Nucleoside reverse transcriptase inhibitor toxicity and mitochondrial DNA

In Silico Pharmacokinetics, Molecular Docking and Molecular Dynamics Simulation Studies of Nucleoside Analogs for Drug Discovery- A Mini Review

Nucleoside analogs have been widely used as antiviral, antitumor, and antiparasitic agents due to their ability to inhibit nucleic acid synthesis. Adenosine, cytidine, guanosine, thymidine and uridine analogs such as didanosine, vidarabine, remdesivir, gemcitabine, lamivudine, acyclovir, abacavir, zidovusine, stavudine, and idoxuridine showed remarkable anticancer and antiviral activities. In our previously published articles, our main intention was to develop newer generation nucleoside analogs with acylation-induced modification of the hydroxyl group and showcase their biological potencies. In the process of developing nucleoside analogs, in silico studies play an important role and provide a scientific background for biological data. Molecular interactions between drugs and receptors followed by assessment of their stability in physiological environments, help to optimize the drug development process and minimize the burden of unwanted synthesis. Computational approaches, such as DFT, FMO, MEP, ADMET prediction, PASS prediction, POM analysis, molecular docking, and molecular dynamics simulation, are the most popular tools to culminate all preclinical study data and deliver a molecule with maximum bioactivity and minimum toxicity. Although clinical drug trials are crucial for providing dosage recommendations, they can only indirectly provide mechanistic information through researchers for pathological, physiological, and pharmacological determinants. As a result, in silico approaches are increasingly used in drug discovery and development to provide mechanistic information of clinical value. This article portrays the current status of these methods and highlights some remarkable contributions to the development of nucleoside analogs with optimized bioactivity.

Kamuvudine-9 Protects Retinal Structure and Function in a Novel Model of Experimental Rhegmatogenous Retinal Detachment

Purpose

Rhegmatogenous retinal detachment (RRD) is a vision-threatening event that benefits from surgical intervention. While awaiting surgical reattachment, irreversible hypoxic and inflammatory damage to the retina often occurs. An interim therapy protecting photoreceptors could improve functional outcomes. We sought to determine whether Kamuvudine-9 (K-9), a derivative of nucleoside reverse transcriptase inhibitors (NRTIs) that inhibits inflammasome activation, and the NRTIs lamivudine (3TC) and azidothymidine (AZT) could protect the retina following RRD.

Methods

RRD was induced in mice via subretinal injection (SRI) of 1% carboxymethylcellulose (CMC). To simulate outcomes following the clinical management of RRD, we determined the optimal conditions by which SRI of CMC induced spontaneous retinal reattachment (SRR) occurs over 10 days (RRD/SRR). K-9, 3TC, or AZT was administered via intraperitoneal injection. Inflammasome activation pathways were monitored by abundance of cleaved caspase-1, IL-18, and cleaved caspase-8, and photoreceptor death was assessed by TUNEL staining. Retinal function was assessed by full-field scotopic electroretinography.

Results

RRD induced retinal inflammasome activation and photoreceptor death in mice. Systemic administration of K-9, 3TC, or AZT inhibited retinal inflammasome activation and photoreceptor death. In the RRD/SRR model, K-9 protected retinal electrical function during the time of RRD and induced an improvement following retinal reattachment.

Conclusions

K-9 and NRTIs exhibit anti-inflammatory and neuroprotective activities in experimental RRD. Given its capacity to protect photoreceptor function during the period of RRD and enhance retinal function following reattachment, K-9 shows promise as a retinal neuroprotectant and warrants study in RRD. Further, this novel RRD/SRR model may facilitate experimental evaluation of functional outcomes relevant to RRD.

Reduction of human Alzheimer's disease risk and reversal of mouse model cognitive deficit with nucleoside analog use

Innate immune signaling through the NLRP3 inflammasome has been implicated in the pathogenesis of Alzheimer's disease (AD), the most prevalent form of dementia. We previously demonstrated that nucleoside reverse transcriptase inhibitors (NRTIs), drugs approved to treat HIV and hepatitis B infections, also inhibit inflammasome activation. Here we report that in humans, NRTI exposure was associated with a significantly lower incidence of AD in two of the largest health insurance databases in the United States. Treatment of aged 5xFAD mice (a mouse model of amyloid-β deposition that expresses five mutations found in familial AD) with Kamuvudine-9 (K-9), an NRTI-derivative with enhanced safety profile, reduced Aβ deposition and reversed their cognitive deficit by improving their spatial memory and learning performance to that of young wild-type mice. These findings support the concept that inflammasome inhibition could benefit AD and provide a rationale for prospective clinical testing of NRTIs or K-9 in AD.

Anti-retroviral treatment with zidovudine alters pyrimidine metabolism, reduces translation, and extends healthy longevity via ATF-4

The human population is aging, and the need for interventions to slow progression of age-related diseases (geroprotective interventions) is growing. Repurposing compounds already used clinically, usually at modified doses, allows rapid implementation of geroprotective pharmaceuticals. Here we find the anti-retroviral nucleoside reverse transcriptase inhibitor (NRTI) zidovudine robustly extends lifespan and health span in C. elegans, independent of electron transport chain impairment or ROS accumulation. Rather, zidovudine treatment modifies pyrimidine metabolism and transcripts related to proteostasis. Testing regulators of mitochondrial stress and proteostasis shows that lifespan extension is dependent on activating transcription factor 4 (ATF-4). ATF-4 regulates longevity induced by mitochondrial stress, specifically communication between mitochondrial and cytosolic translation. Translation is reduced in zidovudine-treated worms, also dependent on ATF-4. Finally, we show ATF-4-dependent lifespan extension induced by didanosine, another NRTI. Altogether, our work elucidates the geroprotective effects of NRTIs such as zidovudine in vivo, via reduction of translation and ATF-4.

HIV Replication Increases the Mitochondrial DNA Content of Plasma Extracellular Vesicles

Extracellular vesicles (EVs) and their cargo have been studied intensively as potential sources of biomarkers in HIV infection; however, their DNA content, particularly the mitochondrial portion (mtDNA), remains largely unexplored. It is well known that human immunodeficiency virus (HIV) infection and prolonged antiretroviral therapy (ART) lead to mitochondrial dysfunction and reduced mtDNA copy in cells and tissues. Moreover, mtDNA is a well-known damage-associated molecular pattern molecule that could potentially contribute to increased immune activation, oxidative stress, and inflammatory response. We investigated the mtDNA content of large and small plasma EVs in persons living with HIV (PLWH) and its implications for viral replication, ART use, and immune status. Venous blood was collected from 196 PLWH, ART-treated or ART-naïve (66 with ongoing viral replication, ≥20 copies/mL), and from 53 HIV-negative persons, all recruited at five HIV testing or treatment centers in Burkina Faso. Large and small plasma EVs were purified and counted, and mtDNA level was measured by RT-qPCR. Regardless of HIV status, mtDNA was more abundant in large than small EVs. It was more abundant in EVs of viremic than aviremic and control participants and tended to be more abundant in participants treated with Tenofovir compared with Zidovudine. When ART treatment was longer than six months and viremia was undetectable, no variation in EV mtDNA content versus CD4 and CD8 count or CD4/CD8 ratio was observed. However, mtDNA in large and small EVs decreased with years of HIV infection and ART. Our results highlight the impact of viral replication and ART on large and small EVs' mtDNA content. The mechanisms underlying the differential incorporation of mtDNA into EVs and their effects on the surrounding cells warrant further investigation.

