Bioconcentration and metabolism of BDE-209 in the presence of titanium dioxide nanoparticles and impact on the thyroid endocrine system and neuronal development in zebrafish larvae

Abstract

Interactions between organic toxicants and nanoparticles (NPs) in the aquatic environment may modify toxicant bioavailability and consequently the toxicant's environmental fate and toxicity. Therefore, we investigated the influence of titanium dioxide NPs (nano-TiO 2 ) on deca-BDE (BDE-209; a polybrominated diphenyl ether congener) bioconcentration, metabolism and its effects on the thyroid endocrine system in zebrafish (Danio rerio) larvae. Zebrafish embryos were exposed to various concentrations of BDE-209 alone or in combination with nano-TiO 2 (0.1 mg/L) until 7-day post-fertilization. Nano-TiO 2 can adsorb BDE-209 and nano-TiO 2 is taken up into developing zebrafish larvae. Chemical measurements showed that BDE-209 was bioconcentrated and metabolized in zebrafish larvae, and BDE-209 uptake was enhanced by nano-TiO 2 . Furthermore, increased BDE-209 metabolites were detected in larvae co-exposed with nano-TiO 2 . BDE-209 exposure significantly increased whole-body thyroid hormone contents (T 3 and T 4 ); T 4 content significantly increased in the larvae co-exposed with nanoTiO 2 . Nano-TiO 2 exposure alone did not induce generation of reactive oxygen species, lipid peroxidative oxidation, gene transcription or thyroid hormone levels. Upregulation of several gene transcriptions (tsh, tg, dio2) in the hypothalamic-pituitary-thyroid axis was also observed. Furthermore, co-exposure of nano-TiO 2 and BDE-209 caused a decrease in locomotion activity and downregulation of specific genes and proteins involved in the central nervous system of developing zebrafish larvae (e.g. myelin basic protein and a1-tubulin). These results indicate nano-TiO 2 enhances BDE-209 bioavailability and metabolism, leading to thyroid endocrine disruption and developmental neurotoxicity in zebrafish.

Impact of co-exposure with lead and decabromodiphenyl ether (BDE-209) on thyroid function in zebrafish larvae

“…We observed increased T 4 and T 3 content during a 6-day exposure to BDE-209, and this result is in accordance with a previous study in zebrafish embryos/larvae exposed to BDE-209 for 6 days (Wang et al, 2014). In contrast, decreased T 4 levels were observed in zebrafish embryos/larvae exposed to BDE-209 for 14 days (Chen et al, 2012).…”

Effects of titanium dioxide nanoparticles on lead bioconcentration and toxicity on thyroid endocrine system and neuronal development in zebrafish larvae

“…Thus, the alterations in the TH levels (decrease or increase) may produce several developmental effects during larval development, especially in the CNS (Chen et al, 2012b;Wang et al, 2014). In the present study, the total T 4 and T 3 concentrations decreased in all the Pb treatment groups.…”

“…In addition, previous studies have pointed out the enrichment of heavy metals in muscle, gills, liver, and kidney of fish (Fazio et al, 2014;Svecevicius et al, 2014;Wei et al, 2014). The NPs enhance the uptake heavy metal and organic toxicants (Baun et al, 2008;Tan et al, 2012;Wang et al, 2012Wang et al, , 2014. The previous studies also reported the enhanced uptake of toxicants in the presence of NPs, can greatly affect the toxicity of potential environmental pollutants (e.g., heavy metal and organic toxicants) Wang et al, 2014).…”

“…The NPs enhance the uptake heavy metal and organic toxicants (Baun et al, 2008;Tan et al, 2012;Wang et al, 2012Wang et al, , 2014. The previous studies also reported the enhanced uptake of toxicants in the presence of NPs, can greatly affect the toxicity of potential environmental pollutants (e.g., heavy metal and organic toxicants) Wang et al, 2014).…”

“…used SEM and TEM to show that nano-TiO 2 relatively little adhere to the surface of the larvae (Bar-Ilan et al, 2012;Wang et al, 2014). In addition, previous studies have pointed out the enrichment of heavy metals in muscle, gills, liver, and kidney of fish (Fazio et al, 2014;Svecevicius et al, 2014;Wei et al, 2014).…”