The Study On The Neuroprotective Effects Of Several Carbohydrate Compounds And The Underlying Mechanisms

As one of three basic nutrients,carbohydrates with various bioactivity wildly exist in the nature.In 2019,a new drug ameliorating Alzheimer's disease?AD?named GV-971 had got conditional approval from CFDA,which provided the possibility of carbohydrates in neuroprotection.Whether other carbohydrates have neuroprotective effects,and if so,what are their mechanisms of action,are two major scientific questions of this paper.In this article,we began with a small molecular compound of glycoside,Gastrodin?Gas?,to discover its neuroprotective effects.PC12 cells treated with Gas showed neurite outgrowth.Western blotting results indicated the process may related with the activation of ERK/MEK signaling pathway.Next,we found Gas could enhance NGF induced neurite outgrowth in PC12 cells.Phosphorylation of ERK in NGF and Gas treated group was also higher than NGF group.Furthermore,using a ERK signaling pathway inhibitor,U0126,the neurite outgrowth of both NGF treated group and NGF and Gas group were suppressed,which indicated this process was exactly relevant to ERK signaling pathway.Since neurite outgrowth might assist recovering damaged neurons,which may help to ameliorate symptoms of AD,we also tried to explore other carbohydrate compounds with anti-AD bioactivity from safer and more complexed polysaccharides.We extracted polysaccharides from traditional Chinese medicine with neuroprotective and memory improvement functions,polygala tenuifolia and dioscorea opposite.We got RG-I type polysaccharide RP02-1 and polysaccharide mixture DOP0.2 respectively.Employing HEK293-APPsw cells and CHO/APPBACE1 cells as AD cell models,through cell proliferation assay,ThT fluorescence assay,and ELISA assay.We found that both polysaccharides showed no apparent cytotoxicity.RP02-1 could decrease A?₄₂ generation,impede A?₄₂ aggregation and promote A?degradation by upregulating IDE and NEP as well as accelerating the uptake of A?by microglia.DOP0.2 could reduce A?₄₂ production,inhibit A?₄₂ aggregation and also promote A?clearance through upregulating IDE,NEP and Prep.The above-mentioned results demonstrated that RP02-1 and DOP0.2 could be candidate leading compound for anti-AD new drug development.To further investigate the bind site of polysaccharide,we labelled fluorescence with the polysaccharide and then applied to the protein chip,eventually identified the gene KCNAB2?voltage gated potassium channel?site?,encoding Kv?.2 protein.We knocked-down KCNAB2 in microglia BV2 cells,and found IDE was downregulated.Moreover,the phagocytosis of A?was also suppressed,which indicated that knocking-down KCNAB2 might influence the clearance of A?in BV2 cells.However,the role of KCNAB2 played in Alzheimer's disease requires further studies.In conclusion,we first illustrated the effect of gastrodin on stimulating neurite outgrowth in PC12 cells and the involved signaling pathway.Besides,we found a homogeneous polysaccharide RP02-1 and another polysaccharide mixture DOP0.2showed anti-AD bioactivity targeting A?.In addition,we preliminarily reported the gene KCNAB2 could be a target of RP02-1.In general,our research provided a good foundation for anti-AD new drug development.