CD137 deficiency does not affect development of airway inflammation or respiratory tolerance induction in murine models

The co-stimulatory molecule CD137 (4-1BB) plays a crucial role in the development and persistence of asthma, characterized by eosinophilic airway inflammation, mucus hypersecretion, airway hyperreactivity, increased T helper type 2 (Th2) cytokine production and serum immunoglobulin (Ig)E levels. We have shown previously that application of an agonistic CD137 monoclonal antibody (mAb) prevented and even reversed an already established asthma phenotype. In the current study we investigated whether deficiency of the CD137/CD137L pathway affects the development of allergic airway inflammation or the opposite immune reaction of respiratory tolerance. CD137^−/− and wild-type (WT) mice were sensitized and challenged with the model allergen ovalbumin (OVA) and analysed for the presence of allergic disease parameters (allergy protocol). Some animals were tolerized by mucosal application of OVA prior to transferring the animals to the allergy protocol to analyse the effect of CD137 loss on tolerance induction (tolerance protocol). Eosinophilic airway inflammation, mucus hypersecretion, Th2 cytokine production and elevated allergen-specific serum IgE levels were increased equally in CD137^−/− and WT mice. Induction of tolerance resulted in comparable protection from the development of an allergic phenotype in both mouse strains. In addition, no significant differences could be identified in CD4⁺, CD8⁺ and forkhead box protein 3 (FoxP3⁺) regulatory T cells, supporting the conclusion that CD137^−/− mice show equal Th2-mediated immune responses compared to WT mice. Taken together, CD137^−/− mice and WT mice develop the same phenotype in a murine model of Th2-mediated allergic airway inflammation and respiratory tolerance.     

Contribution of IL-18-induced innate T cell activation to airway inflammation with mucus hypersecretion and airway hyperresponsiveness

Human bronchial asthma is characterized by airway hyperresponsiveness (AHR), eosinophilic airway inflammation, mucus hypersecretion and high serum level of IgE. IL-18 was originally regarded to induce T(h)1-related cytokines from Th1 cells in the presence of IL-12. However, our previous reports clearly demonstrated that IL-18 with IL-2 promotes Th2 cytokines production from T cells and NK cells. Furthermore, IL-18 with IL-3 stimulates basophils and mast cells to produce Th2 cytokines. Thus, we examined the capacity of IL-2 and IL-18 to induce AHR, airway eosinophilic inflammation and goblet cell metaplasia. Intranasal administration of IL-2 and IL-18 induces AHR, mucus hypersecretion and eosinophilic inflammation in the lungs of naive mice. CD4+ T cells are prerequisite for this IL-2 plus IL-18-induced bronchial asthma, because CD4+ T cells-depleted or Rag-2-deficient (Rag-2-/-) mice did not develop bronchial asthma after IL-2 plus IL-18 treatment. Both STAT6-/- mice and IL-13-neutralized wild-type mice failed to develop AHR, goblet cell metaplasia and airway eosinophilic inflammation, while IL-4-/- mice almost normally developed, suggesting that IL-13 is a major causative factor and IL-4 mainly enhances the degree of AHR and eosinophilic inflammation. Both IL-4 and IL-13 equally induce eotaxin in mouse embryonic fibroblasts. However, only IL-13 blockade inhibited asthma symptoms, suggesting that IL-13 but not IL-4 is produced abundantly and plays a critical role in the pathogenesis of bronchial asthma in this model. As airway epithelial cells store robust IL-18, IL-18 might be critically involved in pathogen-induced bronchial asthma, in which pathogens stimulate epithelial cells to produce IL-18 without IL-12 induction.     

