海马Wnt／β-catenin信号通路在氯化锂预处理改善老龄大鼠术后认知功能中的作用

Role of Wnt/β-catenin signaling pathway in lithium chloride preconditioning-induced improvement in postoperative cognitive function of aged rats

目的评价海马Wnt/β-catenin信号通路在氯化锂预处理改善老龄大鼠术后认知功能中的作用。方法清洁级健康雄性老龄SD大鼠100只，18月龄，体重540～650 g，采用随机数字表法分为5组（n＝20）：对照组（C组）、手术组（S组）、氯化锂预处理组（L组）、sFRP-1组（F组）及氯化锂预处理＋sFRP-1组（L＋F组）。L组和L＋F组术前连续5 d腹腔注射氯化锂2 mmol/kg，1次/d；F组和L＋F组术前1 d脑室注射sFRP-1（浓度10 μg/ml）蛋白液10 μl。于术后1 d每组随机处死10只大鼠，取海马组织，采用Western blot法检测海马组织磷酸化糖原合成酶激酶-3β（p-GSK-3β）、β-catenin及Wnt的表达。术后3～7 d行Morris水迷宫，术后第7天采用ELISA法检测脑脊液β-淀粉样蛋白42（Aβ-42）和磷酸化tau-181蛋白（p-tau-181）浓度。结果与C组比较，其余4组术后3～7 d逃避潜伏期延长，脑脊液Aβ-42浓度升高，S组海马Wnt、p-GSK-3β和β-catenin表达下调，L组和L＋F组海马Wnt、p-GSK-3β和β-catenin表达上调，S组和L＋F组脑脊液p-tau-181浓度升高（P〈0.05）。与S组比较，L组术后3～7 d和L＋F组术后5～7 d逃避潜伏期缩短，L组和L＋F组海马Wnt、p-GSK-3β和β-catenin表达上调，脑脊液Aβ-42和p-tau-181浓度降低（P〈0.05）。与L组比较，L＋F组术后3～6 d逃避潜伏期延长，海马Wnt、p-GSK-3β和β-catenin表达下调，脑脊液p-tau-181浓度升高（P〈0.05）。与F组比较，L＋F组术后3～7 d逃避潜伏期缩短，海马Wnt、p-GSK-3β和β-catenin表达上调，脑脊液Aβ-42和p-tau-181浓度降低（P〈0.05）。结论氯化锂预处理改善老龄大鼠术后认知功能的部分机制与激活Wnt/β-catenin信号通路有关。

Objective To evaluate the role of Wnt/β-catenin signaling pathway in lithium chloride preconditioning-induced improvement in postoperative cognitive function of aged rats.Methods A total of 100 pathogen-free healthy male Sprague-Dawley rats, aged 18 months, weighing 540-650 g, were divided into 5 groups（n=20 each）using a random number table： control group（group C）, surgery group（group S）, lithium chloride preconditioning group（group L）, secreted frizzled-related protein 1（sFRP-1） group（group F）and lithium chloride preconditioning plus sFRP-1 group（group L＋ F）. Lithium chloride 2 mmol/kg was intraperitoneally injected once a day for 5 consecutive days before operation in L and L＋ F groups.In F and L ＋ F groups, sFRP-1 10 μl（concentration 10 μg/ml）was injected into the ventricle at 1 day before operation.Ten rats in each group were randomly sacrificed at 1 day after operation, and the hippocampi were removed for determination of the expression of phosphorylated glycogen synthase kinase-3 beta（p-GSK-3β）, β-catenin and Wnt in hippocampal tissues（by Western blot）. The rest rats underwent Morris water maze test at day 3-7 after operation, and the concentrations of amyloid beta 42（Aβ-42）and phosphorylated tau-181 protein（p-tau-181）in cerebrospinal fluid（CSF）were detected by enzyme-linked immunosorbent assay at day 7 after operation.Results Compared with group C, the escape latency was significantly prolonged at 3-7 days after operation, and the concentration of Aβ-42 in CSF was increased in the other four groups, and the expression of Wnt, p-GSK-3β and β-catenin in hippocampal tissues was down-regulated in group S, the expression of Wnt, p-GSK-3β and β-catenin in hippocampal tissues was significantly up-regulated in L and L＋ F groups, and the concentration of p-tau-181 in CSF was significantly increased in S and L＋ F groups（P〈0.05）. Compared with group S, the escape latency was significantly shortened at 3-7 days after operation in group L and at 5-7 days after operation in group L＋ F, and the expression of Wnt, p-GSK-3β and β-catenin was significantly up-regulated, and the concentrations of Aβ-42 and p-tau-181 in CSF were decreased in L and L＋ F groups（P〈0.05）. Compared with group L, the escape latency was significantly prolonged at 3-6 days after operation, the expression of Wnt, p-GSK-3β and β-catenin was down-regulated, and the concentration of p-tau-181 in CSF was increased in group L＋ F（P〈0.05）. Compared with group F, the escape latency was significantly shortened at 3-7 days after operation, the expression of Wnt, p-GSK-3β and β-catenin was up-regulated, and the concentrations of Aβ-42 and p-tau-181 in CSF were decreased in group L＋ F（P〈0.05）.Conclusion The mechanism by which lithium chloride preconditioning improves in postoperative cognitive function is partially related to activating Wnt/β-catenin signaling pathway in aged rats.