DNA damage by 5-aminolevulinic and 4,5-dioxovaleric acids in the presence of ferritin

Cellular accumulation of 5-aminolevulinic acid (ALA), the first specific in termediate of heme biosynthesis, is correlated in liver biopsy samples of a cute intermittent porphyria affected patients with an increase in the occur rence of hepatic cancers and the formation of ferritin deposits in hepatocy tes, 5-Aminolevulinic acid is able to undergo enolization and to be subsequ ently oxidized in a reaction catalyzed by iron complexes yielding 4,5-dioxo valeric acid (DOVA), The released superoxide radical (O-2(.-)) is involved in the formation of reactive hydroxyl radical ((OH)-O-.) or related species arising from a Fenton-type reaction mediated by Fe-II and Cu-I. This leads to DNA oxidation, The metal catalyzed oxidation of ALA may be exalted by t he O-2(.-) and enoyl radical-mediated release of Fen ions from ferritin, We report here the potentiating effect of ferritin on the ALA-mediated cleava ge of plasmid DNA and the enhancement of the formation of 8-oxo-7,8-dihydro -2'-deoxyguanosine (8-oxodGuo), Plasmid pBR322 was incubated with ALA and v arying amounts of purified ferritin, DNA damage was assessed by gel electro phoresis analysis of the open and the linear forms of the plasmid from the native supercoiled structure. Addition of either the DNA compacting polyami ne spermidine or the metal chelator ethylenediaminetetraacetic acid (EDTA) inhibited the damage. It was also shown that ALA in the presence of ferriti n is able to increase the oxidation of the guanine moiety of monomeric 2'-d eoxyguanosine (dGuo) and calf thymus DNA (CTDNA) to form 8-oxodGuo as infer red from high performance liquid chromatography (HPLC) measurements using e lectrochemical detection. The formation of the adduct dGuo-DOVA was detecte d in CTDNA upon incubation with ALA and ferritin, In a subsequent investiga tion, the aldehyde DOVA was also able to induces strand breaks in pBR322 DN A. (C) 2000 Academic Press.