Ubiquitous applications of metallic oxide nanoparticles in diverse fields are leading to increased occupational and environmental exposure of humans and other species to these nanoparticles. Despite their known cytotoxicity in some cell models, their toxicity to humans is unknown. This project elucidated their effects on neural (astrocytes-like astrocytoma U-87; neurons-like neuroblastorna SK-N-SH) cells and normal human fibroblasts. We hypothesized these nanoparticles enter cells via endocytosis, thereby exerting cytotoxic effects. We are the first to identify several signaling molecules mediating cytotoxicity of SiO 2 nanoparticles in U-87 cells. Additionally, TiO2 micro- and nanoparticles induced, in 87 cells, both apoptosis and necrosis, or possibly a "new" cell death type showing both mechanisms. Our results clearly demonstrate the importance and need for further research in this new area of "nanomaterials pharmacology"; nevertheless, they may have pathophysiological implications in human health risks when exposed to metallic oxide nanoparticles in occupational and/or other environmental settings.
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