[Show abstract][Hide abstract] ABSTRACT: Objective: To evaluate C-C chemokine receptor type 2 (CCR2) on monocyte subsets as a prognostic peripheral blood biomarker of HIV-associated neurocognitive disorders (HAND).Methods: We characterized monocyte populations in HIV-infected individuals with and without HAND from 2 cohorts and assessed their transmigration across an in vitro model of the human blood-brain barrier (BBB). We examined CCR2 expression among the monocyte populations as a prognostic/predictive biomarker of HAND and its functional consequences in facilitating monocyte diapedesis.Results: We determined that CCR2 was significantly increased on CD14+CD16+ monocytes in individuals with HAND compared to infected people with normal cognition. CCR2 remained elevated irrespective of the severity of cognitive impairment, combined antiretroviral therapy status, viral load, and current or nadir CD4 T-cell count. There was no association between CCR2 on other monocyte populations and HAND. There was a functional consequence to the increase in CCR2, as CD14+CD16+ monocytes from individuals with HAND transmigrated across our model of the human BBB in significantly higher numbers in response to its ligand chemokine (C-C) motif ligand 2 (CCL2) compared to the cell migration that occurred in people with no cognitive deficits. It should be noted that our study had the limitation of a smaller sample size of unimpaired individuals. In contrast, there was no difference in the transmigration of other monocyte subsets across the BBB in response to CCL2 in seropositive individuals with or without HAND.Conclusions: Our findings indicate CCR2 on CD14+CD16+ monocytes is a novel peripheral blood biomarker of HAND.
[Show abstract][Hide abstract] ABSTRACT: Macrophages are the primary cell type infected with HIV in the central nervous system, and infection of these cells is a major component in the development of neuropathogenesis and HIV-associated neurocognitive disorders. Within the brains of drug abusers, macrophages are exposed to increased levels of dopamine, a neurotransmitter that mediates the addictive and reinforcing effects of drugs of abuse such as cocaine and methamphetamine. In this study we examined the effects of dopamine on HIV entry into primary human macrophages. Exposure to dopamine during infection increased the entry of R5 tropic HIV into macrophages, irrespective of the concentration of the viral inoculum. The entry pathway affected was CCR5 dependent, as antagonizing CCR5 with the small molecule inhibitor TAK779 completely blocked entry. The effect was dose-dependent and had a steep threshold, only occurring above 108 M dopamine. The dopamine-mediated increase in entry required dopamine receptor activation, as it was abrogated by the pan-dopamine receptor antagonist flupenthixol, and could be mediated through both subtypes of dopamine receptors. These findings indicate that the effects of dopamine on macrophages may have a significant impact on HIV pathogenesis. They also suggest that drug-induced increases in CNS dopamine may be a common mechanism by which drugs of abuse with distinct modes of action exacerbate neuroinflammation and contribute to HIV-associated neurocognitive disorders in infected drug abusers.
PLoS ONE 09/2014; 9(9):e108232. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: HIV infected people are living longer due to the success of combined antiretroviral therapy (cART).However, greater than 40-70% of HIV infected individuals develop HIV associated neurocognitive disorders (HAND) that continues to be a major public health issue. While cART reduces peripheral virus, it does not limit the low level, chronic neuroinflammation that is ongoing during the neuropathogenesis of HIV. Monocyte transmigration across the blood brain barrier (BBB), specifically that of the mature CD14+CD16+ population that is highly susceptible to HIV infection, is critical to the establishment of HAND as these cells bring virus into the brain and mediate the neuroinflammation that persists, even if at low levels, despite antiretroviral therapy. CD14+CD16+ monocytes preferentially migrate into the CNS early during peripheral HIV infection in response to chemotactic signals, including those from CCL2 and CXCL12. Once within the brain, monocytes differentiate into macrophages and elaborate inflammatory mediators. Monocytes/macrophages constitute a viral reservoir within the CNS and these latently infected cells may perpetuate the neuropathogenesis of HIV. This review will discuss mechanisms that mediate transmigration of CD14+CD16+ monocytes across the BBB in the context of HIV infection, the contribution of these cells to the neuropathogenesis of HIV, and potential monocyte/macrophage biomarkers to identify HAND and monitor its progression.
