The role of tyrosine metabolism in tuberculosis pathogenesis

摘要 结核病是全球主要的死亡原因。目前尚不清楚为什么只有一小部分 结核分枝杆菌(Mtb)感染者进展为结核病。众所周知，MTB会重新布线 急性感染后感染的单核细胞来源的吞噬细胞的免疫代谢。始终如一的、系统的 新陈代谢的改变是结核病发病机制的一个标志，因此突出了新陈代谢可能是 干预。酪氨酸，一种芳香族氨基酸，被证明在结核病患者的血清中积累，与 健康对照组。然而，目前尚不清楚酪氨酸代谢缺陷是否以及如何起调节作用。 对结核分枝杆菌感染的易感性或结核病进展的风险。我们发现原发人类髓系结核分枝杆菌感染 细胞下调酪氨酸关键酶富马酸乙酰乙酸酯水解酶的表达 分解代谢。我们还发现了一种与单核细胞来源的FAH低表达相关的遗传变异 发展为结核病的秘鲁人的树突状细胞(DC)。我们之前发现酪氨酸在大脑的 与预期登记的进展为结核病的非洲家庭接触者的血浆比较 非进展型，与酪氨酸分解代谢在预防结核病中的作用一致。重要的是，击倒 小鼠巨噬细胞中的FAH增加了它们对结核分枝杆菌感染的敏感性，这表明受损的酪氨酸 FAH的代谢可能导致结核分枝杆菌控制的丧失。从机制上讲，酪氨酸代谢物可能有助于 结核分枝杆菌感染细胞代谢状态的改变。我们假设Mtb介导的对酪氨酸的干扰 新陈代谢已演变为一种毒力机制，并可能介导向结核病的进展。我们 提出了一系列体外和体内实验来确定宿主酪氨酸代谢的需求 在感染结核分枝杆菌之后。我们将使用原代人类髓系细胞的基因编辑来靶向FAH，以测试 酪氨酸代谢的这一关键步骤是遏制结核分枝杆菌感染所必需的。我们还计划通过转让FAH- 将缺陷性胎肝细胞转化为结核病易感小鼠以检测其对酪氨酸代谢的需求 控制结核分枝杆菌体内感染的细胞。其次，我们将在中定义FAH缺失的代谢后果 代谢通量实验检测结核分枝杆菌感染的单核细胞来源的DC和巨噬细胞及其代谢物 结核分枝杆菌感染的FAH缺陷细胞的互补作用。最后，我们将利用两个样本和数据集 不同结核病州的独立队列。第一个是秘鲁结核病患者的横断面队列。 以及结核分枝杆菌感染和未感染的接触者，我们在那里生物库血浆样本用于靶向分析酪氨酸 代谢产物的高分辨质谱学分析。第二个是前面描述的纵向队列 对结核病患者的非洲家庭接触者进行了2年的跟踪调查，在那里我们还获得了基因分型数据，以 探索代谢基因的多态对酪氨酸代谢物表达的影响。定义 酪氨酸代谢受损与结核病风险之间的因果关系将推动未来的试验 改变现有药物的用途，将酪氨酸代谢的先天错误作为宿主指导的抗结核治疗。

ABSTRACT Tuberculosis (TB) is a leading cause of death globally. It remains unclear why only a small number of Mycobacterium tuberculosis (Mtb)-infected individuals progress to TB disease. Mtb is known to rewire the immunometabolism of infected monocyte-derived phagocytes following acute infection. Consistently, systemic shifts in metabolism are a hallmark of TB pathogenesis, thus highlighting metabolism as a possible target for intervention. Tyrosine, an aromatic amino acid, is shown to accumulate in the serum of TB patients compared to healthy controls. However, it is unknown whether and how defects in tyrosine metabolism could mediate susceptibility to Mtb infection or risk of TB progression. We found that Mtb infection of primary human myeloid cells downregulates expression of Fumarylacetoacetate hydrolase (FAH); a key enzyme involved in tyrosine catabolism. We also identified a genetic variant associated with lower FAH expression in monocyte-derived dendritic cells (DCs) in Peruvians who progressed to TB. We previously showed accumulation of tyrosine in the plasma of prospectively enrolled African household contacts of TB patients who progress to TB compared to non-progressors, consistently with a role for tyrosine catabolism in protection from TB. Importantly, knocking out FAH in murine macrophages increased their susceptibility to Mtb infection, suggesting that impaired tyrosine metabolism by FAH may drive loss of Mtb control. Mechanistically, tyrosine metabolites may contribute to the altered metabolic states of Mtb-infected cells. We hypothesize that Mtb-mediated interference with tyrosine metabolism has evolved as a mechanism of virulence and could mediate progression to TB disease. We propose a series of in vitro and in vivo experiments to define the requirement for host tyrosine metabolism following Mtb infection. We will target FAH using gene editing of primary human myeloid cells to test whether this key step in tyrosine metabolism is required to contain Mtb infection. We also plan to adoptively transfer fah- deficient fetal liver cells into TB-susceptible mice to test the requirement for tyrosine metabolism in hematopoietic cells to control Mtb infection in vivo. Secondly, we will define the metabolic consequences of FAH deletion in Mtb-infected monocyte-derived DCs and macrophages using metabolic flux experiments, and metabolite complementation of Mtb-infected FAH-deficient cells. Finally, we will leverage samples and datasets from two independent cohorts of different TB disease states. The first is a cross-sectional Peruvian cohort of TB patients and Mtb-infected and uninfected contacts, where we bio-banked plasma samples for targeted analysis of tyrosine metabolites by high resolution mass spectrometry. The second is a previously described longitudinal cohort of African household contacts of TB patients followed for 2 years, where we also obtained genotyping data to explore the impact of polymorphisms in select metabolic genes on expression of tyrosine metabolites. Defining a causal association between impaired tyrosine metabolism and TB risk would motivate for future trials to repurpose existing agents to treat inborn errors of tyrosine metabolism as host-directed treatments against TB.