The Use of Mouse Asthma Models to Successfully Discover and Develop Novel Drugs

The past 20 years have seen a proliferation of scientific data on the pathophysiology of asthma. Most of these data were generated in mice using tool reagents, gene-deficient or transgenic animals. In contrast, studies on disease pathogenesis in patients are scarce. Previously, a good novel antiasthma target for drug development was one that abrogated asthma in mice when it was knocked out, neutralized or induced asthma when it was overexpressed. This type of approach led to many drug candidates that worked in mice but unfortunately failed in patients, thereby demonstrating that the results of experiments in mice are not always predictive of clinical efficacy. Currently, there is active debate about the use of mouse models in drug discovery. In this review, we summarize the obstacles and challenges faced when using experimental mouse models of asthma in drug discovery. We propose that the initial selection of a novel drug target begins with defining the unmet medical need and specific patient population, followed by a thorough evaluation of available human data, and, only then, well-planned and executed mouse asthma experiments. Using this approach, we argue that mouse models lend support for the target when the models are tailored for the specific asthma patient population, and that targeted, reliable, and predictive mouse models can indeed improve and accelerate the drug discovery process.

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.