The Effect Of Imperatorin On SIRT1/eIF2α Pathway In Alzheimer’s Disease Model Mice

Objective:To investigate the effect of imperatorin on SIRT1/PERK/e IF2αpathway-related proteins and endoplasmic reticulum stress in Alzheimer’s disease（AD）model mice,Meanwhile,to observe the effect of imperatorin the effect of AMPK/PGC-1α/BDNF signaling pathway on AD model mice.To explore the mechanism of imperatorin in preventing and treating AD.Methods:（1）Mouse brain slices were incubated with 10μM Aβ_1-42to established neurotoxic model in vitro.The use of LDH activity assay for quantifying neuronal damage in mouse brain slices,the brain slices viability was used by MTT and the measurement of the silent information regulator 1（SIRT1）and the immunoglobulin heavy chain binding protein（BIP）protein levels were observed by ELISA.（2）Male BALB/c mice were randomly divided into sham group,AD model group,low-dose imperatorin group（2.5 mg/kg）and high-dose group（5.0 mg/kg）.The AD mouse model was established by injecting Aβ_1-42into the lateral ventricle,and the sham group was given the same volume of sterile water for injection.The intraperitoneal injection was administered on the day of operation for 13 consecutive days,once a day.The sham group and the AD model group were given the same volume of vehicle at the same time.The hippocampus tissue of mice was taken.ELISA was used to detect immunoglobulin heavy chain binding protein（BIP）,silent information regulator 1（SIRT1）,adenylate-activated protease（AMPK）,phosphorylated-AMPK（p-AMPK）,peroxisome proliferator-activated receptor gamma coactivator 1α（PGC-1α）and brain-derived neurotrophic factor（BDNF）protein content in the hippocampus tissue.Western blot was used to detect SIRT1,BIP,protein kinase RNA-like endoplasmic reticulum kinase（PERK）,phosphorylated PERK（p-PERK）,Protein expression of nuclear translation initiation factor 2α（e IF2α）,phosphorylated e IF2α（p-e IF2α）,and CCAAT/enhancer-binding protein homologous protein（CHOP）.Results:（1）In Aβ_1-42induced neuronal damage in mouse brain slices in vitro,compared with vehicle group,10μM Aβ_1-42increased the brain slices activity of LDH,decreased the brain slices viability,and decreased the levels of SIRT1 and increased the levels of BIP.the pretreatment of brain slices with imperatorin significantly reduced the activity of LDH,increased the brain slices viability and the levels of SIRT1,and decreased the BIP contents.（2）In Aβ_1-42induced mouse model of AD in vivo,ELISA results showed that compared with the sham group,the AD model group significantly decreased the levels of SIRT1,AMPK,p-AMPK,PGC-1αand BDNF,and significantly increased the BIP levels.Compared with AD model group,imperatorin can increase the protein contents of SIRT1,AMPK,p-AMPK,PGC-1αand BDNF,and inhibit the production of BIP.Western Blot results showed that compared with the sham group,the protein expression of SIRT1 in the hippocampus of the AD model group was significantly down-regulated,and the protein expressions of BIP,p-PERK,p-e IF2αand CHOP were significantly up-regulated.Compared with AD model group,imperatorin up-regulated the expression of SIRT1,down-regulated the expression of BIP,p-PERK,p-e IF2αand CHOP,the ratios of p-PERK/PERK and p-e IF2α/e IF2αwere decreased.Conclusion:（1）Imperatorin treatment significantly improves the learning and memory impairment.Imperatorin up-regulates SIRT1 levels and attenuates ER stress response in the AD model mice induced by Aβ_1-42,inhibits the phosphorylated activation of PERK/e IF2α,and reduces CHOP protein expression.（2）Imperatorin exerts neuroprotective effect on AD by up-regulating the expression of SIRT1 and inducing the activation of AMPK/PGC-1α/BDNF signaling pathway.