Protective Effects Of Paeoniflorin In A Transgenic Mouse Model Of Alzheimer’s Disease And Its Mechanism

Background:Alzheimer’s disease（AD）is a progressive,age-related neurodegenerative disorder characterized by advanced cognitive and memory deterioration.It is the most common cause of dementia,which occurs in the elderly over 65 years old.The hallmark pathologies of AD include the formation of extracellular beta-amyloid（Aβ）plaques and intracellular neurofibrillary tangles by tau phosphorylation,activation of microglia and astrocytes and inflammatory infiltration.However,the exact aetiology and pathogenesis of AD has not yet been identified,there is still no effective treatment to prevent,halt,or reverse the disease.Hence,it is urgent to develop effective agents for the treatment of AD.In recent years,natural active ingredients in traditional Chinese medicine have gradually attracted global attention owing to their excellent anti-dementia effects.PF,a principal bioactive component purified from the roots of Chinese herb Radix Paeoniae,has been reported to exhibit many pharmacological effects,such as cognition improvement effects,anti-inflammatory effects,anti-oxidative effects,anti-apoptotic effects,analgesic and hypnotic effects,et al.In this study,transgenic mice with five familial AD mutations（5×FAD）were used to determine the protective effects of PF and to identify its possible mechanism.Methods:To investigate the effect of PF on cognitive improvement in AD,six-month-old male5×FAD mice were randomly divided into two groups,which were either injected with PF（5mg/kg,i.p.,PF group）or same amount of vehicle（5×FAD group）for 28 days,respectively.In addition,age-matched wild-type littermates without any treatment were selected as blank controls（WT group）.The function of learning and memory were assessed by MWM and T-maze behavioral tests independently.The deposition of Aβplaques and the expression of astrocytes were detected by immunohistochemistry and immunofluorescence staining.The protein levels of GFAP,TNF-αand IL-1βin the brain were detected by Western blotting analysis（WB）and enzyme-linked immunosorbent assay（ELISA）.To determine whether adenosine A1 receptor（A1R）was involved in the neuroprotective and anti-inflammatory effects of PF,we injected DPCPX（0.3 mg/kg,i.p.）,a selective adenosine A₁R antagonist,to5×FAD transgenic mice 15 min before PF administration.Results:Our data demonstrated that 28 days treatment with PF（5 mg/kg,i.p.）significantly ameliorated the learning and memory deficits in 5×FAD transgenic mice,which was reflected by the decreased escape latency and path length in MWM and increased spontaneous alternation in T-maze test.In addition,PF alleviated Aβplaque burden,attenuated astrocyte activation as well as TNF-αand IL-1βexpression in both cortex and hippocampus of 5×FAD transgenic mice.However,the anti-cognitive deficits,anti-amyloidogenic,and anti-inflammatory effects of PF were abolished by pre-treatment of DPCPX,which was reflected by the decreased spontaneous alternation in T-maze test and increased Aβplaque burden as well as astrocyte.Conclusions:This study demonstrated that PF has a protective effect on cognitive deficit,Aβplaques deposition,astrocytes activation,and neuroinflammation in 5×FAD transgenic mice.In addition,activation of adenosine A₁R might be involved in the neuroprotective effects of PF.Therefore,our data suggests that PF could be developed as a potential therapeutic agent for the treatment of AD.