Memantine for AIDS dementia complex: open-label report of ACTG 301

Restorative effect of NitroSynapsin on synaptic plasticity in an animal model of depression

In the search for new options for the pharmacological treatment of major depressive disorder, compounds with a rapid onset of action and high efficacy but lacking a psychotomimetic effect are of particular interest. In the present study, we evaluated the antidepressant potential of NitroSynapsin (NS) at behavioural, structural, and functional levels. NS is a memantine derivative and a dual allosteric N-methyl-d-aspartate receptors (NMDAR) antagonist using targeted delivery by the aminoadamantane of a warhead nitro group to inhibitory redox sites on the NMDAR. In a chronic restraint stress (CRS) mouse model of depression, five doses of NS administered on three consecutive days evoked antidepressant-like activity in the chronically stressed male C57BL/6J mice, reversing CRS-induced behavioural disturbances in sucrose preference and tail suspension tests. CRS-induced changes in morphology and density of dendritic spines in cerebrocortical neurons in the medial prefrontal cortex (mPFC) were also reversed by NS. Moreover, CRS-induced reduction in long-term potentiation (LTP) in the mPFC was found to be prevented by NS based on the electrophysiological recordings. Our study showed that NS restores structural and functional synaptic plasticity and reduces depressive behaviour to the level found in naïve animals. These results preliminarily revealed an antidepressant-like potency of NS.

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.

Vir2Drug: a drug repurposing framework based on protein similarities between pathogens

We draw from the assumption that similarities between pathogens at both pathogen protein and host protein level, may provide the appropriate framework to identify and rank candidate drugs to be used against a specific pathogen. Vir2Drug is a drug repurposing tool that uses network-based approaches to identify and rank candidate drugs for a specific pathogen, combining information obtained from: (a) ranked pathogen-to-pathogen networks based on protein similarities between pathogens, (b) taxonomy distance between pathogens and (c) drugs targeting specific pathogen's and host proteins. The underlying pathogen networks are used to screen drugs by means of specific methodologies that account for either the host or pathogen's protein targets. Vir2Drug is a useful and yet informative tool for drug repurposing against known or unknown pathogens especially in periods where the emergence for repurposed drugs plays significant role in handling viral outbreaks, until reaching a vaccine. The web tool is available at: https://bioinformatics.cing.ac.cy/vir2drug, https://vir2drug.cing-big.hpcf.cyi.ac.cy.

Memantine Attenuates Cocaine and neuroHIV Neurotoxicity in the Medial Prefrontal Cortex

Individuals with substance use disorder are at a higher risk of contracting HIV and progress more rapidly to AIDS as drugs of abuse, such as cocaine, potentiate the neurotoxic effects of HIV-associated proteins including, but not limited to, HIV-1 trans-activator of transcription (Tat) and the envelope protein Gp120. Neurotoxicity and neurodegeneration are hallmarks of HIV-1-associated neurocognitive disorders (HANDs), which are hypothesized to occur secondary to excitotoxicity from NMDA-induced neuronal calcium dysregulation, which could be targeted with NMDA antagonist drugs. Multiple studies have examined how Gp120 affects calcium influx and how cocaine potentiates this influx; however, they mostly focused on single cells and did not analyze effects in neuronal and vascular brain networks. Here, we utilize a custom multi-wavelength imaging platform to simultaneously study the neuronal activity (detected using genetically encoded Ca²⁺ indicator, GcaMP6f, expressed in neurons) and hemodynamic changes (measured by total hemoglobin and oxygenated hemoglobin within the tissue) in the prefrontal cortex (PFC) of HIV-1 Tg rats in response to cocaine and evaluate the effects of the selective NMDA antagonist drug memantine on cocaine and HIV neurotoxicity compared to those of non-HIV-1 Tg animals (controls). Our results show that memantine improved cocaine-induced deficit in cerebral blood volume while also attenuating an abnormal increase of the neuronal calcium influx and influx duration in both control rats and HIV-1 Tg rats. Cocaine-induced neuronal and hemodynamic dysregulations were significantly greater in HIV-1 Tg rats than in control rats. With memantine pretreatment, HIV-1 Tg rats showed attenuated cocaine’s effects on neuronal and hemodynamic responses, with responses similar to those observed in control rats. These imaging results document an enhancement of neuronal Ca²⁺ influx, hypoxemia, and ischemia with cocaine in the PFC of HIV-1 Tg rats that were attenuated by memantine pretreatment. Thus, the potential utility of memantine in the treatment of HAND and of cocaine-induced neurotoxicity deserves further investigation.

Developments in Neuroprotection for HIV-Associated Neurocognitive Disorders (HAND)

PURPOSE OF REVIEW

Reducing the risk of HIV-associated neurocognitive disorders (HAND) is an elusive treatment goal for people living with HIV. Combination antiretroviral therapy (cART) has reduced the prevalence of HIV-associated dementia, but milder, disabling HAND is an unmet challenge. As newer cART regimens that more consistently suppress central nervous system (CNS) HIV replication are developed, the testing of adjunctive neuroprotective therapies must accelerate.

RECENT FINDINGS

Successes in modifying cART regimens for CNS efficacy (penetrance, chemokine receptor targeting) and delivery (nanoformulations) in pilot studies suggest that improving cART neuroprotection and reducing HAND risk is achievable. Additionally, drugs currently used in neuroinflammatory, neuropsychiatric, and metabolic disorders show promise as adjuncts to cART, likely by broadly targeting neuroinflammation, oxidative stress, aerobic metabolism, and/or neurotransmitter metabolism. Adjunctive cognitive brain therapy and aerobic exercise may provide additional efficacy. Adjunctive neuroprotective therapies, including available FDA-approved drugs, cognitive therapy, and aerobic exercise combined with improved cART offer plausible strategies for optimizing the prevention and treatment of HAND.

