| Objectives: To induce the chronic, low grade and systemic inflammatory model using casein injection in C57BL/6J mice.Methods: Eight week-old male C57BL/6J mice were randomly assigned to be fed with a normal chow diet (NCD, n=6) or NCD plus subcutaneous injection of 0.5 mL 10% casein (NCD+Casein, n=6) every other day or a high fat diet (15% fat, 1.25% cholesterol, 0.5% cholic acid) (HFD, n=6) or HFD plus subcutaneous injection of 0.5 mL 10% casein (HFD+Casein, n=6) every other day. Finally, mice were killed after 18 weeks. Blood samples were taken for cytokines assay, and the tissues were collected for further detection. The serum levels of IL-6, SAA and TNFαwere measured by kits.Results: Serum levels of IL-6, SAA and TNFαsignificantly increased in the casein-injected mice fed with either normal chow diet or high fat diet compared with their respective controls. Besides,there was no significant difference statistically in comparison between NCD and HFD.Conclusion: After the casein injection for 18 weeks,it produced the chronic, low grade and systemic inflammation in C57BL/6J mice.The inflammatory model had established successfully.Objectives: To investigate if inflammatory stress disrupte hepatic cholesterol export and lead to cholesterol accumulation in C57BL/6J mice and HepG2 cells.Methods: We used casein injection in C57BL/6J mice in vivo, tumor necrosis factor alpha (TNFα) stimulation in human hepatoblastoma cell line (HepG2 cells) in vitro to induce inflammatory stress. HepG2 cells were cultured and incubated with serum free medium (Control) or Control plus 20ng/mL TNFα(TNFα) or Control plus 100μg/mL LDL (LDL) or 20 ng/mL TNFαplus 100μg/mL LDL (LDL +TNFα). The lipid accumulation was observed by HE and Oil Red O staining. The intracellular and serum cholesterol level was examined by quantitative analysis. 3[H] cholesterol assay by liquid scintillation counter was performed to evaluate the efflux of cholesterol.Bile acid level was quantified by colorimetric analysis.Results: HE and Oil Red O staining showed inflammation aggravate lipid accumulation in casein-injection mice and TNFα-stimulation HepG2 cells compared with their respective controls. The intracellular cholesterol content increased in HFD/LDL group compared with NCD/Control, and inflammatory stress increased the content more significantly. High fat diet increased the serum cholesterol level, but casein injection reduced the addition. In HepG2 cells TNFαcould reduced cholesterol efflux and LDL loading increased it compared with Control, and cholesterol efflux in LDL plus TNFαgroup obviously decreased than LDL only group. In C57BL/6J mice, bile acid synthesis in gall bladder, liver and small intestine was increased in HFD group. However, the enhanced effect was overridden by inflammatory stress in the mice fed with HFD plus casein injection.Conclusion: The inflammatory stress can exacerbate the hepatic cholesterol accumulation through reducing cholesterol efflux and bile acid synthesis. Objectives: To investigate whether inflammation disrupts LXRαmediated cholesterol export in the livers of C57BL/6J mice and HepG2 cells and explored the molecular mechanisms.Methods: The mRNA and protein expression of PPARα,PPARγ,LXRα,ABCA1,CYP7A1 was examined by real-time polymerase chain reaction (real-time PCR) and western blotting.Results: We demonstrated that inflammatory stress inhibited PPARα,PPARγ,LXRα,ABCA1,CYP7A1 mRNA and protein expression in livers of C57BL/6J mice and in HepG2 cells. High fat diet in mice and LDL loading in HepG2 cells increased the mRNA and protein expression of the above genes. However, the enhanced effect was overridden by inflammatory stress both in vivo and in vitro.Conclusion: Inflammatory stress down-regulated the mRNA and protein expression of PPARα,PPARγ,LXRα,ABCA1,CYP7A1 which were the main factors in cholesterol efflux and bile acid synthesis.
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