Modulation of the cytotoxicity of 3'-azido-3'-deoxythymidine and methotrexate after transduction of folate receptor cDNA into human cervical carcinoma: identification of a correlation between folate receptor expression and thymidine kinase activity.
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Cervical carcinoma is an AIDS-defining illness. The expression of folate receptors (FRs) in cervical carcinoma (HeLa-IU1) cells was modulated by stable transduction of FR cDNA encapsidated in recombinant adeno-associated virus-2 in the sense and antisense orientation (sense and antisense cells, respectively). Although sense cells proliferated slower than antisense or untransduced cells in vivo and in vitro in 2% (but not 10%) FCS, [methyl-3H]thymidine incorporation into DNA was significantly increased in sense cells in 10% serum; therefore, the basis for this discrepancy was investigated. The activity of thymidine kinase (TK) was subsequently directly correlated with the extent of FR expression in single cell-derived clones of transduced cells. This elevated TK activity was not a result of recruitment of the salvage pathway based on the presence of adequate dTTP pools, normal thymidylate synthase (TS) activity, persistence of increased thymidine incorporation despite the exogenous provision of excess 5,10-methylene-tetrahydrofolate, and documentation of adequate folates in sense cells. The increase in TK activity conferred significant biological properties to sense cells (but not antisense or untransduced cells) as demonstrated by augmented phosphorylation of 3'-azido-3'-deoxythymidine (AZT) and concomitantly greater sensitivity to the cytotoxic effects of AZT. Conversely, sense cells were highly resistant to methotrexate, but this was reversed by the addition of AZT. The direct correlation of FR expression and TK activity indicates a previously unrecognized consequence of FR overexpression. (+info)
Inhibition of human immunodeficiency virus type 1 replication by combination of transcription inhibitor K-12 and other antiretroviral agents in acutely and chronically infected cells.
(3/1569)
8-Difluoromethoxy-1-ethyl-6-fluoro-1,4-dihydro-7-[4-(2-methoxyp hen yl)-1- piperazinyl]-4-oxoquinoline-3-carboxylic acid (K-12) has recently been identified as a potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) transcription. In this study, we examined several combinations of K-12 and other antiretroviral agents for their inhibitory effects on HIV-1 replication in acutely and chronically infected cell cultures. Combinations of K-12 and a reverse transcriptase (RT) inhibitor, either zidovudine, lamivudine, or nevirapine, synergistically inhibited HIV-1 replication in acutely infected MT-4 cells. The combination of K-12 and the protease inhibitor nelfinavir (NFV) also synergistically inhibited HIV-1, whereas the synergism of this combination was weaker than that of the combinations with the RT inhibitors. K-12 did not enhance the cytotoxicities of RT and protease inhibitors. Synergism of the combinations was also observed in acutely infected peripheral blood mononuclear cells. The combination of K-12 and cepharanthine, a nuclear factor kappa B inhibitor, synergistically inhibited HIV-1 production in tumor necrosis factor alpha-stimulated U1 cells, a promonocytic cell line chronically infected with the virus. In contrast, additive inhibition was observed for the combination of K-12 and NFV. These results indicate that the combinations of K-12 and clinically available antiretroviral agents may have potential as chemotherapeutic modalities for the treatment of HIV-1 infection. (+info)
Inhibition of nucleoside diphosphate kinase in rat liver mitochondria by added 3'-azido-3'-deoxythymidine.
(4/1569)
The effect of 3'-azido-3'-deoxythymidine on nucleoside diphosphate kinase of isolated rat liver mitochondria has been studied. This is done by monitoring the increase in the rate of oxygen uptake by nucleoside diphosphate (TDP, UDP, CDP or GDP) addition to mitochondria in state 4. It is shown that 3'-azido-3'-deoxythymidine inhibits the mitochondrial nucleoside diphosphate kinase in a competitive manner, with a Ki value of about 10 microM as measured for each tested nucleoside diphosphate. It is also shown that high concentrations of GDP prevent 3'-azido-3'-deoxythymidine inhibition of the nucleoside diphosphate kinase. (+info)
Suppression of replication of multidrug-resistant HIV type 1 variants by combinations of thymidylate synthase inhibitors with zidovudine or stavudine.
