Mitochondrial Myopathy Caused by Long-Term Zidovudine Therapy

Dalakas, Marinos C.; Illa, Isabel; Pezeshkpour, G.; Laukaitis, Joseph P.; Cohen, Bruce H.; Griffin, Jasper

doi:10.1056/nejm199004193221602

Cited by 806 publications

(349 citation statements)

References 28 publications

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“…During the pre-highly active antiretroviral therapy (HAART) era, AZT monotherapy in AIDS patients was closely associated with myopathy, cardiomyopathy, and hepatotoxicity [1][2][3][4][5][6][7][8][9][10]. Subsequent work in HIV negative rat models treated with AZT confirmed the presence of the same type of toxicities in the rat [11,15].…”

Section: Discussionmentioning

confidence: 99%

“…When given in monotherapy at high doses over long periods of time, AZT is known to cause damage to many tissues, including a mitochondrial skeletal muscle myopathy, a dilated cardiomyopathy, and hepatotoxicity [1][2][3][4][5][6][7][8][9][10][11]. These conditions are related to AZT use and not to the progression of AIDS since when patients experiencing one or more of these adverse effects discontinued AZT therapy, the adverse effects would resolve [8,9]. In modern therapy regimens, AZT is given at much lower doses and in combination with other drugs.…”

Section: Introductionmentioning

confidence: 99%

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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

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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

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

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“…Symptoms of myopathy include proximal muscle tenderness and myalgias. Most patients will have an accompanying elevated serum creatine phosphokinase (CPK) [39][40][41]. Histologically, the myopathy is characterized as inflammatory, with raggedred fibers present on trichrome stain [41].…”

Section: Myopathymentioning

confidence: 99%

A Review of the Toxicity of HIV Medications

et al. 2013

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Antiretroviral therapy has changed human immunodeficiency virus (HIV) infection from a near-certainly fatal illness to one that can be managed chronically. More patients are taking antiretroviral drugs (ARVs) for longer periods of time, which naturally results in more observed toxicity. Overdose with ARVs is not commonly reported. The most serious overdose outcomes have been reported in neonates who were inadvertently administered supratherapeutic doses of HIV prophylaxis medications. Typical ARV regimens include a "backbone" of two nucleoside reverse transcriptase inhibitors (NRTI) and a "base" of either a protease inhibitor (PI) or nonnucleoside reverse transcriptase inhibitor. New classes of drugs called entry inhibitors and integrase inhibitors have also emerged. Older NRTIs were associated with mitochondrial toxicity, but this is less common in the newer drugs, emtricitabine, lamivudine, and tenofovir. Mitochondrial toxicity results from NRTI inhibition of a mitochondrial DNA polymerase. Mitochondrial toxicity manifests as myopathy, neuropathy, hepatic failure, and lactic acidosis. Routine lactate assessment in asymptomatic patients is not indicated. Lactate concentration should be obtained in patients taking NRTIs who have fatigue, nausea, vomiting, or vague abdominal pain. Mitochondrial toxicity can be fatal and is treated by supportive care and discontinuing NRTIs. Metabolic cofactors like thiamine, carnitine, and riboflavin may be helpful in managing mitochondrial toxicity. Lipodystrophy describes changes in fat distribution and lipid metabolism that have been attributed to both PIs and NRTIs. Lipodystrophy consists of loss of fat around the face (lipoatrophy), increase in truncal fat, and hypertriglyceridemia. There is no specific treatment of lipodystrophy. Clinicians should be able to recognize effects of chronic toxicity of ARVs, especially mitochondrial toxicity.

