Ochratoxin A (OTA), a nephrotoxic
mycotoxin probably implicated in human
Balkan endemic nephropathy and associated urothelial
tumors, induces
renal carcinomas in rodents and nephrotoxicity in pigs. OTA induces
DNA-adduct formation, but the structure of the adducts and their role in nephrotoxicity and carcinogenicity have only partly been elucidated. In vivo, 2-mercaptoethane sulfonate (
MESNA) protects rats against OTA-induced nephrotoxicity but not against carcinogenicity, indicating two different mechanisms leading to nephrotoxicity or carcinogenicity. To better understand how
DNA-adduct could be generated, opossum kidney cells (OK) have been treated by OTA alone or in presence of several compounds such as
MESNA or
N-acetylcysteine (another agent that, like
MESNA, reduces oxidative stress by increasing of free
thiols in kidney),
buthionine sulfoximine (BSO) (an inhibitor of
glutathione-synthase), and alpha amino-3-chloro-4,5-dihydro-5-isoxazole
acetic acid (
ACIVICIN) (an inhibitor of
gamma glutamyl transpeptidase). Cytotoxicity of OTA on OK cells was evaluated by applying the
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. None of the listed agents diminished OTA cytotoxicity significantly;
ACIVICIN even increases OTA cytotoxicity. In contrast, analysis of the HPLC profiles of OTA metabolites produced during these incubations indicated that the pattern, the quantity of metabolites, and the nature of the derivatives were modulated by these agents.
Ochratoxin B (OTB), open-ring
ochratoxin A (OP-OA), 4 hydroxylated OTA, 10 hydroxylated OTA, OTA without
phenylalanine, OTB without
phenylalanine, and a dechlorinated OTA metabolite could be identified by nano-ESI-IT-MS.