(5/1569)
The replication of recombinant multidrug-resistant HIV-1 clones modeled on clinically derived resistant HIV-1 strains from patients receiving long-term combination therapy with zidovudine (AZT) plus 2',3'-dideoxycytidine was found to regain sensitivity to AZT and stavudine (D4T) as a consequence of a pharmacologically induced decrease in de novo dTMP synthesis. The host-cell system used was phytohemagglutinin-stimulated peripheral blood mononuclear cells; dTMP and dTTP depletion were induced by single exposures to a low level of the thymidylate synthase inhibitor 5-fluorouracil (5-FU) or its deoxynucleoside, 2'-deoxy-5-fluorouridine. The host-cell response to the latter was biphasic: a very rapid decrease in the rate of de novo dTMP formation and, consequently, in intracellular dTTP pools, followed by slower recovery in both indices over 3 to 24 h. With the additional presence of AZT or D4T, however, replication of the multidrug-resistant HIV-1 strains remained inhibited, indicating dependence of HIV DNA chain termination by AZT-5'-monophosphate or 2',3'-didehydro-2', 3'-dideoxythymidine-5'-monophosphate in these resistant strains on simultaneous inhibition of host-cell de novo synthesis of thymidine nucleotides. No effect on viability of control (uninfected) phytohemagglutinin-stimulated/peripheral blood mononuclear cells was noted on 6-day exposures to 5-FU or 2'-deoxy-5-fluorouridine alone or in combination with AZT or D4T, even at drug levels severalfold higher than those used in the viral inhibition studies. These studies may provide useful information for the potential clinical use of AZT/5-FU or D4T/5-FU combinations for the prevention or reversal of multidrug resistance associated with long-term dideoxynucleoside combination therapy. (+info)
Treatment with amprenavir alone or amprenavir with zidovudine and lamivudine in adults with human immunodeficiency virus infection. AIDS Clinical Trials Group 347 Study Team.
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Amprenavir is a human immunodeficiency virus (HIV) protease inhibitor with a favorable pharmacokinetic profile and good in vitro activity. Ninety-two lamivudine- and protease inhibitor-naive individuals with >/=50 CD4 cells/mm3 and >/=5000 HIV RNA copies/mL were assigned amprenavir (1200 mg) alone or with zidovudine (300 mg) plus lamivudine (150 mg), all given every 12 h. After a median follow-up of 88 days, the findings of a planned interim review resulted in termination of the amprenavir monotherapy arm. Among 85 subjects with confirmed plasma HIV RNA determination, 15 of 42 monotherapy versus 1 of 43 triple-therapy subjects had an HIV RNA increase above baseline or 1 log10 above nadir (P=.0001). For subjects taking triple therapy at 24 weeks, the median decrease in HIV RNA was 2.04 log10 copies/mL, and 17 (63%) of 27 evaluable subjects had <500 HIV RNA copies/mL. Treatment with amprenavir, zidovudine, and lamivudine together reduced the levels of HIV RNA significantly more than did amprenavir monotherapy. (+info)
2-mercapto N-(azolyl)benzenesulfonamides. VI. Synthesis and anti-HIV activity of some new 2-mercapto-N-(1,2,4-triazol-3-yl)benzenesulfonamide derivatives containing the 1,2,4-triazole moiety fused with a variety of heteroaromatic rings.
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A series of 2-mercapto-N-(1,2,4-triazol-3-yl)benzenesulfonamide derivatives containing the triazole moiety fused with a variety of heteroaromatic rings [XVI-XXVIII] was obtained by the reactions of 3-methylthio-1,4-2-benzodithiazine 1,1-dioxide derivatives [Ia-d] with 2-hydrazines [IIa-f]. Some of the intermediate 1,1-dioxide-1,4,2-benzodithiazin-3-ylhydrazines [III-XV] initially formed were also isolated. Preliminary screening data indicated that compounds [XVI-XIX and XXVII] were anti-HIV inactive, whereas other compounds showed a high [XXI and XXIII], fairly high [XXIII and XXVI] or moderate [XX, XXIV, XXV and XXVIII] activity. The compound [XXI] exhibited also high activity against ten selected HIV mutants. (+info)
Effects of human immunodeficiency virus type 1 resistance to protease inhibitors on reverse transcriptase processing, activity, and drug sensitivity.
(8/1569)
Human immunodeficiency virus type 1 (HIV-1) variants resistant to protease inhibitors often display a reduced replicative capacity as a result of an impairment of protease function. Such fitness-impaired viruses display Gag precursor maturation defects. Here, we report that some protease inhibitor-resistant viruses also display abnormalities in the processing of reverse transcriptase (RT) by the protease. In three recombinant viruses carrying resistant protease sequences from patient plasma, we observed a marked decrease in the amount of mature RT subunits and of particle-associated RT activity compared to their parental pretherapy counterparts. We investigated the possibility that a decrease in the amount of particle-associated mature RT could affect the sensitivity of the corresponding virus to RT inhibitors. We observed a twofold increase of sensitivity to zidovudine (AZT) when a virus which carried AZT mutations was processed by a resistant protease. Interestingly, the presence of AZT-resistance mutations partially rescued the replication defect associated with the mutated protease. The interplay between resistance to protease inhibitors and to RT inhibitors described here may be relevant to the therapeutic control of HIV-1 infection. (+info)