Liu Ming-Che, Kuo Kuan-Ting, Chien Hsiung-Fei, Tsai Yi-Lin, Liaw Shwu-Jen
Department and Graduate Institute of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
Department of Pathology, National Taiwan University Hospital, Taipei, Taiwan, Republic of China.
Infect Immun. 2015 Mar;83(3):966-77. doi: 10.1128/IAI.02232-14. Epub 2014 Dec 29.
Proteus mirabilis is a common human pathogen causing recurrent or persistent urinary tract infections (UTIs). The underlying mechanisms for P. mirabilis to establish UTIs are not fully elucidated. In this study, we showed that loss of the sigma factor E (RpoE), mediating extracytoplasmic stress responses, decreased fimbria expression, survival in macrophages, cell invasion, and colonization in mice but increased the interleukin-8 (IL-8) expression of urothelial cells and swarming motility. This is the first study to demonstrate that RpoE modulated expression of MR/P fimbriae by regulating mrpI, a gene encoding a recombinase controlling the orientation of MR/P fimbria promoter. By real-time reverse transcription-PCR, we found that the IL-8 mRNA amount of urothelial cells was induced significantly by lipopolysaccharides extracted from rpoE mutant but not from the wild type. These RpoE-associated virulence factors should be coordinately expressed to enhance the fitness of P. mirabilis in the host, including the avoidance of immune attacks. Accordingly, rpoE mutant-infected mice displayed more immune cell infiltration in bladders and kidneys during early stages of infection, and the rpoE mutant had a dramatically impaired ability of colonization. Moreover, it is noteworthy that urea (the major component in urine) and polymyxin B (a cationic antimicrobial peptide) can induce expression of rpoE by the reporter assay, suggesting that RpoE might be activated in the urinary tract. Altogether, our results indicate that RpoE is important in sensing environmental cues of the urinary tract and subsequently triggering the expression of virulence factors, which are associated with the fitness of P. mirabilis, to build up a UTI.
奇异变形杆菌是一种常见的人类病原体，可引起复发性或持续性尿路感染（UTI）。奇异变形杆菌引发尿路感染的潜在机制尚未完全阐明。在本研究中，我们发现介导胞质外应激反应的σ因子E（RpoE）缺失会降低菌毛表达、在巨噬细胞中的存活率、细胞侵袭能力以及在小鼠体内的定植能力，但会增加尿道上皮细胞的白细胞介素-8（IL-8）表达和群集运动能力。这是第一项证明RpoE通过调节mrpI来调控MR/P菌毛表达的研究，mrpI是一个编码重组酶的基因，该重组酶控制MR/P菌毛启动子的方向。通过实时逆转录PCR，我们发现rpoE突变体提取的脂多糖可显著诱导尿道上皮细胞的IL-8 mRNA量，而野生型提取的脂多糖则不能。这些与RpoE相关的毒力因子应协同表达，以增强奇异变形杆菌在宿主体内的适应性，包括避免免疫攻击。因此，rpoE突变体感染的小鼠在感染早期膀胱和肾脏中显示出更多免疫细胞浸润，且rpoE突变体的定植能力显著受损。此外，值得注意的是，尿素（尿液中的主要成分）和多粘菌素B（一种阳离子抗菌肽）可通过报告基因检测诱导rpoE表达，这表明RpoE可能在尿路中被激活。总之,我们的结果表明,RpoE在感知尿路环境信号并随后触发与奇异变形杆菌适应性相关的毒力因子表达以引发尿路感染方面具有重要作用。
