Delta‐like 配體 4 (Dll4)/Notch 訊號途徑在血管系統發育中扮演關鍵角色，負責於血管新生時調控內皮尖端細胞（tip cell）的形成與功能，引導內皮細胞分化為具有遷移能力的尖端細胞或具有增殖能力的莖幹細胞（stalk cell）。先前研究指出，內皮細胞 Dll4 表現在發炎情況下會增加，並且活化 Notch 訊號。因此，本研究假設，在發炎環境中，內皮細胞 Dll4 表現上升並且與巨噬細胞上Notch受體結合會刺激其訊號活化而影響巨噬細胞之分化與功能。為驗證此假設，我們將 THP-1 單核球培養於含有重組人類 Dll4 蛋白（recombinant human Dll4, rhDll4）的培養皿中以誘導 Notch 訊號，並將其分化為 M0 與 M1 巨噬細胞。結果顯示，THP-1於 Dll4 存在下分化為 M0 時，Notch1 訊號被活化，然而於 M1 巨噬細胞中，Notch1 訊號與其下游分子 Hes1 (hairy and enhancer of split 1) 皆顯著降低。同時，促發炎細胞激素腫瘤死因子-α（TNF-α）與白介素-1β（IL-1β）亦顯著減少。然而，我們卻發現 C-C 趨化激素受體 7（CCR7）在 M1 巨噬細胞中基因表現量上升。由於 CCR7具有促進細胞遷移的功能，我們將 THP-1 在 rhDll4 刺激下分化為 M1 巨噬細胞，並以將 CCR7 配體 CCL19 進行趨化實驗。結果顯示 CCL19 促進 M1 巨噬細胞之遷移。在本篇研究中我們發現 Dll4/Notch1 訊號路徑對於 M0 和 M1 具有不同影響，在 M0 時 Dll4 刺激下導致巨噬細胞上 Notch1 活化，然而在分化成 M1 後發炎能力降低卻增加了 M1 的遷移能力，顯示當在長期發炎的環境下 Notch1 訊號降低會使巨噬細胞由發炎狀態轉變為增加遷移的能力。

Delta-like ligand 4 (Dll4)/Notch signaling pathway plays crucial roles in the development of the vascular system. This pathway regulates the formation and function of endothelial tip cells during angiogenesis, directing endothelial cells to differentiate into either migrating tip cells or proliferating stalk cells. Previous studies have shown that endothelial Dll4 expression increases under inflammatory conditions and activates Notch signaling. We hypothesized that macrophages interact with Dll4 on activated endothelial cells upon inflammation, activating Notch signaling to facilitate macrophage differentiation and function. To test this hypothesis, THP-1 monocytic cells were cultured on recombinant Dll4-coated plates to trigger Notch signaling, followed by differentiation into M0 and M1 macrophages. We assessed the impact of Dll4/Notch signaling on macrophage polarization and found that when monocytes were differentiated into M0 in the presence of Dll4, Notch1 signaling was activated. However, it was dramatically reduced in M1 macrophages, accompanied by a significant reduction in the downstream Notch signaling molecule, hairy and enhancer of split 1 (Hes1). Proinflammatory cytokines, including tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) were also significantly reduced. Conversely, C-C chemokine receptor type 7 (CCR7) was increased in M1 macrophages. Given their roles in mediating cell migration, we differentiated THP-1-derived macrophages into the M1 phenotype in the upper chamber of a transwell plate coated with recombinant Dll4. The CCR7 ligand CCL19, placed in the lower chamber, significantly enhanced M1 macrophage migration. We conclude that M0 and M1 macrophages responded differently to Dll4 stimulation. In M0 macrophages, Dll4 stimulation led to the activation of Notch1. In M1 macrophages, reduced Notch signaling resulted in lower inflammatory capacity, increased CCR7 expression and migratory ability, indicating that the decrease of Notch1 ICD during prolonged stimulation shifts cellular responses from inflammation to migration.

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