Dey Anup, Butcher Matthew, Gegonne Anne, Yagi Ryoji, Saeki Keita, Lee Eunju, Singer Dinah S, Zhu Jinfang, Ozato Keiko
Division of Developmental Biology, NICHD, NIH, Bethesda, MD, USA.
Laboratory of Immune System Biology NIAID, NIH, Bethesda, MD, USA.
J Neuroinflammation. 2025 Jun 2;22(1):148. doi: 10.1186/s12974-025-03449-9.
Microglia are resident innate immune cells in the central nervous system (CNS) that provides anti-microbial protection but also promote neuroinflammation. BRD4 is a chromatin reader that binds to acetylated histones and directs transcription of numerous genes. However, it is unknown whether and how BRD4 regulates microglia function. We addressed the role of microglia and BRD4 in a neuroinflammatory disease, experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis. It was reported earlier that in EAE, upon initial T cell activation in the peripheral lymphoid organs, CD4 T cells migrate to CNS and are reactivated by resident or migratory antigen presenting cells resulting in full manifestation of EAE (Rossi and Constantin, Front Immunol 7:506, 2016), (Plastini et al., Front Cell Neurosci 14:269, 2020). Using conditional deletion of Brd4 in CD4 T cells, we reveal that BRD4 regulates T helper cell differentiation and promotes T cell migration to CNS resulting in EAE. It remained unclear whether resident microglia are capable of reactivating migrating T cells to the CNS and if BRD4 plays a role in the process. To determine the role of microglial BRD4 in EAE, we constructed conditional knockout mice lacking Brd4 (Brd4cKO) in microglia. RNA-seq analysis showed that Brd4 deletion led to the downregulation of many microglia genes in both naive and EAE conditions. Consequently, Brd4cKO mice had markedly reduced EAE pathology, namely reduced paralysis, absence of axonal demyelination and inhibited expression of inflammatory cytokines. In vehicle treated mice (vehicle) abundant number of T cells were found to be near microglia that may lead to T cell- microglia interaction and T cell reactivation. In contrast, the number of T cells detected in the CNS of Brd4cKO mice was much fewer. This may lead to reduced T cell- microglia interaction, failure of T cells to get reactivated and hence failed to achieve full manifestation of EAE. These results demonstrate that microglia are critically involved in EAE disease progression for which BRD4 is essential. In summary, BRD4 directs transcription of genes defining microglia function. By so doing BRD4 promotes demyelination and neuroinflammation to exacerbate EAE.
小胶质细胞是中枢神经系统（CNS）中的常驻固有免疫细胞，既能提供抗菌保护，也会促进神经炎症。BRD4是一种染色质阅读器，可与乙酰化组蛋白结合并指导众多基因的转录。然而，BRD4是否以及如何调节小胶质细胞功能尚不清楚。我们研究了小胶质细胞和BRD4在一种神经炎症性疾病——实验性自身免疫性脑脊髓炎（EAE，一种多发性硬化症的小鼠模型）中的作用。此前有报道称，在EAE中，外周淋巴器官中的初始T细胞被激活后，CD4 T细胞迁移至中枢神经系统，并被常驻或迁移的抗原呈递细胞重新激活，从而导致EAE的全面发作（Rossi和Constantin，《Front Immunol》7:506，2016），（Plastini等人，《Front Cell Neurosci》14:269，2020）。通过条件性删除CD4 T细胞中的Brd4，我们发现BRD4调节辅助性T细胞分化，并促进T细胞向中枢神经系统迁移，从而导致EAE。目前尚不清楚常驻小胶质细胞是否能够将迁移的T细胞重新激活至中枢神经系统，以及BRD4在此过程中是否发挥作用。为了确定小胶质细胞BRD4在EAE中的作用，我们构建了小胶质细胞中缺乏Brd4（Brd4cKO）的条件性敲除小鼠。RNA测序分析表明，在未发病和EAE发病的情况下，Brd4的缺失均导致许多小胶质细胞基因的下调。因此，Brd4cKO小鼠的EAE病理明显减轻，即瘫痪减轻、轴突脱髓鞘缺失以及炎性细胞因子表达受到抑制。在接受载体处理的小鼠（载体组）中，发现大量T细胞靠近小胶质细胞，这可能导致T细胞与小胶质细胞相互作用以及T细胞重新激活。相比之下，在Brd4cKO小鼠的中枢神经系统中检测到的T细胞数量要少得多。这可能导致T细胞与小胶质细胞的相互作用减少，T细胞无法被重新激活，因此无法实现EAE的全面发作。这些结果表明，小胶质细胞在EAE疾病进展中起关键作用，而BRD4对此至关重要。总之，BRD4指导定义小胶质细胞功能的基因的转录。通过这样做，BRD4促进脱髓鞘和神经炎症，从而加重EAE。
