Increased hydrogen peroxide concentration in the exhaled breath condensate of stable COPD patients after nebulized N-acetylcysteine.

BACKGROUND: The oxidative burden in the airways is a hallmark of chronic obstructive pulmonary disease (COPD).

AIMS: This prospective, cross-over, placebo (PL)-controlled study was designed to investigate the effect of N-acetyl-l-cysteine (NAC) on hydrogen peroxide (H(2)O(2)), nitrites and nitrates (NO(2)(-)+NO(3)(-)), and thiol (RSH) concentrations in exhaled breath condensate (EBC) in stable COPD patients (n=19, aged 52.6+/-15.6 years, 10 females, mean FEV(1) 95.2+/-23.8%, FEV(1)/FVC 69.1+/-11.4%).

METHODS: H(2)O(2), NO(2)(-)+NO(3)(-) and RSH concentrations in EBC were determined with homovanillic acid, NADPH-nitrite reductase assays and Ellman's reaction, respectively.

RESULTS: Thirty minutes after nebulization, H(2)O(2) concentration increased if levels after NAC (0.45+/-0.25microM) and PL (0.17+/-0.17microM) were compared in COPD patients (p=0.002). This increased H(2)O(2) level in EBC was no longer observed either after 90min: 0.16+/-0.09microM (PL 0.17+/-0.15microM) or 3h: 0.12+/-0.07microM (PL 0.21+/-0.23microM) (p=0.5 and 0.2, respectively). The levels of NO(2)(-) and NO(3)(-) did not differ between NAC and PL. There was no significant difference in RSH levels between nebulized NAC and PL. After nebulized NAC, however, exhaled RSH increased from 1.42+/-1.69microM (0min) to 2.49+/-2.00microM (30min), and 1.71+/-1.83microM (180min) (p=0.009 and 0.03, respectively, compared with 0min).

CONCLUSIONS: These data demonstrate that nebulized NAC transiently increases exhaled H(2)O(2) level, whereas it has no effect on other oxidative parameters.