治疗矽肺炎性反应及肺纤维化的新靶点-MCPIP1 (ZC3H12A）的作用机制研究

Silicosis is a systemic disease caused by inhalation of free crystalline silicon dioxide or silica. Phagocytosis of crystalline silica in the lung causes inflammatory cascade with subsequent fibrosis, resulting in systemic inflammatory response. Although more and more studies were undertaken to dissect the pathological mechanisms underlying the process of silicosis, the primary cause of this often devastaing dissease remains elusive. Diagnosis of silicosis could easily be missed, since which needs carefully documented records of occupational exposure and radiological features, with exclusion of other competing diagnoses. As yet, no curative treatment exists, but comprehensive management strategies help to improve quality of life and slow deterioration. Thus, further efforts are needed to find early molecular marker of diagnosis, new target to control the fibrosis induced by silica. Clinical evidence indicated that activation of alveolar macrophage induced by silica produces a rapid and sustained inflammation characterized by generation of monocyte chemotactic protein 1 (MCP-1) and MCP-1 induced protein 1 (MCPIP1, ZC3H12A). Our previous studies also suggested that MCPIP1 played a critical role in fibroblast proliferation and migration. However, the detailed cellular and molecular mechanisms underlying inflammation and the subsequent fibrosis in response to silica remain unknown. Therefore, we hypothesized that MCPIP1 will be the potential target of curative treatment for silicosis involving in regulation of inflammation and fibrosis. The proposed studies will be initiated in human sample followed by study in intact animals as well as primary cell cultures. Studies using classic pharmacological methods will be combined with molecular biological techniques as well as and immunological methods, all of which are currently well established in our laboratory. This proposal is both novel and innovative in that the efficacy of regulation of MCPIP1 expression can be of value to prevent or halt progression of silicosis in people. Our study will decipher the link between MCPIP1 and inflammation with subsequent fibrosis, induced by silica providing a novel insight into the potential of MCPIP1 in terms of opening up novel therapeutic avenues for silicosis.

矽肺是由长期吸入二氧化硅粉尘引起的以肺组织持续慢性炎症、进行性肺纤维化为主，并伴有全身系统性炎症为特征的全身性疾病。由于对矽肺发生发展机制不明，目前主要面临：1）早期缺少筛检诊断方法，2）后期肺纤维化缺乏特效治疗措施。因此发现矽肺早期诊断标志物及干预肺纤维化进程靶标成为迫切需要解决的问题。申请者前期研究表明，粉尘吸入引起肺部炎症，涉及单核细胞趋化蛋白-1（MCP-1）及其下游分子MCP-1诱导蛋白1（MCPIP1，ZC3CH12A)。进一步研究表明，MCPIP1还参与成纤维细胞增殖与迁移的调控。基于以上结果，申请者提出"MCPIP1是治疗矽肺炎症反应和肺纤维化的有效和关键靶点"这一假设，在原有研究基础上，应用分子生物学手段，结合经典药理学方法，从整体、细胞和分子水平系统揭示MCPIP1在矽肺炎症和肺纤维化中的功能和作用机制，研究成果将为临床治疗策略的选择和治疗药物靶标的遴选提供重要线索。

矽肺是由于长期吸入游离晶体二氧化硅粉尘引起的肺纤维化疾病，吸入的晶体二氧化硅对肺部造成持续的损伤，机体产生内源性免疫应答，修复损伤部位，而过度的修复最终导致了肺纤维化的发生。随着疾病的进行，可引起呼吸衰竭，死亡率高达50%～70%。矽肺病的发生是完全可预防的，但当前由于缺乏矽肺早期筛检的方法，早期患者得不到有效监护，一旦经胸片确诊为矽肺时，肺损伤已无逆转的可能。因此，寻找矽肺的特异性标志物，以及有效的治疗靶标对于矽肺的预防和治疗起着至关重要的作用。单核细胞趋化蛋白1（Monocyte chemoattractant protein-1，MCP-1）主要来源于巨噬细胞和肺泡上皮细胞，能够调节巨噬细胞的迁移和浸润。研究也发现其在SiO2处理的成纤维细胞中表达增加。MCPIP1/ZC3H12A是一种锌指蛋白。因最初在MCP-1处理的单核细胞中发现，又称MCP-1诱导蛋白（MCP1-induced protein，MCPIP1）。然而MCPIP1在矽尘引起的纤维化中的作用还不清楚。.本研究旨在从体内和体外两种矽肺模型下，利用肺成纤维细胞和巨噬细胞在内的不同细胞体系来研究MCPIP1对细胞凋亡、迁移和增殖的影响，从而进一步探讨MCPIP1在矽肺发病过程中可能的功能和作用机制，并初步研究了新藤黄酸（Neogambogic Acid，NGA）对降低实验性矽肺纤维化作用及机制。.本研究结果发现：.1. MCPIP1介导了MCP-1/CCR2在体外SiO2模型中对肺成纤维细胞的作用，且在2D和3D情况下，蛋白表达存在一定的差异；.2. 在体外实验中，MCPIP1通过p53和PUMA信号途径介导自噬的发生，促进了巨噬细胞的凋亡和活化，从而增加了条件培养基的促纤维化能力，显示了巨噬细胞中MCPIP1/p53/PUMA轴在肺纤维化发病机制中的重要作用；.3. NGA能够抑制SiO2引起的RAW264.7细胞凋亡和成纤维细胞中MCPIP1表达，降低了成纤维细胞的活化，进而抑制了纤维化的发生。同时减少了矽肺模型小鼠肺中巨噬细胞数量，并抑制了成纤维细胞中MCPIP1的表达，显示了其显著的抗矽肺纤维化能力。.综上所述，本研究将为现有矽肺炎症和纤维化治疗提供新的理论依据，对临床治疗策略的选择和治疗药物靶标的遴选具有重要的指导意义。