Pharmacology of nucleoside and nucleotide reverse transcriptase inhibitor-induced mitochondrial toxicity

Efficient Elimination of mtDNA from Mammalian Cells with 2',3'-Dideoxycytidine

Mammalian cell lines devoid of mitochondrial DNA (mtDNA) are indispensable in studies aimed at elucidating the contribution of mtDNA to various cellular processes or interactions between nuclear and mitochondrial genomes. However, the repertoire of tools for generating such cells (also known as rho-0 or ρ0 cells) remains limited, and approaches remain time- and labor-intensive, ultimately limiting their availability. Ethidium bromide (EtBr), which is most commonly used to induce mtDNA loss in mammalian cells, is cytostatic and mutagenic as it affects both nuclear and mitochondrial genomes. Therefore, there is growing interest in new tools for generating ρ0 cell lines. Here, we examined the utility of 2',3'-dideoxycytidine (ddC, zalcitabine) alone or in combination with EtBr for generating ρ0 cell lines of mouse and human origin as well as inducing the ρ0 state in mouse/human somatic cell hybrids. We report that ddC is superior to EtBr in both immortalized mouse fibroblasts and human 143B cells. Also, unlike EtBr, ddC exhibits no cytostatic effects at the highest concentration tested (200 μM), making it more suitable for general use. We conclude that ddC is a promising new tool for generating mammalian ρ0 cell lines.

Long-term persistence of mitochondrial dysfunctions after viral infections and antiviral therapies: A review of mechanisms involved

Mitochondria are vital for most cells' functions. Viruses hijack mitochondria machinery for misappropriation of energy supply or to bypass defense mechanisms. Many of these mitochondrial dysfunctions persist after recovery from treated or untreated viral infections, particularly when mitochondrial DNA is permanently damaged. Quantitative defects and structural rearrangements of mitochondrial DNA accumulate in post-mitotic tissues as recently reported long after SARS-CoV-2 or HIV infection, or following antiviral therapy. These observations are consistent with the "hit-and-run" concept proposed decades ago to explain viro-induced cell transformation and it could apply to delayed post-viral onsets of symptoms and advocate for complementary supportive care. Thus, according to this concept, following exposure to viruses or antiviral agents, mitochondrial damage could evolve into an autonomous clinical condition. It also establishes a pathogenic link between communicable and non-communicable chronic diseases.

Metabolic, Mitochondrial, and Inflammatory Effects of Efavirenz, Emtricitabine, and Tenofovir Disoproxil Fumarate in Asymptomatic Antiretroviral-Naïve People with HIV

This study aimed to comprehensively assess the metabolic, mitochondrial, and inflammatory effects of first-line efavirenz, emtricitabine, and tenofovir disoproxil fumarate (EFV/FTC/TDF) single-tablet regimen (STR) relative to untreated asymptomatic HIV infection. To this end, we analyzed 29 people with HIV (PWH) treated for at least one year with this regimen vs. 33 antiretroviral-naïve PWH. Excellent therapeutic activity was accompanied by significant alterations in metabolic parameters. The treatment group showed increased plasmatic levels of glucose, total cholesterol and its fractions (LDL and HDL), triglycerides, and hepatic enzymes (GGT, ALP); conversely, bilirubin levels (total and indirect fraction) decreased in the treated cohort. Mitochondrial performance was preserved overall and treatment administration even promoted the recovery of mitochondrial DNA (mtDNA) content depleted by the virus, although this was not accompanied by the recovery in some of their encoded proteins (since cytochrome c oxidase II was significantly decreased). Inflammatory profile (TNFα, IL-6), ameliorated after treatment in accordance with viral reduction and the recovery of TNFα levels correlated to mtDNA cell restoration. Thus, although this regimen causes subclinical metabolic alterations, its antiviral and anti-inflammatory properties may be associated with partial improvement in mitochondrial function.

Metabolic Dysfunction-Associated Steatotic Liver Disease in People Living with HIV-Limitations on Antiretroviral Therapy Selection

Chronic liver disease is one of the main causes of morbidity and mortality in people living with HIV (PLWH). The increasing life expectancy of PLWH, effective treatment for viral hepatitis, and Western dietary patterns as well as the adverse effects of antiretroviral therapy (ART) have rendered metabolic dysfunction-associated steatotic liver disease (MASLD) the most common chronic liver disease in PLWH. The risk factors for MASLD in PLWH include traditional MASLD risk factors and additional virus-specific factors, including the adverse effects of ART. The management of patients suffering from HIV and MASLD is often challenging. Apart from the conventional management of MASLD, there are also certain limitations concerning the use of ART in this patient population. In general, the appropriate combination of antiretroviral drugs should be chosen to achieve the triad of effective viral suppression, avoidance of mitochondrial dysfunction, and deterrence of worsening the patient's metabolic profile. In the current review, we discuss the epidemiology of MASLD in PLWH, the risk factors, and the disease pathogenesis, as well as the limitations in the use of ART in this patient population, while practical recommendations on how to overcome these limitations are also given.

Pathophysiology and Clinical Management of Dyslipidemia in People Living with HIV: Sailing through Rough Seas

Infections with human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) represent one of the greatest health burdens worldwide. The complex pathophysiological pathways that link highly active antiretroviral therapy (HAART) and HIV infection per se with dyslipidemia make the management of lipid disorders and the subsequent increase in cardiovascular risk essential for the treatment of people living with HIV (PLHIV). Amongst HAART regimens, darunavir and atazanavir, tenofovir disoproxil fumarate, nevirapine, rilpivirine, and especially integrase inhibitors have demonstrated the most favorable lipid profile, emerging as sustainable options in HAART substitution. To this day, statins remain the cornerstone pharmacotherapy for dyslipidemia in PLHIV, although important drug-drug interactions with different HAART agents should be taken into account upon treatment initiation. For those intolerant or not meeting therapeutic goals, the addition of ezetimibe, PCSK9, bempedoic acid, fibrates, or fish oils should also be considered. This review summarizes the current literature on the multifactorial etiology and intricate pathophysiology of hyperlipidemia in PLHIV, with an emphasis on the role of different HAART agents, while also providing valuable insights into potential switching strategies and therapeutic options.

Antiretroviral drugs from multiple classes induce loss of excitatory synapses between hippocampal neurons in culture

Introduction: Antiretroviral (ARV) drugs have improved prognoses for people living with HIV. However, HIV-associated neurocognitive disorders (HAND) persist despite undetectable viral loads. Some ARVs have been linked to neuropsychiatric effects that may contribute to HAND. Synapse loss correlates with cognitive decline in HAND and synaptic deficits may contribute to the neuropsychiatric effects of ARV drugs. Methods: Using an automated high content assay, rat hippocampal neurons in culture expressing PSD95-eGFP to label glutamatergic synapses and mCherry to fill neuronal structures were imaged before and after treatment with 25 clinically used ARVs. Results and Discussion: At a concentration of 10 μM the protease inhibitors nelfinavir and saquinavir, the non-nucleoside reverse transcriptase inhibitors etravirine and the 8-OH metabolite of efavirenz, the integrase inhibitor bictegravir, and the capsid inhibitor lenacapavir produced synaptic toxicity. Only lenacapavir produced synapse loss at the nanomolar concentrations estimated free in the plasma, although all 4 ARV drugs induced synapse loss at Cmax. Evaluation of combination therapies did not reveal synergistic synaptic toxicity. Synapse loss developed fully by 24 h and persisted for at least 3 days. Bictegravir-induced synapse loss required activation of voltage-gated Ca2+ channels and bictegravir, etravirine, and lenacapavir produced synapse loss by an excitotoxic mechanism. These results indicate that select ARV drugs might contribute to neuropsychiatric effects in combination with drugs that bind serum proteins or in disease states in which synaptic function is altered. The high content imaging assay used here provides an efficient means to evaluate new drugs and drug combinations for potential CNS toxicity.