Current HIV Research 05/2014; · 2.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Human immunodeficiency virus-1 (HIV) is a public health issue and a major complication of the disease is NeuroAIDS. In vivo, microglia/macrophages are the main cells infected. However, a low but significant number of HIV-infected astrocytes has also been detected, but their role in the pathogenesis of NeuroAIDS is not well understood. Our previous data indicate that gap junction channels amplify toxicity from few HIV-infected into uninfected astrocytes. Now, we demonstrated that HIV infection of astrocytes results in the opening of connexin43 hemichannels (Cx43 HCs). HIV-induced opening of Cx43 HCs resulted in dysregulated secretion of dickkopf-1 protein (DKK1, a soluble wnt pathway inhibitor). Treatment of mixed cultures of neurons and astrocytes with DKK1, in the absence of HIV infection, resulted in the collapse of neuronal processes. HIV infection of mixed cultures of human neurons and astrocytes also resulted in the collapse of neuronal processes through a KK1-dependent mechanism. In addition, dysregulated DKK1 expression in astrocytes was observed in human brain tissue sections of individuals with HIV encephalitis as compared to tissue sections from uninfected individuals. Thus, we demonstrated that HIV infection of astrocytes induces dysregulation of DKK1 by a HC-dependent mechanism that contributes to the brain pathogenesis observed in HIV-infected individuals. This article is protected by copyright. All rights reserved.
Journal of Neurochemistry 10/2013; · 4.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: HIV entry into the central nervous system (CNS) is an early event after peripheral infection, resulting in neurologic dysfunction in a significant number of individuals despite successful antiretroviral therapy. The mechanisms by which HIV mediates CNS dysfunction are not well understood. Our group recently demonstrated that HIV infection of astrocytes results in survival of HIV infected cells and apoptosis of surrounding uninfected astrocytes by the transmission of toxic intracellular signals through gap junctions. In the current report, we characterize the intracellular signaling responsible for this bystander apoptosis. Here we demonstrate that HIV infection of astrocytes results in release of cytochrome C from the mitochondria into the cytoplasm, and dysregulation of IP3 /intracellular calcium that leads to toxicity to neighboring uninfected astrocytes. Blocking these dysregulated pathways results in protection from bystander apoptosis. These secondary messengers that are toxic in uninfected cells are not toxic in HIV infected cells, suggesting that HIV protects these cells from apoptosis. Thus, our data provide novel mechanisms of HIV mediated toxicity and generation of HIV reservoirs. Our findings provide new potential therapeutic targets to reduce the CNS damage resulting from HIV infection and to eradicate the generation of viral reservoirs. This article is protected by copyright. All rights reserved.
Journal of Neurochemistry 08/2013; · 4.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: As HIV infected individuals live longer, the prevalence of HIV associated neurocognitive disorders is increasing, despite successful antiretroviral therapy. CD14(+)CD16(+) monocytes are critical to the neuropathogenesis of HIV as they promote viral seeding of the brain and establish neuroinflammation. The mechanisms by which HIV infected and uninfected monocytes cross the blood brain barrier and enter the central nervous system are not fully understood. We determined that HIV infection of CD14(+)CD16(+) monocytes resulted in their highly increased transmigration across the blood brain barrier in response to CCL2 as compared to uninfected cells, which did not occur in the absence of the chemokine. This exuberant transmigration of HIV infected monocytes was due, at least in part, to increased CCR2 and significantly heightened sensitivity to CCL2. The entry of HIV infected and uninfected CD14(+)CD16(+) monocytes into the brain was facilitated by significantly increased surface JAM-A, ALCAM, CD99, and PECAM-1, as compared to CD14(+) cells that are CD16 negative. Upon HIV infection, there was an additional increase in surface JAM-A and ALCAM on CD14(+)CD16(+) monocytes isolated from some individuals. Antibodies to ALCAM and JAM-A inhibited the transmigration of both HIV infected and uninfected CD14(+)CD16(+) monocytes across the BBB, demonstrating their importance in facilitating monocyte transmigration and entry into the brain parenchyma. Targeting CCR2, JAM-A, and ALCAM present on CD14(+)CD16(+) monocytes that preferentially infiltrate the CNS represents a therapeutic strategy to reduce viral seeding of the brain as well as the ongoing neuroinflammation that occurs during HIV pathogenesis.
