College of Life Sciences, Wuhan University, Wuhan, China.
Invest Ophthalmol Vis Sci. 2012 May 31;53(6):3241-9. doi: 10.1167/iovs.11-8406.
Endoplasmic reticulum (ER) stress has been demonstrated to contribute to neurodegeneration in multiple ocular diseases. However, whether ER stress can induce vascular degeneration in the retina remains unknown. We investigated the possible role of ER stress in retinal vascular degeneration in vivo, and the effects of resveratrol on tunicamycin and ischemia and reperfusion (I/R)-induced retinal vascular degeneration.
Different dosages of tunicamycin, an ER stress inducer, were injected into the vitreous of mouse eyes. Retinal I/R injury was induced by elevating the intraocular pressure for 60 minutes followed by reperfusion in mice. Two dosages of resveratrol (5 and 25 mg/kg body weight per day) were administrated 2 days before retinal I/R injury, while 100 μM resveratrol were injected into the vitreous together with tunicamycin. Formation of acellular capillaries was assessed 7 days after I/R injury and tunicamycin injection, while cell bodies in ganglion cell layer and brain-specific homeobox/POU domain protein 3A (Brn3a) staining on retinal flat-mounts were analyzed 4 days after I/R injury. ER stress markers, including eukaryotic initiation factor 2α (eIF2α), CCAAT enhancer-binding protein homologous protein (CHOP), immunoglobulin binding protein (Bip), inositol requiring enzyme 1α (IRE1α), C-jun N-terminal kinase (JNK)1/2 and Xbp1 splicing, were examined by RT-PCR, or Western blots or immunostaining from retinas 1 or 2 days after tunicamycin injection and I/R injury.
Tunicamycin caused ER stress and capillary degeneration in vivo, both of which were inhibited by resveratrol. Pretreatment of high dosage of resveratrol also significantly inhibited retinal I/R injury-induced capillary degeneration; however, neither of the dosages prevented the injury-induced neurodegeneration. Levels of CHOP, phosphorylated eIF2α, IRE1α, phosphorylated JNK1/2, Xbp1 splicing and Bip were elevated after I/R injury. High dosage of resveratrol pretreatment inhibited the injury-induced up-regulation of eIF2α-CHOP and IRE1α-XBP1 pathways.
ER stress is an important contributor to vascular degeneration in retina. Resveratrol suppresses I/R injury and tunicamycin-induced vascular degeneration by inhibiting ER stress.
内质网（ER）应激已被证明有助于多种眼部疾病的神经退行性变。然而，ER 应激是否会导致视网膜血管退化尚不清楚。我们在体内研究了 ER 应激在视网膜血管退化中的可能作用，以及白藜芦醇对衣霉素和缺血再灌注（I / R）诱导的视网膜血管退化的影响。
将不同剂量的衣霉素（一种 ER 应激诱导剂）注入小鼠眼玻璃体中。通过升高眼内压 60 分钟然后再灌注来诱导视网膜 I / R 损伤。在视网膜 I / R 损伤前 2 天给予两种剂量的白藜芦醇（每天 5 和 25 毫克/千克体重），同时将 100 μM 白藜芦醇与衣霉素一起注入玻璃体。在 I / R 损伤和衣霉素注射后 7 天评估无细胞毛细血管的形成，而在 I / R 损伤后 4 天分析神经节细胞层中的细胞体和脑特异性同源框/POU 域蛋白 3A（Brn3a）染色。通过 RT-PCR 或 Western blot 或免疫染色从衣霉素注射后 1 或 2 天的视网膜中检测内质网应激标志物，包括真核起始因子 2α（eIF2α）、CCAAT 增强子结合蛋白同源蛋白（CHOP）、免疫球蛋白结合蛋白（Bip）、肌醇需求酶 1α（IRE1α）、c-Jun N-末端激酶（JNK）1/2 和 Xbp1 剪接。
衣霉素在体内引起 ER 应激和毛细血管退化，白藜芦醇均可抑制。高剂量白藜芦醇预处理也显著抑制了视网膜 I / R 损伤诱导的毛细血管退化；然而，两种剂量均不能预防损伤诱导的神经退行性变。IRE1α、磷酸化 eIF2α、IRE1α、磷酸化 JNK1/2、Xbp1 剪接和 Bip 的水平在 I / R 损伤后升高。高剂量白藜芦醇预处理抑制了损伤诱导的 eIF2α-CHOP 和 IRE1α-XBP1 途径的上调。
内质网应激是视网膜血管退化的重要原因。白藜芦醇通过抑制 ER 应激抑制 I / R 损伤和衣霉素诱导的血管退化。
