as two genes associated with airway hyper-responsiveness (AHR). Ormdl3 gene product has been shown to regulate the biosynthesis of ceramides. Allergic asthma was shown to be associated with an imbalance between very-long-chain ceramides (VLCCs) and long-chain ceramides (LCCs). We hypothesized that Fenretinide can prevent the allergic asthma-induced augmentation of Ormdl3 gene expression, normalize aberrant levels of VLCCs and LCCs, and treat allergic asthma symptoms. We induced allergic asthma by house dust mite (HDM) in A/J WT mice and Zpbp2 KO mice expressing lower levels of Ormdl3 mRNA than WT. We investigated the effect of a novel formulation of Fenretinide, LAU-7b, on the AHR, inflammatory cell infiltration, mucus production, IgE levels, and ceramide levels. Although lower Ormdl3 expression, which was observed in Zpbp2 KO mice, was associated with lower AHR, allergic Zpbp2 KO mice were not protected from inflammatory cell infiltration, mucus accumulation, or aberrant levels of VLCCs and LCCs induced by HDM. LAU-7b treatment protects both the Zpbp2 KO and WT mice. The treatment significantly lowers the gene expression of Ormdl3, normalizes the VLCCs and LCCs, and corrects all the other phenotypes associated with allergic asthma after HDM challenge, except the elevated levels of IgE. LAU-7b treatment prevents the augmentation of Ormdl3 expression and ceramide imbalance induced by HDM challenge and protects both WT and Zpbp2 KO mice against allergic asthma symptoms. SIGNIFICANCE STATEMENT: Compared with A/J WT mice, KO mice with Zpbp2 gene deletion have lower AHR and lower levels of Ormdl3 expression. The novel oral clinical formulation of Fenretinide (LAU-7b) effectively lowers the AHR and protects against inflammatory cell infiltration and mucus accumulation induced by house dust mite in both Zpbp2 KO and WT A/J mice. LAU-7b prevents Ormdl3 overexpression in WT allergic mice and corrects the aberrant levels of very-long-chain and long-chain ceramides in both WT and Zpbp2 KO allergic mice.

CD4+CD25+ Regulatory T Cells Decreased CD8+IL-4+Cells in a Mouse Model of Allergic Asthma.

Interleukin (IL)-4-producing-CD8 (cytotoxic T cells, Tc) contribute to lung eosinophilia and airway hyper-responsiveness (AHR) to an antigen. CD4+CD25+ regulatory T cells (Tregs) attenuate airway inflammation and AHR. This study investigated whether Tregs decrease Tc2frequencies in ovalbumin (OVA)-induced asthma model of mice.Female C57BL/6 mice were sensitized with OVA intraperitoneally and challenged with OVA intranasally to induce allergic asthma model. Tregs were sorted by fluorescence activated cell sorting (FACS) and magnetic activated cell sorting (MACS) microbeads. OVA-sensitized mice were injected with Tregs or phosphate buffer saline (PBS) by tail vein ahead of the first challenge. Airway inflammation and airway hyper-responsiveness (AHR)were evaluated by histological analysis and invasive method, respectively. OVA-specific IgE and cytokine levels were detected by ELISA. Flow cytometry was used to detect the percentages of Tc1 and Tc2. Gata3 and T-bet mRNA was determined by quantitative PCR (qPCR).OVA-sensitized and challenged mice displayed typical asthma features, which included eosinophilic airway inflammation, higher levels of Th2 cytokines and AHR. Gata3 mRNA, Tc2 frequencies and OVA-specific IgE levels were significantly increased in OVA-sensitized and challenged mice. Compared to PBS treatment, Tregs decreased Tc2 frequencies, airway inflammation, Th2 cytokine levels and AHR in OVA-sensitized and challenged mice. IL-13 levels were negatively correlated with Tc1 frequencies and with IFNg levels in experimental mice. Our results demonstrated that Tregs could prevent airway inflammation and AHR by decreasing Tc2 frequencies and cytokine levels in OVA-induced asthma model of mice, supporting Tregmight be as a potent therapeutic target for alleviating airway inflammation and AHR.

