Yoshimasa Takahashi

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.

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.

Effects of a New Antiallergic Agent, VUF-K-8788, on Experimental Asthmatic Reactions in Guinea Pigs

The effects of 7-[3-[4-(2-quinolinylmethyl)- 1-piperazinyl]propoxy]-2,3-dihydro-4H-1,4- benzothiazin-3-one (VUF-K-8788) on experimental asthmatic reactions in guinea pigs were investigated. VUF-K-8788 inhibited histamine-induced bronchoconstriction at the doses of 0.3 and 1 mg/kg per os (p.o.). VUF-K-8788 inhibited anaphylactic bronchoconstriction at doses between 0.01 and 1 mg/kg in passively sensitized guinea pigs. Terfenadine used as a reference drug also inhibited an antigen-induced bronchoconstriction. VUF-K-8788 at the doses of 0.3 and 1 mg/kg inhibited immediate- and late-phase asthmathic reactions in actively sensitized guinea pigs. Terfenadine inhibited only the immediate phase reaction. Moreover, VUF-K-8788 inhibited the infiltration of eosinophils and macrophages into bronchoalveolar lavage fluid in guinea pigs. These results indicate that VUF-K-8788 may be useful for the treatment of bronchial asthma.

Effects of RS-601, a Novel Leukotriene D4/Thromboxane A2 Dual Receptor Antagonist, on Asthmatic Responses in Guinea Pigs

The effects of 4-[4-[5,5,6,6,6-pentafluoro-1-(4-fluorobenzene-sulfonamido)hexyl]phenyl]butyric acid (RS-601), a novel leukotriene D4 (LTD4)/thromboxane A2 (TxA2) dual receptor antagonist, on bronchial asthmatic responses in guinea pigs were examined. The effects were compared with those of pranlukast (LTD4 receptor antagonist) and S-1452 (TxA2 receptor antagonist). RS-601 inhibited the increase in airway resistance caused by LTD4 and TxA2 mimetic compound, U-46619, but not by histamine. RS-601 and pranlukast but not S-1452 inhibited an antigen-induced late asthmatic response. In addition, RS-601 inhibited an antigen-induced airway hyperresponsiveness (AHR), whereas pranlukast and S-1452 had no effect on the AHR. The antigen-induced increase in inflammatory cells in airway was not affected by all examined agents. Furthermore, bacterial lipopolysaccharide-induced AHR in guinea pigs was clearly suppressed by RS-601 but not by pranlukast and S-1452. The increase in airway inflammatory cells caused by lipopolysaccharide was not affected by all three drugs. These findings indicate that RS-601 has a potent antiasthmatic efficacy, especially on AHR, but does not affect accumulation of eosinophils in the airways.

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.

The effects of inhaled KP-496, a novel dual antagonist for cysteinyl leukotriene receptor and thromboxane A(2) receptor, on allergic asthmatic responses in guinea pigs.

Aims: The aim of this study was to evaluate the effects of inhaled KP-496, a novel dual antagonist for cysteinyl leukotriene receptor 1 and thromboxane A2 receptor, on the allergic asthmatic responses in guinea pigs. Methods: Actively sensitized animals were repeatedly exposed to antigen, and KP-496 (0.01 and 0.1%) was inhaled for 5 min before every antigen exposure. After evaluating the effects of KP-496 on asthmatic responses, such as immediate and late asthmatic response (IAR and LAR) and airway hyperresponsiveness (AHR), histopathological analyses of the lungs of asthmatic animals were made. Results: KP-496 significantly inhibited both antigen-induced LAR and AHR to acetylcholine, and slightly inhibited antigen-induced IAR. Furthermore, histopathological analyses of the lungs of the asthmatic animals demonstrated the following: (1) KP-496 suppressed infiltration of eosinophils around airway smooth muscle, (2) KP-496 suppressed airway epithelial hypertrophy, and (3) KP-496 suppressed increased mucus production in the airway. Conclusion: In addition to suppression of LAR and AHR, our findings demonstrated that KP-496 inhibits features of airway inflammation. Since these broad ameliorative effects of KP-496 on asthmatic pathology are thought to result from the inhibition of multiple chemical mediators, KP-496 will be a potent agent in the treatment of bronchial asthma.