The role of TNFR2 in ameliorating progressive encephalomyelitis

进行性多发性硬化症（MS）的发病机制仍然是个谜。MS的进展与 患者脑脊液中细胞因子肿瘤坏死因子（TNF）的表达，提示TNF在脑脊液中起重要作用。 疾病过程中的关键作用。因此，靶向TNF被认为是MS的有吸引力的疗法。然而，令人惊讶的是， 在其他自身免疫性疾病中已证实有效的TNF阻断药物可触发MS的发作和恶化， 提供的证据表明，TNF也可以有助于CNS的保护和修复。随后的工作表明，致病性 TNF在EAE中的作用是通过TNF受体（TNFR）1介导的，而TNFR 2信号转导改善疾病并降低EAE的发病率。 脱髓鞘TNFR 2由中枢神经系统中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髓鞘再生。同样，星形胶质细胞可以表达TNFR 2，但TNFR 2的作用是不稳定的。 星形胶质细胞表达的TNFR 2对MS/EAE进展的影响仍未得到解决。具有致病性的星形胶质细胞（A1）或 已经描述了神经保护/抗炎特性（A2）;然而， 有害与有益的星形胶质细胞功能仍然没有完全了解。我们已经获得了令人兴奋的初步 结果支持星形胶质细胞TNFR 2在减少EAE进展中的核心作用， TNFR 2在表达人MS相关MHC II等位基因HLA-DR 2b的“人源化”转基因小鼠模型中， 缺乏TNFR 2分子表达的小鼠，本文称为DR 2b ΔR2小鼠。该模型提供了证据表明，HLA- DR 2b分子有利于Th 17的发育，同时损害Foxp 3 + Treg细胞的形成。重要的是，我们观察到， 当CNS驻留细胞TNFR 2缺陷时，DR 2b ΔR2小鼠发生进行性EAE和星形胶质细胞增生。 此外，在患有EAE的DR 2b ΔR2动物中，星形胶质细胞显示促炎细胞因子的表达增加， CXCR 5的表达增加。此外，CXCL 13在这些小鼠的CNS中上调，与先前的研究一致。 报道CXCL 13的CNS表达加重EAE并促进慢性白色物质病变， 依赖于从外周募集CXCR 5+白细胞，受损神经元表达的CXCL 13可以 激活星形胶质细胞此外，我们观察到星形胶质细胞群体之间TNFR 2表达的显著二分法， 在DR 2b小鼠EAE，表明TNFR 2表达可能有利于星形胶质细胞A2相对于A1亚群。因此，在本发明中， 我们的建议将检验星形胶质细胞中TNFR 2信号传导抑制神经炎症进展的中心假设 通过抑制致病性和促进保护性星形胶质细胞功能。我们将通过（1）确定 TNFR 2在减少致病性星形胶质细胞效应子功能和预防EAE进展中的作用;和（2）确定 TNFR 2调节CXCL 13/CXCR 5信号在进行性EAE中慢性星形胶质细胞活化和功能中的作用 DR 2b ΔR2小鼠。我们将通过采用创新的新方法来实现这一建议的目标， 我们的进行性EAE模型，开发星形胶质细胞特异性TNFR 2和CXCR 5敲除小鼠， 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.