Department of Neurology, The University of Texas Health Science Center at Houston, McGovern Medical School, Houston, TX, 77030, USA.
Department of Neurology, The University of Texas Health Science Center at Houston, McGovern Medical School, Houston, TX, 77030, USA; Department of Neurology, Shanghai Fengxian District Central Hospital, Shanghai, China.
Neurochem Int. 2019 Jul;127:148-157. doi: 10.1016/j.neuint.2018.12.014. Epub 2018 Dec 23.
Interferon regulatory factor 4 (IRF4), a transcription factor recognized as a key regulator of lymphoid and myeloid cell differentiation, has recently been recognized as a critical mediator of macrophage activation. Previously we have reported that IRF4 signaling is closely correlated with anti-inflammatory polarization of microglia in adult mice after stroke. However, IRF4's role in the inflammatory response in the immature brain is unknown. Using a model of neonatal hypoxic ischemic encephalopathy (HIE) we investigated the regulatory action of IRF4 signaling in the activation of microglia and monocytes after HIE. IRF4 myeloid cell conditional knockout (CKO) postnatal day 10 (P10) male pups were subjected to a 60-min hypoxic-ischemic insult by the Rice-Vanucci model (RVM). IRF4 gene floxed mice (IRF4) were used as controls. Brain atrophy and behavioral deficits were measured 7 days after HIE. Flow cytometry (FC) was performed to examine central (microglial activation) and peripheral immune cell responses by both cell membrane and intracellular marker staining. Serum levels of cytokines were determined by ELISA. The results showed that IRF4 CKO pups had increased tissue loss and worse behavioral deficits than IRF4 mice seven days after HIE. FC demonstrated significantly more infiltration of monocytes and neutrophils in the ischemic brains of IRF4 CKO vs IRF4 pups. IRF4 CKO ischemic microglia were more pro-inflammatory as evidenced by higher expression of the pro-inflammatory marker CD68, and increased intracellular TNFα and IL-1β levels compared to controls. In addition, IRF4 deletion from myeloid cells resulted in increased levels of circulating pro-inflammatory cytokines and higher endothelial MMP9 expression after HIE. These data indicate that IRF4 signaling in myeloid cells plays a regulatory role in neuroinflammation and that deletion of myeloid IRF4 is detrimental to HIE injury, suggesting that IRF4 could serve as a potential therapeutic target for neonatal ischemic brain injury.
干扰素调节因子 4（IRF4）是一种转录因子，被认为是淋巴样和髓样细胞分化的关键调节因子，最近被认为是巨噬细胞激活的关键介质。我们之前报道过，IRF4 信号与成年小鼠中风后小胶质细胞的抗炎极化密切相关。然而，IRF4 在未成熟大脑中的炎症反应中的作用尚不清楚。我们使用新生缺氧缺血性脑病（HIE）模型研究了 IRF4 信号在 HIE 后小胶质细胞和单核细胞激活中的调节作用。IRF4 髓样细胞条件敲除（CKO）出生后第 10 天（P10）雄性幼鼠通过 Rice-Vanucci 模型（RVM）接受 60 分钟缺氧缺血性损伤。IRF4 基因 floxed 小鼠（IRF4）用作对照。HIE 后 7 天测量脑萎缩和行为缺陷。通过细胞膜和细胞内标志物染色进行流式细胞术（FC）以检查中枢（小胶质细胞激活）和外周免疫细胞反应。通过 ELISA 测定血清细胞因子水平。结果显示，与 IRF4 小鼠相比，IRF4 CKO 幼鼠在 HIE 后 7 天有更多的组织损失和更严重的行为缺陷。FC 显示，IRF4 CKO 幼鼠缺血大脑中单核细胞和中性粒细胞的浸润明显多于 IRF4 幼鼠。IRF4 CKO 缺血性小胶质细胞表现出更高的促炎表型，表现为促炎标志物 CD68 的表达更高，以及细胞内 TNFα 和 IL-1β 水平的增加，与对照组相比。此外，髓样细胞中 IRF4 的缺失导致 HIE 后循环中促炎细胞因子水平升高和内皮 MMP9 表达升高。这些数据表明，髓样细胞中的 IRF4 信号在神经炎症中起调节作用，髓样细胞中 IRF4 的缺失对 HIE 损伤有害，表明 IRF4 可作为新生儿缺血性脑损伤的潜在治疗靶点。