SARS-CoV-2 infection in patients with serious mental illness and possible benefits of prophylaxis with Memantine and Amantadine

Patients with serious mental illness are a high-risk category of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Patients with schizophrenia are not participatory and have increased mortality and morbidity, patients with dementia cannot be cared for while depression, anxiety, bipolar tubing are associated with low immune status. Social stress is amplified by social isolation, amplifying depression and the mechanisms of decreased immunity. Hygiene measures and prophylactic behavior are impossible to put into practice in conditions of chronic mental illness. In coronavirus disease 2019 (COVID-19), the risk for severe development is associated with the presence of comorbidities and immune system deficiency. Prothrombotic status, cytokine storm and alveolar destruction are mechanisms that aggravate the evolution of patients, especially in the context in which they have dysfunction of the autonomic system. The activity of proinflammatory cytokines is accentuated by hyperglutamatergia, which potentiates oxidative stress and triggers the mechanisms of neural apoptosis by stimulating microglial activation. Activation of M1-type microglia has an important role in pathogenesis of major psychiatric disorders, such as major depression, schizophrenia or bipolar disorder, and may associate hippocampal atrophy and disconnection of cognitive structures. Memantine and Amantadine, N-methyl-D-aspartate (NMDA) glutamate receptor inhibitors, have demonstrated, through their pharmacological profile, psychotropic effects but also antiviral properties. In the conditions of the COVID-19 pandemic, based on these arguments, we suggest that they can be associated with the therapy with the basic psychotropics, Memantine or Amantadine, for the control of neuropsychiatric symptoms but also as adjuvants with antiviral action.

Cognitive disorders in people living with HIV

High rates of cognitive disorders in antiretroviral-treated people living with HIV have been described worldwide. The exact prevalence of such cognitive disorders is determined by the definitions used, and the presence of these cognitive disorders significantly impacts the overall wellbeing of people with HIV. With the cohort of people with HIV becoming increasingly older, and having high rates of comorbidities and concomitant medication use, rates of cognitive disorders are likely to increase. Conversely, interventions are being sought to reduce the size of the latent HIV reservoir. If successful, such interventions are likely to also reduce the HIV reservoir in the brain compartment, which could result in improvements in cognitive function and reduced rates of impairment.

Potential pharmacological approaches for the treatment of HIV-1 associated neurocognitive disorders

HIV associated neurocognitive disorders (HAND) are the spectrum of cognitive impairments present in patients infected with human immunodeficiency virus type 1 (HIV-1). The number of patients affected with HAND ranges from 30 to 50% of HIV infected individuals and although the development of combinational antiretroviral therapy (cART) has improved longevity, HAND continues to pose a significant clinical problem as the current standard of care does not alleviate or prevent HAND symptoms. At present, the pathological mechanisms contributing to HAND remain unclear, but evidence suggests that it stems from neuronal injury due to chronic release of neurotoxins, chemokines, viral proteins, and proinflammatory cytokines secreted by HIV-1 activated microglia, macrophages and astrocytes in the central nervous system (CNS). Furthermore, the blood-brain barrier (BBB) not only serves as a route for HIV-1 entry into the brain but also prevents cART therapy from reaching HIV-1 brain reservoirs, and therefore could play an important role in HAND. The goal of this review is to discuss the current data on the epidemiology, pathology and research models of HAND as well as address the potential pharmacological treatment approaches that are being investigated.

Amantadine and memantine: a comprehensive review for acquired brain injury

This comprehensive review discusses clinical studies of patients following brain injuries (traumatic, acquired, or stroke), who have been treated with amantadine or memantine. Both amantadine and memantine are commonly used in the acute rehabilitation setting following brain injuries, despite their lack of FDA-approval for neuro-recovery. Given the broad utilization of such agents, there is a need to review the evidence supporting this common off-label prescribing. The purpose of this review is to describe the mechanisms of action for memantine and amantadine, as well as to complete a comprehensive review of the clinical uses of these agents. We included 119 original, clinical research articles from NCBI Medline, published before 2019. We focused on the domains of neuroplasticity, functional recovery, motor recovery, arousal, fatigue, insomnia, behavior, agitation, and cognition. Most of the existing research supporting the use of amantadine and memantine in recovery from brain injuries was done in very small populations, limiting the significance of conclusions. While most studies are positive; small effect sizes are usually reported, or populations are subject to bias. Furthermore, evidence is so limited that this review includes research regarding both acute and chronic acquired brain injury populations. Fortunately, reported short-term side effects generally are modest, and stop soon after amantadine/memantine is discontinued. However, responses are inconsistent, and the phenotype of responders remains elusive.

Clinical Treatment Options and Randomized Clinical Trials for Neurocognitive Complications of HIV Infection: Combination Antiretroviral Therapy, Central Nervous System Penetration Effectiveness, and Adjuvants

The etiology and pathogenesis of human immunodeficiency virus type-I (HIV)-associated neurocognitive disorders (HAND) remain undetermined and are likely the produce of multiple mechanisms. This can mainly include neuronal injury from HIV, inflammatory processes, and mental health issues. As a result, a variety of treatment options have been tested including NeuroHIV-targeted regimens based on the central nervous system (CNS) penetration effectiveness (CPE) of antiretroviral therapy (ART) and adjuvant therapies for HAND. NeuroHIV-targeted ART regimens have produced consistent and statistically significant HIV suppression in the CNS, but this is not the case for cognitive and functional domains. Most adjuvant therapies such as minocycline, memantine, and selegiline have negligible benefit in the improvement of cognitive function of people living with HIV (PLWH) with mild to moderate neurocognitive impairment. Newer experimental treatments have been proposed to target cognitive and functional symptoms of HAND as well as potential underlying pathogenesis. This review aims to provide an analytical overview of the clinical treatment options and clinical trials for HAND by focusing on NeuroHIV-targeted ART regimen development, CPE, and adjuvant therapies.

Memantine for dementia

BACKGROUND

Memantine is a moderate affinity uncompetitive antagonist of glutamate NMDA receptors. It is licensed for use in moderate and severe Alzheimer's disease (AD); in the USA, it is also widely used off-label for mild AD.

OBJECTIVES

To determine efficacy and safety of memantine for people with dementia. To assess whether memantine adds benefit for people already taking cholinesterase inhibitors (ChEIs).

