Chemical toxicology of reactive intermediates formed by the glutathione-dependent bioactivation of halogen-containing compounds.
The concept that reactive intermediate formation during the biotransformation of drugs and chemicals is an important bioactivation mechanism was proposed in the 1970s and is now accepted as a major mechanism for xenobiotic-induced toxicity. The enzymology of reactive intermediate formation as well as the characterization of the formation and fate of reactive intermediates are now well-established. The mechanism by which reactive intermediates cause cell damage and death is, however, still poorly understood. Although most xenobiotic-metabolizing enzymes catalyze the bioactivation of chemicals, glutathione-dependent biotransformation has been largely associated with detoxication processes, particularly mercapturic acid formation. Abundant evidence now shows that glutathione-dependent biotransformation constitutes an important bioactivation mechanism for halogen-containing drugs and chemicals and has for many compounds been implicated in their organ-selective toxicity and in their mutagenic and carcinogenic potential. The glutathione-dependent biotransformation of haloalkenes is the first step in the cysteine S-conjugate beta-lyase pathway for the bioactivation of nephrotoxic haloalkenes. This pathway has been a rich source of reactive intermediates, including thioacyl halides, alpha-chloroalkenethiolates, 3-halo-alpha-thiolactones, 2,2,3-trihalothiiranes, halothioketenes, and vinylic sulfoxides. Glutathione-dependent bioactivation of gem-dihalomethanes and 1,2-, 1,3-, and 1,4-dihaloalkanes leads to the formation of alpha-chlorosulfides, thiiranium ions, sulfenate esters, and tetrahydrothiophenium ions, respectively, and these reactions lead to reactive intermediate formation.
Anders
M W
MW
Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 214642, USA.
D000818:Animals; D001711:Biotransformation / Q000502:physiology*; D004798:Enzymes / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006219:Halogens / Q000378:metabolism* / Q000633:toxicity*; D006262:Health; D006801:Humans; D015262:Xenobiotics / Q000378:metabolism / Q000633:toxicity
D004798:Enzymes; D006219:Halogens; D015262:Xenobiotics; D005978:Glutathione