Increased inflammatory markers in the exhaled breath condensate of cigarette smokers

Cigarette smoking induces an inflammatory response in the airways that may play a key role in the pathogenesis of chronic obstructive pulmonary disease. Noninvasive markers of inflammation may, therefore, be useful in monitoring the airways of smokers as well as in the screening of subjects at high risk of developing airway obstruction. The aim of the present study was to determine whether the concentrations of the pro-inflammatory cytokine, interleukin (IL)-6, is increased in the exhaled breath condensate of smokers and whether the number of cigarettes smoked has any influence on the exhaled concentrations. The possibility that exhaled IL-6 levels are related to exhaled carbon monoxide (CO) and lung function has also been explored. Another inflammatory marker, leukotriene (LT), was also measured. Twenty-one smokers (39+/-7 yrs, 13 male) and 14 nonsmokers (45+/-6 yrs, eight male) were recruited. IL-6 and LTB4 levels in the breath condensate were measured with an immunoassay kit and exhaled CO examined by means of a modified electrochemical sensor. Higher IL-6 and exhaled CO concentrations were found in current smokers (5.6+/-1.4 pg x mL(-1) and 16.7+/-5.5 parts per million (ppm)) than in nonsmokers (2.6+/-0.2 pg x mL(-1) and 2.1+/-0.6 ppm). Elevated concentrations of LTB4 were also observed in smokers compared to nonsmokers (9.4+/-0.4 pg x mL(-1) versus 6.1+/-0.3 pg x mL(-1)). In addition, there was a correlation between IL-6 concentrations, the number of cigarettes smoked per day, exhaled CO, LTB4 and lung function. Exhaled interleukin-6 and leukotriene B4 levels may be useful noninvasive markers of airway inflammation in cigarette smokers.