Nitric oxide-mediated regulation of gamma interferon-induced bacteriostasis:: inhibition and degradation of human indoleamine 2,3-dioxygenase
Nitric oxide-mediated regulation of gamma interferon-induced bacteriostasis:: inhibition and degradation of human indoleamine 2,3-dioxygenase
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DOI：
10.1128/iai.72.5.2723-2730.2004
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发表时间：
2004-05-01
影响因子：
3.1
通讯作者：
Däubener, W
中科院分区：
文献类型：
--
作者：
Hucke, C;MacKenzie, CR;Däubener, W
犬尿氨酸途径中由吲哚胺2,3-双加氧酶（IDO）活性引起的色氨酸耗竭是人类细胞中最突出的γ干扰素（ifn - γ）诱导的抗菌效应机制之一。另一方面，一氧化氮（NO）由一氧化氮合酶（iNOS）的诱导异构体产生，在人类细胞中发挥更多的免疫调节作用，从而以多种方式与色氨酸消耗相互作用。我们研究了NO对人上皮细胞系RT4中IDO基因转录、蛋白质合成、酶活性以及IDO介导的抑菌作用的影响。ifn - γ刺激的RT4细胞能够以ido介导的方式抑制金黄色葡萄球菌的生长，而这种抑菌作用被内源性NO所消除。这些发现得到了实验的支持，实验表明，ifn - γ刺激细胞提取物中的IDO活性被化学NO供体二乙基三胺二氮二酸酯，s -亚硝基- l-半胱氨酸和s -亚硝基-n -乙酰- d， l-青霉胺抑制。此外，我们发现内源性和外源性NO均能显著降低RT4细胞IDO蛋白含量水平。这种影响不是由于IDO基因转录或mRNA稳定性的降低。通过使用蛋白酶体蛋白水解活性抑制剂，我们发现NO的产生导致蛋白酶体中IDO蛋白的加速降解。据我们所知，这是第一个证明IDO被蛋白酶体降解并且NO对IDO蛋白稳定性有影响的报告。
Tryptophan depletion resulting from indoleamine 2,3-dioxygenase (IDO) activity within the kynurenine pathway is one of the most prominent gamma interferon (IFN-gamma) -inducible antimicrobial effector mechanisms in human cells. On the other hand, nitric oxide (NO) produced by the inducible isoform of NO synthase (iNOS) serves a more immunoregulatory role in human cells and thereby interacts with tryptophan depletion in a number of ways. We investigated the effects of NO on IDO gene transcription, protein synthesis, and enzyme activity as well as on IDO-mediated bacteriostasis in the human epithelial cell line RT4. IFN-gamma- stimulated RT4 cells were able to inhibit the growth of Staphylococcus aureus in an IDO-mediated fashion, and this bacteriostatic effect was abolished by endogenously produced NO. These findings were supported by experiments which showed that IDO activity in extracts of IFN-gamma-stimulated cells is inhibited by the chemical NO donors diethylenetriamine diazeniumdiolate, S-nitroso-L-cysteine, and S-nitroso-N-acetyl-D,L-penicillamine. Furthermore, we found that both endogenous and exogenous NO strongly reduced the level of IDO protein content in RT4 cells. This effect was not due to a decrease in IDO gene transcription or mRNA stability. By using inhibitors of proteasomal proteolytic activity, we showed that NO production led to an accelerated degradation of IDO protein in the proteasome. This is the first report, to our knowledge, that demonstrates that the IDO is degraded by the proteasome and that NO has an effect on IDO protein stability.