Role of Peritoneal Macrophage in Spontaneous Bacterial Peritonitis

摘要 自发性细菌性腹膜炎(Sbp)是肝硬变的主要并发症，与高血压性腹膜炎有关。 死亡率。此外，目前的护理标准--抗菌疗法的有效性正在恶化。 由于全球出现了多药耐药病原体。因此，发展小说势在必行 管理策略，为此，加深我们对病理生理学的理解是势在必行的。 肝硬变患者肠道代谢紊乱与肠道免疫功能受损协同易位 肠道菌群进入肠系膜淋巴管，随后进入腹膜。尽管这一机制已经 一直被认为是SBP的主要病理生理机制，只有当腹膜与腹膜之间的平衡时才会发生SBP 抗菌免疫和细菌毒力的变化有利于入侵的病原体。 腹膜巨噬细胞(PM)是腹膜中的主要细胞类型，被认为是 抗菌防御能力强，对病原体具有较强的吞噬和吞噬消化能力。 此外，对微生物的PM感应会导致中性粒细胞所需的细胞因子/趋化因子的产生 招募和激活。因此，PM对于触发第二波抗菌药物也是必不可少的 回应。尽管人们意识到PM在SBP中的重要性，但人们对PM在SBP中的作用知之甚少。此外，它还 肝硬变的发展是否会改变PM的抗菌特性，以及如何改变，在很大程度上仍然难以捉摸 它会影响腹膜抗菌免疫的整体效力。 我们对肝硬变大鼠腹膜免疫细胞的单细胞RNA测序分析表明 PM特征的深刻变化，包括大幅下调PM的主监管机构， GATA6，维生素A(VA)诱导转录因子。此外，肝硬变大鼠的PM明显减少。 细菌性腹膜炎时产生炎症介质的能力，导致中性粒细胞受损 招募和激活以及细菌清除不足。我们的研究还显示，有两种常见的 肝硬变的特点，VA缺乏和腹水堆积，都是调节失调的独立原因 PM的抗菌功能，两个过程都涉及GATA6下调。此外，PM与 肝硬变患者表达GATA6的PM数量减少，这与程度相关 抗菌功能受损。这些发现引出了我们的假设：“肝硬变削弱了抗菌素。 通过下调GATA6的表达，促进SBP的发展，从而影响PM的特性。 因此，本提案旨在通过以下方式弥合关于项目经理在SBP中的作用的知识差距 定义：(目标1)肝硬变对PM抗菌功能的影响，(目标2)VA不足的影响 对PM抗菌性能的影响，以及(目的3)肝硬变腹水对PM抗菌活性的影响这个 拟议研究的成功完成将导致我们对SBP的理解发生范式转变 病理生理学，并最终确定治疗目标，以开发新的治疗策略。

Abstract Spontaneous bacterial peritonitis (SBP) is a major complication of cirrhosis and associated with high mortality rate. Moreover, the effectiveness of antimicrobial therapy, the current standard of care, is deteriorating due to the global emergence of multidrug-resistant pathogens. Hence, it is essential to develop novel management strategies, for which furthering our understanding of the pathophysiology is imperative. Gut dysbiosis and impaired intestinal immunity in cirrhosis cooperatively predispose to the translocation of gut flora into the mesenteric lymphatics and, subsequently, to the peritoneum. Although this mechanism has been regarded as the primary pathophysiology, SBP develops only when the balance between peritoneal antibacterial immunity and bacterial virulence shifts in favor of the invading pathogen. Peritoneal macrophage (PM) is the major cell type in the peritoneum and is considered as the first line of antibacterial defense owing to the robust capacity in the engulfment and phagolysosomal digestion of pathogens. Moreover, PM sensing of microbe results in the production of cytokines/chemokines required for neutrophil recruitment and activation. Accordingly, PM is also essential for triggering the second wave of antibacterial response. Despite its perceived importance, the role of PM in SBP has been poorly understood. Furthermore, it remains largely elusive whether the development of cirrhosis alters the antibacterial properties of PM, and how it impacts the overall potency of peritoneal antibacterial immunity. Our single cell RNA sequencing analyses of peritoneal immune cells of rat with cirrhosis demonstrate a profound alteration of PM characteristics, including a substantial downregulation of the master regulator of PM, GATA6, a vitamin A (VA)-inducible transcription factor. In addition, PM of cirrhotic rats exhibit a markedly reduced capacity to produce inflammatory mediators in response to bacterial peritonitis, resulting in impaired neutrophil recruitment and activation as well as the insufficient bacterial clearance. Our studies also reveal that two common features of cirrhosis, VA deficiency and ascites accumulation, both independently contribute to the dysregulation of PM antibacterial function, with both processes involving GATA6 downregulation. Moreover, PM isolated from cirrhosis patients demonstrate a decreased number of GATA6-expressing PM, which correlates with the degree of antibacterial function impairment. These findings led to our hypothesis: “cirrhosis impairs the antibacterial properties of PM through the downregulation of GATA6 expression, which contributes to SBP development”. Accordingly, this proposal aims to close the knowledge gap regarding the role of PM in SBP through defining: (Aim 1) the impact of cirrhosis on PM antibacterial functions, (Aim 2) the influence of VA insufficiency on PM antibacterial properties, and (Aim 3) the effect of cirrhotic ascites on the antimicrobial activity of PM. The successful completion of the proposed studies will result in a paradigm shift in our understanding of SBP pathophysiology and ultimately define therapeutic targets for the development of novel therapeutic strategies.