The Effect Of MTOR Expression After Leucine Intervention On Autophagy In Focal Cerebral Ischemia

Objective:To explore the effect of leucine intervention mTOR expression on autophagy in focal cerebral ischemia, and their effect on ischemic brain damage. Methods:Adult male healthy SD rats were randomly divided into normal saline group(control group), glucose group and leucine group. For each group, middle cerebral artery occlusion(MCAO) model was established in rats with an intraluminal silicon-coated filament. Then 0.9% normal saline, 5% glucose, 1.5% leucine was injected through jugular vein based on grouping immediately after the onset of ischemia. At the time point of 6h, 12 h and 24 h after the occlusion,the rats were sacrificed after anesthetized,the infarction side cortices were collected and mTOR,LC3-Ⅱ levels were detected by the methods of Western blot and immunohistochemistry. The degree of ischemic brain damage were evaluated by behavioral symptoms,dry/wet weight ratio and pathology. Results:Western blot results showed that, in the same period of ischemia, the expression level of mTOR was increased while LC3-Ⅱ was decreased in ischemic cortices in leucine group, there were significant differences compared with normal saline group and glucose group( p < 0.05). The change of mTOR and LC3- Ⅱ in immunohistochemistry had the same significant differences as that in Western blot only at 12 h time point. While, there were no statistical differences of mTOR at 24 h time point and LC3-Ⅱat 6h time point for each group in immunohistochemistry(p>0.05).The pathological examination confirmed that the rats got 1 point to 3 point in neurological dysfunction score were consistent with the change of focal cerebral ischemia. With the prolongation of ischemic time, necrosis and disappearance of the nerve cells were increased. There were no statistical differences of neurological dysfunction and dry/wet weight ratio for each group in the same period of ischemia(p>0.05), but in various time the dry/wet weight ratio had differences(p<0.05). Conclusion:1. To some extent,neurological dysfunction score can reflect the formation of focal cerebral ischemia;2. Leucine promoted the expression of mTOR among 6h to 24 h after cerebral ischemia,and reached peak at 12h;However,LC3-II decreased at this time;3.There was no significant improvement by leucine or mTOR on cerebral ischemia related indicators such as neurological score, brain edema and pathological changes among 6h to 24 h. But with the lasting of ischemia, the brain damage gradually increased.