Novel markers of oxidative stress in actively progressive HIV dementia

The role of oxidative stress in HIV-associated neurocognitive disorders

HIV-associated neurocognitive disorders (HAND) are a leading cause of morbidity in up to 50% of individuals living with HIV, despite effective treatment with antiretroviral therapy (ART). Current evidence suggests that chronic inflammation associated with HIV is especially attributed to the dysregulated production of reactive oxygen species (ROS) that contribute to neurodegeneration and poor clinical outcomes. While ROS have beneficial effects in eliciting immune responses to infection, chronic ROS production causes damage to macromolecules such as DNA and lipids that has been linked to altered redox homeostasis associated with antioxidant dysregulation. As a result, this disruption in the balance between antioxidant-dependent mechanisms of ROS inactivation and ROS production by enzymes such as the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family, as well as from the electron transport chain of the mitochondria can result in oxidative stress. This is particularly relevant to the brain, which is exquisitely susceptible to oxidative stress due to its inherently high lipid concentration and ROS levels that have been linked to many neurodegenerative diseases that have similar stages of pathogenesis to HAND. In this review, we discuss the possible role and mechanisms of ROS production leading to oxidative stress that underpin HAND pathogenesis even when HIV is suppressed by current gold-standard antiretroviral therapies. Furthermore, we highlight that pathological ROS can serve as biomarkers for HIV-dependent HAND, and how manipulation of oxidative stress and antioxidant-dependent pathways may facilitate novel strategies for HIV cure.

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Production of reactive oxygen species has been linked to neurodegenerative diseases.

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ROS production contributes to HIV-associated neurocognitive disorders.

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ROS may be used as a biomarker for HIV-associated neurocognitive disorders.

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Manipulation of antioxidant pathways may present novel HIV cure strategies.

Co-infections as Modulators of Disease Outcome: Minor Players or Major Players?

Human host and pathogen interaction is dynamic in nature and often modulated by co-pathogens with a functional role in delineating the physiological outcome of infection. Co-infection may present either as a pre-existing pathogen which is accentuated by the introduction of a new pathogen or may appear in the form of new infection acquired secondarily due to a compromised immune system. Using diverse examples of co-infecting pathogens such as Human Immunodeficiency Virus, Mycobacterium tuberculosis and Hepatitis C Virus, we have highlighted the role of co-infections in modulating disease severity and clinical outcome. This interaction happens at multiple hierarchies, which are inclusive of stress and immunological responses and together modulate the disease severity. Already published literature provides much evidence in favor of the occurrence of co-infections during SARS-CoV-2 infection, which eventually impacts the Coronavirus disease-19 outcome. The availability of biological models like 3D organoids, mice, cell lines and mathematical models provide us with an opportunity to understand the role and mechanism of specific co-infections. Exploration of multi-omics-based interactions across co-infecting pathogens may provide deeper insights into their role in disease modulation.

Microglia Mediate HIV-1 gp120-Induced Synaptic Degeneration in Spinal Pain Neural Circuits

HIV-1 infection of the nervous system causes various neurological diseases, and synaptic degeneration is likely a critical step in the neuropathogenesis. Our prior studies revealed a significant decrease of synaptic protein, specifically in the spinal dorsal horn of patients with HIV-1 in whom pain developed, suggesting a potential contribution of synaptic degeneration to the pathogenesis of HIV-associated pain. However, the mechanism by which HIV-1 causes the spinal synaptic degeneration is unclear. Here, we identified a critical role of microglia in the synaptic degeneration. In primary cortical cultures (day in vitro 14) and spinal cords of 3- to 5-month-old mice (both sexes), microglial ablation inhibited gp120-induced synapse decrease. Fractalkine (FKN), a microglia activation chemokine specifically expressed in neurons, was upregulated by gp120, and knockout of the FKN receptor CX3CR1, which is predominantly expressed in microglia, protected synapses from gp120-induced toxicity. These results indicate that the neuron-to-microglia intercellular FKN/CX3CR1 signaling plays a role in gp120-induced synaptic degeneration. To elucidate the mechanism controlling this intercellular signaling, we tested the role of the Wnt/β-catenin pathway in regulating FKN expression. Inhibition of Wnt/β-catenin signaling blocked both gp120-induced FKN upregulation and synaptic degeneration, and gp120 stimulated Wnt/β-catenin-regulated FKN expression via NMDA receptors (NMDARs). Furthermore, NMDAR antagonist APV, Wnt/β-catenin signaling suppressor DKK1, or knockout of CX3CR1 alleviated gp120-induced mechanical allodynia in mice, suggesting a critical contribution of the Wnt/β-catenin/FKN/CX3R1 pathway to gp120-induced pain. These findings collectively suggest that HIV-1 gp120 induces synaptic degeneration in the spinal pain neural circuit by activating microglia via Wnt3a/β-catenin-regulated FKN expression in neurons.SIGNIFICANCE STATEMENT Synaptic degeneration develops in the spinal cord dorsal horn of HIV patients with chronic pain, but the patients without the pain disorder do not show this neuropathology, indicating a pathogenic contribution of the synaptic degeneration to the development of HIV-associated pain. However, the mechanism underlying the synaptic degeneration is unclear. We report here that HIV-1 gp120, a neurotoxic protein that is specifically associated with the manifestation of pain in HIV patients, induces synapse loss via microglia. Further studies elucidate that gp120 activates microglia by stimulating Wnt/β-catenin-regulated fractalkine in neuron. The results demonstrate a critical role of microglia in the pathogenesis of HIV-associated synaptic degeneration in the spinal pain neural circuit.

Lipidomic characterization of extracellular vesicles in human serum

There is a wide variety of extracellular vesicles (EVs) that differ in size and cargo composition. EVs isolated from human plasma or serum carry lipid, protein, and RNA cargo that provides insights to the regulation of normal physiological processes, and to pathological states. Specific populations of EVs have been proposed to contain protein and RNA cargo that are biomarkers for neurologic and systemic diseases. Although there is a considerable amount of evidence that circulating lipids are biomarkers for multiple disease states, it not clear if these lipid biomarkers are enriched in EVs, or if specific populations of EVs are enriched for particular classes of lipid. A highly reproducible workflow for the analysis of lipid content in EVs isolated from human plasma or serum would facilitate this area of research. Here we optimized an MS/MSALL workflow for the untargeted analysis of the lipid content in EVs isolated from human serum. A simple sequential ultracentrifugation protocol isolated three distinct types of serum EVs that were identified based on size, targeted protein, and untargeted lipidomic analyses. EVs in the upper and middle fractions were approximately 140 nm in diameter, while EVs in the pellet were approximately 110 nm in diameter. EVs in the upper most buoyant fractions contained the highest concentration of lipids, were enriched with phospholipids, and immunopositive for the cytoskeletal markers actin, α-actinin, and the mitochondrial protein mitofillin, but negative for the typical EV markers CD63, TSG101, and flotillin. A central fraction of EVs was devoid of cytoskeletal and mitochondrial markers, and positive for CD63, and TSG101, but negative for flotillin. The EV pellet contained no cytoskeletal or mitochondrial markers, but was positive for CD63, TSG101, and flotillin. The EV pellet contained the lowest concentration of most lipids, but was enriched with ceramide. These results provided new insights into the lipid composition of EVs isolated from serum using a simple ultracentrifugation isolation method suitable for lipidomic analysis by mass spectrometry.

Dimethyl Fumarate Prevents HIV-Induced Lysosomal Dysfunction and Cathepsin B Release from Macrophages

HIV-associated neurocognitive disorders (HAND) are prevalent despite combined antiretroviral therapy, affecting nearly half of HIV-infected patients worldwide. During HIV infection of macrophages secretion of the lysosomal protein, cathepsin B, is increased. Secreted cathepsin B has been shown to induce neurotoxicity. Oxidative stress is increased in HIV-infected patients, while antioxidants are decreased in monocytes from patients with HIV-associated dementia (HAD). Dimethyl fumarate (DMF), an antioxidant, has been reported to decrease HIV replication and neurotoxicity mediated by HIV-infected macrophages. Thus, we hypothesized that DMF will decrease cathepsin B release from HIV-infected macrophages by preventing oxidative stress and enhancing lysosomal function. Monocyte-derived macrophages (MDM) were isolated from healthy donors, inoculated with HIV-1_ADA, and treated with DMF following virus removal. After 12 days post-infection, HIV-1 p24 and total cathepsin B levels were measured from HIV-infected MDM supernatants using ELISA; intracellular reactive oxygen and nitrogen species (ROS/RNS) were measured from MDM lysates, and functional lysosomes were assessed using a pH-dependent lysosomal dye. Neurons were incubated with serum-free conditioned media from DMF-treated MDM and neurotoxicity was determined using TUNEL assay. Results indicate that DMF reduced HIV-1 replication and cathepsin B secretion from HIV-infected macrophages in a dose-dependent manner. Also, DMF decreased intracellular ROS/RNS levels, and prevented HIV-induced lysosomal dysfunction and neuronal apoptosis. In conclusion, the improvement in lysosomal function with DMF treatment may represent the possible mechanism to reduce HIV-1 replication and cathepsin B secretion. DMF represents a potential therapeutic strategy against HAND.

