Differences in bronchoalveolar cell response to nitrogen dioxide exposure between smokers and nonsmokers

We have previously reported on the bronchoalveolar inflammatory effects of the common air pollutant NO2 in nonsmokers. In this study, we have investigated these effects in tobacco smokers. Eight young nonbronchitic smokers and, as a reference group, eight healthy life-time nonsmokers were exposed to 3.5 ppm NO2 for 20 min. Bronchoalveolar lavage (BAL) was performed 3 weeks before and 24 h after exposure. The first recovered 20 ml was analysed separately and defined as the bronchial portion (BP), and the following fluid recovered as the bronchoalveolar portion (BAP). Before exposure, the smokers had significantly less CD3+ cells and more alveolar macrophages (AMs) in the BP and the BAP, as well as reduced AM phagocytosis in vitro compared to nonsmokers. After NO2 exposure, the smokers reacted with an increase of AMs and neutrophils in BAP. Nonsmokers reacted with an increase of neutrophils in BP, an increase of lymphocytes in BAP, and a tendency to reduced AM phagocytosis. In summary, young smokers and nonsmokers differed to some extent in their reactions to NO2 exposure. This is probably due to the pre-existing airway inflammation and compensatory mechanisms to oxidant stress in the smokers.