右美托咪定通过AMPK/mTOR通路对老年大鼠术后认知功能障碍的影响

Effect of dexmedetomidine through AMPK/mTOR pathway on post-operative cognitive dysfunction in elderly rats

目的探究盐酸右美托咪定通过腺苷酸激活蛋白激酶/雷帕霉素靶蛋白通路(AMPK/mTOR)对老年大鼠术后认知功能障碍(POCD)的改善作用。方法选取SPF级健康SD老年大鼠60只随机分为假手术组、模型组、右美托咪定低剂量组及右美托咪定高剂量组,每组15只,假手术组大鼠手术不切除肝叶,其余3组大鼠手术切除部分肝叶制作认知功能障碍模型;采用Zea-Longa评分法评估各组大鼠术后1、6、12、24、72 h时认知障碍情况,Western blot检测各组大鼠AMPK/mTOR通路相关蛋白AMPK、mTOR与凋亡相关蛋白B淋巴细胞瘤-2基因相关蛋白X(BAX)、半胱氨酸-天冬氨酸蛋白酶3(Caspase-3)等表达水平;Real-time PCR检测AMPK、mTOR、BAX、Caspase-3的mRNA水平,TUNEL染色观察各组海马组织结构,通过ELISA法检测海马组织炎症指标白细胞介素-1β(IL-1β)与肿瘤坏死因子-α(TNF-α)水平。结果术后1、6、12、24、72 h时,模型组、右美托咪定低剂量组、右美托咪定高剂量组Zea-Longa评分显著高于假手术组,低剂量组与高剂量组大鼠神经功能缺损评分显著低于模型组、且高剂量组评分略低于低剂量组,差异有统计学意义(P<0.05);右美托咪定组大鼠海马组织AMPK、mTOR、BAX与Caspase-3的蛋白水平高于假手术组,但明显低于模型组,差异有统计学意义(P<0.05),mRNA结果与蛋白结果较为一致;TUNEL病理染色结果显示,右美托咪定组大鼠海马CA1区神经元数量与模型组比较明显增加,神经元凋亡指数明显降低、且高剂量组凋亡情况低于低剂量组(P<0.05);ELISA结果显示,模型组术后海马组织IL-1β与TNF-α水平高于右美咪定组,而右美咪定低剂量组IL-1β与TNF-α水平高于高剂量组(P<0.05)。结论右美托咪定可改善老年大鼠术后认知障碍情况,减少海马组织神经元凋亡及炎症反应,其机制可能与调控凋亡相关信号通路AMPK/mTOR有关。

Objective To investigate the ameliorative effect of dexmedetomidine hydrochloride on postoperative cognitive dysfunction(POCD)in aged rats through AMPK/mTOR pathway.Methods Sixty SPF SD rats were randomly divided into sham-operated group,model group,dexmedetomidine low-dose group and dexmedetomidine high-dose group,with 15 rats in each group.The liver lobes of the rats in the sham-operated group were remained,and the liver lobes of the rats in the rest 3 groups were resected to make the cognitive dysfunction model.The cognitive dysfunction conditions of each group at 1,6,12,24,and 72 hours after the surgery were evaluated by Zea-Longa;the expression levels of AMPK/mTOR pathway-related proteins(AMPK and mTOR)and apoptosis-related proteins(BAX and Caspase-3)were detected by Western blot;Real-time PCR was used to detect the expression levels of mRNA of AMPK,mTOR,BAX,and Caspase-3.The hippocampal tissue structure of each group was observed through TUNEL staining,and the inflammatory indexes(IL-1βand TNF-α)of hippocampal tissue were detected by ELISA.Results At 1,6,12,24 and 72 h after surgery,the Zea-Longa scores in the model group,dexmedetomidine low-dose group and dexmedetomidine high-dose group were significantly higher than those in the sham-operated group;the neurological deficit scores in the low-dose and high-dose groups were significantly lower than those in the model group,and the scores in the high-dose group were slightly lower than those in the low-dose group,with statistically significant differences(P<0.05);The protein levels of AMPK,mTOR,BAX,and Caspase-3 in hippocampal tissues of rats in the dexmedetomidine group were higher than those in the sham-operated group,but significantly lower than those in the model group,with statistically significant differences(P<0.05),and the mRNA results were consistent with the protein results;TUNEL pathological staining results showed that the number of neurons in the CA1 area of hippocampus of rats in the dexmedetomidine group significantly increased compared with that in the model group,the apoptosis index of neurons decreased significantly,and the high-dose group had lower apoptosis than the low-dose group(P<0.05).The results of ELISA showed that the levels of hippocampal tissues(IL-1βand TNF-α)of the model group after surgery were higher than the high-dose group and the low-dose group,among which the low-dose group had higher levels of IL-1βand TNF-αthan the high-dose group(P<0.05).Conclusion Dexmedetomidine can improve the postoperative cognitive impairment and reduce neuronal apoptosis and inflammatory response in hippocampal tissue in aged rats,and the mechanism may be related to apoptosis-related signaling pathway AMPK/mTOR.