Different role of CD30 in the development of acute and chronic airway inflammation in a murine asthma model

CD30 is a costimulatory molecule of the TNF receptor superfamily, expressed on activated T and B cells. Previously, we have shown in a murine asthma model the crucial role of CD30 signaling for the development of this Th2‐cell‐mediated disease. In the present study, we investigated the role of CD30 in the maintenance of the immune response. In contrast to the acute model, in the chronic model CD30^?/? mice developed a severe asthma‐like phenotype with eosinophilic inflammation and high serum IgE levels. Collagen content, ECM protein deposition and proliferation of smooth muscle cells as signs for airway remodeling were equally increased in both CD30^?/? and WT mice. Reduced expression of the costimulatory molecule OX40 on CD3⁺ T cells in the acute and up‐regulation in the chronic model indirectly supported a compensatory role of OX40 for CD30 signaling. In accordance, application of agonistic OX40 antibody restored the asthma phenotype in CD30^?/? mice in the acute model, whereas chronic airway inflammation was reduced in the presence of an inhibitory anti‐OX40 ligand antibody. These data demonstrate that the crucial role of CD30 signaling in the development of acute asthma may be taken over by other costimulatory molecules like OX40 after long‐term exposure to the antigen.     

Enhanced osteopontin expression in a murine model of allergen-induced airway remodelling

BACKGROUND: Airway remodelling is a central pathophysiological feature of chronic asthma. A wide variety of cytokines and growth factors are likely to be involved in the development of airway remodelling. Osteopontin (OPN) is a cytokine with pro-fibrotic properties; however, its role in airway remodelling in asthma has not been explored. OBJECTIVE: To determine the expression and cellular sources of OPN in a murine model of chronic allergen-induced airway remodelling. METHODS: BALB/c mice were sensitized and exposed to ovalbumin (OVA) or saline inhalations for 5 weeks and killed 24 h after the last inhalation. The following parameters of inflammation and remodelling were assessed: differential cell counts in bronchoalveolar lavage (BAL) fluid lung collagen content (colorimetric biochemical assay) and peribronchial smooth muscle content (immunohistochemistry, followed by image analysis). OPN expression in BAL and lung tissue was determined by PCR and ELISA. The cellular source and distribution of OPN were evaluated by immunohistochemistry and immunofluorescence. RESULTS: OPN expression is up-regulated in lung tissue and in BAL fluid of OVA-treated mice and correlates with collagen content and peribronchial smooth muscle area. In addition, OPN significantly increases collagen deposition in vitro in a murine lung cell line. Cells producing OPN include the airway epithelium and cells of the submucosal inflammatory infiltrate (T cells, eosinophils, and macrophages). Positive staining for OPN was also observed in bronchial tissue from human asthmatic subjects. CONCLUSION: OPN expression in the lungs is increased in a murine model of allergen-induced chronic airway remodelling, suggesting a role for this cytokine in airway remodelling in asthma.     

Non‐eosinophilic Airway Hyper‐reactivity in Mice,Induced by IFN‐γ Producing CD4+ and CD8+ Lung T cells,is Responsive to Steroid Treatment

Non‐eosinophilic asthma is characterized by infiltration of neutrophils into the lung and variable responsiveness to glucocorticoids. The pathophysiological mechanisms have not been characterized in detail. Here, we present an experimental asthma model in mice associated with non‐eosinophilic airway inflammation and airway hyper‐responsiveness (AHR). For this, BALB/c mice were sensitized by biolistic DNA immunization with a plasmid encoding the model antigen β‐galactosidase (pFascin‐βGal mice). For comparison, eosinophilic airway inflammation was induced by subcutaneous injection of βGal protein (βGal mice). Intranasal challenge of mice in both groups induced AHR to a comparable extent as well as recruitment of inflammatory cells into the airways. In contrast to βGal mice, which exhibited extensive eosinophilic infiltration in the lung, goblet cell hyperplasia and polarization of CD4⁺ T cells into Th2 and Th17 cells, pFascin‐βGal mice showed considerable neutrophilia, but no goblet cell hyperplasia and a predominance of Th1 and Tc1 cells in the airways. Depletion studies in pFascin‐βGal mice revealed that CD4⁺ and CD8⁺ cells cooperated to induce maximum inflammation, but that neutrophilic infiltration was not a prerequisite for AHR induction. Treatment of pFascin‐βGal mice with dexamethasone before intranasal challenge did not affect neutrophilic infiltration, but significantly reduced AHR, infiltration of monocytes and lymphocytes as well as content of IFN‐γ in the bronchoalveolar fluid. Our results suggest that non‐eosinophilic asthma associated predominantly with Th1/Tc1 cells is susceptible to glucocorticoid treatment. pFascin‐βGal mice might represent a mouse model to study pathophysiological mechanisms proceeding in the subgroup of asthmatics with non‐eosinophilic asthma that respond to inhaled steroids.     