Childhood maltreatment and HIV-associated neurocognitive disorders share similar pathophysiology: a potential sensitisation mechanism?

HIV-associated neurocognitive disorders (HAND) are increasingly prevalent despite the use of antiretroviral therapies. Previous research suggests that individual host factors play an important role in determining susceptibility to HAND. In this review, we propose that childhood trauma (CT) and HAND share several common aetiological mechanisms, namely hypothalamic-pituitary-adrenal axis dysregulation, neuroinflammation and oxidative stress. These convergent and consequent mechanisms may translate into an increased risk of developing HAND in individuals who have experienced early life stress. We provide an overview of basic and clinical research relating to these pathophysiological mechanisms and suggest that further research examine brain-derived neurotrophic factor and telomere length as common mediating factors and potential therapeutic targets for HAND and CT. Graphical abstract Both childhood trauma and HIV-associated neurocognitive disorders are associated with HPA axis dysregulation, inflammation and oxidative stress.

HIV-associated synaptic degeneration

Human immunodeficiency virus (HIV) infection induces neuronal injuries, with almost 50% of infected individuals developing HIV-associated neurocognitive disorders (HAND). Although highly activate antiretroviral therapy (HAART) has significantly reduced the incidence of severe dementia, the overall prevalence of HAND remains high. Synaptic degeneration is emerging as one of the most relevant neuropathologies associate with HAND. Previous studies have reported critical roles of viral proteins and inflammatory responses in this pathogenesis. Infected cells, including macrophages, microglia and astrocytes, may release viral proteins and other neurotoxins to stimulate neurons and cause excessive calcium influx, overproduction of free radicals and disruption of neurotransmitter hemostasis. The dysregulation of neural circuits likely leads to synaptic damage and loss. Identification of the specific mechanism of the synaptic degeneration may facilitate the development of effective therapeutic approaches to treat HAND.

Marijuana effects on changes in brain structure and cognitive function among HIV+ and HIV- adults

BACKGROUND

The current study examined the independent and interactive effects of HIV and marijuana (MJ) use on brain structure and cognitive function among a sample of HIV-positive (HIV+) and HIV-negative (HIV-) individuals.

METHODS

Participants (HIV+, n=48; HIV-, n=29) individuals underwent cognitive testing, questionnaires about substance use, and brain MRI. The HIV+ group was clinically stable based upon current plasma CD4 count, 50% had undetectable viral load (i.e.,<20 copies/mL), and all were on a stable regimen of cART.

RESULTS

For HIV+ and HIV- participants, higher levels of MJ use were associated with smaller volumes in the entorhinal cortex and fusiform gyrus. HIV status (but not MJ use) was associated with cingulate thickness, such that HIV+ participants evidenced smaller thickness of the cingulate, as compared to HIV- controls. Regarding neurocognitive functioning, there was a HIV*MJ interactive effect on global cognition, such that when the amount of MJ use was less than 1.43g per week, the HIV- group displayed significantly better neurocognitive performance than the HIV+ group (t=3.14, p=0.002). However, when MJ use reached 1.43g per week, there were no significant HIV group differences in global cognitive performance (t=1.39, p=0.168).

CONCLUSIONS

Our results show independent and interactive effects of HIV and MJ on brain structure and cognition. However, our results do not support that HIV+ MJ users are at greater risk for adverse brain or cognitive outcomes compared to HIV- MJ users.

Acrolein enhances epigenetic modifications, FasL expression and hepatocyte toxicity induced by anti-HIV drug Zidovudine

Zidovudine (AZT) remains the mainstay of antiretroviral therapy against HIV in resource-poor countries; however, its use is frequently associated with hepatotoxicity. Not all HIV patients on AZT develop hepatotoxicity, and the determining factors are unclear. Alcohol consumption and cigarette smoking are known risk factors for HIV hepatotoxicity, and both are significant sources of acrolein, a highly reactive and toxic aldehyde. This study examines the potential hepatotoxic interactions between acrolein and AZT. Our data demonstrate that acrolein markedly enhanced AZT-induced transcriptionally permissive histone modifications (H3K9Ac and H3K9Me3) allowing the recruitment of transcription factor NF-kB and RNA polymerase II at the FasL gene promoter, resulting in FasL upregulation and apoptosis in hepatocytes. Notably, the acrolein scavenger, hydralazine prevented these promoter-associated epigenetic changes and inhibited FasL upregulation and apoptosis induced by the combination of AZT and acrolein, as well as AZT alone. Our data strongly suggest that acrolein enhancement of promoter histone modifications and FasL upregulation are major pathogenic mechanisms driving AZT-induced hepatotoxicity. Moreover, these data also indicate the therapeutic potential of hydralazine in mitigating AZT hepatotoxicity.

HIV-associated neurocognitive disorder--pathogenesis and prospects for treatment

In the past two decades, several advancements have improved the care of HIV-infected individuals. Most importantly, the development and deployment of combination antiretroviral therapy (CART) has resulted in a dramatic decline in the rate of deaths from AIDS, so that people living with HIV today have nearly normal life expectancies if treated with CART. The term HIV-associated neurocognitive disorder (HAND) has been used to describe the spectrum of neurocognitive dysfunction associated with HIV infection. HIV can enter the CNS during early stages of infection, and persistent CNS HIV infection and inflammation probably contribute to the development of HAND. The brain can subsequently serve as a sanctuary for ongoing HIV replication, even when systemic viral suppression has been achieved. HAND can remain in patients treated with CART, and its effects on survival, quality of life and everyday functioning make it an important unresolved issue. In this Review, we describe the epidemiology of HAND, the evolving concepts of its neuropathogenesis, novel insights from animal models, and new approaches to treatment. We also discuss how inflammation is sustained in chronic HIV infection. Moreover, we suggest that adjunctive therapies--treatments targeting CNS inflammation and other metabolic processes, including glutamate homeostasis, lipid and energy metabolism--are needed to reverse or improve HAND-related neurological dysfunction.

Heme oxygenase-1 dysregulation in the brain: implications for HIV-associated neurocognitive disorders

Heme oxygenase-1 (HO-1) is a highly inducible and ubiquitous cellular enzyme that subserves cytoprotective responses to toxic insults, including inflammation and oxidative stress. In neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and multiple sclerosis, HO-1 expression is increased, presumably reflecting an endogenous neuroprotective response against ongoing cellular injury. In contrast, we have found that in human immunodeficiency virus (HIV) infection of the brain, which is also associated with inflammation, oxidative stress and neurodegeneration, HO-1 expression is decreased, likely reflecting a unique role for HO-1 deficiency in neurodegeneration pathways activated by HIV infection. We have also shown that HO-1 expression is significantly suppressed by HIV replication in cultured macrophages which represent the primary cellular reservoir for HIV in the brain. HO-1 deficiency is associated with release of neurotoxic levels of glutamate from both HIV-infected and immune-activated macrophages; this glutamate-mediated neurotoxicity is suppressed by pharmacological induction of HO-1 expression in the macrophages. Thus, HO-1 induction could be a therapeutic strategy for neuroprotection against HIV infection and other neuroinflammatory brain diseases. Here, we review various stimuli and signaling pathways regulating HO-1 expression in macrophages, which could promote neuronal survival through HO-1-modulation of endogenous antioxidant and immune modulatory pathways, thus limiting the oxidative stress that can promote HIV disease progression in the CNS. The use of pharmacological inducers of endogenous HO-1 expression as potential adjunctive neuroprotective therapeutics in HIV infection is also discussed.

