孕鼠交通性污染物暴露对其子代雄性睾丸DNA甲基化水平的影响

目的探讨孕鼠交通性污染物暴露对其雄性子代生殖系统和睾丸细胞DNA甲基化水平的影响。方法将孕鼠随机分为对照组和暴露组，暴露组孕鼠置于重庆市主城区某主要交通枢纽的隧道，从受孕第4天（d4）至d14每天染毒8 h，子代分娩后饲养至性成熟。在孕鼠染毒的d4、d8、d12、d14+对交通要道进行交通性污染物的采集和检测。暴露组和对照组各取3只子代雄鼠睾丸进行RRBS甲基化测序并用qRT-PCR方法检测目的基因Aldh7a1和Rpe的mRNA表达水平。结果交通要道的交通性污染物TSP、PM2.5、PM10、NOx的浓度和噪声分贝都超过对照组，差异有统计学意义（P<0.05）。与对照组比较，暴露组子代雄鼠睾丸细胞基因组有23个基因甲基化表达水平升高，35个基因甲基化表达水平降低（P<0.05），这些基因几乎涉及主要生精过程。与对照组相比，暴露组Aldh7a1和Rpe基因相对表达量减少。结论交通性污染物使子代雄性睾丸发生DNA甲基化的改变，可能是导致现代社会男性生殖功能受损的原因之一。

Effects of maternal exposure to vehicle exhaust on the reproductive system and DNA methylation in male offspring mice

Objective To explore the effect of exposure to vehicle exhaust in pregnant mice on the reproductive function and DNA methylation in male offspring mice. Methods Twenty pregnant mice were randomized into control group and vehicle exhaust exposure group (n=10) and exposed to routine laboratory condition and to vehicle exhaust for 10 consecutive days (8 h per day) in a tunnel with a heavy traffic, where the concentrations of TSP, PM10, PM2.5, SO2 and NOX and the decibel of noise were measured. The offspring mice were raised till reaching maturity, and the epididymides of the male mice were collected to test the weight coefficients, DNA methylation level, and mRNA levels of Aldh7a1 and Rpe. Results The body weight and the weight coefficients of the epididymides and testes differed significantly between the exposure group and the control group (P>0.05). The concentrations of TSP, PM2.5, PM10 and NOx and the decibel of noise were significantly higher in the traffic environment and the control environment (P<0.05). Reduced representation bisulphite sequencing (RRBS) and Gene ontology (GO) showed that 58 genes had significantly different methylation levels between the two groups, mostly relating to the process of spermatogenesis (P<0.05). Compared with the control group, Aldh7a1 and Rpe mRNA expressions in the testes were down-regulated significantly in the exposure group (P<0.05). Conclusion Exposure of pregnant mice to vehicle exhaust causes damages of the reproductive function in the male offspring mice.