Toosendanin (TSN) is the main active compound in Toosendan Fructus and Meliae Cortex, two commonly used traditional Chinese medicines. TSN has been reported to induce hepatotoxicity, but its mechanism remains unclear. In this study, we demonstrated the critical role of nuclear factor erythroid 2-related factor 2 (Nrf2) in protecting against TSN-induced hepatotoxicity in mice and human normal liver L-02 cells. In mice, administration of TSN (10 mg/kg)-induced acute liver injury evidenced by increased serum alanine/aspartate aminotransferase (ALT/AST) and alkaline phosphatase (ALP) activities, and total bilirubin (TBiL) content as well as the histological changes. Furthermore, TSN markedly increased liver reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and decreased liver glutathione (GSH) content and Nrf2 expression. In L-02 cells, TSN (2 μM) time-dependently reduced glutamate-cysteine ligase (GCL) activity and cellular expression of the catalytic/modify subunit of GCL (GCLC/GCLM). Moreover, TSN reduced cellular GSH content and the increased ROS formation, and time-dependently decreased Nrf2 expression and increased the expression of the Nrf2 inhibitor protein kelch-like ECH-associated protein-1 (Keap1). Pre-administration of quercetin (40, 80 mg/kg) effectively inhibited TSN-induced liver oxidative injury and reversed the decreased expression of Nrf2 and GCLC/GCLM in vivo and in vitro. In addition, the quercetin-provided protection against TSN-induced hepatotoxicity was diminished in Nrf2 knock-out mice. In conclusion, TSN decreases cellular GSH content by reducing Nrf2-mediated GCLC/GCLM expression via decreasing Nrf2 expression. Quercetin attenuates TSN-induced hepatotoxicity by inducing the Nrf2/GCL/GSH antioxidant signaling pathway. This study implies that inducing Nrf2 activation may be an effective strategy to prevent TSN-induced hepatotoxicity.

中文翻译：

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槲皮素通过诱导Nrf2 / GCL / GSH抗氧化剂信号传导通路来减轻过头丹宁诱导的肝毒性。

Toosendanin（TSN）是Toosendan Fructus和Meliae Cortex（两种常用中药）中的主要活性化合物。据报道，TSN可以诱导肝毒性，但其机制尚不清楚。在这项研究中，我们证明了核因子红系2相关因子2（Nrf2）在预防TSN诱导的小鼠和人类正常肝L-02细胞肝毒性中的关键作用。在小鼠中，给予TSN（10 mg / kg）诱发的急性肝损伤，其血清丙氨酸/天冬氨酸转氨酶（ALT / AST）和碱性磷酸酶（ALP）活性以及总胆红素（TBiL）含量以及组织学检查结果均得到证实变化。此外，TSN显着增加了肝脏活性氧（ROS）和丙二醛（MDA）的水平，并降低了肝脏谷胱甘肽（GSH）含量和Nrf2表达。在L-02细胞中 TSN（2μM）时间依赖性地降低了谷氨酸-半胱氨酸连接酶（GCL）的活性和GCL催化/修饰亚基（GCLC / GCLM）的细胞表达。此外，TSN减少细胞GSH含量和增加的ROS形成，并随时间减少Nrf2表达，并增加Nrf2抑制剂蛋白kelch样ECH相关蛋白1（Keap1）的表达。槲皮素（40，80 mg / kg）的预先给药有效抑制了TSN诱导的肝脏氧化损伤，并在体内和体外逆转了Nrf2和GCLC / GCLM表达的下降。此外，在Nrf2基因敲除小鼠中，槲皮素对TSN诱导的肝毒性的保护作用减弱。总之，TSN通过降低Nrf2表达来降低Nrf2介导的GCLC / GCLM表达，从而降低细胞GSH含量。槲皮素通过诱导Nrf2 / GCL / GSH抗氧化剂信号传导途径来减轻TSN诱导的肝毒性。这项研究表明，诱导Nrf2激活可能是预防TSN诱导的肝毒性的有效策略。