Oxidative phosphorylation in HIV-1 infection: impacts on cellular metabolism and immune function

Human Immunodeficiency Virus Type 1 (HIV-1) presents significant challenges to the immune system, predominantly characterized by CD4+ T cell depletion, leading to Acquired Immunodeficiency Syndrome (AIDS). Antiretroviral therapy (ART) effectively suppresses the viral load in people with HIV (PWH), leading to a state of chronic infection that is associated with inflammation. This review explores the complex relationship between oxidative phosphorylation, a crucial metabolic pathway for cellular energy production, and HIV-1, emphasizing the dual impact of HIV-1 infection and the metabolic and mitochondrial effects of ART. The review highlights how HIV-1 infection disrupts oxidative phosphorylation, promoting glycolysis and fatty acid synthesis to facilitate viral replication. ART can exacerbate metabolic dysregulation despite controlling viral replication, impacting mitochondrial DNA synthesis and enhancing reactive oxygen species production. These effects collectively contribute to significant changes in oxidative phosphorylation, influencing immune cell metabolism and function. Adenosine triphosphate (ATP) generated through oxidative phosphorylation can influence the metabolic landscape of infected cells through ATP-detected purinergic signaling and contributes to immunometabolic dysfunction. Future research should focus on identifying specific targets within this pathway and exploring the role of purinergic signaling in HIV-1 pathogenesis to enhance HIV-1 treatment modalities, addressing both viral infection and its metabolic consequences.

Mechanisms underlying HIV-associated cognitive impairment and emerging therapies for its management

People living with HIV are affected by the chronic consequences of neurocognitive impairment (NCI) despite antiretroviral therapies that suppress viral replication, improve health and extend life. Furthermore, viral suppression does not eliminate the virus, and remaining infected cells may continue to produce viral proteins that trigger neurodegeneration. Comorbidities such as diabetes mellitus are likely to contribute substantially to CNS injury in people living with HIV, and some components of antiretroviral therapy exert undesirable side effects on the nervous system. No treatment for HIV-associated NCI has been approved by the European Medicines Agency or the US Food and Drug Administration. Historically, roadblocks to developing effective treatments have included a limited understanding of the pathophysiology of HIV-associated NCI and heterogeneity in its clinical manifestations. This heterogeneity might reflect multiple underlying causes that differ among individuals, rather than a single unifying neuropathogenesis. Despite these complexities, accelerating discoveries in HIV neuropathogenesis are yielding potentially druggable targets, including excessive immune activation, metabolic alterations culminating in mitochondrial dysfunction, dysregulation of metal ion homeostasis and lysosomal function, and microbiome alterations. In addition to drug treatments, we also highlight the importance of non-pharmacological interventions. By revisiting mechanisms implicated in NCI and potential interventions addressing these mechanisms, we hope to supply reasons for optimism in people living with HIV affected by NCI and their care providers.

Late-onset MELAS syndrome in a 46-year-old man with initial symptom of chest tightness: a case report

Background

Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) syndrome is a rare mitochondrial disorder caused by mutations in mitochondrial DNA, resulting in impaired energy production and affecting multiple organs. We present a suspected MELAS syndrome case with the initial symptom of chest tightness.

Case summary

A 46-year-old man sought medical attention due to progressively worsening chest tightness during physical activity. He had been receiving treatment for type 2 diabetes for 15 years. One year ago, he presented with symptoms of hearing impairment. Transthoracic echocardiography revealed increased thickness of the left ventricular wall. Serum protein electrophoresis showed no evidence of light-chain amyloidosis, and the 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid scan showed no definite uptake in the heart muscle. The patient's head magnetic resonance imaging (MRI) indicated lacunar infarcts. The lactate threshold test was positive. The biopsy of the skeletal muscle showed broken red fibre infiltration on modified Gomori trichrome staining, and electron microscopy revealed signs of mitochondrial cardiomyopathy, including mild mitochondrial swelling, lipid accumulation, and myofibril damage. A whole-exome genetic test was used to detect the m.3243A>G mutation in the MT-TL1 gene. Based on these findings, MELAS syndrome was the most probable diagnosis.

Discussion

The patient presented with chest tightness in adulthood, without any accompanying psychoneurological symptoms. However, the patient presented with other symptoms, including diabetes mellitus, hearing loss, abnormal lactate levels, ischaemic lesions on head MRI, and left ventricular hypertrophy. By identifying a mutation in the MT-TL1 gene and conducting a muscle biopsy, the diagnosis of MELAS syndrome was definitively confirmed.

Vertigo symptom scores and videonystagmographic examinations in recovered coronavirus disease 2019 patients

OBJECTIVE

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may be among the viral agents that affect the audio-vestibular system. This study aimed to investigate vestibular symptoms and videonystagmographic examinations in recovered coronavirus disease 2019 (Covid-19) patients compared with the control group.

METHOD

The patients were evaluated with Vertigo Symptom Scale questionnaire and audiometric, tympanometric, stapedial reflex and videonystagmographic examinations.

RESULTS

A total of 92 of the patients in the coronavirus disease 2019 patients group and 25 of the volunteers in the control group were included in the study. The mean Vertigo Symptom Scale score was found to be significantly higher (p < 0.001) in the coronavirus disease 2019 group. Furthermore, one of the hospitalised patients was diagnosed with vestibular neuritis.

CONCLUSION

The vestibular system may also be affected in some coronavirus disease 2019 patients. Although this may be seen as dizziness in some patients, in rare cases it can cause severe issues, such as vestibular neuritis.

Pathophysiology and mechanisms of hearing impairment related to neonatal infection diseases

The inner ear, the organ of equilibrium and hearing, has an extraordinarily complex and intricate arrangement. It contains highly specialized structures meticulously tailored to permit auditory processing. However, hearing also relies on both peripheral and central pathways responsible for the neuronal transmission of auditory information from the cochlea to the corresponding cortical regions. Understanding the anatomy and physiology of all components forming the auditory system is key to better comprehending the pathophysiology of each disease that causes hearing impairment. In this narrative review, the authors focus on the pathophysiology as well as on cellular and molecular mechanisms that lead to hearing loss in different neonatal infectious diseases. To accomplish this objective, the morphology and function of the main structures responsible for auditory processing and the immune response leading to hearing loss were explored. Altogether, this information permits the proper understanding of each infectious disease discussed.

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.

A Rationale and Approach to the Development of Specific Treatments for HIV Associated Neurocognitive Impairment

Neurocognitive impairment (NCI) associated with HIV infection of the brain impacts a large proportion of people with HIV (PWH) regardless of antiretroviral therapy (ART). While the number of PWH and severe NCI has dropped considerably with the introduction of ART, the sole use of ART is not sufficient to prevent or arrest NCI in many PWH. As the HIV field continues to investigate cure strategies, adjunctive therapies are greatly needed. HIV imaging, cerebrospinal fluid, and pathological studies point to the presence of continual inflammation, and the presence of HIV RNA, DNA, and proteins in the brain despite ART. Clinical trials exploring potential adjunctive therapeutics for the treatment of HIV NCI over the last few decades have had limited success. Ideally, future research and development of novel compounds need to address both the HIV replication and neuroinflammation associated with HIV infection in the brain. Brain mononuclear phagocytes (MPs) are the primary instigators of inflammation and HIV protein expression; therefore, adjunctive treatments that act on MPs, such as immunomodulating agents, look promising. In this review, we will highlight recent developments of innovative therapies and discuss future approaches for HIV NCI treatment.

Hearing impairment in children living with HIV in Haiti

OBJECTIVE

To identify the prevalence of hearing impairment and associated risk factors in children living with human immunodeficiency virus (HIV) in Haiti.

METHODS

A validated smartphone-based platform with pure-tone audiometry was used to screen 341 HIV-infected children for hearing impairment in Port-au-Prince, Haiti from March 2019 to September 2020. If screening was failed, a more comprehensive pure-tone audiometric evaluation was administered. Demographic, otologic, and HIV-related data were obtained through caregiver surveys and medical charts. Statistical analysis included univariate and multivariate logistic regression.

