Water-Insoluble Fraction of Airborne Particulate Matter (PM_(10)) Induces Oxidative Stress in Human Lung Epithelial A549 Cells

摘要

Exposure to ambient airborne participate matter (PM) with an aerodynamic diameter less than 10 μm (PM_(10)) links with public health hazards and increases risk for lung cancer and other diseases. Recent studies have suggested that oxidative stress is a key mechanism underlying the toxic effects of exposure to PM_(10). Several components of water-soluble fraction of PM_(10) (sPM_(10)) have been known to be capable of inducing oxidative stress in in vitro studies. In this study, we investigated if water-insoluble fraction of PM_(10) (iPM_(10)) could be also capable of inducing oxidative stress and oxidative damage. Human lung epithelial A549 cells were exposed to 10 μg/mL of sPM_(10), iPM_(10) or total PM_(10) (tPM_(10)) preparation for 24 h. Here, we observed that all three PM_(10) preparations reduced cell viability and induced apoptotic cell death in A549 cells. We further found that, similar to the exposure to sPM_(10) and tPM_(10), the intracellular level of hydrogen peroxide (H_2O_2) in the iPM_(10)-exposed cells was increased significantly; meanwhile the activity of catalase was decreased significantly as compared with the unexposed control cells, resulting in significant DNA damage. Our data obtained from inductively coupled plasma-mass spectrometry (ICP-MS) assays showed that iron is the most abundant metal in all three PM_(10) preparations. Thus, we have demonstrated that, similar to sPM_(10), iPM_(10) is also capable of inducing oxidative stress by probably inducing generation of H_2O_2 and impairing enzymatic antioxidant defense, resulting in oxidative DNA damage and even apoptotic cell death through the iron-catalyzed Fenton reaction.