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Yungchi Cheng - One of the best experts on this subject based on the ideXlab platform.
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expression of deoxynucleotide carrier is not associated with the mitochondrial dna depletion caused by anti hiv Dideoxynucleoside analogs and mitochondrial dntp uptake
Molecular Pharmacology, 2005Co-Authors: Wing Lam, Chingshin Chen, Shoulun Ruan, Chunghang Leung, Yungchi ChengAbstract:Our previous studies suggested that the dNTP/dNDP transporter systems that exist in mitochondria for transporting dNTP/dNDP from the cytoplasm to the mitochondria for mitochondrial DNA (mtDNA) synthesis play a critical role in delayed cytotoxicity of anti-human immunodeficiency virus (HIV) Dideoxynucleoside analogs in mitochondria. A protein, termed mitochondrial deoxynucleotide carrier (DNC), based on its ability to transport dNTPs in reconstituted proteoliposomes, was recently isolated. Lacking cellular information to substantiate DNC's involvement in the delayed cytotoxicity of Dideoxynucleoside analogs, we expressed DNC and reconstituted it into proteoliposomes. The K m values for dNTPs uptake by reconstituted DNC were in the millimolar range, which is a thousandfold higher than that of the physiological level. Furthermore, we found that overexpressing DNC (wt and G177A-mutated DNC) in RKO cells did not sensitize the cells to the mtDNA depletion caused by β-d-2′,3′-dideoxycytidine (ddC), 2′,3′-didehydro-2′,3′-dideoxythymidine, and 2′,3′-dideoxyinosine or affect the mtDNA recovery rate after ddC treatment. Mitochondria isolated from DNC-overexpressing cells did not significantly differ from that isolated from RKO cells in terms of the rate of uptake or the incorporation of dTTP into mitochondria DNA. Down-regulation of DNC expression by small interfering RNA was also ineffective in changing the action of Dideoxynucleoside analogs on the mtDNA depletion and the rate of dTTP uptake into isolated mitochondria. Down-regulation of both DNC and thymidine kinase-2 also did not cause mtDNA depletion. We conclude that DNC does not play an important role in the delayed cytotoxicity (mtDNA depletion) of anti-HIV Dideoxynucleoside analogs and dNTPs uptake into mitochondria.
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removal of anti human immunodeficiency virus 2 3 Dideoxynucleoside monophosphates from dna by a novel human cytosolic 3 5 exonuclease
Biochemical Pharmacology, 1995Co-Authors: Violetta Skalski, Shwuhuey Liu, Yungchi ChengAbstract:Abstract A 3′ → 5′ exonuclease has been highly purified from the cytosol of human acute lymphoblastic leukemia H9 cells. The apparent molecular weight of this enzyme was approximately 50,000, as indicated by its sedimentation in glycerol gradients. The exonuclease did not copurify with DNA polymerase activity, required MgCl 2 for its exonucleolytic activity, and was inhibited by KCl above 60 mM. The enzyme was active on single-stranded DNA, DNA duplexes and DNA/RNA duplexes, and it was efficient at removing 3′-terminal mispairs from DNA. The products of the exonucleolytic reaction were deoxynucleoside 5′-monophosphates. The behavior of the exonuclease was examined on DNA terminated at the 3′ end with a variety of Dideoxynucleosides that are potent against human immunodeficiency virus type 1. The exonuclease has a broad substrate specificity; however, the rate of the enzymatic reaction varied among the d Dideoxynucleosides tested (ddAMP = ddCMP > d4TMP > AZTMP). Similarly, the enzyme was examined for its reactivity with DNA terminated by either the d or l enantiomers of ddC, SddC or FddC. The removal of analogs with the native d configuration was ] at least 6-fold more rapid than that of the l -compounds, and the type of structural modification had an impact on the rate at which the d enantiomers were removed (SddCMP > ddCMP > FddCMP). The monophosphate forms of AZT, D4T, l -FddC and l -ddC were potent inhibitors of the exonuclease at micromolar concentrations, while d -ddCMP partially inhibited the enzyme at millimolar concentrations. Based on its physical and enzymatic properties, this exonuclease represents a novel enzyme that may have an important role in determining the relative potencies of Dideoxynucleosides against human immunodeficiency virus type 1.
Hiroaki Mitsuya - One of the best experts on this subject based on the ideXlab platform.