RESULTS

Sixty (18%) of 341 HIV-infected children (ages 7-18 years) had hearing impairment. Of those failing their hearing assessment, 17 (28%) had moderate and 5 (8%) had severe or profound hearing loss. Hearing impairment was associated with frequent ear infections (OR 3.37; 95% CI 1.76-6.46; p < 0.001) and family history of hearing loss (OR 5.12; 95% CI 2.14-12.23; p = 0.001) but not viral load (OR 1.00; 95% CI 0.73-1.02; p = 0.28) or antiretroviral therapy duration (OR 0.96; 95% CI 0.79-1.17; p = 0.66). Only 35% of caregivers correctly perceived their child's hearing loss.

CONCLUSIONS

Hearing impairment occurs at a higher prevalence in HIV-infected children in Haiti than what is expected for those living without HIV. Frequent ear infections were significantly associated with hearing loss while antiretroviral therapy duration was not. Despite their potential ototoxicity, antiretroviral therapies should be continued and may decrease incidence of otitis media. Low caregiver perception of hearing loss emphasizes the need for routine hearing screening for HIV-infected children.

Remdesivir does not affect mitochondrial DNA copy number or deletion mutation frequency in aged male rats: A short report

Remdesivir is a leading therapy in patients with moderate to severe coronavirus 2 (SARS-CoV-2) infection; the majority of whom are older individuals. Remdesivir is a nucleoside analog that incorporates into nascent viral RNA, inhibiting RNA-directed RNA polymerases, including that of SARS-CoV-2. Less is known about remdesivir's effects on mitochondria, particularly in older adults where mitochondria are known to be dysfunctional. Furthermore, its effect on age-induced mitochondrial mutations and copy number has not been previously studied. We hypothesized that remdesivir adversely affects mtDNA copy number and deletion mutation frequency in aged rodents. To test this hypothesis, 30-month-old male F333BNF1 rats were treated with remdesivir for three months. To determine if remdesivir adversely affects mtDNA, we measured copy number and mtDNA deletion frequency in rat hearts, kidneys, and skeletal muscles using digital PCR. We found no effects from three months of remdesivir treatment on mtDNA copy number or deletion mutation frequency in 33-month-old rats. These data support the notion that remdesivir does not compromise mtDNA quality or quantity at old age in mammals. Future work should focus on examining additional tissues such as brain and liver, and extend testing to human clinical samples.

Sarcopenia among people living with HIV and the effect of antiretroviral therapy on body composition

To investigate the prevalence of sarcopenia among people living with HIV (PLWH) in Japan and analyze the relationship between HIV infection and ART effects on the body composition of Japanese PLWH for more appropriate drug selection and lifestyle guidance. Cross-sectional observational study. We included male patients aged ≥ 60 years whose body composition was measured by InBody 570 body composition analyzer during outpatient visits. Patients were classified by body shape based on body mass index (BMI) and body fat percentage measurements and by tenofovir alafenamide administration. Hidden obesity is a condition wherein the BMI is within the standard range but the body fat percentage is higher than the reference. Patients with low muscle mass and strength were considered to have sarcopenia, whereas those with only low muscle strength were considered to have pre-sarcopenia. In total, 87 patients were included. Based on body shape determined by BMI and body fat percentage, most patients had hidden obesity (40 patients, 46.0%). Sarcopenia was detected in 9 patients (10.3%) and pre-sarcopenia in 14 patients (16.1%). The tenofovir alafenamide (TAF) use group had significantly higher BMI, higher skeletal muscle mass, body fat mass, and skeletal muscle mass index relative to the non-TAF use group. Hidden obesity is a risk for lifestyle diseases. It is important to recognize it based on body composition measurements because it can be missed by BMI measurement alone. Tenofovir alafenamide therapy increases skeletal muscle mass, which may result in the prevention of sarcopenia. To clarify how TAF affects the development of sarcopenia and lifestyle diseases, future studies on a larger cohort are warranted.

Novel Nanotechnology-Based Approaches for Targeting HIV Reservoirs

Highly active anti-retroviral therapy (HAART) is prescribed for HIV infection and, to a certain extent, limits the infection's spread. However, it cannot completely eradicate the latent virus in remote and cellular reservoir areas, and due to the complex nature of the infection, the total eradication of HIV is difficult to achieve. Furthermore, monotherapy and multiple therapies are not of much help. Hence, there is a dire need for novel drug delivery strategies that may improve efficacy, decrease side effects, reduce dosing frequency, and improve patient adherence to therapy. Such a novel strategy could help to target the reservoir sites and eradicate HIV from different biological sanctuaries. In the current review, we have described HIV pathogenesis, the mechanism of HIV replication, and different biological reservoir sites to better understand the underlying mechanisms of HIV spread. Further, the review deliberates on the challenges faced by the current conventional drug delivery systems and introduces some novel drug delivery strategies that have been explored to overcome conventional drug delivery limitations. In addition, the review also summarizes several nanotechnology-based approaches that are being explored to resolve the challenges of HIV treatment by the virtue of delivering a variety of anti-HIV agents, either as combination therapies or by actively targeting HIV reservoir sites.

The Potential of Spirulina platensis to Ameliorate the Adverse Effects of Highly Active Antiretroviral Therapy (HAART)

The human immunodeficiency virus (HIV) is one of the most prevalent diseases globally. It is estimated that 37.7 million people are infected with HIV globally, and 8.2 million persons are infected with the virus in South Africa. The highly active antiretroviral therapy (HAART) involves combining various types of antiretroviral drugs that are dependent on the infected person’s viral load. HAART helps regulate the viral load and prevents its associated symptoms from progressing into acquired immune deficiency syndrome (AIDS). Despite its success in prolonging HIV-infected patients’ lifespans, the use of HAART promotes metabolic syndrome (MetS) through an inflammatory pathway, excess production of reactive oxygen species (ROS), and mitochondrial dysfunction. Interestingly, Spirulina platensis (SP), a blue-green microalgae commonly used as a traditional food by Mexican and African people, has been demonstrated to mitigate MetS by regulating oxidative and inflammatory pathways. SP is also a potent antioxidant that has been shown to exhibit immunological, anticancer, anti-inflammatory, anti-aging, antidiabetic, antibacterial, and antiviral properties. This review is aimed at highlighting the biochemical mechanism of SP with a focus on studies linking SP to the inhibition of HIV, inflammation, and oxidative stress. Further, we propose SP as a potential supplement for HIV-infected persons on lifelong HAART.

Mapping Adverse Outcome Pathways for Kidney Injury as a Basis for the Development of Mechanism-Based Animal-Sparing Approaches to Assessment of Nephrotoxicity

In line with recent OECD activities on the use of AOPs in developing Integrated Approaches to Testing and Assessment (IATAs), it is expected that systematic mapping of AOPs leading to systemic toxicity may provide a mechanistic framework for the development and implementation of mechanism-based in vitro endpoints. These may form part of an integrated testing strategy to reduce the need for repeated dose toxicity studies. Focusing on kidney and in particular the proximal tubule epithelium as a key target site of chemical-induced injury, the overall aim of this work is to contribute to building a network of AOPs leading to nephrotoxicity. Current mechanistic understanding of kidney injury initiated by 1) inhibition of mitochondrial DNA polymerase γ (mtDNA Polγ), 2) receptor mediated endocytosis and lysosomal overload, and 3) covalent protein binding, which all present fairly well established, common mechanisms by which certain chemicals or drugs may cause nephrotoxicity, is presented and systematically captured in a formal description of AOPs in line with the OECD AOP development programme and in accordance with the harmonized terminology provided by the Collaborative Adverse Outcome Pathway Wiki. The relative level of confidence in the established AOPs is assessed based on evolved Bradford-Hill weight of evidence considerations of biological plausibility, essentiality and empirical support (temporal and dose-response concordance).

