TitleMono-substituted isopropylated triaryl phosphate, a major component of Firemaster 550, is an AHR agonist that exhibits AHR-independent cardiotoxicity in zebrafish.
Publication TypeJournal Article
Year of Publication2014
AuthorsGerlach, CV, Das, SR, Volz, DC, Bisson, WH, Kolluri, SK, Tanguay, RL
JournalAquat Toxicol
Date Published2014 Sep
KeywordsAnimals, Azo Compounds, Cardiotoxins, Cytochrome P-450 CYP1A1, Embryo, Nonmammalian, Embryonic Development, Enzyme Activation, Flame Retardants, Gene Expression Regulation, Developmental, Heart, Organophosphates, Polybrominated Biphenyls, Pyrazoles, Receptors, Aryl Hydrocarbon, Water Pollutants, Chemical, Zebrafish

Firemaster 550 (FM550) is an additive flame retardant mixture used within polyurethane foam and is increasingly found in house dust and the environment due to leaching. Despite the widespread use of FM550, very few studies have investigated the potential toxicity of its ingredients during early vertebrate development. In the current study, we sought to specifically investigate mono-substituted isopropylated triaryl phosphate (mITP), a component comprising approximately 32% of FM550, which has been shown to cause cardiotoxicity during zebrafish embryogenesis. Previous research showed that developmental defects are rescued using an aryl hydrocarbon receptor (AHR) antagonist (CH223191), suggesting that mITP-induced toxicity was AHR-dependent. As zebrafish have three known AHR isoforms, we used a functional AHR2 knockout line along with AHR1A- and AHR1B-specific morpholinos to determine which AHR isoform, if any, mediates mITP-induced cardiotoxicity. As in silico structural homology modeling predicted that mITP may bind favorably to both AHR2 and AHR1B isoforms, we evaluated AHR involvement in vivo by measuring CYP1A mRNA and protein expression following exposure to mITP in the presence or absence of CH223191 or AHR-specific morpholinos. Based on these studies, we found that mITP interacts with both AHR2 and AHR1B isoforms to induce CYP1A expression. However, while CH223191 blocked mITP-induced CYP1A induction and cardiotoxicity, knockdown of all three AHR isoforms failed to block mITP-induced cardiotoxicity in the absence of detectable CYP1A induction. Overall, these results suggest that, while mITP is an AHR agonist, mITP causes AHR-independent cardiotoxicity through a pathway that is also antagonized by CH223191.

Alternate JournalAquat. Toxicol.
PubMed ID24865613
PubMed Central IDPMC4090055
Grant ListP30 ES000210 / ES / NIEHS NIH HHS / United States
P30 ES000210 / ES / NIEHS NIH HHS / United States
P42 ES016465 / ES / NIEHS NIH HHS / United States
P42ES016465 / ES / NIEHS NIH HHS / United States