Mononuclear phagocyte differentiation, activation, and viral infection regulate matrix metalloproteinase expression: implications for human immunodeficiency virus type 1-associated dementia

Early Life Trauma and Social Processing in HIV: The Role of Neuroendocrine Factors and Inflammation

OBJECTIVE

Early life trauma (ELT) and HIV are associated with social processing deficits. In people with HIV (PWH), we examined whether facial emotion identification accuracy differs by ELT and whether neuroendocrine factors including cortisol, oxytocin (OT), and arginine vasopressin, and/or immune system measures play a role in the ELT-performance association.

METHODS

We used secondary data from the placebo condition of a pharmacologic challenge study in PWH. Presence of ELT was measured with the Childhood Trauma Questionnaire (at least moderate experiences of sexual, physical, and/or emotional abuse). Social processing was measured with the Facial Emotion Perception Test (FEPT). Salivary immune system measures and cortisol were sampled across a 5-hour study session. Blood was collected at study session start (12 pm ) to measure OT and arginine vasopressin. We examined the association of ELT with FEPT and five biological moderators (from principal components analysis of 12 biomarkers) of ELT-FEPT associations.

RESULTS

Of 58 PWH (42 men; mean [standard deviation] age = 33.7 [8.9] years), 50% endorsed ELT. ELT-exposed PWH demonstrated lower identification accuracy across all emotional expressions (unstandardized β [ B ] = 0.13; standard error [SE] = 0.05; p = .021, d = 0.63) and had higher OT levels compared with ELT-unexposed PWH ( t(1,56) = 2.12, p = .039; d = 0.57). For total accuracy, an OT/C-reactive protein factor moderated the ELT-FEPT association ( B = 0.14; SE = 0.05; p = .014); accuracy was lower in ELT-exposed PWH versus ELT-unexposed PWH when the factor was low but not when high. Similar results were obtained for fearful, neutral, and happy faces ( p values < .05). Regardless of ELT, a myeloid migration (MCP-1/MMP-9) factor was associated with reduced accuracy ( p values < .05).

CONCLUSIONS

Our pilot findings suggest that ELT may alter social processing in PWH, and OT and C-reactive protein may be a target for improving social processing in ELT-exposed PWH, and myeloid migration markers may be a target in PWH more generally.

Chronic delta-9-tetrahydrocannabinol (THC) treatment counteracts SIV-induced modulation of proinflammatory microRNA cargo in basal ganglia-derived extracellular vesicles

BACKGROUND

Early invasion of the central nervous system (CNS) by human immunodeficiency virus (HIV) (Gray et al. in Brain Pathol 6:1-15, 1996; An et al. in Ann Neurol 40:611-6172, 1996), results in neuroinflammation, potentially through extracellular vesicles (EVs) and their micro RNAs (miRNA) cargoes (Sharma et al. in FASEB J 32:5174-5185, 2018; Hu et al. in Cell Death Dis 3:e381, 2012). Although the basal ganglia (BG) is a major target and reservoir of HIV in the CNS (Chaganti et al. in Aids 33:1843-1852, 2019; Mintzopoulos et al. in Magn Reson Med 81:2896-2904, 2019), whether BG produces EVs and the effect of HIV and/or the phytocannabinoid-delta-9-tetrahydrocannabinol (THC) on BG-EVs and HIV neuropathogenesis remain unknown.

METHODS

We used the simian immunodeficiency virus (SIV) model of HIV and THC treatment in rhesus macaques (Molina et al. in AIDS Res Hum Retroviruses 27:585-592, 2011) to demonstrate for the first time that BG contains EVs (BG-EVs), and that BG-EVs cargo and function are modulated by SIV and THC. We also used primary astrocytes from the brains of wild type (WT) and CX3CR1+/GFP mice to investigate the significance of BG-EVs in CNS cells.

RESULTS

Significant changes in BG-EV-associated miRNA specific to SIV infection and THC treatment were observed. BG-EVs from SIV-infected rhesus macaques (SIV EVs) contained 11 significantly downregulated miRNAs. Remarkably, intervention with THC led to significant upregulation of 37 miRNAs in BG-EVs (SIV-THC EVs). Most of these miRNAs are predicted to regulate pathways related to inflammation/immune regulation, TLR signaling, Neurotrophin TRK receptor signaling, and cell death/response. BG-EVs activated WT and CX3CR1+/GFP astrocytes and altered the expression of CD40, TNFα, MMP-2, and MMP-2 gene products in primary mouse astrocytes in an EV and CX3CR1 dependent manners.

CONCLUSIONS

Our findings reveal a role for BG-EVs as a vehicle with potential to disseminate HIV- and THC-induced changes within the CNS.

Impact of metabolic disorders on the structural, functional, and immunological integrity of the blood-brain barrier: Therapeutic avenues

Mounting evidence has linked the metabolic disease to neurovascular disorders and cognitive decline. Using a murine model of a high-fat high-sugar diet mimicking obesity-induced type 2 diabetes mellitus (T2DM) in humans, we show that pro-inflammatory mediators and altered immune responses damage the blood-brain barrier (BBB) structure, triggering a proinflammatory metabolic phenotype. We find that disruption to tight junctions and basal lamina due to loss of control in the production of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) causes BBB impairment. Together the disruption to the structural and functional integrity of the BBB results in enhanced transmigration of leukocytes across the BBB that could contribute to an initiation of a neuroinflammatory response through activation of microglia. Using a humanized in vitro model of the BBB and T2DM patient post-mortem brains, we show the translatable applicability of our results. We find a leaky BBB phenotype in T2DM patients can be attributed to a loss of junctional proteins through changes in inflammatory mediators and MMP/TIMP levels, resulting in increased leukocyte extravasation into the brain parenchyma. We further investigated therapeutic avenues to reduce and restore the BBB damage caused by HFHS-feeding. Pharmacological treatment with recombinant annexin A1 (hrANXA1) or reversion from a high-fat high-sugar diet to a control chow diet (dietary intervention), attenuated T2DM development, reduced inflammation, and restored BBB integrity in the animals. Given the rising incidence of diabetes worldwide, understanding metabolic-disease-associated brain microvessel damage is vital and the proposed therapeutic avenues could help alleviate the burden of these diseases.

HIV and Proteomics: What We Have Learned from High Throughput Studies

The accelerated development of technology over the last three decades has driven biological sciences to high-throughput profiling experiments, now broadly referred to as systems biology. The unprecedented improvement of analytical instrumentation has opened new avenues for more complex experimental designs and expands the knowledge in genomics, proteomics, and other omics fields. Despite the collective efforts of hundreds of researchers, gleaning all the expected information from omics experiments is still quite far. This paper summarizes what has been learned from high-throughput proteomics studies thus far, and what is believed should be done to reveal even more valuable information from such studies. It is drawn from the background in using proteomics to study human immunodeficiency virus 1 infection of macrophages and/or T cells, but it is believed that some conclusions will be more broadly applicable.

Activation of proprotein convertase in the mouse habenula causes depressive-like behaviors through remodeling of extracellular matrix

The lateral habenula (LHb) attracts a growing interest as a regulator of monoaminergic activity which were frequently reported to be defective in depression. Here we found that chronic social defeat stress (CSDS) increased production of pro-inflammatory cytokines in LHb associated with mobilization of monocytes and remodeling of extracellular matrix by increased matrix metalloproteinase (MMP) activity. RNA-seq analysis identified proprotein convertase Pcsk5 as an upstream regulator of MMP activation, with upregulation in LHb neurons of mice with susceptibility to CSDS. PCSK5 facilitated motility of microglia in vitro by converting inactive pro-MMP14 and pro-MMP2 to their active forms, highlighting its role in mobilization of microglia and monocytes in neuroinflammation. Suppression of Pcsk5 expression via small interfering RNA (siRNA) ameliorated depressive-like behaviors and pathological mobilization of monocytes in mice with susceptibility to CSDS. PCSK5-MMPs signaling pathway could be a target for development of the antidepressants targeting the inflammatory response in specific brain regions implicated in depression.

