Vitamin C modulates DNA damage induced by hydrogen peroxide in human colorectal adenocarcinoma cell lines (HT29) estimated by comet assay in vitro.
BACKGROUND
Cancer cells, compared to normal cells, are under increased oxidative stress associated with oncogenic transformation, alterations in metabolic activity, and increased generation of reactive oxygen species.


METHODS
We investigated the ability of vitamin C to reduce the damage induced by hydrogen peroxide, in human colorectal adenocarcinoma cells in vitro by the comet assay. Additionally, we measured the kinetics and efficacy of the repair of DNA damage after incubation with vitamin C in the presence of H2O2.


RESULTS
The obtained results showed that 1 h pre-incubation with vitamin C and exposure to H2O2 for the last 10 min of incubation caused a statistically significant (p < 0.05) increase in DNA migration in comet tails in all experimental series. For the 10 µM, 25 µM, 50 µM, 100 µM vitamin C concentrations the levels of DNA damage were as follows: 18.6%, 21.1%, 25.3% and 27.2%, respectively, as compared to the untreated cells (3.26%). However, in comparison with H2O2 alone (29.1%), we observed a statistically significant (p < 0.05) decrease of the genotoxic effect in HT29 cells induced by H2O2 for the two lowest of concentrations of vitamin C: 10 µM and 25 µM. The HT29 cells were able to achieve effective repair of the damaged DNA within 60 and 120 min after incubation with the tested compounds. All the values obtained in the test were statistically significant (p < 0.05).


CONCLUSIONS
Vitamin C caused a weaker DNA damaging effect of hydrogen peroxide and positively influences the level of oxidative DNA damage in HT29 cells (decrease ∼ 30%). We noted that DNA damage was effectively repaired during 120 min postincubation in the tested cells and that oxidative damage was the major type of damage.
Laboratory of Cytogenetics, Department of General Genetics, Molecular Biology and Plant Biotechnology, University of Lodz, Poland.
Renata
R
Kontek
Department of General Biochemistry, University of Lodz, Poland.
Bogdan
B
Kontek
Department of Endoscopy and One Day Gastroenterology, Wl. Bieganski Memorial Regional Specialist Hospital, Lodz, Poland.
Krzysztof
K
Grzegorczyk
HT29 cells; comet assay; oxidative DNA damage; vitamin C