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Effects of tumour necrosis factor‐alpha on activity and nitric oxide synthase of endothelial progenitor cells from peripheral blood

The aim of this investigation was to determine whether tumour necrosis factor‐alpha (TNF‐α) has any effect on endothelial progenitor cells (EPCs). Total mononuclear cells were isolated from peripheral blood by Ficoll density gradient centrifugation, and then the cells were plated on fibronectin‐coated culture dishes. After 7 days culture, attached cells were stimulated with tumour necrosis factor‐α (final concentrations: 0, 10, 20, 50 and 100 mg/l) for 0, 6, 12, 24 and 48 h. EPCs were characterized as adherent cells double positive for DiLDL‐uptake and lectin binding, by direct fluorescence staining. EPC proliferation and migration were assayed using the MTT assay and modified Boyden chamber assay, respectively. EPC adhesion assay was performed by re‐plating those cells on fibronectin‐coated dishes, and adherent cells were counted. Tube formation activity was assayed using a tube formation kit. Levels of apoptosis were revealed using an annexin V apoptosis detection kit. Vascular endothelial growth factor Receptor‐1 (VEGF‐R1) and stromal derived factor‐1 (SDF‐1) mRNA, assessed by real‐time RT‐PCR inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) were assayed by western blot analysis. Incubation of EPCs with tumour necrosis factor‐α reduced EPC proliferation, migration, adhesion, tube formation capacity, iNOS and eNOS in concentration‐ and time‐dependent manners. Tumour necrosis factor‐α reduced proliferation, migration, adhesion and tube formation capacity of EPCs. TNF‐α increased EPC apoptosis level, reduced VEGF‐R1 and SDF‐1 mRNA expression; tumour necrosis factor‐α also reduced iNOS and eNOS in the EPCs.