Fetal mitochondrial heart and skeletal muscle damage in Erythrocebus patas monkeys exposed in utero to 3'-azido-3'-deoxythymidine

Induction of ABCG2/BCRP restricts the distribution of zidovudine to the fetal brain in rats

Safety concerns for fetus development of zidovudine (AZT) administration as prophylaxis of vertical transmission of HIV persist. We evaluated the participation of the ATP-binding cassette efflux transporter ABCG2 in the penetration of AZT into the fetal brain and the relevance for drug safety. Oral daily doses of AZT (60mg/kg body weight) or its vehicle were administered between post gestational days 11 (E11) and 20 (E20) to Sprague-Dawley pregnant rats. At E21, animals received an intravenous bolus of 60mg AZT/kg body weight in the presence or absence of the ABCG2 inhibitor gefitinib (20mg/kg body weight, ip) and AZT in maternal plasma and fetal brain were measured by HPLC-UV. ABCG2 protein expression in placenta and fetal brain, as well as mitochondrial function and ultrastructure in fetal brain were also analyzed. In utero chronic exposure to AZT markedly induced ABCG2 expression in placenta and fetal brain whereas did not significantly alter mitochondrial functionality in the fetal brain. The area-under-the-concentration-time-curve of AZT significantly decreased in fetal brains isolated from AZT-exposed fetuses compared to control group, but this effect was abolished by ABCG2 inhibition. Our results suggest that the absence of mitochondrial toxicity in the fetal brain after chronic in utero administration of AZT could be attributed to its low accumulation in the tissue caused, at least in part, by ABCG2 overexpression. We propose that any interference with ABCG2 activity due to genetic, pathological or iatrogenic factors would increase the amount of AZT reaching the fetal brain, which could increase the risk of toxicity of this drug on the tissue.

AZT-induced mitochondrial toxicity: an epigenetic paradigm for dysregulation of gene expression through mitochondrial oxidative stress

Mitochondrial dysfunction causes oxidative stress and cardiomyopathy. Oxidative stress also is a side effect of dideoxynucleoside antiretrovirals (NRTI) and is observed in NRTI-induced cardiomyopathy. We show here that treatment with the NRTI AZT {1-[(2R,4S,5S)-4-azido-5-(hydroxymethyl)oxolan-2-yl]-5-methylpyrimidine-2,4-dione} modulates cardiac gene expression epigenetically through production of mitochondrially derived reactive oxygen species. Transgenic mice with ubiquitous expression of mitochondrially targeted catalase (MCAT) and C57Bl/6 wild-type mice littermates (WT) were administered AZT (0.22 mg/day po, 35 days), and cardiac DNA and mRNA were isolated. In AZT-treated WT, 95 cardiac genes were differentially expressed compared with vehicle-treated WTs. When MCAT mice were treated with AZT, each of those 95 genes reverted toward the expression of vehicle-treated WTs. In AZT-treated WT hearts, Mthfr [5,10-methylenetetrahydrofolate reductase; a critical enzyme in synthesis of methionine cycle intermediates including S-adenosylmethionine (SAM)], was overexpressed. Steady-state abundance of SAM in cardiac extracts from AZT-treated MCAT mice increased 60% above that of vehicle-treated MCAT. No such change occurred in WT. AZT caused hypermethylation (47%) and hypomethylation (53%) of differentially methylated DNA regions in WT cardiac DNA. AZT-treated MCAT heart DNA exhibited greater hypermethylation (91%) and less hypomethylation (9%) compared with vehicle-treated MCAT controls. The gene encoding protein kinase C-α displayed multifocal epigenetic regulation caused by oxidative stress. Results show that mitochondrially derived oxidative stress in the heart hinders cardiac DNA methylation, alters steady-state abundance of SAM, alters cardiac gene expression, and promotes characteristic pathophysiological changes of cardiomyopathy. This mechanism for NRTI toxicity offers insight into long-term side effects from these commonly used antiviral agents.

Neurotoxic effects of AZT on developing and adult neurogenesis

Azidothymidine (AZT) is a synthetic, chain-terminating nucleoside analog used to treat HIV-1 infection. While AZT is not actively transported across the blood brain barrier, it does accumulate at high levels in cerebrospinal fluid, and subsequently diffuses into the overlying parenchyma. Due to the close anatomical proximity of the neurogenic niches to the ventricular system, we hypothesize that diffusion from CSF exposes neural stem/progenitor cells and their progeny to biologically relevant levels of AZT sufficient to perturb normal cell functions. We employed in vitro and in vivo models of mouse neurogenesis in order to assess the effects of AZT on developing and adult neurogenesis. Using in vitro assays we show that AZT reduces the population expansion potential of neural stem/progenitor cells by inducing senescence. Additionally, in a model of in vitro neurogenesis AZT severely attenuates neuroblast production. These effects are mirrored in vivo by clinically-relevant animal models. We show that in utero AZT exposure perturbs both population expansion and neurogenesis among neural stem/progenitor cells. Additionally, a short-term AZT regimen in adult mice suppresses subependymal zone neurogenesis. These data reveal novel negative effects of AZT on neural stem cell biology. Given that the sequelae of HIV infection often include neurologic deficits—subsumed under AIDS Dementia Complex (Brew, 1999)—it is important to determine to what extent AZT negatively affects neurological function in ways that contribute to, or exacerbate, ADC in order to avoid attributing iatrogenic drug effects to the underlying disease process, and thereby skewing the risk/benefit analysis of AZT therapy.

Cardiac effects of in-utero exposure to antiretroviral therapy in HIV-uninfected children born to HIV-infected mothers

OBJECTIVES

We evaluated the potential cardiac effects of in-utero exposures to antiretroviral drugs in HIV-exposed but uninfected (HEU) children.

DESIGN AND METHODS

We compared echocardiographic parameters of left ventricular function (ejection fraction, fractional shortening, and stress-velocity index) and structure (left ventricular dimension, posterior wall/septal thickness, mass, thickness-to-dimension ratio, and wall stress) (expressed as Z-scores to account for age and body surface area) between HEU and HIV-unexposed cohorts from the Pediatric HIV/AIDS Cohort Study's Surveillance Monitoring for ART Toxicities study. Within the HEU group, we investigated the associations between the echocardiographic Z-scores and in-utero exposures to maternal antiretroviral drugs.

RESULTS

There were no significant differences in echocardiographic Z-scores between 417 HEU and 98 HIV-unexposed children aged 2-7 years. Restricting the analysis to HEU children, first-trimester exposures to combination antiretroviral therapy (a regimen including at least three antiretroviral drugs) and to certain specific antiretroviral drugs were associated with significantly lower stress-velocity Z-scores (mean decreases of 0.22-0.40 SDs). Exposure to combination antiretroviral therapy was also associated with lower left ventricular dimension Z-scores (mean decrease of 0.44 SD). First-trimester exposure to combination antiretroviral therapy was associated with higher mean left ventricular posterior wall thickness and lower mean left ventricular wall stress Z-scores.

CONCLUSION

There was no evidence of significant cardiac toxicity of perinatal combination antiretroviral therapy exposure in HEU children. Subclinical differences in left ventricular structure and function with specific in-utero antiretroviral exposures indicate the need for a longitudinal cardiac study in HEU children to assess long-term cardiac risk and cardiac monitoring recommendations.