Effect of nintedanib on airway inflammation in a mouse model of acute asthma

Objective: New treatments are needed for cases of asthma that are refractory to traditional therapies. In this study, we examined the effect of oral nintedanib, an intracellular inhibitor of tyrosine kinases, on airway hyper-responsiveness (AHR) and airway smooth muscle cells, using a mouse model of experimental asthma. Methods: Asthma was experimentally induced in mice via subcutaneous injection of ovalbumin (OVA). A group of saline-injected mice served as a control group. The OVA mice were then divided into four treatment groups according to the dose of nintedanib. AHR was examined via exposure to vaporized methacholine. Airway inflammation was assessed via bronchoalveolar lavage fluid (BALF) cell counts and Th2 cytokine concentrations. Results: Baseline levels of AHR and airway inflammation were higher in OVA mice than in the control group. Treatment with nintedanib lowered AHR, BALF cell counts and BALF cytokine levels in a dose-dependent fashion. The effect of nintedanib was comparable to that of dexamethasone. In particular, treatment with nintedanib lowered the expression of transforming growth factor-β1 and inhibited the expression and phosphorylation of platelet-derived growth factor receptor-β, vascular endothelial growth factor receptor 1 (VEGFR1), VEGFR2, fibroblast growth factor receptor 2 (FGFR2), FGFR3, and extracellular signal-regulated kinase. Conclusions: Nintedanib lowered AHR and the expression of factors associated with airway inflammation and remodeling in a mouse model of experimental asthma. Our results suggest that nintedanib may be useful in the treatment of asthma.

Therapeutic Role for TSP-2 Antibody in a Murine Asthma Model

Background: Specific immunotherapy, including agonists for Toll-like receptor 2 (TLR2), have been shown to protect from allergies and to have a high immunomodulatory capacity. Methods: A new antibody, TSP-2, reactive against an epitope of the extracellular domain of TLR2, was identified. The effect of the antibody on dendritic cells was assessed by immunohistochemistry, Western blot, and flow cytometric analysis. The effect of TSP-2 in a murine asthma model induced with ovalbumin (OVA) was assessed. The model is a form of airway hyperresponsiveness (AHR) and was analyzed by whole-body plethysmography, the measurement of Th1/Th2 cytokines in bronchial alveolar lavage fluid (BALF) and serum by ELISA, and the CCK-8 assay for lymphocyte proliferation. The effect of TSP-2 on the maturation of bone marrow-derived dendritic cells (BMDCs) was assessed by flow cytometric analysis. Results: TSP-2 promoted the maturation of dendritic cells and the proliferation of lymphocyte in vitro and in vivo. The effect of TSP-2 on T helper 1 (Th1)/Th2 cytokine secretion was slightly more powerful than that of Pam₃CSK₄. TSP-2 antibody reduced AHR and OVA-specific IgE levels in allergic asthma. TSP-2 antibody also reduced lung inflammation and decreased leukocyte numbers in an OVA-sensitized and challenged asthma model. TSP-2 antibody increased OVA-stimulated I-A, CD80, CD86, and MHC-II levels on BMDCs. Conclusions: This study identifies a novel therapeutic strategy for AHR, which uses antibodies reactive against TLR2. It also provides theoretical evidence for the control of allergic asthma by targeting TLR2.

