Search

The presence of HIV in sequestered reservoirs is a central impediment to a functional cure, allowing HIV to persist despite life-long antiretroviral therapy (ART), and driving a variety of comorbid conditions. Our understanding of the latent HIV reservoir in the central nervous system is incomplete, because of difficulties in accessing human central nervous system tissues. Microglia contribute to HIV reservoirs, but the molecular phenotype of HIV-infected microglia is poorly understood. We leveraged the unique "Last Gift" rapid autopsy program, in which people with HIV are closely followed until days or even hours before death. Microglial populations were heterogeneous regarding their gene expression profiles but showed similar chromatin accessibility landscapes. Despite ART, we detected occasional microglia containing cell-associated HIV RNA and HIV DNA integrated into open regions of the host's genome (∼0.005%). Microglia with detectable HIV RNA showed an inflammatory phenotype. These results demonstrate a distinct myeloid cell reservoir in the brains of people with HIV despite suppressive ART. Strategies for curing HIV and neurocognitive impairment will need to consider the myeloid compartment to be successful., (© 2024 Schlachetzki et al.)

The catecholamine neurotransmitter dopamine is classically known for regulation of central nervous system (CNS) functions such as reward, movement, and cognition. Increasing evidence also indicates that dopamine regulates critical functions in peripheral organs and is an important immunoregulatory factor. We have previously shown that dopamine increases NF-κB activity, inflammasome activation, and the production of inflammatory cytokines such as IL-1β in human macrophages. As myeloid lineage cells are central to the initiation and resolution of acute inflammatory responses, dopamine-mediated dysregulation of these functions could both impair the innate immune response and exacerbate chronic inflammation. However, the exact pathways by which dopamine drives myeloid inflammation are not well defined, and studies in both rodent and human systems indicate that dopamine can impact the production of inflammatory mediators through both D1-like dopamine receptors (DRD1, DRD5) and D2-like dopamine receptors (DRD2, DRD3, and DRD4). Therefore, we hypothesized that dopamine-mediated production of IL-1β in myeloid cells is regulated by the ratio of different dopamine receptors that are activated. Our data in primary human monocyte-derived macrophages (hMDM) indicate that DRD1 expression is necessary for dopamine-mediated increases in IL-1β, and that changes in the expression of DRD2 and other dopamine receptors can alter the magnitude of the dopamine-mediated increase in IL-1β. Mature hMDM have a high D1-like to D2-like receptor ratio, which is different relative to monocytes and peripheral blood mononuclear cells (PBMCs). We further confirm in human microglia cell lines that a high ratio of D1-like to D2-like receptors promotes dopamine-induced increases in IL-1β gene and protein expression using pharmacological inhibition or overexpression of dopamine receptors. RNA-sequencing of dopamine-treated microglia shows that genes encoding functions in IL-1β signaling pathways, microglia activation, and neurotransmission increased with dopamine treatment. Finally, using HIV as an example of a chronic inflammatory disease that is substantively worsened by comorbid substance use disorders (SUDs) that impact dopaminergic signaling, we show increased effects of dopamine on inflammasome activation and IL-1β in the presence of HIV in both human macrophages and microglia. These data suggest that use of addictive substances and dopamine-modulating therapeutics could dysregulate the innate inflammatory response and exacerbate chronic neuroimmunological conditions like HIV. Thus, a detailed understanding of dopamine-mediated changes in inflammation, in particular pathways regulating IL-1β, will be critical to effectively tailor medication regimens.

Substance use disorders (SUDs) are highly comorbid with HIV infection, necessitating an understanding of the interactive effects of drug exposure and HIV. The relationship between HIV infection and cocaine use disorder is likely bidirectional, with cocaine use directly impacting immune function while HIV infection alters addiction-related behavior. To better characterize the neurobehavioral and immune consequences of HIV infection and cocaine exposure, this study utilizes a humanized mouse model to investigate the outcomes of HIV-1 infection on cocaine-related behaviors in a conditioned place preference (CPP) model, and the interactive effects of cocaine and HIV infection on peripheral and central nervous system inflammation. HIV infection selectively impairs cocaine CPP extinction without effecting reinstatement or cocaine seeking under conflict. Behavioral alterations are accompanied by immune changes in HIV infected mice, including increased prefrontal cortex astrocyte immunoreactivity and brain-region specific effects on microglia number and reactivity. Peripheral immune system changes are observed in human cytokines, including HIV-induced reductions in human TNFα, and cocaine and HIV interactions on GM-CSF levels. Together these data provide new insights into the unique neurobehavioral outcomes of HIV infection and cocaine exposure and how they interact to effect immune responses., (© 2024. The Author(s).)

