Use of an avian hepatocyte assay and the avian toxchip polymerse chain reaction array for testing prioritization of 16 organic flame retardants

Abstract

Risk assessors are challenged with the task of providing data for an increasing number of priority chemicals. High-throughput toxicity screening methods--which permit rapid determination of toxic, molecular, and/or biochemical effects of a wide range of chemicals--are essential to help meet this demand. The avian embryonic hepatocyte in vitro screening method has been utilized in the authors' laboratory to assess the effects of a wide range of environmental contaminants on cytotoxicity and mRNA expression of genes associated with xenobiotic metabolism, the thyroid hormone pathway, lipid metabolism, and growth. Sixteen structurally variable organic flame retardants (OFRs)--including tetrabromoethylcyclohexane (TBECH), tris(2-butoxyethyl) phosphate (TBEP), tricresyl phosphate (TCP), and tris(1,3-dichloro-2-propyl) phosphate (TDCPP)--were screened using the in vitro method in the present study. Hepatocytes from 2 avian species, chicken and herring gull, were prepared, and species differences in hepatocyte viability were observed for several OFRs. For example, TCP was not cytotoxic in chicken hepatocytes up to the highest concentration tested (300 µM), whereas the median lethal concentration (LC50) was 31.2 µM in herring gull hepatocytes. Effects on mRNA expression in chicken embryonic hepatocytes were determined using a 3 × 32 custom-made Avian ToxChip polymerse chain reaction array and were variable among OFRs; TCP, TDCPP, and tris(2,3-dibromopropyl) isocyanurate showed the most significant alterations among the target genes assessed. Overall, this rapid screening method helped prioritize OFRs for further assessment. For example, OFRs that elicited significant effects on cytoxicity or mRNA expression represent prime candidates for egg injection studies that determine adverse effects on the whole animal but are more costly in terms of time, money, and embryo utilization.

In ovo exposure to organophosphorous flame retardants: survival, development, neurochemical, and behavioral changes in white leghorn chickens

“…Our results fit this general pattern. Of all the findings here, the possible reduced survival rate at lower levels (100 ng/g) than observed for other OPFRs seem to support suggestions that TDCIPP might be a priority for further study among OPFRs just as Porter et al (2014) recommended from their in vitro work.…”

“…This study builds upon previous in vitro studies involving embryonic and adult birds showing that toxic responses in avian models can vary among OPFRs. For example,Porter et al (2014) used hepatocyte cultures from chickens and herring gulls to show that changes in gene expression and cytotoxicity can vary following exposure to 16 flame retardant chemicals. Notably TDCIPP and TMPP were among the most active in eliciting in vitro responses, though effects may differ between the liver and the brain.While the present study (that includes both structural and functional measures across multiple levels of biological organization) contributes new knowledge about the potential neurodevelopmental effects of relevant OPFRs towards birds, some limitations of the current study warrant mention.…”

Identification of a group of brominated flame retardants as novel androgen receptor antagonists and potential neuronal and endocrine disrupters

“…Several BFRs along with their metabolites have been shown to disrupt endocrine and reproductive systems (Khalaf et al, 2009;Legler and Brouwer, 2003;Porter et al, 2013;Wang et al, 2013) acting as either agonist or antagonist to different hormone receptors. A number of hydroxylated and methoxylated polybrominated diphenyl ethers (HO-/MeO-PBDEs) have recently been shown to possess antiandrogenic properties (Wang et al, 2013).…”

Review of OPFRs in animals and humans: Absorption, bioaccumulation, metabolism, and internal exposure research

“…Toxicological studies have shown that OPFRs have the potential to cause adverse reproductive, endocrine and systemic effects in animals as a result of long term exposure to animals (Dishaw et al, 2011;Liu et al, 2012;Porter et al, 2014;Van der Veen and de Boer, 2012). Aryl-OPFRs have been shown to contribute to heart toxicity by disturbing the expression of transcriptional regulators in zebrafish (Du et al, 2015).…”