Hayes M P, Freeman S L, Donnelly R P
Division of Cytokine Biology, Food and Drug Administration, Bethesda, MD 20892, USA.
Cytokine. 1995 Jul;7(5):427-35. doi: 10.1006/cyto.1995.0058.
The induction of cytokine expression in monocytes/macrophages by bacterial endotoxin or lipopolysaccharide is a critical, highly regulated host defence response. The augmentation of LPS responses by interferon gamma (IFN-gamma), referred to as priming, is well established. However, the mechanism(s) by which priming occurs is poorly defined. Using tumour necrosis factor (TNF) induction as a model, experiments were designed to analyse in detail the priming effect on the LPS response in human monocytes. Priming by IFN-gamma was primarily manifested at the level of TNF mRNA accumulation. IFN-gamma pre-treatment affected the magnitude rather than the sensitivity of the LPS response. Priming occurred after several hours of treatment, and the primed state was induced by either IFN-gamma or GM-CSF, but not M-CSF. Primed monocytes transcribed TNF mRNA at a higher rate than freshly isolated monocytes upon activation with LPS. The increased transcriptional rate correlated with a marked increase in nuclear factor-kappa B activity in these cells as determined by electrophoretic mobility shift assay using a consensus NF-kappa B oligonucleotide. An additional significant finding was than TNF mRNA induced in primed cells was much more stable than in unprimed cells (T1/2 increased 6-8-fold). Consistent with the increased mRNA stability, the duration of mRNA accumulation was longer following LPS stimulation in primed monocytes, in addition to being of greater magnitude. Finally, primed and unprimed cells possessed a differential sensitivity to the kinase inhibitor H-89. H-89 substantially suppressed LPS-induced TNF mRNA accumulation in unprimed cells, but had no effect on primed monocytes following LPS stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
细菌内毒素或脂多糖诱导单核细胞/巨噬细胞中细胞因子表达是一种关键的、高度调控的宿主防御反应。干扰素γ（IFN-γ）增强脂多糖（LPS）反应，即所谓的致敏作用，已得到充分证实。然而，致敏发生的机制尚不清楚。以肿瘤坏死因子（TNF）诱导为模型，设计实验详细分析致敏对人单核细胞LPS反应的影响。IFN-γ致敏主要表现在TNF mRNA积累水平。IFN-γ预处理影响LPS反应的幅度而非敏感性。致敏在处理数小时后发生，IFN-γ或粒细胞-巨噬细胞集落刺激因子（GM-CSF）均可诱导致敏状态，但巨噬细胞集落刺激因子（M-CSF）不能。致敏单核细胞在用LPS激活后转录TNF mRNA的速率高于新鲜分离的单核细胞。转录速率增加与这些细胞中核因子-κB活性显著增加相关，这是通过使用共有NF-κB寡核苷酸的电泳迁移率变动分析确定的。另一个重要发现是，致敏细胞中诱导的TNF mRNA比未致敏细胞中的稳定得多（半衰期增加6至8倍）。与mRNA稳定性增加一致，致敏单核细胞在LPS刺激后mRNA积累的持续时间更长，且幅度更大。最后，致敏和未致敏细胞对激酶抑制剂H-89具有不同的敏感性。H-89可显著抑制未致敏细胞中LPS诱导的TNF mRNA积累，但对LPS刺激后的致敏单核细胞无影响。（摘要截短于250字）
