Tripchlorolide Ameliorates Cognitive Impairment In SAMP8Mice Via Improving Synaptic Plasticity And APP Processing

Object Alzheimer's disease (AD) affects daily living through memory loss andcognitive impairment.Here we testify if long-term administration of Tripchlorolide wouldameliorate the cognitive dificits and explore the potential mechanisms using in vivo andvitro studies through different levels,including animal,cell and molecular.It is a helpfulexploration for cure AD via aim at different crucial factors during the pathogeny and courseof disease to comprehensive intervention AD progress.Methods1. The7-month-old male senescence-accelerated mouse P8(SAMP8) micewere chronically treated with T₄(0.25,1.0,4.0μg/kg per day, injected intraperitoneally for75days, respectively). The SAMR1mice with the same age were used as normal agingcontrol.The effect of T₄on the learning and memory of SAMP8mice was tested bydifferent behavioral tests including Y maze and Morris.The LTP on the hippocampal slicewas examined by the electrophysiological technology examine, the ChAT expression of thebasal forebrain was detected by immunohistochemistry staining, and the plasticity-relatedproteins in hippocampus were tested by Westernblot.2. N2a/APP695cells,a mutated APP-overexpressing neuronal cell line,was used tomimic the APP metabolism an Aβ generation in vitro.Cell viability was measured by MTTassay and then cell divided into N2a/APP695T₄untreated group, the T₄treatment group(1.25,2.5,5.0,10.0nM), and the wild type N2a (N2a/WT) cells as the negative control.Theinfluence of T₄on Aβ generation was measured by ELISA. And then,we investigatedmechanism of T₄on beta-secretase through PPARγ-BACE1pathways by Real-time PCR,Westernblot and confocal laser scanning microscope respectively.Results1.Long-term intraperitoneal injection of T₄obviously prevents learning andmemory loss in aged SAMP8mice. T₄not only increase the number of ChAT-positiveneurons in the basal forebrain of aged SAMP8mice,but also shows a protective effect onthe hippocampal slices LTP,which was induced by high frequency stimulation,in adose-dependent manner without significant side-effects on the body. 2. T₄can up-regulate the expression of synapse plasticity-related proteins in thehippocamp of aged SAMP8mice,including PSD-95,p－NMDAR1,p－CaMKII,p－CREB/CREB and BDNF.This suggests that T₄alleviate the synaptic plasticity dysfunctionthrough increasing the protein level of BDNF by NMDAR/CaMKII/CREB pathway.3.T₄treatment significantly reduced the extracellular levels of Aβ_1-42and Aβ_1-40inN2a/APP695cells in a dose-and time-dependent manner.Additionally,there was nosignificantly change in APP protein levels after T₄treatment when compare with vehiclealone.T₄can regulate the BACE1transcription through enhacing the PPARγexpression,which decline the activity of BACE1hydrolyze on APP and reduce the Aβ_1-42and Aβ_1-40generation ultimately.Conclusion T₄improve the synaptic plasticity through the NMDAR/CaMKII/CREBpathway rasing the expression of BDNF.And T₄may modify the APP metabolism throughreduce the BACE1activity by enhancing nuclear PPARγ and then attenuate Aβ generationultimately.T₄,as a treatment drug for AD,aim at different crucial factors during thepathogeny of disease to alleviate cognitive impairment.Consequently,T₄may be a effectiveand safe effective therapeutic agent in AD treatment.