右美托咪定预防七氟烷对新生小鼠脑神经毒性的机制:与Tau蛋白磷酸化的关系

Mechanism of dexmedetomidine preventing sevoflurane-indued neurotoxicity to neonatal mice: the relationship with Tau phosphorylation

目的探讨右美托咪定预防七氟烷对新生小鼠脑神经毒性的机制与Tau蛋白磷酸化的关系。方法SPF级健康C57BL/6野生型新生小鼠72只,6日龄,采用随机数字表法分为4组(n=18):正常对照组(C组)、右美托咪定对照组(D组)、七氟烷脑神经毒性组(S组)和右美托咪定预防组(SD组)。在出生后第6、9和12天分别吸入2.1%~3.3%七氟烷麻醉2 h,SD组麻醉前30 min腹腔注射右美托咪定10μg/kg,结束后随机取6只小鼠海马组织,采用Western blot法测定Tau-PS202和Tau-PT205位点磷酸化Tau蛋白(AT8)和Tau46蛋白的表达;在出生后第29~30天行新物体识别实验(观察新物体辨别比);在出生后第31~37天行Morris水迷宫实验(记录逃避潜伏期及穿越平台次数),随后麻醉下取小鼠海马组织,采用Western blot法测定突触后致密物-95(PSD-95)表达。结果与C组相比,S组海马AT8表达上调,PSD-95表达下调,穿越平台次数减少,新物体辨别比降低(P<0.05),Tau46蛋白表达与逃避潜伏期差异无统计学意义,D组和SD组上述指标差异无统计学意义(P>0.05);与S组相比,SD组海马AT8表达下调,PSD-95表达上调,穿越平台次数增加,新物体辨别比升高(P<0.05),Tau46蛋白表达和逃避潜伏期差异无统计学意义(P>0.05)。结论右美托咪定预防七氟烷诱发新生小鼠脑神经毒性的机制与抑制Tau蛋白磷酸化有关。

Objective To investigate the mechanism of dexmedetomidine preventing sevoflurane-indued neurotoxicity to neonatal mice and the relationship with Tau phosphorylation.Methods Seventy-two SPF healthy newly born C57BL/6 wild-type mice of both sexes,aged 6 days,were divided into 4 groups(n=18 each)using a random number table method:normal control group(C group),dexmedetomidine control group(D group),sevoflurane-induced neurotoxicity group(S group),and dexmedetomidine prevention group(SD group).Mice inhaled 2.1%-3.3%sevoflurane 2 h daily on postnatal days 6,9 and 12,and dexmedetomidine 10μg/kg was intraperitoneally injected at 30 min before anesthesia in group SD.Six mice were randomly selected after the end of injection,and the hippocampus tissues were removed for determination of the expression of phosphorylated Tau protein(AT8)and Tau46 protein at Tau-PS202 and Tau-PT205 sites by Western blot.The new object recognition test was performed on postnatal days 29-30(the discrimination ratio of new objects was observed),and the Morris water maze test was performed from postnatal day 31 to 37(the escape latency and the times of crossing the platform were observed).The hippocampi were harvested under anesthesia to detect the expression of postsynapatic density-95 by Western blot.Results Compared with group C,the expression of AT8 was significantly up-regulated,the expression of PSD-95 was down-regulated,the number of crossing the platform and new object discrimination ratio were decreased(P<0.05),and no significant change was found in Tau46 protein expression or escape latency in group S(P>0.05).There was no significant difference in the indexes mentioned above between group D and group SD(P>0.05).Compared with group S,the expression of AT8 was significantly down-regulated,the expression of postsynapatic density-95 was up-regulated,the number of crossing the platform and new object discrimination ratio were increased(P<0.05),and no significant change was found in Tau46 protein expression and escape latency in group SD(P>0.05).Conclusions The mechanism of dexmedetomidine preventing sevoflurane-induced neurotoxicity to neonatal mice is related to the inhibition of Tau phosphorylation.