Effects of Zn2+ chelators, DTPA and TPEN, and ZnCl2 on the cells treated with hydrogen peroxide: a flow-cytometric study using rat thymocytes

Recently, we have revealed that trace Zn2+ partly attenuates Ca2+-dependent cell death induced by A23187, a calcium ionophore, in rat thymocytes. In this study, to see if Zn2+ attenuates the H2O2-induced cell death that is also Ca2+-dependent, the effects of ZnCl2 and chelators for Zn2+ have been examined by using a flowcytometer with propidium iodide. The incubation with H2O2 increased the cell lethality. Simultaneous
application of ZnCl2 greatly augmented the H2O2-induced increase in lethality. DTPA, a chelator for extracellular Zn2+, did not affect the increase in cell lethality by H2O2. However, the H2O2-induced increase in cell lethality was greatly attenuated by TPEN, a chelator for extracellular and intracellular Zn2+. Taken together, it may be likely that intracellular Zn2+ modifies the H2O2-induced cytotoxicity. However, it cannot be ruled out the possibility that TPEN chelates intracellular Fe2+, resulting in inhibiting the formation of hydroxyl radical
from H2O2 that leads to an attenuation of H2O2 cytotoxicity.