Molecular mechanism of cardiac inflammation and dysfunction in Pseudomonas aeruginosa infection

医院感染是当今医疗保健和重症监护病房的一个长期问题，占 每年有超过20万人死亡。呼吸机相关肺炎(VAP)的并发症发生率为8-28% 在接受机械通气的患者中，约占ICU获得性感染的50%。 具体地说，铜绿假单胞菌(P.A.)感染占所有医院获得性感染病例的20% 肺炎病死率约为30%。ICU中60%以上的脓毒症患者有心脏疾病的证据 功能障碍和急性细菌性肺炎给心脏带来压力，抑制心脏功能。也有很多 细菌毒力因子激活心肌细胞的TLRs，抑制心肌细胞的收缩功能。 尽管感染过程中炎症引起的心功能不全被认为是 ICU肺炎患者死亡，广谱消炎药不能有效预防死亡。因此， 了解参与心脏炎症的细胞成分及其对心肌细胞和 成纤维细胞功能有助于肺炎患者心功能不全的预防。我们有 发现活化的髓系细胞渗入P.A.心脏。感染小鼠引起心脏 导致心脏常驻巨噬细胞表型转换的炎症和凋亡及其原因 心脏受损。具体地说，我们确定了PA。感染诱导miR155表达，以许多为靶点 心肌细胞收缩功能所需的基因。我们是第一个发现心脏疾病之间联系的人 巨噬细胞(效应分子miR155)与心肌细胞收缩功能障碍和成纤维细胞活化 (纤维化)在细菌感染期间。因此，我们假设活化的髓系细胞的渗透转移 抗纤维化驻留巨噬细胞(MHC-IIlow)经心脏转导成促纤维化巨噬细胞(MCH-IIHigh) 炎症和细胞凋亡，导致心肌细胞收缩功能障碍和成纤维细胞激活。这个 MiR155作为髓系细胞渗透的全局调节器发挥作用，从而阻止心脏巨噬细胞 表型开关。本研究的目标是：1)明确心肌细胞的分子机制 铜绿假单胞菌感染过程中的收缩功能障碍和成纤维细胞激活。2)研究心脏的作用 巨噬细胞在脓毒症时激活导致心功能不全的内在信号通路。3) 确定局部抑制心脏炎症是否能在侵袭性细菌中保护心脏功能 感染。我们将使用人类可诱导多能干细胞来源的心肌细胞(hiPSC-CMS)，人 心脏成纤维细胞和人类单核细胞来源的巨噬细胞在体外测试我们的假设。用于活体内 研究中，我们将使用基因敲除小鼠模型来实现我们的目标。总的来说，我的实验室的使命是 确定重要的调控途径和效应分子，以创造治疗心功能不全 肺炎患者。我们的基础研究发现将启动开发新的方法和 治疗脓毒症心功能不全的药物。

Nosocomial infection is a persistent problem in healthcare today and in the intensive care units, accounting for over 200,000 deaths annually. Ventilator-associated pneumonia (VAP) develops as a complication in 8 – 28% of patients receiving mechanical ventilation, represents approximately 50% of ICU acquired infections. Specifically Pseudomonas aeruginosa (P.a.) infections account for up to 20% of all cases of hospital acquired pneumonia with mortality rate of ~30%. More than 60% of sepsis patients in ICU show evidence of cardiac dysfunction and acute bacterial pneumonia stresses the heart and suppresses ventricular function. Also many bacterial virulent factors activate TLRs in cardiomycytes and suppress the myocyte contractile function. Although cardiac dysfunction caused by inflammation during infection is thought to be the key driver of mortality in ICU pneumonia patients, broad anti-inflammatories do not effectively prevent death. Thus, understanding the cellular components involved in the cardiac inflammation and their impact on myocyte and fibroblast function would assist in the prevention of cardiac dysfunction in pneumonia patients. We have discovered that the infiltration of activated myeloid cells into the hearts of P.a. infected mice induces cardiac inflammation and apoptosis that leads to phenotypic switch of cardiac resident macrophages and causes cardiac damage. Specifically, we identified that P.a. infection induces miR155 expression which targets many genes required for myocyte contractile function. We are the first to discover the link between cardiac macrophages (effector molecule miR155) and myocyte contractile dysfunction and fibroblast activation (fibrosis) during bacterial infection. Thus we hypothesize that the infiltration of activated myeloid cells shifts anti-fibrotic cardiac resident macrophage (MHC-IIlow) into pro-fibrotic macrophages (MCH-IIhigh) through cardiac inflammation and apoptosis, which results in myocyte contractile dysfunction and fibroblast activation. The miR155 functions as a global regulator of myeloid cell infiltration and thus prevents the cardiac macrophage phenotypic switch. The goals of this research program are to 1) Define the molecular mechanism of myocyte contractile dysfunction and fibroblast activation during P. aeruginosa infection. 2) Investigate the role of cardiac macrophages in activation of intrinsic signaling pathways that cause cardiac dysfunction during sepsis. 3) Determine whether localized inhibition of cardiac inflammation preserves the heart function in invasive bacterial infections. We will use human inducible pluripotent stem cell derived cardiomyocytes (hiPSC-CMs), human cardiac fibroblast, and human monocyte derived macrophages to test our hypothesis in vitro. For in vivo studies we will use knockout mouse models to accomplish our goals. Overall, the mission of my laboratory is to identify the important regulatory pathways and effector molecules to create therapies for cardiac dysfunction in pneumonia patients. Our basic research discoveries will jump-start the development new approaches and drugs to treat cardiac dysfunction in sepsis.