5-Aminolevulinic acid induces single-strand breaks in plasmid pBR322 DNA in the presence of Fe2+ ions.
5-Aminolevulinic acid (ALA), a heme precursor accumulated in chemical and inborn porphyrias, has been demonstrated to produce reactive oxygen species upon metal-catalyzed aerobic oxidation and to cause oxidative damage to proteins, liposomes and subcellular structures. Exposure of plasmid pBR322 DNA to ALA (0.01-3 mM) in the presence of 10 microM Fe2+ ions causes DNA single-strand breaks (ssb), revealed by agarose gel electrophoresis as an increase in the proportion of the open circular form (75 +/- 7.5% at 3 mM ALA) at the expense of the supercoiled form. Addition of either anti-oxidant enzymes such as superoxide dismutase (10 micrograms/ml) and catalase (20 micrograms/ml), or a metal chelator (DTPA, 2.5 mM), or a HO. scavenger (mannitol, 100 mM) inhibited the damage (by 30, 45, 55, and 81%, respectively), evidencing the involvement of O2-., H2O2 and HO. (by the Haber-Weiss reaction) in this process. Hydrogen peroxide (100 microM) or Fe2+ (10 microM) alone were of little effect on the extent of DNA ssb. The present data may shed light on the correlation reported between primary liver-cell carcinoma and intermittent acute porphyria.
Onuki
J
J
Departamento de Bioquímica, Universidade de São Paulo, Brazil.
Medeiros
M H
MH
Bechara
E J
EJ
Di Mascio
P
P
D000622:Aminolevulinic Acid / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D004249:DNA Damage; D004270:DNA, Circular / Q000032:analysis; D004277:DNA, Single-Stranded / Q000187:drug effects*; D004278:DNA, Superhelical / Q000032:analysis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000235:genetics; D005296:Ferrous Compounds / Q000494:pharmacology*; D016166:Free Radical Scavengers; D006801:Humans; D008099:Liver / Q000378:metabolism; D004369:Pentetic Acid / Q000494:pharmacology; D010957:Plasmids / Q000187:drug effects*; D017118:Porphyria, Acute Intermittent / Q000209:etiology
D000975:Antioxidants; D004270:DNA, Circular; D004277:DNA, Single-Stranded; D004278:DNA, Superhelical; D005296:Ferrous Compounds; D016166:Free Radical Scavengers; D004369:Pentetic Acid; D000622:Aminolevulinic Acid