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altered drug sensitivity fitness and evolution of human immunodeficiency virus type 1 with pol gene mutations conferring multi Dideoxynucleoside resistance
The Journal of Infectious Diseases, 1998Co-Authors: Yosuke Maeda, David Venzon, Hiroaki MitsuyaAbstract:Investigations were done to determine whether the replication kinetics of human immunodeficiency virus (HIV)-1 were altered when the virus acquired a set or subsets of five mutations (A62V, V75I, F77L, F116Y, and Q151M) in the pol gene conferring resistance to multiple Dideoxynucleosides. In the absence of drugs, the replication rate of all infectious clones generated was comparable to that of wild type HIV-1. However, in the presence of zidovudine or didanosine, the comparative order for replication was HIV-1(62/75/77/116/151) > HIV-1(77/116/151) > HIV-1(75/77/116/151) approximately HIV-1(151), whereas that for drug resistance was HIV-1(75/77/116/151) > HIV-1(62/75/77/116/151) > or = HIV-1(77/116/151) > HIV-1(151). The virologic features of these infectious mutants suggest that HIV-1 develops drug resistance through one or more mutations, which, however, sacrifice replicative capability; then it finally acquires optimal replication competence by additional mutations when the multi-Dideoxynucleoside-resistant mutant emerges.
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disparate actions of hydroxyurea in potentiation of purine and pyrimidine 2 3 Dideoxynucleoside activities against replication of human immunodeficiency virus
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Wenyi Gao, David G Johns, S Chokekuchai, Hiroaki MitsuyaAbstract:Abstract We and other groups have recently reported the potentiation by ribonucleotide reductase inhibitors such as hydroxyurea of the anti-human immunodeficiency virus type 1 (HIV-1) activity of purine and pyrimidine 2',3'-Dideoxynucleosides in both resting and phytohemagglutinin-stimulated peripheral blood mononuclear cells. Little agreement prevails, however, as to the mechanism of the synergistic effects described. We report here that in phytohemagglutinin-stimulated peripheral blood mononuclear cells, two mechanisms exist for the potentiation of the anti-HIV-1 activity by low-dose hydroxyurea of the purine-based Dideoxynucleoside 2',3'-dideoxyinosine and the pyrimidine-based Dideoxynucleosides 3'-azido-3'-deoxythymidine and 2',3'-dideoxycytidine. For 2',3'-dideoxyinosine, the enhancement arises from a specific depletion of dATP by hydroxyurea, resulting in a favorable shift of the 2',3'-dideoxyadenosine 5'-triphosphate/dATP ratio. For the pyrimidine Dideoxynucleosides 3'-azido-3'-deoxythymidine and 2',3'-dideoxycytidine, the more modest anti-HIV enhancement results from hydroxyurea-induced increases of pyrimidine kinase activities in the salvage pathway and, hence, increased 5'-phosphorylation of these drugs, while depletion of the corresponding deoxynucleoside 5'-triphosphates (dTTP and dCTP) plays no significant role.
Wenyi Gao - One of the best experts on this subject based on the ideXlab platform.
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disparate actions of hydroxyurea in potentiation of purine and pyrimidine 2 3 Dideoxynucleoside activities against replication of human immunodeficiency virus
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Wenyi Gao, David G Johns, S Chokekuchai, Hiroaki MitsuyaAbstract:Abstract We and other groups have recently reported the potentiation by ribonucleotide reductase inhibitors such as hydroxyurea of the anti-human immunodeficiency virus type 1 (HIV-1) activity of purine and pyrimidine 2',3'-Dideoxynucleosides in both resting and phytohemagglutinin-stimulated peripheral blood mononuclear cells. Little agreement prevails, however, as to the mechanism of the synergistic effects described. We report here that in phytohemagglutinin-stimulated peripheral blood mononuclear cells, two mechanisms exist for the potentiation of the anti-HIV-1 activity by low-dose hydroxyurea of the purine-based Dideoxynucleoside 2',3'-dideoxyinosine and the pyrimidine-based Dideoxynucleosides 3'-azido-3'-deoxythymidine and 2',3'-dideoxycytidine. For 2',3'-dideoxyinosine, the enhancement arises from a specific depletion of dATP by hydroxyurea, resulting in a favorable shift of the 2',3'-dideoxyadenosine 5'-triphosphate/dATP ratio. For the pyrimidine Dideoxynucleosides 3'-azido-3'-deoxythymidine and 2',3'-dideoxycytidine, the more modest anti-HIV enhancement results from hydroxyurea-induced increases of pyrimidine kinase activities in the salvage pathway and, hence, increased 5'-phosphorylation of these drugs, while depletion of the corresponding deoxynucleoside 5'-triphosphates (dTTP and dCTP) plays no significant role.