SEARCH METHODS

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group's register of trials (http://www.medicine.ox.ac.uk/alois/) up to 25 March 2018. We examined clinical trials registries, press releases and posters of memantine manufacturers; and the web sites of the FDA, EMEA and NICE. We contacted authors and companies for missing information.

SELECTION CRITERIA

Double-blind, parallel group, placebo-controlled, randomised trials of memantine in people with dementia.

DATA COLLECTION AND ANALYSIS

We pooled and analysed data from four clinical domains across different aetiologies and severities of dementia and for AD with agitation. We assessed the impact of study duration, severity and concomitant use of ChEIs. Consequently, we restricted analyses to the licensed dose (20 mg/day or 28 mg extended release) and data at six to seven months duration of follow-up, and analysed separately results for mild and moderate-to-severe AD.We transformed results for efficacy outcomes into the difference in points on particular outcome scales.

MAIN RESULTS

Across all types of dementia, data were available from almost 10,000 participants in 44 included trials, most of which were at low or unclear risk of bias. For nearly half the studies, relevant data were obtained from unpublished sources. The majority of trials (29 in 7885 participants) were conducted in people with AD.1. Moderate-to-severe AD (with or without concomitant ChEIs). High-certainty evidence from up to 14 studies in around 3700 participants consistently shows a small clinical benefit for memantine versus placebo: clinical global rating (CGR): 0.21 CIBIC+ points (95% confidence interval (CI) 0.14 to 0.30); cognitive function (CF): 3.11 Severe Impairment Battery (SIB) points (95% CI 2.42 to 3.92); performance on activities of daily living (ADL): 1.09 ADL19 points (95% CI 0.62 to 1.64); and behaviour and mood (BM): 1.84 Neuropsychiatric Inventory (NPI) points (95% CI 1.05 to 2.76). There may be no difference in the number of people discontinuing memantine compared to placebo: risk ratio (RR) 0.93 (95% CI 0.83 to 1.04) corresponding to 13 fewer people per 1000 (95% CI 31 fewer to 7 more). Although there is moderate-certainty evidence that fewer people taking memantine experience agitation as an adverse event: RR 0.81 (95% CI 0.66 to 0.99) (25 fewer people per 1000, 95% CI 1 to 44 fewer), there is also moderate-certainty evidence, from three additional studies, suggesting that memantine is not beneficial as a treatment for agitation (e.g. Cohen Mansfield Agitation Inventory: clinical benefit of 0.50 CMAI points, 95% CI -3.71 to 4.71) .The presence of concomitant ChEI does not impact on the difference between memantine and placebo, with the possible exceptions of the BM outcome (larger effect in people taking ChEIs) and the CF outcome (smaller effect).2. Mild AD (Mini Mental State Examination (MMSE) 20 to 23): mainly moderate-certainty evidence based on post-hoc subgroups from up to four studies in around 600 participants suggests there is probably no difference between memantine and placebo for CF: 0.21 ADAS-Cog points (95% CI -0.95 to 1.38); performance on ADL: -0.07 ADL 23 points (95% CI -1.80 to 1.66); and BM: -0.29 NPI points (95% CI -2.16 to 1.58). There is less certainty in the CGR evidence, which also suggests there may be no difference: 0.09 CIBIC+ points (95% CI -0.12 to 0.30). Memantine (compared with placebo) may increase the numbers of people discontinuing treatment because of adverse events (RR 2.12, 95% CI 1.03 to 4.39).3. Mild-to-moderate vascular dementia. Moderate- and low-certainty evidence from two studies in around 750 participants indicates there is probably a small clinical benefit for CF: 2.15 ADAS-Cog points (95% CI 1.05 to 3.25); there may be a small clinical benefit for BM: 0.47 NOSGER disturbing behaviour points (95% CI 0.07 to 0.87); there is probably no difference in CGR: 0.03 CIBIC+ points (95% CI -0.28 to 0.34); and there may be no difference in ADL: 0.11 NOSGER II self-care subscale points (95% CI -0.35 to 0.54) or in the numbers of people discontinuing treatment: RR 1.05 (95% CI 0.83 to 1.34).There is limited, mainly low- or very low-certainty efficacy evidence for other types of dementia (Parkinson's disease and dementia Lewy bodies (for which CGR may show a small clinical benefit; four studies in 319 people); frontotemporal dementia (two studies in 133 people); and AIDS-related Dementia Complex (one study in 140 people)).There is high-certainty evidence showing no difference between memantine and placebo in the proportion experiencing at least one adverse event: RR 1.03 (95% CI 1.00 to 1.06); the RR does not differ between aetiologies or severities of dementia. Combining available data from all trials, there is moderate-certainty evidence that memantine is 1.6 times more likely than placebo to result in dizziness (6.1% versus 3.9%), low-certainty evidence of a 1.3-fold increased risk of headache (5.5% versus 4.3%), but high-certainty evidence of no difference in falls.

AUTHORS' CONCLUSIONS

We found important differences in the efficacy of memantine in mild AD compared to that in moderate-to-severe AD. There is a small clinical benefit of memantine in people with moderate-to-severe AD, which occurs irrespective of whether they are also taking a ChEI, but no benefit in people with mild AD.Clinical heterogeneity in AD makes it unlikely that any single drug will have a large effect size, and means that the optimal drug treatment may involve multiple drugs, each having an effect size that may be less than the minimum clinically important difference.A definitive long-duration trial in mild AD is needed to establish whether starting memantine earlier would be beneficial over the long term and safe: at present the evidence is against this, despite it being common practice. A long-duration trial in moderate-to-severe AD is needed to establish whether the benefit persists beyond six months.

Interventions for Neurocognitive Dysfunction

PURPOSE OF REVIEW

This study aimed to evaluate current barriers to HIV cure strategies and interventions for neurocognitive dysfunction with a particular focus on recent advancements over the last 3 years.

