Background: Cerium nanoparticles (CeNP) have an interesting potential in drug delivery, gene therapy, molecular imaging and medicine. The present study focuses on the effect of exposure of cerium nanoparticles and Cerium oxide (CeO2) on oxidative stress biomarkers in human lymphocytes. Materials and Methods: Lymphocytes were incubated for 24 , 48 and 72 h at 37 °C with different concentrations (15, 30, 60 and 120 mM) of CeNP and CeO2. In lymphocytes samples evaluated oxidative stress biomarkers such as total antioxidant capacity (TAC), lipid peroxidation (LPO) and catalase activity (CAT). All data were analyzed by one way ANOVA with Tukey post hoc test. The results showed that CeNP after 24 ,48 and 72 hours caused a increase in the TAC compared to CeO2 120mg/kg group. CeNP decreased LPO level and CAT activity compared with CeO2 120mg/kg group. Results: The present study showed that after treatment for 24, 48 and 72 hours, CeO2 is able to induce oxidative toxicity in human lymphocytes. Conclusion: The results suggest that ROS intermediates are responsible for Ceinduced oxidative damage in experimental lymphocytes. Therefore, CeNP plays an important role in the alteration of oxidative injuries of human lymphocytes
