School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, Taiwan.
Br J Pharmacol. 2013 Feb;168(4):920-31. doi: 10.1111/j.1476-5381.2012.02227.x.
Hypoxia-mediated neovascularization plays an important role in age-related macular degeneration (AMD). There are few animal models or effective treatments for AMD. Here, we investigated the effects of the flavonoid silibinin on hypoxia-induced angiogenesis in a rat AMD model.
Retinal pigmented epithelial (RPE) cells were subjected to hypoxia in vitro and the effects of silibinin on activation of key hypoxia-induced pathways were examined by elucidating the hypoxia-inducible factor-1 alpha (HIF-1α) protein level by Western blot. A rat model of AMD was developed by intravitreal injection of VEGF in Brown Norway rats, with or without concomitant exposure of animals to hypoxia. Animals were treated with oral silibinin starting at day 7 post-VEGF injection and AMD changes were followed by fluorescein angiography on days 14 and 28 post-injection.
Silibinin pretreatment of RPE cells increased proline hydroxylase-2 expression, inhibited HIF-1α subunit accumulation, and inhibited VEGF secretion. Silibinin-induced HIF-1α and VEGF down-regulation required suppression of hypoxia-induced phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (mTOR) pathway. In the rat model of AMD, silibinin administration prevented VEGF- and VEGF plus hypoxia-induced retinal oedema and neovascularization.
The effects of silibinin, both in vitro and in vivo, support its potential as a therapeutic for the prevention of neovascular AMD.
缺氧介导的新生血管形成在年龄相关性黄斑变性（AMD）中起着重要作用。目前针对 AMD 还没有动物模型或有效的治疗方法。在这里，我们研究了黄酮类化合物水飞蓟宾对大鼠 AMD 模型中缺氧诱导的血管生成的影响。
体外培养视网膜色素上皮（RPE）细胞，通过 Western blot 阐明缺氧诱导因子-1α（HIF-1α）蛋白水平，研究水飞蓟宾对关键缺氧诱导途径激活的影响。通过向褐家鼠玻璃体腔注射 VEGF 建立 AMD 动物模型，并同时使动物暴露于缺氧环境。在 VEGF 注射后第 7 天开始给予大鼠口服水飞蓟宾治疗，并在注射后第 14 天和第 28 天通过荧光素血管造影术来观察 AMD 的变化。
水飞蓟宾预处理 RPE 细胞可增加脯氨酰羟化酶-2 的表达，抑制 HIF-1α亚基的积累，并抑制 VEGF 的分泌。水飞蓟宾诱导的 HIF-1α和 VEGF 下调需要抑制缺氧诱导的磷脂酰肌醇 3-激酶/Akt/雷帕霉素靶蛋白（mTOR）通路。在 AMD 大鼠模型中，水飞蓟宾给药可预防 VEGF 及 VEGF 联合缺氧诱导的视网膜水肿和新生血管形成。
水飞蓟宾在体内外的作用均支持其作为预防新生血管性 AMD 的治疗药物的潜力。
