Cardiac Mitochondrial Compromise in 1-Yr-Old Erythrocebus patas Monkeys Perinatally- Exposed to Nucleoside Reverse Transcriptase Inhibitors

Fetal Metabolic Stress Disrupts Immune Homeostasis and Induces Proinflammatory Responses in Human Immunodeficiency Virus Type 1- and Combination Antiretroviral Therapy-Exposed Infants

Increased morbidity and fetal growth restriction are reported in uninfected children born to human immunodeficiency virus type 1 (HIV-1)-infected women treated with antiretroviral (ARV) therapy. Viruses and/or pharmacological interventions such as ARVs can induce metabolic stress, skewing the cell's immune response and restricting (cell) growth. Novel metabolomic techniques provided the opportunity to investigate the impact of fetal HIV-1 and combination ARV therapy (cART) exposure on the infants' immune metabolome. Peroxidized lipids, generated by reactive oxygen species, were increased in cART/HIV-1-exposed infants, indicating altered mitochondrial functioning. The lipid metabolism was further dysregulated with increased triglyceride species and a subsequent decrease in phospholipids in cART/HIV-1-exposed infants compared to control infants. Proinflammatory immune mediators, lysophospholipids as well as cytokines such as CXCL10 and CCL3, were increased whereas anti-inflammatory metabolites from the cytochrome P450 pathway were reduced in cART/HIV-1-exposed infants. Taken together, these data demonstrate that the fetal metabolism is impacted by maternal factors (cART and HIV-1) and skews physiological immune responses toward inflammation in the newborn infant.

Mitochondrial toxicity and caspase activation in HIV pregnant women

To assess the impact of HIV-infection and highly active anti-retroviral treatment in mitochondria and apoptotic activation of caspases during pregnancy and their association with adverse perinatal outcome. Changes of mitochondrial parameters and apoptotic caspase activation in maternal peripheral blood mononuclear cells were compared at first trimester of pregnancy and delivery in 27 HIV-infected and -treated pregnant women versus 24 uninfected pregnant controls. We correlated immunovirological, therapeutic and perinatal outcome with experimental findings: mitochondrial DNA (mtDNA) content, mitochondrial protein synthesis, mitochondrial function and apoptotic caspase activation. The HIV pregnancies showed increased adverse perinatal outcome (OR: 4.81 [1.14-20.16]; P < 0.05) and decreased mtDNA content (42.66 ± 5.94%, P < 0.01) compared to controls, even higher in naïve participants. This depletion caused a correlated decrease in mitochondrial protein synthesis (12.82 ± 5.73%, P < 0.01) and function (20.50 ± 10.14%, P < 0.001), not observed in controls. Along pregnancy, apoptotic caspase-3 activation increased 63.64 ± 45.45% in controls (P < 0.001) and 100.00 ± 47.37% in HIV-pregnancies (P < 0.001), in correlation with longer exposure to nucleoside analogues. HIV-infected women showed increased obstetric problems and declined genetic and functional mitochondrial parameters during pregnancy, especially those firstly exposed to anti-retrovirals. The apoptotic activation of caspases along pregnancy is emphasized in HIV pregnancies promoted by nucleoside analogues. However, we could not demonstrate direct mitochondrial or apoptotic implication in adverse obstetric outcome probably because of the reduced sample size.

Effects of reduced mitochondrial DNA content on secondary mitochondrial toxicant exposure in Caenorhabditis elegans

The mitochondrial genome (mtDNA) is intimately linked to cellular and organismal health, as demonstrated by the fact that mutations in and depletion of mtDNA result in severe mitochondrial disease in humans. However, cells contain hundreds to thousands of copies of mtDNA, which provides genetic redundancy, and creates a threshold effect in which a large percentage of mtDNA must be lost prior to clinical pathogenesis. As certain pharmaceuticals and genetic mutations can result in depletion of mtDNA, and as many environmental toxicants target mitochondria, it is important to understand whether reduced mtDNA will sensitize an individual to toxicant exposure. Here, using ethidium bromide (EtBr), which preferentially inhibits mtDNA replication, we reduced mtDNA 35-55% in the in vivo model organism Caenorhabditis elegans. Chronic, lifelong, low-dose EtBr exposure did not disrupt nematode development or lifespan, and induced only mild alterations in mitochondrial respiration, while having no effect on steady-state ATP levels. Next, we exposed nematodes with reduced mtDNA to the known and suspected mitochondrial toxicants aflatoxin B1, arsenite, paraquat, rotenone or ultraviolet C radiation (UVC). EtBr pre-exposure resulted in mild sensitization of nematodes to UVC and arsenite, had no effect on AfB1 and paraquat, and provided some protection from rotenone toxicity. These mixed results provide a first line of evidence suggesting that reduced mtDNA content may sensitize an individual to certain environmental exposures.

