Microglia, the brain-resident macrophages perform immune surveillance and engage with pathological processes resulting in phenotype changes necessary for maintaining homeostasis. In preceding studies, we showed that antibiotic-induced perturbations of the gut microbiome of APPPS1-21 mice resulted in significant attenuation in Aβ amyloidosis and altered microglial phenotypes that are specific to male mice. The molecular events underlying microglial phenotypic transitions remain unclear. Here, by generating ‘APPPS1-21-CD11br’ reporter mice, we investigated the translational state of microglial/macrophage ribosomes during their phenotypic transition and in a sex-specific manner. Six groups of mice that included WT-CD11br, antibiotic (ABX) or vehicle-treated APPPS1-21-CD11br males and females were sacrificed at 7-weeks of age (n = 15/group) and used for immunoprecipitation of microglial/macrophage polysomes from cortical homogenates using anti-FLAG antibody. Liquid chromatography coupled to tandem mass spectrometry and label-free quantification was used to identify newly synthesized peptides isolated from polysomes. We show that ABX-treatment leads to decreased Aβ levels in male APPPS1-21-CD11br mice with no significant changes in females. We identified microglial/macrophage polypeptides involved in mitochondrial dysfunction and altered calcium signaling that are associated with Aβ-induced oxidative stress. Notably, female mice also showed downregulation of newly-synthesized ribosomal proteins. Furthermore, male mice showed an increase in newly-synthesized polypeptides involved in FcγR-mediated phagocytosis, while females showed an increase in newly-synthesized polypeptides responsible for actin organization associated with microglial activation. Next, we show that ABX-treatment resulted in substantial remodeling of the epigenetic landscape, leading to a metabolic shift that accommodates the increased bioenergetic and biosynthetic demands associated with microglial polarization in a sex-specific manner. While microglia in ABX-treated male mice exhibited a metabolic shift towards a neuroprotective phenotype that promotes Aβ clearance, microglia in ABX-treated female mice exhibited loss of energy homeostasis due to persistent mitochondrial dysfunction and impaired lysosomal clearance that was associated with inflammatory phenotypes. Our studies provide the first snapshot of the translational state of microglial/macrophage cells in a mouse model of Aβ amyloidosis that was subject to ABX treatment. ABX-mediated changes resulted in metabolic reprogramming of microglial phenotypes to modulate immune responses and amyloid clearance in a sex-specific manner. This microglial plasticity to support neuro-energetic homeostasis for its function based on sex paves the path for therapeutic modulation of immunometabolism for neurodegeneration.

中文翻译：

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翻译分析鉴定了抗生素干扰微生物组的 APPPS1-21 小鼠皮质小胶质细胞/巨噬细胞的性别特异性代谢和表观遗传重编程


小胶质细胞是大脑中的巨噬细胞，执行免疫监视并参与病理过程，导致维持体内平衡所需的表型变化。在之前的研究中，我们发现抗生素引起的 APPPS1-21 小鼠肠道微生物群的扰动导致 Aβ 淀粉样变性显着减弱，并改变了雄性小鼠特有的小胶质细胞表型。小胶质细胞表型转变的分子事件仍不清楚。在这里，通过生成“APPPS1-21-CD11br”报告小鼠，我们以性别特异性方式研究了小胶质细胞/巨噬细胞核糖体在表型转变过程中的翻译状态。六组小鼠，包括 WT-CD11br、抗生素 (ABX) 或媒介物处理的 APPPS1-21-CD11br 雄性和雌性，在 7 周龄时处死（n = 15/组）并用于小胶质细胞/巨噬细胞多聚体的免疫沉淀使用抗 FLAG 抗体从皮质匀浆中提取。使用液相色谱法与串联质谱法和无标记定量相结合来鉴定从多核糖体中分离的新合成的肽。我们发现 ABX 治疗导致雄性 APPPS1-21-CD11br 小鼠的 Aβ 水平降低，而雌性小鼠没有显着变化。我们鉴定了与 Aβ 诱导的氧化应激相关的线粒体功能障碍和钙信号改变所涉及的小胶质细胞/巨噬细胞多肽。值得注意的是，雌性小鼠还表现出新合成的核糖体蛋白的下调。此外，雄性小鼠表现出参与 FcγR 介导的吞噬作用的新合成多肽的增加，而雌性小鼠表现出负责与小胶质细胞激活相关的肌动蛋白组织的新合成多肽的增加。 接下来，我们表明 ABX 治疗导致表观遗传景观的实质性重塑，导致代谢转变，以性别特异性方式适应与小胶质细胞极化相关的增加的生物能和生物合成需求。虽然 ABX 治疗的雄性小鼠中的小胶质细胞表现出向促进 Aβ 清除的神经保护表型的代谢转变，但 ABX 治疗的雌性小鼠中的小胶质细胞由于持续的线粒体功能障碍和与炎症表型相关的溶酶体清除受损而表现出能量稳态的丧失。我们的研究首次展示了接受 ABX 治疗的 Aβ 淀粉样变性小鼠模型中小胶质细胞/巨噬细胞的翻译状态。 ABX 介导的变化导致小胶质细胞表型的代谢重编程，以性别特异性方式调节免疫反应和淀粉样蛋白清除。这种基于性别的小胶质细胞可塑性支持神经能量稳态，为神经退行性疾病免疫代谢的治疗调节铺平了道路。