Long-Term Exposure to Zidovudine Affects<i>in Vitro</i>and<i>in Vivo</i>the Efficiency of Phosphorylation of Thymidine Kinase

Antonelli, Guido; Turriziani, Ombretta; Verri, Annalisa; Narciso, Pasquale; Ferri, Francesca; D’Offizi, Gianpiero; Dianzani, F.

doi:10.1089/aid.1996.12.223

Cited by 71 publications

(43 citation statements)

References 21 publications

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“…3) on the concentrations of metabolites and found no effect for 4Ј-Ed4T and 3TC; however, there was a trend for moderation of the concentration of AZT metabolites by gender (P ϭ 0.17 for gender ⅐ metabolite concentration). When the trajectories of the analog concentrations from monophosphate to triphosphate were analyzed by gender Decreased expression of phosphorylating enzymes has been implicated in the observed resistance to nucleoside analogs (5,25). Thus, we investigated whether the variation in intracellular metabolite concentrations is associated with the activity and/or expression of the cellular kinases involved in the phosphorylation of nucleoside analogs (i.e., 4Ј-Ed4T, AZT, and 3TC).…”

Section: Resultsmentioning

confidence: 99%

Determinants of Individual Variation in Intracellular Accumulation of Anti-HIV Nucleoside Analog Metabolites

Paintsil¹,

Dutschman²,

Hu³

et al. 2011

Antimicrob Agents Chemother

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Individual variation in response to antiretroviral therapy is well-known, but it is not clear if demographic characteristics such as gender, age, and ethnicity are responsible for the variation. To optimize anti-HIV therapy and guide antiretroviral drug discovery, determinants that cause variable responses to therapy need to be evaluated. We investigated the determinants of intracellular concentrations of nucleoside analogs using peripheral blood mononuclear cells from 40 healthy donors. We observed individual differences in the concentrations of the intracellular nucleoside analogs; the mean concentrations of the triphosphate metabolite of ethynylstavudine (4-Ed4T), zidovudine (AZT), and lamivudine (3TC) were 0.71 pmol/10 6 cells (minimum and maximum, 0.10 and 3.00 pmol/10 6 cells, respectively), 0.88 pmol/10 6 cells (minimum and maximum, 0.10 and 15.18 pmol/10 6 cells, respectively), and 1.70 pmol/10 6 cells (minimum and maximum, 0.20 and 7.73 pmol/10 6 cells, respectively). Gender and ethnicity had no effect on the concentration of 4-Ed4T and 3TC metabolites. There was a trend for moderation of the concentrations of AZT metabolites by gender (P ‫؍‬ 0.17 for gender ⅐ metabolite concentration). We observed variability in the activity and expression of cellular kinases. There was no statistically significant correlation between thymidine kinase 1 (TK-1) activity or expression and thymidine analog metabolite concentrations. The correlation between the activity of deoxycytidine kinase (dCK) and the 3TC monophosphate metabolite concentration showed a trend toward significance (P ‫؍‬ 0.1). We observed an inverse correlation between the multidrug-resistant protein 2 (MRP2) expression index and the concentrations of AZT monophosphate, AZT triphosphate, and total AZT metabolites. Our findings suggest that the observed variation in clinical response to nucleoside analogs may be due partly to the individual differences in the intracellular concentrations, which in turn may be affected by the cellular kinases involved in the phosphorylation pathway and ATP-binding cassette (ABC) transport proteins.Individual variation in response, such as viral suppression and adverse effects, to antiretroviral therapy is a well-described phenomenon (19, 49). Epidemiological and limited clinical studies suggest that demographic characteristics (e.g., gender, age, and ethnicity) and the HIV disease state of an individual may be partly responsible for the variation in efficacy and toxicity observed with treatment by nucleoside analog reverse transcriptase inhibitors (NRTIs). For example, published studies show that women experienced a 4-fold lower rate of disease progression than did men while they were on zidovudine (AZT) monotherapy; however, women experienced exaggerated toxicities during NRTI therapy compared to those of men (15-17, 20, 37). Gender and ethnicity have been suggested to be possible variables that explain the observed differences in treatment response to NRTIs (1,16,43).In a cohort of 4 HIV-1-infected women and 29 HIV-1-in...

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Section: Resultsmentioning

confidence: 99%

Determinants of Individual Variation in Intracellular Accumulation of Anti-HIV Nucleoside Analog Metabolites

Paintsil¹,

Dutschman²,

Hu³

et al. 2011

Antimicrob Agents Chemother

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“…It has been observed that decreased TK activity in lymphocytes from HIV-infected patients may be related to prolonged treatment with AZT (jacobsson et al, 1995;Antonelli et al, 1996). In resistant cell lines, prolonged incubation with AZT is also associated with decreased activity of AZT-activating kinases.…”

Section: Discussionmentioning

confidence: 99%

“…AZT was phosphorylated only in extracts from MOLT4/8 cells; no phosphorylation was observed in extracts from MOLT4/grAZT250 cells. AZTresistant CEM and jurkat cells showed a 100-to 1000-fold decrease in phosphorylation efficiency (Vrna/K rn) for thymidine; in both cell lines the K rn value for thymidine was significantly increased (Avramis et al, 1993;Antonelli et al, 1996). MOLT4/grAZT250 cells had an Tl-fold lower phosphorylation efficiency for thymidine than the parental cells.…”

