Gradual alteration of mitochondrial structure and function by β-amyloids: importance of membrane viscosity changes, energy deprivation, ROS production and cytochrome c release.

Intracellular amyloid beta-peptide (Abeta) accumulation is considered to be a key pathogenic factor in sporadic Alzheimer's disease (AD), but the mechanisms by which it triggers neuronal dysfunction remain unclear. We hypothesized that gradual mitochondrial dysfunction could play a central role in both initiation and progression of sporadic AD. Thus, we analyzed changes in mitochondrial structure and function following direct exposure to increasing concentrations of Abeta(1-42) and Abeta(25-35) in order to look more closely at the relationships between mitochondrial membrane viscosity, ATP synthesis, ROS production, and cytochrome c release. Our results show the accumulation of monomeric Abeta within rat brain and muscle mitochondria. Subsequently, we observed four different and additive modes of action of Abeta, which were concentration dependent: (i) an increase in mitochondrial membrane viscosity with a concomitant decrease in ATP/O, (ii) respiratory chain complexes inhibition, (iii) a potentialization of ROS production, and (iv) cytochrome c release.