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.

Transplacental exposure to AZT induces adverse neurochemical and behavioral effects in a mouse model: protection by L-acetylcarnitine

Maternal-fetal HIV-1 transmission can be prevented by administration of AZT, alone or in combination with other antiretroviral drugs to pregnant HIV-1-infected women and their newborns. In spite of the benefits deriving from this life-saving prophylactic therapy, there is still considerable uncertainty on the potential long-term adverse effects of antiretroviral drugs on exposed children. Clinical and experimental studies have consistently shown the occurrence of mitochondrial dysfunction and increased oxidative stress following prenatal treatment with antiretroviral drugs, and clinical evidence suggests that the developing brain is one of the targets of the toxic action of these compounds possibly resulting in behavioral problems. We intended to verify the effects on brain and behavior of mice exposed during gestation to AZT, the backbone of antiretroviral therapy during human pregnancy. We hypothesized that glutamate, a neurotransmitter involved in excitotoxicity and behavioral plasticity, could be one of the major actors in AZT-induced neurochemical and behavioral alterations. We also assessed the antioxidant and neuroprotective effect of L-acetylcarnitine, a compound that improves mitochondrial function and is successfully used to treat antiretroviral-induced polyneuropathy in HIV-1 patients. We found that transplacental exposure to AZT given per os to pregnant mice from day 10 of pregnancy to delivery impaired in the adult offspring spatial learning and memory, enhanced corticosterone release in response to acute stress, increased brain oxidative stress also at birth and markedly reduced expression of mGluR1 and mGluR5 subtypes and GluR1 subunit of AMPA receptors in the hippocampus. Notably, administration during the entire pregnancy of L-acetylcarnitine was effective in preventing/ameliorating the neurochemical, neuroendocrine and behavioral adverse effects induced by AZT in the offspring. The present preclinical findings provide a mechanistic hypothesis for the neurobehavioral effects of AZT and strongly suggest that preventive administration of L-acetylcarnitine might be effective in reducing the neurological side-effects of antiretroviral therapy in fetus/newborn.

Possible role of mtDNA depletion and respiratory chain defects in aristolochic acid I-induced acute nephrotoxicity

This report describes an investigation of the pathological mechanism of acute renal failure caused by toxic tubular necrosis after treatment with aristolochic acid I (AAI) in Sprague-Dawley (SD) rats. The rats were gavaged with AAI at 0, 5, 20, or 80 mg/kg/day for 7 days. The pathologic examination of the kidneys showed severe acute tubular degenerative changes primarily affecting the proximal tubules. Supporting these results, we detected significantly increased concentrations of blood urea nitrogen (BUN) and creatinine (Cr) in the rats treated with AAI, indicating damage to the kidneys. Ultrastructural examination showed that proximal tubular mitochondria were extremely enlarged and dysmorphic with loss and disorientation of their cristae. Mitochondrial function analysis revealed that the two indicators for mitochondrial energy metabolism, the respiratory control ratio (RCR) and ATP content, were reduced in a dose-dependent manner after AAI treatment. The RCR in the presence of substrates for complex I was reduced more significantly than in the presence of substrates for complex II. In additional experiments, the activity of respiratory complex I, which is partly encoded by mitochondrial DNA (mtDNA), was more significantly impaired than that of respiratory complex II, which is completely encoded by nuclear DNA (nDNA). A real-time PCR assay revealed a marked reduction of mtDNA in the kidneys treated with AAI. Taken together, these results suggested that mtDNA depletion and respiratory chain defects play critical roles in the pathogenesis of kidney injury induced by AAI, and that the same processes might contribute to aristolochic acid-induced nephrotoxicity in humans.

Evaluation of Hepatic Mitochondria and Hematological Parameters in Zidovudine-Treated B6C3F(1) Mice

The effects of 12-week exposure to zidovudine (AZT) at 400, 500, and 600 mg/kg/d were examined on expression of 542 mitochondria-related genes and mitochondrial DNA (mtDNA) copy number in the liver of male and female B6C3F₁ mice to understand mitochondrial role in sex-related differences in development of lactic acidosis. Plasma lactate levels and hematologic parameters were also examined. Results indicated increased red blood cell (RBC) count in vehicle-treated controls, whereas a dose-related decline in the RBC count was noted in AZT-treated mice compared to the basal levels before treatments began. These decreases were associated with significant dose-related increases in mean corpuscular volume and mean corpuscular hemoglobin levels. This effect was greater in AZT-treated females compared to males. In both sexes, 12-week AZT or vehicle exposure significantly reduced plasma lactate levels compared to the basal levels. Results also showed modest, but significant, changes in the expression of genes associated with apoptosis and lipid metabolism at 600 mg/kg/d AZT. Neither drug nor sex influenced hepatic mtDNA copy number. Altogether, 12-week AZT exposure as high as 600 mg/kg/d did not impair hepatic mitochondria or induce lactic acidosis in B6C3F₁ mice. However, AZT-mediated hematologic toxicity appeared to be greater in females compared to males.

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.

Highly active antiretroviral therapy drug combination induces oxidative stress and mitochondrial dysfunction in immortalized human blood-brain barrier endothelial cells

The era of highly active antiretroviral therapy (HAART) has controlled AIDS and its related disorders considerably; however, the prevalence of HIV-1-associated neurocognitive disorders has been on the rise in the post-HAART era. In view of these developments, we investigated whether a HAART drug combination of 3'-azido-2',3'-deoxythymidine (AZT) and indinavir (IDV) can alter the functionality of the blood-brain barrier (BBB) endothelial cells, thereby exacerbating this condition. The viability of hCMEC/D3 cells (in vitro model of BBB) that were exposed to these drugs was significantly reduced after 72h treatment, in a dose-dependent manner. Reactive oxygen species were highly elevated after the exposure, indicating that mechanisms that induce oxidative stress were involved. Measures of oxidative stress parameters, such as glutathione and malondialdehyde, were altered in the treated groups. Loss of mitochondrial membrane potential, as assessed by fluorescence microscopy and decreased levels of ATP, indicated that cytotoxicity was mediated through mitochondrial dysfunction. Furthermore, AZT+IDV treatment caused apoptosis in endothelial cells, as assessed by the expression of cytochrome c and procaspase-3 proteins. Pretreatment with the thiol antioxidant N-acetylcysteine amide reversed some of the pro-oxidant effects of AZT+IDV. Results from our in vitro studies indicate that the AZT+IDV combination may affect the BBB in HIV-infected individuals treated with HAART drugs.

Birth defects among a cohort of infants born to HIV-infected women on antiretroviral medication

OBJECTIVE

To determine rate of and risk factors for birth defects in infants born to HIV-infected women receiving nucleoside and protease inhibitor antiretroviral (ARV) therapy.

METHODS

Birth defects were evaluated among infants on the Pediatric AIDS Clinical Trials Group 316 trial that studied addition of peripartum nevirapine to established ARV regimen for prevention of mother-to-child transmission. Maternal therapy was categorized by trimester of earliest exposure. Birth defects were coded using conventions of the Antiretroviral Pregnancy Registry.

