Fung Erik, Tang Sai-Man Timothy, Canner James P, Morishige Kunio, Arboleda-Velasquez Joseph F, Cardoso Angelo A, Carlesso Nadia, Aster Jon C, Aikawa Masanori
Center for Excellence in Vascular Biology, Brigham and Women's Hospital, Harvard Medical School, 77 Ave Louis Pasteur, Boston, MA 02115, USA.
Circulation. 2007 Jun 12;115(23):2948-56. doi: 10.1161/CIRCULATIONAHA.106.675462. Epub 2007 May 28.
Activated macrophages contribute to the pathogenesis of inflammatory diseases such as atherosclerosis. Although Notch signaling participates in various aspects of immunity, its role in macrophage activation remains undetermined.
To explore the role of Notch signaling in inflammation, we examined the expression and activity of Notch pathway components in human primary macrophages in vitro and in atherosclerotic plaques. Macrophages in culture express various Notch pathway components including all 4 receptors (Notch1 to Notch4). Notch3 selectively increased during macrophage differentiation; however, silencing by RNA interference demonstrated that all receptors are functional. The ligand Delta-like 4 (Dll4) increased in macrophages exposed to proinflammatory stimuli such as lipopolysaccharide, interleukin-1beta, or minimally-modified low-density lipoprotein in a Toll-like receptor 4- and nuclear factor-kappaB-dependent fashion. Soluble Dll4 bound to human macrophages. Coincubation of macrophages with cells that expressed Dll4 triggered Notch proteolysis and activation; increased the transcription of proinflammatory genes such as inducible nitric oxide synthase, pentraxin 3 and Id1; resulted in activation of mitogen-activated protein kinase, Akt, and nuclear factor-kappaB pathways; and increased the expression of Dll4 in macrophages. Notch3 knockdown during macrophage differentiation decreased the transcription of genes that promote inflammation, such as inducible nitric oxide synthase, pentraxin 3, Id1, and scavenger receptor-A. These in vitro findings correlate with results of quantitative immunohistochemistry, which demonstrated the presence of Dll4 and other Notch components within macrophages in atherosclerotic plaques.
Dll4-triggered Notch signaling may mediate inflammatory responses in macrophages and promote inflammation.
活化的巨噬细胞参与动脉粥样硬化等炎症性疾病的发病机制。尽管Notch信号通路参与免疫的各个方面，但其在巨噬细胞活化中的作用仍未明确。
为了探究Notch信号通路在炎症中的作用，我们检测了人原代巨噬细胞体外培养物以及动脉粥样硬化斑块中Notch信号通路成分的表达和活性。培养的巨噬细胞表达多种Notch信号通路成分，包括所有4种受体（Notch1至Notch4）。Notch3在巨噬细胞分化过程中选择性增加；然而，RNA干扰沉默实验表明所有受体均具有功能。配体Delta样蛋白4（Dll4）在暴露于促炎刺激（如脂多糖、白细胞介素-1β或轻度氧化的低密度脂蛋白）的巨噬细胞中以Toll样受体4和核因子κB依赖性方式增加。可溶性Dll4与人巨噬细胞结合。巨噬细胞与表达Dll4的细胞共孵育可触发Notch蛋白水解和活化；增加促炎基因（如诱导型一氧化氮合酶、五聚素3和Id1）的转录；导致丝裂原活化蛋白激酶、Akt和核因子κB信号通路活化；并增加巨噬细胞中Dll4的表达。巨噬细胞分化过程中Notch3敲低可降低促进炎症的基因（如诱导型一氧化氮合酶、五聚素3、Id1和清道夫受体-A）的转录。这些体外研究结果与定量免疫组化结果相关，后者表明动脉粥样硬化斑块中的巨噬细胞内存在Dll4和其他Notch成分。
Dll4触发的Notch信号通路可能介导巨噬细胞中的炎症反应并促进炎症。
