Dorothy M. Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Department of Internal Medicine, Ohio State University College of Medicine, Columbus, OH 43210, USA.
Blood. 2011 Jan 6;117(1):323-32. doi: 10.1182/blood-2010-01-261792. Epub 2010 Oct 15.
Macrophages contribute to tumor growth through the secretion of the proangiogenic molecule vascular endothelial growth factor (VEGF). We previously observed that monocytes treated with the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) produce a soluble form of the VEGF receptor-1 (sVEGFR-1), which neutralizes VEGF biologic activity. The VEGF and VEGFR-1 promoters both contain a hypoxia regulatory element, which binds the hypoxia-inducible factor (HIF) transcription factors under hypoxic conditions. Based on this observation, we examined VEGF and sVEGFR-1 production from monocytes cultured at various O(2) concentrations. The amount of sVEGFR-1 production observed from GM-CSF-treated monocytes increased with decreasing levels of O(2). This sVEGFR-1 was biologically active and sequestered VEGF. To evaluate the role of the HIFs in sVEGFR-1 production, we used macrophages with a genetic deletion of HIF-1α. HIF-1α(-/-) macrophages cultured with GM-CSF at hypoxia secreted diminished amounts of VEGF compared with HIF-1α(+/+) macrophages, whereas sVEGFR-1 secretion was unaffected. In contrast, siRNA-mediated knockdown of HIF-2α inhibited the production of sVEGFR-1 in response to GM-CSF and low O(2), whereas VEGF production was unaffected. These studies suggest that hypoxia, generally thought to promote angiogenesis, can induce antiangiogenic behavior from macrophages within a GM-CSF-rich environment. Furthermore, these results suggest specific and independent roles for HIF-1α and HIF-2α in hypoxic macrophages.
巨噬细胞通过分泌促血管生成分子血管内皮生长因子 (VEGF) 促进肿瘤生长。我们之前观察到，用细胞因子粒细胞-巨噬细胞集落刺激因子 (GM-CSF) 处理的单核细胞会产生 VEGF 受体-1 的可溶性形式 (sVEGFR-1)，这种形式可以中和 VEGF 的生物学活性。VEGF 和 VEGFR-1 启动子都包含一个低氧调节元件，该元件在低氧条件下与缺氧诱导因子 (HIF) 转录因子结合。基于这一观察结果，我们检查了在不同 O(2)浓度下培养的单核细胞中 VEGF 和 sVEGFR-1 的产生情况。用 GM-CSF 处理的单核细胞产生的 sVEGFR-1 量随着 O(2)水平的降低而增加。这种 sVEGFR-1 具有生物活性并隔离了 VEGF。为了评估 HIF 在 sVEGFR-1 产生中的作用，我们使用了 HIF-1α 基因缺失的巨噬细胞。与 HIF-1α(+/+)巨噬细胞相比，在低氧条件下用 GM-CSF 培养的 HIF-1α(-/-)巨噬细胞分泌的 VEGF 量减少，而 sVEGFR-1 的分泌不受影响。相比之下，siRNA 介导的 HIF-2α 敲低抑制了 GM-CSF 和低 O(2) 对 sVEGFR-1 产生的抑制，而 VEGF 产生不受影响。这些研究表明，通常被认为促进血管生成的低氧条件可以诱导富含 GM-CSF 的环境中的巨噬细胞产生抗血管生成行为。此外，这些结果表明 HIF-1α 和 HIF-2α 在低氧巨噬细胞中具有特定和独立的作用。
