HIV-associated Neurological Disorders Research Articles

Yin and Yang of PDGF-mediated signaling pathway in the context of HIV infection and drug abuse.

The control and eradication of neurological complications associated with AIDS continues to be an important goal in efforts toward improving the well being of HIV-infected patients. Although combined antiretroviral therapies have contributed significantly to increasing the longevity of patients by suppressing the virus burden in the systemic compartments, the prevalence of HIV-associated neurological disorders continues to be on the rise. This in turn, leads to an impaired quality of life of the infected individuals who continue to suffer from mild to moderate cognitive decline and memory loss. Developing therapeutic interventions that reverse neuronal injury in the context of HIV infection, is thus of paramount importance in the field. Our previous studies have demonstrated that platelet-derived growth factor (PDGF) has a neuroprotective potential against HIV envelope protein gp120 and Tat. Paradoxically, PDGF is also a cerebrovascular permeant with deleterious effects on the blood-brain barrier resulting in increased influx of monocytes in the CNS. Herein, we review the opposing roles of PDGF in the context of HIV-associated neurodegenerative disorder (HAND).

Wingless-type Mammary Tumor Virus Integration Site Family, Member 5A (Wnt5a) Regulates Human Immunodeficiency Virus Type 1 (HIV-1) Envelope Glycoprotein 120 (gp120)-induced Expression of Pro-Inflammatory Cytokines via the Ca2+/Calmodulin-dependent Protein Kinase II (CaMKII) and c-Jun N-terminal Kinase (JNK) Signaling Pathways

HIV-1 infection causes chronic neuroinflammation in the central nervous system (CNS). The spinal cytokine up-regulation induced by HIV-1 gp120 protein depends on Wnt5a/CaMKII and/or Wnt5a/JNK pathways. gp120 stimulates cytokine expression in the spinal cord dorsal horn by activating Wnt5a signaling. The finding reveals Wnt signaling-mediated novel mechanisms by which HIV-1 may cause neuroinflammation. Chronic expression of pro-inflammatory cytokines critically contributes to the pathogenesis of HIV-associated neurological disorders (HANDs), but the host mechanism that regulates the HIV-induced cytokine expression in the CNS remains elusive. Here, we present evidence for a crucial role of Wnt5a signaling in the expression of pro-inflammatory cytokines in the spinal cord induced by a major HIV-envelope protein, gp120. Wnt5a is mainly expressed in spinal neurons, and rapidly up-regulated by intrathecal injection (i.t.) of gp120. We show that inhibition of Wnt5a by specific antagonists blocks gp120-induced up-regulation of IL-1β, IL-6, and TNF-α in the spinal cord. Conversely, injection (i.t.) of purified recombinant Wnt5a stimulates the expression of these cytokines. To elucidate the role of the Wnt5a-regulated signaling pathways in gp120-induced cytokine expression, we have focused on CaMKII and JNKs, the well characterized down-stream targets of Wnt5a signaling. We find that Wnt5a is required for gp120 to activate CaMKII and JNK signaling. Furthermore, we demonstrate that the Wnt5a/CaMKII pathway is critical for the gp120-induced expression of IL-1β, whereas the Wnt5a/JNK pathway is for TNF-α expression. Meanwhile, the expression of IL-6 is co-regulated by both pathways. These results collectively suggest that Wnt5a signaling cascades play a crucial role in the regulation of gp120-induced expression of pro-inflammatory cytokines in the CNS.

HIV-1 Tat C Modulates Expression of miRNA-101 to Suppress VE-Cadherin in Human Brain Microvascular Endothelial Cells

HIV-1 infection leads to the development of HIV-associated neurological disorders. The HIV-1 Tat protein has been reported to exert an adverse effect on blood-brain barrier integrity and permeability. Perturbation in permeability is mainly caused by disruptions in adherens junctions and tight junction proteins. We have identified HIV-1 Tat C-induced disruption of VE-cadherin mediated by miRNA-101 in human brain microvascular endothelial cells (BMVECs). HIV-1 Tat C increased the expression of miR-101, which led to downregulation of VE-cadherin. Overexpression of miR-101 resulted into the suppression of VE-cadherin. Inhibition of miR-101 by the miRNA inhibitor enhanced the expression of VE-cadherin. We have demonstrated that VE-cadherin is a direct target of miR-101 using a luciferase reporter assay, which showed that mutated VE-cadherin 3'UTR and miR-101 cotransfection did not change luciferase activity. By overexpression and knockdown of miR-101, we have demonstrated that the expression level of claudin-5 is governed by the expression of VE-cadherin. These findings demonstrate a novel mechanism for the regulation of barrier permeability by miR-101 via posttranscriptional regulation of VE-cadherin in human BMVECs exposed to the HIV-1 Tat C protein.

