Untargeted DNA Adductomics Identifies Aristolochic Acid III as a Potent DNA-Damaging Agent among 11 Substituted Aromatic Genotoxicants in the Rat Urinary System

An untargeted, data-independent acquisition high-resolution
accurate
tandem mass spectrometry method using an Orbitrap mass spectrometer
was employed to screen for DNA adducts formed from 11 environmental
and dietary aromatic or substituted aromatic carcinogens in the kidney,
urinary bladder, prostate, pancreas, liver, and the lung of male rats
24 h after treatment. Among the carcinogens investigated, DNA adducts
of the structurally related nitrophenanthrenes 3-nitrobenzanthrone
(3-NBA), an atmospheric pollutant, and 8-methoxy-6-nitrophenanthro[3,4-d]-1,3-dioxole-5-carboxylic acid (AA-I), a naturally occurring
genotoxicant from Aristolochiaceae plants, were the most abundant
across most organs, forming both 2′-deoxyguanosine (dG) and
2′-deoxyadenosine (dA) adducts. In contrast, significantly
lower DNA adduct levels were formed with the aromatic amine 4-aminobiphenyl
and 2-nitrofluorene, an oxidized derivative of 2-aminofluorene; the
heterocyclic aromatic amines 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-α-carboline, and 2-amino-3-methyl-α-carboline;
and the polycyclic aromatic hydrocarbon benzo[a]pyrene.
DNA adducts of o-toluidine and 2-naphthylamine were
not detected. Most notably, 10-methoxy-6-nitrophenanthro[3,4-d]-1,3-dioxole-5-carboxylic acid (AA-III), an isomer of
AA-I, which was later identified as a minor contaminant (5.3%) in
the purified herbal extract assayed, exhibited strong organotropism
for DNA damage within the urinary system. Dose-adjusted levels of
dA and dG adducts of AA-III were 30 to 80 times higher than those
of AA-I in the kidney and urinary bladder. This strikingly high organ-specific
DNA adduct formation in the urinary system was unique to AA-III and
was not observed for the structurally related 3-NBA and AA-I, or the
other carcinogens tested. Given that AA-III frequently occurs with
AA-I in Aristolochia herbs, these findings underscore
the need for further research into the carcinogenic potential of AA-III
and its role in renal and urinary bladder cancer associated with traditional
herbal medicines.