Adenosine A1 receptor antagonist versus montelukast on airway reactivity and inflammation

Abstract

Adenosine produces bronchoconstriction in allergic rabbits, primates, and humans by activating adenosine A1 receptors. Previously, it is reported that a high dose of L-97-1, a water-soluble, small molecule adenosine A1 receptor antagonist, blocks early and late allergic responses, and bronchial hyper-responsiveness to histamine in a hyper-responsive rabbit model of allergic asthma. Effects of a lower dose of L-97-1 are compared to montelukast, a cysteinyl leukotriene-1 receptor antagonist on early allergic response, late allergic response, bronchial hyper-responsiveness, and inflammatory cells in bronchoalveolar lavage (BAL) fluid following house dust mite administration. Rabbits received intraperitoneal injections of house dust mite extract within 24 h of birth followed by booster house dust mite injections. Hyper-responsive rabbits received aerosolized house dust mite (2500 allergen units), 1 h after intragastric administration of L-97-1 (1 mg/kg) or montelukast (0.15 mg/kg) and lung dynamic compliance was measured for 6 h. Lung dynamic compliance was significantly higher following L-97-1 at all time points and with montelukast at 60-300 min following house dust mite (P < 0.05). L-97-1 blocks both early and late allergic responses. Montelukast blocks only the late allergic response. Both L-97-1 and montelukast significantly blocked bronchial hyper-responsiveness at 24 h (P < 0.05). Both L-97-1 and montelukast significantly reduced BAL eosinophils at 6 h and neutrophils at 6 and 24 h (P < 0.05). L-97-1 significantly reduced BAL lymphocytes at 6 and 24 h (P < 0.05). Montelukast significantly reduced BAL macrophages at 6 and 24 h (P < 0.05). By blocking both bronchoconstriction and airway inflammation, L-97-1 may be an effective oral anti-asthma treatment. © 2006 Elsevier B.V. All rights reserved.