ABSTRACT
Objective:To investigate the effect of Huangjingwan （HW） on the activities of glycogen synthase kinase-3β （GSK-3β）， protein phosphatase 2A （PP2A） and the mechanism in inhibiting tau protein hyperphosphorylation in the hippocampal neurons of mice with Alzheimer's disease. Method:After subcutaneous injection with 1.0% D-galactose （0.14 g·kg-1·d-1） into the back and neck of mice for 4 weeks， the right ventricle of mice was injected with 2 μL （75 ng） of okadaic acid for one time to make AD model， and the successfully modeled AD mice were selected by Morris water maze. Then， the selected AD mice were randomly divided into AD model group， memantine group （1.3×10-3 g·kg-1·d-1） and HW group （2.5 g·kg-1·d-1）. In addition， the sham model control group and the normal control group were set up. At the same time， 2 μL normal saline was injected into the right ventricle of mouse in the sham model control group for modeling control. Two weeks after modeling， the mice in the two experimental drug groups were given the corresponding dose of the experimental drug by gavage for 4 weeks. In addition， after 2 weeks of AD modeling， mice in control group and AD model group were intragastrically administrated with the same amount of normal saline daily for 4 weeks. The mice in normal control group were only given daily feed. At the end of gavage， all the mice were tested by the open field experiment and jumping platform experiment to evaluate the differences in exploratory activity ability， anxiety level and learning and memory ability. The number of neurons in CA1 and CA3 areas of hippocampus in all the mice was detected by Nissl staining. Quantitative real-time polymerase chain reaction （Real-time PCR） was used to detect mRNA expressions of GSK-3β and PP2A in hippocampus of mice in each group. Protein expressions of GSK-3β， PP2A， phosphorylated tau （p-tau） and total tau protein （t-tau） in hippocampus of mice in each group were detected by Western blot. Result:Compared with the normal control group， mice in AD model group showed an obvious dementia state， which was characterized by a lower spontaneous activity， lower exploration behavior ability， higher anxiety level， less movement and easier to stay and hide， longer learning response time， significantly increased number of learning and memory errors， and decreased numbers of hippocampal neuron in CA1 and CA3 areas， and reduced mRNA and protein expressions of PP2A， mRNA and protein expressions of GSK-3β， p-tau protein and the ratio of p-tau/t-tau were all increased significantly （P<0.01）， while expression of t-tau protein was decreased， with no significant difference. Compared with the AD model group， mice in the HW group showed a higher spontaneous activity， higher exploration ability， lower anxiety level， higher learning and memory performance， and the numbers of hippocampal neuron in CA1 and CA3 areas increased， while mRNA and protein expressions of PP2A increased， and the mRNA and protein expressions of GSK-3β， the expression of p-tau protein and the ratio of p-tau/t-tau were all decreased significantly （P<0.01）， but with no significant difference in the protein expression of t-tau. Conclusion:HW can inhibit tau hyperphosphorylation in hippocampal neurons of AD mice， restore tau protein function， protect hippocampal neurons， and exert an anti-AD effect， which may be related to the regulatory mechanism in the activity balance between GSK-3β and PP2A in hippocampal neurons.
ABSTRACT
Objective:To explore the effect of Huangjingwan （HW） on the expressions of Wnt/β-catenin signal pathway-associated proteins in the hippocampus of mice with Alzheimer's disease （AD） induced by D-galactose and okadaic acid with learning and memory disorders， as well as its mechanism. Method:After subcutaneous injection with 1.0% D-galactose （0.14 g·kg-1·d-1） into the back and neck of mice for 4 weeks， the right ventricle of mice was injected with 2 μL（75 ng） of okadaic acid for one time to make AD model， and the successfully modeled AD mice were selected by Morris water maze. Then， the selected AD mice were randomly divided into AD model group， memantine group （1.3×10-3 g·kg-1·d-1） and HW group （2.5 g·kg-1·d-1）. In addition， the sham model control group and the normal control group were set up. At the same time， 2 μL normal saline was injected into the right ventricle of mouse in the sham model control group as the modeling control. Two weeks after molding， the mice in the two experimental drug groups were given the corresponding dose of the experimental drug by gavage for 4 weeks. In addition， after 2 weeks of AD modeling， mice in sham model control group and AD model group were intragastrically administrated with the same amount of normal saline daily for 4 weeks. There was no special treatment in the normal control group. At the end of gavage， the shuttle experiment was performed to detect the differences in learning and memory levels of mice in each group. The changes of β-catenin and GSK-3β positive neurons in CA1 area of hippocampus in each group were tested by immunohistochemistry. Quantitative real-time polymerase chain reaction （Real-time PCR） was used to measure the mRNA expressions of GSK-3β， β-catenin and CyclinD1 in hippocampus of mice in each group. The Western blot was used to detect the expressions of total GSK-3β （t-GSK-3β）， phosphorylation of GSK-3β at Ser9 （p-Ser9-GSK-3β）， phosphorylation of GSK-3β at Tyr216 （p-Tyr216-GSK-3β）， total β-catenin （t-β-catenin）， phosphorylation of β-catenin （p-β-catenin） and CyclinD1 proteins in hippocampus of mice in each group. Result:Compared with the normal control group， mice in AD model group showed an obvious dementia state， which was characterized by significant declines in learning and memory ability， the number of β-catenin immunoreactive neurons in hippocampal CA1 area， the mRNA and protein expressions of t-β-catenin and CyclinD1， the protein expressions of p-Ser9-GSK-3β， and the ratio of p-Ser9-GSK-3β/t-GSK-3β and p-Tyr216-GSK-3β/t-GSK-3β in hippocampal region （P<0.01）， and significant increases in the number of GSK-3β immunoreactive neurons in hippocampal CA1 area， the mRNA and protein expressions of t-GSK-3β， the protein expressions of p-Tyr216-GSK-3β and p-β-catenin， the ratio of p-β-catenin/t-β-catenin in hippocampal region （P<0.01 respectively）. Compared with the AD model group， the dementia symptoms of mice in HW group were significantly alleviated， and the number of β-catenin immunoreactive neurons in hippocampal CA1 area， the mRNA and protein expressions of t-β-catenin and CyclinD1， the protein level of p-Ser9-GSK-3β， the ratio of p-Ser9-GSK-3β/t-GSK-3β in hippocampal region were all significantly increased （P<0.01 respectively）， whereas the number of GSK-3β immunoreactive neurons in hippocampal CA1 area， the mRNA and protein expressions of t-GSK-3β， the proteins expressions of p-Tyr216-GSK-3β and p-β-catenin， the ratio of p-β-catenin/t-β-catenin in hippocampal region were all significantly decreased （P<0.01 respectively）， but the ratio of p-Tyr216-GSK-3β/t-GSK-3β has no significant statistical difference. Conclusion:HW shows the role of AD treatment， which can down-regulate the expression of GSK-3β in the hippocampus of AD mice and reduce its protein activity， and up-regulate the expression of β-catenin as well as increase its protein activity， so as to enhance the expression of downstream CyclinD1 and promote the transcription of the target genes. Its mechanism may be related to the activation of Wnt/β-catenin signal pathway.