Acquired somatic mutations induced by oxidative stress may contribute to the molecular pathogenesis of chronic inflammatory airway diseases. The objective of this study was to assess the intensity of oxidative DNA damage and the presence of microsatellite
DNA instability (MSI), a marker of acquired somatic mutations, in patients with
COPD, patients with noncystic
fibrosis bronchiectasis, and control subjects.
METHODS: Induced sputum and peripheral blood from 97 subjects were analyzed; 36 patients with
COPD, 36 patients with
bronchiectasis, 15 smokers without
COPD, and 10 healthy control subjects.
DNA was extracted and analyzed for MSI.
8-hydroxy-2'-deoxyguanosine (8-OHdG), a specific marker of
oxidant-induced DNA damage, was measured in serum and sputum supernatants.
RESULTS: None of the patients with
bronchiectasis or control subjects (non-
COPD smokers, healthy subjects) exhibited any genetic alteration. In contrast, MSI was found in 38% of
COPD specimens. Sputum 8-OHdG was statistically significantly increased in
COPD when compared with subjects with
bronchiectasis (P = .0002), smokers without
COPD (P = .0056), and healthy subjects (P = .0003). Sputum 8-OHdG in MSI-positive patients with
COPD differed significantly from that of MSI-negative patients with
COPD (P = .04) and smokers without
COPD (P = .008), but was not statistically different (P = .07) among MSI-negative patients with
COPD and smokers without
COPD. Serum 8-OHdG was significantly increased in MSI-positive compared with MSI-negative patients with
COPD (P = .001), but was not statistically significant in smokers without
COPD (P = .09). Serum 8-OHdG was increased in smokers without
COPD compared with MSI-negative patients with
COPD (P = .009).
CONCLUSIONS: There is a clear disparity in
COPD regarding
oxidant-induced DNA damage and somatic mutations. This may reflect a difference in the oxidative stress per se or a deficient
antioxidant and/or repair capacity in the lungs of patients with
COPD.