Effect of Zn treatment on wild type and MT-null cell lines in relation to apoptotic and/or necrotic processes and on MT isoform gene expression.
It has been shown in various systems that zinc is able to antagonize the catalytic properties of the redox-active transition metals iron and copper, although the process is still unclear. Probably, the protective effect of Zn against oxidative stress is mainly due to the induction of a scavenger metal binding protein such as metallothionein (MT), rather than a direct action. To support this hypothesis, in this study, the effects of Zn, Cu, Fe, Zn + Cu and Zn + Fe treatments were investigated in a fibroblast cell line corresponding to an SV40-transformed MT-1/-2 mutant (MT-/-), and in wild type (MT+/+), by valuing metal concentrations and apoptotic and/or necrotic processes. We also investigated the synthesis of MT and the levels of both MT-1 and MT-2 mRNAs. In MT+/+ cells, co-treatment with Zn + Fe caused a decrease in Fe content compared to treatment with Fe alone. After Zn and Zn + Cu exposure the expression of MT-1 and MT-2 isoforms increased with a concomitant increase in MT synthesis. Annexin V-FITC and propidium iodide staining revealed necrotic or apoptotic cells in terminal stages, especially after Fe treatments. Immunofluorescent staining with an anti-ssDNA Mab and annexin detected a lower signal in co-treated cells compared to the single treatments in both cell lines. The intensity and quantity of fluorescence resulting from anti-ssDNA and Annexin V staining of MT null cells was higher compared to wild type cells. These results suggest that Zn alone does not completely exert an anti-oxidant effect against Cu and Fe toxicity, but that induction of MT is necessary.
Department of Biology, University of Padova, via U. Bassi, 58/B, 35131 Padova, Italy.
Alessandro
A
Santon
Alessia
A
Formigari
Vincenzo
V
Albergoni
Paola
P
Irato
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D002478:Cells, Cultured; D003300:Copper / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology; D005786:Gene Expression Regulation / Q000187:drug effects*; D007501:Iron / Q000494:pharmacology; D008668:Metallothionein / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009336:Necrosis; D020033:Protein Isoforms / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
D020033:Protein Isoforms; D012333:RNA, Messenger; D003300:Copper; D008668:Metallothionein; D007501:Iron; D015032:Zinc