RESULTS

Birth defects were detected in 60/1414 (4.2%; 95% CI 3.3-5.4%) infants including 30/636 (4.7%; 95% CI 3.2-6.7%) with first trimester ARV exposure and 30/778 (3.9%; 95% CI 2.6-5.5%) with exposure only after the first trimester (P=0.51). Rates of classes of defects were similar between first trimester compared to later exposure groups except heart defects which occurred in 16 (2.5%; 95% CI 1.4-4.1%) with first trimester ARV exposure and in six (0.8%; 95% CI 0.3-1.7%) infants with later exposure (P=0.02). Exposure to ARV was not associated with specific types of heart defects. Two cases of cardiomyopathy were noted.

CONCLUSION

ARV use in early pregnancy was not associated with an increased risk of birth defects overall. The possible association of ARV exposure with heart defects requires further surveillance.

Perinatal tobacco smoke exposure increases vascular oxidative stress and mitochondrial damage in non-human primates

Epidemiological studies suggest that events occurring during fetal and early childhood development influence disease susceptibility. Similarly, molecular studies in mice have shown that in utero exposure to cardiovascular disease (CVD) risk factors such as environmental tobacco smoke (ETS) increased adult atherogenic susceptibility and mitochondrial damage; however, the molecular effects of similar exposures in primates are not yet known. To determine whether perinatal ETS exposure increased mitochondrial damage, dysfunction and oxidant stress in primates, archived tissues from the non-human primate model Macaca mulatta (M. mulatta) were utilized. M. mulatta were exposed to low levels of ETS (1 mg/m³ total suspended particulates) from gestation (day 40) to early childhood (1 year), and aortic tissues were assessed for oxidized proteins (protein carbonyls), antioxidant activity (SOD), mitochondrial function (cytochrome oxidase), and mitochondrial damage (mitochondrial DNA damage). Results revealed that perinatal ETS exposure resulted in significantly increased oxidative stress, mitochondrial dysfunction and damage which were accompanied by significantly decreased mitochondrial antioxidant capacity and mitochondrial copy number in vascular tissue. Increased mitochondrial damage was also detected in buffy coat tissues in exposed M. mulatta. These studies suggest that perinatal tobacco smoke exposure increases vascular oxidative stress and mitochondrial damage in primates, potentially increasing adult disease susceptibility.

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.

Six-month repeated dose toxicity of orally administered metacavir in rhesus monkeys

OBJECTIVE

To explore the toxicities of metacavir, a novel deoxyguanosine analog with an anti-hepatitis B virus (HBV) potential, in a 6-month repeated dosing in rhesus monkeys.

METHODS

Rhesus monkeys were divided into four groups with eight animals in each group. Metacavir or blank vehicles were given for up to 6-month, and then the animals were euthanized 3 and 6 months later. Biochemical and hematological parameters, general symptoms, ECG, serum antibodies, and tissue pathology were observed and recorded.

RESULTS

No biologically meaningful influences on body weight, body temperature, ocular examination, ECG, and organ weight were observed. The main toxic effects included: obvious gastrointestinal toxicities were observed in metacavir 200 mg/kg group, in which animals experienced vomiting and decrease in food consumption. Along with the increase of dosing times, animals gradually tolerated the drug and all these effects gradually abated. Hematological damages included increased damage of red blood cells, decrease of red blood cell count and hemoglobin levels. Hepatic functions were also damaged at certain levels, including the decreases in total protein, albumin, and glucose and the fatty degeneration in hepatocytes. Mild stenosis and exfoliation of gastric and duodenal mucosa was observed. The mild necrosis and exfoliation of renal tubules epithelia was found 6 months after the start of dosing. All these toxic effects were dose dependent.

CONCLUSION

The main target organs of the toxic effects of metacavir are gastrointestinal tract, liver, blood, and kidneys. The no-observed-adverse-effect-level (NOAEL) of metacavir for rhesus monkey were considered to be 50 mg/kg/day.

Oral uridine supplementation antagonizes the peripheral neuropathy and encephalopathy induced by antiretroviral nucleoside analogues

OBJECTIVE

Peripheral neuropathy and central nervous system neurodegeneration may result from the mitochondrial toxicity of some antiretroviral nucleoside analogues. We investigated whether this neuropathology may be antagonized by uridine supplementation in vivo.

DESIGN

Because of the obvious difficulties in obtaining human neural tissues, the mitochondrial neurotoxicity of the nucleoside analogues was studied in mice.

METHODS

BALB/C mice (7 weeks of age) were fed for 9 weeks with zalcitabine (13 mg/kg per day) or zidovudine (100 mg/kg per day) with or without mitocnol (340 mg/kg per day), a dietary supplement with high uridine bioavailability. Hippocampal and sciatic nerve mitochondria were analyzed.

RESULTS

Zalcitabine and to a lesser extent zidovudine induced a significant peripheral neuropathy and encephalopathy with disrupted mitochondrial ultrastructure, depleted mitochondrial DNA, reduced levels of cytochrome c oxidase activity and diminished expression of mitochondrial DNA-encoded cytochrome c oxidase subunit I. Mitocnol had no intrinsic effects but attenuated or fully normalized all measured disorder of the peripheral and central nervous system.

CONCLUSION

Zidovudine and zalcitabine induce a mitochondrial disorder in the peripheral and central nervous system, both of which are antagonized by uridine supplementation.

In vivo assessment of mitochondrial toxicity of metacavir in Rhesus monkeys after three months of intravenous administration

AIM

To explore the potential mitochondrial toxicities and their severities of intravenously administered metacavir, a nucleoside analog, in rhesus monkeys.

METHODS

Totally 21 rhesus monkeys were randomly divided into 4 groups: metacavir 120 mg/kg group, metacavir 40 mg/kg group, zidovudine(AZT) 50 mg/kg group, and blank control group. Animals were killed after the completion of dosing or further observed in a 4-week recovery phase. Changes of structure of mitochondria in liver, kidney, skeletal muscles, and cardiac muscles were observed under transmission electron microscope(TEM). Changes of the activities of mitochondrial respiratory chain complexes and mitochondrial DNA were also determined.

RESULTS

In metacavir 120 mg/kg group, some mitochondrial injuries were found in skeletal muscle, cardiac muscle, and liver, including that some cristae was broken and became sparse in density in the skeletal muscle, the morphology and size of mitochondria remained unchanged. Metacavir decreased the activities of respiratory chain complexes I and II and the mtDNA contents in three tissues in a dose-dependent manner; however, the extent of such decrease was lower than that in AZT 50 mg/kg group. The mitochondrial injuries in metacavir 40 mg/kg group were mild in each tissue and no obvious change in mitochondrial function was noted. On week 4 in the recovery phase, results showed that all these injuries were reversible after drug withdrawal.

CONCLUSION

These results suggest that metacavir has not a high risk for potential mitochondrial-related effects in rhesus monkeys.

Antiretroviral exposure and lymphocyte mtDNA content among uninfected infants of HIV-1-infected women

OBJECTIVE

Concern for potential adverse effects of antiretroviral (ARV) chemotherapy used to prevent mother-to-child HIV transmission has led the US Public Health Service to recommend long-term follow-up of ARV-exposed children. Nucleoside reverse transcriptase inhibitor ARV agents can inhibit DNA polymerase gamma, impairing mitochondrial DNA (mtDNA) synthesis and resulting in depletion or dysfunction.

