| Neuroprotective effects and possible mechanisms of GETO on neunons andsynapses damaged by three various fragment of beta-amyloid protein Objective: According to the beta-amyloid (Aβ) cascade hypothesis in Alzheimer's disease (AD), the purpose of this study was to investigate the possible effective mechanism of GETO (extract of Chinese herbal medicine with invigorating the kidney, promoting blood flow, dissipating phlegm) on regulating deposition of Aβ, transportion of Apacross brain-blood barrier (BBB) and neuronal and synaptic toxicity of Aβ.Methods: 1. SH-SY5Y cell lines were incubated with 25-35 fragments of A β at a concentration of 25μmol/L to duplicate AD model used to assess the effect and possible mechanism of GETO on the neuronal and synaptic damage induced by Aβ.To analyze the effect, the number of the cells was counted, morph of the cells was observed and activity of the cells, levels of expression of PSD-95 and phosphorylated cAMP response element binding protein (p-CREB) were determined. 2. 1-42 fragments of Aβ (10ug) was administrated in Sprague-Dawley (SD) with a single right hippocampal injection to duplicate AD animal model. Behavioral changes was observed and the levels of expression of Aβ1-40,PSD-95, Shank, Nerve growth factor (NGF), Tyrosine receptor kinase A (TrkA), Mitogen-activated protein kinase (MAPK) and p-CREB in hippocampi and cortices were determined with immunohistochemistry(IHC). 3. Continuous right external jugular intravenous administration of Aβ1-40 (10ug/200ul, twice a day for 14 days) to explore the influence of vascular-derived Ap on neurons and the neuropropective effect of GETO. The behavioral changes tested in Morris water maze, ultramicrostructure of cortical neurons and expression of Aβ1-40, receptor for advanced glycosylation end product (RAGE), insulin receptor substrate (IRS)-1/2, phosphatidylinositol 3-kinase (PI3K) and p-CREB were analyzed with IHC or Western blotiing. Results: 1. After incubated with Aβ25-35, the number and activity of SH-SY5Y cells decreased, pathologically morphological change appeared, and the levels of expression of PSD-95 and p-CREB decreased; after treated with GETO, the changes above were significant compared to those in model group but there was no significant difference compared to. APP17 peptide group(positive control group). 2. Compared to the model group, the learning and memory of rats in GETO group were improved, expression of Aβ1-40 in brain (10.14 ± 1.58 vs 14.71±3.19 in hippocampus; 11.46 ± 2.05 vs 17.57 ± 5.44 in contex)decreased whereas expression of PSD-95(21.68 ± 8.07 vs 11.80±4.70 in hippocampus; 17.18±4.78 vs 8.68 ± 1.47 in contex), Shank(19.67±3.83 vs 14.35±3.66 in hippocampus; 15.29±11.17 vs 10.02±4.94 in contex), TrkA, MAPKand p-CREB increased, but it was not significantly differnet between GETO group and Aricept group. 3. Compared to the model group, the learning, memory and neuronal pathological changes of rats in GETO group were improved, expression of Aβ1-40 and RAGE in brain decreased whereas expression of IRS-1/2, PI3K and p-CREB increased. The changes were significant but not significantly different compared to those in Aricept group.Conclusions: GETO has a protective effect on neurons and synapses damaged by brain-exogenous Ap (hippocampal injection and intravenous administration) and the mechanism is presumably related to inhibiting transportion of Aβ across BBB into brain, inhibiting the deposition of Ap, activating neuronal survival signal transduction pathways and its APP17mer-like neurotrophic effect simultaneously. This is the first report on mechanisms of Chinese herbal treatment of AD. |
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