A secondary metabolite of Brassicales, 1-methoxy-3-indolylmethyl glucosinolate, as well as its degradation product, 1-methoxy-3-indolylmethyl alcohol, forms DNA adducts in the mouse, but in varying tissues and cells.

ABSTRACT

1-Methoxy-3-indolylmethyl (1-MIM) glucosinolate, a secondary metabolite of Brassicales species, and its breakdown product 1-MIM alcohol are mutagenic in cells in culture after activation by plant ß-thioglucosidase and human sulphotransferase, respectively. In the present study, we administered these compounds orally to mice to study time course, dose dependence, tissue distribution and cellular localization of the 1-MIM DNA adducts formed. We used isotope-dilution ultra-performance liquid chromatography-tandem mass spectrometry to quantify the adducts and raised an antiserum for their immunohistochemical localization. Both compounds formed the same adducts, N(2)-(1-MIM)-2'-deoxyguanosine and N(6)-(1-MIM)-2'-deoxyadenosine, approximately in a 3.31 ratio. 1-MIM glucosinolate primarily formed these adducts in the large intestine, with a luminal-basal gradient, probably due to activation by thioglucosidase from intestinal bacteria. 1-MIM alcohol formed higher levels of adduct than the glucosinolate. Unlike after treatment with the glucosinolate, luminal and basal enterocytes were similarly affected in caecum, and liver and stomach were additional important target tissues. Maximal adduct levels were reached 8 h after the administration of both compounds. The hepatic DNA adducts persisted for the entire observation period (48 h), whereas those in large intestine rapidly declined due to cell turnover, as verified by immunohistochemistry. Hepatic adduct formation was focused on the periportal hepatocytes with concomitant depletion of glycogen, p53 activation and p21 induction. Adduct formation in caecum was associated with massive apoptosis, p53 activation and p21 induction, in particular after treatment with 1-MIM alcohol. It remains to be studied whether similar effects occur in humans after the consumption of Brassicales species.