SIRT1对早期脑缺血大鼠水通道蛋白4表达的影响

目的:检测水通道蛋白4(AQP4)及沉默信息调节因子1(SIRT1)在脑缺血大鼠脑组织中的表达变化,探究SIRT1对AQP4的调节作用,明确二者在脑缺血及脑水肿发生发展中的作用。方法:雄性SD大鼠随机分成假手术组(sham组)和脑缺血模型组(MCAO组),其中MCAO组又分为6 h、12 h、24 h和48 h 4个时点组别。采用线栓法阻塞大脑中动脉建立局灶性脑缺血模型,于相应时点进行神经症状评分,Morris水迷宫检测大鼠学习认知功能,TTC染色观察脑梗死体积,干湿重法检测脑含水量的变化,HE染色观察大脑皮层周围组织神经细胞形态学变化,Western blot检测AQP4、SIRT1和基质金属蛋白酶9(MMP-9)的表达情况。结果:与sham组相比较,随着再灌注时间增加,MCAO组大鼠神经功能评分、脑梗死体积、脑组织通透性和脑组织含水量均持续增加,而大鼠学习认知功能则降低显著,HE染色显示脑缺血大脑皮层周围组织神经元细胞形态不规则,数目减少;Western blot实验结果显示AQP4表达水平呈增高趋势,SIRT1表达降低,MMP-9表达增高,MCAO-48 h组与sham组比较差异最明显(P0.01)。结论:脑缺血后,伴随脑组织损伤的加剧,SIRT1和MMP-9信号通路的表达激活影响了AQP4的表达活化,共同参与了脑水肿的形成。

Effect of SIRT1 on dynamic expression of AQP4 in early stage of cerebral ischemia in rats

AIM: To investigate the pathological changes of aquaporin 4 (AQP4) and related proteins in the rats with focal cerebral ischemia injury, and to observe the effect of silent information regulator 1 (SIRT1) on the AQP4 expression in order to explore the pathological mechanism of cerebral ischemia and brain edema. METHODS: Adult male SD rats were randomly divided into sham group and middle cerebral artery occlusion (MCAO) model group. The MCAO model group was divided into the 4 time point (6 h, 12 h, 24 h and 48 h) subgroups. The animal model of MCAO was established by suture method in mature SD rats. The neural symptom score was measured at the corresponding time points. Morris water maze test was used to study the cognitive function. The cerebral infarction volume was evaluated by TTC staining. The changes of brain water content was analyzed by a dry/wet weight method. The morphological changes of the brain tissues were observed under microscope with HE staining. The protein expression of SIRT1, MMP-9 and AQP4 was determined by Western blot. RESULTS: Compared with sham group, the neural function score of the rats in MCAO model group was significantly elevated. With the increasing reperfusion time, the cerebral infarction volume, brain tissue permeability and the brain water content were also increased. The increases in the protein levels of AQP4 and the related proteins showed apparent changes. The protein expression of SIRT1 was decreased, while the MMP-9 expression was increased. The most obvious differences of the protein level changes in MCAO-48 h model group were observed (P<0.01). CONCLUSION: Accompanied with the aggravating cerebral injury after cerebral ischemia, the process of AQP4 expression is activated with the increasing expression levels of MMP-9 and SIRT1. These factors are combined to induce the formation of brain edema.