Association between serum amylase levels and CD4 cell counts in newly diagnosed people living with HIV: A case-control study

Serum amylase is a direct reflection of pancreatic injury. Several clinical studies have indicated that antiretroviral therapy may be the main cause of increased serum amylase in people living with human immunodeficiency virus (PLWH). However, other probable causes including direct human immunodeficiency virus infection, opportunistic infections and neoplasms, alcohol abuse, and use of illicit drugs, which can also affect pancreatic amylase levels were not considered in these studies. In our study, we collected clinical data from newly diagnosed PLWH who had not received antiretroviral therapy, and examined the association between serum amylase levels and CD4 cell counts. Between November 2018 and September 2021, a total of 344 newly diagnosed PLWH and 344 healthy controls were recruited at Ningbo Yinzhou No 2 Hospital. Serum amylase levels, CD4 cell counts and other clinical features were measured. Relationships between serum amylase levels and clinical parameters were evaluated using correlation analysis. Multiple linear regression analyses were performed to identify the independent risk factors. Newly diagnosed PLWH had lower CD4 cell counts and higher serum amylase levels than healthy controls (P < .05). Serum amylase levels were negatively correlated with CD4 cell counts (r = -0.506, P < .001). In multiple linear regression analyses, CD4 cell counts (β = -0.327, 95% confidence interval = -0.051--0.022, P < .001) were independently associated with serum amylase levels. CD4 cell counts were independently associated with serum amylase levels in newly diagnosed PLWH. Thus, close monitoring of serum amylase may be significant in preventing opportunistic infections of PLWH, since low CD4 cell counts are associated with an increased risk of opportunistic infections.

Comparison of the Effects of Three Dual-Nucleos(t)ide Reverse Transcriptase Inhibitor Backbones on Placenta Mitochondria Toxicity and Oxidative Stress Using a Mouse Pregnancy Model

Nucleos(t)ide reverse transcriptase inhibitors (NRTIs) are the backbone of HIV antiretroviral therapy (ART). ART use in pregnancy has been associated with adverse birth outcomes, in part due to NRTI-induced mitochondrial toxicity. Direct comparison on the effects of commonly used dual-NRTI regimens on placental mitochondria toxicity in pregnancy is lacking. We compared zidovudine/lamivudine, abacavir/lamivudine, and tenofovir/emtricitabine using a mouse model and examined markers of placental mitochondrial function and oxidative stress. Zidovudine/lamivudine and abacavir/lamivudine were associated with lower fetal and placental weights compared to controls, whereas tenofovir/emtricitabine was associated with the least fetal and placental weight reduction, as well as lower resorption rates. Placental mitochondrial DNA content, as well as placental expression of cytochrome c-oxidase subunit-II, DNA polymerase gamma, and citrate synthase, was higher in tenofovir/emtricitabine-treated mice compared to other groups. Zidovudine/lamivudine-treated mice had elevated malondialdehyde levels (oxidative stress marker) compared to other groups and lower mRNA levels of manganese superoxide dismutase and peroxisome proliferator-activated receptor gamma coactivator 1-alpha in the placenta compared to tenofovir/emtricitabine-treated mice. We observed differences in effects between NRTI regimens on placental mitochondrial function and birth outcomes. Tenofovir/emtricitabine was associated with larger fetuses, increased mtDNA content, and higher expression of mitochondrial-specific antioxidant enzymes and mitochondrial biogenesis enzymes, whereas zidovudine/lamivudine was associated with markers of placental oxidative stress.

Mitochondria as the Target of Hepatotoxicity and Drug-Induced Liver Injury: Molecular Mechanisms and Detection Methods

One of the major mechanisms of drug-induced liver injury includes mitochondrial perturbation and dysfunction. This is not a surprise, given that mitochondria are essential organelles in most cells, which are responsible for energy homeostasis and the regulation of cellular metabolism. Drug-induced mitochondrial dysfunction can be influenced by various factors and conditions, such as genetic predisposition, the presence of metabolic disorders and obesity, viral infections, as well as drugs. Despite the fact that many methods have been developed for studying mitochondrial function, there is still a need for advanced and integrative models and approaches more closely resembling liver physiology, which would take into account predisposing factors. This could reduce the costs of drug development by the early prediction of potential mitochondrial toxicity during pre-clinical tests and, especially, prevent serious complications observed in clinical settings.

Retrovirus Drugs-Loaded PEGylated PAMAM for Prolonging Drug Release and Enhancing Efficiency in HIV Treatment

Polyamidoamine dendrimer (PAMAM) with its unique characteristics emerges as a potential drug delivery system which can prolong releasing time, reduce the side effects but still retaining treatment efficiency. In this study, methoxy polyethylene glycol modified PAMAM generation 3.0 (G3.0@mPEG) is prepared and characterized via 1H-NMR, FT-IR, and TEM. Subsequently, two antiretroviral agents (ARV) including lamivudine (3TC) and zidovudine (AZT) are individually encapsulated into G3.0@mPEG. The drug-loading efficiency, drug release profile, cytotoxicity and anti-HIV activity are then evaluated. The results illustrate that G3.0@mPEG particles are spherical with a size of 34.5 ± 0.2 nm and a drug loading content of about 9%. Both G3.0@mPEG and ARV@G3.0@mPEG show no cytotoxicity on BJ cells, and G3.0@mPEG loading 3TC and AZT performs sustained drug release behavior which is best fitted with the Korsmeyer-Peppas model. Finally, the anti-HIV activity of ARV via Enzymatic Assay of Pepsin is retained after being loaded into the G3.0@mPEG, in which about 36% of pepsin activity was inhibited by AZT at the concentration of 0.226 mM. Overall, PAMAM G3.0@mPEG is a promising nanocarrier system for loading ARV in HIV treatment and prevention.

Mitochondrial DNA Instability Is Common in HIV-Exposed Uninfected Newborns

Worldwide, one million HIV-exposed uninfected (HEU) children are born yearly, and chronic health impairments have been reported in these children. Mitochondrial DNA (mtDNA) instability and altered mtDNA content have been evidenced in these children, but an exhaustive characterization of altered mitochondrial genomes has never been reported. We applied deep mtDNA sequencing coupled to the deletion identification algorithm eKLIPse to the blood of HEU neonates (n = 32), which was compared with healthy controls (n = 15). Dried blood spots (DBS) from African HEU children were collected seven days after birth between November 2009 and May 2012. DBS from French healthy controls were collected at birth (or <3 days of life) in 2012 and in 2019. In contrast to the absence of mtDNA instability observed at the nucleotide level, we identified significant amounts of heteroplasmic mtDNA deletions in 75% of HEU children and in none of controls. The heteroplasmy rate of the 62 mtDNA deletions identified varied from 0.01% to up to 50%, the highest rates being broadly compatible with bioenergetic defect and clinical expression. mtDNA integrity is commonly affected in HEU neonates. The nature of the deletions suggests a mechanism related to aging or tumor-associated mtDNA instability. This child population may be at risk of additional mtDNA genetic alterations considering that they will be exposed to other mitotoxic drugs including antiretroviral or anti-tuberculosis treatment.

Long-term treated HIV infection is associated with platelet mitochondrial dysfunction

HIV infection and antiretroviral therapy have been linked to mitochondrial dysfunction. The role of platelet mitochondrial dysfunction in thrombosis, immunoregulation and age-related diseases is increasingly appreciated. Here, we studied platelet mitochondrial DNA content (mtDNA_pl) and mitochondrial function in people living with HIV (PLHIV) and related this to platelet function. In a cohort of 208 treated PLHIV and 56 uninfected controls, mtDNA_pl was quantified, as well as platelet activation, platelet agonist-induced reactivity and inflammation by circulating factors and flow cytometry. In a subgroup of participants, the metabolic activity of platelets was further studied by mitochondrial function tests and the Seahorse Flux Analyzer. PLHIV had significantly lower mtDNA_pl compared to controls (8.5 copies/platelet (IQR: 7.0–10.7) vs. 12.2 copies/platelet (IQR: 9.5–16.6); p < 0.001), also after correction for age, sex and BMI. Prior zidovudine-use (n = 46) was associated with a trend for lower mtDNA_pl. PLHIV also had reduced ex vivo platelet reactivity and mean platelet volume compared to controls. MtDNA_pl correlated positively with both platelet parameters and correlated negatively with inflammatory marker sCD163. Mitochondrial function tests in a subgroup of participants confirmed the presence of platelet mitochondrial respiration defects. Platelet mitochondrial function is disturbed in PLHIV, which may contribute to platelet dysfunction and subsequent complications. Interventions targeting the preservation of normal platelet mitochondrial function may ultimately prove beneficial for PLHIV.

