新生期大鼠化学物暴露对睾丸DNA甲基化及精子生成的影响

目的 通过新生期大鼠暴露DNA甲基转移酶抑制剂(5-Aza-CdR)、镉(Cd)和多氯联苯153(PCB153),探讨化学物新生期暴露对SD大鼠睾丸DNA甲基化变化、细胞凋亡和精子生成的影响.方法 将出生3 d(postnatal day 3,PND3)SD大鼠随机分组,每组24只动物.经口给予溶剂对照5-Aza-CdR(0.025、0.250mg/kg)、PCB153(0.025、0.250、2.500mg/kg)和Cd(1、2、4mg/kg),连续暴露5 d.最后1次暴露24 h后,解剖每组的一半动物,剩余动物在无暴露条件下继续喂养至12周龄(成鼠)解剖.检测睾丸细胞凋亡和DNA甲基化水平.结果 与对照组比较,新生期大鼠5-Aza-CdR、PCB153和Cd暴露后,在12周龄时精子计数均呈下降趋势,差异有统计学意义(P<0.05).新生期化学物暴露后,与对照组相比,基因组整体DNA甲基化水平降低,新生期细胞凋亡上升,差异均有统计学意义(P<0.05). 5-Aza-CdR使p53启动子区BstUI位点甲基化水平下降,p53基因表达上调,提示p53通路可能是DNA甲基化诱导细胞凋亡的通路之一.新生期大鼠Cd暴露可诱导整体DNA甲基化变化,细胞凋亡增加,与对照组比较,差异有统计学意义(P<0.05),但p53 mRNA表达及p53启动子区BstUI位点甲基化水平和对照组相比,差异无统计学有意义(P>0.05),提示Cd暴露诱导的细胞凋亡可能是非p53通路依赖的.PCB153的体内暴露未发现基因组整体甲基化和细胞凋亡的明显变化.结论 新生期化学物体内暴露可诱导成年精子形成障碍.DNA甲基化异常和细胞凋亡可能是其中的机制之一.

Effect of neonatal exposure to environmental pollutants on the DNA methylation of rat testis

Objective To investigate the effects of neonatal exposure of DNA methylation inhibitor, Cadmium and PCB153 on DNA methylation, apoptosis and spermatogenesis in SD rats. Methods Neonatal SD rats were randomly divided into 10 groups and received oral administrations of PCB153 (0.025, 0.250, 2.500 mg/kg), or Cadmium(1, 2, 4 mg/kg), or positive control 5-Aza-CdR (0.025,0.250 mg/kg), or vehicle con-trol for five days from PND3. Half of the rats were killed 24 h after the last administration. The remains were fed until 12 weeks. Sperm numbers, apoptosis and DNA methylation levels in testis were investigated. Results The daily sperm production was significantly decreased in each neonatal exposed group(P<0.05). Neonatal rats exposed to 5-Aza-CdR and Cadmium reduced the global DNA methylation level, increased apoptosis, while PCB153 exposure did not significantly change DNA methylation and apoptosis. Conclusion Neonatal rats ex-posed to chemicals could reduce spermatogenesis via multiple pathways. Lower DNA methylation and in-creased neonatal apoptosis were suggested as one of the causes.