细胞胶质拮抗剂

A2A受体拮抗剂对实验性青光眼的保护作用

【据《InvestigativeOpthalmology&VisualScience》2016年3月...

【据《Investigative Opthalmology & Visual Science》2016年3月报道】题：A2A受体拮抗剂在实验性青光眼中对小胶质细胞活化的作用。（英文题：The Effect of A2A Receptor Antagonist on Microglial Activation in Experimental Glaucoma；作者：钟一声等；单位：上海交通大学附属瑞金医院眼科）

青光眼是一种神经退行性疾病，若控制不当就会引起视网膜神经节细胞的渐进性坏死和视野缺损。尽管高眼压是青光眼的一个明确的高危因素，但在青光眼中也发现了小胶质细胞反应，也就表明炎症反应在青光眼中也起到了重要作用。小胶质细胞可有助于维持中枢神经系统的完整性，但在病理状态下过度活化的小胶质细胞可通过释放有害物质如炎症因子、一氧化氮、活性氧和蛋白酶等引起神经元的损伤。且小胶质细胞介导的这种神经炎症与多种神经退行性病变有关。而A2A受体则被认为是小胶质细胞介导神经炎症所偶联的关键分子。

该研究旨在探究慢性高眼压状态下A2A受体拮抗剂对小胶质细胞活化和神经节细胞存活所起的作用，并通过体外与在体两方面的实验进一步明确小胶质细胞与神经节细胞存活之间的关系。

实验方法：选用雄性SD大鼠，在一只眼睛中结扎3条巩膜静脉以诱导慢性高眼压模型。在慢性高眼压状态下，玻璃体腔注射或不注射A2A受体拮抗剂ZM241385，用荧光定位、定量PCR和蛋白印记的方法分别测定两组神经节细胞的存活和小胶质细胞的活化状态。在体外培养体系中加入谷氨酸和/或ZM241385，然后用ELISA方法检测小胶质细胞分泌的炎症介质。

结果显示：与正常对照组相比，神经节细胞密度在中央视网膜和周边视网膜都有降低（中央：慢性高眼压诱导前2436 4 143 cells/mm2，慢性高眼压诱导后2130 1 148 cells/mm2；周边：慢性高眼压诱导前2219 ± 140 cells/mm2，慢性高眼压诱导后1953 ± 142 cells/mm2）。在慢性高眼压模型中小胶质细胞的分支形态变为变形形式且TNF-α和IL-1β的表达也有升高。然而这些改变在玻璃体腔注射了A2A受体拮抗剂ZM241385后均有改善（神经节细胞密度仅下降到了2287善（神经节细胞密度仅下降2）。而在体外培养体系中加入ZM241385后也可下调在高浓度谷氨酸状态下小胶质细胞分泌的促炎因子的上调。

因此，该研究总结，A2A受体拮抗剂ZM241385可抑制小胶质细胞的活化，且能下调在高浓度谷氨酸和高眼压状态下的促炎因子的表达。这可能就是A2A受体拮抗剂在实验性青光眼中保护神经节细胞的机制之一。

（杨莉报道）

Abstract

Purpose: We investigated the effect of A2A receptor (A2AR) antagonist on microglial activation and retinal ganglion cell (RGC) survival under chronic ocular hypertension (COH), and explored the relationship between microglial activation and RGC survival by means of in vitro and in vivo experiments.

Methods: An animal model of COH was induced in one eye of male Sprague-Dawley (SD) rats by ligation of three episcleral veins. The survival of RGCs and the activation of microglia under COH without or with intravitreous injection of A2AR antagonist ZM241385 were assessed by fluorescent labeling, real time PCR and Western blot. ELISA was used to measure the secretion of inflammatory mediators by microglia when glutamate and/or ZM241385 was added into the culture system.

Results: Compared to the baseline, RGC density 2 weeks after COH induction decreased at the central (2436 ± 143 cells/mm2 pre- and 2130 ± 148 cells/mm2 post-COH induction) and peripheral (2219 ± 140 cells/mm2 pre- and 1953 ± 142 cells/mm2 post-COH induction) retina. The microglia changed their ramified morphology to an amoeboid form with increase in TNF-α and IL-1β expression after COH. These changes, however, were ameliorated with intravitreous ZM241385 (RGC density only dropped to 2287 ± 135 cells/mm2). The upregulation of those proinflammatory cytokines secreted by microglia in vitro under high concentration of glutamate was downregulated when ZM241385 was added into the culture system.

Conclusions: A2AR antagonist ZM241385 could reduce the activation of microglia and downregulate the proinflammatory cytokines expression under the conditions of COH and high concentration of glutamate, which may be one of the mechanisms that protected RGCs in experimental glaucoma.