PLoS ONE 07/2013; 8(7):e69270. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: Maternal thyroid hormones play a fundamental role in appropriate fetal development during gestation. Offspring that have been gestated under maternal hypothyroidism suffer cognitive impairment. Thyroid hormone deficiency during gestation can significantly impact the central nervous system (CNS) by altering the migration, differentiation, and function of neurons, oligodendrocytes, and astrocytes. Given that gestational hypothyroidism alters the immune cell ratio in offspring, it is possible that this condition could result in higher sensitivity for the development of autoimmune diseases. Methods: Adult mice gestated under hypothyroidism were induced with experimental autoimmune encephalomyelitis (EAE). Twenty-one days after EAE induction, the disease score, myelin content, immune cell infiltration, and oligodendrocyte death were evaluated. Results: We observed that mice gestated under hypothyroidism showed higher EAE scores after disease induction during adulthood compared to mice gestated in euthyroidism. In addition, spinal cords sections of mice gestated under hypothyroidism that suffered EAE at the adulthood showed higher demyelination, CD4+ and CD8+ infiltration and increased oligodendrocyte death. Conclusions: These results show for the first time that a deficiency in maternal thyroid hormones during gestation can influence the outcome of a CNS inflammatory disease, such as EAE, in their offspring. These data strongly support evaluating thyroid hormones in pregnant women and treating hypothyroidism during pregnancy to prevent increased susceptibility to inflammatory diseases in the CNS of offspring.
Thyroid: official journal of the American Thyroid Association 06/2013; · 2.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: HIV infection and HIV neurocognitive impairment are major global health problems. The prevalence of HIV associated neurocognitive disorders (HAND) is increasing as people with HIV are living longer due to the success of antiretroviral therapies. Our laboratory identified the soluble form of (sPrP(c)), the cellular non-pathogenic isoform of the prion protein, as a biomarker of HAND. In this review we discuss the published data addressing PrP(c) biology in normal conditions and pathologies, as well as the mechanisms of sPrP(c) shedding and secretion. Lastly, we discuss our studies that demonstrated that sPrP(c) is a biomarker of neurocognitive impairment in the HIV infected population.
Journal of Neuroimmune Pharmacology 04/2013; · 3.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Central nervous system (CNS) complications resulting from HIV infection remain a major public health problem as individuals live longer due to the success of combined antiretroviral therapy (cART). As many as 70 % of HIV infected people have HIV associated neurocognitive disorders (HAND). Many HIV infected individuals abuse drugs, such as cocaine, heroin or methamphetamine, that may be important cofactors in the development of HIV CNS disease. Despite different mechanisms of action, all drugs of abuse increase extracellular dopamine in the CNS. The effects of dopamine on HIV neuropathogenesis are not well understood, and drug induced increases in CNS dopamine may be a common mechanism by which different types of drugs of abuse impact the development of HAND. Monocytes and macrophages are central to HIV infection of the CNS and to HAND. While T cells have not been shown to be a major factor in HIV-associated neuropathogenesis, studies indicate that T cells may play a larger role in the development of HAND in HIV infected drug abusers. Drug induced increases in CNS dopamine may dysregulate functions of, or increase HIV infection in, monocytes, macrophages and T cells in the brain. Thus, characterizing the effects of dopamine on these cells is important for understanding the mechanisms that mediate the development of HAND in drug abusers.
Journal of Neuroimmune Pharmacology 03/2013; · 3.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Perivascular 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. METHODS: To 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. RESULTS: These 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-alpha. CONCLUSIONS: Monocyte 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.
Journal of Neuroinflammation 08/2012; 9(1):203. · 4.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alterations to blood-brain barrier (BBB) adhesion molecules and junctional integrity during neuroinflammation can promote central nervous system (CNS) pathology. The chemokine CCL2 is elevated during CNS inflammation and is associated with endothelial dysfunction. The effects of CCL2 on endothelial adherens junctions (AJs) have not been defined. We demonstrate that CCL2 transiently induces Src-dependent disruption of human brain microvascular endothelial AJ. β-Catenin is phosphorylated and traffics from the AJ to PECAM-1 (platelet endothelial cell adhesion molecule-1), where it is sequestered at the membrane. PECAM-1 is also tyrosine-phosphorylated, an event associated with recruitment of the phosphatase SHP-2 (Src homology 2 domain-containing protein phosphatase) to PECAM-1, β-catenin release from PECAM-1, and reassociation of β-catenin with the AJ. Surface localization of PECAM-1 is increased in response to CCL2. This may enable the endothelium to sustain CCL2-induced alterations in AJ and facilitate recruitment of leukocytes into the CNS. Our novel findings provide a mechanism for CCL2-mediated disruption of endothelial junctions that may contribute to BBB dysfunction and increased leukocyte recruitment in neuroinflammatory diseases.