There is a significant overlap between HIV infection and substance-use disorders. Dopamine (DA) is the most abundantly upregulated neurotransmitter in methamphetamine abuse, with receptors (DRD1-5) that are expressed by neurons as well as by a large diversity of cell types, including innate immune cells that are the targets of HIV infection, making them responsive to the hyperdopaminergic environment that is characteristic of stimulant drugs. Therefore, the presence of high levels of dopamine may affect the pathogenesis of HIV, particularly in the brain. The stimulation of HIV latently infected U1 promonocytes with DA significantly increased viral p24 levels in the supernatant at 24 h, suggesting effects on activation and replication. Using selective agonists to different DRDs, we found that DRD1 played a major role in activating viral transcription, followed by DRD4, which increased p24 with a slower kinetic rate compared to DRD1. Transcriptome and systems biology analyses led to the identification of a cluster of genes responsive to DA, where S100A8 and S100A9 were most significantly correlated with the early increase in p24 levels following DA stimulation. Conversely, DA increased the expression of these genes' transcripts at the protein level, MRP8 and MRP14, respectively, which form a complex also known as calprotectin. Interestingly, MRP8/14 was able to stimulate HIV transcription in latent U1 cells, and this occurred via binding of the complex to the receptor for an advanced glycosylation end-product (RAGE). Using selective agonists, both DRD1 and DRD4 increased MRP8/14 on the surface, in the cytoplasm, as well as secreted in the supernatants. On the other hand, while DRD1/5 did not affect the expression of RAGE, DRD4 stimulation caused its downregulation, offering a mechanism for the delayed effect via DRD4 on the p24 increase. To cross-validate MRP8/14 as a DA signature with a biomarker value, we tested its expression in HIV+ Meth users' postmortem brain specimens and peripheral cells. MRP8/14+ cells were more frequently identified in mesolimbic areas such as the basal ganglia of HIV+ Meth+ cases compared to HIV+ non-Meth users or to controls. Likewise, MRP8/14+ CD11b+ monocytes were more frequent in HIV+ Meth users, particularly in specimens from participants with a detectable viral load in the CSF. Overall, our results suggest that the MRP8 and MRP14 complex may serve as a signature to distinguish subjects using addictive substances in the context of HIV, and that this may play a role in aggravating HIV pathology by promoting viral replication in people with HIV who use Meth.

The neurotransmitter dopamine is a key factor in central nervous system (CNS) function, regulating many processes including reward, movement, and cognition. Dopamine also regulates critical functions in peripheral organs, such as blood pressure, renal activity, and intestinal motility. Beyond these functions, a growing body of evidence indicates that dopamine is an important immunoregulatory factor. Most types of immune cells express dopamine receptors and other dopaminergic proteins, and many immune cells take up, produce, store, and/or release dopamine, suggesting that dopaminergic immunomodulation is important for immune function. Targeting these pathways could be a promising avenue for the treatment of inflammation and disease, but despite increasing research in this area, data on the specific effects of dopamine on many immune cells and disease processes remain inconsistent and poorly understood. Therefore, this review integrates the current knowledge of the role of dopamine in immune cell function and inflammatory signaling across systems. We also discuss the current understanding of dopaminergic regulation of immune signaling in the CNS and peripheral tissues, highlighting the role of dopaminergic immunomodulation in diseases such as Parkinson's disease, several neuropsychiatric conditions, neurologic human immunodeficiency virus, inflammatory bowel disease, rheumatoid arthritis, and others. Careful consideration is given to the influence of experimental design on results, and we note a number of areas in need of further research. Overall, this review integrates our knowledge of dopaminergic immunology at the cellular, tissue, and disease level and prompts the development of therapeutics and strategies targeted toward ameliorating disease through dopaminergic regulation of immunity. SIGNIFICANCE STATEMENT: Canonically, dopamine is recognized as a neurotransmitter involved in the regulation of movement, cognition, and reward. However, dopamine also acts as an immune modulator in the central nervous system and periphery. This review comprehensively assesses the current knowledge of dopaminergic immunomodulation and the role of dopamine in disease pathogenesis at the cellular and tissue level. This will provide broad access to this information across fields, identify areas in need of further investigation, and drive the development of dopaminergic therapeutic strategies., (Copyright © 2023 by The Author(s).)

While the history of neuroimmunology is long, the explicit study of neuroimmune communication, and particularly the role of catecholamines in neuroimmunity, is still emerging. Recent studies have shown that catecholamines, norepinephrine, epinephrine, and dopamine, are central to multiple complex mechanisms regulating immune function. These studies show that catecholamines can be released from both the nervous system and directly from immune cells, mediating both autocrine and paracrine signaling. This commentary highlights the importance of catecholaminergic immunomodulation and discusses new considerations needed to study the role of catecholamines in immune homeostasis to best leverage their contribution to disease processes for the development of new therapeutic approaches., Competing Interests: Conflict of interest statement Nothing declared., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The progressive impairment of immunity to pathogens and vaccines with aging is a significant public health problem as the world population shifts to an increased percentage of older adults (> 65). We have previously demonstrated that cells obtained from older volunteers have delayed and defective induction of type I interferons and T cell and B cell helper cytokines in response to TLR ligands when compared to those from adult subjects. However, the underlying intracellular mechanisms are not well described. Herein, we studied two critical pathways important in the production of type I interferon (IFN), the interferon response factor 7 (pIRF7), and TANK-binding kinase (pTBK-1). We show a decrease in pIRF7 and pTBK-1 in cross-priming dendritic cells (cDC1s), CD4 + T cell priming DCs (cDC2s), and CD14 dim CD16 + vascular patrolling monocytes from older adults (n = 11) following stimulation with pathway-specific agonists in comparison with young individuals (n = 11). The decrease in these key antiviral pathway proteins correlates with decreased phagocytosis, suggesting impaired function in Overall, our findings describe molecular mechanisms which explain the innate functional impairment in older adults and thus could inform us of novel approaches to restore these defects., (© 2022. The Author(s).)

