星形胶质细胞circNCOA2在脑缺血再灌注损伤中的作用及机制

Ischemic reperfusion injury is one of the leading cause of poor clinical outcome for the patients with acute ischemic stroke after endovascular thrombectomy. Circular RNAs(circRNAs) play an important role in ischemic reperfusion injury. But the mechanisms of them are not clear. We have found that microRNA-29a-5p could alleviate ischemic reperfusion injury by directly targeting NOX4 in rat astrocytes oxygen and glucose deprivation/reoxygenation and middle cerebral artery occlusion models. circNCOA2 has potential binding sites of microRNA-29a-5p. Furthermore, we go on our research and find more details in acute ischemic stroke patients’ plasma samples, mouse astrocytes oxygen and glucose deprivation/reoxygenation and middle cerebral artery occlusion models. The results are as fellows. The expression of circular RNA NCOA2(circNCOA2) upregulates in patients’ plasma samples, mouse astrocytes after oxygen and glucose deprivation/reoxygenation and cerebral ischemic penumbra. si-circNCOA2 may alleviate oxidative stress injury partially though downregulating NOX4 expression in astrocytes after oxygen and glucose deprivation/reoxygenation. Therefore, we hypothesized that circNCOA2 play a role in cerebral ischemia reperfusion injury by targeting microRNA-29a-5p and then upregulating the expression of NOX4. We shall systematically research the mechanisms of circNCOA2 in cerebral ischemic reperfusion injury though in vivo/vitro experiments and clinical findings in this study. It may supply implications for circRNAs as novel therapeutic targets for treatment of cerebral ischemic reperfusion injury.

缺血再灌注损伤是急性缺血性卒中血管内介入再通治疗后预后不良的主要原因之一，环状RNA在脑缺血再灌注损伤中起着重要作用，但是机制不明确。我们前期在鼠星形胶质细胞糖氧剥夺(OGD)复氧和MCAO动物模型中，发现miR-29a-5p调控靶基因NOX4减轻了脑缺血再灌注损伤，环状RNA NCOA2(circNCOA2)与miR-29a-5p具有结合位点。初步发现circNCOA2在急性脑梗塞患者血浆中表达增加，其在OGD复氧后鼠星形胶质细胞中也显著上调；抑制circNCOA2后，NOX4表达降低，减轻氧化应激损伤。我们提出假设：circNCOA2通过竞争性结合miR-29a-5p上调星形胶质细胞NOX4表达，参与急性脑缺血机械再通后的再灌注损伤。本项目拟通过体外细胞、动物模型和临床研究，阐明circNCOA2在脑缺血再灌注损伤中的作用机制，为明确环状RNA作为减轻脑缺血再灌注损伤的新靶点提供依据。

脑卒中是我国成年人致死和致残的首位原因。急性缺血性卒中治疗的关键是尽早开通闭塞血管，挽救缺血半暗带。血管内介入再通治疗是颅内大血管闭塞引起的急性中重度缺血性卒中的关键有效治疗策略，研究发现急性缺血性卒中患者血管再通率可达80%以上，但是患者良好临床预后的比例仅为 50%，未获得良好预后的患者为无效再通。颅内出血转化是血管内介入再通治疗后的主要并发症， 也是无效再通的主要原因，其与患者神经功能恶化以及不良预后显著相关。颅内出血转化是脑缺血再灌注损伤的最严重表现。研究表明氧化应激、炎症和凋亡是脑缺血再灌注损伤发生发展的主要机制，环状RNA在脑缺血再灌注损伤中起着重要作用，但是机制不明确。. 我们在临床血浆标本检测人circNCOA2的表达，发现与健康成人相比，急性缺血性卒中患者的血浆 circNCOA2显著上调表达。然后，在小鼠星形胶质细胞体OGD复氧模型中，发现 OGD4 小时复氧后3小时 circNCOA2 表达升高，复氧后24小时circNCOA2 持续上调表达。采用 siRNA 技术沉默 circNCOA2后， 显著抑制了星形胶质细胞OGD复氧后 NOX4 mRNA 的上调表达，减轻ROS引起的氧化应激损伤。我们进一步在小鼠 MCAO 动物模型中，发现急性脑缺血机械再通3小时后半暗带区域脑组织的circNCOA2表达升高，再灌注24 小时后circNCOA2仍持续上调表达。. 阐明 circNCOA2/miR-29a-5p/NOX4/ROS 信号通路在急性脑缺血再灌注损伤发生和发展中的作用及其机制，为明确环状RNA circNCOA2作为脑缺血再灌注损伤干预新靶点提供科学依据。