Regulation of lipopolysaccharide-induced interleukin-12 production by activation of repressor element GA-12 through hyperactivation of the ERK pathway
Regulation of lipopolysaccharide-induced interleukin-12 production by activation of repressor element GA-12 through hyperactivation of the ERK pathway
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DOI：
10.1128/cvi.00075-06
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发表时间：
2006-08-01
影响因子：
--
通讯作者：
Hirai, Yoshikazu
中科院分区：
文献类型：
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作者：
Saito, Shinji;Matsuura, Motohiro;Hirai, Yoshikazu
白细胞介素-12（IL-12）作为脂多糖（LPS）介导剂在先天性免疫和适应性免疫中发挥作用。我们研究了LPS诱导的小鼠巨噬细胞产生IL-12的调节。在对LPS的反应中，腹腔巨噬细胞产生生物活性IL-12 p70，一种亚基的异源二聚体（p40/p35），但巨噬细胞系如J774.1和RAW 264.7没有。在两种细胞系中p35亚基的诱导受损，并且在RAW 264.7细胞中观察到p40诱导的额外损伤。这些结果表明，一些负调控机制对LPS诱导的IL-12 p40的生产是组成性的RAW 264.7细胞，而不是在其他类型的细胞功能。在LPS刺激的RAW 264.7细胞中检测到GA-12（IL-12 p40的阻遏元件）的激活，而不是启动子元件（如NF-κ B、AP-1和IRF-1的结合位点）的抑制，伴随着细胞外信号相关激酶（ERK）的过度激活。当ERK激活被抑制剂（U0126）抑制时，p40的产生从检测不到上升到实质性水平，GA-12激活降低。在腹腔巨噬细胞中，用高剂量LPS刺激减少了p40的产生，增强了ERK的活化。用佛波醇肉豆蔻酸酯乙酸酯预处理细胞以增强ERK活化，从而降低了响应于最佳LPS刺激的p40产生。总之，这些结果表明ERK途径的超活化在GA-12活化的上游信号传导中起作用，导致小鼠巨噬细胞中IL-12 p40产生的抑制。
Interleukin-12 (IL-12) functions as a representative lipopolysaccharide (LPS) mediator in both innate and adaptive immunity. We investigated the regulation of LPS-induced IL-12 production by mouse macrophages. In response to LPS, peritoneal macrophages produced bioactive IL-12 p70, a heterodimer (p40/p35) of subunits, but macrophage lines such as J774.1 and RAW264.7 did not. Induction of the p35 subunit was impaired in both cell lines, and additional impairment of p40 induction was observed in RAW264.7 cells. These results suggest that some negative regulatory mechanisms against LPS-induced IL-12 p40 production are constitutively functioning in RAW264.7 cells but not in the other types of cells. Activation of GA-12 (a repressor element of IL-12 p40), rather than suppression of promoter elements, such as binding sites for NF-kappa B, AP-1, and IRF-1, was detected in LPS-stimulated RAW264.7 cells, accompanying hyperactivation of extracellular signal-related kinase (ERK). When ERK activation was suppressed by an inhibitor (U0126), production of p40 rose from an undetectable to a substantial level and GA-12 activation decreased. In peritoneal macrophages, stimulation with a high dose of LPS reduced p40 production with enhanced activation of ERK. Pretreatment of the cells with phorbol myristate acetate to enhance ERK activation reduced p40 production in response to the optimal LPS stimulation. Taken together, these results demonstrate that hyperactivation of the ERK pathway plays a role in upstream signaling for the activation of GA-12, leading to the repression of IL-12 p40 production in mouse macrophages.