Cerebrospinal fluid miRNA profile in HIV‐encephalitis

MicroRNAs are short non-coding RNAs that modulate gene expression by translational repression. Because of their high stability in intracellular as well as extracellular environments, miRNAs have recently emerged as important biomarkers in several human diseases. However, they have not been tested in the cerebrospinal fluid (CSF) of HIV-1 positive individuals. Here, we present results of a study aimed at determining the feasibility of detecting miRNAs in the CSF of HIV-infected individuals with and without encephalitis (HIVE). We also evaluated similarities and differences between CSF and brain tissue miRNAs in the same clinical setting. We utilized a high throughput approach of miRNA detection arrays and identified differentially expressed miRNAs in the frontal cortex of three cases each of HIV+, HIVE, and HIV- controls, and CSF of 10 HIV-positive and 10 HIV-negative individuals. For the CSF samples, the group of HIV+ individuals contained nine cases of HIV-associated neurological disorders (HAND) and, among those, four had HIVE. All the HIV-negative samples had non-viral acute disseminate encephalomyelitis. A total of 66 miRNAs were found differentially regulated in HIV+ compared to HIV- groups. The greatest difference in miRNA expression was observed when four cases of HIVE were compared to five non-HIVE cases, previously normalized with the HIV-negative group. After statistical analyses, 11 miRNAs were fund significantly up-regulated in HIVE. Although more clinical samples should be examined, this work represents the first report of CSF miRNAs in HIV-infection and offers the basis for future investigation.

HIV-1 Nef in Macrophage-Mediated Disease Pathogenesis

Combined anti-retroviral therapy (cART) has significantly reduced the number of AIDS-associated illnesses and changed the course of HIV-1 disease in developed countries. Despite the ability of cART to maintain high CD4+ T-cell counts, a number of macrophage-mediated diseases can still occur in HIV-infected subjects. These diseases include lymphoma, metabolic diseases, and HIV-associated neurological disorders. Within macrophages, the HIV-1 regulatory protein “Nef” can modulate surface receptors, interact with signaling pathways, and promote specific environments that contribute to each of these pathologies. Moreover, genetic variation in Nef may also guide the macrophage response. Herein, we review findings relating to the Nef–macrophage interaction and how this relationship contributes to disease pathogenesis.

Molecule of the month HIV-1 Tat and miRNA.

miRNAs are a well-established RNA phenomenon derived from the non-coding major portion of the human genome. miRNAs cannot be ignored because they are so heavily involved in the control of gene expression [1]. The study of neurological and neuropsychiatric disease also has miRNA components that are commencing to be mapped and characterized. Due to their high stability, for example miRNA can be found in cerebrospinal fluid (CSF) as well as within cells. In a recent publication, comparisons of miRNAs were made among individuals that were HIV positive, without and with HIV encephalitis (HIVE), in individuals with HIV-Associated Neurological Disorders (HAND), and HIV negative controls. CSF and frontal cortex were studied. Comparing HIV positives with HIV negatives, a total of 66 miRNAs were found differentially upregulated for HIV positive individuals. The HIV negative cases were a type of disease control in that they had non-viral acute encephalomyelitis. Of the 66 upregulated miRNAs, statistical analyses demonstrated that 11 miRNAs were upregulated significantly [2]. HIV-1 Tat is an important virus coded regulator protein produced during HIV-1 infection [3]. HIV-1 Tat disrupts neuronal function via miRNAs. Specifically, miRNA expression becomes altered in neuron cultures exposed to HIV-1 tat. Tat is a high inducer of miR-34a as well as other miRNAs. However, tat also decreased levels of target genes including CREB involving miR-34a [4]. Earlier studies on the effects of Tat specifically and HIV-1 in general need to be reinterpreted in terms of the involvement of miRNAs. For example, PC12 (neuronal) cell cultures demonstrate a rapid (ca. 5 minutes) increase in cAMP and CREB transcription factor levels upon exposure to HIV-1 Tat. The serine-133 (Ser-133) amino acid is phosphorylated on CREB. However, when this experiment is done at later times of addition of Tat (ca. 1-2 hours), there is a continued decline of cAMP and reduction of phosphorylated CREB. The dephosphorylation was shown to be due to activation of a phosphatidyl-inositol-3-kinase, AKT, and cyclic nucleoside phosphodiesterase pathway. In addition, there was increased apoptosis of the treated cells. These findings may be relevant for the mechanisms of pathogenesis for HIV-1-associated dementia (HAD) [5] as well as HAND. In related studies, HIV-1 Tat protein was shown to affect histone deacetylases (HDACs) (that are central in transcriptional epigenetics and remodeling of chromatin). Tat protein upregulates HDAC2 in neuronal cells. This may result in inhibition of transcription in neurons and down regulation for Ca2+/calmodulin-dependent protein kinase II (CaMKII) as well as CREB gene expression. These genes are involved in neuronal function and synaptic plasticity. Moreover, as indicated by findings described above, miRNAs may be involved. These pathways may be components of dysfunction that lead to HAD and HAND. Consequently, specific HDAC2 inhibitors may be of use in NeuroAIDS [6].The manipulation of miRNA expression may become an important component of the attack on disease. The figure illustrates various gene interactions. It is left as a puzzle for the interested reader to identify the various genes and their functions in the (Figure 1) [7, 8]. Figure 1 CREB HDAC2 CaMKII Network. The graph shows interactions among proteins CREB, HDAC2, and CaMKII. As mentioned in the text, the expression of these proteins may be modulated by miRNAs that are consequent to HIV-1 infection. In this figure, line-colors and ...

