Cardona Sandra M, Mendiola Andrew S, Yang Ya-Chin, Adkins Sarina L, Torres Vanessa, Cardona Astrid E
Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, TX, USA.
Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, TX, USA
ASN Neuro. 2015 Oct 29;7(5). doi: 10.1177/1759091415608204. Print 2015 Sep-Oct.
Fractalkine (CX3CL1 or FKN) is a membrane-bound chemokine expressed on neuronal membranes and is proteolytically cleaved to shed a soluble chemoattractant domain. FKN signals via its unique receptor CX3CR1 expressed on microglia and other peripheral leukocytes. The aim of this study is to determine the role of CX3CR1 in inflammatory-mediated damage to retinal neurons using a model of diabetic retinopathy. For this, we compared neuronal, microglial, and astroglial densities and inflammatory response in nondiabetic and diabetic (Ins2(Akita)) CX3CR1-wild-type and CX3CR1-deficient mice at 10 and 20 weeks of age. Our results show that Ins2(Akita) CX3CR1-knockout mice exhibited (a) decreased neuronal cell counts in the retinal ganglion cell layer, (b) increased microglial cell numbers, and (c) decreased astrocyte responses comparable with Ins2(Akita) CX3CR1-Wild-type mice at 20 weeks of age. Analyses of the inflammatory response using PCR arrays showed several inflammatory genes differentially regulated in diabetic tissues. From those, the response in Ins2(Akita) CX3CR1-deficient mice at 10 weeks of age revealed a significant upregulation of IL-1β at the transcript level that was confirmed by enzyme-linked immunosorbent assay in soluble retinal extracts. Overall, IL-1β, VEGF, and nitrite levels as a read out of nitric oxide production were abundant in Ins2(Akita) CX3CR1-deficient retina. Notably, double immunofluorescence staining shows that astrocytes act as a source of IL-1β in the Ins2(Akita) retina, and CX3CR1-deficient microglia potentiate the inflammatory response via IL-1β release. Collectively, these data demonstrate that dysregulated microglial responses in absence of CX3CR1 contribute to inflammatory-mediated damage of neurons in the diabetic retina.
fractalkine（CX3CL1 或 FKN）是一种表达于神经元膜上的膜结合趋化因子，可通过蛋白水解作用裂解以释放可溶性趋化结构域。FKN 通过其在小胶质细胞和其他外周白细胞上表达的独特受体 CX3CR1 发出信号。本研究的目的是使用糖尿病性视网膜病变模型确定 CX3CR1 在炎症介导的视网膜神经元损伤中的作用。为此，我们比较了 10 周龄和 20 周龄的非糖尿病和糖尿病（Ins2(Akita)）CX3CR1 野生型和 CX3CR1 缺陷型小鼠的神经元、小胶质细胞和星形胶质细胞密度以及炎症反应。我们的结果表明，Ins2(Akita) CX3CR1 基因敲除小鼠在 20 周龄时表现出：（a）视网膜神经节细胞层中的神经元细胞数量减少；（b）小胶质细胞数量增加；（c）星形胶质细胞反应减弱，与 Ins2(Akita) CX3CR1 野生型小鼠相当。使用 PCR 芯片对炎症反应进行分析表明，糖尿病组织中有几种炎症基因受到差异调节。其中，10 周龄的 Ins2(Akita) CX3CR1 缺陷型小鼠的反应显示，转录水平上 IL-1β 显著上调，这在可溶性视网膜提取物中的酶联免疫吸附测定中得到证实。总体而言，Ins2(Akita) CX3CR1 缺陷型视网膜中作为一氧化氮产生指标的 IL-1β、VEGF 和亚硝酸盐水平很高。值得注意的是，双重免疫荧光染色显示，星形胶质细胞是 Ins2(Akita) 视网膜中 IL-1β 的来源，而 CX3CR1 缺陷型小胶质细胞通过释放 IL-1β 增强炎症反应。这些数据共同表明，在缺乏 CX3CR1 的情况下，小胶质细胞反应失调会导致糖尿病视网膜中神经元的炎症介导损伤。