RECENT FINDINGS

Optimal anti-retroviral therapy (ART) poses challenges to minimise neurotoxicity, whilst ensuring blood-brain barrier penetration and minimising the risk of cerebrovascular disease. CSF biomarkers, BCL11B and neurofilament light chain may be implicated with a neuroinflammatory cascade leading to cognitive impairment. Diagnostic imaging with diffusion tensor imaging and resting-state fMRI show promise in future diagnosis and monitoring of HAND. The introduction of ART has resulted in a dramatic decline in HIV-associated dementia. Despite this reduction, milder forms of HIV-associated neurocognitive disorder (HAND) are still prevalent and are clinically significant. The central nervous system (CNS) has been recognised as a probable reservoir and sanctuary for HIV, representing a significant barrier to management interventions.

Sonic Hedgehog mimetic prevents leukocyte infiltration into the CNS during acute HIV infection

Infiltration of infected leukocytes culminates in establishment of a brain niche for Human Immunodeficiency Virus (HIV) during acute phase of infection, initiating an ongoing cascade of persistent viral replication and inflammation, that causes irreversible neuronal injury and HIV associated neurocognitive disease (HAND). In this study, humanized mice were treated with Smoothened Agonist (SAG), a Sonic Hedgehog (Shh) mimetic in order to fortify blood brain barrier (BBB) and dampen leukocyte extravasation into CNS during AHI. Results indicate that SAG treatment reduced viral burden in the CNS immediately after HIV transmission, but also conferred extended neuroprotection via increased BBB integrity (elevated levels of tight-junction protein, Claudin 5, and reduced S100B levels in periphery). These mice also showed healthier neurons with thick, uniform dendrites and reduced numbers of activated astrocytes. Additional in vitro experiments suggested SAG treatment was not associated with the establishment or reversal of latency in the target cells. Altogether, these findings validate neuroprotective role of Shh signaling and highlight the therapeutic potential of Shh mimetics against CNS complications associated with HIV infection. Further our results strongly demonstrate that pharmacological interventions to reduce leukocyte mobilization during early HIV infection, can provide prolonged neuroprotection, which might significantly delay the onset of HAND.

Smoothened Agonist Reduces Human Immunodeficiency Virus Type-1-Induced Blood-Brain Barrier Breakdown in Humanized Mice

Human Immunodeficiency Virus type-1 (HIV)-associated neurocognitive disorder is characterized by recruitment of activated/infected leukocytes into the CNS via disrupted Blood Brain Barrier (BBB) that contributes to persistent neuro-inflammation. In this report, humanized NOD/scid-IL2Rγ_c^null mice were used to establish that impaired Sonic hedgehog (Shh) signaling is associated with loss of BBB function and neurological damage, and that modulating Shh signaling can rescue these detrimental effects. Plasma viral load, p24 levels and CD4⁺ T cells were measured as markers of productive HIV infection. These mice also showed impaired exclusion of Evans blue dye from the brain, increased plasma levels of S100B, an astrocytic protein, and down-regulation of tight junction proteins Occludin and Claudin5, collectively indicating BBB dysfunction. Further, brain tissue from HIV⁺ mice indicated reduced synaptic density, neuronal atrophy, microglial activation, and astrocytosis. Importantly, reduced expression of Shh and Gli1 was also observed in these mice, demonstrating diminished Shh signaling. Administration of Shh mimetic, smoothened agonist (SAG) restored BBB integrity and also abated the neuropathology in infected mice. Together, our results suggest a neuroprotective role for Shh signaling in the context of HIV infection, underscoring the therapeutic potential of SAG in controlling HAND pathogenesis.

Neural correlates of working memory training in HIV patients: study protocol for a randomized controlled trial

Background

Potent combined antiretroviral therapy decreased the incidence and severity of HIV-associated neurocognitive disorders (HAND); however, no specific effective pharmacotherapy exists for HAND. Patients with HIV commonly have deficits in working memory and attention, which may negatively impact many other cognitive domains, leading to HAND. Since HAND may lead to loss of independence in activities of daily living and negative emotional well-being, and incur a high economic burden, effective treatments for HAND are urgently needed. This study aims to determine whether adaptive working memory training might improve cognitive functions and neural network efficiency and possibly decrease neuroinflammation. This study also aims to assess whether subjects with the LMX1A-rs4657412 TT(AA) genotype show greater training effects from working memory training than TC(AG) or CC(GG)-carriers.

Methods/Design

60 HIV-infected and 60 seronegative control participants will be randomized to a double-blind active-controlled study, using adaptive versus non-adaptive Cogmed Working Memory Training® (CWMT), 20–25 sessions over 5–8 weeks. Each subject will be assessed with near- and far-transfer cognitive tasks, self-reported mood and executive function questionnaires, and blood-oxygenation level-dependent functional MRI during working memory (n-back) and visual attention (ball tracking) tasks, at baseline, 1-month, and 6-months after CWMT. Furthermore, genotyping for LMX1A-rs4657412 will be performed to identify whether subjects with the TT(AA)-genotype show greater gain or neural efficiency after CWMT than those with other genotypes. Lastly, cerebrospinal fluid will be obtained before and after CWMT to explore changes in levels of inflammatory proteins (cytokines and chemokines) and monoamines.

Discussion

Improving working memory in HIV patients, using CWMT, might slow the progression or delay the onset of HAND. Observation of decreased brain activation or normalized neural networks, using fMRI, after CWMT would lead to a better understanding of how neural networks are modulated by CWMT. Moreover, validating the greater training gain in subjects with the LMX1A-TT(AA) genotype could lead to a personalized approach for future working memory training studies. Demonstrating and understanding the neural correlates of the efficacy of CWMT in HIV patients could lead to a safe adjunctive therapy for HAND, and possibly other brain disorders.

Trial registration

ClinicalTrial.gov, NCT02602418.

Treatment of HIV in the CNS: effects of antiretroviral therapy and the promise of non-antiretroviral therapeutics

The growing recognition of the burden of neurologic disease associated with HIV infection in the last decade has led to renewed efforts to characterize the pathophysiology of the virus within the central nervous system (CNS). The concept of the AIDS-dementia complex is now better understood as a spectrum of HIV-associated neurocognitive disorders (HAND), which range from asymptomatic disease to severe impairment. Recent work has shown that even optimally treated patients can experience not only persistent HAND, but also the development of new neurologic abnormalities despite viral suppression. This has thrown into question what the impact of antiretroviral therapy has been on the incidence and prevalence of neurocognitive dysfunction. In this context, the last few years have seen a concentrated effort to identify the effects that antiretroviral therapy has on the neurologic manifestations of HIV and to develop therapeutic modalities that might specifically alter the trajectory of HIV within the CNS.

