Pathobiology of MRSA-induced Endothelial Permeability and Acute Lung Injury

摘要： 尽管进行了几十年的有针对性的研究，但尚未发现有效的药物干预措施。 急性呼吸窘迫综合征(ARDS)是一种危及生命的疾病过程，其特征是 免疫反应失调。脓毒症是ARDS的主要原因，两者的病理生理学 过程的特点是微循环血流的改变，血管内皮细胞(EC) 功能障碍在器官损伤中起主要作用。需要新的机械洞察力来帮助 开发治疗方法来解决导致ARDS和脓毒症的EC屏障功能障碍。 葡萄球菌(S.)金黄色葡萄球菌是革兰氏阳性败血症中常见的一种微生物， 耐甲氧西林金黄色葡萄球菌(MRSA)菌株的治疗尤其具有挑战性，也是一种主要的 导致急性呼吸窘迫综合征。在MRSA诱导的与ARDS相关的病理生理学方面存在重要的知识空白 以及对EC特定过程的机械性理解，这些过程可以作为治疗的靶点。 内源性鞘氨醇-1-磷酸(S1P)和结构相似的药物化合物FTY720 (FTY)，在ARDS的临床前模型中具有EC屏障增强作用。然而，S1P和FTY也 引发无数其他对危重病人有潜在危害的影响，使他们变得贫穷 治疗候选人。因此，我们探索了新型FTY720类似物的屏障调节特性 为了更好地了解这些化合物是如何调节通透性的。我们的工作揭示了FTY720(S)- 磷酸盐(Tys)在几种临床前模型中具有优越的疗效，并保持了 必需的S1PR1受体，不同于其他导致其降解的激动剂。此外，表观遗传过程 越来越被认为是炎症性急性肺损伤的重要致病步骤 (ALI)/ARDS和脓毒症，以及表观遗传反应(如组蛋白乙酰化)可以通过S1P相关的方式改变 发信号。我们的中心假设是，MRSA通过表观遗传和基因突变导致与ARDS相关的EC功能障碍 Tys/S1PR1相关信号可能针对的其他病理生理机制。使用Chip-seq 分析和其他表观遗传学工具，我们已经产生了新的见解，MRSA触发组蛋白乙酰化在 肺内皮细胞调节参与肺内皮细胞功能障碍的基因。令人兴奋的新数据表明Tys-S1PR1信号 可能会改善这些表观遗传效应的关键方面。目标1将确定通过哪些机制 TYS/S1PR1信号通路对MRSA诱导的肺内皮细胞屏障破坏的保护作用目标2将使用状态- 用最先进的芯片序列和其他方法表征MRSA和Tys/S1PR1诱导的表观遗传学 在肺EC中具有功能后果的变化，包括我们的研究确定的新的MRSA靶点 表观遗传学筛查，细胞色素P1A1。目标#3将通过表征表观遗传学和其他方面在体内扩展这些研究 耐甲氧西林金黄色葡萄球菌致小鼠肺损伤的机制及TYS的疗效观察总体而言，这些研究将 促进我们对MRSA诱导的ARDS的机制的理解，以确定新的治疗靶点。

SUMMARY: Despite decades of targeted research, no effective pharmacologic interventions have been identified for the Acute Respiratory Distress Syndrome (ARDS), which is a life-threatening disease process characterized by dysregulated immune responses. Sepsis is a major cause of ARDS, and the pathophysiology of both processes is characterized by alterations in microcirculatory blood flow, with vascular endothelial cell (EC) dysfunction playing a major role in organ injury. Novel mechanistic insights are needed to assist the development of therapies to address the EC barrier dysfunction that underlies ARDS and sepsis. Staphylococcus (S.) aureus is a frequently identified organism in gram-positive sepsis, and the highly virulent, antibiotic-resistant methicillin-resistant S. aureus (MRSA) strain is particularly challenging to treat and a major cause of ARDS. Important knowledge gaps exist both in MRSA-induced pathophysiology relevant to ARDS and in the mechanistic understanding of EC-specific processes that can be targeted therapeutically. Endogenous sphingosine-1-phosphate (S1P) and the structurally similar pharmaceutical compound, FTY720 (FTY), have EC barrier-enhancing effects in preclinical models of ARDS. However, both S1P and FTY also induce a myriad of other effects that are potentially harmful in critically ill patients and make them poor therapeutic candidates. We therefore have explored the barrier-regulatory properties of novel FTY720 analogs to better understand how these compounds regulate permeability. Our work has revealed that FTY720 (S)- phosphonate (Tys) has superior efficacy in several preclinical models and maintains expression levels of the essential S1PR1 receptor, unlike other agonists which induce its degradation. In addition, epigenetic processes are increasingly being recognized as important pathogenic steps during inflammatory acute lung injury (ALI)/ARDS and sepsis, and epigenetic responses (such as histone acetylation) can be altered by S1P-related signaling. Our central hypothesis is that MRSA causes EC dysfunction relevant to ARDS by epigenetic and other pathophysiologic mechanisms that can be targeted by Tys/S1PR1-related signaling. Using ChIP-seq analysis and other epigenetic tools, we have generated new insights that MRSA triggers histone acetylation in lung EC to regulate genes involved in lung EC dysfunction. Exciting new data suggest Tys-S1PR1 signaling may ameliorate key aspects of these epigenetic effects. Aim #1 will determine the mechanisms by which Tys/S1PR1 signaling protects against MRSA-induced lung EC barrier disruption in vitro. Aim #2 will use state- of-the-art ChIP-seq and other approaches to characterize novel MRSA- and Tys/S1PR1-induced epigenetic changes that have functional consequences in lung EC, including the novel MRSA target identified by our epigenetic screening, CYP1A1. Aim #3 will extend these studies in vivo by characterizing epigenetic and other mechanisms of MRSA-induced lung injury in mice and determine the efficacy of Tys. Overall, these studies will advance our mechanistic understanding of MRSA-induced ARDS to identify novel therapeutic targets.