(1) Background: Retinal pigment epithelial cells (RPE) cells constitutively secrete vascular endothelial growth factor (VEGF) in the retina, protecting the neuronal cells and the choroid. Increased VEGF secretion, however, can result in neovascularization and edema. Many factors regulate VEGF secretion. In this study, we investigated the effect of external stimuli in relation to diurnal rhythm on constitutive VEGF secretion. (2) Methods: Single-eye RPE cell culture was prepared from porcine eyes. RPE cells were cultured in darkness, treated with daylight or room light, and treated with melatonin at different time frames, either respectively or in combination. Supernatants were collected and VEGF content evaluated using ELISA. Expression of the clock protein BMAL1 was evaluated with Western blot. (3) Results: VEGF secretion of the RPE shows a diurnal rhythm. While the rhythm is not influenced by either light or melatonin, the amount of secreted VEGF can be increased by nocturnal melatonin, especially in combination with morning daylight. These findings disclose another layer of VEGF regulation in the retina.

中文翻译：

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褪黑素和光对原代RPE细胞中VEGF分泌的影响

（1）背景：视网膜色素上皮细胞（RPE）细胞在视网膜中组成性分泌血管内皮生长因子（VEGF），保护神经元细胞和脉络膜。但是，增加的VEGF分泌会导致新血管形成和水肿。许多因素调节VEGF的分泌。在这项研究中，我们调查了与昼夜节律有关的外部刺激对组成性VEGF分泌的影响。（2）方法：从猪眼制备单眼RPE细胞培养物。RPE细胞在黑暗中培养，分别在日光或室内光下处理，并在不同的时间范围分别或组合使用褪黑激素处理。收集上清液并使用ELISA评估VEGF含量。用蛋白质印迹评估时钟蛋白BMAL1的表达。（3）结果：RPE的VEGF分泌表现出昼夜节律。虽然节律不受光照或褪黑激素的影响，但夜间褪黑激素可以增加分泌的VEGF的量，尤其是在早晨日光下。这些发现揭示了视网膜中另一层的VEGF调节。