Cytotoxicity and DNA-damage in human lung epithelial cells exposed to respirable α-quartz

Occupational exposure to respirable crystalline silica is associated with the development of silicosis, lung cancer and airways diseases. In order to assess cytotoxic effects and direct–oxidative DNA damage induced by short-term exposure to different doses of respirable α-quartz (NIST SRM1878a), we conducted a study using A549 cells. The cells were exposed to α-quartz at 25, 50, 100 μg/ml for 4 h and analysed by scanning electron microscope (SEM) and LDH release assay for cytotoxic effect evaluation. Cells were also exposed to 10, 25, 50, 100 μg/ml of α-quartz for 2 h and 4 h and analysed by Fpg comet test to evaluate direct and oxidative DNA damage. SEM observations of treated cells showed bleb development at lower doses and alterations of microvilli morphology at the highest dose. A slight LDH release was found only at 100 μg/ml. Fpg comet test showed a dose-related oxidative DNA damage in cells exposed for 2 h to quartz. Cells exposed for 4 h at the same concentrations showed a dose-related direct DNA damage and the presence of oxidative DNA damage at lower doses. The bleb induction on cell surface evidenced by SEM at lower doses correlates with the presence of oxidative DNA damage at 4 h. The cell surface modifications observed by SEM at 100 μg/ml indicate that high doses of quartz induce more evident cytotoxic effects confirmed by LDH analysis and correlate with the genotoxicity showed by comet assay.