红景天苷通过上调端粒酶表达延缓小鼠脑衰老的作用机制

Salidroside Delays Brain Aging in Mice by Up-regulating Telomerase Expression

目的研究红景天苷对衰老小鼠海马组织的影响及作用机制。方法将12个月龄C57小鼠48只自然衰老鼠,按随机数字表法分为老年组、环黄芪醇组(20 mg/kg,阳性药物)、红景天苷低剂量组(25 mg/kg)、红景天苷高剂量组(50 mg/kg),每组各12只。另取2个月龄C57小鼠12只作为青年组。老年组和青年组小鼠给予等体积生理盐水灌胃,其他组给予对应药物灌胃。采用Morris水迷宫试验评价小鼠的学习和记忆能力,HE染色和Nissl染色观察小鼠海马神经元损伤情况,Western blot检测端粒酶逆转录酶(Telomerase reverse transcriptase,TERT)及其激活因子cMyc的表达水平,PCR-ELISA法检测端粒酶活性。结果水迷宫实验,老年组小鼠的逃逸潜伏期明显高于青年组小鼠,差异有统计学意义(P<0.05),而在目标象限停留时间和跨过平台次数则明显少于青年组小鼠,差异有统计学意义(P<0.05)。与老年组比较,红景天苷组和环黄芪醇治疗组小鼠可有效降低逃逸潜伏期,差异有统计学意义(P<0.05),在目标象限停留时间和跨过平台次数明显增加,差异有统计学意义(P<0.05)。老年组小鼠海马神经元数量较青年组小鼠显著减少,结构不清,排列紊乱,细胞核固缩深染,Nissl小体分布不均;给予红景天苷和环黄芪醇后,小鼠海马神经元的形态结构均有不同程度的改善。与青年组小鼠比较,衰老小鼠海马组织的端粒酶活性明显降低,差异有统计学意义(P<0.05);红景天苷和环黄芪醇治疗后,衰老小鼠海马组织的端粒酶活性明显提高,差异有统计学意义(P<0.05)。与青年小鼠比较,衰老小鼠海马组织中的TERT和p-cMyc的表达明显下降,差异有统计学意义(P<0.05),经红景天苷和环黄芪醇处理的小鼠海马组织中TERT和cMyc的表达较衰老小鼠明显升高,差异有统计学意义(P<0.05)。结论红景天苷可以通过提高端粒酶活性而延缓小鼠海马组织衰老。

Objective To observe the effect of salidroside on the hippocampus in aging mice and decipher the un⁃derlying mechanism.Methods Forty-eight 12-month-old C57 mice of natural aging were assigned by the random number table method into model(aging),cycloastragenol(20 mg/kg,positive drug),and low-(25 mg/kg)and high-dose(50 mg/kg)salidroside groups(n=12).In addition,twelve 2-month-old C57 mice were used as the control(young)group.The mice in the model and control groups were administrated with equal volume of normal saline by gavage,while those in other groups were administrated with corresponding drugs.Morris water maze test was carried out to evaluate the learning and memory abilities of mice.Hematoxylin-eosin(HE)staining and Nissl staining were employed to observe the damage of hippocampal neurons.The expression levels of telomerase reverse transcriptase(TERT)and its activator cMyc were determined by Western blotting.PCR combined with enzyme-linked immunosorbent assay was employed to measure the telomerase activity.Results In Morris water maze test,the model group showed longer escape latency,shorter time in the target quadrant,and fewer times of crossing the platform than the control group(P<0.05).Compared with the model group,salidroside and cycloastragenol shortened the escape latency,prolonged the time in the target quadrant,and in⁃creased the times of crossing the platform(P<0.05).Compared with the control group,the model group showed reduced hippocampal neurons,blurred structure,cell disarrangement,karyopyknosis,and uneven distribution of Nissl bodies.The morphology and structure of hippocampal neurons in aging mice were improved after the administration of salidroside or cy⁃cloastragenol.The telomerase activity in the hippocampus of aging mice was lower than that of young mice(P<0.05).Af⁃ter treatment with salidroside or cycloastragenol,the telomerase activity in the hippocampus of aging mice increased(P<0.05).Compared with the control group,the model group showed down-regulated expression of TERT and p-cMyc in the hippocampus(P<0.05).Compared with the model group,salidroside and cycloastragenol up-regulated the protein levels of TERT and cMyc(P<0.05).Conclusion Salidroside can increase the telomerase activity to delay the hippocam⁃pus senescence of mice.