Feasibility of high-intensity training in asthma

ABSTRACTBackground: High-intensity interval training is an effective and popular training regime but its feasibility in untrained adults with asthma is insufficiently described.Objective: The randomized controlled trial ‘EFFORT Asthma’ explored the effects of behavioural interventions including high-intensity interval training on clinical outcomes in nonobese sedentary adults with asthma. In this article we present a sub analysis of data aiming to evaluate if patients’ pre-intervention levels of asthma control, FEV1, airway inflammation and airway hyperresponsiveness (AHR) predicted their training response to the high-intensity interval training program, measured as increase in maximal oxygen consumption (VO2max).Design: We used data from the EFFORT Asthma Study. Of the 36 patients randomized to the 8-week exercise intervention consisting of high-intensity training three times per week, 29 patients (45% females) completed the study and were included in this data analysis. Pre-intervention assessment included the asthma control questionnaire (ACQ), spirometry, fractional exhaled nitric oxide (FeNO) and AHR to mannitol. VO2 max was measured during an incremental cycle test.Results: The majority of included patients had partly or uncontrolled asthma reflected by a mean (SD) ACQ at 1.7 (0.6). Median (IQR) FeNO was 28.5 (23.8) ppb and 75% had a positive mannitol test indicating AHR.The association between patients’ training response measured as increase in VO2max and pre-intervention ACQ scores was not statistically significant (p = 0.49). Likewise, the association between patients’ increase in VO2max and FeNO as well as AHR was not statistically significant (p = 0.80 and p = 0.58).Conclusions: Included asthma patients could adhere to the high-intensity interval protocol and improve their VO2max regardless of pre-intervention levels of asthma control, airway inflammation and AHR.

Placenta growth factor augments airway hyperresponsiveness via leukotrienes and IL-13.

Airway hyperresponsiveness (AHR) affects 55%-77% of children with sickle cell disease (SCD) and occurs even in the absence of asthma. While asthma increases SCD morbidity and mortality, the mechanisms underlying the high AHR prevalence in a hemoglobinopathy remain unknown. We hypothesized that placenta growth factor (PlGF), an erythroblast-secreted factor that is elevated in SCD, mediates AHR. In allergen-exposed mice, loss of Plgf dampened AHR, reduced inflammation and eosinophilia, and decreased expression of the Th2 cytokine IL-13 and the leukotriene-synthesizing enzymes 5-lipoxygenase and leukotriene-C4-synthase. Plgf-/- mice treated with leukotrienes phenocopied the WT response to allergen exposure; conversely, anti-PlGF Ab administration in WT animals blunted the AHR. Notably, Th2-mediated STAT6 activation further increased PlGF expression from lung epithelium, eosinophils, and macrophages, creating a PlGF/leukotriene/Th2-response positive feedback loop. Similarly, we found that the Th2 response in asthma patients is associated with increased expression of PlGF and its downstream genes in respiratory epithelial cells. In an SCD mouse model, we observed increased AHR and higher leukotriene levels that were abrogated by anti-PlGF Ab or the 5-lipoxygenase inhibitor zileuton. Overall, our findings indicate that PlGF exacerbates AHR and uniquely links the leukotriene and Th2 pathways in asthma. These data also suggest that zileuton and anti-PlGF Ab could be promising therapies to reduce pulmonary morbidity in SCD.

Lower airway inflammation and hyperresponsiveness in non-asthmatic patients with non-allergic rhinitis.

Potential associations between non-allergic rhinitis (NAR) and asthma have been verified epidemiologically, but these associations remain not very clear. It is necessary to further explore the possible implication of lower airway abnormities in NAR patients but without asthma. This study aims to determine lower airway hyperresponsiveness (AHR), inflammation and lung function in non-asthmatic patients with NAR. We recruited 262 non-asthmatic patients with NAR, 377 with AR and 264 healthy subjects. All subjects were non-smokers who underwent meticulous history taking, nasal examination, allergen skin prick test (SPT), blood routine test, measurement of fractional exhaled nitric oxide (FeNO), methacholine bronchial challenge test and induced sputum eosinophil count, in this order. Compared with healthy subjects, non-asthmatic patients with NAR yielded markedly lower FEV1/FVC, maximal mid-expiratory flow (MMEF), mid-expiratory flow when 50% of FVC has been expired (MEF50%) and mid-expiratory flow when 75% of FVC has been expired (MEF25%) (P<0.05). Differences in spirometry between group AR and NAR were unremarkable (P>0.05). Patients with NAR yielded higher rate of AHR and higher FeNO levels than healthy subjects but lower than those with AR. The proportion of lower airways disorders (sputum eosinophilia, high FeNO levels or AHR) was highest in group AR (70.8%), followed by NAR (53.4%) and healthy subjects (24.2%) (P<0.01). However, sputum eosinophils in NAR patients were not higher compared with healthy subjects (P>0.05). Sputum eosinophils and FeNO had significant correlation with positive AHR and MMEF in group AR but not in NAR. Non-asthmatic patients with NAR harbor lower AHR, small airways dysfunction and inflammation, despite being less significant than those with AR. This offers clues to unravel the link between NAR and asthma.

