观察新生大鼠缺氧缺血性脑损伤(HIBD)模型的AMP-活化蛋白激酶(AMPK)、核转录因子FOXO3a及凋亡蛋白活化型天冬氨酸特异性半胱氨酸蛋白酶3(CC3)表达水平变化，探讨抑制AMPK/FOXO3a信号通路对新生大鼠缺氧缺血神经元凋亡的保护作用机制。

将64只7 d龄SD大鼠按照随机数字表法分为4组：缺氧缺血组(HI组)、假手术组(sham组)、AMPK特异性抑制剂Compound C干预组(干预组)、二甲基亚砜(DMSO)溶剂组(对照组)，每组SD大鼠各为16只。建模方法：对HI组SD大鼠在乙醚麻醉下进行右侧颈总动脉结扎，采用氧、氮混合气体(8% O₂、92% N₂)缺氧处理2.5 h；对sham组SD大鼠仅分离右侧颈总动脉，不结扎，不进行缺氧处理；对干预组和对照组SD大鼠分别于右侧脑室内注射等量Compound C和DMSO，30 min后，采用氧、氮混合气体(8% O₂、92% N₂)进行缺氧处理。分别于建模24 h后处死4组SD大鼠，取大脑皮质，采用Western印迹法定量检测各组SD大鼠模型大脑皮质的AMPK蛋白、p-AMPKα蛋白、总FOXO3a蛋白、细胞核FOXO3a蛋白、细胞质FOXO3a蛋白及CC3表达水平；应用原位缺口末端标记(TUNEL)染色法，检测凋亡神经元细胞。

①与sham组相比，HI组及对照组SD大鼠模型大脑皮质的AMPK蛋白水平与总FOXO3a蛋白水平均无显著变化，并且差异均无统计学意义(P>0.05)；p-AMPKα蛋白水平及细胞核FOXO3a蛋白水平均显著增高，细胞质FOXO3a蛋白水平均显著降低，CC3表达水平均显著增高，并且差异均有统计学意义(P<0.01)。②与HI组及对照组相比较，干预组SD大鼠模型大脑皮质p-AMPKα蛋白水平及细胞核FOXO3a蛋白水平显著降低，细胞质FOXO3a蛋白水平显著增高，凋亡蛋白CC3表达水平显著降低，差异均有统计学意义(P<0.01)。③与sham组相比，HI组及对照组SD大鼠模型大脑皮质神经元细胞凋亡水平(TUNEL呈阳性细胞表达水平)均显著增高，并且差异均有统计学意义(P<0.01)；干预组SD大鼠模型大脑皮质神经元细胞凋亡水平，较HI组及对照组显著降低，差异亦有统计学意义(P<0.01)。

新生大鼠发生HIBD损伤时，AMPK发生磷酸化，活性增高；而抑制AMPK活性，可抑制FOXO3a核转位，下调凋亡蛋白CC3表达水平，减少神经元细胞凋亡。

To study expression levels of AMP-activated protein kinase (AMPK), FOXO3a transcription factor and apoptotic protein cleaved caspase-3 (CC3) in the neonate rat brains with hypoxic-ischemic brain damage (HIBD), and to explore the mechanisms of neuroprotective effects of AMPK/FOXO3a signaling pathway inhibition on hypoxic-ischemic neuronal apoptosis in neonate rats.

Sixty-four postnatal day 7 SD rats were divided into 4 groups by random number table method: hypoxia-ischemia group (HI group), the sham controls group (sham group), AMPK specific inhibiter Compound C-treated group (treated group), and dimethyl sulfoxide (DMSO) vehicle group (control group), respectively. And 16 SD rats in each group. Modeling methods were as followed. For HI group, the right common carotid artery of SD rats was exposed and ligated by ether anesthesia, and the SD rates were exposed to hypoxia in a chamber filled with 8% oxygen (balanced with 92% nitrogen) for 2.5 h. For sham group, the right common carotid artery of SD rats was surgically exposed without ligation and did not receive hypoxia treatment. For treated group, Compound C was intracerebroventricularly injected into the injured cerebral hemisphere of SD rats 30 min prior to treatment by 8% oxygen (balanced with 92% nitrogen) for 2.5 h. For control group, the SD rates received intracerebroventricular injections of DMSO with the equal amount of compound C in treated group, and 30 min later, the SD rats received hypoxic-ischemic treatment as treated group. SD rats′ cerebral cortexes of 4 groups were collected at 24 h after modeling success. Western blotting method was used to detect the protein expression of AMPK, p-AMPKα, total FOXO3a, nuclear and cytoplasmic FOXO3a and CC3 in cerebral cortexes of SD rats modeling in each group. In situ nick-end labeling (TUNEL) staining of was used to detect the apoptotic cells.

①There were no significant differences between HI group and sham group, control group and sham group in expression levels of AMPK protein and total FOXO3a protein in rat′s cerebral cortexes (P>0.05). However, expression levels of p-AMPKα protein and nuclear protein of FOXO3a in HI group and control group all were much higher than those in sham group, and the cytoplasmic protein of FOXO3a were evidently lower than that in sham group, which up-regulated expression level of CC3 protein after hypoxic-ischemic in HI group and control group compared with sham group, and all the differences were statistically significant (P<0.01). ②Expression levels of p-AMPKα protein and nuclear protein of FOXO3a in treated group were obviously lower than those in HI group and control group, and expression level of cytoplasmic protein was much higher than those in HI group and control group, and meanwhile leading to the decrease of CC3 protein after hypoxic-ischemic in treated group compared with HI group and control group, and all the differences were statistically significant (P<0.01). ③Apoptosis levels of neuronal cell (expression levels of TUNEL positive cells) in HI group and control group both were higher than that in sham group, and both the differences were statistically significant (P<0.01). TUNEL positive cells were obviously reduced in treated group compared with those in HI group and control group, and all the differences were statistically significant (P<0.01).

AMPK activity increased in the neonate rat brain with HIBD. AMPK activity inhibition can inhibit FOXO3a translocation from cytoplasm to nucleus, down-regulate the level of CC3 protein, leading to the reduction of neuronal apoptosis.