Drugs Affecting Body Weight, Body Fat Distribution, and Metabolic Function-Mechanisms and Possible Therapeutic or Preventive Measures: an Update

PURPOSE OF REVIEW

Weight gain and body fat redistribution are common side effects of many widely used drugs. We summarize recent literature on prevalence data and mechanisms associated with drug-induced body fat changes and mechanisms to prevent or treat metabolic side effects.

RECENT FINDINGS

The highest prevalence of metabolic complications is seen with antipsychotics and antiretroviral drugs used in the treatment of HIV and may, at least partly, be responsible for the increased risk for co-morbid diseases such as diabetes, steatosis of the liver, and cardiovascular disease. The pathogenetic mechanisms leading to weight gain from antipsychotics are increasingly known and help to unravel the complex interaction that exists between psychopathology and metabolic complications. Although the classic lipodystrophy mainly occurred with older HIV drugs, also with the newer HIV treatment, weight gain seems to be a major side effect. Early detection of the metabolic consequences of drugs can lead to an early diagnosis of the complications and their treatment. Different medications, including the newer antidiabetics, are being studied in the therapy of drug-induced obesity. Future research should focus on identifying individuals at risk for metabolic side effects and on early markers to identify individuals with side effects so that timely treatment of metabolic complications can be initiated.

Growth, clinical and neurodevelopmental outcomes at school age are similar for children who received 1-year lamivudine or lopinavir/ritonavir HIV prophylaxis in early life

In the ANRS 12174 trial, HIV-exposed uninfected African neonates who received lopinavir-ritonavir (LPV/r) prophylaxis for 1 year exhibited slower growth from birth to week 50 compared with those receiving lamivudine (3TC). We assessed whether this difference in growth persisted over time, and was accompanied by differences in neuropsychological and clinical outcomes. Between February 2017 and February 2018, we conducted a cross-sectional clinical evaluation among former trial participants who completed the 50-week follow-up and who were not HIV-infected. In addition to clinical examination, neuropsychological outcomes were assessed using the tests Kaufman-ABCII, Test of Variables of Attention, Movement Assessment Battery for Children and the Strengths and Difficulties questionnaire, parent version. Of 1101 eligible children, aged 5–7 years, 553 could be traced and analysed (274 in the LPV/r and 279 in the 3TC groups). Growth, clinical and neuropsychological outcomes did not differ between treatment groups. At school age, children exposed to LPV/r and 3TC at birth for 1 year had comparable growth and neuropsychological outcomes without evidence of long-term side-effects of LPV/r. It provides reassuring data on clinical outcomes for all HIV-infected children treated with this antiretroviral drug in early life.

Aloe-emodin relieves zidovudine-induced injury in neonatal rat ventricular myocytes by regulating the p90rsk/p-bad/bcl-2 signaling pathway

BACKGROUND/AIMS

Zidovudine (3'-azido-2',3'-deoxythymidine; AZT) is a first-line drug for treatment of human immunodeficiency virus infection (HIV). However, its application is limited by cardiotoxicity due to cardiomyocyte injury. This study investigated whether Aloe-emodin (AE), an anthraquinone compound, protects against AZT-induced cardiomyocyte toxicity.

METHODS

MTT, JC-1 assays and TUNEL were examined to verify the protective effect of AE against AZT-induced cardiomyocyte injury. Western blotting was performed to explore the anti-apoptotic effect of AE using anti-apoptotic proteins p90rsk, p-bad, and bcl-2 and pro-apoptotic proteins apaf-1, cleaved-caspase-3, and cytochrome c.

RESULTS

We observed a protective effect of AE against cell viability decrease and TUNEL positive cells increase induced by AZT, which was counteracted by BI-D1870. Western blot analysis found that AE significantly inhibited cardiomyocyte apoptosis by activating p90rsk/p-bad/bcl-2 signaling pathway. Furthermore, BI-D1870 counteracted the anti-apoptotic effect of AE.

CONCLUSIONS

Taken together, these results indicate that AE attenuated AZT-induced cardiomyocyte apoptosis by activating p90rsk.

Mitochondrial DNA Parameters in Blood of Infants Receiving Lopinavir/Ritonavir or Lamivudine Prophylaxis to Prevent Breastfeeding Transmission of HIV-1

Children who are human immunodeficiency virus (HIV)-exposed but uninfected (CHEU) accumulate maternal HIV and antiretroviral exposures through pregnancy, postnatal prophylaxis, and breastfeeding. Here, we compared the dynamics of mitochondrial DNA (mtDNA) parameters in African breastfed CHEU receiving lopinavir/ritonavir (LPV/r) or lamivudine (3TC) pre-exposure prophylaxis during the first year of life. The number of mtDNA copies per cell (MCN) and the proportion of deleted mtDNA (MDD) were assessed at day 7 and at week 50 post-delivery (PrEP group). mtDNA depletion was defined as a 50% or more decrease from the initial value, and mtDNA deletions was the detection of mtDNA molecules with large DNA fragment loss. We also performed a sub-analysis with CHEU who did not receive a prophylactic treatment in South Africa (control group). From day seven to week 50, MCN decreased with a median of 41.7% (interquartile range, IQR: 12.1; 64.4) in the PrEP group. The proportion of children with mtDNA depletion was not significantly different between the two prophylactic regimens. Poisson regressions showed that LPV/r and 3TC were associated with mtDNA depletion (reference: control group; LPV/r: PR = 1.75 (CI95%: 1.15–2.68), p < 0.01; 3TC: PR = 1.54 (CI95%: 1.00–2.37), p = 0.05). Moreover, the proportion of children with MDD was unexpectedly high before randomisation in both groups. Long-term health impacts of these mitochondrial DNA parameters should be investigated further for both CHEU and HIV-infected children receiving LPV/r- or 3TC- based regimens.

Recent Advances in the Development of Integrase Inhibitors for HIV Treatment

PURPOSE OF THE REVIEW

The complex multistep life cycle of HIV allows it to proliferate within the host and integrate its genome in to the host chromosomal DNA. This provirus can remain dormant for an indefinite period. The process of integration, governed by integrase (IN), is highly conserved across the Retroviridae family. Hence, targeting integration is not only expected to block HIV replication but may also reveal new therapeutic strategies to treat HIV as well as other retrovirus infections.

RECENT FINDINGS

HIV integrase (IN) has gained attention as the most promising therapeutic target as there are no equivalent homologues of IN that has been discovered in humans. Although current nano-formulated long-acting IN inhibitors have demonstrated the phenomenal ability to block HIV integration and replication with extraordinary half-life, they also have certain limitations. In this review, we have summarized the current literature on clinically established IN inhibitors, their mechanism of action, the advantages and disadvantages associated with their therapeutic application, and finally current HIV cure strategies using these inhibitors.

Mitochondrial and Oxidative Impacts of Short and Long-term Administration of HAART on HIV Patients

BACKGROUND

There may be a possible link between the use of HAART and oxidative stress-related mitochondrial dysfunction in HIV patients. We evaluated the mitochondrial and oxidative impacts of short and long-term administration of HAART on HIV patients attending the Enugu State University Teaching (ESUT) Hospital, Enugu, Nigeria following short and long-term therapy.

METHODS

96 patients categorized into four groups of 24 individuals were recruited for the study. Group 1 comprised of age-matched, apparently healthy, sero-negative individuals (the No HIV group); group 2 consisted of HIV sero-positive individuals who had not started any form of treatment (the Treatment naïve group). Individuals in group 3 were known HIV patients on HAART for less than one year (Short-term treatment group), while group 4 comprised of HIV patients on HAART for more than one year (Long-term treatment group). All patients were aged between 18 to 60 years and attended the HIV clinic at the time of the study. Determination of total antioxidant status (TAS in nmol/l), malondialdehyde (MDA in mmol/l), CD4+ count in cells/μl, and genomic studies were all done using standard operative procedures.

RESULTS

We found that the long-term treatment group had significantly raised the levels of MDA, as well as significantly diminished TAS compared to the Short-term treatment and No HIV groups (P<0.05). In addition, there was significantly elevated variation in the copy number of mitochondrial genes (mtDNA: D-loop, ATPase 8, TRNALEU uur) in the long-term treatment group.

CONCLUSION

Long-term treatment with HAART increases oxidative stress and causes mitochondrial alterations in HIV patients.

