Quercetin is a bioactive flavonoid which abundantly exists in vegetables and fruits. Quercetin exerts a neuroprotective effect against cerebral ischemia. Thioredoxin acts as antioxidant by regulating redox signaling. This study investigated whether quercetin regulates thioredoxin expression in focal cerebral ischemia and glutamate-induced neuronal cell death. Male Sprague Dawley rats (210-230 g) were intraperitoneally injected with vehicle or quercetin (10 mg/kg) 1 h prior to middle cerebral artery occlusion (MCAO). Cerebral cortex was collected 24 h after MCAO. MCAO led to neurological movement deficits, brain edema, and serious histopathological damages in cerebral cortex, and quercetin alleviated these damages following MCAO. We observed the change of thioredoxin expression in MCAO animals with quercetin using proteomic approach, reverse-transcription PCR, and Western blot analyses. Thioredoxin expression decreased in vehicle-treated MCAO animals, while quercetin attenuated this decrease. Moreover, quercetin treatment alleviated the decrease in the number of thioredoxin-positive cells in cerebral cortex of MCAO animals. Furthermore, immunoprecipitation analysis demonstrated that interaction of apoptosis signal-regulating kinase 1 (ASK1) and thioredoxin was decreased in MCAO animals with vehicle, while quercetin prevented MCAO-induced decrease in these binding. In addition, quercetin also alleviated the reduction of cell viability and the decrease in thioredoxin expression in glutamate-treated hippocampal cell line and primary cultures of cortical neurons. However in thioredoxin-silenced cortical neuron, anti-apoptotic effect of quercetin was decreased. Thus, changes of thioredoxin expression by quercetin may contribute to the neuroprotective effect of quercetin in focal cerebral ischemia. Our findings suggest that quercetin mediates its neuroprotective function by regulation of thioredoxin expression and maintenance of interaction between ASK1 and thioredoxin.

中文翻译：

---

槲皮素可减轻局灶性脑缺血和谷氨酸诱导的神经元细胞损伤后硫氧还蛋白的表达减少。

槲皮素是一种生物活性类黄酮，广泛存在于蔬菜和水果中。槲皮素对脑缺血具有神经保护作用。硫氧还蛋白通过调节氧化还原信号而起抗氧化剂的作用。这项研究调查了槲皮素是否在局灶性脑缺血和谷氨酸诱导的神经元细胞死亡中调节硫氧还蛋白的表达。在大脑中动脉闭塞（MCAO）前1小时，对雄性Sprague Dawley大鼠（210-230 g）腹膜内注射媒介物或槲皮素（10 mg / kg）。MCAO后24小时收集大脑皮层。MCAO导致神经运动异常，脑水肿和大脑皮质严重的组织病理学损害，槲皮素减轻了MCAO后的损害。我们使用蛋白质组学方法观察了槲皮素对MCAO动物体内硫氧还蛋白表达的变化，逆转录PCR和蛋白质印迹分析。媒介物治疗的MCAO动物体内硫氧还蛋白的表达下降，而槲皮素减弱了这种下降。此外，槲皮素治疗减轻了MCAO动物大脑皮质中硫氧还蛋白阳性细胞数量的减少。此外，免疫沉淀分析表明，在带有载体的MCAO动物中，凋亡信号调节激酶1（ASK1）和硫氧还蛋白的相互作用降低了，而槲皮素阻止了MCAO诱导的这些结合的降低。此外，槲皮素还减轻了谷氨酸处理的海马细胞系和皮层神经元原代培养物中细胞活力的降低和硫氧还蛋白表达的降低。然而，在硫氧还蛋白沉默的皮质神经元中，槲皮素的抗凋亡作用降低。因此，槲皮素改变硫氧还蛋白的表达可能有助于槲皮素对局灶性脑缺血的神经保护作用。我们的发现表明，槲皮素通过调节硫氧还蛋白的表达并维持ASK1和硫氧还蛋白之间的相互作用来介导其神经保护功能。