内毒素抑制肝细胞白蛋白表达的分子机制研究

Study on molecular mechanisms of indirect suppression of albumin mRNA expression of hepatocytes by lipopolysaccharide in rat

目的 观察内毒素抑制大鼠肝细胞白蛋白表达的分子机制。方法 采用1 mg/L内毒素刺激大鼠肝细胞24 h。使用20、40和100 μmol/L的蛋白合成抑制剂环己酰亚胺预处理30 min。用逆转录-聚合酶链反应检测不同浓度环己酰亚胺预处理后肝细胞白蛋白的表达,同时检测肝细胞上清中白细胞介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)的水平。结果 内毒素刺激肝细胞24 h后白蛋白mRNA表达明显下降;环己酰亚胺预处理可以完全阻断白蛋白mRNA表达的下降,而且这种阻断作用存在剂量依赖性;同时内毒素刺激后肝细胞上清中IL-6和TNF-α水平较对照组明显升高(P均<0.05),环己酰亚胺预处理后两者水平明显下降(P均<0.05)。结论 内毒素通过抑制细胞因子IL-6和TNF-α释放间接抑制大鼠肝细胞白蛋白mRNA的表达。

Objective To explore the molecular mechanisms of relationship between the decreased expresssion of albumin gene of the cultured hepatocytes by lipopolysaccharide(LPS) and cytokines. Methods As an inhibitor of protein synthesis, cycloheximide (CHX) could inhibit the LPS - induced synthesis of cytokines. Therefore,the culture system pretreated with CHX could exclude the influence of cytokines on the regulation of albumin gene expression, then it might prove that LPS induced down - regulation of expression of albumin gene was a through cytokine -dependent pathway. The concentrations of interleukin(IL - 6) and tumor necrosis factor -α(TNF -α) in the supernatant were also assayed. Results The expression of albumin mRNA is inhibited significantly by LPS. CHX could block the path way of LPS - induced down - regulation of expression of albumin gene at least at the transcription level. And the prevention was in a dose - related manner. The increase of IL - 6 and TNF - a induced by LPS was inhibited by CHX (both P < 0. 05). Conclusion The results suggest that LPS can indirectly inhibit the transcription of albuminogene through cytokines such as IL - 6 and TNF -α.