In Vitro Co-Exposure to CeO2 Nanomaterials from Diesel Engine Exhaust and Benzo(a)Pyrene Induces Additive DNA Damage in Sperm and Cumulus Cells but Not in Oocytes

Benzo(a)pyrene (BaP) 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 (CeO2 NMs), which are used in nano-based diesel additives to decrease the emission of toxic compounds and to increase fuel economy. The toxicity of CeO2 NMs on reproductive organs and cells has also been shown. However, the effect of the combined interactions of BaP and CeO2 NMs on reproduction has not been investigated. Herein, human and rat gametes were exposed in vitro to combusted CeO2 NMs or BaP or CeO2 NMs and BaP in combination. CeO2 NMs were burned at 850 degrees C prior to mimicking their release after combustion in a diesel engine. We demonstrated significantly higher amounts of DNA damage after exposure to combusted CeO2 NMs (1 mu g center dot L-1) or BaP (1.13 mu mol center dot L-1) in all cell types considered compared to unexposed cells. Co-exposure to the CeO2 NMs-BaP 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.

Automated summary

Exposure to combusted CeO2 NMs or BaP resulted in significantly higher DNA damage in all cell types considered, while co-exposure to CeO2 NMs-BaP mixture induced additive DNA damage in sperm and cumulus cells. The potential protective effects of cumulus cells on oocytes and the efficient DNA damage repair system of oocytes compared to cumulus and sperm cells may explain the lack of additive effect observed in rat oocytes.