The role of TNFR2 in ameliorating progressive encephalomyelitis

导致进行性多发性硬化症(MS)的机制仍然是个谜。多发性硬化症的进展与 细胞因子肿瘤坏死因子在脑脊液中的表达，提示肿瘤坏死因子在脑脊液中起重要作用 在疾病过程中起关键作用。因此，靶向肿瘤坏死因子被认为是一种对多发性硬化症有吸引力的治疗方法，然而令人惊讶的是， 在其他自身免疫性疾病中被证明有效的肿瘤坏死因子阻断药物会引发多发性硬化症的发病和恶化， 提供的证据表明，肿瘤坏死因子也有助于中枢神经系统的保护和修复。随后的研究表明，致病的 在EAE中，肿瘤坏死因子的作用是通过肿瘤坏死因子受体(TNFR)1介导的，而TNFR2信号可以改善疾病，减少 脱髓鞘。TNFR2在中枢神经系统中由不同类型的细胞表达，包括小胶质细胞和少突胶质细胞，其 这些细胞的表达可以促进修复和重新髓鞘形成。同样，星形胶质细胞可以表达TNFR2，但其作用 星形胶质细胞表达的TNFR2在MS/EAE进展中的作用仍未解决。致病星形胶质细胞(A1)或 已经描述了神经保护/抗炎特性(A2)；然而， 有害的和有益的星形胶质细胞的功能仍然不完全清楚。我们已经得到了令人振奋的初步结果 结果通过研究星形胶质细胞TNFR2的作用，支持其在抑制EAE进展中的核心作用 在人源化的转基因小鼠模型中表达人MS相关MHC II等位基因HLA-DR2b和TNFR2 缺乏TnFR2分子表达的小鼠，这里称为DR2BΔR2小鼠。这一模型提供了证据表明，人类白细胞抗原- DR2b分子有利于Th17的发育，而阻碍Foxp3 Treg细胞的形成。重要的是，我们观察到 当中枢神经系统驻留细胞缺失时，DR2bΔR2小鼠发生进行性脑脊髓炎和星形胶质细胞增生症。 此外，在患有EAE的DR2bΔR2动物中，星形胶质细胞显示促炎症细胞因子和 CXCR5表达增加。此外，CXCL13在这些小鼠的中枢神经系统中表达上调，与以前的研究结果一致 报道称CXCL13的中枢神经系统表达可加重EAE并促进非EAE的慢性白质损害 依赖于CXCR5白细胞从外周的募集，而受损神经元表达的CXCL13可以 激活星形胶质细胞。此外，我们观察到在星形胶质细胞群体中，TNFR2的表达存在显著的二分性。 在患有EAE的DR2b小鼠中，表明TNFR2的表达可能有利于星形胶质细胞A2和A1亚群。因此， 我们的建议将检验中心假设，即星形胶质细胞中的TNFR2信号抑制神经炎症的进展 通过抑制致病和促进保护星形胶质细胞的功能。我们将通过以下方式测试我们的假设：(1)确定 TNFR2在抑制致病星形胶质细胞效应蛋白功能和阻止EAE进展中的作用；以及(2)测定 TNFR2调控的CXCL13/CXCR5信号在进展性EAE中对星形胶质细胞激活和功能的影响 在DR2BΔR2小鼠中。我们将通过应用创新的新方法来实现这项建议的目标，包括 我们的进展性EAE模型，开发了星形胶质细胞特异性的TNFR2和CXCR5基因敲除小鼠，并创新 免疫学和分子生物学方法，包括单细胞RNA-SEQ和RNAScope。

The mechanisms driving progressive multiple sclerosis (MS) remain enigmatic. Progression of MS correlates with the expression of the cytokine tumor necrosis factor (TNF) in cerebrospinal fluid of patients, suggesting that TNF plays a key role in the disease process. Thus, targeting TNF was suggested as an attractive therapy for MS. Surprisingly, however, TNF-blocking drugs with proven efficacy in other autoimmune diseases triggered onset and exacerbations of MS, which provided evidence that TNF can also contribute to CNS protection and repair. Subsequent work showed that pathogenic TNF effects in EAE are mediated via TNF receptor (TNFR) 1, whereas TNFR2 signaling ameliorates disease and reduces demyelination. TNFR2 is expressed by different cell types in the CNS, including microglia and oligodendrocytes, and its expression by these cells can promote repair and remyelination. Likewise, astrocytes can express TNFR2, but the role of TNFR2 expressed by astrocytes for MS/EAE progression remains unresolved. Astrocytes with pathogenic (A1) or neuroprotective/anti-inflammatory properties (A2) have been described; however, the mechanisms orchestrating detrimental versus beneficial astrocyte functions are still not fully understood. We have obtained exciting preliminary results supporting a central role for astrocyte TNFR2 in curtailing EAE progression by investigating the role of TNFR2 in a “humanized” transgenic mouse model expressing the human MS-associated MHC II allele HLA-DR2b and lacking the expression of TNFR2 molecules, herein called DR2bΔR2 mice. This model provided evidence that the HLA- DR2b molecule favored Th17 development, while impairing Foxp3+ Treg cell formation. Importantly, we observed that DR2bΔR2 mice developed progressive EAE and astrogliosis when CNS resident cells were TNFR2 deficient. Moreover, in DR2bΔR2 animals with EAE, astrocytes showed increased expression of pro-inflammatory cytokines and increased expression of CXCR5. Additionally, CXCL13 was upregulated in the CNS of these mice in line with previous reports that CNS expression of CXCL13 aggravates EAE and promotes chronic white matter lesions that is not dependent on recruitment of CXCR5+ leukocytes from the periphery, and that CXCL13 expressed by damaged neurons can activate astrocytes. Moreover, we observed a striking dichotomy in the expression of TNFR2 between astrocyte populations in DR2b mice with EAE, suggesting that TNFR2 expression may favor astrocyte A2 versus A1 subpopulations. Thus, our proposal will test the central hypothesis that TNFR2 signaling in astrocytes curtails progression of neuroinflammation by restraining pathogenic and promoting protective astrocyte functions. We will test our hypothesis by (1) determining the role of TNFR2 for curtailing pathogenic astrocyte effector functions and preventing EAE progression; and (2) determining the role of TNFR2-regulated CXCL13/CXCR5 signaling for chronic astrocyte activation and function in progressive EAE in DR2bΔR2 mice. We will accomplish the objectives of this proposal by applying innovative new approaches including our progressive EAE model, developing astrocyte-specific TNFR2 and CXCR5 knockout mice, and innovative immunological and molecular biological methods, including single-cell RNA-seq and RNAScope.