七氟醚对老龄大鼠海马 Tau 蛋白磷酸化及认知功能的影响

摘要

ABSTRACT:Objective To investigate the effects of sevoflurane on hippocampal tau phosphoryl-ation and cognitivefunction in aged rats.Methods Forty 20-month-old SD rats were randomly di-vided into five groups,with 8 rats in each group.The groups SⅠ a and SⅠ b were given 1.5%sevoflurane anesthesia for 2 and 12 hours,respectively.The groups SⅡa and SⅡb were given 3%sevoflurane anesthesia for 2 and 12 hours,respectively.The controls(group C)were exposed to pure oxygen for 2 hours.The cognitivefunction was assessed by Morris water maze test before and after anesthesia.Rats were sacrificed after Morris water maze test and hippocampal tissues were removed.Themorphological changes in hippocampal neuronswere observed by HE staining.The contents of GSK-3βand PKA in hippocampus were measured by radioimmunoassay.The levels of tau phosphorylation were determined by Western blot.Results Groups SⅠb and SⅡb,the laten-cy was prolonged after anesthesia(P <0.05).Furthermore,compared with groups SⅠa,SⅡa and C,the latency was prolonged in groups SⅠb and SⅡb,especially in group SⅡb(P <0.05).Com-pared with group C,the levels of GSK-3βand PKA and expression of phospho-tau Ser262(tau-pS-er262)were increased in groups SⅠa,SⅡa,SⅠb and SⅡb and the expression of phospho-tau Ser396(tau-pSer396)was increased in groups SⅡa,SⅠb and SⅡb in a dose-and time-dependent manner(P <0.05).The group C showed normal cellular morphology and distribution in the hip-pocampus.However,sevoflurane anesthesia resulted in dilated intercellular spaces and decreased number of cells.In groups SⅠb and SⅡb,some cells showed nuclear pyknosis,condensation and fragmentation.Conclusion Sevoflurane can affect the cognitive function of aged rats through acti-vating the GSK-3βand PKA,increasing the expression of tau-pSer396 and tau-pSer262,and chan-ging the morphology of brain cells.%目的：研究七氟醚对老龄大鼠海马组织 Tau 蛋白磷酸化及认知功能的影响。方法将40只20月龄的老龄 SD 大鼠按随机数字表法分为5组：七氟醚Ⅰa 组（SⅠa 组）、七氟醚Ⅰb 组（SⅠb 组）、七氟醚Ⅱa 组（SⅡa 组）、七氟醚Ⅱb 组（SⅡb 组）和对照组（C 组），每组8只。SⅠa、SⅠb 组用1．5％七氟醚分别麻醉2、12 h，SⅡa、SⅡb 组用3％七氟醚分别麻醉2、12 h，C 组暴露于纯氧中2 h。于麻醉前及麻醉后行 Morris 水迷宫测试大鼠的认知功能；而后取海马脑组织，HE 染色观察细胞核形态的改变，放免法测定脑组织内的 GSK-3β和 PKA 激酶的浓度，免疫印记法测定海马区 Tau 蛋白的磷酸化水平。结果SⅠb、SⅡb 组麻醉后潜伏期均较麻醉前及 SⅠa、SⅡa、C 组麻醉后明显延长（P ＜0．05），SⅡb 组麻醉后潜伏期较 SⅠb 组延长更为显著（P ＜0．05）。SⅠa、SⅡa、SⅠb、SⅡb 组 GSK-3β和 PKA 激酶水平均较 C 组显著上升（P ＜0．05）；其中 SⅠb 组显著高于 SⅠa 组，SⅡb 组显著高于 SⅡa 组，SⅡb组显著高于 SⅠb 组，SⅡa 组显著高于 SⅠa 组，差异均有统计学意义（P ＜0．05）。SⅡa、SⅠb、SⅡb 组 Tau-pSer396磷酸化水平均较 C 组显著上升（P ＜0．05）；其中 SⅠb 组显著高于 SⅠa 组，SⅡb 组显著高于 SⅡa 组，SⅡb 组显著高于 SⅠb 组，差异均有统计学意义（P ＜0．05）。SⅠa、SⅡa、SⅠb、SⅡb 组 Tau-pSer262磷酸化水平均较 C 组显著上升（P ＜0．05）；其中 SⅠb 组显著高于 SⅠa 组，SⅡb 组显著高于 SⅡa 组，差异均有统计学意义（P ＜0．05）。C 组海马区细胞形态及分布正常；七氟醚各组可见细胞间隙增宽，细胞数目减少，其中 SⅠb、SⅡb 组部分细胞出现形态学改变，胞核固缩、浓染甚至破裂。结论七氟醚可通过激活 GSK-3β和 PKA 激酶，使老龄大鼠 Tau 蛋白（Tau-pS-er396、Tau-pSer262）产生一定程度的磷酸化，改变脑细胞的形态，对其认知功能发生一定的影响。