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emergence of human immunodeficiency virus type 1 variants with resistance to multiple Dideoxynucleosides in patients receiving therapy with Dideoxynucleosides
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: T Shirasaka, Wenyi Gao, Mark F Kavlick, Takamasa Ueno, Eiji Kojima, M L Alcaide, Sudhichai Chokekijchai, B M Roy, Edward Arnold, Robert YarchoanAbstract:Abstract A set of mutations [Ala-62-->Val(A62V), V75I, F77L, F116Y, and Q151M] in the polymerase domain of reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) confers on the virus a reduced sensitivity to multiple antiretroviral Dideoxynucleosides and has been seen in HIV-1 variants isolated from patients receiving combination chemotherapy with 3'-azido-3'-deoxythymidine (AZT) plus 2',3'-dideoxycytidine (ddC) or 2',3'-dideoxyinosine (ddI). The IC50 values of AZT, ddC, ddI, 2',3'-dideoxyguanosine, and 2',3'-didehydro-3'-deoxythymidine against an infectious clone constructed to include the five mutations were significantly higher than those of a wild-type infectious clone. The K1 value for AZT 5'-triphosphate determined for the virus-associated RT from a posttherapy strain was 35-fold higher than that of RT from a pretherapy strain. Detailed analysis of HIV-1 strains isolated at various times during therapy showed that the Q151M mutation developed first in vivo, at the time when the viremia level suddenly increased, followed by the F116Y and F77L mutations. All five mutations ultimately developed, and the viremia level rose even further. Analyses based on the three-dimensional structure of HIV-1 RT suggest that the positions where at least several of the five mutations occur are located in close proximity to the proposed dNTP-binding site of RT and the first nucleotide position of the single-stranded template.
Erik De Clercq - One of the best experts on this subject based on the ideXlab platform.
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Potential drugs for the treatment of AIDS
2016Co-Authors: Erik De ClercqAbstract:From our investigations the following compounds have emerged as particularly potent and selective inhibitors of HIV replication: sulphated polysaccharides (i.e. heparin, dextran sulphate, pentosan polysulphate), Dideoxynucleoside analogues such as the 3'-azido- and 3'-fluoro-substituted 2',3'-dideoxyribosides of both purines (i.e. guanine, 2,6-diaminopurine) and pyrimidines (i.e. uracil, thymine), and the 9-{2-phosphonylmethoxyethyl) derivatives of adenine, 2-monoaminopurine and 2,6-diaminopurine. All these compounds yield great promise for the treatment of retro virus infections in humans. Whereas the sulphated polysaccharides interfere with the virus adsorption process, the nucleoside analogues (following intracellular phosphorylation to their 5'-triphosphate) appear to be targeted at the reverse transcriptase
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synthesis and antiviral evaluation of 3 hydroxy 2 methylpyridin 4 one Dideoxynucleoside derivatives
Bioorganic & Medicinal Chemistry Letters, 2003Co-Authors: Karine Barral, Jan Balzarini, Erik De Clercq, Robert C Hider, Johan Neyts, Michel CamploAbstract:Abstract We describe the synthesis and the antiviral evaluation of novel α and β Dideoxynucleoside derivatives in which the base has been replaced by a 3-hydroxy-2-methylpyridin-4-one. The syntheses were successfully achieved by the use of the standard Vorbruggen coupling conditions. Moderate activity of these compounds were found on herpes simplex virus (HSV) type 1 and type 2.
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total syntheses of novel Dideoxynucleoside analogues using chiral amino acids
Tetrahedron Letters, 2000Co-Authors: George Balayiannis, George Karigiannis, Panayiotis Gatos, Dionissios Papaioannou, Erik De ClercqAbstract:N-Tritylated l -a ndd-methionine and l-glutamic acid were used to obtain novel chiral iso-Dideoxynucleoside analogues incorporating a tetrahydrofuranyl or a tetrahyropyranyl ring as the pseudosugar part, and at positions 2 and 3 of the ring an hydroxyethyl group and thymine or adenine, respectively. # 2000 Elsevier Science Ltd. All rights reserved.
