脑源性神经营养因子对缺氧胚脑神经元保护作用的信号传递途径初探

目的 研究胚鼠脑皮质神经元遭受缺氧刺激时,脑源性神经营养因子(BDNF)发挥保护作用的信号传递途径.方法 采用免疫荧光技术结合激光扫描共聚焦显微镜观察不同缺氧时间点(3 h和5 h)实验组(分别于缺氧培养前24 h和缺氧培养即刻加入BDNF 100 ng/mL)和对照组(缺氧培养,无BDNF干预)体外培养脑皮质神经元胞内酪氨酸激酶B(TrkB)、磷酸化TrkB和丝裂原活化蛋白激酶(MAPK)水平的变化并进行半定量分析.结果 与对照组相比,实验组在缺氧后不同时间点神经元胞浆内TrkB及磷酸化TrkB水平均出现上调(P＜0.05),MAPK在胞浆内和核内的表达也增加(P＜0.05),且缺氧培养前24 h加入BDNF者三种蛋白的表达强于缺氧培养即刻加入BDNF者(P＜0.05).结论 BDNF对缺氧神经元的保护作用可能通过诱导TrkB表达上调来实现,以TrkB受体酪氨酸磷酸化起始,经Ras-MAPK途径完成.

Signaling Pathway of BDNF Protecting Embryonic Cortical Neurons from Hypoxia

Objective To investigate the changes of TrkB and Ras-MAPK in brain-derived neurotrophic factor (BDNF) protecting the embryonic rat cerebral cortical neurons against hypoxia-induced neurotoxicity. Methods The immunofluorescence technique, laser scanning confocal microscope and half-quantitative analysis were done to explore the changes of the intracellular levels of tyrosine kinase B (TrkB), phosphorylated TrkB and the mitogen-activated protein kinase (MARK) in rat embryonic cortical neurons cultured in different time groups of hypoxia with or without BDNF pretreatment. Results The fluorescent intensity of TrkB and phosphorylated TrkB in the cytoplasm and the fluorescent intensity of MAPK in both cytoplasm and cell nucleus of the neurons were significantly increased in the presence of BDNF(P<0.05), the fluorescent intensity of neurons pretreated with BDNF 24 h before the hypoxia culture was stronger than those with BDNF just before the hypoxia culture(P<0.05). Conclusion The Ras-MAPK approach may be the major signal transferring way of BDNF in protecting the cortical neurons from hypoxia-induced neurotoxicity. The approach of signal transferring begins with tyrosine phosphorylation of TrkB receptors.