Oxidative stress in rat brain but not in liver following oral administration of a low dose of nanoparticulate silver

While it is known that silver nanoparticles (AgNPs) can enter the brain, our knowledge of AgNP-induced neurotoxicity remains incomplete. We investigated the ability of 10 nm citrate-stabilized AgNPs to generate oxidative stress in brain and liver of adult male Wistar rats after repeated oral exposure for 14 days, using a low dose of 0.2 mg/kg b.w. as compared with the same dose of ionic silver (silver citrate). In AgNP-exposed animals, the level of reactive oxygen species (ROS), lipid peroxidation (MDA) and glutathione peroxidase (GPx) activity were found to be significantly higher in brain relative to the control group receiving saline. Administration of ionic silver (silver citrate) increased ROS and MDA levels in both tissues. Activities of GPx in brain so as superoxide dismutase (SOD) and catalase (CAT) in liver of exposed animals were also elevated. Besides, AgNPs and silver ions were both found to cause statistically significant decrease in the reduced-to-oxidized glutathione ratio (GSH/GSSG) in brain. The results show that exposure to a very low dose of particulate silver generates mild oxidative stress in the brain but not in the liver of rats, indicating a role of oxidative stress in AgNP-induced neurotoxicity.