TRAIL调控Th1/Th2细胞免疫平衡保护放射性肺损伤的机制研究

There is no effective means of prevention of radiation-induced lung injury (RILI), a common complication of lung cancer radiotherapy. We have demonstrated that Th1/2 imbalance existed in RILI process. Further study showed that the expression level of TRAIL decreased with increased Th1 inflammatory reaction in radiation pneumonia，the early phase of RILI. We hypothesize that TRAIL signaling pathway reduces the occurrence of radiation-induced lung injury by maintaining Th1/Th2 immunologic balance. This proposal aims at investigating the immunoregulation mechanism of TRAIL in RILI by a RILI mice model. We will explore the correlation between TRAIL, Th1 and Th2 through flow cytometry. CD4+ cells, separated by magnetic beads, will be induced to differentiate into Th1 and Th2 cells in vitro to explore the molecular mechanism of TRAIL expression differences between Th1 and Th2 cells. TRAIL-/- mice and mice with peritoneal injection of sTRAIL will be established to investigate the regulation of TRAIL on RILI. Finally, RILI mice with Lewis lung cancer will be established to investigate the regulation mechanism of TRAIL on Th1/2 balance in the tumor environment. This study aims at exploring the new immunoregulation mechanism and immunotherapy of RILI.

放射性肺损伤是肺癌放疗的常见并发症，目前尚缺乏有效的防治手段。我们前期发现放射性肺损伤中存在Th1/Th2细胞免疫失衡；且放射性肺损伤早期，TRAIL的表达下降，Th1炎性反应升高。我们推测TRAIL信号通路可通过维持Th1/Th2免疫细胞动态平衡，缓解放射性肺损伤的发生。为探讨TRAIL在放射性肺损伤中的免疫调节功能，本项目拟通过构建小鼠放射性肺损伤模型，采用流式技术探讨放射性肺损伤中Th1、Th2和TRAIL间的表达相关性；通过磁珠分选体外诱导Th1/Th2细胞，探讨TRAIL在Th1/Th2细胞中表达差异的分子机制；通过TRAIL-/-小鼠和体外合成鼠源性sTRAIL干预实验探讨TRAIL对放射性肺损伤的调控作用；最后构建Lewis肺癌放射性肺损伤小鼠模型，探讨在肿瘤环境下TRAIL调控Th1/Th2细胞免疫平衡的情况。旨在探索放射性肺损伤中的免疫调控机制和新的免疫治疗途径。

放射性肺损伤作为肺癌放疗的常见不良反应，可引起放射野内正常肺组织的炎症。这不仅阻碍继续放疗杀伤肿瘤，严重情况下还影响肺功能、威胁生命，目前尚无明确的预防措施。TRAIL作为肿瘤坏死因子超家族的一员，有着诱导细胞凋亡的作用，并且参与Th1/Th2细胞动态平衡，与免疫炎症反应密切相关。我们构建的放射性肺损伤小鼠模型表明，放疗后肺组织炎症加重，TRAIL表达下调，Th1（T-bet、IFN-γ）与Th2（GATA-3、IL-10和IL-13）相关细胞因子表达升高。相较于野生型小鼠，肺部条件性敲除TRAIL基因小鼠肺部炎症减轻，Th1与Th2相关细胞因子表达下调，小鼠外周血和脾脏Th1/Th2细胞比例上升，其中Th1中CD262升高，Th2中CD262表达下降。外源性TRAIL蛋白可下调小鼠外周血和脾脏中初始CD4T细胞Th1/Th2，这些结果提示TRAIL引起Th1/Th2失衡并参与放射性肺炎的进展。TRAIL敲除不影响肿瘤生长，但是Treg相关细胞因子与Th1、Th2相关细胞因子表达下调。本项目从全新的角度说明了TRAIL信号通路导致Th1/2细胞免疫平衡，进而影响放射性肺损伤，可能为放射性肺损伤的治疗提供新的思路。