Mitochondrial dysfunctions in HIV infection and antiviral drug treatment

Introduction: With the introduction of highly active anti-retroviral therapy (HAART), treatment of HIV infection has improved radically, shifting the concept of HIV disease from a highly mortal epidemic to a chronic illness which needs systematic management. However, HAART does not target the integrated proviral DNA. Hence, prolonged use of antiviral drugs is needed for sustaining life. As a consequence, severe side effects emerge. Several parameters involve in causing these adverse effects. Mitochondrial dysfunctions were pointed as common factor among them. It is, therefore, necessary to critically examine mitochondrial dysfunction in order to understand the side effects.Areas covered: There are many events involved in causing drug-induced side-effects; in this review, we only highlight mitochondrial dysfunctions as one of the events. We present up-to-date findings on mitochondrial dysfunction caused by HIV infection and antiviral drug treatment. Both in vivo and in vitro studies on mitochondrial dysfunction like change in morphology, membrane depolarization, mitophagy, mitochondrial DNA depletion, and intrinsic apoptosis have been discussed.Expert opinion: Mitochondrial dysfunction is associated with severe complications that often lead to discontinuation or change in treatment regimen. Prior knowledge of side effects of antiviral drugs would help in better management and future research should focus to avoid mitochondrial targeting of antiviral drugs while maintaining their antiviral properties.

Some Aspects of CD8+ T-Cell Exhaustion Are Associated With Altered T-Cell Mitochondrial Features and ROS Content in HIV Infection

BACKGROUND

Reversing or preventing T-cell exhaustion is an important treatment goal in the context of HIV disease; however, the mechanisms that regulate HIV-specific CD8 T-cell exhaustion are incompletely understood. Since mitochondrial mass (MM), mitochondrial membrane potential (MMP), and cellular reactive oxygen species (ROS) content are altered in exhausted CD8 T cells in other settings, we hypothesized that similar lesions may arise in HIV infection.

METHODS

We sampled cryopreserved peripheral blood mononuclear cells from HIV-uninfected (n = 10) and HIV-infected participants with varying levels and mechanisms of viral control: viremic (VL > 2000 copies/mL; n = 8) or aviremic (VL < 40 copies/mL) due to antiretroviral therapy (n = 11) or natural control (n = 9). We characterized the MM, MMP, and ROS content of bulk CD8 T cells and MHC class I tetramer+ HIV-specific CD8 T cells by flow cytometry.

RESULTS

We observed higher MM, MMP, and ROS content across bulk effector-memory CD8 T-cell subsets in HIV-infected compared with HIV-uninfected participants. Among HIV-specific CD8 T cells, these features did not vary by the extent or mechanism of viral control but were significantly altered in cells displaying characteristics associated with exhaustion (eg, high PD-1 expression, low CD127 expression, and impaired proliferative capacity).

CONCLUSIONS

While we did not find that control of HIV replication in vivo correlates with the CD8 T-cell MM, MMP, or ROS content, we did find that some features of CD8 T-cell exhaustion are associated with alterations in mitochondrial state. Our findings support further studies to probe the relationship between mitochondrial dynamics and CD8 T-cell functionality in HIV infection.

Analysis of Human Mitochondrial DNA Content by Southern Blotting and Nonradioactive Probe Hybridization

A single cell can contain several thousand copies of the mitochondrial DNA genome or mtDNA. Tools for assessing mtDNA content are necessary for clinical and toxicological research, as mtDNA depletion is linked to genetic disease and drug toxicity. For instance, mtDNA depletion syndromes are typically fatal childhood disorders that are characterized by severe declines in mtDNA content in affected tissues. Mitochondrial toxicity and mtDNA depletion have also been reported in human immunodeficiency virus-infected patients treated with certain nucleoside reverse transcriptase inhibitors. Further, cell culture studies have demonstrated that exposure to oxidative stress stimulates mtDNA degradation. Here we outline a Southern blot and nonradioactive digoxigenin-labeled probe hybridization method to estimate mtDNA content in human genomic DNA samples. © 2019 by John Wiley & Sons, Inc.

Pyrimidine 2,4-Diones in the Design of New HIV RT Inhibitors

The pyrimidine nucleus is a versatile core in the development of antiretroviral agents. On this basis, a series of pyrimidine-2,4-diones linked to an isoxazolidine nucleus have been synthesized and tested as nucleoside analogs, endowed with potential anti-HIV (human immunodeficiency virus) activity. Compounds 6a-c, characterized by the presence of an ethereal group at C-3, show HIV reverse transcriptase (RT) inhibitor activity in the nanomolar range as well as HIV-infection inhibitor activity in the low micromolar with no toxicity. In the same context, compound 7b shows only a negligible inhibition of RT HIV.

Cardiac and mitochondrial function in HIV-uninfected fetuses exposed to antiretroviral treatment

BACKGROUND

Mitochondrial toxicity related to maternal combined antiretroviral treatment (cART) may have an impact on the heart of HIV-exposed uninfected (HEU) fetuses. Our objective was to evaluate fetal cardiovascular and mitochondrial biomarkers in HIV pregnancies.

METHODS

Prospective cohort including 47 HIV-infected and 47 non HIV-infected pregnancies. Fetal echocardiography was performed at 26-32 weeks of pregnancy. Umbilical cord blood and placental tissue were collected to study mitochondrial DNA content (mtDNA) (ratio 12SrRNA/RNAseP) and mitochondrial function (cytochrome c oxidase, COX, enzymatic activity) normalized by mitochondrial content (citrate synthase, CS).

RESULTS

HEU fetuses showed hypertrophic hearts (left myocardial wall thickness: HIV mean 3.21 mm (SD 0.81) vs. non-HIV 2.72 (0.42), p = 0.012), with signs of systolic and diastolic dysfunction (isovolumic relaxation time: HIV 52.2 ms (8.85) vs. non-HIV 42.5 ms (7.30); p<0.001). Cord blood mitochondrial content was significantly increased in HIV-exposed fetuses (CS activity: HIV 82.9 nmol/min.mg of protein (SD 40.5) vs. non-HIV 56.7 nmol/min.mg of protein (28.4); p = 0.007), with no differences in mtDNA content and COX activity. Both myocardial and mitochondrial mass parameters were significantly associated with zidovudine exposure.

CONCLUSIONS

HEU fetuses showed signs of increased myocardial and mitochondrial mass associated with maternal zidovudine treatment, suggesting a fetal adaptive response to cART toxicity.

Myoblast mitochondrial respiration is decreased in chronic binge alcohol administered simian immunodeficiency virus-infected antiretroviral-treated rhesus macaques

Work from our group demonstrated that chronic binge alcohol (CBA)-induces mitochondrial gene dysregulation at end-stage disease of simian immunodeficiency virus (SIV) infection in antiretroviral therapy (ART) naïve rhesus macaques. Alterations in gene expression can disrupt mitochondrial homeostasis and in turn contribute to the risk of metabolic comorbidities characterized by loss of skeletal muscle (SKM) functional mass that are associated with CBA, human immunodeficiency virus (HIV) infection, and prolonged ART. The aim of this study was to examine the interaction of CBA and ART on SKM fiber oxidative capacity and myoblast mitochondrial respiration in asymptomatic SIV-infected macaques. SKM biopsies were obtained and myoblasts isolated at baseline and 11 months post-SIV infection from CBA/SIV/ART+ and from sucrose (SUC)-treated SIV-infected (SUC/SIV/ART+) macaques. CBA and ART decreased succinate dehydrogenase (SDH) activity in type 1 and type 2b fibers as determined by immunohistochemistry. Myoblasts isolated from CBA/SIV/ART+ macaques showed decreased maximal oxygen consumption rate (OCR) compared to myoblasts from control macaques. Maximal OCR was significantly increased in control myoblasts following incubation with formoterol, a beta adrenergic agonist, and this was associated with increased PGC-1α expression and mtDNA quantity. Additionally, formoterol treatment of myoblasts isolated from CBA/SIV/ART+ macaques partially restored maximal OCR to levels not significantly different from control. These results show that CBA in combination with ART impairs myoblast mitochondrial homeostasis in SIV-infected macaques. Moreover, our findings suggest that adrenergic agonists can potentially ameliorate mitochondrial dysfunction. Future studies will elucidate whether physical exercise in HIV patients with alcohol use disorder can improve mitochondrial health.