Characterization and function of the human macrophage dopaminergic system: implications for CNS disease and drug abuse

BackgroundPerivascular macrophages and microglia are critical to CNS function. Drugs of abuse increase extracellular dopamine in the CNS, exposing these cells to elevated levels of dopamine. In rodent macrophages and human T-cells, dopamine was shown to modulate cellular functions through activation of dopamine receptors and other dopaminergic proteins. The expression of these proteins and the effects of dopamine on human macrophage functions had not been studied.MethodsTo study dopaminergic gene expression, qRT-PCR was performed on mRNA from primary human monocyte derived macrophages (MDM). Expression and localization of dopaminergic proteins was examined by immunoblotting isolated plasma membrane, total membrane and cytosolic proteins from MDM. To characterize dopamine-mediated changes in cytokine production in basal and inflammatory conditions, macrophages were treated with different concentrations of dopamine in the presence or absence of LPS and cytokine production was assayed by ELISA. Statistical significance was determined using two-tailed Students’ T-tests or Wilcoxen Signed Rank tests.ResultsThese data show that MDM express mRNA for all five subtypes of dopamine receptors, and that dopamine receptors 3 and 4 are expressed on the plasma membrane. MDM also express mRNA for the dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2), tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase (AADC). DAT is expressed on the plasma membrane, VMAT2 on cellular membranes and TH and AADC are in the cytosol. Dopamine also alters macrophage cytokine production in both untreated and LPS-treated cells. Untreated macrophages show dopamine mediated increases IL-6 and CCL2. Macrophages treated with LPS show increased IL-6, CCL2, CXCL8 and IL-10 and decreased TNF-α.ConclusionsMonocyte derived macrophages express dopamine receptors and other dopaminergic proteins through which dopamine may modulate macrophage functions. Thus, increased CNS dopamine levels due to drug abuse may exacerbate the development of neurological diseases including Alzheimer’s disease and HIV associated neurological disorders.

Exosome-mediated shuttling of microRNA-29 regulates HIV Tat and morphine-mediated Neuronal dysfunction

Neuronal damage is a hallmark feature of HIV-associated neurological disorders (HANDs). Opiate drug abuse accelerates the incidence and progression of HAND; however, the mechanisms underlying the potentiation of neuropathogenesis by these drugs remain elusive. Opiates such as morphine have been shown to enhance HIV transactivation protein Tat-mediated toxicity in both human neurons and neuroblastoma cells. In the present study, we demonstrate reduced expression of the tropic factor platelet-derived growth factor (PDGF)-B with a concomitant increase in miR-29b in the basal ganglia region of the brains of morphine-dependent simian immunodeficiency virus (SIV)-infected macaques compared with the SIV-infected controls. In vitro relevance of these findings was corroborated in cultures of astrocytes exposed to morphine and HIV Tat that led to increased release of miR-29b in exosomes. Subsequent treatment of neuronal SH-SY5Y cell line with exosomes from treated astrocytes resulted in decreased expression of PDGF-B, with a concomitant decrease in viability of neurons. Furthermore, it was shown that PDGF-B was a target for miR-29b as evidenced by the fact that binding of miR-29 to the 3′-untranslated region of PDGF-B mRNA resulted in its translational repression in SH-SY5Y cells. Understanding the regulation of PDGF-B expression may provide insights into the development of potential therapeutic targets for neuronal loss in HIV-1-infected opiate abusers.

