Apoptosis induced by titanium dioxide nanoparticles in cultured murine microglia N9 cells

Owing to the rapidly increasing output of nano-scale titanium dioxide (TiO2) particles, their potential risk for central nerve system (CNS) has elicited much concern recently. Microglia is the resident macrophage in CNS and essential for the homeostasis of the CNS microenvironment. They are sup-posed to response to nanoparticles depositing in the brain tissues. Therefore, we investigated the cy-totoxic effects of TiO₂ NPs on microglia N9 cells in vitro. Results of propidium iodide/fluorescein di-acetate (PI/FDA) double staining and MTT test clearly showed that TiO₂ NPs more efficiently affected the viability of microglia N9 cells. Further Hoechst 33258 staining and flow cytometric analysis proved that nano-scale but not normal scale TiO2 induced apoptosis in vitro. These data suggest that TiO₂ NPs can elicit apoptosis of N9 cells in vitro and thus present a potential risk for CNS.