Zinc deficiency induces oxidative stress and AP-1 activation in 3T3 cells

It has been postulated that one mechanism underlying zinc deficiency-induce d tissue alterations is excessive cellular oxidative damage. In the present study we investigated if zinc deficiency can induce oxidative stress in 3T 3 cells and trigger select intracellular responses that have been associate d to oxidative stress. Cells were exposed to control media or to chelated m edia containing 0.5, 5, or 50 mu M zinc for 24 or 48 h. The oxidative statu s of the cells was evaluated as an increase in the fluorescence of the prob e 5(or 6)-carboxy-2'7'-dichlorodihydrofluorescein diacetate (DCDCDHF). Afte r 24 and 48 h of exposure, the fluorescence intensity was significantly hig her (4- to 15-fold) in the 0.5 and 5 mu M Zn groups compared to the 50 mu M Zn and control groups. The activity of the antioxidant enzymes CuZn (CuZnS OD) and Mn (MnSOD) superoxide dismutases was significantly higher in the 0. 5 and 5 mu M Zn cells compared to the 50 mu M Zn and control groups at both the 24 and 48 h time points. These higher activities were associated with higher levels of MnSOD mRNA. After 24 h in culture, the level of activated AP-1 was markedly higher in the 0.5 and 5 mu M Zn cells than in the control (72 and 58%, respectively) and 50 I-LM Zn cells (73 and 60%, respectively) . NF-kappa B binding activity was lower in the 0.5 and 5 mu M Zn cells than in controls. Thus, oxidative stress is induced by zinc deficiency in 3T3 c ells. This oxidative stress results in an upregulation of oxidant defense m echanisms. (C) 2000 Elsevier Science Inc.