Inhibitory effect of ONO-1078 on specific binding of peptide leukotrienes to human lung crude membrane

Increased expression of CysLT2 receptors in the lung of asthmatic mice and role in allergic responses

Compared with CysLT₁ receptors, the functional role of CysLT₂ receptors in asthma has not been clarified. The purpose of this study was to determine 1) whether CysLT₂ receptors are expressed in the lung of mice and if expression increases in asthmatic mice, and 2) whether CysLT₂ receptors are involved in allergic leukocyte infiltration into the lung and in the development of airway remodeling in asthmatic mice. BALB/c mice were sensitized with ovalbumin (OVA) + Al(OH)₃, and intratracheally challenged with OVA 4 times. Lung tissue was isolated before and after the 4th OVA challenge for detection of CysLT₂ receptors by immunohistochemistry and flow cytometry. The effect of a CysLT₂ receptor antagonist BayCysLT₂RA on multiple antigen challenge-induced leukocyte infiltration into the lung and the development of airway remodeling was evaluated. Even in non-challenged mice, CysLT₂ receptors were expressed in bronchial smooth muscle. After multiple challenges, expression was also observed in leukocytes infiltrating into alveolar spaces. CysLT₂R⁺ leukocytes included alveolar macrophages, conventional dendritic cells, and eosinophils. BayCysLT₂RA significantly inhibited multiple antigen challenge-induced increases in eosinophils and mononuclear cells in the lung. The development of airway remodeling was tended to be suppressed by CysLT₂ receptor antagonist. In conclusion, CysLT₂ receptors were constitutively expressed in the lung, and expression was strengthened in asthmatic mice. Activation of CysLT₂ receptors was functionally involved in allergic leukocyte infiltration into the lung. The CysLT₂ receptor can be a molecular target for the development of new pharmacotherapies for asthma.

Expression of CysLT2 receptors in asthma lung, and their possible role in bronchoconstriction

BACKGROUND

The expression and functional role of CysLT2 receptors in asthma have not been clarified. In this study, we evaluated CysLT2 receptors expression, and effects of CysLT2-and CysLT1/2-receptor antagonists on antigen-induced bronchoconstriction using isolated lung tissues from both asthma and non-asthma subjects.

METHODS

CysLT1 and CysLT2 receptors expression in asthma and non-asthma lung tissue preparations was examined in immunohistochemistry experiments, and their functional roles in antigen-induced bronchoconstriction were assessed using ONO-6950, a dual CysLT1/2-receptor antagonist, montelukast, a CysLT1 receptor antagonist, and BayCysLT2RA, a CysLT2 receptor-specific antagonist.

RESULTS

CysLT1 receptors were expressed on the bronchial smooth muscle and epithelium, and on alveolar leukocytes in 5 in 5 non-asthma subjects and 2 in 2 asthma subjects. On the other hand, although degrees of CysLT2 receptors expression were variable among the 5 non-asthma subjects, the expression in the asthma lung was detected on bronchial smooth muscle, epithelium and alveolar leukocytes in 2 in 2 asthma subjects. In the non-asthma specimens, antagonism of CysLT2 receptors did not affect antigen-induced bronchial contractions, even after pretreatment with the CysLT1-receptor specific antagonist, montelukast. However, in the bronchus isolated from one of the 2 asthma subjects, antagonism of CysLT2 receptors suppressed contractions, and dual antagonism of CysLT1 and CysLT2 receptors resulted in additive inhibitory effect on anaphylactic contractions.

CONCLUSIONS

CysLT2 receptors were expressed in lung specimens isolated from asthma subjects. Activation of CysLT2 receptors may contribute to antigen-induced bronchoconstriction in certain asthma population.

Cysteinyl leukotriene-dependent interleukin-5 production leading to eosinophilia during late asthmatic response in guinea-pigs

BACKGROUND

Allergic airway eosinophilia is suppressed by cysteinyl leukotriene (CysLT) receptor (CysLT1 receptor) antagonists in several species including humans and guinea-pigs, suggesting that CysLTs are directly or indirectly involved in induction of the response.

OBJECTIVE

We examined the effect of CysLT antagonists (pranlukast and MCI-826) on antigen inhalation-induced eosinophilia in peripheral blood and lung, and on IL-5 activity in serum during late increase of airway resistance (late asthmatic response, LAR) in sensitized guinea-pigs.

METHODS

Guinea-pigs inhaled ovalbumin (OVA) + Al(OH)3 and OVA mists alternately for sensitization and challenge, respectively, once every 2 weeks. At the fifth challenge, the effects of CysLT antagonists and an anti-IL-5 antibody (TRFK-5) on the occurrence of LAR, and blood and lung eosinophilia, which appeared at 5 h after challenge, were examined. The time-course of IL-5 activity in the serum after the challenge was evaluated by measuring in vitro 'eosinophil survival prolongation activity'. The influence of CysLT antagonists on IL-5 activity was assessed.

RESULTS

CysLT antagonists and TRFK-5 completely abolished blood and lung eosinophilia. LAR was suppressed by both MCI-826 and TRFK-5 by 40-50%. Sera obtained from sensitized, challenged animals 3 h and 4 h after challenge induced an obvious prolongation of eosinophil survival. The activity of the sera was completely neutralized by prior exposure to TRFK-5, suggesting that it reflected IL-5 activity. Increased IL-5 activity in the serum was inhibited by both pranlukast and MCI-826 by over 90%.

CONCLUSIONS

CysLTs produced after antigen provocation sequentially induced IL-5 production from some immune component cells via CysLT1 receptor activation. Thus, it is likely that CysLTs indirectly cause antigen-induced eosinophilia through IL-5 production.

Aspirin-sensitive urticaria: provocation with a leukotriene receptor antagonist

The diagnosis of two patients with aspirin-induced urticaria (AIU) was confirmed by oral provocation with aspirin, other non-steroidal anti-inflammatory drugs, and food additives. Low doses of a novel leukotriene (LT) receptor antagonist, ONO-1078 (ONO, Japan) induced urticaria in these patients, while the same doses of ONO-1078 did not provoke any eruptions in 10 normal healthy volunteers or five patients with aspirin-unrelated chronic urticaria. This is the first report that a selective LTD4/LTE4 receptor antagonist that is effective as an antiasthmatic agent evoked urticaria in patients with AIU. Our observation suggests that the pathogenesis of AIU depends on the stimulation of LT receptors. The accumulation of results of anti-LT therapy may provide clues to resolve the pathogenetic mechanisms of this disorder.