van Aanhold Cleo C L, Yong Qing, Landman Lisa, Sardana Samiksha, Bouwmeester Anouk B, Dijkstra Kyra L, Wolterbeek Ron, Mei Hailiang, Tjokrodirijo Rayman T N, de Ru Arnoud H, van Veelen Peter A, Bruijn Jan A, van Kooten Cees, Baelde Hans J
Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands.
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, The Netherlands.
Angiogenesis. 2025 May 2;28(3):28. doi: 10.1007/s10456-025-09980-w.
Soluble Fms-like Tyrosine kinase-1 (sFLT1) is a native inhibitor of VEGF, best known for its antiangiogenic effects in preeclampsia. sFLT1 also reduces chronic inflammation and promotes tissue repair. In experimental diabetic nephropathy, we previously found that sFLT1 ameliorates kidney fibrosis and reduces the infiltration of macrophages. How sFLT1 regulates inflammation is still incompletely understood. Based on the direct association of sFLT1 with various cell types, we here studied whether sFLT1 interacts with macrophages to modulate inflammation.
Using various macrophage cell lines, sFLT1 cell surface binding was detected with flow cytometry. Enzyme studies, mass spectrometry and RNAseq were employed to identify potential sFLT1 cell surface interactors and effects of sFLT1 on macrophage signaling.
Soluble FLT1 binds to primary macrophages, THP-1 and RAW264.7 macrophages in vitro. Alternative activation with IL-4 increases sFLT1 binding in THP-1 macrophages, whereas proinflammatory activation with IFN-γ and LPS decreases binding. Binding of sFLT1 depends on heparan sulphates, and colocalizes with the membrane heparin sulfate proteoglycan neuropilin-1. Incubation with sFLT1 reduces the gene expression of chemokine receptors.
Our results show that sFLT1, while typically associated with angiogenesis, also directly interacts with macrophages. Alternative activation of macrophages by IL-4 strongly increases binding of sFLT1 to the cell surface membrane, possibly via the VEGF co-receptor neuropilin-1. Considering sFLT1's anti-inflammatory effects in animal studies, our findings indicate a novel function for sFLT1 to directly control anti-inflammatory macrophage function.
可溶性Fms样酪氨酸激酶-1（sFLT1）是血管内皮生长因子（VEGF）的天然抑制剂，以其在子痫前期的抗血管生成作用而闻名。sFLT1还可减轻慢性炎症并促进组织修复。在实验性糖尿病肾病中，我们之前发现sFLT1可改善肾纤维化并减少巨噬细胞浸润。sFLT1如何调节炎症仍未完全明确。基于sFLT1与多种细胞类型的直接关联，我们在此研究sFLT1是否与巨噬细胞相互作用以调节炎症。
使用多种巨噬细胞系，通过流式细胞术检测sFLT1的细胞表面结合情况。采用酶学研究、质谱分析和RNA测序来鉴定潜在的sFLT1细胞表面相互作用分子以及sFLT1对巨噬细胞信号传导的影响。
可溶性FLT1在体外可与原代巨噬细胞、THP-1和RAW264.7巨噬细胞结合。用白细胞介素-4进行替代性激活可增加sFLT1与THP-1巨噬细胞的结合，而用干扰素-γ和脂多糖进行促炎激活则会降低结合。sFLT1的结合依赖于硫酸乙酰肝素，并与膜硫酸乙酰肝素蛋白聚糖神经纤毛蛋白-1共定位。与sFLT1孵育可降低趋化因子受体的基因表达。
我们的结果表明，sFLT1虽然通常与血管生成相关，但也可直接与巨噬细胞相互作用。白细胞介素-4对巨噬细胞的替代性激活可通过血管内皮生长因子（VEGF）共受体神经纤毛蛋白-1强烈增加sFLT1与细胞表面膜的结合。鉴于sFLT1在动物研究中的抗炎作用，我们的发现表明sFLT1具有直接控制抗炎巨噬细胞功能的新功能。
