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In the development process, starting from the primordial germ cells to mature sperm formation in DNA methylation patterns is a dynamic process of change, and plays an important role in order to maintain normal reproductive function. DNA methyltransferase (DNA methyltransferase, DNMT) activity and gene expression by the interference will be caused by abnormal DNA methylation patterns, leading to spermatogenesis disorder; areas of the promoter region of the gene regulation of apoptosis and cell cycle in cell development DNA methylation status change will lead to changes in gene expression, affect the process of apoptosis, also affect sperm formation. 5 - aza-deoxycytidine (5-Aza-2-deoxycytidine ,5-Aza-CdR) is a nucleoside homologues, can be incorporated into the DNA strands, interfering with DNA methylation, resulting in DNA hypomethylation can cause reproductive functions injury. Cadmium (Cadmium, Cd) and 153 (Polychlorinated bipeynel, PCB153), PCBs are persistent pollutants in the environmental media, in vitro experiments reported induced changes in DNA methylation, can cause reproductive function, including kinds of systems and functional injury. The critical period of neonatal testicular germ cells from the stationary phase into the re-split period, also the formation and maintenance of DNA methylation, therefore, the study newborn rats exposed to 5-Aza-CdR, Cd, and PCB153 model, the overall methylation of DNMT activity, Dnmts gene expression, and p53 gene promoter methylation detection of DNA methylation in neonatal chemicals exposure damage caused reproductive function. 3 days after birth (Postnatal Day 3, PND3) neonatal rats, randomized, 24 in each group. Respectively, after oral administration of 5-Aza-CdR of (0.025,0.25 mg / kg), PCB 153 (0.025,0.25,2.5 mg / kg) and Cd (1,2,4 mg / kg), 12 animals were killed after exposure 5d Another 12 animals continue feeding to 12 weeks of age were killed after collecting animal liver, brain, testes, and other organs, histopathological examination and immunohistochemical analysis, as well as the detection of DNA methylation. After exposure to 5-Aza-CdR, PND8 animal body weight compared with the control group significantly reduced, the difference was statistically significant (P <0.05): low dose group of animal 0.25mg/kg body weight still higher than the control group in the 12-week-old killed: PND8 and 12 week-old animals anogenital distance and organ coefficient exposed group compared with the control difference was not statistically significant. Histopathological examination of vacuoles degeneration found that PND8 testicular tissue. Adult testicular histology revealed no obvious abnormalities, but exposure to 5-Aza-CdR sperm production rate lower (P <0.05). Neonatal rat 5-Aza-CdR exposure can make PND8 testicular tissue overall methylation levels, DNA methyltransferase (DNA methyltransferase, DNMTase) decreased activity Dnmt3b as reducing the level of gene expression; 5-Aza-CdR exposure can increase PND8 testicular tissue apoptosis, P53 and Bax gene upregulation, compared with the control group, the difference was statistically significant (P <0.05), and Bcl-2 gene expression did not change significantly. 5-Aza-CdR exposure can reduce the P53 promoter methylation, compared with the control group, the difference was significant (P <0.05). The Cd exposure, PND8, animal body weight of the high-dose group compared with the control group showed statistically significant (P <0.05), while testicular pathology revealed no abnormalities. Pathological examination of the 12-week-old animals mature sperm in the testis seminiferous tubules significantly reduced cellular level disordered arrangement lumen visible clusters shedding of cells. 2,4 mg / kg dose group sperm production rate than the control group decreased significantly (P <0.05). Neonatal rats exposed to Cd, also can reduce the overall level of methylation of testicular tissue the DNMT activity decreased suppression Dnmt3a, Dnmt3b gene expression; exposed to similar 5-Aza-CdR exposure of Cd exposure also led to increased apoptosis of testicular tissue. significant difference with the control group (P <0.05). But with 5-Aza-CdR exposure of Cd exposure P53, bax, Bcl-2 gene expression changes in comparison with the control group showed no significant difference, while P53 methylation of the promoter region compared with the control group differences not statistically significant. PCB153 after exposure, animals, body weight, organ coefficient, anogenital distance and tissue pathology found no obvious abnormalities, sperm production rate in adulthood 0.25,2.5 mg / kg dose group and the control group showed a significant difference (P <0.05) . PCB153 exposure to chemicals of the aforementioned three, PND8 testicular tissue overall methylation, of DNMT activity Dnmts gene expression and control group was no significant difference; apoptosis simultaneously PND8 testicular tissue, apoptosis-related genes P53 Bcl-2 expression and p53 promoter methylation were not changed significantly. Shows that different chemicals affect neonatal testicular DNA methylation and apoptosis through a variety of channels, thereby affecting spermatogenesis, the specific mechanism needs further study.
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