A rapid method to measure beta-amyloid induced neurotoxicity in vitro

β-Amyloid (Aβ) is the primary protein component of senile plaques in Alzheimer's disease (AD) and is believed to be associated with neurotoxicity in the disease. Aβ-induced neurotoxicity is strongly dependent on its structure. The aggregation of the peptide from monomeric form to fibrils is a function of many variables including time. It is because of this dynamic nature of Aβ structure that there is a necessity for an in vitro toxicity assay that is rapid enough to eliminate or at least lower the possibility of Aβ structural changes during the time required for the assay. Here we describe a fast and sensitive method with which to assess Aβ-induced neurotoxicity in SH-SY5Y neuroblastoma cells. The method employs two-color flow cytometry using annexin-phycoerythrin, a marker for cell surface phosphatidylserine that typically indicates early stages of apoptosis, and 7-amino-actinomycin D, a membrane impermeant nucleic acid dye. We compare results using the two-color assay to those obtained using the propidium iodide toxicity assay and demonstrate comparability of results, but in 2 h or less with the two-color assay as opposed to 24–48 h with the propidium iodide assay. The assay described could be a useful tool in evaluating the role of Aβ structure in biological activity of the peptide.