辐射致抗原提呈紊乱及其激活Treg介导放射性肺纤维化发生的机制研究

Radiation-induced pulmonary fibrosis is one of clinically difficult problem in the radiotherapy to the thorax, and become the focus in radiation medical research. Our team recently found that thoracic irradiation induced the activation and proliferation of regulatory T cells (Tregs) in lungs, which mediated development of radiation-induced pulmonary fibrosis. But up to date, the mechanism of activation of Treg by radiation in radiation-induced pulmonary fibrosis has not been clarified. In this project, based on the radiation inducing hyper function of antigen-presenting cells and the relation with activated Treg, we plan to study the specific mechanism of thoracic radiotherapy-induced antigen-presentation and its effect on radiation-induced pulmonary fibrosis, find the interaction of the subsequent activation of Treg, focus on the radiation-induced pulmonary fibrosis treatment based on T cell receptor-specific CRISPR/Cas9 inhabiting activation of Treg subgroup promoted by radiation induced-antigen presentation, in order to provide novel idea for demonstrating pathogenesis and therapeutic measure in radiation-induced pulmonary fibrosis.

无论是在恶性肿瘤放疗还是急性放射病晚期，放射性肺纤维化都是临床治疗面临的一大难题，一直是放射医学研究的热点之一。本课题组前期发现，重要的免疫调节细胞——调节性T淋巴细胞（Treg）在胸部照射后肺内出现异常活化及增殖，并在放射性肺纤维化的发生中发挥重要作用。然而辐射激活Treg的机理仍未明了。本项目根据辐射诱导抗原提呈细胞功能亢进，并与Treg活化存在相关性的科学线索，开展放射性肺纤维化的机制研究：1）辐射诱导肺内抗原提呈紊乱及机制；2）抗原提呈紊乱在放射性肺纤维化发生中的作用；3）抗原提呈紊乱导致肺内特异亚群Treg异常活化机制；4）应用CRISPR/Cas9基因编辑技术阻断抗原提呈紊乱激活的特定Treg亚群，验证其在在放射性肺纤维化中的作用，以期为阐明放射性肺纤维化的免疫发病机制和防治研究提供新思路。

前期发现Treg在胸部照射后肺内出现异常活化及增殖，并通过诱导纤维细胞分化及肺上皮细胞发生EMT在放射性肺纤维化中发挥重要作用，然而其机理仍未明了。本项目着重照射对DC、巨噬及T细胞的作用的研究，同时对自噬及TGF-β3在放射性肺纤维化中的作用进行探讨。结果显示，在细胞及动物水平，辐射可直接或通过肺上皮细胞损伤引起DC、巨噬细胞抗原提呈功能增强，从而诱导Treg分化增殖，促进肺上皮细胞发生EMT，参与放射性肺纤维化的发病，该作用通过下调DC细胞内TSC1而发生，其中MHC-II和IL-6是TSC1调控的重要靶基因。辐射诱导的自噬可介导EMT的发生，HIF-1α诱导表达能够促进辐射引发的自噬反应，而及β-catenin是自噬介导辐射诱导Beas-2B细胞EMT的关键分子。TGF-β3通过调控smad3通路抑制γ射线诱导的EMT，外源性TGF-β3可抑制内源性TGF-β1的表达降低，从而减少辐射诱导的EMT的发生。上述结果为放射性肺纤维化发病机制的研究提供了理论基础，为其防治及诊断提供了新思路。