Comparative CYP-dependent binding of the adrenocortical toxicants 3-methylsulfonyl-DDE and o,p'-DDD in Y-1 adrenal cells.
The environmental pollutant 3-MeSO(2)-DDE [2-(3-methylsulfonyl-4-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichloroethene] is an adrenocortical toxicant in mice, specifically in the glucocorticoid-producing zona fasciculata, due to a cytochrome P450 11B1 (CYP11B1)-catalysed bioactivation and formation of covalently bound protein adducts. o,p'-DDD [2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichloroethane] is toxic and inhibits steroidogenesis in the human adrenal cortex after bioactivation by unidentified CYPs, but does not exert any toxic effects on the mouse adrenal. As a step towards determining in vitro/in vivo relationships for the CYP-catalysed binding and toxicity of 3-MeSO(2)-DDE and o,p'-DDD, we have investigated the irreversible protein binding of these two toxicants in the murine adrenocortical cell line Y-1. The irreversible binding of 3-MeSO(2)-DDE previously demonstrated in vivo was successfully reproduced and could be inhibited by the CYP-inhibitors etomidate, ketoconazole and metyrapone. Surprisingly, o,p'-DDD reached similar levels of binding as 3-MeSO(2)-DDE. The binding of o,p'-DDD was sensitive to etomidate and ketoconazole, but not to metyrapone. Moreover, GSH depletion increased the binding of 3-MeSO(2)-DDE, but not of o,p'-DDD, indicating an important role of GSH conjugation in the detoxification of the 3-MeSO(2)-DDE-derived reactive metabolite. In addition, the specificity of CYP11B1 in activating 3-MeSO(2)-DDE was investigated using structurally analogous compounds. None of the analogues produced histopathological lesions in the mouse adrenal in vivo following a single i.p. injection of 100 mg/kg body weight, but two of the compounds were able to decrease the irreversible binding of 3-MeSO(2)-DDE to Y-1 cells. These results indicate that the bioactivation of 3-MeSO(2)-DDE by CYP11B1 is highly structure-dependent. In conclusion, both 3-MeSO(2)-DDE and o,p'-DDD bind irreversibly to Y-1 cells despite differences in binding and adrenotoxicity in mice in vivo. This reveals a notable in vitro/in vivo discrepancy, the contributing factors of which remain unexplained. We consider the Y-1 cell line as appropriate for studies of the cellular mechanisms behind the adrenocortical toxicity of these substances.
Hermansson
Veronica
V
Department of Environmental Toxicology, Uppsala University, Norbyvägen 18 A, 752 36, Uppsala, Sweden.
Asp
Vendela
V
Bergman
Ake
A
Bergström
Ulrika
U
Brandt
Ingvar
I
D000311:Adrenal Glands / Q000166:cytology* / Q000187:drug effects / Q000473:pathology; D000818:Animals; D002460:Cell Line; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003633:Dichlorodiphenyl Dichloroethylene / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D005260:Female; D005978:Glutathione / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008939:Mitotane / Q000378:metabolism* / Q000633:toxicity; D011485:Protein Binding; D013438:Sulfhydryl Compounds / Q000378:metabolism
D065607:Cytochrome P-450 Enzyme Inhibitors; D013438:Sulfhydryl Compounds; D003633:Dichlorodiphenyl Dichloroethylene; C055238:1-chloro-4-(2,2-dichloro-1-(4-chlorophenyl)ethenyl)-3-(methylsulfonyl)benzene; D008939:Mitotane; D003577:Cytochrome P-450 Enzyme System; D005978:Glutathione