Effects of antiviral nucleoside analogs on human DNA polymerases and mitochondrial DNA synthesis

Martín, José Manuel García; Brown, Claire; Matthews-Davis, N; Reardon, John E.

doi:10.1128/aac.38.12.2743

Cited by 321 publications

(251 citation statements)

References 56 publications

Supporting

Mentioning

238

Contrasting

Unclassified

Order By: Relevance

“…Nonetheless, the cytosolic thymidylate kinase is known to be a highly rate-limiting step in the AZT phosphorylation pathway [20]. This raises the probability that AZTTP is unlikely to ever reach the concentration (>100 μM [17]) required to inhibit the mitochondrial DNA polymerase γ. Alternatively, AZT potently inhibits the phosphorylation of thymidine in both heart and liver mitochondria. The IC 50 for liver mitochondria (14.4 ± 2.6 μM AZT) is higher but still comparable to the IC 50 observed for heart mitochondria (7.0 ± 1.0 μM AZT) [23].…”

Section: Discussionmentioning

confidence: 99%

“…These toxicities are believed to be mediated through mitochondrial damage and are associated with mitochondrial DNA depletion [15][16][17]. The current prevailing hypothesis for this damage is by 3′-azido-3′-deoxythymidine-5′-triphosphate (AZTTP) inhibition of the mitochondrial DNA polymerase γ [18].…”

Section: Introductionmentioning

confidence: 99%

“…The current prevailing hypothesis for this damage is by 3′-azido-3′-deoxythymidine-5′-triphosphate (AZTTP) inhibition of the mitochondrial DNA polymerase γ [18]. However, several groups have demonstrated that relative to other nucleoside analog triphosphates, AZTTP is not a very good inhibitor of polymerase γ (50% inhibitory concentration (IC 50 ) of 100-200 μM AZTTP) [16,17,19]. Further, because 3′-azido-3′-deoxythymidine-5′-monophosphate (AZTMP) is a poor substrate for the cytosolic thymidylate kinase [20,21], levels of AZTTP high enough to inhibit polymerase γ have not been reported even in mitotic tissue [20,22].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

3′-Azido-3′-deoxythymidine (AZT) inhibits thymidine phosphorylation in isolated rat liver mitochondria: A possible mechanism of AZT hepatotoxicity

Lynx

Bentley

McKee

2006

Biochemical Pharmacology

View full text Add to dashboard Cite

Abstract3′-Azido-3′-deoxythymidine (AZT) is a staple of highly active antiretroviral therapy (HAART). Prior to HAART, long-term use of high-dosage AZT caused myopathy, cardiomyopathy, and hepatotoxicity, associated with mitochondrial DNA depletion. As a component of HARRT, AZT causes cytopenias and lipodystrophy. AZT-5′-triphosphate (AZTTP) is a known inhibitor of the mitochondrial polymerase γ and has been targeted as the source of the mitochondrial DNA depletion. However, in previous work from this laboratory with isolated rat heart mitochondria, AZT phosphorylation beyond AZT-5′-monophosphate (AZTMP) was not detected. Rather, AZT was shown to be a more potent inhibitor of thymidine phosphorylation (50% inhibitory concentration (IC 50 ) of 7.0 ± 1.0 μM) than AZTTP is of polymerase γ (IC 50 of >100 μM), suggesting that depletion of mitochondrial stores of TTP may limit replication. This work has investigated whether an identical mechanism might account for the hepatotoxicity seen with long-term use of AZT. Isolated rat liver mitochondria were incubated with labeled thymidine or AZT, and the rate and extent of phosphorylation were determined by HPLC analysis of acid-soluble extracts of the incubated mitochondria. The results showed that in the phosphorylation of thymidine to TMP, liver mitochondria exhibit a higher V max and K m than heart mitochondria, but otherwise heart and liver mitochondria display similar kinetics. AZT is phosphorylated to AZTMP, but no further phosphorylated forms were detected. In addition, AZT inhibited the production of TTP, with an IC 50 of 14.4 ± 2.6 μM AZT. This is higher, but comparable to, the results seen in isolated rat heart mitochondria. KeywordsAZT; Liver mitochondria; Thymidine; Mitochondrial toxicity; Thymidine kinase 2; Reverse transcriptase inhibitors Abbreviations AIDS, acquired immunodeficiency syndrome; AZT, 3′-azido-3′-deoxythymidine; AZTDP, 3′-azido-3′-deoxythymidine-5′-diphosphate; AZTMP, 3′-azido-3′-deoxythymidine-5′-monophosphate; AZTTP, 3′-azido-3′-deoxythymidine-5′-triphosphate; HAART, highly active antiretroviral therapy; HIV, human immunodeficiency virus; IC 50 , 50% inhibitory concentration; S.E.M., standard error of mean

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

3′-Azido-3′-deoxythymidine (AZT) inhibits thymidine phosphorylation in isolated rat liver mitochondria: A possible mechanism of AZT hepatotoxicity

