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Antimicrobial Agents and Chemotherapy, Jun 1997, 1231-1236, Vol 41, No. 6
PG Hoggard, S Kewn, MG Barry, SH Khoo and DJ Back
Drugs commonly administered to patients infected with the human
immunodeficiency virus (HIV) have been studied for their propensity to
alter the intracellular phosphorylation of the anti-HIV nucleoside analog
stavudine (2',3'-dideoxy-2',3'-didehydrothymidine; d4T) in peripheral blood
mononuclear cells (PBMCs) and U937 cells in vitro. PBMCs isolated from the
blood of healthy volunteers were stimulated by the mitogen
phytohemagglutinin (10 microg/ml) for 72 h. Stimulated PBMCs (3 x 10(6)
cells/plate) were then incubated with [3H]d4T (0.65 microCi; 3 microM) and
either acyclovir, dapsone, ddC, ddI, fluconazole, foscarnet, ganciclovir,
itraconazole, lobucavir, ranitidine, ribavirin, rifampin, sorivudine,
sulfamethoxazole, trimethoprim, lamivudine (3TC), zidovudine, or thymidine
(30 and 300 microM) for 24 h. Doxorubicin and drugs showing some evidence
of inhibition were also studied at 0.3 and 3 microM. Cells were extracted
overnight with 60% methanol prior to analysis by radiometric high-
performance liquid chromatography. Additional data for nine of the drugs
were obtained by incubation with [3H]d4T in U937 cells for 24 h. The effect
of d4T (0.2 to 20 microM) on zidovudine (0.65 microCi; 0.018 microCi)
phosphorylation was also studied. Zidovudine significantly reduced d4T
total phosphates in PBMCs and U937 cells (in PBMCs to 33% [P < 0.001]
and 17% [P < 0.001] of that in control cells at 3 and 30 microM,
respectively). A small reduction in zidovudine phosphorylation was seen
with d4T but only at d4T:zidovudine ratios of 100 and 1,000. Of the other
compounds screened, only thymidine, ribavirin, and doxorubicin produced
inhibition of d4T phosphorylation in both PBMCs and U937 cells. However,
doxorubicin was cytotoxic at 3 microM. The decrease in d4T phosphorylation
in the presence of ribavirin is consistent with previous findings with
zidovudine. Although ddC significantly inhibited the phosphorylation of d4T
in PBMCs, this was not seen in U937 cells, and it is probable that the
findings in PBMCs are related to mitochondrial toxicity [based on
3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyl tetrazolium bromide cytotoxicity
assay]. The only drugs screened which may interfere with d4T
phosphorylation at clinically relevant concentrations were zidovudine,
ribavirin, and doxorubicin.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Effects of drugs on 2',3'-dideoxy-2',3'-didehydrothymidine phosphorylation in vitro
Department of Pharmacology & Therapeutics, University of Liverpool, United Kingdom.
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