AIM:To investigate the effect of heat shock protein 75 ( Hsp75 ) over-expression on Aβ-induced neurotoxicity in the neural stem cells and to explore its mechanism.METHODS:An adenovirus-mediated Hsp75 over-ex-pression vector was used in vitro.The mouse neural stem cell C17.2 was cultured in vitro and divided into control group, Aβgroup, negative adenovirus vector transfection group and Hsp75 over-expression adenovirus vector transfection group. The transfection and cellular immune identification were detected by fluorescence microscopy.The cell morphology was ob-served under inverted phase-contrast microscope.The cell viability and apoptosis were detected by MTT assay and flow cy-tometry, respectively.Hsp75 over-expression and cleaved caspase-3 protein level were measured by Western blot.RE-SULTS:Observation by fluorescence microscopy indicated that C17.2 cells were successfully transfected and Hsp75 gene was effectively expressed in the neural stem cells after transfection.In addition, the morphology and viability of the cells did not change and these cells did not differentiate after transfection.As compared with control group, the cell viability in Aβgroup and negative adenovirus vector transfection group was significantly decreased (P<0.05), and the cell apoptotic rate and cleaved caspase-3 level (P<0.05) were increased.As compared with Aβgroup and negative adenovirus vector transfection group, Hsp75 over-expression significantly increased the cell viability, and decreased the cell apoptosis and cleaved caspase-3 level ( P<0.05 ) .CONCLUSION: Hsp75 over-expression protects the neural stem cells against Aβ-induced injury.The mechanism may be related to inhibiting caspase-3 pathway-dependent apoptosis.