Cytotoxic Homo- and Hetero-Dimers of o-toluidine, o-anisidine, and Aniline Formed by In Vitro Metabolism

Abstract

Several aromatic amine compounds are urinary bladder carcinogens. Activated metabolites and DNA adducts of polycyclic aromatic amines, such as 4-aminobiphenyl, have been identified, whereas those of monocyclic aromatic amines, such as o-toluidine (o-Tol), o-anisidine (o-Ans), and aniline (Ani), have not been completely determined. We have recently reported that o-Tol and o-Ans are metabolically converted in vitro and in vivo to cytotoxic and mutagenic p-semidine-type dimers, namely 2-methyl-N 4-(2-methylphenyl) benzene-1,4-diamine (MMBD) and 2-methoxy-N 4-(2-methoxyphenyl) benzene-1,4-diamine (MxMxBD), respectively, suggesting their roles in urinary bladder carcinogenesis. In this study, we found that when o-Tol and o-Ans were incubated with S9 mix, MMBD and MxMxBD as well as two isomeric heterodimers, MMxBD and MxMBD, were formed. Therefore, any two of o-Tol, o-Ans, and Ani (10 mM each) were incubated with the S9 mix for up to 24 h and then subjected to LC–MS to investigate their metabolic kinetics. Metabolic conversions to all nine kinds of p-semidine-type homo- and hetero-dimers were observed, peaking at 6 h of incubation with the S9 mix; MxMxBD reached the peak at 6.1 ± 1.4 μM. Homo- and hetero-dimers containing the o-Ans moiety in the diamine structure showed a faster dimerization ratio, whereas levels of these dimers, such as MxMxBD, markedly declined with further incubation. Dimers containing o-Tol and Ani were relatively stable, even after incubation for 24 h. The electron-donating group of the o-Ans moiety may be involved in rapid metabolic conversion. In the cytotoxic assay, dimers with an o-Ans moiety in the diamine structure and MMBD showed approximately two- to four-fold higher cytotoxicity than other dimers in human bladder cancer T24 cells. These chemical and biological properties of homo- and hetero-dimers of monocyclic aromatic amines may be important when considering the combined exposure risk for bladder carcinogenesis.

Toxicological effects of two metabolites derived from <i>o</i>-toluidine and <i>o</i>-anisidine after 28-day oral administration to rats

“…In the low-dose o-toluidine and o-anisidine groups, approximately half of the unchanged form was detected compared with that in the high-dose groups, whereas bladder lesions and γ-H2AX formation were rarely observed, indicating that these findings were related to the presence of other metabo-lites rather than the unchanged forms of the compounds. We have recently identified several novel metabolites of o-toluidine and o-anisidine (Kobayashi et al, 2022), and it may need to be investigated on the potential of bladder toxicity of these metabolites.…”

Non‐Viral Nucleic Acid Delivery System for RNA Therapeutics

“…[219] Anisidine (AA) is a small molecule compound that can specifically bind to the overexpressed sigma receptor on the membrane of cancer cells. [220] Guo et al developed a PEG gold nanoparticle with anisidine at the end and carried siRNA through complex electrostatic interaction to obtain a nanocomposite (AU110-PEI-PEG5000-AA. siRNA).…”

Green synthesis and characterization of Ni0.25Zn0.75Fe2O4magnetic nanoparticles and study of their photocatalytic activity in the degradation of aniline

“…[ 9 ] This compound causes some biological damages to the body, including carcinogenic, [ 10 ] tumors in animals, [ 11 ] and bladder cancer in humans. [ 12 ] It also converts hemoglobin to methemoglobin, [ 13 ] with rapid reactions, and causes cyanosis. [ 14 ] Other dangers of aniline include complications in the kidneys, [ 15 ] nervous system, [ 16 ] bones, [ 17 ] joints, [ 18 ] and so on.…”