IL-33促进干燥综合征并发间质性肺病的机制研究

Interstitial lung disease (ILD) is the main cause of death in patients with primary Sjögren's syndrome (pSS), with a high incidence, unclear etiology and no effective treatment. Existed researches and our pre-experiment results have shown that the IL-33 can promote pulmonary fibrosis through activating microphages. IL-33 levels of the serum and salivary glands were significantly raised in patients of pSS, while the IL-33 levels of pSS patients with ILD were significantly higher than that of non-ILD complicated patients, and were correlated with impaired pulmonary function. While the mucosal immune system is a whole integrated tissue network, then there may exist a crosstalk between different mucosal immune compartments. All of the aforementioned data lead us to hypothesize that salivary glands-drived IL-33 can induce the alveolar epithelial cells damage and release even more IL-33 in turn. IL-33 can also aggregate and activate macrophages through mST2, thereby secreting a large number of chemokines and inflammatory mediators, further activating and amplifying fibroblasts, and ultimately leading to ILD. In this project, we will construct pSS-ILD animal models and take advantage of the IL-33 and ST2-deficient mice to clarify the specific mechanism of IL-33 in promoting pSS-ILD, verify the internal crosstalk between salivary gland and lung, from the breakthrough point of IL-33, thus provide a scientific basis for exploring the salivary gland-lung bidirectional therapies of delaying pulmonary involvement.

并发间质性肺病（ILD）是原发性干燥综合征（pSS）患者死亡的主要原因，其发生率高，机制不清，目前尚无有效治疗。预实验及已有研究显示：动物模型中IL-33可活化巨噬细胞促进肺纤维化；pSS患者血清及唾液腺中IL-33水平显著升高，且pSS-ILD患者IL-33明显高于未合并ILD组，并与肺功能受损相关；不同的粘膜免疫组织间可存在crosstalk。据此提出假说：唾液腺来源的IL-33可促使肺泡上皮细胞损伤并释放更多IL-33，IL-33通过mST2诱导巨噬细胞的募集与活化，分泌促炎介质、激活成纤维细胞，最终导致ILD。本课题拟借助IL-33及ST2基因缺陷小鼠及pSS-ILD动物模型，通过验证唾液腺-肺crosstalk这一新视角，以IL-33为切入点，明确IL-33-mST2-巨噬细胞参与pSS-ILD的具体机制，为探索延缓肺部受累、开发唾液腺-肺的双向治疗提供科学依据。

干燥综合征（SS）是一种主要累及外分泌腺（如唾液腺、泪腺）的自身免疫性疾病，除外分泌腺外，至少1/3的患者可出现腺体外器官受累（如肺）且是导致患者死亡的重要原因。目前该病的治疗十分有限，主要采用替代和免疫调节疗法。IL33作为损伤相关分子，在局部粘膜免疫中发挥重要作用，但它在SS外分泌腺和腺体外器官损伤中的作用机制仍待深入阐述。我们的结果发现1）原发性SS（pSS）患者和动物模型的唾液腺中均有高水平的IL33及其受体ST2表达，且患者IL33水平与疾病活动度和免疫球蛋白水平正相关，pSS患者外周血中IL33水平较对照组显著升高，这些结果均提示IL33-ST2轴在SS中的潜在致病作用；2）通过IL33和ST2基因敲除鼠的研究则发现，IL33、ST2缺陷显著降低了SS的严重程度（灶指数、唾液流率、水通道蛋白5、ANA滴度、共刺激分子等均改善）；3）体外实验则发现IL33-ST2轴参与SS进程的可能机制是异常释放的IL33通过作用于高表达ST2的细胞（如唾液腺上皮细胞、巨噬细胞），导致黏附分子、趋化因子、细胞因子的释放，进而导致炎症细胞（如T细胞）浸润和T细胞向Th1分化及IFN的释放，进而加重SS；4）我们发现IL33参与纤维化，纤维化的皮肤中IL33、ST2表达均上调，IL33缺陷可缓解博来霉素诱导的皮肤纤维化严重程度，体外实验发现IL33可促进人皮肤成纤维细胞的增殖、迁移和胶原产生；5）SS的唾液腺和肺损伤之间存在密切关联：外源性给予NOD小鼠（自发SS模型）双链RNA类似物Poly(I:C)诱发肺损伤后，可显著加速、加重NOD小鼠的疾病进程，且受损的肺和唾液腺中均有免疫紊乱（IFN、TH1、TH2水平上调）和IL33水平的升高；6）为探索SS的发病机制以寻找新的诊疗靶标，我们也做了一定探索，结果发现SS患者体内IL2（可抑制Th17）水平降低从而导致了Treg-非依赖性的Th17上调；pSS患者外周血CD56bright/CD56dim NK细胞水平升高并对疾病有一定的诊断价值。总之，项目不仅探索了SS唾液腺局部IL33、ST2表达特征及其在SS免疫紊乱中的机制，还探讨了IL33在SS分泌腺和腺体外器官（如肺）之间的密切联系，丰富了人们对SS系统性损伤的认识并提供了新的潜在靶点。

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