MBL抑制Th17分化缓解矽肺病变及其免疫调节机制

We recently found that the serum levels of mannan-binding lectin (MBL) in silicosis patients were significantly lower than those in healthy individuals, which was positively correlated with pulmonary functions but negatively correlated with the frequencies of T helper cell 17 (Th17) in the patients; MBL inhibited the differentiation of CD4+ T cells into Th17 cells in an in vitro Th17-inducing culture system; after exposure to silica particles, the pulmonary pathological changes in MBL–/– mice were more serious than thoses in wild type (WT) mice, and the expression of IL-17a and the frequencies of Th17 cells in MBL–/– mice were higher than thoses in WT mice. On the basis of these findings, we propose the present grant. The effects of MBL on the differentiation processe of Th17 cells, including their phenotype changes and the mechanisms underlining these effects such as the relative signal pathways of calreticulin and Th17 cell differentiation and the roles of cytokines and microRNAs, will be studied. The levels of MBL and the frequencies of Th17 cells in blood or lymphoid tissues will be examined, and the association among the MBL levels or MBL genotypes, Th17 cells’ frequencies, disease severity and pulmonary pathological changes will be analyzed in silicosis patients or in silicosis mouse models. The frequencies of Th17 cells and the disease pathology in MBL–/– mice with silicosis will be also examined after MBL reconstitution or MBL gene therapy. The innovation points and the significance of this project lie in: first, the viewpoint that MBL has a hand in acquired immune responses through regulating the differentiation of Th17 cells will be put forward, which will enrich the basic theory that innate immune system instructs acquired immune responses, and provide new theoretical bases and targets for treatment of diseases resulted from MBL imbalance and Th17 function disorder. Second, the pathogenesis mechanisms of MBL unbalance (deficiency or hyperfunction) will be expounded from a new viewpoint of immunoregulation disorder, which may supply new bases and strategies for treatment of this kind of diseases. Third, the relationship among MBL unbalance, Th17 disorder and silicosis disease severity will be revealed, which may help to elucidate the pathogenesis of silicosis and to develop novel strategies for silicosis therapies.

我们最近发现，矽肺病人血浆MBL浓度降低，其水平与肺功能正相关、与Th17频率负相关；在体外MBL可抑制CD4+ T细胞向Th17分化；染矽尘后MBL–/– 小鼠较WT小鼠急性肺泡炎重、IL-17a表达和Th17频率高。据此提出本项目，拟就MBL抑制Th17分化而缓解矽肺病变及其免疫调节机制进行以下研究：①临床：MBL与Th17及矽肺病变的关系；②体外：细胞表型与调节机制；③动物：MBL–/– 和WT小鼠矽肺模型MBL与Th17及病变的关系、MBL补充治疗/基因治疗的影响。创新点和意义在于：①提出MBL通过调控Th17分化参与免疫调节的新观点，将丰富天然免疫指导获得性免疫应答的基础理论；②从免疫调节紊乱新角度阐述MBL失衡有关疾病发病机制，为其治疗研究提供新的科学依据。③揭示MBL失衡—Th17紊乱—矽肺病变的关系，为靶向MBL调控Th17分化以治疗矽肺提供理论和实验依据。

甘露聚糖结合凝集素（MBL）是天然免疫系统中的关键分子，在抗感染免疫中起重要作用。辅助性T细胞Th17是一类重要的免疫效应细胞, 能参与多种疾病的发生发展。本项目阐明了MBL对Th17细胞的分化的调节及其分子机制，并揭示了MBL对矽肺病变的影响及调控机制。现已获得如下结果：①矽肺患者外周血中MBL水平与患者肺功能指标密切相关；且与Th17水平呈负相关；②MBL可抑制体外诱导CD4+ T细胞向Th17方向的极化；机制研究表明，MBL直接结合CD4+ T细胞中的芳香烃受体AhR，使后者的核转位发生阻滞，从而抑制其转录因子活性，并抑制CD4+T细胞向Th17细胞极化过程中AhR-STAT3正反馈环的活化，进而下调下游靶分子的转录和表达来影响Th17分化；③MBL 基因缺陷会加重小鼠矽肺的发病及后续的肺纤维化，并且MBL缺陷小鼠的Th17细胞比例较高。此外，在本项目的资助下，我们研究了MBL在肝脏微环境中的调控作用，揭示了MBL通过抑制肝细胞中CYP2E1的表达减轻对乙酰氨基酚（APAP）代谢所致肝损伤的作用机制；阐述了MBL可通过调节肝细胞内质网钙稳态与内质网应激反应参与伴有肝损伤的相关疾病的调控；发现MBL可通过作用于肝脏巨噬细胞或者肝星状细胞来调控肝脏免疫微环境，进而影响相关肝脏疾病的进展。总之，本项目的主要意义在于：①揭示了MBL对Th17分化的调控作用及机制，为Th17细胞的基础研究注入了新的内容，为人工干预Th17分化以防治有关疾病提供了新的理论依据；②从调控Th17细胞分化这一新的角度，阐释了MBL缺陷与矽肺发生发展之间的关系，为靶向MBL治疗矽肺及相关疾病提供了理论和实验依据；③ 揭示了MBL对免疫细胞（如MDSC细胞）和非免疫细胞（肝细胞，肝星状细胞）的免疫调控作用及相应的分子机制，为深入研究MBL的免疫调节功能增添了新的内容，有助于阐述MBL失衡（缺陷或过强）有关疾病的免疫病理机制。项目基本完成既定研究目标，发表相关科研论文9篇，其中SCI论文8篇。