Assessment of a long-term in vitro model to characterize the mechanical behavior and macrophage-mediated degradation of a novel, degradable, electrospun poly-urethane vascular graft

An assessment tool to evaluate the degradation of biodegradable materials in a more physiological environment is still needed. Macrophages are critical players in host response, remodeling and degradation. In this study, a cell culture model using monocyte-derived primary macrophages was established to study the degradation, macro-/micro-mechanical behavior and inflammatory behavior of a new designed, biodegradable thermoplastic polyurethane (TPU) scaffold, over an extended period of time in vitro. For in vivo study, the scaffolds were implanted subcutaneously in a rat model for up to 36 weeks. TPU scaffolds were fabricated via the electrospinning method. This technique provided a fibrous scaffold with an average fiber diameter of 1.39 ± 0.76 μm and an average pore size of 7.5 ± 1.1 μm. The results showed that TPU scaffolds supported the attachment and migration of macrophages throughout the three-dimensional matrix. Scaffold degradation could be detected in localized areas, emphasizing the role of adherent macrophages in scaffold degradation. Weight loss, molecular weight and biomechanical strength reduction were evident in the presence of the primary macrophage cells. TPU favored the switch from initial pro-inflammatory response of macrophages to an anti-inflammatory response over time both in vitro and in vivo. Expression of MMP-2 and MMP-9 (the key enzymes in tissue remodeling based on ECM modifications) was also evident in vitro and in vivo. This study showed that the primary monocyte-derived cell culture model represents a promising tool to characterize the degradation, mechanical behavior as well as biocompatibility of the scaffolds during an extended period of observation.

Blood-based inflammation biomarkers of neurocognitive impairment in people living with HIV

Inflammation in people living with HIV (PLWH) correlates with severity of HIV-associated neurocognitive disorders. The objective of this study is to identify blood-based markers of neurocognitive function in a demographic balanced cohort of PLWH. Seven neurocognitive domains were evaluated in 121 seropositive Black/African American, Non-Hispanic White, and White Hispanic men and women using computerized assessments. Associations among standardized neurocognitive function and HIV-related parameters, relevant sociodemographic variables, and inflammation-associated cytokines measured in plasma and cellular supernatants were examined using multivariate and univariate regression models. Outlier and covariate analyses were used to identify and normalize for education level, CD4 T cell count, viral load, CNS and drug abuse comorbidities, which could influence biomarker and neurocognitive function associations. Plasma levels of chemokine (C-C motif) ligand (CCL) 8 significantly associated with memory, complex attention, cognitive flexibility, psychomotor speed, executive function, and processing speed. Plasma tissue inhibitor of metalloproteinases 1 associated with the aforementioned domains except memory and processing speed. In addition, plasma interleukin-23 significantly associated with processing speed and executive function. Analysis of peripheral blood cell culture supernatants revealed no significant markers for neurocognitive function. In this cohort, CD4 T cell count and education level also significantly associated with neurocognitive function. All identified inflammatory biomarkers demonstrated a negative correlation to neurocognitive function. These cytokines have known connections to HIV pathophysiology and are potential biomarkers for neurocognitive function in PLWH with promising clinical applications.

Genetic variation of matrix metalloproteinase enzyme in HIV-associated neurocognitive disorder

Matrix metalloproteinases (MMPs) play a key role in several diseases such as rheumatoid arthritis, HIV-associated neurological diseases (HAND), multiple sclerosis, osteoporosis, stroke, Alzheimer's disease, certain viral infections of the central nervous system, cancer, and hepatitis C virus. MMPs have been explained with regards to extracellular matrix remodeling, which occurs throughout life and ranges from tissue morphogenesis to wound healing in various processes. MMP are inhibited by endogenous tissue inhibitors of metalloproteinases (TIMPs). Matrix metalloproteases act as an interface between host's attack by Tat protein of HIV-1 virus and extracellular matrix, which causes breaches in the endothelial barriers by degrading ECM. This process initiates the dissemination of virus in tissues which can lead to an increase HIV-1 infection. MMPs are diverse and are highly polymorphic in nature, hence associated with many diseases. The main objective of this review is to study the gene expression of MMPs in HIV-related diseases and whether TIMPs and MMPs could be related with disease progression, HIV vulnerability and HAND. In this review, a brief description on the classification, regulation of MMP and TIMP, the effect of different MMPs and TIMPs gene polymorphisms and its expression on HIV-associated diseases have been provided. Previous studies have shown that MMPs polymorphism (MMP-1, MMP-2 MMP3, and MMP9) plays an important role in HIV vulnerability, disease progression and HAND. Further research is required to explore their role in pathogenesis and therapeutic perspective.

Promoter polymorphism MMP-1 (-1607 2G/1G) and MMP-3 (-1612 5A/6A) in development of HAND and modulation of pathogenesis of HAND

The pathogenesis of HIV-associated neurocognitive disorder (HAND) is modulated by host genetic susceptibility factors such as Matrix metalloproteinases (MMPs). Promoter polymorphism of MMP-1 and MMP-3 may modify the expression of the gene. Hence, we evaluated the association of MMP-1-16072G/1G and MMP-3-1612 5A/6A polymorphisms with development of HAND and the modulation of pathogenesis of HAND. We enrolled a total of 180 individuals, 50 HIVinfected individuals with HAND, 130 without HAND, and 150 healthy controls. Polymorphism of MMP-1 and MMP-3 were genotyped by PCR-RFLP. MMP-1-1607 2G1G, -16071G/2G-1G/1G genotypes and -1607 1G allele were associated with the development of HAND (OR = 1.64, P = 0.05; OR = 1.45, P = 0.04; OR = 1.69, P = 0.05). MMP-1- 16071G1G, MMP-3-16125A5A genotypes increased the risk for the development of HAND (OR = 1.78, P = 0.25; OR = 2.39, P = 0.13). MMP-3-1612 5A5A, -1612 6A/5A-5A/5A genotypes and -1612 5A allele were associated with the reduced risk of HAND (OR = 0.40, P = 0.05; OR = 0.53, P = 0.04; OR = 0.40, P = 0.01). Haplotype 5A1G increased the risk of development of HAND (OR = 1.93, P = 0.05). As observed in advanced HIV disease stage, MMP-1-1607 1G1G genotype enhance the risk for advancement of HIV disease (OR = 1.69, P = 0.89). MMP-3-1612 6A5A genotype showed higher risk for development of HAND in alcohol users (0R = 1.65, P = 0.44). MMP-1 genotype may have an influence on development of HAND whereas MMP3-1612 5A5A genotype may reduce risk for pathogenesis of HAND.

Nanotechnology approaches to eradicating HIV reservoirs

The advent of combination antiretroviral therapy (cART) has transformed HIV-1 infection into a controllable chronic disease, but these therapies are incapable of eradicating the virus to bring about an HIV cure. Multiple strategies have been proposed and investigated to eradicate latent viral reservoirs from various biological sanctuaries. However, due to the complexity of HIV infection and latency maintenance, a single drug is unlikely to eliminate all HIV reservoirs and novel strategies may be needed to achieve better efficacy while limiting systemic toxicity. In this review, we describe HIV latency in cellular and anatomical reservoirs, and present an overview of current strategies for HIV cure with a focus on their challenges for clinical translation. Then we provide a summary of nanotechnology solutions that have been used to address challenges in HIV cure by delivering physicochemically diverse agents for combination therapy or targeting HIV reservoir sites. We also review nanocarrier-based gene delivery and immunotherapy used in cancer treatment but may have potential applications in HIV cure.

Subclinical central inflammation is risk for RIS and CIS conversion to MS

Background:

Subtle diffuse intrathecal inflammation is undetectable by conventional neuroimaging, and could influence multiple sclerosis (MS) disease course.

Objective:

To explore the role of subclinical persisting intrathecal inflammation in radiologically isolated syndrome (RIS) or clinically isolated syndrome (CIS) conversion to MS, and in early MS disease reactivation.

Methods:

One-hundred ninety-three subjects with RIS, CIS, relapsing–remitting (RR), or primary progressive (PP) MS were included, along with 76 matched controls. Cerebrospinal fluid (CSF) levels of interleukin-8 (IL-8), a major proinflammatory cytokine, were measured as a biomarker of intrathecal inflammation. Patients were followed up for 2 years. Clinical and imaging measures of disease progression were recorded.

