Department of Pharmacology, CHU Sainte-Justine Hospital, University of Montréal, Montréal, Québec, Canada; Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Center, University of Montréal, Montréal, Québec, Canada.
Department of Pharmacology, CHU Sainte-Justine Hospital, University of Montréal, Montréal, Québec, Canada; Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Center, University of Montréal, Montréal, Québec, Canada.
Am J Pathol. 2015 Feb;185(2):581-95. doi: 10.1016/j.ajpath.2014.10.020. Epub 2014 Dec 3.
Ischemic retinopathies are characterized by sequential vaso-obliteration followed by abnormal intravitreal neovascularization predisposing patients to retinal detachment and blindness. Ischemic retinopathies are associated with robust inflammation that leads to generation of IL-1β, which causes vascular degeneration and impairs retinal revascularization in part through the liberation of repulsive guidance cue semaphorin 3A (Sema3A). However, retinal revascularization begins as inflammation culminates in ischemic retinopathies. Because inflammation leads to activation of proteases involved in the formation of vasculature, we hypothesized that proteinase-activated receptor (Par)-2 (official name F2rl1) may modulate deleterious effects of IL-1β. Par2, detected mostly in retinal ganglion cells, was up-regulated in oxygen-induced retinopathy. Surprisingly, oxygen-induced retinopathy-induced vaso-obliteration and neovascularization were unaltered in Par2 knockout mice, suggesting compensatory mechanisms. We therefore conditionally knocked down retinal Par2 with shRNA-Par2-encoded lentivirus. Par2 knockdown interfered with normal revascularization, resulting in pronounced intravitreal neovascularization; conversely, the Par2 agonist peptide (SLIGRL) accelerated normal revascularization. In vitro and in vivo exploration of mechanisms revealed that IL-1β induced Par2 expression, which in turn down-regulated sequentially IL-1 receptor type I and Sema3A expression through Erk/Jnk-dependent processes. Collectively, our findings unveil an important mechanism by which IL-1β regulates its own endothelial cytotoxic actions by augmenting neuronal Par2 expression to repress sequentially IL-1 receptor type I and Sema3A expression. Timely activation of Par2 may be a promising therapeutic avenue in ischemic retinopathies.
缺血性视网膜病变的特征是血管闭塞，随后出现异常的眼内新生血管化，使患者容易发生视网膜脱离和失明。缺血性视网膜病变与强烈的炎症有关，炎症导致白细胞介素-1β（IL-1β）的产生，从而导致血管退化，并通过释放排斥性导向信号 semaphorin 3A（Sema3A）部分损害视网膜再血管化。然而，在缺血性视网膜病变中，炎症导致血管生成蛋白酶的激活，从而开始视网膜再血管化。由于炎症导致参与血管形成的蛋白酶的激活，我们假设蛋白酶激活受体（Par）-2（正式名称 F2rl1）可能调节 IL-1β 的有害作用。Par2 主要在视网膜神经节细胞中检测到，在氧诱导的视网膜病变中上调。令人惊讶的是，Par2 基因敲除小鼠的氧诱导性视网膜病变引起的血管闭塞和新生血管化没有改变，表明存在代偿机制。因此，我们用 shRNA-Par2 编码的慢病毒条件性敲低视网膜 Par2。Par2 敲低干扰了正常的再血管化，导致明显的眼内新生血管化；相反，Par2 激动肽（SLIGRL）加速了正常的再血管化。体内和体外的机制研究表明，IL-1β 诱导 Par2 表达，进而通过 Erk/Jnk 依赖性过程下调依次 IL-1 受体 I 型和 Sema3A 表达。总的来说，我们的发现揭示了一个重要的机制，即 IL-1β 通过增强神经元 Par2 表达来调节其自身的内皮细胞毒性作用，从而依次抑制 IL-1 受体 I 型和 Sema3A 表达。Par2 的适时激活可能是缺血性视网膜病变的一种有前途的治疗途径。