Neonates exhibit increased susceptibility to respiratory viral infections, attributed to inflammation at the developing pulmonary air-blood interface. IFN I are antiviral cytokines critical to control viral replication, but also promote inflammation. Previously, we established a neonatal murine influenza virus (IV) model, which demonstrates increased mortality. Here, we sought to determine the role of IFN I in this increased mortality. We found that three-day-old IFNAR-deficient mice are highly protected from IV-induced mortality. In addition, exposure to IFNβ 24 h post IV infection accelerated death in WT neonatal animals but did not impact adult mortality. In contrast, IFN IIIs are protective to neonatal mice. IFNβ induced an oxidative stress imbalance specifically in primary neonatal IV-infected pulmonary type II epithelial cells (TIIEC), not in adult TIIECs. Moreover, neonates did not have an infection-induced increase in antioxidants, including a key antioxidant, superoxide dismutase 3, as compared to adults. Importantly, antioxidant treatment rescued IV-infected neonatal mice, but had no impact on adult morbidity. We propose that IFN I exacerbate an oxidative stress imbalance in the neonate because of IFN I-induced pulmonary TIIEC ROS production coupled with developmentally regulated, defective antioxidant production in response to IV infection. This age-specific imbalance contributes to mortality after respiratory infections in this vulnerable population., (© 2022. The Author(s), under exclusive licence to Society for Mucosal Immunology.)

In the era of antiretroviral therapy, inflammation is a central factor in numerous HIV-associated comorbidities, such as cardiovascular disease, cognitive impairment, and neuropsychiatric disorders. This highlights the value of developing therapeutics that both reduce HIV-associated inflammation and treat associated comorbidities. Previous research on monoamine oxidase inhibitors (MAOIs) suggests this class of drugs has anti-inflammatory properties in addition to neuropsychiatric effects. Therefore, we examined the impact of deprenyl, an MAOI, on SIV-associated inflammation during acute SIV infection using the rhesus macaque model of HIV infection. Our results show deprenyl decreased both peripheral and CNS inflammation but had no effect on viral load in either the periphery or CNS. These data show that the MAOI deprenyl may have broad anti-inflammatory effects when given during the acute stage of SIV infection, suggesting more research into the anti-inflammatory effects of this drug could result in a beneficial adjuvant for antiretroviral therapy., Competing Interests: The authors declare no competing interests., (© 2022 The Authors.)

Monocyte-derived macrophages (MDMs) are key players in tissue homeostasis and diseases regulated by a variety of signaling molecules. Recent literature has highlighted the ability for biogenic amines to regulate macrophage functions, but the mechanisms governing biogenic amine signaling in and around immune cells remain nebulous. In the CNS, biogenic amine transporters are regarded as the master regulators of neurotransmitter signaling. While we and others have shown that macrophages express these transporters, relatively little is known of their function in these cells. To address these knowledge gaps, we investigated the function of norepinephrine transporter (NET) and dopamine transporter (DAT) on human MDMs. We found that both NET and DAT are present and can uptake substrate from the extracellular space at baseline. Not only was DAT expressed in cultured MDMs, but it was also detected in a subset of intestinal macrophages in situ. Surprisingly, we discovered a NET-independent, DAT-mediated immunomodulatory mechanism in response to LPS. LPS induced reverse transport of dopamine through DAT, engaging an autocrine/paracrine signaling loop that regulated the macrophage response. Removing this signaling loop enhanced the proinflammatory response to LPS. Our data introduce a potential role for DAT in the regulation of innate immunity.

