Objective:
In this study, male C57BL/6J mice injected with STZ (3 mg/kg) in the lateral ventricle were used as Alzheimer’s disease (AD) animal model. The study aimed to evaluate the effects of Lycium barbarum polysaccharide (LBP) on the learning and memory ability in the model mice and clarify the related mechanisms by which it exerts neuroprotective effects. The main results: (1) Based on Meta-analysis to explore the clinical efficacy of the ZiBuGanShen prescription in the treatment of Alzheimer's Disease (AD), and statistics on the components of the ZiBuGanShen prescription and the frequency of the use of traditional Chinese medicine. (2) Effects of lycium barbarum polysaccharide (LBP) on the learning and memory ability in the ICV-STZ-induced demented mice. (3) The effects of LBP on the brain histopathology and the expression levels of synapse-related protein in ICV-STZ-induced dementia mice. (4) Regulatory effects of LBP on Tau protein phosphorylation in ICV-STZ-induced dementia mice and its effects on the expression levels of proteins related to the IRS1/PI3K/AKT signalling pathway.
Methods:
（1）Randomized controlled trials (RCTS) on treatment of Alzheimer’s disease (AD) by ZiBuGanShen prescription were searched, and meta-analysis was performed using RevMan software. After that, statistics on the components of the ZiBuGanShen prescription and the frequency of use of Chinese medicines were also obtained.
（2）Fifteen 3-month-old male C57BL/6J mice were injected with artificial cerebrospinal fluid (aCSF) in the lateral ventricle as a control group (ICV-aCSF group); Seventy-five mice of the same month were injected with STZ in the lateral ventricle and were randomly divided into five groups with 15 mice in each group, the model group (ICV-STZ), the low-dose LBP group (ICV-STZ+L-LBP, 50 mg/kg), the medium-dose LBP group (ICV-STZ+M-LBP, 100 mg/kg), high-dose LBP group (ICV-STZ+H-LBP, 200 mg/kg), and donepezil group (ICV-STZ+Donepezil, 0.75 mg/kg). After 1 week of modelling, the drug was administered by continuous gavage for 4 weeks, and the effects of LBP on the learning and memory ability of ICV-STZ-induced dementia mice were observed by the Y maze test, Morris water maze test, step-through test and step-down test.
（3）The effects of LBP on neurons in the brain tissue of ICV-STZ-induced dementia mice were evaluated by Nissl staining. The effects of LBP on Aβ desposition in the brain tissue of mice were observed by Th-T staining. The expression level of synapse-associated proteins in the cerebral cortex and hippocampus of mice of each group was determined by Western blot.
（4）Western blot was used to detect the phosphorylation degree of Tau protein at Ser199, Thr205, Ser396 and Ser404 sites as well as the expression levels of protein kinase, protein phosphatase, and protein expression related to IRS1/PI3K/AKT signaling pathway in the brain tissues of mice in each group.
Results:
（1）The results of Meta-analysis show that ZiBuGanShen prescription has significant clinical efficacy in treating AD; it can significantly improve the cognitive function of AD patients; at the same time, it may improve the living ability of AD patients. The composition of ZiBuGanShen prescriptions and the frequency of the traditional Chinese medicines were counted in the literature included in the Meta-analysis. Lycium barbarum polysaccharide was used more frequently, and as one of the main active ingredients of lycium barbarum polysaccharide, LBP has good hypoglycemic, antioxidant, anti-aging, neuroprotective, and insulin sensitivity-enhancing effects. Consequently, LBP was used as a therapeutic agent in animal experiments.
（2）In the Y maze test, compared with the ICV-aCSF group, the exploration times, exploration distance and the time spent in the novel arm were significantly reduced, and the rate of spontaneous alternation was also significantly decreased; After treatment with LBP, the exploration of the novel arm and the rate of spontaneous alternation was significantly increased. In the Morris water maze experiment, mice in the ICV-STZ group had a significantly longer time to the first crossing of the platform and a significantly lower number of crossing times compared with mice in the ICV-aCSF group, and the LBP treatment significantly shortened the time to the first crossing of the platform and increased the number of crossings.
（3）In the step-through test, the latency of ICV-STZ mice was shortened and the number of errors was significantly increased compared with that of mice in the ICV-aCSF group; the latency of mice in the ICV-STZ group was significantly shortened in the step-down test; and LBP treatment significantly prolonged the latency of the step-down test of the mice in the ICV-STZ group, as well as significantly reduced the number of errors in both step-through test and step-down test.
（4）Nissl staining results showed that neuronal deficits were severe in hippocampus and the cortex in ICV-STZ group mice, with neuronal cytosol shrinkage, sparse and discontinuous cell arrangement, increased cell gaps, reduced cytoplasmic Nissl bodys, and non-uniform chromatin distribution. After treatment with LBP, the neuronal deficits were improved, the cell arrangement was tighter and more continuous than that of the ICV-STZ group mice, the cell gap was reduced, and the chromatin distribution was more uniform. Th-T staining results showed that LBP could reduce the deposition of Aβ in the brain tissue of ICV-STZ-induced dementia mice. The results of Western blot experiment showed that LBP could up-regulate the expression levels of PSD95, SV2A, Homer-1 and SYP in the cortex and hippocampus of ICV-STZ-induced dementia mice.
（5）Western Blot results showed that LBP reduced the phosphorylation of Tau protein at Ser199, Thr205, Ser396, Ser404 sites, up-regulated the protein expression level of p-GSK3β (Ser9), and down-regulated the expression level of p-GSK3β (Tyr216), and, at the same time, increased the expression level of the IRS1/PI3K/AKT pathway-related proteins in the brains of ICV-STZ-induced demented mice.
Conclusion:
（1）ZiBuGanShen prescription has a good clinical effect on AD. Lycium barbarum was used more frequently, and LBP, as one of the main active ingredients of Lycium barbarum, has good effects of improving pancreatic islet function, promoting insulin secretion, neuroprotection, and improving cognition, therefore, it was determined that LBP was used as a therapeutic drug in animal experiments.
（2）LBP has a favourable ameliorative effect on learning and memory dysfunction in ICV-STZ-induced dementia mice.
（3）LBP can protect the brain neurons in ICV-STZ-induced dementia mice, reduce the depositionof Aβ in the brain tissue, and increase the expression level of synapse-associated proteins.
（4）LBP can reduce the Tau protein phosphorylation in the brain of ICV-STZ-induced dementia mice, and the mechanism may be related to the up-regulation of the expression of IRS1/PI3K/AKT pathway-related proteins and the regulation of downstream GSK3β protein phosphorylation.
谷歌
火狐