Results:

High central contents of IL-8 were associated to clinical progression in subjects with RIS, and to the risk of conversion to MS in subjects with CIS. Asymptomatic intrathecal inflammation placed subjects at risk for MS conversion, even regardless lesion load. CSF IL-8 levels were higher in RR MS with high disease activity. Higher number of relapses in the first two years since diagnosis and shorter first inter-attack intervals were observed in patients with high levels of IL-8.

Conclusion:

IL-8 might provide utility in determining the presence of active intrathecal inflammation, and could be important in diagnostically undefined cases.

Interleukin-8 is associated with acute and persistent dysfunction after optic neuritis

Background:

Acute optic neuritis is often in association with multiple sclerosis (MS). Proinflammatory cytokines trigger neuronal damage in neuroinflammatory disorders but their role in optic neuritis is poorly investigated.

Objective:

The objective of this work is to investigate the associations of intrathecal contents of proinflammatory cytokines with transient and persistent dysfunctions after optic neuritis.

Methods:

In 50 MS patients followed for up to six months, cerebrospinal fluid (CSF) levels of IL-1β, TNF and IL-8 were determined, along with clinical, neurophysiological and morphological measures of optic neuritis severity.

Results:

Visual impairment, measured by high- and low-contrast visual acuity, and delayed visual-evoked potential (VEP) latencies were significantly correlated to IL-8 levels during optic neuritis. IL-8 at the time of optic neuritis was also associated with persistent demyelination and final axonal loss, inferred by VEP and optical coherence tomography measures, respectively. Contents of IL-8 were correlated to functional visual outcomes, being higher among patients with incomplete recovery. Multivariate analysis confirmed that IL-8 significantly predicted final visual acuity, at equal values of demographics and baseline visual scores.

Conclusion:

Our study points to IL-8 as the main inflammatory cytokine associated with demyelination and secondary neurodegeneration in the optic nerve after optic neuritis.

Chemokine CXCL8 promotes HIV-1 replication in human monocyte-derived macrophages and primary microglia via nuclear factor-κB pathway

BACKGROUND

Chemokine CXCL8 is an important neutrophil chemoattractant implicated in various neurodegenerative disorders. Cytokine/chemokine imbalance, with an increase in proinflammatory cytokines like interleukin-1β and tumor necrosis factor-α within the central nervous system, is a hallmark of human immunodeficiency virus (HIV)-1 infection. We previously reported that HIV-1 infection is linked to upregulation of CXCL8 in brain tissues and human astrocytes. Chemokines play crucial roles in trafficking of leukocytes and trafficking of HIV-1-infected across the blood-brain barrier play an important role in HIV-1 central nervous system disease. In the post-antiretroviral therapy era, low level of productive replication of HIV-1 in brain is a critical component of neuropathogenesis regulation. The present study investigated the effect of CXCL8 on productive infection of HIV-1 in human monocytes-derived macrophages (MDM) and primary human microglia.

RESULTS

Human MDM and microglia were infected with the blood or brain derived HIV-1 isolates, HIV-1ADA or HIV-1JRFL. Treatment with CXCL8 significantly upregulated HIV-1p24 levels in supernatants of both HIV-1-infected MDM as well as microglia. In addition, the formation of 2-long terminal repeat (LTR) circles, a measure of viral genome integration, was significantly higher in CXCL8-treated, HIV-1-infected MDM and microglia. Transient transfection of U937 cells with HIV-1 LTR luciferase reporter construct resulted in increased promoter activity when treated with CXCL8. Moreover, increased nuclear translocation of nuclear factor-κB was seen in HIV-1-infected MDM following CXCL8 treatment. Blocking CXCL8 receptors CXCR1 and CXCR2 abrogated the CXCL8-mediated enhanced HIV-1 replication.

CONCLUSION

Our results show that CXCL8 mediates productive infection of HIV-1 in MDM and microglia via receptors CXCR1 and CXCR2. These results demonstrate that CXCL8 exerts its downstream effects by increasing translocation of nuclear factor-κB into the nucleus, thereby promoting HIV-1 LTR activity.

Matrix metalloproteinase-2 (MMP-2) generates soluble HLA-G1 by cell surface proteolytic shedding

Human leukocyte antigen-G (HLA-G) molecules are non-classical HLA class I antigens with an important role in pregnancy immune regulation and inflammation control. Soluble HLA-G proteins can be generated through two mechanisms: alternative splicing and proteolytic release, which is known to be metalloprotease mediated. Among this class of enzymes, matrix metalloproteinases (MMPs) might be involved in the HLA-G1 membrane cleavage. Of particular interest are MMP-2 and MMP-9, which regulate the inflammatory process by cytokine and chemokine modulation. We evaluated the effect of MMP-9 and MMP-2 on HLA-G1 membrane shedding. In particular, we analyzed the in vitro effect of these two gelatinases on the secretion of HLA-G1 via proteolytic cleavage in 221-G1-transfected cell line, in JEG3 cell line, and in peripheral blood mononuclear cells. The results obtained by both cell lines showed the role of MMP-2 in HLA-G1 shedding. On the contrary, MMP-9 was not involved in this process. In addition, we identified three possible highly specific cleavage sites for MMP-2, whereas none were detected for MMP-9. This study suggests an effective link between MMP-2 and HLA-G1 shedding, increasing our knowledge on the regulatory machinery beyond HLA-G regulation in physiological and pathological conditions.

Matrix metalloproteinase levels in early HIV infection and relation to in vivo brain status

Matrix metalloproteinases (MMPs) have been implicated in human immunodeficiency virus (HIV)-associated neurological injury; however, this relationship has not been studied early in infection. Plasma levels of MMP-1, MMP-2, MMP-7, MMP-9, and MMP-10 measured using Luminex technology (Austin, TX, USA) were compared in 52 HIV and 21 seronegative participants of the Chicago Early HIV Infection study. MMP levels were also examined in HIV subgroups defined by antibody reactivity, viremia, and antiretroviral status, as well as in available cerebrospinal fluid (CSF) samples (n = 9). MMPs were evaluated for patterns of relationship to cognitive function and to quantitative magnetic resonance measurements of the brain derived in vivo. Plasma MMP-2 levels were significantly reduced in early HIV infection and correlated with altered white matter integrity and atrophic brain changes. MMP-9 levels were higher in the treated subgroup than in the naïve HIV subgroup. Only MMP-2 and MMP-9 were detected in the CSF; CSF MMP-2 correlated with white matter integrity and with volumetric changes in basal ganglia. Relationships with cognitive function were also identified. MMP-2 levels in plasma and in CSF correspond to early changes in brain structure and function. These findings establish a link between MMPs and neurological status previously unidentified in early HIV infection.

Modulation of cytokine release and gene expression by the immunosuppressive domain of gp41 of HIV-1

The transmembrane envelope protein gp41 of the human immunodeficiency virus HIV-1 plays an important role during infection allowing fusion of the viral and cellular membrane. In addition, there is increasing evidence that gp41 may contribute to the immunodeficiency induced by HIV-1. Recombinant gp41 and a synthetic peptide corresponding to a highly conserved domain in gp41, the immunosuppressive (isu) domain, have been shown to inhibit mitogen-induced activation of human peripheral blood mononuclear cells (PBMCs) and to increase release of IL-6 and IL-10 from these cells. We recently reported that a single mutation in the isu domain of gp41 abrogated the immunosuppressive properties and that HIV-1 sequences containing such abrogating mutations had never been isolated from infected individuals. Here, we studied the influence of the isu peptide on the release of 66 cytokines and the expression of 27,000 genes in PBMCs. Incubation of PBMCs with isu peptide homopolymers increased the expression of 16 cytokines among them IL-6 and IL-10, and decreased that of IL-2 and CXCL9. Interestingly, the extend of cytokine modulation was donor-dependent. Among the genes up-regulated were IL-6, IL-8, IL-10 but also MMP-1, TREM-1 and IL-1beta. Most importantly, genes involved in innate immunity such as FCN1 and SEPP1 were found down-regulated. Many changes in cytokine expression demonstrated in our experiments were also found in HIV-1 infected individuals. These data indicate that the isu domain of gp41 has a broad impact on gene expression and cytokine release and therefore may be involved in HIV-1 induced immunopathogenesis.