Mitochondrial compromise in 3-year old patas monkeys exposed in utero to human-equivalent antiretroviral therapies

Antiretroviral (ARV) drug therapy, given during pregnancy for prevention of mother-to-child transmission of human immunodeficiency virus 1 (HIV-1), induces fetal mitochondrial dysfunction in some children. However, the persistence/reversibility of that dysfunction is unclear. Here we have followed Erythrocebus patas (patas) monkey offspring for up to 3 years of age (similar in development to a 15-year old human) after exposure of the dams to human-equivalent in utero ARV exposure protocols. Pregnant patas dams (3-5/exposure group) were given ARV drug combinations that included zidovudine (AZT)/lamivudine (3TC)/abacavir (ABC), or AZT/3TC/nevirapine (NVP), for the last 10 weeks (50%) of gestation. Infants kept for 1 and 3 years also received drug for the first 6 weeks of life. In offpsring at birth, 1 and 3 years of age mitochondrial morphology, examined by electron microscopy (EM), was compromised compared to the unexposed controls. Mitochondrial DNA (mtDNA), measured by hybrid capture chemiluminescence assay (HCCA) was depleted in hearts of patas exposed to AZT/3TC/NVP at all ages (P < 0.05), but not in those exposed to AZT/3TC/ABC at any age. Compared to unexposed controls, mitochondrial reserve capacity oxygen consumption rate (OCR by Seahorse) in cultured bone marrow mesenchymal fibroblasts from 3-year-old patas offspring was ∼50% reduced in AZT/3TC/ABC-exposed patas (P < 0.01), but not in AZT/3TC/NVP-exposed patas. Overall the data show that 3-year-old patas sustain persistent mitochondrial dysfunction as a result of perinatal ARV drug exposure. Environ. Mol. Mutagen. 57:526-534, 2016. © 2016 Wiley Periodicals, Inc.

Neurologic Outcomes in HIV-Exposed/Uninfected Infants Exposed to Antiretroviral Drugs During Pregnancy in Latin America and the Caribbean

To evaluate antiretroviral (ARV) drug exposure and other factors during pregnancy that may increase the risk of neurologic conditions (NCs) in HIV-exposed/uninfected (HEU) infants. A prospective cohort study was conducted at 24 clinical sites in Latin America and the Caribbean. Data on maternal demographics, health, HIV disease status, and ARV use during pregnancy were collected. Infant data included measurement of head circumference after birth and reported medical diagnoses at birth, 6-12 weeks, and 6 months. Only infants with maternal exposure to combination ARV therapy (cART) (≥3 drugs from ≥2 drug classes) during pregnancy were included. Microcephaly, defined as head circumference for age z-score less than -2, and NC were evaluated for their association with covariates, including individual ARVs, using bivariable and logistic regression analyses. From 2002 to 2009, 1,400 HEU infants met study inclusion criteria. At least one NC was reported in 134 (9.6%; 95% confidence interval [CI]: 8.1-11.2), microcephaly in 105 (7.5%; 95% CI: 6.2-9.0), and specific neurologic diagnoses in 33 (2.4%; 95% CI: 1.6-3.3) HEU infants. Microcephaly and NC were not significantly associated with any specific ARV analyzed (p > 0.05). Covariates associated with increased odds of NC included male sex (odds ratio [OR] = 1.9; 95% CI: 1.3-2.8), birth weight <2.5 kg (OR = 3.1; 95% CI: 2.1-4.8), 1-min Apgar score <7 (OR = 2.5; 95% CI: 1.4-4.4), and infant infections (OR = 2.5; 95% CI: 1.5-4.1). No ARV investigated was associated with adverse neurologic outcomes. Continued investigation of such associations may be warranted as new ARVs are used during pregnancy and cART exposure during the first trimester becomes increasingly common.

Fetal consequences of maternal antiretroviral nucleoside reverse transcriptase inhibitor use in human and nonhuman primate pregnancy

PURPOSE OF REVIEW

Here we present fetal genotoxicity and mitochondrial toxicity, induced by nucleoside reverse transcriptase inhibitors (NRTIs), in HIV-1-infected pregnant women treated to prevent mother-to-child HIV-1 transmission, and in virus-free pregnant patas monkeys.

RECENT FINDINGS

In the offspring of pregnant patas monkeys given human-equivalent NRTI protocols, aneuploidy was found in cultured bone marrow cells taken at birth, 1, and 3 years of age. In some newborn human infants, the offspring of HIV-1-infected mothers given zidovudine (AZT) therapy, aneuploidy, mitochondrial DNA (mtDNA) depletion, morphologically damaged mitochondria, and reduction in cardiac left ventricular muscle were observed. NRTI-exposed human and patas umbilical cords had similar levels of mtDNA depletion and mitochondrial morphological damage. NRTI-exposed patas offspring showed a compensatory increase in heart mtDNA, and a 50% loss of brain mtDNA at 1 year of age. Mitochondrial morphological damage and mtDNA loss were persistent in blood cells of NRTI-exposed infants up to 2 years of age, and in heart and brain from NRTI-exposed patas up to 3 years of age (human equivalent of 15 years).

