Effect of dihydrokainate on the capacity of repair of DNA damage and apoptosis induced by doxorubicin

The intention of the current study was to investigate the effect of non-toxic doses of dihydrokainate on the capacity of repair of DNA damage and apoptosis induced by doxorubicin in mouse bone-marrow cells. The scoring of micronuclei and olive tail moment was undertaken in the current study as markers of DNA damage and repair. Apoptosis was analysed by the occurrence of a hypodiploid DNA peak. Oxidative stress markers such as bone-marrow reactive oxygen species, lipid peroxidation, reduced and oxidised glutathione were assessed as a possible mechanism underlying this amelioration. In addition, the influence of dihydrokainate on doxorubicin-induced topoisomerase II inhibition was examined. Dihydrokainate was neither genotoxic nor apoptogenic at doses equivalent to 10 or 20mg/kg/day for 7 days. Pre-treatment of mice with dihydrokainate significantly enhances the repair of doxorubicin-induced DNA damage and reduced doxorubicin-induced apoptosis depending on dose. Doxorubicin induced marked biochemical alterations characteristic of oxidative stress, including increased reactive oxygen species, enhanced lipid peroxidation and reduction in the reduced/oxidised glutathione ratio. Prior administration of dihydrokainate ahead of doxorubicin challenge ameliorated these oxidative stress markers. Importantly, dihydrokainate treatment had no antagonising effect on doxorubicin-induced topoisomerase II inhibition. Conclusively, this study provides for the first time that dihydrokainate enhances the repair of doxorubicin-induced DNA damage, which resides, at least in part, in its ability to modulate the cellular antioxidant levels. Based on our data presented, strategies can be developed to enhance the repair of doxorubicin-induced genomic damage in normal cells using dihydrokainate without diminishing doxorubicin's anti-topoisomerase II activity. Thus, improvement of doxorubicin's therapeutic index may be achieved by using dihydrokainate.