Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160, USA.
Toxicol Appl Pharmacol. 2012 Aug 1;262(3):321-9. doi: 10.1016/j.taap.2012.05.010. Epub 2012 May 22.
Oxidative stress and lipid accumulation play important roles in alcohol-induced liver injury. Previous reports showed that, in livers of nuclear factor erythroid 2-related factor 2 (Nrf2)-activated mice, genes involved in antioxidant defense are induced, whereas genes involved in lipid biosynthesis are suppressed. To investigate the role of Nrf2 in ethanol-induced hepatic alterations, Nrf2-null mice, wild-type mice, kelch-like ECH-associated protein 1-knockdown (Keap1-KD) mice with enhanced Nrf2, and Keap1-hepatocyte knockout (Keap1-HKO) mice with maximum Nrf2 activation, were treated with ethanol (5 g/kg, po). Blood and liver samples were collected 6h thereafter. Ethanol increased alanine aminotransferase and lactate dehydrogenase activities as well as thiobarbituric acid reactive substances in serum of Nrf2-null and wild-type mice, but not in Nrf2-enhanced mice. After ethanol administration, mitochondrial glutathione concentrations decreased markedly in Nrf2-null mice but not in Nrf2-enhanced mice. H(2)DCFDA staining of primary hepatocytes isolated from the four genotypes of mice indicates that oxidative stress was higher in Nrf2-null cells, and lower in Nrf2-enhanced cells than in wild-type cells. Ethanol increased serum triglycerides and hepatic free fatty acids in Nrf2-null mice, and these increases were blunted in Nrf2-enhanced mice. In addition, the basal mRNA and nuclear protein levels of sterol regulatory element-binding protein 1(Srebp-1) were decreased with graded Nrf2 activation. Ethanol further induced Srebp-1 mRNA in Nrf2-null mice but not in Nrf2-enhanced mice. In conclusion, Nrf2 activation prevented alcohol-induced oxidative stress and accumulation of free fatty acids in liver by increasing genes involved in antioxidant defense and decreasing genes involved in lipogenesis.
氧化应激和脂质积累在酒精性肝损伤中起重要作用。以前的报告表明，在核因子红细胞 2 相关因子 2 (Nrf2) 激活的小鼠肝脏中，抗氧化防御相关的基因被诱导，而脂质生物合成相关的基因则受到抑制。为了研究 Nrf2 在乙醇诱导的肝改变中的作用，使用 Nrf2 基因敲除（Nrf2-null）小鼠、野生型（Wild-type）小鼠、Kelch 样 ECH 相关蛋白 1 敲低（Keap1-KD）增强 Nrf2 小鼠和 Keap1 肝细胞敲除（Keap1-HKO）最大程度激活 Nrf2 小鼠给予乙醇（5g/kg，po）处理。6 小时后收集血液和肝脏样本。乙醇增加了 Nrf2 基因敲除和野生型小鼠血清中的丙氨酸转氨酶和乳酸脱氢酶活性以及硫代巴比妥酸反应物质，但在增强 Nrf2 的小鼠中没有增加。给予乙醇后，Nrf2 基因敲除小鼠的线粒体谷胱甘肽浓度显著下降，但在增强 Nrf2 的小鼠中没有下降。对来自这四种基因型小鼠的原代肝细胞进行 H2DCFDA 染色表明，Nrf2 基因敲除细胞的氧化应激水平较高，而增强 Nrf2 的细胞比野生型细胞的氧化应激水平较低。乙醇增加了 Nrf2 基因敲除小鼠的血清甘油三酯和肝游离脂肪酸，而在增强 Nrf2 的小鼠中这些增加被减弱。此外，随着 Nrf2 激活程度的增加，固醇调节元件结合蛋白 1(Srebp-1)的基础 mRNA 和核蛋白水平降低。乙醇进一步诱导 Nrf2 基因敲除小鼠的 Srebp-1 mRNA，但在增强 Nrf2 的小鼠中没有诱导。总之，Nrf2 的激活通过增加抗氧化防御相关的基因和减少脂质生成相关的基因，防止了酒精引起的氧化应激和肝内游离脂肪酸的积累。
