Acrylonitrile enhances H2O2-mediated DNA damage via nitrogen-centered radical formation

Acrylonitrile (ACN) is widely used as a monomer in the polymer industry. St udies on carcinogenicity in rats exposed to ACN showed increased incidences of tumors including glial cell tumors of central nervous system and increa sed production of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) in glial c ells. Using a high performance liquid chromatograph equipped with an electr ochemical detector, we revealed that ACN enhanced the formation of 8-oxo-dG induced by H2O2 and Cu(II) whereas ACN itself did not cause DNA damage. Th e enhancing effect of ACN was much more efficient in the double-stranded DN A than that in the single-stranded DNA. Experiments with P-32-labeled DNA r evealed that addition of ACN enhanced the site-specific DNA damage at guani nes, particularly at 5'-site of the CTG and GGG sequences while H2O2/Cu(II) induced piperidine-labile sites at thymine, cytosine, and guanine residues . An electron spin resonance spectroscopy using alpha-(4-pyridyl-1-oxide)-N -tert-butylnitrone showed that a nitrogen-centered radical was generated fr om ACN in the presence of H2O2 and Cu(II). It is considered that ACN enhanc es H2O2-mediated DNA damage via nitrogen-centered radical formation. We wil l discuss the mechanism of the enhancing effect on oxidative DNA damage in relation to expression of ACN carcinogenicity.