The Hypoxia-Inducible Factor 1/NOR-1 Axis Regulates the Survival Response of Endothelial Cells to Hypoxia
The Hypoxia-Inducible Factor 1/NOR-1 Axis Regulates the Survival Response of Endothelial Cells to Hypoxia
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DOI：
10.1128/mcb.00945-09
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发表时间：
2009-11-01
影响因子：
5.3
通讯作者：
Martinez-Gonzalez, Jose
中科院分区：
文献类型：
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作者：
Martorell, Lluis;Gentile, Maurizio;Martinez-Gonzalez, Jose
缺氧诱导细胞凋亡，但也触发适应机制，以确保细胞存活。在这里，我们表明，缺氧诱导因子1（HIF-1）在内皮细胞中的促生存作用是由神经元源性孤儿受体1（NOR-1）介导的。NOR-1的过表达降低了缺氧培养中内皮细胞凋亡的速率，而NOR-1的抑制增加了细胞凋亡。缺氧以时间和剂量依赖性方式上调NOR-1 mRNA水平。针对VEGF或SU 5614（VEGF受体2抑制剂）的阻断抗体不能阻止缺氧诱导的NOR-1表达，表明NOR-1不是由响应于缺氧的VEGF自分泌分泌诱导的。通过小干扰RNA或磷脂酰肌醇-3激酶（PI 3 K）/Akt通路或mTOR抑制剂降低HIF-1 α蛋白水平，可显著抵消缺氧诱导的NOR-1上调。细胞内Ca ~（2+）参与了缺氧诱导的PI 3 K/Akt激活和下游NOR-1上调。缺氧反应元件介导的转录激活NOR-1诱导缺氧，我们表明通过瞬时转染和染色质免疫沉淀试验。最后，NOR-1表达的减弱降低了基础和缺氧诱导的cIAP 2（细胞凋亡抑制蛋白2）mRNA水平，而NOR-1过表达上调cIAP 2。因此，NOR-1是HIF-1信号转导的下游效应物，参与内皮细胞对缺氧的存活反应。
Hypoxia induces apoptosis but also triggers adaptive mechanisms to ensure cell survival. Here we show that the prosurvival effects of hypoxia-inducible factor 1 (HIF-1) in endothelial cells are mediated by neuron-derived orphan receptor 1 (NOR-1). The overexpression of NOR-1 decreased the rate of endothelial cells undergoing apoptosis in cultures exposed to hypoxia, while the inhibition of NOR-1 increased cell apoptosis. Hypoxia upregulated NOR-1 mRNA levels in a time- and dose-dependent manner. Blocking antibodies against VEGF or SU5614 (a VEGF receptor 2 inhibitor) did not prevent hypoxia-induced NOR-1 expression, suggesting that NOR-1 is not induced by the autocrine secretion of VEGF in response to hypoxia. The reduction of HIF-1 alpha protein levels by small interfering RNAs, or by inhibitors of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway or mTOR, significantly counteracted hypoxia-induced NOR-1 upregulation. Intracellular Ca2+ was involved in hypoxia-induced PI3K/Akt activation and in the downstream NOR-1 upregulation. A hypoxia response element mediated the transcriptional activation of NOR-1 induced by hypoxia as we show by transient transfection and chromatin immunoprecipitation assays. Finally, the attenuation of NOR-1 expression reduced both basal and hypoxia-induced cIAP2 (cellular inhibitor of apoptosis protein 2) mRNA levels, while NOR-1 overexpression upregulated cIAP2. Therefore, NOR-1 is a downstream effector of HIF-1 signaling involved in the survival response of endothelial cells to hypoxia.