Off-Target Effects of Drugs that Disrupt Human Mitochondrial DNA Maintenance

Nucleoside reverse transcriptase inhibitors (NRTIs) were the first drugs used to treat human immunodeficiency virus (HIV) the cause of acquired immunodeficiency syndrome. Development of severe mitochondrial toxicity has been well documented in patients infected with HIV and administered NRTIs. In vitro biochemical experiments have demonstrated that the replicative mitochondrial DNA (mtDNA) polymerase gamma, Polg, is a sensitive target for inhibition by metabolically active forms of NRTIs, nucleotide reverse transcriptase inhibitors (NtRTIs). Once incorporated into newly synthesized daughter strands NtRTIs block further DNA polymerization reactions. Human cell culture and animal studies have demonstrated that cell lines and mice exposed to NRTIs display mtDNA depletion. Further complicating NRTI off-target effects on mtDNA maintenance, two additional DNA polymerases, Pol beta and PrimPol, were recently reported to localize to mitochondria as well as the nucleus. Similar to Polg, in vitro work has demonstrated both Pol beta and PrimPol incorporate NtRTIs into nascent DNA. Cell culture and biochemical experiments have also demonstrated that antiviral ribonucleoside drugs developed to treat hepatitis C infection act as off-target substrates for POLRMT, the mitochondrial RNA polymerase and primase. Accompanying the above-mentioned topics, this review examines: (1) mtDNA maintenance in human health and disease, (2) reports of DNA polymerases theta and zeta (Rev3) localizing to mitochondria, and (3) additional drugs with off-target effects on mitochondrial function. Lastly, mtDNA damage may induce cell death; therefore, the possibility of utilizing compounds that disrupt mtDNA maintenance to kill cancer cells is discussed.

Lactate serum concentrations during treatment with nucleos(t)ide analogues in hepatitis B with or without cirrhosis

OBJECTIVE

The aim of this study is to evaluate the clinical implications of lactate concentrations in patients with hepatitis B with or without cirrhosis during treatment with nucleos(t)ide analogues.

PATIENTS AND METHODS

One hundred and seven consecutive patients with chronic hepatitis B and median age 57 (24-85) years were prospectively included. Lactate concentrations were measured at baseline and at 12, 24, 36, 48, and 60 months following the baseline measurements. Eight (n=8, 7.5%) patients received lamivudine, 38 (n=38, 35.5%) patients received tenofovir, 34 (n=34, 31.8%) patients received entecavir, and 27 (n=27, 25.2%) patients received combined therapy.

RESULTS

None of the patients developed lactic acidosis during follow-up [median: 58 (6-155) months]. Overall, no trends of the lactic acid evolution were observed over time; however, there was a nonsignificant increasing trend in patients with cirrhosis up to 24 months of treatment. This increasing trend was significant in female patients with cirrhosis (P=0.016). The age of the patients, the presence of cirrhosis, and hepatocellular carcinoma were strongly associated with the survival of all patients. In the group of cirrhotic patients, the only independent prognostic factor that was associated with patients' survival was the Child-Pugh class.

CONCLUSION

None of the patients developed lactic acidosis. There is an indication of an increasing trend of lactic acid levels up to 24 months of therapy in female cirrhotic patients.

Azidothymidine-triphosphate impairs mitochondrial dynamics by disrupting the quality control system

Highly active anti-retrovirus therapy (HAART) has been used to block the progression and symptoms of human immunodeficiency virus infection. Although it decreases morbidity and mortality, clinical use of HAART has also been linked to various adverse effects such as severe cardiomyopathy resulting from compromised mitochondrial functioning. However, the mechanistic basis for these effects remains unclear. Here, we demonstrate that a key component of HAART, 3ꞌ-azido-3ꞌ-deoxythymidine (AZT), particularly, its active metabolite AZT-triphosphate (AZT-TP), caused mitochondrial dysfunction, leading to induction of cell death in H9c2 cells derived from rat embryonic myoblasts, which serve as a model for cardiomyopathy. Specifically, treatment with 100µM AZT for 48h disrupted the mitochondrial tubular network via accumulation of AZT-TP. The mRNA expression of dynamin-related protein (Drp)1 and the Drp1 receptor mitochondrial fission factor (Mff) was upregulated whereas that of optic atrophy 1 (Opa1) was downregulated following AZT treatment. Increased mitochondrial translocation of Drp1, Mff upregulation, and decreased functional Opa1 expression induced by AZT impaired the balance of mitochondrial fission vs. fusion. These data demonstrate that AZT-TP causes cell death by altering mitochondrial dynamics.

Chemical structure and correlation analysis of HIV-1 NNRT and NRT inhibitors and database-curated, published inhibition constants with chemical structure in diverse datasets

Human immunodeficiency virus (HIV-1) reverse transcriptase is a major target for designing anti-HIV drugs. Developed inhibitors are divided into non-nucleoside analog reverse-transcriptase inhibitors (NNRTIs) and nucleoside analog reverse-transcriptase inhibitors (NRTIs) depending on their mechanism. Given that many inhibitors have been studied and for many of them binding affinity constants have been calculated, it is beneficial to analyze the chemical landscape of these families of inhibitors and correlate these inhibition constants with molecular structure descriptors. For this, the HIV-1 RT data was retrieved from the ChEMBL database, carefully curated, and original literature verified, grouped into NRTIs and NNRTIs, analyzed using a hierarchical scaffold classification method and modelled with best multi-linear regression approach. Analysis of the HIV-1 NNRTIs subset results in ten different common structural parent types of oxazepanone, piperazinone, pyrazine, oxazinanone, diazinanone, pyridine, pyrrole, diazepanone, thiazole, and triazine. The same analysis for HIV-1 NRTIs groups structures into four different parent types of uracil, pyrimide, pyrimidione, and imidazole. Each scaffold tree corresponding to the parent types has been carefully analyzed and examined, and changes in chemical structure favorable to potency and stability are highlighted. For both subsets, descriptive and predictive QSAR models are derived, discussed and externally validated, revealing general trends in relationships between molecular structure and binding affinity constants in structurally diverse datasets. Data and QSAR models are available at the QsarDB repository (http://dx.doi.org/10.15152/QDB.202).

From the Cover: Investigative Nonclinical Cardiovascular Safety and Toxicology Studies with BMS-986094, an NS5b RNA-Dependent RNA Polymerase Inhibitor

BMS-986094, a 2'-C-methylguanosine prodrug that was in development for treatment of chronic hepatitis C infection was withdrawn from Phase 2 clinical trials because of unexpected cardiac and renal adverse events. Investigative nonclinical studies were conducted to extend the understanding of these findings using more comprehensive endpoints. BMS-986094 was given orally to female CD-1 mice (25 and 150 mg/kg/d) for 2 weeks (53/group) and to cynomolgus monkeys (15 and 30 mg/kg/d) for up to 6 weeks (2-3/sex/group for cardiovascular safety, and 5/sex/group for toxicology). Endpoints included toxicokinetics; echocardiography, telemetric hemodynamics and electrocardiography, and tissue injury biomarkers (monkey); and light and ultrastructural pathology of heart, kidney, and skeletal muscle (mouse/monkey). Dose-related and time-dependent findings included: severe toxicity in mice at 150 mg/kg/d and monkeys at 30 mg/kg/d; decreased left ventricular (LV) ejection fraction, fractional shortening, stroke volume, and dP/dt; LV dilatation, increased QTc interval, and T-wave flattening/inversion (monkeys at ≥ 15 mg/kg/d); cardiomyocyte degeneration (mice at 150 mg/kg/d and monkeys at ≥ 15 mg/kg/d) with myofilament lysis/myofbril disassembly; time-dependent proteinuria and increased urine β-2 microglobulin, calbindin, clusterin; kidney pallor macroscopically; and tubular dilatation (monkeys); tubular regeneration (mice 150 mg/kg/d); and acute proximal tubule degeneration ultrastructurally (mice/monkeys); and skeletal muscle degeneration with increased urine myoglobin and serum sTnI. These studies identified changes not described previously in studies of BMS-986094 including premonitory cardiovascular functional changes as well as additional biomarkers for muscle and renal toxicities. Although the mechanism of potential toxicities observed in BMS-986094 studies was not established, there was no evidence for direct mitochondrial toxicity.