SUMMARY

Whereas use of NRTIs in human pregnancy protects many thousands of children worldwide, some HIV-1-uninfected infants born to HIV-1-infected mothers receiving antiretroviral drug therapy sustain toxicities that may have adverse consequences later in life.

In utero exposure to zidovudine and heart anomalies in the ANRS French perinatal cohort and the nested PRIMEVA randomized trial

BACKGROUND

Antiretroviral (ARV) regimens during pregnancy are highly effective in preventing mother-to-child transmission of human immunodeficiency virus (HIV). Congenital heart defects (CHDs) and anomalies in cardiac function have been reported in zidovudine (ZDV)-exposed uninfected children. We explored these associations in a large observational cohort and a randomized clinical trial.

METHODS

Since 1986, the French Perinatal Cohort prospectively enrolled all HIV-infected women in 90 centers and collected follow-up on their children through 2 years of age. All CHDs were reviewed by a specialist blinded to exposures. Additionally, in a randomized trial (PRIMEVA ANRS 135) of 2 ARV regimens during pregnancy, 1 of which was without nucleoside reverse transcriptase inhibitors, infants had a specific follow-up including echocardiography at 1 month and 12 months.

RESULTS

Among 12 888 children included, ZDV exposure in the first trimester was significantly associated with CHD (1.5% vs 0.7%; adjusted odds ratio, 2.2 [95% confidence interval, 1.3-3.7]; P < .001). This association was significant for ventricular septal defects (1.1% vs 0.6%; P = .001) and other CHDs (0.31% vs 0.11%; P = .02). In the randomized trial, among 50 infants, girls (but not boys) exposed in utero to ZDV/lamivudine/ritonavir-boosted lopinavir (LPV/r) had a higher left ventricular shortening fraction at 1 month (40% vs 36%; P = .008), and an increased posterior wall thickness at 1 year (5.4 mm vs 4.4 mm; P = .01) than the LPV/r group.

CONCLUSIONS

This study confirms a specific association between in utero exposure to ZDV and CHDs, and a long-lasting postnatal myocardial remodeling in girls. A potential common mechanism, including the involvement of mitochondrial dysfunction, must be explored, and long-term consequences on cardiac function warrant specific attention.

CLINICAL TRIALS REGISTRATION

NCT00424814.

Tolerance of the newborn to antiretroviral drug exposure in utero

INTRODUCTION

The prevention of mother-to-child HIV-1 transmission by antiretroviral drug treatment is remarkably effective. The risk of transmission to the child is now almost zero for women optimally treated during pregnancy. The rapid expansion of this prophylactic treatment has led the World Health Organization to aspire to the virtual elimination of mother-to-child transmission and pediatric AIDS over the next few years. In 2014, more than 900,000 women worldwide were treated with antiretroviral drugs during pregnancy. The issue of fetal and neonatal antiretroviral drug tolerance is therefore extremely important.

AREAS COVERED

This review focuses on the possible impact of in utero exposure to antiretroviral drug on newborn health. To restrict analysis to this period is justified by the specificities of transplacental drug exposure and fetal vulnerability. Relevant data are available from trials and observational cohorts. The significance of various bio-markers detectable at birth is still unresolved, but merits a careful evaluation. Long-term assessment is associated with various logistical difficulties.

EXPERT OPINION

The health of 'exposed but not infected' children poses no major problem in the immense majority of cases, but a series of biological, clinical and imaging-based warning signs have emerged indicating the need for careful attention to be paid to this issue. Some effects that are straightforward to manage in industrialized countries may have more severe consequences in countries in which access to effective healthcare is limited. Nucleoside/nucleotide analogs are potentially genotoxic to mitochondrial and nuclear DNA, and the principal question to be addressed concerns their potential long-term effects.

Metabolic complications of in utero maternal HIV and antiretroviral exposure in HIV-exposed infants

BACKGROUND

Despite a wide body of literature supporting the use of antenatal antiretrovirals (ARV) for the prevention of mother-to-child transmission, there remains a need for continued monitoring as the intrauterine interval is a critical period during which fetal programming influences the future health and development of the child.

METHODS

We conducted a systematic review of the current literature addressing potential metabolic complications of in utero HIV and ARV exposure. We describe studies evaluating metabolic outcomes such as intrauterine and early postnatal growth, bone health and mitochondrial toxicity.

RESULTS

Overall, infants exposed to HIV/ARV do not appear to exhibit vastly compromised intrauterine or early postnatal growth. However, some studies on the effect of combination antiretroviral therapy on small for gestational age and low birth weight outcomes in low-middle income countries show a risk for small for gestational age/low birth weight while those in the United States do not. Postnatal growth to 1 year does not appear to be affected by intrauterine tenofovir exposure in African studies, but a US study found statistically significant differences in length for age z scores (LAZ) at 1 year. Little data exists on long-term bone health. Mitochondrial toxicity including abnormal mitochondrial morphology and DNA content, as well as neurologic deficits and death, have been demonstrated in HIV/ARV-exposed infants.

