BDNF Play A Important Role In Neuroprotective Mechanism By Up-regulating TRPC3 Expression In Aβ-induced AD Mouse Model

ObjectiveThe neuroprotective effect of BDNF and TRPC3 on AD mice and the relationship between BDNF and TRPC3 were studied by administering BDNFspecific receptor TrkB agonist(7,8-DHF),TRPC3 agonist(OAG)and inhibitor(Pyr3).Methods1.Male ICR mice,5 weeks old,20-24 g,were randomly divided into control group,AD group,AD + OAG group,AD + 7,8-DHF group and AD + 7,8-DHF + Pyr3 group.2.After 5 days of adaptive feeding,the mice were given saline and Aβ1-42 in the control group and the experimental group on the sixth day respectively,and injected into the lateral ventricle to establish animal models.3.The experimental group was given intraperitoneal injection of 7,8-DHF,OAG,and Pyr3,once a day,and the hippocampus tissue and whole brain of mice were taken after 21 days of continuous administration.4.The DigBehv Morris water maze behavior detection system(positioning navigation experiment and space exploration experiment)was used to detect the learning and memory ability of mice.5.Western blot and immunohistochemistry were used to detect the expression and localization of TRPC3 and synapsin-Ⅰ,CaMKⅡ-α in hippocampus of mice.6.ELISA was used to determine the concentration of Aβ in the hippocam pus of each group of mice;Congo red staining was used to detect the depositi on of Aβ in the hippocampus of mice.Results1.Morris water maze behavioral test results showed that the swimming speed of each group of mice was stable for 5 consecutive days.Compared with the control group,the escape latency of the AD group on the fifth day was prolonged [(11.19 ± 2.05)s vs(25.80 ± 4.11)s P<0.001];compared with the AD group,the escape latency of the AD + 7,8-DHF group and AD + OAG group was shorted [(25.80 ± 4.11)s and(15.08 ± 2.47)s and(15.11 ± 1.42)s P<0.01];compared with AD + 7,8-DHF group,AD + 7,8-DHF + Pyr3 group had longer escape latency [15.08 ± 2.47)s and(33.70 ± 8.37)P<0.001].the target quadrant stay time on the sixth day was lower in the AD group than in the control group [(12.47 ± 1.27)s and(26.50 ± 2.7)s P<0.001];compared with AD group,the AD + 7,8-DHF group and AD + OAG group is increased [(12.47 ± 1.27)s and(20.92 ± 1.51)s and(21.51 ± 1.35)P<0.01];AD + 7,8-DHF + Pyr3 group was lower than AD + 7,8-DHF group [(11.09 ± 0.62)s and(20.92 ± 1.51)s P<0.01].compared with the control group,the number of crossing platforms in the AD group decreased on the sixth day [(1.33 ± 1.03)and(3.67 ± 0.82)P<0.05],compared with the AD group,the number of crossing platforms of AD+7,8-DHF group and AD+OAG group increased [(1.33 ± 1.03)and(3.33 ± 1.21)and(3.17 ± 0.98)P<0.05],AD + 7,8-DHF + Pyr3 group was lower than AD + 7,8-DHF group [(1.17 ± 1.16)and(3.33 ± 1.21)P<0.05];The trend of each group’s trajectory chart is the same as the change trend of the target quadrant residence time.2.Western blotting results showed that in the mouse hippocampus,compared with the control group,the relative content of TRPC3 and synapsin-1 and CaMKⅡ-α protein in the AD group were reduced(P<0.01,P<0.001,P<0.001);compared with AD group,the relative contents of TRPC3,synapsin-1 and CaMKⅡ-α protein in AD+7,8-DHF group and AD+OAG group all increased(P<0.01,P<0.001,P< 0.01);compared with the AD + 7,8-DHF group,the relative contents of TRPC3,synapsin-1 and CaMKⅡ-α protein in the AD + 7,8-DHF + Pyr3 group were all reduced(P<0.05,P<0.01,P<0.05).3.The results of immunohistochemistry showed that compared with the control group,the expression of synapsin-1 and CaMKⅡ-α protein in the hippocampal CA1 region of AD group mice was significantly reduced(P<0.05,P<0.01),and the expression of TRPC3 protein was significantly reduced(P<0.05);compared with AD group,the expression of synapsin-1 and CaMKⅡ-α protein in hippocampal CA1 area of AD + 7,8-DHF group increased significantly(P<0.05,P<0.01),and the expression of TRPC3 protein increased significantly(P<0.05),the expression of synapsin-1 and CaMKⅡ-α protein in hippocampal CA1 area of mice in AD + OAG group was significantly increased(P<0.05,P<0.01),and the expression of TRPC3 protein was significantly increased(P<0.01);compared with AD + 7,8-DHF group,synapsin-1 protein expression in hippocampal CA1 area of AD + 7,8-DHF + Pyr3 group was significantly reduced(P<0.001).There was no significant difference in CaMKⅡ-α protein expression,and TRPC3 protein expression was significantly reduced(P<0.01).4.ELISA results showed that in mouse hippocampus,compared with the control group,the concentration of Aβ1-42 in the AD group increased(P<0.001);compared with the AD group,the concentration of Aβ1-42 in the AD + 7,8-DHF and AD + OAG groups decreased(P<0.01;P<0.01);Compared with the AD + 7,8-DHF group,the Aβ1-42 concentration in the AD + 7,8-DHF + Pyr3 group was significantly increased(P<0.001).5.Congo red staining results show that the orange and red uniform and unstructured amyloid deposits in the hippocampal CA1 area of the AD group and AD + 7,8-DHF + Pyr3 group mice can be seen under the microscope.Less amyloid deposits in the control group were seen,and the amount of amyloid deposition in the AD + 7,8-DHF group and AD + OAG group was lower than that in the AD group.ConclusionBDNF up-regulates TRPC3 attenuates abnormal deposition of Aβ and thereby improves synaptic and cognitive functions in AD mice.