IL-25 and IL-33 Contribute to Development of Eosinophilic Airway Inflammation in Epicutaneously Antigen-Sensitized Mice.

BackgroundIL-25, IL-33 and TSLP are produced predominantly by epithelial cells and are known to induce Th2-type cytokines. Th2-type cytokines are involved not only in host defense against nematodes, but also in the development of Th2-type allergic diseases. TSLP was reported to be crucial for development of allergic airway inflammation in mice after inhalation of allergens to which they had been sensitized epicutaneously (EC) beforehand. However, the roles of IL-25 and IL-33 in the setting remain unclear.MethodsMice deficient in IL-25 and IL-33 were sensitized EC with ovalbumin (OVA) and then challenged intranasally with OVA. Airway inflammation, the number of inflammatory cells in bronchoalveolar lavage fluids (BALFs) and airway hyperresponsiveness (AHR) in the mice were determined, respectively, by histological analysis, with a hemocytometer, and by using plethysmograph chambers with a ventilator. Expression of mRNA in the skin and lungs was determined by quantitative PCR, while the BALF levels of myeloperoxidase (MPO) and eosinophil peroxidase (EPO) and the serum levels of IgE were determined by ELISA.Results Normal OVA-specific Th2- and Th17-cell responses of lymph nodes and spleens were observed in IL-25-deficient (IL-25-/-) and IL-33-/- mice after EC sensitization with OVA. Nevertheless, the number of eosinophils, but not neutrophils, in the BALFs, and the levels of Th2 cytokines, but not Th17 cytokines, in the lungs were significantly decreased in the IL-25-/- and IL-33-/- mice pre-sensitized EC with OVA, followed by inhalation of OVA, whereas their levels of AHR and OVA-specific serum IgE were normal.ConclusionsBoth IL-25 and IL-33 are critical for induction of Th2-type cytokine-mediated allergic airway eosinophilia, but not Th17-type cytokine-mediated airway neutrophilia, at the local sites of lungs in the challenge phase of mice sensitized EC with OVA. They do not affect OVA-specific T-cell induction in the sensitization phase.

Respiratory syncytial virus infection increases chlorine-induced airway hyperresponsiveness.

Exposure to chlorine (Cl2) damages airway and alveolar epithelia resulting in acute lung injury and reactive airway hyperresponsiveness (AHR) to methacholine. However, little is known about the effect of preexisting respiratory disease on Cl2-induced lung injury. By using a murine respiratory syncytial virus (RSV) infection model, we found that preexisting RSV infection increases Cl2 (187 ppm for 30 min)-induced lung inflammation and airway AHR at 24 h after exposure (5 days after infection). RSV infection and Cl2 exposure synergistically induced oxygen desaturation and neutrophil infiltration and increased MCP-1, MIP-1β, IL-10, IFN-γ, and RANTES concentrations in the bronchoalveolar lavage fluid (BALF). In contrast, levels of type 2 cytokines (i.e., IL-4, IL-5, IL-9, and IL-13) were not significantly affected by either RSV infection or Cl2 exposure. Cl2 exposure, but not RSV infection, induced AHR to methacholine challenge as measured by flexiVent. Moreover, preexisting RSV infection amplified BALF levels of hyaluronan (HA) and AHR. The Cl2-induced AHR was mitigated by treatment with inter-α-trypsin inhibitor antibody, which inhibits HA signaling, suggesting a mechanism of HA-mediated AHR from exacerbated oxidative injury. Our results show for the first time that preexisting RSV infection predisposes the lung to Cl2-induced injury. These data emphasize the necessity for further research on the effects of Cl2 in vulnerable populations and the development of appropriate treatments.

