Cellular responses induced by cerium oxide nanoparticles: induction of intracellular calcium level and oxidative stress on culture cells

Cerium oxide (CeO2) is an important metal oxide used for industrial products. Many investigations about the cellular influence of CeO2 nanoparticles have been done, but results are contradictory. It has been reported that CeO2 nanoparticles have an anti-oxidative effect in cells, but it has also been reported that CeO2 nanoparticles induce oxidative stress. We investigated the potential influence on cells and the mechanisms induced by CeO2 nanoparticles in vitro. We prepared a stable CeO2 culture medium dispersion. Cellular responses in CeO2 medium-exposed cells were examined. Cellular uptake of CeO2 nanoparticles was observed. After 24-h exposure, a high concentration of CeO2 nanoparticles (similar to 200 mg/ml) induced an increase in the intracellular level of reactive oxygen species (ROS); a low concentration of CeO2 nanoparticles induced a decrease in the intracellular ROS level. On the other hand, exposure of CeO2 nanoparticle for 24 h had little influence on the cell viability. Exposure of CeO2 nanoparticles increased the intracellular Ca2+ concentration and also Calpain was activated. These results suggest that CeO2 nanoparticles have a potential to induce intracellular oxidative stress and increase the intracellular Ca2+ level, but these influences are small.