Division of Clinical Pharmacology & Toxicology, Physiology and Experimental Medicine Program, Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada.
Br J Pharmacol. 2010 Nov;161(5):1111-21. doi: 10.1111/j.1476-5381.2010.00953.x.
Lithocholic acid (LCA), the most toxic bile acid, induces cholestatic liver injury in rodents. We previously showed that LCA activates the oxidative stress-responsive nuclear factor (erythroid-2 like), factor 2 (Nrf2) in cultured liver cells, triggering adaptive responses that reduce cell injury. In this study, we determined whether Nrf2 protects the liver against LCA-induced toxicity in vivo.
Nrf2 disrupted (Nrf2(-/-) ) and wild-type mice were treated with LCA (125 mg·kg(-1) body weight) to induce liver injury. Levels of mRNA, protein and function of important Nrf2 target genes coupled with liver histology and injury biomarkers of mice were examined.
In 4 day LCA treatments, we observed a significantly higher hepatic induction of Nrf2 target, cytoprotective genes including thioredoxin reductase 1, glutamate cysteine ligase subunits, glutathione S-transferases, haeme oxygenase-1 and multidrug resistance-associated proteins 3 and 4 in the wild type as compared with the Nrf2(-/-) mice. Moreover, basal and LCA-induced hepatic glutathione and activities of glutathione S-transferases and thioredoxin reductases were higher in wild-type than in Nrf2(-/-) mice. This reduced production of cytoprotective genes against LCA toxicity rendered Nrf2(-/-) mice more susceptible to severe liver damage with the presence of multifocal liver necrosis, inflamed bile ducts and elevation of lipid peroxidation and liver injury biomarkers, such as alanine aminotransferase and alkaline phosphatase.
Nrf2 plays a crucial cytoprotective role against LCA-induced liver injury by orchestrating adaptive responses. The pharmacological potential of targeting liver Nrf2 in the management of cholestatic liver diseases is proposed.
胆酸（LCA）是毒性最强的胆汁酸，可在啮齿动物中诱导胆汁淤积性肝损伤。我们之前的研究表明，LCA 在培养的肝细胞中激活氧化应激反应性核因子（红系 2 样）2（Nrf2），触发适应性反应，减少细胞损伤。在这项研究中，我们确定了 Nrf2 是否在体内保护肝脏免受 LCA 诱导的毒性。
Nrf2 敲除（Nrf2(-/-)）和野生型小鼠用 LCA（125mg·kg(-1)体重）处理以诱导肝损伤。检测小鼠的 mRNA、蛋白和重要 Nrf2 靶基因的功能，以及肝组织学和损伤生物标志物。
在 4 天的 LCA 处理中，与 Nrf2(-/-)小鼠相比，野生型小鼠肝脏中 Nrf2 靶基因，包括硫氧还蛋白还原酶 1、谷氨酸半胱氨酸连接酶亚基、谷胱甘肽 S-转移酶、血红素加氧酶-1 和多药耐药相关蛋白 3 和 4 的诱导更为显著。此外，野生型小鼠的基础和 LCA 诱导的肝内谷胱甘肽以及谷胱甘肽 S-转移酶和硫氧还蛋白还原酶的活性均高于 Nrf2(-/-)小鼠。这种对 LCA 毒性的保护性基因产生减少使 Nrf2(-/-)小鼠更容易受到多灶性肝坏死、炎症性胆管和脂质过氧化产物增加以及丙氨酸氨基转移酶和碱性磷酸酶等肝损伤生物标志物的影响。
Nrf2 通过协调适应性反应在 LCA 诱导的肝损伤中发挥关键的保护作用。提出了针对肝 Nrf2 管理胆汁淤积性肝病的药理学潜力。