[Show abstract][Hide abstract] ABSTRACT: Macrophages play a significant role in HIV infection, viral rebound, and the development of AIDS. However, the function of host proteins in viral replication is incompletely characterized in macrophages. Purinergic receptors P2X and P2Y are major components of the macrophage immune response to pathogens, inflammation, and cellular damage. We demonstrate that these receptors are necessary for HIV infection of primary human macrophages. Inhibition of purinergic receptors results in a significant reduction in HIV replication in macrophages. This inhibition is independent of viral strain and is dose dependent. We also identify that P2X(1), P2X(7), and P2Y(1) receptors are involved in viral replication. We show that P2X(1), but not P2X(7) or P2Y(1), is necessary for HIV entry into macrophages. We demonstrate that interaction of the HIV surface protein gp120 with macrophages stimulates an increase in ATP release. Thus, we propose that HIV's binding to macrophages triggers a local release of ATP that stimulates purinergic receptors and facilitates HIV entry and subsequent stages of viral replication. Our data implicate a novel role for a family of host proteins in HIV replication in macrophages and suggest new therapeutic targets to reduce the devastating consequences of HIV infection and AIDS.
The Journal of Immunology 03/2012; 188(9):4488-95. · 5.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gap junctions (GJs) are expressed in most cell types of the nervous system, including neuronal stem cells, neurons, astrocytes, oligodendrocytes, cells of the blood brain barrier (endothelial cells and astrocytes) and under inflammatory conditions in microglia/macrophages. GJs connect cells by the docking of two hemichannels, one from each cell with each hemichannel being formed by 6 proteins named connexins (Cx). Unapposed hemichannels (uHC) also can be open on the surface of the cells allowing the release of different intracellular factors to the extracellular space. GJs provide a mechanism of cell-to-cell communication between adjacent cells that enables the direct exchange of intracellular messengers, such as calcium, nucleotides, IP(3), and diverse metabolites, as well as electrical signals that ultimately coordinate tissue homeostasis, proliferation, differentiation, metabolism, cell survival and death. Despite their essential functions in physiological conditions, relatively little is known about the role of GJs and uHC in human diseases, especially within the nervous system. The focus of this review is to summarize recent findings related to the role of GJs and uHC in physiologic and pathologic conditions of the central nervous system.
Journal of Neuroimmune Pharmacology 03/2012; 7(3):499-518. · 3.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: HIV continues to be a global health crisis with more than 34 million people infected worldwide (UNAIDS: Report on the Global AIDS Epidemic 2010, Geneva, World Health Organization). HIV enters the CNS within 2 weeks of infection and establishes a spectrum of HAND in a large percentage of infected individuals. These neurologic deficits greatly impact the quality of life of those infected with HIV. The establishment of HAND is largely attributed to monocyte transmigration, particularly that of a mature CD14(+)CD16(+) monocyte population, which is more susceptible to HIV infection, across the BBB into the CNS parenchyma in response to chemotactic signals. To enter the CNS, junctional proteins on the monocytes must participate in homo- and heterotypic interactions with those present on BMVECs of the BBB as they transmigrate across the barrier. This transmigration is responsible for bringing virus into the brain and establishing chronic neuroinflammation. While there is baseline trafficking of monocytes into the CNS, the increased chemotactic signals present during HIV infection of the brain promote exuberant monocyte transmigration into the CNS. This review will discuss the mechanisms of monocyte differentiation/maturation, HIV infectivity, and transmigration into the CNS parenchyma that contribute to the establishment of cognitive impairment in HIV-infected individuals. It will focus on markers of monocyte subpopulations, how differentiation/maturation alters HIV infectivity, and the mechanisms that promote their increased transmigration across the BBB into the CNS.
Journal of leukocyte biology 03/2012; 91(3):401-15. · 4.99 Impact Factor