Activation and deactivation of quinones catalyzed by DT-diaphorase. Evidence for bioreductive activation of diaziquone (AZQ) in human tumor cells and detoxification of benzene metabolites in bone marrow stroma.
Bioactivation of diaziquone (AZQ) in HT-29 human colon carcinoma cells and detoxification of benzene metabolites in bone marrow stromal cells were used as examples of the potential role of DT-diaphorase in both activation and deactivation processes. HT-29 cell cytosol contained high levels of DT-diaphorase activity and removed AZQ in the presence of either NADH or NADPH. Prior boiling of cytosol, omission of NADH or NADPH or inclusion of dicoumarol, an inhibitor of DT-diaphorase, inhibited removal of AZQ. AZQ-induced cytotoxicity in HT-29 cells was also inhibited by dicoumarol. Chemical reduction of AZQ in a cell free system enhanced formation of a GSH conjugate of AZQ. Two of the major cell types in bone marrow stroma are macrophages and fibroblastoid stromal cells. A fibroblastoid cell line derived from stromal cells contained approximately fourfold higher levels of DT-diaphorase than macrophages. Inclusion of dicoumarol in incubations containing 14C-hydroquinone and the respective stromal cell type, significantly increased covalent binding of radiolabel to macromolecules in stromal fibroblasts but not in macrophages.
Ross
D
D
Molecular Toxicology and Environmental Health Sciences Program, School of Pharmacy, University of Colorado, Boulder 80309.
Siegel
D
D
Gibson
N W
NW
Pacheco
D
D
Thomas
D J
DJ
Reasor
M
M
Wierda
D
D
D000818:Animals; D001388:Aziridines / Q000378:metabolism*; D001554:Benzene / Q000378:metabolism*; D016227:Benzoquinones; D001711:Biotransformation; D001853:Bone Marrow / Q000187:drug effects / Q000378:metabolism*; D001854:Bone Marrow Cells; D002851:Chromatography, High Pressure Liquid; D003110:Colonic Neoplasms / Q000201:enzymology; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008658:Inactivation, Metabolic; D008264:Macrophages / Q000378:metabolism; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D016660:NAD(P)H Dehydrogenase (Quinone); D010084:Oxidation-Reduction; D011808:Quinone Reductases / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000378:metabolism*
D001388:Aziridines; D016227:Benzoquinones; D011809:Quinones; D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases; C029108:diaziquone; D001554:Benzene