The HIV co-receptors, CCR5 and CXCR4, are necessary for HIV entry into target cells, interacting with the HIV envelope protein, gp120, to initiate several signaling cascades thought to be important to the entry process. Co-receptor signaling may also promote the development of neuroHIV by contributing to both persistent neuroinflammation and indirect neurotoxicity. But despite the critical importance of CXCR4 and CCR5 signaling to HIV pathogenesis, there is only one therapeutic (the CCR5 inhibitor Maraviroc) that targets these receptors. Moreover, our understanding of co-receptor signaling in the specific context of neuroHIV is relatively poor. Research into co-receptor signaling has largely stalled in the past decade, possibly owing to the complexity of the signaling cascades and functions mediated by these receptors. Examining the many signaling pathways triggered by co-receptor activation has been challenging due to the lack of specific molecular tools targeting many of the proteins involved in these pathways and the wide array of model systems used across these experiments. Studies examining the impact of co-receptor signaling on HIV neuropathogenesis often show activation of multiple overlapping pathways by similar stimuli, leading to contradictory data on the effects of co-receptor activation. To address this, we will broadly review HIV infection and neuropathogenesis, examine different co-receptor mediated signaling pathways and functions, then discuss the HIV mediated signaling and the differences between activation induced by HIV and cognate ligands. We will assess the specific effects of co-receptor activation on neuropathogenesis, focusing on neuroinflammation. We will also explore how the use of substances of abuse, which are highly prevalent in people living with HIV, can exacerbate the neuropathogenic effects of co-receptor signaling. Finally, we will discuss the current state of therapeutics targeting co-receptors, highlighting challenges the field has faced and areas in which research into co-receptor signaling would yield the most therapeutic benefit in the context of HIV infection. This discussion will provide a comprehensive overview of what is known and what remains to be explored in regard to co-receptor signaling and HIV infection, and will emphasize the potential value of HIV co-receptors as a target for future therapeutic development., (© 2021. The Author(s).)

Despite widespread use of antiretroviral therapy (ART), HIV remains a major public health issue. Even with effective ART many infected individuals still suffer from the constellation of neurological symptoms now known as neuroHIV. These symptoms can be exacerbated by substance abuse, a common comorbidity among HIV-infected individuals. The mechanism(s) by which different types of drugs impact neuroHIV remains unclear, but all drugs of abuse increase central nervous system (CNS) dopamine and elevated dopamine increases HIV infection and inflammation in human myeloid cells including macrophages and microglia, the primary targets for HIV in the brain. Thus, drug-induced increases in CNS dopamine may be a common mechanism by which distinct addictive substances alter neuroHIV. Myeloid cells are generally infected by HIV strains that use the chemokine receptor CCR5 as a co-receptor, and our data indicate that in a subset of individuals, drug-induced levels of dopamine could interfere with the effectiveness of the CCR5 inhibitor Maraviroc. CCR5 can adopt distinct conformations that differentially regulate the efficiency of HIV entry and subsequent replication and using qPCR, flow cytometry, Western blotting and high content fluorescent imaging, we show that dopamine alters the expression of specific CCR5 conformations of CCR5 on the surface of human macrophages. These changes are not affected by association with lipid rafts, but do correlate with dopamine receptor gene expression levels, specifically higher levels of D1-like dopamine receptors. These data also demonstrate that dopamine increases HIV replication and alters CCR5 conformations in human microglia similarly to macrophages. These data support the importance of dopamine in the development of neuroHIV and indicate that dopamine signaling pathways should be examined as a target in antiretroviral therapies specifically tailored to HIV-infected drug abusers. Further, these studies show the potential immunomodulatory role of dopamine, suggesting changes in this neurotransmitter may also affect the progression of other diseases., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Matt, Nickoloff-Bybel, Rong, Runner, Johnson, O’Connor, Haddad and Gaskill.)

Neurokinin-1 receptor (NK1R) signaling can be immunomodulatory and it can lead to preferential transmigration of CD14+CD16+ monocytes across the blood brain barrier, potentially promoting the development of inflammatory neurological diseases, such as neuroHIV. To evaluate how NK1R signaling alters monocyte biology, RNA sequencing was used to define NK1R-mediated transcriptional changes in different monocyte subsets. The data show that NK1R activation induces a greater number of changes in CD14+CD16+ monocytes (152 differentially expressed genes), than in CD14+CD16- monocytes (36 genes), including increases in the expression of NF-κB and components of the NLRP3 inflammasome pathway. These results suggest that NK1R may alter the inflammatory state of CD14+CD16+ monocytes, influencing the development of neuroinflammation., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Antiretroviral therapy (ART) has transformed HIV into a chronic condition, lengthening and improving the lives of individuals living with this virus. Despite successful suppression of HIV replication, people living with HIV (PLWH) are susceptible to a growing number of comorbidities, including neuroHIV that results from infection of the central nervous system (CNS). Alterations in the dopaminergic system have long been associated with HIV infection of the CNS. Studies indicate that changes in dopamine concentrations not only alter neurotransmission, but also significantly impact the function of immune cells, contributing to neuroinflammation and neuronal dysfunction. Monocytes/macrophages, which are a major target for HIV in the CNS, are responsive to dopamine. Therefore, defining more precisely the mechanisms by which dopamine acts on these cells, and the changes in cellular function elicited by this neurotransmitter are necessary to develop therapeutic strategies to treat neuroHIV. This is especially important for vulnerable populations of PLWH with chemically altered dopamine concentrations, such as individuals with substance use disorder (SUD), or aging individuals using dopamine-altering medications. The specific neuropathologic and neurocognitive consequences of increased CNS dopamine remain unclear. This is due to the complex nature of HIV neuropathogenesis, and logistical and technical challenges that contribute to inconsistencies among cohort studies, animal models and in vitro studies, as well as lack of demographic data and access to human CNS samples and cells. This review summarizes current understanding of the impact of dopamine on HIV neuropathogenesis, and proposes new experimental approaches to examine the role of dopamine in CNS HIV infection. Graphical abstract HIV Neuropathogenesis in the Presence of a Disrupted Dopamine System. Both substance abuse disorders and the use of dopaminergic medications for age-related diseases are associated with changes in CNS dopamine concentrations and dopaminergic neurotransmission. These changes can lead to aberrant immune function, particularly in myeloid cells, which contributes to the neuroinflammation, neuropathology and dysfunctional neurotransmission observed in dopamine-rich regions in HIV+ individuals. These changes, which are seen despite the use antiretroviral therapy (ART), in turn lead to further dysregulation of the dopamine system. Thus, in individuals with elevated dopamine, the bi-directional interaction between aberrant dopaminergic neurotransmission and HIV infection creates a feedback loop contributing to HIV associated neurocognitive dysfunction and neuroHIV. However, the distinct contributions and interactions made by HIV infection, inflammatory mediators, ART, drugs of abuse, and age-related therapeutics are poorly understood. Defining more precisely the mechanisms by which these factors influence the development of neurological disease is critical to addressing the continued presence of neuroHIV in vulnerable populations, such as HIV-infected older adults or drug abusers. Due to the complexity of this system, understanding these effects will require a combination of novel experimental modalities in the context of ART. These will include more rigorous epidemiological studies, relevant animal models, and in vitro cellular and molecular mechanistic analysis.