Independent and co-morbid HIV infection and Meth use disorders on oxidative stress markers in the cerebrospinal fluid and depressive symptoms

Both HIV infection and Methamphetamine (Meth) use disorders are associated with greater depressive symptoms and oxidative stress; whether the two conditions would show additive or interactive effects on the severity of depressive symptoms, and whether this is related to the level of oxidative stress in the CNS is unknown. 123 participants were evaluated, which included 41 HIV-seronegative subjects without substance use disorders (Control), 25 with recent (<6 months) moderate to severe Meth use disorders (Meth), 34 HIV-seropositive subjects without substance use disorders (HIV) and 23 HIV+Meth subjects. Depressive symptoms were assessed with the Center for Epidemiologic Studies-Depression Scale (CES-D), and oxidative stress markers were evaluated with glutathione (GSH), 4-hydroxynonenal (HNE), and activities of gamma-glutamyltransferase (GGT) and glutathione peroxidase (GPx) in the cerebrospinal fluid (CSF). Compared with Controls, HIV subjects had higher levels of HNE (+350%) and GGT (+27%), and lower level of GSH (-34%), while Meth users had higher levels of GPx activity (+23%) and GSH (+30 %). GGT correlated with GPx, and with age, across all subjects (p < 0.0001). CES-D scores correlated with CSF HNE levels only in Control and HIV groups, but not in Meth and HIV+Meth groups. HIV and Meth use had an interactive effects on depressive symptoms, but did not show additive or interactive effects on oxidative stress. The differential relationship between depressive symptoms and oxidative stress response amongst the four groups suggest that depressive symptoms in these groups are mediated through different mechanisms which are not always related to oxidative stress.

Interaction of paroxetine with mitochondrial proteins mediates neuroprotection

There are severe neurological complications that arise from HIV infection, ranging from peripheral sensory neuropathy to cognitive decline and dementia for which no specific treatments are available. The HIV proteins secreted from infected macrophages, gp120 and Tat, are neurotoxic. The goal of this study was to screen, identify and develop neuroprotective compounds relevant to HIV-associated neurocognitive disorders (HAND). We screened more than 2000 compounds that included FDA approved drugs for protective efficacy against oxidative stress-mediated neurodegeneration and identified selective serotonin reuptake inhibitors (SSRIs) as potential neuroprotectants. Numerous SSRIs were then extensively evaluated as protectants against neurotoxicity as measured by changes in neuronal cell death, mitochondrial potential, and axodendritic degeneration elicited by HIV Tat and gp120 and other mitochondrial toxins. While many SSRIs demonstrated neuroprotective actions, paroxetine was potently neuroprotective (100 nM potency) against these toxins in vitro and in vivo following systemic administration in a gp120 neurotoxicity model. Interestingly, the inhibition of serotonin reuptake by paroxetine was not required for neuroprotection, since depletion of the serotonin transporter had no effect on its neuroprotective properties. We determined that paroxetine interacts selectively and preferentially with brain mitochondrial proteins and blocks calcium-dependent swelling but had less effect on liver mitochondria. Additionally, paroxetine induced proliferation of neural progenitor cells in vitro and in vivo in gp120 transgenic animals. Therefore, SSRIs such as paroxetine may provide a novel adjunctive neuroprotective and neuroregenerative therapy to treat HIV-infected individuals.

Role of Oxidative Stress in HIV-1-Associated Neurocognitive Disorder and Protection by Gene Delivery of Antioxidant Enzymes

HIV encephalopathy covers a range of HIV-1-related brain dysfunction. In the Central Nervous System (CNS), it is largely impervious to Highly Active AntiRetroviral Therapy (HAART). As survival with chronic HIV-1 infection improves, the number of people harboring the virus in their CNS increases. Neurodegenerative and neuroinflammatory changes may continue despite the use of HAART. Neurons themselves are rarely infected by HIV-1, but HIV-1 infects resident microglia, periventricular macrophages, leading to increased production of cytokines and to release of HIV-1 proteins, the most likely neurotoxins, among which are the envelope glycoprotein gp120 and HIV-1 trans-acting protein Tat. Gp120 and Tat induce oxidative stress in the brain, leading to neuronal apoptosis/death. We review here the role of oxidative stress in animal models of HIV-1 Associated Neurocognitive Disorder (HAND) and in patients with HAND. Different therapeutic approaches, including clinical trials, have been used to mitigate oxidative stress in HAND. We used SV40 vectors for gene delivery of antioxidant enzymes, Cu/Zn superoxide dismutase (SOD1), or glutathione peroxidase (GPx1) into the rat caudate putamen (CP). Intracerebral injection of SV (SOD1) or SV (GPx1) protects neurons from apoptosis caused by subsequent inoculation of gp120 and Tat at the same location. Vector administration into the lateral ventricle or cisterna magna protects from intra-CP gp120-induced neurotoxicity comparably to intra-CP vector administration. These models should provide a better understanding of the pathogenesis of HIV-1 in the brain as well as offer new therapeutic avenues.

Roles of glutathione in antioxidant defense, inflammation, and neuron differentiation in the thalamus of HIV-1 transgenic rats

Inflammation and oxidative stress in the brain are major causes of HIV-associated neurocognitive disorders. Previously we have reported high content of glutathione (GSH) in the thalamus of rats with F344 genetic background. In this study, we investigated the changes of GSH metabolism and GSH-dependent antioxidant enzymes in the rat thalamus in response to HIV-1 transgenesis, and their associations with oxidative stress, inflammation, and neuronal development. Male HIV-1 transgenic (HIV-1Tg) rats and wild type F344 rats at 10 months were used in this study, with 5 rats in each group. Parameters measured in this study included: total and oxidized GSH, glutathione peroxidase (GPx), glutathione-S-transferase (GST), gamma-glutamylcysteine synthetase (GCS), gamma-glutamyl transferase (GGT), cysteine/cystine transporters, 4-hydroxynonenal (HNE), interleukin 12 (IL12), neuronal nuclei (NeuN), microtubule-associated protein (MAP2), and glia fibrillary acidic protein (GFAP). The levels of total GSH, oxidized GSH (GSSG) and MAP2 protein, and enzymatic activities of GCS, GPx and GST were significantly higher in HIV-1Tg rats compared with F344 rats, but the ratio of GSSG/GSH, activity of GGT and levels of HNE, NeuN protein and GFAP protein did not change. HIV-1Tg rats showed a lower level of IL12 protein. GSH positively correlated with GCS, GST and MAP2, GSSG/GSH ratio positively correlated with HNE and IL12, the activities of GPx, GST and GCS positively correlated with each other, and negatively correlated with HNE. These findings suggest an important role of the GSH-centered system in reducing oxidative stress and neuroinflammation, and enhancing neuron differentiation in the thalamus of HIV-1Tg rats.

Macrophage derived cystatin B/cathepsin B in HIV replication and neuropathogenesis

Mononuclear phagocytes including monocytes and macrophages, are important defense components of innate immunity, but can be detrimental in HIV-1 infection by serving as the principal reservoirs of virus in brain and triggering a strong immune response. These viral reservoirs represent a challenge to HIV-1 eradication since they continue producing virus in tissue despite antiretroviral therapy. HIV-1 associated neurocognitive disorders (HAND) involve alterations to the blood-brain barrier and migration of activated HIV-1 infected monocytes to the brain with subsequent induced immune activation response. Our group recently showed that HIV replication in monocyte-derived macrophages is associated with increased cystatin B. This cysteine protease inhibitor also inhibits the interferon-induced antiviral response by decreasing levels of tyrosine phosphorylated STAT-1. These recent discoveries reveal novel mechanisms of HIV persistence that could be targeted by new therapeutic approaches to eliminate HIV in macrophage reservoirs. However, cystatin B has been also associated with neuroprotection. Cystatin B is an inhibitor of the cysteine protease cathepsin B, a potent neurotoxin. During HIV-1 infection cystatin B and cathepsin B are upregulated in macrophages. Reduction in cystatin/cathepsin interactions in infected macrophages leads to increased cathepsin B secretion and activity which contributes to neuronal apoptosis. Increased intracellular expression of both proteins was recently found in monocytes from Hispanic women with HAND. These findings provide new evidence for the role of cathepsin /cystatin system in the neuropathogenesis induced by HIV-infected macrophages. We summarize recent research on cystatin B and one of its substrates, cathepsin B, in HIV replication in macrophages and neuropathogenesis.

