Involvement of zinc in intracellular oxidant/antioxidant balance

The effect of zinc (Zn) on cellular oxidative metabolism is complex and could be explained by multiple complementary interactions. In this study, we evaluated the impact of Zn on the pro-oxidant/antioxidant balance of HaCaT keratinocytes. Cells were submitted to a diffusible metal chelator able to induce intracellular Zn deprivation, TPEN, in combination or not with Zn chloride (ZnCl2), in the culture medium. The intracellular amount of Zn, copper (Cu), and iron (Fe) was determined, as well as CuZnSOD and MnSOD activities and glutathione reserves. The consequence of the modulation of Zn concentration on lipid peroxidation was also evaluated. TPEN induced a significant dose-dependent decrease in intracellular Zn and Cu (from 394-181 and 43-21 mu g/g protein, respectively, after 6 h of TPEN 50 mu M). No significant change in intracellular Fe concentration was found following TPEN exposure. The SOD activities were unchanged after 6 h of TPEN 50 mu M application, either CuZnSOD or MnSOD. Cells exposure to TPEN induced a deep time-and dose-dependent decease in their glutathione content (from 65-8 mu M/g protein after 6 h of TPEN 50 mu M), and a concomittant increase in glutathione in the cell-culture supernatants. No significant change in lipid peroxidation products was detected.