Neuroprotective Effects Of The DA5-CH On STZ-induced Alzheimer's Disease Rat Model

Alzheimer's disease(AD)is the most common neurodegenerative disease afflicting the elderly.At present,there is no effective drug to inhibit the progress of AD.Recent studies have shown a close link between type 2 diabetes mellitus(T2DM)and AD,suggesting that drugs for T2 DM may be effective for AD.Glucagon-like peptide-1(GLP-1)and Gastric inhibitory polypeptide(GIP)are both insulinstimulating hormones and can improve T2 DM.Whether the new GLP-1/GIP doublereceptor agonists DA5-CH have therapeutic effects on Alzheimer's disease has not been reported in the literature.ObjectiveIn this study,we tested a novel GLP-1/GIP double receptor agonist DA5-CH in Streptozotocin(STZ)-induced AD model rats to explore whether DA5-CH can reverse the learning and memory function of AD model rats,reduce the phosphorylated tau protein level of AD characteristic lesions,and improve the Theta frequency band of hippocampus by regulating synapses.Furthermore,the mechanism of DA5-CH exerting neuroprotective effect was further explored whether it was related to apoptosis and growth factor signaling pathway.Methods1.Intraperitoneal injection of saline The experimental group: rats were randomly divided into four groups:(1)control group: rats were injected with artificial cerebrospinal fluid into lateral ventricle and intraperitoneal injection of saline;(2)DA5-CH group: rats were injected with artificial cerebrospinal fluid into lateral ventricle and intraperitoneal injection of DA5-CH dissolved in saline;(3)STZ group: rats were injected with STZ into lateral ventricle and intraperitoneal injection of saline;(4)STZ+DA5-CH group: STZ was injected into lateral ventricle of rats,and intraperitoneal injection of DA5-CH dissolved in saline.2.Drug therapy: After 3 days of intracerebroventricular injection,DA5-CH or saline were injected intraperitoneally for 14 consecutive days.3.Behavioral tests: Y-maze and water-maze tests were performed after drug administration,and water-maze tests were performed after Y-maze.The aim was to test working memory and spatial learning memory in rats.4.Local field potential acquisition: Local field potentials(LFP)in hippocampal region were recorded by in vivo multichannel electrophysiological technique.5.Immunohistochemical: After perfusion with polyformaldehyde,the whole brain tissue was obtained and used to analyze the expression of phosphorylated tau protein,synaptic vesicle protein SYN and postsynaptic dense protein PSD95.6.Western blot: Rats in each group were directly decapitated to obtain hippocampal tissue,The expressions of phosphorylated tau protein and total tau protein,synaptic vesicle protein SYN and postsynaptic dense protein PSD95,apoptotic protein Bax and anti-apoptotic protein Bcl-2,phosphorylated CREB and CREB were detected.7.Detection of oxidative stress: Superoxide Dismutase(SOD)and Maleic Dialdehyde(MDA)were detected simultaneously in rats of each group.The results of the two reacted with oxidative stress in rats.8.Statistical analysis: All data were analyzed by Prism,and the results were expressed by Mean + SEM.The data were analyzed by one-way ANOVA and twoway ANOVA.P < 0.05 was considered to have statistical significance.Results1.The results of Y maze test showed that the accuracy of spontaneous alternation in STZ group was significantly lower than that in control group,while the accuracy of spontaneous alternation was improved after DA5-CH treatment.2.The results of water maze test showed that STZ did not affect the learning ability of rats,but significantly reduced the memory ability of rats.After DA5-CH treatment,STZ-induced memory impairment in AD rats was improved.3.In vivo multichannel electrophysiological recording of LFP and Theta rhythm analysis showed that STZ reduced Theta band energy,while DA5-CH reversed this change.4.Immunohistochemical results showed that STZ induced the increase of phosphorylated tau protein in hippocampus and decreased the expression of synaptic related protein SYN and PSD95 in hippocampus.After DA5-CH treatment,the expression of phosphorylated tau induced by STZ was significantly decreased and the decrease of synaptic protein expression induced by STZ was reversed.5.Western blot results showed that there was no significant difference in total tau expression in hippocampus of rats in each group.Phosphorylated tau increased significantly in STZ group,but decreased after DA5-CH treatment.At the same time,the expression levels of SYN and PSD95 in hippocampus of STZ group decreased significantly,and the expression of SYN and PSD95 increased after DA5-CH treatment.The ratio of Bax/Bcl-2 in hippocampus of rats was significantly increased by injecting STZ into lateral ventricle,while the application of DA5-CH significantly decreased the increase.STZ decreased the expression of phosphorylated CREB in rat hippocampus,while DA5-CH reversed this phenomenon.6.There was no significant difference in SOD and MDA in each group,suggesting that STZ injection into lateral ventricle did not induce oxidative stress in rat brain.ConclusionDA5-CH improved the memory dysfunction of STZ-induced AD rats and decreased the expression of phosphorylated tau protein in hippocampus.In addition,DA5-CH significantly increased the energy of Theta band in hippocampal CA1 region of STZ rats injected into lateral ventricle,and increased the expression of synapticrelated protein in hippocampus.Its mechanism may be through activating AC/PKA/CREB signal transduction pathway,increasing the expression of PCREBS133 and inhibiting the expression of apoptotic protein,while increasing the expression of anti-apoptotic protein,ultimately reducing the ratio of pro-apoptotic protein to anti-apoptotic protein.The final effect is to inhibit the occurrence of neuronal apoptosis in hippocampus.Thus,it played a neuroprotective role in STZ-induced AD model rats,but it does not induce oxidative stress reaction in the process of AD-like lesions induced by lateral ventricular injection of STZ.