TLR9信号分子及其激动剂CPG-ODN对辐射损伤的治疗作用及机制研究

In 2008, Burdelya reported that activating Toll-Like Receptor 5(TLR 5) agonist CBLB502, a polypeptide derived from Salmonella flagellin,effectively protected mice from radiation damage.It mitigated radiation-induced damages both on gastrointestinal and hematopoietic systems,and the survival rate was also increased when CBLB502 was administrated pre- or post-irradiation. The radioprotective effects was thought to be due to the activation of increased nuclear factorκB(NF-κB) levels. As one of the most critical members is TLRs family,TLR9 shares extensive homology with TLR5, which promoted us to verify the potential radioprotective effect of TLR9 angonist Cytosine phosphate Guanosine oligodeoxynucleotides (CpG-ODN). Containing unmethylated cytosine-guanine motifs, CpG-ODN could also activate NF-κB through activating MyD88、IRAKs signaling pathway, thus induced the expression of IFN-I. Previously, we have demonstrated that CpG-ODN effectively mitigated toxicity induced by 60Co-γ-irradiation in mice through TLR9 actication, indicating that TLR9 might be a novel target for radiation sickness.In this project,through CPG-ODN activation of TLR9, we will investigate the therapy effct by the CPG to different radial and different tissue. And wo also will compare the therapy effect in the injure induced by different radial. Firstly, Radiation-induced lung injury (radiation pneumonitis and radiation pulmonary fibrosis) occurred often ,when radiotherapy was used in thoracic tumor. We will study the therapy effect of CPG-ODN to the radiation pneumonitis and radiation pulmonary fibrosis. Secondly, there are not effective therapy drug in the high LET radial at present. We will investigate the therapy effect of CPG-ODN to the injury induced by high LET radial and compare the difference between the low LET and high LET radial. This will provide us a novel target for radioprtection and also provide us strong experimental evidence for CPG-ODN as a novel radioprotectant.

2008年国外学者发现激活TLR5对受照射小鼠具有很好的防护作用，为利用TLRS防治辐射损伤开辟了一条全新的研究思路。TLR9也是TLRs家族的重要成员，其介导的信号转导途径与TLR5类似，通过募集MyD88、IRAKs等分子，激活NF-κB和磷酸化IRAK1，诱导I型干扰素等的表达。我们的前期研究发现TLR9激动剂CPG-ODN对γ射线损伤造血系统和肠道系统具有明确治疗作用，提示TLR9是潜在重要的辐射治疗新靶点。本项目拟利用CPG-ODN激活TLR9信号分子,进一步研究其对不同射线和不同组织的辐射治疗效果，并对其治疗效果进行比较：1. 胸部肿瘤放疗时容易发生放射性肺炎，观察CPG-ODN对放射性肺损伤的治疗效果；2、高LET射线目前尚无有效治疗药物，研究其对高能粒子（高LET射线）辐射损伤治疗效果并同低LET射线(γ射线)进行比较。评价TLR9信号分子作为不同电离射线导致的辐射损伤防治新靶点的研究前景，为其激动剂CPG-ODN作为新型辐射防治药物提供理论基础和实验依据。

2008年国外学者发现激活TLR5对受照射小鼠具有很好的防护作用，为利用TLRS防治辐射损伤开辟了一条全新的研究思路。TLR9也是TLRs家族的重要成员，其介导的信号转导途径与TLR5类似，通过募集MyD88、IRAKs等分子，激活NF-κB和磷酸化IRAK1，诱导I型干扰素等的表达。我们的前期研究发现TLR9激动剂CPG-ODN对γ射线损伤造血系统和肠道系统具有明确治疗作用，提示TLR9是潜在重要的辐射治疗新靶点。本项目拟利用CPG-ODN激活TLR9信号分子,进一步研究其对不同射线和不同组织的辐射治疗效果，并对其治疗效果进行比较：1. 胸部肿瘤放疗时容易发生放射性肺炎，观察CPG-ODN对放射性肺损伤的治疗效果；2、高LET射线目前尚无有效治疗药物，研究其对高能粒子（高LET射线）辐射损伤治疗效果并同低LET射线(γ射线)进行比较。评价TLR9信号分子作为不同电离射线导致的辐射损伤防治新靶点的研究前景，为其激动剂CPG-ODN作为新型辐射防治药物提供理论基础和实验依据。.尽管该课题是一年期的小额资助基金，时间短，经费少。但是本项目执行情况良好，严格按计划任务书所列研究内容进行，并增加做了部分标书中没有列明的内容。首先：初步证实了 CpG-ODN 具有减轻γ射线和12C6+离子照射所致RAW264.7 细胞损伤的作用，并且对减轻12C6+离子照射后的细胞损伤的作用更加明显，其原因可能与提高了电离辐射后细胞的损伤修复能力，促进细胞完成分裂，抑制凋亡反应有关。其次：我们建立了辐射诱导的纤维化小鼠模型，研究发现CPG-ODN对放射性肺损伤具有明确的治疗效果，电离辐射后20 w内IL-4和IL-13的表达升高，呈时间依赖性的维持在高水平波动，而照后给予CpG-ODN处理能显著降低这两种细胞因子的表达。接下来（此部分未列在标书研究计划中）我们研究发现CpG-ODN对5 Gy12C6+离子照射导致的动物损伤具有明确的治疗作用，具体表现为能够提高小鼠受照后的存活率，抑制白细胞的降低，减轻骨髓组织的损伤，缓解胸腺和脾脏的损伤同抑制这两个组织内细胞的凋亡和 DNA 双链的断裂。标注本基金资助SCI论文已经发表2篇；另已经投稿SCI论文1篇。项目负责人先后3次在全国和全军放射医学学术会议中做大会报告。该项目资助培养研究生3名。总之，项目圆满完成。