Polymerase ζ is Involved in Mitochondrial DNA Maintenance Processes in Concert with APE1 Activity

Mitochondrial DNA (mtDNA) damaged by reactive oxygen species (ROS) triggers so far poorly understood processes of mtDNA maintenance that are coordinated by a complex interplay among DNA repair, DNA degradation, and DNA replication. This study was designed to identify the proteins involved in mtDNA maintenance by applying a special long-range PCR, reflecting mtDNA integrity in the minor arc. A siRNA screening of literature-based candidates was performed under conditions of enforced oxidative phosphorylation revealing the functional group of polymerases and therein polymerase ζ (POLZ) as top hits. Thus, POLZ knockdown caused mtDNA accumulation, which required the activity of the base excision repair (BER) nuclease APE1, and was followed by compensatory mtDNA replication determined by the single-cell mitochondrial in situ hybridization protocol (mTRIP). Quenching reactive oxygen species (ROS) in mitochondria unveiled an additional, ROS-independent involvement of POLZ in the formation of a typical deletion in the minor arc region. Together with data demonstrating the localization of POLZ in mitochondria, we suggest that POLZ plays a significant role in mtDNA turnover, particularly under conditions of oxidative stress.

Molnupiravir; molecular and functional descriptors of mitochondrial safety

Molnupiravir is an orally active nucleoside analog antiviral drug that recently was approved by the U.S. FDA for emergency treatment of adult patients infected with the SARS-CoV-2 (COVID-19) virus and at risk for severe progression. The active form of the drug, N-hydroxycytidine (NHC) triphosphate competes for incorporation by RNA-dependent RNA-polymerase (RdRp) into the replicating viral genome resulting in mutations and arrest of the replicating virus. Historically, some nucleoside analog antiviral drugs have been found to lack specificity for the virus and also inhibit replication and/or expression of the mitochondrial genome. The objective of the present study was to test whether molnupiravir and/or NHC also target mitochondrial DNA polymerase gamma (PolG) or RNA polymerase (POLRMT) activity to inhibit the replication and/or expression of the mitochondrial genome leading to impaired mitochondrial function. Human-derived HepG2 cells were exposed for 48 h in culture to increasing concentrations of either molnupiravir or NHC after which cytotoxicity, mtDNA copy number and mitochondrial gene expression were determined. The phenotypic endpoint, mitochondrial respiration, was measured with the Seahorse® XF96 Extracellular Flux Analyzer. Both molnupiravir and NHC were cytotoxic at concentrations of ≥10 μM. However, at non-cytotoxic concentrations, neither significantly altered mitochondrial gene dose or transcription, or mitochondrial respiration. From this we conclude that mitochondrial toxicity is not a primary off target in the mechanism of cytotoxicity for either molnupiravir or its active metabolite NHC in the HepG2 cell line.

Vestibular Cochlear Manifestations in COVID-19 Cases

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a high transmissible infectious disease that primarily impacts the respiratory system and leads to death as it worsens. Ever since the World Health Organization declared the disease as a global pandemic, the pathophysiology, clinical manifestations, and disease prognosis has been discussed in various literature. In addition to impaired respiratory health, the symptoms also indicated the involvement of the cardiovascular and neurological system after SARS-CoV-2 infection. Despite the pulmonary, cardiovascular, and neurological complications, many reports also revealed the prevalence of vestibulocochlear symptoms like dizziness, vertigo, vestibular neuritis, sudden sensorineural hearing loss, and tinnitus. Though many clinical reports and scientific reviews reported the vestibular and cochlear impairments associated with coronavirus disease 2019 (COVID-19) infection, the underlying pathological mechanisms are still unclear and unexplored. In this review, we discussed the published clinical reports, research articles, and literature reviews related to vestibulocochlear manifestations following SARS-CoV-2 infections. We also summarized the current knowledge about the prevalence, epidemiological and clinical features, and potential pathological mechanisms related to vestibular and cochlear manifestations resulting from COVID-19 infections.

Remdesivir; molecular and functional measures of mitochondrial safety

Remdesivir is one of a few antiviral drugs approved for treating severe cases of coronavirus 2 (SARS-CoV-2) infection in hospitalized patients. The prodrug is a nucleoside analog that interferes with viral replication by inhibiting viral RNA-dependent RNA polymerase. The drug has also been shown to be a weak inhibitor of human mitochondrial RNA polymerase, leaving open the possibility of mitochondrial off-targets and toxicity. The investigation was designed to explore whether remdesivir causes mitochondrial toxicity, using both genomic and functional parameters in the assessment. Human-derived HepG2 liver cells were exposed for up to 48 h in culture to increasing concentrations of remdesivir. At sub-cytotoxic concentrations (<1 μM), the drug failed to alter either the number of copies or the expression of the mitochondrial genome. mtDNA copy number was unaffected as was the relative rates of expression of mtDNA-encoded and nuclear encoded subunits of complexes I and IV of the mitochondrial respiratory chain. Consistent with this is the observation that remdesivir was without effect on mitochondrial respiration, including basal respiration, proton leak, maximum uncoupled respiration, spare respiratory capacity or coupling efficiency. We conclude that although remdesivir has weak inhibitory activity towards mitochondrial RNA polymerase, mitochondria are not primary off-targets for the mechanism of cytotoxicity of the drug.

Mitochondrial changes associated with viral infectious diseases in the paediatric population

Infectious diseases occur worldwide with great frequency in both adults and children, causing 350,000 deaths in 2017, according to the latest World Health Organization reports. Both infections and their treatments trigger mitochondrial interactions at multiple levels: (i) incorporation of damaged or mutated proteins into the complexes of the electron transport chain; (ii) impact on mitochondrial genome (depletion, deletions and point mutations) and mitochondrial dynamics (fusion and fission); (iii) membrane potential impairment; (iv) apoptotic regulation; and (v) generation of reactive oxygen species, among others. Such alterations may result in serious adverse clinical events with considerable impact on the quality of life of the children and could even cause death. Herein, we use a systematic review to explore the association between mitochondrial alterations in paediatric infections including human immunodeficiency virus, cytomegalovirus, herpes viruses, various forms of hepatitis, adenovirus, T-cell lymphotropic virus and influenza. We analyse how these paediatric viral infectious processes may cause mitochondrial deterioration in this especially vulnerable population, with consideration for the principal aspects of research and diagnosis leading to improved disease understanding, management and surveillance.

Human PrimPol Discrimination against Dideoxynucleotides during Primer Synthesis

PrimPol is required to re-prime DNA replication at both nucleus and mitochondria, thus facilitating fork progression during replicative stress. ddC is a chain-terminating nucleotide that has been widely used to block mitochondrial DNA replication because it is efficiently incorporated by the replicative polymerase Polγ. Here, we show that human PrimPol discriminates against dideoxynucleotides (ddNTP) when elongating a primer across 8oxoG lesions in the template, but also when starting de novo synthesis of DNA primers, and especially when selecting the 3′nucleotide of the initial dimer. PrimPol incorporates ddNTPs with a very low efficiency compared to dNTPs even in the presence of activating manganese ions, and only a 40-fold excess of ddNTP would significantly disturb PrimPol primase activity. This discrimination against ddNTPs prevents premature termination of the primers, warranting their use for elongation. The crystal structure of human PrimPol highlights Arg²⁹¹ residue as responsible for the strong dNTP/ddNTP selectivity, since it interacts with the 3′-OH group of the incoming deoxynucleotide, absent in ddNTPs. Arg²⁹¹, shown here to be critical for both primase and polymerase activities of human PrimPol, would contribute to the preferred binding of dNTPs versus ddNTPs at the 3′elongation site, thus avoiding synthesis of abortive primers.

