N-乙酰半胱氨酸对术后认知功能障碍模型小鼠认知功能及核因子E2相关因子2/血红素加氧酶-1信号通路的影响

目的 观察N-乙酰半胱氨酸(NAC)对术后认知功能障碍(POCD)模型小鼠认知功能和海马核因子E2相关因子2(Nrf2)/血红素加氧酶-1(HO-1)信号通路的影响。方法 采用随机区组设计,利用随机数字表法将雄性3~4月龄C57BL/6J小鼠54只随机分为3组(n=18),分别为对照组、手术组、手术+NAC组。在异氟醚吸入麻醉下,手术组和手术+NAC组小鼠行左下肢胫骨骨折内固定术。手术+NAC组分别于麻醉前30 min、术后3 h和6 h腹腔内注射NAC 150 mg/kg,对照组和手术组腹腔注射生理盐水。术后第3天利用随机数字表法每组随机取6只小鼠,行Morris水迷宫测试小鼠空间认知和记忆功能,术后第7天完成测试。术后第1、3天取小鼠海马组织,酶联免疫吸附法检测小鼠海马组织中白细胞介素-6(IL-6)、丙二醛(MDA)浓度,Western blot及实时荧光定量PCR检测小鼠海马组织中Nrf2和HO-1的蛋白与mRNA表达。结果 3组小鼠的游泳速度差异均无统计学意义(F=2.135,P=0.114);与对照组和手术+NAC组小鼠相比,手术组小鼠的逃避潜伏期延长(P<0.01),穿越平台次数减少(P<0.01),目标象限停留时间减少(P<0.01)。与对照组相比,手术组和手术+NAC组术后1 d海马组织IL-6和MDA含量均明显增高(P均=0.000),术后第3天手术组仍高于对照组(P=0.000),手术+NAC组IL-6(P=0.251)和MDA(P=0.103)含量降至对照组水平;与手术组相比,手术+NAC组术后第1、3天海马组织IL-6和MDA含量均明显降低(P均=0.000)。与对照组相比,手术组和手术+NAC组海马组织Nrf2和HO-1蛋白表达均增高(P均=0.000);与手术组相比,手术+NAC组海马组织Nrf2和HO-1蛋白表达均明显增高(P均=0.000)。与对照组相比,手术组和手术+NAC组Nrf2和HO-1 mRNA表达在术后第1天均明显增加(P均=0.000),手术+NAC组明显高于手术组(P=0.000)。术后第3天,Nrf2和HO-1的 mRNA表达进一步增强。结论 NAC预处理后的POCD小鼠降低海马组织氧化应激和炎性反应,改善认知功能,此作用与激活Nrf2/HO-1信号通路相关。

Effect of N-acetylcysteine on Cognitive Function and Nuclear Factor Erythroid 2 Related Factor 2/Heme Oxygenase-1 Pathway in Mouse Models of Postoperative Cognitive Dysfunction

Objective To investigate the effect of N-acetylcysteine(NAC)on cognitive function and nuclear factor erythroid 2 related factor 2/ heme oxygenase-1(Nrf2/HO-1)pathway in mouse models of postoperative cognitive dysfunction. Methods Fifty-four male C57BL/6J mice(3-4 months old)were randomly divided into control group,surgery group,and surgery+NAC group by block randomization.The intramedullary fixation for left tibial fracture surgery was performed to establish postoperative cognitive dysfunction models.NAC(150 mg/kg)was administered intraperitoneally in group surgery+NAC 30 minutes before and 3 hours,6 hours after surgery,while saline was given in control group and surgery group.Six mice in each group were selected randomly underwent Morris water maze test on the third day after surgery.Animals were sacrificed at the first and third postoperative days,and the hippocampus was harvested.Enzyme-linked immunosorbent assay was used to quantify the levels of interleukin-6(IL-6)and malondialdehyde(MDA)in hippocampus.Western blot and real-time polymerase chain reaction were used to measure the expressions of Nrf2 and HO-1 in hippocampus. Results There was no significant difference in swimming speed among three groups(F=2.135,P=0.114).Compared with control group and surgery+NAC group,the surgery group had prolonged escape latency(P<0.01),reduced platform crossing times(P<0.01),and shortened time spent in the target quadrant(P<0.01).Compared with the control group,the surgery group and the surgery+NAC group had significantly increased levels of IL-6 and MDA in hippocampus at the first postoperative day(all P=0.000).On the third postoperative day,there was no significant difference in the levels of IL-6(P=0.251)and MDA(P=0.103)between control group and surgery+NAC group.The protein expressions of Nrf2 and HO-1 in hippocampus were significantly higher in surgery group and surgery+NAC group than in control group and significantly higher in surgery+NAC group than in surgery group(all P=0.000).The mRNA expressions of Nrf2 and HO-1 in hippocampus were significantly higher in surgery group and surgery+NAC group than in control group and significantly higher in surgery+NAC group than in surgery group (all P=0.000). Conclusions NAC pretreatment may reduce oxidative stress and inflammatory response in hippocampus and improve cognitive function.Such effect may be relate to the activation of Nrf2/HO-1 pathway.