Identification and characterization of the mechanisms and relevance of inflammasome activation in mast cells

传统上，肥大细胞(MC)主要被认为是适应性免疫系统的效应细胞，因为它们可以介导过敏原诱导的IgE交联引起的过敏反应。然而，MC正在成为先天性免疫反应的关键贡献者：它们表达大量的天然免疫信号受体，包括Toll样受体(TLR)家族的大多数成员、RIG-I样受体和NOD样受体。与巨噬细胞和树突状细胞类似，巨噬细胞可以被病原体发出的危险信号激活，它们可以感知到组织损伤过程中出现的宿主分子的变化。炎性小体是一类重要的先天免疫感受器，负责传递危险信号。通过白介素1β(IL-1β)，它们通过感知许多内源性分子而在组织损伤过程中驱动早期炎症反应，这些内源性分子在细菌感染期间被细胞应激改变或错误定位。西方社会的许多流行疾病，包括慢性阻塞性肺疾病、代谢综合征、动脉粥样硬化和阿尔茨海默病，都受到炎症小体错误激活的影响，如NLRP3，它现在被认为是一个有希望的治疗靶点。最近的研究强调了MC炎性小体激活在自身炎症性疾病患者皮损发生发展中的重要性。超过这些条件的MC炎性小体激活的重要性到目前为止还没有研究过。慢性创面合并细菌重叠感染，在老龄化的西方社会中，发病率为2%，给医疗和经济带来越来越大的负担。慢性伤口感染与肥大细胞和炎症体介质(如IL-1β)的激活增加有关。紫外线照射是一种无菌的炎症体激活剂，会引起MC介导的炎症，与黑色素瘤的发展有关。因此，我们有兴趣研究在这两种情况下MC和炎性小体激活之间的联系。我们的初步数据显示，人类和小鼠的MC表达广泛的功能性炎症体，它们对炎症体刺激的反应不依赖于组胺的释放。在此，我们建议借助炎症体报告小鼠(m-ASC-Culean)研究MC依赖炎症模型中炎症体激活的途径。其次，我们将有选择地用缺乏不同炎症体的MC来重建MC缺陷小鼠，以确定特定的炎症体在疾病发展中的作用。然后，我们将评估MC炎症体激活与人类皮肤炎症的相关性。最后，作为原理的证明，我们将测试高通量筛选确定的小分子作为炎症体激活嵌合体对MC的影响。因此，我们的目标是迅速将我们的发现转化为MC和炎症相关皮肤病的新治疗视角。

Traditionally, mast cells (MCs) are seen mainly as effector cells of the adaptive immune system, since they can mediate anaphylactic reactions upon allergen-induced IgE crosslinking. However, MCs are emerging as key contributors to innate immune responses: They express a large repertoire of innate immune signaling receptors, including most members of the Toll-like receptor (TLR) family, Rig-I like receptors and Nod-like receptors. Similar to macrophages and dendritic cells, MCs can be activated by danger signals derived from pathogens, and they can sense altered host molecules that appear during tissue damage. Inflammasomes are an important class of innate immunity sensors for such danger signals. Via Interleukin 1 beta (IL-1 beta), they drive early inflammatory responses during tissue damage by sensing many endogenous molecules that are altered by cell stress or mislocalized during bacterial infection. Many prevalent diseases in Western societies, including chronic obstructive pulmonary disease, metabolic syndrome, atherosclerosis and Alzheimer disease are influenced by erroneous activation of inflammasomes such as NLRP3, which is now considered a promising therapeutic target. Recent studies have highlighted the importance of MC inflammasome activation for the development of skin lesions in patients with autoinflammatory conditions. The importance of MC inflammasome activation beyond these conditions has so far not been studied. Chronic wounds, complicated by bacterial superinfection, present an increasing medical and economic burden with an incidence of 2% in aging Western societies. Chronic wound infections are associated with increased activation of mast cells and inflammasome mediators such as IL-1 beta. UV-irradiation is a sterile inflammasome activator and causes MC-mediated inflammation that is linked to the development of melanoma. We are, therefore, interested in studying the connection between MCs and inflammasome activation in these two conditions. Our preliminary data show that human and mouse MCs express a wide range of functional inflammasomes and that they respond towards inflammasome stimuli independently of histamine release. We, here, propose to study the pathways of inflammasome activation in MC-dependent models of inflammation with the help of an inflammasome reporter mouse (m-ASC-cerulean). Secondly, we will reconstitute MC-deficient mice selectively with MCs that lack different inflammasomes to identify the role of specific inflammasomes in disease development. We will then assess the relevance of MC inflammasome activation in human skin inflammation. Finally, as a proof of principle, we will test the effect of small molecules identified by high throughput screens as inflammasome activation mosulators on MCs. We thereby aim to swiftly translate our findings and generate new therapeutic perspectives for MC- and inflammasome-related skin diseases.