The Toxicity Of Neodymium Oxide Nanoparticles On Early Development Of Zebrafish Embryos

Objective Neodymium oxide is a new type rare earth oxide material,which is widespread applied in multiple fields.With the nanotechnology application and development,occupational populations exposed to nano-neodymium oxide are also increasingly and the potential threat to health has been paid attention to people.The studies of nano-neodymium oxide are a few at present and the mechanism of toxicity has not been completely elucidated.Based on the background,the study focused on the effect of nanometer neodymium oxide on early development and revealed the mechanism of toxicity by multiple biological methods,in order to provide the practice guidance for workers related-occupational health.Method Nano-neodymium oxide nanoparticles were treated with continuously zebrafish embryos for 5 day at different concentrations.Subsequently,we observed and recorded the change of mortality,malformation rate and heart rate by morphological.We detected the Cmlc2 gene expression by whole-mount in situ hybridization.Meanwhile the protein and RNA of zebrafish embryos were extracted and the expression level of protein and gene related to autophagy and apoptosis were detected using western blot and real-time PCR.The change of cerebrovascular was observed with laser confocal microscope,then TUNEL staining and microinjection of m Cherry-LC3 m RNA were applied in Tg（Flk-1:EGFP）transgenic zebrafish embryos to explore the relationship between autophagy and apoptosis in cerebrovascular development.Results（1）Nano-Nd₂O₃ can be ingested by zebrafish.（2）The mortality and malformation rate of the embryos treated with Nd₂O₃ increased in a dose-dependent manner by morphological observation and statistics.（3）The decreased heart rate and severe arrhythmia were recorded in zebrafish embryos treated with nano-Nd₂O₃.The data of whole-mount in situ hybridization showed Cmlc2 m RNA up-regulation compared with control.（4）Nano-Nd₂O₃ affected the development of cerebrovascular,resulting in the disorder and disappearance of cerebrovascular.And the phenomenon was related to autophagy down-regulation and neuronal cell apoptosis by TUNEL staining and microinjection.（5）According to the results of molecular level detection,nano-Nd₂O₃induced apoptosis（cleaved-caspase 3、Bax、P53 were up-regulated）but not autophagy（LC3 was no significant changed）.Conclusions Nano-Nd₂O₃ can disturb the early embryonic development of zebrafish embryos,and its toxic mechanism may be related to the activation of apoptosis.