ProNGF-p75~(NTR)在异氟醚暴露的老年小鼠认知功能下降中的作用

目的:探讨神经生长因子前体(pro NGF)与其受体p75~(NTR)特异性结合(pro NGF-p75~(NTR))在异氟醚暴露的老年小鼠认知功能障碍中的作用。方法:30只C57BL/6J雄性老年小鼠随机分成3组:正常(control)组、异氟醚(Iso)组和p75~(NTR)抑制剂2-氨基-3-甲基-戊酸酰胺(LM11A-31,LM)+异氟醚(LM+Iso)组。各异氟醚处理组的小鼠每天吸入1%异氟醚3 h,连续7 d;control组每天吸入空气3 h,连续7 d。LM溶于无菌生理盐水,在吸入异氟醚之前按50 mg·kg-1·d-1的剂量对LM+Iso组老年小鼠进行灌胃,连续1个月;control组和Iso组小鼠仅给予同等体积的生理盐水。用动脉血气分析法监测异氟醚暴露后小鼠生理状态。Morris水迷宫实验观察小鼠行为学的改变。Western blot检测各组小鼠海马组织中pro NGF、p75~(NTR)、磷酸化p38 MAPK和cleaved caspase-3蛋白水平的变化。结果:与control组比较,Iso组海马组织中pro NGF和p75~(NTR)的蛋白表达水平显著增加(P0.05)。Iso组海马组织中p38 MAPK的磷酸化水平较control组显著升高(P0.05);LM+Iso组p38 MAPK的磷酸化水平较Iso组显著下降(P0.05)。Iso组海马组织中cleaved caspase-3的蛋白水平较正常组显著升高(P0.05),而LM11A-31干预可以明显下调异氟醚诱导小鼠海马组织中cleaved caspase-3的蛋白水平(P0.05)。与control组相比,Iso组小鼠找寻平台的潜伏期明显延长(P0.05),小鼠穿越原平台次数减少(P0.05);而LM+Iso组小鼠的逃避潜伏期较Iso组小鼠显著缩短(P0.05),穿越原平台次数较Iso组小鼠增加(P0.05)。结论:Pro NGF-p75~(NTR)可能在异氟醚暴露的老年小鼠凋亡信号通路的活化以及认知功能的下降过程中起一定作用,这为临床干预提供了潜在的靶点。

Role of proNGF-p75NTR in isoflurane-induced cognitive impairment in aging mice

AIM: To investigate the role of specific binding of precursor form of nerve growth factor (proNGF) to p75^NTR (proNGF-p75^NTR) in isoflurane-induced cognitive impairment in aging mice. METHODS: Aging C57BL/6J male mice were randomly divided into 3 groups:control group, isoflurane (Iso) group and p75^NTR specific inhibitor 2-amino-3-methyl-pentanoic acid amide (LM11A-31, LM)+ isoflurane (LM+Iso) group. Aging C57BL/6J mice in Iso group and LM+Iso group were exposed to isoflurane, and the mice in control group were exposed to air. The mice in LM+Iso group were treated with LM, which dissolved in normal saline water and was administered daily by oral gavage at 50 mg·kg^-1·d^-1 for 1 month. The mice in control group and Iso group received an equivalent volume of normal saline by the same route. Arterial blood gas analysis was conducted to detect the physiological state of the mice after isoflurane exposure. Morris water maze was performed to evaluate the cognitive function. The protein levels of proNGF, p75^NTR, phosphorylated p38 MAPK and cleaved caspase-3 were determined by Western blot. RESULTS: Compared with the control group, the protein expression of proNGF and p75^NTR in the hippocampus of Iso group was significantly elevated (P<0.05). The phosphorylation level of p38 MAPK was higher in Iso group than that in control group (P<0.05), which was reduced in LM+Iso group significantly (P<0.05). A significant increase in the protein level of cleaved caspase-3 was observed in Iso group as compared with control group (P<0.05), while LM11A-31 treatment reversed this elevation significantly (P<0.05). The escape latency prolonged and the number of crossing the original platform location reduced in Iso group compared with control group (P<0.05), which were reversed by LM11A-31 in LM+Iso group (P<0.05). CONCLUSION: ProNGF-p75^NTR probably plays an vital role in the apoptotic pathway activation and the cognitive dysfunction in aging mice exposure to isoflurane, which provides a potential target for clinical intervention.