Profiling the physiological pitfalls of anti-hepatitis C direct-acting agents in budding yeast

Sofosbuvir and Daclatasvir are among the direct-acting antiviral (DAA) medications prescribed for the treatment of chronic hepatitis C (CHC) virus infection as combination therapy with other antiviral medications. DAA-based therapy achieves high cure rates, reaching up to 97% depending on the genotype of the causative hepatitis C virus (HCV). While DAAs have been approved as an efficient and well-tolerated therapy for CHC, emerging concerns about adverse cardiac side effects, higher risk of recurrence and occurrence of hepatocellular carcinoma (HCC) and doubts of genotoxicity have been reported. In our study, we investigated in detail physiological off-targets of DAAs and dissected the effects of these drugs on cellular organelles using budding yeast, a unicellular eukaryotic organism. DAAs were found to disturb the architecture of the endoplasmic reticulum (ER) and the mitochondria, while showing no apparent genotoxicity or DNA damaging effect. Our study provides evidence that DAAs are not associated with genotoxicity and highlights the necessity for adjunctive antioxidant therapy to mitigate the adverse effects of DAAs on ER and mitochondria.

Protection of Retinal Function by Nucleoside Reverse Transcriptase Inhibitors Following Retinal Ischemia/Reperfusion Injury

Purpose: Retinal ischemia/reperfusion (I/R) injury is a common cause of visual impairment and blindness for which there remain limited treatment options. Nucleoside reverse transcriptase inhibitors (NRTIs), such as zidovudine (AZT), have been shown to block the NLRP3 inflammasome and prevent retinal degeneration in a mouse model of age-related macular degeneration. The NLRP3 inflammasome has also been shown to be triggered in I/R injury. Therefore, we studied the neuroprotective effects of AZT using a pressure-induced retinal ischemia mouse model. Methods: C57BL/6J mice were randomly assigned to 1 of 2 treatment groups: vehicle-treated retinal I/R injury (n = 6) or AZT-treated retinal I/R injury (n = 6). Vehicle (1% dimethyl sulfoxide [DMSO] in phosphate-buffered saline [PBS]) or AZT 50 mg/kg in 1% DMSO in PBS were injected intraperitoneally twice daily for 5 days. On day 2 of treatment, retinal ischemia was induced by transient elevation of intraocular pressure for 45 min. Scotopic electroretinography (ERG) was used to quantify retinal function before and 1 week after retinal ischemic insult. Retinal morphology was examined 1 week after ischemic insult. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays and caspase 1 immunostaining was performed 24 h after retinal I/R injury. Results: Following I/R injury, ERG a- and b-wave amplitudes were significantly reduced in the vehicle-treated mice. AZT treatment significantly attenuated I/R-induced loss of retinal function as compared with vehicle-treated mice. Additionally, AZT-treated mice experienced significantly less inner retinal thinning as compared with vehicle-treated mice. TUNEL-positive cells were prevalent in the vehicle-treated I/R injury mouse retinas compared with the AZT-treated I/R injury mouse retinas. More caspase-1 immunoreactivity was detected in ganglion cell layer and inner nuclear layer (INL) in vehicle-treated I/R injury group than in AZT-treated I/R injury group. Conclusion: AZT treatment resulted in relative preservation of retinal structure and function following ischemic insult as compared with controls. This suggests AZT may have therapeutic value in the management of retinal ischemic diseases.

Beneficial Effects of Cannabis on Blood-Brain Barrier Function in Human Immunodeficiency Virus

BACKGROUND

Human immunodeficiency virus (HIV) infection leads to blood-brain barrier (BBB) dysfunction that does not resolve despite viral suppression on antiretroviral therapy (ART) and is associated with adverse clinical outcomes. In preclinical models, cannabis restores BBB integrity.

METHODS

We studied persons with HIV (PWH) and HIV-negative (HIV-) individuals who had used cannabis recently. We assessed 2 biomarkers of BBB permeability: the cerebrospinal fluid (CSF) to serum albumin ratio (CSAR) and CSF levels of soluble urokinase plasminogen activator receptor (suPAR), a receptor for uPA, a matrix-degrading proteolytic enzyme that disrupts the BBB. A composite index of the BBB markers was created using principal components analysis. Neural injury was assessed using neurofilament light (NFL) in CSF by immunoassay.

RESULTS

Participants were 45 PWH and 30 HIV- individuals of similar age and ethnicity. Among PWH, higher CSF suPAR levels correlated with higher CSAR values (r = 0.47, P < .001). PWH had higher (more abnormal) BBB index values than HIV- individuals (mean ± SD, 0.361 ± 1.20 vs -0.501 ± 1.11; P = .0214). HIV serostatus interacted with cannabis use frequency, such that more frequent use of cannabis was associated with lower BBB index values in PWH but not in HIV- individuals. Worse BBB index values were associated with higher NFL in CSF (r = 0.380, P = .0169).

CONCLUSIONS

Cannabis may have a beneficial impact on HIV-associated BBB injury. Since BBB disruption may permit increased entry of toxins such as microbial antigens and inflammatory mediators, with consequent CNS injury, these results support a potential therapeutic role of cannabis among PWH and may have important treatment implications for ART effectiveness and toxicity.

HIV in Neonates and Infants

Advances in perinatal HIV management have averted a significant number of infections in neonates and have made the possibility of elimination of mother-to-child transmission a reality; however, significant gaps in implementation of early testing programs as well as the expansion of therapeutic strategies to neonates are hindering prevention efforts and access to safer, more effective and easier to administer treatment. This article provides insights on the current state of perinatal HIV, recent advances, and future needs.

CNS Neurotoxicity of Antiretrovirals

The development of novel antiretroviral treatments has led to a significant turning point in the fight against HIV. Although therapy leads to virologic suppression and prolonged life expectancies, HIV-associated neurocognitive disorder (HAND) remains prevalent. While various hypotheses have been proposed to explain this phenomenon, a growing body of literature explores the neurotoxic effects of antiretroviral therapy. Research to date brings into question the potential role of such medications in neurocognitive and neuropsychiatric impairment seen in HIV-positive patients. This review highlights recent findings and controversies in cellular, molecular, and clinical neurotoxicity of antiretrovirals. It explores the pathogenesis of such toxicity and relates it to clinical manifestations in each medication class. The concept of accelerated aging in persons living with HIV (PLWH) as well as potential treatments for HAND are also discussed. Ultimately, this article hopes to educate clinicians and basic scientists about the neurotoxic effects of antiretrovirals and spur future scientific investigation into this important topic. Graphical Abstract.

Targeted Metabolomic Assessment of the Sub-Lethal Toxicity of Halogenated Acetic Acids (HAAs) to Daphnia magna

Halogenated acetic acids (HAAs) are amongst the most frequently detected disinfection by-products in aquatic environments. Despite this, little is known about their toxicity, especially at the molecular level. The model organism Daphnia magna, which is an indicator species for freshwater ecosystems, was exposed to sub-lethal concentrations of dichloroacetic acid (DCAA), trichloroacetic acid (TCAA) and dibromoacetic acid (DBAA) for 48 h. Polar metabolites extracted from Daphnia were analyzed using liquid chromatography hyphened to a triple quadrupole mass spectrometer (LC-MS/MS). Multivariate analyses identified shifts in the metabolic profile with exposure and pathway analysis was used to identify which metabolites and associated pathways were disrupted. Exposure to all three HAAs led to significant downregulation in the nucleosides: adenosine, guanosine and inosine. Pathway analyses identified perturbations in the citric acid cycle and the purine metabolism pathways. Interestingly, chlorinated and brominated acetic acids demonstrated similar modes of action after sub-lethal acute exposure, suggesting that HAAs cause a contaminant class-based response which is independent of the type or number of halogens. As such, the identified metabolites that responded to acute HAA exposure may serve as suitable bioindicators for freshwater monitoring programs.