Gene expression profiles predict emergence of psychiatric adverse events in HIV/HCV-coinfected patients on interferon-based HCV therapy

BACKGROUND

The efficacy of pegylated interferon-α and ribavirin (pegIFN/RBV) in the treatment of Hepatitis C infection is limited by psychiatric adverse effects (IFN-PE). Our study examined the ability of differential gene expression patterns before therapy to predict emergent IFN-PE among 28 HIV/HCV-coinfected patients treated with pegIFN-α2b/RBV.

METHODS

Patients dually infected with HIV and HCV were evaluated at baseline and during treatment by board-certified psychiatrists who classified patients into 2 groups: those who developed IFN-PE and those who did not (IFN-NPE). Gene expression analysis (Affymetrix HG-U133A) was performed using peripheral blood mononuclear cells before and after initiation of treatment. Analysis of Variance, post hoc analysis based on pair-wise comparisons, and functional annotation analysis identified differentially expressed genes within and between groups. Prediction analysis for microarrays was used to test the predictive ability of selected genes.

RESULTS

Twenty-four genes (16 upregulated and 8 downregulated) that were differentially expressed at baseline in patients who subsequently developed IFN-PE compared with the IFN-NPE group showed the ability to predict IFN-PE with an accuracy of 82%. In 16 patients with IFN-PE, 135 genes (117 upregulated; 18 downregulated) were significantly modulated after treatment. Of these, 10 genes have already been shown to be associated with neuropsychiatric illnesses and were significantly modulated only in patients who experienced IFN-PE.

CONCLUSIONS

We describe a novel molecular diagnostic biomarker panel to predict emergent IFN-PE in HIV/HCV-coinfected patients undergoing pegIFN/RBV treatment, which may improve the identification of patients at greatest risk for IFN-PE and suggest candidate therapeutic targets for preventing or treating IFN-PE.

Matrix metalloproteinase dependent cleavage of cell adhesion molecules in the pathogenesis of CNS dysfunction with HIV and methamphetamine

Physiologically appropriate levels of matrix metalloproteinases (MMPs) are likely important to varied aspects of CNS function. In particular, these enzymes may contribute to neuronal activity dependent synaptic plasticity and to cell mobility in processes including stem cell migration and immune surveillance. Levels of MMPs may, however, be substantially increased in the setting of HIV infection with methamphetamine abuse. Elevated MMP levels might in turn influence integrity of the blood brain barrier, as has been demonstrated in published work. Herein we suggest that elevated levels of MMPs can also contribute to microglial activation as well as neuronal and synaptic injury through a mechanism that involves cleavage of specific cell and synaptic adhesion molecules.

PPARα and PPARγ protect against HIV-1-induced MMP-9 overexpression via caveolae-associated ERK and Akt signaling

Activation of matrix metalloproteinase-9 (MMP-9) is involved in HIV-1-induced disruption of the blood-brain barrier (BBB). In the present study, we hypothesize that peroxisome proliferator-activated receptor (PPAR)-α or PPARγ can protect against HIV-1-induced MMP-9 overexpression in brain endothelial cells (hCMEC cell line) by attenuating cellular oxidative stress and down-regulation of caveolae-associated redox signaling. Exposure to HIV-1-infected monocytes induced phosphorylation of ERK1/2 and Akt in hCMEC by 2.5- and 3.6-fold, respectively; however, these effects were attenuated by overexpression of PPARα or PPARγ and by silencing of caveolin-1 (cav-1). Coculture of hCMEC with HIV-1-infected monocytes significantly induced MMP-9 promoter and enzyme activity by 3- to 3.5-fold. Promoter mutation studies indicated that SP-1 (g1940t_g1941t) is an essential transcription factor involved in induction of MMP-9 promoter by HIV-1. In addition, HIV-1-stimulated activity of MMP-9 promoter was inhibited by mutation of AP-1 site 2 (c1918t_a1919g) and both (but not individual) NF-κB binding sites (g1389c and g1664c). PPAR overexpression, ERK1/2 or Akt inhibition, and silencing of cav-1 all effectively protected against HIV-1-induced MMP-9 promoter activity, indicating a close relationship among HIV-1-induced cerebrovascular toxicity, redox-regulated mechanisms, and functional caveolae. Such a link was further confirmed in MMP-9-deficient mice exposed to PPARα or PPARγ agonist and injected with the HIV-1-specific protein Tat into cerebral vasculature. Overall, our results indicate that ERK1/2, Akt, and cav-1 are involved in the regulatory mechanisms of PPAR-mediated protection against HIV-1-induced MMP-9 expression in brain endothelial cells.

Methamphetamine and HIV-1 gp120 effects on lipopolysaccharide stimulated matrix metalloproteinase-9 production by human monocyte-derived macrophages

Monocytes/macrophages are a primary source of human immunodeficiency virus (HIV-1) in the central nervous system (CNS). Macrophages infected with HIV-1 produce a plethora of factors, including matrix metalloproteinase-9 (MMP-9) that may contribute to the development of HIV-1-associated neurocognitive disorders (HAND). MMP-9 plays a pivotal role in the turnover of the extracellular matrix (ECM) and functions to remodel cellular architecture. We have investigated the role of methamphetamine and HIV-1 gp120 in the regulation of lipopolysaccaride (LPS) induced-MMP-9 production in monocyte-derived macrophages (MDM). Here, we show that LPS-induced MMP-9 gene expression and protein secretion are potentiated by incubation with methamphetamine alone and gp120 alone. Further, concomitant incubation with gp120 and methamphetamine potentiated LPS-induced MMP-9 expression and biological activity in MDM. Collectively methamphetamine and gp120 effects on MMPs may modulate remodeling of the extracellular environment enhancing migration of monocytes/macrophages to the CNS.

Proteome bioprofiles distinguish between M1 priming and activation states in human macrophages

Macrophage activation is a dynamic process that results in diverse functional outcomes ranging from immunoregulation to inflammation. The proinflammatory, or M1, response is a complex, bimodal progression composed of a "prime," classically through IFN-gamma, and "trigger," such as LPS. To characterize the physiological response of M1 activation, a systems biology approach was applied to determine the intracellular proteome bioprofiles of IFN-gamma-and LPS-treated primary human macrophages. Our goal was to develop intracellular proteomic fingerprints to serve as novel correlates of macrophage priming and/or activation to augment the existing approaches of analyzing secreted cytokines and cell-surface protein expression. The majority of the proteome, approximately 78%, remained stable during activation, representing the core proteome. In contrast, three distinct patterns defined response proteomes: IFN-gamma-specific, LPS-specific, or IFN-gamma- and LPS-shared or M1-specific. Although steady-state expression levels of proteins involved in energy metabolism and immune response were increased during priming and triggering, changes in protein and fatty acid metabolism, signaling, and transport pathways were most apparent. Unique proteomic fingerprints distinguish among IFN-gamma-specific, LPS-specific, or M1-specific activation states and provide a clear molecular, archeological profile to infer recent history of cells, as well as correlates for chronic macrophage activation in health and disease.

NanoART, neuroAIDS and CNS drug delivery

A broad range of nanomedicines is being developed to improve drug delivery for CNS disorders. The structure of the blood-brain barrier (BBB), the presence of efflux pumps and the expression of metabolic enzymes pose hurdles for drug-brain entry. Nanoformulations can circumvent the BBB to improve CNS-directed drug delivery by affecting such pumps and enzymes. Alternatively, they can be optimized to affect their size, shape, and protein and lipid coatings to facilitate drug uptake, release and ingress across the barrier. This is important as the brain is a sanctuary for a broad range of pathogens including HIV-1. Improved drug delivery to the CNS would affect pharmacokinetic and drug biodistribution properties. This article focuses on how nanotechnology can serve to improve the delivery of antiretroviral medicines, termed nanoART, across the BBB and affect the biodistribution and clinical benefit for HIV-1 disease.

