Smad7 interrupts TGF-β signaling in intestinal macrophages and promotes inflammatory activation of these cells during necrotizing enterocolitis.
Smad7 interrupts TGF-β signaling in intestinal macrophages and promotes inflammatory activation of these cells during necrotizing enterocolitis.
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DOI：
10.1038/pr.2016.18
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发表时间：
2016-06
影响因子：
3.6
通讯作者：
Maheshwari A
中科院分区：
文献类型：
--
作者：
MohanKumar K;Namachivayam K;Chapalamadugu KC;Garzon SA;Premkumar MH;Tipparaju SM;Maheshwari A
坏死性小肠结肠炎（NEC）是早产儿的一种炎症性肠坏死。根据我们最近在受 NEC 影响的手术切除肠道中 Smad7 表达增加的发现，我们假设 NEC 巨噬细胞经历炎症激活，因为 Smad7 表达增加使这些细胞对正常、肠道特异性、转化生长因子 (TGF)-β 介导的炎症途径抑制产生抵抗。我们使用手术切除的人类 NEC 组织、NEC 样损伤的小鼠模型、骨髓源性和肠道巨噬细胞以及 RAW264.7 细胞。通过定量聚合酶链反应 (qPCR)、蛋白质印迹和免疫组织化学来测量 Smad7 和 IκB 激酶-β (IKK-β)。启动子激活在荧光素酶报告基因和染色质免疫沉淀测定中得到证实。 NEC 巨噬细胞显示 Smad7 表达增加，特别是在组织严重损伤和细菌负荷高的区域。 LPS 诱导的 Smad7 表达抑制 TGF-β 信号传导，增强巨噬细胞中 NF-κB 的激活和细胞因子的产生。 Smad7 介导的 NF-κB 激活可能是通过 IKK-β 表达增加介导的，这进一步增加了前馈环中的 Smad7 表达。我们发现 Smad7 通过直接结合 IKK-β 启动子及其转录激活来诱导 IKK-β 表达。 NEC 巨噬细胞中的 Smad7 表达会中断 TGF-β 信号传导，并通过增加 IKK-β 的表达来促进这些细胞中 NF-κB 介导的炎症信号传导。
Necrotizing enterocolitis (NEC) is an inflammatory bowel necrosis of premature infants. Based on our recent findings of increased Smad7 expression in surgically-resected bowel affected by NEC, we hypothesized that NEC macrophages undergo inflammatory activation because increased Smad7 expression renders these cells resistant to normal, gut-specific, transforming growth factor (TGF)-β-mediated suppression of inflammatory pathways. We used surgically-resected human NEC tissue, murine models of NEC-like injury, bone marrow-derived and intestinal macrophages, and RAW264.7 cells. Smad7 and IκB kinase-beta (IKK-β) were measured by quantitative polymerase chain reaction (qPCR), Western blots, and immunohistochemistry. Promoter activation was confirmed in luciferase reporter and chromatin immunoprecipitation assays. NEC macrophages showed increased Smad7 expression, particularly in areas with severe tissue damage and high bacterial load. LPS-induced Smad7 expression suppressed TGF-β signaling and augmented NF-κB activation and cytokine production in macrophages. Smad7-mediated NF-κB activated was likely mediated via increased expression of IKK-β, which, further increased Smad7 expression in a feed-forward loop. We show that Smad7 induced IKK-β expression through direct binding to the IKK-β promoter and its transcriptional activation. Smad7 expression in NEC macrophages interrupts TGF-β signaling and promotes NF-κB-mediated inflammatory signaling in these cells through increased expression of IKK-β.