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“…Each electron photomicrograph was reviewed independently by two investigators for the presence of structurally abnormal mitochondria, for the presence of intramitochondrial lamellar bodies, and for intramitochondrial paracrystals as reported in human AZT-induced skeletal muscle mitochondrial myopathy. 10 Structurally abnormal mitochondria were operationally defined as having loss or dissolution of Z25% of cristae. The number of damaged mitochondria per photomicrograph was quantified and the fraction of mitochondria damaged was defined and analyzed by ANOVA.…”

Section: Pathological Evaluations With Transmission Electron Microscomentioning

confidence: 99%

Transgenic expression of the deoxynucleotide carrier causes mitochondrial damage that is enhanced by NRTIs for AIDS

Lewis

Haase

Miller

et al. 2005

Laboratory Investigation

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Nucleoside reverse transcriptase inhibitors (NRTIs) are antiretrovirals for AIDS with limiting mitochondrial side effects. The mitochondrial deoxynucleotide carrier (DNC) transports phosphorylated nucleosides for mitochondrial DNA replication and can transport phosphorylated NRTIs into mitochondria. Transgenic mice (TG) that exclusively overexpress DNC in the heart tested DNC's role in mitochondrial dysfunction from NRTIs. Two TG lines were created that overexpressed the human DNC gene in murine myocardium. Cardiac and mitochondrial structure and function were examined by magnetic resonance imaging, echocardiography, electrocardiography, transmission electron microscopy, and plasma lactate. Antiretroviral combinations (HAART) that contained NRTIs (stavudine (2 0 , 3 0 -didehydro-2 0 , 3 0 -deoxythymidine or d4T)/lamivudine/indinavir; or zidovudine (3 0 azido-3 0 -deoxythymidine or AZT)/lamivudine/indinavir; 35 days) were administered to simulate AIDS therapy. In parallel, a HAART combination without NRTIs (nevirapine/efavirenz/indinavir; 35 days) served as an NRTI-sparing, control regimen. Untreated DNC TGs exhibited normal cardiac function but abnormal mitochondrial ultrastructure. HAART that contained NRTIs caused cardiomyopathy in TGs with increased left ventricle mass and volume, heart rate variability, and worse mitochondrial ultrastructural defects. In contrast, treatment with an NRTI-sparing HAART regimen caused no cardiac changes. Data suggest the DNC is integral to mitochondrial homeostasis in vivo and may relate mechanistically to mitochondrial dysfunction in patients treated with HAART regimens that contain NRTIs. Keywords: deoxynucleotide; NRTI; AIDS; antiretroviral; mitochondrial import; DNC; cardiac; HIV The inner mitochondrial membrane contains transport proteins to move molecules into and out of the matrix. Members of the mitochondrial carrier family of proteins contain three conserved tandemrepeated sequences (B100 residues with two hydrophobic transmembrane a-helices and a hydrophilic segment thought to be an extramembranous loop 1 ). One of these proteins functions as a deoxynucleotide carrier (DNC) to import phosphorylated precursors of mitochondrial (mt-) DNA synthesis and has been characterized. 1-3 Toxicity to mitochondria from antiretroviral nucleoside reverse transcriptase inhibitors (NRTI) is an established side effect of AIDS therapy that limits effective treatment (reviewed in Lewis et al 4 ). Alternative combinations that are NRTI-sparing may be effective if toxicity is a significant clinical problem (reviewed in Joly et al 5 ).Since DNC provides a route for mitochondrial uptake of NRTIs including zidovudine (3 0 azido-3 0 -deoxythymidine or AZT) and stavudine (2 0 , 3 0 -didehydro-2 0 , 3 0 -deoxythymidine or d4T), its role in mitochondrial NRTI import and toxicity was addressed in vivo using transgenic mice (TG) and HAART treatment. One HAART regimen included NRTIs (with either an AZT or D4T 'backbone'). A second NRTI-sparing regimen was administered in parallel as a control.DNC ov...

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Mitochondrial Myopathy Caused by Long-Term Zidovudine Therapy

Cited by 806 publications

References 28 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

A Review of the Toxicity of HIV Medications

Transgenic expression of the deoxynucleotide carrier causes mitochondrial damage that is enhanced by NRTIs for AIDS

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