HIV-Associated Neurological Disorders

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.

Reliability of the Lay Adherence Counsellor Administered Substance Abuse and Mental Illness Symptoms Screener (SAMISS) and the International HIV Dementia Scale (IHDS) in a Primary care HIV Clinic in Cape Town, South Africa

HIV infection is associated with an increased prevalence of common mental disorders and with the development of HIV associated neurological disorders (HAND). The aim of this research was to determine the reliability of lay adherence counsellors in the administration of the substance abuse and mental illness symptom screener (SAMISS) for common mental disorders and International HIV Dementia Scale (IHDS) for HAND in a South African sample of 269 people living with HIV/AIDS and on HAART in a primary healthcare setting. We used a cross-sectional design with each patient assessed by a mental health nurse and counsellor, 1 week apart. Reliability was fair for the SAMISS overall (κ = 0.39, CI(95) 0.29-0.49, P < 0.01), but was higher for the substance abuse component compared to the mental illness component. Reliability for the IHDS between counsellors and nurses was slight (κ = 0.11, CI(95) 0.00-0.27, P < 0.02). Counsellors tended not to miss symptoms, and detected symptoms more often than nurses for the both the SAMISS and IHDS. Strategies to improve the ability of primary healthcare providers to screen for neurocognitive disorders as well as avoiding over-detection of mental illness and substance abuse symptoms need to be developed and implemented for the primary healthcare setting.

HIV-1 envelope protein gp120 up regulates CCL5 production in astrocytes which can be circumvented by inhibitors of NF-κB pathway

HIV associated neurological disorders (HAND) is a common neurological complication in patients infected with HIV. The proinflammatory cytokines and chemokines produced by astrocytes play a pivotal role in neuroinflammatory processes in the brain and viral envelope gp120 has been implicated in this process. In view of increased levels of CCL5 observed in the CSF of HIV-1 infected patients, we studied the effects of gp120 on CCL5 expression in astrocytes and the possible mechanisms responsible for those effects. Transfection of the SVGA astrocyte cell line with a plasmid encoding gp120 resulted in a time-dependent increase in expression levels of CCL5 in terms of mRNA and protein by 24.6±2.67- and 35.2±6.1-fold, respectively. The fluorescent images showed localization of CCL5 in the processes of the astrocytes. The gp120-specific siRNA abrogated the gp120-mediated increase in CCL5 expression. We also explored a possible mechanism for the effects of gp120 on CCL5 expression. Using a specific inhibitor for the NF-κB pathway, we demonstrated that levels of gp120 induction of CCL5 expression can be abrogated by 44.6±4.2% at the level of mRNA and 51.8±5.0% at the protein level. This was further confirmed by knocking down NF-κB through the use of siRNA.

Platelet-Derived Growth Factor B Chain Is a Novel Target Gene of Cocaine-Mediated Notch1 Signaling: Implications for HIV-Associated Neurological Disorders

Neuroinflammation associated with HIV-1 infection is exacerbated in cocaine-abusing, HIV+ individuals. The underlying mechanisms are, in part, attributable to disruption of the blood-brain barrier modulated by cocaine via platelet-derived growth factor B chain (PDGF-B). Since Notch signaling plays a critical role in CNS homeostasis, we hypothesized that it may have a role in cocaine-mediated induction of PDGF-B. The goal of this study was to link Notch signaling with PDGF-B. Using Western blot analysis, we demonstrate the role of Notch1 signaling in cocaine-mediated induction of PDGF-B in human brain microvascular endothelial cells. Exposure of cells to the γ-secretase inhibitor-DAPT or silencing of Notch1 resulted in abrogation of cocaine-mediated induction of PDGF-B. Reciprocally, activation of the Notch1 receptor by exposing cells to the Notch ligand Jagged-1 resulted in upregulation of PDGF-B expression. Furthermore, it was demonstrated that cocaine-mediated activation of Notch1 signaling leading to targeted expression of PDGF-B involved activation of the downstream effector CSL. Functional implication of Notch1 signaling in regulating expression of the vascular permeant PDGF-B was confirmed in vitro using cell permeability assays. In vivo relevance was further corroborated in cocaine-treated mice that demonstrated increased permeability of the endothelial barrier as evidenced by Evans blue and sodium fluorescein extravasation. Specificity of Notch1 signaling in vivo was validated in mice exposed to DAPT, which failed to demonstrate barrier disruption following cocaine exposure. This is the first evidence of involvement of Notch1 activation in cocaine-mediated regulation of PDGF-B expression.

