Angiogenic effects of prostaglandin E2 are mediated by up-regulation of CXCR4 on human microvascular endothelial cells

Abstract

Stimulation of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) increases the expression of CXCR4 on endothelial cells, rendering these cells more responsive to stromalderived factor 1 (SDF-1), an angiogenic CXC chemokine and unique ligand for CXCR4. Here, we show that prostaglandin E 2 (PGE 2 ) mediates the effects of bFGF and VEGF in up-regulating CXCR4 expression on human microvascular endothelial cells (HMECs). Forskolin or 3-isobutyl-1-methyl xanthine (IBMX), 2 inducers of adenylate cyclase, markedly enhanced, whereas cyclooxygenase (COX) inhibitors including aspirin, piroxicam, and NS398 markedly inhibited CXCR4 expression on HMECs. Furthermore, the ability of PGE 2 to augment in vitro tubular formation in SDF-1␣ containing matrigel was inhibited completely by blocking CXCR4. Treatment of bFGF-or VEGF-stimulated HMECs with COX inhibitors blocked tubular formation by about 50% to 70%. Prostaglandin-induced human endothelial cell organization and subsequent vascularization can be inhibited to a greater extent by a neutralizing antibody to human CXCR4 in severe combined immunodeficient mice. Additionally, VEGF-and bFGFinduced angiogenesis in vivo was also inhibited by about 50% by NS-398 or piroxicam, and this inhibitory effect was accompanied by decreased expression of CXCR4 on murine endothelial cells. IntroductionChemokines induce angiogenesis directly by binding their cognate receptors on endothelial cells or indirectly by promoting inflammatory cell infiltrates, which deliver other angiogenic stimuli. A number of proinflammatory chemokines including interleukin 8 (IL-8), growth-regulated oncogene ␣ (GRO-␣), stromal cell-derived factor 1 (SDF-1), monocyte chemotactic protein 1 (MCP-1), eotaxin 1, and I-309 have been shown to act as direct inducers of angiogenesis. [1][2][3] SDF-1 acts as a chemoattractant for leukocytes, 4 hematopoietic progenitor cells, 5 and endothelial cells. 6-8 SDF-1-deficient mice are grossly normal but die shortly after birth, lack B-cell lymphopoiesis during embryonic development, have defective bone marrow myelopoiesis, have a ventricular septal defect, 9 and have impaired vascularization of the gastrointestinal tract. 10 We previously reported that angiogenic factors, namely, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), can enhance the expression of CXCR4, but not other chemokine receptors on endothelial cells rendering endothelial cells more responsive to SDF-1. Conversely, SDF-1 enhances the production of VEGF and bFGF in a positive feedback loop, therefore, linking classical angiogenic factors to chemokine-induced angiogenesis. 11 In addition to inducing CXCR4, there is copious evidence in the literature that VEGF and bFGF are inducers of cyclooxygenase (COX) with subsequent induction of prostaglandin synthesis in endothelial cells. 12-17 Prostaglandin E 2 (PGE 2 ) is the major COX product of human microvascular endothelial cells (HMECs). [18][19][20][21] Prostaglandins participate in angiogenesis [22...

Roles of Chemokine Receptor 4 (CXCR4) and Chemokine Ligand 12 (CXCL12) in Metastasis of Hepatocellular Carcinoma Cells

“…CXCL12 may be involved in up-regulating expression levels of vascular endothelial growth factor and basic fibroblast growth factor in that subcutaneous injection of CXCL12 into mice induced formation of local small blood vessels (35,36). Endogenous CXCL12 together with CXCR4 mediated a significant portion of primary tumor angiogenesis and angiogenesisdependent tumor growth (37,38).…”

Forkhead transcription factors regulate expression of the chemokine receptor CXCR4 in endothelial cells and CXCL12-induced cell migration

“…Therefore, to our knowledge, our work is the first report that describes the functional link of Fox transcription factors to CXCR4 expression and CXCL12-stimulated endothelial migration. It should also be noted that the VEGF pathway induces CXCR4 expression in endothelial cells [10,11] and acts upstream of Foxc transcription factors in arterial gene expression [27]. Therefore, it will be of significance to test the relationship between VEGF signaling and Foxc transcription factors on the induction of CXCR4 expression in endothelial cells in the future.…”

“…Previous studies have characterized the promoter activity of CXCR4 [11,[14][15][16][17], although the effect of Fox transcription factors on the regulation of the CXCR4 promoter remains unknown. Therefore, to evaluate the direct involvement of Foxc1 and Foxc2 in CXCR4 expression at the transcriptional level, we first generated a luciferase reporter containing a 2.7 kb region upstream of the murine CXCR4.…”

“…As such, the CXCR4 receptor is detected in various types of cells, including hematopoietic and vascular endothelial cells, while it is important to note that CXCR4 expression in endothelial cells of the developing embryo is restricted to arteries such as the dorsal aorta and mesenteric arteries [2,7]. Previous studies also demonstrate the function of the CXCR4-CXCL12 pathway in the process of angiogenesis such as endothelial cell migration and capillary tube formation [8][9][10][11][12]. Several extracellular signals and transcriptional factors such as CXCL12, vascular endothelial growth factor (VEGF), hypoxia and NF-κB have been shown to induce CXCR4 expression in different cell types, including monocytes, cancer cells and endothelial cells [2,10,11,[13][14][15][16][17].…”

“…Previous studies also demonstrate the function of the CXCR4-CXCL12 pathway in the process of angiogenesis such as endothelial cell migration and capillary tube formation [8][9][10][11][12]. Several extracellular signals and transcriptional factors such as CXCL12, vascular endothelial growth factor (VEGF), hypoxia and NF-κB have been shown to induce CXCR4 expression in different cell types, including monocytes, cancer cells and endothelial cells [2,10,11,[13][14][15][16][17]. However, the molecular basis of transcriptional regulation of CXCR4, in particular in vascular endothelial cells, is still not fully understood.…”