Evaluation of Innate Lymphoid Cell subsets and Aryl hydrocarbon Receptor-signaling in mouse models of liver damage and regeneration

肝脏是一个独特的器官，具有重要的代谢和免疫功能，由于其独特的解剖位置，它经常暴露在有害的生物和化学剂中。在肝损伤和肝再生中，免疫系统都起着重要作用。先天淋巴样细胞（ILCs）被认为是组织损伤的早期反应者。除了它们的组织保护作用，它们的反应也可能是有害的，有助于各种病理的发展，包括癌症。肝组织中ILC表达的传感器和ILC激活的模块仍未完全定义。此外，ILC对组织保护或破坏反应的控制机制仍然相当难以捉摸。在前两年的资助期1中，我们研究了在饮食诱导的慢性肝损伤背景下，肝脏、自然杀伤细胞（NK）和肝脏驻留ILC1s中主要ILC亚群的芳烃受体（AhR）驱动反应。我们的研究结果表明，在肝脏中表达nkp46的细胞（包括NK细胞和ILC1s）中，条件删除AhR可显著减少肝脏损伤。这种表型与NK/ILC1s在肝组织中的积累减少有关。NK/ILC1中AhR的激活导致细胞因子IL-10和趋化因子CCL2水平升高，表达ly6c的CCR2+炎性单核细胞数量增加。中和IL-10可显著减少CCL2的产生、炎症单核细胞数量和肝损伤。因此，我们的数据表明，与其公认的抑制作用相反，IL-10在ahr介导的NK/ILC1激活的下游发挥中枢效应调节作用。在下一步，我们将解决损伤相关的AhR配体的性质，以及IL-10的来源和机制（工作包A），以完成我们对AhR和NK/ILC1s在慢性肝损伤中的作用的理解。在第二个资助期内，我们将扩展目前获得的结果，研究ahr驱动的NK/ILC1反应在肝脏再生中的作用。我们将采用成熟的肝部分切除术模型，其中肝细胞介导的再生在手术后两周内恢复肝脏质量和功能。我们将探讨ahr介导的NK/ILC1功能调节是否会影响健康肝组织（工作包B）和患病肝组织（工作包C）的再生和免疫细胞再生，模拟肝病患者的切除。在整个项目（资助期1和2）中获得的数据将有助于了解NK/ILC1在组织损伤与再生中的功能，以及AhR作为NK/ILC1微环境传感器的作用。这一知识可能对设计肝病患者的创新治疗方法具有高度相关性。

The liver is a unique organ with important metabolic and immune functions that due to its distinctive anatomic position is constantly exposed to damaging biological and chemical agents. In both liver damage and regeneration, the immune system plays a significant part. Innate lymphoid cells (ILCs) are considered to be early responders to tissue damage. Besides their tissue protective role, their responses could also be detrimental, contributing to the development of various pathologies, including cancer. The sensors expressed by ILCs and modules of ILC activation in the liver tissue are still incompletely defined. Moreover, the control mechanism(s) poising ILC responses towards tissue protection or destruction remain rather elusive. During the first two years of funding period 1, we investigated the Aryl-hydrocarbon Receptor (AhR)-driven responses of the dominant ILC subsets in liver, Natural Killer (NK) cells and liver-resident ILC1s, in the context of diet-induced chronic liver damage. Our results reveal that conditional deletion of AhR in NKp46-expressing cells, comprising both NK cells and ILC1s in liver, significantly reduced liver damage. This phenotype was associated with decreased accumulation of NK/ILC1s in the liver tissue. AhR activation in NK/ILC1 resulted in enhanced levels of the cytokine IL-10, of the chemokine CCL2 and in increased numbers of Ly6C-expressing CCR2+ inflammatory monocytes. Neutralization of IL-10 significantly reduced CCL2 production, inflammatory monocyte numbers and liver damage. Thus, our data imply that, in contrast to its well-established suppressing role, IL-10 functions as a central effector regulator downstream of the AhR-mediated NK/ILC1 activation. In the next step, we will address the nature of damage-associated AhR-ligands, and the sources and mechanisms of IL-10 (Work Package A) to complete our understanding of the role of the AhR and NK/ILC1s in chronic liver damage.Extending our results obtained so far, during the second funding period, we will address the role of AhR-driven NK/ILC1 responses in liver regeneration. We will apply the well-established model of partial hepatectomy, in which hepatocyte-mediated regeneration restores liver mass and function within two weeks after surgery. We will address whether AhR-mediated regulation of NK/ILC1 function affects regeneration and immune cell repopulation of the healthy liver tissue (Work Package B), and of diseased liver tissue (Work Package C), mimicking resection performed in patients with liver disease. The data obtained during the whole project (funding period 1 and 2) will help understanding NK/ILC1 function in tissue damage vs regeneration and the role of AhR as a microenvironmental sensor in NK/ILC1s. This knowledge could be of high relevance for designing innovative treatments for patients with liver disease.