Combined toxic effects of MWCNTs and ZnO nanoparticle on the liver of common carp

Abstract As important emerging carbon nanostructured materials with large surface areas, carbon nanotubes (CNTs) can affect the fate of some pollutants. The impact of multi-walled CNTs (MWCNTs) on the toxic effects of ZnO nanoparticles (ZnONPs) remains eclusive. In this study, the histological changes and apoptosis of the liver of common carp (Cyprinus carpio) were investigated under four-weeks exposure of single ZnONPs or in combination with MWCNTs. The results demonstrated that ZnONPs individually induced pathological changes and apoptosis in the liver. After co-exposure to 50 mg L− 1 ZnONPs and 0.25 mg L− 1 MWCNTs, the pathological changes alleviation were observed at the microscopic level and ultrastructural level. Apoptotic rate of hepatocytes decreased by 52%. Moreover, the mRNA expression of apoptosis-related genes including caspase3, BAX, and XBP1 were significantly changed, indicating the complex interactions between them. In contrast, co-exposure to 50 mg L− 1 ZnONPs and 2.5 mg L− 1 MWCNTs resulted in more severe damage and apoptosis (apoptotic rate increased by 33%). In conclusion, low concentration of MWCNTs attenuated the toxic effect of ZnONPs on common carp, but high concentration of MWCNTs enhanced it. This study will contribute to the development of future risk assessment and management strategies of carbon nanomaterials.