跑台运动训练对脑缺血大鼠轴突导向因子Netrin-4及其受体DCC蛋白表达的影响

Effects of treadmill training after cerebral ischemia on expression in the brain of axonal guidance factor Netrin-4 and its receptor protein

目的观察跑台运动训练对脑缺血大鼠脑组织中轴突导向因子Netrin-4及其受体结直肠癌缺失（DCC）蛋白表达的影响，旨在探讨运动训练促进脑缺血后神经功能恢复的相关机制。方法取成年雄性SD大鼠63只，按随机数字表法分为假手术组（n=9）、模型组（n=27）和运动组（n=27）。模型组和运动组大鼠采用改良的Longa线栓法制备大脑中动脉闭塞（MCAO）脑缺血模型，假手术组大鼠手术方法同模型组和运动组，但是不插入线栓。运动组于造模成功后24h采用跑台训练器进行运动训练，其余2组则不进行运动训练。采用修正的神经行为学评分方法（mNSS）评价模型组和运动组大鼠造模后第3、7、14天的神经功能，并断头取脑，采用Western blot法以及免疫荧光法检测脑缺血区组织中Netrin-4、DCC蛋白的表达情况。结果造模后第3、7、14天，运动组和模型组的mNSS评分与假手术组比较，差异均有统计学意义（P〈0．01）；造模后第7、14天，运动组的mNSS评分分别为（6．89±1．27）分和（5．22±1．09）分，低于模型组同时间点，差异均有统计学意义（P〈0．05）；造模后第7、14天，运动组的Netrin-4、DCC蛋白表达均较模型组增强（P〈0．05）；造模后第14天，经免疫荧光法检测发现，Netrin-4主要在脑缺血区的血管和星形胶质细胞中表达，而DCC蛋白主要在脑缺血区的神经元轴突和星形胶质细胞中表达。结论跑台运动训练可促进脑缺血大鼠神经功能恢复，其机制可能与上调脑缺血区组织中Netrin-4、DCC蛋白的表达，进而增强了神经、血管的再生和重建有关。

Objective To observe the effects of treadmill training on the expression of axonal guidance factor Netrin-4 and its receptor deleted in eolorectal cancer （DCC） protein in the brains of rats with cerebral ische- mia. Also to explore how training promotes the recovery of neurological function after cerebral ischemia. Methods Sixty-three adult, male Sprague-Dawley rats were randomly divided into a sham group （ n = 9） , a model group （n = 27） and an exercise group （n = 27）. A modified version of Longa＇s method was used to establish an animal model of cerebral isehemia by occluding the right middle cerebral artery （MCAO） in the rats of the model and exercise groups while the rats of the sham group were subjected to the same surgical procedure except that no thread was inserted. The rats of the exercise group were given treadmill training beginning 24 h after the modeling, while those of the other two groups were left on the treadmill without training. The rats＇ neurological functioning was tested by assigning modified neurological severity scores （mNSS） on the 3rd, 7th and 14th day after modeling. Then the ischemic brain tissue was dissected to detect the expression of Netrin-4 and DCC protein using western blotting and immunofluorescent staining and analysis. Results On the 3rd, 7th and 14th day after modeling, the model and exercise groups had significant differences in their average mNSS scores when compared to the sham group. The average mNSS scores of the exercise group on the 7th and the 14th day were significantly lower than those of the model group at the same time point. The average expression level of Netrin-4 and DCC protein in the exercise group was significantly higher in than the model group on the 7th and 14 th days. Immunofluorescent staining showed that Netrin-4 was mainly observed in the blood vessels and astrocytes in the ischemic brain area. DCC protein was found mainly in neural processes and astrocytes in the same area. Conclusions Treadmill training can improve the recovery of neurological function after cerebral ischemia. Its mechanisms may be partly attributed to up-regulating the expression of Netrin-4 and DCC protein in the ischemic brain area, which strengthens the regeneration and reconstruction of nerves and blood vessels.