EARLY-STAGE PROTECTIVE EFFECTS OF TEA POLYPHENOLS ON HIPPOCAMPAL NEUROGENESIS AND COGNITIVE DYSFUNCTION IN ALZHEIMER'S DISEASE MODEL

The activation of glial cells may cause inflammatory responses to brain, leading to cognitive dysfunction. Green tea polyphenols have been reported to be neuroprotective. This study used the method of intracerebroventricular injection of A1-42 to establish an Alzheimer's disease (AD) model, and then treated with tea polyphenols. We aimed to investigate the effects and molecular mechanism of tea polyphenols on antagonizing the neurotoxicity induced by A1-42. Three-month-old male C57BL/6J mice were injected with A1-42 into the lateral ventricle and tea polyphenols were administered immediately after modeling. Morris water maze test was conducted to detect the cognitive function, Western blot assay was used to detect protein expressions of related signaling pathways in hippocampus tissue, and immunofluorescence assay was used to label microglia and astrocyte. Compared with AD model mice without tea polyphenols treatment, the latency to find the hidden platform of AD model mice with tea polyphenols treatment was significantly reduced, and the proportion of time spent in the quadrant was significantly increased. The expressions of BDNF and TrkB were significantly increased. In addition, microglia/astrocyte cell proliferation was significantly reduced and the activation of pro-inflammatory signaling pathway factors was down-regulated, while anti-inflammatory signaling pathway factors was up-regulated. This study indicates that tea polyphenols attenuate A1-42-induced cognition dysfunction and the effects may be related to hippocampal neurogenesis and glial cell-related inflammatory response.