METHODS

We measured the mtDNA content of stored peripheral blood mononuclear cells (PBMCs) of 411 healthy children who were born to HIV-uninfected women and 213 uninfected infants who were born to HIV-infected women with or without in utero and neonatal ARV exposure. Cryopreserved PBMC mtDNA was quantified by using the Primagen Retina Mitox assay.

RESULTS

Geometric mean PBMC mtDNA levels were lower at birth in infants who were born to HIV-infected women. Among HIV-exposed children, mtDNA levels were lowest in those who were not exposed to ARVs, higher in those with exposure to zidovudine alone, and higher still in those with combination nucleoside reverse transcriptase inhibitor exposure. A similar pattern was observed in the corresponding women. Levels of mtDNA increased during the first 5 years of life in all HIV-exposed children but achieved normal levels only in those with ARV exposure.

CONCLUSIONS

Levels of mtDNA are lower than normal in HIV-exposed children. Contrary to expectation, PBMC mtDNA levels are significantly higher in ARV-exposed, HIV-uninfected infants and their infected mothers compared with ARV-unexposed infants and women. By 5 years, levels of PBMC mtDNA rise to normal concentrations in ARV-exposed children but remain depressed in ARV-unexposed children.

Increased mtDNA levels without change in mitochondrial enzymes in peripheral blood mononuclear cells of infants born to HIV-infected mothers on antiretroviral therapy

BACKGROUND

The effects of gestational nucleoside reverse transcriptase inhibitors (NRTIs) on mitochondrial DNA (mtDNA) are controversial. The effects of mtDNA depletion on mitochondrial function have not been assessed.

METHOD

In peripheral blood mononuclear cells (PBMCs) from infants born to HIV-infected women and infants born to HIV-1-uninfected women, mtDNA copy numbers were determined by quantitative PCR; nuclear (COXIV)- and mitochondrial (COXII)-encoded polypeptides of the oxidative phosphorylation enzyme cytochrome c-oxidase (COX or complex IV) were quantified by Western blot.

RESULTS

Overall, 86 infants born to HIV-infected women and 50 controls were studied. HIV-infected mothers had a median CD4 count of 506 cells/microL; 59% had HIV RNA 50 copies/mL. No infant had clinical evidence of mitochondrial disease. The birth weight was lower (p = .016) and the body length higher (p = .002) in the HIV-exposed newborns. Eighty-one HIV-infected women had received gestational NRTIs (median duration 162 days). Median mtDNA copies/PBMC in the HIV-exposed infants were 505 (range, 120-1365) vs. 213 (27-426) in controls (p < .001). COX II/IV ratios were similar in both groups. Although mtDNA levels correlated inversely with maternal lactate, mitochondrial indices did not correlate with maternal CD4+ count, HIV RNA, smoking, or alcohol consumption.

CONCLUSION

We found elevated mtDNA copy numbers in PBMC of infants born to HIV-infected women, the majority of whom received NRTI-based therapy, when compared to those born to healthy HIV-negative controls, but there was no difference in mtDNA-encoded respiratory chain protein. The clinical consequence of these findings is unknown and requires further investigations.

Mitochondrial disorders among infants exposed to HIV and antiretroviral therapy

Although antiretroviral therapy (ART) is critical for preventing mother-to-child transmission of HIV, concern has been raised about the possibility that it may cause mitochondrial dysfunction in infants. There is adequate evidence for a mechanism by which exposure to nucleoside reverse transcriptase inhibitors (NRTIs) could lead to mitochondrial dysfunction; animal studies have shown evidence of mitochondrial dysfunction in the offspring of animals treated with NRTIs and mitochondrial disorders occur in adults treated with NRTIs. This systematic review synthesises the published research on mitochondrial dysfunction and disorders in infants exposed to HIV and antiretrovirals. We found conflicting evidence regarding the possible association of in utero ART exposure with mortality and morbidity due to mitochondrial dysfunction. ART exposure in utero or postpartum was associated with persistent decreases in lymphocytes, neutrophils and platelets as well as an increased risk of transient lactic acidaemia, anaemia and mitochondrial DNA depletion, although these laboratory findings were generally not associated with clinical symptoms. We conclude that large, prospective studies of HIV-exposed infants are needed to resolve the discrepant results regarding morbidity and mortality related to mitochondrial disorders, to ascertain the clinical significance of effects on laboratory values, to determine whether or not the incidence of mitochondrial disorders differs by regimen and to develop predictive models that might identify which infants are at the greatest risk. The challenges that remain to be addressed include the development of a sensitive but affordable screening algorithm in combination with specific diagnostic criteria; consistent collection of data on ART exposure and other risk factors, long-term follow-up of HIV-exposed but uninfected children and implementation in resource-limited settings.

Mitochondrial disease in the offspring as a result of antiretroviral therapy

Nucleoside analogue reverse transcriptase inhibitors (NRTIs) have substantially lowered the risk of the mother-to-child transmission of HIV. Evidence of mitochondrial toxicity in vitro, in animal models and in adult HIV-infected patients, has raised concern about the perinatal safety of these antiretrovirals. In zidovudine-exposed, but HIV-uninfected infants, transient anaemia and additional long-term blood abnormalities (neutropenia, thrombopenia and lymphopenia) and hyperlactatemia have been documented. The overall risk of mortality and congenital abnormalities does not appear to be increased, but rare mitochondrial events cannot be excluded for lack of statistical power. French data suggest an above background incidence of mitochondrial symptomatology. Preclinical data demonstrate zidovudine also to be a carcinogen. Long-term systematic follow-up of exposed babies in large cohorts is needed, as are randomised trials with NRTIs carrying a lower risk of mitochondrial toxicity.

Clinical mitochondrial dysfunction in uninfected children born to HIV-infected mothers following perinatal exposure to nucleoside analogues

Clinical and biological observations of mitochondrial dysfunction in children exposed to zidovudine (azidothymidine, AZT) during the perinatal period rapidly followed similar observations in animal experiments. To date, two different disorders have been identified. The first, asymptomatic hyperlactatemia, is observed during treatment in one third of exposed newborns, and is reversible with treatment cessation. In rare cases, it is associated with symptomatic acidosis. Regression may be slow, taking up to several months after the end of the treatment. The long-term clinical consequences of this biochemical disturbance are unknown. The second disorder involves severe neurological symptoms, which become clinically detectable during the first 2 years of life. These symptoms are associated with a series of biochemical and ultrastructural changes consistent with persistent mitochondrial dysfunction. This latter phenomenon is rare, and affects only 0.3-0.5% of exposed children in the French pediatric cohort, in which observations continue. Despite initial controversy, several similar observations in other cohorts have since confirmed its occurrence. The pathophysiology of these two mitochondrial dysfunctions may differ. Continued efforts to identify and understand clinical mitochondrial toxicities are essential, given the intensification and diversification of perinatal prophylaxis strategies, and the number of pregnant women potentially involved.

