Peroxynitrite Elevation in Exhaled Breath Condensate of COPD and Its Inhibition by Fudosteine

Background: Peroxynitrite (PN) formed by the reaction of nitric oxide and superoxide is a powerful oxidant/nitrosant. Nitrative stress is implicated in COPD pathogenesis, but PN has not been detected due to a short half-life (< 1 s) at physiologic condition. Instead, 3-nitrotyrosine has been measured as a footprint of PN release. Method: PN was measured using oxidation of 2',7'-dichlorofluorescein (DCDHF) in exhaled breath condensate (EBC) collected in high pH and sputum cells. The PN scavenging effect was also evaluated by the same system as PN-induced bovine serum albumin (BSA) nitration. Results: The mean (+/- SD) PN levels in EBC of COPD patients (7.9 +/- 3.0 nmol/L; n = 10) were significantly higher than those of healthy volunteers (2.0 +/- 1.1 mnol/L; p < 0.0001; n = 8) and smokers (2.8 +/- 0.9 mnol/L; p = 0.0017; n = 6). There was a good correlation between PN level and disease severity (FEV1) in COPD (p = 0.0016). Fudosteine (FDS), a unique mucolytic antioxidant, showed a stronger scavenging effect of PN than N-acetyl-cysteine on DCDHF oxidation in vitro and in sputum macrophages, and also on PN-induced BSA nitration. FDS (0.1 mmol/L) reduced PN-enhanced interleukin (IL)-1 beta-induced IL-8 release and restored corticosteroid sensitivity defected by PN more potently, than those induced by H2O2 in A549 airway epithelial cells. Conclusion: This noninvasive PN measurement in EBC may be useful for monitoring airway nitrative stress in COPD Furthermore, FDS has the potential to inhibit PN-induced events in lung by its scavenging effect. (CHEST 2009; 135:1513-1520)