CONCLUSION

Although gross measures of metabolic well-being appear to be reassuring, careful vigilance of even small risks for potential serious adverse effects to infants exposed to intrauterine HIV/ARVs is warranted as intrauterine fetal metabolic programming may substantially impact the future health of the child.

Tempol protects cardiomyocytes from nucleoside reverse transcriptase inhibitor-induced mitochondrial toxicity

Nucleoside reverse transcriptase inhibitors (NRTIs), essential components of combinational therapies used for treatment of human immunodeficiency virus-1, damage heart mitochondria. Here, we have shown mitochondrial compromise in H9c2 rat cardiomyocytes exposed for 16 passages (P) to the NRTIs zidovudine (AZT, 50μM) and didanosine (ddI, 50μM), and we have demonstrated protection from mitochondrial compromise in cells treated with 200μM 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (Tempol) or 200μM 1-hydroxy-4-[2-triphenylphosphonio)-acetamido]-2,2,6,6-tetramethylpiperidine (Tempol-H), along with AZT/ddI, for 16P. Exposure to AZT/ddI caused a moderate growth inhibition at P3, P5, P7, and P13, which was not altered by addition of Tempol or Tempol-H. Mitochondrial oxidative phosphorylation capacity was determined as uncoupled oxygen consumption rate (OCR) by Seahorse XF24 Analyzer. At P5, P7, and P13, AZT/ddI-exposed cells showed an OCR reduction of 8.8-57.2% in AZT/ddI-exposed cells, compared with unexposed cells. Addition of Tempol or Tempol-H, along with AZT/ddI, resulted in OCR levels increased by about 300% above the values seen with AZT/ddI alone. The Seahorse data were further supported by electron microscopy (EM) studies in which P16 cells exposed to AZT/ddI/Tempol had less mitochondrial pathology than P16 cells exposed to AZT/ddI. Western blots of P5 cells showed that Tempol and Tempol-H upregulated expression of mitochondrial uncoupling protein-2 (UCP-2). However, Complex I activity that was reduced by AZT/ddI, was not restored in the presence of AZT/ddI/Tempol. Superoxide levels were increased in the presence of AZT/ddI and significantly decreased in cells exposed to AZT/3TC/Tempol at P3, P7, and P10. In conclusion, Tempol protects against NRTI-induced mitochondrial compromise, and UCP-2 plays a role through mild uncoupling.

Tamoxifen-DNA adduct formation in monkey and human reproductive organs

The estrogen analog tamoxifen (TAM), used for adjuvant therapy of breast cancer, induces endometrial and uterine tumors in breast cancer patients. Proliferation stimulus of the uterine endometrium is likely involved in tumor induction, but genotoxicity may also play a role. Formation of TAM-DNA adducts in human tissues has been reported but remains controversial. To address this issue, we examined TAM-DNA adducts in uteri from two species of monkeys, Erythrocebus patas (patas) and Macaca fascicularis (macaque), and in human endometrium and myometrium. Monkeys were given 3-4 months of chronic TAM dosing scaled to be equivalent to the daily human dose. In the uteri, livers and brains from the patas (n = 3), and endometrium from the macaques (n = 4), TAM-DNA adducts were measurable by TAM-DNA chemiluminescence immunoassay. Average TAM-DNA adduct values for the patas uteri (23 adducts/10(8) nucleotides) were similar to those found in endometrium of the macaques (19 adducts/10(8) nucleotides). Endometrium of macaques exposed to both TAM and low-dose estradiol (n = 5) averaged 34 adducts/10(8) nucleotides. To examine TAM-DNA persistence in the patas, females (n = 3) were exposed to TAM for 3 months and to no drug for an additional month, resulting in low or non-detectable TAM-DNA in livers and uteri. Human endometrial and myometrial samples from women receiving (n = 8) and not receiving (n = 8) TAM therapy were also evaluated. Women receiving TAM therapy averaged 10.3 TAM-DNA adducts/10(8) nucleotides, whereas unexposed women showed no detectable TAM-DNA. The data indicate that genotoxicity, in addition to estrogen agonist effects, may contribute to TAM-induced human endometrial cancer.

[Tolerance of antiretroviral drugs during pregnancy]

Prevention of transmission from mother to child HIV-1 with antire-trovirals is extraordinarily effective. The risk is now almost zero for a woman properly followed, early in her pregnancy. Rapid expansion of this prophylaxis gives hope of a virtual elimination of pediatric AIDS at a global scale. In 2012, more than 500,000 women around the world have received antiretrovirals during pregnancy making the issue of tolerance crucial. Even if the health of children "exposed-uninfected" is not a concern in the vast majority of cases, a series of biological, clinical and imaging alerts justifies attention. Genotoxic profile of zidovudine, and more generally that of antiretroviral nucleoside analogues for mitochondrial and/or nuclear DNA is certainly the main questions regarding the potential long-term effects to the child.

Perinatal exposure of patas monkeys to antiretroviral nucleoside reverse-transcriptase inhibitors induces genotoxicity persistent for up to 3 years of age

BACKGROUND

Erythrocebus patas (patas) monkeys were used to model antiretroviral (ARV) drug in human immunodeficiency virus type 1-infected pregnant women.

