Ascorbate and H2O2 induced oxidative DNA damage in Jurkat cells

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Oxidative stress is implicated in DNA damage and various diseases.
• Vitamin C (ascorbate) is a well-known antioxidant, but its role in modulating oxidative DNA damage is complex.
• Understanding how cellular factors influence DNA repair and damage is crucial for disease prevention.

Purpose of the Study:

• To investigate the effect of intracellular ascorbate concentration on hydrogen peroxide (H2O2)-induced oxidative DNA damage.
• To characterize the types and levels of DNA lesions formed in the presence of varying ascorbate levels.
• To elucidate the mechanism underlying ascorbate's influence on oxidative DNA damage.

Main Methods:

• Cells were incubated with dehydroascorbate to increase intracellular ascorbate levels.
• Cells were subsequently exposed to hydrogen peroxide (H2O2) to induce oxidative stress.
• Oxidative DNA damage was quantified by measuring specific biomarkers: 5-hydroxy-2'-deoxycytidine (5-hmC) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG).

Main Results:

• High intracellular ascorbate concentrations significantly sensitized cells to H2O2-induced DNA damage, particularly increasing 5-hmC levels (15-fold).
• 8-oxo-dG levels also increased, but to a lesser extent (50%).
• Damage was dependent on H2O2 concentration and involved a Fenton reaction, as indicated by modulation with iron and desferroxamine.

Conclusions:

• Ascorbate can paradoxically sensitize cells to H2O2-induced oxidative DNA damage, creating a novel experimental model.
• The study highlights a strong bias towards the formation of 5-hmC lesions over 8-oxo-dG lesions under these conditions.
• This finding necessitates a re-evaluation of ascorbate's role in oxidative DNA damage, particularly in the context of specific reactive oxygen species and cellular conditions.