In Vitro Co-Exposure to CeO Nanomaterials from Diesel Engine Exhaust and Benzo()Pyrene Induces Additive DNA Damage in Sperm and Cumulus Cells but Not in Oocytes.

Benzo(a)pyrene (BP) is a recognized reprotoxic compound and the most widely investigated polycyclic aromatic hydrocarbon in ambient air; it is widespread by the incomplete combustion of fossil fuels along with cerium dioxide nanomaterials (CeO NMs), which are used in nano-based diesel additives to decrease the emission of toxic compounds and to increase fuel economy. The toxicity of CeO NMs on reproductive organs and cells has also been shown. However, the effect of the combined interactions of BP and CeO NMs on reproduction has not been investigated. Herein, human and rat gametes were exposed in vitro to combusted CeO NMs or BP or CeO NMs and BP in combination. CeO NMs were burned at 850 °C prior to mimicking their release after combustion in a diesel engine. We demonstrated significantly higher amounts of DNA damage after exposure to combusted CeO NMs (1 µg·L) or BP (1.13 µmol·L) in all cell types considered compared to unexposed cells. Co-exposure to the CeO NMs-BP mixture induced additive DNA damage in sperm and cumulus cells, whereas no additive effect was observed in rat oocytes. This result could be related to the structural protection of the oocyte by cumulus cells and to the oocyte's efficient system to repair DNA damage compared to that of cumulus and sperm cells.