Diethylhexyl phthalate induces teratogenic effects through oxidative stress response in a chick embryo model.

Diethylhexyl phthalate (DEHP) is known as a persistent environmental pollutant. However, the possible effects of DEHP on human neural tube defects (NTDs) remain elusive. We set out to investigate the exposure of DEHP in human and explore the association of DEHP and NTDs. The level of DEHP in maternal urine was measured and analyzed by GC-MS. To further validate the results in human NTDs, chick embryos were used as animal models. Viability, reactive oxygen species (ROS) level, oxidative stress indicators and apoptosis were detected in DEHP-treated chick embryos. Our research revealed that the detection ratio of positive DEHP and its metabolites in maternal urine were observed dramatically higher in NTDs population than that in normal controls (P < 0.01, P < 0.05, respectively). Moreover, DEHP treatment (10-6 M) led to developmental toxicity in chick embryos via accelerating oxidative stress response and cell apoptosis, and changing the level of oxidative stress-related indicators. Moreover, high dose choline (100 µg/µl) could partially restrain the toxicity effects induced by DEHP. Our data collectively imply that the incidence of NTDs may closely associate with DEHP exposure, which disturbs the development of neural tubes by enhancing oxidative stress.

Oxidative stress response associates with the teratogenic effects of benzyl butyl phthalate (BBP).

Benzyl butyl phthalate (BBP) is a persistent environmental pollutant. BBP exposure and the possible effects on human neural tube defects (NTDs) remain elusive. In this study, we found that the detection ratio of positive BBP and its metabolites in maternal urine was obviously higher in NTDs' population than that in normal controls by GC-MS (P < 0.01, P < 0.05, respectively). Animal experiments showed that BBP treatment induced developmental toxicity in chick embryo by enhancing the levels of oxidative stress and cell apoptosis (P < 0.01). More interestingly, the supplement of high-dose choline (CHO, 10 5  µg/mL) could partially restore the teratogenic effects of BBP by inhibiting the occurrence of oxidative stress. Our data collectively suggest that BBP exposure may disturb neural tube development by strengthening oxidative stress. CHO can partially restore the toxicity effects of BBP. This study may provide new insight for NTD prevention.

Choline, not folate, can attenuate the teratogenic effects ofdibutyl phthalate (DBP) during early chick embryo development.

Dibutyl phthalate (DBP), a persistent environmental pollutant, can induce neural tube abnormal development in animals. The possible effects of DBP exposure on human neural tube defects (NTDs) remain elusive. In this study, the distribution of DBP in the body fluid of human NTDs was detected by GC-MS. Then, chick embryos were used to investigate the effects of DBP on early embryonic development. Oxidative stress indicators in chick embryos and the body fluid of human NTDs were detected by ELISA. The cell apoptosis and total reactive oxygen species (ROS) level in chick embryos were detected by whole-mount TUNEL and oxidized DCFDA, respectively. The study found that the detection ratio of positive DBP and its metabolites in maternal urine was higher in the NTD population than that in normal controls. 8-hydroxy-2 deoxyguanosine (8-OHDG) and malondialdehyde (MDA) were evidently upregulated and superoxide dismutase (SOD) was observably downregulated in amniotic fluid and urine. Animal experiments indicated that DBP treatment induced developmental toxicity in chick embryos by enhancing the levels of oxidative stress and cell apoptosis. MDA was increased and SOD was decreased in DBP-treated embryos. Interestingly, the supplement of high-dose choline (100 µg/µL), not folic acid, could partially restore the teratogenic effects of DBP. Our data collectively suggest that the incidence of NTDs is closely associated with DBP exposure. This study may provide new insight for NTD prevention.

Abnormality of maternal-to-embryonic transition contributes to MEHP-induced mouse 2-cell block.

Mono (2-ethylhexyl) phthalate (MEHP), an environmental contaminant, is known to cause many serious diseases, especially in reproductive system. However, little is known about the effect of MEHP on preimplantation embryo development. In this study, we found that the development of mouse 2-cell embryo was blocked by 10(-3) M MEHP. A significant increase in the level of reactive oxygen species (ROS) was observed in arrested 2-cell embryo following 10(-3) M MEHP treatment for 24 h. However, antioxidants, catalase (CAT), and superoxide dismutase (SOD), reduced intracellular ROS and protected MEHP-exposed embryos from death but failed to return the arrested embryos. Further experiments demonstrated that the level of apoptosis was not altered in live arrested 2-cell embryo and increased in dead arrested 2-cell embryo after MEHP treatment, which implied that ROS and apoptosis were not related with 2-cell block. During analysis of the indicators of embryonic genome activation (EGA) initiation (Hsc70, MuERV-L, Hsp70.1, eIF-1A, and Zscan4) and maternal-effect genes (OCT4 and SOX2), we found that MEHP treatment could significantly decline Hsc70, MuERV-L mRNA level and SOX2 protein level, and markedly enhance Hsp70.1, eIF-1A, Zscan4 mRNA level, and OCT4 protein level at 2-cell to 4-cell stage. Supplementation of CAT and SOD did not reverse the expression tendency of EGA related genes. Collectively, this study demonstrates for the first time that MEHP-induced 2-cell block is mediated by the failure of EGA onset and maternal-effect genes, not oxidative stress and apoptosis.

Effects of choline on sodium arsenite-induced neural tube defects in chick embryos.

Arsenic passes through the placenta and accumulates in the neuroepithelium of embryo, whereby inducing congenital malformations such as neural tube defects (NTDs) in animals. Choline (CHO), a methyl-rich nutrient, functions as a methyl donor to participate in methyl group metabolism. Arsenic methylation has been regarded as a detoxification process and choline (CHO) is the major source of methyl-groups. However, whether CHO intake reverses the abnormal embryo development induced by sodium arsenite (SA) and the relationship between CHO intake and arsenite-induced NTDs are still unclear. In this study, we used chick embryos as animal model to investigate the effects of SA and CHO supplementation on the early development of nervous system. Our results showed that the administration of SA led to reduction in embryo viability, embryo body weight and extraembryonic vascular area, accompanied by a significantly increased incidence of the failed closure of the caudal end of the neural tube. CHO, at low dose (25 µg/µL), reversed the decrease in embryo viability and the increase in the failed closure of the caudal end of the neural tube, which were induced by SA. In addition, CHO (25 µg/µL) inhibited not only the SA-induced cell apoptosis by up-regulating Bcl-2 level, but also the global DNA methylation by increasing the expressions of DNMT1 and DNMT3a. However, less significant difference was found between the embryos co-treated with SA and CHO (50 µg/µL) and the ones treated with SA alone. Taken together, these findings suggest that low dose CHO could protect chick embryos from arsenite-induced NTDs by a possible mechanism related to the methyl metabolism.