METHODS

Pregnant patas dams were given human-equivalent doses of ARVs daily during 50% of gestation. Mesenchymal cells, cultured from bone marrow of patas offspring obtained at birth and at 1 and 3 years of age, were examined for genotoxicity, including centrosomal amplification, micronuclei, and micronuclei containing whole chromosomes.

RESULTS

Compared with controls, statistically significant increases (P < .05) in centrosomal amplification, micronuclei, and micronuclei containing whole chromosomes were found in mesenchymal cells from most groups of offspring at the 3 time points.

CONCLUSIONS

Transplacental nucleoside reverse-transcriptase inhibitor exposures induced fetal genotoxicity that was persistent for 3 years.

Metabolic and mitochondrial effects of antiretroviral drug exposure in pregnancy and postpartum: implications for fetal and future health

Antiretroviral drugs (ARVs) are indispensable in the treatment and prevention of human immunodeficiency virus infection. Although their use before, during and after pregnancy is considered safe for mother and child, there are still lingering concerns about their long-term health consequences and the ramifications of their effects on lipid, glucose, intermediary and mitochondrial metabolism. This article reviews the known effects of ARVs on macromolecular and mitochondrial metabolism as well as the potential maternal, fetal, neonatal and adult health risks associated with abnormal energy metabolism during gestation. Recommendations about enhanced monitoring for these risks in affected populations are being provided.

Effects of in utero antiretroviral exposure on mitochondrial DNA levels, mitochondrial function and oxidative stress

OBJECTIVES

HIV and antiretroviral (ART) exposure in utero may have deleterious effects on the infant, but uncertainty still exists. The objective of this study was to evaluate aspects of mitochondrial DNA (mtDNA) content, mitochondrial function and oxidative stress simultaneously in placenta, umbilical cord blood and infant blood in HIV/ART-exposed infants compared with uninfected controls.

METHODS

HIV-1-infected pregnant women and HIV-1-uninfected healthy pregnant controls were enrolled in the study prospectively. Placenta and umbilical cord blood were obtained at delivery and infant blood was obtained within 48 h of delivery. mtDNA content was determined for each specimen. Nuclear [subunit IV of cytochrome c-oxidase (COX IV)]- and mitochondrial (COX II)-encoded polypeptides of the oxidative phosphorylation enzyme cytochrome c-oxidase were quantified in cord and infant blood. Placental mitochondria malondialdehyde (MDA) concentrations were measured as a marker of oxidative stress.

RESULTS

Twenty HIV-positive/HIV-exposed and 26 control mother-infant pairs were enrolled in the study. All HIV-infected women and their infants received ART. Placental MDA concentration and mtDNA content in placenta and cord blood were similar between groups. The cord blood COX II:IV ratio was lower in the HIV-positive group than in the controls, whereas the infant peripheral blood mtDNA content was higher in the HIV-exposed infants, but the infant peripheral blood COX II:IV ratio was similar. No infant had clinical evidence of mitochondrial disease or acquired HIV infection. In multivariable regression analyses, the significant findings in cord and infant blood were both most associated with HIV/ART exposure.

CONCLUSIONS

HIV-exposed infants showed reduced umbilical cord blood mitochondrial enzyme expression with increased infant peripheral blood mitochondrial DNA levels, the latter possibly reflecting a compensatory mechanism to overcome HIV/ART-associated mitochondrial toxicity.

Progressive mitochondrial compromise in brains and livers of primates exposed in utero to nucleoside reverse transcriptase inhibitors (NRTIs)

Mitochondrial compromise has been documented in infants born to women infected with the human immunodeficiency virus (HIV-1) who received nucleoside reverse transcriptase inhibitor (NRTI) therapy during pregnancy. To model these human exposures, we examined mitochondrial integrity at birth and 1 year in brain cortex and liver from offspring of retroviral-free Erythrocebus patas dams-administered human-equivalent NRTI doses for the last half (10 weeks) of gestation. Additional infants, followed for 1 year, were given the same drugs as their mothers for the first 6 weeks of life. Exposures included: no drug, Zidovudine (AZT), Lamivudine (3TC), AZT/3TC, AZT/Didanosine (ddI), and Stavudine (d4T)/3TC. In brain and liver, oxidative phosphorylation (OXPHOS) enzyme activities (complexes I, II, and IV) showed minimal differences between unexposed and NRTI-exposed offspring at both times. Brain and liver mitochondria from most NRTI-exposed patas, both at birth and 1 year of age, contained significant (p < 0.05) morphological damage observed by electron microscopy (EM), based on scoring of coded photomicrographs. Brain and liver mitochondrial DNA (mtDNA) levels in NRTI-exposed patas were depleted significantly in the 3TC and d4T/3TC groups at birth and were depleted significantly (p < 0.05) at 1 year in all NRTI-exposed groups. In 1-year-old infants exposed in utero to NRTIs, mtDNA depletion was 28.8-51.8% in brain and 37.4-56.5% in liver. These investigations suggest that some NRTI-exposed human infants may sustain similar mitochondrial compromise in brain and liver and should be followed long term for cognitive integrity and liver function.

