干扰素调节因子5可能是流感病毒诱发急性肺损伤的关键调节子

Interferon regulatory factor 5 (IRF5) is a transcription regulatory factor activated by viral infection. The activated IRF5 can translocate into the nucleus where it binds to AAAG-rich sequence in the promoters of its targeted genes and consequently initiates the transcription of pro-inflammatory cytokines and type I interferon (IFN-I). In TLR7 signal pathway, IRF5 plays a central role. Influenza virus is a natural ligand of TLR7. Influenza virus infection can result in cytokine storm, leading to acute lung injury (ALI). The mechanism of influenza virus-induced ALI is unclear so far. Reports show that IFN-I promotes the development of immunological injury in lung during acute influenza virus infection, implying the involvement of IRF5 in ALI development. In previous work, we found that an oligodeoxynucleotide (MS19) with repeated AAAG which is similar to the sequence of IRF5 binding sites in promoters of the genes of pro-inflammatory cytokines and IFN-I could inhibit influenza viral infection-induced ALI in mice, hinting that IRF5 is a driving factor in influenza virus-induced ALI. In this study, we will study the molecular mechanism of influenza virus infection-induced ALI, focusing on IRF5 and its splicing variants, different promoters and gene polymorphisms, and use MS19 as a research tool to proof the role of IRF5 in influenza virus-induced ALI. The study may provide an experimental basis for the treatment of influenza virus induced ALI by targeting IRF5.

干扰素调节因子5（IRF5）是病毒感染活化的转录调控因子，活化的IRF5转位入核并与靶基因启动子上富含AAAG的序列结合，启动炎性细胞因子和I型干扰素（IFN-I）的转录。在TLR7信号通路中，IRF5起枢纽作用。流感病毒是TLR7天然配体，感染人体后可引起细胞因子风暴，诱发急性肺损伤（ALI），其分子机制尚不清楚。研究表明，IFN-I在急性流感病毒感染时可引起免疫损伤，这提示IRF5参与ALI的发生。在前期工作中，我们发现一种与IRF5结合位点序列相似、由AAAG重复序列组成的脱氧寡核苷酸（MS19）在小鼠能抑制流感病毒感染诱发的ALI，这提示IRF5是流感病毒诱发ALI的驱动因子。本课题拟围绕IRF5及其变异体、不同启动子和基因多态性，揭示流感病毒诱发ALI的分子机制，并以MS19为研究工具反证IRF5在流感病毒诱发ALI中的作用。该工作可为流感病毒诱发ALI的靶向治疗提供实验依据。

干扰素调节因子5（IRF5）是病毒感染活化的转录调控因子，活化的IRF5转位入核并与靶基因启动子上富含AAAG的序列结合，启动炎性细胞因子和I型干扰素（IFN-I）的转录。由于IRF5在TLR7信号通路中起枢纽作用，推测：流感病毒作为TLR7天然配体可能在感染人体后通过IRF5的参与引起细胞因子风暴，诱发急性肺损伤。在验证这种假设中取得了如下一些重要结果。1）流感病毒感染可明显上调感染局部或全身IRF5 mRNA水平：流感病毒肺炎患者外周血WBC中IRF5 mRNA水平明显升高；流感模型小鼠外周血WBC、肺、心和肠道组织中IRF5 mRNA水平明显升高；流感病毒感染的CAL-1细胞中IRF5 mRNA水平明显升高。2）社区肺炎（CAP）病人外周血WBC及肺泡灌洗细胞IRF5明显升高：CAP患者外周血WBC中IRF5 mRNA和蛋白水平明显升高，且与病情轻重正相关；重症CAP患者肺泡灌洗液细胞中IRF5 mRNA水平明显升高。3）CAP患者外周血WBC及肺泡灌洗细胞IRF5明显升高，且与其下游炎症细胞因子水平有关联。4）IRF5基因多态性与IRF5表达及CAP病情轻重有关：IRF5 rs77571059多态性基因型及等位频率与CAP病情轻重有关，且与CAP患者外周血WBC中IRF5 mRNA水平升高及与其下游炎症因子蛋白水平有关联。5）IRF5变异剪接体在细胞不同状态的表达有差异：人THP-1细胞中IRF5基因编码区PCR产物不同变异体出现频率有差异。6）干扰IRF5可以明显减轻流感病毒性急性肺损伤及全身过度炎症应答：AAAG ODN（M1）腹腔注射可挽救流感模型小鼠的生命，明显减轻肺部炎症、中性粒细胞浸润和肺部病变程度；AAAG ODN（MS19）对LPS刺激RAW264.7细胞IRF5及其下游炎症因子mRNA水平有明显的抑制作用，对灼伤皮肤无菌性炎症诱发IRF5 mRNA和蛋白水平及灼伤诱导急性肺损伤有明显的抑制作用。7）AAAG ODN (MS19)对IRF5活化后从胞浆向胞核转移有明显抑制作用：AAAG ODN (MS19) (MS19)能作为胞浆诱饵抑制IRF5的核转移。总之，本研究所取得的重要成果可对流感诱发免疫损伤的防治提供分子靶点，并有望将AAAG ODN开发成治疗流感病毒诱发急性肺损伤的免疫调节剂。