Escoll Pedro, del Fresno Carlos, García Lourdes, Vallés Gema, Lendínez Manuel J, Arnalich Francisco, López-Collazo Eduardo
Research Unit, Department of Surgical Research, La Paz Hospital, Madrid 28046, Spain.
Biochem Biophys Res Commun. 2003 Nov 14;311(2):465-72. doi: 10.1016/j.bbrc.2003.10.019.
The exposure of human monocytes to the gram-negative endotoxin LPS provokes them to enter a transient state in which they are refractory to further stimulation by LPS. This phenomenon is known as 'endotoxin tolerance' (ET) and it is characterized by a decrease in leukocyte proinflammatory cytokine production in response to LPS. In the present study, we have analyzed the expression of IRAK-M mRNA and protein in a human model of ET using human monocytes isolated from peripheral blood. In these monocyte cultures, IRAK-M mRNA was expressed 6h after stimulation with different doses of LPS. However, endotoxin pretreatment induced a more immediate up-regulation of IRAK-M gene expression, transcripts appearing only one hour after a second LPS-challenge, and the production of high levels of IRAK-M protein in these tolerant monocytes. We also analyzed the response of monocytes isolated from septic patients within a temporal tolerance timeframe when stimulated ex vivo with LPS. In contrast to monocytes from healthy volunteers and patients outside of the tolerance timeframe, monocytes from septic patients rapidly expressed IRAK-M mRNA when stimulated with LPS ex vivo. Moreover, the expression of IRAK-M mRNA was more rapidly induced in the presence of a PI3K inhibitor, suggesting a connection between these two kinases. Thus, our data indicate that IRAK-M could play a pivotal role in the process of ET in human monocytes and provide evidence that PI3K is involved in regulating its expression.
人类单核细胞暴露于革兰氏阴性内毒素脂多糖（LPS）会促使它们进入一种短暂状态，在此状态下它们对LPS的进一步刺激具有抗性。这种现象被称为“内毒素耐受”（ET），其特征是白细胞促炎细胞因子对LPS刺激的产生减少。在本研究中，我们使用从外周血分离的人类单核细胞，在人类ET模型中分析了IRAK - M mRNA和蛋白的表达。在这些单核细胞培养物中，用不同剂量的LPS刺激6小时后可检测到IRAK - M mRNA的表达。然而，内毒素预处理诱导了IRAK - M基因表达更迅速的上调，转录本在第二次LPS刺激后仅1小时就出现了，并且在这些耐受的单核细胞中产生了高水平的IRAK - M蛋白。我们还分析了在时间耐受范围内从脓毒症患者分离的单核细胞在体外受到LPS刺激时的反应。与来自健康志愿者和不在耐受时间范围内的患者的单核细胞不同，来自脓毒症患者的单核细胞在体外受到LPS刺激时迅速表达IRAK - M mRNA。此外，在存在PI3K抑制剂的情况下，IRAK - M mRNA的表达诱导得更快，这表明这两种激酶之间存在联系。因此，我们的数据表明IRAK - M可能在人类单核细胞的ET过程中起关键作用，并提供了PI3K参与调节其表达的证据。