In utero exposure of female CD-1 mice to AZT and/or 3TC: II. Persistence of functional alterations in cardiac tissue

To delineate temporal changes in the integrity and function of mitochondria/cardiomyocytes in hearts from mice exposed in utero to commonly used nucleoside analogs (NRTIs), CD-1 mice were exposed in utero to 80 mg AZT/kg, 40 mg 3TC/kg, 80 mg AZT/kg plus 40 mg 3TC/kg, or vehicle alone during days 12-18 of gestation and hearts from female mouse offspring were examined at 13 and 26 weeks postpartum. Alterations in cardiac mitochondrial DNA (mtDNA) content, oxidative phosphorylation (OXPHOS) enzyme activities, mtDNA mutations, and echocardiography of NRTI-exposed mice were assessed and compared with findings in vehicle-exposed control mice. A hybrid capture-chemiluminescence assay showed significant twofold increases in mtDNA levels in hearts from AZT- and AZT/3TC-exposed mice at 13 and 26 weeks postpartum, consistent with near doubling in mitochondrial numbers over time compared with vehicle-exposed mice. Echocardiographic measurements at 13 and 26 weeks postpartum indicated progressive thinning of the left ventricular posterior wall in NRTI-exposed mice, relative to controls, with differences becoming statistically significant by 26 weeks. Overall, progressive functional changes occurred in mouse mitochondria and cardiac tissue several months after in utero NRTI exposures; AZT and 3TC acted in concert to cause additive cardiotoxic effects of AZT/3TC compared with either drug alone.

In utero exposure of female CD-1 Mice to AZT and/or 3TC: I. Persistence of microscopic lesions in cardiac tissue

The current study was designed to delineate temporal changes in cardiomyocytes and mitochondria at the light and electron microscopic levels in hearts of mice exposed transplacentally to commonly used nucleoside analogs (NRTIs). Pregnant CD-1 mice were given 80 mg AZT/kg, 40 mg 3TC/kg, 80 mg AZT/kg plus 40 mg 3TC/kg, or vehicle alone during the last 7 days of gestation, and hearts from female mouse pups were examined at 13 and 26 weeks postpartum for histopathological or ultrastructural changes in cross-sections of both the ventricles and the interventricular septum. Using light microscopy and special staining techniques, transplacental exposure to AZT, 3TC, or AZT/3TC was shown to induce significant histopathological changes in myofibrils; these changes were more widespread at 13 weeks than at 26 weeks postpartum. While most light microscopic lesions resolved, some became more severe between 13 and 26 weeks postpartum. Transplacental NRTI exposure also resulted in progressive drug-specific changes in the number and ultrastructural integrity of cardiac mitochondria. These light and electron microscopic findings show that a subset of changes in cardiac mitochondria and myofibrils persisted and progressed months after transplacental exposure of an animal model to NRTIs, with combined AZT/3TC exposure yielding additive effects compared with either drug alone.

A review of nucleoside reverse transcriptase inhibitor use to prevent perinatal transmission of HIV

Worldwide, women comprise > 50% of all people living with HIV and the vast majority of these women are of childbearing age. In fact, a significant proportion of these women are identified as HIV-infected during pregnancy. Preventing perinatal transmission has been one of the greatest prevention successes of the HIV epidemic with < 2% of live births resulting in an HIV-infected infant. The strategic use of combination antiretroviral therapy has been a critical component of this reduction. With more antiretroviral agents available for HIV, the appropriate selection of therapy is often based on provider familiarity with the various agents. Although benefits of antiretroviral use in pregnancy tremendously outweigh the risks, concerns regarding short- and long-term toxicity in mothers and their children, in addition to the risk of the development of HIV resistance, remain subjects of discussion. The choice of antiretroviral 'backbone' is supported by extensive data showing efficacy in the prevention of HIV vertical transmission. Co-formulated zidovudine/lamivudine is the most commonly used combination in pregnancy. Long-term consequences of in utero exposure to antiretroviral agents are not fully understood. In this article, we review the data regarding nucleoside reverse transcriptase inhibitors with a focus on tenofovir.

Tenofovir disoproxil fumarate in pregnancy and prevention of mother-to-child transmission of HIV-1: is it time to move on from zidovudine?

OBJECTIVES

Zidovudine (ZDV) has been the cornerstone of antiretroviral (ARV) therapy for pregnant women infected with HIV-1 in the prevention of mother-to-child transmission (MTCT) and remains the only licensed ARV for use in pregnancy. We explored the current and future roles of tenofovir disoproxil fumarate (TDF) in the prevention of MTCT of HIV-1.

METHODS

We reviewed the published literature by conducting database searches of in vitro, animal and clinical studies, reported in journals and at conferences, using the search terms Tenofovir/gs4331/viread, pregnant/pregnancy, lactate, lactation, natal, reproduce/reproduction, placenta/placental, malformation, and teratogenicity/teratogenic.

