Compartmental and temporal dynamics of chronic inflammation and airway remodelling in a chronic asthma mouse model

Intranasal administration of Acinetobacter lwoffii in a murine model of asthma induces IL-6-mediated protection associated with cecal microbiota changes

BACKGROUND

Early-life exposure to certain environmental bacteria including Acinetobacter lwoffii (AL) has been implicated in protection from chronic inflammatory diseases including asthma later in life. However, the underlying mechanisms at the immune-microbe interface remain largely unknown.

METHODS

The effects of repeated intranasal AL exposure on local and systemic innate immune responses were investigated in wild-type and Il6-/- , Il10-/- , and Il17-/- mice exposed to ovalbumin-induced allergic airway inflammation. Those investigations were expanded by microbiome analyses. To assess for AL-associated changes in gene expression, the picture arising from animal data was supplemented by in vitro experiments of macrophage and T-cell responses, yielding expression and epigenetic data.

RESULTS

The asthma preventive effect of AL was confirmed in the lung. Repeated intranasal AL administration triggered a proinflammatory immune response particularly characterized by elevated levels of IL-6, and consequently, IL-6 induced IL-10 production in CD4+ T-cells. Both IL-6 and IL-10, but not IL-17, were required for asthma protection. AL had a profound impact on the gene regulatory landscape of CD4+ T-cells which could be largely recapitulated by recombinant IL-6. AL administration also induced marked changes in the gastrointestinal microbiome but not in the lung microbiome. By comparing the effects on the microbiota according to mouse genotype and AL-treatment status, we have identified microbial taxa that were associated with either disease protection or activity.

CONCLUSION

These experiments provide a novel mechanism of Acinetobacter lwoffii-induced asthma protection operating through IL-6-mediated epigenetic activation of IL-10 production and with associated effects on the intestinal microbiome.

Differential remodeling in small and large murine airways revealed by novel whole lung airway analysis

Airway remodeling occurs in chronic asthma leading to increased airway smooth muscle (ASM) mass and extracellular matrix (ECM) deposition. Although extensively studied in murine airways, studies report only selected larger airways at one time-point meaning the spatial distribution and resolution of remodeling are poorly understood. Here we use a new method allowing comprehensive assessment of the spatial and temporal changes in ASM, ECM, and epithelium in large numbers of murine airways after allergen challenge. Using image processing to analyze 20-50 airways per mouse from a whole lung section revealed increases in ASM and ECM after allergen challenge were greater in small and large rather than intermediate airways. ASM predominantly accumulated adjacent to the basement membrane, whereas ECM was distributed across the airway wall. Epithelial hyperplasia was most marked in small and intermediate airways. After challenge, ASM changes resolved over 7 days, whereas ECM and epithelial changes persisted. The new method suggests large and small airways remodel differently, and the long-term consequences of airway inflammation may depend more on ECM and epithelial changes than ASM. The improved quantity and quality of unbiased data provided by the method reveals important spatial differences in remodeling and could set new analysis standards for murine asthma models.

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.

Indoleamine 2,3-Dioxygenase in Hematopoietic Stem Cell-Derived Cells Suppresses Rhinovirus-Induced Neutrophilic Airway Inflammation by Regulating Th1- and Th17-Type Responses

Asthma exacerbations are a major cause of intractable morbidity, increases in health care costs, and a greater progressive loss of lung function. Asthma exacerbations are most commonly triggered by respiratory viral infections, particularly with human rhinovirus (hRV). Respiratory viral infections are believed to affect the expression of indoleamine 2,3-dioxygenase (IDO), a limiting enzyme in tryptophan catabolism, which is presumed to alter asthmatic airway inflammation. Here, we explored the detailed role of IDO in the progression of asthma exacerbations using a mouse model for asthma exacerbation caused by hRV infection. Our results reveal that IDO is required to prevent neutrophilic inflammation in the course of asthma exacerbation caused by an hRV infection, as corroborated by markedly enhanced Th17- and Th1-type neutrophilia in the airways of IDO-deficient mice. This neutrophilia was closely associated with disrupted expression of tight junctions and enhanced expression of inflammasome-related molecules and mucin-inducing genes. In addition, IDO ablation enhanced allergen-specific Th17- and Th1-biased CD4⁺ T-cell responses following hRV infection. The role of IDO in attenuating Th17- and Th1-type neutrophilic airway inflammation became more apparent in chronic asthma exacerbations after repeated allergen exposures and hRV infections. Furthermore, IDO enzymatic induction in leukocytes derived from the hematopoietic stem cell (HSC) lineage appeared to play a dominant role in attenuating Th17- and Th1-type neutrophilic inflammation in the airway following hRV infection. Therefore, IDO activity in HSC-derived leukocytes is required to regulate Th17- and Th1-type neutrophilic inflammation in the airway during asthma exacerbations caused by hRV infections.

