Protective effect of EGCG on neurosynaptic damage in APP/PS1 double transgenic mice

Abstract:

Objective：To study the protective effect of EGCG on neurosynaptic damage in APP/PS1 double transgenic mice and its possible mechanism. Methods：APP/PS1 double transgenic mice were randomly divided into two groups：model group（0.1 mL/10 g，normal saline infusion），EGCG group[20 mg/（kg?d），EGCG infusion]. Ten negative mice in the same sex were treated with normal group（0.1 mL/10 g，normal saline infusion）. Morris water maze was used to test the escape latency and platform-crossing changes of mice in each group. Electron microscopy was used to observe the damage of hippocampal neurons in each group. Immunohistochemi－cal method was used to detect the expression of PSD95 and GAP43 in hippocampus of mice. RT-PCR was used to detect the content of PSD95 mRNA and GAP43 mRNA in hippocampus of mice. Results：The escape latency of the model group was significantly pro－longed，the hippocampal neurons were severely damaged，the expression of PSD95 was decreased，and the expression of GAP43 was increased. The results of immunohistochemistry showed that the average optical density of PSD95 in EGCG group was higher than that in model group[（0.11±0.03） vs. （0.05±0.02），P=0.001] and that of GAP43 in EGCG group was lower than that in model group [（0.10±0.03） vs. （0.16±0.04），P=0.002]. The results of RT-PCR showed that the expression of PSD95 in EGCG group was higher than that in model group[（0.82±0.11） vs. （0.50±0.06），P=0.000]. The expression of GAP43 in EGCG group was lower than that in model group[（1.12±0.11） vs. （1.56±0.16），P=0.000]. Conclusion：EGCG can significantly improve the spatial learning，memory and synaptic damage of APP/PS1 transgenic mice. The mech－anism may be related to the effect of EGCG on the synaptic structure of hippocampus，the increase of PSD95 expression and the down-regulation of GAP43 expression.