The role of tyrosine metabolism in tuberculosis pathogenesis

摘要 结核病（TB）是全球主要的死亡原因。目前还不清楚为什么只有少数人 结核分枝杆菌（Mtb）感染的个体进展为TB疾病。众所周知，MTB会重新连接 急性感染后受感染单核细胞衍生的吞噬细胞的免疫代谢。一致性，系统性 代谢的变化是结核病发病机制的标志，因此突出了代谢作为结核病治疗的可能靶点。 干预酪氨酸，一种芳香族氨基酸，显示出在结核病患者的血清中积累， 健康对照然而，目前尚不清楚酪氨酸代谢缺陷是否以及如何介导 Mtb感染易感性或TB进展风险。我们发现，Mtb感染的原发性人类骨髓 细胞下调富马酰乙酰乙酸水解酶（FAH）的表达; FAH是参与酪氨酸 猫我们还鉴定了一种与单核细胞源性白血病中FAH表达降低相关的遗传变异。 树突状细胞（DC）在秘鲁谁进展到结核病。我们以前发现酪氨酸在细胞内的积累， 前瞻性入组的进展为结核病的结核病患者的非洲家庭接触者的血浆， 非进展者，这与酪氨酸激酶在预防TB中的作用一致。重要的是， 小鼠巨噬细胞中的FAH增加了它们对Mtb感染的易感性，这表明受损的酪氨酸 FAH的代谢可能导致Mtb控制的丧失。从机制上讲，酪氨酸代谢物可能有助于 改变了结核杆菌感染细胞的代谢状态。我们假设结核分枝杆菌介导的酪氨酸干扰 代谢已演变为毒力机制，并可介导进展为TB疾病。我们 提出了一系列体外和体内实验，以确定宿主酪氨酸代谢的要求 Mtb感染后。我们将使用原代人类骨髓细胞的基因编辑来靶向FAH，以测试是否 酪氨酸代谢中的这一关键步骤是遏制Mtb感染所必需的。我们还计划收养法- 将缺乏胎肝细胞的小鼠移植到TB易感小鼠中，以测试造血干细胞中酪氨酸代谢的需要。 细胞来控制体内Mtb感染。其次，我们将定义FAH缺失的代谢后果， 使用代谢通量实验和代谢产物分析MTB感染的单核细胞来源的DC和巨噬细胞 Mtb感染的FAH缺陷细胞的互补。最后，我们将利用来自两个 不同结核病状态的独立队列。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，在那里我们生物库血浆样本用于酪氨酸的靶向分析。 通过高分辨率质谱分析代谢物。第二个是先前描述的纵向队列， 与结核病患者有家庭接触的非洲人随访了2年，我们还获得了基因分型数据， 探索所选代谢基因的多态性对酪氨酸代谢物表达的影响。限定 酪氨酸代谢受损和结核病风险之间的因果关系将促使未来的试验， 重新利用现有的药物来治疗先天性酪氨酸代谢缺陷，作为针对TB的宿主导向治疗。

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.