RESULTS

In a macaque model, perinatal exposure to very high dose tenofovir resulted in bone toxicity in some offspring. However, perinatal use of TDF, both single dose and as part of highly active antiretroviral therapy in women, has been well tolerated in the short term by mothers and their infants. Further, the addition of single-dose TDF to single-dose nevirapine (SD-NVP) during delivery following maternal ZDV use during pregnancy significantly reduces the frequency of nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance.

CONCLUSIONS

The addition of TDF to SD-NVP reduces NNRTI resistance. The role of TDF in this setting and during pregnancy for reducing rates of MTCT requires investigation. While short-term toxicity data are encouraging, long-term follow-up of exposed mothers and infants is required.

Mutational analysis of the mitochondrial tRNA genes and flanking regions in umbilical cord tissue from uninfected infants receiving AZT-based therapies for prophylaxis of HIV-1

A sensitive vertical denaturing gradient gel electrophoresis (DGGE) method, using 13 unipolar psoralen-clamped PCR primer pairs, was developed for detecting sequence variants in the 22 tRNA genes and flanking regions (together spanning approximately 21%) of the human mitochondrial genome. A study was conducted to determine (i) if mitochondrial DNA (mtDNA) polymorphisms and/or mutations were detectable in healthy newborns and (ii) if prepartum 3'-azido-2',3'-dideoxythymidine (AZT) based HIV-1 prophylaxis was associated with significant increases in mtDNA mutations and changes in the degree of heteroplasmy of sequence variants in uninfected infants born to HIV-1-infected mothers. DGGE analysis of umbilical cord tissue (where vascular endothelium and smooth muscle cells are the major source of mtDNA) showed that mtDNA sequence variants were significantly elevated by threefold in AZT-treated infants compared with unexposed controls (P < 0.001), with 24 changes observed in 19/52 (37%) treated newborns (averaging 0.46 changes/subject) versus only eight changes found in 7/55 (13%) unexposed newborns (averaging 0.15 changes/subject). Six distinct sequence variants occurring in unexposed controls were predominately synonymous and homoplasmic, representing previously reported polymorphisms. Uninfected infants exposed to a combination of AZT and 2',3'-dideoxy-3'-thiacytidine and "maternal HIV-1" had a significant shift in the spectrum of mutations (P = 0.04) driven by increases in nonsynonymous heteroplasmic sequence variants at polymorphic sites (10 distinct variants) and novel sites (four distinct variants). While the weight of evidence suggests that prepartum AZT-based prophylaxis produces mtDNA mutations, additional research is needed to determine the degree to which fetal responses to maternal HIV-1 infection, in the absence of antiretroviral treatment, contribute to prenatal mtDNA mutagenesis.

Metabolism and pharmacokinetics of the combination Zidovudine plus Lamivudine in the adult Erythrocebus patas monkey determined by liquid chromatography-tandem mass spectrometric analysis

Because of their similarity to humans, non-human primates constitute useful preclinical models in which to examine potential human drug toxicities. Antiretroviral nucleoside reverse transcriptase inhibitor (NRTI) toxicity is currently under investigation in Erythrocebus patas monkeys, and whereas NRTI pharmacokinetics have been studied in other monkey species, pharmacokinetics for Zidovudine plus Lamivudine (AZT/3TC) dosing have not been reported in the patas. Here we present 24 h serum pharmacokinetic parameters after a single oral exposure to the combination of AZT (40 mg) and 3TC (24 mg), doses equivalent to a human daily dose of Combivir. The patas (n=3) AZT/3TC pharmacokinetic profiles were similar to those seen in other primate species. Average maximum serum concentrations (Cmax) for AZT and 3TC were 2.35 and 2.65 microg/ml, respectively, and were observed at 0.83 h (Tmax). Cmax was 13.34 microg/ml for the AZT-glucuronide (AZT-G) and was 0.023 microg/ml for the potentially toxic minor metabolite 3'-amino-3'-deoxythymidine (AMT), both occurring at about 1 h after dosing. Similar elimination half-times, 0.70 and 0.68 h(-1), were found for AZT and AZT-G, respectively, while 3TC was eliminated about half as fast (0.33 h(-1)) resulting in AUC(0-infinity) values of 6.97 microg/ml h for 3TC, 2.99 microg/ml h for AZT, 20.5 microg/ml h for AZT-G and 0.002 for AMT 6.97 microg/ml h. This study shows similar metabolism and pharmacokinetics for oral administration of AZT/3TC in the adult patas monkey, other primate species and humans. The data validate the use of the patas monkey for studies of NRTI toxicity.

In utero nucleoside reverse transcriptase inhibitor exposure and signs of possible mitochondrial dysfunction in HIV-uninfected children

BACKGROUND

There is equivocal evidence of in utero nucleoside reverse transcriptase inhibitor (NRTI) exposure and the occurrence of mitochondrial dysfunction (MD) in HIV-uninfected children born of HIV-infected women.

