Molecular basis of uropathogenic Escherichia coli evasion of the innate immune response in the bladder
Molecular basis of uropathogenic Escherichia coli evasion of the innate immune response in the bladder
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DOI：
10.1128/iai.00069-08
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发表时间：
2008-09-01
影响因子：
3.1
通讯作者：
Klumpp, David J.
中科院分区：
文献类型：
--
作者：
Billips, Benjamin K.;Schaeffer, Anthony J.;Klumpp, David J.
在尿路中，先天免疫系统检测保守的细菌成分，并通过激活促炎转录因子NF-kappa B来响应感染，导致细胞因子分泌和中性粒细胞募集。然而，尿路致病性大肠杆菌（UPEC）已被证明通过抑制尿路上皮细胞NF-kappa B的激活来逃避宿主的先天免疫反应，从而导致细胞因子分泌减少和尿路上皮细胞凋亡增加。为了了解UPEC调节炎症的分子基础，我们对UPEC菌株NU14进行了遗传筛选，以确定调节尿路上皮细胞因子分泌所需的基因。ampG（肽聚糖渗透酶）、waaL（脂多糖O抗原连接酶）或alr（丙氨酸消消酶）的破坏导致尿路上皮细胞培养物中白细胞介素-8 （IL-8）和IL-6释放增加。在UPEC感染期间，这些基因的靶向缺失也导致尿路上皮细胞因子的产生升高。NU14 Delta ampG和NU14 Delta waaL细菌培养的条件培养基中含有一种热稳定因子，比NU14条件培养基中更能刺激尿路上皮分泌IL-8。在小鼠尿路感染模型中，与野生型NU14相比，NU14 Delta ampG、NU14 Delta waaL和NU14 Delta alr被减弱，在竞争实验中表现出较低的适合度。NU14 Delta ampG或NU14 Delta waaL的灌注增加了膀胱中性粒细胞的募集，表明尿路感染期间尿路上皮细胞因子分泌的增强导致了宿主反应的改变。因此，UPEC逃避天然免疫检测细菌成分，如脂多糖和肽聚糖片段，可能是UPEC在尿路定植能力的重要因素。
In the urinary tract, the innate immune system detects conserved bacterial components and responds to infection by activating the proinflammatory transcription factor NF-kappa B, resulting in cytokine secretion and neutrophil recruitment. Uropathogenic Escherichia coli (UPEC), however, has been shown to evade the host innate immune response by suppressing NF-kappa B activation in urothelial cells, which results in decreased cytokine secretion and increased urothelial apoptosis. To understand the molecular basis of UPEC modulation of inflammation, we performed a genetic screen with UPEC strain NU14 to identify genes which are required for modulation of urothelial cytokine secretion. Disruption of ampG (peptidoglycan permease), waaL (lipopolysaccharide O antigen ligase), or alr (alanine racemase) resulted in increased urothelial interleukin-8 (IL-8) and IL-6 release from urothelial cell cultures. Targeted deletion of these genes also resulted in elevated urothelial cytokine production during UPEC infection. Conditioned media from bacterial cultures of NU14 Delta ampG and NU14 Delta waaL contained a heat-stable factor(s) which stimulated greater urothelial IL-8 secretion than that in NU14-conditioned medium. In a mouse model of urinary tract infection, NU14 Delta ampG, NU14 Delta waaL, and NU14 Delta alr were attenuated compared to wild-type NU14 and showed reduced fitness in competition experiments. Instillation of NU14 Delta ampG or NU14 Delta waaL increased bladder neutrophil recruitment, indicating that enhanced urothelial cytokine secretion during urinary tract infection results in an altered host response. Thus, UPEC evasion of innate immune detection of bacterial components, such as lipopolysaccharide and peptidoglycan fragments, is likely an important factor in the ability of UPEC to colonize the urinary tract.