Medical College of Wisconsin
CTSICores SearchResearch InformaticsREDCap

Mechanism of unprecedented hydroxyl radical production and site-specific oxidative DNA damage by photoactivation of the classic arylhydroxamic acid carcinogens. Carcinogenesis 2019 Sep 18;40(9):1153-1163

Date

03/15/2019

Pubmed ID

30870561

DOI

10.1093/carcin/bgz021

Scopus ID

2-s2.0-85077104103 (requires institutional sign-in at Scopus site)   17 Citations

Abstract

The carcinogenicity of N-hydroxy-2-acetamidofluorene (N-OHAAF), the major genotoxic metabolite of the classic model aromatic amine (AA) carcinogen 2-acetylaminofluorene, has been attributed mainly to the formation of DNA adducts via arylnitrenium upon enzymatic activation. Here, we show, unexpectedly, that exposure of N-OHAAF to UV or sunlight irradiation can not only induce the formation of the well-known covalent DNA adducts, but, more interestingly, simultaneous generation of oxidative DNA damage was also observed as measured by the formation of DNA single-/double-strand breaks (SSBs/DSBs) and 8-oxo-2'-deoxyguanosine (8-oxodG), which were partly inhibited by the typical hydroxyl radical (•OH) scavengers. Electron spin resonance spin-trapping and fluorescent studies unequivocally confirmed that the highly reactive •OH was generated from photolysis of N-OHAAF. Further DNA sequencing investigations suggest that photoactivation of N-OHAAF caused preferential cleavage at guanine, thymine and cytosine sites. More importantly, the formation of 8-oxodG and DSBs were also observed when fibroblast Balb/c-3T3 cells were co-exposed to N-OHAAF/UV irradiation as measured by double immunofluorescence staining. Taken together, we propose that both •OH and amidyl radicals can be readily produced via N-OH homolysis in N-OHAAF by photoirradiation, which can induce both oxidative and covalent DNA damage. This represents the first report of •OH production and site-specific DNA damage via photoactivation of the genotoxic hydroxamic acid intermediate, which provides a new free radical perspective to better understand the molecular mechanism for the carcinogenicity of AAs.

Author List

Xu D, Huang CH, Xie LN, Shao B, Mao L, Shao J, Kalyanaraman B, Zhu BZ

Author

Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of Wisconsin