Prolonged allergen challenge in mice leads to persistent airway remodelling

BACKGROUND: Inflammatory infiltrates, airway hyper-responsiveness, goblet cell hyperplasia and subepithelial thickening are characteristic of chronic asthma. Current animal models of allergen-induced airway inflammation generally concentrate on the acute inflammation following allergen exposure and fail to mimic all of these features. OBJECTIVE: The aim of this study was to use a murine model of prolonged allergen-induced airway inflammation in order to characterize the cells and molecules involved in the ensuing airway remodelling. Moreover, we investigated whether remodelling persists in the absence of continued allergen challenge. METHODS: Acute pulmonary eosinophilia and airways hyper-reactivity were induced after six serial allergen challenges in sensitized mice (acute phase). Mice were subsequently challenged three times a week with ovalbumin (OVA) (chronic phase) up to day 55. To investigate the persistence of pathology, one group of mice were left for another 4 weeks without further allergen challenge (day 80). RESULTS: The extended OVA challenge protocol caused significant airway remodelling, which was absent in the acute phase. Specifically, remodelling was characterized by deposition of collagen as well as airway smooth muscle and goblet cell hyperplasia. Importantly, these airway changes, together with tissue eosinophilia were sustained in the absence of further allergen challenge. Examination of cytokines revealed a dramatic up-regulation of IL-4 and tumour growth factor-beta1 during the chronic phase. Interestingly, while IL-4 levels were significantly increased during the chronic phase, levels of IL-13 fell. Levels of the Th1-associated cytokine IFN-gamma also increased during the chronic phase. CONCLUSION: In conclusion, we have demonstrated that prolonged allergen challenge results in persistent airway wall remodelling.     

CD8(+) T cells regulate immune responses in a murine model of allergen-induced sensitization and airway inflammation

The role of CD8(+) T cells in the development of allergic airway disease is controversial. On the one hand, CD8(+) T cells are known to inhibit the development of airway hyperreactivity (AHR) in murine models of asthma. In humans, IL-10-producing CD8(+) T cells were shown to act as regulatory cells, inhibiting both proliferation and cytokine secretion of T cells. On the other hand, CD8(+) T cells can promote IL-5-mediated eosinophilic airway inflammation and the development of AHR in animal models. To examine this, we investigated the role of CD8(+) T cells during the induction of allergen-induced AHR and demonstrated a protective effect of CD8(+) T cells. Depletion of CD8(+) T cells prior to the immunization led to increased Th2 responses and increased allergic airway disease. However, after development of AHR, CD8(+) T cells that infiltrated the lungs secreted high levels of IL-4, IL-5 and IL-10, but little IFN-gamma, whereas CD8(+) T cells in the peribronchial lymph nodes or spleen produced high levels of IFN-gamma, but little or no Th2 cytokines. These data demonstrate protective effects of CD8(+)T cells against the induction of immune responses and show a functional diversity of CD8(+) T cells in different compartments of sensitized mice.     

