Nagamatsu Kanna, Hannan Thomas J, Guest Randi L, Kostakioti Maria, Hadjifrangiskou Maria, Binkley Jana, Dodson Karen, Raivio Tracy L, Hultgren Scott J
Departments of Molecular Microbiology and Microbial Pathogenesis and.
Pathology and Immunology.
Proc Natl Acad Sci U S A. 2015 Feb 24;112(8):E871-80. doi: 10.1073/pnas.1500374112. Epub 2015 Feb 9.
Urinary tract infections (UTIs) are among the most common bacterial infections, causing considerable morbidity in females. Infection is highly recurrent despite appropriate antibiotic treatment. Uropathogenic Escherichia coli (UPEC), the most common causative agent of UTIs, invades bladder epithelial cells (BECs) and develops into clonal intracellular bacterial communities (IBCs). Upon maturation, IBCs disperse, with bacteria spreading to neighboring BECs to repeat this cycle. This process allows UPEC to gain a foothold in the face of innate defense mechanisms, including micturition, epithelial exfoliation, and the influx of polymorphonuclear leukocytes. Here, we investigated the mechanism and dynamics of urothelial exfoliation in the early acute stages of infection. We show that UPEC α-hemolysin (HlyA) induces Caspase-1/Caspase-4-dependent inflammatory cell death in human urothelial cells, and we demonstrate that the response regulator (CpxR)-sensor kinase (CpxA) two-component system (CpxRA), which regulates virulence gene expression in response to environmental signals, is critical for fine-tuning HlyA cytotoxicity. Deletion of the cpxR transcriptional response regulator derepresses hlyA expression, leading to enhanced Caspase-1/Caspase-4- and NOD-like receptor family, pyrin domain containing 3-dependent inflammatory cell death in human urothelial cells. In vivo, overexpression of HlyA during acute bladder infection induces more rapid and extensive exfoliation and reduced bladder bacterial burdens. Bladder fitness is restored fully by inhibition of Caspase-1 and Caspase-11, the murine homolog of Caspase-4. Thus, we have discovered that fine-tuning of HlyA expression by the CpxRA system is critical for enhancing UPEC fitness in the urinary bladder. These results have significant implications for our understanding of how UPEC establishes persistent colonization.
尿路感染（UTIs）是最常见的细菌感染之一，在女性中会引发相当高的发病率。尽管进行了适当的抗生素治疗，感染仍极易复发。尿路致病性大肠杆菌（UPEC）是尿路感染最常见的病原体，它侵入膀胱上皮细胞（BECs）并发展为克隆性细胞内细菌群落（IBCs）。成熟后，IBCs 分散，细菌扩散到邻近的 BECs 以重复这个循环。这个过程使 UPEC 能够在包括排尿、上皮脱落和多形核白细胞流入等固有防御机制面前站稳脚跟。在这里，我们研究了感染早期急性阶段尿路上皮脱落的机制和动态。我们发现 UPEC α-溶血素（HlyA）在人尿路上皮细胞中诱导半胱天冬酶-1/半胱天冬酶-4 依赖性炎性细胞死亡，并且我们证明响应调节因子（CpxR）-传感激酶（CpxA）双组分系统（CpxRA），其响应环境信号调节毒力基因表达，对于微调 HlyA 细胞毒性至关重要。cpxR 转录响应调节因子的缺失会解除对 hlyA 表达的抑制，导致人尿路上皮细胞中半胱天冬酶-1/半胱天冬酶-4 和含 pyrin 结构域的 NOD 样受体家族 3 依赖性炎性细胞死亡增强。在体内，急性膀胱感染期间 HlyA 的过表达会诱导更快速、更广泛的上皮脱落并降低膀胱细菌载量。通过抑制半胱天冬酶-1 和半胱天冬酶-11（半胱天冬酶-4 的小鼠同源物）可完全恢复膀胱健康。因此我们发现，CpxRA 系统对 HlyA 表达的微调对于增强 UPEC 在膀胱中的适应性至关重要。这些结果对于我们理解 UPEC 如何建立持续定植具有重要意义。
