Bioconcentration pattern and induced apoptosis of bisphenol A in zebrafish embryos at environmentally relevant concentrations

Abstract

Bisphenol A (BPA) is a well-known endocrine-disrupting chemical that is ubiquitously present in the environment. In the present study, 4-h post-fertilization (hpf) zebrafish embryos were exposed to various environmentally relevant concentrations of BPA (0.1, 1, 10, 100, and 1000 μg/L) until 72 and 168 hpf, and the accumulation pattern of BPA and its potential to induce toxicity through apoptosis were determined. Compared to BPA concentrations in larvae at 168 hpf, BPA concentrations in embryos exposed until 72 hpf were at relatively higher levels (p < 0.05) with higher bioconcentration factor (BCF) values. The nonlinear fitting analysis indicated that the BCF values of BPA in fish embryos/larvae were significantly correlated to the log10-transformed BPA exposure concentrations in water in an inverse concentration-dependent manner. Fish accumulated more BPA as the exposure concentrations increased; however, their accumulation capacity of BPA declined and tended to be saturated in the high exposure groups of BPA. Moreover, caspase-3 activity was significantly induced upon BPA exposure at 0.1, 1, 10, and 100 μg/L BPA at 72 hpf, and also at 10 and 100 μg/L BPA at 168 hpf. Correspondingly, exposure to 10 and 100 μg/L of BPA significantly increased the DNA fragmentation in the extracted DNA at 168 hpf as determined by DNA ladder analysis. In addition, the expression patterns of four genes related to apoptosis including caspase-3, bax, p53, and c-jun were significantly up-regulated (p < 0.05) in fish embryos/larvae upon BPA exposure at 72 and 168 hpf. Our results revealed that low and environmentally relevant concentrations of BPA could be significantly accumulated in zebrafish and induced apoptosis with involvement of the regulation of caspase-3 and other apoptosis-related genes.

Assaying uptake of endocrine disruptor compounds in zebrafish embryos and larvae

“…Comparing BPA uptake to E2 uptake can further inform future studies using nonsteroidal EDCs. While research testing the effects of BPA on development are abundant, many of these studies use environmentally-relevant low nanomolar concentrations of BPA in treatment water (Kinch et al, 2015; Kinch et al, 2016; Saili et al, 2012; Wu et al, 2017). Based on our results, the amount of BPA available to the embryo is substantially less than the reported EC 50 of BPA for the zebrafish estrogen receptors ERα, 599 nM, ERβ1, 18.9 µM, and ERβ2, 3.8 µM Another explanation for BPA effects at nanomolar concentrations is that BPA prevents the binding of endogenous estrogens to their receptors.…”

“…Wu and colleagues also used HPLC-MS to measure BPA uptake in zebrafish embryos from 4–72 hpf with multiple exposure concentrations (Wu et al, 2017). Comparing their 1 µg/L exposure (4.38 nM) to our 5 nM treatment from 48–72 hpf yields similar results, with 0.196 pmol/embryo via HPLC, and 0.190 pmol/embryo via our isotopic assay.…”

Assaying uptake of endocrine disruptor compounds in zebrafish embryos and larvae

“…Comparing BPA uptake to E2 uptake can further inform future studies using nonsteroidal EEDs. While research testing the effects of BPA on development are abundant, many of these studies use environmentally-relevant low nanomolar concentrations of BPA in treatment water (Kinch et al, 2015; Kinch et al, 2016; Saili et al, 2012; Wu et al, 2017). Based on our results, the amount of BPA available to the embryo is substantially less than the reported EC 50 of BPA for the zebrafish estrogen receptors ERα, 599 nM, ERβ1, 18.9 μM, and ERβ2, 3.8 μM (Pinto et al, 2014).…”

“…Wu and colleagues also used HPLC-MS to measure BPA uptake in zebrafish embryos from 4-72 hpf with multiple exposure concentrations (Wu et al, 2017). Comparing their 1 μg/L exposure (4.38 nM) to our 5 nM treatment from 48-72 hpf yields similar results, with 0.196 pmol/embryo via HPLC, and 0.190 pmol/embryo via our isotopic assay.…”

A Reduced Transcriptome Approach to Assess Environmental Toxicants Using Zebrafish Embryo Test

“…For the DEGs with EC between 0.001~0.01µM, only apoptosis relevant FOXO signaling pathway (FDR= 0.057, covered 4 genes) was enriched. Previous research reported BPA could induced apoptosis of mice spermatocytes 51 and zebrafish embryo 52 . A larger number of pathways, which included liver development, regulation of nucleobase-containing compound metabolic process, sensory organ morphogenesis, and DNA binding, were associated with the DEGs with EC between 0.01~0.1µM.…”