Role of airway lactoperoxidase in scavenging of hydrogen peroxide damage in asthma

Hydrogen peroxide (H(2)O(2)) that is mainly generated by neutrophils and eosinophils in asthma is known to be damaging to the airway and to contribute to airway inflammation. The purpose of the present study was to determine the contribution and the role of lactoperoxidase in scavenging airway hydrogen peroxide, in order to propose a therapeutic approach for asthma. The study was an open clinical trial. Twenty-five nonsmoking asthmatic patients were included in the study. Of them, 16 patients (64%) were male and 9 (36%) were female, with age ranging from 29 to 48 years (45.13 +/- 4.6). Of the 25 patients included in the study, only 16 patients completed the study; and they were eligible for analyses. Exhaled breath condensate was collected from all patients at the time of entering the study; and 2, 4 and 8 weeks later. All patients received dapson as a lactoperoxidase inhibitor at a dose of 50 mg daily for 8 weeks. The study was conducted during the period from January 2006 to end of October 2006. H(2)O(2) concentration was determined by an enzymatic assay. Determination of exhaled breath condensate for hydrogen peroxide concentration after 8 weeks of dapson usage indicated an increase (1.05 +/- 0.36 microM; 95% CI, 0.89-1.21) as compared to that at baseline (P < 0.0001), 2 weeks (P < 0.001) and 4 weeks (P > 0.05). The increase in hydrogen peroxide concentration in exhaled breath condensate after inhibition of lactoperoxidase by dapson advocates a potential role for lactoperoxidase in scavenging of hydrogen peroxide in asthmatic airway.