Effects Of Selectin P On Alzheimer's Disease

Background:Selectin P,belonging to the selectins family,is expressed in platelets or endothelial cells and exists in the plasma in soluble form.The expression of selectin P will be stimulated upon the activation of platelet and endothelial cells,which will then enter cell via endocytosis.Higher expression of Selectin P is an indicator of platelet activation or endothelial cells damage,which is often accompanied with inflammation.Content of Selectin P is found to be increased in the acute or chronic cardiovascular and cerebrovascular diseases,and the activation of platelet is decreased upon the inhibition of selectin P expression.Large bodies of studies have implicated that neuro-inflammation plays important roles in the pathogenesis of Alzheimer’s disease(AD).Thus,in this study,we devote to investigate the role and the underlying mechanism of Selectin P in the neuro-inflammation and the development of AD.Methods:r AAV9 virus with selectin P sh RNA plasmid was injected into the 4-month old mice via tail vein to knock down selectin P expression.After 3 months,several behavioral tests including Open-Field,Cross Elevated Maze,T Maze and Morris Water Maze were carried out to assess the spatial learning and memory abilities,as well as the depression-and anxiety-related behavior of all the mice.Blood indicators including blood glucose,lipid metabolism,liver and kidney function of the mice were detected by the biochemical analyzer.Then,the expression levels of selectin P in the plasma,hippocampus and cortex tissues were determined by fluorescence imaging,western bolt(WB)and Enzyme-linked immunosorbent assay(ELISA).Next,Aβ and tau pathology were studied by thioflavine T(Th T)staining,Aβ immunofluorescence,WB and Glycine silver staining.Neuronal activities and synaptic proteins were determined through Nissl’s staining and WB,respectively.Inflammatory factors such as Trem2,i NOA,IBA-1,SR-BI,GFAP,IL-3,IL-6 and TNF-α in the plasma,cortex and hippocampus tissues were tested by ELISA and WB.Finally,proteomics and metabolomics were applied to estimate the changes of both protein and metabolites in the brains of mic with the knockdown of Selectin P,to explore the potential molecular mechanism of Selectin P on the pathogenesis of AD.Results:The successful transfection and expression of virus with selectin P sh RNA plasmid was confirmed with the green fluorescence observed in the brain and liver tissues of the 7-mo old mice.Subsequently,the reduced levels of selectin P in the plasma,hippocampus and cortex tissues of both AD and wild type(WT)mice were found,although distinct outcomes were demonstrated in these two groups of mice.Detailly,selectin P knock down in WT mice resulted in: 1)impairments of spatial learning and memory abilities,as well as the depression-and anxiety-related behavior;2)decreased levels of HDL-C and urea in the blood;3)elevated levels of Aβ oligomers,senile plaques(SP)and multiple inflammatory factors in the brains.While in the AD mice,with the knockdown of selectin P,their spatial memories and learning abilities were improved.Meanwhile,the levels of LDL-C and Cre-P in the blood were significantly decreased,accompanied with much lower contents of Aβoligomers,SP,neurofibrillary tangles(NFTs)and diverse inflammatory factors in the hippocampus and cortex of 3×Tg AD mice.In addition,the neuronal activities of cortex in AD mice was improved,Furtherly,proteomics and metabolomics were applied to estimate the changes of both protein and metabolites in the brains of mic with the knockdown of Selectin P.For proteomics analysis,50 same differently expressed proteins(DEPs)between WT+SEL-P KD vs WT and AD vs WT,and 29 same DEPs between AD+SEL-P KD vs AD and WT vs AD were dug out,respectively.Interestingly,the same expression change trends of all the shared 50 DEPs between WT+SEL-P KD vs WT and AD vs WT,and 28 out of 29 shared DEPs between AD+SEL-P KD vs AD and WT vs AD,were observed.The metabolomics study figured out 22 same different metabolites between WT+SEL-P KD vs WT and AD vs WT,and 46 ones between AD+SEL-P KD vs AD and WT vs AD in both the positive and negative models.Additionally,there are 5 same DEPs,and 6 same different metabolites between WT+SEL-P KD vs WT and AD+SEL-P KD vs AD,with opposite change trends.Conclusions:This study interfered the expression of selectin P successfully in both the WT and3×Tg AD mice.Selectin P knockdown deteriorated the emotion and cognitive functions of WT mice,with the appearance of Aβ pathology and neuroinflammation and thus increased risk of neurodegenerative disorders.On the other hand,the AD related pathologies of 3×Tg AD mice were significantly ameliorated by selectin P knockdown.The findings in this study suggest that selectin P may play some important roles in the brain function and AD pathogenesis,however,the underlied mechanism has yet to be further elucidated.