Research and Development of Neuroprotective Drugs Targeted for Glial Cells

内皮素受体激动剂对培养的星形胶质细胞中神经营养因子产生的影响：损伤后神经系统的再生由星形胶质细胞产生的神经营养物质支持。在这项研究中，我们研究了内皮素-1（ET-1）的受体激动剂对星形胶质细胞产生神经营养因子的影响。ET-1刺激培养的星形胶质细胞表达胶质细胞源性神经营养因子（GDNF）和脑源性神经营养因子（BDNF）。脑室内注射ET受体激动剂可增加大鼠海马GDNF的mRNA和蛋白水平。ET激动剂还可增加尾壳核和大脑中BDNF的表达。培养的星形胶质细胞有外显子3和外显子4的BDNF转录，但没有外显子1和外显子2的转录。用ET-1处理增加了包含外显子3和外显子4的BDNF转录物。对ET诱导的星形胶质细胞BDNF基因转录的研究表明，DNF基因第3外显子的转录是由ERK和CREB介导的。第4外显子BDNF基因的表达受C/EBPβ介导的机制调控。这些结果提示ET受体可能是神经营养药物的作用靶点。新型神经营养药物T-588（一种具有神经保护作用的脐部药物）的作用机制是通过激活大鼠海马内的Erk来实现的。此外，我们还发现在动物模型中具有认知增强作用的FK 960刺激培养的大鼠星形胶质细胞产生GDNF。新型神经营养药物的这些作用可能是其药理作用的基础。

Effects of Endothelin Receptor Agonists on Neurotrophic Factor Production in cultured Astrocytes: Re-generation of nervous systems after injury is supported by neurotrophic substances produced by astrocytes. In this study, we examined effects of a receptor agonist of endothelin-1 (ET-1), which increased in damages brain, on neurotrophic factor production in astrocytes. ET-1 stimulated expressions of glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) in cultured astrocytes. Intracerebroventircular administration of an ET receptor agonist Into rat brain increases both mRNA and protein levels of GDNF in hippocampus. BDNF expression in caudate putamen and cerebrum also increased by the ET agonist. Cultured astrocytes had exon 3 and exon 4-containing BDNF transcripts, but not exon 1 and exon 2 transcripts. Treatment with ET-1 increased both exon 3 and exon 4-containing BDNF transcripts. Examinations on ET-induced astrocytic BDNF transcription showed that the exon 3 of DNF gene were induced by ERK and CREB-mediated mechanisms. The exon 4 BDNF gene was shown to be mediated by C/EBPβ-mediated mechanisms. These results suggest that ET receptors are possible target of neurotrophic drugs.Mechanisms of novel neurotrophic drugs: T-588, a navel drug showing nouroprotective actions, caused Erk activation in rat hippocampus. Also, we found FK960, which have cognitive enhancing actions in animal models, stimulated GDNF production in rat cultured astrocytes. These actions of novel neurotrophic drugs may underlie their phsrmacological actions.