Objective       To study the effect of hydrogen (H

2

) -rich culture fluid on apoptosis in endothelial cells induced by oxidized low-density lipoprotein (ox-LDL).      Methods       Endothelial cells from human umbilical veins were divided into control group

ox-LDL group

and H

2

group (ox-LDL + H

2

-rich fluid). Apoptosis of endothelial cells and level of intracellular reactive oxygen species (ROS) were assayed by flow cytometry. NF-κB p65 protein was detected by Western blotting.      Results       The apoptosis rate of endothelial cells

intracellular ROS leve

l

and NF-κB p65 protein level were significantly lower in ox-LDL group than in 0.6 mmol/L H

2

group (2.48%±0.21% vs 4.01%±0.39%

2.05±0.22 vs 5.32±1.04，0.29±0.02 vs 0.66±0.07

P0.01)

which increased with the increasing H

2

concentration in culture fluid.      Conclusion       H

2

-rich fluid can protect endothelial cells against ox-LDL-induced apoptosis by reducing intracellular ROS level and inhibiting NF-κB activation.