The Protective Effects Of Fagopyrum Dibotrys Extract Against A? Neurotoxicity And Alzheimer' S Disease

Objectives:Alzheimer's disease(AD)is a neurodegenerative disorder characterized by gradual memory impairment and cognitive decline,hardly to be diagonosed on the early stages of the illness.Till now,there is no any drug able to reverse the couse of AD.Accumulating evidence indicates that the accumulation of amyloid-beta(A?)plays central roles in the development of this progressive dementia because AP could trigger several kinds of pathological events such as hyperphosphorylation of tau,neuroinflammation and oxidative stress.There is a complex cellular and molecular interaction among these different progression.For exmple,the AP plaques activate inflammatory cells and cytokines and chemokines are altered.Also,inflammatory molecules would drive A? aggregates,accelerating the course of the disease.This is the reason why no drug targeting one single target does work on AD.It is reported that the polyphenol compoundes such as ferulic acid and epicatechin exhibit neuroprotective effects against AD,by alleviating neuroinflammations.As there are a number of polyphenols in the Fagopyrum dibotrys like proanthocyanidins,ferulic acid,catechin,gallic acid and so on,the extractions of which have been suggested to be able to perform anti-tumor effect,anti-inflammation,antibacterial activities,the Fagopyrum dibotrys extraction may slow down the pathogenesis of AD.In the present study,we are going to investigate the effects of polyphenol-rich Fagopyrum extraction(FDE)on AP aggregation and deposion,cytotoxicity of A? peptide and inflammation in a transgenic AD mouse model.Also,we want to confirm whether the FDE have the therapeutic effect on AD model.Methods:The extract of Fagopyrum dibotrys was analyzed by high performance liquid column to confirm the identification and determination of compounds in Fagopyrum extracts.The effects of FDE on the A? aggregation were determined by using thioflavin fluorescence and electron microscopy.SH-SY5Y cells were applied for MTT assay,in the presence or absence of A?,to evaluate the protective effects of FDE against cytotoxicity induced by A?.APP/PS1 transgenic mice were provided to be randomly divided into 3 groups,12 mice in each group,male:female = 1:1.The FDE(Tg)group were treated with 0.65%FDE mixed food,Control(Tg)and another age and sex matched wild-type mice group were fed with standard commercial food.From 3 months old,all the mice were fed the above diets for another 9 months.Animal body weight and levels of ALT and AST were detected during treatment period to confirm the safety of FDE.Mice in prevention experiment underwent Morris water maze to investigate the effect of FDE on cognitive deficits in APP/PS1 transgenic mice.After 9 months of treatment,the brain slices were stained with Congo red and A?(6E10)for A? plaques.The brain sections were also stained with monoclonal anti-CD45 and polyclonal anti-GFAP(glial fibrillary acidic protein)for microglia and astrocyte,respectively.The characteristic blue haemosiderin-posotive profiles on the stained brain slices were observed to determine the microhaemorrhage rates.Frozen brain was homogenized by liquid nitrogen and successively extracted with 2%SDS and 70%formic acid solutions.Concentration of A?40 and A?42 in brain extraction and plasma were quantitatively measured by ELISA.The levels of TNF-a.IL-1? and IFN-y in the plasma of mice were measured using ELISA kits.Results:There were gallic acid,protocatechin acid,catechin,dimer gallic acid ester and epicatechin,trimer gallic acid ester,and epicatechin gallate in the extract of Fagopyrum dibotrys.Electro microscopy assays visually confirm that there were hardly any long fibrils exciting,after preformed A? fibrils were further incubated with FDE.The data from fluorescence assay showed that FDE dose-dependently reduced fluorescence intensity induced by A? fibrillation.On the cultured SH-SY5Y cells,FDE had a dose-dependent protective effect against A?-inducing neurotoxicity.The long-term daily consumption of FDE diet in APP/PS1 transgenic mice did not influence their body weight and liver function.The escape latency,distance and speed of swim of FDE-treated mice were similar to transgenic control.The latency to target quadrant of FDE group in the probe trial was reduced,but still similar to the control mice.The total number of brain A?plaques stained by immunohistocheMistry and Congo red was reduced by FDE.The levels of A?40 and A?42 in SDS and FA fractions of brain homogenates of FDE treatment group were declined significantly compared to control group.The mice from FDE treatment group showed significantly lower A? levels in plasma than the control group.The number of microhemorrhage profiles in the treatment group was also declined compared with the control.The levels of activated microglia and astrocyte in FDE group were obviously decreased compared to the transgenic mice in control group.ELISA assay of plasma showed that the level of TNF-,the proinflammatory cytokine,in plasma of the FDE treatment was lower than control group.But no lower levels of IL-1? and IFN-? were observed after FDE treatment.Conclusions:FDE can effectively inhibit A?42 fibril formation and significantly inhibit the neurotoxicity to the SH-SY5Y cells.FDE is well tolerated in APP/PS1 transgenic mice and exhibit limit effect to rescue the cognitive deficits of aged transgenic mice.FDE can reduce both parenchymal and vascular A? burden in brain.FDE can attenuate inflammation in the brain of APP/PS1 mice after prevention treatment.