Cytokine-stimulated GTP cyclohydrolase I expression in endothelial cells requires coordinated activation of nuclear factor-κB and Stat1/Stat3
Cytokine-stimulated GTP cyclohydrolase I expression in endothelial cells requires coordinated activation of nuclear factor-κB and Stat1/Stat3
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DOI：
10.1161/01.res.0000153669.24827.df
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发表时间：
2005-02-04
影响因子：
20.1
通讯作者：
Keaney, JF
中科院分区：
文献类型：
--
作者：
Huang, AN;Zhang, YY;Keaney, JF
一氧化氮 (NO) 的内皮细胞生成依赖于细胞内足够的四氢生物蝶呤 (BH4) 水平，四氢生物蝶呤 (BH4) 是一氧化氮合酶的重要辅助因子。血管疾病通常以血管壁炎症为特征，内皮细胞的细胞因子治疗会增加 BH4 水平，部分是通过诱导 GTP 环水解酶 I (GTPCH I)（BH4 生物合成的限速酶）来实现的。然而，细胞因子介导的内皮GTPCH I诱导的分子机制尚不完全清楚。我们试图研究细胞因子诱导人脐静脉内皮细胞 (HUVEC) 中 GTPCH I 表达的信号通路。干扰素-γ (IFN-γ) 适度诱导内皮细胞 GTPCH I 蛋白和 BH4，而高水平诱导则需要 IFN-γ 和肿瘤坏死因子-α (TNF-α) 的组合。在存在 IFN-gamma 的情况下，TNF-α 以依赖于核因子 kappaB (NF-kappaB) 的方式增加 GTPCH I mRNA，因为这种效应被显性失活 IkappaB 构建体的过度表达所消除。 HUVEC IFN-γ 处理导致信号转导子和转录激活子 1 (Stat1) 激活，并以 Jak2 依赖性方式结合 DNA，因为这被 AG490 抑制。相反，Jak2 的过表达有效地替代了 IFN-γ，支持 TNF-α 介导的 GTPCH I 诱导。 IFN-γ 的作用也是 Stat1 依赖性的，因为 Stat1 缺失细胞对细胞因子的反应没有表现出 GTPCH I 诱导。然而，由于同时有 Stat3 激活，制瘤素 M 激活 Stat1 无法支持 TNF-α 介导的 GTPCH I 诱导。与这一观点一致，siRNA 介导的 Stat3 基因沉默使得制瘤素 M 能够替代该系统中的 IFN-γ。这些数据表明 NF-kappaB 和 Stat1 均参与内皮细胞细胞因子刺激的 GTPCH I 诱导，并强调 Stat3 在调节 Stat1 支持的基因转录中的作用。因此，IFN-γ和TNF-α在内皮细胞中的BH4生物合成中发挥着独特但协同的作用，这可能对血管炎症期间的血管功能具有重要影响。
Endothelial production of nitric oxide ( NO) is dependent on adequate cellular levels of tetrahydrobiopterin (BH4), an important cofactor for the nitric oxide synthases. Vascular diseases are often characterized by vessel wall inflammation and cytokine treatment of endothelial cells increases BH4 levels, in part through the induction of GTP cyclohydrolase I (GTPCH I), the rate-limiting enzyme for BH4 biosynthesis. However, the molecular mechanisms of cytokine-mediated GTPCH I induction in the endothelium are not entirely clear. We sought to investigate the signaling pathways whereby cytokines induce GTPCH I expression in human umbilical vein endothelial cells (HUVECs). Interferon-gamma (IFN-gamma) induced endothelial cell GTPCH I protein and BH4 modestly, whereas high-level induction required combinations of IFN-gamma and tumor necrosis factor-alpha (TNF-alpha). In the presence of IFN-gamma, TNF-alpha increased GTPCH I mRNA in a manner dependent on nuclear factor-kappaB (NF-kappaB), as this effect was abrogated by overexpression of a dominant-negative IkappaB construct. HUVEC IFN-gamma treatment resulted in signal transducer and activator of transcription 1 (Stat1) activation and DNA binding in a Jak2-dependent manner, as this was inhibited by AG490. Conversely, overexpression of Jak2 effectively substituted for IFN-gamma in supporting TNF-alpha-mediated GTPCH I induction. The role of IFN-gamma was also Stat1-dependent as Stat1-null cells exhibited no GTPCH I induction in response to cytokines. However, Stat1 activation with oncostatin M failed to support TNF-alpha-mediated GTPCH I induction because of concomitant Stat3 activation. Consistent with this notion, siRNA-mediated Stat3 gene silencing allowed oncostatin M to substitute for IFN-gamma in this system. These data implicate both NF-kappaB and Stat1 in endothelial cell cytokine-stimulated GTPCH I induction and highlight the role of Stat3 in modulating Stat1-supported gene transcription. Thus, IFN-gamma and TNF-alpha exert distinct but cooperative roles for BH4 biosynthesis in endothelium that may have important implications for vascular function during vascular inflammation.