CysLT(1) antagonists are effective for a subset of patients with asthma; however, there has been no good way to predict a given patient's response. We examined the interaction between the clinical response to a cysLT(1) antagonist, pranlukast, and DNA sequence variant A(-444)C in leukotriene C(4) synthase (LTC(4) S) gene in Japanese patients with moderate asthma. The frequency of LTC(4) S C(-444) allele was 21.6% in the Japanese general population (n = 171) and 19.4% in the asthmatic subjects ( n= 349). A 4-week prospective, open trial of pranlukast (225 mg twice daily) was performed in 50 patients with moderate asthma who had been well controlled with inhaled corticosteroid (beclomethasone 400-800 microg/day or fluticasone 200-400 microg/day). The C(-444) allele carriers (n = 16) responded better to pranlukast compared to the A(-444) allele homozygotes ( n= 31) [14.3 5.3% vs. 3.1 2.4% improvement of forced expiratory volume in one second (FEV(1) ), 0.01], while LTC(4) S genotype-stratified response to inhaled beta-agonist salbutamol (200 microg) was not observed (17.5 2.1% vs. 18.7 2.2% improvement of FEV(1) ). Univariate analysis demonstrated that the better response to pranlukast (more than 10% improvement of FEV(1) ) was correlated with LTC(4) S genotype (P < 0.01) and pretreatment airway reversibility to salbutamol (P < 0.01), but not with sex, age, atopic status, urinary leukotriene E(4) excretion rate, or daily dose of inhaled corticosteroid. Furthermore, multivariate regression analysis suggested that LTC(4) S genotype and the bronchodilatory effect of salbutamol were independent variables to predict the clinical response to pranlukast (P < 0.05). We conclude that LTC(4) S genotype is predictive of the clinical response to a cysLT(1) antagonist, pranlukast, in Japanese patients with moderate asthma.

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Prostaglandins and thromboxanes are important modulators of airway physiology. The synthesis of these mediators depends on two isoforms of cyclooxygenase (COX), constitutive COX-1 and inducible COX-2. COX-2 expression has been observed in various inflammatory diseases, but not all aspects of the expression and the role of COX-2 in conditions of allergic inflammation such as asthma are clear. In the present study, we examined the 72-h kinetics of the expression of COX-isoform mRNA in ovalbumin-sensitized and -challenged guinea-pig lungs. The sensitized animals showed a robust and transient induction of COX-2 mRNA expression within 1 h after ovalbumin challenge, whereas their COX-1 mRNA levels remained unchanged. Upregulation of the level and activity of COX-2 protein followed the induction of COX-2 mRNA. Lung slices harvested from ovalbumin-challenged animals released more prostaglandin D(2) and prostaglandin E(2) spontaneously or in response to A23187 (10 microM) ex vivo than did those from unchallenged animals. This response was significantly blocked by the COX-2 selective inhibitors, NS-398 and JTE-522. In vivo administration of NS-398 significantly inhibited the accumulation of eosinophils and neutrophils in the lungs. In conclusion, de novo COX-2 expression during allergic inflammation modifies prostanoid synthesis in the lung and airway pathophysiology.