Understanding the pathophysiology of GBS UTI in diabetes

摘要 糖尿病患者更容易患上尿路感染（UTI）。具体而言，由以下原因引起的UTI风险 革兰氏阳性无乳链球菌（B族链球菌，GBS）在糖尿病患者中显著增加， 个体此外，糖尿病还促进了GBS-UTI向严重和潜在致命的进展。 结果如肾盂肾炎、菌血症和脓毒症。我们假设“糖尿病患者的泌尿系统 微环境促进尿路感染1）通过增强尿路病原体的毒力 细菌和2）通过抑制宿主免疫防御。为了解决这一假设，我们提出了 有针对性的探索性研究，与R21机制的范围一致，以阐明GBS因素和宿主 在两种机制不同的小鼠模型中， 高血糖症：1）STZ诱导的1型糖尿病和2）db/db，2型糖尿病的遗传模型。 先前的研究已经表征了无数的GBS毒力因子，如表面粘附素、孔形成因子、细胞因子和细胞因子。 毒素和促进GBS在尿路中存活和毒力的基因调节剂。使用小鼠的研究 上升型UTI模型也揭示了由GBS-UTI诱导的独特的尿免疫应答。 然而，在我们对糖尿病中GBS-UTI发病机制的理解中存在两个重要的知识缺口： 1)宿主糖尿病尿微环境对GBS生理学的多效性作用尚不明确， 2)在糖尿病小鼠中观察到的导致尿GBS负荷增加的特异性宿主机制， 完全解密。为了填补这些知识空白，我们建议： 具体目标1识别和表征对糖尿病患者泌尿系发病重要的特定GBS因子 小鼠我们将比较从糖尿病和非糖尿病尿路分离的GBS的RNA测序谱 以确定差异转录毒力，调节和代谢基因表达网络。的 SA 1中提出的实验是基于我们发表的结果，即体外暴露于中度 糖尿显著增加GBS毒力。 具体目的2评价1型和2型糖尿病小鼠中GBS-UTI的病理生理学。为此，我们 将通过STZ-1型和db/db 2型糖尿病小鼠和它们的非糖尿病小鼠中的STZ-1型和db/db 2型糖尿病小鼠诱导UTI上升。 糖尿病同窝仔，并检查疾病参数的差异，如细菌负荷，细胞因子 产生、免疫细胞浸润和泌尿道的组织病理学。在SA 2中进行了实验 根据支持数据，在囊内接种GBS后24小时，db/db糖尿病小鼠表现出显著的 膀胱和肾脏中的细菌负荷较高，并增加了向脾脏的传播。 除了预示着GBS-UTI领域的重大进展外，我们的结果还将为研究铺平道路。 研究糖尿病对其他尿路病原体发病机制的影响，确定新的宿主/病原体靶点 针对该抑制剂的小分子抑制剂最终可被开发为治疗UTI的有效治疗剂。

ABSTRACT Diabetic individuals are more susceptible to urinary tract infections (UTI). Specifically, the risk of UTI caused by Gram positive Streptococcus agalactiae (Group B Streptococcus, GBS) is significantly increased in diabetic individuals. In addition, diabetes also facilitates the progression of GBS-UTI to severe and potentially deadly outcomes such as pyelonephritis, bacteremia, and sepsis. We hypothesize that “the diabetic urinary microenvironment facilitates infection of the urinary tract 1) by augmenting virulence of uropathogenic bacteria and 2) by suppressing host immune defenses.” To address this hypothesis, we have proposed targeted exploratory studies, in alignment with the scope of R21 mechanism, to elucidate GBS factors and host urinary immune defenses central to GBS-UTI pathogenesis in two mechanistically distinct murine models of hyperglycemia: 1) STZ-induced type 1 diabetes and 2) db/db, a genetic model of type 2 diabetes. Previous research has characterized myriad GBS virulence factors such as surface adhesins, pore forming toxins, and gene regulators facilitating GBS survival and virulence in the urinary tract. Studies using mouse model of ascending UTI have also revealed distinctive urinary immune responses induced by GBS-UTI. However, two important knowledge gaps exist in our understanding of GBS-UTI pathogenesis in diabetes: 1) the pleiotropic effects of host diabetic urinary microenvironment on GBS physiology are undefined and 2) specific host mechanisms responsible for increased urinary GBS burden observed in diabetic mice are not fully deciphered. To fill these knowledge gaps we propose: Specific Aim 1 Identify and characterize specific GBS factors important for uropathogenesis in diabetic mice. We will compare RNA-sequencing profiles of GBS isolated from diabetic and non-diabetic urinary tracts to identify differentially transcribed virulence, regulatory and metabolic gene expression networks. The experiments proposed in SA1 are founded on our published results that in vitro exposure to moderate glycosuria significantly increases GBS virulence. Specific Aim 2 Evaluate pathophysiology of GBS-UTI in type 1 and type 2 diabetic mice. In this aim we will induce ascending UTI by inoculating GBS into STZ-type 1 and db/db type 2 diabetic mice and their non- diabetic littermates and examine differences in disease parameters such as bacterial burden, cytokine production, immune cell infiltration and histopathology of the urinary tract. The experiments in SA2 are founded on supporting data that at 24h after intravesicular inoculation with GBS, db/db diabetic mice exhibit significantly higher bacterial burden in bladder and kidneys and increased dissemination to spleen. In addition to heralding significant advances in the field of GBS-UTI, our results will pave the way for research into the effects of diabetes on the pathogenesis of other uropathogens, identifying novel host/pathogen targets against which small molecular inhibitors may ultimately be developed as effective therapeutics to treat UTI.