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Metallothionein protects DNA from oxidative damage
1Department of Biochemistry, University of Sao Paulo, Brazil.
The Biochemical Journal
|April 1, 1993
Summary
Metallothionein (MT), a hydroxyl radical scavenger, protects cellular DNA from oxidative damage. While not preventing cell death from oxidative stress, MT concentrates in the nucleus, safeguarding DNA from hydroxyl radical attack.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Metallothionein (MT) is known as a potent hydroxyl radical scavenger.
- Its in vivo antioxidant properties and protective role against oxidative stress-induced cell death remain unclear.
- The potential of MT to protect specific cellular targets like DNA from oxidative damage has not been thoroughly investigated.
Purpose of the Study:
- To investigate the role of metallothionein (MT) in protecting DNA against oxidative damage in V79 Chinese hamster cells.
- To determine if MT concentration influences cellular resistance to hydrogen peroxide (H2O2)-induced DNA strand scission.
- To assess the impact of MT localization within the cell on its protective functions.
Main Methods:
- V79 Chinese hamster cells were manipulated to either enrich or deplete MT levels.
- Zinc induction was used to increase MT content, while antisense MT-I cDNA transfection was used to reduce MT levels.
- DNA-strand scission induced by H2O2 was measured in cells with varying MT concentrations.
- Levels of glutathione (GSH), superoxide dismutase, and H2O2-destroying enzymes were assessed.
- Indirect immunofluorescence was employed to determine MT localization within the cells.
Main Results:
- Cells enriched in MT showed increased resistance to H2O2-induced DNA-strand scission without changes in GSH levels.
- Cells depleted of MT became more susceptible to H2O2-induced DNA damage.
- No significant difference in resistance to the lethal effects of H2O2 was observed between cells with altered MT expression.
- Indirect immunofluorescence revealed a high concentration of MT within the cell nucleus.
- MT's protective effect on DNA was independent of other antioxidant enzymes like GSH and superoxide dismutase.
Conclusions:
- Metallothionein (MT) confers specific protection to DNA against hydroxyl radical attack, particularly when concentrated in the nucleus.
- While MT does not prevent overall cell death from oxidative stress, it plays a crucial role in preserving DNA integrity.
- The nuclear localization of MT is key to its DNA-protective function against oxidative damage.