Pro-oxidant properties and cytotoxicity of AZT-monophosphate and AZT.
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.
Mak
I Tong
IT
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
Nedelec
Lucie F
LF
Weglicki
William B
WB
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*
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