Both substance use disorder and HIV infection continue to affect many individuals. Both have untoward effects on the brain, and the two conditions often co-exist. In the brain, macrophages and microglia are infectable by HIV, and these cells are also targets for the effects of drugs of abuse, such as the psychostimulant methamphetamine. To determine the interaction of HIV and methamphetamine, we isolated microglia and brain macrophages from SIV-infected rhesus monkeys that were treated with or without methamphetamine. Cells were subjected to single-cell RNA sequencing and results were analyzed by statistical and bioinformatic analysis. In the animals treated with methamphetamine, a significantly increased proportion of the microglia and/or macrophages were infected by SIV. In addition, gene encoding functions in cell death pathways were increased, and the brain-derived neurotropic factor pathway was inhibited. The gene expression patterns in infected cells did not cluster separately from uninfected cells, but clusters comprised of microglia and/or macrophages from methamphetamine-treated animals differed in neuroinflammatory and metabolic pathways from those comprised of cells from untreated animals. Methamphetamine increases CNS infection by SIV and has adverse effects on both infected and uninfected microglia and brain macrophages, highlighting the dual and interacting harms of HIV infection and drug abuse on the brain.

Dopamine is well recognized as a neurotransmitter in the brain, and regulates critical functions in a variety of peripheral systems. Growing research has also shown that dopamine acts as an important regulator of immune function. Many immune cells express dopamine receptors and other dopamine related proteins, enabling them to actively respond to dopamine and suggesting that dopaminergic immunoregulation is an important part of proper immune function. A detailed understanding of the physiological concentrations of dopamine in specific regions of the human body, particularly in peripheral systems, is critical to the development of hypotheses and experiments examining the effects of physiologically relevant dopamine concentrations on immune cells. Unfortunately, the dopamine concentrations to which these immune cells would be exposed in different anatomical regions are not clear. To address this issue, this comprehensive review details the current information regarding concentrations of dopamine found in both the central nervous system and in many regions of the periphery. In addition, we discuss the immune cells present in each region, and how these could interact with dopamine in each compartment described. Finally, the review briefly addresses how changes in these dopamine concentrations could influence immune cell dysfunction in several disease states including Parkinson's disease, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, as well as the collection of pathologies, cognitive and motor symptoms associated with HIV infection in the central nervous system, known as NeuroHIV. These data will improve our understanding of the interactions between the dopaminergic and immune systems during both homeostatic function and in disease, clarify the effects of existing dopaminergic drugs and promote the creation of new therapeutic strategies based on manipulating immune function through dopaminergic signaling. Graphical Abstract.

Induction of innate immune genes in the brain is thought to be a major factor in the development of addiction to substances of abuse. As the major component of the innate immune system in the brain, aberrant activation of myeloid cells such as macrophages and microglia due to substance use may mediate neuroinflammation and contribute to the development of addiction. All addictive drugs modulate the dopaminergic system and our previous studies have identified dopamine as a pro-inflammatory modulator of macrophage function. However, the mechanism that mediates this effect is currently unknown. Inflammatory activation of macrophages and induction of cytokine production is often mediated by the transcription factor NF-κB, and prior studies have shown that dopamine can modulate NF-κB activity in T-cells and other non-immune cell lines. Here we demonstrated that dopamine can activate NF-κB in primary human macrophages, resulting in the induction of its downstream targets including the NLRP3 inflammasome and the inflammatory cytokine IL-1β. These data also indicate that dopamine primes but does not activate the NLRP3 inflammasome in human macrophages. Activation of NF-κB was required for dopamine-mediated increases in IL-1β, as an inhibitor of NF-κB was able to abrogate the effects of dopamine on production of these cytokines. Connecting an increase in extracellular dopamine to NF-κB activation and inflammation suggests specific intracellular targets that could be used to ameliorate the inflammatory impact of dopamine in neuroinflammatory conditions associated with myeloid cell activation such as addiction.