Cell Signaling Pathways and HIV-1 Therapeutics

Host-virus interactions permeate every aspect of both virus life cycle and host response and involve host cell macromolecular machinery and viral elements. It is these intimate interactions that mandate the outcomes of the infection and pathogenesis. It is also these intimate interactions that lay the foundation for the development of pharmaceutical interventions. HIV-1 is no exception in these regards. In the first two decades, HIV/AIDS research has led to the successful development of a number of antiviral inhibitors and the landmark formulation of the suppressive therapy. It has become apparent that this therapy does not offer a complete solution to cure and eradicate the virus. Meanwhile, this therapy has changed the overall landscape of HIV-associated neurological disorders to a more common and prevalent form so-called minor cognitive motor disorder. Thus, there is an important and continued need for new anti-HIV therapeutics. We believe that this is an excellent opportunity to compile and present the latest works being done during the last few years in this exciting field of HIV-host interactions, particularly cell signaling pathways. We hope that this special issue composed of one brief report, eight thematic reviews, and two original articles will serve to foster the exchange of new scientific ideas on HIV-host interactions and anti-HIV therapy and eventually contribute to HIV/AIDS eradication.

HIVBrainSeqDB: a database of annotated HIV envelope sequences from brain and other anatomical sites

BackgroundThe population of HIV replicating within a host consists of independently evolving and interacting sub-populations that can be genetically distinct within anatomical compartments. HIV replicating within the brain causes neurocognitive disorders in up to 20-30% of infected individuals and is a viral sanctuary site for the development of drug resistance. The primary determinant of HIV neurotropism is macrophage tropism, which is primarily determined by the viral envelope (env) gene. However, studies of genetic aspects of HIV replicating in the brain are hindered because existing repositories of HIV sequences are not focused on neurotropic virus nor annotated with neurocognitive and neuropathological status. To address this need, we constructed the HIV Brain Sequence Database.ResultsThe HIV Brain Sequence Database is a public database of HIV envelope sequences, directly sequenced from brain and other tissues from the same patients. Sequences are annotated with clinical data including viral load, CD4 count, antiretroviral status, neurocognitive impairment, and neuropathological diagnosis, all curated from the original publication. Tissue source is coded using an anatomical ontology, the Foundational Model of Anatomy, to capture the maximum level of detail available, while maintaining ontological relationships between tissues and their subparts. 44 tissue types are represented within the database, grouped into 4 categories: (i) brain, brainstem, and spinal cord; (ii) meninges, choroid plexus, and CSF; (iii) blood and lymphoid; and (iv) other (bone marrow, colon, lung, liver, etc). Patient coding is correlated across studies, allowing sequences from the same patient to be grouped to increase statistical power. Using Cytoscape, we visualized relationships between studies, patients and sequences, illustrating interconnections between studies and the varying depth of sequencing, patient number, and tissue representation across studies. Currently, the database contains 2517 envelope sequences from 90 patients, obtained from 22 published studies. 1272 sequences are from brain; the remaining 1245 are from blood, lymph node, spleen, bone marrow, colon, lung and other non-brain tissues. The database interface utilizes a faceted interface, allowing real-time combination of multiple search parameters to assemble a meta-dataset, which can be downloaded for further analysis.ConclusionsThis online resource, which is publicly available at http://www.HIVBrainSeqDB.org, will greatly facilitate analysis of the genetic aspects of HIV macrophage tropism, HIV compartmentalization and evolution within the brain and other tissue reservoirs, and the relationship of these findings to HIV-associated neurological disorders and other clinical consequences of HIV infection.

Potential role of HIV-1 Nef and human M6B in HIV-associated neurological disorders

Background “Highly active antiretroviral therapy” (HAART) has dramatically increased the life expectancies of HIV positive humans. Due to this progress, other HIV-infection associated consequences like the HIV-associated neurological disorders (HIV-ND) are becoming more and more significant. The HIV Nef protein seems to play an important role in progression of HIV-NDs. We set out to identify brain tissue specific ligands of membrane associated Nef.

