Abstract: Objective: To investigate the effects of rutaecarpine on high glucose-induced Alzheimer’s disease-like pathological and cognitive dysfunction and its mechanism in rats. Methods: Adult male SD rats were randomly divided into three groups (n=20): control group, high glucose group and rutaecarpine group. Rats in the control group were fed with conventional feed and tap water. The rats in the high glucose group were fed with conventional feed and 20% sucrose water. The rutaecarpine group was fed with fodder contain 0.01% rutaecarpine and 20% sucrose water. Morris water maze test was used to detect learning and memory and cognitive function of three groups rats after 24 weeks of feeding. Western blot analysis was used to detect tau protein at Thr205 and Ser214 sites in each group. Phosphorylation levels of GSK-3β in serine 9 site (S9-GSK-3β) and PP2A at cycline 307 site (Y307-PP2AC) were also detected. Immunohistochemistry further confirmed tau protein at Thr205 site in each group both in hippocampus and cortex. Results: Compared with the control group, Morris water maze results showed that the latency of finding the hidden platform of the rats in high glucose group was increased significantly and the number of crossing platforms and the target quadrant residence time were significantly decreased (all P＜0.05). Immunohistochemistry showed that the phosphorylation level of tau protein at Thr205 site was significantly increased in the high glucose group compared with the control group, and the phosphorylation level of tau protein at Thr205 site in the rutaecarpine group was higher than that in the high glucose group. Western blot analysis showed that the phosphorylation level of tau protein in the high glucose group was significantly increased at Thr205 and Ser214 site compared with the control group, but the phosphorylation level of pS9-GSK-3β was significantly decreased (all P ＜0.05). Compared with the high glucose group, the latency of finding the hidden platform of the rats in rutaecarpine group was significantly decreased, and the number of crossing platforms and the target quadrant residence time were significantly increased (both P＜0.05). Compared with the high glucose group, the phosphorylation levels of tau protein at Thr205 and Ser214 sites showed a significant decrease, but the phosphorylation level of pS9-GSK-3β was significantly increased (all P＜0.05). Conclusion: Rutaecarpine can alleviate AD-like cognitive dysfunction induced by high glucose, possibly by enhancing pS9-GSK-3β phosphorylation, down-regulating GSK-3β activity, and thus reducing hyperphosphorylation of tau-associated sites.

Key words: Alzheimer', s disease, rutaecarpine, tau protein, rat