Role of the Th2 cytokines in the development of allergen-induced airway inflammation and hyperresponsiveness

Increased production of interleukin (IL)-4 and IL-5 by T-helper cells may be pivotal for the induction and regulation of allergic diseases. We have studied the role of IL-4 and IL-5 in the development of eosinophilic airway inflammation (AI) and airway hyperresponsiveness (AHR) in a mouse model of allergen-induced bronchial asthma. Utilizing different modes of sensitization, we delineated the importance of IL-5-mediated eosinophilic airway infiltration for the development of in vitro and in vivo AHR and demonstrated the inhibition of airway inflammation and AHR by anti-IL-5 antibody treatment. Studies in IL-4- and IL-5 deficient mice revealed the importance of both cytokines for the induction of AI and AHR independently from the production of allergen-specific IgE, and indicated these cytokines as potential targets in novel approaches in the treatment of asthma.     

Respiratory syncytial virus infection provokes airway remodelling in allergen-exposed mice in absence of prior allergen sensitization

Background The mechanisms underlying exacerbation of asthma induced by respiratory syncytial virus (RSV) infection have been extensively studied in human and animal models. However, most of these studies focused on acute inflammation and little is known of its long-term consequences on remodelling of the airway tissue.
Objective The aim of the study was to use a murine model of prolonged allergen-induced airway inflammation to investigate the effect of RSV infection on allergic airway inflammation and tissue remodelling.
Methods We subjected mice to RSV infection before or during the chronic phase of airway challenges with OVA and compared parameters of airway inflammation and remodelling at the end-point of the prolonged allergen-induced airway inflammation protocol.
Results RSV infection did not affect the severity of airway inflammation in any of the groups studied. However, RSV infection provoked airway remodelling in non-sensitized, allergen-challenged mice that did not otherwise develop any of the features of allergic airways disease. Increased collagen synthesis in the lung and thickening of the bronchial basal membrane was observed in non-sensitized allergen-challenged mice only after prior RSV infection. In addition, fibroblast growth factor (FGF)-2 but not TGF-β₁ was increased in this group following RSV infection.
Conclusion Our data show for the first time that RSV infection can prime the lung of mice that are not previously systemically sensitized, to develop airway remodelling in response to allergen upon sole exposure via the airways. Moreover, our results implicate RSV-induced FGF-2 in the remodelling process in vivo .     

Blocking induction of T helper type 2 responses prevents development of disease in a model of childhood asthma

Early-life respiratory viral infections are linked to subsequent development of allergic asthma in children. We assessed the underlying immunological mechanisms in a novel model of the induction phase of childhood asthma. BALB/c mice were infected neonatally with pneumonia virus of mice, then sensitized intranasally with ovalbumin following recovery. Animals were challenged with low levels of aerosolized ovalbumin for 4 weeks to induce changes of chronic asthma, then received a single moderate-level challenge to elicit mild acute allergic inflammation. To inhibit the initial induction of a T helper type 2 (Th2) response, we administered neutralizing antibodies against interleukin (IL)-4 or IL-25, then assessed development of airway inflammation and remodelling. Anti-IL-4 administered during chronic challenge prevented development of chronic and acute allergic inflammation, as well as goblet cell hyperplasia/metaplasia, but features of remodelling such as subepithelial fibrosis and epithelial hypertrophy were unaffected. In contrast, anti-IL-25 had limited effects on the airway inflammatory response but prevented key changes of remodelling, although it had no effect on goblet cells. Both antibodies suppressed development of a Th2 response, while anti-IL-25 also promoted a Th17 response. In further experiments, anti-IL-25 was administered in early life alone, and again had limited effects on airway inflammation, but prevented development of airway wall remodelling. We conclude that in this murine model of childhood asthma, administration of anti-IL-4 or anti-IL-25 prevents development of some key features of asthma, suggesting that suppression of development of a Th2 response during the neonatal period or later in childhood could be effective for primary prevention.     

