Understanding the pathophysiology of GBS UTI in diabetes

摘要 糖尿病患者更容易患尿路感染(UTI)。具体地说，由以下原因引起的UTI风险 糖尿病患者革兰氏阳性无乳链球菌(B群链球菌，GBS)明显增多 个人。此外，糖尿病还促进了GBS-UTI向严重和潜在致命的发展 结果如肾盂肾炎、菌血症和败血症。我们假设“糖尿病患者的尿液 微环境通过增强泌尿系病原菌的毒力促进尿路感染 细菌和2)通过抑制宿主的免疫防御。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 两种不同机制的GBS-UTI小鼠模型中的尿液免疫防御 高血糖：1)链脲佐菌素诱导的1型糖尿病和2)2型糖尿病的遗传模型db/db。 以前的研究已经表征了无数的GBS毒力因素，如表面粘附素、孔洞形成 毒素，以及促进GBS在尿路中存活和毒力的基因调节器。利用小鼠进行研究 GBS-UTI诱导的上行性尿路感染模型也表现出独特的尿液免疫反应。 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负荷增加的特定宿主机制 完全破译了。为了填补这些知识空白，我们建议： 特定目标1确定和表征对糖尿病患者的尿路发病起重要作用的特定的GBS因子 老鼠。我们将比较从糖尿病和非糖尿病尿路分离的GBS的RNA测序图谱 鉴定差异转录的毒力、调节和代谢基因表达网络。这个 在SA1中提出的实验是基于我们发表的结果，在体外暴露于适度的 糖尿显著增加了GBS的毒力。 具体目的2评价GBS-UTI对1型和2型糖尿病小鼠的病理生理学影响。为了实现这一目标，我们 将GBS接种到STZ-1型和db/db-2型糖尿病小鼠及其非糖尿病小鼠体内，诱导尿路感染上升. 糖尿病小鼠并检查疾病参数的差异，如细菌负荷、细胞因子 尿路的产生、免疫细胞的渗透和组织病理学。建立了SA2中的实验 支持数据显示，在囊泡内接种GBS后24小时，db/db糖尿病小鼠表现出显著的 膀胱和肾脏的细菌负荷增加，并增加了向脾的扩散。 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 针对这一点，小分子抑制剂最终可能被开发为治疗尿路感染的有效疗法。

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.