The success of combination antiretroviral therapy (cART) has transformed HIV infection into a chronic condition, resulting in an increase in the number of older, cART-treated adults living with HIV. This has increased the incidence of age-related, non-AIDS comorbidities in this population. One of the most common comorbidities is depression, which is also associated with cognitive impairment and a number of neuropathologies. In older people living with HIV, treating these overlapping disorders is complex, often creating pill burden or adverse drug-drug interactions that can exacerbate these neurologic disorders. Depression, NeuroHIV and many of the neuropsychiatric therapeutics used to treat them impact the dopaminergic system, suggesting that dopaminergic dysfunction may be a common factor in the development of these disorders. Further, changes in dopamine can influence the development of inflammation and the regulation of immune function, which are also implicated in the progression of NeuroHIV and depression. Little is known about the optimal clinical management of drug-drug interactions between cART drugs and antidepressants, particularly in regard to dopamine in older people living with HIV. This review will discuss those interactions, first examining the etiology of NeuroHIV and depression in older adults, then discussing the interrelated effects of dopamine and inflammation on these disorders, and finally reviewing the activity and interactions of cART drugs and antidepressants on each of these factors. Developing better strategies to manage these comorbidities is critical to the health of the aging, HIV-infected population, as the older population may be particularly vulnerable to drug-drug interactions affecting dopamine., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Dopaminergic dysfunction has long been connected to the development of HIV infection in the CNS. Our previous data showed that dopamine increases HIV infection in human macrophages by increasing the susceptibility of primary human macrophages to HIV entry through stimulation of both D1-like and D2-like receptors. These data suggest that, in macrophages, both dopamine receptor subtypes may act through a common signaling mechanism. To define better the mechanism(s) underlying this effect, this study examines the specific signaling processes activated by dopamine in primary human monocyte-derived macrophages (hMDM). In addition to confirming that the increase in entry is unique to dopamine, these studies show that dopamine increases HIV entry through a PKA insensitive, Ca 2+ dependent pathway. Further examination demonstrated that dopamine can signal through a previously defined, non-canonical pathway in human macrophages. This pathway involves both Ca 2+ release and PKC phosphorylation, and these data show that dopamine mediates both of these effects and that both were partially inhibited by the G q/11 specific inhibitor YM-254890. Studies have shown that G q/11 preferentially couples to the D1-like receptor D5, indicating an important role of the D1-like receptors in mediating these effects. These data indicate a role for Ca 2+ flux in the HIV entry process, and suggest a distinct signaling mechanism mediating some of the effects of dopamine in macrophages. Together, the data indicate that targeting this alternative dopamine signaling pathway might provide new therapeutic options for individuals with elevated CNS dopamine suffering from NeuroHIV., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Despite the success of combination anti-retroviral therapy (cART), around 50% of HIV-infected individuals still display a variety of neuropathological and neurocognitive sequelae known as NeuroHIV. Current research suggests these effects are mediated by long-term changes in CNS function in response to chronic infection and inflammation, and not solely due to active viral replication. In the post-cART era, drug abuse is a major risk-factor for the development of NeuroHIV, and increases extracellular dopamine in the CNS. Our lab has previously shown that dopamine can increase HIV infection of primary human macrophages and increase the production of inflammatory cytokines, suggesting that elevated dopamine could enhance the development of HIV-associated neuropathology. However, the precise mechanism(s) by which elevated dopamine could exacerbate NeuroHIV, particularly in chronically-infected, virally suppressed individuals remain unclear. To determine the connection between dopaminergic alterations and HIV-associated neuroinflammation, we have examined the impact of dopamine exposure on macrophages from healthy and virally suppressed, chronically infected HIV patients. Our data show that dopamine treatment of human macrophages isolated from healthy and cART-treated donors promotes production of inflammatory mediators including IL-1β, IL-6, IL-18, CCL2, CXCL8, CXCL9, and CXCL10. Furthermore, in healthy individuals, dopamine-mediated modulation of specific cytokines is correlated with macrophage expression of dopamine-receptor transcripts, particularly DRD5, the most highly-expressed dopamine-receptor subtype. Overall, these data will provide more understanding of the role of dopamine in the development of NeuroHIV, and may suggest new molecules or pathways that can be useful as therapeutic targets during HIV infection.

