SUPEROXIDE FORMATION AND DNA-DAMAGE INDUCED BY A FRAGRANT FURANONE INTHE PRESENCE OF COPPER(II)

2,5-Dimethyl-4-hydroxy-3(2 H)-furanone (2,5-DMHF), a caramel-like frag rant compound found in many processed foodstuffs, has been reported to be mutagenic. 4,5-Dimethyl-3-hydroxy-2(5H)-furanone (4,5-DMHF), which is a similar characteristic fragrant compound, has no report concerni ng its mutagenicity. DNA-damage by 2,5-DMHF and 4,5-DMHF was investiga ted by using DNA fragments obtained from the p53 tumor suppressor gene , 2,5-DMHF induced DNA damage extensively in the presence of Cu(II), b ut only slightly in the presence of Fe(III). 4,5-DMHF did not cause me tal-dependent DNA damage. Bathocuproine, a Cu(I)-specific chelator, an d catalase inhibited DNA damage induced by 2,5-DMHF plus Cu(II), where as free hydroxyl radical scavengers did not, The order of DNA cleavage sites was thymine, cytosine > guanine residues. The site-specific DNA damage and effects of scavengers show that DNA-copper-oxygen complex rather than free (OH)-O-. are involved in the DNA damage. Formation of 8-oxodeoxyguanosine (8-oxodG) by 2,5-DMHF increased with its concentr ation in the presence of Cu(ll), whereas 8-oxodG formation increased o nly slightly in the presence of Fe(III). Degradation of 2,5-DMHF was e fficiently accelerated by Cu(II), but only slightly accelerated by Fe( III). The degradation of 4,5-DMHF was little even in the presence of m etal ions. Examination using cytochrome c suggests that superoxide was generated from 2,5-DMHF. Stoichiometric study of Cu(II) reduction rev ealed that autoxidation of 2,5-DMHF could offer 4-electron reduction. These results suggest that, at least in vitro and in an acellular syst em, 2,5-DMHF generates superoxide and subsequently hydrogen peroxide t o induce metal-dependent DNA damage, (C) 1998 Elsevier Science B.V.