No abstract

Sodium fluoride (NaF) is associated with embryonic and fetal development abnormalities, but the mechanism by which this occurs is unclear. DNA methylation, an important epigenetic reprogramming mechanism, is essential for normal embryonic development. Thus, we investigated the effect of NaF on DNA methylation in early mouse embryos, as well as mouse sperm and liver using bisulfite sequencing and ELISA. Data indicate that H19, a paternally imprinted gene, compared to control embryos, was less methylated in 8-cell embryos from pregnant mice treated with NaF (100 mg/l) in drinking water for 48 h. Peg3, a maternally imprinted gene, and the Line1 repeated sequence were similarly methylated in NaF-treated and control embryos. Oral ingestion of NaF for 35 days did not significantly change Line1 and genomic global DNA methylation in the liver. H19, Rasgrf1, Line1, and genomic global DNA methylation were also similar in NaF-treated and control sperm. Female mice mated with NaF-treated male mice (35 days) had less methylated H19, but Peg3 was significantly more methylated. Line1 was similarly methylated in treated 8-cell embryos, compared to control embryos. NaF treatment of male mice before copulation significantly increased the expression of H19 in blastocysts, whereas H19 expression was not detected in 8-cell embryos. Data suggest that NaF may interact directly with the embryo to disrupt the maintenance of normal gene imprinting during pregnancy. Long-term NaF exposure of males may not directly affect DNA methylation of the sperm and liver, but the sperm may signal to early embryos with abnormal gene imprinting.

No abstract

Laboratory data have demonstrated that cadmium (Cd) may induce neuronal apoptosis. However, little is known about the role of autophagy in neurons. In this study, cell viability decreased in a dose- and time-dependent manner after treatment with Cd in PC-12 cells. As cells were exposed to Cd, the levels of LC3-II proteins became elevated, specific punctate distribution of endogenous LC3-II increased, and numerous autophagosomes appeared, which suggest that Cd induced a high level of autophagy. In the late stages of autophagy, an increase in the apoptosis ratio was observed. Likewise, pre-treatment with chloroquine (an autophagic inhibitor) and rapamycin (an autophagic inducer) resulted in an increased and decreased percentage of apoptosis in contrast to other Cd-treated groups, respectively. The results indicate that autophagy delayed apoptosis in Cd-treated PC-12 cells. Furthermore, co-treatment of cells with chloroquine reduced autophagy and cell activity. However, rapamycin had an opposite effect on autophagy and cell activity. Moreover, class III PI3 K/beclin-1/Bcl-2 signaling pathways served a function in Cd-induced autophagy. The findings suggest that Cd can induce cytoprotective autophagy by activating class III PI3 K/beclin-1/Bcl-2 signaling pathways. In sum, this study strongly suggests that autophagy may serve a positive function in the reduction of Cd-induced cytotoxicity.