Department of Immunopathology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
Department of Research Facilities, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
J Leukoc Biol. 2017 Oct;102(4):1035-1054. doi: 10.1189/jlb.2MA0217-058R. Epub 2017 Jul 21.
Crosstalk between complement component 5a receptors (C5aRs) and TLRs in dendritic cells (DCs) occurs upon pathogen invasion; however, studies on C5aR and TLR crosstalk mainly focused on the modulating effect of C5a on TLR-induced cytokine production. To elucidate the breadth of C5aR and TLR4 crosstalk, the effect of simultaneous treatment with C5a and LPS was investigated in human monocyte-derived DCs (moDCs) 2 h after stimulation using whole transcriptome sequencing analysis. Although the effect of C5a on hallmark genes defining TLR4-induced DC maturation was limited at this time point, RNA sequencing analysis revealed a great variety of novel C5a targets, of which many interfere with TLR4-mediated immune activation. Analysis of functional relationships among these genes uncovered induction of a central immune regulatory network upon C5aR and TLR4 crosstalk, involving the transcription factors forkhead box (FOX)O1 and FOXO3 and the signaling molecules serum- and glucocorticoid-inducible kinase (SGK1), ribosomal S6 kinase 2 (RSK2), and PI3Kβ. C5aR and TLR crosstalk, furthermore, yielded down-regulation of mainly proinflammatory network branches, including IL-12B, IL-2Rα (IL-2RA), and jagged 1 (JAG1) and cooperative induction of predominantly anti-inflammatory network branches, including sphingosine kinase 1 (SPHK1), β2 adrenergic receptor (ADRB2), gastric inhibitory polypeptide receptor (GIPR), and four-and-a-half Lin11, Isl-1, and Mec-3 domains protein 2 (FHL2). Together, these data point toward induction of generalized immune regulation of DC function. Motif enrichment analysis indicate a prominent role for basic leucine zipper (bZIP) and IFN regulatory factor 4 (IRF4) transcription factors upon C5aR and TLR4 crosstalk. Additionally, differences were observed in the modulating capacity of C5a on DCs in the absence or presence of a pathogen (TLR stimulus). Our findings shed new light on the depth and complexity of C5aR and TLR4 crosstalk and provide new foci of research for future studies.
补体成分 5a 受体 (C5aR) 和树突状细胞 (DC) 中的 TLR 之间的串扰发生在病原体入侵时；然而，关于 C5aR 和 TLR 串扰的研究主要集中在 C5a 对 TLR 诱导的细胞因子产生的调节作用上。为了阐明 C5aR 和 TLR4 串扰的广度，在刺激后 2 小时，使用全转录组测序分析研究了同时用 C5a 和 LPS 处理对人单核细胞衍生的 DC (moDC) 的影响。尽管此时 C5a 对定义 TLR4 诱导的 DC 成熟的标志性基因的作用有限，但 RNA 测序分析显示出大量新的 C5a 靶标，其中许多靶标干扰 TLR4 介导的免疫激活。对这些基因之间的功能关系进行分析，揭示了 C5aR 和 TLR4 串扰诱导中央免疫调节网络的诱导，涉及转录因子叉头框 (FOX)O1 和 FOXO3 以及信号分子血清和糖皮质激素诱导的激酶 (SGK1)、核糖体 S6 激酶 2 (RSK2) 和 PI3Kβ。此外，C5aR 和 TLR 串扰导致主要促炎网络分支的下调，包括 IL-12B、IL-2Rα (IL-2RA) 和 jagged 1 (JAG1)，以及主要抗炎网络分支的协同诱导，包括鞘氨醇激酶 1 (SPHK1)、β2 肾上腺素能受体 (ADRB2)、胃抑制多肽受体 (GIPR) 和四个半 Lin11、Isl-1 和 Mec-3 结构域蛋白 2 (FHL2)。总之，这些数据表明诱导了 DC 功能的普遍免疫调节。基序富集分析表明，在 C5aR 和 TLR4 串扰时，碱性亮氨酸拉链 (bZIP) 和 IFN 调节因子 4 (IRF4) 转录因子起着重要作用。此外，在没有或存在病原体 (TLR 刺激) 的情况下，C5a 对 DC 的调节能力存在差异。我们的发现为 C5aR 和 TLR4 串扰的深度和复杂性提供了新的认识，并为未来的研究提供了新的研究重点。
