Abstract
With the development of nanotechnology, more and more nanomaterials have been produced. Titanium dioxide (TiO2) nanoparticle (NP) is one of the important nanoscale materials. Though TiO2 nanoparticles (NPs) have been widely used in industry and biomedical field, they would have some potential risk to human health. Furthermore, animal and cell experiments were found NPs can induce toxic effects against central nervous system, such as cell death, inflammation, and oxidative stress ... etc. In this study, we exposed central nervous system cells (Neuro-2a cell line (N2A), microglial cell line (BV-2), and astrocytes (ALT)) w/wo endotoxin (lipopolysaccharide (LPS)) to TiO2 NPs (5 nm and 30 nm) to investigate the direct effect of neurotoxicity of TiO2 on cells. We also established the co-culture/tri-culture systems, co-existence of two or three cell lines by transwell assay. Then, one of the cells (ALT or BV-2) were treated with TiO2 NPs to study the effects of cell-cell interaction through secreted cytokines and chemokines. The results show that TiO2 NPs induce CNS series cells to generate inflammatory substances, and high concentration of TiO2 NPs have more cytotoxic to ALT and BV2 than N2A. Uptake ability of TiO2 NPs were BV-2 > N2A > ALT, so we speculate that BV-2 microglia is principal cells of uptaking TiO2 NPs in the brain. LPS pre-treatment can activate cells, especially BV-2 which can ingest more nanoparticles and result in more serious damage to the cells, such as cell death, inflammation, oxidative stress... etc. TiO2 NPs in smaller size can induce CNS series cell to release more inflammatory substances. Therefore, we will use 3-5 nm TiO2 NPs to do indirect effect of subsequent experiments. We found that only direct contact with nanoparticles, the declined phenomenon in cell viability was observed except for BV2-N2A co-culture system. In terms of uptake of nanoparticles, the SSC value of the cells also only in contact with the nanoparticles have increased significantly. When exposed to TiO2 NPs and LPS, glia cells generate inflammatory substances and ROS, and these inflammatory substances affect other kinds of cells, such as glia cells and neuron, leading to cell morphology changed, inflammatory substances increased, oxidative stress, and even cells death. We believe that when TiO2 NPs passed into the central nervous system, TiO2 NPs were ingested by ALT or BV-2 cells causing cell death, oxidative stress, inflammation, and these conditions may cause damage to the central nervous system and lead to the generation of neurodegenerative diseases (such as Alzheimer's disease, Parkinson's s disease) . This study provides important information for nano titanium dioxide effects on the central nervous system series cells, and the results can supply a reference for future animal and human experiments.