Isoquercetin (Iso) has been found to have neuroprotective effects against cerebral ischemic stroke. However, the exact molecular mechanism underlying its neuroprotective ability remains unclear. In this study, we aimed to evaluate the neuroprotective effects of Iso in primary culture of rat hippocampal neurons exposed to oxygen and glucose deprivation and reperfusion (OGD/R) injury and in rats subjected to middle cerebral artery occlusion and reperfusion (MCAO/R) injury. We found that rats treated with Iso exhibited a lower degree of infarct volume, and brain water content than the vehicle-treated rats. Treatment with Iso also improved the neurological deficits in MCAO/R rats as shown by the decreased modified neurological severity score. Iso treatment decreased the reactive oxygen species (ROS) and malondialdehyde (MDA) production, and increased the activity of superoxide dismutase (SOD) and catalase (CAT) in brains of MCAO/R rats and primary culture of rat hippocampal neurons exposed to OGD/R. Iso treatment prevents I/R-induced neuronal apoptosis in vivo and in vitro as indicated by increased cell viability and decreased number of TUNEL-positive cells, accompanying with downregulation of cleaved caspase-3 protein and upregulation of Bcl-2 protein. Moreover, Nrf2 knockdown weakened the anti-apoptotic and anti-oxidant activities of Iso in primary culture of rat hippocampal neurons exposed to OGD/R. Interestingly, we found that Iso could induce Nrf2 translocation from cytoplasm to nucleus in primary culture of rat hippocampal neurons exposed to OGD/R. Iso activated the NOX4/ROS/NF-κB signaling pathway in in vivo and in vitro cerebral I/R injury models. Nrf2 knockdown blocked the inhibitory effect of Iso on protein expression of NOX4, p-IκBα and p-p65 in primary culture of rat hippocampal neurons exposed to OGD/R. All the data suggested that Iso protected against oxidative stress and neuronal apoptosis in in vivo and in vitro cerebral I/R injury models via Nrf2-mediated inhibition of the NOX4/ROS/NF-κB signaling pathway. Our findings suggested that Iso could be a potential agent for I/R brain injury.

已发现异槲皮素（Iso）对脑缺血性中风具有神经保护作用。但是，尚不清楚其神经保护能力的确切分子机制。在这项研究中，我们旨在评估Iso对暴露于缺氧和葡萄糖剥夺和再灌注（OGD / R）损伤的大鼠海马神经元以及遭受大脑中动脉闭塞和再灌注（MCAO / R）的大鼠的原代培养的神经保护作用受伤。我们发现，用Iso治疗的大鼠比用赋形剂治疗的大鼠表现出更低程度的梗塞体积和脑含水量。Iso治疗还改善了MCAO / R大鼠的神经功能缺损，如降低的改良神经系统严重性评分所示。异处理降低了活性氧（ROS）和丙二醛（MDA）的产生，并增加了暴露于OGD / R的MCAO / R大鼠大脑和大鼠海马神经元原代培养物中超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的活性。Iso治疗可防止I / R诱导的神经元凋亡细胞活力增强和TUNEL阳性细胞数量减少，以及裂解的caspase-3蛋白下调和Bcl-2蛋白上调伴随着体内和体外的变化。此外，Nrf2敲低削弱了暴露于OGD / R的大鼠海马神经元原代培养物中Iso的抗凋亡和抗氧化活性。有趣的是，我们发现在暴露于OGD / R的大鼠海马神经元的原代培养物中，Iso可以诱导Nrf2从细胞质向细胞核移位。Iso在体内和体外激活了NOX4 / ROS /NF-κB信号通路脑I / R损伤模型。Nrf2敲低阻断了Iso对暴露于OGD / R的大鼠海马神经元原代培养物中NOX4，p-IκBα和p-p65蛋白表达的抑制作用。所有数据表明，Iso通过Nrf2介导的NOX4 / ROS /NF-κB信号通路抑制作用，在体内和体外脑I / R损伤模型中均具有抗氧化应激和神经元凋亡的作用。我们的发现表明，Iso可能是I / R脑损伤的潜在药物。