Dynamic fluorescence imaging analysis to investigate the cholesterol recruitment in lipid monolayer during the interaction between beta-amyloid (1-40) and lipid monolayers.

Extracellular beta-amyloid (Abeta) deposit is considered as one of the primary factors in inducing Alzheimer's disease (AD). However, the mechanism of Abeta deposition on the cell membrane and the induced cytotoxicity are still unclear. On the basis of the previous reports and results, we propose the "Recruiting Hypothesis" on the interaction between the plasma membrane and Abeta. Recently, many studies focused on cholesterol, which is considered as an important factor for AD. The most challenging issue in studying the cholesterol is non-ideal mixing behavior and non-dynamic analysis. In the present study, we investigated the cholesterol recruitment in the lipid monolayer during the interaction between beta-amyloid peptides Abeta (1-40) and lipid monolayers by dynamic fluorescent imaging analysis. Results from lipid monolayer trough studies showed that the rate of Abeta adsorption onto lipid monolayer is mainly due to the electrostatic effect which is sensitive to the lipid monolayer composition. From the fluorescence imaging analysis, the interaction of Abeta with lipid monolayer containing negative charge lipid and cholesterol brings out the recruiting behavior of the cholesterol and reduces the fluidity of lipid. The present study not only demonstrates the technical application for monitoring the dynamic molecular behaviors at the interface but also reveals the roles to distinguish lipid molecules on the Abeta-membrane interaction.