Studies on the inhibitory mechanism of biological molecules and antioxidants for Alzheimer's β-amyloid fibril formation.

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IntroductionWe constructed β-amyloid fibril (fAβ) formation system in vitro as a model of that in the brain of patient with Alzheimer's disease (AD). By the use of this system, we have studied the mechanism of fAβ formation in vitro, and estimated the effects of various biological molecules and chemical compounds on fAβ formation. We also proposed a nucleation-dependent polymerization model to explain the mechanisms of fAβformation in vitro. This model consists of two phases, i.e., nucleation and extension phases. In this study, we analyzed the fAβ formation inhibitors. Additionally, in order to understand the complex fAβ formation in the brain, we studied fAβ formation in the mixture of Aβ variants in vitro, and the formation of nucleus, which probably controls total rate of fAβ formation.ResultsFirst, we established a precise analytical system of fAβ formation from Aβ1-42 (Aβ42) in vitro. By the use of the system, we compared the mechanism of apolipoprotein E- and antioxidants-mediat … More ed inhibition of fAβ formation, and found each inhibitory mechanism was different. Secondly, we analyzed the interaction of two kinds of Aβ variant, I.e., Aβ42 and Aβ1-40(Aβ40), in the kinetics of fAβ formation in vitro. Aβ42 nucleate in the mixture of Aβ42 and Aβ40, then the fibril extension proceed by the consecutive association of Aβ40 onto the end of nuclei and existing fibrils. These results suggested the central role of Aβ42 for fAβ deposition in vivo, among the different co-existing Aβ species. Thirdly, we found that a seeding Aβ, which catalyzes the fAβ formation, is generated from the apically missorted amyloid precursor protein in cultured epithelial cell. The seeding Aβ was generated depending on the presence of cholesterol, and conformationally altered from soluble Aβ.ConclusionsIn the present study, we developed a novel analytical methods of fAβ formation. We also showed several candidates of the nuclei for fAβ formation in the brain. We believe that the analysis of the interaction between biological or synthetic inhibitors and these nucleus candidates will provide us with the important therapeutic target for prevention and treatments of AD. Less