CD38 regulation in activated astrocytes: implications for neuroinflammation and HIV-1 brain infection

Reactive astrogliosis is a key pathological aspect of neuroinflammatory disorders including human immunodeficiency virus type 1 (HIV-1)-associated neurological disease. On the basis of previous data that showedastrocytes activated with interleukin (IL)-1beta induce neuronal injury, we analyzed global gene changes in IL-1beta-activated human astrocytes by gene microarray. Among the up-regulated genes, CD38, a 45-kDa type II single chain transmembrane glycoprotein, was a top candidate, with a 17.24-fold change that was validated by real-time polymerase chain reaction. Key functions of CD38 include enzymatic activities and involvement in adhesion and cell signaling. Importantly, CD38(+)CD8(+) T-cell expression is a clinical correlate for progression of HIV-1 infection and biological marker for immune activation. Thus, CD38 expression in HIV-1 and/or IL-1beta-stimulated human astrocytes and human brain tissues was analyzed. IL-1beta and HIV-1 activation of astrocytes enhanced CD38 mRNA levels. Both CD38 immunoreactivity and adenosine 5'-diphosphate (ADP)-ribosyl cyclase activity were up-regulated in IL-1beta-activated astrocytes. CD38 knockdown using specific siRNAs significantly reduced astrocyte proinflammatory cytokine and chemokine production. However, CD38 mRNA levels were unchanged in IL-1beta knockdown conditions, suggesting that IL-1beta autocrine loop is not implicated in this process. Quantitative immunohistochemical analysis of HIV-seropositive without encephalitis and HIV-1 encephalitis brain tissues showed significant up-regulation of CD38, which colocalized with glial fibrillary acidic protein-positive cells in areas of inflammation. These results suggest an important role of CD38 in the regulation of astrocyte dysfunction during the neuroinflammatory processes involved in neurodegenerative/neuroinflammatory disorders such as HIV-1 encephalitis.

Production and Roles of Glial Tissue Inhibitor of Metalloproteinases-1 in Human Immunodeficiency Virus-1-Associated Dementia Neuroinflammation: A Review

PROBLEM STATEMENT: Tissue Inhibitor of Metalloproteinases-1 (TIMP-1) and its cognate targets, the Matrix Metalloproteinases (MMPs), were differentially expressed in human brain samples with or without HIV-1 infection or HIV-1 Encephalitis (HIVE). APPROACH: A through literature review demonstrated that cell culture models of Central Nervous System (CNS) cell types had been used to illustrate the intricate temporal patterns of TIMP-1/MMP expression, regulated by a variety of inflammatory cytokines. RESULTS: As MMPs and TIMP-1 can significantly altered the extracellular environment and cell signaling, the differential regulation of TIMP-1/MMP expression in neuroinflammation can impact neuronal function and survival in disease conditions. TIMP-1 pro-survival effects had been demonstrated in a variety of cell types including CNS neurons, protecting cells from a wide range of stress and insults. TIMP-1, also known to interact with non-MMP targets, altered cell behavior. In this review, we discussed the possibility that the upregulation of TIMP-1 by glia in acute neuroinflammation may be a neuroprotective response. CONCLUSION: It will be important to delineate the effects of TIMP-1 on neurons and identify receptors and downstream signaling pathways, in order to evaluate TIMP-1 as a therapeutic strategy for neuroinflammatory and neurodegenerative diseases.

CD40-CD40 ligand interactions in human microglia induce CXCL8 (interleukin-8) secretion by a mechanism dependent on activation of ERK1/2 and nuclear translocation of nuclear factor-kappaB (NFkappaB) and activator protein-1 (AP-1)

CXCL8 is a CXC chemokine that recruits leukocytes to sites of inflammation. Expression of CXCL8 in the CNS has been demonstrated in neuroinflammatory diseases, including human immunodeficiency virus (HIV-1) encephalitis, but the mechanism of secretion of this chemokine is not fully understood. CD40 is a 50-kDa protein on the surface of microglia, and we have previously shown that it is increased in expression in HIV-1-infected brain tissue as well as by interferon-gamma (IFNgamma) in tissue culture. We examined the expression and regulation of CXCL8 in cultured human fetal microglia after ligation of CD40 with soluble trimeric CD40 ligand (sCD40L) as well as the expression of CXCL8 on microglia in HIV encephalitic brain tissue sections. Treatment of cultured microglia with IFNgamma + sCD40L resulted in significant induction of CXCL8. This expression was mediated by activation of the ERK1/2 MAPK pathway, as demonstrated by ELISA and Western blot using a specific inhibitor (U0126). Gel shift analyses demonstrated that NFkappaB and AP-1, but not C/EBPbeta, mediate microglial CXCL8 production. We also found increased colocalization of CXCL8 with CD68/CD40-positive cells in HIV encephalitic brain tissue compared with HIV-infected nonencephalitic and normal tissue. Thus, CD40-CD40L interactions facilitate chemokine expression, leading to the influx of inflammatory cells into the CNS. These events can lead to the pathology that is associated with neuroinflammatory diseases.

Opportunistic pathogens in AIDS: trends, diagnosis and priorities

The second International Conference on Opportunistic Pathogens in AIDS was organized by the Department of Laboratory Medicine, All India Institute of Medical Sciences (New Delhi, India). The conference was held at the All India Institute of Medical Sciences in India between the 27th and 29th January 2008, and was attended by 225 participants representing 21 countries. The conference focused on trends, diagnosis and management of coinfections among HIV patients. In addition, as part of this conference, a symposium was held on the links between substance abuse, HIV and neuropathology.

CD16+ monocytes produce IL-6, CCL2, and matrix metalloproteinase-9 upon interaction with CX3CL1-expressing endothelial cells

The CD16+ subset of peripheral blood monocytes (Mo) is expanded dramatically during inflammatory conditions including sepsis, HIV-1 infection, and cancer. CD16+ express high levels of CX3CR1, which mediates arrest onto CX3CL1-expressing endothelial cells (EC) under flow conditions. In contrast, attachment of CD16- Mo onto cytokine-activated EC is independent of CX3CL1. Here, we investigate the ability of CD16+ and CD16- Mo to produce proinflammatory cytokines upon interaction with CX3CL1-expressing HUVEC. We demonstrate that CD16+ but not CD16- Mo produce high levels of IL-6, CCL2, and matrix metalloproteinase (MMP)-9 when cocultured with TNF/IFN-gamma-activated HUVEC or nonactivated HUVEC expressing CX3CL1. Furthermore, supernatants from Mo cocultured with cytokine-activated HUVEC induce neuronal death in vitro. These results suggest that membrane-bound CX3CL1 stimulates production of IL-6, CCL2, and MMP-9 by CD16+ Mo, likely via engagement of CX3CR1. Thus, expansion of CD16+ Mo and their accumulation onto CX3CL1-expressing EC may result in recruitment of Mo and T cell subsets at sites of inflammation in response to CCL2, IL-6-induced cell activation and/or differentiation, and MMP-9-mediated vascular and tissue injury.

Nanomedicine in the diagnosis and therapy of neurodegenerative disorders

Neurodegenerative and infectious disorders including Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke are rapidly increasing as population's age. Alzheimer's disease alone currently affects 4.5 million Americans, and more than $100 billion is spent per year on medical and institutional care for affected people. Such numbers will double in the ensuing decades. Currently disease diagnosis for all disorders is made, in large measure, on clinical grounds as laboratory and neuroimaging tests confirm what is seen by more routine examination. Achieving early diagnosis would enable improved disease outcomes. Drugs, vaccines or regenerative proteins present "real" possibilities for positively affecting disease outcomes, but are limited in that their entry into the brain is commonly restricted across the blood-brain barrier. This review highlights how these obstacles can be overcome by polymer science and nanotechnology. Such approaches may improve diagnostic and therapeutic outcomes. New developments in polymer science coupled with cell-based delivery strategies support the notion that diseases that now have limited therapeutic options can show improved outcomes by advances in nanomedicine.

Reduced secretion and expression of gelatinase profile in Toxoplasma gondii-infected human monocytic cells

The apicomplexan Toxoplasma gondii, an obligate intracellular parasite, can infect humans and a wide range of vertebrates. Following oral infection, the parasite invades tissues by crossing non-permissive biological barriers such as the placenta or the blood-brain barrier. But the molecular mechanisms underlying migration of T. gondii remain poorly characterized. The crossing of various basal membranes and infiltration into the extracellular matrix by T. gondii could involve matrix metalloproteinases (MMPs). We demonstrated a decrease in proMMP-2 and proMMP-9 secretion by THP-1 cells at 24 and 48h post invasion with regulation at the mRNA level throughout infection. This down regulation was associated with a decrease in TIMP-2 secretion and an inhibition of its expression. Moreover, results showed an activation of MT1-MMP; its expression was regulated after 6, 24, and 48h.

