Oxidative stress and ultrastructural changes in brain of rats chronically exposed to silver nanoparticles

Silver nanoparticles (AgNPs) are widely used in different applications, because they demonstrate strong antibacterial and antifungal activities. Over the last decades AgNPs have found applications in the food industry, textile engineering and silver-based consumer products (e.g. cosmetics, cleansers). Nanosilver is also used in a wide range of medical devices. For that reason human exposure to AgNPs is constantly increasing. However, the potentially negative health consequences of using materials which consist of silver nanoparticles have not been fully identified yet. Presently, there are only a few studies dedicated to investigating their neurotoxic potential. Most of them have been conducted using in vitro models. The aim of the present study was to investigate whether commercially available small-sized nanosilver particles induce neurotoxic effects in male adult rats. Animals were exposed to oral application of 10 + or - 4 nm nanosilver for 14 days. Using transmission electron microscopy (TEM) ultrastructural changes in cortical and hippocampal neurons were found mainly related to mitochondria and nuclei. The level of Bax and Bcl-2 protein which are involved in apoptosis was measured using Western blot. To assess oxidative stress in brain homogenates from exposed animals the level of membrane peroxidation was measured by the TBARs method. Additionally, the ratio of reduced to oxidized glutathione was investigated, as was the level of protein glutathionylation. The results indicate that the induction of oxidative stress under conditions of nanosilver exposure is one of the mechanisms of its neurotoxicity.