SECTM1/CD7通路趋化单核细胞并诱导其表型分化在新生儿坏死性小肠结肠炎中的炎症调节作用及机制研究

The direct pathophysiological cause of neonatal necrotizing enterocolitis (NEC) is the abnormally enlarged inflammatory cascade. However, the knowledge of regulatory mechanisms in the inflammatory process is still insufficient. Proinflammatory/antiinflammatory macrophages (Mø) balance of monocyte-macrophage system plays a key role in regulating intestinal inflammatory response. Recent studies have shown that SECTM1 as a ligand for CD7 can chemotaxize monocytes to tumor microenvironment; STAT3 with a binding site in the SECTM1 promoter is a key pathway for Mø phenotype differentiation. Early studies from our group showed that the expression of SECTM1 was not increased significantly while the number of Mø was increased significantly in the NEC patients; The morbidity rate of NEC and the degree of intestinal injury were increased in the NEC model of Sectm1-/- mice. Then we suggest that there is an imbalance of proinflammatory/antiinflammatory Mø in NEC. SECTM1 / CD7 pathway can chemotaxize monocytes to inflammation portion and regulate monocyte phenotype differentiation through STAT3 pathway to regulate the excessive inflammatory response in NEC. The topics proposed will research the role of SECTM1 in the progression of inflammation using NEC model of SECTM1 knockout mice and further explore the mechanism of SECTM1 in chemotaxizing and differentiating of monocytes in cell and molecular level which may provide new ideas and lay the foundation to the NEC treatment.

新生儿坏死性小肠结肠炎（NEC）肠道损伤的直接原因是异常放大的炎症级联反应，而NEC炎症的调控机制尚未阐明。单核巨噬细胞系统的促炎/抗炎型巨噬细胞（Mø）平衡在调节肠道炎症中发挥关键作用。最近发现SECTM1可趋化单核细胞至肿瘤微环境；STAT3作为Mø表型分化的关键通路，在SECTM1启动子序列中存在结合位点。我们前期研究发现，NEC患儿肠管中SECTM1表达增加不明显，Mø浸润增加； Sectm1-/-小鼠NEC模型患病率及肠道损伤程度增加。据此推断：NEC中存在促炎/抗炎Mø的失衡；SECTM1/CD7通路可趋化单核细胞，并通过STAT3通路调控其表型分化，调节过强的炎症反应。为此我们拟采用Sectm1-/-小鼠建立NEC模型，并从细胞及分子水平上探讨SECTM1趋化并诱导分化单核细胞在NEC炎症进展中的作用及机制，为NEC的发病机制及治疗方案的探索提供新的思路。

M2巨噬细胞极化异常是NEC发展的关键机制之一，由于M2巨噬细胞主要依赖氧化磷酸化功能，过度的有氧糖酵解即糖代谢重编程可能在M2巨噬细胞极化异常中起重要作用，但目前为止，其调控因素和机制尚不清楚。我们的研究结果显示，参与NEC进展的关键基因 SECTM1 mRNA在NEC组织中高表达，但SECTM1蛋白却低表达，显示SECTM1必然存在翻译后修饰，但上游具体调控因子及机制尚不清楚。通过RNA转录本测序和生信分析，我们筛选出了与巨噬细胞极化相关的差异表达lncRNA NEAT1，KEGG和GSEA富集分析表明NEAT1参与了细胞代谢调控和泛素化调控。功能实验表明，NEAT1可以干扰人类胎儿小肠细胞系和巨噬细胞的正常迁移功能并促进凋亡。值得一提的是，我们的研究揭示了NEAT1可以通过调控巨噬细胞代谢重编程发挥巨噬细胞极化调节作用。分子机制方面， NEAT1通过泛素化调控下游分SECTM1，促进SECTM1蛋白的降解。 我们的研究结果显示，NEAT1/ SECTM1分子轴通过调控巨噬细胞代谢重编程和极化促进NEC的进展，靶向NEAT1/ SECTM1分子轴具有广阔的科研及临床应用前景。