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Characterization of the activation pathway of phosphoramidate triester prodrugs of stavudine and zidovudine. Mol Pharmacol 56: 693–704
1999Co-Authors: Didier Saboulard, Erik De Clercq, Lieve Naesens, Dominique Cahard, Antonio Salgado, Ranjith Pathirana, Sonsoles Velazquez, Christopher Mcguigan, Jan BalzariniAbstract:The phosphoramidate triester prodrugs of anti-human HIV 29,39-Dideoxynucleoside analogs (ddN) represent a convenient approach to bypass the first phosphorylation to ddN 59-mono-phosphate (ddNMP), resulting in an improved formation of ddN 59-triphosphate and, hence, higher antiviral efficacy. Although phosphoramidate derivatization markedly increases the anti-HIV activity of 29,39-didehydro-29,39-dideoxythymidine (d4T) in both wild-type and thymidine kinase-deficient CEM cells, the concept is far less successful for the 39-azido-29,39-dideoxy-thymidine (AZT) triesters. We now investigated the metabolism of triester prodrugs of d4T and AZT using pure enzymes or different biological media. The efficiency of the first activation step, mediated by carboxylesterases, consists of the formation of the amino acyl ddNMP metabolite. The efficiency of this ste
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glycosyl oxycarbonylaminosulfonyl 2 3 Dideoxynucleoside derivatives as lipophilic nucleotide mimics synthesis and anti hiv activity
Bioorganic & Medicinal Chemistry, 1993Co-Authors: Mariajesus Perezperez, Jan Balzarini, Erik De Clercq, Mariajose CamarasaAbstract:Several lipophilic-2',3'-dideoxynucleotide analogues have been synthesized and tested against Human Immunodeficiency Virus (HIV). Glycosyl-oxycarbonylaminosulfonyl-analogues of 3'-deoxythymidine and 2',3'-dideoxyuridine have been synthesized by reaction of 2,3,4,6-tetra-O-benzoyl-alpha-D-glucopyranose with chlorosulfonyl isocyanate and the corresponding 2',3'-Dideoxynucleoside. Another series of 5'-phosphate-like-3'-deoxythymidine nucleosides (5'-O-alkyl-sulfamoyl- and 5'-O-carbamoyl-3'-deoxythymidine) have also been prepared. Both series of compounds can be considered as lipophilic nucleotide mimics.
Robert Yarchoan - One of the best experts on this subject based on the ideXlab platform.
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emergence of human immunodeficiency virus type 1 variants with resistance to multiple Dideoxynucleosides in patients receiving therapy with Dideoxynucleosides
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: T Shirasaka, Wenyi Gao, Mark F Kavlick, Takamasa Ueno, Eiji Kojima, M L Alcaide, Sudhichai Chokekijchai, B M Roy, Edward Arnold, Robert YarchoanAbstract:Abstract A set of mutations [Ala-62-->Val(A62V), V75I, F77L, F116Y, and Q151M] in the polymerase domain of reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) confers on the virus a reduced sensitivity to multiple antiretroviral Dideoxynucleosides and has been seen in HIV-1 variants isolated from patients receiving combination chemotherapy with 3'-azido-3'-deoxythymidine (AZT) plus 2',3'-dideoxycytidine (ddC) or 2',3'-dideoxyinosine (ddI). The IC50 values of AZT, ddC, ddI, 2',3'-dideoxyguanosine, and 2',3'-didehydro-3'-deoxythymidine against an infectious clone constructed to include the five mutations were significantly higher than those of a wild-type infectious clone. The K1 value for AZT 5'-triphosphate determined for the virus-associated RT from a posttherapy strain was 35-fold higher than that of RT from a pretherapy strain. Detailed analysis of HIV-1 strains isolated at various times during therapy showed that the Q151M mutation developed first in vivo, at the time when the viremia level suddenly increased, followed by the F116Y and F77L mutations. All five mutations ultimately developed, and the viremia level rose even further. Analyses based on the three-dimensional structure of HIV-1 RT suggest that the positions where at least several of the five mutations occur are located in close proximity to the proposed dNTP-binding site of RT and the first nucleotide position of the single-stranded template.