The NF-κB p65 and p50 homodimer cooperate with IRF8 to activate iNOS transcription.
The NF-κB p65 and p50 homodimer cooperate with IRF8 to activate iNOS transcription.
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DOI：
10.1186/s12885-015-1808-6
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发表时间：
2015-10-23
期刊：
影响因子：
3.8
通讯作者：
Liu K
中科院分区：
文献类型：
--
作者：
Simon PS;Sharman SK;Lu C;Yang D;Paschall AV;Tulachan SS;Liu K
诱导型一氧化氮合酶（iNOS）代谢L-精氨酸产生一氧化氮（NO），最初在骨髓细胞中被鉴定为宿主抵抗病原体的防御机制。然而，最近的研究表明，iNOS通常在肿瘤微环境中的肿瘤细胞和骨髓细胞中被诱导。令人信服的实验数据表明，iNOS在某些细胞环境中促进肿瘤发展，并在其他细胞条件下抑制肿瘤发展。iNOS这些不同功能的分子机制尚不清楚。由于iNOS通常由炎症信号诱导，因此iNOS的这些对比功能可能由炎症信号传导途径控制，这仍有待确定。iNOS在结肠癌和肿瘤微环境中的骨髓细胞中表达。结肠癌和骨髓细胞系被用来阐明iNOS表达的分子机制。染色质免疫沉淀和电泳迁移率变动分析检测IFNγ激活的pSTAT 1和NF-κB与nos 2启动子染色质DNA的结合。我们在这里表明，诱导型一氧化氮合酶显着上调，在炎症的人结肠组织和人结肠癌相比，正常结肠组织。iNOS在肿瘤微环境中的结肠癌细胞或免疫细胞中表达。在分子水平上，IFNγ和NF-κB信号诱导人结肠癌细胞表达iNOS。我们进一步证明NF-κB直接与NOS 2启动子结合调节iNOS表达。尽管单独的IFNγ信号通路和NF-κB信号通路都不足以诱导髓样细胞中的iNOS表达，但IFNγ和NF-κB协同诱导髓样细胞中的iNOS表达。此外，我们确定IFNγ上调IRF 8表达以增强NF-κB诱导iNOS表达。更有趣的是，我们观察到p65/p65和p50/p50同源二聚体，而不是典型的p65/p50异源二聚体，直接结合到nos 2启动子，以调节髓样细胞中iNOS的表达。IFNγ诱导的IRF 8与NF-κB协同作用调节结肠癌和髓样细胞中iNOS的表达。在骨髓细胞中，与nos 2启动子结合的NF-κB复合物是p65/p65和p50/p50同源二聚体。
Inducible nitric oxide synthase (iNOS) metabolizes L-arginine to produce nitric oxide (NO) which was originally identified in myeloid cells as a host defense mechanism against pathogens. Recent studies, however, have revealed that iNOS is often induced in tumor cells and myeloid cells in the tumor microenvironment. Compelling experimental data have shown that iNOS promotes tumor development in certain cellular context and suppresses tumor development in other cellular conditions. The molecular mechanisms underlying these contrasting functions of iNOS is unknown. Because iNOS is often induced by inflammatory signals, it is therefore likely that these contrasting functions of iNOS could be controlled by the inflammatory signaling pathways, which remains to be determined. iNOS is expressed in colon carcinoma and myeloid cells in the tumor microenvironment. Colon carcinoma and myeloid cell lines were used to elucidate the molecular mechanisms underlying iNOS expression. Chromatin immunoprecipitation and electrophoretic mobility shift assay were used to determine the IFNγ-activated pSTAT1 and NF-κB association with the chromatin DNA of the nos2 promoter. We show here that iNOS is dramatically up-regulated in inflammed human colon tissues and in human colon carcinoma as compared to normal colon tissue. iNOS is expressed in either the colon carcinoma cells or immune cells within the tumor microenvironment. On the molecular level, the proinflammatory IFNγ and NF-κB signals induce iNOS expression in human colon cancer cells. We further demonstrate that NF-κB directly binds to the NOS2 promoter to regulate iNOS expression. Although neither the IFNγ signaling pathway nor the NF-κB signaling pathway alone is sufficient to induce iNOS expression in myeloid cells, IFNγ and NF-κB synergistically induce iNOS expression in myeloid cells. Furthermore, we determine that IFNγ up-regulates IRF8 expression to augment NF-κB induction of iNOS expression. More interestingly, we observed that the p65/p65 and p50/p50 homodimers, not the canonical p65/p50 heterodimer, directly binds to the nos2 promoter to regulate iNOS expression in myeloid cells. IFNγ-induced IRF8 acts in concert with NF-κB to regulate iNOS expression in both colon carcinoma and myeloid cells. In myeloid cells, the NF-κB complexes that bind to the nos2 promoter are p65/p65 and p50/p50 homodimers.