Differential Inflammasome Regulation in the pathogenesis of S. aureus osteomyelitis

摘要 传染性骨髓炎 (OM) 是一种炎症驱动的骨疾病，最终导致病理性骨髓炎 骨骼结构的改变。骨感染是多因素的，反映了不同因素之间复杂的相互作用 微生物和宿主细胞。金黄色葡萄球菌（S.）是一种已经产生抗生素耐药性的病原体， 是细菌引起的 OM 的主要原因，并已被确定为对人类最大的细菌威胁之一 全球公共卫生。这些感染是痛苦的、使人衰弱的，并且可能会变成慢性的，或者在感染后数年后复发。 初始事件。病原体破坏骨组织并逃避免疫系统清除的能力，甚至 使用适当的抗生素，对 OM 的治疗造成重大障碍。第一个也是最关键的级别 宿主抵抗金黄色葡萄球菌感染的防御是先天免疫，主要是成熟的骨髓谱系细胞，例如 中性粒细胞和巨噬细胞；该病原体的成功取决于其逃避和利用这些病毒的能力 回应。虽然人们对骨髓细胞和金黄色葡萄球菌之间的相互作用了解很多，但相对较少 工作重点是骨感染。这种微环境呈现出独特的特征，包括 相对缺氧、丰富的未成熟骨髓细胞以及独特的骨细胞——破骨细胞（OC）的存在， 成骨细胞和骨细胞 - 与细菌和先天免疫细胞相互作用。此外，路线 感染 - 通过损伤或直接软组织延伸、手术植入或血行传播 - 可以 显着改变细菌和骨骼之间的相互作用，尤其是在感染的早期阶段。值得注意的是， OC 与单核细胞前体细胞分化，提供未成熟骨髓谱系细胞之间的内在联系 和骨稳态。该应用程序的总体目标是了解宿主与病原体的相互作用 骨的 OC 和中性粒细胞谱系细胞与金黄色葡萄球菌之间的建立、进展和 OM 的分辨率。我们的初步研究强烈表明白介素 1 (IL-1) 信号轴是 OM 期间的抗菌免疫和病理性骨变化。感染金黄色葡萄球菌等后， IL-1 家族成员（包括 IL-1β）通常是通过多蛋白复合物的激活产生的 称为炎症小体。然而，人们对炎症小体在 OM 发病机制中的作用知之甚少。 我们发现，与未承诺的前体相比，OC 具有较低的炎性体激活和 允许细胞内金黄色葡萄球菌增殖。我们假设炎症小体活性的差异 骨中存在的骨髓谱系细胞影响 OM 的发病机制，金黄色葡萄球菌利用这些细胞 具有较弱的炎症体和抗菌反应作为增殖生态位，同时导致宿主细胞具有 过度的炎症反应导致组织损伤。目标 1：定义宿主和病原体决定因素 OM 中 OC 谱系的炎症小体激活。目标 2：定义炎症小体的机制和影响 OM 中金黄色葡萄球菌对中性粒细胞谱系的激活。通过检查和操纵宿主病原体 特定骨髓细胞群中的相互作用，我们将学习如何使平衡朝着 OM 的解决方向倾斜。

Abstract Infectious osteomyelitis (OM) is an inflammation-driven disease of bone that culminates in pathological alterations in skeletal architecture. Bone infections are multifactorial and reflect a complex interaction between microorganisms and host cells. Staphylococcus (S.) aureus, a pathogen that has developed antibiotic resistance, is the leading cause of bacterial-induced OM and has been identified as one of the greatest bacterial threats to global public health. These infections are painful, debilitating and can become chronic or recur years after the initial event. The pathogen’s ability to damage bone tissue and evade clearance by the immune system, even with appropriate antibiotics, impose significant obstacles to treatment of OM. The first and most critical level of host defense against infection by S. aureus is innate immunity, primarily mature myeloid lineage cells such as neutrophils and macrophages; the success of this pathogen is dependent on its ability to evade and exploit these responses. While much has been learned about interactions between myeloid cells and S. aureus, relatively little work has specifically focused on infections of bone. This microenvironment presents unique features, including relative hypoxia, abundant immature myeloid cells, and the presence of unique bone cells – osteoclasts (OCs), osteoblasts, and osteocytes - that interact with both the bacteria and innate immune cells. Furthermore, the route of infection - via injury or direct soft tissue extension, surgical implants, or hematogenously spread – can significantly alter the interactions between bacteria and bone, especially during early stages of infection. Notably, OCs differentiate from monocytic precursors, providing an inherent link between immature myeloid lineage cells and bone homeostasis. The overall goal of this application is to understand the host-pathogen interactions between the bone’s OC and neutrophil lineage cells and S. aureus during the establishment, progression, and resolution of OM. Our preliminary studies strongly implicate the interleukin-1 (IL-1) signaling axis as a driver of both antibacterial immunity and pathologic bone changes during OM. Following infections such as with S. aureus, IL-1 family members including IL-1β are canonically generated through the activation of multi-protein complexes known as inflammasomes. However, little is known about the role of inflammasomes in the pathogenesis of OM. We have found that, compared to their uncommitted precursors, OCs have lower inflammasome activation and are permissive of intracellular S. aureus proliferation. We hypothesize that differences in inflammasome activity within myeloid lineage cells present in bone affect the pathogenesis of OM, with S. aureus exploiting those cells with weaker inflammasome and antimicrobial responses as a proliferative niche while leading host cells with an excessive inflammatory response to cause tissue damage. Aim 1: Define host and pathogen determinants of inflammasome activation in the OC lineage in OM. Aim 2: Define the mechanisms and impact of inflammasome activation in the neutrophil lineage by S. aureus in OM. By examining and manipulating the host-pathogen interactions in specific myeloid cell populations, we will learn how to tip the balance towards resolution of OM.