Linked Life Data

17226936

Source:http://linkedlifedata.com/resource/pubmed/id/17226936

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2007-1-17
pubmed:abstractText
Metabolism and bioactivation of 3-methylindole (3MI) were investigated in human liver microsomes. The metabolism of two deuterium-labeled analogues of 3MI permitted a relatively unambiguous identification of multiple metabolites and glutathione (GSH) adducts of reactive intermediates. A total of eight oxidized metabolites were detected, five of which were assigned as previously identified 3-methyloxindole, 3-hydroxy-3-methylindolenine, 3-hydroxy-3-methyloxindole, 5-hydroxy-3-methylindole, and 6-hydroxy-3-methylindole. Among the three new metabolites, one was either 4- or 7-OH-3-methylindole, and the other two were derived from additional oxidation on the phenyl ring of 3-methyloxindole. When GSH was added to the microsomal incubations, seven conjugates that had molecular ions corresponding to the incorporation of GSH and an atom of oxygen at m/z 453 (group I) were produced, and two additional conjugates had molecular ions at m/z 437 that corresponded to the incorporation of GSH with no additional oxygen (group II). Two conjugates in group I (m/z 453) were apparently derived by GSH addition to the 5,6-epoxide metabolite of 3-methyloxindole. These two GSH adducts were tentatively identified as 5-(glutathione-S-yl)-3-methyloxindole and 6-(glutathione-S-yl)-3-methyloxindole. The most abundant conjugate in group I was identified as 3-(glutathione-S-yl)-3-methyloxindole, which substantiated the presence of the putative 2,3-epoxy-3-methylindole intermediate. The remaining four adducts in group I were likely formed by conjugation of GSH at different positions of the phenyl ring, possibly via oxidation of 5-hydroxy-3-methylindole and 6-hydroxy-3-methylindole to two very interesting new electrophilic benzoquinone imine intermediates. For the group II conjugates (m/z 437), two isomers were identified as 2-(glutathione-S-yl)-3-methylindole and 3-(glutathione-S-yl-methyl)-indole. The former adduct was primarily derived from the 2,3-epoxide intermediate by thiol conjugation followed by dehydration. The latter adduct was consistent with our previously published work on the dehydrogenation of 3MI. In those studies, we showed that the reactive intermediate, 3-methylenenindolenine, was formed by hydrogen abstraction at the methyl group and was trapped with GSH. The putative dehydrogenation bioactivation mechanism is also substantiated by the finding that CYP2E1 selectively generated 2-(glutathione-S-yl)-3-methylindole but did not produce 3-(glutathione-S-yl-methyl)-indole. In summary, the results not only confirmed the formation of 2,3-epoxide-3-methylindole in human liver microsomes but also suggested that the phenolic metabolites of 3-methylindole were dehydrogenated to previously uncharacterized reactive intermediates.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0893-228X
pubmed:author
pubmed:issnType
Print
pubmed:volume
20
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
140-8
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
Metabolism and bioactivation of 3-methylindole by human liver microsomes.
pubmed:affiliation
Division of Drug Discovery, Johnson & Johnson Pharmaceutical Research & Development, LLC Spring House, Pennsylvania 19477, USA. zyan@prdus.jnj.com
pubmed:publicationType
Journal Article