新趋化细胞因子FAM3D在结肠稳态和炎症中的作用和机制的研究

The human genome project has been completed. Functions of a lot of genes are still unknown. The relationships of chemokines and their receptors and intestinal immune and inflammatory bowel disease are concerned. We find several novel chemotactic cytokines using the genomics strategies from human genome encoding genes. FAM3D is one of them. We find that the FAM3D has a chemotactic activity in human peripheral blood phagocytic cells. FPR1 and FPR2 are the high affinity receptors of FAM3D. FAM3D is constitutively highly expressed in gastrointestinal tract and significantly upregulated in DSS induced colitis mice tissues. FPR1 and FPR2 are constitutively highly expressed in intestinal epithelial cells and phagocytes. In vivo experiments demonstrated that DSS induced colitis in Fam3d-/- mice were significantly heavier than the wild-type mice. The clearance rate of intestinal bacteria in Fam3d-/- mice was significantly lower than that in wild-type mice. These results are highly consistent with phenotypes of immune defense, intestinal homeostasis and repair reported in Fpr1-/- and Fpr2-/- mice. On this basis, this project will clarify functions and mechanisms of FAM3D in colon homeostasis and development of inflammation at the clinical, animal, cell and molecular levels, which will provide new mechanisms for regional intestinal immunity and new ideas for diagnosis and treatment of inflammatory bowel disease with important theory significance and the latent application value.

人类基因组计划已完成，许多基因功能仍未知。趋化因子及受体与肠道免疫和炎症性肠病关系受到关注。我们利用组学策略原创地从人类基因组编码基因中发现多个潜在新趋化细胞因子，FAM3D是其中之一。我们发现FAM3D对人外周血吞噬细胞具有趋化活性，证明FPR1和FPR2是FAM3D高亲和力受体。FAM3D在胃肠组成性高表达、DSS诱导的小鼠结肠炎组织明显上调。FPR1和FPR2在吞噬细胞和肠道上皮组成性高表达。体内实验显示DSS诱导的Fam3d-/-小鼠结肠炎明显重于野生鼠。Fam3d-/-小鼠肠道菌清除率明显低于野生鼠，与报道的Fpr1-/-和Fpr2-/-小鼠免疫防御、肠道稳态和修复表型高度一致。在此基础上，本课题将在临床水平、动物整体、细胞和分子水平阐明FAM3D在结肠稳态和炎症中的作用和机制，为肠道区域免疫提供新机制，为炎症性肠病诊断治疗提供新思路，具重要的理论意义和潜在的应用价值。

人类基因组计划已完成，许多基因功能仍未知。趋化因子及受体与肠道免疫和炎症性肠病关系受到关注。我们利用组学策略原创地从人类基因组编码基因中发现多个潜在新趋化细胞因子，FAM3D是其中之一。我们发现FAM3D对人外周血吞噬细胞具有趋化活性，证明FPR1和FPR2是FAM3D高亲和力受体。本项目研究显示，FAM3D特异地在消化道，尤其是结肠上皮细胞组成性高表达，可分泌到腺腔成为黏液层的组成成分。其功能性受体FPR1和FPR2也在吞噬细胞和肠道上皮组成性高表达，在肠道稳态和炎症调控中扮演着重要的角色。Fam3D-/-小鼠表现出黏膜增生，免疫细胞浸润和炎性细胞因子表达上调等炎症状态；52周Fam3D-/-小鼠的结肠表现出明显的黏膜增生，免疫细胞浸润和侵入性腺体向肌层发展的肿瘤形成表型，提示Fam3D-/-小鼠存在自发炎症。在Dextran-sulfate sodium（DSS）诱导的急性结肠炎模型中，Fam3D-/-小鼠表现为易感性增强，上皮破坏显著；在DSS诱导的慢性结肠炎模型中，Fam3D-/-小鼠的结肠上皮增生明显，出现有肿瘤形成倾向的入侵性腺体，并向肌层发展；而在AOM（azoxymethane）/DSS诱导的结肠癌模型中，Fam3D-/-小鼠呈现出癌变的症状，结肠形成典型的侵袭性腺癌结构。结肠灌注腺病毒Adv-FAM3D过表达FAM3D可以减轻结肠炎表型。机制研究发现Fam3D-/-小鼠结肠上皮的抗菌肽和干扰素相关基因下调，杯状细胞功能异常，结肠中黏液层厚度降低，缺失酸性黏蛋白，肠道菌群失调。本课题首次揭示了FAM3D是一种在结肠中起到保护作用的细胞因子。提出FAM3D是一种炎症性肠病及其相关肿瘤发生发展生物标志物和潜在治疗靶点的可能性。为肠道区域免疫提供新机制，为炎症性肠病诊断治疗提供新思路，具重要的理论意义和潜在的应用价值。