Glutaredoxin 2 Reduces Asthma-Like Acute Airway Inflammation in Mice

Endogenous redox systems not only counteract oxidative damage induced by high levels of hydroxyl radicals (OH·) under pathological conditions, but also shape redox signaling as a key player in the regulation of physiological processes. Second messengers like hydrogen peroxide and nitric oxide, as well as redox enzymes of the Thioredoxin (Trx) family, including Trxs, glutaredoxins (Grxs), and peroxiredoxins (Prxs) modulate reversible, oxidative modifications of proteins. Thereby redox regulation is part of various cellular processes such as the immune response and Trx proteins have been linked in different disorders including inflammatory diseases. Here, we have analyzed the protein distribution of representative oxidoreductases of the Trx fold protein family—Trx1, Grx1, Grx2, and Prx2—in a murine model of allergic asthma bronchiale, as well as their potential therapeutic impact on type-2 driven airway inflammation. Ovalbumin (OVA) sensitization and challenge using the type-2 prone Balb/c mouse strain resulted in increased levels of all investigated proteins in distinct cellular patterns. While concomitant treatment with Grx1 and Prx2 did not show any therapeutic impact on the outcome of the disease, Grx2 or Trx1 treatment before and during the OVA challenge phase displayed pronounced protective effects on the manifestation of allergic airway inflammation. Eosinophil numbers and the type-2 cytokine IL-5 were significantly reduced while lung function parameters profoundly improved. The number of macrophages in the bronchoalveolar lavage (BAL) did not change significantly, however, the release of nitric oxide that was linked to airway inflammation was successfully prevented by enzymatically active Grx2 ex vivo. The Grx2 Cys-X-X-Ser mutant that facilitates de-/glutathionylation, but does not catalyze dithiol/disulfide exchange lost the ability to protect from airway hyper reactivity and to decrease NO release by macrophages, however, it reduced the number of infiltrating immune cells and IL-5 release. Altogether, this study demonstrates that specific redox proteins and particular enzyme activities protect against inflammatory damage. During OVA-induced allergic airway inflammation, administration of Grx2 exerts beneficial and thus potentially therapeutic effects.

Mechanical forces induce an asthma gene signature in healthy airway epithelial cells

Bronchospasm compresses the bronchial epithelium, and this compressive stress has been implicated in asthma pathogenesis. However, the molecular mechanisms by which this compressive stress alters pathways relevant to disease are not well understood. Using air-liquid interface cultures of primary human bronchial epithelial cells derived from non-asthmatic donors and asthmatic donors, we applied a compressive stress and then used a network approach to map resulting changes in the molecular interactome. In cells from non-asthmatic donors, compression by itself was sufficient to induce inflammatory, late repair, and fibrotic pathways. Remarkably, this molecular profile of non-asthmatic cells after compression recapitulated the profile of asthmatic cells before compression. Together, these results show that even in the absence of any inflammatory stimulus, mechanical compression alone is sufficient to induce an asthma-like molecular signature.

Role of airway epithelial cells in the development of different asthma phenotypes

The term (bronchial) asthma describes a disorder syndrome that comprises several disease phenotypes, all characterized by chronic inflammation in the bronchial epithelium, with a variety of subsequent functional consequences. Thus, the epithelium in the conducting airways is the main localization of the complex pathological changes in the disease. In this regard, bronchial epithelial cells are not passively affected by inflammatory mechanisms induced by immunological processes but rather actively involved in all steps of disease development from initiation and perpetuation to chronification. In recent years it turned out that bronchial epithelial cells show a high level of structural and functional diversity and plasticity with epigenetic mechanisms playing a crucial role in the regulation of these processes. Thus, it is quite reasonable that differential functional activities of the bronchial epithelium are involved in the development of different asthma phenotypes and/or stages of disease. The current knowledge on this topic will be discussed in this review article.

