Objectives To investigate the ameliorative effect of cannabinoid 2 receptor(CB2R)agonist JWH-015 on the cog-nitive impairment of Alzheimer' s disease(AD)model mice and to assess the correlation with microglial phenotype transformation. Methods Twenty adult male C57BL/6J mice were randomly divided into four groups:C57BL/6J solvent group,JWH-015 control group,AD model group,and AD model treated with JWH-015 group. Amyloidβ1-42 oligomers of 4μg and the same volume of saline were intraventricularly administered to construct the AD mouse model and the solvent groups. CB2R agonist JWH-015 or the corre-sponding vehicle at a dose of 0.5 mg/(kg·d)was administered by intraperitoneal injection for 3 weeks. Non-spatial learning and memo-ry was measured using novel object recognition task. Furthermore,the mRNA expression levels of M1 microglia marker inducible ni-tric oxide synthase(iNOS)and M2 microglia marker chitinase-3 like protein(Ym1/2)in brain samples of cortex and hippocampus were evaluated using real-time quantitative PCR(qPCR). In the meantime,fifteen CB2R knockout(CB2RKO)mice and five CB2R wild-type(CB2RWT)littermates were assigned to identify the specificity of CB2R in the research. Based on the genotype and different treatment,the animals were divided into four groups:CB2RKO solvent group,CB2RKO AD model group,CB2RKO AD model treat-ed with JWH-015 group and CB2RWT solvent group. Results Compared with solvent group,there was a significant decrease in nov-el object recognition index in C57BL/6J AD model group(P<0.01). The mRNA expression levels of M1 phenotype microglia marker iNOS in cortex and hippocampus were significantly up-regulated(both P<0.05)and the mRNA expression levels of M2 phenotype mi-croglia marker Ym1/2 were significantly down-regulated(both P<0.01). Interestingly,administration of JWH-015 could reverse the impairment of novel object recognition index(P<0.05);compared with C57BL/6J AD model group,administration of JWH-015 also decreased the iNOS mRNA expression levels(both P<0.05)and increased the Ym1/2 mRNA expression levels(both P<0.05)in cortex and hippocampus;compared with CB2RKO solvent group,the novel object recognition index of CB2RKO AD model group was decreased(P<0.05);the mRNA expression levels of iNOS in cortex and hippocampus were significantly up-regulated(both P<0.05),the mRNA expression level of Ym1/2 in cortex was significantly down-regulated in cortex(P<0.05);compared with CB2RKO AD model group,administration of JWH-015 had no effect on novel object recognition index and the mRNA expression level of M1/M2 in cortex and hippocampus,respectively. Conclusion JWH-015 improves the cognitive impairment of Aβ-induced AD mice by the specific activation of CB2R,the mechanism of which is related to the direct regulation of CB2R on the M1/M2 microglial phenotype transformation and microglia-mediated neuroinflammation in brain.%目的 观察大麻素2型受体(CB2R)激动剂JWH-015对阿尔茨海默病(AD)小鼠认知功能下降的改善作用,并探讨其作用机制是否与脑内小胶质细胞激活表型转化密切相关.方法 20只成年雄性C57BL/6J小鼠随机分为溶剂对照组、JWH-015对照组、AD模型组和JWH-015治疗组.侧脑室注射4μg寡聚态β-淀粉样蛋白1-42(Aβ1-42)和等体积生理盐水构建AD模型和模型对照组后,分别接受连续3周腹腔注射JWH-0150.5 mg/kg或等量溶剂处理.采用新物体识别实验检测小鼠认知功能;实时定量PCR方法检测皮质、海马脑区M1型小胶质细胞标记分子诱导型一氧化氮合酶(iNOS)和M2型小胶质细胞标志物几丁质酶3样蛋白(Ym1/2)mRNA表达水平.同时,取15只CB2R基因敲除C57BL/6J小鼠(CB2RKO)和5只同窝野生型(CB2RWT)小鼠按基因型和处理随机分为CB2RKO溶剂对照组、CB2RKO AD模型组、JWH-015处理组和CB2RWT小鼠溶剂对照组,用来研究CB2R对认知功能改善作用和小胶质细胞激活表型转化作用的特异性.结果 与溶剂对照组相比,C57BL/6J AD模型组小鼠新奇物体识别指数显著降低(P<0.01),同时伴随皮质和海马脑区iNOS mRNA表达显著升高(均为P<0.05)和Ym1/2 mRNA表达显著降低(均为P<0.01);而JWH-015处理可显著提高C57BL/6J AD模型组小鼠新物体识别指数(P<0.05),下调皮质和海马区iNOS mRNA表达水平(均为P<0.05),上调Ym1/2 mRNA表达水平(均为P<0.05);与脑室注射生理盐水的CB2RKO溶剂对照组小鼠相比,CB2RKO AD模型组小鼠识别指数显著降低(P<0.05),皮质和海马脑区iNOS mRNA表达显著升高(均为P<0.05),皮质脑区Ym1/2 mRNA表达显著降低(P<0.05);与CB2RKO AD模型组小鼠相比,JWH-015处理组长时程给药对新奇物体识别指数无显著影响,并对皮质、海马脑区内iNOS及Ym1/2 mRNA的表达水平无显著影响.结论 JWH-015通过特异性激动CB2R改善Aβ诱导的AD模型小鼠的认知能力下降,其机制可能与其直接作用于相关脑区小胶质细胞CB2受体,引起小胶质细胞M1/M2表型转化,减轻脑内小胶质细胞介导的神经源性炎症反应有关.
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