Shenmayizhi Decoction Alleviates Cognitive Impairments Of VaD Rats By Regulating Astrocytes' Function

Background:Vascular dementia is defined as a group of intellectual impairment syndrome caused by cerebral ischemia,cerebral hemorrhage,acute and chronic hypoxic cerebrovascular disease,which is the second common dementia type after Alzheimer's disease.It is becoming one of the major health problems under the aging trend of population as the incidence of VaD increases with age.There is no clear consensus on the pathophysiological criteria for VaD.The pathogenesis is related to oxidative stress injury,neuroinflammation,brain energy metabolism and cholinergic system deficits.Despite a great deal of research in this area,the treatments currently available are symptomatic,only to reduce some cognitive symptoms in short term and do little to slow the progression.Traditional Chinese Medicine(TCM)with multiple targets and pathways,always used to improve memory and control mental symptoms related to dementia,has come to show the advantage for treating VaD.Widely distributed in the brain,astrocytes(AS)possess a number of functions including supporting,passing on messages,maintaining metabolism and regulating cerebral blood flow.Both neurological damage and lesions could make AS to exhibit reactive changes in morphological function and gene expression.Numerous evidences have shown that reactive astrogliosis is a complex and multifaceted process.Hence,studying AS types and its special biological functions of VaD model and discussing the possible function of reactive AS in the course of VaD is crucial to elucidate the occurrence,development and treatment of VaD.Shenmayizhi decoction(SMYZD)invented by Professor Zhou Wenquan is composed of Radix Ginseng,Rhizoma Gastrodiae,Ramulus Euonymi,and Rhizoma Chuanxiong with the functions of supplementing qi deficiency and removing blood stasis in TCM theory.SMYZD has been proved to be clinically effective in treating VaD patients with a TCM pattern of qi deficiency and blood stasis.Therefore,this study aims to investigate whether the effect of SMYZD on improving cognitive function of VaD rats is mediated via regulating astrocytes and to explore its mechanism,so as to provide experimental evidence for clinical application of SMYZD for VaD.Objective:This study aims to explore the effects of SMYZD on cognitive function and astrocytes in VaD rats and to elucidate the mechanism.Methods:The rat model of vascular dementia was established via microsphere embolization.Rats were randomly divided into sham operated(Sham)group,microsphere embolization(ME)group,SMYZD low dose treated(ME+SL)group and SMYZD high dose treated(ME+SH)group.Morris water maze experiment was used to evaluate the spatial learning and memory ability of rats.NeuN and GFAP were labeled by immunofluorescence method and the positive cells(neurons and astrocytes)were counted.The level of cognitive function related proteins in brain tissue was preliminarily screened by antibody array.The proinflammatory factor Il-1? and TNF-?were detected by ELISA.The level of VEGF and Hif-la was detected by Western blot.The mRNA levels of Nrf2 and HO-1 were assessed by RT-qPCR.Results:1.Morris Water Maze experiment showed that compared with Sham group,escape latency of rats in ME group was significantly prolonged(P<0.05),platform crossing times of rats were significantly reduced(P<0.05),and time spent in target quadrant was significantly shortened(P<0.05),indicating that ME rats had impaired spatial learning and memory ability.Escape latency of rats in ME+SH group was significantly shorter than ME group(P<0.05),platform crossing times of the ME+SL group and ME+SH group were significantly higher than ME group(P<0.05),and time spent in target quadrant of ME+SL group and ME+SH group were significantly longer than ME group(P<0.05),suggesting that SMYZD could improve spatial learning and memory ability of VaD rats.2.Immunofluorescence analysis of NeuN showed that the number of NeuN positive cells in the CA1 region of hippocampus in ME group was significantly reduced compared with Sham group(P<0.05),indicating that neurons of ME rats were damaged and lost.The number of NeuN positive cells in the CA1 region of hippocampus in ME+SH group was significantly increased compared with ME group(P<0.05),suggesting that SMYZD could mitigate the loss of neurons in the CA1 region of hippocampus.3.GFAP immunofluorescence showed that compared with Sham group,the number of GFAP positive cells in the CA1 region of hippocampus in ME group significantly increased(P<0.05),and the number of GFAP positive cells in the CA1 region of hippocampus in ME+SH group significantly were increased than ME group(P<0.05).4.Antibody array analysis showed that the expression of TNF-?,Il-1?,IFN-? and VEGFA in ME group were significantly increased than Sham group(P<0.05).5.ELISA analysis showed that the contents of Il-1? and TNF-? in ME group were significantly increased than Sham group(P<0.05).The contents of Il-1? and TNF-? in ME+SL group and ME+SH group were significantly reduced than ME group(P<0.05)6.Western blot analysis showed that the expression of VEGF in ME group was significantly increased than Sham group(P<0.05),and the expression of VEGF in ME+SH group was significantly increased than ME group(P<0.05).The expression of HIF-la in ME group significantly was increased than Sham group(P<0.05),and the expression of HIF-la in ME+SL group and ME+SH group were significantly increased than ME group(P<0.05).7.qPCR analysis showed that the levels of HO-1 and Nrf2 mRNA in ME group were significantly higher than Sham group(P<0.05).The mRNA levels of HO-1 and Nrf2 in ME+SL group and ME+SH group were significantly higher than ME group(P<0.05).Conclusion:SMYZD can improve cognitive function and protect neurons by promoting protective proliferation of reactive astrocyte-type via upregulating Nrf2/ho-1 pathway.In addition,it inhibits the expression of pro-inflammatory factor Il-1? and TNF-?,on the other hand,it promotes the secretion of VEGF by upregulating HIF-1?.