Heat shock protein 70 is a positive regulator of airway inflammation and goblet cell hyperplasia in a mouse model of allergic airway inflammation

Heat shock proteins (Hsps) are highly conserved molecular chaperones that are ubiquitously expressed in all species to aid the solubilization of misfolded proteins, protein degradation, and transport. Elevated levels of Hsp70 have been found in the sputum, serum, and bronchoalveolar lavage (BAL) fluid of asthma patients and are known to correlate with disease severity. However, the function of Hsp70 in allergic airway inflammation has remained largely unknown. This study aimed to determine the role of Hsp70 in airway inflammation and remodeling using a mouse model of allergic airway inflammation. WT and Hsp70 double-knockout (Hsp70.1/.3^-/-) mice were sensitized and challenged intratracheally with Schistosoma mansoni soluble egg antigens (SEAs) to induce robust Th2 responses and airway inflammation in the lungs. The lack of Hsp70 resulted in a significant reduction in airway inflammation, goblet cell hyperplasia, and Th2 cytokine production, including IL-4, IL-5, and IL-13. An analysis of the BAL fluid suggested that Hsp70 is critically required for eosinophilic infiltration, collagen accumulation, and Th2 cytokine production in allergic airways. Furthermore, our bone marrow (BM) transfer studies show that SEA-induced airway inflammation, goblet cell hyperplasia, and Th2 cytokine production were attenuated in WT mice that were reconstituted with Hsp70-deficient BM, but these effects were not attenuated in Hsp70-deficient mice that were reconstituted with WT BM. Together, these studies identify a pathogenic role for Hsp70 in hematopoietic cells during allergic airway inflammation; this illustrates the potential utility of targeting Hsp70 to alleviate allergen-induced Th2 cytokines, goblet cell hyperplasia, and airway inflammation.

CpG-ODNs and Budesonide Act Synergistically to Improve Allergic Responses in Combined Allergic Rhinitis and Asthma Syndrome Induced by Chronic Exposure to Ovalbumin by Modulating the TSLP-DC-OX40L Axis

The experimental model of combined allergic rhinitis and asthma syndrome (CARAS) has shown that CpG oligodeoxynucleotides (CpG-ODNs) are potential inhibitors of type 2 helper cell-driven inflammatory responses. Currently available CpG-ODNs modestly inhibit allergic responses in CARAS, while a combination strategy for upper airway treatment by co-administration of CpG-ODNs and glucocorticoids may show good efficacy. This study aimed to assess the therapeutic effects of CpG-ODNs combined with budesonide (BUD) on upper and lower-airway inflammation and remodeling in mice with CARAS induced by chronic exposure to ovalbumin (OVA), exploring the possible underlying molecular mechanisms. A BALB/c mouse model of chronic CARAS was established by systemic sensitization and repeated challenge with OVA. Treatment with CpG-ODNs or BUD by intranasal administration was started 1 h after OVA challenge. Then, nasal mucosa and lung tissues were fixed and stained for pathologic analysis. The resulting immunologic variables and TSLP-DC-OX40L axis parameters were evaluated. Both CpG-ODNs and BUD intranasal administration are effective on reducing Th2-type airway inflammation and tissue remodeling. Co-administration of CpG-ODNs and BUD was more effective than each monotherapy in attenuating upper and lower-airway inflammation as well as airway remodeling in chronic CARAS. Notably, combination of CpG-ODNs with BUD modulated the TSLP-DC-OX40L axis, as demonstrated by decreased TSLP production in the nose and lung, alongside decreased TSLPR and OX40L in DC. Intranasal co-administration of CpG-ODNs and BUD synergistically alleviates airway inflammation and tissue remodeling in experimental chronic CARAS, through shared cellular pathways, as a potent antagonist of the TSLP-DC-OX40L axis.

Androgen and Androgen Receptor as Enhancers of M2 Macrophage Polarization in Allergic Lung Inflammation

