Abstract: Objective To evaluate the effects of preconditioning with hydrogen peroxide(H₂O₂) on oxidative tolerance(OT) of rat neural stem cells(NSC) in proliferation(PNSC) and differentiation(DNSC) respectively.Methods PNSC and DNSC were cultured in vitro.H₂O₂ was used in following concentrations: 0.05,0.10,0.25,0.50 and 1.0 mmol/L,for 2 h,4 h,8 h,12 h and 24 h respectively to assess the cell injury.Oxidative preconditioning was undertaken with final concentration of 0.50 mmol/L H₂O₂ for 10 min.After 6 h or 12 h preconditioning,0.50 mmol/L H₂O₂ were added to cause insult.Hsp27,Hsp70,catalase(CAT),superoxide dismutase(SOD) assessed by immunohistochemistry(IHC),viability of CAT and SOD were assessed before and 12 h after preconditioning.TEM was used to study the ultrastructure.Results When H₂O₂ reaches 0.25 mmol/L,both PNSC and DNSC develop injury.Twelve hours after 0.50 mmol/L H₂O₂ preconditioning for 10 min in DNSC,the cell injury decrease significantly than the non-preconditioning group.The preconditioning OT can last at lest for 12 h.However,PNSC do not develop OT.DNSC presented significant more cells with positive staining of Hsp27 and Hsp70;however both the staining and viability of CAT and SOD keep no significant difference before and after preconditioning(P<0.05).The TEM demonstrated after preconditioning,more cells keep alive during H₂O₂ insult,and all surviving present characteristics of immature cells.Conclusion Although DNSC develops OT after 0.50 mmol/L H₂O₂ preconditioning for 10 min with 12 h interval,and the OT last for 12 h,the PNSC can't develop.The mechanism may involve the protection of Hsp27,Hsp70,but not CAT nor SOD.In addition,immature NSC get higher OT than differentiated NSC.

Key words: neural stem cell, oxidative tolerance, preconditioning