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Hypochlorous acid-mediated activation of N-acetylbenzidine to form
V M Lakshmi1, F F Hsu, A E McGarry
1VA Medical Center, Department of Biochemistry, St. Louis University School of Medicine, Missouri, USA.
Summary
Hypochlorous acid (HOCl) activates N-acetylbenzidine (ABZ) to form a DNA adduct, N
Area of Science:
- Biochemistry
- Chemical carcinogenesis
- Oxidative stress
Background:
- Hypochlorous acid (HOCl), a reactive oxygen species, is implicated in inflammation and carcinogenesis.
- N-acetylbenzidine (ABZ) is a chemical that may form DNA adducts contributing to cancer risk.
Purpose of the Study:
- To investigate the activation of N-acetylbenzidine (ABZ) by hypochlorous acid (HOCl).
- To identify and characterize the specific DNA adduct formed from ABZ and HOCl.
Main Methods:
- Incubation of radiolabeled ABZ with HOCl at varying concentrations and pH.
- Analysis of reaction products using High-Performance Liquid Chromatography (HPLC).
- Characterization of the adduct using Electrospray Mass Spectrometry (ESI-MS) and Nuclear Magnetic Resonance (NMR).
Main Results:
- HOCl efficiently oxidized ABZ, forming a new product, dGp-ABZ, in the presence of 2'-deoxyguanosine 3'-monophosphate (dGp) and DNA.
- The adduct, N'-(3'-monophospho-deoxyguanosin-8-yl)-N-acetylbenzidine, was confirmed by mass spectrometry and NMR.
- Radical scavengers inhibited the oxidation, suggesting a radical mechanism.
Conclusions:
- HOCl activates ABZ to form the DNA adduct N'-(3'-monophospho-deoxyguanosin-8-yl)-N-acetylbenzidine (dGp-ABZ).
- This adduct may be present in white blood cells of benzidine-exposed workers.
- HOCl provides a convenient method for synthesizing the dGp-ABZ adduct.