Zinc-pyrithione exerts diverse actions on human leukemia K562 cells : A preliminary study on hormetic action

Zinc-pyrithione is widely used as a topical agent. It may be likely that zinc-pyrithione possesses unique cytotoxic action because zinc exerts diverse actions on process of cell death. In this study, we examined the cytotoxicity of zinc-pyrithione on human leukemia K562 cells in order to examine the possibility of hormetic action. Zinc-pyrithione at concentrations ranging from 0.3 μM to 3 μM induced diverse actions on K562 cells. The agent at 0.3 and 1 μM significantly inhibited spontaneous occurrence of cell death during 72 h incubation while it was not the case for 3 μM. Significant decrease in population of shrunken cells was observed when the concentrations of zinc-pyrithione were 0.3 and 1 μM. Cell growth was significantly inhibited by 1 and 3 μM zinc-pyrithione, but not by 0.3 μM. Although the inhibition of cell growth by zinc-pyrithione was concentration-dependent, the inhibition of spontaneous cell death was observed only at lower concentrations (0.3 and 1 μM) of zinc-pyrithione. Results suggest that zinc-pyrithione possesses diverse actions, including hormetic action, on proliferative cells.