Exacerbation of Dopaminergic Terminal Damage in a Mouse Model of Parkinson's Disease by the G-Protein-Coupled Receptor Protease-Activated Receptor 1

Protease-activated receptor 1 (PAR1) is a G-protein-coupled receptor activated by serine proteases and expressed in astrocytes, microglia, and specific neuronal populations. We examined the effects of genetic deletion and pharmacologic blockade of PAR1 in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson's disease, a neurodegenerative disease characterized by nigrostriatal dopamine damage and gliosis. After MPTP injection, PAR1-/- mice showed significantly higher residual levels of dopamine, dopamine transporter, and tyrosine hydroxylase and diminished microgliosis compared with wild-type mice. Comparable levels of dopaminergic neuroprotection from MPTP-induced toxicity were obtained by infusion of the PAR1 antagonist, BMS-200261 into the right lateral cerebral ventricle. MPTP administration caused changes in the brain protease system, including increased levels of mRNA for two PAR1 activators, matrix metalloprotease-1 and Factor Xa, suggesting a mechanism by which MPTP administration could lead to overactivation of PAR1. We also report that PAR1 is expressed in human substantia nigra pars compacta glia as well as tyrosine hydroxylase-positive neurons. Together, these data suggest that PAR1 might be a target for therapeutic intervention in Parkinson's disease.

Macrophages transmit human immunodeficiency virus type 1 products to CD4-negative cells: involvement of matrix metalloproteinase 9

It was previously reported that human immunodeficiency virus type 1 (HIV-1) spreads in CD4 lymphocytes through cell-to-cell transmission. Here we report that HIV-1-infected macrophages, but not lymphocytes, transmit HIV-1 products to CD4-negative cells of either epithelial, neuronal, or endothelial origin in the absence of overt HIV-1 infection. This phenomenon was detectable as early as 1 h after the start of cocultivation and depended on cell-to-cell contact but not on the release of viral particles from donor cells. Transfer of HIV-1 products occurred upon their polarization and colocalization within zones of cell-to-cell contact similar to virological synapses. Neither HIV-1 Env nor Nef expression was required but, interestingly, we found that an HIV-1-dependent increase in matrix metalloproteinase 9 production from donor cells significantly contributed to the cell-to-cell transmission of the viral products. The macrophage-driven transfer of HIV-1 products to diverse CD4-negative cell types may have a significant role in AIDS pathogenesis.

Antiretroviral therapy inhibits matrix metalloproteinase-9 from blood mononuclear cells of HIV-infected patients

OBJECTIVE

To investigate whether antiretroviral therapy (ART) influences the release of matrix metalloproteinase (MMP)-9 from peripheral blood mononuclear cells (PBMC) of HIV-infected individuals.

DESIGN

Culture supernatants were collected from PBMC isolated from 46 HIV-infected subjects and 19 healthy donors (HD). Among the HIV-infected subjects, 30 were receiving ART therapy, while 16 were naive for any ART treatment.

METHODS

Zymography of culture supernatants was followed by determination of MMP-9 using computered scanning densitometry. MMP-9 net enzymatic activity was determined by the sensitive fluorescent-activated substrate conversion assay (FASC) to complement the zymography data.

RESULTS

MMP-9 was significantly elevated in culture supernatants from PBMC of ART-naive subjects in comparison with HD. In the supernatants from 30 HIV-infected subjects receiving ART therapy, MMP-9 was significantly lower than that in those from ART-naive subjects. Analysis by the reverse transcriptase polymerase chain reaction indicated that MMP-9 expression was increased in ART-naive subjects in comparison with HD but ART induced a decrease of MMP-9 expression to levels comparable with those of HD. FASC used as a functional assay showed conversion of fluorescent gelatine in ART-naive subjects, indicating the presence of active MMP-9. By contrast, in both HD and ART-treated subjects, there was no MMP-9 activity, indicating that MMP-9 was completely blocked by binding to its natural tissue inhibitor TIMP-1.

CONCLUSIONS

The present findings show for the first time that ART can reduce the capacity of PBMC from HIV-infected patients to secrete increased amounts of MMP-9.

Investigating the human immunodeficiency virus type 1-infected monocyte-derived macrophage secretome

Mononuclear phagocytes (bone marrow monocyte-derived macrophages, alveolar macrophages, perivascular macrophages, and microglia) are reservoirs and vehicles of dissemination for the human immunodeficiency virus type-1 (HIV-1). How virus alters mononuclear phagocyte immunoregulatory activities to complete its life cycle and influence disease is incompletely understood. In attempts to better understanding the influence of virus on macrophage functions, we used one-dimensional electrophoresis, and liquid chromatography tandem mass spectrometry to analyze the secretome of HIV-1-infected human monocyte-derived macrophages. We identified 110 proteins in culture supernatants of control (uninfected) and virus-infected cells. Differentially expressed cytoskeletal, enzymes, redox, and immunoregulatory protein classes were discovered and validated by Western blot tests. These included, but were not limited to, cystatin C, cystatin B, chitinase 3-like 1 protein, cofilin-1, l-plastin, superoxide dismutase, leukotriene A(4) hydrolase, and alpha-enolase. This study, using a unique proteomics platform, provides novel insights into virus-host cell interactions that likely affect the functional role of macrophages in HIV disease.

Oxidative stress activates protein tyrosine kinase and matrix metalloproteinases leading to blood-brain barrier dysfunction

The blood-brain barrier (BBB) formed by brain microvascular endothelial cells (BMVEC) regulates the passage of molecules and leukocytes in and out of the brain. Oxidative stress is a major underlying cause of neurodegenerative and neuroinflammatory disorders and BBB injury associated with them. Using human BMVEC grown on porous membranes covered with basement membrane (BM) matrix (BBB models), we demonstrated that reactive oxygen species (ROS) augmented permeability and monocyte migration across BBB. ROS activated matrix metalloproteinases (MMP-1, -2, and -9) and decreased tissue inhibitors of MMPs (TIMP-1 and -2) in a protein tyrosine kinase (PTK)-dependent manner. Increase in MMPs and PTK activities paralleled degradation of BM protein and enhanced tyrosine phosphorylation of tight junction (TJ) protein. These effects and enhanced permeability/monocyte migration were prevented by inhibitors of MMPs, PTKs, or antioxidant suggesting that oxidative stress caused BBB injury via degradation of BM protein by activated MMPs and by PTK-mediated TJ protein phosphorylation. These findings point to new therapeutic interventions ameliorating BBB dysfunction in neurological disorders such as stroke or neuroinflammation.

Matrix metalloproteinases, their production by monocytes and macrophages and their potential role in HIV-related diseases

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that are a subfamily of metzincins. Matrix metalloproteinases are responsible for much of the turnover of extra-cellular matrix components and are key to a wide range of processes including tissue remodeling and release of biological factors. Imbalance between the MMPs and endogenous tissue inhibitors of metalloproteinases (TIMPs) can result in dysregulation of many biologic processes and lead to the development of malignancy, cardiovascular disease, and autoimmune and inflammatory disorders. MMP production by monocyte/macrophages is dependent on the cell type, state of differentiation, and/or level of activation and whether they are infected, e.g., by HIV-1. MMP expression by HIV-1 infected monocytes and macrophages may alter cellular trafficking and contribute to HIV-associated pathology such as HIV-associated dementia (HAD). This review will provide a classification of the MMP super-family with particular reference to those produced by monocyte/macrophages, describe their regulation and function within the immune system, and indicate their possible roles in the pathogenesis of disease, including HIV-associated dementia.

