Taisei Masuda

The effect of allergen-induced airway inflammation on airway remodeling in a murine model of allergic asthma.

Abstract.Objective and design: We examined the effect of airway inflammation on airway remodeling and bronchial responsiveness in a mouse model of allergic asthma.¶Materials and methods: BALB/c mice were sensitized to ovalbumin (OA), and exposed to aerosolized OA (0.01, 0.1 and 1%). Twenty-four hours after the final antigen challenge, bronchial responsiveness was measured, and bronchoalveolar lavage (BAL) and histological examinations were carried out.¶Results: Repeated antigen exposure induced airway inflammation, IgE/IgG1 responses, epithelial changes, collagen deposition in the lungs, subepithelial fibrosis associated with increases in the amount of transforming growth factor (TGF)-β1 in BAL fluid (BALF), and bronchial hyperresponsiveness to acetylcholine. The number of eosinophils in BALF was significantly correlated with TGF-β1 production in BALF and the amount of hydroxyproline. Furthermore, significant correlations were found between these fibrogenic parameters and the bronchial responsiveness.¶Conclusion: These findings demonstrated that in this murine model airway eosinophilic inflammation is responsible for the development of airway remodeling as well as bronchial hyperresponsiveness in allergic bronchial asthma.

Augmentation of allergic inflammation in prostanoid IP receptor deficient mice

To evaluate the role of prostaglandin I2 (PGI2) in allergic inflammation, allergic responses in the airway, skin and T cells were studied in mice lacking the receptor for PGI2 (the prostanoid IP receptor) through gene disruption. Three inhalations of antigen caused an increase in plasma extravasation, leukocyte accumulation and cytokine (interleukin (IL)‐4 and IL‐5) production in the airway of sensitized mice. These airway inflammatory responses were significantly greater in IP receptor deficient mice than in wild‐type mice. The vascular leakage caused by passive cutaneous anaphylaxis, substance P and 5‐hydroxytryptamine was markedly increased in the skin of IP receptor deficient mice, compared with comparably treated wild‐type mice. The inhalation of antigen in sensitized mice resulted in increased serum antigen specific IgE, total IgE and IgG levels. The magnitude of the elevations of each immunoglobulin level in IP receptor deficient mice is notably higher than that in wild‐type mice. To elucidate the mechanism of an enhancement of immunoglobulin production, the activity of T cells in sensitized and non‐sensitized mice was studied by means of the production of cytokines. The antigen‐induced IL‐4 production by spleen cells from sensitized IP receptor deficient mice was almost three times greater than that in wild‐type mice. On the contrary, the anti‐CD3 antibody‐induced interferon‐γ production by CD4+ T cells from non‐sensitized IP receptor deficient mice was significantly lower than that in wild‐type mice. The present data indicate that IP receptor deficiency reinforced an allergic airway and skin inflammation by augmentation of vascular permeability increase and the T helper 2 cell function. These findings suggest a regulatory role of PGI2 in allergic inflammation.

Role of Th2 responses in the development of allergen-induced airway remodelling in a murine model of allergic asthma

To clarify the involvement of Th2 responses in the development of allergen‐induced airway remodelling, we investigated the effect of anti‐CD4 monoclonal antibody (mAb) and anti‐CD8 mAb, and the responses of IL‐4 gene‐knockout (KO) mice in a murine model of allergic asthma. Mice were immunized twice by intraperitoneal injections of ovalbumin (OA), and exposed to aeroallergen (OA, 1% w v−1) for 3 weeks. Twenty‐four hours after the final challenge, airway responsiveness to acetylcholine was measured, and bronchoalveolar lavage (BAL) and histological examinations were carried out. Anti‐CD4 mAb (1 mg kg−1) clearly inhibited allergen‐induced increases in airway responsiveness to acetylcholine, the number of eosinophils in BAL fluid, serum OA‐specific IgE levels, IL‐13 and transforming growth factor‐β1 levels in BAL fluid, and amount of hydroxyproline in the lung by 100, 99, 100, 100, 84, and 60%, respectively. Furthermore, the antibody (1 mg kg−1) also attenuated allergen‐induced goblet cell hyperplasia in the epithelium and subepithelial fibrosis by 72 and 83%, respectively. In contrast, anti‐CD8 mAb (1 mg kg−1) showed no effect on each parameter. Furthermore, all these parameters were attenuated in IL‐4KO mice by 57, 93, 100, 45, 84 and 60%, and also 72 and 83%, respectively. These findings suggest that Th2 responses play a critical role for the development of allergen‐induced airway remodelling, and that the inhibition of Th2 responses, e.g. using anti‐CD4 mAb, is a therapeutic approach for the treatment of airway remodelling in asthma.

Mast cells play a partial role in allergen‐induced subepithelial fibrosis in a murine model of allergic asthma

Background Role of mast cells in the development of allergen‐induced airway remodelling has not been fully investigated in vivo.