Effect of tiotropium bromide on airway inflammation and remodelling in a mouse model of asthma

Background Tiotropium bromide, a long acting muscarinic receptor inhibitor, is a potent agent for patients with bronchial asthma as well as chronic obstructive pulmonary disease. Objective The aim of this study was to evaluate whether tiotropium bromide can inhibit allergen‐induced acute and chronic airway inflammation, T helper (Th)2 cytokine production, and airway remodelling in a murine model of asthma. Methods Balb/c mice were sensitized and challenged acutely or chronically to ovalbumin (OVA). The impact of tiotropium bromide was assessed using these mice models by histologic, morphometric, and molecular techniques. Moreover, the effect of tiotropium bromide on Th2 cytokine production from purified human peripheral blood mononuclear cells (PBMCs) was assessed. Results Treatment with tiotropium bromide significantly reduced airway inflammation and the Th2 cytokine production in bronchoalveolar lavage fluid (BALF) in both acute and chronic models of asthma. The levels of TGF‐β1 were also reduced by tiotropium bromide in BALF in a chronic model. The goblet cell metaplasia, thickness of airway smooth muscle, and airway fibrosis were all significantly decreased in tiotropium bromide‐treated mice. Moreover, airway hyperresponsiveness (AHR) to serotonin was significantly abrogated by tiotropium bromide in a chronic model. Th2 cytokine production from spleen cells isolated from OVA‐sensitized mice was also significantly inhibited by tiotropium bromide and 4‐diphenylacetoxy‐N‐methylpiperidine methiodide, which is a selective antagonist to the M3 receptor. Finally, treatment with tiotropium bromide inhibited the Th2 cytokine production from PBMCs. Conclusion These results indicate that tiotropium bromide can inhibit Th2 cytokine production and airway inflammation, and thus may reduce airway remodelling and AHR in a murine model of asthma. Cite this as: S. Ohta, N. Oda, T. Yokoe, A. Tanaka, Y. Yamamoto, Y. Watanabe, K. Minoguchi, T. Ohnishi, T. Hirose, H. Nagase, K. Ohta and M. Adachi, Clinical & Experimental Allergy, 2010 (40) 1266–1275.     

Trichostatin A attenuates airway inflammation in mouse asthma model

BACKGROUND: Histone deacetylase (HDAC) inhibition has been demonstrated to change the expression of a restricted set of cellular genes. T cells are essential in the pathogenesis of allergen-induced airway inflammation. It was recently reported that treatment with HDAC inhibitors induces a T cell-suppressive effect. OBJECTIVE: The purpose of this study was to determine whether treatment with trichostatin A (TSA), a representative HDAC inhibitor, would reduce allergen-induced airway inflammation in a mouse asthma model. METHODS: BALB/c mice were intraperitoneally sensitized to ovalbumin (OVA) and challenged with an aerosol of OVA. TSA (1 mg/kg body weight) was injected intraperitoneally every 2 days beginning on day 1. Mouse lungs were assayed immunohistochemically for HDAC1, a major HDAC subtype, and for infiltration of CD4+ cells. The effect of TSA on airway hyper-responsiveness (AHR) was determined, and the bronchoalveolar lavage fluid (BALF) of these mice was assayed for the number and types of inflammatory cells, and for the concentrations of IL-4, IL-5, and IgE. RESULTS: HDAC1 was localized within most airway cells and infiltrating inflammatory cells of asthmatic lungs. Treatment with TSA significantly attenuated AHR, as well as the numbers of eosinophils and lymphocytes in BALF. TSA also reduced infiltration of CD4+ and inflammatory cells and mucus occlusions in lung tissue, and decreased the concentrations of IL-4, IL-5, and IgE in BALF. CONCLUSION: TSA attenuated the development of allergic airway inflammation by decreasing expression of the Th2 cytokines, IL-4 and IL-5, and IgE, which resulted from reduced T cell infiltration. Our results suggest that HDAC inhibition may attenuate the development of asthma by a T cell suppressive effect.     