Adjuvant therapies for HIV-associated neurocognitive disorders

OBJECTIVE

HIV-associated neurocognitive disorder (HAND) is a frequent and heterogeneous complication of HIV, affecting nearly 50% of infected individuals in the combined antiretroviral therapy (cART) era. This is a particularly devastating statistic because the diagnosis of HAND confers an increased risk of HIV-associated morbidity and mortality in affected patients. While cART is helpful in the treatment of the more severe forms of HAND, there is a therapeutic gap in the milder forms of HAND, where cART is less effective. Multiple adjuvant therapies with various mechanisms of action have been studied (N-methyl D-aspartate [NMDA]-receptor antagonists, MAO-B inhibitors, tetracycline-class antibiotics, and others), but none have shown a clear positive effect in HAND. While this lack of efficacy may be because the appropriate therapeutic targets have not yet been determined, we aimed to discuss that study results may also influenced by clinical trial design.

METHODS

This report is a systematic review of clinical trials of adjuvant therapies for HAND performed from January 1996 through June 2014.

RESULTS

Possible drawbacks in study design, including lack of standardized case definitions, poorly defined target populations, inappropriate dose selection and measurable outcomes, and brief study durations may have masked true underlying mechanistic effects of previously investigated adjuvant therapies for HAND in specific patient populations.

CONCLUSIONS

A proposal for streamlining and maximizing the likelihood of success in future clinical studies using a 'learning and confirming' investigational paradigm, incorporating stronger adaptive Phase I/II study designs, computerized modeling, and population/goal of treatment-specific Phase III clinical trials is presented.

Curcumin ameliorates hippocampal neuron damage induced by human immunodeficiency virus-1

Our previous studies have shown that infection with the gp120 V3 loop can cause human immunodeficiency virus-1 associated neurocognitive disorders. Curcumin has been shown to improve these effects to some degree, but the precise mechanisms remain unknown. The present study analyzed the neuroprotective effect and mechanism of curcumin in relation to hippocampal neurons. Results showed that 1 nmol/L gp120 V3 loop suppressed the growth of synapses. After administration of 1 μmol/L curcumin, synaptic growth improved. Curcumin is neuroprotective against gp120 V3 loop-induced neuronal damage by inhibiting the activation of L-type calcium currents, relieving intracellular Ca(2+) overload, promoting Bcl-2 expression, and inhibiting Bax activation. The effect of curcumin was identical to nimodipine, suggesting that curcumin has the same neuroprotective effects against gp120 V3 loop-induced neuronal damage.

Gene expression changes consistent with neuroAIDS and impaired working memory in HIV-1 transgenic rats

BACKGROUND

A thorough investigation of the neurobiology of HIV-induced neuronal dysfunction and its evolving phenotype in the setting of viral suppression has been limited by the lack of validated small animal models to probe the effects of concomitant low level expression of multiple HIV-1 products in disease-relevant cells in the CNS.

RESULTS

We report the results of gene expression profiling of the hippocampus of HIV-1 Tg rats, a rodent model of HIV infection in which multiple HIV-1 proteins are expressed under the control of the viral LTR promoter in disease-relevant cells including microglia and astrocytes. The Gene Set Enrichment Analysis (GSEA) algorithm was used for pathway analysis. Gene expression changes observed are consistent with astrogliosis and microgliosis and include evidence of inflammation and cell proliferation. Among the genes with increased expression in HIV-1 Tg rats was the interferon stimulated gene 15 (ISG-15), which was previously shown to be increased in the cerebrospinal fluid (CSF) of HIV patients and to correlate with neuropsychological impairment and neuropathology, and prostaglandin D2 (PGD2) synthase (Ptgds), which has been associated with immune activation and the induction of astrogliosis and microgliosis. GSEA-based pathway analysis highlighted a broad dysregulation of genes involved in neuronal trophism and neurodegenerative disorders. Among the latter are genesets associated with Huntington's disease, Parkinson's disease, mitochondrial, peroxisome function, and synaptic trophism and plasticity, such as IGF, ErbB and netrin signaling and the PI3K signal transduction pathway, a mediator of neural plasticity and of a vast array of trophic signals. Additionally, gene expression analyses also show altered lipid metabolism and peroxisomes dysfunction. Supporting the functional significance of these gene expression alterations, HIV-1 Tg rats showed working memory impairments in spontaneous alternation behavior in the T-Maze, a paradigm sensitive to prefrontal cortex and hippocampal function.

CONCLUSIONS

Altogether, differentially regulated genes and pathway analysis identify specific pathways that can be targeted therapeutically to increase trophic support, e.g. IGF, ErbB and netrin signaling, and reduce neuroinflammation, e.g. PGD2 synthesis, which may be beneficial in the treatment of chronic forms of HIV-associated neurocognitive disorders in the setting of viral suppression.

Glutamate metabolism and HIV-associated neurocognitive disorders

HIV-1 infection can lead to neurocognitive impairment collectively known as HIV-associated neurocognitive disorders (HAND). Although combined antiretroviral treatment (cART) has significantly ameliorated HIV's morbidity and mortality, persistent neuroinflammation and neurocognitive dysfunction continue. This review focuses on the current clinical and molecular evidence of the viral and host factors that influence glutamate-mediated neurotoxicity and neuropathogenesis as an important underlying mechanism during the course of HAND development. In addition, discusses potential pharmacological strategies targeting the glutamatergic system that may help prevent and improve neurological outcomes in HIV-1-infected subjects.

