Toxicity Mechanism Of CuO Nanoparticle In Human Lung Cells

With the rapid development of nanotechnology, engineered nanoparticles （ENPs）were used gradually in energy, biological and medicine fields. However, the usage,transport, disposal of ENPs inevitably result in their release into ambient air andpenetrate deep into the lungs, and evoke adverse effects to lung, and then poseunexpected health impacts to humans. As the basic unit of the life activities, cells havecharacteristics to use cells as test organism, such as short test cycle, easy-controlledculture conditions, high sensitivity, and it can reveal toxicity mechanism from themolecular level, so it is widely used in exploring toxicity mechanism of ENPs. In thisstudy, the human lung epithelial （A549） cells were chosen as test cells. The aim wasto investigate the cellular uptake and export copper oxide （CuO） ENPs to cells and theexact toxic mechanism. The results were present as follows:Toxicity of different concentration of CuO ENPs to A549cells was investigatedin this study. CuO ENPs （20to100mg/L） had significant toxicity to A549cellswhereas CuO bulk particles （BPs） showed much lower toxicity （24h IC50,58and15for CuO BPs and ENPs, respectively）. Therefore, A549cells exposed to15mg/L CuOENPs for24h was chosen for the following experiments of toxicity mechanism.Transmission electron microscopic analysis demonstrated CuO NP entry intoA549cells and organelles, including lysosomes, mitochondria and the nucleus.Simultaneously, CuO ENPs were observed in primary lysosome in the cytoplasm ofthe cells, suggesting that particles entry into the cells is through endocytosis ratherthan diffusion. Comparing the uptake content of CuO ENPs between the cells withand without NaN3pretreatment, endocytosis was confirmed to be the primarypathway of CuO ENPs uptake. CuO ENPs （15mg/L） induced mitochondrialdepolarization, possibly mediated by ROS generation. Intracellular CuO ENPs first generate ROS, which subsequently induces the expression of p38and p53andultimately causes DNA damage. A fraction of the CuO ENPs was exported to theextracellular environment and detoxification processes occurred in cells. Additionally,centrifugal ultrafiltration tubes were successfully employed to determine the dissolvedCu²⁺from CuO ENPs in the cell medium. Dissolved Cu²⁺ions contributed less thanhalf of the total toxicity caused by CuO ENPs. Thus, most of cytotoxicity was causedby the CuO ENPs themselves.