Effects Of β-1,3-galactosyltransferase 2 Gene Knockout On Learning/memory And Pathological Changes In The Hippocampus Of Mice With Alzheimer’s Disease

ObjectiveTo investigate the effect of β-1,3-galactosyltransferase 2(B3galt2)gene knockout on soluble amyloid β-protein 1-42(Aβ1-42)induced Alzheimer’s disease(AD)mouse model,and the effects of B3galt2 gene knockout on learning and memory and synaptic,neuronal and neuroinflammation in the hippocampus.To investigate the effect and mechanism of B3galt2 gene on learning,memory and related pathological changes in AD mice.MethodsB3galt2 knockout heterozygous mice were bred,and the genotype was identified by genomic DNA and PCR,and 3-month-old adult wild-type,heterozygous,and homozygous mice were obtained.AD mouse models were established by intracerebventricular injection.Behavioral tests(Y maze)were performed 7 days after operation.According to the genotype and whether Aβ1-42 was injected into the lateral ventricle,the mice were divided into the following 6groups: wild type group,heterozygote group,homozygote group,wild type +Aβgroup,heterozygote +Aβ group,homozygote +Aβ group.Thioflavin S staining was used to observe the expression of amyloid in the hippocampus of mice.Immunohistochemical staining was used to detect the expression of postsynaptic density protein 95(PSD95),synaptoid associated protein 25(SNAP25),microtubule-associated protein 2(MAP2),glial fibrillary acidic protein(GFAP),microglia marker(IBA1)and apolipoprotein E(Apo E)in hippocampus of mice.The levels of interleukin-1β(IL-1β),interleukin-6(IL-6)and tumor necrosis factor α(TNF-α)in mice brain were detected by enzyme-linked immunosorbent assay.Western blot was used to detect the expression levels of B3galt2 and Apo E in the hippocampus.Immunofluorescence staining was used to observe the co-localization of B3galt2 and Apo E.The hippocampal cells of neonatal mice at postnatal day 1-2 were selected and randomly divided into the following groups: control group(Ctrl);Aβ group;B3galt2 c DNA+Aβ group;B3galt2 c DNA group;Apo E c DNA+Aβ group;B3galt2 c DNA+Apo E c DNA+Aβgroup;The protein expression levels of B3galt2 c DNA and Apo E c DNA were verified by Western blot.Immunohistochemical staining was used to observe the expression of MAP2 and SNAP25.Results1.Amyloid deposition occurred in the hippocampus of Aβ1-42-induced AD mice,and B3galt2 gene knockout increased amyloid deposition in the hippocampus of Aβ1-42-induced AD mice.B3galt2 knockout aggravated the impairment of learning and memory ability in AD mice,and reduced the expression of synapsion-associated proteins PSD95,SNAP25 and neuronal dendritic protein MAP2.2.B3galt2 knockout promotes glial cell activation and inflammatory cytokine release in AD mice;B3galt2 can increase the expression of Apo E protein in the hippocampus of AD mice,and B3galt2 and Apo E are partially co-localized in the hippocampus.3.B3galt2 overexpression can improve the effect of Aβ1-42 on MAP2 and SNAP25;Apo E overexpression attenuated the protective effect of B3galt2 overexpression on neuronal toxicity in AD cell models.ConclusionsB3galt2 knockout aggravated the impairment of learning and memory ability in AD mice,reduced the expression of synapsis-associated proteins and neuronal dendritic proteins in the hippocampus of AD mice,and promoted the neuroinflammatory response and increased Apo E expression in the hippocampus of AD mice.Meanwhile,Apo E overexpression reduced the protective effect of B3galt2 overexpression on neuronal toxicity in AD cell model.It is suggested that B3galt2 gene may play a regulatory role in the learning and memory function and related pathological changes of AD mice by affecting the expression of ApoE in hippocampus.