Increase in membrane cholesterol of neurons in culture recapitulates Alzheimer’s disease early phenotypes.. Rattus norvegicus

Levels of membrane-associated cholesterol were shown to be increased in the brain of individuals with sporadic Alzheimer’s disease (AD) and correlated with the severity of the disease. We previously found that heavy membrane cholesterol burden promotes amyloid precursor protein (APP) endocytosis and processing, leading to increased amyloid-A) secretion. We hypothesized that such an increase of cholesterol could trigger sporadic AD. We thus acutely loaded the plasma membrane of neurons in culture with cholesterol to reach the 30 % increase observed in AD brains. We showed by multiplex electro-chemiluminescence immuno-assay that transient membrane cholesterol loading produced a significant increase of A42 secretion. We also found that early endosomes were enlarged and more prone to aggregation using confocal and electron microscopy and that APP vesicular transport in neuronal processes was slowed down using fluorescence live-imaging. In addition, treatment of neurons with cholesterol induced changes in gene expression profile that are reminiscent of early AD. This model of membrane cholesterol increase in cultured neurons reproduces most of early AD changes and could thus be relevant for deciphering early mechanisms and design new targets for sporadic AD. Overall design: In this study, we loaded the plasma membrane of neurons with 30% more cholesterol and observed the effects on gene expression. We compared gene expression of primary hippocampal neurons treated or not with cholesterol using 4 independant replicates in each group.