Institute of NeuroImmune Pharmacology, Seton Hall University, South Orange, NJ, USA.
State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.
J Neuroimmune Pharmacol. 2019 Dec;14(4):551-564. doi: 10.1007/s11481-019-09845-2. Epub 2019 Jun 1.
Nicotine, the active ingredient in tobacco smoke, suppresses antiviral responses. Interferon regulatory factors (IRFs) regulate transcription of type I interferons (IFNs) and IFN-stimulated genes (ISGs) in this response. IRF7 is a key member of the IRF family. Expression of Irf7 is elevated in the brains of virus-infected animals, including human immunodeficiency virus-1 transgenic (HIV-1Tg) rats. We hypothesized that IRF7 affects nicotine's modulation of antiviral responses. Using CRISPR/Cas9 system, IRF7-mutant cell lines were created from human embryonic kidney 293FT cells in which 16 nicotinic acetylcholine receptors (nAChRs) were detected. Decreased expression of IRF7 was confirmed at both the mRNA and protein levels, as was IRF7-regulated cell growth in two IRF7-mutant cell lines, designated IRF7-Δ7 and IRF7-Δ11. In IRF7-Δ7 cells, expression of two nAChR genes, CHRNA3 and CHRNA9, changed modestly. After stimulation with polyinosinic-polycytidylic acid (poly I:C) (0.25 μg/ml) for 4 h to mimic viral infection, 293FT wild-type (WT) and IRF7-Δ7 cells were treated with 0, 1, or 100 μM nicotine for 24 h, which increased IFN-β expression in both types of cells but elevation was higher in WT cells (p < 0.001). Expression was significantly suppressed in WT cells (p < 0.001) but not in IRF7-Δ7 cells by 24-h nicotine exposure. Poly I:C stimulation increased mRNA expression of retinoic-acid-inducible protein I (RIG-I), melanoma-differentiation-associated gene 5 (MDA5), IFN-stimulated gene factor 3 (ISG3) complex, and IFN-stimulated genes (IRF7, ISG15, IFIT1, OAS1); nicotine attenuated mRNA expression only in WT cells. Overall, IRF7 is critical to nicotine's effect on the antiviral immune response. Graphical Abstract Involvement of IRF7 in nicotine's suppression of poly I:C-induced antiviral immune responses. PAMPs, such as a synthetic viral analogue of dsRNA poly I:C attack cells, will be recognized by PRRs, and the host innate immunity against viral infection will be activated. PRRs signaling trigger phosphorylation of IRF7 and IRF3 to induce their translocation to the nucleus and result in the production of type I IFNs. Then IFNs bind to IFNAR to activate the transcription factor ISGF3, a complex consisting of STAT1, STAT2, and IRF9. Further, it induces the expression of ISGs, including IFIT1, OAS1, IRF7, ISG15, etc. Nicotine suppresses the immune responses stimulated by poly I:C. In the IRF7-mutant cells, nicotine's suppressive effects on poly I:C-stimulated immune responses were restrained.
尼古丁是烟草烟雾中的活性成分，它抑制抗病毒反应。干扰素调节因子（IRFs）在这种反应中调节 I 型干扰素（IFNs）和 IFN 刺激基因（ISGs）的转录。IRF7 是 IRF 家族的关键成员。在包括人类免疫缺陷病毒-1 转基因（HIV-1Tg）大鼠在内的病毒感染动物的大脑中，Irf7 的表达水平升高。我们假设 IRF7 影响尼古丁对抗病毒反应的调节。使用 CRISPR/Cas9 系统，从检测到 16 个烟碱型乙酰胆碱受体（nAChRs）的人胚肾 293FT 细胞中创建了 IRF7 突变细胞系。两种 IRF7 突变细胞系（IRF7-Δ7 和 IRF7-Δ11）的 IRF7 表达在 mRNA 和蛋白质水平均降低，证实了 IRF7 调节细胞生长。在 IRF7-Δ7 细胞中，两个 nAChR 基因 CHRNA3 和 CHRNA9 的表达略有改变。用聚肌苷酸-聚胞苷酸（poly I:C）（0.25μg/ml）刺激 4 小时以模拟病毒感染后，用 0、1 或 100μM 尼古丁处理 293FT 野生型（WT）和 IRF7-Δ7 细胞 24 小时，这两种细胞类型中的 IFN-β 表达均增加，但 WT 细胞中的升高幅度更高（p<0.001）。WT 细胞中的表达受到显著抑制（p<0.001），但在 IRF7-Δ7 细胞中不受影响。poly I:C 刺激增加了视黄酸诱导蛋白 I（RIG-I）、黑色素瘤分化相关基因 5（MDA5）、IFN 刺激基因因子 3（ISG3）复合物和 IFN 刺激基因（IRF7、ISG15、IFIT1、OAS1）的 mRNA 表达；尼古丁仅在 WT 细胞中抑制 mRNA 表达。总的来说，IRF7 对于尼古丁对抗病毒免疫反应的影响至关重要。图形摘要IRF7 在尼古丁抑制 poly I:C 诱导的抗病毒免疫反应中的作用。PAMPs，例如合成的双链 RNA 病毒类似物 poly I:C，会被 PRRs 识别，宿主针对病毒感染的先天免疫将被激活。PRRs 信号触发 IRF7 和 IRF3 的磷酸化，诱导它们向核内易位，并导致 I 型 IFNs 的产生。然后 IFNs 与 IFNAR 结合，激活转录因子 ISGF3，这是一个由 STAT1、STAT2 和 IRF9 组成的复合物。进一步诱导 ISGs 的表达，包括 IFIT1、OAS1、IRF7、ISG15 等。尼古丁抑制 poly I:C 刺激的免疫反应。在 IRF7 突变细胞中，尼古丁对 poly I:C 刺激的免疫反应的抑制作用受到限制。
