Frede Stilla, Stockmann Christian, Freitag Patricia, Fandrey Joachim
Institut für Physiologie, Universität Duisburg-Essen Hufelandstrasse 55, D-45122 Essen, Federal Republic of Germany.
Biochem J. 2006 Jun 15;396(3):517-27. doi: 10.1042/BJ20051839.
Inflammatory mediators activate the transcriptional complex HIF-1 (hypoxia-inducible factor-1), the key regulator of hypoxia-induced gene expression. Here we report that bacterial LPS (lipopolysaccharide) induces HIF-1alpha mRNA expression and HIF-1alpha protein accumulation in human monocytes as well as in non-differentiated and differentiated cells of the human monocytic cell line THP-1 under normoxic conditions. LPS and hypoxia synergistically activated HIF-1. Whereas LPS increased HIF-1alpha mRNA expression through activation of a NF-kappaB (nuclear factor kappaB) site in the promoter of the HIF-1alpha gene, hypoxia post-translationally stabilized HIF-1alpha protein. HIF-1alpha activation was followed by increased expression of the HIF-1 target gene encoding ADM (adrenomedullin). Knocking down HIF-1alpha by RNA interference significantly decreased ADM expression, which underlines the importance of HIF-1 for the LPS-induced ADM expression in normoxia. Simultaneously with HIF-1 activation, an increase in p44/42 MAPK (mitogen-activated protein kinase) phosphorylation was observed after incubation with LPS. In cells pretreated with the p44/42 MAPK inhibitor PD 98059 or with RNAi (interfering RNA) directed against p44/42 MAPK, LPS-induced HIF-1alpha accumulation and ADM expression were significantly decreased. From these results we conclude that LPS critically involves the p44/42 MAPK and NF-kappaB pathway in the activation of HIF-1, which is an important transcription factor for LPS-induced ADM expression.
炎症介质激活转录复合物HIF-1（缺氧诱导因子-1），它是缺氧诱导基因表达的关键调节因子。在此我们报告，在常氧条件下，细菌脂多糖（LPS）可诱导人单核细胞以及人单核细胞系THP-1的未分化和分化细胞中HIF-1α mRNA表达及HIF-1α蛋白积累。LPS与缺氧协同激活HIF-1。LPS通过激活HIF-1α基因启动子中的NF-κB（核因子κB）位点来增加HIF-1α mRNA表达，而缺氧则在翻译后使HIF-1α蛋白稳定。HIF-1α激活后，编码肾上腺髓质素（ADM）的HIF-1靶基因表达增加。通过RNA干扰敲低HIF-1α可显著降低ADM表达，这突出了HIF-1在常氧下LPS诱导的ADM表达中的重要性。与HIF-1激活同时，在用LPS孵育后观察到p44/42丝裂原活化蛋白激酶（MAPK）磷酸化增加。在用p44/42 MAPK抑制剂PD 98059预处理的细胞或用针对p44/42 MAPK的RNA干扰（干扰RNA）处理的细胞中，LPS诱导的HIF-1α积累和ADM表达显著降低。从这些结果我们得出结论，LPS在激活HIF-1过程中关键涉及p44/42 MAPK和NF-κB途径，而HIF-1是LPS诱导的ADM表达的重要转录因子。
