EN
Silver nanoparticles (NAg) possess antibacterial properties thus are widely used in many applications in medicine, life sciences and biotechnology. Nanoparticles can be found in vertebrate brain, but little is known about their neurotoxicity. The aim of this study was to investigate how NAg can contribute to neuronal cell death. In the study primary cultures of rat cerebellar granule cells (CGC) were used. We tested hypothesis concerning the role of glutamatergic NMDA receptors in NAg-evoked neurotoxicity. In our study changes in intracellular calcium (Ca2+) homeostasis, uptake of 45Ca2+, reactive oxygen species (ROS) production, mitochondrial membrane potential and cells viability were investigated. We used commercially available 0.2% polyvinylpyrrolidone (PVP)-coated NAg <100 nm. To avoid sedimentation and agglomeration, before application to the CGC culture, NAg were sonicated with fetal calf serum. NAg were applied in concentration 2.5–75 µg/ml for 10, 30 min or 24 h, depending on experiment. As a pharmacological tool 0.5 µM MK801, a noncompetitive inhibitor of NMDA receptor, was used. After 10 min incubation in the presence of 25–75 µg/ ml NAg dose dependent increase of 45Ca2+ concentration was observed in neurons. This increase was comparable to that evoked by 100 µM glutamate and was completely abolished by MK801. Using fluorescent intracellular calcium indicator fluo3 we observed increase in intracellular calcium level by 200% compared to control, which was partially diminished by MK801. ROS production was measured using fluorescent dye DCF. After 30 min incubation with 75 µg/ml NAg the increase by about 35% over control level was observed and application of MK801 reduced it significantly. Changes in mitochondrial membrane potential were determined using rhodamine (R123). We observed significant decrease in mitochondrial potential during 30 min incubation with different concentrations of NAg and also in this case administration of MK801 was protective. Cells viability was assessed after 24 h incubation with NAg µg/ml alone or together with MK801. Application of MK801 increased neuronal survival from 50% up to 80%. Our results show that excitotoxicity via activation of NMDA receptor, followed by calcium imbalance, destabilization of mitochondrial function and ROS production, seems to be important mechanism involved in neurotoxicity evoked by NAg in cultured neurons. Supported by grant NN401619938.