Subtilase cytotoxin enhances Escherichia coli survival in macrophages by suppression of nitric oxide production through the inhibition of NF-κB activation
Subtilase cytotoxin enhances Escherichia coli survival in macrophages by suppression of nitric oxide production through the inhibition of NF-κB activation
复制标题
枯草杆菌酶细胞毒素通过抑制 NF-κB 激活来抑制一氧化氮的产生，从而增强巨噬细胞中大肠杆菌的存活率
DOI：
10.1128/iai.00581-12
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发表时间：
2012
期刊：
影响因子：
3.1
通讯作者：
Noda M
中科院分区：
文献类型：
--
作者：
Tsutsuki H;Yahiro K;Suzuki K;Suto A;Ogura K;Nagasawa S;Ihara H;Shimizu T;Nakajima H;Moss J;Noda M
枯草杆菌酶细胞毒素 (SubAB) 由某些产志贺毒素大肠杆菌 (STEC) 菌株产生，可裂解内质网 (ER) 伴侣 BiP/Grp78，从而诱导 ER 应激和半胱天冬酶依赖性细胞凋亡。 SubAB 改变先天免疫反应。 SubAB 预处理巨噬细胞可抑制脂多糖 (LPS) 诱导的单核细胞趋化蛋白 1 (MCP-1) 和肿瘤坏死因子 α (TNF-α) 的产生。我们在此研究了 SubAB 抑制小鼠巨噬细胞产生一氧化氮 (NO) 的机制。 SubAB 通过抑制诱导型 NO 合酶 (iNOS) mRNA 和蛋白表达来抑制 LPS 诱导的 NO 产生。此外，SubAB 抑制 LPS 诱导的 IκB-α 磷酸化和核因子-κB (NF-κB) p65/p50 异二聚体的核定位。报告基因和染色质免疫沉淀 (ChIP) 检测显示，SubAB 减少了 LPS 诱导的 NF-κB p65/p50 异二聚体与 iNOS 启动子上 NF-κB 结合位点的结合。与天然毒素相反，催化失活的 SubAB 突变体略微增强了 LPS 诱导的 iNOS 表达以及 NF-κB 亚基与 iNOS 启动子的结合。在 NF-κB1 (p50) 缺陷小鼠的巨噬细胞中，SubAB 对 LPS 诱导的 iNOS 表达的影响显着降低，这些小鼠缺乏 p65/p50 异二聚体的 DNA 结合亚基，表明 p50 参与了 SubAB 介导的 iNOS 表达抑制。用 NOS 抑制剂处理巨噬细胞或大肠杆菌表达 SubAB 增加了巨噬细胞中大肠杆菌的存活率，这表明巨噬细胞产生的 NO 导致细菌的有效杀死，而 SubAB 有助于巨噬细胞中大肠杆菌的存活。因此，我们假设 SubAB 可能代表了一种在 STEC 感染期间规避宿主防御的新细菌策略。
Subtilase cytotoxin (SubAB), which is produced by certain strains of Shiga-toxigenic Escherichia coli (STEC), cleaves an endoplasmic reticulum (ER) chaperone, BiP/Grp78, leading to induction of ER stress and caspase-dependent apoptosis. SubAB alters the innate immune response. SubAB pretreatment of macrophages inhibited lipopolysaccharide (LPS)-induced production of both monocyte chemoattractant protein 1 (MCP-1) and tumor necrosis factor α (TNF-α). We investigated here the mechanism by which SubAB inhibits nitric oxide (NO) production by mouse macrophages. SubAB suppressed LPS-induced NO production through inhibition of inducible NO synthase (iNOS) mRNA and protein expression. Further, SubAB inhibited LPS-induced IκB-α phosphorylation and nuclear localization of the nuclear factor-κB (NF-κB) p65/p50 heterodimer. Reporter gene and chromatin immunoprecipitation (ChIP) assays revealed that SubAB reduced LPS-induced NF-κB p65/p50 heterodimer binding to an NF-κB binding site on the iNOS promoter. In contrast to the native toxin, a catalytically inactivated SubAB mutant slightly enhanced LPS-induced iNOS expression and binding of NF-κB subunits to the iNOS promoter. The SubAB effect on LPS-induced iNOS expression was significantly reduced in macrophages from NF-κB1 (p50)-deficient mice, which lacked a DNA-binding subunit of the p65/p50 heterodimer, suggesting that p50 was involved in SubAB-mediated inhibition of iNOS expression. Treatment of macrophages with an NOS inhibitor or expression of SubAB by E. coli increased E. coli survival in macrophages, suggesting that NO generated by macrophages resulted in efficient killing of the bacteria and SubAB contributed to E. coli survival in macrophages. Thus, we hypothesize that SubAB might represent a novel bacterial strategy to circumvent host defense during STEC infection.