Reactive Nitrogen Oxygen Species Metabolize N-Acetylbenzidine

Abstract

A close association has been reported for certain types of cancers influenced by aromatic amines and infection/inflammation. Reactive nitric oxygen species (RNOS), components of the inflammatory response, are bactericidal and tumoricidal, and contribute to the deleterious effects attributed to inflammation on normal tissues. This study assessed the possible transformation of the aromatic amine N-acetylbenzidine (ABZ) by RNOS. RNOS were generated by various conditions to react with ABZ, and samples were evaluated by HPLC. Conditions which generate nitrogen dioxide radical (NO(2)(-) + myeloperoxidase + H(2)O(2), ONOO(-), and NO(2)(-) + HOCl) produced primarily a single new product termed 3'-nitro-ABZ. The myeloperoxidase-catalyzed reaction with 0.3 mM NO(2)(-) was completely inhibited by 1 mM cyanide, and not effected by 100 mM chloride with or without 1 mM taurine. In contrast, conditions which generate N(2)O(3), such as spermine NONOate, did not produce 3'-nitro-ABZ, but rather two compounds termed 4'-OH-AABP and AABP. (1)H NMR and mass spectrometry identified 3'-nitro-ABZ as 3'-nitro-N-acetylbenzidine, 4'-OH-AABP as 4'-OH-4-acetylaminobiphenyl, and AABP as 4-acetylaminobiphenyl. Human polymorphonuclear neutrophils incubated with [(3)H]ABZ and stimulated with beta-phorbol 12-myristate 13-acetate produced 3'-nitro-ABZ in the presence of NO(2)(-) (0.1-1 mM). Neutrophil 3'-nitro-ABZ formation was verified by mass spectrometry and was consistent with myeloperoxidase oxidation of NO(2)(-). The results demonstrate that ABZ forms unique products in the presence of nitrosating and nitrating RNOS, which could influence the carcinogenic process and serve as biomarkers for these reactive species.

Nitrosation and Nitration of 2-Amino-3-methylimidazo[4,5-f ]quinoline by Reactive Nitrogen Oxygen Species

“…Formation of a tyrosine dimer and of a dimer and trimer of acetaminophen during these reactions supports the role of a phenoxyl radical in nitration (60,61). For N-acetylbenzidine, a radical intermediate is thought to be present during 3′-nitro-Nacetylbenzidine formation (46). Previous studies have reported the azo dimer to be an oxidation product of IQ (9).…”

“…RNOS transform the aromatic amine N-acetylbenzidine to distinct products (46). All conditions, which primarily formed nitrated IQ products, converted Nacetylbenzidine to 3′-nitro-N-acetylbenzidine.…”

“…RNOS chemical transformation of the aromatic amine N-acetylbenzidine has recently been demonstrated (46). This carcinogen is both nitrosated and nitrated by RNOS.…”

Transformation and Activation of Benzidine by Oxidants of the Inflammatory Response

“…4′-OH-ABP and ABP. Corresponding N-acetylated products were derived following nitrosation of N-acetylbenzidine by the NO donor spermine NONOate (35). 4′-OH-ABP and ABP can be activated to bind DNA.…”

“…BZ is unique among the compounds that we have studied in that it is not nitrated by the nitrogen dioxide radical (NO 2 • ) derived from the reaction of NO 2 -+ MPO + H 2 O 2 or ONOO - (31,36). Previous studies have demonstrated nitration of acetaminophen, N-acetylbenzidine, and 2-amino-3-methylimidazo[4,5-f]quinoline (35,37,38). Nitration of these compounds was thought to occur by an electron transfer mechanism involving radical combination reactions.…”