Rogers Trisha J, Paton Adrienne W, McColl Shaun R, Paton James C
School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia 5005, Australia.
Infect Immun. 2003 Oct;71(10):5623-32. doi: 10.1128/IAI.71.10.5623-5632.2003.
There is increasing evidence that by facilitating translocation of Shiga toxin (Stx) across the intestinal epithelium and by transporting bound toxin to remote sites such as the renal endothelium, polymorphonuclear leukocytes (PMNs) play a key role in the pathogenesis of Shiga-toxigenic Escherichia coli (STEC) disease. Plasma levels of PMN-attracting CXC chemokines such as interleukin-8 (IL-8) also appear to correlate in humans with the severity of disease. Thus, the capacity of STEC strains to elicit CXC chemokine responses in intestinal epithelial cells may be a crucial step in pathogenesis. Accordingly, we attempted to determine which STEC factors are responsible for CXC chemokine induction in human colonic epithelial cells. Infection of Hct-8 cells with locus for enterocyte effacement (LEE)-negative STEC strains isolated from patients with severe STEC disease resulted in up-regulation of IL-8, macrophage inflammatory protein 2alpha (MIP-2alpha), MIP-2beta, and ENA-78 mRNA significantly higher and earlier than that elicited by several LEE-positive STEC strains, including the O157:H7 strain EDL933. Similarly, levels of IL-8 protein in LEE-negative STEC-infected Hct-8 culture supernatants were significantly higher than in LEE-positive STEC-infected culture supernatants. The difference in responses could not be attributed to the expression or nonexpression of LEE genes, the presence or absence of an STEC megaplasmid, or differences in O serogroups or in the type or amount of Stx produced. Interestingly, however, several of the LEE-negative STEC strains eliciting the strongest chemokine responses belonged to flagellar serotype H21. Incubation of Hct-8 cells with isolated H21 flagellin elicited IL-8 and MIP-2alpha responses similar to those seen in the presence of the most potent LEE-negative STEC strains. Deletion of the fliC gene, but not the stx(2) gene, largely abolished the capacity of O113:H21 LEE-negative STEC strain 98NK2 to elicit IL-8 and MIP-2alpha responses in Hct-8 cells. Taken together, these data suggest that although Stx is capable of inducing CXC chemokine responses, the elevated responses seen in cells infected with certain STEC strains are largely attributable to the production of flagellin.
越来越多的证据表明，多形核白细胞（PMN）通过促进志贺毒素（Stx）跨肠上皮细胞转运，并将结合的毒素转运至肾内皮等远端部位，在产志贺毒素大肠杆菌（STEC）疾病的发病机制中起关键作用。在人类中，吸引PMN的CXC趋化因子如白细胞介素-8（IL-8）的血浆水平似乎也与疾病严重程度相关。因此，STEC菌株在肠上皮细胞中引发CXC趋化因子反应的能力可能是发病机制中的关键步骤。据此，我们试图确定哪些STEC因子负责在人结肠上皮细胞中诱导CXC趋化因子。用从严重STEC疾病患者分离出的肠细胞脱落位点（LEE）阴性STEC菌株感染Hct-8细胞，导致IL-8、巨噬细胞炎性蛋白2α（MIP-2α）、MIP-2β和ENA-78 mRNA的上调显著高于且早于几种LEE阳性STEC菌株（包括O157:H7菌株EDL933）所引发的上调。同样，LEE阴性STEC感染的Hct-8培养上清液中的IL-8蛋白水平显著高于LEE阳性STEC感染的培养上清液。反应差异不能归因于LEE基因的表达或不表达、STEC大质粒的存在或不存在、O血清群的差异或所产Stx的类型或数量差异。然而，有趣的是，引发最强趋化因子反应的几种LEE阴性STEC菌株属于鞭毛血清型H21。用分离的H21鞭毛蛋白孵育Hct-8细胞，引发的IL-8和MIP-2α反应与在最有效的LEE阴性STEC菌株存在时所见反应相似。缺失fliC基因而非stx(2)基因，在很大程度上消除了O113:H21 LEE阴性STEC菌株98NK2在Hct-8细胞中引发IL-8和MIP-2α反应的能力。综上所述，这些数据表明，虽然Stx能够诱导CXC趋化因子反应，但在某些STEC菌株感染的细胞中观察到的反应增强在很大程度上归因于鞭毛蛋白的产生。
