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

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 Egfl7 X 140 +/- 8% of control at 3 hours (n=6; P<0.05) and 385 +/- 50% of control at 6 hours (n=6; P<0.001). Incubation with Egfl7 during the reoxygenation period prevented intercellular adhesion molecule 1 upregulation (mean fluorescence intensity: 5.37 +/- 0.92 versus 3.81 +/- 0.21; P<0.05; n=4 per group). Nuclear factor-kappa B nuclear localization on H/R injury was blocked by Egfl7 administration (cytosolic/nuclear ratio of 0.93 +/- 0.01 versus 1.44 +/- 0.24; P<0.05; n=4 per group). Inhibitor of nuclear factor-KB protein level was significantly reduced on H/R injury (26 +/- 4.6% of control expression; P<0.05; n=4 per group); however, concurrent incubation with Egfl7 attenuated this reduction (46 +/- 6.2% of control expression; P<0.05 when compared with H/R injury alone; n=4 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-kappa B nuclear localization and augmented inhibitor of nuclear factor-kappa B protein levels, suggesting that it inhibits nuclear factor-kappa 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.)