Effects Of Combined Exposure Of Nano-titanium Dioxide And Tetrabromodiphenyl Ether On Transmission Of Maternal Factor(Thyroid Hormone) In Zebrafish

In the real water environment,a variety of pollutants,including pollutants,organic matter,nanoparticles and other pollutants exist in complex state,and the environmental behavior and complex toxic effects of pollutants under their interaction have attracted great attention.However,the current studies are mainly carried out under the condition of high dose（mg/L）combined exposure toxicity,which is insufficient to reflect the environmental authenticity.Therefore,based on the environmental issues in this research field,namely,nano can interact with organic pollutants in natural water,through in-depth study of the physical and chemical characteristics of nano titanium dioxide（TiO₂-NPs）and the new pollutant 2,2’,4,4’tetrabromodiphenyl ether（BDE-47）interaction,Furthermore,the interference effect of single and existing TiO₂-NPs on zebrafish embryos and adults as well as the maternal transmission effect of thyroid hormone were carried out to explore the maternal transmission mechanism,hoping to further explain the nature of the interaction between TiO₂-NPs and BDE-47 in a close to real environment.The mechanism of the effect of TiO₂-NPs on the toxicity of BDE-47 was revealed to provide a reference for the comprehensive assessment of the ecological risk of nanomaterials and pollutants in the real environment.（1）To investigate the bioavailability and developmental toxicity effects of TiO₂-NPs on zebrafish embryos under single exposure conditions.The results showed that the hatchability and survival rate of embryos（larval fish）had little effect,the abnormality rate changed significantly,the content of thyroid hormones T3 and T4changed little,and the expression of related genes did not change significantly.（2）A 28-day toxicity test was carried out on zebrafish embryos at the early life stage to study the developmental toxicity effect and thyroid endocrine disturbance of the zebrafish larvae exposed to long-term low-dose BDE-47 and TiO₂-NPs.The results showed that:Exposure to BDE-47 and TiO₂-NPs resulted in developmental toxicity,including increased mortality,increased malformation rate and decreased body length,affected the transcription levels of genes related to thyroid hormone synthesis,transport and metabolism in hypothalamic-pituitary-thyroid axis（HPT）of zebrafish,and increased the level of thyroid hormone T4 in larvae.In the high concentration exposure group,the combination with TiO₂-NPs enhanced the thyroid endocrine disrupting effect of BDE-47,but in the low concentration group,the effect was not significant in the exposed group.（3）On the basis of the above studies,adult zebrafish were exposed to b DE-47aqueous phase in the presence of TiO₂-NPs and single low-dose zebrafish for a long time,and the bioavailability,distribution differences of major tissues and organs and toxicological effects of parent generation（F0）on TiO₂-NPs and BDE-47 were determined.The results of developmental toxicity study of F1 generation larvae showed that maternal exposure to BDE-47 and TiO₂-NPs affected offspring reproduction and development,including increased mortality rate,deformity rate,body length reduction and hatchability reduction.Combined maternal exposure significantly affected T3 and T4 levels in female zebrafish and offspring,and affected HPT axis related gene expression.