Apoptotic neuronal cell death induced by the non-fibrillar amyloid-β peptide proceeds through an early reactive oxygen species-dependent cytoskeleton perturbation

In the present study, we have determined the nature and the kinetics of the cellular events triggered by the exposure of cells to non-fibrillar amyloid-beta peptide (Abeta). When cortical neurons were treated with low concentrations of soluble Abeta (1-40), an early reactive oxygen species (ROS)-dependent cytoskeleton disruption precedes caspase activation. Indeed, caspase activation and neuronal cell death were prevented by the microtubule-stabilizing drug taxol. A perturbation of the microtubule network was noticeable after being exposed to Abeta for 1 h, as revealed by electron microscopy and immunocytochemistry. Microtubule disruption and neuronal cell death induced by Abeta were inhibited in the presence of antioxidant molecules, such as probucol. These data highlight the critical role of ROS production in Abeta-mediated cytoskeleton disruption and neuronal cell death. Finally, using FRAP (fluorescence recovery after photo bleaching) analysis, we observed a time-dependent bi-phasic modification of plasma membrane fluidity, as early as microtubule disorganization. Interestingly, molecules that inhibited neurotubule perturbation and cell death did not affect the membrane destabilizing properties of Abeta, suggesting that the lipid phase of the plasma membrane might represent the earliest target for Abeta. Altogether our results convey the idea that upon interaction with the plasma membrane, the non-fibrillar Abeta induces a rapid ROS-dependent disorganization of the cytoskeleton, which results in apoptosis.