Allergic asthma is a disease initiated by a breach of the lung mucosal barrier and an inappropriate Th2 inflammatory immune response that results in M2 polarization of alveolar macrophages (AM). The number of M2 macrophages in the airway correlates with asthma severity in humans. Sex differences in asthma suggest that sex hormones modify lung inflammation and macrophage polarization. Asthmatic women have more M2 macrophages than asthmatic men and androgens have been used as an experimental asthma treatment. In this study, we demonstrate that although androgen (dihydrotestosterone) reconstitution of castrated mice reduced lung inflammation in a mouse model of allergic lung inflammation, it enhanced M2 polarization of AM. This indicates a cell-specific role for androgens. Dihydrotestosterone also enhanced IL-4-stimulated M2 macrophage polarization in vitro. Using mice lacking androgen receptor (AR) in monocytes/macrophages (AR^floxLysMCre), we found that male but not female mice exhibited less eosinophil recruitment and lung inflammation due to impaired M2 polarization. There was a reduction in eosinophil-recruiting chemokines and IL-5 in AR-deficient AM. These data reveal an unexpected and novel role for androgen/AR in promoting M2 macrophage polarization. Our findings are also important for understanding pathology in diseases promoted by M2 macrophages and androgens, such as asthma, eosinophilic esophagitis, and prostate cancer, and for designing new approaches to treatment.

Fra2 Overexpression in Mice Leads to Non-allergic Asthma Development in an IL-13 Dependent Manner

Background: Asthma is a complex chronic inflammatory disease characterised by airway inflammation, remodelling and hyperresponsiveness (AHR). Members of the AP-1 transcription factor family play important roles in the activation of the immune system and the control of cellular responses; however, their role in the development of asthma has not been well studied. We aimed to investigate the role of the lesser known AP-1 family member, Fra2 in experimental asthma.

Methods: Phenotypic characterisation and gene expression profiling was performed on Fra2 (TG) overexpressing and wild-type mice. The efficacy of therapeutic interventions in regulating the Fra2 phenotype was determined.

Results: Transcriptional profiling of TG mice revealed a high abundance of regulated genes associated with airway remodelling, inflammation and mucus production. A concomitant increase in peribronchial collagen deposition, smooth muscle thickening and mucus production was observed. TG mice possessed increased inflammatory infiltration in the lung, predominantly consisting of eosinophils and T-cells and elevated expression of Th2 cytokines and eotaxin. Furthermore, TG mice possessed severe AHR in response to increasing doses of methacholine. Glucocorticoid treatment led to a partial improvement of the asthma phenotype, whereas blockade of IL-13 via neutralising antibodies ameliorated AHR and mucus production, but had no effect on collagen deposition.

Conclusion: We here describe a novel model for non-allergic asthma that does not require the application of exogenous allergens, which mimics several key features of the disease, such as airway inflammation, remodelling and hyperresponsiveness. Fra2 may represent a key molecule coordinating multiple aspects of asthma pathogenesis.

Asthma Induction During Development and Adult Lung Function, Behavior and Brain Gene Expression

In developing youth, allergic asthma is the most common chronic condition, with 9%–10% of youth affected. Asthma onset during childhood and adolescence is further associated with other health issues, particularly psychiatric conditions. To understand causal mechanisms by which developmental asthma may lead to altered behavior, brain and health trajectories, we developed a mouse model of developmental allergic asthma. In the current study, we tested for potential long-term effects of developmental asthma on adult lung function and behavior and brain gene expression associated with emotion and stress regulation. We manipulated airway inflammation (AI) and methacholine (MCH)-induced bronchospasm (resulting in labored breathing, LB) in young male and female BALB/cJ mice and measured adult outcomes 3 months after final asthma manipulations. Results indicated that allergen exposure, used to cause AI, and which ended on post-natal day 56 (P56), led to persistent lung AI, mucus buildup and gene expression related to allergic asthma 3 months after final allergen exposure. In addition, at this same age, early allergen exposure led to altered brain gene expression related to stress regulation (prefrontal corticotropin releasing hormone receptor 1, Crhr1 and hippocampal glucocorticoid receptor, GR) and serotonin function (brainstem serotonin transporter, SERT). On the other hand, LB events during development led to altered anxiety-related behavior. Importantly, sex and pre-asthma fear-related behavior (ultrasonic vocalization, USV rates) modulated these adult outcomes. Asthma that develops during childhood/adolescence may have long-term impacts on emotion and stress regulation mechanisms, and these influences may be moderated by sex and pre-asthma temperament.

