RESUMO
BACKGROUND: Reactive oxygen species (ROSS) play an important role in the pathogenesis of asthma, and oxidative stress contributes to the initiation and worsening of inflammatory respiratory disorders (eg, asthma). Thus, antioxidant drugs may have a role in reducing or preventing damage in asthma. OBJECTIVE: The aim of the study was to investigate the antioxidant effect of zafirlukast, a leukotriene receptor antagonist, in asthma. METHODS: This prospective, controlled, in vitro study was conducted at KingKhalid University Hospital, Riyadh, Saudi Arabia. The generation of ROSS by polymorphonuclear neutrophil leukocytes (PMNs) in patients with mild to moderate asthma (forced expiratory volume in 1 second [FEVI], >70% of the predicted value) and healthy volunteers was assessed using chemiluminescence (CL) with phorbol 12-myristate 13-acetate (PMA) and opsonized zymosan (OPZ) in the presence of different concentrations of zafirlukast (1.25-60 µg/mL). The xanthine/xanthine oxidase (X-XOD) reaction was used to test the scavenging effect of the drug. RESULTS: Six asthmatic patients (4 women, 2 men; mean age, 30.8 years; meanFEVI, 82.5% of the predicted value) and 8 healthy volunteers (4 women, 4 men; mean age, 28.8 years) were enrolled. A dose-dependent inhibition of the CL response was observed in both groups. However, patients with asthma required higher concentrations of zafirlukast to achieve an inhibitory effect similar to that in healthy controls. This difference was significant at concentrations of 20 to 60 µg/mL (all, P ≤ 0.05). When PMNs were challenged with OPZ, inhibition was also dose dependent in controls at all concentrations (all, P ≤ 0.05), but the inhibitory effect was not significant in the asthmatic patients at any concentration. The difference in the inhibitory effect between the 2 groups was significant at 30, 40, and 60 µg/mL (P < 0.02, <0.01, and <0.01, respectively). The mean (SEM) viability of the PMNs in the healthy controls was significantly affected only at the highest concentration compared with the control saline dose (86.5% [5.8%] vs 97.0% [8.%]; P < 0.05). No scavenging effect of zafirlukast was found using the X XOD system. Incubating PMA-stimulated cells with zafirlukast (5 and 10 µg/mL) for 10 minutes to 1 hour significantly increased the inhibitory effect of the drug by 15% to 46% (all, P < 0.001). When zafirlukast was tested for reversibility of its inhibitory effect on ROS production, its action was found to be irreversible at a concentration of 30 µg/mL (P < 0.001) and partially reversible at 60 µg/mL compared with the baseline saline control. CONCLUSIONS: Zafirlukast inhibited ROS generation by PMNs in a dose-dependentmanner in asthmatic patients and healthy subjects. However, asthmatic patients required much higher concentrations compared with controls. The incubation of the stimulated cells with zafirlukast increased the inhibitory effect. This finding suggests that the therapeutic effect of zafirlukast in asthma may be in part related to its antioxidant action.
