Iron Oxide Nanoparticle-induced Oxidative Stress and Genotoxicity in Human Skin Epithelial and Lung Epithelial Cell Lines

Iron oxide (Fe3O4) nanoparticles (IONPs) have received much attention for their utility in biomedical applications such as magnetic resonance imaging, drug delivery and hyperthermia. Recent studies reported that IONPs induced cytotoxicity in mammalian cells. However, little is known about the genotoxicity of IONPs following exposure to human cells. In this study, we investigated the cytotoxicity, oxidative stress and genotoxicity of IONPs in two human cell lines; skin epithelial A431 and lung epithelial A549. Prepared IONPs were polygonal in shape with a smooth surface and had an average diameter of 25 nm. IONPs (25-100 mu g/ml) induced dose-dependent cytotoxicity in both types of cells, which was demonstrated by cell viability (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide) and lactate dehydrogenase leakage assays. IONPs were also found to induce oxidative stress in a dose-dependent manner, evident by depletion of glutathione and induction of reactive oxygen species (ROS) and lipid peroxidation. Comet assay revealed that level of DNA damage was higher with concentration of IONPs in both types of cells. Quantitative real-time PCR analysis showed that following the exposure of cells to IONPs, the expression levels of mRNA of caspase-3 and caspase-9 genes were higher. We also observed the higher activity of caspase-3 and caspase-9 enzymes in IONPs treated cells. Moreover, western blot analysis showed that protein expression level of cleaved caspase-3 was up-regulated by IONPs in both types of cells. Taken together, our data demonstrates that IONPs have potential to induce genotoxicity in A431 and A549 cells, which is likely to be mediated through ROS generation and oxidative stress. This study suggests that genotoxic effects of IONPs should be further investigated at in vivo level.