Mechanism of Dihuang Yinzi in Improving Astrocyte Injury and Regulating Synaptic Structure and Function in AD Mice / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo investigate the mechanism of Dihuang Yinzi in improving astrocyte injury and protecting synaptic structure and function in the brain of Alzheimer's disease （AD） mice. MethodForty male APP/PS1 transgenic mice aged four months were randomly divided into a model group and a model + Dihuang Yinzi （0.25 g·kg-1） group， with 20 mice in each group. Forty C57BL/6J mice with the same background and same age were randomly divided into a control group and a control + Dihuang Yinzi （0.25 g·kg-1） group， with 20 mice in each group. The mice in the control + Dihuang Yinzi group and the model + Dihuang Yinzi group were administered with Dihuang Yinzi by gavage， and those in the control group and the model group received an equal volume of sterilized normal saline， once a day for 150 days. The learning and memory ability of mice was tested by the light-dark box test and Y-maze spontaneous alternation test. The content of glutamate （Glu） and glutamine （Gln） was measured by liquid chromatography-tandem mass spectrometry （LC-MS）. Long-term potentiation （LTP） assay was used to detect synaptic plasticity in brain tissues. The protein expression levels of excitatory amino acid transporter 2 （EAAT2）， postsynaptic density protein95 （PSD95）， and synaptophysin （SYN） in brain tissues were measured by Western blot. Immunofluorescence was used to assess the localization and expression of EAAT2. Colorimetry was performed to detect Na+-K+ ATPase activity in mouse brain tissues. ResultAs compared with the control group， the model group showed shortened residence latency （P<0.01）， increased number of errors （P<0.01） in the light-dark box test， reduced spontaneous alternation behaviors （P<0.01）， no significant difference in the total number of arm entries in the Y-maze spontaneous alternation test， down-regulated expression of EAAT2， PSD95， and SYN （P<0.01）， blunted activity of Na+-K+ ATPase （P<0.01）， up-regulated Glu level （P<0.01）， down-regulated Gln level （P<0.01）， and reduced relative population spike （PS） amplitude and the slope of excitatory postsynaptic potential （EPSP） （P<0.05， P<0.01）， while the above experimental indexes were not significantly different in the control + Dihuang Yinzi group. Compared with the model group， the model + Dihuang Yinzi group displayed prolonged residence latency （P<0.05）， decreased number of errors （P<0.01） in the light-dark box test， increased spontaneous alternation behaviors （P<0.01）， no significant difference in the total number of arm entries in the Y-maze spontaneous alternation test， up-regulated expression of EAAT2， PSD95， and SYN （P<0.01）， potentiated activity of Na+-K+ ATPase （P<0.01）， reduced Glu level （P<0.01）， up-regulated Gln level （P<0.01）， and increased PS amplitude and EPSP slope （P<0.01）. ConclusionDihuang Yinzi can improve cognitive dysfunction in AD mice by protecting astrocytes， increasing Glu uptake to reduce its abnormal accumulation， and protecting synaptic structure and function.