Ce3+ Ions Determine Redox-Dependent Anti-apoptotic Effect of Cerium Oxide Nanoparticles

Antioxidant therapy is the novel frontier to prevent and treat an impressive series of severe human diseases, and the search for adequate antioxidant drugs is fervent. Cerium oxide nanoparticles (nanoceria) are redox-active owing to the coexistence of Ce3+ and Ce4+ oxidation states and to the fact that Ce3+ defects, and the compensating oxygen vacancies, are more abundant at the surface. llanoceria particles exert outstanding antioxidant effects in vivo acting as well-tolerated anti-age and anti-inflammatory agents, potentially being innovative therapeutic tools. However, the biological antioxidant mechanisms are still unclear. Here, the analysis on two leukocyte cell lines undergoing apoptosis via redox-dependent or Independent mechanisms revealed that the intracellular antioxidant effect is the direct cause of the anti-apoptotic and prosurvival effects of nanoceria. Doping with increasing concentrations of Sm3+, which progressively decreased Ce3+ without affecting oxygen vacancies, blunted these effects, demonstrating that Ce3+/Ce4+ redox reactions are responsible for the outstanding biological properties of nanoceria.