Tufts Medical Center and Division of Geographic Medicine and Infectious Diseases, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Infect Immun. 2010 Jul;78(7):2984-94. doi: 10.1128/IAI.00383-10. Epub 2010 May 3.
Shiga toxins expressed in the intestinal lumen during infection with Shiga-toxigenic Escherichia coli must translocate across the epithelium and enter the systemic circulation to cause systemic (pathological) effects, including hemolytic uremic syndrome. The transepithelial migration of polymorphonuclear leukocytes in response to chemokine expression by intestinal epithelial cells is thought to promote uptake of Stx from the intestinal lumen by compromising the epithelial barrier. In the present study, we investigated the hypothesis that flagellin acts in conjunction with Shiga toxin to augment this chemokine expression. We investigated the relative contributions of nuclear factor kappaB (NF-kappaB) and mitogen-activated protein kinase (MAPK) signaling to transcription and translation of interleukin-8. Using reporter gene constructs, we showed that flagellin-mediated interleukin-8 gene transcription is heavily dependent on both NF-kappaB and extracellular signal-regulated kinase 1 and 2 (ERK-1/2) activation. In contrast, inhibition of p38 has no detectable effect on interleukin-8 gene transcription, even though flagellin-mediated activation of host p38 is critical for maximal interleukin-8 protein expression. Inhibition of MAPK-interacting kinase 1 suggests that p38 signaling affects the posttranscriptional regulation of interleukin-8 protein expression induced by flagellin. Cotreatment with Stx2 and flagellin results in a synergistic upregulation of c-Jun N-terminal protein kinases (JNKs), p38 activation, and a superinduction of interleukin-8 mRNA. This synergism was also evident at the protein level, with increased interleukin-8 protein detectable following cotreatment with flagellin and Stx2. We propose that flagellin, in conjunction with Shiga toxin, synergistically upregulates stress-activated protein kinases, resulting in superinduction of interleukin-8 and, ultimately, absorption of Stx into the systemic circulation.
在感染志贺毒素产生型大肠杆菌期间，在肠腔中表达的志贺毒素必须穿过上皮细胞并进入体循环，以引起全身（病理）效应，包括溶血尿毒综合征。趋化因子表达促使多形核白细胞穿过上皮细胞迁移，被认为通过破坏上皮屏障促进了从肠腔摄取 Stx。在本研究中，我们假设鞭毛蛋白与志贺毒素协同作用以增强这种趋化因子表达。我们研究了核因子 kappaB (NF-kappaB) 和丝裂原活化蛋白激酶 (MAPK) 信号转导对白细胞介素-8 转录和翻译的相对贡献。使用报告基因构建体，我们表明鞭毛蛋白介导的白细胞介素-8 基因转录严重依赖于 NF-kappaB 和细胞外信号调节激酶 1 和 2 (ERK-1/2) 的激活。相比之下，尽管鞭毛蛋白介导的宿主 p38 激活对于最大程度的白细胞介素-8 蛋白表达至关重要，但抑制 p38 对白细胞介素-8 基因转录没有可检测的影响。抑制丝裂原活化蛋白激酶相互作用激酶 1 表明 p38 信号影响鞭毛蛋白诱导的白细胞介素-8 蛋白表达的转录后调节。Stx2 和鞭毛蛋白的共同处理导致 c-Jun N 末端蛋白激酶 (JNKs)、p38 激活的协同上调和白细胞介素-8 mRNA 的超诱导。这种协同作用在蛋白质水平上也是明显的，与鞭毛蛋白和 Stx2 共同处理后可检测到白细胞介素-8 蛋白的增加。我们提出，鞭毛蛋白与志贺毒素协同上调应激激活蛋白激酶，导致白细胞介素-8 的超诱导，最终导致 Stx 吸收到体循环中。
