The reperfusion after an acute ischemic stroke can lead to a secondary injury, which is ischemia-reperfusion (I/R) injury. During ischemia, the reactive oxygen species (ROS) is over-produced, mostly from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). Besides, miRNAs are also associated with neuronal death in ischemic stroke. MiR-124-5p is selectively expressed within central nervous system (CNS) and is predicted to bind to NOX2 directly. Herein, we successfully set up cerebral I/R injury model in rats through middle cerebral artery occlusion (MCAO) surgery. After 12 h or 24 h of refusion, the superoxide dismutase (SOD) activity was significantly inhibited, accompanied by NOX2 protein increase within MCAO rat infarct area. In vitro, oxygen-glucose deprivation/refusion (OGD/R) stimulation on PC-12 cells significantly increased NOX2 protein levels, ROS production, and the cell apoptosis, while a significant suppression on SOD activity; OGD/R stimulation-induced changes in PC-12 cells described above could be significantly attenuated by NOX2 silence. In vivo, miR-124 overexpression improved, whereas miR-124 inhibition aggravated I/R injury in MCAO rats. miR-124-5p directly bound to the CYBB 3'-untranslated region (UTR) to negatively regulate CYBB expression and NOX2 protein level. In vitro, miR-124 overexpression improved, while NOX2 overexpression aggravated OGD/R-induced cellular injuries; NOX2 overexpression significantly attenuated the effects of miR-124 overexpression. Besides, miR-124 overexpression significantly repressed NF-κB signaling activation and TNFα and IL-6 production through regulating NOX2. In conclusion, miR-124-5p/NOX2 axis modulates NOX-mediated ROS production, the inflammatory microenvironment, subsequently the apoptosis of neurons, finally affecting the cerebral I/R injury.

中文翻译：

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miR-124-5p / NOX2轴调节ROS的产生和炎性微环境，以防止脑I / R损伤。

急性缺血性中风后的再灌注可导致继发性损伤，即缺血再灌注（I / R）损伤。在缺血期间，活性氧（ROS）过量产生，主要是由烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶（NOX）产生的。此外，miRNA还与缺血性中风的神经元死亡有关。MiR-124-5p在中枢神经系统（CNS）中选择性表达，并预计直接与NOX2结合。本文中，我们成功地通过大脑中动脉阻塞（MCAO）手术建立了大鼠脑I / R损伤模型。输注12 h或24 h后，MCAO大鼠梗死区内超氧化物歧化酶（SOD）活性受到显着抑制，并伴有NOX2蛋白增加。体外，对PC-12细胞的氧葡萄糖剥夺/再灌注（OGD / R）刺激显着增加了NOX2蛋白水平，ROS产生和细胞凋亡，同时显着抑制了SOD活性；上述PC-12细胞中OGD / R刺激诱导的变化可以被NOX2沉默大大减弱。在体内，miR-124的过度表达得到改善，而miR-124的抑制作用加剧了MCAO大鼠的I / R损伤。miR-124-5p直接与CYBB 3'-非翻译区（UTR）结合，从而负调控CYBB表达和NOX2蛋白水平。在体外，miR-124的过表达得到改善，而NOX2的过表达加剧了OGD / R引起的细胞损伤。NOX2过表达显着减弱了miR-124过表达的作用。除了，miR-124的过表达通过调节NOX2显着抑制了NF-κB信号的激活以及TNFα和IL-6的产生。总之，miR-124-5p / NOX2轴可调节NOX介导的ROS产生，炎性微环境，进而调节神经元的凋亡，最终影响脑​​I / R损伤。