Alteration of Methamphetamine-induced stereotypic behaviour in transgenic mice expressing HIV-1 envelope protein gp120

The use of drugs for recreational purposes, in particular Methamphetamine, is associated with an increased risk of infection with human immunodeficiency virus (HIV)-1. HIV-1 infection in turn can lead to HIV-associated neurological disorders (HAND) that range from mild cognitive and motor impairment to HIV-associated dementia (HAD). Interestingly, post mortem brain specimens from HAD patients and transgenic (tg) mice expressing the viral envelope protein gp120 in the central nervous system display similar neuropathological signs. In HIV patients, the use of Methamphetamine appears to aggravate neurocognitive alterations. In the present study, we injected HIV/gp120tg mice and non-transgenic littermate control animals with Methamphetamine dissolved in Saline or Saline vehicle and assessed locomotion and stereotyped behaviour. We found that HIVgp120-transgenic mice differ significantly from non-transgenic controls in certain domains of their behavioural response to Methamphetamine. Thus this experimental model system may be useful to further study the mechanistic interaction of both the viral envelope protein and the psychostimulant drug in behavioural alterations and neurodegenerative disease.

HIV-1 Tat Co-Operates with IFN-γ and TNF-α to Increase CXCL10 in Human Astrocytes

HIV-associated neurological disorders (HAND) are estimated to affect 60% of the HIV infected population. HIV-encephalitis (HIVE), the pathological correlate of the most severe form of HAND is often characterized by glial activation, cytokine/chemokine dysregulation, and neuronal damage and loss. However, the severity of HIVE correlates better with glial activation rather than viral load. One of the characteristic features of HIVE is the increased amount of the neurotoxic chemokine, CXCL10. This chemokine can be released from astroglia activated with the pro-inflammatory cytokines IFN-γ and TNF-α, in conjunction with HIV-1 Tat, all of which are elevated in HIVE. In an effort to understand the pathogenesis of HAND, this study was aimed at exploring the regulation of CXCL10 by cellular and viral factors during astrocyte activation. Specifically, the data herein demonstrate that the combined actions of HIV-1 Tat and the pro-inflammatory cytokines, IFN-γ and TNF-α, result in the induction of CXCL10 at both the RNA and protein level. Furthermore, CXCL10 induction was found to be regulated transcriptionally by the activation of the p38, Jnk, and Akt signaling pathways and their downstream transcription factors, NF-κB and STAT-1α. Since CXCL10 levels are linked to disease severity, understanding its regulation could aid in the development of therapeutic intervention strategies for HAND.

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.

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.

HIV‐1 gp120 as Well as Alcohol Affect Blood–Brain Barrier Permeability and Stress Fiber Formation: Involvement of Reactive Oxygen Species

HIV-1 infection commonly leads to serious HIV-1-associated neurological disorders, such as HIV-1-associated encephalopathy and dementia. In addition, alcohol is commonly used and/or abused among AIDS patients, but it is unclear whether alcohol affects the disease progression and if it affects it, how this occurs. We hypothesized that alcohol could affect the blood-brain barrier (BBB) integrity and thus could affect the onset and/or progression of HIV-associated neurological disorders. Human brain microvascular endothelial cells (HBMEC) in a BBB model system were pretreated with alcohol (17 and 68 mM) and subsequently coexposed with HIV-1 gp120. Expression of chemokine receptors CCR3, CCR5, and CXCR4 was assessed by enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Changes in the permeability of the HBMEC monolayer were assessed using paracellular markers [(3)H]inulin or propidium iodide. Actin rearrangements in HBMEC were visualized by fluorescence microscopy and viability assessed using Live/Dead stain. Both gp120 and alcohol increased the permeability of the BBB model by up to 141%, without affecting HBMEC viability. Cotreatment with alcohol and gp120 did not result in a significant synergistic effect. Gp120 permeability involved chemokine receptor CCR5. Alcohol did not affect chemokine receptor expression on brain endothelial cells. Both gp120 and alcohol reorganized the cytoskeleton and induced stress fiber formation. Inhibition of reactive oxygen species (ROS) formation through NADPH blocked the effects of both gp120 and alcohol on permeability and stress fiber formation. These results indicate that both HIV-1 gp120 and alcohol induce stress fibers, causing increased permeability of the human BBB endothelium. Alcohol (68 mM)-mediated permeability increase was linked to ROS formation. The alcohol-mediated physiological changes in the HBMEC monolayers may increase diffusion of plasma components and viral penetration across the BBB. This suggests that alcohol, especially at levels attained in heavy drinkers, can potentially contribute in a negative fashion to HIV-1 neuropathogenesis.