HIV-associated neurocognitive disorders: perspective on management strategies

Potent combination antiretroviral therapy (ART) has resulted in dramatic improvements in AIDS-associated morbidity and mortality. Although combination ART has resulted in a significant reduction in HIV-associated dementia, the most severe of the HIV-associated neurocognitive disorders (HAND), the overall prevalence of HAND among this population is estimated at 40%. It has been recognized that the central nervous system (CNS) serves as a reservoir for HIV, and neuronal damage begins at the time of acute infection and persists due to chronic infection of microglial and perivascular macrophages. Although combination ART has resulted in virologic control in the plasma compartment, virologic breakthrough can potentially ensue within the CNS compartment due to limited ART drug exposure. The purpose of this review is to discuss the definition, clinical spectrum, and risk factors associated with HAND, review the pathogenesis of HAND, and address the pharmacologic challenges associated with ART drug exposure in the CNS compartment.

HIV-associated neurocognitive disorder

Neurological involvement in HIV is often associated with cognitive impairment. Although severe and progressive neurocognitive impairment has become rare in HIV clinics in the era of potent antiretroviral therapy, most patients with HIV worldwide have poor outcomes on formal neurocognitive tests. In this Review, we describe the manifestations of HIV-associated neurocognitive disorder in the era of effective HIV therapy, outline diagnosis and treatment recommendations, and explore the research questions that remain. Although comorbid disorders, such as hepatitis C infection or epilepsy, might cause some impairment, their prevalence is insufficient to explain the frequency with which it is encountered. HIV disease markers, such as viral load and CD4 cell counts, are not strongly associated with ongoing impairment on treatment, whereas cardiovascular disease markers and inflammatory markers are. New cerebrospinal fluid and neuroimaging biomarkers are needed to detect and follow impairment. Ongoing research efforts to optimise HIV therapy within the CNS, and potentially to intervene in downstream mechanisms of neurotoxicity, remain important avenues for future investigation. Ultimately, the full control of virus in the brain is a necessary step in the goal of HIV eradication.

Human immunodeficiency virus-1 Tat protein increases the number of inhibitory synapses between hippocampal neurons in culture

Synaptodendritic damage correlates with cognitive decline in many neurodegenerative diseases, including human immunodeficiency virus-1 (HIV-1)-associated neurocognitive disorders (HAND). Because HIV-1 does not infect neurons, viral-mediated toxicity is indirect, resulting from released neurotoxins such as the HIV-1 protein transactivator of transcription (Tat). We compared the effects of Tat on inhibitory and excitatory synaptic connections between rat hippocampal neurons using an imaging-based assay that quantified clusters of the scaffolding proteins gephyrin or PSD95 fused to GFP. Tat (24 h) increased the number of GFP-gephyrin puncta and decreased the number of PSD95-GFP puncta. The effects of Tat on inhibitory and excitatory synapse number were mediated via the low-density lipoprotein receptor-related protein and subsequent Ca(2+) influx through GluN2A-containing NMDA receptors (NMDARs). The effects of Tat on synapse number required cell-autonomous activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). Ca(2+) buffering experiments suggested that loss of excitatory synapses required activation of CaMKII in close apposition to the NMDAR, whereas the increase in inhibitory synapses required Ca(2+) diffusion to a more distal site. The increase in inhibitory synapses was prevented by inhibiting the insertion of GABAA receptors into the membrane. Synaptic changes induced by Tat (16 h) were reversed by blocking either GluN2B-containing NMDARs or neuronal nitric oxide synthase, indicating changing roles for pathways activated by NMDAR subtypes during the neurotoxic process. Compensatory changes in the number of inhibitory and excitatory synapses may serve as a novel mechanism to reduce network excitability in the presence of HIV-1 neurotoxins; these changes may inform the development of treatments for HAND.

Redox pioneer: Professor Stuart A. Lipton

[Figure: see text] Stuart A. Lipton, M.D., Ph.D. is recognized here as a Redox Pioneer because of his publication of four articles that have been cited more than 1000 times, and 96 reports which have been cited more than 100 times. In the redox field, Dr. Lipton is best known for his work on the regulation by S-nitrosylation of the NMDA-subtype of neuronal glutamate receptor, which provided early evidence for in situ regulation of protein activity by S-nitrosylation and a prototypic model of allosteric control by this post-translational modification. Over the past several years, Lipton's group has pioneered the discovery of aberrant protein nitrosylation that may contribute to a number of neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis (Lou Gehrig's disease). In particular, the phenotypic effects of rare genetic mutations may be understood to be enhanced or mimicked by nitrosative (and oxidative) modifications of cysteines and thereby help explain common sporadic forms of disease. Thus, Lipton has contributed in a major way to the understanding that nitrosative stress may result from modifications of specific proteins and may operate in conjunction with genetic mutation to create disease phenotype. Lipton (collaborating with Jonathan S. Stamler) has also employed the concept of targeted S-nitrosylation to produce novel neuroprotective drugs that act at allosteric sites in the NMDA receptor. Lipton has won a number of awards, including the Ernst Jung Prize in Medicine, and is an elected fellow of the AAAS. Antioxid. Redox Signal. 19, 757-764.

The new small-molecule mixed-lineage kinase 3 inhibitor URMC-099 is neuroprotective and anti-inflammatory in models of human immunodeficiency virus-associated neurocognitive disorders

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) is a significant source of disability in the HIV-infected population. Even with stringent adherence to anti-retroviral therapy, >50% of patients living with HIV-1 will develop HAND (Heaton et al., 2010). Because suppression of viral replication alone is not enough to stop HAND progression, there is a need for an adjunctive neuroprotective therapy in this population. To this end, we have developed a small-molecule brain-penetrant inhibitor with activity against mixed-lineage kinase 3 (MLK3), named URMC-099. MLK3 activation is associated with many of the pathologic hallmarks of HAND (Bodner et al., 2002, 2004; Sui et al., 2006) and therefore represents a prime target for adjunctive therapy based on small-molecule kinase inhibition. Here we demonstrate the anti-inflammatory and neuroprotective effects of URMC-099 in multiple murine and rodent models of HAND. In vitro, URMC-099 treatment reduced inflammatory cytokine production by HIV-1 Tat-exposed microglia and prevented destruction and phagocytosis of cultured neuronal axons by these cells. In vivo, URMC-099 treatment reduced inflammatory cytokine production, protected neuronal architecture, and altered the morphologic and ultrastructural response of microglia to HIV-1 Tat exposure. In conclusion, these data provide compelling in vitro and in vivo evidence to investigate the utility of URMC-099 in other models of HAND with the goal of advancement to an adjunctive therapeutic agent.

