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骼疾病，最终导致病理 骨骼建筑中的变化。骨感染是多因素的，反映了 微生物和宿主细胞。葡萄球菌(S.)金黄色葡萄球菌，一种已经对抗生素产生抗药性的病原体， 是细菌引起OM的主要原因，已被确定为对 全球公共卫生。这些感染是痛苦的，使人虚弱，并可能成为慢性或复发多年后 最初的事件。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，会对OM的治疗造成重大障碍。第一个也是最关键的级别 宿主对金黄色葡萄球菌感染的防御是先天免疫，主要是成熟的髓系细胞，如 中性粒细胞和巨噬细胞；这种病原体的成功取决于其逃避和利用这些细胞的能力 回应。虽然关于髓系细胞和金黄色葡萄球菌之间的相互作用已经了解很多，但相对较少 这项研究的重点是骨骼感染。这种微环境呈现出独特的特征，包括 相对低氧，丰富的未成熟髓系细胞，以及独特的骨细胞-破骨细胞(OCs)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，这条路线 感染--通过损伤或直接软组织延伸、外科植入物或血源性传播--可以 显著改变细菌和骨骼之间的相互作用，特别是在感染的早期阶段。值得注意的是， OCs与单核细胞前体细胞不同，在未成熟的髓系细胞之间提供了固有的联系 和骨骼动态平衡。这个应用程序的总体目标是了解宿主与病原体的相互作用 在骨骼OC和中性粒细胞系细胞和金黄色葡萄球菌的建立、发展和 OM的分辨率。我们的初步研究强烈暗示白介素1(IL-1)信号轴是一种驱动 OM过程中的抗菌免疫和病理性骨改变。在感染金黄色葡萄球菌之后， 包括IL-1β在内的IL-1家族成员是通过激活多蛋白复合体而产生的 被称为炎症体。然而，炎性小体在OM发病机制中的作用知之甚少。 我们发现，与其未被激活的前体相比，OCS具有较低的炎性小体激活和 允许金黄色葡萄球菌在细胞内增殖。我们假设炎症小体活动的差异 在骨髓系中，存在于骨骼中的细胞影响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利基，同时引导宿主细胞与 过度的炎症反应会导致组织损伤。目标1：确定猪瘟的宿主和病原体决定因素 OM中OC谱系中的炎性小体激活。目标2：确定炎症性小体的机制和影响 金黄色葡萄球菌在OM中中性粒细胞系的激活。通过检查和操纵寄主病原体 在特定的髓系细胞群体中的相互作用，我们将学习如何使天平向OM的解决倾斜。

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.