A theoretical model of inflammation- and mechanotransduction-driven asthmatic airway remodelling

Inflammation, airway hyper-responsiveness and airway remodelling are well-established hallmarks of asthma, but their inter-relationships remain elusive. In order to obtain a better understanding of their inter-dependence, we develop a mechanochemical morphoelastic model of the airway wall accounting for local volume changes in airway smooth muscle (ASM) and extracellular matrix in response to transient inflammatory or contractile agonist challenges. We use constrained mixture theory, together with a multiplicative decomposition of growth from the elastic deformation, to model the airway wall as a nonlinear fibre-reinforced elastic cylinder. Local contractile agonist drives ASM cell contraction, generating mechanical stresses in the tissue that drive further release of mitogenic mediators and contractile agonists via underlying mechanotransductive signalling pathways. Our model predictions are consistent with previously described inflammation-induced remodelling within an axisymmetric airway geometry. Additionally, our simulations reveal novel mechanotransductive feedback by which hyper-responsive airways exhibit increased remodelling, for example, via stress-induced release of pro-mitogenic and pro-contractile cytokines. Simulation results also reveal emergence of a persistent contractile tone observed in asthmatics, via either a pathological mechanotransductive feedback loop, a failure to clear agonists from the tissue, or a combination of both. Furthermore, we identify various parameter combinations that may contribute to the existence of different asthma phenotypes, and we illustrate a combination of factors which may predispose severe asthmatics to fatal bronchospasms.

Increased Expression of p22phox Mediates Airway Hyperresponsiveness in an Experimental Model of Asthma

AIM

Chronic airway diseases such as asthma are associated with increased production of reactive oxygen species (ROS) and oxidative stress. Endogenous NADPH oxidases are a major source of superoxide in lung, but their underlying role in asthma pathology is poorly understood. We sought to characterize the involvement of NADPH oxidase in allergic asthma by studying the role of CYBA (p22phox) in human asthma and murine house dust mite (HDM)-induced allergic airway inflammation.

RESULTS

Increased expression and localization of p22-PHOX were observed in biopsies of asthmatic patients. HDM-treated wild-type mice possessed elevated p22phox expression, corresponding with elevated superoxide production. p22phox knockout (KO) mice did not induce superoxide and were protected against HDM-induced goblet cell hyperplasia and mucus production and HDM-induced airway hyperresponsiveness (AHR). IL-13-induced tracheal hyperreactivity and signal transducer and activator of transcription (STAT)6 phosphorylation were attenuated in the absence of p22phox or catalase pretreatment.

INNOVATION

Our study identifies increased expression of p22phox in lungs of asthmatic patients and in experimental model. The induced AHR and mucus hypersecretion are a result of increased ROS from the p22phox-dependent NADPH oxidase, which in turn activates STAT6 for the pathological feature of asthma.

CONCLUSIONS

Together with the increased p22phox expression in lungs of asthmatic patients, these findings demonstrate a crucial role of p22phox-dependent NADPH oxidase for the development of mucus hypersecretion and AHR in HDM-induced model of asthma. This suggests that inhibition of functional NADPH oxidase by selective interference of p22phox might hold a promising therapeutic strategy for the management of asthma. Antioxid. Redox Signal. 27, 1460-1472.

Influenza-derived peptides cross-react with allergens and provide asthma protection

BACKGROUND

The hygiene hypothesis is the leading concept to explain the current asthma epidemic, which is built on the observation that a lack of bacterial contact early in life induces allergic T_H2 immune responses.

OBJECTIVE

Because little is known about the contribution of respiratory tract viruses in this context, we evaluated the effect of prior influenza infection on the development of allergic asthma.

METHODS

Mice were infected with influenza and, once recovered, subjected to an ovalbumin- or house dust mite-induced experimental asthma protocol. Influenza-polarized effector memory T (Tem) cells were transferred adoptively to allergen-sensitized animals before allergen challenge. A comprehensive in silico analysis assessed homologies between virus- and allergen-derived proteins. Influenza-polarized Tem cells were stimulated ex vivo with candidate peptides. Mice were immunized with a pool of virus-derived T-cell epitopes.

RESULTS

In 2 murine models we found a long-lasting preventive effect against experimental asthma features. Protection could be attributed about equally to CD4⁺ and CD8⁺ Tem cells from influenza-infected mice. An in silico bioinformatic analysis identified 4 influenza- and 3 allergen-derived MHC class I and MHC class II candidate T-cell epitopes with potential antigen-specific cross-reactivity between influenza and allergens. Lymphocytes from influenza-infected mice produced IFN-γ and IL-2 but not IL-5 on stimulation with the aforementioned peptides. Immunization with a mixture of the influenza peptides conferred asthma protection, and peptide-immunized mice transferred protection through CD4⁺ and CD8⁺ Tem cells.