The purine analogues abacavir and didanosine increase acetaminophen-induced hepatotoxicity by enhancing mitochondrial dysfunction

BACKGROUND

NRTIs are essential components of HIV therapy with well-documented, long-term mitochondrial toxicity in hepatic cells, but whose acute effects on mitochondria are unclear. As acetaminophen-induced hepatotoxicity also involves mitochondrial interference, we hypothesized that it would be exacerbated in the context of ART.

METHODS

We evaluated the acute effects of clinically relevant concentrations of the most widely used NRTIs, alone or combined with acetaminophen, on mitochondrial function and cellular viability.

RESULTS

The purine analogues abacavir and didanosine produced an immediate and concentration-dependent inhibition of oxygen consumption and complex I and III activity. This inhibition was accompanied by an undermining of mitochondrial function, with increased production of reactive oxygen species and reduction of mitochondrial membrane potential and intracellular ATP levels. However, this interference did not compromise cell survival. Co-administration with concentrations of acetaminophen below those considered hepatotoxic exacerbated the deleterious effects of both compounds on mitochondrial function and compromised cellular viability, showing a clear correlation with diminished glutathione levels.

CONCLUSIONS

The simultaneous presence of purine analogues and low concentrations of acetaminophen significantly potentiates mitochondrial dysfunction, increasing the risk of liver injury. This new mechanism is relevant given the liver's susceptibility to mitochondrial dysfunction-related toxicity and the tendency of the HIV infection to increase oxidative stress.

Decreased Mitochondrial Function Among Healthy Infants Exposed to Antiretrovirals During Gestation, Delivery and the Neonatal Period

BACKGROUND

Antiretroviral (ARV)-associated mitochondrial toxicity in HIV/ARV-exposed healthy infants is a concern. Clinically relevant toxicity is rare. Hyperlactatemia is common but nonspecific, both increased and decreased mitochondrial DNA (mtDNA) level has been reported. Mitochondrial function has scarcely been investigated.

METHODS

In a prospective observational study of 133 HIV/ARV-exposed infants, mtDNA content was measured with quantitative real-time polymerase chain reaction, and mitochondrial respiratory chain enzymatic activity of complex IV (CIV) and mitochondrial mass (MM) were assessed spectrophotometrically from cryopreserved peripheral blood mononuclear cells obtained at 6 weeks and 3, 6 and 12 months of age and compared with a control group.

RESULTS

Most mothers (88%) received combined ARV therapy during pregnancy, and 92% of infants received zidovudine monotherapy. No infant had clinical evidence of mitochondrial disease during follow-up. Nonsignificant higher MM and lower mtDNA levels (normalized by MM) were observed over time in HIV/ARV-exposed infants. MM-normalized CIV activity was consistently lower in HIV/ARV-exposed children than in controls over time (0.09 vs. 0.35, 0.12 vs. 0.38, 0.13 vs. 0.24 and 0.14 vs. 0.24 nmol/min/mg at 6 weeks and 3, 6 and 12 months; P = 0.014, P < 0.0001, P = 0.065 and P = 0.011, respectively) and showed a linear trend toward normalization with age (P < 0.01). In HIV/ARV-exposed infants, an inverse correlation between CIV activity and mtDNA levels was observed until 6 months of age (r = -0.327, P = 0.016; r = -0.311, P = 0.040 and r = -0.275, P = 0.046).

CONCLUSIONS

Mitochondrial-encoded CIV activity was consistently lower among HIV/ARV-exposed healthy infants and inversely correlated with mtDNA levels, suggesting upregulation of the latter.

Effect of Cumulating Exposure to Abacavir on the Risk of Cardiovascular Disease Events in Patients From the Swiss HIV Cohort Study

BACKGROUND

Patients with HIV exposed to the antiretroviral drug abacavir may have an increased risk of cardiovascular disease (CVD). There is concern that this association arises because of a channeling bias. Even if exposure is a risk, it is not clear how that risk changes as exposure cumulates.

METHODS

We assess the effect of exposure to abacavir on the risk of CVD events in the Swiss HIV Cohort Study. We use a new marginal structural Cox model to estimate the effect of abacavir as a flexible function of past exposures while accounting for risk factors that potentially lie on a causal pathway between exposure to abacavir and CVD.

RESULTS

A total of 11,856 patients were followed for a median of 6.6 years; 365 patients had a CVD event (4.6 events per 1000 patient-years). In a conventional Cox model, recent--but not cumulative--exposure to abacavir increased the risk of a CVD event. In the new marginal structural Cox model, continued exposure to abacavir during the past 4 years increased the risk of a CVD event (hazard ratio = 2.06; 95% confidence interval: 1.43 to 2.98). The estimated function for the effect of past exposures suggests that exposure during the past 6-36 months caused the greatest increase in risk.

CONCLUSIONS

Abacavir increases the risk of a CVD event: the effect of exposure is not immediate, rather the risk increases as exposure cumulates over the past few years. This gradual increase in risk is not consistent with a rapidly acting mechanism, such as acute inflammation.

Fibroblast growth factor 23: associations with antiretroviral therapy in patients co-infected with HIV and hepatitis C

OBJECTIVES

Fibroblast growth factor 23 (FGF23) has been associated with cardiovascular mortality. We estimate associations between the level of plasma FGF23 and exposure to abacavir (ABC) and to other components of antiretroviral therapy in patients co-infected with HIV and hepatitis C.

METHODS

Both intact and c-terminal FGF23 were measured in plasma using commercial assays for a sub-cohort of 295 patients selected at random from the 1150 patients enrolled in the Canadian Co-infection Cohort. The multiplicative effects of antiretroviral drug exposures and covariates on median FGF23 were then estimated using a hierarchical Bayesian model.

RESULTS

The median level of intact FGF23 was independent of either past or recent exposure to abacavir, with multiplicative ratios of 1.00 and 1.07, 95% credible intervals 0.90-1.12 and 0.94-1.23, respectively. Median intact FGF23 tended to increase with past use of both nonnucleoside reverse-transcriptase inhibitors and protease inhibitors, but tended to decrease with recent use of either tenofovir, efavirenz or lopinavir. There were no obvious associations between the median level of c-terminal FGF23 and individual drugs or drug classes. Age, female gender, smoking and the aspartate aminotransferase to platelet ratio index were all associated with a higher median c-terminal FGF23 but not with a higher median intact FGF23.

CONCLUSIONS

The level of FGF23 in plasma was independent of exposure to ABC. Lower levels of intact FGF23 with recent use of tenofovir, efavirenz or lopinavir may reflect their adverse effects on bone and vitamin D metabolism relative to other drugs in their respective drug classes.

Probing the structural and molecular basis of nucleotide selectivity by human mitochondrial DNA polymerase γ

Nucleoside analog reverse transcriptase inhibitors (NRTIs) are the essential components of highly active antiretroviral (HAART) therapy targeting HIV reverse transcriptase (RT). NRTI triphosphates (NRTI-TP), the biologically active forms, act as chain terminators of viral DNA synthesis. Unfortunately, NRTIs also inhibit human mitochondrial DNA polymerase (Pol γ), causing unwanted mitochondrial toxicity. Understanding the structural and mechanistic differences between Pol γ and RT in response to NRTIs will provide invaluable insight to aid in designing more effective drugs with lower toxicity. The NRTIs emtricitabine [(-)-2,3'-dideoxy-5-fluoro-3'-thiacytidine, (-)-FTC] and lamivudine, [(-)-2,3'-dideoxy-3'-thiacytidine, (-)-3TC] are both potent RT inhibitors, but Pol γ discriminates against (-)-FTC-TP by two orders of magnitude better than (-)-3TC-TP. Furthermore, although (-)-FTC-TP is only slightly more potent against HIV RT than its enantiomer (+)-FTC-TP, it is discriminated by human Pol γ four orders of magnitude more efficiently than (+)-FTC-TP. As a result, (-)-FTC is a much less toxic NRTI. Here, we present the structural and kinetic basis for this striking difference by identifying the discriminator residues of drug selectivity in both viral and human enzymes responsible for substrate selection and inhibitor specificity. For the first time, to our knowledge, this work illuminates the mechanism of (-)-FTC-TP differential selectivity and provides a structural scaffold for development of novel NRTIs with lower toxicity.

