Activation Of MT2 Receptor Ameliorates Dendritic Abnormalities In Alzheimer’s Disease Via C/EBPα/miR-125b Pathway

Background: Impairments of dendritic trees and spines have been found in many neurodegenerative diseases,including Alzheimer’s disease(AD),in which the deficits of melatonin signal pathway were reported.Melatonin receptor 2(MT2)is widely expressed in the hippocampus and mediates the biological functions of melatonin.It is known that melatonin application is protective to dendritic abnormalities in AD.However,whether MT2 is involved in the neuroprotection and the underlying mechanisms are not clear.Objects: To clarify whether MT2 is involved in the neuroprotection and the underlying mechanisms.Methods: GFP-expressing lenti virus was used to visualize the spines and dendritic trees development.Verified recombinant lentivirus-packaged sponge for miR-125 b was used to inhibit the expression of miR-125 b.Brain slices were collected and used for the MED64 electrophysiological recording.Field excitatory postsynaptic potential(f EPSP)was recorded by the whole cell patch clamp.The development of spines and dendritic trees and distributions of proteins were observed by immuofluorescence;western blot were applied to detect the levels of total and phosphorylated proteins.Results: Here,we found that: 1.MT2 is dramatically reduced in the dendritic compartment upon the insult of oligomer Aβ.2.MT2 activation prevented the Aβ induced disruption of dendritic complexity and spine.3.Activation of MT2 decreased c AMP,which in turn inactivated transcriptional factor CCAAT/enhancerbinding protein α(C/EBPα)to suppress miR-125 b expression and elevate the expression of its target,Glu N2 A.4.Mi R-125 b mimics fully blocked the protective effects of MT2 activation on dendritic trees and spines.5.Injection of a lentivirus containing a miR-125 b sponge into the hippocampus of APP/PS1 mice effectively rescued the dendritic abnormalities and learning/memory impairments.Conclusion: Our data demonstrated that the c AMP-C/EBPα/miR-125b/Glu N2 A signaling pathway is important to the neuroprotective effects of MT2 activation in Aβ induced dendritic injuries and learning/memory disorders,providing a novel therapeutic target for the treatment of AD synaptopathy.Background: Histone deacetylase 2(HDAC2)plays a major role in the epigenetic regulation of gene expression.Previous studies have shown that HDAC2 expression is strongly increased in Alzheimer’s disease(AD),a major neurodegenerative disorder and the most common form of dementia.Moreover,previous studies have linked HDAC2 to Aβ overproduction in AD;however,Here,we show that taken together,the current findings implicate the HDAC2/miR-101/AMPK pathway as a critical mediator of AD pathogenesis.Objects: To elucidate HDAC2’s roless in tau pathology and other memory related functions.Methods: GFP-expressing lenti virus was used to visualize the spines and dendritic trees development.Lentiviruses that expressed HDAC2 and miR-101 b were used to overexpress HDAC2 and miR-101 b,respectively.Verified recombinant lentiviruspackaged si RNA for AMPK was used to inhibit the expression of AMPK.Luciferase reporter that contained wild-type or mutant 3’UTR segments of AMPK m RNA was used to determine whether there is a direct regulation of AMPK by miR-101 b.Filter/trap assay were used to determine the amounts of SDS-insoluble tau aggregates.The development of spines and dendritic trees and distributions of proteins were observed by immuofluorescence;western blot were applied to detect the levels of total and phosphorylated proteins.Results: 1.Increased HDAC2 levels strongly correlate with phosphorylated tau in a mouse model of AD.2.HDAC2 overexpression induced AD-like tau hyperphosphorylation and aggregation,which were accompanied by a loss of dendritic complexity and spine density.3.The ectopic expression of HDAC2 resulted in the deacetylation of the hepatocyte nuclear factor 4a(HNF-4A)transcription factor,which disrupted its binding to the miR-101 b promoter.4.The suppression of miR-101 b caused an upregulation of its target,AMP-activated protein kinase(AMPK).The introduction of miR-101 b mimics or small interfering RNAs(si RNAs)against AMPK blocked HDAC2-induced tauopathy and dendritic impairments in vitro.5.miR-101 b mimic or AMPK si RNAs rescued tau pathology,dendritic abnormalities,and memory deficits in AD mice.Conclusion: The results suggest that the HDAC2 / miR-101 b / AMPK pathway plays a role in learning and memory impairment in AD and that the excessive rise of HDAC2 in AD leads to tau lesions.This study also highlights the importance of epigenetics in AD and provides new therapeutic targets.