Viruses and the brain: from inflammation to dementia

Many viruses cause encephalitis, but understanding the mechanisms by which viral infection leads to encephalopathy or dementia remain elusive. In many cases, inflammation generated by the host's attempt to combat the infection is itself implicated as a primary factor in causing neuronal dysfunction or degeneration. In this review, we outline the current state of knowledge regarding the pathophysiology of CNS (central nervous system) injury in viral infection. We focus our review on the neuropathogenesis of HIV type 1 (HIV-1)-associated dementia, because, within this class of infection, it is the best studied. We will also discuss the key similarities and differences in the pathological mechanisms of other important viral encephalitides. Understanding these mechanisms should ultimately enable development of immunomodulatory therapies for treating these infections, as well as other neuro-inflammatory conditions.

Cell death in HIV dementia

Many patients infected with human immunodeficiency virus type-1 (HIV-1) suffer cognitive impairment ranging from mild to severe (HIV dementia), which may result from neuronal death in the basal ganglia, cerebral cortex and hippocampus. HIV-1 does not kill neurons by infecting them. Instead, viral proteins released from infected glial cells, macrophages and/or stem cells may directly kill neurons or may increase their vulnerability to other cell death stimuli. By binding to and/or indirectly activating cell surface receptors such as CXCR4 and the N-methyl-D-aspartate receptor, the HIV-1 proteins gp120 and Tat may trigger neuronal apoptosis and excitotoxicity as a result of oxidative stress, perturbed cellular calcium homeostasis and mitochondrial alterations. Membrane lipid metabolism and inflammation may also play important roles in determining whether neurons live or die in HIV-1-infected patients. Drugs and diets that target oxidative stress, excitotoxicity, inflammation and lipid metabolism are in development for the treatment of HIV-1 patients.

Novel role of TGF-beta in differential astrocyte-TIMP-1 regulation: implications for HIV-1-dementia and neuroinflammation

Astrocyte production of tissue inhibitor of metalloproteinase (TIMP)-1 is important in central nervous system (CNS) homeostasis and inflammatory diseases such as HIV-1-associated dementia (HAD). TIMPs and matrix metalloproteinases (MMPs) regulate the remodeling of the extracellular matrix. An imbalance between TIMPs and MMPs is associated with many pathologic conditions. Our recently published studies uniquely demonstrate that HAD patients have reduced levels of TIMP-1 in the brain. Astrocyte-TIMP-1 expression is differentially regulated in acute and chronic inflammatory conditions. In this and the adjoining report (Gardner et al., 2006), we investigate the mechanisms that may be involved in differential TIMP-1 regulation. One mechanism for TIMP-1 downregulation is the production of anti-inflammatory molecules, which can activate signaling pathways during chronic inflammation. We investigated the contribution of transforming growth factor (TGF)-signaling in astrocyte-MMP/TIMP-1-astrocyte regulation. TGF-beta1 and beta2 levels were upregulated in HAD brain tissues. Co-stimulation of astrocytes with IL-1beta and TGF-beta mimicked the TIMP-1 downregulation observed with IL-1beta chronic activation. Measurement of astrocyte-MMP protein levels showed that TGF-beta combined with IL-1beta increased MMP-2 and decreased proMMP-1 expression compared to IL-1beta alone. We propose that one of the mechanisms involved in TIMP-1 downregulation may be through TGF-signaling in chronic immune activation. These studies show a novel extracellular regulatory loop in astrocyte-TIMP-1 regulation.

Rho-mediated regulation of tight junctions during monocyte migration across the blood-brain barrier in HIV-1 encephalitis (HIVE)

The blood-brain barrier (BBB) is compromised during progressive HIV-1 infection, but how this occurs is incompletely understood. We studied the integrity of tight junctions (TJs) of brain microvascular endothelial cells (BMVECs) in an in vitro BBB system and in human brain tissues with HIV-1 encephalitis (HIVE). A downregulation of TJ proteins, claudin-5 and occludin, paralleled monocyte migration into the brain during HIVE. Because small G proteins (such as Rho) can play a role in BMVEC TJ assembly, an artificial BBB system explored the relationship among TJs, Rho/Rho kinase (RhoK) activation, and transendothelial monocyte migration. Coculture of monocytes with endothelial cells led to Rho activation and phosphorylation of TJ proteins. Rho and RhoK inhibitors blocked migration of infected and uninfected monocytes. The RhoK inhibitor protected BBB integrity and reversed occludin/claudin-5 phosphorylation associated with monocyte migration. BMVEC transfection with a constitutively active mutant of RhoK led to dislocation of occludin from the membrane and loss of BMVEC cell contacts. When dominant-negative RhoK-transfected BMVECs were used in BBB constructs, monocyte migration was reduced by 84%. Thus, loss of TJ integrity was associated with Rho activation caused by monocyte brain migration, suggesting that Rho/RhoK activation in BMVECs could be an underlying cause of BBB impairment during HIVE.

The role of monocytes and perivascular macrophages in HIV and SIV neuropathogenesis: information from non-human primate models

Perivascular macrophages are located in the perivascular space of cerebral microvessels and thus uniquely situated at the intersection between the brain parenchyma and blood. Connections between the nervous and immune systems are mediated in part through these cells that are ideally located to sense perturbations in the periphery and turnover by cells entering the central nervous system (CNS) from the circulation. It has become clear that unique subsets of brain macrophages exist in normal and SIV- or HIV-infected brains, and perivascular macrophages and similar cells in the meninges and choroid plexus play a central role in lentiviral neuropathogenesis. Common to all these cell populations is their likely replacement within the CNS by monocytes. Studies of SIV-infected non-human primates and HIV-infected humans underscore the importance of virus-infected and activated monocytes, which traffic to the CNS from blood to become perivascular macrophages, potentially drive the blood-brain barrier damage and cause neuronal injury. This review summarizes what we know about SIV- and HIV-induced neuropathogenesis focusing on brain perivascular macrophages and their precursors in blood that may mediate HIV CNS infection and injury.

Astrocytes and microglia differentially regulate trafficking of lymphocyte subsets across brain endothelial cells

Feline brain endothelial cells (BECs), astrocytes, and microglia were combined in different configurations in a cell culture insert system to assess the effect of different cell types on the trafficking of peripheral blood mononuclear cell (PBMC) subsets in response to feline immunodeficiency virus (FIV). The addition of astrocytes to BECs significantly increased the adherence of PBMCs. This increase in adherence was suppressed by microglia, whereas microglia alone had no effect on PBMC adherence. FIV exposure of the glial cells did not alter PBMC adherence as compared to same configurations with untreated cells. All PBMC subsets showed some level of trafficking across the endothelial cell layer. The level of trafficking of monocytes and B cells was significantly increased if astrocytes were present. The presence of microglia with the astrocytes reduced transmigration across all PBMC subsets. FIV exposure of astrocytes significantly increased the percentage of CD8 T cell transmigration from 24% to 64% of the total CD4 and CD8 numbers. The presence of microglia significantly reversed the preferential trafficking of CD8 cells in the presence of astrocytes. The results suggested that interaction between the triad of endothelial cells, astrocytes, and microglia played an important, but varying, role in the trafficking of different PBMC subsets. In general, astrocytes had a positive effect on trafficking of PBMCs, while microglia had a suppressive effect. Effects of FIV on trafficking were largely restricted to increases seen in CD8 T cells and monocytes.

NeuroAIDS: Contributions of the human immunodeficiency virus-1 proteins tat and gp120 as well as CD40 to microglial activation

Microglia are the resident phagocytes of the brain and are an important source of proinflammatory mediators. Human immunodeficiency virus (HIV)-1 infects the central nervous system early in the course of disease, and it is believed that this occurs, in part, through the transmigration of HIV-1-infected cells across the blood-brain barrier. Infected cells release viral proteins, such as Tat and gp120. After microglia interact with these proteins, they become activated and secrete chemokines; up-regulate key surface receptors, such as CD40, and also activate resident cells. This review focuses on the consequences of microglial activation in NeuroAIDS, with an emphasis on chemokine production and CD40 up-regulation after interaction with tat or gp120. The importance of microglial CD40 in two other neurological diseases, Alzheimer's disease and multiple sclerosis, is also discussed.

