TPL-2;ERK1/2 signaling promotes host resistance against intracellular bacterial infection by negative regulation of type I interferon production [Set 1]

Analysis of Mtb infected murine macrophages derived from C57Bl/6 WT, TPL2KO, IFNARKO & TPL2IFNAR DKO mice [Set 1] Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), remains a leading cause of mortality and morbidity worldwide, causing approximately 1.4 million deaths per year. Key immune components for host protection during tuberculosis include the cytokines IL‐12, IL‐1 and TNF‐α, as well as IFN‐γ and CD4+ Th1 cells. However, immune factors determining whether individuals control infection or progress to active tuberculosis are incompletely understood. Excess amounts of type I interferon have been linked to exacerbated disease during tuberculosis in mouse models and to active disease in patients, suggesting tight regulation of this family of cytokines is critical to host resistance. In addition, the immunosuppressive cytokine IL‐10 is known to inhibit the immune response to Mtb in murine models through the negative regulation of key pro-inflammatory cytokines and the subsequent Th1 response. We show here, using a combination of transcriptomic analysis, genetics and pharmacological inhibitors that the TPL-2-ERK1/2 signaling pathway is important in mediating host resistance to tuberculosis through negative regulation of type I interferon production. The TPL-2-ERK1/2 signalling pathway regulated production by macrophages of several cytokines important in the immune response to Mtb as well as regulating induction of a large number of additional genes, many in a type I IFN dependent manner. In the absence of TPL-2 in vivo, excess type I interferon promoted IL-10 production and exacerbated disease. These findings describe an important regulatory mechanism for controlling tuberculosis and reveal mechanisms by which type I interferon may promote susceptibility to this important disease. Macrophages were derived from C57Bl/6 bone marrow, plated and infected with Mtb H37Rv (or not) in duplicate wells. Samples were then harvested for RNA at time 0 (uninfected only), 15m, 30m, 1hr, 3hr, 6hr and 24hr.

源自C57Bl/6野生型（WT）、TPL2基因敲除（TPL2KO）、IFNAR基因敲除（IFNARKO）及TPL2与IFNAR双基因敲除（TPL2IFNAR DKO）小鼠的结核分枝杆菌（Mycobacterium tuberculosis, Mtb）感染巨噬细胞分析【数据集1】。由结核分枝杆菌引发的结核病仍是全球范围内导致死亡与患病的主要病因之一，每年造成约140万人死亡。结核病宿主防御过程中的关键免疫组分包括细胞因子IL-12、IL-1、肿瘤坏死因子-α（TNF-α）以及干扰素-γ（IFN-γ）和CD4+辅助性T细胞1（Th1）。然而，决定个体能否控制感染或进展为活动性结核病的免疫因素仍未完全阐明。在小鼠模型中，过量的I型干扰素与结核病病情加重相关；在患者体内，其也与活动性结核病存在关联，这提示该细胞因子家族的精准调控对于宿主抗感染抵抗力至关重要。此外，已知免疫抑制性细胞因子IL-10可通过负调控关键促炎细胞因子及后续的Th1应答，在小鼠模型中抑制机体针对Mtb的免疫反应。本研究结合转录组学分析、遗传学手段与药理学抑制剂实验证实，TPL-2-ERK1/2信号通路可通过负调控I型干扰素的产生，在介导宿主抗结核病抵抗力中发挥关键作用。TPL-2-ERK1/2信号通路可调控巨噬细胞分泌多种参与抗Mtb免疫应答的细胞因子，同时还可调控大量其他基因的诱导表达，其中多数基因的调控依赖于I型干扰素通路。在体内缺失TPL-2的情况下，过量的I型干扰素会促进IL-10的产生并加重病情。上述研究结果阐明了调控结核病的重要机制，并揭示了I型干扰素可能促进机体对该重大疾病易感性的具体通路。本研究中，巨噬细胞源自C57Bl/6小鼠骨髓，接种培养后以Mtb H37Rv菌株进行感染（设置未感染对照组），每组均设复孔。随后分别在0小时（仅未感染组）、15分钟、30分钟、1小时、3小时、6小时及24小时收集样本以提取RNA。