METHODS

The primary analysis included 1037 HIV-uninfected children born in 1991-2002 and enrolled in Pediatric AIDS Clinical Trials Group protocols 219/219C. Possible cases with unexplained signs of MD according to the Enquête Périnatale Française criteria were identified through retrospective review. Associations between overall in utero NRTI exposure, and trimester of first in utero NRTI exposure and possible MD were estimated with exact logistic regression.

RESULTS

Cases (n = 20) were significantly more likely to be male and to be born in earlier years than non-cases (n = 1017). There was no association between overall in utero NRTI exposure and MD. In unadjusted models there were higher odds of first in utero exposure in the third trimester to lamivudine (3TC) [odds ratio (OR), 3.76 versus 3TC unexposed; 95% confidence interval (CI), 1.09-11.78] and to zidovudine (ZDV) and 3TC in combination (ZDV/3TC) (OR, 3.29 vs. ZDV/3TC unexposed; 95% CI, 0.96-10.25) among cases than noncases. When adjusted for year of birth the odds of first exposure in the third trimester to 3TC (OR, 10.57; 95% CI, 1.93-75.61) and ZDV/3TC (OR, 9.84; 95% CI, 1.77-71.68) were significantly higher among cases than non-cases. Incomplete data precluded control of possible confounding by maternal viral load and psychoactive drug use.

CONCLUSIONS

Our study suggests that first exposure to 3TC or ZDV/3TC in the third trimester may be associated with the occurrence of possible MD. Further studies that rigorously assess MD and better control confounding are needed.

Transplacentally exposed human and monkey newborn infants show similar evidence of nucleoside reverse transcriptase inhibitor-induced mitochondrial toxicity

Effective reduction in maternal-fetal human immunodeficiency virus-1 (HIV-1) transmission has been achieved by administration of nucleoside reverse transcriptase inhibitors (NRTIs) during pregnancy, and although most exposed children are clinically normal at birth, mitochondrial dysfunction has been reported. To examine mitochondrial integrity on a molecular level, we evaluated mitochondrial morphology by electron microscopy (EM) and mitochondrial DNA (mtDNA) quantity in umbilical cords and cord blood from NRTI-exposed and unexposed human and monkey newborns. Human subjects included infants born to HIV-1-infected mothers who received Combivir (Zidovudine [AZT] plus Lamivudine [3TC]) (n = 9) or AZT plus Didanosine [ddI] (n = 2) during pregnancy, and infants born to HIV-1-uninfected mothers (n = 7). NRTI-exposed Erythrocebus patas monkey dams (n = 3 per treatment group) were given human-equivalent dosing regimens containing 3TC, AZT/3TC, AZT/ddI, or Stavudine (d4T)/3TC during gestation. Four infants born to unexposed patas dams served as controls. Mitochondria in umbilical cord endothelial cells from NRTI-exposed monkey and human infants showed substantial abnormal pathology by EM, the extent of which was quantified from coded photomicrographs and shown to be different (P < 0.05) from the unexposed monkey and human newborns. Significant (P < 0.05) mtDNA depletion was found in umbilical cords from both human and monkey NRTI-exposed infants and in human, but not in monkey, cord blood leukocytes. For umbilical cords, an increase in mitochondrial morphological damage correlated with reduction in mtDNA quantity in fetal monkeys (r = 0.94). The treatment-induced mitochondrial compromise in infant monkeys ranked as follows: d4T/3TC > AZT/ddI > AZT/3TC > 3TC. The study demonstrates that transplacental NRTI exposures induce similar mitochondrial damage in cord blood and umbilical cords taken from retroviral-uninfected monkey infants and from human infants born to HIV-1-infected women.

Mitochondrial abnormalities--a link to idiosyncratic drug hepatotoxicity?

Idiosyncratic drug-induced liver injury (DILI) is a major clinical problem and poses a considerable challenge for drug development as an increasing number of successfully launched drugs or new potential drugs have been implicated in causing DILI in susceptible patient subsets. Although the incidence for a particular drug is very low (yet grossly underestimated), the outcome of DILI can be serious. Unfortunately, prediction has remained poor (both for patients at risk and for new chemical entities). The underlying mechanisms and the determinants of susceptibility have largely remained ill-defined. The aim of this review is to provide both clinical and experimental evidence for a major role of mitochondria both as a target of drugs causing idiosyncratic DILI and as mediators of delayed liver injury. We develop a unifying hypothesis that involves underlying genetic or acquired mitochondrial abnormalities as a major determinant of susceptibility for a number of drugs that target mitochondria and cause DILI. The mitochondrial hypothesis, implying gradually accumulating and initially silent mitochondrial injury in heteroplasmic cells which reaches a critical threshold and abruptly triggers liver injury, is consistent with the findings that typically idiosyncratic DILI is delayed (by weeks or months), that increasing age and female gender are risk factors and that these drugs are targeted to the liver and clearly exhibit a mitochondrial hazard in vitro and in vivo. New animal models (e.g., the Sod2(+/-) mouse) provide supporting evidence for this concept. However, genetic analyses of DILI patient samples are needed to ultimately provide the proof-of-concept.