eNOS 过表达加重 OIR 闭塞相的血管闭合，并增加后续增殖期的血管生成驱动力。
eNOS overexpression exacerbates vascular closure in the obliterative phase of OIR and increases angiogenic drive in the subsequent proliferative stage.
机构信息
Centre for Vision and Vascular Science, Queen's University Belfast, United Kingdom.
出版信息
Invest Ophthalmol Vis Sci. 2012 Oct 3;53(11):6833-50. doi: 10.1167/iovs.12-9797.
PURPOSE
In ischemic retinopathies, the misdirection of reparative angiogenesis away from the hypoxic retina leads to pathologic neovascularization. Thus, therapeutic strategies that reverse this trend would be extremely beneficial. Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) is an important mediator of vascular endothelial growth factor (VEGF) function facilitating vascular growth and maturation. However, in addition to NO, eNOS can also produce superoxide (O(2)(-)), exacerbating pathology. Here, our aim was to investigate the effect of eNOS overexpression on vascular closure and subsequent recovery of the ischemic retina.
METHODS
Mice overexpressing eNOS-GFP were subjected to oxygen-induced retinopathy (OIR) and changes in retinal vascularization quantified. Background angiogenic drive was assessed during vascular development and in aortic rings. NOS activity was measured by Griess assay or conversion of radiolabeled arginine to citrulline, nitrotyrosine (NT), and superoxide by immunolabeling and dihydroethidium fluorescence and VEGF by ELISA.
RESULTS
In response to hyperoxia, enhanced eNOS expression led to increased NOS-derived superoxide and dysfunctional NO production, NT accumulation, and exacerbated vessel closure associated with tetrahydrobiopterin (BH₄) insufficiency. Despite worse vaso-obliteration, eNOS overexpression resulted in elevated hypoxia-induced angiogenic drive, independent of VEGF production. This correlated with increased vascular branching similar to that observed in isolated aortas and during development. Enhanced recovery was also associated with neovascular tuft formation, which showed defective NO production and increased eNOS-derived superoxide and NT levels.
CONCLUSIONS
In hyperoxia, reduced BH₄ bioavailability causes overexpressed eNOS to become dysfunctional, exacerbating vaso-obliteration. In the proliferative phase, however, eNOS has important prorepair functions enhancing angiogenic growth potential and recovery in ischemia.
目的
在缺血性视网膜病变中，修复性血管生成的错位导致了病理性新生血管形成。因此，逆转这种趋势的治疗策略将是非常有益的。内皮型一氧化氮合酶（eNOS）产生的一氧化氮（NO）是血管内皮生长因子（VEGF）功能的重要介质，促进血管生长和成熟。然而，除了 NO 之外，eNOS 还可以产生超氧阴离子（O(2)(-)），从而加重病理学。在这里，我们的目的是研究 eNOS 过表达对血管闭合和随后缺血性视网膜恢复的影响。
方法
过表达 eNOS-GFP 的小鼠接受氧诱导的视网膜病变（OIR），并量化视网膜血管化的变化。在血管发育过程中和主动脉环中评估背景血管生成驱动力。通过格里斯测定或放射性标记精氨酸转化为瓜氨酸、硝基酪氨酸（NT）和免疫标记和二氢乙啶荧光测定超氧化物来测量 NOS 活性，通过 ELISA 测定 VEGF。
结果
在高氧环境下，增强的 eNOS 表达导致 NOS 衍生的超氧阴离子和功能失调的 NO 产生、NT 积累以及与四氢生物蝶呤（BH₄）不足相关的血管闭合加剧。尽管血管闭塞更严重，但 eNOS 过表达导致缺氧诱导的血管生成驱动力升高，与 VEGF 产生无关。这与血管分支增加有关，类似于在分离的主动脉和发育过程中观察到的情况。增强的恢复也与新生血管丛的形成有关，其表现为 NO 产生缺陷和增加的 eNOS 衍生的超氧阴离子和 NT 水平。
结论
在高氧环境下，BH₄ 生物利用度降低导致过表达的 eNOS 功能失调，加剧血管闭塞。然而，在增殖期，eNOS 具有重要的促修复功能，增强了缺血时的血管生成生长潜力和恢复能力。
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