Early effects of copper nanoxide on A549 epithelial cells

Purpose Previous in vitro studies on the toxicity of metal oxide nanoparticles demonstrated copper nanoxide (nCuO) as a powerful cytotoxic agent in human lung cells, but the pathways involved are not still clarified. This research aims to investigate the early cellular events occurring after exposure of human alveolar epithelial cells A549 to nCuO. In particular, by coupling the molecular responses with advanced microscopy analyses, cytotoxic effects have been linked to the modality of the cell-particle interaction and internalization. Methods TEM, DLS and AAS analyses were previously performed to characterize NP suspensions. Fluorescence microscopy, laser scanning microscopy and transmission electron microscopy were used to visualize the markers of cell-particle interactions and NP uptake, as well as the morphological changes induced in cells. Markers of oxidative stress, such as the induction of reactive oxygen species and lipid peroxidation, were measured and the quantification of defence proteins, such as HO-1 and HSP70, was performed. Results of the study We observed a significant dose-dependent cytotoxicity of CuO NPs at early exposure time which was only partially mediated by copper release into the medium. Particles demonstrated a great ability to quickly and deeply penetrate into the cell throughout endocytic structures but they appear also free in the cytoplasm or randomely distributed in different organules. The cell membrane and mitochondria appeared to be the main targets of nCuO, since their structural organization and functionality were altered as a consequence of the early oxidative events.