中文摘要：

目的：观察肿瘤坏死因子α（TNF-α）对肝x受体d（LXRα）启动子活性及其下游ATP结合盒转运蛋白（ABCAl和ABCGl）表达的影响，从而探讨TNF-d加速HepG2细胞内胆固醇积聚的分子机制。方法：构建LXRot基因的启动子表达载体，观察炎症因子TNF-α对LXRa启动子活性的影响，进一步将HepG2细胞分为对照组（contr01）、TNF-α组（20g／L）、高脂组（LDL，100mg／L）及联合处理组（TNF-α 20μg／L＋LDL100mg／L）。采用实时定量PCR和Western blotting检测LXRfct、ABCAl和ABCGl的mRNA及蛋白的表达。[3H]标记胆固醇，液体闪烁计数法检测胆固醇外流量。油红O染色和定量比色法分析细胞内胆固醇的含量。结果：成功构建LXRet启动子的萤火虫萤光素酶报告质粒，证明了该启动子有明显活性，TNF-α能明显抑制LXRa启动子的活性。进一步检测发现，和对照组相比，TNF-α下调了LXRa、ABCAl和ABCGlmRNA与蛋白表达。高脂组胆固醇外流量增加，而TNF-α组胆固醇外流量明显降低。油红0染色显示，TNF—α使细胞内脂质染色明显增加。结论：TNF-α可通过抑制LXRα启动子活性从而抑制HepG2细胞内胆固醇外流导致肝细胞内脂质异常积聚。

英文摘要：

AIM： To investigate the exacerbating effect of tumor necrosis factor alpha （TNF-α） on lipid accu- mulation in HepG2 cells by inhibiting liver X receptor alpha （LXRα） signaling pathway. METHODS： Luciferase reporter plasmid driven by the LXRtx promoter （pGL3-Basic-LXRα-P） was constructed and transfected into HepG2 cells to detect the LXRa promoter activity. HepG2 ceils were incubated with serum-free medium （control）, 20 I.Lg/L TNF-α （TNF-et）, 100 mg/L LDL （LDL） and 20 I~g/L TNF-ot plus 100 mg/L LDL （ LDL 4- TNF-α）, respectively. The effects of TNF-et on cholesterol accumulation were examined by oil red O staining and quantitative intracellular cholesterol assay. The expression of LXRot, ABCAI and ABCG1 at mRNA and protein levels was examined by real-time PCR and Western blotting. RE- SULTS ： The pGL3-Basic-LXRet-P was constructed successfully. TNF-e~ decreased the activity of lRa promoter in the ab- sence or presence of LDL. Inflammatory stress inhibited the expression of LXRet, ABCAland ABCG1 at mRNA and protein levels. The cholesterol eftlux was increased after loading of LDL, while TNF-α decreased intracellular cholesterol efflux. The results of oil red O staining and quantitative intracellular cholesterol assay demonstrated that inflammatory stress in- creased cholesterol levels in HepG2 ceils. CONCLUSION： TNF-α exacerbates the cholesterol accumulation in hepatic ceils via inhibiting LXRα promoter activity and gene expression.