The role of 8-hydroxy-2′-deoxyguanosine in rifamycin-induced DNA damage

The effect of rifamycin SV on the formation of 8-hydroxy-2′-deoxyguanosine (8-OHdG) has been investigated in vitro and in vivo. Oxidative modification of 2′-deoxyguanosine has been measured as an indication of DNA damage using high-performance liquid chromatography with electrochemical detection. Rifamycin SV in the presence of copper(II) ions induces the formation of 8-OHdG in calf thymus DNA. The effect is enhanced by increasing the antibiotic concentration and inhibited by catalase and hydroxyl radical (-OH) scavengers, such as thiourea and ethanol, in a rifamycin SV concentration-dependent manner. The reduced glutathione (GSH) inhibits DNA damage, and this effect is proportional to the final concentration of the tripeptide in the incubation medium. A significant increase in the formation of 8-OHdG and of malondialdehyde (MDA) in rat liver DNA was observed only in GSH-depleted animals after 5 days of rifamycin SV treatment. These results support the involvement of hydrogen peroxide (H202) and -OH in the mechanism of the oxidative modification of DNA achieved by rifamycin SV. The role of other reactive species and the antioxidant properties of GSH against oxidative damage is also discussed.