title: Effects of titanium dioxide nanoparticles on lead bioconcentration and toxicity on thyroid endocrine system and neuronal development in zebrafish larvae.
abstract: Nanoparticles (NPs) have attracted considerable attention because of their wide range of applications. Interactions between heavy metals (e.g., Pb) and NPs in aquatic environments may modify the bioavailability and toxicity of heavy metals. Therefore, this study investigated the influence of NPs (e.g., nano-TiO2) on the bioavailability and toxicity of Pb and its effects in the thyroid endocrine and nervous systems of zebrafish (Danio rerio) larvae. Zebrafish embryos (2-h post-fertilization) were exposed to five concentrations of Pb alone (0, 5, 10, 20, and 30μg/L) or in combination with nano-TiO2 (0.1mg/L) until 6 days post-fertilization. Results showed that the bioconcentration of Pb was significantly enhanced when combined with nano-TiO2 than when used alone. Zebrafish exposure to Pb alone at 30μg/L significantly decreased the thyroid hormone levels (T4 and T3), whereas nano-TiO2 treatment alone did not produce detectable changes. The levels of T4 and T3 were further decreased when Pb was combined with nano-TiO2 than when used alone. The transcription of the thyroid hormone-related factor tg gene was remarkably down-regulated by Pb treatment alone but up-regulated when Pb was combined with nano-TiO2. The significant up-regulation of tshβ gene and the down-regulation of TTR gene expression in the hypothalamic-pituitary-thyroid were observed in Pb with or without nano-TiO2 treatment groups. In addition, the transcription of genes involved in central nervous system (CNS) development (α-tubulin, mbp, gfap and shha) were significantly down-regulated by Pb and nano-TiO2 co-exposure as compared with Pb exposure alone. The locomotion activity analyzes confirmed that nano-TiO2 might enhance the toxicity of Pb to CNS development. These results suggest that nano-TiO2 increase bioconcentration of lead, which lead to the disruption of thyroid endocrine and neuronal system in zebrafish larvae.
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Miao
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Graduate University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Biran
authors.initials: B
authors.lastname: Zhu
authors.affiliation: College of Mechanical and Electronic Engineering, China University of Petroleum (East China), Qingdao 266580, China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Xiao
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Niguse Bekele
authors.initials: NB
authors.lastname: Dirbaba
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Bingsheng
authors.initials: B
authors.lastname: Zhou
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: hongjuanwu@hust.edu.cn.
authors.forename: Hongjuan
authors.initials: H
authors.lastname: Wu
mesh_terms: D000818:Animals; D004703:Endocrine System / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D007854:Lead / Q000633:toxicity*; D053768:Metal Nanoparticles; D013961:Thyroid Gland / Q000187:drug effects*; D013963:Thyroid Hormones / Q000235:genetics / Q000378:metabolism; D014025:Titanium / Q000494:pharmacology*; D014874:Water Pollutants, Chemical / Q000494:pharmacology / Q000633:toxicity; D015027:Zebrafish / Q000196:embryology*
chemical_list: D013963:Thyroid Hormones; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D007854:Lead; D014025:Titanium
keywords: Bioconcentration; Developmental neurotoxicity; Pb; Thyroid disruption; Titanium dioxide nanoparticles; Zebrafish larvae