Structural basis for processivity and antiviral drug toxicity in human mitochondrial DNA replicase

The human DNA polymerase gamma (Pol γ) is responsible for DNA replication in mitochondria. Pol γ is particularly susceptible to inhibition by dideoxynucleoside-based inhibitors designed to fight viral infection. Here, we report crystal structures of the replicating Pol γ-DNA complex bound to either substrate or zalcitabine, an inhibitor used for HIV reverse transcriptase. The structures reveal that zalcitabine binds to the Pol γ active site almost identically to the substrate dCTP, providing a structural basis for Pol γ-mediated drug toxicity. When compared to the apo form, Pol γ undergoes intra- and inter-subunit conformational changes upon formation of the ternary complex with primer/template DNA and substrate. We also find that the accessory subunit Pol γB, which lacks intrinsic enzymatic activity and does not contact the primer/template DNA directly, serves as an allosteric regulator of holoenzyme activities. The structures presented here suggest a mechanism for processivity of the holoenzyme and provide a model for understanding the deleterious effects of Pol γ mutations in human disease. Crystal structures of the mitochondrial DNA polymerase, Pol γ, in complex with substrate or antiviral inhibitor zalcitabine provide a basis for understanding Pol γ-mediated drug toxicity.

The brain and HAART: collaborative and combative connections

PURPOSE OF REVIEW

To summarize contemporary observations regarding the effects of highly active antiretroviral therapy (HAART) on the brain.

RECENT FINDINGS

The effects of HAART on the structure and function of the brain during HIV/AIDS is currently a subject of intense interest because the brain is one of the most drug-impenetrable organs that is infected by HIV-1 and as such represents an important reservoir for replication-competent virus. The effects of HAART on neurocognitive impairment caused by HIV-1 infection remain uncertain with both beneficial and adverse outcomes reported with different HAART regimens. Similarly, the effects of individual HAART regimens on viral quantity in cerebrospinal fluid as a surrogate indicator of brain virus burden are variable. Indeed, the situation is further complicated by the ranking of antiretroviral therapies (ARTs) by their central nervous system penetration-effectiveness score on the basis of ART concentrations in cerebrospinal fluid. Experimental studies have also yielded equivocal findings depending on the model and individual ART. At the same time, a burgeoning body of experimental data has demonstrated neurotoxic effects of several ARTs, including nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs).

SUMMARY

HAART selection strategies are currently guided by efficacy, resistance testing, toxicity, potential drug interactions and theoretical brain penetration. As improved strategies are developed to target the viral reservoir within the brain, greater knowledge of the effects of ARTs on neural tissues will be needed to operationalize their use in a rational manner that maximizes antiretroviral efficacy and minimizes the neurotoxic complications.

Caenorhabditis elegans as a Model System for Studying Drug Induced Mitochondrial Toxicity

Today HIV-1 infection is recognized as a chronic disease with obligatory lifelong treatment to keep viral titers below detectable levels. The continuous intake of antiretroviral drugs however, leads to severe and even life-threatening side effects, supposedly by the deleterious impact of nucleoside-analogue type compounds on the functioning of the mitochondrial DNA polymerase. For detailed investigation of the yet partially understood underlying mechanisms, the availability of a versatile model system is crucial. We therefore set out to develop the use of Caenorhabditis elegans to study drug induced mitochondrial toxicity. Using a combination of molecular-biological and functional assays, combined with a quantitative analysis of mitochondrial network morphology, we conclude that anti-retroviral drugs with similar working mechanisms can be classified into distinct groups based on their effects on mitochondrial morphology and biochemistry. Additionally we show that mitochondrial toxicity of antiretroviral drugs cannot be exclusively attributed to interference with the mitochondrial DNA polymerase.

Metabolic and renal adverse effects of antiretroviral therapy in HIV-infected children and adolescents

Worldwide, the benefits of combined antiretroviral (ARV) therapy in morbidity and mortality due to perinatally acquired human immunodeficiency virus infection are beyond question and outweigh the toxicity these drugs have been associated with in HIV-infected children and adolescents to date. In puberty, abnormal body fat distribution is stigmatizating and leads to low adherence to ARV treatment. The other metabolic comorbidities (mitochondrial toxicity, dyslipidemias, insulin resistance and low bone mineral density) and renal toxicity, albeit nonsymptomatic in most children, are increasingly being reported and potentially put this population at risk for early cardiovascular or cerebrovascular atherosclerotic disease, diabetes, pathologic fractures or premature renal failure in the third and fourth decades of life. Evidence from available studies is limited because of methodological limitations and also because of several HIV-unrelated factors influencing, to some degree, the development of these conditions. Current recommendations for the prevention, diagnosis, monitoring and treatment of metabolic and renal adverse effects in HIV-children and adolescents are based on adult studies, observational pediatric studies and experts' consensus. Healthy lifestyle habits (regarding diet, exercise and refraining from toxic substances) and wise use of ARV options are the only preventive tools for the majority of patients. Should abnormal findings arise, switches in one or more ARV drugs have proved useful. Specific therapies are also available for some of these comorbidities, although the experience in the pediatric age is still very scarce. We aim to summarize the epidemiological, clinical and therapeutic aspects of metabolic and renal adverse effects in vertically HIV-infected children and adolescents.

DNA polymerase γ and disease: what we have learned from yeast

Mip1 is the Saccharomyces cerevisiae DNA polymerase γ (Pol γ), which is responsible for the replication of mitochondrial DNA (mtDNA). It belongs to the family A of the DNA polymerases and it is orthologs to human POLGA. In humans, mutations in POLG(1) cause many mitochondrial pathologies, such as progressive external ophthalmoplegia (PEO), Alpers' syndrome, and ataxia-neuropathy syndrome, all of which present instability of mtDNA, which results in impaired mitochondrial function in several tissues with variable degrees of severity. In this review, we summarize the genetic and biochemical knowledge published on yeast mitochondrial DNA polymerase from 1989, when the MIP1 gene was first cloned, up until now. The role of yeast is particularly emphasized in (i) validating the pathological mutations found in human POLG and modeled in MIP1, (ii) determining the molecular defects caused by these mutations and (iii) finding the correlation between mutations/polymorphisms in POLGA and mtDNA toxicity induced by specific drugs. We also describe recent findings regarding the discovery of molecules able to rescue the phenotypic defects caused by pathological mutations in Mip1, and the construction of a model system in which the human Pol γ holoenzyme is expressed in yeast and complements the loss of Mip1.

Mitochondrial disturbances in HIV pregnancies

BACKGROUND

Mitochondrial consequences from foetal exposure to HIV infection and antiretrovirals could be further investigated.

OBJECTIVE

The main objective of this study was to evaluate maternofoetal mitochondrial disturbances in HIV infection and antiretroviral administration in human pregnancies as the aetiopathogenic basis of suboptimal perinatal-clinical features.

DESIGN

Cross-sectional, prospective, observational, exploratory and controlled study.

METHODS

Clinical/epidemiological data of 35 HIV-infected pregnant women and 17 controls were collected. Mitochondrial DNA (mtDNA) and RNA (mtRNA) content (real time-PCR), enzymatic activities and content (spectrophotometry) were measured in leucocytes. Genetic-functional, maternofoetal and molecular-clinical correlations were assessed.

RESULTS

Birth weight was lower in infants from HIV-infected mothers compared with controls. MtDNA values were slightly decreased in HIV cases, although not reaching statistical significance. MtRNA values were lower in HIV-infected mothers. Similarly, binary complex II+III enzymatic activity decreased to 50% in both HIV-infected mothers (44.45 ± 3.77%) and their infants (48.79 ± 3.41%) (P = 0.001 and P < 0.001). Global CI+III+IV enzymatic activity was lower in HIV-infected mothers and infants (90.43 ± 2.39% and 51.16 ± 9.30%) (P < 0.005 and P < 0.05). MtDNA content correlated with function in mothers and infants. Maternofoetal parameters correlated at genetic and functional levels.

