Investigating Whether Epigenetic Changes Occur Following Gestational Exposure to Triphenyl Phosphate in C57Bl/6 Mice

Abstract

Triphenyl phosphate (TPP) is a chemical flame retardant and plasticizer which is added to both consumer and industrial products. While overt toxicity to TPP is relatively low, recent studies have begun to investigate the potential for TPP to act as an endocrine disrupting chemical causing long-term impacts on metabolism. The developmental origins of health and disease postulates that in utero exposures can have later in life effects on the developing fetus. While it has been shown that the maternal environmental, including chemical exposures, can affect fetal gene expression though the mechanism of action of this is still unclear. The aim of this research was to determine whether in utero TPP exposure in mice induced epigenetic changes which could contribute to potential alterations in fetal gene expression, and whether these changes were dose and/or sex-dependent. Pregnant C57Bl/6 mice were treated with 0, 5, 25 or 50 mg/kg of TPP on gestational days 8, 10, 12 and 14 via intraperitoneal injection before euthanization on gestational day 19. Fetal livers were collected and half of the liver was used for immunoblotting to assess changes in histone 3 acetylation, histone 4 hyperacetylation, monomethylation of histone 3 at lysine 9 and trimethylation of histone 3 at lysine 9. The other matched liver half was used to measure global DNA methylation levels using a plate assay. Results showed that there was a significant decrease in fetal DNA methylation following exposure to 50 mg/kg TPP in utero compared to the control independent of the sex of the fetus. There were no significant alterations in any histone modifications at any dose or sex following in utero TPP exposure. These results suggest that epigenetics is a viable pathway to induce changes in gene expression; however further investigation regarding the endocrine disrupting ability of TPP is required.