Program of Immunology, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.
Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States.
Front Immunol. 2023 Jun 2;14:1191838. doi: 10.3389/fimmu.2023.1191838. eCollection 2023.
Compelling evidence has shown that interferon (IFN)-γ has dual effects in multiple sclerosis and in its animal model of experimental autoimmune encephalomyelitis (EAE), with results supporting both a pathogenic and beneficial function. However, the mechanisms whereby IFN-γ may promote neuroprotection in EAE and its effects on central nervous system (CNS)-resident cells have remained an enigma for more than 30 years. In this study, the impact of IFN-γ at the peak of EAE, its effects on CNS infiltrating myeloid cells (MC) and microglia (MG), and the underlying cellular and molecular mechanisms were investigated. IFN-γ administration resulted in disease amelioration and attenuation of neuroinflammation associated with significantly lower frequencies of CNS CD11b myeloid cells and less infiltration of inflammatory cells and demyelination. A significant reduction in activated MG and enhanced resting MG was determined by flow cytometry and immunohistrochemistry. Primary MC/MG cultures obtained from the spinal cord of IFN-γ-treated EAE mice that were re-stimulated with a low dose (1 ng/ml) of IFN-γ and neuroantigen, promoted a significantly higher induction of CD4 regulatory T (Treg) cells associated with increased transforming growth factor (TGF)-β secretion. Additionally, IFN-γ-treated primary MC/MG cultures produced significantly lower nitrite in response to LPS challenge than control MC/MG. IFN-γ-treated EAE mice had a significantly higher frequency of CX3CR1 MC/MG and expressed lower levels of program death ligand 1 (PD-L1) than PBS-treated mice. Most CX3CR1PD-L1CD11bLy6G cells expressed MG markers (Tmem119, Sall2, and P2ry12), indicating that they represented an enriched MG subset (CX3CR1PD-L1 MG). Amelioration of clinical symptoms and induction of CX3CR1PD-L1 MG by IFN-γ were dependent on STAT-1. RNA-seq analyses revealed that treatment with IFN-γ promoted the induction of homeostatic CX3CR1PD-L1 MG, upregulating the expression of genes associated with tolerogenic and anti-inflammatory roles and down-regulating pro-inflammatory genes. These analyses highlight the master role that IFN-γ plays in regulating microglial activity and provide new insights into the cellular and molecular mechanisms involved in the therapeutic activity of IFN-γ in EAE.
大量证据表明，干扰素（IFN）-γ在多发性硬化症及其实验性自身免疫性脑脊髓炎（EAE）动物模型中具有双重作用，其结果既支持其致病性又支持其有益功能。然而，IFN-γ 如何促进 EAE 中的神经保护及其对中枢神经系统（CNS）固有细胞的影响仍然是 30 多年来的一个谜。在这项研究中，研究了 IFN-γ 在 EAE 高峰期的作用、对 CNS 浸润性髓样细胞（MC）和小胶质细胞（MG）的影响，以及潜在的细胞和分子机制。IFN-γ 的给药导致疾病改善和神经炎症减轻，与 CNS CD11b 髓样细胞的频率显著降低以及炎症细胞浸润和脱髓鞘减少有关。通过流式细胞术和免疫组织化学确定了活化 MG 的显著减少和静息 MG 的增强。从小鼠脊髓中获得的 IFN-γ 处理的 EAE 小鼠的原代 MC/MG 培养物，用低剂量（1ng/ml）IFN-γ 和神经抗原重新刺激后，显著促进了与转化生长因子（TGF）-β分泌增加相关的 CD4 调节性 T（Treg）细胞的更高诱导。此外，与对照 MC/MG 相比，IFN-γ 处理的原代 MC/MG 培养物对 LPS 刺激的亚硝酸盐产生明显减少。与 PBS 处理的小鼠相比，IFN-γ 处理的 EAE 小鼠的 CX3CR1 MC/MG 频率显著更高，程序性死亡配体 1（PD-L1）水平更低。大多数 CX3CR1PD-L1CD11bLy6G 细胞表达 MG 标志物（Tmem119、Sall2 和 P2ry12），表明它们代表了一个丰富的 MG 亚群（CX3CR1PD-L1 MG）。IFN-γ 诱导的临床症状改善和 CX3CR1PD-L1 MG 的诱导依赖于 STAT-1。RNA-seq 分析表明，IFN-γ 的治疗促进了稳态 CX3CR1PD-L1 MG 的诱导，上调了与耐受和抗炎作用相关的基因的表达，并下调了促炎基因的表达。这些分析突出了 IFN-γ 在调节小胶质细胞活性方面的主要作用，并为 IFN-γ 在 EAE 中的治疗活性所涉及的细胞和分子机制提供了新的见解。
