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Expression of CD14 by Hepatocytes: Upregulation by Cytokines during Endotoxemia

机译：肝细胞表达CD14：内毒素血症期间细胞因子上调

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Studies were undertaken to examine hepatocyte CD14 expression during endotoxemia. Our results show that lipopolysaccharide (LPS) treatment in vivo caused a marked upregulation in CD14 mRNA and protein levels in rat hepatocytes. Detectable increases in mRNA were seen as early as 1.5 h after LPS treatment; these increases peaked at 20-fold by 3 h and returned to baseline levels by 24 h. In situ hybridization localized the CD14 mRNA expression to hepatocytes both in vitro and in vivo. Increases in hepatic CD14 protein levels were detectable by 3 h and peaked at 12 h. Hepatocytes from LPS-treated animals expressed greater amounts of cell-associated CD14 protein, and more of the soluble CD14 was released by hepatocytes from LPS-treated rats in vitro. The increases in hepatocyte CD14 expression during endotoxemia occurred in parallel to increases of CD14 levels in plasma. To provide molecular identification of the hepatocyte CD14, we cloned the rat liver CD14 cDNA. The longest clone consists of a 1,591-bp insert containing a 1,116-bp open reading frame. The deduced amino acid sequence is 372 amino acids long, has 81.8 and 62.8% homology to the amino acid sequences of mouse and human CD14, respectively, and is identical to the rat macrophage CD14. The expressed CD14 protein from this clone was functional, as indicated by NF-κB activation in response to LPS and fluorescein isothiocyanate-LPS binding in CHO cells stably transfected with rat CD14. A nuclear run-on assay showed that CD14 transcription rates were significantly increased in hepatocytes from LPS-treated animals, indicating that the upregulation in CD14 mRNA levels observed in rat hepatocytes after LPS treatment is dependent, in part, on increased transcription. In vitro and in vivo experiments indicated that interleukin-1β and/or tumor necrosis factor α participate in the upregulation of CD14 mRNA levels in hepatocytes. Our data indicate that hepatocytes express CD14 and that hepatocyte CD14 mRNA and protein levels increase rapidly during endotoxemia. Our observations also support the idea that soluble CD14 is an acute-phase protein and that hepatocytes could be a source for soluble CD14 production.
机译：进行研究以检查内毒素血症期间肝细胞CD14的表达。我们的结果表明，体内脂多糖（LPS）处理可导致大鼠肝细胞CD14 mRNA和蛋白质水平显着上调。早在LPS处理后1.5小时，即可观察到mRNA的可检测的增加。这些增加在3个小时达到20倍的峰值，并在24个小时回到基线水平。原位杂交在体外和体内都将CD14 mRNA表达定位于肝细胞。肝CD14蛋白水平的增加在3 h之前就可以检测到，并在12 h达到峰值。经LPS处理的动物的肝细胞表达更多的细胞相关CD14蛋白，并且更多的可溶性CD14由LPS处理的大鼠的肝细胞在体外释放。内毒素血症期间肝细胞CD14表达的增加与血浆CD14水平的增加平行发生。为了提供肝细胞CD14的分子鉴定，我们克隆了大鼠肝脏CD14 cDNA。最长的克隆由一个1,591 bp的插入片段组成，其中包含1,116 bp的开放阅读框。推导的氨基酸序列长372个氨基酸，分别与小鼠和人CD14的氨基酸序列有81.8和62.8％的同源性，并且与大鼠巨噬细胞CD14相同。从该克隆表达的CD14蛋白具有功能性，如NF-κB活化表明，在稳定转染大鼠CD14的CHO细胞中，LPS和异硫氰酸荧光素-LPS结合荧光素。核运行试验表明，LPS处理的动物的肝细胞中CD14转录速率显着增加，这表明LPS处理后在大鼠肝细胞中观察到的CD14 mRNA水平上调部分取决于转录的增加。体外和体内实验表明，白介素-1β和/或肿瘤坏死因子α参与肝细胞CD14 mRNA水平的上调。我们的数据表明，内毒素血症期间肝细胞表达CD14，并且肝细胞CD14 mRNA和蛋白水平迅速增加。我们的观察结果也支持可溶性CD14是一种急性期蛋白，肝细胞可能是可溶性CD14产生的来源这一观点。

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