Effect of orally active hydroxypyridinone iron chelators on human lymphocyte function

Several iron chelators, 3-hydroxypyridin-4-ones (CP) and desferrioxamine (DF) were compared for their effect on DNA synthesis, cell viability and expression of cell proliferation markers. Short-term (4 h) exposure of human peripheral blood mononuclear cells to CP or DF inhibited the proliferative response of cells to concanavalin A (Con A). Inhibition by CP and DF showed a dose-dependent effect with CP compounds more active than DF. Increased inhibitory activity of CP over DF was partly due to the lipophilic properties of CP. Pre-saturation of CP and DF with exogenous ferric ion either diminished or prevented the inhibitory effect. At high chelator concentrations or prolonged (72 h) exposure of the cells to chelators, inhibition occurred but poor cell viability was observed. In contrast to their inhibition of DNA synthesis, these iron chelators showed little effect on protein synthesis and the expression of transferrin receptors and interleukin-2 (IL-2) receptors. These findings suggest that both DF and CP compounds exert their effect by chelation of ferric ion with subsequent inhibition of DNA synthesis.