Sigma 1 receptor regulates the oxidative stress response in primary retinal Müller glial cells via NRF2 signaling and system xc(-), the Na(+)-independent glutamate-cystine exchanger.
Sigma 1 receptor regulates the oxidative stress response in primary retinal Müller glial cells via NRF2 signaling and system xc(-), the Na(+)-independent glutamate-cystine exchanger.
复制标题
Sigma 1受体通过NRF2信号传导和System XC（ - ），Na（+） - 独立的谷氨酸 - 凝结晶状体交换器来调节原代视网膜Müller神经胶质细胞中的氧化应激反应。
DOI：
10.1016/j.freeradbiomed.2015.04.009
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发表时间：
2015-09
影响因子：
7.4
通讯作者：
Smith SB
中科院分区：
文献类型：
--
作者：
Wang J;Shanmugam A;Markand S;Zorrilla E;Ganapathy V;Smith SB
氧化应激在包括糖尿病视网膜病变和青光眼在内的视网膜疾病中占有重要地位。σ 1 R是一种定位于ER、线粒体、核膜和质膜的独特跨膜蛋白，其配体在体外和体内具有深刻的视网膜神经保护特性。确定σ 1 R介导的视网膜神经保护机制的研究主要集中在神经元上。关于σ 1 R对Müller细胞功能的影响知之甚少，然而这些放射状胶质细胞对于视网膜的稳态支持是必不可少的。在这里，我们研究了σ 1 R是否介导的Müller细胞的氧化应激反应，使用野生型（WT）和σ 1 R敲除（σ 1 RKO）小鼠。我们观察到与WT相比，σ 1 RKO Müller细胞中内源性ROS水平增加，伴随着Sod 1、过氧化氢酶、Nqo 1、Hmox 1、Gstm 6和Gpx 1表达降低。SOD 1、CAT、NQO 1和GPX 1蛋白水平也显著降低。编码这些抗氧化剂的基因含有抗氧化反应元件（ARE），在应激下被NRF 2激活，NRF 2是一种通常存在于细胞质中的转录因子，与KEAP 1结合。在σ 1 RKO Müller细胞中，Nrf 2在基因（和蛋白）水平上表达显著降低，而Keap 1基因（和蛋白）水平显著升高。在σ 1 RKO Müller细胞中，NRF 2-ARE结合亲和力显著降低。我们研究了系统xc−（对GSH合成很重要的胱氨酸-谷氨酸交换剂），并观察到与WT相比，σ 1 RKO Müller细胞的功能降低以及GSH和GSH/GSSG比值降低。这伴随着xc−系统的独特成分xCT的基因和蛋白水平下降。我们的结论是，缺乏σ 1 R的Müller胶质细胞表现出ROS升高，抗氧化平衡紊乱，NRF 2信号转导抑制和xc−系统功能受损。这些数据表明，视网膜Müller神经胶质细胞的氧化应激介导功能可能会受到损害，在σ 1 R的情况下。σ 1 R的神经保护作用可能与支持性胶质细胞的氧化应激介导特性直接相关。论文示意图：以活性氧（ROS）形式存在的氧化应激在视网膜疾病中占有重要地位。Müller胶质细胞是视网膜稳态的主要介质。在这篇论文中，从缺乏σ 1 R（一种假定的分子伴侣）的小鼠中收获的Müller细胞显示出内源性ROS产生的增加。这是伴随着一些抗氧化蛋白，这是已知的港口抗氧化反应元件（ARE）的表达减少。Nrf 2是通过其激活战神的氧化应激的主要调节剂，在基因、蛋白和活性水平上降低;其主要调节蛋白Keap 1增加。在缺乏σ 1 R的Müller细胞中，胱氨酸-谷氨酸交换体的表达和活性也降低。总的来说，这些数据支持σ 1 R在视网膜氧化应激调节中的关键作用。
Oxidative stress figures prominently in retinal diseases including diabetic retinopathy and glaucoma. Ligands for σ1R, a unique transmembrane protein localized to the ER, mitochondria, nuclear and plasma membrane, have profound retinal neuroprotective properties in vitro and in vivo. Studies to determine the mechanism of σ1R-mediated retinal neuroprotection have focused mainly on neurons. Little is known about effects of σ1R on Müller cell function, yet these radial glial cells are essential for homeostatic support of the retina. Here we investigated whether σ1R mediates the oxidative stress response of Müller cells using wildtype (WT) and σ1R knockout (σ1RKO) mice. We observed increased endogenous ROS levels in σ1RKO Müller cells compared to WT, which was accompanied by decreased expression of Sod1, Catalase, Nqo1, Hmox1, Gstm6 and Gpx1. The protein levels of SOD1, CAT, NQO1 and GPX1 were also significantly decreased. The genes encoding these antioxidants contain an antioxidant response element (ARE), which under stress is activated by NRF2, a transcription factor that typically resides in the cytoplasm bound by KEAP1. In the σ1RKO Müller cells Nrf2 expression was decreased significantly at the gene (and protein) level, while Keap1 gene (and protein) levels were markedly increased. NRF2-ARE binding affinity was decreased markedly in σ1RKO Müller cells. We investigated system xc−, the cystine-glutamate exchanger important for synthesis of GSH, and observed decreased function in σ1RKO Müller cells compared to WT as well as decreased GSH and GSH/GSSG ratios. This was accompanied by decreased gene and protein levels of xCT, the unique component of system xc−. We conclude that Müller glial cells lacking σ1R manifest elevated ROS, perturbation of antioxidant balance, suppression of NRF2 signaling and impaired function of system xc−. The data suggest that the oxidative stress-mediating function of retinal Müller glial cells may be compromised in the absence of σ1R. The neuroprotective role of σ1R may be linked directly to the oxidative stress-mediating properties of supportive glial cells. Schematic of paper: Oxidative stress in the form of reactive oxygen species (ROS) figures prominently in retinal diseases. The Müller glial cell is a major mediator of retinal homeostasis. In this paper, Müller cells harvested from mice lacking σ1R, a putative molecular chaperone, showed an increase endogenous production of ROS. This was accompanied by decreased expression of a number of antioxidant proteins, which are known to harbor antioxidant response elements (ARE). Nrf2, which is a major regulator of oxidative stress through its activation of AREs was decreased at the gene, protein and activity level; its major regulatory protein Keap1 was increased. The expression and activity of the cystine-glutamate exchanger was also decreased in Müller cells lacking σ1R. Taken collectively, the data support a key role for σ1R in modulation of oxidative stress in retina.