ABSTRACT
BACKGROUND: Recently, the use of the antiepileptic drug valproic acid (VPA) for the treatment of psychiatric conditions has been on the rise. However, studies have shown that in utero VPA exposure can affect embryonic development, including being associated with congenital heart defects. One proposed mechanism of VPA-initiated teratogenicity is the inhibition of histone deacetylase, which is involved in the regulation of transcription factors that regulate cardiogenesis. Myocyte enhancing factor 2C (Mef2c), a transcription factor involved in the development of cardiac structure and cardiomyocyte differentiation, has been shown to increase in response to in utero VPA exposure, associating with contractile dysfunction and myocardial disorganization. METHODS: To characterize the effects of VPA on murine heart development, pregnant CD-1 mice were dosed with 400 mg/kg of VPA on gestational day (GD) 9. Using high-resolution ultrasound, we examined the effects of VPA on cardiac contractile function on GD 14-18, with fetal hearts being harvested on GD 19 for histological analysis. Lastly, we conducted quantitative real-time polymerase chain reaction to measure the relative Mef2c gene expression in GD 16 murine hearts. RESULTS: We observed structural anomalies at GD 19 in the hearts of VPA-treated mice. Additionally, our results showed alterations in measures of cardiac contractility, with a decrease or increase in cardiac contractile ability in VPA-treated mice depending on the GD and measurement taken. CONCLUSIONS: These results further characterize the effects of VPA on heart development and suggest that alterations in Mef2c gene expression, at least on GD 16, do not mediate VPA-induced cardiotoxicity in CD-1 mice.
Subject(s)
Fetal Development/drug effects , Fetal Heart/drug effects , Valproic Acid/adverse effects , Acetylation , Animals , Cell Differentiation/drug effects , Embryonic Development/drug effects , Female , Gene Expression Regulation, Developmental/drug effects , Heart Defects, Congenital/etiology , Heart Defects, Congenital/genetics , MEF2 Transcription Factors/metabolism , Male , Mice , Mice, Inbred Strains , Myocytes, Cardiac/drug effects , Organogenesis/drug effects , Pregnancy , Prenatal Exposure Delayed Effects , Transcription Factors/metabolism , Valproic Acid/metabolismABSTRACT
Triphenyl phosphate (TPhP) is an organophosphorus flame retardant and plasticizer that has been added to numerous consumer products in recent years. TPhP is not overtly toxic, however recent studies have suggested that it may have metabolic disrupting effects following developmental exposure. The present study aimed to investigate the developmental and potential metabolic effects of TPhP in a murine model. C57Bl/6 dams were exposed on gestational days (GD) 8, 10, 12, and 14 to 0, 5, 25, or 50 mg/kg TPhP via intraperitoneal injection. Dams were euthanized on GD19, maternal organs excised and weighed, fetal measurements taken, and maternal and fetal livers retained for analysis. A significant increase in placenta size of TPhP exposed mice was found. Maternal and fetal liver gene expression of insulin-like growth factor (Igf) 1 and 2, as well as downstream genes involved in Igf signaling were measured. Additionally, Igf1 protein levels were measured in both maternal and fetal liver. A significant decrease in transcript levels of Igf1 and Irs2 was detected in maternal livers, whereas a significant increase in transcript levels of all genes measured was detected in fetal liver. A significant decrease in Igf1 protein levels was detected in maternal liver, however the increase in Igf1 protein levels in fetal livers was not found to be statistically significant. These results support previous findings that TPhP does not cause overt structural developmental toxicity. These data also support the hypothesis that TPhP could disrupt maternal and fetal metabolism, justifying the need for follow-up studies to investigate further.
Subject(s)
Fetus/metabolism , Gene Expression Regulation, Developmental/drug effects , Insulin-Like Growth Factor I/metabolism , Liver/metabolism , Maternal Exposure , Organophosphates/toxicity , Signal Transduction/genetics , Animals , Female , Insulin/metabolism , Liver/drug effects , Liver/embryology , Male , Mice, Inbred C57BL , Organ Size/drug effects , Pregnancy , RNA, Messenger/genetics , RNA, Messenger/metabolism , Signal Transduction/drug effectsABSTRACT
Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon and carcinogen that is released into the environment through natural and anthropogenic sources. BaP toxicity is dependent on its metabolism by cytochrome P450s to the reactive metabolite benzo[a]pyrene diol epoxide (BPDE), which is strongly associated with increased mutation frequency. BaP can also be metabolized to benzo[a]pyrene quinones that can undergo redox cycling and induce oxidative stress. The purpose of this study was to examine if BaP exposure induces DNA double strand breaks (DSBs) and subsequently activate DNA DSB repair pathways in the CHO 3-6 cell line and pKZ1 mouse model. In vitro assessment of homologous recombination (HR) showed significantly increased HR frequency following exposure to 10µM of BaP. In vivo evaluations of BaP-induced DNA DSB repair demonstrated positive staining for intrachromosomal recombination events, which are associated with non-homologous end joining (NHEJ), in the lung and thymus of exposed animals that were statistically significant in the thymus when quantified by Western blotting. Gene expression analyses from mouse tissues showed significantly decreased expression of ATM and Xrcc6 in BaP-treated liver and lung. In addition, BaP exposure significantly reduced the expression of Xrcc5, p53, and DNA-PKcs in lung. Taken together, our results demonstrate that BaP increases DNA DSB repair in vitro and in vivo, and induces expression changes in DNA repair pathway genes. As repair of DNA DSBs is not error-free, aberrant DNA repair may be contributing to the mechanism of BaP-induced toxicity.
