Comparison of the nucleic acid covalent binding capacity of two nitro-substituted benzazolo[3,2- a]quinolinium salts upon enzymatic reduction

• Published in: Toxicology in vitro 2007-09, Vol.21 (6), p.1155-1164
• Main Authors: Zayas, Beatriz, Beyley, Juan, Terron, Maria, Cordero, Marisol, Hernandez, Wigberto, Alegría, Antonio E., Cox, Osvaldo
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents - metabolism; Benzazolo[3,2- a]quinolinium; Bioreductive drugs; Chromatography, High Pressure Liquid; DNA - metabolism; DNA Adducts; Hypoxanthine - metabolism; Hypoxia; Mass spectrometry; Oxidation-Reduction; Prodrugs - metabolism; Quinolinium Compounds - metabolism; Spectrometry, Mass, Electrospray Ionization; Xanthine Oxidase - metabolism
• ISSN: 0887-2333; 1879-3177
• DOI: 10.1016/j.tiv.2007.03.004

The DNA binding capacity of two nitro-substituted benzazolo[3,2- a]quinolinium chlorides (NBQs), NBQ-38 and NBQ-95, was evaluated upon their enzymatic reduction with hypoxanthine (HX)/xanthine oxidase (XO) under anaerobic conditions. In the presence of 2′-deoxyguanosine (2′-dG) or calf thymus DNA, covalent-addition products were monitored. Reactions of each NBQ with 2′-dG or DNA differed in the NBQ to HX molar ratio. Control reactions, one without HX/OX and another under aerobic conditions, were also analyzed. Adducts were isolated and characterized by high performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI-MS). Authentic samples of the reduced forms of these NBQs, identified as ABQ-38 and ABQ-95, were synthesized as standards to monitor bioreduction processes. HPLC analysis showed that the yield of formation of an unknown product (possibly, 2′-dG-NHBQ-38 adduct) from the reaction of NBQ-38 with 2′-dG and DNA was proportional to the HX to NBQ-38 molar ratio. ESI-MS analysis of the DNA hydrolysates showed evidence of an adduct formed upon bioreduction of NBQ-38 by the ions detection at m/z 528.3 and 454.8, consistent with chemical structures of a 2′-dG-NHBQ-38 adduct and a fragment ion. DNA adducts were not observed with NBQ-95, although the corresponding bioreduction product ABQ-95 was detected by ESI-MS. This study provides mechanistic information of these bioreductively-activated pro-drugs with potential therapeutic applications.