In Vitro Exposure of Leukocytes to HIV Preexposure Prophylaxis Decreases Mitochondrial Function and Alters Gene Expression Profiles

The use of antiretroviral therapy (ART) as preexposure prophylaxis (PrEP) is an effective strategy for preventing HIV acquisition. The cellular consequences of PrEP exposure, however, have not been sufficiently explored to determine potential effects on health in individuals without HIV. In this study, peripheral blood mononuclear cells (PBMCs) from people without HIV were exposed to tenofovir disoproxil fumarate (TDF) or emtricitabine (FTC) overnight. Mitochondrial mass and function were measured by flow cytometry and an Agilent XFp analyzer.

The use of antiretroviral therapy (ART) as preexposure prophylaxis (PrEP) is an effective strategy for preventing HIV acquisition. The cellular consequences of PrEP exposure, however, have not been sufficiently explored to determine potential effects on health in individuals without HIV. In this study, peripheral blood mononuclear cells (PBMCs) from people without HIV were exposed to tenofovir disoproxil fumarate (TDF) or emtricitabine (FTC) overnight. Mitochondrial mass and function were measured by flow cytometry and an Agilent XFp analyzer. Monocyte-derived macrophages (MDMs) were differentiated in 20% autologous serum for 5 days in the presence or absence of TDF or FTC, and surface markers, lipid uptake, and efferocytosis were measured by flow cytometry. MDM gene expression was measured using transcriptome sequencing (RNA-seq). Plasma lipids were measured using mass spectrometry. PBMCs exposed to TDF or FTC had decreased maximal oxygen consumption rate (OCR) and reduced mitochondrial mass. Exposure to PrEP also increased reactive oxygen species (ROS) production from monocyte subsets. Compared to MDMs cultured in medium alone, cells differentiated in the presence of TDF (829 genes) or FTC (888 genes) had significant changes in gene expression. Further, PrEP-exposed MDMs had decreased mitochondrial mass and displayed increased lipid uptake and reduced efferocytosis. Plasma biomarkers and lipid levels were also altered in vivo in individuals receiving a PrEP regimen. In conclusion, exposure of leukocytes to TDF or FTC resulted in decreased mitochondrial function and altered functional and transcriptional profiles. These findings may have important implications for the metabolic and immunologic consequences of PrEP in populations at risk for HIV acquisition.

Symptoms of Toxicity and Plasma Cytochrome c Levels in Human Immunodeficiency Virus-infected Patients Receiving Anti-retroviral Therapy in Ghana: A Cross-sectional Study

BACKGROUND

Side effects and toxicity have posed a threat to the positive contribution of Antiretroviral Therapy (ART) in the management of human immunodeficiency virus (HIV) infection and Acquired Immune Deficiency Syndrome (AIDS). Symptoms of mitochondrial toxicity including myopathy, pancreatitis, hyperlipidaemia and lactic acidosis are found among HIVinfected patients on ART. To date, there is not a reliable biomarker for monitoring ART-related mitochondrial toxicity. Plasma level of Cytochrome c (Cyt-c) has been proposed as a potential biomarker for ART-related toxicity due to its strong association with apoptosis.

OBJECTIVE

The present study assessed toxicity and level of plasma Cyt-c among HIV-infected patients receiving ART in Ghana.

METHODS

A total of eighty (80) HIV patients were recruited into the study. Demographic data were obtained from personal interview and medical records. Plasma samples were screened for toxicity from sixty (60) participants due to limited resources, and plasma Cyt-c levels were determined using ELISA. Data were analyzed using Stata version 13.

RESULTS

Out of the 60 participants, 11 (18.3%) were found with symptoms of myopathy, 12 (20%) with pancreatitis, 21 (35%) with hyperlipidaemia and 36 (60%) with at least one of the symptoms. The concentration of plasma Cyt-c was higher (0.122 ng/ml) in patients with toxicity than in those without toxicity (0.05 ng/ml), though the difference was not statistically significant (p = 0.148). There was a weak correlation between plasma Cyt-c level and duration of ART (Spearman rho = 0.02, p = 0.89).

CONCLUSION

This study, therefore, demonstrated a high prevalence of ART-related toxicity and high levels of Cyt-c in HIV-infected patients in support of the argument that plasma Cyt-c levels are potential biomarkers for determining ART-related toxicity in HIV patients.

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.

Pharmacokinetics of lopinavir/ritonavir oral solution to treat COVID-19 in mechanically ventilated ICU patients

Background

The combination lopinavir/ritonavir is recommended to treat HIV-infected patients at the dose regimen of 400/100 mg q12h, oral route. The usual lopinavir trough plasma concentrations are 3000–8000 ng/mL. A trend towards a 28 day mortality reduction was observed in COVID-19-infected patients treated with lopinavir/ritonavir.

Objectives

To assess the plasma concentrations of lopinavir and ritonavir in patients with severe COVID-19 infection and receiving lopinavir/ritonavir.

Patients and methods

Mechanically ventilated patients with COVID-19 infection included in the French COVID-19 cohort and treated with lopinavir/ritonavir were included. Lopinavir/ritonavir combination was administered using the usual adult HIV dose regimen (400/100 mg q12h, oral solution through a nasogastric tube). A half-dose reduction to 400/100 mg q24h was proposed if lopinavir C_trough was >8000 ng/mL, the upper limit considered as toxic and reported in HIV-infected patients. Lopinavir and ritonavir pharmacokinetic parameters were determined after an intensive pharmacokinetic analysis. Biological markers of inflammation and liver/kidney function were monitored.

Results

Plasma concentrations of lopinavir and ritonavir were first assessed in eight patients treated with lopinavir/ritonavir. Median (IQR) lopinavir C_trough reached 27 908 ng/mL (15 928–32 627). After the dose reduction to 400/100 mg q24h, lopinavir/ritonavir pharmacokinetic parameters were assessed in nine patients. Lopinavir C_trough decreased to 22 974 ng/mL (21 394–32 735).

Conclusions

In mechanically ventilated patients with severe COVID-19 infections, the oral administration of lopinavir/ritonavir elicited plasma exposure of lopinavir more than 6-fold the upper usual expected range. However, it remains difficult to safely recommend its dose reduction without compromising the benefit of the antiviral strategy, and careful pharmacokinetic and toxicity monitoring are needed.

Neuropsychiatric Effects of Antiviral Drugs

The adverse events of antiviral drugs are dose-dependent and often reversible. The nervous system is often affected and to date, many studies have been published regarding the central nervous system toxicity of antiviral agents. They may cause significant neuropsychiatric complications, which range from mild symptoms such as irritability and difficulty sleeping to severe complications such as depression, psychosis, and painful peripheral neuropathy, side effects which may necessitate discontinuation of treatment. The pathogenetic mechanisms may involve molecular targets common to other centrally active drugs, including human monoamine oxidase‐A (MAO‐A), serotonin receptors, gamma-aminobutyric acid (GABA) GABA-A receptors, 5-HT2A and 5-HT2C receptors and others. Notable examples include oseltamivir which may act as MAO inhibitor and efavirenz, which has an affinity for serotonin 5-HT2 and GABA-A receptors, the serotonin transporter, the MAO enzyme, and the vesicular monoamine transporter, with subjective effects which may be similar to those of the psychedelic hallucinogen lysergic acid diethylamide (LSD). Other antiviral drugs with prominent nervous system effects include nucleoside reverse transcriptase inhibitors, which are associated with the development of peripheral neuropathy after prolonged use (an effect strongly associated with older drugs which have since fallen into disfavor such as stavudine) and interferons, which may cause depression. Clinicians should be familiar with such adverse effects in order to recognise them promptly once they occur and manage them appropriately.

Don't forget ototoxicity during the SARS-CoV-2 (Covid-19) pandemic!

Aim of this communication is to remind clinical professionals to be aware of ototoxic side effects of several specific drugs proposed for the treatment of the new virus SARS-CoV-2 (Covid-19). In particular, chloroquine and hydroxychloroquine, azithromycin, as well as antiviral drugs such as remdesivir, favipiravir and lopinavir can all present potential ototoxic side effects. The data in the literature do not offer specific information on their potential synergetic effects nor on their interactions.

