Epidermal Growth Factor-Like Domain 7 Suppresses Intercellular Adhesion Molecule 1 Expression in Response to Hypoxia/Reoxygenation Injury in Human Coronary Artery Endothelial Cells

Abstract

Background-Epidermal growth factor-like domain 7 (Egfl7) is a chemoattractant for endothelial cells, and its expression is restricted to endothelial cells. Hypoxia/reoxygenation (H/R) induced endothelial injury that occurs during transplantation contributes to the subsequent development of allograft vasculopathy. We investigated the effect of Egfl7 on endothelial cell intercellular adhesion molecule 1 expression in response to H/R injury. Methods and Results-Human coronary artery endothelial cells were submitted to hypoxia (0.1% O 2 ) followed by normoxia (21% O 2 ) in the presence or absence of Egfl7 (100 ng/mL). Hypoxia alone increased the expression of Egfl7ϫ140Ϯ8% of control at 3 hours (nϭ6; PϽ0.05) and 385Ϯ50% of control at 6 hours (nϭ6; PϽ0.001). Incubation with Egfl7 during the reoxygenation period prevented intercellular adhesion molecule 1 upregulation (mean fluorescence intensity: 5.37Ϯ0.92 versus 3.81Ϯ0.21; PϽ0.05; nϭ4 per group). Nuclear factor-B nuclear localization on H/R injury was blocked by Egfl7 administration (cytosolic/nuclear ratio of 0.93Ϯ0.01 versus 1.44Ϯ0.24; PϽ0.05; nϭ4 per group). Inhibitor of nuclear factor-B protein level was significantly reduced on H/R injury (26Ϯ4.6% of control expression; PϽ0.05; nϭ4 per group); however, concurrent incubation with Egfl7 attenuated this reduction (46Ϯ6.2% of control expression; PϽ0.05 when compared with H/R injury alone; nϭ4 per group). Conclusions-Our study reveals the novel observation that hypoxia upregulates human coronary artery endothelial cells expression of Egfl7 and that Egfl7 inhibits expression of intercellular adhesion molecule 1 subsequent to H/R injury. Mechanistically, Egfl7 prevented nuclear factor-B nuclear localization and augmented inhibitor of nuclear factor-B protein levels, suggesting that it inhibits nuclear factor-B activation, a key step in the inflammatory activation of endothelial cells. Egfl7 may be protective against H/R injury incurred during transplantation and may modulate the events that lead to the development of graft vasculopathy. (Circulation. 2010;122[suppl 1]:S156 -S161.)

Egfl7 Promotes Tumor Escape from Immunity by Repressing Endothelial Cell Activation

“…Egfl7 favors tumor escape from immunity by downregulating the expression of endothelial adhesion molecules through mechanisms that are still elusive. Of note, Egfl7 was recently reported to downregulate the NF-kB pathway in human coronary artery endothelial cells after an ischemia/reoxygenation treatment (27). Based on this observation and our results, it is thus possible that a direct repression of the NF-kB pathway by Egfl7 in endothelial cells contributes to the repression of ICAM-1 and, possibly, that of VCAM-1 and E-selectin.…”

EGFL7: a unique angiogenic signaling factor in vascular development and disease

“…61 Specifically, Egfl7 overexpression in breast and lung carcinoma cells enhances tumor progression in immunocompetent mice and appears to do so by reducing the expression of tumor endothelial leukocyte adhesion molecules, including ICAM-1 and VCAM-1, thus preventing host immune cell infiltration. 61 The repression of ICAM-1 expression by EGFL7 is in keeping with observations made during endothelial cell injury 33,35 and highlights a possible novel mechanism by which EGFL7 promotes tumorigenesis.…”

“…Accordingly, increased levels of Egfl7 are detected in response to hypoxia in both cultured endothelial cells and in the immature rat brain in vivo. 33,34 The mechanism by which Egfl7 expression is up-regulated in response to hypoxia is unknown. Note that the Egfl7 promoter contains 9 potential hypoxia-inducible factor-1␣ binding sites, and it is, therefore, possible that induction of Egfl7 expression is mediated by this transcription factor directly binding to and transactivating the Egfl7 promoter.…”

“…34 EGFL7 may also stimulate vascular regeneration by repressing key steps in the inflammatory activation of endothelial cells. 33,35 Specifically, it has been shown that EGFL7 represses NFB activation and the subsequent expression of ICAM-1 in response to hypoxia/reoxygenationinduced and calcineurin inhibition-induced endothelial injury. 33,35 In contrast to hypoxic conditions, EGFL7 expression is inhibited after hyperoxic exposure in both neonatal lungs in vivo and in endothelial cells in vitro, and reduced levels are associated with endothelial cell death.…”

“…33,35 Specifically, it has been shown that EGFL7 represses NFB activation and the subsequent expression of ICAM-1 in response to hypoxia/reoxygenationinduced and calcineurin inhibition-induced endothelial injury. 33,35 In contrast to hypoxic conditions, EGFL7 expression is inhibited after hyperoxic exposure in both neonatal lungs in vivo and in endothelial cells in vitro, and reduced levels are associated with endothelial cell death. 36 In support, EGFL7 overexpression in endothelial cell lines results in a protective effect against hyperoxiainduced apoptosis by preventing cytochrome c release, inhibiting caspase-3 activation, and preventing the induction of BAX expression, all of which are hallmarks of mitochondria-induced apoptosis.…”