The influence of iron loading and iron chelation on the proliferation and telomerase activity of human peripheral blood mononuclear cells.

Abstract

Iron is an essential trace element in cell proliferation. Several investigations demonstrate that iron deprivation inhibits cell proliferation. However, the impact of iron on telomerase activity of activated lymphocytes remains unexplained to date. In this study, the effect of iron on the proliferation and telomerase activity of lymphocytes stimulated by phytohemagglutinin (PHA) were investigated. Iron loading was performed by incubating peripheral blood mononuclear cells in 500microM FeSO4.7H2O for 24 h and iron chelation was done by exposing cells to desferrioxamine, a potent iron chelator. The effects of silymarin, a flavonoid with both antioxidant and iron chelating activities, on the proliferation and telomerase activity of PHA-activated lymphocytes were also compared with desferrioxamine. Proliferation and telomerase activity were assessed using BrdU incorporation assay and Telomeric Repeat Amplification Protocol (TRAP), respectively. The proliferations of lymphocytes were significantly inhibited by 10 and 20 microg/ml desferrioxamine in a dose dependent manner, while iron loading recovered suppressed cell proliferation to the normal level. Silymarin at 20 microg/ml significantly increased the proliferation of lymphocytes in both normal and iron-treated conditions. Telomerase activity of lymphocytes was markedly increased by iron treatment and suppressed by desferrioxamine. Conversely, iron treatment had no effect on the telomerase activity of lymphocytes incubated with silymarin. Iron plays a significant role in the proliferation and telomerase activity of lymphocytes. The effects of silymarin on the proliferation and telomerase activity of lymphocytes were completely different from those of desferrioxamine, suggesting that the immunomodulatory effect of silymarin is probably not associated with its iron chelating activity.