Pharmacokinetics of nucleoside/nucleotide reverse transcriptase inhibitors for the treatment and prevention of HIV infection

INTRODUCTION

Despite dramatic increases in new drugs and regimens, a combination of two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) remains the backbone of many regimens to treat HIV.

AREA COVERED

This article summarizes the pharmacokinetic characteristics of approved NRTIs that are currently in the international treatment and prevention guidelines.

EXPERT OPINION

Compared to other NRTIs, tenofovir alafenamide fumarate (TAF) is more advantageous in terms of potency and safety. It is therefore a preferred choice in combination with emtricitabine (FTC) in most HIV treatment guidelines. The efficacy of the two-drug combination of NRTI/Integrase strand-transfer inhibitor, i.e. lamivudine/dolutegravir has been approved as an option for initial therapy. This regimen however has some limitations in patients with HBV coinfection. The two NRTI combinations tenofovir disproxil fumarate (TDF)/FTC and TAF/FTC have also been approved for pre-exposure prophylaxis (PrEP). Interestingly, a promising long-acting nucleoside reverse transcriptase translocation inhibitor, islatravir, formulated for implant was well tolerated and remained effective for up to a year, suggesting its potential as a single agent for PrEP. In the next decade, it remains to be seen whether NRTI-based regimens will remain the backbone of preferred ART regimens, or if the treatment will eventually move toward NRTI-sparing regimens to avoid long-term NRTI-toxicity.

Inhibition of human immunodeficiency virus type 1 by niclosamide through mTORC1 inhibition

Niclosamide has been known to inhibit a number of pH-dependent viruses via the neutralization of endosomal acidic pH. It has also been shown to disrupt the mTORC1 signaling pathway. The replication of many viruses requires mTORC1 activation. Here, we investigated the inhibitory activity of niclosamide against HIV-1, and determined whether mTORC1 inhibition was involved. The cytotoxicity and anti-HIV-1 activity of niclosamide were tested in TZM-bl and SupT1 cells. Niclosamide showed a dose- and time-dependent inhibitory activity against HIV-1 replication, but the inhibition did not involve the reverse transcription and transcription steps. The mechanism of mTORC1 inhibition was explored by using MHY1485, an mTORC1 activator, to reverse the mTORC1 inhibition, which could partially restore HIV-1 replication. In addition, niclosamide was found to downregulate mTORC1 via AMPK activation, resulting in a decreased phosphorylation of the downstream substrates of S6K and 4EBP1. Niclosamide could also reduce the synthesis of HIV-1 p24 protein. Likewise, MHY-1485 could partially reverse the inhibitory effect of niclosamide by increasing the phosphorylation in the mTORC1 pathway and HIV-1 viral protein synthesis. Our findings, therefore, demonstrated the antiviral mechanism of niclosamide is via the AMPK-mTORC1 pathway, which could be a common therapeutic target for various viruses.

Mitochondrial Toxicogenomics for Antiretroviral Management: HIV Post-exposure Prophylaxis in Uninfected Patients

Background: Mitochondrial genome has been used across multiple fields in research, diagnosis, and toxicogenomics. Several compounds damage mitochondrial DNA (mtDNA), including biological and therapeutic agents like the human immunodeficiency virus (HIV) but also its antiretroviral treatment, leading to adverse clinical manifestations. HIV-infected and treated patients may show impaired mitochondrial and metabolic profile, but specific contribution of viral or treatment toxicity remains elusive. The evaluation of HIV consequences without treatment interference has been performed in naïve (non-treated) patients, but assessment of treatment toxicity without viral interference is usually restricted to in vitro assays.

Objective: The objective of the present study is to determine whether antiretroviral treatment without HIV interference can lead to mtDNA disturbances. We studied clinical, mitochondrial, and metabolic toxicity in non-infected healthy patients who received HIV post-exposure prophylaxis (PEP) to prevent further infection. We assessed two different PEP regimens according to their composition to ascertain if they were the cause of tolerability issues and derived toxicity.

Methods: We analyzed reasons for PEP discontinuation and main secondary effects of treatment withdrawal, mtDNA content from peripheral blood mononuclear cells and metabolic profile, before and after 28 days of PEP, in 23 patients classified depending on PEP composition: one protease inhibitor (PI) plus Zidovudine/Lamivudine (PI plus AZT + 3TC; n = 9) or PI plus Tenofovir/Emtricitabine (PI plus TDF + FTC; n = 14).

Results: Zidovudine-containing-regimens showed an increased risk for drug discontinuation (RR = 9.33; 95% CI = 1.34–65.23) due to adverse effects of medication related to gastrointestinal complications. In the absence of metabolic disturbances, 4-week PEP containing PI plus AZT + 3TC led to higher mitochondrial toxicity (−17.9 ± 25.8 decrease in mtDNA/nDNA levels) than PI plus TDF + FTC (which increased by 43.2 ± 24.3 units mtDNA/nDNA; p < 0.05 between groups). MtDNA changes showed a significant and negative correlation with baseline alanine transaminase levels (p < 0.05), suggesting that a proper hepatic function may protect from antiretroviral toxicity.

Conclusions: In absence of HIV infection, preventive short antiretroviral treatment can cause secondary effects responsible for treatment discontinuation and subclinical mitochondrial damage, especially pyrimidine analogs such as AZT, which still rank as the alternative option and first choice in certain cohorts for PEP. Forthcoming efforts should be focused on launching new strategies with safer clinical and mitotoxic profile.

The far-reaching HAND of cART: cART effects on astrocytes

Following the introduction of combination antiretroviral therapy (cART), the morbidity and mortality from human immunodeficiency virus (HIV) infection has been drastically curtailed and HIV has now become a chronic manageable disease. Persons living with HIV (PLWH) are living longer and experiencing significant co-morbidities and conditions of aging. NeuroHIV, clinically defined as HIV-Associated Neurocognitive Disorders (HAND) and pathologically manifested by persistent inflammation in the CNS despite cART, is a significant co-morbid condition for PLWH. In the pre-cART era, HIV mediated much of the pathogenesis in the Central Nervous System (CNS); in the cART era, with low to undetectable viremia, other mechanisms may be contributing to persistent neuroinflammation. Emerging data point to the adverse effects at the cellular level of cART, independent of HIV. Astrocytes are the most abundant cells in the CNS, playing vital roles in maintaining CNS homeostasis (e.g. metabolic support to neurons, clearance of neurotransmitters, ion balance, modulation of synaptic functions and maintaining the structural integrity of the blood brain barrier (BBB). Therefore, any disruption of their function will have wide repercussions in the CNS. In this review, we will address current knowledge and gaps on the impact of antiretrovirals (ARVs) on astrocytes and physiologic consequences in the CNS. Understanding the status of this field, will provide a practical framework to elucidate the potential role of cART-mediated dysregulation of astrocytes in neuroHIV pathogenesis and inform therapeutic strategies that are "neuro-friendly". Graphical abstract CNS-penetrating cART have the potential to cause resting astrocytes to become activated into an A1 or neurotoxic phenotype. These cells can in turn secrete inflammatory cytokines that affect surrounding microglia macrophages, as well as neurotoxic factors that impact nearby neurons. In addition, impairment in the physiologic functions of astrocytes will result in altered BBB permeability and disrupted metabolic homeostasis. CNS=Central Nervous System; cART=combined antiretroviral therapy; BBB=blood brain barrier.

Prevalence of hearing loss and tinnitus in a group of adults with Human Immunodeficiency Virus

Background

The Human Immunodeficiency Virus (HIV) has become a global pandemic. With the improvement of antiretroviral (ARV) treatment regimens, life-expectancy of HIV-positive individuals has increased. HIV literature suggests that head and neck manifestations may be the first indication of supressed immunity. Therefore, research regarding the effects of HIV and new treatment regimens on auditory function remains a priority.

Objectives

To describe the audiological characteristics and determine the prevalence of hearing loss and tinnitus in a group of HIV-positive individuals on ARV treatment residing in a rural province.

