Cdk5／p25活性抑制肽TFP5对帕金森病模型小鼠黑质多巴胺能神经元的保护作用

Inhibition of CdkS/p25 by TFP5 protects dopaminergic neurons in MPTP-induced mouse model of Parkin- son＇s disease

目的探讨TFP5对1-甲基-4-苯基-1，2，3，6-四氢吡啶（1-methyl-4-phenyl-1，2，3，6-tetrahydro-pyridine，MPTP）诱导的小鼠帕金森病（Parkinson’s disease，PD）模型黑质多巴胺能神经元的保护作用和机制。方法MPTP腹腔注射建立小鼠PD模型，随机分为对照组、模型组、杂序TFP5肽（scrambled TFP5 peptide，Scb）组、ⅡP5组，和Cdk5激酶活性抑制剂（roscovitine）组，每组10只。采用行为学观察、westernblot和免疫组化等方法，评估各组小鼠的行为学表现、中脑黑质p25的表达水平和肌细胞特异性增强因子2D（Myocyte-specific enhancer factor 2D，MEF2D）的磷酸化水平，以及黑质致密部多巴胺能神经元的损伤情况。结果模型小鼠出现PD样动作及行为，和对照组比较，黑质部位p25表达显著增加[（0．48±0．10）ws（0．26±0．02），P〈0．05]，MEF2D的磷酸化水平显著升高[（0．81±0．10）vs（0．22±0．02），P〈0．05]，黑质致密部多巴胺能神经元数目显著减少[（348．67±24．40）个vs（463．29±19．61）个，P〈0．05]。与模型组相比，TFP5组小鼠黑质MEF2D的磷酸化水平降低[（0．25±0．12）vs（0．81±0．10），P〈0．05]，黑质致密部多巴胺能神经元凋亡减轻[（422．92±8．41）个vs（348．67±24．40）个，P〈0．05]，小鼠各项行为学评分有较好改善（P〈0．05）；roscovitine的作用与TFP5相似；Scb组与模型组比较差异无统计学意义（P〉0．05）。结论TFP5可减轻PD模型小鼠黑质多巴胺能神经元损伤，改善其运动功能，其机制可能与TFP5通过抑制模型小鼠黑质Cdk5／p25活性有关。

Objective To study the neuroprotective role of TFP5 in a MPTP-induced mouse model of Parkinson＇s disease （PD）. Methods C57BL/6 mice were used as experimental animals. Briefly, 5 consecutive days of intraperitoneal injection of 25 mg/Kg 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine （MPTP） was applied to induce mouse PD model. The mice were randomized into 5 groups including control group, model group, scram- bled TFP5 peptide （ Sob ） group, TFP5 group and roseovitine group. On the 7th day after the first injection of MPTP, behavior tests were performed, and then western blot method was employed to detect the expression of p25 and phosphorylated MEF2D in substantia nigra.Tyrosine hydroxylase （TH） immunohistochemical staining was per- formed to observe the apoptosis of dopaminergie neurons in substantia nigra pars eompaeta （ SNpe ） 28 days after the first injection of MPTP. Results MPTP increased the expression of p25 （0.48±0.10 vs 0.26±0.02, P〈0.05） and phosphorylated MEF2D （0.81±0.10 vs 0.22±0.02, P〈0.05 ） in substantia nigra, but decreased the number of dopaminergie neurons in SNpc （348.67±24.40 vs 463.29± 19.61, P〈0.05 ）, resulting in motor impairment in the model mice （P〈0.05）. Intraperitoneal injection of 30mg/Kg of TFP5 for 3 days effectively reduced the excessive phosphorylation of MEF2D （ 0.25±0.12 vs 0.81 ± 0.10, P〈0.05 ） in substantia nigra, rescued dopaminergic neuron reduction of SNpc （422.92±8.41 vs 348.67±24.40, P〈0.05 ）, and improved the motor ability of the model mice （P 〈0.05）. Roseovitine exerted almost same neuroproteetive role as TFP5 ,while Seb had no protective effect. Conclu- sion TFP5 can rescue MPTP-indueed damage of dopaminergie neurons in substantia nigra, and thus improve mo- tor impairment of model mice ,which may be mediated by the inhibition of Cdk5/p25 activity.