Silver Nanoparticle Exposure Attenuates the Viability of Rat Cerebellum Granule Cells through Apoptosis Coupled to Oxidative Stress

The impact of silver nanoparticles (AgNPs) on the central nervous system is a topic with mounting interest and concern and the facts remain elusive. In the current study, the neurotoxicity of commercial AgNPs to rat cerebellum granule cells (CGCs) and the corresponding molecular mechanism are closely investigated. It is demonstrated that AgNPs induce significant cellular toxicity to CGCs in a dose-dependent manner without damaging the cell membrane. Flow cytometry analysis with the Annexin V/propidium iodide (PI) staining indicates that the apoptotic proportion of CGCs upon treatment with AgNPs is greatly increased compared to the negative control. Moreover, the activity of caspase-3 is largely elevated in AgNP-treated cells compared to the negative control. AgNPs are demonstrated to induce oxidative stress, reflected by the massive generation of reactive oxygen species (ROS), the depletion of antioxidant glutathione (GSH), and the increase of intracellular calcium. Histological examination suggests that AgNPs provoke destruction of the cerebellum granular layer in rats with concomitant activation of caspase-3, in parallel to the neurotoxicity of AgNPs observed in vitro. Taken together, it is demonstrated for the first time that AgNPs substantially impair the survival of primary neuronal cells through apoptosis coupled to oxidative stress, depending on the caspase activation-mediated signaling.