The Therapeutic Effect And Mechanism Of Intervention Of Frangipani In Alzheimer's Disease

Objective: Alzheimer’s disease（AD）, also known as senile dementia, is a type of neurodegenerative diseases with brain function decline. Many AD patients have clinical symptoms like poor memory, low orientation, weak understanding et al. accompanied by declined intelligence. Patients with severe disease can not take care of themselves. AD is characterized by two pathological features, the senile plaques composed mainly of amyloid-β（Aβ） peptide and the neurofibrillary tangles（NFT） which are bundles of paired helical filaments（PHF） of protein Tau. As aging population in China increases fast in recent years, AD morbidity rate also increased. For the family and society, This brings a heavy burden to both the family and society. So far, no effective drug has been developed for clinical AD treatment. Therefore, it is imperative to study pathogenesis of AD deeply and to screen new drugs that can be used clinically and effectively to intervene the progression of AD. Jasminin is a kind of secoiridoid glucosides with its monomer having a certain antibacterial activity. A report showed that Jasminin could significantly induce RAW264. 7 cells to secrete TNF-α, and stimulated the mitogen-activated protein kinase（MAPK） signaling pathway, however, its effect on AD has not been reported. In this study, the inhibitory effect of jasminin on Aβ_1-42 aggregation was observed in vitro, and its the impact on the pathological features of AD was also investigated in both AD cell and micemodels.Methods: Nine active ingredients of Chinese medicines were investigated in this paper at different concentrations. 50μmol/L Aβ_1-42 monomer was incubated with those active ingredients in vitro respectively, and the thioflavin-T（Th T） assay was used to measure Aβ_1-42 aggregation in different periods. Circular dichroism（CD） was used to detect structural changes of during the aggregation of Aβ_1-42 monomer（2mmol/L） in vitro to form fibers with the presence of 2mmol/L Jasminin.Atomic force microscope was also used to image the changes of fiber quantity and length of Aβ_1-42 monomer after incubation with Jasminin for 12 hours in vitro. Western-blot analysis was used tomeasure altered expression of proteins participating the AD associated pathways in N2A-SW cells. Immunofluorescence assay was used to image Tau-p S396 and tubulin in the primarily cultured neurons isolated from mice hippocampus. Triple transgenic AD mice treated with 100mg/kg/day Jasminin in drinking water for 30 days were performed behavioral test. Western-blot analysis was used toquantify the expression of proteins invoveled in AD associated pathways in cortex.Results: Nine active ingredients of Chinese medicines were found by the Th T fluorescence assay to inhibit Aβ_1-42 aggregation to a certain extent, in which Ginsenoside Re had the inhibitory effect in the range of 10¹00μmol/L. Panaxatriol, Loganin, Ginsenoside Rg1, Jasminin and Artemisinin had less effect than Ginsenoside Re, with the inhibitory concentrations at the range of 20¹00μmol/L. Helicid and Ginsenoside R0 only had weak effect compared with the other ingredients. Jasminin could inhibit β-sheet production which was imaged by CD. Meanwhile, it could also significantly reduce fiber quantity and polymerization rate of Aβ_1-42 observed by atomic force microscope. Jasminin decreased the express levels of APP（p=0.0001）, Tau-p S396（p=0.0005）, Tau-p S422（p=0.0009） and GSK3β-p Y216（p=0.0294） in N2A-SW cells, while increased the expression levels of Tau5 protein（p=0.0017） and GSK3β-p S9（p=0.0082）. In addition, Jasminin played an important role in synapse protection, which increased the expression of PSD95 in N2A-SW cells（p=0.0017）, reduced Tau-p S396 in primary neurons and stabilized microtubule structure. In the cortex of 3×Tg AD mic, the levels of APP（p=0.0163）, s APPβ（p=0.0115）,Bace-1（p=0.0085）and Aβ（p=0.0078）were significantly reduced, while the levels of Tau-p S396（p=0.0207）,Tau-p S404（p=0.0311）and Tau-p T231（p=0.0474）were also reduced, after the treatment of Jasminin.Conclusion: Jasminin have some inhibitory effects on Aβ_1-42 aggregation in vitro.After treatment by Jasminin, the expression levels of proteins associated with synapse and Tau signal pathway changed obviously in N2A-SW cells. Jasminin could reduce tau phosphorylation, and aggregation to protectneruons, leading to recovery of pathologically damaged neurons. Treatment with Jasminin for 30 daysimproved cognitive abilities of 3×Tg AD mice and decreased the levels of APP, s APPβ and Bace-1 in cortex, resulting in reduction of Aβ production and tau phosphrylation in cortex. Results in this paper implied that Jasminin has potential to be a new drug for ADtreatment.