甲状腺激素调控免疫应答在石英粉尘致炎性反应及肺纤维化中作用机制研究

Silicosis induced by long-term exposure to industrial crystalline silica is a high incidence of occupational disease in our country. Published studies have shown that persistent inflammatory reaction caused by immune imbalance is an important cause of pulmonary fibrosis. Inhibition of excessive immune-inflammatory reaction induced by silica dust is the key point of prevention and control of silicosis. The role of thyroid hormone (TH) in suppressing excessive immune response and maintaining immune balance has attracted attention in recent years. Based on previous studies, this project is intended to use of different doses of silica dust to culture with macrophages and pulmonary epithelial cells. We plan to use western blotting, real-time PCR, flow cytometry and other techniques to determine whether dust activated TH receptors and T3-activating enzyme (DIO2) in macrophages and lung epithelial cells and analyzed the effects of exogenous TH supplementation on silica-induced inflammation cytokines release from macrophage and pulmonary epithelial cell stromal transformation. Furthermore, the mitochondrial pathway and regulatory mechanism by which TH explore the role of immunomodulatory will be investigated. Then, we will observe the change of TH level in animals exposed to different dose of silica dust and evaluate potential mechanism of TH supplementing on Th1/Th2, inhibiting inflammatory reaction and pulmonary fibrosis. Finally, the possible dose-response relationship of silica exposure and peripheral blood TH level, and association of TH level and Th1/Th2, inflammatory response and pulmonary fibrosis will be evaluated in silica exposed workers. This project will provide new ideas for effective prevention and treatment of silicosis.

生产中长期接触石英粉尘所致矽肺是我国高发职业病，研究显示石英粉尘激发的固有免疫及持续性炎性反应是肺纤维化主要原因，基于甲状腺激素（TH）调节免疫应答和抗炎作用，本项目拟探讨TH抑制石英粉尘引起的过度免疫炎性反应和肺纤维化的作用及机制。在前期研究基础上，采用不同剂量纯石英粉尘进行细胞染尘，应用western-blot、RT-PCR、流式细胞术等技术测定巨噬细胞和肺上皮细胞TH受体活性及脱碘活化酶水平，分析补充外源性TH对石英诱导的巨噬细胞炎性因子释放和肺上皮细胞间质转化的影响，并探讨TH发挥免疫调控作用的线粒体途径及相关机制；研究接石英粉尘动物TH水平改变，以及补充TH影响Th1/Th2平衡及抑制炎性反应和纤维化的作用机制；采用分子流行病学方法在石英接触人群中分析接尘量与外周血TH水平，及TH和机体Th1/Th2平衡、炎性反应及肺纤维化程度的关系，为有效防治矽肺提供新思路。

本项目通过石英粉尘染尘细胞和小鼠，发现石英粉尘染毒巨噬细胞，损害了甲状腺激素受体（THRA）的mRNA表达，引起小鼠引起血清甲状腺激素（T3和T4）水平的下降。在细胞实验中，通过给与外源性三碘甲腺原氨酸（T3）和特异性阻断T3/TRα通路抑制T3水平，正反两方面的结果提示：甲状腺激素具有减轻石英粉尘诱导的巨噬细胞细胞毒性、氧化损伤和炎性因子分泌，并可抑制石英粉尘引起的细胞线粒体凋亡的作用，即甲状腺激素可缓解石英粉尘所致巨噬细胞的细胞损伤。在小鼠实验中，通过给与T3，能够减轻小鼠肺部损伤及炎症和肺纤维化，不论在染尘同时给与T3，还是在纤维化形成后（染尘28天后）再给予T3均能减轻矽尘引起的肺部炎性反应，并能抑制肺纤维化的进展。本项目研究结果提示甲状腺激素具有缓解石英粉尘所致小鼠炎症反应和肺纤维化的作用。.本项目进一步探讨了甲状腺激素缓解炎症和纤维化作用的机制，发现石英粉尘在暴露后的不同时间点均能使小鼠肺组织ATP水平和线粒体生物合成功能下降，并且提高肺组织乳酸含量和糖酵解水平，外源性T3可能通过促进PGC-1α调控的线粒体生物合成以及抑制HIF-1α/糖酵解通路来减轻石英粉尘引起的肺组织炎症和纤维化。最后在尘肺患者和非职业接尘对照的病例对照研究中，观察到尘肺患者甲状腺激素T3水平高于对照，T4和促甲状腺激素（TSH）水平低于对照，T3的升高可能是炎性反应和纤维化的代偿反应，TSH由于消耗过多而下降。研究结果提示甲状腺激素T3和TSH与尘肺患病危险度存在一定关联。.