Targeted Deletion of Kynurenine 3-Monooxygenase in Mice A NEW TOOL FOR STUDYING KYNURENINE PATHWAY METABOLISM IN PERIPHERY AND BRAIN
Targeted Deletion of Kynurenine 3-Monooxygenase in Mice A NEW TOOL FOR STUDYING KYNURENINE PATHWAY METABOLISM IN PERIPHERY AND BRAIN
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DOI：
10.1074/jbc.m113.503813
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发表时间：
2013-12-20
影响因子：
4.8
通讯作者：
Muchowski, Paul J.
中科院分区：
文献类型：
--
作者：
Giorgini, Flaviano;Huang, Shao-Yi;Muchowski, Paul J.
背景：犬尿氨酸3-单加氧酶（KMO）被认为在调节健康和疾病中的色氨酸代谢中起关键作用。结果：缺乏KMO的小鼠在几种色氨酸代谢物的水平上发生了变化。结论：KMO是色氨酸代谢的重要调节因子。意义：KMO基因敲除小鼠将为揭示色氨酸代谢的生物学和病理生理作用提供一个有用的研究工具。犬尿氨酸3-单加氧酶（KMO）是色氨酸降解犬尿氨酸途径（KP）的关键酶，已被认为在涉及KP生物活性代谢产物的生理和病理事件中发挥重要作用。为了更详细地探索这一作用，我们产生了Kmo基因靶向破坏的小鼠，并在这里展示了这些突变动物的第一个生化和神经化学特征。Kmo（-/-）小鼠缺乏Kmo活性，但另外四种KP酶的活性没有明显异常。正如预期的那样，Kmo（-/-）小鼠的肝脏、大脑和血浆中酶促产物3-羟基尿氨酸的水平显著降低。与野生型动物相比，突变小鼠的肝脏和血浆中下游代谢物喹啉酸的水平也大大降低，但令人惊讶的是，大脑中仅略微降低（约20%）。Kmo（-/-）小鼠的肝脏、大脑和血浆中，其他三种KP代谢物：犬尿氨酸、犬尿酸和氨基苯甲酸的水平显著升高，但差异很大，而酶级联的主要最终产物NAD（+）的肝脏和大脑含量在Kmo（-/-）和野生型动物之间没有差异。当通过体内微透析评估时，发现Kmo（-/-）小鼠大脑中细胞外尿酸水平显著升高。综上所述，这些结果进一步证明KMO在KP中起着关键的调节作用，并表明KMO（-/-）小鼠将有助于研究个体KP代谢物在健康和疾病中的组织特异性功能。
Background: Kynurenine 3-monooxygenase (KMO) is hypothesized to play a pivotal role in regulating tryptophan metabolism in health and disease. Results: Mice that were generated lacking KMO have alterations in the levels of several tryptophan metabolites. Conclusion: KMO is a critical regulator of tryptophan metabolism. Significance: KMO knock-out mice will be a useful research tool to dissect the biological and pathophysiological roles of tryptophan metabolism.Kynurenine 3-monooxygenase (KMO), a pivotal enzyme in the kynurenine pathway (KP) of tryptophan degradation, has been suggested to play a major role in physiological and pathological events involving bioactive KP metabolites. To explore this role in greater detail, we generated mice with a targeted genetic disruption of Kmo and present here the first biochemical and neurochemical characterization of these mutant animals. Kmo(-/-) mice lacked KMO activity but showed no obvious abnormalities in the activity of four additional KP enzymes tested. As expected, Kmo(-/-) mice showed substantial reductions in the levels of its enzymatic product, 3-hydroxykynurenine, in liver, brain, and plasma. Compared with wild-type animals, the levels of the downstream metabolite quinolinic acid were also greatly decreased in liver and plasma of the mutant mice but surprisingly were only slightly reduced (by approximate to 20%) in the brain. The levels of three other KP metabolites: kynurenine, kynurenic acid, and anthranilic acid, were substantially, but differentially, elevated in the liver, brain, and plasma of Kmo(-/-) mice, whereas the liver and brain content of the major end product of the enzymatic cascade, NAD(+), did not differ between Kmo(-/-) and wild-type animals. When assessed by in vivo microdialysis, extracellular kynurenic acid levels were found to be significantly elevated in the brains of Kmo(-/-) mice. Taken together, these results provide further evidence that KMO plays a key regulatory role in the KP and indicate that Kmo(-/-) mice will be useful for studying tissue-specific functions of individual KP metabolites in health and disease.