Effect of MX‐68 on airway inflammation and hyperresponsiveness in mice and guinea‐pigs

MX‐68 is a newly synthesized antifolate, which is a derivative of methotrexate (MTX). In this paper, the effect of MX‐68 on allergic airway responses in mice and guinea‐pigs was studied. In the first experiment, antigen‐induced airway inflammation and airway hyperresponsiveness (AHR) to acetylcholine in mice were examined and compared with the effects of classical antifolate methotrexate and prednisolone. Mice were sensitized with ovalbumin as an antigen and challenged with ovalbumin inhalation three times. After the last inhalation, AHR and airway inflammation were observed. An increase in Th2 cytokines (IL‐4 and IL‐5) and a decrease in a Th1 cytokine (IFN‐γ) in the bronchoalveolar lavage fluid (BALF), as well as an elevation of the immunoglobulin level in serum, were observed in sensitized mice. Oral administration of MX‐68 had no effect on changes of body weight, but prednisolone reduced body weight during the experiment. The antigen‐induced AHR and increases in the number of eosinophils and lymphocytes in BALF were significantly inhibited by MX‐68. MX‐68 interfered with the elevation of IL‐4 and IL‐5 levels in BALF, but had no effect on the decrease in IFN‐γ. Moreover, MX‐68 significantly inhibited the elevation of serum IgE and IgG levels. In the guinea‐pig model for bronchial asthma, biphasic increases in airway resistance (immediate asthmatic response, IAR, and late asthmatic response, LAR), as well as accumulated inflammatory cells in BALF, were observed after repeated antigen challenge. These asthmatic responses and inflammatory signs were significantly decreased by administration of MX‐68. These results suggest that MX‐68 obviously has an anti‐inflammatory effect in an animal model of asthma and would be useful clinically for the treatment of bronchial asthma.

Disruption of antigen‐induced airway inflammation and airway hyper‐responsiveness in low affinity neurotrophin receptor p75 gene deficient mice

Recently, much attention has been paid to the relationship between the nervous and immune systems. The present study was conducted to clarify the role of neurotrophin low affinity receptor (p75N) in allergic airway inflammation and hyper‐responsiveness (AHR) in mice by employing p75N gene deficient mice. Mice were immunized twice by intraperitoneal injections of ovalbumin (OA) at intervals of 12 days. OA was inhaled 10 days after the secondary immunization and repeated three times at 4 days interval. Twenty‐four hours after the last inhalation, airway responsiveness to acetylcholine was measured and bronchoalveolar lavage fluid (BALF) was obtained for examining the number of inflammatory cells and the level of cytokines. Serum immunoglobulin was measured as a marker of systemic immune response before the final inhalation. In wild‐type mice, repeated antigen provocation resulted in airway eosinophilia, AHR and elevations in serum IgE and interleukin (IL)‐4 and −5 in BALF. In p75N gene deficient mice, none of the above parameters was observed after antigen provocation. The antigen‐induced production of interferon (IFN)‐γ and nerve growth factor (NGF) were not altered by depletion of p75N gene. The present findings suggest that p75 gene deficiency disrupt an allergic airway inflammation and AHR in mice by interfering type 2 helper T (Th2) cell responses.

Time course study on the development of allergen-induced airway remodeling in mice: the effect of allergen avoidance on established airway remodeling.

Abstract. Objective and design: We carried out a time course study on the development of allergen-induced airway remodeling in a mouse model of allergic asthma. Moreover, we examined the effect of allergen avoidance on the established airway remodeling.¶Materials and methods: BALB/c mice were sensitized to ovalbumin (OA) with alum, and exposed daily for 3 weeks to aerosolized OA. At each designated point, bronchial responsiveness was measured, and bronchoalveolar lavage and histological examination were carried out.¶Results: The numbers of inflammatory leukocytes in the airways and the percentage of goblet cells in the epithelium, Th2 cytokine production, IgE production, collagen deposition beneath the basement membrane and bronchial responsiveness to acetylcholine were all markedly increased after repeated antigen challenge for 1-3 weeks. In contrast, after cessation of antigen exposure, goblet cell hyperplasia, inflammatory infiltrates and bronchial hyperresponsiveness were gradually attenuated and had almost resolved 4 weeks after cessation, but subepithelial fibrosis was still observed at this time point.¶Conclusions: The present findings demonstrated that epithelial changes following repeated allergen challenge are rapidly induced and recover after the cessation of exposure, but subepithelial fibrosis has a late onset and relatively irreversible changes, and subepithelial fibrosis in contrast to goblet cells hyperplasia did not appear to contribute to bronchial hyperresponsiveness, at least, in this mouse model.

The effect of leukotriene D (4) inhalation on the antigen-induced airway hyperresponsiveness and inflammation in 5-lipoxygenase gene-deficient mice

Background: The role of 5-lipoxygenase (5-LO) products in the asthmatic bronchoconstriction is evident. However, the role of 5-LO products in airway hyperresponsiveness (AHR) and airway inflammation is still under discussion. The aim of the present study is to investigate the role of leukotriene D4 (LTD4) in AHR and allergic airway eosinophilia in mice. Methods: The effect of LTD4 inhalation on antigen-induced AHR and airway eosinophilia was investigated in 5-LO gene-deficient mice. Results: After three inhalations of LTD4, airway responsiveness to acetylcholine was not altered in normal or allergic wild-type and 5-LO knockout (KO) mice. In contrast, the number of eosinophils in 5-LO KO allergic mice increased to the level of wild-type allergic mice after the inhalation of LTD4. These observations were confirmed by a histopathological study of the lungs. No change in the cytokine levels in bronchoalveolar lavage fluid and serum immunoglobulin levels was shown after LTD4 inhalation. Conclusion: These findings suggest that LTD4 plays a role in eosinophilic airway inflammation but not in AHR in mice.