Targeting the glutamatergic system for the treatment of HIV-associated neurocognitive disorders

The accumulation of excess glutamate in the extracellular space as a consequence of CNS trauma, neurodegenerative diseases, infection, or deregulation of glutamate clearance results in neuronal damage by excessive excitatory neurotransmission. Glutamate excitotoxicity is thought to be one of several mechanisms by which HIV exerts neurotoxicity that culminates in HIV-associated neurocognitive disorders (HAND). Excess glutamate is released upon HIV infection of macrophage/microglial cells and has been associated with neurotoxicity mediated by gp120, transactivator of transcription (Tat) and other HIV proteins. Several strategies have been used over the years to try to prevent glutamate excitotoxicity. Since the main toxic effects of excess glutamate are thought to be due to excitotoxicity from over activation of glutamate receptors, antagonists of these receptors have been popular therapeutic targets. Early work to ameliorate the effects of excess extracellular glutamate focused on NMDA receptor antagonism, but unfortunately, potent blockade of this receptor has been fraught with side effects. One alternative to direct receptor blockade has been the inhibition of enzymes responsible for the production of glutamate such as glutaminase and glutamate carboxypeptidase II. Another approach has been to regulate the transporters responsible for modulation of extracellular glutamate such as excitatory amino acid transporters and the glutamate-cystine antiporter. There is preliminary experimental evidence that these approaches have potential therapeutic utility for the treatment of HAND. These efforts however, are at an early stage where the next steps are dependent on the identification of drug-like inhibitors as well as the development of predictive neuroAIDS animal models.

Neurologic Complications and Considerations in HIV-Infected Persons

Neurologic complications for HIV-infected persons retain significant prevalence despite an increasingly global use of antiretroviral therapies. Such complications are often ascribed to advanced immunosuppression; however, the most common neurologic problems for HIV-infected persons, distal sensory polyneuropathy and HIV-associated neurocognitive disorders, affect a significant proportion of patients who have successfully achieved immunologic restoration with normal or near-normal CD4 count levels and undetectable HIV RNA in the periphery. Understanding specific considerations for HIV-associated complications, including the epidemiology, risk factors, medication-adverse effects, and benefits of appropriate management, is vital for all providers caring for those with HIV. This review will describe such considerations, as well as providing a more detailed review of the most common neurologic complications of HIV infection, and will highlight some of the challenges involved with diagnosis, management, and long-term effects.

HIV-associated neurological disorders: a guide to pharmacotherapy

In the era of highly active antiretroviral therapy (HAART), HIV-1-associated neurocognitive disorder (HAND) continues to be a common and significant morbidity among individuals infected with HIV. The term HAND encompasses a spectrum of progressively severe CNS involvement, ranging from asymptomatic neurocognitive impairment and minor neurocognitive disorder through to the most severe form of HIV-associated dementia (HAD). While the incidence of HAD has declined significantly with HAART, the milder forms of HAND persist. In addition, HAND now develops in individuals with less advanced immunosuppression. The reasons for the persistence of milder forms of HAND in individuals treated with HAART are not entirely known. There are several hypotheses to explain this phenomenon that include the legacy effect, a failure of antiretroviral agents to reverse neurological damage, poor access of antiretroviral agents to the CNS, chronic systemic immune activation associated with microbial translocation products, sustained CNS inflammation, the improved survival of HIV-seropositive individuals and the possible contribution from aging, amyloid deposition and other co-morbidities. In contrast, the incidence of HIV-associated CNS opportunistic processes including progressive multifocal leukoencephalopathy, tuberculosis, CNS toxoplasmosis, cytomegalovirus encephalitis, cryptococcosis and primary CNS lymphoma has declined dramatically with the introduction of HAART. This review briefly summarizes our current understanding of HAND and the pathological mechanisms involved, namely direct injury from HIV-1 and viral proteins, indirect neurotoxicity from proinflammatory cytokines and chronic, sustained immune activation in the CNS. To date, only HAART has been shown to benefit HAND despite numerous controlled trials of adjunctive 'anti-inflammatory' agents. Although HAART has a profound impact on the incidence and severity of HAND, there exists a 'therapeutic gap' as even HAART that is effective at inducing durable virological suppression may only partially reverse HAND. In addition, there may be potential CNS adverse effects of antiretroviral agents. There is an ongoing multicentre clinical trial to investigate the role of the CNS Penetration-Effectiveness index, an indicator of drug permeability and availability in the CNS, to help guide the choice of antiretroviral agents in the treatment of HAND. With recent recommendations for earlier treatment intervention with HAART for HIV-1 infection, it remains to be seen the effects of this on HAND. There is an urgent need to better define the therapeutic guidelines for the prevention and treatment of HAND.

Implications of gliotransmission for the pharmacotherapy of CNS disorders

The seminal discovery that glial cells, particularly astrocytes, can release a number of gliotransmitters that serve as signalling molecules for the cross-talk with neighbouring cellular populations has recently changed our perception of brain functioning, as well as our view of the pathogenesis of several disorders of the CNS. Since glutamate was one of the first gliotransmitters to be identified and characterized, we tackle the mechanisms that underlie its release from astrocytes, including the Ca2+ signals underlying its efflux from astroglia, and we discuss the involvement of these events in a number of relevant physiological processes, from the modulatory control of neighbouring synapses to the regulation of blood supply to cerebral tissues. The relevance of these mechanisms strongly indicates that the contribution of glial cells and gliotransmission to the activities of the brain cannot be overlooked, and any study of CNS physiopathology needs to consider glial biology to have a comprehensive overview of brain function and dysfunction. Abnormalites in the signalling that controls the astrocytic release of glutamate are described in several experimental models of neurological disorders, for example, AIDS dementia complex, Alzheimer's disease and cerebral ischaemia. While the modalities of glutamate release from astrocytes remain poorly understood, and this represents a major impediment to the definition of novel therapeutic strategies targeting this process at the molecular level, some key mediators deputed to the control of the glial release of this excitatory amino acid have been identified. Among these, we can mention, for instance, proinflammatory cytokines, such as tumour necrosis factor-α, and prostaglandins. Agents that are able to block the major steps of tumour necrosis factor-α and prostaglandin production and/or signalling can be proposed as novel therapeutic targets for the treatment of these disorders.

