Copper-dependent DNA damage induced by hydrazobenzene, an azobenzene metabolite

Hydrazobenzene is carcinogenic to rats and mice and azobenzene is carcinoge nic to rats. Hydrazobenzene is a metabolic intermediate of azobenzene. To c larify the mechanism of carcinogenesis by azobenzene and hydrazobenzene, we investigated DNA damage induced by hydrazobenzene, using P-32-5'-end-label ed DNA fragments obtained from the c-Ha-ms-l protooncogene and the p53 tumo r suppressor gene. Hydrazobenzene caused DNA damage in the presence of Cu(I I). Piperidine treatment enhanced the DNA damage greatly, suggesting that h ydrazobenzene caused base modification and liberation. However, azobenzene did not cause DNA damage even in the presence of Cu(II). Hydrazobenzene plu s Cu(II) caused DNA damage frequently at thymine residues. Catalase and a C u(I)specific chelator inhibited Cu(II)-mediated DNA damage by hydrazobenzen e. Typical (OH)-O-. scavengers did not inhibit the DNA damage. The main act ive species is probably a metal oxygen complex, such as Cu(I)-OOH. Formatio n of 8-oxo-7, 8-dihydro-2'-deoxyguanosine was increased by hydrazobenzene i n the presence of Cu(II). Oxygen consumption and W-Visible spectroscopic me asurements have shown that hydrazobenzene is autoxidized to azobenzene with H2O2 formation. It is considered that the metal-mediated DNA damage by hyd razobenzene through H2O2 generation may be relevant for the expression of c arcinogenicity of azobenzene and hydrazobenzene.