An artifact associated with using trypan blue exclusion to measure effects of amyloid beta on neuron viability

It is important to apply an appropriate test for determining cell viability, in order to properly evaluate the role of the amyloid beta protein in neuronal degeneration in Alzheimer's disease. In the current paper, we present evidence that the putative neurotoxic fragment 25-35 of amyloid beta causes loss of trypan blue exclusion in differentiated mouse neuroblastoma N1E-115 cells which suggests a potential neurotoxic effect. Surprisingly, no parallel changes in apparent cell viability were observed when fluorescein diacetate staining or release of lactate dehydrogenase were measured. Positive staining with trypan blue was also induced by incubating cell membranes prepared from N1E-115 cells or rat hippocampus with amyloid beta 25-35. Our results indicate that amyloid beta might induce trypan blue adsorption on the cell membrane. Therefore, caution should be taken when trypan blue exclusion is used in studies of the potential neurotoxicity of amyloid beta peptides.