RESUMEN
The mechanism by which amyloid-ß (Aß) produces brain dysfunction in patients with Alzheimer's disease is largely unknown. According to previous studies, Aß might share perforating properties with gramicidin, a well-accepted membrane-disrupting peptide. Therefore, we hypothesize that the key steps leading to synaptotoxicity by Aß and gramicidin involve peptide aggregation, pore formation, and calcium dysregulation. Here, we show that Aß and gramicidin form aggregates enriched in ß-sheet structures using electron microscopy, and Thioflavin and Congo Red staining techniques. Also, we found that Aß and gramicidin display fairly similar actions in hippocampal cell membranes, i.e. inducing Ca(2+) entry and synaptoxicity characterized by the loss of synaptic proteins and a decrease in neuronal viability. These effects were not observed in a Ca(2+) free solution, indicating that both Aß and gramicidin induce neurotoxicity by a Ca(2+)-dependent mechanism. Using combined perforated patch clamp and imaging recordings, we found that only Aß produced a perforation that progressed from a small (Cl(-)-selective pore) to a larger perforation that allowed the entry of fluorescent molecules. Therefore, based on these results, we propose that the perforation at the plasma membrane by Aß is a dynamic process that is critical in producing neurotoxicity similar to that found in the brains of AD patients.