Alterations of aryl hydrocarbon receptor signaling in autoimmune hepatitis

摘要 自身免疫性肝炎(AIH)是一种原因不明的严重肝病，通常伴随着复发- 缓解病程，通常对常规免疫抑制药物无效。这一重大疾病 可能在几个月或几年内进展到终末期肝病伴黄疸，需要大约 20%的病例。在AIH中，功能失调的Treg与增强的Th17免疫反应共存，这是 免疫调节不佳。CD39是一种胞外核苷酸酶，它能水解胞外ATP，最终 产生免疫抑制的腺苷。这种胞外酶由Tregs和效应器Th17的一个子集表达 细胞，在那里它标志着获得监管性质。CD39结果的诱导，至少部分来自于 激活芳烃受体(AhR)，介导毒素反应调节Treg和Th17细胞 豁免权。AHR结合外源和内源配体，包括外源化合物和血红素衍生物。 未结合胆红素。AHR的功能是通过与芳香烃受体的相互作用来实现的 核转运体或其他非规范的结合因子，如雌激素受体-a(ERA)或Kruppel- AHR也受缺氧诱导因子1α(HIF-1a)、AhR抑制因子(AHRR)和 转化生长因子-β是由核因子-kB通过Rel-A亚基诱导。我们注意到AIH衍生的Tregs和Th17 细胞表达CD39的水平降低。这种改变与Treg功能缺陷和 促炎症的Th17细胞持续存在。我们还观察到Tregs和Th17细胞都不能上调 CD39是对AhR激活的反应。AIH中的Tregs和Th17细胞也表达增强的Era、KLF6、AHRR 和HIF-1a水平。这些数据表明，AhR与非规范伙伴和/或异常AhR结合 调节可能干扰T细胞反应，最终导致AIH中CD39表达下调。因此，我们 AIH患者Treg和Th17细胞嘌呤能功能障碍可能与AhR信号异常有关 和/或监管。这些改变使Treg/Th17细胞失衡持续存在，有利于组织损伤和疾病 AIH的进展。在目标1中，我们将确定异常的AhR与非规范伙伴的相互作用 影响Tregs和Th17细胞的嘌呤能反应、代谢特征和功能； AIH患者的外周血或肝活检。在目标2中，我们将定义细胞调控机制 AHR信号以及这些信号如何影响AIH来源的Tregs和Th17细胞中的CD39。在目标1和目标2中，影响 的改变的AhR信号和调控也将在体内的急性肝炎模型中进行测试 免疫缺陷NOD/SCID/Gamma小鼠中的刀豆蛋白-A。最后，在目标3中，我们将测试创新策略 A)通过药物阻断HIF-1a或AHRR来增强AhR信号；和/或b)直接增强 CD39通过外源ADPase激活。我们的调查将提供机械性的见解 AIH的自身免疫组织损伤，特别是将有助于确定新的治疗靶点来控制 炎症和阻止AIH和其他慢性肝病的疾病进展。

Abstract Autoimmune hepatitis (AIH) is a severe liver disease of unknown etiology that typically follows a relapsing- remitting course and may often become refractory to conventional immunosuppression. This important illness may progress over months or years to end-stage liver disease with jaundice, requiring transplantation in about 20% of cases. Dysfunctional Tregs co-exist, in AIH, along with heightened Th17 immune responses, which are refractory to immunoregulation. CD39 is an ectonucleotidase that hydrolyzes extracellular ATP to ultimately generate immunosuppressive adenosine. This ectoenzyme is expressed by Tregs and a subset of effector Th17 cells, where it marks the acquisition of regulatory properties. Induction of CD39 results, at least in part, from activation of aryl hydrocarbon receptor (AhR), which mediates toxin responses to modulate Treg and Th17 cell immunity. AhR binds exogenous and endogenous ligands, including xenobiotics and heme derivatives e.g. unconjugated bilirubin. AhR functions are mediated through interactions with the aryl hydrocarbon receptor nuclear translocator or other ‘non-canonical’ binding factors like the estrogen receptor-a (Era) or the Kruppel- like factor 6. AhR is also regulated by hypoxia inducible factor 1 alpha (HIF-1a), the AhR repressor (AhRR) and TGF-b and is induced by NF-kB through the Rel-A subunit. We have noted that AIH-derived Tregs and Th17 cells express decreased levels of CD39. This alteration is associated with defective Treg function and persistence of pro-inflammatory Th17 cells. We also observe that both Tregs and Th17 cells fail to upregulate CD39 in response to AhR activation. Tregs and Th17 cells in AIH also express heightened Era, KLF6, AhRR and HIF-1a levels. These data suggest that AhR binding to non-canonical partners and/or aberrant AhR regulation might interfere with T cell responses, ultimately resulting in CD39 downregulation in AIH. We therefore hypothesize that Treg and Th17 cell purinergic dysfunction in AIH can be linked to aberrant AhR signaling and/or regulation. These alterations perpetuate Treg/Th17 cell imbalances that favor tissue damage and disease progression in AIH. In Aim 1, we will determine whether aberrant AhR interactions with non-canonical partners impact the purinergic response, metabolic profiles and function of Tregs and Th17 cells; either derived from the peripheral blood or liver biopsies of AIH patients. In Aim 2, we will define the cellular mechanisms regulating AhR signaling and how these impact CD39 in AIH-derived Tregs and Th17 cells. In both Aims 1 and 2, the effects of altered AhR signaling and regulation will be also tested in an in vivo model of acute hepatitis induced by Concanavalin-A in immunodeficient NOD/scid/gamma mice. Lastly, in Aim 3, we will test innovative strategies a) to enhance AhR signaling, either by pharmacological blockade of HIF-1a or AhRR; and/or b) directly boost CD39 activity through administration of exogenous ADPase. Our investigations will provide mechanistic insights into autoimmune tissue damage in AIH and, notably, will aid identifying novel therapeutic targets to control inflammation and halt disease progression in AIH and other chronic liver illnesses.