3-hydroxykynurenine is a ROS-inducing cytotoxic tryptophan metabolite that disrupts the TCA cycle.
3-hydroxykynurenine is a ROS-inducing cytotoxic tryptophan metabolite that disrupts the TCA cycle.
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3-羟基犬尿氨酸是一种 ROS 诱导细胞毒性色氨酸代谢物，可破坏 TCA 循环。
DOI：
10.1101/2023.07.10.548411
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Taylor,EricB
中科院分区：
文献类型：
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作者：
Buchanan,JaneL;Rauckhorst,AdamJ;Taylor,EricB
色氨酸是一种必需氨基酸，通过吲哚胺2,3脱氧酶（IDO）代谢进入犬尿氨酸途径，被广泛认为是细胞功能的调节剂。然而，尽管对色氨酸代谢进行了数十年的研究，但对其及其代谢物的代谢调节作用尚不清楚。为了解决这个问题，我们在细胞培养中对色氨酸及其大多数已知代谢物进行了活性代谢组学筛选。我们发现用犬尿氨酸的代谢物3-羟基犬尿氨酸（3-HK）治疗人结肠癌细胞（HCT116）可能会破坏TCA循环功能。柠檬酸和乌头酸水平升高，异柠檬酸和所有下游TCA代谢产物下降，提示乌头酸酶功能下降。我们假设3HK或其代谢产物之一增加活性氧（ROS）并抑制乌头酶活性。因此，我们观察到还原性谷胱甘肽几乎完全耗尽，总谷胱甘肽水平下降。我们观察到3HK处理48小时后细胞活力呈剂量依赖性下降。这些数据表明，提高细胞内3HK水平可能足以诱导ros介导的细胞凋亡。在HCT116细胞中，我们通过联合诱导IDO和kynureninase （KYNU）的下调来调节细胞内3HK的水平。与对照组相比，KYNU基因敲除48小时后，细胞活力显著下降，ROS生成增加，Annexin V染色显示细胞凋亡。最后，我们确定了从3-HK产生黄瘤素作为一个候选的自由基产生，细胞毒性机制。我们的工作表明KYNU可能是破坏色氨酸代谢的靶点。有趣的是，许多癌症表现出IDO的过表达，提供了一种癌症特异性的代谢脆弱性，可以通过KYNU抑制来利用。
Tryptophan is an essential amino acid that is extensively characterized as a regulator of cellular function through its metabolism by indoleamine 2,3-deoxygenase (IDO) into the kynurenine pathway. However, despite decades of research on tryptophan metabolism, the metabolic regulatory roles of it and its metabolites are not well understood. To address this, we performed an activity metabolomics screen of tryptophan and most of its known metabolites in cell culture. We discovered that treatment of human colon cancer cells (HCT116) with 3-hydroxykynurenine (3-HK), a metabolite of kynurenine, potently disrupted TCA cycle function. Citrate and aconitate levels were increased, while isocitrate and all downstream TCA metabolites were decreased, suggesting decreased aconitase function. We hypothesized that 3HK or one of its metabolites increased reactive oxygen species (ROS) and inhibited aconitase activity. Accordingly, we observed almost complete depletion of reduced glutathione and a decrease in total glutathione levels. We observed a dose-dependent decrease in cell viability after 48 hours of 3HK treatment. These data suggest that raising the intracellular levels of 3HK could be sufficient to induce ROS-mediated apoptosis. We modulated the intracellular levels of 3HK by combined induction of IDO and knockdown of kynureninase (KYNU) in HCT116 cells. Cell viability decreased significantly after 48 hours of KYNU knockdown compared to controls, which was accompanied by increased ROS production and Annexin V staining revealing apoptosis. Finally, we identify xanthommatin production from 3-HK as a candidate radical-producing, cytotoxic mechanism. Our work indicates that KYNU may be a target for disrupting tryptophan metabolism. Interestingly, many cancers exhibit overexpression of IDO, providing a cancer-specific metabolic vulnerability that could be exploited by KYNU inhibition.