Enhanced TLR4 reactivity following injury is mediated by increased p38 activation
Enhanced TLR4 reactivity following injury is mediated by increased p38 activation
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DOI：
10.1189/jlb.1204698
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发表时间：
2005-08-01
影响因子：
5.5
通讯作者：
Lederer, JA
中科院分区：
文献类型：
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作者：
Maung, AA;Fujimi, S;Lederer, JA
严重损伤启动先天免疫系统，使Toll样受体4(TLR4)诱导巨噬细胞产生促炎细胞因子。在这项研究中，我们检测了烧伤或假手术小鼠脾巨噬细胞中TLR4信号通路的变化，以确定TLR4反应性增加的分子机制(S)。使用流式细胞术和特异性抗体，我们首先寻找损伤诱导的几个TLR相关信号分子表达水平的变化。与假巨噬细胞相比，烧伤组髓系分化主要反应蛋白88(MyD88)和白介素1受体相关蛋白-M(IRAK-M)的表达水平相似，而总p38、细胞外信号调节蛋白(ERK)、中期应激激活蛋白激酶(SAPK)/c-jun氨基末端激酶(JNK)丝裂原活化蛋白激酶(MAPKs)的表达略低。然而，使用针对这三种MAPK的磷酸化(激活)形式的抗体，我们发现烧伤小鼠巨噬细胞在内毒素(LPS)刺激下的p38活性在伤后1天和7天比假手术小鼠的细胞高一倍，而ERK和SAPK/JNK的激活仅在烧伤后第一天被增加。我们使用特异性p38抑制剂(SB203580)证实了内毒素刺激的烧伤巨噬细胞产生的肿瘤坏死因子α的增加需要p38激活。虽然我们证实烧伤后巨噬细胞表面TLR4-MD-2蛋白表达和TLR4-MD-2蛋白表达增加，但巨噬细胞表面TLR4-MD-2蛋白的表达不受烧伤影响。我们的结果表明，损伤诱导的TLR4反应性增加至少部分是通过增强p38信号通路的激活来介导的。
Severe injury primes the innate-immune system for increased Toll-like receptor 4 (TLR4)induced proinflammatory cytokine production by macrophages. In this study, we examined changes in TLR4 signaling pathways in splenic macrophages from burn-injured or sham mice to determine the molecular mechanism(s) responsible for the increased TLR4 responsiveness. Using flow cytometry and specific antibodies, we first looked for injury-induced changes in the expression levels of several TLR-associated signaling molecules. We found similar levels of myeloid differentiation primary-response protein 88 (MyD88) and interleukin-1 receptor-associated kinase-M (IRAK-M) and somewhat lower levels of total p38, extracellular signal-regulated kinase (ERK), mid stress-activated protein kinase (SAPK)/c-jun N-terminal kinase (JNK) mitogen-activated protein kinases (MAPKs) in burn compared with sham macrophages. However, with the use of antibodies specific for the phosphorylated (activated) forms of the three MAPKs, we found that macrophages from burn mice showed a twofold increase in purified lipopolysaccharide (LPS)-stimulated p38 activation as compared with cells from sham mice on days 1 and 7 post-injury, whereas ERK and SAPK/JNK activation was increased by burn injury only on day 1. Using the specific p38 inhibitor (SB203580), we confirmed that the increase in tumor necrosis factor alpha production by LPS-stimulated burn macrophages requires p38 activation. Although we demonstrated that injury increases niacropliage TLR4 mRNA expression and intracellular expression of TLR4-myeloid differentiation protein-2 (MD-2) protein, macrophage cell-surface expression of TLR4-MD-2 was not changed by burn injury. Our results suggest that the injury-induced increase in TLR4 reactivity is mediated, at least in part, by enhanced activation of the p38 signaling pathway.