Oxidative stress and the HIV-infected brain proteome

Human immunodeficiency virus (HIV) is capable of infiltrating the brain and infecting brain cells. In the years following HIV infection, patients show signs of various levels of neurocognitive problems termed HIV-associated neurocognitive disorders (HAND). Although the introduction of highly active antiretroviral therapy (HAART) has reduced the incidence of HIV-dementia, which is the most severe form of HAND, the milder forms have become more prevalent today due to the increased life expectancy of infected individuals. Pre-HAART era markers such as HIV RNA level, CD4+ count, TNF-α, MCP-1 and M-CSF are not able to clearly distinguish mild from advanced HAND. One promising approach for new biomarker discovery is the identification and quantitation of proteins that are post-translationally modified by oxidative and nitrosative species. The occurrence of oxidative and nitrosative stress in HIV-infected brain, both through the early direct and indirect effects of viral proteins and through the later effect on mitochondrial integrity during apoptosis, is well-established. This review will focus on how the reactive species are produced in the brain after HIV infection, the specific oxidative and nitrosative species that are involved in the post-translational modification of the brain proteome, and the methods that are currently used for the detection of such modified proteins. This review also provides an overview of related research pertaining to oxidative stress-related HAND using cerebrospinal fluid and human brain tissue.

A biological perspective of CSF lipids as surrogate markers for cognitive status in HIV

The development and application of biomarkers to neurodegenerative diseases has become increasingly important in clinical practice and therapeutic trials. While substantial progress has been made at the basic science level in understanding the pathophysiology of HIV-Associated Neurocognitive Disorders (HAND), there are significant limitations in our current ability to predict the onset or trajectory of disease, and to accurately determine the effects of therapeutic interventions. Thus, the development of objective biomarkers is critical to further our understanding and treatment of HAND. In recent years, biomarker discovery efforts have largely been driven forward through the implementation of multiple "omics" approaches that include (but are not restricted to): Lipidomics, proteomics, metabolomics, genomics, transcriptomics, and advances in brain imaging approaches such as functional connectomics. In this paper we summarize our progress to date on lipidomic approaches to biomarker discovery, discuss how these data have influenced basic research on the neuropathology of HAND, and implications for the development of therapeutics that target metabolic pathways involved in lipid handling.

Reactive oxygen species from human astrocytes induced functional impairment and oxidative damage

Reactive oxygen species (ROS) have been shown to be a contributor to aging and disease. ROS also serve as a trigger switch for signaling cascades leading to corresponding cellular and molecular events. In the central nervous system (CNS), microglial cells are likely the main source of ROS production. However, activated astrocytes also appear to be capable of generating ROS. In this study we investigated ROS production in human astrocytes stimulated with interleukin (IL)-1β and interferon (IFN)-γ and its potential harmful effects. Although IFN-γ alone had no effect, it potentiated IL-1β-induced ROS production in a time-dependent manner. One of the sources of ROS in IL-1β-activated astrocytes was from increased superoxide production in mitochondria accompanied by enhanced manganese superoxide dismutase and inhibited catalase expression. NADPH oxidase (NOX) may also contribute to ROS production as astrocytes express NOX isoforms. Glutamate uptake, which represents one of the most important methods of astrocytes to prevent excitotoxicity, was down-regulated in IL-1β-activated astrocytes, and was further suppressed in the presence of IFN-γ; IFN-γ itself exerted minimal effect. Elevated levels of 8-isoprostane in IL-1β ± IFN-γ-activated human astrocytes indicate downstream lipid peroxidation. Pretreatment with diphenyleneiodonium abolished the IL-1β ± IFN-γ-induced ROS production, restored glutamate uptake function and reduced 8-isoprostane to near control levels suggesting that ROS contributes to the dysfunction of activated astrocytes. These results support the notion that dampening activated human astrocytes to maintain the redox homeostasis is vital to preserve their neuroprotective potential in the CNS.

Regional variations of antioxidant capacity and oxidative stress responses in HIV-1 transgenic rats with and without methamphetamine administration

HIV infection and methamphetamine (Meth) abuse both may lead to oxidative stress. This study used HIV-1 transgenic (HIV-1Tg) rats to investigate the independent and combined effects of HIV viral protein expression and low dose repeated Meth exposure on the glutathione (GSH)-centered antioxidant system and oxidative stress in the brain. Total GSH content, gene expression and/or enzymatic activities of glutamylcysteine synthetase (GCS), gamma-glutamyltransferase (GGT), glutathione reductase (GR), glutathione peroxidase (GPx), glutaredoxin (Glrx), and glutathione-s-transferase (GST) were measured. The protein expression of cystine transporter (xCT) and oxidative stress marker 4-hydroxynonenal (HNE) were also analyzed. Brain regions studied include thalamus, frontal and remainder cortex, striatum, cerebellum and hippocampus. HIV-1Tg rats and Meth exposure showed highly regional specific responses. In the F344 rats, the thalamus had the highest baseline GSH concentration and potentially higher GSH recycle rate. HIV-1Tg rats showed strong transcriptional responses to GSH depletion in the thalamus. Both HIV-1Tg and Meth resulted in decreased GR activity in thalamus, and decreased Glrx activity in frontal cortex. However, the increased GR and Glrx activities synergized with increased GSH concentration, which might have partially prevented Meth-induced oxidative stress in striatum. Interactive effects between Meth and HIV-1Tg were observed in thalamus on the activities of GCS and GGT, and in thalamus and frontal cortex on Glrx activity and xCT protein expression. Findings suggest that HIV viral protein and low dose repeated Meth exposure have separate and combined effects on the brain's antioxidant capacity and the oxidative stress response that are regional specific.

Regulation of oxidative stress by Nrf2 in the pathophysiology of infectious diseases

The innate immune system, including phagocytic cells, is the first line of defense against pathogens. During infection by microorganisms such as viruses, bacteria, or parasites, phagocytic cells produce an excess of oxidants, a crucial process for the clearance of pathogens. This increase in oxidants creates an imbalance between oxidants and endogenous antioxidants. Left unchecked, this acute or chronic oxidative stress can lead to apoptotic cell-death and oxidative stress-induced diseases including neurodegenerative and cardiovascular disorders, premature aging, secondary infections, and cancer. The activation of nuclear factor E2-related factor 2 (Nrf2) is an efficient antioxidant defensive mechanism used by host cells to counteract oxidative stress. The transcription factor Nrf2 has been identified as the master regulator of several hundred of genes involved in the antioxidant defense response. The review objectives were to collect recent findings on the contribution of oxidative stress to complications of infection, and to highlight the beneficial impact of antioxidants in reducing inflammation and oxidant-related tissue damage. Furthermore, a direct relationship between infection and decline in Nrf2 activity has been demonstrated. Thus, an interesting therapeutic approach in disease prevention and treatment of stress-related diseases may consist in optimizing antibiotic or antiviral therapy with a combination of Nrf2 inducer treatment.

Chemotherapy-related changes in central nervous system phospholipids and neurocognitive function in childhood acute lymphoblastic leukemia

Long-term survivors of childhood leukemia are at risk for neurocognitive impairment, although the neurophysiological basis is not well understood. The purpose of this study was to explore associations between changes in cerebrospinal fluid (CSF) phospholipids and neurocognitive function in children undergoing chemotherapy for acute lymphoblastic leukemia. Seventy-six children were followed prospectively from diagnosis. CSF samples were collected during scheduled lumbar punctures and phospholipids were extracted. Neurocognitive evaluations were conducted annually beginning shortly after diagnosis. Concentrations of sphingomyelin (SM) increased following induction (p = 0.03) and consolidation (p = 0.04), while lysophosphatidylcholine (LPC) increased following induction (p = 0.003). Multivariable analyses demonstrated associations between post-induction SM and motor speed at 1 year (p < 0.001), 2 years (p = 0.001) and 3 years (p = 0.02) following diagnosis. Post-induction LPC was associated with verbal working memory (p = 0.007). Results indicate that early changes in phospholipids are related to neurocognitive decline and suggest a chemotherapy impact on white matter integrity.