The success of anti-retroviral therapy has improved the quality of life and lifespan of HIV + individuals, transforming HIV infection into a chronic condition. These improvements have come with a cost, as chronic HIV infection and long-term therapy have resulted in the emergence of a number of new pathologies. This includes a variety of the neuropathological and neurocognitive effects collectively known as HIVassociated neurocognitive disorders (HAND) or NeuroHIV. These effects persist even in the absence of viral replication, suggesting that they are mediated the long-term changes in the CNS induced by HIV infection rather than by active replication. Among these effects are significant changes in catecholaminergic neurotransmission, especially in dopaminergic brain regions. In HIV-infected individuals not treated with ARV show prominent neuropathology is common in dopamine-rich brain regions and altered autonomic nervous system activity. Even infected individuals on therapy, there is significant dopaminergic neuropathology, and elevated stress and norepinephrine levels correlate with a decreased effectiveness of antiretroviral drugs. As catecholamines function as immunomodulatory factors, the resultant dysregulation of catecholaminergic tone could substantially alter the development of HIVassociated neuroinflammation and neuropathology. In this review, we discuss the role of catecholamines in the etiology of HIV neuropathogenesis. Providing a comprehensive examination of what is known about these molecules in the context of HIV-associated disease demonstrates the importance of further studies in this area, and may open the door to new therapeutic strategies that specifically ameliorate the effects of catecholaminergic dysregulation on NeuroHIV., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Human Immunodeficiency Virus (HIV) is a progressive infection that targets the immune system, affecting more than 37 million people around the world. While combinatorial antiretroviral therapy (cART) has lowered mortality rates and improved quality of life in infected individuals, the prevalence of HIV associated neurocognitive disorders is increasing and HIV associated cognitive decline remains prevalent. Recent research has suggested that HIV accessory proteins may be involved in this decline, and several studies have indicated that the HIV protein transactivator of transcription (Tat) can disrupt normal neuronal and glial function. Specifically, data indicate that Tat may directly impact dopaminergic neurotransmission, by modulating the function of the dopamine transporter and specifically damaging dopamine-rich regions of the CNS. HIV infection of the CNS has long been associated with dopaminergic dysfunction, but the mechanisms remain undefined. The specific effect(s) of Tat on dopaminergic neurotransmission may be, at least partially, a mechanism by which HIV infection directly or indirectly induces dopaminergic dysfunction. Therefore, precisely defining the specific effects of Tat on the dopaminergic system will help to elucidate the mechanisms by which HIV infection of the CNS induces neuropsychiatric, neurocognitive and neurological disorders that involve dopaminergic neurotransmission. Further, this will provide a discussion of the experiments needed to further these investigations, and may help to identify or develop new therapeutic approaches for the prevention or treatment of these disorders in HIV-infected individuals., (Copyright © 2017 Elsevier Inc. All rights reserved.)

In human immunodeficiency virus-1 (HIV) infected individuals, substance abuse may accelerate the development and/or increase the severity of HIV associated neurocognitive disorders (HAND). It is proposed that CD14 + CD16 + monocytes mediate HIV entry into the central nervous system (CNS) and that uninfected and infected CD14 + CD16 + monocyte transmigration across the blood brain barrier (BBB) contributes to the establishment and propagation of CNS HIV viral reservoirs and chronic neuroinflammation, important factors in the development of HAND. The effects of substance abuse on the frequency of CD14 + CD16 + monocytes in the peripheral circulation and on the entry of these cells into the CNS during HIV neuropathogenesis are not known. PBMC from HIV infected individuals were analyzed by flow cytometry and we demonstrate that the frequency of peripheral blood CD14 + CD16 + monocytes in HIV infected substance abusers is increased when compared to those without active substance use. Since drug use elevates extracellular dopamine concentrations in the CNS, we examined the effects of dopamine on CD14 + CD16 + monocyte transmigration across our in vitro model of the human BBB. The transmigration of this monocyte subpopulation is increased by dopamine and the dopamine receptor agonist, SKF 38393, implicating D1-like dopamine receptors in the increase in transmigration elicited by this neurotransmitter. Thus, elevated extracellular CNS dopamine may be a novel common mechanism by which active substance use increases uninfected and HIV infected CD14 + CD16 + monocyte transmigration across the BBB. The influx of these cells into the CNS may increase viral seeding and neuroinflammation, contributing to the development of HIV associated neurocognitive impairments.

Drug abuse is a major comorbidity of HIV infection and cognitive disorders are often more severe in the drug abusing HIV infected population. CD14+CD16+ monocytes, a mature subpopulation of peripheral blood monocytes, are key mediators of HIV neuropathogenesis. Infected CD14+CD16+ monocyte transmigration across the blood brain barrier mediates HIV entry into the brain and establishes a viral reservoir within the CNS. Despite successful antiretroviral therapy, continued influx of CD14+CD16+ monocytes, both infected and uninfected, contributes to chronic neuroinflammation and the development of HIV associated neurocognitive disorders (HAND). Drug abuse increases extracellular dopamine in the CNS. Once in the brain, CD14+CD16+ monocytes can be exposed to extracellular dopamine due to drug abuse. The direct effects of dopamine on CD14+CD16+ monocytes and their contribution to HIV neuropathogenesis are not known. In this study, we showed that CD14+CD16+ monocytes express mRNA for all five dopamine receptors by qRT-PCR and D1R, D5R and D4R surface protein by flow cytometry. Dopamine and the D1-like dopamine receptor agonist, SKF38393, increased CD14+CD16+ monocyte migration that was characterized as chemokinesis. To determine whether dopamine affected cell motility and adhesion, live cell imaging was used to monitor the accumulation of CD14+CD16+ monocytes on the surface of a tissue culture dish. Dopamine increased the number and the rate at which CD14+CD16+ monocytes in suspension settled to the dish surface. In a spreading assay, dopamine increased the area of CD14+CD16+ monocytes during the early stages of cell adhesion. In addition, adhesion assays showed that the overall total number of adherent CD14+CD16+ monocytes increased in the presence of dopamine. These data suggest that elevated extracellular dopamine in the CNS of HIV infected drug abusers contributes to HIV neuropathogenesis by increasing the accumulation of CD14+CD16+ monocytes in dopamine rich brain regions.