Methods

The study employed a cross-sectional descriptive research design. Participants were recruited from the clinic and pharmacy waiting areas of a medical centre in a rural area of Limpopo province, South Africa. Two participant groups, an HIV-positive group (N₁ = 60) and an HIV-negative group (N₂ = 32) were included in the study. The test battery comprised a comprehensive case history and a routine audiological test battery, which included otoscopy, tympanometry and pure tone audiometry (250 Hz to 8000 Hz).

Results

No statistically significant difference was found regarding the prevalence of hearing loss in the two participant groups (p = 0.709). However, the prevalence of tinnitus was significantly higher in the HIV-positive group (p = 0.05).

Conclusion

The insignificant difference in the audiological test battery results found between the two participant groups may be due to improved ARV treatment regimens and management strategies employed at the medical centre. However, the increased prevalence of tinnitus in the HIV-positive group may also be attributed to the ARV regimen and/or the result of subtle damage to the auditory system, which was not identified by the current audiological test battery. More insight may be obtained about the effects of HIV on hearing by employing a longitudinal research design and inclusion of a more ototoxicity sensitive test battery.

Bile duct ligation enhances AZT CNS toxicity partly by impairing the expression and function of BCRP in rat brain

Breast cancer resistance protein (BCRP) is one of ATP-binding cassette (ABC) transporters in brain microvessel endothelial cells that transport their substrates from brain to blood, thus limiting substrates to crossing into brain through blood-brain barrier. Our previous works show that bile duct ligation (BDL) impairs expression and function of brain BCRP in rats. Since zidovudine (AZT) is BCRP substrate, we investigated whether impaired expression and function of BCRP increased brain distribution and toxicity of AZT in BDL-D7 rats. After administration of AZT (10 mg/kg, i.v.), BDL markedly increased brain AZT concentrations, compared with sham-operated (SO) rats. The ratio of AZT brain-to-plasma area under concentration curve (AUC) in BDL rats was increased to 1.6-folds of SO rats. After treatment with AZT (100 mg/kg every day, i.v.) for 7 days, BDL significantly impaired cognitive functions compared with SO rats, evidenced by the significantly decreased percentage of alternation in Y-maze test and prolonged escaped latency in two-way passive avoidance trial. Furthermore, AZT treatment caused significant decrease in copies of mitochondrial DNA and mitochondrial membrane potential in hippocampus of BDL rats. Moreover, AZT treatment caused a significant decrease of cortex microtubule-associated protein 2 and hippocampus synaptophysin levels in BDL rats. AZT-induced CNS adverse alterations in BDL rats were not observed in SO rats treated with AZT. In conclusion, BDL decreases the function and expression of brain BCRP in rats, leading to increased brain distribution of AZT, which in turn enhances AZT CNS toxicity, leading to mitochondrial dysfunction, neuronal damage, and ultimately cognitive dysfunction.

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.

Immunopathologic Effects of Prednisolone and Cyclosporine A on Feline Immunodeficiency Virus Replication and Persistence

Feline immunodeficiency virus (FIV) induces opportunistic disease in chronically infected cats, and both prednisolone and cyclosporine A (CsA) are clinically used to treat complications such as lymphoma and stomatitis. However, the impact of these compounds on FIV infection are still unknown and understanding immunomodulatory effects on FIV replication and persistence is critical to guide safe and effective therapies. To determine the immunologic and virologic effects of prednisolone and CsA during FIV infection, FIV-positive cats were administered immunosuppressive doses of prednisolone (2 mg/kg) or CsA (5 mg/kg). Both prednisolone and CsA induced acute and transient increases in FIV DNA and RNA loads as detected by quantitative PCR. Changes in the proportion of lymphocyte immunophenotypes were also observed between FIV-infected and naïve cats treated with CsA and prednisolone, and both treatments caused acute increases in CD4+ lymphocytes that correlated with increased FIV RNA. CsA and prednisolone also produced alterations in cytokine expression that favored a shift toward a Th2 response. Pre-treatment with CsA slightly enhanced the efficacy of antiretroviral therapy but did not enhance clearance of FIV. Results highlight the potential for drug-induced perturbation of FIV infection and underscore the need for more information regarding immunopathologic consequences of therapeutic agents on concurrent viral infections.

Synthesis of a long acting nanoformulated emtricitabine ProTide

While antiretroviral therapy (ART) has revolutionized treatment and prevention of human immunodeficiency virus type one (HIV-1) infection, regimen adherence, viral mutations, drug toxicities and access stigma and fatigue are treatment limitations. These have led to new opportunities for the development of long acting (LA) ART including implantable devices and chemical drug modifications. Herein, medicinal and formulation chemistry were used to develop LA prodrug nanoformulations of emtricitabine (FTC). A potent lipophilic FTC phosphoramidate prodrug (M2FTC) was synthesized then encapsulated into a poloxamer surfactant (NM2FTC). These modifications extended the biology, apparent drug half-life and antiretroviral activities of the formulations. NM2FTC demonstrated a >30-fold increase in macrophage and CD4+ T cell drug uptake with efficient conversion to triphosphates (FTC-TP). Intracellular FTC-TP protected macrophages against an HIV-1 challenge for 30 days. A single intramuscular injection of NM2FTC, at 45 mg/kg native drug equivalents, into Sprague Dawley rats resulted in sustained prodrug levels in blood, liver, spleen and lymph nodes and FTC-TP in lymph node and spleen cells at one month. In contrast, native FTC-TPs was present for one day. These results are an advance in the transformation of FTC into a LA agent.

DNA polymerase-γ hypothesis in nucleoside reverse transcriptase-induced mitochondrial toxicity revisited: A potentially protective role for citrus fruit-derived naringenin?

Nucleoside reverse transcriptase inhibitors (NRTIs) form the backbone in combination antiretroviral therapy (cARVs). They halt chain elongation of the viral cDNA by acting as false substrates in counterfeit incorporation mechanism to viral RNA-dependent DNA polymerase. In the process genomic DNA polymerase as well as mitochondrial DNA (mtDNA) polymerase-γ (which has a much higher affinity for these drugs at therapeutic doses) are also impaired. This leads to mitochondrial toxicity that manifests clinically as mitochondrial myopathy, peripheral neuropathy, hyperlactatemia or lactic acidosis and lipoatrophy. This has led to the revision of clinical guidelines by World Health Organization to remove stavudine from first-line listing in the treatment of HIV infections. Recent reports have implicated oxidative stress besides mtDNA polymerase-γ hypothesis in NRTI-induced metabolic complications. Reduced plasma antioxidant concentrations have been reported in HIV positive patients on cARVs but clinical intervention with antioxidant supplements have not been successful either due to low efficacy or poor experimental designs. Citrus fruit-derived naringenin has previously been demonstrated to possess antioxidant and free radical scavenging properties which could prevent mitochondrial toxicity associated with these drugs. This review revisits the controversy surrounding mtDNA polymerase-γ hypothesis and evaluates the potential benefits of naringenin as a potent anti-oxidant and free radical scavenger which as a nutritional supplement or therapeutic adjunct could mitigate the development of mitochondrial toxicity associated with these drugs.

Mitochondrial dysfunction in HIV-induced peripheral neuropathy

Mitochondria play an essential role in cellular energy production and calcium homeostasis. Abnormalities in mitochondrial homeostasis and function are seen in several acquired as well as genetic neuropathies, emphasizing their prominent role in neuronal cell activities. Chronic infection with HIV, even when appropriately treated, is a risk factor for developing peripheral neuropathy. In this chapter, we discuss the way in which HIV infection, the resultant toxic viral products that are generated, and some of the viral inhibitors used in its treatment may lead to abnormal mitochondrial function. Of importance are the effects on mitochondrial DNA replication and the neurotoxic effects of the viral gp120 protein. One aspect of mitochondrial dysfunction that remains unexplored is the role of the interaction between mitochondria and the endoplasmic reticulum as a possible target of disruption in HIV neuropathy.