Endogenous metabolite restricts GM-CSF signaling pathway in pathogenic macrophages to ameliorate CNS Autoimmunity

摘要 确定一种可以调节先天免疫应答而不抑制免疫应答的治疗选择。 免疫系统作为一个整体一直是改善MS患者治疗的关键障碍。 代谢谱，我们已经报道，resolvin D1（RvD 1），一种omega-3的促分解脂质代谢物， 多不饱和脂肪酸在MS患者的血浆中显著降低。 研究发现，与对照组相比，MS患者的omega-3代谢物水平较低，omega-3代谢物是消退素的前体。 健康对照，这一发现已在疾病的动物模型中得到复制，实验性自身免疫性 脑脊髓炎（EAE）。值得注意的是，我们发现每天补充RvD 1显著减弱了临床- 慢性和复发缓解型EAE的症状。这些数据是挑衅性的， 潜在的，特别是因为免疫系统不受抑制RvD 1治疗，因为它是与类固醇和 大多数MS疗法。RvD 1的免疫调节作用是通过其受体甲酰基肽介导的 受体2（FPR 2），导致AMP活化蛋白激酶（AMPK）的调节，AMPK是细胞增殖的重要调节因子， 新陈代谢.在其他人类疾病模型中，RvD 1-FPR 2信号级联通过诱导抗- 巨噬细胞中的炎性表型。然而，提供这种保护的机制仍然难以捉摸。 粒细胞-巨噬细胞集落刺激因子（GM-CSF）在MS和MS的病理学中均起关键作用， 和EAE，促进炎症环境和神经元损伤。越来越多的人对抑制 GM-CSF信号作为MS治疗靶点的促炎作用。在我们的初步工作中， 发现RvD 1处理抑制巨噬细胞中的GM-CSF信号传导，这种抑制作用是AMPK去- 悬而未决。然而，RvD 1如何影响AMPK活性和GM-CSF信号转导以减轻EAE尚不清楚。我们 长期目标是确定可用于治疗自体免疫的天然内源性信号传导机制， 我们的总体目标是确定RvD 1在免疫疾病，特别是MS中的作用机制。 解决MS小鼠模型的炎症和残疾。我们的中心假设是RvD 1减弱了 通过消除GM-CSF信号传导导致促炎性细胞因子极化的EAE疾病进展 将其转化为抗炎表型。巨噬细胞表型的潜在机制 开关是通过FPR 2-AMPK依赖性代谢重编程。为了验证这一假设，我们的具体目标是 1）确定RvD 1对CNS浸润巨噬细胞的细胞表型和功能的影响， EAE中的RvD 1;和2）确定RvD 1对巨噬细胞中代谢重编程的影响。 我们将结合免疫学、生物化学和创新的代谢组学方法来实现这些目标。 已经掌握的方法。建议的研究将为发展 创新的治疗策略，以解决MS期间的炎症，没有副作用，并可能适用于 涉及免疫系统致病性激活的其他疾病。

ABSTRACT Identifying a therapeutic option that can modulate the innate immune response without generally suppressing the immune system as a whole has been a key barrier to improving treatment for patients with MS. Using metabolic profiling, we have reported that resolvin D1 (RvD1), a pro-resolving lipid metabolite of omega-3 polyunsaturated fatty acids, is significantly decreased in the plasma of patients with MS. Consistent with this finding, MS patients have lower levels of omega-3 metabolites, which are precursors of resolvins, compared to healthy controls, a finding that has been replicated in animal models of the disease, experimental autoimmune encephalomyelitis (EAE). Notably, we found that daily supplementation with RvD1 significantly attenuated clini- cal symptoms in both chronic and relapsing-remitting EAE. These data are provocative for their translational potential, particularly because the immune system is not depressed by RvD1 treatment as it is with steroids and most other MS therapies. The immunomodulatory effect of RvD1 is mediated through its receptor, formyl peptide receptor 2 (FPR2), leading to modulation of AMP-activated protein kinase (AMPK), an important regulator of cell metabolism. In other human disease models, the RvD1-FPR2 signaling cascade protects by inducing an anti- inflammatory phenotype in macrophages. However, the mechanism affording this protection remains elusive. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a key player both in the pathology of both MS and EAE, promotes an inflammatory environment and neuronal damage. There is a growing interest in inhibiting the pro-inflammatory effects of GM-CSF signaling as a therapeutic target in MS. In our preliminary work, we found that RvD1 treatment inhibited GM-CSF signaling in macrophages and that this inhibition was AMPK de- pendent. However, how RvD1 affects AMPK activity and GM-CSF signaling to attenuate EAE is unclear. Our long-term goal is to identify natural endogenous signaling mechanisms that can be harnessed to treat autoim- mune diseases, particularly MS. Our overall objective here is to determine the mechanism of action of RvD1 in resolving inflammation and disability in mouse models of MS. Our central hypothesis is that RvD1 attenuates EAE disease progression by abrogating GM-CSF signaling resulting in the polarizing of pro-inflammatory mac- rophages into an anti-inflammatory phenotype. And the underlying mechanisms of macrophage phenotype switch are through FPR2-AMPK-dependent metabolic reprogramming. To test this hypothesis our specific aims are: 1) to identify the effects of RvD1 on the cellular phenotype and function of CNS-infiltrating macro- phages in EAE; and 2) to determine the effects of RvD1 on metabolic reprogramming in macrophages. We will address these aims with a combination of immunological, biochemical and innovative metabolomic ap- proaches that are already well in hand. The proposed studies will form the foundation for the development of innovative therapeutic strategies to resolve inflammation during MS with no side effects and will likely apply to other diseases involving pathogenic activation of the immune system.