Investigation on cellular interactions of astrocytes with zinc oxide nanoparticles using rat C6 cell lines

Zinc oxide nanoparticles (ZnO NPs) are widely used in cosmetic industries and have also found important applications in electrical and chemical industries. It is well documented that inhaled ZnO NPs can reach the brain through the olfactory neuronal pathway and can interfere with the brain zinc homeostasis. Most of the studies focus on the toxicity of ZnO NPs on neuronal cells and microglia. Not much work is available on the bio interaction of ZnO NPs with astrocytes, the major cells involved in brain homeostasis. Therefore, this study focuses on the interaction of ZnO NPs with rat C6 glial cells. The results of this study reveal that the nanoparticles are taken up by the astrocytes and induce a time and dose dependent toxicological response which is indicated by the nanoparticle uptake studies and cell viability assays. Also the results of DCFH-DA (2',7'-dichlorofluorescein diacetate) assay show that the ZnO NPs induce strong oxidative stress in cells at 3 and 6h. However, at 24h the reactive oxygen species (ROS) detected in the nanoparticles treated groups were same as that of control. The mode of cell death induced by ZnO NPs was apoptosis as revealed by the nuclear condensation studies, live dead assay using acridine orange/ethidium bromide and apoptosis detection kit. This study, which explores the interaction of ZnO NPs with astrocytes, concludes that the persistence of particle can continue to have a damaging effect on the astrocytes. And hence the time of exposure and particle clearance by the system should be evaluated more thoroughly to prevent the health hazards due to these particles.