CeO(2) Nanomaterials from Diesel Engine Exhaust Induce DNA Damage and Oxidative Stress in Human and Rat Sperm In Vitro

Cerium dioxide nanomaterials (CeO(2) NMs) are widely used in nano-based diesel additives to decrease the emission of toxic compounds, but they have been shown to increase the emission of ultrafine particles as well as the amount of released Ce. The Organization for Economic Cooperation and Development included CeO(2) NMs in the priority list of nanomaterials that require urgent evaluation, and the potential hazard of aged CeO(2) NM exposure remains unexplored. Herein, human and rat sperm cells were exposed in vitro to a CeO(2) NM-based diesel additive (called Envirox(TM)), burned at 850 °C to mimic its release after combustion in a diesel engine. We demonstrated significant DNA damage after in vitro exposure to the lowest tested concentration (1 µg·L(−1)) using the alkaline comet assay (ACA). We also showed a significant increase in oxidative stress in human sperm after in vitro exposure to 1 µg·L(−1) aged CeO(2) NMs evaluated by the H(2)DCF-DA probe. Electron microscopy showed no internalization of aged CeO(2) NMs in human sperm but an affinity for the head plasma membrane. The results obtained in this study provide some insight on the complex cellular mechanisms by which aged CeO(2) NMs could exert in vitro biological effects on human spermatozoa and generate ROS.