Angiogenin在巨噬细胞中的功能及分子机制研究

As one of the most important response cells in the innate immune system, macrophages dysfunction is associated with the pathogenesis of inflammatory bowel disease (IBD) and other inflammatory diseases. Our previous work suggests that angiogenin (ANG) carries anti-inflammatory effect by targeting macrophages, thus contributes to the development of IBD, but its specific functions and mechanisms in macrophages need to be clarified. We have proved that ANG does not affect the macrophage's phagocytosis, intracellular bacterial killing, and chemotaxis functions. In this study we will combine DSS-induced IBD mouse model and in vitro cellular and molecular methods to elucidate the functions and mechanisms of action of ANG in macrophages and IBD. First, we will reveal the functions of ANG in macrophage by analyzing the role of ANG in cell survival, secretion, and M1/​​M2 polarization. Next, we will uncover the underlying molecular mechanisms of ANG-regulated macrophage functions from ANG-regulated gene expression and tiRNA production. Finally, we will verify the "ANG-molecular mechanism-macrophage function" axis in IBD mouse model. This project not only expands our understanding of ANG functions and mechanism, but also deepens our knowledge of the pathogenesis of IBD. Moreover, our study will provide a new direction for the diagnosis and/or prevention of IBD.

巨噬细胞作为天然免疫系统的重要应答细胞，其功能异常与炎症性肠病（IBD）等多种炎症性疾病密切相关。我们的前期工作提示血管生成素（angiogenin，ANG）可能通过靶向巨噬细胞发挥抑炎作用，从而影响IBD的发生发展，但其在巨噬细胞中的具体功能和作用机制有待研究阐明。在已经证明ANG不影响巨噬细胞吞噬、杀菌和趋化能力的基础上，本项目拟以DSS诱导的IBD小鼠为研究模型，并结合体外细胞和分子水平的研究，首先分析ANG对巨噬细胞存活、分泌、M1/M2型极化等的影响，揭示ANG在巨噬细胞中的功能；进一步，从ANG调控基因表达和tiRNA产生的角度阐释ANG影响巨噬细胞功能的分子机制；最后，在IBD小鼠中验证“ANG-分子机制-巨噬细胞功能”作用轴的抑炎效应。本项目研究不仅可拓展对ANG功能机制的了解，而且将深化对IBD发病机制的认识，并有可能从中发展IBD诊治和/或预防的新思路新途径。

髓系细胞与肠上皮细胞间的互作对于肠道屏障完整性维持至关重要。研究发现，髓系细胞能分泌多种细胞因子来调控肠上皮细胞的生物学功能；然而，当前对参与该过程的具体细胞因子及其作用机制的认识还非常有限。在本项目研究中，我们发现髓系细胞能够分泌血管生成素（angiogenin, ANG）来保护肠上皮屏障完整性，进而减轻葡聚糖硫酸盐（Dextran Sulfate Salt, DSS）诱导的小鼠肠炎发病程度。机制上，髓系细胞分泌的ANG通过其功能受体pelxin-B2（PLXNB2）作用于肠上皮细胞，一方面介导胞内tiRNA（tRNA-derived stress-induced small RNA）产生来保护细胞存活，另一方面促进rRNA（ribosomal RNA）的转录来维持细胞增殖。更为重要的是，重组ANG蛋白能够显著改善DSS诱导的小鼠肠炎症状。综上，本研究首次证明ANG作为髓系细胞与肠上皮细胞间对话的新因子，能够通过保护肠上皮屏障完整性来减轻肠炎发生，提示其作为IBD防治新靶点的可能性。

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