CONCLUSION

HAART toxicity caused mitochondrial damage in HIV-infected pregnant women and their newborns, being present at a genetic and functional level with a maternofoetal correlation.

Polymorphisms of the ApoE (Apolipoprotein E) gene and their influence on dyslipidemia in HIV-1-infected individuals

The purpose of this retrospective case-control study was to investigate the frequency of Apolipoprotein E (ApoE) polymorphisms and their influence on antiretroviral therapy (ART)-induced lipodystrophy or dyslipidemia in HIV-infected Thai patients. The clinical characteristics and frequencies of ApoE genotypes were compared between the case (moderate to severe lipodystrophy, n = 67) and control (absent to mild lipodystrophy, n = 18) groups. The ApoE genotype frequencies among the 85 participants were 2.35% (n = 2) for E2/E2, 20% (n = 17) for E2/E3, 9.41% (n = 8) for E2/E4, 36.47% (n = 31) for E3/E3, 30.59% (n = 26) for E3/E4, and 1.18% (n = 1) for E4/E4. None of the ApoE genotypes showed association with ART-induced lipodystrophy. However, the levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-cholesterol), and ApoB were lower in patients carrying the E2 allele but higher in E4 carriers. Interestingly, the ratios between TC and high-density lipoprotein (TC/HDL cholesterol ratio) and ApoB/ApoA-I ratio were significantly higher in the case group. Patients carrying the E2 allele displayed protective lipid profile, while those carrying E4 appeared to be at higher risk of dyslipidemia. In conclusion, ApoE polymorphisms were not associated with lipodystrophy in patients undergoing antiretroviral therapy but influenced lipid alteration.

Polymorphisms in DNA polymerase γ affect the mtDNA stability and the NRTI-induced mitochondrial toxicity in Saccharomyces cerevisiae

Several pathological mutations have been identified in human POLG gene, encoding for the catalytic subunit of Pol γ, the solely mitochondrial replicase in animals and fungi. However, little is known regarding non-pathological polymorphisms found in this gene. Here we studied, in the yeast model Saccharomyces cerevisiae, eight human polymorphisms. We found that most of them are not neutral but enhanced both mtDNA extended mutability and the accumulation of mtDNA point mutations, either alone or in combination with a pathological mutation. In addition, we found that the presence of some SNPs increased the stavudine and/or zalcitabine-induced mtDNA mutability and instability.

•

We studied the effects of 8 human polymorphisms in Pol γ in the model system yeast.

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Most polymorphisms increase mtDNA extended and point mutability.

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Treatment with NRTIs determines mtDNA instability in wt and mutant strains.

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Some polymorphisms make Mip1 more sensitive to NRTIs-induced mtDNA toxicity.

The "fast" and the "slow" modes of mitochondrial DNA degradation

In a living cell, oxidative stress resulting from an external or internal insult can result in mitochondrial DNA (mtDNA) damage and degradation. Here, we show that in HeLa cells, mtDNA can withstand relatively high levels of extracellular oxidant H2O2 before it is damaged to a point of degradation, and that mtDNA levels in these cells quickly recover after removal of the stressor. In contrast, mtDNA degradation in mouse fibroblast cells is induced at eight-fold lower concentrations of H2O2, and restoration of the lost mtDNA proceeds much slower. Importantly, mtDNA levels in HeLa cells continue to decline even after withdrawal of the stressor thus marking the "slow" mode of mtDNA degradation. Conversely, in mouse fibroblasts maximal loss of mtDNA is achieved during treatment, and is already detectable at 5 min after exposure, indicating the "fast" mode. These differences may modulate susceptibility to oxidative stress of those organs, which consist of multiple cell types.

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.

Aging and HIV/AIDS: pathogenetic role of therapeutic side effects

The intersection of aging and HIV/AIDS is a looming 'epidemic within an epidemic.' This paper reviews how HIV/AIDS and its therapy cause premature aging or contribute mechanistically to HIV-associated non-AIDS illnesses (HANA). Survival with HIV/AIDS has markedly improved by therapy combinations containing nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors, and protease inhibitors (PIs) called HAART (highly active antiretroviral therapy). Because NRTIs and PIs together prevent or attenuate HIV-1 replication, and prolong life, the population of aging patients with HIV/AIDS increases accordingly. However, illnesses frequently associated with aging in the absence of HIV/AIDS appear to occur prematurely in HIV/AIDS patients. Theories that help to explain biological aging include oxidative stress (where mitochondrial oxidative injury exceeds antioxidant defense), chromosome telomere shortening with associated cellular senescence, and accumulation of lamin A precursors (a nuclear envelop protein). Each of these has the potential to be enhanced or caused by HIV/AIDS, antiretroviral therapy, or both. Antiretroviral therapy has been shown to enhance events seen in biological aging. Specifically, antiretroviral NRTIs cause mitochondrial dysfunction, oxidative stress, and mitochondrial DNA defects that resemble features of both HANA and aging. More recent clinical evidence points to telomere shortening caused by NRTI triphosphate-induced inhibition of telomerase, suggesting telomerase reverse transcriptase (TERT) inhibition as being a pathogenetic contributor to premature aging in HIV/AIDS. PIs may also have a role in premature aging in HIV/AIDS as they cause prelamin A accumulation. Overall, toxic side effects of HAART may both resemble and promote events of aging and are worthy of mechanistic studies.

Development of a vaginal delivery film containing EFdA, a novel anti-HIV nucleoside reverse transcriptase inhibitor

The aim of this work was to develop a fast-dissolving film formulation containing EFdA for potential use as a topical vaginal microbicide for prevention of HIV sexual transmission. Solid state compatibility approaches were used to screen commonly used polymers for formulation development. Factorial design and desirability function were used to investigate the effect of two variables, the ratio of the polymers and the concentration of selected plasticizer on four mechanical responses including tensile strength, elongation at break, toughness and elastic modulus for optimization of the film formulation. Assessments of EFdA-loaded films included physicochemical characteristics, in vitro cytotoxicity, epithelia integrity, ex vivo permeability and bioactivity test. The optimal placebo film was composed of PVA, HPMC E5 and propylene glycol (7:3:3, w/w), and its mechanical characteristics were comparable to those of VCF(®) film (a commercial vaginal film product). Permeability studies using human ectocervical explants showed that there was no significant difference in cumulative permeated amount of EFdA between EFdA film and free EFdA. The results of in vitro cytotoxicity and bioactivity testing showed that 50% cytotoxic concentration (CC50) was several orders of magnitude higher than 50% effective concentration (EC50) of EFdA. Furthermore, epithelial integrity study showed that EFdA-loaded film had a much lower toxicity to HEC-1A cell monolayers as compared to VCF(®). Therefore, EFdA-loaded vaginal film may be considered as a promising vaginal microbicide for HIV prevention.

Acute pancreatitis in HIV/AIDS patients: an issue of concern

Pancreatitis is a well-described complication of human immunodeficiency virus (HIV) itself and its combination antiretroviral therapy. Historically, this has been predominantly associated with the usage of nucleoside reverse transcriptase inhibitors such as didanosine and stavudine, but only rarely with the usage of protease inhibitors via the induction of hypertriglyceridemia. Pancreatitis rates in HIV/AIDS population may have been exceedingly high because of the comorbid conditions prevalent in HIV/AIDS patients (e.g. ethanol use and biliary disease), and the use of non-combination antiretroviral therapy medications such as pentamidine, corticosteroids, ketoconazole, sulphonamides, metronidazole, isoniazid and opportunistic infections (e.g. cytomegalovirus, cryptosporidiosis, mycobacterial disease). In resource limited settings, where didanosine and stavudine are widely available in cheaper generic fixed dose combinations it is likely that their usage will remain in the first line HIV treatment in common. In such settings management or estimation of a patient's risk of pancreatitis still remains an issue of concern.