Cytotoxicity, Oxidative Stress, and Autophagy in Human Alveolar Epithelial Cell Line (A549 Cells) Exposed to Standardized Urban Dust

Exposure to urban airborne particulate matter (PM) associates with adverse health effects, but the exact mechanisms remain unclear. In this study, we focused on cytotoxicity (MTT), oxidative stress (DCF/FC), DNA damage (PI/FC), necrosis/apoptosis (FC), and autophagy (LC3 expression; WB/FC) triggered by urban dust (UD) in naive human alveolar epithelial A549 cells and in the cells with reduced glutathione (GSH). The A549 cells were grown in F12K/FCS media supplemented with coarse carbon black (CB; Huber990; 260 nm diameter; 200 μg·ml−1) or urban dust (UD; Standard Reference Materials; 200 μg·ml−1) for 24 h. To deplete intracellular glutathione (GSH), l-buthionine-(S,R)-sulfoximine (BSO; 100 mM; 24 h) was used. Pre-treatment with BSO depleted the cellular GSH by about 30%. A similar effect was noticed after UD. The CB was without any effects on the parameters tested, except for LC3 expression (autophagy) which increased by about twofold. However, UD decreased cell viability by about 27%, decreased cell proliferation in BSO pre-treated cells, increased ROS production, and increased both Hsp70 and LC3 proteins by about twofold, but most changes were unrelated to ROS-mediated GSH depletion. We conclude that urban dust-induced oxidative stress is important in PM toxicity, but other as yet unrecognized mechanisms are also involved.