Homocysteine increases the expression of vascular endothelial growth factor by a mechanism involving endoplasmic reticulum stress and transcription factor ATF4
Homocysteine increases the expression of vascular endothelial growth factor by a mechanism involving endoplasmic reticulum stress and transcription factor ATF4
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DOI：
10.1074/jbc.m312948200
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发表时间：
2004-04-09
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;Yang, SJ;Abcouwer, SF
血管内皮生长因子（VEGF）在糖尿病视网膜病变的发生和发展中起着关键作用。我们以前证明，氨基酸剥夺和内质网应激（ER应激）的其他诱导剂上调视网膜色素上皮细胞系ARPE-19中VEGF的表达。由于同型半胱氨酸引起内质网应激，我们假设环境同型半胱氨酸增加了VEGF表达。在融合的ARPE-19培养物中研究DL-同型半胱氨酸诱导的VEGF表达。北方分析表明，同型半胱氨酸增加稳态VEGF mRNA水平的4.4倍。其他含巯基化合物，包括L-同型半胱氨酸硫内酯和DTT，诱导VEGF表达7.9和8.8倍。转录连续测定和mRNA衰减研究表明，VEGF mRNA水平的增加是由转录增加而不是mRNA稳定引起的。VEGF mRNA的诱导超过了ER应激基因GRP 78的诱导。同型半胱氨酸处理引起eIF 2 α的瞬时磷酸化和ATF 4蛋白水平的增加。过表达的显性负性ATF 4废除了血管内皮生长因子对同型半胱氨酸治疗和氨基酸剥夺的反应。ATF 4-/- MEF的VEGF mRNA表达对同型半胱氨酸治疗没有反应，而野生型ATF 4的表达恢复了反应。这些研究表明，促血管生成因子VEGF的表达通过高半胱氨酸和其他含巯基的还原性化合物经由VEGF转录的ATF 4依赖性激活而增加。
Vascular endothelial growth factor (VEGF) plays a key role in the development and progression of diabetic retinopathy. We previously demonstrated that amino acid deprivation and other inducers of endoplasmic reticulum-stress (ER stress) up-regulate the expression of VEGF in the retinal-pigmented epithelial cell line ARPE-19. Because homocysteine causes ER stress, we hypothesized that VEGF expression is increased by ambient homocysteine. DL-Homocysteine-induced VEGF expression was investigated in confluent ARPE-19 cultures. Northern analysis showed that homocysteine increased steady state VEGF mRNA levels 4.4-fold. Other thiol-containing compounds, including L-homocysteine thiolactone and DTT, induced VEGF expression 7.9- and 8.8-fold. Transcriptional run-on assays and mRNA decay studies demonstrated that the increase in VEGF mRNA levels was caused by increased transcription rather than mRNA stabilization. VEGF mRNA induction paralleled that of the ER-stress gene GRP78. Homocysteine treatment caused transient phosphorylation of eIF2alpha and an increase in ATF4 protein level. Overexpression of a dominant-negative ATF4 abolished the VEGF response to homocysteine treatment and to amino acid deprivation. VEGF mRNA expression by ATF4 -/- MEF did not respond to homocysteine treatment and the response was restored with expression of wild-type ATF4. These studies indicate that expression of the pro-angiogenic factor VEGF is increased by homocysteine and other thiol-containing reductive compounds via ATF4-dependent activation of VEGF transcription.