Section: Discussionmentioning

confidence: 99%

“…In paediatric patients under AZT monotherapy, the production of AZT-TP was diminished by about 90% compared to early treatment levels (Avramis et al, 1993). Jacobsson et al (1995) and Antonelli et al (1996) reported significantly lower TK activity in extracts of peripheral blood mononuclear cells from persons treated with AZT than from those who had never been treated.…”

Section: Antiviral Agentsmentioning

confidence: 97%

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Human Immunodeficiency Virus Resistance to AZT in MOLT4/8 Cells is Associated with a Lack of AZT Phosphorylation and is Bypassed by AZT-Monophosphate SATE Prodrugs

Cinatl

Gröschel

Zehner

et al. 1997

Antivir Chem Chemother

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SummaryHuman T lymphoid MOlTAI8 cells were grown continuously for more than 2 years in a medium containing 3'-azido-2',3'-dideoxythymidine (zidovudine; AZT) at a concentration of 250 11M. These cells, designated MOLT-A/srAZT250, were used to test the cytotoxic and antiviral activity of AZT. Intracellular accumulation of AZT, expression of the multidrug resistance 1 (MDR-1) gene, thymidine kinase (TK) gene and activity of the TK enzyme in cellular extracts were measured. The results showed that both the cytotoxic and antiviral activity of AZT were significantly lower in MOlTAI8 rAZT25o than in MOLTAI8 cells; concentrations required to inhibit 50% production of the p2A human immunodeficiency virus type 1 (HIY-l) antigen of two laboratory strains were at least 1DO-fold higher in resistant cells. The MDR-l gene was not expressed in the resistant cells. TK mRNA expression was significantly lower in the resistant than in the sensitive cells. TK enzymatic activity for deoxythymidine phosphorylation was impaired in MOlTA/8 rAZT250 cells compared to the sensitive cells.AZT was phosphorylated only in the sensitive cells whereas no phosphorylation of AZT was found in the resistant cells. We tested whether several AZTmonophosphate triesters, which bypass cellular TK, could overcome resistance to the cytotoxic and antiviral activity of All The bis(t-butyISATE) phosphotriester derivative of AZT showed comparable cytotoxic and antiviral activity in sensitive and resistant cells. The results demonstrated that MOlTA/8 rAZT250 cells exert resistance to the anti-HIY activity of the drug mainly owing to the lack of AZT phosphorylation and that resistance may be bypassed by using AZT-monophosphate SATE prodrugs.

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“…Radioisotopic labeling of the substrate of the enzyme revealed that TK1 enzymatic activity is decreased as well (unpublished data). Patients exposed for long term also present a decrease on the TK 1 enzyme activity [22,23]. Additionally, lack of expression of the active form of the enzyme has been seen in human mammary epithelial cells that do not incorporate AZT into the DNA (Olivero et al, TAAP, in press).…”

Section: Azt Is a Transplacental Carcinogen In Micementioning

confidence: 99%

Relevance of experimental models for investigation of genotoxicity induced by antiretroviral therapy during human pregnancy

Olivero

2008

Mutation Research/Reviews in Mutation Research

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The current incidence of HIV-1/AIDS affects around 7,000 pregnant women in the United States. When given during pregnancy, the nucleoside analog AZT significantly reduces maternal-fetal transmission. It has been previously shown that AZT is incorporated into DNA, where it causes mutations in the HPRT and TK genes. It also changes cell cycle gene expression, and induces S-phase arrest, micronuclei, chromosomal aberrations, sister chromatid exchanges, telomeric attrition, and other genotoxic effects in cultured cells. A predicted consequence of these events is genomic instability that together, with clastogenicity may contribute to the carcinogenic potency of AZT. Various aspects of genotoxicity are explored in this contribution seeking to understand the multiple effects of this antiretroviral agent in animal models and humans. This mini-review describes some of the experimental models used to elucidate the genotoxicity induced by antiretroviral therapy during human pregnancy. The use of diverse methods to detect biomarkers of exposure, such as an AZTspecific radioimmunoassay, micronuclei bearing intact chromosomes, and telomeric DNA attrition highlight the role of in-vitro models to elucidate exposure and risk. The relevance of the in vitro models is followed by the introduction of the role of the nucleoside analogs in transplacental carcinogenesis along with the description of a transplacental perfusion model and a transplacental carcinogenesis rodent model. In a more direct clinical application the use of AZT-DNA incorporation as a biomarker of exposure, in experiments conducted in vivo in Erythrocebus patas monkeys and in humans, addresses the possibility of elucidation of potential cancer risk in those infants exposed in utero.Two relevant aspects of this contribution are the potential application of some of the models described in this mini-review, as diagnostic tools in antiretroviral-exposed populations, and the use of these models to understand the nature of the genotoxicities and minimize the undesirable side effects of the antiretroviral therapy.

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Long-Term Exposure to Zidovudine Affectsin Vitroandin Vivothe Efficiency of Phosphorylation of Thymidine Kinase

Cited by 71 publications

References 21 publications

Determinants of Individual Variation in Intracellular Accumulation of Anti-HIV Nucleoside Analog Metabolites

Determinants of Individual Variation in Intracellular Accumulation of Anti-HIV Nucleoside Analog Metabolites

Human Immunodeficiency Virus Resistance to AZT in MOLT4/8 Cells is Associated with a Lack of AZT Phosphorylation and is Bypassed by AZT-Monophosphate SATE Prodrugs

Relevance of experimental models for investigation of genotoxicity induced by antiretroviral therapy during human pregnancy

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