Abstract Context 5-Caffeoylquinic acid (5-CQA) is one of the most abundant compounds found in natural foods including coffee. Objective We investigated whether 5-CQA had a cytoprotective effect through the NF-E2-related factor 2 (Nrf2)-antioxidant response element (ARE) signalling pathway. Materials and methods Nrf2 activation in response to 5-CQA treatment at the concentration of 10–100 μM is evaluated by Western blotting of Nrf2 and ARE reporter gene assay as well as its target gene expression in HepG2 cells. Intracellular reactive oxygen species (ROS) and glutathione (GSH) levels were measured in the tert-butyl hydroperoxide-induced hepatocytes to examined cytoprotective effect of 5-CQA (10–100 μM). The specific role of 5-CQA on Nrf2 activation was examined using Nrf2 knockout cells or Nrf2 specific inhibitor, ML-385. Results Nuclear translocation of Nrf2 is increased by 5-CQA in HepG2 cells which peaked at 6 h. Consequently, 5-CQA significantly increases the ARE reporter gene activity and downstream antioxidant proteins, including glutamate cysteine ligase (GCL), hemeoxygenase-1 (HO-1), NAD(P)H quinone oxidoreductase 1, and Sestrin2. Nrf2 deficiency or inhibition completely antagonized ability of 5-CQA to induce HO-1 and GCL expression. Cells pre-treated with 5-CQA were rescued from tert-butyl hydroperoxide-induced ROS production and GSH depletion. Nrf2 activation by 5-CQA was due to increased phosphorylation of MAPKs, AMPK and PKCδ. Discussion and conclusions Taken together, our results demonstrate that as a novel Nrf2 activator, 5-CQA, may be a promising candidate against oxidative stress-mediated liver injury. Additional efforts are needed to assess 5-CQA, as a potential therapeutic in liver diseases in vivo and in humans.

中文翻译：

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5-咖啡酰奎宁酸通过激活肝细胞中的 Nrf2 来改善氧化应激介导的细胞死亡

摘要背景 5-咖啡酰奎宁酸 (5-CQA) 是在包括咖啡在内的天然食品中发现的最丰富的化合物之一。目的我们研究了 5-CQA 是否通过 NF-E2 相关因子 2 (Nrf2)-抗氧化反应元件 (ARE) 信号通路具有细胞保护作用。材料和方法 通过 Nrf2 和 ARE 报告基因测定的蛋白质印迹以及其在 HepG2 细胞中的靶基因表达来评估 Nrf2 对 10-100 μM 浓度的 5-CQA 处理的反应。在叔丁基氢过氧化物诱导的肝细胞中测量细胞内活性氧 (ROS) 和谷胱甘肽 (GSH) 水平，以检查 5-CQA (10-100 μM) 的细胞保护作用。使用 Nrf2 敲除细胞或 Nrf2 特异性抑制剂 ML-385 检查 5-CQA 对 Nrf2 活化的具体作用。结果 在 HepG2 细胞中，5-CQA 增加了 Nrf2 的核转位，在 6 小时达到峰值。因此，5-CQA 显着增加了 ARE 报告基因活性和下游抗氧化蛋白，包括谷氨酸半胱氨酸连接酶 (GCL)、血氧合酶-1 (HO-1)、NAD(P)H 醌氧化还原酶 1 和 Sestrin2。Nrf2 缺乏或抑制完全拮抗 5-CQA 诱导 HO-1 和 GCL 表达的能力。用 5-CQA 预处理的细胞从叔丁基过氧化氢诱导的 ROS 产生和 GSH 消耗中解救出来。5-CQA 对 Nrf2 的激活是由于 MAPK、AMPK 和 PKCδ 的磷酸化增加。讨论和结论 综上所述，我们的结果表明，作为一种新型 Nrf2 激活剂，5-CQA 可能是对抗氧化应激介导的肝损伤的有希望的候选者。需要额外的努力来评估 5-CQA，