Modulation of experimental herpes encephalitis-associated neurotoxicity through sulforaphane treatment

Reactive oxygen species (ROS) produced by brain-infiltrating macrophages and neutrophils, as well as resident microglia, are pivotal to pathogen clearance during viral brain infection. However, unchecked free radical generation is also responsible for damage to and cytotoxicity of critical host tissue bystander to primary infection. These unwanted effects of excessive ROS are combated by local cellular production of antioxidant enzymes, including heme oxygenase-1 (HO-1) and glutathione peroxidase 1 (Gpx1). In this study, we showed that experimental murine herpes encephalitis triggered robust ROS production, as well as an opposing upregulation of the antioxidants HO-1 and Gpx1. This antioxidant response was insufficient to prevent tissue damage, neurotoxicity, and mortality associated with viral brain infection. Previous studies corroborate our data supporting astrocytes as the major antioxidant producer in brain cell cultures exposed to HSV-1 stimulated microglia. We hypothesized that stimulating opposing antioxidative responses in astrocytes, as well as neurons, would mitigate the effects of ROS-mediated neurotoxicity both in vitro and during viral brain infection in vivo. Here, we demonstrate that the addition of sulforaphane, a potent stimulator of antioxidant responses, enhanced HO-1 and Gpx1 expression in astrocytes through the activation of nuclear factor-E2-related factor 2 (Nrf2). Additionally, sulforaphane treatment was found to be effective in reducing neurotoxicity associated with HSV-stimulated microglial ROS production. Finally, intraperitoneal injections of sulforaphane into mice during active HSV infection reduced neuroinflammation via a decrease in brain-infiltrating leukocytes, macrophage- and neutrophil-produced ROS, and MHCII-positive, activated microglia. These data support a key role for astrocyte-produced antioxidants in modulating oxidative stress and neuronal damage in response to viral infection.

Inhibition of nuclear factor erythroid 2-related factor 2 exacerbates HIV-1 gp120-induced oxidative and inflammatory response: role in HIV associated neurocognitive disorder

The HIV epidemic continues to be the most severe public health problem and concern within USA and across the globe. In spite of the highly active antiretroviral therapy, HIV infected subjects experience major neurological complications that range from HIV associated dementia to moderate neurocognitive and motor impairments collectively termed as HIV associated neurocognitive disorders (HAND). Astrocytes play an important role in the neuropathogenesis of HAND. Further, in the recent years it has been shown that oxidative stress plays a major role in the neuropathogenesis of HAND. Nuclear factor erythroid 2-related factor 2 (Nrf2), a leucine zipper redox-sensitive transcription factor, is an important regulator of cell survival and adaptive mechanisms and has been shown to possess a protective role in a variety of neurological and inflammatory disorders. Earlier we have shown that Nrf2 is upregulated in response to HIV-1 gp120 and such upregulation of Nrf2 may be a protective mechanism against the HIV-induced oxidative stress. We hypothesize that Nrf2-mediated antioxidant pathways are important in regulating the HIV-induced oxidative stress and that the disruption of Nrf2 makes the cells more susceptible to HIV gp120-induced deleterious effects. Our results indicate that when astrocytes are exposed to gp120 there is an increase in the expression of NOX2, a subunit of NADPH oxidase, and also an upregulated expression of nuclear factor kappa B, tumor necrosis factor-α (TNF-α) and matrix metalloproteinase-9 (MMP-9). However, the degree of expression was significantly higher in those cells where Nrf2 was silenced by siRNA. Taken together, these results suggest a possible protective role of Nrf2 in regulating the levels of pro-oxidative and pro-inflammatory molecules in HAND.

Blood-brain barrier abnormalities caused by HIV-1 gp120: mechanistic and therapeutic implications

The blood-brain barrier (BBB) is compromised in many systemic and CNS diseases, including HIV-1 infection of the brain. We studied BBB disruption caused by HIV-1 envelope glycoprotein 120 (gp120) as a model. Exposure to gp120, whether acute [by direct intra-caudate-putamen (CP) injection] or chronic [using SV(gp120), an experimental model of ongoing production of gp120] disrupted the BBB, and led to leakage of vascular contents. Gp120 was directly toxic to brain endothelial cells. Abnormalities of the BBB reflect the activity of matrix metalloproteinases (MMPs). These target laminin and attack the tight junctions between endothelial cells and BBB basal laminae. MMP-2 and MMP-9 were upregulated following gp120-injection. Gp120 reduced laminin and tight junction proteins. Reactive oxygen species (ROS) activate MMPs. Injecting gp120 induced lipid peroxidation. Gene transfer of antioxidant enzymes protected against gp120-induced BBB abnormalities. NMDA upregulates the proform of MMP-9. Using the NMDA receptor (NMDAR-1) inhibitor, memantine, we observed partial protection from gp120-induced BBB injury. Thus, (1) HIV-envelope gp120 disrupts the BBB; (2) this occurs via lesions in brain microvessels, MMP activation and degradation of vascular basement membrane and vascular tight junctions; (3) NMDAR-1 activation plays a role in this BBB injury; and (4) antioxidant gene delivery as well as NMDAR-1 antagonists may protect the BBB.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

APOE ε 4 allele and CSF APOE on cognition in HIV-infected subjects

The significance of the cerebrospinal fluid (CSF) Apolipoprotein E (APOE) level and whether it might have differential effects on brain function due to the presence of APOE ε 4 allele(s) in HIV-infected patients are unknown. However, APOE ε 4 allele has been associated with greater incidence of HIV-associated dementia and accelerated progression of HIV infection. Here, we show further evidence for the role of APOE ε 4 in promoting cognitive impairment. We measured the APOE levels in the CSF of HIV-infected individuals. HIV+ subjects showed lower CSF APOE proteins than SN controls (-19%, p= 0.03). While SN subjects with or without ε 4 allele showed no difference in CSF APOE levels, ε 4+ HIV+ subjects had similar levels to the SN subjects but higher levels than ε 4- HIV+ subjects (+34%, p= 0.01). Furthermore, while HIV+ subjects with ε 2 or ε 3 allele(s) showed a positive relationship between their CSF APOE levels and cognitive performance on the speed of processing domain (r= +0.35, p= 0.05), ε 4+ HIV+ subjects, in contrast, exhibited a negative relationship such that those with higher levels of CSF APOE(4) performed worse on the HIV Dementia Scale (r= -0.61, p= 0.02), had lower Global Cognitive Scores (r= -0.57, p= 0.03), and had poorer performance on tests involving learning (ε 4 allele x [APOE] interaction, p = 0.01). Our findings also suggest that the relatively higher levels of CSF APOE in ε 4+ HIV+ (having primarily APOE4 isoforms) may negatively impact the brain and lead to poorer cognitive outcomes, while those individuals without the ε 4 allele (with primarily APOE2 or APOE3 isoforms) may show compensatory responses that lead to better cognitive performance.

A failure to normalize biochemical and metabolic insults during morphine withdrawal disrupts synaptic repair in mice transgenic for HIV-gp120

Drug abuse in HIV-infected individuals accelerates the onset and progression of HIV-associated neurocognitive disorders (HAND). Opiates are a class of commonly abused drugs that have interactive effects with neurotoxic HIV proteins that facilitate glial dysfunction, neuronal damage and death. While the combined effects of neurotoxic HIV proteins and morphine have been extensively studied in the setting of chronic and acute morphine use, very little in known about the effects of HIV proteins during drug withdrawal. Since opiate withdrawal can induce considerable neuronal stress, we determined the effects of opiates (morphine) on brain redox balance, sphingolipid metabolism and synaptic integrity during both chronic and withdrawal conditions in non-transgenic mice (nTg), and in mice transgenic for the HIV-coat protein gp120 (gp120tg). In nTg mice, we found that chronic morphine increased brain oxidative capacity and induced synaptic damage that was largely reversed during drug withdrawal. Gp120tg mice showed a similar response to chronic morphine, but the diminished oxidative capacity and synaptic damage failed to normalize during drug withdrawal. In nTg mice, brain sphingolipid content was not affected by morphine during chronic or withdrawal conditions. In gp120tg mice there was a baseline perturbation in sphingolipid metabolism that manifest as decreased sphingomyelin with accumulations of the bioactive lipid ceramide. Sphingolipid metabolism was highly reactive to morphine in gp120tg mice. Chronic morphine increased sphingomyelin content with a consequent reduction in ceramide. During drug withdrawal, these effects reversed, and sphingomyelin levels were reduced with consequent increases of ceramide. We interpret these findings to suggest that neuronal repair during morphine withdrawal is inhibited in the setting of gp120 by mechanisms that involve sustained oxidative insult and accumulations of the highly reactive intermediate ceramide.

