Mechanisms of protectiion by neurotrophins against NO-mediated glutamate neurotoxicity

本项目旨在通过胎鼠大脑皮层培养物来确定神经营养因子对谷氨酸神经毒性的保护作用机制。脑源性神经营养因子（BDNF）有效地防止NMDA受体介导的谷氨酸神经毒性时，培养物暴露于BDNF 24小时前谷氨酸暴露。BDNF的保护作用被蛋白质合成抑制剂所抑制。这些结果表明，BDNF的神经保护作用涉及细胞内蛋白质的重新合成，BDNF诱导其高亲和力受体TrkB的酪氨酸磷酸化，而BDNF的作用不受低亲和力神经营养因子受体p75抗体的影响。BDNF不增加神经酰胺的形成。BDNF阻止了钙离子载体如离子霉素和NO供体如S-亚硝基半胱氨酸诱导的细胞毒性。这些发现表明BDNF选择性地与TrkB相互作用以促进功能分子的从头合成，所述功能分子减轻由包括一氧化氮和超氧化物的自由基触发的神经毒性。我们项目的结果为创造保护神经退行性疾病中神经元死亡的新药提供了新的范围。

This project is aimed to determine the mechanisms of protective action of neurotrophins against glutamate neurotoxicity in the cerebral cortex by using cortical cultures derived from fetal rats. Brain-derived neurotrophic factor (BDNF) potently prevented NMDA receptor-mediated glutamate neurotoxicity when the cultures were exposed to BDNF for 24 hr prior to glutamate exposure. Protective effect of BDNF was inhibited by an inhibitor of protein synthesis. Those results suggest that de novo synthesis of intracellular proteins is involved in the neuroprotective action of BDNF.BDNF induced tyrosine phosphorylation of its high affinity receptor, TrkB.By contrast, the effect of BDNF was not affected by the addition of antibody for p75, a low affinity neurotrophin receptor. BDNF did not increase ceramide formation. BDNF prevented cytotoxicity induced by a calcium ionophore such as ionomycin and a NO donor such as S-nitrosocysteine. Those findings indicate that BDNF selectively interacts with TrkB to promote de novo synthesis of functional molecules which ameliorate neurotoxicity triggered by free radicals including nitric oxide and superoxide. The results of our project give a new scope for the creation of novel drugs protecting neuronal death in neurodegenerative disorders.