Yang Yongbin, Zhao Zhanxue, Liu Yuanjun, Kang Xianjiang, Zhang Haisong, Meng Ming
College of Life Sciences, Hebei University, Baoding, China; Health Science Center, Hebei University, Baoding, China.
J Gastroenterol Hepatol. 2015 Mar;30(3):609-18. doi: 10.1111/jgh.12723.
Hepatic cirrhosis is the final stage of liver dysfunction, characterized by diffuse fibrosis, which is the main response to the liver injury. This study is to investigate the effects of ursolic acid (UA) on liver functions and fibrosis in bile duct ligation (BDL) mice and to determine the underlying mechanisms.
Cultured hepatocytes were treated with lipopolysaccharide (LPS) in the presence or absence of UA. The reactive oxygen species (ROS) level, protein levels of IκBα, iNOS and Cox-2, and NF-κB activation were detected, respectively. C57/BL6 and AMP-activated protein kinase (AMPK)α2(-/-) mice were subjected to BDL for 14 days. UA was administered by gavage. The markers of liver function and oxidative stress, and liver histopathology were analyzed after treatment.
Treatment of hepatocytes with UA dose-dependently activates AMPK, which is abolished by silence of liver kinase B1 (LKB1). LPS significantly increased ROS productions, apoptosis, NF-κB activation, and expressions of iNOS and Cox-2 in cultured hepatocytes. All these effects were blocked by co-incubation with UA. Importantly, silence of LKB1, AMPK, or iNOS/Cox-2 by small interference RNA transfection reversed UA-induced effects in cultured cells. In an animal study, 14-day BDL induced liver fibrosis and liver injury, accompanied with increased oxidative stress and protein expressions of iNOS and Cox-2 in liver. Treatment of UA significantly attenuated the BDL-induced detrimental effects in wild-type mice but not in AMPKα2(-/-) mice.
UA via LKB1-AMPK signaling offers protective effects on BDL-induced liver injury in mice, which may be related to inhibition of oxidative stress.
肝硬化是肝功能障碍的终末期，其特征为弥漫性纤维化，这是肝脏损伤的主要反应。本研究旨在探讨熊果酸（UA）对胆管结扎（BDL）小鼠肝功能和纤维化的影响，并确定其潜在机制。
在有或无UA的情况下，用脂多糖（LPS）处理培养的肝细胞。分别检测活性氧（ROS）水平、IκBα、诱导型一氧化氮合酶（iNOS）和环氧化酶-2（Cox-2）的蛋白水平以及核因子κB（NF-κB）的激活情况。将C57/BL6和AMP激活的蛋白激酶（AMPK）α2基因敲除（-/-）小鼠进行胆管结扎14天。通过灌胃给予UA。处理后分析肝功能和氧化应激标志物以及肝脏组织病理学。
用UA处理肝细胞可剂量依赖性激活AMPK，而肝脏激酶B1（LKB1）沉默可消除这种激活。LPS显著增加培养肝细胞中的ROS产生、细胞凋亡、NF-κB激活以及iNOS和Cox-2的表达。与UA共同孵育可阻断所有这些效应。重要的是，通过小干扰RNA转染沉默LKB1、AMPK或iNOS/Cox-2可逆转UA在培养细胞中诱导的效应。在动物研究中，14天的胆管结扎诱导肝纤维化和肝损伤，同时伴有肝脏氧化应激增加以及iNOS和Cox-2的蛋白表达增加。UA处理显著减轻了野生型小鼠中胆管结扎诱导的有害效应，但在AMPKα2基因敲除（-/-）小鼠中则没有。
UA通过LKB1-AMPK信号通路对胆管结扎诱导的小鼠肝损伤具有保护作用，这可能与抑制氧化应激有关。
