Effects of endothelin-1 on endothelial progenitor cell function

Background: Circulating endothelial progenitor cells (EPCs) contribute to vascular endothelial repair. Endothelin (ET)-1 is associated with endothelial damage and atherogenesis. The experimental aim of this study was to determine, in vitro, the effects of ET-1 on the ability of EPCs to form colonies, migrate, release angiogenic growth factors and resist apoptosis. Methods: Peripheral blood samples were collected from 10 healthy adult humans. Cells with phenotypic EPC characteristics were isolated and EPC colony-forming capacity (CFU assay), migratory activity (Boyden chamber), release of angiogenic growth factors (enzyme immunoassay) and apoptosis (TUNEL assay) were determined in the absence and presence of ET-1 (100 pmol). Results: EPC colony-forming units (42 ±12 vs. 39 ±11), migratory capacity (910 ±146 vs. 936 ±148 AU) and release of vascular endothelial growth factor (202.8 ±68.1 vs. 204.8 ±69.8 pg/mL) and granulocyte-colony stimulating factor (1294.4 ±378.3 vs. 1136.1 ±310.3 pg/mL) were not signifi-cantly affected by ET-1. EPCs treated with ET-1 demonstrated a 20 % increase (p <0.05) in cellular apoptosis. The proapop-totic effect of ET-1 was abolished with ET receptor blockade as well as with apocynin, a nicotinamide adenine dinucleotide phosphate (NADPH) inhibitor. Conclusions: These results indicate that ET-1 does not affect EPC colony formation, migratory capacity or angiogenic growth factor release, but does increase EPC susceptibility to apoptosis through an NADPH-dependent mechanism. Increased EPC apoptosis may contribute to the proathero-genic effects of ET-1.