Overexpression of glial cell line-derived neurotrophic factor using a lentiviral vector induces time-and dose-dependent downregulation of tyrosine hydroxylase in the intact nigrostriatal dopamine system
Overexpression of glial cell line-derived neurotrophic factor using a lentiviral vector induces time-and dose-dependent downregulation of tyrosine hydroxylase in the intact nigrostriatal dopamine system
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DOI：
10.1523/jneurosci.1122-04.2004
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发表时间：
2004-07-21
影响因子：
5.3
通讯作者：
Björklund, A
中科院分区：
文献类型：
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作者：
Georgievska, B;Kirik, D;Björklund, A
采用重组慢病毒（rLV）载体将胶质细胞源性神经营养因子（GDNF）导入大鼠纹状体或黑质（SN），研究GDNF在黑质多巴胺（DA）系统中持续过表达的影响。纹状体内递送rLV-GDNF导致GDNF在纹状体中显著过表达（2-4 ng/mg组织）和GDNF蛋白向SN的顺行转运。纹状体rLV-GDNF递送最初诱导DA周转增加（1-6周），伴随着响应于苯丙胺的显著对侧转向，表明注射侧的DA系统增强。在连续给予GDNF 6周后，我们观察到酪氨酸羟化酶（TH）蛋白的选择性下调（约70%），并一直维持到实验结束（24周）。当rLV-GDNF注射到SN中时观察到类似的效果。TH下调的幅度与GDNF表达水平有关，并且在纹状体GDNF水平超过0.7 ng/mg组织的动物中最为明显。TH蛋白水平的降低与体外TH酶活性的类似降低（约70%）相关;然而，体内L-3，4-二羟基苯丙氨酸产生速率和DA组织水平维持在正常水平。结果表明，TH蛋白的下调反映了一种补偿效应，在响应于连续GDNF刺激的DA神经元介导的组合过度活跃在DA突触和直接GDNF诱导的TH基因表达的行动。这种代偿机制被认为是为了维持正常范围内的长期DA神经元功能。
The effects of continuous glial cell line-derived neurotrophic factor ( GDNF) overexpression in the intact nigrostriatal dopamine (DA) system was studied using recombinant lentiviral (rLV) vector delivery of GDNF to the striatum or substantia nigra (SN) in the rat. Intrastriatal delivery of rLV-GDNF resulted in significant overexpression of GDNF in the striatum (2-4 ng/mg tissue) and anterograde transport of GDNF protein to the SN. Striatal rLV-GDNF delivery initially induced an increase in DA turnover (1-6 weeks), accompanied by significant contralateral turning in response to amphetamine, suggesting an enhancement of the DA system on the injected side. Starting 6 weeks after continuous GDNF delivery, we observed a selective downregulation of tyrosine hydroxylase (TH) protein (approximate to70%) that was maintained until the end of the experiment ( 24 weeks). A similar effect was observed when rLV-GDNF was injected into the SN. The magnitude of TH downregulation was related to the level of GDNF expression and was most pronounced in animals in which the striatal GDNF level exceeded 0.7 ng/mg tissue. The decreased TH protein levels were associated with similar reductions in the in vitro TH enzyme activity (approximate to70%); however, in vivo L-3,4-dihydroxyphenylalanine production rate and DA tissue levels were maintained at normal levels. The results indicate that downregulation of TH protein reflects a compensatory effect in response to continuous GDNF stimulation of the DA neurons mediated by a combination of overactivity at the DA synapse and a direct GDNF-induced action on TH gene expression. This compensatory mechanism is proposed to maintain long-term DA neuron function within the normal range.