Lynx

Bentley

McKee

2006

Biochemical Pharmacology

View full text Add to dashboard Cite

show abstract

“…The pathogenesis of lipoatrophy is not fully understood but several lines of evidence point toward an important role of nucleoside reverse transcriptase inhibitors (NRTIs) in general, and the mitochondrial toxicity of stavudine in particular (Mallal et al, 2000;Joly et al, 2002). In vitro data suggest that clinically relevant concentrations of some NRTIs impair DNA polymerase-gamma and therefore interfere with the replication of mitochondrial DNA (mtDNA) (Martin et al, 1994). Consistent with such mitochondrial toxicity, reduced copy numbers of mtDNA (mtDNA-depletion) were found in HIV-infected individuals treated with NRTIs (mostly stavudine) and linked with increased adipocyte apoptosis and ultrastructural abnormalities of adipocyte mitochondria (Walker et al, 2002;Nolan et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Uridine supplementation in HIV lipoatrophy: pilot trial on safety and effect on mitochondrial indices

et al. 2007

View full text Add to dashboard Cite

Objectives-Uridine abrogates mitochondrial toxicities of nucleoside reverse transcriptase inhibitor in adipocyte cell culture. We aim to study the effect of uridine supplementation on human adipocyte mitochondrial DNA (mtDNA) levels in subjects with human immunodeficiency (HIV) lipoatrophy.Methods-Sixteen patients with lipoatrophy on stavudine-containing antiretroviral therapy were enrolled, and received NucleomaxX, a dietary supplement with a high bioavailability of uridine (36 g TID every other day for 16 weeks). Patients were then followed off-uridine for another 16 weeks. Highly active antiretroviral therapy remained unchanged during the trial.Results-Fourteen patients completed the study. Two subjects dropped out before week 4 for study-unrelated reasons. No adverse events were noted throughout the study. HIV-1 RNA, CD4 counts, liver enzymes and hemoglobin remained unchanged. Body mass index, lactate, lipids, insulin and homeostasis model assessment of insulin resistance were unaltered. Fat and peripheral blood and mononuclear cell mtDNA levels did not correlate with each other and exhibited no changes throughout the study. Lipoatrophy scores by patients and physician improved significantly at weeks 16 and 32 compared to study entry.Conclusion-In this pilot study, NucleomaxX was safe, well tolerated without apparent deleterious effect on HIV indices. In contrast to in vitro data, NucleomaxX did not lead to changes in fat or blood mtDNA levels.

show abstract

“…The current prevailing hypothesis for the mechanism of this toxicity states that mitochondrial damage is mediated through AZTTP inhibition of the mitochondrial DNA polymerase γ (IC 50 of >100 μM AZTTP) [4]. However, other research has shown that AZT is slowly phosphorylated, if at all, beyond AZTMP in many tissues [2,3,5].…”

Section: Introductionmentioning

confidence: 99%

Effect of AZT on thymidine phosphorylation in cultured H9c2, U-937, and Raji cell lines

Lynx¹,

Kang²,

McKee³

2008

Biochemical Pharmacology

View full text Add to dashboard Cite

Abstract3′-azido-3′-deoxythymidine (AZT) has been shown to be a potent inhibitor of thymidine kinase 2 in work from this laboratory. Inhibition results in decreased salvage of thymidine to TTP, which may lead to depletion of the TTP pool and result in the mitochondrial dysfunction and mt-DNA depletion observed with AZT toxicity. The effect of AZT on thymidine phosphorylation in growing cells expressing thymidine kinase 1 has not been shown. Three cell lines were used in these experiments: H9c2, derived from rat cardiomyoblasts; U-937, derived from human monocytes; and Raji, derived from human lymphoblasts. AZT inhibited growth in a concentration dependent manner in U-937 cells, but not the other cell lines. The phosphorylation of [3H]-thymidine or [3H]-AZT was determined during log growth. All cell lines salvaged and phosphorylated thymidine to TTP, with TTP the major product. The U-937 cells had a much more active salvage pathway than the other cells. All cell lines phosphorylated AZT to the triphosphate, but the major product was AZTMP. The AZT inhibition of growth of the U-937 cells did not correlate with levels of phosphorylated AZT. In contrast, pro-drug AZT was shown to inhibit thymidine phosphorylation in all lines with 50% inhibition concentrations (IC50) ranging from 4.4-21.9 μM. Since the U-937 cells expressed higher activity of the salvage pathway than the other cell lines, the U-937 cells may rely more heavily on the salvage pathway for TTP synthesis, accounting for AZT inhibition of growth.

show abstract

Effects of antiviral nucleoside analogs on human DNA polymerases and mitochondrial DNA synthesis

Cited by 321 publications

References 56 publications

3′-Azido-3′-deoxythymidine (AZT) inhibits thymidine phosphorylation in isolated rat liver mitochondria: A possible mechanism of AZT hepatotoxicity

3′-Azido-3′-deoxythymidine (AZT) inhibits thymidine phosphorylation in isolated rat liver mitochondria: A possible mechanism of AZT hepatotoxicity

Uridine supplementation in HIV lipoatrophy: pilot trial on safety and effect on mitochondrial indices

Effect of AZT on thymidine phosphorylation in cultured H9c2, U-937, and Raji cell lines

Contact Info

Product

Resources

About