Predictors of airway hyperresponsiveness in elite athletes.

Elite athletes frequently experience asthma and airway hyperresponsiveness (AHR). We aimed to investigate predictors of airway pathophysiology in a group of unselected elite summer-sport athletes, training for the summer 2008 Olympic Games, including markers of airway inflammation, systemic inflammation, and training intensity. Fifty-seven Danish elite summer-sport athletes with and without asthma symptoms all gave a blood sample for measurements of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor alpha (TNF-α), completed a respiratory questionnaire, and underwent spirometry. Bronchial challenges with mannitol were performed in all 57 athletes, and 47 agreed to perform an additional methacholine provocation. Based on a physician's diagnosis, 18 (32%) athletes were concluded to be asthmatic. Asthmatic subjects trained more hours per week than the 39 nonasthmatics (median (min-max): 25 h·wk (14-30) versus 20 h·wk (11-30), P = 0.001). AHR to both methacholine and mannitol (dose response slope) increased with the number of weekly training h (r = 0.43, P = 0.003, and r = 0.28, P = 0.034, respectively). Serum levels of IL-6, IL-8, TNF-α, and hs-CRP were similar between asthmatics and nonasthmatics. However, there was a positive association between the degree of AHR to methacholine and serum levels of TNF-α (r = 0.36, P = 0.04). Fifteen out of 18 asthmatic athletes were challenged with both agents. In these subjects, no association was found between the levels of AHR to mannitol and methacholine (r = 0.032, P = 0.91). AHR in elite athletes is related to the amount of weekly training and the level of serum TNF-α. No association was found between the level of AHR to mannitol and methacholine in the asthmatic athletes.

Eosinophils contribute to the resolution of lung-allergic responses following repeated allergen challenge

Eosinophils accumulate at the site of allergic inflammation and are critical effector cells in allergic diseases. Recent studies have also suggested a role for eosinophils in the resolution of inflammation. To determine the role of eosinophils in the resolution phase of the response to repeated allergen challenge. Eosinophil-deficient (PHIL) and wild-type (WT) littermates were sensitized and challenged to ovalbumin (OVA) 7 or 11 times. Airway inflammation, airway hyperresponsiveness (AHR) to inhaled methacholine, bronchoalveolar lavage (BAL) cytokine levels, and lung histology were monitored. Intracellular cytokine levels in BAL leukocytes were analyzed by flow cytometry. Groups of OVA-sensitized PHIL mice received bone marrow from WT or IL-10(-/-) donors 30 days before the OVA challenge. PHIL and WT mice developed similar levels of AHR and numbers of leukocytes and cytokine levels in BAL fluid after OVA sensitization and 7 airway challenges; no eosinophils were detected in the PHIL mice. Unlike WT mice, sensitized PHIL mice maintained AHR, lung inflammation, and increased levels of IL-4, IL-5, and IL-13 in BAL fluid after 11 challenges whereas IL-10 and TGF-β levels were decreased. Restoration of eosinophil numbers after injection of bone marrow from WT but not IL-10-deficient mice restored levels of IL-10 and TGF-β in BAL fluid as well as suppressed AHR and inflammation. Intracellular staining of BAL leukocytes revealed the capacity of eosinophils to produce IL-10. After repeated allergen challenge, eosinophils appeared not essential for the development of AHR and lung inflammation but contributed to the resolution of AHR and inflammation by producing IL-10.