Effects Of Cerium Dioxide Nanoparticles Exposure On Embryonic Development And Its Mechanism During The Period Of Embryo Implantation

Lanthanide series Cerium dioxide nanoparticles(CeO2 NPs)are used extensively as catalysts,solar cells,solid fuel cells,ultraviolet absorbents,automotive catalytic converters,gas sensors,oxygen pumps,and metallurgical and glass/ceramic applications.Due to its strong oxidizing property,CeO2 NPs are predominantly employed as a diesel fuel additive.Their benefits include improved fuel-burning efficiency,and reduced green house gases and particle numbers in vehicle exhaust.It is used increasingly in nanotechnology,and subsequent unintentional release to the environment raises the potential for toxicological effects.Their health effects and ecological and environmental implications need to be determined for risk assessment.Due to their small size,nanoparticles can cross the skin,lung,and gut.And the nanoparticles also can penetrate the placental barrier and impair placental function,causing teratogenic effects in mice.Recently,conducted inhalation studies on CeO2 NPs showed the lungs are the major deposit organ while CeO2 NPs could penetrate from the lungs into the systemic circulation as they were found in other body organs.And recent publications have shown that exposure to CeO2 NPs can cause adverse effects to human health through generation of reactive oxygen species(ROS),leading to oxidative stress,inflammation,and stress-induced programmed cell death(apoptosis).Several studies have found that the oxidative stress could induce endoplasmic reticulum stress,influence autophagy,while the unbalance of endoplasmic reticulum stress and autophagy may relate to embryonic development.Nevertheless,the studies of potential toxicity associated with exposure of CeO2 NPs during the pregnancy were very limited.In this study,we builded an animal model in which pregnant mice were exposed to CeO2 NPs during the period of embryo implantation.Our study showed that the fetal loss rate of exposure group was significantly higher than control group(χ2=4.295,P<0.05).And then,we detected the endoplasmic reticulum stress and autophagy in mice uterus and placenta,in order to expore the effects and possible related mechanisms of CeO2 NPs on embryonic development.Next,we also adopted cell model(extravillous trophoblast)to further clarify the effects and related mechanisms of CeO2 NPs on the function of placenta.This will help us fully understand the toxicity of CeO2 NPs on embryonic development.Part Ⅰ Cerium dioxide nanoparticles exposure induced fetal loss during the period of embryo implantationCerium dioxide nanoparticles(CeO2 NPs)which used as a diesel fuel additive can be emitted into the ambient air leading to human inhalation.Although some studies have shown CeO2 NPs can cause adverse health effects,the toxicity of CeO2 NPs on embryonic development has not been well characterized.The exposure of environmental chemicals could disturb the uterine environment,which may affect embryo implantation and embryonic development.In order to expore the effects of CeO2 NPs on embryonic development,we selected the period of embryo implantation(GD3.5-6.5)as window period and dose of 10mg/m3 as inhaled exposure dose.We investigated the toxicity of CeO2 NPs exposure through weight,organ coefficient,pregnant-related indicators.The results showed that the weight and organ coefficient did not change while the mice exposed to CeO2 NPs during the period of embryonic implantation.We determined organism distribution of cerium using inductively coupled plasma mass spectrometry(ICP/MS).CeO2 NPs were clearly observed in lung,liver,kidney and placenta besides fetal liver and fetal brain.Furthermore,our results showed that the number of embryo implantation did not change at GD8,but the fetal loss rate of exposure group was significantly higher than control group(χ2=4.295,P<0.05).And we further found that CeO2 NPs could induce endoplasmic reticulum stress,then influence autophagy in placenta.Taken together,these results suggested that the increase of endoplasmic reticulum stress and autophagy in placenta might be the possible cause of embryonic developmental toxicity induced by CeO2 NPs exposure.Part Ⅱ Effects of cerium dioxide nanoparticles exposure on HTR-8/SVneo cells and its mechanismThe function of trophoblast cells plays an important role in placental formation,embryonic development,and pregnancy.In vivo study had demonstrated that exposure of CeO2 NPs during the period of embryo implantation might affect embryonic development because of the increase of endoplasmic reticulum stress and autophagy.In this study,HTR-8/SVne cells were exposed to Ce02 NPs for 24h,and the effects of CeO2 NPs were then evaluated,in order to further confirm that the effect of CeO2 NPs on embryonic development was due to damage caused by placental function.Our results showed that the relative factors of endoplasmic reticulum stress and autophagy were increased,which mean that CeO2 NPs could induce endoplasmic reticulum stress and influence autophagy.Next,We found that the invasion ability of HTR-8/SVneo cells decreased after CeO2 NPs exposure.Immunofluorescence assays showed that microtubule networks and microfilaments arrangement of HTR-8/SVneo cells altered obviously after being treated with CeO2 NPs.The level of the relative factor of autophagy and invasion(mTOR)in HTR-8/SVneo cells were decreased.Accordingly,the expression level of microRNA-99 family(miR-99a,miR-99b,miR-100),which may regulate mTOR,was significantly increased after CeO2 NPs exposure.Dual luciferase reporter assay indicated that the miR-99 family(mik-99a,miR-99b,mik-100)directly targeted mTOR.Taken together,we hypothesized that CeO2 NPs could induce endoplasmic reticulum stress,activate autophagy and inhibit invasion of HTR-8/SVneo cells,which plays an important role in embryo implantation and placental function,that could alter placental function and embryonic development.