Airway remodelling and inflammation in asthma are dependent on the extracellular matrix protein fibulin‐1c

Asthma is a chronic inflammatory disease of the airways. It is characterized by allergic airway inflammation, airway remodelling, and airway hyperresponsiveness (AHR). Asthma patients, in particular those with chronic or severe asthma, have airway remodelling that is associated with the accumulation of extracellular matrix (ECM) proteins, such as collagens. Fibulin‐1 (Fbln1) is an important ECM protein that stabilizes collagen and other ECM proteins. The level of Fbln1c, one of the four Fbln1 variants, which predominates in both humans and mice, is increased in the serum and airways fluids in asthma but its function is unclear. We show that the level of Fbln1c was increased in the lungs of mice with house dust mite (HDM)‐induced chronic allergic airway disease (AAD). Genetic deletion of Fbln1c and therapeutic inhibition of Fbln1c in mice with chronic AAD reduced airway collagen deposition, and protected against AHR. Fbln1c‐deficient (Fbln1c^–/–) mice had reduced mucin (MUC) 5 AC levels, but not MUC5B levels, in the airways as compared with wild‐type (WT) mice. Fbln1c interacted with fibronectin and periostin that was linked to collagen deposition around the small airways. Fbln1c^–/– mice with AAD also had reduced numbers of α‐smooth muscle actin‐positive cells around the airways and reduced airway contractility as compared with WT mice. After HDM challenge, these mice also had fewer airway inflammatory cells, reduced interleukin (IL)‐5, IL‐13, IL‐33, tumour necrosis factor (TNF) and CXCL1 levels in the lungs, and reduced IL‐5, IL‐33 and TNF levels in lung‐draining lymph nodes. Therapeutic targeting of Fbln1c reduced the numbers of GATA3‐positive Th2 cells in the lymph nodes and lungs after chronic HDM challenge. Treatment also reduced the secretion of IL‐5 and IL‐13 from co‐cultured dendritic cells and T cells restimulated with HDM extract. Human epithelial cells cultured with Fbln1c peptide produced more CXCL1 mRNA than medium‐treated controls. Our data show that Fbln1c may be a therapeutic target in chronic asthma. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Mechanisms preventing allergen-induced airways hyperreactivity: role of tolerance and immune deviation

BACKGROUND: Aeroallergens continuously enter the respiratory tract of atopic individuals and provoke the development of asthma characterized by airway hyperreactivity (AHR) and inflammation. By contrast, nonatopic individuals are exposed to the same aeroallergens, but airway inflammation does not develop. However, the mechanisms that prevent allergen-induced respiratory diseases in nonatopic subjects are poorly characterized. OBJECTIVE: In this study we compared the role of allergen-specific T-cell tolerance and immune deviation in conferring protection against the development of allergen-induced AHR. METHODS: We exposed mice to intranasal ovalbumin (OVA) to induce T-cell tolerance and examined its effects on the subsequent development of AHR and inflammation. RESULTS: We demonstrated that exposure of mice to intranasal OVA resulted in peripheral CD4(+) T-cell unresponsiveness that very efficiently prevented not only the development of AHR but also greatly inhibited airway inflammation and OVA-specific IgE production. The induction of peripheral T-cell tolerance and protection against AHR were not dependent on the presence of IFN-gamma or IL-4. The development of AHR was also prevented by an OVA-specific T(H)1-biased immune response induced by inhalation of OVA in the presence of IL-12. However, the OVA-specific T(H)1 response was associated with a significant degree of pulmonary inflammation. CONCLUSION: These results indicate that both allergen-specific T-cell tolerance and T(H)1-biased immune deviation prevent the development of AHR, but T(H)1 responses are associated with significantly greater inflammation in the lung than is associated with T-cell unresponsiveness. Therefore CD4(+) T-cell unresponsiveness critically regulates immune responses to aeroallergens and protects against the development of allergic disease and asthma.     

