Silver nanoparticles induce apoptotic cell death in cultured cerebral cortical neurons

Silver nanoparticles (SNPs) have been widely produced and exploited in diverse products, primarily because of their antimicrobial properties. The present study investigated the induction of apoptotic cell death and oxidative stress in cultured cortical neurons in response to SNP exposure. In order to assess the toxicity of SNPs, the cultured cortical neurons were exposed to 0.4, 2, and 10 μg/mL of SNPs for 6, 12, and 24 h. Lactate dehydrogenase released from damaged cells was quantified and the levels of intracellular reactive oxygen species (ROS) were measured using 2′-7′-dichlorofluorescin diacetate. Apoptosis induced by SNPs was analyzed using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL), a DNA ladder assay and Western blot analysis. SNPs inhibited the viability of cerebral cortical neurons in a dose- and time-dependent manner. Levels of ROS increased significantly at 12 and 24 h after treatment. TUNEL showed that compared with controls, numerous apoptotic cells appeared in the treated cultures at 12 and 24 h after treatment. DNA fragmentation in SNP-exposed cells suggested apoptosis. Western blot analysis demonstrated that cleaved caspase-3 protein expression increased significantly in a time-dependent manner. These results suggest that SNPs cause cytotoxicity and neuronal apoptosis through increasing intracellular ROS production in cultured cortical neurons.