Wood smoke effects on epithelial cell lines and human airway cells

Abstract

Background: Exposure to emissions from biomass burning contributes to respiratory diseases, including obstructive airway diseases, acute lower respiratory tract infections and tuberculosis. The underlying mechanisms effects are not well understood. Aims and Objectives: To determine if exposure to wood smoke from incomplete combustion would elicit DNA damage on airway cells and epithelial cell lines. Methods: Fourteen healthy subjects underwent controlled chamber exposure on two occasions to filtered air and to sooty wood smoke (PM1 ~ 450 μg/m3), generated by a Swedish wood stove firing birch logs, according to double-blind randomized cross-over design. The subjects alternated exercise (VE=20 L/min/m2) and rest at 15-minute intervals for 2 hours. Bronchoscopies with sampling of bronchial wash (BW) and bronchoalveolar lavage (BAL) were performed 6 hours after exposure. Furthermore, alveolar type II cell line A549 and bronchial epithelial cell line BEAS-2B were exposed to wood smoke particles at four different doses. DNA damage was examined with the Comet assay and olive tail moment (OTM) was quantified. Results: Eosinophil numbers was increased in BAL after exposure to wood smoke, with no changes in other cells. Moreover, there was a dose-dependent increase in DNA damage in vitro when comparing PM concentrations above 75µg ml-1 to air. Conclusion: Short term exposure to sooty wood smoke induced a bronchoalveolar eosinophilic insult. This may link with the development and worsening of asthma after chronic exposure to wood smoke. Moreover, the observed DNA damage in vitro may explain the previously shown reduction in airway cells, which in turn may causally affect cellular immunity and increase the incidence of respiratory infection