Excess homocysteine upregulates the NRF2-antioxidant pathway in retinal Müller glial cells.
Excess homocysteine upregulates the NRF2-antioxidant pathway in retinal Müller glial cells.
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DOI：
10.1016/j.exer.2018.03.022
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发表时间：
2019-01
影响因子：
3.4
通讯作者：
Smith SB
中科院分区：
文献类型：
--
作者：
Navneet S;Cui X;Zhao J;Wang J;Kaidery NA;Thomas B;Bollinger KE;Yoon Y;Smith SB
本研究评价了同型半胱氨酸(Hcy)升高对视网膜Müler神经胶质细胞氧化应激反应的影响。Hcy升高与包括青光眼和视神经病变在内的视网膜疾病有关，这些疾病的特征是视网膜神经节细胞(RGC)丢失。为了了解Hcy诱导的RGC丢失的机制，我们利用了体外和体内的模型。体外分离的RGC对Hcy水平升高非常敏感，而体内高同型半胱氨酸血症(HHcy)小鼠模型显示RGC在多个月的时间内损失较少(~20%)。分离的细胞和完整的视网膜对同型半胱氨酸的这种不同反应表明，视网膜环境启动了缓冲过量同型半胱氨酸的机制。氧化应激被认为是同型半胱氨酸诱导的神经元丢失的机制之一，而NRF2是一种转录因子，在调节对氧化应激的细胞保护反应中发挥重要作用。在目前的研究中，我们研究了HHcy是否上调了Müller细胞中NRF2介导的应激反应，Müler细胞是主要的视网膜神经胶质细胞，负责为视网膜神经元提供营养支持。将原代Müler细胞暴露于L-同型半胱氨酸-硫代内酯[50μM-10 mM]中，检测细胞存活率、活性氧和谷胱甘肽水平。检测同型半胱氨酸(Hcy)暴露的Müller细胞中Nrf2基因/蛋白水平以及NRF2调节的抗氧化剂(NQO1、CAT、SOD2、Hmox1、GPX1)水平。与分离的RGC不同，分离的Müler细胞在广泛的同型半胱氨酸浓度范围内都能存活[50μM-1 mm]。此外，当暴露于升高的同型半胱氨酸时，Müler细胞表现出氧化应激和ROS水平的降低。GSH水平在Hcy染毒后24小时内升高约20%。分子分析显示，Nrf2的表达增加了2倍。抗氧化基因NQO1、Cat、Sod2、Hmox1、GPX1的表达显著增加。同型半胱氨酸暴露的后果也在从NRF2−/−小鼠中获得的Müler细胞中进行了评估。与暴露于同型半胱氨酸后氧化应激降低的WT Müler细胞不同，NRF2−/−Müler细胞的氧化应激显著增加。我们的数据表明，至少在Hhcy的早期阶段，可能存在细胞保护性反应，部分是由Müler细胞中的NRF2介导的。
This study evaluated the effects of elevated homocysteine (Hcy) on the oxidative stress response in retinal Müller glial cells. Elevated Hcy has been implicated in retinal diseases including glaucoma and optic neuropathy, which are characterized by retinal ganglion cell (RGC) loss. To understand the mechanisms of Hcy-induced RGC loss, in vitro and in vivo models have been utilized. In vitro isolated RGCs are quite sensitive to elevated Hcy levels, while in vivo murine models of hyperhomocysteinemia (HHcy) demonstrate a more modest RGC loss (~20%) over a period of many months. This differential response to Hcy between isolated cells and the intact retina suggests that the retinal milieu invokes mechanisms that buffer excess Hcy. Oxidative stress has been implicated as a mechanism of Hcy-induced neuron loss and NRF2 is a transcription factor that plays a major role in regulating cytoprotective responses to oxidative stress. In the present study we investigated whether HHcy upregulates NRF2-mediated stress responses in Müller cells, the chief retinal glial cell responsible for providing trophic support to retinal neurons. Primary Müller cells were exposed to L-Hcy-thiolactone [50μM–10mM] and assessed for viability, reactive oxygen species (ROS), and glutathione (GSH) levels. Gene/protein levels of Nrf2 and levels of NRF2-regulated antioxidants (NQO1, CAT, SOD2, HMOX1, GPX1) were assessed in Hcy-exposed Müller cells. Unlike isolated RGCs, isolated Müller cells are viable over a wide range of Hcy concentrations [50μM – 1mM]. Moreover, when exposed to elevated Hcy, Müller cells demonstrate decreased oxidative stress and decreased ROS levels. GSH levels increased by ~20% within 24h exposure to Hcy. Molecular analyses revealed 2-fold increase in Nrf2 expression. Expression of antioxidant genes Nqo1, Cat, Sod2, Hmox1, Gpx1 increased significantly. The consequences of Hcy exposure were evaluated also in Müller cells harvested from Nrf2−/− mice. In contrast to WT Müller cells, in which oxidative stress decreased upon exposure to Hcy, the Nrf2−/− Müller cells showed a significant increase in oxidative stress. Our data suggest that at least during early stages of Hhcy, a cytoprotective response may be in place, mediated in part by NRF2 in Müller cells.
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影响因子：
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作者：
Cheng LB;Li KR;Yi N;Li XM;Wang F;Xue B;Pan YS;Yao J;Jiang Q;Wu ZF
通讯作者：
Wu ZF
影响因子：
4.4
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影响因子：
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通讯作者：
Smith, SB
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通讯作者：
Smith, Sylvia B.
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作者：
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通讯作者：
Shea, TB