散发型包涵体肌炎中p62/SQSTM1诱导炎性反应的分子机制

散发型包涵体肌炎（sIBM）是中老年人最常见的炎性肌肉疾病，其致病机制的研究长期徘徊在炎症和变性病之间。我们前期发现自噬功能蛋白p62是中国sIBM肌肉病理中阳性率最高的蛋白沉积标记物（91.3%），全外显子测序显示p62/SQSTM1基因变异为sIBM的遗传易感因子，携带该基因变异的患者MHC-I及MHC-II基因有显著高表达。因此p62相关的自噬异常可能诱导了sIBM的炎性反应。本研究拟采取转染质粒诱导产生高表达p62的细胞模型，采取注射重组腺病毒载体诱导骨骼肌p62高表达的大鼠模型，采用免疫组织化学染色和电镜技术观察细胞自噬与炎性因子的关系和骨骼肌病理改变，通过RT-PCR、蛋白印迹法和免疫共沉淀测定自噬和免疫炎性因子的表达和含量。通过上述研究预期证实炎性通路中的炎性小体激活、MHC上调和p62升高有关，明确p62诱导免疫炎性反应的分子机制，为探讨sIBM致病机制提供理论据。

Sporadic inclusion body myositis (sIBM) is a rare disease, but is the most common slowly progressive inflammatory muscle disease among people aged over 50 years old. The pathogenesis of sIBM is still unclear, and it has been hotly debated between inflammation and degeneration pathways. No effective treatment is available so far. We previously found that p62 protein is the most common protein aggregate (91.3%) observed in muscle biopsy of Chinese sIBM patients. P62 is an important functional protein involved in autophagy and immunomodulation. Rare variants in the p62/SQSTM1 gene were suggested to contribute to the genetic susceptibility of sIBM by using whole-exome sequencing. In addition, the patients with p62/SQSTM1 rare variants showed significantly higher expression of MHC-I and MHC-II genes by using whole-genome expression analysis and RT-PCR. Therefore, we hypothesise that the impairment in p62-related autophagy induces the inflammatory reaction in sIBM. In this project, a cell model transfected with p62/SQSTM1 cDNA and an animal model with p62 aggregate in skeletal muscle will be generated. Changes of autophagy, its relationship with inflammatory molecules, and pathology of muscle will be observed by immunohistochemistry and electron microscopy. Expression level of autophagic and inflammatory molecules will be analysed by using RT-PCR, western blotting, and co-immunoprecipitation. We aim to confirm that the activation of inflammasomes and up-regulation of MHC are associated with high expression of p62, and to further identify the mechanism of p62/SQSTM1 induced inflammation. This study will improve our understanding of pathogenesis of sIBM.