Role of Peritoneal Macrophage in Spontaneous Bacterial Peritonitis

摘要 自发性细菌性腹膜炎（SBP）是肝硬化的主要并发症， 死亡率此外，抗菌治疗的有效性，目前的护理标准，正在恶化 因为全球出现了耐多药病原体。因此，发展小说是必要的。 管理策略，其中进一步了解我们的病理生理学是必不可少的。 肝硬化时肠道生态失调和肠道免疫受损共同导致 肠内植物群进入肠系膜血管，随后进入腹膜。虽然这一机制 SBP被认为是原发性的病理生理学，只有当腹膜间平衡时，SBP才会发生。 抗菌免疫力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，被认为是腹膜炎的第一线细胞。 由于吞噬和吞噬溶酶体消化病原体的强大能力而产生的抗菌防御。 此外，微生物的PM感测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也是引发第二波抗菌浪潮的关键 反应尽管它的重要性，PM在SBP中的作用一直知之甚少。而且 肝硬化的发展是否会改变PM的抗菌特性以及如何改变仍然很难确定 它影响腹膜抗菌免疫的总体效力。 我们对肝硬化大鼠腹腔免疫细胞的单细胞RNA测序分析表明， PM特性的深刻改变，包括PM的主调节器的显著下调， GATA 6，一种维生素A（VA）诱导的转录因子。此外，癫痫大鼠的PM表现出明显降低， 对细菌性腹膜炎产生炎症介质的能力，导致中性粒细胞受损 募集和激活以及细菌清除不足。我们的研究还显示， 肝硬化、VA缺乏和腹水积聚的特征，都独立地导致调节异常 PM抗菌功能，这两个过程涉及GATA 6下调。此外，PM分离自 肝硬化患者表现出表达GATA 6的PM数量减少，这与肝硬化程度相关。 抗菌功能受损。这些发现导致我们的假设：“肝硬化损害了 通过下调GATA 6的表达，这有助于SBP的发展”。 因此，本提案旨在通过以下方式填补关于项目管理在战略和业务计划中的作用的知识空白： 定义：（目的1）肝硬化对PM抗菌功能的影响，（目的2）VA不足的影响 （3）腹水对PM抗菌活性的影响。的 这些研究的成功完成将使我们对SBP的理解发生范式转变 病理生理学，并最终确定治疗目标的新的治疗策略的发展。

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.