Oral administration of desloratadine prior to sensitization prevents allergen-induced airway inflammation and hyper-reactivity in mice

BACKGROUND: Histamine-1-receptor (H1R)-antagonists were shown to influence various immunological functions on different cell types and may thus be employed for immune-modulating strategies for the prevention of primary immune responses. OBJECTIVE: The aim of this study was to investigate the effects of an H1R-antagonist on allergen-induced sensitization, airway inflammation (AI) and airway hyper-reactivity (AHR) in a murine model. METHODS: BALB/c mice were systemically sensitized with ovalbumin (OVA) (six times, days 1-14) and challenged with aerosolized allergen (days 28-30). One day prior to the first and 2 h prior to every following sensitization, mice received either 1 or 0.01 microg of desloratadine (DL) or placebo per os. RESULTS: Sensitization with OVA significantly increased specific and total IgE and IgG1 serum levels, as well as in vitro IL-5 and IL-4 production by spleen and peribronchial lymph node (PBLN) cells. Sensitized and challenged mice showed a marked eosinophilic infiltration in broncho-alveolar lavage fluids and lung tissues, and developed in vivo AHR to inhaled methacholine. Oral treatment with DL prior to OVA sensitization significantly decreased production of OVA-specific IgG1, as well as in vitro Th2-cytokine production by spleen and PBLN cells, compared with OVA-sensitized mice. Moreover, eosinophilic inflammation and development of in vivo AHR were significantly reduced in DL-treated mice, compared with sensitized controls. CONCLUSION: Treatment with H1R-anatagonist prior to and during sensitization suppressed allergen-induced Th2 responses, as well as development of eosinophilic AI and AHR. This underscores an important immune modulating function of histamine, and implies a potential role of H1R-anatagonists in preventive strategies against allergic diseases.     

Interleukin‐33 and alveolar macrophages contribute to the mechanisms underlying the exacerbation of IgE‐mediated airway inflammation and remodelling in mice

Allergen‐specific IgE has long been regarded as a major molecular component of allergic asthma. Additionally, there is increasing evidence of the important roles of interleukin‐33 (IL‐33) in the disease. Here, we show that IL‐33 and alveolar macrophages play essential roles in the exacerbation of IgE‐mediated airway inflammation and remodelling. BALB/c mice passively sensitized with ovalbumin (OVA)‐specific IgE monoclonal antibody (mAb) were challenged with OVA seven times intratracheally. The seventh challenge exacerbated airway inflammation and remodelling compared with the fourth challenge; furthermore, markedly increased expression of IL‐33 in the lungs was observed at the fourth and seventh challenges. When anti‐IL‐33 or anti‐ST2 antibody was administered during the fourth to seventh challenge, airway inflammation and remodelling were significantly inhibited at the seventh challenge. Because increases of IL‐33⁺ and ST2⁺ alveolar macrophages and ST2⁺ CD4⁺ T cells in the lungs were observed at the fourth challenge, the roles of macrophages and CD4⁺ cells were investigated. Depletion of macrophages by 2‐chloroadenosine during the fourth to seventh challenge suppressed airway inflammation and remodelling, and IL‐33 production in the lung at the seventh challenge; additionally, anti‐CD4 mAb inhibited airway inflammation, but not airway remodelling and IL‐33 production. Meanwhile, treatment with 2‐chloroadenosine or anti‐CD4 mAb decreased IL‐33‐induced airway inflammation in normal mice; airway remodelling was repressed only by 2‐chloroadenosine. These results illustrate that macrophage‐derived IL‐33 contributes to the exacerbation of IgE‐mediated airway inflammation by mechanisms associated with macrophages and CD4⁺ cells, and airway remodelling through the activation of macrophages.     

Effects of Diet-Induced Mild Obesity on Airway Hyperreactivity and Lung Inflammation in Mice

Purpose

Obesity has been suggested to be linked to asthma. However, it is not yet known whether obesity directly leads to airway hyperreactivity (AHR) or obesity-induced airway inflammation associated with asthma. We investigated obesity-related changes in adipokines, AHR, and lung inflammation in a murine model of asthma and obesity.

