Ba Maowen, Kong Min, Ma Guozhao
Department of Neurology, Yuhuangding Hospital, Yantai City, Shandong, People's Republic of China.
Department of Neurology, Yantaishan Hospital, Yantai City, Shandong, People's Republic of China.
Drug Des Devel Ther. 2014 Dec 19;9:199-206. doi: 10.2147/DDDT.S75495. eCollection 2015.
Abnormality in interactions between N-methyl-d-aspartate (NMDA) receptor and its signaling molecules occurs in the lesioned striatum in Parkinson's disease (PD) and levodopa-induced dyskinesia (LID). It was reported that Fyn-mediated NR2B tyrosine phosphorylation, can enhance NMDA receptor function. Postsynaptic density protein 95 (PSD-95), one of the synapse-associated proteins, regulates interactions between receptor and downstream-signaling molecules. In light of the relationship between PSD-95, NR2B, and Fyn kinases, does PSD-95 contribute to the overactivity of NMDA receptor function induced by dopaminergic treatment? To further prove the possibility, the effects of regulating the PSD-95 expression on the augmented NR2B tyrosine phosphorylation and on the interactions of Fyn and NR2B in LID rat models were evaluated.
In the present study, parkinsonian rat models were established by injecting 6-hydroxydopamine. Subsequently, valid PD rats were treated with levodopa (50 mg/kg/day with benserazide 12.5 mg/kg/day, twice daily) intraperitoneally for 22 days to create LID rat models. Then, the effect of pretreatment with an intrastriatal injection of the PSD-95mRNA antisense oligonucleotides (PSD-95 ASO) on the rotational response to levodopa challenge was assessed. The effects of pretreatment with an intrastriatal injection of PSD-95 ASO on the augmented NR2B tyrosine phosphorylation and interactions of Fyn with NR2B in the LID rat models were detected by immunoblotting and immunoprecipitation.
Levodopa administration twice daily for 22 days to parkinsonian rats shortened the rotational duration and increased the peak turning responses. The altered rotational responses were attenuated by PSD-95 ASO pretreatment. Meanwhile, PSD-95 ASO pretreatment decreased the level of PSD-95 protein expression and reduced both the augmented NR2B tyrosine phosphorylation and interactions of Fyn with NR2B triggered during the levodopa administration in the lesioned striatum of PD rats. However, the protein levels of Fyn and NR2B showed no difference under the above conditions.
The data demonstrate that the inhibition of PSD-95 protein expression suppressed the interactions of Fyn with NR2B and NR2B tyrosine phosphorylation and subsequently downregulated NMDA receptor overactivation, thus providing benefit for the therapy of LID. Therefore, PSD-95 is important for overactivity of NMDA receptor function due to facilitating NR2B tyrosine phosphorylation dependent on Fyn kinase by regulating interactions of Fyn with NR2B under the pathological conditions of LID.
在帕金森病（PD）和左旋多巴诱导的异动症（LID）的损伤纹状体中，N-甲基-D-天冬氨酸（NMDA）受体与其信号分子之间的相互作用出现异常。据报道，Fyn介导的NR2B酪氨酸磷酸化可增强NMDA受体功能。突触后致密蛋白95（PSD-95）是一种突触相关蛋白，可调节受体与下游信号分子之间的相互作用。鉴于PSD-95、NR2B和Fyn激酶之间的关系，PSD-95是否会导致多巴胺能治疗诱导的NMDA受体功能过度激活？为进一步证实这种可能性，在LID大鼠模型中评估了调节PSD-95表达对增强的NR2B酪氨酸磷酸化以及Fyn与NR2B相互作用的影响。
在本研究中，通过注射6-羟基多巴胺建立帕金森病大鼠模型。随后，对有效的PD大鼠腹腔注射左旋多巴（50mg/kg/天，苄丝肼12.5mg/kg/天，每日两次），持续22天以建立LID大鼠模型。然后，评估纹状体内注射PSD-95mRNA反义寡核苷酸（PSD-95 ASO）预处理对左旋多巴激发试验旋转反应的影响。通过免疫印迹和免疫沉淀检测纹状体内注射PSD-95 ASO预处理对LID大鼠模型中增强的NR2B酪氨酸磷酸化以及Fyn与NR2B相互作用的影响。
对帕金森病大鼠每日两次给予左旋多巴，持续22天，可缩短旋转持续时间并增加最大旋转反应。PSD-95 ASO预处理可减弱这种改变的旋转反应。同时，PSD-95 ASO预处理降低了PSD-95蛋白表达水平，并减少了PD大鼠损伤纹状体中左旋多巴给药期间触发的增强的NR2B酪氨酸磷酸化以及Fyn与NR2B的相互作用。然而，在上述条件下，Fyn和NR2B的蛋白水平没有差异。
数据表明，抑制PSD-95蛋白表达可抑制Fyn与NR2B的相互作用以及NR2B酪氨酸磷酸化，随后下调NMDA受体的过度激活，从而为LID的治疗带来益处。因此，在LID的病理条件下，PSD-95通过调节Fyn与NR2B的相互作用促进依赖Fyn激酶的NR2B酪氨酸磷酸化，对NMDA受体功能的过度激活很重要。
