Human umbilical vein endothelial ECV304 cells obtained from Cell Lines Service (Eppelheim, Germany) were maintained in an M199 medium containing 10% fetal bovine serum and 1% penicillin-streptomycin in a humidified atmosphere of 5% CO2 at 37 °C. Dimethyl sulfoxide (DMSO) (0.5% final concentration) was used as a vehicle control in all experiments.