OBJECTIVE To explore the estrogen-like neuroprotective effects and the related mechanism of quercetin by using PC12 cells induced with Aβ25-35,provided thought and strategy for the drug therapy of AD.METHODS Cells were cultured with Aβ25-35 for 24 h,17β-estradiol(0.1 μmol·L~(-1)),genistein(50 μmol·L~(-1)) and three different concentrations of quercetin(200 μmol·L~(-1),300 μmol·L~(-1) and400 μmol·L~(-1)) were respectively added after 24 h.The effects of quercetin on activity of AD model were tested by MTT.Immunohistochemical stain and Western blot were used to detect the expression of estrogen receptors alpha and beta,p-ERK1/2 and apoptosis related proteins.The mechanism of quercetin estrogen-like neuroprotective effects was detected using estrogen receptor antagonist ICI182,780 and MAPKK inhibitor U0126.RESULTS The results revealed thatthe toxic effects showed in a dose-dependent increase of Aβ25-35 on PC12 cells.Comparing with the control group,cells injury was observed after cultured with 10 μmol·L~(-1) Aβ25-35 for 24 h(P<0.01).The MTT results showed that 17β-estradiol,genistein and three different concentrations of quercetin could significantly enhance the cell survival rate compared with the model group(P<0.05).Compared with model group,Immunofluorescence and Western blot results show that quercetin could improve the estrogen receptor alpha and p-ERK1/2 protein expression(P<0.05),and the expression of estrogen receptor beta protein is increased without significant difference.And in the Western blot experiments,the ratio of Bcl-2 and Bax was increased and the expression of Caspase 3 was decreased(P<0.05).When estrogen receptor inhibition ICI182,780 were reduced,the expression of p-ERK1/2 was decreased(P<0.05) and the ratio of Bcl-2 and Bax was decreased,Caspase 3 protein expression was increased(P<0.05).In addition,pretreatment of cells with U0126 would reduce Bcl-2/Bax ratio and increase Caspase 3 protein expression increased(P<0.05).CONCLUSION Quercetin protected PC12 cells,which suffered from Aβ25-35-induced cytotoxicity and exert neuroprotective effects.The estrogen-like neuroprotective effect can reduce the apoptosis in the classic estrogen receptor pathway and MAPK pathway.And quercetin can also active MAPK signaling pathways by the mediation of estrogen receptor alpha. OBJECTIVE To explore the estrogen-like neuroprotective effects and the related mechanism of quercetin by using PC12 cells induced with Aβ25-35, provided thought and strategy for the drug therapy of AD. METHODS Cells were cultured with Aβ25-35 for 24 h, 17β- estradiol (0.1 μmol·L -1), genistein (50 μmol·L -1) and three different concentrations of quercetin (200 μmol·L -1) and 300 μmol·L -1 ) and400μmol·L -1) were respectively added after 24 h.The effects of quercetin on activity of AD model were tested by MTT. Immunohistochemical stain and Western blot were used to detect the expression of estrogen receptors alpha and beta, p-ERK1 / 2 and apoptosis related proteins. The mechanism of quercetin estrogen-like neuroprotective effects was detected using estrogen receptor antagonist ICI 182,780 and MAPKK inhibitor U 0126.RESULTS The results revealed that the toxic effects showed in a dose-dependent increase of Aβ25- 35 on PC12 cells. Comparing with the control group, cells injury was observed after cultured with 10 μmol·L -1 Aβ25-35 for 24 h (P <0.01) .The MTT results showed that 17β-estradiol, genistein and three different concentrations of quercetin could significantly enhance the cell survival rate compared with the model group, Immunofluorescence and Western blot results show that quercetin could improve the estrogen receptor alpha and p-ERK1 / 2 protein expression (P <0.05), and the expression of estrogen receptor beta protein is increased no significant difference. When in Western blot experiments, the ratio of Bcl-2 and Bax was increased and the expression of Caspase 3 was decreased (P <0.05) .When estrogen receptor inhibition ICI182,780 were reduced, the expression of p In addition, pretreatment of cells with U0126 would reduce Bcl-2 / Bax (P <0.05) and the ratio of Bcl-2 and Bax decreased decreased ratio and increase Caspase 3 protein expression increased (P <0.05) .CONCLUSION Quercetin protected PC12 cells, which suffered from Aβ25-35-induced cytotoxicity and exert neuroprotective effects. The estrogen-like neuroprotective effect can reduce the apoptosis in the classic estrogen receptor pathway and MAPK pathway. And quercetin can also be active MAPK signaling pathways by the mediation of estrogen receptor alpha.