Differential effects of APOE polymorphism in neurotoxicity-responsive astrocytes induced by inflammatory factor / 吉林大学学报(医学版)

ABSTRACT

Objective:To discuss the differential effects of apolipoprotein E(APOE)gene polymorphism in the neurotoxicity-reactive astrocytes,and to provide the theoretical basis for the study of the pathogenesis of Alzheimer's disease(AD).Methods:The primary cortical astrocytes from the APOE-knockout mice(APOE-/-)were isolated and cultured in vitro,and the purity of the cells was identified by immunofluorescence staining.The human APOE3 and APOE4 recombinant over-expression plasmids were constructed and separately transfected into the primary APOE-/-astrocytes,and the APOE-/-primary cells were regarded as control.Western blotting method was used to detect the expression levels of APOE and glial fibrillary acidic protein(GFAP)proteins in the cells;enzyme-linked immunosorbent assay(ELISA)method was used to detect the APOE level in the cellular culture supernatant.The inflammatory models were prepared with the primary astrocytes transfected with APOE3 and APOE4 and co-stimulated with interleukin-1α(IL-1α),tumor necrosis factor(TNF),and complement C1q.The cells were divided into APOE3+PBS group,APOE4+PBS group,APOE3+IL-1α+TNF+ C1q group,and APOE4+IL-1α+TNF+C1q group.Cell immunofluorescence staining method was used to observe the morphology of the cells in various groups;real-time fluorescence quantitative PCR(RT-qPCR)method was used to detect the expression levels of glypican 4(Gpc4),glypican 6(Gpc6),thrombospondin 1(Thbs1),thrombospondin 2(Thbs2),SPARC-like protein 1(Sparcl1)and glial cell line derived neurotrophic factor(GDNF),C3,and S100 calcium binding protein B(S100B)mRNA in the cells in various groups;microsphere phagocytosis assay was used to detect the phagocytic capacities of the cells in various groups;Western blotting was used to detect the protein expression levels of B-cell lymphoma 2(Bcl-2),and cysteinyl aspartate specific protease-3(Caspase-3)proteins in the cells in various groups.Results:Compared with APOE-/-group,the expression levels of APOE and GFAP proteins in the cells and the APOE level in the cellular culture supernatant in transfected APOE3 and transfected APOE4 groups were increased(P<0.01).The fluorescence microscope observation results showed that compared with APOE3+PBS and APOE4+PBS groups,the astrocytic processes in APOE3+IL-1α +TNF+Cq1 group and APOE4+IL-1α+TNF+Cq1 group became shorter and the cell bodies became larger;compared with APOE3+IL-1α +TNF+Cq1 group,the astrocytic processes in APOE4+IL-1α +TNF+Cq1 group were even shorter.Compared with APOE3+PBS and APOE4+PBS groups,the expression levels of Gpc4,Gpc6,Thbs1,Thbs2,and Sparcl1 mRNA in the cells in APOE3+IL-1α +TNF+Cq1 group and APOE4+IL-1α +TNF+Cq1 group were significantly decreased(P<0.01);compared with APOE3+IL-1α +TNF+Cq1 group,the expression levels of Gpc4,Gpc6,Thbs1,Thbs2,and Sparcl1 mRNA in the cells in APOE4+IL-1α +TNF+Cq1 group were significantly decreased(P<0.05 or P<0.01).Compared with APOE3+PBS and APOE4+PBS groups,the expression levels of GDNF mRNA in the cells in APOE3+IL-1α+TNF+Cq1 group and APOE4+ IL-1α +TNF+Cq1 group were decreased(P<0.01),and the expression levels of C3 and S100B mRNA were increased(P<0.01);compared with APOE3+IL-1α +TNF+Cq1 group,the expression level of GDNF mRNA in the cells in APOE4+IL-1α+TNF+Cq1 group was decreased(P<0.05),and the expression levels of C3 and S100B mRNA were increased(P<0.05).Compared with APOE3+ PBS group and APOE4+PBS group,the numbers of hagocytosis of microspheres in the cells in APOE3+ IL-1α +TNF+Cq1 group and APOE4+IL-1α +TNF+Cq1 group were significantly decreased;compared with APOE3+IL-1α+TNF+Cq1 group,the number of hagocytosis of microspheres in the cells in APOE4+IL-1α+TNF+Cq1 group was significantly decreased.Compared with APOE3+PBS group and APOE4+PBS group,the expression levels of Bcl-2 protein in the cells in APOE3+IL-1α+TNF+ Cq1 group and APOE4+IL-1α +TNF+Cq1 group were decreased(P<0.05 or P<0.01)and the expression levels of Caspase-3 protein were significantly increased(P<0.01);compared with APOE3+ IL-1α+TNF+Cq1 group,the expression level of Bcl-2 protein in the cells in APOE4+IL-1α+TNF+ Cq1 group was decreased(P<0.01),and the expression level of Caspase-3 protein was increased(P<0.05).Conclusion:The APOE4 genotype has a stronger ability to induce the inflammatory factors compared with APOE3;it can lead to a neurotoxicity-reactive astrocyte phenotype,increase the neurotoxicity,affect the astrocyte apoptosis,and aggravate the neuron damage.