Trauma, the gut, and the brain: the gut microbiota-microglia axis in traumatic brain injury

项目总结/摘要 创伤是美国年轻人死亡和残疾的主要原因。创伤性脑损伤 (TBI)造成了三分之一以上的创伤相关死亡。事实上，TBI相关的医疗支出 每年近800亿美元。TBI的影响不仅突出表现在其高死亡率上，而且还表现在 幸存者长期遭受严重的认知和精神并发症。慢性神经炎症 小胶质细胞的组成性激活引起的细胞凋亡是这一过程的同谋， 小胶质细胞和肠道微生物组之间通过肠-脑轴的相互作用。然而，机制 潜在的肠道微生物群-小神经胶质细胞相互作用尚未阐明。我们实验室发布的数据 显示了TBI后肠道微生物群落的显著改变， 与神经疾病过程密切相关的微生物物种。同样，众所周知， 减少能够将膳食纤维发酵成短链脂肪酸（SCFA）的厌氧菌的丰度 加重了神经损伤后的病变大小和神经炎症。我们实验室的初步数据显示， 在饮食中补充SCFAs乙酸盐、丁酸盐和 脑外伤后的丙酸尽管如此，与TBI诱导的肠道微生物改变相关的机制 社区的发展，随后的神经认知能力下降尚未得到充分阐明。W 假设 提高 e 有针对性的微生物和饮食干预将减弱小胶质细胞的激活， TBI后的神经认知结果。为了验证这一假设，我们将确定是否恢复 通过粪便微生物群移植、靶向微生物群替代或饮食替代， SCFA的补充减弱了野生型、无菌和遗传靶向细胞中小胶质细胞的活化， 替代小鼠我们将使用小胶质细胞的批量细胞分选（FACSorting），然后使用单细胞RNA 测序（scRNAseq）。我们将通过粪便16 S rRNA基因比较候选基因与微生物活性 扩增子测序和粪便代谢物分析。与转录组和肠道微生物相协调 社区分析，所有目标将利用18 kDa转运蛋白（TSPO）的纵向PET/CT成像 用我们小组开发的一种新型氟基放射性示踪剂来跟踪和比较 以及TBI后肠道微生物和饮食干预之前、期间和之后的小胶质细胞活化程度。 总的来说，拟议的研究将确定肠道微生物群落结构和代谢的关键作用， 在TBI的过程中，在组成性小胶质细胞活化的发作和进展中的活性，从而提高了TBI的发病率。 在TBI患者中开发新的治疗和生物标志物的潜力。

Project Summary/Abstract Trauma is the leading cause of death and disability in young adults in the United States. Traumatic brain Injury (TBI) contributes to over one third of all these trauma related deaths. In fact, TBI related healthcare expenditures near 80 billion dollars annually. The impact of TBI is highlighted not only by its high mortality rate, but also the significant long-term cognitive and psychiatric complications suffered by its survivors. Chronic neuroinflammation resulting from the constitutive activation of microglia is complicit in this process and represents a complex interplay between microglia and the gut microbiome via the gut-brain axis. However, the mechanism(s) underlying gut microbiota-microglia interaction have yet to be elucidated. Published Data from our laboratory shows a significantly altered gut microbial community after TBI, with increased relative abundance of several microbial species strongly associated with neurologic disease processes. In the same vein, it is known that reduced abundance of anaerobic bacteria capable of fermenting dietary fiber into short chain fatty acids (SCFAs) exacerbate lesion size and neuroinflammation after neurologic injury. Preliminary Data from our laboratory has shown improved neurocognitive outcomes with dietary supplementation of the SCFAs acetate, butyrate, and propionate after TBI. Nonetheless, the mechanism(s) linking TBI-induced alterations in the gut microbial community to the development of subsequent neurocognitive decline have yet to be fully elucidated. W hypothesize improve e that targeted microbial and dietary intervention will attenuate microglial activation and neurocognitive outcomes after TBI. To test this hypothesis,we will determine whether restoring a pre-injury gut microbial composition via fecal microbiota transplant, targeted microbiota replacement, or dietary supplementation of SCFAs attenuates the activation of microglia in wild type, germ-free, and genetic targeted replacement mice. We will use bulk population cell sorting (FACSorting) of microglia followed by single cell RNA sequencing (scRNAseq). We will compare candidate genes to microbial activity via fecal 16S rRNA gene amplicon sequencing and fecal metabolite analysis. Harmonized with the transcriptomic and gut microbial community profiling, all Aims will utilize longitudinal PET/CT imaging of the 18-kDa translocator protein (TSPO) with a novel fluorine-based radiotracer developed by our group to track and compare the onset, progression, and degree of microglial activation before, during, and after gut microbial and dietary intervention after TBI. Collectively, the proposed studies will identify the key role of gut microbial community structure and metabolic activity in the onset and progression of constitutive microglial activation over the course of TBI, thus raising the potential for novel therapeutic and biomarker development in TBI patients.