Innate and Adaptive Immune Consequences of Necroptosis

提案摘要 先天免疫系统会对感染引起的组织稳态扰动做出反应，但也会 死亡细胞和组织损伤。细胞通过不同的程序性细胞死亡模式死亡，包括细胞凋亡和 坏死性凋亡。细胞凋亡导致的细胞死亡是健康组织生理学的正常组成部分，由细胞平衡 分裂并维持正常的组织大小和功能。细胞凋亡引起的死亡是耐受性的且非 炎症性的，与病理性和炎症性的坏死性凋亡形成对比。坏死性凋亡涉及 受体相互作用丝氨酸/苏氨酸蛋白激酶 RIPK1、RIPK3 和 坏死性凋亡效应混合谱系激酶结构域样蛋白 (MLKL)。直到最近，坏死性凋亡还被认为 主要功能是控制感染，并主要作为对抗病毒封锁的自动防故障策略 细胞凋亡。然而，对小鼠模型的研究表明，细胞凋亡成分的缺陷 caspase-8 或 FADD 等机制会导致坏死性凋亡驱动的胚胎致死，并依赖于 RIPK3 和 MLKL。其他使用肠上皮细胞中 caspase-8 或 FADD 条件性缺失的研究 研究表明，阻断介导稳态细胞凋亡的途径会引发肠道炎症 与 RIPK3 水平升高和坏死性凋亡相关。事实上，程序性细胞死亡显着增加 据报道，炎症性肠病（IBD）患者的肠上皮细胞（IEC）减少，这 损伤与炎症加剧和肿瘤坏死因子 (TNF)-a 水平升高有关， 细胞死亡的重要介质。使用一种新的小鼠模型，我们可以诱导触发 IEC 坏死性凋亡， 我们将确定 IEC 坏死性凋亡如何影响肠道稳态，并定义其性质 炎症反应。我们之前的工作已经确定肠道内的稳态细胞凋亡 上皮是免疫抑制和耐受的主要驱动因素，印记肠道单核吞噬细胞 (MNP) 具有“抑制炎症”和“诱导调节性 CD4 T 细胞”转录特征。这里 我们将定义坏死性凋亡如何影响 MNP 反应。我们将检查其组成和特征 小肠 MNP 群体对坏死性凋亡 IEC 做出反应并破译其在各种先天性中的功能 与炎症介质的产生、先天淋巴细胞的调节相关的免疫功能 功能以及 CD4 T 辅助细胞分化。我们获得的知识将定义坏死性凋亡是如何发生的 通过先天性和适应性细胞群驱动炎症反应，作为治疗的路线图 坏死性凋亡在其他组织中的后果，并为新疗法的开发奠定基础 用于IBD等慢性炎症性疾病。

PROPOSAL SUMMARY The innate immune system responds to perturbations in tissue homeostasis resultant from infection but also dying cells and tissue damage. Cells die by different modes of programmed cell death including apoptosis and necroptosis. Cell death by apoptosis is a normal component of healthy tissue physiology that is balanced by cell division and maintains normal tissue size and function. Cell death by apoptosis is tolerogenic and non- inflammatory, and contrasts with necroptosis, which is pathological and inflammatory. Necroptosis involves the formation of a complex of receptor interacting serine/threonine protein kinases RIPK1, RIPK3 and the necroptosis effector mixed lineage kinase domain-like protein (MLKL). Up until recently, necroptosis was thought to function primarily in the control of infection and mainly as a fail-safe strategy that counters viral blockade of apoptosis. Studies in mouse models, however, have shown that deficiency in components of the apoptosis machinery such as caspase-8 or FADD leads to embryonic lethality driven by necroptosis and dependent on RIPK3 and MLKL. Other studies using conditional deletion of caspase-8 or FADD in the intestinal epithelium revealed that blocking the pathways that mediate homeostatic apoptosis precipitates intestinal inflammation associated with elevated levels of RIPK3 and necroptosis. Indeed, a notable increase in programmed cell death of intestinal epithelial cells (IEC) has been reported in patients with inflammatory bowel disease (IBD), and this damage is associated with heightened inflammation and increased levels of tumor necrosis factor (TNF)-a, an important mediator of cell death. Using a novel mouse model where we can inducibly trigger necroptosis of IEC, we will determine how IEC necroptosis impacts intestinal homeostasis and we will define the nature of the inflammatory response. Our previous work has established that homeostatic apoptosis within the intestinal epithelium is a major driver of immune suppression and tolerance, imprinting intestinal mononuclear phagocytes (MNP) with ‘suppression of inflammation’ and ‘induction of regulatory CD4 T cell’ transcriptional signatures. Here we will define how necroptosis impacts MNP responses. We will examine the composition and characteristics of the small intestinal MNP population that responds to necroptotic IEC and decipher its function in various innate immune functions relating to the production of inflammatory mediators, modulation of innate lymphoid cell function as well as the CD4 T helper cell differentiation. The knowledge we gain will define how necroptosis drives inflammatory responses by innate and adaptive populations of cells, serve as a roadmap for the consequences of necroptosis in other tissues, and lay the foundation for the development of novel therapeutics for chronic inflammatory diseases such as IBD.