Safety of Agents Used to Prevent Mother-to-Child Transmission of HIV

Antiretroviral drugs have been used routinely to reduce the risk of mother-to-child transmission of HIV infection since 1994, following the AIDS Clinical Trials Group 076 trial, which demonstrated the efficacy of zidovudine in reducing the risk of in utero and intrapartum transmission. The use of antiretroviral drugs in pregnancy varies geographically, with widespread use of highly active antiretroviral therapy (HAART) in resource-rich settings for delaying maternal HIV disease progression as well as the prevention of mother-to-child transmission; however, in low- and middle-income settings, abbreviated prophylactic regimens focus on the perinatal period, with very limited access to HAART to date. The potential risks associated with antiretroviral exposure for pregnant women, fetuses and infants depend on the duration of this exposure as well as the number and type of drugs. As the benefits of HAART regimens in reducing the risk of mother-to-child transmission and in delaying disease progression are so great, their widespread use has been accepted, despite the relative lack of safety data from human pregnancies. Animal studies have suggested an increased risk of malformations associated with exposure to specific antiretroviral drugs, although evidence to support this from human studies is limited. Trials, cohorts and surveillance studies have shown no evidence of an increased risk of congenital malformations associated with in utero exposure to zidovudine, or other commonly used antiretroviral drugs, with an estimated 2-3% prevalence of birth defects (i.e. similar to that seen in the general population). Exposure to prophylactic zidovudine for prevention of mother-to-child transmission is associated with a usually mild and reversible, but rarely severe, anaemia in infants. However, a medium-term impact on haematological parameters of antiretroviral-exposed infants has been reported, with small but persistent reductions in levels of neutrophils, platelets and lymphocytes in children up to 8 years of age; the clinical significance of this remains uncertain. To date, there is no evidence to suggest that exposure to antiretroviral drugs in utero or neonatally is associated with an increased risk of childhood cancer, but the potential for mutagenic and carcinogenic effects at older ages cannot be excluded. Nucleoside analogue-related mitochondrial toxicity is well recognised from studies in non-pregnant individuals, whilst animal studies have provided evidence of mitochondrial toxicity resulting from in utero antiretroviral exposure. Clinically evident mitochondrial disease in children with antiretroviral exposure has only been described in Europe, with an estimated 18-month incidence of 'established' mitochondrial dysfunction of 0.26% among exposed children. Regarding pregnancy-related adverse effects, increased risks of prematurity, pre-eclampsia and gestational diabetes mellitus have been reported by a variety of observational studies with varying strengths of evidence and with conflicting results. Based on current knowledge, the immense benefits of antiretroviral prophylaxis in prevention of mother-to-child transmission far outweigh the potential for adverse effects. However, these potential adverse effects require further and longer term monitoring because they are likely to be rare and to occur later in childhood.

Increased incidence of necrotizing enterocolitis in premature infants born to HIV-positive mothers

OBJECTIVE

To examine if being born to an HIV-positive mother may increase the risk of necrotizing enterocolitis in premature infants.

DESIGN

Case-control study.

SETTING

Neonatal unit of a level 3 perinatal centre.

METHODS

: Over a period of 8.5 years, all cases of necrotizing enterocolitis occurring in premature infants admitted to the neonatal unit were identified. For each case, two controls were retrospectively chosen that matched for postmenstrual age at birth, intrauterine growth and year of birth. Perinatal characteristics were studied in all infants.

MAIN RESULTS

There were 79 cases of necrotizing enterocolitis, which were compared with 158 controls. Using multivariate analysis, multiple pregnancy [odds ratio (OR), 2.29; 95% confidence interval (CI), 1.23-4.25; P = 0.009], abnormal umbilical artery velocity (OR, 2.21; 95% CI, 1.08-4.54; P = 0.030), abnormal fetal heart rate (OR, 2.14; 95% CI, 1.05-4.36; P = 0.036) and HIV-positive mother (OR, 6.63; 95% CI, 1.26-34.8; P = 0.025) were significantly more frequent in fetuses who subsequently developed necrotizing enterocolitis.

CONCLUSIONS

This preliminary report suggests an association, not previously reported, between maternal HIV-positive status and an increased risk of necrotizing enterocolitis in premature infants. Despite the limitations of this study, we suggest that premature newborn infants of HIV-positive mothers should be monitored very carefully for a possible increased risk of necrotizing enterocolitis.

The safety of antiretroviral drugs in pregnancy

Advances in HIV therapy and mother-to-child transmission (MTCT) prophylaxis have led to increasing use of antiretroviral drugs in pregnancy. Highly active antiretroviral therapy in pregnancy has been associated with prematurity, pre-eclampsia and gestational diabetes. Women may be at increased risk of nevirapine-associated hepatotoxicity but whether or not pregnancy is an additional risk is uncertain. Although animal studies suggest a possibility of congenital abnormalities with specific antiretrovirals, such as efavirenz, results from registries and cohort studies do not support an excess of congenital malformations associated with in utero antiretroviral exposure. Concerns regarding the health of uninfected, antiretroviral-exposed children include the potential for cancers, mitochondrial disease and haematological abnormalities. However, the absence of any excess mortality in large observational cohort studies of uninfected, antiretroviral therapy-exposed children born to HIV-infected women is reassuring. Based on current knowledge, the immense benefits of antiretroviral prophylaxis in reducing the risk of MTCT, far outweigh the potential for adverse effects.

Prenatal Environmental Tobacco Smoke Exposure Promotes Adult Atherogenesis and Mitochondrial Damage in Apolipoprotein E −/− Mice Fed a Chow Diet

Background— Environmental tobacco smoke (ETS) exposure is recognized as a cardiovascular disease risk factor; however, the impact of prenatal ETS exposure on adult atherogenesis has not been examined. We hypothesized that in utero ETS exposure promotes adult atherosclerotic lesion formation and mitochondrial damage.

Methods and Results— Atherosclerotic lesion formation, mitochondrial DNA damage, antioxidant activity, and oxidant load were determined in cardiovascular tissues from adult apolipoprotein E −/− mice exposed to either filtered air or ETS in utero and fed a standard chow diet (4.5% fat) from weaning until euthanasia. All parameters were significantly altered in male mice exposed in utero to ETS.

Conclusions— These data support the hypothesis that prenatal ETS exposure is sufficient to promote adult cardiovascular disease development.

Mitochondrial damage and DNA depletion in cord blood and umbilical cord from infants exposed in utero to Combivir

OBJECTIVE

Although most uninfected infants born to women infected with HIV-1 show no clinical evidence of mitochondrial compromise, mitochondrial dysfunction has been reported in children born to women receiving zidovudine and/or lamivudine during pregnancy. In this pilot study we examined mitochondrial integrity in HIV-1-uninfected infants born to HIV-1-infected women receiving Combivir during pregnancy.

DESIGN

: Samples of umbilical cord and cord blood were obtained from HIV-1-uninfected infants born to either HIV-1-infected women receiving Combivir therapy during pregnancy (n = 10) or HIV-1-uninfected women (n = 9).

METHODS

Mitochondrial morphological integrity was examined in umbilical cords (n = 16) by electron microscopy and mtDNA quantity was determined in DNA from cord blood (n = 18) and umbilical cord (n = 18) by PCR-chemiluminescence immunoassay detection.

RESULTS

In umbilical cords from six of nine infants born to HIV-1-infected mothers taking Combivir moderate to severe mitochondrial morphological damage was observed (P = 0.011), while none of seven unexposed infants showed similar damage. Compared to unexposed infants, statistically significant mtDNA depletion was observed in umbilical cord (P = 0.006) and cord blood (P = 0.003) from drug-exposed infants.

