HIF-1alpha and HIF-2alpha are differentially activated in distinct cell populations in retinal ischaemia.
HIF-1alpha and HIF-2alpha are differentially activated in distinct cell populations in retinal ischaemia.
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DOI：
10.1371/journal.pone.0011103
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发表时间：
2010-06-14
期刊：
影响因子：
3.7
通讯作者：
Bainbridge JW
中科院分区：
文献类型：
--
作者：
Mowat FM;Luhmann UF;Smith AJ;Lange C;Duran Y;Harten S;Shukla D;Maxwell PH;Ali RR;Bainbridge JW
缺氧在视网膜缺血性和新生血管性疾病中起关键作用。细胞对氧的反应由低氧诱导转录因子（HIF）介导，HIF在低氧中稳定并诱导多种基因的表达。本研究的目的是确定视网膜缺血中HIF-1 α和HIF-2 α的细胞特异性，并确定它们与视网膜缺氧模式和诱导分子介质表达谱的相关性。我们使用生物还原剂哌莫硝唑研究了小鼠氧诱导视网膜病变（OIR）过程中视网膜缺氧的组织分布。采用Western blotting法检测OIR发生发展过程中HIF-1 α和HIF-2 α蛋白的表达水平，免疫组化法检测其细胞分布，ELISA法检测两种下游介质血管内皮生长因子（VEGF）和促红细胞生成素（Epo）的表达。Pimonidazole标记是明显的，特别是在视网膜内层。标记在缺氧开始后2小时达到峰值，此后逐渐下降。在OIR的早期缺氧阶段，与Müller胶质细胞的显著结合是明显的。在视网膜缺氧期间，HIF-1 α和HIF-2 α蛋白水平均显著增加，但在不同的细胞分布中是明显的; HIF-1 α稳定在整个视网膜内层的神经元细胞中是明显的，而HIF-2 α仅限于Müller胶质细胞和星形胶质细胞。视网膜中的缺氧和HIF-α稳定化之后紧接着是下游介质VEGF和EPO的表达上调。HIF-1 α和HIF-2 α都与视网膜缺氧密切相关，但具有相反的细胞特异性，与视网膜缺血中的不同作用一致。我们的研究结果表明，HIF-2 α激活在调节Müller胶质细胞对缺氧的反应中起着关键作用。
Hypoxia plays a key role in ischaemic and neovascular disorders of the retina. Cellular responses to oxygen are mediated by hypoxia-inducible transcription factors (HIFs) that are stabilised in hypoxia and induce the expression of a diverse range of genes. The purpose of this study was to define the cellular specificities of HIF-1alpha and HIF-2alpha in retinal ischaemia, and to determine their correlation with the pattern of retinal hypoxia and the expression profiles of induced molecular mediators. We investigated the tissue distribution of retinal hypoxia during oxygen-induced retinopathy (OIR) in mice using the bio-reductive drug pimonidazole. We measured the levels of HIF-1alpha and HIF-2alpha proteins by Western blotting and determined their cellular distribution by immunohistochemistry during the development of OIR. We measured the temporal expression profiles of two downstream mediators, vascular endothelial growth factor (VEGF) and erythropoietin (Epo) by ELISA. Pimonidazole labelling was evident specifically in the inner retina. Labelling peaked at 2 hours after the onset of hypoxia and gradually declined thereafter. Marked binding to Müller glia was evident during the early hypoxic stages of OIR. Both HIF-1alpha and HIF-2alpha protein levels were significantly increased during retinal hypoxia but were evident in distinct cellular distributions; HIF-1alpha stabilisation was evident in neuronal cells throughout the inner retinal layers whereas HIF-2alpha was restricted to Müller glia and astrocytes. Hypoxia and HIF-alpha stabilisation in the retina were closely followed by upregulated expression of the downstream mediators VEGF and EPO. Both HIF-1alpha and HIF-2alpha are activated in close correlation with retinal hypoxia but have contrasting cell specificities, consistent with differential roles in retinal ischaemia. Our findings suggest that HIF-2alpha activation plays a key role in regulating the response of Müller glia to hypoxia.
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