HIV-associated neurocognitive disorder: pathogenesis and therapeutic opportunities

Human immunodeficiency virus type 1 (HIV) infection presently affects more that 40 million people worldwide, and is associated with central nervous system (CNS) disruption in at least 30% of infected individuals. The use of highly active antiretroviral therapy has lessened the incidence, but not the prevalence of mild impairment of higher cognitive and cortical functions (HIV-associated neurocognitive disorders) as well as substantially reduced a more severe form dementia (HIV-associated dementia). Furthermore, improving neurological outcomes will require novel, adjunctive therapies that are targeted towards mechanisms of HIV-induced neurodegeneration. Identifying such molecular and pharmacological targets requires an understanding of the events preceding irreversible neuronal damage in the CNS, such as actions of neurotoxins (HIV proteins and cellular factors), disruption of ion channel properties, synaptic damage, and loss of adult neurogenesis. By considering the specific mechanisms and consequences of HIV neuropathogenesis, unified approaches for neuroprotection will likely emerge using a tailored, combined, and non-invasive approach.

HIV-1 gp120-induced injury to the blood-brain barrier: role of metalloproteinases 2 and 9 and relationship to oxidative stress

Blood-brain barrier (BBB) disruption occurs during human immunodeficiency virus encephalopathy, but the mechanisms involved are not understood. We studied how acute and ongoing exposure to human immunodeficiency virus 1 envelope gp120 alters BBB structure and permeability. Intravenous Evans blue, given before stereotaxic gp120 injection into the caudate putamen of rats, was rapidly extravasated. Gelatinolytic activity, studied by in situ zymography, was increased after gp120 administration and was localized within cerebral vessel walls. The gp120 increased the expression of matrix metalloproteinases (MMPs) 2 and 9. Laminin and claudin-5, key BBB components and targets of both MMPs, were greatly reduced upon gp120 administration. The gp120 increased lipid peroxidation in the vascular endothelium and in neurons. Prior administration of rSV40 vectors carrying the antioxidant enzymes Cu/Zn superoxide dismutase or glutathione peroxidase protected from gp120-induced BBB damage. N-methyl-D-aspartate receptor activation upregulated pro-MMP-9 and increased MMP-9 gelatinase activity, and memantine, an N-methyl-D-aspartate receptor blocker, mitigated gp120-induced BBB abnormalities. Using intra-caudate putamen SV(gp120) to test the effects of chronic exposure to expressed gp120, we determined that oxidant stress and increased BBB permeability occurred as in acute exposure. These data indicate that both direct administration and cellular expression of gp120 lead to disruption of the BBB by increasing MMPs and reducing vascular tight junction proteins via mechanisms involving reactive oxygen species generation and oxidant injury.

HIV neurotoxicity: potential therapeutic interventions

Individuals suffering from human immunodeficiency virus type 1 (HIV-1) infection suffer from a wide range of neurological deficits. The most pronounced are the motor and cognitive deficits observed in many patients in the latter stages of HIV infection. Gross postmortem inspection shows cortical atrophy and widespread neuronal loss. One of the more debilitating of the HIV-related syndromes is AIDS-related dementia, or HAD. Complete understanding of HIV neurotoxicity has been elusive. Both direct and indirect toxic mechanisms have been implicated in the neurotoxicity of the HIV proteins, Tat and gp120. The glutamatergic system, nitric oxide, calcium, oxidative stress, apoptosis, and microglia have all been implicated in the pathogenesis of HIV-related neuronal degeneration. The aim of this review is to summarize the most recent work and provide an overview to the current theories of HIV-related neurotoxicity and potential avenues of therapeutic interventions to prevent the neuronal loss and motor/cognitive deficits previously described.

Biomarkers predicting progression of human immunodeficiency virus-related disease

Biomarkers in predicting the progression of HIV infected individuals to a state of HIV disease (AIDS) are studied over more than a decade. Use of surrogate markers in the past for tracking clinical progression of the disease was limited, as little knowledge existed about the disease. The aim of this review was to address various changes in biomarker related studies taking place over the last five years, especially the trend towards use of newer biomarkers and experimentation with novel molecules in a quest for halting HIV disease progression. An open search of PUBMED database was made with search 'key words' such as 'Biomarkers' and 'AIDS (Acquired Immunodeficiency Syndrome)'.The following were the inclusion criteria for articles: a) all articles published in English language, b) years of publication between 2002-2008 and c) articles limited to adult population. This yielded a total of 417 articles. The criteria used for further judging these studies considered a) type of research design, b) number of biomarkers studied, c) validity of the biomarkers, d) techniques to assess the biomarkers and the impact of the studies in furthering biomarker research, e) sample size for the studies and f) article title or abstracts having the following key words 'biomarker' or 'biomarkers' and 'predict progression to AIDS'. A total of 27 abstracts were reviewed and 12 studies met the above criteria. These 12 different studies consisted of three reviews, four cohort designs, three cross-sectional designs, one each of an observational, and an in-vitro design. The various biomarkers emerging as a results were primarily a mix of viral, neural, immunological, HLA (human leukocyte antigen) markers along with lymphocyte counts. Although there have been quite a few advancements in biomarker-related studies, majority of the novel biomarkers discovered need to be further evaluated and replicated in bigger, long-term efficacy trials. Efforts should also be made to discover newer genetic markers of disease progression. Biomarker feedback, a new concept, can be utilized in future studies addressing prevention of HIV infection or halting disease progression.

Neuroprotective effects of the drug GVT (monosodium luminol) are mediated by the stabilization of Nrf2 in astrocytes

Oxidative stress is implicated in various kinds of neurological disorders, including human immunodeficiency virus (HIV) associated dementia (HAD). Our laboratory has been studying the murine retrovirus ts1, a pathogenic mutant of the Moloney murine leukemia virus (MoMuLV), as a model for HAD. Like HIV in humans, ts1 induces oxidative stress and progressive neurodegeneration in mice. We have shown previously that an antioxidant and anti-inflammatory drug GVT or MSL (monosodium luminol) suppresses ts1-induced oxidative stress, attenuates the development of spongiform encephalopathy, and delays hind limb paralysis in infected mice. It is known that upregulation of the nuclear transcription factor NF-E2-related factor 2 (Nrf2) is involved in upregulating cellular antioxidant defenses. Since Nrf2 is associated with elevation of antioxidant defenses in general, and since GVT suppresses ts1-induced neurodegeneration, our aim in this study was to determine whether GVT neuroprotection is linked to Nrf2 upregulation in the brain. We report here that GVT upregulates the levels of Nrf2, both in primary astrocyte cultures and in brainstem of ts1-infected mice. Significant upregulation of Nrf2 expression by GVT occurs in both the cytosolic and nuclear fractions of cultured astrocytes and brainstem cells. Notably, although GVT treatment increases Nrf2 protein levels in cultured astrocytes and brainstem tissues, Nrf2 mRNA levels are not altered. This suggests that the neuroprotective effects of GVT may be mediated by the stabilization of the Nrf2 protein, allowing continuous upregulation of Nrf2 levels in the astrocytes.

Blood-brain barrier abnormalities caused by exposure to HIV-1 gp120--protection by gene delivery of antioxidant enzymes

HIV-1 effects on the blood-brain barrier (BBB) structure and function are still poorly understood in animal models based on direct administration of recombinant HIV proteins. We therefore injected HIV-1 envelope glycoprotein, gp120, into rat caudate-putamens (CPs) and examined vascular integrity and function. Gp120 coimmunostained with endothelial cell marker, CD31. It induced apoptosis of endothelial cells in vitro and in vivo. BBB function was assessed by administering Evans Blue (EB) intravenously before injecting gp120. EB leaked near the site of gp120 administration. Within 1h after intra-CP gp120 injection, structures positive for endothelial markers ICAM-1 and RECA-1 were greatly decreased. Vascular density assessed by laminin immunostaining remained decreased 1 month after gp120 injection. RECA-1-positive cells expressed hydroxynonenal, a marker of lipid peroxidation and rSV40-mediated gene delivery of antioxidant enzymes protected the BBB from gp120-related injury. Extravasated IgG accumulated following intra-CP SV(gp120) injection, an experimental model of continuing gp120 exposure. Thus: acute and chronic exposure to gp120 disrupts the BBB; gp120-mediated BBB abnormalities are related to lesions of brain microvessels; and gp120 is directly toxic to brain endothelial cells.

Selegiline and oxidative stress in HIV-associated cognitive impairment

OBJECTIVE

To assess the effectiveness of the selegiline transdermal system (STS) in reversing HIV-induced metabolic brain injury (as measured by proton magnetic resonance spectroscopy [MRS]) and in decreasing oxidative stress, measured by CSF protein carbonyl concentration.

