Decreased K5 receptor expression in the retina, a potential pathogenic mechanism for diabetic retinopathy
Decreased K5 receptor expression in the retina, a potential pathogenic mechanism for diabetic retinopathy
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视网膜 K5 受体表达减少，糖尿病视网膜病变的潜在致病机制
作者：
Li, Chaoyang;Shao, Chunkui;Gao, Guoquan;Yang, Xia
目的纤溶酶原kringle 5（K5）是一种有效的血管生成抑制剂，与电压依赖性阴离子通道（K5R）特异性结合。为了探讨K5 R在糖尿病视网膜病变中的作用，本研究检测了K5 R在糖尿病视网膜病变模型视网膜中的表达水平。在培养的视网膜Müller细胞中，K5抑制血管内皮生长因子（VEGF）的表达，如酶联免疫吸附试验和蛋白质印迹分析所示，表明K5对Müller细胞有直接作用。方法采用实时荧光定量RT-PCR和配体结合试验，检测视网膜Müller细胞中K5R的表达。~（125）I-K5与培养的Müller细胞呈饱和结合。这种结合可以被过量的未标记K5竞争，但不能被血管抑素竞争，证明K5与Müller细胞结合的特异性。与结合试验一致，使用电压依赖性阴离子通道特异性引物的逆转录聚合酶链反应检测到Müller细胞中的K5 R mRNA。结果糖尿病缺氧高糖条件下Müller细胞K5 R mRNA表达下调。与K5配体一起孵育可防止低氧诱导的K5R下调。此外，在氧诱导的视网膜病变模型（缺血诱导的视网膜新生血管模型）的视网膜中，K5 R表达也下调。在1型糖尿病大鼠模型中，糖尿病5周和8周的大鼠视网膜中的K5R表达显著抑制。结论视网膜Müller细胞表达K5受体，K5受体可能介导K5抑制VEGF表达。在糖尿病条件下，视网膜中K5R表达水平降低，这可能导致糖尿病视网膜病变中VEGF过表达。这些结果表明，K5R水平的降低也可能在糖尿病视网膜病变中发挥致病作用。
Purpose Plasminogen kringle 5 (K5) is a potent angiogenic inhibitor and specifically binds to the voltage-dependent anion channel believed to function as the K5 receptor (K5R). To investigate the role of K5R in diabetic retinopathy, the present study measured the expression levels of K5R in the retina of diabetic retinopathy models. In cultured retinal Müller cells, K5 inhibited vascular endothelial growth factor (VEGF) expression as shown with enzyme-linked immunosorbent assay and western blot analysis, suggesting that K5 has a direct effect on Müller cells. Methods To identify K5R in retinal Müller cells, ligand binding and competition assays as well as real-time reverse transcriptional polymerase chain reaction were performed in Müller cells. 125I-K5 showed saturable binding to cultured Müller cells. The binding can be competed off by an excess amount of unlabeled K5 but not by angiostatin, demonstrating the specificity of the K5 binding to Müller cells. Consistent with the binding assay, reverse transcriptional polymerase chain reaction using voltage-dependent anion channel–specific primers detected the K5R mRNA in the Müller cells. Results Interestingly, K5R mRNA expression in Müller cells was downregulated by diabetic conditions including hypoxia and high glucose medium. Incubation with K5 ligand prevented hypoxia-induced downregulation of K5R. Furthermore, K5R expression was also downregulated in the retina of the oxygen-induced retinopathy model, a model of ischemia-induced retinal neovascularization. In a type 1 diabetic rat model, K5R expression in the retina was significantly suppressed in rats that had diabetes for 5 and 8 weeks. Conclusions These results suggest that K5R is expressed in retinal Müller cells, which may mediate the inhibitory effect of K5 on VEGF expression. In diabetes conditions, K5R expression levels are decreased in the retina, which could contribute to the VEGF overexpression in diabetic retinopathy. These findings suggest that the decreased levels of K5R may also play a pathogenic role in diabetic retinopathy.
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影响因子：
3.6
作者：
Xia Yang;R. Cheng;Chaoyang Li;Weibin Cai;Jian-xing Ma;Qian-ping Liu;Zhonghan Yang;Zhi-hong Song;Zuguo Liu;G. Gao
通讯作者：
Xia Yang;R. Cheng;Chaoyang Li;Weibin Cai;Jian-xing Ma;Qian-ping Liu;Zhonghan Yang;Zhi-hong Song;Zuguo Liu;G. Gao
影响因子：
4.4
作者：
Lois E. H. Smith;Eva Wesoloiuski;Angela McLellan;Sandra K. Kostyk;Robert D'Amato;Richard Sullivan
通讯作者：
Lois E. H. Smith;Eva Wesoloiuski;Angela McLellan;Sandra K. Kostyk;Robert D'Amato;Richard Sullivan
影响因子：
4.8
作者：
Gao, GQ;Li, Y;Ma, JX
通讯作者：
Ma, JX
影响因子：
6
作者：
Zhang, SX;Ma, JX;Lambrou, GN
通讯作者：
Lambrou, GN
影响因子：
8.2
作者：
Zhang, D;Kaufman, PL;Ma, JX
通讯作者：
Ma, JX