Effect Of EGCG Combined With Vitamin E On The Oxidative Stress And The Level Of Related Protein In Hippocampus Of Lead-exposed Mice

ObjectivesBy studying the protective effects of epigallocatechin gallate（EGCG）and vitamin E（VitE）on mice Alzheimer’s disease（AD）-like amyloidosis caused by lead exposure of maternal mice during their different growth periods,we explored whether EGCG and vitamin E exist the synergistic effect on lead-induced AD-like lesions or not and its possible mechanism.MethodsTotal of 33 SPF Kunming mice（22 female and 11 male）were randomly divided into three groups according to the weight: control group（2 female and 1 meal）,progestational lead group（10 female and 5 male）and lactational lead group（10female and 5 male）.The female mice of progestational lead group were exposed to0.2% lead acetate aqueous solution for 21 days,and kept with the male mice of this group in one cage to obtain their offspring.Then the offspring were given lead-free deionized water until they were weaned.The lactational lead group were given leadfree deionized water and feed in one cage.After delivery,the maternal were given0.2% lead acetate aqueous solution for 21 days until their offspring weaned.The control group were fed in one cage and given lead-free deionized water until their offspring weaned.After weaning,the offspring of progestational and lactational lead group were divided into 7 groups randomly and respectively : physiological saline group,corn oil group,EGCG group（3.0 mg/kg）,VitE group（30 IU/kg）,EGCG combined with VitE group（1）（EGCG 3.0 mg/kg + VitE 30 IU/kg）,EGCG combined with VitE group（2）（EGCG 1.5 mg/kg + VitE 60 IU/kg）,EGCG combined with VitE group（3）（EGCG6.0 mg/kg + VitE 15 IU/kg）.There were 14 mice in each group,the mice were intervened for 28 days before the next step.Fourteen offspring of the control group were randomly selected and were free to drink lead-free deionized water.After gavage,the learning and memory abilities of them were measured byMorris water maze.The blood lead level of them were measured by the method of voltammetry and the activities of superoxide dismutase（SOD）and the concentration of malondialdehvde（MDA）in hippocampus were measured by the corresponding kits.The content of Aβ_1-40 and Aβ_1-42 in the hippocampus were detected by ELISA kits.The expression level of amyloid precursor protein（APP）and β-secreatase-1（BACE1）protein in hippocampus were detected by Western blot.All statistical analyses were performed using SPSS version 21.0.Inspection level was 0.05.Results1.The weight results showed: the weights of the mice in the physiological saline group,the corn oil group and other different intervention groups were significantly lower than those in the control group since 5-week（P<0.05）.At 9-week old,for progestational lead group,the combined intervention group（1）and（3）were significantly higher than those in the physiological saline group and corn oil group（P<0.05）.For the lactational lead group,the mice in the combined intervention group（1）had higher body weight than the corn oil group（P<0.05）.2.Morris water maze test results showed: in progestational and lactational lead group,the mean escape latency of the physiological saline group and the corn oil group was higher than that of the control group（P<0.05）.The mean escape latency of the EGCG group and the VitE group was lower than those of the physiological saline group and the corn oil group respectively（P<0.05）.For the progestational lead group,the mean escape latency of the combined intervention group（1）decreased（P<0.05）when compared with the single intervention groups（P<0.05）.For the lactational lead group,the mean escape latency of the combined intervention group（1）and（3）both decreased（P<0.05）as compared with the single intervention groups.The times across the platform in the physiological saline group and the corn oil group were significantly lower than those in the control group（P<0.05）.Compared with the physiological saline group and the corn oil group respectively,the times across the platform were significantly increased（P<0.05）in the combined intervention groups.Compared with the single intervention groups,the times across the platform of the combined intervention group（1）and（3）increased significantly（P<0.05）.3.The blood lead level results showed: the blood lead levels in the physiological saline group and the corn oil group were significantly higher than those in the control group（P<0.05）.The blood lead levels of the single intervention groups and the three combined intervention groups were lower than those of the physiological saline group（P<0.05）.But there were no significant difference between the single intervention groups and the combined intervention groups（P>0.05）.4.The results of oxidative stress indexs showed: compared with the control group,the activity of SOD was significantly decreased（P<0.05）and the content of MDA was increased in the physiological saline group and the corn oil group（P<0.05）.Compared with the physiological saline group and the corn oil group respectively,the activity of SOD in the single intervention groups and the three combined intervention groups increased（P<0.05）,and the content of MDA was decreased（P<0.05）.Compared with the single intervention groups,the activity of SOD in the combined intervention group（1）and（3）increased（P<0.05）.However,there was no significant difference in MDA content between the combined intervention groups and the single intervention groups（P>0.05）.5.The results of Aβ_1-40 and Aβ_1-42 content showed: for the progestational and the lactational groups,the Aβ_1-40 and Aβ_1-42 content in the physiological saline and the corn oil groups were significantly higher than those in the control group（P<0.05）.Compared with the physiological saline group and the corn oil group respectively,the Aβ_1-40 and Aβ_1-42 content of the single intervention groups and the combined intervention groups were significantly decreased（P<0.05）.For the lactational group,compared with the single intervention groups,the Aβ_1-42 content in the combined intervention group（3）was lower than the VitE group（P<0.05）.The difference was not statistically significant among the other groups（P>0.05）.6.The results of APP and BACE1 protein showed: for the progestational and the lactational groups,the levels of APP and BACE1 protein in the physiological salinegroup and the corn oil group were significantly enhauced when compared with the control group（P<0.05）.Compared with the physiological saline group and the corn oil group,the levels of APP and BACE1 protein were significantly decreased in different intervention groups（P<0.05）.Compared with the single intervention groups,the levels of APP and BACE1 protein were significantly decreased in the combined intervention groups（P<0.05）.Conclusions1.Lead exposure during progestation and lactation of maternal mice can increase the blood lead level,affect growth development and injury the spatial learning and memory ability of their offspring.At the same time,it brings a series of change to the hippocampus,such as the levels of oxidative stress lower,the levels of APP and BACE1 protein increased,and finally the content of Aβ_1-40 and Aβ_1-42 in hippocampus elevated.2.EGCG,VitE and EGCG combined with VitE can improve the learning and memory ability of immature mice whose mother had lead exposure,decrease the content of Aβ_1-40 and Aβ_1-42 in the hippocampus of AD mice,and decrease the levels of APP and BACE1 protein.What is more,the combined effect under the appropriate dose is superior to the single action of EGCG or VitE.