Materials and Methods

We developed mouse models of chronic asthma via ovalbumin (OVA)-challenge and of obesity by feeding a high-fat diet, and then performed the methacholine bronchial provocation test, and real-time PCR for leptin, leptin receptor, adiponectin, adiponectin receptor (adipor1 and 2), vascular endothelial growth factor (VEGF), transforming growth factor (TGF) β, and tumor necrosis factor (TNF) α in lung tissue. We also measured cell counts in bronchoalveolar lavage fluid.

Results

Both obese and lean mice chronically exposed to OVA developed eosinophilic lung inflammation and AHR to methacholine. However, obese mice without OVA challenge did not develop AHR or eosinophilic inflammation in lung tissue. In obese mice, lung mRNA expressions of leptin, leptin receptor, VEGF, TGF, and TNF were enhanced, and adipor1 and 2 expressions were decreased compared to mice in the control group. On the other hand, there were no differences between obese mice with or without OVA challenge.

Conclusion

Diet-induced mild obesity may not augment AHR or eosinophilic lung inflammation in asthma.     

Transgenic mice expressing the T cell antigen receptor specific for an immunodominant epitope of a major allergen of house dust mite develop an asthmatic phenotype on exposure of the airways to allergen

BACKGROUND: Current studies on mechanisms underlying allergen-induced pulmonary inflammation and asthma are hampered by the lack of appropriate physiological in vivo models that reflect the natural route of allergen exposure and sensitization. OBJECTIVE: To generate and phenotype a transgenic mouse strain expressing the T cell receptor (TCR) specific for an immunodominant domain of the major inhalant allergen Dermatophagoides pteronyssinus species of house dust mite (Der p 1), for the development of an in vivo model of allergic asthma. METHODS: Der p 1 transgenic mice were generated using TCR-alphabeta derived from a CD4+ T cell hybridoma reactive with Der p 1 residues p 110-131. The frequency and functional activity of peripheral T cells were determined and parameters of airway inflammation assessed following allergen challenge of the airways with Der p 1. RESULTS: CD4+ T cells are functionally active, exhibiting dose-dependent proliferation and IL-4 production on primary stimulation with Der p 1 or Der p 1, p 110-131 in vitro, independent of in vivo antigen priming. On sensitization of the airways with allergen, in the absence of systemic priming or the application of adjuvants, the TCR transgenic mice develop airway inflammation characterized by a marked lymphocytic and eosinophilic infiltrate with goblet cell hyperplasia and enhanced mucin production. CONCLUSION: The Der p 1 TCR transgenic mice provide a model for investigating the pathophysiological mechanisms of pulmonary inflammation following sensitization by exposure of the airways to allergen and for investigating the mode of action and efficacy of novel immunotherapeutics.     

Ovalbumin aerosols induce airway hyperreactivity in naïve DO11.10 T cell receptor transgenic mice without pulmonary eosinophilia or OVA-specific antibody

The pathobiology of allergic asthma is being studied using murine models, most of which use systemic priming followed by pulmonary challenges with the immunizing antigen. In general, mice develop eosinophilic pulmonary inflammation, increased antigen-specific immunoglobulins, and airway hyperreactivity (AHR), all of which are dependent on antigen-specific T cell activation. To establish a model of allergic asthma, which did not require systemic priming, we exposed DO11.10 T cell receptor transgenic mice, which have an expanded repertoire of ovalbumin (OVA), peptide-specific T cells, to limited aerosols of OVA protein. DO11.10 +/- mice developed AHR in the absence of increases in total serum IgE, OVA-specific IgG, or eosinophilia. The AHR was accompanied by pulmonary recruitment of antigen-specific T cells with decreased expression of CD62L and CD45RB and increased expression of CD69, a phenotype indicative of T cell activation. Our results support recent hypotheses that T cells mediate AHR directly.