Comparison of 8-Isoprostane and Interleukin-8 in Induced Sputum and Exhaled Breath Condensate from Asymptomatic and Symptomatic Smokers

Abstract

Background: Markers of airway inflammation and oxidative stress have been mainly investigated in moderate/severe chronic obstructive pulmonary disease (COPD) or during its exacerbation. They have not been compared in noninvasive specimens such as exhaled breath condensate (EBC) and induced sputum in healthy nonsymptomatic smokers or in those who have symptoms and are at risk for COPD development. Objectives: To compare the relative proportions of 2 potential COPD biomarkers, 8-isoprostane and interleukin- 8 (IL-8) in the induced sputum and EBC sampled from the same subjects: nonsmokers (n = 14), healthy smokers (n = 17) and symptomatic smokers (n = 9) who are considered to be at risk for COPD. COPD patients with acute exacerbation (n = 10) were employed as positive controls. Methods: The levels of the aforementioned biomarkers in induced sputum and EBC were investigated using commercial biochemical techniques. Results: In induced sputum, the levels of 8-isoprostane and IL-8 were at least 10-fold higher compared to EBC levels in all groups. Healthy nonsmokers had the lowest levels, and patients with exacerbation of COPD the highest levels of 8-isoprostane in induced sputum and EBC. The same observation held true for IL-8 in induced sputum. Inverse correlations with lung function parameters were observed for both mediators. Conclusions: The levels of both potential markers were clearly higher in the induced sputum than in EBC. The results point to an advantage of induced sputum over EBC for assessing the degree of airway oxidative stress and inflammation in smokers with a potential risk for COPD development.