HIV-related neurocognitive impairment--a review

Neurocognitive impairments following central nervous system opportunistic infections and HIV-associated dementia (HAD) were common clinical features of HIV infection prior to anti-retroviral therapy. As HIV infection has evolved from an invariably fatal disease with a poor prognosis to a condition requiring long-term management, HIV-related neurocognitive disorders have been the subject of increasing research. This review will examine the recent changes in the understanding of the HIV-associated neurocognitive disorders (HAND) including the changing epidemiology, risk factors associated with its development, methods for screening for the disorders and evolving treatment options.

Pathogenesis of HIV in the central nervous system

HIV can infect the brain and impair central nervous system (CNS) function. Combination antiretroviral therapy (cART) has not eradicated CNS complications. HIV-associated neurocognitive disorders (HAND) remain common despite cART, although attenuated in severity. This may result from a combination of factors including inadequate treatment of HIV reservoirs such as circulating monocytes and glia, decreased effectiveness of cART in CNS, concurrent illnesses, stimulant use, and factors associated with prescribed drugs, including antiretrovirals. This review highlights recent investigations of HIV-related CNS injury with emphasis on cART-era neuropathological mechanisms in the context of both US and international settings.

HIV-1 infection and cognitive impairment in the cART era: a review

With the introduction of combination antiretroviral therapy AIDS dementia complex or HIV-associated dementia, as it was termed later, largely disappeared in clinical practice. However, in the past few years, patients, long-term infected and treated, including those with systemically well controlled infection, started to complain about milder memory problems and slowness, difficulties in concentration, planning, and multitasking. Neuropsychological studies have confirmed that cognitive impairment occurs in a substantial (15-50%) proportion of patients. Among HIV-1-infected patients cognitive impairment was and is one of the most feared complications of HIV-1 infection. In addition, neurocognitive impairment may affect adherence to treatment and ultimately result in increased morbidity for systemic disease. So what may be going on in the CNS after so many years of apparently controlled HIV-1 infection is an urgent and important challenge in the field of HIV medicine. In this review we summarize the key currently available data. We describe the clinical neurological and neuropsychological findings, the preferred diagnostic approach with new imaging techniques and cerebrospinal fluid analysis. We try to integrate data on pathogenesis and finally discuss possible therapeutic interventions.

HIV-associated neurocognitive disorders: a changing pattern

Combination antiretroviral therapy has dramatically decreased the incidence of HIV-related mortality and serious opportunistic diseases, among which is HIV-associated dementia. However, minor forms of cognitive dysfunction have not disappeared and may even have increased in frequency. Aging of HIV+ patients, insufficient penetration of antiretroviral drugs into the brain with continuous low-grade viral production and inflammation may play a role. A putative neurotoxicity of combination antiretroviral therapy is controversial. In this article, we will discuss these aspects, as well as clinical and pathophysiological features shared by HIV-associated neurocognitive disorders and other neurodegenerative diseases, especially Alzheimer’s disease. This article will briefly summarize the current clinical trials on neuroprotective agents, and the management of patients with neurocognitive disorders will be discussed.

HIV-Tat elicits microglial glutamate release: role of NAPDH oxidase and the cystine-glutamate antiporter

Excitotoxicity and/or microglial reactivity might underlie neurologic dysfunction in HIV patients. The HIV regulatory protein Tat is both neurotoxic and pro-inflammatory, suggesting that Tat might participate in the pathogenesis of HIV-associated neurocognitive disorders (HAND). The present study was undertaken to evaluate if Tat can increase extracellular glutamate, and was specifically designed to determine the degree to which, and the mechanisms by which Tat could drive microglial glutamate release. Data show that application of Tat to cultured primary microglia caused dose-dependent increases in extracellular glutamate that were exacerbated by morphine, which is known to worsen Tat cytotoxicity. Tat-induced glutamate release was decreased by inhibitors of p38 and p42/44 MAPK, and by inhibitors of NADPH oxidase and the x(c)(-) cystine-glutamate antiporter. Furthermore, Tat increased expression of the catalytic subunit of x(c)(-) (xCT), but Tat-induced increases in xCT mRNA were not affected by inhibition of NADPH oxidase or x(c)(-) activity. Together, these data describe a specific and biologically significant signaling component of the microglial response to Tat, and suggest that excitotoxic neuropathology associated with HIV infection might originate in part with Tat-induced activation of microglial glutamate release.

Brain dysfunction in the era of combination antiretroviral therapy: implications for the treatment of the aging population of HIV-infected individuals

Improvements in the treatment of HIV infection and in the advancement of combination antiretroviral therapy (cART) have led to an increase in the number of individuals with HIV who are surviving to an older age. Preventing the development of neurocognitive abnormalities has become an increasingly important issue in this aging patient population, which is already at risk for cognitive impairment as a result of the neuropathological effects of HIV. cART has been critical in reducing the overall severity of HIV-associated neurocognitive disorders (HAND), but numerous challenges remain, as the prevalence of HAND continues to be high. There are several key areas in which treatment could be improved to reduce the incidence and severity of HAND. The use of well-tolerated cART medications that are able to penetrate the blood-brain barrier hold particular promise, as these agents may enable increased viral suppression in the parenchyma and may reduce neurocognitive dysfunction. In addition, the improved treatment of comorbid medical conditions that are common in patient populations with HIV (eg, HCV, liver failure and metabolic syndrome) is critical, as several of these conditions are known to have a significant effect on neural functions. Various research approaches indicate that the development of agents that control free radicals, neurotoxicity, proinflammatory processes and apoptosis may also have substantial potential in this field.