Neuroinflammatory responses from microglia recovered from HIV-1-infected and seronegative subjects

Microglial and macrophage infection and immune activation underlie the pathogenesis of HIV-1-associated dementia (HAD). To assess microglial function in HAD, we isolated cells from brain tissues recovered from an HIV-1-infected patient within 4 h of death. Brain tissue from seronegative patients served as controls. Regional neuropathology was correlated to microglial function. HIV-1-patient microglia formed multinucleated giant cells and produced progeny virions. These microglia secreted reduced basal and LPS-stimulated TNF-alpha levels compared to controls. Monocytes from seronegative donors paralleled these diminished immune responses following repeated LPS-activation. These results demonstrate changes in innate microglial function following viral infection or chronic immune activation.

Cross talk between growth factors and viral and cellular factors alters neuronal signaling pathways: implication for HIV-associated dementia

HIV-associated dementia (HAD) is a serious neurological disorder affecting about 7% of people with AIDS. In the brain, HIV-1 infects a restricted number of cell types, being primarily present in macrophages and microglial cells, less abundant in astrocytes, and rarely seen in oligodendrocytes and neurons. Lack of a productive HIV-1 infection of neuronal cells suggests the presence of an indirect pathway by which the virus may determine the brain pathology and neuronal dysfunction seen in AIDS patients. Among the participants in this event, viral proteins including gp120 and Tat, along with host factors including cytokines, chemokines, and several signaling pathways have received considerable attention. In this article, we discuss the most recent concepts pertaining to the mechanisms of HIV-1-induced neuronal dysfunction by highlighting the interplay between signal transduction pathways activated by viral and host factors and their consequences in neuronal cell function.

HIV-1 interaction with human mannose receptor (hMR) induces production of matrix metalloproteinase 2 (MMP-2) through hMR-mediated intracellular signaling in astrocytes

Astrocytes are susceptible to HIV-1 infection. We have recently demonstrated that human mannose receptor (hMR) is directly involved in CD4-independent HIV-1 infection of astrocytes. The apparent paradox between the vivid binding affinity of HIV-1 gp120 protein to hMR and the low efficiency of hMR-mediated HIV-1 infection raises the possibility that HIV-1 binding to hMR alone may negatively affect astrocyte function. In this study, we examined the relationship between HIV-1 interaction with hMR and the production of matrix metalloproteinases (MMPs) in astrocytes. We took advantage of an astroglial cell line U87.MR stably expressing hMR as an in vitro astrocyte model system and human primary astrocytes, and demonstrated that HIV-1 binding to astrocytes induced the production of MMP-2. This induction appeared to be most potent with M-tropic HIV-1 viruses. Increased MMP-2 production was not due to hMR-mediated HIV-1 entry and/or HIV-1 viral gene expression, as the transfection of HIV-1 proviral DNA did not result in MMP-2 production, and the infection of AT-2-treated HIV-1 viruses did not inhibit MMP-2 production. Direct involvement of hMR in HIV-induced MMP-2 production was confirmed by the inhibition of the yeast mannan, an hMR ligand antagonist, and an anti-hMR serum. Furthermore, HIV-induced MMP-2 production in astrocytes was shown to involve hMR-mediated intracellular signaling. Taken together, these results suggest that HIV-1 binding to astrocytes in the absence of HIV-1 viral entry is sufficient to alter astrocyte function through hMR-mediated intracellular signaling. In addition, these results provide new evidence to support the notion that hMR is capable of eliciting intracellular signaling upon ligand binding.

Viral expression and leukocyte adhesion after in vitro infection of goat mammary gland cells with caprine arthritis-encephalitis virus

A characteristic lesion in goats infected by the lentivirus CAEV is mastitis with lymphoid hyperplasia. In order to investigate the mechanism of lesion formation, cultures highly enriched in microvascular endothelial cells, mature and immature luminal epithelial cells, fibroblasts and myoepithelial cells were established from goat mammary gland biopsies. Their susceptibility to in vitro infection with two distinct types of CAEV was investigated by PCR, antigen expression and cytopathy. The capacity of infected mammary gland cells to bind uninfected caprine leukocytes was determined by flow cytometry. All cell types tested were susceptible to CAEV infection in vitro, with different levels of sensitivity according to cell phenotype. Our results suggest that the limited extent of natural infection of mammary gland cells reflects a protective local immune response, and that the myoepithelial cell could act as a reservoir cell. After infection, the mature luminal cell acquires the capacity to bind leukocytes in vitro, which could indicate a facilitation of cellular interactions. The distinct reactions of the different cell types to CAEV infection may be correlated with events leading to progressive lesion development during the natural infection.

ACE inhibition reduces activity of the plasminogen/plasmin and MMP systems in the brain of spontaneous hypertensive stroke-prone rats

The spontaneously hypertensive stroke-prone rat (SHR-SP) is an experimental model of malignant hypertension which lead to secondary alterations of the extracellular matrix. Our aim was to determine ACE-inhibitor related changes of proteases involved in the reconstruction of the extracellular matrix in the brain. Twelve SHR-SP rats were randomized into two groups. Each group was treated with either an antihypertensive dose of ramipril or placebo for 6 months. Brain tissue plasminogen activator (t-PA) and urokinase (u-PA) were quantified by using casein-dependent plasminogen zymography, matrix metalloproteinase (MMP)-2 and MMP-9, by MMP-zymography, and tissue inhibitor of MMP (TIMP)-1 and -2, by reverse zymography. The amounts of u-PA, t-PA, and MMPs were significantly reduced in animals treated with ACE inhibitor. Plasminogen zymography showed a 39% reduction of u-PA in the basal ganglia (p < 0.0001); t-PA expression was reduced by 26% in the cortex and by 33% in the basal ganglia (p < 0.0001). MMP-2 expression was reduced by 15% in the cortex (p < 0.05) and by 10% in the basal ganglia (p < 0.05); MMP-9 expression significantly decreased by 37% in the cortex and by 25% in the basal ganglia (p < 0.0001 each). No differences were observed in the amount of TIMP-1 or TIMP-2. These findings provide new insights into the biochemical mechanisms underlying extracellular matrix proliferation and its modulation by ACE inhibitors. Therapeutic alterations that influence the proteolytic systems might prove important in the prevention of extracellular matrix accumulation and secondary microvascular vessel wall changes.

Role of microglia in central nervous system infections

The nature of microglia fascinated many prominent researchers in the 19th and early 20th centuries, and in a classic treatise in 1932, Pio del Rio-Hortega formulated a number of concepts regarding the function of these resident macrophages of the brain parenchyma that remain relevant to this day. However, a renaissance of interest in microglia occurred toward the end of the 20th century, fueled by the recognition of their role in neuropathogenesis of infectious agents, such as human immunodeficiency virus type 1, and by what appears to be their participation in other neurodegenerative and neuroinflammatory disorders. During the same period, insights into the physiological and pathological properties of microglia were gained from in vivo and in vitro studies of neurotropic viruses, bacteria, fungi, parasites, and prions, which are reviewed in this article. New concepts that have emerged from these studies include the importance of cytokines and chemokines produced by activated microglia in neurodegenerative and neuroprotective processes and the elegant but astonishingly complex interactions between microglia, astrocytes, lymphocytes, and neurons that underlie these processes. It is proposed that an enhanced understanding of microglia will yield improved therapies of central nervous system infections, since such therapies are, by and large, sorely needed.

Destruction of extracellular matrix proteoglycans is pervasive in simian retroviral neuroinfection

Disruption of the perineuronal matrix has been reported in human immunodeficiency virus (HIV) encephalitis. To better understand the extent of matrix disruption during lentiviral encephalitis, we characterized the extracellular matrix (ECM) damage in brains of 12 macaques infected with simian immunodeficiency virus (SIV). Matrix integrity was assessed by Wisteria floribunda lectin histochemistry. Confocal microscopy was used to quantify matrix loss, macrophage infiltration, and synaptic damage. Disruption of brain ECM was present shortly after retroviral infection, preceding parenchymal macrophage infiltration. In agreement with previous observations, reduced staining of presynaptic and postsynaptic proteins in SIV encephalitis occurred concurrently with matrix abnormalities. Lentiviral infection induced microglial and macrophage expression of two disintegrins and metalloproteinases with thrombospondin motifs (ADAMTS-1 and ADAMTS-4), with high substrate specificity for matrix proteoglycans. Matrix damage is pervasive during SIV neuroinfection, which suggests interventions to conserve brain matrix proteoglycans might avert or delay retroviral-induced neurodegeneration.