CONCLUSIONS

A cohort of HIV-1-uninfected Combivir-exposed infants with no clinical symptoms showed morphological and molecular evidence of mitochondrial damage.

Mitochondrial toxicity in fetal Erythrocebus patas monkeys exposed transplacentally to zidovudine plus lamivudine

This study was designed to investigate fetal mitochondrial toxicity in Erythrocebus patas monkeys exposed in utero to zidovudine (AZT) and lamivudine (3TC), and taken at term. Pregnant patas monkeys were given a daily dose of 40 mg AZT (86% of the human daily dose, based on body weight), for the last 10 weeks (50%) of gestation, and a daily dose of 24 mg 3TC (84% of the human daily dose, based on body weight) for the last 4 weeks of gestation. At term, AZT was found to be incorporated into fetal mitochondrial DNA from skeletal muscle, liver, kidney, and placenta. By transmission electron microscopy (EM) drug-exposed fetal cardiac and skeletal muscle cells showed mitochondrial membrane compromise, mitochondrial proliferation, and damaged sarcomeres, while mitochondria in brain cerebrum and cerebellum were morphologically normal. Substantial depletion of oxidative phosphorylation (OXPHOS) Complex I specific activities was observed in heart (87% reduction in mean, p = 0.02) and skeletal muscle (98% reduction in mean, p = 0.002) from drug-exposed fetuses, compared to unexposed fetuses. In addition Complex IV activity was highly depleted (85% reduction in mean, p = 0.004) in skeletal muscle from the drug-exposed fetuses (p = 0.004). Brain cerebrum and cerebellum showed no statistically significant OXPHOS changes with drug exposure. Mitochondrial DNA quantity was substantially depleted (>50%) in heart, skeletal muscle, cerebellum, and cerebrum from drug-exposed fetuses compared to unexposed controls. Overall, the data indicate that significant mitochondrial damage was observed at birth in monkey fetuses exposed in utero to AZT plus 3TC in a human-equivalent dosing protocol.

Dilated cardiomyopathy in an adult human immunodeficiency virus type 1-positive patient treated with a zidovudine-containing antiretroviral regimen

We describe an adult woman infected with human immunodeficiency virus type 1 (HIV-1) who developed dilated cardiomyopathy (DCM) with histologically confirmed mitochondrial damage while receiving anti-HIV-1 combination therapy that included nelfinavir, lamivudine, and zidovudine. DCM resolved after discontinuation of the regimen, and cardiac function remained normal after initiation of treatment with nelfinavir, lamivudine, and abacavir, which indicates that DCM was induced by mitochondrial toxicity, most likely caused by zidovudine.

The chemical bases of the various AIDS epidemics: recreational drugs, anti-viral chemotherapy and malnutrition

In 1981 a new epidemic of about two-dozen heterogeneous diseases began to strike non-randomly growing numbers of male homosexuals and mostly male intravenous drug users in the US and Europe. Assuming immunodeficiency as the common denominator the US Centers for Disease Control (CDC) termed the epidemic, AIDS, for acquired immunodeficiency syndrome. From 1981-1984 leading researchers including those from the CDC proposed that recreational drug use was the cause of AIDS, because of exact correlations and of drug-specific diseases. However, in 1984 US government researchers proposed that a virus, now termed human immunodeficiency virus (HIV), is the cause of the non-random epidemics of the US and Europe but also of a new, sexually random epidemic in Africa. The virus-AIDS hypothesis was instantly accepted, but it is burdened with numerous paradoxes, none of which could be resolved by 2003: Why is there no HIV in most AIDS patients, only antibodies against it? Why would HIV take 10 years from infection to AIDS? Why is AIDS not self-limiting via antiviral immunity? Why is there no vaccine against AIDS? Why is AIDS in the US and Europe not random like other viral epidemics? Why did AIDS not rise and then decline exponentially owing to antiviral immunity like all other viral epidemics? Why is AIDS not contagious? Why would only HIV carriers get AIDS who use either recreational or anti-HIV drugs or are subject to malnutrition? Why is the mortality of HIV-antibody-positives treated with anti-HIV drugs 7-9%, but that of all (mostly untreated) HIV-positives globally is only 1.4%? Here we propose that AIDS is a collection of chemical epidemics, caused by recreational drugs, anti-HIV drugs, and malnutrition. According to this hypothesis AIDS is not contagious, not immunogenic, not treatable by vaccines or antiviral drugs, and HIV is just a passenger virus. The hypothesis explains why AIDS epidemics strike non-randomly if caused by drugs and randomly if caused by malnutrition, why they manifest in drug- and malnutrition-specific diseases, and why they are not self-limiting via anti-viral immunity. The hypothesis predicts AIDS prevention by adequate nutrition and abstaining from drugs, and even cures by treating AIDS diseases with proven medications.

Mitochondrial dysfunction and nucleoside reverse transcriptase inhibitor therapy: experimental clarifications and persistent clinical questions

Nucleoside reverse transcriptase inhibitors (NRTIs) in combination with other antiretrovirals (HAART) are critical in current AIDS therapy, but mitochondrial side effects have come to light with the increased use of these compounds. Clinical experience, pharmacological, cell and molecular biological evidence links altered mitochondrial (mt-) DNA replication to the toxicity of NRTIs in many tissues, and conversely, mtDNA replication defects and mtDNA depletion in specific target tissues are observed. The shared features of mtDNA depletion and energy depletion became key observations and related the clinical and in vivo experimental findings to inhibition of mtDNA replication by NRTI triphosphates in vitro. Subsequent to those findings, other observations suggested that mitochondrial energy deprivation is concomitant with or the result of mitochondrial oxidative stress in AIDS (from HIV, for example) or from NRTI therapy itself. With increased use of NRTIs, mtDNA mutations may become increasingly important pathophysiologically. One important future goal is to prevent or attenuate the side effects so that improved efficacy is achieved.

Site-specific differences in the action of NRTI drugs on adipose tissue incubated in vitro with lymphoid cells, and their interaction with dietary lipids

Existing theories of the origin of HIV-related adipose tissue redistribution syndrome cannot adequately explain simultaneous hypertrophy of certain depots and atrophy of others, or its occasional occurrence in untreated HIV infection. These experiments explore the hypothesis that hypertrophy of lymphoid tissue-containing adipose depots arises from drug-induced disruption to local interactions between perinodal adipocytes and activated lymphoid cells. Guinea pigs were fed on plain or lipid-supplemented (10% suet, sunflower or fish oil) chow ad libitum or restricted, and the popliteal lymph nodes were activated by repeated injection of lipopolysaccharide. Explants of perinodal and other samples from popliteal, mesentery, omentum and nodeless perirenal and epididymal depots were incubated with lymphoid cells and zidovudine, didanosine, lamivudine or stavudine at physiological concentrations (0.1-1 microg/ml) or interleukin-10 and interleukin-6, and basal and maximum lipolysis was measured. All drugs increased lipolysis from perinodal adipocytes, especially mesenteric, though less than exogenous cytokines. Effects on adipocytes from non-perinodal sites and nodeless depots were minimal. The sunflower-oil diet enhanced, and the fish-oil and restricted diets reduced, these effects. We conclude that these NRTI antiretroviral drugs modulate the local interactions between perinodal adipocytes and activated lymphoid cells. Local interactions, and hence the selective hypertrophy of node-containing adipose depots, may be curtailed by dietary manipulation.