CONCLUSION

For the first time, our results illustrate heterologous immunity of virus-infected animals toward allergens. This finding extends the original hygiene hypothesis.

Tiron ameliorates oxidative stress and inflammation in a murine model of airway remodeling

Airway remodeling includes lung structural changes that have a role in the irreversibility of pulmonary dysfunction shown in chronic bronchial asthmatics. The current experiment investigated the effect of the mitochondrial antioxidant, tiron in comparison with dexamethasone (DEXA) on airway remodeling in chronic asthma. Sensitized BALB/c mice were challenged with ovalbumin (OVA) aerosol for 8weeks, OVA sensitized-challenged mice were treated with either DEXA or tiron, respectively. After that, lung tissue and bronchoaveolar lavage fluid (BALF) were used for measurement of different biological markers. Lungs were examined for histopathological changes and immunohistochemistry. Upon comparing with vehicle treated animals, trion or DEXA treatment significantly reduced eosinophils, lymphocytes, neutrophils and macrophages count in the BALF. Both drugs significantly alleviated chronic OVA-induced oxidative stress as illustrated by decreased pulmonary malondialdenhyde (MDA) and increased glutathione (GSH) and superoxide dismutase (SOD) levels. Asthmatic mice exhibited elevated levels of NOx, IL-13 and TGF-β1 that were reduced by DEXA and tiron. Histopathological changes and increased immunoreactivity of nuclear factor-Kappa B (NF-κ B) in OVA-challenged mice were minimized by tiron and DEXA treatment. In conclusion, in this model of chronic asthma DEXA and tiron ameliorated airway remodeling and inflammation in experimental chronic asthma with no difference between the effect of tiron and DEXA. Tiron has a potential role as adjuvant treatment in chronic asthma.

House Dust Mite-Specific Sublingual Immunotherapy Prevents the Development of Allergic Inflammation in a Mouse Model of Experimental Asthma

BACKGROUND

Evidence regarding sublingual immunotherapy (SLIT) efficacy and its good safety profile has been demonstrated with pollen and house dust mite (HDM) allergens in the treatment of airway allergies. In addition, the use of grass pollen presents a SLIT disease-modifying treatment for respiratory allergies.

OBJECTIVES

The aim of this study was to demonstrate the efficacy of HDM-based SLIT in mouse models of allergic airway inflammation and to gain insights into the involved local immunological mechanisms.

METHODS

Balb/c mice were sensitized/challenged with Dermatophagoides farinae (Der f) extract and underwent Der f-SLIT in prophylactic and therapeutic settings. The SLIT efficacy was assessed using lung function measurements, analysis of local inflammatory responses by bronchoalveolar lavage cell differentiation and lung histology. Humoral and cellular responses were monitored by ELISA, cytokine bead array and flow cytometry analyses.

RESULTS

In a prophylactic setting, Der f-SLIT with 12 development units per dose reduced the eosinophil-dominated inflammatory response in the lung paralleled by a marked reduction in airway hyperresponsiveness. Local Th2 responses were prevented as demonstrated by significantly lower levels of IL-5 and IL-13. Additionally, SLIT-treated mice revealed a lower proportion of CD4-CD8- x03B3;δ cells and a higher frequency of CD8+CD25+IFNx03B3;+ T cells in the lungs compared to sham-treated mice. In a therapeutic setting, Der f-SLIT also resulted in reduced inflammatory responses in the lung.

CONCLUSION

The efficacy of Der f-SLIT was demonstrated in prophylactic and therapeutic conditions using experimental mouse models of HDM-induced airway inflammation. A potential role of a so far underestimated lymphocyte subpopulation was also indicated.

Parabromophenacyl bromide inhibits subepithelial fibrosis by reducing TGF-β1 in a chronic mouse model of allergic asthma

BACKGROUND

Our previous study showed that parabromophenacyl bromide (PBPB) inhibits the features of allergic airway inflammation and airway hyperresponsiveness (AHR). However, its effect on airway remodeling, e.g. subepithelial fibrosis in a chronic allergic asthma model, was not investigated. We examined this issue in this study.

METHODS

PBPB was administered to mice with an induced chronic asthmatic condition. AHR was estimated at the end of the experiment, followed by euthanasia. Lung sections were stained with hematoxylin and eosin, periodic acid-Schiff and Masson's trichrome to determine airway inflammation, goblet cell metaplasia and subepithelial fibrosis, respectively. Transforming growth factor-β1 (TGF-β1) was estimated in lung homogenates. To determine the effect of PBPB on smooth-muscle hyperplasia, immunohistochemistry against α-smooth-muscle actin was performed on the lung sections.

