孕期低剂量镉暴露对不同性别胎鼠肝脏发育的影响及其分子调控机制的研究

Effects of maternal cadmium exposure on the development of fetal livers of different genders and its molecular mechanisms

为探究镉对胎儿肝脏发育的毒性作用.拟选用15只性成熟的8周龄的雌性C57BL/6小鼠,与雄鼠交配见栓后,于妊娠第7.5 d(Embryonic 7.5,E7.5)时,随机分为3组(每组5只),分别通过饮用水暴露法饲喂0、20和40 mg·L^(-1)的氯化镉溶液,并于E14.5 d时收集各组小鼠的胎儿肝脏等组织.通过Ki67和TUNEL染色方法探究镉对不同性别胎鼠肝脏的增殖功能和凋亡功能的影响,并通过PCR芯片筛查和实时定量PCR方法检测镉处理组的雌性和雄性胎鼠肝脏中与细胞增殖和凋亡功能相关基因的表达变化.此外,我们还将通过石墨炉火焰原子吸收技术对镉处理组的雌性和雄性胎鼠的镉含量进行检测.结果显示:孕期低剂量镉暴露对胎儿体重、胎肝重量和肝脏指数均无显著性影响.在本实验条件下,镉对胎鼠肝脏的凋亡功能无显著性影响,但对增殖功能具有抑制作用,且该抑制作用具有雌性依赖性的特征.镉特异性诱导雌性胎鼠肝脏中NF1等多个细胞增殖功能相关基因以及TGF⁃β1信号通路分子的表达失衡;但对雄性胎鼠肝脏中相关基因的表达水平无显著性影响.镉在雌性胎儿组织中的积累量显著高于雄性胎儿组织.综上所述,孕期低剂量镉暴露特异性抑制雌性胎儿肝脏的细胞增殖功能,并诱导雌性胎儿肝脏中NF1等多个增殖功能相关基因以及TGF⁃β1信号通路分子的表达失衡,该性别依赖性的抑制作用可能与镉在雌性胎儿中相对较高的积累量相关.

The study investigated the toxic effects of maternal cadmium(Cd)exposure on the fetal livers.The pregnant C57BL/6 mice in the control and treated(20 mg·L^(-1)and 40 mg·L^(-1)groups had the drinking water without and with Cd,respectively,from the Embryonic Day(E)7.5 to E14.5 when the mice were sacrificed and the required tissues were sampled.Ki67 and TUNEL staining methods were employed for the analyses of cell proliferation and apoptosis,respectively.PCR array and quantitative real-time PCR were performed to quantify the gene expressions.Our results showed that the maternal Cd exposure had no effects on the fetal body and liver weights as well as the apoptosis in the liver.However,the accumulation of Cd in the liver occurred in a dose⁃dependent manner,which was a higher level in the female fetuses than that in the male counterparts.In the mice treated with 40 mg·L^(-1)Cd,the cell proliferation in the liver was inhibited,alongside with the up-regulation of several genes associated with the inhibition of cell proliferation,such as NF1 and those in the TGF⁃β1 signaling pathway.In conclusion,the results suggest that the Cd treatment causes Cd accumulation preferentially in the liver of the female fetuses,which signals to increase the expressions genes associated with proliferation inhibition,leading to the inhibition of the cell proliferation.It appears that there is a gender⁃associated difference in Cd metabolism,at least in mice.