Evaluation of mitochondrial DNA content and enzyme levels in tenofovir DF-treated rats, rhesus monkeys and woodchucks

The antiviral compound tenofovir DF (Gilead Sciences) was evaluated for possible mitochondrial toxicity in rats, rhesus monkeys and woodchucks. Animals were treated by oral gavage with tenofovir DF, and the levels of mitochondrial enzymes cytochrome c oxidase and citrate synthase were assayed. In rats (6/group) treated daily for 28 days with 300 mg/kg tenofovir DF the enzyme levels were unchanged versus control in liver, kidney, and skeletal muscle. In a parallel study, rats (6/group) were treated with 40 mg/kg of the antiviral adefovir dipivoxil (Gilead Sciences) and enzyme levels were also unchanged versus control. In rhesus monkeys (6/group) treated daily with 30 mg/kg or 250 mg/kg tenofovir DF for 56 days, and in woodchucks (6/group) treated daily with 15 mg/kg or 50mg/kg tenofovir DF for 90 days, the enzyme levels were unchanged in liver, kidney, skeletal muscle and cardiac muscle. Mitochondrial DNA (mtDNA) content was determined in tissue from treated versus control animals by utilizing a quantitative real-time PCR (QPCR) technique, where the relative ratios of mitochondrial cytochrome b gene to the genomic actin gene were measured. The relative mtDNA content from rats, rhesus monkeys and woodchucks were unchanged in the various treatment groups. Variations in mtDNA content between animals in the same treatment group were noted. The actual species-dependent mitochondria/genomic ratios were estimated from the QPCR assay. In summary, treatment with tenofovir DF, or with adefovir dipivoxil, did not affect mtDNA content or level of mitochondrial enzymes, and no liver, muscle or renal microscopic abnormalities were observed in tenofovir-treated animals.

Prolonged perinatal AZT administration and early maternal separation: effects on social and emotional behaviour of periadolescent mice

Zidovudine (AZT) is an effective treatment in preventing perinatal transmission of HIV-1; however, a continuous re-evaluation of the risk-benefit ratio of human exposure to this drug is suggested by both clinical and animal studies. The objective of this study was to assess the medium and long-term effects of pre-postnatal AZT treatment on mouse social and emotional behaviour and the possible interactions between AZT exposure and disruptions in the mother-infant relationship. Pregnant CD-1 mice were administered per os with AZT (160 mg/kg) from pregnancy day 10, throughout delivery, to lactation day 10. In half of the litters, the offspring was separated from the mother for 3 h from postnatal days 2 (PND2) to PND14. On PND35, a 30-min social interaction test was performed and corticosterone levels were measured at the end of the session. On PND80, long-term effects of AZT on emotionality were assess by means of an elevated plus-maze. Results indicate that, on PND35, previous AZT exposure affected social behaviour of the experimental subjects, reducing aggressive interactions in males, while decreasing investigative behaviours in females. At adulthood, AZT inhibited exploratory behaviour in the plus-maze while increasing the frequency of risk-assessment postures in male mice. As for maternal deprivation, this early manipulation exerted a pro-aggressive effect in adolescent male mice, deprived subjects being overall characterised by higher activity levels and a deficit in habituation, an effect also observed in the plus-maze. A significant interaction between AZT and maternal deprivation was found for affiliative behaviours. As for corticosterone levels, no AZT effect was found, while maternal deprivation tended to reduce elevations of this hormone in response to stressful stimuli. Overall results from this study indicate that both AZT exposure and maternal deprivation induced gender-dependent changes in social and emotional behaviour both during adolescence and at adulthood.

Mitochondrial DNA replication, nucleoside reverse-transcriptase inhibitors, and AIDS cardiomyopathy

Nucleoside reverse-transcriptase inhibitors (NRTIs) in combination with other antiretrovirals (HAART) are the cornerstones of current AIDS therapy, but extensive use brought mitochondrial side effects to light. Clinical experience, pharmacological, cell, and molecular biological evidence links altered mitochondrial (mt-) DNA replication to the toxicity of NRTIs in many tissues, and conversely, mtDNA replication defects and mtDNA depletion in target tissues are observed. Organ-specific pathological changes or diverse systemic effects result from and are frequently attributed to HAART in which NRTIs are included. The shared features of mtDNA depletion and energy depletion became key observations and related the clinical and in vivo experimental findings to inhibition of mtDNA replication by NRTI triphosphates in vitro. Subsequent to those findings, other observations suggested that mitochondrial energy deprivation is concomitant with or the result of mitochondrial oxidative stress in AIDS (from HIV, for example) or from NRTI therapy itself.

Nucleoside reverse transcriptase inhibitors impair endothelium-dependent relaxation by increasing superoxide

Nucleoside reverse transcriptase inhibitors (NRTIs) have been used successfully to reduce acquired immunodeficiency syndrome mortality. However, the use of these compounds is associated with numerous tissue toxicities, including cardiomyopathy. These studies address the effects of NRTIs on vascular function. Functional assays of contraction and relaxation were performed on isolated mouse aorta segments obtained from FVB/n mice exposed to zidovudine (AZT), stavudine, or water for 35 days. AZT and stavudine treatment impaired sensitivity to endothelium-dependent relaxation by acetylcholine. Dihydroethidium staining revealed that AZT treatment was associated with an increase in superoxide levels. Pretreatment of AZT-treated vessels with tiron (1 mM), a free radical scavenger, restored endothelium-dependent relaxation in mice. In cellular preparations, electron spin resonance measurements revealed elevated superoxide in cultured endothelial cells exposed to AZT; elevation was dependent on the length of exposure. These results indicate that NRTIs impair endothelium-dependent relaxation by increasing superoxide levels and suggest that NRTI therapy contributes to cardiovascular complications in acquired immunodeficiency syndrome.

Safety of antiretroviral prophylaxis of perinatal transmission for HIV-infected pregnant women and their infants

Worldwide, more than 1600 infants become infected with HIV each day. Almost all infections are a result of mother-to-child transmission of HIV, with most of these infections occurring in resource-poor countries. In developed countries, antiretroviral prophylaxis has dramatically reduced perinatal transmission to <2%. The potential now exists to extend this success to resource-poor countries using effective but shorter and less expensive antiretroviral regimens. With the potential widespread use of antiretroviral therapy for perinatal HIV prevention in resource-limited settings, there will be exposure of increasing numbers of infants to in utero and postpartum antiretroviral drugs for which long-term toxicity data is unknown. This article focuses on a review of what is known about safety of antiretroviral regimens used to interrupt mother-to-child transmission for women and their children.

