Triphenyl phosphate-induced developmental toxicity in zebrafish: potential role of the retinoic acid receptor.
Using zebrafish as a model, we previously reported that developmental exposure to triphenyl phosphate (TPP) - a high-production volume organophosphate-based flame retardant - results in dioxin-like cardiac looping impairments that are independent of the aryl hydrocarbon receptor. Using a pharmacologic approach, the objective of this study was to investigate the potential role of retinoic acid receptor (RAR) - a nuclear receptor that regulates vertebrate heart morphogenesis - in mediating TPP-induced developmental toxicity in zebrafish. We first revealed that static exposure of zebrafish from 5-72h post-fertilization (hpf) to TPP in the presence of non-toxic concentrations of an RAR antagonist (BMS493) significantly enhanced TPP-induced toxicity (relative to TPP alone), even though identical non-toxic BMS493 concentrations mitigated retinoic acid (RA)-induced toxicity. BMS493-mediated enhancement of TPP toxicity was not a result of differential TPP uptake or metabolism, as internal embryonic doses of TPP and diphenyl phosphate (DPP) - a primary TPP metabolite - were not different in the presence or absence of BMS493. Using real-time PCR, we then quantified the relative change in expression of cytochrome P450 26a1 (cyp26a1) - a major target gene for RA-induced RAR activation in zebrafish - and found that RA and TPP exposure resulted in a ∼5-fold increase and decrease in cyp26a1 expression, respectively, relative to vehicle-exposed embryos. To address whether TPP may interact with human RARs, we then exposed Chinese hamster ovary cells stably transfected with chimeric human RARα-, RARβ-, or RARγ to TPP in the presence of RA, and found that TPP significantly inhibited RA-induced luciferase activity in a concentration-dependent manner. Overall, our findings suggest that zebrafish RARs may be involved in mediating TPP-induced developmental toxicity, a mechanism of action that may have relevance to humans.
Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
Gregory M
GM
Isales
Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
Rachel A
RA
Hipszer
Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
Tara D
TD
Raftery
Division of Environmental Sciences and Policy, Nicholas School of the Environment, Duke University, Durham, NC, USA.
Albert
A
Chen
Division of Environmental Sciences and Policy, Nicholas School of the Environment, Duke University, Durham, NC, USA.
Heather M
HM
Stapleton
Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA. Electronic address: volz@mailbox.sc.edu.
David C
DC
Volz
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D004357:Drug Synergism; D004625:Embryo, Nonmammalian / Q000187:drug effects; D047108:Embryonic Development / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D010755:Organophosphates / Q000633:toxicity*; D018168:Receptors, Retinoic Acid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000633:toxicity; D015027:Zebrafish / Q000196:embryology*
D010755:Organophosphates; D018168:Receptors, Retinoic Acid; D014874:Water Pollutants, Chemical; D003577:Cytochrome P-450 Enzyme System; C005445:triphenyl phosphate
Flame retardant; Retinoic acid receptor; Triphenyl phosphate; Zebrafish