妊娠期至性成熟期砷暴露对仔代小鼠海马组织中蛋白激酶A和环磷酸腺苷反应元件结合蛋白mRNA表达的影响

Effects of arsenic exposure from gestation to sexual maturity on expression of PKA and CREB mRNA in hippocampus of offspring of mice

目的通过研究妊娠期至性成熟期亚砷酸钠暴露对子代小鼠海马组织中蛋白激酶A(protein kinase A,PKA)和环磷酸腺苷反应元件结合蛋白(c AMP response element-binding protein,CREB)mRNA水平的影响,探讨砷暴露引起仔鼠学习记忆能力损伤的可能机制。方法将24只SPF级妊娠昆明小鼠随机分为对照(蒸馏水)组和15、30、60 mg/L亚砷酸钠染毒组,每组6只;从妊娠第1天至断乳前[出生后(postnatal day,PND)20 d],采用自由饮水方式进行染毒。仔鼠自断乳后至PND40继续染毒。采用水迷宫实验检测PND40仔鼠的学习记忆能力,分别于PND10、PND20、PND40,采用实时荧光定量RT-PCR(Real-time RT-PCR)法检测海马组织中PKA和CREB mRNA的表达水平。结果与对照组相比,训练第4天时60 mg/L亚砷酸钠染毒组仔鼠及训练第5天时各浓度亚砷酸钠染毒组仔鼠寻找平台的潜伏期均延长,仅60 mg/L亚砷酸钠染毒组仔鼠的停留时间缩短,差异有统计学意义(P<0.05);且随着亚砷酸钠染毒浓度的升高,仔鼠寻找平台的潜伏期均呈延长趋势,停留时间呈缩短趋势。与对照组相比,各浓度亚砷酸钠染毒组PND20仔鼠及60 mg/L亚砷酸钠染毒组PND40仔鼠海马组织中PKA mRNA的表达水平均较低,差异有统计学意义(P<0.05);而各浓度亚砷酸钠染毒组PND10仔鼠海马组织中PKA mRNA的表达水平无明显改变。且随着亚砷酸钠染毒浓度的升高,PND20及PND40仔鼠海马组织中PKA mRNA的表达水平均呈逐渐下降趋势。与对照组相比,60 mg/L亚砷酸钠染毒组PND20仔鼠及30、60 mg/L亚砷酸钠染毒组PND40仔鼠海马组织中CREB mRNA的表达水平均较低,差异有统计学意义(P<0.05);而各浓度亚砷酸钠染毒组PND10仔鼠海马组织中CREB mRNA的表达水平无明显改变。且随着亚砷酸钠染毒浓度的升高,PND20仔鼠海马组织中CREB mRNA的表达水平呈逐渐下降趋势。结论妊娠期至性成熟期砷暴露可使仔鼠海马组织中PKA和CREB mRNA的表达水平降低,进而影响仔鼠的学习和记忆能力。

Objective To explore the effects of arsenic on the expression of PKA and CREB mRNA in the hippocampus of offspring of mice, to understand the mechanism of learning and memory damage induced by arsenic exposure from gestation to sexual maturity. Methods A total of 24 pregnant Kunming mice were randomly divided into four groups, six in each, and exposed to sodium arsenite（Na2 As O3） through drinking water at the doses of 0, 15, 30 and 60 mg/L respectively. The pregnant mice and their offspring in the control group drank distilled water. The pregnent mice were treated with Na2 As O3 from the first day of pregnancy to weaning [postnatal day（PND）20]. After weaning, the offspring were still exposed to Na2 As O3 through drinking water till PND40. Morris water maze was performed to detect the effects of Na2 As O3 exposure on the learning and memory ability.At PND10, 20 and 40, the expression levels of PKA and CREB mRNA in hippocampus were measured by q RTPCR respectively. Results Compared with the control, the escape latencies in the 60 mg/L Na2 As O3 group at the fourth training day and in the Na2 As O3-exposed groups at the fifth training day were obviously longer, the time spent in the quadrant（platform existed previously） in 60 mg/L group in the probe trail was significantly shorter（P〈0.05）. As the concentration of Na2 As O3 increased, the escape latencies of the offspring showed a prolonged trend and the time spent in the quadrant（platform existed previously） was shortened. Compared with the control, expression levels of PKA mRNA in Na2 As O3-exposed groups at PND20,in 60 mg/L group at PND40 were significantly lower（P〈0.05）. The differences of PKA mRNA levels among groups at PND 10 failed to show any significance. As the concentration of Na2 As O3 increased, the expression levels of PKA mRNA in the hippocampus of mice at PND20 and PND40 decreased gradually. Compared with the control, expression levels of CREB mRNA in 60 mg/L Na2 As O3 group at PND20, in 30 and 60 mg/L Na2 As O3-exposed groups at PND 40 were significantly lower（P〈0.05）.There were no significant differences of CREB mRNA levels among Na2 As O3-exposed groups at PND 10. As the concentration of Na2 As O3 increased, the expression levels of CREB mRNA in hippocampus at PND20 decreased gradually. Conclusion Arsenic exposure from gestation to sexual maturity has adverse effects on the expression of PKA and CREB mRNA in the hippocampus of offspring of mice and cause learning and memory damage.