Effect Of Ethanol On β-amyloid Protein Aggregation And The Study Of Grape Seed Proanthocyanidins And Vitamin B₁

The aggregation ofβ-amyloid protein（Aβ）is considered critical to the pathogenesis of Alzheimer’s disease（AD）.In both patient and animal models of AD,aggregation dynamics in vivo have been shown to correlate with the rate of disease progression.In this study,the effect of ethanol on the in vitro aggregation of Aβ_1-40 and Aβ_1-42,which can be changed by thioflavin T fluorescence,circular dichrospection,and field emission scanning electron microscopy,was studied in detail,and the inhibition effects of grape seed proanthocyanidins and vitamin B₁,which have great potential in the treatment of AD,were studied.1.The results of the study of ethanol affecting the Aβin vitro aggregation state of Aβ_1-40 and Aβ_1-42showed that compared with the control group,1%to 50%ethanol had no significant effect on the fluorescence intensity of Aβ_1-40 at 24 h,and the Th T fluorescence intensity of Aβ_1-40 at 1%to 50%ethanol decreased by 74%,77%,77%,58%,59%,53%,67%and 89%at 48 h（p<0.01）,respectively.Ethanol also causes Aβ_1-40to aggregate to form a small amount of fibrils and most of them are still oligomeric,and the effect on Aβ_1-40 is mainly achieved by promoting the conversion ofβ-sheet toα-helix in the secondary structure.Among them,the higher concentrations of ethanol（40%and 50%）although significantly reducing the fibrils and fibrous structure of Aβ_1-40,but produce oligomeric structures other than self-aggregation.Compared with the control group,1%to 10%ethanol had no significant effect on the aggregation state and process of Aβ_1-42;30%～50%ethanol reduced the fluorescence intensity of Aβ_1-42 by 25%,61%and 71%,respectively at 24h（p<0.05）,while 20%to 50%ethanol reduced the fluorescence intensity of Aβ_1-42 at 48 h by 15%,31%,67%and 85%（p<0.05）,respectively,and had concentration and time dependence.Combined with the presence of ethanol in CD analysis resulted in a reduction inβ-sheet and FESEM characterization to reveal fractures of its fibers and changes in oligomeric structure,and it is believed that 20%to 50%alcohol has an inhibitory effect on the aggregation of Aβ_1-42,but it does not manifest itself in the self-aggregation path,and reduces the degree of aggregation by destroying its fiber structure and promoting fiber agglomeration to form other hypermers.The results of this study can fill the gap in the current Aβstudy of ethanol in vitro,and also provide a reference for subsequent studies on the relationship between ethanol intake and AD.2.Two molecule compounds of grape seed proanthocyanidins（GSPC）and vitamin B₁（VB₁）were selected to represent their effects on the aggregation fluorescence intensity,secondary structure and surface morphology of Aβ_1-42,and analyze the effect of Aβ_1-42 aggregation.The results show that,the presence of GSPC had a significant effect on the change of Th T fluorescence intensity of Aβ_1-42,and GSPC at 0.05 mg/m L,0.15 mg/m L,and 0.25 mg/m L reduced fluorescence intensities by 25%,61%,and 71%,respectively（p<0.01）;It also decreased the fluorescence intensity of Aβ_1-42 at 48 h by 70%,77%and 82%,respectively（p<0.01）;But this is contrary to the significant increase in theβ-sheet in the results of the secondary structure content,therefore,it is still questionable whether GSPC has an inhibitory effect on Aβ_1-42.Vitamin B₁ can reduce the aggregation of Aβ_1-42 and show a certain inhibitory effect;vitamin B₁significantly reduces the fluorescence intensity of Aβ_1-42 for 48 h by 16%（p<0.05）,while the addition of vitamin B₁ reduces theβ-sheet content,which can effectively reduce fiber production and decompose fibrils to form small oligomers,indicating that vitamin B₁ has an inhibitory effect on Aβ_1-42aggregation.This also provides new ideas for the subsequent development or design of new inhibitors.