METHODS

Sixty-two subjects with HIV-associated cognitive impairment were coenrolled in a 24-week placebo-controlled study (AIDS Clinical Trial Group protocol A5090) and were randomly assigned to receive STS 3 mg/24 h, STS 6 mg/24 h, or matching placebo. Cognitive performance was evaluated using the neuropsychological z score (NPZ)-8 and NPZ-6, as well as cognitive domain scores. Subjects underwent proton MRS at study entry and weeks 12 and 24. CSF protein carbonyl was measured at baseline and week 24.

RESULTS

A slight increase in N-acetyl aspartate/creatine from baseline to week 24 was found in the basal ganglia (p = 0.023) and centrum semiovale (p = 0.072) of the placebo group compared with the STS groups; however, there were no significant changes when the absolute metabolite concentrations were analyzed. The levels of choline/creatine in the midfrontal cortex were also significantly higher during the week 12 visit in the combined STS groups. This persisted to the week 24 visit (p = 0.002). Evaluation of the change in NPZ-8, NPZ-6, and cognitive domain scores from baseline to weeks 12 and 24 revealed no significant differences between treatment arms. Protein carbonyl analysis revealed no significant changes among the groups.

CONCLUSION

In this 24-week study, the selegiline transdermal system (STS) had no effect on either magnetic resonance spectroscopy (MRS) metabolites or oxidative stress, as measured by CSF protein carbonyl concentration. The lack of effect on these biomarkers is also reflected in the lack of cognitive improvement in the STS groups compared to placebo.

LEVEL OF EVIDENCE

This study provides Class II evidence that STS had no effect on either MRS metabolites or oxidative stress, as measured by CSF protein carbonyl concentration over a period of 24 weeks.

Combined effects of hyperglycemic conditions and HIV-1 Nef: a potential model for induced HIV neuropathogenesis

Hyperglycemic conditions associated with diabetes mellitus (DM) or with the use of antiretroviral therapy may increase the risk of central nervous system (CNS) disorders in HIV-1 infected patients. In support of this hypothesis, we investigated the combined effects of hyperglycemic conditions and HIV-1 accessory protein Nef on the CNS using both in vitro and in vivo models. Astrocytes, the most abundant glial cell type required for normal synaptic transmission and other functions were selected for our in vitro study. The results show that in vitro hyperglycemic conditions enhance the expression of proinflammatory cytokines including caspase-3, complement factor 3 (C3), and the production of total nitrate and 8-iso-PGF2 α as reactive oxygen species (ROS) in human astrocytes leading to cell death in a dose-dependent manner. Delivery of purified recombinant HIV-1 Nef protein, or Nef expressed via HIV-1-based vectors in astrocytes showed similar results. The expression of Nef protein delivered via HIV-1 vectors in combination with hyperglycemia further augmented the production of ROS, C3, activation of caspase-3, modulation of filamentous protein (F-protein), depolarization of the mitochondria, and loss of astrocytes. To further verify the effects of hyperglycemia and HIV-1 Nef protein on CNS individually or in combination, in vivo studies were performed in streptozotocin (STZ) induced diabetic mice, by injecting HIV-1 Nef expressing viral particles into the sub-cortical region of the brain. Our in vivo results were similar to in vitro findings indicating an enhanced production of caspases-3, ROS (lipid oxidation and total nitrate), and C3 in the brain tissues of these animals. Interestingly, the delivery of HIV-1 Nef protein alone caused similar damage to CNS as augmented by hyperglycemia conditions. Taken together, the data suggests that HIV-1 infected individuals with hyperglycemia could potentially be at a higher risk of developing CNS related complications.

A rat model of human immunodeficiency virus 1 encephalopathy using envelope glycoprotein gp120 expression delivered by SV40 vectors

Human immunodeficiency virus 1 (HIV-1) encephalopathy is thought to result in part from the toxicity of HIV-1 envelope glycoprotein gp120 for neurons. Experimental systems for studying the effects of gp120 and other HIV proteins on the brain have been limited to the acute effects of recombinant proteins in vitro or in vivo in simian immunodeficiency virus-infected monkeys. We describe an experimental rodent model of ongoing gp120-induced neurotoxicity in which HIV-1 envelope is expressed in the brain using an SV40-derived gene delivery vector, SV(gp120). When it is inoculated stereotaxically into the rat caudate putamen, SV(gp120) caused a partly hemorrhagic lesion in which neuron and other cell apoptosis continues for at least 12 weeks. Human immunodeficiency virus gp120 is expressed throughout this time, and some apoptotic cells are gp120 positive. Malondialdehyde and 4-hydroxynonenal assays indicated that there was lipid peroxidation in these lesions. Prior administration of recombinant SV40 vectors carrying antioxidant enzymes, copper/ zinc superoxide dismutase or glutathione peroxidase, was protective against SV(gp120)-induced oxidative injury and apoptosis. Thus, in vivo inoculation of SV(gp120) into the rat caudate putamen causes ongoing oxidative stress and apoptosis in neurons and may therefore represent a useful animal model for studying the pathogenesis and treatment of HIV-1 envelope-related brain damage.

Apoptosis and telomeres shortening related to HIV-1 induced oxidative stress in an astrocytoma cell line

BACKGROUND

Oxidative stress plays a key role in the neuropathogenesis of Human Immunodeficiency Virus-1 (HIV-1) infection causing apoptosis of astroglia cells and neurons. Recent data have shown that oxidative stress is also responsible for the acceleration of human fibroblast telomere shortening in vitro. In the present study we analyzed the potential relations occurring between free radicals formation and telomere length during HIV-1 mediated astroglial death.

RESULTS

To this end, U373 human astrocytoma cells have been directly exposed to X4-using HIV-1IIIB strain, for 1, 3 or 5 days and treated (where requested) with N-acetylcysteine (NAC), a cysteine donor involved in the synthesis of glutathione (GSH, a cellular antioxidant) and apoptosis has been evaluated by FACS analysis. Quantitative-FISH (Q-FISH) has been employed for studying the telomere length while intracellular reduced/oxidized glutathione (GSH/GSSG) ratio has been determined by High-Performance Liquid Chromatography (HPLC). Incubation of U373 with HIV-1IIIB led to significant induction of cellular apoptosis that was reduced in the presence of 1 mM NAC. Moreover, NAC improved the GSH/GSSG, a sensitive indicator of oxidative stress, that significantly decreased after HIV-1IIIB exposure in U373. Analysis of telomere length in HIV-1 exposed U373 showed a statistically significant telomere shortening, that was completely reverted in NAC-treated U373.

CONCLUSION

Our results support the role of HIV-1-mediated oxidative stress in astrocytic death and the importance of antioxidant compounds in preventing these cellular damages. Moreover, these data indicate that the telomere structure, target for oxidative damage, could be the key sensor of cell apoptosis induced by oxidative stress after HIV infection.

Role of metabolic syndrome components in human immunodeficiency virus-associated stroke

Metabolic syndrome (MetS) is a cluster of risk factors, including elevated mean arterial pressure (MAP), atherogenic dyslipidemia (elevated triglycerides [TRG]), abdominal obesity (increased body mass index [BMI]), glucose intolerance (elevated glucose [GLU]), and prothrombotic/inflammatory state (increases in uric acid [UA]), that are associated with increased risk of cerebrovascular disease. We studied if an association existed between MetS components and human immunodeficiency virus (HIV)-associated cryptogenic strokes-those not caused by HIV complications, endocarditis, or stimulant abuse. We performed a retrospective case-control study. Eleven cryptogenic strokes were identified from 2346 HIV-infected (HIV+) participants. Each case was matched by age, sex, and date of stroke diagnosis to five HIV+ controls without stroke. Nonparametric stratified Wilcoxon ranked sum tests with subsequent mixed effect logistic regression determined the influence of each MetS component on HIV-associated cryptogenic stroke. Although each MetS component appeared higher for HIV+ cases with cryptogenic strokes than HIV+ controls, only MAP (odds ratio [OR] = 5.70, 95% confidence interval [CI] = 1.15-28.3) and UA (OR = 1.88, 95% CI = 1.06-3.32) were statistically different. A significantly higher percentage of HIV-associated cryptogenic stroke cases met criteria for MetS (4/11 = 36%) compared to HIV+ controls (6/55 = 11%). This observational study suggests a possible role for MetS components in HIV+ cryptogenic stroke cases. Although MetS is defined as a constellation of disorders, elevated hypertension and hyperuricemia may be involved in stroke pathogenesis. Reducing MetS component levels in HIV+ patients could therefore protect them from subsequent stroke.

