Department of Intensive Care Medicine, Shanghai Jiaotong University Affiliated Sixth People's Hospital, No. 222 Huanhuxisan Road, Pudong, Shanghai 201306, China.
Department of Hyperbaric Oxygen Therapy, Shanghai Jiaotong University Affiliated Sixth People's Hospital, No. 222 Huanhuxisan Road, Pudong, Shanghai 201306, China.
Biomed Pharmacother. 2017 Oct;94:140-149. doi: 10.1016/j.biopha.2017.07.074. Epub 2017 Jul 28.
Oxidative stress is a leading cause to liver injury. Rac2 is a Ras-associated guanosine triphosphatase, an important molecule modulating a large number of cells and involved in the regulation of reactive oxygen species (ROS). For the study described here, we supposed that Rac2 knockout protects mice against CCl-induced acute liver injury. We found that Rac2 expressed highly in CCl-induced liver tissues. CCl-treated Rac2 knockout (Rac2-/-) mice had reduced CD24 levels and steatosis. In addition, CCl-induced high expression of pro-inflammatory cytokines and chemokine were reversed by Rac2 deficiency compared to CCl-treated wild type (WT) mice. We also found that fibrosis-related signals of MMP-9, MMP-2 and TGF-β1 were also down-regulated in Rac2 knockout mice induced by CCl. Significantly, oxidative stress induced by CCl was also suppressed owing to the lack of Rac2, evidenced by enhanced superoxide dismutase (SOD) activity, and reduced malondialdehyde (MDA) levels, superoxide radical, HO, xanthine oxidase (XO), xanthine dehydrogenase (XDH) and XO/XDH ratio. Moreover, c-Jun N-terminal protein kinase mitogen-activated protein kinases (JNK MAPK) was activated by CCl, which was reversed in the liver of Rac2-/- mice through western blot and immunohistochemical analysis. In vitro, endotoxin (LPS) was treated to hepatocytes isolated from WT mice and Rac2-/- mice. The data further confirmed the role of Rac2 deficiency suppressed pro-inflammatory cytokines and chemokine, as well as fibrosis-related signals. Of note, production of ROS induced by LPS was reduced in Rac2-/- cells, accompanied with enhanced SOD1, SOD2 and reduced XO and phosphorylated-JNK expressions. Our results indicated that Rac2 played an essential role in acute liver injury induced by CCl, providing the compelling information of the effects of Rac2 on liver injury, and revealing a novel regulatory mechanism for acute liver injury.
氧化应激是肝损伤的主要原因。Rac2 是一种 Ras 相关鸟苷三磷酸酶，是调节大量细胞的重要分子，参与活性氧（ROS）的调节。在本文所述的研究中，我们假设 Rac2 敲除可保护小鼠免受 CCl 引起的急性肝损伤。我们发现 Rac2 在 CCl 诱导的肝组织中表达水平较高。与 CCl 处理的野生型（WT）小鼠相比，CCl 处理的 Rac2 敲除（Rac2-/-）小鼠的 CD24 水平降低且脂肪变性减少。此外，与 CCl 处理的 WT 小鼠相比，Rac2 缺失可逆转 CCl 诱导的促炎细胞因子和趋化因子的高表达。我们还发现，在 CCl 诱导的 Rac2 敲除小鼠中，纤维化相关信号 MMP-9、MMP-2 和 TGF-β1 也下调。值得注意的是，由于缺乏 Rac2，CCl 诱导的氧化应激也受到抑制，证据是超氧化物歧化酶（SOD）活性增强，丙二醛（MDA）水平降低，超氧自由基、HO、黄嘌呤氧化酶（XO）、黄嘌呤脱氢酶（XDH）和 XO/XDH 比值降低。此外，CCl 激活 c-Jun N-末端蛋白激酶丝裂原活化蛋白激酶（JNK MAPK），通过 Western blot 和免疫组织化学分析，在 Rac2-/- 小鼠肝脏中得到逆转。在体外，用内毒素（LPS）处理从 WT 小鼠和 Rac2-/- 小鼠分离的肝细胞。数据进一步证实了 Rac2 缺失抑制促炎细胞因子和趋化因子以及纤维化相关信号的作用。值得注意的是，LPS 诱导的 ROS 产生在 Rac2-/- 细胞中减少，同时 SOD1、SOD2 表达增强，XO 和磷酸化-JNK 表达减少。我们的结果表明，Rac2 在 CCl 诱导的急性肝损伤中发挥重要作用，为 Rac2 对肝损伤的影响提供了有力的信息，并揭示了急性肝损伤的新调控机制。