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.

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.

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.

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.

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-α., 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.

The prevalence of human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) that result from HIV infection of the central nervous system is increasing. Macrophages, the primary target for HIV within the central nervous system, play a central role in HIV-induced neuropathogenesis. Drug abuse exacerbates HAND, but the mechanism(s) by which this increased neuropathology results in more severe forms of HAND in HIV-infected drug abusers is unclear. The addictive and reinforcing effects of many drugs of abuse, such as cocaine and methamphetamine, are mediated by increased extracellular dopamine in the brain. We propose a novel mechanism by which drugs of abuse intensify HIV neuropathogenesis through direct effects of the neurotransmitter dopamine on HIV infection of macrophages. We found that macrophages express dopamine receptors 1 and 2, and dopamine activates macrophages by increasing ERK 1 phosphorylation. Our results demonstrate for the first time that dopamine increases HIV replication in human macrophages and that the mechanism by which dopamine mediates this change is by increasing the total number of HIV-infected macrophages. This increase in HIV replication is mediated by activation of dopamine receptor 2. These findings suggest a common mechanism by which drugs of abuse enhance HIV replication in macrophages and indicate that the drug abuse-heightened levels of central nervous system dopamine could increase viral replication, thereby accelerating the development of HAND.

Cell-to-cell communication coordinates the development of multicellular systems, and is mediated by soluble factors, gap junctions and the recently described tunneling nanotubes (TNT). Both TNT and gap junctions facilitate the transfer of intracellular mediators between the cytoplasm of connected cells. We recently described that HIV induced the formation of TNT in human primary macrophages in correlation with viral replication. Based on these results we hypothesized that during HIV infection, TNTs are hijacked by HIV to spread infection. TNT like structures may be a novel mechanism of amplification of HIV infection. Our findings and those of others require further investigation to identify the specific mechanisms by which pathogens use TNT.

Cell to cell communication is essential for the organization/coordination of multicellular systems and cellular development. Cellular communication is mediated by soluble factors, including growth factors, neurotransmitters, cytokines/chemokines, gap junctions, and the recently described tunneling nanotubes (TNT). TNT are long cytoplasmatic bridges that enable long range directed communication between cells. The proposed function for TNT is the cell-to-cell transfer of large cellular structures such as vesicles and organelles. We demonstrate that HIV-infection of human macrophages results in an increased number of TNT, and show HIV particles within these structures. We propose that HIV "highjacks" TNT communication to spread HIV through an intercellular route between communicated cells, contributing to the pathogenesis of AIDS.

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infect and productively replicate in macrophages and T lymphocytes. Here, we show that SIV virions derived from macrophages have higher levels of infectivity than those derived from T cells. The lower infectivity of T-cell-derived viruses is influenced by the quantity or type of mannose residues on the virion. Our results demonstrate that the cellular origin of a virus is a major factor in viral infectivity. Cell-type-specific factors in viral infectivity, and organ-specific or disease stage-specific differences in cellular derivation of virions, can be critical in the pathogenesis of HIV and AIDS.

HIV is found in the brains of most infected individuals but only 30% develop neurological disease. Both viral and host factors are thought to contribute to the motor and cognitive disorders resulting from HIV infection. Here, using the SIV/rhesus monkey system, we characterize the salient characteristics of the virus from the brain of animals with neuropathological disorders. Nine unique molecular clones of SIV were derived from virus released by microglia cultured from the brains of two macaques with SIV encephalitis. Sequence analysis revealed a remarkably high level of similarity between their env and nef genes as well as their 3' LTR. As this genotype was found in the brains of two separate animals, and it encoded a set of distinct amino acid changes from the infecting virus, it demonstrates the convergent evolution of the virus to a unique brain-adapted genotype. This genotype was distinct from other macrophage-tropic and neurovirulent strains of SIV. Functional characterization of virus derived from representative clones showed a robust in vitro infection of 174xCEM cells, primary macrophages and primary microglia. The infectious phenotype of this virus is distinct from that shown by other strains of SIV, potentially reflecting the method by which the virus successfully infiltrates and infects the CNS. Positive in vivo selection of a brain-adapted strain of SIV resulted in a near-homogeneous strain of virus with distinct properties that may give clues to the viral basis of neuroAIDS.