Activation of the oxidative stress pathway by HIV-1 Vpr leads to induction of hypoxia-inducible factor 1alpha expression

The detection of biomarkers of oxidative stress in brain tissue and cerebrospinal fluid of patients with human immunodeficiency virus, type 1 (HIV)-associated dementia indicates the involvement of stress pathways in the neuropathogenesis of AIDS. Although the biological importance of oxidative stress on events involved in AIDS neuropathogenesis and the HIV-1 proteins responsible for oxidative stress remain to be elucidated, our results point to the activation of hypoxia-inducible factor 1 (HIF-1) upon HIV-1 infection and its elevation in brain cells of AIDS patients with dementia. HIF-1 is a transcription factor that is responsive to oxygen. Under hypoxic conditions, HIF-1alpha becomes stable and translocates to the nucleus where it dimerizes with aryl hydrocarbon receptor nuclear translocator and modulates gene transcription. Activation of HIF-1 can also be mediated by the HIV-1 accessory protein Vpr. In addition, cellular components, including reactive oxygen species, contribute to the induction of HIF-1alpha. Our results show that Vpr induces reactive oxygen species by increasing H(2)O(2) production, which can contribute to HIF-1alpha accumulation. Interestingly, increased levels of HIF-1alpha stimulated HIV-1 gene transcription through HIF-1 association with HIV-1 long terminal repeat. These observations point to the existence of a positive feedback interplay between HIF-1alpha and Vpr and that, by inducing oxidative stress via activation of HIF-1, Vpr can induce HIV-1 gene expression and dysregulate multiple host cellular pathways.

Biomarkers of HIV-1 associated dementia: proteomic investigation of sera

Background

New, more sensitive and specific biomarkers are needed to support other means of clinical diagnosis of neurodegenerative disorders. Proteomics technology is widely used in discovering new biomarkers. There are several difficulties with in-depth analysis of human plasma/serum, including that there is no one proteomic platform that can offer complete identification of differences in proteomic profiles. Another set of problems is associated with heterogeneity of human samples in addition intrinsic variability associated with every step of proteomic investigation. Validation is the very last step of proteomic investigation and it is very often difficult to validate potential biomarker with desired sensitivity and specificity. Even though it may be possible to validate a differentially expressed protein, it may not necessarily prove to be a valid diagnostic biomarker.

Results

In the current study we report results of proteomic analysis of sera from HIV-infected individuals with or without cognitive impairment. Application of SELDI-TOF analysis followed by weak cation exchange chromatography and 1-dimensional electrophoresis led to discovery of gelsolin and prealbumin as differentially expressed proteins which were not detected in this cohort of samples when previously investigated by 2-dimensional electrophoresis with Difference Gel Electrophoresis technology.

Conclusion

Validation using western-blot analysis led us to conclude that relative change of the levels of these proteins in one patient during a timeframe might be more informative, sensitive and specific than application of average level estimated based on an even larger cohort of patients.

Antioxidant enzyme dysfunction in monocytes and CSF of Hispanic women with HIV-associated cognitive impairment

HIV-associated cognitive neurological disorders (HAND) prevail in the antiretroviral therapy era. Proteomics analysis of CSF revealed expression of Cu/Zn superoxide dismutase (Cu/Zn SOD) in Hispanic women with cognitive impairment (CI). We tested the hypothesis that there is reduced capacity of antioxidant enzymes in CI by measures of expression and activity of Cu/Zn SOD, catalase, and Se-glutathione peroxidase in HAND. Our results showed that the function of these antioxidants was decreased in the CSF and monocytes of women with CI. These findings have important implications regarding their possible contribution to oxidative stress and in the diagnosis and therapy for HAND.

N-acetylcysteine prevents HIV gp 120-related damage of human cultured astrocytes: correlation with glutamine synthase dysfunction

Background

HIV envelope gp 120 glycoprotein is released during active HIV infection of brain macrophages thereby generating inflammation and oxidative stress which contribute to the development of the AIDS-Dementia Complex (ADC). Gp120 has also been found capable to generate excitotoxic effect on brain tissue via enhancement of glutamatergic neurotransmission, leading to neuronal and astroglial damage, though the mechanism is still to be better understood.

Here we investigated on the effect of N-acetylcysteine (NAC), on gp120-induced damage in human cultured astroglial cells and the possible contribution of gp120-related reacting oxygen species (ROS) in the imbalanced activity of glutamine synthase (GS), the enzyme that metabolizes glutamate into glutamine within astroglial cells playing a neuroprotective role in brain disorders.

Results

Incubation of Lipari human cultured astroglial cells with gp 120 (0.1–10 nM) produced a significant reduction of astroglial cell viability and apoptosis as evaluated by TUNEL reaction and flow cytometric analysis (FACS). This effect was accompanied by lipid peroxidation as detected by means of malondialdehyde assay (MDA). In addition, gp 120 reduced both glutamine concentration in astroglial cell supernatants and GS expression as detected by immunocytochemistry and western blotting analysis. Pre-treatment of cells with NAC (0.5–5 mM), dose-dependently antagonised astroglial apoptotic cell death induced by gp 120, an effect accompanied by significant attenuation of MDA accumulation. Furthermore, both effects were closely associated with a significant recovery of glutamine levels in cell supernatants and by GS expression, thus suggesting that overproduction of free radicals might contribute in gp 120-related dysfunction of GS in astroglial cells.

Conclusion

In conclusion, the present experiments demonstrate that gp 120 is toxic to astroglial cells, an effect accompanied by lipid peroxidation and by altered glutamine release. All the effects of gp120 on astroglial cells were counteracted by NAC thus suggesting a novel and potentially useful approach in the treatment of glutammatergic disorders found in HAD patients.

Protection against human immunodeficiency virus type 1 Tat neurotoxicity by Ginkgo biloba extract EGb 761 involving glial fibrillary acidic protein

Human immunodeficiency virus (HIV)-1 Tat protein is an important pathogenic factor in HIV-associated neuropathogenesis. Despite recent progress, the molecular mechanisms underlying Tat neurotoxicity are still not completely understood. However, few therapeutics have been developed to specifically target HIV infection in the brain. Recent development of an inducible brain-specific Tat transgenic mouse model has made it possible to define the mechanisms of Tat neurotoxicity and evaluate anti-neuroAIDS therapeutic candidates in the context of a whole organism. Herein, we demonstrate that administration of EGb 761, a standardized formulation of Ginkgo biloba extract, markedly protected Tat transgenic mice from Tat-induced developmental retardation, inflammation, death, astrocytosis, and neuron loss. EGb 761 directly down-regulated glial fibrillary acidic protein (GFAP) expression at both protein and mRNA levels. This down-regulation was, at least in part, attributable to direct effects of EGb 761 on the interactions of the AP1 and NF-kappaB transcription factors with the GFAP promoter. Most strikingly, Tat-induced neuropathological phenotypes including macrophage/microglia activation, central nervous system infiltration of T lymphocytes, and oxidative stress were significantly alleviated in GFAP-null/Tat transgenic mice. Taken together, these results provide the first evidence to support the potential for clinical use of EGb 761 to treat HIV-associated neurological diseases. Moreover, these findings suggest for the first time that GFAP activation is directly involved in Tat neurotoxicity, supporting the notion that astrocyte activation or astrocytosis may directly contribute to HIV-associated neurological disorders.

Mechanisms of neutrophil death in human immunodeficiency virus-infected patients: role of reactive oxygen species, caspases and map kinase pathways

Neutrophils from human immunodeficiency virus-positive (HIV+) patients have an increased susceptibility to undergo programmed cell death (PCD), which could explain neutropenia during advanced disease. In this work, key steps of PCD have been evaluated in neutrophils from HIV+ patients. The role of caspase-3, caspase-8, mitogen activated protein kinase (MAPK) and reactive oxygen species (ROS) was analysed. Spontaneous neutrophil death is dependent upon caspase-3 but independent of caspase-8, suggesting that the intrinsic pathway is involved as a pathogenic mechanism of PCD. Inhibition of ROS decreased spontaneous PCD and caspase-3 hydrolysis, connecting oxidative stress and caspase-3 activation with neutrophil PCD in HIV-infected patients. Additionally, an increased neutrophil death was observed in HIV+ patients, following inhibition of p38 MAPK, suggesting a role for p38 MAPK in cell survival during the disease. We conclude that oxidative stress secondary to HIV infection can accelerate neutrophil death.