| Background: Alzheimer’s disease(AD)is the most common chronic neurodegenerative disease worldwide.Intracellular neurofibrillary tangles(NFT)and extracellular β-amyloid protein(Aβ)plaques are the main pathological changes of AD.Patients with AD have significant cognitive impairment and persistent neuroinflammation.Microglia cells are the main cells that cause neuroinflammation.Platelet endothelial cell adhesion molecule-1(PECAM-1,CD31)is present in most hematopoietic system cells and at the junction of vascular endothelial cells.CD31 is widely involved in signal transduction and inflammation as an adhesion molecule and scaffold protein.Whether CD31 is involved in the pathological process of AD and whether CD31 is expressed in nerve cells is unknown.Objective: To investigate the role and molecular regulatory mechanism of CD31 in the pathological process of AD and the expression of CD31 in nerve cells.Methods:1.The expression of CD31 in the brain of AD patients and AD transgenic mice was detected by Western blot and real-time fluorescence quantitative PCR.2.The CRISPR/Cas9 gene editing technique was used to construct transgenic mice that systematically knocked out CD31.Open field experiment,new object recognition experiment,Morris water maze experiment and conditional fear experiment were used to detect the effects of systematic CD31 knockout on brain cognitive function of 5×FAD mice.3.Western blotting,ELISA,immunofluorescence and histochemical staining were used to detect the effects of systemic CD31 knockout on brain Aβ plaques,proinflammatory factors,Tau protein phosphorylation and synapse-related protein expression levels in 5×FAD mice.4.Immunofluorescence staining was used to detect the expression of CD31 in nerve cells.Primary microglia were cultured,and the effect of CD31 knockout on Aβphagocytosis of microglia was detected by immunofluorescence staining.Results:1.CD31 was significantly increased in the hippocampus of AD patients.2.CD31 increased in an age-dependent manner in the hippocampus of AD transgenic mice.3.Systemic CD31 knockout improved cognitive dysfunction in 5×FAD mice.4.Systemic CD31 knockout decreased the level of brain Aβ and the content of plaques in 5×FAD mice.5.Systemic CD31 knockout reduced the level of proinflammatory factors in the brain of 5×FAD mice.6.Systemic CD31 knockout decreased the phosphorylation level of Tau in brain of 5×FAD mice.7.Systemic CD31 knockout reversed synapse-associated protein damage in5×FAD mice.8.CD31 was highly expressed on microglia cells.9.Aβ promotes the expression of CD31 in microglia.10.CD31 knockout decreased the phagocytosis of Aβ by microglia.Conclusion:1.In AD transgenic mice,systematic knockout of CD31 can significantly reduce Aβ levels and plaque amount,reduce proinflammatory factors and Tau phosphorylation levels,and improve synaptic related proteins and cognitive impairment.2.In the course of acute Aβ treatment,CD31 knockout impaired the phagocytic function of microglia to Aβ. |
