n-3多不饱和脂肪酸调节小胶质细胞激活及极化改善APPPS1小鼠学习记忆能力

polyunsaturated fatty acids ameliorate learning and memory abilities in APPPS1 mice by regulating microglial activation and polarization

目的 建立Fat-1/APPPS1转基因小鼠的体内模型及小胶质细胞体外模型,探讨n-3多不饱和脂肪酸(n-3 polyunsaturated fatty acids, n-3 PUFAs)调节小胶质细胞激活及极化改善APPPS1小鼠学习记忆能力的效果和机制。方法 将杂合子Fat-1雄性小鼠与杂合子APPPS1雌性小鼠进行杂交,筛选子代得到WT、Fat-1、Fat-1/APPPS1以及APPPS1雄性小鼠,培育至9月龄。运用Morris水迷宫实验评估小鼠的学习记忆能力;气-质联用技术(GS-MS)测定小鼠脑组织内多不饱和脂肪酸水平;运用免疫组织化学法检测小鼠大脑海马区β淀粉样蛋白(β-amyloid protein, Aβ)沉积情况;运用组织免疫荧光、qRT-PCR及酶联免疫吸附实验检测各组小鼠中枢神经系统(central nervous system, CNS)炎症水平,小胶质细胞激活及极化水平,基因Iba-1的转录及表达小胶质细胞激活水平,基因CD86、CD206的转录及表达小胶质细胞极化水平。采用脂多糖(LPS)诱导小鼠来源的永生化BV2小胶质细胞损伤建立细胞炎症模型,用二十二碳六烯酸(docosahexaenoic acid, DHA)和二十碳五烯酸(eicosapentaenoic acid, EPA)对细胞预处理,运用细胞免疫荧光、qRT-PCR和蛋白免疫印迹技术检测各组小胶质细胞炎症、激活及极化水平,采用的激活与极化指标与动物实验相同。结果 与APPPS1小鼠相比,内源性表达n-3 PUFAs的Fat-1/APPPS1小鼠学习记忆障碍明显改善(P<0.05),海马区Aβ沉积有效缓解(P<0.05),CNS炎症水平以及小胶质细胞激活水平显著降低(P<0.05),同时小胶质细胞激活表型从M1向M2型转化(P<0.05)。DHA+EPA预处理显著降低了LPS诱导的BV2细胞炎症水平(P<0.05),且促使细胞从M1向M2型转化(P<0.05)。结论 n-3 PUFAs可以抑制APPPS1小鼠大脑小胶质细胞激活,调节小胶质细胞由M1向M2转化,降低中枢神经炎症水平,改善APPPS1小鼠学习记忆障碍。

Objective To construct a model of Fat-1/APPPS1 transgenic mice and a cellular model of microglia and explore the improvement effect and underlying mechanism of n-3 polyunsaturated fatty acids(n-3 PUFAs)on the learning and memory abilities of APPPS1 mice by regulating microglial activation and polarization.Methods After the male mice with heterozygous Fat-1 genotype were mated with the female ones with heterozygous APPPS1 genotype,genetic identification was used to screen the male offspring with Fat-1/APPPS1 genotype.Then after the male wild-type(WT)mice and those with Fat-1,Fat-1/APPPS1,and APPPS1 genotypes were bred until 9 months old,their learning and memory abilities were evaluated with Morris water maze(MWM)test.In addition,gas chromatography-mass spectrometry(GC-MS)was performed to detect the concentration of PUFAs in the brain,and immunohistochemistry(IHC)was applied to detect the deposition ofβ-amyloid protein(Aβ)in the hippocampal regions.Moreover,immunofluorescence assay,qRT-PCR,and enzyme-linked immunosorbent assays(ELISA)were conducted to measure inflammation,and transcription and expression of Iba-1(indicating the microglial activation)and CD86 and CD206(indicating microglial polarization)in central nervous system(CNS).After pretreated with DHA+EPA(25μmol/mL∶25μmol/mL),microglial model of inflammatory injury was established in immortalized mouse BV2 cells induced by LPS(1μg/mL).Afterwards,immunofluorescence assay,qRT-PCR and Western blotting were used to detect inflammation and microglial activation and polarization.Results Compared with the APPPS1 mice,endogenous n-3 PUFAs effectively improved the learning and memory disorders in Fat-1/APPPS1 ones(P<0.05),remarkably alleviated Aβdeposition in the hippocampal regions(P<0.05),evidently reduced CNS inflammation and microglial activation(P<0.05)and transformed the activated microglia from M1 to M2(P<0.05).Furthermore,BV2 cells with DHA+EPA pretreatment obviously resisted LPS-induced cellular inflammation and induced activated ones from M1 to M2(P<0.05).Conclusion n-3 PUFAs inhibit the microglial activation,regulate the microglial polarization from M1 to M2,reduce CNS inflammation,and thus alleviate learning and memory disorders in APPPS1 mice.