Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.
International Associated Laboratory (LIA) CNRS "IM-TB/HIV" (1167), Toulouse, France.
Front Immunol. 2018 Jun 12;9:1123. doi: 10.3389/fimmu.2018.01123. eCollection 2018.
DC-SIGN (CD209/CLEC4L) is a C-type lectin receptor (CLR) that serves as a reliable cell-surface marker of interleukin 4 (IL-4)-activated human macrophages [M(IL-4)], which historically represent the most studied subset within the M2 spectrum of macrophage activation. Although DC-SIGN plays important roles in (Mtb) interactions with dendritic cells, its contribution to the Mtb-macrophage interaction remains poorly understood. Since high levels of IL-4 are correlated with tuberculosis (TB) susceptibility and progression, we investigated the role of DC-SIGN in M(IL-4) macrophages in the TB context. First, we demonstrate that DC-SIGN expression is present both in CD68 macrophages found in tuberculous pulmonary lesions of non-human primates, and in the CD14 cell population isolated from pleural effusions obtained from TB patients (TB-PE). Likewise, we show that DC-SIGN expression is accentuated in M(IL-4) macrophages derived from peripheral blood CD14 monocytes isolated from TB patients, or in macrophages stimulated with acellular TB-PE, arguing for the pertinence of DC-SIGN-expressing macrophages in TB. Second, using a siRNA-mediated gene silencing approach, we performed a transcriptomic analysis of DC-SIGN-depleted M(IL-4) macrophages and revealed the upregulation of pro-inflammatory signals in response to challenge with Mtb, as compared to control cells. This pro-inflammatory gene signature was confirmed by RT-qPCR, cytokine/chemokine-based protein array, and ELISA analyses. We also found that inactivation of DC-SIGN renders M(IL-4) macrophages less permissive to Mtb intracellular growth compared to control cells, despite the equal level of bacteria uptake. Last, at the molecular level, we show that DC-SIGN interferes negatively with the pro-inflammatory response and control of Mtb intracellular growth mediated by another CLR, Dectin-1 (CLEC7A). Collectively, this study highlights a dual role for DC-SIGN as, on the one hand, being a host factor granting advantage for Mtb to parasitize macrophages and, on the other hand, representing a molecular switch to turn off the pro-inflammatory response in these cells to prevent potential immunopathology associated to TB.
树突状细胞特异性细胞间黏附分子 3 摄取非（DC-SIGN）是一种 C 型凝集素受体（CLR），作为白细胞介素 4（IL-4）激活的人巨噬细胞[M（IL-4）]的可靠细胞表面标志物，M（IL-4）巨噬细胞是巨噬细胞活化的 M2 谱中研究最多的亚群。尽管 DC-SIGN 在结核分枝杆菌（Mtb）与树突状细胞相互作用中发挥重要作用，但它在 Mtb-巨噬细胞相互作用中的贡献仍知之甚少。由于高水平的 IL-4 与结核病（TB）易感性和进展相关，我们研究了 DC-SIGN 在 TB 背景下 M（IL-4）巨噬细胞中的作用。首先，我们证明 DC-SIGN 表达存在于非人类灵长类动物结核性肺病变中发现的 CD68 巨噬细胞中，也存在于从结核患者胸腔积液中分离出的 CD14 细胞群中（TB-PE）。同样，我们表明，来自结核患者外周血 CD14 单核细胞或用无细胞 TB-PE 刺激的 M（IL-4）巨噬细胞中 DC-SIGN 的表达增强，这表明表达 DC-SIGN 的巨噬细胞与 TB 相关。其次，我们使用 siRNA 介导的基因沉默方法对 DC-SIGN 耗尽的 M（IL-4）巨噬细胞进行了转录组分析，并发现与对照细胞相比，Mtb 刺激后促炎信号上调。该促炎基因特征通过 RT-qPCR、细胞因子/趋化因子基于蛋白阵列和 ELISA 分析得到证实。我们还发现，与对照细胞相比，尽管摄取的细菌量相同，DC-SIGN 的失活会使 M（IL-4）巨噬细胞对 Mtb 细胞内生长的容纳能力降低。最后，在分子水平上，我们表明 DC-SIGN 负干扰另一种 CLR Dectin-1（CLEC7A）介导的促炎反应和 Mtb 细胞内生长的控制。总的来说，这项研究强调了 DC-SIGN 的双重作用，一方面作为赋予 Mtb 寄生巨噬细胞优势的宿主因素，另一方面作为关闭这些细胞中促炎反应的分子开关，以防止与 TB 相关的潜在免疫病理学。
