孕哺期铅暴露对小鼠脑组织8-羟基脱氧鸟苷和沉默信息调节因子1表达的影响

Effects of maternal lead exposure on expression of 8-OHd G and SIRT1 in brain tissue of mice offspring

目的研究孕哺期铅暴露对成年仔鼠脑组织中DNA氧化损伤标志物8-羟基脱氧鸟苷（8-hydroxy deoxy guanosine,8-OHd G）、沉默信息调节因子1（silent information regulator 1,SIRT1）表达及学习记忆能力的影响。方法通过饮用2 g/L乙酸铅水溶液建立C57BL/6小鼠孕期染铅模型,并对哺乳期母鼠持续铅暴露至子代小鼠断乳,分娩3周后将仔鼠分笼以无铅去离子水饲养至12周龄,同时设立无染铅对照组。于仔鼠12周龄时以Morris水迷宫实验检测其学习记忆能力,以免疫组化方法检测8-OHd G在两组仔鼠脑组织中的表达和分布,采用Western blot测定其脑组织中SIRT1蛋白的表达水平。结果水迷宫实验结果显示,第3~5天铅暴露组成年仔鼠在定位航行实验中的平均逃避潜伏期长于对照组,最后一天穿越平台次数及在目标象限停留时间低于对照组,差异均有统计学意义（P〈0.05）。铅暴露组仔鼠海马组织CA1区8-OHd G表达水平高于对照组,差异有统计学意义（P〈0.05）,但大脑皮层8-OHd G表达水平无明显差异（P〉0.05）。铅暴露仔鼠脑组织胞核内SIRT1水平低于对照组,胞浆内SIRT1水平高于对照组,差异均有统计学意义（P〈0.05）。结论孕哺期铅暴露对成年仔鼠学习记忆能力的影响可能与脑组织（特别是海马组织）DNA氧化损伤有关;铅暴露使成年仔鼠脑组织中SIRT1发生核质转移,该现象可能与SIRT1对铅暴露小鼠的神经保护作用有关。

Objective To study the effects of lead exposure during pregnancy and lactation on capability of learning and memory and the expression of 8-OHd G and SIRT1 in brain tissue of their offspring in mice. Methods Lead exposure was conducted through drinking the lead acetate solutions with dosages of 2 g/L. After weaning, all of the offspring drank deionized water up to 12 weeks old. The ability of learning and memory of the offspring mice was assessed by the Morris maze test. The expression level of 8-OHd G protein in the brain tissue of all the offspring was detected by immunohistochemistry and the expression of SIRT1 protein was determined by Western blot. Results In Morris maze experiment, the escape latency between two groups was significantly different（P〈0.05）. The crossing platform times and the time when the mice stayed in the target quadrant at last day of lead exposure group were less than that of the control group（P〈0.05）. The 8-OHd G expression level in the hippocampus CA1 region of mice at lead exposure group was higher than that of control group（P〈0.05）, but the 8-OHd G expression in the frontal cortex between two group was no significant difference（P〉0.05）. The protein expression of nuclear SIRT1 decreased and the protein expression of cytoplasm SIRT1 significantly increased in lead exposure group compared with the control group（P〈0.05）. Conclusion Maternal lead exposure may induce the nuclear translocation of SIRT1 and DNA oxidative damage in brain tissue of their offspring, which is involved in learning and memory damage.