Animal models of anti-HIV drugs exposure during pregnancy: effects on neurobehavioral development

In the last 10 years, zidovudine (AZT) has become the main prophylactic therapy against vertical HIV-1 transmission. AIDS Clinical Trials Group (ACTG) 076 have demonstrated that the administration of AZT to HIV-infected women during their third trimester of pregnancy, trough labor and given orally to babies for 6 weeks, reduced by two-thirds the rate of vertical infection. Although the rapid diffusion of this regimen into clinical practice together with the implementation of HIV counseling and testing practices have dramatically reduced the vertical transmission rate in the US and Western Europe, there is a growing concern on the adverse effects of antiretroviral therapy on the fetus and the newborn. In fact, even though shorter regimen therapies that are less complex and expensive to implement in poor countries have been demonstrated as effective as ACTG 076 regimen, the distribution of the risk of vertical transmission in the developing countries is still very high. Consequently, a large number of unborns will be a candidate to developmental exposure to antiretroviral agents. To date, data on the transplacental mutagenicity, carcinogenicity and mitochondrial dysfunction induced by developmental exposure to AZT have been reported in several animal models. Furthermore, one study reported severe yet few human cases of cardiomyopathy and neurological disease likely associated with mitochondrial dysfunction in uninfected infants of seropositive mothers perinatally exposed to AZT. For all of these reasons, many investigations have been focusing on the assessment of the potential adverse effects of nucleoside reverse transcriptase (RT) inhibitors (NRTI) administration during development. A survey of the main results derived from clinical and animal studies is reported here, focusing on those neurobehavioral studies that have been looking for specific and/or aspecific changes in the nervous system induced by NRTI exposure in utero.

Mitochondrial dysfunction and antiretroviral nucleoside analog toxicities: what is the evidence?

Mitochondrial dysfunction has been associated with long-term toxicities of human immunodeficiency virus (HIV) therapy, particularly with the nucleoside analog reverse transcriptase inhibitors (NRTIs). Lactic acidosis, hepatic steatosis, myopathies, cardiomyopathies, neuropathies, and lipodystrophy are frequently attributed to mitochondrial toxicity. Since mitochondrial toxicity could pose a major threat to the long-term success of HIV therapy, the scientific evidence underlying an association between mitochondrial toxicity and antiretroviral therapies, must be carefully examined. There is some data to support the association between NRTIs and mitochondria dysfunction. In this review, we examine human, animal, and in vitro data implicating mitochondrial dysfunction as the causal mechanism of NRTI-associated toxicity in HIV-infected patients.

Antiretroviral therapy in pregnancy: a focus on safety

Antiretroviral compounds differ from most other new pharmaceutical agents in that they have become widely prescribed in pregnancy in the absence of proof of safety. They are prescribed for the treatment of the mother and to reduce the risk of transmission of HIV to the fetus. In the animal models tested to date, no increased risk of malformations has been demonstrated for some compounds whereas others have been associated with malformations or developmental abnormalities in rats, mice or rabbits and, in the case of efavirenz, monkeys. Zidovudine monotherapy is still prescribed to reduce the risk of mother-to-child transmission of HIV. Combinations of 3 or more compounds are recommended when treatment of the mother is deemed necessary because of advanced HIV infection. Until recently, in vitro toxicity studies relevant to pregnancy were restricted to single agents; no animal teratogenicity or carcinogenesis studies of combination therapy have been published. Despite many thousands of women having taken antiretroviral therapy to reduce the risk of transmission, documented experience in human pregnancy remains sadly lacking, with the possible exception of zidovudine which has been prescribed in clinical trials to several hundred mother-infant pairs. For other compounds and for the numerous permutations of combination therapy, data are available only from small phase I/II studies, from retrospective investigations and from the prospective arm of the Antiretroviral Pregnancy Register (i.e. pregnancies in women taking antiretrovirals who were registered before delivery and then followed up). Antiretroviral monotherapy and combination therapy is widely prescribed in pregnancy because: (i) with appropriate management, which includes antiretroviral therapy, the risk of mother-to-child transmission can be reduced from 15 to 25% to less than 1%; (ii) pregnant women with advanced HIV infection require therapy; (iii) combination therapy with at least 3 compounds significantly reduces morbidity and mortality compared with dual or monotherapy; and (iv) the benefits of therapy for both the mother and the infant outweigh the risk. The choice of antiretroviral therapy in pregnancy may be influenced by the indication (prevention of transmission or maternal treatment), past antiretroviral therapy exposure/drug resistance, effects of pregnancy on the pharmacokinetics of the drug and factors influencing tolerability and adherence. In pregnancy, tolerability may be even more important than usual, especially if therapy exacerbates common complications of pregnancy, such as vomiting and glucose intolerance.

Combined antiretroviral therapy causes cardiomyopathy and elevates plasma lactate in transgenic AIDS mice

Highly active antiretroviral therapy (HAART) is implicated in cardiomyopathy (CM) and in elevated plasma lactate (LA) in AIDS through mechanisms of mitochondrial dysfunction. To determine mitochondrial events from HAART in vivo, 8-week-old hemizygous transgenic AIDS mice (NL4-3Delta gag/pol; TG) and wild-type FVB/n littermates were treated with the HAART combination of zidovudine, lamivudine, and indinavir or vehicle control for 10 days or 35 days. At termination of the experiments, mice underwent echocardiography, quantitation of abundance of molecular markers of CM (ventricular mRNA encoding atrial natriuretic factor [ANF] and sarcoplasmic calcium ATPase [SERCA2]), and determination of plasma LA. Myocardial histologic features were analyzed semiquantitatively and results were confirmed by transmission electron microscopy. After 35 days in the TG + HAART cohort, left ventricular mass increased 160% by echocardiography. Molecularly, ANF mRNA increased 250% and SERCA2 mRNA decreased 57%. Biochemically, LA was elevated (8.5 +/- 2.0 mM). Pathologically, granular cytoplasmic changes were found in cardiac myocytes, indicating enlarged, damaged mitochondria. Findings were confirmed ultrastructurally. No changes were found in other cohorts. After 10 days, only ANF was elevated, and only in the TG + HAART cohort. Results show that cumulative HAART caused mitochondrial CM with elevated LA in AIDS transgenic mice.

Cisplatin exposure induces mitochondrial toxicity in pregnant rats and their fetuses

High levels of cis-diamminedicholorplatinum II (cisplatin)-DNA adducts have previously been observed at term in mitochondrial DNA (mtDNA) from organs of pregnant rats, and from their offspring, after administration of a single injection of cisplatin 15 mg/kg body weight (bw) to the pregnant rat on day 18 of gestation. The consequences of such DNA damage may be clinically relevant as cisplatin is given to pregnant women discovered to have ovarian cancer during pregnancy. In this study, kidneys, livers, and brains of exposed pregnant rats and their offspring were examined for mitochondrial functional integrity. Consistent with previous literature, the most severe toxicity occurred in maternal kidney, where oxidative phosphorylation (OXPHOS) enzyme activities were significantly (approximately 50%) impaired for Complexes II, III, and IV, mtDNA levels in drug-exposed animals were higher than in the unexposed controls, and abnormal mitochondrial morphology was observed by transmission electron microscopy (TEM). In fetal kidneys and livers, cisplatin exposure did not alter mitochondrial morphology or mtDNA quantity, but specific activities of OXPHOS Complexes II and IV were significantly decreased. Fetal brain sustained no discernible mitochondrial toxicity. Therefore, cisplatin-induced mitochondrial toxicity in maternal rat kidney is severe, while damage to mitochondria in fetal kidney and liver, occurring as a result of the transplacental drug exposure, appears to be mild.