Involvement of oxidative DNA damage and apoptosis in antitumor actions of aminosugars

We investigated the mechanisms of apoptosis and DNA damage induced by amino sugars in relation to their antitumor actions. The order of cytotoxic effec ts of aminosugars was D-mannosamine (ManN) >> D-galactosamine (GalN) > D-gl ucosamine (GlcN). A comparison of the frequency of apoptotic cells showed t he same order. DNA ladders were formed hp only ManN and the formation of DN A ladders was inhibited by a caspase inhibitor. Pulsed-field gel electropho resis showed that ManN caused cellular DNA cleavage at a lower concentratio n than those causing apoptosis. Cellular DNA cleavage was inhibited by cata lase and enhanced by a catalase inhibitor. Flow cytometry showed that ManN enhanced the production of intracellular peroxides. These results suggest t hat ManN induced a poptosis is preceded by H2O2-mediated DNA damage. The or der of the extent of damage to P-32-labeled DNA fragments by aminosugars pl us Cu(II) was ManN >> GalN > GlcN. The DNA damage was inhibited by catalase and bathocuproine, suggesting that H2O2 reacts with Cu(I) to form the meta l-peroxide complex capable of causing DNA damage. live mechanisms of H2O2 g eneration from aminosugars were proposed: one is the major pathway to form a dioxo compound and NH4+; the other is the minor pathway to form a pyrazin e derivative through the condensation of two molecules of an aminosugar. Th e order of reactivity to generate these products was ManN >> GalN > GlcN. O n the basis of these results, it is concluded that aminosugars, especially ManN, produce H2O2 to cause DNA damage, which mediates apoptosis resulting in tumor growth inhibition.