Tanito Masaki, Agbaga Martin-Paul, Anderson Robert E
Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
Free Radic Biol Med. 2007 Jun 15;42(12):1838-50. doi: 10.1016/j.freeradbiomed.2007.03.018. Epub 2007 Mar 24.
We tested the hypothesis that stress responses mediated by the Nrf2-antioxidant responsive element (ARE) pathway are involved in the initiation of retinal neuroprotection provided by bright-cyclic-light rearing. Albino rats born and raised in dim (5 lux) or bright (400 lux) cyclic light were exposed to damaging light (3000 lux, 6 h). After exposure, the outer nuclear layer thickness and area and the electroretinogram a- and b-wave amplitudes were significantly reduced in the dim-light-reared rats compared to the bright-light-reared rats, demonstrating a light adaptation neuroprotection phenomenon. In bright-cyclic-light-reared rats, the retinal levels of thioredoxin (Trx) (2.4-fold), Trx reductase (TrxR) (2.9-fold), and proteins modified by 4-hydroxynonenal (4-HNE) (1.5-fold) were upregulated by Western blot analyses, and the nuclear translocation of Nrf2 (2.2-fold) and the DNA binding activity of Nrf2, small Maf, and cJun to the ARE were increased as determined by electrophoretic mobility shift assays. In mouse photoreceptor-derived 661W cells, pretreatment with a sublethal dose of 4-HNE protected against H(2)O(2)-induced cell damage. Treatment with 4-HNE upregulated cellular Trx, TrxR, and heme oxygenase-1 (HO-1) levels in addition to DNA binding activity of Nrf2, small Maf, and cJun to the ARE. Downregulation of Nrf2 using RNA interference technology diminished 4-HNE-mediated upregulation of Trx and Trx reductase but did not affect the upregulation of HO-1 by 4-HNE. Cytoprotection by 4-HNE pretreatment against H(2)O(2)-induced cell damage was not observed in 661W cells with a silenced Nrf2 gene. The results suggest that upregulation of the Trx system by 4-HNE via the Nrf2-ARE pathway may be involved in the molecular mechanism of the retinal neuroprotection phenomenon.
由Nrf2-抗氧化反应元件（ARE）途径介导的应激反应参与了明亮循环光饲养所提供的视网膜神经保护作用的起始过程。在昏暗（5勒克斯）或明亮（400勒克斯）循环光下出生并饲养的白化大鼠暴露于损伤性光（3000勒克斯，6小时）。暴露后，与明亮光饲养的大鼠相比，昏暗光饲养的大鼠的外核层厚度和面积以及视网膜电图a波和b波振幅显著降低，表明存在光适应神经保护现象。通过蛋白质印迹分析，在明亮循环光饲养的大鼠中，硫氧还蛋白（Trx）（2.4倍）、硫氧还蛋白还原酶（TrxR）（2.9倍）和4-羟基壬烯醛（4-HNE）修饰的蛋白质（1.5倍）的视网膜水平上调，并且通过电泳迁移率变动分析确定，Nrf2的核转位（2.2倍）以及Nrf2、小Maf和cJun与ARE的DNA结合活性增加。在小鼠光感受器来源的661W细胞中，用亚致死剂量的4-HNE预处理可保护细胞免受H2O2诱导的损伤。用4-HNE处理除了上调Nrf2、小Maf和cJun与ARE的DNA结合活性外，还上调了细胞Trx、TrxR和血红素加氧酶-1（HO-1）水平。使用RNA干扰技术下调Nrf2可减少4-HNE介导的Trx和Trx还原酶上调，但不影响4-HNE对HO-1的上调。在Nrf2基因沉默的661W细胞中未观察到4-HNE预处理对H2O2诱导的细胞损伤的细胞保护作用。结果表明，4-HNE通过Nrf2-ARE途径上调Trx系统可能参与了视网膜神经保护现象的分子机制。
