The oxidative stressor arsenite activates vascular endothelial growth factor mRNA transcription by an ATF4-dependent mechanism
The oxidative stressor arsenite activates vascular endothelial growth factor mRNA transcription by an ATF4-dependent mechanism
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DOI：
10.1074/jbc.m411275200
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发表时间：
2005-05-27
影响因子：
4.8
通讯作者：
Abcouwer, SF
中科院分区：
文献类型：
--
作者：
Roybal, CN;Hunsaker, LA;Abcouwer, SF
导致新生血管形成的血管内皮生长因子（VEGF）的异常视网膜表达是年龄相关性黄斑变性和糖尿病性视网膜病变的中心特征，这两种疾病是视力丧失的两个主要原因。氧化应激被认为发生在视网膜组织中的年龄相关性黄斑变性和糖尿病视网膜病变，并怀疑在这些疾病中的VEGF表达的机制。亚砷酸盐是一种巯基反应性氧化应激因子，通过HIF-1 α非依赖性机制诱导VEGF表达。以前，我们证明同型半胱氨酸，内质网应激，增加VEGF转录的机制依赖于激活转录因子ATF 4。由于ATF 4是在氧化应激反应中表达的，我们假设ATF 4也负责增加VEGF转录反应亚砷酸盐。我们现在表明，亚砷酸盐增加了VEGF mRNA的稳态水平，并激活了VEGF启动子结构的转录。亚砷酸盐诱导eIF 2 α磷酸化，导致ATF 4蛋白水平升高。ATF 4的失活或丢失大大降低了VEGF对亚砷酸盐治疗的反应。ATF 4的过表达足以激活VEGF启动子，亚砷酸盐与外源ATF 4协同作用进一步激活启动子。含有ATF 4的复合物在相对于VEGF转录起始位点的+1767 bp处结合DNA元件，并且通过亚砷酸盐处理增加DNA结合活性。此外，巯基抗氧化剂N-乙酰半胱氨酸抑制亚砷酸盐对VEGF表达影响的能力与其抑制eIF 2 α和ATF 4蛋白表达磷酸化的能力一致。因此，亚砷酸盐诱导的VEGF基因转录上调通过ATF 4依赖性机制发生。
Aberrant retinal expression of vascular endothelial growth factor (VEGF) leading to neovascularization is a central feature of age-related macular degeneration and diabetic retinopathy, two leading causes of vision loss. Oxidative stress is suggested to occur in retinal tissue during age-related macular degeneration and diabetic retinopathy and is suspected in the mechanism of VEGF expression in these diseases. Arsenite, a thiol-reactive oxidative stressor, induces VEGF expression by a HIF-1 alpha-independent mechanism. Previously, we demonstrated that homocysteine, an endoplasmic reticulum stressor, increases VEGF transcription by a mechanism dependent upon activating transcription factor ATF4. Because ATF4 is expressed in response to oxidative stress, we hypothesized that ATF4 was also responsible for increased VEGF transcription in response to arsenite. We now show that arsenite increased steady state levels of VEGF mRNA and activated transcription from a VEGF promoter construct. Arsenite induced eIF2 alpha phosphorylation, resulting in increased ATF4 protein levels. Inactivation or loss of ATF4 greatly diminished the VEGF response to arsenite treatment. Overexpression of ATF4 was sufficient to activate the VEGF promoter, and arsenite cooperated with exogenous ATF4 to further activate the promoter. A complex containing ATF4 binds a DNA element at +1767 bp relative to the VEGF transcription start site, and DNA binding activity is increased by arsenite treatment. In addition, the ability of a thiol antioxidant, N-acetylcysteine, to inhibit the effect of arsenite on VEGF expression coincided with its ability to inhibit phosphorylation of eIF2 alpha and ATF4 protein expression. Thus, arsenite-induced up-regulation of VEGF gene transcription occurs by an ATF4-dependent mechanism.