Hei Xiaoyaosan Affects Synaptic Plasticity of Hippocampal Neurons in APP/PS1 Double Transgenic Mice of AD via cAMP/PKA/NMDAR Signaling Pathway / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo explore the effect and mechanism of Hei Xiaoyaosan in modulating the synaptic plasticity in APP/PS1 mice by regulating the cyclic adenosine monophosphate （cAMP）/protein kinase A （PKA）/N-methyl-D-aspartate receptor （NMDAR） signaling pathway. MethodTwelve 4-month-old male C57BL/6J mice were selected as the blank control group， and 60 4-month-old male APP/PS1 double transgenic mice were randomized into model， KW-6002 （adenosine receptor antagonist， 3 mg·kg-1）， and high-， medium-， and low-dose （22.10， 11.05， 5.53 g·kg-1， respectively） Hei Xiaoyaosan groups， with 12 mice in each group. Mice were administrated with corresponding drugs for 90 days. Transmission electron microscopy was employed to observe the synaptic ultrastructure of hippocampal neurons， and Golgi staining was used to observe the dendritic spine density of neurons in hippocampal CA1 region. Western blot was employed to measure the protein levels of cAMP， PKA， N-methyl-D-aspartate receptors 1， 2A， and 2B （NR1， NR2A， and NR2B， respectively）， postsynaptic density protein 95 （PSD95）， and synapsin 1 （SYN1）. Real-time fluorescence quantitative polymerase chain reaction（Real-time PCR） was performed to determine the mRNA levels of cAMP， PKA， and NR1. Enzyme-linked immunosorbent assay was employed to determine the content of interleukin-12 （IL-12） and interleukin-4 （IL-4） in the hippocampus. ResultCompared with the blank group， the model group showed blurred boundaries between presynaptic membrane and postsynaptic membrane in hippocampal CA1 region， reduced and scattered synaptic vesicles， and decreased density of postsynaptic membrane， and irregular， disarranged， and loosened dendritic spines of neurons in hippocampal CA1 region （P<0.01）. In addition， the model group presented down-regulated protein levels of cAMP， PKA， NR1， NR2A， NR2B， PSD95， and SYN1 and mRNA levels of cAMP， PKA， and NR1， elevated IL-12 level， and lowered IL-4 level in the hippocampus （P<0.01）. Compared with the model group， the drug intervention groups showed clear and intact boundaries between presynaptic membrane and postsynaptic membrane in hippocampal CA1 region， increased synaptic vesicles with dense arrangement， increased density of postsynaptic membrane， and improved morphology， arrangement， and density of neuronal dendritic spines （P<0.05， P<0.01）. In addition， the drug interventions up-regulated the protein levels of cAMP， PKA， NR1， NR2A， NR2B， PSD95， and SYN1 （P<0.05，P<0.01） and mRNA levels of cAMP， PKA， and NR1 （P<0.01）， lowered the IL-12 level （P<0.01）， and elevated the IL-4 level （P<0.01） in the hippocampus. ConclusionHei Xiaoyaosan can improve the structure and morphology of hippocampal neurons in APP/PS1 mice by activating the cAMP/PKA/NMDAR signaling pathway and repairing synaptic plasticity.