米诺环素抑制星形胶质细胞活化改善老年小鼠70%肝切除手术后远期学习和记忆能力

Minocycline improves postoperative long-term learning and memory ability in aged mice after 70% hepatectomy by inhibiting astrocytic activation

目的:评价米诺环素对老年C57BL/6小鼠术后30 d学习和记忆能力的影响,并探讨星形胶质细胞在此过程中的作用。方法:45只雄性C57BL/6老年小鼠随机分为3组(每组15只):假手术组,仅接受皮肤切开手术;手术组,该组小鼠接受70%肝切除手术但不接受药物治疗;米诺环素组,术后每天腹腔注射45 mg/kg米诺环素,连续30 d,每组15只。利用Morris水迷宫测试其逃避潜伏期和游泳距离以判断小鼠术后学习记忆能力的改变,行为学测试结束后即刻取小鼠海马组织,利用realtime PCR检测炎性细胞因子TNF-α和IL-6 mRNA的相对表达量,利用Western blot检测胶质纤维酸性蛋白(GFAP)和离子钙接头蛋白抗体-1(Iba-1)的表达水平,另外取部分海马组织制作冰冻切片样本行免疫组织化学检测。结果:Morris水迷宫测试显示手术组小鼠逃避潜伏期和游泳距离均延长,显著长于假手术组和米诺环素组(P<0.05);手术组小鼠海马组织TNF-αmRNA表达水平显著高于假手术组和米诺环素组(P<0.05),米诺环素组小鼠TNF-αmRNA的表达显著少于手术组(P<0.05);手术组和米诺环素组小鼠IL-6 mRNA的表达水平显著高于假手术组(P<0.001),米诺环素组小鼠IL-6 mRNA的表达显著少于手术组(P<0.001);手术组和米诺环素组GFAP的表达显著高于假手术组(P<0.001),米诺华素组GFAP的表达水平显著少于手术组(P<0.001),3组Iba-1的表达水平无差异(P>0.05);海马组织免疫组化星形胶质细胞的变化与GFAP的变化一致。结论:海马组织星形胶质细胞活化可能与部分肝切除老年小鼠远期学习和记忆能力下降有关,米诺环素可能通过降低TNF-α和IL-6mRNA的表达,抑制星形胶质细胞的活化改善老年小鼠术后远期学习和记忆能力。

Objective：To evaluate the effect of minocycline on the long-term learning and memory ability for 30 days afte surgery in C57BL/6 aged mice,and to explore the role of astrocytes in the process. Methords：Forty-five male C57/BL6 aged mice were randomly divided into 3 groups with 15 in each group：sham operation group only received skin incision,operation group received 70% hepatectomy without drugs administration,minocycline group intraperitoneally injected with 45 mg/kg minocycline once a day for 30 days after surgery. Hippocampal-dependent spatial learning and memory ability was evaluated using the Morris water maze（MWM）. Then mice hippocampal tissue was sampled. The hippocampal mRNA relative expression levels of tumor necrosis factor α（TNF-α） and interleukin 6（IL-6） were tested using a real- time PCR. The expression levels of hippocampal glial fibrillary acidic protein （GFAP） and ionized calcium-binding adaptor molecule-1（Iba-1） were detected with Western blot. The remained hippocampal tissue was collected for immuno-histochemistry. Results：MWM tests showed that the escape latency and swimming distance in operation group was longer than that of sham and minocycline groups （P 〈 0.05）. The relative expression of TNF-α mRNA of operation group was significantly higher sham and minocycline groups （P 〈 0.05）,and the expression of TNF-α mRNA of minocycline group was less than operation group（P 〈 0.05）. The expression of IL-6 mRNA in operation and minocycline group was significantly higher than that in sham group （P 〈 0.001）,and the expression of IL-6 mRNA in minocycline groups was markedly less than that of operation group （P 〈 0.001）. Compared with sham group,the expression of GFAP in operation and minocycline group was higher（P 〈 0.001）,and the expression level of GFAP in minocycline group was less than that in operation groups（P 〈 0.001）. There was no significant difference in Iba-1 expression among the three groups（P 〉 0.05）. The changes of astrocytes in hippocampal tissue immunohistochemistry were consistent with the changes of GFAP. Conclusion：The activation of astrocytes in the hippocampus was likely to contribute to long-term decline of learning and memory ability in aged mice undergone partial hepatectomy. Minocycline can improve postoperative spatial learning and memory ability by decreasing the expression levels of TNF-a and IL-6 mRNA and inhibiting astrocyte activation.