纳米氧化钛致神经元树突发育抑制过程中NMDA受体/Wnt信号通路的调控机制

Exposure to nano TiO2 during the prenatal period for women may influence nerve system for fetus, infant and children since nano TiO2 has been widely used in daily life. It has been demonstrated that exposure to nano TiO2 during the pregnancy or lactation resulted in neurotoxicity of offspring mice, however, whether the exposure associates with suppression of development of neuron dendrites is little reproted. Our previous study suggested that exposure to nano TiO2 led to downregulation of NMDA receptor expression, affected expression of Wnt pathway-related factors and dendric development inhibition of primary cultured neuron (for exmplae, the total length, number and density of dendritic spines in neurons were significantly lower than those in the control group). Accordingly, we hypothesize that nano TiO2 may interfere modulation of NMDA receptor activating Wnt signal pathway in development of neuron dendrites. To further study the mechanisms, we will in vivo and in vitro investigate the impacts of nano TiO2 on dendritic and synaptic development of offspring mice following exposure to nano TiO2 during perinatal period, and on dendritic development of primary cultured hippocampal neuron cells; we will interfere expression of signal pathway-related factors by employing techniques of gene (NMDA recptors, β-catenin and Wnt5a) over expression and SiRNA silencing GSK-3β expression, and demonstrate interaction of NMDA receptor/Wnt pathway related factors and key target molecules under nano TiO2- suppressed dendric development. These studies would help to understand toxic mechanisms of neural development, and provide protection and therapeutic target points under nano TiO2-induced neurotoxicity.

孕期和母乳期的妇女长期接触纳米TiO2产品后可能会影响胎儿、婴幼儿神经系统的发育。已证实孕期或母乳期纳米TiO2染毒可引起仔鼠神经毒性，但是否涉及树突发育的抑制报道较少。我们前期研究发现纳米TiO2可引起原代培养神经元NMDA受体表达下调，影响Wnt信号通路相关因子表达，抑制树突发育。推测可能是纳米TiO2干预了NMDA受体激活Wnt信号通路调控树突发育的作用。为深入研究其分子机制，本课题研究纳米TiO2对出生后仔鼠树突和突触发育及原代培养神经元树突发育的影响；通过NMDA受体、β-catenin或Wnt5a基因过表达及SiRNA沉默GSK-3β表达技术，干预信号通路相关因子表达，探讨这些因子在纳米TiO2影响树突发育中的相互作用关系及纳米TiO2作用关键靶分子。旨在进一步阐明纳米TiO2神经发育毒性的分子机制及为其诱导的神经发育毒性提供预防和治疗靶点。

纳米TiO2已在日常生活中广泛应用, 孕期和母乳期的妇女长期接触这些产品后可能会影响胎儿、婴幼儿童神经系统的发育。已证实孕期或母乳期纳米TiO2染毒可引起仔鼠神经毒性，但是否涉及树突发育的抑制报道较少。.开展了纳米TiO2染毒原代培养大鼠海马神经元细胞，研究了纳米TiO2对海马神经元树突发育影响及其分子作用机制。结果表明在海马神经元培养的纳米TiO2染毒后, 观察到神经元树突丝总长度、树突棘数和密度均明显降低。为明确纳米TiO2染毒后Wnt/通路对树突发育的调节作用, 我们分析了Wnt通路相关蛋白在原代培养神经元细胞中的表达，发现纳米TiO2染毒后Wnt3a、Wnt5a、β-catenin、CyclinD1、p-GSK-3β、MKLP1、CRMP3、ErbB4和 KIF17蛋白表达明显下调，而GSK-3β 表达显著上调。这些结果表明，纳米TiO2染毒可抑制海马神经元树突的发育，且与Wnt/β-catenin信号通路和非经典Wnt信号通路活化的抑制密切相关。.用纳米TiO2对母鼠从妊娠第7d至断乳期。实验观察到纳米TiO2暴露后仔鼠海马神经元树突丝长度明显低于对照，并发生过度自噬作用。同时凋亡和自噬相关分子的表达上调或表达下调。因此，纳米TiO2母体暴露可抑制仔鼠海马神经元树突发育并与过度自噬作用发生有关，而过度自噬作用的发生又与自噬相关分子的改变相关。.研究了纳米TiO2对出生后21d仔鼠海马神经元树突发育影响，表明纳米TiO2可从母体转运到子代海马积累，导致海马CA1锥体细胞轴突的发育抑制，仔鼠学习记忆下降，高尔基染色显示出的纳米TiO2染毒的仔鼠海马神经元树突丝长度、分支和树突棘数和密度减少。纳米TiO2染毒可抑制仔鼠海马神经元树突的发育，也与Wnt/β-catenin信号通路和非经典Wnt信号通路活化的抑制密切相关。表明纳米TiO2可以跨越血胎屏障和胎盘屏障，从而延缓胎盘和胚胎发育并诱导胎鼠骨骼畸形。.原计划发表SCI源期刊论文4-6篇，实际超额完成，实际已发表第一标注论文9篇,其中SCI论文 8篇，另有一篇投Journal of biomedical Nanotechnology(SCI刊物)后最近已被录用,(正在出版中)。

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