Natrium Fluoride Influences Methylation Modifications and Induces Apoptosis in Mouse Early Embryos

Abstract

This study epigenetically examined the effect of fluoride on early embryos of Kunming mice administered with 0, 20 (low), 60 (medium), and 120 mg/L (high) sodium fluoride (NaF). The results showed that NaF repressed oocyte maturation, fertilization and blastocyst formation in all NaF-treated groups. Meanwhile, TUNEL assay showed that embryo apoptosis was induced dramatically in blastocyst stage at either low or medium doses, and in 8-cell stage at high dose, compared to the control, suggesting a dose-dependent effect. Furthermore, the immunostaining displayed global increases of DNA methylation, H3K9m2 and H3K4m2 with increasing dose, which were consistent with gene expression results, exhibiting general increases of DNMT1, DNMT3a, G9a, LSD1, and MLL1 and a reduction of JHDM2a in transcription and protein levels. More closely, the differential methylation domain in parentally imprinted gene H19 showed low methylation, while materanlly imprinted gene IGF2 showed high methylaiton in NaF-treated groups compared to the control group, which corresponded with high expression of H19 and low expression of IGF2 confirmed by qPCR. Collectively, we demonstrated that fluoride epigenetically impaired mouse oocyte maturation and embryonic development, supplying a better knowledge of fluoride in toxicology and a deeper evaluation of its potential influence in physiological and clinical implications.

Fluoride impairs oocyte maturation and subsequent embryonic development in mice

“…We found the fertilization and blastocyst formation to be significantly impaired after exposure to NaF, suggesting that oocytes exposed to excessive levels of NaF in vivo are characterized by reduced development potential. These data are in agreement with previous reports of reduced IVF success rate and decreased embryo development rates in in vitro ‐matured oocytes after exposure to NaF (Fu et al, ). After one month of feeding, there was no difference for the health of the mice between control and treatment group, and there was no abnormal behavior of the treated mice.…”

“…Epidemiological data shows that fluoride may cause adverse effects in the male and female reproductive systems of people living in fluorosis endemic areas (Susheela and Jethanandani, 1996;Ortiz-P erez et al, 2003). Importantly, there are growing evidences of a close link between increasing environmental fluoride levels and decreasing fertility rates (Freni, 1994;Zhou et al, 2013;Fu et al, 2014). In addition, in vitro exposure of human sperm to fluoride elicits a significant decline in sperm motility (Chinoy and Narayana, 1994).…”

Sodium fluoride disturbs DNA methylation of NNAT and declines oocyte quality by impairing glucose transport in porcine oocytes

“…If mice were administered with NaF, it increased DNA methylation globally and the expression of DNMT1 and DNMT3a in embryos. And the differential methylation domain in the parentally imprinted gene H19 showed low methylation, while the maternally imprinted gene IGF2 showed high methylation in NaF‐treated embryos (Fu et al, ). Taken together, NaF affected the development of embryos and fetus by disturbing the methylation pattern of important imprinted genes.…”

Sodium Fluoride Affects DNA Methylation of Imprinted Genes in Mouse Early Embryos

“…Over-intake of fluorine causes pathological changes such as dental fluorosis and liver damage although it is important for the metabolism of calcium and phosphor [Gupta et al, 2007]. Moreover, fluorine was recently reported to cross the placental barrier, affecting early embryonic development as well as testicular spermatogenesis in which DNA methylation is erased and re-established [Zhu et al, 2014].DNA methylation, especially methylation of imprinted genes, is an important epigenetic mechanism during early embryonic development and is susceptible to a series of environmental factors such as alcohol, fluorine, and radiation [Ge et al, 2013[Ge et al, , 2014Fu et al, Key Words DNA methylation · Embryonic development · H19 · Peg3 · Sodium fluoride …”

“…DNA methylation, especially methylation of imprinted genes, is an important epigenetic mechanism during early embryonic development and is susceptible to a series of environmental factors such as alcohol, fluorine, and radiation [Ge et al, 2013[Ge et al, , 2014Fu et al, 2014;Liang et al, 2014;Salah et al, 2014]. Pathological changes often ensue from DNA methylation defects.…”