Amato Rosario, Biagioni Martina, Cammalleri Maurizio, Dal Monte Massimo, Casini Giovanni
Department of Biology, University of Pisa, Pisa, Italy.
Department of Biology, University of Pisa, Pisa, Italy 2Interdepartmental Research Center Nutrafood "Nutraceuticals and Food for Health," University of Pisa, Pisa, Italy.
Invest Ophthalmol Vis Sci. 2016 Jun 1;57(7):3066-76. doi: 10.1167/iovs.16-19285.
Growing evidence indicates neuroprotection as a therapeutic target in diabetic retinopathy (DR). We tested the hypothesis that VEGF is released and acts as a survival factor in the retina in early DR.
Ex vivo mouse retinal explants were exposed to stressors similar to those characterizing DR, that is, high glucose (HG), oxidative stress (OS), or advanced glycation end-products (AGE). Neuroprotection was provided using octreotide (OCT), a somatostatin analog, and pituitary adenylate cyclase activating peptide (PACAP), two well-documented neuroprotectants. Data were obtained with real-time RT-PCR, Western blot, ELISA, and immunohistochemistry.
Apoptosis was induced in the retinal explants by HG, OS, or AGE treatments. At the same time, explants also showed increased VEGF expression and release. The data revealed that VEGF is released shortly after exposure of the explants to stressors and before the level of cell death reaches its maximum. Retinal cell apoptosis was inhibited by OCT and PACAP. At the same time, OCT and PACAP also reduced VEGF expression and release. Vascular endothelial growth factor turned out to be a protective factor for the stressed retinal explants, because inhibiting VEGF with a VEGF trap further increased cell death.
These data show that protecting retinal neurons from diabetic stress also reduces VEGF expression and release, while inhibiting VEGF leads to exacerbation of apoptosis. These observations suggest that the retina in early DR releases VEGF as a prosurvival factor. Neuroprotective agents may decrease the need of VEGF production by the retina, therefore limiting the risk, in the long term, of pathologic angiogenesis.
越来越多的证据表明神经保护是糖尿病视网膜病变（DR）的一个治疗靶点。我们检验了这样一个假说，即血管内皮生长因子（VEGF）在早期DR中于视网膜释放并作为一种存活因子发挥作用。
将离体小鼠视网膜外植体暴露于与DR特征相似的应激源，即高糖（HG）、氧化应激（OS）或晚期糖基化终产物（AGE）。使用奥曲肽（OCT）（一种生长抑素类似物）和垂体腺苷酸环化酶激活肽（PACAP）这两种有充分文献记载的神经保护剂来提供神经保护。通过实时逆转录聚合酶链反应（RT-PCR）、蛋白质印迹法、酶联免疫吸附测定（ELISA）和免疫组织化学获得数据。
HG、OS或AGE处理在视网膜外植体中诱导了细胞凋亡。与此同时，外植体还显示出VEGF表达和释放增加。数据显示，外植体暴露于应激源后不久且在细胞死亡水平达到最大值之前就有VEGF释放。OCT和PACAP抑制了视网膜细胞凋亡。同时，OCT和PACAP也降低了VEGF的表达和释放。血管内皮生长因子原来是应激视网膜外植体的一种保护因子，因为用VEGF陷阱抑制VEGF会进一步增加细胞死亡。
这些数据表明，保护视网膜神经元免受糖尿病应激也会降低VEGF的表达和释放，而抑制VEGF会导致细胞凋亡加剧。这些观察结果提示，早期DR中的视网膜释放VEGF作为一种促存活因子。神经保护剂可能会减少视网膜产生VEGF的需求，因此从长远来看限制了病理性血管生成的风险。
