RESUMO
Objective To investigate the toxic effect of the carboxyl-terminal peptide of β-amyloid precursor protein (APPC31) on Neuro2a cells as well as its role in the toxic process in Neuro2a cells induced by Aβ42 in vitro.Methods The plasmid vector and the APPC31 construct were transiently transfected into Neuro2a cells respectively by lipofectamine 2000.The viability of the cells was measured by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at 48 h after transfection,and their morphocytology was observed by 4', 6-diamidino-2-phenylindole (DAPI) nucleus staining.Afterword different constructs including vector, WTAPP695, APP( D664A), the amino-terminal peptide of β-amyloid precursor protein (APP△C31) and APPC31 were transiently transfected into Neuro2a cells respectively via the same method.At 24 h after transfection Aβ42 was added into the culture medium of Neuro2a cells with the desired concentration for another 24 h for cell studies.The viabihty and morphocytology of the cells were measured by using the MTT assay and DAPI nucleus staining, respectively.Results When incubated in the absence of Aβ42, the viability of cells transfected with vector and APPC31construct were 0.81 ±0.10 and 0.88 ±0.12 respectively, and accordingly there was no significant difference between the these two groups (t = - 0.78, P = 0.48 ); meanwhile no obvious cell nuclear morphological changes of apoptosis or death occurred.However when incubated in the presence of Aβ42, the viability of cells transfected with vector, WTAPP695, APP( D664A), APP△C31 and APPC31 constructs were 0.82 ±0.01, 0.78 ±0.03, 0.55 ±0.04, 0.81 ±0.04, 0.78 ±0.02 and 0.54 ±0.02 respectively.The viability of cells transfected with WTAPP construct and APPC31 construct decreased significantly ( F = 47.53, P ＜0.05) compared with the control group, meanwhile cells displayed condensed nuclear and even nuclear fragmentation.Conclusions In vitro, over-expression of a certain level of APPC31 in Neuro2a cells fails in causing cell death, but this short peptide enhances cytotoxicity induced by Aβ42 in Neuro2a cells.Thus,these results provide the experimental basis for the further explication of the pathogenesis of Alzheimer's disease.