title: Pro-oxidant properties and cytotoxicity of AZT-monophosphate and AZT.
abstract: The effects of zidovudine (AZT) and AZT-monophosphate (AZT-MP) on lipid peroxidation and oxidative cell injury were studied. When microsomal membranes from rat livers were peroxidized by a superoxide-driven, Fe-catalyzed oxy-radical system (ORS), both AZT-MP and, to a lesser extent AZT, but not thymidine, concentration dependently (2-100 microM) enhanced lipid peroxidation (TBARS formation) up to 51% above control. Significance (p < 0.05) was achieved by 6.7 microM AZT-MP. When cultured bovine aortic endothelial cells were incubated with the ORS for 60 min, total glutathione (GSH) decreased by 40% and 24-h cell survival, determined by the tetrazolium salt MTT assay, decreased by 38%. Using this cell system, AZT-MP (7-100 microM) promoted cell death further; at 20 microM 50% (p < 0.01), cell death was induced. In comparison, AZT was less effective. Concurrently, AZT-MP significantly promoted ORS-mediated loss of GSH. These cytotoxic effects were further exacerbated by low extracellular magnesium. Interestingly, when the endothelial cells were exposed to an iron-independent peroxynitrite generating system (SIN-1), the AZT-MP effects were absent. We propose that these pro-oxidant properties of AZT-MP are iron dependent. Because AZT-MP is a major phosphorylated metabolite, the data suggest that potential pro-oxidative activities may be associated with AZT use when catalytic iron is present.
authors.affiliation: Division of Experimental Medicine, Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, 2300 Eye St. NW, Ross Hall, Room 443, Washington, DC 20037, USA. itmak@gwu.edu
authors.forename: I Tong
authors.initials: IT
authors.lastname: Mak
authors.forename: Lucie F
authors.initials: LF
authors.lastname: Nedelec
authors.forename: William B
authors.initials: WB
authors.lastname: Weglicki
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D054306:Dideoxynucleotides; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008274:Magnesium / Q000378:metabolism; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016877:Oxidants / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013936:Thymidine / Q000494:pharmacology; D013942:Thymine Nucleotides / Q000633:toxicity*; D015215:Zidovudine / Q000031:analogs & derivatives* / Q000633:toxicity*
chemical_list: D054306:Dideoxynucleotides; D005609:Free Radicals; D016877:Oxidants; D013942:Thymine Nucleotides; C057287:3'-azido-3'-deoxythymidine 5'phosphate; D015215:Zidovudine; C002385:linsidomine; D008981:Molsidomine; D005978:Glutathione; D008274:Magnesium; D013936:Thymidine