Glutathione depletion, lipid peroxidation, DNA double-strand breaks and the cytotoxicity of 2-bromo-3-(N-acetylcystein-S-yl)hydroquinone in rat renal cortical cells.
The mechanisms involved in the cytotoxicity of 2-bromo-3-(N-acetylcystein-S-yl)hydroquinone, a model compound for hydroquinone derived mercapturic acids, were investigated in rat renal proximal tubule cells. 2-Bromo-3-(N-acetylcystein-S-yl)hydroquinone induced a time- and concentration-dependent decrease in cell viability and in the levels of cellular glutathione. Antioxidants such as N,N'-diphenyl-p-phenylene diamine and ascorbic acid and the iron chelator desferrioxamine very efficiently protected the cells from 2-bromo-3-(N-acetylcystein-S-yl)hydroquinone without influencing glutathione depletion. The acetoxymethyl ester of the Ca2+ chelator Quin-2, the inhibitor of the Ca(2+)- and Mg(2+)-dependent endonucleases, aurintricarboxylic acid and the poly(ADP-ribose)-polymerase inhibitor 3-aminobenzamide also ameliorated 2-bromo-3-(N-acetylcystein-S-yl)hydroquinone cytotoxicity. Moreover, 2-bromo-3-(N-acetylcystein-S-yl)hydroquinone depleted Ca2+ from isolated kidney mitochondria, increased the amount of malondialdehyde in rat kidney cells and induced DNA double-strand breaks in renal cells in culture. These results suggest that renal cells oxidize 2-bromo-3-(N-acetylcystein-S-yl)hydroquinone to the corresponding quinone; this soft electrophile reacts rapidly with glutathione, thus depleting cellular glutathione concentrations as indicated by the tentative identification of a 2-bromo-3-(N-acetylcystein-S-yl)hydroquinone thioether in the incubation medium of renal cells treated with the mercapturate. As a result of the massive glutathione depletion, peroxidative mechanisms then cause an elevation of the cytosolic concentrations of ionized calcium; impairment of the ability of the mitochondria to sequester Ca2+ plays an important role in the elevation of the Ca2+ concentration. Finally, activation of Ca(2+)- and Mg(2+)-dependent endonucleases results in DNA damage and cell death.
Vamvakas
S
S
Institut für Toxikologie, Universität Würzburg, FRG.
Bittner
D
D
Koob
M
M
Glück
S
S
Dekant
W
W
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000633:toxicity; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D005978:Glutathione / Q000378:metabolism*; D006873:Hydroquinones / Q000633:toxicity*; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000166:cytology / Q000187:drug effects*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects; D008054:Lipid Peroxides / Q000378:metabolism*; D008315:Malondialdehyde / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D013552:Swine
D006873:Hydroquinones; D008054:Lipid Peroxides; C065981:2-bromo-3-(N-acetylcystein-S-yl)hydroquinone; D008315:Malondialdehyde; D005978:Glutathione; D002118:Calcium; D000111:Acetylcysteine