铅对大鼠海马神经细胞凋亡及Bcl-2、Bax基因表达的影响

目的　观察铅对大鼠学习记忆行为、海马神经元细胞凋亡及Bcl 2、Bax基因表达的影响 ,探讨铅对大鼠学习记忆行为及神经毒性损伤的可能机制。方法　 32只SD大鼠随机分为对照组和低、中、高铅剂量组 ,采用自由饮水染毒90d后建立动物模型。用TUNEL法测定海马神经元细胞凋亡状况 ;SP免疫组织化学技术观察Bcl 2、Bax蛋白表达。结果　TUNEL染色结果显示 :海马CA1、CA3、DG区各染铅组与对照组间神经元细胞凋亡指数 (AI)有非常显著性差异 (P <0 .0 1)。免疫组化染色结果显示 ,在海马CA1、CA3、DG区 ,Bcl 2蛋白表达阳性神经细胞均随染铅剂量增大而减少 ,各染铅组与对照组间有非常显著性差异 (P <0 .0 1) ;Bax蛋白表达阳性神经元细胞随染铅剂量增大而逐渐增多 ,各染铅组与对照组间比较有非常显著性差异 (P <0 .0 1)。结论　铅引起海马神经元细胞凋亡可能是铅损害学习记忆的重要机制之一 ,而铅可能通过影响凋亡调控基因Bcl 2、Bax诱导海马神经元细胞凋亡。

Effect of lead exposure on rat neuronal apoptosis and expression of Bcl-2 and Bax gene in hippocampus

Objective To find out the mecha ni sm of the effects of lead on learning and memory, and neurotoxic injury and obse rve the effects of sub-chronic lead exposure on rats' learning and memory beha vior, neuronal apoptosis and the expression of Bcl-2 and Bax in hippocampus. Methods A total of 32 SD rats were randomly divided into cont rol group, the low, middle and high Pb groups. They had been assigned to distill ed water containing 0, 0.002%, 0.02% and 0.2% lead acetate (PbAc·3H 2O) by drinking water for 90 days. We observed neuron apoptosis by TUNEL (terminal deo xynucleotidyl transferse mediated dUTP nick end labeling) and the expression of Bcl-2 and Bax in hippocampus by SP immunohistochemistry. Results The results of TUNEL showed that there were obvious significant differenc es between the low, middle, high lead exposure groups and control group (P<0 .01). The results of immunohistochemistry indicated that the positive expression of Bcl-2 in hippocampus CA1, CA3, and DG region was decreased with increased e xposure to lead. The exposed groups had significant difference from control grou p (P<0.01); the positive expression of Bax in hippocampus CA1, CA3, and DG r egion was increased with increased exposure to lead. There were obviously signif icant differences between the low, middle, high lead-exposure groups and contro l group (P<0.01). Conclusion Sub-chronic lead exposure can induce the abnorm ality of neuronal apoptosis and decrease the positive expression of Bcl-2, incr ease the positive expression of Bax in the rat hippocampus CA1, CA3, and DG regi on. As a regulating gene of PCD, Bcl-2 and Bax may participate in hippocampus n euron apoptosis induced by lead.