Inflammatory stress exacerbates lipid accumulation in hepatic cells and fatty livers of apolipoprotein E knockout mice
Inflammatory stress exacerbates lipid accumulation in hepatic cells and fatty livers of apolipoprotein E knockout mice
复制标题
炎症应激加剧载脂蛋白E基因敲除小鼠肝细胞和脂肪肝中的脂质积累
DOI：
10.1002/hep.22423
复制
发表时间：
2008-09-01
期刊：
影响因子：
13.5
通讯作者：
Varghese, Zac
中科院分区：
文献类型：
--
作者：
Ma, Kun L.;Ruan, Xiong Z.;Varghese, Zac
非酒精性脂肪性肝病（NAFLD）的流行理论是“两次打击”假说。第一次打击主要包括脂质积聚，第二次是随后的全身炎症。本研究旨在探讨炎症应激是否加重肝脏脂质蓄积及其机制。我们使用白细胞介素-1 β（IL-1 β）和肿瘤坏死因子α（TNF-α）刺激人肝母细胞瘤细胞系（HepG 2）细胞和原代肝细胞在体外，和酪蛋白注射载脂蛋白E基因敲除小鼠在体内诱导炎症应激。通过组织化学染色和定量细胞内胆固醇测定来检查炎症应激对胆固醇积聚的影响。通过实时聚合酶链反应（PCR）和蛋白质印迹检测参与胆固醇转运的分子的基因和蛋白质表达。酶联免疫吸附试验测定载脂蛋白E基因敲除小鼠血浆中细胞因子的产生。我们的研究结果表明，炎症应激增加胆固醇积累在肝细胞和载脂蛋白E基因敲除小鼠的肝脏。进一步分析表明，炎症应激增加了低密度脂蛋白（LDL）受体（LDLr）、固醇调节元件结合蛋白（SREBP）裂解激活蛋白（SCAP）和SREBP-2的表达。共聚焦显微镜观察显示，IL-1 β可增加HepG 2细胞中SCAP/SREBP-2复合物从内质网（ER）向高尔基体的移位，从而激活LDLr基因的转录。酪蛋白注射诱导的IL-1 β、TNF-α和全身炎症也抑制三磷酸腺苷结合盒转运蛋白A1（ABCA 1）、过氧化物酶体增殖物激活受体-α（PPAR-a）和肝X受体-α（LXR α）的表达。这种抑制作用可能导致胆固醇流出减少。结论：炎症应激在体内和体外上调LDL r介导的胆固醇流入并下调ABCA 1介导的胆固醇流出。这可能会通过破坏胆固醇运输控制来加剧NAFLD的进展，特别是在肝损伤的第二次打击阶段。
The prevailing theory in non-alcoholic fatty liver disease (NAFLD) is the "two-hit" hypothesis. The first hit mainly consists of lipid accumulation, and the second is subsequent systemic inflammation. The current study was undertaken to investigate whether inflammatory stress exacerbates lipid accumulation in liver and its underlying mechanisms. We used interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha) stimulation in human hepatoblastoma cell line (HepG2) cells and primary hepatocytes in vitro, and casein injection in apolipoprotein E knockout mice in vivo to induce inflammatory stress. The effects of inflammatory stress on cholesterol accumulation were examined by histochemical staining and a quantitative intracellular cholesterol assay. The gene and protein expressions of molecules involved in cholesterol trafficking were examined by real-time polymerase chain reaction (PCR) and western blot. Cytokine production in the plasma of apolipoprotein E knockout mice was measured by enzyme-linked immunosorbent assay. Our results showed that inflammatory stress increased cholesterol accumulation in hepatic cells and in the livers of apolipoprotein E knockout mice. Further analysis showed that inflammatory stress increased the expression of low-density lipoprotein (LDL) receptor (LDLr), sterol regulatory element-binding protein (SREBP) cleavage activating protein (SCAP), and SREBP-2. Confocal microscopy showed that IL-1 beta increased the translocation of SCAP/SREBP-2 complex from endoplasmic reticulum (ER) to Golgi in HepG2 cells, thereby activating LDLr gene transcription. IL-1 beta, TNF-a, and systemic inflammation induced by casein injection also inhibited expression of adenosine triphosphate-binding cassette transporter A1 (ABCA1), peroxisome proliferator-activated receptor-a (PPAR-a), and liver X receptor-a (LXR alpha). This inhibitory effect may cause cholesterol efflux reduction. Conclusion: Inflammatory stress up-regulates LDLr-mediated cholesterol influx and down-regulates ABCA1-mediated cholesterol efflux in vivo and in vitro. This may exacerbate the progression of NAFLD by disrupting cholesterol trafficking control, especially during the second hit phase of liver damage.