大鼠颅脑损伤后脑组织miR-122-5p含量变化及其对神经功能的影响

目的 探讨大鼠颅脑损伤后脑组织miR-122-5p含量变化及其对神经功能的影响。方法 将40只成年SD大鼠随机分为假手术组，TBI模型组，乱序miRNA组，miR-122-5p模拟物组。采用Feeney法制备TBI大鼠模型；乱序miRNA组造模24 h后，立体定向注射乱序miRNA 5 μl（20 μmol/L）；miR-122-5p模拟物组造模24 h后，立体定向注射miR-122-5p模拟物组5 μl（20 μmol/L）。qRT-PCR法检测大鼠脑组织miR-122-5p的表达变化；免疫印迹法法检测p53蛋白表达水平；水迷宫法检测学习记忆功能；TUNEL法检测脑组织细胞凋亡情况；流式细胞术检测脑细胞线粒体膜电位的变化。结果 与假手术组大鼠比较，模型组和乱序miRNA组大鼠脑组织miR-122-5p表达明显减少，p53蛋白显著上调，脑组织细胞凋亡数明显增多，线粒体膜电位下降显著，水迷宫测试大鼠寻找隐形平台时间显著延长；与模型组大鼠比较，miR-122-5p模拟物组大鼠miR-122-5p表达明显增加，并伴随p53蛋白低表达，细胞凋亡水平下降，神经功能障碍得到明显逆转。结论 颅脑损伤后miR-122-5p的表达下调可能导致p53蛋白的表达升高，促进神经细胞凋亡。

Abnormal expression of miR-122-5p in brain tissues and its effects on neurological functions after traumatic brain injury in rats

Objective To study the effects of the changes in miR-122-5p expression in brain tissues on the neurological functions after traumatic brain injury (TBI). Method Forty rats were randomly divided into 4 groups, i.e. group A, in which 10 animals received sham operation, group B, in which 10 animals underwent TBI, group C, in which 10 animals were treated by scrambled miRNA after IBI, and group D, in which 10 animals were treated by miR-122-5p mimics after TBI. The changes in memory were determined by Water Maze method in all the rats. The expression of miR-122-5p in the injured brain tissues was detected by qRT-PCR. The expression of p53 protein in the injured brain tissues was determined by Western Blot method. Cells apoptosis in the injured brain tissues and the change in brain cell mitochondrial membrane potential (MMP) were determined respectively by TUNEL method and Flow cytometry. Results The level of miR-122-5p expression in the injured brain tissues was significantly lower and the level of p53 protein expression was significantly higher in groups B and C than those in group A (P<0.05). The number of cells of apoptosis was significantly more and brain cell MMP was significantly lower in the injured brain tissues in groups B and C than those in group A (P<0.05). The time needed to find hidden platform was significantly longer in group B and C than that in group A (P<0.05). In the injured brain tissues the levels of miR-122-5p expression was significantly enhanced and the level of p53 protein expression and the number of cells apoptosis was significantly decreased and the time needed to find the hidden platform was significantly shortened in group D compared to those in group B (P<0.05). Conclusions The decrease in level of miR-122-5p expression might promote the expression of p53 protein in the injured brain tissues, in which the upregulation of p53 protein expression might cause the increase in the level of apoptosis of the cerebral cells after TBI. The miR-122-5p mimics can inhibit the expression of p53 protein, reducing the apoptosis of the cerebral cells and effectively relieve the damaged neurological function in the rats with TBI.