Early Zebrafish Embryogenesis Is Susceptible to Developmental TDCPP Exposure

Abstract

Background: Chlorinated phosphate esters (CPEs) are widely used as additive flame retardants for low-density polyurethane foams and have frequently been detected at elevated concentrations within indoor environmental media.Objectives: To begin characterizing the potential toxicity of CPEs on early vertebrate development, we examined the developmental toxicity of four CPEs used in polyurethane foam: tris(1,3-dichloro-2-propyl) phosphate (TDCPP), tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), and 2,2-bis(chloromethyl)propane-1,3-diyl tetrakis(2-chlorethyl) bis(phosphate) (V6).Methods: Using zebrafish as a model for vertebrate embryogenesis, we first screened the potential teratogenic effects of TDCPP, TCEP, TCPP, and V6 using a developmental toxicity assay. Based on these results, we focused on identification of susceptible windows of developmental TDCPP exposure as well as evaluation of uptake and elimination of TDCPP and bis(1,3-dichloro-2-propyl)phosphate (BDCPP, the primary metabolite) within whole embryos. Finally, because TDCPP-specific genotoxicity assays have, for the most part, been negative in vivo and because zygotic genome remethylation is a key biological event during cleavage, we investigated whether TDCPP altered the status of zygotic genome methylation during early zebrafish embryogenesis.Results: Overall, our findings suggest that the cleavage period during zebrafish embryogenesis is susceptible to TDCPP-induced delays in remethylation of the zygotic genome, a mechanism that may be associated with enhanced developmental toxicity following initiation of TDCPP exposure at the start of cleavage.Conclusions: Our results suggest that further research is needed to better understand the effects of a widely used and detected CPE within susceptible windows of early vertebrate development.

Toxicogenomic Responses of Zebrafish Embryos/Larvae to Tris(1,3-dichloro-2-propyl) Phosphate (TDCPP) Reveal Possible Molecular Mechanisms of Developmental Toxicity

“…8 Furthermore, by serial exposure scenarios, the cleavage period was recognized as a sensitive window for developmental TDCPP exposure. 8 However, no morphological alterations were observed during this period (cleavage). 8 In this study, we increased the observation time and found that exposure to 3 μM TDCPP inhibited cell rearrangement at 4 hpf, caused delay in epiboly at 5.7 and 8.5 hpf, and lead to abnormal development (e.g., short tail, reduced body size) and lethality between 14 and 45 hpf.…”

“…8 However, no significant effects on cell morphology during cleavage (0.75−2 hpf) were observed. 8 Developmental toxicity of TDCPP was reported in a number of previous studies, but the molecular mechanisms involved remain largely unknown. In this study, we used the zebrafish embryo/larvae as a vertebrate model to further evaluate the teratogenic effects of TDCPP during development and to investigate the molecular mechanisms of toxicity of this compound using a combination of transcriptomics and proteomics.…”

“…8,10 Furthermore, by testing a series of exposure scenarios, McGee et al identified the cleavage period as a susceptible window for developmental TDCPP exposure, and further genome methylation analysis suggested that delays in remethylation at 2 hpf might be responsible for developmental toxicity of TDCPP to zebrafish embryos. 8 However, no significant effects on cell morphology during cleavage (0.75−2 hpf) were observed. 8 Developmental toxicity of TDCPP was reported in a number of previous studies, but the molecular mechanisms involved remain largely unknown.…”

Multiple bio-analytical methods to reveal possible molecular mechanisms of developmental toxicity in zebrafish embryos/larvae exposed to tris(2-butoxyethyl) phosphate

“…Previous studies have demonstrated that several OP esters cause developmental toxicity and endocrine disruption in vivo and in vitro (Crump et al, 2012;Dishaw et al, 2012;Farhat et al, 2013;Fu et al, 2013;Liu et al, 2012bLiu et al, , 2013McGee et al, 2012McGee et al, , 2013Wang et al, 2013). For example, exposure of zebrafish embryos to tris(1,3-dichloro-2-propyl) phosphate (TDCPP) disrupted embryogenesis and caused larval malformation, with median lethal concentrations (LC 50 ) ranging from 3.7 to 7.0 mg/L (Fu et al, 2013;Liu et al, 2013;McGee et al, 2012;Wang et al, 2013).…”

“…For example, exposure of zebrafish embryos to tris(1,3-dichloro-2-propyl) phosphate (TDCPP) disrupted embryogenesis and caused larval malformation, with median lethal concentrations (LC 50 ) ranging from 3.7 to 7.0 mg/L (Fu et al, 2013;Liu et al, 2013;McGee et al, 2012;Wang et al, 2013). In chicken embryos, Farhat et al (2013) reported that injection of TDCPP or tris(1-chloro-2-propyl) phosphate (TCPP) delayed pipping, reduced tarsus length, and changed hormone concentrations and mRNA levels included in xenobiotic metabolism and thyroid hormone pathways.…”