RESULTS

Chronic ovalbumin challenges in a mouse model of allergic asthma caused significant subepithelial fibrosis and elevated TGF-β1, along with significant AHR. PBPB attenuated subepithelial fibrosis with a reduction of lung TGF-β1, airway inflammation and AHR without affecting goblet cell metaplasia. It also attenuated smooth-muscle hyperplasia with a reduction in the expression of α-smooth-muscle actin in the lungs.

CONCLUSION

Our findings indicate that PBPB attenuates some crucial features of airway remodeling such as subepithelial fibrosis and smooth-muscle hyperplasia. These data suggest that PBPB could therefore be a therapeutic drug for chronic asthma.

Nanoparticle uptake by airway phagocytes after fungal spore challenge in murine allergic asthma and chronic bronchitis

Background

In healthy lungs, deposited micrometer-sized particles are efficiently phagocytosed by macrophages present on airway surfaces; however, uptake of nanoparticles (NP) by macrophages appears less effective and is largely unstudied in lung disease. Using mouse models of allergic asthma and chronic obstructive pulmonary disease (COPD), we investigated NP uptake after challenge with common biogenic ambient air microparticles.

Methods

Bronchoalveolar lavage (BAL) cells from diseased mice (allergic asthma: ovalbumin [OVA] sensitized and COPD: Scnn1b-transgenic [Tg]) and their respective healthy controls were exposed ex vivo first to 3-μm fungal spores of Calvatia excipuliformis and then to 20-nm gold (Au) NP. Electron microscopic imaging was performed and NP uptake was assessed by quantitative morphometry.

Results

Macrophages from diseased mice were significantly larger compared to controls in OVA-allergic versus sham controls and in Scnn1b-Tg versus wild type (WT) mice. The percentage of macrophages containing AuNP tended to be lower in Scnn1b-Tg than in WT mice. In all animal groups, fungal spores were localized in macrophage phagosomes, the membrane tightly surrounding the spore, whilst AuNP were found in vesicles largely exceeding NP size, co-localized in spore phagosomes and occasionally, in the cytoplasm. AuNP in vesicles were located close to the membrane. In BAL from OVA-allergic mice, 13.9 ± 8.3% of all eosinophils contained AuNP in vesicles exceeding NP size and close to the membrane.

Conclusions

Overall, AuNP uptake by BAL macrophages occurred mainly by co-uptake together with other material, including micrometer-sized ambient air particles like fungal spores. The lower percentage of NP containing macrophages in BAL from Scnn1b-Tg mice points to a change in the macrophage population from a highly to a less phagocytic phenotype. This likely contributes to inefficient macrophage clearance of NP in lung disease. Finally, the AuNP containing eosinophils in OVA-allergic mice show that other inflammatory cells present on airway surfaces may substantially contribute to NP uptake.

The role of inflammation resolution speed in airway smooth muscle mass accumulation in asthma: insight from a theoretical model

Despite a large amount of in vitro data, the dynamics of airway smooth muscle (ASM) mass increase in the airways of patients with asthma is not well understood. Here, we present a novel mathematical model that describes qualitatively the growth dynamics of ASM cells over short and long terms in the normal and inflammatory environments typically observed in asthma. The degree of ASM accumulation can be explained by an increase in the rate at which ASM cells switch between non-proliferative and proliferative states, driven by episodic inflammatory events. Our model explores the idea that remodelling due to ASM hyperplasia increases with the frequency and magnitude of these inflammatory events, relative to certain sensitivity thresholds. It highlights the importance of inflammation resolution speed by showing that when resolution is slow, even a series of small exacerbation events can result in significant remodelling, which persists after the inflammatory episodes. In addition, we demonstrate how the uncertainty in long-term outcome may be quantified and used to design an optimal low-risk individual anti-proliferative treatment strategy. The model shows that the rate of clearance of ASM proliferation and recruitment factors after an acute inflammatory event is a potentially important, and hitherto unrecognised, target for anti-remodelling therapy in asthma. It also suggests new ways of quantifying inflammation severity that could improve prediction of the extent of ASM accumulation. This ASM growth model should prove useful for designing new experiments or as a building block of more detailed multi-cellular tissue-level models.