Effect Of Di-(2-ethylhexyl) Phthalate Exposure During Pregnancy On Male Fetal Neurodevelopment

Background Phthalates?PAEs?has been widely used as plasticizer in various plastic products,causing high population exposure.PAEs has endocrine disrupting effects and neurodevelopmental toxicity of thyroid hormones?THs?.The previous study also found that the exposure of di-?2-ethylhexyl?phthalate?DEHP?in the early stage of birth could affect the THs transporter and its receptor in the hippocampus of mice,down the expression of the postsynaptic dense protein 95?PSD 95?and synaptophysin I?synapsin I?in the hippocampus of mice.THs is mainly transported by the mother body through the placenta,and the placenta plays a key role in the THs transport and synthesis of fetal development.PAEs is likely to interfere with the development of the offspring by interfering with the transhipment of THs through the placenta.Objective The role of placenta in THs endocrine disruption and neurodevelopmental toxicity was investigated by using DEHP as a representative.Methods After ICR mice conceive naturally,during the period of fetal mice neural tube closure?embryonic day 9.5,E9.5d?to begin synthesis of THs?E15.5d?,all pregnant mice were administered with different concentration of 0 mg/kg?emulsion of Tween80and 1%corn oil?,10 mg/kg,50 mg/kg and 200 mg/kg DEHP by gavage once a day?10mice per group?.All pregnant mice were conducted with 50 mg/kg bromodeoxyuridine?BrdU?administration in E14.5 d by subcutaneous injection.Seven pregnant mice from each group were sacrified underwent chloral hydrate in E15.5 d?volume of perfusion?,serum and amniotic fluid were collected to determinate the levels of THs including free triiodothyronine?FT3?,free thyroxine?FT₄?,triiodothyronine?T₃?and thyroxine?T₄?.by the automatic biochemical analyzer.Western blotting was used to detect the levels of fetal mices placental monocarboxylate transporter 8?MCT8?,organic anion transporting polypeptide 1C1?OATP1C1?and the thyroid hormone metabolic enzyme?Deiodinase?&?,DIO₂ and DIO₃?,thyroid hormone receptor?TR?1,TR?1?.Each group of the remaining three pregnant mice were killed after anesthesia in E18 d,take the male fetal brain,BrdU immunohistochemistry was used to detect the proliferation and migration of fetal brain cortical neurons.Results?1?The pregnant mice in each treatment group had no abnormalities in drinking water,body weight and general activities.There was no difference in body weight,brain weight,and brain ratio in each group.?2?There was no difference in serum THs among the pregnant mice in each group.The levels of FT₃ in amniotic fluid of 50 mg/kg and 200 mg/kg DEHP groups were significantly decreased?compared with the control group,P<0.05?.?3?In 50 mg/kg and 200 mg/kg DEHP group,the protein level of MCT8 and DIO₂ were decreased in male fetuses placenta,and the protein level of OATP1C1 and TR?1 in200mg/kg group was decreased?compared with the control group,P<0.05?,and there were no difference between the DIO₃ and TR?1 protein level in each group.?4?The number of BrdU positive cells in the cerebral cortex of male mice in 200mg/kg DEHP group decreased,56.3%was distributed in VZ-SVZ layer?control group:41.2%?,and the percentage of BrdU positive cells in the IZ layer of 50mg/kg group increased?compared with the control group,P<0.05?.Conclusion Exposure to higher doses of DEHP during pregnancy did not affect the level of maternal THs,but decreased the level of FT₃ in amniotic fluid,affecting the proliferation and migration of the cerebral cortex nerve cells in fetal rat,which may be related to the reduction of the level of MCT8,OATP1C1,and nuclear receptor TR alpha1 protein in the placental THs transporter.DEHP may affect the neural development of offspring by interfering with THs transport through placenta.