Endotoxin downregulates rat hepatic ntcp gene expression via decreased activity of critical transcription factors
Endotoxin downregulates rat hepatic ntcp gene expression via decreased activity of critical transcription factors
复制标题
DOI：
10.1172/jci1680
复制
发表时间：
1998-05-15
影响因子：
15.9
通讯作者：
Karpen, SJ
中科院分区：
文献类型：
--
作者：
Trauner, M;Arrese, M;Karpen, SJ
在脓毒症期间，胆汁酸通过肝基底外侧膜的钠依赖性摄取迅速而深刻地减少，从而促成脓毒症相关胆汁淤积的发病机制。这种效应是由内毒素或效应细胞因子介导的，它们减少了几种肝胆转运蛋白的表达，包括钠依赖性胆汁酸转运蛋白基因ntcp。我们在这里测试的假设，内毒素治疗导致受损的ntcp启动子反式作用因子的结合活性，导致ntcp mRNA表达的减少。内毒素管理后，ntcp mRNA水平达到最低点，16小时，和核运行的分析表明显着减少ntcp基因转录。在16小时后，核结合活性的两个关键因素，反式激活ntcp启动子，肝细胞核因子（HNF）1和足迹B结合蛋白（Fp B RP），分别下降到44和47%的预处理水平，而其他已知的ntcp启动子反式激活因子，信号转导和转录激活因子5的水平，不受影响。与此相反，通用炎症反应因子核因子κ B和活化蛋白I均显著上调。在连续时间点获得的核提取物的检查显示，HNF 1和FpB BP的核活性的最大降低先于ntcp mRNA表达的最低点6-10 h。此外，在48小时观察到ntcp mRNA水平恢复之前，这两种核因子恢复到正常水平。由于HNF 1 α mRNA水平在所有时间点均未改变，因此HNF 1可能受内毒素的转录后调节，我们的结论是，内毒素下调ntcp基因表达是在转录水平介导的，通过串联减少两个关键的核结合活性，转录因子这些发现为脓毒症期间肝胆转运蛋白的协同下调提供了新的见解。
Sodium-dependent uptake of bile acids across the hepatic basolateral membrane is rapidly and profoundly diminished during sepsis, thus contributing to the pathogenesis of sepsis-associated cholestasis. This effect is mediated by endotoxin or effector cytokines, which reduce expression of several hepatobiliary transporters, including the sodium-dependent bile acid transporter gene, ntcp. We test here the hypothesis that endotoxin treatment leads to impaired binding activity of ntcp promoter trans-acting factors, resulting in reduction of ntcp mRNA expression. After endotoxin administration, ntcp mRNA levels reached their nadir by 16 h, and nuclear run-on assays demonstrated a marked reduction in ntcp gene transcription. At 16 h after treatment, nuclear binding activities of two key factors that transactivate the ntcp promoter, hepatocyte nuclear factor (HNF) 1 and Footprint B binding protein (FpB RP), decreased to 44 and 47% of pretreatment levels, respectively, while levels of the other known ntcp promoter transactivator, signal transducer and activator of transcription 5, were unaffected. In contrast, the universal inflammatory response factors nuclear factor kappa B and activating protein I were both upregulated significantly. Examination of nuclear extracts obtained at sequential time points revealed that the maximal decrease in nuclear activities of both HNF1 and FpB BP preceded the nadir of ntcp mRNA expression by 6-10 h. Furthermore, those two nuclear factors returned towards normal levels before the recovery of ntcp mRNA levels observed by 48 h, Since HNF1 alpha mRNA levels were unchanged at all time points, HNF1 is likely to be regulated posttranscriptionally by endotoxin, We conclude that the downregulation of ntcp gene expression by endotoxin is mediated at the level of transcription through tandem reductions in the nuclear binding activity of two critical transcription factors. These findings provide new insight into the coordinated downregulation of hepatobiliary transporters during sepsis.